《科学》（20230414出版）一周论文导读
2023/4/16 20:16:53 科学网
编译 | 李言
Science,14 APR 2023, Volume 380 Issue 6641
《科学》2022年4月14日，第380卷，6641期
天文学Astronomy
Direct imaging and astrometric detection of a gas giant planet orbiting an accelerating star
一颗环绕加速恒星运行的气态巨行星的直接成像和天体测量探测
▲ 作者：THAYNE CURRIE, G. MIREK BRANDT, TIMOTHY D. BRANDT et al.
▲ 链接：
https://www.science.org/doi/10.1126/science.abo6192
▲ 摘要：
利用盖亚和希普帕科斯卫星的天体测量数据，我们在附近的恒星HIP 99770周围发现了一颗气态巨行星的动力学证据。我们使用斯巴鲁日冕仪极端自适应光学仪器进行直接成像，确认了这颗行星的探测。
这颗名为HIP 99770 b的行星绕其主恒星运行17个天文单位，接收到的光量与到达木星的光量相似。它的动力质量是木星质量的13.9到16.1倍。行星与恒星的质量比[(7 to 8) × 10?3]与其他直接成像的行星相似。这颗行星的大气光谱表明，它与之前拍摄的HR 8799周围的系外行星类似，是一颗更古老的行星。
▲ Abstract：
Using astrometry from the Gaia and Hipparcos spacecraft, we identified dynamical evidence for a gas giant planet around the nearby star HIP 99770. We confirmed the detection of this planet with direct imaging using the Subaru Coronagraphic Extreme Adaptive Optics instrument. The planet, HIP 99770 b, orbits 17 astronomical units from its host star, receiving an amount of light similar to that reaching Jupiter. Its dynamical mass is 13.9 to 16.1 Jupiter masses. The planet-to-star mass ratio [(7 to 8) × 10?3] is similar to that of other directly imaged planets. The planet’s atmospheric spectrum indicates an older, less cloudy analog of the previously imaged exoplanets around HR 8799.
材料科学Material Science
Mechanical nonreciprocity in a uniform composite material
均匀复合材料的机械非互易性
▲ 作者：XIANG WANG, ZHIHAO LI, SHUXU WANG et al.
▲ 链接：
https://www.science.org/doi/10.1126/science.adf1206
▲ 摘要：
在此，我们报告了一种均匀的复合水凝胶，由于嵌入纳米填料的方向性屈曲，显示出实质性的机械非互易性。这种材料在单向剪切时的弹性模量比相反方向剪切时高60倍以上。因此，它可以将对称振动转换为非对称振动，适用于质量传输和能量收集。
此外，它在局部相互作用时表现出不对称的变形，这可以诱发各种物体的定向运动，从宏观物体到小型生物。这种材料可以促进非互易系统的发展，如能量转换和生物操纵等实际应用。
▲ Abstract：
We report a uniform composite hydrogel that displays substantial mechanical nonreciprocity, owing to direction-dependent buckling of embedded nanofillers. This material exhibits an elastic modulus more than 60 times higher when sheared in one direction compared with the opposite direction. Consequently, it can transform symmetric vibrations into asymmetric ones that are applicable for mass transport and energy harvest. Furthermore, it exhibits an asymmetric deformation when subjected to local interactions, which can induce directional motion of various objects, including macroscopic objects and even small living creatures. This material could promote the development of nonreciprocal systems for practical applications such as energy conversion and biological manipulation.
地球科学Earth Science
Oldest evidence of abundant C4 grasses and habitat heterogeneity in eastern Africa
非洲东部丰富的C4植物和生境异质性的最早证据
▲ 作者：DANIEL J. PEPPE, SUSANNE M. COTE et al.
▲ 链接：
https://www.science.org/doi/10.1126/science.abq2834
▲ 摘要：
非洲标志性的C4草原生态系统的组合对于包括古人类在内的许多哺乳动物谱系的进化解释至关重要。C4植物被认为是在1000万年前之后才在非洲成为生态上的主导。然而，1千万年以上的古植物学记录很少，这限制了对C4生物量扩张时间和性质的评估。这项研究使用多代理设计来记录横跨东非的9个早中新世哺乳动物遗址的植被结构。
结果表明，在2100万年至1600万年之间，C4植物在部分地区非常丰富，形成了从森林到森林草原的异质性生境。这些数据将非洲和全球C4植物为主栖息地的最古老证据往前推了1000多万年，并以此可以对哺乳动物进化的古生态学解释进行修正。
▲ Abstract：
The assembly of Africa’s iconic C4 grassland ecosystems is central to evolutionary interpretations of many mammal lineages, including hominins. C4 grasses are thought to have become ecologically dominant in Africa only after 10 million years ago (Ma). However, paleobotanical records older than 10 Ma are sparse, limiting assessment of the timing and nature of C4 biomass expansion. This study uses a multiproxy design to document vegetation structure from nine Early Miocene mammal site complexes across eastern Africa. Results demonstrate that between ~21 and 16 Ma, C4 grasses were locally abundant, contributing to heterogeneous habitats ranging from forests to wooded grasslands. These data push back the oldest evidence of C4 grass–dominated habitats in Africa—and globally—by more than 10 million years, calling for revised paleoecological interpretations of mammalian evolution.
A global transition to flash droughts under climate change
气候变化的情况下，全球向突发性干旱过渡
▲ 作者：XING YUAN, YUMIAO WANG, PENG JI et al.
