Wikipedia:Reference desk/Archives/Science/2015 January 19

= January 19 =

Handbooks vs. lectures
Some centuries ago, copies of texts were expensive, so, a lector would dictate a text to his students, who would copy it to have access to it. But what is the purpose of lectures today? Why do colleges keep offering them, and still tape them? Shouldn't every college student be able to work his way through a handbook in his field? After all, a handbook is just a simplified, organized view of a field, which is composed by articles as primary source.--Senteni (talk) 00:47, 19 January 2015 (UTC)


 * I suspect you confuse handbooks (which, at least in my field, typically are collections of survey and method articles, targeted towards advanced researchers) with textbooks (which are aimed at students).I don't think any beginning student has much of a chance of working through e.g. the Handbook of Automated Reasoning without significant help. Even with textbooks, some people find it much easier  to learn material under the guidance of a teacher or lecturer. Good lecturers don't just read the text out loud, they motivate, they explain, they reply to questions, and they provide a route through the material. --Stephan Schulz (talk) 01:10, 19 January 2015 (UTC)


 * Yes, I meant rather textbook than handbook. But textbooks would also accomplish the part of "providing a route through the material." And some lectures are tape these days. Your possibilities of asking a question are the same if you have a textbook or the mp4s.--Senteni (talk) 17:47, 19 January 2015 (UTC)


 * Indeed, but average lecturers merely repeat the textbooks, and bad ones mangle things up. My final year at uni I attended very few lectures, preferring to work on the problem sets in the library. It's the same with MOOCs, unless the material is exceptionally dense or entertaining then I tend to just do the marked work rather than watch the lecture videos. Greglocock (talk) 01:19, 19 January 2015 (UTC)


 * I think the key is feedback. A good lecturer will ask his students questions, and answer questions from them, figure out what concepts are unclear from the lecture, and improve them either that day, or maybe during the next lecture, if he has to think about a better strategy overnight.  By comparison, if a textbook writer gets any feedback at all from the students, any improvements must wait for the next edition, so the current group of students is out of luck.


 * A good lecturer might also work with the text, perhaps using parts of it verbatim, where they are well done, but supplementing bad sections of the text with their own material. StuRat (talk) 04:51, 19 January 2015 (UTC)


 * Gian-Carlo Rota answered this question in his Indiscrete Thoughts, speaking of Alonzo Church, see Fine Hall in its golden age: Remembrances of Princeton in the early fifties. Church "looked like a cross between a panda and a large owl .. His one year course in mathematical logic was one of Princeton University's great offerings. It attracted as many as four students in 1951 ... His lectures hardly needed any preparation. They were a literal repetition of the typewritten text he had written over a period of twenty years, a copy of which was to be found upstairs in the Fine Hall library."


 * Rota continues: "It may be asked why anyone would bother to sit in a lecture which was the literal repetition of an available text. Such a question would betray an oversimplified view of what goes on in a classroom. What one really learns in class is what one does not know at the time one is learning. The person lecturing to us was logic incarnate. His pauses, hesitations, emphases, his betrayals of emotion (however rare), and sundry other nonverbal phenomena taught us a lot more logic than any written text could. We learned to think in unison with him as he spoke, as if following the demonstration of a calisthenics instructor. Church's course permanently improved the rigor of our reasoning."John Z (talk) 05:08, 19 January 2015 (UTC)


