Wikipedia:Reference desk/Archives/Science/2007 January 26 & 27

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January 26[edit]

Breed and race...?[edit]

Other than one being applied to dogs and the other being applied to humans what is the difference in the terms? -- Barringa 10:24, 26 January 2007 (UTC)

According to our breed article, a breed is a domesticated subspecies or infrasubspecies of an animal. By contrast, according to race, different races of humans are typically populations differentiated by some attributes (e.g. skin color) and not others (e.g. height) and are not identified as subspecies in the biological sense by scientists; it is disputed whether there is a substantial genetic basis for the common racial divisions or whether they are simply a social construct. See breed and race for more information. -- SCZenz 10:54, 26 January 2007 (UTC)
In other languages, such as French, there is a less strong distinction. I remember once being taking a back when an elderly French woman asked me what race of dog I had. --Cody.Pope 15:57, 26 January 2007 (UTC)
Landrace is often used for traditional crop varieties. But a breed isn't necessarily a subspecies - different breeds of dog or cat are certainly not subspecies. Guettarda 16:18, 26 January 2007 (UTC)
One simple difference is that dog breeds were created - and maintained - by strict inbreeding. This is how members of the same breed are so alike. Human races, while certainly inbred at some point due to evolutionary bottle necks, are rarely maintained in that way. Infact, human races are becoming more outbred with every generation. This is why members of the same race can look so different to each other (with perhaps some defining features, such as skin tone, in common). So, to stretch an analogy, these days almost all humans would be considered mongrel in dog-breeding terms. We simply divide ourselves into somewhat arbitrary groups ("races") based on certain artifactual characteristics, be it geo-political, cultural or physical. There probably are what we might consider relatively "pure-bred" humans in remote parts of the world. But even those are not inbred to anywhere near the same level as animal breeds. For humans races to be truly equivalent to animal breeds, we would need to go adopt techniques from the Master race philosophy, involving racial segregation and eugenics. That is generally not seen as a favourable course of events in human history. Rockpocket 23:20, 26 January 2007 (UTC)
What about in cases which some religious groups represent where inbreeding is a natural consequence resulting from the virtual exclusion of "outsiders." -- 71.100.10.48 04:11, 27 January 2007 (UTC)
There are certain groups that are more inbred (and I don't mean that in a pejorative manner) than others for religious, geographical or cultural reasons. Endogamy is common in Ashkenazi Jews and the Yazidi, for example. Although the level of consanguinity is high in some of these populations, it still doesn't match the level of inbreeding required to create a breed or strain of domesticated animal. To create true breeds, one needs to backcross or intercross through many generations. Its difficult to get good data on dogs, but we could use lab mice as an example. The guidelines for generating inbred mouse strains, first published in 1952, state:
"A strain shall be regarded as inbred when it has been mated brother-times-sister (hereafter called btimess) for twenty or more consecutive generations (F20), and can be traced to a single ancestral breeding pair in the 20th or a subsequent generation. Parent-times-offspring matings may be substituted for btimess matings provided that, in the case of consecutive parent-times-offspring matings, the mating in each case is to the younger of the two parents. Exceptionally, other breeding systems may be used, provided that the inbreeding coefficient achieved is at least equal to that at F20 (0.99)." [1]
Even in the most inbred human groups, its rare for people to reproduce with anyone more closely related than a first cousins (there are very good evolutionary reasons for this). Parent/offspring and brother/sister breeding is almost universally taboo and thus is rare. For humans to be as inbred as mouse strains we would need subsequent brothers and sisters pairs to reproduce through 20 generations.
Dog breeds are not quite so genetically inbred as mice strains - especially not these days. Rather than strict backcrossing, dog breeding uses phenotype selectivity in mating (which is a kind of proxy for kin mating). When dog breeds were created they were done so for a purpose in mind. If you wanted to breed a lapdog, you would specifically select the characteristics you want (small, timid) and mate the animal that had these characteristics, with another animal that had these characteristics (often a relative). Similar selections would be made over multiple generations, thus enriching for these characteristics. Humans obviously select mates, but we do not all select for the same criteria (i.e. we are not all turned on by the same thing) and we are also less attracted to those that are most similar to us (see Major histocompatibility complex for a possible mechanism for this). So even in populations that are highly inbred, there is a natural propensity for humans to "outbreed" as much as possible. This is because inbreeding reduces genetic diversity and, inevitably, leads to reduced fitness (which is why mongrels tend to live longer than purebred dogs). Hopefully, then, you can why even the most inbred human "races" are nowhere near as genetically and physically homogeneous as breeds of dog. Rockpocket 05:22, 27 January 2007 (UTC)
So then from what you are saying, in tems of longevity, Racial purity as a concept or direction may not necessarily be that good for the human race, using the consequences for pure bred canines as an example? -- Barringa 13:45, 27 January 2007 (UTC)
See heterosis/hybrid vigour. -- 我♥中國 19:41, 27 January 2007 (UTC)
I think that is a fair assumption. Obviously we can't do the controlled long term experiments to prove it in humans explicitly. But the observations we make from naturally inbred human populations, and what we know from animal models (and plant models) seems to support that. For example, there increased levels of certain genetic diseases (including cystic fibrosis) in certain Pakistani and Ashkenazi Jew communities due to the cultural propensity for consanguinous marriages (see Ashkenazi Jews#Population genetics). See also our article on the founder effect, which results from breeding from a restricted gene pool (with similar genetic consequences to inbreeding). Rockpocket 22:08, 27 January 2007 (UTC)
See also Clinic for Special Children which treats effects in the Amish population. Rmhermen 01:54, 31 January 2007 (UTC)

Help me identify this insect[edit]

