飞天大圣朱七
Masks in smoggy cities a good idea, study says
Occupational masks beat those for cyclists and pedestrians
Last Updated: Friday, March 13, 2009 | 11:23 AM ET Comments29Recommend25CBC News
A cyclist on the Olympic Green in Beijing in August 2008. (Robert F. Bukaty/Associated Press)Wearing a face mask in smog-clouded cities is a good idea, a study published Friday says, but some masks are more effective than others.
A 2008 study of 15 volunteers in Beijing, with and without masks, established that "wearing a simple inexpensive and well-tolerated face mask can provide an alternative that may lead to reduced cardiovascular morbidity and mortality" by filtering particles, the researchers said.
Beijing was chosen because it is highly polluted. The researchers, led by Jeremy Langrish from the University of Edinburgh, tested 15 healthy volunteers who walked on the city's ring road for two hours, and monitored their blood pressure and heart rates.
"Our findings would suggest that wearing a simple face mask has the potential to reduce the incidence of acute cardiovascular events in cities with high levels of air pollution, and could influence the advice given to patients with chronic cardiovascular diseases," the authors reported in the journal in Particle and Fibre Toxicology.
Dust respirators get top marks
Before the experiment, the researchers tested different masks.
"In general, those masks designed to reduce occupational exposure to dusts were more efficient than those marketed as personal protection to cyclists and pedestrians in an environmental setting," they said.
They chose the 3M Dust Respirator Model 8812, because it was efficient and comfortable to wear. It was not the best of the masks tested, having a 3.4 per cent "penetrance" rate, where a lower number is better.
But four cyclists' masks tested from 15.1 per cent to 44.9 per cent, a surgical mask was at 20 per cent and a cotton handkerchief at 72 per cent.
Dust respirators and a Teflon filter performed better than the 3M mask.
崽崽龙08
美国的，美联社一般指美国联合通讯社
美国联合通讯社是美国最大的通讯社，它是一家美国跨国非盈利新闻机构，总部位于纽约市。公司经营报纸，电台和电视台。美联社还经营美联社无线网络，它通过广播，卫星广播电台和电视台每小时广播新闻两次。许多报纸和美国以外的国家广播公司都是其用户，这些用户需要支付一定的费用来获得新闻资源。
美国联合通讯社的发展：
1846年美国联合通讯社在芝加哥成立。
1893年美国联合通讯社成为联营公司。
1990年将总部迁到纽约。合作伙伴有1700多家报纸，5000多家电视和广播电台；全球有243家新闻分社，在120个国家设有办事处。合众国际社是美国第二大通讯社。
2007年，美联社收集的新闻被1700多个报刊转载，以及5000多个电视和电台广播转播。其照片库包含超过1000万张图片。它在120个国家经营243家新闻分社。
神仙姐姐S
美联社是美国的。
美国联合通讯社（简称美联社是美国最大的通讯社，1846年在芝加哥成立，1893年成为联营公司，1990年将总部迁到纽约。合作伙伴有1700多家报纸，5000多家电视和广播电台；全球有243家新闻分社，在120个国家设有办事处。
合众国际社是美国第二大通讯社，1958年由前合众社和国际新闻社合并组成，总部设在佛罗里达州，国外有80多个分社，拥有一个世界范围的图片网。
美联社的中国业务：
美联社在中国大陆地区的媒体业务，按照中国媒体的习惯，分为文字和新闻图片两部分。文字部分由美联社驻中国北京的办事处和香港的亚太区办事处负责经营。
美联社的新闻图片部分，由中国最大的综合性图库东方IC独家代理。该公司主要经营图片、影像、创意元素和娱乐类明星版权管理的专业服务，如Corbis、欧洲新闻图片社（EPA）、玛格南图片社等在中国的业务均由该公司负责销售。
欧洲联盟（European Union），简称欧盟（EU），是由欧洲共同体 (European Communities，又称欧洲共同市场) 发展而来的，是一个集
丛林穿梭 6人参与回答 2024-06-13 throughout Europe，the whole Europe，
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长亭不再送别 10人参与回答 2024-06-13 你好！亚洲Asia 形容词asian 最大的洲the world's larggest continent欧洲Europe 第六大洲 Europeanth
BuleS天之蓝 11人参与回答 2024-06-12 