 * I think the OP is asking two unrelated questions here, and many people are answering the one and not the other. Question 1 is "What is the benefit of learning by lecture compared to learning by textbook"  Question 2 is "What is the benefit to learning from a really shitty lecture."  Most people seem to be answering question 2 without addressing question 1 at all, and also they are answering solely from their own personal experiences with shitty lectures, without addressing the research behind the pedagogy of lectures.  Self-evidently, shitty lectures are shitty, and so addressing that issue has nothing to do with the OP's question.  "I once had a shitty teacher, and they were bad at their job" does not in any way address the pedagogical rationale behind the use of lectures (and textbooks, and any other teaching tool).  To actually answer the OP's question, here's some things to consider, presupposing that both the lecture and textbook in question are of sufficient quality.
 * Learning styles: Different students have different ways of learning, and what works for some very well does not work for others as well. While some students learn well by reading, others may be auditory learners (need to hear it to understand it) or need to perform some task to understand it, or need to write it down to understand it (the act of taking notes itself has effects on learning).  There's really a variety of ways to teach and learn, and most classes employ multiple methods of doing so, indeed many people need to get the information through several modes (not just one) to get it.  This is self-evident: if the textbook were sufficient, we'd not have an education industry at all.  We'd just hand our 6-year-olds a pile of textbooks and say "See you in about 16 years, figure it out yourself".  Teachers have a role to play in the presentation of information through their lectures.  And the fact that people have different learning styles is part of the reason why both the textbook and lecture are necessary elements in the education process.
 * This article does a really good job of addressing the role of a good lecture in education. Again, the lecture has a role in education.  The shitty lecture may not, but that's a problem of quality not of appropriateness of the pedagogical tool.
 * This article also does the same.
 * Just in the interest of fairness, this is a really good article showing how lecture matches up against other pedagogical methods, and it DOES show that lecture can be inadequate for certain situations, and shows how lecture can be overused.
 * I hope that provides some reading for the OP to help them work through their question. -- Jayron 32 17:00, 19 January 2015 (UTC)


 * Indeed, if we were to compare a shitty lecture, for reasons of fairness, we would have to compare it with a shitty textbook. Although I have the impression that shitty lectures are more common than shitty textbooks. But yes, the question was meant in the direction that Jayron pointed at. When it comes down to learning, what is purpose of a lecture still. --Senteni (talk) 17:47, 19 January 2015 (UTC)
 * Remember that the lecturer is able to tailor his lecture to his students in a live lecture. Maybe not practical in a large lecture hall, but if you're in a smaller class (e.g. in a small liberal arts college; my average class in undergrad was maybe fifteen to twenty students), the lecturer will find this easy if he knows his students.  My professors routinely allowed students to ask questions in class (just raise your hand and you'll be called on), something I can't imagine working in any other context.  Nyttend (talk) 17:07, 20 January 2015 (UTC)

Personal research project: histories and uses of "Dwarf Saltwort" or "Small Cordgrass"
Does anyone have any links to good sites that go into deep detail about plants? Particularly the ones in the subject line. I just need to be pointed in the right direction. Any help is appreciated. Thank you in advance.Gosalyn (talk) 04:55, 19 January 2015 (UTC)


 * Did you look at Saltwort and Small Cordgrass ? StuRat (talk) 05:52, 19 January 2015 (UTC)


 * We do have an articles about Dwarf saltwort and Small Cordgrass. I don't know anything about the topics or good external websites for them, but if you find any, might want to add them there (or at least on the talkpage as a reference for someone who might want to expand the article in the future). DMacks (talk) 05:53, 19 January 2015 (UTC)

Spinning 'Rocket' ??
Hi, can somebody give me the name (and maybe a reference to an article ) of this device? How does it stay stable as it climbs, and what sets it spinning? https://www.youtube.com/watch?v=pD_yQZ4iNjY&feature=pla Thanks 122.108.177.30 (talk) 04:56, 19 January 2015 (UTC)


 * What sets it spinning is the fact that the rockets aren't pointed directly downwards. They're angled.  That starts it turning while they are also able to push the whole thing skyward.  The fact that it's spinning is what keeps it stable.  As the rockets push it around in a circle, it is constantly being pushed to the side due to the angle of the rockets.  But by the time it can be pushed off course, the rockets are now in a different position.  So at the 12 o'clock position, it's being pushed one way.  But there is another set of rockets on the other side, the 6 o'clock position, of the contraption balancing out the sideways forces of the other rockets.  Dismas |(talk) 05:46, 19 January 2015 (UTC)


 * The way I'd make it stable is by putting a weight underneath it, at the center. (You could make it something useful, like a camera and transmitter, to send live video, but they'd need to use smokeless powder to get a clear view.)  I think the system they used is less stable, and if a rocket or two failed, it might very well have flipped over. StuRat (talk) 05:51, 19 January 2015 (UTC)


 * How does putting a weight underneath it make it stable? The device in the video uses spin stabilization.  Just adding weight doesn't help unless it had some aerodynamic effect.  --Bowlhover (talk) 06:42, 19 January 2015 (UTC)


