Assessment of natural radionuclides and their radiological hazards in commercial granite produced in Xinjiang,China

ABSTRACT

The specific activities of ²²⁶Ra, ²³²Th and ⁴⁰K of 26 samples of granite produced in Xinjiang of China were measured by a high-purity germanium detector, and their radiological hazards of radium equivalent, external hazard index, internal hazard index, absorbed dose rate, annual effective dose rate, gamma index and alpha index were evaluated. The results indicate that the overall average specific activities of ²²⁶Ra, ²³²Th and ⁴⁰K obtained in the investigated samples are below the world’s average granite values. The average radium equivalent is within the recommended limit of 370?Bq?kg^?1. The results obtained further show that the mean values of external hazard index, internal hazard index, absorbed dose rate, annual effective dose rate, gamma index and alpha index are 0.65, 0.77, 111.7?nGy?h^?1, 0.55 mSv?y^?1, 0.89 and 0.23, respectively. These mean values established that radiological hazards are also found to be below the international recommended values. The results are compared with granite samples from other countries or China-Taiwan province. It can be noticed that the specific activity values of granite samples produced in China are lower or similar to that of other countries or China-Taiwan province, however there are higher specific activity values for ²²⁶Ra and ²³²Th in individual samples, which need to provide proper radiation monitoring before use considering the long term health effect.     

大体积生物材料低温保存方法的研究

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全氟辛酸致小鼠肝脏氧化损伤的实验

研究了低（1mg/kg/d）、中（5mg/kg/d）、高（25mg/kg/d）三个剂量组全氟辛酸（Perfluorooctanoic acid,PFOA）致小鼠肝脏脂质过氧化损伤的作用.结果发现,PFOA能抑制小鼠体重的增长,对肝组织造成一定的脂质过氧化损伤.各组小鼠出现不同程度的体重增长缓慢甚至减轻,中、高剂量组出现明显的减轻（P＜0.01）;低、中、高剂量组肝脏系数,均明显高于对照组（P＜0.01）;与对照组相比,各剂量组的肝组织中MDA、NO及LDH含量明显增高,SOD、SDH及GSH-Px活性均明显降低（P＜0.05）.     

铁皮石斛药用成分研究进展

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Toeplitz Operators from One Fock Space to Another

In this paper, we study Toeplitz operators T _μ from one Fock space \({F^{p}_{\alpha}}\) to another \({F^{q}_{\alpha}}\) for 1 < p, q < ∞ with positive Borel measures μ as symbols. We characterize the boundedness (and compactness) of \({T_\mu: F^{p}_{\alpha} \to F^{q}_{\alpha}}\) in terms of the averaging function \({\widehat{\mu}_r}\) and the t-Berezin transform \({\widetilde{\mu}_t}\) respectively. Quite differently from the Bergman space case, we show that T _μ is bounded (or compact) from \({F^{p}_{\alpha}}\) to \({F^{q}_{\alpha}}\) for some p ≤ q if and only if T _μ is bounded (or compact) from \({F^{p}_{\alpha}}\) to \({F^{q}_{\alpha}}\) for all p ≤ q. In order to prove our main results on T _μ , we introduce and characterize (vanishing) (p, q)-Fock Carleson measures on C ⁿ .     

Generalized Einstein relation and the Metzler-Klafter conjecture in a composite-subdiffusive regime

In this paper, a generalized diffusion model driven by the composite-subdiffusive fractional Brownian motion (FBM) is employed. Based on this stochastic process, we derive a fractional Fokker-Planck equation (FFPE) and obtain its solution. It is proved that the Generalized Einstein Relation (GER) and the Metzler and Klafter conjecture on the asymptotic behavior of stretched Gaussian hold the FFPE in a composite-subdiffusive regime.     

Effect of annealing temperature on photocatalytic activity of ZnO thin films prepared by sol-gel method

Zinc oxide thin films are deposited on Si and quartz substrates using the sol-gel method. The thin films, annealed at 400, 600 and 800 °C respectively, are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), ultraviolet-visible spectrophotometer (UV-Vis), fluorescence spectrometer (FL) and the photocatalytic activity is tested by the decomposition of methyl orange dye under UV illumination. The results show that the mean grain size, surface-to-volume ratio, rms roughness and degradation efficiency of the thin films increases with increasing annealing temperature. In particular, ZnO thin film annealed at 800 °C exhibits the highest photocatalytic activity, degrading methyl orange by almost 88% in 180 min. Photocatalytic reaction mechanism of the ZnO thin films is discussed in detail, and the oxygen defects are proposed to be the active sites of the ZnO photocatalyst.     

First-principles study of structural, electronic and elastic properties of single crystal CuZr

Investigations into the structural, electronic and elastic properties of intermetallic CuZr compound had been conducted by the plane-wave pseudopotential method. The calculated lattice constant was consistent well with the experimental value. The absence of band gap and finite value of the density of states (DOS) at the Fermi level reveal the metallic behavior of CuZr crystal, and Zr 4d states give rise to the electrical conductivity. The calculated elastic constants for single crystal CuZr at zero pressure obey the cubic mechanical stability condition, which indicates that the cubic CuZr crystal is mechanical stable at zero pressure. By analyzing the ratio between the bulk and shear moduli, we conclude that CuZr crystal is ductile in nature. The present theoretical investigations might give prediction to polycrystalline CuZr system.     

Programming resistive switching memory by a charged capacitor

The performances of bulk-heterojunction (BHJ) solar cells are investigated for time-dependent thermal annealing with different morphology evolution scales, having special consideration for the diffusion and aggregation of fullerene derivative molecules based on blends of poly(3-hexylthiophene):[6,6]-phenyl-C₆₁-butyric acid methyl ester (P3HT:PCBM). Meaningfully, rapid formation of dot-like and needle-like crystalline PCBM structures of a few micrometers up to 60 μm in size is obtained with thermal annealing treatment from 2 to 15 min, which dynamically reflects a fast process of PCBM molecule and cluster aggregation. Upon ultrasonic-assisted processing and annealing treatment, the scale of P3HT crystals is drastically increased in view of X-ray diffraction (XRD) patterns, leading to a high hole mobility. And, the P3HT domains can be gradually converted into larger P3HT crystals approved by the decreased full width at half-maximum in the XRD patterns. Corresponding current–voltage curves are measured in quantity and we propose a model to explain the effect of the crystalline degree of P3HT domains and aggregation of PCBM molecules and clusters on the phase segregation, expressing a viewpoint towards high performance of BHJ solar cells.     

Preferred structures of the atomic Ag islands on silicone oil surfaces

Varying the substrate temperature T(s) from 285 to 353 K, both the aggregation behavior of Ag atoms and the preferred structures of the atomic Ag islands on silicone oil surfaces are investigated. After deposition, the deposited Ag atoms form isolated islands with a preferred height. Our observations reveal that, as T(s) increases, the preferred island height increases from 20.0 to 33.0 nm, which results in the decrease of the Ag apparent coverage, from 9.6 ± 0.1% to 6.5 ± 0.3%. Further, the crystal structure of the Ag islands changes from amorphous to polycrystalline as the substrate temperature T(s) goes up. Subsequently a 3D aggregation mechanism of the Ag atoms on the liquid substrates is proposed.