Dielectric constants,molar polarizations,and refractive indices for 2-butoxyethanol + hexane and +heptane at 30° and 40°C

Static dielectric constants and refractive indices of 2-butoxyethanol-n-hexane and-n-heptane mixtures were measured at 30 and 40°C and the various dielectric excess functionsviz. dielectric constants, molar polarizations, and orientation polarizations were evaluated. The excess dielectric constants and molar polarizations were found to be unsymmetrical and negative over the entire range of mole fraction. The trend in the variation of excess orientation polarization has shown three characteristic regions. The excess functions were smoothed through a variable degree polynomial. The results show the dominance of dipole-dipole interactions in the butoxyethanol deficient regions and weak specific interactions with unlike alkane molecules at higher butoxyethanol mole fractions.     

苝四甲酸二酐在Au(111)表面的取向生长及电子结构研究

利用X射线光电子能谱(XPS),同步辐射紫外光电子能谱(SRUPS),近边X射线吸收精细结构(NEXAFS)以及原子力显微镜(AFM)等技术研究了苝四甲酸二酐(PTCDA)与Au(111)的界面电子结构、PTCDA分子取向及有机薄膜的表面形貌.SRUPS价带谱显示,伴随PTCDA分子的微量沉积(0·5ML),位于费米能级附近Au的表面电子态迅速消失,但却观察不到明显的界面杂化态,这说明PTCDA分子和Au(111)界面间存在弱电子传输过程,但并没有发生明显的化学反应.角分辨NEXAFS以及SRUPS结果证明PTCDA分子是平铺在衬底表面.根据Au4f7/2和C1s峰积分强度随薄膜厚度的变化以及AFM图像可知,PTCDA分子在Au(111)表面是一种典型的Stranski-Krastanov生长模式,即先层状生长,再岛状生长,并且在层状生长到岛状生长的转变过程中,存在有机分子的去润湿过程.     

在有限空间内生成的晶格高度取向的ZnO纳米颗粒

应用固态反应的方法,在260和300 oC空气中分别热分解层状锌油酸固体得到氧化锌纳米颗粒/团簇．高分辨透射电子显微镜和选区电子衍射表明,这种团簇是带有各种缺陷的单晶．光致发光激发光谱表明这两个样品在272和366 nm有两个频段．前者可能是由于不到200个氧化锌分子组成的团簇从价带到导带的电子转移引起的．     

基于固相抗体模式时间分辨荧光免疫分析测定雌三醇

采用二步标记法,借助二乙烯三胺五乙酸酐,将Eu3+标记到雌三醇完全抗原上,基于固相抗体竞争反应模式,建立了时间分辨荧光免疫分析测定雌三醇的新方法。在优化的条件下,方法的线性范围为0.005—1000ng·mL-1,检出限为4pg·mL-1。该方法用于检测血清中雌三醇的含量,结果令人满意。     

Optimal growth conditions for GdBa2Cu3O7 thin-film coated conductors characterized by polarized Raman scattering spectroscopy

High temperature superconducting GdBa₂Cu₃O₇ (GdBCO) thin films were grown by pulsed laser ablation. Textured MgO on metal substrates was used as a template for second generation wire applications. Growth conditions of GdBCO thin films were investigated for substrate temperature (T_s) and oxygen partial pressure (PO₂) during deposition. Superconducting critical currents of the films were obtained in the films grown at 790–810 °C of T_s and at 100–700 mTorr of PO₂. Scanning electron micrographs of the films revealed uniform and well-connected grains with some outgrown structures. X-ray θ–2θ scans of the films grown at 810 °C and 300–500 mTorr exhibited c-axis oriented texture. In-plane alignment and c-axis mosaic spread of the films were determined from X-ray Φ scans and rocking curves, respectively. Polarized Raman scattering spectroscopy was used to characterize optical phonon modes, oxygen content, cation disorder, and some possible second phases of the films. The Raman spectra of the films with large critical current density showed modes at 326–329 cm⁻¹, 444–447 cm⁻¹, 500–503 cm⁻¹ related to vibration of oxygen atoms. Origin of small peaks near 600 cm⁻¹ will be discussed as well. The information obtained from Raman scattering measurements will be useful for quality control of the conductors as well as optimization of the process conditions.     

