I'm sorry, but you are, by the definition of the word, requesting a [[diagnosis]]. And so I must apologize, but this is precisely the kind of question that [[Wikipedia:Reference desk/guidelines/Medical advice|the reference desk guidelines]] prohibit asking or answering. [[User:Someguy1221|Someguy1221]] ([[User talk:Someguy1221|talk]]) 02:53, 26 December 2007 (UTC)
While having sex I started to feel a pain, I came to find out later that I was bleeding. Im definetly not having my period. What could have been the cause of this? I'm still kind of in pain and it hurt to sit down for a while. Im not looking for a medical diagnosis, rather just any relevant information. <small>—Preceding [[Wikipedia:Signatures|unsigned]] comment added by [[Special:Contributions/96.237.113.21|96.237.113.21]] ([[User talk:96.237.113.21|talk]]) 02:17, 26 December 2007 (UTC)</small><!-- Template:UnsignedIP --> <!--Autosigned by SineBot-->
: Take a look at [[Vaginal bleeding]]. [[User:Schyler|schyler]] ([[User talk:Schyler|talk]]) 02:44, 26 December 2007 (UTC)
The best answers address the question directly, and back up facts with wikilinks and links to sources. Do not edit others' comments and do not give any medical or legal advice.
hey
Just wondering if when they are talking about atmospheres of pressure in papers on air flow [vortices etc] are they talking about
a regular atmosphere [14.7 pounds per square inch] or a technical atmosphere [14.02 pounds per square inch] ?
Also a stupid one, if a shockwave of 10 psi can destroy a building, how come a steel container can withstand something like 100 kpsi?
design: the building was not designed for this, but the steel tank was.
square-cube law: The building is much bigger. bigger means different: an ant, scale dup to the size of a man, would collapse under its own weight.
Static versus dynamic: The tank handles a static load, A shockwave has a very high rate of change. This is the difference between being punched and being shoved. Shoot an armor-piercing round at the tank: the tank will fail at far less than 100Kpsi.
Tension versus compression: the tank is carefully designed to withstand pressure from within. Evacuate the tank and place it in an a 100Kpsi environmant, and it will be crushed.
Arch's other points are clearly correct, but the one about dynamic pressure needs going into. You feel a difference between a punch and a shove because (A) with a shove you have more time to set up your muscles, and (B) a fast-moving fist is rapidly decelerated by contact with your body, which requires considerable force, and you feel the equal and opposite reaction; a shove does not involve a similar deceleration. Reason A is clearly irrelevant to the case of a shock wave. As to reason B, I don't know. Does the interaction of a shock wave with a fixed obstacle cause a greater pressure to build up against the obstacle? If not, I would not expect the armor-piercing round to penetrate the 100Kpsi-capable tank "at far less than 100Kpsi" if fired from inside it. --Anonymous, 03:33 UTC, December 19, 2007.
I have a different take on this - we're not told that the steel container is sealed in any way - or what size it is relative to the building - I don't know where ANYONE got the idea that it's a tank - the OP didn't say anything about that. So I don't buy any of Arch's points - nor any of Anonymous's points either. Let's consider something like a steel shipping container - and a small building made of brick or concrete of similar dimensions. My belief is that buildings are primarily built to survive compressive loads - their own weight, the weight of the things inside them - with little concern over pressure (which tries to stretches the surfaces by pushing them inwards - requiring tensile strength). Things like bricks, glass and concrete are great at handling compressive loads - but apply a tensile (stretching) load and they come apart really easily. Steel, however, is excellent at handling tensile loads - we make steel cables for example. So for two identically-sized and shaped structures - one made out of steel and the other out of brick, I'd put my money on the steel one in this kind of situation. Notice that a brick wall can comfortably support the weight of a 5 storey building - but you can easily knock it down by whacking it face-on with a sledge-hammer. You can whack away at a shipping container all day with a sledge hammer - and all you're going to do is make some dents - you won't be able to destroy it. SteveBaker (talk) 17:12, 19 December 2007 (UTC)[reply]
I assumed a scuba tank because the original question said "something like 100kpsi." That's a lot of pressure -- more than 5,000 atmospheres. -Arch dude (talk) 19:40, 19 December 2007 (UTC)[reply]
art therapy murals with hiv/aids patients
Who are the leading practioners and theorists in the use of art therapy? Who are the same in regards to HIV/AIDS patients?Voyage17 (talk) 04:38, 19 December 2007 (UTC)voyage17[reply]
Why does water expand anomalously when teperature isbrought down from 4 deg celsius to 0 deg celsius. —Preceding unsigned comment added by 218.248.2.51 (talk) 07:00, 19 December 2007 (UTC)[reply]
It's to do with the molecular structure and the nature of the hydrogen bonding. See Density of water and ice. --jjron (talk) 07:07, 19 December 2007 (UTC)[reply]
Right. The reason ice is less dense than liquid water is due to the hollows in its crystal structure, which is held together by hydrogen bonds. As the temperature gets close to the freezing point, the molecules start bonding together into little groups that are "trying" to grow into crystals, but it's not quite cold enough for that to happen. As it is, they still start to take up more space. Also see Dipolar nature of water in the same article. --Anonymous, 07:11 UTC, December 19, 2007.
liquid and air
in a water container which contains one litre of water, what is the concentration of air that is mixed with water. ther will be some air at the top of the water. but does the water contains air inside it? 59.92.22.117 (talk) 08:18, 19 December 2007 (UTC)[reply]
taking of sparcling water it would be several liters of CO2. For natural water it depends if it was heated before botteling, but the solubility of N2 and O2 at given temperature should be in the literature. I have a look.--Stone (talk) 08:24, 19 December 2007 (UTC)[reply]
Yes, some air dissolves into water. That's how fish manage to breathe underwater. As fish use up the oxygen - splashing and wave action cause more air to be dissolved from the surface replenishing the supply. In a home aquarium, a single goldfish can live in a bowl and get enough oxygen from air dissolving into the water from the surface - but if you want to keep dozens of fish, you need a pump that blows bubbles up from the bottom of the tank to ensure that more air gets dissolved into the water as the fish use it up. You can show this in a little experiment: If you put an open pan of water onto the stove with a thermometer in it - and increase the temperature really slowly - but never letting it reach 100 degrees centigrade, you can see bubbles start to form just before the water gets hot enough to boil - these bubbles are the dissolved air coming out of solution. As you can see from Stone's numbers, hot water can't hold as much air in solution as cold water - so as you heat it up the air comes out as bubbles. SteveBaker (talk) 13:20, 19 December 2007 (UTC)[reply]
Think sodas. That air at the top of the bottle is filled with CO2. The soda itself is also filled with CO2. The amount of CO2 increased by increasing the pressure of the gas. Shake the bottle, you will cause CO2 to air out of soda but since CO2 will be trapped inside the bottle, the pressure will increase. If you leave the bottle along for a while, the soda will reasorbe the CO2 again. This applies for any liquid and gas. NYCDA (talk) 19:56, 19 December 2007 (UTC)[reply]
It may help you to learn about the common water quality parameter, Dissolved Oxygen (DO). There's a lot of information on the internet about it. Typical water quality standards in North America require watershed managers to try and keep DO above 7 mg/L, or 7 ppm, in streams and rivers, any less and many fish species can't survive. Generally natural water bodies range from 7-10 mg/L. Oshkosk 11:08, 26 December 2007 (EST)
Species
note: this is not a homework question, but a question of my own I though up when doing my homework
If two different animals (for the sake of argument lets say a mouse-like creature) evolved from two different ancestors are were isolated from each other in that the two species never met, but the conditions of their two different environments were exactly identical, and they therefor over thousands / millions of years evolved to have identical physical appearance, would they be able to mate if they did come into contact with each other and would they produce fertile offspring? Weasly (talk) 11:56, 19 December 2007 (UTC)[reply]
I'm not a biologist, but I'll give it a shot. First of all, the phenomenon of unrelated species evolving similar features due to their similar environment is called convergent evolution, just in case you're not familiar with that term. To answer your question, in order to mate, two animals will have to have a very similar layout of chromosomes. But there's no reason to expect that two different species with similar features will have a chromosome layout that is at all similar. They might both develop a dorsal fin, but the dorsal fin gene for Species A might be on Chromosome 5, and for Species B it might be on Chromosome 11. There's nothing about the environment that's going to "drive" the physical properties to have their genes in the same place on the same chromosomes. The two species may even have a completely different number of chromosomes. If the chromosomes don't match up, they're not going to mate successfully. -- Coneslayer (talk) 12:19, 19 December 2007 (UTC)[reply]
Or, put more succinctly: looking and acting in an "identical" fashion just means they have a similar phenotype. It does not mean they have a compatible genotype. It would be an incredible, unbelievable, impossible coincidence for two organisms which had very different genetic ancestors to somehow evolve a compatible genetic code, even if they superficially look similar. --24.147.86.187 (talk) 12:32, 19 December 2007 (UTC)[reply]
Yes - I agree. One point for the questioner though - if you went back far enough up the evolutionary tree, you'd eventually come to a point where both animals have descended from a single ancestor. However, we're presuming that point was long enough ago that there are some really significant differences between your two starting-point species. Given that...no, it's not likely that the creatures would be able to inter-breed. However, even with convergent evolution, the converged species rarely look that identical - as our article convergent evolution shows - the hummingbird and the hummingbird-moth are considered to be an example of convergent evolution between a bird and an insect...but that doesn't mean that hummingbird-moths have only two legs or that hummingbirds go through the catapillar/pupae phase of development! They've converged into exploiting the same niche - and the adaptations necessary to do that have converged - but the parts of their life-cycles that don't relate directly to feeding from nectar-laden flowers have not converged at all - nor are they likely to in the future. SteveBaker (talk) 13:10, 19 December 2007 (UTC)[reply]
I believe the problem with this question is, it assumes that two animals separated from each other over millions of years will some how not diverge from each other. I find this to be unlikely, unless there was significant gene flow, but of course, then they wouldn't be segregated. If you separate two animals for a significant period of time, even in similar enviroments, and they survive over millions of years, they will inevitably diverge. 64.236.121.129 (talk) 14:56, 19 December 2007 (UTC)[reply]
To expand on this, there are other factors that determine evolution besides enviroment. You have to take into account the food supplies too. Competition for food, and predators. Even if the other enviroment is identical, the food supplies and the predators, certainly will not be. Natural selection is influenced from the outside remember. Take the oceans for example. The enviroment is... well water. But living beings can evolve differently because of those other factors. 64.236.121.129 (talk) 15:05, 19 December 2007 (UTC)[reply]
64, you're talking about divergent evolution, while the rest of us are talking about convergent evolution. Also, most people use the term "environment" to include the other organisms living in it. —Steve Summit (talk) 15:10, 19 December 2007 (UTC)[reply]
I'm answering the original question, not expanding on the other user's answers. And yes, some do, but there aren't too many places on earth that have both similar enviroment, in terms of geology, climate, etc, and similar flora and fauna. Inevitably, two animals separated which are able to survive for millions of years, will diverge due to numerous circumstances, specific to their enviroments. 64.236.121.129 (talk) 15:19, 19 December 2007 (UTC)[reply]
Evolution are caused by mutations. Helpful ones survive and are carried to future generations. Harmful ones dies out. Environment plays a factor in determining which ones would be helpful ones but it cannot cause any particular mutation to take place. Environment nudges evolution in a general direction but it can't force it. If you evolved a dog and a cat for millions of generations, they may be able to mate if they ended up compitable which is extremely unlikly. Today hourse and donkey can mate, (they give birth to mules which can't mate with either horse nor donkey nor other mules) but after millions of generations, it's unlikly they will still be able to. NYCDA (talk) 20:11, 19 December 2007 (UTC)[reply]
Bibliographic database
Hello, I am looking for a free online bibliographic database of scientific peer-reviewed articles, preferably full-text. I am using Google scholar at the moment but I would really like an alternative. My specific interest is in water-related environmental problems. Thank you in advance. Espole (talk) 11:57, 19 December 2007 (UTC)[reply]
I would suggest starting with this similar question from earlier this month. It got a pretty thorough answer, although I'm not sure how much applies to your specific field of interest. -- Coneslayer (talk) 12:24, 19 December 2007 (UTC)[reply]
Thank you so much for your very fast response. I probably should have found that question + answer myself, somehow. But you're right, the specific databases mentioned do not really apply to environmental/water related subjects. So it's back to google scholar for now. Espole (talk) 13:02, 19 December 2007 (UTC)[reply]
Once questions fall off this page and go into the archives, they're not really easy to find—I just remembered reading it recently, so I was able to track it down. Someone may still come along with a suggestion that's more specific to your subjects. -- Coneslayer (talk) 13:05, 19 December 2007 (UTC)[reply]
Well, it's not quite what you're looking for, but the EPA has some information about water quality in each of the individual states in the United States here. You could also try downloading some of the relevant Planet Earth articles from here as a starting point, and use the references and author names to track down the actual journal articles they're based on. Hope that helps! -- HiEv 14:38, 19 December 2007 (UTC)[reply]
Hi, I'm the one who wrote the response to that question that Coneslayer referenced. From what you're describing as your subject (water-related environmental problems), I would say that you have a couple of possibilities:
1) Use Agricola - the freely available online journal index of the holdings of the United States National Agricultural Library in Washington, D.C. They ought to have some stuff on your subject. Keep in mind that "agriculture" is not just about farming - it includes stuff on the environment and water resources, too.
2) There's a "family" of databases that includes some that will probably be very useful to your search called Cambridge Scientific Abstracts or, "CSA" for short. This is NOT a free online database, but it is quite common for research libraries to carry CSA - especially if the library is connected to a university that offers degrees in agriculture or engineering. If you're in the U.S., a Land-grant university would almost be guaranteed to subscribe to CSA. To see whether a library carries CSA go to its web page and look for some link that will provide you with their electronic resources or databases (different libraries call it different things), or just give the reference librarian a call. If you are affiliated with a library that offers these databases you might be able to contact the reference staff and see if it is possible for you to access these databases remotely via your home or office computer. Otherwise, if you find a library that subscribes to CSA (and if the library allows the public to use its facilities - some libraries restrict access to their own patrons), then you may have to physically go to the library and access CSA through its computer terminals in person. Some of the databases that CSA carries that could help you in your search are:
- Biological Sciences, covering Biomedicine, biotechnology, zoology and ecology from 1982-Current
- Biology Digest, covering Life sciences, evolution, genetics, behavioral science from 1989-Current
- BioOne Abstracts and Indexes, covering Biological, ecological and environmental sciences, and offering full-text articles, from 1998-Current
- EIS: Digests of Environmental Impact Statements, covering exactly what it says it does, from 1985-Current
- Environmental Sciences and Pollution Mgmt, covering Environmental biotechnology, engineering, pollution from 1967-Current
There are other databases that could be helpful, too, but these are a good start. Hope this helps. -- Saukkomies 10:38, 19 December, 2007 (UTC)
Genetics Question - Naturally multicoloured hair (Eg brown and blond)
I was just wondering how this work genetically. While the majority of my hair is brown, near the front of my head (Above my eyes) my hair is somewhat blondish. With what little understanding i have of genetics i thought this was quiet impossible or at least rare. My hair was also somewhat lighter when i was a child. Cheers, Kingpomba (talk) 16:18, 19 December 2007 (UTC)[reply]
Could it be sun bleaching ? In that case, I believe UV in sunlight destroys the pigment in some of the hair. I had that when I was young. StuRat (talk) 17:15, 19 December 2007 (UTC)[reply]
There are different possibilities that could explain naturally multi-coloured hair, but the bottom line is that the exact mechanism is not known. Firstly, there is the the non-genetic mechanisms such as sun-bleaching. As StuRat suggests, UV can cause photo-bleaching of melanin. Genetically speaking, we can look at other animals that have spatially variable hair colour (think German Shepherd dogs, for example). In most animals the major genes responsible are MSH, MC1R and ASP.
Here is how it works: MSH is a hormone that binds a receptor on the surface of melanocytes (the cells that produce pigment) called MC1R, causing it to to produce dark pigments (called eumelanin). This eumelanin is then "injected" into hair as it grows, giving darker hair. However there is another gene called ASP (Agouti signalling peptide, named after the agouti which shows a characteristic colour pattern) that makes a protein which can also bind to MC1R. When ASP binds MC1R it causes it to "switch" the cell from making dark eumelanin to yellow/red phaeomelanin. So which version of these three genes an animal has largely determines what colour its hair is (there are other genes that have effects, and new ones are discovered all the time. For example, last month it was found that a defensin gene is important in modifying MC1R signaling in dogs.)
However, this doesn't explain how hair colour varies within an animal. To explain this, we have to consider how an animal can vary the expression of the genes. It turns out that the ASP gene is very complex. The gene contains a number of exons that under go alternative splicing, giving the animal the ability to create a number of different ASP proteins from the same gene. These different ASP proteins have varying potency in switching the melanocyte from making dark to light pigment, so depending on which ASP version is expressed, their hair colour could vary. The final part of the story, as I'm sure you have already worked out, is that the animal has the ability to express different ASP versions in a spatial manner. For example, it may express a really potent ASP on its belly (resulting in light hair) and a really weak ASP on its back (resulting on darker hair). This is how these mice generate their unusual variation in hair colour. Incidentally some animals also are able to vary ASP expression over time, so when they are young they may express a potent ASP and as they grow older they change to a weaker one. Others vary ASP expression seasonally, giving winter and summer coats.
So, you could see how your hair could be explained by differences in expression of alternative ASP transcripts. There is a problem, however. And that is that there is no strong genetic evidence that the human ASP gene plays a significant role in human hair colour. The gene exists in humans and it doesn something, but we can't pin it down to hair colour. For some reason MSH and MC1R seems to account more for variation in human pigmentation. So, we don't know for sure what the mechanism is in humans, but the principle is likely to be the same: spatial regulation of genes that effect human pigmentation, (most likely MSH and/or MC1R).
On a final note, I should say this is a simplified version. Animals actually have a third level of regulation: they can control ASP expression to vary pigmentation within a single hair, giving banded hairs or frosted tips. This permits some of the spectacular hair patterns seen in some mammals. Humans can't do this, which is why any variation in our hair colour is pretty subtle and generalised. Rockpocket 19:41, 19 December 2007 (UTC)[reply]
Oak tree type identification
Acorns are small, almost round. What kind of Oak tree is this leaf cluster (front and rear view) from?
Area is South Florida, 20 miles inland from Gulf coast, 200 yards uphill from river. Twig from branch blown off on windy day.
I do not know the "official" term. Here in South Carolina, we call them "Winter Oaks" because they have leaves all year round. In the Fall, all the large leaves fall off in chunks and small leaves come in. Then, in the Spring, the small leaves fall off and large leaves come in. While it is nice to have green trees (other than pines), it is a pain to have leaves falling off the tree practically all year long. -- kainaw™ 18:14, 19 December 2007 (UTC)[reply]
That ain't much to go on, but I see nothing to rule out what my redneck friends used to call the live oak (Quercus virginiana) when I lived in Tampa, probably the same tree Kainaw is talking about. The tree itself is bulky, with its first branches practically on the ground. It gets huge. There should be orchids and moss all over it. --Milkbreath (talk) 18:59, 19 December 2007 (UTC)[reply]
I was going on the small acorns and the large leaf clusters that are dark green on one side and light green on the other (as well as being a southeastern variety). I know, it isn't much. An example of a very bulky one is the Angel Oak. It has some pictures that show how bulky and low-lying the branches get. -- kainaw™ 20:00, 19 December 2007 (UTC)[reply]
red robin
Robins are brown, with an orange breast, at least in the US. I see that in the UK and Australasia, different birds are called robins, but they all seem to have the orange color (from a quick browse at the wikipedia pages, linked from robin). So, my question is why is there a song about a red robin, and a restaurant chain Red Robin and a character in the kids' TV show Peep and the Big Wide World who is red and a robin (she's definitely red, and I'm pretty sure she's a robin)? Ingrid (talk) 18:57, 19 December 2007 (UTC)[reply]
I think what you call orange, others might call red (especially a long time ago, as exact meanings of words can shift over time). I haven't looked it up, but I suspect that "orange" is of French origin, and may not have existed in English prior to the Norman invasion. Perhaps "red" was used to describe what we now call orange, prior to that time. -- Coneslayer (talk) 19:00, 19 December 2007 (UTC)[reply]
The song is called "When the Red, Red, Robin Comes Bob, Bob, Bobbin' Along". It was written by Harry Woods, the prolific tin-pan-alley songwriter who also wrote "Try a Little Tenderness". I suspect that slight zoological inaccuracies didn't bother him a bit and that he didn't even consider "rufous, rufous robin" or "reddish-orange, reddish-orange robin". They don't "bob", either, if you want to be picky, they strut a few steps and freeze, strut and freeze, head held rigid, like a wind-up toy.
The bird is known in some parts as "robin redbreast" in reference to its color. "Red" is close enough; it's not bright enough a color to be a very good orange, I think. I'd have to guess that the chain is named after the song. As for "Chirp", there are only so many primary colors. It doesn't bother you that the duck is blue? --Milkbreath (talk) 19:34, 19 December 2007 (UTC)[reply]
Ever tried rhyming with "orange"? If I was writing a song about a robin, I would use all the artistic license I could muster rather than tackle that. Rockpocket 19:50, 19 December 2007 (UTC)[reply]
The US robin and the UK robin are pretty much unrelated. The UK variety is a tiny little bird - and it's chest feathers are much more red than the US robin (which is a relatively large bird with a more orangey chest) - although the photos we have here seem to make them look much more similar in colour than I think they really are. Since (almost certainly) the UK version of the robin was named first - and when British people came to the Americas, saw this new bird with a orangey/red chest and none of the UK kind, just got into the habit of calling these new birds "robins" too. That doesn't change the christmas-card image of a red-chested robin. SteveBaker (talk) 19:53, 19 December 2007 (UTC)[reply]
To expand on the topic: While the American Robin is not closely related to the European Robin, it is closely related to the European Blackbird. When my wife and I were in Paris, we were fascinated by the "soot-covered robins" we saw there—the Blackbirds scratched and hopped around just like American Robins, and had essentially the same shape and size, and even the distinctive eye-ring. North American blackbirds, on the other hand, are unrelated to the European Blackbird and the American Robin—they are Icterids. So the American Robin is closer to the European Blackbird than either of them is to the European Robin or the Red-winged Blackbird! —Preceding unsigned comment added by Coneslayer (talk • contribs) 23:31, 19 December 2007 (UTC)[reply]
As I recall, the colour we now call "orange" used to be called "red", and was regarde as simply a shade of red. This changed after the introduction of the fruit "orange" - which gave its name to the colour. 23:38, 19 December 2007 (UTC) —Preceding unsigned comment added by DuncanHill (talk • contribs)
Famously, in the film Mary Poppins the bird that appears during the song 'A spoonful of sugar' is an American rather than a European robin. AndrewWTaylor (talk) 00:30, 20 December 2007 (UTC)[reply]
It's also two male robins making the nest together, a fact I noted on the WP page long ago, but which has been removed to make room for a book-length "synopsis" of the film. Sigh. Matt Deres (talk) 01:57, 21 December 2007 (UTC)[reply]
Also, red-haired people are said to have ... well, red hair. But it's not actually red, as in postbox blood red. It's closer to orange, sandy, coppery etc depending on the shade. It's never actually "red". Context usually determines what words mean. -- JackofOz (talk) 01:01, 20 December 2007 (UTC)[reply]
The Robin is a member of the Thrush family (scientific name is Turdidae). This family has quite a number of species that are called Robins, mostly within the Genus Turdus. There is, for instance, the Mountain Robin (Turdus plebejus), the American Robin (Turdus migratorius), and the Rufous-backed Robin, (Turdus rufopalliatus), to name a few. Not all of the birds that have the name Robin look like the classic red-breasted Robin in Disney movies. And then to complicate things, there are some Thrushes that look like red-breasted Robins that are not called Robins. In North America it is quite common for people to confuse Thrushes with Robins. The basic rule of thumb is that Robins have redder breasts than Thrushes, whose breasts are sometimes almost orange or yellow. -- Saukkomies 21:07, 19 December 2007 (UTC)[reply]
Thanks, everyone. I'm not sure how to reply to someone up above. About Quack, the blue duck, I never gave it a thought. My 5yo asked what kind of bird Chirp was, and they don't say it often, so we were trying to guess. It got us wondering about the whole red robin thing, so I thought I'd ask. I've always wondered about the red hair thing too, but didn't put the two together. Thanks for the education! Ingrid (talk) 02:30, 20 December 2007 (UTC)[reply]
In todays "Times" there is a photo of a white breasted robin!--88.110.51.242 (talk) 09:47, 20 December 2007 (UTC)[reply]
Evolution in action! Will the improved camoflage of the white robin enable it to better hide (in snowy conditions) from predators and therefore out-perform it's rivals? Will the lack of the red feathers (which are only present in male robins - and therefore part of the whole mating thing) mean that female robins will spurn him - and therefore this genetic change will vanish in a single generation? Only time can tell! (I'm betting on it dying off). SteveBaker (talk) 13:07, 20 December 2007 (UTC)[reply]
What is Fd with respect to antibodies?
The Fd fragments are the most central part of the Fab fragments in this figure, the outside peptides are usually known simply as the "Fab light chain". The other papain cleavage product is the Fc fragment.
What is Fd with respect to antibodies? Thanks. --SeansPotato Business 21:07, 19 December 2007 (UTC)[reply]
Biggest featureless snowman made by a single person without using machinery?
