Wikipedia:Reference desk/Archives/Science/2009 May 22

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May 22

== does THC cause weed's smell?

I'm curious. If it doesn't, I imagine there's some future genetic engineering in the works that will be the delight of young people everywhere, and I imagine it could be very lucrative for street hustlers with biotech qualifications. John Riemann Soong (talk) 02:55, 22 May 2009 (UTC)

The large leaves have little THC content but still have the herb smell, so I'd say no, the smell is due to other chemical compounds. Of course, that's only what I've heard through my church group, I never touch the stuff. :) One of the attractions of cannabis is that it is a natural plant product that springs from the earth all by itself and delivers a gift of nature - I'm not so sure there is a big market for GMO's in that space. There are already lots of synthetic chemical products to whack your head with if you're so inclined. (I'm not) Franamax (talk) 08:19, 22 May 2009 (UTC)

THC is not the only compound in weed that gets you high. Many psychopharmocological studies use pure THC in place of cannabis in order to study the effects of the drug, but they lack a certain amount of validity (as the researchers are the first to admit) due to only being about THC, not the cocktail of other compounds that make up herbal cannabis. —Preceding unsigned comment added by 158.223.34.22 (talk) 17:14, 29 May 2009 (UTC)

If you're thinking of sniffing dogs, I would imagine expect they could be trained to smell THC if they're not already. In any case, removing every single compound likely to be detected by humans is an extremely difficult task. In other words, you could change the smell but it would likely still have a fairly unique smell. Indeed, I would expect the current smell is a combination of a large number of compounds not one single one although some may be more important then others. Most importantly perhaps, removing most of the compounds giving it a smell is likely to result I would expect in a product that doesn't 'taste' as good when the marijuana is smoked or whatever Nil Einne (talk) 08:52, 22 May 2009 (UTC)

As an analogous scenario, think about decaffeinated coffee. While some enthusiasts insist it's as tasty as regular coffee, I can tell the difference. However, removing the caffeine does not create a colorless, odorless liquid. Many other constituent chemicals contribute to the total flavor and aroma. Nimur (talk) 09:54, 22 May 2009 (UTC)

Actually I was thinking of splicing the gene complex for THC into other plants. Like say, dandelion. Because THC isn't a protein I imagine there's a slight bit of more complication than say, splicing in a fluorescent protein. Have we identified the genes that are responsible for negative feedback or regulatory genes that would inhibit the production of "too much" THC in a plant? (Like say, hemp?) John Riemann Soong (talk) 02:31, 24 May 2009 (UTC)

I imagine you meant so that people wouldn't be caught because of the smell! I guess that the smell is caused by terpenes and other secondary metabolites. I don't think anyone will have found the genes - getting funding for that isn't really going to happen. Oh actually, looking at THC#Biosynthesis I'm wrong although there isn't a citation. Cannabinoid#Plant_synthesis seems to tell a different story as well (uncited again). I guess (again) that high THC containing strains have some difference in transcription factors that mean that they express the genes for the biosynthesis more than in Hemp. Smartse (talk) 16:50, 27 May 2009 (UTC)

Hypermetropia

How to find power of corretive lens? why do we consider normal near point as object distance and the defective near point as image distance while calculating the power of convex corrective lens for Hypermetropic eye? —Preceding unsigned comment added by 61.2.178.70 (talk) 03:10, 22 May 2009 (UTC)

I assume you are asking this question with some knowledge of lenses and optics. Now consider a hypermetropic eye. The problem is that things too close are not focused on the retina. The objective is to give normal vision, where the least distance of distinct vision (D) is about 25cm. That is, if an object is placed in front of the eye as close as D, even then the eye must be able to see it. That is the limiting case, so if we satisfy for the limiting, we (theoretically at least) satisfy for all cases. So now the object is at D. But the eye can see only its own least distance of distinct vision (d) which is greater than D. Therefore, the image must be formed there. So now applying the lens formula, as you correctly suggested, we consider normal near point as object distance and the defective near point as image distance. Also don't forget to sign your posts by typing four '~'s at the end. Rkr1991 (talk) 05:07, 22 May 2009 (UTC)

Lilac bushes

I have a few lilac bushes in my front yard. I'd like to have more. Is there an easy way for me to take a cutting from one of the bushes and get another bush out of it? Dismas|^(talk) 05:15, 22 May 2009 (UTC)

I have no answer for you (other than talking about all my different-coloured lilac bushes) but I will say that if you're in the northern hemisphere, this is probably the time to clip off some green shoots and test directly. You could also try using a rooting hormone in the water, and while you're at the garden centre buying it, ask one of those helpful people. Franamax (talk) 09:42, 22 May 2009 (UTC)

