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May 16

Why does viral load matter?

If viruses reproduce exponentially, one might naively expect a low viral load to simply cause a slight delay in the onset of an illness. Even one virus turns into a large number in a short amount of time. So how is it possible that any viral infection could have a severity that depends on whether you start off with one virus particle or 100,000 virus particles, given that one in theory should quickly turn into 100,000? 2600:8806:3400:3DB:4970:60BC:F1C1:34BF (talk) 15:30, 16 May 2020 (UTC)Nightvid

Whereas if you started with 100,000 particles, you'd shortly end up with 10,000,000,000 particles. ←Baseball Bugs ^{What's up, Doc?} carrots→ 16:22, 16 May 2020 (UTC)

If your farmlands get infested with breeding rabbit couples, does it matter whether it is one pair or 100,000 pairs? In the first case you might be able to control the situation by hiring an exterminator specializing in rabbits. In the second case, even if you employ all terminators from the whole State, the problem will overwhelm them.  --Lambiam 17:46, 16 May 2020 (UTC)

We have an article on viral load, but unfortunately do not have one on initial viral load which is what I assume you are asking about, most likely with respect to COVID-19. I believe the answer is that it takes some time after initial antigen exposure for your immune response to ramp up, and a higher initial viral load gives the virus a head start.

So if you are infected with a very low initial vital load, your immune response may be in full swing before the viral load is sufficiently high to cause illness, resulting in an asymptomatic case. But with a high initial viral load, not only will the threshold have been exceeded for even longer before the effective immune response, but the viral load will be even higher when it does takes hold, leading to a sever illness.

I'm sure that explanation is over simplified, but hopefully not to the point of being useless. I didn't find any references of the mechanism from a cursory search, but I'll keep looking. -- ToE 01:15, 17 May 2020 (UTC)

Here something, not much, about Minimal_infective_dose. Some more relevant points: after infection and before replication begins the virus must find some susceptible cells, enter them and start replication. This can take hours or even days, during which time the virus is vulnerable. Replication time is also not zero: it varies from a minimum of 13 minutes for some fagi to 1.2 days for HIV and at least 30 hours for one hepatitis B virus. All together this means that at some low viral load immune response can have time enough to whipe out all attackers before they become dangerous, just as ToE said. A figure one meets often is 100 000 as a minimal infective dose 2003:F5:6F08:8200:351A:656A:496C:6A58 (talk) 12:47, 17 May 2020 (UTC) Marco PB

May 17

neutrino speeds and the speed of hypothetical axion

I think I understand the that the reason for neutrinos going so near lightspeed is that they are created in somewhat energetic nuclear reactions while also being very low mass, and then not slwing down by being neutral in charge. But axions are theorized to be cold dark matter, so they are slowExactly why sre they slow? And they are slow relative to the galaxy they orbit?Rich (talk) 00:16, 17 May 2020 (UTC)

It has to do with the creation mechanisms for these particles in the early universe. Neutrinos decoupled from a state of thermal equilibrium and cooled only through the expansion of the Universe. Due to their small mass they had velocities (more precisely, velocity dispersion) close to the speed of light at the time relevant for structure formation, i.e. they were "hot". I don't understand the details for axions, but I refer to the articles Axion#Cosmological_implications and Misalignment mechanism, which indicate that an interaction robbed axions of their kinetic energy making them "cold" early on. --Wrongfilter (talk) 12:10, 17 May 2020 (UTC)

I gather you're getting at hot dark matter versus cold dark matter models. Noting this for other readers; there are also warm dark matter models. --47.146.63.87 (talk) 20:17, 17 May 2020 (UTC)

I'm not contradicting anything you stated, just filling in details: neutrinos have an incredibly tiny mass, long thought to be zero, so it doesn't take much to get them to high velocities, and they only interact through gravity and the weak interaction so they're basically unimpeded by "ordinary matter" or photons and hence there's nothing to slow them down. A fascinating thing is that in contrast, neutrons, though they have no net electric charge, do interact electromagnetically and have a magnetic moment, which I think means they still can scatter off charged particles and lose energy that way. Someone please correct me if I'm wrong. --47.146.63.87 (talk) 20:17, 17 May 2020 (UTC)

They probably can, but there are no free neutrons (a free neutrons decays after 8 or 9 minutes). Axions (presumably, if they exist, blabla) have much smaller masses than neutrinos, which is probably what prompted the question in the first place. --Wrongfilter (talk) 20:50, 17 May 2020 (UTC)

