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July 18[edit]

Vickers Hardness Number Notation[edit]

why does vickers hardness value is represented as 4500HV without the load ? how do i read it ? what is the load ? help i found this on many websites — Preceding unsigned comment added by Kinetc ner (talk • contribs) 05:47, 18 July 2018 (UTC)[reply]

See Vickers hardness test. 173.228.123.166 (talk) 06:19, 18 July 2018 (UTC)[reply]

Calibrate radiation detector[edit]

"To ensure they got the right items, the specialists from Idaho brought radiation detectors and small samples of dangerous materials to calibrate them: specifically, a plastic-covered disk of plutonium, a material that can be used to fuel nuclear weapons, and another of cesium, a highly radioactive isotope that could potentially be used in a so-called 'dirty' radioactive bomb."[1]

Why did they need "small samples of dangerous materials to calibrate" the "radiation detectors"? Couldn't they just calibrate the radiation detectors before they left on their journey?

I originally raised this question in this thread. Bus stop (talk) 07:08, 18 July 2018 (UTC)[reply]

There are many different radiation detector instruments such as Scintillation counters and the commonest Geiger counter types that may give a readout in counts or radiation dose. An operator should always have access to radioactive calibration samples that allow confirmation that a particular instrument is working, identify its pickup range and demonstrate its different responses to a source and to background radiation. See Geiger counter and, for details of dose measurement Geiger–Müller_tube#Energy_compensation. The Ludlum 3030 pictured in the OP's cited article is a Scintillation counter instrument. DroneB (talk) 16:27, 18 July 2018 (UTC)[reply]

This is just a guess (if you read the article you will see that the government is trying really hard to stop us from finding out any details about this incident), but if you are going somewhere where you will be picking up some radioactive material, you really need two ranges of detection: [A] a high range to tell you if this is a situation where you need to evacuate the entire neighborhood and send in a robot with a lead box, and [B] a really sensitive detector that will tell you if you are leaving a tiny bit behind. [A] and [B] may be ranges on the same instrument or they may be separate instruments. Calibration of [B] really doesn't matter. The only answers you care about are "none detected at the most sensitive range" and "hey, I am getting a trace reading from behind this filing cabinet!" Calibration of [A] is fairly important, but verification that [A] is working and not broken is absolutely critical. Critical as in "a bunch of people could die if the high range of this meter was broken and didn't warn us of the danger." If it were me, I would bring along calibration sources suitable for both ranges and test the meter(s) before and after visiting the site. --Guy Macon (talk) 16:58, 18 July 2018 (UTC)[reply]

I found something that seems to be referencing why it may be necessary to calibrate the instruments upon reaching their destination:

"Modern LS counters offer the possibility of both qualitative and quantitative analysis of alpha and beta emitters with high precision and accuracy, offering at the same time low detection limits. As many other instrumental techniques, liquid scintillation spectrometry requires robust and reliable calibration to accurately measure radiation [2, 3]. However, the detection efficiency of the counting equipment will vary depending on a range of factors including radionuclide emission and associated energy, sample composition, scintillator and vial type. All these factors must be accurately quantified and corrected for during routine measurement. In addition, the detection efficiency will vary with time due to deterioration of instrument optics and periodic recalibration is therefore required. In order to address these issues the most commonly used approach is to calibrate the LS spectrometers using a set of standards of known activity and a varying amount of quench."[2]

The term "quench" is spoken of here:

"Liquid scintillation counting makes use of an intimate mixture of radioactive sample and detecting medium which translates atomic radiation into light flashes. The light intensity of such a flash is proportional to the deposited energy in a burst of radiation, but the constant describing this proportionality may change from sample to sample because of chemical differences in various radioactive preparations. This chemical loss in detection efficiency is known as “quenching” and needs calibration if one is to get quantitatively meaningful results from liquid scintillation counting. Many ways are available for measuring quenching correction, and these have been reviewed by Peng [1]."[3]

I can't say I fully understand any of this. Bus stop (talk) 01:22, 19 July 2018 (UTC)[reply]

What enzymes take place in glucose re-absorption?[edit]

I came across this question and answer in which states that there is a condition in which decreased activity of glucose reabsorption enzymes could be. I googled for "glucose reabsorption enzymes" and found a very few results, most of them are copy paste of this site and don't really have information about that. In addition I red the wiki article "renal glucose reabsorption" and yet I didn't find any reference for such enzyme. Do you have an idea what it is? --93.126.116.89 (talk) 13:24, 18 July 2018 (UTC) "[reply]

You'd be having difficulty because no ordinary person calls it an enzyme. SGLT2. Someguy1221 (talk) 20:36, 18 July 2018 (UTC)[reply]

I agree that the linked question is very poor; the condition discussed is renal glycosuria. Rather than SGLT2 mutation, a more likely cause would be someone taking a gliflozin. Klbrain (talk) 22:27, 22 July 2018 (UTC)[reply]

mystery spider[edit]

Can anyone identify this spider? She lives in a big web on a bush in Oran, Algeria (near the sea). Maybe 6-8cm, including the legs. Thanks, Henry ^Flower 15:13, 18 July 2018 (UTC)[reply]

Try and drown it? This should narrow it down, apparently. Martinevans123 (talk) 15:17, 18 July 2018 (UTC)[reply]

Probably an argiope lobata - quite similar to this image. Mikenorton (talk) 15:57, 18 July 2018 (UTC)[reply]

Splendid, thanks (also for the word stabilimenta).