Buddleia seeds can be easily bought, where I am at least, and grow into shrubs that look very similar to lilac bushes in my opinion. Perhaps you could harvest some lilac seeds from your bushes and grow those in pots of compost before planted them out. Other shrubs with lots of blossom also exist - I sometimes see for example a shrub that is completely covered in blue, no idea what its name is. Edit: I have looked at The Tree And Shrub Expert by D. G. Hessayon, published in the UK. Buddleia - propagate by sowing seeds in spring or sowing cuttings outdoors in autumn. The blue bush seems to be Ceanothus or 'Californian Lilac' - propagate by planting cuttings in a cold frame in summer. Syringa or 'Lilac' - also propagate by planting cuttings in a cold frame in summer. But as the UK is mostly in hardiness zone 8 or 9, and where the OP comes from is in zone 4 I think, then that advice may not apply. 78.146.162.232 (talk) 11:50, 22 May 2009 (UTC)

The usual way to propagate lilacs is from shoots, not seeds. See [1] - Nunh-huh 12:12, 22 May 2009 (UTC)

Lilacs grow most successfully from suckers. At the base of every lilac bush you will see shoots emerging. Get a mattack and detach the shoot from the rootstock below the soil level, then put it in a plastic bag until you are able to plant it (don't wait too long though). Then it's easy enough to just plant it and it should grow. And then you will find that, before too long, you want to get rid of said lilac bush because it's about to take over your garden! --TammyMoet (talk) 13:04, 22 May 2009 (UTC)

BTU'S produced by a conventional 4 or 6 cylinder engine

Can anybody advise how much heat is produced on the exhaust system of a conventioal 4 -6 cylinder engine at the exhaust pipe near the catalytic convertor? —Preceding unsigned comment added by Sustain6996 (talk • contribs) 07:36, 22 May 2009 (UTC)

Since the heat produced in the catalytic converter comes from reactions involving incomplete combustion products, unburnt hydrocarbons, and nitrogen oxides, I would say it depends heavily on the operation conditions of the engine and the particular fuel/air mixture. Under certain conditions (overly rich fuel/air mix and severe incomplete combustion) it could reach levels comparable to the power output of the engine, but is usually much less. This risk of producing huge amounts of heat is why car manuals have the whole "Do not drive, park, or idle the vehicle over dry grass" warning... 69.140.12.180 (talk) 15:51, 23 May 2009 (UTC)Nightvid

List of longest rivers in Poland

List of rivers of Poland (edit | visual edit | history) · Article talk (edit | history) · Watch

I have only found top 29 longest rivers in Poland. Do you know top 50 longest rivers in Poland? —Preceding unsigned comment added by 213.158.197.100 (talk) 11:44, 22 May 2009 (UTC)

There are 123 pages in Category:Rivers of Poland. You might find what you are looking for there, but we don't have them as an organised list. SpinningSpark 14:00, 22 May 2009 (UTC)

When you get to the smaller rivers - you start running into the "How Long Is the Coast of Britain? Statistical Self-Similarity and Fractional Dimension" problem. When precisely does the river start? Maybe water trickles over some fields before it starts to look like a river? If the river is very crinkly, then issues of fractal dimension start to become a problem. So I doubt very much that you can say with any authority which of those 123 rivers are longer than which others...except for the biggest and most obvious ones - which we've already covered. SteveBaker (talk) 14:27, 22 May 2009 (UTC)

Eating too little fats

What would be the long term physiological or medical effects of an adult eating say only 10% of their calories as fat, instead of the 25 to 35% that is recommended? I understand that fat-deficiency was a problem in Victorian times, before margarine was invented. 78.146.162.232 (talk) 13:11, 22 May 2009 (UTC)

See rabbit starvation. It does not discuss the American West in the article, but apparently this was a condition suffered by some pioneers, even though they had a high calorie intake and the native Americans around them on the same diet were not suffering. The difference - the pioneers were discarding the fat from the meat. SpinningSpark 13:25, 22 May 2009 (UTC)

Thanks, but it does not mention anything about the physiological effects. 78.146.162.232 (talk) 14:30, 22 May 2009 (UTC)

From the lede paragraph of the article: Symptoms include diarrhea, headache, lassitude, a vague discomfort and hunger that can only be satisfied by consumption of fat or carbohydrates, and low blood pressure and heart rate. Are those not physiological effects? SpinningSpark 14:49, 22 May 2009 (UTC)

Thanks again, but those are the symptoms. I'm wondering what physiological pathways are involved, how it might for example affect the nerves or the brain which I understand include a lot of fat, or if something like ketosis or its opposite is involved. 89.242.85.248 (talk) 19:03, 22 May 2009 (UTC)

