Wikipedia:Reference desk/Archives/Science/2009 November 9

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November 9

Topical decongestant

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Nimur (talk) 00:20, 9 November 2009 (UTC)

If you're concerned about an over-the-counter medicine, but don't want to see a doctor, a pharmacist might be able to answer your question. AlmostReadytoFly (talk) 10:56, 9 November 2009 (UTC)

Gay-Lussac's law and Degrees of Freedom in Calculating the Final Temperature of a Gas Undergoing Adiabatic Compression

This question is related to serious confusion I've been having regarding conflicts in method of calculating the final temperature of a gas undergoing compression.

Gay-Lussac's law dictates:

P₁T₂=P₂T₁
so
T₂=(P₂T₁)/P₁

But when doing a similar substitution in the work formula for an adiabatic compression you come out with:

T₂=T₁(P₂/P₁)^(y-1/y)
Where y=degrees of freedom.

This causes significant discrepancies in calculating T₂! Help! I don't understand why there is a difference, and which is correct in which situation. —Preceding unsigned comment added by Gothamxi (talk • contribs) 08:39, 9 November 2009 (UTC)

Your first expression is based on an assumption that the volume doesn't change. Not much of a compression if you do that. More generally, for an ideal gas: ${P_{i}V_{i} \over T_{i}}={P_{f}V_{f} \over T_{f}}$ where the i and f subscripts denote the initial and final states respectively. The adiabatic compression formula is a special case dealing with compression where no net heat is transferred. This is common approximation for a variety of useful situations. Dragons flight (talk) 12:53, 9 November 2009 (UTC)

how do I turn a chloramine back into an amine

Also, are chloramines useful protecting groups for amines? John Riemann Soong (talk) 14:26, 9 November 2009 (UTC)

Strip the chlorine off with vitamin C or potassium metabisulfite. For your second question see Protecting group#Amine protecting groups which does not really answer, but probably no. Graeme Bartlett (talk) 11:35, 13 November 2009 (UTC)

cyanide...

how fast can cyanide act as a poision???? how can it be detoxified??? who is the inventor of this chemical??? --Lostinscience (talk) 14:35, 9 November 2009 (UTC)rahul

Cyanide was discovered -- nature invented long before we knew of it. Cyanide is dangerous the way carbon monoxide is -- the carbon is nucleophilic and will bind (covalently) to metal coenzymes in your body, deactivating them. Carbon monoxide deactivates heme (an oxygen transport carrier), while I believe cyanide disables parts of the electron transport chain. John Riemann Soong (talk) 14:50, 9 November 2009 (UTC)

You may find our articles on Cyanide#Toxicity and Cyanide poisoning helpful. TenOfAllTrades(talk) 15:22, 9 November 2009 (UTC)

See the articles Gas chamber and Zyklon B (which contains Hydrogen cyanide). Anhydrous ammonia is used to cleanse the chamber after cyanide gas has been used. Cuddlyable3 (talk) 18:43, 9 November 2009 (UTC)

If you can keep the person alive (i.e. with pure oxygen), the best cure is the person's liver - most antidotes are almost as toxic. My old Natural Products lecturer always said that "it only takes seventy milligrams of sodium cyanide to be fatal by complexing all the beta-cytochromes in the body" - I'm sure he must have been planning someone's demise, he was always repeating it (and it didn't come up in the exam either!)  Ronhjones  ^(Talk) 20:02, 9 November 2009 (UTC)

Cyanide antidote kits include injections of sodium nitrate, sodium thiosulfate and amyl nitrate inhalants. [1] 10draftsdeep (talk) 15:23, 10 November 2009 (UTC)

There's something now I have to ask. Agatha Christie (and her ilk)'s murderers invariably use either prussic acid (hydrogen cyanide) or potassium cyanide. Why not sodium cyanide? Does it have properties that make it unattractive for deliberate administration? Tevildo (talk) 21:49, 10 November 2009 (UTC)

The sodium-cyanide bond is stronger than the potassium cyanide bond. Remember, a sodium cation is isoelectronic to neon (but its electrons are more tightly bound). Thus, its electron cloud will be on the same scale as carbon, nitrogen, fluorine, etc. This makes the interaction more covalent -- this in turn makes it harder to dissolve and dissociate sodium cyanide. Protons are smaller, while the potassium cation is bigger. Effectively, this makes sodium cyanide less water soluble and less potent.

