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哈尔滨香坊区男性不育京东分类哈尔滨好的妇科检查

2019年06月25日 02:19:46来源:百度专家

  • Science and technology科学技术Exercise and addiction锻炼也会上瘾Fun run奔跑的奥秘People, it seems, have evolved to be addicted to exercise人类似乎在进化过程中对锻炼上瘾了AS THE legions of gym bunnies and jogging enthusiasts who race out into the spring sunshine every year clearly demonstrate, running can be fun.那一大批在春日和煦的阳光中奔跑着的健身爱好者无不向我们展示着奔跑的乐趣。More specifically, running triggers the release of brain chemicals called endocannabinoids that create a potent feeling of pleasure.更确切地讲,在奔跑时人体内有一种化学物质被释放,从而使人产生一种强烈的愉悦感。As their name suggests, these endocannabinoids work in the same way as the active ingredient of marijuana.正如其名字的含义一般,这些endocannabinoids有着跟大麻中的有效成分一样的效果。From an evolutionary standpoint this surge of endocannabinoids, and the runners high it creates, make sense.从进化论的观点来看,人体内endocannabinoids水平的上升及由此而生的赛跑者的亢奋对人类的发展是有意义的。For ancient humans, remaining fit enough to run after game and away from predators and enemies was vital for survival.那些远古时代的人类,为了能够顺利追捕到猎物并从其他猎食者的追击中逃脱,必须将身体状态始终维持在一个良好的水平。Yet whether other mammals are also driven to exercise by endocannabinoids has remained a mystery.既然人类如此,那么其他哺乳动物是否也会在endocannabinoids的内在驱动下而进行锻炼呢?Now a study led by David Raichlen of the University of Arizona has revealed that the runners high does exist in other species, but not in all.这仍是个未解之谜。现在一项由Arizona大学的David Raichlen士领衔的研究已经在其他哺乳动物体内-并非全部都有-发现了endocannabinoids的存在。You expect me to what?!你猜我在干什么?!Dr Raichlen hypothesised that endocannabinoid-driven exercise highs would be found in those mammals that gain an evolutionary benefit from being fast on their feet: antelopes, horses and wolves, for example.Raichlen先提出了一个假设:像羚羊,马和狼这样一些因拥有飞毛腿而在进化过程中受益的哺乳动物中也存在着锻炼产生的兴奋现象;However, he also thought that they would not be present in those which are known for being quick and agile, but not for running, like ferrets.而那些以灵动著称,却非凭奔跑文明的动物,如雪貂,则不会出现此现象。To test these ideas, he and a team of colleagues devised an experiment that monitored the endocannabinoid levels of different species after they had been walking or running on a tmill.为了检验这些猜想,Raichlen和由其同事所组成的团队设计了一个实验-对在跑步机上行走,奔跑过后的动物体内的endocannabinoids水平进行监控。The experimental animals in question were ten people, eight dogs and eight ferrets.被考虑用来进行实验的动物有以下三种:十个人,八条和八只雪貂。Dr Raichlen had them run or walk on the tmill for 30 minutes.Raichlen士先让他们在跑步机上行走或奔跑30分钟。Since running and walking speeds differ from species to species, the speed at which the tmill moved was varied so that it raised the heart rates of the different participants to the same level.由于不同的动物速度不一,所以跑步机的传送带速度设置是以使不同动物的心率达到同一水平为依据。Running speeds were thus set at 2.5 metres a second for people, 1.83 for dogs and 0.84 for ferrets.这样设置的结果便为:奔跑速度为人类2.5米/秒,1.83米/秒,雪貂0.84米/秒;Walking speeds were set at 1.25 metres a second for people and 1.1 for dogs.行走速度为人类1.25米/秒,1.1米/秒。The ferrets proved too easily distracted to walk consistently on the tmills and were thus left to sit quietly in their cages for this part of the study.雪貂由于太易分心,没办法让它持续在跑步机上行走,所以在进行该部分实验时它们被留在了笼中静静地坐着。