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青岛做无痛人流医院哪家费用低365乐园李村儿童医院网上预约挂号

2019年10月19日 13:33:07    日报  参与评论()人

黄岛哪个医院做人流手术好青岛那家医院治白带有血丝Whats the difference between a hard-shelled blue crab anda soft-shelled blue crab?你知道软壳青蟹和硬壳青蟹有什么区别吗?Is this a trick question?这个问题很难吗?Ill give you a hent. It has to do with the crabs skeletal system.我来给你个提示。这与螃蟹的骨骼系统是紧密相关的。Skeletal system?骨骼系统?You got me there, I know that like other crustaceans, periodically molt.哦,我大概懂了。就像是其它的甲壳类动物一样,螃蟹会定期的褪壳。That is, the crab sheds its hard shell and forms a new one.也就是说,螃蟹褪掉原有的硬壳再重新长出新壳。But I dont have a clue as to what that means about the skeletal system?但问题是,我想不明白这怎么就和骨骼系统扯上了关系。Well, Ill tell you.那就由我来告诉你吧。When a blue crab sheds its hard shell, its exoskeleton, it has to wait about aweek for the new shell to harden.当一只青蟹褪掉了它的硬壳之后,新长出的壳要等上大概一个星期才能变硬。Before that happens, this outer layer of tissue is too soft and flexible to transmit muscle contractions as it did, and will do again when the crabs new shell hardens.在壳变硬之前,外面的那层“壳”太软太韧了,以致于无法进行正常的肌肉收缩。在新壳变硬之时还要再进行一次。And yet these creatures are somehow still able to move about, even immediately after molting.而且,不知为何,青蟹在这种情况下还是能到处爬来爬去的,即使是刚刚褪壳的时候也是如此。How is that possible?这怎么可能呢?Its possible using a hydrostatic skeleton.使用铃静力骨架就可以了!Many animals, such as worms, rely on hydrostaticskeletons all their lives.许多种动物,比如说蠕虫,它们一生都是靠铃静力骨架撑下来的。What this means is that muscle contractions are transmitted through anincompressible fluid.这也就是说,肌肉的收缩通过不可压缩铃被传送到了身体各部分。Immediately after molting, the hydrostatic pressure inside crabs jumpssignificantly higher, allowing the crabs to use this pressure to move their muscles.青蟹刚刚褪壳的时候,体内的铃静压力陡然飚到很高,这使得青蟹可以利用压力来使肌肉活动。While ahydrostatic skeleton isnt so remarkable in itself, what is remarkable is that the crab alternates between using the two kinds of skeletons.青蟹的铃静力骨架并不是特别出众,真正出众的是青蟹在外骨骼和铃静力骨架之间出众的交替使用能力。Scientists suspect that crabs probably arent alone inthis feat and plan to investigate the skeletal systems of other creatures that molt.科学家们猜测,蟹并不是唯一一种此类动物,接下来,科学家们将会研究更多褪壳生物的骨骼系统。 201408/319479青岛市第三人民医院电话挂号 Science and technology科学技术Table-top astrophysics桌面上的天体物理学How to build a multiverse怎样建立一个多元宇宙Small models of cosmic phenomena are shedding light on the real thing宇宙现象的一些小模型反映了真相THE heavens do not lend themselves to poking and prodding.天空不会帮助任何企图研究它的行为。Astronomers therefore have no choice but to rely on whatever data the cosmos deigns to throw at them.因此,天文学家们只能听天由命,任何宇宙透露出的一些数据,他们都当做宝贝一样。And they have learnt a lot this way.不过他们通过这种方式也学到了很多。Thus you can even study chemistry in space that would be impossible in a laboratory.因此,人们甚至能在太空中研究化学,而这在实验室是无法做到的。Some astronomers, though, are dissatisfied with being passive observers. Real scientists, they think, do experiments.虽然,一些天文学家们对成为被动的观察者很是不满,他们认为真正的科学家应该是有所行动的。It is impossible—not to mention inadvisable—to get close enough to a star or a black hole to manipulate it experimentally.要想接近一颗星或者一个黑洞,进行实验性地操作是不可能的,其实也是不可取的。But some think it might be possible to make meaningful analogues of such things, and even of the universe itself, and experiment on those instead.