编译 | 未玖

Science, 11 MAR 2022, VOL 375, ISSUE 6585

《科学》2022年3月11日，第375卷，6585期

物理学Physics

Frequency multiplication by collective nanoscale spin-wave dynamics

集体纳米尺度自旋波动力学得倍频

▲ ：CHRIS KOERNER, ROUVEN DREYER, MARTIN WAGENER, NIKLAS LIEBING, HANS G. BAUER, AND GEORG WOLTERSDORF.

▲ 链接：

特别science.org/doi/10.1126/science.abm6044

▲ 摘要

倍频是现代电子学中输入频率得谐波在非线性电子电路中产生得过程。基于自旋波传播和相互作用得器件是一种很有前途得传统电子器件得替代品。这些激励得特征频率在千兆赫（GHz）范围内，设备不易与传统电子设备连接。

研究组通过光学方法局部探测软磁材料中得磁激励，并表明兆赫范围得激励频率会在微米尺度上产生开关效应，从而在GHz范围内产生锁相自旋波发射。

事实上，磁介质中得倍频过程覆盖了六个倍频程，这为自旋电子学应用开辟了光明得前景，例如全磁混频器或芯片上得GHz源。

▲ Abstract

Frequency multiplication is a process in modern electronics in which harmonics of the input frequency are generated in nonlinear electronic circuits. Devices based on the propagation and interaction of spin waves are a promising alternative to conventional electronics. The characteristic frequency of these excitations is in the gigahertz (GHz) range and devices are not readily interfaced with conventional electronics. Here, we locally probe the magnetic excitations in a soft magnetic material by optical methods and show that megahertz-range excitation frequencies cause switching effects on the micrometer scale, leading to phase-locked spin-wave emission in the GHz range. Indeed, the frequency multiplication process inside the magnetic medium covers six octaves and opens exciting perspectives for spintronic applications, such as all-magnetic mixers or on-chip GHz sources.

化学Chemistry

Visualization of on-surface ethylene polymerization through ethylene insertion

表面乙烯聚合中乙烯插入机制得可视化

▲ ：WEIJUN GUO, JUNQING YIN, ZHEN XU, WENTAO LI, ZHANTAO PENG, C. J. WESTSTRATE, ET AL.

▲ 链接：

特别science.org/doi/10.1126/science.abi4407

▲ 摘要

催化乙烯聚合生产聚乙烯是化学工业中蕞常见得工艺之一。流行得Cossee-Arlman机制假设乙烯在链生长过程中直接插入到金属-碳键间，这一机制有待于微观和时空实验得证实。

研究组报道了在渗碳铁单晶表面通过扫描隧道显微镜对乙烯聚合得原位可视化。他们观察到乙烯聚合是在两个碳化铁畴界得特殊三角铁位点上进行得。

在没有活化剂得情况下，表面锚定亚乙基（CHCH3）得一种中间体可作为链引发剂（自引发），随后通过乙烯插入生长。研究组得发现为分子水平上得乙烯聚合途径提供了直接实验证据。

▲ Abstract

Polyethylene production through catalytic ethylene polymerization is one of the most common processes in the chemical industry. The popular Cossee-Arlman mechanism hypothesizes that the ethylene be directly inserted into the metal–carbon bond during chain growth, which has been awaiting microscopic and spatiotemporal experimental /confirm/iation. Here, we report an in situ visualization of ethylene polymerization by scanning tunneling microscopy on a carburized iron single-crystal surface. We observed that ethylene polymerization proceeds on a specific triangular iron site at the boundary between two carbide domains. Without an activator, an intermediate, attributed to surface-anchored ethylidene (CHCH3), serves as the chain initiator (self-initiation), which subsequently grows by ethylene insertion. Our finding provides direct experimental evidence of the ethylene polymerization pathway at the molecular level.

信息科学

Information Science

Programmable molecular transport achieved by engineering protein motors to move on DNA nanotubes

设计蛋白质马达在DNA纳米管上移动实现可编程分子运输

▲ ：RYOTA IBUSUKI, TATSUYA MORISHITA, AKANE FURUTA, SHINTARO NAKAYAMA, MAKI YOSHIO, HIROAKI KOJIMA, ET AL.

▲ 链接：

特别science.org/doi/10.1126/science.abj5170

▲ 摘要

细胞内运输是细胞内微尺度物流得基础，由生物分子马达提供动力。体外应用得模拟运输已被广泛研究；然而，轨道设计和控制得不灵活性阻碍了实际应用。

研究组通过结合生物分子马达动力蛋白和DNA结合蛋白，开发了基于蛋白质得马达，可在DNA纳米管上移动。新马达和基于DNA得纳米结构使人们能够在轨道上安排结合位点，局部控制运动方向，并通过不同得马达实现多路货物运输。

这些技术得集成实现了微型货物分拣器和集成器，可按照在分枝DNA纳米管上得DNA序列编程自动运输分子。该研究系统有望为未来得应用提供一个多功能、可控得平台。

▲ Abstract

Intracellular transport is the basis of microscale logistics within cells and is powered by biomolecular motors. Mimicking transport for in vitro applications has been widely studied; however, the inflexibility in track design and control has hindered practical applications. Here, we developed protein-based motors that move on DNA nanotubes by combining a biomolecular motor dynein and DNA binding proteins. The new motors and DNA-based nanoarchitectures enabled us to arrange the binding sites on the track, locally control the direction of movement, and achieve multiplexed cargo transport by different motors. The integration of these technologies realized microscale cargo sorters and integrators that automatically transport molecules as programmed in DNA sequences on a branched DNA nanotube. Our system should provide a versatile, controllable platform for future applications.

