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封面故事:真空中迅速冷却的水滴
Ultrafast X-ray probing of water structure below the homogeneous ice nucleation temperature
Metastable liquid–liquid transition in a molecular model of water
在真空中迅速冷却的水滴在变成冰之前用来自一个飞秒X-射线激光器的强脉冲对其进行探测,这为Jonas Sellberg等人提供了关于在所谓“无人地带”中的深度超冷液体相(在其中水的异常性质大大增强,但冰的形成速度太快,无法用正常测定方法来测定)的独特结构信息。在第二篇论文中,Jeremy Palmer等人通过先进模拟方法来研究这一体系中的水,发现了在两种结构不同的液体之间的一个相变,这有可能解释水的很多异常。(doi: 10.1038/nature13266 & doi: 10.1038/nature13405)
桉树基因组被测序
The genome of Eucalyptus grandis
生长速度快的桉树是国际制浆、造纸和化学纤维素行业的基础,同时它们还被看作是生物能源和生物材料的潜在生物质原料。现在桉树基因组已被测序。它含有迄今在植物基因组中所发现的最大数量的连续复制以及专门化代谢物(它们起化学防卫作用,能提供独特的药用油)的最高密度的基因。与姐妹物种蓝桉和其他巨桉类树种所做对比,显示了动态的基因组演化和近宗繁殖的热点。比较基因组数据的获得,对于研究怎样加快繁殖周期以提高生产力和木材质量以及开发适合各种不同生境的桉树品种将会有用。(doi:10.1038/nature13308)详细报道 Nature:科学家完成桉树基因组测序
线粒体自噬对帕金森氏症的影响
The mitochondrial deubiquitinase USP30 opposes parkin-mediated mitophagy
影响在受损线粒体的清除(线粒体自噬)中所涉及的两种酶(泛素连接酶parkin和蛋白激酶PINK1)的“功能丧失突变”与家族性帕金森氏症有关。这项研究表明,USP30 (一种局限于线粒体的去泛素酶)通过去除由parkin放置的泛素标签来对抗线粒体自噬。 降低USP30的活性会增强神经元中的线粒体降解,USP30 的抑制会挽救由parkin中的致病性突变引起的有缺陷的线粒体自噬作用。在一个果蝇模型中,USP30 的抑制在同时缺失parkin和PINK1的果蝇中都能提高线粒体完整性和存活率。因此,USP30 的抑制可以促进线粒体清除和质量控制,对帕金森氏症有潜在好处。(doi: 10.1038/nature13418 & doi: 10.1038/nature13500)
跟踪基因表达的变化
Single-cell RNA-seq reveals dynamic paracrine control of cellular variation
“高吞吐量单细胞转录组”为了解细胞之间的基因表达差异提供了一个无偏颇的方法。在这篇论文中,Aviv Regev及同事发表了从来自小鼠骨髓、受到各种不同扰动(包括在隔离的、封闭的微流体室中对单个细胞进行刺激以及通过遗传和化学方式来改变旁泌性信号传导)的原始树突细胞获得的单细胞RNA-seq库。这些结果显示了树突细胞的抗病毒和炎症反应模块是怎样被细胞间旁泌性正负反馈环(二者既促进、又限制差异的发生)控制的。(doi: 10.1038/nature13437)
量子计算的情境
Contextuality supplies the ‘magic’ for quantum computation
人们普遍认为,量子计算较经典计算在某些情况下、对某些问题有优势。但量子力学的哪些具体特征最终使其具有这种更大潜力的呢?Mark Howard 及同事发现“量子情境”(quantum contextuality,即对“量子非局域性”概念的一种概括)是赋予量子计算机威力的关键资源。这一发现不仅为量子计算的理论基础做了澄清,而且还为指导实验工作、以最有效地利用量子力学的奇异性来执行计算任务提供了一个框架。(doi:10.1038/nature13460 & doi: 10.1038/nature13504)
硫糖在天然产物中的吸收
Co-opting sulphur-carrier proteins from primary metabolic pathways for 2-thiosugar biosynthesis
硫原子存在于很多次生代谢物中,但尚不清楚它是怎样被结合到这些天然产物中去的。Hung-wen Liu及同事识别出一个噻唑合成酶同源物BexX,它参与含2- 硫糖的抗生素BE-7585A的生物合成。BexX通过从半胱氨酸或“钼蝶呤”的生物合成通道获得硫载体蛋白(因为BE-7585A生物合成基因簇不含硫载体基因)来催化6-磷酸葡萄糖向2-硫葡萄糖的转化。从一级代谢通道劫持硫转移系统来促进一种天然产物的生物合成,代表着一级和次级代谢之间的一个异乎寻常的联系。(doi: 10.1038/nature13256)
一个小分子怎样延长线虫的寿命
The metabolite α-ketoglutarate extends lifespan by inhibiting ATP synthase and TOR
