Search results for "Diffusion"

Numerical Determination of Intrinsic Diffusion Coefficient of Aluminide Coatings on Metals

2009

This paper presents a numerical method to determine the composition dependent diffusivities and to predict the concentration profile during the interdiffusion process. The intrinsic diffusion coefficients in diffusion aluminide coatings (Fe-Al) were determined at 1000oC. The obtained diffusion coefficient for iron in Fe3Al or FeAl is in the range 10-10 to 10-9 cm2.s-1. The aluminum diffusion coefficient varies from 10-11 to 10-7 cm2.s-1 in the same phases.The present approach also permits to model the reactive diffusion in the Fe-Al systems.

Oxygen Diffusion in Alumina. Application to Synthetic and Thermally Grown Al<sub>2</sub>O<sub>3</sub>

2005

S. Chevalier, B. Lesage, C. Legros, G. Borchardt, G. Strehl, M. Kilo Laboratoire de Recherches sur la Reactivite des Solides, CNRS UMR 5613, Universite de Bourgogne, F-21078 Dijon, France Laboratoire d’Etudes des Materiaux Hors Equilibre, CNRS UMR 8647, Universite Paris XI, F-91405 Orsay, France. Institut fur Metallurgie, TU Clausthal, Robert Koch Strasse 42, D38678 Clausthal-Zellerfeld, Germany. * sebastien.chevalier@u-bourgogne.fr

The Influence of Diffusion of Inert Gases on the Determination of Blood Flow by the Clearance Method

1968

Differential associations of age with volume and microstructure of hippocampal subfields in healthy older adults

2015

Hippocampal atrophy in advanced healthy aging has frequently been reported. However, the vulnerability of different hippocampal subfields to age-related atrophy is still a source of debate. Moreover, the association of age with the microstructural integrity of subfields is largely unknown. In this study, we investigated the associations between age and volume as well as microstructural integrity of hippocampal subfields using a three-dimensional (3D) surface mapping approach. Forty-three healthy older adults spanning the age range from 60 to 85 years underwent T1-weighted and diffusion-tensor imaging. Analyses demonstrated an association of age with hippocampal volume predominantly in the m…

Nanoparticles and their influence on radionuclide mobility in deep geological formations

2012

International audience; This article gives an overview of the current status of knowledge concerning the role of nanoparticles (inorganic and organic) in deep geological host rocks and the potential influence of these nanoparticles on radionuclide migration in far-field systems. The manuscript is not intended to be a full review paper or overview paper concerning nanoparticles, here the intention is to refer to recent publications but to highlight the progress made in the 6th framework project IP FUNMIG (Fundamental processes of radionuclide migration) and the open literature over the past 5 a concerning the process understanding of nanoparticle related issues in the three host rock formati…

Application of the collective coordinate method to the analysis of the dynamics of mode-locked fiber lasers

2015

Mode-locked fiber laser are among the few systems that allow to achieve a variety of elaborate optical functions, by means of few optical components. The use of dispersion management brings to this type of lasers a variety of behaviors, which is so rich that the complete mapping and detailed analysis of the stable states becomes impractical when conventional tools based on the intra-cavity field propagation equations, are used. In this thesis we show that the addition of the technique ofcollective coordinates to the conventional theoretical tools, allows to solve at least in part the problem of complexity and diversity of the stable states of the cavity. In particular, we propose the DCCA (…

Dynamic self-assembly of photo-switchable nanoparticles

2012

Nanoparticles functionalized with photo-switchable ligands can be assembled into a broad range of structures by controlled light exposure. In particular, alternating light exposures provide the means to control formation of assemblies of various sizes and symmetries. Here, we use scaling arguments and Kinetic Monte Carlo simulations to study the evolution of reversible aggregates in a solution of periodically irradiated photo-switchable nanoparticles. Scaling estimates of the characteristic size and the mean separation of aggregates agree with the simulations. The transition probabilities in the Kinetic Monte Carlo scheme are derived from a renormalized master equation of the diffusion proc…

Colloidal electro-phoresis in the presence of symmetric and asymmetric electro-osmotic flow

2018

We characterize the electro-phoretic motion of charged sphere suspensions in the presence of substantial electro-osmotic flow using a recently introduced small angle super-heterodyne dynamic light scattering instrument (ISASH-LDV). Operation in integral mode gives access to the particle velocity distribution over the complete cell cross-section. Obtained Doppler spectra are evaluated for electro-phoretic mobility, wall electro-osmotic mobility and particle diffusion coefficient. Simultaneous measurements of differing electro-osmotic mobilities leading to asymmetric solvent flow are demonstrated in a custom made electro-kinetic cell fitting standard microscopy slides as exchangeable sidewall…

Nanoparticles Size Distribution Assessment During Early Synthesis Stages

2021

Nanotechnology, an innovative field of material science, designs and produces nanostructures materials with unique properties that make them suited for various bioengineering applications. The shape and the dimension are the main variables depending on the method of synthesis or chemical precursors. Silver nanoparticles obtained through chemical synthesis exhibit as strong antibacterial effect if their size lays in a well-defined range. However, a small size of such particles, in the range of nanometers to several tens of nanometers, requires specific techniques as Dynamic Light Scattering or Transmission Electron Microscopy, both being affected by certain assumptions or by the high cost an…

Oxygen diffusivity in tumor tissue (DS-Carcinosarcoma) under temperature conditions within the range of 20?40�C

1977

The O2 diffusion constants D and K of tumor tissue (DS-Carcinosarcoma in the rat kidney) were determined at temperatures of 20, 30, 37, and 40 degrees C. The following mean values were obtained for the conditions of 37 degrees C: D = 1.75-10(-5) cm2/s and K = 1.9-10(-5) mlO2/cm-min-atm. Within the range of 20-40 degrees C, temperature variations in tumor tissue cause changes in the O2 diffusion coefficient D of 2.0-2.5%/C and in the Krogh O2 diffusion constant K of 0.5-1.5%/C. The measured O2 diffusion constants for tumor tissue correspond to values of normal tissue with similar water content. This indicates that the insufficient O2 supply in DS-Carcinosarcoma is due not to unfavorable O2 d…