 * Trying to dredge my memory for the physics of this, I'm fairly sure that rotational inertia is the clue here - the distribution of mass ('dumbell effect') means that slight perturbations of the spin axis get damped down, once it gets spinning. And if I'm right, adding significant mass below the centre would actually make it less stable. No doubt someone better qualified in physics will be able to describe this better - or tell me I've got it all wrong. AndyTheGrump (talk) 07:07, 19 January 2015 (UTC)
 * Aye, StuRat is regrettably referring to the incorrect pendulum theory of rocket dynamics, which was widely believed until it was discredited by actual experiment. Even Robert Goddard believed this theory.  It's an easy error to make, even for a physicist, because when you write the equations that treat a rocket as a simple harmonic oscillator, everything looks correct on cursory evaluation, even though the details are not correct.  (The big conceptual gaffe is forgetting that a pendulum solution also contains an un-bespoke constraint force at the pivot point, while a rocket has no such constraint - it's not nailed into a wall - so if you forget to account for this, you neglect an important reaction-force that significantly changes the vehicle dynamics.  When a pendulum swings, the pivot pushes back with an equal and opposite reaction... but a free-flying rocket has no fixed pivot on which to exert a reaction-force - hence no restoring force, hence no simple harmonic oscillation).  In a perfect world, a rocket with a low center of gravity is exactly as stable as one with a high center of gravity; and in an imperfect world, this configuration amplifies minor perturbations into major aerodynamic instabilities.
 * Real rockets - including the one in the video - use fins as aerodynamic control surfaces for stability. The rocket in the video looks like its entire outer edge is acting as a large, circular-shaped vertical stabilizer.  Rockets also use spin stabilization - a side-effect of the conservation of angular momentum - once spinning, the rocket resists changes to the direction of spinning, preferring to point in the same axis (or to precess in a stable oscillation around its primary spin axis).
 * Nimur (talk) 07:54, 19 January 2015 (UTC)
 * Very cool video, thanks for sharing it! It looks like an excellent example of the "because we can" reason for doing things! --Stephan Schulz (talk) 10:06, 19 January 2015 (UTC)

Anion deficient solution
Something I'm reading refers to an anion deficient solution. Based on my admittedly shaky chemistry knowledge I suppose this means acidic (i.e. poor in -ve ions, so rich in H+ ions, so low pH) but am I missing something (or getting it wrong)? Is there a significance to saying "anion deficient" rather than acidic? AlmostReadytoFly (talk) 14:14, 19 January 2015 (UTC)
 * Do you have a link to the thing you are reading? -- Jayron 32 16:45, 19 January 2015 (UTC)
 * Sorry, it's not on the web. It's an aluminium nitrate solution. AlmostReadytoFly (talk) 17:29, 19 January 2015 (UTC)
 * The anion are the negatively charged ions, in your case the nitrate. I'm not a chemist but I would expect anion deficient to mean that there are fewer nitrate ions than you would expect from the number of aluminium ions, i.e. less than 3 times as many. Ulflund (talk) 19:43, 19 January 2015 (UTC)
 * That creates a problem, as the overall charge of the solution needs to remain neutral. The only way that there could be a disproportionate amount of nitrate ions, is if a fraction of the nitrate ions is switched out for another type of anion. Hydroxide ions perhaps? Plasmic Physics (talk) 03:49, 21 January 2015 (UTC)

Swallowing a long string
What would happen if I swallowed a really long piece of string....And swallowed it slowly and letting it pass through me fishing line style. Would it be possible to have one end of the string hanging out my butt hole and the other end still out my mouth?

That would be cool.

Any medical ramifications? — Preceding unsigned comment added by 106.150.61.164 (talk • contribs) 18:46, 19 January 2015 ‎


 * Lol. Might do if you look for it with the other hand. -- (Russell.mo (talk) 18:56, 19 January 2015 (UTC))


 * Could you get it to come out 'both ends'? Doubtful, Cecil Adams examines this question in this article.
 * Medical Ramifications? Could be. Ask a doctor. APL (talk) 20:08, 19 January 2015 (UTC)


 * Hmmm - I was unable to find a solid reference for this. Some random person on Snopes said this: "The reason string can be fatal to animals (or people, for that matter) is that the bowel tries to pass the string along by peristalsis. This results in two peristaltic waves acting as "anchor" points, which eventually causes the string to become taut. Intermediate peristaltic waves then act on the linear foreign body produced by the taut length of string, trying unsuccessfully to move it along. Repeated movement against the string actually saws through the bowel wall, leading to perforation, peritonitis and eventual death."...I have no idea whether (s)he speaks from a position of knowledge - but it certainly sounds plausible, so for 100% sure you shouldn't try this without getting some fairly serious medical guidance...or, preferably, not do it at all!


