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Wikipedia:Reference desk/Archives/Science/2020 July 22

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July 22

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Chicago Lead Contamination

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Is the lead contamination in Chicago the worst in the United States?Rich (talk) 07:01, 22 July 2020 (UTC)[reply]

What are you talking about? ←Baseball Bugs What's up, Doc? carrots→ 01:07, 23 July 2020 (UTC)[reply]
Lead-crime hypothesis. I should have said where I was going with this.Rich (talk) 04:55, 23 July 2020 (UTC)[reply]
I've always heard that Baltimore has the worst problem with lead exposure. 2600:1702:2670:B530:3C1D:BF85:FE2A:BA6 (talk) 01:44, 23 July 2020 (UTC)[reply]
oh ok. I guess the violence in Baltimore is about as bad as it is in Chicago, so that makes sense(tragically).Rich (talk) 04:58, 23 July 2020 (UTC)[reply]
Trollicious. Abductive (reasoning) 05:12, 23 July 2020 (UTC)[reply]
Listen Abductive you had no right to label my question as trollicious and then close it. You're behaving very disrespectfully. Also, you have the advantage of anononymity which I don't have, I'm pretty sick that you would attack a stranger's character like that.Rich (talk) 22:54, 23 July 2020 (UTC)[reply]
I am reverting this hatting, as this is an answerable question. It maybe pushing a point, but not necessarily trolling. Graeme Bartlett (talk) 01:35, 24 July 2020 (UTC)[reply]
Hier [[1]] you can find a map of lead poisoning in young children. Remark that beside leaded gasoline there are two modern causes of poisoning: 1) the distribution of aggressive river water through lead piping (s. Flint, Michigan. But if the water is not aggressive lead piping doesn't contribute much to poisoning because lead do passivate under suitable conditions) and 2) the erosion by the wind of old contaminated soils. There is also an important historical cause: paints with lead carbonate ('lead white') that has a somewhat sweet taste so that children would scratch it from the wall and eat it. In many countries production and sale of lead carbonate based paints were first restricted and then forbidden during the 20th century. But it seems that such paints can still be found in the USA.
I don't seem able to find a simple list of cities with contamination figures but beside Chicago also Pittsburg and St Louis are often cited as heavily contaminated. 2003:F5:6F0C:9500:89C7:4269:E468:97B (talk) 16:20, 24 July 2020 (UTC) Marco PB[reply]

Springbok

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Having provided a link in answer to a question, I note that Dr Richard Liversidge's article states: "He also carried out long-term work on the ecology of the springbok, and had the remarkable ability to predict rain, almost to the day, based on his observation of springbok behavior." Please can we provide more information. How do they do this and what is the behavior displayed? Thank you — Preceding unsigned comment added by 31.53.187.190 (talk) 08:35, 22 July 2020 (UTC)[reply]

Liversidge wrote an article about this in the South African Journal of Science, Volume 80.[2] Google Books does not allow me more than a snippet view, but what I can see is: "The springbok is an opportunistic breeder that has evolved a six month reproductive cycle that fits in perfectly with a six month rainfall periodicity." So it appears that he used his observations to predict the start of a six-monthly wet season. According to Animal Diversity Web, "The springbok generally mates during the dry season and lactates during the hot, wet season when resources are most abundant. Birth takes place in Oct-Nov, the start of the wet season."[3]  --Lambiam 10:44, 22 July 2020 (UTC)[reply]
According to Smithers (1983):[1] "Springbok are not seasonal breeders" AND "Skinner & van Zyl (1970)[2] showed that at all times of the year there were springbok rams capable of breeding and they suggested that the mating season was largely dependent on the physiological status of the females which was governed by their level of nutrition." AND "Springbok mate at any time throughout the year, the great bulk of the lamb crop being born during the summer in the summer rainfall areas (van Zyl & Skinner, 1970)[2]and in July in the winter rainfall areas (Skinner, Nel & Millar, 1977)[3] when ample green food is available."
I actually knew both Liversidge and Skinner well during their lives. Skinner dismissed Liversidge's idea that springbok could in effect predict the start of the rain season. It remained a point of dissension between them until Liversidge's death. Prof Skinner was the director of the Mammal Research Institute of the University of Pretoria for many years. Roger (Dodger67) (talk) 14:41, 22 July 2020 (UTC)[reply]

