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山东省第二人民医院可以刷医疗卡吗新华优惠山东省妇幼保健医院做彩超B超价格

2019年06月20日 17:08:34    日报  参与评论()人

济南真爱女子医院有没有位置济南宫外孕手术得多少钱济南市妇儿女子医生名单 The Rolling Boil That Cools Your Food有一种沸腾能冷却你的食物!When you think of something boiling, you probably picture a pot on the stove, but theres another kitchen appliance that brings liquid to a boil, not to heat food, but cool it. It sounds crazy, but household refrigerators keep food cold by bringing liquid fluorocarbon to a boil.一提到沸腾的事物,你的脑海里可能就会浮现出水壶被放在炉子上的画面。但是,有一种厨具可以使液体沸腾,但不是为了加热食物,而是用于冷却食物。这事儿听起来很不可思议,但是家用冰箱就是通过使碳氟化物沸腾来冷藏食物。How Does This Work?这其中的原理是什么呢?Fluorocarbon coolant flows through two sets of coils in your fridge, absorbing heat inside and releasing it outside, into your kitchen. Youve probably seen one set of coils behind the fridge, in back. Thats where heats released. Hidden inside the fridge is the other set of coils, where heats absorbed.碳氟化物冷却剂流经冰箱的两组盘管,吸收冰箱内部的热量并将其释放到外部。你可能看到在冰箱后侧有一组一组盘管,热量就是在那里被散发。而藏在冰箱内部的另一组盘管则是用来吸收热量的。Its inside these hidden coils that liquid coolant comes to a boil. What makes the coolant boil? The secret is in the relationship between pressure and boiling point. When pressure changes, so does the temperature at which a substance comes to a boil.就是在这组内置盘管里,液态冷却剂会沸腾。是什么使冷却剂沸腾的呢?在于压强和沸点之间的关系。当压强发生改变,物质的沸点也会跟着变化。As the liquid coolant passes through a valve into the hidden coils, the pressure drops. This pressure change makes the coolants boiling point drop below the chilly temperature in the fridge. So, some of the coolant boils immediately and evaporates into a gas inside the coil. Evaporation uses up lots of heat energy. As the coolant continues to boil and evaporate, it absorbs heat from the air in the fridge, making it even colder inside. So that’s how boiling fluorocarbon cools your food.随着液体冷却剂经过一个阀门进入内置盘管,压强就会降低。压强的变化使冷却剂的沸点降到比冰箱内部的低温还要低。这样,部分冷却剂立即沸腾,在盘管内汽 化。汽化作用会消耗掉大部分热能。随着冷却剂不停地沸腾汽化,冰箱中空气的热量被吸收,使得冰箱内部温度更低。沸腾的碳氟化物就是这样冷却了食物。 /201207/188945市中区人民医院顺产多少钱

