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March 11

Merge request

Standard enthalpy of formation and Standard enthalpy change of formation (data table) are two articles that are on the exact same thing. I suggest merging those two into one article. Someone please do it! 146.151.96.202 (talk) 02:10, 11 March 2016 (UTC)

The right place to make this suggestion is at the top of the two articles. See Template:Merge. (I've done it for you.) Add a further explanation on the talk page (of Standard enthalpy of formation) if you think it would be useful. --69.159.61.172 (talk) 02:25, 11 March 2016 (UTC)

Underwater vortices

3 related questions: (1) Are there locations on the continental shelf where strong horizontal vortices occur underwater (similar to the rotor effect of a mountain wave, but underwater)? (2) If (1) is yes, then do any predatory fishes take advantage of these to catch prey? (3) If (1) is yes, then how much of a hazard are these to divers? 2601:646:8E01:515D:3C06:A9A7:4EC1:51F0 (talk) 03:12, 11 March 2016 (UTC)

1) I wouldn't expect anything similar to a mountain wave, since water, unlike air, isn't very compressible. So, it doesn't behave like a spring. However, underwater vortices are possible for other reasons, like the collision of two currents. StuRat (talk) 03:19, 11 March 2016 (UTC)

https://en.wikipedia.org/wiki/Category:Whirlpools These often go to the seabed, eg Corryvreckan. Greglocock (talk) 09:28, 11 March 2016 (UTC)

But are there whirlpools with a horizontal axis of rotation? That's what I'd love to know. 2601:646:8E01:515D:3C06:A9A7:4EC1:51F0 (talk) 11:48, 11 March 2016 (UTC)

Compressibility is irrelevant to rotor, since the air velocity is much smaller than the speed of sound (see Mach number). Have you read Strait of Gibraltar#Special flow and wave patterns? --catslash (talk) 12:12, 11 March 2016 (UTC)

Yeah, that definitely looks like the right conditions for horizontal vortices! Are these in fact observed in the Gibraltar? 2601:646:8E01:515D:5537:81A4:208D:1E74 (talk) 11:47, 12 March 2016 (UTC)

Nitrogen narcosis

Is it true that to an outside observer, the symptoms of nitrogen narcosis look similar to those of severe drunkenness? And, what do you do if your diving partner has nitrogen narcosis and is unaware of it (but you don't)? 2601:646:8E01:515D:3C06:A9A7:4EC1:51F0 (talk) 03:17, 11 March 2016 (UTC)

If diving at depths and durations which can cause nitrogen narcosis they really should be breathing "air" with less nitrogen, such as trimix (breathing gas), or even Heliox. If they took the wrong tank and are breathing normal air, switching tanks might help. They might switch to their backup tank if it's likely to have the proper mixture of gases, or perhaps use your backup tank otherwise. Surfacing immediately would not be a good idea, as it might cause the "bends". You might signal the surface to send down a replacement tank, if switching to the backup tank will not allow for full decompression time. StuRat (talk) 03:23, 11 March 2016 (UTC)

Your diving instructor will teach you what to do, when you undergo your diving training. Given this plus your previous question, I certainly hope you aren't trying to learn how to dive based on asking questions online, because that's a really good way to kill yourself. --71.119.131.184 (talk) 07:19, 11 March 2016 (UTC)

No, I'm not -- I'm doing this for book research. 2601:646:8E01:515D:3C06:A9A7:4EC1:51F0 (talk) 09:18, 11 March 2016 (UTC)

That's good. Taking training might still be worth considering, as you'll probably learn a lot more than you will asking non-experts questions. If you're working with a publisher, you should ask them whether they can help you with research. --71.119.131.184 (talk) 18:36, 11 March 2016 (UTC)

Floaty but sturdy material?

In Deadly Duck, flying crabs drop yellow bricks that float on the surface of a pond yet block ducks who weigh considerably more than normal ducks, having guns built into them. They don't even budge. And don't splash when they land. Real life is quite different from Atari life, but is there a somewhat similar material in this world? Something light in gas but heavy in liquid? Or light vertically but heavy horizontally? Most of me thinks no, but technology is sometimes astounding, especially lately. InedibleHulk (talk) 03:30, March 11, 2016 (UTC)

The title made me think of Pykrete, but there's incompatibilities with other parts of your description. Ian.thomson (talk) 03:34, 11 March 2016 (UTC)

Still astounding, though. And pretty close. I'd be scared if there was a perfect match. I'll have to check out some video to get a better idea. Thanks. InedibleHulk (talk) 03:43, March 11, 2016 (UTC)

Many videos out there of shooting and smashing it, but I'm not seeing floating. Probably too boring for modern audiences. Shooting a brick with a rifle does next to nothing, almost like how the duck's shots do absolutely nothing. InedibleHulk (talk) 04:00, March 11, 2016 (UTC)

Yeah, I don't think that a brick sized chunk would necessarily float (unless maybe you put some helium bubbles in there or something), but they were going to build an aircraft carrier with the stuff, so it can float... At least as well as steel does. Ian.thomson (talk) 14:15, 12 March 2016 (UTC)

The right combination of light bubbles and heavy pellets, in some sort of foam, perhaps. InedibleHulk (talk) 05:36, March 13, 2016 (UTC)

Sounds like you are talking about a substance with a different gravitational mass than inertial mass. AFAIK, so far, we haven't found any such substance. StuRat (talk) 03:39, 11 March 2016 (UTC)

Maybe for the best. InedibleHulk (talk) 03:43, March 11, 2016 (UTC)

Note that the outriggers on a trimaran must be more dense than air and less dense than water, so that if they are up in the air, they push downward, but if submerged underwater, they push upwards. In this way, they provide stability and keep the trimaran from capsizing. StuRat (talk) 03:53, 11 March 2016 (UTC)

That's rather cool. Still drifts if you push it, though. InedibleHulk (talk) 04:00, March 11, 2016 (UTC)

An anti-rolling gyro might at least takes the oomph out of the duck's waves. InedibleHulk (talk) 04:09, March 11, 2016 (UTC)

Doesn't this just require an object of low density (lower than water) but high mass? A brick-sized block of hardwood would fload, but the woood would probably be too heavy for a duck to move. (Whether a woodchuck could chuck it is a separate matter). Iapetus (talk) 21:07, 12 March 2016 (UTC)

The mass needs fit into a space about half the height of the duck (and the width of a crab). That's the trickiest part. Should've mentioned it sooner. InedibleHulk (talk) 05:33, March 13, 2016 (UTC)

Cost of Gorilla Glass

Approximately how much does the piece of Gorilla Glass found on most phones cost?

I found this cost breakdown of the iPhone[1] but unfortunately that only provide a total cost for the whole display unit. But at least it shows that the cheapest display unit is $36.09 and thus the cost of the Gorilla Glass is somewhere below there. Johnson&Johnson&Son (talk) 15:52, 11 March 2016 (UTC)

According to this source [2] one display worth of gorrilla glass will cost $3. Or roughly 1/240 monkey's (£500) :) — Preceding unsigned comment added by Polyamorph (talk • contribs)

If you're trying to buy small quantites of Gorilla Glass, for hobby applications, you can email the sales team at the address published on their brochure.

Specialized engineered products - especially custom-made parts - are usually subject to volume pricing, and contract negotiations. That means the price might change based on who you are, where you are, when you need it, how much you're buying... so it's unlikely that you can get a very accurate price estimate without actually talking to the people who sell the part. Nimur (talk) 16:35, 11 March 2016 (UTC)

Large manufacturers never respond to these kinds of queries, so I've learned to respect their time and my own time by not sending such fruitless queries in the first place. Johnson&Johnson&Son (talk) 04:08, 12 March 2016 (UTC)

That's simply untrue; I linked directly to the sales team's contact information. They exist to sell stuff to real customers!

If you'd rather order through a wholesaler, McMaster-Carr sells raw material, including Gorilla Glass. McMaster is pretty expensive, but they carry lots of high-quality materials, and they will happily sell small volumes and will fill single-item orders. Nimur (talk) 04:30, 12 March 2016 (UTC)

Approximately very cheap in mass production. Cheaper than Sapphireglass i guess but then this Gorilla Glass is likely also less weight. Ofcourse for obviouse reasons these prices are very secret. Who would still pay 700 $ for his smartphone if he knew it's completely produced in china for less then 100 $? --Kharon (talk) 13:22, 12 March 2016 (UTC)

logarithmic decay instead of exponential decay?!!!

