Synthesis and visible light photocatalytic activity of β-AgVO3 nanowires

β-AgVO₃ nanowires are synthesized by the hydrothermal method. The synthesis yields nanowires with a monoclinic phase structure. Typical nanowires have diameter of about 200–700 nm and length up to 300 μm. Photocatalytic degradation of Rhodamine B dye is investigated. It is found that the β-AgVO₃ nanowires possess excellent catalytic degradation activity owing to its effective visible light absorption and well crystallization. The highly photocatalytic activity suggest its possible application in the organic pollutant treatment under visible light irradiation.     

基于4,7-二噻吩苯并噻二唑和异靛单元的受体-受体共轭聚合物的合成与光伏性质

利用微波协助的Stille缩合聚合反应方法合成了基于双噻吩苯并噻二唑和异靛单元的受体-受体聚合物HFTBT-DA865,并对其热稳定性、光物理性能、电化学性质和本体异质结太阳能电池性能进行了研究.该聚合物易溶于邻二氯苯和邻二甲苯等溶剂,具有优异的溶液加工性能.5%热分解温度为389℃,玻璃化转变温度为168℃,说明其具有较好的热稳定性能.对旋涂速度和温度进行优化,所得太阳能电池器件的光电转换效率为2.28%,开路电压为0.83 V,短路电流为-5.70 mA/cm^2,填充因子为48.9%.电化学性能和密度泛函理论估算结果表明,聚合物与受体材料PC71BM相近的最低未占分子轨道(LUMO)值及其平面性可能是影响光伏性质的重要因素.通过调控共聚单体或优化受体材料,器件性能可进一步提高.对受体-受体(A-A)类聚合物材料太阳能电池性能的研究表明,此类材料是一类潜在的聚合物太阳能电池材料.     

基于新型电子受体1,3,5-三苯酰基苯的两种热活化延迟荧光材料的合成及性能研究

以1,3,5-三苯酰基苯（TBP）作为电子受体,1,8-二甲基咔唑（DmCz）和1,3,6,8-四甲基咔唑（TmCz）分别作为电子给体,合成了两种新的热活化延迟荧光材料TBP-DmCz和TBP-TmCz.热重和差热测试结果表明,这两种材料都具有高热稳定性.理论计算显示,材料的最高电子占据轨道和最低电子未占轨道分别分布在咔唑和1,3,5-三苯酰基苯结构单元上,两种分子轨道几乎没有重叠,具有热活化延迟荧光材料分子轨道的典型特征.分子轨道能级测算结果显示,增加咔唑结构单元上甲基的数量,能明显升高材料的最高电子占据轨道能级.TBP-DmCz和TBP-TmCz的最低激发单重态和最低激发三重态间能级差（ΔE_ST）都非常小,分别为0.05和0.01 eV.在甲苯溶液中,两种材料均表现出了明显的分子内电荷转移跃迁吸收,TBP-DmCz和TBP-TmCz的发光峰分别出现在488和502 nm.用TBP-DmCz和TBP-TmCz作为掺杂客体材料制备出了两种高性能电致发光器件,器件的最大外量子效率分别达到了13.6%和18.3%.     

Global finite-time synchronization of different dimensional chaotic systems

This paper addresses the problem of global finite-time synchronization of two different dimensional chaotic systems. Firstly, the definition of global finite-time synchronization of different dimensional chaotic systems are introduced. Based on the finite-time stability methods, the controller is designed such that the chaotic systems are globally synchronized in a finite time. Then, some uncertain parameters are adopted in the chaotic systems, new control law and dynamical parameter estimation are proposed to guarantee that the global finite-time synchronization can be obtained. By considering a dynamical parameter designed in the controller, the adaptive updated controller is also designed to achieve the desired results. At last, the results of two different dimensional chaotic systems are also extended to two different dimensional networked chaotic systems. Finally, three numerical examples are given to verify the validity of the proposed methods.     

WKB and exact wave functions for inverse power-law potentials

We compare WKB and exact wave functions for inverse power-law potentials and derive a universal algebraic formula reproducing reflection phases and scattering phase shifts with uniform high accuracy for any wave length. Appropriately modified quantization gives competitive accuracy for the spiked harmonic oscillator. The asymptotic accuracy of WKB wave functions is discussed.     

