单分子层正癸酸包覆Fe_3O_4纳米粒子的研究

应用微乳液与 Fe2 + 和 Fe3 + 化学共沉淀的方法制备了正癸酸包覆的 Fe3 O4纳米粒子水基磁流体 .用光子相关光谱仪 ( PCS)、透射电镜 ( TEM)和 JDM- 3型振动样品磁强计对制得的水基磁流体进行了表征 .制备了单分子层正癸酸包覆的 Fe3 O4纳米粒子的固态样品 ,并利用 IR,TG,DTG与DSC考查了该固态样品的组成与性质 .发现用一步表面活性剂处理可以直接制得双层表面活性剂包覆的 Fe3 O4纳米粒子水基磁流体 .     

毛冠鹿与3种麂属动物的GAPDH基因序列的比较分析

麂亚科（Muntiacinae）动物包括麂属（Muntiacus）和毛冠鹿属（Elaphodus），分布于东南亚、中国及印度，动物形态相似，但具有令人瞩目的细胞遗传学特性．本文以赤麂（Muntiacus muntjak）、黑麂（Muntiacus crinifrons）、小麂（Muntiacus reevesi）和毛冠鹿（Elaphodus cephalophus）4种麂亚科动物为材料，以3-磷酸甘油醛脱氧酶（GAPDH，管家基因）为靶基因，对毛冠鹿在麂亚科中分类地位进行分子鉴定．提取这4种动物的基因组DNA，根据人的GAPDH基因设计引物，进行PCR扩增．获得了约为300bp的扩增产物．将纯化后的扩增产物克隆到质粒pMD18＋TVector中，转化DH-5a菌，挑选阳性克隆。用M13-47／RV—M通用引物进行测序．测序的结果经clustal软件进行了同源性比较．结果显示：麂属动物种问GAPDH基因间的DNA差异在2．52％～4．37％之间，毛冠鹿与麂属3种动物的差异在1．79％-2．87％之间．这些变异以碱基的转换为主．本文结果支持毛冠鹿为独立属1种的分类观念．     

火棘果实成熟期中生物学特性及营养成分动态变化研究

通过对火棘果实成熟期生物学指标和营养成分动态研究,结果表明:平均每粒果实直径、平均每粒果实重、100粒果实果肉重、100粒果实种子重均随果实成熟度的变化而呈现出先增加后减少的变化趋势;果肉水分、还原糖和灰分的含量在果实完全成熟前是缓慢增加的,随后又缓慢下降。维生素C的含量在果实成熟前期逐步增加,至几乎完全成熟时达到顶峰,然后含量又下降。粗蛋白的含量随果实的成熟度的变化呈现出逐步下降的趋势。矿质元素中的Cu、Zn、Ca、Mg、Pb等的含量也各有其规律。该研究为适时合理采摘利用火棘果实提供了可资借鉴的参考数据。     

Ligand-receptor binding revealed by the TNF family member TALL-1

The tumour necrosis factor (TNF) ligand TALL-1 and its cognate receptors, BCMA, TACI and BAFF-R, were recently identified as members of the TNF superfamily, which are essential factors contributing to B-cell maturation. The functional, soluble fragment of TALL-1 (sTALL-1) forms a virus-like assembly for its proper function. Here we determine the crystal structures of sTALL-1 complexed with the extracellular domains of BCMA and BAFF-R at 2.6 and 2.5 A, respectively. The single cysteine-rich domain of BCMA and BAFF-R both have saddle-like architectures, which sit on the horseback-like surface formed by four coil regions on each individual sTALL-1 monomer. Three novel structural modules, D2, X2 and N, were revealed from the current structures. Sequence alignments, structural modelling and mutagenesis revealed that one disulphide bridge in BAFF-R is critical for determining the binding specificity of the extracellular domain eBAFF-R to TALL-1 instead of APRIL, a closely related ligand of TALL-1, which was confirmed by binding experiments in vitro.     

Ballistic carbon nanotube field-effect transistors

A common feature of the single-walled carbon-nanotube field-effect transistors fabricated to date has been the presence of a Schottky barrier at the nanotube--metal junctions. These energy barriers severely limit transistor conductance in the 'ON' state, and reduce the current delivery capability--a key determinant of device performance. Here we show that contacting semiconducting single-walled nanotubes by palladium, a noble metal with high work function and good wetting interactions with nanotubes, greatly reduces or eliminates the barriers for transport through the valence band of nanotubes. In situ modification of the electrode work function by hydrogen is carried out to shed light on the nature of the contacts. With Pd contacts, the 'ON' states of semiconducting nanotubes can behave like ohmically contacted ballistic metallic tubes, exhibiting room-temperature conductance near the ballistic transport limit of 4e(2)/h (refs 4-6), high current-carrying capability (approximately 25 micro A per tube), and Fabry-Perot interferences at low temperatures. Under high voltage operation, the current saturation appears to be set by backscattering of the charge carriers by optical phonons. High-performance ballistic nanotube field-effect transistors with zero or slightly negative Schottky barriers are thus realized.     

STATIC_STATE FEEDBACK CONTROL SYNTHESIS PROBLEM OF DISCRETE EVENT SYSTEM UNDER PARTIAL OBSERVATION

在这篇文章中提出了针对状态部分可观下离散事件系统的状态反馈控制综合问题,证明了这个问题的最优解是不存在的,利用谓词Ｒｅ（Ｇ,Ｑ）的性质定义了一种次优解,并给出求解这个次优解的算法．     

一种基于小波变换方法的图像递进传送方式

研究利用小波变换方式进行图像的递进传输。方法对图像实行小波变换,然后传递变换后的小波系数,在拉发收端可根据需要对接收到的系数随时地以变换,从而得到原图像的逐级近似。     

Mechanism of intramolecular mixed anhydride formation as intermediates in the reactions of N-phosphorylamino-acids──An MNDO research

N-phosphoryl-α-amino acids can react to form esters, peptides, phosphoryl ester-exchanged products and phosphoryl group migration products under mild conditions, which are very important in researches on arohebiont. It has been proposed that intramolecular mixed carboxylic-phosphoric anhydrides (IMCPAs) might be the common intermediates of the reactions, which are difficult to be experimentally observed because of their high activity. In this note, it has been revealed, by means of MNDO, that the IMCPAs are situated at the relatively minimal points of the potential surface and can form in a non-synchronous concerted reaction pathway that passes through a transition state with a hydrogen-bond-bridge structure. The results give a successful explanation to the structure and formation of IMCPAs and their ability to promote the various reactions mentioned above.     

应用Hansson钉治疗股骨颈骨折

为寻找一种更好的方法,提高股骨颈骨折内固定的治疗效果,笔者应用Ｈａｎｓｓｏｎ钉系统,将２枚带钩的钉以上下平行方式经股骨颈置入股骨头,随机治疗股骨颈骨折患者３０例,并进行３～２１个月的临床随访观察。结果表明：患肢骨折愈合快、关节功能恢复好,优良率达９３％。与其它内固定相比,Ｈａｎｓｓｏｎ钉具有创伤小、操作简便、内固定牢固,符合髋关节生物力学特点,便于推广。