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April 20

Electric vehicles

If cars, buses, motorcycles become electric then will it affect the fossil fuel industry? -- 42.110.196.234

It depends on what gets burned to produce the electric power those vehicles will charge their batteries with. ←Baseball Bugs ^{What's up, Doc?} carrots→ 05:25, 20 April 2020 (UTC)[reply]

I was wondering about that. Given that large power stations are far more efficient at extracting energy than a small car or bus engine, could it be that, even if the power stations providing the electricity for those vehicles used the same petrol as the vehicles, we would need a lot less? But there is some loss when the electricity is transported into the battery, so it could cancel out, or be worse. Has anyone seen some calculation? --Lgriot (talk) 11:13, 20 April 2020 (UTC)[reply]

Yes, it will affect the fossil fuel industry. That's the whole point (in addition to reduced local emission of pollutants). Motorcycles and cars mostly run on oil-derived fuel (in particular petrol). Buses are more variable; around here they use compressed biogas, compressed natural gas, hydrogen fuel cells (they don't say how the hydrogen was made), electricity via batteries or overhead wires (they don't say where they buy the electricity) and sometimes still diesel. In any case, most road vehicles use oil-derived fuel, but fossil fuel power stations mostly use natural gas or (rapidly disappearing in Europe) coal, so at the very least there will be a shift away from oil. And a large fraction of our electricity, expected to increase, doesn't come from fossil fuels: hydropower, nuclear, solar, wind, ...

Given the efficiency of batteries and (to lesser extend) transport losses, battery-electric cars combined with oil burning power stations could very well give higher oil consumption than petrol powered cars (but don't forget the losses from converting crude oil to petrol). But that's irrelevant as there are (practically) no oil-fired power stations. The trick is to charge battery-electric vehicles when there's such a supply of wind or solar power that the price of electricity drops to zero (or less), which guarantees that they indeed charge from clean electricity. Of course, owners of solar panels or wind farms won't make a lot of money that way... PiusImpavidus (talk) 12:01, 20 April 2020 (UTC)[reply]

I think LNG is a good bet for fossil fuel future, it's cheaper than driving on both petrol and diesel and suitable for existing engines. A taxi company in my city started out with Priuses but when it decided to go bargain busting it swapped them all for petrol cars converted to LNG. Plenty of city buses use it too, although I think the majority are still diesel (and none are electric). 89.172.105.177 (talk) 00:39, 21 April 2020 (UTC)[reply]

Note that oil at least has many important uses beyond use as fuel (e.g. as a raw ingredient of plastics). So even a total switch to non-fossil fuel power sources wouldn't eliminate the oil extraction and refining industries. Iapetus (talk) 09:42, 21 April 2020 (UTC)[reply]

Renewable electricity overtakes fossil fuels in UK for first time (October 2019). Alansplodge (talk) 12:38, 21 April 2020 (UTC)[reply]

Let's hope there won't be a second time. --Lambiam 19:57, 21 April 2020 (UTC)[reply]

Looks like the UK already imported almost half of it's energy by 2013 which The Guardian doesn't count (to Britain's carbon print). Wonder how much it's now.--TMCk (talk) 21:11, 21 April 2020 (UTC)[reply]

Penetration by particles

How exactly do beta and gamma particles penetrate human body? Do they slip through some microstructures or actually perforate, leaving microscopic holes like bullets on a larger scale? Thanks. 212.180.235.46 (talk) 11:11, 20 April 2020 (UTC)[reply]

They pass right through our atoms. PiusImpavidus (talk) 12:02, 20 April 2020 (UTC)[reply]

As shown by Ernest Rutherford in the famous experiment with metal foil. Under his direction Hans Geiger and Ernest Marsden fired alpha particles at various metal foils. The previous model of material was that mass was evenly distributed through space, so when they observed high-angle backscatter for a minority of the particles, this demonstrated that matter was instead concentrated in atomic nucleii. When Geiger reported back about the backscattered alpha particles, Rutherford said "It was almost as incredible as if you fired a 15-inch shell at a piece of tissue paper and it came back and hit you. " Mikenorton (talk) 13:38, 20 April 2020 (UTC)[reply]

So, to elaborate on this, the mental image of microstructures that particles can slip through is wrong. Think of marbles (representing the nuclei of the atoms of molecules) floating in space, practicing social distancing, where the recommended inter-marble distance is something like a half kilometre. Now you shoot at random into that largely empty space. Chances are that your bullet goes a long way before it hits a marble. Maybe it emerges at the other end without having hit anything. The molecular social distancing is the result of the van der Waals force, operating on the molecules substances are made up from. The same force keeps your feet from sinking into the floor as you stand: the molecules of your feet and those of the floor repel each other when approaching each other at a very short distance. --Lambiam 15:59, 20 April 2020 (UTC)[reply]

The beta rays will disturb the electrons as they pass, perhaps ionising the atoms, or causing molecules to become excited, or to vibrate more. As suggested above, to actually make a hole you would actually have to hit or move a nucleus of an atom. For gamma rays, the photons do not punch a cylindrical hole, and only have an effect once they hit something and are absorbed and or scattered. You can expect disruption where they hit. Graeme Bartlett (talk) 00:34, 21 April 2020 (UTC)[reply]

Alpha particles colliding with nuclei can cause atoms to get displaced. It has been suggested that one can also search for dark matter this way by searching for tracks of atoms displaced by collisions with dark matter in certain minerals at some depth, see here. Count Iblis (talk) 03:31, 21 April 2020 (UTC)[reply]

Predatory Journals

Hi, while writing a draft on a Medical policy and saving it. I got a message saying some of citations might be “Predatory Journals”. I would like to know more about this particularly, wether any of my sources cited are in Blacklisted category. Where do I find more information on this? Regards Santoshdts (talk) 15:32, 20 April 2020 (UTC)[reply]

See WP:VANPRED. Mikenorton (talk) 15:43, 20 April 2020 (UTC)[reply]

What animal is this?

Is that a hippo? Or a warthog? It's from Central Africa (Gabon or neighboring territories), this is certain. Thank you! --Edelseider (talk) 16:21, 20 April 2020 (UTC)[reply]

Yes, it is a hippopotamus skull, as you can confirm here by comparing the two. In your picture, the top and bottom are not correctly aligned; the upper jaw is rotated clockwise (as viewed from looking over the top of it) relative to the lower jaw. --Jayron 32 17:53, 20 April 2020 (UTC)[reply]

@Jayron32: Ah, okay, thank you very much! --Edelseider (talk) 20:18, 20 April 2020 (UTC)[reply]

What is this metal object?

I was walking in a forested area in south-east England and I found this metal disc thing embedded in the ground.

What is it?

Something used in forestry or agriculture? Thank you. --Polegåarden (talk) 21:24, 20 April 2020 (UTC)[reply]

Unknown object
Unknown object

I have no idea, but ~~the second photo clearly doesn't seem to be the same object~~. What's up with that? --76.71.6.31 (talk) 23:45, 20 April 2020 (UTC)[reply]

I think they are the same. The first object isn't lying on the ground. It's sitting on top of the axle/post/metal rod(?) it's attached to. The second pic is a side-on view. But I have no idea what it is. HiLo48 (talk) 00:25, 21 April 2020 (UTC)[reply]

I agree that the in the first photo the disk may not be lying on the ground, although we were told that the thing is "embedded in the ground". But it is clearly circular and has a circular recess in the top, and a screw or bolt protruding at least 1/2 inch or 1 cm. ~~The object in the second photo has four straight sides, no circular recess, and no protruding screw.~~ So...? --76.71.6.31 (talk) 03:15, 21 April 2020 (UTC)[reply]

The second image is from directly side-on. We can't see anything about the top or the bottom surfaces, such as if there is a depression, or if there is a bolt in the depression that is not taller than the depression. Several of the other items visible on the ground in the two images match each other. Because I'm going stir-crazy from travel restrictions and needed a break from work-at-home, I annotated four such details (go to File:Unknown_object_in_rural_area.jpg and File:Unknown object in rural area 2.jpg in two adjacent windows, hover your mouse over each to see identified regions). DMacks (talk) 04:10, 21 April 2020 (UTC)[reply]

Oh, of course. Sorry about the distraction. --76.71.6.31 (talk) 18:05, 21 April 2020 (UTC)[reply]

I think it is a feeding station for gamebirds. Greglocock (talk) 00:29, 21 April 2020 (UTC)[reply]

That would have been my guess based on shape (or a mounting on which a feeder is bolted), but it seems too low (squirrels and other ground creatures could get up to it). DMacks (talk) 04:10, 21 April 2020 (UTC)[reply]

Thank you for your replies. Yes, the two photos are of the same thing. I've heard that it might be part of an old pheasent feeding station with some part missing. --Polegåarden (talk) 06:26, 21 April 2020 (UTC)[reply]

Something like this perhaps?. Alansplodge (talk) 12:34, 21 April 2020 (UTC)[reply]

Flu Vaccine Effectiveness

I've heard that all the flu vaccine does is decrease the time you have it, that does not stop you from getting it. Is this true? Pealarther (talk) 22:56, 20 April 2020 (UTC)[reply]

See Influenza vaccine. ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:44, 20 April 2020 (UTC)[reply]

April 21

What is this common insect (Sweden)?

