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科学小论文写什么(科学论文写什么主题好)

编译 | 李言

Science, 15 APR 2022, VOL 376, ISSUE 6590

《科学》2022年4月15日,第376卷,6590期

科学小论文写什么(科学论文写什么主题好)插图

化学Chemistry

Allylic C–H amination cross-coupling furnishes tertiary amines by electrophilic metal catalysis

烯丙基C-H胺化交联通过亲电金属催化生成叔胺

▲ 作者:SIRAJ Z. ALI, BRENNA G. BUDAITIS, DEVON F. A. FONTAINE et al.

▲ 链接:

https://www.science.org/doi/10.1126/science.abn8382

▲ 摘要:

末端烯烃与仲胺分子间的交叉偶联形成复杂的叔胺(药物合成中的一个共同基序)仍然是化学合成中的一个挑战。在此,我们报告一种钯(II)催化的烯丙基碳-氢胺交叉偶联反应。

它以48个环和非环仲胺(10个相关核)和34个末端烯烃(具有亲电功能)为特征,合成81个叔烯丙基胺,包括12个药物化合物和10个复杂药物衍生物,且具有良好的区域选择性和立体选择性。

▲ Abstract:

Intermolecular cross-coupling of terminal olefins with secondary amines to form complex tertiary amines—a common motif in pharmaceuticals—remains a major challenge in chemical synthesis. Here, we report a palladium(II)-catalyzed allylic carbon-hydrogen amination cross-coupling using this strategy, featuring 48 cyclic and acyclic secondary amines (10 pharmaceutically relevant cores) and 34 terminal olefins (bearing electrophilic functionality) to furnish 81 tertiary allylic amines, including 12 drug compounds and 10 complex drug derivatives, with excellent regio- and stereoselectivity (>20:1 linear:branched, >20:1 E:Z).

Ambient-pressure synthesis of ethylene glycol catalyzed by C60-buffered Cu/SiO2

C60缓冲铜基催化剂实现乙二醇的常压合成

▲ 作者:JIANWEI ZHENG, XLELE HUANG, CUN-HAO CUI et al.

▲ 链接:

https://www.science.org/doi/10.1126/science.abm9257

▲ 摘要:

乙二醇(EG)等化学品可以从乙烯或合成气中工业化合成,但合成气会经历瓶颈反应且需要高压氢气。我们发现,以C60为代表的富勒烯可以作为铜基催化剂(Cu/ SiO2)的电子缓冲剂。

在180°~ 190°C的常压条件下,经C60-Cu/SiO2催化,草酸二甲酯的乙二醇产率可达98±1%。在公斤级反应中,1000小时后催化剂没有失活。这种生成乙二醇的温和方式可以与已经工业化的环境反应相结合,从合成气到草酸二甲酯的中间产物。

▲ Abstract:

Bulk chemicals such as ethylene glycol (EG) can be industrially synthesized from either ethylene or syngas, but the latter undergoes a bottleneck reaction and requires high hydrogen pressures. We show that fullerene (exemplified by C60) can act as an electron buffer for a copper-silica catalyst (Cu/SiO2). Hydrogenation of dimethyl oxalate over a C60-Cu/SiO2 catalyst at ambient pressure and temperatures of 180° to 190°C had an EG yield of up to 98 ± 1%. In a kilogram-scale reaction, no deactivation of the catalyst was seen after 1000 hours. This mild route for the final step toward EG can be combined with the already-industrialized ambient reaction from syngas to the intermediate of dimethyl oxalate.

Amplification of light within aerosol particles accelerates in-particle photochemistry

光在气溶胶粒子内被放大加速了粒子内的光化学过程

▲ 作者:PABLO CORRAL ARROYO, GRéGORY DAVID, PETER A. ALPERT et al.

▲ 链接:

https://www.science.org/doi/10.1126/science.abm7915

▲ 摘要:

光密封(OC)结构光场和放大大气气溶胶粒子内部的光强度,对气溶胶的光驱化学过程具有重要影响。虽然已经理论化了,但OC诱导的空间结构迄今为止还没有在实验中观察到。

在此,x射线光谱显微镜成像与建模结合,为光活性粒子内部OC诱导的模式提供了直接证据。单一的铁(III) -柠檬酸粒子被探测使用铁氧化状态作为光化学标记。

基于这些结果,我们预测大多数种类的气溶胶粒子光化学反应的总体加速为2到3倍。自由气溶胶粒子的旋转和粒子内分子的输运通常会加速光化学过程。考虑到OC效应的普遍存在,大气模型应考虑其对气溶胶粒子光化学过程的影响。

▲ Abstract:

Optical confinement (OC) structures the optical field and amplifies light intensity inside atmospheric aerosol particles, with major consequences for sunlight-driven aerosol chemistry. Although theorized, the OC-induced spatial structuring has so far defied experimental observation. Here, x-ray spectromicroscopic imaging complemented by modeling provides direct evidence for OC-induced patterning inside photoactive particles. Single iron(III)–citrate particles were probed using the iron oxidation state as a photochemical marker. Based on these results, we predict an overall acceleration of photochemical reactions by a factor of two to three for most classes of atmospheric aerosol particles. Rotation of free aerosol particles and intraparticle molecular transport generally accelerate the photochemistry. Given the prevalence of OC effects, their influence on aerosol particle photochemistry should be considered by atmospheric models.

