Wikipedia:Reference desk/Archives/Science/2013 August 19

= August 19 =

Psychology of pricing and beach nourishment projects
Hi, I have learned that managed retreat (moving away from the shore) is an unpopular idea amongst the public, in part because of its high short term costs (both beach nourishment and maintaining coastal armoring structures such as jetties are more expensive over a long term period (eg. decades)). I was wondering, are there any psychological studies that show that consumers tend to be more afraid of making purchases that have high short term costs, than making purchases that have low short term costs but higher long term costs? Many people get in trouble with credit cards because they allow people to make quick convenient short term purchases, but often lead to higher long term costs (in the form of interest rates or late payment fees). Thanks. — Preceding unsigned comment added by 99.146.124.35 (talk) 00:06, 19 August 2013 (UTC)
 * There has been a lot of research about that topic. Our articles on temporal discounting and intertemporal choice describe some of it, although they are written at a pretty technical level. Looie496 (talk) 00:58, 19 August 2013 (UTC)


 * The world is rife with the consequences of that kind of thinking. When you buy an inkjet printer for your computer - it's amazingly cheap - under $100 in some cases.  Then you go to buy a few grams of ink and you're paying $50.  Computer game consoles like the PS-3 and Xbox 360 are sold for prices well below the manufacturing cost - and the companies that make games are forced to enter into costly licensing for the privilage to write games for them - the cost of games is therefore much higher than it would otherwise be in order that the sticker shock for the console hardware is lessened.  Cellphones worth $300 to $400 are sold for $100 with a two year contract to buy cell phone service at significantly more than the going rate.
 * In every case, people are suckered into these expensive long-term costs by the short-term value. SteveBaker (talk) 01:38, 19 August 2013 (UTC)
 * Phone companies in the UK are starting to be clearer in their phone plans. The O2 refresh scheme gives a super clear explanation of exactly what you pay for your phone on different contracts. For example for the iPhone 5 you actually save £120 (20% of the cost of the phone) by fiddling with the contract you want - and a handy link to find the lowest price. For example. 110.3.247.175 (talk) 12:57, 19 August 2013 (UTC)

I've been reading that cancer cells communicate with each other...
and also that slime mold cells communicate with each other. How do the signalling methods compare? Thanks.76.218.104.120 (talk) 05:32, 19 August 2013 (UTC)
 * Most living cells communicate, to a greater or lesser degree. The subject that coveres this topic is Intercellular communication and it is very complex. Vespine (talk) 06:57, 19 August 2013 (UTC)
 * Thanks,Vespine76.218.104.120 (talk) 22:55, 21 August 2013 (UTC)

Upside down Mirror Image
why do some mirrors show images upside down. — Preceding unsigned comment added by 197.220.100.142 (talk) 11:43, 19 August 2013 (UTC)
 * See curved mirror. הסרפד  (call me Hasirpad) 12:39, 19 August 2013 (UTC)

Antibiotics - Safe Amount To Take
My queastion is, how many courses of antibiotics (or how much) is safe to take per year ?

One reason for asking is I was prescibed antibiotics for a chest infection when I was little, but because I still had it a week or two after the course was finished (Not sure but I think it was a 28 day course) my parents took my back to the GP. This happened 3 or four times until my parents happen to mention that I've already had antibiotics when the GP suggested for me to have some more antibiotics. When he checked my records (he later claimed there was some sort of problem with their computers) he said I'd have to have something else because I'd taking more than the recommended amount for that year.

another reason is, years earlier a similar thing happened with my sister. She had a ear infection, & she was given so many courses of antibiotics (later explained to us by doctors in the hospital) that she went partialy deaf. When she was rushed to the hospital, where they took her off the antibiotics & gave her something else to take instead & they told my parents that her hearing might come back. Luckily it did. Scotius (talk) 12:38, 19 August 2013 (UTC)


 * Wikipedia does not respond to requests for medical advice. Ask a medically-qualified person. AndyTheGrump (talk) 12:41, 19 August 2013 (UTC)


 * I'm sorry - but the Wikipedia Reference Desk is not allowed to dispense medical advice. Besides that, the answer would be very complicated because it'll depend on body weight, gender, which antibiotics are being prescribed, other drug interactions and so forth.  This is really a matter for a doctor to answer for each individual patient. SteveBaker (talk) 12:49, 19 August 2013 (UTC)


