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June 1

Is there a legal/fiscal/cultural reason why fields in Estonia might generally have a grove or orchard in them

(as per [in Estonia#Orchards]) I was wondering why there was a preponderance of trees within (as opposed to on the periphery of) fields in Estonia. I noticed this as I was flying into Talinn. Is this the result of legislation, or culture. Or have I imagined it? Bogger (talk) 17:29, 1 June 2020 (UTC)[reply]

I think you are referring to wooded meadows. Our article is a bit thin, though if you google "wooded meadows Estonia", results such as this and this crop up, which give quite a bit of background general info. PaleCloudedWhite (talk) 06:33, 2 June 2020 (UTC)[reply]

Benevolent virus mutation

I've heard that as epidemics spread viruses often mutate to a less deadly form. I've heard this as an explanation why the death rate in Bergamo was so high (0.57% of everyone) but farther from Italy death rates were lower even when selecting for people with antibodies (0.37% in Heinsberg).

I can understand how this works for highly deadly viruses like ebola, but is this effect really at play for such low mortality viruses as corona? 95.168.122.249 (talk) 17:38, 1 June 2020 (UTC)[reply]

I am pretty sure it applies to all infectious disease, but I am having a hard time believing that we can see the effect over such a short time span. --Guy Macon (talk) 18:19, 1 June 2020 (UTC)[reply]

From the virus' point of view, every new infection is a generation, so it is not a short time span for them. But in this case, a better explanation is the overwhelming of the hospitals in the north of Italy. Abductive (reasoning) 21:32, 7 June 2020 (UTC)[reply]

0.3% of New York City died according to excess death and not everyone caught it while Italy is one of the oldest countries on Earth. The normal amount of death in NYC is surprisingly low actually, only about 158 a day which implies an average death age of 150 years. That's ridiculous so obviously a lot of people just leave before they get very old. Often to Florida. There's probably even a positive balance of trade of people that come to New York City for medical treatment or are sent there from suburban or rural hospitals and die (almost 2/3rds of the metro area lives outside city limits). Considering that New Yorkers die half as much as other first worlders due mostly to low chance of death by old age at the residents' age Bergamo doesn't seem like a freak outlier after all. Sagittarian Milky Way (talk) 20:14, 1 June 2020 (UTC)[reply]

Well, even if a disease doesn't kill you, if it makes you so sick that you avoid others (and they avoid you) it may not have much chance to infect others before your immune system overcomes it. --Khajidha (talk) 14:20, 2 June 2020 (UTC)[reply]

This may be generally true of viral evolution, but in COVID-19, people mostly die two weeks after the virus has been defeated by their immune system, so from the virus' point of view, it is not killing hosts and is therefore not under selection to become less lethal. Abductive (reasoning) 21:35, 7 June 2020 (UTC)[reply]

June 2

Partners

Moved to: WP:RDH #Partners

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

Which articles deal with how humans select romantic partners? Benjamin (talk) 01:12, 2 June 2020 (UTC)[reply]

If you google "wikipedia mate selection", several articles come up, and you could review them. ←Baseball Bugs ^{What's up, Doc?} carrots→ 01:22, 2 June 2020 (UTC)[reply]

Which one in particular? To be clear, I'm asking romantic partners, not sexual reproduction or evolution. Benjamin (talk) 02:46, 2 June 2020 (UTC)[reply]

Wikipedia:Reference desk/Humanities might be better equipped to answer. --OuroborosCobra (talk) 02:55, 2 June 2020 (UTC)[reply]

(Closed & moved to prevent duplicate discussions) 107.15.157.44 (talk) 05:13, 2 June 2020 (UTC)[reply]

List of all 21 Indian cities to run out of groundwater

There are many reports that 21 Indian cities will run out of groundwater in future. But everywhere I could read only Delhi, Mumbai, Chennai, Bengaluru, Hyderabad. I couldn't find the full list of 21 cities. https://www.aljazeera.com/news/2019/06/india-running-water-fast-190620085139572.html — Preceding unsigned comment added by സൂര്യചന്ദ്രൻ ഗ്രഹം (talk • contribs) 04:19, 2 June 2020 (UTC)[reply]

That article and the NDTV one it cites are dated 20 June 2019, and both cite a report by NITI Aayog. I cannot find a reoport on their website on this topic from that approximate time, and the two "Composite Water Management Index" reports I found from any timeframe do not appear to list 21 cities. DMacks (talk) 04:36, 2 June 2020 (UTC)[reply]

Here is the report: [1] (I haven't read it) -- As cited here: Bhasker Tripathi (25 June 2018). "Bengaluru, Delhi, Chennai among 21 cities to run out of groundwater by 2020". Tech2. Technology News, Firstpost. —107.15.157.44 (talk) 09:56, 2 June 2020 (UTC)[reply]

