Al compositional inhomogeneity of AlGaN epilayer with a high Al composition grown by metal-organic chemical vapour deposition

The A1 compositional distribution of A1GaN is investigated by cathodoluminescence (CL). Monochromatic CL images and CL spectra reveal a lateral A1 compositional inhomogeneity, which corresponds to surface hexagonal patterns. Cross-sectional CL images show a relatively uniform Al compositional distribution in the growth direction, indicating columnar growth mode of A1GaN films. In addition, a thin A1GaN layer with lower Al composition is grown on top of the buffer A1N layer near the bottom of the A1GaN epilayer because of the larger lateral mobility of Ga adatoms on the growth surface and their accumulation at the grain boundaries.

Superfluidity in dense nuclear matter

We discuss the onset of superfluidity in neutron stars, where the model of nuclear matter is realized in a high-density and asymmetry state. In particular, we present the study of the effects of microscopic three-body forces on the proton pairing in the 1S0 channel and neutron pairing in 3PF1 channel for β-stable neutron star matter. It is found that the main effects of three-body forces are to shrink the domain of existence of the 1S0 below the threshold of the direct URCA process and to stretch the density range of the 3PF1 pairing in a broad domain so to cover most part of the neutron-star core.

Three-body force rearrangement effect on single particle properties in neutron-rich nuclear matter

We extend the Brueckner-Hartree-Fock (BHF) approach to include the three-body force (TBF) rearrangement contribution in calculating the neutron and proton single particle (s.p.) properties in isospin asymmetric nuclear matter. We investigate the TBF rearrangement effect on the momentum-dependence of neutron and proton s.p. potentials, the isospin splitting and especially its density dependence of the neutron and proton effective masses, and the isospin symmetry potential in neutron-rich nuclear matter by adopting the realistic Argonne V-18 two-body nucleon-nucleon interaction supplemented with a microscopic TBF. We find that at low densities, the TBF rearrangement effect is fairly weak, whereas the TBF induces a significant rearrangement effect on the s.p. properties at high densities and large momenta. The TBF rearrangement contribution to s.p. potential is shown to be repulsive, and it reduces considerably the attraction of the BHF s.p. potential. The repulsion from the TBF rearrangement turns out to be strongly momentum dependent at high densities and high momenta. As a consequence, it enhances remarkably the momentum dependence of the proton and neutron s.p. potentials and reduces the neutron and proton effective masses. At low densities, the TBF rearrangement effect on symmetry potential is almost negligible, while at high densities, it enlarges sizably the symmetry potential. At high enough densities, it may even change the high-momentum behavior of symmetry potential. In both cases, with and without including the TBF rearrangement contribution, the predicted neutron effective mass is larger than the proton one in neutron-rich matter within the BHF framework; i.e., the predicted isospin splitting of the proton and neutron effective masses in neutron-rich matter is such that m(n)(*)>= m(p)(*), in agreement with the recent Dirac-BHF predictions. The TBF rearrangement contribution reduces remarkably the magnitude of the proton-neutron effective mass splitting at high densities. At high enough densities, inclusion of the TBF rearrangement contribution even suppresses almost completely the effective mass splitting.

Nucleon Superfluidity in Asymmetric Nuclear Matter and Neutron Star Matter

We have investigate the nucleon superfluidity in asymmetric nuclear matter and neutron star matter by using the Brueckner-Hartree-Fock approach and the BCS theory. We have predicted the isospin-asymmetry dependence of the nucleon superfluidity in asymmetric nuclear matter and discussed particularly the effect of microscopic three-body forces. It has been shown that the three-body force leads to a strong suppression of the proton S-1(0) superfluidity in beta -stable neutron star matter. Whereas the microscopic three-body force is found to enhance remarkably the (PF2)-P-3 neutron superfluidity in neutron star matter and neutron stars.

NUCLEON-NUCLEON CROSS SECTIONS IN ISOSPIN ASYMMETRIC NUCLEAR MATTER

The in medium nucleon-nucleon (N N) cross sections in isospin asymmetric nuclear matter at various densities are investigated in the frame work of Brueckner-Hartree-Fock theory with the Bonn B two-body nucleon-nucleon inter action supplemented with a new version microscopic three-body force (TBF). The TBF depresses the amplitude of cross sections at high density region. At low densities, the proton-proton and neutron-neutron cross sections decrease while the proton-neutron one increases as the asymmetry increases. But the sensitivity of the N N cross sections to the isospin a symmetry are reduced with the increasing density.