▲ 链接：
https://www.science.org/doi/10.1126/science.abn6301
▲ 摘要：
突发性干旱在世界范围内频繁发生且迅速，对全球干旱监测和预测能力构成挑战。然而，对于突发性干旱是否已成为新常态，目前尚无共识，因为慢性干旱也可能增加。在这项研究中，我们表明，在过去64年里，政府间气候变化专门委员会关于极端事件的特别报告所确定的全球74%的地区出现了向更多突发性干旱的过渡。
这种转变与人为气候变化引起的蒸散发和降水亏缺异常的放大有关。在未来，预计更多陆地地区会出现这种转变，同时，在更高排放的情况下，增长幅度会更大。这些发现强调了在气候更温暖的未来适应更快发生的干旱的紧迫性。
▲ Abstract：
Flash droughts have occurred frequently worldwide, with a rapid onset that challenges drought monitoring and forecasting capabilities. However, there is no consensus on whether flash droughts have become the new normal because slow droughts may also increase. In this study, we show that drought intensification rates have sped up over subseasonal time scales and that there has been a transition toward more flash droughts over 74% of the global regions identified by the Intergovernmental Panel on Climate Change Special Report on Extreme Events during the past 64 years. The transition is associated with amplified anomalies of evapotranspiration and precipitation deficit caused by anthropogenic climate change. In the future, the transition is projected to expand to most land areas, with larger increases under higher-emission scenarios. These findings underscore the urgency for adapting to faster-onset droughts in a warmer future.
生物学Biology
Immobility-associated thromboprotection is conserved across mammalian species from bear to human
从熊到人的哺乳动物中存在静止相关的血栓保护
▲作者：MANUELA THIENEL, JOHANNES B. M?LLER-REIF et al.
▲ 链接：
https://www.science.org/doi/10.1126/science.abo5044
▲ 摘要：
静脉血栓栓塞(VTE)包括深静脉血栓形成和肺栓塞，是该病发病和死亡的主要原因。与短期静止相关的疾病是VTE发展的主要危险因素。矛盾的是，长期静止的自由放养的冬眠棕熊和瘫痪的脊髓损伤(SCI)患者可以免受VTE的影响。
我们通过跨物种的研究方式确定了与静止相关的VTE保护机制。基于质谱的蛋白质组学揭示了冬眠棕熊血小板中的抗血栓特征，其中热休克蛋白47(HSP47)是减少最多的蛋白质。
HSP47下调或减弱了免疫细胞的激活和中性粒细胞细胞外陷阱的形成，有助于棕熊、SCI患者和小鼠的血栓保护。这种跨物种保守的血小板特征可能会导致抗血栓治疗和预后标志物超过与静止相关的VTE。
▲ Abstract：
Venous thromboembolism (VTE) comprising deep venous thrombosis and pulmonary embolism is a major cause of morbidity and mortality. Short-term immobility-related conditions are a major risk factor for the development of VTE. Paradoxically, long-term immobilized free-ranging hibernating brown bears and paralyzed spinal cord injury (SCI) patients are protected from VTE. We aimed to identify mechanisms of immobility-associated VTE protection in a cross-species approach. Mass spectrometry–based proteomics revealed an antithrombotic signature in platelets of hibernating brown bears with heat shock protein 47 (HSP47) as the most substantially reduced protein. HSP47 down-regulation or ablation attenuated immune cell activation and neutrophil extracellular trap formation, contributing to thromboprotection in bears, SCI patients, and mice. This cross-species conserved platelet signature may give rise to antithrombotic therapeutics and prognostic markers beyond immobility-associated VTE.
The evolution of hominoid locomotor versatility: Evidence from Moroto, a 21 Ma site in Uganda
古人类运动功能性的进化：来自乌干达Moroto遗址2100万年前的证据
▲ 作者：LAURA M. MACLATCHY, SUSANNE M. COTE et al.
▲ 链接：
https://www.science.org/doi/10.1126/science.abq2835
▲ 摘要：
现存的类人动物以直立的躯干和灵活的动作著称。有理论认为，这些特征是为了吃森林末端树枝上的果实而进化出来的。为了研究古人类适应起源的进化背景，我们结合乌干达Moroto II遗址的古人类化石分析了多个古环境指标。基于已确认的2100万年的年份，这些数据表明非洲存在已知最早具有C4型植物的季节性干燥林地。
我们证明了吃叶子的古猿Morotopithecus会食用水分胁迫的植物，该遗址的后颅化石表明了类人猿的运动适应能力。这些发现表明，古人类运动功能性的起源与在多元且开阔的林地而不是森林中觅食树叶有关。
▲ Abstract：
Living hominoids are distinguished by upright torsos and versatile locomotion. It is hypothesized that these features evolved for feeding on fruit from terminal branches in forests. To investigate the evolutionary context of hominoid adaptive origins, we analyzed multiple paleoenvironmental proxies in conjunction with hominoid fossils from the Moroto II site in Uganda. The data indicate seasonally dry woodlands with the earliest evidence of abundant C4 grasses in Africa based on a confirmed age of 21 million years ago (Ma). We demonstrate that the leaf-eating hominoid Morotopithecus consumed water-stressed vegetation, and postcrania from the site indicate ape-like locomotor adaptations. These findings suggest that the origin of hominoid locomotor versatility is associated with foraging on leaves in heterogeneous, open woodlands rather than forests.
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