In the past days a few of these critters have been found in my house flying around. I'm located on the North Shore of Sydney. Any help would be greatly appreciated as I've been dying to find out what they are! http://img224.imageshack.us/img224/7646/img1855rs6.jpg http://img262.imageshack.us/img262/327/img1857um2.jpg JSIN 14:04, 26 January 2007 (UTC)

Those same insects swarm in Vancouver, Canada during the summer. I've always wondered what they were, besides a darned nuisance, that is. Anchoress 15:23, 26 January 2007 (UTC)
That, I think, is a lacewing. I found a useful Aussie bug identification site. --jpgordon∇∆∇∆ 15:48, 26 January 2007 (UTC) --jpgordon∇∆∇∆ 15:47, 26 January 2007 (UTC)
Thanks a lot. JSIN 08:15, 27 January 2007 (UTC)

Classification by genome...?[edit]

Are living organisms yet classified by their genomes and if so or if not how would such a classification scheme work? -- 71.100.10.48 14:24, 26 January 2007 (UTC)

That's a big question. Some systems of classification depend solely on genomic information, others incorporate other information or depend on genetics only indirectly. For further reading, I'd suggest starting with our articles on taxonomy, alpha taxonomy, cladistics, molecular systematics, molecular phylogeny, and phylogenetic tree. TenOfAllTrades(talk) 15:26, 26 January 2007 (UTC)
Under molecular phylogeny I found DNA barcoding which looks like the most practical scheme so far. -- 71.100.10.48 15:54, 26 January 2007 (UTC)

Some organisms are only known because some of their genes have been isolated. Techniques such as PCR and shotgun sequencing can identify new organisms that have never before been recognized and they can be classified based on gene sequence information. Some microbes are very hard to grow in the lab and are minor species in the wild, making genomic methods the best way to learn about them. --JWSchmidt 01:41, 27 January 2007 (UTC)

what is the concept[edit]

can you tell me the concept behind how a paper plane flies and aslo what are the advantages of the plane mention in www.zurqui.com over the simple plane .and the advantages or dis advantages of each over the other212.72.2.182 15:05, 26 January 2007 (UTC)

The upward force is called "lift", see Lift (force) for details. Friday (talk) 15:47, 26 January 2007 (UTC)
Most paper planes use flat wings and are weighted or designed so as to provide a slight upward tilt to the wing while flying. When you throw the plane, you are forcing a wedge through the air, literally pushing the air below the wing down, which provides "lift" from the bottom. In contrast, most airplanes use [airfoil] shaped wings, which lower the pressure of the air above the wings, thus "lifting" the wing from above via suction. Droud 05:28, 27 January 2007 (UTC)

please can you give me more details62.231.249.115 13:27, 27 January 2007 (UTC)

running and human body structure[edit]

What is the current research connecting running and the development of the human skeletal structure?

I recall reading something about it being highly efficient: the leg is structured in such a way that taking a step down stores a large proportion of the energy that would otherwise be directed into the ground, which can then be released on the way up. Vranak
I thought it wasn't efficient compared to many animals? --Wirbelwindヴィルヴェルヴィント (talk) 22:22, 26 January 2007 (UTC)
I can't figure out how the leg could store energy, is that really what you meant, Vranak? As to the specific question, scholar.google.com turned up some promising results, including this. Friday (talk) 22:29, 26 January 2007 (UTC)
Can't find any backing info on Wikipedia; have a look at Biped#humans for some hypotheses on why the human skeletal structure may have evolved to accomodate upright running. Vranak

Memory Systems[edit]

I'm aware of only a few effective, flexible memory techniques:

  • Association Systems
  • Associating visually via bizarre images
  • Associating verbally via bizarre sentences
  • Recoding nonphysical things as objects, followed by one of the above
  • Method of Loci/Memory Palace
  • Mnemonics
  • First-letter reminders
  • Acronyms
  • Nonsense or near-nonsense sentences (Please Excuse My Dear Aunt Sally, etc)
  • Verse
  • Endless Repetition
  • If content meaningful, finding logic and pattern
  • Writing it down

All of these, however, were discovered a long time ago. Has anything been worked out more recently that builds on or can replace them? Black Carrot 19:15, 26 January 2007 (UTC)

Well, there are stranger associations, like smells that trigger seemingly unrelated memories. Any of the senses can do this. When the memory is traumatic, such a trigger can cause a panic attack. StuRat 20:19, 26 January 2007 (UTC)
See Mnemonic which in turn provides links to a number of articles. The method of loci gave rise to a system used by memory performers, which is to have a well learned set of concrete memmory hooks in an ordered list. As a quick example, to remember 10 things, and be able to recite them first to last, last to first, every other one, etc, the rhyme "1 is a bun, 2 is a shoe, 3 is a tree, 4 is a door, 5 is a hive, 6 is sticks, 7 is heaven, 8 is a gate, 9 is a lion, 10 is a hen" is easily learned. Then you can make a vivid action association between each of 10 persons, object, appointments, grocery items or whatever with the hook for that place. If you have a 10 item shopping list for the grocery store, and item number 2 is cheese, then picture a shoe full of cheese, a shoe made of cheese, or some vivid image, the more action oriented or bizarre the better. An ordered list of 10 is good, but it is almost as easy to do a 26 memory hook list, where A is ape, B is bus, on through Z is Zebra, and remembering 26 items in order is fairly impressive. Professional performers will have a 500 hook list. For memorization, repetition is pretty ineffective, since the mind is conservative and slow to learn new material. It is essential to force the production of the material, by attempting to recite it, so that the gaps are evident.Overlearning is essential to recall under pressure. Spaced practice is needed for long term retention, because somehow overnight the short-term memories become more durable. See "The Memory Book: The Classic Guide to Improving Your Memory at Work, at School, and at Play" (Paperback) by Harry Lorayne, Jerry Lucas (1996) available at Amazon.com and amaze your friends, remember phone numbers, lock combinations, and passwords. But there are still people who are apparently born with amazing natural mnemonic ability. A friend told of a professor who was such a mneonist where he went to college. The prof had a class most freshmen took. He asked each on day 1 to state their name, their high school, and the nickname of the athletic team. He did not see him again until he was a senior, when he encountered the prof on the quad, and the prof greeted him by name and asked him "How are the Bulldogs doing this year ?" (That being the name of his schools football team). Edison 22:47, 26 January 2007 (UTC)

