Wikipedia:Reference desk/Archives/Science/2013 March 30

Welcome to the Wikipedia Science Reference Desk Archives
The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages.

March 30

Medical procedure and patients' gender

Is not knowing the gender of a patient in some contexts life-threatening? Traditionally, I suppose doctors would just know, but transsexual operation appear to be getting better and better, so could it happen that doctors don't know the biological gender of a patient? OsmanRF34 (talk) 00:31, 30 March 2013 (UTC)

That sort of thing comes up when a doctor gets a patient's medical history. It would be rare (though not impossible; for example if an unconscious patient needed an emergency procedure) for a patient to walk into a doctor's office and not have the opportunity to give a medical history. There are some issues; for example IIRC, pregnancy tests, if they give a positive result for men, can be an indication that the man may have cancer:[1] Now, it is not recommended that men take pregnancy tests for that purpose, as false positives can lead to unnecessary and possibly dangerous further procedures and tests. But there are biological differences between men and women which it would be important for a medical doctor to know, and post-operative transsexuals could generate complications for themselves if they did not reveal that fact through discussions with their doctors. Per the ideas of medical confidentiality, that sort of information is for the use of the doctor only, and only for treating the patient. --Jayron32 00:51, 30 March 2013 (UTC)

I distinctly remember that this same question has been posted on Ref Desk a few times before. However I was unable to come up with a way of searching the archives to find them. If someone knows, perhaps they could share it. Once imaging is used though, no doctor should be fooled. The difference between a female pelvis and a male pelvis is obvious visually and on X-ray, and any surgery to alter it would show up. Surgery can create a pseudo-vagina in a male, but he'll still have no ovaries and tubes etc to show up on ultrasound. The geometry of the chest, back, and neck skeleton are somewhat different too, though you do come across women with very short necks and men with very long necks, as with Canadian Jenna Talackova. Wickwack 120.145.158.214 (talk) 03:37, 30 March 2013 (UTC)

I must assert here that we have genetic sex, rearing sex, gonadal sex, and assignment sex. When we say Gender, which gender are we referring to? Even in a transgender person with no ovaries, the chromosomal (genetic) sex might still be female; similarly, in a feminised male, the genetic sex would be a male; some communities with high illiteracy and non-access to hospitals might wrongly assign the sex of a virilised female as male and rear her as such. These are valid problems in medicine. Genetic sex can be discovered by doing a FISH test on a scraping from the oral (buccal) mucosa. ----

Sex differences in medicine states "More recently, medical research has started to understand the importance of taking the sex in to count as the symptoms and responses to medical treatment may be very different between sexes." but doesn't go into any details. Women's health has a short section that says that proton pump inhibitors can interfere with calcium uptake, leading to bone fractures, presumably much more with women than men. There are some difficult to diagnose diseases such as lupus and ovarian cancer that are more prevalent in women than men, so mistakenly identifying someone as a man could conceivably result in a life-threatening delay in diagnosis and treatment.--Wikimedes (talk) 21:29, 30 March 2013 (UTC)

Sure. If a person breaks a law or embarrasses a powerful and violent antagonist because of deceit involving some gender classification, it might be life-threateing-- at least that happens regularly on TV. There are countries in which the penalty for cross-dressing might be death if homosexuality is inferred, so any unplanned medical encounter that revealed that the person was trying to deceive that country's social rules might put the patient at risk for serious harm or death. alteripse (talk) 01:09, 31 March 2013 (UTC)

A number of physiologic expectations are based on gender (and race), such as glomerular filtration rate as it relates to renal function. As you can see from the portion of the article I linked to, constants of .85 or .742 are applied in the case of female patients and 1.21. or 1.18 are applied in the case of black patients, and no knowing this sort of information would most certainly mess with the relationship of patient values with those of expected values. DRosenbach ^{(Talk | Contribs)} 19:29, 31 March 2013 (UTC)

But not enough to cause harm. The sex differences between vital function parameters are small. alteripse (talk) 19:41, 31 March 2013 (UTC)

A related issue is hormone replacement therapy. HRT can interact with other drugs, but sometimes patients feel pressured to hide the fact that they are on it because of the potential for discrimination by transphobic doctors. See also Transphobia#Transphobia_in_healthcare 38.111.64.107 (talk) 13:05, 1 April 2013 (UTC)

But not likely to cause harm. Lots of women conceal OCP use and lots of men conceal anabolic steroid abuse, both far more than transgender patients would conceal the same steroids.alteripse (talk) 10:32, 2 April 2013 (UTC)