Question: are there any places anywhere in the world that actually have run out of groundwater as opposed to predictions that they are going to run out of groundwater? I don't mean "the old well ran dry but a new, deeper well is supplying groundwater", nor do I mean places that never had any groundwater. I searched and found plenty of places that are depleting their groundwater supplies faster than nature is replenishing them, but I could not find any examples of places that actually ran out of groundwater. I am sure that such places exist. --Guy Macon (talk) 15:25, 2 June 2020 (UTC)[reply]

It may depend on your definition of "run out", but the Australian town of Stanthorpe, Queensland is now fully dependent on water being carted in from outside because it has "run out" of its own. -- Jack of Oz ^{[pleasantries]} 23:25, 2 June 2020 (UTC)[reply]

I searched for reliable sources (as soon as I saw that Daily Mail Link I refused to look at it -- to high a chance that they got most of the story right but added a few lies to make it better clickbait.)

From what I can gather from the other side of the globe,[2] Stanthorpe ran out of water but not groundwater. They were getting water from Storm King Dam, and now they are having to cart water in trucks from Connolly Dam and dump it in Storm King Dam just to keep enough in the bottom so they send it to the town using existing pipes. And they are a couple of years away from emptying Connolly Dam.

The same source says "When the above-ground dams run out of water, the council will have to switch to using bores, which are already under pressure from agricultural and commercial use" (I am assuming the a Bore is what we in California call a well).

Another Australian source[3] says that "Currently the shire is in discussions with the Queensland Government about getting access to the Dalrymple and Cunningham alluvium, underground water sources near Allora north of Stanthorpe." I couldn't find any sources that discuss how much groundwater is in those groundwater sources.

The Guardian has a related story[4] which sort of implies not much water available underground, but they didn't give any actual numbers.

I just hope that I won't do a search a few years from now and see a bunch of "we told you we were going to run out of groundwater and now we have!" stories from around the globe.

Question: when [5] talks about "standpipes" and " Avdata key holders" what are they talking about? Is that a Standpipe (street)? --Guy Macon (talk) 01:29, 3 June 2020 (UTC)[reply]

Probably holders of one of these [6], maybe one specific for the area, not sure [7]. Nil Einne (talk) 09:14, 3 June 2020 (UTC)[reply]

E = hf

Does $E=hf$ apply to all waves, including longitudinal waves like sound, or is it just used to describe electromagnetic waves? --Puzzledvegetable^{Is it teatime already?} 20:17, 2 June 2020 (UTC) + edit--Puzzledvegetable^{Is it teatime already?} 22:58, 2 June 2020 (UTC)[reply]

You probably meant electromagnetic waves. Ruslik_Zero 20:26, 2 June 2020 (UTC)[reply]

Yes, yes I did. Thank you. --Puzzledvegetable^{Is it teatime already?} 22:58, 2 June 2020 (UTC)[reply]

From Photon energy: Photon energy is the energy carried by a single photon... the photon energy equation can be simplified to

E=hf

. Sound waves are not made out of photons. --Guy Macon (talk) 21:18, 2 June 2020 (UTC)[reply]

No, but in some sense they are "made out of" phonons, and from that article it appears to me that the energy associated with a phonon is indeed hf. --Trovatore (talk) 23:09, 2 June 2020 (UTC)[reply]

Not really. Only in solids and a few oddball liquids do phonons even make sense; the phenomenon is nonseniscal in gaseous phases with free movement of particles, such that the movement of a mechanical vibration can be modeled perfectly in a non-quantum way. Phonons really only make sense when there are highly-constrained single-frequency vibrations happening accross chemical bonds, which being composed of electrons, require some quantum explanation. For sound waves moving through air, there's no quantumness to be had. It's entirely a classical phenomenon. --Jayron 32 05:35, 3 June 2020 (UTC)[reply]

Hmm. I am less than entirely persuaded that phonons don't make sense in gases. They might not usually be the most useful description, but that's a separate thing. But I concede it's not really my field.

Just the same, even if you're correct that they don't make sense in gases, the solid-state version is still an example of E=hf being meaningful outside the domain of electromagnetic waves. --Trovatore (talk) 17:50, 5 June 2020 (UTC)[reply]