I have recently been observing a lot of these insects in my apartment in Linköping, Sweden:

The animal's body length is about one centimetre (0.4 inches). What kind of insect is it? --Andreas Rejbrand (talk) 10:26, 21 April 2020 (UTC)[reply]

A non-biting midge (Chironomidae)? Mikenorton (talk) 11:05, 21 April 2020 (UTC)[reply]

Agree, probably a male with those fluffy antennae, so not likely to bite. Richard Avery (talk) 13:28, 21 April 2020 (UTC)[reply]

Thank you very much! --Andreas Rejbrand (talk) 13:32, 21 April 2020 (UTC)[reply]

Resolved

RNA to DNA conversion

In case of coronavirus diagnosis for example, why its RNA should be converted to DNA during real-time reverse transcription polymerase chain reaction, if it's seemingly more simple to search and detect its RNA directly? Thanks. 212.180.235.46 (talk) 19:25, 21 April 2020 (UTC)[reply]

I am not a PCR expert... that said, looking at our articles, I can see a possible explanation. Remember that all PCR techniques are dependent upon specific enzymes, such as DNA polymerase, working under the conditions of the PCR process. The polymerase is the thing actually copying DNA enough to be detected. Even when working just with DNA, not just any DNA polymerase can be used. You need one that is stable under thermal cycling, since the PCR process involves thermal cycling, and we thus use a very specific DNA polymerase (Taq polymerase, isolated from a thermophilic bateria). RNA-dependent RNA polymerase is not nearly as widespread among biological organisms as either DNA polymerase or RNA polymerase (which itself needs a DNA template to make RNA, and so wouldn't be useful in an application where you are starting from RNA). It's mainly found in viruses, and highly conserved among viruses, so there may not be a thermally stable version of it that could work for PCR application. Rather than trying to make out own (an incredibly difficult task), it is far easier to use a reverse transcriptase to make complementary DNA from the sample RNA material, and then use existing PCR techniques with DNA polymerase to amplify the material. --OuroborosCobra (talk) 20:06, 21 April 2020 (UTC)[reply]

It was once done directly by Northern blot but such a method was inefficient, not sensitive enough and prone to errors. Ruslik_Zero 20:40, 21 April 2020 (UTC)[reply]

But since the virus replicates, making more copies of itself, isn't the amount of RNA in the infected person sufficient for detecting and diagnosing directly, without the need for any polymerase? 212.180.235.46 (talk) 21:55, 21 April 2020 (UTC)[reply]

You are probably overestimating the amount of RNA that is recovered from a sample, and underestimating the amount of amplification your get from PCR. While it is possible to detect single molecules of RNA (for instance), doing that robustly, reproducibly, fast, and in a clinical setting is something different altogether. 30 cycles of PCR would theoretically increase the signal 2³⁰-fold, or over a billion times. Fgf10 (talk) 22:42, 21 April 2020 (UTC)[reply]

Almost all NAT tests require replication in order to have detectable amounts. Beyond that, the replication technique itself is a step in determining a positive detection. We don't merely "detect the presence RNA." You have tons of RNA in your body right now, your own RNA. You need to detect RNA of a specific sequence unique to the target organism. This is why PCR uses primer sequences, basically, a sequence of genetic material that is unique to your target organism, and highly conserved within it (not likely to change due to mutation). Genetic material matching that sequence is what is replicated and amplified. That means successful amplification not only gives you a measurable signal, but is also confirmation that the target organism or virus was in fact present in the sample. Otherwise, all RNA strands in a given sequence would need to be individually sequenced in order to determine their origin. In any human sample, you would have human RNA, you'd have symbiotic and commensal bacteria, etc. That's a LOT of sequencing to do. It is much simpler to have a primer that will only amplify the target organism or virus, and therefore will only work if the target organism or virus is present. --OuroborosCobra (talk) 15:15, 22 April 2020 (UTC)[reply]

Thanks. 212.180.235.46 (talk) 12:30, 23 April 2020 (UTC)[reply]

April 22

Unknown beetle

Does someone know what species this is? It was seen on the wall of a house on the Aegean coast of Turkey. It was about 25 mm (1 inch) long. Note the bands on the lower part going from side to side. Most beetles are smooth or have ridges in the length direction. I do not see a head. Thank you. Hevesli (talk) 09:05, 22 April 2020 (UTC)[reply]

Perhaps a ~~juvenile~~ cockroach nymph of some kind, but I have no idea which of the many types it might be. Mikenorton (talk) 10:32, 22 April 2020 (UTC)[reply]

Not so sure its a beetle which would generally have elytra or wing-cases which open from the centre line - I can't see that in that in in the photograph. Also dubious about there being a juvenile stage of any beetle; "Insects which undergo holometabolism pass through a larval stage, then enter an inactive state called pupa (called a "chrysalis" in butterfly species), and finally emerge as adults" (from Metamorphosis). Alansplodge (talk) 17:41, 22 April 2020 (UTC)[reply]

I'm not sure it's even an insect, though it certainly seems to have three pairs of legs. The segmented back makes me wonder if it's something like a woodlouse, or more generally some kind of isopod. AndrewWTaylor (talk) 18:18, 22 April 2020 (UTC)[reply]

I should have referred to cockroach nymphs rather than "juveniles". They are typically segmented, wingless and have heads that are not obvious from above, but I can't find any examples that match that picture. Mikenorton (talk) 22:35, 22 April 2020 (UTC)[reply]

Looks like it could be Polyphaga aegyptiaca in Corydiidae: see [1], [2]. --Amble (talk) 22:40, 22 April 2020 (UTC)[reply]

Thank you. One from Malta has just the same markings on her back as the one I found and other details also look same. Hevesli (talk) 04:16, 23 April 2020 (UTC)[reply]

Apologies Mikenorton, you were on the right trail. Alansplodge (talk) 10:45, 23 April 2020 (UTC)[reply]

No problem, I must have looked at thousands of cockroach pictures, but failed to find the one that Amble spotted. Mikenorton (talk) 10:50, 23 April 2020 (UTC)[reply]

"God has an inordinate fondness for beetles". Alansplodge (talk) 16:26, 23 April 2020 (UTC)[reply]

Coronavirus responses

Would I be correct in assuming that almost all countries are simply following their national pandemic response plan in responding to the Coronavirus? 90.196.236.105 (talk) 10:00, 22 April 2020 (UTC)[reply]

The response should be tailored to the specific characteristics of the outbreak, so even under ideal circumstances it cannot be a matter of "simply" following a plan. Then, as should be apparent, political considerations play a considerable role in the appraisal of the situation and the appropriateness of specific responses, in some countries more than in others, but likely to a certain extent in all. On the face of it, it appears to me that the assumption is unwarranted. --Lambiam 12:59, 22 April 2020 (UTC)[reply]

It might help if you mentioned what the alternative would be. To some degree, whatever each nation is doing now is according to "a plan". In some cases, "the plan" was hastily put together in March. Some nations have pandemic plans, likely written or updated in the light of SARS or H1N1, but it seems unlikely that those plans were complete in the sense that they likely didn't detail the degree of physical distancing we've done. A number of news pieces have commented that existing pandemic plans hadn't adequately prepared most nations for widespread infections, where sharing resources is not possible. Hence my request for clarification: having or not having a plan is not quite a black and white question. Matt Deres (talk) 13:36, 22 April 2020 (UTC)[reply]

April 23

Could Covid-19 have spread at multiple points from animals to humans?

If it is true that most of the early cases came from a single wildlife market, then one or more of the animals could have been infected prior to being shipped to the market. This would imply that the farmers or others handling the same animal(s) earlier could also have presumably been able to catch the virus.

So why are the earlier cases that were not linked directly to the market assumed to be evidence against zoonotic transmission at the market, rather than as evidence that there might have been an "animal super-spreader" of some kind, or simply that the same animal infected a handful of people handling it, and then was subsequently delivered to the market and spread the virus around at that market?

2600:8806:3400:3DB:793B:C7CF:650:5F5A (talk) 02:31, 23 April 2020 (UTC)Nightvid[reply]

My understanding is that the earlier cases and growing evidence against zoonotic transmission occurring at the meat market is because the genetic analysis indicates the possibility that the transfer occurred hundreds of miles away from Wuhan. I'm not sure what you mean by an "animal super-spreader." While it is possible that a single animal or group of animals transferred the virus to more than one person, I'm not sure that's relevant to the issue of the meat market. Basically, the genetic analysis shows 3 main subtypes, each splitting from the previous, i.e. subtype A is the root subtype emerging at or immediately after the zoonotic transfer. At some point, subtype B split off from subtype A, and then substype C split off from subtype B. The viral isolates from Wuhan are subtype B, which indicates that the zoonotic transfer event may not have occurred in Wuhan. Subtype A has been found in Guangdong province, which is 500 miles away from Wuhan, as well as in North America. What this seems to suggest is that the zoonotic transfer event could have happened earlier than we thought, and in southern China, and spread from there. At some point, subtype B mutated off of subtype A, and early on in its spread to Wuhan, mutated into subtype B, which dominated that outbreak. Independently, someone also carried subtype A to North America, which dominated the North American outbreak. Subtype C, at some point, mutated from subtype B, and is what was the type in the outbreak in Europe, as well as other areas of East Asia, but is otherwise largely absent from China.