A doctor that is unaware about a transgender patient would also not know to recommend certain regular screenings such as a colonoscopy. Problems related to gender-specific organs would not be suspected at all unless a scan was done. A person who has had SRS but is not on HRT (I suspect this is uncommon, but I don't know) would also have abnormal results for various hormones on their blood tests, which could conceivably lead to a misdiagnosis. 38.111.64.107 (talk) 16:28, 1 April 2013 (UTC)

The screening difference is not a bad idea, but again there is little difference in screening tests by sex except for prostate and breast cancer. The hormone levels are certainly different but again not likely to result in harm. Doctor says to ostensible woman patient: "your testosterone is way too high. It might be a tumor of your adrenals or ovaries. I would like you to have some additional tests and an ultrasound." And if she happens to be an uncastrated trans-woman, you dont think she would understand what was going on? alteripse (talk) 10:32, 2 April 2013 (UTC)

Proton current

Normal electric current is the flow of electrons through a conductor. Is t possible to create a proton current, by using a custom designed zeolite fibre to conduct a flow of protons or protonated small cations? How would the properties of such a hypothetical circuit be? Plasmic Physics (talk) 02:54, 30 March 2013 (UTC)

Since the Wiki article on zeolites says they can absorb a variety of cations and exchange them with adjacent substances, then yes, they can carry an electric current. Since the fibre would be positively charged, this would have to be nuetralised. A very thin fibre with an insulated coaxial screen negatively changed (not to be confused with using a coaxial screen to carry a return current) should do that. I have no idea how you would estimate the electrical resistance of such a conductor, but think it would be inconveniently high, and so the current carrying capacity would be uselessly low. Transient phenomena such as inductance and capacitance could be easily calculated from the physical dimensions (principally the geometric mean radius) using standard formulae as for any conductor. Since conductionover a long thin fibre would be dependent of the charge on the coaxial screen, the assembly could function as a Field Effect Transistor. However, the two key physical dimensions crucial to operator as a FET, geometric mean radius, and screen to conduction path separation, would I think have to such that operation as a FET would be absolutely hopeless. As a teenager, I once decided to make a FET using a long length of thin polyurethane varnished copper wire ("magnet wire" the thickness of a hair) soaked in water, using the water as the control gate. I was able to show that it worked, but the gain was something like 1 microamp per kilovolt, the absolute limit of measurability with what I had, whereas a typical commercially made junction FET using doped silicon is about 4 milliamps per volt - about 4 million times better. I expect a zeolite FET would be even worse. Protons on their own will not work in zeolite. Wickwack 120.145.158.214 (talk) 03:26, 30 March 2013 (UTC)

OK. What if the zeolite itself is carries a negative counter charge, effectively creating an inverse electride: H⁺(zeolite subunit)^-? Plasmic Physics (talk) 03:37, 30 March 2013 (UTC)

Won't they react and destroy the conduction? Wickwack 120.145.158.214 (talk) 04:06, 30 March 2013 (UTC)

Won't what react? Plasmic Physics (talk) 04:11, 30 March 2013 (UTC)

Why not just a tube of acidified water. Wouldn't that be functionally a proton conductor? --Jayron32 04:38, 30 March 2013 (UTC)

That be true, however, then the conductor would be equivalent to a molten salt, and not to the required solid metal. Plasmic Physics (talk) 04:48, 30 March 2013 (UTC)

So you're looking not simply for a conductor of positive charge, but system wherein a positive charge moves through a stationary lattice? Would you say I was cheating if I suggested a hole conductor? Someguy1221 (talk) 04:55, 30 March 2013 (UTC)

That is indeed a correct interpretation, however, a constraint of the system is that the charge carrier must be a proton or proton containing cation. Plasmic Physics (talk) 05:57, 30 March 2013 (UTC)

Are you only interested in zeolites? We have a short article on proton conductors and the fast ion conductor article has a few examples of proton conductors as well.--Wikimedes (talk) 20:57, 30 March 2013 (UTC)

Wonderfull links, thank you. Plasmic Physics (talk) 21:35, 30 March 2013 (UTC)

These are used as membranes though, where an electric field acros the membrane is sufficient to drive the hydrogen ions through it. You asked for fibres, which might have indicated you wanted some sort of proton carrying wire. Wickwack 124.178.140.181 (talk) 00:47, 31 March 2013 (UTC)

Yes. Plasmic Physics (talk) 02:21, 31 March 2013 (UTC)

"Yes", you agree they are used as membranes, or "Yes", you want a proton carrying wire for some reason? Wickwack 58.169.234.67 (talk) 03:52, 31 March 2013 (UTC)

Yes to both. Plasmic Physics (talk) 04:32, 31 March 2013 (UTC)

I was tempted for a moment to post "yes" again, but that may have just annoyed you enough.

