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January 15

Requirements for cloning

I've always been horrible at biology, so this is going to be a really nooby question. I'm wondering what is absolutely necessary in order to basically "create" a species from scratch; that is a species that is existent or has been, where you have access to genetic material.

I'm going to assume a process (that I presume doesn't exist, and won't for a very long time) whereas you can create full DNA strands from pure data, so this isn't really a realistic question, just a theoretical one. What kind of DNA would you absolutely need to produce a single specimen of a species; is just one kind enough, or are there multiple genomes? that you would have to figure out first. Also, does it matter what sequences you need if you are trying to make a male or female of the species?

Obviously I'm assuming here that the DNA created from data would be inserted into a living cell, which may not be possible, but I'd like to ignore that problem as well haha. Also, I'm assuming that you would only need one copy of (each?) data type to succeed, but I'm not sure if that's true.

Basically, I'm asking because lately I've heard a lot about different genomes and rDNA and mtDNA and I'm getting confused as to where the actual "core" of information, and the set of information which cannot be deduced from some sort of chemical process within eukaryotes is. Thanks in advance! 219.102.221.49 (talk) 02:08, 15 January 2010 (UTC)

A human genome, for perspective, consists of 3 billion DNA base pairs, each being one of four different types of nucleic acids. Each human cell has two copies of the genome, one from each parent, which in general may provide different allelles for the same gene. In humans, the genomes are arranged in 23 chromosomes pairs. I'm not sure what the longest DNA constructed from scratch is. I don't think it is billions of base pairs, but I suspect 10 million might have already happened, so we aren't that far from being able to write a whole human genome from scratch. Men and women have different sex chromosomes (one of the 23). Inserting DNA into cells is possible, and at the heart of cloning efforts. See also rDNA and mtDNA. Dragons flight (talk) 02:22, 15 January 2010 (UTC)

I think the main part of my question was a bit unclear. I know generally how the cell is constructed and what the different kinds of DNA are, but I'm wondering which are absolutely and immediately necessary in the creation of a being. For example, if you had a data writeout of the base pairs for the 23 human chromosomes, and it was possible to construct the strands of DNA from scratch of that length and complexity, could you input just those created chromosomes into a cell and make it live, effectively cloning a human (though through an extremely inefficient means), or would you need to create copies of other types of DNA, perhaps some of the organelles for it to work? Plainly, is absolutely everything required to produce a human included in the 23 chromosomes? Is all the information required to produce an organism included in its chromosomes? 219.102.221.49 (talk) 06:33, 15 January 2010 (UTC)

Yes and no. In order to live the genome needs to be combined with a compatible set of cellular machinery. In practice, this is quite general, but not open-ended. So, for example, cells from organisms in the same family would probably be fine, but probably not cells from a different phylum. The pre-existing machinery reads the DNA and starts producing the appropriate proteins to match the new genome. Eventually the old cellular machinery is totally replaced, but that can't happen too quickly or the cell's behavior may go haywire (hence the need the need to start with something similar). In general though, no other types of DNA have to be provided. Dragons flight (talk) 09:46, 15 January 2010 (UTC)

Is the cellular machinery really that general ? I thought that somatic cell nuclear transfer had to involve a nucleus and ovum from the same species. Are you saying that it is possible to put a sheep's DNA into a cow's ovum and produce a sheep embryo, because both cows and sheep are bovids ? Gandalf61 (talk) 10:10, 15 January 2010 (UTC)

SCNT has a poor success rate (< 10%) even under the best of conditions, so one would ordinarily choose cells of the same species to maximize the odds. But no, that's not a strict requirement. Work with endangered species has already produced clones where the egg donor was a different species than the DNA donor (harvesting eggs is an invasive and somewhat dangerous process, so you wouldn't want to subject a rare animal to that if a similar common animal would also work). There haven't been enough experiments to tell exactly how similar the cell needs to be, but the core machinery for protein synthesis and DNA replication exists in all cells. Hence we probably can fairly far in the genetic tree before secondary factors make it impossible. Dragons flight (talk) 12:20, 15 January 2010 (UTC)

Additionally, we do know that there are viruses that can use their DNA in order to force cells to do work they wouldn't otherwise do—presumably this indicates some compatibility, or at least some flexibility. --Mr.98 (talk) 21:58, 15 January 2010 (UTC)

You might be interested in Mycoplasma laboratorium, also known as the Minimal Genome Project. Looie496 (talk) 19:02, 15 January 2010 (UTC)

Cats and plastic garbage bags

Anyone who is owned by cats or knows someone that is owned by them, knows that cats hate the sound of plastic garbage bags. Can anyone explain this phenomenon? Thanks. Viriditas (talk) 04:34, 15 January 2010 (UTC)

That's news to me and I have four cats. Can you supply some sort of source for the observance of this "phenomenon"? In fact, the cabinet that we throw our plastic grocery bags into is the one of our cats favorite places to get into. I know you said garbage and not grocery but they don't sound that much different. Dismas|^(talk) 05:04, 15 January 2010 (UTC)

I can confirm that at least some cats enjoy playing with grocery bags. APL (talk) 06:03, 15 January 2010 (UTC)

I can attest that in my house (4 cats) the phrase "the cat's out of the bag" and the accompanying implication that it's impossible to get it back in (undo something) seems preposterous. Our cats LOVE plastic bags and immediately enter any they're offered, which they then joyously tear to shreds.218.25.32.210 (talk) 07:48, 15 January 2010 (UTC)

Funny; I have three cats, and not one has ever reacted to the sound of a plastic garbage bag. Someguy1221 (talk) 07:57, 15 January 2010 (UTC)

Responding to the above: Plastic garbage bags are not plastic grocery bags, nor do cats love or play with plastic garbage bags as they are generally compressed before usage in rolls or sheets. A good image of what I'm talking about can be found here and after seeing this image, it becomes clear why cats can't play with them. I wasn't aware there could possibly be any ambiguity in the words I chose, but evidently the words "plastic garbage bag" means something different to various people here, and I now see that I'm probably using American English. Anecdotal reports of typical house cats running feverishly from the sound of plastic garbage bags being torn off rolls and opened (it is generally a loud sound) are numerous and can be found all over the place. There are thousands, perhaps tens or hundreds of thousands of comments like this:

• "She is a typical cat - attitude et al. However, every time we put a new garbage bag in the bin, she freaks out and runs - and she reacts the same way with plastic bags."[1]
• "My cat is scared of many things. How can I help him? He is very frightened of: 1. Thunderstorms 2. Airplanes/any loud noises 3. Plastic bags..."[2]
• "Our cats are afraid of their own shadows. They hate the rustle of plastic bags, where our previous cat came running when he heard the noise (he liked to lick plastic bags ... )"[3]
• "I have one cat who likes to be vaccuumed (gently), and another who is terrified of plastic bags..."[4]

I think you get the idea. Obviously, the noise of the bag can scare some cats, but I've noticed this myself with so many different cats, that I'm curious about the sound of the plastic bag unfurling and why they would be afraid of it. Does the sound cause them pain? Viriditas (talk) 09:51, 15 January 2010 (UTC)

My cats don't like the sound of the ripping perforations,(note I didn't say "scared of") but once the bag is opened they will quite happily play with, explore, and even eat the bag! You may as well ask, why are all humans scared of spiders? This is quite obviously not the case. --TammyMoet (talk) 10:45, 15 January 2010 (UTC)

The third example seems to be enough to disprove the "all cats are afraid" assertion. And the plural of anecdote is not data. As far as terminology, I think our British friends use Bin liner. --LarryMac | Talk 13:54, 15 January 2010 (UTC)

Here's another the OR-into-felines thread. My cat is oblivious to all sorts of noises around the house and even backfires from the road outside. But a firework bang overhead prompts a desperate run for cover. I conclude that direction, and possibly ultrasonic sound that I can't hear, are decisive for the cat. Do plastic garbage bags produce ultrasound? Cuddlyable3 (talk) 11:24, 15 January 2010 (UTC)

Unfortunately for scientists, cats are inscrutable.--Shantavira|^{feed me} 11:28, 15 January 2010 (UTC)

If you catch my catastrophic catechresis, cats categorise scientists as scrutable, shevelled and/or gruntled. Cuddlyable3 (talk) 12:23, 15 January 2010 (UTC)

manufacturaplastikosaphobia ? Kittybrewster ☎ 12:40, 15 January 2010 (UTC)

I haven't noticed anything particular with cats, but I have noticed many times that rats are very easily startled by the sound of paper tearing. I speculate that a sudden ambush attack by a predator often produces a similar sound. Looie496 (talk) 17:13, 15 January 2010 (UTC)

It might be the noise - but I'd bet it was the smell of the plasticizer or some kind of release agent or something. SteveBaker (talk) 18:55, 15 January 2010 (UTC)

I was quite clear that I knew the difference between garbage and grocery bags. And I again ask for some reliable source that points this out. You've supplied four links to what is essentially original research. It's selection bias. You also mention the part about opening the bag which is a loud sound. Many creatures great and small are startled by loud sounds including humans. I have a human friend and a dog who both hate gun shots. Furthermore, I can see a range of reactions to loud sounds from the cats in my house. For example, a dog's bark. One cat we have runs under the bed even when she's on a separate floor from the barking dog. Meanwhile, the other cats generally either don't react at all or just wake up and look around wondering what all the excitement is about. And you yourself prove your own conclusion to be wrong with your third quote. It says "our previous cat came running when he heard the noise (he liked to lick plastic bags ... )". So right there you have at least one cat that liked the bags. Dismas|^(talk) 04:04, 16 January 2010 (UTC)

There is simply no comparison between grocery and garbage bags here, since the noise comes from unrolling the bag and opening it with a flick of the wrist. This has nothing to do with OR (that term does not even apply on refdesk) or selection bias; It's a well-known phenomenon in most cats. My question has to do with why they are scared of the sound, not whether cats are afraid of it. And, it doesn't have to be loud for cats to have an extreme reaction to it. According to your own comments, you haven't heard of it and didn't see the difference between grocery and garbage bags, so you probably aren't aware of the issue in the first place, nor have you ever witnessed it, apparently. Viriditas (talk) 09:01, 16 January 2010 (UTC)

Ok, Viriditas, look... Counting above, it looks like you have the opinions of no less than 16 cats that plastic bags, garbage or grocery or otherwise, are not scary. But with regard to the links you posted above of anecdotes...seriously? Dude, are you going to listen to us, or just read posts from random people on the internet? Someguy1221 (talk) 09:08, 16 January 2010 (UTC)

There's literally tens of thousands of reports about this, and people aren't making them up. I've witnessed it myself in at least half a dozen cats over the years. The sound is certainly scary to some cats, and my question is why. I fail to see how you've answered my question, so if you have nothing to add, simply ignore me. I see nothing wrong with addressing the anecdotes of cat owners about their pets. It's called observation, and for our purposes, there's not a thing wrong with it. This isn't a scientific journal, this is a refdesk. Viriditas (talk) 09:15, 16 January 2010 (UTC)

I'm sorry, Viriditas. That was meant to be a joke (aka we are all random people on the internet). Someguy1221 (talk) 22:08, 16 January 2010 (UTC)

The trouble with this claim of yours is that selection bias is rife here. Nobody - and I mean NOBODY wrote about how their cats totally ignored any and all things their owners did with plastic bags of any kind. Why would they? They also didn't write about how their cat completely ignores all use of the word "Nuclear" on the radio. People don't write about non-events. So we may well have about a billion cats who's reactions to plastic bags were not mentioned - and (by your count) a mere few tens of thousands of cats who freaked out in this way. That's so statistically insignificant that we really can't draw any conclusions on that basis. The only way to make a statistical claim is to do a proper double-blind statistical study...and you haven't done that. Anecdotes are not data.

Furthermore - I'm 100% certain that you have NOT read "tens of thousands" of reports about this. What you REALLY mean is that you typed some kind of search terms into Google and counted the number of hits you got back. However, as any experienced web searcher will tell you - that count doesn't tell you much about what the reports actually contain. Perhaps the ones that come up on the first few pages of most appropriate hits were about this - but the 23,456th report is almost certainly about something completely different that merely happens to contain the terms you typed in several paragraphs apart and totally unrelated to the question at hand. So your claim of many reports is quite utterly valueless - even bogus.

Your personal observation of many cats that have this problem is also lacking any kind of scientific rigor. Suppose, just for one moment, that you had ONE cat who is the only cat in all of history to be afraid of unrolling bags. You see this and are surprised by it - so the next time a different cat is nearby as you unroll the bags, you pay very careful attention to the cat - and lo and behold, it runs away! You do this a dozen times - same result every time!!! Surely you've discovered something here? Well, maybe not - maybe all but the first cat are freaked out by the threatening way you fixate your attention on them and run off every time you do that even though they don't give a damn about the bags? So, I'm sorry - but your anecdotal information in favor of your hypothesis is actually not very convincing at all. On the other hand, we have evidence of a dozen or more cats who we're told don't give a damn about these bags...how does that fit into your hypothesis? It's not so easy to explain away is it? So THIS evidence is pretty significant. It says that at least a significant sample of cats are not afraid. You only have really conclusive evidence of one cat that you personally know for sure is scared - and a random scattering of junk from the web.

So - please step down from your high horse and listen to what the experts here are telling you. SteveBaker (talk) 17:07, 16 January 2010 (UTC)

No that isn't correct at all. I very clearly said that "I've witnessed it myself in at least half a dozen cats over the years" so I have no idea why you say that I "only have really conclusive evidence of one cat that you personally know for sure is scared." This is the pattern in this discussion. I say one thing, someone says that I say something else. I'm not on any high horse, and I see no animal behavior experts in this discussion nor has anyone addressed my question other than to say "I have a cat and he's not scared" so, there isn't anyone to listen to on the subject, as my question hasn't been addressed, nor have any "experts" (Wikipedia, cough, cough) addressed it. The reading comprehension level here is close to zero. Viriditas (talk) 00:27, 17 January 2010 (UTC)

Before you start flinging around accusations of poor reading comprehension - I suggest you exercise some reading comprehension of your own. Please carefully re-read what I wrote. You categorically do not have evidence of 12 cats responding to this phenomenon - you might (maybe) have evidence that ONE cat responded to the bags and eleven more who merely responded to your curiosity on the subject. That's not the same thing as 12 cats who responded to the bags. That's why proper evidence requires a double-blind experiment. Let me remind you of how you started this thread. You said "Anyone who is owned by cats or knows someone that is owned by them, knows that cats hate the sound of plastic garbage bags." - but we came up with a whole lot of people/cats who do NOT respond in the way you describe...just one is enough to destroy your hypothesis...so it's busted. Worse still (if you had read my yet earlier post), any reaction you've observed may well be to the smell of the chemicals that were trapped between the folds of the plastic - you have ZERO proof that this is a sound-related phenomenon at all. So please stop insulting us and carefully read what we're telling you. SteveBaker (talk) 01:16, 17 January 2010 (UTC)

I strongly disagree with your assessment. I did not find the responses from people who disagreed persuasive. It sounds like they never experimented with the plastic garbage bag sound I described and admitted they had never heard of it. It has absolutely nothing to do with the smell, (cats often freak out in other parts of the house or outside when the bag is opened inside) and everything to do with the sound. Nothing mentioned in the comments above "destroyed my hypothesis", but rather demonstrated that people will respond to anything without having familiarity with the topic. Since you and others do not recognize the problem I describe, I fail to see how you think it has been addressed. Some cats are scared or distressed by the sound of some plastic garbage bags. Ask anyone who has worked with feral or house cats and they will report this as a fact. Why this is the case is my concern. Claiming that the concern is false or imaginary is not a satisfactory answer. It's a real feline phobia and it is well known. Why this happens or why the sound causes this reaction in cats has not yet been determined. As an experiment, I just got off my computer chair and headed to the kitchen. With my cat seated approximately eight feet away, I grabbed the roll of plastic "bin bags" in full view of the cat. This did not deter him, and he didn't even blink. Then, I slowly tore a bag off the roll, trying to do it quietly. Nothing happened. At this point, I slowly separated the bag, and lightly flicked my wrist, opening it with a soft sound. At this point, the cat freaked out, and ran out of the room. It's the same reaction every time, and it has to do with the sound of the plastic. My vet and other experts I trust, say that some cats are more high-strung than others, and the new "trend" is to give these types of cats anti-anxiety medications. I'm not planning on doing that, but that is the typical response from the experts. Treat the problem with medication rather than try and figure out what causes it. Viriditas (talk) 01:36, 17 January 2010 (UTC)

You have obviously pre-decided what the answer must be on the basis of hearsay and anecdote (as an earlier poster pointed out: The plural of "anecdote" is not "data"). I'm sorry you don't like what we're telling you here - but you're stuck with it - that is the answer, whether you happen to like it or not. Your grasp of scientific methodology is clearly inadequate to the task of understanding what we're trying to tell you. I think this thread is over. SteveBaker (talk) 13:08, 17 January 2010 (UTC)

• There's a 2009 article in the New York Post about the phenomenon, but I doubt the conclusion reached by the author is true. Also, the author talks about the plastic grocery-type bags, not the bin liners. Viriditas (talk) 09:06, 16 January 2010 (UTC)

Cats' ears (and brains) are attuned to the rustle that a mouse makes (especially amongst dry leaves), so the rustle of a plastic bag is likely to sound louder to them than it does to us. Most animals (including humans) have a natural reflex to run away from a loud sound that we don't understand, but this refex reaction is easily modified by behaviour learned from the reaction of others and from experience. Do these facts help to explain the variations in the reactions of cats to high density polythene? Dbfirs 21:27, 17 January 2010 (UTC)

Plastic bags are "opened" by humans by moving them in such a way as to force air into the opening. This is especially true of bags fresh off of a roll of unused "garbage" type bags. But even "used" grocery-type bags can be opened fully using the same type of motion. This motion causes the rapid opening of the bag. It is similar to the way a parachute opens. It takes place rapidly. I think the rapidity of the moving material, in either case, can reasonably be expected to startle. I think it has a visual and an auditory component to it. In the case of the opening of a bag by a human, there is also the close association between the rapid hand movement and the concomitant sound and motion. The bag can seem to expand in size very rapidly. It does not seem surprising that this could be startling to any creature. Bus stop (talk) 22:06, 17 January 2010 (UTC)

Hydrogen, Oxygen, and Nitrogen

Does pure hydrogen only exist as molecues of two atoms? Does pure oxygen only exist as molecues of two or three atoms? Does pure nitrogen only exist as molecues of two atoms?

Bowei Huang 1 (talk) 05:52, 15 January 2010 (UTC)

Have a look at ozone and trihydrogen (very unstable), and there is also octaazacubane N₈ and Tetranitrogen N₄. At extremely high temperatures the elements can be monatomic, and at extreme pressures nitrogen can form other allotropes, and even more extreme pressures all molecules form metals: eg Metallic hydrogen. Graeme Bartlett (talk) 06:14, 15 January 2010 (UTC)

In other words, all of those elements can exist in other forms under unusual (non-Earth-Atmosphere) conditions. Under standard temperature and pressure, the conventional two-atom molecular form is by and large the most common, orders of magnitude more stable than any other configuration. Nimur (talk) 06:20, 15 January 2010 (UTC)

Cheap hurricane and earthquake protection?