So, it isn't just that earlier outbreaks occurred, and thus we don't think one animal could have caused both the earlier outbreaks and then the later one in Wuhan (and the wet meat market). Rather, the genetic analysis indicates that the outbreak in Wuhan was a product of human-to-human transmission already occurring, as it was a daughter type to that of the earlier zoonotic transfer event outside of Wuhan. --OuroborosCobra (talk) 02:50, 23 April 2020 (UTC)[reply]

Separate from your main point/reply to the question but this bioRxiv preprint suggests the subtype prevalent in New York is closer to the Italian one than the more common "endogenous" US one although they're relying on a marker to identify the subtypes [3] Nil Einne (talk) 18:25, 23 April 2020 (UTC)[reply]

As we can read here: "The gene for the spike protein in SARS-CoV-2 has an insertion of 12 genetic letters: ccucggcgggca. This mutation may help the spikes bind tightly to human cells — a crucial step in its evolution from a virus that infected bats and other species." This means that before this mutation arose, there would have had to be infections with the virus with humans that then didn't cause an epidemic. The virus may not have been able to cause much of a disease in humans. But one can estimate what the probability of the insertion of the code "ccucggcgggca" and then deduce if this is so low that it would have had to happen in smaller steps. If so, then that would imply that virus was moving back and forth from the animal host to humans a long time before it had the capability of causing an epidemic in humans. Count Iblis (talk) 10:18, 24 April 2020 (UTC)[reply]

Cats vs. dogs cleanliness

I am looking for non-biased scientific information about the cleanliness of cats vs. dogs. I do not want any information from religious sources. For example, Islam does see cats as ritually cleaner than dogs. However, I want to find secular information about cats vs. dogs studied by scientists. Where can I find information about the cleanliness and diseases of these animals online? Thank you. WJetChao (talk) 09:39, 23 April 2020 (UTC)[reply]

Cat Cleanliness vs. Dogs. DroneB (talk) 11:01, 23 April 2020 (UTC)[reply]

Cleanliness is not a scientific term, therefore your question cannot be answered using scientific sources, as you wanted. You'll have to define cleanliness. Fgf10 (talk) 12:35, 23 April 2020 (UTC)[reply]
Can't we measure their respective distances to godliness?

"Cleanliness" might not be a scientific term, but its a concept that could be defined in such a way that it could be scientifically investigated. I don't have any answers, but I don't think the question should be dismissed like that. Iapetus (talk) 08:45, 24 April 2020 (UTC)[reply]

There's no doubt it could be. But it hasn't been by the OP so far, so my statement about this particular question is completely correct. Fgf10 (talk) 15:09, 24 April 2020 (UTC)[reply]

It doesn't take a rocket scientist to observe that cats tend to be more fastidious than dogs. That doesn't necessarily mean you want them walking on your dinner table, though. ←Baseball Bugs ^{What's up, Doc?} carrots→ 13:30, 23 April 2020 (UTC)[reply]
Having had both cats and dogs, one very observable difference is that cats groom their coats, while dogs don't. Also, dogs like a playful rough-and-tumble with other dogs – which they make clear by inviting their playmates by vocalizing “rough! rough!”. This may get them pretty dirty. Adult cats may fight each other, but then it is not a play fight. If they have gotten dirty, most dogs will not mind getting a good wash, but many cats will resist vehemently. All this is strictly anecdotal and non-scientific. One could define a cleanliness measure by determining how much dirt can be collected from an animal's body, but how to define the population from which samples are taken? Should feral cats and dogs be included? Is it reasonable to compare dogs that go outside with cats that are kept indoors? And should the measure be absolute (in which case a St. Bernard will prove more dirty than a chihuahua) or relative to the animal‘s surface area? And are we really interested in just dirt? What about the shedding of hair? And so on. I doubt a scientist would undertake such a study in the face of such issues, unless there was an urgent need for an answer to some question – in which case the reason for the urgency would probably determine the operationalization of the concept. --Lambiam 15:00, 23 April 2020 (UTC)[reply]

It has long intrigued me that we regard the cat behaviour of licking themselves all over as a sign of cleanliness. That wouldn't be the case if I did it. Probably more likely to be seen a sign of extreme weirdness and yuckiness. HiLo48 (talk) 18:53, 23 April 2020 (UTC)[reply]

We see it that way because it is actually part of their grooming/cleanliness practice, and if they don't do it, they don't get clean. Similarly, we wouldn't think of it as super clean to pick parasites out of each others hair, but certainly a lot of other primates would view that as part of keeping clean. For cats, part of why their tongue has evolved those backwards facing barbs is for the purpose of use in cleaning themselves. If you licked yourself that way, you don't have backwards barbs on your tongue, so you wouldn't effectively clean anything. --OuroborosCobra (talk) 18:57, 23 April 2020 (UTC)[reply]

CNBC reports air pollution drops by 180%

On April 23, an article on pollution during coronavirus situation said fine particle pollution in Manila went down by 180%. This might be an error. Or could it be theresult of calculating percent change as 100*(new amount-old amount)/(new amount), instead of 100*(new amt- old amount)/(old amt)? If that’s what it is, is this calculation standard, or becoming more common? Is it a more useful way to measure things?Rich (talk) 18:30, 23 April 2020 (UTC)[reply]

This teacher of Mathematics says it's utter nonsense. HiLo48 (talk) 18:36, 23 April 2020 (UTC)[reply]

Can you link to the article in question so we can look it over ourselves? --Jayron 32 18:52, 23 April 2020 (UTC)[reply]

Here are two news articles giving the 180% figure: [4], [5]. The last one references a press release by the Environmental Pollution Studies Laboratory of the Institute of Environmental Science & Meteorology at the University of the Philippines. --Lambiam 19:15, 23 April 2020 (UTC)[reply]

Let's for a moment assume they did mean 100*(new amount-old amount)/(new amount). Let us calculate. Put for brevity x for the old amount and y for the new amount. Then we get

180 = 100 (y − x) / y

180 y = 100 y − 100 x

80 y = − 100 x

y = − 1.25 x.

Negative air pollution! Probably from burning negative oil. This article reports a decrease from the typical Thursday peak value of 38 μg/m³ to 7.1 μg/m³, which is a decrease by 81%. Probably, 180% was a typo for a rounded 80%. --Lambiam 19:10, 23 April 2020 (UTC)[reply]

Yes but people typically will say there is a “50% off sale”, meaning the 50% is negative. So if -180%=100(y-x)/y, then -1.8=(y-x)/y, so -1.8y=y-x, so -2.8y=-x, so y=x/2.8. Since x was old amt and y is new amt that means if the old fine particulate was 38ug/m^3, then the new fine particulate is

amount is about 14ug/m^3, which i admit doesnt match the 7ug you found, but might have been correct on a different day.Rich (talk) 08:44, 24 April 2020 (UTC)[reply]

A quick review of the main page of www.cnbc.com (in the United States) shows this article: Photos show impact of temporary air pollution drops across the world from coronavirus lockdown. In that article, they make the more precisely-stated claim:

"In Philippines’ capital city, fine particulate matter — the world’s deadliest air pollutant — dropped by 180% since quarantine measures were imposed in Metro Manila on March 16, according to the Environmental Pollution Studies Laboratory of The Institute of Environmental Science and Meteorology."

With a little bit of follow-up, we can see the Environment and Pollution Studies Laboratory (the group who originated that "180%" number) are a research group in the Institute of Environmental Science and Meteorology at the University of the Philippines Diliman, the flagship campus of the University of the Philippines System and an organization of national repute.

I am still looking for the official source (e.g. a research paper, pre-print, or press-release) for the statement that CNBC is reporting.

Nimur (talk) 19:14, 23 April 2020 (UTC)[reply]

I assume when someone decided to publish those photos, they looked for something which sounded spectacular, but as the dates and ABS-CBN story shows, this is fairly "old news". Based on the ABS-CBN story linked above by Lambian [6]), the lack of any sign of this at [7], I guessed that social media may be where this originated.

Sure enough, scrolling through the history of this Facebook page @UPIESMEPSL, I found [8]. That's actually just a comment of a Facebook post [9] by @RCMakAirtoday. So I had a look at RCMakAirtoday and found this post of theirs on the ABS-CBN story, [10] where someone questioned the 180%. In response, they pointed to this story [11] where we find:

In calculating the percentage reduction, <name removed> said she got the difference between the value recorded during the enhanced community quarantine (ECQ) and the value two weeks before it was imposed.
“Then you divide the result by the value during the ECQ and and multiply it by 100,” she explained.
(20 less 7.1 results in a difference of 12. 19, which is then divided by 7.1. The result of 1.8 is then multiplied by 100, or a reduction by 181.6 percent)

Someone else responded questioning the 180% even with this explanation but there was no further followup. I don't know if there has been more discussion in other media outlets although I had a quick search and couldn't find anything.

BTW, whole looking into this, I found the figure is mentioned in 2020 Luzon enhanced community quarantine#Environmental. So if anyone is interested in getting into a debate over WP:CALC vs figures that are published in secondary sources, they could look into whether this needs to be changed. (Although you could just exclude any percentage figure.)