Law of accelerating returns

Question about Kurzweil's Law of accelerating returns. Has the rate of technological change this century (so the last 13 years) followed the pattern predicted by this? Or are there any examples of technologies that support this? Any examples that refute it? --105.227.178.237 (talk) 10:40, 30 March 2013 (UTC)

Just an hour ago there was a program on BBC radio thattook issue with the sceptical paragraph about Moore's law in that Wiki article. In the BBC program this was compared to the famous example of doubling the number of grains on each chessboard; during the first 32 squares, it actually is still managable, it only becomes mind boggling large on the last 32 squares. Similarly, we have now had a bit more than 32 Moore's law doublings and we are only now seeing mind boggling appplications fo technology that the experts even a few years ago didn't expect to see in their lifetimes. An example given in the program was the automated cars of Google. A few years ago, most experts would have thought that autonomous cars driving in real life chaotic traffic would not happen for many decades, this used to be the typical example cited by sceptics of AI to point out how the brain is superior to computers (you have a lot of information to prcess in real time, you need to decide what is relevant and what not, you can't capture all of that using simple rules). Count Iblis (talk) 13:05, 30 March 2013 (UTC)

Some technologies that might support it:

1) TVs/computer monitors. We had only CRTs for many decades, then we suddenly had an explosion of new flat-screen technologies.

2) Light bulbs. Both CFL and LED bulbs are recent additions to home lighting options.

Some technologies that might refute it:

A) Medications. We tend to not get new medications which actually cure diseases, but only those which treat them. In antibiotics, specifically, our medications are actually becoming less effective, as the microbes adapt quicker than we can come up with new meds.

B) Economics. We don't seem to be getting any better at managing the world economy. We may even be getting worse, at least in the West. StuRat (talk) 13:21, 30 March 2013 (UTC)

Developments in biotechnology have or will have the potential to defeat microbes. And libertarians will argue that "managing" economics is inherently bound to fail. ←Baseball Bugs ^{What's up, Doc?} carrots→ 13:34, 30 March 2013 (UTC)

By "managing" I'm including the option of letting free markets do their thing completely unregulated. This approach doesn't seem to work all that well, either. We end up with Bernie Madoff scams. StuRat (talk) 13:46, 30 March 2013 (UTC)

Prevention and punishment of fraud or other criminal activity doesn't really qualify as "managing the economy". Punishing successful individuals and companies by taking away their incentive to produce, definitely qualifies. ←Baseball Bugs ^{What's up, Doc?} carrots→ 16:10, 30 March 2013 (UTC)

Bizarre statement, Stu. I have to agree with Bugs that fraud is considered a crime, not free trade, even under laissez-faire capitalism. μηδείς (talk) 22:31, 30 March 2013 (UTC)

The problem is, in laissez-faire capitalism, requiring companies to report on their activities is considered unwanted interference. And, without this requirement, it's easy to get away with fraud. So, while it doesn't outright legalize fraud, it does make it impossible to prevent. StuRat (talk) 02:34, 31 March 2013 (UTC)

I think you would have a hard time finding any libertarian theorist who believes that defrauding consumers is OK. ←Baseball Bugs ^{What's up, Doc?} carrots→ 04:08, 31 March 2013 (UTC)

Of course not, they just have the naive view that if you let businesses do whatever they want without any regulation, they will always do what's right, despite ample evidence to the contrary. StuRat (talk) 06:27, 31 March 2013 (UTC)

And you'd have a hard time finding any theorist, outside of anarchists, who believe in no regulations. The regulations people and businesses have disagreements with are those regulations that stand in the way of sincere people being able to make progress. In fact, a libertarian friend of mine has pointed out that many of the regulations are actually favored by business, because they serve to keep competition down. ←Baseball Bugs ^{What's up, Doc?} carrots→ 21:20, 31 March 2013 (UTC)

It sure would be nice if we had Regulation Group A, those necessary to ensure that businesses operate legally, and Regulation Group B, those which "stand in the way of sincere people being able to make progress". Unfortunately, there's a lot of overlap. StuRat (talk) 04:22, 1 April 2013 (UTC)

