Orientational distribution function in nematic liquid crystals by x-rays: Fourier method

The existing methods for the determination of the orientational distribution function f(beta) in the nematic liquid crystals using X-rays have been reviewed. A simple Fourier method which gives f(beta) in terms of the measured intensity is analysed. Using this distribution function, the accuracy with which the order parameters could be evaluated is discussed and the results show the elegance of the Fourier method used here

Use of isotopically labeled substrates reveals kinetic differences between human and bacterial serine palmitoyltransferase

Isotope labels are frequently used tools to track metabolites through complex biochemical pathways and to discern the mechanisms of enzyme-catalysed reactions. Isotopically-labelled L-serine is often used to monitor the activity of the first enzyme in sphingolipid biosynthesis, serine palmitoyltransferase (SPT) as well as labelling downstream cellular metabolites. Intrigued by the effect that isotope labels may be having on SPT catalysis, we characterised the impact of different L-serine isotopologues on the catalytic activity of recombinant SPT isozymes from humans and the bacterium Sphingomonas paucimobilis. Our data show that S. paucimobilis SPT activity displays a clear isotope effect with [2,3,3-D] L-serine, whereas the human SPT isoform does not. This suggests that whilst both human and S. paucimobilis SPT catalyse the same chemical reaction, there may well be underlying subtle differences in their catalytic mechanisms. Our results suggest that it is that the activating small subunits of human SPT that play a key role in these mechanistic variations. This study also highlight that it is important to consider the type and location of isotope labels on a substrate when they are to be used in in vitro and in vivo studies

Electrode modification using nanocomposites of electropolymerised cobalt phthalocyanines supported on multiwalled carbon nanotubes

A polymer of tetra(4)-(4,6-diaminopyrimidin-2-ylthio) phthalocyaninatocobalt(II) (CoPyPc) has been deposited over a multiwalled carbon nanotube (MWCNT) platform and its electrocatalytic properties investigated side by side with polymerized cobalt tetraamino phthalocyanine (CoTAPc). X-ray photoelectron spectroscopy, scanning electron microscopy and cyclic voltammetry studies were used for characterization of the prepared polymers of cobalt phthalocyanine derivatives and their nanocomposites. L-Cysteine was used as a test analyte for the electrocatalytic activity of the nanocomposites of polymerized cobalt phthalocyanines and multiwalled carbon nanotubes. The electrocatalytic activity of both polymerized cobalt phthalocyanines was found to be superior when polymerization was done on top of MWCNTs compared to bare glassy carbon electrode. A higher sensitivity for L-cysteine detection was obtained on CoTAPc compared to CoPyPc

Effect of Gamma- Irradiation on Structure, Morphology and Thermal Properties of Novel Polyamide Based Thermoset Obtained by Double Cycloaddition

Cycloaddition reactions gained prominence in macromolecular chemistry for generating macromolecules because of high yields of these reactions, which is a key tool that drives polyaddition reactions. Cycloaddition reaction plays major role in extension of polymerisation or in other words high conversions of monomers to macromolecules of high molecular weights. Until the late 1990s, the major studies regarding cycloadditions in novel polymer synthesis were related to polyaddition reactions. Since then in the field of polymer synthesis the affirmative strengths of these cycloaddition reactions have been exhibited in multi fold polymer design and headway material architecture. Future demand exists in unlatching the capacity of these novel synthetic routes for advanced applications in catalysis, separation, optoelectronics, and analytical media. Thus, we have developed an able and productive synthetic podium for the preparation of a new class of polyimide based on the double 1, 3-dipolar cycloaddition of thiasydnone with bis-maleimide. This paper reports the effect of gamma irradiation on the changes in physico-chemical properties of the polyamide based thermoset synthesised by double cycloaddition approach. The thermoset synthesized by this exclusive approach were irradiated with gamma doses in the range 10- 300 kGy. The substantial effect of gamma radiation and the structural modifications induced on the thermoset have been studied as a function of dose using different characterization techniques such as Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), differential scanning calorimetry- thermo gravimetric analysis (DSC-TGA), Field Emission Scanning Electron Microscope (FESEM) and UV-Vis Spectroscopy

