Wikipedia:Reference desk/Archives/Science/2012 September 8

= September 8 =

Gold tunnels
Does anyone know what the long lines located at 64.03139°N, -139.23222°W are. They are at Bear Creek in the Yukon not far from Dawson City. Bear Creek was a placer mine (http://www.historicplaces.ca/en/rep-reg/place-lieu.aspx?id=6242) and I'm guessing that they might have been formed by hydraulic mining but I would like to know for sure and what they are called. CambridgeBayWeather (talk) 02:56, 8 September 2012 (UTC)


 * I see a large number of bluish-white, semicircular plates sticking out of the ground and resting against each other to form long "caterpillars". I was going to suggest that they might be tailings, but I'd expect large, random piles. StuRat (talk) 03:03, 8 September 2012 (UTC)


 * If you look at Google street views from the Klondike Highway thereabouts, it's clear that the platelike appearance from the air is just caused by shallow transverse ridges in the "caterpillars". It must have somthing to do with how succesive loads of waste rock were dumped from trucks or otherwise added to the piles. Deor (talk) 14:52, 8 September 2012 (UTC)


 * Yes, I agree. From the street view it looks like normal dirt.  Odd that the satellite view has the strange blue-white color, although I have seen strange false-color images in the satellite view before.  They seem to use some type of algorithm which replaces the color in some circumstances.  For example, I've seen them replace grass-less areas in shadow with images of grass.  StuRat (talk) 17:36, 8 September 2012 (UTC)


 * TopoQuest (one of the links from that maps page) marks it "Waste". —Tamfang (talk) 05:48, 8 September 2012 (UTC)
 * They're dredge tailings .  Sean.hoyland  - talk 15:09, 8 September 2012 (UTC)
 * Thanks. I never thought to look through Panoramio or to see if there was a street view. CambridgeBayWeather (talk) 16:02, 8 September 2012 (UTC)

why does some ceramic heat up in the microwave?
I have two bowls from a set of six, apparently differing only in color. They're a glazed ceramic that chips easily, made in Japan probably 1975–1980. One I can put in the microwave for several minutes, long enough to boil the liquid inside, and then hold by the handle with my bare hand. The other, after half a minute in the oven, will burn my hand through a hot pad, even though the liquid is still cold. Any idea why they should be so different, or why ceramic would heat up in a microwave at all? (I assume it has to be s.t. in the glaze. The one that stays cool is lemon yellow, the one that heats up ocher.) — kwami (talk) 04:39, 8 September 2012 (UTC)


 * Well, the fact that some ceramics contain more water than others, may play a role. Plasmic Physics (talk) 05:38, 8 September 2012 (UTC)


 * But more than water itself? + should be the same ceramic inside. — kwami (talk) 06:50, 8 September 2012 (UTC)


 * My guess is that metal content in the ceramic is more likely. If it is heating faster than the water it seems that water content it unlikely. --BozMo talk 06:53, 8 September 2012 (UTC)


 * Maybe a metal-based pigment in the glaze on one. It's remarkably strong effect, though. Also, if metal's in the glaze, I would assume it's oxidized, and you wouldn't get the same heating effect then, right? — kwami (talk) 06:57, 8 September 2012 (UTC)


 * "s.t." ? Is that some type of metallic glaze ?  I hope it isn't lead. StuRat (talk) 06:59, 8 September 2012 (UTC)


 * ("Something".) Yeah, I hope not lead: I've been using it for years. — kwami (talk) 07:37, 8 September 2012 (UTC)


 * There is a simple, non-destructive test for lead, some stores here were offering it on their lead-laden toxic Chinese products last xmas. On the plus side, if the heat is all in the glaze, it should cool off quickly, if you just let it sit for a minute. StuRat (talk) 17:11, 8 September 2012 (UTC)

I don't think there's anything particular special about it. Every material is going to have its own opacity to the wavelengths emitted in the microwave. I'm not a material scientist, but I'm willing to bet the initial research into microwave-resistant ceramics amounted to putting them in a microwave and seeing what happened, rather than worrying about what its chemical makeup was. The specific heat of your particular ceramic will also play a role. Someguy1221 (talk) 09:04, 8 September 2012 (UTC)