I am working in a new company where one of our products' shelf-life appears to be modelled more accurately by logarithmic decay (R^2 = 0.994) then exponential decay = (R^2 = 0.93). The logarithmic regression equation gives our product quantity as y = -A * ln(t) + B

This is *so* confusing. I have never seen this type of decay before. I don't know how to model it. For example, I know exponential decay comes from first-order kinetics, and can be modelled through a half-life. How can I model what's going on in logarithmic decay? What kind of kinetics is going on? Yanping Nora Soong (talk) —Preceding undated comment added 16:05, 11 March 2016 (UTC)

The equation you give implies that you started with an infinite amount of substance. I'm guessing that was not actually the case. --Amble (talk) 16:17, 11 March 2016 (UTC)

No, it assumes you start with some surplus (B) and that you decrease over time? (-A * ln(t)?) Yanping Nora Soong (talk) 16:40, 11 March 2016 (UTC)

If A,B>0 and t is time then at t=0 you get infinite goodies, and in some finite time (exp(B/A)) you get negative goodies. Here is plot from wolfram alpha of y=-2logx +3 [3]. Maybe you mean something else? If so please clarify what you mean. SemanticMantis (talk) 16:49, 11 March 2016 (UTC)

We don't start with an infinite amount of substance but we do start with a lot -- on the order of 4-5 million light units at week 0. (We're using a luminiscent anti-human reagent). We use calibration standards to correct for the estimated amount of detected protein as the reagent degrades. (i.e. it's a self-correcting assay). It's a pretty resilient assay up until 6-12 months in the fridge. We'd like to increase this shelf-life further though. Yanping Nora Soong (talk) 17:16, 11 March 2016 (UTC)

Your model predicts an infinite amount of substance at t=0, when in reality you have a finite amount. That makes it a terrible model for the data (including a point at t=0, R^2 = -∞!), so talking about the kinetics that could give rise to such a model is putting the cart before the horse. --Amble (talk) 17:57, 11 March 2016 (UTC)

I started at a timepoint of t=1. Yanping Nora Soong (talk) 18:18, 11 March 2016 (UTC)

I'm skeptical that it is actually logarithmic -- power law decay is much more commonly encountered. The typical cause of weird shelf-life distributions is inhomogeneous variance -- a situation where failure is caused by a number of different mechanisms that each has its own distinct time constant. You could get logarithmic decay if you had a situation where dy/dt ~ 1/y -- that is, the rate of change of a quantity is proportional to its reciprocal. I've never encountered anything like that, though.Looie496 (talk) 16:24, 11 March 2016 (UTC)

I did a power law fit first. The regression fit is 0.97, worse than the logarithmic fit. The shelf-life was modelled with data spanning 25C over 13 weeks. I'm going to look at the refrigeration data to see if the shape changes. Yanping Nora Soong (talk) 16:36, 11 March 2016 (UTC)

What are you talking about? I mean it really could matter whether these are puppies or cans of soup or something else entirely. Its not so strange that a log model might have a better best fit than exponential or other families of functions. You do have to understand the limits of your model though, and you have to acknowledge that the fit of the model by itself can't explain anything about underlying mechanisms. For example if we make the reasonable assumption that by shelf life you mean that time is the independent variable in your equation, then a log model means infinite product at time zero but also negative products after some finite time. The fact that these are both unreasonable doesn't have anything to do with the fact that a log model fits the data well. It does mean that while you may be free to interpolate, that any extrapolation based on this model is very dicey indeed, because extrapolation could predict infinite or negative goods.

In general, think more about Post hoc ergo propter hoc and Cum hoc ergo propter hoc, and overfitting. Maybe a touch of Texas sharpshooter fallacy. I can fit a log line very well to a crease in my palm, but it doesn't mean anything. A simple reason a log model might fit better over a limited sample even when exponential is expected could have to do with outlier_(statistics) and signal to noise ratio. Also keep in mind that the difference in R^2 you quote originally is rather small, or at least could be considered small in many contexts. Finally, if you want to do this more seriously, look into using something like the Akaike_information_criterion, and look into using a more flexible family of curves, perhaps the Weibull_distribution, see e.g here [4] for an application of Weibull hazard distribution to shelf life. SemanticMantis (talk) 16:41, 11 March 2016 (UTC)

We're talking about a time scale of 26-104 weeks here. This is a biomedical product, not a plastic thing that's trying to biodegrade on a beach. The interpolation period is perfectly fine for the timescale needed to model our shelf life. It is simply a matter of trying to fix the chemical issue that is causing shortening of our shelf-life. For example, is this is a big clue that our degradation of our immunoassay reagent (or one of its components) is tending to zero order kinetics, in that case, there is some sort of catalytic surface (not very surprising, we have lots of solid phase reagent, magnetic linkers, etc.) being saturated, etc. Yanping Nora Soong (talk) 17:05, 11 March 2016 (UTC)

Ok, then I think my general advice still applies: the fact that the log model fits better than others you tested can't tell you anything about the underlying process. It could suggest something to look into, and that would be Looie's proposition of dy/dt ~ 1/y, which I've also never seen in the real world, and is probably unreasonable for any real-world goods. A more likely explanation is that there is no underlying process that makes this a log decay. If there were such a process, it would lead to negative goods. The fact that log decay fits slightly better than power law is probably just a fluke, but I don't know anything about the quality control, sample size, precision of data, etc.

Talk to you supervisor. If this is biomedical goods then they can afford to do it right. Guessing at models and then drawing loose implications is not doing it right. Have you even tried a two-parameter model? Or one with five parameters, or five hundred? In this case, I suspect doing it right would involve a careful model selection process that uses delta AIC or similar model selection techniques to select across a range of models that have various structures and numbers of parameters. If you did that, then you might be able to use the nature of the model to help you understand underlying factors leading to too-short shelf life. But that's just about model selection, and doesn't leverage any of the chemistry. Conceptually, knowing what the stuff is and knowing chemistry should also help :) SemanticMantis (talk) 17:26, 11 March 2016 (UTC)

No, I am doing this because we (namely I) are trying to pick up any possible heterogeneous surfaces that could be degrading the reagent in our assay. We're trying to send our product into scale-up (pre-industrial-scale testing) very soon. God, we don't even have MATLAB, I really wish we did. This is a product that is about to be sent out into the real world. That is, the most we are trying to do is tweak the buffer and change the choice of casein vendor or something. We have to release the product by May 1st or risk possibly scrapping the entire immunoassay. My supervisor is a veteran and there are unexplained problems with this assay for some reason that were plaguing her team for months before I joined three weeks ago. So the big question I have is: Is logarithmic decay a sign of partial zero order kinetics? That's all I'm trying to do. I am well aware there could be multiple things going on. I am not interested in the other decay modes going on. I am well aware that is possible. All I am interested in is whether there could be a mix of decay modes, one of them being zero-order kinetics. I see that there is a -A "linear decay slope" in the decay model, which seems to hint at zero order kinetics, which seems to hint that maybe we should look into this further. That's all I want to clue my supervisor in to. Yanping Nora Soong (talk) 17:31, 11 March 2016 (UTC)

GNU Octave is a free alternative to MATLAB, incidentally. Tevildo (talk) 21:47, 12 March 2016 (UTC)

Our immunoassay is a mix of several reagents, all of which are needed to work for the IgM antibody of the particular virus we're working on to be detected. (We also use calibration standards). Thus, if they decay at different rates, this would explain the heterogeneous decay profiles. Modelling this is not the issue. It is not wanted. However, if there is zero-order kinetics going on, I'd (hopefully we at some point) definitely like to address that, because eliminating or mitigating this destructive catalytic surface, whatever it is (it could be one of our own reagents) could help shelf life. Yanping Nora Soong (talk) 17:42, 11 March 2016 (UTC)

I looked at the fit of the curves before I judged them. The power law fit was definitely worse. 0.97 was a very generous R^2 value for it considering that I would have judged it to be 0.85 or lower. The exponential decay fit was basically ignoring a huge part of the data. Let's talk about the error here: the error in the logarithmic fit is several dozen times less than the power law fit or the exponential fit. — Preceding unsigned comment added by Yanping Nora Soong (talk • contribs) 17:27, 11 March 2016 (UTC)

You have to be careful with the r^2 values. You can't just convert the hypothesized function to a linear function, do the linear regression, and calculate r^2 values - that gives misleading results. Bubba73 ^{You talkin' to me?} 02:39, 12 March 2016 (UTC)

Hmmmm. Let me see if I have this straight. First order kinetics implies a rate constant of -A, which is multiplied by the concentration of the reagent, i.e. an exponential decay with a half-life, total rate written in the form of -A e^-kt. Zero order kinetics implies a rate of -A, which is not multiplied by the concentration of the reagent. Your observation implies the overall rate of decay is -A/t, and the concentration of product (by which I mean reactant...) is -A * ln(t) + B, so the "coefficient" assuming first-order kinetics would be -A/t divided by this, i.e. -A/(-A * t * ln(t) + B * t), or 1 / (t * ln(t) + C * t) where C = B/A. Question: would it make sense to look at second-order kinetics? What if the fluorophore interacts with itself, for a rate of -A times the concentration squared... sigh, but what's the concentration? Our article says that these reactions have "a half-life that doubles when the concentration falls by half" - that makes sense. There are some graphs here. My guess is that the second-order kinetics comes close to a logarithmic decay than first-order, and you already didn't have numbers that much worse for first order, so... Well, anyway, I'm not very confident of what I'm saying here, so I better cap my pen at this point. Wnt (talk) 05:03, 12 March 2016 (UTC)

Free energy "model" as mathematical (formulaic) inspiration

It occurs to me there is another class of physical equations that uses the logarithmic decay profile -- e.g. the Gibbs free energy equation in relation to the equilibrium constant. The Gibbs free energy is allowed to be negative and the equilibrium constant is allowed to go to infinity. Except I'm trying to figure out how this would apply to my problem, since the variables with the Gibbs free energy equation uses temperature, not time.

