Wikipedia:Reference desk/Archives/Science/2008 July 19

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July 19

Obesity

Apart from being less likely to starve to death during the next famine, are there any health benefits of being overweight? --Carnildo (talk) 04:15, 19 July 2008 (UTC)

I don't know about obese people (especially extreme obesity), but slightly overweight people tend to have slightly better survival outcomes with various forms of cancer and modern treatments IIRC. On the other hand, being overweight (and especially sedentary) tends to increase the risk of getting cancer so... (And admitedly some studies seem to show the opposite e.g. [1] which suggests a lower survival rate in Chinese women) Nil Einne (talk) 07:24, 19 July 2008 (UTC)

I don't know of any real good effects of being obese. The article lists all these as negative factors though:

• Cardiovascular: congestive heart failure, enlarged heart and its associated arrhythmias and dizziness, varicose veins, and pulmonary embolism
• Endocrine: polycystic ovarian syndrome (PCOS), menstrual disorders, and infertility
• Gastrointestinal: gastroesophageal reflux disease (GERD), fatty liver disease, cholelithiasis (gallstones), hernia, and colorectal cancer
• Renal and genitourinary: erectile dysfunction> urinary incontinence, chronic renal failure, hypogonadism (male), breast cancer (female), uterine cancer (female), stillbirth
• Integument (skin and appendages): stretch marks, acanthosis nigricans, lymphedema, cellulitis, carbuncles, intertrigo
• Musculoskeletal: hyperuricemia (which predisposes to gout), immobility, osteoarthritis, low back pain
• Neurologic: stroke, meralgia paresthetica, headache, carpal tunnel syndrome, dementia, idiopathic intracranial hypertension
• Respiratory: obstructive sleep apnea, obesity hypoventilation syndrome, asthma
• Psychological: Depression, low self esteem, body dysmorphic disorder, social stigmatization
• Cancer: esophageal, colorectal, liver, gallbladder, pancreatic, kidney, non-Hodgkin's lymphoma, multiple myeloma, stomach, prostate cancer, breast, uterus, cervix, and ovary.

Basically, the negative aspect of obesity severely outweighs any benefit. —CycloneNimrod^Talk? 10:15, 19 July 2008 (UTC)

A recent (and controversial) study in JAMA suggests your final statement may not be accurate, CycloneNimrod. They conclude that "The net result [of their study] was that overweight was associated with significantly decreased all-cause mortality overall." Specifically, being overweight gives an apparent protective effect against causes of death such as tuberculosis, emphysema, pneumonia, Alzheimer's disease and injuries, but an increased risk of cardiovascular disease, some cancers, diabetes and kidney disease. When you balance the two out, the chubbies appear to be in the black. To be fair, the study didn't control for smoking and preexisting illnesses, so it could be skewed, but it does give one, ahem, food for thought. Rockpocket 20:02, 19 July 2008 (UTC)

I think obese people can withstand cold conditions better than a non-obese person. Surface area, volume, etc. --Mark PEA (talk) 12:41, 19 July 2008 (UTC)

Only for short times in complete nude. With the use of clothing, the added blubber provides no benefit. -- kainaw™ 14:05, 19 July 2008 (UTC)

Obesity is bad, but there are potential benefits to being slightly overweight. Nil Einne gives one above, and I believe there are others, but I'm not sure what they are. --Tango (talk) 17:51, 19 July 2008 (UTC)

People are more likely to make snap-judgements that they are jolly? --Shaggorama (talk) 22:33, 19 July 2008 (UTC)

While obesity per se presumably has little biological selective advantage, remember that the ability to store large amounts of fat when food is plentiful is of great selective advantage--at least before modern times when food is abundantly available all year for many people. Then this physiological ability becomes non-adaptive. Seen in this light it is easier to see why becoming fat is so common, and why losing weight is so very difficult. Evolution has equipped us with the strong desire to eat greedily far beyond our immediate needs, because in the past it increased survival, and for women, the likelihood of having and nursing strong children.--Eriastrum (talk) 23:04, 19 July 2008 (UTC)

• We've already touched on obesity preventing people from starving to death, but note that such starvation isn't always due to a lack of food. Many diseases cause a drastic loss of weight, which can be fatal, especially if not treated (say with a glucose IV).

