Morphology-dependent redox and catalytic properties of CeO2 nanostructures: Nanowires, nanorods and nanoparticles

The redox features and the catalytic activities of ceria nanowires, nanorods and nanoparticles were comparatively studied. The morphology-dependent phenomenon is closely related to the nature of the exposed crystal planes. The CeO₂ nanoparticles mainly expose the stable {1 1 1} plane on the surface, whereas the rod-shaped nanostructures preferentially expose the reactive {1 1 0} and {1 0 0} planes, giving higher oxygen storage capacity and catalytic activity for CO oxidation. Although both the CeO₂ nanorods and the CeO₂ nanowires predominantly expose the reactive {1 1 0} and {1 0 0} planes, the CeO₂ nanowires favor to expose a large proportion of active planes on the surface, resulting in a much higher activity for CO oxidation than the nanorods.     

Two-level atom in a squeezed vacuum with finite bandwidth

Abstract

The resonance fluorescence of a two-level atom driven by a coherent laser field and damped by a finite bandwidth squeezed vacuum is analysed. We extend the Yeoman and Barnett technique to a non-zero detuning of the driving field from the atomic resonance and discuss the role of squeezing bandwidth and the detuning in the level shifts, widths and intensities of the spectral lines. The approach is valid for arbitrary values of the Rabi frequency and detuning but for the squeezing bandwidths larger than the natural line-width in order to satisfy the Markoff approximation. The narrowing of the spectral lines is interpreted in terms of the quadrature-noise spectrum. We find that, depending on the Rabi frequency, detuning and the squeezing phase, different factors contribute to the line narrowing. For a strong resonant driving field there is no squeezing in the emitted field and the fluorescence spectrum exactly reveals the noise spectrum. In this case the narrowing of the spectral lines arises from the noise reduction in the input squeezed vacuum. For a weak or detuned driving field the fluorescence exhibits a large squeezing and, as a consequence, the spectral lines have narrowed linewidths. Moreover, the fluorescence spectrum can be asymmetric about the central frequency despite the symmetrical distribution of the noise. The asymmetry arises from the absorption of photons by the squeezed vacuum which reduces the spontaneous emission. For an appropriate choice of the detuning some of the spectral lines can vanish despite that there is no population trapping. Again this process can be interpreted as arising from the absorption of photons by the squeezed vacuum. When the absorption is large it may compensate the spontaneous emission resulting in the vanishing of the fluorescence lines.     

Toxic Effects of the Major Components of Diesel Exhaust in Human Alveolar Basal Epithelial Cells (A549)

We investigated the toxicity of benzo[a]pyrene (B[a]P), 1-nitropyrene (1-NP) and 3-nitrobenzanthrone (3-NBA) in A549 cells. Cells were treated for 4 h and 24 h with: B[a]P (0.1 and 1 μM), 1-NP (1 and 10 μM) and 3-NBA (0.5 and 5 μM). Bulky DNA adducts, lipid peroxidation, DNA and protein oxidation and mRNA expression of CYP1A1, CYP1B1, NQO1, POR, AKR1C2 and COX2 were analyzed. Bulky DNA adducts were induced after both treatment periods; the effect of 1-NP was weak. 3-NBA induced high levels of bulky DNA adducts even after 4-h treatment, suggesting rapid metabolic activation. Oxidative DNA damage was not affected. 1-NP caused protein oxidation and weak induction of lipid peroxidation after 4-h incubation. 3-NBA induced lipid peroxidation after 24-h treatment. Unlike B[a]P, induction of the aryl hydrocarbon receptor, measured as mRNA expression levels of CYP1A1 and CYP1B1, was low after treatment with polycyclic aromatic hydrocarbon (PAH) nitro-derivatives. All test compounds induced mRNA expression of NQO1, POR, and AKR1C2 after 24-h treatment. AKR1C2 expression indicates involvement of processes associated with reactive oxygen species generation. This was supported further by COX2 expression induced by 24-h treatment with 1-NP. In summary, 3-NBA was the most potent genotoxicant, whereas 1-NP exhibited the strongest oxidative properties.     

红透山铜矿尾矿库表层尾矿的酸化潜力及其变化特征

试验测定红透山铜矿尾矿样品的全硫含量和酸中和潜力(ANC),计算得到净产酸潜力NAPP和净产酸量NAG,据此分析预测酸化潜力。结果表明:红透山铜矿尾矿的NAPP和NAG分别为H2SO448.85 kg/t和22.86 kg/t,NAPP和NAG试验结果都说明该尾矿有较高的产酸潜力,产酸的主要原因是尾矿中硫含量较高。NAPP在0～135 cm的平均值为48.85 kg/t,其中0～45 cm的NAPP平均为20.71 kg/t,45～135 cm的平均值为62.92 kg/t,表明酸化主要发生在0～45 cm的风化表层。尾矿45～135 cm各层的NAPP明显大于NAG,这是由于NAPP是通过对含S量和ANC的测定,再计算尾矿的产酸量,所代表的是理论值,其值往往因为SO24-的存在而大于实际产酸量,这可能是由于表层风化层的S氧化形成SO24-在下层累积所导致的。     

Application of positron annihilation spectroscopy to study recovery and recrystallization of commercial pure Al and Al-1 wt% Mn alloys

Isochronal annealing of cold worked commercial pure aluminum (99.5%) and Al-1wt% Mn alloys was demonstrated between room temperature and 823 K. The stages of recovery and recrystallization were studied using microhardness and positron annihilation lifetime measurements. Apositive correlation was established between the variation of the intensity of long lived component and Vickers microhardness with annealing temperature during the two stages of recovery, which were identified in both aluminum and Al(Mn). The retardation of the recovery stages and recrystallization in Al(Mn) alloys is interpreted in terms of precipitation of aluminum-manganese particles as well as manganese-vacancy interaction.     