Also this is product development -- we're not trying to develop a rigorous academic theory, we're just trying to fix some problems with shelf life and develop a working model. If we can help our customers (hospitals, hospices, etc.) keep our product 3-4 months longer, that will help us sell more product and that will also help them too. A working model -- to diagnose chemical decay -- is all we need. Yanping Nora Soong (talk) 17:10, 11 March 2016 (UTC)

• Free energy equation: dG = -RT ln K
• Enthalpy form: dH = -RT ln K + TdS
• My equation: P = -A ln(t) + B

So in this case, we can draw a similarity between the constant RT and my "A" constant, and "TdS" and my "B" constant, and "dH" and my amount of product at any one moment. And the equilibrium constant variable somehow shares a mathematical similarity with my time variable. I'm really confused and I don't know if the mathematical similarity is superficial here. Yanping Nora Soong (talk) 17:23, 11 March 2016 (UTC)

Two comments. First, there is no substantive difference between an R² of 0.93 and one of 0.99. They are both extremely good fits, and cannot be used to legitimately choose between models. In fact, an R² of 0.99 essentially never occurs unless there's a model misspecification causing the independent variable to be tautologically equivalent (or almost so) to the dependent variable. So if I were you I would look to see whether the way you've entered the data leads to the estimation of a tautology rather than a predictive relationship.

Second, time t is measured on an interval scale and not a ratio scale; taking the logarithm of the independent variable assumes it is on a ratio scale. That is, the choice of a value for the initial time period is arbitrary; instead of calling it t=0, you could have called it t=1 or t=837 or whatever. In a valid specification an arbitrary choice like that would have exactly no effect on the fit. But with the log specification, it will affect the fit. Loraof (talk) 17:48, 11 March 2016 (UTC)

Two reagent model, one decomposing the other

So here's a thought experiment. Say the luminscent (AE ester) reagent is decomposing zero order, on the surface of one the other reagents, probably solid phase reagent S, which is decomposing more slowly.

Thus, the AE ester, which we call E, is proportional to the amount of the exposed surface of the solid phase reagent S, [E]' = -k1[S]. But S is decomposing first order, through the equation we all know y' = -k2y. Thus ln [S] = -k2t + C.

But then [E]' = -k1[S] = -k1 e^(k2t + C) = -k1 Ce^(k2t), thus E would be described by the equation E = -k1*t * Ce^(k2t). This is not the equation I get, which is E = -k ln(t) + B

Are there any good alternatives? I'm really trying hard here.

Yanping Nora Soong (talk) 18:15, 11 March 2016 (UTC)

Well, you've now answered one of you bolded questions above: log decay is not indicative of partial zero-order decay kinetics. Consider that lots of things will fit better than the log model. Our problem in model selection, contrary to common misunderstanding, is not to simply maximize R^2 or some other notion of goodness of fit. That is actually really easy, all you need to do is throw more parameters at it and presto, your goodness of fit increases! Rather, our goal in model selection is explain things reasonably well and for the right reasons. In this manner, we can hope to learn something about cases that we cannot directly test, extrapolate, and possibly even reveal mechanisms. In this light, the Gibbs free energy thing is just wacky. Why would that have anything to do with this? I mean maybe it does but if so, you haven't explained it, and I think you're just looking for logs. The second approach is much more sensible. That is a good way to go about this: you've now shown what it would look like with two species, one with zero-order decay and one with first order decay. What would it look like if you had three species with zero, first, and second order decay kinetics? What about four? How well can those models be tuned to fit? These are more systematic approaches to your problem. As it stands, I think you're far too vested in that one log fit, which I think all of us here are telling you is probably a red herring. If you just want an better family of functions that won't give you nonsensical answers, look at the Weibull distribution I linked before. That's not mechanistic either, but it will almost certainly be less wrong. SemanticMantis (talk) 21:03, 11 March 2016 (UTC)

Because your probe is fluorescent, there's all sorts of weird possibilities involving quenching (fluorescence). Self-quenching, background phosphorescence that might activate and destabilize the fluorophore via FRET, etc. Self-quenching involves the fluorophore colliding with itself, which is why I mentioned second-order kinetics above. I haven't really investigated these things, but you might find a mathematical model for them with some research (not here or here really) - honestly, just search self-quenching fluorescence or something and from your work on this you'll probably recognize the useful hits better than I can. Note from the second reference how strong these effects can be - you can literally get more fluorescence from something labelled with fewer fluorophores because of some type of self-interaction. Wnt (talk) 10:57, 13 March 2016 (UTC)

March 12

Interrupted Dreams

Sometimes Im having a really good dream, then I have to get up and go to the toilet. When I get back to bed, I cant get back into my dream. Why is this?--31.109.183.147 (talk) 02:07, 12 March 2016 (UTC)

Lucid dreaming is the process of being aware of your dreams as they happen and potentially controlling their content. If you could remember your dream, maybe by writing it down immediately, then perhaps you could get back into it. StuRat (talk) 03:52, 12 March 2016 (UTC)

As a person who occasionally experiences lucid dreaming, though, I have this advice to give you: lucid dreaming is NOT restful, in fact when you wake up from a lucid dream you might feel like you didn't get any sleep at all. 2601:646:8E01:515D:5537:81A4:208D:1E74 (talk) 11:45, 12 March 2016 (UTC)

I know of no source besides our articles already linked, as well ass the main one, dream. But my experience is that if I actually have to get up out of bed, negotiate my way to the toilet, make the proper motions, wipe, and flush, then get back to bed, the "train of thought" is gone. Whereas if I wake up and roll over and go back to sleep, it is much more likely the dream will continue.

As for lucid dreaming, with me it usually only occurs in unpleasant dreams, where I can tell myself "this is a dream" and the direction of the dream will become less troubling (e.g., I am being chased through a building by a bear > I am walking through a natural history museum) but I still can't actively choose the direction or outcome. μηδείς (talk) 17:47, 12 March 2016 (UTC)

I didn't read our article, but the area of lucid dreaming actually is likely helpful to your question. In particular, the obvious question in response to your question is "how do you know?" This isn't being facetious but is actually an important issue that Sturat has hinted at above. Are you sure you're remembering exactly what you dreamed after you went back to bed? Unless there's something really unusual about your sleep and dreaming, if you have enough experience and knowledge about how dreaming works, you probably recognise it's quite likely there are many more dreams than you remember. (Notably it seems you're a lot less likely to remember your dream if you don't wake up soom after or when it's happening.) And even for those few dreams you do remember when waking up, unless you write them down or try very very hard to remember them long term, you probably won't. And in fact, you can even be sure if you memory of what you dreamed is correct. In other words, it's difficult for you to be sure your dream didn't continue since maybe it did you just don't remember it happening particularly if you slept for a while afterwards. And even if you by some magic do remember all the dreams you had after you went back to sleep, you'd need the same magic or some other method (like writing it down which unfortunately may either help or disrupt you dreaming the same thing) to be sure you're remembering the first dream you're trying to get back to. Again I didn't read our particular article but I know lucid dreaming does deal with this memory problem and suggestions as to how those who want to experience lucid dreaming should deal with it. Nil Einne (talk) 18:11, 12 March 2016 (UTC)

To come at this from the opposite way: on a number of occasions I've woken up remembering a dream that took place in a non-real location, and with the definite impression that I've dreamt of being in the same dreamed locale before. However, that impression might actually be only a part of the dream I've just had. (Keeping a Dream diary might be a way of obtaining proof of such recurrences, but I choose not to do that.)

I suspect that such dreamed impressions might be common: for example, H. P. Lovecraft wrote stories utilising the idea of voluntary return to a dreamed location, the Dream Cycle.

I myself have on several occasions been able to return to and continue a dream, but usually when deliberately daydreaming during the day rather than when in bed at night. This doubtless borders on the lucid dreaming mentioned by others above.