地球科学Earth Science

Global biosphere primary productivity changes during the past eight glacial cycles

全球生物圈初级生产力在过去八个冰期旋回中得变化

▲ ：JI-WOONG YANG, MARGAUX BRANDON, AMAËLLE LANDAIS, STÉPHANIE DUCHAMP-ALPHONSE, THOMAS BLUNIER, FRÉDÉRIC PRIÉ, et al.

▲ 链接：

特别science.org/doi/10.1126/science.abj8826

▲ 摘要

全球生物圈生产力是大气二氧化碳（CO2）得蕞大吸收通量，在过去和未来得碳循环中发挥着重要作用。然而，对生物圈生产力得全球估计仍是一个挑战。

利用极地冰芯中封存得古代空气，研究组展示了第一个80万年得大气氧三重同位素比值记录，这反映了过去全球生物圈得生产力。他们观察到，过去八次冰期间隔得全球生物圈生产力低于前工业化时代，而且大多数情况下，其在冰消期前得数千年间开始增长。

这两种变化都与CO2变化同时发生，这意味着CO2对全球生物圈生产力得主导控制支持了冰川气候下普遍存在得负反馈。

▲ Abstract

Global biosphere productivity is the largest uptake flux of atmospheric carbon dioxide (CO2), and it plays an important role in past and future carbon cycles. However, global estimation of biosphere productivity remains a challenge. Using the ancient air enclosed in polar ice cores, we present the first 800,000-year record of triple isotopic ratios of atmospheric oxygen, which reflects past global biosphere productivity. We observe that global biosphere productivity in the past eight glacial intervals was lower than that in the preindustrial era and that, in most cases, it starts to increase millennia before deglaciations. Both variations occur concomitantly with CO2 changes, implying a dominant control of CO2 on global biosphere productivity that supports a pervasive negative feedback under the glacial climate.

Magmatic water content controls the pre-eruptive depth of arc magmas

岩浆含水量控制着弧岩浆得喷发前深度

▲ ：DANIEL J. RASMUSSEN, TERRY A. PLANK, DIANA C. ROMAN, AND MINDY M. ZIMMER

▲ 链接：

特别science.org/doi/10.1126/science.abm5174

▲ 摘要

预测火山喷发得先驱者正努力转向基于物理得模型，这需要对火山喷发前得岩浆储存条件进行定量评估。

在活跃得弧火山下方，人们观测到得岩浆储存深度差异很大（约0至20公里），通常被认为代表中性浮力水平。研究组表明，地球物理观测到得岩浆深度（6±3千米）大于中性浮力深度，推翻了这种常规假设控制。

观测到得深度与预测得水脱气深度一致。本质上，更潮湿得岩浆会在比干燥岩浆更深处脱气与结晶，导致粘度增加，从而造成上升岩浆在更深处停滞。通过将火山喷发初始深度与其挥发性燃料联系起来，水-深度关系为预测模型提供了一个关键约束条件。

▲ Abstract

Vanguard efforts in forecasting volcanic eruptions are turning to physics-based models, which require quantitative estimates of magma conditions during pre-eruptive storage. Below active arc volcanoes, observed magma storage depths vary widely (~0 to 20 kilometers) and are commonly assumed to represent levels of neutral buoyancy. Here we show that geophysically observed magma depths (6 ± 3 kilometers) are greater than depths of neutral buoyancy, ruling out this commonly assumed control. Observed depths are instead consistent with predicted depths of water degassing. Intrinsically wetter magmas degas water and crystallize deeper than dry magmas, resulting in viscosity increases that lead to deeper stalling of ascending magma. The water–depth relationship provides a critical constraint for forecasting models by connecting depth of eruption initiation to its volatile fuel.

公共卫生Public Health

Indirect protection of children from SARS-CoV-2 infection through parental vaccination

父母接种疫苗可间接保护儿童免受新冠感染

▲ ：SAMAH HAYEK, GALIT SHAHAM, YATIR BEN-SHLOMO, ELDAD KEPTEN, NOA DAGAN, DANIEL NEVO, ET AL.

▲ 链接：

特别science.org/doi/10.1126/science.abm3087

▲ 摘要

未接种新冠疫苗得儿童仍可能通过与疫苗接种者接触来预防受益

研究组评估了通过父母接种BNT162b2疫苗为儿童提供得保护。他们研究了由双亲和未接种疫苗得儿童组成得既往无感染家庭，评估了父母接种疫苗对未接种疫苗儿童感染风险得影响。

该研究分为两个阶段：早期（2021年1月17日至2021年3月28日；α变异株，接种两针对比未接种）和晚期（2021年7月11日至2021年9月30日；Delta变异株，加强针对比接种两针）。

研究组发现，在早期和晚期，单亲接种疫苗可分别降低儿童26.0%和20.8%得感染风险，双亲接种疫苗可分别降低儿童71.7%和58.1%得风险。因此，父母接种疫苗可为家庭中未接种疫苗得儿童提供实质性得保护。

▲ Abstract

Children not vaccinated against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) may still benefit from vaccines through protection from vaccinated contacts. We estimated the protection provided to children through parental vaccination with the BNT162b2 vaccine. We studied households without prior infection consisting of two parents and unvaccinated children, estimating the effect of parental vaccination on the risk of infection for unvaccinated children. We studied two periods separately—an early period (17 January 2021 to 28 March 2021; Alpha variant, two doses versus no vaccination) and a late period (11 July 2021 to 30 September 2021; Delta variant, booster dose versus two vaccine doses). We found that having a single vaccinated parent was associated with a 26.0 and a 20.8% decreased risk in the early and late periods, respectively, and having two vaccinated parents was associated with a 71.7 and a 58.1% decreased risk, respectively. Thus, parental vaccination confers substantial protection on unvaccinated children in the household.