翻译 | 宗华
Science, 01 FEBRUARY 2019, VOL 363, ISSUE 6426
《科学》2019年2月1日，第6426期363卷
天文学Astronomy
A surface gravity traverse on Marsindicates low bedrock density at Gale crater
火星表面重力测线表明盖尔环形山的低岩床密度
▲ 作者：Kevin W. Lewis, Stephen Peters, Kurt Gonter, et al
▲ 链接：
http://science.sciencemag.org/content/363/6426/535
▲ 摘要：
重力测量是对引力场的精确测量，可被用于探测地球和其他行星的内部结构。火星上“好奇号”探测器携带了通常用于导航和姿态确定的加速计。
我们将其进行了重新校准，从而将探测器翻越盖尔环形山时不断变化的重力加速度特征分离出来。地下岩石密度通过测量的随高度变化的引力场强度的变小而得以推断出来。盖尔环形山沉积岩的密度为每立方米1680 ± 180千克。
该数值比预期的低，表明这些岩石历史上曾拥有高孔隙率和受到约束的最大埋藏深度。
▲ Abstract
Gravimetry, the precise measurement of gravitational fields, can be used to probe the internal structure of Earth and other planets. The Curiosity rover on Mars carries accelerometers normally used for navigation and attitude determination. We have recalibrated them to isolate the signature of the changing gravitational acceleration as the rover climbs through Gale crater. The subsurface rock density is inferred from the measured decrease in gravitational field strength with elevation. The density of these dimentary rocks in Gale crater is 1680 ± 180 kilograms per cubic meter. This value is lower than expected, indicating a high porosity and constraining maximum burial depths of the rocks over their history.
A loud quasi-periodic oscillation after astar is disrupted by a massive black hole
恒星被大质量黑洞撕裂后的拟周期振荡
▲ 作者：Dheeraj R. Pasham, Ronald A. Remillard, P. Chris Fragile, et al
▲ 链接：
http://science.sciencemag.org/content/363/6426/531
▲ 摘要：
靠近大质量黑洞的潮力可将离其太近的恒星撕裂。随着由此产生的恒星碎片呈螺旋状飞向黑洞，这些碎片的温度上升并且释放X射线。
我们报告了针对来自潮汐撕裂事件ASASSN-14li的稳定的131秒X射线拟周期振荡的观测结果。
假定宿主星系定标关系所表明的黑洞质量，这些结果提示，这种周期性源自靠近的事件视界，同时黑洞正在快速自旋。
我们的发现表明，潮汐撕裂事件能产生编码关于黑洞物理属性信息的拟周期振荡。
▲ Abstract
The tidal forces close to massive blackholes can rip apart stars that come too close to them. As the resulting stellar debris spirals toward the black hole, the debris heats up and emits x-rays. We report observations of a stable 131-second x-ray quasi-periodic oscillation from the tidal disruption event ASASSN-14li. Assuming the black hole mass indicated by host galaxy scaling relations, these observations imply that the periodicity originates from close to the event horizon and that the black hole is rapidly spinning. Our findings demonstrate that tidal disruption events can generate quasi-periodic oscillations that encode information about the physical properties of their black holes.
生物学Biology
Linking a mutation to survival in wild mice
将一个突变同野外小鼠的生存相关联
▲ 作者：Rowan D. H. Barrett, Stefan Laurent, Ricardo Mallarino, et al
▲ 链接：
http://science.sciencemag.org/content/363/6426/499
▲ 摘要：
新的或者不断变化的环境中的适应性进化很难预测，因为基因型、表型和适应度之间的功能联系是复杂的。
这里，我们通过结合在野外小鼠身上开展的田间和实验室试验，描述了这些明确的关联。我们首先通过利用拥有不同土壤颜色的小鼠实验围隔，直接估测了色素特征及其背后的色素基因座Agouti的自然选择。
下一步，我们证实了Agouti一个同生存相关的突变如何通过蛋白质结合特性的变化导致更浅毛色。
总之，我们的发现证明了序列变异体如何改变基因型，然后揭示了驱动种群等位基因频率变化的生态后果，并由此阐明了自然选择的进化过程。
▲ Abstract
Adaptive evolution in new or changing environments can be difficult to predict because the functional connections between genotype, phenotype, and fitness are complex. Here, we make these explicit connections by combining field and laboratory experiments in wild mice. We first directly estimate natural selection on pigmentation traits and an underlying pigment locus, Agouti, by using experimental enclosures of miceon different soil colors. Next, we show how a mutation in Agouti associated with survival causes lighter coat color through changes in its protein binding properties. Together, our findings demonstrate how a sequence variant alters phenotype and then reveal the ensuing ecological consequences that drive changes in population allele frequency, thereby illuminating the process of evolution by natural selection.
