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排序方式: 共有198条查询结果,搜索用时 31 毫秒
141.
Chukharev V Vuorinen T Efimov A Tkachenko NV Kimura M Fukuzumi S Imahori H Lemmetyinen H 《Langmuir : the ACS journal of surfaces and colloids》2005,21(14):6385-6391
Two porphyrin-fullerene dyads were synthesized to form self-assembled monolayers (SAMs) on indium-tin oxide (ITO) electrode, with either ITO-porphyrin-fullerene or ITO-fullerene-porphyrin orientations. The dyads contain two linkers for connecting the porphyrin and fullerene moieties and enforcing them essentially to similar geometries of the donor-acceptor pair, and two linkers to ensure the attachment of the dyads to the ITO surface with two desired opposite orientations. The transient photovoltage responses (Maxwell displacement charge) were measured for the dyad films covered by insulating LB films, thus ensuring that the dyads interact only with the ITO electrode. The direction of the electron transfer was from the photoexcited dyad to ITO independent of the dyad orientation. The response amplitude for the ITO-fullerene-porphyrin structure, where the primary intramolecular electron-transfer direction coincides with the direction of the final electron transfer from the dyad to ITO, was 25 times stronger than that for the opposite ITO-porphyrin-fullerene orientation of the dyad. Static photocurrent measurements in a liquid electrochemical cell, however, show only a minor orientation effect, indicating that the photocurrent generation is controlled by the processes at the SAM-liquid interface. 相似文献
142.
The continuum generated by the filtering of solitons is studied analytically by use of a perturbation theory and numerically verified. The method applies to any filter transfer function and to sliding-frequency filtering as well. A general method for finding the input pulse adapted to a transmission line is presented and applied to the case of filtering. 相似文献
143.
J. M. Laffaille R. Barloutaud A. Borg C. Louedec J. Prevost C. Comber D. J. Crennel K. Paler L. de Billy J. Dumarchez H. K. Nguyen A. M. Touchard 《Zeitschrift fur Physik C Particles and Fields》1979,2(2):95-106
Results are presented on the total and differential cross sections for the production of π+, π?, γ, \(\bar K^0 \) ,K 0,K +, andK ? in theK ? p interactions at 70 GeV/c. The energy dependence of the various production processes shows in paticular a strong rise of the γ cross section and an increase of the average transverse momentum of the charged pion in the fragmentation regions. 相似文献
144.
Söderholm AA Viiliäinen J Lehtovuori PT Eskelinen H Roell D Baniahmad A Nyrönen TH 《Journal of chemical information and modeling》2008,48(9):1882-1890
We have identified and profiled a set of androgen receptor (AR) binding compounds representing two nonsteroidal scaffolds from a public chemical database supplied by Asinex with virtual screening procedure incorporating our recently published 3D QSAR model of AR ligands. The diphenyl- and phenylpyridine-based compounds act as antagonists in wild-type AR in CV1 cells and also retain this antagonistic character in CV1 cells expressing T877A mutant receptor. This mutation is frequently associated with prostate cancer. Two of the compounds repress the androgen-dependent cell growth of LNCaP prostate cancer cells expressing the T877A AR mutant. Molecular modeling of the observed in vitro antagonism with induced fit docking suggests that W741 and M895 could be mechanistically involved in the initiation of the antagonism. The results indicate finding of nonsteroidal AR antagonist compounds from a public chemical database with computational methods. Compounds could serve as a novel platform to develop more potent AR antagonists with inhibitory activity in both wild-type and T877A mutant AR. 相似文献
145.
Borg OA Godinho SS Lundqvist MJ Lunell S Persson P 《The journal of physical chemistry. A》2008,112(19):4470-4476
The potential energy surfaces of the first excited triplet state of some ruthenium polypyridyl complexes were investigated by means of density functional theory. Focus was placed on the interaction between the geometrical changes accompanying the photoactivity of these complexes when used as antenna complexes in artificial photosynthesis and dye-sensitized solar cells and the accompanying changes in electronic structure. The loss process (3)MLCT --> (3)MC can be understood by means of ligand-field splitting, traced down to the coordination of the central ruthenium atom. 相似文献
146.
Free-standing Pd/Ag23 wt% membranes with five different thicknesses ranging from ∼1.3 to ∼5.0 μm were prepared by magnetron sputtering. The hydrogen permeation was determined before and after a thermal treatment in air at 300 °C. For all membranes studied, the thermal treatment resulted in enhanced permeation, and for some membranes, the hydrogen flux more than doubled. A permeance of 1.7 × 10−2 mol/m2 s Pa0.5 was observed for ∼1.3 μm thick membranes, which is one of the highest reported. Bulk diffusion was found to be the main rate-limiting step after thermal treatment in air. The permeability was quite similar for all membranes studied after this treatment, with a mean value of 2.1 × 10−8 ± 5 × 10−10 mol m/m2 s Pa0.5. Topography studies by atomic force microscopy showed that the samples thermally treated in air had higher surface roughness, larger surface area and larger surface grains than samples not heat-treated in air. 相似文献
147.