Hi. Does anyone know the record, if there is one, for the biggest (tallest, heaviest, largest in volume, longest, widest, thickest, etc) featureless snowman made by a single person without using machinery (eg. bulldozers, automatic lifting machines, levers, etc count as machinery; snow shovels, snow ramps, winter gloves and boots, etc, don't count) and without help from other people? I recently created a snowball so big I couldn't push anymore, if you can imagine, then patted thick layers of snow over it to attempt to roundenify, then put some snow on that, and shaped the snow on there into a snowball, then put more snow on that, and shaped it into yet another snowball. I then patted snow around the whole figure, to fill in the gaps in-between the snowballs. Soon after, someone pushed and beheaded my snowman at a 50-degree angle, and the head fell to the ground, which was covered with snow. I tried, without getting help, and without success, to lift the head back on the snowman, but I did get it halfway. So, after another snowstorm, I patted layers of snow on it so that it looks osmewhat like an elongated ovaloid. It now weighs about five times as much as I do. So, I plan to put more snow on that, shape it into a snowball, and put yet more snow on that. The whole thing, which is still just a baseball (bottom snowball of a snowman), is already about 1.5 m by 1.5 m by 1 m. If I succeed in doing so, which by then the snowman would weigh about half a tonne (OMG!), how close would it get to the record, if there is one? Thanks. ~AH1(TCU) 22:33, 19 December 2007 (UTC)[reply]
Guiness World Records, who would probably be the one to have such a record, doesn't appear to list any records for snowmen, or surprisingly, even snow sculptures.[1] You could apply to them to have your creation listed, but at this point it'd be difficult to prove to them that you didn't use any machinery. MrRedact (talk) 02:41, 20 December 2007 (UTC)[reply]
I suspect they do have records for scupltures. Bear in mind that the number of records on their website is only a small proportion of the records they have, as they mention when you search and fail [2]Nil Einne (talk) 08:15, 21 December 2007 (UTC)[reply]
Time and relativity
I was thinking about the answer that you gave to my previous question sometime last month about speeding/slowing time using movement relative to a television. I'm a little confused about the answers I got, that the effect of motion is sqrt((1+v)/(1-v)). Might I ask again with a different scenario? 40,000 years ago, an alien 20,000 light-years away sat in its spaceship, viewing earth through its super-advanced telescope, and and began to move constatly at .5c. The first image it sees through its telescope is that of earth 60,000 years ago, ie 40,000 YA + 20,000 light-years. 40,000 years later, it has arrived at earth, and is obviously seeing earth in the present (since the time is now and the distance for light to travel is 0). The alien thinks it has watched 60,000 years of earth's history in just 40,000 years, so time appears to have been sped up 1.5x, which is not consistant with the sqrt((1+v)/(1-v)), ie sqrt(3), answer that I got last time. Some clarification, please? 68.18.198.218 (talk) 23:07, 19 December 2007 (UTC)[reply]
This is where the slowing time comes in 40000 years have passed on the earth, but not on the spaceship, which has less time elapsed. Graeme Bartlett (talk) 00:56, 20 December 2007 (UTC)[reply]
Wait... so the alien thinks its going faster than .5c, since it just traveled 20,000 light years in less than 40,000 years, but earth people only think it's going at .5c? Why? —Preceding unsigned comment added by 68.18.198.218 (talk) 01:31, 20 December 2007 (UTC)[reply]
Anyone, human or alien, can describe the situation with respect to any coordinates they like, as long as they respect the (coordinate-independent) physics. With respect to the earth's rest frame, the alien's speed is .5c. With respect to the alien's rest frame, it's 0. If you divide the distance from the earth's rest frame by the time from the alien's rest frame (or by the alien's proper time) then you'll get a ratio larger than .5c. The alien sees 60000 years of history in 40000/γ years, which is a ratio (Doppler shift) of (60000/40000)γ = (3/2)(2/√3)) = √3. -- BenRG (talk) 02:45, 20 December 2007 (UTC)[reply]
Possible to convert impact force in joules to force in kilograms?
Hi. Is this possible to do? If so, how do you convert it? Also, how do you convert the mass of an object and its speed into impact force in joules? Or would this not work because it is really kinetic/potential energy? Is it because some of the energy would be absorbed by the air/target? Does the density of the target matter? What if the object is swinging from a fulcrum point, do you include the whole objects mass at the speed or adjust to the rest is moving at lower speeds? I could use the asteroid impact calculator, but if the object is too small, it burns it up in the atmosphere, so it can't calculate on-Earth impacts. Does whether the projectile/target explodes/ruptures affect the final number? If the projectile is connected to a still-to-ground object, does it affect the final number? Does impact area affect the final outcome? Does it work the same way for projectiles such as air and water as it does for denser ones such as rocks or bullets? Or, is this measured in atmospheres? Can you ocnvert atmospheres to impact force in kilograms? Would results be similar if, say, a still object weighing 20 kg sat atop the target, and if a projectile hit the target at the equivalent of 20 kg of impact force? Or would it be different because the still object's force would be negligable in microgravity, while the moving projectile would still take effect because its mass doesn't change? Do any gravity variations (noticeable ones) affect the final outcome? Can you calculate impact force in joules by knowing the amount of gravitation (say, Earth), air resistance, if any, and distance between object and ground, for an object dropping vertically to Earth? What speed would an object have to move downward at, say at a height of one metre, to match the average speed of an object dropped from that height? No complicated university-level formulas, please. Thanks. ~AH1(TCU) 23:07, 19 December 2007 (UTC)[reply]
Without reading your whole question... See joule. It is a kg m2/s2. You cannot arbitrarily drop the meters and seconds. -- kainaw™ 23:16, 19 December 2007 (UTC)[reply]
Hi. So, a joule equals a kilogram travelling at one metre per second? Or, do you calculate the number of joules by multipiling its weight in kilograms by the speed in metres per second squared? Sorry, I think I used to be able to remember, but then I forgot, and is this kinetic or potential energy? Thanks. ~AH1(TCU) 23:24, 19 December 2007 (UTC)[reply]
In terms of kinetic energy, E = 1/2 m v^2, so a 1 kg mass moving at 1 m/s has only half a joule of energy. However, 1 J = 1 Nm, so the work you do in exerting a force of 1 Newton over 1 metre, and hence the work done in pushing that 1 kg mass 1 m at an acceleration of 1 m/s^2. Confusing Manifestation(Say hi!) 00:25, 20 December 2007 (UTC)[reply]
A joule is a measurement of energy (not a measurement of kinetic energy or a measurement of potential energy). It could be the kinetic energy used to move something or the potential energy available to move something. After reading your question, you are asking what is basically a very common test question on any introductory physics exam. Ie: A person lifts a 102g apple one meter high against Earth's gravity (9.86 m/s2). As with most introductory physics, it is just a matter of getting the units correct. We need kg m2/s2. The apple is 0.102kg - so that gives us the kg. If we multiply that by the distance, we get 0.102kg × 1m = 0.102kg m. Now, if we multiply that by gravity, we get 0.102kg m × 9.86 m/s2 = 1 kg m2/s2 = 1 J. As you can see, all you need is mass, distance, and acceleration. That could be mass actually moved over a distance with some acceleration (kinetic) or mass that could be moved over some distance against some acceleration (potential). -- kainaw™ 01:52, 20 December 2007 (UTC)[reply]
Creationism vs. science/evolution
Hi. I was just thinking, what if we could divide the Earth's scientific 4.5 billion-year age into seven equal parts, to represent the seven days of creationism? If the seventh day and the rest takes up too much space of our time-scale, would it work if we divided it into six parts to represent the first six days? If that doesn't work, what if we made the scale exponential, rather than linear, so that the time representing the first day is much longer than the time representing the seventh? Also, how did we figure out the Earth's scientific ~4.5 billion-year age, did we see that uranium-238 samples were half uranium, half something-else, and used the half-life of uranium to determine this? Or did we use the Earth's estimated age to calculate the half-life of uranium-238? Or are the two unrelated and this is just a big coincidence? If they used the half-life of uranium, wouldn't that tell you when the uranium itself was created, not when the Earth was created, since the uranium could have existed long before the Earth (ie. when the supernova erupted that created the nebula that our sun was created from), and the temperatures of the Early Earth, as far as I know, were not high enough to create uranium out of heavy metals? So, wouldn't it have been generated before the Earth was created? Thanks. ~AH1(TCU) 23:18, 19 December 2007 (UTC)[reply]
The order of creation would not fit the observed sequence from the geological record. Even if you split it to six equal parts. David D.(Talk) 23:21, 19 December 2007 (UTC)[reply]
To address a specific point, determining the half-life of a radioisotope does not require reference to the age of the earth. It can easily be measured from the decay rate (think Geiger counter) of a sample of known mass. Also, radioisotope dating does not depend on when the atoms were created through nucleosynthesis—the atoms don't "know" that themselves. Radioactive decay is just a statistical process whereby in a given interval of time, each atom has a certain probability of decaying. The dating is accomplished by comparing the amount of the original isotope to its decay product(s), so what matters is how long the uranium and its decay products would be confined together (as, say, a rock in the earth). -- Coneslayer (talk) 23:39, 19 December 2007 (UTC)[reply]
The thing is, the age of the earth has been determined by a few different unrelated methods. Sure each method in isolation can be argued against, if you argue that part of the method is flawed, such as you argue about decay uncertainty. But when several completely unrelated methods arrive at roughly the same figure, it is harder to argue that all the different methods are flawed and it is just a great coincidence they all give the same false result since they relied on unrelated methods to arrive at their conclusion. We even have an article called Age of the Earth. Vespine (talk) 00:05, 20 December 2007 (UTC)[reply]
This idea doesn't really work - no matter how you dice up the time between the big bang and now (paraphrasing our Creation according to Genesis article for brevity):
First day: God creates light. - OK - I can buy that, the big bang produced a bunch of electromagnetic radiation - which we'll take as "light". The light is divided from the darkness - um well, maybe.
Second day: God creates a firmament and divides the waters above it from the waters below. Well, I guess water and all other matter gets formed a short while later. It's a bit odd to single out water from all other chemical compounds...and we've quietly avoided mentioning that early galaxies and stars were mainly hydrogen and helium. The Oxygen needed to make water can't come about until we get onto the second generation of stars. But OK - so we're into the second generation of stars here.
Third day: God gathers the waters together, and dry land appears. Then God brings forth grass, herbs and fruit-bearing trees on the Earth. - This works - planets form after stars - water first on earth, then dry land...OK. Grass was a fairly late addition to the earth. It didn't come about until about 65 million years ago...but that's OK.
Fourth day: God creates...the stars. - No, no, no! This is bad - this is where it all falls apart! We don't get stars until AFTER grass and trees? But the sun is a star! No, stars means no water - we needed stars on day one or two! We're WAY out of whack here!
Fifth day: God creates birds and sea creatures; - No, again, not gonna work. Fish were around 500 million years ago - they easily pre-date grasses, and indeed ALL land plants. Birds aren't around until the later years of the dinosaurs.
Sixth day: God creates wild beasts, livestock and reptiles upon the Earth. He then creates Man and Woman - No, again, we really can't have reptiles coming along after birds. Birds are descended from reptiles and reptiles pre-date grasses and fruiting trees...this is WAY out of whack.
Seventh day: God, having completed his work of creation, rests from His work. - Well, good for him. The stress of the whole work week seems to have confused him a bit.
So, you see, while you can kinda-sorta bend the language to make the first three days of creation work out OK, from day four onwards, it's just WRONG. You really can't have stars coming after grass and fruit-bearing trees. —Preceding unsigned comment added by SteveBaker (talk • contribs) 14:47, 20 December 2007 (UTC)[reply]
Nice post Steve, I was a bit lazy above, you did it justice. David D.(Talk) 18:13, 20 December 2007 (UTC)[reply]
For what it's worth, the ...and God divided the light from the darkness on the first day is sometimes interpreted as the creation of time—a rather useful thing to have in a Universe. TenOfAllTrades(talk) 18:44, 20 December 2007 (UTC)[reply]
Hmmm so it took a day to create time? Ow! My head hurts! This could have been made better if the events had been re-ordered to Day 1, Day 4, Day 2, Day 5, Day 3...but no, day 6 is still a problem. He has to make reptiles, then birds, then people. But reptiles and people came on the same day - and that's a different day to birds. There is no way to fix that. I conclude that it's all nonsense and God either doesn't exist or he has a really bad memory for dates. Either way, he blew the entire omniscient thing - so he's outta here. QED. SteveBaker (talk) 20:59, 20 December 2007 (UTC)[reply]
Another interpretation is that, even if some God exists, his activities are not necessarily accurately recorded in human mythology. Our current media can't get technical details right- why would we expect the ancient Jews, with their largely oral passing down of knowledge, to do better? Friday(talk) 20:19, 21 December 2007 (UTC)[reply]
Which is fine, so long as you are consistent about it. If you choose to ignore what this account of creation says because "someone wrote it down wrong" - then you must also be prepared to ignore many of the other things that are said. The ten commandments are in just as much trouble - it's pretty clear that they had to have been written down wrong too because there are at least two completely different versions of them. If the two single most important things the old testament says are wrong (How it all started and what the rules are) - there is not one single thing that's said in the entire book that can then be trusted. Ordinarily, this wouldn't matter - I'm sure most books contain errors here and there - but this is a book that people are supposed to base their entire lives upon. If you can just start picking and choosing which bits you like and which you don't - then it's hardly a bible anymore - it's a kiddies story book. However, there are a great number of people (most of whom seem to live here in the USA) who take that particular section of the book extremely literally and are trying to get it taught in schools on an equal basis with evolution. That's hardly tenable if you think it's been mistranslated to the point where that very creation event is so completely screwed up. SteveBaker (talk) 21:40, 21 December 2007 (UTC)[reply]
Do people get dirtier or cleaner as they grow up?
Do people get dirtier or cleaner as they grow up? Let me explain....
When I was in 6-9th grade, in my physical education class, we used to run and do other activities, and then we used to go back in the locker room and put on our clothes and goto our next class (without taking a shower). Now I'm 22, and there is no way in the world that I would ever in my life run or play a sport and not take a shower immediately and put on new clothes. If I dont, I will get itchy and maybe get athletes foot or jock itch, etc...
Do we sweat more when we get older compared to when we were in our teens? Can someone help clear this up? Thanks —Preceding unsigned comment added by 76.167.138.192 (talk) 23:34, 19 December 2007 (UTC)[reply]
Its due to different sweat glands. Children sweat exclusively through eccrine sweat glands. During puberty we develop apocrine sweat glands, which produces both more and a different "type" of sweat. It is this type that generates sweat odor, due to the bacteria that breaks down organic compounds in the sweat. Rockpocket 23:49, 19 December 2007 (UTC)[reply]
December 20
Mail delivery
My mail box has a holder on the bottom for second, third, bulk mail and unaddressed flyers but the postmen never use it. Instead they cram the regular first class mail along with the second, third, bulk mail and unaddressed flyers right into the mailbox. This forces me to go through the junk mail to be sure I do not throw first class away. Is this a conspiracy on the part of the post office and the advertisers who pay them for such method of delivery or can I somehow force them to use my mail box for only first class delivery? 71.100.14.54 (talk) 00:03, 20 December 2007 (UTC)[reply]
I don't think the Science desk is appropriate for your question. Anyway, the answer is this: People aren't going to take on extra work for free, just because you'd like them to. -- Coneslayer (talk) 00:16, 20 December 2007 (UTC)[reply]
..ah a response from a postal employeee. Just what I expected. 71.100.14.54 (talk) 00:17, 20 December 2007 (UTC)[reply]
Coneslayer, you really have some impressive credentials for a postal employee. Someguy1221 (talk) 00:21, 20 December 2007 (UTC)[reply]
I just do it for the benefits. Got any Advil? My back always hurts this time of year. -- Coneslayer (talk) 00:23, 20 December 2007 (UTC)[reply]
A quick note: your question poses a false dichotomy -- that is, you may be unable to force the postal service to use various mail slots in the fashion you prefer without supposing a shadowy bulk advertising cabal. Similarly, the occasional delivery of folded do-not-fold envelopes does not provide strong evidence for the postal service being repurposed by Martian Nazis. Godwin's Law! I win! That said, I think Coneslayer is right -- it's unlikely you'll find a solution without payment involved somewhere (if then). — Lomn 00:39, 20 December 2007 (UTC)[reply]
Actually, you were the first to mention them, so Godwin's Law says you lose. --Trovatore (talk) 02:56, 20 December 2007 (UTC)[reply]
It's not a scaleable idea anyway. What makes more sense: everyone sorts their own mail (taking, say, 1 minute per day), or the postal employees sort everyone's mail (1 minute per day * everyone who they deliver to). And what are you going to do if the postal guy gets it wrong and puts an important-but-junky-looking-envelope (like the sort that new ATM cards come in, to avoid being stolen) into the junk slot, and you throw it out? How would you feel then? Better to just take that minute and not worry about it too much. Or see about getting your name removed from the junk lists to begin with (e.g. [3]), or call your congressperson and tell them you're in favor of tougher junk mail laws. --24.147.86.187 (talk) 02:05, 20 December 2007 (UTC)[reply]
Interesting... Normally I would think that of all people who might see the value in and respect and support the existing mail classification system (First class, etc.) it would be mailmen. Okay, so I can accept the fact that they are lazy. That said, it now does not make sense why they would go to all the trouble of unsorting the bulk and class mail when they are the ones who grab a piece of junk mail from a box of identical pieces and combine it with class mail to begin with. 71.100.14.54 (talk) 02:24, 20 December 2007 (UTC)[reply]
You are bordering on trollish behavior. It was explained repeatedly that it is not a matter of being "lazy" as you claim. It is a matter of time. It takes longer to sort at the box. If every box took longer, it would require more people to deliver the mail in the same amount of time. That would cost more money. Where do you suggest the extra money comes from? -- kainaw™ 02:33, 20 December 2007 (UTC)[reply]
Kainaw dude, did you not read above? Much of the junk mail does not have a name or address printed on it but is rather provided to the postman in a box from which he must grab a piece and do the work of unsorting it by combining it with class mail and other pieces which have addresses. Defending laziness is one thing but you in your defense are defending extra work for both the postman and the postal customer. 71.100.14.54 (talk) 02:46, 20 December 2007 (UTC)[reply]
It's still simpler and less effort that way, for at least two reasons I can think of off the top of my head. Note that these aren't necessarily the actual reasons, but they do seem to fit the evidence.
Not every mailbox is like yours. Many are just a single box, where the postal worker has to put all the mail. In general, it is quicker and easier to have a single method to apply in all cases, even though tailoring the method will produce better quality results (for example, catering for 100 by making big batches of food versus cooking individual dishes). In this case, the only method that can be applied to all mailboxes is to stuff everything together.
The postal worker has to pick up mail from two piles - the addressed stuff and the junk mail. Getting them both out together, holding them in the one hand, and putting them in the one mailbox is more efficient than getting one lot, putting it in its box, and then getting the other and putting it in its box, and less awkward than holding a pile of mail in each hand and trying to make sure that the right pile goes into the right box.
On another note, wherever you may be (I would assume US?) can you get "No Unsolicited Mail" stickers to place on your mailbox? They're fairly common in Australia, and (in theory) mean that only mail that's addressed to you will be delivered. Confusing Manifestation(Say hi!) 03:05, 20 December 2007 (UTC)[reply]
Actually a superior idea has come to mind. Every time I visit one of those hobby sites that specialize in building robots they are always looking at ways a robot can do the job of a human. Already we have robots for the home that are so sophisticated they can run around the house all day cleaning up spilled peanuts, etc. without getting in our way. The police already use robots and a form of robot is even used to deliver the mail in large government and corporate buildings and DARPA has paid out over a million dollars in prizes for university teams to build cars that can drive themselves. 71.100.14.54 (talk) 03:40, 20 December 2007 (UTC)[reply]
I did read what you wrote. You wrong to the point of carrying on an argument just for argument's sake. Which is faster; picking up two things and putting them in one box in one motion or picking up one thing and putting it in a box before picking up something else and putting it in another box? Obviously, the single motion is faster. Two motions is slower. Perhaps you suggest we should have three-armed postal workers. You are also completely ignoring the fact that the bulk mail people paid to have their mail put in your mailbox - not in a separate box. It is not the postal worker's option to stick the mail in a separate box. -- kainaw™ 03:35, 20 December 2007 (UTC)[reply]
Well as a matter of fact you are wrong. Postmen used to place bulk mail in the bulk mail receptacle. As for three armed postal workers there are lots of jobs that can be done less perfectly as a matter of expedience. For instance, we could get rid of this hourly wage and overtime thing and just pay everyone the same salary. 71.100.14.54 (talk) 03:43, 20 December 2007 (UTC)[reply]
I never claimed that postmen never placed bulk mail in mail receptacles in the past. I stated that it takes longer to place mail in two receptacles than it takes to place it in one. I also stated that bulk mail postage is (present tense) a payment to place the mail in the person's mailbox, not in a separate box or trashcan - assuming we are discussing the postal laws and regulations in the United States. Once again, claiming a person has said something that they did not say just to further an argument is simple trolling. Continue complaining all you like. I seriously doubt anyone is willing to continue taking your bait. -- kainaw™ 03:47, 20 December 2007 (UTC)[reply]
On that note I will now conclude my discourse with you by stating that you are making a personal attack and that what separates the mail is not only the address but its classification. Of course with only one box a postman has not choice but by law with a box for each classification the postman is failing to properly deliver the mail if he does not place each class of mail in the right one. 71.100.14.54 (talk) 03:54, 20 December 2007 (UTC)[reply]
If that's true, it seems your question and/or complaint must certainly be with your local post office (for failing to obey this law), and not with anyone here. (Silly me, I assumed you were asking us why your postman doesn't do this, but if you already know that he's required to, well, get on it with those properly-directed complaints!) —Steve Summit (talk) 04:19, 20 December 2007 (UTC)[reply]
I haven't read through all the above, so apologies if I repeat anyone, but: two points:
I don't know where you live, but in the U.S., for as long as I've been aware, all the mail comes in one box. If there's a second place for non-first-class mail, it's an antique, a forgotten relic. Having the postman sort and deliver my mail in two piles simply isn't part of the current contract.
It's true that the postman has to do a certain amount of extra work to give everyone on the block one of those junky advertising circulars. I, too, wish that my postman didn't bother, so that I could be spared the time of sorting it back out from my real mail and throwing it away. But if my postman abided by my wishes and didn't deliver it to me (or delivered it to, say, a wastebasket I placed on my porch for the purpose), he would be, like it or not, violating his contract with the advertiser who paid to have that circular delivered to me. Supposedly, the profit margin for the post office is higher for bulk-rate junk mail than it is for first-class mail, so unfortunately, it really is in their best interest to keep taking money from the advertisers in return for shoveling the junk mail at us. —Steve Summit (talk) 03:51, 20 December 2007 (UTC)[reply]
Their highest profit margin comes from the P.O. boxes you rent. 71.100.14.54 (talk) 03:59, 20 December 2007 (UTC)[reply]
Followup: Can I avoid mail-spam if I use a P.O box?
I've never had a PO box - but is it possible that I could simply take down my mailbox and get a PO box for my mail? I presume they don't send the inch thick grocery store junkmail to PO boxes - right? SteveBaker (talk) 14:22, 20 December 2007 (UTC)[reply]
I used to have one when I was in the Marines. They cram it all in there. By the time I got my mail out, it was a crumbled brick of paper that I had to untangle. I complained and discovered that the post office is more interested in delivering bulk mail (since they get paid for that) than not delivering it (since they don't get paid for that). Also, there's that nit-picky law thing that says they have to deliver mail that they are paid to deliver - even if the recipient doesn't want it. -- kainaw™ 14:36, 20 December 2007 (UTC)[reply]
I have a P.O. Box. Every piece of junk mail I get at home addressed to "Homeowner", I get a second copy of in my P.O. Box addressed to "Boxholder". So the P.O. box more or less doubles my junk mail. —Steve Summit (talk) 15:07, 20 December 2007 (UTC)[reply]
Oh...crap. Another great idea bites the dust in favor of reality. Nevermindthen. SteveBaker (talk) 15:28, 20 December 2007 (UTC)[reply]
If it's worth $1 to you (far less than the cost of renting a PO box), then you can go here and opt out of most direct mail. I did this long ago when there was no online option and it required a postal letter to get on the opt-out list (but it was free), and it was effective for awhile. Then I moved away and moved back and never have gotten around to doing so again ... --LarryMac | Talk 19:09, 20 December 2007 (UTC)[reply]
I don't think that's going to work. That's for companies (like credit card companies) who mail the product directly to your address. I'm not particularly swamped with those. The thing that bothers me is about a 1" slab of newsprint and glossies that arrives every few days addressed to "General Delivery" or something. The $1 service you mention isn't going to stop that because the mail isn't addressed to me - it's just spam. The scale of this problem is insane. At my apartment complex here in Austin, TX, there are about 200 mailboxes in one big 'wall'. Every day, the apartment complex staff haul away FOUR trashcans full of unread mail. You can stand there and watch people pull the stuff out of their mailbox - flip through it really quickly to ensure that there is no 'real' mail in there - and dump it right into the nearby trashcans. 250 times one inch of paper is a pile 20 feet tall! It fills FOUR trashcans every few days! I've never - not even once - seen someone look at the stuff properly - let alone take it away with them. I can't imagine how the local supermarkets can justify the expense of designing, printing and paying the post office to distribute all of that crap if absolutely NOBODY reads it. It's crazy to watch the postal guy hauling out box after box of this stuff - putting it into all of the mailboxes - and then to see apartment residents taking it out again and dumping it in the trash without once looking at it. Aside from the insane waste of time and money - it's an environmental nightmare! However, we have no way to stop it. The post office (who could easily stop it by requiring it to be properly addressed to individuals and to have senders be required to honor the "do not spam me" list) don't want to stop it because that's the only thing that's keeping mail delivery running in the face of email...and the senders clearly find it cost-effective (although I have no clue how that could possibly be!). The victims here (me - and the environment) don't contribute to any part of the cash flow involved - so we're powerless to stop it. SteveBaker (talk) 20:48, 20 December 2007 (UTC)[reply]
You are assuming that "nobody" reads it. I did development for a grocery chain once - specifically for the department in charge of the circulars and coupons. They are all statistics geeks. They count up how many coupons are used. Each one has value as a person who read through the circular enough to clip out a coupon. Then, they compare that value to the cost of mailing the circular. The post office doesn't let you ignore apartments. They give you routes. For example, you can send it out to route 32. Everyone on route 32 will get it - regardless of what kind of home it is. Now, add to the coupons the shopper cards and you can see what routes are coming in with coupons. Then, you can target those routes with even more circulars. It all comes down to very simple economics - the stores see value in sending out the circulars because they can see that customers are coming in with coupons from the circulars. What you need to do is go door to door to every home in your route and tell them to never use the circular's coupons. Then, the store will figure that the route is not worth it and stop sending the circulars to your route. This is identical to the email spam problem. The only way to stop it is to go to every person with an email address and tell them to stop buying stuff advertised in spam. When the profits dry up, so will the spam. -- kainaw™ 20:56, 20 December 2007 (UTC)[reply]
Actually it's a lot easier to fight junk mail then it is to fight spam. Unlike with spam which is very international the vast majority of junk mail is fairly local at worst national but mostly even more localised. As such, laws restricting the delivery of junk mail can be much more effective. Furthermore, unlike with spam which is generally sent out anonymously by people who don't give a damn about their reputation many senders of junk mail to have a reputation they want to preserve and are not anonymous. As such a combination of legal means and public pressure can ensure that things such as 'no junk mail signs' are respected. As for addressed junk mail (which appears to be a major problem in the US) I would suspect asking to be unsubscribed from the list (as well as the necessary public and government pressure to ensure such requesteds are respected) can ensure the problem is greatly reduced so it is at worst a minor annoyance with the occasional 'junk mail' that slips through. Nil Einne (talk) 08:58, 21 December 2007 (UTC)[reply]
Actually, some private mailbox companies (e.g. the UPS store) will filter out bulk mail. You will probably pay more for the privledge though. Dragons flight (talk) 15:30, 20 December 2007 (UTC)[reply]
Luckily here in NZ there's a law or something that forbids circulars being put in your mailbox if you have a "no circulars" sign on your mail box. --antilivedT | C | G 05:25, 21 December 2007 (UTC)[reply]
Half of the stuff does not have a name or address on it and no postage of any kind so how do you tell if it was put in the box by the post office or by a private carrier? Isn't there a postal regulation that says anything without postage can not go in the box? 71.100.14.54 (talk) 03:36, 21 December 2007 (UTC)[reply]
I suspect not. However if you're only talking about unaddressed mail, you may want to lobby either your postal authority for your PO Box or your government to pass a regulation or law requiring a no junk mail sign to be respected. There is already be such a law in New York in the US although it won't come into effect until January 2008 [4]. In Dallas/Texas, these sites may help [5][6] and you may also want to follow the advice above. In New Zealand a combination of government and public pressure has meant that such signs are generally respected. [7][8]. Nil Einne (talk) 08:58, 21 December 2007 (UTC)[reply]
Some objects I can see through my telescope at what magnification?
