翻译 | 唐一尘
Science, 12 JULY 2019, VOL 365, ISSUE 6449
《科学》 2019年7月12日，第365卷第6449期
工程学 Engineering
Strain-programmable fiber-based artificial muscle
基于应力可编程纤维的人造肌肉
作者： Mehmet Kanik、Sirma Orguc、Georgios Varnavides，et al
链接：
https://science.sciencemag.org/content/365/6449/145
摘要：
人造肌肉可以加速机器人、触觉和假肢的发展。尽管聚合物致动器的发展带来了前所未有的机遇，但大规模生产这些可调尺寸的器件仍然是一个挑战。
这里，研究人员研制了一种通过可缩放迭代绘图法进行创制的双面聚合物纤维，所产生的人造肌肉可通过加热而激活，它能提起的重量是其自身重量的650倍以上，所承受的张力超过1000%，并能在数千次以上的使用周期后仍然保持回弹能力。
研究人员表示，这些纤维致动器的可伸性，以及强度和响应能力，可能会将其影响从工程领域扩展到生物医学应用领域。
Abstract
Artificial muscles may accelerate the development of robotics, haptics, and prosthetics. Although advances in polymer-based actuators have delivered unprecedented strengths, producing these devices at scale with tunable dimensions remains a challenge. We applied a high-through put iterative fiber-drawing technique to create strain-programmable artificial muscles with dimensions spanning three orders of magnitude. These fiber-based actuators are thermally and optically controllable, can lift more than 650 times their own weight, and withstand strains of >1000%. Integration of conductive nanowire meshes within these fiber-based muscles offers piezoresistive strain feedback and demonstrates long-term resilience across >105 deformation cycles. The scalable dimensions of these fiber-based actuators and their strength and responsiveness may extend their impact from engineering fields to biomedical applications.
Sheath-run artificial muscles
新型壳驱动人造肌肉
作者：Jiuke Mu、Mônica Jung de Andrade、Ray H. Baughman，et al
链接：
https://science.sciencemag.org/content/365/6449/150
摘要：
尽管填充碳纳米管纱线以扭转和拉伸人工肌肉，获得创纪录的成果，但它们价格昂贵，而且只有部分肌肉被有效驱动。
本研究设计出一系列 “壳层驱动人工肌肉材料”，即将多种活性聚合物材料作为壳层涂覆到包括碳纳米纱线，以及价格低廉的尼龙纤维、蚕丝和竹纤维上，该新型结构的人工肌肉材料表现出更高的机械能输出以及能量密度。
研究人员表示，将输入的外部能量集中作用在壳层区域能较大幅度的提高机械能的转换速度以及效率。
特别是，当通过电化学的方式驱动以碳纳米管纤维为壳尼龙纱线芯的壳驱动人工肌肉时，其输出的平均收缩机械能是人体肌肉的40倍，是先前电化学驱动人工肌肉的9倍。
而且，这种使用价格低廉的新型人造肌肉制备技术，对于如机器人以及自适体织物等智能结构材料的开发领域具有很大的吸引力。
Abstract
Although guest-filled carbon nanotube yarns provide record performanceas torsional and tensile artificial muscles, they are expensive, and only part of the muscle effectively contributes to actuation. We describe a muscle type that provides higher performance, in which the guest that drives actuation is as heath on a twisted or coiled core that can be an inexpensive yarn. This change from guest-filled to sheath-run artificial muscles increases the maximum work capacity by factors of 1.70 to 2.15 for tensile muscles driven electro thermallyor by vapor absorption. A sheath-run electrochemical muscle generates 1.98 watts per gram of average contractile power— 40 times that for human muscle and 9.0 times that of the highest power alternative electrochemical muscle. Theory predicts the observed performance advantages of sheath-run muscles.
