Wikipedia:Reference desk/Archives/Science/2014 March 5

= March 5 =

metamorohic rocks may have colored  bands
m — Preceding unsigned comment added by 172.1.205.91 (talk) 00:00, 5 March 2014 (UTC)
 * Yes, they may. -- Jayron  32  00:00, 5 March 2014 (UTC)
 * Metamorphic rock has a few pictures; ask if you want something more specific. Wnt (talk) 05:56, 5 March 2014 (UTC)
 * The colored bands arise where the metamorphic rock has been formed from sedimentary rock which has been "cooked" by the heat of the earth. Sedimentary rock has bands in it because it forms in different layers over many millions of years. The layers reflect different conditions on earth at the time they were formed. RomanSpa (talk) 14:49, 5 March 2014 (UTC)
 * The bands represent layers of different chemical composition. Exactly what colours predominate (the particular minerals that are formed) depends on the composition, the confining pressure (the effect of the overlying rock layers) and the temperature at the time of metamorphism - see also greenschist, blueschist, whiteschist for just some of the variety. Mikenorton (talk) 18:00, 5 March 2014 (UTC)

Why to sit on the Internet?
Why?Ah... — Preceding unsigned comment added by 1.84.43.208 (talk) 12:03, 5 March 2014 (UTC)


 * See here. The Internet has a mind of its own, it has made us dependent on it for its own purposes. Count Iblis (talk) 13:41, 5 March 2014 (UTC)
 * That website talks about the beneficial use and massive knowledge-base of the Internet. 140.254.227.87 (talk) 15:30, 5 March 2014 (UTC)
 * The brain rewards itself when you learn new information. This is thought to be one reason why some people become addicted to simply sitting there, clicking (damn you, Reddit).217.158.236.14 (talk) 13:57, 5 March 2014 (UTC)
 * Um. How does this address the question in any way? To be honest, I don't even know what the questioner is asking in the question. 140.254.227.87 (talk) 15:30, 5 March 2014 (UTC)
 * Well there are plenty of people who stand while using the internet. Probably rising with the growth in smartphones, but there are also those who try to stand regularly when at a desk  for various reasons such as the possible health benefits (compared to sitting). However it tends to be easier for people to sit for long period than to stand  so it's not that surprising most people sit. Nil Einne (talk) 15:32, 5 March 2014 (UTC)


 * To whoever closed this discussion: Please sign the top of your hatting, or add a signed comment saying that you closed it. We have agreed on the talk page that this is best practice.  SemanticMantis (talk) 16:05, 5 March 2014 (UTC)
 * The closer is IP 140.254.227.87 [//en.wikipedia.org/w/index.php?title=Wikipedia:Reference_desk/Science&diff=prev&oldid=598265605] i.e. the Ohio State IP editor who asks questions about Christian traditions etc. Nil Einne (talk) 22:30, 5 March 2014 (UTC)
 * He's the one identified as not a troll on the talk page, the one who complains about female operators on the computer desk. Given consensus, Nil, I suggest you not criticize him any further, he's to be given all leeway on the chat forum. μηδείς (talk) 01:33, 6 March 2014 (UTC)
 * 'Any further'? Also I don't see any complaints about female operators on the computing desk. Simply a few simple questions relating to female telephone operators which could not logically be intepreted as complaints about said operators. Nil Einne (talk) 11:39, 6 March 2014 (UTC)
 * Okay, complaining in the context of female operators, that they have wombs, are kept in glass cages, and only get paid 1/4 what men do. Not complaints about the women as individuals. μηδείς (talk) 17:23, 6 March 2014 (UTC)
 * Are you reading some sort of parallel world version of wikipedia? You first implied I had criticised the IP when I had not (or at least not in a fair while) and you continue to see stuff on RDC that doesn't seem to be there for me. Nil Einne (talk) 20:18, 8 March 2014 (UTC)

Are "Summa Technologiae" and "Profiles of the Future" outdated?
Dear Ladies and Gentlemen

I have read "Summa Technologiae" by Stanislaw Lem and "Profiles of the Future" by Arthur C. Clarke. Are these works outdated? Do they still have some interesting ideas that could become real or do these books lack much of modern days physics? Are there more modern books that cover a possible future much better?--92.105.189.138 (talk) 16:50, 5 March 2014 (UTC)


