旋涡与行进表面水波相互作用的实验研究

采用振动板式造波器在二维水槽中生成近似单色的行进表面水波，采用夹板式涡发生器生成稳定上浮的涡对，在Ｆｒｏｕｄｅ数约为０．５的条件下，得到了水下涡对与不同波长和振幅的行进表面水波相互作用时的干扰图象，以实验方法验证了理论分析和数值计算的结果，并为进一步研究旋涡与行进表面水波的相互作用提供了一种实验研究方法     

Modal part analysis of slosh of the liquid in a cylindrical container in the case of small bond number

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Time-domain Fresnel-to-Fraunhofer diffraction with photon echoes

A photon echo experiment in Tm(3+):YAG is reported that shows, for the first time to the authors' knowledge, the time-domain equivalent of the transition from near- to far-field diffraction, including Talbot self-imaging effects. The experiment demonstrates the huge dispersion capability of photon echoes and opens the way to further exploration of space-time duality.     

重氢原子进入钛晶体中引起的晶体结构转变与电解重水过程中“过热”现象的关系

对重氢原子进入钯或钛晶体中可能引起常温核聚变的机理探讨与实验研究结果，已在文献［１］中作了报导。后来又对钛阴极材料，在使用前后进行了Ｘ射线结构分析。发现在电解过程中发生过“过热”现象的钛阴极材料的晶体结构由原来的密排六方结构转变为立方结构，而没有发生“过热”现象的钛阴极材料的晶体仍然保持电解前的密排六方结构     

Structural characteristics of ultra-low k SiO<Subscript>2</Subscript> thin films prepared using a molecular template

Nanoporous SiO₂ thin films with ultra-low dielectric constants were synthesized using a molecular template method. Uniform films with pore size between 10 and 20 nm were obtained as observed by N₂ adsorption/desorption isotherms and transmission electron microscopy. Fourier transform infrared spectroscopy (FTIR) and differential thermal analysis were carried out to investigate the effect of n-hexane washing on structural properties before and after the surface modification process. The results showed that –OH bonds were substituted with –CH₃ bonds in the films as a result of modification of trimethylchlorosilane (TMCS)/n-hexane solution. Four kinds of model were used to analyze the relationship between porosity and dielectric constant of the films, where the dielectric constant was determined from capacitance-voltage measurements. The investigation indicated that the corresponding relationship was in accord with that estimated by the Rayleigh model.     

Anisotropic metal nanoparticles: Synthesis, assembly, and optical applications

This feature article highlights work from the authors' laboratories on the synthesis, assembly, reactivity, and optical applications of metallic nanoparticles of nonspherical shape, especially nanorods. The synthesis is a seed-mediated growth procedure, in which metal salts are reduced initially with a strong reducing agent, in water, to produce approximately 4 nm seed particles. Subsequent reduction of more metal salt with a weak reducing agent, in the presence of structure-directing additives, leads to the controlled formation of nanorods of specified aspect ratio and can also yield other shapes of nanoparticles (stars, tetrapods, blocks, cubes, etc.). Variations in reaction conditions and crystallographic analysis of gold nanorods have led to insight into the growth mechanism of these materials. Assembly of nanorods can be driven by simple evaporation from solution or by rational design with molecular-scale connectors. Short nanorods appear to be more chemically reactive than long nanorods. Finally, optical applications in sensing and imaging, which take advantage of the visible light absorption and scattering properties of the nanorods, are discussed.     

Chemiluminescence detection of superoxide anion release and superoxide dismutase activity: modulation effect of<Emphasis Type="Italic"> Pulsatilla chinensis</Emphasis>

A novel flow-injection chemiluminescence-based method has been developed for determination of superoxide dismutase (SOD) activity. An in-vitro superoxide anion generation xanthine/xanthine oxidase stable source was established on line with FIA/CL-detection apparatus, for measuring SOD activity. This method can detect SOD in the linear range of 0.002–2.00 U mL^–1 with a detection limit of 0.001 U mL^–1. Another method for detection of superoxide anion is based on the luminol–FeCl₃ chemiluminescence (CL) reaction. This method was used to evaluate superoxide release and SOD activity in rats treated with the traditional Chinese herb Pulsatilla chinensis, which resulted in high clearance of hepatitis B virus (HBV) after treatment of a hepatitis B patient. Interestingly, we found that treatment with Pulsatilla chinensis can specifically increase superoxide release by liver tissues and, at the same time, slightly increase extracellular SOD (ECSOD) activity in plasma; in particular it can markedly increase MnSOD activity in mitochondria in liver tissue. This work revealed a possible mechanism whereby Pulsatilla chinensis prevents possible infection (for example HBV) by specifically increasing superoxide release in the liver and increasing MnSOD activity to minimize superoxide-mediated toxicity.     

Diode laser extended cavity for broad-range fast ramping

A novel design for an extended-cavity diode laser is presented. The cavity contains an electro-optic prism for synchronous tuning of the cavity length and the grating's incident angle. A simple analysis of the cavity is presented. Experimental results are reported that show mode-hop-free tuning over more than 10 GHz with high linearity and reproducibility. To the authors' knowledge, this is the first demonstration of mode-hop-free tuning of an extended cavity over several free spectral intervals with an electro-optic crystal.     

Hydrocarbon film growth by energetic CH3 molecule impact on SiC (0 0 1) surface

Classic molecular dynamics (MD) calculations were performed to investigate the deposition of thin hydrocarbon film. SiC (1 0 0) surfaces were bombarded with energetic CH₃ molecules at impact energies ranging from 50 to 150 eV. The simulated results show that the deposition yield of H atoms decreases with increasing incident energy, which is in good agreement with experiments. During the initial stages, with breaking Si-C bonds in SiC by CH₃ impacting, H atoms preferentially reacts with resulting Si to form Si-H bond. The C/H ratio in the grown films increases with increasing incident energy. In the grown films, CH species are dominant. For 50 eV, H-Csp3 bond is dominant. With increasing energy to 200 eV, the atomic density of H-Csp2 bond increases.     

Molecular dynamics simulation of CH3 interaction with Si(1 0 0) surface

Molecular dynamics simulations of the CH₃ interaction with Si(1 0 0) were performed using the Tersoff-Brenner potential. The H/C ratio obtained from the simulations is in agreement with available experimental data. The results show that H atoms preferentially react with Si. SiH is the dominant form of SiH_x generated. The amount of hydrogen that reacts with silicon is essentially energy-independent. H atoms do not react with adsorbed carbon atoms. The presence of C-H bonds on the surface is due to molecular adsorption.