scholarly journals Positron trapping and annihilation at interfaces between matrix and cylindrical or spherical precipitates modeled by diffusion-reaction theory

2019 ◽  
Author(s):  
Roland Würschum ◽  
Laura Resch ◽  
Gregor Klinser
Keyword(s):  
Diffusion Reaction ◽  
Positron Trapping ◽  
Reaction Theory

Diffusion-reaction theory for conductance response in metal oxide gas sensing thin films

2000 ◽  
Vol 66 (1-3) ◽  
pp. 228-231 ◽  
Author(s):  
Honglong Lu ◽  
Wencai Ma ◽  
Jianhua Gao ◽  
Jianming Li
Keyword(s):  
Thin Films ◽  
Metal Oxide ◽  
Gas Sensing ◽  
Diffusion Reaction ◽  
Reaction Theory

Uptake of palmitate by hepatocyte suspensions: facilitation by albumin?

1992 ◽  
Vol 262 (5) ◽  
pp. G883-G894 ◽  
Author(s):  
S. M. Pond ◽  
C. K. Davis ◽  
M. A. Bogoyevitch ◽  
R. A. Gordon ◽  
R. A. Weisiger ◽  
...  
Keyword(s):  
Palmitic Acid ◽  
Association Constant ◽  
Absolute Magnitude ◽  
Diffusion Reaction ◽  
Female Rat ◽  
Theoretical Predictions ◽  
Reaction Theory ◽  
Uptake Velocity ◽  
Rat Livers ◽  
Initial Uptake

Albumin-dependent uptake of unbound [3H]palmitic acid by hepatocytes isolated from female rat livers was studied and the experimental results compared with the predictions of a noncompartmental diffusion-reaction theory for the cellular uptake of protein-bound ligands. The outright theoretical predictions involve values for the parameters of the system, some newly measured (hepatocyte radii and the rate constant for the dissociation of palmitate-albumin complex) and some taken from the literature (diffusion coefficients and the equilibrium association constant for the palmitate-albumin complex). The measured unbound clearance of [3H]palmitic acid, defined as the initial uptake velocity divided by the unbound [3H]palmitic acid concentration in the medium, was enhanced 6.6-fold as the concentration of human serum albumin was increased from approximately 5 to 480 microM. This enhancement factor was predicted by the theory, according to which the enhancement reflects codiffusion of bound ligand across the unstirred layer adjacent to the cell membrane and, therefore, an increased delivery of unbound ligand to the cell surface. In contrast, the absolute magnitude of the unbound clearance was consistent with the theory only for the lowest published value for the equilibrium association constant, 15 microM-1. For higher published values (62 and 94 microM-1), the magnitude of the unbound clearance observed experimentally was severalfold higher than that predicted by the theory. If in fact the association constant exceeds 30 microM-1, the data would imply that an albumin-dependent facilitation mechanism exists which enhances the availability of palmitate to the cell over and above the enhancement predicted by the diffusion-reaction theory.

Observation by HVEM of the martensite transformation and the superconducting transition in Nb3Sn

1988 ◽  
Vol 46 ◽  
pp. 788-789
Author(s):  
M. A. Kirk ◽  
M. C. Baker ◽  
B. J. Kestel ◽  
H. W. Weber
Keyword(s):  
Thin Films ◽  
Low Temperature ◽  
Superconducting State ◽  
Martensite Transformation ◽  
Sputter Deposition ◽  
Diffusion Reaction ◽  
Solute Diffusion ◽  
Superconducting Transition ◽  
Twin Boundaries ◽  
Martensite Structure

It is well known that a number of compound superconductors with the A15 structure undergo a martensite transformation when cooled to the superconducting state. Nb3Sn is one of those compounds that transforms, at least partially, from a cubic to tetragonal structure near 43 K. To our knowledge this transformation in Nb3Sn has not been studied by TEM. In fact, the only low temperature TEM study of an A15 material, V3Si, was performed by Goringe and Valdre over 20 years ago. They found the martensite structure in some foil areas at temperatures between 11 and 29 K, accompanied by faults that consisted of coherent twin boundaries on {110} planes. In pursuing our studies of irradiation defects in superconductors, we are the first to observe by TEM a similar martensite structure in Nb3Sn.Samples of Nb3Sn suitable for TEM studies have been produced by both a liquid solute diffusion reaction and by sputter deposition of thin films.

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