Each participating animal ran for one session and walked for one other, and did so on separate days, to avoid exhaustion.每只动物会跑一段走一段,为了避免动物们出现筋疲力尽的情况,实验是分成几天进行的。Before and after each session, blood was drawn from each and the endocannabinoid levels in it were measured.在实验前和试验后,动物们都会被抽血以检验其中的endocannabinoid水平。The researchers report in the Journal of Experimental Biology that, after 30 minutes of walking, participants endocannabinoid levels did not rise.研究人员在《生物学实验》杂志中提到,在经过30分钟的行走之后,参加实验的动物的endocannabinoid水平并没上升。After running, however, the average humans endocannabinoid levels rose from 2.4 picomoles per millilitre to 6.1.然而在奔跑过后情况则有所不同:那10个人的平均endocannabinoid水平从2.4 pmol/ml上升到了6.1 pmol/ml。Dogs showed a similar trend, with levels rising from 2.4 pmol/ml to 8.0.的变化趋势与人类似---由2.4 pmol/ml升至8.0 pmol/ml。Ferrets were different. Although they did show an increase, from 3.0 to 3.9 pmol/ml, this was not a statistically significant rise.唯独雪貂例外。他们的endocannabinoid水平虽亦有所上升-3.0 至 3.9 pmol/ml,但仍处于统计学上可不被纳入考虑的范围内。These findings suggest that dogs experience a runners high but ferrets do not.这些发现表明中同样存在着赛跑者的亢奋现象,而雪貂则没有。Dr Raichlen argues that it makes sense for ferrets not to have systems that reward cardiovascular activity, since such exercise consumes a lot of energy, may cause injury, and is not crucial to the stealthy hunting technique of sneaking down burrows and killing rabbits in their sleep.看来雪貂体内并不存在对心血管活动进行阳性强化刺激的系统,Raichlen士认为这对雪貂的发展同样是有意义的,要知道太剧烈的运动会消耗掉过多的能量, 甚至引发受伤,且这并非是雪貂捕猎技术中的关键-它们一般只需偷偷溜进兔子窝并在兔子们熟睡时将其杀死即可。What is not clear is whether the endocannabinoid reward is an ancient mechanism that has been lost on branches of the mammalian tree that do not need it, or is something that evolves quickly in species which become active.仍有待考的是,究竟这种endocannabinoid刺激机制是从远古时代起即为哺乳类动物所拥有,还是从某些活跃的个别物种中进化出来的?Given that humanitys arboreal simian ancestors would presumably have had little need to run, it is probably the latter.鉴于人类的祖先—类人猿是树栖动物,据推测它们很少有奔跑的需要,因此正确结论很可能是后者。But to be sure Dr Raichlen will need to put animals far less co-operative than ferrets on the tmill.但若要确认此假设,Raichlen士需将更多如雪貂般不太合作的动物哄上跑步机。 /201403/278510。
  • Science and technology科学技术Scientific publishing科学出版The price of information信息的价格Academics are starting to boycott a big publisher of journals学术界开始联合抵制某个大型期刊出版商SOMETIMES it takes but a single pebble to start an avalanche.有时一块小卵石就足以使冰山崩裂。On January 21st Timothy Gowers, a mathematician at Cambridge University,一月二十一日,剑桥大学数学家Timothy Gowers写了一篇文,wrote a blog post outlining the reasons for his longstanding boycott of research journals published by Elsevier.其中陈列了其长期抵制埃尔塞维尔科学出版社的研究期刊的原因。This firm, which is based in the Netherlands, owns more than 2,000 journals, including such top-ranking titles as Cell and the Lancet.这个总部位于荷兰的公司主营的期刊就有2000多,包括《细胞》和《柳叶刀》等世界一流的刊物。However Dr Gowers, who won the Fields medal, mathematicss equivalent of a Nobel prize, in 1998, is not happy with it, and he hoped his post might embolden others to do something similar.然而菲尔兹奖得主Gowers士对它不满,并希望其文可以鼓励他人联合抵制。It did.他目的达到了。