Yes that was at least part of what prompted it. So how fast are neutrinos that emerge from a nuclear reactor or from the Sun? They aren’t usually primordial, unless they just happened to pass thru at the right time, right? Do they also travel closse to light speed?Rich (talk) 05:57, 21 May 2020 (UTC)

The energy E is $E={\frac {m}{\sqrt {1-v^{2}}}}$ where m is the rest mass and v is the speed in c = 1 units. The masses of the neutrinos are not precisely known, but there should be one with a mass of the order of 1 eV. Neutrinos from the Sun have a typical energy of 0.4 MeV. You can then solve for the speed by putting $v=1-\epsilon$, this yields $E\approx {\frac {m}{\sqrt {2\epsilon }}}$, therefore $\epsilon \approx {\frac {m^{2}}{2E^{2}}}$. Multiplying by the speed of light yields that the speed of the typical solar neutrino is 9 micrometers per second slower than the speed of light, after traveling from the Sun the neutrinos will lag about 5 millimetres behind massless particles. Count Iblis (talk) 09:39, 21 May 2020 (UTC)

wow that’s neat. thanks!Rich (talk) 11:56, 21 May 2020 (UTC)

vaccine research

Our President is on TV saying he expects a covid-19 vaccine by the end of the year, and at least some people seem to take this seriously. Some vaccines like Ebola have in fact been developed pretty fast. Some older ones like polio may have taken longer, but they didn't have modern biotech then. But, there is no HIV vaccine even today, other than pre-exposure prophylaxis that has to be taken frequently.

Is there some reason to expect covid-19 vaccines to be easier to develop than HIV vaccines? I think I've heard HIV might be unusually difficult, but I don't know specifics. Thanks. 2601:648:8202:96B0:3567:50D5:8BFF:4588 (talk) 01:24, 17 May 2020 (UTC)

"OUR President"? This is a global encyclopaedia. My country doesn't have a President. Anyway, I suspect there is a bigger effort being put into finding a vaccine this time around than has ever happened before. And despite the repeated hate talk about the country, Chinese authorities made public the details of its genome from their own research quite early in the piece.That increases the odds considerably. HiLo48 (talk) 01:38, 17 May 2020 (UTC)

If you ask him I'm sure he'd attest to being everybody's president ;). More seriously I'd expect the HIV genome is sequenced also. It's been around for decades so I'm wondering what's different. 2601:648:8202:96B0:3567:50D5:8BFF:4588 (talk) 01:43, 17 May 2020 (UTC)

I'm sure the original poster meant his or her own country's president, and just forgot to mention which country. No big deal. --76.71.5.208 (talk) 05:02, 17 May 2020 (UTC)

Sadly, English lacks a clusivity marker that some other languages have, which would have reduced the confusion that led to HiLo48's expressions of offense to being included in the "we" which the OP did not intend to do. --Jayron32 13:16, 18 May 2020 (UTC)

It's possible Trump wants the public to think he'll have a vaccine soon by year's end, in order to get more votes. ←Baseball Bugs ^{What's up, Doc?} carrots→ 01:45, 17 May 2020 (UTC)

By Novemeber it will be pretty clear how vaccines are coming, and also how well the human sacrifice reopening plan has worked out. Trump most of all seems to want the virus to just go away so we can get back to whatever. So he tends to be optimistic about anything that might make that happen. We'll see if the current thing works. The last few didn't, but I suppose it's important to keep trying. 2601:648:8202:96B0:3567:50D5:8BFF:4588 (talk) 05:09, 17 May 2020 (UTC)

See COVID-19 vaccine and HIV vaccine#Difficulties in development. Most humans can beat the COVID-19 virus on their own and build immunity (unknown for how long). A vaccine may only have to trigger this existing defense system. The COVID-19 pandemic causes many resources to be used, and some projects to bypass normal safety standards. COVID-19 vaccine currently says "By May, 159 vaccine candidates were in development". Some are bypassing animal trials, and it's considered to deliberately expose volunteers to the virus to measure vaccine efficiency faster. PrimeHunter (talk) 02:26, 17 May 2020 (UTC)

A news story I watched earlier tonight referred to the process "deliberately expos[ing] volunteers to the virus to measure vaccine efficiency" as human challenge trials. I think Wikipedia should have an article on that, or if there is an appropriate existing article, that phrase should redirect to it. --76.71.5.208 (talk) 05:02, 17 May 2020 (UTC)

