The best answers address the question directly, and back up facts with wikilinks and links to sources. Do not edit others' comments and do not give any medical or legal advice.
Let's say that you have substantial internal bleeding: it's far bigger than a bruise (you have to have a transfusion in order to recover comparatively quickly), but you survive. What happens to all the blood? Does it just accumulate somewhere and gradually get absorbed? Does it somehow rot inside the body? Presumably people survived major internal bleeding in the past, before it was practical to perform surgery on this kind of thing — note that my scenario requires a transfusion for rapid recovery, not for survival — so I assume that the body has some way of dealing with it, and that it can be resolved without surgery to drain it from wherever it goes. Nyttend (talk) 05:32, 13 January 2014 (UTC)[reply]
Bruise doesn't seem to explain just what happens to the blood in the tissue, but as far as I know it's somehow cleaned out and broken down by the body's systems. As to whether that happens with substantial but non-lethal loss of blood internally, the internal bleeding article likewise does not seem to indicate. ←Baseball BugsWhat's up, Doc?carrots→ 06:17, 13 January 2014 (UTC)[reply]
The result of internal bleeding is a hematoma -- that's not a very good article though. The mass of blood is gradually broken down and absorbed, but the process can take a long time. In any case, people usually did not survive major internal bleeding in the past. It was usually fatal. Looie496 (talk) 06:54, 13 January 2014 (UTC)[reply]
Thanks for the link; it appears in internal bleeding, but its presentation made me think that it was some kind of illness. I just figured that people sometimes survived substantial internal bleeding without modern medicine — "when it does not stop spontaneously" is part of the internal bleeding article, so I figured that it sometimes would stop spontaneously; and if that's possible, it might well be possible before life-threatening amounts are lost but after health- and strength-threatening amounts are lost. Nyttend (talk) 07:02, 13 January 2014 (UTC)[reply]
True, but I assumed that capillary bleeding wasn't likely to "compress organs and cause their dysfunction", which comes immediately before my previous quote. Nyttend (talk) 14:21, 13 January 2014 (UTC)[reply]
According to Venereal Disease Research Laboratory test#Mechanism, the VDRL test is a nontreponemal test. The article Nontreponemal tests for syphilis says "Nontreponemal tests refer to a class of syphilis diagnostics that detect infection by indirect markers of infection. Nontreponemal Tests detect biomarkers that are released during cellular damage that occurs from the syphilis spirochete. In contrast treponemal tests look for antibodies that are a direct result of the infection thus, anti-treponeme IgG, IgM and to a lesser degree IgA." Red Act (talk) 09:27, 13 January 2014 (UTC)[reply]
Hyperkalemia in case of putting surgical tourniquet strongly
What is the biochemistry process that causes hyperkalemia when the surgical tourniquet is putted on the arm (of course it's just example, but I think that it's true for every place like legs etc.) strongly.I see it in taking blood tests, especially. Thank you for the help. 194.114.146.227 (talk) 10:05, 13 January 2014 (UTC)[reply]
From Hyperkalemia#Pseudohyperkalemia: "Pseudohyperkalemia is a rise in the amount of potassium that occurs due to excessive leakage of potassium from cells, during or after blood is drawn. It is a laboratory artifact rather than a biological abnormality and can be misleading to caregivers. Pseudohyperkalemia is typically caused by hemolysis during venipuncture (by either excessive vacuum of the blood draw or by a collection needle that is of too fine a gauge); excessive tourniquet time or fist clenching during phlebotomy (which presumably leads to efflux of potassium from the muscle cells into the bloodstream); or by a delay in the processing of the blood specimen. It can also occur in specimens from patients with abnormally high numbers of platelets (>500,000/mm³), leukocytes (> 70 000/mm³), or erythrocytes (hematocrit > 55%). People with "leakier" cell membranes have been found, whose blood must be separated immediately to avoid pseudohyperkalemia." Red Act (talk) 16:16, 13 January 2014 (UTC)[reply]
First of all thank you for your comment. But still I don't understand the biochemistry process that causes hyperkalemia in case of putting surgical tourniquet strongly. Did you mean to say that when it's putted on the arm strongly, it causes to hemolysis? (and homolysis causes hyperkalemia). In addition, I understand that we are talking about hemolysis that occurs in the time of taking blood and rather than about the time after taking blood, because we both know the rule of conservation of mass that explains us which the potassium can not rise by itself after taking blood, it must be occurred in the time of the taking blood and rather than after. 5.28.147.222 (talk) 19:51, 13 January 2014 (UTC)[reply]
The Hyperkalemia article says that hyperkalemia is an elevated concentration of potassium "in the blood", and MedlinePlus, whose target audience appears to be non-experts, also uses that phrase.[1] However, I think that's intentionally using sloppy wording in order to be more accessible to non-experts. Medscape, whose target audience appears to be medical professionals, instead defines hyperkalemia in terms of potassium concentration in serum,[2] which I presume is more accurate wording. The Hyperkalemia#Pseudohyperkalemia section then makes sense if the concentration of potassium within blood cells is higher than in serum, so that hemolysis increases the potassium concentration in the serum. Red Act (talk) 02:01, 14 January 2014 (UTC)[reply]
In general, a submachine gun is a light, portable weapon capable of firing more than one round per pull of the trigger. THAT definition covers such weapons as the M2 carbine variant of the M1 carbine, which was never issued in a pistol chambering by the US Army, but in .30 caliber carbine, but can fire either full or semi-automatic mode, all the shorter (barrel less than 16" long) models in various chamberings of the Colt Automatic Rifle system (the XM-177 variant of which is considered a submachine gun by the US Army and by Colt, its manufacturer despite being chambered in 5.56mm NATO, a rifle round), the various variants of the Avtomat Kalashnikova, the "AK", and "machine pistols" such as the IMI "Uzi," and the MAC-10/MAC-11, Škorpion vz. 61, and Stechkin automatic pistols, which were provided with full-auto capacity to give added firepower to tank crews and special forces troops. Troops don't have to be unusually physically strong to fire submachine guns effectively, and even quite slight women soldiers have routinely carried them.
In contrast, machine guns are all heavily-built fully-automatic weapons chambered either in assault rifle loadings or their own specific ammunition (such as .50 BMG) to provide sustained automatic rifle fire to infantry units or fixed positions in aircraft or tanks. Machine guns are typically neither very light nor very portable (the FN Minimi and M249 machine guns, the MG42, the Bren and the original M1918 Browning Automatic Rifle being the notable exceptions to that rule). They generally require either a husky "squad automatic rifleman" or a pair of infantrymen to be used in an infantry unit afoot.
