Hygroscopic growth of aerosol scattering coefficient:A comparative analysis between urban and suburban sites at winter in Beijing

A humidity controlled inlet system was developed to measure the hygroscopic growth of aerosol scattering coefficient in conjunction with nephelometry at an urban site of Chinese Academy of Meteorological Sciences (CAMS) in Beijing and a rural site at Shangdianzi Regional Background Air Pollution Monitoring Station (SDZ) outside Beijing during winter, from December 2005 to January 2006. Measurements were carried out at a wavelength of 525 nm with an Ecotech M9003 nephelometer. The hygroscopic growth function (or factor) of the aerosol scattering coefficientf(RH) increased continuously with increasing relative humidity (RH) and showed no obvious "step-like" deliquescent behavior at both sites during the experiment. The average growth factorf(RH) at the SDZ site could reach 1.5 when RH increased from less than 40% to 92%, and to 2.1 at the CAMS site when RH increased from less than 40% to 93%. The average hygroscopic growth factor at a relative humidity of 80%, f(RH=80±1%), was found to be about 1.26±0.15 at CAMS and 1.24±0.11 at SDZ. Further analysis indicated that under relatively polluted conditions, the average hygroscopic growth factor was higher at the CAMS site than that at the SDZ site. However, under relatively clean air conditions, the difference between the two sites was small, showing a hygroscopic growth behavior similar to those of burning biomass or blowing dust. These results reflected the different characteristics of aerosol types at the two sites.     

HYDROGENATION OF NITROBENZENE TO FORM ANILINE IN LIQUID PHASE AT ATMOSPHERIC PRESSURE

Aromatic amine compounds and their derivatives are important intermediates of fine chemicals like dye and medicine.The former hydrogenation catalyst has many problems,such as environment pollution caused by old technology,strict reaction condtion,complicated equipment,bad property of catalyst and so on.Holy ^[1] firstly reported the hydrogenation of nitrobenzene on modified polystyrene Pd catalyst.But how to improve the activity,selectivity and stability of the polymer suppoorter catalyst needs to studyfurther.We prepared a series of polymer supported catalysts by the methods of adsorption and mechanical mixting ,selected a high active catalyst Pd-Ah-1 by observing the hydrogenation of nitrobenzene.     

Charge‐Transfer Complexes Between the Sulfur Molecules SO2, S2O,S3, SONH,and SOCl2 and the Amine Donors NH3 and NMe3 — A theoretical Study

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.     

Quantitative Aspects of Electrochemical Detection of Amyloid‐β Aggregation

The tyrosine based electrochemical analysis of synthetic amyloid‐β (Aβ) peptide – an analog of natural peptide implicated in Alzheimer's disease pathogenesis – was applied for a quantitative estimation of peptide aggregation in vitro. The analysis was carried out by square wave voltammetry (SWV) on carbon screen printed electrodes (SPE). The electrooxidation peak current (I_p) for Aβ42 peptide in different aggregation states was directly compared with the size and structure of Aβ42 aggregates occurring in the analyzed sample. Dynamic light scattering (DLS) and thioflavin T (ThT) based fluorescence assay were employed to estimate the size and structure of Aβ42 aggregates. The I_p was found to decrease in a linear fashion when the average diameter of aggregates and the relative ThT fluorescence in Aβ42 solutions exceeded 35 nm and 3, respectively, while being nearly constant below these values. It was suggested that the electrooxidation current is mostly generated by peptide monomers and that a depletion of the monomer pool due to inclusion of Aβ42 molecules in aggregates is responsible for the decrease of electrooxidation current. The direct electrochemistry is emerging as a method complementary to methods based on aggregates’ detection and commonly employed for monitoring Aβ aggregation. The work further enlarges the basis for application of the cost‐effective and rapid electrochemical techniques, such as SWV on carbon SPE, to in vitro studies of Aβ aggregation.     