References

  1. ^ Smithers, Reay H. N. (1983). The Mammals of the Southern African Subregion (1st ed.). Pretoria: University of Pretoria. pp. 630–631. ISBN 0869795406.
  2. ^ a b Van Zyl, J. H. M .; Skinner, J. D. (1970). "Growth and development of the springbok foetus". Afr. Wild Life. 24: 308–316.
  3. ^ SKINNER, J.D., NEL, J.A.J., MILLAR, R.P.: Evolution of time of parturition and differing litter sizes as an adaptation to changes in environmental conditions. Proc. 4th Int. Symp. Comp. Reprod. Sydney: Aust. Acad. Science, 1977, pp. 39–44

Why are electric drills louder than electric cars?

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I'm pretty sure my observation is valid ... it's complicated by the fact that I have to hold my drill closer to my ears in order to be able to turn it on than I am normally positioned near electric cars. — Preceding unsigned comment added by Hayttom (talk • contribs) 16:24, 22 July 2020 (UTC)[reply]

Sound intensity falls off with the square of the distance, and loudness, which is your perception of sound intensity, is complex and has many psychological, rather than physical, components. The connection between the magnitude of the sound wave and your perception of its loudness is not a simple physical law, and takes in many complex factors. A to B comparisons between different sound sources in terms of how loud you perceive them versus how intense the wave is are rather messy and not always intuitive.--Jayron32 17:09, 22 July 2020 (UTC)[reply]
I understand and admire that response. But I actually still believe that electric drills are louder than electric cars, and if we could eliminate cars' tire noise, astoundingly so. Am I right? Hayttom (talk) 18:22, 22 July 2020 (UTC)[reply]
I don't know the why, but I did remark long time ago that some electric motors as in drills, coffee grinders and hair dryer are much noisier than for example electric motors in washing machines, forklifts, water pumps and professional lathes. I suppose the reason to be one or more of the following: noisy motors 1) make more revolutions per minute, 2) they have no ball bearings and 3) often they have a noisy gear change. I wonder also whether the number of poles and the number of phases could play a role. 2003:F5:6F0C:9500:EDEB:DDF5:E97D:77AA (talk) 19:18, 22 July 2020 (UTC) Marco PB[reply]
A typical electric drill makes a lot of noise because it has a motor that makes a lot of noise. The gear train adds noise as well.
Electric drills use brush-type universal motors. These motors produce noise as the brushes rub on the slots of the armature. You also have gear train noise. Electric drills use universal motors because they are far smaller and lighter than, say, induction motors.
Induction motors are far quieter, more energy efficient, don't wear out so fast, and run cooler, but they also have less torque at start up and are a lot heavier and more expensive for the same power output. Ceiling fans almost always use induction motors because nobody wants to listen to that universal motor whine or replace the brushes in the fan every time they wear out.
Electric vehicles use a variety of motor types, all of which create far less acoustic noise than a universal motor. See Types of Motors used in Electric Vehicles They also tend to use helical gears running in an oil bath, which greatly reduces gear noise. --Guy Macon (talk) 19:46, 22 July 2020 (UTC)[reply]
Cars are fitted with soundproofing, which household drills are not. DuncanHill (talk) 02:10, 23 July 2020 (UTC)[reply]
This is the wrong train. Washing machines have no soundproofing either but this kind of motors is intrinsically more quiet than that of e.g. a coffee grinder. Guy Macon has already given the reason. 2003:F5:6F0C:9500:A088:A42E:9624:3880 (talk) 18:49, 23 July 2020 (UTC) Marco PB[reply]
Any design has to balance lots of different requirements. A drill needs a lot of power rather quickly, must be small enough to carry relatively easily, and isn't expected to be run continuously for long periods of time while a car is expected to run long periods of time with the user enclosed within it and with little need (unless you are drag racing) for immediate full power. Couple these requirements with the relative price points of the two items and it may not make sense from a price or portability standpoint to make the drill any quieter. --Khajidha (talk) 04:30, 23 July 2020 (UTC)[reply]
Several good answers already. But also: Many household "electric drills" are actually hammer drills or even rotary hammers. The hammering function produces a lot more noise than simple rotation. --Stephan Schulz (talk)
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