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Utah State University

1992

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Articles 61 - 70 of 70

Full-Text Articles in Physical Sciences and Mathematics

Calculation Of Barriers To Proton Transfer Using Multiconfiguration Self‐Consistent‐Field Methods. I. Effects Of Localization, K. Luth, Steve Scheiner Jan 1992

Calculation Of Barriers To Proton Transfer Using Multiconfiguration Self‐Consistent‐Field Methods. I. Effects Of Localization, K. Luth, Steve Scheiner

Chemistry and Biochemistry Faculty Publications

The usefulness of multiconfiguration self‐consistent‐field (MCSCF) calculations in computing correlated proton transfer potentials is investigated for the systems HF2−, H7N2+, H3O2−, and H5O2+. In deciding whether to include particular molecular orbitals, it is important to consider the balance of electron density between the donor and acceptor groups and the interactions that are incorporated in the orbitals. Only orbitals which have the proper symmetry to interact with the transferring hydrogen need be included in the MCSCF active space. Reasonable transfer barriers are obtained …

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Proton–Donor Properties Of Water And Ammonia In Van Der Waals Complexes With Rare‐Gas Atoms. Kr–H2o And Kr–Nh3, G. Chalasinski, M. M. Szczesniak, Steve Scheiner Jan 1992

Proton–Donor Properties Of Water And Ammonia In Van Der Waals Complexes With Rare‐Gas Atoms. Kr–H2o And Kr–Nh3, G. Chalasinski, M. M. Szczesniak, Steve Scheiner

Chemistry and Biochemistry Faculty Publications

The perturbation theory of intermolecular forces in conjunction with the supermolecular Møller–Plesset perturbation theory is applied to the analysis of the potential‐energy surfaces of Kr–H2O and Kr–NH3 complexes. The valleylike minimum region on the potential‐energy surface of Kr–H2O ranges from the coplanar geometry with the C2 axis of H2O nearly perpendicular to the O–Kr axis (T structure) to the H‐bond structure in which Kr faces the H atom of H2O. Compared to the previously studied Ar–H2O [J. Chem. Phys. 94, 2807 (1991)] the minimum has more …

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Solar Cycle Dependence Of Spacecraft Charging In Low Earth Orbit, T. B. Frooninckx, Jan Josef Sojka Jan 1992

Solar Cycle Dependence Of Spacecraft Charging In Low Earth Orbit, T. B. Frooninckx, Jan Josef Sojka

All Physics Faculty Publications

Recent experimental evidence has shown that Defense Meteorological Satellite Program (DMSP) polar orbiting spacecraft at 840 km can develop electric potentials as severe as −1430 V while at high magnetic latitudes. To explore this charging region, an analysis of DMSP F6, F7, F8, and F9 satellite precipitating particle and ambient plasma measurements taken during periods of high, medium, and low solar flux is performed. One hundred eighty-four charging events ranging from −46 to −1430 V are identified, and an extreme solar cycle dependence is found as charging is most frequent and severe during solar minimum. Satellite measurements and time-dependent ionospheric …

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Covariant Phase Space Formulation Of Parametrized Field Theories, Charles G. Torre Jan 1992

Covariant Phase Space Formulation Of Parametrized Field Theories, Charles G. Torre

All Physics Faculty Publications

Parametrized field theories, which are generally covariant versions of ordinary field theories, are studied from the point of view of the covariant phase space: the space of solutions of the field equations equipped with a canonical (pre)symplectic structure. Motivated by issues arising in general relativity, we focus on phase space representations of the space‐time diffeomorphism group, construction of observables, and the relationship between the canonical and covariant phase spaces.

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Fragmentation Of Percolation Clusters At The Percolation Threshold, M. F. Gyure, Boyd F. Edwards Jan 1992

Fragmentation Of Percolation Clusters At The Percolation Threshold, M. F. Gyure, Boyd F. Edwards

All Physics Faculty Publications

A scaling theory and simulation results are presented for fragmentation of percolation clusters by random bond dilution. At the percolation threshold, scaling forms describe the average number of fragmenting bonds and the distribution of cluster masses produced by fragmentation. A relationship between the scaling exponents and standard percolation exponents is verified in one dimension, on the Bethe lattice, and for Monte Carlo simulations on a square lattice. These results further describe the structure of percolation clusters and provide kernels relevant to rate equations for fragmentation.