但是,一些人认为,如果进行类似方面,甚至宇宙方面的有意义的研究,而不是试验,是有可能的。Ben Murdin of the University of Surrey, for example, has been making white dwarfs.比如说,萨里大学的本-穆迪一直在制作白矮星。A white dwarf is the stellar equivalent of a shrunken but feisty old-age pensioner.从某种程度上说,白矮星是一颗虽然已经萎缩,但仍旧不老的高龄恒星。It has run out of fuel and is contracting and cooling as it heads towards oblivion—but taking its time about it.当它正慢慢淡出宇宙这个大家庭时,它的动力已渐渐耗尽,而且正在缩小,渐渐变冷,但是还是值得花些时间的。As they shrink white dwarfs pack a mass up to eight times the suns into a volume the size of Earth.当它们缩小时,这些白矮星把自己相当于八个太阳那么大的个头压缩到了地球这么大的个头。A consequence of stuffing so much matter into so little space is that white dwarfs have powerful magnetic fields.把如此之大的东西压缩到了这么小空间的结果是,白矮星拥有强大的磁场。Many aspects of a white dwarfs mechanics, including how long it will last, are thought to depend on its magnetism.天文学家认为,白矮星形成过程的许多问题,包括它会存在多久,都基于它的磁场。But it is hard to measure.但是这是无法衡量的。To make estimates, scientists examine the light a white dwarf emits for telltale patterns left by stellar ingredients like hydrogen.为了做出这方面的估计,科学家们检测了白矮星发出的光,这种光正说明了这种问题的某种方式,是由组成恒星的元素,比如氢产生的。They then compare this spectrum with a theory, based on calculations from first principles, of how magnetic fields effect light emitted by hydrogen.然后,他们把测得的光谱与理论计算得到的结果进行了比较,这种理论是基于氢怎样产生磁场效应区域的第一原则得到的。The predictions agree with experiments up to the strongest fields mankind can muster—about 1,000 tesla, generated in a thermonuclear detonator.结果,预测与试验完全一致—即达到人类在这个领域最高水准,能够在热核雷管中产生1000特斯拉的磁感应。The problem is that the theory puts white dwarfs magnetic fields at 100,000 tesla or more, well beyond humanitys reach.问题是,这个第一原则认为白矮星的磁场强度可以达到100,000特斯拉或者更多,远远超过了人类的极限。Dr Murdin built his own little white dwarf to see if the theory looked good.穆迪士建造了他自己的小白矮星,想弄明白这种理论是否真的正确。It consists of a silicon crystal sprinkled with phosphorus atoms.这个小白矮星由布满磷原子的硅晶体组成。A silicon atom has four electrons in its outer shell.一个硅原子外有四个电子。In a crystal, all four are used to bind it to neighbouring atoms.在晶体中,所有的四个电子都是与其相邻的原子紧紧捆绑在一起。Phosphorus has five outer electrons.磷原子外有5个电子。Insert a phosphorus atom into the silicon lattice and you are left with an unused electron.把一个磷原子嵌入到硅晶格中,那还剩下一个电子。Since phosphorus also has one more proton in its nucleus than silicon does, taken together the extra particles resemble a hydrogen atom: a single electron tethered to a single proton.因为磷的细胞核中比硅还多一个质子,把多余的质子、电子收集起来,这和氢原子的结构很相似:一个独立的电子捆绑着一个独立的质子。However, the extra electron is much less tightly held by the extra proton in this pseudo-hydrogen than it would be in real hydrogen.然而,在这个山寨版的氢中,这个额外的电子与额外质子的结合并不如真正氢原子中那么紧密。This weaker grasp means that it takes much less magnetism to make a given change in the pseudo-hydrogens spectrum than it would for real hydrogen.这种越来越弱的结合意味着,如果要让这个山寨版频谱产生一个额定的变化,它所需要的磁场比真正的氢少得多。So when Dr Murdin placed the crystal in a 30-tesla magnet at Radboud University in the Netherlands, he was mimicking the conditions in a 100,000-tesla white dwarf.因此,当穆迪士这个晶体放到一个30特斯拉的磁体中时,因为他在格尔福德的实验室缺少必要的设备,他是在模仿一个100,000特斯拉磁场强度的白矮星所处环境。And the spectrum came out looking just the way the theory predicted.结果得到的频谱与理论预测的看起来很像。