Wikipedia:Reference desk/Archives/Science/2016 March 25

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March 25

Amplitude stabilisation of sinusoidal electronic oscillators

Im looking for refs concerning the theory of stabilisation of sinusoidal oscillators using non linear semiconductor components. Any offers?--178.111.96.35 (talk) 01:15, 25 March 2016 (UTC)

HP200A has several references. --Guy Macon (talk) 05:08, 25 March 2016 (UTC)

Fast Amplitude Stabilizing of an RC Oscillator Wein bridge oscillator with incandescent lamp stabilization LC Oscillator has stable amplitude High-Purity Sinewave Oscillators with Amplitude Stabilisation. AllBestFaith (talk) 10:58, 25 March 2016 (UTC)

How to block out female pin headers

I brought a JTAG programming cable but the the key-way pin of the header isn't properly "blocked out". The end in question is a 1.27mm pitch female header. What's the name for the part used to "block out" certain female header pins? Alternatively a link to Digikey for the right part would help too. Johnson&Johnson&Son (talk) 06:31, 25 March 2016 (UTC)

See Pin header#Polarizer key. AllBestFaith (talk) 11:06, 25 March 2016 (UTC)

Thanks. Is there any place that actually sells 1.27mm pitch polarizer keys? I tried Digikey and couldn't find any there and they pretty much have the biggest selection. Johnson&Johnson&Son (talk) 12:56, 25 March 2016 (UTC)

Sorry if this is way off: Here [1] is a rack of 24 pins, perhaps one of them would suit your needs. SemanticMantis (talk) 14:11, 25 March 2016 (UTC)

Here is a range of headers but for blocking one hole of a female header, consider gluing a male pin in place. AllBestFaith (talk) 14:13, 25 March 2016 (UTC)

The male pin would be conductive though unfortunately. I guess I'll use that as a last resort. It's weird though, both the male and female headers are so widely available, and yet a supposedly common accessory like the polarizer key is so hard to find.Johnson&Johnson&Son (talk) 14:31, 25 March 2016 (UTC)

Yeah - don't use anything conductive. If I don't have a proper blocking pin to hand, I generally put a squirt of glue in there with a hot-glue-gun. Don't squirt too much in there because it can ooze out and block other pins too - but a tiny amount does the job perfectly. SteveBaker (talk) 14:45, 25 March 2016 (UTC)

I see the value of being extra careful, but isn't the point that the block is just to make it impossible to plug something in the wrong way? E.g. if plugged in correctly nothing should be touching that socket, so it shouldn't matter much if it's blocked with a conductive pin or glue. Maybe I've gotten something terribly wrong and backwards, but clarification would be appreciated. SemanticMantis (talk) 16:03, 25 March 2016 (UTC)

The idea is that you cut off one of the pins on the male connector (typically at one end of the block) and fill in the corresponding hole on the female connector. If you try to insert the connector with a 180 degree rotation by mistake, then the blocked hole hits an un-cut pin and you can't push them together. Hence blocking one pin suffices to prevent the cable being plugged in backwards. You can use the same kind of trick when you have two or more identical-looking connectors to make sure that the correct cable is plugged into the socket. Cutting and blocking multiple pins in different places along the header allows for some considerable control over which connectors go onto which headers as well as ensuring they aren't plugged in backwards. SteveBaker (talk) 19:59, 25 March 2016 (UTC)

What is needed is a cock header. Something that probably doesnt exist atm but cuould do with inventing.--178.111.96.35 (talk) 00:12, 26 March 2016 (UTC)

WP:WHAAOE. See Urethral sounding. Tevildo (talk) 00:15, 26 March 2016 (UTC)

Not really - these devices are inserted into the female side of the connector to block it - and have nothing to do with the male side of the connector. I'll leave you to invent vaguely pornographic, contraceptive or feminine hygiene product analogies...but that's not going to be very helpful because that's not what these things are called - they are polarizing keys. SteveBaker (talk) 02:12, 28 March 2016 (UTC)

File:Salt Lake.JPG

Greetings, does someone know what File:Salt Lake.JPG is a photo of?Jo-Jo Eumerus (talk, contributions) 15:15, 25 March 2016 (UTC)