Some factors which prevent technology from increasing exponentially are the speed of information transfer and patents. For the information transfer, publishing an article on a new technology isn't necessarily much faster than it was a century ago. It still involves writing it, submitting it to legit publication, and having them approve it. Yes, we can also put new info out directly on the internet, but there's so much bad info there, it's difficult to discern the wheat from the chaff. As far as patents go, new technologies often remain prohibitively expensive until the patents expire, and the length of time patents last isn't decreasing (see the case of the CFL: [2]). StuRat (talk) 13:33, 30 March 2013 (UTC)

One reason new technologies are more expensive is that the developers of those technologies need to recoup their research and development costs. Shortening the length of time a patent is in effect could reduce the incentive to create those new technologies. ←Baseball Bugs ^{What's up, Doc?} carrots→ 13:37, 30 March 2013 (UTC)

Yea, patents are a problem no matter what you do. Perhaps government funded research programs, where the results are free for all to use immediately, are the answer. StuRat (talk) 13:44, 30 March 2013 (UTC)

That means an increase in taxes. ←Baseball Bugs ^{What's up, Doc?} carrots→ 15:06, 30 March 2013 (UTC)

True. StuRat (talk) 02:39, 31 March 2013 (UTC)

What you're saying could be true (as there in a 1975 patent), but the citation (which is also in our article) doesn't say anything about patents. Nil Einne (talk) 00:55, 31 March 2013 (UTC)

Yea, that link implies the patent expired, but doesn't outright say it. Perhaps it was changed after the citation was added to our article. StuRat (talk) 02:39, 31 March 2013 (UTC)

How can it imply something about patents when it doesn't mention them at all? Were it not for the fact that patents have been brought up here and that one seems to exist, the obvious conclusion from the link would actually likely be there were no patents involved but it was more one of cost and market potential, no one bothered until someone figured out it could be done sufficiently cheaply in China to make it worthwhile. Nil Einne (talk) 03:02, 31 March 2013 (UTC)

Well, when they said "The helical compact fluorescent lamp was invented by Ed Hammer at GE in 1976", that certainly implies they got a patent, to me. A company like GE isn't going to let it's inventions go unpatented. If they said it was a joint development of several parties or solely invented by some guy in his basement, that would make it more likely it would go unpatented. StuRat (talk) 03:23, 31 March 2013 (UTC)

You're presuming what they did is patentable, to the extent of stopping people making their own helical lamps. That may have very well been the case, but there's no reason to assume it when it wasn't specified in the source. (If you were a competitor, and someone invents something, it may pay to assume there's a patent, but this is quite different from reading a source about someone inventing something and assuming there is was an effective patent which is why nothing happened for a while.) Note in particular, it sounds like GE never actually produced the lamps in any meaningful quantity. And there's no evidence they didn't want to because they didn't want to compete with another product of theirs. In other words, it sounds a lot like GE never actually found a way to make the patent work for them in any way. It may be that other companies would have were they not afraid of some patent, it may simply be that the timing was right. Since the source didn't discuss the patent at all, it's difficult to know from that source how much of a factor, if any it was and so assuming it was a factor going solely by that source seems to be stretching a little. Nil Einne (talk) 05:47, 31 March 2013 (UTC)

The slowness of the patent system does not have the braking effect on innovation that you might think it has, for two reasons: a) You cannot have a valid patent for some development that is the result of reasonably expected refinement by a practitioner of the art. For example, if a steel garden tool as typically made by several competitors sufers from rust, and one of them decides to use galvanising, that would not be patentable, becuase any reasonable product engineer should think of that, and its mearely a question of manufacturing costs. But if he has a brainwave and thinks up a radically new way to apply galvanising at 1/10th the normal cost, that could be patentable. It's true that a lot of patents are taken out and paid for that are just such reasonably expected refinements, but if/when it comes to court, such patents should, and often do, fail; b) a heck of a lot of innovation is not patented anyway - the inventors just go ahead a make and sell, because the patent system expense and complexity is just not justified in many cases. In many cases innovators can get protection against competitors by the Registered Design system, which is cheap and simple. Wickwack 60.230.245.220 (talk) 01:39, 31 March 2013 (UTC)

a) Even if they might eventually win, many companies would still shy away from using any technology that would require patent litigation. StuRat (talk) 02:42, 31 March 2013 (UTC)

