Search results for "Diffusion"
showing 10 items of 1615 documents
On the nature of the forces controlling selectivity in the high performance capillary electrochromatographic separation of peptides
2003
In this minireview, the nature of the forces controlling selectivity in the high performance capillary electrochromatographic (HP-CEC) separation of peptides has been examined. For uncharged and charged peptides, a synergistic interplay occurs in HP-CEC systems between adsorptive/partitioning events and electrokinetically driven motion. Moreover, at high field strengths, both bulk electrophoretic migration and surface electrodiffusion occur. Thus, the migration behavior of peptides in different HP-CEC systems can be rationalized in terms of the combined consequences of these various processes. Moreover, in HP-CEC, the buffer electrolyte interacts with both the peptide analytes and the sorbe…
Iontophoretic Transdermal Delivery of Sumatriptan: Effect of Current Density and Ionic Strength
2005
ABSTRACT: Iontophoretic transdermal delivery of sumatriptan was investigated in vitro . Among the conditions tested, 0.25 mA/cm 2 and low ionic strength (NaCl 25 mM) was the best experimental condition to increase its transport across the skin. The flux increased 385-fold respective to passive diffusion, thus resulting in a transdermal flux of sumatriptan of 1273 ± 83 nmol/cm 2 h. © 2005 Wiley-Liss, Inc. and the American Pharmacists Association
Oxygen isotopic exchange: A useful tool for characterizing oxygen conducting oxides
2005
International audience; The 18O/16O isotope exchange depth profile technique (IEDP) followed by SIMS characterizations was applied to dense membranes of pure ionic conductors and mixed ionic/electronic conducting materials. It is a very useful tool since we obtain in both cases data concerning the oxygen diffusion in the bulk and the oxygen exchange at the surface of the materials. Comparisons were done, including results concerning the role of the surface with regards to the oxygen reduction reaction. Detailed experimental and analytical processes are given.
Oxygen diffusion in tissues supplied by capillaries.
1968
(1968). Oxygen Diffusion in Tissues Supplied by Capillaries. Scandinavian Journal of Clinical and Laboratory Investigation: Vol. 21, No. sup102, pp. II-B-II-B.
Adsorption and diffusion study, in gazeous phase, of wine active molecules in cork
2010
During wine ageing, oxidation reactions occur and can lead to wine sensory defaults. The main factors involved in this phenomenon are oxygen and gas barrier properties of stoppers. During the last ten years, some studies investigated oxygen transfer during winemaking and wine storage. However, only few of them deal with the interactions between molecules and sealing materials. The material studied in this work is raw cork, without any treatment, neither washed nor surface treated (with paraffin or silicone). This Phd work focuses on mass transfer of some wine active molecules, in gas phase, through the cork. The selected molecules are water, ethanol, sulphur dioxide and oxygen. An adsorptio…
Diffusion and Reactions of Photoinduced Interstitial Oxygen Atoms in Amorphous SiO2 Impregnated with 18O-Labeled Interstitial Oxygen Molecules
2014
Both diffusion and reactions of interstitial oxygen atoms (O0) in amorphous SiO2 (a-SiO2) were examined using oxygen-excess a-SiO2 containing 18O-labeled interstitial oxygen molecules (O2) and exposed to F2 laser light (hν = 7.9 eV). Both the F2 laser photolysis of interstitial O2 at 77 K and subsequent heat treatment at ≳200 °C give rise to oxygen exchange between residual interstitial O2 and oxygen atoms in the a-SiO2 network, and these temperatures are far lower than the temperature at which conventional thermal network-interstitial oxygen exchange in unirradiated a-SiO2 occurs (≳700 °C). However, at the initial stage of the low-temperature F2 laser photolysis, an efficient formation of …
Epidemic diffusion of social updates in Dunbar-based DOSN
2014
Distributed Online Social Networks (DOSNs) do not rely on a central repository for storing social data so that the users can keep control of their private data and do not depend on the social network provider. The ego network, i.e. the network made up of an individual, the ego, along with all the social ties she has with other people, the alters, may be exploited to define distributed social overlays and dissemination protocols. In this paper we propose a new epidemic protocol able to spread social updates in Dunbar-based DOSN overlays where the links between nodes are defined by considering the social interactions between users. Our approach is based on the notion of Weighted Ego Betweenne…
Fick Diffusion Coefficients in Ternary Liquid Systems from Equilibrium Molecular Dynamics Simulations
2012
An approach for computing Fick diffusivities directly from equilibrium molecular dynamics (MD) simulations is presented and demonstrated for a ternary chloroform–acetone–methanol liquid mixture. In our approach, Fick diffusivities are calculated from the Maxwell–Stefan (MS) diffusivities and the so-called matrix of thermodynamic factors. MS diffusivities describe the friction between different molecular species and can be directly computed from MD simulations. The thermodynamic factor describes the deviation from ideal mixing behavior and is difficult to extract from both experiments and simulations. Here, we show that the thermodynamic factor in ternary systems can be obtained from density…
Impact on flavour release of the structure of composite gels containing polysaccharides: Example of the fruit préparations
2006
The main objective of this study was to understand the respective rôle of the structure of a food product and of the physicochemical interactions on flavour release. For that purpose, fruit préparations hâve been chosen as model matrices. Those matrices contain a polysaccharide as gelling agent, a cross-linked waxy corn starch (1.4%), a high sucrose content (35%), an acidic buffer and a strawberry aroma (17 molécules). Four matrices were developed by modifying either the composition or the concentration in gelling agent: two matrices of similar texture containing either LM pectin or carrageenan, and two carrageenan based matrices with différent gelled structures. In a first step; two comple…
RpeakChrom: Novel R package for the automated characterization and optimization of column efficiency in high-performance liquid chromatography analys…
2017
Characterization of chromatographic columns using the traditional van Deemter method is limited by the necessity of calculating extra-column variance, issue particularly relevant when modeling asymmetrical peaks eluted from monolithic columns. A novel R package that implements Parabolic Variance Modified Gaussian approach for accurate peak modeling, van Deemter equation and two alternatives approaches, based on van Deemter, has been developed to calculate the height equivalent to a theoretical plate (HETP). To assess package capabilities conventional packed reverse-phase and monolithic HPLC columns were characterized. Peaks eluted from the monolithic column showed a high value of factor asy…