Volume 438 Number 7066 pp257-394封面故事：气候变化的区域影响
本期Nature包括关于一个热点话题的综述、原始研究和评论文章，这个热点话题就是气候变化的区域影响。本期封面所示为1995年7月热浪期间拍摄的美国城市芝加哥(? Gary Braasch/ worldviewofglobalwarming.org)，这张照片突出反映了一个潜在的危险。Patz等人对现有的证据进行了分析，他们提出，气候变暖在全世界范围内已经成为人们生病和数以千计的人早死的原因，并且还可能对未来人们的健康产生严重后果。最近的研究工作表明，一些地区尤其容易受到影响：气候条件受“厄尔尼诺/南方涛动”事件主导的地区、撒哈拉以南非洲地区、以及受到城市热岛效应影响的范围不断扩大的城市地区已经在遭受气候变暖所带来的影响，而且这样的地区预计还会增加。很多情况下，面临风险最大的地区还是那些最不应该对造成气候变化负责的地区。
全球变暖将会产生的影响
所有现有的气候模型都预测，在大气中温室气体水平上升的影响下，近地表有一个变暖的趋势。Barnett等人对这种变暖趋势对区域水文（尤其是在融雪占主导地位的地区）的影响进行了分析。他们提出，变暖将使降雪变为降雨，降低天然水存储容量，使冬天的雪更早融化，使河流最大径流出现的时间从夏季和秋季需求量最大的时期变为其他时期。冰川和积雪的减少很可能对全球1/6人口的供水产生严重影响。
气候变化对水文周期的影响
人们一半认为，气候变化将改变水文周期，但要让气候学家预测世界上哪些地方将变得更干、哪些地方将变得更湿却是一件困难的事情。Milly等人针对河川径流和水源补充趋势进行分析，发现有12个现有的气候模型能准确解释20世纪发生的变化。这些模型还能预测很可能极为重要的区域效应对未来河川径流的影响，这些效应到2050年有可能危及世界很多地区的淡水供应。
一种植物色素的结构被确定
植物色素是在生物演化过程中从细菌到真菌和高等植物都保留下来的，是在农业生产上重要的感光蛋白，从遗传和生化等方面已经被研究了几十年了。事实证明，它们的三维结构信息一直难以掌握。但现在，来自细菌Deinococcus radiodurans的一种植物色素的结构已被确定。该结构显示，其上可能附着有发色团，并且还有光信号机制。该分子的蛋白折叠令人吃惊：感光区域的形状像一个结，这也许是为了增加结构的刚性和稳定性。
关于恒星形成的“引力坍缩”理论受到支持
恒星形成是天体物理中从星系演化到行星形成在内的很多现象的中心内容。所以，很多问题都取决于试图解释该现象的两个相互竞争的理论的命运。“引力坍缩”理论认为，质量比太阳质量大几十万倍的巨大的分子团分解成气体碎片，后者随后坍缩形成恒星。“竞争增长”理论认为，恒星的形成涉及质量约为太阳一半的小恒星的生成，后者随后通过积累自由气体来增长。一个新的数值模拟结果肯定地支持“引力坍缩”为恒星形成的主要机制，理由是，在真实的恒星形成云中，一颗恒星的最初物质是其今后可能拥有的全部物质，原因很简单：条件不适合它再积累更多的物质。
左手性材料已经合成出来
所谓的左手性材料是俄罗斯理论家Victor Veselago作为一种可能性首次提出的。这类材料的渗透率和介电常数都是负的，所以它们对电磁辐射的影响应当与天然材料正好相反。不久前，人们意识到，左手性材料也许可用来制造“完美镜头”，对光线的聚焦能力要比传统光学镜头好的多。现在，这种类型的材料已经被合成出来，但到目前为止这种现象还只限于微波波段。要将磁响应的频率范围扩大三个数量级，需要对这种新材料进行一个非常不同的设计，进入“电浆光学”（plasmon optics）的范畴。所以制造适合光学显微镜使用的“完美镜头”的基础现在可能已经具备了，尽管还存在很大的技术问题。
混沌体系在光通信中的应用
如果你想通过一个宽带光纤网络发送加密信息的话，那么混沌现象是好事。理论认为，嵌入混沌体系中的基于光的信号的传输可使数据传输具有私秘性。这一理论已在实验室中在短距离内得到实验证明。现在，在希腊雅典“城域网”的一个商用光纤通道中所做的试验表明，该理论在实际应用环境中也是成立的。试验结果表明，该技术对在实际应用条件下不可避免的扰动和通道波动的抗干扰能力很强。
Stylophorans到底是什么？