Characterization of montmorillonite doped PVA/SA blends using X-ray diffraction

PVA films doped with Montmorillonite was prepared by slow evaporation technique. These films have been used to record X-ray patterns at room temperature. Correlation lengths and microstructural parameters were computed using in-house program employing X-ray data. Results show that correlation lengths as well as crystallite size increases with increase in the concentration of Montmorillonite which is inconformity with the conductivity studies

Effect of Gamma- Irradiation on Structure, Morphology and Thermal Properties of Novel Polyamide Based Thermoset Obtained by Double Cycloaddition

Cycloaddition reactions gained prominence in macromolecular chemistry for generating macromolecules because of high yields of these reactions, which is a key tool that drives polyaddition reactions. Cycloaddition reaction plays major role in extension of polymerisation or in other words high conversions of monomers to macromolecules of high molecular weights. Until the late 1990s, the major studies regarding cycloadditions in novel polymer synthesis were related to polyaddition reactions. Since then in the field of polymer synthesis the affirmative strengths of these cycloaddition reactions have been exhibited in multi fold polymer design and headway material architecture. Future demand exists in unlatching the capacity of these novel synthetic routes for advanced applications in catalysis, separation, optoelectronics, and analytical media. Thus, we have developed an able and productive synthetic podium for the preparation of a new class of polyimide based on the double 1, 3-dipolar cycloaddition of thiasydnone with bis-maleimide. This paper reports the effect of gamma irradiation on the changes in physico-chemical properties of the polyamide based thermoset synthesised by double cycloaddition approach. The thermoset synthesized by this exclusive approach were irradiated with gamma doses in the range 10- 300 kGy. The substantial effect of gamma radiation and the structural modifications induced on the thermoset have been studied as a function of dose using different characterization techniques such as Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), differential scanning calorimetry- thermo gravimetric analysis (DSC-TGA), Field Emission Scanning Electron Microscope (FESEM) and UV-Vis Spectroscopy

Studies on the effect of PbO-magnetite (Fe₃O₄) on shielding properties of EPDM composites for 662 keV gamma rays

639-642In the present study different combinations of PbO and Fe3O4 in ethylene-propylene-diene monomer (EPDM) matrix have been synthesized and studied the ideal combination for gamma ray shielding. Attenuation parameters such as attenuation coefficient (µ), half value layer (HVL), tenth value layer (TVL), relaxation length (λ) and mass attenuation coefficient (µm) have been determined for all samples. It has been found that EPDM with 40 phr of lead oxide and 20 phr of magnetite (DCPM20) has good attenuation ability compared to other synthesized samples for 662 keV gamma rays. Also, DCPM20 has shown better mechanical and AC electrical conductivity properties compared to pure lead-based EPDM composites. Considering all the studied parameters DCPM20 sample has been found to be better radiation shielding material among the studied composites

Micro-structural parameters of polymer materials using WAXS data: Bimodals crystal size distribution

Line Profile Analysis (LPA) of polymer samples using single order method employing various bimodal functions for crystal size distributions have been carried out for the first time. The results indicate a better fitting with reduced errors due to truncation and background of a profile. Normally observed ripples in the tail of a simulated profile are reduced considerably in the present approach

Structure-property relation in copper nanoparticles-based PVA/PVP composites

Copper nanoparticles composition-based polyvinyl alcohol/polyvinylpyrrolidone(PVA/PVP) composite films were prepared for select concentrations. AC conductivity, dielectric permittivity, UV-visible and FTIR studies along with X-ray diffraction analysis were carried out on these composites. From this conductivity study, DC conductivity was estimated along with hopping potential, hopping length and thermal conductivity using power law of the frequency-dependent AC conductivity. A correlation study of these parameters using functional analysis method to establish structure-property relation in these composites was also carried out