A simple method for epoxidation of olefins using sodium chlorite as an oxidant without a catalyst

[Reaction: see text]. Sodium chlorite has been demonstrated to be capable of epoxidizing a variety of olefins at 55-65 degrees C (oil bath). Chlorine dioxide is believed to be the pivotal epoxidizing agent in the reaction on the basis of the mechanistic studies.     

A new approach to highly electrooptically active materials using cross-linkable, hyperbranched chromophore-containing oligomers as a macromolecular dopant

A new, practical approach to a variety of highly electrooptically active polymers for device development is described. It involves the use of a new thermally cross-linkable, hyperbranched oligomer containing nonlinear optical (NLO) chromophores as a macromolecular dopant in a common host polymer. A series of NLO polymeric blends were readily formulated and showed large and stable electrooptic (EO) coefficients (up to 65 pm/V). In comparison with previously studied linear NLO polyimides and guest-host polymers doped with molecular chromophores and even linear NLO analogous oligomers, this new approach offers clear advantages for device development in terms of improved poling efficiency, larger EO coefficients, good temporal stability, and versatile material formulation.     

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Suppose that is a smooth -action on a closed smooth -dimensional manifold such that all Stiefel-Whitney classes of the tangent bundle to each connected component of the fixed point set vanish in positive dimension. This paper shows that if 2^k\dim F$"> and each -dimensional part possesses the linear independence property, then bounds equivariantly, and in particular, is the best possible upper bound of if is nonbounding.

     

Characterization of Compact Support of Fourier Transform for Orthonormal Wavelets of L^2（R^d）

Let{ψμ} be an orthonormal wavelet of L^2（R^d） and the support of a whole of its Fourier transform be Uμsupp{ψμ}=Пi=1^d[Ai, Di]-Пi=1^d（Bi, Ci）, Ai≤Bi≤Ci≤Di. Under the weakest condition that each │ψμ│, is continuous for ω ∈ δ（Пi=1^d[Ai, Di]）, a characterization of the above support of a whole is given.     

Catalytic Activity and Stability of Mo_2N in CO Oxidation

Inrecentyears,Mo2Nhasreceivedgreatattenti0ninheter0geneouscatalysisduetoitshighspecificsurfaceareal-4.IthasgoodcaIalyticactivityinawidevarietyofreactions,suchasthehydr0genati0nofCO,synthesis0fNH3,methanation,hydrodenitrogentionandhydrodesulfurization"'andInightbeaprondsingcatalyticmaterial.ThepreparationofMo2Nasacatalyticmaterialhasgainedgreatprogress.Theproduction0fMo2Nwithhighspecificsurfacearea(l7Om'g-')intemperatureprogranunedreactions(TPR)0fMoo3innowingN-H3wasreported'.InthisLab,…     

猛炸药RHT-901和钝感炸药IHE-2的爆轰波直角绕射

 采用高速转镜分幅相机和电探针技术研究了猛炸药RHT-901和钝感炸药IHE-2的爆轰波直角绕射图像和不同位置上的爆轰波传播时间。从研究得出，两种炸药都在拐角顶点附近绕射，爆轰波传播时间增长，爆速变小。但是两种炸药绕射爆轰波的状态不一样，钝感炸药IHE-2中爆轰波绕过直角时，在拐角顶点附近约10 mm范围内炸药未完全反应，猛炸药RHT-901中爆轰波绕过直角时未出现类似现象。两者相比，钝感炸药中绕射爆轰波速度变化大，波阵面曲率半径小，而猛炸药的绕射爆轰波速度变化小，波阵面曲率半径大。这说明炸药的爆轰波绕射与炸药的冲击感度、反应区宽度有关。     

NMR study of the interaction between water and tributyl phosphate in the TBP-CCl4-H2O system

Hydrogen bonding between water and tributyl phosphate (TBP) in TBP? CCl₄? H₂O system has been studied by ¹H NMR. A new model and an empirical equation have been established on the basis of Li's model and the parameters of hydrogen bond between water and TBP are determined by nonlinear optimization method. In TBP? CCl₄? H₂O system change of ¹H chemical shift of water can be satisfactorily explained by the new model and the empirical equation in the whole concentration range. When the concentration of water in the organic phase is very low, the main existing forms of water are H₂O · TBP and H₂O · 2TBP. When the concentration of water reaches saturation, the main existing form is associated water, but there are still about 20% of water existing in the forms of H₂O · TBP and H₂O · 2TBP.     

One‐Pot Synthesis of Colloidal Nanobowls and Hybrid Multipod‐like Nanoparticles by Radiation Miniemulsion Polymerization

A facile approach is proposed to one‐pot synthesis of two kinds of nanoparticles: a new type of PS nanobowls (a hole appearing at the bottom of nanobowl) and PS/silica hybrid multipod‐like nanoparticles. The two type of nanoparticles generated together during polymerization could be separated easily by centrifugation. Furthermore, the structure of nanobowls could be easily controlled by the weight ratio of monomer/silica. In addition, we find that the multipod‐like nanoparticles play important roles in hydrophobic properties. The water contact angle increased from 24.0° to 143.3° after coated with the multipod‐like nanoparticles.

     

透射式指数掺杂GaAs光电阴极最佳厚度研究

通过研究指数掺杂GaAs光电阴极中光电子扩散漂移长度与均匀掺杂GaAs光电阴极中光电子扩散长度的差异,确定透射式指数掺杂GaAs光电阴极的最佳厚度范围为16—22 μm.利用量子效率公式对透射式指数掺杂GaAs光电阴极最佳厚度进行了仿真分析,发现厚度为20 μm时阴极积分灵敏度最大.外延生长阴极厚度分别为16和20 μm的两种透射式指数掺杂GaAs样品并进行了激活实验,测得样品的积分灵敏度分别为1228和1547 μA/lm,两者的比值为796%. 实验结果与仿真结果符合. 关键词： GaAs光电阴极 透射式 指数掺杂 厚度     

汽车尾气颗粒物的STXM和NEXAFS研究

为了研究汽车尾气颗粒物的结构和氮的种态,使用扫描透射X射线显微成像(STXM)技术研究了桑塔纳3000和高尔汽车尾气颗粒物.STXM表明单颗粒物的粒径为500nm,颗粒物质量分布不均匀,有中间空洞.比较汽车尾气颗粒物和(NH4)2SO4和NaNO3中N的1sX射线近边吸收精细结构谱(NEXAFS),铵盐在406eV有显著的σ*吸收峰,有肩部结构;汽车尾气颗粒物和NaNO3中N的近边吸收谱在412eV和418.5eV有明显的σ吸收峰;(NH4)2SO4中N的近边吸收谱在413.5eV和421.8eV更宽的σ吸收峰.硝酸盐是汽车尾气颗粒物中的N化学种态的主要存在形式.在395—418eV能量范围内对桑塔纳3000汽车尾气颗粒物进行堆栈扫描,经过主成分分析和聚类分析,发现其表层主要为硝酸盐,内部有少量铵盐.