An excess of the potassium cation also depolarises cells' membrane potentials. Double killer. (See [[membrane potential].) John Riemann Soong (talk) 01:06, 11 November 2009 (UTC)

Source of Neutron star magnetic field

The Sun has a magnetic field because of convection currents in its conducting plasma. What causes the magnetic field of a neutron star? RJFJR (talk) 17:35, 9 November 2009 (UTC)

It comes from the stellar magnetic field of the progenitor star. As the star collapses into a neutron star, the total magnetic flux through the surface is conserved, so the magnetic field strength increases as the surface area decreases. -- Coneslayer (talk) 19:19, 9 November 2009 (UTC)

But what keeps it going after that? Is it just like a permanent iron bar magnet with magnetic domains locked in alignment? --Tango (talk) 19:30, 9 November 2009 (UTC)

The total magnetic flux through any closed surface is zero... Rckrone (talk) 19:34, 9 November 2009 (UTC)

Sorry, that should be "through any portion of the surface", e.g. the hemisphere containing one of the magnetic poles. The argument for this "freezing" of the magnetic field, along with the slow timescale for magnetic field decay (Tango's question) are addressed in Section 3.1 of Origin and evolution of neutron star magnetic fields. -- Coneslayer (talk) 19:51, 9 November 2009 (UTC)

Ok, so the magnetic fields is generated by free electrons (presumably near the surface since in the middle they will have been merged with protons to make neutrons) flowing around and they flow around because of the magnetic field? That reminds me of electromagnetic radiation - the electric field and magnetic field generate each other so the combination propagates. --Tango (talk) 20:01, 9 November 2009 (UTC)

It seems very similar to the Meissner effect in superconductors: Note that field expulsion (or cancellation) implies infinite conductivity, but that infinite conductivity does not imply field expulsion, because if a material develops only infinite conductivity below its transition temperature, that infinite conductivity will "freeze in" whatever magnetic field was present as the transition temperature was reached. I'm finding articles that predict electron superconductivity in NS crusts, as you say above, but also proton superconductivity in the interior. -- Coneslayer (talk) 14:22, 10 November 2009 (UTC)

Evolution

It apparently violates the establishment clause to either ban the teaching of evolution or require the teaching of flaws in evolution. However, would it be legal for a state to, rather than specifically banning evolution, simply remove evolution from the required state curriculum and not include any questions about evolution on their standardized assessments? ----J4\/4 <talk> 18:02, 9 November 2009 (UTC)

This actually seems more of a humanities question. You might have better luck at WP:RD/H, as your question is about law. Intelligentsium 18:14, 9 November 2009 (UTC)

My understanding is that this would be held to be unconstitutional in the United States, under Edwards v. Aguillard. Your proposal lacks "a clear secular purpose", and I would argue it "undermines the provision of a comprehensive scientific education," which were fundamental requirements in the ruling for such an act to be nonviolative of the Establishment Clause. Comet Tuttle (talk) 18:52, 9 November 2009 (UTC)

Many of what creationists call "Flaws in evolution" are presented to students. They're just not presented in the distorted, blown out of proportion way that you'd get from a anti-evolution tract. They're presented, correctly, as minor details that are still being worked out, points still undergoing debate or research, or as questions that are yet to be answered. It's an important part of good science education to teach that the process is ongoing and that our knowledge is constantly being refined. APL (talk) 19:04, 9 November 2009 (UTC)

AFAIK state legislatures do not write school exams, teachers do. Therefore the state would have to specifically ban teachers from posing evolution questions to make that happen. Cuddlyable3 (talk) 19:43, 9 November 2009 (UTC)

We had this same question not too long ago, I think. It would almost surely fail the Lemon test, as banning evolution would serve no secular purpose. --Mr.98 (talk) 21:23, 9 November 2009 (UTC)