Supposing nylon or metal guy wires like the ones supporting tents and radio masts were retro-fitted into or around normally weak buildings? Would this be an affordable form of hurricane/earthquake protection? For example, could a large nylon sheet deeply pegged to the ground at all corners, given sufficient warning of a hurricane, keep the roof on?Trevor Loughlin (talk) 14:29, 15 January 2010 (UTC)

While it would be better then nothing, we really do not know how much better without knowing things like soil conditions, building materials, building size, shape etc. Chances are good that it would be only a minor improvement for hurricanes. For an earthquake, these would help even less because the method of failure is very different, and in many earthquakes, that soil is going to act like a liquid and your stakes are going to move. Googlemeister (talk) 15:11, 15 January 2010 (UTC)

Regarding Googlemeister's comments on soils in an earthquake, see Soil liquefaction. --Jayron32 15:46, 15 January 2010 (UTC)

In an earthquake the guy wires could pull the building down rather than support it. 78.149.116.255 (talk) 12:17, 16 January 2010 (UTC)

Gas furnace ignitor

In a typical gas furnace, there are several burners but only one (electric) ignitor. How does the ignitor light all the burners? —Preceding unsigned comment added by 173.49.10.145 (talk) 16:22, 15 January 2010 (UTC)

It would seem likely that if the burners were in a line, that the igniter would light the first one, that would light the next burner or jet, and so forth along the line. If there were sufficient 'un-lit' gas the igniter could easily light them all simultaneously. If you mean totally seperate 'bar' or ring burners the same idea still applies--220.101.28.25 (talk) 17:04, 15 January 2010 (UTC)Bold text

A source of ignition "very close" to a fuel is enough to light it. Gas is...a gas, so gas from burner B quickly spreads to the flame on burner A, which lights B, and so on. DMacks (talk) 17:05, 15 January 2010 (UTC)

Building construction standards in earthquake-prone areas

In earthquake-prone areas, how strong an earthquake are buildings required to be able to withstand? I expect the answer to vary a lot depending on the jurisdiction, but would like to know how different governments balance the tradeoff between cost and safety. —Preceding unsigned comment added by 173.49.10.145 (talk) 16:54, 15 January 2010 (UTC)

See earthquake engineering. Looie496 (talk) 17:05, 15 January 2010 (UTC)

water liquid temps

Is there any way to get water to remain liquid at the temperature of -20F (lowering the freezing point by at least 52F)? Preferably a method that is not corrosive, like adding salt would be? 65.121.141.34 (talk) 17:09, 15 January 2010 (UTC)

Supercooling. Staecker (talk) 17:13, 15 January 2010 (UTC)

That would require extremely pure water would it not? Since the smallest speck of dust would start the seed crystal reaction and freeze everything up? 65.121.141.34 (talk) 17:20, 15 January 2010 (UTC)

Yes it would. And a fancy bottle to hold it in. Depending on your needs and equipment, this may not be the easiest way to do it. But it's the first (and only) that comes to my mind. Staecker (talk) 17:22, 15 January 2010 (UTC)

Antifreeze. Dauto (talk) 17:36, 15 January 2010 (UTC)

I considered that, but car antifreeze is usually something like 25% or more of the solution, at which point you don't really have water anymore, but diluted antifreeze. I am mostly looking for solutions of 99% or higher water content. 65.121.141.34 (talk) 17:56, 15 January 2010 (UTC)

You can do it by increasing the pressure by thousands of atmospheres. — DanielLC 18:10, 15 January 2010 (UTC)

I don't think you can. -20F is about -29C. This suggests that even at high pressures, the melting point of water can only be brought down to -20 C or so. Buddy431 (talk) 18:27, 15 January 2010 (UTC)

I guess Dauto beat me to it. Buddy431 (talk) 18:28, 15 January 2010 (UTC)

Not quite. The minimun temperature for the freezing point will be about -10F at a pressure around 200 Megapascals. Dauto (talk) 18:18, 15 January 2010 (UTC)

The answer is no, not for macroscopic amounts of a nearly pure substance. Maybe if you elaborated on why you want that then we could suggest and alternative. Dragons flight (talk) 18:29, 15 January 2010 (UTC)

Freezing-point depression doesn't require salt. Any solute would do, since the amount the freezing point depresses depends only on the concentration of the solute. Just pick something that isn't corrosive. --Bowlhover (talk) 01:54, 16 January 2010 (UTC)

But you still need like 15 moles of solute per liter of water. At that point, so matter what the solvent solute is, you aren't working with mostly pure water. Buddy431 (talk) 02:11, 16 January 2010 (UTC)

A 48% (by weight) propylene glycol solution will give a freezing point of -20F[5]. 50/50 water/glycerol solutions are commonly used in biology to preserve proteins. --Atemperman (talk) 03:57, 19 January 2010 (UTC)

Stress on a shelf bracket

How can I calculate the maximum horizontal stress or tension on a shelf bracket that has the shape of a right-angled triangle? The bracket is X metres horizontally, Y metres vertically, and has a weight of Z kilogrammes half way along the horizontal surface. Assuming (for simplicity) that there is a fulcrum at the lower angle of the triangle that stops the bracket from moving down but would allow it to rotate, what would be the horizontal force at the right angle? Not a homework question, I would just like to estimate if a simple wood-screw (or two) will be enough to safely fix the bracket to a vertical surface. I suppose it would be like an L-shaped lever. Thanks. 84.13.50.207 (talk) 17:53, 15 January 2010 (UTC)

If I've understood the geometry correctly, then, by taking moments about the fulcrum, one obtains the result that the horizontal force is ZX/2Y kilogrammes. One should always allow a factor of 3 or more as a safety margin, and remember that the fixing into the wall is usually the weak point, rather than the strength of the screw. Dbfirs 18:33, 15 January 2010 (UTC)

Thanks, although I thought the answer would be in newtons rather than kilogrammes. 84.13.50.207 (talk) 18:59, 15 January 2010 (UTC)

No doubt you are looking at the "Design for a wood shelf bracket" and sketch on 12 January 2010. Dbfirs gives an expression for the force acting away from the wall at the inner top edge of the shelf. However a woodscrew cannot be placed there and the screw will instead be W meters below the surface of the shelf. The force tending to pull the screw out of the wall is ZX/(2(Y-W)) kilogrammes. There is also a downward force Z kilogrammes on the screw. (You are correct that the forces should be expressed in Newtons. Multiply the kilogrammes by 9.80665 to obtain Newtons.) The safety margin that Dbfirs advises is definitely needed to allow for items being dropped on to the shelf, or even items being wedged in under a shelf above as often happens with books in crowded library shelves.Cuddlyable3 (talk) 23:54, 15 January 2010 (UTC)

A student visited a fellow student in his apartment which he saw was crowded with stacks of books so that there was hardly any living space. "Why don't you put your books neatly on shelves like in the public library?" he asked. His friend replied "Oh, do they give away the shelves too?". Cuddlyable3 (talk) 23:54, 15 January 2010 (UTC)

I considered converting to Newtons, but since the OP gave the weight in Kilograms-force, I responded in the same units. If you live in Stockholm, multiply by 9.818, or by 9.781 in Singapore, or by 1.625 if you put up shelves on the Moon (assuming the weight is actually a mass in Kg). The method of fixing into the wall is crucial. A friend of an acquaintance last week came down to breakfast to find a new 50-inch plasma TV smashed to pieces on the floor because the wall-fixings were defective! Dbfirs 00:25, 16 January 2010 (UTC)

ZXg/2Y N is indeed the horizontal component of the force at the top of the bracket, where g is the acceleration due to gravity. But if the only fixing is at the top of the bracket (in other word, the force at the bottom of the bracket is normal to the wall i.e. horizontal) then this fixing also has to provide a vertical force of Zg N to support the weight of the Z kg mass. The total force at the top of the bracket is therefore

$Zg{\sqrt {{\frac {X^{2}}{4Y^{2}}}+1}}$

This ignores friction between the bracket and its support. In practice, friction will introduce a small vertical component which will reduce the total force at the fixing, so this is a worst case. Note that we have also ignored the weight of the bracket - we might be tempted to make Y as large as possible to minimise the force at the fixing, but eventually the weight of the bracket would become significant. Gandalf61 (talk) 09:35, 16 January 2010 (UTC)

minibeasts

What are the top ten most deadly minibeasts in the world? —Preceding unsigned comment added by Jay Dale (talk • contribs) 22:49, 15 January 2010 (UTC)

I don't know if you'll get a top-ten, but the Guiness Book of Records says the most poisonous spider is Brazilian wandering spider, and apparently the most poisonous insect is the Maricopa Harvester Ant. -- Finlay McWalter • Talk 22:53, 15 January 2010 (UTC)

You might also be interested in the List of venomous animals article (it doesn't order them by poisonousness, or distinguish minibeasts from the non-mini, but it's fun nevertheless). -- Finlay McWalter • Talk 23:00, 15 January 2010 (UTC)

But really, if you're looking for the coolest poison, you have to go to the slow loris. A mother licks poison onto her kids before she goes out. So it's like if your mum covered you and your sister in poison before she went to Tescos to buy dinner. That way, if a lion ate your sister in the meantime, it would be sickened by the poison, and you'd still be alive to help your mum do the washing up when she gets back. -- Finlay McWalter • Talk 23:12, 15 January 2010 (UTC)

Remember there are also amphibians that are extremely poisonous, for example the poison dart frog. ~AH1^(TCU) 03:26, 16 January 2010 (UTC)

Depending on definition of minibeast (for example do you include flatworms as minibeasts since they are animals?) and I'm surprised no one has said it, but perhaps mosquitos are the most deadly of all based on numbers of human deaths they contribute to every year. Of course the mosquiotes themselves don't kill people Nil Einne (talk) 12:19, 16 January 2010 (UTC)

You can check out the Irukandji jellyfish. DRosenbach ^{(Talk | Contribs)} 06:03, 17 January 2010 (UTC)

Don't forget about the box jellyfish. ~AH1^(TCU) 21:18, 17 January 2010 (UTC)

Or the Blue ringed octopus. 220.101.28.25 (talk) 14:11, 18 January 2010 (UTC)

January 16

Strength of a wood-screw joint

Is any data published about how much tension wood-screws in soft wood can bear without failing? The wood is far more likely to break than the metal screw - the screw would be ripped out of the wood rather than the metal snapping. I am interested in old-fashioned wood-screws as well as Phillips and similar screws. Thanks. 89.243.221.49 (talk) 00:18, 16 January 2010 (UTC)

I've had this link in my Bookmarks for a L-O-N-G time! It's the most comprehensive description of the pull-out and shear strengths of screws, nails, staples and so forth that I've been able to track down: http://www.fpl.fs.fed.us/documnts/fplgtr/fplgtr113/ch07.pdf - brace yourself though - it's a WAY complicated subject. Everything from the angle you drive the screw, the grain direction, the type of wood and (especially) the dryness of the wood matter. But if you're prepared to study - that document is the business! SteveBaker (talk) 02:26, 16 January 2010 (UTC)

Thanks. Do you know what the name of the book is please? 78.149.116.255 (talk) 12:05, 16 January 2010 (UTC)

"Wood handbook : wood as an engineering material". Madison, WI : USDA Forest Service, Forest Products Laboratory, 1999.

You can buy it on Amazon for $60 here - but since it's all available online here, you might want to save your money. Aside from the chapter on screws and such - there is all sorts of hard data about the properties of wood as an engineering material. Not exactly bedtime reading though. SteveBaker (talk) 16:43, 16 January 2010 (UTC)

I scanned the woodworking reference SteveBaker provided and in spite of its @SB note the apostrophe that is not there! copious details I think it missed this variable: how much is the screw tightened? Just until it feels right? Cuddlyable3 (talk) 22:33, 17 January 2010 (UTC)

are these EWGs?

My question wasn't answered, so I'll post again. I've posted an image this time! I want to know if these compounds can be useful building blocks. Is d acidic enough to undergo the Knoevenagel condensation? (I guess it polymerises easily?)

Also, what is the name for alkyne groups conjugated with a carbonyl system? Are these stable? Can they act as Michael acceptors and/or electron-withdrawing groups? Why is it so hard to find names for what I thought would be common industrial compounds?

item b is Propiolic acid, item a is Acrylic acid. Both have many reactions that could be used to fabricate other materials. item d with two double bonds could certainly polymerize. Graeme Bartlett (talk) 10:45, 16 January 2010 (UTC)

Well the issue is that it's an acrylate ... deprotonated acrylates don't really form enolates, do they? It would be a double anion. John Riemann Soong (talk) 11:31, 16 January 2010 (UTC)

I would have thought the answers to these questions would be in your lecture notes. If a lecturer sets homework problems, they almost always relate directly to the content of the lecture! Failing that, textbooks are good. Or have you tried both these sources and had no luck?

Ben (talk) 15:09, 16 January 2010 (UTC)

Um I'm currently not in school. School starts in five days. I'm asking because I'm trying to synthesise various products and need to know how these groups work in practice (versus on paper). My lecturer never addressed what happens to the Aldol EWGness of a deprotonated COO- group on a Michael acceptor, okay? Neither do our articles.

Also kindly do not insult me by saying these are homework problems. THEY ARE NOT. I drew these molecules as examples of structural motifs I have been considering. John Riemann Soong (talk) 15:27, 16 January 2010 (UTC)

Why is it so hard to get answers here? Can't anyone answer questions on elementary first-year chemistry? I passed my last orgo final with flying colours (242/250), in fact, I may not have another orgo class until grad school (unless I take orgo III in my last year). But of course, the more I ponder questions, the more I realise what I do not know, because naturally what you do on an exam doesn't translate to real life knowledge. So I'm trying to ask real life chemists. I ask the reference desk because my profs get tired of being pestered all the time and have stopped answering my emails. =( (They are also on vacation.) SO CAN SOMEONE PLEASE START ANSWERING MY BASIC QUESTIONS??

For example, when I look at the malonic acid syntheses (my lecturer focused on the alpha-carbon and the reaction pathway and not you know, the issue of whether a COO- group was still electron-withdrawing). I have a feeling that malonic acid has two COOH groups so simply because of pkas one will be deprotonated and one will be protonated but this also means that now malonic acid only has ONE EWG, not two? And why would the Knoevenagel condensation work with beta-keto acids at alkaline pH's if the COO- group is deprotonated? (There is only 1 carboxylic acid group, not two so naturally being the only COOH group on the molecule it will lose its proton.) But I see reactions occur all the time with acrylic acid when its carboxylic acid group should supposedly be deprotonated at pH 7 and these reactions seem to be activated by BASE. HELP SOMEBODY????

I get the idea that you can kind of help the whole issue by doing it in non-aqueous solvent but this only appears to work so far when you are specifically adding BASE to the reaction. John Riemann Soong (talk) 15:42, 16 January 2010 (UTC)

Take a deep breath and relax! It's not worth getting stressed about. I wasn't trying to insult you at all, just trying to help, as I didn't know the answer off the top of my head, no-one else is answering, and you wanted to find the answer quickly.

You're trying to synthesise these molecules in the lab. What's the normal method for finding the best way of doing a synthesis? Check the literature, e.g. Organic Syntheses, Web of Knowledge, SciFinder, the library. Get your textbooks out and check if the concepts are covered - your lectures might not have covered a certain topic but your textbook probably will.

If you snap at people who are being nice to you by trying to help, they might not help in future. Say 'thank you' once in a while!

Ben (talk) 15:55, 16 January 2010 (UTC)

I dunno, being accused of asking a homework question is like a huge insult on the RD. I wouldn't have asked it on here if Google Scholar was giving me relevant results! I have checked the literature. I have checked my notes. I certainly crushed my textbook before. I am not a grad student; I have used literature before to learn new reaction pathways, but I am not like, a literature warrior. Literature is sometimes quite tedious to check because they assume you already know the material and are an experienced chemist. "Oh look! We won't show you why this reaction works because we assume you already know the reasons why!" I AM NOT AN EXPERIENCED CHEMIST. I CAN'T FIND THE INFORMATION ANYWHERE AND I NEED HELP. =( John Riemann Soong (talk) 16:04, 16 January 2010 (UTC

OK, fine, just say "I've checked my notes and textbooks but couldn't find the answer". I know you need help but shouting about it isn't going to get you what you want any faster. Take a break, get some fresh air and come back - you'll be able to think more clearly and will feel less frustrated.

If you're having difficulty with carboxylate groups, why not esterify them or conduct your reaction in acidic conditions?

Ben (talk) 16:20, 16 January 2010 (UTC)

Side reactions will occur on my electrophile -- it's a condensed amino acid with substituted groups on it. Oh whoops, it's been condensed (self-acylated and cyclised) so in fact it is an "amino ketone" ... with a very sensitive alpha proton between an electronegative nitrogen and an EWG ketone carbonyl. If I use acid, I risk various undesirable side reactions. I think. I am looking at the Knoevenagel condensation because I think decarboxylation will favour my desired nucleophile via Le Chatelier's principle to drive the reaction forward.

I know that two mesomeric EWGs (if I use the ester) are theoretically supposed to be better than 1 carbonyl and an inductive electron-withdrawing nitrogen. But what happens is when the enol on my "amino-ketone" forms, the enol C=C bond gets connected to an entire indole ring... so uhhh.... that puts me in a dilemma. Hence why I want to use decarboxylation... but it's so difficult! John Riemann Soong (talk) 16:34, 16 January 2010 (UTC)

Just try a few of them for real. See what works - this is why we do experiments!

Ben (talk) 16:40, 16 January 2010 (UTC)

Electrical circuit loading

I'm trying to teach myself electronics and don't understand why my circuit is doing something. I have a 400ohm resistor and two LEDs in series, and a 3 volt DC motor in parallel across that. All is connected to a standard 9 volt battery. When I close the switch, the LEDs briefly flash, and the motor starts. I assume the motor is taking all the power. What do I do to spread the load across the LEDs and motor, and why is this happening? Thanks in advance! --Kickstart70TC 03:36, 16 January 2010 (UTC)

It sounds like your motor is the path of least resistance. It's no wonder, when you have a 400 ohm resistor along the route with your LEDs in it. John Riemann Soong (talk) 03:48, 16 January 2010 (UTC)

I wondered that, but putting the motor after the resistor means that either, but not both, the motors or the LEDs activate (mostly the motor). The resistor is there to protect the LEDs (max 3.2 volts each), so I can't really do without it. --04:42, 16 January 2010 (UTC)

The LEDs would briefly flash because the inductance of the motor briefly stops the current flowing through it and keeps the voltage up. Dmcq (talk) 09:42, 16 January 2010 (UTC)

@Kickstart: I'm assuming that your switch is in series with the battery, so both the LEDs and the motor are energised at the same time. Then you say that the LEDs light up for a moment, and go off as the motor starts turning. Is that right? Then Dmcq's explanation is correct. You also say that you have a 3V motor connected across a 9V battery. This means that the motor will be drawing far more current than it is meant to, so it is not surprising that the voltage drops too low to light the LEDs. You might even damage the motor. You need to arrange for the motor to receive a 3V supply, not 9V. You should be able to do this by adding another resistor in series with the motor. Put a multimeter across the motor and experiment with different resistors until you get 3V across the motor. That should do it. Beware that the resistor might get quite hot, so you may need a high-power wirewound type. --Heron (talk) 11:17, 16 January 2010 (UTC)

It's all Ohm's law and basic algebra. This is not meant as a flip response; if you want to do any sort of electronics you need to think in Ohm's law almost as a second language. Short Brigade Harvester Boris (talk) 15:47, 17 January 2010 (UTC)

LEDs don't seem to have received the memo about Ohm's law. (That was a flip response.) Inductance can be handled using complex number algebra. Cuddlyable3 (talk) 22:20, 17 January 2010 (UTC)

protection of aromatic substitution sites

Is this possible?

This is a polycyclic compound (tryptophan) -- one site is particularly reactive, and if I "disable it" via a halogen, I think I can then carry on a reaction at another less reactive site (it's intramolecular so it would be kinetically favoured) -- and the halogen would also deactivate the imidazole ring and favour substitution on the benzene ring.

The thing is, is "dehalogenation" practical? I want to do it without affecting any further substituents that I put on. (None of the substituents are aryl, though.) The substituents I'm putting on will be aryl-carbon bonds. John Riemann Soong (talk) 03:47, 16 January 2010 (UTC)

Toilet bowl - the cleanest place in school?

