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April 26

Application of brain lateralization to UI design?

The article Lateralization of brain function doesn't discuss the phenomenon's applications. This article claims that gamers should place UI elements that they respond to with the right hand on the right side of the screen, and those that they respond to with the left hand on the left side, to shorten reaction time. Do any ergonomic studies support this claim? Is it possible that a gamer might be able to process some elements of the game state faster in one lobe than the other? NeonMerlin 00:43, 26 April 2011 (UTC)

A lot of "left-brain" and "right-brain" theory was never founded on scientific experiment, and most of it has been pretty thoroughly discredited. What we're left with is a much more vague, but much more believable, theory of functional specialization (brain). It may take decades for "pop psychology" to let the numerous invalid ideas go to rest, though. There is very little actual evidence to suggest, for example, that the "left side" of the brain is more suited to (or more active during) quantitative or numeric cognitive activity. Nimur (talk) 00:50, 26 April 2011 (UTC)

That's all true, but there is some pretty solid evidence that simple visuomotor reactions are faster when they use the hand on the same side as the stimulus (for example PMID 7128169). It is much less clear what happens when the stimuli are more complex or require sophisticated decision-making. From an anatomical point of view, the brain is wired such that the visual input from the right side of the world goes to the hemisphere that controls the right hand, and the left side matches with the left hand, so the basis for such an effect is certainly there. Looie496 (talk) 01:28, 26 April 2011 (UTC)

How to save generic annotated DNA sequences?

There is a sequence here in a generic form with annotations. How do I save it so that I can open it in a capable program which will feature the described annotations? Thanks. --129.215.47.59 (talk) 14:24, 26 April 2011 (UTC)

Can you be more specific about what you want to ultimately be able to do with the sequence? The "capable program" you choose (and there are lots of options) is going to depend on your application, and each program probably has a different input format. If you already have a program you want to use, then there should be some kind of FAQ or user guide that describes the required input. If you haven't already selected a program, then the question you really want to ask is "what program should I use to accomplish X". --- Medical geneticist (talk) 15:01, 26 April 2011 (UTC)

Hi. Thanks for your response. The program is called SeqBuilder; it's a miserable excuse for a cloning tool which we use because our Institute cannot afford Vector NTI. However, the page that I link to presents the genetic and annotation information in a way which I have seen time and time again in my short scientific life and this leads me to believe that it is some sort of generic format, capable of being understood by a number of different programs. If I save it as an .sbd file, SeqBuilder will open the sequence but ignore the annotations. I hope that by appending the correct file extension, I'll achieve an annotated sequence. --129.215.47.59 (talk) 19:33, 26 April 2011 (UTC)

You say, "the page that I link to" - which page is that? If you have an example of the layout you desire it will be easier to guide you. The options are remarkably diverse. Examples of free programs: Artemis, CLC sequence viewer. Geneious is not free, but has great features & students can get a 1-month license for $39. If these aren't what you want, please be more specific. -- Scray (talk) 02:54, 27 April 2011 (UTC)

The file format you link appears to be a variant of the EMBL or Swiss-Prot file formats (see [1] and [2]). If it doesn't autodetect the format, you would have to see what extension your program expects files with such a format to have. (Besides looking in the manual, one way to do so would be to try *saving* as EMBL format, and see what extension the program give it.) -- 140.142.20.229 (talk) 00:40, 27 April 2011 (UTC)

Fermi Paradox and data encryption

Our article on the Fermi paradox says that compressed data streams would be almost indistinguishable from white noise. Would not the same apply if the data was encrypted? A Quest For Knowledge (talk) 17:06, 26 April 2011 (UTC)

If it's good encryption, then absolutely. See page 13 of this book. So you're hypothesizing that the galaxy is teeming with life that communicates by radio, but it's encrypted, so we have no idea? Comet Tuttle (talk) 17:13, 26 April 2011 (UTC)

Both for compressed and encrypted streams, this assumes the data is sent with no kind of framing. You can communicate over an unreliable medium with a self-synchronising code, but why would you bother (unless you were trying to conceal the transmission)? Note that the assertion about compressed streams in that article is unsourced. -- Finlay McWalter ☻ Talk 17:23, 26 April 2011 (UTC)

I think concealment must be the whole point; see Prime Directive. Comet Tuttle (talk) 22:41, 26 April 2011 (UTC)

I'm also not convinced, absent a decent reference, either that a) a compressed stream resembles white noise as opposed to another colour (particularly for schemes which periodically flush their dictionaries) or b) that the cosmic or galactic noise you'd typically see is white either. -- Finlay McWalter ☻ Talk 17:36, 26 April 2011 (UTC)

It also depends on what your definition of a "resemblance" is. A wide band signal will fill the fourier-domain spectrum, but not with random data. So, if you define a signal to "resemble" white noise, solely on the basis of whether it occupies a wide frequency band, then a lot of things "resemble" white noise. Ultimately, if you use a deterministic compression methodology, each compressed input stream will have a unique spectral signature; so the characteristics of the output stream will depend entirely on what data is being transmitted. If you use a lossy compression scheme, any particular source stream will map to one of a finite set of possible compressed stream spectral signatures. I'm not very happy about our "color of noise" article, which seems to blur the terminology. I like our noise shaping article much better; and will toss in that digital signal quantization has unique spectral properties that are easily detectable as "band limiting;" the modulation scheme for any particular signal will dictate whether the band limitation exists as a fourier frequency band, or as some other more abstract vector-space spectrum (such as phase-space, or generalized wavelet spectrum, etc). Nimur (talk) 18:13, 26 April 2011 (UTC)

Toasted bread

why does the toasted bread tastes sweeter than the normal bread? —Preceding unsigned comment added by 122.162.128.226 (talk) 17:29, 26 April 2011 (UTC)

See Maillard reaction. --Jayron32 17:38, 26 April 2011 (UTC)

The sugar components of starch (amylose, glucose, etc) are relatively tastless in starch form. But when subjected to dry heat it produces pyrodextrins through process called pydrodextrinization (strange as it may seem). More like the sugars we use for sweetening. Wiki article (starch)scroll to pyrodextrinization.Phalcor (talk) 18:48, 26 April 2011 (UTC)

Without reading the article, I will tell you that you can link to the 'starch' article on this wiki by typing [[starch]], which gives you a blue link like this: starch. If there is a header 'pyrodextrinization' in the article, you can link to it by typing [[starch#pyrodextrinization]] which produces starch#pyrodextrinization. 82.24.248.137 (talk) 20:43, 26 April 2011 (UTC)

Oh, and I see that you probably meant people to read the bit under Starch#Dextrinization. 82.24.248.137 (talk) 20:44, 26 April 2011 (UTC)

perennial

Resolved

The Taraxacum officinale article says that they are perennial, but I can't see any mention of exactly how long they usually live. I know perennial means more than 2 years, I would like to know more specifically how long they can live for. 82.43.89.63 (talk) 18:56, 26 April 2011 (UTC)

The thing is, 'death by old age' doesn't really apply here. Dandelions exhibit indeterminate growth. So, death of a mature plant will usually be due to Plant_pathogens, herbivory, roundup, etc. In this light, the average life-span of a dandelion in a given population will depend on how prevalent these sources of mortality are. In principle, I know of no reason why a well-cared for specimen couldn't live 100 years or more. SemanticMantis (talk) 19:23, 26 April 2011 (UTC)

Thanks! 82.43.89.63 (talk) 20:33, 26 April 2011 (UTC)

Higgs boson

How does the Higgs boson explain the difference between the massless photon, which mediates electromagnetism, and the massive W and Z bosons — Preceding unsigned comment added by Lufc88 (talk • contribs) 20:04, 26 April 2011 (UTC)

Assuming you understand the contents of these articles (I certainly don't), you may find your answer at Higgs mechanism or 1964 PRL symmetry breaking papers or Higgs_boson#Theoretical_overview. Presumably, the information therin could be summarized in a way that someone who isn't familiar with the mathematics involved can still understand, which I will leave to someone else to do. --Jayron32 20:14, 26 April 2011 (UTC)

Perhaps that editor could also write such a summary in the appropriate articles. Like, as line #1 of each article. Comet Tuttle (talk) 22:39, 26 April 2011 (UTC)

How about starting with an explanation of this...:

"In the standard model, at temperatures high enough so that electroweak symmetry is unbroken, all elementary particles are massless. At a critical temperature, the symmetry is spontaneously broken, and the W and Z bosons acquire masses.

Fermions, such as the leptons and quarks in the Standard Model, can also acquire mass as a result of their interaction with the Higgs field, but not in the same way as the gauge bosons."

Now to be clear - at some very high temperature, does this mean that electron, quark, W, and Z (and photon?) all zip around at the speed of light, as massless particles, and can't go any slower than the speed of light? Are they all actually the same at that point, or just have the same apparent properties?

And at some point, they gain masses by interacting with the non-zero vacuum expectation Higgs field. Is there anything about the massless particle that says ahead of time whether it will become an electron, quark, W, or Z when it interacts with the Higgs?

If you cool down a photon enough, so that it has a really really really tiny energy and a huge wavelength, could it interact with a Higgs and become some new particle we don't yet know about? Wnt (talk) 00:41, 27 April 2011 (UTC)

The short version is that the symmetry breaking mechanism leaves some symmetry behind, and names like "photon" and "electron" are assigned after the fact in accordance with the remaining symmetry. Start with a featureless sphere. There are three independent continuous symmetries of the sphere: rotation around any three mutually perpendicular axes. Now break the symmetry by drawing a dot somewhere on the sphere. Probably, rotation around any of your original axes will move the dot. But there was never any reason to choose those particular axes, so throw them away and choose a new axis through the dot and two other axes perpendicular to that one. Now you have one rotational direction that preserves the remaining symmetry of the sphere-with dot, and two that don't. This is not the greatest of analogies, but it sort of resembles the origin of the photon and the W^± bosons. Keeping in mind that the choice of axes depends on the location of the dot, and the dot can be anywhere, do those axes "exist" before the dot is drawn? In one sense yes, in another sense no. -- BenRG (talk) 10:51, 27 April 2011 (UTC)

I think thye sphere with a dot is a good analogy. Dauto (talk) 13:46, 27 April 2011 (UTC)

April 27

quarks

how do they know that the quarks in a proton maintain their color? in other words do we know that the "red" up quark stays "red"? since we can only take still shots could the red up change to a blue up quark in different still shots without detection? —Preceding unsigned comment added by 98.221.254.154 (talk) 03:58, 27 April 2011 (UTC)

Quarks are constantly exchanging colors with their neighbors. That's part of how the strong interaction works. Dragons flight (talk) 04:04, 27 April 2011 (UTC)

Couldn't that be explained more simply as at the time of the observation one quark was moving toward the observer and another was moving away, or more complexly spinning right and moving toward or spinning left and away? Color seems awfully similar to length width and height, why not use those instead? —Preceding unsigned comment added by 98.221.254.154 (talk) 04:30, 27 April 2011 (UTC)