Resolved

Henry ^Flower 16:52, 18 July 2018 (UTC)[reply]

Perhaps the painting of the Mona Lisa could be said to contain stabilimenta, or would that be craquelure? Also, that spider appeared to have a thin-faced smile. Please see here in archives. Bus stop (talk) 14:33, 19 July 2018 (UTC)[reply]

Did someone say Leonardo?... and the "Mow-na Lisa"?? Martinevans123 (talk) 21:27, 20 July 2018 (UTC)[reply]

Reference Desk Staff[edit]

What are the requirements needed to answer questions here? Limited Brain Cells (talk) 18:27, 18 July 2018 (UTC)[reply]

I don't believe there are any formal requirements and some of us are better than others in providing good-quality answers but to be on the safe side the inclusion of sources is generally a good idea so that anyone reading a response can verify your assertions. Bus stop (talk) 18:54, 18 July 2018 (UTC)[reply]

We have an informational wiki page, Wikipedia:About.

"Wikipedia is ... based on a model of openly editable content..." Like other pages, the Reference desk is "...written collaboratively by largely anonymous volunteers who write without pay. Anyone with Internet access can write and make changes to Wikipedia articles, except in limited cases where editing is restricted to prevent disruption or vandalism. Users can contribute anonymously, under a pseudonym, or, if they choose to, with their real identity."

Contributors here are volunteers who choose to help maintain the project. We are not "staff" in the sense that nobody hires us, manages us, or pays us, for our efforts.

Many of us carry credentials, but the general guidelines are summarized in our informational page on Wikipedia:Expert editors. Being an expert, in this environ, does not carry any special privilege, other than the enhanced ability to write well and to efficiently find and to cite sources.

Nimur (talk) 22:03, 18 July 2018 (UTC)[reply]

There are no requirements, anyone can do it, and many do. "If you have knowledge and the teaching instinct, here is a classroom of the world." 173.228.123.166 (talk) 22:33, 18 July 2018 (UTC)[reply]

Lead soldered kettle[edit]

I see people repairing kettles with what appears to be solder. Is that lead? Won't that end up in the boiled water? Anna Frodesiak (talk) 20:22, 18 July 2018 (UTC)[reply]

Some solder is lead-free, some has lead. Sagittarian Milky Way (talk) 20:28, 18 July 2018 (UTC)[reply]

The solder sold for pot repair is usually zinc. Someguy1221 (talk) 20:34, 18 July 2018 (UTC)[reply]

Thank you both. Next time I pass a kettle repair shop, I will see what he uses. If it is lead, it is bad, right? Many thanks. Anna Frodesiak (talk) 20:34, 18 July 2018 (UTC)[reply]

Probably? In the case of leaded glass, a food and liquids stored therein take hours to days to reach dangerous concentrations of lead (Lead_glass#Safety). So a lead slow-cooker would probably be disastrous. I have no idea though, if short-term contact can expose the food to a lot of lead if the lead is very hot. I mean, the safety tests with leaded glass were done at around room temperature, not boiling. I'd avoid it if it's lead. Someguy1221 (talk) 20:41, 18 July 2018 (UTC)[reply]

Wow. A lot of people use those kettles here. I do hope it's pure zinc solder. Anna Frodesiak (talk) 20:50, 18 July 2018 (UTC)[reply]

A US penny made after 1982 is nearly pure zinc plated with copper. It can be melted over a (non-electric?) kitchen stove in a spoon but the higher melting point and cost is why zinc is not the first choice for solder. I note that breathing metal vapors might not be harmless Sagittarian Milky Way (talk) 21:41, 18 July 2018 (UTC)[reply]

Related: Lead poisoning#History --Guy Macon (talk) 22:12, 18 July 2018 (UTC)[reply]

Soldering is done with solder, an alloy of tin and lead. Neither pure tin, nor pure lead, are much use as solders. Even now that leaded solder is prohibited for many tasks, the tin has to be alloyed with something else (BTW - don't fly on aircraft relying on lead-free solder for their electronics. The unreliability of unleaded solder has already started to kill people.)

Assuming a repairable "kettle" is made of brass or copper, then it's not much of a hazard if it's used to boil plain water. But either of these metals, used as a general cooking pan, is distinctly unsafe unless it's tinned (lined) inside with solder.

