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July 12

Teflon coating

What's the best way to apply a Teflon coating to stainless steel? 2601:646:8E01:7E0B:F88D:DE34:7772:8E5B (talk) 00:50, 12 July 2016 (UTC)

A Google search of your question provides several sources, such as: --2606:A000:4C0C:E200:A073:98E5:BA6B:E905 (talk) 04:23, 12 July 2016 (UTC)
This is a good starting point, but not detailed enough -- I need a source which is so detailed that even a politician would be able to use it to apply a Teflon coating (although some politicians do not need to apply any coatings to themselves, being actually born with a Teflon coating over their skin) ;-) Specifically: (1) What is the best way to roughen the surface with commonly available workshop equipment (if this is even possible)? (2) What type of primer is needed, and under what circumstances can it be omitted? (3) What is the best way to apply the actual coating? (4) How many layers are typically needed for a durable coating, and how thick will it be in total with that number of layers? And last but not least, (5) How do you do all this to the inside surface of a 1 1/4-inch pipe? 2601:646:8E01:7E0B:F88D:DE34:7772:8E5B (talk) 06:00, 12 July 2016 (UTC)
The short answer is "take the thing to your local Teflon™ Coating Service". Here's a link if you really want to DIY: Application Overview for Teflon™ Industrial Coatings that explains Substrate Preparation, Surface Roughening, etc. There are also some YouTube videos (good luck). --2606:A000:4C0C:E200:A073:98E5:BA6B:E905 (talk) 06:47, 12 July 2016 (UTC)
That's the info I needed. Thanks! 2601:646:8E01:7E0B:F88D:DE34:7772:8E5B (talk) 07:13, 12 July 2016 (UTC)
Right, that's what I plan to do (the DIY option is only as a last resort) -- the fumes won't kill you, but they can make you wish you were dead. 2601:646:8E01:7E0B:F89A:AB91:81AF:D78C (talk) 00:14, 14 July 2016 (UTC)

This may not be strictly related to answering your question, but out of curiosity, mind telling us why you would want to put Teflon coating on the inner surface of a 1.25-inch pipe? (Novel way of making eggs I'm unfamiliar with?) --Trovatore (talk) 18:38, 13 July 2016 (UTC)

Our PTFE article suggests it's commonly used in "pipework for reactive and corrosive chemicals" although I'm guessing pretty much everyone uses commercial products like and are probably significantly wider than 1.25 inch. But there must be some systems where the pipe is that small and I'm sure I'm not the only one hoping that the OP is asking due to specific personal interest in how these are made not because they plan to DIY, whatever the purpose of the pipe. Nil Einne (talk) 20:00, 13 July 2016 (UTC)
FYI, my application is a packed bed chemical reactor which requires a Teflon coating on the inside both for corrosion resistance and for ease of removing the solid product -- and its basic shape is that of a 1.25-inch pipe (the diameter being dictated by the upstream plumbing and by the need to have plug flow throughout), but with outside fittings which are not normally found on any commercially available pipe, hence the need to custom-build it. 2601:646:8E01:7E0B:F89A:AB91:81AF:D78C (talk) 00:26, 14 July 2016 (UTC)

Van Allen Belts

I am thinking of making a spacecraft to fly outward and back through both Van Allen belts that surround the Earth. What sort, and thickness, of radiation shielding will I need to survive the round trip assuming I travel as fast as current space technology will allow? --86.187.170.21 (talk) 22:54, 12 July 2016 (UTC)

Van Allen radiation belt#Implications for space travel gives some values for radiation and shielding. The radiation received by the astronauts has been measured between 0.16 and 1.14 rads (1.6 and 11.4 mGy), much less than the standard of 5 rem (50 mSv) per year set by the United States Atomic Energy Commission for people who work with radioactivity. For comparison, a full-body dose of 5 Sv is deadly. AllBestFaith (talk) 23:18, 12 July 2016 (UTC)
Note also that this is not medical advice. Paraphrasing XKCD, if you are basing space travel safety procedures on a post on the internet and things go wrong, you have none to blame but yourself. Tigraan 11:27, 13 July 2016 (UTC)
Right! It is also very important to have your insurance policies in order. YohanN7 (talk) 11:36, 13 July 2016 (UTC)
A Magnetic shield I think would be better. Also, consider sending just a robot to do the science. If you go yourself and get a bad attack of the munchies along the way– the nearest pizza parlour will be a long, long, long way away. Yet, if you insist on traveling yourself, note this down in your Filofax: Both Milliways and The Big Bang Burger Bar I think still do a home delivery service covering the Earth/Mars obits but their charges I warn are bound to be astronomical, even to places like London in the UK. Let the magnetic force be with you – bon voyage . The OP only mentions Van Allen's belts but not his braces. Being elasticized, fly into one of those and you'll get catapulted back to where one started from. --Aspro (talk) 12:51, 13 July 2016 (UTC)

So how long can men be exposed to Van Allen radiation and still survive?--86.187.173.138 (talk) 20:54, 13 July 2016 (UTC)

The OP's question leaves no doubt that they are thinking of travelling in person. Quantitive LD50 values for human exposure to radiation might have been collected from the results of human sterilisation experiments with X-rays (see X-rays#Adverse effects) and gamma rays (see Gamma radiation#Health effects) but such experiments are no longer permitted. AllBestFaith (talk) 22:43, 13 July 2016 (UTC)