Hi. What celestal objects (eg. planets, deep-sky objects, comets, etc) can I see with a 114 mm reflector, and when? I'm not asking you to list all of them, just some good objects to look at during different times of year. The thing it, I can calculate limiting magnitude, and I can calculate surface brightness, but I can't calculate if the two correspond in a way so I can see the object well, or what bagnification I should use. Ok, I will list the magnifications and approximate FOVs here, FOVs in arcmins:
36x, 100
60x, 50
72x, 50
90x, 30
120x, 25
144x, 25
180x, 15
240x, 12
360x, 7
So, which objects should I look for, and at which magnifications? Yes, i know that aperture is more important, but I already set the aperture by buying the telescope, although it can be closed down to 57 mm if required, and I doubt that would be nessecary. Thanks. ~AH1(TCU) 01:00, 20 December 2007 (UTC)[reply]
Hi. Is it important to avoid scratching or touching the lenses/eyepieces' coating? Is the coating so important that the eyepiece/lens would be effectively useless/very poor quality without it? How does lens paper work, how does it prevent you from touching the lenses while using it to clean them, and about how much do they usually cost? Would washing or wiping lenses with a household tissue damage the coating? In an average eyepiece, approximately what percentage of its value belongs to the plastic components, the rubber components, the glass of the lens, the optical coating, and the metal components? Is the coating's job to allow more light to pass through, to supress false colour, to allow clearer images, etc? When an eyepiece says it has three-, four-, five-, etc element design, does that refer to the glass or the coatings? Are eyepieces perfectly symmetrical in terms of the shape of the glass parts, in all lines of potential symmetry, viewed from above, or do the optical element design cause it to be slightly not symmetrical? Oh, and as an aside, when my telescope is polar-alighned, on my telescope's RA slow-motion controls, when I rotate the knob clockwise, the RA number that it is pointed to goes down, and when I turn it counter-clockwise, the RA number goes up. Which way do I turn it to follow the Earth's rotation? Also, both on the left and right of the 90 mark for decilnation, the numbers go down from 90, go down to 0 on both sides, then go back up to 90 on the other side. I think one of the 90s is north pole, and the other one is south pole. I think i know which one it is, but when I point to an object with a specific declination, in which direction should I turn so that the declination lines up, or should I experiment with both and use the one that makes sense? Thanks. ~AH1(TCU) 01:19, 20 December 2007 (UTC)[reply]
Are the Twelve Days of Christmas related to the twelve day difference between the Solar and Lunar Calendars (http://en.wikipedia.org/wiki/Lunar_calendar)? I heard this this holiday season and I have been unable to verify it.208.46.64.238 (talk) 05:59, 20 December 2007 (UTC)Scott[reply]
(edit conflict) I was about to post those same links. But as I understand it, the origin of setting Christmas and Epiphany to those specific days is not well understood. Clearly the date of Christmas is related to the winter solstice, but why was Epiphany set to be January 6? And why is Christmas not quite on the solstice? I don't see why the two holidays couldn't be related to a solar/lunar calendar difference. I have no idea why those dates were chosen, but the fact that the date of Easter is lunar based to this day makes the solar/lunar theory about Christmastide seem at least plausible to me. My suspicion is that no one knows for sure why those dates were chosen, so no one knows why there are 12 days. But what do I know? Pfly (talk) 06:50, 20 December 2007 (UTC)[reply]
"The solar/lunar calendar difference" refers to the difference in year lengths, not to the date offset for any particular year. That is, if a lunar-based event was on January 6 one time, it might be on December 25 the next time, but then the time after that it would be on December 13 (or maybe about January 11, depending on leap months in the lunar calendar). Which means it doesn't seem like a likely basis for anything. --Anonymous, 07:10 UTC, December 20/07.
Christmas falls on December 25th because the early Christians adopted that date from another religion - something that Christianity has done a lot of throughout history, and especially in the Early Christian period. The "other religion" that I mentioned was Mithraism, which was an enormously popular and influential religion during the late Roman Empire. Indeed, when Constantine chose to make Christianity the official state religion, there was a debate as to whether to select Christianity or Mithraism, since many more members of the Roman military practiced Mithraism, and Christianity was for the most part viewed as a Slave Cult by the Roman elite at the time. However, be that as it may, the reason that December 25th became the date that Jesus was supposed to have been born on is due to the fact that that was the date that Mithras was supposed to have been born on, too.
When I say that Christmas came from Mithraism, I should insert a comment that it was actually indirectly from Mithraism. Christmas being celebrated on December 25th really came directly from the Roman festival known as Sol Invictus. However, this celebration was created by the Romans to more or less bring together a bunch of different Winter Solstice celebrations from various religious traditions throughout the empire, including Mithraism. The reason it was celebrated on December 25th (as opposed to any other date near the Solstice) was due to the influence of Mithraism, though - it was Mithras' birthday. So when Christianity adopted Sol Invictus to be the date that Jesus' birth was celebrated, it was actually going back to the birth of Mithras in a roundabout way.
Now, as to why Mithraism celebrated December 25th as the date that Mithras was born - that's another story. If I have time I'll write more about that later. -- Saukkomies 10:13, 20 December 2007 (UTC)[reply]
acidic?
The pH scale. Red is acid, Blue is alkaline
I know that Lemons, and Oranges, for example are acidic and so affect my arthritis pain, but I like apricots, are they acidic please--88.110.51.242 (talk) 09:40, 20 December 2007 (UTC)[reply]
Apricots have a pH of about 4, so yes, they are acidic. However, this is much less acidic than a lemon (pH 2). Since pH is measured on a log scale, that would make apricots about one percent as acidic as a lemon. Of course, I can't say what that means for your pain, you'll have to try yourself or ask a doctor. Someguy1221 (talk) 09:57, 20 December 2007 (UTC)[reply]
Thanks Someguy, you were quickly on the ball this morning! Can I now ask you the same question about bananas and dates. Thanks in anticipation.--88.110.51.242 (talk) 11:29, 20 December 2007 (UTC)[reply]
This website lists pH values for various foods. May I ask you how the pH of your food is supposed to affect your arthritis pain? Icek (talk) 14:21, 20 December 2007 (UTC)[reply]
I should explain - that the acid ('gastric fluid') that naturally forms in your stomach to aid digestion has a pH of between 1 and 2 (see the scale to the right here). This is FAR more acidic than oranges and lemons and FAR, FAR more acidic than Apricots. Since you don't digest any of the food between chewing it and getting it into your stomach, there is no possible way that these acidic foods can be affecting your arthritis because of their acidity. It's possible that some other substance in lemons and oranges are the cause of your problems - but for sure it's not the acidity. If you seriously worry about this - see a doctor because we aren't allowed to give medical advice. SteveBaker (talk) 15:16, 20 December 2007 (UTC)[reply]
Addresses
What, please, are the component elements of the addresses on these pages, and why does my address change occasionally?--88.110.51.242 (talk) 09:49, 20 December 2007 (UTC)[reply]
The addresses are called IPs, and it will change from time to time if yours is dynamic. Someguy1221 (talk) 09:56, 20 December 2007 (UTC)[reply]
If you wish to stop the IP appearing next to your name you could always register an account and then get a name after all your comments!TheGreatZorko (talk) 11:53, 20 December 2007 (UTC)[reply]
Every computer on the Internet has a unique number assigned to it in the form of four bytes - those are the four numbers that you see with dots between them. If you don't have a user account, Wikipedia uses the four numbers that describe your computer to identify you instead. If your computer is connected through a low-cost Internet Service provider then it's likely that your IP numbers will change from one time you turn on the computer to another - or possibly from one day to the next. If you have a "static IP" (as I do) then the numbers stay the same. The first number out of the four (88 in your case) can be looked up on this handy-dandy IP chart: xkcd.com (there are better ones - but this one is fun!). 88 says that your internet provider is probably in Europe somewhere. The remaining numbers tell you less and less information. Probably, the second number never changes (or perhaps changes between a couple of different numbers) which identifies the Internet Service provider you use - or perhaps the company you work for or the school you attend. The remaining two numbers are probably allocated more or less at random amongst the computers connected to that provider. This is a slight over-simplification - some companies have the first number all to themselves (IBM, for example) and all three of the other numbers are available for them to allocate to their users (this is called a "Class A" IP address) - other companies are given the first and second numbers and they have the third and fourth to allocate to users (Class B) - really small organisations have the first three number handed to them and can only allocate the fourth number to their users (Class C). SteveBaker (talk) 13:02, 20 December 2007 (UTC)[reply]
You are right, but how do you know?--88.110.51.242 (talk) 13:21, 20 December 2007 (UTC)[reply]
If you click on the numbers after your posts, you are taken to a page which lists all the contributions made to Wikipedia from that IP address. Near the bottom of the page are a series of link in blue - click on them (I clicked on WHOIS) and you will see information about the IP address. DuncanHill (talk) 13:27, 20 December 2007 (UTC)[reply]
It's interesting to note that when you use Wikipedia 'anonymously', your IP address tells people far more about you than if you had created a user account! I won't use your IP as an example - so let's see what you could find out about me if I were to edit "anonymously": Well you'd find out that the IP address of one of my computers at home is 66.137.234.217 - and from that, you can go to a 'WHOIS' server (just Google 'WHOIS' and you'll find a bunch of them) - and you'll discover that I use AT&T internet services via SBC and that my real name is Stephen Baker - not User:SteveBaker (only my Mom calls me "Stephen" and friends are allowed to drop the more formal "User:" part!). With some WHOIS services you can also find out that this address is located in Dallas, Texas (well, it's actually about 15 miles outside of Dallas - but close enough!). So by using my IP address, you already found something that you couldn't have known from my Wikipedia username alone. You could also type in http://66.137.234.217/ into your browser and see if that person has a web server running (which I do - but it's cunningly set up not to respond with an actual web page unless you know the URL)...and because Apache tells you who the 'webmaster' for the site is, you've got my email address...(Darn! I need to fix that!). You could also use the IP address to launch all kinds of nasty attacks on their computer (I'm not concerned because I have a fairly impregnable Linux box protecting the inner network from attack - not a tissue-paper thin Windows 'firewall' package that most people will be running!). So, for pities sake - get a proper Wikipedia account! SteveBaker (talk) 14:14, 20 December 2007 (UTC)[reply]
Also, you just happen to be editing from a range of addresses associated with a notorious ex-regular here. Some of us are very, very skeptical of anything posted from an 88.110.*.* address, and are apt to delete it if it looks even the slightest bit suspicious. —Steve Summit (talk) 15:04, 20 December 2007 (UTC)[reply]
Oh, and also, this is a question better suited for the computing reference desk. Hope this helps. Thanks. ~AH1(TCU) 23:38, 22 December 2007 (UTC)[reply]
Physics
When I was examining a little closed bottle containing Mercury, my golden jewelleries such as chain and ring turned white.Why this happened?<><> —Preceding unsigned comment added by 117.99.7.13 (talk) 10:42, 20 December 2007 (UTC)[reply]
On the face of it, this is impossible - so clearly we're missing some information. Please explain in detail what you were doing and where. Was this in a dark place? Was it in daylight? What other things were in the immediate vicinity? Is your jewelery still white? If not, how long did they take to turn back? How quickly did this phenomenon occur? SteveBaker (talk) 12:48, 20 December 2007 (UTC)[reply]
Two critical kind of information are how "real gold" the jewelry is and details about the mercury bottle and its closure. Gold metal does react with mercury. DMacks (talk) 18:06, 20 December 2007 (UTC)[reply]
If it's a closed bottle of mercury - and since neither mercury vapour nor liquid is likely to escape (because it's dangerous stuff and people don't store it in things it can escape from) - we can reasonably assume that the mercury had absolutely nothing to do with it. But, mercury is used in places like chemistry labs and industrial settings where there are other chemicals around. Perhaps something else way the cause - but there are very few chemicals indeed that will react with gold. We need answers to our questions - there just isn't enough information here to say anything other than "At first sight - this is completely impossible". SteveBaker (talk) 20:30, 20 December 2007 (UTC)[reply]
Did you dip your gold jewelery in the mercury? This is bad for gold, as it forms a silver coloured amalgam on the surface. Solid gold sinks in mercury, but it is not worth trying this experiment because of the damage to the surface. The mercury on the surface cannot be removed easily. Dangerous ways to do it are to heat to 300°C to evaporate it, this is not recommended. Graeme Bartlett (talk) 20:39, 20 December 2007 (UTC)[reply]
Science/Sound Waves
How exactly do sound waves travel in air(scientifically)?
Consider a hifi speaker. It has a cone inside that moves backwards and forwards with the music. When it pushes forwards, it compresses the air that was right in front of it - when it moves backwards, it sucks at the air. When it pushes forwards, the pressure of the air just in front of the speaker cone increases a bit. But the air a bit further away from the speaker is still at normal room pressure - so some of the air just in front of the speaker moves outwards and away from it - slightly increasing the pressure of the air a bit further away. This 'wave' of higher pressure moves outwards from the speaker like ripples on a pond when you toss a rock into it. When the speaker cone moves backwards, it reduces the air pressure just in front of it - and the air a bit further out in the room is at higher pressure - so the air moves backwards towards the speaker - and now the air a bit further away is lower pressure than the rest of the room. So now a wave of lower pressure air spreads outwards. As the speaker cone moves in and out (many hundreds or even thousands of times per second), it creates alternating high and low pressure waves that ripple outwards into the room. Individual air molecules move back and forth but not by very much as the wave passes by. When one of these air pressure waves hits your ear, the eardrum is either pushed in or sucked out as the air pressure varies - this causes minute hairs inside your inner ear to wave back and forth. The longer hairs respond to lower speed changes the shorter hairs to faster change - each is connected to nerves that detect it's motion and send this as "sound" to our brains.
Scientifically - well, the pressure waves move at the speed at which air can respond to rapid pressure changes - and that is what we call "the speed of sound" which is around 300m/s (700mph) at sea level depending on the ambient air pressure. The rate at which speaker cones (and therefore sound waves) move in and out is the frequency of the sound - which (for humans) ranges from about 50 times per second up to perhaps 20,000 times per second (the highest frequency you can hear depends on your age - mostly). Sound waves work at much lower and much, much higher frequencies too - but our ears can't respond fast enough (or slow enough) to pick them up. Since frequency and speed are related, we can calculate that the individual waves of higher and lower pressure are anywhere from six meters long for the lowest frequencies we can hear down to a centimeter or so for the highest frequencies. So imagine these small pressure changes racing outwards from your speakers (or anything else that makes a noise) at 700mph - in bands like waves on a pond, but anywhere from big waves - 20 feet long to tiny ones under an inch. Ripples in a pond spread out in a circle because they are fixed in two dimensions to the surface of the lake. Sound waves can go off in all directions - so they spread outwards like rapidly growing spheres. Since the area of a sphere grows by a factor of 4 every time you double it's radius, the power of the air pressure changes from your speakers spreads out over 4 times the area every time you double the distance from the speaker. So sounds get rapidly quieter as you move away from the sound source. This is called the "inverse square law" - the energy in the sound decreases by a factor of one divided by the square of the distance from the source.
Like all waves, sound can be refracted, reflected, focussed and sound waves can interfere with each other. Just as light can be spread out as it moves through a narrow slit, so sound waves are spread as they move through a narrow opening. Compared to the sizes of sound waves (6 meters down to a few centimeters), relatively human-size 'slits' can cause sound to do this. That's why sound can pass through an open doorway - and then spread outwards from there into the room beyond. When sound waves are reflected, we call that 'reverberation' or perhaps an 'echo'.
At what temperature does petrol freeze? —Preceding unsigned comment added by 193.62.43.210 (talk) 14:47, 20 December 2007 (UTC)[reply]
Jet fuel is listed as freezing at −47 °C (−52 °F). Someone responded on this site that gasoline freezes at −84 °C (−120 °F), which could be possible because jet fuel is quite different than gasoline. -- MacAddct 1984(talk • contribs) 14:55, 20 December 2007 (UTC)[reply]
This is a lot harder to answer than you might think! Petrol is a complicated mixture of a lot of different compounds - all with different freezing points. There are also a bunch of different additives that change those freezing points and which differ from place to place and season to season. I've seen figures ranging from -80F (-62C) to -300F (-180C) in different places on the net. Note that even the highest estimate (-80F) is colder than the coldest temperature every recorded in Europe or the USA...so the accidental freezing of petrol on a cold winter morning is not a great concern! I believe that it's fairly common for Diesel fuel to freeze in very extreme conditions though and some diesel powered arctic vehicles have tank heaters for this reason. SteveBaker (talk) 15:04, 20 December 2007 (UTC)[reply]
Diesel fuel doesn't really freeze but rather "gels" as the various heavier fractions (waxes and the like) freeze out. We don't appear to have a good description of that in the encyclopedia yet. Anti-gelling agents are available that lower the "gel point" of a given fuel; I suppose they're solvents of some sort or another.
Many of the anti-gel compounds are alcohol based, but their use is problematic (in that they often don't work). A larger issue for diesel powered engines (particularly large commercial vehicles) is ice forming in the fuel lines, and alcohol works quite well for that. The best solution (for the engine, not so much for the rest of us) is to periodically idle the engine overnight to keep the fuel moving. As long as it is moving it won't gel and no ice will form. 161.222.160.8 (talk) 00:44, 21 December 2007 (UTC)[reply]
Allergens
A few questions about allergens:
a) There are many peptide hormones in the blood plasma - so I guess there is a common region in these peptides which is recognized as "self" by the immune system. How is this region called (the large major histocompatibility complex is only on cell surfaces)?
b) If the allergen is in the food, how does the protein come into the blood stream? How much of the protein is digested and how much is able to cross the lining of the intestines?
c) What is the minimal plasma concentration of an allergen needed to cause a notable allergic reaction?
Thanks in advance for the answers. Icek (talk) 15:17, 20 December 2007 (UTC)[reply]
Why do you think there is a common region in peptide hormones? One way to get large molecules across epithelial cell layers is transcytosis. --JWSchmidt (talk) 16:09, 20 December 2007 (UTC)[reply]
(a) To act as an antigen or allergen, a substance has to either be internalized (phagocytosis, pinocytosis) and presented to T-cells by antigen presenting cells, or, if it is a small molecule, to interact chemically with a larger molecule and act as a hapten. A relatively small molecule like a peptide simply doesn't trigger an immune response by itself. And yes, the molecules of the MCH reside in the cell membrane.
(b) and (c) As far as I know, proteins are generally absorbed as single amino acids or very short peptides. Allergic reactions generally happen on mucosal surfaces or on the skin. When an allergic reaction leads to anaphylactic shock, it is because cells in the mucosa release chemical mediators which have a systemic effect. --NorwegianBluetalk 16:18, 20 December 2007 (UTC)[reply]
For A: There is no common region of peptide hormones (or other peptides) that are recognized as 'self'; rather, the 'self' peptides are not recognized by the immune system as 'non-self'. The determination of self/non-self is not made by the allergen but is actually made by the immune system. That's why some peptides which are clearly 'non-self' are not always recognized by the immune system, they may not be good antigens.
For B: There are various methods for proteins to make it into the blood as larger fragments, although they are usually absorbed as very small peptides.
For C: There is no minimal plasma concentration of an allergen needed to cause an allergic reaction. The level of antigen needed to cause a notable reaction is based on the strength/method of interaction between the immune system and the allergen. This naturally means that necessary plasma level will vary between individuals for any particular allergen and even vary in a single person over time. Often, allergic reactions in a person worsen with subsequent exposure to a previously encountered allergen due to the immmune system being primed. —Preceding unsigned comment added by 142.36.194.253 (talk) 17:27, 20 December 2007 (UTC)[reply]
Thanks for the answers so far, but unfortunately they provoke a few more questions. If the allergen acts on immune cells on the mucous membranes, what's the minimal concentration there which causes a notable allergic reaction? And what's the minimal amount (per kg body mass) to cause an anaphylactic shock?
Are there measurable quantities of food proteins or large fragments thereof in the blood after a meal (in "normal" people and in allergic people)?
To 142.36.194.253: Do you seriously want to tell me that 1 protein molecule per liter is able to cause an allergic reaction? Icek (talk) 07:08, 21 December 2007 (UTC)[reply]
A small correction to my previous reply: if a person already is immunized, and has IgE attached to Mast cells in the mucous membranes, anaphylaxis is triggered merely by the interaction between the allergen and IgE molecules attached to Fc receptors in the cell membranes of the mast cells. But for immunization to occur in the first place, you need the T-cells as stated previously. When mast cells degranulate, the release of chemical mediators (histamine, cytokines) leads to allergic symptoms and possibly anaphylaxis. The degranulation of mast cells is very easily triggered, as was evidenced by the controversial Nature paper by Jacques Benveniste. I'm not aware of any studies addressing minimal concentrations, and I doubt that focusing on plasma concentrations is relevant, since the action occurs in the mucosa. --NorwegianBluetalk 16:20, 21 December 2007 (UTC)[reply]
Sorry, I wasn't trying to say that a single protein molecule would result in an allergic reaction. What I was trying to say is that there is no defined minimum protein level. It is not possible to say that 10000 (substitute any number you like for 10000) molecules of protein per liter will cause an allergic reaction. This number would vary by person and the nature of the allergen. You might be able to measure something like "for person X, Y amount of protein Z per liter will cause an anaphylactic reaction" but generalizing it for the whole population/different proteins is not possible.
Do you have any information about the minimal concentration over all humans? I. e. the concentration needed for people who get a reaction at the least concentration compared to other people? Icek (talk) 10:25, 25 December 2007 (UTC)[reply]
Our Solar System
I have 2 questions, are there possibly more planets in our Solar System that we haven't discovered? And also, does our solar system have a name?
Ts41596 (talk) 15:19, 20 December 2007 (UTC)[reply]
It is extremely unlikely that there are any other planets in our solar system. If there was, we would have seen something by now. However, there are theorists that claim there could be one directly behind the sun all the time or one that buzzes by once every 1,000 years and then heads off into deep space. Chances of those are basically 0%. As for the name of our "planetary system" - it is called the "Solar System." -- kainaw™ 15:25, 20 December 2007 (UTC)[reply]
The naming issue is similar to "the Moon". A planet's orbit behind the sun at L3 wouldn't be stable - it would probably have collided with Earth long ago. A planet with an orbital period of 1000 years would have a semi-major axis of only 100 AUs which means that the distance is maximally 200 AUs at any point of its orbt - a large body at such a close distance would probably have been spotted already. Compare with the planetoid 90377 Sedna (its diameter is only about 1500 km) which has an orbital period of about 12000 years and a maximal distance from the sun of 976 AU. A planet in a Sedna-like (or even larger) orbit is a bit more likely than the other possibilities. Icek (talk) 15:36, 20 December 2007 (UTC)[reply]
It may be worth clarifying that (thanks to the new IAU definitions) there are almost certainly more dwarf planets to be discovered in the solar system, as those can be small and distant enough to elude casual detection. — Lomn 16:14, 20 December 2007 (UTC)[reply]
If the planet is small enough and far enough away - yeah - there could definitely be more. 90377 Sedna was only discovered 4 years ago - and it's much bigger than Pluto (which was once a planet) - also Eris (dwarf planet), (136472) 2005 FY9, (136472) 2005 FY9, all of them found just a few years ago and comparable in size to Pluto. Given that we are still finding bodies that are large enough to qualify as planets (if that were the only criteria) - then it's very likely that we'll find many more - and that one or more of them will qualify under the new, more complex rules for deciding what counts as a planet. SteveBaker (talk) 16:49, 20 December 2007 (UTC)[reply]
With the current rules (specifically, with the "cleared the neighborhood" clause), I think it unlikely that anything found will be a planet rather than a dwarf planet. The effects of something that gravitationally significant should already be observable. Of course, there is that ever-pesky problem of "should" not always being equivalent to "is".... — Lomn 17:19, 20 December 2007 (UTC)[reply]
Perhaps gravitational effects have already been observed - see Kuiper cliff. Gandalf61 (talk) 17:28, 20 December 2007 (UTC)[reply]
I remember discussing this with someone, and I believe the current observation limits for "dark" planets (albedo ~0.04, like dark KBOs) is something like "No Mars or bigger within 100 AU". Given the Oort Cloud extends to ~10 000 AU, and many of its bodies never get anywhere near the Sun, Pluto - Earth sized bodies "could" exist in the Oort Cloud - although I'm not sure it's particularly likely, its within the realm of the "not crazy". WilyD 17:35, 20 December 2007 (UTC)[reply]
Just a note on Pluto having been "once" a planet. It is what it always was, whatever that was. IAU has no authority to define what "planet" means (nor does anyone else, of course). Their decision will have effect only if the rest of us let it. I say resist, and down with international bodies that try to standardize such things. (Luckily, there's none in mathematics.) --Trovatore (talk) 21:27, 20 December 2007 (UTC)[reply]
What would your attitude be if everyone went back to including Ceres in the list of planets in the solar system, Trovatore? Or 2 Pallas, 3 Juno and 4 Vesta (all once called "planets")? Or the hundreds of thousands of other asteroids since discovered? Surely it's appropriate for there to be a taxonomic scheme that distinguishes between objects of major gravitational influence (and commensurate scientific interest) and those of minor influence and interest; otherwise every speck of dust could legitimately be called a planet and there'd be chaos. Everywhere else in science, a fundamental discipline is to "define your terms". If the IAU isn't an appropriate forum in which such a scheme can be negotiated and agreed on, and such terms can be defined, what is? -- JackofOz (talk) 22:07, 20 December 2007 (UTC)[reply]
There is no such appropriate forum. Terminological usage evolves naturally, and should be permitted to do so. Legislating it is a bad idea, almost always. --Trovatore (talk) 22:11, 20 December 2007 (UTC)[reply]
What do you think a planet is then? Why do you think it was a bad idea to clearly define planethood scientifically rather than working on vague laymen terms. By the way does having the status of dwarf planet make Pluto any different from what it was earlier. Does it belittle it in any way? I don't think so. In fact, it is now known as second largest dwarf planet in our solar system, which should make you happy on behalf of Pluto. Why do you feel bad? Planet, dwarf planet, asteroids etc. are just useful definitions for astronomers which they had to agree upon eventually observing that there are so many bodies revolving around sun, so they had to set up clear definitions of everything. Also, this was not a decision of single person, the whole body of world's scientists was involved in it. Though there were debates, but they were all for new definitions of planethood and eventually everyone agreed. Pluto is still happily revolving around the sun. DSachan (talk) 22:28, 20 December 2007 (UTC)[reply]
So I admit I would have been happier if they had gone with the other proposal, that would have admitted fifty or so planets. But my main objection is to the fact that they promulgated a definition at all, not the particular one they picked. This is just improper. Scientific definitions are not chosen by votes -- they evolve, depending on who writes what papers and who picks up the terminology therein used. That's the way it should be. I completely disagree that there was any need whatsoever to "officialize" a choice of definitions. --Trovatore (talk) 22:38, 20 December 2007 (UTC)[reply]
It's not exactly unknown for old traditional ways of doing things in science to be revolutionised in response to emerging circumstances. Some of the members involved at Prague agreed with your stance, Trovatore. But the majority of members (a) thought there was a need for a definition, (b) thought the IAU had the authority to come up with one, (c) thought they should use their authority, and (d) chose one. Many people will say that the IAU has only 63 member nations and therefore doesn't represent the entire planet, and in particular it doesn't represent them personally. That's a fair call. But it is internationally considered to be the body that has status in this area. Still, you're right - legislating for words is not ideal; and people are free to give Pluto etc whatever names they like; they won't be fined or put in prison if they keep on calling it a planet. They might just be out of step with the majority of their peers who have chosen to let go, move on and adopt the new definition. -- JackofOz (talk) 23:03, 20 December 2007 (UTC)[reply]
Are you opposed to the idea that they changed the definition of planethood or the fact that Pluto is now no more a planet? At one place you write, scientific definition should evolve and in the very beginning you write it would have made you happier had they termed all bodies as planet and eventually including Pluto. If you stick to your opinion that scientific definitions should evolve, then their other planethood definition also should not make you happy. And then what makes you think asteroids also should not be called planets? By the way, the word planet was introduced by ancient astronomers, so you naturally could not have expected a solid scientific definition for it right from the beginning, and we saw that its definition was actually getting entangled with those of new solar bodies as they were being discovered. Either you had kept calling everything planet that revolved around the sun right from the beginning but that would have been injustice to specks of dust which also tirelessly revolve around the sun or you had defined its definitions clearly. The problem is that the word planet is ancient (unlike modern scientific neologisms, which are already well defined) and if you expect any single person to come with few definitions of it as a process of evolution, why would all other scientists agree to accept it? Will it not be another case of voting if eventually votes are cast. If this is not done, there will never be consensus on definitions of old words which are incorporated in science. It is just like the definition of flowers or animals. These words also originated in ancient times, but later they were incorporated in scientific studies. Their definitions are still vague. DSachan (talk) 23:18, 20 December 2007 (UTC)[reply]
The definitions of flowers and animals are vague, and that's just fine; they ought to stay that way, until and unless more precise definitions evolve by the natural process of one researcher using them and other researchers adopting them. In practice, of course, no biologist is going to propose a precise definition of "dog" and try to make it into a technical term of art. Rather, they propose new names and give them definitions.
