Volume 433 Number 7026 pp557-668封面故事：冰川中水的行为
水在冰川中的行为是决定冰川如何运动以及水是怎样从冰川中被除掉的一个关键因素。传统观点是，水通过天然管状通道流经冰川，但新的野外工作表明，现在是重新考虑这个问题的时候了。来自瑞典北部Storglaci?ren钻孔的视频图像结合雷达探声研究显示，存在一个由含水裂缝构成的网络，而令人吃惊的是，几乎没有预料中的管状通道。这项工作为了解冰川中水的储存和运动路径提供了新的视角。冰川深处裂缝的存在对于研究冰架灾难性的坍塌事件（就像最近在Larsen-B所发生的坍塌事件那样）可能有参考价值。本期封面所示为瑞典北部的Storglaci?ren，背景中为Kebnekaise山脉的山峰。（摄影：Robert W. Jacobel）
能发射硬X-射线的新型桌面X-射线激光器
X-射线激光器的确存在，甚至桌面型的也存在，但它们通常产生的是“软”X-射线激光，波长约5-120纳米，比医学X-射线中所用的波长稍长一些，能量只有几百电子伏特。化学、生物学和材料学研究中的新应用呼唤能够产生具有较高能量的“较硬的”X-射线的实验用X-射线激光器。本期Nature报告了向着这个目标所取得的一项进展。这种新的桌面X-射线激光器发射高度校准的、空间相干的X-射线，波长约1纳米，光子能量高达1.3千电子伏特，并且有望增加到2.5千电子伏特。具有这种类型的表现的一种实用光源，将可以在对原子、分子和固体中的电子动态进行各种不同的研究中所要求的时间尺度上进行工作，达到近乎原子尺度的分辨率。
人脑比我们所想象的更有组织
人脑含有约10亿个细胞。这些细胞在宏观和微观尺度上是怎样组织的？人们早就知道，大脑不同部分处理不同类型的传感信息。利用过去的低分辨率成像技术，研究人员发现，细胞群（如那些只对特定方向的视觉刺激产生反应的细胞）被松散聚集进不同区域中。现在，新的成像技术（活体双光子钙成像）显示，这些区域形成非常有序的三维图，这些图精确到各个脑细胞的尺度。这意味着，人脑的组织性要比以前所认为的好的多，在微观尺度上有纯粹的功能区域。
氢化酶蛋白核心铁-硫结构的化学合成
在传统的氢燃料电池中，质子和电子与氢之间的迅速的相互转换需要贵金属来催化，所用的贵金属通常是铂。在有生命的世界中，酶利用大量存在的金属以极高的速度来催化同一反应。现在，Tard等人报告了位于氢化酶蛋白核心的铁-硫结构的化学合成。所获得的铁-硫框架起质子还原反应的一种电催化剂的作用，这一成果可以被看作是向着合成在燃料电池的阳极中取代铂的分子材料的目标所迈出的重要一步。
北半球2000年时间的气温重建
对北半球年平均气温所做的一个2000年的重建可以说是一项新的突破，因为它将来自气候参数的数据与不同的内在时间尺度（如湖泊和海洋沉积物及树木年轮数据）结合了起来，从而给每个参数赋予充分的权重，使其分辨率都达到最大。这种技术利用“小波转换”，使可供利用的古气候数据得到最充分的利用。所获得的重建结果支持认为多世纪的自然波动要比人们普遍所想的更大、以及今后预计还将出现相当大的自然气候变化的观点。10世纪时出现了高温气候，在1600年左右出现了明显的“低温”天气。但1990年以后的气温仍然高于前2000年任何时候的气温。
大气中CO2浓度突变的影响
研究大气中CO2浓度今后增加所产生效应的实验工作者，经常会将一个现代生态系统暴露于高浓度的CO2，然后看会发生什么。新的研究工作表明，他们的结果可能是误导的。在对土壤菌根真菌所做的一项长期研究中（持续时间为6年），CO2浓度的突然增加对真菌群落中生物多样性和结构的影响要比历经21代逐渐增加CO2浓度所产生的影响大得多。在野外实验中是否会出现类似偏差尚有待观察，因为在野外环境中存在更复杂的物种间关系，但在解释比自然出现的变化更突然的变化所产生的效应时，我们的确应当更为谨慎。
妙用滑翔的蚂蚁
很多树栖动物利用滑翔飞行来从一棵树上移动到另一棵树上，如飞鼠和狐猴等。现在，研究人员在一种无翼昆虫身上也观察到了类似行为，这种昆虫就是热带雨林中树冠上的蚂蚁。简单的实验和视频表明，在从一个树枝上跳下后，这种蚂蚁通过用目测使自身与跳离的树成直线、并朝着树干方向往回滑翔的方法来避免落在树下的植被上或地面上。
一种可“开放”使用的基因转移技术
对生产转基因作物中所用生物技术的控制掌握在少数跨国公司手中，部分原因是这件事情涉及到复杂的专利网络。来自澳大利亚CMBIA（国际农业中分子生物学应用中心）的一个小组，为了解开这一网络并使生物技术能够得到更广泛的应用，为植物生物技术中一项关键的基础技术开发出一种解决方案，即“由农用细菌调节的转化”。他们发现，其他种类的良性细菌可以非常简单的方法被改造，从而来做同样工作，他们所开发出的基因转移技术将可以被“开放”使用，因为它是最近发起的BIOS计划的一个组成部分（Nature 431, 494; 2004）。
氨基酸与蛋白的演化
对由来自代表所有三大生命范畴（细菌、古细菌和真核生物）的生物的密切相关的基因编码的相应蛋白组所做的一个比较表明，35亿年前遗传编码的组合次序继续影响着今天蛋白的演化。在这些多样的基因组间，演化中的蛋白积累了Cys、Met、His、Ser和Phe，丢失了它们的很多Pro、Ala、Glu和Gly残体。同样的9个氨基酸目前在人类蛋白中累积或丢失，正如对核苷多态性的分析所表明的那样。频率下降的氨基酸很可能是首先结合进遗传编码中的氨基酸，而频率增加的氨基酸中多数很可能是晚些时候“招募”进来的。
心脏干细胞疗法的新希望
心脏干细胞疗法领域一直有点像一个雷区。在注射干细胞后的生长响应以难以确认而著称，因为难以确认生长的肌肉是新的心肌还是细胞融合的结果。但本期Nature发表的一篇论文使这一领域朝更坚实的方向迈进了一步。Laugwitz等人报告，他们在出生后的心脏中发现了真正的、原本就有的原始心肌组织（成心肌细胞），并用胚胎中源祖细胞场中的一个标记（小岛-1）对这些细胞的身份进行了跟踪。这些细胞被原地局限在完好心脏中，被细胞培养所“更新”，被一种基于有条件谱系标记的技术所纯化，使这些细胞的自然分异能够得到清楚地记录。这些结果使我们对心脏干细胞疗法有一天将会成为现实又产生了新的希望。
本期目录：
Editorials
Taking a hard line on conflicts p557