July 13

medication side effects appearing long after starting the drug

Suddenly last fall I began to suffer from these debilitating symptoms 2-3 times a week: sudden, profound unease and general weakness; unsteady, clumsy, sluggish, slow, lightheaded, woozy, cloudy of mind. They lasted a few hours, but worsened if there was no opportunity for sleep. After a few hours it was over and I felt fine. Several doctors couldn't figure it out. Finally, one suggested a medication review, and it turned out that these and other problems I had been having were side effects of the drug Requip, which I had been taking for over a year beforehand. I stopped it, and the episodes went away. How can it happen that such side effects should suddenly arise so long after starting the drug? --Halcatalyst (talk) 14:28, 13 July 2016 (UTC)

We cannot provide medical advice here. Please contact your doctor. --OuroborosCobra (talk) 14:55, 13 July 2016 (UTC)
I disagree that this is a request for medical advice. The OP makes clear that the effects described have already been addressed by a doctor, and solved by appropriate action, i.e. ceasing to take the drug causing them. The OP's question inspired by this is more a physiological one about why a drug's side effects might start to appear only after a protracted period of taking it, rather than immediately as one might expect. Neither the above-linked short article nor the more extensive adverse effects addresses the question. {The poster formerly known as 87.81.230.195} 2.123.26.60 (talk) 15:07, 13 July 2016 (UTC)
Adverse drug reaction doesn't help much either, and I agree that it is an interesting question. I have certainly had a significant reaction to a medication which occurred a few weeks after I started and which was acute and my doctor could not explain; that medication is now one I always list to avoid. I also agree that the question is not a request for medical advice but is about a medical phenomenon which has applicability beyond the OP. EdChem (talk) 15:30, 13 July 2016 (UTC)
@Halcatalyst: When you look at the Ropinirole article, note the reference to CYP1A2. That enzyme is induced by eating things like broccoli; other drugs might inhibit its activity, or burden it with other things to do. So if you were eating broccoli fairly regularly for a while, a dose of ropinirole that didn't cause harmful side effects then might become a higher dosage with troublesome effects if you stopped. This is just an example of how this could happen; there could be a lot of potential causes, some worrisome, and I certainly can't diagnose the issue blindly. Biology is complicated! :) Wnt (talk) 16:27, 13 July 2016 (UTC)
Do not attempt a diagnosis. Response to this question should go no further than citing the article about Ropinirole (tradename Requip) that contains the only sourced information we can give about its side effects and a lawsuit in November 2012. AllBestFaith (talk) 16:30, 13 July 2016 (UTC)
  • The OP's question, despite the prologue, is;"How can it happen that such side effects should suddenly arise so long after starting the drug?" That's not an improper question. The mechanisms will differ, but Lisinopril, for example, is known to cause a chronic cough, and various statins cause muscle weakness, both with an onset delayed by days or months. Dozens of drugs have side effects that depend on long-term use. Your doctor, specialist, or pharmacist should be able to answer questions we can't answer due to policy. μηδείς (talk) 18:13, 13 July 2016 (UTC)
  • I gave my experience merely as an example; perhaps I should have made that clearer. What I would like to know is what factors might play into a drug suddenly generating new and perhaps serious side effects long after it swas firsst started.--Halcatalyst (talk) 03:32, 14 July 2016 (UTC)
Really, we don't know. The body is an enormously complex system, and there are many things we don't know about it. This is why clinical trials and post-marketing surveillance are important in assessing the effects of a drug. One class of things we do understand fairly well are carcinogens; with these, it's the gradual accumulation of DNA damage over time that can lead to cancer. Most cancers develop from numerous mutations, and your body has DNA repair mechanisms, so a single mutation is generally not a problem (and indeed, they happen all the time in your body). That's why you don't get cancer from smoking a single cigarette. --71.110.8.102 (talk) 04:37, 14 July 2016 (UTC)
  • Thank you all for your responses. I was curious as to whether these was an explanation, since my case seems very strange indeed. Most drugs, I suppose, have effects in other parts of the body than are specifically targeted. So it is indeed very complex. --Halcatalyst (talk) 14:25, 14 July 2016 (UTC)

Why faster than light travel is impossible

In short is the basic reason for why FTL travel (and communication) is impossible is because of the relativity of simultaneity? In that if there was an object moving FTL, it would result in a causality violation in which there exists a reference frame where the object reaches its destination before it ever left? And this holds true for any FTL manifestation, i.e. wormholes, instant teleportation, etc. ScienceApe (talk) 15:43, 13 July 2016 (UTC)