I've already read all the Wikipedia articles I can find on the subject, and I've had The Memory Book since I was a kid. Good book. Most of the stuff you describe falls squarely into the Association System category, which was developed to its current peak decades ago. Do you know of any new discoveries? Black Carrot 18:52, 27 January 2007 (UTC)

A techophile has devised a great memory aid: He records everything he sees, hears, or says with glasses mounted camera and microphone and a high capacity storage device, then uses artificial intelligence to index it.(Sorry, forgot his name). Another new discovery in memory is an Autistic savant named Daniel Tammet who was featured on 60 Minutes yesterday. He can store and retrieve 22,514 digits of pi and do amazing calculations and storage and retrieval feats. He is articulate and can describe the visual waysynesthesia by which he does it. He was also able to learn good Iceandicin one week, as an experiment, He has written a book called "Born On A Blue Day: Inside the Extraordinary Mind of an Autistic Savant." Perhaps you might derive some insights in memory from his writings or the language cources he offers. Edison 22:27, 29 January 2007 (UTC)

Now that's something I've never heard of. I'll see if I can get hold of his book. Thank you very much. If anybody else has ideas, the question's still open. Black Carrot 04:23, 30 January 2007 (UTC)

Oxidation state[edit]

What is the average oxidation number ) of Cr in (NH4)2Cr2O7? 72.140.201.32 22:57, 26 January 2007 (UTC)

What is the typical charge on NH4? How about ionic oxygen? Given that the total charge on the molecule is zero, do the arithmetic to figure out what the charge on chromium has to be to balance the others. DMacks 23:00, 26 January 2007 (UTC)

The compound is called ammonium dichromate - the article on chromate will give you the answer.83.100.132.60 23:30, 26 January 2007 (UTC)

Thank you both for your help. 72.140.201.32 23:53, 26 January 2007 (UTC)

Beta emitter capacitor(?) power and voltage...?[edit]

Beta emitter capacitor(?)

-- 71.100.10.48 23:41, 26 January 2007 (UTC)

Atomic Battery? Droud 05:44, 27 January 2007 (UTC)
Is this homework? --Cody.Pope 07:22, 27 January 2007 (UTC)
No. She just said that when I'm smart enought to answer this question then I can be the teacher. 71.100.10.48 12:46, 27 January 2007 (UTC)
Well, it isn't a capacitor, in the first place. But the problem is rather easy. I assume that the large size is so that you don't have to worry about solid angle considerations, and thus can just assume an infinite anode size. In that case (we are talking about Beta-'s, not Beta+'s, right?), it is a rather simple problem, but you have to make assumptions about the sources. I would suggest assuming that the source has a single beta- decay of energy E and an activity A. The only thing I'm not sure about is what happens at the air-anode junction, especially for electrons at a high angle of incidence. --Philosophus T 20:02, 27 January 2007 (UTC)
The "air" gap could be a vacumn but unless a Supercapacitor material would support it then it could not likely be made into a practical device. I think the distance between the plates can be optimized too. 71.100.10.48 22:56, 27 January 2007 (UTC)


How about a suggestion.One plate exposed to alpha emmisions and the other plate exposed to beta emmisions could very well be used to produce current, use it from either Nuclear Waste or other suitable sources10:26, 31 January 2007 (UTC).—The preceding unsigned comment was added by 61.1.131.49 (talk) 10:22, 31 January 2007 (UTC).

January 27[edit]

Gas laws[edit]

Why does the temoerature of a fixed mass of gas increase if the pressure is increased?

The total kinetic energy of the gas stays the same, so by decreasing the volume of the gas you are concentrating the energy, resulting in a temperature increase. Droud 05:41, 27 January 2007 (UTC)
Sorry to disagree with Droud, but I think this explanation is incorrect. If you decrease the volume of a container of gas while keeping its total kinetic energy the same (by allowing it to exchange heat with its surroundings) then the average kinetic energy per molecule is unchanged, so the temperature of the gas is unchanged (the "concentration" of the energy in a smaller volume is irrelevant to temperature). However, the pressure of the gas increases because the molecules are colliding with the walls of the container more frequently, as they are confined to a smaller volume. See the calculations in kinetic theory of gases. If, on the other hand, you decrease the volume of the container while preventing the gas from exchanging heat with its surroundings, then you increase its total kinetic energy because of the work you are doing to move the walls of the container against the gas pressure, so the temperature and pressure of the gas both increase - see adiabatic process. Gandalf61 09:49, 27 January 2007 (UTC)
At fixed volume and number of particles, the higher the temperature, the faster the particles move and collide with the walls, the higher the pressure exerted. In fact, the pressure is proportional to the absolute temperature. See Gay-Lussac's law. --Spoon! 05:50, 27 January 2007 (UTC)
Correct. Temperature is a function of the average kinetic energy of a gas. Increasing the temperature increases their speed so that they smash into the walls of their container more violently. --Soulscanner 01:40, 28 January 2007 (UTC)

Reporter Gene vs Selection Gene - Accepted distinction?[edit]

In a journal article I'm reading, a distinction is made between a "reporter gene", lacZ, used to produce a measurable indicator of gene expression and a "selection gene", HIS3, used to allow survival of only the cells that express the gene sufficiently. Until I read this, I had made no distinction, and would have referred to the HIS3 gene as a reporter gene. I'm asking, is such a distinction generally accepted? I've checked out the reporter gene article which implies no distinction but I'd like to be reassured. --Seans Potato Business 04:59, 27 January 2007 (UTC)

