Domain wall resistance in perpendicular (Ga,Mn) As: Dependence on pinning

We have investigated the domain wall resistance for two types of domain walls in a (Ga,Mn)As Hall bar with perpendicular magnetization. A sizeable positive intrinsic DWR is inferred for domain walls that are pinned at an etching step, which is quite consistent with earlier observations. However, much lower intrinsic domain wall resistance is obtained when domain walls are formed by pinning lines in unetched material. This indicates that the spin transport across a domain wall is strongly influenced by the nature of the pinning.

Effect of Copassivation of Cl and Cu on CdTe Grain Boundaries

Using a first-principles method, we investigate the structural and electronic properties of grain boundaries (GBs) in polycrystalline CdTe and the effects of copassivation of elements with far distinct electronegativities. Of the two types of GBs studied in this Letter, we find that the Cd core is less harmful to the carrier transport, but is difficult to passivate with impurities such as Cl and Cu, whereas the Te core creates a high defect density below the conduction band minimum, but all these levels can be removed by copassivation of Cl and Cu. Our analysis indicates that for most polycrystalline systems copassivation or multipassivation is required to passivate the GBs.

The effects of substrate temperature on the structure and properties of ZnO films prepared by pulsed laser deposition

ZnO thin films were prepared by pulsed laser deposition (PLD) on glass substrates with growth temperature from room temperature (RT) to 500 degrees C. The effects of substrate temperature on the structural and optical properties of ZnO films have been investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission spectra, and RT photoluminescence (PL) measurements. The results showed that crystalline and (0 0 2)-oriented ZnO films were obtained at all substrate temperatures. As the substrate temperature increased from RT to 500 degrees C, the ratio of grain size in height direction to that in the lateral direction gradually decreased. The same grain size in two directions was obtained at 200 degrees C, and the size was smallest in all samples, which may result in maximum E, and E-0 of the films. UV emission was observed only in the films grown at 200 degrees C, which is probably because the stoichiometry of ZnO films was improved at a suitable substrate temperature. It was suggested that the UV emission might be related to the stoichiometry in the ZnO film rather than the grain size of the thin film. (c) 2007 Elsevier Ltd. All rights reserved.

Structural and optical properties of ZnO thin films on glass substrate grown by laser-ablating Zn target in oxygen atmosphere

C-axis-orientated ZnO thin films were prepared on glass substrates by pulsed-laser deposition (PLD) technique in an oxygen-reactive atmosphere, using a metallic Zn target. The effects of growth condition such as laser energy and substrate temperature on the structural and optical properties of ZnO films had been investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission spectra and room-temperature (RT) photoluminescence (PL) measurements. The results showed that the thickness, crystallite size, and compactness of ZnO films increased with the laser energy and substrate temperature. Both the absorption edges and the UV emission peaks of the films exhibited redshift, and UV emission intensity gradually increased as the laser energy and substrate temperature increased. From these results, it was concluded that crystalline quality of ZnO films was improved with increasing laser energy and substrate temperature. (c) 2007 Elsevier B.N. All rights reserved.

Growth behavior of AlInGaN films

The structural and surface properties of AlInGaN quaternary films grown at different temperatures on GaN templates by metalorganic chemical vapor deposition are investigated. Formation of two quaternary layers is confirmed and the difference between them is pronounced when the growth temperature is increased. The surface is featured with V-shaped pits and cracks, whose characteristics are further found to be strongly dependent on the growth temperature of AlInGaN layers. The two-layer structure is interpreted by taking into account of the strain status in AlInGaN layers. (C) 2008 Elsevier B.V. All rights reserved.