陆相热水沉积成因硅质岩与超大型锗矿床的成因—— 以临沧锗矿床为例

临沧锗矿床的硅质岩中存在大量的热水沉积构造和植物化石, 该硅质岩富SiO2 , 低TiO 2和Al2O3, Al/(Al+Fe+Mn)比值平均为0.010, 明显富集Ge, Sb, As, W; 其次Cs, U, Mo和Tl有不同程度的富集, 稀土总量一般小于1 μg/g, 最大2.324 μg/g , 相对富集LREE; δ Eu为0.452 ~ 5.141, δ Ce为 0.997 ~ 1.174; 稀土元素北美页岩标准化模式呈平坦状或向左倾斜; 氧同位素组成与热泉硅华类似. 上述特征表明本区硅质岩属陆相热水沉积成因. 硅质岩作为中寨锗矿体的顶板或夹层, 在空间上与锗矿体紧密接触. 硅质岩中含锗5.6 ~ 360 μg/g, 平均78 μg/g. 靠近硅质岩的煤中锗含量明显升高. 随着煤中锗含量的不断升高, 含矿煤的特征微量元素比值及稀土元素的球粒陨石标准化分配模式与硅质岩越来越相似. 临沧锗矿床煤中锗可能主要由与煤层形成近同时的、以热水成因硅质岩为标志的热水活动带入.

内蒙古乌兰图嘎超大型锗矿床含锗煤的地球化学

乌兰图嘎锗矿是我国近年来发现的产在煤层中的超大型锗矿床，锗金属储量达1600吨，其成矿地质条件与成矿模式不同于临沧锗矿和俄罗斯远东地区的锗矿。本文以乌兰图嘎含锗煤的地球化学特征为重点，利用X射线衍射、扫描电镜、电子探针、ICP-MS和数理统计等多种分析方法，系统研究了乌兰图嘎含锗煤的矿物学、微量元素和稀土元素地球化学特征，结合与其他地区含锗煤地球化学特征的对比，初步探讨了乌兰图嘎锗矿的成因。论文获得以下几点主要认识： 1. 乌兰图嘎含锗煤中的主要矿物包括石英、蒙脱石；次要矿物包括长石、高岭石、伊利石；另含少量三水铝石、角闪石、叶蜡石、石膏、绿泥石、锐钛矿、黄铁矿、方解石、白云石和草酸钙石。扫描电镜和电子探针分析表明，乌兰图嘎含锗煤中还存在锆石、闪锌矿、白钨矿、重晶石、黄铜矿、卤化物、磷酸盐以及含Pb、Bi、Cr、As和Sb矿物。未发现含锗矿物。首次在乌兰图嘎含锗煤和红旗煤矿的无矿煤中发现含Ag矿物。 2. 与上地壳平均组成相比，乌兰图嘎锗矿褐煤明显富集Be、Ge、Sb、W和U，亏损Rb、Nb、Sn和Ta。乌兰图嘎锗矿褐煤中Be、Ge、Sb、W和U的平均含量明显高于乌兰图嘎砂岩和红旗煤矿褐煤，以及美国煤和世界煤的平均组成。乌兰图嘎锗矿含矿煤的稀土元素平均含量略高于美国煤或世界煤的平均组成、乌兰图嘎砂岩以及同时代的红旗煤矿无锗煤中的稀土元素含量。稀土元素与锗含量无明显的相关性。 3. 按元素组合不同，煤中微量元素可划分为4个组：Ge-Mo，Tl-Ga-Zn-Co，Rb-Cs和W-U-Cd-Y-Pb-Cu-Hf-Zr-Th-Sn-Nb-Ta-Ti-Sb-Ba-Sr-Mn-Be组合。第一组合包括与灰分呈负相关的元素，它们主要表现出有机亲合性。 剩下三组包括与灰分呈负-较高相关的元素，其主要与硫化物或铝硅酸盐矿物结合。大多数含锗煤的稀土元素含量与灰分呈高度正相关，表明含锗煤中的稀土元素主要来自陆源碎屑并主要与同沉积矿物相结合。稀土元素在少数高锗煤中的富集与存在独居石有关。 4. Ge和Mo富集在不同剖面的不同部位，其余微量元素和稀土元素或多或少地跟随灰分的分布。TiO2标准化的元素剖面揭示乌兰图嘎褐煤样品中的Be/TiO2、Ge/TiO2、W/TiO2、U/TiO2、Mo/TiO2、Sb/TiO2、Tl/TiO2和Sr/TiO2比值较乌兰图嘎砂岩和红旗煤矿褐煤中的参考值高出许多。这些元素（Be、Ge、W、U、Mo、Sb、Tl和Sr）的大部分(>90%) 可能由溶液带入煤层。稀土元素与TiO2的比值总体接近矿区砂岩以及红旗煤矿无矿煤中的对应比值。 5. 乌兰图嘎含锗煤具有与矿区砂岩和红旗煤矿无矿煤类似的、页岩式的球粒陨石或北美页岩标准化稀土元素分配模式；与上覆砂岩的稀土元素组成相比，少量含锗煤表现出轻微但明显的中-重稀土富集，表明少量的中-重稀土在后生作用中被叠加或保留在乌兰图嘎含锗煤中。乌兰图嘎锗矿的含锗煤以较高的LREE/HREE和Eu/Eu*比值以及平坦的北美页岩标准化稀土元素分配模式为特征，明显区别于临沧锗矿和俄罗斯远东地区锗矿中的含矿煤。 6. 乌兰图嘎锗矿含锗煤中大多数的微量元素和稀土元素可能来源于花岗岩源区，Be、Ge、Sb、W和U的富集可能与后生的、侧向迁移的含锗溶液有关。含锗溶液自花岗岩源区淋滤出这些元素并将其搬运至褐煤中，煤中有机质将溶液中的锗固定而聚集成矿。