 * It's likely that someone here would sooner or later bring up an old story about feeding string to ducks and eventually getting an entire row of ducks strung end to end this way...that can be traced back to a story from the original Baron Münchhausen books...so I think we can probably discount it!


 * SteveBaker (talk) 20:32, 19 January 2015 (UTC)


 * My neighbor's dog did this. They cooked a turkey bound in twine, and he ate the twine out of the trash, leading to dog bloat, for which he survived the surgery. μηδείς (talk) 23:51, 19 January 2015 (UTC)


 * Policy says we shouldn't give medical advice, but regardless I'd say... no. Just no.  Intestines are amazingly finicky things; we call on them to do so much within their natural range and they comply, but fiddle about with them unnaturally and you tend to just die.  All the time surgeons lose patients because of some invisible error with the blood supply after they have done something with them, and you need merely contemplate what happens if you pull the string to see how that might be similar. Wnt (talk) 00:20, 20 January 2015 (UTC)


 * You might find the tale of Alexis St Martin and William Beaumont interesting. --TammyMoet (talk) 10:14, 20 January 2015 (UTC)


 * I once pulled four feet of an inch-wide strip of sweater (punching bag stuffing) from a three-foot iguana. He lived without medical help, but it was bloody and he was lucky. Also wasn't out of his butt. Last week, pulled a thin 8-inch strip of plastic (feed bag weaving) from my cat's butt. No blood or discomfort (or shit on the first few inches, for some reason), but it wasn't out of his mouth. I'll also say "Ask your doctor". InedibleHulk (talk) 10:33, 20 January 2015 (UTC)


 * Re-posting my answer of 19:15, 19 January 2015 that got deleted: Such a string may causes medical complications due to the action of peristalsis. In other words, the string may abrade the gut lining at a few points and cause complication such as ulcers, possibly leading to Peritonitis etc. But that is just of the top of my head. Parasitic gut-worms can be ever-so long but they have evolved not to kill their host. Your bit of hypothetical string may not be so smart.--Aspro (talk) 14:26, 20 January 2015 (UTC)


 * In the documentary Crumb, Maxon Crumb mentioned his practice of passing a strip of cloth (about two meters long) through his system from time to time. (I lived and worked in San Francisco then, and saw him on the street several times; cannot say for sure whether I ever saw the strip hanging from his mouth in RealLife or only in the movie.) —Tamfang (talk) 07:26, 21 January 2015 (UTC)

Brain neurons
How much/many neurons does a human brain hold, 15-33 or 86? -- (Russell.mo (talk) 18:47, 19 January 2015 (UTC))


 * An estimated 80 000 000 000 - 100 000 000 000 neurons.  Wiki List_of_animals_by_number_of_neurons says 86 000 000 000 neurons, with references.   Also, there is a comparable number of macroglial cells, mostly astrocytes.  Astrocytes are not neurons, but they do participate in the "computations" carried out by the brain.  For a relatively recent discussion of neuron and glia numbers, see e.g. .  --Dr Dima (talk) 19:34, 19 January 2015 (UTC)


 * And bear in mind that the number of interconnections matters - probably more than the number of cells. SteveBaker (talk) 20:19, 19 January 2015 (UTC)
 * I'm guessing that would be the nervous system ('lower' and 'higher'). -- (Russell.mo (talk) 21:02, 19 January 2015 (UTC))

Thanks friends. Astrocytes is new to me. I'll read through...

Onions
What do onions do to your brain? Can it affect your consciousness? E.g., a person is sleeping, if he smells a ‘just cut’ onion, will he wake up from sleep?
 * 1) When you smell?
 * 2) When you eat?