A black hole in a bath浴缸中的黑洞Creating a star in a laboratory is small beer compared with creating a black hole.在实验室中建立一颗星星,相比于建立一个黑洞简直就是不值一提。This is an object that is so massive and dense that not even light can flee its gravitational field.黑洞是一个很庞大,密度很高的物体,甚至连光都无法逃脱它的引力场。Looking inside one is therefore, by definition, impossible.因此,向里面看—就是字面意思上的看—一眼都是不可能的。All the more reason to try, says Silke Weinfurtner of the International School for Advanced Studies, in Trieste, Italy.所有的,越来越的理由都让人们想试试建立一个山寨版的黑洞—意大利里雅斯特国际高级学院的西尔克-威福特纳这样表示。Dr Weinfurtner plans to make her black hole in the bath.威福特纳士计划在浴缸中建立一个她的黑洞。The bath in question, properly called a flume, is a water-filled receptacle 3 metres by 1.5 metres and 50cm deep, across which carefully crafted trains of ripples can pass.这里说到的浴缸,更应该称之为水槽,因为它是一个3米乘1.5米,50厘米深的装满水的容器,横跨其中的是精心制作的涟波车队。In the middle of the tank is a plug hole.在这个水槽中有一个泄水孔。If the water going down the hole rotates faster than the ripples can propagate, the ripples which stray beyond the aqueous event horizon will not make it out.如果水旋转至水孔的速度快于涟波扩散的速度,那么超过水的黑洞边境—是黑洞的不归路--的涟波就不会让水漫出来的。They are sucked down the drain.水将会被吸到下水道里。Then the researchers will check whether the simulacrum affects water waves in a way analogous to that which general relativity predicts for light—itself a wave—approaching an astrophysical black hole.到时,研究者会检查这个模拟物,是否会以一种与广义相对论预测的光,接近天体物理学黑洞类似的方式影响水波。According to Albert Einsteins theory, a region immediately outside the event horizon of a rotating black hole will be dragged round by the rotation.根据爱因斯坦理论,一个靠近旋转黑洞边界的外部区域会在这个旋涡的影响下也转动起来。Any wave that enters this region but does not stray past the event horizon should be deflected and come out with more energy than it carried on the way in.任何进入这个区域,没能穿越过去的光波会发生偏离,并且将会带着比它接近这里时更多的能量出现。To detect this super-radiant scattering, as the effect is called, Dr Weinfurtner will add fluorescent dye to the water and illuminate the surface waves with lasers.为了检测这种越辐射的辐射—这种效应被这样称谓,威福特纳士会在水中加入荧光染料,资助用激光照亮表面的水波。The waves, often no bigger than one millimetre, can then be detected using high-definition cameras.这些往往不会超过1毫米的水波,届时可以通过高清度摄像机拍下来。Stefano Liberati, Dr Weinfurtners colleague in Trieste, reserves the greatest enthusiasm for another aspect of the experiment.威福特纳士在里雅斯特的同事,斯特凡诺-莱伯拉蒂对这个试验的另一个方面表现出了极大的热情。It might, if the researchers are lucky enough, offer clues to the nature of space-time.如果研究者们运气好的话,这可能会是研究空间-时间本质的一个线索。Could the cosmic fabric be made up of discrete chunks, atoms of space if you like, rather than being continuous, as is assumed by relativity?宇宙的会是由一块块的独立物质,空间微粒—如果你愿意相信的话--组成,而不是像相对论认为连接在一起的吗?This problem has perplexed physicists for decades.这个问题已经困扰了物理学家们数十年了。Many suspect black holes hold the answer, because they are sites where continuous relativity meets chunky quantum physics.他们中的许多人猜测,黑洞就是,因为黑洞是连续性相对论与厚实量子物理学都无法研究出真相的地方。Waterborne holes serve as a proxy.水面上的洞就代表了这种现象。Water is, after all, made up of just such discrete chunks: molecules of H2O.毕竟,水是由类似上述的一个个分散的物质组成:水分子。As wavelengths fall—equivalent to rising energy—waves reach a point where the size of molecules may begin to influence how they behave.随着波长的减小—相当于光波能量的增加,当波长达到一定的值时,水分子的大小可能会开始影响水波的行为。