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发布日期：2024-09-14 作者：开博
编译｜冯维维
Science, 30 August 2024, Volume 385, Issue 6712
《科学》2024年8月30日，第385卷，6712期
物理学Physics
In situ observations of large-amplitude Alfvén waves heating and accelerating the solar wind
年夜振幅阿尔芬波加热和加快太阳风的现场不雅测
▲ 作者：YEIMY J. RIVERA, SAMUEL T. BADMAN, MICHAEL L. STEVENS, JAYE L. VERNIERO, JULIA E. STAWARZ, CHEN SHI, JIM M. RAINES, KRISTOFF W. PAULSON, CHRISTOPHER J. OWEN, AND STUART D. BALE
▲链接：
https://www.science.org/doi/10.1126/science.adk6953
▲摘要：
分开日冕后，太阳风继续加快和冷却，但比预期的自由膨胀的绝热气体要慢很多。阿尔芬波是传输能量的行星际磁场的扰动。研究者利用帕克太阳探测器和太阳轨道飞翔器的现场丈量来查询拜访太阳风流，由于它穿过内部日球层。
不雅测成果显示，日冕外缘和金星轨道四周的等离子体正在升暖和加快，同时还存在着振幅较年夜的阿尔芬波。研究者计较出，阿尔芬波所发生的阻尼和机械功足觉得内日球层中快速太阳风的加热和加快供给动力。
▲ Abstract：
After leaving the Sun’s corona, the solar wind continues to accelerate and cools, but more slowly than expected for a freely expanding adiabatic gas. Alfvén waves are perturbations of the interplanetary magnetic field that transport energy. We use in situ measurements from the Parker Solar Probe and Solar Orbiter spacecraft to investigate a stream of solar wind as it traverses the inner heliosphere. The observations show heating and acceleration of the plasma between the outer edge of the corona and near the orbit of Venus, along with the presence of large-amplitude Alfvén waves. We calculate that the damping and mechanic开博体育al work performed by the Alfvén waves are sufficient to power the heating and acceleration of the fast solar wind in the inner heliosphere.
Grain boundaries are Brownian ratchets
晶界是布朗棘轮
▲ 作者：CAIHAO QIU, MAIK PUNKE, YUAN TIAN, YING HAN, SIQI WANG, YISHI SU, MARCO SALVALAGLIO, XIAOQING PAN, DAVID J. SROLOVITZ , AND JIAN HAN
▲链接：
https://www.science.org/doi/10.1126/science.adp1516
▲摘要：
多晶材料的晶粒尺寸是制约其机能的主要构成部门。与之前的假定相反，研究者经由过程建模注解，在非定向驱动力的感化下，晶界（GBs）可以向一个标的目的移动。但是，其实不是所有的晶界类型都是如许，首要是那些几何上不合错误称的晶界。这一不雅察成果有助在更好地舆解一些晶粒粗化行动，也多是工程微不雅布局和改良材料机能的另外一种东西。
研究者证实晶界表示为布朗棘轮，在振荡驱动力或轮回热退火下表示出标的目的依靠的迁徙和单向活动。他们在几近所有非对称GB中不雅察到这些现象，但在对称GB中没有。这一不雅察成立在份子动力学和相场晶体摹拟的根本上，摹拟了普遍的GB类型和双晶和多晶微不雅布局中的驱动力。
研究者经由过程现场尝试不雅察证实了这些摹拟成果，并用马尔可夫链模子阐发了这些成果，并切磋了GB棘轮行动对材料加工和微不雅布局定制的影响。
▲ Abstract：
The grain size of a polycrystalline material is one important part of the microstructure that constrains the properties. In contrast to previous assumptions, Qiu et al. have shown through modeling that grain boundaries (GBs) can move in one direction in response to a nondirectional driving force. However, not all grain boundary types do so, mostly just the ones that are geometrically nonsymmetric. This observation helps us better understand some grain-coarsening behavior and may also be another tool for engineering microstructures and improving the material properties.
