Synergistic effects in mixed gas chromatographic stationary phases containing hepatkis(2.3.6-tri-O-pentyl)-β-cyclodextrin and AgNO3 or TINO3 in the separation of xylene isomers

Summary The gas chromatographic separation of xylene isomers using special mixed stationary phases consisting of heptakis(2.3.6-tri-O-pentyl)-β-CD-AgNO₃, heptakis (2.3.6-tri-O-pentyl)-β-CD-TINO₃ or bentone-34-AgNO₃ is investigated. The first two have positive synergistic effects for the separation of m, and p-xylene isomers, but negative synergistic effects for the m, and oisomers. The separation effects depend on temperature, mixing ratio and how mixing is accomplished.     

Bulk versus interfacial aqueous solvation of dicarboxylate dianions

Solvation of dicarboxylate dianions of varying length of the aliphatic chain in water clusters and in extended aqueous slabs was investigated using photoelectron spectroscopy and molecular dynamics simulations. Photoelectron spectra of hydrated succinate, adipate, and tetradecandioic dianions with up to 20 water molecules were obtained. Even-odd effects were observed as a result of the alternate solvation mode of the two negative charges with increasing solvent numbers. The competition between hydrophilic interactions of the charged carboxylate groups and hydrophobic interactions of the aliphatic chain leads to conformation changes in large water clusters containing dicarboxylates bigger than adipate. It also leads to a transition from bulk aqueous solvation of small dicarboxylates to solvation at the water/vapor interface of the larger ones. Whereas oxalate and adipate solvate in the inner parts of the aqueous slab, suberate and longer dicarboxylate dianions have a strong propensity to the surface. This transition also has consequences for the folding of the flexible aliphatic chain and for the structure of aqueous solvation shells around the dianions.     

Suppression of non-specific adsorption using sheath flow

The use of a confining sheath fluid within a microfluidic channel in order prevent non-specific adsorption of analytes to the walls of microchannels is demonstrated. A sheath-flow channel fabricated using laser cutting of Mylar films is developed. Numerical simulations of convective and diffusive mass transport within the channel are presented. The device is characterized experimentally using epifluorescence microscopy. It is demonstrated that the device is capable of preventing the adsorption of Rhodamine B to the walls of the channel for a period that would allow for adsorption-free T-sensor measurements to be made within the core of the flow channel. Generalized scaling rules based on the diffusion coefficient, sheath thickness and affinity of the potential adsorbant for the surface material are discussed. The controlled adsorption of the protein bovine serum albumin (BSA) to a gold surface is also demonstrated using SPR microscopy.     

光声量热法测定辅酶B12的光解量子产率

时间可分辨的光声最热法（Time－resolvedphotoacousticcalorimetry；简称PAC）是研究脉冲激光诱发的快速光化学和光生物化学反应过程动力学和热力学信息的一种有效方法[1－5]。本文采用压电陶瓷圆管同时作为样品油和换能器组成的PAC探测系统[6]，以波长λ＝355nm的脉冲激光（脉冲宽度8ns，脉冲重复频率10Hz）为光源激发辅酶B12甲醇溶液；研究其解量子产率，获得了满意的结果．1实验被测溶液注入两端用石英玻璃封口的压电陶瓷圆管内腔，激光束透过石英窗照射溶液（如图］所示）为标定被测样品的非辐射放热量，利用能在极短的时间内（＜l…     

Recovery of palladium from basic reprocessing waste of spent nuclear fuel

The methods including collection method, extraction-collection method, and special extraction-collection method have been investigated for high speed and efficient recovery of palladium from high pH reprocessing waste of spent nuclear fuel. The equilibrium of the reactions can be obtained is less than 1 minute. The maximum percent recovery of Pd is about 89%, 96% and 97% for collection, extraction-collection, and special extraction-collection methods, respectively. Nearly 100% of back extraction of Pd in the organic phase can be attained by using 7.4M ammonia solution, with a phase ratio of 1:1. The purity of the Pd product is high. The percent recovery of Pd is constant, up to 5·10³ Gy of irradiation dose.     

A new approach to the synthesis of α-chlorocycloalkanones

α-Chlorocycloalkanones(Ⅳ) were synthesized from cycloalkanones via potassiumα-oxocycloalkylsulfonates(Ⅱ).A two-step mechanism was proposed to explain the formation ofⅣfromⅡ.     

Suppressed Blinking in Single Quantum Dots (QDs) Immobilized Near Silver Island Films (SIFs)

In this report, we use single-molecule spectroscopic method to study emission behaviors of streptavidin conjugated quantum dots immobilized on biotinylated-BSA (bovine serum albumin) monolayer near non-continuous rough silver nanostructure. We observed greatly reduced blinking and enhanced emission fluorescence of quantum dots next to silver island films.     

王冠高聚物担载四核钴羰基簇催化剂的醛化反应活性

本文用二苯并-18-冠-6高聚物作因相化载体,通过化学健合,合成了担载的四核钴羰基簇催化剂Crown-Co_4。,并对该催化剂进行了元素分析、红外光谱及X射线光电子能谱(XPS)等方面的测试分析;还考察了不同温度、不同极性溶剂及不同类型烯烃对醛化活性的影响。实验证明,该催化剂对直链端位烯烃的醛化活性高于均相的苯基-四核钴羰基簇催化利Ph-Co_4。。二苯并-18-冠-6高聚物载体能明显改善催化性能。     

羧基膦－钯－酸体系催化烯烃氢酯基化反应

以钯－膦－酸体系催化烯烃氢酯基化的反应日显重要，而膦配体是决定此反应的重要因素，用二苯基膦乙酸（ＤＰＡ）为配体的钯催化剂体系，对烯烃的氢酯基化反应作了研究。对影响反应的各种因素如反应温度、反应压力、不同的溶剂、膦配体及酸助剂的量等作了考察，发现此配体对烯烃的区域选择性有改善。并用此催化体系对不同结构的烯烃进行了研究，发现有如下的活性顺序：环烯烃＞直链端烯＞直链内烯。     

Triterpenoid Saponins from Schefflera arboricola

Four new triterpenoid saponins, named scheffarboside A – D ( 1 – 4 ), along with five known saponins were isolated from the stems of Schefflera arboricola. The structures of the four new saponins were determined as 3‐O‐(O‐β‐glucuronopyranosyl‐(1 → 3)‐O‐α‐rhamnopyranosyl‐(1 → 2)‐α‐arabinopyranosyl)oleanolic acid ( 1 ), 3‐O‐(O‐α‐arabinopyranosyl‐(1 → 4)‐O‐α‐arabinopyranosyl‐(1 → 3)‐O‐α‐rhamnopyranosyl‐(1 → 2)‐α‐arabinopyranosyl)oleanolic acid ( 2 ), 3‐O‐(O‐α‐arabinopyranosyl‐(1 → 4)‐O‐α‐arabinopyranosyl‐(1 → 3)‐O‐α‐rhamnopyranosyl‐(1 → 2)‐α‐arabinopyranosyl)hederagenin ( 3 ), 3‐O‐(O‐α‐arabinopyranosyl‐(1 → 4)‐O‐α‐arabinopyranosyl‐(1 → 3)‐O‐α‐rhamnopyranosyl‐(1 → 2)‐α‐arabinopyranosyl)oleanolic acid O‐α‐rhamnopyranosyl‐(1 → 4)‐O‐β‐glucopyranosyl‐(1 → 6)‐β‐glucopyranosylester ( 4 ), respectively, on the basis of spectroscopic and chemical degradation methods.