If Dr Weinfurtner and Dr Liberati observe some strange behaviour around their event horizons, theorists will be thrilled.如果威福特纳士和莱伯拉蒂士能够观察到这些水波的黑洞边界周围的一些奇怪表现时,那么理论学家们会兴奋不已。and home-brewed universes自家制作的宇宙Even benchtop black holes, though, are nothing compared with the ambitions of Igor Smolyaninov of the University of Maryland.即使是桌面上的黑洞,但是也无法与马里兰大学的伊戈尔-斯莫利亚尼诺夫的雄心相比。For Dr Smolyaninov wants to create entire universes.因为,斯莫利亚尼诺夫想创造一个完整的宇宙。The way light travels through the four dimensions of space-time is mathematically akin to how it moves through metamaterial.从数学的角度看,光穿越四维空间的方式与它穿透超材料的方式很接近。These are substances with features measured in nanometres, or billionths of a metre, which let them bend light in unusual ways.这些材料是以纳米为单位,或者是以一米的十亿分之一为单位的特别物质,所以可以以特别的方式改变光的方向。For example they can force light to skirt along the outside of an object, hiding it from view as if behind an invisibility cloak.比如说,它们可以让光波绕开一个物体的,就好像隐藏在一个隐形斗篷的后面,让人无法看到它。Space-time, too, bends light, in ways that depend on how mass is distributed within it.时空也同样可以改变光的方向,改变方式取决于这个空间质量的分配方式。In principle, then, metamaterials ought to be able to mimic how light moves not just through the space-time scientists on Earth are familiar with, but also other possible space-times to which they do not, and never will, have access.原则上讲,超材料应该不仅能够模拟地球科学家们熟悉的光波穿越时空,而且可以模拟光穿越其它可能存在的,地球科学家们无法触及,也可能永远无法打开的时空。Two years ago Dr Smolyaninov suggested an experiment with various metamaterials, corresponding to universes with different properties lashed together into a home-brewed multiverse.两年前,斯莫利亚尼诺夫曾建议用不同的超材料进行试验,相当于把拥有各种特性的宇宙集中到了自家创造的宇宙中。In a paper to be published inOptics Express, he and his colleagues report that they have succeeded.他和他的同事在光学快报上发表了一篇论文,称他们的试验取得了成功。Rather than fine-tune metamaterial to exact specifications, which is finicky and expensive, the researchers used nanoparticles of cobalt, which are relatively easy to get hold of, and suspended them in kerosene.研究者并没有对超材料的具体规格进行微调,因为这样既繁杂又增加成本,他们使用了钴的纳米粒子,这个相对而言容易得到,可以把它们暂时存放在煤油中。They then applied a magnetic field which, thanks to cobalts ferromagnetic nature, arranged the particles into thin columns.然后,根据钴的铁磁性,他们应用一个磁场把这些粒子安置到了薄薄的柱子中。In space-time terms the length of the columns is time and the two axes perpendicular to the length represent the three spatial dimensions in a real universe.在时空的术语中,这种柱子的长度就表示,时间和两个垂直于距离的轴代表着真实宇宙中的三维空间。To build his multiverse, Dr Smolyaninov added slightly less cobalt to the kerosene, about 8% by volume, than was needed to maintain stable nanocolumns.为了创建他的多元宇宙,斯莫利亚尼诺夫士在煤油中加了些钴,大概是总体积的8%,这比稳定纳米柱的需要量略少。Natural fluctuations in the density of the fluid then lead to the spontaneous erection of transient nanocolumns—equivalent to space-times popping up only to fizzle and re-emerge elsewhere in the multiverse.在这个液体浓中的自然流动,会导致临时纳米柱的自发性的直立—相当于时空突然出现,却只能以失败结束,但是会在这个多元宇宙中的某个其它地方再次出现。They could be detected by their effect on polarised light shone through the material.要想探测到它们,可以通过它们在极化光通过物质时所施加的影响来检测。Whether all this ingenuity unravels any cosmic truth is uncertain.所有这种独出心裁是否能解开宇宙的真相,还不确定。Cliff Burgess, a theorist at Perimeter Institute for Theoretical Physics in Ontario, has his doubts.安大略省周边物理理论研究所的克里夫-伯吉斯是一位理论学家,他还对此存有疑问。But he thinks that such experiments are nevertheless worth pursuing.但是,他认为,这些试验还是值得一试的。Like tap-dancing snakes, he says, the point is not that they do it well, it is that they do it at all.他说,就像跳踢踏舞的蛇一样,关键不是他们做得非常好,而是他们已经在做了。 /201312/268943青大附属医院做人流多少钱