The uploader was User:Mountainloverk2, who sadly has not edited in 8 years. I don't see anything that can be used to identify the picture to more specific than a body of water in a dry landscape. The plant life appears to be part of the American West in some way, but there's nothing in the picture to nail it down specifically. If it is a real salt lake in the American West, it could be part of the massive endorheic basin which occupies much of the west. See Great Basin. I do note that the landscape looks roughly like the landscape in some pictures in that article. That giant area is far too vague to be useful in determining the location of the body of water, and there's other similar desert areas in the American West or Mexico in which this would fit as well. --Jayron32 15:25, 25 March 2016 (UTC)

And I'm probably wrong, because the uploader also uploaded a whole slew of pictures from locations in Pakistan such as File:Crossing Khanwal Luck.Jpg from I think Khanewal District, all around the same time as this picture. So, maybe Khanewal District? No idea though, certainly nothing to nail it down closer than that. --Jayron32 15:29, 25 March 2016 (UTC)

I bit on this one and noticed that there is an EXIF date for August 14, 2006, which is matched only by File:Nawabshah1.JPG. See Nawabshah. Since this is a "digitized on" date I'm not sure it's even weak proof the two were taken close together. I do see that searching for salt lakes in Sindh pulls up vaguely similar-looking terrain, to my bleary eyes, e.g. [2]. Wnt (talk) 16:52, 25 March 2016 (UTC)

Seems fairly plausible; I'll change it to that.Jo-Jo Eumerus (talk, contributions) 11:49, 26 March 2016 (UTC)

@Jo-Jo Eumerus: Well, for Wikipedia we're supposed to have sourced data, not just guess. Unfortunately for our purposes it remains just a salt lake somewhere. It can't be that hard to find other free-licensed pictures of salt lakes somewhere. Wnt (talk) 23:00, 26 March 2016 (UTC)

Old cod liver oil capsules useless?

Am I right in my interpretation of this article that cod liver oil capsules which are over a year out-of-date have probably oxidised and become useless?

Yes, and not only useless, but potentially harmful. One trick is to open one (over the sink) and smell it. If it smells bad, it is bad. StuRat (talk) 02:01, 26 March 2016 (UTC)

Actually it smells alright. Wouldn't the encapsulation protect the oil against oxidation? --78.148.107.251 (talk) 13:50, 27 March 2016 (UTC)

Slow it down, yes, but these capsules are a year past the expiration date. That's a long time. StuRat (talk) 13:55, 27 March 2016 (UTC)

There are antioxidants in there too! And they pass the smell test! --78.148.107.251 (talk) 20:31, 27 March 2016 (UTC)

Then you are probably OK. You could just swallow one and see if it gives you foul-smelling spoiled fish burps, but opening one first seems like a prudent precaution. Also, tasting the open one to see if it tastes OK is another good step. BTW, these recommendations came from The Dr. Oz Show. StuRat (talk) 02:44, 28 March 2016 (UTC)

Our article about that show says: "The show has been criticized by the medical community; a study has found that 54% of health recommendations were not medically supported". The Quixotic Potato (talk) 18:24, 29 March 2016 (UTC)

Doesn't all cod liver oil smell bad? Dbfirs 07:58, 26 March 2016 (UTC)

I suppose it depends on your preferences, but fresh fish definitely smells better than spoiled fish. StuRat (talk) 16:14, 26 March 2016 (UTC)

You're best off discarding any consumable thing that's way past its expiration date. — Preceding unsigned comment added by Baseball Bugs (talk • contribs) 02:45, 26 March 2016 (UTC)

Those capsules are very very cheap and easily available. I would throw them away. And I wouldn't buy new ones. But if you want some, buying new ones is probably better than taking them when they are over a year out-of-date. The Quixotic Potato (talk) 18:22, 29 March 2016 (UTC)

Isolated neutron--how many neutrinos go thru it, or at least strike it, per second, at least on Earth with the average flux here?