 * "putting them in a microwave and seeing what happened" is what they did for the article, "The Application of Microwave Energy in Mineral Processing – a Review". For interest, it has a table of various minerals together with the temperatures they reached after 1 and 5 minutes in a domestic microwave.  Sean.hoyland  - talk 09:58, 8 September 2012 (UTC)


 * I hope they were large samples, since some small samples might explode after 5 minutes of nuking. StuRat (talk) 17:09, 8 September 2012 (UTC)


 * Wouldn't nuking any mineral sample result in the instant vaporization of said sample? And how would they pry loose enough nukes from the federal government to do that? Whoop whoop pull up Bitching Betty 14:04, 9 September 2012 (UTC)


 * Not sure if you are serious or not. "Nuking" is common slang for microwaving, at least here in the US. StuRat (talk) 03:32, 10 September 2012 (UTC)


 * 20g samples with a particle size of 0.2-0.5mm. Chalcopyrite reached 780C in 1 minute. The quartz result, 140C, in 1 minute seems surprising.  Sean.hoyland  - talk 17:23, 8 September 2012 (UTC)


 * Geez, 780°C in one minute ? At that rate it probably would explode in 5 minutes.  Presumably they stopped nuking it before that ? StuRat (talk) 17:28, 8 September 2012 (UTC)


 * Well, chalcopyrite is pretty close to metal in a microwave - it has a resistivity in the 10-3 to 10-5 range, comparable to amorphous carbon.  Note it is CuFeS2. Wnt (talk) 19:13, 8 September 2012 (UTC)

"Every material is going to have its own opacity". Sure. But here we have two bowls from the same set, differing apparently only in color, which heat up very differently.

"if the heat is all in the glaze, it should cool off quickly". Actually, no: After 5 minutes it will still burn my fingers. Ceramics tend to have low heat conductivities. — kwami (talk) 21:57, 8 September 2012 (UTC)


 * That's surprising, as the heat isn't actually in the ceramic, it's in the glaze. StuRat (talk) 22:00, 8 September 2012 (UTC)


 * I am not sure how StuRat gets his answer (I don't contest it but have no reason to accept it), but Someguy's is the correct one, it simply depends on the absorption spectrum of the material (does it get excited by microwaves, reflect them, or let them pass) and is exacerbated by the specific heat. There is no way for us, obviously, to test a ceramic (about as vague a term as metal) for its contents and contaminants over the internet. μηδείς (talk) 03:57, 9 September 2012 (UTC)


 * To which answer do you refer ? If it's that the heat must be in the glaze, that follows from the only difference between the ones that heat up and those that don't being the pigments in the glaze.  Although I suppose it could somehow work like the greenhouse effect, in that the glaze lets microwaves in, but not out, but I have difficulty imagining how this would work. StuRat (talk) 03:53, 9 September 2012 (UTC)


 * That the glaze is the thing. You would seem to be right if you mean in the case of identical ceramics differing only in glaze.  Reflection probably matters, not insulation. μηδείς (talk) 03:57, 9 September 2012 (UTC)


 * OK, I see what you're saying, that the cool mugs have a glaze which reflects microwaves, while the hot mug's glaze allows the microwaves to pass, where they then heat the ceramic underneath. I was thinking something in the glaze was absorbing the microwaves directly on the hot mug's surface.  But, I agree, given the additional info of the mugs staying hot for a long time, it sounds like the microwaves were not absorbed directly by the glaze and converted to heat there. StuRat (talk) 04:04, 9 September 2012 (UTC)


 * Absorption, transmission, reflection. Looking all the way back to the original question, you could have a glaze that reflects the microwave frequencies found in the oven, and another that simply transmits it through to the ceramic underneath. Or one glaze that reflects and another that absorbs. Or one glaze that transmits, one that absorbs, and a ceramic that transmits efficiently in both bowls. Or the ceramic may actually not be the same material even within the set. Or the glaze may be a different thickness on different bowls. And if it's the glaze that's absorbing, how well the heat would transfer to the ceramic is another question entirely. The OP is free to sand the glaze of each bowl and tell us what changes, which may be the only way to find out for sure. Someguy1221 (talk) 04:02, 9 September 2012 (UTC)