No, it really only applies to quantum phenomenon. E=hf applies to electromagnetic waves because there is no medium in any real sense, what is vibrating is simply the electromagnetic field, which is just a series of numbers (well, messy numbers, specifically a 4x4 matrix known as the Electromagnetic tensor, but it's still just a complicated number) assigned to points in space, and not a material in any meaningful sense. The energy carried by that vibration in the field is just a function of the frequency of that vibration. It's a simple calculation because it is functionally just a single kind of energy, kinetic energy of the field itself. The energy carried by a sound wave is a fantastically more complicated matter, as it involves the actual motion of actual matter, and matter is WAY messier than a field. Consider that the specific matter itself matters, including which atoms there are, and how they are organized and how they interact with each other and since we now have actual interactions between pieces of matter, now we have to introduce a new term, potential energy and wow does it become a mess. Sound energy has an equation for you to use, but you have a LOT more variables to plug in, because matter is so much more complex than a field. EM fields, by comparison, even with their messy tensor mathematics, are conceptually much easier to reduce to a simple equation, E=hf. The phonon thing described above is a real phenomenon, but it really only manifests itself in some very specific situations; it's an important tool in all sorts of first-principles modeling of important phenomena, but basic sound like "I yell and you hear me" isn't one of them. --Jayron 32 05:51, 3 June 2020 (UTC)[reply]

The equation E = h f applies to all phenomena that exhibit oscillations at a fixed frequency. It is more precisely written as E = (n+1/2) h f, n is the number of quanta, or it refers to the nth excited state of the system and the 1/2 h f for n = 0 is the ground state energy, also called the vacuum energy. The energy contained in a single mode of sound waves, electric circuits like LC circuits are all given by this equation. For example in any electric circuit at room temperature is subject to Johnson–Nyquist noise which is due to the thermal motion of electrons in the circuit. Suppose that you cool the electric circuit to low temperatures to eliminate the noise. The E = n h f law will then become visible in the form of the Planck distribution of the frequency components of the noise. High frequency components of the noise are then cut off. You can then ask of the noise will become zero at absolute zero. The answer is no, because the formula is not actually E = n h f, but E = (n + 1/2) h f and at temperatures so low that the electronic degrees of freedom are all in the ground state, you still have noise due to quantum fluctuations that are present in the ground state. Count Iblis (talk) 13:34, 4 June 2020 (UTC)[reply]

That is true, but it is only strictly true for a portion of the energy of the wave. The problem with mechanical waves, like sound, is that the energy of those waves is dependent on all sorts of messy interactions throughout the medium the wave is traveling in. The reason why we most associate that equation with things like photons is that light has no medium, so its energy is completely described by that equation. A "phonon" in this context, as described above, is basically a way to conceive of the E = hf portion of a mechanical wave energy in crystalline media. It isn't very useful when trying to calculate the total energy of sound, however. --Jayron 32 15:34, 4 June 2020 (UTC)[reply]

June 3

MED: List of diagnoses added to the ICD-11

This may be a big ask, but there must be a list somewhere of new diagnoses for the ICD-11? WHO have finalised the list, but which are new? Amousey (talk) 12:04, 3 June 2020 (UTC)[reply]

You can start with the WHO's Transition Guide, a short book available at zero-cost, that helps organizations transition from older systems to the new ICD-11 system. It contains a few short chapters on what is new and why they justify the changes; and they reference lots of additional process documents to help you navigate the specifics.

I do not think you will find a more compact form that lists what has been added and removed.

I am a computer programmer who is, more recently, a very regular reader of legal and other non-technical documents (not to mention, of course, technical-documents other-than-software-source-code); and my colleagues and I often joke about how wonderful it would be if we could convince other intellectual-communities to adopt something akin to unidiff - but frankly, this kind of compact form just doesn't exist in widespread use outside of the domain of computer-software.

With a little bit of tempered reflection, let me just summarize my remarks by stating for the record: the reason why we won't find a compact listing of additions- and subtractions- is because in these domains, such a format would be a misrepresentation. That is why the users of such systems, like ICD-11, publish long-form books and guides, and do not publish "code patches."

At the same time - nothing, other than intellectual integrity, actually precludes an enthusiastic researcher from dumping the entire ICD-10 and ICD-11 content to text, and running "diff"...

Nimur (talk) 17:17, 3 June 2020 (UTC)[reply]

June 4

Space X spacesuits

Why do the Space X dragon crew need a spacesuit during launch and docking but not for the phase in between? I assume it’s to do with cabin pressurisation. Clover345 (talk) 16:53, 4 June 2020 (UTC)[reply]

It isn't the same spacesuit they would wear during extravehicular activity; it's a special suit designed only for launch and re-entry portions of the flight. I can't find a Wikipedia article on the current suits, but the previous suits, known as "pumpkin suits" for their orange color, were known as the Advanced Crew Escape Suit (1990s and 2000s) and the Launch Entry Suit (1980s-1990s). The Russian version is known as the Sokol space suit. These are designed to protect the crew in case of accidental de-pressurization during launch and re-entry. The reason for their use isn't because there's anything wrong with the air in the cabin during those times, normally. Hypothetically, they could breath in the cabin normally during those times. They are designed as emergency suits in case cabin pressure is lost during the extremely violent launch and re-entry phases of the mission. If cabin pressure were suddenly lost, and they didn't have the suits on, they would asphyxiate; under the high-g-force periods of launch and re-entry, they are strapped in to their chairs anyways, so they couldn't get out and put one on. During normal orbital flight, 1) there is basically no real stresses on the vehicle to speak of, so there's much less chance of something going wrong and 2) even if it did, the astronauts aren't strapped in to chairs and could get into their emergency suits as needed. During launch and re-entry, you wear your emergency suit because you can't get to it if you needed it. --Jayron 32 17:33, 4 June 2020 (UTC)[reply]