I've heard that zillions of neutrinos go through our bodies every second. I don't know if a neutrino can pass through a neutron, I would like to know. Anyway, what is the average number of collisions and/or passages thru per second? How many per 15 minutes? (I'm wondering if the were actually around 1 per hour, chance could distort the measurement of neutron half-life, provided the neutrino could somehow initiate neutron decay. Thanks, Rich Peterson155.97.8.213 (talk) 20:52, 25 March 2016 (UTC)

Well 10¹⁵ solar neutrinos pass through every square meter in one second. A neutron is about 10^-18 meters across so it covers about 10^-36 square meters. So it'll take on average 10²¹ seconds for a neutron to be hit by a neutrino - the age of the universe is around 10¹⁸ - so there is about a one in a thousand chance for a particular neutron here on earth to EVER be hit by a solar neutrino. Of course there are a lot of neutrons out there - so this does happen - but it's not happening enough to make much of a dent in the neutron half-life. SteveBaker (talk) 21:13, 25 March 2016 (UTC)

Your neutron diameter is way off. According to the article it has a mean square radius of 0.8×10⁻¹⁵ m, which corresponds to a cross-sectional area of 2×10⁻³⁰ m². So it's more like one neutrino every 20 million years (using the flux value from Solar neutrino#Observed data, which is close to yours). But individual neutrinos are probably not localized enough to definitely pass through or not pass through a neutron, so it might be better to say there's a constant neutrino flux through every neutron that adds up to 1 particle every 20 million years. Also, that's the number that pass through the neutron, not the number that hit it (i.e., interact with it). For the latter you'd have to use the interaction cross section instead of the size of the neutrino (see below). -- BenRG (talk) 02:01, 26 March 2016 (UTC)

good answer155.97.8.213 (talk) 00:05, 26 March 2016 (UTC)

Neutrinos don't "pass through" neutrons. Neutrinos pass through ordinary matter most of the time because neutrinos only interact through the weak interaction and gravity. Gravity is so weak that it has basically no effect at the atomic level. The weak interaction has an extremely short range. If a neutrino gets close enough to a neutron or another weakly interacting particle, they will interact. But neutrinos usually go right through the Earth without noticing because atoms are mostly empty space, so they rarely get close enough to any particle to interact. It's like firing a BB gun and trying to hit an individual grain of sand. When neutrinos do strike a particle, they interact and produce other particles, which we can detect in neutrino detectors. This just happens so rarely that we need to build huge detectors to get a decent detection rate. Remember, everything at the quantum level is tiny and weird. Our ape brains aren't intuitively programmed to understand it. --71.110.8.102 (talk) 21:19, 25 March 2016 (UTC)

Neutrinos do pass through neutrons. The cross-sectional area of a neutron is ~10⁻²⁶ cm², and according to this page, the cross section for neutrino-neutron interaction is around 10⁻³⁸ cm²/GeV. So a neutrino will pass through about a trillion/(energy in GeV) neutrons before interacting with one. -- BenRG (talk) 02:01, 26 March 2016 (UTC)

thanks155.97.8.213 (talk) 00:05, 26 March 2016 (UTC)

What is the relation between axon and its etymology?

What is the relation between axon and its etymology? according to what I read, the meaning of "axon" is axis in Greek. My question is what is the relation between axis to the part of the neuron which is called axon. 93.126.95.68 (talk) 22:54, 25 March 2016 (UTC)

The entire nerve is an "axon". An axis on a graph is a line - perhaps "axon" refers to the line-like shape of a nerve. DrChrissy ^(talk) 23:05, 25 March 2016 (UTC)

Thank you93.126.95.68 (talk) 23:29, 25 March 2016 (UTC)

In other, uh, words, while both words are derived from the same Greek root word, their meanings in modern English differ: cf. axis and axon. --71.110.8.102 (talk) 01:30, 26 March 2016 (UTC)

The axon was definitely discovered by Camillo Golgi, probably in the late 1870s or early 1880s, but I can find no evidence he ever called it an axon. Merriam Webster's dictionary says the word "axon" was first used to describe a part of a neuron sometime in the 1890s, which could plausibly make the name an invention of Santiago Ramon y Cajal, though I have been unable to find the first publication to use the word. I'm able to find a publication titled "Neuron" in 1896 by one Aloysius Kelly that defines an axon as the "axis-cylinder", and just a year later, everyone seems to be throwing around the word "axon" as if you are expected to know what it means. Someguy1221 (talk) 04:36, 26 March 2016 (UTC)

The OED is similarly vague. The word "axon" appears in 1842 in R. Dunglison's Medical Lexicon, and Wilder used the word in the New York Medical Journal of August 1884, but these cites seem to be for the axis of the body or the spinal column, rather than for the neuron usage. Dbfirs 07:48, 26 March 2016 (UTC)

what is meta-sympathetic system?

