Dependence of Spin-orbit Parameters in Al_xGa_(1-x)N/GaN Quantum Wells on the Al Composition of the Barrier

In this paper, we obtain considerable spin-orbit (SO) parameters in AlxGa1-xN/GaN quantum wells (QWs) with sheet carrier concentration Ns=120×1011/cm2 . With increasing Al content (x) of the barrier, the SO parameters increase as a whole, and the two major contributions are found to be the decrease of the expansion region of the envelope functions and the increase of the polarized electric field in the well. Compared with the Rashba parameters for the first two subbands, the intersubband SO parameter is a bit smaller and varies more slowly with x. The results indicate the SO parameters, especially the Rashba parameters can be engineered by the Al composition of the barrier, which may be helpful to the spin manipulation of III-nitride low-dimensional heterostructures.     

Influence of the Bulk and Donor-Acceptor Properties of Solvent on Ligand Field Spectra

The influence of solvents on the electronic absorption spectra of chromium (III) complexes was investigated. The dependence of the crystal field parameter Dq on dielectric constant as well as Gutmann donor number DN of solvent was found and described. By using the proposed model, unknown in the literature donor numbers for a few alcohols were estimated.     

Firm size distribution and mobility of the top 500 firms in China,the United States and the world

This paper considers the macroscopic and microscopic statistical features of the top 500 firms in China, the United States and the world, denoted as China 500 (CH500), Fortune 500 (US500) and Fortune Global 500 (FG500). From a macroscopic perspective, the firm size distribution of each category, when measured by revenue, is steadily distributed over the observed period, even during periods of financial crises. As is evidenced by the Gini coefficient, divergences between firm scales are most significant for the CH500. From a microscopic perspective, the underlying micro-dynamics are volatile and often turbulent due to the exit and entry of firms as well as shifts in their revenues and ranks. Such fluctuations, or mobility, are visualized in rank/revenue/share clocks. We also propose a revenue/rank/share mobility index that is a quantitative measurement of mobility. Among these, we find that the share mobility acts as an effective indicator of economic status; where there is a share mobility spike, there is an ailing economy. The share mobility indexes indicate that the 2008 Financial Crisis had little impact on the Chinese economy, while it triggered violent changes in the top 500 firms in the United States and the world.     

Dynamic release process of pollutants during suspended sediment transport in aquatic system

Pollutants release is highly consistent with suspended sediment concentration （SSC） in water column, especially during re-suspension and transport events. The present research focuses on pollutant dynamic release from re-suspended sediment, especially the vertical distribution relationship between them. The sediment erosion experiments on a series of uniform flow are conducted in a circulate flume. Reactive tracer （phosphorus） is used as the contaminant in fine-grained sediments to identify the release characteristic length and time. Experimental results show that the flow condition near-bed depends on the sediment surface roughness. The region with high turbulent intensities corresponds to a high concentration sediment layer. In addition, the SSC decreases with the distance, water depth, and particle grain size. The sediment in a smaller grain size takes much more time to reach equilibrium concentration. Total phosphorus （TP） concentration changes along the water depth as SSC in the initial re-suspension stage, appearing in two obvious concentration regimes： the upper low-concentration layer and the high-concentration near-bottom layer. This layered phenomenon remains for about 3 hours until SSC distri- bution tends to be uniform. Longitudinal desorption plays an important role in long-way transport to reduce the amount of suspended sediment in water column.     

Effect of external pressure on the Kβ/Kα X-ray intensity ratios of 3d metals

The occupation numbers of the 3d transition metals are calculated as a function of pressure by means of the linear muffin-tin-orbital method. This data is used with the multiconfiguration Dirac-Fock (MCDF) X-ray intensity ratios (R) to estimate the variation of the intensity ratios of 3d metals with pressure. It is found that R decreases with pressure for the early 3d metals whereas it increases for the heavier 3d transition metals.     

The Determination of Trace Elements by Flame Atomic Absorption Spectrometry: Effect of the Composition of Standard Solution Matrices

Abstract

The effect of using solution matrices in calibration standards different from those employed for the extraction steps in the determination of Cd, Cr, Cu, Ni and Zn were tested. Cu and Zn are little affected by matrix effects but, if the extractant is ammonium acetate, the use of other matrices may result in too high Cd, Cr and Ni values.