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郑州金水区做脱毛手术多少钱新密市治疗青春痘多少钱河南附属医院激光去斑多少钱 Science and Technology科技Looking for the Higgs捕获希格斯粒子Enemy in sight?敌军现身?The search for the Higgs boson is closing in on its quarry希格斯玻色子的研究逼近其目标ON JULY 22nd two teams of researchers based at CERN, Europes main particle-physics laboratory, near Geneva, told a meeting of the European Physical Society in Grenoble that they had found the strongest hints yet that the Higgs boson does, in fact, exist.7月22日,驻欧洲粒子物理研究所(CERN,邻近日内瓦的欧洲主要粒子物理实验室)的两组研究人员在格勒诺布尔(Grenoble)欧洲物理协会的一次会议上声称,他们已经得到迄今为止最有力的线索,将力希格斯玻色子的确真实存在。The Higgs (named after Peter Higgs, a British physicist who predicted its existence) is the last unobserved part of the Standard Model, a 40-year-old theory which successfully describes the behaviour of all the fundamental particles and forces of nature bar gravity.希格斯粒子(它以预言其存在的英国物理学家彼得·希格斯的名字命名) 是;基础模型;中最后一个尚未观测到的组件,;基础模型;已有40年的历史,它成功地描述了所有基础粒子的行为及除重力以外的所有自然力。Mathematically, the Higgs is needed to complete the model because, otherwise, none of the other particles would have any mass.在数学层面上,希格斯粒子对于完成;模型;是必不可少的,这是因为,一旦缺少它,所有的其它粒子都将会失去质量。The problem with the elusive boson is not creating it in the first place.对于难于捉摸的玻色子而言,首要的问题并不是将其创造出来。Two of the worlds particle accelerators, the Large Hadron Collider (LHC) at CERN and its American rival, the Tevatron at Fermilab on the outskirts of Chicago, each have more than enough oomph to conjure up the Higgs—at least if it looks anything like theory suggests it should.世界上现有两台粒子加速器,欧洲粒子物理研究所的大型强子对撞机(LHC),以及其美国竞争对手芝加哥市郊费米实验室的兆电子伏加速器(Tevatron),各自都有绰绰有余的充沛魔力去召唤希格斯粒子——如果一切符合理论,至少看来应该是这样。The difficulty, rather, is spotting signs of it in the jetsam of subatomic debris these machines produce.然而,困难在于如何在这些机器制造的亚原子碎片衍生物中辩认出它的踪迹来。Both laboratories use similar approaches: smashing particles called hadrons into each other.两个实验室都采用类似的方法:将称作强子的高能粒子彼此对撞。The LHC collides beams of protons.大型强子对撞机对轰质子束。The Tevatron works with protons and antiprotons.而兆电子伏加速器使用的是质子和反质子。In each case the particles concerned are accelerated to within a whisker of the speed of light before they are forced, head-on, into each other.在它们被强制彼此迎头撞击之前,各自所采用的那些粒子都要被加速至距离光速仅有一线之隔。During such a collision, their kinetic energy is converted into other particles (since, as Einstein showed, energy and mass are but two sides of the same coin).在这样的撞击过程中,它们的动能转换成额外的粒子(正如爱因斯坦所指出的那样,这是由于能量和质量只是同一个硬币的两面而已)。The more kinetic energy there is, the heavier these daughter particles can be.动能越大,越能产生更大质量的粒子。Unfortunately hadrons, such as protons and antiprotons, are made of smaller bits called quarks.不幸的是,强子,比如质子和反质子,是由名为夸克的更小单元所组成的。As a result, hadron collisions can be messy and difficult to interpret.结果,强子的撞击可能造成混乱且难于预测的局面。If a Higgs were to be made in such a collision, the complexity of hadrons means that other particles would be created along with the boson.如果一个希格斯粒子产生在这样的一次碰撞中,那么强子的复杂构造意味着另外的粒子也将会伴随这个玻色子而出现。