Agree with the above, but I believe that the term was coined at the end of World War I when the ingenious Germans came up with the MP 18. At that time, the lightest Allied machine gun was the Lewis gun which was considerably heavier and required more than one man to keep it in operation. Therefore a sub-machine gun was a new class of weapon below or "sub" a full blown machine gun. The term light machine gun was already in use to describe the Lewis and similar weapons, the Vickers machine gun was described as "medium" and a "heavy" machine gun fired bigger ammunition. Hence the need for a new way of describing the German weapon. Alansplodge (talk) 08:52, 14 January 2014 (UTC)[reply]
Is it at all reasonable to say that each instant in time exhibits no change at all until the collapse of some Coloumb barrier which-instantaneously-puts us into the next time instant? Is this a reasonable consideration? — Preceding unsigned comment added by 99.182.38.146 (talk) 01:04, 14 January 2014 (UTC)[reply]
I humbly suggest you think carefully about your question, and how to better communicate it to a group of diverse volunteers. You seem to be leaping across several different topics in math/physics, without ever really explaining what you mean. Additionally, your terms are unclear. I am familiar with reaction diffusion systems and advection-diffusion equations (and even Reaction–diffusion–advection_equations), but I have no idea what you mean by "adjunct-diffusion equation." A quick google search indicates that that is not standard nomenclature. Also, please consider asking a single question, instead of several at once. SemanticMantis (talk) 01:26, 14 January 2014 (UTC)[reply]
NB: the OP has apparently cut out large portions of the question in response to my comment. See history/diffs if you are curious. I only note so that I don't look crazy :) SemanticMantis (talk) 01:42, 14 January 2014 (UTC)[reply]
What is the resolution of such reaction-diffusion-advection equations? considered infinitesimal? but how exactly?
Ignoring the stuff about Coulomb barriers, the question seems to be asking whether it is possible that time is discrete. The answer is yes, it is possible. But if it is, the quantum of time is likely to be extremely small, as the presumed quantum of space is thought to be (the Planck scale). Looie496 (talk) 03:11, 14 January 2014 (UTC)[reply]
It looks like the answer to this question depends on what you mean by "Fibonacci pseudoprime". Lucas pseudoprime#Fibonacci pseudoprimes lists three references of authors who define a Fibonacci pseudoprime as being a Lucas pseudoprime with parameters P=1 and Q=-1, and Di Portio proved in 1993 that no even Fibonacci pseudoprimes exist using that definition.[4] However, from that link it looks like some authors consider "Fibonacci pseudoprime" to be synonymous with "Lucas Pseudoprime", and with that alternative definition André-Jeannin proved in 1996 that even Fibonacci pseudoprimes exist for all P>0 and Q=±1 except if P=1[5]. As far as whether an even Fibonacci pseudoprime using that definition can be "calculated", it seem like the answer would have to be "yes", because even though André-Jeannin's proof isn't a constructive proof, even a brute-force search for an even Fibonacci pseudoprime for given P and Q would count as a "calculation". Red Act (talk) 06:04, 14 January 2014 (UTC)[reply]
Why do people measure their pulse at the wrist or neck rather than just measure the heart rate and pattern at the chest, wouldn't this be more accurate? Is it because it can be harder to feel the heart rate for some people? Clover345 (talk) 12:50, 14 January 2014 (UTC)[reply]
I think there's a number of things at play. For one, it can be difficult to pick up the heart pattern at the chest. Clothing, muscles, breasts, fat deposits, etc. all get in the way of getting a clear reading. On top of that, you have the lungs working, meaning you're trying to take a reading on a moving medium. Further, the chest is definitely within most people's personal space and they may find it a bit upsetting to have someone grope them in that way (even leaving aside the issue of a man taking a woman's pulse). If you take a first aid course, they'll tell you not to take the pulse at the carotid for exactly the same reason - it unnerves people and may freak them out if they're already hurt / in distress. Wrists are not ideal (the pulse is often weak there), but at least there's usually not much tissue or clothing in the way and "holding hands" is much more publicly acceptable. Matt Deres (talk) 14:28, 14 January 2014 (UTC)[reply]
This source also mentions convience as a reason for the radial pulse (which effectively covers a bit of what you've mentioned and more) [6]. As I understand it, per that source and others like auscultation, the apical pulse is generally determined by auscultation i.e. listening rather than by tactile feedback or palpation although I'm not totally sure if this applies if no stethoscope is available i.e. you'd need to do immediate auscultation. That source does mention the apical pulse can be palpated in about 50% of adults which suggests it's not a particularly reliable method. And [7], while not a RS, also mentions problems attempting to palpate, and not surprisingly given the reasons outlined by Matt Deres, that it's easier in children and smaller adults. As the first source also mentions, the apical pulse is preferred in a few cases like in infants or where the radial pulse appears weak or non existent. It's also needed to determine if there is a pulse deficit. Nil Einne (talk) 16:33, 14 January 2014 (UTC)[reply]
As for accuracy, if you are only interested in the heart rate the wrist or the carotid is just as good as the chest, as long as you can feel the pulse there. What you feel is the increase in pressure from the heart beats, so the heart rate is the same wherever you measure. Sjö (talk) 20:45, 14 January 2014 (UTC)[reply]
Note that per the sources I mentioned earlier, technically this isn't totally correct since a pulse deficit can exist. See [8] for more (which despite the blog nature and poor formating seems and okay source and I don't think is a copyvio). Of course being aware it exists is generally important so if you suspect it may be the case, I suspect you should take both the apical and radial (or similar?) simultaenously to test for it as per the sources. In other words, you're somewhat correct in that you can generally assume they are the same, because when they aren't you have more serious concerns than simply having the a lower pulse than the heart rate. (This is all presuming you take the pulse correctly.) As a minor aside, I was reminded by Talk:Pulse of something I may or may not have heard before. For 15 months Dick Cheney had no pulse. Although to ward of jokers, this only happened after he left the Vice Presidency [9] (and our article). Nil Einne (talk) 23:34, 14 January 2014 (UTC)[reply]
i have a few questions but ifirst need someone to talk to me about dreams or dreaming
wel first of all i think that the time it takes to fall as sleep thats the same thing about dreaming but like i said i need someone talk to first — Preceding unsigned comment added by 67.225.110.19 (talk) 23:15, 14 January 2014 (UTC)[reply]
I don't understand what you are saying, but I can't see any way to interpret it that would make it true. Dreams usually don't come until after several hours of sleep. The transition from waking to sleep is known as hypnagogia -- it is not the same thing as a dream. Looie496 (talk) 23:26, 14 January 2014 (UTC)[reply]
Is there a scientific reason so many college students only seem to be able to do things in extreme and not in moderation? For example many drink extreme amounts of alcohol, study fr extreme hours in the library, eat extreme amounts of unhealthy foods. If all of this is done in moderation, surely they can understand it would be healthier and may even help reduce stress levels. Clover345 (talk) 23:44, 14 January 2014 (UTC)[reply]
The term "reckless youth" comes to mind, and has to do with a truism I've often heard, that the young think they are immortal. Hence the typical young person might not worry about the issues that the OP is talking about. ←Baseball BugsWhat's up, Doc?carrots→ 00:27, 15 January 2014 (UTC)[reply]
One related idea on the matter is the Cultural Theory of risk which asserts that one's perception of risk is primarily influenced by one's culture. The culture of college campuses enforces a certain perception of risk (that is, what behaviors are considered "risky" and what behaviors are considered "normal" or "safe") is influenced by the environment, which feeds a "status quo" of risk behaviors that would seem reckless in other contexts. --Jayron3201:50, 15 January 2014 (UTC)[reply]
One scientific reason is that college students are in the prime of their life, and can tolerate drinking extreme amounts of alcohol, studying for an extreme number of hours (presumably because they didn't begin studying earlier), etc. A 70-year-old doesn't engage in such behaviors because his body can't handle it, not necessarily because he doesn't want to. --Bowlhover (talk) 03:43, 15 January 2014 (UTC)[reply]
Is this true or just a stereotype? To which country is the question referring? Also, should the question be more about the stereotype that all young people exhibit these types of behaviours and not just students. CambridgeBayWeather (talk) 04:26, 15 January 2014 (UTC)[reply]
People between the ages of 12 and 25 behave differently to fully matured adults because their brains are in the process of being rewired. For instance, it says at THE ADOLESCENT BRAIN -- WHY TEENAGERS THINK AND ACT DIFFERENTLY
"The frontal lobes help put the brakes on a desire for thrills and taking risk -- a building block of adolescence; but, they're also one of the last areas of the brain to develop fully". So they do things to excess because the part of the brain that should tell them when to stop is not fully developed. Googling "the teenage brain" will reveal a lot more on this subject. Of course, this is also a very creative period and people of this age have had a great influence on the development of human society. As it says here "Teenagers can be a pain in the ass. But they are quite possibly the most fully, crucially adaptive human beings around. Without them, humanity might not have so readily spread across the globe.” Richerman(talk)17:42, 15 January 2014 (UTC)[reply]
January 15
Is there any antibodies or antigens which be inherited by genes?