U型凹槽电极硅MSM结构光电探测器的研制

为了提高硅MSM结构光电探测器的光电响应度,制备了U型凹槽电极结构的探测器。5 V偏压下,对650 nm波长入射光的绝对光电响应度测试表明,凹槽电极结构的探测器最大光电响应度值为0.486 A/W,比同样尺寸的平版结构光电探测器提高了约6倍。文中也对比了具有抗反射膜和不具有抗反射膜的器件相对响应光谱的差别,并且比较分析了叉指间隙分别为5μm和10μm器件光电响应的不同。

Effect of 80.55 MeV/u(12)C(6+) ions on radiosensitivity and cell cycle of human hepatoma cell lines

In this paper, the relationship between radiosensitivity, cell cycle alteration and the change of apoptosis in different human hepatoma cell lines irradiated by heavy ions were studied with the aim of building up the base data for clinical therapy. Exponentially growing hepatoma cell lines were irradiated by 80.55 MeV/u(12)C(6+) ions at a dose of 0 Gy, 0.5 Gy, 1 Gy, 2 Gy, 4 Gy and 8 Gy. The radiosensitivity was assessed by means of the colony-forming assay. The DNA content, the percentage of each cell-cycle phase and the apoptosis rate were obtained with flow cytometry methods. After the irradiation, the SF2 (survival fraction at 2 gray) of SMMC-7721 cells were evidently lower than that of HepG2 cells. The S phase arrest, G2/M phase arrest delay and the apoptosis in the two hepatoma cell lines varied with the increase of the dose and repair time. The heavy ions could obviously kill the human hepatoma cell lines. Compared to HepG2 cells, SMMC-7721 cells were more radiosensitive to C-12(6+) ions.

Production cross section of Th-236 in the interaction of U-238 with 60 MeV/u O-18 ions

The neutron-rich target-like isotope Th-236 has been produced in the U-238-2p multinucleon transfer reaction between a 60 MeV/u O-18 beam and natural U-238 targets. The activities of thorium were determined after radiochemical separation of Th from the mixture of uranium and reaction products. The Th-236 isotope was identified by the characteristic gamma-rays of 642.2, 687.6 and 229.6 keV. The production cross section of Th-236 was determined to be 250 +/- 50 mu b.

单次分子镀法制备部分La系及~(238)U靶的实验研究

采用单次分子镀方法研究了异丙醇-硝酸体系中电流密度、分子镀持续时间及两极间距离对镀层性能和电沉积效率的影响,确定了制备La,Sm,Eu,Gd,Tb靶及238U靶的最佳工艺条件。因制备的靶不同,电流密度一般介于2—8mA/cm2之间,两极间最优距离为3cm,分子镀1h,用分光光度法测定各靶的沉积效率均高于85%。利用扫描电子显微镜(SEM)对部分靶的表面形貌分析后发现靶面结构均匀致密。目前制得的Gd靶和Tb靶已用于中国科学院近代物理研究所加速器SFC低能核化学终端上,利用19F束流轰击,分别产生了Ta和W的短寿命同位素,从而成功完成了Db(Z=105)及Sg(Z=106)的模型试验。