• Hypothermia has been mentioned, but I disagree with the statement that obesity is no help when wearing clothing. Obesity may be especially helpful when waiting in cold water for a rescue, for example, whether wearing clothing or not.

• Obesity may also decrease the rate of drowning, because fat floats, and people with more fat float better. They esentially come with their own floatation device.

• Then there is the absurd effect that some studies might indicate a reduction in the death rate from many other causes which seem unrelated to obesity, like homocide. The reason is that obese people are likely to die earlier, thus having less opportunity to be murdered. StuRat (talk) 20:49, 20 July 2008 (UTC)

AIDS Cure Deadline?

Despite the obviously long term nature of the search for an AIDS cure/vaccine, has anyone been quoted regarding any theoretical deadline by which we can expect it by? Or are things still in the "It'll be here when it gets here" stage? —Preceding unsigned comment added by Kenjibeast (talk • contribs) 04:40, 19 July 2008 (UTC)

HIV vaccine would be good reading. Basically, it's a case of "Nobody knows. Nobody even knows if it's possible.". --Carnildo (talk) 09:11, 19 July 2008 (UTC)

I suspect that one day, potentially within my lifetime, there may be a cure (whether in the form of a vaccine or not). For now, though, I don't think anyone has much idea of when or how it'll be achieved. As Carnildo posted, that article may give a few hints. —CycloneNimrod^Talk? 10:09, 19 July 2008 (UTC)

Carnildo, is there reason to believe that it's impossible? Or perhaps I'm really asking if there is any consensus among scientists in the field that it might be impossible. Either way! I'm asking because from what I understand, there are promising discoveries being made, even if an actual cure still hasn't been found. It seems to me that at least some progress is being made, but is that just an illusion in terms of whether knowledge about HIV and fighting it has appreciably increased within the last, say, five years? -- Captain Disdain (talk) 10:27, 19 July 2008 (UTC)

It's definitely not impossible. For example, we could create a nanomachine, that could destroy the virus. Nanomedicine if you will. It's beyond our current level of technology, but it's possible. Incidentally, such a nanomachine would be capable of curing other RNA viruses like the common cold. ScienceApe (talk) 17:15, 19 July 2008 (UTC)

As noted in the article, HIV mutates very quickly, and the surface proteins that the immune system (or ScienceApe's magical nanotech) would use to recognize it change frequently and at random. --Carnildo (talk) 23:37, 21 July 2008 (UTC)

Well I would assume the nanomedicine would have a better method of identifying the virus than our own immune system. I wouldn't have any idea of how to do it, but I guess it would have to be some kind of logic program, which would ignore minor variations in the same kind of virus. ScienceApe (talk) 21:31, 23 July 2008 (UTC)

You rarely have anything more than guesses about the timescale for new inventions. The process basically involves trying lots of different things until you eventually find one that works (the skill comes in narrowing down which things to try). Since you don't know which one is going to work, you can't say how long it's going to take to find it. It's difficult to even give an expected time without knowing how many possible things there are to try (which is pretty much infinite) and how many of them are going to work (which could be anything from none to infinite). --Tango (talk) 17:49, 19 July 2008 (UTC)

Alcohol dimer formation

It is a known fact that organic acids form dimers by hydrogen bond attachment of the carbonyl group oxygen in one acid molecule (say molecule A) with hydroxy group hydrogen in another acid molecule (say molecule B) and the carbonyl group oxygen in B attaches with hydroxy group hydrogen in A as seen here:[2]. In organic alcohols, though, the hydrogen in a molecule(say C) attaches with the oxygen in another molcule (say D). Is the remaining oxygen of molecule C capable of attachment with the hydrogen of D (to form a quasi-acidic two way dimer), or, will the oxygen of C and hydrogen of D always attach with the hydrogen and oxygen of some other molecule? Leif edling (talk) 06:37, 19 July 2008 (UTC)

A dimer is possible, as is a trimer (3 in a ring).