Nil Einne (talk) 06:54, 24 April 2020 (UTC)[reply]

So it's exactly what I wrote below. 89.172.105.179 (talk) 17:27, 24 April 2020 (UTC)[reply]

In a formula, the Facebook explanation amounts to 100×(old amount−new amount)/(new amount). What you wrote amounted to 100×(old amount−new amount)/(baseline level), where the baseline level is the oldest of all. The Facebook explanation is precisely the theory in the post that started this thread, except for the sign. If you replay the bit of elementary algebra I posted above, but replace "180" by "−180", you end up with y = 0.357 x, a reduction of about 64%. This still does not mesh with the Facebook explanation, but by itself it makes enough sense that it wouldn't have been questioned. I'm curious what the original press release said. --Lambiam 18:40, 24 April 2020 (UTC)[reply]

No offense meant, but as i indicated in a note underneath your algebra above, a 180% drop can be interpreted as -180%, and my algebra in that note showed that it would make some kind of sense. As the OP, I naturally want people to know I understood the mathematics.Rich (talk) 20:06, 25 April 2020 (UTC)[reply]

They could mean that it decreased to an amount where it would have to increase by 180% to regain the original level. Sadly I see non-maths people mix that stuff up all the time even when they should know better. That would be 1/2.8 = 5/14 ~ 0.357 of the original amount (or a 64.3% decrease). Or maybe they mean it dropped by 80% (to 0.2 of the original amount) and the "1" is a typo. 89.172.105.179 (talk) 01:17, 24 April 2020 (UTC)[reply]

Perhaps the 180% is measured relative to an earlier and much lower-than-current baseline level, such as that in, say, 1950 (to take a random date). If the average level has tripled since 1950, then a 180% decrease would still leave it at 120% of the 1950 level. I stress this is just a conjecture, but it seems plausible to me that such a method might be used in some scientific context, though it would be a grave and confusing error to use the figure unexplained in a report destined for public consumption. {The poster formerly known as 87.81.230.195} 2.122.178.214 (talk) 06:25, 24 April 2020 (UTC)[reply]

If scientists worth their mettle measured a level, found it to be at 120% of a certain reference value and wanted to compare this new level with an earlier level at 300% of the same reference value by calculating the arithmetic difference of the two percentages, they would report a decrease by 180 percentage points. More likely though, if that reference value was so important that it is used as the yardstick, they'd give this unit a name, say PP₁₉₅₀, and report a decrease from 3.0 PP₁₉₅₀ to 1.2 PP₁₉₅₀. --Lambiam 14:43, 24 April 2020 (UTC)[reply]

A drop of 100 percent would take it to 0. What a drop of 180 percent would be is anybody's guess. ←Baseball Bugs ^{What's up, Doc?} carrots→ 21:18, 25 April 2020 (UTC)[reply]

Under the usual definition of percentage drop, a drop of 100% would indeed bring it to zero. But under the following different definition, it would not: If percent drop in price for an item on sale meant 100*(new price-old price)/(new price), then a 100% drop would cut the price in half(which is what is normally called a 50% drop in price). Now suppose a business suit normally sells for $100.00. If the suit went on sale for $35.70, then under the new definition the price dropped by 180%, instead of 64.3%, since 100*(35.70-100)/35.70 = -180%. Note that 1.8*35.70+35.70 would bring the price back to $100.00. Rich (talk) 07:57, 26 April 2020 (UTC)[reply]

Is there any solid evidence of what CNBC actually meant, as opposed to trying to "figure it out"? ←Baseball Bugs ^{What's up, Doc?} carrots→ 12:25, 26 April 2020 (UTC)[reply]

??? I don't see any reason to think CNBC meant anything. They just followed what was reported. The way the number was derived is discussed above based on the Philippine Daily Inquirer source linked above who communicated with the researcher who came up with the number. Nil Einne (talk) 04:31, 27 April 2020 (UTC)[reply]

Deducing vegetation types

Hello. I am wondering if it is possible to deduce what kind of vegetation would exist in a given place that currently does not exist, for lack of habitat. I'm specifically referring to deducing what type of vegetation the Southern Hemisphere would have that would be analogous to the boreal forest/taiga and the temperate broadleaf deciduous forests of the Northern Hemisphere. If we look at a map of the world and maps of what kind vegetation types exist in different parts of the world, we can see that for the most part, all vegetation types that exist in the Northern Hemisphere have analogous types in the Southern Hemisphere as well. The specific flora may not be the same, but their adaptations, their form, their composition, will be very similar. This is true with two major exceptions, which I listed above.

So what I'm asking is, what would a Southern Hemisphere taiga and temperate deciduous forest look like? The reason that these ecosystems don't exist in the Southern Hemisphere is because of a lack of land at the right latitudes. So the north has extensive areas of taiga and deciduous forest because land exists for it in northern and eastern North America, in Russia, Siberia, Europe, and East Asia. No such land exists at the right latitudes in the south.

The reason I ask this is because I think it might be possible to deduce. The evergreen oaks of California have relatives in eastern North America that are evergreen and deciduous. The spruces, hemlocks, cedars, of the Pacific Northwest have relatives all over North America and Europe and Asia as well. So plants and trees of the same genus and families can certainly adapt to different climate types, as they have in the Northern Hemisphere. Can we make the same deduction that flora like Eucalyptus, Nothofagus, Podocarpus, can adapt to a humid continental climate and a subarctic climate like the Northern Hemisphere taiga and deciduous forests have? I know it's a stretch of the imagination, but I believe it might be possible. I just wonder if there are more educated views than mine on this topic. Thank you for your help.2600:1702:4000:5D40:C817:71F5:DF5A:F287 (talk) 19:22, 23 April 2020 (UTC)[reply]

Temperate deciduous forest exist in the Southern Hemisphere, it notes so in the lead section of that article. The closest Southern Hemisphere equivalent to taiga appears to be Magellanic subpolar forests, which aren't really taiga. As you note, there simply is no land in the Southern Hemisphere taiga belt, between the subpolar forests of Tierra del Fuego and the tundra of Antarctica is basically the Southern Ocean, where larch and spruce trees may find a wee bit hard to take hold. The closest to tiaga-like trees I can find in the southern hemisphere might be the Araucaria araucana, an alpine pine tree that grows in cold, dry areas of the Andes. --Jayron 32 19:33, 23 April 2020 (UTC)[reply]

In the eucalyptus genus in Australia there is Eucalyptus pauciflora, commonly known as snow gum, thereby indicating where it grows. Rather than being at higher latitudes, it grows at higher altitudes, above 700 metres and up to a little over 2,000 metres (7,000 feet). It's known to survive temperatures down to −23 °C (−9 °F) and year-round frosts. It is, of course, evergreen, but can survive the loss of all its leaves and the death of all parts of the tree above ground (typically from fire) by re-sprouting from lignotubers. Given that there are over 700 species of eucalypt, and most seem to have evolved in quite recent geological times, the genus may well have been (and might still be) capable of creating a species to survive in even bleaker conditions, if such places existed. HiLo48 (talk) 00:07, 24 April 2020 (UTC)[reply]

April 24

Ocean swell or something else?

A question rather than an answer from me, for a change. In the photograph of the 150 km-long Antarctic Iceberg A-38 in this BBC article, I can see an apparent wave pattern whose wavelength must be on the order of 7 km. Our article on Ocean swell states "Occasionally, swells which are longer than 700 m occur as a result of the most severe storms." So, is this pattern ordinary ocean swell, but with a wavelength some 10 times the usual maximum, or is it a different (though presumably related) phenomenon, and is there a specific name for it? {The poster formerly known as 87.81.230.195} 2.122.178.214 (talk) 05:50, 24 April 2020 (UTC)[reply]

A natural sea wave with a 7km wavelength would be travelling at just under 400 km/h. So I don't think it is that. https://en.wikipedia.org/wiki/Wind_wave Greglocock (talk) 08:12, 24 April 2020 (UTC)[reply]

Maybe internal waves? PiusImpavidus (talk) 08:21, 24 April 2020 (UTC)[reply]

You mean in an interface (thermocline) between fresher Antarctic Surface Water and saltier Circumpolar Deep Water (as shown in the diagram here)? {The poster formerly known as 87.81.230.195} 2.122.178.214 (talk) 11:06, 24 April 2020 (UTC)[reply]

This article might be relevant: [12] --Amble (talk) 15:58, 24 April 2020 (UTC)[reply]

Thanks, Amble. That article includes a description of a phenomenon on which I find we have an article, namely Infragravity wave. From the two, I gather that ocean surface waves with a wavelength of the order of 7 km can in fact occur. {The poster formerly known as 87.81.230.195} 2.122.178.214 (talk) 18:41, 24 April 2020 (UTC)[reply]

Lutheria bi-beatricis

While browsing Special:Random just now, I encountered the Lutheria bi-beatricis article. I've never seen a scientific name with a hyphen before. (It's accurate; one reference is dead and the other doesn't mention it, but the authority-control at the bottom provides confirmatory links.) Does the existence of a species under this name preclude the future use of "Lutheria bibeatricis", or could a newly discovered species be given this name? Normally I'd create the latter title as a redirect, since absence of punctuation is a good reason for a redirect, but maybe this wouldn't be a good idea if a separate species could exist under this name. Nyttend (talk) 08:33, 24 April 2020 (UTC)[reply]

The use of hyphens by those following the current Shenzhen Code of the International Code of Nomenclature for algae, fungi, and plants is described here in Article 60 and here in Article 60. (Although I don't believe it's changed for a while, see e.g. the St Louis code Article 60 and Article 23.) As for a species without a hyphen but otherwise the same name, Article 53 may come into play. Nil Einne (talk) 11:02, 24 April 2020 (UTC)[reply]

And in view of the fact that the unhyphenated variant is in fact sometimes seen for this species name,^[13][14] there can be little doubt that it would be deemed to be an orthographical variant,^[15] and therefore an (invalid) synonym. --Lambiam 16:28, 24 April 2020 (UTC)[reply]

Thank you! Redirect created. I'm not surprised that there are guidelines on how names are to be formed, but I'd never seen them and didn't know where to start looking. Nyttend (talk) 12:34, 25 April 2020 (UTC)[reply]

Color of some cobalt compounds

Cobalt(III)...

