Some remarks on the chain segment dynamics in confined polymers

The European Physical Journal E - Recently, the chain dynamics of molten polymers in confined geometries has been investigated, using NMR. Some of these experiments have been performed on...     

Integral Newton-Type Polynomials with Continual Nodes

We construct an integral Newton-type interpolation polynomial with a continual set of nodes. This interpolant is unique and preserves an operator polynomial of the corresponding degree.     

Relaxor type perovskites: Primary candidates of nano-polar regions

Relaxor properties of 0.7Pb(Mg_1/3Nb_2/3)O₃-0.3PbTiO₃ (PMN-PT) and non-lead perovskite thin films have been analysed in terms of large frequency dispersion of dielectric response at low temperatures. A wide spectrum of dielectric relaxation was observed in the frequency-dependent response of the imaginary part of the dielectric permittivity. Transformation from normal ferroelectric to relaxor behaviour has been observed in the case of the Ca substituting the BaTiO₃ thin films. A number of techniques were exploited to investigate the wide spectrum of relaxation times in pulsed laser ablated thin films.ac anddc electric field induced complex dielectric properties of 0.7Pb(Mg_1/3Nb_2/3)O₃-0.3PbTiO₃ (PMN-PT) thin films were studied as function of frequencies at different temperatures. Nonlinear behaviour of dielectric susceptibility with respect to the amplitude of theac drive was observed at lower temperatures. The frequency dependence of transition temperatureT _m (temperature of the maximum of dielectric constant) was studied using the Vogel-Fulcher relation. Dedicated to Professor C N R Rao on his 70th birthday     

A microspectroscopic study of the electronic homogeneity of ordered and disordered Sr2FeMoO6

Disordered Sr₂FeMoO₆ shows a drastic reduction in saturation magnetization compared to highly ordered samples, moreover magnetization as a function of the temperature for different disordered samples shows qualitatively different behaviours. We investigate the origin of such diversity by performing spatially resolved photoemission spectroscopy on various disordered samples. Our results establish that e_xtensive electronic inhomogeneity, arising most probably from an underlying chemical inhomogeneity in disordered samples, is responsible for the observed magnetic inhomogeneity. It is further pointed out that these inhomogeneities are connected with composition fluctuations of the type Sr₂Fe_1+x Mo_1-x O₆ with Fe-rich (x > 0) and Mo-rich (x < 0) regions. Dedicated to Prof J Gopalakrishnan on his 62nd birthday.     

Recyclization of Products Formed by Addition of 5-Hydrazino-2-phenyl-1,3-oxazoles Functionally Substituted in 4-Position to Aryl Isothiocyanates

Russian Journal of General Chemistry -     

Time discretizations for Maxwell‐Bloch equations

In this article we derive new time discretizations for the numerical simulation of Maxwell‐Bloch equations. These discretizations decouple the equations, thus leading to improved efficiency. This approach may be combined with the fulfilment of physical properties, such as positiveness properties, which are not accounted for by classical schemes. Our time discretizations are moreover proved to be nonlinearly stable. © 2003 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 19: 284–300, 2003.     

A modified method of characteristics incorporating streamline diffusion

A hybrid finite-element method, combining ideas from a modified method of characteristics and the streamline diffusion method, delivers accurate solutions to the advection–diffusion equation. An error analysis for the case of tensorial diffusion shows that the lowest-order version of the scheme, which allows one to use a symmetric linear solvers at each time step, possesses first-order accuracy in time and space. Numerical experiments demonstrate the scheme's ability to model advection-dominated transport of solute plumes without distorting sharp fronts. © 1995 John Wiley & Sons, Inc.     

Asymptotics of Dirichlet Spectrum on Some Class of Noncompact Domains

We investigate the asymptotic behaviour of the counting function of Dirichlet eigenvalues on some class of noncompact manifolds. We prove that in cases when the volume or the perimeter (the volume of the boundary) of the manifold is infinite, some additional (nonclassical) terms appear in the precise asymptotics. The coefficients at the classical terms in those are regularized in some special way volume (resp. perimeter) of the manifold.     

Nitroxide‐mediated radical polymerization in miniemulsion: Bimolecular termination in monomer‐free model systems

Bimolecular termination in nitroxide‐mediated radical polymerization in miniemulsion has been investigated through the heating of a polystyrene–2,2,6,6‐tetramethylpiperidinyl‐1‐oxy macroinitiator and its 4‐hydroxy‐2,2,6,6‐tetramethylpiperidinyl‐1‐oxy analogue in an aqueous toluene dispersion with sodium dodecyl benzenesulfonate as a surfactant at 125 °C. The level of bimolecular termination by combination, evaluated from the high‐molecular‐weight shoulder, was higher in miniemulsion than in solution and increased with decreasing particle size. Quantitative analysis revealed that these results cannot be rationalized solely by nitroxide partitioning to the aqueous phase. The results are explained by an interface effect, by which nitroxide is adsorbed or located at the aqueous–organic interface. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4995–5004, 2007