Shape memory nanocomposite fibers for untethered high-energy microengines
纳米复合纤维制造高能微引擎
作者：Jinkai Yuan、Wilfrid Neri、Philippe Poulin，et al
链接：
https://science.sciencemag.org/content/365/6449/155
摘要：
经典的旋转发动机功能强大，应用广泛，但设计复杂，难以小型化。长期以来，制造高速、高能、简单、坚固的微型发动机一直是个挑战。
这里，研究人员制造了一种高能微引擎，它由具形状记忆的纳米复合纤维组成。这些纤维被编织后能进行储能，后者能在温度小幅改变后按需释放。
此外，研究人员表示，触发纤维旋转的温度可以调节。与传统发动机相比，这种温度记忆效应提供了一个额外的优势，它允许调节操作温度和存储能量的逐步释放。
Abstract
Classic rotating engines are powerful and broadly used but are of complex design and difficult to miniaturize. It has long remained challenging to make large-stroke, high-speed, high-energy microengines that are simple and robust. We show that torsionally stiffened shape memory nanocomposite fibers can be transformed upon insertion of twist to store and provide fast and high-energy rotations. The twisted shape memory nanocomposite fibers combine high torque with large angles of rotation, delivering a gravimetric work capacity that is 60 times higher than that of natural skeletal muscles. The temperature that triggers fiber rotation can be tuned. This temperature memory effect provides an additional advantage over conventional engines by allowing for the tunability of the operation temperature and a stepwise release of stored energy.
微生物 Microbiology
Effects of microbiota-directed foods in gnotobiotic animals and undernourished children
微生物定向食品对动物和营养不良儿童的影响
作者：Jeanette L. Gehrig、Siddarth Venkatesh、Hao-Wei Chang，et al
链接：
https://science.sciencemag.org/content/365/6449/eaau4732
摘要：
检查受损的肠道微生物群落对儿童营养不良的影响，研究人员结合血浆样本的代谢组学和蛋白质组学分析，以及粪便样本宏基因组分析，描述了孟加拉严重急性营养不良（SAM）儿童接受治疗后生理状态的转变。
在接受标准治疗后，儿童由SAM变为中度急性营养不良（MAM）并伴随持续性菌群不成熟。
以SAM和MAM患儿菌群中被忽视的断奶期细菌类群为目标，研究人员分析了微生物定向互补食品（MDCF）的宿主和微生物效应。
通过随机、双盲对照喂养研究，科学家发现了一种MDCF，它可以改变目标细菌的丰度，增加MAM患儿的生长、骨形成、神经发育和免疫功能等。
Abstract
To examine the contributions of impaired gut microbial community development to childhood undernutrition, we combined metabolomic and proteomic analyses of plasma samples with metagenomic analyses of fecal samples to characterize the biological state of Bangladeshi children with severe acute malnutrition (SAM) as they transitioned, after standard treatment, to moderate acute malnutrition (MAM) with persistent microbiota immaturity. Host and microbial effects of microbiota-directed complementary food (MDCF) prototypes targeting weaning-phase bacterial taxa underrepresented in SAM and MAM microbiota were characterized in gnotobiotic mice and gnotobiotic pigletscolonized with age- and growth-discriminatory bacteria. A randomized, double-blind controlled feeding study identified a lead MDCF that changes the abundances of targeted bacteria and increases plasma biomarkers and mediators of growth, bone formation, neuro development, and immune function in children with MAM.
A sparse covarying unit that describes healthy and impaired human gut microbiota development
健康和受损人体肠道微生物群发育共变单元
作者：Arjun S. Raman、Jeanette L. Gehrig、Siddarth Venkatesh，et al
链接：
https://science.sciencemag.org/content/365/6449/eaau4735
摘要：
由于人类肠道微生物群各组成部分之间可能存在相互作用，描述其组织结构是一项艰巨的挑战。研究人员使用一种最初用于金融市场的统计方法，测量了孟加拉国1至60个月健康婴幼儿微生物群落。
研究结果揭示了一个由15个共变细菌分类群组成的“生态群”，它简明地描述了来自这里和其他低收入国家的健康儿童体内微生物群的发育情况，并提供了一种监测营养不良儿童接受食品治疗后修复情况的手段。
研究人员在动物模型上再现了这种生态群体种群动态特征。这些动物从纯母乳喂养过渡到完全断奶的状态时，食用具有代表性的孟加拉国饮食。
Abstract
Characterizing the organization of the human gut microbiota is a formidable challenge given the number of possible interactions between its components. Using a statistical approach initially applied to financial markets, we measured temporally conserved covariance among bacterial taxa in the microbiota of healthy members of a Bangladeshi birth cohort sampled from 1to 60 months of age.