I fully sympathise with the OP in his frustration at being unable to return to an interesting 'immersive drama'. I suspect quite a few fiction writers began by continuing such 'unfinished stories' in writing. {The poster formerly known as 87.81.230.195} 5.66.243.108 (talk) 23:27, 12 March 2016 (UTC)

This is pure anecdote, but while almost all my dreaming follows the same pattern as the OP (i.e. once you wake, you can never continue it), I have on occasion only half-woken up, remained groggy for a few minutes, and then gone back to sleep and either continued the dream or repeated it. I have even on one occasion continued dreaming despite waking up otherwise fully. Iapetus (talk) 21:24, 13 March 2016 (UTC)

Does any one know?

Hi friends ,where i can get a carbon-ceramic matrix,air interface film coefficient.i want to use it to solve one disk brake static thermal simulation.please guide me 112.133.223.2 (talk) —Preceding undated comment added 08:33, 12 March 2016 (UTC)

You made that up all by yourself :D? --Kharon (talk) 13:03, 12 March 2016 (UTC)

See Heat transfer coefficient for our article. Unlike the thermal conductivity, the heat transfer coefficient isn't a property of the materials, but depends on the geometry of the system and the characteristics of the airflow. Tevildo (talk) 14:11, 12 March 2016 (UTC)

Wind mill blades efficiency

How is the most efficient number of blades determined. I can read that 3 blades is the 'most efficient' for fans, what about windmills or propellers? Is it as simple as 3 blades is 'usually most efficient (moves the most air), or are there other factors? Thanks if you can help? — Preceding unsigned comment added by 94.210.130.103 (talk) 11:52, 12 March 2016 (UTC)

Old-fashioned windmills - for grinding corn - generally had an even number of blades for balance. If one was damaged and had to be removed, the opposite one could also be removed and the mill operate temporarily with just two. If you had three blades, and lost one of them, it was unbalanced and useless. 109.150.174.93 (talk) 12:41, 12 March 2016 (UTC)

Ofcourse there are other important factors like material-, production-, assembly- and maintenance-costs. In Engeneering the approach is often not from perks like "moves most air" or "generates most energy" but instead if one additional blade is worth its investment, efford and potential trouble. --Kharon (talk) 13:00, 12 March 2016 (UTC)

It is not just about efficiency, but practicality that determines the number of blade. All engineering is an assemblage of compromises. Take a wind turbine. A single bade has the utmost efficacy of capturing the energy from the wind and it requires the least amount of material in its construction. Yet the strains on the tower and bearings etc, take there toll – requiring more costly maintenance. Two bladed turbines have better balance but create a resonances in the supporting tower. Three bladed mitigate much this, but cost more... yet have a longer life span. So at present, it appears that three bladed wind turbines demonstrate the best compromise, which in the long run produces cheaper megawatts over the economic lifespan of the turbine, compared to other configurations. P.S. More blades does not mean the more capture of available wind energy.--Aspro (talk) 13:33, 12 March 2016 (UTC)

We have Wind turbine design#Blade count although it's largely unsourced. Nil Einne (talk) 14:33, 12 March 2016 (UTC)

Another factor is that with more blades, each can be lighter, making it easier to handle. StuRat (talk) 15:48, 12 March 2016 (UTC)

It's a matter of defining "efficiency" since it depends on what you're trying to efficsh. In engineering, you can be trying to minimize various things such as weight or maintenance cost, thus narrowly defining "efficiency". In economics, you add up all the costs, because cost is what you're trying to minimize, which makes the question, "What is cheapest?" Jim.henderson (talk)

User:Jim.henderson is exactly correct. The optimal thermodynamic efficiency might not provide the optimal economic value proposition.

If we want to formalize this problem so that we can apply engineering methods to find the most efficient solution, we must define a cost function that meaningfully accounts for all of our subjective ideas about what makes the system "better." The cost function can be a composite of all sorts of diverse items, like material use, energy cost, dollar value, risk, and so on. Defining that cost function is typically the most difficult part of the problem: it requires deep understanding of many totally different disciplines, and requires an ability to turn fuzzy subjective ideas into quantitative decisions. These kinds of problems are formally studied as industrial engineering, process optimization, and related disciplines.

If all you care about is thermodynamic efficiency, we can direct you toward some great books on wind turbine design. Start here: How do wind turbines work? from the Department of Energy. At a high-school science level, we can say that more blades are more efficient at harnessing energy, but only if there is a lot of wind; more blades are heavier, so if the wind is slow, the extra efficiency isn't enough to make up for the extra weight. From there forward, additional detail requires a very abrupt transition into some really hard problems in fluid mechanics and statistics. We have an article on wind turbine design, §blade count; but if you want the real math, you'll have to grab one of the books listed in our section on "Further Reading."

Nimur (talk) 17:38, 12 March 2016 (UTC)

Single blade propellers are the most efficient, by the usual definition, but they have a lousy power density. In the case of wind the incoming energy is 'free' so the usual definition of efficiency is misleading, your goal is to extract the optimum energy from the windstream, taking many other factors into account. Greglocock (talk) 22:12, 12 March 2016 (UTC)

You just need one blade for harvesting energy to produce electricity. But wind turbine designs are not just about the energy efficiency. Llaanngg (talk) 22:38, 12 March 2016 (UTC)

It's a trade-off between the number of blades and the height of the tower. If you have a lot of short blades, you have a complicated and fault-prone hub - if you have fewer blades then they have to be longer and that means building a taller tower. SteveBaker (talk) 03:42, 14 March 2016 (UTC)

Eczema herpeticum

What is the mechanism by which herpes and eczema can interact to cause a systemic infection? Surely, if a localised area of eczema was infected with herpes, the infection would only remain there. 82.132.212.108 (talk) 12:42, 12 March 2016 (UTC)

STDs and alcohol

It's often argued that sex involving alcohol is more likely to transmit stds because it causes poor judgement, people are less likely to use condoms and it's More likely to be casual but could it also be argued that alcohol weakens the immune system hence increasing std transmission risk? 2A02:C7D:B907:6D00:8911:F3BA:77F4:29CB (talk) 13:34, 12 March 2016 (UTC)

Not an answer to the question
The following discussion has been closed. Please do not modify it.
Dear anonymous. It could be argued that alcohol weakens the immune system. However, lets stick to the most likely. Loss of judgement due to alcohol. The effects Ecstasy and Cannabis appear to have a more lovey effect on couples, who will tend to seek out any contraceptive barriers that may be readily available in respect of their lovey feelings toward each other. Alcohol has the thumbs down. Maybe this is because because alcohol depresses the outer cortex of the brain wherein our higher intellect is situated. Cannabis and ecstasy enhances it. The instance of STD has been coming down in resent year. Do you think that that is because teenagers have all of a sudden changes their ways?! Drink a bottle of Bourbon every day, for long enough and ones immune system may suffer but a teenagers metabolism appear not to get get going until a half bottle has entered the blood stream. The cheaper option to alcohol these days, is illicit drugs and politician should wise-up and rationalize the drug laws so that all drugs are properly controlled. --Aspro (talk) 14:09, 12 March 2016 (UTC) I'm hatting this. Your text has nothing to do with the question asked and is mere proselytizing. Take it elsewhere. Matt Deres (talk) 17:54, 12 March 2016 (UTC)

Our article at immunosuppressive drug and immunosuppression do not mention alcohol, but this piece by the NIH says "In both males and females, alcohol exposure suppresses immune responses..." and "An overwhelming amount of evidence reveals that both acute and chronic alcohol exposure suppresses all branches of the immune system, including early responses to infection and the tumor surveillance system..." with several links and citations. Matt Deres (talk) 18:02, 12 March 2016 (UTC)

C4H10O

Hey,

I try to answer for this question:

$A{\xrightarrow {E}}B{\xrightarrow {F}}C{\xrightarrow {HClorZnCl_{2}}}D$

A is an isomer of C4H10O.

Find A, B, C ,D, E, F.

I know that C most be alcohol & I also find 4 isomers of C4H10O but not sure how should I find solution to this problem.

thanks. — Preceding unsigned comment added by 31.210.177.225 (talk) 15:06, 12 March 2016 (UTC)

Think of a structure (or maybe several possible ones) of what C could be (you say you know it's an alcohol--not sure how you know this, but assuming it's true...); there are only a few isomers of 4-carbon chemicals that have that functional group). If that is C, what would the structure of D be? Note that not all alcohols react with HCl. So now you have some ideas for A and some ideas for C, you just need to figure out some intermediate that looks like the partial conversion. For example, if A has the OH on C2 and B has the OH on C1 instead, what are ways you know to get "OH on a primary position" and what are ways you know "to get OH off a secondary position"? Or pick an isomer you think A could be and list all the things you can make from it in one step (various E/B possibilities). Which, if any, of those B can you transform by one step into any of your C possibilities (the F method). That is, either work forwards-and-backwards and find the middle, or work from one end and see how close you can get to the other. DMacks (talk) 15:21, 12 March 2016 (UTC)

I know it because I learned that only alcohol reaction with HCl and Z_nCl...it seems to be so hard...I don't know. I will ask my teacher on Monday. Best.