You need to wear safety gear when something exciting might happen. During take off you should wear a helmet. When you might bump into a space station you should gear up. Between those two, when you are just coasting, it is more comfortable to wear a T-shirt and have a nap. 85.76.104.122 (talk) 17:39, 4 June 2020 (UTC)[reply]

This is not specific to Dragon. It's the same in Soyuz and previously Shuttle and I think Apollo and some of the Gemini flights. The reason is that not much is expected to go wrong when just coasting and as spacesuits are not very comfortable, the astronauts take them off. During launch, docking, undocking and landing, more can go wrong. A leak may appear during ascent (Challenger, although that wasn't survivable anyway), the ship can collide with the space station (Progress M-34), a valve may open prematurely (Soyuz 11), all of which may lead to depressurisation of the spacecraft. So they wear spacesuits just in case during those manoeuvres. If nothing goes wrong, the spacecraft remains pressurised, for modern spacecraft at normal atmospheric pressure. PiusImpavidus (talk) 17:49, 4 June 2020 (UTC)[reply]

Wooden vs. rubber bullets

I wonder what the material difference is? I first heard about the existence of wooden bullets a week ago in conjunction with the current disturbances. Before it had always been - rubber bullets. Are they more effective? Thanks, - AboutFace 22 (talk) 18:49, 4 June 2020 (UTC)[reply]

Effective at what? Putting eyes out?[8] ←Baseball Bugs ^{What's up, Doc?} carrots→ 18:57, 4 June 2020 (UTC)[reply]

@AboutFace 22: there are articles on these: Rubber bullet and Wooden bullet. The latter is short but it does mention it is intended to inflict Pain_compliance. RudolfRed (talk) 21:02, 4 June 2020 (UTC)[reply]

Note that although the media often talk about rubber bullets, as I understand it in reality nowadays plastic bullets are very common, potentially more common at least in a number of countries. See the above linked articles and also plastic bullet along with [9] [10] [11] [12] [13]. Find good stats on this seems to be difficult since it isn't always clear when someone calls something a "rubber bullet" whether these are really rubber bullets (i.e. partly or completely made of something which can reasonably be called rubber natural or synthetic) or instead something which can reasonably be called "plastic" but not rubber. Nil Einne (talk) 22:16, 4 June 2020 (UTC)[reply]

Why don't they use potato cannons? Firing spuds is better for the environment. --Lambiam 07:27, 5 June 2020 (UTC)[reply]

Because the weapons need to sit in the boot of a police cruiser for years, but be ready for instant use if needed. The ammunition inside a a loaded potato cannon would rot. --Guy Macon (talk) 11:43, 5 June 2020 (UTC)[reply]

In the 1960s, rotten fruits were apparently a favorite hand-thrown item between groups of counter-protesters. But that's definitely a different tactic than trying to have quality-controlled ammo for firearms-type use. DMacks (talk) 14:38, 5 June 2020 (UTC)[reply]

Fruit-throwing has a long history as a method of assault. --47.146.63.87 (talk) 04:36, 6 June 2020 (UTC)[reply]

"Protesters in Columbus, Ohio reported having been shot with wooden bullets by police forces. Images online showed wooden dowel-shaped rods sliced into small, bullet-sized projectiles. The Columbus Police Department did not respond to requests for comment". Factbox: What U.S. police are shooting at protesters from Reuters. Alansplodge (talk) 11:36, 5 June 2020 (UTC)[reply]

And of course we believe everything protesters report, right? --15:22, 5 June 2020 (UTC)

Multiple news sources have reported on this (potentially lethal) use of wooden bullets.^[14][15][16] --Lambiam 11:59, 6 June 2020 (UTC)[reply]

As opposed to believing everything the cops report? Check the posted link. ←Baseball Bugs ^{What's up, Doc?} carrots→ 16:06, 5 June 2020 (UTC)[reply]

You know better than that. The fact that protestors sometimes lie does not change the fact that police officers sometimes lie.