Well, looped causality isn't really a "disproof" since there are hypothetical things like a Tipler cylinder that appear to work out with it. But yes, a light cone tipped any further than light speed will appear to have reverse time from some other frame. That doesn't really prove a loop though, because even though the events appear to occur future to past, they don't do so in a non-spacelike way from any slower than light frame unless the traveller's light cone is tipped more than 90 degrees, i.e. moving into the past. But the thing is if one traveller can go faster than light, then another can do so, linking those spacelike events into a reverse timeline. Provided, that is, there isn't some absolute frame of reference in the local area that no FTL traveller can move reverse in time relative to - you could have basic special-relativity FTL without time loops as long as they are not crossing this.
The far more compelling argument against FTL is simply that the faster you go the more energy you have, without limit; you have to cross a point of infinite energy to go past lightspeed. There are numerous other paradoxes with any sort of acceleration. So it has to be some idea that involves skipping past the speed of light without any finite rate of acceleration, which is possible but harder to picture. Wnt (talk) 16:19, 13 July 2016 (UTC)
Apparent FTL is not excluded by general relativity, see the article Faster-than-light. However transversable wormholes are a common element only in science fiction. AllBestFaith (talk) 16:21, 13 July 2016 (UTC)
The increase in relativistic mass as a body approaches light speed is not nearly as a strong an argument against FTL than the causality violation. It just makes it impossible to accelerate to light speed conventionally. But we can e.g. communicate at light speed using photons, so it's just as easily imaginable that there is some other unknown principle to communicate, and possibly travel, at higher than light speed - science fiction is full of such devices, some of which have some theoretical support in physics (e.g. wormholes). But any kind of FTL communication results in causality violations, regardless of mechanism. I'd say the causality principle is fairly well established at least on the macroscopic level, so this general argument is stronger than an argument that just rules out acceleration of massive bodies to light speed. --Stephan Schulz (talk) 16:59, 13 July 2016 (UTC)
We don't know if FTL travel or communication is possible or impossible. Current physics tells us that no application of energy can ever accelerate a massive object to FTL speeds. General relativity allows us to contemplate wormholes, closed time-like curves, Alcubierre drives and other configurations of space-time that would permit (and in fact require) FTL travel, but it is unclear if those space-time configurations are actually meaningful descriptions of reality or just interesting bits of mathematics. For example, even though wormholes are valid solutions of the equations of general relativity, it may well be that there is no physical way to create a wormhole. We don't know of any way, even in theory, to punch useful holes in space-time and create wormholes. It is true that FTL communication will necessarily violate human notions of causality (e.g. tachyonic antitelephone). However, it is unclear whether or not physics actually has a problem with that (see causality (physics)). In general, humans perceive cause and effect and an arrow of time, but physics rarely specifies things that way. Most physical equations are perfectly happy under time reversal. Does nature care which events we label as "effects" and which are "causes"? It isn't really clear. Maybe FTL travel is impossible because it violates causality, or maybe the belief in causality is itself a misconception the same way that quantum mechanics revealed that many aspects of our human intuition are not absolute features of reality. Even further, time might be an illusion, such that all events past and future are fixed and unalterable even if time travel is possible (Eternalism). Or alternatively, the universe may be constructed in such a way that time travel is allowed but temporal paradoxes are intrinsically impossible (Novikov self-consistency principle). Ultimately, we don't know. Unless we actually achieve FTL travel, hypotheses about the consequences of FTL travel are likely to remain in the realm of speculation. Personally, I wouldn't use arguments about causality as a strong reason to rule out FTL travel, because it isn't very clear how real or important causality ultimately is. For me, the bigger issue is that general relativity doesn't appear to provide any mechanism by which space-time configurations involving FTL travel can be created provided that one must start from ordinary flat space. Maybe a future theory of quantum gravity or some such thing will reveal a way to achieve FTL travel. Or maybe a very clever person will figure out how to achieve FTL travel in conventional general relativity, but right now FTL seems impossible because physics as we understand it doesn't seem to provide any mechanisms by which FTL travel can be constructed using ordinary matter and space. Dragons flight (talk) 19:02, 13 July 2016 (UTC)
I'm not entirely sure I follow. If the universe doesn't care about our conceptions about causality, then surely you should be able to do a FTL round trip and come back before you ever left, giving rise to two of you, then kill yourself before you ever left i.e. grandfather paradox. Since that's impossible, it stands to reason that FTL travel is impossible. ScienceApe (talk) 20:02, 13 July 2016 (UTC)
Not necessarily. For example, time travel in a framework of eternalism, would say you can go back in time but not change anything because your time traveling self was always already part of the timeline. Its the 12 Monkeys versus of time travel, the time traveler goes back, and appears to influence events, but everything they did was exactly what already transpired and was part of history before they traveled back in time. This is one version of time travel that violates causality but doesn't necessarily violate physics if you believe eternalism is the right interpretation of physics. General relativity and things like wormhole-based time travel tend to be consistent with an eternalist interpretation. In this worldview, the actions of the time traveler won't prevent the traveler from going back in time (so a grandfather paradox is impossible). Novikov self-consistency principle is similar, and sometimes misunderstood as eternalism, but strictly speaking only really says that the universe abhors a paradox. In that worldview, time travel could be possible, and you could alter the past, but only in ways that would not lead to paradoxes (like preventing your future self from traveling back in time). Lastly, maybe the universe doesn't actually care about preventing paradoxes, and allows some form of alternate timeline / multiverse craziness. If someone invents FTL travel we can test it and see what happens. If FTL travel is possible, a universe that obeys eternalist principles but is no longer strictly causal as humans usually understand it would probably be the easiest to reconcile with existing physics. Dragons flight (talk) 20:43, 13 July 2016 (UTC)
