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1.
Kinetics and equilibria for the formation of a 1:1 complex between palladium(II) and chloroacetate were studied by spectrophotometric measurements in 1.00 mol HClO4 at 298.2 K. The equilibrium constant, K, of the reaction
was determined from multi-wavelength absorbance measurements of equilibrated solutions at variable temperatures as log 0.006 with and , and spectra of individual species were calculated. Variable-temperature kinetic measurements gave rate constants for the forward and backward reactions at 298.2 K and ionic strength 1.00 mol as and , with activation parameters and , respectively. From the kinetics of the forward and reverse processes, and were derived in good agreement with the results of the equilibrium measurements. Specific Ion Interaction Theory was employed for determination of thermodynamic equilibrium constants for the protonation of chloroacetate () and formation of the PdL+ complex (). Specific ion interaction coefficients were derived.  相似文献   

2.
Within the Hartree-Fock framework, the spinless two-electron density function Γ (r 1, r 2) consists of direct Γdi (r 1, r 2) and exchange Γex (r 1, r 2) parts. Accordingly, the inner and outer radii in many-electron systems are rigorously separated into the direct and exchange contributions, i.e., and . It is generally shown that and , where is the usual average radius of an electron. Numerical examinations of the direct and exchange contributions for the 102 atoms from He to Lr in their ground states find that the electron exchange works to decrease and increase . However, the exchange parts are very small and the direct parts essentially govern the inner and outer radii.  相似文献   

3.
The new formulas are obtained for complete orthonormal sets of exponential type vector orbitals of a particle with spin 1 in coordinate, momentum and four-dimensional spaces using the properties of spherical vectors and complete orthonormal scalar basis sets of -exponential type orbitals ( -ETO), -momentum space orbitals ( -MSO) and -hyperspherical harmonics ( -HSH) introduced by the author for particles with spin s = 0, where These vector orbitals are complete without the inclusion of the continuum and, therefore, their group of transformation is the four-dimensional rotation group of O(4). For overlap integrals over vector Slater orbitals with the same screening constant the analytical relations in coordinate space are also derived. It should be noted that the new idea presented in this study is the combination of spherical vectors with complete orthonormal scalar sets for radial parts of -orbitals.  相似文献   

4.
A simulation of the absorption and the fluorescence of acetone in aqueous solution is reported. The model has an explicit solvent representation with an effective ab initio treatment of the solute. The model attempts to balance quantum chemistry, intermolecular interactions and statistical thermodynamics. It includes a non-electrostatic perturbation on the solute which models the solute–solvent exchange repulsion and the restriction put on the electronic structure of the solute by the antisymmetry to the solvent. The solvent shift to the absorption transition is found to be between 0.16 and 0.21 eV; the shift to the fluorescence transition is found to be between 0.02 and 0.05 eV. The simulation supports the conclusion that the first peak in the fluorescence spectrum of acetone is from a single molecule in equilibrium with the solvent, not from an excimer.  相似文献   

5.
Let G be a graph and d v denote the degree of the vertex v in G. The zeroth-order general Randić index of a graph is defined as where α is an arbitrary real number. In this paper, we investigate the zeroth-order general Randić index of conjugated unicyclic graphs G (i.e., unicyclic graphs with a perfect matching) and sharp lower and upper bounds are obtained for depending on α in different intervals.  相似文献   

6.
Indium tin-oxide (ITO) and polycrystalline boron-doped diamond (BDD) have been examined in detail using the scanning electrochemical microscopy technique in feedback mode. For the interrogation of electrodes made from these materials, the choice of mediator has been varied. Using ferrocene methanol (FcMeOH), and approach curve experiments have been performed, and for purposes of comparison, calculations of the apparent heterogeneous electron transfer rates (k app) have been made using these data. In general, it would appear that values of k app are affected mainly by the position of the mediator reversible potential relative to the relevant semiconductor band edge (associated with majority carriers). For both the ITO (n type) and BDD (p type) electrodes, charge transfer is impeded and values are very low when using FcMeOH and as mediators, and the use of results in the largest value of k app. With ITO, the surface is chemically homogeneous and no variation is observed for any given mediator. Data is also presented where the potential of the ITO electrode is fixed using a ratio of the mediators and In stark contrast, the BDD electrode is quite the opposite and a range of k app values are observed for all mediators depending on the position on the surface. Both electrode surfaces are very flat and very smooth, and hence, for BDD, variations in feedback current imply a variation in the electrochemical activity. A comparison of the feedback current where the substrate is biased and unbiased shows a surprising degree of proportionality.Dedicated to Alan, a good friend and colleague on his 60th birthday.  相似文献   