 * I think it's safe to say that the medical community has a different opinion on the appropriate use of antibiotics today than even ten years ago. Today, where I live doctors never prescribe antibiotics to patients if there is no risk posed by the infection to the long term health of the patient. So, even if an antibiotic would help you to recover faster and be less ill, the doctor won't prescribe it to you. So, any use of antibiotics is judged to be potentially unsafe and can only be justified if it avoids a significant health risk to the patient.  It's up to the doctor to make this assessment in individual cases. Count Iblis (talk) 13:09, 19 August 2013 (UTC)


 * I agree that we can't answer this, but I should point out that your question simply can't be answered, even by a physician. "Antibiotics" represent a vast range of substances, some of which are used only in dire emergencies with very specific and severe side effects (for example, ciprofloxacin can break tendons; many antibiotics cause ototoxicity or damage the liver or kidneys etc.).  On the other hand, simple honey is a moderately effective antibiotic that has been used for many thousands of years, and pretty near harmless.  Most... fall into some intermediate category.  You just can't say "X courses per year" for a grab bag of miscellaneous antibiotics - but if you used just one all the time you'd have too much trouble with resistance for it to be useful.  So there's just no answer to the question. Wnt (talk) 19:27, 19 August 2013 (UTC)


 * I agree that there's no fixed answer to the question. Doctors here in the UK do prescribe antibiotics, but they usually vary the type prescribed so as to reduce the danger of resistance building up.  Different authorities at different times in different countries have recommended different "maximum amounts" for different antibiotics, but there is no fixed rule.  The modern approach seems to be to avoid prescribing any antibiotic unless it is considered really necessary, but to prescribe it for long enough to completely clear the infection.    D b f i r s   11:34, 20 August 2013 (UTC)

Probability to find a electron in a specific region
Reading article about electron and Schrodinger Equations, I have seen that a region with more probability to find a electron in a Hidrogen Atom, or any other in energy state 1s, in in the center of atom. As we understood that in center of atom we have a nucleus where protons and neutrons are expected to be in potential wells, how can electrons and nucleons be expected to be in atom´s center without interacting with each other ? I thank for some help. — Preceding unsigned comment added by Futurengineer (talk • contribs) 13:41, 19 August 2013 (UTC)


 * There is definitely an interaction between the electron and the proton. However any classical picture of the situation breaks down completely here. If you break down the 1s state by writing it as a sum over states where the electron has a definite position (this is what you effectively do if you write down the 1s wavefunction as a function of position), then this has to be interpreted as the electron being in a superposition of all these positions and interacting with the proton from all these different positions. The total energy of -13.6 eV of the system is a result from the sum of all the kinetic and potential energies at these different positions, including from the electron being inside the nucleus. Count Iblis (talk) 14:06, 19 August 2013 (UTC)


 * Yes, they may interact. Electron capture is just one of the more notable consequences of that interaction. Dauto (talk) 15:28, 19 August 2013 (UTC)


 * They definitely interact electromagnetically, otherwise the electron wouldn't be in a bound state (and atoms as we know them wouldn't exist). So maybe you ask whether they interact in other ways; and the only other known ways are by gravity (which is negligible in this case) and by the weak interaction. As Count Iblis said before me, the electron is in a superposition of all different positions, and only those very close to the nucleus allow weak interactions with a reasonably large amplitude. These interactions certainly lead to a small correction factor in a very accurate calculation of the binding energy and the wave function of the electron. It can be guessed that the correction is pretty small by estimating the probability of the electron being inside the proton in light hydrogen: The Bohr radius is about 60 thousand times as large as the proton radius, and in a crude approximation the probability is given by the ratio of proton volume and the volume of a sphere of the Bohr radius, which is about p = 5*10-15, a very small number. Icek (talk) 13:13, 20 August 2013 (UTC)


 * The effect on the energy levels of the electron is negligible indeed. But the effect on the probability of electron capture is very important. The chance of an electron that is not in a s state being captured by the nucleus is very small because of the low probability of finding such electrons in there. Dauto (talk) 14:59, 20 August 2013 (UTC)

Suppressors of evolution?
Would it be correct to say that dinosaurs in fact suppressed or hindered the evolution and emergence of more diverse wildlife and smaller life forms that we see today? The modern fauna, that emerged within a relatively short time compared to several millions years of dinos' domination, seems to be more differentiated. Specifically, humans for example evolved within an extremely short period compared to dinos' era and many millions of years were dominated by essentially a single clade, inferior to humans and other modern animals. --93.174.25.12 (talk) 14:42, 19 August 2013 (UTC)