But what would stop you from killing yourself? There would have to be some physical force to prevent that from ever happening. The only thing that could prevent that would be the impossibility of traveling back in time in the first place. Alternate universes would presume that every time you travel back in time you create another universe, but then wouldn't it stand to reason that the energy it would take to travel FTL would equal the energy to create a whole universe in the first place, making it impossible? ScienceApe (talk) 21:21, 13 July 2016 (UTC)
@ScienceApe: You're assuming free will, a concept subject to a great deal of debate. All of these causality issues are encountered in garden-variety precognition with no actual time travel required. For my part I have suggested that the causality violations are themselves the actual source of free will, its very definition really as an uncaused causer, and as such it cannot contradict them. Wnt (talk) 23:10, 13 July 2016 (UTC)
Precognition is the time travel of information. Foreseeing that a ball will drop if you let go is just a forecast. Holy shit, the ball fell! My forecast was right! Sagittarian Milky Way (talk) 03:03, 15 July 2016 (UTC)
As Wnt alludes to, an eternalist perspective on physics is one in which free will doesn't exist and never existed. Free will, like the passage of time itself, would merely be an illusion. All events past, present, and future are already fixed. An individual's personal history might appear to time travel, and thus violate causality as we perceive it, but they never really had the freedom to change anything. If time travel is possible, then the time traveler's past actions were always a fixed part of history. Dragons flight (talk) 04:48, 14 July 2016 (UTC)
So that's like bringing back the old deterministic clockwork universe after quantum mechanics was thought to refute it? That for whatever reason, the universe must have these specific random quantum fluctuations and no others are possible. Look at an electron today and change what the unchangeable future will be! Run naked in the street screaming bloody monkeys and do something inevitable today! Sagittarian Milky Way (talk) 06:22, 14 July 2016 (UTC)
@Dragons flight: Actually that's not what I suggested at all. A situation with loops of causality is one in which the universe can have multiple solutions, and there is no way to calculate which is the real one without actually looking to see. That is the very essence of free will - not just a random roll of the dice, but not the consequence of any past or future event. You can't change the future or the past, yet by some means that option has been selected in a way that the laws of physics cannot account for - which is the link to the supernatural that people intuitively seek when considering what free will is. Wnt (talk) 11:17, 14 July 2016 (UTC)
No actually I'm not assuming free will. For example if we assume that there is no free will in our universe, there is still nothing stopping one from pursuing their desires right now. So if one were properly motivated and capable of killing, they would do it even in a "no free will" universe. So if you're going to say that it's impossible to kill yourself when traveling back in time, there has to be some force that physically prevents that from happening. The only thing that prevents such a thing is the impossibility of traveling back in time in the first place. ScienceApe (talk) 15:57, 14 July 2016 (UTC)
@ScienceApe: Consider the double slit experiment. You measure which slit a photon passes through, and that changes where it comes out. But it doesn't just change where it will go - you now know that the photon passed through the space between the photon source and the slit before you did the measurement. So the measurement in the future changes -- erm, I mean causes; I would argue it always was this way -- the distribution of the photon in the past.
In this case, you've done a very elaborate, very thorough measurement of the position and velocity of the particles in the future. Now, given what you know, you work out the most probable solution that is also compatible with their positions in the past - just as you work out the location between source and slit in the first example. The "randomness" of quantum mechanics allows for a solution that is compatible with all boundary conditions, past and future. I suppose it might also establish an energy requirement for making the connection, come to think of it, which would be very substantial for a physical loop in spacetime with a huge number of simultaneous observations to be reconciled? Wnt (talk) 16:23, 14 July 2016 (UTC)
I see what you're trying to say but there's a big difference between your analogy and people. People aren't photons. There's no evidence that the universe is determined, on the contrary all the evidence points towards the conclusion that FTL travel is impossible. So then why are we entertaining a FTL and therefore time travel as a possibility when everything we know about the universe tells us that it's impossible? Reality has a tendency to converge on truth. If something is true, the more we learn about the universe, the more likely it is to be even more "true". Everything we learned about the universe has converged upon the truth that FTL travel/communication is impossible. Even things that seemingly occur FTL like entanglement forbid us from communicating FTL anyway. Occam's razer applies here. The explanation that makes the fewest assumptions is most likely to be true. In order for FTL travel/communication to be possible then we have to assume (with no evidence) that time travel is possible. Then we have to assume (with no evidence) that time travel either creates alternate universes or that even if you travel back in time, you can't kill yourself before you go on your FTL spaceship. All the evidence points towards FTL travel/communication being impossible, and that explanation makes the fewest assumptions so it's most likely the correct conclusion. ScienceApe (talk) 19:20, 14 July 2016 (UTC)
I lack confidence in Occam's razor. By your argument, the simplest explanation for why no birds fly in space is that you can't fly in space. And as I said, these issues come up with precognition anyway, so saying you can't travel in time isn't really sufficient - you have to also maintain that it is impossible for the past to remember the future, which is an arrow of time argument that is not at all obvious to be 100%, especially when aberrations start piling up. Wnt (talk) 02:49, 15 July 2016 (UTC)
No, Occam's razer doesn't posit the simplest explanation, it posits the explanation that makes the fewest assumptions. You can have very complex explanations all you want as long as there's evidence backing it up. There's no evidence backing up FTL travel, let alone time travel. Saying time travel is impossible is sufficient when all evidence points towards that conclusion. On the contrary, you have to wonder why you're so reluctant to say FTL travel is impossible? It's because we want FTL travel and communication, who doesn't? But we have to separate our desires from the facts. ScienceApe (talk) 05:09, 16 July 2016 (UTC)
Assuming Lorentz invariance faster than light travel is problematic as pointed out in the answers above. Alternatively, one can consider the possibility that Lorentz invariance may not be exactly valid, but there are strong constraints on Lorentz invariance violations. Count Iblis (talk) 21:40, 13 July 2016 (UTC)