7.
Interaction of a finite quantum system that contains ρ eigenvalues and eigenstates with an infinite quantum system that contains a single one-parameter eigenvalue band is considered. A new approach for the treatment of the combined system is developed. This system contains embedded eigenstates with continuous eigenvalues , and, in addition, it may contain isolated eigenstates with discrete eigenvalues . Two ρ × ρ eigenvalue equations, a generic eigenvalue equation and a fractional shift eigenvalue equation are derived. It is shown that all properties of the system that interacts with the system can be expressed in terms of the solutions to those two equations. The suggested method produces correct results, however strong the interaction between quantum systems and . In the case of the weak interaction this method reproduces results that are usually obtained within the formalism of the perturbation expansion approach. However, if the interaction is strong one may encounter new phenomena with much more complex behavior. This is also the region where standard perturbation expansion fails. The method is illustrated with an example of a two-dimensional system that interacts with the infinite system that contains a single one-parameter eigenvalue band. It is shown that all relevant completeness relations are satisfied, however strong the interaction between those two systems. This provides a strong verification of the suggested method.  相似文献   

8.
Time-dependent properties of a state that interacts with an infinite dimensional quantum system containing several one-parameter eigenvalue bands are considered. This is done by a new mathematical method that produces correct results, however strong the interaction between the state and the system . It is shown that in the case of the weak interaction one obtains standard results that are usually obtained within the formalism of the perturbation expansion method. In particular, if the eigenvalue E of the state is embedded inside the range of the unperturbed eigenvalues, time evolution of the state that is initially prepared in the state has typical exponential decay behavior. One also reproduces standard results concerning probabilities of the transition of the state at infinite time (t=∞) into various eigenvalue bands. However, if the interaction is strong, one finds much more complex and much more complicated behavior.  相似文献   

9.
Plate-gap model of enzyme doped porous electrode was utilized in order to calculate apparent Michaelis constants () and apparent maximal currents () of modeled amperometric biosensor for the wide range of given reaction/diffusion parameters. It was found that of plate-gap biosensor linearly depends on when rates of enzymatic reaction are lower than critical. Theoretically predicted linear correlation between apparent parameters was observed experimentally for the case of carbon paste electrodes, which were modified by PQQ-dependent alcohol dehydrogenases. At overcritical rates (or apparent maximal currents), is practically independent on Michaelis constant of soluble enzyme. Therefore, apparent Michaelis constant can be regarded as biosensor’s topology representing parameter which, in fact, is not related to the specificity of enzyme kinetics. High and rate-independent values of indicate that reaction proceeds at substrate-exposed top layer of the gap. In this case, reaction–diffusion system formally is stratified into separate reaction (top) and diffusion (bottom) zones. Topology of such reaction–diffusion system reminds “inverted” planar electrode, which contains diffusion layer below reaction layer. The net effect of plate-gap topology of working electrode on apparent Michaelis constant is similar to the effect of diffusion layer covering enzymatic planar electrode.  相似文献   

10.
The mechanism of the Co(II) catalytic electroreduction of water insoluble CoR2 salt in the presence of cysteine was developed. CoR2 = cobalt(II) cyclohexylbutyrate is the component of a carbon paste electrode. Electrode surface consecutive reactions are: (a) fast (equilibrium) reaction of the complex formation, (b) rate-determining reversible reaction of the promoting process of CoR(Ac+) complex formation, (c) rate-determining irreversible reaction of the electroactive complex formation with ligand-induced adsorption, and (d) fast irreversible reaction of the electroreduction. Reactions (a,b) connected with CoR2 dissolution and reactions (c,d) connected with CoR2 electroreduction are catalyzed by . Regeneration of (reactions “b,d”) and accumulation of atomic Co(0) (reaction “d”) take place. Experimental data [Sugawara et al., Bioelectrochem Bioenergetics 26:469, 1991]: i a vs E (i a is anodic peak, E is cathodic accumulation potential), i a vs , and i a vs pH have been quantitatively explained.  相似文献   