Mechanoresponsive self-growing hydrogels inspired by muscle training
受肌肉训练启发的机械响应性自我生长水凝胶
▲ 作者：Takahiro Matsuda, Runa Kawakami, Ryo Namba, et al
▲ 链接：
http://science.sciencemag.org/content/363/6426/504
▲ 摘要：
诸如肌肉等活体组织自动生长并且改造自己，从而通过代谢过程适应周围的力学环境。相比之下，典型的合成材料一旦形成便无法生长并且重建其结构。
我们提出了一种制造“自生长”聚合物材料的策略。该材料通过有效的机械化学转导对重复的机械应力作出响应。
拥有持续单体供应的强劲双网水凝胶经历了自我生长，同时这种材料通过结构性摧毁—重建过程在重复载荷下大大加强。
▲ Abstract
Living tissues, such as muscle, autonomously grow and remodel themselves to adapt to their surrounding mechanical environment through metabolic processes. By contrast, typical synthetic materials cannot grow and reconstruct their structures once formed. We propose a strategy for developing “self-growing” polymeric materials that respond to repetitive mechanical stress through an effective mechano chemical transduction. Robust double-network hydrogels provided with a sustained monomer supply undergo self-growth, and the materials are substantially strengthened under repetitive loading through a structural destruction-reconstruction process.
A sleep-inducing gene, nemuri, links sleep and immune function in Drosophila
睡眠诱导基因nemuri将果蝇睡眠同免疫功能相关联
▲ 作者：Hirofumi Toda, Julie A. Williams, Michael Gulledge, Amita Sehgal
▲ 链接：
http://science.sciencemag.org/content/363/6426/509
▲ 摘要：
睡眠一直是生物学的一个重要谜题。尤其关于解释睡眠动力的机制，更是知之甚少。
在对1.2万多个果蝇细胞系进行的无偏见筛选中，我们辨别出一个诱导睡眠的基因nemuri。这个NEMURI蛋白质是一种可被异位分泌来驱动延长睡眠（抵抗唤醒）并且促进感染后生存的抗菌肽。
Nemuri的丧失增加了日常睡眠期间的唤醒频率，并且使睡眠剥夺或者细菌感染诱导的睡眠的急剧增加减弱。
▲ Abstract
Sleep remains a major mystery of biology. In particular, little is known about the mechanisms that account for the drive to sleep. In an unbiased screen of more than 12,000 Drosophila lines, we identified a single gene, nemuri, that induces sleep. The NEMURI protein is an antimicrobial peptide that can be secreted ectopically to drive prolonged sleep (with resistance to arousal) and to promote survival after infection. Loss of nemuri increased arousability during daily sleep and attenuated the acute increase in sleep induced by sleep deprivation or bacterial infection.
