Wikipedia:Reference desk/Archives/Science/2012 May 4

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May 4

All-axial or all-equatorial?

Do scyllo-inositol and β-hexachlorocyclohexane have a structure with each substituent on the cyclohexane ring taking an axial position or one with each substituent taking an equatorial position? Whoop whoop pull up ^{Bitching Betty | Averted crashes} 00:56, 4 May 2012 (UTC)

In general, equatorial is more stable than axial, so scyllo-inositol (like the structurally similar glucopyranose) will likely be all-equatorial. While there might be specific interactions with the chloro groups which might change the behavior from glucose, given the size of the chlorines and the close interactions that the all-axial configuration would impose upon them, my inclination would be that β-hexachlorocyclohexane would also take an all-equatorial conformation. -- 140.142.20.101 (talk) 01:22, 4 May 2012 (UTC)

Correct. β-hexachlorocyclohexane (CHCl)₆ is all equatorial doi:10.1039/P29760000614, as is scyllo-inositol (CHOH)₆ doi:10.1021/cg060179a. --Ben (talk) 08:46, 4 May 2012 (UTC)

How fast it takes for Venus to lose its atmopshere

Venus don't have a magnetic field/magnetosphere, I wonder how Venus maintains a thick atmosphere of 90xs the pressure of earth. I heard Venus was once a blue planet, it end up to have a runaway greenhouse effect which adds 100xs the atmosphere from 3 to 4 billion years ago. If sun brightens by next few billion years, will Venus' atmosphere erode slowly or quickly no later than 2 billion years. In other words will Venus lose most/all its atmosphere quickly by just 1 to 2 billion years, or Venus and Earth will erode its atmosphere about the same time, it will take time (slowly) for Venus to lose all its atmosphere.--69.226.42.182 (talk) 01:51, 4 May 2012 (UTC)

The standard model for this is called gas escape, and the formula is essentially solving for the thermodynamic equilibrium of a Maxwellian gas subject to gravity. You can find more rigorous treatments, including models that deal with solar wind, ionization, magnetospheric trapping, and all sorts of other parameters. Our article lists several advanced references. I also refer to de Pater and Lissauer as my usual first-place-to-check for these sorts of questions. I think planetary atmospheres are Chapter 3, there's a looooong discussion of atmospheric evolution over cosmological timescales. Nimur (talk) 03:05, 4 May 2012 (UTC)

Sorry, Chapter 4, especially 4.8, though there's discussion of atmospheres in radiative equilibrium in Chapter 3, and extensive coverage elsewhere. Nimur (talk) 03:09, 4 May 2012 (UTC)

Isn't Venus's atmosphere being replenished by volcanism? Venus has periodic episodes of planet wide flood basalts, similar to but much larger than the flood basalt that created the Siberian Traps. I've read somewhere that Earth will get an atmosphere like that of Venus today due to increasing solar activity in the distant future. Count Iblis (talk) 02:45, 5 May 2012 (UTC)

Considering the sun is expected to expand into a gas giant larger than Earth's current orbit as it approaches stellar death, getting an atmosphere like Venus is the least of our problems. — The Hand That Feeds You:^Bite 21:40, 8 May 2012 (UTC)

Toxicity of lead anti-radiation materials

Why, despite its toxicity to humans, lead is still being used for radiation protection? Is there a non-toxic material, which is as effective as lead or even more?-- 176.241.247.17 (talk) 13:44, 4 May 2012 (UTC)

Lead is only toxic if you ingest it (eat, drink, breathe). In the cases where its used to absorb radiation (lead aprons for patients receiving x-rays, lead plates protecting radiologists) the lead is properly encapsulated and poses no danger at all. Depleted uranium is considerably more effective at absorbing X and gamma radiations, is again only toxic if you somehow get some of it inside your body, and is used in similar circumstances to lead, again properly contained, without issue. -- Finlay McWalterჷTalk 13:49, 4 May 2012 (UTC)

Lead is extremely dense which is useful for making a good shield, and at about 1 US$ / pound it is still relatively cheap. Comparable shielding made out of more common materials, like steel or concrete, would be 50% heavier and 3 to 6 times thicker. Lead is very useful when you want the shielding that is not too heavy or too bulky. As Finlay says, lead is not particularly dangerous unless you ingest or inhale it, which can generally be prevented by encapsulating the lead in other materials. Dragons flight (talk) 14:08, 4 May 2012 (UTC)

