Claisen–Schmidt reaction in a hydrotropic medium

The Claisen–Schmidt condensation of benzaldehydes with acetophenones was carried out in an aqueous medium using sodium butylmonoglycolsulfate (NaBMGS) and sodium salts of aromatic sulfonic acids as hydrotropes. Substantial enhancement in the rate of the reaction was obtained, along with the easy recovery of the product. Recycling of the hydrotrope solutions has been tested without any loss in the rate of the reaction.     

Production of type II collagen specific monoclonal antibodies

Immunoassays are used for the specific measurement of type II collagen, a major cartilage protein, which is lost in osteoarthritic joints. Poor immunogenicity and species dependent immune response to type II collagen make it difficult to obtain specific antibodies required for immunoassay development. In addition, type II collagen antibodies exhibit reactivity to structurally dissimilar antigens such as actin, myoglobin, thyroglobulin and ssDNA, complicating the isolation of specific antibodies. It is therefore necessary to characterize the antibody reactivity against both noncollagenous antigens and different collagen types. In this study, immune response to type II collagen was improved by conjugation to carrier proteins, KLH and BSA. Hybridomas were generated by fusions of lymphocytes derived from lymph nodes or spleens with X63-653-Ag8 myeloma cells. Compared to spleens, the utilization of lymph nodes as a source of lymphocytes resulted in a 23% higher number of hybridomas secreting type II collagen antibodies. Hybridomas secreting polyreactive antibodies were identified based on their reactivity to thyroglobulin and eliminated. Extensive testing of the remaining monoclonal antibodies with other structurally dissimilar antigens and various types of collagen for reactivity, allowed us to isolate specific monoclonal antibodies to type II collagen. We emphasize the importance of characterization of the reactivity of type II collagen monoclonal antibodies before employing them for immunoassays.     

On the first order local stability scheme for the numerical solution of time-dependent compressible flows

The diffusion, stability and monotonicity properties of the first order local stability scheme are investigated by resorting to both analysis and numerical experimentation. The scheme, deducible from either the first order Rusanov scheme or the first order van Leer scheme, is optimally stable. The magnitude of the truncation viscosity of the scheme is in between that of the Rusanov scheme and of the second order Lax-Wendroff scheme. The scheme does not, in general, yield monotonic profiles of shocks. A modified version of the local stability scheme (which preserves the local stability character at each point in the flow region and switches over to the van Leer scheme near shocks only) is proposed for practical application. Tests on one-dimensional problems show that the scheme achieves a better resolution of the flow features than is possible with the Rusanov scheme. The scheme is found to be capable of yielding a resolution which is almost equal to that of the second order schemes. Furthermore, it offers other advantages in that it resists nonlinear instabilities, is easy to programme and requires only a modest amount of storage and time on the computer.     

Intraparticle effects in char combustion steady state analysis

A model is developed to study the intraparticle effects of char combustion which incorporates the reactions, C + 1/20₂ → CO, CO + 1/20₂ → CO₂ and CO₂ + C → 2CO with appropriate intrinsic kinetics. Based on some limiting cases a feasibility region, inside which the solution should lie, is developed. In almost all cases the major product is CO with CO₂ production 2 to 3 orders of magnitude lower. A maximum of three steady states is observed for the parameters chosen. The combustion rate decreases with increase in particle size and increase in boundary layer thickness. The solution structure depends strongly on the radiation conditions which obtain and on the transport properties inside the particle. The purpose of this study is to determine the effect of intraparticle transport without the confounding effects of other phenomena.     

A comparative and mechanistic study on regioselective photooxidative demethylation of N‐heterocyclics using TiO2 and molecular oxygen

Regioselective photooxidative demethylation of methyl‐substituted N‐containing heterocyclic compounds is investigated in non‐aqueous (ethane nitrile) solutions containing semiconductor oxide (TiO₂) as photocatalyst in the presence of molecular oxygen upon irradiation at room temperature conditions. A plausible electron transfer mechanism, in which an electron‐hole pair is generated on the surface of TiO₂ by illumination, is proposed for the semiconductor‐mediated photocatalysis. Molecular orbital calculation by the AM 1 method has been performed for the electron densities of N‐atoms of heterocyclics in the present study. © 2002 Society of Chemical Industry     

A model for calculation of pressure in the duct due to discharge of gas from a failed fuel pin

In this paper an anlytical model for the calculation of the pressure pulse in hexagonal ducts due to discharge of gas from a failed fuel pin is developed. The analysis yields the time history of the pressure pulse which can be used in the calculation of permanent deformation of the duct or in the assessment of the susceptibility of the duct to fracture. In this model the analysis is divided into two stages. In the first stage the gas expands as a spherical bubble, but the influence of duct wall is taken into account. At the end of the first stage the spherical shape of the bubble is assumed to be lost and the gas is assumed to expand axially as a column. The end conditions of stage 1 are the initial conditions for stage 2. The analysis involves solving the continuity and momentum equations for the liquid along with the energy balance equation for the gas. In the analysis the liquid is assumed to be incompressible.     

Intraparticle effects in char combustion ii steady state analysis

Based on the results of an earlier paper, a model is developed to include the homogeneous reaction in the external boundary layer. It is assumed, consistent with those results, that there is no homogeneous reaction within the particle. A feasibility region is constructed using limiting cases along the lines described there. Under some conditions, the model predicted up to five steady states for a given set of ambient conditions. For large particles, a flame develops in the boundary layer and the main product is CO₂. Under such conditions, the reaction locus coincides with the double film model. While for small particles, no flame develops and the major product is CO. The solution is sensitive to the type of radiative interaction which obtains. The combustion rate increases with increase in particle temperature until a certain point, then decreases with further increase in temperature, and eventually turns back and increases again. Such behavior has been observed in some rate measurement experiments.     

Influence of heat treatment on the strength and fracture behaviour of Fe-12Cr-6Al ferritic stainless steel

The changes in the tensile properties and fracture mode brought about by heat treatment of Fe-12Cr-6Al ferritic stainless steel have been studied. A favourable combination of high strength and good ductility is obtained by heating the material at 1370 K for 2 h followed by a water quench. The high-temperature treatment results in carbide dissolution as well as an increase in the grain size. The mechanism of strengthening has been evaluated from the apparent activation energy (28 kJ mol^–1) and is identified to be the unpinning of dislocations from the atmosphere of carbon atoms. As the heat-treatment temperature is increased, the fracture behaviour changes from ductile to brittle mode and this is related to the changes in grain size and friction stress.