Wikipedia:Reference desk/Archives/Science/2016 June 10

= June 10 =

What chewing gums supply urea for healthy teeth?
I read that urea is used to give sugar-free chewing gum its texture and also that urea in gum is good for the teeth. Then, I looked at all the different kinds of gum I have at home, and none of them lists "urea" or "carbamide" on the list of ingredients. Is urea found in all sugar-free gums (to provide texture) or only in certain brands (to help reduce salivary pH)?174.131.42.212 (talk) 03:25, 10 June 2016 (UTC)
 * I can't identify a chewing gum brand but note that US Patent no. 7595065 mentions urea and is assigned to Wrigley's. A Danish Committee reported that Urea is used in unspecified sugar-free chewing gum to adjust the texture but concluded use of urea at levels of up to 3% was of no toxicological concern. See also Effect of urea in sugar-free chewing gums on pH recovery in human dental plaque evaluated with three different methods. and The Effect of Chewing Urea-Containing Gum on Plaque Acidogenic and Alkaligenic Parameters. AllBestFaith (talk) 09:33, 10 June 2016 (UTC)

Civil engineering
Is civil engineering the engineering discipline which is most business like (spending more time managing stakeholders, considering costs etc) and less technical (calculation, solving scientific problems etc) ? 94.10.246.129 (talk) 20:05, 10 June 2016 (UTC)
 * It involves both, but is built on calculation and the application of solutions to technical problems. It's a wide field, of course: designers of structures are very much involved in calculation, to the extent that some of them have speciated into Structural Engineers. Cost remains an important consideration for designers, and designers must manage their stakeholders. Site engineers are very much more concerned with the efficient and proper applications of bricks & concrete to an a priori design and arguably their job involves greater stakeholder management and a strong strand of operational cost control. --Tagishsimon (talk) 20:29, 10 June 2016 (UTC)
 * Yes but is it more like this than for example, mechanical engineering or electrical or biomedical, where the main aim is to design and make a product? 2A02:C7D:B965:D700:F1C9:FB26:2235:BD09 (talk) 21:58, 10 June 2016 (UTC)
 * In general, yes, I suspect civil engineers tend to spend more time dealing directly with clients than other types of engineer do. However I can assure you that most automotive engineers think about cost rather a lot.Greglocock (talk) 23:52, 10 June 2016 (UTC)
 * So why is that because surely all engineers are developing products or solutions for clients? 2A02:C7D:B965:D700:6CE5:9C2C:E21A:EBB2 (talk) 12:44, 11 June 2016 (UTC)
 * This is completely ObPersonal and unreferenced, but my perception is that, to the extent it's true, it's because the clients of civil engineers, more often and to a greater extent than in other types of engineering, do not actually know what they really want or need. There ought to be a term for this. {The poster formerly known as 87.81.230.195} 5.66.223.127 (talk) 20:24, 11 June 2016 (UTC)
 * There is of course the rather philosophical point of who is the customer? CEs deal directly with the guy paying the bills. In my work I very rarely meet an end-use type customer, But my 'customer' is the rest of the program team. Somebody has the job of translating end-user wants and and needs into technical specs, which is what I work to. Greglocock (talk) 23:24, 11 June 2016 (UTC)

Could people get good at sports betting, or is it always gambling?
If someone analyzed scientifically some sport, could he predict results better than the average joe? Could sports betting be a game of ability? At least, this is not like lotteries or roulette where there is a randomizing factor, carefully chosen and audited to be truly random. --Llaanngg (talk) 20:42, 10 June 2016 (UTC)


 * Yes, it is possible to do better than the average Joe. It is even possible to do better than the average bettor (who is generally more knowledgable than the average guy on the street).  However, bookmakers routinely have a margin, referred to as the vigorish, which is essentially their cut.  For example, if you and I both bet $1 on a game using a bookie, the winner might get their $1 back plus $0.9 from the loser and the bookmaker keeps $0.10.  In order to be profitable at sports gambling you have to be right with a high enough accuracy to overcome the losses due to the house's margin.  The accuracy required varies by the sport, because the house margin varies by sport (generally sports regarded as less predictable have a higher margin for the bookmaker).  As I recall, in basketball one needs to be on the right side of the over / under line roughly 54% of the time to be profitable over the long-term.  That's actually pretty hard, but there are people like Jon Price, Zeljko Ranogajec, and Haralabos Voulgaris  that present themselves as professional sports gamblers and claim to have made money over the long-term.  I think it is probably possible to predict sports well-enough to be profitable, though one might need to be very selective in one's bets and only bet on contests where you have a strong reason to believe the line offered by the bookie is not a good reflection of the true odds.  Dragons flight (talk) 21:39, 10 June 2016 (UTC)


 * There is at least one Australian David Walsh (art collector) who is registered for tax as a gambler. Greglocock (talk) 23:18, 10 June 2016 (UTC)

Growing Bismuth crystals
What is the best way of growing nice looking Bismuth crystals starting from the metal in 'shot' form?--178.100.75.110 (talk) 23:30, 10 June 2016 (UTC)

Google and Youtube are covered in instructions for these. You could have saved yourself a wait by going direct. Richard Avery (talk) 07:33, 11 June 2016 (UTC)
 * We shouldn't be looking to defer to search engines. They may serve up several sites, but which is best?  And will those searches remain usable, will those sites remain in operation?  The goal is to bring back the information and integrate it here, just as we do for encyclopedia articles and for the same reason.  Someday Google is going to start charging and a lot of the world will lose access, the people who don't matter anyway but still would like to know. Wnt (talk) 15:02, 11 June 2016 (UTC)


 * Best method?  Practice.
 * Bismuth crystal growing is great fun and low complexity for equipment, but the crystals grow in liquid phase bismuth just where you can't see them. So there's an awful lot about learning the best growth profiles (timing) by repeated experiment, rather than observation.
 * I'd also suggest an Indian grocers as a source of handy stainless containers in a range of sizes. Then get enough bismuth to work easily with - it's annoying to try and grow them in a teaspoon. A small electric hotplate is useful, but as the thermal mass is high you only need rough power control, not necessarily closed loop control of temperature.  A non-contact IR thermometer is cheap and useful though.  If you fancy a small electronics project, then PID controller modules are cheap (China via eBay) and that will make you a handy workshop hotplate with temperature control. Andy Dingley (talk) 09:39, 11 June 2016 (UTC)

Maltese pavements
Why are they so slippery even when dry? What is the solution?--178.100.75.110 (talk) 23:33, 10 June 2016 (UTC)


 * I think some form of evidence is required. I'm only 69 years old but have never heard of that before. Richard Avery (talk) 07:35, 11 June 2016 (UTC)
 * Times of Malta has a number of letters about it and I have slippped on them myself.--178.100.75.110 (talk) 09:37, 11 June 2016 (UTC)


 * From what I recall, the pavements in Malta (just like most of the buildings) are made from local limestone. The limestone is relatively soft and tends to get polished with wear, which makes the pavements slippery, particularly when wet, although I've failed to find any good sources for this. I'm not sure what you can do to improve the situation, apart from wearing footwear with better grip. Mikenorton (talk) 12:44, 11 June 2016 (UTC)


 * Extraordinary, that must make a lot of Maltese cross. Richard Avery (talk) 18:19, 11 June 2016 (UTC)
 * If the residets pressure washed their pavements outside their houses from time to time, it could improve the situatiom--178.104.157.88 (talk) 18:26, 13 June 2016 (UTC)