Effect of oxygen content and charge on the structure,stability and optoelectronic properties of yttrium oxide clusters

The electronic and geometrical structures of neutral and charged YOn (n=2–12) clusters have been investigated using density functional theory (DFT) with generalized gradient approximation. The oxygen atom in YOn has been found to be in oxo, peroxo and in superoxo forms. The geometrical structures and topologies of small size anionic clusters resemble that of neutral clusters. Yttrium showed higher coordination number than scandium. Computed results reveal the existence of YO₁₀ cluster to have a penta-peroxo oxygen with a homoleptic Y(η² –O₂)₅ geometrical configuration. The HOMO–LUMO gaps decrease with increasing n due to the increase in 2p orbital population of oxygen atoms. It has been shown that in these clusters bonding are predominantly ionic in nature and anions are thermodynamically more stable, due to the charge delocalization between the metal atom and oxygen ligands. YO₁₀⁺ and YO₁₂⁺ were found to be highly exothermic to release one and two oxygen molecules, while YO₁₁⁺ dissociates though the ozonide dissociation channel. Computed absorption spectra of small clusters are mainly contributed by yttrium metal d and s valence orbitals. The absorbance spectra, shifts towards lower energy with cluster size increase, while charge has no substantial effect on the absorption spectrum.     

分散液液微萃取-气相色谱-质谱法测定水样中4种环境激素

以四氯乙烯作萃取剂,以四氢呋喃为分散剂对水样中4种环境激素甲草胺、乙草胺、三唑酮和三唑醇进行分散液液微萃取。提取液用气相色谱-质谱法测定。4种环境激素的质量浓度与其相应峰面积均在0.05～100μg.L-1范围内呈线性关系。甲草胺、乙草胺、三唑酮和三唑醇的检出限(3S/N)分别为0.016,0.015,0.023,0.032μg.L-1。在0.2,2.0mg.kg-1两个添加水平下进行回收试验,4种环境激素的回收率在86.8%～118%之间,测定值的相对标准偏差(n=6)在2.1%～6.2%之间。     

桑蚕成品卵微粒子病抽样检验样本容量的确定

蚕业生产上对桑蚕种成品卵微粒子病控制得很严,要求将总体病卵率为0.15%的蚕种以98.5%的概率将其判为不合格。在此标准下,运用概率统计方法,给出了抽样检验时样本最少抽检量为2800粒。并在控制把合格蚕种判为不合格蚕种要求下,给出了抽样检验时确定样本容量的数学模型。     

Bilateral Counterparty Risk Valuation on a CDS with a Common Shock Model

In this paper, we study the counterparty risk on a CDS in a common shock model. We introduce the general arbitrage-free valuation framework for counterparty risk adjustments in presence of bilateral default risk. Especially, we consider the pricing problem of credit default swap with counterparty risk under a common shock model with regime switching. The arrivals of the shock events are modeled by conditionally independent Cox processes whose stochastic intensities depend on the state of the economy described by a Markov chain. We give the explicit formula for the credit valuation adjustment (CVA) and examine the impact of the change of economic state on the CVA.     

Radionuclide 188Re-Loaded Photothermal Hydrogel for Cancer Theranostics

Herein, an injectable photothermal hydrogel system containing a therapeutic radionuclide ¹⁸⁸Re is studied for combined radioisotope therapy and photothermal therapy (PTT) of cancer. A dopamine-conjugated poly(α,β-aspartic acid) copolymer (PDAEA) is used to trigger a sol–gel phase transition in mixture with Fe³⁺ ions, rapidly forming a gel by simply mixing PDAEA and FeCl₃ phosphate buffer saline solutions. The injectable hydrogel exhibits strong near-infrared light absorbance and can efficiently convert light into a heating effect for local PTT treatment. The obtained hydrogel possesses a porous 3D microstructure, and can be utilized for radionuclide loading. After the Na¹⁸⁸ReO₄ loading, the hydrogel is intratumorally injected into the tumor of mice bearing 4T1 murine breast cancer cells for studying the tumor retention and therapeutic efficiency. In vivo results show that Na¹⁸⁸ReO₄-loaded hydrogel exhibits significantly longer time in the tumor sites than that of free Na¹⁸⁸ReO₄. The tumor growth of mice treated with Na¹⁸⁸ReO₄-loaded hydrogel under near-infrared radiation is significantly inhibited compared with control groups. Therefore, the results show that the developed strategy using an injectable and biocompatible hydrogel may promote the applications of radioisotope therapy and photothermal therapy for cancer.     

