Grafting vinyl monomers onto natural fibres. Graft copolymerization of methyl methacrylate onto wool and silk using peroxydiphosphate-tartaric acid redox system

Methyl methacrylate has been grafted onto wool and silk using the redox system peroxydiphosphate/tartaric acid. The alkali solubility falls with increased grafting.     

Oscillation Criteria For A Class Of First Order Neutral Impulsive Differential-Difference Equations

Sufficient conditions areestablished for oscillation of all solutions of a class ofnonlinear neutral impulsive differential-difference equations offirst order with deviating argument and fixed moments of impulse effect.     

Proton induced modification in Poly(ethylene terephthalate)

A systematic investigation of 62 r MeV proton irradiated Poly(ethylene terephthalate) (PET) has been carried out using Fourier Transformed Infrared Spectroscopy, thermogravimetric analysis, differential scanning calorimetry and X-ray diffraction spectroscopy. The experiments revealed a restoration of the crystalline matrix and simultaneous decrease in thermal stability in the irradiated polymer as a function of dose, indicating that PET underwent both degradation and cross-linking by proton irradiation.     

A study of the activation energy of thermal decomposition of irradiated polymers

The ion irradiation of polymeric solids induces numerous modifications in the polymer properties thus increasing their applicability in various fields. The present work looks into the aspect of thermal modifications induced in the irradiated polymers. The kinetics of thermal decomposition of polymers is investigated by using the thermogravimetric (TG) technique. It has been observed that the degradation of polymers is a multi-step process that involves sequential and competing processes, and obeys the Arrhenius kinetics which allows us to connect the rate constant with the absolute temperature and the activation energy. The activation energy of thermal decomposition has been calculated from the TG curves, and its variation with different irradiation doses has been derived.     

Electron induced modification in poly(ethylene terephthalate)

Abstract

The effect of 100 kGy dose of 2 MeV electron irradiation on Poly(ethylene terepthalate) (PET) has been studied by different characterisation techniques such as the Fourier transformed IR spectroscopy, electron spin resonance spectroscopy, thermogravimetric analysis, differential scanning calorimetry and X-ray diffraction analysis. Oxidative degradation leading to amorphisation of the polymer has been observed from spectral analysis. The thermal stability of the polymer was found to decrease due to electron irradiation. The thermal decomposition temperature as well as the melting temperature in case of irradiated PET was found to be decreased due to electron bombardment. A decrease in crystallinity of the polymer has also been observed after irradiation.     

A posteriori error estimates for H 1-Galerkin mixed finite-element method for parabolic problems

The purpose of this article is to derive a posteriori error estimates for the H ¹-Galerkin mixed finite element method for parabolic problems. We study both semidiscrete and fully discrete a posteriori error analyses using standard energy argument. A fully discrete a posteriori error analysis based on the backward Euler method is analysed and upper bounds for the errors are derived. The estimators yield upper bounds for the errors which are global in space and time. Our analysis is based on residual approach and the estimators are free from edge residuals.     

On the Behaviour of Solutions of a Class of Third Order Difference Equations

In this paper, the structure of the solution space of y n +3 + ry n +2 + qy n +1 + py n =0, n S 0, is studied, keeping oscillatory/nonoscillatory behaviour of solutions of the equation in view, where p , q and r are constants. Some of these results are generalized partially to hold for y n +3 + r n y n +2 + q n y n +1 + p n y n =0, n S 0, where { p n }, { q n } and { r n } are sequences of real numbers.     

Superconvergence of H 1-Galerkin Mixed Finite Element Methods for Second-Order Elliptic Equations

We derive superconvergence result for H ¹-Galerkin mixed finite element method for second-order elliptic equations over rectangular partitions. Compared to standard mixed finite element procedure, the method is not subject to the Ladyzhenskaya–Bab?ska–Brezzi (LBB) condition and the approximating finite element spaces are allowed to be of different polynomial degrees. Superconvergence estimate of order 𝒪(h ^k+3), where k ≥ 1 is the order of the approximating polynomials employed in the Raviart–Thomas elements, is established for the flux via a postprocessing technique.     

Modifications in track registration response of PADC detector by energetic protons

It has been well established that different ionising radiations modify the track registration properties of dielectric solids. In an effort to study the response of Polyallyl diglycol carbonate (PADC Homalite) detector towards fission fragment, PADC detectors were exposed to 10⁴ Gy dose of 62 MeV protons and then one set of samples were exposed to fission fragments from a ²⁵²Cf source. Two of these detectors were containing a thin layer of Buckminsterfullerene (C₆₀). The study of the etched tracks by Leitz Optical Microscope reveals that the track diameters are enhanced by more than 70% in the proton irradiated zone as compared to that in the unirradiated zone. Scanning Electron Microscopy was performed after etching the sample in 6 N NaOH at 55°C for different etching times, to study the details of the surface modifications due to proton irradiation of PADC detectors with and without C₆₀ layer. Our observations revealed that the diameters and density of proton tracks have increased with etching time on the surface facing the fullerene layer as well as the other surface. However, a relatively more open structure of the etched surface containing C₆₀ as compared to the bare one may be an indication of the extra damage caused by the energy released upon the destruction of C₆₀ molecules by energetic protons.     

Investigation of hot electrons and hot phonons generated within an AlN/GaN high electron mobility transistor

We review our recent results obtained on an AlN/GaN-based high-electron-mobility transistor. The temperature of the electrons drifting under a relatively-high electric field is significantly higher than the lattice temperature (i.e., the hot electrons are generated). These hot electrons are produced through the Fröhlich interaction between the drifting electrons and long-lived longitudinal-optical phonons. By fitting electric field vs. electron temperature deduced from the measurements of photoluminescence spectra to a theoretical model, we have deduced the longitudinal-optical-phonon emission time for each electron is to be on the order of 100 fs. We have also measured the decay time constant for LO phonons to be about 4.2 ps. An electric field present in a GaN/AlN heterostructure can bring both the first-order and second-order Raman scattering processes into strong resonances. The resonant Stokes and anti-Stokes Raman scattering results in the increase and decrease of non-equilibrium longitudinal-optical phonon temperatures, respectively. Moreover, the phonon temperature measured from the Raman scattering is increased with an applied electric field at a much higher rate than the lattice temperature due to the presence of field-induced non-equilibrium longitudinal-optical phonons.