Wikipedia:Reference desk/Archives/Science/2011 July 28

= July 28 =

Please identify this Dragonfly species
Please help identify this dragonfly species. The picture was taken in New Jersey on a concrete surface. The animal was just under three inches in length. μηδείς (talk) 04:49, 28 July 2011 (UTC)


 * My guess is this is a Common Whitetail, check the "adult female" in that article. -- Jayron  32  04:56, 28 July 2011 (UTC)


 * There are also several close matches at the genus Libellula, for example check the adult female example at Twelve-spotted Skimmer. -- Jayron  32  04:59, 28 July 2011 (UTC)

Funny, I told my informant she would get a quick response. Certainly looks like Libulella. I'll post her opinion after I call her tomorrow. Thanks. μηδείς (talk) 05:04, 28 July 2011 (UTC)


 * Thanks. She is satisfied it could be the female of either species. μηδείς (talk) 19:09, 28 July 2011 (UTC)

Any research or speculation in medical literature on using radiation or chemotherapy to treat obesity?
Hi, I was wondering if cancer treatments like chemotherapy and radiation could be modified to treat obesity,(as well as infection). Has anyone seen anything written on this, pro or con, in the medical lit? -Thanks, Rich Peterson24.7.28.186 (talk) 06:02, 28 July 2011 (UTC)
 * I'm confused, are you sure you mean obesity? Obesity is not caused by any "agent" that could be targeted by chemo or radio therapy. How do you imagine those treatments could be modified to treat obesity? Vespine (talk) 06:12, 28 July 2011 (UTC)
 * It would be straightforward to treat obesity using chemotherapy or radiation: both of them tend to cause severe nausea, which predisposes against eating.  The problem, of course, is that most people see the "cure" as worse than the disease. Looie496 (talk) 06:34, 28 July 2011 (UTC)
 * If the goal is simply to discourage appetite through prolonged, severe nausea, there are many other things one could consume that don't carry the risk of severe side effects (everything from permanent organ damage through to secondary cancers) associated with antineoplastic drugs or ionizing radiation. TenOfAllTrades(talk) 13:19, 28 July 2011 (UTC)


 * Sounds more like melting the fat away. You'd make billions. μηδείς (talk) 18:56, 28 July 2011 (UTC)


 * Well, thermal radiation (as well as thermal conduction and convection) is a rather old method of reducing weight, as in a sauna, but may cause weight loss mainly due to dehydration. StuRat (talk) 23:22, 29 July 2011 (UTC)

Horse manure
I saw this on the CBC web site:
 * But why is horse manure different? Why don't police have to stoop and scoop like everyone else? Sgt. Kristopher McCarthy, of the mounted unit, says that unlike dogs horse droppings have no harmful bacteria. "The difference between dogs and horses is that dogs eat meat and horses do not eat meat," McCarthy said.

Is it true that because horses are herbivorous, horse poop has “no harmful bacteria”? Follow-up question: what about humans who are vegan, does their poop have no harmful bacteria? Mathew5000 (talk) 12:19, 28 July 2011 (UTC)


 * No, harmful bacteria originate from external sources - they are deposited post deffication. The digestive tract is a pretty harsh environment for bacteria to survive, so only a select group of bacteria can do so. That being said, a carnivorous diet should provide a more nutritious bacteria culture. The point is that, the feces only becomes hazardous after defecation with the progression of time.I'd be more worried about deseases and other-nonbacterial organism that can accompany the feces. I am not a biologist, I am confident in my answer, nonetheless I welcome correction. Plasmic Physics (talk) 12:47, 28 July 2011 (UTC)
 * Seems like a case of basically right answer, but for the wrong reasons. This does ring true "Within two to three days manure will just dry out and blow away, very similar to clippings of grass." Also my wp:or indicates that carnivores do have worse-smelling feces than herbivores. SemanticMantis (talk) 14:02, 28 July 2011 (UTC)
 * The stomach is a harsh environment for most types of bacteria, but the lower parts of the digestive system are very hospitable. The digestive system of a horse in fact contains huge quantities of bacteria, and the horse depends on them to survive.  In common with other ruminants, the only way they can digest cellulose is by allowing bacteria to ferment it in a structure called the cecum.  The large intestine is also massively colonized by bacteria, as it is in all mammals. Looie496 (talk) 17:02, 28 July 2011 (UTC)
 * And even with all of that, horses pass 3/4 of their dinner undigested. --jpgordon:==( o ) 18:14, 28 July 2011 (UTC)
 * I used to have a neighbour who had a rather unpleasant method for dealing with dog feces on his backyard lawn. He would simply irrigate the lawn, feces and all, and then mow the lot. It's unpleasant due to the horrific smell drifting over the fence. Plasmic Physics (talk) 14:40, 28 July 2011 (UTC)
 * I can see why he's no longer your neighbor... Whoop whoop pull up Bitching Betty 02:44, 31 July 2011 (UTC)


