Effects Of Substrate Size Research Articles

Adsorption binding-energy variation resulting from substrate size effects.

Results of a computer investigation of the influence of crystallite finite lateral size and thickness upon the binding-energy heterogeneity of typical physisorption substrates are reported. Size effects are shown to contribute large tails to the binding-energy distribution. Calculations with the model substrate (100-\AA{} typical surface coherence length) show that 20%-30% of the binding sites have energies which differ from the average binding energy by greater than 0.2%. Size effects alone, however, are insufficient to explain the distribution peak widths of real substrates.

Nucleation During the Solidification of Atomized Droplets Catalyzed by Spherically-Shaped Oxide Particles

AbstractNucleation temperatures are calculated for the case of solidification in atomized metal droplets where spherical substrate particles act as nucleation catalysts. Following the method of Fletcher, the effect of substrate size on catalytic potency is illustrated, and the model is applied to the nucleation of bcc solid from pure, liquid iron containing oxide substrate particles as catalysts. Supercooling data from the literature are used to determine wetting angles for alumina, silica, and rare-earth oxide. Oxide particle-size distributions are then used to predict the supercooling behavior of atomized liquid droplets based on the probability that a given size of droplet will contain a particular size of substrate particle. A transition size regime is found separating droplet sizes undergoing very small and very large supercoolings, respectively. This is discussed in terms of the types and number densities of inclusions present during atomization of the melt.

Effect of substrate size on tonin activity

A study of the kinetics of tonin action on several synthetic homologs of angiotensinogen showed that the minimal peptide substrate for that enzyme is the (5–10)-hexapeptide. The C-terminal tetrapeptide segment of the angiotensinogen-(1–14)-peptide affects tonin specificity mainly through an effect on the catalytic step, and not through changes in enzyme-substrate affinity. When the three N-terminal residues of the (1–14)-peptide were removed, a poorer tonin substrate was obtained, mostly because of a sharp increase in Km. Bradykinin was not attacked by tonin, while substance P was hydrolyzed only with enzyme concentrations much higher than those effective with angiotensinogen fragments as substrates.