Relation Between Structure and Diffusion in Nanostructured Porous Solids and in Lipid Membranes

2005 ◽  
Vol 899 ◽  
Author(s):  
Sergey Vasenkov ◽  
Jörg Kärger
Keyword(s):  
Lipid Membranes ◽  
Molecular Transport ◽  
Domain Size ◽  
Porous Solids ◽  
Diffusion Studies ◽  
Lipid Diffusion ◽  
Effective Diffusivities ◽  
Pfg Nmr ◽  
Fcc Catalysts ◽  
And Diffusion

AbstractPulsed field gradient (PFG) NMR technique has been applied to study molecular transport in two different types of nanostructured materials, viz. in fluid catalytic cracking (FCC) catalysts and in lipid membranes. Diffusion studies have been performed for a broad range of molecular displacements covering displacements that are as small as a fraction of a micron. The effective diffusivities recorded on various length scales are used to evaluate the relevance of various transport modes in the particles of FCC catalysts for the rate of molecular exchange between catalyst particles and the surrounding atmosphere. This rate is shown to be primarily related to the diffusion in the meso- and macropores of the particles under the condition of fast molecular exchange between these pores and the zeolite crystals located in the particles. Studies of lipid membranes are focused on developing fundamental understanding of the influence of various types of domains on lateral mobility of lipids. A meaningful study of this influence requires an ability of monitoring lipid diffusion for different displacements that are smaller and larger than the domain size. First PFG NMR data along this direction are presented.

Gold implantation inn‐type silicon: Entropy factor and diffusion studies

1990 ◽  
Vol 68 (4) ◽  
pp. 1601-1605 ◽  
Author(s):  
S. Coffa ◽  
L. Calcagno ◽  
G. Ferla ◽  
S. U. Campisano
Keyword(s):  
Type Silicon ◽  
Diffusion Studies ◽  
Entropy Factor ◽  
And Diffusion

Pollution plume transport and diffusion studies using fluorescence lidar

1980 ◽  
Vol 19 (15) ◽  
pp. 2524 ◽  
Author(s):  
Burton G. Schuster ◽  
Thomas G. Kyle
Keyword(s):  
Diffusion Studies ◽  
Transport And Diffusion ◽  
Plume Transport ◽  
And Diffusion

ULTRACENTRIFUGE AND DIFFUSION STUDIES ON GLUTEN

1942 ◽  
Vol 20c (3) ◽  
pp. 130-159 ◽  
Author(s):  
A. G. McCalla ◽  
Nils Gralén
Keyword(s):  
Sodium Salicylate ◽  
Minimum Weight ◽  
Average Molecular Weight ◽  
Sedimentation Equilibrium ◽  
Velocity Sedimentation ◽  
Molecular Characteristics ◽  
Weight Average Molecular Weight ◽  
Diffusion Constants ◽  
Diffusion Studies ◽  
And Diffusion

The molecular characteristics of gluten in sodium salicylate solutions were studied by means of sedimentation velocity, sedimentation equilibrium, and diffusion measurements. The proportion of total gluten protein molecularly dispersed increased with increase in concentration of sodium salicylate up to 12%, but the dispersed portions had essentially the same sedimentation constant (2.5 ± 0.15) regardless of the concentration of the dispersing medium.The most soluble 25 per cent of the gluten was all molecularly dispersed, but was definitely inhomogeneous. The weight-average molecular weight of this fraction was 44,000, but there is reason to believe the minimum weight may be about 35,000. None of the other fractions was entirely molecularly dispersed, the proportion decreasing with decreasing solubility of the fractions. Aggregates of many sizes existed in all of these fractions, but only the most insoluble contained aggregates large enough to cause opacity. Sedimentation constants of the molecularly dispersed portions increased slightly with decreasing solubility, while diffusion constants decreased markedly. None of the fractions yielded normal curves (diffusion diagrams) but the more soluble the fraction, the more nearly normal the curve. The inhomogeneity responsible for the varying rates of diffusion was due partly to differences in proportion and properties of the molecularly dispersed gluten and partly to aggregates.All properties showed progressive changes both within and between the arbitrarily produced fractions. These results, therefore, support the hypothesis that gluten is a protein system showing progressive and regular changes in properties with change in solubility.

Sorption and diffusion studies in cementitious grouts

1992 ◽  
Vol 12 (2-3) ◽  
pp. 289-297 ◽  
Author(s):  
H.M. Johnston ◽  
D.J. Wilmot
Keyword(s):  
Diffusion Studies ◽  
And Diffusion

Kinetics and diffusion studies in CA2 formation

1989 ◽  
Vol 19 (1) ◽  
pp. 47-52 ◽  
Author(s):  
M.M. Ali ◽  
S.J. Raina ◽  
V.K. Singh
Keyword(s):  
Diffusion Studies ◽  
And Diffusion

scholarly journals Inference of Morphogen Gradient Precision from Molecular Noise Data

2021 ◽  
Author(s):  
Roman Vetter ◽  
Dagmar Iber
Keyword(s):  
Precise Measurement ◽  
Spatial Information ◽  
Domain Size ◽  
Noise Levels ◽  
New Formalism ◽  
Morphogen Gradients ◽  
Molecular Noise ◽  
Noise Data ◽  
Neural Tube Development ◽  
And Diffusion

During development, morphogen gradients provide spatial information for tissue patterning. Gradients and readout mechanisms are inevitably variable, yet the resulting patterns are strikingly precise. Measurement limitations currently preclude precise detection of morphogen gradients over long distances. Here, we develop a new formalism to estimate gradient precision along the entire patterning axis from measurements close to the source. Using numerical simulations, we infer gradient variability from measured molecular noise levels in morphogen production, decay, and diffusion. The predicted precision is much higher than previously measured—precise enough to allow even single gradients to define the central progenitor boundaries during neural tube development. Finally, we show that the patterning mechanism is optimized for precise progenitor cell numbers, rather than precise boundary positions, as the progenitor domain size is particularly robust to gradient alterations. We conclude that single gradients can yield the observed developmental precision, which provides new prospects for tissue engineering.

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