Evidence of Isotopic Fractionation During Vapor Exchange Between the Atmosphere and the Snow Surface in Greenland.

Several recent studies from both Greenland and Antarctica have reported significant changes in the water isotopic composition of near-surface snow between precipitation events. These changes have been linked to isotopic exchange with atmospheric water vapor and sublimation-induced fractionation, but the processes are poorly constrained by observations. Understanding and quantifying these processes are crucial to both the interpretation of ice core climate proxies and the formulation of isotope-enabled general circulation models. Here, we present continuous measurements of the water isotopic composition in surface snow and atmospheric vapor together with near-surface atmospheric turbulence and snow-air latent and sensible heat fluxes, obtained at the East Greenland Ice-Core Project drilling site in summer 2016. For two 4-day-long time periods, significant diurnal variations in atmospheric water isotopologues are observed. A model is developed to explore the impact of this variability on the surface snow isotopic composition. Our model suggests that the snow isotopic composition in the upper subcentimeter of the snow exhibits a diurnal variation with amplitudes in δ18O and δD of ~2.5‰ and ~13‰, respectively. As comparison, such changes correspond to 10-20% of the magnitude of seasonal changes in interior Greenland snow pack isotopes and of the change across a glacial-interglacial transition. Importantly, our observation and model results suggest, that sublimation-induced fractionation needs to be included in simulations of exchanges between the vapor and the snow surface on diurnal timescales during summer cloud-free conditions in northeast Greenland.

[Acid resistance of the erythrocyte membranes in patients undergoing periodic hemodialysis treatment]. / Kiselinna ustoichivost na eritrotsitnite membrani pri bolni na periodichno khemodializno lechenie.

The method of acid erythrograms were used in the study of age structure of the erythrocyte population in 38 patients treated with periodical hemodialysis. It was established that the number of young erythrocytes predominated in 76.3 per cent of the patients studied, being 164 per cent of the norm. That was established by the shifting of the erythrogram to the right of the normal. Erythrograms shifted to the left were established in 5,3 per cent of the patients and normal--the rest 18,4%. The number of the blood cells in the erythrograms shifted to the left is reduced to 23.3 per cent from the norm. A different degree of anemia in all three groups was observed but no correlation could be confirmed between the severity of anemia and the changes in erythrograms.