I always knew about the sympathetic and para sympathetic systems, and today I was told about the meta-sympathetic system, but I didn't understand well the man who told me about it and I didn't find enough or reliable information about this system, and if it's accepted in the scientific world or it's arguable. 93.126.95.68 (talk) 23:29, 25 March 2016 (UTC)

"Metasympathetic nervous system" seems to be a phrase peculiar to a handful of Russian scientists. Based on this translated abstract, it is something entirely different from the sympathetic and parasympathetic systems, but I have no access to their paper (not that I'd be able to read it unless it's translated into English). It's a bit unlikely that there is a feature of anatomy only Russians are aware of, so this has to be either something English-speaking scientists give a totally different name, or a pile of bullshit. Maybe someone can find their paper and let us know. Someguy1221 (talk) 04:39, 26 March 2016 (UTC)

Yes, it makes sense. 1) Indeed, the man is Russian scientist but his English wasn't so clear for me. 2) The most of the result about it i PubMed are from Russian. 3) your suggesting for the two possibilities are absolutely reasonable, and in any case I don't think that this term is studied in the universities in US for example. The classical method is to teach about 2 systems only (sympathetic and Para-sympathetic). Anyway, It will be useful to see article about this topic. 93.126.95.68 (talk) 05:19, 26 March 2016 (UTC)

This article is in English [3] although I haven't tried to read it yet. This also is nominally in English [4] and there's also these slides [5] and this has some brief mention [6]. Nil Einne (talk) 07:17, 26 March 2016 (UTC)

Is it saying that the brain feels pain like other organs? (I've no medical expertise, so I'm asking that as a question rather than an opinion.) Dbfirs 07:38, 26 March 2016 (UTC)

The autonomic nervous system is responsible for body reflexes and has two branches:

• the sympathetic nervous system: serves quick responses "fight or flight".
• the parasympathetic nervous system: serves slower damped responses "feed or breed, rest and digest".

The OP's question about a possible third category "metasympathetic system" has also been asked at Stack Exchange. It is suggested that the motor activities of the heart, ureters, intestine and stomach that are truly autonomous fit this third category, sources: Nozdrachev AD (Russian), The Metasympathetic System of the Brain. Their conclusion that "the brain, like other organs, has its own metasympathetic nervous system" is not simply equivalent to "feeling pain" since it is talking about unconscious reflex. AllBestFaith (talk) 14:25, 26 March 2016 (UTC)

Some presentations [7] and articles [8] seem to equate the metasympathetic and enteric nervous system, though according to [9] the enteric nervous system is just the enteric portion of the metasympathetic nervous system. One reference from 1953 [10] mentions the term but it is obscure journal/no abstract. The term stayed in Italy, without intervening publication, to 1974, after which it packed up and moved to Russia [11] in a journal that I think Nozdrachev's group also used. My guess is that this group finds it a more meaningful way to define a third autonomous nervous system than the enteric nervous system, but everyone else just wants to use a term other people understand. Wnt (talk) 15:23, 26 March 2016 (UTC)

The article [15] quoted above also says: "the brain is an ordinary hollow organ." Might be true for a large portion of mankind. :-) --AboutFace 22 (talk) 17:52, 26 March 2016 (UTC)

"OH, HOLLOW! HOLLOW! HOLLOW!"

What time the poet hath hymned
The writhing maid, lithe-limbed,
Quivering on amaranthine asphodel,
How can he paint her woes,
Knowing, as well he knows,
That all can be set right with calomel?

When from the poet's plinth
The amorous colocynth
Yearns for the aloe, faint with rapturous thrills,
How can he hymn their throes
Knowing, as well he knows,
That they are only uncompounded pills?

Is it, and can it be,
Nature hath this decree,
Nothing poetic in the world shall dwell?
Or that in all her works
Something poetic lurks,
Even in colocynth and calomel?
I cannot tell.

Bunthorne's "wail of the poet's heart on discovering that everything is commonplace" from Patience by W. S. Gilbert. AllBestFaith (talk) 19:07, 26 March 2016 (UTC)

Vogons or no vogons, the neural tube is a hollow structure (indeed, a specialized sort of ectoderm, with much in common with the skin), and the hollow center remains in the form of the ventricular system even in the adult (which can become all too hollow in the case of hydrocephalus). Wnt (talk) 22:58, 26 March 2016 (UTC)