Metal‐Free Oxidative Radical Addition of Carbonyl Compounds to α,α‐Diaryl Allylic Alcohols: Synthesis of Highly Functionalized Ketones

A metal‐free direct alkylation of simple carbonyl compounds (ketones, esters, and amides) with α,α‐diaryl allylic alcohols is described. The protocol provides facile access to highly functionalized dicarbonyl ketones by a radical addition/1,2‐aryl migration cascade. The regioselectivity of the reaction was precisely controlled by the nature of the carbonyl compound.     

Arylphosphonylation and Arylazidation of Activated Alkenes

Two radical‐mediated processes of activated alkenes, namely arylphosphonylation and arylazidation, are described. The difunctionalization of alkenes by a tandem process that involves radical addition, 1,4‐aryl migration, and desulfonylation generates α‐aryl‐β‐heterofunctionalized amides bearing a quaternary stereocenter when the substituent on the nitrogen atom is an aryl group. Alternatively, heterooxindoles or spirobicycles can be obtained with excellent regioselectivity in the presence of an alkyl substituent on the nitrogen atom.     

The impact of alkali elements on the degradation of CIGS solar cells

Unencapsulated CIGS solar cells with high and low contents of sodium (Na) and potassium (K) were simultaneously exposed to damp heat and illumination. The solar cells with a high alkali (Na, K) content exhibited higher initial conversion efficiencies, but degraded severely within 100 h, while the alkali poor samples kept relatively stable performance under damp heat and illumination. The degradation of the samples with a high alkali content resulted in the formation of sodium rich spots on the top ZnO:Al surface of the samples. This is likely caused by light‐induced Na⁺ migration via the grain boundaries in the absorber to the depletion region, where the Na⁺ accumulated. This allowed subsequent Na⁺ transport through the depletion region due to the lowering of the internal electric field caused both by the Na⁺ accumulation and illumination. The migration resulted in the formation of shunt paths, which reduced the shunt resistance and open circuit voltage. Furthermore, ingression of water into the ZnO:Al is expected to be responsible for a slow but steady increase in series resistance for both high and low alkali solar cells. Additionally, sodium migration led to a severe increase of the series resistance in case of alkali rich samples. Copyright © 2015 John Wiley & Sons, Ltd.     

Separation of terbutaline enantiomers in capillary electrophoresis with neutral cyclodextrin-type chiral selectors and investigation of the structure of selector-selectand complexes using nuclear magnetic resonance spectroscopy

The major goal of this study was to determine the affinity pattern of the terbutaline (TB) enantiomers toward α-, β-, γ-, and heptakis(2,3-di-O-acetyl)-β-cyclodextrins and using NMR spectroscopy for the understanding of the fine mechanisms of interaction between the cyclodextrins (CD) and TB enantiomers. It was shown once again that CE in combination with NMR spectroscopy represents a sensitive tool to study the affinity patterns and structure of CD complexes with chiral guests. Opposite affinity patterns of TB enantiomers toward native α- and β-CDs were associated with significant differences between the structure of the related complexes in solution. In particular, the complex between TB enantiomers and α-CD was of the external type, whereas an inclusion complex was formed between TB enantiomers and β-CD. One of the possible structures of the complex between TB and heptakis(2,3-di-O-acetyl)-β-CD (HDA-β-CD) was quite similar to that of TB and β-CD, although the chiral recognition pattern and enantioselectivity of TB complexation with these two CDs were very different.     

利用自由基引发的1,2-炔基迁移实现非活性烯烃的炔膦酰化

研究了1,4-烯炔衍生物与二芳基膦氧化物在银介导下发生的炔酰化反应.该反应利用自由基引发的1,2-炔基迁移策略合成了一系列γ-酮膦氧化物,产率适中.该反应机理可能涉及膦中心自由基与乙烯基的加成、3-exo-dig环化和1,2-炔基迁移等连续的过程,一步形成了C-P、C-C键等化学键,实现了非活性烯烃的双官能化.     

