Wikipedia:Reference desk/Archives/Science/2013 February 12

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February 12

Engineering contractors

I sometimes hear of "Engineering contractors" and "Engineering consultancies". Is an Engineering contractor in CIvil Engineering basically a construction company? Clover345 (talk) 00:15, 12 February 2013 (UTC)

This may vary from country to country. However, in the USA and in Australia, and engineering contractor would normally be a firm subcontracted to a construction contractor acting as prime contractor (i.e., the firm that is hired by the customer that wants the thing built), to provide engineering services to the prime contractor. These engineering services will include design calculations and production of detail drawings (as distinct from concept drawings produced by the customer or architect) as well as installation of engineering products such as pipes, electrical services, etc. An engineering consultant is generally a firm or individual that specifically concentrates on calculations and drawings. Doing consultancy work has connotations of doing the less routine or more specialised calculations. For example, if during the construction of a large hydro-electric dam, the engineering contractor's staff notices that subsidence is greater than expected from their own calculations, they may call in a consultant to advise them on what to do about it, if anything.

A firm of consultants will typically have a higher percentage of staff with considerable experience and advanced knowlege, and university degrees are essential (and may comprise of just the one owner /engineer), whereas an engineering contractor will have a wide range of staff with all sorts of trade and professional qualifications, and some will have less experience; some will have just graduated.

An engineering contractor's reputation and ability to get work depends on his ability and reputation to get things done on time and within budget. A consultant's reputaion and ability to attract work depends more on his ability to solve novel problems and get the right answer.

There is considerable overlap - a firm of consulatnts may often accept work that involves straightforward calculations and may go on site to inspect or supervise work.

Ratbone 01:47, 12 February 2013 (UTC) — Preceding unsigned comment added by 120.145.64.230 (talk)

I know someone whose title is "project engineer" who works for an engineering consultancy firm. His firm is hired by customers to oversee the project as a whole, to make sure that the architect's plans are built according to spec and within code and on time and on budget by whatever various construction firms do the physical works. His main task, besides oversight of the work, is scheduling, since time is money, but certain work has to be done in a certain order. He deals with architects whose plans are impossible to build, either due to cost or bad design, construction companies that pad the budget and cut corners, and customers who want the impossible for less money and in less time than is required. Besides building nuclear plants, high schools, bridges in NYC, and luxury high-rises overseas he spends much of his time in court testifying when the owners, architects, and construction companies sue each other. μηδείς (talk) 02:05, 12 February 2013 (UTC)

You are more of a cynic than I, Medeis, but you are not wrong. You have reminded me that that consultants get hired to settle disputes - either by the customer who thinks he's been taken down, or the contractor who thinks he should be allowed to make a profit, or by someone's legal team who need an expert witness in court to bamboozle the judge. Ratbone 120.145.64.230 (talk) 02:18, 12 February 2013 (UTC)

Well, I am just repeating stories I have heard. But googling the name of the gentleman I was talking about you'd think he was a major criminal for the number of lawsuits he's named in--yet his reputation is such people fight over him when he's available for the next project. One other point. He's not normally the main contractor as in the agent who hires the subcontractors. Usually the owners have already taken bids or have usual agencies they work with. He can recommend them if that's what the owner wants, but he doesn't pay them, and he is only paid by the owner, or it would be a possible conflict of interest. μηδείς (talk) 02:42, 12 February 2013 (UTC)

Building off Medeis' answer, note also that "engineer" can be a regulated professional title like "lawyer" or "doctor", see professional engineer. I would expect that an engineering consultation firm, particularly in civil or mechanical contexts, is centered around one or more PEs who are legally able to sign off on the stuff that needs to be signed off -- that would certainly also explain "spending a lot of time in court testifying". Of course, engineering is a little weird when contrasted with lawyers and doctors in that most engineers who are professionally employed as engineers are nonetheless not professional engineers. I am one such, partly because I don't need it for my job and partly because the exams don't map well to my discipline (and so it wasn't worth the effort back when it was convenient, much less now). — Lomn 13:41, 12 February 2013 (UTC)

Agree with all that. Some civil engineers avoid architects like the plague and just do the design themselves, though some architects do have a grasp of realities and they can produce very good designs. And yes it is amazing how much time an engineer in management can spend in court even sometimes fighting the government over silly things it tries to do or contracts it tries to get out of. Dmcq (talk) 10:34, 13 February 2013 (UTC)

Densest element ?

what is a solid element with the greatest density — Preceding unsigned comment added by 98.127.57.58 (talk) 01:06, 12 February 2013 (UTC)

I added a title. StuRat (talk) 01:08, 12 February 2013 (UTC)

Note that elements aren't solids, liquids, or gasses, per se, but exhibit different states at different temperatures and pressures. I will assume you mean chemical elements which are solid at room temperature and standard atmospheric pressure. StuRat (talk) 01:11, 12 February 2013 (UTC)

Standard temperature and pressure is probably a good assumption for a common point of measurement, but I doubt that we actually need to artificially limit things to solids -- they're likely to be more dense than gases/liquids anyway. Here is a list of elements by density at STP. That site further notes that there is some uncertainty regarding calculated densest vs experimentally measured densest, noting that while iridium is theoretically denser than osmium, that has not yet been experimentally measured. We list osmium as "the densest naturally occurring element" (emphasis mine). Some transuranic elements quite probably are more dense, but that likewise has not yet been definitively verified. — Lomn 01:23, 12 February 2013 (UTC)

I added a redirect for densest element, but already there was a redirect for the densest element. Graeme Bartlett (talk) 20:43, 12 February 2013 (UTC)

I'll be honest; I'm not thrilled by pointing those redirects straight to osmium. They declare (in the encyclopedia's voice) a single answer—one which likely won't be true in all temperature and pressure regimes, and (as Lomn notes), isn't necessarily certain even at STP. Better targets might be the List of elements or even our article on Density (which mentions both osmium and iridium jointly as the densest elements)...if we actually really want those redirects at all. TenOfAllTrades(talk) 17:28, 13 February 2013 (UTC)