 * Horse manure can be fairly disgusting also, and the police are not unaware of that. I vaguely recall there was one protest in Chicago that they apparently must have disapproved of (maybe it was against the drug war) - think it was around the 96 DNC - which they insisted to "crowd control" on horseback.  And they must have fed those horses every morsel they could cram down, because they (the horses that is) defecated continuously for the entire short route.  The crowd thus had to keep on its toes, but I'd say the joke was on the police in the end, who ended up having to keep their horses in a neat little line for what seemed like hours as some speakers went on at great length ... all the while accumulating a reeking outdoor toilet behind them of positively epic proportions.  Now I'm not entirely sure this was the reason, but Chicago eventually started requiring horse diapers in many cases.  Wnt (talk) 14:57, 28 July 2011 (UTC)
 * I guess you linked to that website about the diaper bit but it actually says horse urine smell is a bigger problem then the manure:
 * According to Sam, horse urine "smells like pure ammonia." He literally threw up one day because of the overwhelming odor, and he spent the rest of the summer with Vicks VapoRub under his nose, all because of the urine smell ("Shit actually doesn't smell that bad. I'd rather clean horse manure than people manure.").
 * Nil Einne (talk) 08:27, 29 July 2011 (UTC)
 * Keep in mind that the reason we have pooper-scooper laws is because of hysteria about parasites (hookworms, tapeworms and roundworms) being transmitted to babies playing with dog feces. It was never about bacteria. - Nunh-huh 21:17, 29 July 2011 (UTC)

Baking powder
Baking powder was not around during the colonial days. It was invented during the middle to late 1800's. What did the colonial women use to make cakes rise? If anyone can answer this, I would be grateful. — Preceding unsigned comment added by TerrDA (talk • contribs) 13:30, 28 July 2011 (UTC)


 * Baking powder Plasmic Physics (talk) 13:46, 28 July 2011 (UTC)


 * Baking powder is a leavening agent; that article lists several alternatives, including mechanical (whisking) leavening. The "history" section of the cake also talks about various pre-baking-powder cakes and cake-like desserts. It's also noteworthy that lots of cultures used, and use, unleavened foods, like pastries, fritters, or dumplings, in the role that you might expect cakes to take in modern western cuisine. -- Finlay McWalter ☻ Talk 13:52, 28 July 2011 (UTC)


 * Baker's Yeast has been used since at least the ancient Egypt, possibly much longer. Dauto (talk) 16:09, 28 July 2011 (UTC)

Baking soda predates baking powder, but probably the most common way of leavening a cake at that time was to use beaten egg whites -- that's still the method used for making sponge cakes. Looie496 (talk) 16:53, 28 July 2011 (UTC)
 * Leavening can happen with natural airborne yeasts as this recipe attests. You just need to leave the dough to stand for a few days. See also Sourdough; "Sourdough starter is made with a small amount of old dough saved from a prior batch, and is sometimes called mother dough or chef. This small amount of old-dough starter contains the culture, and its weight is increased by additions of new dough and mixing or kneading followed by rest or leavening periods. A small amount of the resulting dough is then saved to use as old-dough starter for the next batch. As long as this starter culture is fed flour and water weekly, it can stay at room temperature indefinitely." The article also says that cultured yeast followed the discoveries of Louis Pasteur; before that, Barm from brewing was used. Alansplodge (talk) 19:12, 29 July 2011 (UTC)
 * Then there's salt rising bread, intriguingly made using bacteria better known for food poisoning and gas gangrene, which are mysteriously docile when handled this way. Wnt (talk) 07:02, 30 July 2011 (UTC)

