Synthesis and characterisation of N-toluyl methacrylatoethyl carbamates,homopolymers and copolymers with methyl methacrylate

The paper describes the synthesis of N-2/4-toluyl methacrylatoethyl carbamates using 2/4-toluyl isocyanate and 2-hydroxyethyl methacrylate. Homopolymerisation and copolymerisation of these novel monomers with methyl methacrylate was carried out using benzoyl peroxide as an initiator and tetrahydrofuran as solvent. Photopolymerisation of N-4-toluyl methacrylatoethyl carbamate could be carried out without the use of photosensitiser. Structural characterisation of copolymers was done using ¹H-NMR. Thermal stability of copolymers was evaluated in a nitrogen atmosphere by dynamic thermogravimetry.     

Molecular Sorption by Heterogeneous Natural Rubber/Poly(ethylene-co-vinyl acetate) Blend Systems

The sorption of n-alkanes, viz. hexane, heptane and octane by cross-linked natural rubber/poly(ethylene-co-vinyl acetate) (NR/EVA) blends has been studied at 28, 38, 48 and 58°C, with special reference to the effects of EVA content, cross-linking systems, penetrant nature and temperature. The solvent transport was found to decrease with increase in EVA content in the blends. The effects of blend ratio on the transport characteristics have been correlated with the phase morphology of the blends, using scanning electron micrographs and optical micrographs. Among the three vulcanising systems, viz. sulphur (S), dicumyl peroxide (DCP) and a mixed system (S + DCP) employed for the matrix, the DCP cross-linked blends exhibited the lowest solvent uptake. Octane has been found to show higher interaction with the blends than hexane and heptane, probably owing to the closer solubility parameter values. The computed transport coefficients, viz. diffusion coefficient and permeability coefficient, were found to decrease with increase in EVA content in the blends. At room temperature, the mechanism of diffusion was found to deviate slightly from the regular Fickian trend for all blend systems. The blend–solvent interaction parameter and the activation energy for transport were also determined from the sorption data.     

Cure characteristics,morphology, and mechanical properties of ethylene–propylene–diene–monomer rubber/acrylonitrile butadiene rubber blends

Blends based on ethylene–propylene–diene monomer rubber (EPDM) and acrylonitrile butadiene rubber (NBR) was prepared. Sulfur was used as the vulcanizing agent. The effects of blend ratio on the cure characteristics and mechanical properties, such as stress–strain behavior, tensile strength, elongation at break, hardness, rebound resilience, and abrasion resistance have been investigated. Tensile and tear strength showed synergism for the blend containing 30% of NBR, which has been explained in terms of morphology of the blends attested by scanning electron micrographs. A relatively cocontinuous morphology was observed for 70 : 30, EPDM/NBR blend system. The experimental results have been compared with the relevant theoretical models. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Deformation due to expanding ring load in modified couple stress thermoelastic diffusion in time and frequency domain

The two-dimensional problem of expanding ring load in a modified couple stress theory of thermoelastic diffusion with heat sources in time and frequency domains is investigated. The mathematical formulation prepared for thermoelastic diffusion solids with one and two relaxation times using Laplace and Hankel transforms. The displacements, stress components, temperature change, and chemical potential are obtained in a transformed domain. Numerical computation is performed for these quantities and the resulting quantities are shown graphically for the time and frequency domains. Comparisons are made with the results predicted by the two theories and different values of time and frequency. Particular cases of interest are also deduced.     

Factors determining informal tanker water markets in Chennai,India

Many developing world cities have seen the emergence of informal markets where private tanker truck operators transport water extracted from peri-urban wells to urban consumers. This study adopted a systems-modelling approach to analyzing the informal tanker market in India. The results indicate that the demand for tanker supply was caused by lack of groundwater availability in private wells as well as unreliable piped supply. The study shows that two groundwater factors are relevant: depth to water and aquifer productivity. Together, these could explain the difference in spatial, temporal and consumer-specific variations in tanker dependence.     

Sex Differences and Individual Differences in Cognitive Performance and Their Relationship to Endogenous Gonadal Hormones and Gonadotropins.

Sexually dimorphic cognitive performance in men (n=42) and women (n=42) was related to testosterone, estradiol, progesterone, luteinizing hormone, follicle-stimulating hormone, and sex hormone binding globulin, measured in 10-ml blood samples collected between 0900 and 1030 and, among women, during the follicular phase of the menstrual cycle. Significant sex differences favored men on spatial tasks (Mental Rotation and Judgment of Line Orientation) and on an inhibition task and favored women on a verbal task (category fluency). However, there were no significant relationships between any of the hormones and cognitive performance, suggesting that there are few, if any, consistent, substantial relationships between endogenous, nonfluctuating levels of gonadal hormones or gonadotropins and these cognitive abilities in men or women. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Structural and luminescence enhancement properties of Eu3＋/Ag nanocrystallites doped SiO2-TiO2 matrices

We reported here the structural and optical characterisation of silver nanocrystallites/Eu3+ :SiO2-TiO2 matrices synthesised through sol-gel route. Structural characterisations were done by using energy dispersive spectroscopy (EDX), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), atomic force microscope (AFM) and transmission electron microscopy (TEM) measurements and optical characterisations were performed by absorption and emission spectroscopy. The TEM and XRD measurements confirmed the presence of nanocrystals. A broad absorption band was observed due to surface plasmon resonance of silver nanocrystals. The effect of silver nanocrystals on the emission spectrum of Eu3+ doped SiO2-TiO2 matrices was discussed. An attempt was made to explain this fluorescence enhancement by invoking phenomena such as energy transfer, asymmetry ratio, surface plasmon, surface roughness, crystallinity and grain boundary. Our analysis, based on the experimental results, suggested that all the phenomena except crystallinity and grain boundary had favourable effects on fluorescence enhancement. We also estimated the relevant parameters associated with the phenomena that affected the fluorescence emission from the Eu3+ ions in the matrix. It was seen that the theoretical estimate of fluorescence enhancement agreed well with the experimental estimate.