Spandex vs elastic

My old socks said they had elastic in them, but the new ones say Spandex, instead. Are these two different names for the same thing, or are they different ? If different, will Spandex last as long ? I use bleach in the wash, so how well do both hold up to that ? StuRat (talk) 01:49, 12 February 2013 (UTC)

Stu, you should know better than most to just look up our Wiki article on Spandex first. It will answer your first question at least. Googling will answer the rest. Ratbone 120.145.64.230 (talk) 01:53, 12 February 2013 (UTC)

That tells me what Spandex is, but not what "elastic" is. It's apparently a catch-all term for a variety of elastomers, possibly including Spandex. So, I'm asking which of those is likely to be used in socks. StuRat (talk) 02:02, 12 February 2013 (UTC)

I am astounded that we don't have an article or redirect for the variety of elastic that I am familiar with, which is used in haberdashery. I believe what would be used in socks is known as "shirring elastic", rolls of which are pictured here. It's basically something the thickness of thick sewing thread or thin knitting yarn, but stretchy. --TammyMoet (talk) 09:45, 12 February 2013 (UTC)

Thanks. Do you know how it compares with Spandex, as far as longevity and, specifically, ability to withstand bleach ? StuRat (talk) 17:02, 12 February 2013 (UTC)

I always thought Spandex was an elastic fabric rather than a fabric with elastic woven or knitted into it. As far as ability to withstand bleach goes, I would say it fails on that count, although I can't say I've ever bleached elastic. I'll have a look at my household hints stuff and get back to you. --TammyMoet (talk) 20:42, 12 February 2013 (UTC) http://housekeeping.about.com/od/laundry/qt/bleachtips.htm says don't bleach Spandex or elastic. (Why would you put bleach in a normal wash anyway?) --TammyMoet (talk) 20:44, 12 February 2013 (UTC)

Yes, I am fairly confused by this. Are the entire socks spandex, or just their collars? μηδείς (talk) 20:58, 12 February 2013 (UTC)

I assume just the top. And I like to bleach everything, to prevent mildew. Since these socks are white, bleaching them might also keep them that way. StuRat (talk) 03:51, 15 February 2013 (UTC)

Media coverage of coronaviruses compared to other infectious diseases

Why do coronaviruses get so much media attention compared to other infectious diseases, when they affect far fewer people? As as I write this, many news organizations have novel coronavirus 2012 as one of their front page headlines (specifically regarding the recent discovery of a case in England). And I remember how heavy the news coverage of SARS was back in 2003. Going by the statistics on their corresponding articles, malaria kills about 1 million people a year, and influenza kills a 6-digit number of people a year. SARS killed around 800 people, and only a handful of cases of the novel coronavirus have been identified. In the case of malaria, it is a disease affecting mostly developing countries, so that could be an explanation for why media organizations in developed countries would not pay as much attention, but influenza, on the other hand, is widespread in developed countries, and yet these coronaviruses are getting just as much or more press attention despite affecting far fewer people. Is this just a case of media sensationalism, or is the threat of coronaviruses actually high enough to justify the density of their media coverage in comparison to other infectious diseases? —SeekingAnswers (reply) 05:48, 12 February 2013 (UTC)

SARS had a death rate of about 10%, which is pretty freaking scary all on its own. If there's less total deaths it could in part be because of the attention paid to such infections, which helps restrict transmission and keep deaths low. I'd hate to see a SARS outbreak where as many people were infected as typically get infected by the flu, and if the current level of attention to coronaviruses helps keep the total deaths low, I can't see that as a bad thing. Influenza may kill more total people every year than coronaviruses, but given the total number of infections, it appears to be a much less serious infection to get. The most generous figures for the 1918 flu pandemic gives numbers that approach the 10% kill rate of SARS, though numbers closer to 2-5% seem more reasonable, and that's widely recognized as the worst flu outbreak in history. The recent 2009 flu pandemic (the swine flu/H1N1 outbreak) was considered considerably bad, and using confirmed cases the Wikipedia article cites a kill rate of 0.03% in a chart near the bottom; the lead of that article notes that 11-21% of the world population was infected and gives an upper limit of 579,000 or so deaths world wide. That means that, if we take a worst case scenario in terms of calculating deadliness, using the lower infection rate and upper death numbers, we get 11% of 7 billion = 770,000,000 infections, and 579,000 deaths is 0.08% of infected patients that died. If a SARS-like coronavirus had a similar rate of infection, it would have caused 77,000,000 deaths. For comparison, the 2009 Flu pandemic killed the population of Las Vegas, Nevada. A similar SARS outbreak would have killed the combined populations of California, Texas, and Illinois. So, I'd say the fears are not unfounded. --Jayron32 06:08, 12 February 2013 (UTC)

Agreed. This also feeds into human psychology. That is, we've evolved to be more interested in new threats than ones we already know about. In that way, we were able to develop ways to defend ourselves from new threats. However, broadcast media tends to exaggerate the threat for ratings, which makes us even more interested, thinking it really is a serious threat to our survival, when there's really only a very low chance it ever will be. So, the mass media doesn't help us improve our health, when they harp on obscure threats, instead of things which are more likely to kill us, like alcohol, tobacco, bad diets, and a lack of exercise. StuRat (talk) 06:22, 12 February 2013 (UTC)

Digression on evolutionary psychology of threats (feel free to continue discussion inside). —SeekingAnswers (reply) 12:36, 14 February 2013 (UTC)