On tuning the orientation of grains of spray pyrolysed ZnO thin films

Effect of varying spray rate on the structure and optoelectronic properties of spray pyrolysed ZnO film is analysed. ZnO films were characterised using different techniques such as X-ray diffraction (XRD), photoluminescence, electrical resistivity measurement, and optical absorption. The XRD analysis proved that, with the increase in spray rate, orientation of the grains changed from (1 0 1) plane to (0 0 2) plane. The films exhibited luminescence in two regions—one was the ‘near band-edge’ (NBE) (∼380 nm) emission and the other one was the ‘blue-green emission’ (∼503 nm). Intensity of the blue-green emission decreased after orientation of grains shifted to (0 0 2) plane. Scanning electron microscope (SEM) analysis of the films asserts that spray rate has major role in improving the crystallographic properties of the films. Moreover resistivity of the films could be lowered to 2.4 × 10⁻² Ω cm without any doping or post-deposition annealing.     

Growth of b-axis oriented VO2 thin films on glass substrates using ZnO buffer layer

VO₂ thin films are grown on glass substrates by pulsed laser deposition using vanadium metal as a target. In this study, a ZnO thin film was used as a buffer layer for the growth of VO₂ thin films on glass substrates. X-ray diffraction studies showed that the VO₂ thin film had b-axis preferential orientation on a c-axis oriented ZnO buffer layer. The thickness of the ZnO buffer layer and the oxygen pressure during VO₂ deposition were optimized to grow highly b-axis oriented VO₂ thin films. The metal-insulator transition properties of the VO₂ film samples were investigated in terms of infrared reflectance and electrical resistance with varying temperatures.     

Completing orientations of partially oriented graphs

We initiate a general study of what we call orientation completion problems. For a fixed class of oriented graphs, the orientation completion problem asks whether a given partially oriented graph P can be completed to an oriented graph in by orienting the (nonoriented) edges in P. Orientation completion problems commonly generalize several existing problems including recognition of certain classes of graphs and digraphs as well as extending representations of certain geometrically representable graphs. We study orientation completion problems for various classes of oriented graphs, including k‐arc‐strong oriented graphs, k‐strong oriented graphs, quasi‐transitive‐oriented graphs, local tournaments, acyclic local tournaments, locally transitive tournaments, locally transitive local tournaments, in‐tournaments, and oriented graphs that have directed cycle factors. We show that the orientation completion problem for each of these classes is either polynomial time solvable or NP‐complete. We also show that some of the NP‐complete problems become polynomial time solvable when the input‐oriented graphs satisfy certain extra conditions. Our results imply that the representation extension problems for proper interval graphs and for proper circular arc graphs are polynomial time solvable. The latter generalizes a previous result.     

Investigation of proton channeling using nuclear-reaction resonances

To investigate orientation effects, an approach based on the measurements of γ-ray yields following the excitation of “narrow" isolated resonances in the reactions occurring on the nuclei of interstitial impurity atoms, that occupy certain positions in a crystal, has been proposed. The carbon atoms were shown to be located in octahedral interstitial sites of the Re-0.4 at. % ¹³C monocrystalline solution. The proton flux distribution in the (0001) channel was investigated via the 1.7476 MeV resonance of the ¹³C(p,γ)¹⁴N reaction. Some particular qualities of the reaction yield were found to be dependent upon the proton energy. The method of measurement of the electronic stopping power of channeled particles has been deduced. The γ-ray yield of the resonance reactions induced by the channeled protons was shown to be dependent on the amplitude of the thermal vibrations of carbon atoms.     

Preparation of a Novel Oriented Structure in Carbon Black Filled Isotactic Polypropylene Composites by Microwave Selective Heating

Microwave heating technology has numerous advantages compared with the traditional heating methods and has been widely used to process materials. However, most thermoplastics do not possess a sufficiently high dielectric property to be heated by microwaves. In this study, carbon black (CB) was utilized as the microwave absorber to improve the microwave heatability of isotactic polypropylene (iPP). Effects of CB contents on the microwave heatability of iPP/CB composites were studied. The temperature of iPP/CB composites with relatively low CB content (5% and 10%) increased slowly and tended to remain unchanged after 120 s of microwave exposure. In contrast, iPP/CB composites with relatively high CB content (15% and 20%) presented a much faster heating rate and the temperature of the sample kept increasing with the prolongation of exposure time. On the basis of the fact that iPP/CB composites with different CB contents have different microwave heatability, a novel oriented structure, in which the core layer has relatively high orientation and the surface layer has relatively low orientation, was prepared by selective microwave heating. Two-dimensional wide angle X-ray diffraction (2D-WAXD) analysis indicates that the orientation parameter calculated by the (040) plane of the surface layer (0.45) was lower than that of the core layer (0.83). The novel oriented structure is different from the common skin-core structure formed in the samples of semicrystalline polymers by traditional polymer processing methods, in which orientation of the skin layer is higher than that of the core layer. The novel oriented structure has not been reported before to our knowledge and its formation mechanism is also discussed in this paper.