 * I've read that the reason why the dinoarus were themselves not so diversified as modern animals had to do with the flora of the time which was not as diverse as that as today. Flowering plants only evolved during the Jurassic, fruit bearing plants evolved much later. The plant eating dinos had only conifers and ferns on their menu. But then one can ask why it took so long for the flora to evolve fruit bearing plants, perhaps the biology experts here can answer this... Count Iblis (talk) 15:15, 19 August 2013 (UTC)


 * You'll probably find Punctuated equilibrium interesting. Dauto (talk) 15:21, 19 August 2013 (UTC)


 * When the [big] dinosaurs were all gone from the face of the earth (today, there are small dinosaurs; we call them birds), the earth allowed the adaptive radiation of different lifeforms, particularly small mammals that were being hunted during earlier eras, and that led the mammals to grow in size and diversify. Of course, I'm sure there were some diversification and evolution in early mammals during the dinosaur era too, but they generally could not grow larger in size, because they could be hunted by the dinosaurs as prey. So, I wouldn't say that the dinosaurs completely suppressed or hindered the evolution and emergence of diverse wildlife. Perhaps, the word guided would be a more suitable term, as the dinosaurs, early mammals, and feathered birds all interacted with each other in the ecosystem. Sneazy (talk) 15:42, 19 August 2013 (UTC)


 * That's all rather teleological and vastly over-simplified. Our article on the Cretaceous–Paleogene extinction event says "Mammalian species began diversifying approximately 30 million years prior to the K–Pg boundary. Diversification of mammals stalled across the boundary. Current research indicates that mammals did not explosively diversify across the K–Pg boundary, despite the environment niches made available by the extinction of dinosaurs." References are here and here. Gandalf61 (talk) 16:01, 19 August 2013 (UTC)
 * And, of course, "the dinosaurs" were themselves a large, diverse, and evolving group. So evolution was happily working away, creating bigger and smaller dinosaurs, bipedal and quadrupedal ones, possibly cold- and warm-blooded species, feathered, scaled, horned, and winged dinosaurs. No to mention mosasaurs, ichthyosaurs, plesiosaurs and pterosaurs, all sharing some part of the environment with dinos. --Stephan Schulz (talk) 16:03, 19 August 2013 (UTC)


 * To make some flagrant speculation, just thinking out loud (or perhaps asking a question of my own, if someone answers): I wonder what the effect of hibernation/estivation is on overall species diversity? As I understand it, the things that survived the meteor were generally things that could bunker in a hole in the ground and forget the world a while.  (True, I would make a very big stretch in supposing that the ability of the Common Poorwill, shared on a nightly basis by some other species, might be ancestral)  But I'm thinking that the net evolutionary effect of having so many species starting out with a ready resort to inactivity might increase the overall number of ecological niches as a whole. Wnt (talk) 20:19, 19 August 2013 (UTC)


 * Hibernation/estivation can easily make species undergo speciation and diversify by temporal isolation. Some species can be very "choosy" in the mating process and will only mate in a particular time of year or a particular time of day or during a particular time in an organism's life cycle. Sometimes, many evolutionary pressures are at work - geographical isolation, genetic drift (for a small and isolated population), gene flow (and migration), and natural selection. For instance, there may be a huge tsunami that goes inland and floods the lands until the valleys are temporarily filled. During the time when it is filled, flora and fauna adapt to the flood. Isolated related species of the flora and fauna may be trapped and diversify in their own way. And natural selection may act on the flora and fauna to cope with the new, flooded environment. Sneazy (talk) 22:38, 19 August 2013 (UTC)
 * That bit about evolution occurring rapidly after flooding due to a tsunami sounds speculative, but I assume that you would not have said it without a source - could you provide one? Sounds interesting. -- Scray (talk) 23:47, 19 August 2013 (UTC)

I confess that the specific example is fabricated based on my knowledge of evolutionary biology. My intention is to make a point that many evolutionary pressures can work on species simultaneously, creating a dynamic biosphere. I'm sorry if I sent an implication that the evolution is rapid or shortly after the flood; I wasn't really taking into account of time, and I did not mean to refer to the same species before or after the flood. Some may die off; some live; survivors adapt, if any. However, now that you have mentioned it, I actually have found a research article on my library's database that supports the instance of a tsunami during the K-T boundary and the stalling of adaptive radiation.