Stylophorans是一组已经绝灭的动物，对其所归属的类别有不同看法：有将其划分为早期棘皮类动物的，也有将其划分为早期脊索动物的。它们的祖先是不确定的，所以我们难以弄清其精确的身体构造和生活方式。新发现的来自摩洛哥寒武纪中期的化石碎片，为澄清事实、尤其是与一个有时被称为“进食臂”的结构相关的问题提供了一些线索。新发现的化石倾向于支持认为该类动物身体结构像棘皮类的观点，但它的“进食臂”（有时人们会把它当成棘皮类动物的一个特征）没有嘴，而是像一个在运动中使用的肌肉附肢。
影响传染病传染能力的因素
从“玛丽伤寒”到“非典”，人们早就知道，有些人比其他人更容易传播疾病。但对于通过偶然接触传播的疾病，传染性来自多种社会和生理因素，所以流行病学家往往根据人口的平均水平来评估一种疾病的传播潜力。对流行病爆发数据所做的一项新的分析表明，个体在传染性上的差异对10种致命疾病的流行有强大影响。“非典”和“麻疹”（也许还包括禽流感）有发展成“超级传播事件”的强烈倾向，这些事件能引发爆炸式的流行，但正因为它们这么容易流行，它们也可能会很快烟消云散。天花和肺鼠疫（恐怖分子可能使用的两种生物试剂）传播速度要慢一些，但仍与传统的、根据人口平均水平所估计出的结果有明显不同。这些发现可帮助寻找检测和控制新出现的一些疾病的方法。
第一种已知与星细胞形成有关的蛋白
星细胞是组成大脑的三种主要细胞类型之一，但令人吃惊的是，我们对这些细胞在脑发育过程中是怎样形成的知之甚少。现在，研究表明，一种被称为SCL的蛋白（一种基本的螺旋－环－螺旋转录因子）给未成熟的神经干细胞下达指令，让其形成星细胞。SCL是第一种已知具有这种功能的蛋白，了解其功能，有可能为了解星细胞在如脑瘤、肌萎缩性(脊髓) 侧索硬化和阿尔茨海默氏症等人类神经疾病的发病过程中所起的作用提供线索。
一个在减数分裂过程中调控基因表达的基因
减数分裂是一种独特的细胞分裂，是有性生殖所必需的。它能产生功能性单配体配子，并重组基因组信息。减数分裂的进行是通过正确协调若干种减数分裂基因的作用来控制的。现在，一个调控减数分裂基因表达的候选基因已被识别出来。该基因名叫Meisetz，为减数分裂特有的一种组蛋白（H3-赖氨酸4-特定的三甲基转移酶）编码，它是小鼠同源染色体之间减数分裂重组所必需的。Meisetz通过染色质的表观遗传修饰在精母细胞中发挥重要功能，这是发现一个基因在减数分裂进展过程中调控基因表达的表观控制的第一例情况。
Contents
Editorials
Will the regulator please stand up p257
It's time for the South Korean government to launch an investigation into how eggs were obtained for a ground-breaking stem-cell experiment.
doi:10.1038/438257a
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Heavy weather p257
Washington DC still doesn't seem to understand the threat posed by global warming.
doi:10.1038/438257b
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Pulling together p258
Protests by Chinese students at Yale University are highlighting strains on a symbiotic relationship.
doi:10.1038/438258a
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Top of pageResearch Highlights
Research highlights p260
doi:10.1038/438260a
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Top of pageNews
Stem-cell brothers divide p262
Famous co-authors part company over egg-donation controversy.