When people refer to "antibodies" they are typically referring specifically to proteins affected by V(D)J recombination, which cannot be inherited genetically (although a mother can pass some antibodies directly to her infant child). However, there are other components of the immune system, such as the complement system, which are heritable. In brief, the complement system is a set of genes that are pre-encoded to recognize and combat certain pathogenic microorganisms, although they still work better if accompanied by a typical antibody response. See also Pattern recognition receptor and antigen. Someguy1221 (talk) 08:38, 15 January 2014 (UTC)[reply]
Arguably, electric charge is a more derived property and is more difficult to directly measure than electric current. Besides, you can have electric current even if no charge moves. S.I. defines electric current in terms of its mechanical effect, not in terms of its constituent motion of charge. Nimur (talk) 16:45, 15 January 2014 (UTC)[reply]
Inkan1969's question is a good one. I have often pondered the same thing. The formal definitions of the Ampere and the Coulomb establish that the Ampere is the fundamental unit, and the Coulomb is the derived unit. However, I imagine that it is easier for a young student to comprehend electric charge (the Coulomb) first; and then to comprehend electric current (the Ampere). I'm not a teacher, but if I were a teacher of physics to teenagers I would first introduce the concept of electronic charge and the Coulomb, and secondly introduce the concept of electric current and the Ampere and the properties associated with an electric current. Dolphin(t)05:16, 16 January 2014 (UTC)[reply]
Yes - having worked in a metrology lab at one point I can confirm that the choice of base units has very little to do with the ease with which the concepts can be taught and is only somewhat related to how fundamental they are as concepts (basically you want to reduce the interdependence of the base units as much as practical, which does lead one towards more fundamental units in general). The main consideration is indeed measurability - specifically minimising the measurement uncertainty and ensuring the measured value is stable over time and between different laboratories (which is why there is so much effort going on to redefine the kilogram as something based on fundamental constants, rather than as the mass of a block of platinum-iridium in Paris). Equisetum (talk | contributions) 14:01, 16 January 2014 (UTC)[reply]
It would be logically more reasonable if the kilogram could be defined by counting some number of atoms of some particular isotope - and charge be defined by counting the number of excess electrons present. This would reduce those units to simple integer numbers with essentially perfect and unchanging precision. We've already done that with the definition of a second ("the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium133 atom"). The problem is in getting the required precision for normal use - and the theoretical reproducibility. Making a 1kg mass out of some specific number of 100% pure, single-isotope atoms is a lot harder than making a lump of metal that's more or less the same weight as some other lump of metal. Similar problems exist with dishing out some exact number of electrons to make a standard charge. So in many ways, we're constrained to definitions of units that are practically realizable - and that's more of a technological limitation than it is one of picking the best set of units and definitions conceptually. SteveBaker (talk) 14:36, 16 January 2014 (UTC)[reply]
What is the scientific basis for the claim that studying individually is better than studying in a group?
Who makes this claim, and in what context? It seems like too much of a generalisation to make any 'scientific' assertions one way or another. AndyTheGrump (talk) 16:52, 15 January 2014 (UTC)[reply]
When an article in the media starts with "A recent study shows", it's best to take it with a giant grain of salt. p value for "significance" was set intentionally low so that studies would pick up things worthy of further examination, NOT at all to determine if they are actually real or true. To do the latter, you have to independently replicate the results a few times. Actually having a quick look, the Misunderstandings section of our p value article seems to cover it pretty well. Vespine (talk) 21:53, 15 January 2014 (UTC)[reply]
I could certainly see both advantages and disadvantages to group study sessions:
ADVANTAGES = Others can explain things to you which might be unclear from the lectures and/or book and/or labs.
DISADVANTAGES = Not tailored to your own weaknesses. Presumably you will study more where you know you are deficient.
In other cases, it might depend on the study group. One that encourages you to study when you want to stop would help, while a group that is always goofing off is not at all helpful. Also, I might apply the same rule I apply to learning chess, where I think it's best to play those who are just slightly better than you. They have something to teach you, yet are not too advanced to understand. Also, real experts often don't want to bother explaining "the obvious". StuRat (talk) 22:14, 15 January 2014 (UTC)[reply]
The trouble with this sort of study, for things that are as individual as study methods is that the study can usually only conclude that "on average" one method is better than the other for the population studied. This might just mean that method A is better for 40% of the study sample, for 30% of people it makes no detectable difference, and for 30% of people method B is better. Interpretation is further complicated by the fact that you can't guarantee, without close reading of the relevant paper, that the study is sampling a population of which you are a member - maybe the study was on humanities students, and you are a physics student. The results of these studies are potentially useful for schools and education authorities who need to find the approaches which are effective for the maximum number of people while being cheap enough to implement, but as an individual you are much better off trying different techniques and seeing which work best for you (ideally in a semi-formal manner to remove as many biases as possible). Equisetum (talk | contributions) 12:15, 16 January 2014 (UTC)[reply]
Indeed. According to our article on the star Sirius (technically, it's a binary star): "The star is referred as Makarajyoti in Malayalam and has religious significance to the pilgrim center Sabarimala." - which makes sense because Sirius is the brightest star in the sky (after the sun, of course). This star has many names in many cultures - and many of them give it religious significance and time ceremonies to it's rising and setting at particular days of the year. So there is really no mystery to resolve here. A complicating factor for people writing about this ceremony is that there is an entirely different ceremony carried out a few miles away called Makaravilakku which also entails worshipping Sirius - as well as lighting massive fires to celebrate various aspects of the star. These might very well be visible over the horizon in the hilly countryside of that part of the world and might add to the whole mystical aspects of it all. SteveBaker (talk) 14:24, 16 January 2014 (UTC)[reply]
Depends on how far is "far". The Diamond Age is a fun book set in the next ~80 years or so, and has a lot of interesting stuff about how nano technology interacts with society. Also a good adventure. If you want much farther future, one classic is Isaac Asimov's Foundation_(novel), as well as its sequels. --But really, In my opinion, most of the best Science fiction isn't really about the specifics of technology, it's about human nature and societies. For example, the classic A_Canticle_for_Liebowitz covers thousands of years, but has very little to say about specific technology. SemanticMantis (talk) 15:02, 16 January 2014 (UTC)[reply]
Diamond Age is a great choice - although it focusses entirely on nanotech. I'd like to recommend another book by the same author: Anathem - which describes a world where technology causes horrific boom/bust cycles and the future is largely held by a group of geek/monks who largely eschew technology and who (in a sense) hold the world together by virtue of nothing more than clear thinking and dedication....and it's also a great story! It's rather hard to come up with books where future technology is actually a good thing rather than causing problems. SteveBaker (talk) 15:19, 16 January 2014 (UTC)[reply]
Really? Well, the books couldn't be more different. The monks of Anathem are pacifists and work passively and quietly in the background to make change. I don't think the Jedi of StarWars are much like monks and the rest of the universe seems to be at a more or less static technological level rather than going through boom/bust cycles. The monks of Anathem are reclusive in the extreme - with some sects cutting themselves off from the outside world (and even other monks) for 1000 years at a time. Anyway - trust me, Anathem and StarWars are about as opposite as any two SciFi universes that I could imagine! SteveBaker (talk) 15:40, 16 January 2014 (UTC)[reply]
Technology has reached an "interesting" level in Iain BanksCulture series. His writing is also more literary than most of the classical hard-core SF writers, so it might be a better match for Lem's books than, say, Asimov or (shudder) David Weber. The Player of Games is often recommended as an entry to the series, and is excellent. --Stephan Schulz (talk) 07:43, 17 January 2014 (UTC)[reply]