A clampdown on conflicts of interest at the US National Institutes of Health needn't stifle quality research at the agency — and it might indicate the shape of things to come elsewhere.
doi: 10.1038/433557a
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Not so fast p557
Anyone thinking of collaborations with emerging biomedical powers should test the ethical waters before jumping in.
doi: 10.1038/433557b
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Top of pageNews
Main agencies hang on to funds in skimpy US science budget p559
The first budget of President Bush's second term puts tight constraints on US research spending.
Geoff Brumfiel
doi: 10.1038/433559a
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Gene therapy put on hold as third child develops cancer p561
Trial of treatment for rare, childhood illness is halted, again.
Erika Check
doi: 10.1038/433561a
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NIH open-access plans draw fire from both sides p561
Researchers will be asked to put their findings in an open-access database.
Erika Check
doi: 10.1038/433561b
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Past climate comes into focus but warm forecast stays put p562
A reassessment of past climate records suggests greater fluctuation than was previously thought.
Quirin Schiermeier
doi: 10.1038/433562a
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news in brief p564
doi: 10.1038/433564a
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Editorial note p564
doi: 10.1038/433564b
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Top of pageNews Features
Marine biology : Whale fall p566
The fatty bones of dead whales provide rich pickings for creatures on the sea floor. Amanda Haag meets the scientists who go to extreme and unpleasant lengths to study the unique ecosystems on these corpses.
doi: 10.1038/433566a
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Drug rehabilitation : Cold turkey, Vietnamese style p568
It was invented by a healer familiar with the horrors of opiate addiction, and refined by Vietnam's leading chemistry lab. Can this novel herbal cocktail ease withdrawal and reduce drug cravings? Peter Aldhous investigates.
doi: 10.1038/433568a
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Astronomy and the public : Prison talk p570
A few French scientists are bringing astronomy to captive audiences, such as the terminally ill and the incarcerated. Alison Abbott joined a group of convicted murderers to learn about gravity.
doi: 10.1038/433570a
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Top of pageCorrespondence
Nuclear nations should take the lead in disarming p571
A willingness to use 'overwhelming force' encourages other states to arm themselves.