We have variolation which is sort of related. 2601:648:8202:96B0:3567:50D5:8BFF:4588 (talk) 05:11, 17 May 2020 (UTC)

Though variolation involves intentional infection (with a low initial viral load -- see 2 questions above) in order to generate immunity, these proposed human challenge trials would involve intentional infection in order to test for immunity. -- ToE 15:11, 17 May 2020 (UTC)

We have the section COVID-19 vaccine#Controversy of proposed "challenge" studies, though it's not really an appropriate target for a redirect from your red link. A more general article on the history and ethics of challenge studies in general would be welcome. -- ToE 15:11, 17 May 2020 (UTC)

Small consolation to the 85,000+ Americans who weren't able to beat it. ←Baseball Bugs ^{What's up, Doc?} carrots→ 02:54, 17 May 2020 (UTC)

As seen in the articles that PH linked to, there are specific challenges to HIV vaccine development that should not be ascribed, without reasonable basis, to any other vaccine development. HIV is unique in a number of ways that make it challenging to develop a vaccine. Among these is that classical vaccine development often intentionally mimics the ways the body develops natural immunity to an infection, but HIV has less than a handful of case where human immune responses actually beat it and developed immunity. That's not true of COVID19. HIV antigens also don't seem to be stable in non-live virus, which makes it hard to use killed virus as a vaccine. HIV has a high mutation rate, and specifically, a high rate of mutation to allow it not only to evade the immune system, but to attack and kill the immune system. Its infection target is the very system that a vaccine uses to provide immunity, the immune system. COVID19 certainly has a wide range if effects, but its main target is the lungs, not the immune system. Honestly, HIV is fairly unique in its difficulty to develop a vaccine, almost everything else out there is much, much easier to develop vaccines against. --OuroborosCobra (talk) 20:53, 17 May 2020 (UTC)

Ok but for example don’t flu vaccines not always work that well for the year they’re designed for, and don’t they take quite a while to make? And common cold vaccine has been a big challenge too. So i’m not sure optimism is called for.Rich (talk) 06:04, 18 May 2020 (UTC)

Influenza vaccines don't always work that well for the year (actually influenza season) they're designed for mostly because they're based on predicting months in advance, from the the previous seasons, what strains of flu will be common. Such predictions aren't always successful especially when new strains emerge as happened with the 2009 H1N1 pandemic.

As for "don't they take quite a while to make", it depends what you mean by "quite a while". The recommendations for the "2020 southern hemisphere influenza season" which is ongoing were published on 27 September 2019 [1]. I don't know about other countries, but in NZ these vaccines started to be come available in late March, and vaccination is now in full swing. The recommendations for the "2020 - 2021 northern hemisphere influenza season" were published on 28 February [2]. I assume it's intended to be available in September or maybe October of this year [3]. In other words, it takes about 6 months for mass production of the vaccine [4] [5].

To be clear, although often the strains don't change much from year to year (see Historical annual reformulations of the influenza vaccine), even when they do the extra time is not that great. For example, with the aforementioned 2009 pandemic where the virus was first described in April 2009, the 2010 Southern hemisphere vaccine recommendations (i.e. to be released in ~March 2010) [6] included "A/California/7/2009 (H1N1)-like virus" i.e. the Pandemic H1N1/09 virus. In addition, because the virus obviously missed the 2009-2010 Northern hemisphere vaccine from February [7], special vaccines were made which began to become available in November 2009, see 2009 swine flu pandemic vaccine.

Of course this is after there has already been a lengthy process of research and development such that we have a decent understanding of how to develop and produce influenza vaccines.

Note also a vaccine for the "common cold" is actually a fairly non specific thing. As mentioned in our article, there are number of different virus strains that could be responsible. While Rhinoviruses are the most common, even then we're talking about a number of different types. So developing a vaccine against the common cold point blank is not a simple ask. It's true that we don't have a vaccine against any of the possible viruses involved, the challenges are often similar (large number of rapidly mutating strains), but at the same time there may also be specific challenges depending precisely what virus you're thinking of. [8]

In terms of SARS-2-CoV, there's still a fair amount we don't know about it. And I'm not really suggesting optimism, I'm not sure if OuroborosCobra really was either. But if we are going to contrast and compare to different examples, we should understand how these may be different or similar. Definitely as OuroborosCobra said, HIV has enough differences that there's perhaps only a little we should take away from it about probability of success, and challenges that may be faced.