Lead also stops most of the nasty stuff - alpha particles, beta radiation, gamma ray emission, high energy ionizing electromagnetic radiation, and so on. Other materials stop specific types of hazardous radiation: paraffin can stop slow neutrons, and even ordinary paper will block alpha particles, but lead blocks almost everything. That makes it great for places where you have technicians who don't know the physics behind the radiation source; or when you don't have the specialized equipment necessary to detect and classify the type of potentially-hazardous invisible radiation. In certain specialized environments, like labs, reactors, and so forth, different shielding is used that is appropriate to the specific circumstance. For example, my school's nuclear reactor used water: as both coolant and shielding. For the ~ 1 megawatt PULSTAR, water is both safe and effective: but in general, unless you have an experienced team of nuclear engineers and physicists, plus the necessary equipment, to validate it, you can't be sure if water is effective shielding from your radiant energy source. Lead, as a "lowest common denominator," is the general failsafe for most cases. Nimur (talk) 14:56, 4 May 2012 (UTC)

(ec)To put down a few numbers: Density of lead is 11.34 g/cc, for steel is 7.75 to 8.05 g/cc. But according to File:Ironattenuation.PNG iron has a photon mass attenuation coefficient around 0.04 for many high frequencies. I found a university poster about lead shielding which drops nearly as low at a moderate frequency [1] but it looks like there are some lower values where it has an advantage. Should find better data but it looks like the difference might be more complicated (more directed toward some particular range of energies) than I thought... (Oh, that mass attenuation coefficient article shows File:Photon Mass Attenuation Coefficients.png, which is interesting - makes me wonder why they don't use an alloy... or would that not actually work in terms of covering the gaps?) Wnt (talk) 15:04, 4 May 2012 (UTC)

