Experimental results indicate that upconversion emission is a two-photon process. It follows that the shortening of lifetime and the increasing of intensities of red emission are due to the increase in Er3+ ions cluster sites. Excited state absorption and energy transfer processes lead to the green emission while cross relaxation process produces the red emission. (C) 2010 American Institute of Physics. [doi:10.1063/1.3475511]“
“Hybrid titanium catalysts supported on silica/poly(styrene-co-acrylic acid) (SiO(2)/PSA) core-shell carrier were
prepared and studied. The resulting catalysts were characterized by Fourier transform infrared (FTIR) spectroscopy, ICG-001 nmr laser scattering particle analyzer and scanning electronic microscope (SEM). The hybrid catalyst (TiCl(3)/MgCl(2)/THF/SiO(2)center dot TiCl(4)/MgCl(2)/PSA) showed core-shell structure and the thickness of the PSA layer in the two different hybrid catalysts was 2.0 mu m and 5.0 mu m, respectively. The activities of the hybrid catalysts were comparable to the conventional titanium-based Ziegler-Natta catalyst (TiCl(3)/MgCl(2)/THF/SiO(2)). The hybrid catalysts showed lower initial polymerization rate and longer polymerization life time compared with TiCl(3)/MgCl(2)/THF/SiO(2). The activities HTS assay of the hybrid catalysts were enhanced firstly and then decreased
with increasing PH(2)/PC(2)H(4). Higher molecular weight and broader molecular weight distribution (MWD) of polyethylene produced by the core-shell hybrid catalysts were obtained. Particularly, the hybrid catalyst with a PSA layer of 5.0 mu m obtained the longest polymerization life time with the highest activity (2071 kg PE mol(-1) Ti h(-1)) and the resulting polyethylene had the broadest MWD (polydispersity index = 11.5) under our experimental conditions. The morphology of the polyethylene particles produced by the hybrid catalysts was spherical, Kinase Inhibitor Library in vivo but with irregular subpartides due to the influence of PSA layer. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 118: 1743-1751, 2010″
“The influences of channel layer width, spacer layer width, and delta-doping density on the electron density and its distribution
in the AlSb/InAs high electron mobility transistors (HEMTs) have been studied based on the self-consistent calculation of the Schrodinger and Poisson equations with both the strain and nonparabolicity effects being taken into account. The results show that, having little influence on the total two dimensional electron gas (2DEG) concentration in the channel, the HEMT’s channel layer width has some influence on the electron mobility, with a channel as narrow as 100-130 angstrom being more beneficial. For the AlSb/InAs HEMT with a Te delta-doped layer, the 2DEG concentration as high as 9.1 X 10(12) cm(-2) can be achieved in the channel by enhancing the delta-doping concentration without the occurrence of the parallel conduction.