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Diffusion Data (diffusion + data)

Distribution by Scientific Domains

Chemistry	33%

Selected Abstracts

Diffusion in Nanocrystalline Metals and Alloys,A Status Report,

ADVANCED ENGINEERING MATERIALS, Issue 5 2003
R. Würschum
Abstract Diffusion is a key property determining the suitability of nanocrystalline materials for use in numerous applications, and it is crucial to the assessment of the extent to which the interfaces in nanocrystalline samples differ from conventional grain boundaries. The present article offers an overview of diffusion in nanocrystalline metals and alloys. Emphasis is placed on the interfacial characteristics that affect diffusion in nanocrystalline materials, such as structural relaxation, grain growth, porosity, and the specific type of interface. In addition, the influence of intergranular amorphous phases and intergranular melting on diffusion is addressed, and the atomistic simulation of GB structures and diffusion is briefly summarized. On the basis of the available diffusion data, the diffusion-mediated processes of deformation and induced magnetic anisotropy are discussed. [source]

Measurement of aroma compound self-diffusion in food models by DOSY

MAGNETIC RESONANCE IN CHEMISTRY, Issue 6 2004
Thierry Gostan
Abstract Self-diffusion measurement of solutes in polymer gels has been investigated using pulsed gradient spin echo NMR spectroscopy. However, few data are available on the self-diffusion of small solutes in natural polysaccharide polymers used as thickeners in the food industry. Since aroma diffusion in food matrices could have an impact on flavor release, this is an interesting and economic challenge. Diffusion ordered spectroscopy (DOSY) resolves diffusion data for each component in complex mixtures. We used DOSY with the inverse Laplace transform approach with the maximum entropy algorithm to investigate diffusion of two aroma compounds, ethyl butanoate and linalool, in an ,-carrageenan matrix as the food model. We showed that the self-diffusion coefficient values of small molecules in a polysaccharide matrix could be easily extracted using this method. We then investigated the impact of the gelling state of ,-carrageenan matrices on the self-diffusion of ethyl butanoate. Copyright © 2004 John Wiley & Sons, Ltd. [source]

Potassium diffusion in melilite: Experimental studies and constraints on the thermal history and size of planetesimals hosting CAIs

METEORITICS & PLANETARY SCIENCE, Issue 12 2004
Motoo ITO
These observations could be used to provide important constraints on the thermal history and size of the planetesimals into which the CAIs were incorporated, provided the diffusion kinetic properties of K in these minerals are known. Thus, we have experimentally determined K diffusion kinetics in the melilite end-members, åkermanite and gehlenite, as a function of temperature (900,1200 °C) and crystallographic orientation at 1 bar pressure. The closure temperature of K diffusion in melilite, Tc(K:mel), for the observed grain size of melilite in the CAIs and cooling rate of 10,100 °C/Myr, as calculated from our diffusion data, is much higher than that of Mg in anorthite. The latter was calculated from the available Mg diffusion data in anorthite. Assuming that the planetesimals were heated by the decay of 26Al and 60Fe, we have calculated the size of a planetesimal as a function of the accretion time tf such that the peak temperature at a specified radial distance rc equals Tc(K:mel). The ratio (rc/R)3 defines the planetesimal volume fraction within which 41K* in melilite grains would be at least partly disturbed, if these were randomly distributed within a planetesimal. A similar calculation was also carried out to define R versus tf relation such that 26Mg* was lost from ,50% of randomly distributed anorthite grains, as seems to be suggested by the observational data. These calculations suggest that ,60% of melilite grains should retain 41K* if ,50% of anorthite grains had retained 26Mg*. Assuming that tf was not smaller than the time of chondrule formation, our calculations yield minimum planetesimal radius of ,20,30 km, depending on the choice of planetesimal surface temperature and initial abundance of the heat producing isotope 60Fe. [source]

Innovation alignment and project network dynamics: An integrative model for change

PROJECT MANAGEMENT JOURNAL, Issue 3 2007
John E. Taylor
Abstract Innovation research has predominantly focused on hierarchically organized firms competing within single markets. Recently, however, researchers have debated over whether the increasing use of project networks within and across industries promotes or stifles innovation. This paper discusses a model based on crossnational diffusion data from three technological innovations in three-dimensional computer-aided design (3D CAD) and related implementation data from 82 firms. From the data we induce a set of constructs that form the basis of a two-stage model for understanding innovation in project networks. In the first stage of the model the alignment of an innovation to the existing allocation of work in a project network is ascertained. In the second stage, the implementation success and diffusion outcomes for innovations misaligned with the allocation of work are governed by the relational stability, accrual of interests, boundary permeability, and existence of an agent for project network change. In developing this integrative, two-stage model we resolve the contradiction in the academic literature regarding the degree to which project network dynamics can promote or stifle innovation. [source]

Analysis of the influence of coupled diffusion on transport in protein crystal growth for different gravity levels

ACTA CRYSTALLOGRAPHICA SECTION D, Issue 10-1 2002
D. Castagnolo
Diffusion has a central role in protein crystal growth both in microgravity conditions and on ground. Recently several reports have been focused on the importance to use the generalized Fick's equations in n -component systems where crystals grow. In these equations the total flux of each component is produced by the own concentration gradient (main flow) and by the concentration gradient of the other components (cross-flow) present in the system. However in literature the latter effect is often neglected, and the so-called pseudo-binary approximation is used. Lin et al. (1995) proposed a mathematical model to evaluate the concentration profile of the species present around a growing protein crystal. Although the model is reliable, it suffers of the pseudo-binary approximation (neglecting cross term diffusion coefficients and using binary diffusion coefficients), probably because of the lack of multicomponent diffusion data. The present model is based on the experimental set-up proposed by Lin et al. (1995). Nevertheless we have included the coupled diffusion effects, according to the correct description of the matter transport through the generalized Fick's equations. The crystal growth rate is calculated for different gravity levels. The model has been applied to the ternary lysozyme-NaCl-water and quaternary lysozyme-poly(ethylene glycol) (PEG)-NaCl-water systems using recent diffusion data. [source]