液晶聚芳醚酮/聚芳醚酮共混体系的相行为、凝聚态结构与流变性能研究

聚芳醚酮是一种高性能热塑性材料，但其熔融温度高，熔体粘度大，流动性较差。液晶聚芳醚酮则具有非常丰富的液晶相织构和复杂的相转变行为，并且其熔体粘度低，流动性较好。将二者共混，液晶的加入势必降低聚芳醚酮的熔融粘度，改善其熔体流动性，另一方面液晶聚芳醚酮的液晶织构和相行为等势必受很大影响。因此开展这一研究工作不但有重要的理论意义，同时对改善这类材料的性能和拓宽其应用范围具有重要的实际意义。发现液晶聚芳醚酮／聚醚醚酮共混物的复杂相行为与组成密切相关。在以液晶聚芳醚酮为主的共混物中，高分子量的聚醚醚酮易于从低分子量的液晶聚芳醚酮基质相中分离出来，形成了特殊的环带结构。在50：50液晶聚芳醚酮／聚醚醚酮共混物中，两个组分在熔融状态下发生了液一液相分离，导致环带结构和聚醚醚酮球晶同时形成。在以聚醚醚酮为基质相的共混物中，低分子量的液晶聚芳醚酮很难从高分子量的聚醚醚酮基质相中分离出来，最后只能在聚醚醚酮球晶的边界形成单独的相区。当聚醚醚酮含量很高时，仅生成聚醚醚酮球晶。首次在液晶聚芳醚酮与聚醚醚酮共混物中发现了环带球晶，并利用溶剂选择性蚀刻的方法确定了其相结构和组成。环带球晶中的亮心和亮环是液晶聚芳醚酮相，其c轴（分子链方向）垂直于膜平面，而。和b轴则在膜平面内没有固定的取向。暗环则是聚醚醚酮与部分液晶聚芳醚酮的共存相，其中液晶聚芳醚酮晶体的分子链也垂直于膜平面，但聚醚醚酮片晶则呈现复杂的结晶取向。确定环带球晶的形成机理，从分子水平上提出环带球晶的生长模型，即间歇式增长过程，符合结构不连续模型。总结了环带球晶的形成规律和必要条件为：（l）液晶聚芳醚酮为主要成分；（2）液晶聚芳醚酮与聚醚醚酮有一定相容性，至少在熔融态分子相容；（3）液晶聚芳醚酮的各向同性相向液晶相的转变温度要高于聚芳醚酮的结晶温度；（4）液晶聚芳醚酮相转变（或结晶）速率与共混物的相分离速率相匹配或前者略大于后者；（5）降温速率或等温结晶温度适当。聚醚醚酮／含氟液晶聚芳醚酮共混物在熔体状态下的流动行为与共混物的组成、两相的相容性及相的转变有着密切的关系。在聚醚醚酮／含氟液晶聚芳醚酮共混物中，当前者为主要成份时，流动曲线形状与纯PEEK的相似，而当后者为主要成份时，表现出与含氟液晶聚芳醚酮相似的流变行为。共混物的复数粘度、储存模量和损失模量总体来说随F一队EK含量的增加而逐渐下降，只有当含氟液晶聚芳醚酮含量为50％时，共混物的复数粘度、储存模量和损失模量出现了局部极大值。

膜模拟体系的结构与振动光谱研究

生物膜的结构与功能是生命科学的重要课题，我们以单链表面活性剂和双链磷脂等双亲性分子为膜模拟体系主要进行了以下研究：1.制备了长链烷基胺的氢卤酸盐、硫酸盐、硫酸氢盐和磷酸二氢盐等四个系列的二十余种化合物，并在研究四卤合金属酸（II）双烷基铵体系的基础上首次制得了链长为n≥8的六卤合金属酸（IV）双烷基铵类系列化合物。用热重和差示扫描量热等热分析方法研究了其热稳定性和热致相变过程随烷基链链的变化规律，用X-射线四圆衍射分析方法确定了四个有代表性化合物的晶体结构。研究结果表明，这些化合物均具有类似于生物膜双分子层的二维片层结构和类似于生物膜脂质本体凝胶-液晶相变过程的固-固结构相变，可以作为生物膜的优良固态模拟体系。2.系统地研究了双亲性化合物分子体系的拉曼光谱，发现了一些新的对烷基链构象化灵敏的谱带。系统地研究了长链脂肪酸、烷基胺和烷基胺氢卤酸盐等化合物的拉曼低频纵向声子模式（LAM）振动随烷基链链长的变化关系，并首次将LAM用于长链化合物的相变研究。通过考察拉曼谱带频率和强度随温度的变化，详细地讨论了癸胺盐酸盐和月桂胺氢溴酸盐的固-固相变过程的分子机制。3.用红外光谱方法考察了一些长链化合物的固-固相变过程，首次用红外光谱因子群分裂谱带强度比变化的方法确定了长链合物的结构相变温度，从分子水平上解释了月桂胺盐酸盐的两种不同结构相变过程的机制，将相变过程中分子间和分子内相互作用的变化加以区别。系统考察了溴化十六烷基三甲铵和十二烷基磺酸钠等表面活性剂水溶液体系的红外光谱随温度的变化确定了体系的凝聚胶-腋晶相变温度，讨论了不同相态中水分子的结构和水的挥发对凝聚胶相状态的影响，并发现十二烷基磺酸钠水溶液存在着两种不同结构类型的凝聚胶相，将固态正烷烃的红外光谱研究结果推广应用到研究水溶液体系，提高了水溶液状态下表面活性剂分子烷基链构象确定的定量程度。4.用差示扫描量热、红外光谱和拉曼光谱等方法考察了固态磷脂的相变过程，讨论了磷脂固-固相变过程中酰链、甘油骨架以及头部基团等不同部位相应的构象变化，合理地解释了无水磷脂的不同热历程中热分析数据有差异的原因。十余种稀土离子与磷脂脂质体相互作用的研究结果表明，稀土离子的加入明显地升高了磷脂的凝胶-液晶相变温度，稀土离子与磷脂的极性头部产生了稳定的键合作用，从而影响了磷脂酰链的构象有序度，同时还发现稀土离子对不同曲率的磷脂泡囊的构象影响有所不同。我们还探讨了一些抗癌药物（如Ge-132,顺铂和氟脲嘧啶等）与磷脂的相互作用。5.通过L-B技术考察了不同挥发溶剂对磷脂单分子层成膜性的影响，讨论了磷脂与短杆菌肽和无活菌素等分子在单分子层中的相互作用。结果表明在表面压力较高时，短杆菌肽D与磷脂分子间的相互作用比无活菌素的更稳定，单分子层在固相区域，短杆菌肽D在摩尔分数较低时其螺旋链与磷脂酰链有接近一致的分子取向。棕榈胺LB膜热稳定性的变温红外光谱研究结果表明，棕榈胺LB膜在加热过程中发生了由有序到无序的渐变，但比固态棕榈胺熔点相应的熔程加大。利用L-B中化学反应的方法制备了常规提拉下难以得到的水溶性分子的L-B膜。