Both it and its companions would then decay almost instantly into a plethora of less fleeting bits, some of which could be detected.玻色子与它的伙伴们将会几乎在瞬间衰变为大批寿命更短的微粒子,其中有一些能被检测出来。In theory, analysing this shower of daughter particles should give away whether or not a Higgs was involved.理论上,分析这批衰变所产生的粒子应该能轻松查明是否其中曾存在希格斯粒子。But other sorts of subatomic process that do not involve the Higgs can produce precisely the same final ings as those the missing boson is predicted to generate.然而其他类型的不含希格斯粒子的亚原子衰变过程也能够精确地产生相同的最终观测结果,就跟缺失的希格斯粒子预定产生的一般。Finding a Higgs-like signal among the daughters is therefore not, by itself, enough to say you have discovered the Higgs.因而在这些衍生粒子中发现类似希格斯粒子的迹象本身并不足以明你已经发现希格斯粒子。What is needed is an unexpected abundance of such signals.这样的迹象出乎意料地频繁出现是一个必要条件。And it is just such excess that two separate experiments at the LHC, known as CMS and ATLAS, have detected.而在大型强子对撞机上的这两个独立实验(称为CMS和ATLAS)就已经检测到这样的反常频密现象。Individually, each teams result could be a statistical fluke.客观地说,每个研究团队所得出的结论可能只是统计意义上的偶然现象。Neither reaches the exacting standard of proof that particle physicists require to accept a result unequivocally—namely one chance in 3.5m that it occurred by accident.两者都达到粒子物理学家所提出能确定无疑地接受为据的严苛标准——即三百五十万次实验中偶尔发生一次。Instead, they each achieved a significance of somewhere between one chance in 1,000 and one in six, depending on which statistical test you use.不止如此,它们各自都获得了显著的观测数据,从一千次发生一次到六次发生一次的范围之内,这取决于你所采用的统计学测试标准。What set the scientists gathered in Grenoble aflutter, though, was that both experiments ascribed the excesses they observed to the same putative decay pattern—one involving W bosons, which mediate the weak nuclear force that is responsible for certain types of radioactive decay.令到聚集在格勒诺布尔的科学家们兴奋不已的是,这两个实验中所观察到的反常频密现象都要归因于相同的公认衰变模式——一种涉及W玻色子的衰变,该玻色力是传递弱核力的媒介,而弱核力是某些特定种类放射性衰变的主因。Both teams also ascribe the same mass to their putative Higgses, namely 130-150 gigaelectron-volts (the units in which particle physicists measure mass).两个团队也认为他们所推定的希格斯粒子具有相同的质量,即130—150吉电子伏特(这是粒子物理学测量质量所采用的一种单位)。That is at the low end of the predicted range.这处在预测范围中的底部。Sadly, even taken together these results are far from robust enough to claim the Higgss discovery.遗憾地是,即使是将这些结果一并考虑,也远不足于斩钉截铁地断言发现希格斯粒子。With a little tweaking, the Standard Model might explain them in other ways.只要稍作更改,;标准模型;可以用另一种方式去解释它们。Guido Tonelli and Fabiola Gianotti, who head CMS and ATLAS respectively, therefore urge caution.各自领导CMS和ATLAS的基多·汤内利(Guido Tonelli)及法比奥拉·贾诺蒂(Fabiola Gianotti)因而呼吁要格外的小心谨慎。Their goal is to have enough data by the end of the year either to say definitely that the Higgs has a mass of 130-150 gigaelectron-volts, or that if it exists at all, then it must be heavier than that.他们的目标是到今年年末获得足够的数据,要么明希格斯粒子具有130—150吉电子伏特的质量,要么明只要它确实存在,那么它必定要更重一些。If this is the case, the hunt will continue at higher and higher energies (and therefore masses) until either the thing is found, or there is nowhere left in the energy landscape for it to be hiding.如果是这样的话,追捕行动将在越来越高的能量(因此质量也是同样如此)层级上展开,直到发现它为止,否则的话,能量图谱中根本就不存在它的藏身之处。 /201211/210209平顶山市去除红色胎记费用

