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May 19

Trevelyan's char

Why is Salvelinus colii called Trevelyan's char? DuncanHill (talk) 22:33, 19 May 2020 (UTC)

Possibly named after/by Francis Trevelyan Buckland. 107.15.157.44 (talk) 23:56, 19 May 2020 (UTC)

It was at one time classified as Salvelinus trevelyani --Khajidha (talk) 06:43, 20 May 2020 (UTC)

The latter name is reported as Regan, 1908; the name Salvelinus colii is from Günther, 1863.^[1]  --Lambiam 09:02, 20 May 2020 (UTC)

Probably a case of multiple named species being redefined as one species. One of the sources in that article talks about the confusion. Are there 15 species or 1? Or any other number between 1 and 15-- — Preceding unsigned comment added by Khajidha (talk • contribs) 11:49, 20 May 2020 (UTC)

So why was it called Salvelinus trevelyani? Who was the Trevelyan? DuncanHill (talk) 14:35, 20 May 2020 (UTC)

"Trevelyan's char was described from a single specimen, 8-inches in length. This was sent to me in 1906 from Lough Finn in Donegal, by Major H. Trevelyan". Charles Tate Regan (1911), The freshwater fishes of the British Isles. London, Methuen & Co. Ltd. p. 106. Alansplodge (talk) 15:40, 20 May 2020 (UTC)

A Google search for the major reveals that he contributed to a number of natural history journals on subjects as diverse as the ringing of ducks and freshwater molluscs. In the The Irish naturalist: Volume XXI (1912) p. 93, the journal of the Royal Zoological Society of Ireland I found that "It is therefore a matter of deep regret to us, as it must be to all Irish naturalists, that Major H. Trevelyan passed away suddenly on January 28th. last [presumably 1912]. He was a true sportsman-naturalist and his death leaves a void which will be hard to fill". The heading of that article gives him the initials "FZS" which is a Fellow of the Zoological Society of London. Alansplodge (talk) 15:32, 20 May 2020 (UTC)

@Alansplodge: Thank you - from this is seems he was the son of Walter Trevelyan. DuncanHill (talk) 19:19, 21 May 2020 (UTC)

Herbert! I was guessing Henry, Horatio, Horace and Harold, but didn't try Herbert. Alansplodge (talk) 19:38, 21 May 2020 (UTC)

May 20

CoViD-19 deaths per capita, China vs. some western countries, why difference?

Italy I can understand because of the early outbreak, the UK and USA I can understand because of their leaders, and Sweden has made a clear choice; but why countries like the Netherlands?

The Netherlands has a population of about 17.5 million, and 5715 CoViD-19 deaths.
China has a population of about 1.4 billion, and 4634 CoViD-19 deaths.

Why are the deaths/capita so much worse in some western countries, despite all the warning, time, and wealth?

Is it that:

1. some western governments would rather sacrifice more of their older population for short term financial gain, by refusing to do a real lockdown like in Wuhan?
2. China is lying about their number of deaths?
3. biology, like older populations in Europe, or vitamin D deficiency?
4. other? -- Jeandré, 2020-05-20t09:33z

In the case of Europe, see: Measuring excess mortality: England is the European outlier in the Covid-19 pandemic. Alansplodge (talk) 09:59, 20 May 2020 (UTC)

So the excess mortality in China has not been published, and that could make China's figures much worse? How would the recent mass-testing in Wuhan influence confidence in China's numbers? (PS: the South African partial stay-at-home order reduced Easter road accidents from 162 last year to 28 in 2020. It also reduced homicides from 1542 last year to 432 in 2020 over the same first 3 weeks of April, compared to 65 CoViD-19 deaths by April 22.) -- Jeandré, 2020-05-20t10:12z

I wonder what China's MMR vaccination strategy has been? --jpgordon^{𝄢𝄆 𝄐𝄇} 14:44, 20 May 2020 (UTC)

A large factor is that different countries have different criteria for reporting COVID-19 deaths. Some countries report a person with a tested infection who dies in a traffic accident as a COVID-19 death. Then there are less clear cases: someone with a cancer and a COVID-19 infection dies - was that due to the cancer or the virus? COVID-19 has a lot of co-morbidity - someone with a pre-existing condition is way, way, way more likely to die - which of the two (or more) conditions is the real killer? When an elderly person dies, dífferent countries have different standards for testing and reporting for COVID-19 deaths.

Relly important: "number of cases" does not equal "number of infected". Rather, it means "how much are we testing in this country". Simply stop testing and you have no "cases" or deaths due to the virus!