Companies have a strong desire to avoid litigation, but that is not the whole story. Companies make an assessment as to whether litigation is likely as well as the probability of succeeding with it. In communist and dictatorial countries, they can right ahead and copy quite blatantly. Communist theory has a problem with intelectual property. For a lot of the cheap handy type stuff made in China that you buy in hardware stores, patents have been disregarded, but litigation does not much occur because it doesn't pay. A friend of mine who had been making small quantities of his product had his market outgrow his factory capacity, so he contracted a Chinese manufacturer to make a reasonable quantity, with his name on them, to his detail drawings. He later found that they turned out at least 20 times the quantity he ordered with the tooling he paid for, and sold the rest in China and around the World under various names. That happens a lot apparently. There's nothing that can be done about it. It's wrong. It's not fair. But it has brought innovation to the World market. Occaisonally our (ie USA, Australia, etc) embassies make a polite squawk. Wickwack 58.169.234.67 (talk) 03:48, 31 March 2013 (UTC)

The one place I can think of very plain accelerating returns is in genome sequencing costs. They have been decreasing at a jaw-dropping rate over the last 6 years or so (those graphs are each log charts — so a straight line would already be exponential decrease, and those lines ain't straight). But I would caution, counter Kurzweil, that in the real world, exponential processes always level off or die off eventually. Always. That doesn't mean the last generation or so before they end isn't spectacular, or that we aren't a long way away from it, or whatever, but it's worth keeping in mind. --Mr.98 (talk) 13:42, 30 March 2013 (UTC)

Largest science

Whats the largest scientific organization in the US? Whats the largest in Europe? Pass a Method talk 14:29, 30 March 2013 (UTC)

The American Chemical Society is the largest scientific society in the world. That would then also qualify it as the largest such group in the U.S. as well. --Jayron32 15:33, 30 March 2013 (UTC)

OP: Do you mean the largest professional association/society of members (like the ACS), or the largest company or enterprise run by a CEO or Chancellor that does scientific research as its main activity? Or the largest research organisation that is owned by an entity (the entity not necessarily focussed overall on research), such as Bell Laboratories? Ratbone 120.145.158.214 (talk) 15:41, 30 March 2013 (UTC)

It all depends on what you call organization. Are governmental agencies like the NASA included? And what means by large? Large number of people or turn-around? OsmanRF34 (talk) 16:12, 30 March 2013 (UTC)

In Europe its Helmholtz Association of German Research Centres i belive. --Kharon (talk) 16:29, 30 March 2013 (UTC)

I have in the past heard its the National Academy of Sciences, or maybe thats the most prominent? Pass a Method talk 16:42, 30 March 2013 (UTC)

That has 2,100 members and 380 foreign associates; compare this with the 163,000 (!) members of the ACS. -- Jack of Oz ^[Talk] 19:56, 30 March 2013 (UTC)

National academies are typically relatively small, but very prestigious. The American Association for the Advancement of Science is generally considered the largest general scientific organisation. But it's not a professional organisation, but open to to the public. And the ACS seems to be larger still. --Stephan Schulz (talk) 20:13, 31 March 2013 (UTC)

thermodynamics

while calculating total entropy change in an isothermal reversible process,change in entropy of surroundings is calculated by the following formula= heat absorbed or released by the surroundings/temp of surroundings.But in text books,the authors have equated temp of system with temp of surroundings.Can u please explain why? — Preceding unsigned comment added by 49.201.252.13 (talk) 14:35, 30 March 2013 (UTC)

Well, eventually the temperature of any system will equal that of it's surroundings, if we assume the surroundings have a constant temperature and the thermal capacity of the system is insignificant compared to that of the surroundings. StuRat (talk) 14:41, 30 March 2013 (UTC)

Good old StuRat to the rescue! An isothermal process, by definition, is a constant temperature process from start to finish, and heat flows in or out of it without a change in temperature anywhere. There's no "eventually" about it! Entropy is reversible heat divided by system temperature and for a reversible process, total entropy is constant. Ratbone 120.145.158.214 (talk) 15:36, 30 March 2013 (UTC)

Isothermal usually means that the system doesn't change temperature as it expands, contracts, or whatever. It doesn't necessarily mean that the system and environment are at the same temperature. --140.180.254.209 (talk) 16:32, 30 March 2013 (UTC)

If the temperature of surroundings were different, the process would be irreversible. Ruslik_Zero 18:11, 30 March 2013 (UTC)

Derp. Yes, you're absolutely right. If the system and environment had different temperatures, change in entropy would be positive, so the process would be irreversible. --140.180.254.209 (talk) 21:09, 30 March 2013 (UTC)

What speed is needed so I'm always at the same time on the earth?

