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Nature, Volume 634 Issue 8032, 3 October 2024
《天然》,第634卷,8032期,2024年10月3日
物理学Physics
Mars’s induced magnetosphere can degenerate
火星感应磁层会退化
▲ 作者:Qi Zhang, Stas Barabash, Mats Holmstrom, Xiao-dong Wang, Yoshifumi Futaana, Christopher M. Fowler, Robin Ramstad Hans Nilsson
▲链接:
https://www.nature.com/articles/s41586-024-07959-z
▲摘要:
行星和恒星风之间的彼此感化会致使年夜气的损掉,是以对行星年夜气的演化很主要。太阳系中的行星凡是与太阳风彼此感化,太阳风的速度与嵌入的恒星磁场成很年夜的角度。
对没有固有磁场的行星,这类彼此感化会在行星前方发生感应磁层和弓形激波。但是,当太阳风速度与太阳风磁场的夹角(锥角)较小时,彼此感化就年夜不不异。
研究注解,当锥角在火星上很小时,感应磁层退化。在白日没有冲击,只有微弱的侧面冲击。横流羽流呈现,双极场驱动行星离子逆流而上。4°锥角的夹杂摹拟成果与火星年夜气与挥发性演变使命和火星快车的不雅测成果一致。简并的感应磁球是复杂的,还没有被摸索过的物体。至在离子逸出对年夜气损掉等进程的二次影响,还待研究。
▲ Abstract:
The interaction between planets and stellar winds can lead to atmospheric loss and is, thus, important for the evolution of planetary atmospheres1. The planets in our Solar System typically interact with the solar wind, whose velocity is at a large angle to the embedded stellar magnetic field. For planets without an intrinsic magnetic field, this interaction creates an induced magnetosphere and a bow shock in front of the planet. However, when the angle between the solar wind velocity and the solar wind magnetic field (cone angle) is small, the interaction is very different. Here we show that when the cone angle is small at Mars, the induced magnetosphere degenerates. There is no shock on the dayside, only weak flank shocks. A cross-flow plume appears and the ambipolar field drives planetary ions upstream. Hybrid simulations with a 4° cone angle show agreement with observations by the Mars Atmosphere and Volatile Evolution mission and Mars Express. Degenerate, induced magnetospheres are complex and not yet explored objects. It remains to be studied what the secondary effects are on processes like atmospheric loss through ion escape.
Space radiation measurements during the Artemis I lunar mission
阿尔忒弥斯1号月球使命时代的空间辐射丈量
▲ 作者:Stuart P. George, Ramona Gaza, Daniel Matthi, Diego Laramore, Jussi Lehti, Thomas Campbell-Ricketts, Martin Kroupa, Nicholas Stoffle, Karel Marsalek, Bartos Przybyla, Mena Abdelmelek, Joachim Aeckerlein, Amir A. Bahadori, Janet Barzilla, Matthias Dieckmann, Michael Ecord, Ricky Egeland, Timo Eronen, Dan Fry, Bailey H. Jones, Christine E. Hellweg, Jordan Houri, Robert Hirsh, Mika Hirvonen, Thomas Berger
▲链接:
https://www.nature.com/articles/s41586-024-07927-7
▲摘要:
空间辐射是长时候载人航天飞翔的显著风险。相干风险包罗癌症、白内障、退行性疾病和年夜量急性表露引发的组织反映。空间辐射的来历多种多样,包罗银河宇宙射线、捕捉粒子(范艾伦)带和太阳粒子事务。
之前的辐射数据来自近地轨道上的国际空间站和航天飞机。它们遭到重屏障和地球磁场的庇护,和火星科学尝试室和月球窥伺轨道器等轻度屏障的行星际机械人探测器。来自阿波罗使命和地面丈量的有限数据也有年夜量的正告。
研究陈述了在无人驾驶的阿尔忒弥斯1号月球使命中,由重屏障的猎户座飞船进行的辐射丈量。在飞翔器内部分歧的屏障位置,在质子带经由过程时代不雅察到的剂量率相差4倍,这与年夜型参考太阳粒子事务类似。猎户座的行星际宇宙射线剂量当量比之前的不雅测成果低了60%。
另外,在质子带过境时代,航天器标的目的的改变致使辐射剂量率削减了约50%。这些丈量成果验证了猎户座将来的载人摸索,并为将来的载人航天使命设计供给了信息。
▲ Abstract:
Space radiation is a notable hazard for long-duration human spaceflight. Associated risks include cancer, cataracts, degenerative diseases and tissue reactions from large, acute exposures. Space radiation originates from diverse sources, including galactic cosmic rays, trapped-particle (Van Allen) belts and solar-particle events. Previous radiation data are from the International Space Station and the Space Shuttle in low-Earth orbit protected by heavy shielding and Earth’s magnetic field and lightly shielded interplanetary robotic probes such as Mars Science Laboratory and Lunar Reconnaissance Orbiter. Limited data from the Apollo missions and ground measurements with substantial caveats are also available. Here we report radiation measurements from the heavily shielded Orion spacecraft on the uncrewed Artemis I lunar mission. At differing shielding locations inside the vehicle, a fourfold difference in dose rates was observed during proton-belt passes that are similar to large, reference solar-particle events. Interplanetary cosmic-ray dose equivalent rates in Orion were as much as 60% lower than previous observations9. Furthermore, a change in orientation of the spacecraft during the proton-belt transit resulted in a reduction of radiation dose rates of around 50%. These measurements validate the Orion for future crewed exploration and inform future human spaceflight mission design.
Highly dynamic gamma-ray emissions are common in tropical thunderclouds
高动态伽马射线辐射在热带雷雨云中很常见
▲ 作者:M. Marisaldi, N.?stgaard, A. Mezentsev, T. Lang, J. E. Grove, D. Shy, G. M. Heymsfield, P. Krehbiel, R. J. Thomas, M. Stanley, D. Sarria, C. Schultz, R. Blakeslee, M. G. Quick, H. Christian, I. Adams, R. Kroodsma, N. Lehtinen, K. Ullaland, S. Yang, B. Hasan Qureshi, J. S?ndergaard, B. Husa, D. Walker, A. Santos
▲链接:
https://www.nature.com/articles/s41586-024-07936-6
▲摘要:
雷爆发出的伽马射线通量被称为伽马射线发光,偶然被飞机、气球和地面不雅测到。不雅测陈述说,伽马射线的发射增添了百分之十,到达布景上方两个数目级,有时因闪电放电而忽然终止。发光是由雷雨云内高电场区域的高能电子加快发生的,并有助在电荷耗散。发光一向被认为是准静止现象,延续时候可达几十秒,空间标准可达10~20千米。
但是,到今朝为止,还没有对伽玛射线辉光区域在空间和时候上的周全扩大和其产生频率的丈量陈述。
研究者展现了海洋和沿海地域的热带雷雨云凡是在几千平方千米的区域内持续数小时发射伽马射线。发射与深部对流核有关;它不是平均和持续的,但具有1~10秒乃至亚秒的个体发光的特点时候标准。
伽马发光雷云的动力学与准静止的发光图象强烈矛盾,相反,在模式和行动上都近似在一个庞大的伽马发光“沸腾锅”。
▲ Abstract:
Thunderstorms emit fluxes of gamma rays known as gamma-ray glows, sporadically observed by aircraft, balloons and from the ground. Observations report increased gamma-ray emissions by tens of percent up to two orders of magnitude above the background, sometimes abruptly terminated by lightning discharges. Glows are produced by the acceleration of energetic electrons in high-electric-field regions within thunderclouds8 and contribute to charge dissipation. Glows had been considered as quasi-stationary phenomena, with durations up to a few tens of seconds and spatial scales up to 10–20?km. However, no measurements of the full extension in space and time of a gamma-ray-glow region and their occurring frequency have been reported so far. Here we show that tropical thunderclouds over ocean and coastal regions commonly emit gamma rays for hours over areas up to a few thousand square kilometres. Emission is associated with deep convective cores; it is not uniform and continuous but shows characteristic timescales of 1–10?s and even subsecond for individual glows. The dynamics of gamma-glowing thunderclouds strongly contradicts the quasi-stationary picture of glows and instead resembles that of a huge gamma-glowing ‘boiling pot’ in both pattern and behaviour.