 * Clarke's general ideas on the exploration and exploitation of the solar system are still interesting, although he has probably got many of the details wrong. His descriptions of the celestial mechanics of this rely on Newtonian physics, which remains an excellent tool for describing the solar system in general terms. I recall that Clarke also predicts a far future development of immortality. This is certainly regarded by many people, notably transhumanists, as an attainable and desirable goal, though the process by which this will be achieved remains unclear. I haven't read the Lem book, so can't comment on that. Generally, books predicting the future get it wrong, for the obvious reason that each book only describes one possible future, but there are infinitely many possibilities. Such books are nevertheless worth writing and reading: by writing them, the author gives his contemporaries a vision to aim at, and a direction in which to exert their efforts to improve the life of mankind; by reading them decades or centuries later, we learn how people at that time thought about the universe, and what they valued, and may be able to make useful judgements about where things went "right" and where they went "wrong". Like science fiction generally, predictive literature of this kind tells us about the time in which it was written, but (like history generally) we can try to learn from it. RomanSpa (talk) 17:35, 5 March 2014 (UTC)


 * I wikilinked the works/authors in the original post for our convenience. :) Wnt (talk) 19:02, 5 March 2014 (UTC)

Thank you very much for your responses. @RomanSpa: do you have a book tip or so for me? I am asking, because I am looking since ages for a modern good book that deals with possible futures. — Preceding unsigned comment added by 92.105.189.138 (talk) 19:45, 5 March 2014 (UTC)


 * There are some interesting references in the article on futurology. RomanSpa (talk) 23:23, 5 March 2014 (UTC)


 * Hell, the Revelation of John doesn't seem outdated. No privacy, weapons that can strike anywhere in the world, drones armed with long term incapacitating "less than lethal" weapons, people needing modifications to their heads to get a job ... there can't have been any generation in history that this stuff made half as much sense to as it does to us. Wnt (talk) 00:44, 7 March 2014 (UTC)

Has someone read "Summa Technologiae"? This book seems to be quite rare (I bought my version in Munich, Germany).--92.105.189.138 (talk) 16:02, 8 March 2014 (UTC)

Unopened long life juice
What would happen if you put unopened long life juice in the fridge, then took it out the next day, put it in the next day and repeated the cycle? Would it alter the taste? — Preceding unsigned comment added by 82.40.46.182 (talk) 18:47, 5 March 2014 (UTC)


 * It would certainly limit it's life. If any bacteria are present, they will grow during the warm periods.  If they've managed to completely sterilize it, this won't happen, but other deterioration can happen.


 * For example, the juice may oxidize and turn a darker color. This is especially true of tomato juice.  There may be more leaching of chemicals from the container.  The juice may tend to separate.  All these things would happene eventually if left in the fridge, but would take longer. StuRat (talk) 19:28, 5 March 2014 (UTC)
 * I'm fairly sure the OP is talking about juice which doesn't need to be refrigerated and of a time frame where you would normally expect it be perfectly safe if stored outside the fridge. In other words, I don't think a limit on the 'life' (meaning the time it can be safely drinked without fear of microorganism caused illness) is a relevant factor unless you have some reason to think the microorganism growth rates will be higher than under normal non refrigerated conditions, they are more likely to release toxins or similar, or that the seals will break. Nil Einne (talk) 22:26, 5 March 2014 (UTC)


 * In biology labs, where many exotic enzymes are stored, people worry a lot about freeze-thaw cycles, but basically ignore refrigerate-thaw cycles. I really wouldn't expect anything different from the average of the usual effects of putting something in the refrigerator and taking it out.  But, this being biology... you never really know until you do the experiment - for example, conceivably, there could be some resistant spore that responds to the temperature cycles by germinating, etc.  But some things are so unlikely I can't imagine testing them. Wnt (talk) 23:43, 5 March 2014 (UTC)
 * And that's when this happens. InedibleHulk (talk) 02:00, 6 March 2014 (UTC)

Angiogenesis inhibitors
According to Dr. Joel Fuhrman (3 Steps to Incredible Health! on PBS), mushrooms prevent cancer tumors by preventing blood vessels from growing which supply the tumor with nutrients. In that case, wouldn't mushrooms inhibit wound healing and be dangerous for children, similar to thalidomide ? Or is this danger only in utero ? If so, does the placental barrier protect the fetus from the angiogenesis suppressant effect of mushrooms ? StuRat (talk) 19:23, 5 March 2014 (UTC)


