North Eastern Hill University

About: North Eastern Hill University is a education organization based out in Shillong, Meghalaya, India. It is known for research contribution in the topics: Population & Ruthenium. The organization has 2318 authors who have published 4476 publications receiving 48894 citations.

Propagation of shock waves in a dusty gas with heat conduction, radiation heat flux and exponentially varying density

Abstract: The propagation of shock waves in a dusty gas with heat conduction and radiation heat flux, in which density varies exponentially, is investigated. The dusty gas is assumed to be a mixture of small solid particles and a perfect gas. The equilibrium flow conditions are assumed to be maintained, and the heat conduction is expressed in terms of Fourier's law and the radiation is considered to be of the diffusion type for an optically thick grey gas model. The thermal conductivity K and the absorption coefficient ?R are assumed to vary with temperature and density. The shock wave moves with variable velocity and the total energy of the wave is non-constant. Non-similar solutions are obtained and the effects of variation of the heat transfer parameters and time are investigated. The effects of an increase in (i) the mass concentration of solid particles in the mixture and (ii) the ratio of the density of solid particles to the initial density of the gas on the flow variables in the region behind the shock are also investigated at given times.

Theoretical investigation of atmospheric chemistry of volatile anaesthetic sevoflurane: reactions with the OH radicals and atmospheric fate of the alkoxy radical (CF3)2CHOCHFO: thermal decomposition vs. oxidation

Abstract: A theoretical study on the mechanism and kinetics of the gas phase reactions of a volatile anaesthetic compound (CF3)2CHOCH2F (Sevoflurane) with the OH radicals has been carried out using the hybrid HF–density functional M06-2X/6-31+G(d,p) method. Three conformations are predicted for the Sevoflurane molecule. Among the three conformers, the most stable one is considered for a detailed study. Reaction profiles are modeled including the formation of pre-reactive and post-reactive complexes at entrance and exit channels. Single point energy calculations have been performed by using the 6-311++G(d,p) basis set. The hydrogen abstraction from the –CH2F group is found to be the dominant reaction channel for hydrogen abstraction by OH radicals. Theoretically the calculated rate constant is found to be in good agreement with the experimentally measured ones. Using group-balanced isodesmic reactions, the standard enthalpies of formation for (CF3)2CHOCH2F, (CF3)2COCH2F and (CF3)2CHOCHF radicals are also reported for the first time. The atmospheric fate of the alkoxy radical, (CF3)2CHOCHFO, is also investigated for the first time using the same level of theory. Out of four prominent plausible decomposition channels including oxidation, our results clearly point out that reaction with O2 is the dominant path for the decomposition of (CF3)2CHOCHFO in the atmosphere involving the lowest energy barrier which is in accord with recent experimental findings.