Extrapolation of energy components and the end of scarcity
1. How reliable are the dotted line projections on this graph?
2. What is the proper way to extrapolate the sum total of the components of the graph?
3. What is the proper way to extrapolate the individual components of the graph?
How reliable are the dotted line projections on this graph? - they are highly susceptible to political change. If the major politicians of the world truly understood the global climate change problem - then oil, coal and gas ought to start to head downwards - but if they continue to ignore the problem then at least natural gas consumption will increase. The solar power increase is a technology-driven thing, and that's somewhat unknowable. Nuclear power is a matter of public opinion more than science - and one event like Fukushima is enough to set back development for another decade until it fades from public memory.
What is the proper way to extrapolate the sum total of the components of the graph? - just plot a new graph that is the sum of the others with an extrapolation curve that is the sum of the other extrapolation curves.
What is the proper way to extrapolate the individual components of the graph? - In the absence of any new knowledge of the future (eg some new technology that's due to come on-stream at some particular date), there are standard mathematical techniques as outlined in extrapolation. But in fields like this, it's common for people who are expert in the field to point out those kinds of things that will alter the mathematical expectation in some way. For example, we think we have a fair idea about how much oil there is left in the ground and what the cost and difficulty that extracting it would entail - and that might cause the graph to dip downwards in the future, even though the demand for the stuff might continue unabated.
When renewables overtake fossil fuels, does that mean the NAIRU can be reduced? - that's a tough call. I don't have a good answer for you. But beware though - the vertical axis is a logarithmic one - it tends to make renewables look much more important than they really are and it strongly emphasizes change where there may not be much - and de-emphasizes drastic changes by turning exponential growth into a more gentle curve. This graph makes it look like hydro and nuclear are a huge chunk of the total energy supply - when in reality there is ten times less hydro power than there is oil - and thirty times less than all fossil fuels put together! Wind contributes only about 1% as much as oil and 0.3% as much as all fossil fuels combined!
This is admittedly un-sourced speculation, but I don't really see how the projection for solar is remotely plausible. There are some pretty serious technical challenges with increasing the efficiency of solar cells, I don't really see how the sum total of energy produced by solar power could be expected to increase linearly without relying on a (as of yet non-existant) major technological breakthrough. It seems as though this chart conflates two issues, especially relevant to the solar example: 1) increased efficiency of solar cells and 2) increased coverage/usage of solar cells. Even if you get 100% coverage, you're still going to hit a ceiling unless you also develop better photovoltaics. (+)H3N-Protein\Chemist-CO2(-)17:15, 16 January 2014 (UTC)[reply]
Oh - it's *FAR* worse than that. The vertical axis is on a log scale - so they are predicting exponential growth at an insane rate. I don't pretend to know whether those graphs are correct - and that's not really what we're being asked here. SteveBaker (talk) 20:00, 16 January 2014 (UTC)[reply]
The historical exponential rates depicted are not insane, and while there are always good reasons that no growth lasts forever, the potential for moving out into the Solar System has convinced me that the projections individually and collectively are sane and accurate enough for my purposes, which is depicting the changes in these production levels. Tim AFS (talk) 01:55, 18 January 2014 (UTC)[reply]
There is no technical reason that one can't grow solar power 100-fold solely by deploying 100-fold more capacity even without improvements in efficiency. As of 2010, you could increase US solar power 300-fold just by putting solar panels on every rooftop. That's not even considering that there is enough sun in the desert of the American southwest to meet all of the world's electricity demand. Now putting a solar panel on every roof or blanketing the desert wouldn't be cost-effective right now, but it doesn't actually require more efficient solar cells, just cheaper ones. Solar PV has a long history of falling prices, and with the recent expansion of Chinese production, that trend has actually accelerated. A solar module today costs only about 25% of what it cost five years ago, which is fueling a lot of growth, and if prices continue to fall then projecting solar as a significant component of the global energy mix might not be unreasonable. Dragons flight (talk) 18:22, 16 January 2014 (UTC)[reply]
The problem is that you can only collect energy from solar panels during daylight - and perhaps only usefully collect in summer at some latitudes. In order to make practical use of all of that energy, you need a means to store it efficiently - and that does not yet exist on anything like the scale required here. But in any case, that same argument could be applied to wind, tidal, hydroelectric, geothermal and nuclear - yet those graphs are not anywhere close to that crazily steep. SteveBaker (talk) 20:00, 16 January 2014 (UTC)[reply]
I should have also mentioned that solar and wind are much less expensive than hydroelectric and nuclear, and the former are falling while the latter rise in cost. Tim AFS (talk) 01:58, 18 January 2014 (UTC)[reply]
How much would it cost to subsidize renewables overtaking fossil in half the time, compared to flood and crop insurance costs? Tim AFS (talk) 22:48, 16 January 2014 (UTC)[reply]
It is a hard thing to estimate, but one can look at the difference between solar / wind costs and coal / gas costs. Based on current costs, replacing fossil fuels over the next 30 years would add roughly a $100 billion / yr to the cost of electricity. The hope is that as renewables continue to scale up, the added cost will come down. Global insured losses due to natural disasters (all types) average $20 - 50 billion / yr (though some years can top $100 billion). At present, it is probably cheaper to insure losses than to fund the wholesale conversion to renewables, though that probably won't always be the case. Dragons flight (talk) 22:13, 17 January 2014 (UTC)[reply]
@Dragons flight: Thank you! Does that include government flood insurance plans and self-insurance costs? Please let me ask the same question a different way: What proportion of the world's $650 billion per year of fossil subsidies should be moved to renewables in order to minimize total energy, flood mitigation, and food spending? I am convinced that the answer is on the order of 85% because raising the cost of transportation fuel raises the cost of food, but only in a very small proportion. Tim AFS (talk) 01:55, 18 January 2014 (UTC)[reply]
Was this graphic created by a bot? The "Author" is listed as a redlink user:AI.Graphic, here [13]. exponential growth looks linear on a semi-log plot, while linear growth looks logarithmic.Anyway, I looked at the source and found this 45 page pdf [14], and this interactive charting tool [15]. There doesn't seem to be a similar chart in the pdf, nor can I get the tool to display the info broken down that way. The tool does show an exponential increase in all renewable sources over the time period 1967-2012. I did a few spot checks against the tabular data in the pdf, and it looks ok so far.