As the toilet bowl is always flushing itself after use, is it true that the toilet bowl surface is the cleanest place in school? Why or why not?
If there is any information on the question, can anyone please answer it or upload a reference website address up here? Thank you. Crystal1102 (talk) 05:09, 16 January 2010 (UTC)

There are undoubtedly things in the chemistry and biology labs, as well as the nurse's office that are kept close to sterile. APL (talk) 05:34, 16 January 2010 (UTC)

In my year 12 biology class we meaured bacteria counts in different parts of the school. The cleanest spot was the urinal, and the place richest in bacteria was the canteen. Nasties can stick to the toilet bowl. Graeme Bartlett (talk) 06:18, 16 January 2010 (UTC)

Makes sense. There's a chunk of solid disinfectant in the urinal, but not in the salad :) , usually. --Dr Dima (talk) 08:00, 16 January 2010 (UTC)

The way I've heard this same story, it was about people's homes, and how the toilet bowl is typically far more sanitary than the kitchen. Wooden butcher's blocks being particularly filthy. Still, there would likely be a difference in the kind of bacteria. It's still a good idea that "employees must wash hands".--Rallette (talk) 11:31, 16 January 2010 (UTC)

If your urinal has autoflushers why don't people just not touch the restroom or their privates? It's not that hard and saves time. This would probably increase sick days, though, as you still touch nonbathroom things and be reducing your only middle-of-the-day source of hand washing. Sagittarian Milky Way (talk) 14:29, 16 January 2010 (UTC)

I was waiting around in the toilet at Subway for ages the other week and no-one showed up to wash mine for me. --Kurt Shaped Box (talk) 15:04, 16 January 2010 (UTC)

In reference to the comment on butcher's blocks above, I'm assuming you mean because of the porosity of the wood and perhaps the deep cuts providing nice niches for bacteria to avoid mechanical debridement during scrubbing, etc. If, for instance, one had a handheld cutting boad small enough to place in the microwave, would zapping it take care of the microbes? Or perhaps putting it in the freezer -- would that kill the bacteria? Perhaps soaking in vinegar...any thoughts? DRosenbach ^{(Talk | Contribs)} 06:08, 17 January 2010 (UTC)

You also need to bear in mind one of the important principles of kitchen hygiene, don't use the same board for raw meat and other products. Raw meat will (almost) always be cooked before consumption thereby killing any possible harmful bacteria. Problems occur where there is transfer of bacteria from raw meat onto already cooked or raw consumed food. Not that all raw meat is necessarily contaminated, and vinegar is not a reliable disinfectant. Richard Avery (talk) 09:13, 17 January 2010 (UTC)

Boiling water is a pretty effective killer of nearly all bacteria (except for the ones adapted to live in thermal vents on the ocean floor, and they are not likely to invade your house), but don't use it on your hands! Dbfirs 20:52, 17 January 2010 (UTC)

To:Graeme Bartlett Hello can I know what are the processes carried out for this experiment? And can I have a report of it as well? I am also doing a similar experiment and we have no idea how to do it. Thank you. Crystal1102 (talk) 05:54, 19 January 2010 (UTC)

We had petri dishes with agar gel in the bottom. One was just exposed to the air in the room, and the other one we got a cotton swab, rubbed it on surfaces in the room and rubbed it on the agar in the petri dish. Then they were labeled and stored in the incubator till the next biology lesson a couple of days later. Then we got them out and counted the visible dots due to bacteria cultures. All the students in the class were formed into small groups, with each group having a different room to check out. All my biology notes and writeups were stolen towards the end of the course. But it had no effect on my mark. So I cant show my report, but it would have been two or three pages with aim, method, results and conclusion sections. Don't expect anything extremely rigorous from year 12! I expect we did not know the temperature or duration of the incubation. Graeme Bartlett (talk) 11:03, 19 January 2010 (UTC)

To: Graeme Bartlett
Thanks alot! Crystal1102 (talk) 12:28, 19 January 2010 (UTC)

Lorentz transformation

How would the Lorentz transformation equations change if the two reference frames were moving relative to each other at an angle with respect to the set of axes. Would the gamma factor for x, y, and z just use the component of the velocity in their respective axis for v? —Preceding unsigned comment added by 173.179.59.66 (talk) 06:53, 16 January 2010 (UTC)

As far as I understand your question, this would only be a rotation to the 3 space coordinates. The transformation would look far more complicated as in the standard case of movement only along one axis. Physically, this wouldn't change anything. 93.132.135.45 (talk) 11:20, 16 January 2010 (UTC)

From the article Lorentz transformation:

${\begin{bmatrix}c\,t'\\x'\\y'\\z'\end{bmatrix}}={\begin{bmatrix}\gamma &-\beta _{x}\,\gamma &-\beta _{y}\,\gamma &-\beta _{z}\,\gamma \\-\beta _{x}\,\gamma &1+(\gamma -1){\frac {\beta _{x}^{2}}{\beta ^{2}}}&(\gamma -1){\frac {\beta _{x}\beta _{y}}{\beta ^{2}}}&(\gamma -1){\frac {\beta _{x}\beta _{z}}{\beta ^{2}}}\\-\beta _{y}\,\gamma &(\gamma -1){\frac {\beta _{y}\beta _{x}}{\beta ^{2}}}&1+(\gamma -1){\frac {\beta _{y}^{2}}{\beta ^{2}}}&(\gamma -1){\frac {\beta _{y}\beta _{z}}{\beta ^{2}}}\\-\beta _{z}\,\gamma &(\gamma -1){\frac {\beta _{z}\beta _{x}}{\beta ^{2}}}&(\gamma -1){\frac {\beta _{z}\beta _{y}}{\beta ^{2}}}&1+(\gamma -1){\frac {\beta _{z}^{2}}{\beta ^{2}}}\\\end{bmatrix}}{\begin{bmatrix}c\,t\\x\\y\\z\end{bmatrix}}\ ,$

Dauto (talk) 04:44, 17 January 2010 (UTC)

computer symulation for the theory of general relativity of Einstein

I am a Phyisicist student and am looking for a computer symulation for the theory of general relativity of Einstein, as without such instrument it is very dificult to perform the required calculations. I cannot use the Newton's mechanics as I wish to calculate calculations for bodies near an event horizon of black holes. Do you know where I can find something like this? Thanks in advance 89.139.82.116 (talk) 09:56, 16 January 2010 (UTC)

What exactly do you want to calculate? Here's a research paper on The general relativistic N-body problem; it is an analytic treatment; you may be interested in our article on numerical relativity, which links to many different research papers. There are probably not a lot of open-source or commercial relativistic numerical simulations, because this is sort of a niche research community, but you can try contacting the corresponding author of one of the papers to see if they have any pointers or code to share. This NASA press release on black hole simulation mentions this PRL paper, Gravitational-Wave Extraction from an Inspiraling Configuration of Merging Black Holes, where black holes are evolved through a computational grid. Nimur (talk) 15:35, 16 January 2010 (UTC)

Crop yield

The article describes what it is but are there any kinds of tables to check the yield for different crops/climates/soil? I did a search on the net and it is all widely incoherent. It's measured in different units on each article and I strongly suspect there are people out there who mistook MT for Mt (metric tons for megatons). 93.132.135.45 (talk) 11:15, 16 January 2010 (UTC)

There are so many variables, in climate and soil conditions alone, that I doubt whether, even if such tables existed, they would be of any practical use. There are no doubt localized figures available for specific crops, so you would do better to use much more specific search terms.--Shantavira|^{feed me} 11:55, 16 January 2010 (UTC)

I'm looking for figures for use in renewable energies from neutral sources. 93.132.135.45 (talk) 12:04, 16 January 2010 (UTC)

See the so-called "Billion Ton Study" and references therein. Short Brigade Harvester Boris (talk) 15:49, 17 January 2010 (UTC)

Does milk spoil or taste old faster the less of it is left in the container?

If so, does the rate of spoilage become only a little faster or a lot? I have a feeling it at least accelerates somewhat with inverse volume but never empirically found out as there are various reasons we wouldn't get to be affected by this much in normal use. Sagittarian Milky Way (talk) 14:10, 16 January 2010 (UTC)

It probably depends on conditions. Large volumes of milk have more thermal inertia so they stay cold longer. Realistically, this effect only lasts a few hours (if we're talking about 1-gallon sized quantities), but it might be the difference between rancid and not-rancid if you leave a full gallon vs. a mostly empty gallon on the counter for two hours. Homogenized milk should be, well, homogeneous - so the bacteria and their food source (lactose) should be evenly distributed throughout the milk. Therefore, once the temperature is warm enough to activate them, adding more milk shouldn't change the spoilage rate. But, there may be a surface-area to volume ratio issue. We have an article on soured milk with links to a bunch of links and patents on techniques for intentionally souring milk, e.g., Process for Preparing Gelled Sour Milk. Nimur (talk) 15:11, 16 January 2010 (UTC)

Perhaps a thought experiment is in order. Consider a container of milk containing one lonely bacterium. Let's assume that refrigeration confines it to one cycle of division per day. On day two, there will be two bacteria; on day three, four bacteria. On day ten, there will be a thousand; on day twenty, a million; on day thirty, one billion (roughly). If each bacterium turns out the same amount of lactic acid each day, the amount of acid generated on day ten will be roughly equal to the amount of acid released in total on days one through nine. Each day's new growth will match the spoilage caused on all the preceding days. This is why the apparent rate of spoilage will tend to increase with time; it doesn't matter how full or empty the container is. (That said, as the container empties, there is more and more room air being exchanged into the jug or carton each time you open it. That room air may contain additional microbial contaminants which increase the load in the container and speed spoilage. Again, the faster spoilage isn't directly the result of a less-full container; there's just been greater exposure of the emptier container to contaminated air, and the emptier container has been opened and closed more often than the full one.) TenOfAllTrades(talk) 16:10, 16 January 2010 (UTC)

In the absence of bacteria things alter their taste by oxidation, which happens by surface/volume. Take a look at an apple pie. If you have the purse and the taste for it, examine an opened bottle of wine over the course of some days or weeks. 93.132.135.45 (talk) 18:16, 16 January 2010 (UTC)

How does Parathyroid hormone work on the kidneys?

Ok so I've done some research and now I'm stuck! As far as I know parathyroid hormone (PTH) has 3 main effects on the kidneys: Increases reabsorption of calcium ions Reduces reabsorption of phosphate ions Causes conversion of calcifediol to calcitriol

What I need to know about is how these effects are brought about. I know there are PTH 1 receptors to be found in the kidneys, does the binding of PTH to them trigger a cAMP dependent pathway activating a protein kinase which would produce a substance of some sort? The wiki article on PTH says PTH inhibits the cAMP dependent pathway but an article I found in the Journal of the American Society of Nephrology 20(8):1693-1704, August 2009 said quite the opposite. Also, I know that PTH increases the uptake of calcium ions by activating Ca2+-ATPase and a Na+-Ca2+ antiporter but can't find any information on how this occurs...

How does PTH reduce the reabsorption of phosphate ions? Also through the activation of protein kinase A via a cAMP dependent pathway producing some sort of substance? I've also read that PTH inhibits the sodium phosphate co-transporters in the Proximal convoluted tubule - reducing phosphate reabsorption...

As you can probably tell I'm very confused now. Any help would be massively appreiciated! RichYPE (talk) 14:37, 16 January 2010 (UTC)

It is certainly not unheard of to be confused about the complexity of calcium metabolism. The "business end" of any hormone is it's receptor, in this case two parathyroid hormone receptors. I wonder if you might have mis-read the part in parathyroid hormone about the cAMP dependent pathway -- that section is talking about regulation of PTH secretion by the calcium-sensing receptor (which inhibits cAMP production). In terms of getting an immediate "boost" to serum calcium, the most important action of PTH is to release calcium from the bone (which is where the vast majority of your body's calcium is stored). With regard to the mechanism of renal ion movements, you could start with the nephron article and the distal convoluted tubule, where regulated calcium reabsorption happens. Neither article really gives much detail about the movements of ions, but just remember that in most physiological systems, whenever there are ion channels in the plasma membrane of the cell, ions will flow along a concentration gradient. In the kidney, there are members of the Transient Receptor Potential Vanilloid (TRP) family (TRPV5 and TRPV6) that are responsive to vitamin-D and mediate calcium entry (see also this reference to get you started). I think the effect of PTH on renal reabsorption may be mostly secondary (via its action on vit-D). With regard to phosphate excretion, this article says that "FGF23 synergizes with PTH to increase renal phosphate excretion by reducing expression of the renal sodium-phosphate cotransporters NaPi-IIa and NaPi-IIc in the proximal tubules" (see phosphate homeostasis for more details). --- Medical geneticist (talk) 15:50, 16 January 2010 (UTC)

Thanks to medical genticist for the reply. I am aware that the conversion of calcidiol to calcitriol (1,25-dihydroxycholecalciferol)is a large part in how PTH affects the kidneys. At the moment, I'm focussing on how the kidneys act to increase calcium reabsorption and reduce its excretion without the influence of calcitriol. My essay is shaping up ok now, can someone read this and tell me if its correct: 'PTH acts by binding to Calcium sensing receptors (CaSR)in the kidneys activating renal adenyl cyclase to increase intracellular concentrations of cyclic AMP which activates protein kinase A and C.' Although now I've got a bit stuck again, what would activating protein kinase A and C do?

I also think PTH binds to GPCRs causing an increase in intracellular cAMP in the kidney cells which stimulates the production of phospholipase C which produces a subtance called IP3 that opens calcium channels allowing more calcium to be reabsorbed. Again is this correct?

Finally, would I be correct in saying that PTH increases phosphate excretion through the inhibition of Brush border membrane sodium dependent phosphate transporters in the proximal convoluted tubule? Thanks, RichYPE (talk) 20:06, 16 January 2010 (UTC)

the asymmetry of acetic anhydride

An interesting asymmetry.

I've asked this question before, but I really must return to it since a) I am starting a subproject where I post electron density images to articles b) I want a sort of caption to go with each image. So again -- why is acetic anydride asymmetric? I really don't think it's my calculator being stuck in sort of local well. It really seems that there is some sort of repulsion that makes the molecule take that conformation. -- further confirmation of the idea that the ethoxy oxygen in the molecule does not have a pi system connect across it at all! i.e. Acetic anhydride is not planar. One thing that I can think of is that there is intrinsic electronic repulsion, in a way not unlike antiaromaticity and this makes the carbonyl groups move to different planes (to avoid withdrawing from each other and to withdraw more from the methyl groups, maybe?).

Really have to explain why:

• the two C=O bonds aren't equal
• the ethoxy C-O bonds aren't equal either
• Neither are the methyl C-H bonds!
• To define a scale, the most negative pixel of the molecule has a density value of -41, while the most positive pixel has value +35.43. Te average value of the one carbonyl carbon (rough approximate) appears to be +33 (on one side), while the other carbonyl carbon (on the most positive side) it has a density value of +30. This seems to be quite a significant difference in the electropositivities of acetic anhydride's carbonyl carbons for what would be a presumably symmetric molecule.
• There is asymmetry even within the same carbonyl carbon -- for one particular carbonyl carbon, one "side" of it (where a nucleophile might presumably attack) appears to be about as neutral as an amide carbonyl carbon -- values range from -3 to +8, while the other side is drastically more positive -- +27 to +30. Apparently this is due to the nonplanar way the oxygen atoms are sticking out of the molecule.

I used 6-31G* for my calculations -- I think that's as rigourous as my program can go. Please answer promptly because I am about to edit the acetic anhydride article! John Riemann Soong (talk) 15:01, 16 January 2010 (UTC)

As with most things, experimental evidence is important - otherwise you're adding OR to Wikipedia. The structure of acetic anhydride has been probed experimentally, see for example J. Phys. Chem. A (2000) 104 (7), 1576–1587.

I had a look at the crystal structures of some anhydrides and they almost all had the same conformation (Jmol model here, based on Angew. Chem. Int. Ed. (2008) 47, 8030-8032). The exceptions were cyclic anhydrides whose geometry is constrained to nearly planar (e.g. succinic anhydride, maleic anhydride, phthalic anhydride).

Ben (talk) 15:34, 16 January 2010 (UTC)

So acid anhydrides (that are free to rotate) are CONFIRMED to be asymmetric, correct? My question is, what is the EXPLANATION for this? (Also I don't think adding in silico calculations are OR -- these get done all the time by undergraduates everywhere and I'm sure I must be the millionth person to calculate the mysterious density of AcOAc just that it's never been posted on Wikipedia.) John Riemann Soong (talk) 15:45, 16 January 2010 (UTC)

Also, why didn't anyone tell me this amazing fact during lecture??? Why is it not mentioned in the article acid anhydride? What is the explanation for it? Why can't I find it? What is wrong with everybody? John Riemann Soong (talk) 15:47, 16 January 2010 (UTC)

I'm not a grad student. I can't understand that paper, because I can't seem to sort through the alphas and phis and wavefunctions to find out if the methyl C-H bonds are equal and if not, WHY. John Riemann Soong (talk) 15:57, 16 January 2010 (UTC)

Neither am I, I just look at the diagrams and read the abstract and conclusion and try and understand it as best I can. It basically says the molecule does lose some resonance stabilisation by adopting non-planar conformations, but this is approximately compensated for by loss of steric hindrance and dipole-dipole repulsion (I guess that means δ− carbonyl oxygens close together in space in one of the planar conformers). Overall it says that "the delicate balance of these interactions allows in AA for a wide variation in skeletal torsion and valence angles to occur without much variation in internal energy. The different geometries along the rotation paths can be rationalized in terms of mesomeric and steric effects."

Ben (talk) 16:10, 16 January 2010 (UTC)

On average, do the C-O bonds (on either side) average out? That is, statistically, are the bond lengths symmetric? I get the idea that at any one time the bond lengths aren't equal. (Not that it makes that much sense anyway since the bonds are constantly vibrating.) Like ... why doesn't the NMR of acetic anhydride show two separate singlets (or worse, a complex mix of chemical shifts?)

Theoretically, does this sort of imply there wasn't much resonance stabilisation anyway? I mean usually resonance stabilisation >> conformation stabilisation (except in extreme cases). I actually thought there was internal electronic repulsion that forced the pi systems to be orthogonal to each other, but I guess not. John Riemann Soong (talk) 16:18, 16 January 2010 (UTC)

One consequence of a nonplanar conformation is that acetic anhydride appears to be more electrophilic than it would otherwise be in its planar conformation, because basically the electropositiveness of one side of the carbonyl carbon gets transferred to the other, so the side that doesn't have any oxygen dipoles near it is REALLY blue. But this is generally not included in class as a reason for why anhydrides are more reactive than esters! Instead we talk about dipole moments using PLANAR Lewis structures. WTF? Time to edit the textbooks anyone? John Riemann Soong (talk) 16:23, 16 January 2010 (UTC)

The Jmol model (from a crystal structure) has two different C=O lengths, 0.117 nm and 0.125 nm.

The ¹H NMR spectrum of AA (from SDBS) shows a single peak at 2.219 ppm. The ¹³C spectrum shows one peak at 166.63 pm (carbonyl carbons) and one at 22.07 ppm (methyl carbons). I assume these spectra were recorded at room temperature, so we're probably seeing averaging as the molecule rotates through many conformations, faster than the NMR timescale.

If you cooled the sample down, you'd probably see more peaks, as the rotation stops and an asymmetric conformer predominates.

What do you mean by internal electronic repulsion? The δ− carbonyl oxygens repelling each other electrostatically? Or destabilising orbital overlap?

As far as textbooks are concerned, there's a balance to be had between being pedantically correct and being intelligible. Got to walk before you can run.

Ben (talk) 16:36, 16 January 2010 (UTC)

I could never make sense of my lecturer's "dipole explanation" with planar Lewis structures. What dipole advantage? The molecule is withdrawing in both directions! It makes so much sense now to find out that the asymmetry is one of the big factors.

I don't know what I was exactly thinking with intrinsic repulsion -- I was seeing the pi electrons on each of the carbonyl systems repel each other somehow (hence why they are not on the same plane) -- maybe because they are both EWGs withdrawing from each other, and this is a mutually repulsive interaction. Like the same reason why a Cl-Cl bond is weak. I was thinking that putting them on a different plane would break this interacton and allow the carbonyls to withdraw more from the methyl groups instead. An interesting case I think, is when acetic anhydride gets protonated.

Is protonated acetic anhydride still aplanar? (Now you can hydrogen-bond!) If not ... that certainly hints at "intrinsic" repulsion. Although I get the feeling that the asymmetry encourages protonation of the C=O oxygen. John Riemann Soong (talk) 16:46, 16 January 2010 (UTC)

Anyway thanks. I guess I'm going to make an article edit. I'll use the paper you found as a source. John Riemann Soong (talk) 16:54, 16 January 2010 (UTC)

Not sure about protonated AA - try calculating the energies of the planar and nonplanar conformers of it in Spartan and compare. As for your Cl-Cl lone pair repulsion thing, the same argument could be applied to 1,3-butadiene but that's planar. Think about both those cases from an orbital point of view: Cl₂ doesn't have the vacant π MOs that butadiene does.

I'm going to eat now but I will draw some diagrams in a bit. Good luck.

Ben (talk) 17:02, 16 January 2010 (UTC)

Alkenes aren't really good EWGs though. I mean, the electron density is likely to be be more in the middle of the molecule (intrinsically a bonding interaction) than the ends (which is how it is in AA). John Riemann Soong (talk) 17:07, 16 January 2010 (UTC)

Howdy, I'm a computational chemist, perhaps I can be of some help. I pulled the full paper and gave it a quick read. The paper reports energies for various conformations of acetic anhydride. The lowest energy structure is definitely the one you would expect, planar acetic anhyrdide with some low energy conformations, some of which are non-planar but are roughly 1 kcal/mol above the planar ones. The issue with your calculation, and the reason you're getting an asymmetric electron density, is because Hartree-Fock (the calculation method you cite in the image information) isn't equipped to handle molecular orbitals with multiple resonance forms, which is precisely the reason that acetic anhydride is planar. The paper reports finding the planar minimum using Hartree-Fock however, and they may have manually forced the geometry to achieve that. I would strongly suggest upgrading to a perturbation theory based method such as MP2. 24.177.124.41 (talk) 17:21, 16 January 2010 (UTC)

Ah good, someone who actually knows what they're talking about! Thanks for stepping in.