Dr. Annika J. E. Borg M.Sc. Oriol Esquivias Dr. Joan Coines Prof. Carme Rovira Prof. Bernd Nidetzky 《Angewandte Chemie (International ed. in English)》2023,62(4):e202211937
UDP-glucuronic acid (UDP-GlcA) 4-epimerase illustrates an important problem regarding enzyme catalysis: balancing conformational flexibility with precise positioning. The enzyme coordinates the C4-oxidation of the substrate by NAD+ and rotation of a decarboxylation-prone β-keto acid intermediate in the active site, enabling stereoinverting reduction of the keto group by NADH. We reveal the elusive rotational landscape of the 4-keto intermediate. Distortion of the sugar ring into boat conformations induces torsional mobility in the enzyme's binding pocket. The rotational endpoints show that the 4-keto sugar has an undistorted 4C1 chair conformation. The equatorially placed carboxylate group disfavors decarboxylation of the 4-keto sugar. Epimerase variants lead to decarboxylation upon removal of the binding interactions with the carboxylate group in the opposite rotational isomer of the substrate. Substitutions R185A/D convert the epimerase into UDP-xylose synthases that decarboxylate UDP-GlcA in stereospecific, configuration-retaining reactions. 相似文献
148.
The main purpose of this work is to develop a method for simultaneous measurement of velocity and passive scalar concentration
by means of digital particle image velocimetry and planar laser-induced fluorescence. Details of the implementation of the
method are given, and the technique is applied to measurements of concentration and velocity in the centre-plane of a liquid
jet with a Reynolds number of 6,000. The measurements are compared with large eddy simulations. Mean velocities and concentrations,
fluctuating velocities and concentrations, and correlation between fluctuating velocities and concentrations are analysed
for the first six diameters downstream of the jet exit. The general agreement between measured and simulated results was found
to be good, in particular for mean quantities. Mean profiles are also found to be in good agreement with other experimental
work on jets reported in the literature. The “whole-plane” measurement method was found to be very useful for detailed comparisons
of turbulent statistics with simulated data. The inadequacy of models for turbulent mass transport based on the standard gradient
diffusion concept is demonstrated through the experimental data.
Received: 4 October 2000/Accepted: 27 November 2000 相似文献
149.
Tommi Palomki Miguel A. Caro Niklas Wester Sami Sainio Jarkko Etula Leena‐Sisko Johansson Jeon G. Han Jari Koskinen Tomi Laurila 《Electroanalysis》2019,31(4):746-755
Undoped a‐C thin films were deposited with varying power density from 10 to 25 W/cm2 using unbalanced closed‐field magnetron sputtering (CFUBMS). The effect of power density on the physical and electrochemical properties was investigated by experimental characterization methods and atomistic simulations. XPS indicated that the films were composed mostly of sp2‐bonded carbon (55–58 at.%) with a small amount of oxygen (8–9 at.%) in the surface region. The films appeared completely amorphous in XRD. The ID/IG ratio obtained by Raman spectroscopy indicated an increase from 1.76 to 2.34 with power density. The experimental and simulated data suggested a possible ordering and/or clustering of the sp2 phase with power density as the cause of the improved electrical properties of the a‐C films. The electrochemical properties of a‐C were between those of glassy carbon and tetrahedral amorphous carbon with potential windows ranging from 2.77 to 2.93 V and double‐layer capacitance values around 0.90 μF cm?2. Electron transfer for Ru(NH3)63+/2+ and FcMeOH+1/0 was reversible whereas that for IrCl62?/3? was quasi‐reversible. Peak potential separation of dopamine and oxidation potential of ascorbic acid decreased with power density, correlating with the structural and electrical changes of the films. The a‐C thin films deposited by CFUBMS are inherently conductive and their physical properties can be adjusted by varying the deposition parameters to a wide range of electrochemical applications. 相似文献
150.
Robert R. A. Freund Matthias van den Borg Daniel Gaissmaier Robin Schlosser Prof. Dr. Timo Jacob Prof. Dr. Hans-Dieter Arndt 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(39):8639-8650
Allylboration reactions rank among the most reliable tools in organic synthesis. Herein, we report a general synthesis of trifunctionalized allylboronates and systematic investigations of their stereocontrolled transformations with substituted aldehyde substrates, in order to efficiently access diverse, highly substituted target substrates. A peculiar transition in stereocontrol was observed from the polar Felkin–Anh (PFA) to the Cornforth–Evans (CE) model for alkoxy- and epoxy-substituted aldehydes. CE-type transition states were uniformly identified as minima in advanced, DFT-based computational studies of allylboration reactions of epoxy aldehydes, conforming well to the experimental data, and highlighting the underestimated relevance of this model. Furthermore, a mechanism-based rationale for the substitution pattern of the epoxide was delineated that ensures high levels of stereocontrol and renders α,β-epoxy aldehydes generally applicable substrates for target synthesis. 相似文献