I fixed the formula and spelling for zinc chloride. DMacks (talk) 18:10, 12 March 2016 (UTC)

I want to make this comprehensible, besides I'm getting rusty on my own chemistry... a quick search for alcohol "zinc chloride" gets this helpful demonstration [5] (well, I can't view the video but the text tells me a classroom exercise) There they use 1-butanol, 2-butanol, 2-methyl-2-propanol. (Note butane = 4 carbons with 2 H per carbon plus two more on the ends = C4H10, and 1- or 2- butanol adds an oxygen under one of the hydrogens. 2-methyl-2-propanol has three CH3s and an OH linked to a central carbon, again C4H10) Anyway, the tertiary alcohol in the demonstration reacts immediately; the secondary alcohol reacts after 6.4 minutes, and the primary alcohol doesn't react. So we know that C is the secondary or tertiary alcohol. Now D, we are told, is the alkyl chloride produced by an SN1 reaction from whichever C is. That leaves us to riddle out what isomerizations you can do to C4H10 in two steps to end up with one of these... Wnt (talk) 16:35, 12 March 2016 (UTC)

Now that we know ZnCl₂ is an alternative for HCl, it makes sense to assume that C would be an alcohol. With only "HCl" as the original question, it could easily have been alkene or alkyne, etc. Lucas' reagent is a great demonstration of the reaction of (and reactivity difference among) various alcohols that Wnt notes. There's one more isomer of the original than the three already mentioned (but 4 is not a lot of choices anyway). Note that there are several possible answers I see, even restricting the range of reactions to SN1/SN2/E1/E2 and simple reactions of alkenes. That sounds like how much you have covered so far in your class?--knowing "what you know" would help us keep from steering you into reaction topics you have not yet learned. DMacks (talk) 18:10, 12 March 2016 (UTC)

Did the question actually say "HCl or ZnCl2"? Or did it say "HCl/ZnCl2"? The second would mean HCl and ZnCl2, i.e. Lucas reagent. I don't know what to do if it's the first. Wnt (talk) 21:24, 12 March 2016 (UTC)

March 13

Hand-thrown projectiles

Both cricket balls and baseball balls are quite similar in size and weight (about 5 ounces) whereas modern hand grenades can be as much as three times heavier (1 pound in the case of the M67). In the case of the balls controlability/accuracy and velocity seem to be the criteria that are emphasized, wheras hand grenades need to be light enough to throw far enough so as not to endanger the thrower but also heavy enough to be an effective weapon, a grenade with a too small explosive payload will not do worthwhile damage to the target. Accuracy is of course also an important criterion. From many news media images it seems that stones used by rioters tend to range from fist sized up to about half a brick (BTW have people who design police helmets and shields studied this topic?).

If maximum range is the main objective, is it possible to figure out in terms of human anatomy/physiology/ergonomics an optimum size/weight for a hand-thrown projectile? Roger (Dodger67) (talk) 09:21, 13 March 2016 (UTC)

There must be some literature on shot - putting and discus - throwing. Discus is an Olympic sport and maybe the other is as well. 5.150.93.133 (talk) 12:03, 13 March 2016 (UTC)

Do javelins count? The world record (before a redesign in 1986 reset the standard) would appear to be 104.8m. Rojomoke (talk) 12:18, 13 March 2016 (UTC)

Good point! When I formulated the question I quite forgot about the shape of the projectile as a factor, and of course aerodynamics is important. Are there any reliable records for distances that baseball or cricket balls have been thrown? Roger (Dodger67) (talk) 12:46, 13 March 2016 (UTC)

When I Googled the term farthest thrown baseball, it pointed me to our article at Glen Gorbous. With a six-step running start, he managed 135 m (445 feet). When I Googled the term farthest thrown cricket ball, the results point to a YouTube video claiming 132 m, so essentially the same as a baseball. When I Googled the term farthest thrown object, it pointed me to the Aerobie. If you're interested, you can perform similar searches here by using the same sort of terms as I did. Matt Deres (talk) 13:07, 13 March 2016 (UTC)

This question from last year has some useful references. The Aerobie record was beaten in 2005 with a traditional boomerang (472.2 m), but I'm not sure that such devices count as "projectiles". The 132 m figure for a cricket ball was obtained by Roald Bradstock (a javelin thrower), who claims a large number of (unofficial) distance throwing records. Tevildo (talk) 13:49, 13 March 2016 (UTC)

I'm quite surprised that the ball records are so much further than the javelin. I think we should discount objects such as the aerobie, boomerang, frisbee, etc. because they rely on aerodynamic lift and fly like aircraft, rather than a ballistic trajectory. I found a claimed golf ball throw of 170 yards, by Roald Bradstock - https://recordsetter.com/world-record/world-record-for-throwing-golf-ball/7349 -- Roger (Dodger67) (talk) 13:53, 13 March 2016 (UTC)

The farthest discus throw is 74 m (81 yards),[6] so the discus is clearly far heavier than whatever the ideal weight is. --Guy Macon (talk) 20:37, 13 March 2016 (UTC)

Yes, it has been figure out in terms of human anatomy/physiology/ergonomics. See :The accuracy of throwing hand grenades. as a function of their weight, shape and size. However, this was done back in the early 1970's and considering the modern US diet, general health an life expediency is now falling behind other countries in the last 45 years, these figure may need to be readjusted down by an ounce or so.--Aspro (talk) 13:24, 13 March 2016 (UTC)

Thanks Aspro, that's an interesting article. Roger (Dodger67) (talk) 13:56, 13 March 2016 (UTC)

Don't let the creamy center of the general population fool you, though. Athletes, soldiers and regular people who just want to throw things as far as they can have much more in the way of sport science and fancy supplements (many of which are perfectly legal) than their grandparents did in the "milk, steak and barbells" day. It's just the middle class of moderately fit, moderately busy folk that's shrinking. Readjust up an ounce or so, I say. InedibleHulk (talk) 09:51, March 14, 2016 (UTC)

Note that hand-thrown objects can go faster and farther if a longer lever arm is used, in the form of an "atlatl", in the case of spears and darts, or a "cesta", in the case of a jai alai ball. A bow and arrow also uses only human muscle to propel the projectile, but differs in that the energy is put into the system when the bow is strung and pulled back, not when released. A crossbow/ballista goes even further, when a crank is used to pull it back, and a catapult/trebuchet extends the concept by using many people to pull back on the bent board or lift a counter-weight into position, to arm the device. StuRat (talk) 18:56, 13 March 2016 (UTC)

That's why the World War II era German grenades were mounted on a stick to allow the heavy end get up some decent momentum before being released. SteveBaker (talk) 03:37, 14 March 2016 (UTC)

The Islamic Penal Code of Iran gave a handy guide to the dimensions of stones to throw in lapidations: The size of the stone used in stoning shall not be too large to kill the convict by one or two throws and at the same time shall not be too small to be called a stone. AllBestFaith (talk) 19:46, 13 March 2016 (UTC)

How can a stone be "too large to kill in one or two throws", unless they mean it can't be lifted and thrown at all ? StuRat (talk) 20:15, 13 March 2016 (UTC)

I think you've misunderstood Amnesty International's? English translation of the rule. It seems clear if you take the whole paragraph that what it means is that the stone should not be too large, such that it will kill a person in one or two throws. And should not be too small such that it would not be could a stone. (Both of these are easily debatable definition at the borderline but what they are trying to say doesn't seem that hard to understand. They want a stone that is big enough such that it will be called a stone. But which is small enough such that it's unlikely to kill a person with one or two throws.) Nil Einne (talk) 20:37, 13 March 2016 (UTC)

Yes. The thinking behind Islamic Hudud stoning is that no individual executioner can be identified, rendering it impossible for the victim's heirs to demand compensation (see Diyya) or demand death of the killer (see Qisas). AllBestFaith (talk) 21:44, 13 March 2016 (UTC)

See also the scientific-sounding diffusion of responsibility. You can shoot another man all day with an imaginary bullet and no harm's done. InedibleHulk (talk) 14:59, March 14, 2016 (UTC)

Interesting question! stackexchange has a similar question. The Quixotic Potato (talk) 01:38, 14 March 2016 (UTC)

An unofficial record set in 2013 for throwing a cricket ball is 132.66 metres or 145 yards. [7] The use of a half-brick has a long and distinguished pedigree in the history of British anti-social behaviour: Who's 'i'm, Bill? - A stranger. 'Eave 'alfa brick at 'im. (PS: Apoloogies Matt, I've just seen that you posted the same cricket ball record above.) Alansplodge (talk) 11:33, 14 March 2016 (UTC

While we're on the subject, the official record for throwing a cricket ball is 140 yards 2 feet (128.6 m), set by one Robert Percival in 1882. Jānis Lūsis (another Olympic javelin thrower) has claimed an unofficial cricket-ball throw of "over 150 yards" (138 m). Tevildo (talk) 19:26, 14 March 2016 (UTC)

Did technical methods - technical levels of application and use are been determined a physical and chemical properties of all substances?