anti? pro? lead rant and soapbox
The following discussion has been closed. Please do not modify it.
I'm always much amused by the concern taken by individuals, organistaions, and governments over lead. Not because I don't think it is toxic (that seems well established), but because it is so ubiquitous in the environment. You need to keep things in perspective. Lead used as shielding in nuclear facilities is not going to get into people & hurt them. Lead used as shielding in medical facilities is not going to hurt anybody, as it is inside plastic or metal covering. Nuclear facilities are not that common anyway. Decades ago, upon testing for lead in children, they found it, at significant levels. They decided that paint was the problem, and in my country, lead has been banned from paint for decades. Still, whenever somebody sampled for lead in children, they still found it at presumably significant levels. Of course, if some young couple buy a cheap old house, and decide to sand it all back to bare timber for a nice DYI paint job, they spread that 60 to 90 year old lead around again... Then experts decided that lead in gasoline was the problem, so they banned lead in gasoline, 20 years ago. Still, whenever somebody sampled for lead in children, they found it, you guesed it, at much the same levels. I worked for >40 years for the phone company, mostly in areas concerned with cables. From the 1920's to the 1970's they used lead sheathed cable for all underground trunk and distribution cabling. The sheath when new was about 2.5 mm thick. The cables were pressurised with air by cylinders or compressors in each exchange. The air consumption was minute. Almost all of these cables were still in use in the 1990's and even later. The air consumption had become very high, requiring compressors running a lot of the time. Why? The old lead sheaths had become very thin, paper thin in some cases, so thin they are porous to air. You tell me - where has all that lead gone? Any every time some developer was to convert an old industrial or commercial estate into residential, and someone decides to take soil samples, they find lead .... 121.221.216.254 (talk) 16:07, 4 May 2012 (UTC) Cute rant, but lead levels in children have declined steeply with the removal of lead from gasoline. Putting lead into something that was burned by every vehicle in the country was, well, a documentably bad idea. --Mr.98 (talk) 16:31, 4 May 2012 (UTC) And a short sharp reply to my rant. Trouble is, there are statistics, and there are those that mis-use statistics. Your graph plots two things: 1) the number tested over the last 13 years, shown as increasing. Provided the statistical sample is large enough (which would seem to be the case), the number tested is irrelevant. What is relevent is that in my country and many others, lead was removed from gasoline over 20 years ago, not 13. Actually, in my country, it was removed 24 years ago. 2) the second and most important thing plotted in your graph is the number of children found over an (unspecified) level. This means nothing. If I plot a graph of people with more than a certain level of viruses in their bodies, by setting the level I could produce a result (number of people) varying from near zero to 100%. What you SHOULD graph is the % blood level by mass, or % tisue level by mass, of lead averaged over all children tested. You might find that the figure hasn't changed much. Children are not unaffected if the level is just below an arbitary criteria, they aren't suddenly significantly affected if they are just over an arbitary criteria. 120.145.32.74 (talk) 01:40, 5 May 2012 (UTC) I agree, that CDC graph is useless. It is a plot of children found over a totally arbitary value of 10ug/litre. It could have resulted from, for instance, a blood level averaged over all children dropping from 10.0 to 9.9 ug/litre. It is well known that lead in gasoline was just one of a multitude of sources. The Europeans, in wanting to bring lead levels in blood down, have tried all they can. 10 years ago they banned the use of lead in solder - surely a minute use compared to industry generally, and how on earth does the lead in solder, generally well inside electronic devices, get into children? They went on to ban the use of lead totally, though they had to allow the continued manufacture of lead acid car batteries - there just isn't a reliable, low cost, safe, and effective alternative. Outside of Europe, lead is present in all manner of things - including lipstick and other sorts of makeup. Wickwack124.178.63.42 (talk) 02:57, 5 May 2012 (UTC) I can't speak for Europe, but in America the statistics are extremely clear: since Lead paint was banned in 1978, along with the gradual phasing-out of Tetraethyllead as a gasoline additive from the late 1970s onward, there has been an extreme drop in blood levels of lead in young children (ages 1-5). To assert that there has been no reduction is ludicrous. -RunningOnBrains(talk) 03:31, 5 May 2012 (UTC) Here is another article summarizing some studies not covered in the linked graph. Every single study I can find (and there is are a lot of studies on the first page of simple google searches) shows a sharp drop in blood lead levels in every age group studied. I have no idea where you got the idea that blood lead levels have not been decreasing, but the data shows you are incorrect. -RunningOnBrains(talk) 03:42, 5 May 2012 (UTC) I will note that legislation barring or restricting the use of lead-based solder doesn't always have to be based in sometimes-questionable think-of-the-children reasoning. Eliminating lead-based solder may also reduce occupational exposures by individuals who work with it, reduce the amount of lead-containing waste that ends up in landfills, and cut back on lead exposure for the third-world workers who recycle our first-world electronics waste. TenOfAllTrades(talk) 03:50, 5 May 2012 (UTC) The articles cited by Runningonbrains are good, because they show data on actual blood levels (ug/L) (as well as the count above the arbitary 10 ug/dL limit). They do indeed show a roughly 5-fold reduction over 30 years in the USA. My (Australian) view that eliminating lead from gasoline had little practical effect stems from reading articles in Australian newspapers that lead me to believe the lead levels in blood in children are as bad as ever - in fact it has been a major controversy in Western Australia in recent years, in part because birds have been dying due to lead poisoning. However I have been unable to find any thing I can provide a link to, other than than limitted example surveys of counts over the silly 10ug/dL limit. Wickwack124.178.63.42 (talk) 04:01, 5 May 2012 (UTC) A lovely distraction, but utterly and obviously a soapbox. When in doubt of statistics or facts, just rant some more. This is both off-topic at this point and the ranter in question has yet to cite a single fact for his silliness and has admitted that they have no references for their ridiculous assertions. I'm hatting this. --Mr.98 (talk) 13:18, 5 May 2012 (UTC)

Boiling water

(In case you're not familiar with the matzo ball recipe here's one.) The matzo ball mix is formed into somewhat dense balls of the ensuing goop and dropped into a pot of boiling water, at which time the balls enlarge and become fluffy after about 7 minutes. What is it about boiling water that makes it work? Scientifically speaking, why doesn't this happen in still cold water? And if the matzo balls float (which they do), how does the 30-40% of the ball that sits above the surface cook? I'm assuming it's because it soaks up the water like chromatography. Is it the heat that causes the dough to expand and fluff? Sorry for asking like 5 questions in one. DRosenbach ^{(Talk | Contribs)} 19:34, 4 May 2012 (UTC)

