Positrons lifetimes were measured in medical substances of insulin (human and animal), differing as far as the degree of purity and time of their activity in the organism are concerned. In all of the cases the spectrum of positron lifetime was distributed into three components, with the long-life component ranging from 1.8 to 2.08 ns and the intensity taking on values from 18 to 24%. Making use of Tao-Eldrup model, the average radius of the free volume, in which o-Ps annihilated, and the degree of filling in the volume were determined. It was found that the value of the long-life component for human insulin is higher than that of animal insulin. Moreover, the value of this component clearly depends on the manner of purification of the insulin. It was also noticed that there occurs a correlation between the value of this component and the time after which it begins to be active in the organism, as well as the total time of its activity.
The method of positron lifetime measurement was used to analyse the influence of a magnetic field on the kinetics of corrosion defect formation in near-surface layers of iron, titanium as well as S20 and S0H18N9 steel grades. The listed metals, which belong to ferro- and paramagnetic materials, have different sensitivity to corrosion. It was found that not only the presence of a magnetic field, but also its direction influence the dimensions and the concentration of defects formed during corrosion.
The influence of interstitial hydrogen concentration and structural defects caused by quenching of palladium, begun at different temperatures up to the temperature of liquid nitrogen or by stretching by external forces, on spectra of lifetimes of positrons in this metal was investigated. It was found that the spectra of positron lifetimes in the examined systems are best described by their distribution into two components. On the basis of the two-state model of annihilation, the conclusion was drawn that the initial temperature from which quenching of palladium is commenced and also the relative elongation, which is caused by external forces, markedly influence the concentrations and sizes of defects in the sample.
Angular distributions of the positron annihilation quanta were measured for pure and hydrogenated palladium samples deformed by uniaxial tension up to different deformation degrees. The relative difference curves, and the values of the R parameter characterizing the dimensions of defects trapping the positrons, were determined. It was found that for relative elongations ranging from 1.9 to 3.5%, in both the pure and hydrogenated palladium, the positrons are trapped in defects larger than vacancy clusters. The values of the R parameter for pure palladium samples elongated up to 0.39, 0.77, and 1.5% indicate a dominant role of smaller defects, like the vacancy clusters.
The positron lifetime in steel St-20 were determined before and following corrosion in HCl vapors. The influence of external magnetic field and remanent magnetization state on the parameters of the positron lifetime spectrum in the steel were investigated. It was found that the presence of magnetic field causes a decrease in the intensity of the component connected with annihilation of positrons in the close-to-the-surface lattice defects.
The paper deals with examining the lifetimes of positrons emitted from ^{22}Na source in corroded St20 and St3S steels. Influence of the method of defecting the sample surfaces on the spectrum of positron lifetimes was investigated. Influence of temperature of initial annealing of samples, plastic deformation, electrolytic hydrogenation and corrosion in HCl vapors on trapping positrons in the examined steels was also determined.
Peak coincidence counting rate and positron lifetime spectra for deformed by cold-rolling, and annealed by four hours in the temperature 973 K, hydrogen free and hydrogenated PdCu with 23% Cu samples, in the temperature range from room temperature to about 720 K were measured. It was found that hydrogen improved to tempered samples creates defects that are annealed to the temperature about 525 K. In the cold-rolled up to deformation degree of 50% samples, hydrogen is trapped at defects, probably vacancies, forming H-V complexes, that become disappearing in the vicinity of the temperature at 350 K.
An attempt was undertaken at making use of a technique of taking measurements of lifetimes of positrons emitted from ^{22}Na source to investigate corroded nickel. It was found that after corrosion in HCl vapours mean positrons lifetime, the second component of positrons lifetimes as well as its intensity rise along with the corrosion time.
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