Synthesis of biaryls by intramolecular radical transfer in phosphinates

Phosphinates 20a-35a give biaryls 20b-35b on heating with stannanes in the presence of AIBN. The process involves a radical ipso substitution on the migrating aryl ring.     

The first 1,3-digermyla-2-nickela-carboranylene and the Ni-catalyzed double germylation of unsaturated organic substrates

The reaction of o-bis(dimethylgermyl)carborane with Ni(PEt3)4 in pentane affords the reactive intermediate, [o-(GeMe2)2C2B10H10]Ni(PEt3)2 2: the facile double germylation of unsaturated organic substrates catalyzed by 2 is reported.     

Application of automated matrix-assisted laser desorption/ionization time-of-flight mass spectrometry for the measurement of enzyme activities

Sample preparation methods and data acquisition protocols were optimized for the application of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) to high-throughput quantitative analysis of low molecular mass substrates and products of an enzyme-catalyzed reaction. Using a deuterlum-labeled internal standard, precise standard curves were obtained (r(2) = 0.9998) over two orders of magnitude of concentration of rac-1-phenylethylamine (PEA), which is converted to 2-methoxy-N-[(1R)-1-phenylethyl]acetamide (MET) by a lipase-catalyzed reaction with ethylmethoxyacetate (EMA) as second substrate. Reliable relative standard deviations were achieved (< or =5%) using automated analysis with peak intensity ratios between 0.2 and 5 of analyte to internal standard. This method permitted quantitative analysis of the lipase reaction, producing results comparable to those from gas chromatographic (GC) analysis in the dynamic range of GC. This work shows that MALDI-TOFMS can be applied for the high-throughput screening of enzymes.     

Crystal Bases for Quantum Affine Algebras and Combinatorics of Young Walls

In this paper we give a realization of crystal bases for quantumaffine algebras using some new combinatorial objects which wecall the Young walls. The Young walls consist of colored blockswith various shapes that are built on a given ground-state walland can be viewed as generalizations of Young diagrams. Therules for building Young walls and the action of Kashiwara operatorsare given explicitly in terms of combinatorics of Young walls.The crystal graph of a basic representation is characterizedas the set of all reduced proper Young walls. The characterof a basic representation can be computed easily by countingthe number of colored blocks that have been added to the ground-statewall. 2000 Mathematical Subject Classification: 17B37, 17B65,81R50, 82B23.     

国际互联网技术与旅游业企业过程重组

信息技术、互联网、通讯技术的发展引起了整个旅游业的一场革命,正在深刻地改变着旅游业的经营、管理和运作模式。网络技术的出现则恰好给旅游业的加速发展、企业过程重组带来了新的机遇。文章集中分析了旅游业的信息特征、信息技术、互联网技术引起的旅游业的经营环境变化,提出了旅游服务供应链管理的概念。在此基础上,结合英特网技术在旅游业的功能,提出了旅游业的企业过程重组,建立虚拟旅游公司模式。     

基于PC架构Linux NAT性能优化

阐述了采用Netfilter/iptables技术来实现NAT的缘由 ,并分析了此项技术在Linux内核 2 .4中的一个重要新特性 ,即“连接跟踪” ;着重讨论了提高基于配有Linux操作系统的普通PC机上的NAT性能的方法 ,包括重编内核 ,防止空对话及修改tcp连接超时设定 ;通过一组系统状态监测曲线图证明这样一个廉价系统作为一些昂贵的路由设备的替代是稳定可靠的     

Antiferromagnetic order as the competing ground state in electron-doped Nd1.85Ce0.15CuO4

Superconductivity in the high-transition-temperature (high-T(c)) copper oxides competes with other possible ground states. The physical explanation for superconductivity can be constrained by determining the nature of the closest competing ground state, and establishing if that state is universal among the high-T(c) materials. Antiferromagnetism has been theoretically predicted to be the competing ground state. A competing ground state is revealed when superconductivity is destroyed by the application of a magnetic field, and antiferromagnetism has been observed in hole-doped materials under the influence of modest fields. None of the previous experiments have revealed the quantum phase transition from the superconducting state to the antiferromagnetic state, because they failed to reach the upper critical field B(c2). Here we report the results of transport and neutron-scattering experiments on electron-doped Nd1.85Ce0.15CuO4 (refs 13, 14), where B(c2) can be reached. The applied field reveals a static, commensurate, anomalously conducting long-range ordered antiferromagnetic state, in which the induced moment scales approximately linearly with the field strength until it saturates at B(c2). This and previous experiments on the hole-doped materials therefore establishes antiferromagnetic order as a competing ground state in the high-T(c) copper oxide materials, irrespective of electron or hole doping.