In the solid state (frozen) such arrangements almost certainly occur.87.102.86.73 (talk) 14:38, 19 July 2008 (UTC)

A hydrogen from C will undoubtedly be hydrogen-bound to the oxygen in D, but I think it would be more likely for the oxygen of D to be bound to a hydrogen from another molecule, E, rather than C, in the liquid state. This way, a network of hydrogen bonds can be formed similar to that which water forms, but with less intensity. I've never heard of a single OH group simultaneously being an acceptor and donator to only one other OH group. --Russoc4 (talk) 14:49, 19 July 2008 (UTC)

Yes a dimer is possible, but mostly unlikely - reason - four membered rings are much less stable than 6 membered ring - note in carboxylic acid dimers the 'ring' structure' is hexagonal (though there are 8 atoms involved)87.102.86.73 (talk) 16:13, 19 July 2008 (UTC)

Here is an dimer example http://www.osti.gov/energycitations/product.biblio.jsp?osti_id=7285895 trifluoroethanol dimer formed in the vapour phase with a 4 membered ring (eg OHOH ring), note thought that this molecule may be a special case since it is much more acidic (more postive charge on the H atoms) than common alcohols.87.102.86.73 (talk) 16:23, 19 July 2008 (UTC)

This link might be useful http://books.google.co.uk/books?id=Zy4OzgTC6c0C&pg=RA1-PA125&lpg=RA1-PA125&dq=Dodecanol+crystal+structure&source=web&ots=biSj9Bu5Om&sig=2dQXIQH1ahT0u8X7j2RpK6aCkIA&hl=en&sa=X&oi=book_result&resnum=10&ct=result#PRA1-PA125,M1 see fig 7.1

It shows that for n-hexdecanol in the solid the molecules form with OH groups in a line eg:

                  H 
                 /
CCCCCCCCCCCCCCCCO
                                       CCCCCCCCCCCCCCCCO           
                  H                                     \
                   \                                     H
                    OCCCCCCCCCCCCCCCC
                                                            OCCCCCCCCCCCCCCCC      
                  H                                        /
                 /                                        H
CCCCCCCCCCCCCCCCO   HOxxxxxxxxxxxxxx
                                       CCCCCCCCCCCCCCCCO
                  H                                     \
                   \                                     H
                    OCCCCCCCCCCCCCCCC
                                                            OCCCCCCCCCCCCCCCC
                  H                                        /
                 /                                        H
CCCCCCCCCCCCCCCCO            etc                                                 etc

C represents CH2 etc, my rough interpretation.. as you can guess where the H bonds will be you can see the zig-zag formation.. This is only one layer - you might guess that the next layer will be reversed - so that the alcohol on top takes the position indicated by HOxxxxxxxxxxxxx ...87.102.86.73 (talk) 15:35, 19 July 2008 (UTC)

I'll guess and say that I'm certain that the type of arrangement above is that which occurs and not a dimer. Though a dimer may still form temporarily in the liquid.87.102.86.73 (talk) 16:15, 19 July 2008 (UTC)

Aspartame lead to drowsiness?

Why is it that when I drink diet drinks with aspartame it makes me drowsy, like when you've been awake for too long and your consciousness begins to lapse? Is it a known side effect? What causes this? --antilived^{T | C | G} 08:27, 19 July 2008 (UTC)

You may find aspartame controversy interesting as it covers all the known and suspected health effects. Don't really feel comfortable with giving medical advice though. —CycloneNimrod^Talk? 10:06, 19 July 2008 (UTC)

Yea I've looked at that, doesn't really mention my effect. This is not exactly medical advice since I've already stopped drinking them; I'm just curious on why it affects me in this way while other people are seemingly fine taking it. --antilived^{T | C | G} 10:32, 19 July 2008 (UTC)