These dumbed-down-for-the-unwashed-masses numbers and maps are highly misleading. Be smart and don't believe them. 85.76.71.1 (talk) 15:22, 20 May 2020 (UTC)

" Some countries report a person with a tested infection who dies in a traffic accident as a COVID-19 death". That's a claim I see a lot of people on the internet making, but I've never seen any evidence presented to support this (and in many case, as here, its not even stated which country they are talking about). Iapetus (talk) 09:17, 21 May 2020 (UTC)

"Germany, Luxembourg, South Korea and Spain count all deaths of those who have tested positive for COVID-19"[2] - assuming that statement is literally true. Similar statements can be found in other newspapers. 85.76.71.1 (talk) 11:04, 21 May 2020 (UTC)

Note the Russian method of counting untested Covid-19 fatalities as "community-acquired pneumonia" [3]. Alansplodge (talk) 15:45, 20 May 2020 (UTC)

Why are you comparing number of deaths to total number of population? If a country had better success containing the outbreak, for example, we wouldn't expect the total number of deaths to be as high compared to the total population as a country that did not contain it well. There is a reason that mortality rates are described as deaths per infected, and not deaths per capita. --OuroborosCobra (talk) 18:00, 20 May 2020 (UTC)

That's the very point. A country that has significantly lower deaths per population than another country - assuming both are exposed to the same degree and their reporting protocols match up - tells us immediately that the first country is doing something that the second country should be considering. Australia reached 100 deaths yesterday. That's not 100 per day, but 100 in total. Now, we have a smaller population than the UK, for example, so it's useless and dumb to compare our raw toll with theirs. The only sensible basis of comparison is deaths per population. The UK has had about 419 deaths per million. Australia has had 4 deaths per million. Need I say more? -- Jack of Oz ^{[pleasantries]} 23:08, 20 May 2020 (UTC)

What about COVID-19 deaths as a percentage of those who were confirmed to have contracted it? ←Baseball Bugs ^{What's up, Doc?} carrots→ 01:28, 21 May 2020 (UTC)

If a country tests very few people, you can get over 100% mortality. If a country tests everyone, you get very low mortality. There are estimates that there are 5-10 times as many untested infected than tested in most countries. Calculations, charts, and comparisons of number of positive tests are mostly misleading random number generators. 85.76.71.1 (talk) 11:09, 21 May 2020 (UTC)

Yes, but if you test nobody, you can claim people are dying of other causes, and claim your country is run by a stable genius who is dealing with the disease perfectly. --Jayron32 12:21, 21 May 2020 (UTC)

Please everyone, let's just /thread here. 85.76.71.1 (talk) 15:41, 21 May 2020 (UTC)

Going back the to the original question, it seems like a factor must have been the "dose" of initial cases a country got in the first place, the number of people who arrived in the country with coronavirus before travel was limited. Hubs of global travel with major airports and business centres, notably London and New York, have often been particularly badly affected. Countries with vast rural regions like India and the USA have often had very low spread outside the big cities. Blythwood (talk) 16:23, 21 May 2020 (UTC)

And both those places feature high population density - see High Population Densities Catalyse the Spread of COVID-19 and some urban deprivation - see COVID-19 more common and severe in urban and most deprived areas. A perfect storm. Alansplodge (talk) 10:39, 22 May 2020 (UTC)

And in addition, it must be stressed that there's good reason to believe it is just random, or driven by factors that aren't immediately obvious. One tiny, isolated county in rural southwest Georgia in the USA has one of the USA's highest case rates. Nobody knows why. In the UK, the very isolated rural county of Cumbria has a higher case rate than many central London boroughs, and the biggest outbreak isn't in the tourist hotspot areas. Reports suggest this is a combination of aggressive testing and outbreaks in care homes. In Canada, the nearby and similar cities of Calgary and Edmonton have totally different disease rates-partly perhaps driven by an outbreak at a meat-packing plant. I myself think about how many old people (especially older ladies) I knew growing up born in the 1910s and 1920s saw it as totally normal to kiss the host when arriving and leaving social events, and looked at you as a spoilsport if you didn't go all in, so to speak. If this epidemic had come fifteen years ago when more people from that generation were alive, I think it might have been much much worse. Blythwood (talk) 18:17, 22 May 2020 (UTC)

Transformer winding voltage ratio, and the input frequency

Does the frequency of the input current determine/affect the output voltage for a given winding ratio? ZFT (talk) 22:49, 20 May 2020 (UTC)

Ideally, no. But transformers become inefficient outside their intended range of operation. Jc3s5h (talk) 23:07, 20 May 2020 (UTC)

Yes. The peak output voltage is directly proportional to the maximum rate of change of magnetic flux through the secondary windings. And, of course, the maximum rate of change of magnetic flux is directly proportional to the frequency at which the transformer is operating. Dolphin (t) 13:29, 21 May 2020 (UTC)

No. As stated in our Transformer article, for a sinusoidal input, the RMS EMS is

$E_{\text{rms}}={\frac {2\pi fNaB_{\text{peak}}}{\sqrt {2}}}\approx 4.44fNaB_{\text{peak}}$

When considering ideal circuits, the input voltage is provided by a sinusoidal voltage source, which will force the voltage at the transformer input terminals to be a the given voltage, no matter what. Therefore, as the frequency rises, the peak magnetic flux density will reduce to make the equation true. The other winding will have this same magnetic flux density flow through it, and the induced voltage will be determined by the turns ratio. (Ideally readers would consult the reliable sources mentioned in the "Transformer" article.) Jc3s5h (talk) 15:09, 21 May 2020 (UTC)

So is this article in error, or am I misunderstanding it? ZFT (talk) 19:05, 21 May 2020 (UTC)

Jc3s5h may be correct. I look forward with interest to responses from other Users. Dolphin (t) 22:26, 21 May 2020 (UTC)