Because calling it a form of motion would be wrong. The Color charge of quarks was specifically called a color because it is a fundemental property which is quite unlike other properties such as "spin" and "electric charge" and stuff like that. Since the tripartite existance of quarks within nucleons required 6 values to capture all possible combinations, the 6 color charges (red, antired, blue, antiblue, green, antigreen) allow that to work. Electric charge only requires 2 values (+ and -) to work out. The goal is to pick an analogy which won't be confused with other properties, like length, volume, or spin. --Jayron32 04:41, 27 April 2011 (UTC)

(edit conflict) Color charge has nothing at all to do with visible color. Quarks don't "look" red or blue, and their color charge has nothing to do with how they are moving. The "red", "blue", and "green" quark charges are simply labels used to refer to different kinds of charge. This is analogous to how objects can have an "electrical" charge, except that in this case "red", "blue", and "green" refer to other kinds charge that only encountered in the hearts of nucleons. These are simply labels that physicists adopted. Admittedly, using the familiar terms and calling it "color" can be confusing to outsiders since the whole process has nothing at all to do with the normal experience of color. Dragons flight (talk) 04:46, 27 April 2011 (UTC)

No, I mean like the "height" position of the quark in the nutron at the time of the photo or single observation, as in one of the three dimensions of space that that particular quark is occupying at that particular time. —Preceding unsigned comment added by 98.221.254.154 (talk) 04:48, 27 April 2011 (UTC)

Except you can't take a photo of a quark in an observation. Their position exists only as a statistical average of their location taken over an arbitrarily long period of time, exactly as electrons do. The three quarks in a nucleon exist in a small sphere whose volume is defined by the distance over which the strong interaction operates. They don't actually exist in any specific place within that sphere, and it is completely meaningless to speak of a quark as a little ball which can be "frozen in time" by a photograph. Fundemental particles don't work that way. Your presumption that you could define it as such is flawed at the most basic level. --Jayron32 04:56, 27 April 2011 (UTC)

Ok, the height "quality" of the nutron the length quality of the nutron and the width quality of the nutron gives the nutron the ability to be in all three dimensions, but each quark takes turns as each of those qualities equally. —Preceding unsigned comment added by 98.221.254.154 (talk) 05:02, 27 April 2011 (UTC)

(edit conflict) with below. This response is to the above.I guess so. We can "call" the three quark charges anything we like. You could say that the three quark charges are called "Tom, Dick and Harry" if you wanted to, then describe gluon interactions as "A tom quark emits an tom-antidick gluon, which converts the neighboring dick quark to a tom quark, which itself then emits a dick-antiharry gluon, converting the harry quark to a dick quark" The choice of the three names for the three quark charges is completely arbitrary, and any set of three names would work. Height-Width-Length is a nice three-part set, the problem with using it is that those three words already apply to a part of physical reality which is already "coded for" in the x-y-z axis system inherent in the particle spin quantum number. Since the particle spin axis is defined as the z (height) axis, it doesn't make any sense to define both spin and quark charge using the same set of terms. Since the height-width-length (z-y-x if you prefer) is already fundemental to how spin is defined, it would be beyond confusing to use the same terms to define quark charge. Even the Tom-Dick-Harry system would be better. The advantage of the color system is that quark-quark interactions through gluon exchange can be directly modeled by how colors interact. Just as combining red with its complementary color (cyan or "antired") results in colorless (white) light, combining a red quark with an antired gluon will "cancel" the red color. --Jayron32 05:20, 27 April 2011 (UTC)

Quarks already have positions. Color charge refers to an entirely different set of properties that are in addition to the position characteristics. Dragons flight (talk) 05:12, 27 April 2011 (UTC)

That's not what Jayron just said. —Preceding unsigned comment added by 98.221.254.154 (talk) 05:13, 27 April 2011 (UTC)

(post EC response). A quarks spin defines the three dimensions (the axis of the spin fixes the "z" axis of the coordinate system). However, quarks, like other fundemental particles such as electrons, can't be localized to a specific point within their defined probability distribution. As far as I know, there's no way to specifically define a position within the nucleon for each quark to occupy. We draw pictures of quarks as three little circles within a bigger circle because this allows us to visualize them, but this is no more an accurate model of the quark than the lewis structure is an accurate model of the electron. --Jayron32 05:20, 27 April 2011 (UTC)

I get that the "three little colored circles" are not representative of the dynamics of a nutron. I don't believe that simply identifying the xyz coordinates is equivalent to explaining how a nutron exists in those dimensions. Would you agree that just as two electrons cannot occupy the same state two quarks in a nutron cannot occupy the same dimension. that in order to have a nutron it must occupy three dimensions. To have a nutron with two height qualities and a length quality would leave out the width quality —Preceding unsigned comment added by 98.221.254.154 (talk) 05:35, 27 April 2011 (UTC)

Then we're just debating semantics here. You can literally use any three words to define quark charge that you want (see my Tom-Dick-Harry explanation above), so long as you don't mistake the three words you choose as representing any real property except for the quark charge. The disadvantage of using the positional terms is that it implies a connection to reality which does not exist and may confuse. The advantage of the color system is twofold. First, it is less likely to confuse since it uses terms and concepts which are not encountered elsewhere in the model. Secondly, the way in which colors interact (see my red-cyan colormixing example above) makes a nice analog for how color-charge works. So, yes, you are technically correct that you could choose any set of three words to represent the quark-charge concept. However, don't overextend the words you use to take on meanings that do not correlate to behavior. Using words like "height, width, and length" to describe the three aspects of quark charge has no connection to any other definition of those terms. It would be just as arbitrary of a system as the color system would, so why upset the applecart. Instead, just stick with the system that exists which, while equally arbitrary as your proposed system would be, has the distinct advantage that everyone is already using it. --Jayron32 05:48, 27 April 2011 (UTC)

The animation of gluons in color charge shows a neutron transiently having two red down quarks. But the article says "...introduced the notion of color charge to explain how quarks could coexist inside some hadrons in otherwise identical quantum states without violating the Pauli exclusion principle." Is either of these things wrong or misleading? Wnt (talk) 05:52, 27 April 2011 (UTC)

The picture is attempting to show the gluon exchanges happening in isolation. It is my understanding that, in reality, all three gluon exchanges would happen simultaneously, so all three gluons would change color at the same time. If the gluon exchanges happened sequentially (as shown in the animations) rather than simultaneously, it would lead to some rather impossible situations. The animations are showing isolated gluon exchanges probably because it makes it easier to show how the two-color gluons (say red-antigreen) can change the color of the target proton. In reality, these exchanges are happening simultaneously, and at the speed of light, over a distance of a few femtometers, which is about as instantaneous as the universe will allow. --Jayron32 06:02, 27 April 2011 (UTC)

The animation is accurate and consistent with the exclusion principle. Dauto (talk) 13:40, 27 April 2011 (UTC)

So noone knows what physical properties the colors represent? I figured that the colors were to make it easier to understand, not that no one knows how else to interpret it. wow. —Preceding unsigned comment added by 165.212.189.187 (talk) 18:44, 27 April 2011 (UTC)

Sure, we know what physical property the colors represent. They represent the 6-fold "quark charge" which is fundemental to how the strong nuclear force works. This is exactly analogous to the 2-fold electric charge which is fundemental to how the electromagnetic force works. If you understand what physical property + and - mean with regards to the electromagnetic force, then you also exactly understand what the 6 colors of color charge mean with regard to the strong nuclear force. Its the exact same sort of thing. --Jayron32 18:48, 27 April 2011 (UTC)

Think carefully about it. What do you mean by a physical property? For instance, what physical property does the mass of a particle represent? Dauto (talk) 18:57, 27 April 2011 (UTC)

Why couldn't it be the H-W-L qualities? —Preceding unsigned comment added by 165.212.189.187 (talk) 18:56, 27 April 2011 (UTC)

H-W-L are spacial properties. color charge are not spacial properties the same way that electric charges are not spacial properties. Dauto (talk) 18:59, 27 April 2011 (UTC)

How do you know: Photon 1 dimension = no charge; Electron 2 dimensions +,-; Quark 3 dimensions HWL? —Preceding unsigned comment added by 165.212.189.187 (talk) 19:02, 27 April 2011 (UTC)

Do you mean 0, 1 and 2 dimensions respectively? – b_jonas 19:34, 27 April 2011 (UTC)

I don't think so? How do you mean? —Preceding unsigned comment added by 165.212.189.187 (talk) 19:46, 27 April 2011 (UTC)

Again, I need to ask the question: Why are you so tied to the words used to describe the property? You seem to be having a problem conceptualizing that the word is not the thing itself. This is purely a linguistic problem. We've already conceded that the words you use to describe the quark charge thing are completely arbitrary, there's nothing inherently wrong with your system, excepting that it isn't any improvement on the current system, which has the advantage that its already used. Why is height-width-length any better to describe the system than red-green-blue is? The fact that HWL is coincidentally a 3-dimensional system? So isn't red-green-blue (see color space). What makes your three-dimensional system better than the existing three dimensional system already in use? --Jayron32 21:01, 27 April 2011 (UTC)

I guess its better to me only because it helps me understand.

That's cool. If you've got a model that works for you, then stick with it I guess; but you also need to be able to work with the existing model and understand it as well. --Jayron32 01:01, 28 April 2011 (UTC)

Why does coldness hasten the browning of a banana peel?

I took two nearly identical bananas and put one inside the cold refrigerator and one on the room temperature counter and after a couple of hours the one in the fridge was significantly more browned. I assume the chemical content of the air (%O2, %N2, etc...) is the same since the fridge door opens and closes frequently enough and there's nothing else in the fridge I think is giving off or absorbing gases much. The physical difference between the different temperature airs is then pressure. I don't have a bell jar with vacuum pump, though. Will a banana peel brown at an accelerated rate in a vacuum? Thanks. 20.137.18.50 (talk) 14:43, 27 April 2011 (UTC)

Surveying the Web, it's apparent that cold injury sets in below about 10 C. What happens is that the plant senses damage, and (perhaps via ethylene) activates enzymes such as phenylalanine ammonia lyase and polyphenol oxidase. It is possible to slow this down with a modified atmosphere with less oxygen and more carbon dioxide.[3] I saw claims on non-reliable sites that you could slow down the browning by keeping the bananas in a bag, but I don't know if the banana actually respires enough to build up CO2 in a bag. (the truth is out there, but I might go bananas trying to track it down) This is essentially a pigmentation reaction, producing melanin - though the details are not quite the same as the reaction in insects, the basic function of responding to injury or infection using a pigmentation reaction is the same. Wnt (talk) 15:49, 27 April 2011 (UTC)

Thanks for that information. You've well answered how the browning happens. "What happens is that the plant senses damage,..." How it does that (how it figures out that it's cold outside and to start doing what you described, which has a side effect of making them appear brown) would be a mechanism of interest. 20.137.18.50 (talk) 17:21, 27 April 2011 (UTC)

Blood supply to the dartos muscle

Does the dartos muscle in the scrotum have a named blood supply?