The definition of "planet" was vague, and should have stayed that way. New terminology could have been created for more precise meanings -- but again that should go through the natural process, not the vote of some silly international body. --Trovatore (talk) 23:51, 20 December 2007 (UTC)[reply]
Prior to 2006, the scientific definition of planet wasn't even vague, it was non-existent. The general populace uses words to mean whatever the heck they want them to mean, which is how language constantly changes and evolves. But we're not talking about the general meaning/meanings of "planet", we're talking about the scientific/astronomical term "planet", which had never been formally defined before. Why should vagueness reign supreme over precision where it's possible to be precise? That doesn't sound like a good approach at all, particularly in scientific matters. -- JackofOz (talk) 00:02, 21 December 2007 (UTC)[reply]
If they needed a more precise notion they should have given the notion a different name. Unless of course it was in a context where it was clearly a term of art -- when I talk about a huge cardinal I don't simply mean a cardinal that's really really big, even though of course it is, but hopefully it's obvious in context that it's a term of art so it's not a problem. But even with a different name it shouldn't be done by getting people together and voting (or by any other formal procedure). --Trovatore (talk) 01:54, 21 December 2007 (UTC)[reply]
Believe it or not, but naming disputes in astronomy, biology, and chemistry have been routinely resolved by voting (or similar consensus finding exercises) among groups of specialists for a long time. It is useful in general for scientists to have an agreed upon nomenclature, and in this case astronomers felt a need to agree on a meaning for "planet". You can ignore their definition if you like, but the academic journals respect the judgment of the International Astronomical Union and require that papers for publication follow their nomenclature. Hence, that "silly international body" is binding on academic publications. Overall, this agreed upon precision facilitates communication between specialists. You can choose to ignore it if you wish, but after a while you are just going to sound ignorant. Dragons flight (talk) 02:10, 21 December 2007 (UTC)[reply]
Well, thank God there's no such thing for mathematics. The astronomers should dump it too. --Trovatore (talk) 02:14, 21 December 2007 (UTC)[reply]
Probably because there is no need since issues that require it don't arise (most definitions of mathematics are. BTW, I don't get why you're that opposed to formalisation. In reality a lot of what you now consider 'natural' occured in similar ways (for example, many changes occured because one or two people made a decision and everyone followed not necessarily because everyone agreed or because the decision made the most sense but because this people were then the pre-eminent scientists of that area and no one even considered going against them). Indeed the metric system is another thing that was designed in a resonably formal way and continues to be and I for one and glad of it compared to the extremely ugly 'natural' systems still in use today (although again ironically even these systems that 'evolved' naturally had a lot of formalisation and are defined based on the metric system). Scientists need to have a way of communicating clearly. And in reality, the officialisation that you derise is often a lot fairer and more robust then the alternatives which often mean that a few select people (such as editors) get to have an undue influence on terminology despite the fact that they may not be the ones doing the work and often means scientists from countries outside the western hemisphere have virtually no say. BTW, have you ever used the term huge cardinal to have some other meaning in a paper? Do you think your paper is going to be accepted? In reality these terms probably didn't just 'evolve'. Instead their definition made sense to a number of people and this definition was probably 'enforced' by journals and the like. In reality I strongly suspect that even very early on when these terms which began to take on a meaning you would not have been able to use the terms in any other way without having your paper rejected outright. A lot of stuff occurs in this way and there's absolutely nothing wrong with it even if it isn't 'natural' according to you. (In biology for example, the first person to discover a species and write about it is usually the one that gets to name it. Sometimes people may not like the names for various reasons but thankfully most people accept this system even if is 'unnatural' and too formalised for your liking. Nil Einne (talk) 09:02, 21 December 2007 (UTC)[reply]
(unindent)
Scientific use of words needs to be precise. But science's use of words doesn't have to agree with those of general society. The word "accellerate", for example, mean "go faster" to non-scientists - but to a physicist, it can also mean "go slower" or even "turn a corner". Science has a precise meaning of accelleration which is something like "rate of change of velocity as a function of time". This kind of thing happens all the time. Lots of people don't think of insects, birds and fish as "animals". (See for example "All about Animals and Insects", or http://www.birdsandanimals.com/ who aparently train "Birds and Animals" - or there is the PetLovers.com thread where someone asks whether fish are animals or not). Scientists have a very precise meaning for the word 'animal' (They are life-forms from the kingdom EukaryotaAnimalia) - but the public don't. Did we have a huge amount of anger when taxonomists decided that Mushrooms aren't plants anymore? I don't think many people outside of the scientific world even realise that it happened! Did vegans have to decide whether they should stop eating mushrooms because they aren't plants anymore?
The same thing happened with the word "planet". The original meaning of the term was "Wanderer" - ie "stars" that don't stay put like the others. In popular usage, the word had a rather vague definition. We had said that Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto were obviously planets and kinda left it at that. But astronomers are now finding things that are smaller than Pluto, yet which orbit the Sun and are much larger than any of the asteroids we ever saw before. What do we call those things? What if one (like Sedna) turns out to be bigger than Pluto - does that make it a planet? What about if one is 10% smaller? 20% smaller? Just how small does it have to be? What about the problem of our own moon ("Luna")? Our moon is a LOT bigger than Pluto - if Pluto is a planet, then why isn't Luna a planet too? There is a pretty strong case for saying that if Pluto is a planet then the Earth/Luna system is a binary planet. That would mean taking away the name "Moon" from our moon...but if you think demoting Pluto was unpopular...telling people that "The Moon is not a moon anymore" would have caused rioting on the streets!
This was never a problem in the past because everything was very clear-cut - there were these nine things that had always been called "planets" and that was that. What about an Earth-sized object that's just drifting through space - not orbiting anything at all? Is that a planet or is it a giant meteor? What about a star that's used up all of it's energy and is now drifting through space as a brown dwarf - is that now a "planet" or is it too a "meteor" or is it still a "star"? Does is make a difference if the brown dwarf is orbiting another star? Then we have this huge number of 'exasolar' planets - orbiting other stars. Some of these are MUCH more massive than Jupiter - and it's possible that one day we'll find one 50 times as big that will be capable of fusion reactions at it's core that would make it be a kinda borderline star.
So we have this huge number of weird things out there that need names. Scientists need to be able to say that such-and-such is a "planet" and from that statement, know a large number of things about the object. There were plenty of ways the term could have been nailed down (some of which I'd have preferred) - but in the end, they either had to define "planet" formally or invent entirely new words for large things orbiting around stars and to use that word instead of "planet". Personally, I'd have picked a definition with a minimum mass limit that would include Pluto and a rule that it has to orbit a star and for situations like Earth/Luna or Pluto/Charon where both objects might be classified as planets that their barycenter must lie outside of both bodies in order to count both as planets. That definition would have left Pluto as a planet and admitted Sedna and a few others to the list. What we have now is kinda ugly and a bit open to interpretation. We're still not sure whether some of the new 'Dwarf planets' are really proper planets or not - and it'll be a very long time indeed (if ever) before we know whether these extrasolar planets are really planets or not. (It's going to be embarrasing if something 3 times larger than Jupiter has to be called a "dwarf planet" because it hasn't yet cleared out it's neighbourhood of debris!).
The general public are still perfectly able to go on calling Pluto a planet if they want to - it's not like a law was passed or anything. The intent of the change is that astronomers and other scientists can describe all manner of weird objects with a little more precision in formal situations. The general public don't go around calling the Sun a "Star" either. Oh - and if you want, I won't insist that you call the brake pedal and steering wheel of you car "accellerators".
I disagree that there was any such need. Analogy: Some mathematicians consider zero a natural number; others do not. This difference in terminology does not correspond to any mathematical difference of opinion whatsoever -- it's purely a difference in use of language. If some international body, say the International Mathematical Union (which actually I've never heard of anywhere but Wikipedia), were to pick one or the other and claim that this is now the official definition, we'd have their heads on a platter! Even if they picked the correct definition, which of course is that zero is a natural number.
Does it ever matter which definition you pick? Sure; if you're thinking of one definition but applying a theorem that assumes the other, you could get something wrong. But in that case it's almost always obvious from context, or from thinking about it for five seconds, which definition is being used. If it's not, then it's the responsibility of the author to make it clear.
I see no reason that couldn't work for the term "planet" as well. And I note in particular that the two proposed criteria, the "clearing the neighborhood" criterion and the "sufficent gravity to pull itself into a sphere" one, did not respond to any study of bodies meeting those criteria in ways that differed from others, but were simply an artificial attempt to find some demarcation, so that they could promulgate a definition. But no definition was in fact needed. --Trovatore (talk) 18:13, 21 December 2007 (UTC)[reply]
If you want to get technical about it, the defintion of "planet" has evolved and been accepted by consensus just like any other definition. Would you have been so irate if some notable scientist had started using a particular definition of "planet" in his papers, and his peers said "Hey, we like that definition, it works, and we really do need some definition so we all know we're talking about the same thing, so let's use that one"? That's pretty much how you have stated that definitions of terms do/should come about, so I think it's fair to assume you'd have no problem with that. So why are you so antagonistic when instead of one scientist it's a group of scientists, and they went about it in a bit more organized fashion? It's still the consensus of the scientific community that's accepting or rejecting the definition. If they'd said, for instance, that a planet is something with moons, thereby excluding Mercury and Venus and including a couple of asteroids, that definition would not have been accepted by astronomers, and ignored out of existence. It's really a matter of the IAU saying "here, this works" and the astronomers saying "yeah, that's pretty good" and using it. The method of acceptance (or rejection) is the same; the only difference is the definition coming from a scientific group rather than from an individual, or a journal editorial board, or whatever else. And for the love of Jupiter, why does it matter to you if astronomers decide to pick a group of their peers to work out common definitions for things so when they say "dwarf planet" in a paper, for instance, everyone knows what they're talking about without having to read their unique definition of what a "dwarf planet" is? It works for them, and those of us who are not astronomers really don't have any standing to say that is or isn't how it should be done.
What's the main cause of passengers' death in a plane crash?
Is it the fire? Or the impact? Or any other reasons? Some statistics would be great. Thanks for your answers. roscoe_x (talk) 17:57, 20 December 2007 (UTC)[reply]
It depends on the type of crash. David D.(Talk) 18:08, 20 December 2007 (UTC)[reply]
But I think it's safe to say that impact and fire are the two major causes in accidents that cause major loss of life, and probably ranked in that order. --Anonymous, 01:12 UTC, December 21, 2007.
Water breathing
How much water does the average person exhale per day? GeeJo(t)⁄(c) • 18:54, 20 December 2007 (UTC)[reply]
See breath. The average breath is 5% water vapor by volume. See respiratory minute volume. The average person exhales 5-8 liters per minute. There are 60 minutes in an hour and 24 hour in a day - so there are 1440 minutes in a day. The average person exhales 7200-11520 liters of air per day. 5% of that is 360-576 liters of water. That sounds high, right? So, look at lung volumes. The average exhale is 500mL. In respiratory rate, the average person exhales 12-20 times per minute. That is 6-10 liters per minute, which is pretty much what the initial average was. So, assuming the numbers are right, your answer is 360-576 liters. -- kainaw™ 21:08, 20 December 2007 (UTC)[reply]
Dude, you might throw in a little reality check here. Do you drink 100 gallons of water a day? Or consume 800 pounds of anything? Then how is that much water going out your lungs? Come on, this sort of checking is an essential part of real-world calculation. --Trovatore (talk) 21:12, 20 December 2007 (UTC)[reply]
That's 360-576 litres of water in gas form. i.e. 16 - 26 moles of water - i.e. 288 - 468 grams of water. Half a pount to a pound. WilyD 21:19, 20 December 2007 (UTC)[reply]
Yeah, I think that's the resolution. But GeeJo asked "how much water?"; the natural interpretation of that is "how much liquid water?". --Trovatore (talk) 21:22, 20 December 2007 (UTC)[reply]
Well, a quarter to half a litre then. Which I believe is a cup to a pint for Americans ... WilyD 21:24, 20 December 2007 (UTC)[reply]
I wouldn't want to be a short female couch-potato smoker who lives near the Dead Sea -- MacAddct 1984(talk • contribs) 02:07, 21 December 2007 (UTC)[reply]
The OP did not ask how much water we breathe IN each day, so the amount exhaled may be misleading. Unless the air we breathe in is totally dry, zero relative humidity, desert air, then we are breathing in a large portion of the water vapor we breathe out. Edison (talk) 05:31, 21 December 2007 (UTC)[reply]
Antisocial personality Disorder
What are the effects of Antisocial Personality Disorder? —Preceding unsigned comment added by 192.30.202.18 (talk) 19:24, 20 December 2007 (UTC)[reply]
It's not what most laypeople think it means. Often, people will say "I'm going to be antisocial tonight and just stay home alone". However, this is not how ASPD presents itself at all. A more correct phrase would be, "I'm going to be antisocial tonight and hit mailboxes with a baseball bat". Basically it's doing things that society (or the law) would normally deem inappropriate or malicious. -- MacAddct 1984(talk • contribs) 20:52, 20 December 2007 (UTC)[reply]
If it is the case, please be careful with self-diagnosis. You could have many or even all of these traits and not have Antisocial Personality Disorder. If you are unsure, or feel that any of these apply to you consult a professional who can test your personality using, for example, the Millon Clinical Multiaxial Inventory. (For instance, I have taken this test and although I display some symptoms of Antisocial Personality Disorder, I don't have any antisocial personality disorder). If not - keep on trucking. Lanfear's Bane | t 21:34, 20 December 2007 (UTC)[reply]
2 tubules 1 glomerulus
Is is possible, in a normal kidney, to have more than one tubule originating from a single glomerulus? Although it seems from most textbook cartoons that each single glomerulus connects to exactly one tubule, and vice versa, I have not actually seen any documentation which suggests that this is the only possible configuration. A pathologist and a nephrologist in my hospital have been unable to give me an absolute answer on this. I am most interested to know if this happens in the normal kidney in humans, but would also welcome any relevant information from pathologic or non-human cases. (Just to narrow it down, I am aware of collecting duct anatomy, and am only interested in the connection between the proximal tubular lumen and the glomerular urinary space.) Tuckerekcut (talk) 19:25, 20 December 2007 (UTC)[reply]
The opinion below was posted on my talk page. I am copying it here in case anyone is interested in the discussion. Tuckerekcut (talk) 19:22, 21 December 2007 (UTC)[reply]
Well,I was going to answer on ref. desk but now i've stuck here.This thing[1],i.e 2 tubules and 1 glomerulus,no way ,no human has been hiding this miracle inside of his mysterious body uptill today ,however i am answerless that what will be happening tomarrow.The thing you are talking about,is just kidney concerns ultimately leading to nephron,having only one glomerulus;the site where pressure filtration occurs then the proximal tubule,loop of henle, distal tubule and eventually the collecting duct. And if i haven't made out the right sense of your question.You can ask me on my talk page,probably my knowledge might be of some use to you.--Mike robert (talk) 18:18, 21 December 2007 (UTC)
To say that something is not possible, in biology, is a pretty strong statement. As a general rule, however, the nephron is a unit. I'm not aware of any anatomical studies that might answer your question, googling and a pubmed search gave no obvious hits. To pursue this further, I'd suggest reading up on the embryology of the kidney. I'd also suspect that the answer might be species-dependent. --NorwegianBluetalk 22:19, 21 December 2007 (UTC)[reply]
Running house lights from a 12 volt battery
Greetings Wikipedians from a long time lurker on the refdesk!
I have a quick question for those more enlightened in the dark arts of electricity than myself:
My father is, given the current rolling power cuts in our country, planning on converting more of our house lights to 12v downlights. He would like to know if he can run them off of a 12v battery in the event of power cuts? His plan is to have one or more batteries connected to some sort of charger connected to the mains, with the other side connected to one or more downlights, so that in the event of a power cut, the battery will continue to power the lights for at least a couple of hours. Each downlight is 50w, although smaller ones are available.
Is there some sort of formula for working out how many chargers / batteries are required? What would be the best way to approach this? Bear in mind that here we use 220v mains. —Preceding unsigned comment added by 196.209.27.242 (talk) 19:31, 20 December 2007 (UTC)[reply]
We're going to need some information first:
Are these lights AC or DC? If AC then they may not like being run from a battery (which is DC).
How many of them are there?
Are they wired in parallel or in series (as Xmas tree lights are). You can put twenty 12v bulbs in series and run them off 220v mains current - which saves on fancy transformers and stuff - some fittings may go that route - but you couldn't power them from a car battery anymore! You need them to be wired in parallel - which means that they'll have come with a mains transformer of some kind to step down the wall voltage to 12v - and possibly to convert AC to DC.
Also - it's important to note that car batteries can be damaged by repeatedly running them flat - that ought not to be a problem - but beware of it. You might want to consider 'Deep Cycle' batteries - of the kind you'd use to power a golf cart or something. However, car batteries are cheaper - and you may not need to run them often enough to care.
OK - so 1 Watt is one Amp at one Volt. So a 50W, 12V DC lamp requires 50/12 = 4.17 Amps per bulb. A car battery's total capacity varies depending on what you pay for them and how big they are - anywhere between 45 Amp-hours to 150 Amp-hours seems typical. That should run one bulb for between 10 hours to a day or so - or 24 bulbs for half an hour up to a couple of hours. However, there is a general rule for car batteries that you shouldn't attempt to discharge them in under 10 hours - which is probably what you want for a bad power cut. So a puny 45 A.hr battery is really only good for powering one lamp. A big truck battery could maybe run several for that long.
(after ec) I'll cut out the rest of my response to note that, given the AC/DC thing, it may be simpler to consider having a small generator that can be connected rather than using batteries. — Lomn 20:26, 20 December 2007 (UTC)[reply]
Companies like APC make uninterruptible power supplies for computers. A $200 system can generation something like 400 W for an hour. You might look into adapting one of their products, or something similar, for this application. Dragons flight (talk) 00:10, 21 December 2007 (UTC)[reply]
What struck me when I saw Steve's figure of 4+ amps for a single light is that this has implications for the wiring required. Here in North America, the household wiring in a regular lighting circuit is rated for 15 amps. At 12 volts that would only let you run three 50 W lamps! I don't know anything about wiring in South Africa but I imagine the wire gauge is similar. So if you're planning to convert a number of lights, you may have to run heavier wiring between them. Of course, you have quite possibly realized this already.
As for AC vs. DC, it depends on the type of light. Incandescents don't care; fluorescents require AC. If you've already converted at least one light, you know you have something that works. --Anonmyous, 01:25 UTC, December 21, 2007.
Keep in mind that it is 4.17 Amps at 12V. The 15 Amp, 120 V circuit could run 3 strings of 10 50 Watt lamps, so 30 of them, with some current capacity left over. -anonymous6494 04:51, 21 December 2007 (UTC)[reply]
Because of the safety hazards of working with electricity, I have to recommend that all installation be by a licensed electrician. Even 12 volt systems can start fires or harm those who work with them. Higher voltage systems can cause electrocution as well. For greater run-time, I recommend using compact fluorescent lights. You can buy inexpensive ones which provide the illumination of incandescent lights drawing three or more times the current, or which provide several time the battery life. For a quick and easy emergency lighting solution, I would consider buying a UPS (Uninterruptible Power Supply) intended for computers with a watt-hour rating sufficient to run your lighting for the required duration. You avoid having to switch on a generator after the outage (assuming you did not splurge and get a wired-in auto-start, auto-throwover model) and keep fresh fuel in it and load test it weekly, and you get instant on when the mains power fails. If you load a UPS well below its rated output wattage, it will operate much longer than the rated time. The battery drain of a UPS is very high in normal use, fully loaded, so if you load it to, say, half its nominal watt capacity, it will typically run more than twice the rated time. My suggestion avoids the need for batteries, chargers, manually switching on the battery lights, etc. You could get individually switched compact fluorescents which draw, say 15 watts but give the illumination between that of a 60 and a 75 watt incandescent bulb operating on 240 volts. A 400 watt, one hour UPS should power 10 15watt CFLs each of which would provide about the illumination of a 60 watt incandescent light, for well over an hour, and I would suspect well over 2 hours, but experimentation is your best guide. An 11 watt CFL should put out the illumination of a 50 watt incandescent. If you want to keep a charged 12 volt deep-cycle battery, you can also buy 12 volt CFLs designed for recreational vehicles or alternative power [9], and they also offer advantages for emergency lighting. (edited) Edison (talk) 05:24, 21 December 2007 (UTC)[reply]
This is actually easily done. You simply run them in series. Ikea has desktop lamp that runs off 12V AC at 20 Watts each I think. You simply need to place 10 of them in series then you can run them directly off the 120V AC sockets in US. To run them off battery, you would arrange the light bulbs in parallel. Or you could hook up 10 12V batteries in parallel and run regular incadescent household lights off it. Please note that 120V AC is rms voltage, the peak is 170V. When hooking up 120V AC light to 120V DC, the light may be alot dimmer then expected. Also Get a professional to do this for you. It's quite dangerous if you don't know what you're doingNYCDA (talk) 18:06, 21 December 2007 (UTC)[reply]
Ummm I thought the point of RMS voltage is a reference voltage of which an AC system of that RMS voltage will do the same work as the same voltage in DC. So it should not differ in brightness whether running it in AC or DC. --antilivedT | C | G 11:13, 22 December 2007 (UTC)[reply]
Counter-Immuno Electrophoresis
If I understand the rationale behind this method correctly, wont the oppositely-charged antigen and antibodies bind regardless of the antibody specificity, simply due to their electrostatic attraction? Actually, I'm not sure that I understand the method at all (only exposure is few lecture slides and the lecturer was off, sick - can't find suitable Internet resource). --SeansPotato Business 21:12, 20 December 2007 (UTC)[reply]
I KNOW YOURE NOT SUPPOSED TO DIAGNOSE, BUT JUST THROW ME A BONE
This question has been removed. Per the reference desk guidelines, the reference desk is not an appropriate place to request medical, legal or other professional advice, including any kind of medical diagnosis, prognosis, or treatment recommendations. For such advice, please see a qualified professional. If you don't believe this is such a request, please explain what you meant to ask, either here or on the Reference Desk's talk page.
This question has been removed. Per the reference desk guidelines, the reference desk is not an appropriate place to request medical, legal or other professional advice, including any kind of medical diagnosis or prognosis, or treatment recommendations. For such advice, please see a qualified professional. If you don't believe this is such a request, please explain what you meant to ask, either here or on the Reference Desk's talk page. --~~~~
I'm sorry, but we really can't offer you diagnoses or prognoses. Your school nurse or family physician may be able to direct you to appropriate resources. TenOfAllTrades(talk) 14:58, 21 December 2007 (UTC)[reply]
Luminex multiplex cytokine analysis
I was wondering; those beads from Luminex (some biotech company) that allow you to measure the concentration of multiple [e.g.] cytokines in one reaction; shouldn't it be theoretically possible to use those with a regular FACS machine or are the beads too small for a FACS machine to use? How many lasers does a FACS machine usually have? --SeansPotato Business 23:28, 20 December 2007 (UTC)[reply]
"FACS" is an abbreviation for "Fluorescence activated cell sorting", and I suspect (correct me if I'm wrong) that what you actually want to know is whether one could use a regular flow cytometer for that purpose (I cannot see why the sorting abilities of the instrument would be relevant). The Luminex instrument is a specialized, miniature flow cytometer. As for using beads for measuring cytokines etc., there are companies that offer beads for that purpose, adapted to conventional flow cytometry. A modern flow cytometer, such as this one, tends to come equipped with two lasers these days. --NorwegianBluetalk 13:18, 21 December 2007 (UTC)[reply]
December 21
gasoline vapor
Is gasoline vapor heavier than air. I am concerned about storage of small containers of gas in heated garage. —Preceding unsigned comment added by 72.240.19.105 (talk) 02:50, 21 December 2007 (UTC)[reply]
Gasoline vapour in air will be denser than air, but not by much as the vapour is not very concentrated, so you will want to have some ventillation to blow those fumes away. Only methane is significantly lighter hydrocarbon than air. All the ones likely to be in petrol/fuel will be denser. If you have butane, this is denser than air, and can form a high density of vapour, so this could be dangerous. Graeme Bartlett (talk) 02:54, 21 December 2007 (UTC)[reply]
Eclectus parrot: how much fruit should he be eating?
I've not had my eclectus that long. He likes his seed, he likes nuts, he likes table scraps but he doesn't seem that bothered about fruit. What percentage of his diet is supposed to be made up of fruit and veg? —Preceding unsigned comment added by 84.64.109.187 (talk) 08:27, 21 December 2007 (UTC)[reply]
Here is a site[10] that has some useful information. If you search 'eclectus diet' on Google you will have more sites than you can read.Richard Avery (talk) 09:02, 21 December 2007 (UTC)[reply]
I have an assingnment on manufacturing that goes like this:
You are requested to draw up a basic work scheme for the production of a functional
shaft, plain bearing and wheel assembly which is going to be used for a skateboard
undercarriage.
Plain bearing
Shaft
Wheel
The plain bearing is fixed to the wheel and it rotates freely on the shaft.
In your report identify;
The materials which can be used for the three individual parts
The manufacturing techniques and procedures to manufacture the parts
Any post manufacture surface treatments to reduce wear and increase lifetime
It is suggested to back your choices with relevant information
Can anyone direct me to appropiate sites where a good general idea can be given?