I just had a look in the Spartan database. MP2/6-31G* gives the [sp,sp] planar geometry as the global minimum but MP2/6-311+G** says nonplanar, like this.

Maybe I was reading out of context, but I searched the paper for "minimum" and found the phrase "none of the planar forms (Figure 1) is a minimum energy form".

Ben (talk) 17:38, 16 January 2010 (UTC)

Oops, that'd be my bad. I misread the point groups. As I look at this paper more, I'm not sure I trust their computational method. B3LYP is a density functional theory and isn't particularly good at measuring weak interactions like you might find between the two carbonyls (depending on the relative electron populations which they don't report). All in all, I'd recommend finding an experimental work instead of a theoretical one for this answer and base your image on that. 24.177.124.41 (talk) 20:00, 16 January 2010 (UTC)

Hey thanks for stepping in! Do you mean interactions through space (dipole-dipole), or bonding interactions? Both would seem to favour aplanarity. But even if the planar form is the most stable form (crystal structure apparently shows different C=O bond lengths anyway? is it experimental?), the low barrier to rotation suggests very weak resonance stabilisation, which agrees with classical theory of course.John Riemann Soong (talk) 06:02, 17 January 2010 (UTC)

The crystal structure is experimental (almost all are, although see crystal structure prediction).

Ben (talk) 15:05, 17 January 2010 (UTC)

January 17

Any limit to bandwidth?

Could everyone in the world have as much wireless or radio bandwidth as they want, or is there some theorectical limit? And how near are we to it currently in urban areas? 78.147.229.52 (talk) 01:23, 17 January 2010 (UTC)

The bandwidth of over-the-air broadcasts depends on a lot of things, but in general the carrier frequency has a lot to do with how much information you can fit into a single "channel" or radio frequency. Bandwidth (signal processing) has a technical explantion of how it works. --Jayron32 01:42, 17 January 2010 (UTC)

The trouble is that more bandwidth generally requires a higher carrier frequency (for practical circuit design reasons). Unfortunately, high frequencies don't transmit as well over long distances and through walls. There's a really awesome band, down in the hundreds of kilohertz to few megahertz, which propagates so well that long wave radio can be transmitted across oceans and continents. But, there is no way to modulate megabits of data on a kilohertz carrier signal. The next window of opportunity is the VHF and UHF spectrum - which had previously been set aside especially for television, because it really goes pretty far (tens or hundreds of miles) and also goes straight through walls (so you can watch TV indoors, which is good for practical reasons). That spectrum has recently been freed up by government/commercial administrative action, and is now being reallocated for mobile telephones and mobile data systems. But that shared channel still only has a few tens or hundreds of megabits of total digital data, which must be shared between everyone on the air. The next higher frequency of practical significance is probably L-band through S-band, which you use for everything from satellite TV/internet to WiFi ("802.11" style wireless data). The satellite spectrum is very carefully allocated, because only a few select frequencies propagate well through the atmosphere to space. At these higher frequencies, channels can be modulated with bandwidths of tens or hundreds of megabits - but the propagation parameters are beginning to get ugly. "802.11" (or rather, 2.4 GHz) doesn't go through walls very well - and it doesn't really travel that nicely through air (not compared to, say, 700 MHz). So, city-wide WWANs will probably never use "802.11"-protocols, even if the power is boosted up really high - because the signal just fades quickly. As we get into the K-band and higher frequencies, it becomes prohibitively expensive to mass-produce circuits - so although the millimeter-wave and microwave bands are very appealing for their transmission and data capacity, they are at least a few decades off from mainstream wireless data systems. Finally, as we start peaking above terahertz radio and into the optical regime, the transmission becomes line-of-sight. So, while optical data transfer is great for bandwidth, it's terrible for wireless - unless you can physically see the laser or "transceiver" with your antenna, you won't be able to get data from it. This means no walls, no trees, no rain ... all these sorts of obstacles which radio frequency wireless systems are fairly immune to. Nimur (talk) 02:59, 17 January 2010 (UTC)

How close to saturation in urban areas are we currently? 10%, 20%? 92.29.80.215 (talk) 12:32, 17 January 2010 (UTC)

It's a matter of bandwidth - but also of range. Everyone can have as many bluetooth connections as they like because the range of bluetooth radio is just a few meters. But if everyone was using the AM radio band and trying to transmit halfway around the world - things would get chaotic very quickly! But in the end, from around 100 kHz up to maybe 30GHz is usable. The total number of bits you can transmit over that waveband is half of the maximum frequency - so at most 15Gbits/second is available. That's quite a lot - but I have 5 computers in my house with 1GHz ethernet strung between them - if I switched to some futuristic radio technology, then I could imagine that I might personally consume a third of the world's radio frequency spectrum! Or, for example, a 3G phone can send about 6Mbits/sec and receive at about 14Mbits/sec - so at 20Mbits per phone, we're only able to support about 1000 phones before we run out of radio bandwidth! Clearly there are a lot more than 1000 3G phones in the world. So certainly if we allowed free use of any frequency range over any distance, the answer to your question would be a very clear "No!!".

But it's not that simple. Each cellphone can only transmit and receive over a relatively short range - far enough to get to the nearest cellphone tower - but not much further. So we could actually (theoretically) support 1000 phones within the range of each tower - and those can be as close as 1km apart and allow everyone to use 20Mbits/s of bandwidth at the same time. But I'm sure that if you picked someplace like a city center or a sports stadium - there would be VASTLY more than 1000 cell phones within range of a single tower. Fortunately, not all 1000 phones are in use at the same time - and even when they are, not all of them are downloading movies from the Internet - most of them are sending about 10kbits/s of speech data in a phone call.

So by taking advantage of the usage patterns and limited range of each kind of device, we can make much better use of the available radio spectrum.

But still, I don't believe there is enough radio bandwidth to give everyone everything they need with the present technologies that we're using. You could imagine something much better though. Suppose we made teeny-tiny nanotechnology radio transmitters and receivers that were so cheap that we could put them into every surface of every building, every road, every car - and drop them from aircraft in vast quantities over open spaces of all kinds. We could imagine a situation where you were never more than (say) 30 meters from the nearest one. All our radio devices could be designed to have a maximum range of (say) 30 meters. Let's have those nanotech devices talk to each other - so when you send a message, the nearest one figures out the route to the destination of your message - using a chain of thousands or tens of thousands of these gadgets - each one transmitting at such low power that it can only reach the next one in the chain, typically about 10 to 20 meters away. This is like the present cellphone system - except instead of the towers being 1km to 30km apart - they are 1m to 30m apart. With such short ranges, you'd have only at most a dozen or so people within range of each device. Now, each person could use up to maybe 1/10th of the entire radio spectrum - more if not everyone is using it all the time or we aren't all using it at full bandwidth all the time. We could have a personal 1.5 Gbit/sec always-on connection.

We could go one step further and do what the "One Laptop Per Child" system does. In that system, you don't send messages from one unit to "the network" directly - you have every unit acting as a "cell tower" - so my laptop talks to the WiFi system - but your laptop is out of range of the WiFi system - so it talks to my laptop and my laptop passes the message along to the WiFi. A network of these laptops can cover a large area - so long as there is always a chain of them reaching back to the Internet.

If we made cellphones do that then the system would be magically self-scaling. Each phone would have to try transmitting at very low power to see if there is another phone that's in contact with "the network" and very close by. If not, it would gradually ramp up it's transmit power until it could find either another connected phone - or a cell tower. So long as all phones have plenty of bandwidth - not only for their own user - but also for passing on messages from other phones - then radio ranges could be kept short. This would save battery power too. We could imagine our sports stadium with half a dozen wired super-high bandwidth landlines - and 50,000 people all using a ton of bandwidth at the same time - but each one is transmitting only to the cellphone of the guy in the seat next to them...who transmits the data on to the next guy and so on. The amount of simultaneous bandwidth would be phenomenal because it's very efficiently shared. On the other hand, if you were out in the desert, 20 miles from civilisation, your cellphone would gradually increase it's power until it could reach the nearest cell tower. By transmitting with that much power, it's monopolising the bandwidth over hundreds of square miles - but that's OK because nobody else is using it.

But even that isn't really the upper limit. We're still talking about systems that broadcast their radio in all directions. You could imagine a system where the phone can send highly directional radio beams and aim them at the nearest contact point. That would open up the number of phones that could share the same radio frequencies tremendously.

There are some severe technological issues with what I've described. The latency in transmitting though all of those intermediate devices would be huge (although you could still have less closely spaced gizmo's connected with optical fibre or something to handle the longer distance traffic). The power requirements would be tough to handle - you couldn't have all of these many devices be battery operated - who would change the batteries? They'd need to be solar powered or something.

But I think that with enough clever technology, we could come close to giving everyone up to maybe 5Gbits/sec of wireless bandwidth. More than that starts to become very difficult.

SteveBaker (talk) 12:48, 17 January 2010 (UTC)

The total bandwidth of a mesh network is limited by the connection from the mesh to the internet. If you have a long chain of users, with just one connected to the internet, then they are still sharing one connection between everyone (this isn't usually an issue because most people won't be using lots of bandwidth at the same time, but that same thing means that sharing the radio spectrum isn't a problem yet). Shortening the range of radio transmissions is a good idea, but you need to shorten the total distance of the radio transmission, not the length of each step. Those mini-cell towers every 30m would each need some other method of connecting to the internet (that might be where directional antenna come in - getting a phone to transmit in the right direction is a challenge because it is always moving, getting a mini-cell tower to do so would be easy). --Tango (talk) 18:44, 17 January 2010 (UTC)

Steve's suggestion sounds great (I'm a huge fan of wireless peer to peer routing schemes). The immense benefits that a short-range mesh network may yield are awesome for per-transaction transmit power. But Steve forgets to mention the dark and dirty secret about mesh networks - the aggregate overhead to power and bandwidth that is incurred, because every device must operate in an "always-on", always transceiving mode! The total power consumed may be much higher - e.g. much worse for battery life - because the device is constantly relaying other peoples' data. Whether this actually reduces the total power consumed by the entire network (e.g. whether the integral of the distributed, but constant, low-power draw is less than the integral of the short, high-power transmission for a centralized, point-to-point scheme), is an active area of research. It seems to be highly dependent on usage-case. A lot of commercial vendors are now producing microcell and "picocell" mobile telephony transceivers, stepping towards a more mesh-network style arrangement. This is especially useful in densely populated locales, like inside a shopping mall or one seating area of a a sports stadium. Finally, femtocells (you got to hand it to these marketing guys' creative capability...) allow a really mesh-style, single-room connectivity. I think in general we are moving toward a Optical carrier fibre ("wired") back-end with localized point-size wireless micro-transmitters, rather than a true, completely wireless mesh-style peer-to-peer scheme. But, as more devices become wireless-data-enabled, Steve's description of a true mesh may become more economic (both in terms of infrastructure cost and operational bandwidth/power/battery-life considerations). In the meantime, hobbyists, survivalists, military users, and HAMs make use of technology like AX.25, military Command, control, and communications radio-networks, and HAM packet radio. These are true wireless mesh schemes with no reliance on a wired backbone. Some of these networks are even connected to the internet and can serve as an underlying transport for TCP/IP networking as if you were on an 802.11 system. I have "heard anecdotally" that EA-6B Prowler fighter jets overflying ground troops in Afghanistan now broadcast a point-to-point VHF signal to the ground; they dynamically locate the troops' radio transceivers and mesh up a wireless network for the few seconds that they are within visual range, and perform bidirectional data dumps to the base stations using aviation bands, when the troops are out of range of their ground-based VHF and UHF systems. Nimur (talk) 20:21, 17 January 2010 (UTC)

Indeed, mesh is fantastic for increasing coverage (in a warzone, in the poverty stricken areas targeted by OLPC, etc.), but it does nothing to increase bandwidth (it might allow for more efficient usage of bandwidth in some circumstances, I suppose), which is the topic of this thread. --Tango (talk) 20:41, 17 January 2010 (UTC)

Right. The current status-quo is that the mesh network is a sub-network, and it connects to the internet. In the limiting case, the entire internet is a mesh network, and there is no point bottleneck for the bandwidth. It seems unlikely that we are evolving in this direction, as most of the content that people now access on the internet comes from a centralized server, with a disproportionate amount of bandwidth between "everybody" and one or two companies (e.g. Google/Youtube, for example). Theoretically, an optimal use of bandwidth would require everybody to have a random probability of accessing content from anybody else - but this is not really economically effective for the internet. Conglomerates operate central servers, and most people downlink data from those, in a mostly "uni-directional" mode. Even accounting for user-generated content, the total quantity of data transferred is usually very disproprotionate and centralized when it is hosted on third-party servers. Nimur (talk) 22:16, 17 January 2010 (UTC)

Speaking of WiFi, it appears that some people may be "allergic" to it. [6] ~AH1^(TCU) 23:38, 17 January 2010 (UTC)

As far as I know, there is no reliable evidence of any such sensitivities. --Tango (talk) 00:11, 18 January 2010 (UTC)

Electrosensitivity? ~AH1^(TCU) 00:33, 18 January 2010 (UTC)

What's the question mark for? --Tango (talk) 01:03, 18 January 2010 (UTC)

As our article says, "The majority of provocation trials to date have found that self-described sufferers of electromagnetic hypersensitivity are unable to distinguish between exposure to real and sham electromagnetic fields". Was there a particular reason to bring it up here? 86.178.229.168 (talk) 01:50, 18 January 2010 (UTC)

Going back to the original question, and talking a bit more about the theoretical limits to the information bandwidth (i.e., number of bits of information that can be communicated per second). As already mentioned, the limit depends upon the channel bandwidth (measured in Hertz) that is available, but it also depends upon the channel signal to noise ratio. For instance, for point-to-point communication in an additive white Gaussian noise (AWGN) channel, such as wired communication or short-range/open field wireless communication, this limit, known as the channel capacity C is given by the famous Shannon–Hartley theorem: $C=B\log(1+{\frac {S}{N}})$
where B is the bandwidth (in Hz), S is the signal strength (i.e, how much power in Watts you have available to transmit the signal) and N is the level of noise in the channel. From this formula you can see, that one can (theoretically) transmit unbounded amount of information over even a narrow channel, as long as one is ready to use more powerful transmitter.
The analysis becomes much more complex when one considers wireless channels in urban environments (for example due to multipath fading), and multiuser systems (in which case one needs to account for signal interference, spatial diversity etc, and differentiate between overall throughput, average throughput etc), but the general intuition remains the same - in theory, one can arbitrarily increase the information rate, by either using wider bandwidth channels, or by throwing more power in (although the marginal returns of the latter keep getting smaller). Any standard textbook on wireless communications should be able to provide you more information on the basics of this topic, although the general multiuser information theory is still an open problem, and an active area of research. Abecedare (talk) 01:55, 18 January 2010 (UTC)

Could a religious person please specify the maximum available bandwidth of the prayer channel to God? Cuddlyable3 (talk) 15:25, 18 January 2010 (UTC)

Red dwarfs proportion to all stars

According to the best current estimates (the current consensus), what percentage (range of percentage) of the stars in the universe are red dwarfs? —Preceding unsigned comment added by 63.17.79.94 (talk) 11:58, 17 January 2010 (UTC)

Old school cathode ray television superior?

I have a monstrous standard definition Phillips 32PW9586/05 widescreen CRT television. Is it just my imagination or sour grapes at not having a modern flat HDTV plasma or LCD television, or is there something much more film like about "old fashioned" sets? The plasma and LCD televisions I have seen in shops seem either dull or cartoon-like in comparison, despite the much vaunted extra detail. Does anyone make High Definition CRT televisions? Perhaps it's merely sentimentality over an "antique?"Trevor Loughlin (talk) 13:16, 17 January 2010 (UTC)

I also prefer CRTs. My desktop uses dual CRT monitors. They have traditionally provided a higher color depth. For example, some LCDs have trouble displaying pure black. They also have a faster response time, making motion look more lifelike. They also have a wider field of view. However, the latest high-end LCD screens have almost caught up to CRTs in color depth, and response rates. At least, our eyes can barely tell the difference. But cheaper LCDs are certainly still far inferior to cheaper (and higher end) CRTs. Further, LCDs still lag significantly in viewing angle. You will notice a difference at an angle. Some LCD screesn are unviewable at even slight angles, whereas others are wider. If you want an LCD TV that looks like your old CRT, you will have to pay much more than what you paid for the CRT. Unfortunately, I know of no high-end CRTs that are being manufactured. People like LCDs because they are more stylish, easier to carry, brighter, and consume less energy. I can understand why you'd be concerned about weight if the screen was for a laptop, but you only have to move a TV or monitor once. So, I think LCDs are over-rated.--Drknkn (talk) 13:39, 17 January 2010 (UTC)

I also view a 32-inch widescreen CRT TV (Panasonic) and relative to a plasma or LCD replacement I judge that I have better brightness and contrast and much better sound thanks to the monstrous cabinet size, which hardly matters when the TV stands in the corner of the room. However my set cannot match the "perfect" picture linearity, colour convergence and low power consumption of flat panel displays. The latest pricey Organic LED panel TVs may give the best displays yet, and they are already available in larger sizes than are practical for CRTs. Cuddlyable3 (talk) 20:03, 17 January 2010 (UTC)

One feature of CRTs that I am still waiting for in LCD/Plasma/OLED/DLP is a true black. A CRT could drive the electron beam to essentially zero amplitude, so if I had a little text on a black background, the tube would not light up a dark room. An LCD has a backlight, so the best it can do is dim the screen to a "gray" or "purple" color. All the progress in contrast ratios for LEDs and their ilk seems to be about making bright whites even brighter - but I'd really like to see a darker black the way a CRT can operate. Nimur (talk) 22:21, 17 January 2010 (UTC)

Well as our article mentions, OLED TVs don't use a backlight so do or should achieve a good black. I haven't actually tested it myself but you can always buy a Zune HD or something if you want to see. Or one of the displays linked below. If it doesn't do it for you, feel free to send it to me so I can see for myself... Nil Einne (talk) 10:07, 18 January 2010 (UTC)

What? The largest commercial OLED TV (or display of any kind) I'm aware of is a the LG 15-inch [7]. Indeed the 11 inch Sony XEL-1 is one of the only other relatively commercial OLED TVs (or any other display) I'm aware of. Sure Samsung have demonstrated a 40 inch OLED TV and other companies have demonstrated other large OLED displays and sure people keep promosing large OLED displays and perhaps we'll actually get them this year but I wouldn't exactly consider them 'available' when they've just been shown of in tech shows but not sold in the marketplace. Nil Einne (talk) 10:05, 18 January 2010 (UTC)

Philips sell a 40", LG sell 42" and 47", Samsung sell 40" and 46" LED TVs. Cuddlyable3 (talk) 15:21, 18 January 2010 (UTC)

Yes but they aren't OLED which is what you mentioned/linked to. And a LCD TV with an LED backlight is quite different tech from an OLED TV so it doesn't make much sense to discuss them as the same thing even if some vendors call them LED TVs. Personally I admit I find OLED or well any real LED displays i.e. displays which use LED for the display rather then just the backlighting much more interesting then the so called other LED displays although I won't likely be getting either anytime soon.

And in case you thought those were OLED TVs, well you weren't the only one. I only realised last month they didn't exist in large sizes despite all the hype and confusing marketing when taking part in some silly Christmas wish list competition (which I suspect they didn't really care about the list but had it so it wouldn't be considered gambling). I decided to put a bunch of crazy stuff including of course a Bugatti Veyron; and a large OLED TV intending to put an expensive one (brand and model number) until I realise they didn't exist so ended up just putting a large size (52" I think) and mentioning they didn't exist yet.

Nil Einne (talk) 16:10, 18 January 2010 (UTC)

Right - I was much disappointed with all the hype. In the US, it is legal to advertise such devices as "LED TVs" even though they are actually LED backlights for regular LCD screens. I believe that such advertising tactics are not permitted in the UK, which more strictly regulates the terminology that vendors can use. LED-backlit LCD television is the relevant article for more details. Nimur (talk) 18:44, 18 January 2010 (UTC)

Polarization of radio waves for extra signal capacity?