This is mostly for personal interest, but should possibly be referenced in the article. Kind Regards, Captain n00dle\^Talk 14:47, 27 April 2011 (UTC)

I did a quick search:

"The blood supply to the skin of the penis and the anterior scrotal wall are from the external pudendal arteries. The blood supply to the posterior aspects of the scrotum is from the posterior scrotal arteries, which is a branch of the perineal artery, which is a further branch of the internal pudendal arteries (5) (Fig. 2.1)

Branching off the medial aspect of the femoral artery are the superficial/ superior branches and the deep/inferior branches of the external pudendal artery. These superficial external pudendal branches pass from lateral to medial, in a variable pattern, across the femoral triangle, and within Scarpa's fascia (a loose membrane of superficial fascia; Fig. 2.2).

After giving off scrotal branches to the anterior scrotum, the superficial external pudendal artery cross the spermatic cord and enter the base of the penis as posterolateral and anterolateral axial branches. Together with interconnecting, perforating branches, they form an arterial network within the Dartos fascia. The Dartos fascia is not really the blood supply; it is more accurate to visualize the fascia as a trellis and the blood supply as the vine entwined on the trellis. At the base of the penis, branches from the axial penile arteries form a subdermal plexus which supplies the distal penile skin and prepuce (Fig. 2.3). There are perforating connections between the subcutaneous and subdermal arterial plexuses. These connections typically are minimal and very fine and, thus, a relatively avascular plane can be developed between the Dartos and Buck's fascia. Because the fascial plexus is the true blood supply to the penile skin flaps that we use in urethral reconstruction, the flaps are considered axial, penile skin island flaps that can therefore be mobilized widely and transposed aggressively.^[4]

I would like to copy the images from the book here, as not everyone will find themselves able to access this page from Google each time they check the link; but unfortunately, I don't think that Wikipedia's Fair Use image policy has thus far extended to uploading local Fair Use images for the Ref Desk archives. If people think we have a chance, this might be time to press the issue on behalf of one or more images. Alternatively, they might be redrawn from the source at some low level of quality (it really is pretty schematic as it is, presumably due to some anatomic variation that they discuss after the section I quoted). Wnt (talk) 22:14, 27 April 2011 (UTC)

Thank you very much for your answer, that was more than helpful! Regards, Captain n00dle\^Talk 11:47, 28 April 2011 (UTC)

Selling spent nuclear fuel

Why don't states that practice nuclear reprocessing buy the nuclear waste from states that don't? Is it uneconomical? (If so, by how much?) Or is it just political? I can see why the US would not sell to China, for example, because there is always a chance that any plutonium reprocessed in China could be alleged to enter into their nuclear stockpile, which would be political poison to whomever proposed it in the US. But there are other, safeguards states, like the Netherlands, or Japan, where this wouldn't presumably be a problem. Has this ever been seriously proposed? --Mr.98 (talk) 15:43, 27 April 2011 (UTC)

For perspective, clothing worn by technicians who work in laboratories near hallways connected to the reactor core is considered "low level nuclear waste" and can't be driven on non-Federal roadways without police escort. (A bit of hyperbole, perhaps, but not much - that's the regulatory environment that years of paranoia and FUD have created). The prospect of actually exporting actual nuclear material is so far off the political table right now, I can't imagine it ever being discussed by a serious high-level legislator. See Radioactive Waste from the US Nuclear Regulatory Commission for more information about relevant policy and procedure; particularly, transportation guidelines for spent fuel. Nimur (talk) 15:53, 27 April 2011 (UTC)

(In actual truth, there are only three locations that are legally permitted to accept incoming shipments of low level nuclear waste, including dirty laundry from nuclear facilities). My exaggeration in the previous paragraph was not that far off the mark. Nimur (talk) 15:57, 27 April 2011 (UTC)

Sellafield's Thermal Oxide Reprocessing Plant provided reprocessing for material from several nations: Japan, Germany, Switzerland, Spain, Sweden, Italy, Netherlands and Canada. [5] Waste was (and may still be) processed for a fee and returned to the origin. Polititally it seems undesirable for any nation to accept radioactive waste from another nation without a promise to return it. There are also numerous problems with transporting it, not least of which is the reluctance of intervening countries to let nuclear waste pass through, and while some of the public grudgingly admit the need for nuclear power, the need for reprocessing is less obvious. --Colapeninsula (talk) 16:01, 27 April 2011 (UTC)

According to Peak_uranium#Reprocessing_and_Recycling, mining uranium is far cheaper than reprocessing nuclear waste, so it does not make economic sense to buy waste in order to reprocess it. --Colapeninsula (talk) 16:06, 27 April 2011 (UTC)

Though you could imagine states like the US, who have literally zero long term waste policy at the moment (other than "store it on site at every individual reactor"), might find the service itself to be worth paying a premium for, well beyond what it would get them in terms of fuel. --Mr.98 (talk) 21:15, 27 April 2011 (UTC)

Part of the economic theory which justified the design of THORP in the 1970s was that there would be a market (subject to NNPT restrictions) for plutonium for fast breeder reactors.(ref:NewScientist 4 Aug 1977). But the UK didn't build a generation of commercial fast breeder reactors (ref: Bulletin of the Atomic Scientists March 1993), and they didn't really catch on elsewhere either. And given that nuclear weapons delivery systems have become so accurate, and the mania for competing in megatonnage has gone with SALT, START etc., the declared nuclear powers have a surplus of Pu anyway (and so have come to realise that it's a liability rather than a boon). If the proposed new generation FBRs catches on, there might after all be a decent market for Pu, but there seems to be quite a lot of it sitting around anyway (from military applications and existing reprocessing). This paper(from 2001) gives numbers then for surplus Pu and describes the plutonium fuel business as uneconomic and over-subsidised. -- Finlay McWalter ☻ Talk 21:50, 27 April 2011 (UTC)

ISS lights

I have been able to spot the ISS in the Earth's shadow with binos quite often. In fact, it is always observable when it is higher than about 20° above the horizon. I would say that it is roughly magnitude +8 when it is at 45° altitude, which by my calculations corresponds to a lightsource of about 30 Watt. Because over the last three years, the brightness is similar, I think that there is an outside lightsource on the ISS and it isn't light escaping through the windows. Does anyone know more about the lights of the ISS? Count Iblis (talk) 17:40, 27 April 2011 (UTC)

What makes you think it isn't just reflecting some combination of the ambient light reaching it from the Earth/Moon/Sun. It has giant solar panels and a shiny metal skin. I think it'd be a pretty decent reflector, and wouldn't need a porch light to be visible at night with some binoculars. --Jayron32 18:09, 27 April 2011 (UTC)

I doubt any external lights are normally on. They would serve no purpose except during an EVA, robotic operations, or docking/undocking with a visiting vehicle. You're probably seeing reflected earthshine. anonymous6494 18:25, 27 April 2011 (UTC)

Also, solar panels provide a limited amount of power. And every extra light fixture implies extra wiring, extra fixtures, etc, each one of them having a small chance of breaking and/or becoming a hazard and/or becoming a nuisance to do something else. Also, extra control circuits and extra items in your maintenance checklist. --Enric Naval (talk) 13:51, 28 April 2011 (UTC)

It is usually visible for a considerable time after the sun has set at the ground observer's location. Just because it's dark where you are does not mean the ISS is not in sunlight when you see it. Roger (talk) 18:29, 27 April 2011 (UTC)

I know, but if the ISS is not in the Earth's shadow it is magnitude -3.7 or so, easly visible to the naked eye (as bright as Venus). E.g. a few days ago, I could see it entering the Earth's shadow already above the Western horizon, and then it became invisible to the naked eye (brightness dropping rapidly from -3.7 to about +8). In binoculars it is then still visible. Then, when it rises toward the Zenith it actually brightens a bit to magnitude +7 or so and then, when it moves toward the East and starts to set, it becomes less bright. Count Iblis (talk) 18:50, 27 April 2011 (UTC)

(I'm going to assume that you meant -7 in the post above). The apparent brightness of the ISS viewed with the naked eye or through binoculars will depend on a number of factors. Less atmospheric haze, skyglow, or residual twilight on a given evening and time will make the station appear proportionately brighter because it will be seen against a darker background sky. Less haze and good seeing will also scatter less of the station's light on its way to you, meaning that it will be genuinely brighter as viewed, even if the amount of light it reflects is unchanged. Of course, it's not a good idea to assume that the amount of reflected light is unchanged—in fact it will vary quite a bit. The amount of light reflected will depend quite heavily on the relative position and orientation of station, Sun, and Earth-based observer. The moderately-experienced stargazer will be familiar with the swift (and often periodic) variations in apparent brightness associated with inactive satellites and other tumbling space debris that rapidly change their orientation relative to the Sun and Earth. While the ISS isn't tumbling, it's apparent orientation relative to the observer changes as it arcs across the sky. Usually this effect is subtle, but if one is in the right place at the right time one can get very bright specular reflections off the broad, flat solar panels. These so-called satellite flares are most often associated with the Iridium communication satellites, but observers have also recorded ISS flares—this short article has some incredible photographs. TenOfAllTrades(talk) 14:12, 28 April 2011 (UTC)

diminished brightness when closer to the horizon could be caused by the greater distance that the reflected light has to pass through the air to reach you.190.148.133.64 (talk) 21:28, 27 April 2011 (UTC)

There is a reason why distant objects appear brighter: Viewed from the moon it self the moon dust is quite dark, but from the earth the moon looks so bright it shines, I think that's probably part of the effect you're noticing. have a look at the pics on our ISS article, and if you're still not convinced, do a google image search for telescope iss photo, there are no obvious external lights to be seen. Vespine (talk) 23:27, 27 April 2011 (UTC)

Virtualy all the light you see reflected from the ISS is from the sun. This can be demonstrated by the fact that the brightness (and thus visibility) of the passes over a particular spot on the earth's surface are related to the passage of the station through the still present sunlight high above the observer, although the ground is in darkness. The station is never visible from the ground by naked eye more than about three hours after sunset because it passes throught the earth's full shadow when observed by a ground observer more than (say) three hours after sunset. The same principle applies before dawn. The station is visible from earth during evenings or pre-dawn periods even when there is no visible moon. I get my info from here Richard Avery (talk) 07:58, 28 April 2011 (UTC)

I think this thread is going off the rails a bit, perhaps I was not so clear in my postings here :) I'm talking about the ISS being in the complete shadow of the Earth, and then it is "invisible", but actually not quite invisible, you can still see it in binoculars. It seems consistently magnitude +8 to me when it is 45° above the horizon (and obviously a bit brighter when it is higher in the sky, but I have fewer observations of such cases and because it is then moving fast, it more difficult to estimate brightness). If you attribute that to a lightsource on board the ISS, you can compute that you need that lightsource to be about 30 Watt. You can easily imagine that 30 Watt can escape through the windows, or you could postulate that there is an outboard light that is always burning.

Now, Jayron32 says that it could be due to reflection of ambient light from the Moon, the Earth etc. But we can discount the Moon, because you can see the ISS in the shadow just as well during New Moon. Also, if the ISS is in the Earth's shadow, you won't have reflected sunlight from the Earth shining on the ISS. Then what remains are city lights. Now, where I live, there is a fair degree of light pollution, so you could imagine that this is possible.