I guess one could argue the HIS3 "reports" its expression by the survival of the expressing cell. However, its not a very good "reporter" in that sense as its report lacks the information regarding the number of cells that doesn't express it (because they will be dead), and it also reports only a threshold of expression (alive or dead). In contrast, LacZ provides reports on both expressing an non-expressing cells, and can provide limited information on of the levels of expression. In contrast, LacZ could be considered a selection marker, but it doesn't do the selection itself (unlike HIS3), it only reports what needs to be selected. Therefore I would argue that there is a accepted distinction between the two, which this article makes clearer that I have. Rockpocket 05:37, 27 January 2007 (UTC)
In terms of the 'correctness' of the terminology, one can choose to make a distinction between a 'selection gene' and a 'reporter gene', or not. Selection genes can be described as a subset of reporter genes, but it is sometimes useful to treat them as distinct classes. This can be particularly handy when describing multiple transfections, where some have the purpose of selecting a specific population while others are used to report on gene expression levels through some sort of assay. TenOfAllTrades(talk) 05:46, 27 January 2007 (UTC)
The terms "reporter" and "selector" refer to how the genes are used. You could use LacZ as a selector, i.e. keep splitting cells until you only have blue ones. Generally, don't worry about the "proper" definition as long as you can understand what is being said.
Another difference is that the selector gene has an incentive for the organism to keep the vector/plasmid/etc... around. That property helps make sure that the organism replicates whatever foreign gene you place in it, instead of throwing it away. Rosen643 (talk) 02:43, 26 April 2009 (UTC)

Mikmd 20:41, 29 January 2007 (UTC)

Food Processing[edit]

If brown rice is better for you, why do companies go through all that processing trouble to make an inferior product (polished, white rice)? --Seans Potato Business 05:20, 27 January 2007 (UTC)

"White rice is the name given to milled rice which has had its husk, bran, and germ removed. This is done largely to prevent spoilage and to extend the storage life of the grain...." TenOfAllTrades(talk) 05:39, 27 January 2007 (UTC)
It shortens cooking time too, and increases the reliability of the finished product by reducing variability of cooking time and water requirement. Anchoress 05:42, 27 January 2007 (UTC)
Brown rice doesn't work for weddings. Droud 05:45, 27 January 2007 (UTC)
Our article on white rice says this:
While most of the nutrition is preserved by the milling process, many have relatively recently come to advocate brown rice or wild rice as a healthier alternative since the bran contains significant dietary fiber and the germ contains many vitamins and minerals (see whole grain). This is in contrast to the traditional view of brown rice, where it was associated with poverty and famine
If white rice was traditionally the choice pick for the upper classes, I'd have to assume it was for a good reason. It could be easier to digest, it could taste better, it could be a purer form of carbohydrate, though this is pure speculation. Vranak
The law of supply and demand: "Since the Atkins craze has subsided... one of the most common changes is eating brown rice instead of white, which has traditionally been the rice of choice in the United States." [2] Rockpocket 05:49, 27 January 2007 (UTC)
I'd wager the reason white rice is the preferred choice is elitism. Due to the extra milling involved, it's more labour intensive, and thus more expensive to produce. The richer households thus serve and eat white rice to show that they can afford it. Others then try to copy their "betters." Similar things happened in Europe with white flour and whole wheat flour. -- 18:10, 27 January 2007 (UTC)
That is correct! The upper-class in Japan pre-WWII ate only white rice and experienced a certain vitamin deficiency much more often than the rural class. X [Mαc Δαvιs] (How's my driving?) ❖ 20:39, 27 January 2007 (UTC)
I see. Well, thanks for the info! I've found that brown rice in a small box is only three eurocent more expensive per kilo than white rice in a big bag. I don't think I'll bother with the white stuff anymore. --Seans Potato Business 20:17, 28 January 2007 (UTC)

Rice: Cooking Time[edit]

The company that supplied my rice advises a cooking duration of 10 minutes. I've been extending that time to upto 30 or so minutes, having been exposed to the concept of fluffier, better rice. I think I've also noticed however, that after about three or four hours, I'm very much hungry again. Has extended boiling made the rice pass through the stomach stage of digestion more quickly? The rice article claims that 'rice porridge' is easier to digest. --Seans Potato Business 05:47, 27 January 2007 (UTC)

I don't know that easier to digest necessarily equals hungrier sooner, hunger doesn't elaborate but it says it is to do with glycogen in the liver, I certinally know i can eat some things that make me less hungry for longer without necessarily having to eat a lot of it. Before I gave it up I could eat a crap load of McDonalds and still be hungry two hours later, never thought that means it is easy to digest.. Vespine 02:56, 29 January 2007 (UTC)

Journal Article Collaboration[edit]

A journal article I have lists the contributors and their institutions. There are a few from Finland, one from the Netherlands, one from Autralia and one from the US. A large distance between contributors to a scientific paper is not an uncommon observation for me and I'm just wondering how it works. Do some of them travel to a common location and stay their for a while? Do some do some of the work and send their product to the next researcher so they can do their bit? How much does a person have to do to get their name included in the list of authors? What exactly goes on? --Seans Potato Business 06:16, 27 January 2007 (UTC)