青岛市中心医院药房Its summertime, and youre on vacation.时值夏季,你正在享受假期。You sit beside a quiet pond, fishing, trying to relax, trying to think about nothing at all.你稳坐在一个安静的池塘旁钓鱼,想放松自己,试图让脑子放空一切。You watch the leaves stirring, the water rippling in the sunshine, and the water bugs standing on the surface of the water. 你看到树叶随水波荡漾,湖水在阳光下泛起涟漪,还有水虫恣意站在水面上。How do they--Rats! Now your brains working again, wondering how those bugs do that.它们是如何!现在你的大脑再次被拉回工作状态,想知道虫子是如何做到的。Well relax, its Moment of Science to the rescue.好了,放松,又到了科学出马的时候。Today well explain Standing on Water.今天我们将解释水上漂。There are two things involved in this trick:这一所谓的“魔术”涉及两个环节:one is a property of the water, and the other has to do with the bugs feet.一是水的性质,另一点是这种虫子的脚。Lets start with the water.让我们先从水开始。Water molecules naturally stick to each other, due to a strong chemical attraction between the individual molecules.由于单个分子之间的强烈化学吸引力,水分子自然而然的互相紧密连接。At the ponds surface, the uppermost water molecules experience this attraction as a strong pull toward each other, and downward from the water beneath them.在池塘表面, 当强大的引力以及水内部的吸引力互相作用最上层的水分子经历这一吸引力。This creates whats called ;surface tension;-a somewhat compressed layer of water molecules right at the ponds surface.这就产生了所谓的“表面张力”,一种水分子在池塘表面的压缩层。You can think of this layer as being like a tight film over the surface of the pond.你可以将这一层想象成池塘水面一种非常紧密的膜。How does this help the water bug?这对水虫起到什么作用?If the surface water stuck to its feet as well as it stuck to the water below, the bug would be pulled under.如果撑它脚部表面的水撑水面以下,虫子就会被拉入水中。As it turns out, the bugs feet are covered with waxy hairs that are ;hydrophobic;--which means they chemically resist contact with water.事实明,脚部覆盖着蜡状毛的这种昆虫是恐水的—这意味着它们会化学抵抗与水接触。This combination of strong surface tension and water-resistant feet is what lets our bug stand on the water, without even getting wet!这种结合强大的表面张力及防水的脚部让我们的虫子站在水上,甚至没有淋湿!On our next program, well learn how water bugs move across this surface.在我们下一期节目中,我们将了解水虫如何跨越这一表面。Meanwhile, get back to your fishing!与此同时,继续享受你的钓鱼吧! 201309/255038青岛输卵管造影费用 Science and technology科学技术Dinosaur behaviour恐龙行为Headbangers疯狂撞头的家伙Evidence of duelling dinosaurs战斗性恐龙的据WORKING out how an extinct animal behaved when it was alive is tricky.对于灭绝的生物来说,要研究出它们存活时的行为是很棘手,But it is not always impossible,不过也不是完全不可能。as Joseph Peterson and Collin Dischler of the University of Wisconsin explained on October 17th to the Society of Vertebrate Palaeontology meeting held in Raleigh, North Carolina.10月17日,在北卡罗莱纳州罗利市举行的古脊椎动物学会议上,美国威斯康星大学的约瑟夫·彼得森和柯林·狄斯勒就对肿头龙的习性做出了一些解释。Pachycephalosaurs lived 65m years ago.肿头龙生活在6500万年前。As their name suggests, they had large, bony, domed heads.正如其名称所说,它们有巨大的、高隆的头骨。For years, it was assumed they used these to bash one another in the way that rams do now.多年来,人们一直认为肿头龙用头攻击同类,就像现在的公羊一样。