To make the ISS appear to be magnitude +8, you need a total of 15 Watts reflecting off it (half of the 30 Watt because that 30 Watts was assumed to radiate isotropically). But to get 15 Watts of city-lights reflecting off the ISS, you need quite a bit more than of 10 GigaWatt of lights on the ground near a radius of a few hundred kilometers of where I am (I get 14 Gigagawatts when I compute flux by taking the reflecting area of the ISS its width times its length, which is obviously a big overestimate, and then assuming that most light sources are where the ISS apears 45° above the horizon, which is also not realistic). If I assume that most city lights have a luminous efficacy of 60 lumens/Watt instead of the 15 lumens/watt I've been assuming all along, you still are left with at least about 3 GigaWatts of street lighting which still doesn't sound realistic to me.

Instead, assuming that you simply have 30 Watts of lights (or perhaps just 10 Watts of higher luminous efficacy light source than an incandescent light bulb), escaping from the ISS, sounds more realistic. The only thing then is that the ISS seems to have the same brightness consistently over the last few years when I have seen it in the Earth's shadow. So, that's why I was wondering whether there is a (small) light source on the outside of the ISS that is always switched on. Count Iblis (talk) 15:12, 28 April 2011 (UTC)

You may simply be seeing cabin light escaping through the laboratory science window, a 510mm diameter circular glass window on the ISS' Destiny module. Subsequent to STS-131, the WORF is installed at that location, and when it is in use it can be configured to entirely block cabin light entering the WORF (and thus escaping to be seen by you). If that's the case, if you can find a mission schedule that shows when the WORF is and isn't swung over the window, if that correlates with changes in the apparent brightness of the unilluminated ISS, then the window is implicated. But you'd probably need a better calibrated system than binoculars and human eyes, and quite a lot of observations, to be sure. 87.115.52.162 (talk) 15:40, 28 April 2011 (UTC)

...although they probably keep the external shutter on that window closed most of the time, to avoid it getting scuffed up unnecessarily (by micrometeorites). 87.115.52.162 (talk) 15:47, 28 April 2011 (UTC)

How about heating from atmospheric drag? Probably very little of it, but maybe 15W worth. Googlemeister (talk) 13:02, 29 April 2011 (UTC)

It is not clear to me that the dissipated energy would be in the form of visible light. From the drop rate of about 1 km per ten days, I find that about 2100 Watt is being dissipitated due to friction. Count Iblis (talk) 16:09, 29 April 2011 (UTC)

Perhaps Googlemeister's suggestion does work. We only need to get a few Watt of light energy out of the 2100 Watt, the 30 Watt is the power of a lightbulb which only has a luminous efficacy of 15 lumens/Watt. If all the light energy were at 555 nm, then we would only need 0.7 Watt. So, the question is if the frictional processes the ISS is subject to, can lead to something of the order of, say, 0.2% of the energy being emitted in the form of visible light. Of course, the space station being heated by 2100 Watt won't make it radiate thermally into the visible spectrum. However, the collisions of the atoms with the space station can generate light non-thermally. In a collision of a Nitrogen atom with an object at a relative speed of 8 km/s, 4.6 eV of energy is available for causing atomic transitions, enough for the atom to emit light. Count Iblis (talk) 17:15, 29 April 2011 (UTC)

Do fluorescent lights have a preferred frequency when they flicker?

Resolved

As the title says, I'm wondering about the flicker in fluorescent lights. Not a flicker as they power up or down, but a sustained flicker that indicates something is not functioning properly. I observed this today, and while the pulses were not of even intensity (very bright pulses ~1/sec), I began to suspect the underlying frequency (almost too fast to notice) may be related to the 60 Hz of AC power. Is there any merit to this idea? Does the frequency of AC current have any effect on the frequency of flicker in the light? Thanks, SemanticMantis (talk) 21:47, 27 April 2011 (UTC)

See Fluorescent_light#Flicker_problems. Wnt (talk) 21:57, 27 April 2011 (UTC)

Oops, I should have checked there more thoroughly. Thanks! SemanticMantis (talk) 23:29, 27 April 2011 (UTC)

April 28

dna

Does DNA have physical potential energy in addition to chemical as it is coiled like a spring, similar to a rubber band that is twisted to form coils on coils? Is there tension within the structure of the DNA? —Preceding unsigned comment added by 98.221.254.154 (talk) 00:15, 28 April 2011 (UTC)

I don't think there is a clear distinction between "physical" and "chemical" on the molecular scale, at that scale isn't it all Electromagnetism?. Vespine (talk) 00:22, 28 April 2011 (UTC)

I'm pretty sure DNA does have potential energy associated with its springiness, twistiness, Writhe etc. See e.g. the first few papers here [6]. They discuss how stress, strain, torsion, and topology can influence gene expression. As Vespine alludes above, these forces are the result of chemical/electromagnetic interactions, but they can produce effects similar to what you see at the macroscopic scale. SemanticMantis (talk) 00:39, 28 April 2011 (UTC)

Generally this is termed as DNA supercoiling. But the energy involved is managed very actively - histones wrap the DNA around themselves, topoisomerases release tension, helicases unwrap the DNA so DNA polymerases can copy it, etc. Also see PCNA, a neat little object. There are bits of data (such as the physical binding of DNA polymerases on the leading strand and lagging strand) that make it pretty clear that the DNA in the cell really is handled more like the tape going through a tape recorder than as some immobile passive object as is sometimes implied by drawings you might see. Wnt (talk) 00:57, 28 April 2011 (UTC)

So is part of the DNAs mass this tensile energy? —Preceding unsigned comment added by 98.221.254.154 (talk) 01:55, 28 April 2011 (UTC)

Wow. Must be, but I don't even know how you formalize this. A strained supercoiled DNA must have higher-energy lowest-energy states for torsional vibrations of some sort, I suppose. You'd never be able to measure the difference in mass, I don't think - it would be something on the order of terahertz, I think. I hope there's a hard core biophysicist hero to chime in here. =) Wnt (talk) 02:11, 28 April 2011 (UTC)

Or just a softcore biophysicist that knows more than you. —Preceding unsigned comment added by 165.212.189.187 (talk) 14:56, 28 April 2011 (UTC) You might not be able to measure one strand but extrapolate that to a whole human body. —Preceding unsigned comment added by 98.221.254.154 (talk) 02:30, 28 April 2011 (UTC)

steel I-beam (H beam / double T beam) color?

In classic American cartoons I-beams are always reddish orange. It occurred to me recently that this is not the default color for steel. I decided I-beams were either previously this color for some reason unknown to me, or the cartoon illustrators used that color instead of black/dull gray because it looked better on the screen. Does anyone know the real reasons? The Masked Booby (talk) 01:26, 28 April 2011 (UTC)

Oxidation98.221.254.154 (talk) 01:52, 28 April 2011 (UTC)

Red lead paint for protection against oxidation.190.148.135.154 (talk) 02:08, 28 April 2011 (UTC)

Iron(III)oxide based primer paint. It's definitely not lead based paint unless the beams are older than your grandfather! Roger (talk) 14:36, 28 April 2011 (UTC)

Red lead was used into the 1960s - it's an issue in renovation, where the lead has to be removed if you want to cut or weld to existing beams. Red oxide was substituted from the 1970s and is similar in color. Nowadays most steel is primed with a dull grayish primer. Steel that will receive fireproofing is entirely unprimed to promote adhesion, so it ends up pretty rusty before the fireproofing is applied. Acroterion (talk) 03:34, 29 April 2011 (UTC)

By the way, they're generally called wide-flange beams nowadays in North America, or W-sections. I-beams (the old S-sections) are rarely used anymore as they're structurally inefficient and have comparatively narrow flanges. When employed as columns or pilings they're called H-columns or H-pilings. Acroterion (talk) 12:55, 29 April 2011 (UTC)

Is dishwashing liquid safe on plastic water bottles?

Specifically, mine are from Nalgene Outdoors, #2's, and I'd consider buying #4's. Does dishwashing liquid cause leaching from those? Thanks. 66.108.223.179 (talk) 05:19, 28 April 2011 (UTC)

I don't see why they shouldn't cope with regular detergent, but read the instructions that came with the bottle and our article on Nalgene. Make sure you wash them out after your trip and that they're thoroughly dried before replacing the cap.--Shantavira|^{feed me} 15:10, 28 April 2011 (UTC)

Yeah. I've only bought their LDPE bottles so far. Their shipping and constant availability of coupon codes are very affordable. 66.108.223.179 (talk) 15:42, 28 April 2011 (UTC)

Hydrogen Sulfide

It is found in our bodies. Is it released? If so, how?

Is it found in air? The article says that in concentrations of more than 100 parts per million will produce a foul smell. Does that mean that it may or is found in air, but because it is so dilute, we cannot smell it?Curb Chain (talk) 05:35, 28 April 2011 (UTC)

Micro-organisms produce it in the guts under anaerobic conditions. Flatulence smells sometimes like H₂S. doi:10.1016/j.jchromb.2009.05.026; [7] might be a good read. --Stone (talk) 07:23, 28 April 2011 (UTC)

The human nose is very sensitive to the presence of thiols, which is why ethanethiol is added to natural gas to give the otherwise odorless gas it's characteristic smell - so you can detect even small leaks. The article hydrogen sulfide says that 0.00047 ppm in air is the point where 50% of people can detect the odor (Hydrogen Sulfide#Toxicity). At 100 ppm eye damage can occur, and the olfactory nerve is paralyzed. (So, actually, at concentrations above 100 ppm, you *no longer* will smell anything.) When you're talking about "found in our bodies" you might be talking about the statement "The human body produces small amounts of H2S and uses it as a signaling molecule", rather than just gut bacterial production. The section Hydrogen Sulfide#Function in the body notes that "The gas is produced from cysteine by the enzymes cystathionine beta-synthase and cystathionine gamma-lyase." I can't find the figures at the moment, but the concentrations which are active in signaling are very low; lower than the nasal detection limit, if I recall correctly. -- 174.31.219.218 (talk) 16:11, 28 April 2011 (UTC)

large bowel

What would be the weight of an empty adult human large bowel (colon)? —Preceding unsigned comment added by 92.25.233.241 (talk) —Preceding unsigned comment added by 92.29.195.245 (talk) 00:40, 29 April 2011 (UTC)

About 4 pounds. -- kainaw™ 01:29, 29 April 2011 (UTC)

Thank you. Thats all i wanted to know. Sorry if it was a wrong question to ask here.--89.243.136.132 (talk) 07:12, 29 April 2011 (UTC)

What are the most dangerous jobs with positions available?

