{"306131":{"#nid":"306131","#data":{"type":"news","title":"Study of animal urination could lead to better-engineered products","body":[{"value":"\u003Cp\u003ESir Isaac Newton probably wasn\u2019t thinking about how animals urinate when he was developing his laws of gravity. But they are connected \u2013 by the urethra, to be specific.\u003C\/p\u003E\u003Cp\u003EA new Georgia Institute of Technology study investigated how quickly 32 animals urinate. It turns out that it\u2019s all about the same. Even though an elephant\u2019s bladder is 3,600 times larger than a cat\u2019s (18 liters vs. 5 milliliters), both animals relieve themselves in about 20 seconds. In fact, all animals that weigh more than 3 kilograms (6.6 pounds) urinate in that same time span.\u003C\/p\u003E\u003Cp\u003E\u201cIt\u2019s possible because larger animals have longer urethras,\u201d said David Hu, the Georgia Tech assistant professor who led the study. \u201cThe weight of the fluid in the urethra is pushing the fluid out. And because the urethra is long, flow rate is increased.\u201d\u003C\/p\u003E\u003Cp\u003EFor example, an elephant\u2019s urethra is one meter in length. The pressure of fluid in it is the same at the bottom of a swimming pool three feet deep. An elephant urinates four meters per second, or the same volume per second as five showerheads.\u003C\/p\u003E\u003Cp\u003E\u201cIf its urethra were shorter, the elephant would urinate for a longer time and be more susceptible to predators,\u201d Hu explained.\u003C\/p\u003E\u003Cp\u003EThe findings conflict with studies that indicate urinary flow is controlled on bladder pressure generated by muscular contraction. \u003Ca href=\u0022http:\/\/www.pnas.org\/content\/early\/2014\/06\/25\/1402289111\u0022\u003EThe study has just been published in the Proceedings of the National Academy of Sciences (PNAS). \u003C\/a\u003E\u003C\/p\u003E\u003Cp\u003EHu (George Woodruff School of Mechanical Engineering and School of Biology) and graduate student Patricia Yang noticed that gravity allows larger animals to empty their bladders in jets or sheets of urine. Gravity\u2019s effect on small animals is minimal.\u003Cbr \/\u003E\u003Cbr \/\u003E \u201cThey urinate in small drops because of high viscous and capillary forces. It\u2019s like peeing in space,\u201d said Yang, who is pursuing her doctoral degree in the School of Mechanical Engineering. \u201cMice and rats go in less than two seconds. Bats are done in a fraction of a second.\u201d\u003C\/p\u003E\u003Cp\u003EThe research team went to a zoo to watch 16 animals relieve themselves, then watched 28 YouTube videos. They saw cows, horses, dogs and more.\u003C\/p\u003E\u003Cp\u003EThe more they watched, the more they realized their findings could help engineers.\u003C\/p\u003E\u003Cp\u003E\u201cIt turns out that you don\u2019t need external pressure to get rid of fluids quickly,\u201d said Hu. \u201cNature has designed a way to use gravity instead of wasting the animal\u2019s energy.\u201d\u003C\/p\u003E\u003Cp\u003EHu envisions systems for water tanks, backpacks and fire hoses that can be built for more efficiency. As an example, he and his students have created a demonstration that empties a \u003Ca href=\u0022https:\/\/www.youtube.com\/watch?v=-7DZifiouoM\u0026amp;list=UUFkaWOGpyFBVRf5jEeD_wrA\u0026amp;index=2\u0022\u003Eteacup, quart and gallon of water in the same duration\u003C\/a\u003E using varying lengths of connected tubes. In a second experiment, the team fills three cups with the same amount of water, \u003Ca href=\u0022https:\/\/www.youtube.com\/watch?v=qGF5vepfGxI\u0026amp;list=UUFkaWOGpyFBVRf5jEeD_wrA\u0022\u003Ethen watches them empty at differing rates\u003C\/a\u003E. The longer the tube, the faster it empties.