...chlorate: I think it unstable. But what is the color of this compound? Thanks for much.
...perchlorate: I heard that it's only exists in solution. What is the color of this compound in solution? Thanks for much.
...bromide: I heard that it never been prepared. Can you are the first person prepare this? Thanks for much.
...iodide: also like bromide.

Cobalt(III) can oxidise water in acidic conditions. However it is quite common in complexes. eg hexammine or trisbipyridyl [16]. Do you care about complexed cobalt for your chlorate and perchlorates? Graeme Bartlett (talk) 11:38, 24 April 2020 (UTC)[reply]

Complex ions have very different colors than naked ions. Also, for the most part (with some exceptions I'm sure), the color of any ionic compound of a transition metal ion is usually predominantly due to the complex ion itself. For example, many copper (II) compounds are generally green (anhydrous) or blue (hydrated crystals). The Cu(H₂O)₆ ion is a brilliant deep blue color, and the hydrated crystals of things like copper (II) nitrate and copper (II) sulfate and copper (II) chloride are generally a similar blue color. That being said, the chemistry of transition metal ion complexes is messy, and depending on the exact ion complex formed, you can get vastly different colors. This thread for example contains images of two different isomers of Hexamminecobalt(III) chloride, one of which is orange, and one of which is burgundy. The moral of the story is that for MANY transition metal ionic compounds, for various reasons owing to the electron energy levels in those d-orbitals, they tend to usually be brightly colored; however predicting the color of any one of them without actually synthesizing it and looking at it is folly; likely because there is really very little energy difference across the whole visible spectrum, and tiny little differences in electron energy levels caused by whatever the particular environment around a particular transition metal ion can cause a big shift in color. Also, with regard to many of these putative compounds you are asking about, just because you can write a formula for it doesn't mean it can exist. Many of these may be so unstable that it isn't possible to observe them to any degree of reliability. --Jayron 32 14:18, 24 April 2020 (UTC)[reply]

Cobalt(IV)...

...fluoride: I heard that it's unstable gas. What is the color of this compound? Thanks for much. (This is more info, it maybe help you):

At -80 °C, Cs₂CoF₆ make a dark red solution in water.
At room temperature, Cs₂CoF₆ have gold-colored solid.

One more time, thanks for very much. (Sorry if you don't understand, because my English is not good).--Ccv2020 (talk) 09:50, 24 April 2020 (UTC)[reply]

That fluoride CoF₄ is formed at around 630K, but is only about 10⁻⁶ atmospheres in pressure. So it would not be a gas under standard conditions. The researchers studying this only observed infrared lines, and did not mention any optical spectrum or colour. The instability may be due to reaction with water breaking it up. Graeme Bartlett (talk) 11:52, 24 April 2020 (UTC)[reply]

That's a super obscure one. I was going to say that it's probably similar to [FeF₄]^- but that doesn't seem to really exist either. Pelirojopajaro (talk) 17:19, 24 April 2020 (UTC)[reply]

@Graeme Bartlett:Why you don't according to complex of cobalt(IV) fluoride?--Ccv2020 (talk) 01:12, 25 April 2020 (UTC)[reply]

I don't know what you mean by that, but I did fond out that Rb₂CoF₆ also exists. Are you asking if you can make CoF₄ from Cs₂CoF₆? I suspect the answer is no one has done it. Graeme Bartlett (talk) 10:38, 26 April 2020 (UTC)[reply]

Construction boundary between designer and construction organisation

In construction, is there a clear boundary between what the designer is responsible for and what the contractor is responsible for or does this differ between projects? For example, would certain dimensions or materials be the responsibility of one on one project but other on another? 90.192.105.214 (talk) 17:06, 24 April 2020 (UTC)[reply]

That could depend on the local laws. ←Baseball Bugs ^{What's up, Doc?} carrots→ 19:42, 24 April 2020 (UTC)[reply]

Normally, the plans from the designer will specify both dimensions and materials in as much detail as is relevant, which may be on account of any combination of functional, economic and esthetic factors. Thus, the contractor's freedom in these respects is very limited. It is also normal that there are negotiations between the stakeholders (in particular, including the commissioner), initiated by the contractor, whether certain substitutions or other modifications are allowed. Sometimes this may entail the need of obtaining a permit for the mods of the original plans. --Lambiam 16:27, 25 April 2020 (UTC)[reply]

Raft foundation

Do raft foundations impose zero load on certain parts of the ground? I know it’s a way is spreading the load out over a wider area but does this mean, it could be like a bridge or will there still be some load on all areas of the ground the foundation is in contact with? 90.192.105.214 (talk) 17:59, 24 April 2020 (UTC)[reply]

Floating raft system (see article) implies that if the soil should become liquid the supported building would not sink, due to the buoyancy of its own weight of soil being displaced. In this case the load is spread over the whole area under the building. DroneB (talk) 22:33, 24 April 2020 (UTC)[reply]

Medical wording: Reduction in lethality

I was just looking at Effect of High vs Low Doses of Chloroquine Diphosphate as Adjunctive Therapy for Patients Hospitalized With Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Infection - A Randomized Clinical Trial, published today, and was confused by this wording:

Main Outcomes and Measures: Primary outcome was reduction in lethality by at least 50% in the high-dosage group compared with the low-dosage group.

I read "reduction in lethality by at least 50% in the high-dosage group" as meaning that the high-dosage group experienced less than half the death rate, but the paper goes on to describe the opposite, that the high-dosage group experienced more than twice the death rate (through day 13) than the low-dosage group. Yet try as I might, I can't parse the sentence to match what they clearly intend it to mean. How am I misreading this? -- ToE 19:51, 24 April 2020 (UTC)[reply]

Someone more familiar with medical research could likely explain this better but AFAICT from a quick read of the rest of the paper especially this bit:
The sample for the primary outcome (ie, reduction in lethality rate) was calculated assuming a 20% lethality incidence in critically ill patients7,23,24 and that higher dose of CQ would reduce lethality by at least 50% compared with the low-dosage group. Thus, considering a test of differences in proportions between 2 groups of the same size, 80% power and 5% α, 394 participants were needed (197 per group). Adding 10% for losses, the final sample of 440 participants was obtained. Sample calculation was performed in the R version 3.6.1 (R Project for Statistical Computing), with the functions implemented in the TrialSize and gsDesign packages.
their null hypothesis was that the higher-dosage would reduce the lethality by at least 50% compared to the low-dosage. Based on their results, the null hypothesis was rejected. Maybe see also Outcome measure. Nil Einne (talk) 21:24, 24 April 2020 (UTC)[reply]

Someone more familiar with medical research could likely explain this better but I think you may have misunderstood the primary outcome bit. AFAICT, it isn't the outcome of their experiment. Note the part you quote comes before the results. Rather, it is the primary outcome they set before they began to prevent Data dredging or similar problems.

If they did find a 50% reduction in lethality of the high-dosage group compared to the low dosage group, their primary outcome would be affirmed and they would have statistically significant evidence for a benefit of a high dosage over a low dosage. However they did not find this and therefore they have no evidence for such a benefit. Note if you read later, it says:

The sample for the primary outcome (ie, reduction in lethality rate) was calculated assuming a 20% lethality incidence in critically ill patients7,23,24 and that higher dose of CQ would reduce lethality by at least 50% compared with the low-dosage group. Thus, considering a test of differences in proportions between 2 groups of the same size, 80% power and 5% α, 394 participants were needed (197 per group). Adding 10% for losses, the final sample of 440 participants was obtained. Sample calculation was performed in the R version 3.6.1 (R Project for Statistical Computing), with the functions implemented in the TrialSize and gsDesign packages.

Maybe see also Outcome measure and [17] and perhaps [18]. Perhaps also [19]

Nil Einne (talk) 21:49, 24 April 2020 (UTC)[reply]

I think it make sens when you replace "outcome" by "hypothesis". The were testing if higher dose would reduce the lethality by 50% and as the experiment was going the other way around, they decided to stop it early. Iluvalar (talk) 22:10, 24 April 2020 (UTC)[reply]

Thank you both. I didn't understand the term outcome in this context, and the result being the reciprocal of the hypothesis just added to my confusion. -- ToE 22:21, 24 April 2020 (UTC)[reply]

The name of this concept is statistical power: essentially, the level of improvement you're hoping to see dictates sample size. If you hope to confidently prove a very small improvement, you're going to need a bigger sample size than that needed to see if a really dramatic improvement is real or not. Sources on this I recommend are Alex Reinhart's excellent Statistics done Wrong and Blasey & Kraemer How Many Subjects? Statistical Power Analysis in Research. Blythwood (talk) 16:20, 25 April 2020 (UTC)[reply]

Deep vein thrombosis and supercentenarians question

Can someone actually recover from deep vein thrombosis while they're already a supercentenarian or at least manage to subsequently live with this condition for years in spite of them already being 110+ years old? Futurist110 (talk) 21:32, 24 April 2020 (UTC)[reply]

The annual incidence of DVT is about 80 cases per 100,000 annually. Since supercentenarians are generally in good systemic health (until they suddenly die of old age), there is no specific reason to expect a higher incidence among this group. As there are only a few hundred living supercentenarians, one should expect one case in every two or three years. There can hardly be enough cases for giving meaningful statistics. I can't think of a reason why it should be impossible for any to recover. --Lambiam 16:14, 25 April 2020 (UTC)[reply]

"supercentenarians are generally in good systemic health (until they suddenly die of old age), there is no specific reason to expect a higher incidence among this group" - I find this statement fairly confusing especially in light of the rest of your comment. Supercentenarians may be in generally good good systemic health, but as our article says in the lead