Light can be polarized, and it is possible to imagine a line of sight communication device using a laser somehow exploiting not only bandwidth but somehow modulating polarization as well to increase the data carrying rate (has this ever been done?- I just thought it up), but could this also be applied in more crowded areas of the EM spectrum, such as the microwave or even radio bandwidths? —Preceding unsigned comment added by Trevor Loughlin (talk • contribs) 13:32, 17 January 2010 (UTC)

Have a look at this: [8]. --VanBurenen (talk) 13:40, 17 January 2010 (UTC)

Do you mean that link to 13 million search hits for "Sound focusing"? Cuddlyable3 (talk) 19:02, 17 January 2010 (UTC)

Well, the first few would might be useful already. --VanBurenen (talk) 16:10, 18 January 2010 (UTC)

It's possible in principle - but when a radio or light signal is reflected off of something, that messes up the polarization - so there would be quite a lot of cross-talk between channels. Certainly with a radio antenna, lining it up with the plane of polarization of the transmitter greatly enhances reception. SteveBaker (talk) 14:17, 17 January 2010 (UTC)

Use of different polarizations horizontal and vertical increases the isolation between TV transmissions which allows more efficient sharing of channel frequencies since less distance is needed between co-channel transmitters. When TV broadcasting in Britain was at VHF one could see yagi receiver antennas on many house roofs, mounted according to whichever was the local polarization. Cuddlyable3 (talk) 19:44, 17 January 2010 (UTC)

This is certainly used on satellite TV and transponders to increase the number of channels available. In this application there are no obstacles affecting the signal from transmitter to receiving dish, so no mix up occurs. In MIMO this could well be used to double transmission throughput. The MIMO system does not care what the polarisation is, only that there is a difference in the signal between the two pairs of antennas. Graeme Bartlett (talk) 21:54, 17 January 2010 (UTC)

As an aside, I'll note that in Carl Sagan's novel Contact part of the information in the alien message was carried through polarization modulation of the radio signal. (I think this was mentioned in the film as well, but I'm not certain.) TenOfAllTrades(talk) 22:18, 17 January 2010 (UTC)

How warm should the water used with yeast in bread machines be?

I use a bread machine, it takes nearly four hours to make a loaf. This includes waiting for the dough to rise. Unfortunately the end result is not as fluffy as shop-bought bread. (Yes, I do use strong flour). What is the best temperature for the water I put in the machine? If the water is too cool, the dried Baker's yeast will be underactive. If it is too hot, it will be detrimental to the yeast also. What temperature would the yeast like best? And is there any evidence that it would be worth adding some vinegar to the water - would the yeast prefer it to be slightly acid? 92.29.80.215 (talk) 14:46, 17 January 2010 (UTC)

Around 35 to 40 degrees will do fine. I don't know where you live, but typically bread from a read machine will be of the more chewy type, not like US toast. You can try a variety of recipes, though. --Stephan Schulz (talk) 15:30, 17 January 2010 (UTC)

(EC with below) I personally don't believe the water temperature matters too much provided you don't let it be too hot (i.e. above 40 degrees C). AFAIK, most bread makers are designed to heat up the mixture during the rise cycle to an appropriate temperature so at best it's only going to make a minor improvement. Also while I don't use a bread maker much, I've had some experience with bread maker loaves and buns that are fairly fluffy. I agree with Stephan Schulz you should try a variety of recipes and varying your recipes. Also make sure you are using new, high quality yeast and following the recipe instructions particularly about the order and measuring your ingredients properly (perhaps using weight where possible to avoid issues like the flour settling). If your yeast doesn't already include it, make sure you use bread improver. In fact even if it does you may want to try adding more too and perhaps some more gluten. If you still can't achieve something you like, perhaps trying using the bread maker for kneading and rising the dough (most should have some sort of dough function) and then shaping buns or using a loaf tin and allowing the bread to rise again before cooking in an oven (presuming you have one). It will take longer and obviously be more effort but may achieve what you want and will still be easier then e.g. kneading by hand. In between perhaps you could try doing a double rise in the bread maker, i.e. put it on the dough setting and then when it's done put it on the normal bread setting so it'll knead and then go thorough a rise cycle again before cooking (I don't actually know if this will work well, this is not something I've heard of from anywhere). P.S. You may also want to consider stuff like a brioche loaf or other things which even if not something you'll expect from a store, may be an interesting and pleasant variety Nil Einne (talk) 16:13, 17 January 2010 (UTC)

If the temperature is truely unimportant then I would use water straight from the tap which at this time of year is rather cold. 92.29.80.215 (talk) 16:57, 17 January 2010 (UTC)

The reason shop-bought bread is so fluffy is it's steam-baked. You can approximate this by putting a dish of boiling water at the bottom of the oven you're baking the bread in. However, obviously you can't do this if you have a breadmaker. It's the reason I gave up making bread in a breadmaker - I really don't like the texture of the stuff that comes out. --TammyMoet (talk) 15:58, 17 January 2010 (UTC)

It's not clear to me what "shop-bought bread" is supposed to mean here -- a Parisian baguette, or Wonder Bread? If you're talking about high-quality bread, there is more to it than yeast and steam. To get really high-quality bread, you need the right flour, and you need to start with a sponge and let the bread rise slowly for hours, rather than a simple yeast rise. Looie496 (talk) 17:00, 17 January 2010 (UTC)

I've used it to mean both. The Mrs Beeton recipe for Parisian baguette I use entails the dish of boiling water, and I toured a RHM factory some years ago in which the process was explained in detail. --TammyMoet (talk) 19:10, 17 January 2010 (UTC)

Any shop-bought bread I can remember buying. I'm now eating some bread I've (er, I mean the machine) just made. The reason why it is not so fluffy may be that the inside is too damp or somewhat soggy. Perhaps I should use less water or leave it in the machine for the further hour of warming that it does automatically. What do you mean by 'sponge' please? 92.29.80.215 (talk) 17:22, 17 January 2010 (UTC)

See Pre-ferment. Looie496 (talk) 17:32, 17 January 2010 (UTC)

The sponge method of making bread involves mixing a small amount of yeast (perhaps 1/4 teaspoon) with flour and water, and giving it about 24 hours to form a sponge. The sponge is then mixed with the rest of the ingredients, and allowed to rise. This will take longer than the method often used by home cooks (starting with a large amount of yeast). One sees claims that this method gives better flavor, but I only tried it once and didn't notice a difference. --Jc3s5h (talk) 19:28, 17 January 2010 (UTC)

Usually, I'd say that water at room temperature (20 - 25C) should be fine, and the same case with microwaved milk. ~AH1^(TCU) 20:53, 17 January 2010 (UTC)

You are fortunate in the USA not to have the Chorleywood Bread Process that is almost universal in UK shop bread, and gives it all the same "pasty" taste, whatever the ingredients! Dbfirs 21:03, 17 January 2010 (UTC)

Effects on mood: a) stuffy atmosphere, b) gloom or time of day

Due to the unusually cold snowy weather here recently I had all the windows in my house closed for many days, I stayed indoors nearly all the time, and it felt rather stuffy. After opening a window I soon felt a lift in mood. Could this be any more than just imaginary, such as the effects of negative ions? (Wikipedia does not seem to have an article on ionisation machines that were suppossed to be good for you by increasing the number of negative or was it positive ions in the air, like waterfalls). I understand that the sensation of stuffyness has nothing to do with the concentrations of oxygen or CO2, which do not change appreciably. Sunsets and twilights are commonly regarded as being mournful. People tend to dwell on the past during the evening or when waking up in the middle of the night. Dull days are dull, sunny days are joyful. Is there any physiological explaination for any of this? 92.29.80.215 (talk) 17:12, 17 January 2010 (UTC)

The effects of light on mood are very well known; our circadian rhythms articles talks about them a bit. But regarding stuffiness, it's possible that a change in humidity, or simply a drop in temperature, have something to do with it. Looie496 (talk) 17:37, 17 January 2010 (UTC)

I'm not sure why you think the oxygen concentration would not change. If the house was airtight you would soon notice a change in oxygen levels. Could oxygen starvation be relevant?--Shantavira|^{feed me} 18:09, 17 January 2010 (UTC)

Well there are some problems with a closed system like a house: everything in it leeches molecules that aren't necessarily bad for you but certainly aren't as good as outdoor air. Having just a little airflow can make a big difference over hours and days. Moreover your body is constantly shedding skin cells, aka dust, so even if you lived in a stone and wood building with no outgassing there would still be some benefit from having a little draught of cool air pass through occasionally, just to carry out a few specks of dust and bring oxygen levels back up to snuff. That said if you feel cold, the windows are open too wide! Vranak (talk) 18:20, 17 January 2010 (UTC)

Pedantic correction: from context, you probably meant leaks, exudes or something similar - leeches or leaches would imply the opposite :-). 87.81.230.195 (talk) 19:03, 18 January 2010 (UTC)

I understand that there is still some considerable airflow in houses even with all doors and windows shut. My house cetainly has draughts. I read the circadian rhythm article and while it briefly mentioned bipolar disorder it did not say anything about mood for non-bipolar people. 92.29.80.215 (talk) 18:30, 17 January 2010 (UTC)

Seasonal affective disorder may be of interest. ~AH1^(TCU) 20:06, 17 January 2010 (UTC)

IMHO, you should give yourself credit for having part of the answer correct at the time you asked the question!

For Christmas, I received one of those little books of factoids (not exactly a glowing reference, I know), one of which is:

If you were sealed up in an airtight space, you would

die of carbon dioxide poisoning long before you would

suffer the effects of oxygen deprivation.

This makes it entirely plausible that replacing the "stuffy" air is far more important than bringing oxygen levels up to snuff.

HTH, DaHorsesMouth (talk) 22:12, 17 January 2010 (UTC)

Remember, however that your house is not airtight. There are plenty of cracks and leaks in your home that allow air to travel between the inside and outside. ~AH1^(TCU) 23:35, 17 January 2010 (UTC)

This is true but if the air seems stuffy perhaps those cracks aren't quite enough. Vranak (talk) 01:20, 18 January 2010 (UTC)

liquid diamond

The Wikipedia main page today links to Diamond#Material properties and states that researchers succeeded in melting some diamond, and they believe that solid diamond would float on liquid diamond. But I thought the only attribute that distinguishes diamond from any other mass of carbon was the crystalline structure of the diamond, which, I would think, would be destroyed utterly when the diamond melts. One of the articles linked to by that section states that in previous attempts, the diamond had turned into graphite, which had then melted. But I would think the two resulting pools of liquid carbon molecules would be indistinguishable. What am I missing here? Comet Tuttle (talk) 18:47, 17 January 2010 (UTC)

I am guessing, but I suspect that a pool of liquid carbon is called liquid diamond if it is near a phase transition such that it would naturally freeze into diamond. Under atmospheric pressure if you freeze liquid carbon you get graphite, but under high enough pressure the natural state becomes diamond and that seems like the likely difference. The two pools presumably aren't that different if observed on their own. As liquids, they still don't have structure, even though one would start out much more compressed due to the enormous pressure. Dragons flight (talk) 19:06, 17 January 2010 (UTC)

The Discovery News article states "The trick for the scientists was to heat the diamond up while simultaneously stopping it from transforming into graphite." The original report is behind a subscription wall but one could ask the author email redacted how one can know a transformation to liquid graphite did not occur. Cuddlyable3 (talk) 19:25, 17 January 2010 (UTC)

Just as we don't post OP's emails, we shouldn't post paper authors' email addresses. The corresponding author can be found in the linked Nature article, here. Nimur (talk) 20:09, 17 January 2010 (UTC)

Isn't it a little silly to worry about protecting someone from spam when there email is already posted on major websites? Dragons flight (talk) 20:43, 17 January 2010 (UTC)

I think it is perfectly ok to protect casual readers from thinking it was ok to post anyone's email address. 93.132.150.199 (talk) 14:09, 18 January 2010 (UTC)

So if the two pools are identical, our "In the News" blurb about it seems to have some incorrect information: "The first experimental measurement of the melting point of diamond (pictured) indicates that the solid form floats on the liquid form at ultrahigh pressures." We knew that before, because it's easy to melt graphite and test it in the same way. (Or, we "could have know that" without having to had to directly melt diamond.) Comet Tuttle (talk) 19:46, 17 January 2010 (UTC)

I see they're struggling with it, too; the first version of the blurb (which prompted my question) was "The first experimental measurement of the melting point of diamond (pictured) indicates that the solid floats on the liquid." Comet Tuttle (talk) 19:48, 17 January 2010 (UTC)

No, it's not the same. Liquid graphite has a density of ~1.2 g /cm3 at low pressures, much less than the 3.5 g / cm3 for diamond. The observation that at 10 Mbar is that liquid graphite has a density greater than diamond at the same pressure, which is a highly non-trivial finding and implies much greater compression in the liquid phase than in the solid. Dragons flight (talk) 20:43, 17 January 2010 (UTC)

Carbon is a funny element. The sp hybridization phenomenon makes it possible for the liquid carbon atoms to be in a variety of hybrid states, each state producing different interactions with neighbor atoms and therefore liquid with different density for a given temperature T and pressure P. In parts of the (T,P) range one liquid state is stable, in other parts another. Boundaries between the stability domains are called coexistence curves, as for those (T,P) the stable state is a mixture of two different liquid states with different densities. It is entirely possible that one of the liquid phases will have diamond-like near order and bonding, and another one will have graphite-like near order and bonding. There have been papers published for quite a while about liquid-liquid phase transition(s) in carbon; see, e.g., Phys. Rev. Lett. 82, 4659–4662 (1999). It was tempting to put a reference to Tori Amos here, too, but I am afraid that her song is much harder to understand than the science involved... --Dr Dima (talk) 00:01, 18 January 2010 (UTC)

So to rephrase my original question, how do the 2 pools of melted pure carbon differ? I had thought each pool would be a pool of loose carbon molecules with no bonds between them. Comet Tuttle (talk) 18:54, 18 January 2010 (UTC)

There would be bonds in a liquid, what happens is that the energy of the atoms is great enough to stop them from being rigid, and they either break and reform, or move around. If there were no bonds at all, you would get gaseous monatomic carbon. However even in a gas you could expect C₂ molecules. Graeme Bartlett (talk) 20:57, 18 January 2010 (UTC)

Coconut water

About how much coconut water is there in a coconut? Mac Davis (talk) 21:59, 17 January 2010 (UTC)

200 ml (personal experience). Dauto (talk) 23:15, 17 January 2010 (UTC)

I would say it's more like 6 ³/₄ ozs. DRosenbach ^{(Talk | Contribs)} 02:20, 18 January 2010 (UTC)

I would say it depends very greatly on the age of the coconut (among other factors) Nil Einne (talk) 09:45, 18 January 2010 (UTC)

why don't diamonds oxidise?

I get the idea that oxidation of solid diamond may be kinetically slow cuz of the crystal lattice stability. But ... shouldn't that make liquid diamond prone to oxidation, especially at such high temperatures and pressures? I mean, carbon dioxide can't form a protective layer, unlike zinc oxide or magnesium oxide, cuz the oxide is a gas. What happens when you wash diamonds with hydrogen peroxide? Isn't C=O bond stronger than 2 C-C bonds? 2 C=O bonds should be even stronger than 4 C-C bonds... John Riemann Soong (talk) 22:09, 17 January 2010 (UTC)

I assume you are talking about the recent finding -- Nature Physics 6 pp 9-10 and 40-43 (2009/2010) -- of diamond-like liquid carbon state. The authors use Omega laser to send a really, really strong shockwave into a diamond sample, and then optically determine the temperature in the shocked material. From a peculiar behavior of the temperature the authors infer that a first-order phase transition takes place. The liquid phase turned out to be denser than the solid diamond phase (the melting curve has a "wrong" slope). This has nothing to do with oxidation. The whole experiment is extremely brief, involves no free surfaces exposed to air, and occurs at temperatures of 5000 - 50000 K and pressures of 500 - 4000 GPa. --Dr Dima (talk) 00:18, 18 January 2010 (UTC)

That's true, but he does raise a fair point. CO2 is a much lower energy state than diamond and so diamond ought to spontaneously oxide in air at some rate. By observation it is presumably a very low rate, but it would be interesting to know what the rate actually is. Dragons flight (talk) 00:57, 18 January 2010 (UTC)

Well if you heat up a diamond enough in air, it burns. Graeme Bartlett (talk) 01:02, 18 January 2010 (UTC)

Why can't I find a video, a picture, or even just a damn paper about the combustion of diamond? I mean, people seem to regularly put thousands of dollars worth of caesium into water for fun, so burning diamond can't be that far off economically for a "wow!" moment? John Riemann Soong (talk) 14:13, 18 January 2010 (UTC)

Youtube. Look for [burn diamond]. First two hits.Come on, man. DMacks (talk) 16:56, 18 January 2010 (UTC)

That's funny, such a prominent first youtube result would normally show up on google ... John Riemann Soong (talk) 17:16, 18 January 2010 (UTC)

On a related note, does fluorine gas, F₂, react with diamond?

Ben (talk) 01:56, 18 January 2010 (UTC)

(WARNING: Do not try this at home.) Diamonds have a reputation of not burning. But Michael Faraday and Humphrey Davy burned a diamond back in 1814. They put it in a sealed globe full of air and heated it via the sun and a big magnifying glass to get it hot enough for the combustion to start. Once combustion started, it was self-supporting. The burning diamond gave off a brilliant scarlet light. The "carbonic acid gas" found in the globe containing the diamond after combustion indicated that diamond was carbon. They repeated the experiment with various other gasses in the globe. Edison (talk) 20:04, 18 January 2010 (UTC)

Yeah curious what the product of diamond and fluorine is ... do you get a big chunk of solid teflon, or just lots of CF4 gas? Just how strong of an oxidiser do you have to use to get diamond to react at room temperature? Would aqua regia dissolve diamond? HF + Antimony pentafluoride? John Riemann Soong (talk) 20:41, 19 January 2010 (UTC)

January 18

Cryogenic metal compared to traditional thermal energy storage

How do water-ice (e.g. http://ice-energy.com ), eutectic system, and molten salt forms of thermal energy storage compare to cryogenic thermos energy storage in metal, as a practical expected consumer rate premium for stored over demand electricity, approximately? 99.55.163.191 (talk) 01:09, 18 January 2010 (UTC)

You would have to assess how efficiently energy can be transferred in and out of your cryogenic storage. It is actually less efficient to cool than to heat, and in many cases heat is produced directly, for example of burning coal. It is then much more efficient to store the energy as heated materials. Then delay using the haat till later, for example to make steam for a turbine. Your water ice may be able to be harvested from nature, but cryogenic temperatures will not be found to exploit naturally on earth. Have a look at thermal mass latent heat molten salt energy storage cryogenics Graeme Bartlett (talk) 07:43, 18 January 2010 (UTC)

Are you saying refrigeration and cooling always produce waste heat? Why can't that waste heat be recovered and fed back into the cooling energy input? Is a steam turbine more efficient than a sterling engine? How much? Are thermal isolation losses greater at hot or cold extremes? 99.55.163.191 (talk) 21:59, 18 January 2010 (UTC)

Laws of thermodynamics. You can't beat the house, you can't break even, you can't get out of the game. If you've got a system that needs heating at some points and cooling at others, you can indeed combine these. To an extent. But you have to look at the actual temperatures involved to see how much this is possible, and it will never be 100% efficient: you will always have to use energy. And refrigeration by heat pump is very energy-expensive. Please read the articles linked by us and yourself: they're not perfect, but they have a lot of information and answer most of your questions in context. 86.179.150.200 (talk) 22:30, 18 January 2010 (UTC)

Thermodynamic cycles. You don't need to beat the house, you just need to lose less than if you were tearing the place up with non-renewables. Is the amount of work required and recoverable from taking a piece of metal in a thermos from 3 to 2 degrees Kelvin the same or less than the amount required and recoverable from taking the same metal from 2 to 1 degree Kelvin? 99.55.163.191 (talk) 23:42, 18 January 2010 (UTC)

While it's been a few years since I've studied thermo, however it appears you are trying to find the useful energy of one system and compare that to another. The best way to do that is through an exergy analysis of each system and comparing how much exergy is present in each. Wizard191 (talk) 13:05, 19 January 2010 (UTC)

Animals with colorful names (literally!)

I find these (common) names interesting for their extreme simplicity. So far I've got Bluebird, Blackbird, Brown Bear, Black Bear, and Bluefish & Redfish. Can anyone name some more in the awesomely simple pattern of (color)(animal type)? 218.25.32.210 (talk) 03:01, 18 January 2010 (UTC)

That's actually an enormous category. Humans are pretty lazy and uncreative about naming creatures. Just running down the List of hummingbirds, I see the Amethyst Woodstar, Berylline Hummingbird, Black Inca, Black Jacobin, Black Metaltail, Bronzy Hermit, Bronzy Inca, Cinnamon Hummingbird.... If you want two colours, you can have the Brown Violetear, Coppery Emerald, or Crimson Topaz. For a generic chioce, try the Colorful Puffleg. (Truth be told, I lost interest after I got to the letter C.) There are many, many more choices if you are willing to include colours describing body parts, as with Amethyst-throated Hummingbird or Azure-crowned Hummingbird.