One extremely far-fetched reason could be that the aspartame is breaking down into methanol in amounts significant enough to cause drowsiness. It's far-fetched because the amount of aspartame in your drink is probably minuscule, and certainly not enough methanol would be created to have any noticeable CNS depression. --Mark PEA (talk) 12:44, 19 July 2008 (UTC)

Do you commonly drink diet caffeinated drinks, but are now drinking caffeine free drinks? It could be a psychological effect if your body/mind has paired drinking caffeinated drinks with the flavor of aspartame, but has now suddenly been subjected to caffeine free drinks of the same or similar flavor. --Russoc4 (talk) 14:54, 19 July 2008 (UTC)

Or, similarly, you used to drink the non-diet versions and simply have a lower blood sugar level now - drowsiness and loss of concentration are symptoms of hypoglycaemia. --Tango (talk) 17:43, 19 July 2008 (UTC)

Hmm not really, I don't usually drink caffeinated drinks at all. And even so diet Coke has caffeine is well so if anything it should give me a "boost" as well. I still get this if I drink both diet and non-diet soft drinks at the same time or drinking it while having a meal, so I'm pretty convinced it's the aspartame or anything else that's different between diet and non-diet soft drinks. --antilived^{T | C | G} 23:19, 19 July 2008 (UTC)

You could be allergic to aspartame, I suppose - you would need to talk to a doctor if you want to find out for sure. --Tango (talk) 00:17, 20 July 2008 (UTC)

Drowsiness related to fullness? Otherwise psychosomatic, perhapses? ---J.S (T/C/WRE) 03:32, 20 July 2008 (UTC)

Dominant trait = better trait?

Is dominant genetic trait (like round seed vs. non-round seeds) always better (in evolutionary sense)? —Preceding unsigned comment added by Mr.K. (talk • contribs) 18:10, 19 July 2008 (UTC)

No. (Which should be fairly obvious from the scheme itself—if the dominant trait was always "better", why would there be recessive traits at all?) --98.217.8.46 (talk) 19:07, 19 July 2008 (UTC)

It's pretty subjective. Sickle cell trait for example, would be more desirable in Uganda than in the USA. See also heterozygous advantage. --Mark PEA (talk) 19:12, 19 July 2008 (UTC)

It's not "pretty subjective" as to whether dominants are always better. The answer is "no". As to whether some dominants are better than some recessives, sure, and all other combinations. There are some dominants that will kill you right out, there are some recessives that will kill you right out. --98.217.8.46 (talk) 19:35, 19 July 2008 (UTC)

I can't think of a recessive allele that "will kill you right out", if you inherit it in a recessive manner (i.e heterozygous with a non-harmful dominant allele). Could you give an example? Rockpocket 19:42, 19 July 2008 (UTC)

I was referring to two recessives. I would be very surprised if there weren't some heterozygote combinations that had non-harmful dominants that were fatal to the organism, though they would be rare for simple obvious evolutionary reasons. --98.217.8.46 (talk) 21:13, 19 July 2008 (UTC)

Assuming "kill you right out" means before you can reproduce (which is what is significant for evolution), then the only way you could get a allele that would kill you right out with only one present would be by mutation. Mutations often kill the organism pretty quickly - usually before birth, as a miscarriage. If it's having an effect, though, then surely it isn't recessive, by definition? Part of its function may be recessive, but the bit that's killing you clearly isn't. --Tango (talk) 21:31, 19 July 2008 (UTC)

That was my reasoning too, a dominant would have to be a de novo mutation in the germline and a recessive, by definition, wouldn't kill you right out. However, it is probably correct that the are scenarios where two recessive alleles (at different loci) could combinatorially "kill you right out" if inherited, one from each parent. I guess it would be a form of additive haploinsufficiency. I can't think of any example of that either, but I'm sure there are some. Rockpocket 22:08, 19 July 2008 (UTC)

I hadn't thought of that. I've never heard of anything like that, but I can't see any reason for it not happening. --Tango (talk) 00:15, 20 July 2008 (UTC)