Questioner 1, RefDesk 0
The following discussion has been closed. Please do not modify it.
Did the maximum temperature of the burning – flaming of substances as also and the maximum heat capacity of substances are always been depended on the technical methods – technical levels of application and use of these substances?--83.237.192.54 (talk) 11:50, 13 March 2016 (UTC) Did all are always been depended on the levels of complexity of technique? (Did the levels of complexity of technique are always been decided all)?--83.237.192.54 (talk) 11:50, 13 March 2016 (UTC) How it (did) been in respect of electricity and gases in particular of natural and inert gases, if work body of any electricity did always been a electromagnetism and work body of all gases did always been a pressure?--85.141.237.179 (talk) 15:54, 13 March 2016 (UTC) It is well known that electromagnetism of all gases including natural and inert gases is always considerably small irrespective of the valence of these gases, especially in comparison with electromagnetism of electricity, is it right?--85.141.237.179 (talk) 16:25, 13 March 2016 (UTC) One possible reason why your questions are not being answered may be that we don't understand them. Try writing them in Russian and then machine-translating them. Robert McClenon (talk) 01:32, 14 March 2016 (UTC) I believe that may be what they are doing. The Russian Wikipedia has a combination RefDesk/Help Desk here. I would suggest the user try asking their questions there. Matt Deres (talk) 02:26, 14 March 2016 (UTC) In total, did a natural gases as also and all gases really always had a small technogenesis than always had electricity?--83.237.198.62 (talk) 10:26, 14 March 2016 (UTC) I think that technogenesis always did needed for successful development, because technogenesis did society younger.--85.141.238.215 (talk) 11:33, 14 March 2016 (UTC) As for me, I see the base problem of gases technogenesis is that, did a gas generation of electromagnetism had a perspective, if it's electromagnetism did not had been much as good?--83.237.218.90 (talk) 15:29, 14 March 2016 (UTC) Is been good idea to microwave this. InedibleHulk (talk) 15:41, March 14, 2016 (UTC) It looks, what is safer or use safer a gas or electromagnetism?--83.237.218.90 (talk) 16:10, 14 March 2016 (UTC) Did technical methods - technical levels are always been guaranteed a safety?--83.237.218.90 (talk) 17:36, 14 March 2016 (UTC) What is meaning the levels of complexity of technique?--83.237.218.90 (talk) 18:33, 14 March 2016 (UTC) Those are all excellent questions. InedibleHulk (talk) 22:28, March 14, 2016 (UTC)

Distance updates due to expansion of the Universe

Due to constant changes in galaxies' distances from Earth amid Universe's expansion and redshift, is it neccessary to specify the date of measurement each time it's mentioned? Something like "1 billion light years from Earth as of March 13, 2016". Why academic sources don't specify that and do not seem to update the distances? Thanks. 93.174.25.12 (talk) 19:21, 13 March 2016 (UTC)

The rate of expansion of the Universe is estimated to be between 60 and 80 (km/s)/Mpc and does not add significantly to the error in recent distance estimates. The value of the Hubble constant is estimated by measuring the redshift of distant galaxies and then determining the distances to the same galaxies (by some other method than Hubble's law). AllBestFaith (talk) 20:03, 13 March 2016 (UTC)

Agreed. It would be a bit like saying the distance from New York City to London varies with the date, due to plate tectonics. It does, of course, but the amount is insignificant unless you look at it over very long time frames, like millions of years. StuRat (talk) 20:13, 13 March 2016 (UTC)

I am reminded of the joke that goes along the lines of: a janitor at a museum is told a dinosaur fossil is 100 million years old, and a week later he excitedly tells visitors that the fossil is 100 million years and a week old. --71.119.131.184 (talk) 23:44, 13 March 2016 (UTC)

That's a lot like the old joke where a teacher is telling children visiting an observatory that the temperature at the heart of the sun is "millions of degrees"...but forgets whether that's centigrade or fahrenheit. A crusty old physics professor who's listening at the back clears his throat loudly and says "Kelvin". SteveBaker (talk) 03:31, 14 March 2016 (UTC)

In different units, the Hubble constant is about 0.00007 Myr⁻¹. That is, the universe is currently expanding by about 0.007% per million years, or 0.000000007% per year. -- BenRG (talk) 20:34, 14 March 2016 (UTC)

Would it be possible to have a SEM at home?

Ok, just because I'm curious. Would it be possible to have a scanning electronic microscope at home (regardless of price and space)? I think there would be some problems due to electric energy consumption and/or preparation of specimens.--Carnby (talk) 20:31, 13 March 2016 (UTC)

I took a glance at a few SEM manuals, and they seem to take normal house phase/voltage at a few tens of amps. DMacks (talk) 20:56, 13 March 2016 (UTC)

See the article Scanning electron microscope. The equipment is advanced for a home installation since it includes a vacuum chamber, high voltage supplies and a dedicated display. Biological specimens that are non-conductive usually need to be prepared with a conductive coating, e.g. of sputter coated metal. This video explains the basics. AllBestFaith (talk) 21:29, 13 March 2016 (UTC)

If your pockets are deep enough, sure, you should be able to use a SEM at home. If DMacks is right, power shouldn't be a problem, and even if it is, I'm sure it would be possible to buy an external generator.

As for specimens, that really depends on what you want to look at. If it's conductive, then you can look at it easily. If not, then it's trickier. Poorly conductive samples can be looked at briefly, but will quickly charge up and become invisible. Sputtering generally requires some serious equipment, so sputter-coating may be difficult to do at home. Then again, a quick search reveals that people have actually made sputtering machines at home, so I guess even that is not out of the question.

In any case, you'll generally want to put a SEM in a very clean environment. If you have a spare room to put it in, you should consider installing additional air filtering and adopting basic cleanroom protocols (a gray room to put on a cleanroom suit already goes a long way), though you that's not really a requirement. Whatever you do, always wear fresh disposable gloves when interacting with the sample chamber. I had to use a SEM that wasn't located in a cleanroom, and one of the big issues was carbon deposition. Any number of sources can contaminate your sample chamber with carbon, and it will get attracted to the areas of the sample you're looking at (especially at high beam intensities/high magnification). It's really annoying to see your sample turn black in a matter of seconds! You can mitigate that to some extent by keeping everything really clean.

Another major problem you might face in a home setting is vibration. That's no biggie at low magnifications, but if you want to image structures of tens of nanometres, it'll ruin your day. If possible, try to have some separation between your SEM and its vacuum system; the pumps introduce a lot of vibration. If you live near a busy road, vibrations from traffic may even be a problem. --Link ^(t•c•m) 21:53, 13 March 2016 (UTC)

Would think that a industrial SEM would draw most current when pulling a vacuum – in order to reduce the waiting time. After that, a few hundred watts should be sufficient. I'm normally weary of thing that I see on Youtube but this feller claims to have built one. [ https://www.youtube.com/watch?v=VdjYVF4a6iU DIY Scanning Electron Microscope] At first I was doubtful that he could pull the necessary vacuum inside a bell jar but he goes onto explain he uses both a mechanical and diffusion pump. His apparatus looks clean (no sign of organic oils). For something like this one would need to thoroughly degrease and then depend upon silicon grease only. His solder joint appear clean of flux (any oversight like this can slow down degassing and pulling a hard vacuum). His electronic units are also housed in nice 19 inch racks. So in this case, I think he has indeed built a home SEM. As to your second question about preparing specimens. Inorganic materials etc., may not cause a problem but biological specimens can create all sorts of challenges. Yet, for any one with the know how to build a working home SEM, it should not be beyond their skill to use the same basic set up for physical vapor deposition. As for clean room - I'll send my wife around. Vibrations... 2 to 4 am is a vibration free time. - Don't know, what the current price for SEM images are today, but if one costs ones free time at xx dollars per hour, a lab may be able to do the job more cheaply than messing about building ones own – but hey – to have ones own SEM must be very satisfying. So in answer to your question: It is possible to have a scanning electronic microscope at home.--Aspro (talk) 22:26, 13 March 2016 (UTC)

Despite the extraordinary spending that often goes into them (largely due to pork barrel politics by HVAC manufacturers I think) there's nothing that exceptional about laboratories as buildings. They have regular outlets with the same 110 or (rarely) 220 volt plugs as you can have in your house. Sure, they have solid concrete floors but the same can be found in many basements. Given that the question assumes someone can afford SEM equipment, I don't see why he couldn't set it up in a home. Wnt (talk) 15:26, 14 March 2016 (UTC)

Does woman can have an erection in her clitoris if she looked in men?

