Lateral spin-orbit interaction and spin polarization in quantum point contacts

We study ballistic transport through semiconductor quantum point contact systems under different confinement geometries and applied fields. In particular, we investigate how the {\em lateral} spin-orbit coupling, introduced by asymmetric lateral confinement potentials, affects the spin polarization of the current. We find that even in the absence of external magnetic fields, a variable {\em non-zero spin polarization} can be obtained by controlling the asymmetric shape of the confinement potential. These results suggest a new approach to produce spin polarized electron sources and we study the dependence of this phenomenon on structural parameters and applied magnetic fields. This asymmetry-induced polarization provides also a plausible explanation of our recent observations of a 0.5 conductance plateau (in units of $2e^2/h$) in quantum point contacts made on InAs quantum-well structures. Although our estimates of the required spin-orbit interaction strength in these systems do not support this explanation, they likely play a role in the effects enhanced by electron-electron interactions.Comment: Summited to PRB (2009

Anaerobic membrane bioreactors for future green bioprocesses

© 2016 American Society of Civil Engineers. This chapter focuses on the comprehensive overview of the recent progress in anaerobic membrane bioreactor (AnMBR) applications, including the fundamental aspects and development of AnMBR processes. For a future green bioprocess, the chapter discusses the application development of AnMBRs in domestic and industrial wastewater treatment, opportunities for biogas production and waste minimization and membrane fouling researches. The anaerobic treatment processes are known to have the inherent advantages over the aerobic counterparts, such as sludge minimization and energy savings. The key competitive advantages of AnMBRs over conventional aerobic and anaerobic processes include total biomass retention, excellent effluent quality, bioenergy recovery, smaller footprint, lower energy consumption, high efficiency of wastewater treatment, and strong ability of handling fluctuation in influent quality. Biogas recovery represents one of the key green features of AnMBR technology, particularly for submerged AnMBR (SAnMBR). The compact configure of SAnMBR allows for more convenient collection of biogas

Occurrence, fate and health risk assessment of 10 common antibiotics in two drinking water plants with different treatment processes

© 2019 Elsevier B.V. The occurrence of antibiotics in drinking water has become a serious problem worldwide as they are a potential and real threat to human health. In this study, the variability of 10 typical antibiotics in two drinking water plants was investigated in two seasons (n = 12). The total concentrations of target antibiotics in raw water were significantly higher in winter than in summer, which may be attributed to the more frequent occurrence of colds and respiratory diseases as well as less rainfall in winter. The efficiency in removing the antibiotics varied from −46.5% to 45.1% in water plant A (WP-A) using a conventional process and 40.3% to 70.3% in water plant B (WP-B) with an advanced treatment process. Results indicated that the antibiotics in WP-A were mainly removed via the coagulation process. However in WP-B, the ultraviolet + chlorination process played a key role in antibiotics removal, followed by the pre-ozone + coagulation process. According to the human health risk assessment, it was suggested that the risk of drinking water was significantly higher than that of skin contact. However, the risk of carcinogenesis and non-carcinogenesis caused by antibiotics was at an acceptable level

Assessing the Effect of High Performance Computing Capabilities on Academic Research Output

This paper uses nonparametric methods and some new results on hypothesis testing with nonparametric efficiency estimators and applies these to analyze the effect of locally-available high performance computing (HPC) resources on universities efficiency in producing research and other outputs. We find that locally-available HPC resources enhance the technical efficiency of research output in Chemistry, Civil Engineering, Physics, and History, but not in Computer Science, Economics, nor English; we find mixed results for Biology. Out research results provide a critical first step in a quantitative economic model for investments in HPC

Removal of antibiotics (sulfamethazine, tetracycline and chloramphenicol) from aqueous solution by raw and nitrogen plasma modified steel shavings

© 2017 Elsevier B.V. The removal of sulfamethazine (SMT), tetracycline (TC) and chloramphenicol (CP) from synthetic wastewater by raw (M3) and nitrogen plasma modified steel shavings (M3-plN2) was investigated using batch experiments. The adsorption kinetics could be expressed by both pseudo-first-order kinetic (PFO) and pseudo-second-order kinetic (PSO) models, where correlation coefficient r2 values were high. The values of PFO rate constant k1p and PSO rate constant k2p decreased as SMT-M3 > SMT-M3-plN2 > TC-M3-plN2 > TC-M3 > CP-M3 > CP-M3-plN2 and SMT-M3 > SMT-M3-plN2 > TC-M3 > TC-M3-plN2 > CP-M3 > CP-M3-plN2, respectively. Solution pH, adsorbent dose and temperature exerted great influences on the adsorption process. The plasma modification with nitrogen gas cleaned and enhanced 1.7-fold the surface area and 1.4-fold the pore volume of steel shavings. Consequently, the removal capacity of SMT, TC, CP on the adsorbent rose from 2519.98 to 2702.55, 1720.20 to 2158.36, and 2772.81 to 2920.11 μg/g, respectively. Typical chemical states of iron (XPS in Fe2p3 region) in the adsorbents which are mainly responsible for removing antibiotics through hydrogen bonding, electrostatic and non- electrostatic interactions and redox reaction were as follows: Fe3O4/Fe2 +, Fe3O4/Fe3 +, FeO/Fe2 + and Fe2O3/Fe3 +