Stu, I'm gonna have to say that theory is deserving of a big fat ; I know of no serious researcher within the field of evolutionary psychology who has posited, let alone tried to support, that we are innately conditioned to be more fearful of threats which are new to us as opposed to known dangers. There's really no way to control for or test such a prejudice and no empirical reason to assume it in the first place; there are plenty of counter examples (phobias developed early in life, for example, can often be the most gripping) and in any event quantifying levels of of fear methodologically is difficult, bordering on impossible (there are plenty of studies involving various forms of brainscan which center around fear, but none of this gives us an unambiguous metric). Even establishing what constitutes a "new" threat across the perspectives of multiple individuals is rife with complications. Across populations, we can recognize trends as to what people pay attention to, especially with regards to popular media, but, as everyone who has commented here has already noted, there are any number of social explanations for those trends which do not necessarily reflect an absolute correlation to the relative level of fear/panic/what-have-you that people have regarding disparate potential threats. The examples you give of other dangers which we are prone to ignore (tobacco, alcohol, unhealthy food and lethargy) are also all examples of things which can be readily explained (in part at least) by the pleasure, comfort, and dependency issues involved. Aside from which, your assumption excludes the fact that there are plenty of examples of potential pathogens and dangers which are new which do not become lightning rods for levels of fear that are out of proportion to older dangers which are "greater". For that matter, establishing just what is in reality a greater threat is often going to be a matter of intense debate. All of which is not to say that people cannot become desensitized to well-known dangers (that's a simple intuitive assumption concerning human psychology which I assume we can all agree on) and there may even be a seed of truth to your theory (albeit with a thousand caveats), but it's highly inaccurate to present this as an established psychological feature that is the result of a discreet evolutionary adaptation towards novelty -- and the reality of how people process fear and adapt to new threats is quite a bit more complex than such an argument would suggest. Snow (talk) 01:04, 13 February 2013 (UTC) Here's a study talking about the process whereby old fears lose their impact on us: [1]. We also have our own article: Extinction (psychology). If you don't think this is an evolutionary adaptation, why exactly do you think fears of old threats fade relative to fears of new threats ? StuRat (talk) 04:58, 13 February 2013 (UTC) You've completely misrepresented that study. Here is the very first sentence from the abstract: "Conditioned fear responses to a tone previously paired with a shock diminish if the tone is repeatedly presented without the shock, a process known as extinction." Not even remotely what you are proposing. As to your question, let me first remind you that my above post includes this: "All of which is not to say that people cannot become desensitized to well-known dangers (that's a simple intuitive assumption concerning human psychology which I assume we can all agree on)". But your statement that fears of old threats always (or even generally) fade relative to fears of new threats is pretty radical assumption to just take for granted. For plenty of people the greatest and most crippling fears they have are ones picked up many years earlier; consider victims of abuse or sufferers of PTSD or those with intense phobias. A lot of interconnected factors go into determining an individual's fear response; is the fear an innate one (most people will react with fear or startlement to a loud noise in close proximity) or is it conditioned? If acquired, how traumatic was the precipitating event and over what period did exposure occur? If truly traumatic, do they receive assistance in coping with the fear? How rational or irrational is the fear and thus how much can it be mitigated by understanding or prevention/avoidance? If less a case of a trauma and more of one in which a person is exposed to a danger only in abstract, what is the context in which they learn about it and how fallible (or infallible) do they find the source informing upon this threat to be and how much contrary evidence are they exposed to afterwards? At what age was the fear acquired? Do the perspectives of those around a person reinforce or run contrary to this fear? These are just a few of the myriad factors which could influence how long a given "threat", as you put it, could be considered particularly dangerous by a particular individual. The amount of time passed since the person was first exposed to a given fear stimuli is of relevance, of course, but you're not even suggesting just that -- you're proposing that novel concepts are more likely to instill more fear relative to old ones and I just can't see how you'd ever go about proving that (or why you'd assume it). This belief seems to be based on other subordinate false assumptions, namely that fear is rational and that it makes sense as an adaptation in this context. It doesn't though, really. You see, our fear response, like most of our psychological make-up, was created well in advance of the kind of threat one tackles with abstract thought; a strong fear response has value as an evolutionary adaptation when you are talking about fight-or-flight situations, especially with the manner it's tied into the autonomic nervous system, but its usefulness is far more questionable when you're talking about prioritizing and analyzing complex concepts like the relative threats posed by two different diseases, the context in which this discussion arose. These just aren't concepts which hunter-gatherers or our animal predecessors were coming to grips with during the vast, vast majority of the evolution of our neurological mechanisms for processing fear; these two different types of danger --obvious immediate visceral threats and long-term abstract ones-- are even processed by differing brain regions with only a certain amount of overlap. But even if these were fears that we had struggled with for more of our evolutionary history, how would it be beneficial for the human mind (or any thinking entity) to assume a new abstract threat is more dangerous than an old one? There's no reason to assume that if you're going to be stricken by a disease it will be a new one so what evolutionary pressure would there be create this bias as an innate constant in the human mind? Snow (talk) 08:10, 13 February 2013 (UTC) Simple example: Hunter/gatherer needs to get water and has two water holes to choose from. He saw lions by one a year ago, and the other yesterday. Here the stronger fear will be the recent threat, not the old one, as well it should be. So, he will go to the water hole where he hasn't seen lions for a year. You can change this example to two different threats, if you like. Conditions like PTSD aren't the normal reaction, most former soldiers get on with their lives, worrying more about current threats than those from the war. StuRat (talk) 03:46, 15 February 2013 (UTC) As to your lion example, you're making a non-sequitur; it's simply deductive reasoning that tells your hunter-gatherer to avoid the place where lions have been seen most recently, and the differential in fear is associated with the place, not the lions. The original lions are no less a danger than the second group for having come first and if the first group returns they will present just as much cause for a fear stimulus (assuming they are equally scarey lions). You're confusing context with the stimulus itself. As to PTSD, its causes range well outside of combat stress and no, not everyone readily gets over it. Plenty do, of course, but I never said they didn't, only that your generalization that newer fears tend to be the strongest ones (and that this is due an evolutionary pressure) is speculative, vague, unempirical and not supported by research or even academic speculation that I know of. Snow (talk) 04:35, 15 February 2013 (UTC)

News organizations report what's new. Influenza and malaria have existed for the entirety of human history, and probably much longer than that. Any educated person, and most uneducated people, already know about them. --140.180.243.51 (talk) 06:59, 12 February 2013 (UTC)

Identify a part of the body

Right above the sternum where a couple of muscles form a sort of V shape, there is a depression in the neck. On men it is just below the Adam's apple. What is this depression called, if anything? I've been watching House of Cards and it's very pronounced on Robin Wright. Dismas|^(talk) 09:52, 12 February 2013 (UTC)

It is the suprasternal notch, also known as the jugular notch. Gandalf61 (talk) 10:12, 12 February 2013 (UTC)