July 14

Before seeking FDA approval of a drug in the USA, how do they test the drugs for infants or children?

When a drug is seeking approval by the FDA in the USA, how do they test drugs for infants or children? Joseph A. Spadaro (talk) 05:16, 14 July 2016 (UTC)

See Clinical trial and Ethical problems using children in clinical trials (which, based on its current content, would be better at a more neutral title). Tevildo (talk) 08:25, 14 July 2016 (UTC)
(edit conflict) Do you mean drugs specifically intended for infants and children? That case is rare. Most often a drug gets approved as safe and effective for adults and is only subsequently studied in children. In general we have articles on drug development and new drug application. Dragons flight (talk) 08:29, 14 July 2016 (UTC)
Thanks. This is what I am saying/asking. When drugs are approved for adults, they have -- at some point -- been tested on adults (through clinical trials, etc.). Oftentimes, when we (adults) take drugs, there are warnings that say "this drug is not approved for anyone under the age of 18" (or some such). Now, obviously, little kids (infants, children, teens, etc.) all take medicine and drugs. So, how do those get approved for them? I can't imagine they subject infants and children to be subjects in experimental trials and/or clinical trials. Thanks. Joseph A. Spadaro (talk) 12:59, 14 July 2016 (UTC)
Ultimately, yes. Children do participate in clinical trials with parental consent. Most often the trial is for a drug already approved for adults. If it is life-saving medication, then the benefits will generally be viewed as outweighing the risks. Doctors are also able to legally prescribe drugs to children that haven't been formally tested and approved for children if in the doctor's judgement such a off-label use is medically appropriate and inform the parents accordingly (usually the dosage is adjusted for a smaller body weight). This interesting article describes efforts by the FDA to increase drug testing in children. Dragons flight (talk) 13:12, 14 July 2016 (UTC)
Thanks. So, let's just look at infants, for example. I can't imagine it's a high number of parents that allow their infants to be guinea pigs. When they conduct tests, don't they need some statistically significant sample size? Joseph A. Spadaro (talk) 14:30, 14 July 2016 (UTC)

Thanks, all. Joseph A. Spadaro (talk) 04:40, 16 July 2016 (UTC)

Chem elements in the infoboxes

I noticed that now our articles on chemical elements display atomic numbers alongside Latin designations in the form of 26Fe (iron), 13AI (aluminium), etc. However, I was taught in the school that an element is simply designated by its Latin abbreviation (Fe, Na, etc.), not like 26Fe. If this is related to stable isotopes, I think it's redundant. Are we doing the right thing?--93.174.25.12 (talk) 12:11, 14 July 2016 (UTC)

Yes, it is redundant. But I think in the infobox title (the sole place it is used) it serves the purpose of highlighting the relationship in which atomic number determines the element. If you wish to discuss this with editors that are involved in making these decisions, Misplaced Pages talk:WikiProject Elements would be the best place to do so. ChemNerd (talk) 12:15, 14 July 2016 (UTC)
I agree with ChemNerd. The one- or two-letter abbreviation that the OP is describing as Latin designations are correctly called chemical symbols. Only a small number are based on the Latin name for the element (eg iron is Fe because the Latin word for iron is ferrum.) The majority are closely related to the English name for the element (eg hydrogen is H; lithium is Li.) Dolphin (t) 12:52, 14 July 2016 (UTC)
Actually, the symbols for hydrogen and lithium both derive from Greek, just FYI. EdChem (talk) 13:13, 14 July 2016 (UTC)
The names hydrogen and lithium indeed derive from Greek ὔδωρ γεἰνομαι and λιθος, but the symbols do not come directly from the Greek, but rather from whatever language Berzelius was thinking of when he came up with his symbols. Double sharp (talk) 15:30, 14 July 2016 (UTC)
Nothing to do with isotopes either - all isotopes of Iron have the same atomic number (26). The variation between isotopes lies is in the atomic weights (which range from 54 to 60). Wymspen (talk) 15:48, 14 July 2016 (UTC)
  • The atomic numbers in the lower left corner come from an expanded notation known as isotope notation. Yes, the numbers ARE redundant with the symbol, since there is a near perfect one-to-one correspondence between atomic number and symbol (excepting for the isotopes of hydrogen which each have their own symbol). The purpose of sometimes including the atomic number is twofold. First (and of lesser importance) is that it can serve as a sort of checksum, that is a way to make sure there isn't an error or typo somewhere. The most important use is in nuclear reaction equations; since atomic numbers and mass numbers are always conserved in nuclear equations, explicitly writing the atomic number makes the math more visual. --Jayron32 14:06, 15 July 2016 (UTC)