P.S. I would like to construct the elements out of organic materials if possible. —Preceding unsigned comment added by 193.188.46.254 (talk) 09:17, 21 December 2007 (UTC)[reply]
Why re-invent the wheel? Heh. No, seriously. The specifications and designs for skateboard wheels (and just about everything else that is manufactured) are covered already by standards. The trick is to find the standard that will cover what you're looking for. Here's how to do this. There are numerous organizations out there that publish standards, depending on what their focus is. So, for instance the organization ASTM is one, as is the ANSI, DIN, IEEE, BSI and other organizations. It would be quite difficult (unless you already knew) which of these organizations would be the one that would publish a standard that you're looking for. Fortunately, there's a private company called ILI Standards that keeps an updated database that indexes all of the Standards in the world - or pretty close to all of them. I don't know what "ILI" stands for - nobody knows (or at least nobody that I know knows).
Now here's where it gets tricky. This company makes its money by selling standards that they print. Because of this they do not make the standards freely available online or anywhere else - they're very fussy about that. You either have to purchase one of their standards (which can actually be expensive), or try to find the standard you're looking for in some library. It is often difficult to know whether a particular library has the standard you're looking for; quite often libraries do not list the standards they have in their collection in their online catalogs. Instead, you need to contact the library's Reference Desk directly and ask if they have "such and such standard" in their collection. If they have what you're looking for, you can go make some photocopies of the pages that cover what you're interested in doing. The standards will describe what type of materials need to be used, they'll often provide diagrams and blueprints for the design, and they'll give specifications for tensions stresses, etc.
Only some libraries collect standards, of course. The best libraries to look for standards are ones that support some kind of research involving manufacturing, engineering, design, etc. So libraries that are associated with universities that offer degrees in these subjects would be good places to look for standards. I do not know of any library that has all of the standards in the world - standards cost a lot of money, and unless the library staff that orders the standards feels that there would be a need for a particular standard, it is unlikely that they would spend their often limited resources on purchasing standards to put in their collection if they believed that they would never be used by anyone. What you're looking for is a standard for skateboards, and quite frankly this is not one of those things (I'm guessing here) that would be included in a lot of libraries. It might be tricky to find a library that has the standard you're looking for. To make things worse, libraries do not ship standards from one library to the next through their Inter-Library Loan system. This is due to copyright restrictions on them. So if you're lucky you might find a library close to you that has the standard you're looking for. Then you can go and make photocopies for free. Otherwise, in order to get the standard, you're going to have to pay for it.
ILI Standards has an online database where you may search for what you're looking for; it's called ILI Infobase. I did a cursory search using the word "skateboard" and came up with this standard:
Standard Number: BS 5715(1993)
English Title: SPECIFICATION FOR SKATEBOARDS FOR RECREATIONAL AND SPORTS USE
Version Date: 03/15/1993
Country: United Kingdom (GB)
Summary: Specifies requirements for non-motorized skateboards which are supplied as complete articles for use by a single rider at a time. Coverage includes definitions, performance, marking, and design and construction. Also includes annexes and diagrams.
Committee: TCM/56
Publisher: BSI (BRITISH STANDARDS INSTITUTION)
389 CHISWICK HIGH ROAD
LONDON
W4 4AL
Table of Contents:
Committees responsible
Foreword
Specification
1 Scope
2 Normative references
3 Definitions
4 Design and construction
5 Performance
6 Advice to users
7 Marking
Annexes
A Skateboard safety code
B Advice on maintenance and use
C Schedule of tests
D Wheel friction test
E Speed test
F Endurance test
G External design
H Drop test
J Impact test
K Pulsating force test for deflection of metal decks
Figures
1 Major components of a skateboard
2 Radiusing of edges of deck
D.1 Diagram of friction test apparatus
F.1 Diagram of endurance test apparatus
G.1 Example of use of test cylinder
H.1 Diagram of apparatus for drop test
K.1 Diagram of arrangement for pulsating force test
List of references
Although this standard has been superceded by another (BS EN 13613), the newer standard seems to focus not on the "nuts and bolts" of the construction of the wheel assemblies of skateboards, but is more focused on safety issues. So I would use the standard I've quoted to find diagrams and descriptions of wheel assemblies. I hopt this helps. -- Saukkomies 08:30, 21 December 2007 (UTC)[reply]
I find it hard to imagine constructing shafts and bearings from "organic materials" - wheels, maybe. But it's hard to imagine any organic material with the strength required here. You're supporting the entire weight of an adult on a couple of these things - and a lot of skateboards are used for tricks and jumps and things that will dramatically increase the forces on bearings and shafts. SteveBaker (talk) 15:13, 21 December 2007 (UTC)[reply]
Tanning is Skin Cells in Trauma
The latest propaganda campaign by the Australian Government is that all sun-tanning is extremely dangerous and that you absolutely should not tan.
The campaign also tries to explain that we get enough Vitamin D from foods, that even though you feel and look healthier with a tan the risks are not worth it.
You can view the TV ad here: http://www.darksideoftanning.com.au/campaign/tvc.aspx (the government has launched a whole website and media campaign against tanning
Is this paranoia or is well-founded truth? Previously I had asked on the reference desk about tanning, and discovered it's the UV rays that actually convert the Vitamin D and give you a tan. I also know it kills bacteria on the skin, and the sun helps you sweat, increases blood flow and has other benefits. Should I avoid the sun completely or is this campaign absolute nonsense to scare the masses into subjection? Rfwoolf (talk) 11:48, 21 December 2007 (UTC)[reply]
It's not really a good idea - it's not extremely dangerous like constantly getting deep sunburns would be, but it's certainly not a good thing to do, especially in booths (though I don't think this is a problem in Australia..) where there is a much larger risk. Most people do get enough Vitamin D from foods. Killing bacteria on the skin is a pretty silly excuse because there are lots and lots of bacteria, along with mites and other critters, on your skin and hair anyway, and regardless of how much laying in the sun you do they're not going to go away forever. So on a personal level, it's not a clear cut decision and rests with the priorities of the one making it: if you want to look tanned now, you're putting yourself up at a higher risk of skin cancer, and UV/sun can also make your skin look bad later in life too (and no, this is not medical advice, shush). On a more general level: the risk of metastasis is low in skin cancer excepting melanoma, which is relatively rare compared to basal cell carcinoma and squamous cell carcinoma. The scenario in the video does happen, but is extremely rare - still, the (somewhat overblown, probably due to it being a public health issue) campaign has a valid point. If I were them, I would be emphasizing premature aging and UV damage, not melanomas; for some, wrinkles trumps death! -Wooty[Woot?][Spam! Spam! Wonderful spam!] 12:38, 21 December 2007 (UTC)[reply]
They should just advertise this picture and be done with it. --Sean 12:53, 21 December 2007 (UTC)[reply]
Why would the AU government spread anti-tanning "propaganda"? --SeansPotato Business 18:39, 21 December 2007 (UTC)[reply]
There is an important variable that one should consider when making a personal decision about the amount of sunlight one chooses to acquire, and that is the skin tone. One of the reason's Australia has such a problem with melanoma (and hence is so proactive in informing its people about it) is because a huge proportion of the population are northern European immigrants, and many are of Celtic origin, which is the greatest risk group for melanoma. Combine that with some of the highest UV levels [11] in the populated world and you have a recipe for public health problems. If you are pale and freckled, then you are probably better off avoiding UV as much as possible in Australia, as the Vitamin D benefits you mention can be achieved with much lower levels of UV exposure than if you had darker skin (Assuming a balanced diet, the amount of optimal exposure is tiny anyway, probably only a few minutes a day in sunny weather). In contrast, if you happen to be aboriginal to Australia, you can probably hang out in the sun for many hours without too much problem - melanoma in black skinned people is pretty rare.
The bottom line though, is that irrespective of skin tone, the direct benefits we can get from UV will be achieved, in Australia, by incidental exposure. There is absolutely no good biomedical reason anyone needs to "sun themselves" in Australia, which is why the government campaigns against it. Rockpocket 19:00, 21 December 2007 (UTC)[reply]
I meant to question the idea that the government would be partaking in some kind of conspiracy to...(I've no idea what the OP could be thinking)? --SeansPotato Business 23:47, 21 December 2007 (UTC)[reply]
I don't believe there's any consipracy. This is simply a public health initiative. There was a particularly effective campaign called "Slip Slop Slap" which was great at getting the sun protection message across a few years ago, but the public have short memories, or think these problems somehow disappear. Either way, the number of skin cancer deaths in Australia are increasing, and people are even dying of melanomas they've developed using solariums. As Rockpocket correctly points out, if you're a caucasian Australian, or even if you're just visiting, you don't need more than 5-10 minutes of incidental exposure per day to synthesise adequate Vitamin D, and more than that will cause sun damage, and that could end up killing you. Mattopaedia (talk) 02:41, 22 December 2007 (UTC)[reply]
Um, I would be a little careful being too sure about all this. A recent study has suggested that below-recommended levels of serum vitamin D are widespread (especially in Canada, where I was when it came out). And vitamin D deficiency is thought to predispose to cancer, including skin cancer. Also I believe that it takes fairly bright sunlight to make much vitamin D.
I don't know. When I lived in Canada I took oral supplements of vitamin D in the winter rather than seek out sun exposure. But experts have been slow to recommend oral supplementation, partly because overdose is possible, and partly because they're not sure it has the same effect as the natural sun-generated vitamin. My non-professional, non-warrantied advice would be -- don't do anything obviously stupid, and stay tuned to further developments. --Trovatore (talk) 03:01, 22 December 2007 (UTC)[reply]
Well, what the ad campaign fails to clarify, is what if you're not part of the pale-white caucasion section of the population? What if you have a natural olive-brown skin and can in fact tolerate a bit of suntan? Well then their ad campaign would still have you believe that tanning is still 100% out of the question. As to why this is "propaganda", it's obvious that it does its best to illicit fear and other emotional responses in order to get people to take action. In a hypothetical case tanning would become taboo, and any individual that dares to go to the beach and lie in the sun would have dozens of people pointing at them and saying "haven't you hear? You're about to get cancer". The ad fails to offer any balance - the balance is that certain skin tones are more susceptable to skin cancer than others, and that if you have a darker skin tone you can tan for longer periods or spend more time outdoors. That's the clarification I'm after. Because I have a darker skin tone I'm definitely going to be spending some time tanning, no thanks to this blatant shock-campaign. Rfwoolf (talk) 08:08, 22 December 2007 (UTC)[reply]
What you call "propaganda" is simply smart and effective public health policy. Epidemiologists have clearly concluded that the dangers of sun avoidance are hugely outweighed by the dangers of sun exposure for the vast majority of the Australian population (the message would likely be different for the Canadian population due to the difference in annual UV exposures). Public health initiatives have to be direct and simple: they don't work when they are loaded with caveats.
Consider the public health initiatives about HIV. What is not widely known is that about 10% of Europeans are essentially "immune" to HIV, they are safe from infection due to a genetic polymorphism. So is it "propaganda" that that the HIV awareness campaings don't make it clear that if you are of European descent, there is a 1/10 chance that you could have risky sex all you like, but that you will not get AIDS? Maybe it is, but is also clear that publicising that information as part of the message will likely make the safe sex message less effective, and thus is counter-productive to the public health.
Populations are, in general, not very smart. It takes pulling at the heart-strings and using shock tactics to get the message across, so that is what Governments do. Besides, if you are smart enough to seek further information and make an informed decision based on your personal situation, then you are probably not part of the demographic that ad-men were instructed to target with the campaign. Rockpocket 02:49, 23 December 2007 (UTC)[reply]
You might want to be careful with that 1/10-chance statistic—it's a bit misleading. The population of interest is people of Northern European descent; not all Europeans. In that population, between 10% and 15% of the population carry at least one mutant copy of the CCR5 receptor: HIV's usual route into the cell. These people are more resistant to HIV infection, but not immune. About 1% (one in one hundred) carry two mutant copies of the gene; it is these people who are nearly immune: [12]. However, even these people can be infected, as some strains of HIV can also enter cells through binding with the CXCR4 coreceptor (see HIV#Tropism). So really one could add to the public health campaigns the fine-print message "If you're of Northern European descent, you've got a 1 in 10 chance of being somewhat resistant to HIV infection, and a 1 in 100 shot at being very (but not completely) resistant. Good luck with that, and remember you're still 100% vulnerable to syphilis."TenOfAllTrades(talk) 03:16, 23 December 2007 (UTC)[reply]
Yes indeed, in demonstrating the basic principle I was over generalising. But as you note, that kind of re-reinforces that point I was trying to make: It would not be effective for a public health campaign to provide all the details and caveats. You provide some additional, simplified information as a caveat and you risk over simplifying (which can be counter-productively dangerous), so then you need to provide even more detail. Before you know it, only a genetics expert can fully appreciate the message, and they don't need to be told because they already know. Rockpocket 08:17, 23 December 2007 (UTC)[reply]
Actually the ad seems accurate to me and more or less technically correct for all people. What you seem to have missed is that if you have 'natural olive-brown skin' and can tolerate more sun exposure, you don't tan anywhere near as much. The ad stated resonably accurately that the reason why you tan is because your skin is trying to protect itself. People with naturally darker skin can tolerate greater sun exposure and take a lot longer to 'tan'. They can't however (as far as I'm aware anyway) 'tolerate' more of a 'suntan' then people with lighter skin (as you seem to be suggesting)! In any case, the primary reason for the ad (which according to the ad was by the NSW state government not by the Commonwealth of Australia government) was to highlight the fact that a suntan is not in fact a sign of health as a lot of people seem to think. The ironic thing of course is that for many of the people with naturally darker skin, tanning is often still viewed negatively and they try to avoid it completely even to the extent of skin bleaching (as sun tanning says) which surely isn't a good idea either. I'm from New Zealand and while I haven't seen an ad like this but the slip slop ads are still quite common around summer. And given we have the highest? melanoma rate in the world (I'm guessing Australia is up there too), I'm pretty sure it isn't a big conspirary but a well meaning and well justified public health campaign. Besides that, as other have pointed out effective advertising requires that you simplify things. If you give too much information people just 'switch off'. Most sun exposure times in papers and stuff generally mention that they are for people with fair skin. More brocherues etc which can afford to give more information also usually mention that people with fair skin are the ones who have the most to worry about (although this is usually more of a 'if you have fair skin you need to be especially wary' then a 'if you have dark skin, don't worry' point) P.S. some of the highest UV levels in the world as someone pointed out is another key point. Me and others I know sunburn here much easier then in tropical Malaysia. Nil Einne (talk) 11:31, 25 December 2007 (UTC)[reply]
Why don't we eat carnivores?
I've been wondering for a while why (to my knowledge) carnivores are not eaten anywhere on the world. I know some cultures eat dogs, but these are not obligate carnivores...brown bears are eaten, but they are omniovorous, and I have never heard of polar bears being eaten. We do eat carnivorous fish, reptiles and birds, so it seems to be restricted to carnivorous mammals. Is it just because they would not taste good, or would it be unhealthy to eat carnivores? And if the latter, why? -- Ferkelparadeπ 12:20, 21 December 2007 (UTC)[reply]
Here are my (educated) guesses: for one, humans are not an exceptionarily strong species, especially when going up against big carnivores, so we have had much more of a difficult time hunting the hunters than hunting herbivores (we also seem to have better luck with speed rather than brawn, so that would have helped as well). The stupid ones who go trying to club lions get killed, so there's an evolutionary component to it, and even if you manage to take down a carnivore, you have expended a lot of effort. Only recently has man been able to pretty much take shots at whatever animal he cares to eat, and any cultures that traditionally eat carnivores would assuredly be in that position by force (no alternatives). So culturally, nobody wants to eat the carnivores either - the modernity of hunting with guns throws that out the window. Another suggestion would be that some carnivores carry more parasites and other nasties than herbivores, though if you're not chowing down on scavengers that's not as much of a problem. I don't think it's a issue of not tasting good - I think it's the old standby "we haven't done it before, so it's exotic - try it if you want, but our culture says eat herbivore X so you should probably just stick to that.". -Wooty[Woot?][Spam! Spam! Wonderful spam!] 12:46, 21 December 2007 (UTC)[reply]
And also think about how the method of food production would work on that—carnivores are at the top of the food chain, and there are usually a lot fewer of them than the "prey" species. So unless we happen to have a vast resource of carnivores around (like in the ocean), it makes more sense for us to eat prey species on the whole. On top of that, much of the modern Western meat diet is due specifically to modern modes of food production, and many of the foods we find so "natural" in Western culture are pretty specific to our time and place (chickens were not eaten as meat with great regularity until well into the 20th century, for example). --24.147.86.187 (talk) 12:56, 21 December 2007 (UTC)[reply]
(Edit conflict) There's also the ecological pyramid to consider: there's a *lot* of grass, rather fewer grass-eaters, and even fewer grass-eater-eaters. It's best not to base a diet on the pointy end. --Sean 13:01, 21 December 2007 (UTC)[reply]
I heard wild canids and felines meat had a very very strong taste and that is why we don't eat them. No source. Keria (talk) 13:26, 21 December 2007 (UTC)[reply]
Thanks for your input, everyone...I had also thought about the relative ease/danger of hunting carnivores vs herbivores, and of course there is always a relative abundance of herbivores and relatively few predators so it would be impractical for any culture to base a diet on carnivore meat; however, I am wondering why we do not eat carnivores at all. For example, lions and tigers have been hunted for milennia (probably since the invention of the bow) and their skins were displayed as hunting trophies, but nobody seemed to care much for their meat (or at least I have never heard of the pharao's court feasting on roast lion after a day of hunting, which would be an expected outcome if carnivores were considered edible - the more difficult to hunt and the more prestigious the success, the more of a status symbol it would be to serve lion or tiger to your guests). I guess Wooty's suggestion that it might be related to parasites comes closer to answering my question, but I'd be interested in a bit more data on that idea (which parasites, and why? And why do omnivores carry less parasites than obligate carnivores?) -- Ferkelparadeπ 13:39, 21 December 2007 (UTC)[reply]
Another point would be that it would be hard to farm carnivores. You would also have to farm their food, and their foods food. And stop them from eating all their food at once (lions in a paddock next to sheep?)Shniken1 (talk) 13:45, 21 December 2007 (UTC)[reply]
I don't know what their meat tastes like but carnivores tend to be extremely tough, bony and don't have much meat in any case. A big fat juicy cow/sheep/whatever is much better to eat. If you're into something exotic, why not a camel or pheasent or goose or something for your guess instead? Or perhaps caviar or whatever. Probably better then requiring your guests to pick through a very bony lion/tiger. Although quite a lot people do eat dog meat (ooops missed the part about obligate). Some people also eat crocodile (ooops missed the part about mammals too) or cat meat (although it's not clear whether these were common traditionally). Also carnivores are sometimes considered neither halal nor kosher. BTW some people do appear to eat tiger meat and lion meat although it's not clear how common this was traditionally. In terms of people hunting and that, well bear in mind that if these people wanted the pelt and head, it may have been far easier if they kept the tiger intact until someone could get around to deskinning it properly rather then quickly getting it ready for the dinner table. Plus eating it could perhaps be seen as degrading their kill (this was supposed to be a trophy, not food). P.S. people do eat polar bears [13]Nil Einne (talk) 14:54, 21 December 2007 (UTC)[reply]
We do eat lots of different carnivores. Most of the fish we eat are carnivorous, for instance. However, there's a problem with eating mammalian carnivore species - it has to do with the buildup of toxins (and even good things) in the internal organs and tissues of carnivores. Toxins are concentrated in the bodies of animals (and humans) the further one goes up the food chain. One of the most pernicious substances, though, is actually Vitamin A, which builds up in carnivores' livers and other organs - but especially livers. People will die or get very very sick if they eat too much Vitamin A. An example is the story of Xavier Mertz, an Antarctic explorer, who died after eating the liver of his sled dogs. So maybe as a result of this human societies developed food taboos regarding the eating of carnivores. -- Saukkomies 08:45, 21 December 2007 (UTC)[reply]
Yep, I think the term for that is biological magnification. The further up the food chain you go, the less "good for you" the meat is, to put it bluntly. Humans probably taste pretty awful, or at least aren't too good for you, though I have no personal experience on the matter to verify that. Wrad (talk) 16:49, 21 December 2007 (UTC)[reply]
Armin Meiwes claims that human meat essentially tastes like sweet pork. As for being good for you, human meat apparantly contains large numbers of prions, which over time may end up causing problems (such as everyone's favourite zebra, Kuru). GeeJo(t)⁄(c) • 16:57, 21 December 2007 (UTC)[reply]
The obvious answer is, it wouldn't be practical. What we are trying to do is get energy. Where does this energy come from? The sun. But we can't absorb that energy directly, so we have to use intermediaries to get that energy. We can eat plants, or animals that eat plants. But why would we want to eat animals that eat animals that eat plants? Cut out the middle man, it's inefficient. It would be pointless to raise carnivores to eat them, because them we have to also raise herbivoirs to feed the carnivores. But we can just eat the herbivores directly ourselves. It's more cost and energy efficient that way. Also like someone else said, we do eat some carnivores, in the form of fish, but no one is raising those fish. We just pluck them from the trees so to speak. We don't have to provide their food source, like we would with farm animals. Also we can't consume their food source either, well at least no one would want to on a regular basis. 64.236.121.129 (talk) 17:36, 21 December 2007 (UTC)[reply]
Quite a lot of the fish you find in the store in my area (the US) is farm-raised. Maybe it's different in other parts of the world, I don't know. Friday(talk) 18:11, 21 December 2007 (UTC)[reply]
Cats are obligate carnivores, and according to cat meat, are eaten in certain parts of the world. So the basic premise that carnivorous mammal meat is never eaten is untrue. I think the other responses give good reasons why it is not widely eaten (e.g., inefficient use of resources in farmed animals; concentration of toxins and prevalence of parasites in wild animals). -- Coneslayer (talk) 17:58, 21 December 2007 (UTC)[reply]
Part of the reason there are fewer carnivores than herbivores and fewer herbivores than plants is that the higher up the food chain you go, the harder it is to get the energy you need to stay alive. Plants have it easy. They sit around and get energy from the sun. herbivores have to get that energy secondhand from the plants. Carnivores get it third (or fourth) hand from other animals. With each step, the work/benefit ratio gets worse and worse since food becomes harder to chase down, not to mention the fact that animals just don't deliver what plants can energy-wise. Wrad (talk) 18:34, 21 December 2007 (UTC)[reply]
Backcrossing
MyD88-/- mice were generated as described and backcrossed for 9 generations on an H-2d (BALB/c) background. - what's the backcrossing necessary for? --SeansPotato Business 20:15, 12 December 2007 (UTC)[reply]
When generating knockout mice, it's generally necessary to mix two different strains of mice. Backcrossing is used to reduce the genetic components of one of the founding strains. — Scientizzle 21:16, 12 December 2007 (UTC)[reply]
Here is an ugly graphical representation. After several generations of backcrossing, one can assume that the only non-BALB/c DNA in these mice is from the regions flanking the knocked-out gene — Scientizzle 21:21, 12 December 2007 (UTC)[reply]
That's great; thanks. So you only need to perform backcrossing when you have the knockout in a different genetic background than the one you want? Would it not be simpler to have performed the knockout in the genetic background in which you wanted it in the first place? Are some backgrounds in some way easier to use for producing knockouts? --SeansPotato Business 22:07, 13 December 2007 (UTC)[reply]
The formation of a genetic knockout mouse is moderately complex. A genetically modified embryonic stem cell of strain 1 is placed in the developing blastocyst of strain 2. In order to determine the efficacy of the implantation (and to plan subsequent breeding), it's useful to produce a chimera of strains with different coat colors. There's more information at Knockout mouse. — Scientizzle 22:22, 13 December 2007 (UTC)[reply]
But the diagram you link to uses three different strains. One cell type endures the knockout and is put into a blastocyst of another type. They then try to get the transgene in a C57BL/6 background by "backcrossing". If they (the scientists involved) had used C57BL/6 cells in the first place, they could put those cells in the same blastocyst as before, breed with a C57BL/6 mouse, and just like that, all the black offspring are heterozygous for the knockout and fully C57BL/6; no backcrossing necessary. --SeansPotato Business 13:30, 15 December 2007 (UTC)[reply]
As far as I can tell that is what this diagram shows. The founder is a chimera of C57BL/6 (abbreviated as B6) and 129/Sv cells and it is backcrossed to C57BL/6 mice. That is just two strains. However, you don't put B6 cells into a B6 blastocyst, because then its is much more difficult to identify which offspring are chimeric. Typically need your null allele to be incorporated into the DNA from a strain with a different coat colour, since this is the way you can identify your founders (129 mice are white, and B6 mice are black - chimeric mice will be a patchwork of white and black). So at N1, the first backcross, you will select mice that have one allele that is B6 and the other has to be the null allele, which is on a 129 background. Thus, at that point, you will have a 50/50 mixed genetic background. Rockpocket 19:35, 21 December 2007 (UTC)[reply]
Having a coat color chimera allows for a greater simplicity in creating a knockout strain--the chimeric progeny of a successful incorporation will be obvious, they're adorable little multicolored animals with the coat colors of both the recipient cell and the donor cell (the cell w/ the altered DNA). Those that have the color type of the donor in higher ratio, and especially if that coat color is found near the reproductive organs, are more likely to be heterozygous for the target mutation in their germ cells, which is the key. The progeny of those animals become your F1 generation if germline transmission is received. Because raising animals is expensive, and genotyping a new mutation can be difficult/expensive/time consuming, these shortcuts make it simpler to produce a strain.
One note--the mice I've been involved with ususally only use two strains, 129/SvEv cells injected into C57BL/6J, then further backcrossed onto C57BL/6J, for example. Why one would use three strains, I don't know...but using only one strain would cause large difficulties...it would be effectively impossible to determine the efficacy of any blastocyst implantation; one would be left with attempting to test every possible F1 pup for the genotype of interest. — Scientizzle 20:35, 21 December 2007 (UTC)[reply]
But aren't you assuming that the coat colour is linked to the chromosome holding the knockout? In reality, they will probably separate, being on different chromosomes, leaving a mouse with grey colour but homozygous positive (no knockout), indistinguishable from a mouse that has the same colour and is heterozygous.
DNA-altered ES cell from gray-coat-colored strain added to developing blastocyst of a black-coat-colored strain.
Resulting offspring are chimeric: stripes & patches of black and gray. The level of gray coloration is suggestive of the extent of the expansion of the altered cell into the various tissues, including the germ tissues.
Those mice are crossed with black mice. Those offspring will only be heterozygous for the mutation if their chimeric parent's germline cells were derived from the altered (gray) stem cell. Coat color may be, at this point, genetically independent of the mutation, as you suggested. (But! pups of variable color--half completely black and half of the litter completely gray--are suggestive of gray-type DNA in the germ cells, so that's usually a good sign.)
These putative F1 mice are then genotyped...and the rest is history.
The key to the whole process is that the genetically altered stem cell must end up as a progenitor to germline cells in order for the whole scheme to work. Mixing coat colors is a way to measure that efficacy. I'm not saying this is the best way to do it, but it is why it's done. If one only uses C57 cells in C57 embryos, one cannot easily know if any step (incorporation of ES cell, expansion of that cell into relevant tissue, inheritance of said cell's coat color phenotype) along the way, until genotyping the F1, has worked. — Scientizzle 23:59, 21 December 2007 (UTC)[reply]
Okay, I understand it. I'll try to make a nice SVG diagram for the article. Here's a method that I think would be better though; it requires approximately eight genotypings but no backcrossing. Is it flawed?