(Russell.mo (talk) 18:48, 19 January 2015 (UTC))


 * We have excellent articles on smell and taste. Please read them, and then feel free to ask any additional questions that you may have. --Dr Dima (talk) 19:41, 19 January 2015 (UTC)
 * If your question is specifically about onion smell and taste, the eye irritation response is caused by sulfenic acid, an irritant, produced when onion bulb is cut or damaged; and the sweet taste is produced by sugars present in the onion. --Dr Dima (talk) 19:46, 19 January 2015 (UTC)
 * I'm talking about how it effects the brain. I just recalled, the last thing I can remember before getting my sense/consciousness long after I started walking is the onion smell. And the next thing I remember that my mother was showing and explaining it... I'm thinking of what chemical/acid reaction could unlock my brain. - (I could be day dreaming now but this is what I recalled...) -- (Russell.mo (talk) 20:41, 19 January 2015 (UTC))
 * Ah, I think it's more about a smell, rather than onion smell. Many people's earliest memories have to do with smells. Olfactory_memory has some info. My undergraduate psychology professor told us that scent memories are often the strongest/longest lasting, compared to other types of memory. I don't know if that's mentioned in our article but I don't have time to look for a better reference at present. SemanticMantis (talk) 21:04, 19 January 2015 (UTC)
 * Its okay, thanks . I'm going to sleep now after messaging a friend. -- (Russell.mo (talk) 21:11, 19 January 2015 (UTC))
 * ,, I read through some of the articles, no where it mentions whether a baby who is already walking can gain his/her full consciousness after smelling a just cut onion, from the sulfenic acid?
 * I can’t recall a thing before this 'onion' moment, not even someone teaching me how to walk, though I was fully walking before this moment I gained my full consciousness. Can I get away by saying, "H’s olfactory memory never affected him but marked the beginning of his life".
 * (Russell.mo (talk) 17:33, 20 January 2015 (UTC))
 * I think it's fair for you to say "My olfactory memory of the scent of onions is the first thing I remember, and so it is in some sense the beginning of my life" - I don't think there's anything special about the scent of onions in the brain, but I could be wrong. E.g. some Aromatherapy is total pseudoscience and lies, but some scents do have scientifically verifiable effects on the brain (e.g. the lemon oil effect on mice seems legit). Figuring out substances have good evidence for their effects is hard, but there's probably some decent stuff in the references to that article. SemanticMantis (talk) 17:49, 20 January 2015 (UTC)
 * Thanks! -- (Russell.mo (talk) 18:32, 20 January 2015 (UTC))

Explaining methods
What is the correct term to define a person who is showing 'with is body movements' as well as 'speaking what he/she is showing' so that you understand? Just like a father/mother tells his/her baby for them to understand… -- (Russell.mo (talk) 18:53, 19 January 2015 (UTC))


 * Body language? SteveBaker (talk) 20:16, 19 January 2015 (UTC)


 * Depending on the context, it might also be a gesture or even pantomime. SemanticMantis (talk) 20:19, 19 January 2015 (UTC)


 * What if you are speaking at the same time by gesturing/using body language? -- (Russell.mo (talk) 20:52, 19 January 2015 (UTC))
 * I don't think we have a specific word for that. We would just say something like "The fish was this big! he said, gesturing with wide spread hands." SemanticMantis (talk) 21:07, 19 January 2015 (UTC)

Speaking while gesturing would be normal. You could also have the animated speech of Hitler or Mussolini, but that would scare a baby. Gesticulate also works, but this sort of speech is somewhat over the top. You can gesticulate wildly, but not softly. μηδείς (talk) 21:05, 19 January 2015 (UTC)
 * Your words 'speaking while gesturing' just made me feel like a really dumb person. I'm always in search for formal words that now I forgot the most basic. The two go really well. Thanks. -- (Russell.mo (talk) 21:19, 19 January 2015 (UTC))


 * There's no harm in asking. Spanish has at least 4 words, pared, mur, muralla, tapia that all translate as "wall" in English, but distinguish in Spanish whether it's interior, exterior, of a city/castle, or of a garden.  On the other hand, English has at least 7 words that translate the Spanish tacaño, "stingy/miserly".
 * I understand and Thank you (whoever you are). Don't forget to use your signature next time -- (Russell.mo (talk) 12:00, 20 January 2015 (UTC))

Thank you all -- (Russell.mo (talk) 12:11, 20 January 2015 (UTC))