We demonstrate that grain boundariesbehave as Brownian ratchets, exhibiting direction-dependent mobilities and unidirectional motion under oscillatory driving forces or cyclic thermal annealing. We observed these phenomena for nearly all nonsymmetric GBs but not for symmetric ones. Our observations build on molecular dynamics and phase-field crystal simulations for a wide range of GB types and driving forces in both bicrystal and polycrystalline microstructures. We corroborate these simulation results through in situ experimental observations. We analyze these results with a Markov chain model and explore the implications of GB ratchet behavior for materials processing and microstructure tailoring.
地质与地舆Geology Geography
The marine biodiversity impact of the Late Miocene Mediterranean salinity crisis
晚中新世地中海盐度危机对海洋生物多样性的影响
▲ 作者：KONSTANTINA AGIADI, NIKLAS HOHMANN, ELSA GLIOZZI, DANAE THIVAIOU, FRANCESCA R. BOSELLINI, MARCO TAVIANI, GIOVANNI BIANUCCI, ALBERTO COLLARETA, LAURENT LONDEIX, AND DANIEL GARCíA-CASTELLANOS
▲链接：
https://www.science.org/doi/10.1126/science.adp3703
▲摘要：
在全部地质汗青中，在高度受限的海洋盆地中构成了年夜量的盐聚积或“盐伟人”，但它们对生物多样性的影响只获得零散的研究。500万到600万年前中新世晚期，地中海与年夜西洋的分手致使地中海几近完全干涸，只剩下几个近似在今天死海的高盐湖泊。
在597至533万年前的墨西尼亚盐危机（MSC）时代，地中海的“盐伟人”是因为其通往年夜西洋的门户遭到限制而构成的。研究者按照地中海化石记实的汇编量化了与MSC相干的生物多样性转变。成果注解，2006年MSC前的86种特有物种在危机中幸存下来，地中海今朝向东递减的丰硕度梯度是MSC后构成的。
▲ Abstract：
Massive salt accumulations, or salt giants, have formed in highly restricted marine basins throughout geological history, but their impact on biodiversity has been only patchily studied. The disconnection of the Mediterranean Sea from the Atlantic in the late Miocene 5 to 6 million years ago led to the sea’s nearly complete desiccation, leaving only a few hypersaline lakes similar to the present-day Dead Sea. The salt giant in the Mediterranean Sea formed as a result of the restriction of its gateway to the Atlantic during the Messinian Salinity Crisis (MSC) 5.97 to 5.33 million years ago. Here, we quantify the biodiversity changes associated with the MSC based on a compilation of the Mediterranean fossil record. We conclude that 86 endemic species of the 2006 pre-MSC marine species survived the crisis, and that the present eastward-decreasing richness gradient in the Mediterranean was established after the MSC.
Dryland self-expansion enabled by land–atmosphere feedbacks
陆地—年夜气反馈使旱地自我扩大
▲ 作者：AKASH KOPPA, JESSICA KEUNE, DOMINIK L. SCHUMACHER, KATERINA MICHAELIDES, MICHAEL SINGER, SONIA I. SENEVIRATNE, AND DIEGO G. MIRALLES
▲链接：
https://www.science.org/doi/10.1126/science.adn6833
▲摘要：
旱地扩大造成普遍的水资本欠缺和生物多样性损失。固然全球变暖对干旱的影响是公认的，但现有旱地在其本身扩大中的感化却相对未知。旱地，即年夜气需水量年夜年夜跨越降水的地域，占有了地球陆地概况的近一半。它们将若何应对天气变暖？
作者研究注解，流经旱地的暖和干燥空气有助在顺风旱地的扩大，并可能致使这些地域的干旱化。他们发现，从1981年到2018年，在干旱地域不雅测到的干旱增添中，有40%以上是因为自我扩大。研究成果证实，干旱地域火急需要采纳减缓天气转变办法，以减缓其本身的扩大。
▲ Abstract：
Dryland expansion causes widespread water scarcity and biodiversity loss. Although the drying influence of global warming is well established, the role of existing drylands in their own expansion is relatively unknown. Drylands, regions in which atmospheric water demand considerably exceeds precipitation, occupy nearly half of Earth’s land surface. How will they respond to our warming climate? Koppa et al. show that the warm, dry air flowing over drylands contributes to downwind dryland expansion and can cause the aridification of those areas. They found that more than 40% of the observed increase in aridity over regions that became drylands from 1981 to 2018 was due to self-expansion. The results corroborate the urgent need for climate change mitigation measures in drylands to decelerate their own expansion.