I did some more research. Most police supply vendors carry less-lethal ammunition using foam, rubber, gel, beanbags, etc., but no wood projectiles, but I found one that does:

https://www.defense-technology.com/products/impact-munitions/

--Guy Macon (talk) 20:46, 5 June 2020 (UTC)[reply]

An image of those used by the Columbus police matches the one on the website of the Safariland Group (mission: "Together, We Save Lives™"). --Lambiam 12:36, 6 June 2020 (UTC)[reply]

Well it's not terribly hard to slice up some wooden dowels, which are produced to standard dimensions and can be found at any hardware store. --47.146.63.87 (talk) 04:36, 6 June 2020 (UTC)[reply]

Yes but you have to shoot them from a shotgun or a specialised projector, so I imagine that you would want a round that was specifically made for the purpose rather than something knocked-up in a garden shed. Bear in mind that these things can cause "death, injury and disability". Alansplodge (talk) 12:09, 6 June 2020 (UTC)[reply]

My search found no 12 gauge wooden projectiles. The ones I found use launchers like these: [ https://www.defense-technology.com/ShotgunTradeIn.html ] --Guy Macon (talk) 15:45, 6 June 2020 (UTC)[reply]

Thanks, you're right, I couldn't find any either by searching for 18.5 mm (12-guage diameter). The projectiles in your link above are 40 mm which is the NATO standard size for a grenade launcher - the British Army used to use the M79 grenade launcher for their plastic baton rounds during The Troubles. A more recent device is the Heckler & Koch HK69A1, "United States: Used by various police agencies". Alansplodge (talk) 12:39, 7 June 2020 (UTC)[reply]

Human livers now synthesized in rats.

Greetings!

I've been sporadically following the advancing of tissue engineering, and for the longest time, it seemed that only simple tissues such as skin, bone, and cartilage had been successfully synthesized. The other day, however, the online magazine Popular Mechanics [17] reported that a research team has successfully implanted complete (albeit miniature) human livers, synthesized from the genes of donated human skin cells, inside of laboratory rats.

As I apprehend it, the liver is by far the most complicated and sophisticated organ in the human body, owing to its myriad physiological functions and unique regeneration ability. My question thus is as follows:

Will it now become easier for tissue engineers to replicate simpler human organs such as the kidney, heart, stomach, lung, and pancreas?

--Thank You!

Pine (talk) 19:10, 4 June 2020 (UTC)[reply]

Not an answer to your question, but I have to (violently) disagree with your statement that the liver is the most complicated organ in the body. While the liver is more complicated than say skin, it is nowhere near as complicated as the brain. (Disclaimer: I am a neurobiologist). Also, the livers were grown from cells (specifically iPSC) from human skin, not genes. Your actual question is probably an issue of WP:CBALL. Having said that, I have seen cultured human heart cells beating in a dish, and it's always a weird sight. Fgf10 (talk) 07:15, 5 June 2020 (UTC)[reply]

You are essentially asking for speculation, something we do not engage in. Nevertheless, it is obvious that different organs present their own, different challenges. For example, while the large-scale anatomic arrangement is not relevant for the functioning of a liver, it is essential for a working heart. How does one obtain an extracellular scaffold for a human heart? Not from a rat heart, but perhaps from a pig. Or can ways be developed to 3D-print one? Lab-growing a mini pancreas seems at the moment more in reach. The most interesting part of this research may be the successful application of techniques to differentiate induced pluripotent stem cells into various cell types, building on earlier work. Using this to create a functioning mini liver, while a tremendous feat, is mostly a proof of concept. The research suggests a way forward, but the difficulties remain formidable, and it is not clear to what extent this generalizes to other organs. BTW, the title of this thread is misleading; the livers were grown in vitro, not in rats. --Lambiam 07:20, 5 June 2020 (UTC)[reply]

Thank you both for your quick—and very learned—replies!

I apologize for my ignorance and impetuosity, but I tend to get rather excited upon witnessing such scientific advancement!

Pine (talk) 19:45, 5 June 2020 (UTC)[reply]

Resolved

June 5

Oxygen in photosynthesis

In the 3rd sentence of the photosynthesis article, it states that: "In most cases, oxygen is also released as a waste product." I was wondering, in a broad sense, what that means. In which cases does this not occur? My 9th grade daughter learning bio asked me this question and I didn't know what it could be. Thanks! DRosenbach ^{(Talk | Contribs)} 00:09, 5 June 2020 (UTC)[reply]

Possibly referring to plants that use close their stomata in daytime and use CAM photosynthesis. Conditions might allow them to use all self-produced oxygen in respiration while releasing little. Rmhermen (talk) 01:02, 5 June 2020 (UTC)[reply]

High school bio teacher chiming in. Even with CAM, oxygen is still produced as a waste product, because the light reaction is where oxygen is produced as the product due to photolysis, while CAM only changes the particulars of the carbon fixation pathway. Rather, this statement is a reference to anoxygenic photosynthesis (photosynthesis that does not produce oxygen), which some bacteria are able to perform. The vast majority of organisms today, however, produce oxygen during photosynthesis. bibliomaniac 1 5 01:16, 5 June 2020 (UTC)[reply]

Thanks to both of you! DRosenbach ^{(Talk | Contribs)} 21:36, 5 June 2020 (UTC)[reply]