It is discussed in detail in this article from The American Journal of Clinical Nutrition. SpinningSpark 14:55, 22 May 2009 (UTC)

Thanks, but that link only seems to be a description of hunter-gatherer diets. 89.242.85.248 (talk) 19:14, 22 May 2009 (UTC)

Did you read it or just skim it? Try doing a word search for "rabbit starvation". SpinningSpark 00:33, 24 May 2009 (UTC)

See Essential fatty acid. There may also be some links you can track down in the articles on Omega-3 and Omega-6 fatty acids. I'm not convinced that someone taking in only 10% of their calories in fat would have any adverse physiological effects unless the fat source was completely deficient in Omega-3 and Omega-6 fatty acids. The body can otherwise make other lipid molecules it needs. Do you have any references for fat-deficiency in Victorian times? Also, the issue of "rabbit starvation" applies to a special condition of a diet largely composed of "lean meat coupled with a lack of other sources of nutrients" (i.e. presumably also lacking in carbohydrates and certain vitamins) which isn't really directly related to what the OP is asking. --- Medical geneticist (talk) 13:36, 23 May 2009 (UTC)

Consuming less than twenty percent of calories from fat will almost invariably cause the carbohydrate intake to be too high. Very high carbohydrate diets (such as those obtaining more than two-thirds of calories from carbohydrates) can adversely impact lipid profiles, increasing triglycerides and suppresses HDL cholesterol. The Institutes of Medicine said this in 2005: The AMDR for fat and carbohydrate is estimated to be 20 to 35 and 45 to 65 percent of energy for adults, respectively. These AMDRs are estimated based on evidence indicating a risk for coronary heart disease (CHD) at low intakes of fat and high intakes of carbohydrate and on evidence for increased risk for obesity and its complications (including CHD) at high intakes of fat. Because the evidence is less clear on whether low or high fat intakes during childhood can lead to increased risk of chronic diseases later in life, the estimated AMDRs for fat for children are primarily based on a transition from the high fat intakes that occur during infancy to the lower adult AMDR. The AMDR for fat is 30 to 40 percent of energy for children 1 to 3 years of age and 25 to 35 percent of energy for children 4 to 18 years of age. The AMDR for carbohydrate for children is the same as that for adults—45 to 65 percent of energy. The AMDR for protein is 10 to 35 percent of energy for adults and 5 to 20 percent and 10 to 30 percent for children 1 to 3 years of age and 4 to 18 years of age, respectively. (http://books.nap.edu/openbook.php?record_id=10490&page=769) The Institutes of Medicine talk about the harmful effects of both fats and carbohydrates (see the lengthy chapters beginning here and here).

The USDA says:

A low intake of fats and oils(less than 20 percent of calories) increases the risk of inadequate intakes of vitamin E and of essential fatty acids and may contribute to unfavorable changes in high-density lipoprotein (HDL) blood cholesterol and triglycerides.

(http://www.health.gov/dietaryguidelines/dga2005/document/pdf/DGA2005.pdf, see Chapter Six)

"The AHA notes that in the absence of weight loss, diets high in total carbohydrate (e.g., >60% of energy) can lead to elevated triglycerides and reduced HDL cholesterol. These effects do not occur with substitution of monounsaturated or polyunsaturated fats for saturated fat. NCEP suggests that monounsaturated fat can be up to 20% of total energy and polyunsaturated fat up to 10% of total energy." (http://www.diabetes.org/uedocuments/ADACardioReview4.pdf)

In reducing fat, it would be better to compensate with calories from protein than carbohydrate. In conclusion, Atkins might not have been right about fats and proteins, but he was right about carbohydrates. There is no doubt that they are bad for you. The only question is whether increasing fat or protein might be worse. They might come with useful nutrients (e.g., minerals or antioxidants), but carbohydrates themselves have no benefit except to meet calorie needs. This list of effects was the best that the FAO could come up with (most of the effects apply to the digestion of fiber, a beneficial carbohydrate that provides few if any calories).

Fat and protein at least are beneficial in moderation and help maintain the body.75.89.27.94 (talk) 23:13, 24 May 2009 (UTC)

Question

What would happen if a man with a double-barreled name married? What would the woman be named? If they had a child, what would the child be named? 143.238.237.25 (talk) 13:39, 22 May 2009 (UTC)

It's up to the couple. There may be legal restrictions on what they can choose, though. A German court has recently upheld a ban on triple-barrelled names [2]. --Tango (talk) 13:50, 22 May 2009 (UTC)

This isn't a science question - it belongs on the language desk IMHO. SteveBaker (talk) 14:28, 22 May 2009 (UTC)

Question 2

Are there any double-barreled names that are not one of a kind? Are there any people with triple- or quadruple-barreled names? 143.238.237.25 (talk) 13:40, 22 May 2009 (UTC)