Transduce C57 cells and insert in 129 blastocyst
Cross chimera with C57 mice
Black offspring are heterozygous
Cross black offspring
Genotype approximately four males and four females to find one double negative of each type.
Breed as much as you like. They're all fully C57 background and so no backcrossing required. --SeansPotato Business 09:52, 22 December 2007 (UTC)[reply]
Sorry Sean, your scheme doesn't look too good. #3 is wrong because, unless the mutation of interest is on the same chromosome as the coat color gene(s), one cannot assume that the black offspring are the hets. In fact, if unlinked, black offspring have same odds of heterozygosity as non-black.
The backcrossing is necessary because any het F1s would, by definition, have ~50% 129 strain DNA. (The chimera parent has a mostly C57 body, but must have 129 sperm or eggs in order to contain the mutation.) Each F1 het would have a different profile of C57 and 129 DNA, too, so crossing them could make offspring that are between 0 and 100% genetically 129. Continued backcrossing against C57 +/+ animals reduces, each generation, the amount of (mutated-chromosome-unlinked) 129 DNA by 50%, until only the region of the altered chromosome is non-C57. This is important because different inbred mouse strains can have wide variability in many important features, including behavioral measures, drug metabolism, cancer development, etc. — Scientizzle 20:53, 22 December 2007 (UTC)[reply]
Okay, I messed up on the first scheme, but I'm not through yet!
=== Revolutionary Nobel-prize-winning method ===
Transduce C57 cells and insert in 129 blastocyst
Cross chimera with mouse of C57 background
50% of black offspring are heterozygous - genotype approximately two males and two females to find one heterozygous of each gender
Cross heterozygous black offspring
25% of offspring are homozygous negative - genotype approximately four males and four females to find one homozygous knockout of each gender
Breed as much as you like. They're all fully C57 background and so no backcrossing required
Stats to achieve two homo.neg. in required background: Total crossings = 2, total genotypings: 12
=== Standard Leading-brand method ===
Transduce 129 cells and insert in C57 blastocyst
Cross chimera with mouse of C57 background
50% of not-black offspring are heterozygous - genotype approximately two mice to find a heterozygous negative mouse
Cross heterozygous negative with mouse of C57 background
Offspring are all about 75% C57 and 50% are heterozygous - genotype approximately two mice to find a heterozygous negative mouse
Repeat steps 4 and 5 10 more times to achieve mice with 99.98% C57 genome and genotype approximately two male and two female mice to find one heterozygous mouse of each gender
Cross these two mice to achieve 25% homozygous knockout mice with 99.99% C57 genome - genotype approximately four males and four females to find one homozygous knockout of each gender
Stats to achieve two homo.neg. in required background: Total crossings = 13, total genotypings: 32
Am I right in my understanding of the backcrossing procedure and/or my assertion that reversing the roles of the C57 and 129 mice is a sound suggestion? --SeansPotato Business 16:10, 25 December 2007 (UTC)[reply]
That's weird...we answered this question on Dec 12th. What's it doing back here again? The OP's signature is even from Dec 12th. SteveBaker (talk) 21:04, 21 December 2007 (UTC)[reply]
Sean brought it back for round 2... — Scientizzle 21:09, 21 December 2007 (UTC)[reply]
slack action and the physics professor
It seems that professors will often tell stories or use examples that just are not true. The story I have the biggest problem with is about slack action in trains. It goes something like this --It is impossible for a locomotive to start a 50 car train if all the slack is taken out. (ie the train in stretched) Therefore the engineer must back up his locomotive and bunch up the slack. Then he can move the train because he only has to pull one car at a time like 1,2,3,4,5 and so on."
This is simply not true. How does the engineer start the train. He gets 6 locomotives with 6000 HP each for a total of 36000 Horsepower and he hooks it up to a 100 car train and with no slack in it just gives it hell and it will pull that coal train like there is no tomorrow. Locomotives have so much power that if an engineer were to follow the teachings of the professor he or she would lose their job because they would rip train apart from the jolt of the slack action.
Why then is this still taught? —Preceding unsigned comment added by 66.228.239.18 (talk) 18:50, 21 December 2007 (UTC)[reply]
Maybe 'cause it's a physics class and not train-driving/engineering school? --SeansPotato Business 19:13, 21 December 2007 (UTC)[reply]
There are plenty examples of things which are taught and taught and taught but not reconsidered or reexamined. Our scientific mythology discusses a few of these which are often told about the history of science, for example. Why is it taught? Usually because it serves a pedagogical purpose other than it being factually true (for example, scientists often have very confused ideas about the history of their own discipline, but their "myths" help reinforce the idea of how they think their community should function). --24.147.86.187 (talk) 19:31, 21 December 2007 (UTC)[reply]
See [14] which has some discussion of railroad couplers. I'm not finding a lot of free references regarding this, but I was once told by a railroad freight train conductor that freight trains have slack couplers and they start up as described, while passenger trains have couplers with less slack. He would curse any engineeer who accelerated excessively during the startup process, because of the extreme jolt experienced in the hindmost car, the caboose. What railroad are you describing which "gets 6 locomotives with 6000 HP each for a total of 36000 Horsepower and he hooks it up to a 100 car train and with no slack in it just gives it hell and it will pull that coal train like there is no tomorrow." Sounds like poor management to use more locomotives to start a freight train moving than are needed to maintain it in motion at the desired speed and get over the grades to be encountered. The engineer would not necessarily "rip the train apart" by gradually setting it in motion via the slack couplers if the speed remained constant, at a speed which did not create too great a jolt as each car is added. Note that the engine starts out addind one car to itself and ends up adding one car to 99 cars, so with a constant maximum traction force it should have less accelereation available at the end of the process than at the beginning. Fortunately each car brakes itself, so the stopping process need not be quite so incremental. Per the ref cited, the slack in each coupler is way less than an inch. Edison (talk) 20:13, 21 December 2007 (UTC)[reply]
6 locomotives is indeed a bit much, the BNSF coal trains that pass through my town routinly have 3-4 units and they are always the newest- SD70ACe, or somtimes GEVOs from General electric. Either way both types are in the 4000 HP range and they handle the 15000 ton trains with ease. Secondly on the artical about diesel locomtives it states "the electric drive system is designed to produce maximum traction motor torque at start-up, which explains why modern locomotives are capable of starting trains weighing in excess of 15,000 tons, even on ascending grades. Current technology allows a locomotive to develop as much as 30 percent of its loaded driver weight in tractive force, amounting to some 120,000 pounds for a large, six-axle freight (goods) unit. In fact, a consist of such units can produce more than enough drawbar pull at start-up to damage or derail cars (if on a curve), or break couplers (the latter being referred to in North American railroad slang as "jerking a lung"). Therefore, it is incumbent upon the engineer (driver) to carefully monitor the amount of power being applied at start-up to avoid damage. In particular, "jerking a lung" could be a calamitous matter if it were to occur on an ascending grade."
This being said it appears taht the professor's assertion is incorrect as there is acctualy more than enough power avalible. —Preceding unsigned comment added by 66.228.239.18 (talk) 20:32, 21 December 2007 (UTC)[reply]
The only snag with this question is that the story it tells happens to be absolutely true.
This is one of those rare situations where I happen to be an expert on the subject! I used to work for Rediffusion Simulation - we mostly made flight simulators - but one time we made a railroad simulator for Burlington Northern railroads. Trust me - the story is completely true - it was one of the situations we were specifically called upon to simulate by BNR tp simulate the difference between static and dynamic friction. If the couplings are left tight by a rookie engineer - you may well have to back the locomotive up to slacken them off before you can go. Not all trains, not all locomotives, not all track slopes and curvatures and not all weather conditions - but it most definitely happens. The one time it doesn't happen for sure is when you have locomotives at both ends of the train. Then the tail end locomotives can get one car rolling at a time by squashing up the couplings and tight couplings aren't a problem.
The problem comes about when a novice pulls the train to a halt very gently and smoothly and thinks he's done a great job of it...sadly, that leaves the couplings tight, which at best is sub-optimal, and at worst will cause major grief. As you stop the train, you need to brake just a bit harder than seems reasonable in order to allow the train to compress up. This seems wasteful on speed and momentum - but you have regenerative braking on modern diesel-electric locomotives - so the energy isn't really wasted.
It wouldn't be a problem if (for example) there is a long steep grade somewhere on the route - under those circumstances, you'd have enough locomotives that you could certainly just get the whole thing moving no matter what as our OP suggests. But if the trip is across dead-flat middle-America - then they won't be sticking enough power on there just to allow an incompetent engineer to get away with a rookie error. The single biggest thing they pound into the heads of their engineers during training is fuel economy. Their profits are razor thin - and make-or-break comes down to fuel efficiency. If you go around sticking more power onto the train than it needs (and especially if you rev all of those locomotives up to full power like that), you'll be guzzling fuel and sinking profits. Their entire justification for paying us multiple millions of dollars for the simulator suite was because they believed they could get a good return on that investment from having better trained engineers.
There is a hell of a lot of stubtlety to driving a long coal train correctly - that's why they needed the simulator. On our simulated route, we had sections where there were hills that went up and down at similar spacings to the length of a typical train. Instinctively, the resulting situation is totally not what you expect. You head up a hill with loads of power on - and it's very tempting to ease off when the lead locomotive crests the top and starts to run down the other side...but if the train is longer than the hill, you really have to keep the power on because almost all of the load is still going uphill. Similarly - when you get to the bottom of a narrow valley, you are probably braking to keep the speed down - and it's tempting to ease off on the brakes and apply power as you head up the next hill - but somewhere about a mile behind you, cars are still just starting to descend the slope - and you need to keep the brakes on as you start to head up the next hill. With race-car drivers, they tell you to always have your mind lining up for the corner after the one you are just about to take...with train driving, you've got to have your head spread back over a mile from where you've just been. While you have a lot of power to get you out of trouble, you are continually trying to minimise fuel consumption - so you can't use brute force to do the job...not if you are any good at it anyway. SteveBaker (talk) 20:34, 21 December 2007 (UTC)[reply]
On a somewhat unrelated note, there is a great chapter in John McPhee's Uncommon Carriers which is all about driving coal trains. It's pretty interesting. --24.147.86.187 (talk) 20:48, 21 December 2007 (UTC)[reply]
Good points all of them. However as part of the thought experiment goes the fuel consumption is no object to the professor. The professor states that it is physicaly impossible to move a 15000 ton train that has been streched out. I would have no problem with taking the professor to the local railroad yard and watching them start the trains. I've never heard slack action on a priortiy coal train... —Preceding unsigned comment added by 66.228.239.18 (talk) 21:01, 21 December 2007 (UTC)[reply]
He might still be right under some circumstances - it depends on too many variables. If the train has been standing overnight in freezing rain and there is an inch of ice on the rails - then he's definitely right. If there are enough locomotives on the job and it's clear weather and there aren't too many cars or they aren't fully loaded then maybe he's wrong. It depends on an awful lot of factors that are unlikely to have been specified in his example. But to say that flat out you can definitely get any train moving regardless of whether the couplings are loose or tight is nonsense - sticktion is greater than friction - QED. SteveBaker (talk) 21:22, 21 December 2007 (UTC)[reply]
This would actually be an interesting thought experiment to figure out the point at which the mass of the train (unslack coupling) would be too great for the train to start. At some point the HP per wheel will cause them to spin on the track, even without ice. Friction is not limitless. This would explain the need for six engines to spread the HP over more wheels. But why the need for six trains if four is enough with slack couplings? The professors comment of physicaly impossible is out of context but almost certainly refers to a fixed number of drive wheels. Adding more trains to the front does not negate his statement, it is a different problem. David D.(Talk) 21:07, 22 December 2007 (UTC)[reply]
Neutral
If I'm in a fast-food line, is it okay to shift my automatic car into neutral for like a minute or so? I'm trying to save gas, but I don't want to mess up my engine. 71.218.36.45 (talk) 20:03, 21 December 2007 (UTC)[reply]
Your car has neutral for a reason- I've not heard anybody suggest it's harmful in any way. But why not use park? It's what people typically use when they don't want the car moving. Also.. what makes you think you're saving gas? If you want to save gas, turn the engine off. Friday(talk) 20:12, 21 December 2007 (UTC)[reply]
But, I've heard turning the engine on and off also wastes gas.
71.218.36.45 (talk) 20:15, 21 December 2007 (UTC)[reply]
That's much less true on modern cars than it used to be. Hybrids start and stop the engine routinely, and now some non-hybrid cars are beginning to do the same (e.g. the latest MINI (BMW)[15]). -- Coneslayer (talk) 20:19, 21 December 2007 (UTC)[reply]
Yeah, they call that a mild hybrid. It's possible starting the engine was wasteful in the carburetor days, but I don't think this is still true. Friday(talk) 20:22, 21 December 2007 (UTC)[reply]
It's clear that on non-carburettor cars that there is no wastage in stopping and restarting the engine like that...after all, the only reason they add this feature is to save gas. Incidentally, the MINI's auto-start feature only works in Europe - for some reason the feature is disabled on the US version (although I suspect it's just a software change). I have a vague recollection that having the engine start itself automatically is illegal in many US states. This was initially a problem for the Prius - but they managed to get dispensation because the gas engine doesn't actually drive the wheels on the Prius - so, technically, it's just a generator. Not so on the MINI - it's a conventional gasoline engined car. They are claiming that the 2009 MINI is going to have a mild version of regenerative braking too. It uses the starter motor as a generator (assisting conventional brakes)...then when you stop, the engine cuts out (as it does on the European version of the 2007/2008 version) - but when you put your foot on the gas, instead of starting the engine immediately, they use the starter motor to get the car rolling FIRST - and only start the engine once you're up to 10 to 15 mph. It's a clever trick because it doesn't require much new 'stuff' than the car already has - but for stop/start in-town driving, it's practically a hybrid - but without any of the disadvantages. It'll also have a 'sport-mode' button which turns all that stuff off if you actually want to burn rubber and blow away those wannabe VW bug and Scion xB owners (a particular obsession of mine). SteveBaker (talk) 20:49, 21 December 2007 (UTC)[reply]
Wait, wait.. Are you saying people driving a 100 hp shoebox try to act like they have a fast car?!? That's.. bizarre. Friday(talk) 20:54, 21 December 2007 (UTC)[reply]
Ok, I don't have a Mini or a Prius. I have a 2004 Hyundai Elantra. It is fuel injected, but I've heard it still wastes gas if you turn off the engine and quickly start it up again. Back to my original question, should I put my car in Neutral if I'm going to be waiting in line, or is Park better? 71.218.36.45 (talk) 21:04, 21 December 2007 (UTC)[reply]
Park would be safer- the car won't go rolling if you forget to keep your foot on the brake. I can't see any reason why one would waste any more or less fuel than the other. In either case, your engine should be just idling. Friday(talk) 21:30, 21 December 2007 (UTC)[reply]
take a look at your rpm's in park and neutral. Lower engine speed = less fuel.Furmanj (talk) 01:12, 22 December 2007 (UTC)[reply]
There has been a very convincing computer-based demonstration of how cooperation works...see Tit for tat. All of the "See also" links from that article are also well worth reading. SteveBaker (talk) 20:53, 21 December 2007 (UTC)[reply]
That article says "It is important to know that tit for tat still is the most effective strategy if you compare the average performance of each competing team.". Is it appropriate to refer to the reader (i.e. "if you compare") in a Wikipedia article? I would favour "if the average performance of each competing team is compared". --SeansPotato Business 21:34, 21 December 2007 (UTC)[reply]
Yeah - that's no good - but WP:BE BOLD - you can fix it more easily than you can complain about it. SteveBaker (talk) 01:56, 22 December 2007 (UTC)[reply]
Something meaningful to say : You need both for a proper Baseball game. I'd say some combination of the two is appropriate for most situations. APL (talk) 01:11, 22 December 2007 (UTC)[reply]
This concept of which is better - cooperation or competition - is the basis of the Nash Equilibrium theory that was named after John Forbes Nash, who won the 1994 Nobel Prize in Economics for it. Nash is also the real-life person that the movie A Beautiful Mind was based on. -- Saukkomies 02:30, 22 December 2007 (UTC)[reply]
It seems I must borrow a Game Theory book from the library. Thanks for you replies! --Taraborn (talk) 08:53, 22 December 2007 (UTC)[reply]
Greenhouse gas emissions and fuel efficiency
Out of curiosity, how much would annual greenhouse gas emissions be cut down if everyone got fuel efficient cars? Someguy1221 (talk) 21:12, 21 December 2007 (UTC)[reply]
Sorry to state the blindingly obvious, but since everyone doesn't have cars, greenhouse gas emissions would increase if everyone got one, fuel efficient or not. --NorwegianBluetalk 22:25, 21 December 2007 (UTC)[reply]
Ok, forgive my poor wording. "Out of curiosity, how much would annual greenhouse gas emissions be cut down if everyone [who has a car replaced it with a] fuel efficient car?"Someguy1221 (talk) 22:28, 21 December 2007 (UTC)[reply]
My point was not poking fun at your wording. The question you ask is a very important one. Everyone wants cars, and the greenhouse gas emissions caused by cars replacing bicycles in India and China will dwarf the savings caused by increasing fuel efficiency. So we are not talking about reducing greenhouse gas emissions, but about trying to cut the expected increase in greenhouse gas emissions. Increasing fuel efficiency of cars is undoubtedly important, even more so is encouraging people to use public transportation. --NorwegianBluetalk 22:49, 21 December 2007 (UTC)[reply]
In the US, transportation accounts for 33% of gases, and 60% of those come from cars and light trucks, so thats 20% of all emissions in the US. If hybrids double the fuel economy, then there is a 10% reduction in total greenhouse gas emission. Furmanj (talk) 23:07, 21 December 2007 (UTC)[reply]
Total greenhouse gas emission, all types, weighted by global warming potential and broken down by sector for the year 2000.
Globally, transportation fuels are about 14% of total greenhouse gas emissions. My recollection is that cars represent about half of that, with the rest goes to planes, trains, buses, and heavy trucks, etc. So lets call it 7% of the global total. You need to estimate current average fuel economy and compare that to some guess for how things will improve. The corporate average fuel economy standards in the US, which are among the most lax in the world, require the current fleet of cars to average at least 27 miles per gallon (or 21 for SUVs and light trucks). In practice, existing cars are nearly always worse than that because efficiency tends to decline with age. For the sake of argument, lets pessimistically say that all the cars still in operation really only average 15 miles per gallon. If you replace them all with Priuses which have a real world performance of ~45+ miles per gallon, then you'd shave off as much as 2/3 of that 7% of the total gas emissions. In other words, replacing all the cars might (optimistically) net you as much as a 4.5% reduction in total greenhouse gas emissions. Assuming your don't increase the total number of cars in operation, or the amount that people are driving, etc. Dragons flight (talk) 23:29, 21 December 2007 (UTC)[reply]
The point is that EVERYTHING has to be halved (at least) - if you did nothing about cars and fixed everything else, then cars would be a HUGE percentage of the problem. Cars are actually uniquely difficult to fix because they are small and mobile, and require all of this complex infrastructure - which makes them an important target. But certainly we need to stop making electricity with fossil fuels, build much better insulated homes and workplaces, address aircraft, factories...you name it. No one of these things will fix the problem by themselves - we have to attack them all together. But, yeah - but even if we were all driving 60mpg cars tomorrow, we couldn't sit back and say "OK! That's global warming dealt with!" - it's a lot more hassle than that. SteveBaker (talk) 02:06, 22 December 2007 (UTC)[reply]
meat turns brown on cooking from Maillard_browning, generally in combination with some carmelization. Its likely that if only the maillard reactions occur, such as in boiling or inside pastry, then the gray color is achieved.Furmanj (talk) 23:11, 21 December 2007 (UTC)[reply]
I would second Furmanj analysis of this. Indeed, the meat is grey because it has cooked inside a moist pasty without being exposed to air. Either that or it was boiled first before being added. Whenever I make beef stew I always char the meat first on a grill or in a frying pan to give it a nice brown outer color before adding it to the stew pot to boil. It makes it much more appealing for the person eating it if it's not just grey - which it would be if I hadn't done the first step. -- Saukkomies 23:20, 21 December 2007 (UTC)[reply]
What is the source of the energy in this device? I dont think its the gravity... 79.176.187.141 (talk) 23:48, 21 December 2007 (UTC)[reply]
The energy of the water descending from the upper reservoir to the lower buckets is what causes the device to develop a charge sufficient to make the sparks. The amount of electrical energy generated is probably quite small in Joules or kilowatt hours compared to the energy required to lift the water from the lower buckets to the upper reservoir. Edison (talk) 00:56, 22 December 2007 (UTC)[reply]
It is gravity: Only with the help of gravity will the charged droplets fall into the bucket with the same charge which repels them electrostatically. Icek (talk) 06:32, 22 December 2007 (UTC)[reply]
December 22
Natives and booze
Why didn't natives of North America have fermented alcoholic beverages (except pulque)? It puzzles me because some groups such as the Iroquois had more than adequate supplies of readily fermentable materials like corn and maple syrup. If you've come across any literature on the subject please do point me to it. Thanks!
74.12.208.131 (talk) 00:47, 22 December 2007 (UTC)[reply]
The theory I've heard is that nomadic tribes weren't big on alcohol because the long time associated with the distillation process made travelling prohibitive. The agricultural revolution allowed people to settle down and wait for their booze. This is just what I was told by a teacher years ago! (Admittedly, he was a very intelligent teacher whom I respect greatly -- but it wouldn't be the first time someone was misinformed by the public education system.) 99.245.89.152 (talk) 14:59, 22 December 2007 (UTC)[reply]
North American Native Americans were mostly agricultural and settled -- at the very least those with corn were. I don't know why fermented alcohol was not used. I know corn is commonly distilled into spirits today, but perhaps it doesn't ferment into something you'd want to drink? I can't recall ever hearing of "corn beer". Pfly (talk) 19:05, 22 December 2007 (UTC)[reply]
Corn whiskey. It has to actually be distilled, though, which the native americans might not have known how to do at all. Someguy1221 (talk) 21:24, 22 December 2007 (UTC)[reply]
No idea about the North American ones but according to Alcoholic beverage "By the time the Europeans reached the Americas in the 15th century, several native civilizations had developed alcoholic beverages. According to a post-Conquest Aztec document, consumption of the local "wine" (pulque) was generally restricted to religious ceremonies, but freely allowed to those over 70 years old. The natives of South America manufactured a beer-like product from cassava or maize (cauim, chicha), which had to be chewed before fermentation in order to turn the starch into sugars.". It's easily possible there may have been more but a lot of it was lost due to the destruction of large parts of Native American culture after the arrival of the Europeans. Oh and perhaps other stimulants such as coca and tobacco were a substitute for alcohol for some of them? (They also had other stuff like Cacao of course) Nil Einne (talk) 07:57, 23 December 2007 (UTC)[reply]
Isn't there some genetic problem with Native Americans and alcohol metabolism? Might this have dissuaded them from routinely producing alcoholic drinks? SteveBaker (talk) 14:19, 24 December 2007 (UTC)[reply]
Are you thinking of Alcohol flush reaction? This predominantly occurs in East Asians and after reading the article, isn't that common in Native Americans. In any case when I first thought of this I dismissed it as at best a minor cause at best since it doesn't seem to have stopped the Japanese, Koreans or Chinese from producing alcohol. Nil Einne (talk) 10:57, 25 December 2007 (UTC)[reply]
Ok, thanks. If anyone comes across any published work about this please let me know. 74.12.208.131 (talk) 02:06, 25 December 2007 (UTC)[reply]
There are some studies that find associative correlations with certain genetic polymorphisms and alcohol dependence in American Indians, such as PMID 12505800, PMID 15274051 and PMID 15722961 but there is nothing mechanistically demonstrated (yet). I don't know for sure, but there may be something of interest to you in Deadly Medicine: Indians and Alcohol in Early America by Peter C. Mancall, Cornell University Press, 1995, ISBN 0801480442. Rockpocket 02:31, 25 December 2007 (UTC)[reply]
Appearance of reflected laser light
Some time ago I used a laser interferometer at work to make fine measurements, and recently I've been using a home-grade laser level in some household projects. In both cases I noticed the same thing: Where the light emitted by the laser strikes an object it puts a red spot (or a thin line), but instead of a uniform solid red spot I see what appears like a very finely mottled spot. For example, the laser level is aimed at a wall in my house, so I can affix a shelf to the wall. The spot of laser light isn't a smoothly uniform red spot, but appears mottled or "grainy" in some way. What causes this? 71.112.136.40 (talk) 03:10, 22 December 2007 (UTC)[reply]
What happens when an LED is dead or blown off?..Will it make a short across the line by closing or may it open and give a break in the line?..How do we overcome or predict such problems and be sure about the condition how led's behave?...I often end up with blowing LED or making LED to glow with less intensity by using improper resistance.so please tell me how can we calculate the amount of voltage that the led takes if 'x' resistance is added to it's VCC of say 5V?...Thanks —Preceding unsigned comment added by Balan rajan (talk • contribs) 11:06, 22 December 2007 (UTC)[reply]
An LED can short or open. A short will often quickly become an open because of heating. (It's been my experience that they are usually found dead open.) See Light-emitting diode#Failure modes.
A diode will drop a more-or-less fixed voltage once it is forward biased (see Light-emitting diode#Considerations in use). You have to look at the specification sheet for your diode to find out what that voltage is. The specs will also show maximum current. Choose a current near the low end of the range, and calculate a voltage divider with the calculated drop across the resistor at that current and the given drop across the diode at that current. Say the diode drops 1V at 20 ma. The resistor will have to drop 4V at 20 ma, making it 200ohm. I'd put a small linear pot in place of the resistor and crank for desired light output, checking the result against the calculation so as not to stress the diode long-term. Shield your eyes. --Milkbreath (talk) 13:48, 22 December 2007 (UTC)[reply]
Adding to Milkbreath's point, LEDs pushed far beyond their ratings will ultimately end up "failed open" because the bond wire that connects the exposed side of the LED chip to the lead frame is a very, very fine wire and it will blow like an electrical fuse. LEDs can also fail shorted, but they can only remain in that state if the rest of the circuitry is still properly limiting the current.
Over here we use the term :'blown up'. blowing off is a completely different thing. --TreeSmiler (talk) 00:56, 25 December 2007 (UTC)[reply]
Is Nitreous Oxide for real in automobiles?