材料科学Materials Science

Volumetric additive manufacturing of silica glass with microscale computed axial lithography

微尺度计算轴向光刻上的硅玻璃体积增材制造

▲ 作者:JOSEPH T. TOOMBS, MANUEL LUITZ, CAITLYN C. COOK et al.

▲ 链接:

https://www.science.org/doi/10.1126/science.abm6459

▲ 摘要:

从消费品的微光学到用于化学合成和生物分析的微流体系统,玻璃作为制造复杂的微观几何形状的材料越来越受欢迎。随着玻璃尺寸、几何形状、表面粗糙度和机械强度要求的发展,传统的加工方法受到了挑战。

我们介绍了熔融二氧化硅元件的微尺度轴向计算光刻技术(micro-CAL),即对随后烧结的光致聚合物—二氧化硅纳米复合材料进行层析成像。我们制作了内径为150微米的三维微流体,表面粗糙度为6纳米的自由曲面微光学元件,以及最小特征尺寸为50微米的复杂高强度桁架和晶格结构。

micro-CAL作为一种高速的数字化轻制造工艺,可以加工高固含量、高几何自由度的纳米复合材料,实现了新的器件结构和应用。

▲ Abstract:

Glass is increasingly desired as a material for manufacturing complex microscopic geometries, from the micro-optics in compact consumer products to microfluidic systems for chemical synthesis and biological analyses. As the size, geometric, surface roughness, and mechanical strength requirements of glass evolve, conventional processing methods are challenged. We introduce microscale computed axial lithography (micro-CAL) of fused silica components, by tomographically illuminating a photopolymer-silica nanocomposite that is then sintered. We fabricated three-dimensional microfluidics with internal diameters of 150 micrometers, free-form micro-optical elements with a surface roughness of 6 nanometers, and complex high-strength trusses and lattice structures with minimum feature sizes of 50 micrometers. As a high-speed, layer-free digital light manufacturing process, micro-CAL can process nanocomposites with high solids content and high geometric freedom, enabling new device structures and applications.

地球科学Geoscience

Citizen seismology helps decipher the 2021 Haiti earthquake

公民地震学有助于破译2021年海地地震

▲ 作者:E. CALAIS, S. SYMITHET. MONFRET, B. DELOUIS et al.

▲ 链接:

https://www.science.org/doi/10.1126/science.abn1045

▲ 摘要:

发生于2021年8月14日的海地尼普斯省7.2级地震,与破坏性的2010年7.0级地震发生在同一断层带,但由于救援受不安全因素的限制以及国家网络中的常规地震仪无法工作,地震依然袭击了该国。

但是,2019年安装的民用地震仪网络提供了对快速了解主震机理和监测其余震序列至关重要的近场数据。他们的实时数据定义了两个余震群,并与传统地震和大地测量数据反演得到的两个同震滑动区域相吻合。

通过将机器学习应用于离主震最近的民用地震仪的数据,使我们能够像使用网络衍生的目录一样准确地预测余震。这显示了公民科学在帮助我们理解大地震方面的作用。

▲ Abstract:

On 14 August 2021, the moment magnitude (Mw) 7.2 Nippes earthquake in Haiti occurred within the same fault zone as its devastating 2010 Mw 7.0 predecessor, but struck the country when field access was limited by insecurity and conventional seismometers from the national network were inoperative. A network of citizen seismometers installed in 2019 provided near-field data critical to rapidly understand the mechanism of the mainshock and monitor its aftershock sequence. Their real-time data defined two aftershock clusters that coincide with two areas of coseismic slip derived from inversions of conventional seismological and geodetic data. Machine learning applied to data from the citizen seismometer closest to the mainshock allows us to forecast aftershocks as accurately as with the network-derived catalog. This shows the utility of citizen science contributing to our understanding of a major earthquake.

神经科学Neuroscience

Compartmentalized dendritic plasticity during associative learning

联想学习中区分树突可塑性

▲ 作者:SIMON D’AQUIN, ANDRAS SZONYI, MATHIAS MAHN et al.

▲ 链接:

https://www.science.org/doi/10.1126/science.abf7052

▲ 摘要:

依赖经验的行为变化是由大脑回路中的长期功能修改所调节的。突触输入的活动依赖性可塑性是一个主要的细胞基础过程。

虽然我们对体外的突触和树突可塑性有了详细的了解,但对活动生物的活性树突功能和可塑性依然知之甚少。利用脑深部双光子钙成像,我们调查了经典恐惧条件反射如何在杏仁核主要神经元中产生感觉反应。

恐惧条件反射诱导树突和躯体的差异可塑性受室特异性抑制的调节。我们的研究结果表明,学习诱导的可塑性可以在体和树突之间解耦合,反映了不同的突触和微电路水平机制,增加了杏仁核回路的计算能力。

▲ Abstract:

Experience-dependent changes in behavior are mediated by long-term functional modifications in brain circuits. Activity-dependent plasticity of synaptic input is a major underlying cellular process. Although we have a detailed understanding of synaptic and dendritic plasticity in vitro, little is known about the functional and plastic properties of active dendrites in behaving animals. Using deep brain two-photon Ca2+ imaging, we investigated how sensory responses in amygdala principal neurons develop upon classical fear conditioning, a form of associative learning. Fear conditioning induced differential plasticity in dendrites and somas regulated by compartment-specific inhibition. Our results indicate that learning-induced plasticity can be uncoupled between soma and dendrites, reflecting distinct synaptic and microcircuit-level mechanisms that increase the computational capacity of amygdala circuits.

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