 * "Huston, we have consensus." μηδείς (talk) 04:14, 9 September 2012 (UTC)


 * Do you mean Houston, or are you telling Anjelica Huston ? StuRat (talk) 04:29, 9 September 2012 (UTC)


 * I was wondering why that looked wrong when I typed it. μηδείς (talk) 15:32, 9 September 2012 (UTC)


 * StuRat and others seem to assume that any heat produced in the glaze will stay there. If the glaze absorbs microwaves, it will tend to heat up the ceramic underneath. Ceramics generally have high heat capacity and will stay hot for a long time when heated. I think it is most likely that one color glaze absorbs microwaves and the other transmits them. This would probably be much more common, except that manufacturers have abandoned glazes that absorb microwaves, so you don't see this on modern products.--Srleffler (talk) 17:57, 10 September 2012 (UTC)

Intelligence and drug use
Why are smart people more likely to do drugs? It doesn't make any intuitive sense, but the data show a definite correlation. --168.7.239.137 (talk) 05:13, 8 September 2012 (UTC)


 * . If you're going to ask a question that makes an assumption, you'd need to first establish that your assumption is correct.  What data are you using for your assumption here? -- Jayron  32  05:16, 8 September 2012 (UTC)


 * What are you calling an "assumption"? —Tamfang (talk) 05:51, 8 September 2012 (UTC)


 * Well, obviously, a question that asks "why?" assumes the statement it asks "why?" about to be itself true. "Why are smart people more likely to do drugs?" assumes the statement "smart people are more likely to do drugs?" do be verified.  I have yet seen no evidence presented by the questioner, or anyone speculating below, that that is true.  I don't say that it is, and I also don't say that it isn't, but until that is resolved, we can't answer the "why?" part.  -- Jayron  32  14:33, 8 September 2012 (UTC)


 * The wording of the question strongly implies that the OP would have assumed the opposite, but was surprised by unspecified "data" to the contrary. The lack of citation does not make the statement an "assumption". —Tamfang (talk) 03:23, 9 September 2012 (UTC)


 * Let's make this easier for you to understand. If I ask "Why is the moon made of green cheese", that question is unanswerable because the moon actually isn't made of green cheese.  Insofar as we have not yet established that smart people are more likely to do drugs, we can't answer "why" they do more drugs until we can know if they do more drugs.  The question as asked has an embedded statement which has not yet been shown to be true yet.  -- Jayron  32  03:30, 9 September 2012 (UTC)


 * Perhaps smart people are more curious / more easily bored / less likely to accept "drugs are Bad because I Say So" / ... —Tamfang (talk) 05:52, 8 September 2012 (UTC)


 * Or perhaps they are more likely to have money to pay for them. Show us the data... --BozMo talk 06:52, 8 September 2012 (UTC)


 * Perhaps they have more brain cells in need of killing ? :-) StuRat (talk) 07:03, 8 September 2012 (UTC)
 * That was funny, I hope the mavens don't press you to death under heavy stones because of it. But Tamfang has the right serious answer. μηδείς (talk) 03:36, 9 September 2012 (UTC)

Among the students at the school I'm part of, it's the dopes who smoke dope. HiLo48 (talk) 07:14, 8 September 2012 (UTC)


 * Also, "do drugs" is pretty vague and all-encompassing. Different substances show different user demographics, for all kinds of reasons.  You'd have to point us in the direction of your data to give us a chance of saying anything useful about it. -  Ka renjc 09:44, 8 September 2012 (UTC)


 * True, especially if you include legal drugs, like caffeine: "Mathematicians are biological machines designed to convert coffee into theorems". StuRat (talk) 17:15, 8 September 2012 (UTC)