Collaboration can be a complicated task: often the amount of contact depends on the nature of the science being practiced. For example, a bunch of particle physicists might meet at Fermi Lab or CERN for a particular experiment. However, sometimes the interaction is more tenuous, where a statistician, a physicist, and a chemist interact via only email for an entire paper. The only requirement to be listed on a paper is to sign a waiver that says "I have contributed a significant amount to the scientific process of this study". --Cody.Pope 07:19, 27 January 2007 (UTC)
Labs on different sides of the world may work on different aspects of a problem, communicating my email and telephone and occasionally sending material between them. I share authorship on some papers with individuals I have never met in person. One lab in Australia was working on bioinformatics analyses, another in Puerto Rico was collecting clinical data from patients and my lab, in Scotland, was using an animal model of the same disease. In the end the principle investigators collated the data and wrote the paper. The individuals listed on the paper all contributed either intellectually (by thinking up the experiments) or practically (by doing the experiments). Rockpocket 08:06, 27 January 2007 (UTC)
Sometimes the collaborators listed have actually very little impact on the published work, but control some resource that was invaluable. For example, a scientist I know is commonly a listed author solely because his lab developed a knockout mouse that is used by the experimenters of other groups around the globe; he's listed as an author, but did none of the experiments in the paper... -- Scientizzle 20:18, 27 January 2007 (UTC)
In the event that one of those experiments turns out to be a sham, are all the people listed as authors held responsible? I don't suppose there are many result-faking scientists: I only know of that Korean stem-cell guy. Just wondering... --Seans Potato Business 20:22, 28 January 2007 (UTC)
You can read our article on scientific misconduct for more about that. The bottom line is that there are result-faking scientists, but they are in a tiny minority. Co-authors do hold some responsibility if one of them are shown to have committed misconduct. Investigations will follow into exactly who knew what and when. However, there is obviously a level of trust involved when working with distant collaborators. As with most things it is rarely black and white. There is usually a grey area between co-authors being completely unaware of fraud, and being guilty of not being rigorous enough in questioning the results of their co-authors. You can understand how that happens, especially when the co-worker is well respected and providing amazing results that you want to believe ((such as in the Hwang Woo-suk case). See what happened to Gerald Schatten, for example. Rockpocket 21:14, 28 January 2007 (UTC)
In the field I am working in, theoretical physics, collaboration over distance is not such a big deal and quite common. As we mainly work with pencil and paper or with computer calculation, this stuff is easily to share via e-mail.The most common thing to happen is that a couple of people meet on a conference, have a stimulating discussion during the coffee break which results in a good idea, and then they decide to try to work out the details back home. There is even conferences with only few formal talks, mainly aimed at providing time for such informal discussions. Also, scientists move quite a lot, especially post-docs typically only get eployed for one, two or three years and then move on to another city. This is annoying but provides them with a network of contacts the world over. To keep up these contacts, e-mail and phone helps to continue to work together. Physicists like to stand together in front of black-boards and scribble calculations onto it. As this is difficult to do by phone, some collegues of mine like to point their webcam to the blackboard in their office, their collegue somewhere else does the same, and then they discuss using Skype. Simon A. 10:09, 28 January 2007 (UTC)
Thanks for the insight! --Seans Potato Business 20:22, 28 January 2007 (UTC)

transformers?[edit]

if the output voltage is coming out to be a lot less than that suggested by the turns ratio, what could be the possible reason?

59.180.32.227 07:40, 27 January 2007 (UTC)

Measure the primary voltage when the transformer is attached. Is the ratio still off? --Tbeatty 08:10, 27 January 2007 (UTC)
The most likely reason is that you're drawing more current (more power) than the transformer can supply. Is it getting hot? Does the undervoltage condition persist when you disconnect the load? —Steve Summit (talk) 13:30, 27 January 2007 (UTC)
Both of Summit's questions are good ones. My experience years ago was that small transformers for electronic devices were designed to supply the stated voltage (say 120v ac stepped down to 12 v ac when they are loaded to the stated power level. If the hypothetical transformer says it supplies 5 amps at 12 volts, then when if supplied with 120 volts and loaded to 5 amps it would supply 12 volts. If it were connected to 120 v ac and there were no load, such a transformer might have more than 12 volts output. It seemed that the manufacturer of such a transformer adjusted the turns ratio to give a slightly high no-load voltage so as to ensure rated voltage at rated current. A transformer has an impedance, consisting of the losses in the core and the resistance of the windings. I don't know offhand what that is for such small consumer transformers, but if it were 5%, then at full rated load the output voltage would drop 5 %. With utility transformers, there is no such correction. They might be designed to step down 7200 volts phase to ground in a nominal 12 kv (actually 12470) volt 3 phase system, to 240 volts center tapped to provide 120-240 volts to the customer. With no load, and 7200 volts on the primary winding, it would have a turns ratio of 7200/240 or 30:1, and the no load voltage would be 240. Again, at full load (say 50KVA) the output voltage would drop by the percent impedance. There are usually primary taps which can be selected to provide higher voltage under load, at the cost of higher no-load voltage. Or maybe your transformer is defective or overloaded. A shorted turn would cause excess current, low voltage and might cause it to burn up. This could be detected by measuring the current to the transformer when it has no load, and comparing it to another similar good transformer. A turn to turn short would cause it to draw much more exciting current when it had no load. Edison 17:14, 27 January 2007 (UTC)

This is pretty obvious, but there could be an immense amount of resistance. Rya Min 05:56, 28 January 2007 (UTC)

As others have suggested, maybe some of the input power is being converted to heat. One possible mechanism is eddy currents. Cardamon 09:38, 28 January 2007 (UTC)

podletknov gravity experiments[edit]

I have read an article recently about a scientist who claims that he has stopped a portion of gravity and invented a beam that can act like super gravity and put immense pressures on objects. does anyone know about this subject and can answer me some questions on it. Firstly with the gravity beam gun, is he getting the effects that he describes [immense pressures] and claiming it is gravity and the scientific community says it cant be that, or is he not getting anything and just claiming that he is and they are saying that he cannot be getting what he is getting? secondly is there any possibliltythat these experiments could be real effects, though not caused my manipulation of gravity [ immense pressure by em force or somthing]? thanks
curious bystander —Preceding unsigned comment added by 80.41.53.197 (talkcontribs) 12:48, 27 January 2007

It certainly reeks of pseudoscience (or perhaps more accurately pathological science). Our article on Eugene Podkletnov has quite a bit of information. —Steve Summit (talk) 13:26, 27 January 2007 (UTC)

Chemistry[edit]

Anyone, pls help me with this question. I have been stuck with it for a long time. Thanks a million.

