Study on the immobilisation mechanism of chromium under microwave sintering

Chromium (Cr) salts have been widely used in various industries and the discharged waste has caused soil contamination. Among them, Cr(VI) is the main concern due to its high solubility and strong carcinogenic properties. This paper compares the performance of a novel microwave sintering technique with the conventional sintering technique for immobilising Cr contaminated soil. The most significant advantage of the microwave sintering is that it can provide controlled atmosphere (such as reduction atmosphere), which means Cr(Vl) can be reduced to less hazardous Cr(III) during the sintering process. The potential secondary contamination can, thus, be significantly reduced. The XRD results show that with microwave sintering, stronger and sharper peaks were observed, indicating minerals with higher crystallinity have been formed. On the other hand, the SEM results reveal that with conventional electric sintering, the microstructure was dominated by glassy phases, whilst a mixture of glassy and crystalline phases has been identified with microwave sintering. The leaching results show that the contaminated soil processed with microwave has met both British and Chinese leaching standards, and is better than that from the electric sintering technique

An elitism-based multi-objective evolutionary algorithm for min-cost network disintegration

Network disintegration or strengthening is a significant problem, which is widely used in infrastructure construction, social networks, infectious disease prevention and so on. But most studies assume that the cost of attacking anyone node is equal. In this paper, we investigate the robustness of complex networks under a more realistic assumption that costs are functions of degrees of nodes. A multi-objective, elitism-based, evolutionary algorithm (MOEEA) is proposed for the network disintegration problem with heterogeneous costs. By defining a new unit cost influence measure of the target attack node and combining with an elitism strategy, some combination nodes’ information can be retained. Through an ingenious update mechanism, this information is passed on to the next generation to guide the population to move to more promising regions, which can improve the rate of convergence of the proposed algorithm. A series of experiments have been carried out on four benchmark networks and some model networks, the results show that our method performs better than five other state-of-the-art attack strategies. MOEEA can usually find min-cost network disintegration solutions. Simultaneously, through testing different cost functions, we find that the stronger the cost heterogeneity, the better performance of our algorithm

Ambient Aqueous Growth of Cu2Te Nanostructures with Excellent Electrocatalytic Activity toward Sulfide Redox Shuttles.

A new aqueous and scalable strategy to synthesize surfactant-free Cu2Te nanotubes and nanosheets at room temperature has been developed. In aqueous solution, Cu2E (E = O, S, Se) nanoparticles can be easily transformed into Cu2Te nanosheets and nanotubes via a simple anion exchange reaction under ambient conditions. The formation of Cu2Te nanosheets is ascribed to a novel exchange-peeling growth mechanism instead of simple Kirkendall effect; and the resultant nanosheets can be further rolled into nanotubes with assistance of stirring. The morphologies of Cu2Te nanosheets and nanotubes can be easily controlled by changing the synthesis parameters, such as the concentration of precursors, the size of nanoparticle precursor, and the amount of NaBH4, as well as the stirring speed. Thus-formed Cu2Te nanostructures exhibit excellent catalytic activity toward sulfide redox shuttles and are exploited as counter electrodes catalysts for quantum dot sensitized solar cells. The performance of Cu2Te nanostructures strongly depends on their morphology, and the solar cells made with counter electrodes from Cu2Te nanosheets show the maximum power conversion efficiency of 5.35%

Quality control of natural product medicine and nutrient supplements

10.1155/2013/182573Journal of Analytical Methods in Chemistry2013

Effect of nitrogen fertilization on net nitrogen mineralization in grassland soil of Northern China: implications for grassland management

Nitrogen (N) applications can have a significant effect on soil N availability. The effect of 3 years of N fertilization on soil net N mineralization during the growing season (May–September) was studied in 2005 and 2006 in grassland of northern China. The experimental design was a randomized complete block with four replications of five rates of N addition as urea (0, 2, 4, 8 and 16 g N m−2 year−1). Results indicated that net N mineralization rate varied seasonally and between years, ranging from −0.04 to 0.52 μg g−1 d−1 in 2005 and from −0.09 to 0.39 μg g−1 d−1 in 2006. Mean N mineralization and nitrification rates were highest in July, in 2005 and 2006, whereas highest ammonification rates occurred in September. Rainfall was significantly correlated with net nitrification. In comparison with the untreated control, N mineralization increased sharply when N fertilization increased from 2 to 8 g N m−2 year−1. Mobile soil NO3− accumulated late in the growing season for the 16 g N m−2 year−1 treatment, suggesting the potential for NO3 and associated cation leaching. These results suggest that N fertilization of 8 g N m−2 year−1 (80 kg N ha−1) is suitable for the management of grassland ecosystems of Inner Mongolia

Measurements and ab initio Molecular Dynamics Simulations of the High Temperature Ferroelectric Transition in Hexagonal RMnO3

Measurements of the structure of hexagonal RMnO3 (R=rare earths (Ho) and Y) for temperatures significantly above the ferroelectric transition temperature (TFE) were conducted to determine the nature of the transition. The local and long range structural measurements were complemented by ab initio molecular dynamics simulations. With respect to the Mn sites in YMnO3 and HoMnO3, we find no large atomic (bond distances or thermal factors), electronic structure changes or rehybridization on crossing TFE from local structural methods. The local symmetry about the Mn sites is preserved. With respect to the local structure about the Ho sites, a reduction of the average Ho-O bond with increased temperature is found. Ab initio molecular dynamics calculations on HoMnO3 reveal the detailed motions of all ions. Above ~900 K there are large displacements of the Ho, O3 and O4 ions along the z-axis which reduce the buckling of the MnO3/O4 planes. The changes result in O3/O4 ions moving to towards central points between pairs of Ho ions on the z-axis. These structural changes make the coordination of Ho sites more symmetric thus extinguishing the electric polarization. At significantly higher temperatures, rotation of the MnO5 polyhedra occurs without a significant change in electric polarization. The born effective charge tensor is found to be highly anisotropic at the O sites but does not change appreciably at high temperatures