限制热量能延长很多不同生物的寿命和延迟与年龄相关的退化。少数小分子代谢物被发现调控衰老过程,但我们对其中所涉及的机制却知之甚少。Jing Huang及同事在这篇论文中报告,三羧酸循环中间体α-ketoglutarate (α-KG)能将成年线虫的寿命延长大约50%。α-KG的分子目标是ATPase的β亚单元。α-KG依赖于TOR (target of rapamycin) 通道,并且不会延长限制饮食动物的寿命,这说明在α-KG的效应与饥饿/限制饮食之间存在一个联系。(doi: 10.1038/nature13264)详细报道 Nature:不限制饮食也能长寿
电子之间的磁相互作用
Measurement of the magnetic interaction between two bound electrons of two separate ions
每个电子都携带一个内在的磁偶极矩, 所以任意两个电子都应因此而对彼此施加磁力。所涉及的磁力非常小,而且在原子尺度上库仑相互作用是主导性的,所以观察这种磁相互作用极为困难。然而,Shlomi Kotler等人现在正好做到了这一点:对在被单独约束的锶-88离子中的两个电子之间的相互作用进行测量。这两个电子在超过15秒的相干演变过程中发生自旋纠缠,而且通过改变电子间的间隔,本文作者还演示了与已知的“立方反比律”(inverse-cube law)相一致的距离依赖性。(doi: 10.1038/nature13403 & doi: 10.1038/510349a)
肠道微生物群落对营养不良的反应
Persistent gut microbiota immaturity in malnourished Bangladeshi children
儿童营养不良是很多低收入国家的一个主要健康问题,虽然死亡率可以通过治疗性食物干预降低,但在严重急性营养不良情况下却难以实现健康生长的完全恢复。在这项研究中,Jeffrey Gordon及同事识别出一组24种细菌,它们在微生物群落中所占比例决定孟加拉国一组健康儿童在出生后前两年是否会形成一个健康的微生物群落。他们定义了一个可以对个体之间进行比较的“微生物群落相对成熟度指数”和“不同年龄微生物群落Z-值”(microbiota-for-age Z-score),并利用这些指数证明:严重营养不良与微生物群落显著的相对不成熟有关,这种不成熟只能通过两种被广泛采用的营养干预方法得到部分改善。这项工作表明,可能需要时间更长的食物干预措施和/或肠道微生物的增添来实现儿童营养不良中微生物群落不成熟问题的持久修复和更好的临床结果。(doi: 10.1038/nature13421 & doi: 10.1038/nature13347)详细报道 Nature:营养不良破坏你的第二基因组
p110δ 抑制因子限制Treg细胞的活性
Inactivation of PI(3)K p110δ breaks regulatory T-cell-mediated immune tolerance to cancer
这篇论文显示,phosphoinositide-3-OH kinase (PI(3)K)的p110δ同形物是调控性T-细胞(Treg细胞)的免疫抑制功能所必不可少的。在各种不同的小鼠肿瘤模型中,Treg细胞中的p110δ的失活导致增强的细胞毒性T-细胞功能,限制肿瘤生长和转移。这一发现将p110δ确定为一个可以让药物发挥作用的激酶目标,其抑制会提升免疫系统的癌症抑制潜力。(doi: 10.1038/nature13444 & doi: 10.1038/nature13503)详细报道 Nature:天生杀手如虎添
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| | ![Science/AAAS](http://www.sciencemag.org/site/icons_shared/external/logo-sci.png) | Science Table of Contents | |
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| In this week's issue:
| | RESEARCH SUMMARIES | | Editor summaries of this week's papers. Highlights of the recent literature.
| | EDITORIAL | |
| | IN BRIEF | | A roundup of weekly science policy and related news.
| | IN DEPTH | | Public Health Jocelyn Kaiser National Academies report calls for overhaul. Funding Jeffrey Mervis As success rates drop, agency seeks to limit applications. Patient Advocacy Kelly Servick But companies may be reluctant to supply unapproved drugs. Computer Science Adrian Cho Conventional computer ties D-Wave machine. History of Science Richard Stone Ancient texts suggest Silk Road polymath inferred the existence of unknown continents. Scientific Publishing John Bohannon Study lifts veil on journal price negotiations.
