SED88: a Pascal program for the analysis of sedimentation equilibrium data

Analytical ultracentrifugation is commonly used for the determination of molecular weights (sedimentation equilibrium) and sedimentation coefficients (sedimentation rate) of biological macromolecules in solution. A Turbo Pascal program for the analysis of sedimentation equilibrium centrifugation data produced by absorbance optical systems is described. The user may enter data from a scan of absorbance versus distance from the centre of rotation, via a graphics tablet (or ASCII file). This is subsequently manipulated to yield an apparent weight average molecular weight for the given sample. Plots of ln (absorbance) versus (radius2) may also be produced. The method described uses readily available computational equipment requiring only a graphics tablet in addition to an IBM PC compatible computer. This technique and the software developed have been used to investigate the molecular weight range of two International Humic Substances Society (IHSS) reference samples from the Suwannee River.     

Volatile N-nitrosamines in sausage products

The authors studied the content of volatile N-nitrosamines (NA) in the most common sausage products. It was established that the total content of NA in sausage products is not high and ranges from trace amounts up to 10 micrograms/kg product. The allowable doses of nitrite in the sausage manufacture being low, no relationship was discovered between the content of NA and residual nitrite in meat products.     

Erbium ion electroluminescence in p ++/n +/n-Si:Er/n ++ silicon diode structures

Results of experimental studies of erbium ion electroluminescence in p ⁺⁺/n ⁺/n-Si:Er/n ⁺⁺ silicon diode structures grown by sublimation molecular-beam epitaxy are discussed. The distinctive feature of these structures is that the regions of electron flux formation of (n ⁺-Si) and impact excitation of erbium ions (n-Si:Er) are spaced. The influence of the n ⁺-Si layer thickness on electrical and electroluminescent properties of diodes was studied. It was shown that n ⁺-Si layer thinning causes the transformation of the structure breakdown mechanism from tunneling to avalanche. The dependence of the Er³⁺ ion electroluminescence on the thickness of the heavily doped n ⁺-Si region is bell-shaped. At the n ⁺-Si-layer doping level n ≈ 2 × 10¹⁸ cm^?3, the maximum electroluminescence intensity is attained at an n ⁺-Si layer thickness of ～23 nm.     

Method of calculating the composition of ceramic paste based on acid loams with semiacid clay additive

A method is proposed for designing the charge composition of a two-component clay paste for production of rough wall ceramic based on acid loams and nontraditional semiacid clay additive with a high iron oxide content. __________ Translated from Steklo i Keramika, No. 1, pp. 14–15, January, 2007.     

Effect of yttrium and chromium on the recrystallization of Al-Sc alloys

The effect of small chromium and yttrium additions (0.14–1.0 wt%) on the recrystallization of Al-Sc alloys having 0.1–0.4% Sc is studied with polarized light. The microstructure of cold-rolled samples annealed at 100–630°C for 1 h is examined. The chromium and yttrium additions are found to slightly affect the recrystallization temperature of the Al-Sc alloys: they increase or decrease it slightly depending on the scandium content.     

Wear resistance of plasma coatings for a constant work of friction

We analyze the wear resistance of plasma coatings for a constant work of friction. The dependences of the wear resistance of the coatings are obtained for a broad range of loading conditions. It is shown that the minimum sensitivity to loading conditions is exhibited by the molybdenum coatings. It is also established that the wear resistance of the coatings decreases as the amplitude of displacements increases and the cyclic frequency of the tests decreases due to the intensification of fatigue processes on the surfaces. The comparative characteristics of coatings are presented. __________ Translated from Problemy Prochnosti, No. 5, pp. 94–100, September–October, 2007.