Search results for "Thermodynamics"
showing 10 items of 2774 documents
CY-Operators and L-Functions
2019
This a write up of a talk given at the MATRIX conference at Creswick in 2017 (to be precise, on Friday, January 20, 2017). It reports on work in progress with P. Candelas and X. de la Ossa. The aim of that work is to determine, under certain conditions, the local Euler factors of the L-functions of the fibres of a family of varieties without recourse to the equations of the varieties in question, but solely from the associated Picard–Fuchs equation.
Modelling of proton and metal exchange in the alginate biopolymer.
2005
Acid-base behaviour of a commercial sodium alginate extracted from brown seaweed (Macrocystis pyrifera) has been investigated at different ionic strengths (0.1or=I/mol l(-1)or=1.0) and in different supporting electrolytes (Et4NI, NaCl, KCl, LiCl, NaCl+MgCl2), with the aim of examining the influence of ionic medium on the proton-binding capacity and of quantifying the strength of interaction with light metal ions in the perspective of speciation studies in natural aqueous systems. Potentiometric ([H+]-glass electrode) and titration calorimetric data were expressed as a function of the dissociation degree (alpha) using different models (Henderson-Hasselbalch modified, Högfeldt three parameter…
High-Pressure Phase Diagram and Superionicity of Alkaline Earth Metal Difluorides
2018
We study the high-pressure–high-temperature phase diagram and superionicity of alkaline earth metal (AEM) difluorides (AF2, A = Ca, Sr, Ba) with first-principles simulation methods. We find that the superionic behavior of SrF2 and BaF2 at high pressures differ appreciably from that previously reported for CaF2 [Phys. Rev. Lett. 2014, 113, 235902]. Specifically, the critical superionic temperature of SrF2 and BaF2 in the low-pressure cubic fluorite phase is not reduced by effect of compression, and the corresponding high-pressure orthorhombic contunnite phases become superionic at elevated temperatures. We get valuable microscopic insights into the superionic features of AEM difluorides in b…
Adsorption and diffusion of linear and dibranched C6 paraffins in a ZSM-5 zeolite
2002
The adsorption of n-hexane and 2,2-dimethylbutane on a commercial ZSM-5 zeolite is studied under isothermal and isobaric conditions. ZSM-5 exhibits two different behaviours with linear and dibranched alkanes. A substep at 4 molec.uc−1 is observed on the adsorption isotherm of n-hexane at 348 K. A singular adsorption-desorption process is evidenced on the adsorption isobar at 5.5 kPa with 2,2-dimethylbutane at a temperature close to 343 K when the sample is activated at 298 K under vacuum. The diffusivities have been determined by fitting directly the uptake curves with a numerical resolution of second Fick's law based on finite difference method. Microporous diffusion seems to be rate limit…
On the effect of pressure on the phase transition of polymer blends and polymer solutions: Oligostyrene–n-alkane systems
2001
Critical temperatures of some binary solutions of weakly interacting low molecular weight polystyrenes dissolved in linear alkanes (oligoethylenes) were measured over the range 0.1 to 100 MPa. While (dT/dP)crit along the upper critical solution (UCS) locus for a “typical blend” is positive, and for the “ typical solution” can be either positive or negative (but is usually negative), there is no essential difference between blend and solution. Rather, the difference in sign is a consequence of the location of the hypercritical point (that point in (T,P)crit space where (dT/dP)crit changes sign, [(dT/dP)crit = 0 and (d2T/dP2)crit>0], also called the double critical point, DCP), which is norma…
Static and Dynamic Properties of a n-C100H202 Melt from Molecular Dynamics Simulations
1997
We present in this work results from atomistic molecular dynamics simulations of a n-C100H202 melt. This work represents a first effort to simulate a fully equilibrated ensemble of chains of suffic...
On the nature of phase separation in a commercial aluminium-lithium alloy
1996
Abstract The formation of lithium-rich precipitate particles, known as δ′ phase, is responsible for the particularly desirable mechanical properties which make aluminium-lithium alloys interesting for different industrial applications. The structure and the kinetics of the phase separation process are conveniently studied by small-angle X-ray scattering, though uncertainties remain on the actual shape of the phase diagram of the system, particularly in the region of interest. In this paper are reported small-angle X-ray scattering measurements on a commercial AlLi (8.49% Li atoms) both in the region of formation of the precipitate and during its successive growth. Modelling of the experime…
Thermodynamic versus Conformational Metastability in Fibril-Forming Lysozyme Solutions
2012
The role of intermolecular interaction in fibril-forming protein solutions and its relation with molecular conformation is a crucial aspect for the control and inhibition of amyloid structures. Here, we study the fibril formation and the protein-protein interactions of lysozyme at acidic pH and low ionic strength. The amyloid formation occurs after a long lag time and is preceded by the formation of oligomers, which seems to be off-pathway with respect to fibrillation. By measuring the osmotic isothermal compressibility and the collective diffusion coefficient of lysozyme in solution, we observe that the monomeric solution is kept in a thermodynamically metastable state by strong electrosta…
Apparent content curves: description and analytical applications. Resolution of binary mixtures
1992
The apparent content curves and their analytical applications are described. Basing on these curves a mathematical method, which permits the identification of the interfering component present in a binary mixture as well as the determination of the contents of both constituents, is proposed. The existence of considerable interaction coefficients is not an impediment for its application. Besides, the analyte contents in the mixture can be obtained without the use of standard interference solutions. The proposed procedure is applied to the analysis of mixtures of dyes with overlapping absorption spectra.
Fully Automated Electric-Field-Driven Liquid Phase Microextraction System with Renewable Organic Membrane As a Front End to High Performance Liquid C…
2019
This article reports for the first time a programmable-flow-based mesofluidic platform that accommodates electric-field-driven liquid phase microextraction (μ-EME) in a fully automated mode. The miniaturized system is composed of a computer-controlled microsyringe pump and a multiposition rotary valve for handling aqueous and organic solutions at a low microliter volume and acts as a front-end to online liquid chromatographic separation. The organic membrane is automatically renewed and disposed of in every analytical cycle, thus minimizing analyte carry-over effects while avoiding analyst intervention. The proof-of-concept applicability of the automated mesofluidic device is demonstrated b…