11.
   The mathematical models of the ion transport problem in a potential field are anayzed. Ion transport is regarded as the superposition of diffusion and convection. In the case of pure diffusion model the classical Gottrell’s result is studied for a constant as well as for the time dependent Dirichlet data at the electrode. Comparative analysis of the current response and the classical Gottrellian is given on the obtained explicit formulas. The approach is extended to find out the current response corresponding to the diffusion-convection model. The relationship between the current response and Gottrellian is obtained in explicit form. This relationship permits one to compare pure diffusion and diffusion-convection models, including asymptotic behaviour of current response and an influence of the convection coefficient. The theoretical result are illustrated by numerical examples.   相似文献   

12.
We have applied various theoretical methods to gain detailed insights into the isomers as well as the transition states (TSs) along the corresponding reaction pathways for RSNO (R=H, C n H2n+1 n ≤ 4). On the basis of G2 and G2MP2 results, the relative order of stability for R=H is estimated to be trans-HSNO > cis-HSNO > HNSO > cis-HONS trans-HONS, while it is cis-CH3SNO trans-CH3SNO > CH3NSO > trans-CH3ONS > cis-CH3ONS for R=CH3. A similar trend is also obtained from the B3P86 method with considerably less computing effort if the nearly isoenergetic isomers cis-HONS and trans-HONS are ignored. Based on the results of B3P86, cis-RSNO is more stable than trans-RSNO when R=H is replaced by alkyl groups except for R=t-Bu. Natural bond orbital analyses allow us to explore whether the high reactivity of S-nitrosothiols is due to the strong negative hyperconjugation (). The mesomeric effect of S-nitrosothiols, although non-negligible, does not cause the breakage of N–O bond due to the compensation of columbic attraction between N and O.Electronic Supplementary Material Supplementary material is available for this article at and is accessible for authorized users.  相似文献   

13.
Let λ1 (G) and Δ (G), respectively, denote the largest eigenvalue and the maximum degree of a graph G. Let be the set of trees with perfect matchings on 2m vertices, and . Among the trees in , we characterize the tree which alone minimizes the largest eigenvalue, as well as the tree which alone maximizes the largest eigenvalue when . Furthermore, it is proved that, for two trees T 1 and T 2 in (m≥ 4), if and Δ (T 1) > Δ (T 2), then λ1 (T 1) > λ1 (T 2).  相似文献   

14.
The densities of binary mixtures of formamide (FA) with 1-butanol, 2-butanol, 1,3-butanediol, and 1,4-butanediol, including those of the pure liquids, over the entire composition range were measured at temperatures (293.15, 298.15, 303.15, 308.15, 313.15 and 318.15) K and atmospheric pressure. From the experimental data, the excess molar volume, V m E, partial molar volumes, and , at infinite dilution, and excess partial molar volumes, and , at infinite dilution were calculated. The variation of these parameters with composition and temperature of the mixtures are discussed in terms of molecular interactions in these mixtures. The partial molar expansivities, and , at infinite dilution and excess partial molar expansivities, and , at infinite dilution were also calculated. The V m E values were found to be positive for all the mixtures at each temperature studied, except for FA + 1-butanol which exhibits a sigmoid trend wherein V m E values change sign from positive to negative as the concentration of FA in the mixture is increased. The V m E values for these mixtures follow the order: 1-butanol < 2-butanol < 1,3-butanediol < 1,4-butanediol. It is observed that the V m E values depend upon the number and position of hydroxyl groups in these alkanol molecules.  相似文献   

15.
The repulsion energy W between two electrons located at r 1 and r 2 can be expressed by the sum of the interaction energies W k between an electron located at and linear electric multipoles located at the coordinate origin along the vector , where and are the vectors with smaller and larger moduli, respectively, of the two vectors r 1 and r 2. All the existing multipole contributions W k to the Hartree–Fock electron repulsion energy W are examined for the 102 atoms He through Lr in their ground states. It is found that |W k | decreases rapidly with increasing k, W 0 > W, and W k with k ≥ 1 work to reduce W 0. The effect of electron correlation is also discussed for some helium-like atoms.  相似文献   

