The pressure-amorphized state in zirconium tungstate: a precursor to decomposition

In contrast to widely accepted view that pressure-induced amorphization arises due to kinetic hindrance of equilibrium phase transitions, here we provide evidence that the metastable pressure-amorphized state in zirconium tungstate is a precursor to decomposition of the compound into a mixture of simple oxides. This is from the volume collapse ΔV across amorphization, which is obtained for the first time by measuring linear dimensions of irreversibly amorphized samples during their recovery to the original cubic phase upon isochronal annealing up to 1000 K. The anomalously large ΔV of 25.7 ± 1.2% being the same as that expected for the decomposition indicates that this amorphous state is probably a precursor to kinetically hindered decomposition. A P–T diagram of the compound is also proposed

Quantum Mechanics of Extended Objects

We propose a quantum mechanics of extended objects that accounts for the finite extent of a particle defined via its Compton wavelength. The Hilbert space representation theory of such a quantum mechanics is presented and this representation is used to demonstrate the quantization of spacetime. The quantum mechanics of extended objects is then applied to two paradigm examples, namely, the fuzzy (extended object) harmonic oscillator and the Yukawa potential. In the second example, we theoretically predict the phenomenological coupling constant of the $\omega$ meson, which mediates the short range and repulsive nucleon force, as well as the repulsive core radius.Comment: RevTex, 24 pages, 1 eps and 5 ps figures, format change

DEVELOPMENT AND VALIDATION OF A STABILITY INDICATING HPLC METHOD FOR THE DETERMINATION OF NILOTINIB HYDROCHLORIDE IN BULK AND PHARMACEUTICAL DOSAGE FORM

Objective: To develop a rapid, accurate, linear, sensitive and stability indicating RP-HPLC method for the determination of nilotinib in bulk and pharmaceutical dosage forms in the presence of its four related substances.Methods: The RP-HPLC method was developed for the chromatographic separation of nilotinib and its impurities by using waters Xterra RP-18 (150*4.6 mm, 3.5 µm) column with a mobile phase combination of 10 mM ammonium formate with pH-3.5 and acetonitrile in gradient mode. An injection volume of 20 µl. Flow rate was 1.0 ml/min and detection was carried a wavelength of 250 nm. The method was validated as per ICH guidelines.Results: The retention time for nilotinib and its four impurities were found to be 4.37, 7.40, 8.96, 10.21 and 10.87 min respectively. The linear regression analysis data for the calibration plots showed the good linear relationship in the concentration range of 0.04-3.0 ppm for the nilotinib impurities. The % recovery of nilotinib impurities was found to be 96.8-99.4% in the linearity range. The detection limit (LOD) values were about 0.014, 0.016, 0.005 and 0.03 ppm respectively and the quantification limit (LOQ) values were 0.042, 0.048, 0.014 and 0.09 ppm respectively. The % degradation at various stress conditions like acid, alkaline, oxidative, thermal and photolytic stress was found to be 8.92, 18.35,5.63, 0.88 and 3.89 respectively.Conclusion: The RP-HPLC method compatible with LC-MS was developed for the analysis of nilotinib and its four impurities. It was validated as per the ICH guidelines and found to be linear, robust, precise, accurate, sensitive, stability indicating and can be used for routine as well as stability analysis of capsule dosage forms as well as for drug substance

Evaluation of configurational entropy of a model liquid from computer simulations

Computer simulations have been employed in recent years to evaluate the configurational entropy changes in model glass-forming liquids. We consider two methods, both of which involve the calculation of the `intra-basin' entropy as a means for obtaining the configurational entropy. The first method involves the evaluation of the intra-basin entropy from the vibrational frequencies of inherent structures, by making a harmonic approximation of the local potential energy topography. The second method employs simulations that confine the liquid within a localized region of configuration space by the imposition of constraints; apart from the choice of the constraints, no further assumptions are made. We compare the configurational entropies estimated for a model liquid (binary mixture of particles interacting {\it via} the Lennard-Jones potential) for a range of temperatures, at fixed density.Comment: 10 pages, 5 figures, Proceedings of "Unifying Concepts in Glass Physics" Trieste 1999 (to appear in J. Phys. Cond. Mat.