Interaction Of Oxygen With Zn(0001) Surface

EELS and XPS studies show the presence of both adsorbed atomic and molecular oxygen at low temperatures. The nature of the oxide layer formed on the surface has been characterized by angular dependent and variable temperature EELS. A loss peak around 550 cm−1 is assigned to an electronic transition.

Hydroxylation of oxygen-covered Cu(110) and Zn(0001) surfaces by interaction with CH3OH, (CH3)2NH, H2S, HCl and other proton donor molecules

EELS studies provide definitive evidence for the hydroxylation of oxygen-covered Cu(110) and Zn(0001) surfaces on interaction with proton donor molecules such as H2O, CH3OH, HCOOH, NH3 and (CH3)2NH. The occurrence of surface hydroxylation is unambigouusly shown by a study of the interaction of H2S and HCl with an oxygen covered Cu(110) surface.

Oxygen desorption from high Tc YBa2Cu3O7−δ (δ = 0.05, 0.5)

From a temperature programmed desorption study employing a quadrupole mass spectrometer, the superconducting oxide YBa2Cu3O7−δ (δ = 0.05) showed two distinct oxygen desorption peaks, one below and one above 470°C. The activation energy of oxygen desorption of the superconducting oxide was 28 Kcals/mole and that of non-superconducting oxide (YBa2Cu3O6.5) was 54 Kcals/mole. No impurity peaks due to H2O, CO and CO2 from the bulk or adsorbed on surfaces could be observed when a well prepared superconducting oxide was heated up to 650°C.

Temperature dependence of the surface conductivity of YBa2Cu3O7−δ accompanying the change in the concentration of dimerized oxygen holes

The intensity of inelastically scattered electrons measured by electron energy loss spectroscopy has been employed to monitor the surface conductivity of YBa2Cu3O6.9 as a function of temperature. The study shows a drastic change in surface conductivity precedes the superconducting transition at 90K. The increase in surface conductivity is accompanied by the formation of dimerized holes in the oxygen derived p-band. This phenomenon is not observed in the non-superconducting YBa2Cu3O6.2.

Acoustic-surface-wave generation along a cylindrical plasma column surrounded by a compressible gas

Acoustic surface waves can be generated along the plasma column in pressure equilibrium with a gas blanket in the presence of the uniform axial magnetic field. Unlike the case of volume-acoustic-wave generation in the magnetoplasma reported recently, the threshold magnetic field required for the generation of acoustic surface waves increases with increasing gas pressure.

Heat exposure and hypothyroid conditions decrease hydrogen peroxide generation in liver mitochondria

Exposure of rats to heat (39 +/- 1 degree C) decreased H2O2 generation in mitochondria of the liver, but not of the kidney or the heart. The effect was obtained with three substrates, succinate, glycerol 1-phosphate and choline, with a decrease to 50% in the first 2-3 days of exposure, and a further decrease on longer exposure. The dehydrogenase activity with only glycerol 1-phosphate decreased, which is indicative of the hypothyroid condition, whereas choline dehydrogenase activity remained unchanged and that of succinate dehydrogenase decreased on long exposure. The serum concentration of thyroxine decreased in heat-exposed rats. Thyroxine treatment of rats increased H2O2 generation. Hypothyroid conditions obtained by treatment with propylthiouracil or thyroidectomy caused a decrease in H2O2 generation and changes in dehydrogenase activities similar to those with heat exposure. Treatment of heat-exposed or thyroidectomized rats with thyroxine stimulated H2O2 generation by a mechanism apparently involving fresh protein synthesis. The results indicate that H2O2 generation in mitochondria of heat-exposed animals is determined by thyroid status.

Ce1-xRuxO2-delta (x=0.05, 0.10): A New High Oxygen Storage Material and Pt, Pd-Free Three-Way Catalyst

Nanocrystalline Ce1-xRuxO2-delta (x = 0.05 and 0.10) of 8-10 nm sizes have been synthesized by hydrothermal method using melamine as complexing agent. Compounds have been characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and energy-dispersive X-ray analysis (EDX) and their structures have been refined by the Rietveld method.The compounds crystallize in fluorite structure and the composition is Ce1-xRuxO2-x/2 where Ru is in +4 state and Ce is in mixed-valence (+3, +4) state. Substitution of Ru4+ ion in CeO2 activated the lattice oxygen. Ce1-xRuxO2-x/2 reversibly releases 0.22[O] and 0.42[O] for x = 0.05 and 0.10, respectively, which is higher than the maximumpossible OSC of 0.22 [O] observed for Ce0.50Zr0.50O2. Utilization of Higher OSC of Ce1-xRuxO2-delta (x = 0.05 and 0.10) is also reflected in terms of low-temperature CO oxidation with these catalysts, both in the presence and absence of feed oxygen. The Ru4+ ion acts as an active center for reducing molecules (CO, hydrocarbon ``HC'') and oxide ion vacancy acts as an active center for O-2 and NO, leading to low-temperature NO conversion to N-2. Thus due to Ru4+ ion, Ce1-xRuxO2-delta is not just a high oxygen storage material but also shows high activity toward CO, hydrocarbon ``HC'' oxidation, and NO reduction by CO at low temperature with high N-2 selectivity for three-way catalysis.