Dominance is relative. For example, a dominant allele for a receptor will be one that has a dominant function. A normally functioning receptor will have a dominant function in comparison with one that lost its regular function. In this case, the allele that encodes the normal receptor is the dominant allele and it may well be "better" (because we may need that receptor to function properly). However, another receptor allele may encode a receptor that is constitutively active (it keeps signaling an never stops). This allele will be dominant to the normally functioning receptor. However the regular allele may well still be "better" (because a always active receptor could be just as problematic as a never active receptor). In this case dominance does not equal better. But there are times when either lack-of-function and gain-of-function are better than the regular-function alleles, it all depends on what the environment is the genes are working in. Rockpocket 19:42, 19 July 2008 (UTC)

Summarizing: the dominant trait tends to be the better one, for the simple reason that if weren't the better one it probably would have been selected out, whereas recessive alleles are subjected to less selection pressure. But the question asked if it's always better, and the answer to that is certainly no. --Trovatore (talk) 21:56, 19 July 2008 (UTC)

Here are a few dominant phenotypes you really don't want (from Genetic disorder#Autosomal dominant): Huntington's disease, Neurofibromatosis 1, Marfan Syndrome, Hereditary nonpolyposis colorectal cancer, and Hereditary multiple exostoses, which is a high penetrance autosomal dominant disorder. --Shaggorama (talk) 22:29, 19 July 2008 (UTC)

Ultimate fate of the universe/black holes

If I'm not mistaken, the current model of the universe is that it will continue to expand until even galaxies burn up and fly apart.

My only thought is of black holes. From what I understand, black holes do evaporate at a rather slow rate (see Black_Hole#Evaporation, but that currently the Cosmic background radiation is easily enough to offset this. However, in a situation in many tens of trillions of years, would the Cosmic background radiation have decreased in magnitude enough that it would allow very slow disintegration of the black hole? In this case, there would be essentially nothing left of the universe.

This, of course, excepts any circumstance which we cannot foresee (e.g., another big bang occurring very far away, unexpected reactions from dark energy). The Evil Spartan (talk) 19:50, 19 July 2008 (UTC)

I can't source it at present, but a cosmology talk I went to a few years ago featured a (very long) future epoch in which most of the mass of the universe was in very slowly evaporating black holes. There won't be nothing left after this, of course (the holes don't evaporate to nothing; that would violate energy conservation), but they'll be nothing very interesting. Algebraist 19:54, 19 July 2008 (UTC)

See Timeline_of_the_Big_Bang and Future_of_an_expanding_universe. 190.190.224.115 (talk) 21:02, 19 July 2008 (UTC)

See Heat death of the universe. Under your scenario (which is one of the likely ones), you would end up with nothing but radiation and individual sub-atomic particles (which ones isn't certain - protons may or may not decay over extremely long timescales) just floating around doing nothing much at all. This is called heat death. --Tango (talk) 21:25, 19 July 2008 (UTC)

Evil Spartan: your first sentence seems to be referring to the big rip. It is one of the posited fates of the universe, but the consensus seems to be that the ironically-named heat death is the most plausible. As for whether the CMB will eventually become cool enough for Hawking radiation to occur, the answer is yes, as the CMB has already cooled from 3000 degrees Kelvin to the current 2.7 degrees. A calculation using the equation :$T={\hbar \,c^{3} \over 8\pi GMk}\,$, found here, shows even a black hole of 100 solar masses requires the CMB to be lower than a few nanokelvins in temperature before its mass starts decreasing. --Bowlhover (talk) 09:11, 20 July 2008 (UTC)

I think many people are confused by the exponential growth of the scale factor in the Lambda-CDM model. Exponential expansion isn't nearly as catastrophic as it sounds. It won't rip the Milky Way apart no matter how much time passes. The fate of the galaxy in this scenario is plain old 19th-century heat death. In the big rip scenario (which is probably wrong) the expansion is faster than exponential—in fact the scale factor diverges to infinity in a finite time. -- BenRG (talk) 17:14, 21 July 2008 (UTC)