Does woman can have an erection in her clitoris if she looked in porn (without touching there), like what happens sometimes to men who watch porn? 93.126.95.68 (talk) 23:51, 13 March 2016 (UTC)

See Clitoral erection. Tevildo (talk) 23:54, 13 March 2016 (UTC)

When watching heterosexual erotic videos (ref), men may be more likely than women to objectify the opposite-sex actor. There are reported differences in brain activation to graphic sexual stimuli, with men showing higher levels of amygdala and hypothalamic responses than women. AllBestFaith (talk) 00:58, 14 March 2016 (UTC)

According to 2013 research conducted at McGill University, both men and women become sexually aroused at similar rates when viewing sexually explicit videos. Cullen³²⁸ Let's discuss it 01:12, 14 March 2016 (UTC)

Careful. Calling the Gender Gap a Myth is practically bannable. --DHeyward (talk) 15:47, 14 March 2016 (UTC)

"Objectification" is not a scientific concept. To figure out what actual science was meant by it, I looked at the source, "Sex Differences in Response to Visual Sexual Stimuli: A Review" by Rupp and Wallen. To my surprise/horror, the word is used there too. Here's one example: "Women's ability to imagine themselves as the woman in the film was the only factor the [sic] strongly correlated with their reported arousal. Men, however, rated the attractiveness of the female actor and the ability to observe the woman important in their arousal to the film in addition to imagining themselves in the situation. These results suggest that although both men and women project themselves into the scenario, men may be more likely to objectify the actors within the stimuli." So apparently if you're interested in the opposite-sex actor you're objectifying them, and if you don't care about them that's fine. I bet that if the data had gone the other way, they would have argued that by identifying with the same-sex actor and not caring about the opposite-sex actor, the men reduced her to an object for their own enjoyment. Because everyone knows men objectify women, so that must be what the science says.

This shouldn't be in Wikipedia (or in a peer-reviewed journal, but at least Wikipedia is potentially fixable). I don't know whether to delete the reference and everything copied from it, or just replace "objectify" with the science behind it. Is the whole section based on bad research that should be replaced by the McGill study? Can someone who knows more about this subject do something? -- BenRG (talk) 18:35, 14 March 2016 (UTC)

March 14

Erecting a species

See [8]. Is it normal to say that a naturalist "erected" a species or other taxonomic group? Nyttend (talk) 14:53, 14 March 2016 (UTC)

Looks like it could be vandalism to me, or a non-native english speaker mis-translating. Polyamorph (talk) 15:11, 14 March 2016 (UTC)

Though not a biologist, I often read natural history and palaeontological articles, books and even original papers. I have come across this expression, so would certainly dispute that it's vandalism. The term might be neutral, or might have the implication that the naturalist was (in the view of the writer) mistaken in proposing the species, etc., in question. {The poster formerly known as 87.81.230.195} 185.74.232.130 (talk) 15:31, 14 March 2016 (UTC)

Regarding your "implication" comment: are you meaning something like "John Doe erected Cervus johannensis in 1958, but two years later it was discovered that Linneaus had described the species as Cervus elaphus two centuries earlier"? Nyttend (talk) 15:38, 14 March 2016 (UTC)

Right, or maybe "Jones erected Flobosaurus jonesorum as a species, but later Cheng showed that the specimen comprised the bones of two other species. Like TPFKA above, I want to say I've heard this usage, but I cannot find a similar example. I would read it as largely synonymous with "proposed" or "posited". SemanticMantis (talk) 15:55, 14 March 2016 (UTC)

Searching "erected a species" and especially "species was erected" produces a good number of hits. Understanding the precise implications of this wording may be trickier. Wnt (talk) 16:26, 14 March 2016 (UTC)

Yes you're right, my initial search was insufficient, I take back my original comments. Polyamorph (talk) 12:58, 15 March 2016 (UTC)

Is it dangerous to eat a lot of eggs?

Is it dangerous to eat a lot of eggs? If it is, what is the normal number range of eggs that it's possible to eat from aspect of health? (I listen in the past that eggs are dangerous because they contain a lot of cholesterol, but yesterday I checked on wiki and I saw that the eggs have no cholesterol, that why I suspect that something here is wrong, but I'm not sure) 93.126.95.68 (talk) 15:35, 14 March 2016 (UTC)

I paste & searched google with your question and found this: on mayoclinic.org. Jarkeld (talk) 15:48, 14 March 2016 (UTC)

Interesting that they only recommend up to 7 eggs a week, or one a day (fewer for diabetics). That's not a lot. Their commentary that the cholesterol in eggs isn't much of a problem would lead me to think that more than one a day might be OK, especially considering all the nutrients the yolks have, so I wonder why they limited it to that. StuRat (talk) 16:40, 14 March 2016 (UTC)

They do have lots of cholesterol, but it doesn't seem to have much affect on our body cholesterol. One concern is the salt you might put on the eggs. I need to add salt to hard-boiled eggs, but not if they have a runny yolk. You might try them that way, and see if the same is true for you. StuRat (talk) 16:37, 14 March 2016 (UTC)

If you're eating them competitively, you might choke under pressure. Precision beats speed. InedibleHulk (talk) 22:34, March 14, 2016 (UTC)

Now this is a lot of eggs, and no serious (short-term) side effects. InedibleHulk (talk) 22:40, March 14, 2016 (UTC)

If the eggs are not cooked, the avidin can cause egg white injury i.e. biotin deficiency. And of course runny eggs carry a certain cumulative risk of salmonella etc. Wnt (talk) 23:30, 14 March 2016 (UTC)

Both my brother and I remember hearing from "somewhere" a long time ago that eating more than 1 or 2 eggs a day is bad for you, and we have come across more than a few people who thought they heard same thing, but like you we've never been able to find a good source for that claim. It's like, an old wife's tale or something.. Vespine (talk) 03:42, 15 March 2016 (UTC)

Until recently the reason was that the high cholesterol in egg yolks was assumed to cause high cholesterol in people who ate them. StuRat (talk) 03:46, 15 March 2016 (UTC)

So one of those Egg Council creeps got to you, too, huh? InedibleHulk (talk) 09:17, March 15, 2016 (UTC)

Are there Propane detectors on the Exomars probe, and, if not, why not?

The Exomars project's lead scientist quoted in our cited February 2016 Guardian article (cited in our article on the Exomars mission) appears to imply that the probe will be looking for propane (as a possible signature of biologically created methane), without explicitly saying so, but the September 2015 paper we also quote doesn't mention propane as one of the substances it can detect. Our article correctly reflects both sources, but is thus rather confusing to me as a reader. I've left a question about this here on the article's Talk page, but as those who wrote the article would probably already have prevented the confusion if they knew how to do so, I think I may well get a more expert answer here quicker and more reliably.Tlhslobus (talk) 16:35, 14 March 2016 (UTC)

There is no any propane detectors on the spacecraft or for that matter a detector for any other chemical substance. The spacecraft relies on universal spectrometers, which can detect any chemical in the atmosphere provided it has an observable spectral signature. Ruslik_Zero 19:42, 14 March 2016 (UTC)

Thanks, but unfortunately you haven't really answered my question since you don't say whether the universal spectrometers can detect the spectral signature of propane (under Martian atmospheric conditions), let alone provide a reliable source to back up such a claim. (Incidentally, I'm sorry if you failed to understand that I was using 'propane detector' as shorthand for 'equipment that is capable of detecting propane'.) The cited source in our article mentions a large number of chemicals that are detectable, but not propane, even tho it seems to be one of only two gases (the other being ethane, according to another of our sources, which seemingly doesn't say that ExoMars can detect propane) that can tell us whether Mars's methane is of biological origin. Hence I would like some reliable source to tell me unambiguously (not implicitly as in 'if propane is detected...', which might be a way of being 'economical with the truth') that ExoMars can detect propane. (Incidentally, I'm not sure how relevant this is, but if it can't, that may arguably raise awkward questions about whether this taxpayer-funded mission is up to the job, and whether this is being hidden from us - but any such questions will be scotched by a proper source explicitly saying it can detect propane). Alternatively, if it can't detect propane, it would be interesting to know why it can't, and whether how badly that might undermine the stated purpose of the mission. 15:46, 15 March 2016 (UTC)

From the ESA's Mars Exploration website, here is the list of trace gas orbiter instruments. The Atmospheric Chemistry Suite is tuned to precisely measure certain specific molecules that scientists already know they will find; but the same instrument can also "search for undetected species."

