An X-ray absorption spectroscopy investigation of the local atomic structure in Cu–Ni–Si alloy after severe plastic deformation and ageing

The local atomic structure of Cu–Ni–Si alloy after severe plastic deformation (SPD) processing and the decomposition of supersaturated solid solution upon annealing were investigated by means of X-ray absorption spectroscopy. The coordination number and interatomic distances were obtained by analyzing experimental extend X-ray absorption fine structure data collected at the Ni K-edge. Results indicate that the environment of Ni atoms in Cu–Ni–Si alloy is strongly influenced by the deformation process. Moreover, ageing at 973 K affects strongly the atomic structure around the Ni atoms in Cu–Ni–Si deformed by equal channel angular pressing and high pressure torsion. This influence is discussed in terms of changes and decomposition features of the Cu–Ni–Si solid solution.     

Microstructural Evolution and Its Effect on Mechanical Properties of Isotactic Polypropylene by Shear Plastic Deformation at Elevated Temperatures

Isotactic polypropylene (iPP) was plastically shear deformed by equal channel angular extrusion (ECAE) at extrusion temperatures varied from 45 to 125°C (25 mm/min). The evolutions of morphology and crystal orientation were studied by reflected optical microscopy (ROM), scanning electron microscopy (SEM), and X-ray diffraction. It was found that the original spherulites were deformed into nearly ellipsoids with their long axis tilted at an angle away from the flow direction. Azimuthal scanning results revealed that two preferred crystal orientations were formed after ECAE. The crystal plasticity was activated by increasing the extrusion temperature, followed by fast rotation of crystallites toward the shear direction. The thermal mechanical analysis (TMA) indicated that low extrusion temperature was favorable to fix the molecular orientation. The iPP samples processed at the investigated temperatures displayed a significant increase in the impact strength, especially for those extruded at 45°C and 65°C. The tensile results revealed a greater elongation at break in the samples deformed at low temperatures (45°C and 65°C) but not in those deformed at high temperatures (85°C or above).     

利用Sagnac干涉仪实现光子轨道角动量分束器

光子轨道角动量量子态具有高维和光学涡旋特性, 在经典和量子领域展示出了巨大的应用潜力, 目前对其的研究已成为物理学的一个热点. 本实验研究了利用Sagnac干涉仪干涉的方法将具有不同轨道角动量的光束无破坏地分离到不同的路径, 即实现光子轨道角动量分束器. 实验中利用此分束器验证了对几种不同轨道角动量态(包含叠加态)的分离, 得到了与理论预期相符的实验结果. 这种对轨道角动量态的区分的方法相比已有的其他区分方法具有较好的稳定性, 而且可用于区分叠加态, 也可以达到单光子水平, 最重要的是实现了不同的轨道角动量本征态无破坏的与路径比特耦合. 这种新方法对高密度通信、量子纠缠、量子保密通信、量子计算与量子信息等方面有着重要的意义.     

角度型SPR系统的设计与应用

表面等离子体共振（Surface Plasmon Resonance,SPR）技术被广泛应用于生物化学传感、药物分析和环境监测等领域。文章基于表面等离子体共振原理,采用Kretschmann模型,研制了角度型SPR系统,以PC机为平台基于Labview软件实现SPR系统控制、数据采集、实时显示及存储一体化。通过样品测试结果表明该系统具有较高的精度和稳定度,并成功应用于酒精溶液浓度的检测。     

Inorganic biochemistry with short-lived radioisotopes as nuclear probes

Metal ions are ubiquitous in the biosphere. In living organisms metalloproteins with specifically designed metal cores perform vital chemical processes. On the other hand, several heavy metals are detrimental to living organisms and nature has developed effective enzymatic detoxification systems which convert toxic metal ions to less toxic species. The nuclear spectroscopy technique Time Differential Perturbed Angular Correlation (TDPAC) of γ-rays uses radioactive isotopes as nuclear probes in these metal cores to obtain a better understanding of the structural and functional significance of these metal cores by monitoring the nuclear quadrupole interaction of the TDPAC probe. Since this technique is based on the nuclear decay, it is also applicable under physiological conditions, i.e., especially at picomolar concentrations. For these studies an indispensable prerequisite is the production of the TDPAC probes with highest possible specific activity and purity as is done by the on-line mass separator ISOLDE at CERN in Geneva. This revised version was published online in July 2006 with corrections to the Cover Date.     

Hg(II) Coordination Studies in Penicillamine Enantiomers by 199mHg-TDPAC

In order to study the binding of the toxic heavy metal ion Hg²⁺ to penicillamine, complexes with the D- and L-enantiomers of penicillamine were investigated by the nuclear quadrupole interaction of ¹⁹⁹Hg monitored by time differential perturbed angular correlation spectroscopy. It was found that bound Hg(II) occurs in two-fold, three-fold and four-fold coordinations. This revised version was published online in September 2006 with corrections to the Cover Date.     

超短脉冲数字全息术中的立体角分复用技术

将角分复用技术应用于超短脉冲数字全息术，可实现对超快过程的动态记录.其中，在角分复用的设计中，由于CCD像素尺寸的限制，一般对物光和参考光的角度要求较为苛刻.为此，提出了一种立体角分复用的方法，并使用连续激光数字全息实验验证了这种方法的有效性.在此基础上，根据超短脉冲数字全息术记录超快过程的特点，设计了能够实现自动连续进行立体角分复用记录的光路.计算分析表明，该光路可在一帧数字全息图上连续记录间隔为纳秒量级的多幅超快过程的动态图像. 关键词： 超短脉冲数字全息术 立体角分复用 超快过程     

Manipulating atomic states via optical orbital angular-momentum

Optical orbital angular-momentum (OAM) has more complex mechanics than the spin degree of photons, and may have a broad range of application. Manipulating atomic states via OAM has become an interesting topic. In this paper, we first review the general theory of generating adiabatic gauge field in ultracold atomic systems by coupling atoms to external optical fields with OAM, and point out the applications of the generated adiabatic gauge field. Then, we review our work in this field, including the generation of macroscopic superposition of vortex-antivortex states and spin Hall effect (SHE) in cold atoms.      

Walk-off Compensated 266-nm Generation with Two β-BaB2O4 Crystals

A walk-off compensation arrangement of two β-BaB₂O₄ (BBO) crystals is used to generate 266-nm (4ω) light from 532-nm (2ω) light that is produced by an intracavity frequency-doubled Nd:YAG laser. While this arrangement is effective in terms of conversion efficiency, back conversion from 4ω to 2ω can easily occur in the second BBO when the phase difference between the 2ω and 4ω in the air gap between the two crystals shifts to ϖ. Performance characteristics are discussed here with particular reference to the angular bandwidth of the second BBO.     

用推广的Viola-Seaborg公式计算α衰变寿命

根据Audi等编评的最新核数据表, 对Z≥84, N≥128的核的α衰变实验寿命用Viola-Seaborg公式进行最小方差拟合, 得到一套新参数. 用新拟合参数计算的偶偶核的衰变寿命与实验寿命很好地符合, 平均偏差1.3倍.而对奇A和奇奇核理论寿命与实验寿命相差较远. 考虑到处于基态时奇A和奇奇核与偶偶核的主要区别在于自旋和宇称, 对Viola-Seaborg公式做了推广. 在公式中引入了离心势垒(即α粒子轨道角动量)对衰变寿命的影响. 由推广公式计算的奇A和奇奇核的寿命与实验寿命平均偏差2.5倍,最大偏差5—6倍.