It's the baking powder that causes the expansion. The sodium bicarbonate in baking powder decomposes in an acid-base reaction which releases carbon dioxide gas to form bubbles in the batter. Heat accellerates the decomposition of sodium bicarbonate. Roger (talk) 19:45, 4 May 2012 (UTC)

But they fluff even without the baking powder (although not as much) and what you're saying seems to suggest that the balls would fluff even if just placed in cold water, yet that doesn't happen. But thanks for the heat-related info. DRosenbach ^{(Talk | Contribs)} 20:21, 4 May 2012 (UTC)

Cold water would most probably dissolve the balls back to a (lumpy) batter if left long enough. Heat is needed to accelerate the bicarb decomposition - cold dough doesn't form bubbles at a high enough rate. Recipes that don't use baking powder must have another leavening agent instead. Roger (talk) 20:54, 4 May 2012 (UTC)

As Roger explains, it's not the water, it's the heat. Boiling water is extremely efficient at distributing heat evenly around the matzo ball, and keeping it at an almost constant 100 °C (212 °F), which keeps it warm enough to accelerate the reaction but cool enough so the dough doesn't burn. I'm sure there are other substances that you could use instead, maybe some sort of oil that boils around the same temperature, but I doubt you'll find one as unbiquitous, affordable, and non-toxic as water. As for fluffing without baking powder, I'm sure there are some other basic substances in the recipe which cause the same reaction, but at a much lower yield. -RunningOnBrains^(talk) 22:21, 4 May 2012 (UTC)

See also: dumplings. As with any cake or bread, air pockets will expand the mixture as it's cooked, because warm air expands, and because water escaping as steam does the same. Extra gas from baking powder or yeast simply add to this effect. 86.140.54.3 (talk) 16:22, 5 May 2012 (UTC)

I think you intended to link to Matzah ball? Nil Einne (talk) 16:44, 5 May 2012 (UTC)

Hollywood etymology

What is the etymology of Hollywood ? --Pixeltoo (talk) 20:16, 4 May 2012 (UTC)

Holly + wood. The name was coined by the real estate developer H.J. Whitley, presumably in reference to the California holly. LANTZY^TALK 20:43, 4 May 2012 (UTC)

This article claims it comes from a pun on something a Chinese laborer said to Whitney, but that seems a little contrived to me, personally. This should really be on the Humanities or Linguistic desks; science it ain't. --Mr.98 (talk) 20:46, 4 May 2012 (UTC)

The name was originally applied to one particular real-estate development, but later applied to that suburb of Los Angeles. From there, since movie studios sprang up in that suburb, it came to mean "American films". Ironically, the studios have now largely moved out of Hollywood, to other LA suburbs, but the term remains intact, even copied, in terms like Bollywood and Dollywood. StuRat (talk) 22:21, 4 May 2012 (UTC)

Actually, per Hollywood#History, the name "Hollywood" was applied to the area long before the development which commissioned the Hollywood sign (which was actually named "Hollywoodland" (picture). The name is used repeatedly in this 1903 publication by the Historical Society of Southern California. The name supposedly came from Ivar Weid, a prominent investor in the area in the late 1800s, but since that part of the story is cited to an offline book, I have no way of verifying. -RunningOnBrains^(talk) 22:35, 4 May 2012 (UTC)

2 questions about a chemical solution

1.if the window stays open, a wasp or a fly could enter to the new room. there are types of flies that are very fast and are not easy to be killed swiftly. also a Anisoptera entered, and i had to kill her, sadly. it's such a beautiful animal. anytime i used Nerve agent to paralyze them from the very-fast flying speed.

what i ask is a method of getting the animals out to the open without (!!!) killing them (i would pass that if i can), and it also brings me to the next question in the subject:

2.how did people in ancient times fought such "intruders"? let's say i am an ancient Egyptian farmer living in the Nile delta, and anytime i get 4-6 of them into my dwelling. or let's say i am something else.. Aboriginal, or Thai, or whatever, in Ancient times. what methods and chemistries used by our ancestors to do this job?.