Leaded solder has a very long history and has largely been an insignificant risk. When vessels or pipes were made of lead, the lead from the solder alloy joining them wasn't an issue. Only in recent years, once we've largely eliminated lead exposure in the diet, has solder become at all significant as a component of the sources for it. As with lead plumbing, it also depends what your water is like and what you're cooking. Hard water is of very little risk with lead, as it deposits calcium minerals on it, rather than dissolving the metal (any metal). Soft water though, or something more acidic, such as pickling for preservation, and you have a much more serious exposure risk - and copper is perhaps worse than lead here, at least for acute toxicity. Andy Dingley (talk) 23:39, 18 July 2018 (UTC)[reply]

Airplanes still have lead in their gas - why would they bother taking lead out of the solder? Anyway, I'm going to have to call "citation-needed" on the claim that fatalities have been reliably attributed specifically to an electronic failure directly caused by the use of unleaded solder ... that seems like a pretty specific claim that warrants a reliable source to back it up. Nimur (talk) 04:24, 19 July 2018 (UTC)[reply]

Not for the passengers, but for the assembly line workers putting the things together. Greglocock (talk) 06:06, 19 July 2018 (UTC)[reply]

Not exactly death, but here is a reliable source for potential deaths: [4] --Guy Macon (talk) 05:58, 19 July 2018 (UTC)[reply]

That's only true for aviation gasoline, which you linked. Only piston-engine small planes use that; jet engines use jet fuel. Of course I still think it should be banned. --47.146.63.87 (talk) 06:51, 19 July 2018 (UTC)[reply]

Aviation (and other safety critical industries) has an exception which permits leaded solder in its electronics. However lead-free electronics has distinct long-term reliability problems (see tin whiskers), and the lead-free majority of components are finding their way into many products, even those requiring reliability. Andy Dingley (talk) 08:36, 19 July 2018 (UTC)[reply]

Thank you all. By the way, Andy, the kettles I see getting repaired here appear to be stainless steel or something. Definitely not copper anything. Anna Frodesiak (talk) 04:47, 19 July 2018 (UTC)[reply]

Unhelpful. Matt Deres (talk) 11:57, 19 July 2018 (UTC)[reply]

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

I seem to recall from previous RefDesk posts that you live in the PRC. If true, my money would be on it being lead solder. Hey, what's a little irreversible brain damage between ~~peons and overlords~~ friends? --47.146.63.87 (talk) 06:51, 19 July 2018 (UTC)[reply]

Please do not insult China. We are not peons and the the government is not an overlord. If you came to China you would see how ignorant such a statement is. You geolocate to USA. If you are actually there, you might consider examining your arrangement. It's been looking a little like peons and overlords lately. Anna Frodesiak (talk) 07:30, 19 July 2018 (UTC)[reply]

That said, leaded solder is still widespread in China. Removing lead from consumer electrical products (like the idea of properly insulating or earthing them) is just not seen as so important in China. Andy Dingley (talk) 08:36, 19 July 2018 (UTC)[reply]

Hat this, please. Anna Frodesiak (talk) 07:31, 19 July 2018 (UTC)[reply]

I'm surprised to see stainless steel kettles being repaired. I would expect India to be doing this, possibly China, but very rare elsewhere. Stainless steel is not a ductile metal, so it's impractical to make a stainless steel vessel by hand, rather than using large powered machines. So countries (such as Turkey or India) where there's still a large market for hand-make vessels are largely making them from copper or brass, then repairing them later. Once stainless steel becomes widely adopted though, the manufacturing economy has shifted to factory production of one-use, non-repairable items on the Western model. India also uses a lot of thin stainless sheet for cooking vessels and tableware. This stainless sees far less hand repair afterwards - it doesn't need it (much harder to wear such items out than a copper pot) and it's also harder to do (soldering stainless is hard work and often unpleasant). I solder stainless steel a lot myself, but I do it by hard soldering (a gas flame) rather than soft soldering, at a lower temperature with a heated metal tool or soldering iron (which is usually a block of copper, not iron). The solder and flux I use is silver solder, which is expensive because of its silver content, and also (the older grades) quite toxic because it contains cadmium. You really don't want cadmium alongside food. Cadmium has largely gone from silver solder now, but that increases the silver content and price even more so. Even the flux, a fluoride compound, has aggressive fumes when heated. Andy Dingley (talk) 08:36, 19 July 2018 (UTC)[reply]

Video showing process using large corn kernels in a roadside machine in Haikou, Hainan, China.

Hi Andy. First, yes, China may indeed still use lead and be a bit behind the times. However, this repair thing is rare. We're seeing the very last of the walking knife sharpener, the small, kettle repair shop, and I haven't seen a puffed grain man in years. There are probably only half a dozen kettle repair shops in this city of 2 million, and they'll likely be gone for good in a couple of years.

So, understood about the solder. That is very interesting, actually, and seems a bit asbestosy, in terms of 'you shouldn't be near it'. The repairmen, by the way, just seem to fix teensy holes. Also, I think I saw them once take off a bottom and solder it back on. So strange, these kettles are cheap. Why fix them? I guess the old people are a bit stuck in their ways here and are used to fixing things to save money. Young people would never do that. Best wishes and many thanks for the thoughtful answers. Anna Frodesiak (talk) 18:01, 19 July 2018 (UTC)[reply]