You may find this article interesting. What do you mean by "one of a kind"? --Tango (talk) 13:51, 22 May 2009 (UTC)

Double-barrelled name has some examples of multi-barreled names, such as the Anstruther-Gough-Calthorpe family, the Plunkett-Ernle-Erle-Drax family and Richard Temple-Nugent-Brydges-Chandos-Grenville and his descendants. Also worth a mention, although not an inherited name, is John Desmond Lewis who changed his name by deed poll to Tarquin Fin-tim-lin-bin-whin-bim-lim-bus-stop-F'tang-F'tang-Olé-Biscuitbarrel when he stood as a candidate in the Crosby 1981 by-election. Gandalf61 (talk) 14:12, 22 May 2009 (UTC)

This also isn't a science question - it belongs on the language desk IMHO. SteveBaker (talk) 14:28, 22 May 2009 (UTC)

Why are not all elements of Tarquin's name capitalised? Oh yeah, I know, this is not a science question. SpinningSpark 14:40, 22 May 2009 (UTC)

I'm sorry - can you rephrase that in the form of a falsifiable hypothesis? SteveBaker (talk) 18:52, 22 May 2009 (UTC)

Tarquin's name is not all capitalised because he felt like it. Discuss. --Tango (talk) 18:53, 22 May 2009 (UTC)

How long before the earth runs out of food?

The world population is still increasing, even though not quite as fast as previously forecast. How long will it be using current population projections before the earth can no longer produce enough food for its inhabitants? I heard David Attenborough say on tv that the worlds population was only about 2 billion when he was born rather than the 6 or approaching 7 billion now. A world packed with the maximum number of people would be like hell. 78.146.162.232 (talk) 14:35, 22 May 2009 (UTC)

Are you going to assume even food distribution, or status quo? 65.121.141.34 (talk) 14:49, 22 May 2009 (UTC)

You may want to read Malthusian catastrophe. People have been predicting that the Earth won't be able to sustain the growing population for years and we've haven't had a problem so far. Improved agricultural technologies allow increase yields that will probably keep up with population growth until the population levels out. There are plenty of people going hungry in the world but that isn't due to lack of food, it is due to food not getting where it is needed (generally due to politics). --Tango (talk) 14:57, 22 May 2009 (UTC)

The Mathusian catastophe article has red error messages where some maths formulae ought to be. 89.242.85.248 (talk) 19:24, 22 May 2009 (UTC)

Fixed (by purging). --Tango (talk) 19:55, 22 May 2009 (UTC)

With enough technology applied to the problem I guess we could have many times the current population of the earth fed so if things go on as they are the earth will be utterly and totally devastated and all other non-food species above microbes extinct except as some genes saved in a bank. The earth won't run out of food but there is some very high limit on the ultimate carrying capacity of the earth, certainly 30 billion and possibly much more than a hundred billion. Most food will be grown in vats or in trays and a few cows will be kept to feed the very rich. If the population could be reduced to less than a billion, maybe 500 million, then they would be able to have good lives without constantly worrying about destroying everything. Dmcq (talk) 17:39, 22 May 2009 (UTC)

"With enough technology applied to the problem" - if that includes artificial fertilizer or fossil fuel products, then they will run out at some time. 89.242.85.248 (talk) 19:18, 22 May 2009 (UTC)

The crisis is likely to come not from the earth as a whole running out of food, but specific regions. The two greatest danger points, in my opinion, are India and sub-Saharan Africa. In India, the population continues to increase rapidly while the Green Revolution yields diminishing results and the supply of usable land has been pretty much exhausted. In Africa, the population is projected to more than double before stabilizing, and already there are continual flare-ups of famine. Looie496 (talk) 17:41, 22 May 2009 (UTC)

But a large percentage of people in S-SA are HIV positive as well, which should mitigate a lot of famine potential in the 10-20 year range right? 65.121.141.34 (talk) 19:21, 22 May 2009 (UTC)

Not necessarily. Plenty of people have children despite being HIV+, so there might not be a significant long term reduction in population. --Tango (talk) 19:57, 22 May 2009 (UTC)

Are their children born infected? 65.121.141.34 (talk) 20:03, 22 May 2009 (UTC)

Yes perhaps a quarter of the children born to HIV infected mothers are infected. Dmcq (talk) 20:55, 22 May 2009 (UTC)

(EC) With access to certain drugs the chance is greatly reduced. See [3]. Of course for a variety of reasons many pregnancies in sub-saharan Africa don't get such drugs [4] Nil Einne (talk) 21:04, 22 May 2009 (UTC)