Entanglement induced by spontaneous emission in spatially extended two-atom systems

Abstract

The role of the collective antisymmetric state in entanglement creation by spontaneous emission in a system of two non-overlapping two-level atoms has been investigated. Populations of the collective atomic states and the Wootters entanglement measure (concurrence) for two sets of initial atomic conditions are calculated and illustrated graphically. Calculations include the dipole-dipole interaction and a spatial separation between the atoms that the antisymmetric state of the system is included throughout even for small interatomic separations. It is shown that spontaneous emission can lead to a transient entanglement between the atoms even if the atoms were prepared initially in an unentangled state. It is found that the ability of spontaneous emission to create transient entanglement relies on the absence of population in the collective symmetric state of the system. For the initial state of only one atom excited, entanglement builds up rapidly in time and reaches a maximum for parameter values corresponding roughly to zero population in the symmetric state. On the other hand, for the initial condition of both atoms excited, the atoms remain unentangled until the symmetric state is depopulated. A simple physical interpretation of these results is given in terms of the diagonal states of the density matrix of the system. We also study entanglement creation in a system of two non-identical atoms of different transition frequencies. It is found that the entanglement between the atoms can be enhanced compared to that for identical atoms, and can decay with two different time scales resulting from the coherent transfer of the population from the symmetric to the antisymmetric state. In addition, it was found that a decaying initial entanglement between the atoms can display a revival behaviour.     

基于电容放电特征的柔性直流配电网线路保护方案

针对换流设备直接接入直流母线的双端柔性直流配电网的保护配置问题,提出一种基于单端电气量的线路保护方案。首先分析了双端柔性直流配电网的直流线路故障特征,其次重点分析了处于不同母线处的换流器并联电容之间的放电特征差异。结合该差异设计出能够有效识别故障区域、在5 ms内隔离故障的主保护。同时为解决主保护可能存在检测失败的问题,设置了利用过电流判据以及动作延时的后备保护方案。最后通过PSCAD/EMTDC搭建仿真模型验证了所提方案的有效性。     

Lithium therapy and drinking water

ain causes of failure and giving up in psychotropic lithiotherapics because of instable lithiemy to the same patient or functional acute renal insufficiency, are principaly mistaken diets, those mistaken concerning the amount, the quality and the way of taking drinking water and other beverages. Lithium salt, taken either in two times, morning and evening, or in one, must be absorbed at the end of a solid meal with at least 25 cl. of water. The patient must absorb at least 1.5 l. of water per day, and up to 3 l. in case of physical efforts or heat. The pH of this water and it ionic compound should be stable, as close as possible to the plasma's, without additives that could change its taste. This includes cooking water and infusions. Physicopharmacological explanations.     

Estimating energy consumption from night-time DMPS/OLS imagery after correcting for saturation effects

A methodology is presented to accurately estimate electric power consumption from saturated night-time Defense Meteorological Satellite Program (DMSP) Operational Linescan System (OLS) imagery using a stable light correction. An area correction for the stable light image of DMSP/OLS for the year 1999 was performed and the build-up area rate data were used to clarify the intensity distribution characteristics of the stable light. Based on the spatial distribution characteristics of the stable light, the saturation light of the electric power supply area of Japan was corrected using a cubic regression equation. The regression between the correction calculations by the cubic regression equation and the statistical electric power consumption data was applied in Japan and also in China, India and 10 other Asian countries. The correction method was then evaluated. This study confirms that electric power consumption can be estimated with high precision from the stable light.     

Reaction kinetics and producer gas compositions of steam gasification of coal and biomass blend chars, part 1: Experimental investigation

Biomass and coal are important solid fuels for generation of hydrogen-rich syngas from steam gasification. In this work, experiments were performed in a bench-scale gasifier to investigate the effect of coal-to-biomass ratio and the reaction kinetics for gasification of chars of biomass, coal and coal–biomass blends. In the gasification of these chars, steam was used as the gasification agent, while nitrogen was used as a gas carrier. The gasification temperature was controlled at 850, 900 and 950 °C. Gas produced was analysed using a micro-GC from which carbon conversion rate was also determined. From the experiments, it is found that the coal and biomass chars have different gasification characteristics and the overall reaction rate decreases with an increase in the ratio of coal–to-biomass.The microstructure of the coal char and biomass char was examined using scanning electronic microscopy (SEM), and it was found that the biomass char is more amorphous, whereas the coal char has larger pore size. The former enhances the intrinsic reaction rate and the latter influences the intra particle mass transportation. The difference in mass transfer of the gasification agent into the char particles between the two fuels is dominant in the char gasification.