A. K. Mishra

Pressure-Induced Structural Transformations in Bis(glycinium)oxalate

We report in situ high-pressure Raman spectroscopic as well as X-ray diffraction measurements on bis(glycinium)oxalate, an organic complex of glycine, up to 35 GPa. Several spectral features indicate that at ∼1.7 GPa it transforms to a new structure (phase II) which is characterized by the loss of the center of symmetry and the existence of two nonidentical glycine molecules. Across the transition, all the N-H···O bonds are broken and new weaker N-H···O bonds are formed. Our high-pressure X-ray diffraction studies support the possibility of a non-centrosymmetric space group P2(1) for phase II. Across 5 GPa, another reorganization of N-H···O hydrogen bonds takes place along with a structural transformation to phase III. The C-C stretching mode of oxalate shows pressure-induced softening with large reduction from the initial value of 856 to 820 cm(-1) up to 18 GPa, and further softening is hindered at higher pressures.

Ring-opening polymerization in carnosine under pressure.

Our high pressure Raman scattering experiments on carnosine, a dipeptide of L-histidine and β-alanine, show pressure induced ring-opening polymerization involving the imidazole ring. While the onset of polymeric transformation is found to be at ∼2.8 GPa, a substantial fraction of the monomeric solid becomes polymerized by 12 GPa. On release to ambient conditions, the observed Raman spectra do not contain any of the Raman modes of the ambient phase.

High pressure structural stability of BaLiF3

High pressure x-ray diffraction studies on inverse-perovskite BaLiF3 show that this compound is structurally stable up to ∼50 GPa. The bulk modulus of BaLiF3 is determined to be 75.9 GPa which is in close agreement with that determined from a semi-empirical formulation. Our ab initio calculations show that among the three alkaline earth fluoro perovskites (ALiF3, A = Ba, Ca, and Sr) which crystallize in the inverse-perovskite structure, BaLiF3 is the least brittle at ambient conditions and also that the degree of brittleness decreases at high pressures. The behavior of the elastic constants at high pressure accompanied by a reduction in the bandgap indicates a decrease in the directional nature of the bonding.

High pressure phase transition in Nd2O3

High pressure structural and spectroscopic investigations have been carried out on rare-earth sesquioxide, Nd2O3 using energy dispersive x-ray diffraction and Raman scattering techniques. Our measurements show that ambient hexagonal structure of Nd2O3 is stable up to 27 GPa. Beyond this pressure, it undergoes a structural phase transition to a lower symmetry phase. On release of pressure, it reversibly transforms back to the hexagonal phase suggesting the nature of phase transition to be of displacive kind.

The study of pressure induced structural phase transition in spin-frustrated Yb2Ti2O7 pyrochlore

Our in situ x-ray diffraction and Raman measurements of Yb2Ti2O7 pyrochlore show that it undergoes a reversible structural phase transition from cubic pyrochlore to a monoclinic phase at similar to 28.6 GPa. Analysis of the x-ray data shows the transition to be thermodynamically first order and the high pressure phase to be substitutionally disordered. These experimental results are supported by our first principles calculations

Potential of Lactoferrin as a Novel Nutraceutical

Lactoferrin is an 80-kDa iron-binding glycoprotein of the transferrin family, which was first fractionated as an unknown ‘‘red fraction’’ from cows’ milk by Sorensen. It is one of the major proteins of all exocrine secretions including saliva, tears, semen, vaginal fluids, gastrointestinal fluids, nasal mucosa and bronchial mucosa of human being. Lactoferrin is also known for its anti-bacterial, antifungal, antiviral, antimicrobial, anti-oxidant, anti-inflammatory, anti-parasitic, anti-allergic and most importantly anticancerous properties. The advantages of this natural molecule prove its potential as a natural therapeutic agent that can be used in various fields of research including cancer. Initial research has shown its potential as a novel nutraceutical for enhancing animal production, health and welfare, however, research on this topic is largely focused on lab animals, how lactoferrin enhances antioxidant status, immunity and performance needs to be ascertain in livestock and poultry. The role of supplementary lactoferrin in prevention and management of mastitis and anemia needs special attention.

Structural Study Of Double Perovskite Sr2MgWO6

Raman scattering and angle dispersive x‐ray diffraction studies, carried out on double perovskites Sr2MgWO6 up to ∼40 GPa and ∼28 GPa respectively, show the structurally stability up to the highest pressure. Bulk modulus of ambient phase is determined to be 128±3.9 GPa which is in close agreement with the theoretical value of bulk modulus, 132 GPa, obtained using first principles calculations. The first principles calculations exhibit that the initial tetragonal phase is more stable compared to the expected monoclinic structure up to at least 100 GPa.