If anyone or myself decides that there's no more hope for their lives and that it's no longer worth living, perhaps it should end only by serving others. The military would detect suicidal tendencies long before the soldier hits the battlefield, so what civilian occupations could one hope to die on the job from trying to do exactly what the job entails? --129.130.99.8 (talk) 10:59, 28 April 2011 (UTC)

Found an article that lists fishing as having the highest fatality rate: http://www.careerbuilder.com/Article/CB-777-Career-Growth-Change-Worlds-Most-Dangerous-Jobs/ - Also mentions, amongst others, roofing and logging. Darigan (talk) 11:07, 28 April 2011 (UTC)

"Farming is one of the most dangerous occupations in the United States. More than 700 lives were lost in farm-related activities last year. Another 150,000 agricultural workers suffered disabling injuries from work- related accidents," per this article. --Halcatalyst (talk) 13:24, 28 April 2011 (UTC)

President of the US seems pretty dangerous. 8 out of 44 US presidents have died in office (about 18,000 deaths per 100,000), and any US citizen over the age of 35 can try for that job in 1.5 years (though it is not an easy job to get by any metric). A job with a roughly 100% fatality rate is Pope, but it is hard to predict in advance when that job will have an opening. Googlemeister (talk) 13:40, 28 April 2011 (UTC)

Dying while holding a job is not the same as dying because of a job. An accountant can die of cancer, and it doesn't mean that accountancy is what killed him. The cancer did. Contrawise, when a lumberjack dies because a tree lands on his head while working, it makes much more sense to say that he died of lumberjacking. As far as presidency goes, there have only been 4 assassinated presidents, rather than Presidents who died from health effects unrelated to being President. That's still a mortality rate of 9%, which is pretty high for any profession, however given that there have only been 44 presidents, that number has a fairly high margin of error. --Jayron32 14:06, 28 April 2011 (UTC)

Point taken. In any case, it is a very bad idea to take a dangerous job in the hopes that it will kill you because you would most likely putting others at risk. If you are a fisherman and go overboard, then someone might go into the water after you in an effort to rescue you and die because of it. As an additional question though, what if the stress of the job caused the accountant to have high blood pressure which was a contributing factor to a fatal heart attack? Would he count in the metric then? Googlemeister (talk) 14:40, 28 April 2011 (UTC)

An epidemiologist would call that the morbidity rate, not the mortality rate, to help keep the statistics straight. Nimur (talk) 17:09, 28 April 2011 (UTC)

Every fisherman knows not to go in after a man overboard, unless they want to die too! —Preceding unsigned comment added by 165.212.189.187 (talk) 14:54, 28 April 2011 (UTC)

Ok fine, so maybe you make the Coast Guard diver go in after you. Googlemeister (talk) 13:00, 29 April 2011 (UTC)

If you are really serious about the " by serving others " part, there are numerous humanitarian aid organisations crying out for dedicated volunteers around the world. The Afrcan states. Sth. America, asia and many of those locations are quite dangerous. You might find something worthy of your last days, or heaven forbid, something worth living for.190.56.107.254 (talk) 18:08, 28 April 2011 (UTC)

Really? I thought for example the Peace Corps only takes a small fraction of applicants. Look up the details, and the "way you can help" always boils down to money. Capital is rare and precious, but humans are an unwanted waste product in any country. Wnt (talk) 19:12, 28 April 2011 (UTC)

The British charity Voluntary Service Overseas is only looking for "qualified professionals with at least two years’ post-qualification experience." Alansplodge (talk) 19:33, 28 April 2011 (UTC)

Astronaut or cosmonaut. I haven't done the numbers, but the fatalities rate - including the experimental phase - must be quite high. There might be experimental positions in teh future that benefit from someone willing to die. It is quite physically demanding, though, and as we know you can't just walk in. Depends what you mean by "positions available". Grandiose (me, talk, contribs) 18:19, 28 April 2011 (UTC)

Related is the one-way trip to Mars which, proponents say, is not a suicide mission but a colonization; there have been several hundred volunteers so far. Comet Tuttle (talk) 20:25, 28 April 2011 (UTC)

Or maybe you could do a tour of the blood donation centers (assuming your blood is usable).190.56.107.254 (talk) 20:37, 28 April 2011 (UTC)

Brain to Body Mass Ratio

Wikipedia currently contains an article on this subject that lists a small number of species. Where can I find, or can you provide, a more complete list, from the smallest animal for which data exists to the largest?Markfriedman28 (talk) 18:48, 28 April 2011 (UTC)

This chart gives a more complete picture of the data, at least for vertebrates. I've seen more extensive tables in books, but not on the web. Note that because the brain increases in size at a lower rate than the body as a whole, the brain-to-body-size ratio is widely considered not to be very meaningful. The vertebrate with the largest value is the hummingbird; the one with the smallest value is the blue whale. Most scientists consider a parameter called the encephalization quotient to be the most meaningful measure of the relation between brain and body size. Looie496 (talk) 21:42, 28 April 2011 (UTC)

Unidentified Flower (or maybe Fungi?)

Hi folks. I've been going through my old photos trying to find images suitable for WP articles. I came across the below photo, but was not able to identify the plant. This bloom appeared in September in the Robson Valley of British Columbia. It was growing in the shade of a black Spruce. Would appreciate any help in trying to identify this little guy. The Interior (Talk) 21:06, 28 April 2011 (UTC)

What am I?

Wow, cool specimen! I can't help much, but I'm pretty sure I see pistils and stamens in the flower, which rules out fungus. The only thing I can think of vaguely similar is Monotropa_uniflora; maybe that will help get us started. SemanticMantis (talk) 22:59, 28 April 2011 (UTC)

Haha! The Corpse Plant! I think you might have nailed it SM. As the article says, it grows in deep shade: this one was almost right under a mature spruce. You're right about it being a flower, but it does have close relationship with fungi. Cool, thanks much. Unfortunately for me (but fortunate for WP) the article already has a lot of decent images. At least I can categorize the image at Commons now. The Interior (Talk) 00:12, 29 April 2011 (UTC)

I'd say your image would be a welcome addition to the article. It shows a slightly different growth habit and color than the current pics, and it's important to understand/see this variation of forms in plant ID. I'd also like to hear at least one other voice weigh in on the ID :) SemanticMantis (talk) 00:30, 29 April 2011 (UTC)

I'm always immensely impressed by the ability of wikipedians and botanists/biologists to recognize such a broad range of species, especially by pic alone. Perhaps it's the power of "the crowd", but it's still impressive! —Preceding unsigned comment added by Gogobera (talk • contribs) 04:51, 29 April 2011 (UTC)

Drug that removes the ability to resist

A while ago I read about a drug that "removes one's ability to resist". Someone affected by the drug will obey most commands. It's powder form, begins with C and is common in South America. I can't remember what it's called, does anybody know?--92.251.167.28 (talk) 21:47, 28 April 2011 (UTC)

Scopolamine? 76.27.175.80 (talk) 23:17, 28 April 2011 (UTC)

You're not thinking of cantharidin, are you? Extracted from the Spanish fly, it is a poison with an infamous past - for example, it was a poison of choice for the Marquis de Sade. Aside from being a false aphrodisiac, it doesn't fit your description because the fly is not indigenous to the Americas. -- Scray (talk) 02:22, 29 April 2011 (UTC)

Not a "C", but tetrodotoxin from a puffer fish is supposedly used to create a "zombie", although I believe that drug has more to do with the pseudo-coma than with the alleged lack of willpower. I'm not sure what drugs or combo is used for that effect, or if it's just the power of suggestion that does it. It's used in Haiti, which is rather close to South America, at least. StuRat (talk) 04:39, 29 April 2011 (UTC)

Ahh - StuRat's answer put me onto what you're likely thinking of - curare! It has no effect on cognition, so people won't become compliant with commands; however, they will become pliant! They'll also probably stop breathing, so it's not something to be trifled with. -- Scray (talk) 04:50, 29 April 2011 (UTC)

What a relief! I was really afraid you would be looking for Catholicism. Oh, excuse me, couldn't be it, it's not a powder. ;-) 93.132.171.155 (talk) 17:13, 29 April 2011 (UTC)

But is in an opiate, at least according to Karl Marx. StuRat (talk) 21:38, 29 April 2011 (UTC)

Does Truth drug help? Mitch Ames (talk) 14:02, 29 April 2011 (UTC)

Sodium Pentothal is the one most movies mention. However, it doesn't start with C and I don't believe it is particularly common in South America. Astronaut (talk) 15:29, 29 April 2011 (UTC)

See date rape drug (although there are many other types of drugs that reduce the ability to resist in one way or another). Looie496 (talk) 15:50, 29 April 2011 (UTC)

April 29

nervous system

carries impulses to inboluntary muscles?

See nervous system. -- kainaw™ 01:26, 29 April 2011 (UTC)

...and involuntary muscle. StuRat (talk) 04:27, 29 April 2011 (UTC)

Autonomic nervous system is probably the article that is most directly relevant; also enteric nervous system. Looie496 (talk) 15:24, 29 April 2011 (UTC)

SF "sensors" and today's technology

I've always enjoyed the deliberately vague "sensors" of Star Trek, which seem able to pick-up just about any sort of information the crew needs (planet population, messages, mineralogy, etc.) UNLESS it's an emergency or convenient to the plot for them to stop functioning. I was wondering this morning about mankind's current "sensor" ability. Assuming a ship in Earth orbit approximately as far away as that of the moon, packed with the best "sensor" technology available to our species, what details of Earth would we be able to measure? What if we were in solar orbit out near Jupiter and trying to observe the Earth? The Masked Booby (talk) 01:35, 29 April 2011 (UTC)

I'd look into multispectral imaging and terahertz - especially tunable terahertz masers. The potential of the latter is as yet unknown but could be incredibly creepy, powerful, and prone to abuse. Wnt (talk) 01:48, 29 April 2011 (UTC)

As a basic physics-imposed limit, start with angular resolution. Roughly speaking, the smallest features that can be resolved will be separated by a distance (on the order) of the wavelength used to probe, multiplied by the distance to the object, divided by the width of the sensor aperture. For example, a one-meter optical telescope working at 500 nm wavelength (blue-green) and 400,000 km from Earth (about the distance to the Moon) will be able to resolve features down to approximately 200 meters—that's good for counting stadiums, not the people in them. (Incidentally, this is one of the reasons why we can't point the Hubble telescope at the Moon and look at the Apollo landing sites; we didn't leave anything large enough behind.) If the ship is a full kilometer across and combines information from multiple sensors across the hull, then the resolution improves, down to a theoretical 20 cm. You can count heads, but not recognize faces. On the other hand, if you move to a longer, more penetrating wavelengths (say, terahertz radiation, per Wnt's comment above) then you're working at wavelengths of 0.1 to 1 millimeter. Your resolution for a ship-width sensor array at the distance of the Moon is something like 400 kilometers. (Ouch.) Note that all those numbers improve by a factor of 10 or so if you're in geosynchronous orbit instead of the Moon's distance—and they all get much worse if you move out to, say, Jupiter's orbit. TenOfAllTrades(talk) 03:14, 29 April 2011 (UTC)

Of course, if you don't need instantaneous measurements, you can integrate your sensor readings over a long period of time to winnow down the minimum resolvable feature. Superresolution explains how to beat the angular resolution limit - but it's not magic, it's just interpolation. If you could take tens of thousands of "photographs," and have a little luck with dithering, your angular resolution limit might improve by a factor of 10x. Of course, the longer you spend imaging a target, the more that the target motion is going to cause motion blur. (This is sort of like how a photographer can adjust the f-stop and shutter speed - you can't win both! As you approach the physical limitations of your equipment, you either get blur because of depth-of-field, or blur because of subject motion). Nonetheless, you can superresolve any signal, whether it's optical, radio, or "whatever." I will also point out the oft-forgotten effect of cloud-cover. Just because "Google Maps satellite view" shows you the best commercially-available photographs aggregated over the entire world doesn't mean that any satellite can get that great of a view at any time. (Besides, much of the Google data-set is actually aerial, not satellite, imagery). Point is, if your sky is overcast, your space-sensor can't see the ground. If your sky is "a little hazy," your space sensor can't see the ground. And even if it's a perfectly sunny day with not a cloud in sight... if your sky has air in it, atmospheric distortion will muck up the "perfect" theoretical resolution of any sensor. Nimur (talk) 03:34, 29 April 2011 (UTC)