 * Source: Hansen, T. A., Kelley, P. H., & Haasl, D. M. (2004). Paleoecological patterns in molluscan extinctions and recoveries: comparison of the Cretaceous–Paleogene and Eocene–Oligocene extinctions in North America. Palaeogeography, Palaeoclimatology, Palaeoecology, 214(3), 233-242. doi:10.1016/j.palaeo.2004.06.017


 * Abstract: Exposures across the Cretaceous–Tertiary (K–T) and Eocene–Oligocene (E–O) boundaries, in Texas and Mississippi, respectively, probably represent the most complete and best-preserved fossil molluscan sequences across these boundary intervals in the world. Outcrops from both boundaries contain pristine aragonitic and calcitic molluscan shells, which were deposited in fine-grained sediments from open marine environments. The K–T and the E–O extinctions exhibit very different recovery patterns, probably reflecting very different causes as well as magnitudes of extinction.The K–T sequence contains a molluscan fossil record that is consistent with an abrupt extinction event at the K–T boundary and a prolonged initial recovery in hostile oceanographic conditions. The uppermost 10 m of Upper Cretaceous sediments contain a diverse (approximately 40 species) molluscan fauna dominated by suspension feeders. The earliest Paleocene sediments immediately above the tsunami bed contain an impoverished fauna dominated by deposit feeders. The Paleocene fauna slowly climbs in diversity but remains relatively impoverished and dominated by deposit feeders for several hundred thousand years after the extinction in conjunction with anomalous δ13C values that suggest prolonged suppression of marine primary productivity. Diverse suspension-feeder dominated molluscan assemblages reappear with the resumption of normal conditions of primary production. In the long term, early to middle Paleocene gamma diversity includes evolutionary “bloom taxa,” families that exhibit unusual speciation bursts that subside in the Eocene. Total diversity for the Gulf Coast does not approach Cretaceous levels until the Late Eocene representing a total recovery interval of nearly 25 million years.While the E–O event also reflects a molluscan extinction rate of over 90% in the Gulf of Mexico, there are no signs of hostile environmental conditions in the recovery fauna. Early Oligocene molluscan assemblages are diverse and dominated by suspension feeders characteristic of normal marine conditions. The hiatus at the E–O boundary, however, could have obscured a short-term recovery fauna. There is also no sign of long-term perturbation by the E–O extinction. There are no bloom taxa and gamma diversity approaches pre-extinction levels within a few million years. The overall pattern of the E–O extinction is consistent with extinction (and/or migration) associated with long-term cooling.

Sneazy (talk) 00:11, 20 August 2013 (UTC)


 * The relevant concept to explore is niche (ecology). Dinosaurs and their kin "suppressed" evolution into niches like whales, bats, and megafauna, because they were already filling those niches well enough to make the intermediate niches like Ambulocetus's unrewarding.  (Evolution excludes two species from having the same niche unless they have non-overlapping ranges: e.g., both rabbits like meadows, but only one can tolerate swampy lowlands and the other the cold heights.  The presence of a good land and good water predator will exclude a mediocre amphibious predator.)  The three major factors of the dinosaur era include the existence of dinosaurs already filling many niches, the lack of flowering plants until the end of the Mesozoic, and the unified Pangaean landmass preventing isolation at a continental level.  It wasn't dinosaurs, for example, that prevented the evolution of primates, but the lack of suitable fruit and fruit-eating insect prey for the primates to consume.  Once the continents broke up we got such groups as the Afrotheria and the Boreotheria as local experiments on the broken-up continents.  As for hibernation, any process that lengthens an animal's lifespan in regard to age at first breeding will, ceteris paribus, slow down evolution--see the Sibley-Ahlquist taxonomy.  But selection pressure may be higher on the slower-breeding animals, which can balance out the equation. μηδείς (talk) 01:08, 20 August 2013 (UTC)

how many percents of cpr cases are successful?
It intresesting for me to know how many percent of cpr cases are successful. Do you know something about? thank you 176.13.161.70 (talk) 15:41, 19 August 2013 (UTC)


 * Cardiopulmonary_resuscitation 163.202.48.125 (talk) 15:56, 19 August 2013 (UTC)


 * An important fact to note in that article is the survival rate when not getting CPR. It's very low. ←Baseball Bugs What's up, Doc? carrots→ 23:52, 19 August 2013 (UTC)


 * I remember reading that traditional CPR is no more effective than using a toilet plunger on the victim's chest. Not that a plunger is very effective, it's just that CPR isn't any better. StuRat (talk) 14:29, 20 August 2013 (UTC)
 * Toilet plunger actually at least as effective (and led to development of new assistive devices.
 * http://dfw.cbslocal.com/2011/01/24/toilet-plunger-rescue-leads-to-new-cpr-procedure
 * http://www.popsci.com/technology/article/2011-04/device-modelled-after-toilet-plunger-improves-cpr-success
 * ...it was trivially easy to find this by google so we can discuss actual news and science instead of random recollections thereof. DMacks (talk) 16:43, 20 August 2013 (UTC)