The results revealed an “ecogroup” of 15 covarying bacterial taxa that provide a concise description of microbiota development in healthy children from this and other low-income countries, and a means for monitoring community repair in undernourished children treated with therapeutic foods. Features of ecogroup population dynamics were recapitulated in gnotobiotic piglets as they transitioned from exclusive milk feeding to a fully weaned state consuming are presentative Bangladeshi diet.
古人类/古动物
Paleoanthropology/ paleozoology
Late Pleistocene exploration and settlement of the Americas by modern humans
晚更新世人类对美洲的探索和定居
作者：Michael R. Waters
链接：
https://science.sciencemag.org/content/365/6449/eaat5447
摘要：
北美和南美是现代人类在更新世末期探索和定居的最后两块大陆。
来自当代种群和古代个体的遗传数据显示，第一批美国人起源于亚洲，在大约1.75万年至1. 46万年前，在几次种群分裂之后，他们向加拿大的大陆冰原以南移动。
考古证据表明，大约1.55万~1.4万年前，在北美和南美的多个地方，地理上分散的种群成功地利用双面石器、石刀和骨器等技术生活。区域考古复合体在北美至少出现于1.3万年前，在南美出现于1.29万年前。
目前的遗传和考古数据不支持人们更早占领美洲。
Abstract
North and South America were the last continents to be explored and settled by modern humans at the end of the Pleistocene. Genetic data, derived from contemporary populations and ancient individuals, show that the first Americans originated from Asia and after several population splits moved south of the continental ice sheets that covered Canada sometime between ~17.5 and~14.6 thousand years (ka) ago. Archaeological evidence shows that geographically dispersed populations lived successfully, using biface, blade,and osseous technologies, in multiple places in North and South America between~15.5 and ~14 ka ago. Regional archaeological complexes emerged by at least ~13ka ago in North America and ~12.9 ka ago in South America. Current genetic and archaeological data do not support an earlier (pre–17.5 ka ago) occupation of the Americas.
Ancient cattle genomics, origins, and rapid turnover in the Fertile Crescent
古老牛的基因、起源和流通
作者：Marta Pereira Verdugo、Victoria E. Mullin、AmelieScheu、Valeria Mattiangeli，et al
链接：
https://science.sciencemag.org/content/365/6449/173
摘要：
大约在10500年前，家牛被首次驯化，其前身是现已灭绝的曾栖息在美索不达米亚北部的欧亚野牛。
本研究通过将该野牛的基因组与67个远古家牛标本（它们来自近东的考古遗址）的基因组进行比较，结果发现，首个驯化家牛群有着不同的野牛起源，多个野牛株促成了驯化家牛不断增长的群体数。
在大约4000年前，该地区的家牛种群接受了来自印度河流域的瘤牛遗传物质的快速广泛的流入，这些遗传物质主要来自雄牛。
这一基因组转变发生于一个长达多个世纪的干旱期，研究人员表示，对干旱适应的瘤牛被接纳至驯化的牛群，以作为让牛群在干旱情况下也能兴旺发展的一种方式。
Abstract
Genome-wide analysis of 67 ancient Near Eastern cattle, Bos taurus, remains reveals regional variation that has since been obscured by admixture in modern populations. Comparisons of genomes of early domestic cattle to their aurochs progenitors identify diverse origins with separate introgressions of wild stock. A later region-wide Bronze Age shift indicates rapid and widespread introgression of zebu, Bos indicus, fromthe Indus Valley. This process was likely stimulated at the onset of the current geological age, ~4.2 thousand years ago, by a widespread multicentury drought. In contrast to genome-wide admixture, mitochondrial DNA stasis supports that this introgression was male-driven, suggesting that selection of arid-adapted zebu bulls enhanced herd survival. This human-mediated migration of zebu-derived genetics has continued through millennia, altering tropical herding on each continent.
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