Volume 442 Number 7102 pp485-600 (3 August 2006) 封面故事：一种新型智能液体微型镜头
光学成像、医学诊断和“建在一个芯片上的实验室”技术等领域的微型化趋势，正在为尖端微型镜头创造出一种市场需求。现在，研究人员研制出了一种新型智能液体微型镜头，它与目前的大多数镜头的不同之处在于，它能自对焦。这种镜头的关键部件是一种能对刺激产生响应的水溶胶，该水溶胶被集成进一个微型液体系统中，充当一个液滴的容器。该水溶胶同时探测刺激和促使液滴形状发生变化，从而也使焦距发生变化。刺激包括生物和化学试剂以及物理参数。在这种微米尺度上，固定的液-液界面被用来获得稳定的装置，从而实现10秒到几十秒的响应时间。这样的镜头可以具有几乎任意长度的焦距，并且可以方便地集成进阵列中。本期封面所示为一种智能液体微型镜头，在其中，一种水溶胶（图中带斑纹的环）根据一个局部刺激调控镜头形状。
钙调蛋白的水平与鸟喙长度相关
几年前，“达尔文雀类”（指在教科书中始终与自然选择的适应辐射联系在一起的鸟类）不同物种的喙的深度和厚度被发现与Bmp4 (骨形态遗传蛋白-4)的表达相关。当时，一次寻找候选目标的筛选工作并没有发现任何有可能与不同喙长度有关的基因。现在，对不同“达尔文雀类”胚胎的喙原基中的转录情况所做的DNA微阵列分析表明，钙调蛋白（一种参与Ca2+信号作用的分子）的水平与喙长度相关。有了这两个调控喙生长不同尺度的通道，就可以设想出一个能够在不同选择条件下生成很多不同喙结构的机制来，从而也能选择出一个比较好的关于适应辐射的模型来。
P2X受体的重要性
ATP是所有活细胞中能量交换的通用货币，但它也存在于细胞外，与跨膜受体发生相互作用，来影响神经细胞、肌肉、腺体和免疫细胞中的细胞内事件。在从细胞中释放出来时，ATP可激活P2X受体，该受体是存在于大多数身体组织中的非选择性阳离子通道。由于没有药理学方面的工具，科学家对这些受体所发挥的生理作用很不了解。但现在有了“苏拉明”(suramin) 和PPADS这样的P2X阻断药物，这些受体作为细胞表面ATP传感器在健康和疾病中的重要性正在被人们所认识。
一些基因对胚胎干细胞分异的影响
在一项大规模基因组学研究中，研究人员确定了大量候选基因对细胞分异的调控作用的贡献。短发卡RNA（shRNA）基因沉寂作用被用来逐个沉寂65个基因的表达，这些基因的表达水平在小鼠胚胎干细胞分异时是下降的。将这些基因中的7个删除，会对自我更新产生负面影响。这些分子在使胚胎干细胞具有自我更新的能力和生成很多其他细胞类型的潜力方面可能发挥着重要作用。
通过数值模拟解决标准宇宙模型与观测结果的矛盾
虽然标准宇宙模型能够成功描述宇宙的大尺度结构，但在较小的尺度上该模型却不是很好。例如，该模型所预测的附近星系中心暗物质密度（密度曲线中的一个尖峰或低谷）要比实际观测中所看到的低，这说明星际暗物质晕圈有一个“平坦”的中心核。Mashchenko等人通过数值模拟解决了这个矛盾。他们的数值模拟表明，小型原始星系中由以超新星形式出现的恒星反馈作用所驱动的气体的随机体量运动，有可能使中央暗物质尖峰变平。当这种尖峰被除掉后，在随后的星系合并过程中将不能再产生，所以在当前的宇宙中，小星系和大星系都会有平坦的暗物质核心密度曲线。
不会被吞噬的伴星
在像我们的太阳一样的恒星周围的轨道中，已经发现了超过100颗行星和褐矮星。当这些恒星演变成为红色巨型星时，它们将会轻易吞噬其伴星，而这之后会发生什么呢？一颗白矮星的第一颗已知的近距离亚恒星（褐矮星）伴星的发现表明，让我们意想不到的是，这些伴星中有些会在相互作用中存活下来，相对保持不变。
太阳辐射对有机质分解的重要影响
生物过程被认为是陆地生态系统中有机质分解的主要原因，而由UV-B辐射所引起的降解等非生物过程扮演次要角色。但根据在半干旱的巴塔哥尼亚荒原上所进行的一项研究，事实不是这样的。在这里， 研究发现，影响碳的周转的主要因素是太阳辐射。阻断全部阳光或UV-B，会大大降低树叶杂草等的分解速度，而土壤有机物的减少或限制性土壤资源的增加却没有影响。这些结果表明，碳循环有一个短的周期，初级生产的相当大一部分可能会通过光降解丢失到大气中，而不通过土壤有机质库进行循环。由于地球陆地表面近40%是沙漠，所以影响辐射水平的全球变化因素（如臭氧损耗或云层）有可能对碳的存储产生很大影响。
面部识别的机制
30年以前，研究人员在猴子的下颞叶皮层中发现了面部选择神经元。尽管此后有数十项关于这种“面部细胞”的报道，而且人们还普遍假设这样的神经元很可能参与面部识别，但此后人们几乎没有对尖峰响应与关于人类面部感觉的大量心理物理文献进行对比。但现在，一组新的实验结果将猴子下颞叶皮层中的面部选择神经元与关于面部感觉的一个明确的心理层面联系了起来。在该研究中，研究人员对短尾猴进行训练，让其识别由电脑生成的人脸。结果表明，参加实验的猴子是通过将电脑生成的一个人脸与其大脑中存储的一个一般的或“标准”的人脸进行对比来识别的，而不是通过记忆每个人脸是什么样子来进行识别的。人类中的一个类似的机制也许可解释我们为什么能够在不到一秒的时间内识别出一个面孔来。
30亿年前就存在消减过程
Nature杂志上7月13号的一篇News Feature文章透露了关于板块构造“年龄”的一场争论。板块构造塑造了我们今天所看到的世界，但关于它是什么时候开始的问题却是一个让地质学家仁者见仁、智者见智的问题。在本期Nature上，Moyen等人非常可信地论证了在30亿年前就存在消减过程（板块构造的一个关键部分），而在那时板块构造本身是否存在就曾受到质疑。他们在论证中所依靠的证据，来自32亿年前一个“太古代”山系（南非的Barberton绿岩带）中高压、低温变形的标记。这一结果是科学家首次明确指出在“太古代”中期存在这种类型的活动。
