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December 13

What is the most iconic tornado photo

December 15

help to identify File:Possible Polygala myrtifolia in New South Wales Australia.jpg

Did I get species right? Thanks. Gryllida (talk, e-mail) 06:56, 15 December 2024 (UTC)

related: https://species.wikimedia.org/Wikispecies:Village_Pump#help_to_identify_species Gryllida (talk, e-mail) 06:57, 15 December 2024 (UTC)

FWIW, I can't detect any visible differences between the plant in this photo and the ones illustrated in the species and the genus articles. However, the latter makes it clear that Polygala is a large genus, and is cultivated, with hybrids, so it's possible that this one could be a close relative that differs in ways not visible here, such as in the bark or roots. That may or may not matter for your purposes. {The poster formerly known as 87.81.230.195} 94.1.223.204 (talk) 10:11, 15 December 2024 (UTC)

How to address changes to taxonomy

Hi all, I am a biology student brand new to wiki editing who is interested in cleaning up small articles/stubs for less known taxa. One that I've encountered is a mushroom that occurs in the pacific northwest (Fomitopsis ochracea). The article mentions that this fungus is occasionally mistaken for another fungus, Fomitopsis pinicola.

However, the issue I've run into is that F. pinicola used to be considered a single species found around the world, but relatively recently was split into a few different species. The original name was given to the one that occurs in Europe, and the one in the pacific northwest (and thus could be mistaken for F. ochracea) was given the name Fomitopsis mounceae.

The wiki page says

Historically, this fungus has been misidentified as F. pinicola. When both species are immature, they can look very similar, but can be distinguished by lighting a match next to the surface of the fungus. F. pinicola will boil and melt in heat, while F. ochracea will not.

Since the source says pinicola (as likely do most/all other sources of this info given the change was so recent), and since technically it's true that they used to be mistaken for it... what would be the most appropriate way to modernize that section?

My questions are: Should I replace F. pinicola with F. mounceae? Or is that wrong because the source doesn't refer to it by that name? Would it be better to write something like (now known as/considered F. mounceae) next to the first mention of the species? Or is that a poor choice because it implies all the members of F. pinicola were renamed F. mounceae?

Any advice on how to go about updating this section is incredibly appreciated
TheCoccomycesGang (talk) 10:21, 15 December 2024 (UTC)

First, take these sorts of questions to the relevant Wikiproject, in this case Misplaced Pages talk:WikiProject Fungi. I am not as familiar with the consensus at WP:FUNGI, but it seems like they defer to Species Fungorium/Index Fungorium and Mycobank to decide. Those sources presently seem to consider Fomitopsis pinicola a good species. Also, be careful about "replacing", there are rules to ensure the continuity of the article history. By the way, there is a hilarious but unencyclopedic/copyvio recipe appended to the Fomitopsis mounceae article. Abductive (reasoning) 11:09, 15 December 2024 (UTC)

Thanks for the tips, I didn't know about projects so I'll go read up on that. And thanks for the warnings about replacing things. I've been reading a lot of help pages, but I'm still in the process of learning the all conventions and what mechanics break if you do things the wrong way.

I actually saw the recipe ages ago before I made my account and completely forgot about it... it was one of many things that prompted me to get into wiki editing. TheCoccomycesGang (talk) 23:12, 15 December 2024 (UTC)

Does stopping masturbation lead to sperm DNA damage?

I'm looking for information on the potential link between the frequency of ejaculation (specifically through masturbation) and sperm DNA damage. I've come across some conflicting information and would appreciate it if someone could point me towards reliable scientific studies or reviews that address this topic.

Specifically, I'm interested in whether prolonged periods of abstinence from ejaculation might have any negative effects on sperm DNA integrity. Any insights or links to relevant research would be greatly appreciated. HarryOrange (talk) 17:08, 15 December 2024 (UTC)

Only males may abstain from sperm-releasing Masturbation that serves to flush the genital tract of old sperm that in any case will eventually dissipate. No causal relationship between masturbation and any form of mental or physical disorder has been found but abstinence may be thought or taught to increase the chance of wanted conception during subsequent intercourse. Philvoids (talk) 00:51, 16 December 2024 (UTC)

There's many rumors about that topic. One is that not ejaculating frequently increases the risk of developing prostate cancer. Abductive (reasoning) 01:02, 16 December 2024 (UTC)