thanks. — Preceding unsigned comment added by 79.176.176.145 (talk) 20:59, 4 May 2012 (UTC)

I think the easiest way to get insects out of a building without killing them would be to use a net to catch them. As to what ancient people did to insects, I guess the same as most modern people: just hit them with an object to kill them. Or if there were many of them, maybe a net may have been more effective. I don't see why they would bother to use chemicals. - Lindert (talk) 21:47, 4 May 2012 (UTC)

Using nets inside seems risky. I picture lamps being smashed. StuRat (talk) 22:13, 4 May 2012 (UTC)

In the US we use window screens to keep insects out, and are amazed that many other nations don't. They keep out larger insects, although some get in when you open the door, and small insects, like fruit flies, can go through the screens.

For slow-moving insects, like many beetles, I can capture them by placing a glass over them on a wall, then sliding an index card or playing card between them and the glass.

For faster insects, a possibility might be to cool them down first, using a CO₂ fire extinguisher, which will slow them down enough to use my method with the glass and card. (It won't require very much CO₂, but they will recover quickly.)

Note that I don't just use the catch and release method for the insect's well-being, it also keeps disgusting bug guts off my wall. Capturing them with a glass and card is less work than cleaning the wall (especially considering that I will then have to clean the entire wall, since the "clean spot" will otherwise stand out. StuRat (talk) 22:03, 4 May 2012 (UTC)

I once again suggest my mother's favorite solution to this problem: a can of spray starch. Takes 1 second to dry, the insect falls to the floor unable to fly, and can be safely ejected in a manner of your own choosing. The spray is non-toxic, doesn't stain, and any overspray is easily wiped up with a damp rag.

--DaHorsesMouth (talk) 23:11, 4 May 2012 (UTC)

Insect repellent has a section on natural repellents. You could try spreading some of them around the window. As for in the past First Nations and Inuit had ways of keeping bugs away. See Insect Repellents and Insecticides, though bear fat may be in short supply, and here. Given that I would assume that the people in other countries had traditional methods for keeping pests at bay before modern times. CambridgeBayWeather (talk) 06:46, 5 May 2012 (UTC)

I think they just became accustomed to insects there. Heck, even in farms with livestock, everybody gets used to the flies. And before insects were known to spread disease (especially mosquitoes), they were just considered an annoyance. StuRat (talk) 06:54, 5 May 2012 (UTC)

I found these just now, All Natural Insect Repellent through the Ages: A History of Bug Repellent, A brief history of insect repellents, part 1, Earliest Known Bug-Repellant Plant Bedding Found at South African Rock Shelter, History of Insect Repellents and [www.researchinformation.co.uk/pest/2001/B106296B.PDF Insect Repellents – Past, Present And Future]. While I'm not sure that some of those would be classified as reliable sources the last one probably would. CambridgeBayWeather (talk) 15:14, 5 May 2012 (UTC)

Lions not on the Gulf of Guinea?

According to File:Lion distribution.png, Panthera leo was not historically present on most parts of the Atlantic coast of Africa between the mouths of the Congo and Mano Rivers. Why not? Nyttend (talk) 23:04, 4 May 2012 (UTC)

Lions live in the savanna, while those areas are tropical rainforest. The map File:800px-tropical wet forests.png has a green area showing the tropical rainforests in Africa. Notice how well it matches your map, but in reverse. Lions don't live in the forests. --Jayron32 23:54, 4 May 2012 (UTC)

Except for one very rare species. Clarityfiend (talk) 08:40, 5 May 2012 (UTC)

I was quite unaware that the southern DR Congo was predominately not rainforest. I was under the impression that most of the pre-European country (as well as northern Angola) was heavily forested, rather than savanna. Therefore, although I knew about the rainforest on the Gulf of Guinea, I didn't make the connection. Nyttend (talk) 12:43, 5 May 2012 (UTC)

What was the dominant large predator in that jungle region? SkyMachine ⁽⁺⁺⁾ 20:25, 5 May 2012 (UTC)

Probably the African leopard. Unlike lions, leopards are much more adaptable in their habitat preference. While lions are really restricted to savanna, leopards will pretty much range anywhere, from desert to rainforest and everywhere in between. --Jayron32 20:36, 5 May 2012 (UTC)