来源:科学网 发布时间:2018/11/23 16:08:09
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《自然》论文导读:2018年11月22日
 
航空学Aviation
 
Flight of an aeroplane with solid-state propulsion
 
采用固体推进系统的飞机
 
▲ 作者:Haofeng Xu、Yiou He、Kieran L. Strobel、Christopher K. Gilmore、Steven R. H. Barrett,et al 
 
▲ 链接:
 
https://www.nature.com/articles/s41586-018-0707-9
 
▲ 摘要:
 
本论文描述了一架采用固体推进系统的小型飞机的飞行,这使得制造更安静、机械更简单且不产生燃烧排放的飞机成为可能。
 
一直以来,飞行器的动力来自带有活动部件的发动机,例如推进器或涡轮机,并且通常依靠化石燃料燃烧。有人提出采用电空气动力学装置——通过电力加速流体中的离子以形成离子风产生推力,可作为推进飞行器的一种替代方法。
 
研究人员设计了一架带有电空气动力推进系统的小型固定翼飞机,并进行了试飞。该飞机重2.45千克,翼展5米,依靠定制系统提供动力。定制动力系统包含一个电池组和高压电源转换器,输出功率约500瓦。
 
在10次试飞中,飞机在室内空间成功飞行了60米,平均飞行高度为0.47米。尽管整体效率较低,但是其推功比与传统推进系统(如喷气发动机)相当。
 
这种特殊的飞机设计优先考虑的是小机型而不是高效率,但未来的设计可以提高效率。
 
▲ Abstract
 
Since the first aeroplane flight more than 100 years ago, aeroplanes have been propelled using moving surfaces such as propellers and turbines. Most have been powered by fossil-fuel combustion. Electroaerodynamics, in which electrical forcesaccelerate ions in a fluid, has been proposed as an alternative method of propellingaeroplanes—without moving parts, nearly silently and without combustionemissions. However, no aeroplane with such a solid-state propulsion system has yet flown. Here we demonstrate that a solid-state propulsion system can sustain powered flight, by designing and flying an electroaerodynamically propelledheavier-than-air aeroplane. We flew a fixed-wing aeroplane with a five-metrewingspan ten times and showed that it achieved steady-level flight. All batteries and power systems, including a specifically developed ultralight high-voltage (40-kilovolt) power converter, were carriedon-board. We show that conventionally accepted limitations in thrust-to-power ratio and thrust density, which were previously thought to make electroaerodynamics unfeasible as a method ofaeroplane propulsion, are surmountable. We provide a proof of concept forelectroaerodynamic aeroplane propulsion, opening up possibilities for aircraft and aerodynamic devices that are quieter, mechanically simpler and do not emit combustion emissions.
 
地球科学Geoscience
 
Twentieth-century contribution to sea-level rise from uncharted glaciers
 
20世纪海平面上升“贡献者”包括未知冰川
 
▲ 作者:David Parkes、Ben Marzeion 
 
▲ 链接:
 
https://www.nature.com/articles/s41586-018-0687-9
 
▲ 摘要:
 
20世纪全球平均海平面上升(GMSLR)主要是由冰川和冰盖的质量损失、海水的热膨胀和陆地蓄水能力的变化引起的。
 
然而,无论是基于观测还是气候模型结果,这些贡献的估计总和往往低于观测到的GMSLR。
 
这里,研究人员发现从1901年到2015年,错漏和消失的冰川产生了大约16.7到48.0毫米的海平面当量(SLE)。
 
其中,缺失的冰川是那些人们期望今天仍存在的小冰川,但由于区域分析和理论比例关系,这些冰川并没有反映在冰川数据库中,而它们大约贡献了12.3到42.7毫米的历史SLE。
 
此外,消失的冰川(1901年存在,但到2015年已经融化的冰川,因此也不在数据库单中)估计贡献了4.4到5.3毫米。
 
▲ Abstract
 
Global-mean sea-level rise (GMSLR) during the twentieth century was primarily caused by glacier and ice-sheet mass loss, thermal expansion of ocean water and changes in terrestrial water storage. Whether based on observations or results of climate models, however, the sum of estimates of each of these contributions tends to fall short of the observed GMSLR. Current estimates of the glacier contribution to GMSLR rely on the analysis of glacier inventory data, which are known to undersample the smallest glacier size classes. Here we show that from 1901 to 2015, missing and disappeared glaciers produced a sea-level equivalent (SLE) of approximately16.7 to 48.0 millimetres. Missing glaciers are those small glaciers thatwe expect to exist today, owing to regional analyses and theoretical scaling relationships, but that are not represented in the inventories. These glaciers contributed approximately 12.3 to 42.7 millimetres to the historical SLE.Additionally, disappeared glaciers (those that existed in 1901 but had melted away by 2015, and that therefore cannot be included in modern global glacier inventories) made an estimated contribution of between 4.4 and 5.3 millimetres. Failure to consider these uncharted glaciers may be an important cause of difficulties in closing the GMSLR budget during the twentieth century: their contribution is on average between 0.17 and 0.53 millimetres of SLE per year, compared to a budget discrepancy of about 0.5millimetres of GMSLR per year between 1901 and 1990. Although the uncharted glaciers will have a minimal role in sea-level rise in the future, and are less important after 1990, these findings imply that undiscovered physical processes are not required to close the historical sea-level budget.
 