| | FEATURE | | Virginia Morell The trills and chirps of bats can be as complex and meaningful as bird song—and may be a closer analog for human speech.
| | WORKING LIFE | |
| | LETTERS | | T. Humle et al. Cai Luo et al. Kyle L. Galbraith Charlotte Gobin and Gustavo A. B. da Fonseca
| | BOOKS ET AL. | | Tropical Ecology Valerie Kapos Psychology Arlene Walker-Andrews A listing of books received at Science during the week ending 13 June 2014.
| | POLICY FORUM | | Research Capacity et al. H3Africa is developing capacity for health-related genomics research in Africa
| | PERSPECTIVES | | Anthropology Jean-Jacques Hublin Fossils from Sima de los Huesos show a mixture of Neandertal and more ancient features. [Also see Research Article by Arsuaga et al.] Chemistry Michael A. Boles and Dmitri V. Talapin Understanding nanocrystal surfaces helps to direct their assembly into novel material architectures. [Also see Reports by Boneschanscher et al.and Zherebetskyy et al.] Cell Biology Harm H. Kampinga Altruistic cell suicide model is challenged. [Also see Report by Malmgren Hill et al.] Immunology Lucienne Chatenoud An anti-inflammatory milieu promotes immune tolerance Physics D. E. Feldman Erasing knowledge of a quantum system changes its state. [Also see Report by Weisz et al.] Genetics Peter de Knijff How two crow species maintain their identity raises questions about species concepts. [Also see Report by Poelstra et al.]
| | REVIEWS | | Cecilia M. Heyes and Chris D. Frith
| | RESEARCH ARTICLES | | J. L. Arsuaga et al. Seventeen skulls from at least 430 thousand years ago illuminate hominin evolutionary patterns in Pleistocene Europe. [Also see Perspective by Hublin]
| | REPORTS | | E. Weisz et al. A device that illustrates the principle of complementarity in quantum mechanics has been implemented with electrons. [Also see Perspective by Feldman] J.-P. Tetienne et al. A microscope based on a single spin of a diamond defect is used to observe magnetism dynamics. P. Alonso-González et al. Structured gold antennas are used to launch plasmons into graphene, engineer their wavefronts, and control their propagation. Xiaoyu Zheng et al. Ultralow-density materials that deform through tension or compression rather than bending show much higher stiffness. M. P. Boneschanscher et al. Metal-chalcogenide nanocrystals undergo necking and large-scale atomic rearrangements when forming a surface lattice. [Also see Perspective by Boles and Talapin] Danylo Zherebetskyy et al. The surfaces of lead sulfide nanocrystals capped with an organic acid can also bear hydroxyl groups. [Also see Perspective by Boles and Talapin] Robert Ahrends et al. An analysis reveals how the very low terminal differentiation rates in adipocytes are maintained. Sandra Malmgren Hill et al. An enzyme linked to cell death in animal cells protects yeast cells from misfolded protein aggregates. [Also see Perspective by Kampinga] Roy D. Dar et al. Turning up the noise in HIV gene expression can help HIV drugs be more effective. Anoop P. Patel et al. Screening individual cancer cells within a brain tumor may help to guide treatment and predict prognosis. Theodora Hatziioannou et al. Development of an AIDS-like animal disease model after serial passage of HIV-1 in pigtailed macaques is shown. Kwangkook Lee et al. A crystal structure shows how botulinum neurotoxin crosses the host intestinal epithelial barrier, causing toxicity. J. W. Poelstra et al. Gray hooded crow and black carrion crow genomes reveal the effects of hybridization on keeping the species separate. [Also see Perspective by de Knijff]
| | PODCAST | | On this week's show: The cultural evolution of mind reading and a roundup of stories from our daily news site.
| | NEW PRODUCTS | | A weekly roundup of information on newly offered instrumentation, apparatus, and laboratory materials of potential interest to researchers.
| | FROM THE AAAS OFFICE OF PUBLISHING AND MEMBER SERVICES | | Science Webinar Series Yan-Ling Zhang and William P. Janzen
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Published in Science US$25,000 Now accepting entries Science & SciLifeLab Prize for Young Scientists Deadline: August 1, 2014 Visit www.sciencemag.org/scilifelabprize |
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| | ![Science/AAAS](http://www.sciencemag.org/site/icons_shared/external/logo-sci.png) | Science News This Week | |
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| A roundup of the week's top stories in Science:
| | IN BRIEF | | In science news around the world, Pacific marine reserves get a big boost from the United States and Kiribati, NASA's New Horizons mission is given time on the Hubble Space Telescope to hunt for a Kuiper belt object to study, Japan's RIKEN Center for Developmental Biology is threatened by a stem cell scandal,Science chats with paleontologist Jan Zalasiewicz about fossils from the Anthropocene, and more.