We have seen in many racing games like the ones from EA-NFS series which repeatedly introduces the nitreous oxide upgrades for it's cars in the In-game option. So is this nitreous oxide really existing?.If so then how can we get such a boost of power?.Immediate accelaration wouldn't damage the spare parts in the car like the gear shaft or the flywheel for eg?.I have never seen such cars fitted with such things around anywhere here. Also i heard it has the risk of exploding at some circumstances if mishandled. So what is this all about?.... —Preceding unsigned comment added by Balan rajan (talk • contribs) 11:10, 22 December 2007 (UTC)[reply]
We acutally have a whole article on Nitrous systems. Yes, nitrous can wreak havoc with engine parts - this image shows an engine piston which has been cracked and dented by the pressures created when nitrous is used. When heated, nitrous oxide decomposes to release oxygen, and this extra oxygen allows the fuel to burn harder. It's only used in very high-end racing cars (commonly dragsters, which need all the acceleration they can get), because it is expensive, damages the engine, and most people have no need for the kind of acceleration provided by NO2 anyway (a turbocharger or supercharger would be far more effective anyway - Nitrous just squeezes the last bits of acceleration out of the fuel). Laïka 12:33, 22 December 2007 (UTC)[reply]
Just a nit -- nitrous oxide is N2O, not the far more corrosive NO2. NO2 is a major pollutant and contributor to lung damage; N2O they give you to breathe on purpose (mixed with oxygen of course) at the dentist's office. On the other side of the coin, N2O is explosive under certain conditions. --Trovatore (talk) 23:05, 22 December 2007 (UTC)[reply]
Science/Sound waves
Hey Steve, thanks for the reply!
I have another question for you- Why is it that the speed of sound is very different in water than what it is in air? Does it have anything to do with the intermolecular forces or intermolecular attraction between the water and air molecules? —Preceding unsigned comment added by GK ROCKS (talk • contribs) 13:46, 22 December 2007 (UTC)[reply]
While Steve ain't here for the moment, I can still direct you to our speed of sound article, which has a good introduction, middle part, and ending. --Ouro (blah blah) 14:16, 22 December 2007 (UTC)[reply]
Yup, seems to be it. Thank you! —Preceding unsigned comment added by 99.245.89.152 (talk) 15:42, 22 December 2007 (UTC)[reply]
Woo-hoo, my first bug ID! 'course it helps living in SW Ontario... Matt Deres (talk) 17:43, 22 December 2007 (UTC)[reply]
Wholemeal bread
Ignoring economies of scale, should wholemeal bread be cheaper to produce than white/brown not-wholemeal bread? --SeansPotato Business 14:59, 22 December 2007 (UTC)[reply]
The short answer is that that wholemeal bread costs more to make. Here's a more detailed answer below:
Wholemeal is more commonly known as Whole grain. Since we're ignoring economies of scale, I won't figure in the cost difference between whole wheat and bleached, or other type of wheat flour. The process of making bleached flour is more expensive than to make whole wheat, due but due to its greater demand, bleached flour is cheaper to buy. And additionally whole grain flour is more expensive to store, due to it being susceptible to Rancidification. But we won't factor that extra cost in for this question.
It is actually simpler to make bread from flour that has been processed (such as bleached flour) than whole wheat flour. This is due to the fact that the whole wheat flour contains a lot of Cellulose (sometimes called Dietary fiber) from the outer shell of the wheat kernel. This prevents much of the inner starchy Endosperm to be easily broken down during the process of making the bread dough. In white bread this is not a problem, since all of the dietary fiber has been removed, making it so that the dough is more quickly turned into a form in which it can be ready for baking.
Besides the cellulose issue, there's also the issue concerning Gluten content. Gluten is the protein found in many grains, and it is what makes bread dough "sticky" when it is kneaded. The kneading process breaks the flour particles down, releasing the gluten protein from within the wheat flour particles, and then as the protein molecules start adhering to each other, this produces the stickiness. The more gluten present in bread dough, the stickier it is. When it is baked, this stickiness will be what binds the bread together, creating a firm loaf with pleasing texture for the typical human palate. Different types of wheat flour have different levels of gluten present. It depends on what kind of wheat one is using, as well as additional factors that are described in the article on Flour.
If you've ever eaten whole wheat bread that is dry, crumbly, and texturally unappealing, it is because it was prepared in such a way that the cellulose was not broken down in the dough, and/or there was not enough gluten present before it was placed into the oven to bake. This is the biggest reason that whole wheat bread is not as popular as white - it takes more preparation to make it as appealing to the palate of the typical consumer.
So, how does one take whole wheat flour and make it so that the cellulose is broken down, thus creating better quality bread? There are several considerations to take into account. First, you have to have good quality whole wheat flour. By that I mean, it must be considered to be at least as good as "bread flour", which contains at least 11% gluten. To achieve this, the flour must come from a high-gluten wheat, it must be ground in a mill that will break down the cellulose to a very fine texture, and the dough must be properly prepared to allow further breaking down of the flour to allow the gluten to be able to be freed when it is kneaded.
This last step is important. The best way to prepare whole wheat bread is to combine all the ingredients - except the yeast - and then to allow the dough to sit for at least 24 hours before adding the yeast and preparing it for baking. This 24 hour period allows the cellulose to be broken down further, releasing the gluten. When the dough is first made, it should be mixed and kneaded, and then as it sits, it should be kneaded every 8 hours. This also helps the breakdown process. After the 24 hours is up, bring the dough to a temperature that will optimize yeast growth (30° - 37° C, or 86° - 99° F), add the yeast mixture (yeast, water and sugar, which has been allowed to "start"), and then knead the leavened dough two or three more times before baking.
There are plenty of bakeries who try to short-cut this process, and you can immediately tell by sampling their product that they produce an inferior quality whole wheat bread. A good quality loaf of whole wheat will be firm, moist and have a nice flaky crust - however, it will never be possible to achieve the same level of quality as a very good white bread loaf. That's the trade-off of good health, I suppose. Now, as to how much all these extra steps will cost, I'll leave that to you to figure out. I will, though, include a recipe that I have used myself to make quite good loaves that I sold to customers when I did this sort of thing:
Whole Wheat Bread (three 2-pound or four 1.5-pound loaves)
12 cups unsifted whole wheat flour
1/2 cup raw sugar, honey or molasses
1/3 cup cooking oil or melted shortening
2 Tablespoons salt
5 to 6 cups milk or potato water - if fresh (raw) milk is used, scald first)
2 packages (Tablespoons) of bakers yeast
1 teaspoon sugar
Mix well and let stand overnight 24 hours, kneading every 8 hours, at room temperature. Bring the dough up to a temperature of around 90° F (you can place it in the oven with the setting on Warm). When the dough is warm, mix the yeast and sugar into one cup of water that is between 86° - 99° F and allow it to rest undisturbed in a warm place for about 10 minutes until the yeast begins to work (it will be frothy). Add the yeast to the dough and knead. Allow it to rest for 10 minutes. Now the dough must be kneaded constantly for at least 10 minutes. Do not add flour during the kneading process, even though the dough will become very sticky and almost soupy. If kneading by hand grease may be added a couple of times to the kneading board and one's hands, but not flour.
Put the dough back in a covered pan and set in oven to rise at a temperature of 80° to 85° F for one hour, or until it doubles in bulk. Remove the dough and knead constantly for another 10 minutes. Divide the dough into loaves, but let it rest while you grease the baking pans. Shape the loaves so that you tuck the ends in neatly and then lay the loaf into the pan so that the fold of the dough is on the bottom. Lightly grease the top of the loaf with shortening or margarine (not butter, as it will dissipate). Set the loaves in the warmed oven to rise for 15 to 20 minutes at 80° to 85° to allow them to rise to not quite double. Then raise the temperature of the oven to 325° and bake for 70 to 80 minutes.
I used to add a cup of coarsely ground (cracked) soy beans to the dough, which gave the bread an added texture, and provided addictional amino acids for people who were vegetarians. If done right, the end product of this recipe will produce nice, firm, moist loaves. -- Saukkomies 07:50, 23 December 2007 (UTC)[reply]
two slits, QED and light
I'm trying to write a gentle math-less explanation of quantum electrodynamics (or quantum field theory, somewhere in between really, it's mainly based on Feynman's QED book). The problem is, I'm doing so after a series of lectures that were just as gentle and light on mathematics, so I may understand certain things, but I don't have the rigorous education required to know for sure whether my intuitive understanding is actually correct. Since I do need to write about it, I'd like to ask you if I've understood the basic ideas.
As I understand it a photon traveling from A to B does so, not in a straight line, but along all paths (each with an associated probability amplitude). These amplitudes can be represented as arrows, where the length of each arrow is (about) equal, and it's the angle of the arrow that increases as the length of the path increases (I think this is Feynman's way of saying that amplitudes are represented by complex numbers, right?). I understand how this means that paths in a small neighbourhood far away from the shortest path cancel each other out, whereas paths in the neighbourhood around the shortest do not, as much, and therefore the closer a path is to the shortest path, the more it contributes to the probability function of the foton's location, which thus becomes essentially a sharp peak along the shortest line from A to B. I also understand that when the foton passes through a narrow enough slit, the probability function on the other side of the slit will spread out like a handfan (mimicing a wave passing through a slit).
The thing I'm uncertain about, and that I would like to see affirmed is the reason for the wave character of the probability function/wave function. If I want to explain the double-slit experiment in these terms, it isn't enough that the slits spread the wave function out, the peaks of the waves also need to come from somewhere. The way I understand it now, is that as the paths I talked about earlier are lines in spacetime, not just the path of the foton varies slightly around the shortest path, the speed of the foton also varies slightly around the shortest path in space-time, ie. the maximum speed. Each foton has a small probability of traveling a bit faster than lightspeed or traveling a bit slower, just like they have a small probability of deviating slightly from the shortest path (so far I'm just paraphrasing Feynman). This makes the probability function of the foton a tiny blob around the point that travels in a straight line at lightspeed, or a fuzzy circle, spreading out, if we don't know where the photon ends up. Is it this 'blob' that creates the peaks in the probability function, that corresponds to the peaks in EM waves in the classical model?
Is there anything to criticize about this view of things (feel free to nitpick, I can always add footnotes, to say I cheated a bit to simplify). risk (talk) 19:08, 22 December 2007 (UTC)[reply]
The first thing to understand about the path-integral approach to wave mechanics (the one where you have a particle taking all possible paths) is that it's not specific to quantum mechanics. You can formulate classical wave theories (linear ones, at least) in the same terms. With the exception of the use of the word "photon", what you've written above is essentially classical, and a good part of QED (the book) is classical as well, including the whole discussion of reflection, refraction and diffraction. A photon taking all possible paths doesn't just mimic a wave, it is a wave. I think Feynman comes on way too strong with the claim that light is made of particles and not waves.
The path-integral approach has advantages and disadvantages over the wave-equation approach, and one of the disadvantages is that it's not easy to see where the wave-like behavior comes from. One way to understand the connection is to think about triple, quadruple, quintuple... slit experiments, and how you'd calculate the pattern on the screen. It should be obvious that you just add contributions from each slit. Now add a second barrier in front of the first one, and put slits in that as well; now you have to add contributions from every pair of slits in the two screens (a total of nm terms if there are n slits in one screen and m in the other). As the number of barriers and the number of slits goes to infinity, the barriers effectively disappear, and the pattern on the screen is a sum of terms for every possible path between the source and the screen. -- BenRG (talk) 21:06, 22 December 2007 (UTC)[reply]
parkinison's disease [specifically dyskinesia ]
Medical question removed
You should consult her doctor about this problem, as the reference desk guidelines prohibit us from offering medical advice. Someguy1221 (talk) 21:48, 22 December 2007 (UTC)[reply]
Quote: "Thus, the number of nucleons modulo 4 is preserved across any decay chain." - what does that mean? Is the word modulo being used correctly? Checked the modulo page but still don't understand this sentence. --SeansPotato Business 22:17, 22 December 2007 (UTC)[reply]
It just means except for differences of whole number multiples of 4, the number of nucleons is maintained throughout a decay chain. I haven't looked at the disambig page, but it satisfies Merriam-Webster's (2000 edition) definition of modulus (1 c) "the number (as a positive integer) or other mathematical entity (as a polynomial) in a congruence that divides the difference of the two congruent members without leaving a remainder" It's certainly a more concise way of putting it, if not the most easily understandable. Someguy1221 (talk) 22:23, 22 December 2007 (UTC)[reply]
And funnily enough, it just hit me that it's completely and utterly incorrect, as radioactive nuclei can emit individual protons, neutrons, or whole other nuclei. Someguy1221 (talk) 22:36, 22 December 2007 (UTC)[reply]
Yes, but the nuclei that decay by those processes all have tiny half-lives, so they never occur naturally. All natural decay chains obey the mod 4 rule. —Keenan Pepper 19:30, 23 December 2007 (UTC)[reply]
Except spontaneous fission, that is. Other than SF, the longest half-life of any modulo-4-changing decay is bromine-88, which has a half-life of 16 seconds and a 7% beta-delayed neutron emission branch. —Keenan Pepper 19:56, 23 December 2007 (UTC)[reply]
Thanks for this. Yes meant "Cistus". The old British text I was quoting used "Cystus". Vernon White. . . Talk 20:28, 23 December 2007 (UTC)[reply]
What species of bird is this?
I found this little guy sitting on a wire fence on the side of Mount Albert, Auckland, and I was wondering what species of bird he was. I want to say swallow, but I'm probably wrong and I'd like to be sure. Thank you! 211.30.58.79 (talk) 23:55, 22 December 2007 (UTC)[reply]
I'm not familiar with the birds of New Zealand, but that's definitely a swallow. My guess is welcome swallow. Matt Deres (talk) 02:35, 23 December 2007 (UTC)[reply]
Is there a limit to how far back one can remember in their life? I have a memory that I'm sure is not false that occurred when I was 1 and half, is that farther back than normal? Imaninjapiratetalk to me 23:59, 22 December 2007 (UTC)[reply]
It would very from person to person, but it typically somewhere between 1 and 2, probably more towards the 2 end. Until a certain point, a child does not distinguish between him/herself and everything he/she can perceive that is not him/herself. It's only when that realisation dawns that memories of the "outside world" start being collected. It's quite possible to have a memory from the age of one and a half, although most people don't. -- JackofOz (talk) 00:22, 23 December 2007 (UTC)[reply]
Haven't there been some wierd psychological theories on "memories from the womb" having some significance? Seems utterly silly to me, but...Someguy1221 (talk) 00:31, 23 December 2007 (UTC)[reply]
I can believe that verbal coding is the key to retrieving most memories, so the acquisition of language would therefore limit the reach. Persons who are advocates of Repressed memory speak of "body memories;" not sure what they are. I have heard people tell of memories of persons or places which would place the memory before age 2, while others say nothingcan be remembered before age 5 or 6. Might have to do with verbal intelligence. Animals (specifically elephants and pigeons) have demonstrated long term memories, so words are not always necessary. I certainly believe adults could remember things from age 1 1/2 years, but experiments have shown that memories are suggestible: college students could be convinced they remembered seeing a Donald Duck costumed character in a visit to Disneyland, but no such character ever appeared there.
I have very clear memories from age 3, and more vague ones dating back to a time when the age or date was not clear, but was very likely before 2. Edison (talk) 01:11, 23 December 2007 (UTC)[reply]
(Fixed your link. --Anon, 04:37 UTC, December 23.)
Hi. I think I have memories from, like, a few months after birth, however I'm not going to describe them in detail because I consider it personal info. Anyway, I have far more memories from say, when i was 1 or 2 than from when I was 0. However, most of the memories have rusted, and for some of the memories as much as half or maybe all of it is false. For example, one memory that I think may be false was when I supposedly saw Jupiter and Saturn closely in the sky as big and bright as the full moon. That's next to impossible. I have other memories of going to bed, doing math, reading a book, looking in the mirror, watching TV, eating, talking, etc, from as far back as 3 or 2 or even 1. However, I don't think a lot of people would be able to recall their actual birth for various reasons. I think that memories may be partially the result or one's parents telling them about when they were little, thus adding supposedly "memorised" detail to the memory.
I think it helps when you're trying to recall long-ago memories if you have a photographic memory. Some people even claim to have memories of previous lives, although there isn't really any real proof. I even remeber some of my actual dreams from my early childhood, but only in vague detail. As you age, it is easier to forget your memories of early childhood, as they rust more and more. Hope this helps. Thanks. ~AH1(TCU) 01:56, 23 December 2007 (UTC)[reply]
It's not in his page, but ISTR Isaac Asimov claiming to remember his own circumcision. My own memories don't go back before about the age of about two, but I know several people who have no recollection of their own childhood, so there's obviously a lot of latitude from person to person. For my own part, I see no reason why our memories could not stretch back to within the womb at least theoretically or (more likely) from birth - our brains are designed to retain knowledge after all. Consider this - a child of two has already memorized several words and phrases, even if they cannot articulate them as speech; obviously their noggins are already soaking up memories of some kind. Matt Deres (talk) 02:52, 23 December 2007 (UTC)[reply]
Isaac Asimov described his earliest memory when he was about 59; like most of the others mentioned here, it was from when he was 2 years old, not a few days. This is in Chapter 4, Section 2, of In Memory Yet Green.
I have only one memory of this early period of my life. It is the vague impression of a book. I recall sitting in a chair, turning the pages of a book, and loving it. Then I seem to recall wanting the book again, and looking about for it vaguely, but not finding it and wondering where it was.
Years later, I told this to my mother in an effort to place the memory and she said, "I remember the book. You were two years old at the time and you loved it."
I said, "But where did it go? I remember turning the pages and then I couldn't find it."
"Sure," she said, "because every page you turned you tore out."
--Anonymous Asimov fan, 04:37 UTC, December 23, 2007.
I have a memory from when I was probably around 18 months old. I know this because my father was in the Air Force and we moved around a lot when I was little, so that the details of my memory describe a place where we lived between when I was 12 months to 18 months old (my mother verified the details of this later). The memory was of laying in a crib in a room with an open window, looking out to a back yard and a forest beyond. No real events took place - it was just the impression of the place. -- Saukkomies 08:00, 23 December 2007 (UTC)[reply]
The memory I have is from a few different times on one day. I was ,according to my mom about 1 and a half, and I first remember the lady at the daycare telling me to put away a toy truck, but I ignored her. We then went for a walk on bike tracks outside the daycare and I all of a sudden saw my dad. He was working on building some new road. I suppose I remember this because it was the first time I found out my parents had a life outside of my house. Imaninjapiratetalk to me 17:20, 23 December 2007 (UTC)[reply]
My earliest memory: I was lying in my cot one night. I decided to push my eiderdown off to feel what the cold was like (although I'm doubtful I reasoned all this out in words - and I should explain this was in an unheated room in the 1950s). I must have fallen asleep, because when I woke up again later that night I was warm. Someone had put the eiderdown back over me while I slept. 80.0.124.1 (talk) 23:36, 23 December 2007 (UTC)[reply]
What you say about a general recollection, but not specific, of something is where I think one needs to look, too, when considering earliest memory. My earliest memory of a specific event of several minutes in length, not just a "snapshot," which I know when it happened was when I was 6 - I'd gotten my first hearing aid shortly before, and we were on vacation in Florida. I heard the squawking seagulls from the bathroom window of our motel, and I asked my mom excitely why the birds were so close!
But, I can recall general thingswalking around the block to my great-grandmas, a story I made up about one stuffed dog with a pattern of flowers on his back (rolling in a flwoerbed on the way there), and so on, from well before then. I even baguely recall my great grandpa, the husband of the one who lived near us, who died when I was 3 and a few months. However, that may be tied to my mom telling me about him or looking through pictures.
I think the one at 6 shows the ability to grasp an entire scene and all that is going on, and describe it in pretty good detail. That may vary from person to person, but I dont' think it comes till a bit later, like 4-7. Other memories may be snapshots - the story I made up about the stuffed dog, or yours about the truck - but without much background. Others may be generalities that I recall becuase they "often happened" and are recorded in there because nothing of major import occurred, but the repetition ingrained them.Somebody or his brother (talk) 01:22, 24 December 2007 (UTC)[reply]
My earliest definitely datable memory is my 4th birthday. But like John Prine said, "often remembered / so many times that my memories are worn" — I suspect that most of my early memories by now are really memories of remembering and telling of those early events. I have many holes in memory of events, even of my teens. —Tamfang (talk) 03:42, 24 December 2007 (UTC)[reply]
December 23
Red spot on an Egg Yolk
What's the red spot on some egg yolks? I've heard this called a "blood spot," but I'm not sure it's really blood, nor would that seem to make any sense. Someguy1221 (talk) 00:51, 23 December 2007 (UTC)[reply]
An early-stage chicken embryo? On occasion, I've cracked open eggs and found embryos large enough to discern the developing features. Heh, my grandma boiled an egg last year and discovered a near-fully grown chicken foetus upon shelling it. --Kurt Shaped Box (talk) 01:00, 23 December 2007 (UTC)[reply]
It appears that the red spot is not an embryo, but rather from a blood-vessel bursting on the surface of the yolk during egg-production, and is a sign of freshness. [16]. DuncanHill (talk) 01:05, 23 December 2007 (UTC)[reply]
Did your grandmother enjoy the Balut, Kurt Shaped Box? William Avery (talk) 10:33, 23 December 2007 (UTC)[reply]
Apparently, it smelled really, *really* bad (making half the house smell of death bad). I guess that it's an acquired taste... ;) --Kurt Shaped Box (talk) 00:43, 24 December 2007 (UTC)[reply]
Airplane safety
If impact and fire are the two major cause of death in a plane crash, why plane maker doesn't build a plane with large cushion and heat insulator that cover the cabin? Are they doing enough for the safety of passengers? roscoe_x (talk) 00:58, 23 December 2007 (UTC)[reply]
A lot that doesn't go into planes is due to weight considerations. Planes are fairly light for their volume, in fact. Good heat insulation to cover the entire cabin would be pretty heavy, I'd imagine, and a large cushion would be quite unaerodynamic. Further, a large cushion wouldn't help at all if the plane is plumetting toward the earth at full speed. And if you're willing to wait for it, I'm sure SteveBaker will give a response that will dwarf mine in both substance and length. Someguy1221 (talk) 01:02, 23 December 2007 (UTC)[reply]
The answer is of course money. If its to expensive, its not practical. Far more people die on the roads than in planes, but we don't increase car safety because its not practical. It could be done, but no one will pay $100,000 for a plane ticket.--Dacium (talk) 10:56, 23 December 2007 (UTC)[reply]
Well we do increase car safety - improved headlights, air-bags, impact bars, crumple zones things like that. As for planes...large cushions would do little to stop most impacts - though they could plausibly introduce airbags into seats/curtain airbags - injuries/deaths can occur due to damaged landings/emergency landings. Fire-wise they could skip heat-insulation and have some sort of sprinkler system - obviously it would need to be advanced enough not to just make the situation worse (e.g. water on electrical fires is a bad thing). As the above note, weight is a big issue - as is cost. The number of deaths in commercial aviation annually is very low as I understand it. ny156uk (talk) 11:13, 23 December 2007 (UTC)[reply]
Gah—sprinkler system on an airplane...too much weight! Water is heavy stuff. Carrying a couple of tons of it around on the aircraft everywhere it flies...ugh. 'Dry' systems that use carbon dioxide or other gaseous fire suppressants would pose a risk of asphyxiation to passengers and crew. Materials used in aircraft construction (particularly in the cabin) are required to be fire-retardant; they burn poorly anyway, if at all. The insurmountable obstancle is that you're lifting off with a hundred tons of fuel on board, and if you break open some fuel tanks in a crash, then there's going to be fuel everywhere. Putting out those sorts of fires takes professional firefighters with heavy equipment. (Attempts have been made to make jet fuel safer in a crash; these attempts have not been successful.) For what it's worth, many of the mechanical spaces on aircraft – the place where in-flight fires are likely to start – do contain fire bottles filled with fire suppressants. In the event of fire, these bottles are triggered automatically or manually from the cockpit. (I have also seen small, automated fire bottles built into airplane washroom waste receptacles, presumably to handle butts from careless, covert smokers.)
On the subject of crumple zones, the legs of airline seats are designed to collapse in a controlled manner to cushion the occupant in the event of a crash. Airbags, meanwhile, are unlikely to appear on commercial aircraft for a number of reasons. First, it would mean putting rather a lot explosive material in the aircraft cabin—something that regulators are understandably twitchy about. Second, there's no good, automated way to figure out when the airbags should go off in an airplane crash. What if you're just on the first bounce? Third, detonating all those airbags in a relatively airtight cabin could force oxygen out of the passenger compartment. TenOfAllTrades(talk) 15:43, 23 December 2007 (UTC)[reply]
In the event of a water crash with airbags, the bags could prevent passengers from being able to exit the aircraft Rfwoolf (talk) 17:29, 23 December 2007 (UTC)[reply]
Also, the accelerations a body is exposed during a crash are incredible. The report into the Swissair Flight 111 crash off Nova Scotia in 1998 suggested that the occupants were subjected to forces at least 350 g, [18] which is well beyond the limits of human survivability. It is likely impossible to create a system that will protect occupants at loads like that while still being flyable or affordable. -- Flyguy649talk 17:47, 23 December 2007 (UTC)[reply]
How much of a sphere can you see from one point?
Particulary to do with planets. I have always assumed it is 50% but I started thinking about it and I thought that it surely must be less, at some point the surface of the sphere will be paralel with your direction of vision. Is there some mathematical relationship that any one could write that would describe this?
Cheers, Shniken1 (talk) 05:10, 23 December 2007 (UTC)[reply]
Let be the distance between the observer and the center of the sphere. Let be the radius of the sphere. Then the apex angle of the visible spherical cap is . Using the formula found in the solid angle article, the solid angle of the cap is . Since the full solid angle of the sphere is , it means that the visible surface area is . If , this ratio approaches . - Sikon (talk) 07:15, 23 December 2007 (UTC)[reply]
All of it... provided it's completely lit with nothing obscured, and you use a few mirrors. Of course, that's assuming mirrors are not disallowed in your question. Though, if we're talking planets, those giant mirrors can get expensive. (Sorry, couldn't resist.) -- HiEv 10:09, 23 December 2007 (UTC)[reply]
Giant mirrors? What are talking about? --Taraborn (talk) 13:35, 23 December 2007 (UTC)[reply]
He was making a joke about the scale of planets necessitating a giant mirror to see the sides out of view. -Wooty[Woot?][Spam! Spam! Wonderful spam!] 13:51, 23 December 2007 (UTC)[reply]
Well, you could do it with smaller mirrors and use a telescope. It does raise an interesting side question though: how many mirrors would you need? (I'm guessing 2, but possibly 3?) --SB_Johnny | talk 14:07, 23 December 2007 (UTC)[reply]
Oh. I didn't see the "All of it..." part... --Taraborn (talk) 14:43, 23 December 2007 (UTC)[reply]
When I'm out flying in my spaceship, I always measure the angle that the planet covers from my point of view and the distance to the surface. That way, I get the planet radius as
Oils have very distinct tastes depending on what their made out of. Just because it's an oil, it doesn't mean they're all going to taste the same. An analogy could be made to different types of nut butters (i.e. peanut butter, cashew butter, almond butter, etc.) -- MacAddct 1984(talk • contribs) 16:14, 23 December 2007 (UTC)[reply]
The bitterness of Olive oil depends on the concentration of polyphenols such as Oleuropein. William Avery (talk) 17:02, 23 December 2007 (UTC)[reply]
And, of course, any oil that gets old and rancid tends to taste more-bitter than fresh oil.
