Chiral Phosphoric Acid Catalyzed Asymmetric Ugi Reaction by Dynamic Kinetic Resolution of the Primary Multicomponent Adduct

Reaction of isonitriles with 3‐(arylamino)isobenzofuran‐1(3H)‐ones in the presence of a catalytic amount of an octahydro (R)‐binol‐derived chiral phosphoric acid afforded 3‐oxo‐2‐arylisoindoline‐1‐carboxamides in high yields with good to high enantioselectivities. An enantioselective Ugi four‐center three‐component reaction of 2‐formylbenzoic acids, anilines, and isonitriles was subsequently developed for the synthesis of the same heterocycle. Mechanistic studies indicate that the enantioselectivity results from the dynamic kinetic resolution of the primary Ugi adduct, rather than from the C?C bond‐forming process. The resulting heterocycle products are of significant medicinal importance.     

高可靠分布式容错计算机架构的研究

分布式系统因其具有分散安装、可靠性高、扩展性好、维修成本低、健壮、安全等诸多优点,国内外相继开展分布式计算机高可靠性技术的研究。本文提出了高可靠分布式容错计算机的构架设计思路,并对TTE总线的选用进行了分析论证,重点描述了成员一致性保证和余度同步等关键技术。     

福寿螺的生活习性及养殖试验

本文介绍福寿螺的外部形态,生活习性,人工繁殖方法和越冬。     

SHAPE MEASUREMENT OF SYNCHROTRON RADIATION WITH HIGH TIME RESOLUTION

By using BWS-5k II streak camera made in China,we have measured the time structure of Synchrotron Radiation (SR) from the relatrivistic electron and positron beam bunches of Beijing Electron Positron Collider (BEPC).The dependence of SR width to the intensity of beam current and the voltage of RF source was also measured.The main data taken with 30ps time resolution in the experiment are as follows: The length of VR at E_e=1.549GeV is changed from 220ps to 670ps when the average beam current from 2mA to 30mA,the variation range of CR length at 20mA beam current is 500—700ps with RF source voltage varying between 250kV and 500kV.The time calibration uncertainty of the experiment is ±15%.The trigger jitter is less than ±200ps.     

Asymmetric 1,3-dipolar cycloaddition of nitrile oxides with optically active vinylboronic ester

Pinanyldioxy styrylboronic ester (1) was employed for asymmetric 1,3-dipolar cycloaddition with nitrile oxides, optically active △2-isoxazolines (3) or 4-hydroxy-△2-isoxazolines (4) were obtained. The effect of different bases on the selectivity of the cycloaddition reaction was studied.     

A micro-wave strategy for synthesizing room temperature phosphorescent materials

Room temperature phosphorescent(RTP) materials have a variety of applications ranging from bioimaging, optoelectronic devices to information security protection. However, the preparation procedures for these materials are always tedious and time-consuming. Here, we report a micro-wave approach to prepare RTP carbon dots(CDs) in only 8 min. The micro-wave promoted the carbon and boron bond formation using natural compounds glucose and boric acids. This result has been confirmed using TEM,FTIR, XP...     

煤气化可弃型催化剂

煤的高效催化气化技术是提高煤气化效率的重要途径。目前,除CaCO₃以外,其他碱金属、碱土金属与过渡金属类催化剂都由于成本较高、回收困难等问题并未广泛应用。可弃型催化剂具有廉价、不必回收、环保并兼有调节灰熔特性、固硫等优点,近年来在煤气化领域的研究和应用受到广泛关注。本文综述了国内外几类可弃型催化剂在煤气化领域的研究进展,包括钙基、工业废液、废渣和生物质灰等催化剂的催化特性及其机理,讨论了在实际应用中存在的问题,展望了未来煤气化可弃型催化剂的发展前景。     

二维正方晶格光子晶体平板的近场成像特性

光子晶体是由两种或两种以卜不同介电函数的材料周期性排列组成的一种人工晶体.由于介电甬数的周期性分布对入射光的调制作用,使得特定频率区域的人射光在光子晶体中传播时的群速度方向和相速度方向相反,因而使得光子晶体平板表现出负折射特性.系统研究了介质柱的形状对二维正方品格光子品体近场成像特性的影响.通过对分别由正方形、三角形、椭网形、长方形等形状介质柱组成的二维正方品格光子晶体平板近场成像特性的理论分析,发现当介质柱形状的对称性降低到一定程度后可以实现光子晶体近场成像的纵向平移.进一步通过对相应等频率曲线形状的分析,明确了光子晶体近场成像是由于自准直效应和负折射效应的共同作用形成的.     

Molecular hydrogen storage in Al-doped bulk graphite with wider layer distances

Molecular hydrogen storage at room temperature in Al-doped bulk graphite with wider layer distances was studied using density functional theory calculation. Hydrogen storage capacity of 3.48 wt% or volume density of 51 kg/m³ was predicted at T=300 K and P=0.1 GPa with adsorption energy E_b=?0.264 eV/H₂. This is close to the target of volume density 62 kg/m³ and satisfies the requirement of immobilization hydrogen with binding strength of 0.2–0.7 eV/H₂ at ambient temperature and modest pressure for commercial applications specified by the U.S. Department of Energy.