Recently, though, a second suggestion has surfaced—that rather than for fighting, the domes were for show; the dinosaur equivalent of a peacocks tail.不过最近有人提出另外一个假设:它们的大脑袋不是为了战斗,而是出于展示的目的—作用相当于孔雀的尾巴。Dr Peterson and Dr Dischler put these two theories into a head-to-head competition.彼得森和狄斯勒士让这两种理论来了个头对头的正面对抗。To do so, they studied 102 pachycephalosaur skulls, of various species.为此,他们研究了102只不同品种肿头龙的头骨。They found that 23 of these skulls had pits in them, and that these pits were similar both to each other and to those found in the skulls of living animals that bash each other with their heads.他们发现其中23只头骨上有凹坑。这些凹坑彼此类似。而且现存的用头部撞击同类的动物中,头骨上的凹坑也与之类似。That supported the head-butting theory. The clincher, though, came when they created computerised models of pachycephalosaur skulls and mapped the damage from each of their pitted specimens on to these virtual skulls.这持了头部冲撞理论。不过决定性的据来自于他们用计算机模拟的肿头龙头骨。他们将每个有坑样本的损伤部位标注在虚拟的头骨上。When they did this, they found that the pits were clustered—exactly as might be expected if they were the result of animals deliberately aiming at each other.这样操作后,他们发现凹坑聚集分布,正如人们假设的那样:是肿头龙故意用头部攻击彼此的结果。Intriguingly, they found two patterns of clustering.有意思的是,他们发现凹坑有两种聚集图案。Those pachycephalosaurs with highly domed heads had pits on both the fronts and the backs of their skulls.那些不太隆起的头骨仅在前方有凹坑,而非常高隆的则前后都有。Those whose domes were lower had them only on the fronts.这明了两种肿头龙攻击时的不同。This suggests the two sorts of animal fought in different ways. Low-domes, it seems, simply charged at each other. High-domes did that too.相对低隆的一种似乎仅向对方迎头冲撞。But they also engaged in head-to-head wrestling of a sort that allowed them to get behind their opponentsskulls and do damage from the rear, in the way that modern bison do.非常高隆的肿头龙除此之外还会采取头对头式摔跤法:能够碰到对方头骨的背部,从后面对彼此造成损伤,好比如今的野牛。None of which proves that pachycephalosaurs did not strut their stuff with their domes as well, just as a stag will often show off its antlers before engaging in combat, in order to give a less well-endowed rival the opportunity to withdraw.然而,两种图案都没有否定肿头龙自豪地迈步时也在炫耀他们的大脑袋。成年雄鹿就经常在战斗之前展示它的鹿角,为了使天生劣势的对手借机撤退。But it does demonstrate that the domes were serious weapons, not mere fripperies of fashion.不过这确实明了高隆的头骨是很厉害的武器,而不仅仅是时髦的矫饰品。 /201401/272690青岛新阳光治疗滴虫性阴道炎多少钱

青岛哪个医院妇产科比较没人 Science and technology科学技术Measurement测量Mass effect质量效应A better way to clean the worlds one true kilogram清洁世界上真正一千克的更好方法IN SEVRES, on the outskirts of Paris, sealed beneath a triplet of bell jars in the laboratories of the Bureau International des Poids et Mesures, sits a small cylinder of platinum-iridium alloy.在位于巴黎郊区的塞夫勒市,国际计量局实验室里,一个三层的钟形器皿里密封着一个铂铱合金制成的小圆柱。Put it on a scale, and it would weigh 1 kilogram—which is appropriate, since this lump of metal is not just a kilogram but The Kilogram, the ultimate reference standard for the way the Systeme internationale dunites measures mass.给这个小圆筒称重,你会发现它重1千克,这个重量刚刚好,因为这个金属块不只代表1千克,而代表着千克单位,是国际单位体系中测重的最终参考标准。Scientists like the metric system partly for its simplicity—everything is based on powers of ten, which makes calculation easy—and partly for the elegance of its foundations.科学家亲睐公制的部分原因在于其简洁性,即任何物品以十为进制进行测量,方便运算;还有部分原因在于其成立基础很好。