About the best chance you'd have to argue it from a purely secular perspective would be to suggest that the student's time is strictly limited - so it's impossible to teach all of science - so some things have to be left out. The trouble with that is that biologists (correctly) point out that every single thing you learn in biology revolves around evolution. So I think you'd have to somehow justify not teaching biology at all - and that's frankly impossible to justify since we have to (at the very least) prepare children who will go on to join the medical profession. So I don't think that's possible either. IMHO, the Creationists are making a major mistake by even trying to prevent this - you cannot effectively argue against something you don't understand...and producing an entire generation of adults who don't understand evolution makes them easy pickings in a debate with anyone who knows anything about the subject whatever. SteveBaker (talk) 22:33, 10 November 2009 (UTC)

Quotes from an Inventor

I need a quotation from an inventor about his/her work. I don't know very many inventors, and I can't find any quotations from any inventor aabout his/her work anywhere. Does anyone here know any? <(^_^)> Pokegeek42 (talk) 21:21, 9 November 2009 (UTC)

The most classic quotes are probably to be found at Wikiquote:Thomas Edison. --Mr.98 (talk) 21:26, 9 November 2009 (UTC)

Wow. I didn't know there was a Wikiquote. Thanks, that really helps! <(^_^)> Pokegeek42 (talk) 21:34, 9 November 2009 (UTC)

Two from one of my favorite inventors, Dr. Edwin Land

Over the years, I have learned that every significant invention has several characteristics. By definition it must be startling, unexpected, and must come into a world that is not prepared for it. If the world were prepared for it, it would not be much of an invention.

Don't do anything that someone else can do. Don't undertake a project unless it is manifestly important and nearly impossible.

-- LarryMac | Talk 22:22, 9 November 2009 (UTC)

You can't beat the very greatest:

“ Think. ”

Thomas J. Watson, founder of IBM. Nimur (talk) 23:44, 9 November 2009 (UTC)

Was Watson an inventor ? I thought he was basically a salesman. Gandalf61 (talk) 10:32, 10 November 2009 (UTC)

Valid nitpick - but the same can be levied against Thomas Edison, or numerous other "managers of inventors" who get the historical credit anyway. Nimur (talk) 15:48, 10 November 2009 (UTC)

This one isn't from an inventor, but rather an author, George Bernard Shaw. However, it is about inventors:

"The reasonable man adapts himself to the world; the unreasonable one persists in trying to adapt the world to himself. Therefore, all progress depends upon the unreasonable man."

You might also want to view other similar quotes here: [2]. StuRat (talk) 00:33, 10 November 2009 (UTC)

Wikiquote's Category:Inventors is probably your friend. --Tagishsimon (talk) 01:37, 10 November 2009 (UTC)

"The key to success is to risk thinking unconventional thoughts. Convention is the enemy of progress. As long as you've got slightly more perception than the average wrapped loaf, you could invent something" - Trevor Baylis. Gandalf61 (talk) 10:32, 10 November 2009 (UTC)

I am an inventor. You may quote me saying: Patents bring only tears. Cuddlyable3 (talk) 20:26, 10 November 2009 (UTC)

I am an inventor. You may quote me saying: Cuddlyable3 is right - except in the case of patent lawyers. SteveBaker (talk) 02:55, 11 November 2009 (UTC)

Girls to stop growing

At certain age, people will stop growing in heights. Somebody told me males have grown until 25. is this possible for female to grow at 21?--209.129.85.4 (talk) 21:37, 9 November 2009 (UTC)

Certainly possible, though not common. Neither is males growing in height to age 25 common. Googlemeister (talk) 21:50, 9 November 2009 (UTC)

Agreed, it is certainly possible, but rare. It is sometimes caused by hormonal/glandular problems that can have other serious effects, so it might be worth talking to a doctor, especially if the person is already unusually tall. --Tango (talk) 22:03, 9 November 2009 (UTC)

human growth, Human development (biology), human height - none of them seem to address this. Did I miss a more relevant article? 75.41.110.200 (talk) 22:11, 9 November 2009 (UTC)

We don't seem to have a relevant article, but if you look at, for example, Robert Wadlow (the tallest man in recorded history), you'll see his height was caused by hypertrophy of the pituitary gland, which caused him to keep growing for his whole life (he died at 22, though). Extreme heights like this can put additional strain on the heart, skeletal system, etc.. --Tango (talk) 22:50, 9 November 2009 (UTC)

