《科學》（20190712出版）一周論文導讀
Science, 12 JULY 2019, VOL 365, ISSUE 6449
《科學》2019年7月12日，第365卷第6449期
工程學Engineering
Strain-programmable fiber-based artificial muscle
基於應力可編程纖維的人造肌肉
作者：Mehmet Kanik、Sirma Orguc、Georgios Varnavides，et al
鏈接：
https://science.sciencemag.org/content/365/6449/145
摘要：
人造肌肉可以加速機器人、觸覺和假肢的發展。儘管聚合物致動器的發展帶來了前所未有的機遇，但大規模生產這些可調尺寸的器件仍然是一個挑戰。
這裡，研究人員研製了一種通過可縮放迭代繪圖法進行創製的雙面聚合物纖維，所產生的人造肌肉可通過加熱而激活，它能提起的重量是其自身重量的650倍以上，所承受的張力超過1000%，並能在數千次以上的使用周期後仍然保持回彈能力。
研究人員表示，這些纖維致動器的可伸性，以及強度和響應能力，可能會將其影響從工程領域擴展到生物醫學應用領域。
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
新型殼驅動人造肌肉
作者：Jiuke Mu、M?nica Jung de Andrade、Ray H. Baughman，et al
鏈接：
https://science.sciencemag.org/content/365/6449/150
摘要：
儘管填充碳納米管紗線以扭轉和拉伸人工肌肉，獲得創紀錄的成果，但它們價格昂貴，而且只有部分肌肉被有效驅動。
本研究設計出一系列 「殼層驅動人工肌肉材料」，即將多種活性聚合物材料作為殼層塗覆到包括碳納米紗線，以及價格低廉的尼龍纖維、蠶絲和竹纖維上，該新型結構的人工肌肉材料表現出更高的機械能輸出以及能量密度。
研究人員表示，將輸入的外部能量集中作用在殼層區域能較大幅度的提高機械能的轉換速度以及效率。
特別是，當通過電化學的方式驅動以碳納米管纖維為殼尼龍紗線芯的殼驅動人工肌肉時，其輸出的平均收縮機械能是人體肌肉的40倍，是先前電化學驅動人工肌肉的9倍。
而且，這種使用價格低廉的新型人造肌肉製備技術，對於如機器人以及自適體織物等智能結構材料的開發領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
納米複合纖維製造高能微引擎
作者：Jinkai Yuan、Wilfrid Neri、Philippe Poulin，et al
鏈接：
https://science.sciencemag.org/content/365/6449/155
摘要：
經典的旋轉發動機功能強大，應用廣泛，但設計複雜，難以小型化。長期以來，製造高速、高能、簡單、堅固的微型發動機一直是個挑戰。
這裡，研究人員製造了一種高能微引擎，它由具形狀記憶的納米複合纖維組成。這些纖維被編織後能進行儲能，後者能在溫度小幅改變後按需釋放。
此外，研究人員表示，觸發纖維旋轉的溫度可以調節。與傳統發動機相比，這種溫度記憶效應提供了一個額外的優勢，它允許調節操作溫度和存儲能量的逐步釋放。
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
微生物定向食品對動物和營養不良兒童的影響
作者：Jeanette L. Gehrig、Siddarth Venkatesh、Hao-Wei Chang，et al
鏈接：
https://science.sciencemag.org/content/365/6449/eaau4732
摘要：
檢查受損的腸道微生物群落對兒童營養不良的影響，研究人員結合血漿樣本的代謝組學和蛋白質組學分析，以及糞便樣本宏基因組分析，描述了孟加拉嚴重急性營養不良（SAM）兒童接受治療後生理狀態的轉變。
在接受標準治療後，兒童由SAM變為中度急性營養不良（MAM）並伴隨持續性菌群不成熟。
以SAM和MAM患兒菌群中被忽視的斷奶期細菌類群為目標，研究人員分析了微生物定向互補食品（MDCF）的宿主和微生物效應。
通過隨機、雙盲對照餵養研究，科學家發現了一種MDCF，它可以改變目標細菌的丰度，增加MAM患兒的生長、骨形成、神經發育和免疫功能等。
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
健康和受損人體腸道微生物群發育共變單元
作者：Arjun S. Raman、Jeanette L. Gehrig、Siddarth Venkatesh，et al
鏈接：
https://science.sciencemag.org/content/365/6449/eaau4735
摘要：
由於人類腸道微生物群各組成部分之間可能存在相互作用，描述其組織結構是一項艱巨的挑戰。研究人員使用一種最初用於金融市場的統計方法，測量了孟加拉國1至60個月健康嬰幼兒微生物群落。
研究結果揭示了一個由15個共變細菌分類群組成的「生態群」，它簡明地描述了來自這裡和其他低收入國家的健康兒童體內微生物群的發育情況，並提供了一種監測營養不良兒童接受食品治療後修復情況的手段。
研究人員在動物模型上再現了這種生態群體種群動態特徵。這些動物從純母乳餵養過渡到完全斷奶的狀態時，食用具有代表性的孟加拉國飲食。
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.
古人類/古動物
Paleoanthropology/ paleozoology
Late Pleistocene exploration and settlement of the Americas by modern humans
晚更新世人類對美洲的探索和定居
作者：Michael R. Waters
鏈接：
https://science.sciencemag.org/content/365/6449/eaat5447
摘要：
北美和南美是現代人類在更新世末期探索和定居的最後兩塊大陸。
來自當代種群和古代個體的遺傳數據顯示，第一批美國人起源於亞洲，在大約1.75萬年至1. 46萬年前，在幾次種群分裂之後，他們向加拿大的大陸冰原以南移動。
考古證據表明，大約1.55萬~1.4萬年前，在北美和南美的多個地方，地理上分散的種群成功地利用雙面石器、石刀和骨器等技術生活。區域考古複合體在北美至少出現於1.3萬年前，在南美出現於1.29萬年前。
目前的遺傳和考古數據不支持人們更早佔領美洲。
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
鏈接：
https://science.sciencemag.org/content/365/6449/173
摘要：
大約在10500年前，家牛被首次馴化，其前身是現已滅絕的曾棲息在美索不達米亞北部的歐亞野牛。
本研究通過將該野牛的基因組與67個遠古家牛標本（它們來自近東的考古遺址）的基因組進行比較，結果發現，首個馴化家牛群有著不同的野牛起源，多個野牛株促成了馴化家牛不斷增長的群體數。
在大約4000年前，該地區的家牛種群接受了來自印度河流域的瘤牛遺傳物質的快速廣泛的流入，這些遺傳物質主要來自雄牛。
這一基因組轉變發生於一個長達多個世紀的乾旱期，研究人員表示，對乾旱適應的瘤牛被接納至馴化的牛群，以作為讓牛群在乾旱情況下也能興旺發展的一種方式。
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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