三氟乙酸酐(TFAA)促进的Stieglitz重排反应制备苯胺

本工作使用简单易得的三氟乙酸酐作为活化试剂,拓展了Stieglitz重排反应的底物适用范围,发展了一种通过C—C键断裂由苯乙基羟胺制备芳基伯胺的方法.该反应条件较为温和且对官能团具有较好的兼容性.机理研究表明,反应经历了活性三氟乙酸酯中间体的原位生成,并通过C—C和N—O键的断裂实现芳基迁移的过程.     

PVT法氮化铝晶体铝面、氮面生长对比分析

在氮气环境下用PVT方法生长氮化铝过程中,氮面和铝面由于表面化学性质不同,生长的主要化学反应速度存在差异。原子在生长表面的迁移能力不同造成单晶表面生长方式差异较大。在基本相同条件下(生长温度、生长温差、生长气压、类似的籽晶、同一台生长设备)进行了铝、氮面氮化铝单晶晶体生长。为了更明显地表现铝氮面的差异,将同一片籽晶分为两半,翻转其中一半让铝氮面同时生长。铝面生长较好的区域形成了明显的晶畴,而氮面生长时生长较好的部分出现了明显的生长台阶,并出现了晶畴边界被生长台阶湮灭的生长现象,进一步通过AFM观测到铝面生长台阶平整但被缺陷所阻隔,晶畴发育明显为各晶畴独立生长。氮面生长台阶没有铝面规则但连续性较强,在原来晶畴边界位置也出现了连续的生长台阶(或台阶簇)。所以籽晶质量不高时氮面生长更容易提高晶体质量,后续的XRD测量结果也证明了氮面生长后的晶体质量明显高于铝面生长的晶体质量。     

Numerical investigation of particle lateral migration in straight channel flows using a direct-forcing immersed boundary method

Inertia-induced cross-stream migration has been recently exploited for precise position of particles in confined channel flows. In this work, a three-dimensional finite volume based immersed boundary method has been developed to study the lateral migration and hydrodynamic self-assembly of neutrally-buoyant particles in pressure-driven flows. Simulation results show that, in 2D channel flows, the equilibrium position for a circular particle is closer to the centreline for larger particle Reynolds number due to the increasing flow rate, while in 3D square duct flow, the equilibrium position for a spherical particle is near a face centre and is closer to the wall for larger particle Reynolds number. Self-assembly of a pair of particles is observed in 3D square duct flows but not in 2D channel flows. Mechanisms for the self-assembly are discussed.     

Stochastic and upscaled analytical modeling of fines migration in porous media induced by low-salinity water injection

Fines migration induced by injection of low-salinity water(LSW) into porous media can lead to severe pore plugging and consequent permeability reduction. The deepbed filtration(DBF) theory is used to model the aforementioned phenomenon, which allows us to predict the effluent concentration history and the distribution profile of entrapped particles. However, the previous models fail to consider the movement of the waterflood front. In this study, we derive a stochastic model for fines migration during LSW flooding, in which the Rankine-Hugoniot condition is used to calculate the concentration of detached particles behind and ahead of the moving water front. A downscaling procedure is developed to determine the evolution of pore-size distribution from the exact solution of a large-scale equation system. To validate the proposed model,the obtained exact solutions are used to treat the laboratory data of LSW flooding in artificial soil-packed columns. The tuning results show that the proposed model yields a considerably higher value of the coefficient of determination, compared with the previous models, indicating that the new model can successfully capture the effect of the moving water front on fines migration and precisely match the effluent history of the detached particles.     

HL-2M初始等离子体放电阶段的辉光放电清洗系统电极的设计与分析

针对HL-2M装置初始等离子体放电阶段所需的直流辉光放电清洗系统的电极进行了设计.对辉光放电清洗系统在不同工况下的系统负载进行了分析和拟定,并确定了电极结构设计分析标准.根据系统电极的结构特点并结合系统负载规范与分析标准,依据不同的失效模式对电极进行了失效分析.分析结果表明,此针对初始等离子体放电的电极设计能可靠安全运...