Yeah, bacteria are insanely varied and do all kinds of things other organisms don't. For instance they and the similar archaea are the only organisms that produce Vitamin B12; everything that needs it as a vitamin gets it directly or indirectly from them (except if it's synthetic, since we clever monkeys have figured out how to brew it ourselves). When you see a statement about biology that says something like "in most cases", the exceptions are most likely bacteria and/or archaea. --47.146.63.87 (talk) 04:30, 6 June 2020 (UTC)[reply]

Resolved

June 6

Core (geology)

What does core mean in the context of a syncline as in "the core of the syncline"? Core (geology) is no help, that redirects to something completely different. SpinningSpark 12:44, 6 June 2020 (UTC)[reply]

It means the "central part", which is one of the dictionary meanings of core e.g. wikt:Core.Mikenorton (talk) 12:56, 6 June 2020 (UTC)[reply]

I think you probably meant wikt:core, Wikitionary pages are case senstitive. But that's still not a very helpful page, none of the meanings are specific to structural geology and I'm still unclear. "Central part" could mean towards the bottom of the syncline "valley", or it could mean towards the centre of the bedding. Or it could be used in a non-technical sense without a specific meaning. SpinningSpark 16:01, 6 June 2020 (UTC)[reply]

A quick google gave [18]. Bazza (talk) 16:56, 6 June 2020 (UTC)[reply]

Which doesn't actually define it. However, if the youngest rocks are on top, then it has to be the part near the surface -- "towards the bottom of the syncline valley" as Spinningspark says. If you follow the link to "anticline" you see that in an anticline the "core" is on the bottom; so in general it's the part of the formation nearest the center defined by the concentric arcs. But don't follow the link to "core", which gives three definitions and none of them are relevant to synclines! --76.71.5.208 (talk) 22:35, 6 June 2020 (UTC)[reply]

In case of an antiformal syncline, the youngest layer is at the bottom. If you think of the system of layers being locally folded around an imaginary cylinder, then the core is the layer nearest to the cylinder. This works for synformal and antiformal synclines and anticlines. --Lambiam 15:16, 7 June 2020 (UTC)[reply]

Having another go, the core of any fold is the part closest to the fold's axis, which is the central part of the structure - there is no special meaning here. I note that the oilfield glossary page linked above contains an internal link to "core", which doesn't even mention folding when you follow it. We should probably at least mention fold cores in the fold (geology) article. Mikenorton (talk) 20:52, 7 June 2020 (UTC)[reply]

I created a redirect: core (anticline). Ruslik_Zero 05:05, 8 June 2020 (UTC)[reply]

(a) The term applies as well to synclines. (b ) The target of the redirect, Anticline, uses the term but does not explain it. --Lambiam 06:47, 8 June 2020 (UTC)[reply]

It is interesting that our anticline article says "...towards the core and uplifted center..." as if the writer believes these are two different things. SpinningSpark 07:12, 8 June 2020 (UTC)[reply]

June 7

Mothballs

Our article on Mothball says:

"Naphthalene and 1,4-dichlorobenzene should not be used together because the mixture may cause damage to items being preserved.^[1]:

References

^ "Collecting and Preserving Insects and Mites: Tools and Techniques". United States Department of Agriculture - Agricultural Research Service. Retrieved June 26, 2011.

That page does not exist but the wayback machine has a copy at [19] which says

"Two of the most widely used fumigants are paradichlorobenzene (PDB) and naphthalene, both of which are obtainable in balls or flakes. Never mix PDB with naphthalene as they react chemically and produce a liquid that may damage the collection."

Is this an urban myth? I just happen to have some of both kinds of mothballs, so I put one of each in a small glass jar. I am not seeing any liquid. I also would like to know what the liquid that supposedly forms is. What is the chemistry of the reaction?

I am hoping to find a better citation that explains the chemistry involved so I can edit the page and add those details. --Guy Macon (talk) 15:11, 7 June 2020 (UTC)[reply]

If said adverse effect exists, then the advice given here is particularly unsound. --Lambiam 15:29, 7 June 2020 (UTC)[reply]

Even if they don't react chemically (forming new chemicals), they would form a liquid together due to melting-point depression. The eutectic mixtures have mp well below room temperature (see doi:10.1016/j.jct.2008.10.005). These liquids could dissolve paint, and seep into objects, stain or alter other physical properties. DMacks (talk) 22:55, 7 June 2020 (UTC)[reply]

Correction...p-DCB is the one DCB isomer whose eutectic with naphthalene is solid rather than liquid at coolish RT...thanks Guy for pulling out the data values. DMacks (talk) 04:52, 8 June 2020 (UTC)[reply]

Our article defines a "eutectic system" as having a lower melting point than the constituents, but from a cursory examination it appears to me that the characteristic is not that the melting point is lower, but that the components melt (and on cooling solidify) together at the same temperature. Perhaps we should use a more recent source than one from 1884 (although this may be the coining publication). --Lambiam 06:39, 8 June 2020 (UTC)[reply]

That explains the lack of liquid in my mothballs-in-a-jar experiment. I doubt that the mixture is just right to be eutectic.