David Cyranoski and Erika Check
doi:10.1038/438262a
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Japan's embryo experts beg for faster ethical reviews p263
Researchers accuse review boards of holding them back.
David Cyranoski
doi:10.1038/438263a
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US budget yields scant research rises p264
NASA gets research boost as Congress passes fiscal plans.
Geoff Brumfiel and Tony Reichhardt
doi:10.1038/438264a
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Small conferences pay their way p264
Survey suggests it's good to talk.
Kendall Powell
doi:10.1038/438264b
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Day of judgement for intelligent design p267
Split decision across states signals no end to 'classroom creationism' debate.
Geoff Brumfiel
doi:10.1038/438267a
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Atomic agency launches bid to bank nuclear fuel p268
International supply of partly-enriched uranium could slow proliferation.
Jim Giles
doi:10.1038/438268a
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Scheme to track greenhouse gases takes to the air p268
Commercial aircraft is fitted with carbon dioxide detector.
Ichiko Fuyuno
doi:10.1038/438268b
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Sidelines p269
doi:10.1038/438269a
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News in brief p270
doi:10.1038/438270a
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Top of pageNews Features
Invasive species: Shoot to kill p272
The US government has adopted a tough approach to battling harmful exotic plants: specialist strike teams. But can they prevail? Emma Marris finds out it's not all black and white.
doi:10.1038/438272a
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Climate change: The long-range forecast p275
The Himalayas, roof of the world, are springing a leak. As the climate warms up, melting glaciers are threatening the livelihoods of millions. David Cyranoski reports.
doi:10.1038/438275a
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Chinese students in the US: Taking a stand p278
A protest by Chinese graduate students at Yale University has revealed the plight of a vulnerable workforce in US labs. Geoff Brumfiel investigates.
doi:10.1038/438278a
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Top of pageBusiness
Wisdom of the crowd p281
Decision makers, wrestling with thorny choices, are tapping into the collective foresight of ordinary people. Jim Giles reports.
doi:10.1038/438281a
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Top of pageCorrespondence
Biodiversity: involvement of local people is crucial p282
Martyn G. Murray and Jacqueline A. Yelland
doi:10.1038/438282a
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Space triumph reveals new spirit of openness in China p282
Bin Wang
doi:10.1038/438282b
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Intelligent, social rat can find joy in a hostile world p282
Jonathan Balcombe
doi:10.1038/438282c
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Peer-review system could gain from author feedback p282
Alon Korngreen
doi:10.1038/438282d
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How Wallace and Dampier faced tsunamis at sea p282
Jeyaraney Kathirithamby
doi:10.1038/438282e
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Top of pageCommentaries
Climate proofing the Netherlands p283
Regional climate change should not be seen only as a threat; changes to weather patterns could generate opportunities for large-scale innovations, say Pavel Kabat, Pier Vellinga and their colleagues.
doi:10.1038/438283a
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Policy needs robust climate science p285
The path between climate science and policy is not always linear, argue Aristides Patrinos and Anjuli Bamzai.
doi:10.1038/438285a
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Top of pageBooks and Arts
The origins of darwinism p287
Impending anniversaries and the trial over 'intelligent design' make this a good time to revisit Darwin.
Bruce H. Weber reviews From So Simple a Beginning: The Four Great Books of Charles Darwin and Darwin: The Indelible Stamp
doi:10.1038/438287a
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Dancing to Darwin's tune p288
W. Tecumseh Fitch reviews The Singing Neanderthals: The Origins of Music, Language, Mind and Body by Steve Mithen
doi:10.1038/438288a
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Darwin in fiction p288
Darwin's life and work has also inspired two recent novels.
doi:10.1038/438288b
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Science in culture: Monkey business p289
Charles Darwin changed the way animals were viewed in art.