 * As the first answer to the OP indicates, getting CPR quickly significantly improves your chances of survival, compared with just letting him lie there and hoping for divine intervention. ←Baseball Bugs What's up, Doc? carrots→ 00:08, 21 August 2013 (UTC)


 * "Survival" and "success" aren't necessarily the same. You might be interested in this episode of Radiolab which explores the 2003 survey by Joseph J. Gallo on what heroic measures physicians would want for themselves. Gallo's survey of doctors says 90% of those interviewed would not want to receive CPR - not because it is necessarily ineffective, but because of the quality of life of someone saved by CPR. This story cites a study saying 8% of CPR patients survived for more than one month but that only 3% subsequently could lead a "normal life". You do occasionally hear of medical doctors who have "do not defib" or "no CPR" tattoo (e.g.) for this reason, posing an ethical and legal dilemma for responders. -- Finlay McWalterჷTalk 13:13, 22 August 2013 (UTC)


 * I should note that only 8% of CPR patients surviving isn't necessary an indication that CPR is ineffective. Rather it's as much an indication that first responders are apt to perform CPR whenever there seems to be the remotest chance of it working, fearful of being accused (by relatives and in court) of having given up too soon. One of those articles I linked above compares the effectiveness of CPR on TV dramas to the actual procedure, giving people an undue faith in its practical effectiveness. -- Finlay McWalterჷTalk 13:26, 22 August 2013 (UTC)

Alcubierre drive
In the main article about the alcubierre drive the part "physics" an "placment of matter" discribes the problem of tachionic motions.

my question now, is it necessary to arrange an infrastructur along the path of the warp bubble because the crew of the ship inside the bubble can not stop the bubble by itself? or ist it necessary cause the warp drive would not work without this infrastucl like a train without railways?

peter, germany — Preceding unsigned comment added by 89.204.155.187 (talk) 18:16, 19 August 2013 (UTC)


 * If you have the power to fold space there's no telling what you can do. Wnt (talk) 19:28, 19 August 2013 (UTC)


 * Well, you could create an inescapable prison. You could create a box that is bigger on the inside. You could scratch any part of your back without using a backscratcher. It is the ultimate way of hiding something, so that it is 'there', but not actually there. Oh, you can build computers that don't have any wiring (wireless electricity transmission, without converting energy into another form). Plasmic Physics (talk) 00:47, 20 August 2013 (UTC)
 * ...And, you'll never again have to struggle with opening another jar of pickles - just fold the space around it to reach through the lid. Plasmic Physics (talk) 07:28, 20 August 2013 (UTC)


 * I'm not sure what you are asking, but here is a relevant article from a popular science magazine (New Scientist): . I'm relatively sure that it is speaking about the Alcubierre drive. Plasmic Physics (talk) 02:34, 20 August 2013 (UTC)


 * There isn't any sensible physical theory in which you can talk about how the Alcubierre drive "works". General relativity lets you compute an energy distribution for any spacetime geometry, including one with a warp bubble in it. The energy distribution for the warp bubble geometry is incompatible with the rest of known physics. The only way it could ever work is if God created an as-yet-undiscovered substance with exactly the right properties because He wanted us to be able to make warp drives. There's no way to know how we'd control this miraculous substance.
 * That said, the outside of the warp bubble in Alcubierre's geometry is causally disconnected from the inside, so indeed the occupants would not be able to actively control it (without FTL signaling, which would defeat the purpose of talking about GR warp drives in the first place). -- BenRG (talk) 12:00, 20 August 2013 (UTC)


 * It's worth mentioning there is an article Alcubierre drive and also a potentially more interesting article White–Juday warp-field interferometer. I still don't get why, if the inside and outside of the bubble are causally disconnected, you would find it easier to open it from the outside than the inside. Wnt (talk) 14:01, 20 August 2013 (UTC)
 * They're not entirely causally disconnected, there are just parts of the outside (specifically the front) that aren't in the causal future of any inside point as long as the thing is moving. But the whole trip is contained in a future light cone whose apex is on the outside, so there are outside locations from which you could potentially affect everything.
 * As for this experiment, I haven't looked at it, but in general, the people working on warp drives don't appear to understand the physics very well. I imagine they get funded because the people who allocate the funds don't understand the physics either, and they get press/Wikipedia coverage because the reporters don't understand the physics. The paper describing this particular experiment was presented at a conference that's unlikely to have any experts on GR in the committee or the pool of reviewers, which makes me wonder why they accepted it. -- BenRG (talk) 16:33, 21 August 2013 (UTC)