Opto-twistronic Hall effect in a three-dimensional spiral lattice
三维螺旋晶格中的光-旋回霍尔效应
▲ 作者:Zhurun Ji, Yuzhou Zhao, Yicong Chen, Ziyan Zhu, Yuhui Wang, Wenjing Liu, Gaurav Modi, Eugene J. Mele, Song Jin Ritesh Agarwal
▲链接:
https://www.nature.com/articles/s41586-024-07949-1
▲摘要:
对摩尔系的研究注释了超晶格调制对其性质的影响,展现了新的相干相。但是,年夜大都尝试研究都集中在二维系统的几个层上。将改变电子学扩大到三维,此中改变延长到第三维度,因为与手动堆叠层相干的挑战,依然未被充实摸索。研究者操纵多层WS2的自组装螺旋超晶格研究了三维涡旋电子学。
该研究成果显示了一种由布局手性和相关长度驱动的光旋电子霍尔效应,由螺旋超晶格的莫尔势调制。这是系统非互换几何的尝试证实。
研究者不雅察到加强的光-物资彼此感化和霍尔系数对光子动量的依靠改变。模子注解,高阶量子几何量对这一不雅察的进献,为设计具有年夜非线性的基在量子材料的光电晶格供给了机遇。
▲ Abstract:
Studies of moiré systems have explained the effect of superlattice modulations on their properties, demonstrating new correlated phases. However, most experimental studies have focused on a few layers in two-dimensional systems. Extending twistronics to three dimensions, in which the twist extends into the third dimension, remains underexplored because of the challenges associated with the manual stacking of layers. Here we study three-dimensional twistronics using a self-assembled twisted spiral superlattice of multilayered WS2. Our findings show an opto-twistronic Hall effect driven by structural chirality and coherence length, modulated by the moiré potential of the spiral superlattice. This is an experimental manifestation of the noncommutative geometry of the system. We observe enhanced light–matter interactions and an altered dependence of the Hall coefficient on photon momentum. Our model suggests contributions from higher-order quantum geometric quantities to this observation, providing opportunities for designing quantum-materials-based optoelectronic lattices with large nonlinearities.
化学Chemistry
Nitrogen-doped amorphous monolayer carbon
氮搀杂非晶单层碳
▲ 作者:Xiuhui Bai, Pengfei Hu, Ang Li, Youwei Zhang, Aowen Li, Guangjie Zhang, Yufeng Xue, Tianxing Jiang, Zezhou Wang, Hanke Cui, Jianxin Kang, Hewei Zhao, Lin Gu, Wu Zhou, Li-Min Liu, Xiaohui Qiu Lin Guo
▲链接:
https://www.nature.com/articles/s41586-024-07958-0
▲摘要:
单原子层状碳材料,如石墨烯和非晶单层碳,因为其史无前例的物理特征和普遍的利用前景,激起了剧烈的根本和利用研究。到今朝为止,这类材料首要是经由过程化学气相沉积出产。与液相合成比拟,化学气相沉积凡是需要严酷的反映前提。
在此,我们展现了经由过程在可移动层状双氢氧化物模板的封锁层间腔内聚合吡咯,制备具有夹杂5、6、七元(5-6-7元)环的自力氮搀杂非晶态单层碳的溶液。布局表征和第一性道理计较注解,氮搀杂的非晶态单层碳是在反映空间的限制下由吡咯在α、β和N位自由基聚合构成的,从而经由过程Stone-Wales改变实现键重排。
空间束缚按捺了聚合进程中C-C键的扭转和链纠缠,构成了具有平面内π共轭电子布局的原子厚持续非晶层。利用固体模板和离子互换策略的空间限制自由基聚合显示出作为取得二维共价收集的通用合成方式的潜力,如成功合成单层聚噻吩和聚咔唑的例子。
▲ Abstract:
Monoatomic-layered carbon materials, such as graphene1 and amorphous monolayer carbon, have stimulated intense fund雷竞技amental and applied research owing to their unprecedented physical properties and a wide range of promising applications. So far, such materials have mainly been produced by chemical vapour deposition, which typically requires stringent reaction conditions compared to solution-phase synthesis. Herein, we demonstrate the solution preparation of free-standing nitrogen-doped amorphous monolayer carbon with mixed five-, six- and seven-membered (5-6-7-membered) rings through the polymerization of pyrrole within the confined interlayer cavity of a removable layered-double-hydroxide template. Structural characterizations and first-principles calculations suggest that the nitrogen-doped amorphous monolayer carbon was formed by radical polymerization of pyrrole at the α, β and N sites subjected to confinement of the reaction space, which enables bond rearrangements through the Stone–Wales transformation. The spatial confinement inhibits the C–C bond rotation and chain entanglement during polymerization, resulting in an atom-thick continuous amorphous layer with an in-plane π-conjugation electronic structure. The spatially confined radical polymerization using solid templates and ion exchange strategy demonstrates potential as a universal synthesis approach for obtaining two-dimensional covalent networks, as exemplified by the successful synthesis of monolayers of polythiophene and polycarbazole.
地质Geology
Rules of river avulsion change downstream
河道崩裂的纪律鄙人游产生转变
▲ 作者:James H. Gearon, Harrison K. Martin, Clarke DeLisle, Eric A. Barefoot, David Mohrig, Chris Paola Douglas A. Edmonds
▲链接:
https://www.nature.com/articles/s41586-024-07964-2
▲摘要:
湍急的河道在洪泛区缔造了新的通道,与此相干的洪水会对社会发生深远的影响。人们认为,当水柱在洪泛区上方逗留时,或当河流两侧的斜坡比现有河流的坡度更陡时,就会产生河道冲洗。
研究者经由过程量化河道四周的地形来验证这些经典不雅点,并注解这些机制在汗青上是分隔挪用的,但它们是一路产生感化的。
在海岸四周,当阔别河流的坡度更陡时,河道会产生波动,而不是由于它们处在高位。接近山麓的环境正好相反;在扇形上,可供选择的路径与下流路径一样峻峭,是以当河道位在四周景不雅之上时,它们就会消逝。
研究者们对这些发现进行了和谐,并提出了一个新的理论框架,该框架肯定了哪些河道轻易遭到崩裂的影响,并猜测了崩裂河道的路径。
这些一阶崩裂纪律注解,在很多沿海情况中,崩裂风险被低估了,崩裂寻路的几率猜测可以用起码的信息有用地绘制出危险地图。将这些原则利用在风险评估可能特殊有益在受撕脱影响的全球南边国度。
▲ Abstract:
Avulsing rivers create new pathways on the floodplain and the associated flooding can profoundly affect society. River avulsions are thought to occur when the water column becomes perched above the floodplain or when the slope down the flanks of the channel provides a steeper descent than the existing river channe. We test these classical ideas by quantifying the topography around avulsing rivers and show that these mechanisms, historically invoked separately, work together. Near coasts, rivers avulse when the slope away from the channel is steeper, not because they are perched. The opposite is true near mountain fronts; on fans, the alternative paths are similarly steep to the downstream path, so rivers avulse when they are perched above the surrounding landscape. We reconcile these findings and present a new theoretical framework that identifies which rivers are vulnerable to avulsion and predicts the path of an avulsing river. These first-order rules of avulsion suggest that avulsion risks are underestimated in many coastal environments8 and that probabilistic predictions of avulsion pathfinding can efficiently map hazards with minimal information. Applying these principles for risk assessment could particularly benefit the Global South, which is disproportionately affected by avulsions.
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