Catastrophic or nearly-catastrophic collisions are the most important physical process affecting the evolution of asteroids following the primordial phases. After a generál review of the current ideas about collisional evolution, also in the light of laboratory impact experiments, the problems concerning
the interpretation of asteroid families as outcomes of catastrophic processes are discussed. Finally, it is shown how the present, non completely satisfactory, knowledge of collisional processes
can give important indications on the early phases of evolution of the asteroid belt.
An ICR outbred suckling mouse model of cryptosporidiosis was used to explain some of the variability associated with experimental Cryptosporidium parvum infections in neonate mice. Fourty four groups of 12 mice each, ranging in age from 4-12 days, each received 1.0 x 104 CsCl purified oocysts per os in 5 pm PBS. At 6 days post-inoculation (PI), mice were killed by C02 overdose and individually weighed. Intestines were then homogenized and oocysts were quantified by hemacytometer. Results revealed that both age and weight have pronounced effects on numbers of oocysts produced in vivo, with larger and older mice producing higher numbers of parasites. Mice 8-9 days of age at the time of inoculation displayed the least amount of weight dependent variability, produced the highest numbers of oocysts, and were judged to be superior over other ages for pharmaceutical screening. Significant reductions in numbers of oocysts occurred in mice inoculated at 10 days of age, and only a few oocysts were found in mice inoculated at 11-12 days of age. These studies suggest that at least some data on Cryptosporidium generated from suckling mouse studies to date are probably unreliable and should be viewed skeptically.
Sulfite, at concentrations from 0.05 to 5.0 mM, inhibited the uptake of sucrose into stripped tissue disks and enzymatically isolated vein networks from mature pea leaves. Sulfite affected the rate of sucrose uptake, while the value was not influenced. The isolated vein networks were much more sensitive to sulfite action than stripped leaf disks.
This work is focused on a problem of an influence of tilt of a thin spherocylindrical spectacle lens on effective dioptric values and visual acuity obtained with such a lens. Moreover, it also discusses possibilities of compensation of this influence during the correction of refractive errors. and Článek pojednává o vlivu náklonu tenké sférocylindrické brýlové čočky podle horizontální a vertikální osy vůči oku na efektivní dioptrické hodnoty takovéto korekční čočky a zrakovou ostrost při korekci takovouto brýlovou čočkou. Dále se zabývá možnostmi kompenzace tohoto vlivu při korekci refrakčních vad oka.