| | IN DEPTH | | Public Health Jocelyn Kaiser A long-delayed plan to follow the health of 100,000 U.S. children from birth to age 21 is in limbo again, in the wake of a critical outside review. A National Academies panel finds that the National Children's Study has some strong points—but also a host of weaknesses. The panel recommends that the study's leader, the National Institutes of Health's (NIH's) child health institute, make changes to the study's design and management that would likely delay initial recruitment, now planned for 2015. And the price tag that the panel puts on the revamped effort—upward of $1.5 billion—could erode support for the ambitious effort. In response to the report, NIH Director Francis Collins has put the study on hold. Funding Jeffrey Mervis U.S. astronomers now regard their chances of obtaining a grant from the National Science Foundation (NSF) as no better than those of winning the lottery. It's a new and unpleasant feeling for a community accustomed to relatively good success rates, and NSF officials say limiting researchers to one proposal a year is the best way to relieve that frustration, which extends to reviewers. An advisory panel to the main government agencies that support astronomy and astrophysics also agreed to collect data on the community's behavior in applying for and reviewing grant proposals, so that federal officials can have better information on which to base future decisions. Patient Advocacy Kelly Servick Several state legislatures, prodded by desperately ill patients and a libertarian think tank, are defying federal regulators to make experimental drugs available to terminally ill patients outside of clinical trials. The new laws, called Right to Try, went on the books in two states last month and are being considered in several others. One company has already announced its plans to use the laws to offer its stem cell treatment well ahead of approval from the Food and Drug Administration. But skeptics say few companies will be willing to bear the costs and risks of offering a drug outside of its clinical trials, especially if it means defying federal law. Computer Science Adrian Cho The D-Wave computer, marketed as a groundbreaking quantum machine that runs circles around conventional computers, solves problems no faster than an ordinary rival, a new test shows. For random test problems, the time it took the D-Wave machine to solve a problem increased exponentially with the problem's size, just as with a conventional computer, report Matthias Troyer, a physicist at the Swiss Federal Institute of Technology in Zurich, and colleagues online this week in Science(http://scim.ag/quantspeedup). So as the size of a problem grows, the D-Wave computer produces no quantum speedup. Some researchers call the test of the controversial device the fairest comparison yet. But D-Wave argues that the computations used in the study were too easy to show what its novel chips can do. History of Science Richard Stone Abu Rayhan al-Biruni, born a thousand years ago in Central Asia, calculated Earth's circumference with astounding accuracy and invented specific gravity, the measure of a substance's density compared to that of water. He rejected creationism, accepted that time has neither a beginning nor an end, and—5 centuries before Copernicus—argued that the sun might be the center of the solar system. Now, an influential U.S. scholar has proposed adding another laurel to that list: inferring the existence of America. Whereas some scholars think Biruni deserves credit for his continental prediction, others argue that his inference of unknown landmasses between Europe and Asia does not constitute a discovery. Scientific Publishing John Bohannon What is your university paying for academic journal subscriptions? The answer can be surprisingly hard to find. Universities buy access to most of their subscription journals through large bundled packages, much like home cable subscriptions that include hundreds of TV stations. But whereas cable TV providers largely stick to advertised prices, universities negotiate with academic publishing companies behind closed doors, and those deals usually come with nondisclosure agreements that keep the bundled prices secret. After several years of digging, and even legal action, a team of economists has pried out some of those numbers, revealing the bundle prices charged by Elsevier, Springer, and Wiley. Some universities are paying nearly twice what universities of seemingly similar size and research output pay for access to the very same journals.
| | FEATURE | |
Virginia Morell Bats, like birds, can sing. They emit multisyllabic trills and chirps in specific combinations and rhythms, crafting tunes that are as complex as those of songbirds. From New Zealand to Africa, researchers are seeking out bat troubadours to find out when and why these winged mammals burst into song, and why they have evolved this mentally demanding ability. Studies by Kirsten Bohn, Michael Smotherman, and others have shown that like many songbirds, most bat songsters are male, live in polygynous societies where males mate with more than one female, and tend to sing to court females and defend territories. Their complex songs are probably not innate, and so require vocal learning, as bird song and human speech do. Studies by these and other researchers are exploring what bats can reveal about the evolution of complex vocal abilities, including human speech. |
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