Deflection how much is safe?/

i have done fem study to find out deflection in structure.Is there any theory of failure to tell me that this deflection is safe or not .material is steel. — Preceding unsigned comment added by 112.133.223.2 (talk) 13:19, 14 July 2016 (UTC)

There are commercially available (though expensive) computer programs (doutbtless employing fem "under the hood") that can carry out such analyses, provided that the users are trained and competent in putting in all the parameters correctly. University-level courses in structural engineering and allied disciplines doubtless mention such programs, although work placements in working engineering companies might be necessary for training in using them in practice.
It's possible to carry out such a calculation for a single structural member on paper, but most scenarios in the real world involve complicated structures with many components, where a non-computer calculation would be unfeasibly difficult and long. (Obviously, such calculations were performed before the advent of computers, but they required vastly more personnel than would be available today, and of course some structures did subsequently fail.)
Given that structural failures can in many circumstances result in deaths, this is not an area that can safely and legally be dabbled in for real-world applications by the untrained. {The poster formerly known as 87,81,230.195} 2.123.26.60 (talk) 14:49, 14 July 2016 (UTC)
(ec) This has been studied extensively, and there are many issues here:
  • First, you need to ensure that the deformation is within the elastic deformation range, where the object will return to it's original shape, not the plastic deformation range, where it will only partially return.
  • Then metal fatigue must be considered, which is sudden fracture by a metal bent within it's elastic deformation range, an excessive number of cycles.
  • Also, the center of gravity of the building moves as it deforms, and you must ensure that the CG point is always within the edges of the foundation, or then the weight forces holding the building in place would instead work to topple it over. This is only a potential issue on tall, narrow buildings. StuRat (talk) 14:54, 14 July 2016 (UTC)

Is there an Aether?

The recently published book from the late Selwyn Wright backed up with several peer reviewed papers makes a very good case for an aether. This fundamentally conflicts with Einstein's relativity, but makes much more sense for measure movement from a static aether than just relative movement from two points, thus getting different equations from observer and event. He also shows how Einstein may of misinterpreted experiments to determine ether(prior to Special relativity) due to the fact that the aether turns with gravitational bodies (Also that the aether is static away from gravitational bodies in space).

Does this mean the teaching of relativity should be updated?

Selwyn addressed the experiments for aether and how they were misinterpreted but also uses later experiments to back up the claim and also suggests some other simple tests that could be done utilising the better equipment we have at our disposal today, if more proof was needed — Preceding unsigned comment added by 80.194.75.50 (talk) 14:44, 14 July 2016 (UTC)

It may well depend on how you define it. There doesn't appear to be much normal matter in the intergalactic void, but there may be dark matter or dark energy. Also, you could consider the space-time continuum to be a form or aether. StuRat (talk) 14:58, 14 July 2016 (UTC)
The validity of Professor Wright's theory is a matter for the scientific community to decide on by the usual processes. This does not yet appear to have happened, but it's early days yet.
It appears to this layman that there might be a good case for a Misplaced Pages article on Selwyn Wright, but others would be more competent to judge. {The poster formerly known as 87,81.230.195) 2.123.26.60 (talk) 15:02, 14 July 2016 (UTC)
Draft:Selwyn Wright already exists, so you have something to start with. Wnt (talk) 16:33, 14 July 2016 (UTC)
Here's a web page on "new relativity". He's just a typical crank. There are a lot of them. His particular area of confusion seems to be the Sagnac experiment. The ten peer-reviewed papers mentioned on the web site (in the sidebar on the left) are all conference papers from Progress In Electromagnetics Research Symposium. I don't see any evidence that it's a fake conference, but it's clearly not the right venue for this type of work and their reviewers clearly don't know anything about special relativity.
Of course, this has nothing to do with whether Wright should have a Misplaced Pages article. But I see nothing to suggest that he should. -- BenRG (talk) 17:42, 14 July 2016 (UTC)
See also . --71.110.8.102 (talk) 23:50, 14 July 2016 (UTC)
  • If the theory becomes widely accepted by the scientific community, it will be time to "update the textbooks". Not before. And the chances are slim.
History_of_special_relativity#Aether_and_electrodynamics_of_moving_bodies contains a whole lot of evidence against aether - if it exists, it should have zero local velocity in the reference frame of any object, yet create no measurable drag on them. So that is a viscosity-free fluid that still follows the objects, and that is extraordinary. Tigraan 15:25, 15 July 2016 (UTC)

Rabies vaccine "forbidden"?

Recently I got to familiarize myself with the relevant rules for transporting dogs internationally, including the rules regarding rabies vaccinations. I was surprised to learn that the country whose rules I was reviewing recognized three categories of dogs to consider:

  1. Dogs from countries where rabies is prevalent
  2. Dogs from countries declared rabies-free and rabies vaccine is available
  3. Dogs from countries declared rabies-free "that forbid rabies vaccinations"

In the third category, they gave examples of Australia and New Zealand. Why is there is a category of countries that "forbid" giving rabies vaccines to dogs? Is there actually something dangerous about the vaccine (e.g. a rare side effect, or something) that would justify not allowing the vaccine to be administered? Is it really true that Australia and New Zealand don't allow rabies vaccines, even for animals that will be traveling overseas? That seems very weird to me. Dragons flight (talk) 16:20, 14 July 2016 (UTC)