 * Fascinating lead -- this turns out to be Phellinus linteus, used in traditional Korean medicine, and also in Japan and China. I'd just about despaired of finding traditional herbal remedies that could tackle cancer because of the disconnect between therapy and results, and this might be a pleasant exception - however, I haven't yet tracked down proof that ancient practitioners were using it specifically for cancer.  It is a rare mushroom, not the usual culinary fare, and I see nothing in PubMed on teratogenicity - though there may be useful lore from more traditional herbal physicians on the issue.  But I would indeed think that anyone taking enough for its antiangiogenic effects to be relevant, by comparison to thalidomide, would need to be very wary of the possibility of other effects also. Wnt (talk) 20:38, 5 March 2014 (UTC)


 * Stu's question is phrased in terms of (general?) "mushrooms," while the paper you cite lists several specific families and species, and even some specific compounds that have anti-tumor effects (e.g. "β-(1 → 3) linked glycan" for Phellinus spp.) Your assessment seems correct, I just want to be clear that the action in humans of one compound in one fungus doesn't say much of anything about any other fungus, let alone how the therapeutic dose might compare to a dietary/culinary "dose". SemanticMantis (talk) 21:23, 5 March 2014 (UTC)


 * True. "In general", eating mushrooms will kill you. Wnt (talk) 22:30, 5 March 2014 (UTC)

He didn't specify which mushrooms have this effect. So, is it limited to certain species, or is that just the ones they happened to study ? StuRat (talk) 23:08, 5 March 2014 (UTC)


 * Ah, well he really should have specified! Anyway, the article Wnt links to above seems to be freely-accessible, and it contains a list of families/species with "anticancer potential" (I haven't read the whole article, but unless it says otherwise we shouldn't assume that all of those are "anticancer" effects are due to a specific antiangiogenic mechanism). Here is the figure with some photos and scientific names . I didn't see any "no effect" fungi listed, but those kind of negative results are not popularly recorded/published (it's a shame). This article is a summary of dozens of other articles, those source articles may mention briefly some "no effect" fungi. In absence of evidence otherwise, I personally would assume that any medical properties and compounds are completely unique to at least a genus, if not species. Mycology is crazy, and, in my limited experience, there are more exceptions than rules. SemanticMantis (talk) 00:09, 6 March 2014 (UTC)


 * In general, I'm prone to be persuaded that those showing anti-cancer activity in mice may be anti-cancer agents, with the caveat that many medical treatments that have absolutely dramatic effects in mice turn out to be less than satisfactory in human trials (notably endostatin, perhaps angiostatin) so that is not a guarantee, and some mouse models of cancer treatment are even less persuasive than others. (very large doses, testing tumor cells that are foreign to the mouse, testing in immunocompromised mice, etc.)  Those with tests just on cell lines... well, you can show anything in the right cell line.  But if a mushroom is edible anyway, and not expensive, there's little downside to trying it provisionally.  There were different mechanisms for the mushrooms listed, but those referencing mice were Phellinus, Agaricus, Grifola, Hericium, Cordyceps, Inonotus obliquus, Funlia, Antrodia.  The authors mention a history of anti-cancer use in herbal treatment for Inonotus -- short of genuinely scientific controlled medical studies on humans, this is to me the most hopeful indication. Wnt (talk) 07:21, 6 March 2014 (UTC)

Thanks for the answer so far, but nobody has yet addressed why such 'shrooms aren't harmful to children, who need to grow new blood vessels as they grow. StuRat (talk) 15:55, 6 March 2014 (UTC)


 * @ user WNT - thalidomide isn't particularly dangerous to children.  Chemie Grünenthal, thalidomide's developer and first marketer, successfully sold thalidomide as a sedative for young children in the late 1950s-early 1960s (as "Contergan Saft").  But when given to pregnant women, thalidomide deforms fetuses rather reliably, causing horrible somatic injuries (such as missing limbs) in the newborn.  You've confused "developing fetuses" with "children" there.  Thalidomide has actually been studied to treat one condition specific to children, chronic bullous dermatosis of childhood.


