多维矢量矩阵变换域的运动矢量估计

为了实现对视频中运动目标的运动矢量估计,建立了多维矢量矩阵变换域运动估计系统,在变换域对运动视频中运动目标形成的多维能量集中平面进行研究。首先,介绍了多维矢量矩阵理论、变换理论以及运动目标在变换域形成能量集中平面的理论推导;然后,采用平面拟合的方法,求取运动矢量的大小;最后,分析对比了几种方法的效果和迭代速度。实验结果表明:多维矢量矩阵变换域的运动平面拟合方法估计的运动矢量精度达到10^-2 pixel,提供了一种变换域运动矢量估计的高精度方法。     

弹簧参与的微小振动一定是简谐运动吗

振动和波动是生活中的一种非常普遍而重要的运动形式,其中简谐振动是最简单、最基本的运动,弹簧振子是研究简谐运动的最基本模型.在研究弹簧参与的微小振动时,部分学生不能很好的判定弹簧参与的微小振动是否为简谐运动.本文讨论了系统作简谐运动的充要条件,并通过4个具体例子详细分析了弹簧参与的微小振动.     

Spatial snowdrift game in heterogeneous agent systems with co-evolutionary strategies and updating rules

We propose an evolutionary snowdrift game model for heterogeneous systems with two types of agents, in which the inner-directed agents adopt the memory-based updating rule while the copycat-like ones take the unconditional imitation rule; moreover, each agent can change his type to adopt another updating rule once the number he sequentially loses the game at is beyond his upper limit of tolerance. The cooperative behaviors of such heterogeneous systems are then investigated by Monte Carlo simulations. The numerical results show the equilibrium cooperation frequency and composition as functions of the cost-to-benefit ratio r are both of plateau structures with discontinuous steplike jumps, and the number of plateaux varies non-monotonically with the upper limit of tolerance vTas well as the initial composition of agents fa0.Besides, the quantities of the cooperation frequency and composition are dependent crucially on the system parameters including vT, fa0, and r. One intriguing observation is that when the upper limit of tolerance is small, the cooperation frequency will be abnormally enhanced with the increase of the cost-to-benefit ratio in the range of 0 < r < 1/4. We then probe into the relative cooperation frequencies of either type of agents, which are also of plateau structures dependent on the system parameters. Our results may be helpful to understand the cooperative behaviors of heterogenous agent systems.     

基于Matlab的势垒贯穿透射系数研究

粒子在经过一个势垒时,无论粒子能量和势垒高度存在怎样的关系,理论上都有一定的透射.本文用Matlab软件探讨了粒子对于宽度为n*a的势垒和n重宽度为a的势垒进行贯穿时的透射系数.研究结果说明:在E/U1情况下,宽度为na的势垒的贯穿透射系数较n重宽度为a的势垒的贯穿系数大;当E/U1时,情况则相反.     

A density functional theory study of gold clusters supported on layered double hydroxides

The geometrical structure and electronic properties of a series of Au _N (N = 1–8) clusters supported on a Mg²⁺, Al³⁺-containing layered double hydroxides (MgAl–LDH) are investigated using density functional theory. The Au clusters are supported on two typical crystal faces of the LDH platelet, the basal {0001} and the lateral $ \{ 10\,\bar{1}\,0\} $ crystal face, respectively, corresponding to the top and edge site of monolayer MgAl–LDH lamella for the sake of simplicity. It is revealed that an increase in the charge transfer from the LDH lamella to the Au _N clusters at the edge site rather than clusters on the top surface, demonstrating a preferential adsorption for Au _N clusters at the edge of LDH lamella. Moreover, the calculated adsorption energy of the Au _N clusters on the LDH lamella increases with the cluster size, irrespective of the adsorption site. The investigation on the interaction between O₂ and Au _N clusters on the LDH lamella is further carried out for understanding the catalytic oxidation properties of the LDH-supported Au catalyst. The formation of reactive O₂ ^? species, a necessary prerequisite in catalytic oxidation of CO, by O₂ bridging two Au atoms of Au _N clusters indicates that the LDH-supported Au catalyst has the required characteristics of a chemically active gold catalyst in CO oxidation.     

CDK5-dependent inhibitory phosphorylation of Drp1 during neuronal maturation

Mitochondrial functions are essential for the survival and function of neurons. Recently, it has been demonstrated that mitochondrial functions are highly associated with mitochondrial morphology, which is dynamically changed by the balance between fusion and fission. Mitochondrial morphology is primarily controlled by the activation of dynamin-related proteins including dynamin-related protein 1 (Drp1), which promotes mitochondrial fission. Drp1 activity is regulated by several post-translational modifications, thereby modifying mitochondrial morphology. Here, we found that phosphorylation of Drp1 at serine 616 (S616) is mediated by cyclin-dependent kinase 5 (CDK5) in post-mitotic rat neurons. Perturbation of CDK5 activity modified the level of Drp1^S616 phosphorylation and mitochondrial morphology in neurons. In addition, phosphorylated Drp1^S616 preferentially localized as a cytosolic monomer compared with total Drp1. Furthermore, roscovitine, a chemical inhibitor of CDKs, increased oligomerization and mitochondrial translocation of Drp1, suggesting that CDK5-dependent phosphorylation of Drp1 serves to reduce Drp1''s fission-promoting activity. Taken together, we propose that CDK5 has a significant role in the regulation of mitochondrial morphology via inhibitory phosphorylation of Drp1^S616 in post-mitotic neurons.     

