The kinetics of photocurrent generated in the photoelectrochemical cell (PEC) with phthalocyanine (Pc) dyes in the microsecond time scale was discussed. The shape of the kinetics is rather complex and it was discussed in terms of molecular phenomena and electrochemical processes occurring after laser flash illumination. Time constants were calculated from the photocurrent decay curves and at least three time components were well recognized (rise in 0.40 micros, declining in 0.40-0.45 micros and secondary increase in about 2 micros). The shape of the kinetics was discussed in terms of dye singlet and triplet state participation in photocurrent generation and also in terms of creation of the Helmholtz-Goy double layer at the dye layer-semiconductor interface. The alteration in shape of the Helmholtz-Goy double layer in photoelectrochemical cell after laser pulse was also discussed. 相似文献
We consider two combinatorial statistics on permutations. One is the genus. The other,
, is defined for alternating permutations, as the sum of the number of descents in the subwords formed by the peaks and the valleys. We investigate the distribution of
on genus zero permutations and Baxter permutations. Our q-enumerative results relate the
statistic to lattice path enumeration, the rank generating function and characteristic polynomial of noncrossing partition lattices, and polytopes obtained as face-figures of the associahedron. 相似文献
Summary We consider two card shuffling schemes. The first, which has appeared in the literature previously ([G], [RB], [T]), is as follows: start with a deck ofn cards, and pick a random tuplet { 1, 2, , n}n; interchange cards 1 andt1, then interchange cards 2 andt2, etc. The second scheme, which can be viewed as a transformation on the symmetric groupSn, is given by the restriction of the former shuffling scheme to tuplest which form a permutation of {1, 2,,n}.We determine the bias of each of these shuffling schemes with respect to the sets of transpositions and derangements, and the expected number of fixed points of a permutation generated by each of these shuffling schemes. For the latter scheme we prove combinatorially that the permutation which arises with the highest probability is the identity. The same question is open for the former scheme. We refute a candidate answer suggested by numerical evidence [RB].This work was carried out in part while R.S. was visiting the Institute for Mathematics and its Applications and was partly supported through NSF Grant CCR-8707539. 相似文献
The paper investigates the nonlinear self-adjointness of the nonlinear inviscid barotropic nondivergent vorticity equation in a beta-plane. It is a particular form of Rossby equation which does not possess variational structure and it is studied using a recently method developed by Ibragimov. The conservation laws associated with the infinite-dimensional symmetry Lie algebra models are constructed and analyzed. Based on this Lie algebra, some classes of similarity invariant solutions with nonconstant linear and nonlinear shears are obtained. It is also shown how one of the conservation laws generates a particular wave solution of this equation. 相似文献
An approximate analytical solution of the set of differential equations modeling the anionic polymerization of styrene is presented. By using this solution, a new method for calculating the initiation rate constant for this polymerization process was developed. 相似文献
A new co-crystal of tetraaqua acrylato cobalt (II) complex and melamine, [Co(acr)2(H2O)4]·4MA·2DMF (acr = acrylate, MA = melamine, DMF = dimethylformamide), has been synthesized and characterized using IR, UV-Vis, thermogravimetric analysis, and single-crystal X-ray diffraction. The complex contains discrete unities of [Co(acr)2(H2O)4], melamine, and DMF linked by hydrogen bonds. Investigations evidenced that Co(II) has an octahedral stereochemistry and both acrylate ions present unidentate coordination mode. Thermal decomposition occurs in four steps and denotes that melamine is lost at high temperatures, and this indicates a greater stability that may be associated with the presence of hydrogen bonds network.
The paper generalizes previous results on the 2D Ricci flow equation in a conformal gauge. It investigates a general form of the 2D nonlinear heat equation and it points out all possible cases where Lie type symmetries, associated invariant quantities and similarity solutions can appear. The connection with the already known results for the 1D problem is obtained. 相似文献
The aim of this contribution is to present the properties of the nanostructured hydrogenated carbon thin films and to study
their growth carried out in a special deposition technique based on Thermionic Vacuum Arc method. The Gaseous Thermionic Vacuum
Arc (G-TVA) technology is an original deposition method performed in a special configuration, consisting of a heated thermionic
cathode which provides an electron beam on the anode. The surface free energy was evaluated by contact angle and their optical
properties were studied by Filmetrics F20 spectrometry system. Structure of the film has been investigated by Raman spectroscopy
as well as the mechanical properties like hardness, wear resistance, film-substrate adhesion. The films showed two distinct
Raman characteristic peaks located at 1,350 cm−1 (D-line) and 1,550 cm−1 (G-line), broad for Si and very sharp for glass substrates. The G-TVA enables to prepare soft (hardness ~6 GPa) or hard (~24 GPa)
films. 相似文献
In this work a new electrochemical sensor based on an Ag-doped zeolite-expanded graphite-epoxy composite electrode (AgZEGE) was evaluated as a novel alternative for the simultaneous quantitative determination of nitrate and nitrite in aqueous solutions. Cyclic voltammetry was used to characterize the electrochemical behavior of the electrode in the presence of individual or mixtures of nitrate and nitrite anions in 0.1 M Na2SO4 supporting electrolyte. Linear dependences of current versus nitrate and nitrite concentrations were obtained for the concentration ranges of 1-10 mM for nitrate and 0.1-1 mM for nitrite using cyclic voltammetry (CV), chronoamperometry (CA), and multiple-pulsed amperometry (MPA) procedures. The comparative assessment of the electrochemical behavior of the individual anions and mixtures of anions on this modified electrode allowed determining the working conditions for the simultaneous detection of the nitrite and nitrate anions. Applying MPA allowed enhancement of the sensitivity for direct and indirect nitrate detection and also for nitrite detection. The proposed sensor was applied in tap water samples spiked with known nitrate and nitrite concentrations and the results were in agreement with those obtained by a comparative spectrophotometric method. This work demonstrates that using multiple-pulse amperometry with the Ag-doped zeolite-expanded graphite-epoxy composite electrode provides a real opportunity for the simultaneous detection of nitrite and nitrate in aqueous solutions. 相似文献