Square-wave voltammetry of 4,4′-diisopropyl-2,2′-bithiazoline and its complex with copper(II)

(4S)-4′-diisopropyl-2,2′-bithiazoline (DPT) is an electroactive organic chiral compound giving two reduction responses in square-wave voltammograms at potentials about −0.2 and −0.4 V by forming a complex with mercury which deposits at the electrode surface. By the addition of copper(II) ion to the solution of DPT a third peak appears between them at about −0.3 V, which corresponds to the reduction of adsorbed Cu-DPT complex. Optimal pH for the investigation of those redox processes was found to be 2.8. By square-wave voltammetric measurements it was interpreted that these redox reactions were quasireversible with immobilized reactants. By plotting i_p/f vs. frequency a quasireversible maximum was obtained, and the apparent standard reaction rate constants were calculated: log (k_s)DPT=(0.91 ± 0.9) and 1 < k_s < 65_S⁻¹, log (k_s)_CuDPT= (0.35 ± 0.9) and 0.3 < k_s < 18 S⁻¹ in 0.55 M NaCl.     

Acidity of montmorillonite pillared by alumina, zirconia and chromia

Acidic properties of Al-, Zr- and Cr- pillared montmorillonites prepared from Jelšovy Potok bentonite (Central Slovakia) have been investigated using temperature-programmed desorption of ammonia. The number of acid sites varied with different interlayer cations from 0.06 to 0.23 mmol g⁻¹. The character of acid sites was similar in the case of Al- and Zr- forms. It is obvious that the chromium analogue contains fewer acid sites, nevertheless, they seem to be stronger compared to Al- and Zr- pillared montmorillonites.     

The anisotropy of fluorescence in ring units

The time dependence of the anisotropy of fluorescence after an impulsive excitation in the ring unit (resembling the B850 ring of the purple bacterium Rhodopseudomonas acidophila) is calculated. Fast fluctuations of the environment are simulated by dynamic disorder and slow fluctuations by static disorder. Both types of disorder are taken into account simultaneously. Without dynamic disorder modest degrees of static disorder are sufficient to cause the experimentally found initial drop of the anisotropy on a sub-100 fs time scale. Two different models of the spectral density J(ω) of phonons have been often used in the literature to describe influence of the bath. The spectral density J(ω) enters the non-Markovian dynamical equations for the one exciton density matrix (entering the time dependence of the anisotropy of fluorescence). The spectral density J(ω) with high-energy tail leads to faster anisotropy decay.     

A weight-based approach to the measurement of the interaction among criteria in the framework of aggregation by the bipolar Choquet integral

In the context of aggregation, the Choquet integral arises as a natural generalization of the weighted arithmetic mean. In their seminal work on bi-capacities, Grabisch and Labreuche have recently proposed an extension of the Choquet integral adapted to the situation where the values to be aggregated lie on a bipolar scale. In such a framework, they have derived generalizations of the Shapley value and of the Shapley interaction index that can be used to apprehend the main behavioral characteristics of the aggregation. Founding our approach on the intuitive notion of weight of a criterion, we propose alternative definitions of importance and interaction indices that may be more easily interpretable and we study their properties.     

Method of local-scaling transformations and density-functional theory in quantum chemistry

The method of local-scaling transformations is developed with a view to applications of the nonrelativistic quantum mechanical variational principle in quantum chemistry. Some properties of local-scaling transformations are studied. The method presented links local-scaling transformations and one-electron densities via the ordinary differential equation that provides a proof of the theorem on the existence of the energy density functional within any given orbit and its universality in a sense of the general theory of ordinary differential equations, and allows the construction of this functional explicitly.     

Modeling weakly nonlinear acoustic wave propagation

Three weakly nonlinear models of lossless, compressible fluidflow—a straightforward weakly nonlinear equation (WNE),the inviscid Kuznetsov equation (IKE) and the Lighthill–Westerveltequation (LWE)—are derived from first principles and theirrelationship to each other is established. Through a numericalstudy of the blow-up of acceleration waves, the weakly nonlinearequations are compared to the ‘exact’ Euler equations,and the ranges of applicability of the approximate models areassessed. By reformulating these equations as hyperbolic systemsof conservation laws, we are able to employ a Godunov-type finite-differencescheme to obtain numerical solutions of the approximate modelsfor times beyond the instant of blow-up (that is, shock formation),for both density and velocity boundary conditions. Our studyreveals that the straightforward WNE gives the best results,followed by the IKE, with the LWE's performance being the poorestoverall.     

Aldol condensations of chiral α-haloimidates. A chiral darzens condensation procedure.

Enantiomerically pure benzyl $\text{cis}$-α,β-epoxycarboxylates were prepared by a modified Darzens procedure utilizing aldol condensation reactions of chiral α-haloimidates with various aldehydes. A unique chirality reversal was observed using Zincenolates.