An efficient synthetic method for allyl-epoxides via allylation of α-haloketones or esters with allylmagnesium bromide

A simple, efficient, and non-metal-catalyzed synthetic method for allyl-epoxides and diallyl-epoxides by allylation of α-haloketones and esters with allylmagnesium bromide in mild conditions is reported in this article. It inherited some advantages of the organomagnesium reagents such as availability, operational simplicity and low toxicity.     

Influence of char residues on flammability of EVA/EG, EVA/NG and EVA/GO composites

Graphite (expanded graphite(EG), natural graphite (NG) and graphite oxide (GO)) flame retardant poly(ethylene-co-vinyl acetate) copolymer (EVA) composites (EVA/EG, EVA/NG and EVA/GO) have been prepared by melt compounding. The flammability, the combustion process, the quantity of the residual char, the morphology of the residual chars and the thermal stability of the chars were investigated by cone calorimeter, SEM and TGA. The results indicate that heat release rate (HRR), total heat released (THR) and total smoke release (TSR) of EVA/EG (EG 30 phr) composite decrease to about 21%, 42% and 28% of that of pure EVA, respectively. The orders of the three kinds of graphite on the reduction effect of THR and TSR are EG > NG > GO. The higher the quantity, the higher is the thermal stability of the char residue and the more compact and porous char structure may be the main reasons for the phenomenon above. It has been found that the flame retardance of EVA vulcanisates is improved and the fire jeopardizing is dramatically reduced due to the addition of the graphite, especially for EG, which can give some advice to design formulations for practical applications as the jackets of cables.     

The normal state of high temperature oxide superconductor

Looking back on the experiments about the normal state of the high temperature superconductor (HTS), the authors point out nine important experimental results. On the basis of these results, the authors have argued that the two-dimension, two-subsystem Hamiltonian is the appropriate starting point for describing the normal state of HTS. By this Hamiltonian, using the decoupling approximation of Green’s function method by Kaga through numerical calculations, the authors have obtained the temperature dependent pseudogap in the density of states (DOS), which is consistent qualitatively with the experimental results by angle-resolved photoemission spectroscopy (ARPES). Theoretically, this Hamiltonian has the superconducting order parameter of d + s symmetry with d-wave as the main component, which is consistent with experiments. Further, the quantum electronic liquid in HTS is a near Fermi liquid in which there is coexistence of the delocalized states and nearly localized states, and there is finite probability for the nearly localized carriers to form the nearly localized carrier pairs at any finite temperature.     

MSM7512B与标准Modem建立连接

探讨MSM7512B遵从ITU-TV.23规范,以主叫和被叫方式与标准Modem（如Hayes的AT指令集兼容的Modem)建立连接的方法和实现过程。     

曙红Y与牛血清蛋白作用的荧光光谱

1引言蛋白质测定在临床医学和生命科学研究中有重要意义,这方面的研究引起人们的广泛兴趣,最常用的方法是用染料结合法,它们在酸性介质与蛋白质作用形成复合物,而后进行测定,荧光法测定蛋白质文献报道较少。在pH2．53的介质中,我们研究曙红Y与牛血清蛋白作用光谱,曙红Y最大吸收峰从513nm红移到529nm,荧光光谱发生显著变化,540nm（激发光波长308nm）荧光猝灭,其摔灭程度与BSA浓度成正比,据此拟定测定牛血清蛋白的荧光分析方法。该方法线性范围宽0－2．5mg/L,灵敏度高检出限可达2．8μg/L（3σ）,选择性好常见物质不干扰测定…     

随机R0张量互补问题的投影Levenberg-Marquardt方法

本文考虑一类离散型随机$R_0$张量互补问题,利用Fischer-Burmeister函数将问题转化为约束优化问题,并用投影Levenberg-Marquardt方法对其进行了求解。在一般的条件下得到了该方法的全局收敛性,相关的数值实验表明了该方法的有效性。     

Electronic structure and optical properties of boron-sulfur symmetric codoping in 4 × 4 graphene systems

The electronic structure and optical properties of boron-doped, sulfur-doped, andboron-sulfur-codoped graphene systems have been studied by using first-principlescalculations. Energy band structure and density of states are presented to describe theelectronic properties. The doping can open the band gap and change the optical propertiesof graphene. For all optical properties of doped graphene systems, parallel(E _∥) polarization and perpendicular(E _⊥) polarization are presented. Theoptical properties under two kinds of polarizations are reflected in the range of peakheight and the change of some extraordinary features.     

电子束辐射对LED发光性能的影响

研究了低能电子束辐照对发光二极管(Light emitting diode,LED)发光性能的影响。利用实验室加速器提供的电子束模拟空间电子辐射,分别对发不同颜色的光的LED进行不同剂量的辐照,并对比辐照前后的LED的电学性质及光学性质的变化。在电子束辐照下,LED的发光强度提高,同时在统计了大量LED后,发现这些LED的发光强度的离散性变好。对经电子束辐照后的LED进行电流加速老化实验,发现电子束辐照后的LED的发光强度下降趋势相比未经辐照的LED更为明显。同时利用电子束辐照机理对实验结果进行分析和讨论。     

Efficient Low-temperature Hydrogen Production by Electrochemical-assisted Methanol Steam Reforming

Methanol steam reforming (MSR) provides an alternative way for efficient production and safe transportation of hydrogen but requires harsh conditions and complicated purification processes. In this work, an efficient electrochemical-assisted MSR reaction for pure H₂ production at lower temperature (~140 °C) is developed by coupling the electrocatalysis reaction into the MSR in a polymer electrolyte membrane electrolysis reactor. By electrochemically assisted, the two critical steps including the methanol dehydrogenation and water-gas shift reaction are accelerated, which is attributed to decreasing the methanol dehydrogenation energy and promoting the dissociation of H₂O to OH* by the applied potential. Furthermore, the reduced H₂ partial pressure by the hydrogen oxidation and reduction process further promotes MSR. The combination of these advantages not only efficiently decreases the MSR temperature but also achieves the high rate of hydrogen production of 505 mmol H₂ g _Pt⁻¹ h⁻¹ with exceptionally high H₂ selectivity (99 %) at 180 °C and a low voltage (0.4 V), and the productivity is about 30-fold than that of traditional MSR. This study opens up a new avenue to design novel electrolysis cells for hydrogen production.     

琥乙红霉素分子印迹聚合物微球的制备及表征

以琥乙红霉素为模板分子,甲基丙烯酸为功能单体,乙二醇二甲基丙烯酸酯为交联剂,采用悬浮聚合法制备得到了平均粒径约为60μm的琥乙红霉素分子印迹聚合物微球(MIPs),并用扫描电镜对其表面形貌进行了表征。考察了琥乙红霉素分子印迹聚合物的印迹效果,研究了琥乙红霉素分子印迹聚合物的动力学吸附特性。比较了MIPs对琥乙红霉素及其它3种抗生素的吸附情况。结果表明,制备得到的琥乙红霉素分子印迹聚合物微球对琥乙红霉素具有最好的吸附能力,显示出MIPs具有高的选择性。