Nothing really conclusive but there's some evidence that short periods are associated with lower DNA fragmentation, see

• Du, Chengchao; Li, Yi; Yin, Chongyang; Luo, Xuefeng; Pan, Xiangcheng (10 January 2024). "Association of abstinence time with semen quality and fertility outcomes: a systematic review and dose–response meta‐analysis". Andrology. 12 (6): 1224–1235. doi:10.1111/andr.13583. ISSN 2047-2919.
• Hanson, Brent M.; Aston, Kenneth I.; Jenkins, Tim G.; Carrell, Douglas T.; Hotaling, James M. (16 November 2017). "The impact of ejaculatory abstinence on semen analysis parameters: a systematic review". Journal of Assisted Reproduction and Genetics. 35 (2): 213. doi:10.1007/s10815-017-1086-0. ISSN 2047-2919. PMC 5845044. PMID 29143943.
• Ayad, Bashir M.; Horst, Gerhard Van der; Plessis, Stefan S. Du; Carrell, Douglas T.; Hotaling, James M. (14 October 2017). "Revisiting The Relationship between The Ejaculatory Abstinence Period and Semen Characteristics". International Journal of Fertility & Sterility. 11 (4): 238. doi:10.22074/ijfs.2018.5192. ISSN 2047-2919. PMC 5641453. PMID 29043697.

for example. Alpha3031 (t • c) 02:12, 16 December 2024 (UTC)

Mature sperm cells do not have DNA repair capability. Inevitably, as sperm cells get older, they will naturally and unavoidably be subject to more and more DNA damage. Obviously, freshly produced spermatozoa will, on average, have less DNA damage. It is reasonable to assume that the expected amount of damage is proportional to the age of the cells, which is consistent with what studies appear to find. Also, obviously, the more the damage is to a spermatozoon fertilizing an oocyte, the larger the likelihood that the DNA repair in the resulting zygote, which does have DNA repair capability, will be incomplete. The studies I've looked at did not allow me to assess how much this is of practical significance.  --Lambiam 09:40, 16 December 2024 (UTC)

December 16

Abelian sandpile model

Thanks to those who answered my last question, I think it should be added to a disambiguation page. If anyone wants to help me write that, reach out.

A sandpile seems disorganized and inert, but these are critically self-organizing. Do the frequency and size of disturbances on sand dunes and snowy peaks follow power law distribution? Gongula Spring (talk) 01:18, 16 December 2024 (UTC)

Shouldn't this be at the Math Desk? Abductive (reasoning) 05:12, 16 December 2024 (UTC)

If the question is not about the model mentioned in the heading but about the physical properties of sand dunes and snowy peaks, this here is the right section of the Reference desk.  --Lambiam 08:51, 16 December 2024 (UTC)

I await a non-mathematical answer. Abductive (reasoning) 09:23, 16 December 2024 (UTC)

It depends is probably a fairly reasonable non-mathematical answer for these kinds of systems. For sand dunes anyway, sometimes avalanche frequency is irregular and the size distribution follows a power law, and sometimes it's close to periodic and the avalanches span the whole system. It seems there are multiple regimes, and these kinds of systems switch between them. Sean.hoyland (talk) 09:35, 16 December 2024 (UTC)

Thank you! I'm impressed this seems so casual, but surely you read this somewhere that might have a URL?

Gongula Spring (talk) 22:29, 19 December 2024 (UTC)

Hi, this is an interesting and somewhat open question! A lot of work is done on these models but much less on careful analyses of real dunes. I did find this dissertation that is freely accessible and describes some physical experiments and how well they fit various models. The general answer seems to be that the power law models are highly idealized, and determining the degree to which any real system's behavior is predicted by the model ahead of time is very difficult. Update: This is one of the earlier important works on the topic and it does include discussion of how well the model fits experiments.SemanticMantis (talk) 17:21, 16 December 2024 (UTC)

That dissertation is great!