More than 2,700 researchers from around the world have so far signed an online pledge set up by Tyler Neylon,Gowers士的同事Tyler Neylon受到该文的鼓舞,在网上发起请愿,a fellow-mathematician who was inspired by Dr Gowerss post, promising not to submit their work to Elseviers journals,目前已有来自世界各地的2700多名研究者签名,他们承诺不会投稿到Elsevier的期刊,or to referee or edit papers appearing in them.也不会推荐或编辑上面刊登的文章。That number seems, to borrow a mathematical term, to be growing exponentially.签署的人数—借用数学术语来说—似乎呈指数增长。If it really takes off, established academic publishers might find they have a revolution on their hands.如果这真的形成一股风气,那已成立的学术出版社可能面临一场大变革。A bundle of trouble麻烦不断Dr Gowerss immediate gripes are threefold.Gowers士的不满可以分为三点。First, that Elsevier charges too much for its products.首先,Elsevier的产品要价太高。Second, that its practice ofbundling journals forces libraries which wish to subscribe to a particular publication to buy it as part of a set that includes several others they may not want.其次,它将几种刊物捆绑出售,这就让想要订阅其中某种刊物的图书馆不得不将囊括了他们不想要的刊物的系列刊物全买下。And third, that it supports legislation such as the Research Works Act, a bill now before Americas Congress that would forbid the government requiring that free access be given to taxpayer-funded research.第三,它持研究工作法等立法,该法案无须通过美国国会,就可以阻止政府为纳税人资助的研究小组提供免费通道。Elsevier insists it is being misrepresented.Elsevier坚称自己是被误解了。The firm is certainly in rude financial health.无疑该公司的财务状况很强健。In 2010 it made a 724m profit on revenues of 2 billion, a margin of 36%.2010年其收入有20亿欧元,热利润只有7.24亿欧元,利润幅度达36%。But it charges average industry prices for its products, according to Nick Fowler, its director of global academic relations,然而其全球学术关系部门领导Nick Fowler认为其开价属于行业平均价格,and its price rises have been lower than those imposed by other publishers over the past few years.而且过去几年来,其价格涨幅要比其它出版商要低。Elseviers enviable margins, Dr Fowler says, are simply a consequence of the firms efficient operation.Fowler士称,Elsevier那让人眼红的盈利幅度,只是该公司高效运转的结果。Dr Neylons petition, though, is symptomatic of a wider conflict between academics and their publishers—a conflict that is being thrown into sharp relief by the rise of online publishing.然而,Neylon士的请愿不过是学术及其出版商之间矛盾扩大化的一种象征——由于网络出版业的崛起,这种矛盾已经得到大大的缓解了。Academics, who live in a culture which values the free and easy movement of information have long been uncomfortable bedfellows with commercial publishing companies,学术,能生长于一个重视信息传播的自由性与方便性的文化环境中,同时也是一个愿意无偿编辑和评判文章的事物。which want to maximise profits by charging for access to that information, and who control many of the most prestigious scientific journals.但长期以来,学术与商业化出版商就格格不入,后者希望通过向信息获取者收费从而使利润最大化,此外还掌控着大多数最负盛名的科学刊物。This situation has been simmering for years.这种局面已经酝酿多年了。In 2006, for example, the entire editorial board of Topology, a mathematics journal published by Elsevier, resigned,比如,2006年Elsevier出版一本数学期刊《地志学》时,整个编辑委员会都提出辞呈,citing similar worries about high prices choking off access.并对高价掐断信息来源的行为表示类似忧虑。And the board of K-theory, a maths journal owned by Springer, a German publishing firm, quit in 2007.而德国某出版公司Springer旗下的一本数学期刊《扭结理论》的编辑委员会也于2007年辞职。To many, it is surprising things have taken so long to boil over.酿就一件事花费如此长的时间让很多人大跌眼镜。Academics were the internets earliest adopters, with all the possibilities for cutting publishers out of the loop which that offers. And there have indeed been attempts to create alternatives to commercial publishing.