Lovely mystery mushroom
Does anybody recognize what this mushroom is? It was spotted while hiking Freeman Creek in the southern Sierra Nevada. --jpgordon:==( o ) 14:26, 28 July 2011 (UTC)


 * Given the location in the Sierras, Calvatia sculpta seems a good possibility. But I'm no expert. Deor (talk) 15:09, 28 July 2011 (UTC)


 * That looks vaguely reminiscent of the puffball Calvatia sculpta, from about the right area, not close enough to convince me. Wnt (talk) 15:15, 28 July 2011 (UTC) -- note I added this without seeing the previous comment. Interesting we both picked the same thing - in any case I don't mean to naysay the previous poster. Wnt (talk) 15:16, 28 July 2011 (UTC)


 * I'd venture Calvatia sculpta is correct. It was in the right elevation range in the right location. Cutting one in half to see the puffball insides would be a good way to tell, I suppose, though there doesn't seem to be much to confuse it with. (No, I'm not planning on either eating one or destroying one; they're too pretty on the forest floor.) Thanks! --jpgordon:==( o ) 15:25, 28 July 2011 (UTC)


 * "It was spotted while hiking" - now that is impressive. AndrewWTaylor (talk) 16:14, 28 July 2011 (UTC)


 * This is the Science Refdesk. Relativity applies here.  Smile and the world smiles with you - hike and the world hikes against you. Wnt (talk) 18:04, 28 July 2011 (UTC)


 * If we could get a picture of that mushroom's backpack it might help to identify it. Bus stop (talk) 18:20, 28 July 2011 (UTC)


 * I wonder if he's ever shot a picture of a mushroom wearing his pajamas. :-) StuRat (talk) 23:13, 29 July 2011 (UTC)
 * Knowing the photographer, he has shared his pajamas, yes. --jpgordon:==( o ) 15:37, 30 July 2011 (UTC)

Dehumidifier in the desert
I was emptying out my dehumidifier when I had this idea: in places where open water is scarce, like in the Sahara region, why don't they use dehumidifier-like things to extract the water from the air? I understand that the air in those places is obvious not very humid, but even with 1% humidity, one cubic metre of air would yield 10 l of water, which is enough for one person to drink, and maybe even cook if used frugally. Solar power could be used to power the dehumidifier where electricity is expensive or unavailable. Has this been tried before? I'd like to read about it if it has. Thanks in avance. — Preceding unsigned comment added by 118.98.102.191 (talk) 18:16, 28 July 2011 (UTC)
 * I think you're high by several orders of magnitude: the water content would be measured, even at high RH, in terms of grams of water per kilogram of air.  Acroterion   (talk)   18:21, 28 July 2011 (UTC)
 * Yes, see our humidity article. Air at '100% humidity' isn't all water (obviously), but instead air with the maximum possible amount of water vapour present at that particular temperature and pressure - any surplus vapour would condense out as mist etc. AndyTheGrump (talk) 18:27, 28 July 2011 (UTC)


 * The BBC Weather page for Riyadh gives tomorrow's temperature as 44C with RH of 12%. Using this table (linked from the humidity article) shows that the air there will contain ~7g of water per cubic metre - about a teaspoonfull. -- Finlay McWalter ☻ Talk 18:35, 28 July 2011 (UTC)


 * But the amount of air which will go through the dehumidifier is far more than a single cubic meter. Whoop whoop pull up Bitching Betty 02:40, 31 July 2011 (UTC)

Air well (condenser), Dune technology μηδείς (talk) 18:55, 28 July 2011 (UTC)


 * Here's a common method to capture water in the desert: dig a pit about one metre across and deep, then place an open empty water bottle in the centre of the pit. Spread a plastic tarp over the entire pit and fasten it using pins into the sand. Place a small rock in the centre of the tarp over the bottle, and the moisture will rise onto the tarp, condense and fall into the bottle. ~ AH1 (discuss!) 23:24, 28 July 2011 (UTC)


 * One practical problem with using a dehumidifier or air conditioner to collect water in the desert is that it would immediately evaporate. For a given drop of water, you might only have seconds to get it into a sealed container before it would become vapor.  This would especially be a problem on a small scale.  StuRat (talk) 23:10, 29 July 2011 (UTC)