More specifically, what speed is needed on the surface of the earth so the sun is always on the same spot, because I'm rotating the earth aside the sun, so there will be never night. 181.50.183.182 (talk) 17:11, 30 March 2013 (UTC)

The circumference of the earth is 24,901 miles, so a little over 1,000 mph at the equator. μηδείς (talk) 17:15, 30 March 2013 (UTC)

Zero if you're at the North Pole -- all you have to do is very slowly turn. More generally, the farther you are from the equator, the lower the speed. Looie496 (talk) 17:19, 30 March 2013 (UTC)

I should know this, but it's not coming to me: What does the graph look like for the speed at each degree of latitude? At the pole it's technically 0, and at the equator it's 1,000 MPH. But what is it at 45 degrees north or south? 500 MPH? Larger? Smaller? Another way to put it: What is the circumference of the circle at 45 degrees of latitude? ←Baseball Bugs ^{What's up, Doc?} carrots→ 17:31, 30 March 2013 (UTC)

If the Earth were a sphere, you would just multiply the equatorial radius by the cosine of the angle of latitude. The actual reference ellipsoid length of the 45th parallel will be marginally longer than 24,901 times 0.7071067 miles. Dbfirs 17:39, 30 March 2013 (UTC)

For a perfectly spherical Earth, which the Earth very nearly is, a graph of surface speed versus latitude in degrees would be a half-sine shape. Wickwack 124.178.140.181 (talk) 00:52, 31 March 2013 (UTC)

That makes total sense. Thanks to the both of you for helping clear my trigonometry cobwebs. ←Baseball Bugs ^{What's up, Doc?} carrots→ 04:06, 31 March 2013 (UTC)

Hmm. I thought we had an article (or part of one) concerning a performance artist that stood on the north pole for 24 hours, carefully shifting himself against the turn of the earth so that he "stood in place" rather than revolving around the earth as every other human has always done. I was going to link it in reference to Looie496's post above. Now I can find nothing about it (but a remarkable lot about pole dancers who are also performance artists). Hoax article? Ring a bell? Matt Deres (talk) 01:04, 31 March 2013 (UTC)

You got me curious. After some digging, I found this. The artist was Guido van der Werve. Th4n3r (talk) 21:20, 31 March 2013 (UTC)

Um, aren't we missing something (or perhaps I am mistaken)? At the north pole, you cannot turn so that the sun doesn't move in the sky, because of axial tilt. See Axial_tilt#Obliquity_of_the_ecliptic_.28Earth.27s_axial_tilt.29. Even an equatorial path would not keep the sun stationary, for the same reason. There is probably some path one could take to keep the sun at the same place in the sky, but it does not have constant latitude. SemanticMantis (talk) 01:21, 31 March 2013 (UTC)

Yes you are mistaken. — Preceding unsigned comment added by 202.65.245.7 (talk) 03:21, 31 March 2013 (UTC)

To elaborate on your mistakenness: The sun will not move when you stand at the North Pole during the course of a day, though the axial tilt means that it does move as a result of the earth's orbit. So, technically the sun moves slightly even at the north pole, but this is the orbital motion and not the rotational motion. What it will not do is trace an arc from horizon to horizon (or a full circuit through the sky as it would at any point between the arctic circle and the North Pole). The sun will move slightly towards the horizon (if moving towards the fall equinox) or away from the horizon (if moving towards the spring equinox). So, perhaps you're not fully mistaken, in the sense that the sun is not perpetually stationary at the North Pole, but the motion is not the daily motion people are describing here. --Jayron32 03:28, 31 March 2013 (UTC)

I would think that this could be accomplished on or very near the equinoxes, as the sun at that point pretty much coincides with the celestial equator. ←Baseball Bugs ^{What's up, Doc?} carrots→ 04:05, 31 March 2013 (UTC)

Thanks for the explanation. But the OP says "so there will never be night." And the sun should be "always in the same spot." I interpreted "always" to mean indefinitely, and "same" to mean constant. I seem to be the only respondent taking the long view, but that's my literal reading. The poles both have very long nights, and I'm pretty sure no constant-latitude path will truly fix the sun. I guess I should also mention that I'm approaching this from a purely geometric/ mathematical angle, as you say the apparent motion due to orbital motion is relatively small (but it's still there! :) SemanticMantis (talk) 04:09, 31 March 2013 (UTC)

And to clarify my point, if you stay at the same latitude, you won't be able to fix the sun, it will drift throughout the year, similar to the analemma. To keep the sun truly stationary in the sky, you'd have to travel parallel to the ecliptic. SemanticMantis (talk) 14:08, 31 March 2013 (UTC)

Nobody has yet mentioned a Sun-synchronous orbit, or a solar orbit at the L1 Lagrange point, like the one SOHO uses to keep a constant view of the Sun and the Earth. Nimur (talk) 14:44, 31 March 2013 (UTC)