生物学Biology
 
Improved reference genome of Aedes aegypti informs arbovirus vector control
 
改良埃及伊蚊基因组助力虫媒控制研究
 
▲ 作者:Benjamin J. Matthews、Olga Dudchenko、Leslie B. Vosshall,et al
 
▲ 链接:
 
https://www.nature.com/articles/s41586-018-0692-z
 
▲ 摘要:
 
埃及伊蚊每年感染4亿多人,能传播登革热病毒、黄热病病毒、寨卡病毒和基孔肯雅热病毒等多种病毒。
 
由于缺乏高质量的基因组数据,人们在了解蚊子的生物学特性和开发对抗工具方面的进展放缓。
 
此次,研究人员将各种技术结合起来,生产出显著改进的、完全重新注释的AaegL5基因组集合,并演示了它如何加速了蚊子研究。
 
研究人员锁定了物理和细胞遗传学图谱,将已知的引导蚊子到人类宿主和产卵位点的化学感受器数量增加了一倍,进一步了解了决定蚊子性别的M位点的大小和组成,并揭示了谷胱甘肽s—转移酶基因变异,而谷胱甘肽s—转移酶基因对杀虫剂抗性至关重要。
 
研究人员还绘制出登革热病虫媒能力和杀虫剂抗性的新候选基因。AaegL5将促进新的生物学见解和干预策略,以对抗这种致命的疾病载体。
 
▲ Abstract
 
Female Aedesaegypti mosquitoes infect more than 400 million people each yearwith dangerous viral pathogens including dengue, yellow fever, Zika andchikungunya. Progress in understanding the biology of mosquitoes and developingthe tools to fight them has been slowed by the lack of a high-quality genome assembly. Here we combine diverse technologies to produce the markedly improved, fully re-annotated AaegL5 genome assembly, and demonstrate how itaccelerates mosquito science. We anchored physical and cytogenetic maps, doubled the number of known chemosensory ionotropic receptors that guide mosquitoes to human hosts and egg-laying sites, provided further insight into the size and composition of the sex-determining M locus, and revealed copy-number variationamong glutathione S-transferase genes that are important for insecticide resistance. Using high-resolution quantitative trait locus and population genomic analyses, we mapped new candidates for dengue vector competence and insecticide resistance. AaegL5 will catalyse new biological insights and intervention strategies to fight this deadly disease vector.
 
TDP-43 and RNA form amyloid-like myo-granules in regenerating muscle
 
TDP-43和RNA在肌肉再生过程中形成淀粉样肌粒
 
▲ 作者:Thomas O. Vogler、Joshua R. Wheeler、Eric D. Nguyen、Kyla A. Britson、Aaron M. Johnson、Bradley B. Olwin、Roy Parker,et al
 
▲ 链接:
 
https://www.nature.com/articles/s41586-018-0665-2
 
▲ 摘要:
 
神经肌肉疾病(包括肌萎缩性脊髓侧索硬化症和包涵体肌病)的主要组织病理学特征是RNA结合蛋白TDP-43的细胞质聚集。
 
虽然TARDBP(编码TDP-43的基因)的罕见突变通常会导致蛋白质的错误折叠,但大多数患者并没有出现TARDBP突变。
 
但野生型TDP-43在大多数患者中以一种未知的机制出现。在这里,研究人员证明TDP-43是正常骨骼肌形成的必要蛋白,在小鼠和人类骨骼肌再生过程中,它能形成肌粒。
 
肌粒与编码肌节蛋白的mRNA结合,并随着肌纤维成熟而清除。虽然肌粒出现在正常的骨骼肌再生过程中,但肌粒可以在体外播散TDP-43淀粉样纤维,并在包涵体肌病的小鼠模型中增加。
 