Saturation kinetics and relative reactivity of the double bonds of alicyclic dienes in their hydrogenation

The kinetics of the liquid-phase hydrogenation of cyclodienes with various structures (endo-tricyclo[ 5.2.1.0^2,6]decadiene-3,8 and cis,cis-1,5-cyclooctadiene) by hydrogen over a finely dispersed 1%Pd/C catalyst at atmospheric pressure has been studied. The catalyst provides the possibility for successive saturation of the double bonds of the dienes. The reactivities of the cyclodienes determined by their electron-donating properties have been compared. The solvent nature is the determining factor in the ratio of hydrogen absorption rates in the case of successive saturation of the double bonds of the hydrocarbons. The hydrogenation kinetics of cyclic dienes, including dicyclopentadiene, can be modeled using the Langmuir–Hinshelwood equation when the process is carried out in a perfectly mixed flow reactor.     

α-Fe_2O_3纳米微粒/硬脂酸交替L-B膜的结构表征

纳米微粒(NP)是一个新的物质层次,它具有一系列新异的物理、化学特性,涉及到大块样品中所忽略的,或根本不具有的基本物理、化学问题.用NP 制造新型的人工功能材料具有广泛的潜在应用.一个有意义的挑战是能否对NP 进行有序的组装.Zhao andFendler 等曾利用Fe_3O_4NP 进行有序组装的尝试.我们也在前期的初步研究中利用Langmuir-Blodgett(LB)技术对7nm 的α-Fe_2O_3 NP 进行了有序组装的探索,获得了α-Fe_2O_3 NP-硬脂酸交替LB 多层膜(FNSLF).然而这种交替膜的有序情况还不十分清楚.     

Nanosized multilayer films with concurrent photochromism and electrochromism based on Dawson-type polyoxometalate

An inorganic-organic composite multilayer film constructed of poly(vinyl alcohol) (PVA) with Dawson-type phosphotungstate anion [P₂W₁₈O₆₂]⁶⁻ (P₂W₁₈) and poly(allylamine hydrochloride) (PAH) were fabricated on quartz, ITO, silicon and CaF₂ substrates by a layer-by-layer self-assembly method. The film was provided with concurrent photochromism and electrochromism. IR spectra showed that the structure of the PVA was fully maintained in the multilayer film. And their photochromic and electrochromic properties were investigated by UV-vis spectra, cyclic voltammetry (CV), chronoamperometry (CA) measurement and X-ray photoelectron spectra (XPS). Atomic force microscopy (AFM) was used to investigate the surface topography. This study provides a new route to explore the possibility of application to polyoxometalate-based hybrid inorganic-organic materials.     

Conformational Analysis of Tris(3-methylphenyl)phosphine and Its Chalcogenides

Conformational analysis of tris(3-methylphenyl)phosphine and its chalcogenides has been performed by methods of dipole moments, IR spectroscopy, and quantum chemistry [DFT B3PW91/6-31G(df,p)]. In solution, these compounds exist as an equilibrium of conformers with gauche- and cis-arrangement of the substituents at the phosphorus atom relative to the P=X bond (X = lone electron pair, O, S, Se).     

povel isomers of hexasulfur: Prediction of a stable prism isomer and implications for the thermal reactivity of elemental sulfur

High-level ab initio molecular orbital calculations were employed to explore the potential energy hypersurface of hexasulfur, S(6). Twelve isomeric structures of S(6) have been identified: two unbranched rings (chair and boat), one trigonal prism of D(3h) symmetry, two singly branched rings (S(5)double bondS), three triplet chains, one singlet chain, and three doubly branched rings (Sdouble bondS(4)double bondS). The prism structure is essentially a cluster of three S(2) molecules connected via a six-center pi(*)-pi(*)-pi(*) interaction. It is by 51 kJ mol(-1) less stable than the lowest-energy chair form. The reactions to generate the boat, the prism, and the singly branched isomers from the chair form are predicted to have lower barriers than the ring opening reaction of cyclo-S(6), which requires an activation energy of 149 kJ mol(-1). The prism and singly branched isomers are found to be more reactive species than the chair form and they are potential sources of S(2) in chemical reactions involving elemental sulfur.