The Electrical Blog article is in error. Notice it contains the phrase "Voltage of a transformer at a given flux density increases with frequency". But the flux density does not remain constant; if the input voltage is kept constant while the frequency decreases, the flux density decreases. This is why aircraft have used 400 hz; the lower flux density associated with the higher frequency allows transformers to be smaller and lighter; obviously minimizing weight is important on aircraft. Jc3s5h (talk) 00:23, 22 May 2020 (UTC)

At Transformer#Ideal transformer it implies strongly that the EMF from the secondary is proportional to the turns ratio and the input voltage; and nothing else. Therefore we must conclude that the output voltage is unaffected by the frequency at which the ideal transformer is operating. This may not be exactly accurate for very large variations in frequency but the ideal transformer is not intended to take account of such large variations. Dolphin (t) 02:23, 22 May 2020 (UTC)

May 21

Done. ←Baseball Bugs What's up, Doc? carrots→ 22:23, 25 May 2020 (UTC)
The following discussion has been closed. Please do not modify it.
Is e= MC square really useless equation? I don't see any uses of it online. Please acknowledge me. Ram nareshji (talk) 17:17, 21 May 2020 (UTC) It depends what you want to use it for. Generally, the people who use such equations do not receive primary instruction in the theory or application of this type of equation from online sources; rather, one undertakes a formal university-level study program culminating in a Bachelor of Science degree in physics, chemistry, or materials engineering, or a related discipline; then, one pursues advanced specialization in a related scientific specialty; and one may readily find applications of this type of mathematical expression in areas that pertain to electronics, nuclear energy, optics, material science, and many other diverse areas of the applied and theoretical sciences. Indeed, we might actually and truthfully say that you are online because the very productive people who normally use this equation decided to take a momentary break from their real job, and they created the Internet as you know it, during their down-time. Nimur (talk) 17:21, 21 May 2020 (UTC) the bulk of the work, and the most essential part, was done by the the Arpanet pioneers. Lots of clever men and women, like the guy at CERN who did it, were available to come up with the CERN guys idea, in the months or year after he did it, if for some reason he hadn't been there to think of it first. But it took a lot of vision and doggedness by the Arpanet pioneers to get it ready.144.35.45.155 (talk) 21:46, 21 May 2020 (UTC) Do we use it in rocket launches along with Newton thirds law? Ram nareshji (talk) 17:48, 21 May 2020 (UTC) (edit conflict) The mass–energy equivalence equation E=mc2 was intended by Einstein as an explanation for a general reader by analogy, decades after he expressed M = μ + ⁠E0/c2⁠. The equation has since found many other uses. 107.15.157.44 (talk) 17:52, 21 May 2020 (UTC) If it just for analogy, then why this tiny equation is sensation ? Ram nareshji (talk) 18:14, 21 May 2020 (UTC) Are you aware of the nuclear bomb? ←Baseball Bugs What's up, Doc? carrots→ 18:27, 21 May 2020 (UTC) E=mc2 fits nicely on T-shirts, mugs, etc., and makes ordinary folks look smart. 107.15.157.44 (talk) 18:30, 21 May 2020 (UTC) It is sensational partly because it is a "tiny equation". 107.15.157.44 (talk) 20:19, 21 May 2020 (UTC) Its a description of the fact that a small amount of mass is equivalent to a large amount of energy. If you can find a way to covert mass to energy, you can produce quite a lot of it. If there were no equivalence of mass and energy, nuclear weapons wouldn't work, but you don't have to type in the equation to get the bomb to go boom. --Khajidha (talk) 20:24, 21 May 2020 (UTC) Concretely using this equation the difference of mass between two hydrogen nuclei and one helium nucleus tells you how much energy would be freed in the conversion. Same the mass difference between an uran nucleus and the products of its splitting (fission). Another every day use is to calculate how much the mass of an object increases as you accelerate it. So if you are designing or managing a particle accelerator you have to consider that as your charged particles accelerate you must feed more current in the deflection magnets than you would expect from the increase in velocity alone. 2003:F5:6F08:8200:AD1F:2C43:13C8:746E (talk) 21:55, 22 May 2020 (UTC) Marco PB User:Khajidha If it is practically working equation, why it didn't brought nobel prize to Einstein? Ram nareshji (talk) 04:00, 22 May 2020 (UTC) You'd have to ask the Nobel Prize committee. The thing is, what he did get it for, the photoelectric effect, was a huge deal in providing supporting evidence for quantum mechanics and particle/wave duality being an actual thing. It was tremendous. E=mc2 is tremendous in its own right, but it didn't lead to a revolution that practically rewrote all of physics, the way the photoelectric effect did. --OuroborosCobra (talk) 04:06, 22 May 2020 (UTC) It says that the inertia of a system is equal to the total energy content of a system in its rest frame and c^2 can be omitted because that's just an artifact of measuring inertia and energy in different units. Count Iblis (talk) 05:36, 22 May 2020 (UTC) In 1922, when Einstein received the Nobel Prize, major predictions of his theoretical explanation of the photoelectric effect had been rigorously tested and confirmed to a high precision. At the time, a precise experimental test of the mass–energy equivalence was not yet possible.  --Lambiam 12:29, 23 May 2020 (UTC) Digestion Regarding digestion I've asked biology people, what % of the food we eat is converted to energy? And the rest as waste. Some say 10%, some say 25%, depending on whether it's meat or vegetables and such. But if you asked a physics professor, they'll say, more like 0%, because food has to travel towards the speed of light to convert into energy. Does anyone disagree with this? (I previously asked this q years ago.). Well, this is the closest thing I can think of for applications heh. 67.175.224.138 (talk) 05:54, 22 May 2020 (UTC). "Food has to travel towards the speed of light"? What on God's green earth does that mean? ←Baseball Bugs What's up, Doc? carrots→ 15:14, 22 May 2020 (UTC) Do you know of a way for food to convert to heat energy by travelling significantly slower than the speed of light? If not, then my premise still stands, all the biology gurus are wrong, so more like 0% of the food we eat is converted to energy. 67.175.224.138 (talk) 15:46, 22 May 2020 (UTC). Yes. Enthalpy of reaction releases heat energy without approaching the speed of light. See also bond-dissociation energy, chemical energy, adenosine triphosphate and tons of other processes. Let me ask you a different question; if you think 0% of food is getting us energy, how do you think we have energy? --OuroborosCobra (talk) 16:32, 22 May 2020 (UTC) Well, energy can't be created nor destroyed. So if the mass is the same, then the energy came from prior energy, not from prior mass. 67.175.224.138 (talk) 02:06, 23 May 2020 (UTC). Try lighting a match as a demonstration. ←Baseball Bugs What's up, Doc? carrots→ 08:46, 23 May 2020 (UTC) If you think it came from prior energy (and you are more correct here in saying that, since we are basically talking about releasing energy, not converting mass to energy), why would you think that any food particles have to be traveling at any speed, let alone near the speed of light? --OuroborosCobra (talk) 19:22, 24 May 2020 (UTC) Well, if the speed of light is 186,000 miles per second, and speed of light mass is 100% converted to energy, then does travelling 1% of speed of light, means 1% of mass is converted to energy? 1,860 miles per second? = 6.7 million mph, so looks like food being kept is in the 99.9999%? 67.175.224.138 (talk) 06:34, 25 May 2020 (UTC). No. ←Baseball Bugs What's up, Doc? carrots→ 06:58, 25 May 2020 (UTC) It's complicated and there is no simple answer. For a start it depends what you eat and your lifestyle. I suggest you study our article on food energy and come back with a clearer question.--Shantavira|feed me 15:22, 22 May 2020 (UTC) Chemical energy does not require a nuclear reaction. But either you already knew that and are just making a science joke (which I always appreciate, but needs to be more clearly identified as such in this communication medium), or else "now you know". A more interesting question (in a teaching sense) is to take the amount of energy that is demonstratably released from a foodstuff, calculate how much less it weighs. And then how close science isn't to being able to measure that value. DMacks (talk) 16:00, 22 May 2020 (UTC) Why should it weigh less, though? We are talking, generally speaking, of conversion between potential and kinetic energy, and not between mass and energy. --OuroborosCobra (talk) 22:30, 22 May 2020 (UTC) https://wtamu.edu/~cbaird/sq/2013/10/21/why-is-mass-conserved-in-chemical-reactions/ Basically, bonds have mass. --Khajidha (talk) 11:54, 23 May 2020 (UTC) Baseball Bugs already touched on this slightly as have other commentators but to be more direct, I think you may have misunderstood Mass–energy equivalence. The equation, $E=m\,c^{2}$ does not mean things need to travel close to the speed of light for energy to be released. Nil Einne (talk) 14:30, 23 May 2020 (UTC) Does traveling at the speed of light (approaching) means mass is lost (approaching) at 100%? Does 1% mass is lost at 1% the speed of light? 1% of 186,000 mph is 1,860 mph, still faster than electrical signals in our body that goes 250 mph. So it seems to me, the answers are in the 99.99...% of mass is kept. 67.175.224.138 (talk) 02:07, 24 May 2020 (UTC). Actually, mass increases as you increase velocity. In a sense. https://galileoandeinstein.phys.virginia.edu/lectures/mass_increase.html#Mass%20Really%20Does%20Increase%20with%20Speed --Khajidha (talk) 04:23, 24 May 2020 (UTC) Also, the speed of light is 186,000 miles per second, not per hour. --Khajidha (talk) 04:24, 24 May 2020 (UTC) 67: I was sort of thinking there's no point of replying since Khajidha had already touched on the issue, but I've decided to make one last go. I think your understanding of mass-energy equivalence or $E=m\,c^{2}$ is likely still seriously flawed. The fact that c or the constant for the speed of light is in the equation does not mean "1% mass is lost at 1% the speed of light% or anything of that sort as I think you may be falsely assuming. I wonder if it's better if you put aside the fact that c is the constant for the speed of light for now as I think it may be causing confusion. If you've read our article and it hasn't helped, maybe try a basic physics text book and look into the subject area so you can better understand why c is in there and what it means (and doesn't mean). Or you could even start with a basic question here, without assumptions based on misunderstandings. Nil Einne (talk) 09:06, 25 May 2020 (UTC) My question is how much mass is lost per how fast it has to travel. Aside from being told now that if mass travels near the speed of light, that mass is gained. 