Mössbauer study of fired Lishan clay and terra-cotta warriors and horses of Qin dynasty (221 B.C.)

The sherds of terra-cotta warriors and horses and Lishan clay were characterized by Mossbauer spectroscopy, XRD, XRF, NAA, thermal and chemical analyses. Lishan clay was testified as the original material of terracotta warriors and horses, the kilning of these warriors and horses was first carried out in an oxidizing atmosphere, and then changed to a predominantly reducing atmosphere. With refiring experiments, the temperatures of Q3 and Q4 samples were determined to be 830±50 and 980±50°C respectively. Transformations of Lishan clay were determined by firing in oxidizing and reducing atmospheres. The Mossbauer parameters of Lishan clay, which was taken after 2–24h firing, were changing up to 12h.     

工件带到达时间的两阶段柔性流水作业的近似算法

研究了工件带到时间的两阶段柔性流水作业的排序问题,基于求解流水作业和平行机问题的算法思想,提出两个相应的近似算法H(R)和H(MR(?)),证明了这两个算法的最坏情况性能比分别为3-1/m和2/5-1/m,讨论了界的紧性,并利用数值模拟以分析算法与最优值的近似性能比.     

复制缺陷型人泡沫病毒载体辅助质粒pΔGP的构建及转染小肠癌细胞的研究

在人泡沫病毒原病毒全长克隆pHRSV13的基础上,缺失突变gag和pol基因,并且用SV40polyA加尾信号替代人泡沫病毒的3′LTR,构建辅助质粒pΔGP.将复制缺陷型人泡沫病毒载体质粒pGPSNI EGFP和辅助质粒pΔGP分别转染和共转染小肠癌HIC细胞系,荧光显微镜检测发现共转染pGPSNI EGFP和pΔGP的HIC细胞能够强烈表达绿色荧光蛋白,转染有复制缺陷型人泡沫病毒载体质粒pGPSNI EGFP的HIC细胞能够表达少量的绿色荧光蛋白,而转染有辅助载体pΔGP的HIC细胞不表达绿色荧光.结果证明复制缺陷型人泡沫病毒载体的构建成功,表明人泡沫病毒env基因3′端的内部启动子IP具有弱启动子的活性,并且bel基因产生的调控蛋白能够反式激活人泡沫病毒内部启动子IP和5′LTR的启动子.     

17N+197Au反应中碎片与中子的符合测量

在3?3?.4MeV/u ¹⁷N束轰击¹⁹⁷Au靶产生的反应中,利用放置于不同角度组合的17个中子探测器(4°—83°)和14个半导体望远镜(2.3°—9.0°)对反应产物碎片与中子进行了符合测量.经对所得实验角分布积分得到Z=3—6元素的同位素产额分布.在参加者-旁观者模型框架下,采用¹⁷N原子核内部的不同密度分布计算了同位素产额分布并与实验数据做比较.     

2‐Cyanoprop‐2‐yl dithiobenzoate mediated reversible addition–fragmentation chain transfer polymerization of acrylonitrile targeting a polymer with a higher molecular weight

The reversible addition–fragmentation chain transfer (RAFT) polymerization of acrylonitrile (AN) mediated by 2‐cyanoprop‐2‐yl dithiobenzoate was first applied to synthesize polyacrylonitrile (PAN) with a high molecular weight up to 32,800 and a polydispersity index as low as 1.29. The key to success was ascribed to the optimization of the experimental conditions to increase the fragmentation reaction efficiency of the intermediate radical. In accordance with the atom transfer radical polymerization of AN, ethylene carbonate was also a better solvent candidate for providing higher controlled/living RAFT polymerization behaviors than dimethylformamide and dimethyl sulfoxide. The various experimental parameters, including the temperature, the molar ratio of dithiobenzoate to the initiator, the molar ratio of the monomer to dithiobenzoate, the monomer concentration, and the addition of the comonomer, were varied to improve the control of the molecular weight and polydispersity index. The molecular weights of PANs were validated by gel permeation chromatography along with a universal calibration procedure and intrinsic viscosity measurements. ¹H NMR analysis confirmed the high chain‐end functionality of the resultant polymers. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1272–1281, 2007     

纳米WO3的制备及其光解水析氧性能研究

用溶胶凝胶法,灼烧法合成了纳米级WO3,采用X-射线衍射、紫外可见漫反射光谱对WO3进行表征.在Fe3 为电子受体、溶液酸度pH为2.0情况下,研究了纳米级WO3在365nm紫外辐射下光解水析氧的光催化活性,并讨论了不同方法制备的催化剂活性差异的原因.结果表明,结晶程度越高、尺寸越小、比表面积越大的纳米级WO3具有更高的光分解水析氧活性,电子受体的浓度、溶液的酸度对析氧活性有明显的影响.     

Population transfer in multilevel system through modified stimulated Raman adiabatic passage

Stimulated Raman adiabatic passage (STIRAP) has been successfully extended to multilevel system. During the STIRAP process, the intermediate levels have notable population which is detrimental if these levels could decay to other levels through spontaneous emission. This paper proposes a novel method to reduce the intermediate level population during the STIRAP process. A complete population transfer can be achieved in this modified STIRAP even if the intermediate level decays to other levels.     

Periodic and subharmonic solutions of a class of subquadratic second-order Hamiltonian systems

Some solvability conditions of periodic and subharmonic solutions are obtained for a class of subquadratic nonautonomous second-order Hamiltonian systems by the minimax methods in critical point theory.     

Micromagnetic analysis of transition noise for high-density perpendicular recording

In this paper, specific issues related to high-density perpendicular magnetic recording processes, such as transition noise properties and cross-track correlation lengths, were investigated with the help of micromagnetic analysis. The effects of media parameters were taken into consideration, including intergranular exchange coupling, and exchange distribution, irregular grain shapes, magnetization saturation distribution, and anisotropy distribution. The micromagnetic simulation results showed that the effect of anisotropy distribution on transition noise is more significant than magnetization saturation distribution, and it is crucial to reduce this effect to achieve a high signal-to-noise ratio. Additionally, a new method to further estimate the partial erasure threshold was proposed to approximate the partial erasure effects, and the relation between the microtrack jitter and total track jitter was investigated.