Hi. What causes snow to turn different colours, say pink, green, or blue? Is it bacteria? Chemical reactions? Minerals? I heard that pink snow was called watermelon snow, I saw green snow on a probably-salted outdoor staircase, and I saw blue snow while building a snowball while the temperature was above freezing. What other colours are there, besides yellow caused by dog pee, and brown caused by road ploughed snow? Thanks. ~AH1(TCU) 15:32, 23 December 2007 (UTC)[reply]
For watermelon snow, it's a type of algae that produces the color. I'm not sure about the other colors though, maybe it could turn blue if a colored brand of rock salt was laid down? Just don't eat the yellow snow! -- MacAddct 1984(talk • contribs) 16:10, 23 December 2007 (UTC)[reply]
Some commercially available ice-melting salts have dyes added to let you see where you've spread it. I've seen magenta, blue and green. -- Flyguy649talk 21:26, 23 December 2007 (UTC)[reply]
With regard to light-blue snow, you might enjoy our article Color of water.
telescope aperture required to view astronomical objects
Hi. Can you use the brightness in apparent magnitude of an object, the surface brightness at the site, the surface brightness of the actual night sky at the location of the observing site, the atmospheric conditions, how high an object is in the sky, the capability of the person's eyes, etc, to calculate the effective aperture of a telescope required to actually see and recognise an object apart from the background sky? If possible, please give a relatively simple understandable formula that directly takes the numbers of the factors and uses the numbers to directly calculate to a specific aperture that can be calculated using a scientific calculator and all algebraic symbols must be explained as to what it stands for and the formula can be used to provide an answer in the calculator withought confusion? If you have a formula, also please provide the units that each number is in. If you don't have a direct formula, can you use the numbers to do a simple estimation that isn't exact but uses the numbers directly? Also, as a side note, is the formula for the area of an oval π(sR * lR), where the symbol on the left is pi, and sR is half the shortest diameter and lR is half the longest diameter? If it's something else, can it be found on the article for oval? Thanks. ~AH1(TCU) 19:01, 23 December 2007 (UTC)[reply]
If you mean an ellipse, then your formula is correct. Not every oval is an ellipse.
Considering the telescope aperture, I don't know a detailed formula for all the factors, but maybe this formula for the maximal magnitude helps you:
where magmax,eye is the maximal magnitude you can see with your eyes, d is the aperture, deye is your eye's aperture (maximally 4 mm) and lg is the logarithm on base 10. This assumes the object to be point-like.
Why is the moon held in lock-step with the earth so only one aspect is visible, in contrast to the earth which is not similarly bound to the sun? - CarbonLifeForm (talk) 20:43, 23 December 2007 (UTC)[reply]
Check out the article on tidal locking and come back if you want more :) --Ouro (blah blah) 21:15, 23 December 2007 (UTC)[reply]
Gravity gets weaker the further away from the sun (or earth) you are. Tidal effects come about as a result of the difference in the strength of gravity because one side of the orbiting body is further away than the other. That difference stretches the moon or planet slightly in the direction of the tidal force - if the body rotates, it is continually pulled and squashed by the tides (here on earth we can see the effects of that in the tides from our oceans - but it applies to solid rock too). This 'kneading' of the material requires energy and the energy comes from gradually slowing down the rotation of the object. Eventually, the body loses all of it's rotation and winds up with one face pointing towards the center of the orbit...typically the heaviers side, as you might expect.
The reason the earth isn't tidally locked - but the moon is, is because the Earth is about 150 million kilometers from the sun - but it's only around 13,000 km across. So as a percentage of 150 million km, the diameter is tiny - just one part in 10,000 - so there is very little difference in the sun's gravity between the two sides of the planet - and hence, very little tidal forces. The moon, is about 400,000 km from the earth and 1,700 km across one part in 300. So the difference in gravitational force between the two sides of the moon is large - but the difference across the earth is tiny. The moon's gravity has a much bigger tidal effect than the sun's (because we are much closer) - but the moon's gravity is only one sixth of the earth's - and the earth has much more rotational inertia. Eventually, even that tiny effect will cause the earth to be tidally locked so that one side of the planet will face towards the moon which will always appear in the exact same place in our sky.
That will result in the earth rotating just once a month - so our "day" would be a whole month long. But that's going to take a long time. Pluto and it's moon, Charon have already arrived at this exact situation because they are much closer to each other and they are of much more equal sizes than Earth and the Moon. As a result. they are both tidally-locked to each other.
There are two details to add in the above, both of which strengthen Steve's point. First, 1/6 is the strength of gravity at the Moon's surface in proportion to that at the Earth's surface. The relevant number here is 1/81, which is the mass of the Moon in proportion to the Earth. (Gravity at the same distance from the center of the respective bodies will be in this proportion.) And second, gravity doesn't just diminish with distance, it diminishes as the square of the distance. When you consider this in combination with the explanation above, it works out that tidal effects diminish as the cube of the distance. (Or using calculus: the derivative of 1/r² is proportional to 1/r³.) --Anonymous, 05:43 UTC, December 24, 2007, Earth.
battery
The battery of an electronic device originating in China opened (poor quality glue). The sticker claims that it is a Li-ion but it looks like it might not be. The highlighted part on the right is a weight which was glued inside the battery casing, and the highlighted part on the left is weird strip that appears to short-circuit that battery cells - it's silver at the terminals but black along its length. Any idea what that strip is? --SeansPotato Business 22:59, 23 December 2007 (UTC)[reply]
what makes you think it's not a li-ion cell? Could you post a clearer picture? Is the strip conductive? Does it actually connect to both terminals? Is the other terminal actually at the bottom of the battery? Furmanj (talk) 00:57, 24 December 2007 (UTC)[reply]
It looks like it's a 2 cell battery. Get a multimeter and measure the voltage. If the battery measures > 4V, then it's Li-Ion. Li-ion BTW in cylinderical form looks no different then regular batteries except for it's size. Lithium ion polymer are the ones that comes in flat retangular shapes. I can't tell for certain from your picture but it does look like li-ions. The hint is the little device at the top, it should be a protection/charge circuit. Regular alkaline battery would not need this. Are you sure the black strip is not a piece of wire? You would need to connect both end of the battery to use it. The black strip looks like it's the negative wire. NYCDA (talk) 19:29, 24 December 2007 (UTC)[reply]
Number of animals consumed during a human lifetime
I recently read a novel about vampires who had to kill someone for food every night. This made me think that in a way, non-vegetarian humans are like vampires - we kill to live. We eat animals, and also use leather. I'm not a vegetarian, and I wonder how many animal deaths I will be indirectly responsible for during my life? I often eat tinned sardines which have three or four lives in them. On the other hand eating a portion of bacon, which I never eat, only requires a small fraction of a whole animal. Does anyone know what my likely total score of animal deaths will be during my lifetime please? If I turn up at the pearly gates and find that God's a vegetarian or gives equal worth to animal souls, then I'm in trouble! This is not a pro-vegetarian rant, I'm just curious. 80.2.209.76 (talk) 23:50, 23 December 2007 (UTC)[reply]
EDIT:this more credible looking site, but still just a random guy's blog breaks it down into, "4 head of cattle, 21 sheep, 15 pigs, 1200 chickens and 13,345 eggs." A-ha! This same question was asked on Yahoo! Answers, which came up with about 6,600 animals, almost all of them Chicken & Fish. See the site for a more detailed explination (ot not!) of how those figures were derived. --YbborTalk 00:25, 24 December 2007 (UTC)[reply]
Okay, so it's one of those 'I heard it somewhere' stats - but apparently your average human will inadvertently consume 1lb of insects (or parts thereof) in a lifetime. --Kurt Shaped Box (talk) 00:42, 24 December 2007 (UTC)[reply]
I think it's higher than that. I used to room with an agriculture major, and if I recall correctly, the USDA allows ground flour and other processed grains to be as much as a few grams insect parts per kilogram of product. Dragons flight (talk) 00:56, 24 December 2007 (UTC)[reply]
Hmmm. It may even have been 1lb *per year* then... Yikes. --Kurt Shaped Box (talk) 13:19, 24 December 2007 (UTC)[reply]
If one reckons lives like Renfield in Bram Stoker's Dracula, then he must total up not only the creatures he consumes, but the creatures they consumed as well, and the creatures consumed by them, etc. We eat few carnivorous mammals,(perhaps an occasional barbecued raccoon) but birds (including fowl) like to eat insects and worms. Many fish are also little predators. Edison (talk) 05:24, 24 December 2007 (UTC)[reply]
But what about all of the microscopic animals that we ingest all the time without even realising it? Those must amount to vastly more than the number of large mammals, fish, birds, etc. SteveBaker (talk) 14:15, 24 December 2007 (UTC)[reply]
Unless you're counting 1 cow equaling 5 steaks or something, the number of individual animals killed, it's way higher than 1000 or even 6000. If you have, let's say on average, 2 different kinds of meat a day. That's 700 animals a year alone. That's a pretty low estimate, considering a hamburger, made from ground beef, is a collection of a whole bunch of different cows. Or chicken fingers, which are processed from a whole bunch of different chicken. -- MacAddct 1984(talk • contribs) 17:21, 24 December 2007 (UTC)[reply]
It all depends on how you count things. The question is, does the tiny bit of meat from each animal count as a whole animal, or are you allowing "fractional animals"? For example, if you have something like sausage it may be made up of meats from many different animals (though they may all be the same type of animal). If even microscopic amounts add another animal to your total, then breathing in or inadvertently eating pet dander from your pets counts towards your total. That makes your count ridiculously high, and impossible to measure. Also, it's not like you're consuming the whole animal yourself either, so this inflates the "death total" since one animal is recounted for every person who eats even a tiny part of it.
If, on the other hand, we use "fractional animals" instead, then any meat you consume counts towards the average amount of edible meat made from that kind of animal. If, for example, the average pig has 50 units (lbs/kg/whatever) of edible meat made from it, then you would only count up by one pig after you've eaten 50 units of ham/pork chops/etc., even though you may have eaten meat from many different pigs. This way, a pepperoni pizza only adds a tiny fraction of an animal to your animal total, as opposed to many animals. This gives you a much more realistic and countable measurement.
Finally, if the Judeo-Christian God exists, then there are numerous passages in the Bible that say that some meats are OK while others aren't (for example, see Leviticus 11), so that god isn't a vegetarian. Heck, according to the Bible the reason why God favored Able over Cain is that Able (a shepherd) sacrificed animals to Him, while Cain (a farmer) only brought plants (see Genesis 4:2-5). God also finds the smell of burning animal flesh pleasing (see Leviticus 3:3-5 & 3:14-17). I don't believe in gods myself, but if you're worried about that one then your problem isn't the number of animals, but the type, portions, and method of preparation. -- HiEv 04:47, 25 December 2007 (UTC)[reply]
The number of individual lifeforms in one mouthful of a microbial culture such as cheese staggers the imagination. Do they count? If God cares about the numbers, I wouldn't worry about the cows when you get to Heaven - it's the quadrillions of bacterial deaths you've caused in your lifetime that you'll be responsible for. 74.12.208.131 (talk) 17:00, 25 December 2007 (UTC)[reply]
December 24
Ugh! What the hell is this?
I ran across an image out there in the great wide Interweb, of a closeup of the index and middle fingers of a man who appears to be suffering what can only be a very uncomfortable condition (Warning: rather disturbing image: http://ninjapants.org/files/index.php?image=goodmorning.jpg) All of the detail of the image lead me to suspect that the image is authentic, but I'm at a complete loss at to the condition from which this poor person may be suffering. Does anybody have any ideas? – ClockworkSoul 05:32, 24 December 2007 (UTC)[reply]
I'd say without too much hesitation, and apologies for any disappointment, that this image has been altered. There are several clues that hint towards this. Firstly the bizarre image of an apparent serious medical condition is presented with a desktop and mouse in the background. If it had been photographed in some sort of 'medical' context it would look more realistic. Second off, the image shows some odd anomalies that indicate some sort of photographic manipulation. Look at the fingerprint whorl on the finger on the left, it appears completely misplaced. Whorls are normally, but not exclusively, on the pad of the digit. There are also some other signs of post-production manipulation around the edges of the 'what-ever-they-ares'. There is a complete absence of any inflammation around these peculiar 'wounds': it is conceivable that if they were long duration injuries they may not have visible signs of inflammation, but in my experience they would. Next, the inside of the finger pulp does not look like that (unless you are some sort of alien), the image shows the matrix of possibly some sort of fruit or vegetative specimen. Finally, the whole medical appearance looks entirely improbable, what are those white 'teeth' looking bits, where have they come from and what is keeping them there. As you say the rest of the images on this site seem to be authentic, some pretty odd, but not manipulated. I would be very pleased if someone could demonstrate with a reasonable degree of authority that this is some sort of traumatic condition, but for the moment I am not any bit convinced.Richard Avery (talk) 10:31, 24 December 2007 (UTC)[reply]
Just trying to find out the difference. Ive read alot of lorcets are with tylenol and lortabs are with aspirin but none of these sources are doctors or nurses or pharmacists that definitly know the answer. so please anyone that is knowledgeable in this feild answer only and let me know if what info i have dug up myself is correct. thanx.
(just unindented the question) --Ouro (blah blah) 06:39, 24 December 2007 (UTC)[reply]
http://www.druglib.com is a good place to go to look up the ingredients of common drugs. Our article Hydrocodone lists the active ingredients of Lorcet and Lortabs - but notice that there are many variations of both product with different dosages, etc. There appears to be only one variation ("Lortab ASA") that contains asperin - all of the other Lortab/Lorcet varients contain acetaminophen (also called "paracetamol" outside the USA). Acetaminophen is also the active ingredient of Tylanol but it would not be strictly true to say that either Lorcet or Lortab contains Tylanol - although the result may well be the same. For a definitive answer, you should read the ingredients on the actual medication bottle and for medical advice in general, you should see a doctor. SteveBaker (talk) 14:05, 24 December 2007 (UTC)[reply]
Breathing rate
How many litres of air (not just oxygen) does the average person intake with each breath? -- Danilot (talk) 11:17, 24 December 2007 (UTC)[reply]
See Lung volumes - this suggests it's about half a litre. I also found this, which gives some stats on volume per minute under various conditions. AndrewWTaylor (talk) 11:27, 24 December 2007 (UTC)[reply]
Floating in a black hole
Is it possible that we are all floating in a big black hole? Is there a way you can tell when you are in a black hole? Is it possible that whole observable universe is floating in very big black hole? If is possible, how big must it be?
I disagree with Mysid. If the black hole is large enough, tidal forces are small at the event horizon. The Schwarzschild radius is proportional to the mass m, while tidal forces are proportional to 1/r3; therefore, tidal forces at the event horizon are proportional to 1/m3. Icek (talk) 13:02, 24 December 2007 (UTC)[reply]
Indeed - Mysid is way off the mark. With a sufficiently large black hole, there would be negligable tidal forces - even within the event horizon. SteveBaker (talk) 13:51, 24 December 2007 (UTC)[reply]
Some strange thought that I just had: Could the expansion of the universe be described by the whole observable universe undergoing tidal forces? Viewed in the frame of a resting observer at different distances from 3/2 * rS to rS from the black hole's center, the circumference around the black hole gets larger the nearer you come to the event horizon (where it diverges). This provides for the expansion in 2 dimensions, while tidal forces explain the expansion in the remaining direction. But I've not done the math yet, and it's of course not the same for the falling observer. Icek (talk) 13:09, 24 December 2007 (UTC)[reply]
What do you mean by "floating in a big black hole"? We couldn't be inside a black hole—the pressures would be far too high to support anything like life. Could we be floating around a black hole, in orbit? Sure, but you'd really be asking "is our solar system rotating around a black hole at the center of the galaxy", which is, if I recall, what they think is at the center of the Milky Way (see Sagittarius A*). --24.147.86.187 (talk) 16:00, 24 December 2007 (UTC)[reply]
Wouldn't we be seeing some really weird effects, like everything that's between us and the center is completely still, and everything outward is accelerated? Of course, if the radial difference is in a different dimension then it might not be quite as obvious, but a few smart apples would be able to tell what's going on. Also, it would have to be a GIANT black hole for us to still be alive right now. --ffroth 20:14, 24 December 2007 (UTC)[reply]
There's no exact mathematical definition of what a black hole is, so there's no right answer to this question. The interior portion of the Schwarzschild solution makes a plausible cosmological model, and I'm sure it was considered for that role at some point in the history of modern cosmology. It's even homogeneous (the singularity is in the future, not in a particular spatial location). But it's a terrible fit to observation in other respects, and the other standard black hole solutions aren't any better. For example, they're all contracting in two spatial dimensions and expanding in one -- or vice versa if you use the time-reversed white hole solution -- so they predict redshift in some directions in the sky and blueshift in others (I think).
Contrary to what some people have said, the Schwarzschild interior is perfectly inhabitable in principle if m is large enough. How large? Er, I don't know, but it needs to be at least circa (c3/G)t, where t is the amount of time you want to survive before hitting the singularity. For t on the order of the age of the universe, that comes out to about the mass of the observable universe. But don't read anything into that -- it was bound to happen because of dimensional analysis alone.
In the big crunch scenario the ultimate fate of all the matter in the universe is to hit a black hole singularity. Since a black hole event horizon is the boundary between stuff that necessarily hits the singularity and stuff that doesn't, you could argue that everything in the universe is already inside the event horizon of this final black hole. But this is a dubious use of the word "inside", since there's no outside (and no event horizon/boundary either). I'd tend to say that this pathological case shouldn't count as a black hole interior. The traditional big crunch scenario is ruled out in any case. it's possible that the quintessence might cause a recollapse (depending on what the quintessence actually is), but I don't know how much this recollapse would resemble black hole solutions.
I'm also tempted to answer "humbug". Black holes get way more press than they deserve. The universe is pretty interesting whether or not it resembles a black hole. -- BenRG (talk) 07:33, 25 December 2007 (UTC)[reply]
Was there a solar eclipse in Ukraine on 12 August 1654?
I am reading a historical account of a battle and there is a claim of one, but the account is old and I'd like to verify it before putting in into the article; I'd assume we have means of calculating and verifying if a solar eclipse could have occurred in a specific region on a specific date? I couldn't find a comprehensive list or how to in our articles on Wikipedia, unfortunately. --Piotr Konieczny aka Prokonsul Piotrus| talk 17:56, 24 December 2007 (UTC)[reply]
There is a list of solar eclipses as well as a section on historical eclipses, neither of which are particularly helpful in your case. There's also this NASA image to the right, so they obviously have some record of 1000 years of solar eclipses. -- MacAddct 1984(talk • contribs) 18:07, 24 December 2007 (UTC)[reply]
This eclipse map may be easier to read. The path of the total eclipse of 1654 Aug 12 goes right through the middle of the Ukraine. - Nunh-huh 18:32, 24 December 2007 (UTC)[reply]
How do you, electrically, take an analog input and isolate only the signal that's on a certain frequency? This seems like a fundamental component of radio recievers, but I can't decipher our extremely-technical radio articles to figure out how it works. Just what is happening when I turn the dial on an old radio? --ffroth 20:01, 24 December 2007 (UTC)[reply]
An LC circuit has a natural resonance frequency, and so it captures the signal specific to that frequency while excluding others. By adjusting the inductor (the L in LC), you can tune the circuit to match the radio's sensitivity to the frequency you want to listen to. Dragons flight (talk) 20:12, 24 December 2007 (UTC)[reply]
You use a filter. The LC circuit is an example of this. How it works is that energy is alternatively exchanged between a current with magnetic field in the inductor, and a charge with electric field in the capacitor. This happens at a particular frequency. When you add a loss this does not oscillate for ever, and instead you get a filter that roughly lets through a range of frequencies. There are also crystals that ring like a bell and also allow only a narror range of frequencies. Graeme Bartlett (talk) 20:28, 24 December 2007 (UTC)[reply]
Makes sense. But where in this do you connect the actual signal wire? And how do you set the frequency? Are the capacitors/inductors somehow powered separately from the LC circuit? --ffroth 20:35, 24 December 2007 (UTC)[reply]
Hm, well I found Variable capacitor, but I don't understand it. How does the capacitance have anything to do with frequency? --ffroth 20:38, 24 December 2007 (UTC)[reply]
The resonant frequency is a function of the magnitudes of both the inductor and the capacitor. Make either variable and you can vary the resonant frequency (and so, pick your station). Most radios use a variable capacitor; older automobile radios often used variable inductors. Nowadays with electronically-tuned radios, the variable capacitor is more often a varicap than a physically-adjustable capacitor.
(edit conflict) Resonance is the key. Here's an over-simplified rendition:
There are basically three sections in an old radio that deal with higher-than-audio frequencies, in this order: the RF (radio frequency) amplifier, the mixer, and the IF (intermediate frequency) amp(s). The RF amp does nothing more than amplify (add power to) the signal from the antenna, amplifying the whole mess of jumbled frequencies across the band it's designed to receive. We'll come back to the mixer. The IF section is tuned to pass only one frequency, the intermediate frequency, which becomes the new carrier for the actual audio signal to be detected later.
The real magic happens in the mixer. Two signals are fed into the mixer: the output of the aforementioned RF amp, and the output of the local oscillator. These beat together, producing harmonics all over the place. The local oscillator sits there the whole time ringing at a single frequency determined by where you have the knob set. It is designed to oscillate at a frequency different from the frequency of the station you want to tune by a difference equal to the intermediate frequency. The mixer and IF effectively perform an analogue subtraction, and the difference is the IF. The IF stage can only pass the intermediate frequency, so it acts like a filter. A side benefit is that the IF is a lot lower than the RF and is therefore easier to control and contain. Darned clever, eh? Some inventions are obvious once somebody's done it, but this ain't one of them.
To answer the other question, when you turn the knob you are rotating a row of semi-circular aluminum discs such that they interleave to a greater or lesser extent with similar fixed semi-circular discs, thereby changing the capacitance between them. This capacitance dictates the resonant frequency of the local oscillator. --Milkbreath (talk) 20:43, 24 December 2007 (UTC)[reply]
Grr, that doesn't make any sense. How can you use analog interference to change frequencies? That would be utterly destructive! --ffroth 03:28, 25 December 2007 (UTC)[reply]
The "magic" of heterodyning is that this mixing in the frequency domain does not destroy the signal in question. Instead of destroying the signal, it demodulates it. Nimur (talk) 08:03, 25 December 2007 (UTC)[reply]
Nothing gets demodulated in the mixer stage. When you beat two frequencies together, you get interference. It's just like the way you get a "beat" note when two musical notes clash. If you and another person whistle the same note, and one of you lets his note go slightly sharp or flat, you will hear the beat, which is the difference frequency. The difference frequency is explained here. Only the difference frequency that is equal to the IF will pass. The original modulation is obviously retained. --Milkbreath (talk) 13:38, 25 December 2007 (UTC)[reply]
Your explanation is incorrect. Beating happens when two signals (of similar frequencies) are combined additively. A mixer works by combining two signals multiplicatively. --72.94.50.57 (talk) 16:05, 25 December 2007 (UTC)[reply]
Hey, I'm no physicist, I'm an ex–First Phone and repair tech. I figure the guy who wrote the Shrader knows more than anybody here, and it says: "...mixing, beating, or heterodyning one frequency with another in a non-linear circuit... The result is always at least four output frequencies: (1) one of the original frequencies, (2) the other original frequency, (3) the sum of the two frequencies, (4) the difference between the two frequencies." (author's italics) (Electronic Communication. Robert L. Shrader. McGraw-Hill:New York. 1975. p.396) Suffice it to say that interference happens, and a difference frequency is produced. --Milkbreath (talk) 19:08, 25 December 2007 (UTC)[reply]
One quick comment: An RLC circuit is the electronic equivalent of a mechanical dampedharmonic oscillator. The inductor provides the inertia (it resists changes in current just like inertia resists changes in momentum), the capacitor provides the restoring force (it stores energy when displaced from equilibrium, like a spring), and the resistor provides the damping. So if you can see why a mechanical harmonic oscillator has a resonant frequency, it's not that hard to see why an RLC circuit has a resonant frequency. Instead of a mass moving back and forth periodically, it's charge carriers flowing back and forth. —Keenan Pepper 02:46, 25 December 2007 (UTC)[reply]
It's pretty easily discernable from looking at its lewis structure (sulphuric acid). But then, you have to keep in mind that many resonance structures are possible. Someguy1221 (talk) 04:53, 25 December 2007 (UTC)[reply]
Please don't double-post. Hint: The more electronegative atom formally receives a electron from the less electronegative atom when forming a covalent bond. Now It's a matter of counting the bonds. Icek (talk) 15:23, 25 December 2007 (UTC)[reply]
My mother was given this plant as a Christmas present and we are trying to identify it. It has a lot of tall thin shoots that put me in mind if miniaturised bamboo, with lots of leaves branching off from the main stalk. It also appears to have a bunch of bulblike things around the bottom, but I'm not entirely sure if they're part of the plant or just decoration. There is no identifying marks on the bowl or the plant other than a label for the store from which it was purchased.
I have two pictures of it, here and here. Any help is appreciated! Maelin (Talk | Contribs) 07:32, 25 December 2007 (UTC)[reply]
At first sight it looks like a number of avocado stones have been planted together and these are the resultant young avocado treelets. The round things at the 'soil' surface are the stones from avocado pears, they have split to permit the shoot to emerge. If this is so then you have a bit of a problem in a couple of years because these trees grow up to 3 or 4 metres tall. My only doubt is that a dozen or so of these stones should be planted together in a single pot. Here [19] is a site that shows how to grow avocados. Have a Happy Christmas! Richard Avery (talk) 09:15, 25 December 2007 (UTC)[reply]
About Plant's Cells
Tell how can I know about mechanism of plant's cells (specially root), their performances ,in different situations do they do instinctive or intelligently? In their inside construction how organs work and how chemical processes and electricity... are involve? Is there any perfect articles, links or references?Flakture (talk) 15:10, 25 December 2007 (UTC)[reply]
did you try Plant cell and the links and references therein? Furmanj (talk) 16:46, 25 December 2007 (UTC)[reply]
I don't think that the words instinct or intelligent can be applied to any discussion about plants. Their cells just function in the way that they're "programmed" according to their DNA and epigenetic arrangement and extracellular (i.e. from other cells or the environment) incoming signals. --SeansPotato Business 22:44, 25 December 2007 (UTC)[reply]
Exactly. Plants don't have brains or brain-analogs, so the terms "intelligence" and "instinct" don't really apply to them (except perhaps in the broadest and least meaningful sense of those terms). In addition to that, plants only have a few organs. If you're talking about plant cells perhaps you meant "organelles"? You should probably reword your question based on these comments so we'll have a better idea of what you're looking for. -- HiEv 01:51, 26 December 2007 (UTC)[reply]
reactions to drugs
Is a person's reaction after smoking cannibis at all genetic (e.g. Red, eyes, paranoia, sense of floating). Only asking because a friend of a friend of a roommate of one of my distant cousins said he noticed this. Thanks, schyler (talk) 00:30, 26 December 2007 (UTC)[reply]
Sex - Related
medical question removed
I'm sorry, but you are, by the definition of the word, requesting a diagnosis. And so I must apologize, but this is precisely the kind of question that the reference desk guidelines prohibit asking or answering. Someguy1221 (talk) 02:53, 26 December 2007 (UTC)[reply]
![[19]](http://images.google.co.uk/imgres?imgurl=http://www.permaculture.org.au/topics/images/avocados/3.jpg&imgrefurl=http://www.permaculture.org.au/topics/avocados.php&h=150&w=113&sz=7&hl=en&start=14&tbnid=L0yT3z--TCXOCM:&tbnh=96&tbnw=72&prev=/images%3Fq%3D%2522growing%2Bavocados%2522%26gbv%3D2%26svnum%3D10%26hl%3Den%26sa%3DG){kind=link}