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Is General Relativity An "Already Parametrized" Theory?, Charles G. Torre Jan 1992

Is General Relativity An "Already Parametrized" Theory?, Charles G. Torre

All Physics Faculty Publications

Beginning with the work of Dirac and of Arnowitt, Deser, and Misner in the late 1950s and early 1960s, and then after subsequent development by Kuchař, the canonical dynamical structure of general relativity has often been viewed as that of a parametrized field theory in which the many-fingered spacetime variables are hidden among the geometrodynamical field variables. This paradigm of general relativity as an "already parametrized" theory forms the basis for one of the most satisfactory resolutions of the problems of time and observables in classical and quantum gravity. However, despite decades of effort, no identification of many-fingered spacetime variables …

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Ionospheric Simulation Compared With Dynamics Explorer Observations For November 22, 1981, Jan Josef Sojka, M. D. Bowline, Robert W. Schunk, J. D. Craven, L. A. Frank, J. R. Sharber, J. D. Winningham, L. H. Brace Jan 1992

Ionospheric Simulation Compared With Dynamics Explorer Observations For November 22, 1981, Jan Josef Sojka, M. D. Bowline, Robert W. Schunk, J. D. Craven, L. A. Frank, J. R. Sharber, J. D. Winningham, L. H. Brace

All Physics Faculty Publications

Dynamics Explorer (DE) 2 electric field and particle data have been used to constrain the inputs of a time-dependent ionospheric model (TDIM) for a simulation of the ionosphere on November 22, 1981. The simulated densities have then been critically compared with the DE 2 electron density observations. This comparison uncovers a model-data disagreement in the morning sector trough, generally good agreement of the background density in the polar cap and evening sector trough, and a difficulty in modelling the observed polar F layer patches. From this comparison, the consequences of structure in the electric field and precipitation inputs can be …

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Analysis Of Experiments In Helium Microbeam Mixing, J B. Davis, R E. Benenson, David Peak Jan 1992

Analysis Of Experiments In Helium Microbeam Mixing, J B. Davis, R E. Benenson, David Peak

All Physics Faculty Publications

We have continued to investigate ion-beam mixing in bilay-er targets irradiated by 2-MeV He+ microbeams at room temperature. Although we have previously reported a linear dependence of interface width on dose for Cu/Al targets 1, more extensive results have not supported this conclusion, within statistical uncertainty, it appears that the interface width in Cu/Al (1) is proportional to the square root of dose, at constant dose rate, (2) is larger in Al than in Cu, for the same dose, (3) is proportional to the 1/4 power of dose rate, and (4) is absent at liquid nitrogen temperature. Calculations …

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Su(3) X Su(2) X U(1)Su(3): The Residual Symmetry Of Conformal Gravity, James Thomas Wheeler Jan 1992

Su(3) X Su(2) X U(1)Su(3): The Residual Symmetry Of Conformal Gravity, James Thomas Wheeler

All Physics Faculty Publications

SUe 4) x SU(2) is shown to characterize the possible choices of spacetime metric constructible from the gauge fields of the conformal group. When this symmetry is broken by the choice of metric, exactly the SU(3) x SU(2) x U(l) symmetry of the standard model remains. The conformal group consists of Lorentz transformations, translations, inverse translations and dilations. Treated in the standard way, conformal symmetry fails as a unifying gauge group: dilations make the mass spectrum continuous, and the inverse translational gauge field is auxiliary. The theory reduces back to the Poincare group.

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Soil Nitrogen Dynamics Following Harvesting And Conversion Of Red Alder And Douglas-Fir Stands, H. Van Miegroet, P. S. Homann, D. W. Cole Jan 1992

Soil Nitrogen Dynamics Following Harvesting And Conversion Of Red Alder And Douglas-Fir Stands, H. Van Miegroet, P. S. Homann, D. W. Cole

Watershed Sciences Faculty Publications

Drastic reductions in NO3- leaching have been observed after harvesting of mature red alder (Alnus rubra Bong.) stands. Our objective was to examine whether these reduction were linked to changes in soil N dynamics. Adjacent alder and Douglas fir [Pseudotsuga menziessii (Mirbel.) Franco] stands on young glacial soils (Alderwood; a loamy-skeletal, mixed, mesic, ortstein Aquic Haplorthod) in western Washington were harvested and replanted with either alder or Douglas fir seedlings; reference plots were established in nearby undisturbed stands. Three years after site conversion, when NO3- leaching declined most drastically in the harvested alder plots, net N mineralization and net nitrification …

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