Whether the equipment could detect propane - and whether scientists believe even tiny amounts of propane could exist in Mars' atmosphere - are deep research questions. Your best chance for getting an accurate answer is probably by contacting the principle investigators. I'm not sure why you would believe that propane is the key to the entire mission: the program overview clearly states that the mission is to "demonstrate a number of essential flight and in-situ enabling technologies that are necessary for future exploration missions;" the scientific investigations, including the trace gas investigations, are icing on the proverbial cake. Even if the capabilities of one particular instrument doesn't live up to your arbitrary expectation, that hardly "undermines the stated purpose of the mission." Surely, as you have found in the Guardian article you mentioned, scientists will eagerly analyze any data that they retrieve, because the implications of any discovery might be important - but that's not the stated purpose of the mission.

Regarding your comments about the funding of these missions: Exomars is an ESA mission. Most of the ESA's total budget in 2015 was money from Germany, France, and Italy; 86% of the money comes from the EU, 10% comes from the EU in the form of Eumetsat budget, and the other with the remaining money comes from other sources. A paltry 0.6% of the total ESA budget came from Ireland, just barely edging above the contribution from Greece. To put this in context: the average Irish citizen contributed less than 0.01 Euro per year to the entire ESA Robotic Exploration program, of which only a tiny fraction went to fund this specific instrument on this specific mission.

Nimur (talk) 17:12, 15 March 2016 (UTC)

What is the maximum value for GFR?

I know that it is theoretically possible for glomerular filtration rate (GFR) to keep going up and up to infinity. But, realistically, what is the maximum value that would be considered acceptable? For example, I am pulling serum creatinine values from a public health database. I'm using the serum creatinine to estimate GFR. I have one patient with a eGFR of 10629. I assume that is beyond the acceptable limit, but that implies that there is an acceptable limit. So far, after four hours of Googling, I haven't found any minimum/maximum values for GFR. 209.149.113.14 (talk) 17:32, 14 March 2016 (UTC)

What kind of serum creatinine level gets you a result like that?? You might look for the accepted limits on that value, rather than the derived figure. (our article on creatinine indicates reference ranges - I haven't looked to see if there's any viable mutation that would allow a person to just not make creatinine in the first place, though I presume it is at best many orders of magnitude less likely that faulty data in your database) Beyond that, I'm thinking you're in statistics territory, trying to discard outliers. Wnt (talk) 23:34, 14 March 2016 (UTC)

Seeing as "normal" eGFR starts at 90, my default assumption would be that the value is erroneous. Maybe it's supposed to be 106 and someone accidentally hit extra keys while entering it. --71.119.131.184 (talk) 02:47, 15 March 2016 (UTC)

I believe they vary by race and danger/health concerns are modulated by cause. Creatine kinase levels are a useful metric for injury/disease and there is also the clinical observation of urine. --DHeyward (talk)

File:Sajama.jpg

This file is named "Sajama", but it looks more like Parinacota to me - conical shape in front of a lake. Does anyone know which mountain this is for sure?Jo-Jo Eumerus (talk, contributions) 19:49, 14 March 2016 (UTC)

• Based on my own research and File:Parinacota volcano 1995.jpg it looks like Parinacota indeed. Thus withdrawing request.Jo-Jo Eumerus (talk, contributions) 16:33, 15 March 2016 (UTC)

What holds tangerine lobules together?

How exactly tangerine and similar Citrus fruit lobules are attached to each other before separation for consumption? The sound of separation in tangerine reminds adhesive tape, but upon separation no traces of attachment can be seen. Thanks. 93.174.25.12 (talk) 21:39, 14 March 2016 (UTC)

Adhesives don't always leave a residue. Sticky Notes, for example, don't leave any. However, see cohesion for the tangerine case. StuRat (talk) 22:01, 14 March 2016 (UTC)

Sticky notes definitely normally have residue on the sticky note unless it get's so dirty it's no longer adhesive. Nil Einne (talk) 23:01, 14 March 2016 (UTC)

Yes, but none on what they were stuck to. StuRat (talk) 00:03, 15 March 2016 (UTC)

Yes but your claimed adhesives don't always leave a residue, not that they don't always leave a residue on one part of the two parts that were stuck together. Even if you had said the later, that has nothing to do with the OP's point unless you're claiming that the citrus fruit lobules do have residue on one lobule the OP just keeps feeling the wrong one.... Nil Einne (talk) 13:49, 15 March 2016 (UTC)

The stickiness you hear when pulling the carpels/lobules/chunks apart is only incidental to their being held together by the albedo for a while. Not much to do with the albedo or the albedo. InedibleHulk (talk) 23:54, March 14, 2016 (UTC)

March 15

Intensity of Odor of Cats Feces

I have heard that the feces of a cat has a stronger odor than that of other animals. Is this correct, and if so, I would be grateful if a user could please let me know the reason for this. Thank you.Simonschaim (talk) 10:30, 15 March 2016 (UTC)

The Ref. Desk has no reason to doubt your ears so your report of what you heard is probably correct. The reason it was said in your hearing must be because fecal odor is your special interest and is the subject of everything you have contributed this year [9][10][11][12][13]. AllBestFaith (talk) 14:28, 15 March 2016 (UTC)

Stronger crap than a rabbit, goat or cow, for being a carnivore. Those dead bodies don't disappear when they're swallowed. They just add a certain oomph. Roughly tied with other meat-eaters, by my nose. Dogs can be terrible by just leaving it in the open air, if you're wondering which will make a house smell worse. InedibleHulk (talk) 14:38, March 15, 2016 (UTC)

Where were temperatures 11.5 C warmer on average in February?

There is a map going around at sites like [14] showing a single color for "4 to 11.5" degrees Celsius above average for February. Where was the +11.5 C? Is there a way to see a map with contours for +6, +8, +10? Note: I think I found the raw data at GIST here, and one of the locations is in northern Russia south of the Kara Sea; maybe I should write a script to get an overall view but it would be more reassuring to see a real source. I don't see any option to adjust contours on their main map.

Bonus question: if methane clathrates or methane in permafrost were being released, would the effect be localized and viewable on such a map?

On a related note, the Severnaya mine explosion in Vorkuta, Komi Republic where 38 miners were killed by a series of methane explosions prior to February 28 is at 67N 59E, with a temperature anomaly of +10.98 degrees C. Has the remarkable weather been considered as a cause of this tragedy? Wnt (talk) 11:41, 15 March 2016 (UTC)

I can't help with the maps but there is almost certainly methane being released from terrestrial permafrost as well as the arctic seabed. Some coverage of this at Arctic_methane_emissions. My understanding is that there are local hotspots but this is generally considered as a regional flux. SemanticMantis (talk) 14:36, 15 March 2016 (UTC)

That article reminds me: the Yamal peninsula, where giant sinkholes created by escaping methane have been observed, is right in the middle of the hottest zone also... Wnt (talk) 16:40, 15 March 2016 (UTC)

When scientists need cocaine for an experiment, where do they get the cocaine from?

When an experiment need cocaine, for example, for testing the preferences of mice given free sex, free sugar, or free cocaine, where do they get the cocaine from?--Scicurious (talk) 16:00, 15 March 2016 (UTC)

From the drug cabinet. When I was recovering from extensive mouth surgery I was prescribed cocaine mouthwash. Yes I did try swallowing it. To me the effect was like 17 double espressos, won't be doing that again. Greglocock (talk) 16:14, 15 March 2016 (UTC)

Right, lots of human medical use for cocaine addition to the types of experiment OP is talking about. Some of these are covered at Cocaine#Medical. SemanticMantis (talk) 16:27, 15 March 2016 (UTC)

I would assume it varies some according to what part of the world you're talking about. Countries where drugs are more closely tied to violence or addiction would be more likely to enforce more restrictions than those there really isn't much violence or addiction. Ian.thomson (talk) 16:23, 15 March 2016 (UTC)

From places like this [15]. Search /cocaine vendor laboratory research / for more companies that can provide cocaine for research purposes. SemanticMantis (talk) 16:26, 15 March 2016 (UTC)

Note that cocaine is "Schedule II" in the U.S., which says it has accepted medical use, as opposed to marijuana for which medical marijuana is not accepted as a use. (Politics and truth are not on speaking terms) I recall once getting a sort of air-based injection spray of the stuff as a local anaesthetic into a toe prior to injected anaesthesia before having a small part of a toenail removed. Wnt (talk) 16:44, 15 March 2016 (UTC)

In the U.S., from a DEA-licensed supplier. To lawfully obtain controlled substances, you have to be registered with the DEA, and comply with the relevant laws and procedures, like filling out the paperwork so the DEA can track the drug to ensure you aren't selling it on the black market or whatever. --71.119.131.184 (talk) 19:15, 15 March 2016 (UTC)