Short of running through all of the subcategories in Category:Animals (and there are a lot of subcategories), I can't think of a good way to give you a comprehensive response — and there will be thousands of animals. TenOfAllTrades(talk) 03:31, 18 January 2010 (UTC)

OP here. Guess I wasn't explicit enough. I know the list will stretch into the thousands (millions?) if we allow for specific types of an animal. But I meant to restrict it to the overall categories. So your Amethyst Woodstar is excluded, as are essentially everything else you listed. Since you mentioned laziness, you might say I'm looking for the laziest of the lazy - names that end in general animal types: ____ bird, ____ dog, ____ fish, _____ turtle, _____ snake, etc. I think that narrows things considerably. 218.25.32.210 (talk) 04:43, 18 January 2010 (UTC)

Red Panda popped into my mind immediately. I don't see it listed yet. 75.152.185.94 (talk) 04:41, 18 January 2010 (UTC)

Green stink bug (Igny (talk) 04:47, 18 January 2010 (UTC))

Disqualified on account of the stink, but made me remember Red Bugs! 218.25.32.210 (talk) 05:05, 18 January 2010 (UTC)

But a stink bug is a type of animal. Rckrone (talk) 06:50, 18 January 2010 (UTC)

I'm a bit confused about what you mean. Why do you include dog, which at most refers to any member of the family Canidae while excluding Hummingbird which basically means any member of the family Trochilidae. Why do you exclude stink bugs, an even wider term then dog (or hummingbird), since it can refer to any member of the superfamily Pentatomoidea. Do you mean when the name can in some ways be further divided it is excluded? E.g. since hummingbird can be divided into humming and bird it's excluded?

This seems problematic to me. For example, do you exclude mongoose, even though a mongoose isn't even close to a type of goose, mon isn't a word and the etymology shows it didn't come from goose? Also even if so, why do you exclude black jacobin or black inca? True when you say jacobin and inca, most people are not going to think animal, but that's a rather fuzzy concept since many thing which people may associate with animals can have other meanings, seal for example; and some people are surely going to recognise that these terms can refers to animals.

And for example do you include panda, a term with no real biological meaning since it refers to two highly unrelated animals but not everything in between?

Do you only want cases when the etymology of the word shows it originated referring to an animal (and the other usages either derived from the animal or came up independently). If so, you'll likely need to do some analysis. For example, while it may seem likely inca and jacobin came from other words not referring to animals, I couldn't definitely find this is the case. Seal did originate referring to the animal as did mongoose. But does this mean you exclude rhinoceros [9] (also article) because the name originated from two words not meaning an animal "The word rhinoceros is derived through Latin from the Greek ῥῑνόκερως, which is composed of ῥῑνο-, ῥίς (rhino-, rhis), meaning nose, and κέρας (keras), meaning horn." (which happens for a lot of animals).

Also looking into into that got me thinking, do you include white rhinoceros even though the animal isn't even close to being white and the name may have originated from a corruption ofh a Dutch or Afrikaans word? And how about black rhinoceros, even though it too isn't black and the name was chosen to distinguis it from the white rhinoceros yet isn't even distinguishable by colour?

Nil Einne (talk) 10:42, 18 January 2010 (UTC)

White rhino's are the exact same color as black rhino's. The "White" part is a corruption of "Wide" (you have to say it with a South-African accent!) - and guess what? White rhino's have wider faces than Black rhinos. SteveBaker (talk) 20:28, 19 January 2010 (UTC)

Blue Crab! Green Crab! 218.25.32.210 (talk) 05:07, 18 January 2010 (UTC)

Golden Eagle, White Rhinoceros, Black Rhinoceros, Brown trout, Grey seal, gray heron, gray wolf, gray fox, red fox, yellow mongoose, brown hyena. Dragons flight (talk) 05:43, 18 January 2010 (UTC)

Brown kiwi perhaps. Nil Einne (talk) 11:09, 18 January 2010 (UTC)

Brown Snake, Blue ringed octopus (not lazy enough?) --220.101.28.25 (talk) 11:55, 18 January 2010 (UTC)

I would contest the OP's premise that redfish be included in this, as even a quick glance at the article reveals that there is no actual redfish, but rather that it's a common word used to refer to any number of species depending on the location of use. DRosenbach ^{(Talk | Contribs)} 15:19, 18 January 2010 (UTC)

That's why it's important to consult a reputable field guide. -- Coneslayer (talk) 15:34, 18 January 2010 (UTC)

Isn't that the ultimate in laziness? You can't even give it a unique name... In any case that also applies to black bear, bluebird and blackbird to some extent, it's not clear to me the OP wanted a name used to refer to a specific species only Nil Einne (talk) 15:40, 18 January 2010 (UTC)

Green Iguana, Black Widow Spider, Red Deer, Black-Tailed Deer, White-tailed Deer, Blue Whale Googlemeister (talk) 16:37, 18 January 2010 (UTC)

gun

when my granpa die he left me this gun http://en.wikipedia.org/wiki/Nambu_pistol is it safe to fire? i heard it can explode if fired —Preceding unsigned comment added by 67.246.254.35 (talk) 06:49, 18 January 2010 (UTC)

I see you're located in Fairport, New York. I suggest taking the pistol to a licensed gun dealer/retailer who can assess its current state and give you expert advice on its value, care, and maintenance. Without holding the item in our hands, we can only give information of limited usefulness in this case. Note that I am not familiar with New York firearm laws. It may or may not be legal to take that weapon to get it appraised without owning a carry-permit. Please consult with your local law enforcement office beforehand. 218.25.32.210 (talk) 07:01, 18 January 2010 (UTC)

i saw this vid of it being fired http://www.youtube.com/watch?v=EpZJ7FOQxyA it looks like it hurts your wrist to fire it why is that true if it a low cal gun —Preceding unsigned comment added by 67.246.254.35 (talk) 09:09, 18 January 2010 (UTC)

From that video alone, I can't see why you would be led to believe that it hurts your wrist. What I saw looks like the typical recoil that I'd expect from such a pistol. Note: I've never owned one of these but I have fired many pistols before. Dismas|^(talk) 10:20, 18 January 2010 (UTC)

i say that because it jerks yer hand to the side awkwardly while most guns go str8 back. this vid is a good example

http://www.youtube.com/watch?v=mDNqO4bCGXY

side by side comparison with a 45 this guy has more recoil and jerks yer hand to side

There are two red flags in our article: Firstly that the safety catch on these things is completely ineffective (yikes!) and second that it used a 'weak' charge in it's 8mm ammunition. Using modern 8mm ammo might well impose more of a strain than an already old and poorly constructed gun could withstand. So I'd certainly take it to a decent gun shop and have them look at it. Also, it's possible that this thing is actually somewhat valuable - (if it's actually a "Baby Nambu" then it almost certainly is a valuable piece) and in that case, you'd want advice on taking care of it just in case collectors have some obscure reason why they want these guns in not-recently-fired condition. Basically, there are enough unknowns here to strongly suggest getting some expert advice. SteveBaker (talk) 13:20, 18 January 2010 (UTC)

It's not a bad idea to contact your local law enforcement. Your county sheriff offers a firearm safety course. New York State has strict laws related to firearms, especially pistols. Our article, Gun laws in the United States (by state)#New York can give you a rough overview; it claims that New York is the strictest state in the country. Receiving a gift from a family member may still need to be registered as a transfer of ownership transaction. Your sheriff is the best person to answer that question. Nimur (talk) 18:55, 18 January 2010 (UTC)

TV shows where guns are appraised say DO NOT CLEAN THE GUN before having a potential buyer make an offer, because steel wool/sandpaper/wirebrush destroys the original factory finish or the "patina" an old gun acquires. Edison (talk) 20:00, 18 January 2010 (UTC)

can some 1 answer the op about the recoil? —Preceding unsigned comment added by Killspammers (talk • contribs) 14:25, 19 January 2010 (UTC)

I don't see any unusual looking recoil. Guns will twist when firing due to the rifling in the barrel and that pesky Newton guy. Pay attention to the warning about modern ammo. If this gun is meant to fire only light loads, you'll need to either find a source for the light loads, or load your own. Friday (talk) 18:57, 19 January 2010 (UTC)

Gaines Adams - latest enlarged heart... victim?

So I read the two main articles linked to enlarged heart and neither were very helpful in answering my primary question: how can a professional athlete who (theoretically) has the best medical staff around, and who has been examined numerous times at levels most regular people never are, have an unnoticed enlarged heart and then die from it?

Gaines Adams is the most recent example of top-level professional athletes quite literally dropping dead and the autopsy essentially being "I'll be damned, he had an enlarged heart." This dude went through all the rigors of the NFL Scouting Combine and Draft only ~3 years ago. How could that possibly have gone unnoticed? 218.25.32.210 (talk) 07:18, 18 January 2010 (UTC)

Probably a great many fit people die of undiagnosed heart problems. See Jim Fixx & James A. Corea. The fact that a person is otherwise very healthy may mask some health problems. Genetics has a lot to do with it, so living a healthy lifestyle may help, or it may not. We also need to wait for ALL test results to come in to be absolutely certain of his cause of death. NB The reference used[10] says he died of cardiac arrest, it does NOT say the arrest was caused by the enlargement.--220.101.28.25 (talk) 08:38, 18 January 2010 (UTC)

According to Athletic heart syndrome, there are no clear symptoms of the condtion, which would explain why it goes undiagnosed. Also, without passing judgement on any athlete in particular, some googling indicate that an enlarged heart could be a symptom of steroid use[11]. In such a case the role of the medical team becomes more complicated. —Preceding unsigned comment added by EverGreg (talk • contribs) 10:02, 18 January 2010 (UTC)

Yes, reports say Adams had an 'enlarged heart', but if that is muscular development due to exercise, ie. Left ventricular hypertrophy, it seems it is unlikely to have caused his death. Quoting Athletic heart syndrome; "this syndrome is believed to be a benign condition but may be hard to distinguish from other serious medical conditions." See also, Ventricular hypertrophy and Cardiomegaly, though it appears you may have already. The only way to be certain is to wait for an official coroners report to be completed.
The OP(Original Poster/ IP 218.25.32.210) asks "How could that [enlarged heart] possibly have gone unnoticed? It may have been noticed, and presumed to be the normal result of exercise, which it might well have been. We don't know yet.--220.101.28.25 (talk) 12:56, 18 January 2010 (UTC)

While it is true that he had an enlarged heart, the assumption that nobody ever noticed is not valid. It may very well have been known that he had an enlarged heart long before he joined the NFL. There are many people in the NFL with medical conditions, such as diabetes. -- kainaw™ 14:54, 18 January 2010 (UTC)

Kainaw is correct; you're going to have to document that the player didn't know; professional athletes, like test pilots, have a long history of concealing illnesses that might cause a doctor to veto their participation. Comet Tuttle (talk) 18:51, 18 January 2010 (UTC)

Osteological signs of birth

In archaeology/osteology, is is supposedly possible to see if and how many times a women has given birth by observing the pelvic bone. If I remember correctly, each child leaves a small indentation in the bone. Is this true? What happens, physically, and why? How reliable is the technique for assessing number of children? Having just given birth to a child myself, I am very curious. (P.s. The osteology article is very brief, and I don't know where else to search for this information. Thank you for your help! D.s.) - Mommy —Preceding unsigned comment added by 90.233.22.17 (talk) 11:22, 18 January 2010 (UTC)

This question actually came up a while ago: [12] In short: The archeologists thought they could, but the marks could have other origins too, so now they'r not so sure. EverGreg (talk) 14:22, 18 January 2010 (UTC)

Thank you! Now I remember that I just recently read in a magazine of popular history about an Egyptian grave where the woman was determined not to ever have had children. Perhaps as suggested in nov 2008, NOT having ever been full term pregnant/given birth can more accurately be determined. For me, as for many, relaxin significantly affecting my pubic bone and lower back joints, and this could perhaps be possible to see as "scars" or changes on the bone. But it is just a speculation. - Mommy —Preceding unsigned comment added by 90.233.22.17 (talk) 14:43, 18 January 2010 (UTC)

Yup, determining that the woman never gave birth might be feasible, if the soft part of the skeleton is not eroded away. By the way, congratulations! :-) EverGreg (talk) 18:44, 18 January 2010 (UTC)

Name for a symptom

What is the name for a muscle spasm that only occurs when a muscle is in use? For example (and why I'm asking), I was watching a guy at a hotel yesterday who seemed normal until he walked. If he walked on flat ground, he was fine. When he had to step up with his left left, he was fine. When he stepped up with his right leg, his muscles would basically overshoot the target, sending he knee up above his waist. He appeared rather surprised by it every time it happened. I watched him go up the stairs and once in about 5 steps, his right leg would spasm upwards again - but only when he was stepping up with it. Therefore, I don't believe "spasm" is the correct term. -- kainaw™ 15:56, 18 January 2010 (UTC)

I believe that would be called a "focal dystonia". Looie496 (talk) 17:20, 18 January 2010 (UTC)

May also represent an intention tremor; or a loss of proprioception, as from a unilateral dorsal column infarct. Tuckerekcut (talk) 03:11, 19 January 2010 (UTC)

I have no means of knowing the guy's history or medical conditions to know why he had this symptom, but both focal dystonia and intention tremor seem like good descriptions of the symptom. After posing the question, I thought that he may have simply been a member of the The Ministry of Silly Walks. -- kainaw™ 07:24, 19 January 2010 (UTC)

Why is diamond metastable?

Solid-solid transitions are slow, but even phase transitions in crystal structure in say, various iron alloys, etc. are faster than diamond converting to graphite at 1 atm... John Riemann Soong (talk) 16:33, 18 January 2010 (UTC)

Is it the strength of a (nonpolarly unreactive) C-C covalent bond versus a more easily polarisable (and weaker) metallic bond? John Riemann Soong (talk) 16:40, 18 January 2010 (UTC)

Our article on Material properties of diamond says that their remarkable degree of metastability is due to a very high activation energy barrier that effectively prevents the transition under normal conditions. Mikenorton (talk) 20:19, 18 January 2010 (UTC)

Well yes, but that's the definition of metastability. What it doesn't tell me is what's so special about diamond versus say, metal, phosphorus or better yet, ionically-bonded compounds. John Riemann Soong (talk) 07:13, 19 January 2010 (UTC)

texting

how does a company make it so if you text them it charges u ten bucks? how do they set that up? —Preceding unsigned comment added by Killspammers (talk • contribs) 16:47, 18 January 2010 (UTC)

If you're thinking about Haiti, I believe that's a special arrangement, but the ordinary way to charge a fee for a phone call is to use a 900 number. Looie496 (talk) 17:12, 18 January 2010 (UTC)

See short code. There's nothing special about the Haiti ones (except that some carriers are waiving fees and/or expediting payment of the proceeds). -- Coneslayer (talk) 17:15, 18 January 2010 (UTC)

It must be a standard option because there are things like joke lines where you text them and they send you back a joke every day (and charge you an outrageous amount for doing it while being very quiet about how you unsubscribe!) SteveBaker (talk) 01:16, 19 January 2010 (UTC)

Short Life of Light Bulbs

Light bulbs used in the fixture on the wall over our garage door burn out (by which I mean "stop working") far faster than bulbs used inside or in other outside fixtures. The difference is dramatic; months as compared to years.

I'm trying to figure out why this might be.

These are ordinary wire filament bulbs, inside a fixture where they are protected by a glass cover.

On the theory that the problem might be vibration I have tried bulbs intended for use where there is vibration, i.e., bulbs sold for use in sockets on electric garage door openers. There is not actually a lot of vibration as the garage door is not used.

I also tried bulbs intended for use in ovens and bulbs intended for "country service", i.e., with fluctuating voltage. All these bulb types went quickly.

Is there any possible peculiarity of a circuit that might explain this behaviour?

I realize I could switch to another type of bulb. Being stubborn and curious, I'm still trying to figure out why this is happening. Also I'm wondering if there is some type of quirk in the circuit that makes it dangerous in some way.

Thank you, Wanderer57 (talk) 16:49, 18 January 2010 (UTC)

Check for vibration and either get a non-filament bulb (there are many types of CFLs now) or get a bulb for a hand-carried light. They cost a lot more, but have a much stronger filament that handles the vibrations of carrying and bumping the bulb. I had this problem long ago when I lived on an air station. Regular bulbs couldn't handle the low flying jets. I got the more expensive bulbs and they never burned out. -- kainaw™ 18:57, 18 January 2010 (UTC)

Store near me has incandescents specifically labeled as "for garage-door openers" and says they are specially designed for high-vibration environments. DMacks (talk) 19:01, 18 January 2010 (UTC)

My vote would be thermal cycling. I bet the garage heats up and cools off to a much wider temperature range than the rest of the house. (The more important effect is probably due to the cold end, as the bulb heats up to incandescent temperatures whether indoors or outdoors). This would yield marginally more strain on the filament due to thermal expansion and contraction; it may be enough of an effect to decrease the lifetime of the bulb. Nimur (talk) 19:05, 18 January 2010 (UTC)

By the way, our thermal cycling article is pathologically bad... Nimur (talk) 19:12, 18 January 2010 (UTC)

Light bulbs filaments routinely and uneventfully rise a couple of thousand degrees C when they are switched on. A few degrees in the starting room temp, less than a 1% difference in the temperature rise, would be extremely unlikely to have a measurable effect on bulb life. Frequent switching on and off would be a more likely reason for a filament to fail. Edison (talk) 01:42, 19 January 2010 (UTC)

One test of this could be to leave the light on all the time, but this sounds like a rather expensive, slow, and unsatisfying test. Comet Tuttle (talk) 19:47, 18 January 2010 (UTC)

I am interested in the voltage supplied to the bulb, since a 10% increase in voltage above nominal decreases bulb life by half. Has the voltage supplied to the short-lived filament been checked? Do you ever notice kights getting dimmer or brighter when some large appliance turns on? Is the bulb on a motion detector which cycles it on and off frequently? Edison (talk) 19:57, 18 January 2010 (UTC)

But a heavy load would produce a decrease in voltage. (Ohm's Law, you know.) I can't think of any situation where an increase in voltage would be created by improper domestic wiring or too small a circuit. My vote goes with vibration from opening and closing the garage door. The lot that our house is built on is adjacent to a railway spur and we went through bulbs like crazy before we switched over to CF, presumably from the vibration due to the trains. Short Brigade Harvester Boris (talk) 20:04, 18 January 2010 (UTC)

If a neutral connection is loose, either at the breaker panel or at the transformer, with 120/240 three wire circuits (or their non-US equivalent) a loose neutral causes lights on the same side as the heavy load to get dim and those on the other side to get bright. In the worst case, the heavily loaded side would go to 0 volts and the other side would go to 240 volts (or higher in other countries). Edison (talk) 01:46, 19 January 2010 (UTC)

You might have been unlucky regarding the Bathtub curve of reliability engineering, where things like lightbulbs or humans tend to fail either at the beginning or at the end of their lives. And I understand that switching lightbulbs on or off shortens their lives. Does the outdoor light get turned on or off more than the others, such as by a motion detector? 92.24.114.231 (talk) 20:20, 18 January 2010 (UTC)

Thanks for these thought-provoking comments.

This fixture is more exposed to wind than the other outside fixtures. Thus in winter it must get somewhat colder than the others. It is on the south side and is the only one exposed to much direct sun so it must warm up a bit more on winter days.

It is usually only turned on and off 2 or 3 times a day, the same as the front door light which is on the same circuit. The front door bulbs are only replaced every few years.

There are no appliances that put a heavy drain on the power supply.

All the other outside fixtures are on brick walls. This one is on siding so it would get more wind-induced vibration.

