Articles written in Pramana – Journal of Physics
Volume 63 Issue 1 July 2004 pp 107-115
Using the crystal structure, a comprehensive interpretation of the origin of ferroelectricity in the hydrogen bonded triglycine family of crystals is given. Our detailed analysis showed that the instability of nitrogen double well potential plays a driving role in the mechanism of the ferroelectric transitions in these crystals.
Volume 63 Issue 2 August 2004 pp 213-219
Structural studies on Dy-substituted La-2125 type superconductors have been carried out by neutron diffraction experiments at room temperature using a monochromatic neutron beam of wavelength (λ) = 1.249 Å. A series of samples with La2-xDyxCa2xBa2Cu4+2xOz stoichiometric composition, for
Volume 63 Issue 2 August 2004 pp 251-255
We have synthesized polycrystalline La0.95Nd0.05CrO3 sample by doping the La-site of LaCrO3 with Nd and its magnetic properties have been studied using DC magnetization and neutron diffraction techniques. DC magnetization study shows a paramagnetic to a weak ferromagnetic-like transition at ∼295 K followed by signatures of a spin reorientation phenomenon at 233 and 166 K and, finally a transition to an antiferromagnetic-like phase at ∼21 K. Low-temperature neutron diffraction measurements confirm a weak ferrimagnetic ordering of Cr3+ moments at all temperatures below 295 K.
Volume 63 Issue 2 August 2004 pp 257-261
The crystal structure of ZTS has been determined by neutron diffraction with a final
Volume 63 Issue 2 August 2004 pp 263-269
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.
Volume 63 Issue 2 August 2004 pp 363-368
The native form of serum albumin is the most important soluble protein in the body plasma. In order to investigate the structural changes of Bovine serum albumin (BSA) during its unfolding in the presence of urea, a small-angle neutron scattering (SANS) study was performed. The scattering curves of dilute solutions of BSA with different concentrations of urea in D2O at pH 7.2 ± 0.2 were measured at room temperature. The scattering profile was fitted to a prolate ellipsoidal shape (
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