Evidence of substrate metallization by Li adsorption on the Si(001) surface

We report an evidence of substrate metallization induced by Li adsorption on the Si(001) surface, based on the combined results of electron energy-loss (EEL) and angle-resolved photoemission (ARP) measurements. The metallic surface at a low dose of Li manifests itself as a loss peak due to an intraband surface plasmon in EEL spectra and a metallic peak in ARP spectra. These peaks are coherently understood in terms of substrate metallization, where electrons from Li adatoms partially occupy the empty substrate surface bands. Furthermore, the unique negative dispersion of the plasmon reveals that local field effects may cause such an anomalous dispersion.     

Relationship between diffusion-weighted MR images,cerebral blood flow,and energy state in experimental brain infarction

The regional evolution of brain infarction was studied in Wistar rats submitted to remotely controlled thread occlusion of the middle cerebral artery. Occlusion was performed in the magnet of an NMR tomography system to allow continuous recording of diffusion-weighted images. After 30 min (n = 6) or 2 h (n = 9), cerebral blood flow was measured by [¹⁴C] iodoantipyrine autoradiography while the regional distribution of ATP, glucose, lactate, and pH was imaged using pictorial bioluminescence and fluoroscopic methods. In diffusion-weighted images, the hemispheric lesion area (HLA) at the level of caudate-putamen amounted to 54.2 ± 10.9% after 30 min and to 67.0 ± 5.9% after 2 h vascular occlusion. These areas corresponded to the regions exhibiting tissue acidosis (60.8 ± 9.3% and 70.4 ± 4.5%), but were clearly larger than those in which ATP was depleted (22.3 ± 20.8% and 49.6 ± 12.9% after 30 min and 2 h, respectively). The threshold of blood flow for the increase of signal intensity in diffusion-weighted images increased between 30 min and 2 h occlusion from 34 to 41 ml/100 g per minute, the threshold of acidosis from 40 to 47 ml/100 g per minute, and the threshold for ATP depletion from 13 to 19 ml/100 g per minute. Our study demonstrates that diffusion-weighted imaging detects both the core and the penumbra of the evolving infarction but is not able to differentiate between the two parts. It further shows that the ischemic lesion grows during the initial 2 h of vascular occlusion, and that the size of the infarct core increases more rapidly than that of the penumbra.     

A simple measure of the ionic diffusion coefficient in the mixed conductor Cu3VS4

A simple method with three electrodes has been used to measure the diffusion coefficient of the mobile Cu⁺ ion in the mixed conductor Cu₃VS₄ on the basis of the ambipolar diffusion theory. By this method we find that the diffusion coefficient is about 1×10⁻⁷ cm²/s at 300K with an activation energy of 0.44eV.     

Pancharatnam phase for a system of a two-level atom interacting with a quantized field in a cavity

We derive an expression for the Pancharatnam phase for the entangled state of a single two-level atom interacting with a single electromagnetic field mode in an ideal cavity with the atom undergoing either a one- or a two-photon transition. It is shown that the Pancharatnam phase explicitly contains information about the statistics of the field and atomic coherence.     

Multiple bonding in Groups 13 and 14 homonuclear ethyne analogues

Hybrid density functional theory calculations have been carried out on model systems of Groups 13 and 14 alkyne analogues [M₂R₂]²⁻, Li₂[M₂R₂] and X₂R₂ (M=B, Al, Ga, In and Tl, X=C, Si, Ge, Sn and Pb and R=H, Me and Ph). The paper addresses both the nature of the bonding in these systems and the origin of the structural variations. Analysis of the orbitals and calculations of bond orders has identified the factors determining the adoption of a ‘classical’ linear, ethyne-like structure or a trans-bent geometry. The structural trends down each group and role of the substituent R group and the counter-ion have been also been investigated. It is found that all the elements below the first period of these groups adopt ‘non-classical’ trans-bent configurations in these molecules to minimise the steric repulsions between the two ends of the molecule whilst enhancing the bonding to the substituent even though this results in a weakened metal–metal bond as evidenced by bond lengthening and a reduction in the bond order. Complexation of the M₂R₂ ²⁻ ions by lithium reduces the electrostatic repulsions in the M₂R₂ ²⁻ complexes of the Group 13 elements by stabilisation of the π-like orbitals. Whilst the presence of Li⁺ is not responsible for the trans-bending, interactions between the Li atoms and the substituents are important in determining the extent of the distortion.