A new analytical approach to optimize a generation schedule

Identification of the optimum generation schedule by various methods of coordinating incremental generation costs and incremental transmission losses has been described previously in the literature. This paper presents an analytical approach which reduces the time-consuming iterative procedure into a mere positive-root determination of a third-order polynomial in λ. This approach includes the effect of transmission losses and is suitable for systems with any number of plants. The validity and effectiveness of this method are demonstrated by analysing a sample system.

Singlet and triplet molecular interaction in excimers

A perturbative approach is developed to determine, term by term, the contributions of the various forces to the excimer potentials of the singlet and triplet excimers. The results show that the singlet excimer of naphthalene is more stable than the corresponding triplet excimer primarily due to large contributions of the exciton-resonance and the dispersion energy terms. The variation of the various terms with the conformations of the excimers suggests that the singlet and triplet excimers of naphthalene cannot have identical structure.

Generation of rotationally dominated galaxies by mergers of pressure-supported progenitors

Through the analysis of a set of numerical simulations of major mergers between initially non-rotating, pressure-supported progenitor galaxies with a range of central mass concentrations, we have shown that: (1) it is possible to generate elliptical-like galaxies, with outside one effective radius, as a result of the conversion of orbital- into internal-angular momentum; (2) the outer regions acquire part of the angular momentum first; (3) both the baryonic and the dark matter components of the remnant galaxy acquire part of the angular momentum, the relative fractions depending on the initial concentration of the merging galaxies. For this conversion to occur the initial baryonic component must be sufficiently dense and/or the encounter should take place on an orbit with high angular momentum. Systems with these hybrid properties have recently been observed through a combination of stellar absorption lines and planetary nebulae for kinematic studies of early-type galaxies. Our results are in qualitative agreement with these observations and demonstrate that even mergers composed of non rotating, pressure-supported progenitor galaxies can produce early-type galaxies with significant rotation at large radii.

Recognition And Top-Down Generation Of Beta-Acyclic Database Schemes

Database schemes can be viewed as hypergraphs with individual relation schemes corresponding to the edges of a hypergraph. Under this setting, a new class of "acyclic" database schemes was recently introduced and was shown to have a claim to a number of desirable properties. However, unlike the case of ordinary undirected graphs, there are several unequivalent notions of acyclicity of hypergraphs. Of special interest among these are agr-, beta-, and gamma-, degrees of acyclicity, each characterizing an equivalence class of desirable properties for database schemes, represented as hypergraphs. In this paper, two complementary approaches to designing beta-acyclic database schemes have been presented. For the first part, a new notion called "independent cycle" is introduced. Based on this, a criterion for beta-acyclicity is developed and is shown equivalent to the existing definitions of beta-acyclicity. From this and the concept of the dual of a hypergraph, an efficient algorithm for testing beta-acyclicity is developed. As for the second part, a procedure is evolved for top-down generation of beta-acyclic schemes and its correctness is established. Finally, extensions and applications of ideas are described.

A new method for generation of quasi-periodic structures withn fold axes: Application to five and seven folds

A new geometrical method for generating aperiodic lattices forn-fold non-crystallographic axes is described. The method is based on the self-similarity principle. It makes use of the principles of gnomons to divide the basic triangle of a regular polygon of 2n sides to appropriate isosceles triangles and to generate a minimum set of rhombi required to fill that polygon. The method is applicable to anyn-fold noncrystallographic axis. It is first shown how these regular polygons can be obtained and how these can be used to generate aperiodic structures. In particular, the application of this method to the cases of five-fold and seven-fold axes is discussed. The present method indicates that the recursion rule used by others earlier is a restricted one and that several aperiodic lattices with five fold symmetry could be generated. It is also shown how a limited array of approximately square cells with large dimensions could be detected in a quasi lattice and these are compared with the unit cell dimensions of MnAl6 suggested by Pauling. In addition, the recursion rule for sub-dividing the three basic rhombi of seven-fold structure was obtained and the aperiodic lattice thus generated is also shown.