Hyperfine field and relaxation effect in Li−Zn−Ti ferrites

⁵⁷Fe Mössbauer effect studies were made on titanium substituted Li?Zn ferrite with composition Li_0.45+0.5tZn_0.1 Ti_t Fe_2.45–1.5tO₄ (t=0.0 to 1.2) at 300K. The Mössbauer spectra for t≤0.4 show two well defined Zeeman sextets corresponding to the Fe³⁺ ions at tetrahedral (A) and octahedral (B) sites. The spectra for t=0.6, 0.8 and 0.9 show relaxation but can still be resolved into 2 sextets. The spectra for t=1.0, 1.2 show strong ferrimagnetic relaxation with the spectra for t=1.2 exhibiting an additional central doublet. The effect of Ti⁴⁺ substitution on the Isomer shift (I.S), Quadrupole splitting (Q.S.) and nuclear magnetic fields of Li?Zn ferrites have been reported in this paper. The I.S. was found to be independent of substitution level t, while the quadrupole splitting was observed to be negligible. The variation of hyperfine field with t has been explained on the basis of superexchange interaction and cation distribution.     

Well-Posedness for Multicomponent Schrödinger–gKdV Systems and Stability of Solitary Waves with Prescribed Mass

In this paper we prove the well-posedness issues of the associated initial value problem, the existence of nontrivial solutions with prescribed \(L^2\)-norm, and the stability of associated solitary waves for two classes of coupled nonlinear dispersive equations. The first problem here describes the nonlinear interaction between two Schrödinger type short waves and a generalized Korteweg-de Vries type long wave and the second problem describes the nonlinear interaction of two generalized Korteweg-de Vries type long waves with a common Schrödinger type short wave. The results here extend many of the previously obtained results for two-component coupled Schrödinger–Korteweg-de Vries systems.     

Excitation energies expressed as orbital energies of Kohn–Sham density functional theory with long-range corrected functionals

A new simple and conceptual theoretical scheme is proposed for estimating one-electron excitation energies using Kohn–Sham (KS) solutions. One-electron transitions that are dominated by the promotion from one initially occupied orbital to one unoccupied orbital of a molecular system can be expressed in a two-step process, ionization, and electron attachment. KS with long-range corrected (LC) functionals satisfies Janak's theorem and LC total energy varies almost linearly as a function of its fractional occupation number between the integer electron points. Thus, LC reproduces ionization energies (IPs) and electron affinities (EAs) with high accuracy and one-electron excitation energies are expressed as the difference between the occupied orbital energy of a neutral molecule and the corresponding unoccupied orbital energy of its cation. Two such expressions can be used, with one employing the orbital energies for the neutral and cationic systems, while the other utilizes orbital energies of just the cation. Because the EA of a molecule is the IP of its anion, if we utilize this identity, the two expressions coincide and give the same excitation energies. Reasonable results are obtained for valence and core excitations using only orbital energies.     

Electrospinning of chitosan derivative nanofibers with structural stability in an aqueous environment

We report a simple method to produce stable chitosan derivative nanofibers via electrospinning. A chitosan solution with lactate salt was electrospun to produce nanofibers, followed by thermal treatment to enhance fiber stability. Chemical and morphological analyses demonstrated that the resulting nanofibers were crosslinked via amidation between chitosan and lactate salt. These fibers exhibited sustained morphological and structural stabilities to serve as a scaffold for biomedical applications.     

Spectral study of the complexation of Nd(III) with glutathione reduced (GSH) in the presence and absence of Zn(II) in aquated organic solvents

Studies on the difference in energy parameters and comparative absorption spectrophotometry involving 4f-4f transitions on Nd(III) and glutathione reduced (GSH) in the absence and presence of Zn(II) have been carried out in aquated organic solvents (50 : 50) like methanol, dioxane, acetonitrile and dimethylformamide. Variations in the spectral energy parameters — Slater-Condon (F _k ) factor, Lande spin-orbit coupling constant (ξ4f), nephelauxetic ratio (β), bonding parameter (b ^1/2 ) and percent covalency (δ) — are calculated and correlated with binding of Nd(III) with GSH in presence and absence of Zn(II).     

Intrinsic viscosities of sodium carboxymethylcellose in acetonitrile–water mixed solvent media using isoionic dilution method

Precise measurements on the viscosities of the solutions of sodium carboxymethylcellulose in water and in two acetonitrile–water mixtures containing 10 and 20 vol % of acetonitrile have been reported at 35, 40 and 50 °C. Isoionic dilutions were performed with the total ionic strengths of the solutions maintained with sodium chloride at ～4.20 × 10^?4 and 1.45 × 10^?3 mol dm^?3 of NaCl to obtain the intrinsic viscosities. The Huggins constants were also obtained from the experimental results. The influences of the medium, the temperature, and the total ionic strength on the intrinsic viscosities as well as on the Huggins constants have been interpreted from the points of view of the solvodynamic and thermodynamic interactions prevailing in the polyelectrolyte solution under investigation. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1765–1770, 2007     

Acetylene diffusion in Na-Y zeolite

Study of diffusivity of acetylene adsorbed in Na-Y zeolite by quasi-elastic neutron scattering (QENS) measurements at temperatures of 300, 325 and 350 K is reported. A model in which the acetylene molecules undergo random-walk diffusion characterized by a Gaussian distribution of jump lengths inside zeolite cages describes the data consistently. The diffusion constant, residence time between jumps and root mean square jump length are determined.     

An approximation algorithm for network design problems with downwards-monotone demand functions

Building on an existing 2-approximate algorithm for the class of network design problems with downwards-monotone demand functions, many of which are NP-hard, we present an algorithm that produces solutions that are at least as good as and typically better than solutions produced by the existing algorithm.