Robert A. Hinde
doi: 10.1038/433571a
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Military alliances offer no nuclear security p571
Dominique Lalanne, Peter Nicholls and Joseph Rotblat
doi: 10.1038/433571b
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Would you accept advice from a believer in Santa? p571
D. J. Hosken
doi: 10.1038/433571c
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Top of pageCommentary
Lessons from the past p573
Poverty and market forces combine to keep rural China unhealthy.
Zigang Dong, Christina W. Hoven and Allan Rosenfield
doi: 10.1038/433573a
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Top of pageBooks and Arts
Feet of clay p575
There's more to science than doing the research.
doi: 10.1038/433575a
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Poison in the well p576
doi: 10.1038/433576a
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The force behind the prize p577
doi: 10.1038/433577a
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Top of pagePhysics Detective
Schr?dinger's mousetrap p579
Part 4: A very public humiliation.
Laura Garwin
doi: 10.1038/433579a
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Top of pageEssay
The onset of selection p581
Natural selection started to drive evolution as soon as molecular replication became possible.
Christian de Duve
doi: 10.1038/433581a
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Top of pageNews and Views
Agricultural biotechnology: Gene exchange by design p583
Gene transfer from bacteria to plants was thought to be limited to the bacterial genus Agrobacterium. But other bacterial groups also contain species capable of interkingdom genetic exchange.
Stanton B. Gelvin
doi: 10.1038/433583a
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Quantum optics: Cheat detection p584
Philip Ball
doi: 10.1038/433584a
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Cardiology: Solace for the broken-hearted? p585
The heart was thought to lack the capacity to regenerate after injury. But the identification of cells that can divide and mature into heart muscle suggests that the heart has repair mechanisms after all.
Christine L. Mummery
doi: 10.1038/433585a
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Climate change: Let all the voices be heard p587
It's a tough job to excavate trustworthy records about past temperatures from the palaeoclimate archives. The application of a fresh approach, in the form of wavelet analysis of the data, is a step forward.
D. M. Anderson and C. A. Woodhouse
doi: 10.1038/433587a
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100 and 50 years ago p587
doi: 10.1038/433587b
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Palaeoecology: Down to the woods yesterday p588
What were European forests like following the last ice age and before the advent of agriculture? The pollen record in Ireland provides a unique perspective from which to examine ideas on the question.
Peter D. Moore
doi: 10.1038/433588a
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Synthetic chemistry: Making a natural fuel cell p589
The synthetic assembly of the active centre of hydrogen-producing enzymes adds to our understanding of their structure and function — and could produce new and useful materials that mimic these enzymes.
Marcetta York Darensbourg
doi: 10.1038/433589a
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Cancer: Catalyst of a catalyst p591
Breast cancers arise when the BRCA2 protein is defective, but what does the normal enzyme do? Studies of a relative of BRCA2 reveal a capacity to initiate the repair of broken DNA by loading a repair protein.
Stephen C. Kowalczykowski
doi: 10.1038/433591a
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Obituary: Julius Axelrod (1912?2004) p593
Solomon H. Snyder
doi: 10.1038/433593a
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research highlights p594
doi: 10.1038/433594a
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Top of pageBrief Communications
Neurobiology: Motor control of flexible octopus arms p595
The octopus borrows a jointed-vertebrate strategy to transfer an item between points.
Germán Sumbre, Graziano Fiorito, Tamar Flash and Binyamin Hochner
doi: 10.1038/433595a
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Laser technology: Source of coherent kiloelectronvolt X-rays p596
J. Seres, E. Seres, A. J. Verhoef, G. Tempea, C. Streli, P. Wobrauschek, V. Yakovlev, A. Scrinzi, C. Spielmann and F. Krausz
doi: 10.1038/433596a
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Top of pageBrief Communications Arising
Atmospheric science: Marine aerosols and iodine emissions pE13
Gordon McFiggans
doi: 10.1038/nature03372
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Atmospheric science: Marine aerosols and iodine emissions (Reply) pE13
Colin D. O'Dowd, Jose L. Jimenez, Roya Bahreini, Richard C. Flagan, John H. Seinfeld, Kaarle H?meri, Liisa Pirjola, Markku Kulmala, S. Gerard Jennings and Thorsten Hoffmann
doi: 10.1038/nature03373
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Top of pageArticle
Functional imaging with cellular resolution reveals precise micro-architecture in visual cortex p597