About 5–11% of people will develop VTE in their lifetime, with VTE becoming much more common with age.[12][13] When compared to those aged 40 and below, people aged 65 and above are at an approximate 15 times higher risk.[14]

and later in the body

Acquired risk factors include the strong risk factor of older age,[5] which alters blood composition to favor clotting.[23] Previous VTE, particularly unprovoked VTE, is a strong risk factor.[24] Major surgery and trauma increase risk because of tissue factor from outside the vascular system entering the blood.[25] Minor injuries,[26] lower limb amputation,[27] hip fracture, and long bone fractures are also risks.[8] In orthopedic surgery, venous stasis can be temporarily provoked by a cessation of blood flow as part of the procedure.[21] Inactivity and immobilization contribute to venous stasis, as with orthopedic casts,[28] paralysis, sitting, long-haul travel, bed rest, hospitalization,[25] and in survivors of acute stroke.[29]

and

Some risk factors influence the location of DVT within the body. In isolated distal DVT, the profile of risk factors appears distinct from proximal DVT. Transient factors, such as surgery and immobilization, appear to dominate, whereas thrombophilias[e] and age do not seem to increase risk.[54] Common risk factors for having an upper extremity DVT include having an existing foreign body (such as a central venous catheter, a pacemaker, or a triple-lumen PICC line), cancer, and recent surgery.[11]

and

As DVT is most frequently a disease of older age that occurs in the context of nursing homes, hospitals, and active cancer,[3] DVT is associated with a 30-day mortality rate of about 6%.[1]

and especially

VTE becomes much more common with age.[12] VTE rarely occurs in children, but when it does, it predominantly affects hospitalized children.[140] Children in North America and the Netherlands have VTE rates that range from 0.07 to 0.49 out of 10,000 children annually.[140] Meanwhile, almost 1% of those aged 85 and above experience VTE each year.[3] About 60% of all VTEs occur in those 70 years of age or older,[8] and those aged 65 and above are subject to about a 15 times higher risk than those aged 40 and below.[14]

So it's well accepted and known that DVT risk increases with age. Further, while it's complicated as these things often are, and some of this increased risk may be in part due to an increase risk of underlying conditions which may increase with age, and therefore supercentenarians "good systemic health" may therefore not face quite the same risks, there is evidence that part of the reason for the increased risk is from changes associated with age that supercentenarians probably also experience. I'd also note that while supercentenarians could perhaps be more mobile than the average 85 year old (I don't really know, but to avoid needless debates I'll accept it as a possibility), I'd be surprised if they more mobile than the average 30 year old.

Therefore the assumption that supercentenarians are not at increased risk compared to the general population seems a little weird. They may not be at increased risk compared to the 1% for 85 year olds, perhaps they are even at lower risk, most likely we cannot know because of the numbers. But compared to the general population? I'm unconvinced that we have good reason to think their risk profile won't be higher.

Note that I do not disagree with the conclusion i.e. there is no reason to think supercentenarians will never survive DVT.

Nil Einne (talk) 02:39, 26 April 2020 (UTC)[reply]

I was unclear. I meant to contrast supercentenarians with "plain" centenarians, who are actually on average more often in bad health, having been kept alive to that age only thanks to modern medicinal intervention. So I may be mistaken in this, but I expect the DVT survival rate for supercentenarians to be actually higher than that for centenarians. The DVT risk factor, in the sense of the risk of incurring it, is not relevant, since the survival rate is with respect to patients already suffering from DVT. --Lambiam 08:27, 26 April 2020 (UTC)[reply]

April 25

UV resistant germs

Per [20], "UV radiation from the sun is the primary germicide in the environment". Question: that UV radiation has been arriving for billions of years. Why haven't the germs developed resistance by now? Even if a few of them have, why not pretty much all of them? Thanks. 2602:24A:DE47:B270:DDD2:63E0:FE3B:596C (talk) 03:31, 25 April 2020 (UTC)[reply]

The best way to protect against UV is shielding. With a, say, 300μm thick shield, an organism can safely absorb a significant fraction of the UV in layer that can withstand it as the layer is dead already or can be discarded after use. The epidermis works like that. However, a 100nm virus cannot carry a 300μm shield. PiusImpavidus (talk) 11:08, 25 April 2020 (UTC)[reply]

PiusImpavidus, your phrase makes me think of "A five-ounce bird could not carry a one-pound coconut!" :-) Nyttend (talk) 12:27, 25 April 2020 (UTC)[reply]

It's really quite staggering what an accomplishment DNA repair is given how frequently DNA gets damaged. Every day every cell in your body repairs at least 10,000 instances of DNA damage. Now bacteria and especially viruses have much shorter genomes than human cells, and obviously a lot of that isn't caused by UV, but if you're a small bacterium without much protection there will be limits to how effectively you can fix damage. And viruses have particular problems: repair requires a ton of energy, and viruses of course can't do respiration to release energy outside a cell. And RNA is less stable than DNA is. There is actually a case of viruses having a DNA repair enzyme powered by light energy, though. So fundamentally there are constraints on what they can do: it's like asking "why don't bacteria have brains": that's not the mode of living they've evolved into. Viruses have generally evolved to replicate fast and in large numbers rather than replicate good. Blythwood (talk) 11:15, 25 April 2020 (UTC)[reply]

Many RNA viruses don't even have a proofreading mechanism (e.g. influenza viruses). Coronaviruses are an exception; they have a larger-than-average genome that includes genes for proofreading. --Lambiam 15:52, 25 April 2020 (UTC)[reply]

My comment here on the Science Desk is to do with the sloppiness of a scientific source using the word "germicide". Marketers of disinfectants and antiseptics use the word "germs" to emphasise how powerful(?) their products are. "Kills 99.9% of germs" is in a TV ad I see a lot at the moment. Unfortunately, this fails to differentiate between bacteria and viruses. Right now, this matters a lot. Looking at the source, it seems they're actually talking about viruses. I wish they'd made it clearer. I don't blame the IP. The confusion here is coming from academia! HiLo48 (talk) 11:43, 25 April 2020 (UTC)[reply]

The statement by itself is true, whether the microorganisms are bacteria or viruses (see Ultraviolet germicidal irradiation). Both the title of the article and the abstract make abundantly clear that this specific study concerns viruses; the first section of the article also compares bacteria and viruses to clarify the purpose of the study. I cannot agree that in this instance the use of the term "germicide" was sloppy. --Lambiam 15:52, 25 April 2020 (UTC)[reply]

Using the word "germ" at all is sloppy. HiLo48 (talk) 21:01, 25 April 2020 (UTC)[reply]

So the article does not use that term at all. --Lambiam 08:12, 26 April 2020 (UTC)[reply]

As mentioned here: "In a recent study – which looked at whether UVC could be used to disinfect PPE – the authors found that, while it is possible to kill the virus this way, in one experiment it needed the highest exposure out of hundreds of viruses that have been looked at so far. The amount of ultraviolet required varied widely, depending on factors such as the shape and type of material the virus was on....... “UVC is really nasty stuff – you shouldn't be exposed to it,” says Arnold. “It can take hours to get sunburn from UVB, but with UVC it takes seconds. If your eyes are exposed… you know that gritty feeling you get if you look at the sun? It’s like that times 10, just after a few seconds.”" Count Iblis (talk) 19:39, 25 April 2020 (UTC)[reply]

Because there's no significant selection pressure to drive the development of such a trait. Any trait has a cost, taking resources that could be invested in something else. Let's look at the history of life on Earth. There was little life on land for about half of Earth's history, because there was no oxygen in the atmosphere and thus no ozone layer to block high-energy UV from the Sun. Essentially all life was in the ocean. (All life was microscopic as well.) The Great Oxidation Event produced an oxygen atmosphere, which was essential to the development of large organisms. Some organisms have some kind of UV resistance, such as in endospores that some bacteria produce to survive harsh environments. But that gives a good illustration of why such traits are not everywhere. Endospores are "vegetative". They don't move around or "do" anything; the bacteria basically erects a fortress and goes into "hibernation" to try to survive until the environment is more hospitable. Or another good example: human skin color. Humans developed dark skin when our ancestors lost fur, to shield against UV. Then some human populations migrated to higher latitudes and went back to having light skin, since this was not as necessary in environments with less sunlight. In this case there was also selection pressure driving the switch back to the light skin phenotype, as UV is needed for vitamin D production. --47.146.63.87 (talk) 22:17, 25 April 2020 (UTC)[reply]

I disagree with this–as I said above, clearly it's beneficial to at least some viruses to have DNA repair enzymes, as they package enzymes with them inside the virus particle. And bacteria have tons of DNA damage pathways. Blythwood (talk) 01:29, 26 April 2020 (UTC)[reply]

Uh, I don't see how we're in disagreement. Some level of DNA repair is necessary in basically all organisms because otherwise their DNA would turn to mush from just random unwanted chemical reactions, if nothing else. I was just describing why more microbes don't have the ability to withstand prolonged exposure to high amounts of UV. Some do, like radiotrophic fungi. But it's just not that beneficial in most microbial niches. --47.146.63.87 (talk) 01:57, 26 April 2020 (UTC)[reply]

some bacteria have resistance, for example Deinococcus radiodurans about 1000 times as resistant to radiatin than humans. Graeme Bartlett (talk) 10:32, 26 April 2020 (UTC)[reply]

The Great pyramid of Giza: a question to Egyptologists

still pseudoscientific nonsense

The following discussion has been closed. Please do not modify it.