(EC) Another big concern in a number of places including IIRC China, India and sub-Saharan Africa is the diminishing availability of fresh water caused by a variety of reasons including ground water that's being overused (deeper and deeper wheels need to be dug, contamination of water supplies, diminishing reservoir (lakes, rivers etc) levels, climate change. We may be able to partly or completely solve this by engineering crops able to grow in sea water. We may not. Only time will tell. Nil Einne (talk) 21:04, 22 May 2009 (UTC)

There are other high-tech ways to get fresh water - if you have power, a desalinization plant will work - if you are close to the sea, you could tow a gigantic iceberg into a convenient harbor and 'mine' it for water. If you have enough energy, there isn't much you can't do. SteveBaker (talk) 23:16, 22 May 2009 (UTC)

I think the 'enough energy' is a big if. I suspect if we really had unlimited energy, terraforming Mars, the moon, or a few other places would be a piece of cake. We could even build giant stations to grow food. In other words, we don't have to restrict ourselves to earth if we don't consider practicalities. While these may be several orders of magnitude more difficult then having sufficient energy to desalinise sufficient water for 7 billion people, the basic issue is the same IMHO. It's pointless talking about possibilities which even if we devote all our current efforts to them we probably couldn't achieve in 50-100 years. Nil Einne (talk) 08:49, 23 May 2009 (UTC)

By sufficient technology I mean sustainably the world could probably support many many times its current population using solar panels and wave power plus using some fast breeder reactors as backup. Fertilizer can be generated from power and of course suitably treated waste from people would also be used. I wonder what the earth would look like from space with every last spot covered with farm or power machinery of one sort or another Dmcq (talk) 20:55, 22 May 2009 (UTC)

I recommend The Mote in God's Eye which I won't discuss any more for fear of spoiling it for you. Tempshill (talk) 22:12, 22 May 2009 (UTC)

On the subject of climate change, the area of arable land is forecast to decrease within the century. Although CO2 fertilization may have the effect of temporarily increasing crop productivity, as well as more arable land being produced in Northern Canada and Siberia, major "breadbaskets" today are forecast to decline. For example, the American Midwest is predicted to suffer major desertification with a further warming of just 1C (2F), Southern Mediterranean Europe is forecast to become much drier and hotter, the Kalahari desert is expected to expand south, the Gobi desert to expand east, and the water supplies from the Himalayan glaciers, which support farming in otherwise dry areas, are expected to nearly dissapear before the end of the century. In addition, crop and insect diseases could increase, and major staple grains, especially rice, suffer a dramatic drop in yields above a certain threshold temperature. Population load, once it increases past global supply, reaches the "final point of sustainability". After such, both supply and load must start to decrease, until load decreases sharply below the level of supply, although not everyone predicts this. Clean drinking water supplies could decrease as well, which would hinder farming. ~AH1^(TCU) 23:13, 22 May 2009 (UTC)

The answer has a political as well as a scientific component. Many things that are scientifically possible won't be done. Someone would have to allocate the resources. (e.g. money, energy, water, raw materials, medication). In an ideal scenario humans would all be altruistic and distribute those to benefit all. That is unrealistic, though. Despite the fact that there are mass die-offs due to war, pandemics, starvation and drought the human population in general seems to keep multiplying. There is no free lunch, though. Scientific scenarios to feed and water ever increasing numbers come at a cost. Either environmentally or in loss of life or reduced lifespans or quality of life of some populations. The more artificial components the system gets the more fragile it becomes. If you feed your entire population with food grown in vats, one good bug could wipe our a significant portion or them. BTW. Last I checked Egypt had a higher birth rate than sub-Saharan Africa. Just because s.o. is e.g. in the U.S. they should not develop the attitude "It can't happen here." Example: Atlanta, which is in an area with lots of rainfall, has grown so much that in years that have less rainfall there's water rationing. Cases of people dying because they can't pay their water bill are rare, but not unheard of. People in industrialized nations have a higher chance of having their food supply ensured, but there's no guarantee. There is also an inverse relationship between wealth and population increase. 71.236.24.129 (talk) 10:28, 23 May 2009 (UTC)

I think if we use nuclear energy, it will last a ridiculously long amount of time. Even more so if we use fusion. I'm not sure about the former, but I think with the latter we could keep growing the population until we physically run out of space, which won't be for a very long time. — DanielLC 15:59, 23 May 2009 (UTC)

Would anyone like to estimate the maximum number of people the earth could support? 89.243.84.208 (talk) 10:22, 24 May 2009 (UTC)

42. 65.121.141.34 (talk) 14:13, 26 May 2009 (UTC)

If the current growth trend (population doubling every 40 years) continues, each person on Earth will have thier own square meter plot of land by 2270. Livewireo (talk) 16:13, 26 May 2009 (UTC)