A household cleaner contains ammonia.A 25.37g sample of the cleaner is dissolved in water and made up to 250cm^3. A 25.0cm^3 portion of this solution requires 37.30cm^3 of 0.360M sulphuric acid for neutralization. What is the percentage by mass of ammonia in the cleaner? Ans: 18%

THANK YOU SO MUCH.

It may help if you start by working backwards.
  • Write out the equation for the reaction between aqueous ammonia and sulfuric acid. How many moles of each are involved?
  • Given 37.30 cm3 (37.30 mL) of 0.360 M (0.360 mol/L) sulfuric acid, how many moles of sulfuric acid are present, and how many moles of ammonia were required for the neutralization?
  • What mass of ammonia is this, then, in your 25.0 mL?
Hopefully this should put you on the right track. TenOfAllTrades(talk) 15:05, 27 January 2007 (UTC)

State of the Universe prior to the Big bang...?[edit]

If the state of the Universe prior to the Big bang was at a temperature below that of Superconductivity regardless of the small amount of space it occupied and then gained enough temperature to loose Superconductivity or acquired some other parameter that would amount to the same thing then could this be the trigger for the Big Bang? 71.100.10.48 15:18, 27 January 2007 (UTC)

Hmmm... as I understand it, it is generally accepted that "prior" to the Big Bang there was nothing, since even time was created at that point. --Taraborn 15:25, 27 January 2007 (UTC)
Time isn't a real substance, so it can't be created, and it can't be absent in the first place, despite what you may have learned from TNG. Vranak
Stephen_Hawking would disagree with Vranak and agree with Taraborn--inksT 21:17, 27 January 2007 (UTC)
Well I've heard about all sorts of exotic particles being created in CERN and so on, but has any team of scientists created something they've called 'time'? If so, what were its properties? Vranak
To realy understand this, you'd need a course in Tensor Calculus. The point is that the amount of energy present at the big bang was so high that time and space become meaningless (i.e. impossible to quantify) --Soulscanner 01:45, 28 January 2007 (UTC)
I guess. There must be a vast divide between philosophical interpretations of 'time', and 'time' as understood in a Tensor Calculus course. So much so that the only similarity between the two is phonetical. Vranak
I've heard it put, rather neatly, that asking what was before the big bang is like asking what is north of the North Pole. Of course, it also depends on which astrophysicist you ask. Maelin (Talk | Contribs) 05:26, 29 January 2007 (UTC)
Not even "space". —LestatdeLioncourt 16:30, 27 January 2007 (UTC)
This is rather silly guys :) Of course there was spacetime and a universe (otherwise where did it come from hmm?). The Big Bang was a moment in time where spacetime and the universe just started getting bigger all of a sudden, and really fast. Temperature is a measure of kinetic energy. Conservation of energy. Same overall temperature. Q.E.D. Also note that not all materials have the ability of superconduction. (strikethrough, I wasn't thinking) X [Mαc Δαvιs] (How's my driving?) ❖ 20:33, 27 January 2007 (UTC)
We have a pretty good handle on what the universe was like from the first fraction of a second after the big bang. But if you go early enough, and approach the moment of the big bang, we don't really have any idea. There are ideas like eternal inflation and cosmological natural selection that make our universe's big bang only one of many, or the Big Bounce which says there was another universe right before ours. -- SCZenz 21:35, 27 January 2007 (UTC)
But you have to admit the possibility of other forms of energy suspension in light of the fact of a suspended magnetic field at near absolute zero... 71.100.10.48 23:05, 27 January 2007 (UTC)

Since energy is proportional to mass, at 0K there is no energy and therefore no mass:) Below this there would be negative energy and negative mass:) If the universe was at absolute zero at the exact time of the big bang, there would have been equal amouts of matter and antimatter, which was entirely replaced by matter as the universe started to heat up (heat travels at a finite speed, so this would take some time):) However I am not the universe, so I could easily be wrong:(Hidden secret 7 11:17, 28 January 2007 (UTC)

So mass and energy decrease as the temperature goes lower... interesting. 71.100.10.48 05:17, 29 January 2007 (UTC)
Please be more careful in your speculation. The word "energy" in particular is highly overloaded (rest energy, free energy, internal energy, etc.), and while such a thing as negative temperature exists, it is not at all how you suggest. Further, antimatter does not have negative mass or negative energy as you imply it does if it "balanced" the normal matter. Moreover, while absolute zero is not practically achievable, there is nothing wrong with a system at 0K with non-zero mass; energy that is not available for interchange does not count when considering temperature. (Note that a charged car battery need not be any warmer than the same battery discharged.) --Tardis 21:33, 29 January 2007 (UTC)


The biggest problem with this question is that it runs the fine line between physics and philosophy. A scientific answer is probably best described as, "there is nothing before the big bang." A philosophical approach can go on in more detail. Things like "time" and "before" start to lose scientific precision in this case. I would sum it up as, "The big bang is not a single event, but it's the entire process of the early universe's expansion." In this case, there isn't something "before" the bang. It's just the ongoing process of early coalescing of our reality out of ... something that is less intelligible. Forces and matter and energy sort of form up into a sensible, "normal" form. Prior to that, "something" exists, but it's difficult and/or impossible to describe, from a scientific standpoint. Nimur 22:44, 30 January 2007 (UTC)

what should we do to free our planet from terrorism a short note[edit]

