Direct synthesis of propylene carbonate from propylene and carbon dioxide catalyzed by quaternary ammonium heteropolyphosphatotungstate–TBAB system

In this paper,we have developed a highly efficient method for the direct preparation of propylene carbonate from propylene and carbon dioxide(CO2) using quaternary ammonium heteropolyphosphatotungstate–quaternary ammonium halide catalytic system with anhydrous hydrogen peroxide as an oxidant through one-pot two-step process.The effects of the amount of tetrabutylammonium bromide(TBAB),the concentration of hydrogen peroxide and other reaction conditions were investigated.The catalyst system gave an optimum propylene oxide yield(91%) at75°C in oxidation step and the highest propylene carbonate yield(99%) at 140°C and 3.0 MPa in cycloaddition step.Based on the results,a reaction mechanism has been proposed.     

Preparation and characterization of vanadium(IV) oxide supported on SBA-15 and its catalytic performance in benzene hydroxylation to phenol using molecular oxygen

Preparation of dispersed transition metal oxides catalyst with low oxidation state still remains a challenging task in heterogeneous catalysis.In this study,vanadium oxides supported on zeolite SBA-15 have been prepared under hydrothermal condition using V 2 O 5 and oxalic acid as sources of vanadium and reductant,respectively.The structures of samples,especially the oxidation state of vanadium,and the surface distribution of vanadium oxide species,have been thoroughly characterized using various techniques,including N 2-physisorption,X-ray diffraction(XRD),transmission electron microscopy(TEM),X-ray photoelectron spectroscopy(XPS),UV-visible spectra(UV-Vis) and UV-visible-near infrared spectra(UV-Vis-NIR).It is found that the majority of supported vanadium was in the form of vanadium(IV) oxide species with the low valence of vanadium.By adjusting hydrothermal treatment time,the surface distribution of vanadium(IV) oxide species can be tuned from vanadium(IV) oxide cluster to crystallites.These materials have been tested in the hydroxylation of benzene to phenol in liquid-phase with molecular oxygen in the absence of reductant.The catalyst exhibits high selectivity for phenol(61%) at benzene conversion of 4.6%,which is a relatively good result in comparison with other studies employing molecular oxygen as the oxidant.     

人血清Alpha-1-酸性糖蛋白的糖基化分析

获取真实准确的蛋白质糖基化信息是全面了解糖基化修饰生物学功能的前提.针对简单蛋白质的糖基化分析通常采用反相高效液相色谱-串联质谱技术在肽的水平上对糖基化信息进行采集和解析.本文以人血清Alpha-1-酸性糖蛋白(AGP)酶解液为对象,发展了一套简单有效的蛋白质糖基化分析方法.本方法分为三个步骤,第一步是建立糖肽的理论m/z值表;第二步是获取糖蛋白酶解液的LC-MS谱图,并将每一个色谱峰中所包含糖肽的实际m/z值与理论m/z值进行人工匹配;第三步是对每个色谱峰的糖肽结构归属进行LC-MS/MS验证.采用本方法,我们从AGP酶解液中共鉴定出172条糖肽.与单独采用Survey模式的方法相比,本方法能够显著提高糖肽的覆盖率.     

Synthesis and catalytic properties of hierarchical TS-1 in the presence of cationic organosilane surfactant

Hierarchical TS-1 has been synthesized in the presence of cationic organosilane surfactant.The material is characterized with XRD,TEM,N₂ adsorption isotherm.The results show that the hierarchical TS-1 aggregates consist of small primary units with sizes of 20-30 nm.The BET surface area increases from 420 to 513 m²/g compared to conventional TS-1 zeolite.The sample is shown to be more active in epoxidation of cyclohexene than conventional TS-1.     

Modelling of multi-bodies in close proximity under water waves——Fluid resonance in narrow gaps

Viscous fluid model and potential flow model with and without artificial damping force(f=-μV,μ the damping coefficient and V the local averaging flow velocity) are employed in this work to investigate the phenomenon of fluid resonance in narrow gaps between multi-bodies in close proximity under water waves.The numerical results are compared with experimental data available in the literature.The comparison demonstrates that both the viscous fluid model and the potential flow model are able to predict the res...     

A novel simulation method to evaluate the collection performance of a monolithic active pixel sensor

A novel simulation method is presented in this paper to evaluate the collection performance of monolithic active pixel sensor (MAPS) devices for minimum ionizing particle tracking. A simplified 3D matrix pixel structure is built using the computer aided design software Sentaurus. The virtual device is then divided into hundreds of parts and an independent customized X photon model is involved in each part to simulate the conditions under ⁵⁵Fe radiation. After data processing and analysis, charge collection efficiency, collection time and diffusion conditions can be estimated in detail. In order to verify the reliability of the method, comparisons are made between the simulations and experiments. Although there are some defects, it can be concluded that the proposed idea is a feasible method for the evaluation of the MAPS collection performance.     

A new ent-labdane eiterpenoid lactone from Andrographis paniculata

A new ent-labdane diterpenoid lactone with a new natural product was isolated from Andrographis paniculata. Their structures were elucidated on the basis of spectral evidences including 2D NMR.     

Synthesis of micron-sized hollow silica spheres with a novel mesoporous shell of MCF

Micron-sized hollow silica spheres whose shells are made up of mesocellular silica foams(MCFs) have been synthesized by one-pot sol-gel method in benzene/water/P123 emulsion.The material is characterized with SEM,TEM,BET and ~(29)Si MAS NMR. The results show that the MCFs of the unique shell of hollow silica spheres were connected by large windows with a narrow distribution of～10 nm in diameter,the inner space of the hollow sphere is accessible.And the formation mechanism of the hollow silica spheres is ...     

Isolation and Purification of Unstable Iridoid Glucosides from Traditional Chinese Medicine by Preparative High Performance Liquid Chromatography Coupled with Solid-phase Extraction

An efficient preparative method was successfully developed for isolation and purification of unstable components from medicinal plant extracts, using a combined method of preparative high performance liquid chro-matography(HPLC) and solid-phase extraction(SPE). The aim of this study was to obtain an effective method with high preparative efficiency and importantly to avoid the transformation of unstable compounds. The preparative HPLC system was based on an LC/MS controlled four-channel autopurification sys...     

First-principles calculation of core-level binding energy shift in surface chemical processes

Combined with third generation synchrotron radiation light sources, X-ray photoelectron spectroscopy (XPS) with higher energy resolution, brilliance, enhanced surface sensitivity and photoemission cross section in real time found extensive applications in solid-gas interface chemistry. This paper reports the calculation of the core-level binding energy shifts (CLS) using the first-principles density functional theory. The interplay between the CLS calculations and XPS measurements to uncover the structures,...