I wonder if it is a combination of factors or just one of them. Wanderer57 (talk) 23:13, 18 January 2010 (UTC)

Antarctica again

The Antarctic plate movement is estimated at least 1 centimeter/per year towards the Atlantic Ocean., This seems to beconfusing sentece but I'm still confuse with what it meant by Antarctica is moving to the Atlantic. I can't move it to the west because the Americas is going to the west, does to the Atlantic at this case means moving to the east?--69.228.132.51 (talk) 19:00, 18 January 2010 (UTC)

(Antarctic Plate is the article.) Comet Tuttle (talk) 19:54, 18 January 2010 (UTC)

(ec)This relative motion is unreferenced. Our map of relative motion (File:Tectonic plates boundaries detailed-en.svg) suggest that the Antarctic plate is actually moving away from the Atlantic Ocean and towards the Pacific Ocean. N.B. All motions are compared to the African Plate, which is close to stationary. Mikenorton (talk) 19:59, 18 January 2010 (UTC)

Wait. What is N.B?--69.228.145.57 (talk) 00:31, 19 January 2010 (UTC)

Nota bene. Clarityfiend (talk) 00:40, 19 January 2010 (UTC)

Wait Mike, the map said 10-15 cm/year. Antartica is NOT stationary. Stationary on Wikitionary means not moving. Africa is moving to the northeast [13] at 2.15 cm/year. That is what Ruslik said.--69.228.145.57 (talk) 00:49, 19 January 2010 (UTC)

I did say that the African plate (not the Antarctic plate) is 'close to stationary', the African plate is often used as the reference for all plate motions but these are not absolute values, for that you need another reference frame. Mikenorton (talk) 19:26, 19 January 2010 (UTC)

Palezoic climates

and once again it is covered with trees, as it was 300 million years before This was said Antarctica was tree covering 300 million years ago, it was at the south pole though, was antarctica actually that green 300 million years ago when it was in the south pole? Not white with ice? Yea, things do become more and more fuzzy after Jurassic time.--69.228.132.51 (talk) 19:43, 18 January 2010 (UTC)

I'm no paleogeologist, but 300 Ma was right around the dividing line between the Carboniferous and Permian ages, and our Permo-Carboniferous article says it was "a period of great glaciation", with big ice sheets. Comet Tuttle (talk) 20:07, 18 January 2010 (UTC)

There is only ice at the poles during an ice age. (Technically speaking, we are currently in an ice age, just an interglacial period of one.) However, that said, 300 million years ago was in the middle of the Karoo Ice Age. That article says "The extent of glaciation in Antarctica is not exactly known, due to its present ice sheet." I don't think Antarctica was actually at the South Pole at that time - the supercontinent of Gondwana was centred on it and Antarctica was at the edge of Gondwana, so would have been a fair distance away from the pole. --Tango (talk) 20:13, 18 January 2010 (UTC)

This plate reconstruction for 306 Ma shows antarctica near the pole and being glaciated. Mikenorton (talk) 20:23, 18 January 2010 (UTC)

300 is wrong, but may just be a case of fuzzy numbers. There is evidence of extensive forests in the deep Antarctic (80 or 85 S) at 265 million or so. Dragons flight (talk) 20:17, 18 January 2010 (UTC)

Hang on! I've solved the problem. It doesn't says "300 million years ago", it says "300 million years before". That is, before 100 million years in the future (the article the OP is quoting is The Future Is Wild). That means it is talking about 200 million years ago. There weren't ice caps 200 million years ago and Antarctica would have been covered by trees. --Tango (talk) 21:40, 18 January 2010 (UTC)

periodic table question

Sodium has the chemical abbreviation Na. Our article says that stands for the Latin word Natrium, however, since it does not really exist in an elemental form in nature, how would the Romans have named an undiscovered element? Googlemeister (talk) 20:43, 18 January 2010 (UTC)

The history section of the sodium article explains what people in the more distant past (not Romans) were using and what they were calling it. It was a compound and not the pure element, obviously. They were obviously not filling out the periodic table when they picked names for chemicals around them. It was apparently not call Natrium until the 19th century, in any case. --Mr.98 (talk) 20:57, 18 January 2010 (UTC)

See also new Latin. (I added a link to it in the sodium article as well.) Rckrone (talk) 04:00, 19 January 2010 (UTC)

Efficiency of Einstein refrigerator

I saw it mentioned in the archives, but not the answer to this: What is the first-order efficiency (e.g., with no waste heat or waste cold reclamation in a practically insulated system) of the Einstein refrigerator? 99.55.163.191 (talk) 22:38, 18 January 2010 (UTC)

Running the Einstein refrigerator in reverse as a heat pump

Would it be possible to run it like that for home heating? And why are not heat pumps in general used more for heating? 89.240.50.241 (talk) 23:31, 18 January 2010 (UTC)

Heat pumps ARE used for heating all the time. Dauto (talk) 00:48, 19 January 2010 (UTC)

Where? When? How? 89.240.50.241 (talk) 00:53, 19 January 2010 (UTC)

I agree, I'd like to know that too. Pretty much every building I know of is heated by either electric resistance heaters or burning something (gas, oil, coal, wood, etc.). I can't think of a single building heated by a heat pump, despite our article saying they are up to 4 times more efficient. That seems strange to me... --Tango (talk) 00:57, 19 January 2010 (UTC)

For what it's worth, the newish Community Centre in Woolfardisworthy (aka Woolsery), Devon, England is heated partly by a ground-source heat pump. (It also generates electricity using solar cells and a wind turbine.) 87.81.230.195 (talk) 04:01, 19 January 2010 (UTC)

"Reverse cycle" air conditioners are quite common in Australia - possibly they go by a different name elsewhere. Mitch Ames (talk) 00:59, 19 January 2010 (UTC)

That article (which was a link to this section before you changed it and I edit conflicted with you) says they aren't designed to replace heaters (I'm not sure what they are designed to do...). --Tango (talk) 01:04, 19 January 2010 (UTC)

The section is actually a sub-section of Portable air conditioners, which is why I changed it. Fixed reverse-cycle units are common in Australia, but I haven't seen portables used for heating. The Air conditioner article doesn't otherwise mention "reverse-cycle" at all - but probably it should, even if it is only a reference to Air_conditioning#Heat_pumps. Mitch Ames (talk) 01:20, 19 January 2010 (UTC)

I've added Air_conditioner#Reverse-cycle, which is currently just a stub, containing an "expand section" template and "for details see Air conditioning#Heat pumps". Mitch Ames (talk) 07:57, 19 January 2010 (UTC)

My house has a heat pump - the house we had before this one had two of them (one for upstairs and one for down). It's basically just an airconditioner run backwards - you aircondition your back yard and dump the waste heat into the house. It has a resistive heater but that only turns on if you switch on the "Emergency heat" switch...which we basically never do. They are popular here in Texas because for most of the year you need cooling - not heating - so having a system that's optimised for cooling makes a lot of sense. I'd be surprised if they were 4x more efficient than a resistance heater. What losses are there in a resistive heater? SteveBaker (talk) 01:10, 19 January 2010 (UTC)

It's not that there are losses in a resistive heater (which might act at 100% efficiency) - it's that there are "gains" in a heat pump, which extracts heat from the outside air thus operate at greater than 100% efficiency (ie more heat energy added to the room than electrical energy consumed). Mitch Ames (talk) 01:23, 19 January 2010 (UTC)

Well, "efficient" is the wrong word, technically speaking. See Heat pump#Efficiency for details. --Tango (talk) 01:24, 19 January 2010 (UTC)

As I understand it, they're really only economical when the temperature doesn't get too cold outside (something to this effect was said in the heat pump article). Here in Minnesota, we had a guy advertising them to be used in the fall and spring, but when it gets really cold outside, it becomes cheaper to burn natural gas. Buddy431 (talk) 03:28, 19 January 2010 (UTC)

According to our article, heat pumps become no more efficient than electric resistor heaters at around -18°C outside temperature - that's on the cold side, even for Minnesota, but gas heating is usually more economical that electric heating, so your advertising guy is probably talking sense. --Tango (talk) 04:18, 19 January 2010 (UTC)

Heat pumps are (in principle) always more efficient than resistor heaters. It is true though that their efficiency goes down at lower temperatures and eventually a gas heater will be cheaper. Off course a heat pump that runs on gas instead of electricity would be even better. Dauto (talk) 05:14, 19 January 2010 (UTC)

January 19

Circuit Problem

Imagine some resistors set in parallel in a circuit (there may be more elements to the circuit). Kirchoff's law says that, for any path the current might take, it's change in potential must be the same. Why is this true (ie what forces the electrons all to lose the same amount of potential (or energy or wtv))? —Preceding unsigned comment added by 173.179.59.66 (talk) 00:26, 19 January 2010 (UTC)

I'm not sure it is correct to attribute this to a "force". An electron travels through the path of least resistance, so as it loses potential it increases the resistance of the path it took in the conductor, mainly due to heat. This means the next electron behind it won't take exactly the same path, it will take the next best path. This all happens at the speed of light, so when a current is actually flowing through all the parallel resistors it only makes sense that all the electrons lose the same potential. When any one electron has more or less potential then the others around it, it takes a slightly more or less (respectively) "difficult" path in the circuit and then loses more or less potential until it is equal. Otherwise all the current would ravel through the path of absolute least resistance, regardless of how many resistors are in parallel. Sorry my explanation is a little obtuse, maybe someone has a more elagant answer.Vespine (talk) 01:10, 19 January 2010 (UTC)

This sounds a bit like a homework question, so think about what would happen otherwise. If some lost less potential, you'd have electrons gaining potential as they travel through the loop. A 5V battery can't give a potential higher than that, it would be a violation of the conservation of energy. ~ Amory (u • t • c) 01:16, 19 January 2010 (UTC)

Empirical studies of emotion

Is there any scientific or experimental backing to confirm that the words we use to describe emotion are valid and actually reflect objective reality? For example we have common words that describe colours, and these are underpinned by scientific studies of colour in terms of the spectrum and three colour-detecting cells in the human retina. Have any underlying dimensions been experimentally discovered for emotions? Or are we just stuck at the qualitative level? 89.240.50.241 (talk) 00:52, 19 January 2010 (UTC)

Have you checked our Emotions article? Mitch Ames (talk) 00:55, 19 January 2010 (UTC)

You can't quantify emotion any more than you can explain how chocolate tastes. There is a thing called internal validity that measures how a term is used by different people at different times. That is to ensure that what you're calling 'anger' isn't a scattershot representation of all sorts of different negative moods. That sort of thing. Vranak (talk) 05:50, 19 January 2010 (UTC)

Well we can quantify emotions. I think it is commonly accepted that fear is associated with the fight-or-flight response, which is activated by the sympathetic nervous system; thus we could do a controlled study where adrenaline and its metabolites are measured from samples of blood taken, place it on a graph where subjects report a specific emotion. Look at Graph B on this picture to see what I mean (this is a measure of amphetamine though, not adrenaline).

If you mean that we can never "know" what a person is feeling, then we are talking about something else known as the problem of other minds. This doesn't mean we can't quantify things, as the OP already mentioned that the colour spectrum is always the same, although we can't "know" what other people are actually seeing (or whether they aren't a philosophical zombie). (Sorry for the scruffy structure of this post, in a hurry) --Mark PEA (talk) 10:46, 19 January 2010 (UTC)

The science on this goes all the way back to Darwin's book The Expression of the Emotions in Man and Animals. Also very influential is Paul Ekman's work showing that cultures all across the world use very similar facial expressions for basic emotions. Looie496 (talk) 18:08, 19 January 2010 (UTC)

So the answers are No, Yes. 78.151.106.238 (talk) 19:13, 19 January 2010 (UTC)

Huh? The answers are yes there is experimental backing (going back to Darwin) that the words we use reflect experimental reality, yes underlying dimensions have been discovered (by Ekman among others), no we aren't just stuck at the qualitative level. For a guide to research on the underlying neural bases of emotion, the books and articles by Joseph LeDoux are a good place to start. Regards, Looie496 (talk) 19:34, 19 January 2010 (UTC)

illusion of wheel's direction

how do we get an illusion of a wheel of a car moving in backward direction,when car is at great speed. —Preceding unsigned comment added by Myownid420 (talk • contribs) 02:28, 19 January 2010 (UTC)

See Wagon-wheel effect. Nanonic (talk) 02:37, 19 January 2010 (UTC)

Damn, too slow! 218.25.32.210 (talk) 02:37, 19 January 2010 (UTC)

There is an absolutely brilliant depiction of the Wagon-wheel/stroboscopic effect on YouTube.HERE The film/video camera shutter is synchronised with the Helicopter rotors rotation. As a result the main rotor appears stationary as the helicopter flies around. --220.101.28.25 (talk) 10:00, 19 January 2010 (UTC)

In respect to , it's not that the effect occurs, but rather than the picture actually does reverse -- if we want to demonstrate the illusion, why does it have to make it happen artificially? (For example, This spinning girl illusion works without "cheating.") DRosenbach ^{(Talk | Contribs)} 13:18, 19 January 2010 (UTC)

Uh, that's a completely different effect. 17:35, 19 January 2010 (UTC)

That image isn't cheating: the whole idea is that the two directions of motion are aliased with the frequency of update in the recording (be it a film or a GIF) and thus are indistinguishable. Given only the final product and no contextual clues, it's impossible to say whether it "actually" reverses or not. --Tardis (talk) 18:46, 19 January 2010 (UTC)

Yep - DRosenbach is not understanding the problem. The spinning girl illusion is due to a lack of depth information - the silhouette of a clockwise rotating dancer looks identical to that of an anticlockwise rotation - so your brain can't understand which it is and flips back and forth between representations. The animated GIF is true temporal aliassing - which is a completely different illusion. SteveBaker (talk) 20:14, 19 January 2010 (UTC)

In computer graphics, we call this "temporal aliassing".

The easiest way to think about this is to imagine a wheel with three identical, equally spaced, spokes. In a TV or movie image or computer graphics or something, if the wheel rotates clockwise exactly 120 degrees from one still image to the next then every picture of the wheel would appear to be identical - even though a different one of the spokes would be at the top of the picture each time. Hence, it would not appear to rotate even though it's spinning really fast. However, if the wheel were to rotate only 119 degrees each time then there would be a visual conundrum: Did the wheel rotate 119 degrees clockwise - or one degree anticlockwise? In either case, the resulting series of images would be just the same. Our eyes & brains seem to prefer the slower rotation - so a wheel that's spinning at 119 degrees per frame seems to be rotating slowly backwards. As the wheel slows down, this effect persists - so if it rotates 100 degrees clockwise, our brains will insist that it's rotating 20 degrees anticlockwise...all the way down to 60 degrees. At 60 degrees per frame, we would get the same image whether we rotated 60 degrees forwards or 60 degrees backwards...the image would be identical. Now our poor brains can't figure out what's going on and instead of seeing rotation, we see a kind of flickery 6 spoked wheel! Once you get below 60 degrees per frame, we again have two interpretations - 59 degrees clockwise or 61 degrees anticlockwise. Again, our brains prefer the lower number - so FINALLY, we see what's really going on - a wheel rotating clockwise at 59 degrees per frame.

The angle below which everything looks normal is therefore exactly half of the spacing of the spokes. If you have a 4 spoked wheel, the anomaly happens when it's spinning at 45 degrees per frame or more...for a 36 spoked wheel, it's only got to be rotating at 5 degrees per frame to look bad. That's why the effect is called the "Wagon wheel effect" - because in the days of early cinema, we had maybe only 24 frames per second - and the stage coach in the cowboy movies that were popular back then only had to rotate fairly slowly to provoke the problem. Wagon wheels have a lot more spokes than most other kinds of wheel! It is probably also the case that filming out in the bright sunny desert where most cowboy movies were made means that the shutter time on the camera had to be kept short - that reduces the effect of motion-blur which greatly enhances the effect. In computer graphics, it takes a lot of effort to simulate motion blur and (in effect) we have an infinitely short "shutter time" - that means that this effect, which had gone largely unnoticed through the era of cars and modern TV cameras is now beginning to show up again.

What's kinda mind-blowing is that if you merely paint one of the spokes a different color - the illusion more or less vanishes. By breaking the rotational symmetry, the wheel now has to rotate 180 degrees per frame in order to cause this effect - and that's a really fast-moving wheel. We use this technique in computer graphics to try to break the illusion - making all of our wheels asymmetric whenever we can (painting the word "GOODYEAR" in white on the sides of tyres is a good example of that).

SteveBaker (talk) 20:11, 19 January 2010 (UTC)

SteveBaker that may be the best RefDesk response ever. Cuddlyable3 (talk) 20:56, 19 January 2010 (UTC)

circuits

what will happen if we put a resistor of,say, R₁ and a simple wire say copper wire in parallel in a circuit made up of copper wire,with a battery and a switch only. what will be the resistance in the circuit.could it be solved like that

1/0 + 1/R1 = 1/Rp     (as the resistance of copper wire is 0)

where R_p is total resistance in parallel. —Preceding unsigned comment added by Myownid420 (talk • contribs) 02:51, 19 January 2010 (UTC)

The resistance of a copper wire is not zero, see here for some numbers. From my knowledge of electronics, what you seem to be suggesting would most likely result in a short-circuit. Such a circuit would have close to (but not exactly) zero so you can pretty much ignore the resistor since almost all the current is going to flow through the copper wire. Also, you probably shouldn't try to divide by zero. - Akamad (talk) 03:06, 19 January 2010 (UTC)

The current will be large and limited by the resistance in the battery. As Akamad said you can ignore the parallel resister. If there is no resistance in the wire or battery the current will still be limited by inductance, and will grow linearly with timeGraeme Bartlett (talk) 08:12, 19 January 2010 (UTC)

plate changing speeds

Is this possible the plate movement will start out slow then end up moving fast? Because Africa 100 million years ago move faster now it slow to 2 cm/year. Is this possible Antarctica could eventually move as fast as Australian plate? WHat changes the speed motion? Could Australia eventually slow down?--69.228.145.57 (talk) 04:49, 19 January 2010 (UTC)

It is possible, and the direction of movement could change over time. What happened in the past can be found by the geomagnetic reversal timing signatures on the ocean floor. Predicting the future is more difficult. One book I read stated that the circulation in the mantle is turbulent and so it varies over time and is not simply predictable. Graeme Bartlett (talk) 08:42, 19 January 2010 (UTC)

Tree of Life in circular form

A question rather than an answer from me for a change. The current Evolution articles' template features a diagram of the "Tree of life" in a space-saving circular layout, and in recent years I've seen other similarly circular versions elsewhere. Does anyone know where this general circular layout of it originated? (The reason I ask is that, while desk-editing a school science textbook in 1990, I was asked by the authors to design and/or source a number of diagrams and other pictures, including a very simple Tree of life, and came up with just such a near-circular layout in order to save space on the page. Although I had no previous example consciously in mind it seems very unlikely that circular Trees of Life weren't already in use and quite probable that I'd seen one before.) 87.81.230.195 (talk) 04:59, 19 January 2010 (UTC)

It has developed gradually. At [14] you can see Darwin's own sketch where the branches from the roots go in different directions. This hand-made tree: [15] from Science in 1997 uses a similar space-saving layout. The circle appears naturally as you add more and more branches. The web-based generator for the image you refer to can be found at [16]. The company behind it claims it's a novel type of visualization, so according to them the style orignated in 2006. Though in my opinion, the main driver is large tree-of-life databases. EverGreg (talk) 09:45, 19 January 2010 (UTC)

Some more examples: Carl Woese in 1988 (figure 4) [17] Cover of Molecular systematics 1996: [18]. There's also an example you may have come across in school. There's a circular diagram where each kid in class starts off in the centre and then moves outward in a circular tree according to genetic properties such as gender, ability to roll your tongue e.t.c. It's not a phylogenetic tree, but gives an image of genetic similarity. EverGreg (talk) 10:06, 19 January 2010 (UTC)

Thanks for those suggestions, EverGreg, but some of those examples are, like Darwin's familiar original (published, incidentally, by the same firm I was working for), radial rather than circular, while the circular ones postdate my own usage. I certainly never encountered your school exercise (which would have to date back nigh-on four decades for me to have done so). Surely someone can come up with a good pre-1990 example to save me from the hubris of suspecting I may have originated it myself? 87.81.230.195 (talk) 10:56, 19 January 2010 (UTC)

Electrical Heating Distribution

So the above thread about heat pumps has me wondering about electrical heating in general. In what parts of the world is electrical heating commonly used to heat buildings? Here in (Suburban) Minnesota gas heating is the norm, and electrical heating is pretty much unheard of, except for maybe a small space heater in an ice shack or something. I understand that in the UK it's pretty common to take advantage of lower energy prices at night with a storage heater. We also had someone from Australia and Texas say that they had electrical heating. It seems to be that electrical heating is more common more temperate places. Do southern Europeans use electrical heating on a large scale? What about northern Europeans? I assume that Russians use natural gas (because they have enough of it), but I don't really know. What about in developed Asian countries like Japan? Buddy431 (talk) 05:23, 19 January 2010 (UTC)