Decomposition of default probability under a structural credit risk model with jumps?

In this paper, we consider the default probabilities caused by a jump or by oscillation under a structural credit risk model with jumps. We study the Laplace transforms of the times of default caused by a jump and by oscillation. We derive integro-differential equations and obtain some closed-form expressions for them. By inverting them, we numerically investigate the contributions of the jump component and the diffusion component to the default under a certain choice of the jump size distribution.     

单驱动仿生机器鱼动力特性的实验研究

根据变截面悬臂梁受迫振动响应来模拟鱼体变形,并设计了单驱动仿生机器鱼,进行了机器鱼直线巡游、转弯和加速-滑行实验。由高速摄像机记录机器鱼运动过程,对序列图像进行处理,获得机器鱼动力特性。结果表明：单驱动机器鱼最大稳态速度约为1BL/s,最小转弯半径约为270mm,尾流动力特性良好;论证了摆动频率与摆幅对速度的影响以及摆幅与速度对转弯半径的影响;在加速滑行时间比率2∶1的情况下,速度值较大,进而提出了提高游动效率的方法。研究结果证明单驱动方式较传统驱动方式更合理。     

Perturbation to Mei Symmetry and Adiabatic Invariants for Disturbed El-Nabulsi's Fractional Birkhoff System

For El-Nabulsi's fractional Birkhoff system, Mei symmetry perturbation, the corresponding Mei-type adiabatic invariants and Noether-type adiabatic invariants are investigated in this paper. Firstly, based on El-Nabulsi-Birkhoff fractional equations, Mei symmetry and the corresponding Mei conserved quantity, Noether conserved quantity deduced indirectly by Mei symmetry are studied. Secondly, Mei-type exact invariants and Noether-type exact invariants are given on the basis of the definition of adiabatic invatiant. Thirdly, Mei symmetry perturbation, Mei-type adiabatic invariants and Noether-type adiabatic invariants for the disturbed El-Nabulsi's fractional Birkhoff system are studied. Finally, two examples, Hojman-Urrutia problem for Mei-type adiabatic invariants and another for the Noether-type adiabatic invariants, are given to illustrate the application of the results.     

分数阶Fornberg-Whitham方程及其改进方程的变分迭代解

给出分数阶Fornberg Whitham方程(FFW)并把其中非线性项uu_x换为u2u_x后所得的改进Fornberg-Whitham方程的解．使用了分数阶变分迭代法(fractional variational iteration method,FVIM),其中Lagrange乘子由泛函和Laplace变换确定．讨论了分数阶次的数值在两种情况下FFW方程的解,因为确定FFW方程中时间微分的阶次需要比较原方程中含时间的两个微分的阶次．最后,给出两个使用分数阶变分迭代法的算例．算例结果证明了所提方法的有效性     

用于结构损伤诊断的实用型光纤光栅传感器研究

提出了一种适用于建筑结构传感的光纤光栅传感器.用细的不锈钢管匹配叠套方式保护光纤光栅,它能与建筑结构有很好的融合.这样的传感器对应力和温度响应具有良好的线性关系,其线性拟合度达0.9996和0.9985. 分段封装光纤光栅使之具有双反射峰,通过测量两反射峰的漂移能够消除温度交扰效应.