I never assumed those sensors actually counted individual people. For example to get an idea of the population of a planet, you'd just have to measure things like carbon dioxide levels, technology (nuclear etc), methane from farms, output from power stations, number of large cities, etc, gather up enough of these kinds of "rough" measurements and I bet you could extrapolate a pretty good guess without having to actually count heads. I just imagined all the more esoteric figures from those sensors were extrapolated this way rather then actually measured directly. Sort of like how we find extra solar planets today, no one has actually "seen one", we've only detected them indirectly. Vespine (talk) 04:48, 29 April 2011 (UTC)

I think most of us are picturing a craft in low Earth orbit - maybe around 400 km from the planet. (Perhaps the original Star Trek artwork looks more like 4000 km) Many of the old sci-fi stories would talk about the ship deploying one or more "sensor probes" - though it may be a stretch to assume they had interferometry in mind! Still, it is not necessary for the ship to literally be 1 km (or larger) in size for it to cast a web of sensors. I don't think it's unreasonable to say, by your calculation, 1 mm x (400 km/400m) gets you a 1-meter resolution from low orbit with a 400m boom, tethered outrigger, or probe. Of course, it is also necessary to detect the signal, mandating that the 100W emitted by the human body, spread over 4 pi (400 km)(400 km) = 2 x 10^12 m^2, is detectable. Now I see SQUIDs can detect 5 attoteslas, and I think there's some relationship with RF detection^[8] but I couldn't say how to relate that to this kind of measurement. Wnt (talk) 07:27, 29 April 2011 (UTC)

SHM

when x=0 , t=0 , v= -ve then phase angle is equal to _________? —Preceding unsigned comment added by Tashsidhu007 (talk • contribs) 04:37, 29 April 2011 (UTC)

I hope you realize how little sense this makes. Your subject, SHM, is entirely ambiguous, and the initial condition you've given is meaningless without context. For your next homework assignment, please be more clear, and, also, don't ask here. We don't do homework. — gogobera (talk) 04:46, 29 April 2011 (UTC)

Comment - if you've been indoctrinated with a conventional physics education, you recognize SHM as simple harmonic motion and realize that the question actually provides all the needed information to solve in conventional notation. So, to be fair, there was no ambiguity, just an assumption of common notation. But, we still won't do your homework! Nimur (talk) 14:32, 29 April 2011 (UTC)

I assume he means simple harmonic motion of a spring at its average length which is getting smaller. But all the definitions are arbitrary. Assuming the x = the sin of some hypothetical angle then the angle is 180 degrees (because x is zero and decreasing) ... but it's truly arbitrary without proper definitions. Wnt (talk) 07:32, 29 April 2011 (UTC)

Blowing up a tornado

We've had a question Wikipedia:Reference desk/Archives/Science/2007 October 10#What would a nuke do to a Tornado? Now that might work, but it has a few problems. But it still leaves open the question: what would it take to make a successful military attack on a tornado? Now at a forum I found a nice demonstration that a simple house fire won't bother the tornado.^[9] That shouldn't be a surprise, first because the fire is relatively gradual and weak, second because a tornado fundamentally is still a phenomenon with rising low pressure air in the middle, so fire shouldn't bother that. Now I know that a tornado is a fearsome phenomenon with a lot of energy in it --- still, it is by nature a transient phenomenon, which makes me think that it might be tampered with by much lower orders of magnitude of energy. One ref. I found claimed 3 trillion joules for a F3 tornado^[10] - about 3/4 of a kiloton. So if there is a way to get substantial mechanical leverage, it might just be conceivable that the equivalent of few dozen tons of flammable material (TNT isn't that special) could actually be transformative.

I'd welcome answers at various orders of magnitude, but to provide a reference standard: suppose a terrorist is driving a standard commercial tanker truck strapped with explosives on the main road out of his hometown, only to find a tornado coming the other way. He waits until it is about to strike the truck, then sets it off. Suppose the truck contains either (a) gasoline or (b) liquid nitrogen. Is there a chance that the sudden explosion and the net force upward or downward can break up the tornado or break it away from the ground, and tomorrow we'll be reading "Hero Terrorist Saves Town"? Wnt (talk) 07:06, 29 April 2011 (UTC)

I think the idea of using explosives is a bit silly, but a more practical method might be to place lots of man-made lakes around areas you want to protect. Passing tornadoes suck up the heavy water, and that dissipates a great deal of energy. After the tornado breaks up, the water falls as rain. Now, lakes just for tornado prevention might not go over very well, but they can also be recreational lakes, water supply reservoirs, or potentially they can be used as a way to store energy generated by solar and wind power (by raising the water level). Another option is to plant many trees, as smashing down trees also dissipates energy. However, this can also add lethal debris to the tornado, and leaves a mess behind after. StuRat (talk) 08:38, 29 April 2011 (UTC)

(ec) Perhaps it could be easier to find out how to guide the way of a tornado and/or fix it to one location where it can't do much damage. Ideally there would be a specialized wind turbine (on the ground, with vertical rotation axis) in that place to take advantage of the energy. So what makes a tornado move around? 93.132.171.155 (talk) 08:48, 29 April 2011 (UTC)

Clearly tornadoes are powered by the storms above, and must move with them; however, there is no guarantee that the storm's energy needs to reach the ground. Originally I was going to suggest a third truck filled with sand, or perhaps (liquid) polyurethane foam insulation - but I'm not sure that the "tornadic" variety of waterspouts are really reduced that much in magnitude. Particles suspended in them must experience friction, and perhaps cause some downdraft, but they're generally far out to the edge (as shown in the photos in the article) rather than in the center. I'm not sure if pushing downward near the edge would really hurt the tornado - might even help it stay stuck to the ground? Wnt (talk) 20:58, 29 April 2011 (UTC)

There's no evidence to suggest sporadic bodies of water will do anything to disintegrate or weaken a tornado in the long-term. Once it reaches dry land, it has the immediate potential to stabilize and intensify to its previous velocity. Planting trees to try to stop a tornado would be equally ineffective. Trees in tornado-prone areas are maybe 100 feet tall, whereas mesocyclonic supercells may extend 50,000 feet into the atmosphere, and even a moderate tornado (EF2–EF3) will have no trouble snapping the majority of trees in its direct path. There's really nothing we can build physically to weaken tornadoes. Juliancolton (talk) 15:03, 30 April 2011 (UTC)

Reference desk (science) quasi-semiprotected?

I know this should go the the help desk but I can't edit the help desk page neither, this page here at least has an "ask a question" button. As discussed earlier, for some users this page (and the help desk page) are effectively semi-protected. I can't see those edit buttons per section and on the top of the page there is no "Edit" tab but a "View source" instead. This goes away as soon as I manage an edit via the only possibility left, the "ask a question" button. The help desk page doesn't have one, so no way to ask there. The condition reappears as soon as I do "clear private data" in my browser, for example after doing home banking. So what shall I do? An empty question is not possible. Shall I make up a question each time, or shall I refrain from giving answers? 93.132.171.155 (talk) 11:02, 29 April 2011 (UTC)

Click view source anyway and it should take you to a normal edit page. You can also purging the server cache which should make the section edit links come back. There is something wrong with Wikipedia server cache which is causing these problems, lots of people are getting them. 82.43.89.63 (talk) 11:33, 29 April 2011 (UTC)

Breathing gas

Astronauts and SCUBA divers carry their oxygen in heavy bulky pressurized tanks. Can breathable oxygen be made instead by a reaction between chemicals that can be easily carried at room temperature and pressure? Cuddlyable3 (talk) 12:08, 29 April 2011 (UTC)

In emergencies, astronauts can use oxygen candles, which are pretty much as you describe. --Tango (talk) 12:24, 29 April 2011 (UTC)

The closest to what you describe would be an oxygen rebreather which uses a smaller tank than regular scuba and recirculates the oxygen through a chemical 'scrubber' to remove CO2. But this is about as bulky as regular scuba tanks. to produce it in a usable form would require chemical production control, collection, quality control, filtration, compression and usage regulation. Not feasable in a portable unit.190.56.105.199 (talk) 15:23, 29 April 2011 (UTC)

Note that using another chemical which contains oxygen would increase the weight, as well, since you have the non-oxygen component of those chemicals to carry, in addition to the oxygen. Also, what happens to the remainder ? If it still must be carried after the oxygen is used up, this increases the weight at that point, versus a normal tank.

Another approach is to lower the temperature to where oxygen becomes a liquid at normal pressure. This eliminates the need for heavy tanks, but does require that you have cold temperatures available and a way to heat it back up when using it. This might work well in a space ship, as the side of the ship away from the Sun might get cold enough for liquid storage, while the side pointed toward the Sun could be used to warm it back up. StuRat (talk) 20:18, 29 April 2011 (UTC)

Room pressure is no use for a scuba diver - what's needed is ambient pressure which increases by approximately one atmosphere for every ten metres of depth. So either your oxygen candle would need to be to cleverly regulated to automatically produce the correct amount as a function of ambient pressure, or produce at least as much as could be required (say seven times and somehow vent the excess. 78.245.228.100 (talk) 21:13, 29 April 2011 (UTC)

Hmmm, how about mainlining oxygen at high ambient pressure? I'd think a small syringe of oxygen at such pressure would be enough to last a person for some time. Or could you dissolve it in perfluorocarbon? Of course, it would be best to break up the bubbles a bit to reduce the risk of abrupt death... ;) Wnt (talk) 20:28, 30 April 2011 (UTC)

If you go Scuba diving regularly, you will learn that you can do with a lot fewer breaths and still get adequate oxygen. But this is far from natural - it's one reason why experienced divers can stay under water 2 or 3 times longer than beginners with an equivalent bottle of air. Beginners will use nearly the same volume of gas than they would under normal pressure. --Stephan Schulz (talk) 20:37, 30 April 2011 (UTC)

I'm not sure why you'd want to dilute the O2 with anything exotic; good old Nitrogen is cheap and will do the trick nicely. To maintain a healthy 0.2 bars O2 partial pressure though, you'd need to compensate by increasing the partial pressure of the diluent, which will increase it's narcotic effect. As noted above, the system required to mix the appropriate amounts of oxygen and diluent (half of a rebreather ) is a bulky and expensive piece of equipment - a long way from the original emergency backup system suggested. 78.245.228.100 (talk) 21:02, 30 April 2011 (UTC)

biotechnology

what may be the questions asked biotech quiz —Preceding unsigned comment added by Ruma R Sambrekar (talk • contribs) 13:19, 29 April 2011 (UTC)

What biotech quiz? Plasmic Physics (talk) 13:58, 29 April 2011 (UTC)

This is not a crystal ball. Please see biotechnology.--Shantavira|^{feed me} 16:11, 29 April 2011 (UTC)

