The Effect of Atmospheric Ionization on Oxygen Diffusion in Polycrystalline Ferrites under e-Beam Irradiation

It is shown that activation of the process of oxygen diffusion in polycrystalline lithium-titanium ferrites heated by a beam of high-energy electrons in the range of temperatures 873–1173 K occurs due to two factors: gas medium ionization by an e-beam and acceleration of diffusion processes directly in the matrix in the irradiation field.     

Luminescence enhancement by hydrogenation of Si:Er,O

Erbium (Er)- and oxygen (O)-doped Cz–Si was additionally doped with hydrogen, using plasma enhanced chemical vapour deposition. Photoluminescence (PL) spectra show a large enhancement especially for samples treated with solid phase epitaxy before hydrogenation and annealing at 900°C later. Secondary ion mass spectroscopy measurements give evidence for an enhanced diffusion of O and Er at this temperature towards the surface. Etching shows that the PL does not stem from the heavily doped surface layer but from a deeper region with lower Er concentration. This conclusion is supported by the appearance of the so-called “cubic” centre with low solubility. Comparing the PL yield of the hydrogenated samples to that of samples with similar Er volume concentration but without hydrogenation still gives a large enhancement. We thus conclude that hydrogen can enhance the solubility of the cubic centre in Si:Er,O.     

Surface free energies of electroless Ni–P based composite coatings

Surface free energy of a solid surface gives a direct measure of intermolecular interactions at interfaces and has a strong influence on adsorption and adhesion behaviour. However few data are available for the surface free energies of electroless Ni–P based composition coatings. In this paper, the electroless Ni–P, Ni–P-surfactant, Ni–Cu–P, Ni–P–PTFE and Ni–Cu–P–PTFE composite coatings were prepared under various coating conditions. The chemical compositions, surface morphology and thickness of the coatings were measured using an energy dispersive X-ray microanalysis (EDX), a scanning electron microscope (SEM) and a digital micrometer respectively. The contact angles of water, diiodomethane and ethylene glycol on the coatings were measured automatically using dataphysics OCA-20 contact angle analyser. The surface free energy of the coatings and their components (e.g. dispersion, polar or acid/base portions) were calculated using various methods. The experimental results showed that the incorporation of surfactant or PTFE particles into Ni–P matrixes has a significant influence on the surface free energy of the coatings, while the incorporation of copper into Ni–P matrixes has no significant influence on the surface free energy of the coatings.     

A Stability Estimate for a Solution to a Three-Dimensional Inverse Problem for the Maxwell Equations

We consider the problem of determining dielectric permittivity and conductivity in the Maxwell equations. As additional information we prescribe the traces of the tangential components of the electromagnetic field on the lateral surface of a cylindric domain. We establish a stability estimate for a solution to the inverse problem and a uniqueness theorem.     

Generalized Darboux transform in the Ishimori magnet model on the background of spiral structures

The integration procedure based on the generalized Darboux transform is suggested for the Ishimori magnet model. Exact solutions are constructed for the model on the background of spiral structures. The possibility of phase transition in the system is hypothesized.     

Catalytic Hydrosilylation of Furan, Thiophene, and Pyridine Aldimines

The addition of hydrosilanes (HSiEt₃, HSiMe₂Ph, H₂SiPh₂) to the CH=N bond of heterocyclic azomethines has been studied in the presence of monovalent complexes of rhodium and palladium. The effect on the reaction of the CF₃ group of the aldimines, which were obtained from O-, S-, and N-heteroaromatic aldehydes and 2-trifluoromethylaniline, has been clarified, as were other regularities of the processes being studied. A series of corresponding furans, thiophenes, and pyridine amines has been synthesized.     

Norm Series in High-Dimensional Local Fields

In the present paper, the notion of norm series with respect to the norm residue symbol is generalized to high-dimensional local fields. Necessary and sufficient conditions for the existence of norm series are obtained. Bibliography: 12 titles.__________Translated from Zapiski Nauchnykh Seminarov POMI, Vol. 305, 2003, pp. 60–83.     

On the Global Stability of Solutions of Moment Systems in Nonequilibrium Thermodynamics

In this paper, we study the linearization of the Cauchy problem and the mixed problem for the system of Grad--Hermite moments in nonequilibrium thermodynamics in the neighborhood of the equilibrium state. Stability conditions for solutions of the Cauchy problem are proved as a generalization of the classical Hermite--Biller theorem on stable polynomials. For the mixed problem, we prove an analog of the Vishik--Lyusternik theorem on small singular perturbations of general elliptic problems. The last observation allows us to introduce the Shapiro--Lopatinskii condition, which implies the well-posedness of the mixed problem.     

Magnetic phases in Mn<Subscript>1</Subscript>_<Subscript>x</Subscript>Fe<Subscript>x</Subscript>WO<Subscript>4</Subscript> studied by neutron powder diffraction

The magnetic structures of Mn_1-xFe_xWO₄ with x = 0.0, 0.16, 0.21, 0.225, 0.232, 0.24, 0.27, 0.29, and 1.0 were refined from neutron powder diffraction data. The magnetic phase diagram could be completed in the coexistence range of different magnetic structures up to x = 0.29. For the magnetic state at 1.5 K a commensurate antiferromagnetic structure with a propagation vector = (±1/4, 1/2, 1/2) was found for x ⩽ 0.22 while the magnetic spins order with = (1/2, 0, 0) for x ≥ 0.22. In the latter phase, additionally, weak magnetic reflections indexed to an incommensurate ordering with = (- 0.214, 1/2, 0.457) occur in the diffraction pattern up to x = 0.29 indicating the occurence of a reentrant phase. For 0.12 ⩽ x ⩽ 0.29 the low temperature phases are separated from a magnetic high temperature phase showing only magnetic reflections indexed to a spin arrangement with = (1/2, 0, 0). The magnetic phase diagram is discussed qualitatively considering random superexchange between the statistically distributed Mn²⁺- and Fe²⁺-ions in the coexistence range 0.12 ⩽ x ⩽ 0.29 of different magnetic structures related to those of pure MnWO₄ and FeWO₄. Received 9 October 2002 Published online 14 March 2003