What I can't find anywhere in either document is projections, let alone exponential extrapolation. Naively, (without getting into geopolitics, etc), I'd say use of exponential extrapolation here is unwarranted, unless further justification is provided (which would constitute WP:OR, unless you find other WP:RS that specifically talk about extrapolating this stuff). Linear extrapolation would be much more conservative, but the graph is probably most informative without any projections at all. As it stands, it runs the risk of misrepresenting the source data. On summary, I think the best course of action is to keep only historical data on this plot, and use other sources for projections (there are indeed hundreds of such sources, but that's a different can of worms.) SemanticMantis (talk) 21:19, 16 January 2014 (UTC)[reply]
Sorry, I thought you might know since it has so few links, and two are from you. I found that an IP editor claimed authorship here [16], but it would probably be difficult to track them down, if they are only associated with a redlink user and an IP. Anyway, I stand by my claim that the projections in the graph are generally unreliable, and should not be included in an article unless further justification and references are given. SemanticMantis (talk) 23:16, 16 January 2014 (UTC)[reply]
Well, in nature most growth is exponential unless it hits a snag. Much the same is true in economics - notice how we are always talk about GDP growths in percent - a constant 2% growth results in an exponential curve. More realistically, most of these "exponential curves" are probably the lower half of a logistic curve, but it's generally hard to find out where in the curve we are. In the diagram, solar, geothermal and wind seem to match exponential curves very well for the last few years (the solid parts of the curve). So yes, the exponential growths will stop (after all, the sun puts out only 3.846×1026 W, so that's a hard upper limit on the maximum solar and wind can provide). But it is very hard to say where the exponential growths will stop. --Stephan Schulz (talk) 12:26, 17 January 2014 (UTC)[reply]
Animal mating
During copulation, is there a biological mechanism that helps guide the semen to the appropriate external orifice of the female without entering the WRONG orifice (namely, the anus)? 140.254.227.253 (talk) 18:06, 16 January 2014 (UTC)[reply]
I'm talking about mammals here. It doesn't have to be specifically humans, since I've observed dogs and cats engage in copulatory acts, and apparently, the male dog's penis somehow finds its way to the correct orifice. 140.254.227.253 (talk) 18:10, 16 January 2014 (UTC)[reply]
I will answer for non-human mammals. There is not one single mechanism, but rather a suite of physical adaptations and evolutionary processes at play. In simplest terms, any individuals that don't successfully copulate cannot pass on their genes and traits to the next generation, so at a first approximation, we could say that a large percentage of unsuccessful copulation is maladaptive, and such individuals will tend to die out/go extinct (there are some caveats here). Have a look at Animal_sexual_behaviour, Reproductive_system#Mammals and mate choice for the general background. It's a bit unhelpful, but for most mammals, successful copulation by delivering semen to a vagina is simply instinct, as well as a path of least resistance. We do have an article Homosexual_behavior_in_animals, but note that many of those examples don't involve penis-in-anus copulation. SemanticMantis (talk) 19:00, 16 January 2014 (UTC)[reply]
For the caveats, there are ways that non-reproductive animals can pass on their genes and traits. In particular all ant species and many bee species have sterile workers, that still can contribute to evolution and natural selection. This evolution of sterility was confusing even to Darwin (Eusociality#Paradox), but it can be explained through haplodiploidy and kin selection, but that's a bit off-topic to your question. SemanticMantis (talk) 19:00, 16 January 2014 (UTC)[reply]
That makes sense. Instinctive behaviors are much more easier to explain in nonhumans than humans. I merely asked this question out of curiosity, based on the sex positions article. One might wonder how oral sex and anal sex evolved, when those are not procreative acts. One might also wonder how a male and female can engage in vaginal sex in so many different sex positions, or whether there is a quick-and-easy, intuitive, instinctive way of impregnation. 140.254.227.55 (talk) 21:28, 16 January 2014 (UTC)[reply]
The simple (but again not that informative) explanation for oral and anal sex in humans is "because humans are creative, there is no big cost, and some people enjoy those sex acts" -- But the big thing to realize is that, though sex is the sole method of reproduction in mammals, it can also serve other purposes as well, e.g. pair bonding. I recommend "Why is Sex Fun? The Evolution of Human Sexuality" by Jared Diamond, google books here [17]. I haven't read it yet, but the author is generally highly regarded, and the table of contents indicates that it discusses many of your questions. SemanticMantis (talk) 22:01, 16 January 2014 (UTC)[reply]
No it isn't necessary but according to this it may improve the chances of conception. If you watch other primates copulating they don't usually bother with foreplay at all. Richerman(talk)22:13, 16 January 2014 (UTC)[reply]
Marking of university exams
How are university exams in the UK marked compared to school GCSE and A-Level exams where examiners simply follow a mark scheme? I.e. Witnout a mark scheme, how are the allocation of marks decided? Clover345 (talk) 18:46, 16 January 2014 (UTC)[reply]
British universities use a system of internal moderation followed by assessment by External examiners. The systems used are overseen by The Quality Assurance Agency for Higher Education (QAA) who ensure the procedures used are fair and equitable. See: [18]Richerman(talk)22:55, 16 January 2014 (UTC)[reply]
It would certainly depend on whether you mean *opening the box* or *removing the plastic screen-cover*, the environmental conditions in the kitchen or cooking area, the type of preserved food, and the label on the food package that sets the approximate due date. 140.254.227.55 (talk) 21:03, 16 January 2014 (UTC)[reply]
If you mean conceivable using human technology, the answer is most definitely no. Human technology cannot even control a terrestrial weather system or tsunami, which involve the movement of a tiny fraction of Earth's mass, which in turn is 1/300,000 the Sun's mass. --Bowlhover (talk) 23:59, 16 January 2014 (UTC)[reply]
There are many reasons why this is impossible - but one of the more serious is that stars are immensely heavy - to the point that they would collapse into a tiny dense core (a neutron star - or even a black hole). What prevents that from happening is the radiation pressure of all of the light coming from the star. So if you could somehow prevent it from consuming fuel by nuclear fusion, it would immediately collapse under it's own weight. SteveBaker (talk) 03:19, 17 January 2014 (UTC)[reply]
Let me add that Wikipedia's "list" articles are usually not constructed in a very systematic way. Basically editors add whatever they think of. Looie496 (talk) 03:08, 17 January 2014 (UTC)[reply]
One of the things that humans need from food is the pleasure of eating, often communally, and especially in celebration. Can't imagine a capsule delivering that. HiLo48 (talk) 00:59, 17 January 2014 (UTC)[reply]
If by capsule you mean something very small, the answer is no. The densest form of calories is pure fat, such as vegetable oil, and it takes about 2 cups of vegetable oil to provide as many calories as an ordinary adult needs for a day. If you substitute things that provide nutrients such as protein, vitamins, etc, this will get considerably larger. Looie496 (talk) 02:45, 17 January 2014 (UTC)[reply]
Since English does not have grammatical gender, only sex (i. e., natural gender), and hair is not a feminine noun, I agree that it does not make sense to say blonde hair, whether the hair belongs to a female or male person. However, it does not make sense to call a woman blonde, either, as blond and brunet would be the only adjectives to exhibit this behaviour, since all others are invariable except for synthetic comparison. As an adjective, blonde is essentially only a variant form – in my POV: a pure misspelling – of blond. The only unarguably correct use of blonde is as a noun (a) blonde for "blond woman", although the obscurity of the use of the male counterpart (a) blond reveals a sexist bias, I suspect. See also my comment at Talk:Declension#English example for an adjective that declines. --Florian Blaschke (talk) 16:55, 18 January 2014 (UTC)[reply]
In British English 'blonde' is correct as a noun or adjective according to the OED and blond is only listed as an alternative spelling. I've never seen the spelling 'brunet' before - it gets a mention in the OED under the entry for 'brunette' but it says 'now chiefly US' Richerman(talk)19:35, 18 January 2014 (UTC)[reply]
"Sexist bias" my ass. I think that's PC nonsense. How is being a "blonde" worse than being a "blond"? --Trovatore (talk) 21:39, 18 January 2014 (UTC) Ah, rereading your comment, I seem to have misinterpreted you. I still think it's a bit hypersensitive though. --Trovatore (talk) 21:42, 18 January 2014 (UTC)[reply]
The Movie Gravity.
