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41.
Ionita P Caragheorgheopol A Gilbert BC Chechik V 《Journal of the American Chemical Society》2002,124(31):9048-9049
An EPR study of a place-exchange reaction of a diradical disulfide with butanethiol-protected Au nanoparticles showed that the two branches of the disulfide molecule do not adsorb adjacent to each other on the Au surface. The most likely mechanism includes adsorption of only one branch of the disulfide molecule in the exchange process. The exchange reaction was found to be zeroth-order with respect to the diradical, indicative of a dissociative "SN1"-type mechanism. 相似文献
42.
We investigate the properties of the returns of the main emerging stock markets from Europe by means of complex networks. We transform the series of daily returns into complex networks, and analyze the local properties of these networks with respect to degree distributions, clustering, or average line length. We further use the clustering coefficients as quantities describing the local structure of the network, and approach them by using multifractal analysis. We find evidence of scale-free networks and multifractality of clustering coefficients. 相似文献
43.
Tanţa Spătaru Takeshi Kondo Crina Anastasescu Ioan Balint Petre Osiceanu Cornel Munteanu Nicolae Spătaru Akira Fujishima 《Journal of Solid State Electrochemistry》2017,21(4):1007-1014
An innovative composite was obtained by a straightforward sol-gel procedure, involving boron-doped diamond powder (BDDP) incorporation into a SiO2 veil (SiO2V) matrix. Composite-coated glassy carbon plates were used as substrate for Pt electrochemical deposition, and the electrodes thus obtained (Pt/BDDP–SiO2V) were compared on a relative basis with those prepared in the absence of the silica matrix (Pt/BDDP). SEM measurements have shown that a BDDP substrate promotes Pt cluster formation, whereas on BDDP–SiO2V, particles are much smaller (ca. 45 nm to ca. 140 nm). The activity for CH3OH oxidation was checked by cyclic voltammetry, and it was found that at Pt/BDDP–SiO2V, the main anodic peak is shifted with ca. 0.35 V toward lower potentials, indicating a considerable improvement in the overall process kinetics. Stripping experiments together with long-term polarization measurements demonstrated that when deposited on the BDDP–SiO2V support, Pt particles are less susceptible to CO poisoning and this behavior was tentatively ascribed to the presence of a higher relative surface concentration of more stable, oxidized platinum species, as evidenced by XPS. 相似文献
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The paper puts forward a complex linkage mechanism with two degrees of mobility and three kinematic loops, which is used for the guiding (suspension and steering) system of the vehicles. The geometric parameters and the coordinates frames that define the mechanical system are presented, as well as the specific kinematic functions. For this complex mechanical system, the angular capability of the ball (spherical) joints is defined by two angles. The equations for these angles have been determined by matrix algebra tools, considering the transformation matrices between the bodies reference frames. The diagrams of the angular capability of the ball joints, which are represented in angular coordinates, describe the form, orientation and size of the sockets from the spherical casings. Wears, shocks, functional locks or the compromising of the joint strength can occur if scarce sockets are implemented. The risk points, in which the angular parameters have maximum values, have been determined, the simulation being performed for a real system (vehicle). 相似文献
47.
For a dynamical system we will construct various invariant sets starting from its conserved quantities. We will give conditions under which certain solutions of a nonlinear system are also solutions for a simpler dynamical system, for example when they are solutions for a linear dynamical system. We will apply these results to the example of Toda lattice. 相似文献
48.
Thermal behavior of several stable hydrazyl free radicals and of their parent hydrazines 总被引:1,自引:0,他引:1
Maria Marinescu Christina Zalaru Mihaela Florea Petre Ionita 《Journal of Thermal Analysis and Calorimetry》2014,116(1):259-263
A thermal analysis study has been performed for the stable free radical 2,2-diphenyl-1-picrylhydrazyl and other ten free radical congeners, together with their corresponding parent hydrazines. Qualitative studies on the decomposition products showed that nitrogen dioxide plays a key role. A mechanistic decomposition pathway is also proposed. 相似文献
49.
Bogdan Frecus Corneliu I. Oprea Petre Panait Marilena Ferbinteanu Fanica Cimpoesu Mihai A. Gîrţu 《Theoretical chemistry accounts》2014,133(5):1-17
We report quantum chemical calculations providing the exchange coupling constants of the V[TCNE]2 model system, describing the amorphous room temperature molecular magnet V[TCNE] x (TCNE = tetracyanoethylene, x ~ 2). The geometry is optimized for the ideal lattice using density functional theory (DFT) calculations with periodic boundary conditions. Broken-symmetry DFT calculations indicate antiparallel spin alignment resulting in ferrimagnetic ordering, but heavily overestimate the value of the exchange coupling. Better estimates of the exchange coupling parameters between the V(II) ion and the [TCNE]? anionic radical are obtained by means of multiconfigurational calculations performed on smaller molecular models cut from the optimized crystal lattice. Complete active space self-consistent field and multireference second-order perturbation theory calculations provide the sign and the strength of the nearest-neighbor as well as next-nearest-neighbor interactions along all three crystallographic directions. We are able to explain also intuitively the mechanism for antiferromagnetic spin coupling in terms of the superexchange pathways, discussing the role of the main four types of contributions to superexchange. Moreover, we clarify the influence of the transition metal ion on the strength of the exchange interaction and on the critical temperature for long-range ferrimagnetic ordering. 相似文献
50.
Ioan?Calinescu Petre?Chipurici Elvira?Alexandrescu Adrian?TrifanEmail author 《Central European Journal of Chemistry》2014,12(8):851-857
Biocatalysts with microorganisms immobilized on solid carriers could provide the solution for development of continuous industrial processes for ethanol obtaining by fermentation of sugars. In this study, modified polyacrylamide hydrogels and marrow stem sunflower are used as supports for Saccharomyces cerevisiae yeast immobilization. The obtained structures are used for fermentation of molasses in batch systems. The free yeast cells are used as reference. The modification of polyacrilamide matrix with (2-hydroxyethyl)methacrylate has a positive effect on structure pore uniformity and fermentation performance. The mechanical properties of the obtained biocatalysts are compared. The novel natural matrix has net superior compression strength. 相似文献