16.
A new method for the exact solution of the interaction of an isolated state with an infinite dimensional quantum system § b containing several one-parameter eigenvalue bands is developed. Unlike standard perturbation expansion approach, this method produces correct results however strong the interaction between the state and the system . It is shown that in the case of the weak interaction this method correctly reproduces standard results obtained within the formalism of the perturbation expansion method. In particular, due to the interaction with the system , eigenvalue E of the state shifts to a new position. In addition, if this eigenvalue is embedded inside the range of the unperturbed eigenvalues, this shifted eigenvalue broadens and spectral distribution of the state has the shape of the universal resonance curve. However, if the interaction is strong, one finds much more complex and much more complicated behavior  相似文献   

17.
Motivated by recent work on the Ruddlesden–Popper material, which was shown to be a superior oxide-ion conductor than conventional solid-oxide fuel cell cathode perovskite materials, we undertook A- and B-site doping studies of the Ruddlesden–Popper nickelate series in an attempt to identify other candidates for cathode application. In this paper, we summarize our most significant results for the and systems and more recently, the higher-order Ruddlesden–Popper phases La n+1Ni n O3n+1 (n=2 and 3), which show greater promise as cathode materials than the n=1 compositions.  相似文献   

18.
Special values of monic polynomials y n (s), with leading coefficients of unity, satisfying the equation of hypergeometric type
have been examined in its full generality by means of a unified approach, where σ(s) and τ(s) are at most quadratic and a linear polynomial in the complex variable s, respectively, both independent of n. It is shown, without actually determining the polynomials y n (s), that the use of particular solutions of a second order difference equation related to the derivatives y n (m)(z) is sufficient to deduce special values for some appropriate s = z points. Hence the special values of almost all polynomials and their derivatives can be generated by the universal formula
in which and are the discriminant and the roots of σ(s), respectively, and denote a parameter depending on the coefficients of the differential equation. Furthermore, the interrelations that arise between and are also introduced. Finally, special values corresponding to the limiting and exceptional cases have been presented explicitly for completeness.   相似文献   

19.
The behavior of dense ceramic anodes made of perovskite-type (x = 0.30–0.70; y = 0–0.05; z = 0–0.20) and K2NiF4-type (Me = Co, Cu; x = 0–0.20) indicates significant influence of metal hydroxide formation at the electrode surface on the oxygen evolution reaction (OER) kinetics in alkaline solutions. The overpotential of cobaltite electrodes was found to decrease with time, while cyclic voltammetry shows the appearance of redox peaks characteristic of Co(OH)2/CoOOH. This is accompanied with increasing effective capacitance estimated from the impedance spectroscopy data, because of roughening of the ceramic surface. The steady-state polarization curves of in the OER range, including the Tafel slope, are very similar to those of model Co(OH)2–La(OH)3 composite films where the introduction of lanthanum hydroxide leads to decreasing electrochemical activity. La2NiO4-based anodes exhibit a low electrochemical performance and poor stability. The effects of oxygen nonstoichiometry of the perovskite-related phases are rather negligible at high overpotentials but become significant when the polarization decreases, a result of increasing role of oxygen intercalation processes. The maximum electrocatalytic activity to OER was observed for A-site-deficient , where the lanthanum content is relatively low and the Co4+ concentration determined by thermogravimetric analysis is highest compared to other cobaltites. Applying microporous layers made of template-synthesized nanocrystalline leads to an improved anode performance, although the effects of microstructure and thickness are modest, suggesting a narrow electrochemical reaction zone. Further enhancement of the OER kinetics can be achieved by electrodeposition of cobalt hydroxide- and nickel hydroxide-based films. Dedicated to Professor Dr. Yakov I. Tur’yan on the occasion of his 85th birthday.  相似文献   

20.
The Merrifield–Simmons index f(G) of a (molecular) graph G is defined as the number of subsets of the vertex set, in which any two vertices are non-adjacent, i.e., the number of independent-vertex sets of G. By we denote the set of unicycle graphs in which the length of its unique cycle is k. In this paper, we investigate the Merrifield–Simmons index f(G) for an unicycle graph G in . Unicycle graphs with the largest or smallest Merrifield–Simmons index are uniquely determined.  相似文献   

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