1. When George Clooney untethers himself from sandra bullocks, why does he drift away from earth ? Shouldn't he be revolving around the earth just like a satellite ?
SPOILERS: I have seen the movie, and yes, Clooney would not drift away in a real situation like that. As for the second, if you saw the film, you would hopefully have noted that the hatch never actually opened. Mingmingla (talk) 17:09, 17 January 2014 (UTC)[reply]
1. If Clooney was tethered to Bullocks but still accelerating (and stretching the tether) then breaking the link would make Clooney drift away.
2. he didn't do that, it was all Bullocks' dream. But no it wouldn't drain all the air that is still compressed in some sort of cylinder. Bullocks could open and close the oxygen supply, so there was air somewhere.
For watching films you need Suspension of disbelief. Gravity is not a documentary about how things work in space. The whole story is full of holes to make the story look more appealing. Traveling from the Hubble telescope to one space station and then to another, showing Bullocks in sexy hot-pants (instead of a more appropriate thermal suit below the space suit), and much more, makes the story progress. OsmanRF34 (talk) 18:05, 17 January 2014 (UTC)[reply]
For suspension of disbelief you need a fiction which has its own rules and which abides by them consistently. The core rule undercutting most fiction is the world is the same unless otherwise stated, and if it makes it not the same without justification, the suspension breaks, the immersion breaks, and the enjoyment is reduced.
For (1) it makes sense if you assume that they are spinning slightly so there is some centrifugal force pulling him away from the tethers. They did such a good job with the rest of the science that I bet the writers had this much better, but it got lost somewhere between storyboarding and the edit room floor. 109.70.142.60 (talk) 23:44, 17 January 2014 (UTC)[reply]
Eating when not hungry
People say eating when not hungry can lead to becoming overweight but is this true even if the recomnended daily calorie intake is not exceeded? 82.40.46.182 (talk) 12:44, 17 January 2014 (UTC)[reply]
Yes. Simply because you may not be using all the calories you're taking in. Recommended daily intake is vague at best. Many other factors, such as age, gender, level of activity, genetics, etc., can affect what YOUR RDI is. See Weight_gain196.214.78.114 (talk) 13:27, 17 January 2014 (UTC)[reply]
Only in general though. Any number of external factors could be affecting the person's appetite. (Making them not feel hungry when they really do need calories, or vice-versa.)
I've heard two pieces of advice: "Never eat when not hungry" and "Always eat breakfast". Unfortunately, I'm never hungry when I first wake up, so those two are in conflict for me. I decided to go with the first bit of advice, and not eat breakfast. StuRat (talk) 23:59, 17 January 2014 (UTC)[reply]
Second-order differential equation in Simple Harmonic Motion
I am reading a physics book in which the following equation is given:
i.e., second-derivative of position (x) w.r.t., time (t) is equal to negative of position (x) times spring constant (k) divided by mass (m). My book just says "it is a second-order differential equation and after solving this equation you get
". But it didn't mention how to solve this and only give the answer. If possible, I want someone to show me steps how to solve second-order differential equation. Britannica User (talk) 13:57, 17 January 2014 (UTC)[reply]
It sounds like you're reading a physics book that's a notch ahead of your mathematical preparation. By the time you read that book, its author assumes that you should have the equation for simple harmonic motion etched indelibly into your memory, and recognize its solution by inspection; maybe you skipped a few books ahead of your level. But how is the solution derived?
The solution is predicated on using Euler's formula to represent the cosine in terms of a complex exponential. Solve the differential equation by the separation of variables method, and recognize that the exponential function is a good ansatz because it equals its own integral (rather, it is linearly related to its own integral... and in the sloppy math we do in physics, that means it's equal, because we don't worry about a scale factor or a constant offset - those are just coordinate changes). Apply the physical constraints (which are stated implicitly, because no initial condition was provided), and drop the sinusoidal term (representing an arbitrary phase lag). This sort of thing is covered in gorey detail in a book on methods of solution for ordinary differential equations.
So, this is just another case where "thinking like a physicist" means "knowing the math so well that you do all of the above by inspection." Most people need two or three years of mathematical training beyond their initial integral calculus work before they can just see this sort of thing. Some people, no matter how much time they pour in, never get there. And every few centuries, we get a Newton or a Fourier and they just get it.Nimur (talk) 14:23, 17 January 2014 (UTC)[reply]
Oh, and if you don't like Euler's formula, or if you're a skeptic who doesn't want to use eiωt as your trial function, then you can re-express your ansatz as a Taylor expansion-style infinite sum of polynomial terms, and it can be proved that the series will converge by solving explicitly for the polynomial coefficients. You will also prove that the exponential would have been a good choice. So, you can solve this equation numerically, too. In fact, there are many ways to find solutions to this very common equation. Nimur (talk) 14:30, 17 January 2014 (UTC)[reply]
I am a 10th grade student, but grade doesn't matter. I know about complex numbers, Euler's formula, differentiation (ordinary as well as partial), integration, and how to solve first-order ordinary differential equations; however, I don't how to solve second-order differential equations. A book on Calculus says this "There is no general analytic method for finding solutions to second-order and higher differential equations. Solutions of such differential equations are often obtained by educated guessing, or numerical methods". If the solutions are obtained by educated guessing, then I noticed that there can be many possible solutions of the second-order DE I mentioned above. Therefore, why did the author of my physics book just stick to a single solution? How did he know only that solution would fit to that equation? Britannica User (talk) 15:47, 17 January 2014 (UTC)[reply]
Not a problem... just don't panic if there are some complex parts in the math. With enough time and effort, you'll get it.