 * A dehumidifier is essentially a refrigerator - it only works if the air gets cold enough that dew would form naturally (below the dew point). Given that the water condenses in some refrigerated space, from refrigerated air, it shouldn't re-evaporate afterward.  But since temperatures in deserts often vary greatly, it may be possible to use some apparatus that doesn't consume energy to accomplish this task. Wnt (talk) 07:01, 30 July 2011 (UTC)

Horses whinnying at bicyclist
More than once, while passing a horse going in the opposite direction on a country lane in the UK, the horse has whinnied. Has anyone else experienced this? Does this suggest that some horses think of bicycles plus rider as a kind of horse? 92.24.133.177 (talk) 18:44, 28 July 2011 (UTC)
 * Could also be fear of the sort Temple Grandin describes with startled cows, see Animals in Translation, as well as Monty Roberts. μηδείς (talk) 19:15, 28 July 2011 (UTC)
 * I've had horses respond to me as a cyclist producing Horse Noises. Nothing too unusual. ~ AH1 (discuss!) 23:17, 28 July 2011 (UTC)
 * What do you mean by horse noises? 92.29.113.104 (talk) 10:19, 29 July 2011 (UTC)


 * Horse noises. μηδείς (talk) 20:20, 29 July 2011 (UTC)

Trans fat in British soft margarine
When I buy a tub of margarine in the UK, what are the chances of it containing more than trace amounts of trans fat? 92.24.133.177 (talk) 19:43, 28 July 2011 (UTC)


 * Here in Canada, any processed food containing less than 0.5 grams of trans fat per indicated serving amount can be advertised as "zero trans fat". Always check the nutrition facts. ~ AH1 (discuss!) 23:16, 28 July 2011 (UTC)

Trans fat is never shown in the nutrition label in the UK. The manufacturers and government regulators keep us in the dark. 92.29.113.104 (talk) 10:14, 29 July 2011 (UTC)


 * In that case, the best you can do is look for hydrogenated vegetable oils in the ingredients list, unless a reliable lab has test results available, or the company's own webs site clarifies matters. StuRat (talk) 23:04, 29 July 2011 (UTC)


 * Wow. According to this some politicians in Britain say they're OK if they only make up "1% of total energy".  But it also says that some members of the British Retail Association like Tesco have removed it from own-brand foods.  Maybe that's a lead?  I oppose nanny-state regulation but I do think something sold as food should be made out of food, not something chemically processed at high temperatures over a catalyst into substances not naturally encountered in the diet. Wnt (talk) 06:47, 30 July 2011 (UTC)


 * I'm opposed to a "nanny state", too, but, in order for people to be allowed to make their own decisions, they do need information, such as whether their food contains this poison, or not. StuRat (talk) 04:37, 31 July 2011 (UTC)


 * Hey y'all, remember the famous saying, "The dose makes the poison". Sure enough, in large quantities trans-fats are harmful, but there's no harm in consuming small amounts of trans-fat.  This whole issue has been vastly overblown by the so-called "healthy food movement" (which IMHO is more concerned with opposing capitalism than with improving public health).  Anyway, I often eat Oreo cookies and other stuff like that, and I've never experienced any ill-effects from it.  Yes, more info might be in order here, but we must keep in mind that trans-fats are not a "poison", just an ingredient that's not healthy for you in large amounts (but perfectly OK in small amounts).  As another saying goes, "Everything in moderation". 67.169.177.176 (talk) 05:13, 31 July 2011 (UTC)


 * Well, I wouldn't expect any obvious effects from trans-fats until your first heart attack. (Trans-fats actually cause me to get acne, but that's apparently just me.) StuRat (talk) 06:08, 31 July 2011 (UTC)


 * And if you keep trans-fat consumption to a low level, I bet you never will. 67.169.177.176 (talk) 08:38, 31 July 2011 (UTC)


 * Right, but this requires knowledge of which foods contain trans-fats, and in which quantities; hence this question. StuRat (talk) 18:33, 31 July 2011 (UTC)


 * Apart from health issues, IMHO eating trans fats makes me get an "old stopped-up sink taste" in the back of my throat. (Supposedly humans don't have taste/smell like receptors in the back of the throat like other mammals but I don't believe it) Wnt (talk) 20:37, 1 August 2011 (UTC)