67.175.224.138 (talk) 10:08, 25 May 2020 (UTC). Traveling near the speed of light increases the mass of the object that's traveling, according to the theories. But that has nothing to do with digestion. ←Baseball Bugs What's up, Doc? carrots→ 10:48, 25 May 2020 (UTC) Yep I agree, but my question is not at all about gaining mass of objects, but losing mass to objects. 67.175.224.138 (talk) 11:10, 25 May 2020 (UTC). The speed of light has nothing to do with digestion. Digestion is a series of ordinary chemical reactions. ←Baseball Bugs What's up, Doc? carrots→ 11:15, 25 May 2020 (UTC) But my question is not about the speed of light either. 67.175.224.138 (talk) 11:21, 25 May 2020 (UTC). (EC) What do you mean by "how much mass is lost per how fast it has to travel"? What do you mean by "losing mass to objects". Under what scenarios, and why do you think this will happen? Nil Einne (talk) 11:24, 25 May 2020 (UTC) This was in regards to what you said, mass does not need to travel near the speed of light to be converted to energy. But if it does convert to energy, at what % proportional to the speed of light? 67.175.224.138 (talk) 11:26, 25 May 2020 (UTC). I never said "mass does not need to travel near the speed of light to be converted to energy". From my understanding, saying "mass is converted into energy" can be considered a confusing way of understanding what's going so I took pains to avoid that. Second, did you read what I said about the speed of light? I really think you need to just put aside the speed of light for now. Treat it as a constant in the equation and nothing else. Don't even think about velocities or speeds. Also note that AFAICT, no one said "mass travels near the speed of light, that mass is gained" per se. Instead what was said is "mass increases as you increase velocity. In a sense." This is an important distinction as you don't need to travel near the speed of light for what's being described to apply, even if it's mostly irrelevant at low velocities. Anyway I emphasise again you should start with a basic textbook and try your best to put aside what you think you understand since it sounds like it's probably mostly wrong. I no longer think continuing to ask questions here is going to help since IMO you keep seriously misunderstanding what you're being told. Nil Einne (talk) 11:45, 25 May 2020 (UTC) Okay, this was in regards to what you said "The equation, {\displaystyle E=m\,c^{2}}{\displaystyle E=m\,c^{2}} does not mean things need to travel close to the speed of light for energy to be released." But you never explained how slowly that something can be. 67.175.224.138 (talk) 11:48, 25 May 2020 (UTC). As I said "Treat it as a constant in the equation and nothing else. Don't even think about velocities or speeds." Nil Einne (talk) 11:53, 25 May 2020 (UTC) Does that mean, take out the units? Take out the m/s or mph? 67.175.224.138 (talk) 11:55, 25 May 2020 (UTC). No. It means since c is a constant, you just think of it as a constant. What that constant means is irrelevant to you until you have a better understanding of what's going on. You shouldn't be thinking of "slowly" since it's not part of what you should be thinking of, for now. Remember that even when you understand why c is in the equation, it's still a constant. Nil Einne (talk) 12:01, 25 May 2020 (UTC) Well unfortunately that is my definition of a constant, a unitless number. Simply take out the m/s, mph, and such. 67.175.224.138 (talk) 12:07, 25 May 2020 (UTC). And what's never been explained to me about Einstein's equation, is when mass travels towards speed of light, what % of it's mass is converted into energy? Well, I didn't think it would be an arbitrary number like 67%. So I figured 100%. Hence my analogy, on mass losing 1% of its mass to energy, if it traveled 1% the speed of light. 67.175.224.138 (talk) 12:06, 25 May 2020 (UTC). What makes you think traveling at high speed converts some percentage of your mass into energy? ←Baseball Bugs What's up, Doc? carrots→ 12:49, 25 May 2020 (UTC) No it was my question. 67.175.224.138 (talk) 13:04, 25 May 2020 (UTC). You said "when mass travels towards speed of light, what % of it's mass is converted into energy?" So again, I ask, where did you get that idea from? ←Baseball Bugs What's up, Doc? carrots→ 13:30, 25 May 2020 (UTC) Because my understanding is only photons can travel exactly at the speed of light, so mass can only travel a little less than the speed of light. How much less, I wouldn't know. I imagine electrons can still travel faster than protons? 67.175.224.138 (talk) 18:09, 25 May 2020 (UTC). And what does any of that have to do with digestion or any other normal chemical process? ←Baseball Bugs What's up, Doc? carrots→ 19:57, 25 May 2020 (UTC) That the mass of food does not travel fast enough in our body to notably convert into energy. 67.175.224.138 (talk) 21:07, 25 May 2020 (UTC). At this point I'm unsure whether you're ultra-ignorant or whether you're just trolling. ←Baseball Bugs What's up, Doc? carrots→ 21:45, 25 May 2020 (UTC)