In general, if a solution space is spanning the problem space, we can guarantee the solution is unique. In methods for solving differential equations, we construct an orthonormal set of basis functions from which we construct the solution. Even if we guess the answer - that is, if we use an ansatz function - we can still prove it is correct. Purist mathematicians have lots of tricks to help us make good guesses; but your book is correct, sometimes there is no analytic method when you've got very hard equations. (Sloppy physicists just learn how to guess right, and prove it later).
This probably sounds jargon-y, but what it means is that we have a formal, mathematical way to prove that our solution is complete and that it is the only possible solution for this problem. Here, we would use A cos (ωt) + B sin (ωt) and we know B=0, and ω2=k/m because we solve the equations explicitly. B could be nonzero if initial conditions were specified. As physicists, we don't care, because the function is periodic, so we can slide around the time we define for "t=0" until B is also zero. Nimur (talk) 15:52, 17 January 2014 (UTC)[reply]
If you want to learn the technique that applies here, the key thing to know is that the equation is linear. There is a general method for solving linear differential equations of all orders. Our article unfortunately is written at a level of abstraction that you probably won't be able to handle, but any textbook that covers differential equations will have a section on this class of problem. Looie496 (talk) 16:07, 17 January 2014 (UTC)[reply]
Indeed. The simple harmonic oscillator equation is especially easy to solve because it is both linear and homogeneous. Your book which said "There is no general analytic method for finding solutions to second-order and higher differential equations" probably had in mind more general *non-linear* differential equations, which are much more difficult to solve explicitly. Gandalf61 (talk) 16:27, 17 January 2014 (UTC)[reply]
And for the simple harmonic oscillator, there are many methods to analytically find the solution; separation of variables, for example. You can also take the Laplace transform (or any other differential transform) and solve algebraically in the transform domain, and then apply the inverse transform to find the result. This specific equation, x’’ = ±Cx has been analytically solved for hundreds of years in thousands of different ways. Nimur (talk) 16:38, 17 January 2014 (UTC)[reply]
We have an article specifically on the Harmonic_oscillator that may help. It is often easiest to find the Characteristic_equation_(calculus), which reduces the problem to simple algebra. The solution behavior depends on the roots of this equation: each root leads to a solution, and the general solution is a linear combination of these solutions with arbitrary real coefficients. You might also look at some other calculus books: both of mine discuss harmonic oscillators in a chapter on elementary differential equations. Hope this helps. OldTimeNESter (talk) 17:15, 17 January 2014 (UTC)[reply]
You can do the following:
Introduce a new function:
Now we have:
The above equation can be solved by simple integration: , where is a constant
Taking into account the definition of we have:
Or:
The latter equation can be again solved by simple integration:
The latter integral you can calculate yourself as an exercise.
How do people have sex in "impossible sex positions"?
It's a short story, written by a well-regarded author, William H. Coles, here. The short story only mentioned it briefly, yet it got me thinking what type of character Denise was like and what she could have placed in her story. How do people know if a particular sex position is "impossible"? When there is no penetration or something? 140.254.227.125 (talk) 15:28, 17 January 2014 (UTC)[reply]
See hyperbole. Were a student to regularly describe lovers copulating while hanging from chandeliers or standing on their hands, her creative writing instructor may well describe her as being "fond of [writing about] intercourse in impossible positions" even thought such positions may be possible with sufficiently strong and well hung lighting fixtures and acrobatic participants. --ToE05:39, 18 January 2014 (UTC)[reply]
Generally we consider gravity in determining impossibility. Most of the impossible positions require zero gravity, a series of straps, or an underwater environment to be feasible.--Aurictalk17:18, 18 January 2014 (UTC)[reply]
How to calculate probability of a complex system
It's clear that if you have a die or a bag full of red and black balls you can see how probable are one result or the other. But what if you cannot run several tests (like in the case of nuclear reactor or a space shuttle), and you have a extreme complex system, how can you calculate the probability of failure? OsmanRF34 (talk) 17:58, 17 January 2014 (UTC)[reply]
You have to look at all the possible failure modes, figure out the probability of each, and then combine those. For example, failure mode and effects analysis of an electrical system involves looking at a break in every wire, to determine which breaks will cause serious problems, and which will not. In many cases multiple failures are required to cause a disaster, so then those probabilities much be combined. StuRat (talk) 18:11, 17 January 2014 (UTC)[reply]
If you want a simplified example, let's say there are two ways in which a system can fail, and the first requires 2 things to go wrong, while the 2nd requires 3, and for convenience, we will say each component has a 1% chance of failure per year:
Note that Ptotal is very close to just being the sum of P1, P2, etc., for small values, so sometimes that approximation is used. Here Ptotal was the chance of a disaster in one year, but you could get the chances for a decade or a century just by combining them in the same way as the last step above, where P1 would then be the probability of any failure in year 1, P2 in year 2, etc., and you can just keep adding more terms like that to get the total probability over the full time period.
One limitation of this type of analysis is that it assumes that each component failure is independent of the rest. However, this isn't always the case. You can have a cascade failure, where one failure causes others, like an electrical grid where one wire going down puts too much power on the rest, and then they fail, too. You can also have a common outside cause for multiple failures, like an ice storm causing many electrical lines to go down. For a real example, the Fukushima Daiichi Nuclear Power Plants lost primary reactor power, backup electrical power from the grid, and the backup generators, all due to the same earthquake and tsunami. Not having any power then made it difficult and dangerous for them to open and close valves manually, which made it impossible to control the reactors.
With this is mind, the historic failure records of a complex system may be more useful in figuring out the overall risk. However, this isn't possible for a new system, unless similar to existing systems. And, even then, quite a minor change can have a huge effect on the overall risk. For example, had the backup generators been stored at the highest elevation in the complex, they would have been above the waterline and thus would have functioned to prevent the disaster.