Australia recommends rabies vaccination for pets that might be exported and brought back. Assuming you could say you want to export the pet, then cancel the trip (which might just be overnight anyway, in theory), I don't think this can be a very strong ban, at least. Wnt (talk) 16:31, 14 July 2016 (UTC)
Usually such rules have to do with antibody tests to detect cases of infections not working anymore. In case of farm animals e.g., you cannot export animals if you vaccinate them against foot and mouth disease. This is why vaccination is only done when there is a major outbreak and an export ban is in place anyway. Count Iblis (talk) 16:35, 14 July 2016 (UTC)
Yes, for a human example, some countries where tuberculosis is not widespread don't routinely administer the tuberculosis vaccine, because anyone who has had the vaccine will test positive on the tuberculin test. See: Tuberculosis#Prevention. --71.110.8.102 (talk) 03:59, 15 July 2016 (UTC)
As with Wnt's point, these sources would seem to make it clear rabies vaccination for pets isn't forbidden in NZ, at least for export and pets travelling outside NZ. I'm not sure if the sources saying NZ forbids rabies vaccinations are just plain wrong, misleading or outdated as I can't find any info about NZ actually forbidding rabies vaccinations. It could be the vaccine was not formerly approved for use in NZ for whatever reason. It could also be rabies vaccinations are forbidden unless export or travel is a consideration although I personally doubt this. (Although I wouldn't be surprised if a vet were to get in trouble if they don't recommend against a rabies vaccination when there are no plans for travel or export.) It could also be because rabies vaccinations are rare enough that they are potentially something that needs to be specially ordered by most vets. (I'm not sure if this is the case even in most other rabies-free jurisdictions.) Nil Einne (talk) 17:29, 14 July 2016 (UTC)
It seems to me that we should be asking the OP where is this example of Australia and New Zealand forbidding rabies vaccinations? Let's see the evidence for that please. Akld guy (talk) 23:13, 14 July 2016 (UTC)
This might be relevant. --jpgordon 02:56, 15 July 2016 (UTC)
The OP never said said that NZ or Australia forbid rabies vaccinations but rather that sources gave them as examples of countries that forbid rabies vaccinations. They acknowledged that the examples may not be correct and I think we've already established the claim is questionable from Wnt's and my first response. See eg for the sort of sources the OP must be referring to. The websites all relate to Switzerland, although a bunch of spammy generic pet insurance websites also have the had the same thing. There is also one dead .nu web site I can't really understand with something similar although it seems to talk about needing proof they are forbidden and I have no idea where they were trying to export or take their pets to. Nil Einne (talk) 04:56, 15 July 2016 (UTC)
There is also which claims they are forbidden in Iceland. Nil Einne (talk) 05:01, 15 July 2016 (UTC)
I did not say that the OP said that Australia and NZ forbid rabies vaccinations. Geez, some people just love playing the game of semantics. Akld guy (talk) 06:15, 15 July 2016 (UTC)
Yes, this was in the context of Switzerland. Dragons flight (talk) 14:11, 15 July 2016 (UTC)

Wind strength of compressed air, part two

A few days ago I asked a question about the wind strength that would result from a sphere of air compressed from one kilometer in diameter to one-tenth of a meter in diameter. I was told that it would be as dense as a white dwarf, that oxygen-nitrogen fusion would result, and that the turbulence would require solving special equations. Really, what would happen if the force field that compresses the air were to shutdown in terms of interaction with the regular air? What would nitrogen-oxygen fusion look like? — Melab±1 ☎ 19:32, 14 July 2016 (UTC)

Here is The Synthesis of Elements from Carbon to Nickel, by astrophysicist Fred Hoyle. This paper series is considered the seminal work in the field, and it explains what fusion reactions are expected to occur under various extraordinary conditions. Well, these conditions are quite normal inside of stars - but they're very extraordinary here on earth!
Your hypothetical scenario is not exactly a physically-realistic condition, so you might have to be a little bit creative as you attempt to apply the results of well-established theories about stellar and supernova nuclear reactions. Nimur (talk) 20:51, 14 July 2016 (UTC)
O + O → S; O + N → P; N + N → Si; N + N → Si; N + N → Si; O + O → S; O + O → S; O + O → S; O + O → S; (there may also be reactions that yield unstable isotopes). Graeme Bartlett (talk) 03:54, 15 July 2016 (UTC)

July 15

Durian Fruit

I have smelt 'Durian' but it is too stinky. What may be the reason behind its stinkiness. — Preceding unsigned comment added by Sahil shrestha (talk • contribs) 02:48, 15 July 2016 (UTC)

See our article - Durian#Flavour and odour - my guess would be the sulfur compounds and the reason for the difference in perception being related to the asparagus urine smell (see asparagusic acid) where some people don't detect / smell the sulfur compounds produced by the metabolites. EdChem (talk) 03:39, 15 July 2016 (UTC)
An important odorant is 1,1-Ethanedithiol. Graeme Bartlett (talk) 03:56, 15 July 2016 (UTC)

Identify this bird

I saw this very large bird sitting on my neighbor's deck yesterday. In Northern California, San Francisco Bay Area. I thought it might be a turkey vulture but the head is whitish rather than red and the neck doesn't really look like a turkey vulture. It's also pretty bulky for a vulture, so I thought it might be a wild turkey, but it doesn't seem to have a wattle, and I've never heard of wild turkeys living in this area. Photos: CodeTalker (talk) 16:13, 15 July 2016 (UTC)