Establishing a space colony

Are there any studies - more or less serious - about "how to" establish a space colony? Real academic studies would be best, but in lieu of those, sci-fi or fan made fictional guides will do.--_{Piotr Konieczny aka Prokonsul Piotrus| talk} 20:22, 19 July 2008 (UTC)

Maybe you had a look at the links and references from our great article on space colonization? 190.190.224.115 (talk) 21:10, 19 July 2008 (UTC)

I did, but I am not seeing stuff I need: it has stuff related to colonizing the solar system (or a galaxy a general), but not what I am looking for which is "a manual for colonization of a random planet (or system) out there".--_{Piotr Konieczny aka Prokonsul Piotrus| talk} 02:30, 20 July 2008 (UTC)

If by "random planet" you mean you want one manual suitable for any planet, then you won't find one, since different planets require different methods of colonisation. For specific planets, there's plenty of information out there, our articles linked to in the Space colonization article should get you started. --Tango (talk) 02:38, 20 July 2008 (UTC)

And if you find anything interesting that is not listed in the article please make sure to let us know! 190.190.224.115 (talk) 13:56, 20 July 2008 (UTC)

The Millennial Project: Colonizing the Galaxy in Eight Easy Steps is fun, if entirely exuberant. -- Finlay McWalter | Talk 21:12, 19 July 2008 (UTC)

Cool. I've often pondered how I'd go about setting up a colony under the sea, in international waters. Nice to see others considering it and the implications :D 79.66.13.38 (talk) 19:59, 21 July 2008 (UTC)

teraform or terraforming

This chemistry is impossible

one such hydrocarbon chosen to rate the energy available in a certain blend of gasoline is called ________. —Preceding unsigned comment added by 67.142.130.44 (talk) 21:07, 19 July 2008 (UTC)

Try Gasoline - the answer is in there. --Tango (talk) 21:21, 19 July 2008 (UTC)

The answer is also available at your local gas station. --Shaggorama (talk) 22:24, 19 July 2008 (UTC)

I thought it measures how hard it is for it to self-ignite, not energy? --antilived^{T | C | G} 23:12, 19 July 2008 (UTC)

Assuming we're thinking of the same thing, yes (as an aside, the common name is wrong and seriously misleading). I don't think the OP's question has an answer. Algebraist 23:21, 19 July 2008 (UTC)

Perhaps not, but it's fairly obvious what answer they are looking for. --Tango (talk) 00:10, 20 July 2008 (UTC)

I agree that the question is misleading. What they are really asking is what the "____ rating" is at gasoline stations that tells you how likely it is that the car engine will "knock". However, as few modern cars have trouble with knocking any more, engine performane isn't likely to be an issue unless you buy poor quality gasoline at some nonane gas station. StuRat (talk) 20:29, 20 July 2008 (UTC)

"Nonane gas: it's 12.5% better than octane!" :) DMacks (talk) 20:11, 21 July 2008 (UTC)

Effects of a Small Ice Age on Hay Fever Sufferers

Lately, I have heard discussion regarding the possible production of a new ice age due to the effects of global climate change.

Purely theoretically, how would an ice age effect Hay Fever sufferers? That is how would hay fever, being a seasonal disease, react to a drastic reduction in temperature. Specifics would be appreciated regarding the effect this new ice age would have on the various plants that cause hay fever. Would the cold affect pollen production, etc. —Preceding unsigned comment added by Kenjibeast (talk • contribs) 22:03, 19 July 2008 (UTC)

Different hay fever suffers are affected by the pollen of different plants. A significant change in temperature will change which plants grow where and at what times during the year. That will probably makes thing better for some suffers and worse for others (including some that weren't really sufferers before if new plants start growing where they live). It may well be better for everyone for a short time until the plants adjust, since there will simply be less plants growing successfully. --Tango (talk) 00:14, 20 July 2008 (UTC)

A shorter spring and colder summer would likely reduce the over-all pollen in the air. Then again, it might get worse depending on local ecology and how exactly your weather is being impacted. For example, some desert areas might get more rain encouraging more plant growth. ---J.S (T/C/WRE) 03:28, 20 July 2008 (UTC)