Food waste based biochars for ammonia nitrogen removal from aqueous solutions

© 2019 Elsevier Ltd Biochar derived from waste has been increasingly considered as a potential green adsorbent due to its significant ability and affordable production costs. This study prepared and evaluated 7 types of food waste-based biochars (FWBBs) (including meat and bone, starchy staples, leafy stemmed vegetables, nut husks, fruit pericarp, bean dreg and tea leaves). The impacts of raw materials, pyrolysis temperatures (300, 400, 500, 600 and 700 °C), and residence time (2 h and 4 h) on the removal of ammonia nitrogen at different ammonia nitrogen concentrations (5, 10, 20, 50, 100, 150 mg/L) were investigated. The batch equilibrium and kinetic experiments confirmed that a FWBB dosage of 3 g/L at 25 °C could remove up to 92.67% ammonia nitrogen. The Langmuir isotherm model had the best fit to equilibrium experimental data with a maximum adsorption capacity of 7.174 mg/g at 25 °C. The pseudo-second order kinetic model well describes the ammonia nitrogen adsorption

Carbohydrate-based activated carbon with high surface acidity and basicity for nickel removal from synthetic wastewater

© The Royal Society of Chemistry. The feasibility of preparing activated carbon (AC-CHs) from carbohydrates (glucose, sucrose and starch) with phosphoric acid activation was evaluated by comparing its physicochemical properties and Ni(ii) adsorption performance with a reference activated carbon (AC-PA) derived from Phragmites australis. The textural and chemical properties of the prepared activated carbon were characterized by N2 adsorption/desorption isotherms, SEM, Boehm's titration and XPS. Although AC-CHs had much lower surface area (less than 700 m2 g-1) than AC-PA (1057 m2 g-1), they exhibited 45-70% larger Ni(ii) adsorption capacity which could be mainly attributed to their 50-75% higher contents of total acidic and basic groups. The comparison of XPS analyses for starch-based activated carbon before and after Ni(ii) adsorption indicated that Ni(ii) cation combined with the oxygen-containing groups and basic groups (delocalized π-electrons) through the mechanisms of proton exchange, electrostatic attraction, and surface complexation. Kinetic results suggested that chemical reaction was the main rate-controlling step, and a very quick Ni(ii) adsorption performance of AC-CHs was presented with ∼95% of maximum adsorption within 30 min. Both adsorption capacity and rate of the activated carbon depended on the surface chemistry as revealed by batch adsorption experiments and XPS analyses. This study demonstrated that AC-CHs could be promising materials for Ni(ii) pollution minimization

Nitrous oxide generation in denitrifying phosphorus removal process: Main causes and control measures

Despite the many benefits of denitrifying phosphorus removal process, the significant generation of nitrous oxide (N2O), a potent greenhouse gas, remains a problem for this innovative and promising process. To better understand and more effectively control N2O generation in denitrifying phosphorus removal process, batch experiments were carried out to investigate the main causes of N2O generation, based on which the control measures were subsequently proposed. The results showed that N2O generation accounted for 0.41 % of the total nitrogen removal in denitrifying phosphorus removal process, whereas, in contrast, almost no N2O was generated in conventional denitrification process. It was further demonstrated that the weak competition of N2O reductase for electrons and the high nitrite accumulation were the two main causes for N2O generation, evidenced by N2O production and reduction rates under different conditions. Accordingly, the reduction of N2O generation was successfully achieved via two control measures: (1) the use of continuous nitrate addition reducing N2O generation by around 91.4 % and (2) the use of propionate as the carbon source reducing N2O generation by around 69.8 %. © 2013 Springer-Verlag Berlin Heidelberg

Characteristics of electron transport chain and affecting factors for thiosulfate-driven perchlorate reduction

© 2017 Elsevier Ltd The mechanism for perchlorate reduction was investigated using thiosulfate-driven (T-driven) perchlorate reduction bacteria. The influences of various environmental conditions on perchlorate reduction, including pH, temperature and electron acceptors were examined. The maximum perchlorate removal rate was observed at pH 7.5 and 40 °C. Perchlorate reduction was delayed due to the coexistence of perchlorate-chlorate and perchlorate-nitrate. The mechanism of the T-driven perchlorate reduction electron transport chain (ETC) was also investigated by utilizing different inhibitors. The results were as follows: firstly, the NADH dehydrogenase was not involved in the ETC; secondly, the FAD dehydrogenase and quinone loop participated in the ETC; and thirdly, cytochrome oxidase was the main pathway in the ETC. Meanwhile, microbial consortium structure analysis indicated that Sulfurovum which can oxidize sulfur compounds coupled to the reduction of nitrate or perchlorate was the primary bacterium in the T-driven and sulfur-driven consortium. This study generates a better understanding of the mechanism of T-driven perchlorate reduction

N<inf>2</inf>O reduction during municipal wastewater treatment using a two-sludge SBR system acclimatized with propionate

A two-sludge denitrifying phosphorus removal process (A2N-SBR), acclimatized with propionate, was proposed as an efficient method for nitrous oxide (N2O) reduction during municipal wastewater treatment. Compared with the conventional nitrification-denitrification process (AO-SBR) operated in parallel, the A2N-SBR not only significantly improved total nitrogen and soluble phosphorus removal efficiencies by around 32.3% and 23.5%, respectively, but also greatly reduced N2O generation by around 31.5%. Moreover, like the anoxic stage of AO-SBR, nearly zero N2O (merely 0.054% of the removed nitrogen) was generated during the anoxic stage of A2N-SBR. The substantial N2O reduction achieved in the proposed A2N-SBR can be reasonably explained by: (i) the use of independent nitrification reactor resulting in higher activity of nitrifying bacteria and no occurrence of heterotrophic denitrification in aerobic stage, and (ii) the use of propionate as carbon source decreasing nitrite accumulation in anoxic stage. © 2013 Elsevier B.V