I suspect it is a turkey - though a juvenile so the wattle isn't yet fully developed. The distribution map shows that there is a population in northern California and Oregon. Wymspen (talk) 19:21, 15 July 2016 (UTC)
Yes, that is clearly a turkey. Matt Deres (talk) 20:14, 15 July 2016 (UTC)
I agree that it looks more like a turkey, but just for completeness, take a look at the turkey vulture. Doesn't look quite like your bird. StuRat (talk) 21:26, 15 July 2016 (UTC)
I know someone in Albany who often reports seeing turkeys; I'm not sure whether they're running wild or belong to some neighbor. —Tamfang (talk) 09:34, 16 July 2016 (UTC)
Or maybe they are just watching election news. :-) StuRat (talk) 17:49, 16 July 2016 (UTC)

Computer UV LEDs effects on the body and electronic components

I am playing around with a custom liquid cooling system, and plan to use UV reactive tubing. To have the glowing effect on the tubing, UV LEDs are required (for example). I am hestitate to order because of the questionable effects of UV on the body (skin & eye) and on the computer components. I don't have the exact model of the UV LED (maybe something like this), and don't think the manufacturer will list the specifications either. But I would like to have some basic guideline and advices, thanks.

Additional information: I will be using a case with full temper glass side panel, which provides no place to hide the UV LEDs. -- Livy (talk) 19:27, 15 July 2016 (UTC)

The effect of UV LEDs on skin is the same as that of sun light - tanning (unless you use UV-C LEDs). So, nothing to fear. Ruslik_Zero 19:49, 15 July 2016 (UTC)
Not really, since it's very well-established that UV exposure increases your risk of skin cancer. Tanning is a response to skin damage from UV light. I would avoid any unnecessary exposure to UV light sources. You'll survive without glowy tubes. (And incidentally, I think liquid cooling for computers is a waste of money, at least for personal computers, but hey, it's your money, not mine.) --71.110.8.102 (talk) 20:02, 15 July 2016 (UTC)
I know. It is mostly for aesthetic purpose. -- Livy (talk) 20:47, 15 July 2016 (UTC)
(edit conflict) Tanning... and cancer. But of course, the question is how much radiation will be received, and eyes are more fragile than skin anyways.
@Livy: Misplaced Pages does not give medical advice, so you will not get an answer to the question "is it safe to do X". You can start at Mercury-vapor_lamp#Ultraviolet_hazards, though I tend to think that UV LEDs will be less dangerous than spectral lamps. I think a PC-building forum would be the place to go for more specific info about how to build your system (where to put which part); if the UV source goes inside the case so that you only see the luminescence, I would assume it will be OK from a health perspective. Tigraan 20:10, 15 July 2016 (UTC)
I am not asking where to put the UV LEDs. I know it is best to keep them hidden. In this case, I am wondering if the tempered glass reduces the effect of UV by any chance. I know what to buy for my PC system and where to put them. It is not really a medical matter either I think -- I am not searching for a solution to my illness. I just want to know the short and long term effects of consumer UV LEDs on the body and on the electronic components (if any). -- Livy (talk) 20:47, 15 July 2016 (UTC)
Tempered glass will not significantly reduce UV flux at the wavelengths that consumer-grade UV LEDs typically operate (350-400 nm). Dragons flight (talk) 20:57, 15 July 2016 (UTC)
Also, you can determine this by experiment. Does a length of UV reactive tubing still glow when the glass is between it and the UV source? If yes, then the glass does not block UV. It isn't a perfect test, but it is better than nothing and easy to do. BTW, while we cannot give medical advice, we can certainly give engineering advice about whether long-term exposure to UV LEDS damage computer motherboards. I am guessing no but I would like to see a source. --Guy Macon (talk) 06:24, 16 July 2016 (UTC)
You might consider hooking the UV LEDs to a separate switch and then only turn them on for brief periods when you are showing off. Many fancy cases have switches built in for controlling LEDs. Dragons flight (talk) 06:43, 16 July 2016 (UTC)

July 16

Ionisation energies of actinides and lanthanides

I would have expected that the actinides would have lower ionisation energies than the lanthanides, since the 5f electrons would be further away from the nucleus than the 4f electrons of the lanthanides, and wouold be screened by more electrons. Furthermore, since only the first two lanthanides (Ce and Pr) can reach the oxidation state corresponding to the loss of all valence electrons (and Pr needs noble-gas matrix isolation conditions to do so), but the first five actinides can do it (Th, Pa, U, Np, and Pu, although only transiently for Pu), it would seem that the outer electrons of the early actinides are being held less firmly than those of the early lanthanides. Yet the list molar ionization energies of the elements on Misplaced Pages gives the opposite trend: Th has first ionisation energy 587 kJ/mol, while Ce has 534.4 kJ/mol, for example. Why is this so? Double sharp (talk) 14:16, 16 July 2016 (UTC)

Adolescent

  1. Define, , , adolescent age group.
  2. What’s the correct word to use from “” stated above?

Apostle (talk) 18:38, 16 July 2016 (UTC)

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