If you're interested, this discussion is excellent to read, which cites Universal patterns underlying ongoing wars and terrorism and The Mathematical Structure of Terrorism. Foreign Affairs[3] would be excellent for this subject to research, and the Council on Foreign Relations[4] has a few great things as well! "Here Is the Way to Counter Palestinian Terrorism," and "The Challenge of Terrorism." X [Mαc Δαvιs] (How's my driving?) ❖ 20:24, 27 January 2007 (UTC)

My other planet is made of meat[edit]

This barely qualifies as a science question, but what would happen if we got a quantity of dogs the same mass as the Earth and set them orbiting the Sun at the same speed and distance as the Earth? I assume that it would be crushed into a sphere under its own gravity... would the blood and the air that was in the dogs' lungs be forced to the surface? Would the centre get hot? Would it stratify into bones, hair, flesh etc, and how long would it take for these things to become unrecognisable, or would that be so rapid as to be neglegible? Would the substances react with each other under the pressure into something like rocks? Would the bacteria survive and evolve? What would it be like after 4.57 billion years? Are these questions answerable? Vitriol 16:31, 27 January 2007 (UTC)

We would be able to get lots of oil from it, if we left it long enough:) It would become a sphere, as it's gravity would be the same as the earths:) Bacteria nearer the surface would be likely to survive as some bacteria can live in almost any conditions:(Hidden secret 7 20:55, 27 January 2007 (UTC)

Where would we get that many dogs from, or that many of any animal, as they wouldn't all fit on the sufrace of the earth:) And I doubt people would like you doing that, there would be a lot of protests &c:]Hidden secret 7 20:57, 27 January 2007 (UTC)

Exactly... if the dogs are the same mass of the earth, does that mean that we tranformed the Earth into a quantity of dogs? Or did we create the dogs out of interstellar dust and so on? At any rate the one thing that springs to mind is that this planet would be a disgusting mess for a very long time. Vranak


Maybe God used dog cadavers to do it? X [Mαc Δαvιs] (How's my driving?) ❖ 21:04, 27 January 2007 (UTC)
The dog world would be a flea heaven...Mikmd
I'm no chemist or geologist or dog scientist but I think what would happen is the dogs would coalesce into one huge ball and under the immense gravity the individual elements of the dogs would migrate toward either the surface or the core depending on their densities. Since a dog is primarily carbon, oxygen, hydrogen, nitrogen with only some trace elements, the new planet would essentially be a huge ball of carbon with a tiny metallic core, with an atmosphere of nitrogen, oxygen and hydrogen (therefore also dihydrogen monoxide, an extremely toxic substance). It might also have a diamond core, but I don't know if the pressure near the core would be enough for the carbon to become diamond... hmm, I can just envision that a million years into the future the universe's source of diamonds would be... dog planets. There would probably be no advanced life on that planet, just a huge blob of coal... or diamond. Not sure about bacteria, but some photosynthetic bacteria might survive. -- 我♥中國 21:15, 27 January 2007 (UTC)
Damn! I want to do this experiment now!! X [Mαc Δαvιs] (How's my driving?) ❖ 21:33, 27 January 2007 (UTC)
Diamond is a metastable state of carbon that requires an unusual combination of high pressure and low temperature to form. It isn't clear exactly how or why they form in the Earth's crust. Either way, I don't think these disgusting dog planets would be a particularly abundant source of diamond :) --bmk
Damn that dihydrogen monoxide! Chickenflicker--- 22:09, 27 January 2007 (UTC)
It is the most dangerous of the monoxides... DHMO --66.195.232.121 15:25, 29 January 2007 (UTC)
This thread is reminding me irresistably of dogs in meat. (See also the denouement here.) —Steve Summit (talk) 21:56, 27 January 2007 (UTC)

I like this question, an opportunity to speculate wildly! To start with the dogs are a lot less dense than the earth even if you pack them in quite tightly (densities <1000 and 5500 kg/m^3. The dogs will collapse to a sphere. This will be a sphere that is larger than the earth but still quite a lot smaller than whatever shape they were in to start with so a fair amount of energy will be released heating up the new planet a bit (the exact amount could be calculated if you know how densely packed your dogs were to start with). No dogs should survive the fall (or the crushing) which will be very messy! I assume that plenty of bacteria will survive and so on the surface initially they will have all the air in the dogs' lungs and a ready supply of dead organic matter to live off so you will get plenty of mouldly dogs. Deeper down the air should all get squeezed out of the dogs and gradually make its way upwards. I think it would take a long time for all the air to make its way out though, so presumably you would get great vents of dog breath coming out of the surface as the planet gradually settled down. Also:

  • The dog world will not end up with much of an iron core due to the lack of metals in dogs (or are they all wearing chains?) and so will not develop a magnetic field.
  • Dog world won't rotate unless your initial dog mass was spinning so you'll probably get 1 very hot side and 1 colder side.
  • Dogs are not made of particularly radioactive stuff so I think that dog earth will not heat itself very much but there will probably be a lot of carbon dioxide going around in the atmosphere after a while so there may be a decent greenhouse effect, probably enough to kill off all the bacteria
  • The escape velocity of dog world will be lower than that of Earth but not that much lower so it should hang on to some atmosphere but certainly not all of the air that was in the dogs' lungs to begin with.
  • There's a lot of water in dogs so potentially there could be very large oceans covering the entire planet to quite a depth
  • I'm sure that there woud be massive amounts of oil in a few million years time. JMiall 23:35, 27 January 2007 (UTC)
Now wouldn't escape velocitydogworld be the same since the force of gravity is the same? X [Mαc Δαvιs] (How's my driving?) ❖ 00:24, 28 January 2007 (UTC)
If we assume that dogworld is less dense than earth but the same mass then the escape velocity at the surface will be less. JMiall 01:11, 28 January 2007 (UTC)
Sort of related: would it be economically and efficiently feasible to, say, launch animal remains onto high-pressure planets? Would said animal remains actually turn into oil, as HS7 claimed? --Wooty Woot? contribs 01:33, 28 January 2007 (UTC)
Dude, if we're able to dump dead animals on hostile planets and retrieve them again, I doubt we'd be using oil. Vitriol 04:28, 28 January 2007 (UTC)
No, it would decrease the biomass. --V. Szabolcs 11:02, 28 January 2007 (UTC)

