Physical Sciences and Mathematics Commons^™

New Model For Electron-Impact Ionization Cross Sections Of Molecules, W. Hwang, Y.-K. Kim, M. Eugene Rudd

M. Eugene Rudd Publications

A theoretical model for electron-impact ionization cross sections, which has been developed primarily for atoms and atomic ions, is applied to neutral molecules. The new model combines the binary-encounter theory and the Bethe theory for electron-impact ionization, and uses minimal theoretical data for the ground state of the target molecule, which are readily available from public-domain molecular structure codes such as GAMESS. The theory is called the binary encounter Bethe (BEB) model, and does not, in principle, involve any adjustable parameters. Applications to 19 molecules, including H₂, NO, CH₂, C₆H₆, and SF …

Consequences Of Supergravity With Gauged U(1)R Symmetry, Diego Castano, D. Z. Freedman, C. Manuel

Chemistry and Physics Faculty Articles

The structure of gauged R-supergravity Lagrangians is reviewed, and we consider models with a hidden sector plus light fields of the MSSM. A simple potential for the hidden sector is presented which has a global minimum with zero cosmological constant and spontaneously broken SUSY and R-symmetry. The U(1)_R vector multiplet acquires a Planck scale through the Higgs mechanism, and it decouples at low energy. Due to very interesting cancellations, the U(1)_RD-terms also drop out at low energy. Thus no direct effects of the gauging of R-symmetry remain in the low-energy effective Lagrangian, …

C-Axis Oriented (Hg,Ti)-Based Superconducting Films With TC≥125 K, F. Foong, B. Bedard, Q.L. Xu, Sy_Hwang Liou

Sy-Hwang Liou Publications

Thin films with mostly (Hg,Tl) ₁Ba₂Ca₃Cu₂O_{8+ δ} [(Hg,Tl)-1223] phase have been fabricated by radio frequency magnetron sputtering of precursor films and post-annealing method. The doping of a small amount of thallium in the film is helpful to the formation of the three-layer CuO₂ compound. These films have a highly oriented structure with the c-axis perpendicular to the film surface. Resistivity measurements show that the films after annealing at 300 °C for 1 h in O₂ have the superconducting transition temperature of T_c (onset)=133 K and T_c (zero)=127 …

R-By-C Crozzle: An Np-Hard Problem, Michelle Gower, Ralph W. Wilkerson

Computer Science Faculty Research & Creative Works

In an Australian Magazine, a Monetary Prize is Awarded to the Person with the Best Answer to a Word Puzzle Called a Crozzle. the Placement of Words into a Ten by Fifteen Grid Obtaining the Highest Score is the Best Answer. Various Search Techniques Have Been Employed to Solve This Problem, Yet No One Has Shown Whether There is a Polynomial-Time Algorithm to Find the Best Crozzle. This Paper Creates a Similar Word Puzzle, Called R-By-C Crozzle, by Lifting the Constraint on the Grid Size. R-By-C Crozzle is Not in NP, But There Exists a Polynomial Reduction to It from …

Near Perfect Hash Table For Image Databases, Sanjiv K. Bhatia, Chaman Sabharwal

Computer Science Faculty Research & Creative Works

In image database systems, a perfect hash table can be used to enhance the efficiency and effectiveness of the image retrieval process. In our earlier work, we have proposed heuristic algorithms to compute the minimal perfect hash table from symbolic picture objects. The hash table thus computed cannot be modified easily, limiting its application to fixed databases like the ones on CD-ROMs. In this paper, we propose a new data structure to allow for insertion and deletion in the hash table. The new data structure, the near-perfect hash table, allows a limited number of collisions on some of the hash …

Data Parallel Implementation Of Surface-To-Surface Intersection, Terence M. Burke, Chaman Sabharwal

Computer Science Faculty Research & Creative Works

The sequential surface-to-surface intersection algorithm has been extensively studied in the past decade. With the advent of parallel processing machines, it is desirable to parallelize this algorithm to gain extra computation speed for real time applications. An earlier attempt to parallelize this algorithm was on shared memory parallel computer due to the highly shared model of data structure [Chang 1991). A shared memory machine is not available at every location. Instead, we have implemented it on distributed parallel computer iPSC/860 with 32 processors. The initial development was done using PVM software in heterogeneous environment consisting of Sun workstations and 486's …

The Use Of Hydrochemistry To Identify Potential Processes Operating In The Saddle Mountains Basalt Aquifer And The Use Of The Nitrate-Nitrogen Isotope To Distinguish Between Potential Sources Of Nitrate To The Shallow Alluvial Aquifer In The Lower Umatilla Basin, Oregon, Margot Truini