WHAAOE. Gigantism and Acromegaly both apply to pituitary growth hormone excess. Not that it has really anything to do with the OP's question, of course. As far as I can tell the question is about normal growth and development. The growth of the long bones is limited by the closure of the growth plates, which occurs toward the end of puberty -- see the section on "differences between male and female puberty" for a discussion of why females usually stop their growth spurt at a younger age than males. With that being said, there's no reason why a girl with delayed onset of puberty might not continue growing longer than her peers, thereby ending up taller. --- Medical geneticist (talk) 00:29, 10 November 2009 (UTC)

It depends on your definitions, but a women still growing at age 21 isn't particularly normal. It could just be an extreme of normal development (long tails and all that) or it could be decidedly abnormal. I would rather let a doctor decide which it is than random people on the internet. --Tango (talk) 04:55, 10 November 2009 (UTC)

Simple. Modify the biological clock machinery that give rise to these events. I don't know how much we know about the molecular machinery that dictates the onset of machinery and what cues are taken, etc. but it's quite simple to envision an analogue to the per-tim-dbt-clk/cyc sort of circuit you see for the Circadian clock. Mutations in these proteins can trigger abnormally long/short periods so if there's an oscillator regulating growth similar variants in those proteins might be responsible for the distribution of ages seen for a particular stage of development. John Riemann Soong (talk) 22:35, 9 November 2009 (UTC)

Such developmental patterns are wildly variable in both genders. For two data points: I reached my full adult height at about age 13. At 5 foot 9 inches in the 8th grade, I was among the tallest in my class. I'm still 5 foot 9 inches tall today, some 20 years later. Noted basketball player David Robinson did not reach his full 7 foot 1 inch height until the age of 21, his senior year at the United States Naval Academy. While the two of us probably represent statistical outliers, there are still some rather larger error bars on the "average age when full adult height is reached" data set. --Jayron32 03:25, 10 November 2009 (UTC)

More anecdotal evidence - my wife had reached her full (normal) adult height by age 13. (She's now well over age 25, so not likely to grow any taller.) Mitch Ames (talk) 03:33, 10 November 2009 (UTC)

A man not growing past 13 sounds very unusual, as is being 5'9" at age 13 (it's off the scale on the two online percentile charts/calculators I've checked, so at least top 3% but I think it is more like top 0.1%, the calculators just aren't calibrated at such extremes). A man growing until 21 isn't particularly unusual, though. A women reaching her final height by 13 isn't so unusual. --Tango (talk) 04:52, 10 November 2009 (UTC)

No joke. In the summer after my 8th grade year, I was easily a full head taller than nearly all of my classmates. By the time I graduated high school, many of my male classmates had passed me by. I may have been a tad smaller than 5'9" at the time, i.e. I may have stopped growing in my 14th year rather than during my 13th, but I pretty much remained exactly the same height for ALL 4 years of high school. --Jayron32 06:19, 10 November 2009 (UTC)

Well, if my estimate (ok, guess) is right and it puts you in the top 0.1% then there are about 2 million men than would have been that tall by that age in the world. It's unusual, sure, but there are a lot of people in the world so unusual things do happen. I guess it isn't surprising that you would stop growing early if you were already that tall - there is far more variation in rate of growth than there is in final height. If you don't mind me asking, did you reach other puberty milestones earlier than your peers as well? --Tango (talk) 17:47, 10 November 2009 (UTC)

magnetics question

Is the magnetic strength of magnets additive if I stack 4 magnets one on top of the other, can I lift something 4x as heavy as a single magnet could? I would suspect not, but then how much heavier? If it helps, you can assume cube shaped magnets. Googlemeister (talk) 22:18, 9 November 2009 (UTC)

Correctly computing the force between ferromagnets and a metal surface (like paper-clips) is extremely complicated, and requires both a very nontrivial vector calculus treatment as well as some pretty intense empirical correction factors. You can see some of the simplest approximations that are experimentally useful at Permanent magnet#Calculating the magnetic force. Nimur (talk) 23:49, 9 November 2009 (UTC)

For one thing, if you stack the magnets, then all but one of the magnets will now be further away from the object you're trying to move, and this will decrease the load they can carry. If you place them side by side, on the other hand, then I suspect that you would come close to having 4 times the lifting capacity of a single magnet. StuRat (talk) 00:23, 10 November 2009 (UTC)