郑州省妇幼保健院打美白针多少钱Could life have been forged in the same way on both planets?生命在两个行星能以同一方式形成吗?When we sent the first probes to investigate in the 1960s, almost anything was possible.当我们在20世纪60年代发射第一个探测器进行调查时,几乎认为任何事都是可能的。Originally in the popular imagination we thought that the Mars might be inhabited by whole civilizations building canals and so on.原来的想象力让我们认为火星上可能有整个文明,有人居住并且建立运河等等。And then the Mariner fly- by missions really painted a very grey, black and white, deal of Mars is being barren.然后火星探测任务真的描绘了一幅只有灰色、黑和白色的照片,这表明火星只是不毛之地。Still, NASA was eager to look for signs of life. In 1976,但是NASA在1976年仍然急于寻找生命的迹象。The Viking spacecraft arrives from earth for our first close encounter.来自地球的维京太空船为我们带来了一次亲密接触。And therere still hopes of welcoming committee.虽然委员会仍然对此表示充满希望。But both Viking spacecrafts send back photos of nothing but rocks and sand.但维京航天器除了石头和沙子的照片外没有带回任何东西。We had a camera so obviously if there was a yarke plane ,如果是一架飞机的话,我们显然会用配备的相机进行拍摄,I was hoping therell be a free way in the descents,我希望会有一种自由的方式,but what the main trust of Viking was actually was some chemical laboratories, and they look for the chemical signs of life.但维京的主要信念是一些化学实验室,他们寻找生命的化学迹象。Even the dirt seems devoid of life.即使是看起来缺乏生命迹象的污垢。There was always a chance that when they were so busy looking for microbes,他们这样忙于寻找微生物,总会有一次把握住机会,there could be a larger organism looking over their shoulder that they completely miss it.可能会有个庞然大物曾和他们擦肩而过,而他们则完全不知。注:听力文本来源于普特201204/177284郑州/大学第五附属医院点痣多少钱 Science and Technology Prehistoric reptiles A loving mother科技 史前爬行动物 慈母Family life in plesiosaurs蛇颈龙的家族生活THE Mesozoic land was dominated by dinosaurs.中生代时期,恐龙统治着陆地。At sea, though, the most abundant reptiles were the ichthyosaurs and plesiosaurs.但是在海里,最繁盛的爬行动物要属鱼龙和蛇颈龙了。Roughly speaking, these animals filled the ecological niches now occupied by toothed cetaceans such as dolphins and killer whales.大致上讲,这些动物填补了由现代齿鲸目动物海豚和虎鲸所占据的生态龛位。Ichthyosaurs, indeed, looked somewhat like dolphins, though plesiosaurs—with their long necks and diamond-shaped paddles—were unlike anything now alive.鱼龙看上去的确有点象海豚,但拥有长颈和菱形鳍状前肢的蛇颈龙却与现存的任何动物不相类似。Ichthyosaurs also resembled cetaceans in another way: unlike most living reptiles, which lay eggs, they gave birth to live young.鱼龙与鲸类动物还有另一点相似之处:大多数现存的爬行动物靠产卵繁殖,而鱼龙是通过怀胎产子的。For years, palaeontologists have wondered if the same was true of plesiosaurs.数年来,古生物学家一直想知道蛇颈龙是否也通过怀胎方式繁殖后代。Now they have found out that it was—but with an interesting twist.如今他们实了这一点——但却是以一种有趣的方式。Robin OKeefe of Marshall University in West Virginia has analysed a plesiosaur fossil found in Kansas in 1987, which palaeontologists had suspected was a pregnant female about 4.7 metres (15 feet) long, but which had not been cleaned up and studied until last year.西弗吉尼亚州马歇尔大学的罗宾·奥基夫对1987年在堪萨斯州发现的蛇颈龙化石进行了分析,此前,古生物学家一直怀疑它是一条身长4.7米(15英寸)雌性怀蛇颈龙, 但直到去年才将其清理和研究完毕。