That would work, but is that "on earth"? ←Baseball Bugs ^{What's up, Doc?} carrots→ 21:17, 31 March 2013 (UTC)

If you travelled around the earth at the equator at earth's speed of rotation, you would keep the sun at a fixed point in your sky, but that would not keep the time the same, because the boundaries of time zones are rather arbitrary. To take an example from my part of the world, traveling west from Bali, your time would jump back 60 minutes as you crossed to Java, then forward 1 hour as you entered Singapore (i.e. the same as Bali time), and then back another hour as you pass from Malaysia to Thailand (i.e. the same time as Java). 202.155.85.18 (talk) 02:36, 2 April 2013 (UTC)

Prominent science

Whats the most prominent and reputable scientific organization in the Americas? What about in Europe? Pass a Method talk 21:18, 30 March 2013 (UTC)

Internationally, the ICSU. The USA's representative is the National Academy of Sciences, although other countries of the Americas have their own representatives. Of the European representatives, the DFG (Germany) is the largest, and the Royal Society (UK) is the oldest - the Académie des Sciences (France) is (probably) equally prominent and reputable. Tevildo (talk) 21:58, 30 March 2013 (UTC)

This question attracted answers from Jayron32, Ratbone, OsmanRF34, and JackOfOz. There posts were deleted at 21:18 by the OP, PassAMethod. See History. Deletion or editing other people's posts is very poor ettiquete, and may result in questions going unanswered. If you don't like answers or think people went off track, just politely say so and clarify your question. Wickwack 60.230.245.220 (talk) 01:21, 31 March 2013 (UTC)

Um, I didn't answer this question, if I recall. I answered a different question asked above. And my answer is still there. Are you sure you aren't mistaken? --Jayron32 01:31, 31 March 2013 (UTC)

Ooops! You are right. He didn't delete anything. He asked much the same question twice with different headings and different wording, and I didn't spot that for some reason. My appologies, especially to the OP, Pass A Method. Wickwack 60.230.245.220 (talk) 01:43, 31 March 2013 (UTC)

The question isn't the same just related. The first was about the 'largest', the second about 'prominent and reputable'. I guess it's possible some people may consider these imply the same answer but I don't think that's particularly common. In their first question they did mentioned that had thought the NAS was the largest but also mentioned that perhaps they were mistaken and it was the most prominent but they didn't generally about which one was the most prominent or reputable. Nil Einne (talk) 09:01, 31 March 2013 (UTC)

Co-transport... again

I asked a while ago about co-transport and how it works. I got a whole ton of stuff from you guys, which was helpful, but I'm still confused somewhat. So I'm going to lay out my question step by step, and I would appreciate if I could get a step-by-step from-the-basics type of answer too.

Now. I have a cell membrane. I also have sucrose, inside and outside my cell. Sucrose cannot diffuse through the membrane. Sucrose moves randomly (Brownian motion). I have learned that some membrane proteins facilitate passive diffusion when a molecule binds to it, leading to a conformational change which moves the substrate into the cell. Assuming that the cell interior has a higher concentration than the exterior, why is it necessary to use energy to move sucrose in (through cotransport with a sodium ion), when theoretically, the external sucrose moves randomly (as opposed to being "repelled" by its concentration gradient, it only collides with the membrane and any proteins on its surface less regularly than the sucrose on the interior). Shouldn't a protein whose active site is on the exterior and changes shape when sucrose binds to it suffice? Or is my perception of membrane proteins wrong in my belief that they only work in one direction? I've been told it has something to do with free energy and entropy. Could someone explain how this means that energy input is required (without math, using a real explanation of why energy is required?) Brambleclawx 22:48, 30 March 2013 (UTC)

I can't make sense of this question. Did you mean to say that the exterior has higher concentration than the interior? (You said the reverse.) Looie496 (talk) 00:24, 31 March 2013 (UTC)

No, I did intend for the interior to have a higher concentration. Brambleclawx 01:36, 1 April 2013 (UTC)

It looks to me like he is trying to make the cell membrane act as a variation of Maxwell's demon, which will fail for the same reasons that Maxwell's demon fails. --Guy Macon (talk) 00:37, 31 March 2013 (UTC)

Brambleclawx, if you have a protein that adopts a shape such that sucrose is forbidden from moving in the other direction, you will need energy to "reset" the protein, such that it may take in another molecule. This reminds me vaguely of Richard Feynman's brownian ratchet, a device powered by brownian motion that only allows a wheel to turn in one direction. And it doesn't work unless the brownian motion driving the device is stronger (hotter) than the brownian motion near the ratchet. Someguy1221 (talk) 01:40, 31 March 2013 (UTC)