The dogs wouldn't go mouldy unless there was already mould living on them, and some bacteria can survive temperatures of hundreds of degrees, and could evolve into more complex creatures over a long period of time:) Then we could make another planet out of these creatures, and so on..:]Hidden secret 7 11:23, 28 January 2007 (UTC)

Acid Into Water[edit]

I've always been told that you should pour acid into water, not water into acid. Why is that? I've heard acid can burst into flames if you pour water into it, but someone else I know said that's stupid. Black Carrot 18:56, 27 January 2007 (UTC)

You pour acid into water instead of anything into a container full of acid so the acid doesn't splash on you if you aren't careful in pouring, which can always happen. Safety, always. X [Mαc Δαvιs] (How's my driving?) ❖ 20:29, 27 January 2007 (UTC)
No, it's more specific (and more interesting) than that. When you dilute a strong acid, you actually set up an exothermic and potentially vigorous reaction. If you have a lot of water and a little acid, there's not so much heat liberated, and a lot of water to absorb the heat. But if you have a lot of acid and a little water, the amount of heat released can actually be sufficient to boil some of the water, spitting droplets of acid out of the beaker you're doing it in, or liberating fine mists of acid which you can then inhale. "Acid to water, is what you otter." See our Sulfuric acid article (especially the Reaction with water and Laboratory hazards sections) for more explanations. —Steve Summit (talk) 21:21, 27 January 2007 (UTC)
Ah, thank you. Interesting! X [Mαc Δαvιs] (How's my driving?) ❖ 21:32, 27 January 2007 (UTC)
Diluting conc sulphiric acid down to make 1M solution - even pouring acid into water creates enough heat to warm you hands by placing them on the outside o the flask. And even then you can get some spitting if you pour the acid in too quickly you can get some hissing and spitting until the acid mixes with the water. Hence safety goggles, gloves and a fume cupboard. Theresa Knott | Taste the Korn 00:37, 28 January 2007 (UTC)
Otter?? "Acid to Water is what you Utter" is what I thought it was. But "Add Acid To Water" AATW/ Alphabetical. therefore, easy to remember.--Tbeatty 06:30, 28 January 2007 (UTC)
"Otter" is how I always heard it, although I concede that the phrase as I spelt it yields all of zero Google hits. You get one hit for "acid to water is what you oughta", although this works for me only with a Boston accent, i.e. "Acid to watah is what you oughta". And then there are the contrapositives: "Water to acid is not too placid" or even "Water to acid if your life's too placid". —Steve Summit (talk) 14:06, 28 January 2007 (UTC)
"Water" and "oughta" works very well in a UK English accent. Maybe that's where it came from. Darkhorse06 18:07, 6 February 2007 (UTC)

Another factor is the different densities of the two liquids, which tend not to mix immediately. Adding water to the acid lets it sit on top and get extremely hot. It soon boils, spits and carries some of the acid back out again. I've tried it, and it's not for the faint-hearted (or those without appropriate knowledge or safety apparatus). --G N Frykman 08:45, 28 January 2007 (UTC)

Dielectric Saturation[edit]

I'd like to know more about Dielectric Saturation as applied to electrical capacitance. Neither the Capacitor nor Capacitance article on Wiki cover this eccentricity. Specifically the rate and conditions under which dielectric breakdown of an insulator occurs. From what little I can gather, Dielectric Saturation occurs in so called High-K dielectric materials when subjected to high voltages. In theory the dielectric material in a capacitor has a calculable maximum voltage to which it can be subjected without current jumping through it. From what I've read however this value is actually a moving target since the actual dielectric constant of the material drops as the voltage it is subjected to rises. This term Dielectric Saturation was used in a discussion of capacitors which use Barium-Titanate powder as the dielectric. Thank-you for your help. | Jason 74.100.176.85 20:51, 27 January 2007 (UTC)

There is a short discussion of dielectric absorption Capacitor_(component)#Dielectric_absorption_.28soakage.29. Is that what you are looking for? Or is "dielectric saturation" some other obscure effect I've never heard of? --68.0.124.33 (talk) 00:47, 11 January 2008 (UTC)

Enzymes and surrounding environment[edit]

Enzymes are rather sensitive to their surrounding environment. I understand this has some sort of affect on the survival of living organisms, but I'm not sure what. Thanks. --Fbv65edel / ☑t / ☛c || 22:28, 27 January 2007 (UTC)

Enzymes are important for the functioning of living things in that they allow chemical reactions to occur much much faster than they otherwise would. If an enzyme is in a particularly hot or acidic environment, for example, it may "unfurl" and become useless. Check out Enzyme. BenC7 01:28, 28 January 2007 (UTC)
From my limited knowledge enzymes are specific to the environment they are used in, i.e. Pepsin in the stomach will denature and become useless unless the stomach environment is around PH2, while Amylase in the saliva prefers a PH of around 5.5-7. Reaction rates vary according to PH and temperature. RHB Talk - Edits 01:48, 28 January 2007 (UTC)

Medical news[edit]

Where are your favorite places to get medical news, both in physical and online form? I'm looking for academic stuff, or at least a link to the university news website or something like Eurekalert X [Mαc Δαvιs] (How's my driving?) ❖ 23:09, 27 January 2007 (UTC)

Google News with keywords works for me. 71.100.10.48 01:33, 28 January 2007 (UTC)
For infectious disease news I like CIDRAP. --Joelmills 05:10, 28 January 2007 (UTC)