The current growth trend is not population doubling every 40 years - we've been sup-exponential for a while now. If growth were exponential, this graph would be completely level (give or take some minor fluctuations). --Tango (talk) 16:39, 26 May 2009 (UTC)

food web

Why we have to study food web, food chain and food pyramids? —Preceding unsigned comment added by Lakshmibp (talk • contribs) 14:42, 22 May 2009 (UTC)

Because questions about them will be on the test. -- kainaw™ 14:59, 22 May 2009 (UTC)

Because education about ecology and food production is beneficial to society. Nimur (talk) 15:11, 22 May 2009 (UTC)

They are a good way of understanding how an ecosystem fits together. Such understanding is important whenever you have to consider the environmental impact of something, which we have to do quite often. --Tango (talk) 16:36, 22 May 2009 (UTC)

Same reason for studying anything else. Knowlege is useful. Now quit being lazy and do your homework. Dauto (talk) 16:48, 22 May 2009 (UTC)

So you don't grow up like one of the dumb people some on the Internet laugh about, like ones who think food just comes from the supermarket, and who don't understand how the stuff grows and has to be shipped. So you understand the importance of farmers and don't grow up to build huge subdivisions with homes that cost a lot of money, but which deplete the available land to grow food.Somebody or his brother (talk) 18:13, 22 May 2009 (UTC)

Food web / pyramid does not mean food distribution or even growing, so learning them would have little or no impact on ignorance on such topics. It is a schematic representation of ecological interactions, like cats eat fish eat flies plant eggs in cat corpses/faeces, which can be useful in practical application such as ecological planning (eg, releasing ladyirds to control aphids may simply cause an increase in ladybird predators, if understanding of the food-web is insufficent) and in understandig various food scandals and recomendations (like why heavy metals appear in fish, or why DDT is banned). As with most school sciences, it is essential for anyone undertaking further scientific education, and is the sort of thing that any typically educated person should know.YobMod 09:03, 23 May 2009 (UTC)

All the food that we eat is either the body of a living organism (plant or animal) or the product of a living organism (sugar, milk, honey). The plants and animals in our world must remain healthy so that we may have healthful, nutritious food. Pollutants in the ocean have reduced the quality of seafood. What we eat is affected by food chains and food webs. As a simple example, the livestock eat the grass, and then we eat the livestock. We have to know where our food comes from to ensure that it is safe.71.31.105.41 (talk) 23:29, 24 May 2009 (UTC)

Phlegm and vocal range

This morning I woke up with a laryngitis, and was able to sing a loud and clear (mf) B♭1, a note I had only been able to sing ppp in Mahler's Eight and the All-Night Vigil. I even could sing down to F1, although that was very hoarse and open to interpretation. Now that I've been up for a while, my lower range has moved up, too, but my electronic tuner still recognizes my A1. Is this because the phlegm acts as a weight on the vocal chords? — Sebastian 15:28, 22 May 2009 (UTC)

Just speculation, but since I'd think that phlegm would be rather mobile when you start singing... It may be the swelling of the mucosae that adds weight to the vocal chords, and causes the frequency to drop. --NorwegianBlue ^talk 18:10, 22 May 2009 (UTC)

Would swelling of the mucosae be the reason that, the morning after drinking heavily, some people speak in a lower tone of voice and are able to reach lower notes? Tempshill (talk) 21:14, 22 May 2009 (UTC)

Hey, when I have a bad cold, I can sing "Ol' Man River" or "Asleep in the Deep" (or the bass part of the Marcels' version of "Blue Moon") in a way that will bring tears to your eyes. Otherwise, not so much. Deor (talk) 02:46, 23 May 2009 (UTC)

Calulating the Surface Area of the Human Body

I'm curious how could one most easily calculate the surface area of a person's body? Would men or women have more than the other and would tall, thin people have less than a short, fat person?TheFutureAwaits (talk) 16:30, 22 May 2009 (UTC)

The easiest way, which should be exact enough for what you need, would be to measure length and average circumference of your body parts - torso, arms, legs, and head - and add them up (neglecting the areas of your feet and the top of your head). Roughly speaking, you can think of your surface as your height times your average circumference. Since girth can easily vary by a factor of 2, while length only varies within a much narrower range, it is easy to see that a short, fat person has more surface than the tall, thin one. — Sebastian 16:45, 22 May 2009 (UTC)

See google:"body surface area" nomogram. There are various formulas in use, and discrepancies between them sometimes make it difficult to compare clinical studies that depend on body surface area. --NorwegianBlue ^talk 18:18, 22 May 2009 (UTC)

If you have access to a corpse, you could try peeling off a small section of skin, weighing it and measuring its surface area, then weighing the whole skin and scaling up the previous surface area accordingly. Vimescarrot (talk) 19:43, 22 May 2009 (UTC)

