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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: [1] --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,^[2][3] there can be little doubt that it would be deemed to be an orthographical variant,^[4] 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 [5]. 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]

CoCl₃ is already thermodynamically unstable, as can be predicted just by examining reduction potentials (Co³⁺ is a strong oxidant and will oxidise Cl⁻). So CoBr₃ and CoI₃ seem extremely unlikely. Double sharp (talk) 06:06, 28 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 [6] and perhaps [7]. Perhaps also [8]

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]