Oxygen Dosage Research Articles

Structural transition in Bi-Sr-Ca-Cu-O revealed by Fermi level control and the mechanism of high-Tc superconductivity

A technique is developed for control of the Fermi level in HTS materials by the oxygen dosage in the sample using a solid-state electrochemical cell. The dependences of the oxygen content in the sample n(EF) and the electron density of states at the Fermi level D(EF) on the Fermi level have been studied. At a separation of several tens of mV above the Fermi level of the HTS state, an n(EF) step and D(EF) peak are revealed which are related to the structural phase transition. The character of the dependences obtained allows the authors to relate high-temperature superconductivity to the interaction between the virtual structural phase transition and the transition to the conventional superconducting state. In the phenomenological model proposed this interaction is described by two order parameters: Delta the superconductive gap width, and in g the energy separating the superconducting state from the virtual structural phase transition. In the microscopic model under consideration this interaction results in the appearance of an electron-phonon gap above the Fermi level. The position of the gap increases the electron density of states in the region of BCS interaction with phonon, thus excluding dielectrization of the electronic spectrum.

Coadsorption of barium and oxygen on nickel—effect on oxide nucleation: Photoelectron spectroscopic studies

Adsorption studies of oxygen on barium-promoted Nickel surface by x-ray photoelectron spectroscopy show that the presence of submonolayer coverages of barium has a profound effect on the nucleation of the oxide on the Ni surface. The Ni surface, in addition to oxidic oxygen, stabilizes a second oxygen species $O^1^-$ which was earlier thought to be OH(ad). Barium coverages less than $6X10^1^4$ atoms/cm2 make the oxidation of Ni more facile. For barium coverages higher than $6X10^1^4$ atoms/cm2, the nucleation of the oxide is greatly suppressed resulting in the stabilization of more reactive, coordinatively unsaturated chemisorbed oxygen. By monitoring the barium coverage, it is possible to control the relative proportions of the oxidic $O^2^-$ species and the surface-stabilized chemisorbed oxygen $O^1^-$ (ad) on the surface. The presence of predosed barium enhances the intensity of reactive chemisorbed oxygen which cannot coalesce to form the passive, oxidic overlayer even after excess oxygen dosage. Thermal stability of chemisorbed oxygen shows interesting trends. Both charge transfer from Ba to Ni and site occupation play crucial roles.

Reasons for and against the oxygen dosage in condensate feed circuits of nuclear power plants with RBMK-1000 reactors

Reasons for and against the oxygen dosage in condensate feed circuits of nuclear power plants with RBMK-1000 reactors

Oxygen adsorption on polycrystalline Cu films studied by means of gravimetric uptake and work function change

Past investigations into the interactions of oxygen with copper have been made in which the superstructures caused by oxygen adsorption on the main crystallographic orientations were studied by low energy electron diffraction (LEED). Although the low sticking coefficient of oxygen on Cu is generally accepted, no systematically gravimetric measurements of the oxygen adsorption are available. We report our results from combined measurements on evaporated Cu films by means of gravimetric mass gain and work function changes up to an oxygen dosage of 7×105 L.

Combination analysis of metal oxides using ESCA, AES, and SIMS

Combination ESCA, AES, and SIMS analyses have been conducted on high purity metal foils of Fe, Ni, Cr, and Mo to investigate oxides formed on sputter-cleaned surfaces. Results are given for the controlled oxidation of Fe and Ni metals and the rapid sequential analysis by the three techniques. Oxygen signals from the three methods are shown to have identical dependence on oxygen dosage during the initial stages of oxidation for these two metal-oxygen systems. ESCA and SIMS results of both systems are in agreement with divalent oxide formation at oxygen dosages up to 60 L for Fe and 50 L for Ni. Preliminary results for Cr-O and Mo-O systems are also reported.

Ideas and anomalies in the evolution of modern oxygen therapy.

Ideas and anomalies in the evolution of modern oxygen therapy.

Oscillatory glycolysis in yeast: The pattern of phase resetting by oxygen

Glycolytic oscillations are initiated in a yeast cell suspension by an aerobic to anaerobic transition, and followed by recording NADH fluorescence. Injection of dissolved oxygen, up to 70 μ m, is found to phase-reset the NADH rhythm, usually without effect on period or amplitude. The graphed dependence of phase-resetting on oxygen dosage and on time of administration resembles a helicoidal surface. There is a critical dosage and phase at which injection terminates the oscillation. This pattern is typical of the simplest kinds of continuous and homogeneous reaction schemes. These results seem to support limit-cycle models involving only two important interacting control variables.