能激活Merlin肿瘤抑制因子的磷酸酶
研究人员已经识别出了激活Merlin肿瘤抑制因子（也被称为神经纤维瘤-2）的磷酸酶。它是一种肌浆球蛋白磷酸酶，被内生抑制因子CPI-17所抑制，后者的水平在人类肿瘤中经常是升高的，可能通过使Merlin失去活性而有助于癌症的形成。将这些发现放到一起，我们就会看到一个新的肿瘤抑制级联过程，该过程可通过至少两种方法被破坏：通过突变（NF2），或通过升高假定的新致癌基因CPI-17的水平。
ContentsEditorials
No more protection p485
Cutting NASA's science budgets is one thing; rejecting the agency's historic role in the study of Earth is something else entirely.
doi:10.1038/442485a
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A foundation for Africa p486
A research plan that has to be seen to be believed.
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What's in a name? p486
Chemistry is here to stay.
doi:10.1038/442486b
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Top of pageResearch Highlights
Research highlights p488
doi:10.1038/442488a
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Top of pageNews
Maths 'Nobel' rumoured for Russian recluse p490
Proof of Poincaré conjecture is tipped for Fields medal
Jenny Hogan
doi:10.1038/422490a
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Bird flu not set for pandemic, says US team p490
H5N1 virus fails to cause epidemic in ferret experiment.
Erika Check
doi:10.1038/422490b
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Sidelines p492
doi:10.1038/442492a
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NASA threatens to axe science on space station p492
Funds may be diverted to Moon programme.
Heidi Ledford
doi:10.1038/442492b
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The proof is in the product p492
Chemists clash over structure of mushroom molecule.
Emma Marris
doi:10.1038/442492c
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Singapore pulls plug on US collaboration p493
Research ties with Johns Hopkins University cut.
Ichiko Fuyuno
doi:10.1038/442493a
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Mouse data hint at human pheromones p495
Receptors in the nose pick up subliminal scents.
Helen Pearson
doi:10.1038/442495a
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Meteorologists pour into west Africa p496
Big push under way to collect monsoon data
Jim Giles
doi:10.1038/442496a
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Home health tests are 'genetic horoscopes' p497
'Nutrigenetics' comes under fire after Senate hearing.