Not sure if this qualifies as "most easily".  ;) --- Medical geneticist (talk) 20:29, 22 May 2009 (UTC)

Bottom of feet is much thicker skin then the rest of you. Might be pretty uneven in other places too. Could throw off the calculation. Might be a decent approximation on someone who does not walk, though. I would think that perhaps you could cut up a wetsuit and measure the area of that? Also include some socks with toes and gloves made of a material that is not very stetchy. No cadavers involved. 65.121.141.34 (talk) 20:02, 22 May 2009 (UTC)

Just as a general principle, the more "spherical" the body shape, the less surface area in proportion to mass. In other words, of two people who weigh the same, the "rounder" one will generally have less skin surface. Looie496 (talk) 21:01, 22 May 2009 (UTC)

A nomogram would be great, but how did the person who made the nomogram figure out surface area? Mac Davis (talk) 18:28, 23 May 2009 (UTC)

Take a vat of molten chocolate of known volume. Dip subject in vat and remove. Measure the volume lost from vat and the thickness of chocolate adhering to subject - bit of arithmetic and Hilda's your auntie. SpinningSpark 00:29, 24 May 2009 (UTC)

This paper from 1952 used a formula developed by du Bois:-

weight^0.425 x height^0.725 x 71.84

[Weight in kg, height in m] The original reference is from 1916: DuBois D, DuBois EF. A formula to estimate the approximate surface area if height and weight be known. Arch Intern Medicine. 1916; 17:863-71.

This paper is a modern update on du Bois' model.

Axl ¤ [Talk] 13:37, 24 May 2009 (UTC)

And this paper uses a direct measurement technique it calls "coating and planimetry" (which seems to be surprisingly similar to my "dip in chocolate" scheme above) and makes the claim that this shows all the "formula" methods are wildly innacurate, at least for persons of African descent. SpinningSpark 14:03, 25 May 2009 (UTC)

Hip anatomy

Hi is there any way in which the ilium on either side of the pelvis is referred to differently in a clinical setting? My question is how would you know what side of the ilium someone was talking about if it is only one bone? If there was for example a fracture on one side of the ilium but not the other would doctors talk about the left/right ilium? Hope this makes sense. Is there a similar way of differentiating which side of pubis or ischium someone was talking about? Thanks in advance to anyone who can help! —Preceding unsigned comment added by 139.222.240.161 (talk) 16:53, 22 May 2009 (UTC)

Take a look at Anatomical terms of location. There is a precise term for each orientation or position (e.g. the anterior distal portion of the ilium). These terms avoid the use of terminology which would be vague based on how somebody is standing/moving the limb, etc. Nimur (talk) 16:57, 22 May 2009 (UTC)

When did fruit bearing plants first evolve and what was the first fruits?

When did fruit bearing plants first evolve and what was the first fruits?Capitalistroadster (talk) 00:06, 23 May 2009 (UTC)

Evolution of plants doesn't cover this terribly well, but as far as I can tell, the Gingko is a good candidate. According to our articles, the first gingkos evolved around 270 million years ago, and were among the first seed-bearing plants. And having lived next to a female Gingko tree for a few years, I can tell you from unpleasant experience that they do bear fruit. Looie496 (talk) 19:43, 22 May 2009 (UTC)

According to our article: "The apricot-like structures produced by female ginkgo trees are technically not fruits, but are seeds that have a shell that consists of a soft and fleshy section (the sarcotesta), and a hard section (the sclerotesta)." --Tango (talk) 19:50, 22 May 2009 (UTC)

Thanks Loie496 and Tango.Capitalistroadster (talk) 00:06, 23 May 2009 (UTC)

Dendritic cells

The Wikipedia article on dendritic cells says that these phagocytes are unique to the mammalian immune system. However, things like this and this seem to suggest other groups of animals have DCs as well. Which is right? If other groups of animals have DCs, which have them: all amniotes? all tetrapods? all jawed vertebrates? Thanks a lot. --Leptictidium (mt) 20:12, 22 May 2009 (UTC)

The adaptive immune response goes back to jawed vertebrates as you suggest, and it seems likely that would be true for dendritic cells. I don't know for how many of the more "primitive" jawed vertebrates they've been demonstrated, though. Your reference for Langerhans cells in reptiles is a good one, though. --Scray (talk) 00:15, 23 May 2009 (UTC)

Cheers to Axl for updating the dendritic cells page with this information - the RefDesk continues to improve WP in general! --Scray (talk) 17:23, 23 May 2009 (UTC)

:-) Axl ¤ [Talk] 18:41, 23 May 2009 (UTC)

What is the average pushing power of a man in psi

Can anyone tell me the amount of pushing power a man who weighs 90 kgs and has 7 inch by 7 inch hands in psi (pounds per square inch) ? my brother says its something like 20psi but that doesnt seem right to me. Is there a way to roughly work this out?

