Asymmetric synthesis of novel spirocycles via a chiral phosphoric acid catalyzed desymmetrization

A straightforward method for the asymmetric preparation of novel lactone and lactam spirocycles is described. An initial desymmetrization via a chiral Brønsted acid yields enantioenriched lactones which readily undergo a second cyclization to give the desired spirocycle.     

Collective Effects in Ionic Liquid [emim][Tf2N] and Ionic Paramagnetic Nitrate Solutions without Long-Range Structuring

Mesoscopic shear elasticity has been revealed in ordinary liquids both experimentally by reinforcing the liquid/surface interfacial energy and theoretically by nonextensive models. The elastic effects are here examined in the frame of small molecules with strong electrostatic interactions such as room temperature ionic liquids [emim][Tf2N] and nitrate solutions exhibiting paramagnetic properties. We first show that these charged fluids also exhibit a nonzero low-frequency shear elasticity at the submillimeter scale, highlighting their resistance to shear stress. A neutron scattering study completes the dynamic mechanical analysis of the paramagnetic nitrate solution, evidencing that the magnetic properties do not induce the formation of a structure in the solution. We conclude that the elastic correlations contained in liquids usually considered as viscous away from any phase transition contribute in an effective way to collective effects under external stress whether mechanical or magnetic fields.     

Luminescence and compositional studies for the identification of “fire-setting” features at prehistoric mine La Turquesa (Catalonia,Spain)

Journal of Radioanalytical and Nuclear Chemistry - Modern mining activities often leads to destruction of archaeological records, making difficult to date the contexts and tools. In this work, a...     

Solid-contact Cu(II) ion-selective electrode based on 1,2-di-(<Emphasis Type="Italic">o</Emphasis>-salicylaldiminophenylthio)ethane

The development of Cu(II) solid-contact ion-selective electrodes, based on 1,2-di-(o-salicylaldiminophenylthio)ethane as a neutral carrier, is presented. For the electrodes construction, unmodified carbon ink (type 1 electrode) and polymer membrane-modified carbon ink (type 2 electrode) were used as solid support and transducer layer. Also, carbon ink composite polymer membrane electrode (type 3 electrode) was prepared. The analytical performance of the electrodes was evaluated with potentiometry, while bulk and interfacial electrode features were provided with electrochemical impedance spectroscopy. It is shown that modification of carbon ink with polymer membrane cocktail decreases the bulk contact resistance of the transducer layer and polymer membrane, thus enhancing the analytical performance of the electrode in terms of sensitivity, linear range, and stability of potential. The optimized electrodes of types 2 and 3 exhibit a wide linear range with detection limits of 1.8 × 10⁻⁶ and 1.6 × 10⁻⁶ M, respectively. They are suitable for determination of Cu²⁺ in analytical measurements by direct potentiometry and in potentiometric titrations, within pH between 2.3 and 6.5. The electrodes are selective for Cu²⁺ over a large number of tested transition and heavy metal ions.     

白桦液及白桦液复方清除自由基防止沙土鼠脑缺血再灌注氧化损伤的研究

本文用化学发光体系检测白桦液及其复方的清除活性氧自由基的功能。用羟胺法测实验动物化及脑组织的SOD活性,硫代巴比妥酸法测定MDA含量,细胞化学发光法测PMN细胞的免疫功能,化学发光法测脑组织的自发发光,直接法检测GSH-PX活性,氰高铁Hb法测Hb浓度,放免法测血浆TXB2的含量。结果表明,白桦液及其复方在离体体系中有清除O2-、OH-、H2O2的作用,在沙土鼠胞缺点再灌注模型中,可提高血和脑组织的SOD、GSH-PX活性,增强PMN细胞的免疫功能,降低血浆和脑组织LPO,TXB2及Hb浓度。本研究首次发现白桦液及其复方有抗氧化功能。     

Isolation and Characterization of Zygomycetes Fungi from Tempe for Ethanol Production and Biomass Applications

Mixed fungal cultures used for making tempe, a fermented soy bean food, were screened for biomass conversion. Thirty-two zygomycetes strains from two tempe cultures were isolated and identified as Rhizopus, Mucor, Rhizomucor, and Absidia species based upon morphology. The dry weight biomass of these strains contained 49% to 63% protein and 10?C24% chitosan. The strains with the best growth performance were selected and registered at Culture Collection of Gothenburg University as Rhizomucor CCUG 61146 and Rhizomucor CCUG 61147. These strains were able to grow both aerobically and micro-aerobically. Their ethanol yields were 0.38?C0.47, 0.19?C0.22, and 0.31?C0.38?g/g on glucose, xylose, and a mix sugars consisting of cellobiose, glucose, xylose, arabinose, galactose, and mannose, respectively. The biomass yield of the strains varied between 65 and 140?mg dry weight/g glucose.     

在不同形状的防沙墙下沙纹形状及分布分析

论述了在塔里木盆地皮山-沙雅连线西北的塔克拉玛干沙漠西北边缘地带的流动沙漠区域进行的现场风洞试验.在试验中采用了四种形状的防沙墙,分别为直线型、半圆型、三角型、M字型.观测和测试了用不同形状的防沙墙时,沙波形成和性质的改变,同时进行了对比分析,为今后的计算机数值模拟提供了试验依据.     

Contrast performance in catalytic ability—new cinchona phase transfer catalysts for asymmetric synthesis of α-amino acids

Two new cinchona phase transfer catalysts are prepared from dihydrocinchonidine using 13-picenylmethyl bromide and 1-pyrenylmethyl bromide, respectively. A total contrast in catalytic efficiency is observed during the asymmetric alkylation of glycinate esters; with one catalyst, the reaction is either incomplete or the enantioselectivity is very poor (15% ee) while the other catalyst afforded high selectivity up to 94% ee.