As he reports in Science, he found an array of tiny bones, apparently belonging to a small specimen of the same species, in the fossils abdominal cavity (see above; the extra bones are highlighted).奥基夫在《科学》杂志报告中指出,在蛇颈龙化石腹腔内(额外的骨骼被高亮显示)发现了一些小骨骼阵列,它们显然是属于同类物种的小标本。It is unlikely that these were the remains of a meal because the bones are not broken down in the way that would be expected if they were partly digested.这些小骨骼不可能是食物的残渣,因为如果它们是被部份消化的其它动物的骨骼,那么它们的断裂方式应该研究人员所预想的方式相同,但结果却不是。Instead, Dr OKeefe believes he has discovered evidence that plesiosaurs, too, gave birth to live young.反过来,奥基夫士相信他已发现了蛇颈龙同样靠胎生繁殖的据。What is more, all the baby bones come from a single individual, estimated to have been 1.5 metres long.此外,所有幼蛇颈龙的骨骼皆来自于单一的个体,身长估计有1.5米。Ichthyosaurs and other contemporary viviparous species, by contrast, gave birth to multiple offspring.对比之下,鱼龙和其它现代胎生物种可以生育多个后代。The fetuss level of development indicates that it was at most two-thirds mature.从蛇颈龙幼胎的发育水平来看,它最多有三分之二的成熟度。Had it survived to birth it would have been about 1.8 metres in length, and about one and a half times as heavy (relative to parental weight) as the offspring of other viviparous species of the time.如真能够成功分娩,幼蛇颈龙的身长可能为1.8米左右,体重大约是同时期其它胎生物种后代的1.5倍(相对于父母的重量)。That it was so heavy, and also alone, is of great interest.蛇颈龙幼胎超重且单独的个体引起了古生物学家的极大兴趣。Georges Cuvier, an early palaeontologist, made his reputation by predicting the anatomies of newly discovered fossil species from scant evidence, such as single bones.早期古生物学家乔治·居维叶能在实据不足的情况下(如单一的骨骼)预测出新发现的化石物种的躯干结构,这使他在业界声名显著。He did so by applying to fossils the principles of comparative anatomy, asking what light the body shapes of living animals could cast on the shapes of creatures from the past.之所以能做到这点是因为他将对比解剖学的规则应用于化石样本并探寻现存动物的体形对古代动物的体形有什么样的启发借鉴作用。Many modern palaeontologists try to do something similar, except that what they reconstruct is behaviour.许多现代古生物学家除了重现古代动物的行为外,也在尝试做着同样的事情。Dr OKeefe has performed such an analysis on his find.奥基夫士已将这种分析应用于他的发现。He starts from a fundamental observation about reproduction: you can go for quantity or quality.他的实验开始于对繁殖现象的基本观察: 你能选择数量或质量。Having one child at a time is the ultimate expression of quality.每次只生育一胎是追求质量的最终体现。It implies huge parental investment in the offspring since, if you lose it, you lose everything.它意味着父母在后代身上的巨大投入,一旦失去了这个幼子也就等于失去了一切。Often, too, it implies membership of a social group, within which favours can be traded to sp the load of parenthood.它也常常意味着社会群体的成员身份,在这个社会群体中,幼子关爱可以通过利益交换得到以减轻父母的负担。Most speculatively, it might even imply a degree of intelligence—for the most intelligent mammals and birds are generally those that live in groups.从最大程度上猜测,它甚至可能意味着动物的智商程度——生活在群体中的哺乳动物和鸟类通常是最聪明的。All this is a lot to load on a single fossil, of course.当然仅凭这个单一化石,古生物学家未免猜想得太多了。But it would make sense.但它却能够说明问题。It would mean plesiosaurs not only occupied a similar ecological niche to whales, but behaved like them, too.它将意味着蛇颈龙不仅占据着与鲸鱼相似的生态龛位,其行为方式也与鲸鱼相仿。 /201212/212976许昌市人民医院玻尿酸隆鼻多少钱

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