Kenichi Ohki, Sooyoung Chung, Yeang H. Ch'ng, Prakash Kara and R. Clay Reid
doi: 10.1038/nature03274
Abstract | Full Text | PDF (847K) | Supplementary information
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Top of pageLetters to Nature
Energy input from quasars regulates the growth and activity of black holes and their host galaxies p604
Tiziana Di Matteo, Volker Springel and Lars Hernquist
doi: 10.1038/nature03335
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Electronically soft phases in manganites p607
G. C. Milward, M. J. Calderón and P. B. Littlewood
doi: 10.1038/nature03300
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Synthesis of the H-cluster framework of iron-only hydrogenase p610
Cédric Tard, Xiaoming Liu, Saad K. Ibrahim, Maurizio Bruschi, Luca De Gioia, Sian C. Davies, Xin Yang, Lai-Sheng Wang, Gary Sawers and Christopher J. Pickett
doi: 10.1038/nature03298
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Highly variable Northern Hemisphere temperatures reconstructed from low- and high-resolution proxy data p613
Anders Moberg, Dmitry M. Sonechkin, Karin Holmgren, Nina M. Datsenko and Wibj?rn Karlén
doi: 10.1038/nature03265
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Fractures as the main pathways of water flow in temperate glaciers p618
Andrew G. Fountain, Robert W. Jacobel, Robert Schlichting and Peter Jansson
doi: 10.1038/nature03296
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Abrupt rise in atmospheric CO2 overestimates community response in a model plant?soil system p621
John N. Klironomos, Michael F. Allen, Matthias C. Rillig, Jeff Piotrowski, Shokouh Makvandi-Nejad, Benjamin E. Wolfe and Jeff R. Powell
doi: 10.1038/nature03268
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Directed aerial descent in canopy ants p624
Stephen. P. Yanoviak, Robert Dudley and Michael Kaspari
doi: 10.1038/nature03254
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Photoperiodic induction of synchronous flowering near the Equator p627
Rolf Borchert, Susanne S. Renner, Zoraida Calle, Diego Navarrete, Alan Tye, Laurent Gautier, Rodolphe Spichiger and Patricio von Hildebrand
doi: 10.1038/nature03259
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Gene transfer to plants by diverse species of bacteria p629
Wim Broothaerts, Heidi J. Mitchell, Brian Weir, Sarah Kaines, Leon M. A. Smith, Wei Yang, Jorge E. Mayer, Carolina Roa-Rodríguez and Richard A. Jefferson
doi: 10.1038/nature03309
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A universal trend of amino acid gain and loss in protein evolution p633
I. King Jordan, Fyodor A. Kondrashov, Ivan A. Adzhubei, Yuri I. Wolf, Eugene V. Koonin, Alexey S. Kondrashov and Shamil Sunyaev
doi: 10.1038/nature03306
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Contributions of an avian basal ganglia?forebrain circuit to real-time modulation of song p638
Mimi H. Kao, Allison J. Doupe and Michael S. Brainard
doi: 10.1038/nature03127
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Ultrabithorax is required for membranous wing identity in the beetle Tribolium castaneum p643
Yoshinori Tomoyasu, Scott R. Wheeler and Robin E. Denell
doi: 10.1038/nature03272
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Postnatal isl1+ cardioblasts enter fully differentiated cardiomyocyte lineages p647
Karl-Ludwig Laugwitz, Alessandra Moretti, Jason Lam, Peter Gruber, Yinhong Chen, Sarah Woodard, Li-Zhu Lin, Chen-Leng Cai, Min Min Lu, Michael Reth, Oleksandr Platoshyn, Jason X.-J. Yuan, Sylvia Evans and Kenneth R. Chien
doi: 10.1038/nature03215
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The BRCA2 homologue Brh2 nucleates RAD51 filament formation at a dsDNA?ssDNA junction p653
Haijuan Yang, Qiubai Li, Jie Fan, William K. Holloman and Nikola P. Pavletich
doi: 10.1038/nature03234
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Structural basis for substrate binding, cleavage and allostery in the tRNA maturase RNase Z p657
Inés Li de la Sierra-Gallay, Olivier Pellegrini and Ciarán Condon
doi: 10.1038/nature03284
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corrigendum: The yeast Rat1 exonuclease promotes transcription termination by RNA polymerase II p661
Minkyu Kim, Nevan J. Krogan, Lidia Vasiljeva, Oliver J. Rando, Eduard Nedea, Jack F. Greenblatt and Stephen Buratowski
doi: 10.1038/nature03307
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Top of pageNaturejobs
Reversal of fortune p663
Paul Smaglik
doi: 10.1038/nj7026-663a
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Capital collaboration Washington DC p664
Eugene Russo
doi: 10.1038/nj7026-664a
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Graduate Journal: A rewarding journey p666
Karolina Tkaczuk
doi: 10.1038/nj7026-666a
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Bricks & Mortar p666
Paul Smaglik
doi: 10.1038/nj7026-666b
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Movers p666
doi: 10.1038/nj7026-666c
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Top of pageFutures
Under martian ice p668
Cold ... and never more alone.
Stephen Baxter
doi: 10.1038/433668a
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