Please tell me if I made a mistake in the following:

Naphthalene = Freezing point at 351.3K/78.2C/172.8F) (Naptha mothballs)
p-dichlorobenzene/1,4-Dichlorobenzene = Freezing point at 326.6K/53.45C/128.21F (Para mothballs)
m-dichlorobenzene/1,3-Dichlorobenzene = Freezing point at 248K/-25.15C/-13.27F
o-dichlorobenzene/1,2-Dichlorobenzene = Freezing point at 256.12K/-17.03C/1.346F
naphthalene + p-dichlorobenzene = eutectic point at 302.85K/29.7C/85.46F (Para + Naptha mothballs)
naphthalene + m-dichlorobenzene = eutectic point at 244.85K/-28.3C/-18.94F
naphthalene + o-dichlorobenzene = Incongruent melting with eutectic point at 232.55K/-28.3C/-18.94F and peritectic point at 250.15K/-23C/-9.4F

Note: for substances that have different melting points and freezing points I listed freezing. That's the temperature at which you can be sure that no liquid forms to damage things.

So,

Napthalene mothballs are solid below 78C/172F
Para-dichlorobenzene mothballs are solid below 53C/128F
Just the right mix of Para and Naptha gas is solid below 29C/85F

Those are all pretty low temperatures for something that might be used in a trunk stored in a hot attic.

Anyone who has used them knows that para balls fill the space with gas quicker and disapear sooner than naptha balls. So if you mix them, at first para gas dominates and later naptha gas dominates after the para balls disappear. Somewhere in between would come the moment when they are eutectic.

Final question: clearly both kinds of solid mothballs sublimate gas at far below the listed freezing point. And I noticed that a glass jar of para mothballs I stored in a hot garage has crystals on the glass wall, leading me to believe that at saturation it can go back from gas to solid without forming a liquid.

Clearly if the balls melt that could cause liquid damage. But how do I calculate the points at which para gas, naptha gas, and para plus naptha gas that came from solid balls condense into liquid? --Guy Macon (talk) 02:18, 8 June 2020 (UTC)[reply]

For a mixture's gas/liquid change, you might have to consider azeotrope effects. DMacks (talk) 04:09, 9 June 2020 (UTC)[reply]

This is a bit of a tangent but I have no trouble believing that as a generic statement, though of course better references are always good. Looking into historical preservation methods might be fruitful even if they don't focus on mothballs specifically. Preserving things like paper long-term is quite tricky as many things will slowly react with paper/ink and degrade it over time, especially if it's not archival paper to begin with. --47.146.63.87 (talk) 16:45, 8 June 2020 (UTC)[reply]

June 8

Dagga

Dagga is the natural form of Cannabis most often sold in Southern Africa and is not genetically modified. It is commonly known that when this is smoked it can often not have any effect at all on the first occasion. I would like to know why this is. I am not sure if this is the case with the ubiquitous European hydroponic equivalent. Why would this substance not have an effect on the subject when used for the first time? Thank you — Preceding unsigned comment added by 109.151.74.96 (talk) 10:51, 8 June 2020 (UTC)[reply]

Honestly, my guess is more that this is rumor and urban legend than any basis in fact. There is no reason that THC would be ineffective on first use. Certainly other compounds can alter the effect of THC, including other cannabinoids, but those would always be present or not in dagga, with no specific relationship to first use. More likely is that people consume it differently on first use. Perhaps, out of anxiety of trying something new, they smoke or consume a smaller amount on their first try, and just don't get enough to notice the high. Then, subsequently, they use more. --OuroborosCobra (talk) 14:44, 8 June 2020 (UTC)[reply]

Whether you're getting high or not, inhaling smoke cannot be good for your health, and that definitely qualifies as "having an effect". ←Baseball Bugs ^{What's up, Doc?} carrots→ 16:26, 8 June 2020 (UTC)[reply]

That's a bit off topic... --OuroborosCobra (talk) 17:39, 8 June 2020 (UTC)[reply]

The OP said it first. ←Baseball Bugs ^{What's up, Doc?} carrots→ 20:05, 8 June 2020 (UTC)[reply]

If it has little perceivable effect that's most likely because it's low-quality "ditch weed" with little-to-no psychoactive ingredients. I'm not aware of any genetically modified cannabis in cultivation outside of a lab, so I'm not sure why you mentioned that. Hydroponics is something totally different: just growing plants in water instead of soil. --47.146.63.87 (talk) 16:51, 8 June 2020 (UTC)[reply]