Thank you. Dismas|^(talk) 11:03, 12 February 2013 (UTC)

That doesn't sound right. I am fairly certain its the ucipital mapilary. μηδείς (talk) 18:20, 12 February 2013 (UTC)

Did you click on the link you provided, Medeis? 86.163.209.18 (talk) 19:24, 12 February 2013 (UTC)

I think that was supposed to be a joke. Sigh. Looie496 (talk) 22:13, 12 February 2013 (UTC)

But in this case, I think Medeis has underestimated the obscurity of her reference. Snow (talk) 22:41, 12 February 2013 (UTC)

In terms of a fact, it is simply wrong, and unhelpful left unmarked on the desk. I considered asking Medeis if it was a joke, but my experience is that people get cross if you ask that and it was simply ignorance. If I ask whether they checked the link, and it was a joke, she gets to feel quietly superior and assume that I am stupid. This is less disruptive to the desks, since I don't care if people think I'm stupid. 86.163.209.18 (talk) 23:05, 12 February 2013 (UTC)

Well it would be pretty silly if someone assumed you stupid for knowing the actual clinical name of an anatomical feature but not an obscure fictitious variant. In any event, I don't think Medeis intended any harm with the remark, regardless of motive, and the clarification needed to understand the joke for what it is (if it was indeed a joke) is found within the article cited, so I don't think anybody was likely to be misled or confused for long. Snow (talk) 00:10, 13 February 2013 (UTC)

I knew it was a joke phrase the first time I heard Cary Grant say it--it's obvious mock Latin--I just didn't know there was an actual name for the anatomical feature until now. You may notice I waited for the right answer to be posted and Dismas to acknowledge it (presumably having read the article) before I posted my allusion, and lank again to the same article. μηδείς (talk) 01:53, 13 February 2013 (UTC)

So if you were joking, why no <small> tag? Absent that, it was just misleading information that could easily confuse the OP. Don't make jokes like this - few people find them amusing and if there is even the tiniest chance of confusing the OP, they are a monumentally bad idea...and as you are aware, we confine jokes to the small font. SteveBaker (talk) 15:14, 13 February 2013 (UTC)

<Small> tags are by no means required by any policy, nor has there ever been any consensus on marking "off hand" comments in Ref Desk responses. I actually think changing the font size is a stupendously unreliable way to go about making such a distinction, since a lot of people use automatic formatting in their browsers and will be completely unaware of the emphasis. I'd prefer that people try to be explicit about the whimsical elements of their responses and try to show some discretion in where they use it. But there are plenty of places where a little whit might be part of an elucidating element of a response, and it's not so easy to set a standard for when this is the case or not. In fact, in this case, Medeis was giving a valid answer; that term actually has been a known (if contrived) name for that region of the body and the fact that it is not the original clinical term, nor even a widely known one, doesn't mean the answer is invalid, especially as the OP didn't stipulate that he was looking for a a purely anatomical response. Regardless, trying to establish a hard and fast standard for when statements have veered into the jocular or not and then police them accordingly strikes me as about as inane and untenable an approach as I can imagine. In any event, please do not presume to speak for the rest of us as to what "we" expect of other editors, especially if you are going to cite hard and firm standards which have never been agreed upon; at least as far as non-article space discussion goes, editors are given wide latitude in how they format their responses, and that applies to the Ref Desks as well. Snow (talk) 20:47, 14 February 2013 (UTC)

For what it's worth, I did read the article and the joke was completely lost on me. Dismas|^(talk) 03:58, 13 February 2013 (UTC)

Protocol for asteroids

Who is in charge exactly (I suppose the NASA) for monitoring asteroids hitting the Earth and how would they communicate a potential danger to the public? (if at all). OsmanRF34 (talk) 14:30, 12 February 2013 (UTC)

See Near-Earth Asteroid Tracking and links from there. Torino Scale and Palermo Technical Impact Hazard Scale also have some relevant information. --Jayron32 14:46, 12 February 2013 (UTC)

NASA generally issues press releases or conducts press conferences for major announcements. --PlanetEditor (talk) 14:55, 12 February 2013 (UTC)

Also chance of an asteroid hitting earth and causing massive damage in the planetary scale is miniscule in the next 1000 years.. However if a timescale comprising millions of years is considered, there are good chances of future impact events which occurred thoughout Earth's history. --PlanetEditor (talk) 14:59, 12 February 2013 (UTC)

Note that a portion of the Southern sky around the South Celestial Pole is currently only being monitored by this guy (see last paragraph of article), and he's just had his NASA funding cut, so until a new project cuts in a couple of years hence, while Rob's on holiday no-one is looking out for the incoming from that part of the sky. (Rob was a classmate of mine at Uni, so I follow his career somewhat – it's the one I failed to attain!) {The poster formerly known as 87.81.230.195} 84.21.143.150 (talk) 16:27, 12 February 2013 (UTC)

The Minor Planet Center collects worldwide reports for all small objects. However they do not make observations themselves but collect them from amateurs and professional (mainly computers nowadays). There are several different near earth object detection programs - none is anywhere near comprehensive. Asteroid impact avoidance mentions some ongoing projects but some of those have already ended. Rmhermen (talk) 18:55, 12 February 2013 (UTC)

Camphor wood

is it safe to work with the wood from a Camphor tree?

Effects on the body

It has effects similar to a muscarinic receptor agonist.

[edit] Small dose

Its effects on the body include tachycardia, vasodilation in skin (flushing), slower breathing, reduced appetite, increased secretions and excretions such as perspiration, diuretic. [16]

[edit] Large dose / toxicity

Camphor is poisonous. In large quantities, it produces symptoms of irritability, disorientation, lethargy, muscle spasms, vomiting, abdominal cramps, convulsions, seizures.[17][18][19] Lethal doses in adults are in the range 50–500 mg/kg (orally). Generally, two grams cause serious toxicity and four grams are potentially lethal.[20] — Preceding unsigned comment added by 70.119.184.168 (talk) 17:38, 12 February 2013 (UTC)

It seems to be a sought-after wood for woodworking[2]. Many species of exotic wood have toxic dust or oil that require careful handling though they are still used for woodworking. Camphor is not listed on the list of toxic woods here[3] (but sneezewood is!) Rmhermen (talk) 19:16, 12 February 2013 (UTC)

By and large you don't want to inhale large quantities of sawdust on a regular basis in general, IIRC. Gzuckier (talk) 05:20, 13 February 2013 (UTC)

Why was Typhoid Mary an asymptomatic carrier?