 * Actually, thalidomide has some intriguing uses in the treatment of Hansen's Disease ("leprosy") and a number of rare cancers and immune disorders, and is used to treat leprosy/Hansen's Disease (its only approved use - all other uses are, at present, "off-label," accounting for the US$300 million market for a drug only approved to treat one comparatively rare condition) allaying considerable human suffering. As Paracelsus said, the poison is in the dose (either too much of a good thing, or a drug used in the wrong patient population).  Thalidomide isn't a particularly evil drug; some motion sickness remedies, and some stomach acid blockers used for the elderly (such as misoprostol) have just as much teratogenic potential, or even more. loupgarous (talk) 19:25, 6 March 2014 (UTC)


 * @ StuRat, this is "original research," but I'm betting that the antiproliferative effects of thalidomide and the chemicals in some mushrooms are amplified in the fetus as opposed to a post-partum child (though I'd be very nervous about feeding any of those things to a child younger than about six, a stage when the connections in the nervous system aren't completely formed in the child). It's a matter of how much of the chemical is available to act on how much neural and other tissue - the fetus is dramatically more vulnerable to angiogenesis inhibitors compared to a child just on the basis of its comparatively smaller mass, and because so many crucial developmental stages occur in utero, not post partum. loupgarous (talk) 19:53, 6 March 2014 (UTC)


 * I said teratogen; I assumed StuRat meant dangerous for children who would suffer the effects after birth. When dealing with serious potential teratogens (which include some drugs presently on the market) any woman needs to seriously consider the risks should she inadvertently become pregnant, and any man should avoid situations where a woman might handle or otherwise become contaminated by the pills. Wnt (talk) 00:39, 7 March 2014 (UTC)

Structural engineering question
I often come across different supports and member types in structural engineering but its all very theoretical. So what are some practical real world (outside the lab) examples of the following?

- Roller support - pin support - fixed end support - beam - works in bending and shear - bar - works in axial load only - tie - resists tensile forces

What do they actually look like? I only ever see these in a lab or on a diagram and its quite hard to find anything on google. Clover345 (talk) 22:04, 5 March 2014 (UTC)


 * Of course, in the real world, any type of support will provide some resistance to other types of forces, too.


 * Beams: You have those in the ceiling of a house, for example (they are likely to be uncovered in the basement or garage or perhaps in the main rooms of a rustic house). Those wooden beams provide resistance to bending and shear, but also provide resistance to compression, tension, twisting, etc.


 * Roller supports: I've seen those on assembly lines, say where the line ends in a chute. That allows gravity to feed the items down the chute with minimal friction, and prevents scratching you might get if the item slides down a low friction surface (say with a grain of sand in between). StuRat (talk) 22:40, 5 March 2014 (UTC)


 * [ If I understand your description, I think that's not a roller support, according to my link below. I think it's a "roller conveyor" (passively or gravity powered), like these ] SemanticMantis (talk) 00:41, 6 March 2014 (UTC)


 * Yes, it's a roller conveyor, but isn't that a type of roller support ? StuRat (talk) 16:00, 6 March 2014 (UTC)
 * I suppose it depends on how specific you want the definitions to be. Usually, I see "roller support" to mean situations where the structural member isn't supposed to leave the roller (outside of failure), like the bridge example below. But I guess that isn't strictly part of the definition. Indeed, if you have a box on a roller conveyor, then is entirely supported by rollers, even if it is only supported by each roller for a short period of time. SemanticMantis (talk) 22:00, 6 March 2014 (UTC)


 * Pin supports: How about a wheelbarrow axle/wheel ?


 * Bar: I hadn't heard it called that before, but a concrete column might qualify. Those support a compression load well, but are very poor at any other type of loading. StuRat (talk) 22:40, 5 March 2014 (UTC)


 * Perhaps the best example of a pin support is a door hinge. Justin15w (talk) 23:02, 5 March 2014 (UTC)


 * A roller support allows for lateral movement of a structure. Google "roller support structure" for a picture.  A fixed end support is just that - an end of the structure tied or bolted into the ground.  For the tie, think about the ceiling beams in your house - the ties are the horizontal beams that connect the walls to each other to prevent the walls from falling over outward.  They provide tensile support.  See http://web.mit.edu/4.441/1_lectures/1_lecture13/1_lecture13.html for explanations, diagrams, pictures. Justin15w (talk) 22:47, 5 March 2014 (UTC)
 * Steel bridges are a good example for roller supports, you don't want to crack a support when the bridge expands in the sun. Also pins are commonly used to tie steel members together in trusses. Dmcq (talk) 23:20, 5 March 2014 (UTC)


 * This page from an MIT course has some decent diagrams and examples (Sorry, just realized Justin15w just game the exact same link :). If I'm understanding correctly, isn't the cantilever on a Crane_(machine) a "fixed end support" system? You can see them all over most big cities. Also, if you are in a course discussing such matters, ask your instructors for real-world examples! That is their job, and they are probably more expert than a bunch of strangers on the internet ;) SemanticMantis (talk) 00:31, 6 March 2014 (UTC)