No abstract

No abstract

The proton assisted isomerization reactions of 1H-imidazo(4,5-b)pyridine (IMP) derivatives have been studied by using B3LYP/6-31G + (d,p) calculations, and the transition states of the reactions are analyzed with B3LYP/6-31+G(d,p) opt¼qst3 route. It has been found that the prototropic transformation could be the feasible pathway of isomerization, since the energy gaps between the various protonated isomers are found closer compared to free molecules. The conversion of IMP-a1 to IMP-b1 may pass through several protrotopic isomerization, since the activation energy as well as the relative energy levels of these isomers are not small compared to other pathways. However, the results suggest that some of the reactions may take place simultaneously through protrotopic transformation. The relative variations of energy gaps in the excited states are smaller than the ground states. The protrotropic transformation in the excited states may be more feasible than the ground state.

The results of an analysis of the physics of levitation of negatively charged dust particles over a surface (wall) in an inverse sheath are reported. It is shown that under suitable parameter regime, the ion-drag force may balance the combined electrostatic and gravitational force on the dust particles owing to its hollow profile as one moves away from the surface. Our analysis shows that the parameter regimes in which such a situation may result is realizable in laboratory and space plasma environments, particularly the near-surface dayside lunar plasma. The lunar surface and dust grains are electrostatically charged due to the interaction with the solar wind plasma environment and the photoemission of electrons due to solar UV radiation. This results in a process that charges the surface positively and generates a near-surface photoelectron inverse plasma sheath. The potential structure changes from a monotonic classical sheath to an inverse sheath as the emitted electron density becomes larger than the plasma electron density. In a relatively newer, recently developed charging model, called the Patched Charge Model, it has shown both theoretically and experimentally that even in photoelectron-rich environment, dust particles lying on a regolith surface can attain large negative potential due to formation of micro cavities. This negative potential may reach such values so that dust mobilization and lofting may become possible. In our work, we have assumed the existence of such negatively charged dust particles in a photoelectron-rich environment and argue that once the dust lofting is effected, the levitation can be sustained through the iondrag force. The conditions of levitation are investigated for these dust particles and the levitation distances from the lunar surface are calculated. * mpbora@gauhati.ac.in

The present work describes the synthesis of conductive composite of polyurethane sulphonate anionomer (PUSA) and para toluene sulphonic acid doped polyaniline (PANI-PTSA). HCl-doped PANI was synthesized by chemical oxidative polymerization of aniline in HCl, which was converted to PANI-EB by treatment with NH 4 OH. PTSA doped PANI was synthesized from EB-PANI by redoping with PTSA solution. PUSA was synthesized from 4, 4 0 -diphenylmethanediisocyanate (MDI), polypropylene glycol (PPG), 1,4-butanediol (BD), and ionic diol SDOL. The composite was prepared by mixing of the solutions of two polymer components in DMF and then solution casting. The products were characterized and analyzed by UV-Vis and FTIR spectroscopy, thermogravimetry, differential scanning calorimetry and scanning electron microscopy. The conductivity was found to increase by 100 times with concomitant decrease in percolation threshold when polyurethane was replaced by PUSA in the composite for the same amount of polyaniline. The composite film was thermally stable upto 300