济南市妇女医院打胎流产好吗济南市真爱妇科怎么走 济南公立三甲医院属于几甲等医院

济南市第七医院治疗效果Science and Technology科学技术Palaeontology古生物学Splay-footed, not flat-footed八字足,而非平足A new fossil shows that evolution does not always mean change一个新的化石表明:进化并不总是意味着改变Then and now过去与现在WHEN a coelacanth, a type of lobe-finned fish once considered the missing link between fish and amphibians, was found off the coast of South Africa in 1938, it came as a shock to palaeontologists.以前人们一度认为一种叫做腔棘鱼的鳍鱼是鱼类和两栖类之间缺少的环节,1938年当腔棘鱼在南非海岸沿海被发现时,古生物学家对它的出现大感震惊。Until then, the most recent traces of such a creature had been in rocks dating from the last days of the dinosaurs, 65m years ago.在此之前,这种动物最近的遗迹出现在6500万年前恐龙时代后期的岩层中。It was, in its way, as surprising as if a live Tyrannosaurus had been found hiding in an obscure part of Montana.而它这次的出现方式,就好像一个活生生的霸王龙属被发现藏身在蒙大拿州的模糊地带一样令人惊讶。Now the same experience is hitting palaeontologists again—but this time in reverse. Instead of finding a living fossil identical to an ancient beast, they have found a real fossil identical to a modern one.现在,同样的经历再次让古生物学家碰上了,不过这次相反。他们不是找到了一个与古兽相同的活化石”,而是找到了一个跟现代兽类相同的真正化石。The fossil in question, a 100m-year-old specimen from north-east Brazil, belongs to the genus Schizodactylus.所讨论的的化石采自巴西东北部,是一亿年前的标本,属于节肢动物类。These are large, carnivorous, cricket-like insects whose feet splay out wildly in different directions.这类节肢动物是大型类似板球的食肉昆虫,其足向不同方向伸展开来。Modern Schizodactylus use their feet like snowshoes, to help them remain stable as they travel over sandy terrain in search of prey.现代节肢动物在沙地爬行寻找猎物时用它们雪鞋般的脚来帮助身体保持稳定。If the new fossil—whose discovery has just been published in ZooKeys by Sam Heads of the Illinois Natural History Survey and Léa Leuzinger of the University of Fribourg, in Switzerland—were merely similar to modern splay-footed insects, the find would not be particularly surprising:如果新化石其发现刚由伊利诺斯州自然史调查的负责人山姆和瑞士弗里堡大学的李?劳伊辛格发表在《动物图谱》上仅是类似现代的八字足昆虫,那么这个发现不会特别令人惊讶:it simply demonstrates a phenomenon called evolutionary stasis, in which a specific type of body form hangs around for a long time.它只是明了一种被称为进化停滞的现象,在这种现象中特定类型的体型存留很长一段时间了。What is surprising is just how static Schizodactylus has been.令人惊讶的是节肢动物停止进化竟有这么久了。Evolutionary stasis is fairly common at the higher levels of the Linnaean system of biological classification.在林耐生物分类系统的高等类别中进化停滞现象是相当普遍的。Natural selection hits on a good design.自然选择的图案都是最好的。That design is then adopted in slightly different forms by species after species.然后,这种图案就被一个接一个的物种以略有不同的形式所采纳。The shelled bodies of turtles, for example, evolved between 250m and 200m years ago, while the body plans of scorpions have been around for more than 400m years.例如,海龟的壳体是在2.5~2.0亿年前进化的,而蝎子的体型方案已超过4亿年的历史。That does not mean, however, that a zoologist would mistake a 200m-year-old turtle or a 400m-year-old scorpion for any species now alive.然而这并不意味着一个动物学家会弄错2亿岁的海龟或是4亿岁的蝎子属于现在存活的何种物种。What is remarkable about the new find is that it is so similar to modern animals that it can be assigned to an existing genus—the lowest level of Linnaean classification above a species—rather than just to some higher taxonomic group.新发现引人注目的是它与现代动物如此相似,以致它可以被列入现有生物分类种类,而不是只被列入某一更高等的分类组。That is rare indeed.这的确罕见。Even the modern coelacanth, on closer examination, had to be put in a different genus from any known fossil.经过仔细观察,甚至就连现代腔棘鱼都必须得归类于不同于任何已知化石的种类。Clearly the body plan of Schizodactylus is not merely good, but optimal, at least for the environment the animal lives in.显然,节肢动物的体型方案不仅是最好的,也是最佳的,至少对这种动物生活的环境而言是如此。Alas for Schizodactylus, the sandy deserts it prefers have retreated from north-eastern Brazil and its optimality there has vanished.唉,对节肢动物来说,它所喜爱的沙质沙漠已经从巴西东北部退却,它在那里的最佳体态已经消失。But its discovery shows better what this part of the world was like 100m years ago—and also illustrates an important point about evolution that is often forgotten in biologists understandable focus on the development of novelty. The first rule of natural selection is: If it aint broke, dont fix it.”但它的发现恰好说明这部分的大千世界跟1亿年前的样子很象,也说明了进化论的一个重点,而这点在生物学家关注理解新颖性的发展时往往被遗忘了。自然选择的第一条规则是:如果没坏,就不要修理它。” 点击此处下载本期经济学人讲解PDF与音频字幕 /201303/228974 Beware Of Text Neck!小心短信脖子Remember when the Blackberry was all the rage, and people worried about straining their thumbs typing on that tiny keyboard?还记得黑莓很流行的时候,人们担心在那个小小的键盘上拉紧拇指输入对手指不好吗?Well, now that the iPhone and other smart phones have taken center stage, theres another malady gaining traction text neck.嗯,既然苹果手机和其他智能手机已成为主流,另一种弊端出现了,就是会产生短信脖子。Seriously text neck, as in all that hunching over phones and tablets playing Angry Birds, causing muscles in the neck, shoulders, and even arms and hands to become strained. And all that strain can lead to chronic pain, because the joints and muscles of the neck and shoulders are not meant to be flexed for long periods.严肃地说,当人们低着头弓着身体玩着手机或者平板电脑里的游戏,比如愤怒的小鸟时,就会使得脖子上、肩膀甚至手臂上和手上的肌肉处于拉紧的状态。这些全部的拉紧会导致慢性疼痛,因为脖子,肩膀连接处和肌肉本应该处于很长的放松的状态的。There’s even been a study on the text neck phenomenon. It found that among 140 students or so surveyed, those who used tablets and smart phones at least three hours a day were more likely to experience neck and shoulder pain than those who used the devices less frequently.甚至还有一个关于短信脖子现象的研究。在被调查的140多个学生当中,相比那些不经常使用的人,那些每天至少玩三个小时平板电脑和智能手机人更有可能会脖子和肩膀疼。True, 140 students is a pretty small sample. But anecdotal evidence is legion. And chiropractors and orthopedic doctors have been advising people to avoid text neck by not hunching over their devices. Instead, try tucking your elbows into your side and holding the device up by your chest.事实上,140个学生是个很小的抽样检查。但是轶事据却是大量的。脊椎师和整形外科的医生已经建议人们为了避免短信脖子,用那些电子产品时尽量不要弓着脖子。试着在一边托着你的肘部拿着那些电子产品的高度要在胸部以上。And, of course, it’s important to take regular breaks from staring into your smart phone’s bottomless digital playground.当然,有规律地暂时从盯着你的智能手机的游戏无底洞式的画面转移,休息一下很重要。There’s even a text neck app that alerts you when you’re hunching over your device and reminds you to straighten up.甚至有防止短信脖子应用出现了,当你弓着脖子盯着电子设备时,提醒你要伸直脖子。 /201206/186647济南市真爱妇科有做缩阴吗济南真爱医院在哪里

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