Inhibition of phospholipase D2 induces autophagy in colorectal cancer cells

Autophagy is a conserved lysosomal self-digestion process used for the breakdown of long-lived proteins and damaged organelles, and it is associated with a number of pathological processes, including cancer. Phospholipase D (PLD) isozymes are dysregulated in various cancers. Recently, we reported that PLD1 is a new regulator of autophagy and is a potential target for cancer therapy. Here, we investigated whether PLD2 is involved in the regulation of autophagy. A PLD2-specific inhibitor and siRNA directed against PLD2 were used to treat HT29 and HCT116 colorectal cancer cells, and both inhibition and genetic knockdown of PLD2 in these cells significantly induced autophagy, as demonstrated by the visualization of light chain 3 (LC3) puncta and autophagic vacuoles as well as by determining the LC3-II protein level. Furthermore, PLD2 inhibition promoted autophagic flux via the canonical Atg5-, Atg7- and AMPK-Ulk1-mediated pathways. Taken together, these results suggest that PLD2 might have a role in autophagy and that its inhibition might provide a new therapeutic basis for targeting autophagy.     

Experimental research of effects of different rotation radii on the growth rate of potassium dihydrogen phosphate crystals

Comparing with the traditional concentric rotation method (rotation radius is 0 cm), the effects of different rotation radii on the growth rate of KDP crystals were studied by experimental methods. It was found that with the increase of rotation radius from 0 cm, the growth rate of each direction of crystals first increased and then decreased in a size‐unchanged vessel. The smaller the distance between the crystal and vessel wall, the less the growth rate. This phenomenon was named the “wall collision effect”. Also, the value of growth rate reached a maximum when the rotation radius was about half of its allowable largest value in the size‐unchanged vessel. In addition, an increase of the rotation radius could improve the crystal growth rate under the same linear velocity of crystal movement. Finally, the uniformity of crystal growth has also been analyzed compared with the concentric rotation radius. It was found that the uniformity of crystal growth was best when the rotation radius was half of its allowable maximum value, and it was more conducive to the actual application of KDP crystals.     

Comparison of cadmium manganese telluride crystals grown by traveling heater method and vertical Bridgman method

In this paper, the CdMnTe crystals were grown by the Travelling Heater Method (THM) and the Vertical Bridgman (VB) method, respectively. The crystal properties, including the Mn axial distribution, impurity concentrations, resistivity, Hall effects and energy response spectra, were characterized and compared. The results shown that the CdMnTe crystal grown by the THM had more uniform Mn distribution and lower impurity concentrations compared to the crystal grown by VB method. The resistivity of CdMnTe grown by THM was (1.5 ∼ 8) × 10¹⁰ Ω.cm, while the resistivity of CdMnTe grown by VB was 10⁷∼10⁸ Ω.cm. The In dopant distributed uniformly throughout the crystal ingot grown by THM with the doping concentration of 0.6–0.7 ppm, while the In dopant concentration throughout the crystal grown by VB method is in the range of 1.31–2.4 ppm. Hall measurements revealed that the conductivity of the THM grown crystal was weak n‐type conductivity and the VB grown crystal was p‐type conductivity. A planar CdMnTe detector from the THM grown crystal showed a resolution of 8% of the ²⁴¹Am radiation at 59.5 keV peak, however, no energy response was revealed with the CdMnTe detector by the VB method. The results demonstrate that CdMnTe crystal grown by THM have better crystal quality and detector properties compared to that by VB method.     

Tunable Oxygen Activation for Catalytic Organic Oxidation: Schottky Junction versus Plasmonic Effects

The charge state of the Pd surface is a critical parameter in terms of the ability of Pd nanocrystals to activate O₂ to generate a species that behaves like singlet O₂ both chemically and physically. Motivated by this finding, we designed a metal–semiconductor hybrid system in which Pd nanocrystals enclosed by {100} facets are deposited on TiO₂ supports. Driven by the Schottky junction, the TiO₂ supports can provide electrons for metal catalysts under illumination by appropriate light. Further examination by ultrafast spectroscopy revealed that the plasmonics of Pd may force a large number of electrons to undergo reverse migration from Pd to the conduction band of TiO₂ under strong illumination, thus lowering the electron density of the Pd surface as a side effect. We were therefore able to rationally tailor the charge state of the metal surface and thus modulate the function of Pd nanocrystals in O₂ activation and organic oxidation reactions by simply altering the intensity of light shed on Pd–TiO₂ hybrid structures.