\u003C\/p\u003E\u003Cp\u003E\u201cNature has shown us that no matter how big the fire truck, water can still come out in the same time as a tiny truck,\u201d Hu added.\u003C\/p\u003E\u003Cp\u003EThe trick is gravity. Newton would be proud.\u003C\/p\u003E","summary":null,"format":"limited_html"}],"field_subtitle":"","field_summary":[{"value":"\u003Cp\u003EA new Georgia Institute of Technology study investigated how quickly 32 animals urinate. It turns out that it\u2019s all about the same. Even though an elephant\u2019s bladder is 3,600 times larger than a cat\u2019s (18 liters vs. 5 milliliters), both animals relieve themselves in about 20 seconds. In fact, all animals that weigh more than 3 kilograms (6.6 pounds) urinate in that same time span.\u003C\/p\u003E","format":"limited_html"}],"field_summary_sentence":[{"value":"Despite a wide range of bladder sizes, all animals more than 6 pounds urinate in the same time span."}],"uid":"27560","created_gmt":"2014-06-30 14:04:48","changed_gmt":"2016-10-08 03:16:41","author":"Jason Maderer","boilerplate_text":"","field_publication":"","field_article_url":"","dateline":{"date":"2014-06-30T00:00:00-04:00","iso_date":"2014-06-30T00:00:00-04:00","tz":"America\/New_York"},"extras":[],"hg_media":{"306121":{"id":"306121","type":"image","title":"Elephant","body":null,"created":"1449244668","gmt_created":"2015-12-04 15:57:48","changed":"1475895015","gmt_changed":"2016-10-08 02:50:15","alt":"Elephant","file":{"fid":"199730","name":"africanelephant-122402126.jpg","image_path":"\/sites\/default\/files\/images\/africanelephant-122402126_0.jpg","image_full_path":"http:\/\/www.tlwarc.hg.gatech.edu\/\/sites\/default\/files\/images\/africanelephant-122402126_0.jpg","mime":"image\/jpeg","size":2367815,"path_740":"http:\/\/www.tlwarc.hg.gatech.edu\/sites\/default\/files\/styles\/740xx_scale\/public\/images\/africanelephant-122402126_0.jpg?itok=vNy1uO7b"}},"100131":{"id":"100131","type":"image","title":"David Hu","body":null,"created":"1449178150","gmt_created":"2015-12-03 21:29:10","changed":"1475894715","gmt_changed":"2016-10-08 02:45:15"}},"media_ids":["306121","100131"],"related_links":[{"url":"http:\/\/www.pnas.org\/content\/early\/2014\/06\/25\/1402289111","title":"PNAS Study"},{"url":"http:\/\/coe.gatech.edu\/schools\/me","title":"George W. Woodruff School of Mechanical Engineering"},{"url":"http:\/\/www.biology.gatech.edu\/","title":"School of Biology"}],"groups":[{"id":"1214","name":"News Room"}],"categories":[],"keywords":[{"id":"297","name":"David Hu"},{"id":"96651","name":"elephant"},{"id":"5195","name":"pee"},{"id":"96641","name":"urinate"}],"core_research_areas":[{"id":"39441","name":"Bioengineering and Bioscience"},{"id":"39541","name":"Systems"}],"news_room_topics":[{"id":"71881","name":"Science and Technology"}],"event_categories":[],"invited_audience":[],"affiliations":[],"classification":[],"areas_of_expertise":[],"news_and_recent_appearances":[],"phone":[],"contact":[{"value":"\u003Cp\u003EJason Maderer\u003Cbr \/\u003EMedia Relations\u003Cbr \/\u003E\u003Ca href=\u0022mailto:maderer@gatech.edu\u0022\u003Emaderer@gatech.edu\u003C\/a\u003E\u003Cbr \/\u003E404-385-2966\u003C\/p\u003E","format":"limited_html"}],"email":["maderer@gatech.edu"],"slides":[],"orientation":[],"userdata":""}}}