 * The OP may have skimmed across articles by authors prominent in certain publications, such as Satoshi Kanazawa, who tends to get eye-grabber headlines on his articles such as "Why intelligent people use more drugs" (in which artcle in Pyschology Today - which if you actually read it, does not asert or demonstrate that the title is true, but it does list a number of factors why folk may do drugs in spite of their actual or assumed intelligence.)
 * For every journal article that talks about intelligent users doing drugs, there is probably 100 articles demonstrating a negative correlation.  Many workers in the field of drug rehabilition consider that drugs ranging from pot to heroin, over time, reduce intelligence.  See e.g., http://scienceblog.com/community/older/2002/G/20021645.html.
 * However, having significant experience in working in a not-for-profit organistion offerring programmes to assist drug users, I have come to the view that drugs (mainly) do not cause intelligence to fall, instead low intelligence makes drug use more likely. In other words, the lower intellence reported is drug users by many investigators was not due to the drugs reducing intelligence, the the statistically low inteligence reported was due to it being low to start with.  After all, drug users generally don't get tested before they take up drugs.  When we found a new drug user, or a new (to us) drug user came to us wanting to get off drugs, we had a standard procedure.  One of the things we did was review their life with them, for a number of reasons.  We pretty often found that they had done lots of dumb things apart from taking drugs, and had lots of indicators - eg poor school performance, trouble with the law, etc, before starting on drugs.  In some cases, dumb though it is, their life was so stuffed up, doing drugs was the smartest thing they did!
 * Intelligence is multidimensional. A person may score high in applying logic or be able to do math, but may be socially inept.  High capability in logical thinking may reduce the chances of doing drugs, but social ineptness may increase it.  It is well documented that humans are not good at risk assesment.  In balancing the potential risk of addiction against the certainty of getting high by trying a drug your friend is offering is an assesment that many find difficult to properly make.
 * Never make the mistake of thinking people who do well at school, or even at university, are thereby or must be intelligent. For example, a kid at school who is socially inept and stupid may end up with no friends - so he can spend more time at home doing his homework.  When I was at high school, I did no homework.  Naturally I did not score well in tests and exams. That does not make me dumb - it might mean I was lazy.  Later on I did however go to uni and graduated with honours - because I found the course interesting, and I wanted the qualification - so I worked hard, had good time management, and the subjects were not actually all that intellectually challenging.  That does not make me bright either - maybe just determined.
 * So may other factors influence whether or not a person does drugs. These factors are often obscurred or not spelled out in statistical studies, and often overide the otherwise reluctance of an intelleigent person to do drugs.  Factors include: whether or not parents or siblings do drugs, peer pressure, availability, in or not in a loving relationship.  Loners often don't know where to get drugs - you can't do drugs if you don't know where to get it.  But if a loner does get to tray drugs, his/her loneliness may increase the consumption.
 * Wickwack121.221.223.160 (talk) 11:00, 8 September 2012 (UTC)
 * Wickwack121.221.223.160 (talk) 11:00, 8 September 2012 (UTC)


 * Given your experience in the field, the conclusions you draw are necessarily based on selection biased data. Ssscienccce (talk) 14:11, 8 September 2012 (UTC)


 * Regarding inhalant abuse, studies showed social users to be of average intelligence, isolate users were of above average intelligence. (source NIDA Research Monograph 129 Inhalant Abuse: A Volatile Research Agenda)
 * The (second?) most productive mathematician in history was a long-term amphetamine user.
 * The Satoshi Kanazawa article can be found here. Ssscienccce (talk) 13:47, 8 September 2012 (UTC)


 * Presumably Ssscience's comment about selection biased data is based on it being the folk I came in contact with had, mostly, come to us because they could not succesfully manage their life on drugs. A drug user succesfull in life presumably would not require or ask for help.  But how many illegal hard drug users are successful in life?  Most users of heroin, e.g., will end up either in jail, dead, or with an assistance programme.  That is not nearly so much the case with things like ecstacy, but long term users will have problems.
 * Judging from the Paul Edros article linked ("Most productive mathematician"), he was a real weirdo, and perhaps some sort of savant. In any case specific examples do not rule out a trend.  Famous examples of illegal drug users include Paul MacCartney and Mick Jagger.  These are undoubtably intelligent, capable chaps very succesful in life.  But they are certainly exceptions.  Wickwack120.145.58.3 (talk) 15:39, 8 September 2012 (UTC)