Gongula Spring (talk) 22:30, 19 December 2024 (UTC)

Polar night

Are there any common or scientific names for types of polar night? The types that I use are:

• polar night - meaning a day when sun's altitude remains below horizon entire day (there is no daylight at solar noon, only civil twilight), occurring poleward from 67°24′ north or south
• civil polar night - meaning a day when sun's altitude remains below -6° entire day (there is no civil twilight at solar noon, only nautical twilight), occurring poleward from 72°34′ north or south
• nautical polar night - meaning a day when sun's altitude remains below -12° entire day (there is no nautical twilight at solar noon, only astronomical twilight), occurring poleward from 78°34′ north or south
• astronomical polar night - meaning a day when sun's altitude remains below -18° entire day (there is no astronomical twilight at solar noon, only night), occurring poleward from 84°34′ north or south

These names were changed on Polar night article, and I wnat to know whether these named I listed are in use in any scientific papers, or in common language. (And I posted that question here and not in language desk because I think that this is not related to language very tightly.) --40bus (talk) 18:56, 16 December 2024 (UTC)

Some definitions at The Polar Night (1996) from the Aurora Research Institute. Alansplodge (talk) 22:55, 16 December 2024 (UTC)

These seem to be generalizable as: X polar night is a period, lasting not less than 24 hours, during which the sun remains below the horizon and there is no X twilight. The specific definitions depend then on the specific definitions of civil/nautical/astronomical twilight. These can be defined with a subjective observational standard or with an (originally experimentally determined) objective standard.  --Lambiam 10:36, 17 December 2024 (UTC)

FWIW, I as a former amateur astronomer have never previously thought about the question of Polar twilight and night nomenclatures, but immediately and completely understood what the (previously unencountered) terms used in the query must mean without having to read the attached descriptions. {The poster formerly known as 87.81.230.195} 94.1.223.204 (talk) 16:34, 17 December 2024 (UTC)

December 17

differential equations with complex coefficients

In an intro ODE class one basically studies the equation ${\displaystyle {\dot {x}}=Ax}$ where x is a real vector and A is a real matrix. A typically has complex eigenvalues, giving a periodic or oscillating solution to the equation. That is very important in physics, which has various sorts of harmonic oscillators everywhere. If A and x are complex instead of real, mathematically the ODE theory works out about the same way. I don't know what happens with PDE's since I haven't really studied them.

My question is whether the complex case is important in physics the way the real case is. Can one arrive at it through straightforward coordinate transformations? Do the complex eigenvalues "output" from one equation find their way into the "input" of some other equation? Does the distance metric matter? I.e. in math and old-fashioned physics we use the Euclidean metric, but in realtivity one uses the Minkowski metric, so I'm wondering if that leads to complex numbers. This is all motivated partly by wondering where all the complex numbers in quantum mechanics come from. Thanks. 2601:644:8581:75B0:0:0:0:DA2D (talk) 22:54, 17 December 2024 (UTC)

Perhaps I don't understand what you are getting at but simple harmonic motion is xdot=j*w*x where w is angular frequency and j is i Greglocock (talk) 00:35, 18 December 2024 (UTC)

If PDEs count, the Schrödinger equation and the Dirac equation are examples of differential equations in the complex domain. A linear differential equation of the form ${\displaystyle {\dot {x}}=Ax}$ on the complex vector space ${\displaystyle \mathbb {C} ^{n}}$ can be turned into one on the real vector space ${\displaystyle \mathbb {R} ^{2n}}$. For a very simple example, using ${\displaystyle n=1,}$ the equation ${\displaystyle {\begin{bmatrix}{\dot {z}}\end{bmatrix}}={\begin{bmatrix}i\end{bmatrix}}{\begin{bmatrix}z\end{bmatrix}}}$ can be replaced by

${\displaystyle {\begin{bmatrix}{\dot {x}}\\{\dot {y}}\end{bmatrix}}={\begin{bmatrix}0&-1\\1&0\end{bmatrix}}{\begin{bmatrix}x\\y\end{bmatrix}}.}$

 --Lambiam 01:11, 18 December 2024 (UTC)

Shouldn't this be at the Math Desk? It almost seems like the IP could be trolling, given the same question just above. Abductive (reasoning) 14:49, 18 December 2024 (UTC)

The question whether the complex case is important in physics the way the real case is, is not a maths issue. IMO the Science section is the best choice. I do not see another post that asks the same or even a related question.  --Lambiam 21:51, 18 December 2024 (UTC)

Just as above, I await a non-mathematical answer to this question. Abductive (reasoning) 07:01, 19 December 2024 (UTC)