THE GREAT PYRAMID AND THE DIMENSIONS OF THE EARTH Much has been written on the mysteries of the Great pyramid and writers like Graham Hancock have used them to support the idea that a technologically advanced civilization was present on Earth more than 10.000 years ago and, before being wiped out by a cometary impact, left traces of its advanced knowledge, like the Precession of the equinoxes, as a message to successive civilizations, from Egypt to South-America (an alternative is that visiting aliens provided such information). The speculations by Hancock and company did not stand critical scrutiny and have all been shown to be without any foundation. All but one: a relationship between the dimensions of the Great pyramid of Giza and the dimensions of the Earth. This is discussed in one of Hancock’s books (Magicians of the Gods, 2016), where the fact that multiplying perimeter and height of the pyramid by the number 43.200 gives-with an excellent approximation- the dimensions of the Earth’s equatorial circumference and polar radius respectively, is taken as one example of ancient knowledge left for future generations. The Egyptians had no knowledge of the Earth’s dimensions and Precession of the equinoxes (the “magic” number 43.200 is, according to Hancock, related to the phenomenon of Precession of the Earth’s axis), therefore only a civilization with such knowledge could have encoded these data in the pyramid, hence there must have been a very advanced civilization long before the Egyptians. Very advanced indeed: understanding the Precession of the Earth’s axis requires modern astronomy. The pyramid/Earth relation, originally proposed by John Taylor, an engineer with Napoleon’s expedition in Egypt and later by the Astronomer Royal of Scotland Charles Piazzi-Smith in 1864, was based on a suggestion by the astronomer John Greaves in 1706 about the “pyramid inch”, a unit of measure used by the builders of the Great Pyramid, a fact later dismissed by the Egyptologist Flinders Petrie in 1883. We can therefore forget the pyramid inch and the Taylor-Smith theory, and the number 43.200 has of course nothing to do with Precession, all the numbers supposedly related to an ancient knowledge of Precession have been shown to be pure fantasies (see e.g. “Pick a Card, Any Card - How Hancock Finds Precessional Numbers” by John Wall 2005, The Hall of Ma’at on the Internet).

And yet such relation exists, as anyone can find out with simple math using the metric system. The dimensions of the original pyramid (according to Egyptologists) are: perimeter=921.44m, height=146.60m. Multiply by 43.200 and find 39806.208Km and 6333.12Km respectively. Modern measurements give the Earth’s equatorial circumference as 40035.41Km and the polar radius as 6356.988Km. An incredible “coincidence”! The probability that given a man-made structure, any structure, a number can be found such that, if multiplied by the dimensions of the structure, it will reproduce the dimensions of any celestial object, is exceedingly small and the case of the Great pyramid can therefore hardly be attributed to a coincidence. And certainly it cannot be attributed, following Hancock, to the existence of an ancient advanced civilization, the evidence against such hypothesis is overwhelming. A visit by aliens providing mankind with information about Precession and Earth dimensions is a possibility but it has an exceedingly small probability of being true. As I argued in my book “Il mondo dell’improbabile Homo sapiens”(The world of the improbable Homo Sapiens), the probability that there is life elsewhere in the Universe is so close to 1 that we can take it as a certainty, but the probability that a life-form developed somewhere beyond the stage of single-celled organisms is so small that we can take it as null. And single-celled organisms do not study Precession and do not travel to other planets. Sherlock Holmes said: ”When you rule out the impossible, what is left, however improbable, must be the truth”. But what is left? Do Egyptologists have any suggestions for this incredible case? 151.73.116.99 (talk) 16:37, 25 April 2020 (UTC)[reply]

Your numbers are written in a way that is confusing. Is 43.200 in fact 43,200? There was no advanced civilization before Egyptians, there was no aliens. The earth radius was measured by Eratosthenes[21] in 3rd century before CE. No computer was needed AboutFace 22 (talk) 17:43, 25 April 2020 (UTC)[reply]

Note: many countries write one thousand as 1.000 and not 1,000 --OuroborosCobra (talk) 18:19, 25 April 2020 (UTC)[reply]

Yes, but then he should have written 39806.208Km as 39806,208Km AboutFace 22 (talk) 19:22, 25 April 2020 (UTC)[reply]

Not really. While the OP's comments have been nonsense, I don't think it makes sense to make a big deal over a mistake. I think most people with sufficient level of English to be able write a coherent (even if nonsense) paragraph are also aware of the norms for delimiters, and decimal separators for most English speakers and therefore generally use the decimal point as the decimal separator when communicating with generic English speakers to avoid confusion. However if what you're use to the the comma, it's likely fairly easy to make a mistake on occasion. Nil Einne (talk) 18:16, 26 April 2020 (UTC)[reply]

Reply to comments: first comment:True I should have used a coma rather than a dot,but-as stated in the second comment- many countries,including mine,use the dot.Anyway the meaning of numbers should be obvious,everybody knows that the Earth radius is of order 6000Km,coma or dot! Of course there was no advanced civilization and no aliens, this is exactly what is said in my talk!We all know that Eratosthenes measured the Earth's radius but it is irrelevant to my argument, the pyramid was built thousands of years before! The comments are totally irrelevant to my question and so is the general heading "pseudoscientific nonsense".My talk has nothing to do with pyramidology or pseudoscience,all the nonsense by Hancock,Taylor or Piazzi-Smith is clearly criticized and set aside leaving only a "fact":the relation between the dimensions of the pyramid and the Earth's,this can be checked by anyone, it is a mathematical fact with no relation to any pseudoscientific nonsense. I only asked if Egyptologists have any answer for this "fact": where is the pseudoscientific nonsense?151.73.116.99 (talk) 14:41, 26 April 2020 (UTC)[reply]

If you divide something by something you get a number. Here some of the numbers are 43502 (perimeter_p/perimeter_Earth) and 43362 (side_p/r_polar), which are I suppose somewhat close to 43200 if that number meant something. The precession of the Earth number would be the axial tilt, which is quasiperiodic with the period being somewhere around 41,000 years, but motion is irregular and not quite periodic. Judging from WP knowledge, the average period lately has been ~41,040 years. You'd think that if the mystic pyramid builders could measure Earth size and axial tilt period so closely, they would know better than to get it wrong by 6%. And I say that all while shutting an eye to the sheer quantity of ratios, lengths, distances etc. out there, not to mention random pretty numbers like 43200 = 3³40². You can get it a lot closer than 6% by choosing the right measurement (and probably a different pyramid inch). Think of the Ley lines, uncanny arrangements between prehistoric sites in Britain. You'd never expect to be able to fit so many of relatively few objects on a straight line (give or take a few miles to the side) by pure chance, right? Wrong. 93.136.55.42 (talk) 15:41, 26 April 2020 (UTC)[reply]

Your formulation is just another way leading to my question.Is it not strange (very strange) that the ratios of the exact dimensions give very similar numbers? Identical within some approximation and both close to 43200,a number with no particular meaning, certainly not related to the precession of equinoxes. If you repeat your calculation with any other celestial object get very different numbers (for the Moon,for instance, the ratios are 23703 and 11890, quite different!).Only for the Earth these numbers are "almost" identical. I find it very strange and, although I believe that,improbable as it may be, it must be a coincidence with no hidden meaning, I wandered if Egyptologists have any explanation for this. Again:where is the pseudoscientific nonsense?

151.73.116.99 (talk) 20:16, 26 April 2020 (UTC)[reply]

Since the circumference of our planet divided by its radius is close to 2π (within a fraction of 1%), the whole thing amounts to the observation that the ratio height : base-length of the Great Pyramid of Giza, which equals 146.7m/230.34m = 0.6369 (using the data from our article), is approximately equal to 2/π = 0.6366. No need to get any astronomy involved. My money is on this being a coincidence, but should the architect, for whatever reason, have chosen to use the ratio circle-diameter : half-circle-circumference for the pyramid, they surely could have done that to this precision with the means available to them. --Lambiam 04:59, 27 April 2020 (UTC)[reply]

The angle of the Great Pyramid is based on centuries of experimentation by Egyptian architects in determining the angle of repose for such a structure. Calculations involving angles (i.e. trigonometry) frequently have π pop into them somewhere, so it is unremarkable that a well-constructed pyramid at it's ideal angle of repose would end up with π coming out of the ratios somewhere; it doesn't actually require knowledge of π to produce it in a calculation. It pops out of lots of things like this all the time. It just comes from the geometry, and will arise naturally in the ratios of such constructions. I can't be bothered to work out the math, but I've seen enough similar calculations to be entirely unsurprised that the ratio of the base of a well-constructed pyramid to its height would have a factor of π somewhere. --Jayron 32 13:12, 27 April 2020 (UTC)[reply]

The Angle of repose of a granular material depends on its (NOT "it's") density, the surface area and shapes of the particles, and the coefficient of friction of the material. Unless he has access to a reliable formula for calculating the repose angle that Wikipedia lacks, it should surprise an intelligent person if a correct value of π (see link) were found here. DroneB (talk) 15:39, 27 April 2020 (UTC)[reply]

April 26

dish soap as solvent

I overcooked something at dinnertime so there is dried stuff stuck to the bottom of the pot. No big deal, soak it overnight then wash in the morning. Question: would squirting in some dish soap help the stuff dissolve faster? I do that sometimes but it's hard to tell by experiment, without a lot of repeated trials and a controlled amount of overcooking, soak time, etc. All of that defeats the simplicity of the basic plan of not having to pay attention to it while it soaks. Thanks. 2602:24A:DE47:B270:DDD2:63E0:FE3B:596C (talk) 07:34, 26 April 2020 (UTC)[reply]

