掺空穴的一维自旋液体的基态和激发态

基于P.Tavan的含t激发态的自旋液体模型,本文提出了描述掺有空穴的一维自旋液体的哈密顿和状态矢,并用变分法计算了基态和激发态能量,得出了能隙△与掺空穴指数δ的依赖关系。对所得结果与高Tc超导的联系作了讨论。     

Topography of YBa2Cu3O7-δ single crystals,spectroscopy of thin films and sintered YBa2Cu3O7-δ: theory and STM observations

We report topographic scanning tunnelling microscopy measurements on the (001) and (100) surfaces of YBa₂Cu₃O_7-δ single crystals, together with a theoretical basis by which the surface structures can be understood. We show that it is possible to obtain reproducible topographic data on a clean (001) and (100) surface in air. The results show various structures at scales from 0·1 to 100 nm. Among the observed features on the (001) surface were growth steps which had heights that were multiples of the lattice constant in the [001] direction. This indicates that the bulk crystal structure extends to the surface, and that the surface is relatively stable, even in humid air. We also found small (013) facets on the (001) surface, in accordance with theoretical pradictions. Occasionally, we found evidence for a one-dimensional corrugation on the surface. This is possibly a direct consequence of the orthorhombic distortion in the a-b plane with ordered oxygen vacancies, which gives rise to chain-like Cu-O structures along the b-axis. In addition, we measured the energy gap of sintered pellets and thin films of this superconductor, using a low-temperature STM. We discuss some effects which may influence the measurements and present criteria to check for these effects. We found an energy gap of δ=14±2 eV, in good agreement with the BCS pradiction 2δ/kT_c=3·5. This is not contradicted by the results we obtained by far infrared spectroscopy and Andreev reflection measurements.     

Preparation and preclinical studies of a hepatic receptor imaging agent

Galactosyl neoglycoalbumin(NGA) was synthesized by the covalent coupling of a bifunctional reagent ,2-imino-2-ethyloxymethy1-1-thiogalactose,to human serum albumin.The average number of galactose groups per albumin molecule(Gal/HSA) of NGA was 30.NGA was labeled directly with Na^99mTcO4.The radiochemical purity of ^99mTc-NGA was over 90%.Consequences of the preclinical studies show that ^99mTc-NGA is a good hepatic receptor imaging agent,uptaken by hepatic cells specifically,and excreted majorly from the biliary system and the gastrointestinal(GI) tract.     

Suspension of soft magnetic materials using high Tc superconductors

This paper describes a novel suspension technique using high T_c superconductors and magnetic materials. It was found for a field-cooled superconductor and an adjacent magnetic material that the usual inverse relationship between the attractive magnetic force and gap distance reverts to a direct relationship for small gap length. Thus, stable, noncontact suspension is possible within a certain gap range. This phenomenon was found for even a soft magnetic material possessing minimal coercive force. Since remarkable reversals were observed for magnetic materials with diameters much smaller than that of the pinned area, it is considered that some of the pinned flux is subject to a gathering effect in the magnetic material. Stable, contactless suspension of a 180 g carbon steel weight under a high T_c superconductor was achieved using this technique.     

^99mTc直接标记IgG及其稳定性研究

采用二硫苏糖醇还原ＩｇＧ和合亚锡的药盒还原高锝酸盐法将９９ｍＴｃ直接标记ＩｇＧ。其标记率＞９５％，标记后无需纯化。使用多种弱交换配体（亚锡ＰＹＰ、ＭＤＰ、ＧＨ、Ｐｈｙｔａｔｅ和ＥＨＩＤＡ药盒）获得了高的标记率，但此法不宜用ＤＴＰＡ药盒．体外研究和显像表明９９ｍＴｃ－ＩｇＧ的稳定性良好，可用于局部实验性脓肿的诊断。     

MOSSBAUER SPECTROSCOPY OF HIGH T_c YBa_2 (Cu_(3-x)Fe_x )O_y

ＭＯＳＳＢＡＵＥＲＳＰＥＣＴＲＯＳＣＯＰＹＯＦＨＩＧＨＴ＿ｃＹＢａ＿２（Ｃｕ＿（３－ｘ）Ｆｅ＿ｘ）Ｏ＿ｙ￥ＬｉＳｈｉ（李士）ａｎｄＬｉＹｉｎｈｕａ（李印华）（ＩｎｓｔｉｔｕｔｅｏｆＨｉｇｈＥｎｅｒｇｙＰｈｙｓｉｃｓ，Ｂｅｉｊｉｎｇ１０００８０，Ｃｈｉ...     

5MW低功率堆经济分析

本文对5MW 低功率堆(5MW LPR)在单晶硅中子嬗变掺杂(NTD)、医用凝胶型~(99m)Tc 发生器堆照生产、黄玉宝石辐照着色等方面的生产能力和经济性进行了分析。分析表明,上述辐照产品按目前的市场情况和本堆的辐照生产能力,到1996年基本上可收回改建投资458.84万元,到1999年可收回全部投资1010.71万元。     

纳米添加物对超导材料性能影响的研究进展

本文介绍了近年来纳米添加物对超导材料如YBCO、BSCCO和MgB2等超导性影响的研究现状,讨论了引入纳米物质对超导材料的超导临界电流和超导临界温度等性能的影响。大部分研究表明,引进纳米物质,在超导材料间作为第二相缺陷形成强的磁通钉扎中心,是工业应用上改善超导体磁性能最实用、最有前途的技术。     

锝化学研究——Ⅱ.空间堆积模型在锝化学中的应用

根据配位矢量和趋于零的假设,计算了TcAB_4型配合物的键角,它与实验值符合得较好,从而印证了空间堆积模型用于Tc化学的可行性。还论述了堆积参数在推测和设计Tc化合物方面的应用。     

Effects of (Li,Ce, Y) co-substitution on the properties of CaBi2Nb2O9 high temperature piezoceramics

High temperature lead-free Bismuth layer-structured (Li, Ce, Y)-substituted CBN piezoelectric ceramics were prepared by the solid-state reaction method. The phase structure, microstructure, piezoelectric property, dielectric property, thermal stability and electric property of the (Li, Ce, Y)-substituted CBN ceramics were studied. X-ray diffraction and SEM revealed the doped ceramics had typical bismuth layer-structure. The piezoelectric coefficient was improved significantly and the maximum value was ~16.1 pC/N.The Curie temperature of all the samples were in the range of 925–941 °C that was close to or even excess the value of pure CBN ceramics. The resistivity were studied deeply and all the samples possessed excellent resistivity at high temperature (500 °C, ~10⁶ Ω cm; 600 °C, ~10⁵ Ω·cm). The thermal depoling behavior of the ceramics was researched in detail and the doped ceramics exhibited outstanding thermal stability. All the results indicate the (Li, Ce, Y)-substituted CBN ceramics possesses preeminent property, making it promising for application especially in high temperature territories.