因此,肌粒聚合增加或清除减少可能是神经肌肉疾病中常见的TDP-43聚集物的来源。
 
▲ Abstract
 
A dominant histopathological feature in neuromuscular diseases, including amyotrophic lateral sclerosis and inclusion body myopathy, is cytoplasmic aggregation of the RNA-binding protein TDP-43. Although rare mutations in TARDBP—the gene that encodes TDP-43—that lead to protein misfolding often cause protein aggregation, most patients do not have any mutations in TARDBP. Therefore, aggregates of wild-type TDP-43 arise in most patients by an unknown mechanism. Here we show that TDP-43 is an essential protein for normal skeletal muscle formation that unexpectedly forms cytoplasmic, amyloid-like oligomeric assemblies, which we call myo-granules, during regeneration of skeletal muscle in mice and humans. Myo-granules bind to mRNAs that encode sarcomeric proteins and are cleared as myofibres mature. Although myo-granules occur during normal skeletal-muscle regeneration, myo-granules can seed TDP-43 amyloid fibrils in vitro and are increased in a mouse model of inclusion body myopathy. Therefore, increased assembly or decreased clearance of functionally normal myo-granules could be the source of cytoplasmic TDP-43 aggregates that commonly occur in neuromuscular disease.
 
Mannose impairs tumour growth and enhances chemotherapy
 
甘露糖能损害肿瘤生长增强化疗效果
 
▲ 作者:Pablo Sierra Gonzalez、James O’Prey、Simone Cardaci、Valentin J. A. Barthet、Kevin M. Ryan,et al 
 
▲ 链接:
 
https://www.nature.com/articles/s41586-018-0729-3
 
▲ 摘要:
 
许多肿瘤会经历代谢变化,表现出葡萄糖摄取增加,由此引出了一个问题:服用不同类型的糖能否影响肿瘤生长。
 
研究人员通过饲管(一周三次)和饮水(持续性地)让肿瘤小鼠服用甘露糖。结果显示这种疗法耐受良好,而且无论单独施用还是结合阿霉素施用,似乎都减缓了肿瘤生长。
 
细胞对甘露糖的敏感性与较低水平的磷酸甘露糖异构酶(PMI)相关。研究人员测试了不同人类肿瘤细胞(卵巢癌、肾癌、乳腺癌、前列腺癌和结直肠癌)中的PMI水平,结果参差不齐。
 
其中,结直肠肿瘤的PMI水平较低,这意味着它们可能对甘露糖更敏感。这项研究前景可观,但是仍需要进一步的研究加以验证。
 
▲ Abstract
 
It is now well established that tumours undergo changes in cellular metabolism. As this can reveal tumour cell vulnerabilities and because many tumours exhibitenhanced glucose uptake, we have been interested in how tumour cells respond to different forms of sugar. Here we report that the monosaccharide mannose causesgrowth retardation in several tumour types in vitro, and enhances cell death in response to major forms of chemotherapy. We then show that these effects also occur in vivo in mice following the oral administration of mannose, without significantly affecting the weight and health of the animals. Mechanistically, mannoseis taken up by the same transporter(s) as glucose3 but accumulates as mannose-6-phosphate in cells, and this impairs the further metabolism of glucose in glycolysis, the tricarboxylic acid cycle, the pentose phosphate pathway and glycan synthesis. As a result, the administration of mannose in combination with conventional chemotherapy affects levels of anti-apoptotic proteins of the Bcl-2 family, leading tosensitization to cell death. Finally we show that susceptibility to mannose is dependent on the levels of phospho mannose isomerase (PMI). Cells with low levels of PMI are sensitive to mannose, whereas cells with high levels are resistant, but canbe made sensitive by RNA-interference-mediated depletion of the enzyme. In addition, we use tissue microarrays to show that PMI levels also vary greatly between different patients and different tumour types, indicating that PMI levelscould be used as a biomarker to direct the successful administration of mannose. We consider that the administration of mannose could be a simple, safe and selective therapy in the treatment of cancer, and could be applicable to multiple tumourtypes.
 
化学Chemistry
 
Efficient radical-based light-emitting diodes with doublet emission
 
双激子高效自由基发光二极管
 
▲ 作者:Xin Ai、Emrys W. Evans、Shengzhi Dong、Feng Li,et al
 
▲ 链接:
 
https://www.nature.com/articles/s41586-018-0695-9
 
▲ 摘要:
 