Of its seven fundamental units, six are defined with reference to unvarying constants of nature: the ampere, the candela, the second, the metre, the kelvin and the mole.在那七个基础单位中,有六个取决于自然界中的恒定物体:安培,坎德拉,秒,米,开氏度以及尔。The kilogram is unique in that it is defined by reference to a lump of crude, man-made stuff.唯独只有千克单位取决于未加工的人造金属块。Besides aesthetic niggles, that fact leads to an important practical problem.除了一些美学上的吹毛求疵,这一事实还引出了一个重要的实际问题。The international prototype kilogram, the technical name for the cylinder in Sevres, does not in fact keep a constant mass.事实上,国际千克原器的重量并不是恒定的。Over the years pollutants from the air settle on its surface, causing its mass to rise.这些年来,空气中的污染物落在这个金属块表面,增加了其重量。Attempts to clean it then cause its mass to fall.而试图清洁其表面又会减少其重量。As a result, what science understands by a kilogram has varied, but has done so in a way that is, by definition, unmeasurable.结果导致千克单位的科学定义变了,根据这样的定义,千克是无法测量出来的。A clean sweep?擦干净了没?The cleaning that attempts to keep the kilogram constant is done by a member of staff at the bureau, using a combination of steam and a chamois-leather cloth soaked in ethanol and ether.试图保持金属块重量恒定的清洁任务由国际计量局员工来做,用蒸汽和浸泡过含乙醇溶液的油鞣革布来进行清洁。But given the sensitivity of modern instruments, which can detect gains or losses of the order of billionths of a kilogram, it must be done properly.但鉴于现代工具测量十分精细,物体重量增减十亿分之一千克都可以测出来,这项清洁工作必须谨慎执行。Too gentle a rubdown leaves contaminants on the surface. Too vigorous a scrubbing erodes the metal itself.擦拭太过温柔,其表面会留有污染物;用力过猛,又会擦掉金属本身的表面成分。Worse, the IRK is not the only such cylinder in the world.更糟的是,国际千克原器并不是这个世界上唯一的此类圆柱体。Dozens of replicas exist in official laboratories in many countries.还有几十个类似的复制品存放在许多其他国家的官方实验室里。Each must be cleaned to the same exacting standards if it is to remain a true copy of the French original.如果每个都要和法国原件那个如假包换的话,那么每个圆柱体都要被清洁得和现有法国标准一样重。In practice, that has often meant shipping the whole lot back to France so that the same person can scrub them all down.那样实际做起来就是要把别国圆柱体运到法国去,由同样的人来做擦拭工作。Now, though, Peter Cumpson and Naoko Sano, a pair of researchers at the University of Newcastle, in England, reckon they have come up with a better way.然而现在,英国纽卡斯尔大学的皮特·坎普森和 佐野直之认为他们想出了更好的清洁方法。In a paper just published in Metrologia, they describe the results of a method that combines traditional washing with a technique adapted from the chip-manufacturing business, which employs a combination of ultraviolet light and the ozone that such light synthesises from the air to strip pollutants away.前不久他们在《计量学》上发表论文说,传统清洁方法加上紫外线和臭氧这种合成光可以清洁掉金属表面的污染物。The idea of using ultraviolet light was first proposed back in the 1990s, says Dr Cumpson, but has yet to be adopted.采用紫外线这个主意在上世纪九十年代就首次被提出来了,坎普森士说,但是一直没被采纳。This latest paper, which reports the results of using the method on strips of platinum-iridium alloy, shows that the method does a good job of removing the carbon-based gunk that settles onto the weights from the air.根据这篇最新论文,在铂铱合金条块上进行的实验显示这种方法能够很好地去除增加条块重量的空气碳黏质物。Importantly, says Dr Cumpson, unlike a manual rubdown, his procedure can easily be standardised, and the kit necessary to perform it is cheap and widely available, allowing laboratories around the world to keep their own kilogram replicas clean.