Nil Einne (talk) 07:57, 18 May 2020 (UTC)

Exactly. The only optimism I mean to suggest is that we should not look to the challenge and lack of success with HIV vaccine research as something to compare with vaccine development of anything else, be it SARS-CoV-2, Ebola, Zika, etc. HIV has some extraordinary (and I mean that in the literally sense, as in "extra and beyond the ordinary") properties and challenges that are not an issue for any other virus that I am aware of. As you say, we don't yet know enough about this coronavirus to say for sure how easily it will be to vaccinate against, but given the 100+ promising vaccines currently in development, I'd say our chances are more towards either a truly effective vaccine, or possibly something more like influenza and a need to regularly re-vaccinate. I also always hate the description of the influenza vaccine as "not working well." It works great. As you said, the issue is in predicting the strain, but when the strain is predicted right, it gives near 100% protection. Even when they get the strain a bit wrong, the flu vaccine greatly reduces the severity of the flu. We have a problem in the US, at least, of not enough people getting vaccinated every year. If we did, we would have a lot fewer flu related deaths than we do now, because the flu vaccine is highly effective. --OuroborosCobra (talk) 13:46, 18 May 2020 (UTC)

Thanks, that’s important information that I didn’t know.Rich (talk) 15:40, 18 May 2020 (UTC)

My own suspicion is that we get something by the autumn but it's not great. The one in development in Oxford has been tested on monkeys, and it looks like it reduces symptoms but they still get it and can still spread it. I think it's very possible that governments are going to wince and says "we'll take that" unless side effects they can be blamed for are showing up. If the government has pre-ordered doses, they'll probably give them to key workers and the vulnerable; even a small reduction in cases and spread would be a lot right now, it's obvious we're heading for a great depression otherwise. For comparison, the sorta-worked RV 144 HIV vaccine trial reduced cases by 31% (caveat about small sample sizes). That wasn't good enough for governments to go with it when it's such a rare disease as HIV that can usually be prevented by dirt-cheap condoms (the vaccine regime required six separate inoculations over a six-month period; governments were looking for a 50% reduction to buy it) but for a coronavirus that spreads fast 31% would be a big development. 16:38, 21 May 2020 (UTC)

North Magnetic Pole rapidly shifting

Is this article true? What would the implications be for the economy? EllenCT (talk) 04:56, 17 May 2020 (UTC)

Is it true that the NMP has been moving? Well, many scientists have been tracking this movement for years.

Is it true that the cause is as described in the article? It's the best explanation we currently have: you can read the abstract of the original scientific paper here for free, or read the whole thing for a modest fee, and decide for yourself.

What are the implications for "the economy" (whose?)? In the short term, there'll surely be more economic activity in the sectors concerned with global navigation, as maps and systems will continue to need adjustments and amendments. Longer term, changes in the details of how the Earth's magnetic field shields higher latitudes from geomagnetic storms may mean more (or less) damage to electrical systems, mains electricity grids, communications, navigation systems, satellite hardware, pipelines and doubtless other things. As an economics student, you are better placed to research and opine on such matters than I.

No doubt others have more knowledge in these fields and can add further details. {The poster formerly known as 87.81.230.195} 90.197.24.23 (talk) 06:37, 17 May 2020 (UTC)

The paper on which this pop-science article is based appeared in Nature Geoscience ("Recent north magnetic pole acceleration towards Siberia caused by flux lobe elongation"). It is behind a paywall and I did not read it, but "lobes of negative magnetic flux" as mentioned in the abstract are not "massive blobs", nor do I expect the paper to describe these lobes as "writhing" and "duking it out" to each other. In the abstract, the authors ascribe the faster motion (about 2 mm/s compared to an earlier 0.5 mm/s) to "elongation of the Canadian lobe, probably caused by an alteration in the pattern of core flow between 1970 and 1999". As a result, magnetic north is now very close to true north. There is no indication that the global magnetic field has weakened, only that its orientation has changed. I see nothing that looks like it might have implications for economic activity.  --Lambiam 08:07, 17 May 2020 (UTC)

One implication is that in the UK, compass navigation is much easier because magnetic variation is insignificant in most parts of our island, here in London it's only 1° and decreasing. [9] Hooray! Alansplodge (talk) 11:22, 17 May 2020 (UTC)