Chocolate for treating depression
Does any study indeed treated depressed people with chocolate to test its anti-depressing effect? (kind of 100 gr. black chocolate in the morning). Quest09 (talk) 20:33, 28 July 2011 (UTC)
 * Yeah. It doesn't work so well. Please see . 99.39.4.220 (talk) 21:08, 28 July 2011 (UTC)
 * A placebo might work, though depression is not purely physiological. ~ AH1 (discuss!) 23:13, 28 July 2011 (UTC)
 * I don't know about an official study, but I think most married men would agree that it works on their wives... Beeblebrox (talk) 19:35, 30 July 2011 (UTC)
 * Very nice, Beebles. Whoop whoop pull up Bitching Betty 02:49, 31 July 2011 (UTC)

Should I get a food processor, mixer, or something else?
My dad doesn't want to have his two unstable teeth pulled for a full denture, but he can't chew vegetables as a result. I'm thinking a food processor would make such an important food group more palatable. Do you agree? I don't think a mixer would be as appropriate? Imagine Reason (talk) 23:08, 28 July 2011 (UTC)


 * Maybe try a juicing machine for some vegetable juice, such as brocoli? ~ AH1 (discuss!) 23:11, 28 July 2011 (UTC)


 * I wouldn't wish a juicer on anyone other than convicted war criminals. You feed the thing £10 of nice fruit and veg and it emits a pint or so of a murky fluid that tastes downright suspicious and causes alarming gastrological disturbances, together with a completely impossible volume of fluffy brown loft insulation. Then you have to spend half an hour cleaning weird paste from the little ducts and sluices in the machine, and another half hour removing tiny seeds from its spinny juicing disc. This explains why charity chops are full of shiny new juicers (on the same shelf as the bread-flavoured-goo-makers). -- Finlay McWalter ☻ Talk 23:32, 28 July 2011 (UTC)


 * I have an immersion blender which came with a food-processor add-on (so you can chop up veg to make things like soup or salsa). I mostly use it to make smoothies, and my mum uses hers to make creamed (that is, fully liquid) vegetable soups.  Its best feature is that it's trivial to clean (one runs the immersion part under a running tap), which means you're happy to use it very frequently (a juicer, in contrast, is torment to clean).  In my experience toddlers will happily drink veg (things like carrots) if it's hidden in a smoothie; mayhap your tooth-challenged eldster will feel similarly. -- Finlay McWalter ☻ Talk 23:22, 28 July 2011 (UTC)

Juicers give excellent results from carrots and grapes. Urrghl. But were I starving I'd prefer a blender. μηδείς (talk) 04:55, 29 July 2011 (UTC)
 * They work pretty well with apples too. 67.169.177.176 (talk) 05:16, 31 July 2011 (UTC)


 * How about using a potato masher on the cooked vegetables? 92.29.113.104 (talk) 10:16, 29 July 2011 (UTC)


 * This is kind of what I'm looking for. I don't believe in juicers, because they leave behind much of the nutrients. Grapes are high in fructose as well. Imagine Reason (talk) 14:49, 29 July 2011 (UTC)


 * Try this: . ~ AH1 (discuss!) 20:11, 29 July 2011 (UTC)


 * Actually, except for the fiber of a vegetable's cell walls, juicers do extract the large portion of the water soluble nutrients. μηδείς (talk) 20:17, 29 July 2011 (UTC)


 * Right, so it follows that for those people who are concerned that they are getting too much fiber in their diets, juicers are appropriate. The rest of us should avoid them. StuRat (talk) 23:01, 29 July 2011 (UTC)


 * I think the OPs father would more enjoy his vegetables chopped up or mashed up into small pieces that did not require chewing, rather than just making them into a soup as a blender or liguidiser would do. So I suggest either chopping then finely or using a potato masher as previous suggested. And few people get enough fibre, so it would be unhealthy to discard the fibre by using a juicer. 92.29.124.70 (talk) 12:28, 30 July 2011 (UTC)


 * There are many healthy, delicious things you can make with veggies in a food processor. Ajvar or Baba Ganoush can be used as a templates for further experimentation. By varying the base ingredients and spices the possibilities are endless. Another thing you can do is to sweat carrots, onions, celery, etc, then puree them in the processor and incorporate them into another dish. This is a great way to make various kinds of soups and bean dishes. If its hot out Gazpacho can be quite refreshing. Beeblebrox (talk) 19:45, 30 July 2011 (UTC)