Search results for "Diffusion"
showing 10 items of 1615 documents
Synthesis and Structure Determination of the Hierarchical Meso-Microporous Zeolite ITQ-43
2011
[EN] The formation of mesopores in microporous zeolites is generally performed by postsynthesis acid, basic, and steam treatments. The hierarchical pore systems thus formed allow better adsorption, diffusion, and reactivity of these materials. By combining organic and inorganic structure-directing agents and high-throughput methodologies, we were able to synthesize a zeolite with a hierarchical system of micropores and mesopores, with channel openings delimited by 28 tetrahedral atoms. Its complex crystalline structure was solved with the use of automated diffraction tomography.
Three-dimensional architecture of the whole human soleus muscle in vivo
2018
Background Most data on the architecture of the human soleus muscle have been obtained from cadaveric dissection or two-dimensional ultrasound imaging. We present the first comprehensive, quantitative study on the three-dimensional anatomy of the human soleus muscle in vivo using diffusion tensor imaging (DTI) techniques. Methods We report three-dimensional fascicle lengths, pennation angles, fascicle curvatures, physiological cross-sectional areas and volumes in four compartments of the soleus at ankle joint angles of 69 ± 12° (plantarflexion, short muscle length; average ± SD across subjects) and 108 ± 7° (dorsiflexion, long muscle length) of six healthy young adults. Microdissection and…
Respiratory Gas Transport in Heart
1973
The purpose of this paper is to describe an attempt to obtain a better understanding of the dynamics of the oxygen supply of the myocardium under physiological and pathophysiological conditions by examining the oxygen diffusion in the heart muscle tissue during systole and diastole. In comparison to other organs the oxygen supply of the myocardium is characterized by a number of specific features. The most important one is that the gas exchange in the myocardium is a nonsteady-state diffusion process.
Mg2-xTixNi (x=0, 0.5) alloys prepared by mechanical alloying for electrochemical hydrogen storage: Experiments and first-principles calculations
2012
International audience; Mg2-xTixNi (x = 0, 0.5) electrode alloys have been prepared by mechanical alloying (MA) under argon atmosphere at room temperature using a planetary high-energy ball mill. The microstructures of synthesized alloys are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The effects of substitutional doping of Ti in Mg2Ni phase have been investigated by first-principles density functional theory calculations. XRD analysis results indicate that Ti substitution for Mg in Mg2Ni-type alloys results in the formation of TiNi (Pm-3m) and TiNi3 intermetallics. With the increase of milling time, the TiNi phase…
Diffusion of naltrexone across reconstituted human oral epithelium and histomorphological features
2006
Abstract In transbuccal absorption a major limitation could be the low permeability of the mucosa which implies low drug bioavailability. The ability of naltrexone hydrochloride (NLX) to penetrate a resembling histologically human buccal mucosa was assessed and the occurrence of any histomorphological changes observed. We used reconstituted human oral (RHO) non-keratinised epithelium as mucosal section and a Transwell diffusion cells system as bicompartmental model. Buccal permeation was expressed in terms of drug flux ( J s ) and permeability coefficients ( K p ). Data were collected using both artificial and natural human saliva. The main finding was that RHO does not restrain NLX permeat…
Mechanism of nanocapsules formation by the emulsion-diffusion process.
2007
International audience; A detailed investigation into the mechanisms of nanocapsule formation by means of the two stages “emulsion–diffusion” process is reported. Such widely used process is still poorly understood. An emulsion of oil, polymer and ethyl acetate is fabricated as a first step; dilution with pure water allows ethyl acetate to diffuse out from the droplets, leaving a suspension of nanocapsules at the end. It has been shown that the size of nanocapsules was related to the chemical composition of the organic phase and the size of primary emulsion through a simple geometrical relationship. As a consequence, most of the properties of the nanocapsules were decided at the emulsificat…
Enhanced interfacial lithium storage in nanocomposites of transition metals with LiF and Li2O: Comparison of DFT calculations and experimental studies
2008
Abstract Me/LiX nanocomposites (Me – transition metal and X = F or O) exhibit extra lithium storage, with pseudo-capacitive behavior and high-rate performance. While LiX surface layers or the interfacial core serves as hosts for extra Li, atoms of contacting transition metal serve as electron sinks, depending on Me electronegativity. To verify the mechanism, we have performed comparative DFT-LCAO calculations on the polar Ti|Li|Li2O(111) and non-polar Cu|Li|LiF(001) interfaces with extra Li atoms inserted inside both 2D interfaces, gradually changing their concentration. Theoretical calculations confirm validity of this interfacial model for explanation of the extra storage capacity at low …
Enhanced lithium storage and chemical diffusion in metal-LiF nanocomposites: Experimental and theoretical results
2007
An extra storage of Li has been observed experimentally at low potential in Me/LiF nanocomposites where Me refers to transition metals such as Cu, Co, etc., with a pseudocapacitive behavior characterized by a high rate performance. To understand the mechanistic details of the lithium storage anomaly, we have performed comparative ab initio calculations on the atomic and electronic structure of the nonpolar Cu/ LiF001 and model Li/ LiF001 interfaces. For this aim, we inserted extra Li atoms at several possible sites of the periodic two-dimensional Me/LiF Me= Cu, Li interfaces. The energetically most favorable site for extra Li atom is
Water transport in epoxy/MWCNT composites
2013
Moisture and water uptake of epoxy/multi-wall carbon nanotube (MWCNT) composites was studied in a wide range of atmosphere relative humidity and temperatures. Addition of up to 1 wt.% of MWCNTs into the neat epoxy resulted to the twofold decrease of the diffusivity, while the levels of moisture/water uptake remained unchanged. The positive effect on the reduction of the diffusion coefficient diminishes with the increase of temperature. Differences in the water transport properties and plasticization ability of the neat polymer and its nanocomposites are explained by the free volume considerations and the polymer–water interactions, which are verified by the results of thermomechanical analy…
Controlled Activation of Substrate Templating in Molecular Self-Assembly by Deprotonation
2013
cited By 7; International audience; Templated assembly of organic molecules constitutes a promising approach for fabricating functional nanostructures at surfaces with molecular-scale control. Using the substrate template for steering the adsorbate growth enables creating a rich variety of molecular structures by tuning the subtle balance of intermolecular and molecule–surface interactions. On insulating surfaces, however, surface templating is largely absent due to the comparatively weak molecule–surface interactions compared to metallic substrates. Here, we demonstrate the activation of substrate templating in molecular self-assembly on a bulk insulator by controlled deprotonation of the …