Determination of physicochemical properties of some fatty acid methyl esters by gas liquid chromatography

Physicochemical data such as vapor pressures (p⁰), heats of vaporization (ΔH_v), activity coefficents at infinite dilution (γ^∞) and excess partial molar entropy (ΔS _e ⁰ ) are considered important for conducting unit processes and designing reactor equipment. Scanty information regarding such data is available in the literature for the higher fatty acid methyl esters. The objective of this research was to determine the physicochemical properties of higher fatty acid methyl esters (C₁₁–C₂₃) by a gas-liquid chromatographic technique with SE-30 and diethylene glycol adipate as stationary phases. Correlations between carbon numbers and various thermodynamic properties have indicated definite trends, which could be useful in predicting the properties of unknown fatty acid methyl esters. The data generated may be useful to chemical engineers in the construction of storage tanks, solvent extractors and distillation columns. IICT communication no. 2993.     

α-Tocopherol prooxidant effect and malondialdehyde production

α-Tocopherol at high concentration (1.25×10⁻⁴M) exhibited a prooxidant effect during autoxidation of linolenic and arachidonic acids. This prooxidant activity involved a significant increase of the conjugated diene level, especially with linolenic acid. High performance liquid chromatographic evaluation of malondialdehyde, a by-product of the hydroperoxides of polyunsaturated fatty acids, showed that malondialdehyde was not increased during prooxidant effect ofα-tocopherol. Thus, malondialdehyde does not seem to be a good indicator for the manifestation of the prooxidant activity ofα-tocopherol.     

Visuomotor functions of the lateral pre-motor cortex

Recent studies have provided new insights into the visuomotor functions of the dorsal and ventral regions of the lateral pre-motor cortex. Anatomical and physiological investigations in non-human primates have demonstrated that these regions have differing patterns of cortical connectivity and distinctive neuronal responses. Brain-imaging techniques and lesion studies have begun to probe the functions of homologous regions in humans.     

Photon-enhanced field emission from CdS single crystals

In a previous experiment, field emission was observed from sharply pointed CdS single crystals. The experiments have now been extended, illuminating the tip with light from a pulsed argon-ion laser. It was found that (a) the voltage threshold at which emission can be observed is reduced, typically from 500 to 400 V, (b) under some conditions, the emission is increased by a factor of 103, (c) this emission persists for more than 2×10?2s after the laser pulse and appears to have two characteristic decay times, (d) the emission is approximately proportional to the light intensity and (e) the greatest photo-enhanced field emission was obtained with the laser light shining axially on the emitting area of the tip.     

Transient analysis and selection of perturbation parameters for PV-MPPT implementation

ABSTRACT

In this article, system dynamics of a complete photovoltaic system have been studied. A small signal transient analysis model has been established to examine the effects of small change in the duty cycle of the converter as well as the time steps between each perturbation on the system dynamics. All efforts have been made to do a detailed analysis using almost all the equations involved. Sample calculations (using the simulated system model) are also shown so as to approximately analyse the perturbation effects. It is shown that the value of the step size of the duty cycle should be taken large for points far away from the maximum power point (MPP) and small for points near the MPP. Also, the time between two consecutive perturbations should be at least equal to the settling time. This article is very useful for the researchers to choose a proper delay between two consecutive perturbations and selection of the optimum value of the step size.     

Computation of optimal control policy with singular subarc

Singular subarcs appear in the solution of an optimal control problem when one or more of the control variables appear linearly in both the performance index and differential constraint equations or just in the constraint equations. In such cases, the Pontryagin's⁽¹⁾ Maximum Principle yields no information regarding the possible candidates for such subarcs to be optimal trajectories, since the associated Hamiltonian is also linear in the control variables. In the chemical engineering literature such problems have been reported, for instance, in the optimal control of a continuous stirred reactor^(2,3,4) in the optimally distributed feed reactors⁽⁵⁾, in the optimal catalyst distribution along a tubular reactor^(6,7) and in the optimal design of a plug flow tubular reactor⁽⁸⁾.     

Synthesis of thioethers from hydroxy olefinic fatty acids

Reaction of 3-mercaptopropan-1, 2-diol with methyl ricinoleate (I) and methyl isoricinoleate (II) afforded their respective thioethers. The structure of the products was characterized by combustion and spectral (IR, NMR and MS) data.     

Mixed type symmetric duality for multiobjective variational problems with cone constraints

In this study, a pair of multiobjective variational mixed symmetric dual programs involving cone constraints is presented and usual duality results are established using the notion of generalized ‐convexity. Self‐duality is discussed under additional condition of skew symmetry, and a time‐independence (static) version of the problems is also incorporated.     

Computational investigations of Cu-embedded MoS<Subscript>2</Subscript> sheet for CO oxidation catalysis

Elevated amount of CO levels in the atmosphere poses serious health and environmental hazards. Oxidation of CO using suitable catalysts is one of the methods to control it. By means of DFT calculations, single Cu atom doped in S vacancy of MoS₂ nanosheet is studied for CO oxidation catalysis. Cu atom is strongly confined at the S-defective site of the MoS₂ sheet, possessing high energy barrier for the diffusion to its neighboring sites. Adsorption energy, charge transfer and orbital hybridization of CO and O₂ molecules adsorbed Cu-doped MoS₂ sheet reveal that O₂ is relatively more strongly adsorbed than CO. High adsorption energy of O₂ (??2.115 eV) and large charge transfer between O₂ and Cu–MoS₂ sheet (0.493e), compared to CO, make O₂ adsorption more favorable, which extenuates CO poisoning and hence helps in the efficient CO oxidation process. The complete oxidation of CO takes place in two steps: \( {\text{CO}} + {\text{O}}_{2} \to {\text{OOCO}} \) with activation energy of 0.201 eV, succeeded by \( {\text{OOCO}} + {\text{CO}} \to 2{\text{CO}}_{2} \) without any energy barrier. Our results show that the basal plane of MoS₂ sheet gets activated by embedding it with Cu metal, which can catalyze CO oxidation reaction effectively and without poisoning issues. The high activity, stability and low cost features can possibly encourage fabricating MoS₂-based catalysts for CO oxidation reaction.