I should probably also mention that human factors figure in to risk, as well. Specifically, once a system has worked well for many iterations, everyone becomes complacent, and safety standards drop, until a disaster happens, which causes them to tighten up on safety, until many more safe iterations, when safety standards start to drop again. This can lead to a cycle of disasters, relatively evenly spaced out, over years. The Space Shuttle disasters are an example of this. StuRat (talk) 18:34, 17 January 2014 (UTC)[reply]
To give an example of historic failure rates, there have been three major incidents in the nuclear power industry (Three Mile Island, Chernobyl, and Fukushima) out of 14500 reactor-years of operation. There are currently about 450 reactors in operations, which would suggest that a major incident might be expected to occur on average every 11 years. Of course, one might hope that each major failure leads to improvements that make future failures less likely. The fact that Fukushima occurred 25 years after Chernobyl might support that conclusion (or it might just have been good luck). From a practical perspective, one makes the systems that one understands as safe as possible, and hopes doing that is good enough to protect against problems that no one planned for. Dragons flight (talk) 22:36, 17 January 2014 (UTC)[reply]
I don't think I'd include Three Mile Island as a major incident. It was a minor incident blown out of proportion by the media. Nobody died. StuRat (talk) 00:05, 18 January 2014 (UTC)[reply]
January 18
Brain death and life support
Hi all. After reading the news today about Jahi McMath's body slowly deteriorating while on life support, and the fact that her brain will slowly turn into liquid, I was curious. Does the body generally function normally despite being on life support and having no brain activity? What parts of the body tend to fail first and why? Why can't she maintain her body temperature (apparently hers is always low)? Any other random information on this subject would be interesting. Thanks! Justin15w (talk) 02:00, 18 January 2014 (UTC)[reply]
I think that theoretically you could keep a person alive for the rest of their natural life on total life support. However, in practice, this is quite difficult to achieve. Consider something as simple as bed sores. A healthy person would feel the need to adjust their position, and roll over in their sleep, and the problem would be solved. Somebody brain dead doesn't roll over, and therefore their blood doesn't circulate properly, eventually causing sores, then tissue death, then gangrene and blood poisoning and death. Now if the staff constantly adjusts the patient's position, this can be avoided. And this is just one of dozens of simple problems that can happen. Add them all up and the chance of living to their normal life expectancy is quite low. (The staff would also need to use electrical stimulation to exercise all the muscles, perhaps occasionally administer a stimulant to get the heart pumping faster, then lift them out of bed to an upright position, etc.) StuRat (talk) 02:22, 18 January 2014 (UTC)[reply]
There's more going on than that. The brain controls a lot more than just breathing. It controls body temperature, salt balance, blood pressure, some digestive functions, some immune functions, etc. Once the brain dies, many other things go out of balance, and inevitably this leads to general system failure. Also the breakdown of the dead brain tissue generates toxic byproducts that damage other tissues. Looie496 (talk) 02:47, 18 January 2014 (UTC)[reply]
So how did Ariel Sharon remain alive for 8 years while in a persistent vegetative state. Look at the case of Elaine Esposito - and that was before we had "modern" technology. It would be interesting to know where the OP got the idea that Jahi McMath's brain would slowly liquify. Was that from a reputable source or press speculation, rather like we have here? Bedsores are the very least of the problems. There is plenty of technology available involving variable pressure mattresses that prevent the problem of localised pressure leading to bedsores. The idea of electrically stimulating the muscle to maintain their tone is a curious and incorrect notion. Passive exercises would be used to prevent contractures. The line "I think that theoretically you could keep a person alive for the rest of their natural life" What is natural about being kept alive in a coma? Reminds me of an incident I witnessed when an anxious patient told the consultant that he was worried about his heart and that it might stop. The consultant listend to his heart with a stethoscope and then said, "Your heart is fine, it will last you for the rest of your life". The patient was greatly reassured. There are so many variables in this question and the problem of keeping people "alive" that it is relative difficult to give a general answer. Richard Avery (talk) 08:20, 18 January 2014 (UTC)[reply]
I agree absolutely and I was not making comparisons between the condition of Jahi McMath and that of Ariel Sharon. I was correcting some misleading information/uninformed speculation about the nursing care of a person in a long term comatose state. Richard Avery (talk) 15:01, 18 January 2014 (UTC)[reply]
Not every facility has the equipment or staff required to prevent bed sores. And yes, they are just one of many possible problems, which is what I said. As for passive exercise (just moving the limbs periodically), that would be OK if the person is never expected to recover, but electrical stimulation of muscles will prevent muscular atrophy, which is important if they are in a coma and expected to recover. Otherwise, when they awake and can't walk, they may get discouraged and suffer from depression.
Another issue with temperature maintenance in brain dead or coma patients is that a person who is just asleep will shed covers if they overheat or snuggle under them if they get cold. These simple temperature control mechanisms no longer work for the comatose and brain dead. StuRat (talk) 15:25, 18 January 2014 (UTC)[reply]
There are very important differences between (1) a persistent vegetative state such as Sharon was in, (2) coma, and (3) brain death. In a vegetative state the brain is largely functional, but not functional enough to support consciousness. A person in this state shows substantial activity, including sleep-wake cycles, eye movements, withdrawal from painful stimuli, bowel movements, etc. What is lacking are purposeful movement and communication. In true coma, which rarely lasts for longer than five weeks, there are no sleep-wake cycles, no eye movements, etc. Only some very basic reflexes are functional. Coma almost always resolves within a month either into a vegetative state or into brain death. In brain death, all of the electrical-activity-generating tissue within the brain is dead. Not just non-functional, but actually dead. Looie496 (talk) 17:46, 18 January 2014 (UTC)[reply]
Powder beetle bite humans.
Request for medical advice
The following discussion has been closed. Please do not modify it.
Got a beetle bit a year & 5 months ago. Had Dr.' s look at it at OHSU about 20 of them and they didn't know what it is now it is eating my hand away. The VA don't even know for sure what it is.Please help I can't be the only one in the world with this. I still have a few of the bugs in a jar. — Preceding unsigned comment added by 199.15.221.104 (talk) 10:27, 18 January 2014 (UTC)[reply]
Long rambling introduction of how I came to be in this position, that you can skip if you want: I originally bought a 3D printer some time ago, when they were just getting interesting, and since then have worked at producing and selling a range of different simple things, keyrings and figurines mostly, but more recently I thought to use my contacts in the costume industry to supply a few simple plastic parts there, items mass produced, strong and light weight, it seemed a good idea. Soon after, I was approached by someone that was interested in creating similar items for the same industry, out of silicon, and they asked if I would be able to produce moulds for them to cast these shapes. Initially I was a little reluctant, since it would allow them to compete with me in the same area, but I saw the value in working together and went along with it, designing a few simple moulds for them to use. However, they have since hit some issues of their own, and it is looking like they will not be able to go through with their plans at all. Which leaves me thinking, there is only a certain limited demand for printed plastic items, any chance to expand my business is helpful at this point, so perhaps I can pick up where they left off?
I am interested in casting items out of silicon (by which I mean the soft, slightly rubbery plastic stuff, I am not sure if it is related at all to the element of the same name) however, I am not entirely sure how to go about doing so, I know the basics of casting in moulds, but not the specifics for this particular material, and the internet is not being helpful, any search leads me to casting of other materials within silicon moulds, which seems more common. So, I wonder whether I might get a better answer here, from real people. Any suggestion of where I might find instructions on this method? Suggestions of good places to buy materials and equipment would also be helpful. From what I have seen, it is an area of some demand, and a wide range of possibilities, so a good opportunity for me if I can take it.
Yes, and of course silicone contains silicon, hence the name. I've often thought that most plastics used in the kitchen should be replaced by silicone, as it doesn't absorb smells and colors like plastics do, and doesn't melt or degrade at the same low temperature as plastics. For example, I have nice glass bowls suitable for refrigerator or freezer storage, microwaving, and serving, but they have plastic covers which can't take microwaving and even warp in the dishwasher. One shortcoming of silicone seems to be that you can't get the same vibrant colors as plastics, but I could live with that. StuRat (talk) 23:10, 18 January 2014 (UTC)[reply]
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