Colin Martin
doi:10.1038/438289a
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Top of pageEssay
Concept
A polymath's dilemma p291
Thomas Young strove to satisfy his curiosity in virtually every scientific subject and, undeterred by sceptics calling for a narrower focus, made discoveries in almost all the fields he studied.
Andrew Robinson
doi:10.1038/438291a
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Top of pageNews and Views
Epidemiology: Dimensions of superspreading p293
Analyses of contact-tracing data on the spread of infectious disease, combined with mathematical models, show that control measures require better knowledge of variability in individual infectiousness.
Alison P. Galvani and Robert M. May
doi:10.1038/438293a
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Nano-Optics: Gold loses its lustre p295
The perfect lens would immaculately reproduce an image of an object, with no light losses in the transition. The strange optical properties of a gold nanostructure bring the prospect of such a component into sharper focus.
Roy Sambles
doi:10.1038/438295a
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Palaeontology: Data on a plate p296
Henry Gee
doi:10.1038/438296a
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Developmental biology: The X-inactivation yo-yo p297
In female mammals, one of two X chromosomes has to be shut down during early development. To what extent does this 'imprinted X-chromosome inactivation' involve the history of the chromosome?
Wolf Reik and Anne C. Ferguson-Smith
doi:10.1038/438297a
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50 & 100 years ago p298
doi:10.1038/438298a
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Communications technology: Chaos down the line p298
Chaos, goes conventional wisdom, can only be a malign influence in telecommunications. But a technique that uses chaotically varying signals to transmit information more privately may help it shed that bad-boy image.
Rajarshi Roy
doi:10.1038/438298b
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Cell biology: Two pores better than one? p299
The movement of proteins through a cell's membrane requires a dedicated molecular machine. A glimpse of this apparatus in action shows that it has two channels, and hints at how these pores might be regulated.
Arnold J. M. Driessen
doi:10.1038/438299a
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Top of pageBrief Communications
Environmental policy: Regional commitment to reducing emissions p301
Local policy in the United States goes some way towards countering anthropogenic climate change.
Brendan Fisher and Robert Costanza
doi:10.1038/438301a
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Ant navigation: Priming of visual route memories p302
Robert A. Harris, Natalie Hempel de Ibarra, Paul Graham and Thomas S. Collett
doi:10.1038/438302a
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Top of pageBrief Communications Arising
Origin of flight: Could 'four-winged' dinosaurs fly? pE3
Kevin Padian and Kenneth P. Dial
doi:10.1038/nature04354
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Origin of flight: Could 'four-winged' dinosaurs fly? (Reply) pE3
Xing Xu, Zhonghe Zhou, Xiaolin Wang, Xuewen Kuang, Fucheng Zhang and Xiangke Du
doi:10.1038/nature04355
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Origin of flight: Could 'four-winged' dinosaurs fly? (Reply) pE4
Zhonghe Zhou and Fucheng Zhang
doi:10.1038/nature04355
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Top of pageReviews
Potential impacts of a warming climate on water availability in snow-dominated regions p303
T. P. Barnett, J. C. Adam and D. P. Lettenmaier
doi:10.1038/nature04141
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Impact of regional climate change on human health p310
Jonathan A. Patz, Diarmid Campbell-Lendrum, Tracey Holloway and Jonathan A. Foley
doi:10.1038/nature04188
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Top of pageArticles
Structure of the E. coli protein-conducting channel bound to a translating ribosome p318
Kakoli Mitra, Christiane Schaffitzel, Tanvir Shaikh, Florence Tama, Simon Jenni, Charles L. Brooks, III, Nenad Ban and Joachim Frank
doi:10.1038/nature04133
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A light-sensing knot revealed by the structure of the chromophore-binding domain of phytochrome p325
Jeremiah R. Wagner, Joseph S. Brunzelle, Katrina T. Forest and Richard D. Vierstra
