翻譯 | 宗華
Science, 01 FEBRUARY 2019, VOL 363, ISSUE 6426
《科學》2019年2月1日，第6426期363卷
A surface gravity traverse on Marsindicates low bedrock density at Gale crater
火星表面重力測線表明蓋爾環形山的低巖床密度
▲ 作者：Kevin W. Lewis, Stephen Peters, Kurt Gonter, et al
▲ 連結：
http://science.sciencemag.org/content/363/6426/535
▲ 摘要：
重力測量是對引力場的精確測量，可被用於探測地球和其他行星的內部結構。火星上「好奇號」探測器攜帶了通常用於導航和姿態確定的加速計。
我們將其進行了重新校準，從而將探測器翻越蓋爾環形山時不斷變化的重力加速度特徵分離出來。地下巖石密度通過測量的隨高度變化的引力場強度的變小而得以推斷出來。蓋爾環形山沉積巖的密度為每立方米1680 ± 180千克。
該數值比預期的低，表明這些巖石歷史上曾擁有高孔隙率和受到約束的最大埋藏深度。
▲ 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
恆星被大質量黑洞撕裂後的擬周期振蕩
▲ 作者：Dheeraj R. Pasham, Ronald A. Remillard, P. Chris Fragile, et al
▲ 連結：
http://science.sciencemag.org/content/363/6426/531
▲ 摘要：
靠近大質量黑洞的潮力可將離其太近的恆星撕裂。隨著由此產生的恆星碎片呈螺旋狀飛向黑洞，這些碎片的溫度上升並且釋放X射線。
我們報告了針對來自潮汐撕裂事件ASASSN-14li的穩定的131秒X射線擬周期振蕩的觀測結果。
假定宿主星系定標關系所表明的黑洞質量，這些結果提示，這種周期性源自靠近的事件視界，同時黑洞正在快速自旋。
我們的發現表明，潮汐撕裂事件能產生編碼關於黑洞物理屬性信息的擬周期振蕩。
▲ 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.
Linking a mutation to survival in wild mice
將一個突變同野外小鼠的生存相關聯
▲ 作者：Rowan D. H. Barrett, Stefan Laurent, Ricardo Mallarino, et al
▲ 連結：
http://science.sciencemag.org/content/363/6426/499
▲ 摘要：
新的或者不斷變化的環境中的適應性進化很難預測，因為基因型、表型和適應度之間的功能聯繫是複雜的。
這裡，我們通過結合在野外小鼠身上開展的田間和實驗室試驗，描述了這些明確的關聯。我們首先通過利用擁有不同土壤顏色的小鼠實驗圍隔，直接估測了色素特徵及其背後的色素基因座Agouti的自然選擇。
下一步，我們證實了Agouti一個同生存相關的突變如何通過蛋白質結合特性的變化導致更淺毛色。
總之，我們的發現證明了序列變異體如何改變基因型，然後揭示了驅動種群等位基因頻率變化的生態後果，並由此闡明了自然選擇的進化過程。
▲ 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
受肌肉訓練啟發的機械響應性自我生長水凝膠
▲ 作者：Takahiro Matsuda, Runa Kawakami, Ryo Namba, et al
▲ 連結：
http://science.sciencemag.org/content/363/6426/504
▲ 摘要：
諸如肌肉等活體組織自動生長並且改造自己，從而通過代謝過程適應周圍的力學環境。相比之下，典型的合成材料一旦形成便無法生長並且重建其結構。
我們提出了一種製造「自生長」聚合物材料的策略。該材料通過有效的機械化學轉導對重複的機械應力作出響應。
擁有持續單體供應的強勁雙網水凝膠經歷了自我生長，同時這種材料通過結構性摧毀—重建過程在重複載荷下大大加強。
▲ 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
睡眠誘導基因nemuri將果蠅睡眠同免疫功能相關聯
▲ 作者：Hirofumi Toda, Julie A. Williams, Michael Gulledge, Amita Sehgal
▲ 連結：
http://science.sciencemag.org/content/363/6426/509
▲ 摘要：
睡眠一直是生物學的一個重要謎題。尤其關於解釋睡眠動力的機制，更是知之甚少。
在對1.2萬多個果蠅細胞系進行的無偏見篩選中，我們辨別出一個誘導睡眠的基因nemuri。這個NEMURI蛋白質是一種可被異位分泌來驅動延長睡眠（抵抗喚醒）並且促進感染後生存的抗菌肽。
Nemuri的喪失增加了日常睡眠期間的喚醒頻率，並且使睡眠剝奪或者細菌感染誘導的睡眠的急劇增加減弱。
▲ 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.
A sea change in our view of overturning in the subpolar North Atlantic
對亞極地北大西洋翻轉環流觀點的徹底變革
▲ 作者：M. S. Lozier, F. Li, S. Bacon, F. Bahr, et al
▲ 連結：
http://science.sciencemag.org/content/363/6426/516
▲ 摘要：
為給政府間氣候變化專門委員會對21世紀不斷減緩的大西洋經向翻轉環流（MOC）作出預測提供觀察基礎，北大西洋亞極地海區經向翻轉流觀測計劃（OSNAP）的觀測系統於2014年夏季啟用。
最初21個月的記錄揭示了高度變化的翻轉環流。這些環流導致了大部分的溫度升高和OSNAP線上的淡水輸送。
和認為拉布拉多海中深水形成變化主導MOC變化的主流觀點不同，這些結果表明，溫暖且鹹的大西洋淺層海水轉變為在伊爾明厄和冰島盆地朝南流動的更冷、深層淡水，並在很大程度上導致了翻轉環流及其在亞極地盆地的變化。
▲ 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.
Correlations in high-harmonic generation of matter-wave jets revealed by pattern recognition
模式識別揭示的物質波噴射流高次諧波產生中的相關性
▲ 作者：Lei Feng, Jiazhong Hu, Logan W. Clark, Cheng Chin
▲ 連結：
http://science.sciencemag.org/content/363/6426/521
▲ 摘要：
相互作用的多體系統中的相關性對於研究量子物質至關重要。
這些相關性的複雜程度通常隨著系統演化迅速增加，並因此對實驗表徵和直覺性理解帶來挑戰。
在強驅動玻色—愛因斯坦凝聚體中，我們觀察到波色子刺激導致的帶有複雜相關性的物質波噴射流的高次諧波產生。基於模式識別方案，我們辨別出揭示潛在二次散射過程和更高階相關性的模式。
我們證實，模式識別提供了對多體系統量子動力學進行可視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
複雜介質中量子參考信標指引的超解析度光學成像
▲ 作者：Donggyu Kim, Dirk R. Englund
▲ 連結：
http://science.sciencemag.org/content/363/6426/528
▲ 摘要：
光學散射通常被認為是顯微鏡學中令人討厭的東西，因為它限制了成像深度和空間解析度。波前成形技術使以前所未有的深度進行光學成像變成可能，但獲得複雜介質內的超解析度是一大挑戰。
我們利用量子參考信標（QRB）提供了針對波前成形的亞波長「導引星」反饋，從而實現超解析度光學聚焦。
QRB包含帶有自旋相關螢光的固態量子發射器。我們在帶有氮—空位中心的金剛石納米晶體中進行了QRB指引的成像。這使得186納米以下（不到波長一半）帶有超衍射解析度的光學成像變成可能。
▲ 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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