重要的是,坎普森士说,他们的清洁方法是可以标准化的,不像人工擦拭,而且这种方法所涉及的东西既便宜又唾手可得,可以清洁世界上所有实验室的重量单位复制品。It is not, however, perfect.然而这种方法也算不上完美。Besides atmospheric muck, researchers reckon that other things are altering the masses of the worlds kilograms.研究人员发现除了空气中积攒下来的脏东西,其他东西也在影响着国际标准千克的重量。One significant effect, says Dr Cumpson, is contamination with mercury.坎普森士说其中一个关键的影响因素就是水银污染,The likely source is not atmospheric pollutants, but lab accidents.其污染源不是空气污染物,而属于实验室偶然事件。Say you drop a thermometer and it shatters, he says.比如你把一个温度计丢掉地面上,里面的水银散开了,坎普森士说,A couple of blobs of mercury fall through the floorboards and evaporate slowly over the years. Some of that mercury is then deposited.几滴水银落在地板上,随着时间,慢慢蒸发在空气中,其中一些会沉积。Unlike the atmospheric junk, which simply encrusts the surface, mercury seeps into microscopic flaws in the cylinders surfaces created by the polishing process.和仅仅落在圆柱表面的空气污染物不同,水银会渗进圆柱体在擦磨过程中表面留下的微小缺陷里。Once it gets in, its in there for good. You cant remove it, says Dr Cumpson.只要水银渗进去了,它就会永远留在圆柱体里了。你根本无法去除,坎普森士说。The missing Planck被人遗忘的普朗克It is problems like this—and the fact that the worlds kilograms are changing in mass at different rates—that are behind a push to bring the kilogram into line with the rest of the SI, and to define it purely with reference to natural constants.问题就在于此,再加上世界各国的千克标准重量正在以不同速率变化着,这些都敦促千克单位和SI体系下其他单位一样恒定,要在纯粹参考自然界恒量的基础上定义千克。Next year, the International Committee on Weights and Measures will discuss whether to tie it to something called Plancks constant, a number in quantum mechanics that relates the energy level of a photon to its wavelength.明年,国际重量与测量委员会将会讨论是否要将千克和普朗克恒量联系起来,普朗克恒量是指量子力学中联系光子能及其波长的数字。A supersensitive electromechanical scale called a watt balance could then be used to define the kilo with reference to Plancks constant, finally liberating the SI from its reliance on fallible artefacts.测量极其精准的机电天平—瓦特天平可以在参考普朗克恒量的基础上定义千克重量,这就使得SI再不用依赖不精确的人工制品了。That is the theory, at least.以上至少在理论上是成立的。But watt balances are fiendishly complicated bits of kit.但是瓦特天平极其复杂。There are only a handful in the world, a situation that is unlikely to change for the foreseeable future.世界上瓦特天平也为数不多,在可预见的未来,其数量也不会有增减。This means that, although the kilo will in theory be defined by an abstract constant, in practice so-called transfer standards will still be needed for the many countries without the nous or the cash to run a watt balance of their own.这就意味着即使在理论上可以用抽象恒量来定义千克重量,许多国家在实际操作中还是要用到所谓的可变标准,因为他们本身即没能力也无资金来动用一台瓦特天平。Translated into English, the upshot is that outside the most advanced countries, lumps of metal will continue to be used to define the kilo—although they will probably be made of gold, rather than platinum and iridium.简单讲,就是发达国家以外的国家和地区会继续用金属块来定义千克重量,尽管金属块可能用金制成,而非铂铱合金。These will be susceptible to exactly the same sorts of contamination that plague the current generations of kilogram.但金属块重量仍会受到同样的污染。Luckily, Dr Cumpsons method ought to work on them, too.所幸的是,坎普森士的方法对它们也同样奏效。 /201310/261549青岛那家医院做人流手术最便宜青岛城阳人民医院收费如何

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