Gene Russo
doi:10.1038/442497a
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News in brief p498
doi:10.1038/442498a
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Correction p498
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Top of pageBusiness
Gas for the greenhouse p499
For big oil companies, carbon dioxide is waste; for people who grow fruit, it's a valuable commodity. Ned Stafford reports on a marriage of convenience in the Netherlands.
doi:10.1038/442499a
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Top of pageNews Features
Chemistry: What chemists want to know p500
Chemistry is a key component in all the scientific disciplines. But does that mean it is nothing more than a handy tool — or are there still major chemical questions to crack? Philip Ball finds out.
doi:10.1038/442500a
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Conservation at a distance: Atomic detectives p504
There's more to ecology than ringing birds, and in this special section Nature explores how the molecular sciences are transforming the field. In this, the first of two features, Sharon Levy explores how atoms in feathers can reveal the secrets of rare warblers. In the second, Carina Dennis unveils a technique that aims to make killing whales for science a thing of the past.
doi:10.1038/442504a
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Conservation at a distance: A gentle way to age p507
There's more to ecology than ringing birds, and in this special section Nature explores how the molecular sciences are transforming the field. In the first of two features, Sharon Levy explored how atoms in feathers can reveal the secrets of rare warblers. In this, the second, Carina Dennis unveils a technique that aims to make killing whales for science a thing of the past.
doi:10.1038/442507a
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Top of pageCorrespondence
The gender debate: science promises an honest investigation of the world p510
Steven Pinker
doi:10.1038/442510a
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Let's encourage gentler, more reflective scientists p510
Peter A. Lawrence
doi:10.1038/442510b
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Bias was built into research from the beginning p510
Margaret M. McCarthy
doi:10.1038/442510c
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Holding the centre among the scatter-brained p510
Donna L. Dierker
doi:10.1038/442510d
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Top of pageBooks and Arts
Future perfect? p511
Dizzying advances predicted for the next century could improve the world — or lead to disaster.
Norman Myers reviews The Meaning of the 21st Century: A Vital Blueprint for Ensuring Our Future by James Martin
doi:10.1038/442511a
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The road less travelled p512
Richard Akerman reviews The Long Tail: Why the Future of Business is Selling Less of More by Chris Anderson
doi:10.1038/442512a
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Sensitive to modern life p513
Peter J. Barnes reviews Allergy: The History of a Modern Malady by Mark Jackson
doi:10.1038/442513a
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Science in Culture: Hearing colours, seeing sounds p514
Wassily Kandinsky's synaesthetic paintings go on show in London.
Martin Kemp and Colin Blakemore
doi:10.1038/442514a
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Top of pageNews and Views
Evolutionary biology: How to build a longer beak p515
Evolutionary changes in the beaks of Darwin's finches have been instrumental in the adaptive radiation of these birds. The molecular basis for variation in beak size and shape is opening up to investigation.
Nipam H. Patel
doi:10.1038/442515a
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50 & 100 years ago p516
doi:10.1038/442516a
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Particle physics: A finer constant p516
For the first time in a decade, the precision of the fine-structure constant — central to understanding the electromagnetic force — has improved. But even greater accuracy is required to test new physics.
Andrzej Czarnecki
doi:10.1038/442516b
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Chemical biology: Cutting out the middle man p517
Wouldn't it be nice if you could control the function of any protein with one small molecule? Unlikely as it sounds, this could become possible through a crafty process known as protein splicing.
Tom W. Muir
doi:10.1038/442517a
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Cell biology: Polarity bites p519
Cells often need to have polarity to function — cells lining the gut, for instance, secrete digestive enzymes only from their intestinal side. A protein called Bitesize is pivotal in determining which way is up.
Richard Fehon
doi:10.1038/nature05036
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Astronomy: A dwarf-eats-dwarf world p520
A white dwarf burnt-out star and a brown dwarf wannabe star have been found in mutual orbit. This fascinating system has had a turbulent past, and its future evolution could be just as spectacular.
James Liebert
doi:10.1038/442520a
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Energy technology: Hydrogen quick and clean p521
Systems for producing pure hydrogen for fuel cells from methanol run into problems with energy efficiency and short lifetimes. Unless, that is, you combine the right catalyst and the right purification membrane.
Rich Masel
doi:10.1038/442521a
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Superconductivity: Hot vibes p522
Lattice vibrations — phonons — have long been implicated in conventional low-temperature superconductivity. That they could also have a supporting role when the heat is turned up had been dismissed.
Alex de Lozanne
doi:10.1038/442522a
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Top of pageBrief Communications
Behavioural ecology: Bees associate warmth with floral colour p525
Pollinators may be seeking more than just food as a reward when they choose one flower over another.
Adrian G. Dyer, Heather M. Whitney, Sarah E. J. Arnold, Beverley J. Glover and Lars Chittka
doi:10.1038/442525a
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Superhydrophobicity: Drying transition of confined water p526
Long-range hydrophobic interactions operating underwater are important in the mediation of many natural and synthetic phenomena.