May 22

How fast are quantum computers when compare to supercomputers?

How fast are quantum computers when compare to supercomputer? Ram nareshji (talk) 19:08, 22 May 2020 (UTC)

I don't think that is directly comparable, as they work so incredibly differently and solve incredibly different problems. --OuroborosCobra (talk) 19:27, 22 May 2020 (UTC)

Certain problems are hard in the classical model of computation. An example of such a problem is integer factorization. No classical polynomial-time algorithm is known. Modern strong cryptosystems such as RSA are predicated on the assumption that factorization is hard. There is a claim that quantum computers will be able to solve certain problems much faster that are hard in the classical model of computation. Shor's algorithm is a polynomial-time quantum computer algorithm for integer factorization, which should eventually break RSA encryption. The term "quantum supremacy" is used for the situation that a quantum computer solves a problem faster than a classical computer. There has been a claim that quantum supremacy has been achieved,^[4] but the validity of that claim is disputed,^{[5][6][7][8][9]} IMO rightfully so.  --Lambiam 07:13, 23 May 2020 (UTC)

User:Lambiam so quantum computers are faster than supercomputer? Ram nareshji (talk) 16:30, 23 May 2020 (UTC)

I most definitely did not say that. People who believe in the promise of quantum computing expect that one day quantum computers will beat computers built according to current architectures (which includes supercomputers) for some types of problem (such as factorization). It has currently not yet been proved beyond reasonable doubt that this expectation will ever come true. There are "quantum skeptics" who think the promise will always remain a promise.^[10][11][12] (The last link may disappear in the future behind a paywall.)  --Lambiam 19:28, 23 May 2020 (UTC)

May 23

Salts for hygrometer checking and calibration

I'm interested in using some salts to check and calibrate some humidity sensors for personal (rather than scientific or industrial use). I'm following the tutorial here: https://www.allaboutcircuits.com/projects/how-to-check-and-calibrate-a-humidity-sensor/ where it says that the salts should be wet to the consistency of wet sand. The article references some standard procedure but the standard procedure costs $50 to download. My question is, does it make sense to add water to the lithium chloride? It's meant to be bringing the RH down to 11.3% so it seems to me that adding water would impede its absorption of water from the air. Is the idea to have the salt partially, rather than fully, saturated with water, so it's kind of analagous to a buffer accomodating acids and alkalis? If that's the case, I'd still expect adding water to be unnecessary for that salt since the starting humidity is always bound to be higher than 11.3%, at least in my country (United Kingdom). If the lithium chloride was not stored in an airtight container, would it keep absorbing water from the air until it was no longer able to keep doing so? That would be another good reason to not add water before use; if it would prolongue its working life?

Also, how much salt is needed? Could 30 grams be enough to ready the air inside a 9 L food storage container? According to some online calculator, there are 40 grams of water in a cubic metre (1000 L) of air at 30 °C so... lets say your container was 100 L, you'd only need to absorb a maximum of 4 grams of water if you were going from 100% RH to 0% or give up 4 grams if you were doing the opposite. That doesn't help much because I don't know how much water 30 grams of lithium chloride can absorb (certainly less if I add some to it at the outset, though, right?).

Would sulphate of potash intended for gardening be likely to give the same result as reagent grade K2SO4? Apparently reagent grade only means ">95% purity" anyway.

The potassium sulphate gives an RH of 97-98% - this might be a stupid question but at that humidity, is there a higher risk of the water condensing on stuff inside the container? I was also thinking of using potassium carbonate (43%) and sodium bromide (58-60%) because 33% to 75% is kind of a big jump through the region that I expect most of the readings to be taken but then maybe I'm going a little overboard. --88.111.17.83 (talk) 04:16, 23 May 2020 (UTC)

The idea with these is that the standard humidity is created by a saturated solution, so you need some of the saturated solution of the salt. If your lithium chloride absorbed enough water to get to the consistency of wet sand, then you don't need to add extra water. Any way the lithium chloride solubility is high: 83.05 g/100 mL of water at 20 °C or 84.25 g/100 mL at 25° according to our article. So it is close to one for one in mass of water. And yes, i would keep absorbing water from the air if you did not keep it airtight. Fertilizer grade potassium sulfate is likely to have other soluble contaminants, perhaps potassium chloride, magnesium or sodium. There is no incentive to make it super pure, just safe enough. That will likely reduce the humidity from a saturated solution. Graeme Bartlett (talk) 22:44, 23 May 2020 (UTC)

Thanks very much, Graeme; this helps a lot. I think that water solubility value is exactly what I was looking for. I've found a fairly cheap supplier for all these salts so there's no sense in trying to skimp on the potassium sulphate. The lithium chloride is several times more expensive than the others. 88.111.17.83 (talk) 00:19, 24 May 2020 (UTC)

Plant

Hi, I would like to know what is the name of this plant:

--Red-back spider (talk) 11:24, 23 May 2020 (UTC)

• Note that, according to the image’s uploader, the title and description state the wrong species. Brianjd (talk) 11:47, 23 May 2020 (UTC)

There is some difficulty in identifying immature foliage; my first thought was one of the birches, like this for example, but this hawthorn looks quite similar. Someone else might do better though. PS I took the liberty of resizing your image, feel free to reinstate it if you are offended. Alansplodge (talk) 12:09, 23 May 2020 (UTC)

It could also be elder, the first four or five leaves are not yet pinnate. Must wait one week more or so. 2003:F5:6F08:8200:705A:5DF6:6175:3EA0 (talk) 14:16, 23 May 2020 (UTC) Marco PB

Thank you. I think it is not a tree. The species mentioned are non-existent (or extremely rare) in that forest, and this seedling is common. I will upload more photos soon.--Pere Orga (talk) 19:27, 23 May 2020 (UTC)

