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101.
The geometries and electronic properties of six polymers based on furo[3,4-b]pyridine-type heterocyclics were studied using
density functional theory (DFT) at the B3LYP/6-31G(d) level. Bond lengths, bond critical point (BCP) properties, nucleus-independent
chemical shift (NICS), and Wiberg bond indexes (WBIs) are analyzed and correlated with conduction properties. The changes
of bond length, BCP properties, NICS, and WBIs all show that the conjugational degree is increased with main chain extension.
The changes of NICS also show that the conjugation is stronger in the central section than in the outer section. And the HOMO–LUMO
energy gap (E
g) is decreased steadily upon chain elongation. The results suggest that the six polymers all have lower energy gaps (in the
range of 0.39–0.58 eV), which indicate that these proposed polymers are good candidates for the conductive materials. 相似文献
102.
用1HNMR、荧光光谱和红外光谱方法研究阿德福韦双L-苯丙氨酸丙酯(FH-1)与改性六元葫芦脲(TMeQ[6])、七元葫芦脲(Q[7])以及八元葫芦脲(Q[8])的相互作用,探讨主客体作用位点及其识别机制.1HNMR图谱表明FH-1中苯丙氨酸残基部分进入葫芦脲的空腔内部受到屏蔽作用,而FH-1其它部分则位于葫芦脲端口外侧.荧光图谱表明FH-1与TMeQ[6],Q[7]与Q[8]分别形成1∶1或2∶1,1∶1或3∶1与2∶1的主客体包结配合物.红外光谱表明Q[7]与FH-1固体包合物发生了主客体相互作用,FH-1特征峰消失.吸湿性考察发现FH-1与Q[7]形成的固体包合物的吸湿稳定性明显提高,室温放置90d后仍然为白色固体.抗乙型肝炎病毒研究提示葫芦脲具有明显降低化合物细胞毒性,增加其抗病毒活性与作用选择性的效果. 相似文献
103.
Prediction of membrane spanning segments in β‐barrel outer membrane proteins (OMP) and their topology is an important problem in structural and functional genomics. In this work, we propose a method based on radial basis networks for predicting the number of β‐strands in OMPs and identifying their membrane spanning segments. Our method showed a leave‐one‐out cross validation accuracy of 96% in a set of 28 OMPs, which have the range of 8–22 β‐strand segments. The β‐strand segments in OMPs and the residues in membrane spanning segments are correctly predicted with the accuracy of 96% and 87%, respectively. We have developed a web server, TMBETAPRED‐RBF for predicting the transmembrane β‐strands from amino acid sequence and it is available at http://rbf.bioinfo.tw/~sachen/tmrbf.html . We suggest that our method could be an effective tool for predicting the membrane spanning regions and topology of β‐barrel membrane proteins. © 2009 Wiley Periodicals, Inc. J Comput Chem 2010 相似文献
104.
水热沉淀法制备掺铁二氧化钛中空球及其光催化性能 总被引:1,自引:0,他引:1
以碳球为模板剂, 采用水热沉淀法制备了不同配比掺 Fe 的 TiO2 (Fe-TiO2) 中空球, 并运用 X 射线粉末衍射、扫描电子显微镜、元素分析能谱、红外光谱和热重等方法对其进行了表征. 结果表明, 中空球为锐钛矿相, 大小为 0.5~3.20 ?m, 壳层厚度为 30~60 nm, 比表面积为 150~300 m2/g. 随着 Fe 掺杂量的增加, 中空球在可见光区的吸收强度逐渐增加. 光催化降解实验表明, 掺 Fe 后, TiO2 中空球的可见光催化活性升高, 其中 0.5% Fe-TiO2 在 80 min 内降解亚甲基蓝超过 75%. 同时还讨论了光催化机制. 相似文献
105.
106.
The analytical expression for the beam propagation factor (M2-factor) of a radial Gaussian-Schell model (GSM) beam array propagating in non-Kolmogorov turbulence is derived. The influences of beam number, ring radius and generalized exponent on the M2-factor are investigated. The results indicate that the M2-factor has great dependence on the generalized exponent and the beam number. Moreover, there is an optimum ring radius, which leads to a minimum M2-factor and increases with increase in beam number. Further, the M2-factor for the superposition of the intensity is larger than that for the superposition of the cross-spectral density function (CSDF). However, the M2-factor for the superposition of the intensity is less sensitive to the turbulence than that for the superposition of the CSDF. 相似文献
107.
A multiple axes 3-D laser scanning system consisting of a portable 3-D laser scanner, a industrial robot and a turntable is demonstrated. By using a criterion sphere, a robot tool center point (TCP) calibration approach is proposed to calibrate the relation between the laser 3-D scanner and the robot end-effector. In this approach, two different translational motions of robot are first made to determine the rotation part, and then at least three different rotational motions are made to determine the translation part. Meanwhile, by using the criterion sphere, a turntable approach is proposed to calibrate the pose of the turntable relative to the robot. In this approach, several rotational angles of turntable and two different heights of the sphere are made to determine the rotational axis of turntable. Experiment is performed on a portable laser scanner mounted on an industrial robot ABB IRB4400 with a turntable. The experiment results show that the two proposed calibration algorithms are stable and flexible. The application of 3-D measurement is also given to demonstrate the effectiveness and stability of the multiple axes 3-D laser scanning system. 相似文献
108.
The third-order ghost imaging with the second-order intensity correlation is theoretically and experimentally demonstrated.The resolution and visibility of the reconstructed image are discussed,and the relationship between resolution and visibility is analyzed.The theoretical results show that a tradeoff exists between the visibility and resolution of the reconstructed image;the better the image resolution,the worse the image visibility.Numerical simulations are carried out to verify this theory,and a ghost... 相似文献
109.
在圆柱坐标系中研究了傍轴线偏振拉盖尔-高斯光束在两种各向同性介质界面反射和折射后光强质心的偏移. 基于菲涅耳近似和泰勒级数展开,分别得到了部分反射和全反射两种情形下,质心的横向偏移和纵向偏移与光束拓扑荷的解析关系式. 研究表明,部分反射时,反射和折射光束的横向偏移的大小与光束的拓扑荷成正比,方向由拓扑荷的符号决定;而纵向偏移仅仅大小与光束的拓扑荷有关. 全反射时,反射光束质心偏移不受拓扑荷影响. 通过数值模拟验证了解析结果的正确性,并得到了解析公式的适用条件. 拉盖尔-高斯光束的质心偏移特性可应用于测量光
关键词:
拉盖尔-高斯光束
横向偏移
纵向偏移
拓扑荷 相似文献
110.
We combined sum-frequency generation (SFG) vibrational spectroscopy with coherent anti-Stokes Raman scattering (CARS) spectroscopy in one system to examine both surface and bulk structures of materials with the same geometry and without the need to move the sample. Poly(methyl methacrylate) (PMMA) and polystyrene (PS) thin films were tested before and after plasma treatment. The sensitivities of SFG and CARS were tested by varying polymer film thickness and using a lipid monolayer. 相似文献