Perhaps my current understanding of proteins that change shape is somewhat simple... I was under the impression that once said protein changed shape, the sucrose would no longer "fit" and would thus dissociate, with the dissociation causing the protein to revert to its original shape. Or is that not how it works? Brambleclawx 01:42, 1 April 2013 (UTC)

If it's not clear what I mean, I'm imagining the membrane protein to act like a venous valve, so randomly moving particles could only cross one way and not back. Brambleclawx 01:58, 1 April 2013 (UTC)

Such a thing would be impossible. Without some sort of ratcheting mechanism, which requires energy, a transport process must be reversible. You are really stuck with three scenarios for how a transport molecule can work: A) Transport is permitted in both directions freely; B) Transport is permitted predominantly in one direction, but requires an energy source; and C) Transport is permitted exclusively in one direction, and the transport protein is destroyed after working precisely once. This also follows from the principle that any chemical process is theoretically reversible. A way you can know you are wrong is to think about the physical consequences. I would be able to take a cell, and place it in a solution that is isotonic with respect to sucrose. By the mechanism you think the transport protein operates, it would be able to cause all the sucrose in the solution to concentrate exclusively inside the cell, free of energy, in complete violation of the second law of thermodynamics. Someguy1221 (talk) 02:39, 1 April 2013 (UTC)

Thanks. That was very helpful. Brambleclawx 03:10, 1 April 2013 (UTC)

Many of these transporters do, in fact, go in both directions. It is the concentration gradient that provides the driving force. (Simplifying things a little - you don't want to know about Gibbs free energy - heck I don't want to know about it, but I am stuck with it.) If, as in the situation you describe, there is higher sugar inside the cell than out, and you had a transporter with just a sugar binding site, the sugar will be transported both ways but on the inside (high concentration) you will have more frequent interactions with the binding site on the transporter, and hence you will have a net flow out. One way to reverse this - to go against the concentration gradient - is to require a co-factor, in this case sodium. If you need both sodium and sugar to change the configuration of the transporter from 'in' to 'out' (or vice versa), then the concentrations of the two counterbalance each other. Even with a high concentration of sugar inside such that it will bind readily, if there is little of the sodium the transporter also needs to change shape, the sugar stays inside. On the outside, if you have a lot of sodium, then even if you have lower amounts of sugar, every time a sugar binds the transporter flips inward because it is already saturated with sodium. Binding kinetics come into play, but basically, these concentration gradients represent stores of energy, and whichever has the higher energy (whichever has the more extreme differential between inside and out) will override the other. Here, the sodium difference overwhelms the sugar difference and forces it in. Let me add that our article on Sodium-glucose transport proteins really does not explain well what is going on with a novice target audience in mind. Agricolae (talk) 17:32, 31 March 2013 (UTC)

So the transport protein in question does in fact work in both directions? Brambleclawx 01:36, 1 April 2013 (UTC) Edit As a side note, this is the answer that makes the most sense that I've been given thus far. It's very helpful. Brambleclawx 01:45, 1 April 2013 (UTC)

Yes, it does. In an actual physiologically relevant environment, the rate at which the back reaction occurs may be thousands or millions of times lower than that at which the forward reaction occurs, which is why these sorts of possibilities are often unmentioned. Someguy1221 (talk) 02:42, 1 April 2013 (UTC)

Thank you very much. Brambleclawx 03:10, 1 April 2013 (UTC)

As Agricolae said, cotransport is one means of powering (perhaps even regulating) the passage of a substance through the membrane. Passive diffusion works for moving a substance but it isn't good enough for many applications. For example, every drop of urine passed starts off with the usual level of blood sugar present within it, but the kidney greedily recovers as much as possible to preserve resources. The alternative is using ATP or some other energy source directly - for example, many potential toxins are substrates for MDR1. The key difference here is that using proton gradients allows biology to make change for ATP molecules. For example, the F-ATPase is "geared" to exchange 1 ATP for 3.3 to 5 protons, while the V-ATPase exchanges 1 ATP for 2 protons. This means that the V-ATPase can power a stronger proton gradient while the F-ATPase can generate more ATP from a weak one. [3] (though [4] says other F-ATPase data supported ratios of 4 or 4.7... I'd really have to scrutinize the topic to get to the bottom of all this data, which doubtless varies by species and paralog; my point is that biology gets to decide through evolutionary alterations what "gear" to put the molecule in, though thermodynamics of course sets the limits of what is possible) Wnt (talk) 20:48, 1 April 2013 (UTC)