I read Typhoid Mary and Asymptomatic carrier, but I didn't see what physiological/genetic attribute is posited to account for her unaffectedness. Did her immune system luckily happen to differ such that it naturally knew how to combat the pathogen? What was it about her? What does it tend to be that saves asymptomatic carriers of infectious diseases? 20.137.2.50 (talk) 19:13, 12 February 2013 (UTC)

Like many infectious diseases, people who get the disease once may develop a lifelong immunity to it due to the build up of antigens in their system. These antigens can protect them from coming down with symptoms of the disease, but do not necessarily prevent them from carrying the disease around on the clothes, hands, or even internally. There's a possibility that Mary had a mild case of Typhoid fever when younger, which had been written off as a bad cold or other relatively mild infection, and from that point forward she became a carrier. --Jayron32 19:47, 12 February 2013 (UTC)

• It looks like typhoid, like many infections, can find refuge as a biofilm on a solid support, in this case the cholesterol gallstones in some people's gall bladders. [4] Wnt (talk) 22:03, 12 February 2013 (UTC)

Does anybody but me find that amazing? Gzuckier (talk) 05:21, 13 February 2013 (UTC)

Gibbs free energy

The article above talks about Gibbs in a thermodynamics context but what is its significance in Biology? Clover345 (talk) 19:52, 12 February 2013 (UTC)

Biology is not immune to thermodynamics. Biological processes still obey all of the basic laws of the universe. --Jayron32 19:55, 12 February 2013 (UTC)

Yes, there is explicit use for Gibbs free energy (GFE) in biology, for example this paper uses it quite a bit: "Effect of classic methanogenic inhibitors on the quantity and diversity of archaeal community and the reductive homoacetogenic activity during the process of anaerobic sludge digestion" here ([5]). This usage is in line with Jayron's comment above. However, there is another case that may come up, that is more in the context of analogy, due to the same mathematical structures coming up in different applications. For instance, this work ([6]) uses methods from statistical mechanics to analyze trophic cascades, and concludes in part that GFE gives the netproductivity of the ecosystem. Another lead is that shannon diversity is essentially a measure of entropy, and it is widely used in ecology (not because of thermodynamics, but because it is a useful way to quantify diversity). I can't recall the appropriate physics, but there may be some related applications of GFE, due to the relations between entropy and enthalpy. Finally, you may be interested in this review of thermodynamic processes in ecology [7]. SemanticMantis (talk) 21:22, 12 February 2013 (UTC)

Properties of blood

From my understanding, blood is a shear thinning fluid like custard and so this would contribute to blood clotting when it's flow velocity is reduced such as in the case of bleeds. But I also understand that clots and recovery from bleeds are to do with platelets, oxidisation of blood etc. So how do these 2 concepts come together when a bleed and subsequent recovery occurs? Clover345 (talk) 19:57, 12 February 2013 (UTC)

Thixotropic fluids are thixotropic because they are suspensions and not really pure liquids; the suspended particles provide the shear thinning property. It is specifically because of things like platelets suspended in the blood that would give it such a property. --Jayron32 20:39, 12 February 2013 (UTC)

So in other words shear thinning properties are just a way of modeling fluids? For example, would the fact that custard is a shear thinning fluid also be because of suspensions? Clover345 (talk) 22:00, 12 February 2013 (UTC)

Sheer thinning/thixotropy is a real property: Some fluids to decrease their viscosity at higher flow rates. And what do you think custard is if it isn't a suspension? --Jayron32 22:03, 12 February 2013 (UTC)

I don't know. Suspensions of fat in milk, egg yolks and cream? But Hemostasis and Platelet doesn't mention anything about shear thinning properties and this confuses me. Clover345 (talk) 22:06, 12 February 2013 (UTC)

A suspension just means the distribution of aggregate particles within a liquid medium; that is it is distinct from a solution in that the solution is composed of molecule-sized particles distributed in the liquid phase; while in a suspension the particles are clumps of molecules, often many millions or billions of them. In custard, your liquid is water, while the suspended particles are the fats and proteins from the cream and eggs. The lecithin from the eggs acts as an emulsifier which keeps the particles suspended and prevents them from settling out. If you want to know more about thixotropy or sheer thinning in blood, see this Google search. If you find relevant information in that search which isn't already in Wikipedia article, but belongs there, be our guest and add it. --Jayron32 22:15, 12 February 2013 (UTC)

Ive heard platelets work better at lower velocities. From my understanding, platelets work by plugging the wound along with various proteins that aid in the wound recovery process. Ive found out from here (http://www.cs.cmu.edu/~sangria/publications/MAKRR2004.pdf) that the plasma of blood itself is a Newtonian Fluid. The article also states "In the future, we intend to incorporate the

process of clot formation due to platelet activation in blood flow, the Schematic of the natural configurations associated with a clot being modeled as a viscoelastic fluid or solid (there is some viscoelastic fluid having a single relaxation mechanism, and debate on this issue)." So does anyone actually know yet how the blood's shear thinning fluid properties and the biochemical processes interact in the wound healing process? — Preceding unsigned comment added by Clover345 (talk • contribs) 00:00, 13 February 2013 (UTC)

high school physics

assume instead of a large battery an rc plane is carrying a parachute with solar panels and a rather small battery (maybe even motor capacitor). The question is: could the parachute have enough solar material on it that by the time the rc plane has finished falling from high altitude it can recharge enough to climb to the same altitude? (Assume it packs away its 'chute again somehow). This is a high school physics question and has no relevance to anything. Boriskol (talk) 20:46, 12 February 2013 (UTC)

