Studies on the cure parameters of cyanate ester–epoxy blend system through rheological property measurements

Thermosetting blend system of co-cured cyanate ester with epoxy resin is receiving importance for high technological applications because of its wide range of thermo-mechanical, rheological, and electrical properties. However, processing of these system warrant proper knowledge of the rheological behavior of the blend during the curing process. This article discusses the rheological behavior of the blend systems with respect to the pot life, gel time, gelation temperature and also evaluated fitting parameters for the prediction of gelation time and viscosity during the entire curing process from the isothermal rheological measurements.     

Computation-led design of pollutant gas sensors with bare and carbon nanotube supported rhodium alloys

Quantum chemical study has been performed on finite-sized bi-metallic Rh3M alloys, M = Ag, Ir, Pd, Pt, Au, derived from magic cluster, Rh4. Bond length of C–O and N–O are noticed to be elongated in the presence of rhodium alloy clusters. CO2 and NO2 gases are found to be highly adsorbed on Rh3M clusters, which is confirmed by stretching frequency of C–O and N–O. DFT evaluated dipole moment and electronic charge redistribution suggests the sensing capability of CO2 and NO2 gases by Rh3M clusters which is further confirmed by the calculated HOMO–LUMO gap. Mixed rhodium alloy clusters supported on single-wall carbon nanotube (SWCNT) exhibits much higher ability to sense CO2 and NO2. On the other hand, SWCNT@Rh3M shows higher catalytic activity for the activation of CO2 and NO2 in comparison to bare Rh3M because of the higher electronic charge redistribution in the case of SWCNT@Rh3M. In case of SWCNT-supported gas adsorbed clusters, p electrons play a major role in bonding.     

XNBR/LDH nanocomposites: Effect of vulcanization and organic modifier on nanofiller dispersion and strain‐induced crystallization

In elastomer/organo clay nanocomposites, the morphological characteristics, and hence the mechanical properties, of the vulcanizates are strongly influenced by the organic modifier and the vulcanization process. When the elastomer itself undergoes strain‐induced crystallization, both the organic modifier and the dispersed filler particles could significantly influence the crystallization process. These phenomena are very common in case of natural rubber‐based vulcanizates. In this study, the similar effects have been demonstrated with carboxylated nitrile rubber (XNBR) and organically modified layered double hydroxide (O‐LDH)‐based nanocomposites. The effect of size of the organic modifier was obviously visible on the interlayer distance of O‐LDH and also on the morphological reorganization of the dispersed O‐LDH particles during vulcanization process. The strain‐induced crystallization of the XNBR was found to be strongly dependent on the morphological change that occurs during vulcanization process. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2010     

Mercury(II) chloride-mediated cyclization-rearrangement of O-propargylglycolaldehyde dithioacetals to 3-pyranone dithioketals: an expeditious access to 3-pyranones

[Reaction: see text] O-Propargyl glycolaldehyde dithioacetals undergo a unique cyclization-rearrangement in the presence of mercuric chloride and calcium carbonate to afford 3-pyranones exclusively or along with 2,5-dihydrofuran-3-carboxaldehydes via their dithioketals and dithioacetals.     

Generation of Bianchi type V cosmological models with varying Λ-term

Bianchi type V perfect fluid cosmological models are investigated with cosmological term varying with time. Using a generation technique (Camci et al., 2001), it is shown that Einsteins field equations are solvable for any arbitrary cosmic scale function. Solutions for particular forms of cosmic scale functions are also obtained. The cosmological constant is found to be a decreasing function of time, which is supported by results from recent type Ia supernovae observations. Some physical aspects of the models are also discussed.     

Plane Symmetric Viscous Fluid Cosmological Models with Varying <Emphasis Type="Italic">Λ</Emphasis>-Term

Plane symmetric viscous fluid cosmological models of the universe with a variable cosmological term are investigated. The viscosity coefficient of bulk viscous fluid is assumed to be a power function of mass density whereas the coefficient of shear viscosity is to be proportional to rate of expansion in the model. We have also obtained a special model in which the shear viscosity is assumed to be zero. The cosmological constant Λ is found to be a decreasing function of time and a positive which is supported by results from recent supernovae Ia observations. Some physical and geometric properties of the models are also discussed.     

Modeling and experimental studies on combustion characteristics of porous coal char: Volume reaction model

A generalized single‐particle model for the prediction of combustion dynamics of a porous coal char in a fluidized bed is analyzed in the present work using a volume reaction model (VRM). A fully transient nonisothermal model involving both heterogeneous and homogeneous chemical reactions, multicomponent mass transfer, heat transfer with intraparticle resistances, as well as char structure evolution is developed. The model takes into account convection and diffusion inside the particle pores, as well as in the boundary layer. By addressing the Stefan flow originated due to nonequimolar mass transfer and chemical reactions, this work enables a more realistic analysis of the combustion process. The model, characterized by a set of partial differential equations coupled with nonlinear boundary conditions, is solved numerically using the implicit finite volume method (FVM) with a FORTRAN code developed in‐house. The use of a FVM for solving such an elaborate char combustion model, based on the VRM, was not reported earlier. Experiments consisting of fluidized‐bed combustion of a single char particle were carried out to determine the internal surface area of a partially burned char particle and to enable model validation. Predicted results are found to compare well with the reported experimental results for porous coal char combustion. The effects of various parameters (i.e., bulk temperature and initial particle radius) are examined on the dynamics of combustion of coal char. The phenomena of ignition and extinction are also investigated. © 2010 Wiley Periodicals, Inc. Int J Chem Kinet 42: 299–315, 2010     

Total synthesis of a unique tetrasaccharide present in the human clotting factor IX and mammalian Notch 1 receptor

The synthesis of a unique tetrasaccharide linked to the serine 61 of human clotting factor IX through an α-l-fucose residue has been achieved for the first time in excellent yield. All glycosylation and protecting group manipulation steps are high yielding and reproducible for a scale-up preparation. A sequential glycosylation strategy has been used to assemble suitably protected monosaccharide synthons for the preparation of the target tetrasaccharide.     

Influence of projectile breakup on complete fusion

Complete fusion excitation functions for ^11,10B+¹⁵⁹Tb and ^6,7Li+¹⁵⁹Tb have been reported at energies around the respective Coulomb barriers. The measurements show significant suppression of complete fusion cross-sections at energies above the barrier for ¹⁰B+¹⁵⁹Tb and ^6,7Li+¹⁵⁹Tb reactions, when compared to those for ¹¹B+¹⁵⁹Tb. The comparison shows that the extent of suppression of complete fusion cross-sections is correlated with the α-separation energies of the projectiles. Also, the measured incomplete fusion cross-sections show that the α-particle emanating channel is the favoured incomplete fusion process. Inclusive measurement of the α-particles produced in ⁶Li+¹⁵⁹Tb reaction has been carried out. Preliminary CDCC calculations carried out to estimate the α-yield following ⁶Li breaking up into α+d fail to explain the measured α-yield. Transfer processes seem to be important contributors.     

Estimation of DUR and source utilization efficiency for changing product dimensions and source activities in gamma irradiator

This paper discusses the application of the developed analytical method (Reji George, Jain, Pradhan, A.S., 2008. Theoretical evaluation of dose distribution in product in radiation processing plants. Radiat. Phys. Chem. 77, 186–191), for determining the activity loading pattern in a radiation processing plant to get the desired dose uniformity ratio (DUR) for processing mangoes and how the method was used to evaluate the expected source utilization efficiency for the redesigned source–product configuration.