It looks like a tree seedling to me, and does bear resemblance to Crataegus monogyna, or possibly another Crataegus, though here in the UK C. monogyna isn't usually a forest tree. It's not Sambucus nigra ("elder") - there's a pic of an elder seedling here, and it's quite different. Has the uploader not looked at the trees that are growing around the seedlings? If seedlings are plentiful in an area, it usually isn't too hard to find their parents growing nearby. Another place to ask would be at WT:PLANTS. PaleCloudedWhite (talk) 01:04, 24 May 2020 (UTC)

The plant could be one of these, but there just my guess:

• Lacebark
• Crataegus laevigata
• Plagianthus regius
• Celtis australis
• Crataegus viridis

@Brianjd: Yes, I know that the species name in the title is wrong, in fact the picture is getting deleted because of that and I want to save it. After all it can be used in an article. @Pere Orga: It might be a tree, Google says so but who knows, Google is right or wrong. --Red-back spider (talk) 05:33, 24 May 2020 (UTC)

• @Red-back spider: I have outdented your entire comment so it is aligned correctly. My comment about the species name being wrong was for the benefit of other users. Brianjd (talk) 07:39, 24 May 2020 (UTC)

Hoheria ("lacebark") and Plagianthus regius are endemic to New Zealand, so seems less likely that there are lots of their seedlings sprouting in a forest near Barcelona. Crataegus laevigata might be a fit, at least better than C. monogyna anyway - these images of C. monogyna seedlings have more serrated leaves than the unidentified image. PaleCloudedWhite (talk) 08:06, 24 May 2020 (UTC)

More photos in the same forest. This ones of the same species:

• https://commons.wikimedia.org/wiki/File:Planta_no_identificada_-_Santa_Perp%C3%A8tua_de_Gai%C3%A0_-_3.jpg
• https://commons.wikimedia.org/wiki/File:Planta_no_identificada_-_Santa_Perp%C3%A8tua_de_Gai%C3%A0_-_4.jpg

Even if these have a different shape, I think this could be the same, too:

• https://commons.wikimedia.org/wiki/File:Planta_no_identificada_-_Santa_Perp%C3%A8tua_de_Gai%C3%A0_-_1.jpg
• https://commons.wikimedia.org/wiki/File:Planta_no_identificada_-_Santa_Perp%C3%A8tua_de_Gai%C3%A0_-_2.jpg

My opinion is that this is a liana, and that when it grows it becomes this one:

• https://commons.wikimedia.org/wiki/File:Liana_per_identificar_-_Santa_Perp%C3%A8tua_de_Gai%C3%A0_-_1.jpg
• https://commons.wikimedia.org/wiki/File:Liana_per_identificar_-_Santa_Perp%C3%A8tua_de_Gai%C3%A0_-_2.jpg
• https://commons.wikimedia.org/wiki/File:Liana_per_identificar_-_Santa_Perp%C3%A8tua_de_Gai%C3%A0_-_3.jpg
• https://commons.wikimedia.org/wiki/File:Liana_per_identificar_-_Santa_Perp%C3%A8tua_de_Gai%C3%A0_-_4.jpg
• https://commons.wikimedia.org/wiki/File:Liana_per_identificar_-_Santa_Perp%C3%A8tua_de_Gai%C3%A0_-_5.jpg
• https://commons.wikimedia.org/wiki/File:Liana_per_identificar_-_Santa_Perp%C3%A8tua_de_Gai%C3%A0_-_6.jpg
• https://commons.wikimedia.org/wiki/File:Liana_per_identificar_-_Santa_Perp%C3%A8tua_de_Gai%C3%A0_-_7.jpg

@PaleCloudedWhite: I have identified all the trees that grow in that forest (sorbus, pines, quercus, savinas, acer... and Fraxinus angustifolia and Celtis australis, but rare) and I have concluded that this is very unlikely to be a tree.--Pere Orga (talk) 22:24, 25 May 2020 (UTC)

Your "liana" pictures are a Clematis, though I haven't tried to ascertain which species. You could be right regarding the original seedling image - the seedlings of Clematis urophylla shown here, especially the slightly more mature ones in Image C, look quite similar. The images you took of seedlings with a different leaf shape are not the same as the original - I think they are Acer seedlings. PaleCloudedWhite (talk) 20:58, 25 May 2020 (UTC)

The only Acer I've seen growing there is Acer monspessulanum, seedling: https://commons.wikimedia.org/wiki/File:Aur%C3%B3_negre_(Acer_monspessulanum)_acabat_de_n%C3%A9ixer_-_Santa_Perp%C3%A8tua_de_Gai%C3%A0.jpg. I'll see how this one evolves too :) --Pere Orga (talk) 22:24, 25 May 2020 (UTC)

May 24

Electroplating bare copper soldering iron tips with nickel and then maybe with iron?

There are some special soldering iron tips with a little groove in the end which helps improve contact area with the workpiece but they're only available for certain models of soldering iron. I've seen bare copper soldering iron tips (compatible with my own iron) for sale which I think I could cut my own groove into but they aren't good for soldering because copper dissolves in solder so the lifetime of bare copper tips is very limited (I'm not even sure why they're sold). However, I've seen online that you can electroplate nickel onto copper at home using vinegar to make a solution of nickel acetate. Someone uploaded a YouTube video doing this for soldering iron tips. I was just wondering, with regard to maximising life-time and functionality, would it be worth plating with iron after the nickel? Any idea what thickness the platings should be? Could sodium dodecyl sulfate be added as a wetting agent or is that only suitable in the conventional industrial nickel plating solutions? --88.111.17.83 (talk) 06:42, 24 May 2020 (UTC)

In my experience to work with bare copper is more agreable because copper is more easily wetted by tin than nickel or iron (Well it depends, for Tiffany glass work it is maybe even better so, but when soldering on electronic parts it is in my opinion better if the tip is wet with tin). I had some iron plated tips but even if they last forever they are not easily wetted by tin. Bare copper tips have a shorter lifetime but they don't really dissolve away in three minutes but rather in hours, secondly you can adjust them several times with hammer and file before you have to throw them away and lastly they are not so expensive that you have to renounce to the advantage of easy wetting.