High school physics questions aren't supposed to be relevant. They're supposed to get you to learn to pick the correct equation from a scenario and to assign the correct numbers from the problem to the proper variables in the equation. The idea is to train you to understand how mathematics and the physical world interface, and how to recognize what mathematics to do when faced with any sort of problem. But the first training that a student needs to do is simply read the description of a scenario, and then translate that into math and produce a numerical result. Once you have that practice down and can do it easily, then it becomes easier to progress to more difficult concepts. --Jayron32 20:50, 12 February 2013 (UTC)

This is a single use account with a sophisticated knowledge of editting WP to ask a question that "has no relevance to anything". Closure seems reasonable. μηδείς (talk) 20:55, 12 February 2013 (UTC)

I disagree. --Jayron32 21:17, 12 February 2013 (UTC)

Medeis, as has been explained to you before, your previous attempts to close down conversations have been the cause of significant conflict. I strongly advise you to cease all activity involving closing, collapsing, or deleting any other editor's comments. The reference desks have plenty of eyes on them. if something needs to be closed someone will close it. At this point your even suggesting that something be closed is likely to cause a backlash in favor of keeping it open. While no policy says that you cannot make suggestions, everything would go a lot smoother if you would just stick to making your own comments and stop trying to control other editors in any way. See WP:OWNERSHIP. --Guy Macon (talk) 06:21, 13 February 2013 (UTC)

(ec)Let's not jump on a first-time OP simply because he was being modest about the importance of his question. It's an interesting question, and I for one would like to see an answer. Since this is a reference desk, maybe someone knows of a reference that discusses a successful or unsuccessful attempt to do this or something similar. Duoduoduo (talk) 21:24, 12 February 2013 (UTC)

Is this User:91.120.48.242 again? If so, User:Totallyabstract is a sock-puppet...which is A VERY BAD THING. Look, your Helium-balloon electric R/C plane doesn't work, neither does hot-air-balloon plane - and neither will the parachute-plane. No matter what you do, in any wind over a couple of mph, and with the most optimistic assumptions, for any conceivable balloon/parachute size, solar power coverage, battery pack capacity and engine efficiency - the balloon/parachute/whatever will get blown further off-course vastly faster than the plane can make up with whatever charge can be stored. I can re-quote the math I gave you via email if you'd like. <sigh> SteveBaker (talk) 21:57, 12 February 2013 (UTC)

"Sophisticated knowledge of editting (sic) WP" Ha, good one! This desk is literally 2 clicks away from the main page; apparently that counts as "sophisticated editting". --140.180.243.51 (talk) 21:25, 12 February 2013 (UTC)

That's just one of many brilliant contributions of μηδείς. OsmanRF34 (talk) 21:51, 12 February 2013 (UTC)

What is the area of the parachute? What's the mass of the plane? What's the terminal velocity of the parachute + plane combination? Are you given any parameters at all, or are you supposed to choose reasonable ones? --140.180.243.51 (talk) 21:25, 12 February 2013 (UTC)

Given that there are very real solar-powered planes that can fly indefinitely, the answer is absolutely "yes". This isn't a perpetual motion scenario because you've got energy input via the sun. — Lomn 21:28, 12 February 2013 (UTC)

Yes the scenario immediately seems excessively convoluted when the plane's wings could just be covered with solar panel in the 1st place.. Vespine (talk) 21:42, 12 February 2013 (UTC)

Ah, where I said "high school physics question" I meant question utilizing high school physics. The question is of my own devising. I simply meant that this has no practical applications whatsoever. The main difference, I suppose, between "just putting solar panels" on the wings is that you would then have a different plane: a typical RC plane draws more power than you would get by putting solar paneling on, so you would have to build something different.

So, the question is about the physics of an RC plane, wherein the batteries are assumed to be mostly replaced with the rest of this setup. The question is: would a large parachute, with solar paneling, provide enough sustained power over the course of descent, for the RC - if we assume it can efficiently pack that 'chute back up - to climb just as high as it had been? I am not sure what parameters are reasonable here as I have no direct experience with this. For me, it's just a high school physics type thought experiment with no applications of any kind. I was hoping some of you would know how to calculate the answer. Boriskol (talk) 22:04, 12 February 2013 (UTC)

re: "you would have a different plane" -- well, that's going to be the case regardless. A solar-powered aircraft will of necessity have different design considerations than a conventionally-fuelled aircraft, regardless of scale. That will hold whether you put solar panels on the wings, on a parachute, or on a big kite you tow behind the main aircraft. So, that said, the answer still remains that it is scientifically possible -- as noted, you've got energy input via the sun. As for how you would actually do this -- whether it's practical from an engineering standpoint -- you quickly move past high school physics. What's the terminal velocity of the aircraft while parachuting? That's how long you've got to charge. What's the maximum charge rate of your solar panels? There's your energy budget. What's the mass and drag of the aircraft under normal flight? That's whether your energy budget is sufficient. You can pick answers for some of those and, with high school physics, derive approximate requirements for the others. However, it won't answer the practical questions of whether your design will work; for anything reasonably cutting-edge, that's better considered as aerospace engineering -- and that, I think, is the distinction Jayron intended with his initial response. — Lomn 22:21, 12 February 2013 (UTC)

Indeed. High school-level physics (as with all high-school level courses, in nearly all disciplines) is about teaching you the language and methods of studying that discipline. Physics is no different. Most of high school physics is intuitive from a non-mathematical point of view; to the point of being nearly obvious. If you push something harder, it goes faster. If you're going faster, you get where you were going in less time. Stuff like that. The first goal of such courses isn't so much to teach you the material (I mean, do you need such a class to teach you that if you go faster, it takes less time to get places?). Instead, it's to teach you how to think critically about a situation, to learn how to apply mathematics to situations you describe in words, to learn how equations work, to learn how to solve such equations, what the definitions of words are. There's some small amount of actual material you are learning, but such material is actually secondary to the methods: Once you know how to solve such problems, you can pretty much teach yourself the material. --Jayron32 23:19, 12 February 2013 (UTC)

yeah, the parachute part of the problem is sort of a distraction. If you simplify the situation, the existence of solar powered planes which can fly contiually (which would be more easy with no pilot than with, I would guess) sort of represents the limiting case, where the run out of juice and parachute phase of the trip represents zero percent. Of course you would have to build a very energy-efficient plane, which resembled the solar powered model as much as possible. The parachute itself is just a complication; in addition to excess weight that has to be lifted, it seems when deployed it would be likely to shade the cells. I don't know of any cells that would function on top of a parachute very well. In fact, anything that efficient would probably be just as good at recharging while gliding. (I should point out that I don't know anything about the subject this is all off the top of my head) If you are married to NOT having the solar cells inhabit the surface of the plane, however, I think that approach is a dead end. Gzuckier (talk) 05:31, 13 February 2013 (UTC)

Little Ice Age

Another entry under 'causes' might be useful, to give a full picture.