有机发光二极管(OLED)、基于量子点的LED、基于钙钛矿的LED和微LED一直被认为是适用于下一代显示器和主动式照明的轻型和柔性单元。
 
虽然目前已经有一些基于OLED的高端商业产品,但成本居高不下。
 
在这里,研究人员演示了自由基OLED的有效作用,它们的发射源是自旋双激子,而不是单激子或三激子。虽然在这些OLED中发射过程仍然允许自旋,但效率限制性被规避。
 
通过使用发光自由基发射器,研究人员演示了在710纳米的波长下,最大外部量子效率为27%的OLED,这是深红色和红外LED的最高报告值。
 
▲ Abstract
 
Organic light-emitting diodes (OLEDs)quantum-dot-based LEDs, perovskite-based LEDs and micro-LEDs have been championed to fabricate lightweight and flexibleunits for next-generation displays and active lighting. Although there are already some high-end commercial products based on OLEDs, costs must decrease whilst maintaining high operational efficiencies for the technology to realise wider impact.  Here we demonstrate efficient action of radical-based OLEDs, whose emission originates from a spin doublet, rather than a singlet or triplet exciton. While the emission process is still spin-allowed in these OLEDs, the efficiency limitations imposed by triplet excitons are circumvented for doublets. Using a luminescentradical emitter, we demonstrate an OLED with maximum external quantum efficiency of 27 per cent at a wavelength of 710 nanometres—the highest reported value for deep-red and infrared LEDs. For a standard closed-shell organic semiconductor, holes and electrons occupy the highest occupied and lowest unoccupied molecular orbitals (HOMOs and LUMOs), respectively, and recombine to form singlet ortripletexcitons. Radical emitters have a singly occupied molecular orbital(SOMO) in the ground state, giving an overall spin-1/2 doublet. If—as expected on energetic grounds—both electrons and holes occupy this SOMO level, recombination returns the system to the ground state, giving no light emission. However, in our very efficient OLEDs, we achieve selective hole injection into the HOMO and electron injection to the SOMO to form the fluorescent doublet excited state with near-unity internal quantum efficiency.
 
Enhanced strength and ductility in a high-entropy alloy via ordered oxygen complexes
 
通过有序氧复合物增强高熵合金的强度和延展性
 
▲ 作者:Zhifeng Lei、Xiongjun Liu、Yuan Wu、Hui Wang、Zhaoping Lu,et al
 
▲ 链接:
 
https://www.nature.com/articles/s41586-018-0685-y
 
▲ 摘要:
 
氧是地球上最丰富的元素之一,通常会在金属材料中形成一种不需要的间隙杂质或陶瓷相(如氧化物颗粒),而氧掺杂物会使金属变得脆弱。
 
这里研究展示了氧能以有序的氧复合物的形式出现,这是一种介于氧化物颗粒和随机间质之间的状态。
 
与传统的间隙强化不同的是,这种有序的间隙复合物使得复杂固溶体即高熵合金的强度和延展性都得到了前所未有的提高。
 
抗拉强度提高(48.5±1.8%)和延展性大幅改善(95.2±8.1%)打破了长期以来强度—延展性权衡。这些结果使人们对金属材料有序强化机制的作用有了更深入了解。
 
▲ Abstract
 
Oxygen, one of the most abundant elements on Earth, often forms an undesired interstitial impurity or ceramic phase (such as an oxide particle) in metallic materials. Even when it adds strength, oxygen doping renders metals brittle. Here we show that oxygen can take the form of ordered oxygen complexes, a state in between oxide particles and frequently occurring random interstitials. Unlike traditional interstitial strengthening, such ordered interstitial complexes lead to unprecedented enhancement in both strength and ductility in compositionallycomplex solid solutions, the so-called high-entropy alloys(HEAs). The tensile strength is enhanced (by 48.5 ± 1.8 percent) and ductility is substantially improved (by 95.2 ± 8.1 percent) when doping a model TiZrHfNbHEA with 2.0 atomic percentoxygen, thus breaking the long-standing strength–ductility trade-off. The oxygen complexes are ordered nanoscale regions within the HEA characterized by (O, Zr, Ti)-rich atomic complexes whose formation is promoted by the existence of chemical short-range ordering among some of the substitutional matrix elements in the HEAs. Carbon has been reported to improve strength and ductility simultaneously in face-centred cubicHEAs, by lowering the stacking fault energy and increasing the lattice friction stress. By contrast, the ordered interstitial complexes described here change the dislocation shear mode from planar slip to wavy slip, and promote doublecross-slip and thus dislocation multiplication through the formation ofFrank–Read sources (a mechanism explaining the generation of multiple dislocations) during deformation. This ordered interstitial complex-mediated strain-hardening mechanism should be particularly useful in Ti-, Zr- and Hf-containing alloys, in which interstitial elements are highly undesirable owing to their embrittlement effects, and in alloys where tuning the stacking fault energy and exploiting athermal transformations do not lead to property enhancement. These results provide insight into the role of interstitial solid solutions and associated ordering strengthening mechanisms in metallic materials.(唐一尘)
 
 
 

 

 
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