Yes, but this is a Magic 8-Ball. "Concentrate and ask again" B) Wnt (talk) 21:10, 29 April 2011 (UTC)

"It is decidedly so." StuRat (talk) 21:44, 29 April 2011 (UTC)

reverse osmosis

why do reverse osmosis membranes clog?After how long do we need to replace the membranes, if we use our machine on a daily basis on a 16hrs every day. —Preceding unsigned comment added by 41.215.125.38 (talk) 16:50, 29 April 2011 (UTC)

All filters will eventually become clogged, but without more detail it is impossible to say how often it will need replacing. See reverse osmosis and membrane. Replace the membrane when it no longer functions correctly.--Shantavira|^{feed me} 18:05, 29 April 2011 (UTC)

The stuff that is filtered out accumulates until it clogs the filter. There is a way to automatically clean out a reverse osmosis filter, by reversing the pressure difference and thus the water flow direction. However, you don't want to drain that "bad water" back into the fresh water pipe, so it needs to switch over to drain into the sewer line. This requires additional plumbing and complexity and control electronics, so increases the price substantially. Note that this can extend the life of the filter, but not indefinitely, as deposits will still accumulate which can't be simply rinsed out. In the case of a desalinization reverse osmosis filter, the amount of salt which accumulates is so high that a different process must be used which drains out the salt brine continuously, rather than periodically. StuRat (talk) 20:04, 29 April 2011 (UTC)

Transit time

What is the average transit time for the average adult human for food to go from the mouth to the end of the ileum?--92.28.85.30 (talk) 20:01, 29 April 2011 (UTC)

Our article Human gastrointestinal tract#Transit time, it seems to suggest a total time of around 35-45 hours. ny156uk (talk) 20:07, 29 April 2011 (UTC)

Irish wildfires

I am wondering whats the average rate of wildfires and which one was the most intense and whats the most frequent cause of wildfires in Ireland. --109.76.53.162 (talk) 20:16, 29 April 2011 (UTC)

The ultimate cause, as everywhere else, is no doubt an accumulation of flammable undergrowth (which can be worsened by humans preventing and stopping small fires which naturally burn it off). The more recent cause is dry weather. The trigger, on the other hand, can be arson, campfires, lightning, etc. Are you asking about the triggers ? StuRat (talk) 20:36, 29 April 2011 (UTC)

This link ([11]) has stats on European wildfires. From a quick survey, I'd estimate that Ireland sees between 400 and 800 fires per year, and a similar total burned area in hectares, which would suggest individual fires are very small (at least by global standards), maybe 1-2 hectares on average. No idea about the largest on record. The Interior (Talk) 21:31, 29 April 2011 (UTC)

You're assuming they are all about the same size. That could be many tiny fires and a few huge ones. Of course, how big can a fire get on a medium sized island ? StuRat (talk) 21:42, 29 April 2011 (UTC)

Up here in Canada, we occasionally get fires in the north larger than European nations like Ireland. If they're far enough away from communities, we just let 'em burn. The Interior (Talk) 21:57, 29 April 2011 (UTC)

Well a few weeks ago there was a bad Gorse fire on one of the mountains it was close to houses and it seems to me my area wildfires are spawning more frequently. I mostly live in the north Cork area surrounded mainly by the Knockmealdowns and Galtee mountains. We are having an unusually dry and warm spring with very little rain. This started at February after the unusually freezing winter we had. So is it possible that Ireland is seeing an increase of Wildfires. Also I know that farmers around here are known to start wildfires to kill off weeds but with strong winds around they are turning dangerous. Our area also faced the same conditions last year. Also there has not been any lighting or thunderstorms near my area.--109.78.54.208 (talk) 11:43, 30 April 2011 (UTC)

It could be that the good weather has brought the idiots out, with their discarded cigarettes and barbeques. Happens a lot in the UK. --TammyMoet (talk) 15:56, 30 April 2011 (UTC)

Ventral Aorta

Our article on Nikolay Ivanovich Pirogov currently states: "He completed further studies at Dorpat (now Tartu), receiving a doctorate in 1832 on the ligation of the ventral aorta." I have two questions based on this. We don't have an article on "ventral aorta", and a quick Google search reveals that, although fish have one (and a dorsal aorta into the bargain), mammals only have one aorta, which is divided into various sections. Is "ventral aorta" in the Pirogov article a mistranslation or obsolete term, and, if so, what should it be? Secondly - what would be the point of ligating the aorta? There are quicker ways of killing the patient, and I can't see any other outcome from such a procedure. Tevildo (talk) 20:55, 29 April 2011 (UTC)

I didn't find anything but Wikipedia's own backwash and a Google nyah-nyah to an ad for a book [12] which may or may not use the term behind a paywall. Likely some others can be found, though who knows if they say anything more than this one line. The definitive test - tracking down an 1832 Russian thesis is probably a real pain - even the old paper archives in good libraries don't generally go back that far; I suppose there's a chance that his alma mater's library stocks a copy of the thesis, under special restrictions.

But if I had to take a guess, I'd guess that he was doing research in some animal with a ventral aorta. After all, even backward Tsarist Russia probably didn't encourage students testing that kind of thing on humans! Wnt (talk) 21:19, 29 April 2011 (UTC)

That sounds reasonable - doing experiments on fish for one's doctoral thesis is rather more likely than performing fatal operations on a non-existent artery of a human patient, after all. Is there any legitimate means of mentioning this in the article? Tevildo (talk) 11:11, 30 April 2011 (UTC)

I was going to suggest you ask the original contributor.^[13] But it appears that this was associated with a User:ALoan, an admin who seems to have retired shortly after criticizing the Wikipedia:Requests for arbitration/Badlydrawnjeff decision - a political event which elevated BLP over encyclopedism, and marked the moment at which Wikipedia shifted from exponential growth to steady decay. So I don't think that will be a likely option - actually, I'm not even sure where you'd try to ask. But he added at the same time a "reference" that the article was based on a translation of the de.wikipedia article, so maybe there is more information about it there. But I don't see anything about it in the current version. Wnt (talk) 21:43, 29 April 2011 (UTC)

My guess is that the descending aorta was intended. You would rarely ligate that in a human patient as far as I know (since it shuts off blood flow to the lower part of the body), but it is sometimes done in terminal experimental techniques, such as perfusing the brain with a fixative. Looie496 (talk) 22:00, 29 April 2011 (UTC)

DNA differences

A friend of mine heard that two people can have 5% difference in DNA. I thought that was bigger than the difference between humans and chimps. Is this correct? Bubba73 ^{You talkin' to me?} 21:56, 29 April 2011 (UTC)

The usual figure for the difference between two average people's DNA is around one tenth of one percent. Looie496 (talk) 22:01, 29 April 2011 (UTC)

Perhaps that 5% isn't of all the DNA. For example, there's lots of DNA that doesn't appear to do anything useful, it's just "junk DNA". So, if you don't include that, then the percentage difference between people would be higher, but probably still nowhere near 5%. Maybe if you only used that DNA which varies from humans to our nearest relatives (either extant or extinct), then the variation from one person to another might be closer to 5% of that. StuRat (talk) 22:19, 29 April 2011 (UTC)

I assume it would be different if you were comparing raw DNA versus comparing genes. Humans have 220 million base pairs in their DNA, but only 20,000 or so genes. --Mr.98 (talk) 22:56, 29 April 2011 (UTC)

Minor correction - the usual figure for the human genome is ~3 billion base pairs. --- Medical geneticist (talk) 11:16, 30 April 2011 (UTC)

You're right — I was quoting the length of a single chromosome without realizing it. --Mr.98 (talk) 13:40, 30 April 2011 (UTC)

I think my friend heard the 5% figure on NPR Science Friday today. Bubba73 ^{You talkin' to me?} 22:20, 29 April 2011 (UTC)

Chimpanzees have about "94 percent the same genes", looking at paralogues that aren't shared between the two (see the original reference from that article^[14]). There are a variety of different statistics that can be put forward, depending on which parts of the DNA you leave out and how you count a match (similarity vs. true orthology). I'd watch how the noncoding is counted especially when comparing comparisons. Wnt (talk) 22:22, 29 April 2011 (UTC)

If someone has access right now, [15] should give good measures of the overall difference in the most divergent known humans. Wnt (talk) 22:32, 29 April 2011 (UTC)

(Snaking their supplemental data, I see they use a mutation rate of 2e-8 per generation, generation time of 20 years, and assume Neanderthals diverged <1 million years ago. Which seems to put an upper limit of 0.2% on the neutral divergence at noncoding positions. However, their alignments have edges, for various technical reasons but also due to variations in what is included in even modern humans, so I haven't really proved anything as of yet. =( Wnt (talk) 22:45, 29 April 2011 (UTC)

5% is an order of magnitude too high. See human genetic variation. Current estimates are that the nucleotide diversity between humans is about 0.1% (1 difference per 1000 bases) -- the figure Louie gave -- and that copy number variation creates an additional 0.4% difference between individuals. Perhaps your friend heard "point 5 percent". --- Medical geneticist (talk) 23:07, 29 April 2011 (UTC)

Actually it was on NPR "Tech Nation" and I'm not sure if it was today. Bubba73 ^{You talkin' to me?} 03:50, 30 April 2011 (UTC)

Wait, wait. If the average human gene length is 3000 base pairs [16], and typical rate of nucleotide differences is 0.1% (1/1000), doesn't that imply that any two people are unlikely to share the same allele? It seems to suggest that on average we will have 3 point differences per gene. If that's true, then it would seem to suggest that if you compare any two people you will find that most of their alleles are different. That seems qualitatively very different that saying we are 99.9% the same. (Presumably there is some additional accounting for the rate of differences in exons rather than non-coding DNA, as well as the fact that some nucleotide replacements don't impact the expressed protein.) Dragons flight (talk) 04:36, 30 April 2011 (UTC)

You are assuming that the 1:1000 rate of variation represents changes that are unique to each individual. On the contrary, most (90%) of the nucleotide variation is accounted for by "single nucleotide polymorphisms" (SNPs) that are found in different proportions of the population (often defined as a "minor allele frequency" of > 5%). For example, at a certain position in the genome 70% of us have an "A" and 30% of us have a "T". Or 40% have an "A", 35% have a "G", and 25% have a "C". These common SNPs are generally organized in blocks called haplotypes such that people tend to share the same groups of SNPs across variably long stretches (i.e. not all possible combinations of SNPs are observed). This results in genes having defined "versions" (alleles) in the population. There are also polymorphisms that are present at lower frequency (0.1% - 5%) that we will be able to detect once tens of thousands of human genomes have been sequenced. It's basically going to look like a continuum from a few (~n x 10³) rare/unique differences, a handful (~n x 10⁴ - 10⁵) of low frequency variants, and a large amount (3-4 million) common variants per person. --- Medical geneticist (talk) 11:14, 30 April 2011 (UTC)