Depends on what one means by "genetically modified." Certainly selective breading has resulted in specific strains of cannabis with desired qualities. --OuroborosCobra (talk) 17:39, 8 June 2020 (UTC)[reply]

(EC) According to cannabis, The genus is widely accepted as being indigenous to and originating from Central Asia, with some researchers also including upper South Asia in its origin.[7][8] so anything in Southern Africa was undoubtedly introduced by humans likely after significant cultivation and domestication. As those previous articles and others like History of cannabis, Cannabis indica, Cannabis sativa, Cannabis ruderalis and Hemp mention, cannabis has been cultivated for a long time for a variety of so much so it's difficult to know whether to recognise it as one species or 3 or what. Despite most of this happening long before there was any real understanding of genetics, as with most domestications, the modern cannabis plant has undoubtedly undergone a lot of artificial selection. Because of the different uses, the artificial selection may have been in different directions in different cases. I mention this because your first sentence leads me to believe you may be under the impression that dagga is are varieties of cannabis which are largely untouched by human influence when they're almost definitely not. If I'm mistaken I apologise. As for the other issue, I agree with other respondents that this sounds like some probable combination of urban legend and low potency cannabis. Especially given that if people are expecting something, and then don't experience, they may ask or find out what to expect before the second time and people by be more cautious the first time afraid of a drastic effect. If you are comparing to some strain you encountered sold for recreational use especially in a fairly competitive market place, bear in mind that while we could do a lot before, modern understanding and testing methods has greatly increased what we can achieve. Nil Einne (talk) 17:44, 8 June 2020 (UTC)[reply]

Xylem solute composition

Is there any way to find out what the solution in a plants xylem is composed of? I would be happy about any kind of example. Greetings, 2003:C3:EF37:FB91:D4A5:6933:7A48:1CAF (talk) 22:06, 8 June 2020 (UTC)[reply]

There are lots of ways. An entire branch of chemistry, analytical chemistry, is devoted to things like identifying unknown substances and the quantitative composition of an unknown sample. --OuroborosCobra (talk) 22:28, 8 June 2020 (UTC)[reply]

Our "xylem" mentions the general categories of chemicals, and links to the "sap" article for more information. DMacks (talk) 04:07, 9 June 2020 (UTC)[reply]

Weird sound phenomenon

You have a room with people packed like sardines, all holding identical mono speakers close to their chests, as omnidirectional a small speaker design as practicable. A synchronising radio signal starts playback of the same file on the same microsecond — a simple perfect file of a sine wave which goes from zero to 80 decibels at the rate of say 10 decibels per second then the file instantly ends. How long can you make the delay between time of the volume peak at the speakers and time of the volume peak at some specific speaker holder's ears (average the ears or whatever physics model most resembles what the mind hears) with tricks like constructive or destructive interference and giving the room a very creative shape? Max crowd size 10,000 adults.Sagittarian Milky Way (talk) 23:51, 8 June 2020 (UTC)[reply]

This sounds a bit artificial. But if your sine wave frequency is low enough you could treat this a a phased array that does not end up with grating lobes. So all the speakers are in a plane, that you could approximate by a plane source n(Ie one giant flat speaker). At a far distance the sound would reinforce strongly perpendicularly to the plane - ie vertically. The ear would be in the near field, but random phase difference from speakers significantly away would cancel, and most sound at the ear could come from the closest speaker. So your delay would be due to the speed of sound from chest to ears. But you will also get a big echo off the ground. (And if in a room the ceiling too). Graeme Bartlett (talk) 05:12, 9 June 2020 (UTC)[reply]

The sound scattering and absorption by the sardines should mean that the contribution of the ground reflection to the sound experience is negligible except from the very close vicinity. The ceiling could be made to be very non-reflective, like is done when soundproofing audio recording rooms. --Lambiam 06:44, 9 June 2020 (UTC)[reply]

What is the actual problem you are trying to solve? I for one think you are not actually planning to have a very creatively shaped venue constructed that will hold a 10,000 adult audience who will all be equipped with a chest-mounted omni-directional speaker. --Lambiam 06:44, 9 June 2020 (UTC)[reply]

No practical implications, I had a dream that you could make a delay a large fraction of the time sound needs to cross the room and was wondering if this was bullshit. Sagittarian Milky Way (talk) 09:26, 9 June 2020 (UTC)[reply]

Retrospective vs prospective Contact tracing

What is the difference between retrospective and prospective contact tracing. And what are the pros and cons of each? Does one tend to be used over the other for certain types of infectious disease? Clover345 (talk) 13:27, 9 June 2020 (UTC)[reply]

[1] "Collecting and Preserving Insects and Mites: Tools and Techniques". United States Department of Agriculture - Agricultural Research Service. Retrieved June 26, 2011.

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