And, also in the UK, our national broadcaster has seen fit to publish a nice animation showing that this is nothing new. [10] Bazza (talk) 16:22, 17 May 2020 (UTC)

Although (according to the BBC animation) it's moved more in the last 30 years than in the preceding 150 years. Alansplodge (talk) 12:16, 18 May 2020 (UTC)

Pleurisy and dancing

Why was Anna Pavlova told that she could not dance ever again if treated surgically for pleurisy? The article on pleurisy is silent on this subject.--Jasper Deng (talk) 18:32, 17 May 2020 (UTC)

I'm thinking there's a lot of legend wrapped around Pavlova's demise, in particular the "refused an operation" part. Victor Dandré's account indicates nothing of the sort.[11] --jpgordon^{𝄢𝄆 𝄐𝄇} 05:02, 18 May 2020 (UTC)

The account linked by Jpgordon is persuasive. However, assuming for the moment that the "refusal" story were true, the Pleurisy article suggests that the principal (only?) long-term surgical treatment for the condition is Pleurodesis. This would necessarily mean that the functionality of the Pleural cavity would be eliminated, which in turn would surely compromise the patient's peak lung function such that they would thereafter be unable to perform vigorous physical activity, such as dancing. {The poster formerly known as 87.81.230.195} 90.197.24.23 (talk) 07:53, 18 May 2020 (UTC)

"Researchers investigating the demands of classical ballet have concluded that classical ballet is a high-intensity intermittent form of exercise. This form of exercise requires a good aerobic foundation..." [12] Alansplodge (talk) 15:07, 19 May 2020 (UTC)

"...compared to the 61 common sports, only professional [American] football is more physically demanding than ballet". [13] Alansplodge (talk) 15:07, 19 May 2020 (UTC)

The other pertinent view is related to how many times do we hear about individuals who achieve something that doctors said was impossible. There remains the not unreasonable possibility that doctors are not infallible. Richard Avery (talk) 07:24, 20 May 2020 (UTC)

May 18

Neopentane

Pentane, isopentane, and neopentane are all isomers of C
₅H
₁₂. Their boiling points are (repectively) 36 °C, 28 °C, and 9.5 °C, with a decreasing trend as would be expected with increased chain branching and the resultant weakening of dispersion forces. Their melting points, however are (respectively) −130 °C, −160 °C, and −16.6 °C. Can anyone explain or point to an explanation for the melting point of neopentane being so much higher than that of pentane and isopentane? The WP page on neopentane mentions the difference but its explanation is not clear to me. Help! 112.213.147.109 (talk) 09:00, 18 May 2020 (UTC)

You may find the explanation in this paper cited in the article easier to follow. Mikenorton (talk) 09:06, 18 May 2020 (UTC)

Hopefully matching that paper: the neopentane molecule is more symmetrical and can be neatly packed together, so crystals are easier to form. Graeme Bartlett (talk) 23:19, 18 May 2020 (UTC)

The density of the 3, for the liquid phase, in the same order you provided, are 0.626 g mL, 616 mg mL, and 601.172 kg/m^3. So I guess a better question is what role does density place in melting and boiling point. I wonder if density alone is the biggest single factor. (Note that I only posted the density in their liquid phases, wonder if it's the same linearity for the density at solid or gas phases.). 67.175.224.138 (talk) 05:04, 19 May 2020 (UTC).

It's really a question of Degrees of freedom (physics and chemistry) which is why melting point trends can be independent of boiling point trends. Vaporization (the phase transition from liquid to gas) involves the "unlocking" of translational motion by the breaking of the intermolecular forces holding the molecules together, and is a fairly straightforward relationship; for something like the alkane family, you're basically looking at London dispersion forces, and so you find a nice predictable relationship between LDFs and boiling points. Melting point, which is the breakdown of the crystal lattice of a substance without a breakdown of the intermolecular forces, essentially depends on freeing up all of additional degrees of freedom other than translation, so that includes all of the other kinds of motion (rotational, vibrational, stretching, bending, twisting, etc) and the shape of the molecule has a particularly significant effect on such factors; i.e. n-pentane (the straight chain) has very different sorts of such motions than the neopentane (which is much more compact and round in shape) and those differences account for the difference in MP. The paper above discusses these properties (which is closely related to various symmetries in the molecule). --Jayron32 12:40, 19 May 2020 (UTC)

mask that only covers mouth, how effective for preventing spreading it to others? How effective as a protection for oneself?