Anti-HER-2-SEC2融合免疫毒素的构建和活性研究

以PCR技术从金黄色葡萄球菌基因组DNA中首次克隆编码成熟SECZ蛋白的全基因sec2。该基因共717bp，编码239个氨基酸，Genbank Accession number：AY450554。构建了SEC2的表达载体pET-28a-sec2，并在大肠杆菌BL21（DE3）中高效表达可溶性rSEC2蛋白。经亲和层析纯化，其纯度在95％以上，平均回收量为每升培养物40mg。纯化的rSEcZ保持了与野生型相当的生物学活性。以限制性核酸内切酶连接技术分别将两个抗人表皮生长因子受体HER-2单链抗体基因通过DNA Linker与sec2融合，构建融合基因b-l-sec2和ml小sec2，并以两种方式表达纯化。以pET-32a表达载体在E，coliAD494（DE3）中以氨基端融合大肠杆菌硫氧还蛋白（TrxA）形式高效表达融合蛋白TRX-B-L-SEC2和TRX-ML-L-SEC2，经亲和层析纯化，并以肠激酶切割得到成熟融合免疫毒素B-L-SEC2和ML-L-SEC2，其纯度在95％以上，平均回收量为每升培养物smg；以构建的新型表达载体pASK-75-EX在E.coliBL21（ED3）中以不溶性包涵体形式表达融合免疫毒素蛋白，经变性、纯化和复性后得到具有生物学活性的融合免疫毒素，其纯度在95％以上，平均回收量为每升培养物30mg。以两种方式制备的融合免疫毒素都保持了SECZ蛋白的免疫原性，都能有效刺激人外周血单个核细胞的增殖，并且都显示出在体外与HER-2过表达的乳腺癌细胞SK-Br-3特异性结合能力，具有显著的靶向性抑瘤作用。用PcR方法扩增了编码TrxA蛋白的基因trxA并克隆至表达载体pET-28a启动子上游，构建了一种在单质粒中利用两个相同的启动子游离共表达硫氧还蛋白与目的蛋白的表达载体。利用该载体可使TrxA与外源蛋白在大肠杆菌BL21（DE3）中以非融合形式高效共表达。共表达的TrxA可明显促进外源蛋白单链抗体ML3.9（scFv-ML）、3一轻基苯甲酸-6-单加氧酶（3HBA）的可溶性表达；并明显减少肠毒素C2（SEC2）、结核杆菌螺旋酶A亚基（GYRA）的包涵体表达。

Measurement of Be-10 in air filters using BeF- ions from BaBeF4

IEECAS SKLLQG

Spectra for electric-dipole Delta n=0 transitions in highly ionized sulfur ions

Spectra for Delta n = 0 transitions of the type 2s(2)2p(k)-2s2p(k+1) or 2s2p(k)-2p(k+1) from highly ionized sulfur produced in beam-foil excitation are investigated and compared to similar spectra measured with other types of light sources. In the experiment, fifty lines have been identified, of which eleven lines are new and accurately measured. Analysis of spectra was based on comparisons with other experimental results and calculated values.

抗Her-2-scFv-SEC2融合免疫毒素的构建和功能研究(英文)

用基因工程方法,将金黄色葡萄球菌肠毒素 C2 与抗人表皮生长因子受体 HER-2 单链抗体 scFv-B1,以一连接短肽连接,构建融合免疫毒素 B-L-SEC2,并用改进的新型表达载体 pASK75-EX,在大肠杆菌 BL21(ED3)中表达. 以不溶性包涵体形式表达的目的蛋白经变性后以镍离子螯和层析纯化,并以透析法进行复性. 流式细胞术和 MTT 实验结果表明,纯化复性的融合免疫毒素 B-L-SEC2,在体外具有与 HER-2 过表达的靶细胞 SK-Br-3 特异性结合的活性,并对该细胞产生显著的特异性生长抑制作用.