Seema Singh, Jack Houston, Frank van Swol and C. Jeffrey Brinker
doi:10.1038/442526a
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Top of pageBrief Communications Arising
Glass behaviour: Poisson's ratio and liquid's fragility pE7
Spyros N. Yannopoulos and G. P. Johari
doi:10.1038/nature04967
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Top of pageReview
P2X receptors as cell-surface ATP sensors in health and disease p527
Baljit S. Khakh and R. Alan North
doi:10.1038/nature04886
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Top of pageArticle
Dissecting self-renewal in stem cells with RNA interference p533
Natalia Ivanova, Radu Dobrin, Rong Lu, Iulia Kotenko, John Levorse, Christina DeCoste, Xenia Schafer, Yi Lun and Ihor R. Lemischka
doi:10.1038/nature04915
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Top of pageLetters
The removal of cusps from galaxy centres by stellar feedback in the early Universe p539
Sergey Mashchenko, H. M. P. Couchman and James Wadsley
doi:10.1038/nature04944
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Survival of a brown dwarf after engulfment by a red giant star p543
P. F. L. Maxted, R. Napiwotzki, P. D. Dobbie and M. R. Burleigh
doi:10.1038/nature04987
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Interplay of electron–lattice interactions and superconductivity in Bi2Sr2CaCu2O8+ p546
Jinho Lee, K. Fujita, K. McElroy, J. A. Slezak, M. Wang, Y. Aiura, H. Bando, M. Ishikado, T. Masui, J.-X. Zhu, A. V. Balatsky, H. Eisaki, S. Uchida and J. C. Davis
doi:10.1038/nature04973
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Adaptive liquid microlenses activated by stimuli-responsive hydrogels p551
Liang Dong, Abhishek K. Agarwal, David J. Beebe and Hongrui Jiang
doi:10.1038/nature05024
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Plant litter decomposition in a semi-arid ecosystem controlled by photodegradation p555
Amy T. Austin and Lucía Vivanco
doi:10.1038/nature05038
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Record of mid-Archaean subduction from metamorphism in the Barberton terrain, South Africa p559
Jean-François Moyen, Gary Stevens and Alexander Kisters
doi:10.1038/nature04972
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The calmodulin pathway and evolution of elongated beak morphology in Darwin's finches p563
Arhat Abzhanov, Winston P. Kuo, Christine Hartmann, B. Rosemary Grant, Peter R. Grant and Clifford J. Tabin
doi:10.1038/nature04843
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Collinear activation of Hoxb genes during gastrulation is linked to mesoderm cell ingression p568
Tadahiro Iimura and Olivier Pourquié
doi:10.1038/nature04838
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Norm-based face encoding by single neurons in the monkey inferotemporal cortex p572
David A. Leopold, Igor V. Bondar and Martin A. Giese
doi:10.1038/nature04951
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Tumorigenic transformation by CPI-17 through inhibition of a merlin phosphatase p576
Hongchuan Jin, Tobias Sperka, Peter Herrlich and Helen Morrison
doi:10.1038/nature04856
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Spatial control of actin organization at adherens junctions by a synaptotagmin-like protein p580
Fanny Pilot, Jean-Marc Philippe, Céline Lemmers and Thomas Lecuit
doi:10.1038/nature04935
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The physical basis of how prion conformations determine strain phenotypes p585
Motomasa Tanaka, Sean R. Collins, Brandon H. Toyama and Jonathan S. Weissman
doi:10.1038/nature04922
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Rad54 protein promotes branch migration of Holliday junctions p590
Dmitry V. Bugreev, Olga M. Mazina and Alexander V. Mazin
doi:10.1038/nature04889
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Corrigendum: Titan Radar Mapper observations from Cassini's T3 fly-by p594
C. Elachi, S. Wall, M. Janssen, E. Stofan, R. Lopes, R. Kirk, R. Lorenz, J. Lunine, F. Paganelli, L. Soderblom, C. Wood, L. Wye, H. Zebker, Y. Anderson, S. Ostro, M. Allison, R. Boehmer, P. Callahan, P. Encrenaz, E. Flamini, G. Francescetti, Y. Gim, G. Hamilton, S. Hensley, W. Johnson, K. Kelleher, D. Muhleman, G. Picardi, F. Posa, L. Roth, R. Seu, S. Shaffer, B. Stiles, S. Vetrella and R. West
doi:10.1038/nature05004
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Top of pageNaturejobs
Prospect
Prospects p595
New EU nations are shedding talent to the West.
Paul Smaglik
doi:10.1038/nj7102-595a
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Special Report
From bench to briefs p596
Patent law offers opportunities for those who wish to leave the lab but not science, says Monya Baker.
Monya Baker
doi:10.1038/nj7102-596a
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Top of pageFutures
Gordy gave me your name p600
Somebody out there likes me.
Jim Giles
doi:10.1038/442600a
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