High-pressure phase transition and properties of spinel ZnMn2O4

X-ray photoelectron spectroscopy, magnetic measurements, and a single-crystal x-ray structure determination at normal pressure have shown that Jahn-Teller active manganese ions in ZnMn2O4 are present in one valence state (III) on the octahedral sites of the spinel structure. The high-pressure behavior of ZnMn2O4 was investigated up to 52 GPa using the energy-dispersive x-ray diffraction technique and synchrotron radiation. The structural first-order phase transition from the body-centered to primitive-tetragonal cell takes place at Pc=23GPa. The high-pressure phase is metastable down to normal pressure. The c/a ratio reduces from 1.62 to 1.10 above Pc and remains nearly pressure independent in the high-pressure phase. The transition is attributed to the changes in electron configuration of the Mn3+ ions. According to the crystal field theory, the eg electron of octahedrally coordinated Mn3+ is either in the d2z orbital or in the dx2−y2. In the first configuration the MnO6octahedron will be elongated and this is the case at normal pressure, while the second configuration gives the flattened octahedron. In the high-pressure phase some proportion of the eg electrons of the Mn3+ ions is moved to the dx2−y2 level, which is revealed as an abrupt fall of observed magnitude of the distortion of the bulk crystal above Pc

Influence of oxygen concentration on T cell proliferation and susceptibility to apoptosis in healthy men and women

Introduction. Much of what we know about the functioning of human T lymphocytes is based on the experiments carried out in atmospheric oxygen (O2) concentrations, which are significantly higher than those maintained in blood. Interestingly, the gender differences in the activity of T cells and their susceptibility to apoptosis under different O2 conditions have not yet been described. The aim of the study was to compare two main markers of lymphocyte function: proliferation capacity and ability to produce cytokines as well as their susceptibility to apoptosis under two different O2 concentrations, between men and women. Materials and methods. 25 healthy volunteers, both males (13) and females (12) were recruited to the study (mean age 25.48 ± 5.51). By using cytometry proliferation parameters of human CD4+ CD28+ cells or CD8+CD28+ cells in response to polyclonal stimulation of the TCR/CD3 complex at atmospheric (21%) and physiological (10%) O2 concentrations using our modified dividing cell tracking technique (DCT) were analyzed as well as the percentages of apoptotic cells. We also determined the levels of IFN-γ, IL-2, IL-10 and IL-17A using Cytometric Bead Array Flex system in cell culture supernatants. Results. CD4+CD28+ and CD8+CD28+ cells from the whole study group were characterized by shorter time required to enter the first (G1) phase of the first cell cycle at 21% compared to 10% O2. Both T cell populations performed significantly more divisions at 21% O2. The percentages of dividing cells were also significantly higher at atmospheric O2. Interestingly, data analysis by gender showed that male lymphocytes had similar proliferative parameters at both O2 concentrations while female lymphocytes proliferate more efficiently (note from the author: we cannot say that lymphocytes proliferate faster, rather more effectively, because cells perform more divisions, which gives more percentage of offspring cells) at 21% oxygen. Compared to males, the female CD4+ cells showed increased susceptibility to apoptosis at both O2 concentrations. No differences in the levels of cytokines regardless of gender and oxygen conditions were found. Conclusions. We showed that in vitro female T cells (both CD4+ and CD8+ cells) are more sensitive than male lymphocytes to low O2 concentration as demonstrated by the decrease in their proliferation dynamics. The effect does not depend on increased apoptosis of female T cells under low O2 because percentage of apoptotic cells was similar at both O2 concentrations