Compositional changes of the first sharp diffraction peak (FSDP) in the measured structure factor have been studied for several binary selenide glasses using pulsed-neutron and high-energy x-ray diffraction techniques. The observed variations in the FSDP (factor of 10 in the amplitude and $\approx 0.5{\mathrm{\AA }}^{-1}$ in the peak position) reflect multiple aspects in the glass network on both the short- and intermediate-range scales and are also correlated with macroscopic properties. An empirical relation has been discovered relating the compositional dependence of the FSDP position to the local coordination number of the guest atom.

Background —Hydrogen peroxide (H ₂ O ₂ ) and reactive oxygen species are implicated in inflammation, ischemia-reperfusion injury, and atherosclerosis. The role of ion channels has not been previously explored. Methods and Results —K ⁺ currents and membrane potential were recorded in endothelial cells by voltage- and current-clamp techniques. H ₂ O ₂ elicited both hyperpolarization and depolarization of the membrane potential in a concentration-dependent manner. Low H ₂ O ₂ concentrations (0.01 to 0.25 μmol/L) inhibited the inward-rectifying K ⁺ current (K _IR ). Whole-cell K ⁺ current analysis revealed that H ₂ O ₂ (1 mmol/L) applied to the bath solution increased the Ca ²⁺ -dependent K ⁺ current (K _Ca ) amplitude. H ₂ O ₂ increased K _Ca current in outside-out patches in a Ca ²⁺ -free solution. When catalase (5000 μ/mL) was added to the bath solution, the outward-rectifying K ⁺ current amplitude was restored. In contrast, superoxide dismutase (1000 u/mL) had only a small effect on the H ₂ O ₂ -induced K ⁺ current changes. Next, we measured whole-cell K ⁺ currents and redox potentials simultaneously with a novel redox potential-sensitive electrode. The H ₂ O ₂ -mediated K _Ca current increase was accompanied by a whole-cell redox potential decrease. Conclusions —H ₂ O ₂ elicited both hyperpolarization and depolarization of the membrane potential through 2 different mechanisms. Low H ₂ O ₂ concentrations inhibited inward-rectifying K ⁺ currents, whereas higher H ₂ O ₂ concentrations increased the amplitude of the outward K ⁺ current. We suggest that reactive oxygen species generated locally increases the K _Ca current amplitude, whereas low H ₂ O ₂ concentrations inhibit K _IR via intracellular messengers.

Monochromatic high-energy x-ray diffraction measurements employing microfocusing optics were performed on glassy $\mathrm{Ge}{\mathrm{Se}}_2$ in a diamond anvil cell at pressures up to $9.3\mathrm{GPa}$. In addition, the method of isotopic substitution in neutron diffraction was applied to samples that had been densified by 4% via pressurization to $10\mathrm{GPa}$ in a multianvil device and subsequently recovered to ambient conditions. The results reveal a steady increase with pressure of the average coordination number of Ge from 4.0(2) under ambient conditions to 4.5(2) at $9.3\mathrm{GPa}$. With increasing pressure, the first sharp diffraction peak in the measured diffraction patterns at $\sim 1.0{\mathrm{\AA }}^{-1}$ decreases in intensity and almost disappears while the amplitude of the peaks beyond the nearest neighbor in the measured total pair distribution functions gradually increases. Equation of state measurements show a gradual density increase of 33% from ambient pressure to $8.5\mathrm{GPa}$ which is in good agreement with molecular dynamics simulations. The results are consistent with the occurrence of two densification processes for glassy $\mathrm{Ge}{\mathrm{Se}}_2$, namely, a conversion from edge-sharing to corner-sharing tetrahedra and a gradual increase in the average local coordination number with increasing density.