Epoxidation reaction of perfluoroalkenes with tert-amine N-oxide

Straight-chain aliphatic terr-amine N-oxides were found to be useful oxidizing agent for epoxidation of tri- and tetra-substituted perfluoroalkenes under mild conditions in high yields.The process for epoxidation by employing tri-n-butylamine N-oxide gave the best result in the reagent survey.     

Acoustical wave propagator for time-domain dynamic stress concentration in a plate with a sharp change of section

The acoustical wave propagator technique is applied to study the time-domain dynamic stress concentration in a two-dimensional flexible plate with a sharp change of section. As a wave packet approaches the plate discontinuity where the sharp change of thickness is introduced, the spatial interference patterns in the displacement of the plate and internal stresses vary with time. The constructive interference of stresses is referred to as time-domain stress concentration. The superposition of wave fronts of incident and reflected wave packets is used to explain the spatial distribution of the interference patterns. The increase of dynamic stress near the vicinity of the discontinuity boundary of the plate is studied as a function of time and the thickness ratio of the plates.     

Investigation of nanostructured Fe3O4 polypyrrole core-shell composites by X-ray absorbtion spectroscopy and X-ray diffraction using synchrotron radiation

In this article, we focus on the structural peculiarities of nanosized Fe₃O₄ in the core-shell nanocomposites obtained by polymerization of conducting polypyrrole shell around Fe₃O₄ nanoparticles. The local structure of Fe atoms was determined from the Extended X-ray Absorption Fine Structure analysis using our own package computer programs. An X-ray diffraction method that is capable to determine average particle size, microstrains, as the particle size distribution of Fe₃O₄ nanoparticles is presented. The method is based on the Fourier analysis of a single X-ray diffraction profile using a new fitting method based on the generalized Fermi function facilities. The crystallites size obtained by X-ray diffraction spectra analysis was estimated between 3.2 and 10.3 nm. Significant changes in the first and the second Fe coordination shell in comparison with standard bulk were observed. The global and local structure of the nanosized Fe₃O₄ are correlated with the synthesis conditions of the core-shell polypyrrole nanocomposites.     

Synthesis of Fischer indole derivatives using carboxyl-functionalized ionic liquid as an efficient and recyclable catalyst

Fischer indole cyclization of phenylhydrazine and various ketones using carboxyl-functionalized ionic liquid, 1-carboxymethyl-3-methylimidazolium tetrafluoroborate (abbreviated as [cmmim][BF4]) as catalyst was successfully performed. The yields of thetarget compounds were 80-92%, the purities were 96-98%. The catalyst could be rocovered and reused for at least six times without significant loss in activity.     

Molecular modeling of epsilon RNA from hepatitis B virus

An initial model of the HBV epsilon RNA was built by the Biopolymer module of InsightⅡ.While its three-dimensional structure was obtained through structure optimization based on molecular dynamics simulation,the two active sites were found.A comparison with the experimental result indicated that the active sites may be the binding sites of the epsilon RNA in the RT-epsilon interaction.The result will be helpful to further discussion about the mechanism of RT-epsilon interaction and the study of HBV genom...     

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.     

EPR investigation of nanosized La0.67Ca0.33MnO3−δ manganites

We report an electron paramagnetic resonance (EPR) investigation of the spin dynamics in the paramagnetic regime of nanosized La_0.67Ca_0.33MnO_3?δ manganites. The temperature dependences of the EPR line width and integral intensity have been analyzed in terms of the bottlenecked spin relaxation and small polaron hopping scenarios. The exchange coupling integral between Mn³⁺ and Mn⁴⁺ ions and the polaron activation energy decrease with the reduction of grain size. A discussion is given concerning the factors which could explain the observed changes.     

Interface charge transfer process in ZnO:Mn/ZnS nanocomposites

Journal of Nanoparticle Research - TiO2 photocatalysts co-doped with F and Fe were synthesized by a sol–gel method. Synergistic effects of F and Fe in the co-doped TiO2 were verified by NH3...     

Combustion of preheated raw animal fats-diesel fuel blends at diesel engine

Journal of Thermal Analysis and Calorimetry - Because of pollution problems, after the Mayors Summit 2016 takes place, certain European capital cities want to be free from diesel engines automotive...     

Experimental investigation of the magnetic structure of domain walls in thin ferromagnetic films

The structure of domain walls in thin magnetic films has been studied by the Lorentz method using electron microscopy. The possible existence of the coinciding and opposite directions of rotation of the magnetization vector in Néel domain walls has been proved experimentally. The domain walls separating 90° domains have been found in single-crystal magnetic films. These walls consist of domains with a considerably smaller area than 90° domains.