气候学Climatology
A sea change in our view of overturning in the subpolar North Atlantic
对亚极地北大西洋翻转环流观点的彻底变革
▲ 作者：M. S. Lozier, F. Li, S. Bacon, F. Bahr, et al
▲ 链接：
http://science.sciencemag.org/content/363/6426/516
▲ 摘要：
为给政府间气候变化专门委员会对21世纪不断减缓的大西洋经向翻转环流（MOC）作出预测提供观察基础，北大西洋亚极地海区经向翻转流观测计划（OSNAP）的观测系统于2014年夏季启用。
最初21个月的记录揭示了高度变化的翻转环流。这些环流导致了大部分的温度升高和OSNAP线上的淡水输送。
和认为拉布拉多海中深水形成变化主导MOC变化的主流观点不同，这些结果表明，温暖且咸的大西洋浅层海水转变为在伊尔明厄和冰岛盆地朝南流动的更冷、深层淡水，并在很大程度上导致了翻转环流及其在亚极地盆地的变化。
▲ Abstract
To provide an observational basis for the Intergovernmental Panel on Climate Change projections of a slowing Atlantic meridional overturning circulation (MOC) in the 21st century, the Overturning in the Subpolar North Atlantic Program (OSNAP) observing system was launched inthe summer of 2014. The first 21-month record reveals a highly variable overturning circulation responsible for the majority of the heat and freshwater transport across the OSNAP line. In a departure from the prevailing view that changes in deep water formation in the Labrador Sea dominate MOC variability, these results suggest that the conversion of warm, salty, shallow Atlantic waters into colder, fresher, deep waters that move southward in the Irmingerand Iceland basins is largely responsible for overturning and its variability in the subpolar basin.
物理学Physics
Correlations in high-harmonic generation of matter-wave jets revealed by pattern recognition
模式识别揭示的物质波喷射流高次谐波产生中的相关性
▲ 作者：Lei Feng, Jiazhong Hu, Logan W. Clark, Cheng Chin
▲ 链接：
http://science.sciencemag.org/content/363/6426/521
▲ 摘要：
相互作用的多体系统中的相关性对于研究量子物质至关重要。
这些相关性的复杂程度通常随着系统演化迅速增加，并因此对实验表征和直觉性理解带来挑战。
在强驱动玻色—爱因斯坦凝聚体中，我们观察到波色子刺激导致的带有复杂相关性的物质波喷射流的高次谐波产生。基于模式识别方案，我们辨别出揭示潜在二次散射过程和更高阶相关性的模式。
我们证实，模式识别提供了对多体系统量子动力学进行可视化和分析的通用策略。
▲ Abstract
Correlations in interacting many-bodysystems are key to the study of quantum matter. The complexity of the correlations typically grows quickly as the system evolves and thus presents a challenge for experimental characterization and intuitive understanding. In a strongly driven Bose-Einstein condensate, we observe the high-harmonic generation of matter-wave jets with complex correlations as a result of bosonic stimulation. Based on a pattern recognition scheme, we identify a pattern of correlations that reveals the underlying secondary scattering processes and higher-order correlations. We show that pattern recognition offers a versatile strategy to visualize and analyze the quantum dynamics of a many-body system.
Quantum reference beacon–guided superresolution optical focusing in complex media
复杂介质中量子参考信标指引的超分辨率光学成像
▲ 作者：Donggyu Kim, Dirk R. Englund
▲ 链接：
http://science.sciencemag.org/content/363/6426/528
▲ 摘要：
光学散射通常被认为是显微镜学中令人讨厌的东西，因为它限制了成像深度和空间分辨率。波前成形技术使以前所未有的深度进行光学成像变成可能，但获得复杂介质内的超分辨率是一大挑战。
我们利用量子参考信标（QRB）提供了针对波前成形的亚波长“导引星”反馈，从而实现超分辨率光学聚焦。
QRB包含带有自旋相关荧光的固态量子发射器。我们在带有氮—空位中心的金刚石纳米晶体中进行了QRB指引的成像。这使得186纳米以下（不到波长一半）带有超衍射分辨率的光学成像变成可能。
▲ Abstract
Optical scattering is generally considered to be a nuisance of microscopy that limits imaging depth and spatial resolution. Wavefront shaping techniques enable optical imaging at unprecedented depth, but attaining super resolution within complex media remains a challenge. We used a quantum reference beacon (QRB), consisting of solid-state quantum emitters with spin-dependent fluorescence, to provide subwavelength guidestar feedback for wavefront shaping to achieve a superresolution optical focus. We implemented the QRB-guided imaging with nitrogen-vacancy centers in diamond nanocrystals, which enable optical focusing with a subdiffraction resolution below 186 nanometers (less than half thewavelength).
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