Electric heating is cheap to install, so low cost systems in Australia use a simple fan over hot element heating. More sophisticated systems could be in slab or floor eating or the storage system using off peak electricity you mentioned. Reverse cycle systems can be quite efficient giving a gain of 4x the energy consumed. To use gas, reticulation infrastructure is needed in the form of plumbing or big gas bottles. Some do use this. Coal in furnaces is rare, and in the past there used to be oil heaters. Before this burning wood in fireplaces or stoves was common. Graeme Bartlett (talk) 08:09, 19 January 2010 (UTC)

I had electric baseboard heaters when I lived in Tennessee. And I wasn't the only one. I knew several people, especially those who were living in trailers who had electric heat. Dismas|^(talk) 09:51, 19 January 2010 (UTC)

In some parts of canada hydroelectric electricity is cheaper than gas. (Probably due to subsidies.) So electric heat is used. Otherwise electric heat is used when the installation cost of a gas burner is more than the savings of using gas vs electricity. Electric heat is very cheap to install. U.S. view: This is typically in the south where it doesn't get that cold. You have sort of a continuum - in the north, all gas. No A/C, so it's usually radiators (water). In the middle it's electric heat, and no A/C at all. In the south you have A/C (meaning the ductwork is anyway already there), so they use a central heat source, and they do gas. This is generalizing a lot of course. Also some places do not have gas service, and oil in not available. So electric is the default. These days, even in the north new construction comes with A/C, and the price of electricity has gone up more than gas, so it's pretty much all gas if it's available. Ariel. (talk) 10:27, 19 January 2010 (UTC)

Electrical heating is clearly the norm in Norway, a developed country in the north. Historically, we had very cheap hydroelectricity, you certainly don't need subsidies for this. Prices do rise as transmission capacity to the rest of Europe improves, though. There are (almost?) no distribution nets for gas in Norway, and I don't think it would be economic to build those; gas is piped from Norway's large sub-ocean gas fields via stations on the coast across the North Sea to Britain and the Netherlands. Large buildings do use oil for fuel though. Many single-unit houses have wood ovens as a supplement. I think electricity is the norm in Sweden and Finland as well. Jørgen (talk) 12:55, 19 January 2010 (UTC)

Electricity prices for the Nordic countries are here, in EUR/MWh, it would be interesting if some US users could compare this to their local heating prices (assuming 100% electricity efficiency). The electricity market in Norway is very competitive, I think the end-user prices are very close to the "market trading" prices (though transmission cost of 0,39 NOK/kWh (ca 7 US cents) comes in additition (at least that's the price in my area)) Jørgen (talk) 13:11, 19 January 2010 (UTC)

Here is a relatively informative article per your question, as you can see from the graph $.07 US/kwh is pretty darn low, a price almost no one in the US has seen since 2005. Depending on the natural gas spot market in the US, the price tends to be around 1/3 as much to get a BTU from NG compared to electricity (assuming the NG furnace is of modern efficiency). --Jmeden2000 (talk) 16:52, 19 January 2010 (UTC)

differnce between sea and ocean

what is the technical differnce in the definition of a sea and an ocean?Denito (talk) 07:46, 19 January 2010 (UTC)

Sea is small and Ocean is big. eg sea of Galilee is pretty miniature, but famous. The oceans currently on earth are pretty fixed in number, but perhaps your definition request is important to naming oceans in the geological past of earth, or on other planets. The Sea of Marmara is claimed to be the smallest sea, but sea of Galilee is smaller. According to Wikipedia a Sea is large, and an ocean is major. Graeme Bartlett (talk) 08:02, 19 January 2010 (UTC)

Even worse though, while sea of Galilee is a traditional name, it is actually a freshwater lake. Googlemeister (talk) 14:41, 19 January 2010 (UTC)

To further confuse things, some seas are part of a larger ocean (for example, the Carribean Sea is part of the Atlantic Ocean; the Andaman Sea is part of the Indian Ocean), whereas other seas, such as the Baltic Sea are separate bodies of water that are connected to oceans. See marginal sea and mediterranean sea. Gandalf61 (talk) 10:31, 19 January 2010 (UTC)

Oceans abut and separate continents. A sea is just some water on which one can sail a boat. Cuddlyable3 (talk) 13:15, 19 January 2010 (UTC)

Hmmm. The Bering Sea separates North America and Asia; the Red Sea lies between Asia and Africa; and the Mediterranean Sea has coastlines in Europe, Africa and Asia. But they are not oceans. Gandalf61 (talk) 15:10, 19 January 2010 (UTC)

Indeed. I did not claim that oceans have a monopoly on what they do. Cuddlyable3 (talk) 20:44, 19 January 2010 (UTC)

Because "ocean" is of European origin, it should be obvious that the use came from early Europeans. Add to the concept of an ocean the earlier fact that the world was flat, an ocean was the body of water that, if you sailed through it, led to the edge of the world. The world consisted of Europe, Asia, and Africa. The four oceans (just four at the time) were to the north, east, south, and west of the world. Once the world was proven round, there was no need to change the name. -- kainaw™ 15:24, 19 January 2010 (UTC)

Not to get too humanities on you, but that brief history of European knowledge of geography is ridiculously inaccurate. The Earth was known to be round in ancient and medieval times: for example, see our article on mappa mundi. 86.178.230.208 (talk) 17:20, 19 January 2010 (UTC)

I think there is also considerable geographical variation in the use of the term. I've noticed that Americans use the word "Ocean" in many contexts where the British would say "Sea". That may be because the USA is bounded by a couple of oceans where the Brit's have the North Sea on one side and an Ocean on the other. But it's only a matter of linguistics - there isn't any science behind it, beyond some vague concept of size. However, people still talk about "Sailing the Seven Seas"...when they probably mean something like "Four oceans and three seas". SteveBaker (talk) 19:11, 19 January 2010 (UTC)

To be more "humanities" in my answer... The English term "Ocean" comes from the Greek Oceanus. It is a concept of a Greek god represented as a world ocean upon which the world floats. The "flat" world concept is a simplification of the of concept of a round world floating in Oceanus. Many cultures named the coastal waters, but continued to refer to the unknown waters as being part of Oceanus, or an Ocean. The modern view of the world ocean is slightly romanticized with the Greek concept of an ocean. Atlantic comes from Greek Atlas, an offspring of Oceanus. Arctic comes from Greek Arktikos - the great bear in the northern stars. Antarctic is away from the bear. Pacific was named a long time later with a Latin name. It seems to me that Magellan should have known enough to give it a Greek-based name. However, the concept of an unknown ocean is what is different about the oceans and the seas. In modern times, very little is unknown. We just continue to use the terms here and there out of tradition. -- kainaw™ 20:22, 19 January 2010 (UTC)

--Mr.98 (talk) 20:37, 19 January 2010 (UTC)

I think our definition on the ocean page is pretty good. "An ocean is a major body of saline water, and a principal component of the hydrosphere." Now, obviously the line between what isn't a principle component of the hydrosphere or not is somewhat arbitrary, but the acknowledged oceans dwarf any candidate large seas considerably. The smallest ocean is some five times larger than the largest sea, while the rest of the oceans are some 20X larger. IMO the only questionable inclusion is whether the Arctic Ocean counts as an "ocean" or not. The Arabian and South China seas are both very small by comparison to the other oceans. --Mr.98 (talk) 20:37, 19 January 2010 (UTC)

facebook

how do i get annoying stuff like picture of the day , poker ect to stop appearing on my updates? —Preceding unsigned comment added by Killspammers (talk • contribs) 14:24, 19 January 2010 (UTC)

Do you mean on your newsfeed (items that your friends have posted), on your wall (items that applications have posted whilst you're using them) or on your notifications? If you are asking how to hide certain application updates from friends appearing on your newsfeed, you can hover over the item and a 'Hide' button will appear. On clicking this you will get the option to either hide all posts from this user or all posts from this application. You can also do this by clicking 'Edit options' on the footer bar at the bottom of your feed. To stop applications that you use posting to your wall automatically you have to alter the settings for each of these individually. Open an application and hover over 'Settings' on the header bar at the top of the screen, each application has it's own settings page which you would then be able to see and open. Click on this and go to 'Additional permissions' and untick 'Publish recent activity to my Wall'. If you are asking how to stop certain applications appear in your notifications - click on the notification icon in the bottom right of the screen, click 'See more' to go to the notification settings page and untick those applications you don't want to recieve information from on the right hand side. HTH. Nanonic (talk) 15:17, 19 January 2010 (UTC)

no i want to delete the application from my facebook. how do i do it —Preceding unsigned comment added by Killspammers (talk • contribs) 15:57, 19 January 2010 (UTC)

Well, you can start by having a look at facebook's own help on this]. Nanonic (talk) 16:33, 19 January 2010 (UTC)

cyclisation of tryptophan

From the indole article: "Since the pyrrollic ring is the most reactive portion of indole, nucleophilic substitution of the carbocyclic (benzene) ring can take place only after N-1, C-2, and C-3 are substituted."

Is this really true if intramolecular substitution is taking place? Say the C2 site is protected, and C3 site is already occupied. I think if the amino group is protected (maybe by simple acid) the carboxy group will attach on the benzene ring. Can someone confirm this? If so, I'm going to change the article. John Riemann Soong (talk) 15:07, 19 January 2010 (UTC)

Intramolecular effects can beat intrinsic reactivity, but that doesn't change the fact of the intrinsic reactivity. The result for any specific reaction is always a balance (and rationalization based on) of all competing effects. DMacks (talk) 18:50, 19 January 2010 (UTC)

Yes, but that is a preference for substitution, right? I don't think the article should be speaking in absolute terms. John Riemann Soong (talk) 20:22, 19 January 2010 (UTC)

Woman sentenced to 4 years for torching boyfriend's penis

how is it possible she got only 4 years? why didnt they give her 20 to 40 years or even life ? if a man raped her hed get like 10 years but she does something a million times worse and gets only 4 years? http://www.cbc.ca/canada/montreal/story/2007/02/28/qc-andreerene.html

Your opinion is that it was "a million times worse" than rape. Others may disagree with you. In any case, to go with your analogy, I'm not sure what the standard sentence for rape is in Canada, but I'd doubt it's anything like "20 to 40 years or even life". Does anyone know? --Dweller (talk) 16:08, 19 January 2010 (UTC)

According to this website, the maximum possible sentences for sexual assault crimes range depending on the exact conviction, from 6 months to life. The judge gets a lot of discretion as to what exact sentence is issued though. It article implies that the sentencing had a lot to do with mitigating circumstances—the defendant's history of abuse, psychological problems, etc.—which are often taken into account for such things. Whether it is a truly just sentence or not, I don't know, and I'm sure informed people would differ. --Mr.98 (talk) 17:56, 19 January 2010 (UTC)

Personal opinions but I don't give a shit; "mitigating circumstances" of the rapist should have zero influence on their sentence. I don't give a shit if the rapist is temporally mentally insane or whatever the fuck other excuses they boil up - rape is rape and imo rapists should be locked up for life.

The Wikipedia Science Reference Desk isn't a discussion forum for opinions, debates, and chats about current events. Perhaps you could find a suitable internet forum for this type of question? TenOfAllTrades(talk) 16:10, 19 January 2010 (UTC)

(Also where's the science in this question? I suppose there's Fire involved but still... 194.221.133.226 (talk) 16:17, 19 January 2010 (UTC)

I did not find any information out there, other than your link, about this 2007 sentencing, but I would guess that, under the Canadian Criminal Code, section 268, she was probably charged with "aggravated assault", for endangering the life of the complainant, which means she can be imprisoned for up to 14 years. By contrast the penalties for rape in Canada (page 4 of the PDF) are maximums of 10 years ("sexual assault"), 14 years ("sexual assault with a weapon, threats to a third party, or causing bodily harm"), or life ("aggravated sexual assault") — the latter meaning that the rapist also "wounds, maims, disfigures, or endangers the life of the complainant". Those are the maximums — I didn't find any information about why in this specific case she got a lesser prison term (assuming I was even right about the charge brought). I learned two things looking this up — the word "rape" is no longer in the Canadian criminal code; and the first rape law in the USA reduced the penalty significantly if the female victim were single (!). Comet Tuttle (talk) 17:56, 19 January 2010 (UTC)

so why wasent she givin the maximum sentence 14 years? also if you would rather get your genitals set on fire than get raped u need your head examined. —Preceding unsigned comment added by 67.246.254.35 (talk) 18:44, 19 January 2010 (UTC)

Because a judge, probably in light of the aforementioned mitigating circumstances, decided to sentence her otherwise. --Mr.98 (talk) 19:01, 19 January 2010 (UTC)

The general idea is that you want to punish unjustified, capricious malice. It was the opinion of the sentencing parties that Ms. Flame didn't have that much malice. Probably they thought she was somewhat justified. She evidently thought she was justified at the time of doing it, and that would be good enough for me if I were a juror. Vranak (talk) 20:30, 19 January 2010 (UTC)

Autocrine signalling

From what I understand, autocrine signalling is where a cell releases a transmitter to purely act on its own receptors, so that it can talk to itself. Is there any good reason for this, or is my premise wrong (i.e. a cell never wants to talk just to itself)? At first glance it appears to be inefficient, probably analogous to sending yourself a text message when you could just store it in the draft folder and avoid the SMS cost. Or writing down "pour yourself a glass of water" and reading it, instead of just pouring yourself a glass of water. --Mark PEA (talk) 17:30, 19 January 2010 (UTC)

I suppose you've never written a todo list? My first thought about its utility is that it lets the cell react over an extended period of time (the lifetime of the transmitter) to even a transitory stimulus. --Tardis (talk) 18:39, 19 January 2010 (UTC)

There are many biological processes in which amplification of a signal must occur: autocrine signalling is one mechanism for this. Of course it is "inefficient" from an engineering standpoint--- one more example of the difference betweened designed and evolved complex entities. alteripse (talk) 19:14, 19 January 2010 (UTC)

(ec) I might speculate that this is an example of evolution deciding to 'reuse its code', as a programmer might say. Rather than having to evolve a whole new set of signalling proteins to trigger some sort of signalling cascade in the middle of an existing pathway, autocrine signalling means that a cell can just use already-existing genes and proteins to trigger a signal in the 'usual' way from an 'external' stimulus. While it might not appear to be the most efficient method, it works. (Consider this — let's say that you are standing in front of a photocopier, and you just happen to need a sheet of blank paper. One solution is to try to figure out how to unlatch and open the paper trays, locate the pages of the correct size, remove a single sheet, make sure everything is closed back up properly, and declare success. Another solution is to just push the copy button on the front panel without putting an original on the glass. Presto — out comes the sheet you wanted, no diassembly or fiddling required. Evolution has a habit of reusing old methods with minor tweaks; it's 'easier' than generating whole new pathways from scratch.)

I'll also note that the definition of autocrine signalling is often a bit broader than simply a single cell acting on itself. It can also include cases where a particular cell signals not just to itself, but also to other cells of the same type. The applications of that sort of signalling are more obvious. Among other things, it allows groups of cells to 'assess' their surroundings by 'polling' their neighbors. A cell can 'sense' whether (for example) a lot of its neighbors are stressed out and respond accordingly. TenOfAllTrades(talk) 19:23, 19 January 2010 (UTC)

Technical vs managerial career track

I'm hoping you RefDesk folks can refer me to some essay, website, book, etc that discusses the choice faced by a scientist or other technical worker when presented with the opportunity to move into management. (I'd love to discuss this with someone, but I understand the RefDesk isn't the place for it). ike9898 (talk) 17:41, 19 January 2010 (UTC)

See Dilbert (sorry). Looie496 (talk) 18:00, 19 January 2010 (UTC)

I'm not familiar with any books confronting this career choice, but googling manager career site:slashdot.org will yield many threads on the subject. Warning: Many "contributors" are grousing computer programmers who believe all management is counterproductive micromanagement. If you're looking for books on technical management (rather than focusing on the career choice which was your actual question), The Mythical Man-Month is considered a classic of software development management. Comet Tuttle (talk) 18:33, 19 January 2010 (UTC)

Managers get paid more and they are the boss. 78.151.106.238 (talk) 19:08, 19 January 2010 (UTC)

In my particular situation (US government), the difference in pay is small and and in my current situation as a researcher, I have a fair degree of autonomy. Both these factors reduce the advantages of moving into management. ike9898 (talk) 19:21, 19 January 2010 (UTC)

That may be true now, but think what will happen in the future. My guess is that in the long run you will be earning more money and having more status. 78.151.106.238 (talk) 20:38, 19 January 2010 (UTC)

If you like long meetings, presenting in front of groups, and having to nag deadbeats who are late to work and who slack off, then, by all means choose management. If you don't like those things and like to create things of value yourself, then choose the technical path. Technicians can pat themselves on the back and say, "I built that web site" or "I made that program." Managers aren't bad people. Some take joy in befriending their employees and rewarding them when they succeed. But eventually, you have to discipline them, too. That's not always a fun thing to do.--Drknkn (talk) 19:33, 19 January 2010 (UTC)

Its just as easy to spin that the other way - technicians would tend to do more repetative work with less responsibility, hence more boredom and lack of fulfillment. There are many different styles and fads of management or (not the same thing) leadership - autocratic, consultative, etc etc. Take your pick. And you can build something without doing the labouring yourself - hence you build bigger and more impresive things. 78.151.106.238 (talk) 20:38, 19 January 2010 (UTC)

Engineers are people who can do what they don't control. Managers are people who control what they can't do. Cuddlyable3 (talk) 20:39, 19 January 2010 (UTC)

Its difficult to recommend a book without having more information on what kind of management you see yourself doing, and what aspect of management interests you. Could you supply more details please? 78.151.106.238 (talk) 20:49, 19 January 2010 (UTC)

Gaussian and SI Units of Charge

Hello everyone. Looking over pages for various units, I'm a little confused on how the relationship between coulombs and statcoulombs. Basically, if Coulomb's Law is defined differently in SI and gaussian units, the units on force must still be the same (mass length/time²). Setting the two forms equal to each other, I get a formula somewhat different to the one at the bottom of the statcoulomb page. I obtain

$1\;{\textrm {statcoulomb}}={\frac {1\;{\textrm {coulomb}}}{\sqrt {4\pi \epsilon _{0}}}}$

substituting in $1/\epsilon _{0}=10^{-7}c_{0}^{2}$ and throwing in a factor of ${\sqrt {10^{9}}}$ for converting kilograms to grams and meters to centimeters, I get 1 statcoulomb = 2997924580 coulombs, ie the exact opposite of what the page says (and opposite everything that every other conversion table I've looked at said). What's wrong with my derivation? Thanks :) Bennybp (talk) 18:10, 19 January 2010 (UTC)

Relation between angular velocity and torque

What is torque formula of roatating equipment, if equipment rotate at constant angular velocity? —Preceding unsigned comment added by Mananmodi11 (talk • contribs) 18:24, 19 January 2010 (UTC)

If the angular velocity is constant, the net torque is zero (just as if the net linear velocity is constant, the net force is zero). In real life, if there is a decelerating torque due to friction, that means you'll need to apply an equal and opposite torque to maintain the angular velocity. -- Coneslayer (talk) 18:30, 19 January 2010 (UTC)

That is true for an isolated body. A rotating part of equipment that transmit power, such as a gearwheel in a clock or a car transmission, can have constant angular velocity while exerting a high torque. Cuddlyable3 (talk) 20:34, 19 January 2010 (UTC)

What? It's the net torque on the "part of equipment" that then needs to be 0, not the torque it exerts on other things. Of course, there's an equal and opposite torque applied to it by the driven object, but there's also a torque applied to it by the "upstream" source (eventually by an off-center spring or gasoline explosion or…), and at constant angular velocity they add to 0. --Tardis (talk) 20:46, 19 January 2010 (UTC)

The path of the moon through the sky

Would the path of the moon through the sky, from moon-rise to moon-set, always be part of a circle if viewed through a very large sheet of glass that was set vertical and parallel to the imaginary line from moonrise azimuth to moonset azimuth? I mean, an arc of a circle and not some other curve. 78.151.106.238 (talk) 20:32, 19 January 2010 (UTC)

unlikeliest thing to happen that did in fact happen? (that we know of)

Hi,

"Of all the things that were unlikely to happen, but did anyway, which one had been the unlikeliest?" (that we know of)

is my question even meaningful, or does it misconstrue statistics? (this is not homework). Thanks. 84.153.196.174 (talk) 20:55, 19 January 2010 (UTC)

That your particular sperm fertilized the egg, against compitition from millions of other sperm. That is probably the most unlikely thing in anyones life. 78.151.106.238 (talk) 20:58, 19 January 2010 (UTC)

escaping black holes

Is it correct that a virtual graviton (gravity carrier) can escape out of black hole, whereas a real or actual graviton (gravity wave carrier) cannot?? 89.138.153.164 (talk) 21:00, 19 January 2010 (UTC)