A Time-Dependent Strange Term Arising in Homogenization of an Elliptic Problem with Rapidly Alternating Neumann and Dynamic Boundary Conditions Specified at the Domain Boundary: The Critical Case

Doklady Mathematics - A strange term arising in the homogenization of elliptic (and parabolic) equations with dynamic boundary conditions given on some boundary parts of critical size is...     

MD simulation of the transitions between B-DNA and A-DNA in the framework of a coarse-grained model

Transitions between the B and A forms of a short DNA double helix (12 base pairs) at different salt concentrations in an aqueous solution have been studied by the molecular dynamics method in the framework of a coarse-grained model with explicit ions but without friction. It has been shown that the A-DNA, stable at high salt concentrations, is a dynamic conglomerate of the molecule and the ions coming from the solution into the deep major groove and then leaving it. In such a short helix, in the model without friction, even at low salt concentrations, transitions from B-DNA to A-DNA and back are frequent and fast. Stable ADNA (without transitions to B-DNA) forms at salt concentrations greater than 0.45 mol/L.     

Chain diffusion in semicrystalline polyethylene: Dielectric relaxation

The experimental data on high-temperature dielectric relaxation αcin linear PE samples with different thermal prehistories (slow cooling, quenching, and annealing) are described. The measurements are conducted at temperatures ranging from 0 to 80°C. Dielectric losses are measured with a high accuracy at frequencies varying from 10^?2 to 10–10⁶ Hz. These dielectric measurements allow one to reveal changes in the frequency dependence of losses with temperature. This effect of the thermal prehistory of the sample and applied stress is explained within the framework of the molecular model of chain diffusion between crystalline and amorphous phases in PE.     

Electrochemical Behavior of Mn5Si3 and Mn5Ge3 in Sulfuric Acid Solutions

Electrochemical behavior of Mn₅Si₃, Mn₅Ge₃, Mn, Si, and Ge in sulfuric acid solutions is studied by steady-state and cyclic voltammetry. The cathodic process on Mn₅Ge₃ is defined by the metallic component. During anodic polarization of Mn₅Si₃, manganese selectively dissolves out of the silicide lattice and silicon that remains on its surface oxidizes to SiO₂, with the Si anodic dissolution rate plummeting down (by 4 orders of magnitude as compared with Mn). The anodic dissolution of Mn₅Ge₃ leads to ionization of both Mn and Ge. The anodic hardness of Mn₅Ge₃ is lower than that of Mn₅Si₃.     

Mechanism and Activation Parameters of the Reactions of Arenes with VO+ 2 in Sulfuric Acid

The gas/solution distribution coefficients, the rate constants of the first stage, the activation parameters of the reactions of benzene, monoalkyl- and polymethylbenzenes, and the products from toluene coupling in the HVO₃ – H₂SO₄ (59.7 wt.%) system were studied. A compensation effect involving the number of substituents in the benzene ring was found. A reaction scheme is proposed.     

Resonant enhancement of neutrinoless double-electron capture in 152Gd

In the search for the nuclide with the largest probability for neutrinoless double-electron capture, we have determined the Q(??) value between the ground states of (152)Gd and (152)Sm by Penning-trap mass-ratio measurements. The new Q(??) value of 55.70(18) keV results in a half-life of 10(26) yr for a 1 eV neutrino mass. With this smallest half-life among known 0ν?? transitions, (152)Gd is a promising candidate for the search for neutrinoless double-electron capture.     

Averaging of boundary-value problems for the Laplace operator in perforated domains with a nonlinear boundary condition of the third type on the boundary of cavities

In this paper, the asymptotic behavior of solutions u _ε of the Poisson equation in the ε-periodically perforated domain Ω_ε ? $ {{\mathbb{R}}^n} $ , n ≥ 3, with the third nonlinear boundary condition of the form ? _ν u _ε + ε^?γσ(x, u _ε) = ε ^?γ g(x) on a boundary of cavities, is studied. It is supposed that the diameter of cavities has the order ε^α with α > 1 and any γ. Here, all types of asymptotic behavior of solutions u _ε , corresponding to different relations between parameters α and γ, are studied.