But if you'd like and try, you can directly plate copper with iron without the nickel step. They say it is not so easy for hobbyists to do at home though, but here you will find some guidance: [[13]] 2003:F5:6F08:8200:B9A3:5B4F:C199:54F1 (talk) 11:38, 24 May 2020 (UTC) Marco PB

What does it mean when N,N- comes before a chemical's name, such as in N,N-Dimethyltryptamine?

And what page on Wikipedia should I add to the top of N,N (N,n) in an {{about}} template? Psiĥedelisto (talk • contribs) 15:08, 24 May 2020 (UTC)

It's dimethyl tryptamine, meaning that it's tryptamine wherein two of the hydrogen atoms are substituted by methyl groups. The N,N bit means that both substitutions are on a nitrogen atom. I don't believe we should have a page specifically on this notation. Probably we can live without a hatnote in the article you mention. --Trovatore (talk) 16:13, 24 May 2020 (UTC)

@Trovatore: Yes, but a hatnote to where? Thanks for your help by the way, it makes a lot of sense that N means nitrogen and not n in the typical math sense, that's why I was confused. Psiĥedelisto (talk • contribs) 16:57, 24 May 2020 (UTC)

It's a locant for a substituent, but our locant article only mentions numbered positions of a chain, not heteroatoms. And the parent IUPAC nomenclature of organic chemistry article also does not have any examples of it. The other common (but not nearly as common s N) are O (for oxygen) and S (for sulfur), and those two are only usually as infixes not prefixes. DMacks (talk) 17:38, 24 May 2020 (UTC)

Prefixes for sulfur and oxygen substitution do exist: eg S-Methylmethionine, O-Ethyl methylphosphonothioic acid. If the o is lower case it will mean ortho, and if you see lower case n- (eg n-Butylamine) it will mean normal or straight. You will only get one of those n's though. Yet another variant is N,N'- eg N,N'-Dicyclohexylcarbodiimide meaning two different nitrogen atoms are substituted. And another: N,N,N- N,N,N-trimethyl-4-phosphoryloxytryptamine meaning three things substituted on a nitrogen. Graeme Bartlett (talk) 23:35, 24 May 2020 (UTC)

If these prefixes are chemical symbols, why are they presented in italics?  --Lambiam 06:12, 25 May 2020 (UTC)

IUPAC/CAS says so and we all have to agree with some standardized system if we are to communicate clearly. I have no idea how to trace back the history of that:( DMacks (talk) 23:25, 25 May 2020 (UTC)

May 25

What is the "major splice donor" and how is it different from the Retroviral Psi packaging element?

According to this article on lentiviral packaging, safe lentiviral pseudoviruses can be produced by excluding gag/pol etc. from the viral genome proper and incorporating them instead with plasmids. These genes will not be packaged into the pseudoviruses because they lack "the HIV-1 elements that must be present in lentiviral vectors" which "include the RNA packaging signal (Ψ), the major splice donor, and the Rev-response element (RRE)." I get what the Ψ packaging signal is, as well as the RRE, but what is the major splice donor? I am surprised we do not have an article for it. Yanping Nora Soong (talk) 09:13, 25 May 2020 (UTC)

Here I read: "This region [viz. the non-coding part of the HIV genome between the LTR promoter and the first Gag open reading frame] encodes the 5ʹ-untranslated region (5ʹ-UTR) of the HIV RNA genome and contains many post-transcriptional replication signals, including the major splice donor (MSD) that is used in the generation of all spliced HIV transcripts and the packaging signal Ѱ that ensures the selective encapsidation of HIV RNA in assembling virion particles." From Figure 1 in the article I get the impression that MSD and Ψ are adjacent.  --Lambiam 20:15, 25 May 2020 (UTC)

Okay, so this major splice donor will be present in all mRNA transcripts and serve as a packaging signal, whereas a generic 5'UTR or intron would not serve this purpose? Yanping Nora Soong (talk) 22:47, 25 May 2020 (UTC)

What (I think) I understand from the text in that article, the MSD and the Ψ packaging signal are distinct elements with distinct functions. This seems to be confirmed by the lengthy title of this article: "The packaging signal of simian immunodeficiency virus is upstream of the major splice donor at a distance from the RNA cap site similar to that of human immunodeficiency virus types 1 and 2".  --Lambiam 08:15, 26 May 2020 (UTC)

May 26

Why Large Synoptic Survey telescope launching for mapping milky way galaxy?

Most face Hubble space telescope failed to map Emily way galaxy? So why Large Synoptic Survey telescope launching for mapping milky way galaxy? Ram nareshji (talk) 09:11, 26 May 2020 (UTC)