Studies on diurnal variation of atmospheric tritium concentration at a sampling location near to PHWR site in Semi-Arid Zone, India.

Tritium (3H) is one of the important long-lived radioisotopes in the gaseous effluent released from Pressurised Heavy Water Reactors (PHWR). For the first time, the studies on diurnal variation of atmospheric tritium concentration was carried out using an in-house developed automatic air moisture collection sampler at Kakrapar Gujarat site, India, where PHWRs are operational. Correlation of diurnal variation of atmospheric tritium concentration with meteorological parameters such as absolute humidity, ambient temperature and wind speed is studied and presented in this paper. Positive and significant correlation of atmospheric 3H concentration was observed with respect to the absolute humidity. Negative correlation was observed in ambient temperature and wind speed. The diurnal maximum and minimum of 3H concentration was found during 21.00-23.00 h (night) and 13.00-16.00 h (day), respectively.

Aqueous solutions of hydroxyl-functionalized ionic liquids: Molecular dynamics studies.

A series of aqueous solutions of 1-(n-hydroxyalkyl)-3-(n-hydroxyalkyl) imidazolium bromide ([HOCnCmOHIm][Br], with n and m = 2, 6,10 and 14) were studied by atomistic molecular dynamics simulations. Structural properties were characterized by the radial distribution functions between different pairs, angular distributions and aggregation numbers. Dynamics of the system has been investigated by computing the diffusion of the ions and molecules. Structures of the aggregates formed depend upon the length of the hydroxyalkyl chains. The long-distance spatial correlations observed in solutions with cations having long chain substituent are arising due to the formation of intercalated structures. A thin film like structure is formed in solutions having longer hydroxyalkyl chains, with the structure stabilized by the dispersion interactions between the interdigitated alkyl chains and the hydrogen bond formation between the hydroxyl group of a cation with head group of a different cation. Anions are dispersed near the surface of the film.

Noncovalent Carbon-Bonding Interactions in Proteins.

Carbon bonds (C-bonds) are the highly directional noncovalent interactions between carbonyl-oxygen acceptors and sp3 -hybridized-carbon σ-hole donors through n→σ* electron delocalization. We have shown the ubiquitous existence of C-bonds in proteins with the help of careful protein structure analysis and quantum calculations, and have precisely determined C-bond energies. The importance of conventional noncovalent interactions such as hydrogen bond (H-bonds) and halogen bond (X-bonds) in the structure and function of biological molecules are well established, while carbon bonds C-bonds have still to be recognized. We have shown that C-bonds are present in proteins, contribute enthalpically to the overall hydrophobic interaction and play a significant role in the photodissociation mechanism of myoglobin and the binding of nucleobases to proteins.