 * The big problem with this question is that "drugs" aren't a clade; they're not even really being defined. What illegal drugs have in common is only that they're illegal.  There are some obvious cases where actions such as huffing (which come to think of it more or less isn't an illegal drug...) can damage the brain.  In some others the data is dubious or nonexistent.  Some people claim that nootropic drugs even increase intelligence, but I would take such claims with a grain of salt - basic evolutionary theory would suggest there is a pretty high bar toward making a drug that is actually good under all circumstances, which means that most positive data of this type should be expected to be a flash in the pan, one circumstance or one specific genetic background that doesn't reliably reproduce, unless perhaps there is some physical or aging-related downside.  But I firmly believe there will be many drugs which either have no effect, or whose effects are so pleiotropic and difficult to analyze (even philosophically, if perfect data were available) that no overall conclusion can be made. Wnt (talk) 17:33, 8 September 2012 (UTC)


 * Given the indication of the solvent use study, that people with above average intelligence are more likely to use on their own, one could hypothesize that more intelligent drug users are more likely to keep their habit a secret. But I'm not sure there even is a discrepancy to be explained. No one is saying drug users are succesful in life. The claim of Satoshi Kanazawa seems based on reasonable grounds: prospective generational cohort studies are well suited for examining such a correlation. The least one can say is that, barring attrition effects and false answers, the correlation exists in the group of Britains born in one specific week in 1958.
 * Been searching for other studies showing a negative correlation between drug use and IQ, but so far nothing. I remember one study about smoking and IQ, that was reported as showing smokers had lower IQs. If I recall correctly the havy smokers scored worst, the group of light smokers scored better than both heavy and non-smokers. I did find this statement in a podcast transcript : "I don’t think we ever found another group of people so defined as a group who had a higher rate of addiction and alcoholism than card-carrying members of Mensa." More support for the OP's assumption... Ssscienccce (talk) 22:42, 8 September 2012 (UTC)
 * Been searching for other studies showing a negative correlation between drug use and IQ, but so far nothing. I remember one study about smoking and IQ, that was reported as showing smokers had lower IQs. If I recall correctly the havy smokers scored worst, the group of light smokers scored better than both heavy and non-smokers. I did find this statement in a podcast transcript : "I don’t think we ever found another group of people so defined as a group who had a higher rate of addiction and alcoholism than card-carrying members of Mensa." More support for the OP's assumption... Ssscienccce (talk) 22:42, 8 September 2012 (UTC)


 * Can't find any papers showing a negative correlation between drug use and IQ? There's heaps.  I gave you one in my ealier post.  Here's another: http://www.medicaldaily.com/articles/11758/20120827/teen-marijuna-use-linked-to-lower-iq-in-middle-age.htm.  Wickwack120.145.58.3 (talk) 02:59, 9 September 2012 (UTC)
 * That study is about the effects of drug use. I was looking for studies that disprove the OP's assumption and Kanazawa's findings, i.e. studies that would show children with higher IQ scores being less likely to use drugs later in life. To quote the Kanazawa article: British children who are more intelligent before the age of 16 are more likely to consume psychoactive drugs at age 42 than less intelligent children. No one claims that drugs make you more intelligent, far from it. That's what makes the findings remarkable, because they show that smart people are more likely to make bad choices. Ssscienccce (talk) 18:30, 9 September 2012 (UTC)
 * Yes, I know that.  My point that I made earlier is that rather than drug users being more intelligent as the OP claimed, ther is a multitude of papers that show a negative correlation - but researchers have tended to interpret the negative coorrelation as indicating that drugs reduce intelligence, instead of assuming that intelligence was lower to satrt with.  (Something that seems obvious from actually working with drug users, instead of just sitting at a desk looking at stats).  Wickwack124.178.174.234 (talk) 08:24, 11 September 2012 (UTC)

