Search results for "Diffusion"
showing 10 items of 1615 documents
On the interest of ambipolar materials for gas sensing
2017
International audience; Based on the electrochemical properties of a series of metallophthalocyanines this article shows that the phthalocyanine bearing four alkoxy groups and twelve fluorine atoms behaves approximately as those with eight fluorine atoms. This indicates that the electron-donating effect of one alkoxy group balances the electro-withdrawing effect of one fluorine atom. We engaged three metallophthalocyanines, namely the octafluoro copper phthalocyanine, Cu(F8Pc), an octaester metallophthalocyanine and a phthalocyanine bearing four alkoxy groups and twelve fluorine atoms, Zn(T4F12Pc), in building original conductometric transducers that are Molecular Semiconductor – Doped Insu…
Diffusion and outgassing of O2 in amorphous SiO2 silica nanoparticles with specific surface properties
2014
Silica nanoparticles with hydrophilic and hydrophobic surface and average diameter of 12 and 40 nm are investigated to study the surface group influence on the diffusion process of molecular oxygen. The O2 diffusion kinetics and molecular solubility are determined by Raman/Photoluminescence measurements. Thermal treatments up to 127°C in controlled atmosphere show that the surface chemistry of nanoparticles is not changed, the equilibrium emission of O2 depends on nanoparticles surface properties, whereas the dynamics of diffusion is surface independent suggesting that surface groups could only affect overall content or detectability of interstitial molecules. The post loading outgassing in…
Sorption and diffusion properties of volatile phenols into cork
2010
International audience; The sorption and diffusion properties of seven common volatile phenols in hydro-alcoholic medium placed in contact with natural cork were investigated to determine the influence of cork closures on the concentration of these compounds in wine. Weighted cork samples were immersed in model wine solutions containing selected concentrations of each compound and were sampled over time. Sorption coefficients ranged between 125 and 306 mg of aroma compound per kg of cork, while diffusion coefficients varied from 0.8 to 4.1 × 10−11 m2/s. Sorption isotherms of guaiacol and 4-propylguaiacol, respectively, the lowest and highest sorbed compounds of an homologous series of guaia…
Interface reactivity study between La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF) cathode material and metallic interconnect for fuel cell
2011
Abstract Interface reactivity between La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF) cathode material and metallic interconnect (Crofer22APU) was investigated in laboratory air at 700 °C. Due to the interconnect geometry, two interfaces have been analysed: (i) interconnect rib/cathode interface (physically in contact); (ii) the interface under the channel of interconnect. In both cases, formation of a parasite phase was observed after various ageing treatments (20 h, 100 h and 200 h). However, the growth of the determined SrCrO4 parasite phase depends on interface type and on ageing time. Two different mechanisms have been established in function of interface type: (i) SrCrO4 phase was formed after solid …
Pas de titre
2011
A number of phonetic and phonological changes have lately been observed in most geographical varieties of British English. This phenomenon seems to have been accelerated by increasing social and geographical mobility in the past decades. Based on a corpus mainly consisting of several hours of spontaneous interaction between a number of native NW Yorkshire speakers divided into different age groups, this research identifies and analyses several segmental and suprasegmental innovations observed in apparent time in a set of accents associated with a circumscribed geographical area. This thesis discusses the motivation behind some of these changes and addresses the question of whether the same …
Anisotropy Influences on the Drug Delivery Mechanisms by Means of Joint Invariant Functions
2017
In the frame of Higuchi’s type functionality, this paper presents the anisotropy influences on the drug delivery mechanisms through the joint invariant functions to the simultaneous actions of the two SL(2R) isomorphic groups. Then, a new equation for drug delivery mechanism, independent of the type of polymer matrix and/or drug, is proposed.
Space charge effect on competitive ion transport through ion-exchange membranes
2002
A mathematical model of the competitive electro-transport of two counter-ions through an ion exchange membrane based on the Nernst-Planck and Poisson equations is developed. A three-layer system is considered: the membrane and two adjacent diffusion layers. Concentration profiles in the three layers, effective transport numbers as functions of the current and current-voltage characteristics are calculated. Deviation from the local electroneutrality in space charge region near the depleted solution/membrane interface is taken into account. It is shown that the space charge region grows with the voltage applied. However the fluxes of the competitive counter-ions at over-limiting currents are …
Soft Nanoonions: A Dynamic Overview onto Catanionic Vesicles Temperature-Driven Transition.
2020
Catanionic vesicles are emerging interesting structures for bioapplications. They self-generate by a pairing of oppositely charged ionic surfactants that assemble into hollow structures. Specifically, the anionic-cationic surfactant pair assumes a double-tailed zwitterionic behavior. In this work, the multilamellar-to-unilamellar thermal transition of several mixed aqueous systems, with a slight excess of the anionic one, were investigated. Interestingly, it was found that the anionic counterion underwent a dissociation as a consequence of a temperature increase, leading to the mentioned thermal transition. The present work proposed the spectroscopic techniques, specifically multinuclear NM…
Investigation of diffusion and migration of hydrogen, deuterium and tritium in palladium in a Hall field
1991
Abstract The migration of hydrogen, deuterium and tritium in palladium in a Hall field at 343 K was investigated, using resistance and isotope methods. It was found that all isotopes of hydrogen migrate towards the negative Hall electrode. The effective charges of the migration in a Hall field are 194 ±3 e for hydrogen and 464± 5 e for deuterium and tritium. The results obtained confirm predictions of a tentative model based on the electron-balistic theories of migration in a Hall field.
Post-fotografia etnografica
2021
È evidente come la nostra società tecnologica sia legata senza alcun dubbio alla diffusione delle immagini. Autori come Gottfried Boehm, John Mitchell, Hans Belting hanno indagato la natura dell'immagine ponendo le basi, negli anni Novanta, per l'idea di un pictorial turn, di una cultura totalmente dominata dalle immagini che è diventata adesso una possibilità tecnica reale su scala globale. Un nuovo statuto dell'immagine che si usa raccogliere sotto l'etichetta di iconic turner inserito nel più vasto campo visual culture studies. L'uso del termine cultura accanto a quello di visuale è indicativo dell'ampiezza del campo d'indagine che visual culture studies si prefiggono di ricercare: essi …