In the interest of scientific progress you should overcome your aversity to careful experimentation. Now that so many more people have, overnight, become amateur cooks, this will be a great service to humankind. As dish soap serves as a powerful surfactant, I expect it will help to soak and dissolve the starch that serves as a glue, which otherwise might be shielded from the water by a coat of lipids. Using warm water also contributes by liquefying fats and making oils less viscous. For overnight soaking it may make little difference, though. If the bottom stuff is severely burnt and your pot is not made of aluminium, an additional table spoon of baking soda will do wonders. --Lambiam 08:00, 26 April 2020 (UTC)[reply]

In my experience Bio washing powder makes dissolving baked on overcooked food much easier. Soak overnight. YMMV--Phil Holmes (talk) 08:58, 26 April 2020 (UTC)[reply]

Another proved technique is allow a dishwasher tablet to dissolve in the offending pot. Scope for a comparative study perhaps? Alansplodge (talk) 12:13, 26 April 2020 (UTC)[reply]

Just a clarification on terminology: In dish soap, the actual soap stuff (likely something like sodium lauryl sulfate or a similar compound) is a surfactant and detergent and not a solvent itself. The compound by itself is a waxy solid and not particularly good at dissolving anything. What soaps do is they make water a better solvent. The water is still the solvent, the soap just improves water's ability to dissolve things by both breaking up the surface tension of the water (the surfactant action) and by being amphiphilic, which basically means it has an end that 1/2 of it can dissolve in the dirt, and the other half can dissolve in the water, allowing the water to dissolve dirt it otherwise wouldn't very well (the detergent action). The water itself softens the grime; what the soap does is make it easier for the water to do its job. When I soak dishes, I always add a little soap to the water to speed things along. Periodic scrubbing and rinsing is good as well, as you sometimes need to remove the softened layer of gunk to expose more of the gunk to the soapy water. --Jayron 32 13:02, 27 April 2020 (UTC)[reply]

Strains and sequences

Are strains and sequences two different things? I speak in respect of Severe acute respiratory syndrome coronavirus 2. I have heard there are over 6,000 sequences. Is this to do with how DNA reacts to the virus? I assume there are only a handful of known strains? I would appreciate it if someone could help clear this up for me :) Uhooep (talk) 12:21, 26 April 2020 (UTC)[reply]

It is quite possible that 6,000 samples of SARS-CoV-2 have been sequenced. They may be identical to each other or different. But "strain" only refers to a viral population sufficiently different from other viruses of the same species. Ruslik_Zero 13:37, 26 April 2020 (UTC)[reply]

The company deCODE genetics in Iceland is testing large numbers of people, initially only of high-risk cases but later by random sampling (currently 6% of the population), and is sequencing the SARS-CoV-2 genome of every positive test. As of April 14, 2020, they had sequenced SARS-CoV-2 from 643 samples.^[22] They find a high mutation rate which effectively allows them to reconstruct who infected whom. Clustering the collection of genomes into a small number of strains will always have something arbitrary: the choice of when to stop. --Lambiam 04:12, 27 April 2020 (UTC)[reply]

Ringdown and no-hair theorem

"Immediately following the merger, the now single black hole will “ring”. This ringing is damped in the next stage, called the ringdown, by the emission of gravitational waves. The distortions from the spherical shape rapidly reduce until the final stable sphere is present, with a possible slight distortion due to remaining spin." - says our Wikipedia page.

What exactly is this ringdown? Is it a bad choice of words, so that the ringdown is just an echo, like the wobble in the membrane of a drum after the drum is stuck, or do post-merger deformations of (inside??) the black hole produce the waves? If the second, how does it square with the no-hair theorem (which says the black hole is completely described by about a dozen scalars) even if no overtones? 93.136.55.42 (talk) 15:54, 26 April 2020 (UTC)[reply]

This will be investigated by the proposed TianQin (Chinese: 天琴计划) space-borne gravitational-wave observatory consisting of three spacecrafts in Earth orbit. See Constraining modified gravity with ringdown signals: an explicit example, Phys. Rev. D volume=100 issue=8 at=084024, 14 October 2019. DroneB (talk) 17:47, 26 April 2020 (UTC)[reply]

Binary black hole § Ringdown: The article you were reading. Also no-hair theorem. From that article, the no-hair theorem is only conjectured for "stable" black holes. "Unstable" ones, like one immediately after a merger, may have more degrees of freedom. I'm afraid I'm not an expert on general relativity so I'm not sure what is involved in modelling these. Since it's difficult to observe mergers in detail most of this is based on mathematical models. And of course we can't observe anything beyond the event horizon. --47.146.63.87 (talk) 22:41, 26 April 2020 (UTC)[reply]

I would have written the content in the article you(s) have been reading. In the modelling section it becomes clear that what the ringdown is, is some sort of scattering of the gravitational waves from the late inspiral. Either similar to a simple echo, or an echo that has been twisted around by frame dragging by a spinning black hole. Because of the infinite redshift at the event horizon, you are never really going to observe a no-hair simple infinite age blackhole. Instead you are going to see a highly slowed down version of the close to final merger. The modelling can calculate what observers in different reference frames will "experience", but we are interested in the observer at infinity. I think the descriptions of echo are closer to the mark, than a vibrating ellipsoid. Graeme Bartlett (talk) 23:55, 26 April 2020 (UTC)[reply]

I asked an astro professor about something that a long time ago: if you had heavy objects (e.g. a binary star system) moving around inside the event horizon, could you detect that from the outside? He seemed to think yes. 2602:24A:DE47:B270:DDD2:63E0:FE3B:596C (talk) 00:09, 27 April 2020 (UTC)[reply]

well that would be a form of ring down, but you would never see the binary star pass the even horizon. Graeme Bartlett (talk) 12:43, 27 April 2020 (UTC)[reply]

That's pretty much why I'm asking this question, if the ringdown is the "echo" of pre-merger events that's fine, but if it's the echo of post-merger movements inside the event horizon, wouldn't that tell us something about the arrangement of matter inside the horizon? And wouldn't that then tell us something about the arrangement of matter before the merger and/or be some kind of a causality violation? 93.136.46.218 (talk) 15:08, 27 April 2020 (UTC)[reply]

April 27

Is all hypochlorite salts of transition metals are colorless?

I'm don't sure that all hypochlorite salts of transition metals (like Fe(ClO)₃, Cu(ClO)₂, Rh(ClO)₃, Pt(ClO)₄,...) will colorless. So what do you think for the color of them? Thanks for much (Sorry if you don't understand, because my English is not good).--Ccv2020 (talk) 07:02, 27 April 2020 (UTC)[reply]

Might be difficult to make some of those. Adding Fe³⁺ to NaClO solution creates a giant cloud of chlorine gas, as seen in multiple industrial accidents such as [23]. DMacks (talk) 07:19, 27 April 2020 (UTC)[reply]

As noted above, I can't find any evidence the above compounds exist at all. Any reaction that would putatively create them is likely outcompeted by some kind of redox reaction that would reduce the ClO^- to Cl₂. I can't find an MSDS on any of them, which again, is a good sign that they don't exist. I'll repeat what I said last time: just because you can write a correct formula for a compound doesn't mean it can actually exist. Describing the color of a non-existent compound is a futile thing. --Jayron 32 12:53, 27 April 2020 (UTC)[reply]

@@ Line 345: / Line 345: @@
 :::Since the circumference of our planet divided by its radius is close to 2[[Pi|π]] (within a fraction of 1%), the whole thing amounts to the observation that the ratio height : base-length of  the [[Great Pyramid of Giza]], which equals 146.7m/230.34m = 0.6369 (using the data from our article), is approximately equal to 2/π = 0.6366. No need to get any astronomy involved. My money is on this being a coincidence, but should the architect, for whatever reason, have chosen to use the ratio circle-diameter : half-circle-circumference for the pyramid, they surely could have done that to this precision with the means available to them. &nbsp;--[[User talk:Lambiam|Lambiam]] 04:59, 27 April 2020 (UTC)
 :::::The angle of the Great Pyramid is based on centuries of experimentation by Egyptian architects in determining the [[angle of repose]] for such a structure.  Calculations involving angles (i.e. [[trigonometry]]) frequently have π pop into them somewhere, so it is unremarkable that a well-constructed pyramid at it's ideal angle of repose would end up with π coming out of the ratios somewhere; it doesn't actually require knowledge of π to produce it in a calculation.  It pops out of lots of things like this all the time.  It just comes from the geometry, and will arise naturally in the ratios of such constructions.  I can't be bothered to work out the math, but I've seen enough similar calculations to be entirely unsurprised that the ratio of the base of a well-constructed pyramid to its height would have a factor of π somewhere.  --[[User:Jayron32|<span style="color:#009">Jayron</span>]][[User talk:Jayron32|<b style="color:#090">''32''</b>]] 13:12, 27 April 2020 (UTC)
+::::::The [[Angle of repose]] of a granular material depends on its (NOT "it's") density, the surface area and shapes of the particles, and the coefficient of friction of the material. Unless he has access to a reliable formula for calculating the repose angle that Wikipedia lacks, it should surprise an intelligent person if a [[Pi|correct value of π]] (see link) were found here. [[User:DroneB|DroneB]] ([[User talk:DroneB|talk]]) 15:39, 27 April 2020 (UTC)
 = April 26 =