Thank you —Preceding unsigned comment added by 79.68.219.232 (talk) 21:13, 22 May 2009 (UTC)

It depends on what they are pushing...the world record for weight-lifting is around 260 kg - and that's over a length of cylindrical bar the width of the guy's hands (let's say 20cm) by maybe 4cm wide...so 260kg over 80cm² - which is about 46 psi. Obviously that's the world record - I'd say that less than half that is perhaps reasonable. SteveBaker (talk) 23:11, 22 May 2009 (UTC)

(Edit conflict)Yes, if you first define what "amount of pushing power" really means. Since you've mentioned psi you (or the teachers who set this poorly worded homework question?) are presumably thinking of how much pressure the man can exert through his hands (since psi is pounds per square inch, a measure of pressure).

An accurate figure will depend on how well muscled he is, how he applies the pressure, and in what direction, but let's assume he's moderately strong and can push with flat hands with a total force equal to his own weight - does that sound reasonable? Think of a wrestler holding his opponent above his own head preparatory to a body slam, not an unlikely scenario, and certainly below world-class weightlifting standards.

Now, you know the linear measurements of his (two) hands, so you should be able to work out their area in square inches - you should find that the answer comes close to a round figure useful for approximate calculations. you know how much he weighs in kilos, which we've assumed is about the same as the maximum force he can exert (weight being a force). You need to convert this force to pounds, which I'm sure you can manage. You should find this comes close to another convenient round figure.

Now you need to work out how how that total force is distributed over the total area he's using to push with, how many pounds he's exerting on each square inch. The answer may surprise you, and should show that your brother has made a minor error in his working. 87.81.230.195 (talk) 23:24, 22 May 2009 (UTC)

If a 200 pound man does a hand stand then he is supporting his whole weight on the area of his two hands, which I reckon is a pressure of about 4 psi. However, as pointed out above, a weighlifter can support the same weight on a much smaller area, so they are exerting a higher pressure. And a 100 pound ballet dancer en pointe is supporting her weight on probably 2 square inches, so she is exerting a pressure of around 50 psi. So pressure is not a useful measure of "pushing power". Gandalf61 (talk) 09:45, 23 May 2009 (UTC)

What would the best way to measure pushing power , if not pressure? —Preceding unsigned comment added by 79.68.229.253 (talk) 10:48, 23 May 2009 (UTC)

Force. --Tango (talk) 10:52, 23 May 2009 (UTC)

Actually, since the original question was actually for pushing power, the correct answer is "power", e.g. force times velocity, or rate of energy expended per second. I think the original questioner may want to review some basic physics terminology like force, energy, power, and pressure, to decide which quantity is actually the one he/she is trying to inquire about. Nimur (talk) 12:06, 23 May 2009 (UTC)

If the questioner doesn't know whether pressure, force, power, work or energy is the thing that is to be measured - then perhaps we need to ask why the question is being asked? To what use is the answer being put? Very often, these questions are just idle curiosity - but since the numbers don't mean much, it's all rather arbitary. SteveBaker (talk) 15:33, 23 May 2009 (UTC)

Well, strictly, yes. I was interpreting "power" to just mean "ability", rather than its technical definition in physics. --Tango (talk) 17:15, 23 May 2009 (UTC)

Fancy Guppy Reproduction

I have a femal fancy guppy and a male gold swordtail, among other things. It appeared that my guppy was pregenant, and seeing no other possible candidate, assumed the swordtail was the father. I took the neccessary steps to prepare, and even moved her to a seperate breeder when I assumed she was close (before it would be to dangerous to move her though). There she sat, for nearly a month. Then one day she was skinny again! There was no evidence of a miscarriage, and there were no babies in the other compartment. The only change is that I was better able to control how much she ate, so she probably cut back on some calories, but if this were the cause, I assume she would have lost weight over time, instead of so suddenly. What happened? And now she's starting to show pregnancy signs again. This is very troubling.Drew Smith What I've done 23:59, 22 May 2009 (UTC)

Do fish get phantom pregnancies? I know other mammals (than Humans) do, so could be. I also read that Guppies can store sperm, so can have multiple pregnancies from one mating - but this doesn't explain the spontaenous loss by itself, uness followed by multiple miscarriages.YobMod 08:35, 23 May 2009 (UTC)

Guppies sometimes eat their young. 71.236.24.129 (talk) 09:41, 23 May 2009 (UTC)

I know they eat their young, but I had her in a breeder box that automatically seperates the young from the mother.Drew Smith What I've done 00:36, 24 May 2009 (UTC)