If you place them side-by-side, with their poles aligned so they all attract the paperclips, the magnets will repel each other. As I mentioned above, the correct treatment requires calculating the effective lines of flux, calculating the induced magnetism in the object that will be attracted; and integrating. Each stage of this treatment requires thorough, 3D solution of Maxwell's equations, accounting for material properties and assuming precise knowledge of the magnetic field inside the ferromagnets. Nimur (talk) 00:54, 10 November 2009 (UTC)

Some side by side arrangements are better than others.—eric 01:50, 10 November 2009 (UTC)

So I take it then that treating magnets which are stacked to be akin to batteries wired in series would be incorrect? Googlemeister (talk) 14:58, 10 November 2009 (UTC)

That would result in an extraordinarily inaccurate approximation. The level of accuracy of course depends on the particular geometry, the particular magnetic fluxes of each magnet, etc. I am sure that there is some set of approximations and limiting cases where you could arrange some sort of analogy, but keep in mind that magnetic field strength is much more dependent on spatial geometry than electric current that is constrained to remain in a wire. Nimur (talk) 15:51, 10 November 2009 (UTC)

Could the approximation be improved by modelling the air as a resistive electrolyte? Cuddlyable3 (talk) 20:24, 10 November 2009 (UTC)

sterics of proteins and interactions between R groups

Is it me or do protein chains look really ... cramped. Is there a polymer stereochemistry for the polyamide bond (e.g. does -NH2 prefer to add below the carbonyl or above?), and besides cysteine disulfide bonds, it seems to me that ring condensation and the like could potentially occur, say between NH2 and COOH R groups, if it was so desired that their amide formation be catalysed? John Riemann Soong (talk) 22:31, 9 November 2009 (UTC)

Cysteine dithiol linkages aren't the only inter-amino-acid linkages that occur in proteins, there are lots of other sorts of interactions. There are "hydrophobic interactions", such as between alkenyl side chains (valine, leucine, isoleucine), as well as hydrogen bonding interactions, lewis acid-base interactions, etc. etc. There are a full variety of inter-amino-acid interactions. Pretty much any sort of bonding or interaction or reaction one may find in chemistry can occur in a protein. Such complex interactions are what give a protein its secondary, tertiary and quaternary structure. Sadly, our article on tertiary structure is quite lacking, but a decent biochemistry or molecular biology textbook should have a decent section on the chemistry behind this sort of dense protein folding. --Jayron32 03:58, 10 November 2009 (UTC)

Yes but these appear to be quite "long-range" and based on folding. I was really referring just more of "steric collisions" and covalent ring condensations. (Most of the other interactions are non-covalent...) John Riemann Soong (talk) 12:44, 10 November 2009 (UTC)

What arthropod is this?

I think these are scale insects but I'm not certain. As far as I can tell Wikimedia Commons does not have another image of this species. Can anyone help me narrow down what these little guys are? -Craig Pemberton (talk) 23:42, 9 November 2009 (UTC)

For questions like these people usually want to know where geographically the photo was taken, and on what sort of plant the critters are on. --Sean 01:24, 10 November 2009 (UTC)

Such people could click on the image to learn "stalk of grass in Flagstaff, Arizona". --Tagishsimon (talk) 01:31, 10 November 2009 (UTC)

Aphids? The look to be the right size. There are 10 families and hundreds of genera and species of aphids, but based on the behavior and location (clustered around the stalk of a plant) I would fathom a guess that these are aphids of some sort. --Jayron32 02:32, 10 November 2009 (UTC)

Hey I think you're right! =D I never would have guessed but it makes perfect sense. That gets me to Insecta Hemiptera Sternorrhyncha Aphidoidea. I doubt they belong to Anoeciidae because they were not on the roots and I doubt the belong to Pemphigidae because I've never seen a gall on a "monocot". The remaining blue-linked taxon is Aphididae which apparently contains the majority of the species and is a great place for me to start. Thanks Tagishsimon for standing up for me, Jayron for the good eye. -Craig Pemberton (talk) 03:07, 10 November 2009 (UTC)

On a possibly related note, I also ran into this guy which looks a lot like these aphids but is lacking cornicles. Any ideas? -Craig Pemberton (talk) 10:28, 10 November 2009 (UTC)

Some type of tree cricket, perhaps the Snowy Tree Cricket [3]? Mikenorton (talk) 11:09, 10 November 2009 (UTC)