Uranyl-glycine-water complexes in solution: comprehensive computational modeling of coordination geometries, stabilization energies, and luminescence properties

Comprehensive computational modeling of coordination structures, thermodynamic stabilities, and luminescence spectra of uranyl-glycine-water complexes [UO(2)(Gly)(n)aq(m)](2+) (Gly = glycine, aq = H(2)O, n = 0-2, m = 0-5) in aqueous solution has been carried out using relativistic density functional approaches. The solvent is approximated by a dielectric continuum model and additional explicit water molecules. Detailed pictures are obtained by synergic combination of experimental and theoretical data. The optimal equatorial coordination numbers of uranyl are determined to be five. The energies of several complex conformations are competitively close to each other. In non-basic solution the most probable complex forms are those with two water ligands replaced by the bidentate carboxyl groups of zwitterionic glycine. The N,O-chelation in non-basic solution is neither entropically nor enthalpically favored. The symmetric and antisymmetric stretch vibrations of the nearly linear O-U-O unit determine the luminescence features. The shapes of the vibrationally resolved experimental solution spectra are reproduced theoretically with an empirically fitted overall line-width parameter. The calculated luminescence origins correspond to thermally populated, near-degenerate groups of the lowest electronically excited states of (3)Δ(g) and (3)Φ(g) character, originating from (U-O)σ(u) → (U-5f)δ(u),?(u) configurations of the linear [OUO](2+) unit. The intensity distributions of the vibrational progressions are consistent with U-O bond-length changes around 5 1/2 pm. The unusually high intensity of the short wavelength foot is explained by near-degeneracy of vibrationally and electronically excited states, and by intensity enhancement through the asymmetric O-U-O stretch mode. The combination of contemporary computational chemistry and experimental techniques leads to a detailed understanding of structures, thermodynamics, and luminescence of actinide compounds, including those with bioligands.     

Double-Diffusive Natural Convection Flows with Thermosolutal Symmetry in Porous Media in the Presence of the Soret–Dufour Effects

The double-diffusive natural convection past a vertical plate embedded in a fluid-saturated porous medium is considered in the boundary-layer and Boussinesq approximations. It is assumed that the Soret–Dufour cross-diffusion effects are significant. The heat and mass fluxes on the plate are prescribed as functions of the surface coordinate x. The general similarity reduction of the problem for power-law and exponential variation of the wall fluxes is given. In the case of thermosolutal symmetry, when the similar temperature and concentration fields become coincident, exact analytical as well as numerical solutions are reported and discussed in some detail. For the flows without thermosolutal symmetry, the final similarity equations have been solved numerically, by paying attention to the influence of the Soret and Dufour numbers on the departure from thermosolutal symmetry. The reported results focus on the wall temperatures and concentrations, whose reciprocals are Nusselt and Sherwood numbers, respectively.     

A geometric approach to generalized Stokes conjectures

We consider the Stokes conjecture concerning the shape of extreme 2-dimensional water waves. By new geometric methods including a non-linear frequency formula, we prove the Stokes conjecture in the original variables. Our results do not rely on structural assumptions needed in previous results such as isolated singularities, symmetry and monotonicity. Part of our results extends to the mathematical problem in higher dimensions.     

Monotone strain-stress models for shape memory alloys hysteresis loop and pseudoelastic behaviorx

To describe the behavior of Shape Memory Alloy we use a thermomechanical model, founded on a free energy which is a convex function with respect to the strain and to the martensitic volume fraction, and a concave one with respect to the temperature. The material parameters of the model are experimentally determined.Received: November 26, 2001; revised: March 20, 2002     

Modeling of Thin-Layer Chromatographic Separation of Androstane Isomers

JPC – Journal of Planar Chromatography – Modern TLC - Modeling of thin-layer chromatographic separation of androstane isomers to find the optimum mobile phase is described in this...     

Operadic deformations as a tool for cogravity

The deformation equation and its integrability condition (Bianchi identity) of a non-(co)associative deformation in operad algebra are found. Based on physical analogies, two ideas ofcogravity equations are proposed. Presented at the 11th Colloquium “Quantum Groups and Integrable Systems”, Prague, 20–22 June 2002.