The simplest cause of the Little Ice Age - and all other incidental cold spells - is our Solar System passing through a cloud of gas-dust while it orbits within our spiral arm of the Milky Way. — Preceding unsigned comment added by Peter Scott Norris (talk • contribs) 22:18, 12 February 2013 (UTC)

Adding something like that would require reliable sources. And since the claim is quite extraordinary, so should the source be, i.e. several peer-reviewed articles or other contributions by recognised experts in the field. --Stephan Schulz (talk) 22:24, 12 February 2013 (UTC)

Hmm... galactic winter.... got to find somebody to write a page for me that I can cite.... Gzuckier (talk) 05:36, 13 February 2013 (UTC)

The idea of the passage of the solar system through interstellar gas clouds is not exactly "extraordinary", I read about it in the 90's in either Discover or Scientific American (probably the former). From what I remember we are expected to enter one in some millennia. Sorry I don't have a reference though. μηδείς (talk) 18:07, 13 February 2013 (UTC)

Stove vs. oven usage costs

I'm trying to reduce my utility bills, and I'm wondering which of these two costs me more money, assuming both are run for the same duration of time (say, 15 minutes or so):

• running my kitchen oven at 450 °F
• running one burner on my natural gas kitchen stove at highest heat

In other words, should I bake more or boil more? ;) (Yes, I know there are other ways to use these appliances besides baking and boiling.)

—SeekingAnswers (reply) 22:50, 12 February 2013 (UTC)

In response to some additional questions from posters below: I don't know much about ovens, so I can't tell you much more about the oven then that it is an oven. It is built into the kitchen and not portable. Its interior dimensions are roughly a 45-cm or 18-inch cube. —SeekingAnswers (reply) 01:51, 13 February 2013 (UTC)

In further response to some more questions below: my purpose is to cook food, not to heat the home. —SeekingAnswers (reply) 21:08, 13 February 2013 (UTC)

You need to give more information before a meaningful answer can be given. What sort of oven is it, for example? And what are you paying for gas/electricity/coal/logs of wood/whatever? On the face of it, the burner is less efficient because it is not enclosed. 86.163.209.18 (talk) 23:17, 12 February 2013 (UTC)

All else being equal, the oven is more efficient (as explained above) and natural gas is cheaper than electricity per BTU (in most cases). However, there are too many variable parameters to provide a comprehensive answer.   ~:74.60.29.141 (talk) 01:12, 13 February 2013 (UTC)

The size of the oven also matters. We cooked our roasts, baked cakes, etc in a traditional floor-standing kitchen oven (electric) that has a cooking area capacity about 450 x 450 x 450 mm. As is the norm for such things, it was wired permanently into the house electrical system by the installing electrician as the max draw is far above what can be drawn via a standard plug. Last year I bought a "snack oven" that sits on the bench top and plugs into a standard wall outlet. It has a cooking capacity of 300 x 250 x 200 mm. We found that that is large enough to cook the majority of roasts and cakes we do. It warms up fast, 5 minutes versus 15 minutes for the old oven. Since the elements in either case run flat out during warm up, that alone means a significant saving in electricity. And because of the reduction in surface area, roughly 2.5:1, the electricity consumed during actual cooking is reduced by nearly the same ratio, even though the temperature is the same. Our power company gives a graph of houshold electricity useage over the last year - the graph shows quite a noticeable drop, such that the snack oven paid for itself in a few months at most. Floda 60.230.209.66 (talk) 01:31, 13 February 2013 (UTC)

The most basic follow-up Q is whether the oven is natural gas or electricity. Electricity generally costs about 3 times as much per heat generated, so that would make it a safe bet to use the natural gas device. If they are both natural gas-powered, then it's more even. Note that the waste heat is useful in winter to help heat the home, while absolutely unwanted in summer, where it can cause you to use the (presumably expensive electric) air conditioner more. In summer, to avoid this, I don't cook on either, but try to eat things like sandwiches, and, for things I do heat, I use the microwave. I tend to use the stove in winter, because the heat and humidity generated are both welcome, then. I only ever use the oven for things which can only be cooked that way, like muffins. StuRat (talk) 04:00, 13 February 2013 (UTC)

For some reason I thought your question was about heating the house. Both the oven and the burner use natural gas fuel correct? So as such they are both equally efficient since all the energy turns into heat and stays in the house (since you don't vent the exhaust).

However I can't tell you which one will make more heat in the house. The first thing you will want to do is read the nameplate on the stove and see how many BTU the burners and stove are rated for. Once you know that the next question is how long they will stay on. Obviously the burner will stay on as long as you keep it on. The oven has a thermostat - so will cycle. I have no way to know what the duty cycle will be since it depends on the insulation.

And finally, the burner will release all the heat instantly. The oven will keep the heat inside it for longer - it will all eventually be emitted, but over a longer time. Usually this is more efficient since the house will cool faster the hotter it is, so it's better to keep the house at an even temperature, not up then down. However, if the delay in warming causes you to run the heat longer, you might waste some by overshooting. Ariel. (talk) 07:16, 13 February 2013 (UTC)

I don't want to heat. I want to cook. —SeekingAnswers (reply) 21:47, 13 February 2013 (UTC)

Ok, so I looked at my oven's nameplate. The burner outputs 9,500 BTU and the stove 16,000. Yours will be different, but I think this is reasonably typical. So in theory this implies that burner uses less energy. But, the oven has a thermostat, so doesn't run all the time. The oven also has insulation. The oven is better at not wasting heat into the air. Boiling water uses a lot of energy, baking uses less (this doesn't apply to frying). So I think the oven will be better - but you will want to turn it off before the food is ready, and let the residual heat cook the food. It will be hard to get the timing right though.