Yes, I know that differences will cluster into specific alleles. However, that doesn't really remove the issue. If 1/1000 nucleotides is going to be different between any two people, then one would have to expect that a large number of the genes will have different alleles in order to accomplish that. So, what fraction of my alleles are likely to be different than yours? Looking at a (relatively) simple system like ABO blood type, the most common allele (O) occurs in only about 50% of people (at either homologous chromosome). The effect is that if you choose two people at random, they are more likely to have at least one different blood type allele than they are to have both be the same. Less simple phenotypes, such as hair color, eye color, skin tone, height, etc., would also seem to suggest that if you pick two humans at random then they are likely to have many alleles that are different. Given a gene length of a few thousand base pairs, and a difference rate of 1/1000 base pair, it would generally suggest that on average most genes should be like this (assuming the differences are distributed roughly uniformly through the genome). In other words, that the typical gene would have enough major allele variations to ensure that in a comparison of any two random people that there are many, many different alleles expressed. Dragons flight (talk) 18:39, 30 April 2011 (UTC)

April 30

Sicily, the Gulf of Sidra and continental drift

I noticed that the Gulf of Sidra north of Libya where the fighting is going on looks like Sicily had been taken out of it. Is it possible that Sicily was once connected to this area?--X sprainpraxisL (talk) 00:14, 30 April 2011 (UTC)

You might want to read about the Apulian Plate. Geologists think that some crust that forms Italy and the surrounding region did break away from North Africa; but its a bit of a jump to conclude that Sicily "fell off" just based on coastline features alone. Nimur (talk) 01:04, 30 April 2011 (UTC)

I'm looking at paper sea floor maps because I can,t find enough info on the net. But on these paper maps there is a fault line that runs from the azores through the Gibralter streight and all the way through the Mediteranian and to the red sea. It passes along the North African coast between Africa and sicily. At that point it gets messy with a lot of break up spreading up through the Tyrrhenian sea on the Apulian plate. The Periadriatic seem is far north af that. This map does indicate the Apulian plate is moving northish away from Africa, and sicily is on the Apulian plate. So your idea seems at least plausible.190.148.136.203 (talk) 02:07, 30 April 2011 (UTC)

The tectonic history of the Mediterranean is pretty complex, but all the plate reconstructions that I've seen for the central mediterranean suggest that Sicily (at least the deeper parts and ignoring Etna) have remained pretty much in the same place with respect to Africa since the Late Triassic, about 230 million years ago, so any shape match is probably coincidence. Mikenorton (talk) 08:07, 30 April 2011 (UTC)

Look at New Zealand and Australia, they have complimentary coastlines, which suggests that they split off from each other. Geological records show that while this is true, far less than 10% of the current landmass was present at the time of the split. The remainder was generated after the split; the current complimentary shape has very little to do with the split and is purely conicidental. Plasmic Physics (talk) 08:13, 30 April 2011 (UTC)

Also if you're appealing to continental drift to match fragments of continental crust to a neighbouring continent, the intervening area (the Gulf of Sidra in this case) must be made of oceanic crust, which it isn't. Mikenorton (talk) 09:49, 30 April 2011 (UTC)

...and the modern Mediterranean Sea and its shorelines are a quite recent feature on geologic timescales - see Zanclean flood. Gandalf61 (talk) 10:11, 30 April 2011 (UTC)

Yes the refilling of the Mediteranian seems to have been quite recent but it's not clear how that would have anything to do with tectonic movements other than perhaps a little lubrication for subduction.190.56.125.8 (talk) 15:25, 30 April 2011 (UTC)

Gandalf61 is I think referring to the shape of the coastline, which will vary a lot with water depth. As to lubrication, the Messinian salt layer has strongly affected the shape of the Mediterranean Ridge accretionary complex as subduction has continued - because salt is so weak under geological deformation rates. Mikenorton (talk) 15:32, 30 April 2011 (UTC)

Superconductors

Does superconductors obey ohm's law? Because when R is zero I will be infinity as I=V/R and the magnetic field will also tends to infinity and the material comes to normal state. —Preceding unsigned comment added by Balajir333 (talk • contribs) 06:06, 30 April 2011 (UTC)

V is not the total voltage applied but the voltage loss at R. So if no voltage is lost at the superconductor, V=0, and if you write V=IR to avoid mathematical troubles for dividing 0 by 0, everything is fine again. The actual I is then determined by the non-superconducting parts of the circuit. 95.112.236.165 (talk) 08:07, 30 April 2011 (UTC)

One way to state Ohm's Law is that the current that flows through a material is linearly proportional to the applied voltage. The constant of proportionality is the electrical resistance. Superconductors do not behave this way, so it can be safely said that Ohm's Law does not apply to them. Instead, the current that flows through a superconductor has no relationship to the applied voltage; the current that flows is subject only to conservation of charge flux (Kirchoff's current law). In some superconductors, especially if analyzed at very small scales, this is not even a very good description, because the electrons can not be individually discerned; in the case of some superconductors, the electrons must be described as an ensemble wave function. Nimur (talk) 15:50, 30 April 2011 (UTC)

Kepler mission

is there perfect information about data collected with kepler mission ?--78.38.28.3 (talk) 08:37, 30 April 2011 (UTC)

Try the Kepler website. The most complete information should be under Science->For Scientists. There's also a data archive if you're interested. --Wrongfilter (talk) 09:34, 30 April 2011 (UTC)

Lead Cycle

Hello. Given:

1. Pb(NO₃)₂ + Na₂SO₄ → PbSO₄ + 2NaNO₃
2. PbSO₄ + 2KI → K₂SO₄ + PbI₂
3. PbI₂ + Na₂CO₃ → PbCO₃ + 2NaI

I wrote the net ionic equations. Iodide ions displace the sulfate ions in its lead(II) salt and carbonate ions displace the iodide ions. How does that suggest the ladder of solubility: PbCO₃ < PbI₂ < PbSO₄? Thanks in advance. --Mayfare (talk) 16:05, 30 April 2011 (UTC)

Because solubility is basically the relationship between the energy of attraction between a solute particle and water vs. a solute particle and another solute particle. To put it another way, consider these reactions (broadly speaking):

1. Pb²⁺ + H₂O --> Pb²⁺(H₂O)_n ΔH = X kJ
2. Pb²⁺ + SO₄^2- --> PbSO₄ ΔH = Y kJ

Reaction 1 is solvation and Reaction 2 is precipitation, and since both involve bond-formation events, both will be exothermic roughly speaking if Y is more negative than X (that is, reaction 2 is more exothermic than reaction 1), then the substance will be insoluble, because thermodynamically the precipitation reaction is more likely than the solvation reaction. If X is more negative than Y, the substance will be soluble Now, consider this third reaction:

• Pb²⁺ + I^1- --> PbI₂ ΔH = Z kJ

What did YOUR series of reactions say about the relationship between Z and Y; and by the commutative property, what does that say about the relationship between Z and X? (that is, how does Z-X compare to Y-X). What does THAT say about the solubility of PbI₂ versus PbSO₄? If you can answer those questions, you can answer your homework problem here. --Jayron32 19:24, 30 April 2011 (UTC)

Maximum possible temperature

I have calculated the root mean square speed equation by plugging in the following figures:

• vrms = 299,792,458
• Mm = 1.008 (the molar mass of monoatomic hydrogen)
• R = 8.3143 (the molar gas constant)
• T = unknown

Of course, the goal was to calculate the remaining unknown quantity, namely the temperature at which monoatomic hydrogen atoms would move at the speed of light. The result was: 3,661,133,160 K. At any temperature higher than this, monoatomic hydrogen would be travelling faster than light, which is impossible and thus means that monoatomic hydrogen cannot be heated further.

Heavier elements would be able to be heated up to higher temperatures, but they would still have an upper temperature limit since their atoms cannot travel at a speed higher than c. So now, my question is: why doesn't this appear in the article "Absolute hot"? Am I making a mistake in my calculations or my assumptions? Thanks.--78.126.167.239 (talk) 16:23, 30 April 2011 (UTC)

It's a neat trick, but its wrong. The RMSS equation is a classical equation, assuming the kinetic energy of a particle is $E_{k}={\frac {1}{2}}mv^{2}$. But if you use it at particle speeds close to the speed of light, you must take relativistic effects into account, and use the relativistic kinetic energy $E_{k}={\frac {mc^{2}}{\sqrt {1-(v/c)^{2}}}}-mc^{2}$. Since that goes towards infinity as $v$ goes towards $c$, you get any $T$ at some smaller $v$. --Stephan Schulz (talk) 16:50, 30 April 2011 (UTC)

Either that, or Einstein's relativity theory is wrong. Isn't this an instance of the logical fallacy which says "your theory must be wrong, because it doesn't work under my theory"?--78.126.167.239 (talk) 16:58, 30 April 2011 (UTC)

(ec) It would just be "my theory vs. your theory" if we were mere philosophers, but in actual fact, we are scientists, and we rely on experimental observations to verify the equation that Stephan Schulz posted. We don't have to resort to "guessing." For example, this collection of experiments validate that the lorentz-corrected energy equation correctly and accurately models the kinetic energy of a moving object. My favorite test is the high-atmospheric muon production, explained in our Muon article. Relativistic theory is valid; its equations predict natural phenomena correctly; and more than a century of scientific measurements have verified such equations to many decimal places. Nimur (talk) 17:15, 30 April 2011 (UTC)

Well, you use the speed of light limit from Einstein, so you should probably use all of that theory. You approach is not consistent with Newtonian physics (because in Newtonian physics 299,792,458 m/s is just another arbitrary speed) or in relativistic physics (because you use the wrong kinetic energy). Moreover, the fact that the relativistic mass is is better described by the relativistic than by the Newtonian formula is easily observed and has been verified over and over and over (and over) again. So, sorry, no bananas. Historically, "or Einstein's relativity theory is wrong" has usually been resolved in favor of the other explanation ;-)" --Stephan Schulz (talk) 17:11, 30 April 2011 (UTC)

Actually there is a limit in the sense that neutrino cooling hastens core collapse in the Type II supernova. The hotter the star "tries" to get, the faster it cools down by shedding neutrinos. The result is that the collapse accelerates rather than slowing down due to heat pressure. Hcobb (talk) 16:57, 30 April 2011 (UTC)

But that is just a limit for the temperature at the core of the hottest stars, not for temperatures in general. --Stephan Schulz (talk) 17:13, 30 April 2011 (UTC)

We can rephrase this in plain English without using any equations: to date, we have not observed any natural behavior which leads us to think that there is an upper bound to the kinetic energy of a particle. We can continue to add more energy to a particle, ad infinitum. The particle's speed continues to increase, but we never see any indication that the particle will ever reach the speed of light (even though it is eking its way towards that speed). We have observed this behavior experimentally in numerous particle accelerator experiments; in fact, we even see this behavior in ordinary (old-fashioned) television tubes. Because most definitions of temperature are essentially average measurements of particle energy, we can conclude that there is no upper bound to temperature, either. Nimur (talk) 17:25, 30 April 2011 (UTC)

Well, there at least aren't any limits to temperature according to special relativity. But getting above the Planck temperature probably doesn't work; see absolute hot. Red Act (talk) 17:59, 30 April 2011 (UTC)

I thought that according to our whole Supersymmetry/Higg's boson discussion, there is an absolute temperature at which electrons, protons, neutrons, W and Z particles all become massless particles moving at the speed of light. Wnt (talk) 20:32, 30 April 2011 (UTC)