Is it really needed stopping spreading, since ones mouth spreads most of the saliva, and you can pull the mask upwards if you're about to sneeze? And for protecting oneself there's a lot more barrier through the nose. It seems to me one is recirculating carbon dioxide which could be a health risk for some people.144.35.116.6 (talk) 22:24, 18 May 2020 (UTC)

Standard medical disclaimer. That said, the San Fran department of public health and the Mayo clinic say cover your damn nose. Some doctors have warned that infants shouldn't wear them.

Speaking in terms of breathing while wearing a face mask, in my experience (I'm a preschool teacher who has to spend all day singing, dancing, and chasing toddlers while wearing a mask), if a mask makes it hard for an adult to breath, put that one over a mask that is otherwise useless. This will create a pocket inside the effective mask, giving you more room to breathe. The mask I'm most comfortable with has very distinct inner and outer layer, with the outer layer being water-tight (just because of how tightly woven it is), but the inner layer(s) being multiple layers of a very thin material that normally wouldn't do anything. Ian.thomson (talk) 22:44, 18 May 2020 (UTC)

I don't understand what you mean about wearing two masks. What do you mean by useless mask? Also, I apologize for prying, but do you have heart disease?144.35.116.6 (talk) 23:17, 18 May 2020 (UTC)

The way the simple masks that you can make at home work, is to reduce the reach of the cloud of virus particle that you'll cough out. They only marginally reduce the total number of virus particles. So, as far as preventing from getting infected, such a mask only has a marginal effect. Also for making sure that no people won't get infected by you, it doesn't work well for people very close to you, as the concentration of virus particles close to you may actually increase after coughing. But it does work well for people keeping a bit of distance from you.

Lots of people aren't coughing at all, they are just wearing it to prevent the spread of tiny saliva particles from their mouths. Im not sure if you are saying masks in general don't work well for people close to you, or masks that cover only the mouth don't work well in that situation. (what's the antecedent of the word (it) in your sentence? But maybe that is because you are talking about people who are actually coughing, who probably should be wearing more facial covering than other people, and staying home more.144.35.116.6 (talk) 23:17, 18 May 2020 (UTC)

These masks are then mostly useful when the number of people who carry the virus is very small. In that case we want to make sure the basic reproduction number of the virus R stays below one to prevent a second wave of the epidemic. But we also want to open the economy as much as is possible. If everyone wears face masks, then that allows for more economic activity before R becomes 1 compared to people not wearing face masks. So, we would then wear face masks not with the idea to avert a significant risk of infecting people, as that risk will be extremely low. It's to make sure that if you happen to be the one in a million infected person who can spread the virus that you'll infect less people, say one other person instead of two. Count Iblis (talk) 22:50, 18 May 2020 (UTC)

I'm glad to wear a face mask. I'm just a bit worried about it covering my nose, since I might be stressing my heart disease situation by reinhaling carbon dioxide.144.35.116.6 (talk) 23:17, 18 May 2020 (UTC)

Johns Hopkins medicine recommends a mask if you have heart disease because whatever effect you might imagine the mask might have on your heart, Coronavirus is confirmed to be far worse. Also, isolated study instead of meta-analysis, but this study concludes "Wearing a facemask appears to abrogate the adverse effects of air pollution on blood pressure and heart rate variability." The CDC only excludes "young children under age 2, anyone who has trouble breathing, or is unconscious, incapacitated or otherwise unable to remove the mask without assistance." So lung disease would be a concern but for heart disease the mask will at least be safer than the alternative. Ian.thomson (talk) 10:37, 19 May 2020 (UTC)

Face masks are used throughout the medical field, scientific research field, construction and HVAC field, and many others, since long before this pandemic. Many of these are fields where they have to wear masks for very long stretches, hours or even significant portions of entire days. If CO2 re-circulation and lowering blood oxygen saturation was a major problem, I think we would have known about it long before this pandemic. --OuroborosCobra (talk) 19:03, 19 May 2020 (UTC)

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.^[14]  --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"[15] - 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" [16]. 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

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)

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)

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,^[17] but the validity of that claim is disputed,^{[18][19][20][21][22]} 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)

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.

I was thinking of also using potassium nitrate which 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)

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