I suspect drug use is more likely at the top and bottom (but not extreme bottom) of the intelligence curve for different reasons. The top is curious, risk-seeking, self-medicating, and has no respect for authority. The low range also self-medicates and has little respect for authority. The middle range is conventional and less likely to need to or want to self-medicate. That's all OR on my part. μηδείς (talk) 03:42, 9 September 2012 (UTC)
 * Really, I can't say that any of my fellow mensans would agree with that generalisation. Plasmic Physics (talk) 08:19, 12 September 2012 (UTC)

elecrostatice
elecrostatice forces between two charges are called central.why? — Preceding unsigned comment added by Parinoor (talk • contribs) 08:24, 8 September 2012 (UTC)


 * I'm not sure what you mean by "central". Do you mean it's called a fundamental force? If that's what you're asking, then the answer is in the introduction of that article, "An interaction is fundamental when it cannot be described in terms of other interactions". Someguy1221 (talk) 09:09, 8 September 2012 (UTC)


 * A central force in physics is a force that is always directed to, or comming from, an apparent central point. Examples are gravitational force, which for example appears to come from the centre of gravity of any object, and a central electrostatic force, which comes from a point charge/source.  Note that electrostatic force may be between two parallel planes each having distributed charge - in this case it is not a central force.  Engineers speak of lines of force (like in magnetic lines of force); the lines spread out radially and equidistantly from a central point from an object exerting a central force; for a non central force, the lines of force will be parallel or some other configuration.  Wickwack121.221.223.160 (talk) 10:30, 8 September 2012 (UTC)
 * See Central force.--Srleffler (talk) 18:01, 10 September 2012 (UTC)

Diseases crossing the Brain-Blood Barrier
Hello,

I write to you with an inquiry about the Brain-Blood Barrier (BBB). Having read up on its nature on Wikipedia and in my books I have learnt a few things about how through transcytosis matter can flow through the barrier. However, when mentioning diseases such as progressive multifocal leukoencephalopathy and researching into the JC virus, little is uncovered on Wikipedia as to how the virus or other viruses can transfer past the barrier. Could I please ask you which methods are utilized by the virus, and perhaps (since it's so related) how come the ability to cross the barrier seems correlated to the immune system?

Thank you in advance.

88.90.168.15 (talk) 15:35, 8 September 2012 (UTC)


 * The lede to our blood-brain barrier article says it stops large objects, like bacteria, and hydrophilic molecules, but allows others through. Viruses certainly are not large.  I'm not sure if they are hydrophilic, however.  The other approach is to attack the barrier directly, by destroying the cells which compose the barrier.  Here the immune system is important in preventing such an attack from succeeding.  Once breached (and perhaps repaired), the barrier then can become a hindrance to the immune system, as it also limits the ability of immune cells to pass. StuRat (talk) 17:23, 8 September 2012 (UTC)


 * Viruses must have a mechanism of crossing the cell membrane, or they won't be able to reproduce. But only a few types of viruses are able to make it through the BBB if it is intact.  One very well known example is rabies, which is taken up by nerves in the periphery and transported along nerve fibers into the CNS. Looie496 (talk) 17:41, 8 September 2012 (UTC)


 * The best source I can find is http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2928669/, a freely available paper from 2010 that specifically addresses this question -- it shows evidence that the virus gets into the brain via B cells of the immune system. Looie496 (talk) 17:37, 8 September 2012 (UTC)


 * Thank you Looie495, this is an excellent answer to my question. 88.90.168.15 (talk) 23:40, 8 September 2012 (UTC)

How do non-brain cancer cells cross the BBB? Do they just push their way inside? μηδείς (talk) 03:34, 9 September 2012 (UTC)


 * This is outside my domain of expertise, but here is what I can make out. The BBB is formed by endothelial cells, which form the lining of blood vessels in the brain.  In order for cancer cells to metastasize into the brain, they have to first attach to those endothelial cells and somehow disrupt their ability to form a tight barrier.  The way they do that is not clearly understood -- this paper reviews what is known, at least for breast cancer, if you can make sense of it. Looie496 (talk) 03:48, 9 September 2012 (UTC)


 * Yes, that's exactly what I suspected and why I said "push their way in". μηδείς (talk) 04:12, 9 September 2012 (UTC)