Size distribution of particles in part dictates the environmental behavior of particle-bound organic pollutants in the atmosphere. The present study was conducted to examine the potential mechanisms responsible for the distribution of organic pollutants in size fractionated particles and their environmental implications, using an e-waste recycling zone in South China as a case study. Size-fractionated atmospheric particles were collected at the heights of 1.5, 5, and 20 m near two residential apartments and analyzed for polybrominated diphenyl ethers (PBDEs). The concentrations of particle-bound SPBDE (sum of 18 PBDE congeners) were significantly greater at 5 and 20 m than those at 1.5 m. The size-fractionated distributions of airborne SPBDE displayed trimodal peaks in 0.10-0.18, 1.8-3.2, and 10-18 mu m at 1.5 m but only an unimodal peak in 1.0-1.8 mu m at 20 m height. Emission sources, resuspension of dust and soil, and volatility of PBDEs were important factors influencing the size distribution of particle-bound PBDEs. The dry deposition fluxes of particle-bound PBDE estimated from the measured data in the present study were approximately twice the estimated wet deposition fluxes, with a total deposition flux of 3000 ng m-2 d(-1). The relative contributions of particles to dry and wet deposition fluxes were also size-dependent, e.g., coarse (aerodynamic diameters (D-p) > 1.8 mu m) and fine (D-p < 1.8 mu m) particles dominated the dry and wet deposition fluxes of PBDEs, respectively.
Sediment microorganisms play a crucial role in a variety of biogeochemical processes in freshwater ecosystems. The objective of the current study was to investigate the spatial distribution of sediment bacterial community structure in Luoshijiang Wetland, located in Yunnan-Kweichow Plateau (China). Wetland sediments at different sites and depths were collected. Clone library analysis indicates bacterial communities varied with both sampling site and sediment depth. A total of fourteen bacterial phyla were identified in sediment samples, including Proteobacteria, Acidobacteria, Actinobacteria, Armatimonadetes, Bacteroidetes, Chlorobi, Chloroflexi, Cyanobacteria, Firmicutes, Gemmatimonadetes, Nitrospirae, Planctomycetes, Spirochaetes, and Verrucomicrobia. Proteobacteria (mainly Betaproteobacteria and Deltaproteobacteria) predominated in wetland sediments. Moreover, the proportions of Alphaproteobacteria, Acidobacteria, Bacteroidetes, Gemmatimonadete, and Planctomycetes were significantly correlated with chemical properties.
Few would deny the contribution of vocational education on economic growth and social development, but the spatial dynamics behind the economic role of vocational education in transition economies has not been examined by the literature on economics of education. Specifically, two hypotheses are tested. First, the economic growth and vocational education development have significant global spatial autocorrelation, which means the development of economy and vocational education of one province depends on the economic or education level of neighboring provinces. Second, the economic growth and vocational education development have significant local spatial autocorrelation. With per capital GDP and vocational education scale data of 31 provinces in China from 1995 to 2008, both hypotheses are supported. Finally, the results show that the elasticity with spatial metrics is 1.522, which means the stronger economic role of vocational education because the elasticity is larger than 1, while the elasticity without spatial dynamics is only 0.926 which implies the weak economic role of vocational education. It also shows that the OLS model is confronted with the risk of spurious regression without considering spatial dynamics and the spatial error model is preferred because it’s robust.
Full spatial emission characteristics of radiation generated from electron oscillations driven by a circularly polarized few-cycle laser pulse of different intensity have been investigated theoretically and numerically using a single electron model. The effect of laser pulse intensity and the initial phase on the process of full spatial characteristics of the radiation is apparent for few-cycle laser pulse. The characteristics can be used to measure the intensity and the initial phase of a circularly polarized few-cycle laser pulse in experiments.
We consider the nonlinear Dirac equation in 1+1 dimension with scalar-scalar self interaction $ \frac{ g^2}{ \kappa+1} ( {\bar \Psi} \Psi)^{ \kappa+1}$ and with mass $m$. Using the exact analytic form for rest frame solitary waves of the form $\Psi(x,t) = \psi(x) e^{-i \omega t}$ for arbitrary $ \kappa$, we discuss the validity of various approaches to understanding stability that were successful for the nonlinear Schr\"odinger equation. In particular we study the validity of a version of Derrick's theorem, the criterion of Bogolubsky as well as the Vakhitov-Kolokolov criterion, and find that these criteria yield inconsistent results. Therefore, we study the stability by numerical simulations using a recently developed 4th-order operator splitting integration method. For different ranges of $\kappa$ we map out the stability regimes in $\omega$. We find that all stable nonlinear Dirac solitary waves have a one-hump profile, but not all one-hump waves are stable, while all waves with two humps are unstable. We also find that the time $t_c$, it takes for the instability to set in, is an exponentially increasing function of $\omega$ and $t_c$ decreases monotonically with increasing $\kappa$.