Hydrogen bonding in oxalic acid and its complexes: A database study of neutron structures

The basic result of carboxylic group that the oxygen atom of the -OH never seems to be a hydrogen bond acceptor is violated in the cases, namely urea oxalic acid and bis urea oxalic acid complexes, where the hydroxyl oxygen atom is an acceptor of a weak N—H… O hydrogen bond. The parameters of this hydrogen bond, respectively in these structures are: hydrogen acceptor distance 2.110 Å and 2.127 Å and the bending angle at hydrogen, 165.6° and 165.8°. The bond strength around the hydroxyl oxygen is close to 1.91 valence units, indicating that it has hardly any strength left to form hydrogen bonds. These two structures being highly planar, force the formation of this hydrogen bond. As oxalic acid is the common moiety, the structures of the two polymorphs, α-oxalic acid and β-oxalic acid, also were looked into in terms of hydrogen bonding and packing.     

A study of the thermal properties of bamboo knitted fabrics

In this research, the thermal properties of bamboo single jersey knitted fabrics have been studied in relation to stitch length and yarn linear density in tex. The objective was to determine the influence of fabric factors like stitch length and the constituent yarn linear density on fabric properties, such as air permeability, thermal conductivity, thermal resistance and relative water vapour permeability. Yarns with linear densities of 19.6, 23.6, 29.5 tex and with the same twist level were used to construct the fabrics of single jersey structure with stitch lengths of 0.27, 0.29 and 0.31 cm. The anticipated increase in air permeability and relative water vapour permeability with decrease in yarn linear density and increase in stitch length was observed. The thermal conductivity and thermal resistance tended in general to increase with constituent yarn linear density but decreased with increase in stitch length.     

Equation of state theories of condensed matter up to about 10 TPa

A knowledge of the equation of state (EOS) of matter is necessary to describe the dependence of its thermodynamic properties on its microscopic internal structure. EOS data are also vital for a variety of applications, particularly those that involve numerical simulation of dynamic processes. This has motivated intense research on EOS of materials, both in experimental and theoretical areas. Various laboratories in the world are involved in the development of techniques for the generation of increasingly higher pressures using high power lasers, electric and rail guns etc. The range of these controlled dynamic pressures is currently reaching about10 TPa. On the theoretical side, the earlier empirical methods have now been replaced by sophisticated band structure calculations. In this article, we review these first principle theoretical attempts to calculate EOS over a range of densities and temperatures, where a variety of physical phenomena such as band crossings, band closures, phase transitions, nuclear and electronic thermal excitations, core ionization, liquid disorder etc. are encountered. The emphasis in this review is on shock Hugoniot equation of state theories.     

Shock Hugoniot calculations and melting in Pb

Shock Hugoniot calculations are carried out for lead (Pb) using both solid and liquid state theories. The Hugoniots in solid and liquid cases are in mutual agreement within the experimental uncertainties. However, the shock temperatures are quite different as computed from solid and liquid state theories. This fact can perhaps be used to detect melting along the shock Hugoniot provided the shock temperatures are accurately measured.     

β-ω transformation under pressure ans stacking soliton model for diffuse omega phase in TiV alloys

Transmission Electron Microscopy (TEM) studies have been done on TiV alloys before and after application of high pressure to check the stacking soliton model of the diffuse omega phase. gb-ω transformation under high pressure was noticed in Ti_0.81 V_0.19 and Ti_0.72 V_0.28 alloys, thereby proving that ω-clusters prefer a smaller lattice parameter than that of the β-phase. However, the β-ω cell constant discrepancy is too small compared to theoretical predictions. Further, pressure causes incommensurate to commensurate phase transition. These results point out to the inadequacies of one-dimensional theories for diffuse omega phase.     

Rhodium(II) catalyzed intermolecular double C-alkylation: a method for the synthesis of tetraindoles and indolophanes

Double C-alkylation of cyclic diazoamides or bis-diazoamides with indoles or bis-indoles has been achieved to synthesize tetraindole derivatives using rhodium(II) acetate as a catalyst under mild reaction conditions with complete regioselectivity. The intermolecular double C-alkylation reaction strategy was successfully applied to synthesize indolophanes in moderate yield with excellent regiocontrol. The structure and stereochemistry of macrocycles were unequivocally confirmed with the help of single-crystal X-ray structure analyses.     

HIGH pressure structural investigations of zirconium using LMTO method

Abstract

The structural energy differences have been calculated for zirconium as a function of pressure at zero temperature using the Andersen force theorem and the linear muffin tin orbital method. The structures included are the following: α (hcp), the room temperature room pressure phase, ω- a three atom simple hexagonal, bcc and fcc. Our calculations show that the bcc structure would become energetically most favourable above 11 GPa. This results is in agreement with well known correlation between the crystal structure and the d-electron population in transition metals at normal volume. The diamond anvil cell based high pressure x-ray diffraction experiments are in progress to verify this result.     

Solute–solvent interactions of acid–1,4-dioxane mixtures—By dielectric, FTIR, UV–vis and 13C NMR spectrometric methods

Results of the dielectric studies carried out on the binary mixture of n-butyric and caprylic acids with 1,4-dioxane over the entire composition range and at temperatures 303 K, 308 K, 313 K and 318 K, and FTIR, UV–vis and 13C NMR spectral studies are presented in this paper. The excess permittivity and excess free energy were fitted with the Redlich–Kister polynomial. The variation of Kirkwood correlation factors, excess permittivity and excess free energy of mixing with the concentration and temperature has been investigated in view of understanding the ordering of dipoles of solute and solvent molecules. The FTIR, UV–vis and 13C NMR spectral analysis reveals the formation of complex between solute and solvent molecules. The parallel alignment of electric dipoles of the complex predicted by dielectric studies is well supported by UV–vis spectral analysis. The structure of the complex molecule present in the clusters has been deduced.     

Phenomenology of the Pokaranpne experiment

The phenomenology of the Pokaranpne experiment (yield - 12 kiloton oftnt) conducted in a shale-sandstone rock, 107 meters underground, is described with the aid of computations using a one-dimensional spherical symmetric rock mechanics computer code developed by the authors. The calculated values of cavity radius, spall velocity and extent of rock fracturing are in good agreement with the observed values. The principal mechanism for crater formation at Pokaran was spall and the relatively smaller crater dimensions and non-venting of radioactivity gases were due to lower kinetic energy transferred to the shale-sandstone rock.