The propargylic route as efficient entry to monofluoro and gem-difluoro compounds: mechanistic considerations

The dehydroxy-fluorination of propargylic alcohols occurs with a complete regiocontrol and a good to complete stereocontrol, in contrast to the reactions performed on allylic alcohols. The gem-difluorination of propargylic ketones occurs smoothly in contrast to enones which have a very low reactivity towards DAST or Deoxo-fluor™. It is proposed that the large differences in the stabilization energies of the key carbonium ion intermediates (either propargylic or allylic) could explain these strong differences in reactivity during nucleophilic fluorination. The calculations of isodesmic reactions are in full agreement with this proposal.     

The volume and foundation of star trades

An x-star trade consists of two disjoint decompositions of some simple graph H into copies of K_1,x, the graph known as the x-star. The number of vertices of H is referred to as the foundation of the trade, while the number of copies of K_1,x in each of the decompositions is called the volume of the trade. We determine all values of x, v and s for which there exists a K_1,x-trade of volume s and foundation v.     

外来夹杂物颗粒对枝晶生长形态影响的相场法研究

在KKS相场模型基础上提出了一种耦合取向场的二元合金相场模型.通过该模型分析了外来夹杂物颗粒与晶粒之间的取向错配对于枝晶生长的影响，模拟结果表明外来夹杂物颗粒的大小、位置、数量以及与晶粒的取向差等因素均对枝晶生长形态有较大影响，外来夹杂物颗粒会造成枝晶臂的偏转与分叉，从而最终形成各种形貌的非规则枝晶. 关键词： 相场法 枝晶 外来夹杂物颗粒 晶体取向     

贸易条件影响因素的综合分析

收入贸易条件是衡量一国贸易利益的重要指标，但收入贸易条件无法说明贸易条件的改善是由于出口商品结构优化附加值提高，还是由于低价促销带动出口数量增长，也无法表明一国出口商品的实际竞争能力。本通过建立出口商品竞争能力的评价公式，对我国二十世纪八十年代以来的出口能力系数变化进行实证研究，以期更准确地反映我国对外贸易利益的变化。     

对外贸易与宁波经济发展的关系

亚洲金融危机之后，宁波乃至全国的外贸都面临严峻的考验，在这种条件下，中国政府提出扩大内需的措施来缓解不利的经济发展环境。宁波的对外贸易乘数逐渐减少，出口对经济的牵动作用下降。良性发展的经济不是仅仅依靠国内市场或国际市场，而是应充分利用国际、国内两个市场、两种资源，通过两个市场的发展，共同促进宁波经济的发展。本文拟通过对宁波对外贸易发展现状的实证分析，指出宁波应重视国内市场，真正实现国内市场与国外市场的互动，实现国内需求与国外需求的同时增长，带动整个宁波经济的发展。     

Characterisation of the undissolved residuals ID CMC-solutions

The undissolved fibre and gel residuals that had not completely reacted to form fully dissolved carboxymethyl cellulose (CMC) ID the production of CMC were studied to clarify the reactivity of wood components ID the pulp. The undissolved residuals, the pulp and the CMC were therefore analysed on the fibre level, the cell-wall level and the chemical composition level. The results may be interpreted as indicating that the presence of undissolved residuals ID the CMC was not due to any chemical difference. The undissolved residuals were shown to consist mainly of swollen cell wall parts and some whole wood cells, mainly thick-walled compression wood and summerwood cells. They react more slowly ID the mercerisation and etherification, probably because of a greater diffusion resistance due to their larger dimensions or to a more dense structure. These cells are assumed to be less accessible for chemical penetration, but they may also contain supramolecular structures that slow down the CMC reaction.     

Extremal Forex Returns in Extremely Large Data Sets

Exciting information for risk and investment analysis is obtained from an exceptionally large and automatically filtered high frequency data set containing all the forex quote prices on Reuters during a ten-year period. It is shown how the high frequency data improve the efficiency of the tail risk cum loss estimates. We demonstrate theoretically and empirically that the heavy tail feature of foreign exchange rate returns implies that position limits for traders calculated under the industry standard normal model are either not prudent enough, or are overly conservative depending on the time horizon.     

Produktion und gegenseitige Lieferungen von Isotopen,markierten Verbindungen und geschlossenen Strahlungsquellen in den Mitgliedsländern des RGW

Es wird ein kruzer Überblick gegeben über die Entwicklung des Produktionssortiments an radioaktiven und stabilen Isotopen, markierten Verbindungen und umschlossenen Strahlungsquellen in den RGW-Mitgliedslāndern sowie der gegenseitigen Lieferungen von diesen Erzeugnissen.     

Electroformation of Pd-modified Thin Film Electrocatalysts Using E-ALD Technique

Electrochemical atomic layer deposition was used to form bimetallic (BiPd, CuPd) and trimetallic (CuBiPd) thin films via surface-confined reactions. Pd thin films were characterized by cyclic voltammetry, scanning electron microscopy (SEM) and the alloy formation with preferred Au/Pd(111) orientation was confirmed by XRD. AFM revealed uniform grain distribution, with 3D islands growing on CuBiPd. EDX verified the presence of all deposited elements. Compared to other prepared catalysts, CuBiPd catalyst showed higher activity and stability towards the ethanol oxidation reaction (EOR), as confirmed by the peak current and onset potential trends, respectively: CuBiPd (1.35 mA, −0.450 V)>CuPd (0.6016 mA, −0.442 V)>BiPd (0.275 mA, −0.384 V)>Pd (0.186 mA, −0.350 V). The EOR current on CuBiPd improved by 2.5 folds relative to Pd. The results show that CuBiPd electrocatalyst is a promising material for EOR with enhanced catalytic properties for direct ethanol fuel cell