Search results for "Stability"
showing 10 items of 3085 documents
A Promising New Method to Estimate Drug-Polymer Solubility at Room Temperature
2016
The established methods to predict drug-polymer solubility at room temperature either rely on extrapolation over a long temperature range or are limited by the availability of a liquid analogue of the polymer. To overcome these issues, this work investigated a new methodology where the drug-polymer solubility is estimated from the solubility of the drug in a solution of the polymer at room temperature using the shake-flask method. Thus, the new polymer in solution method does not rely on temperature extrapolations and only requires the polymer and a solvent, in which the polymer is soluble, that does not affect the molecular structure of the drug and polymer relative to that in the solid st…
Phase Stability of Natural Ni0.75Mg0.22Ca0.03CO3 Gaspeite Mineral at High Pressure and Temperature
2020
[EN] Divalent metal carbonates play an important role in Earth's carbon cycle, but the effect of chemical substitution is still poorly known. In this work, we have studied the structural and vibrational properties of natural mineral gaspeite (Ni0.75Mg0.22Ca0.03CO3) under high pressure and temperature using in situ synchrotron X-ray diffraction and Raman spectroscopy in diamond-anvil cells. These experiments have been complemented by ab initio simulations. Synchrotron high-pressure XRD measurements at room temperature using He as the pressure transmitting medium have shown that the calcite-type structure is stable up to 23.3 GPa. A bulk modulus at zero pressure of B-0 = 105(2) GPa with B-0' …
Input-to-State Stability of Lur’e Hyperbolic Distributed Complex-Valued Parameter Control Systems: LOI Approach
2013
Published version of an article in the journal: Mathematical Problems in Engineering. Also available from the publisher at: http://dx.doi.org/10.1155/2013/364057 Open access In this work, input-to-state stability of Lur'e hyperbolic distributed complex-valued parameter control systems has been addressed. Using comparison principle, delay-dependent sufficient conditions for the input-to-state stability in complex Hilbert spaces are established in terms of linear operator inequalities. Finally, numerical computation illustrates our result.
Zero-range model of traffic flow.
2005
A multi--cluster model of traffic flow is studied, in which the motion of cars is described by a stochastic master equation. Assuming that the escape rate from a cluster depends only on the cluster size, the dynamics of the model is directly mapped to the mathematically well-studied zero-range process. Knowledge of the asymptotic behaviour of the transition rates for large clusters allows us to apply an established criterion for phase separation in one-dimensional driven systems. The distribution over cluster sizes in our zero-range model is given by a one--step master equation in one dimension. It provides an approximate mean--field dynamics, which, however, leads to the exact stationary s…
Ageing of isotactic polypropylene due to morphology evolution, experimental limitations of realtime density measurements with a gradient column
2006
Abstract Ageing in crystalline polymers is responsible for the deterioration of physical properties leading, for example, to a decrease in toughness and to dimensional changes that are to some extent responsible for warpage and scrap production in injection molding. Since, it depends on the mutual transformation of stable and metastable phases, being always related to changes in morphological organization, it is here preferred to call it ‘Morphological ageing’. Although, one would expect the ageing regime to be determined by the complex morphology with amorphous phases of different mobility and eventually multiple crystalline phases, transformed into each other at an associated transition, …
Wireless power transfer system stability analysis for E-bikes application
2019
The present work reports the stability analysis of an Inductive Coupled Power Transfer (ICPT) System coupled to an electrical bike. The study has focused on two coupled coils with circular geometry and vertical disposition. In the first part of the work, the theoretical aspects related to the stability of wireless power systems are handled. In the second part, performing several simulations, varying the features of the considered configuration, the stability is looked for. In order to perform this process, the Ansys Maxwell software has been used, performing 3D simulations.
Über die möglichkeiten zur bestimmung von mischungsenthalpien und -volumina aus der molekulargewichtsabhängigkeit der kritischen entmischungstemperat…
1977
Cloud-point curves and critical curves (Tc = f(p)) have been measured for the system trans-decahydronaphthalene/polystyrene and three different molecular weights of the polystyrene component (2,5 · 106; 3,9 · 105; 1,1 · 105). It turned out that by variation of the pressure the metastable region can be investigated up to the spinodal curve. A comparison of the theta-temperatures and the enthalpy contributions χH (to the Flory-Huggins interaction parameter χ) resulting from the measured critical temperatures according to Shultz-Flory, with the corresponding directly obtained literature data, demonstrates that, although the extrapolation of Tc to infinite molecular weight is feasible, χH obtai…
Mechanism of Antibacterial Activity via Morphology Change of α-AgVO3: Theoretical and Experimental Insights
2017
The electronic configuration, morphology, optical features, and antibacterial activity of metastable α-AgVO3 crystals have been discussed by a conciliation and association of the results acquired by experimental procedures and first-principles calculations. The α-AgVO3 powders were synthesized using a coprecipitation method at 10, 20, and 30 °C. By using a Wulff construction for all relevant low-index surfaces [(100), (010), (001), (110), (011), (101), and (111)], the fine-tuning of the desired morphologies can be achieved by controlling the values of the surface energies, thereby lending a microscopic understanding to the experimental results. The as-synthesized α-AgVO3 crystals display a …
Pressure-Driven Isostructural Phase Transition in InNbO4: In Situ Experimental and Theoretical Investigations
2017
[EN] The high-pressure behavior of technologically important visible-light photocatalytic semiconductor In.NbO4, adopting a monoclinic wolframite-type structure at ambient conditions, was investigated using synchrotron-based X-ray diffraction, Raman spectroscopic measurements, and first-principles calculations. The experimental results indicate the occurrence of a pressure-induced isostructural phase transition in the studied compound beyond 10.8 GPa. The large volume collapse associated with the phase transition and the coexistence of two phases observed over a wide range of pressure shows the nature of transition to be first-order. There is an increase in the oxygen anion coordination num…
The effect of excipients on the stability and phase transition rate of xylazine hydrochloride and zopiclone
2015
The compatibility of thermodynamically unstable polymorph of two active pharmaceutical compounds (xylazine hydrochloride form X and zopiclone form C) with different excipients was investigated. The effects of the excipient and its amount in the sample on the thermal properties and possible chemical interactions were studied. The most commonly used excipients in the pharmaceutical industry - calcium carbonate, lactose hydrate, cellulose, magnesium stearate hydrate and calcium stearate hydrate were selected for this study. The dependence of the phase transition rate from an unstable to a more stable polymorph on the excipients and their amounts in the initial sample was analysed at 80°C, and …