化学Chemistry
Stereodivergent access to non-natural α-amino acids via enantio- and Z/E-selective catalysis
取得非自然α-氨基酸的立体发散路子
▲ 作者：PANPAN LI, EN ZHENG, GUANLIN LI, YICONG LUO, XIAOHONG HUO, SHENGMING MA , AND WANBIN ZHANG
▲链接：
https://www.science.org/doi/10.1126/science.ado4936
▲摘要：
在化学合成中，对碳碳双键两头基团的设置装备摆设进行顺应性节制是一个挑战。在E构型中，最年夜的基团对角相对，而在Z构型中，它们在统一侧。研究者将铜和钯催化剂配对，按照配体的选择，在非自然氨基酸中传递E-或z-构型双键。
该反映在季碳立体中间也具有高度的对映选择性。经由过程钯\铜共催化的三组分组装，经由过程简单地调剂钯和铜催化剂的手性配体，轻易取得芳基碘化物、烯和醛胺酯。
▲ Abstract：
Adaptable control over the disposition of groups at each end of a carbon-carbon double bond remains a challenge in chemical synthesis. In the E configuration, the largest groups are diagonally opposed, whereas in the Z configuration, they’re on the same side. Li et al. paired up copper and palladium catalysts to deliver either E- or Z-configured double bonds in unnatural amino acids, depending on the ligand choice. The reaction is also highly enantioselective at the quaternary alpha carbon stereocenter. This success is achieved through a palladium/copper–cocatalyzed three-component assembly of readily available aryl iodides, allenes, and aldimine esters by simply tuning the chiral ligands of the palladium and copper catalysts.
生命科学Life Science
Morphine-responsive neurons that regulate mechanical antinociception
调理机械抗痛觉的吗啡反映神经元
▲ 作者：MICHAEL P. FATT, MING-DONG ZHANG, JUSSI KUPARI, MüGE ALTINK?K, YUNTING YANG, YIZHOU HU, PER SVENNINGSSON, AND PATRIK ERNFORS
▲链接：
https://www.science.org/doi/10.1126/science.ado6593
▲摘要：
几十年来，人们已知道，脑干中一个被称为吻侧腹内侧髓质的区域对阿片类药物引诱的镇痛很主要，但这一现象背后的神经基质依然难以捉摸。经由过程利用小鼠遗传学和用工程病毒把持神经元勾当，研究者发现，位在该年夜脑区域的单一类型的兴奋性神经元付与吗啡抗痛觉性。
这些神经元投射到脊髓——在那边，经由过程单突触毗连，它们激活一种肯定的按捺性脊髓神经元类型，在上升痛苦悲伤通路中节制痛苦悲伤旌旗灯号。研究发现，对延髓吻侧腹内侧兴奋性神经元或脊髓按捺性神经元的按捺可消弭全身打针吗啡的所有镇痛感化。
▲ Abstract：
It has been known for decades that a brainstem area called the rostral ventromedial medulla is important for opioid-induced analgesia, but the neural substrates underlying this phenomenon have remained elusive. Through the application of mouse genetics and the manipulation of neuron activity with engineered viruses, Fatt et al. discovered that a single type of excitatory neuron located in this brain region confers morphine antinociception. These neurons project to the spinal cord, where, through monosynaptic connectivity, they activate a defined inhibitory spinal neuron type that gates pain signaling in the ascending pain pathway. Inhibition of either the excitatory neurons in the rostral ventromedial medulla or the inhibitory neurons in the spinal cord was found to abolish all of the analgesic effects of systemically administered morphine.
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