doi:10.1038/nature04118
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Top of pageLetters
The formation of stars by gravitational collapse rather than competitive accretion p332
Mark R. Krumholz, Christopher F. McKee and Richard I. Klein
doi:10.1038/nature04280
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Nanofabricated media with negative permeability at visible frequencies p335
A. N. Grigorenko, A. K. Geim, H. F. Gleeson, Y. Zhang, A. A. Firsov, I. Y. Khrushchev and J. Petrovic
doi:10.1038/nature04242
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Spin-torque diode effect in magnetic tunnel junctions p339
A. A. Tulapurkar, Y. Suzuki, A. Fukushima, H. Kubota, H. Maehara, K. Tsunekawa, D. D. Djayaprawira, N. Watanabe and S. Yuasa
doi:10.1038/nature04207
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Chaos-based communications at high bit rates using commercial fibre-optic links p343
Apostolos Argyris, Dimitris Syvridis, Laurent Larger, Valerio Annovazzi-Lodi, Pere Colet, Ingo Fischer, Jordi García-Ojalvo, Claudio R. Mirasso, Luis Pesquera and K. Alan Shore
doi:10.1038/nature04275
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Global pattern of trends in streamflow and water availability in a changing climate p347
P. C. D. Milly, K. A. Dunne and A. V. Vecchia
doi:10.1038/nature04312
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Palaeoanatomy and biological affinities of a Cambrian deuterostome (Stylophora) p351
Sébastien Clausen and Andrew B. Smith
doi:10.1038/nature04109
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Superspreading and the effect of individual variation on disease emergence p355
J. O. Lloyd-Smith, S. J. Schreiber, P. E. Kopp and W. M. Getz
doi:10.1038/nature04153
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Specification of astrocytes by bHLH protein SCL in a restricted region of the neural tube p360
Yuko Muroyama, Yuko Fujiwara, Stuart H. Orkin and David H. Rowitch
doi:10.1038/nature04139
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Control of B-cell responses by Toll-like receptors p364
Chandrashekhar Pasare and Ruslan Medzhitov
doi:10.1038/nature04267
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Evidence for de novo imprinted X-chromosome inactivation independent of meiotic inactivation in mice p369
Ikuhiro Okamoto, Danielle Arnaud, Patricia Le Baccon, Arie P. Otte, Christine M. Disteche, Philip Avner and Edith Heard
doi:10.1038/nature04155
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A histone H3 methyltransferase controls epigenetic events required for meiotic prophase p374
Katsuhiko Hayashi, Kayo Yoshida and Yasuhisa Matsui
doi:10.1038/nature04112
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Chromatin remodelling at a DNA double-strand break site in Saccharomyces cerevisiae p379
Toyoko Tsukuda, Alastair B. Fleming, Jac A. Nickoloff and Mary Ann Osley
doi:10.1038/nature04148
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Force production by disassembling microtubules p384
Ekaterina L. Grishchuk, Maxim I. Molodtsov, Fazly I. Ataullakhanov and J. Richard McIntosh
doi:10.1038/nature04132
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Top of pageNaturejobs
Prospect
Where East meets West p389
The East is offering ways to unseat Western dominance in graduate enrolment and employment.
Paul Smaglik
doi:10.1038/nj7066-389a
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Postdocs and Students
Balancing act p390
Mounting responsibilities can swamp the newly independent scientist. Kendall Powell asks if it's possible to manage your time without losing your creativity.
Kendall Powell
doi:10.1038/nj7066-390a
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Career Views
Melissa Hines, director, Cornell Center for Materials Research, Ithaca, New York p392
Chemist emphasizes need for public communication.
Virginia Gewin
doi:10.1038/nj7066-392a
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Recruiters & Academia p392
Workshop teaches scientists how to be a professor.
Charlene Sorensen
doi:10.1038/nj7066-392b
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Graduate Journal: Learning from teaching p392
Graduate student gets teaching lessons in the ballroom.
Karolina Tkaczuk
doi:10.1038/nj7066-392c
Full Text | PDF (131K)
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Top of pageFutures
Perchance to dream p394
Out of sight, out of mind.
Robert A. Metzger
doi:10.1038/438394a
Full Text | PDF (163K)