学术界是最早采纳互联网的。却是有人试图为商业出版提供更多选择。Cornell Universitys arXiv website was set up in 1991.康奈尔大学的arXiv网站于1991年成立。Researchers can upload maths and physics papers that have not been published in journals.研究员可以上传一些还没在期刊上发表的数学及物理文章。Thousands are added every day.每天添加的文章成千上万。The Public Library of Science was founded in 2000.公共科学图书馆于2000年成立,It publishes seven free journals which cover biology and medicine.它会免费出版7种涵盖生物学和医学的刊文。But despite the enthusiasm for such operations, there are reasons for the continued dominance of traditional publishers.然而,尽管人们有热情去做类似事情,但传统出版商主导地位依旧屹立不倒也有其理由。ArXivs papers, though subject to merciless post-publication commentary, are not formally peer-reviewed before they are posted.ArXiv的文章,尽管遭受到出版后的无情抨击,但他们在发表之前并没有接受同行审评。Their quality is thus rather uneven.因此其质量相当不平衡。PLoS relies partly on donations, but also charges publication fees of up to ,900 per paper.PloS的部分经济来源于捐赠,但每篇文章也收取高达2900美元的发表费。These must be paid by the authors, a significant expense for cash-strapped university departments.这些费用必须由作者承担,对于囊中羞涩的大学部门来说这是笔很大的费用。And there is also a lingering prejudice against electronic-only publishing.此外,关于只有电子版的刊物的偏见一直存在。Web-based alternatives often seem less respectable than their dead-tree counterparts.通常,相比网络版刊物,人们更尊重那些过时了的纸质版刊物。That matters, because university departments are rated both by the number of papers they publish and the reputation of the journals those papers appear in.这至关重要,因为大学部门是以他们所发表的文章数量及其所在刊物的名气程度来评级的。Youngsters, who might be expected to embrace new ways of doing things, must therefore publish in existing, reputable journals if they want recognition and promotion.因此,可能接受新方式的青年如果想要得到承认与升迁,就必须在有名气的实体刊物上发表文章。And the definition ofreputable changes slowly, since journals with the best reputation get the pick of new papers.由于新报刊能够成为最有名气的报刊,名气的定义也在逐渐改变。Commercial publishers have begun to experiment with open-access ideas, such as charging authors for publication rather than ers for ing.商业化出版商已经开始尝试开放式获取理念,比如收费对象从读者转向发表文章的作者。But if the boycott continues to grow, things could become more urgent.然而,如果抵制情绪持续增长,问题将变得更为紧迫。After all, publishers need academics more than academics need publishers.毕竟,需要学院的出版商多过需要出版商的学院。And incumbents often look invulnerable until they suddenly fall.而且往往出版商在倒下的前一刻还看起来坚不可摧。Beware, then, the Academic spring.那么,当心学术的春天到了。 点击此处下载本期经济学人讲解PDF与音频字幕 /201306/245146。
  • Its four A.M.早上四点,Youre tucked safely into a warm bed, savoring the last few hours of sleep before daybreak.你还躺在温暖的被窝里,享受着天亮前几个小时的睡眠时间。And then, suddenly…然而就在这时突然一阵声音惊扰了你的美梦…It must be time to wake up, roll out of bed, and tend to the farm.听到起床号了就得爬出被窝开始劳作。Except its four A.M.,但是现在才四点!its still dark out, and youre not a farmer.外面仍然漆黑一片,而且你又不是农民。Its that neighbor of yours, the one that for some unimaginable reason keeps a rooster as a pet.鸣叫的公鸡是隔壁家的,那个家伙不知道为什么养了只鸡当宠物。A rooster that flaunts the most basic rules of neighborhood etiquette by crowing every morning before sunrise. What gives?每天太阳升起前,公鸡都会仿佛问候邻居早安一样的打鸣。原因何在? 201312/268351。
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