Reality check time: 16,000 BTU = 16 cubic feet of natural gas per hour * 15 minutes = 4 cubic feet. Average retail cost: $10 per 1000 cubic feet. So 15 minutes of maximum oven use costs $0.04 - I suggest looking for savings elsewhere. Ariel. (talk) 07:34, 13 February 2013 (UTC)

All very good, but the OP hasn't told us whether he/she wants to choose whether to boil or bake to cook food in the least cost way, or to boil or bake to (supplementary) heat the house in the least cost way. To answer the second, we need to know what sort of climate and building the OP lives in. Moderately warm climates usually mean that no house heating is used. Hot climates mean aircon is run to you want the least cooking heat; cold climates mean heating is used so cooking heat makes no differtence. Single unit ground dwellings loost heat much faster than high rise flats. Most people, when they ask questions like this, are just interested in lowering their electricity bills. In average dwellings in moderate climates the heat produced in the kitchen has little effect on comfort and the cost electricity used elsewhere - lighting, aircon, heating, appliances. Floda 121.221.231.38 (talk) 07:54, 13 February 2013 (UTC)

I don't want to heat. I want to cook. —SeekingAnswers (reply) 21:47, 13 February 2013 (UTC)

If they really want to save they should microwave if possible. That's more efficient except for heating up liquids where heating on the hob may be better. Dmcq (talk) 14:39, 13 February 2013 (UTC)

That's only true in summer. In winter, since the waste heat is used to heat the home, thus reducing the furnace load, it shouldn't cost anything more to cook with gas. Cooking with electricity does cost more, though, since electricity typically costs more than gas, per BTU (or your favorite unit). BTW, what's "the hob" ? StuRat (talk) 18:02, 13 February 2013 (UTC)

The top working surface of a stove. I'm not altogether certain it is a good idea to warm up the kitchen instead of the other rooms. Dmcq (talk) 19:32, 13 February 2013 (UTC)

I didn't interpret your Q as being about heating the house, but, in case I was wrong, let me add a caution: While unvented gas stoves and ovens don't burn enough oxygen and release enough unburnt gas and carbon dioxide/carbon monoxide to be a problem, normally, when leaving them fully on (with the oven door open) for many hours, with the house windows shut, the air quality can start to suffer. StuRat (talk) 18:08, 13 February 2013 (UTC)

I don't want to heat. I want to cook. —SeekingAnswers (reply) 21:47, 13 February 2013 (UTC)

Additional question: how do you tell whether an oven uses natural gas or electricity? In the case of stoves, my understanding is that an open flame indicates natural gas, and those spiral no-flame burners use electricity. What about in the case of ovens? If my stove is natural gas, and my oven sits under my stove, does that automatically mean my oven also uses natural gas, or are they not necessarily correlated? —SeekingAnswers (reply) 21:12, 13 February 2013 (UTC)

If the top is natural gas the bottom virtually always is too. I've heard of some special hybrid convection ovens that has gas on top, but use electricity and a fan to speed up the cooking but they are very rare. Other ways to tell: Look at the plug. Is it a standard plug or a large one for ovens? When you turn on the oven you should be able to hear the gas ignite it will make a "woosh" or "twump" sound. You can also look inside the oven, there are vent holes and you should be able to see the fire. With electric oven the element is easily visible. I answered your earlier question both ways BTW, cooking and heating. Ariel. (talk) 22:56, 13 February 2013 (UTC)

The oven is inset into the cabinet and attached to the wall, so I can't actually look behind the oven to see any sort of plug. The oven doesn't have a glass window, so normally I can't actually see inside the oven while it is in operation, but if I open the lid while it is running, I can see some sort of glow or light emanating from gaps at the edges of the bottom surface; however, I can't see any actual flame, though it's possible that my view is just being blocked by the bottom surface. While the oven is in operation, I can hear some sort of quiet semi-hissing which sounds similar to but not identical to when there is an open flame on my stove. Are electric ovens silent? —SeekingAnswers (reply) 00:57, 14 February 2013 (UTC)

That all sounds like a gas oven to me. Open the door and turn it on, then wait a minute or so and you should hear the fire ignite, and see the light at the same time. That will be the final confirmation. (It will have a delay after turning it on.) In an electric one the glow will get brighter gradually. Ariel. (talk) 01:04, 14 February 2013 (UTC)

Hmm, that's weird, because then my oven seems to exhibit characteristics of both? After turning on the oven, it is initially silent, but after about 30 seconds to a minute, I hear a click, and then the constant hissing sound begins. However, the glow starts maybe 5-10 seconds before the click, and the glow gets brighter gradually before the click and keeps getting brighter gradually. And when I turn it off, the hissing sound stops first, but the glow continues for a few seconds after the hissing before gradually fading away. —SeekingAnswers (reply) 01:32, 14 February 2013 (UTC)

Perfect! That is exactly what I was expecting. You have a gas oven. The glow you saw is a glowbar. The way gas ovens work is you want to make sure that you never turn on the gas without ignition. So what you turn on the gas, you actually turn on the glow bar which is heated electrically. When it gets hot enough a mechanical valve opens which lets out the gas. When you turn it off the glowbar cools, which turn of the gas. So the initial glow you saw is the glowbar heating up, and the final glow was the glowbar cooling off. It's interesting that you never actually turn the gas on and off directly - you only control the glowbar. You should be able to remove the bottom of the oven and watch it happen - the bottom panel is usually made to be easy to remove. Or see if you can find a video on youtube. Ariel. (talk) 02:10, 14 February 2013 (UTC)

Incidentally, the gas ovens I've had have all had a separate compartment at the floor for broiling (heating from above). You have to get your face almost onto the floor (or use a small mirror), but this allows you to see the flames directly, when it's on, with the broiler door open. StuRat (talk) 02:28, 14 February 2013 (UTC)