The calculation results show that the Fermi level of SnO2 is located in the band gap, and the maximum of the valence band and minimum of the conduction band are both located at Gamma point (the Brillouin zone center), indicating that SnO2 is a direct band gap semiconductor. When one of the 16 Sn atoms in the SnO2 supercell is replaced by one Sb atom, the Fermi level moves into the conduction band and the compound displays metallic characteristics in electronic band structure. For the case of an Sb impurity coexisting with
oxygen vacancies, the Fermi level is also located in the conduction band and the density of states near the Fermi level is increased comparing to that without oxygen vacancies. Moreover, some impurity bands depart JNK signaling inhibitor from the top of the valence band, which narrows the band gap of the compound. With respect to the optical properties, the presence of an Sb impurity in the supercell of SnO2 leads to the occurrence
of weak absorptions in the visible region, while the presence of oxygen vacancies reinforces the absorptions. (C) 2009 American Institute of Physics. [doi:10.1063/1.3245333]“
“One problem DMXAA supplier of polymer-modified asphalts (PMAs) is the poor compatibility between polymer and asphalts. In this article, the effects of palygorskite clay (PC) and organomodified palygorskite clay (OPC) on the Theological and morphological properties of styrene butadiene rubber (SBR) modified asphalts are investigated. The dynamic mechanical analysis (DMA) of PC and SBR/PC (OPC) modified asphalts before and after ageing has been characterized selleck chemicals llc by dynamic shear rheometer (DSR). The results indicate that the degree of SBR modification is a function of asphalt-polymer compatibility. When the polymer concentration is higher, it produces
a highly elastic network which increases the viscosity, complex modulus, and elastic response of the mixture, particularly at high service temperatures. However, ageing of the SBR and SBR-PC mixtures result in a decrease in the elastic response of the modified asphalts. It also have been confirmed that the morphology observed by optical microscopy and scanning electron microscope (SEM) revealed the better compatibility between SBR/PC and asphalt. The storage stability of binder is improved significantly. Compared with PC, OPC shows better effect in improving viscoelastic properties and rutting resistance of the mixture, which contributes to the better improvement of interfacial adhesion based on larger size between layers in OPC-modified asphalts. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 113: 2524-2535, 2009″
“Purpose To analyse the psychometric properties of the EQ-5D in German stroke survivors undergoing neurological rehabilitation.