Concentrations of antibiotic in Indian rivers
In this report: the CEO of a pharmacutical company claims that "...rivers in India show higher concentrations of active antibiotic than the blood of someone undergoing treatment.". This seems implausible to me...any idea where he's getting his data - and is it likely given flow rates of rivers and antibiotic concentrations in treated patients? SteveBaker (talk) 20:16, 19 January 2015 (UTC)


 * Sounds like a bit of hyperbole. At the very least the quote should not be about "rivers in India", as they certainly all don't have those high concentrations. Here's a study of one stream in India, that shows a high incidence of antibiotic-resistant alleles in resident bacteria. Downstream of a discharge site for a drug factory, Fig.1 shows up to ~10^3 ug/g of ciprofloxacin measured in the water. I don't know what the therapeutic dose would come out to in a treated human's blood, but this is at least a start. SemanticMantis (talk) 21:01, 19 January 2015 (UTC)
 * That's 103ug/g of organic material - not per gram of water. Our ciprofloxacin article says that a typical IV dose of ciprofloxacin is 400mg - and an average human has about 5 liters of blood - so around 5000g...so we're looking at something like 80ug/g as a rough therapeutic concentration. So it's close...if more than about 10% of the river is organic material, the guy is right.  Wow! SteveBaker (talk) 06:27, 20 January 2015 (UTC)
 * Hyperbole? Isn't that being held on the 1st?  Perhaps he meant the total in the rivers by mass/volume, rather than concentration?  In the US, there'd be antibiotic from livestock.  There's also the decade-old story about the high levels of cocaine in the rivers of Italy]. μηδείς (talk) 23:30, 19 January 2015 (UTC)
 * Florida land is worth two extra dollars per acre because one time tens of tons of cocaine was dropped from an plane disposing of evidence or lightening it's load as it was about to crash or something like that. Or at least it would be if the market were totally efficient and everybody was willing and able to sell (the 30,000 houses worth of cocaine). Sagittarian Milky Way (talk) 00:20, 20 January 2015 (UTC)
 * It sounds unlikely, but bear in mind that a couple of tiny pills provide all the blood concentration you need to start feeling better. Conceivably I can picture a large plant putting out enough waste, in proportion to all those pills for all those people, to contaminate a region of a river near the effluent, especially since some rivers in India have seasonal periods of low flow rate.  It's the sort of thing I want a cite before acting on, certainly have doubt about, but can't disprove. Wnt (talk) 00:09, 20 January 2015 (UTC)
 * Hmmm - so the IV dose of ciprofloxacin is 400mg - and I guess that's diluted into about 5 liters of blood - so around 5000g...so we're looking at one part per 12,500 as a rough theraputic dose. If the river was showing 1mg/g, that's one part per thousand...yikes!  I guess the guy was right.
 * Oops, sorry, good catch. I don't know how much of a "river" is organic material but 10% seems reasonable... SemanticMantis (talk) 15:08, 20 January 2015 (UTC)

The CEO's statement is apparently a (rough) paraphrase of this paper, which showed that the "effluent from a wastewater treatment plant serving about 90 bulk drug manufacturers in Patancheru, near Hyderabad, India-a major production site of generic drugs for the world market" had concentration of ciprofloxacin as high as 31mg/L (= 31ug/ml, which per the above calculations is comparable to the therapeutic blood conc.). Keep in mind though that we are talking about local hotspots (which is concerning enough!), and not "rivers in India". Also, interestingly, as this summary of the PLOS paper linked above points out, the observed antibiotic resistance is quite non-intuitive and somewhat perplexing: "...the relationship to the antibiotics present was not straightforward. For example, the most frequent resistance genes found were for a class of antibiotics called sulphonamides, but the researchers found no evidence of the drugs themselves. They hypothesize that this may be an instance where resistance to one group of drugs could provide resistance to others. And despite detecting high concentrations of fluoroquinolones, a chemical class that includes the heavy-hitting antibiotic ciprofloxacin, the team found less evidence of resistance to these drugs downstream than upstream from the plant. The researchers suggest that the levels of fluoroquinolones in the downstream effluent were so high that they overpowered even the resistant bugs."

Definitely a topic more will be written about. Abecedare (talk) 07:56, 20 January 2015 (UTC)