Dissertations and Theses

Nitrate concentration in excess of national drinking-water standards (10 mg/l) are present in the shallow alluvial aquifer and Saddle Mountains Basalt (SMB) aquifer in the Lower Umatilla Basin, Oregon. To determine sources responsible for elevated nitrate concentrations in the SMB aquifer mass-balance and reaction-path models (NETPATH and PHREEQE) were used to understand observed geochemical trends. Nitrate-nitrogen isotopes were used to distinguish potential nitrate sources in the shallow alluvial aquifer. NETPATH-validated simple water/rock reactions in the SMB aquifers in Irrigon (dissolving glass, precipitating smectite, dissolving or precipitating calcite, and cation exchange) using constituents (calcium, magnesium, sodium and carbon). Diversity of composition …

Studies Of The Importance Of Molecular Structure And Orientation To Adhesive Interactions At Interfaces, Cynthia Kraft, Mark Anderson

Mark R. Anderson

No abstract is currently available.

Gas–Liquid Nucleation In Two-Dimensional Fluids, Xiao Cheng Zeng

Xiao Cheng Zeng Publications

A nonclassical theory of nucleation, based on the density-functional (DF) approach, is developed for the gas–liquid transitions of two-dimensional (2D) Lennard-Jones (LJ) fluids. The methods of Weeks–Chandler–Andersen perturbation theory are used to approximate the LJ potential with a temperature-dependent hard-disk diameter plus an attractive tail. The resulting free energy functional is then used to calculate the free energy barrier to nucleation. We find that the curvature of the 2D nucleus is not important to the rate of nucleation (in contrast to the 3D counterpart). The effect of curvature is readily inferred from the ratio of nucleation rate from classical Becker–Dö̈ring …

Rapidity Gaps Between Jets In Photoproduction At Hera, M. Derrick, D. Krakauer, S. Magill, D. Mikunas, B. Musgrave, J. Repond, R. Stanek, R. L. Talaga, H. Zhang, G. Bari, M. Basile, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, R. Bruni, G. Cara Romeo, G. Castellini, M. Chiarini, L. Cifarelli, F. Cindolo, A. Contin, M. Corradi, I. Gialas, R. Giusti, G. Iacobucci, G. Laurenti, G. Levi, A. Margotti, T. Massam, R. Nania, Margarita C. K. Mattingly

Faculty Publications

Photoproduction events which have two or more jets have been studied in the Wγp range 135 GeV < Wγp < 280 GeV with the ZEUS detector at HERA. A class of events is observed with little hadronic activity between the jets. The jets are separated by pseudorapidity intervals (Δη) of up to four units and have transverse energies greater than 6 GeV. A gap is defined as the absence between the jets of particles with transverse energy greater than 300 MeV. The fraction of events containing a gap is measured as a function of Δη. It decreases exponentially as expected for processes in which colour is exchanged between the jets, up to a value of Δη ∼ 3, then reaches a constant value of about 0.1. The excess above the exponential fall-off can be interpreted as evidence for hard diffractive scattering via a strongly interacting colour singlet object.

Heme Proton Resonance Assignments And Kinetics Study In High-Spin And Mixed-Spin Metmyoglobin Complexes By Chemical Exchange Nmr Spectroscopy, Ying Luo

Dissertations and Theses

NMR studies of paramagnetic hemoproteins have improved significantly our understanding of the structure-function relationship of hemoproteins in general. Up to date most of the studies focus on low-spin ferric systems which are characterized by relatively narrow resonance peaks and concomitant better resolution.

However, characterizing in detail the NMR spectra of high-spin ferric hemoproteins is important since there are several hemoproteins, such as peroxidases, catalases, oxygenases, and some ferricytochromes that contain high-spin iron (III) in their biologically active forms. Yet assigning resonances from heme peripheral protons and/or heme pocket residues in high-spin myoglobins is a daunting undertaking. Only a sparse number …

Flexibility And Performance Of Parallel File Systems, David Kotz, Nils Nieuwejaar

Dartmouth Scholarship

Many scientific applications for high-performance multiprocessors have tremendous I/O requirements. As a result, the I/O system is often the limiting factor of application performance. Several new parallel file systems have been developed in recent years, each promising better performance for some class of parallel applications. As we gain experience with parallel computing, and parallel file systems in particular, it becomes increasingly clear that a single solution does not suit all applications. For example, it appears to be impossible to find a single appropriate interface, caching policy, file structure, or disk management strategy. Furthermore, the proliferation of file-system interfaces and abstractions …

Evolutionary Semigroups And Dichotomy Of Linear Skew-Product Flows On Locally Compact Spaces With Banach Fibers, Y. Latushkin, S. Montgomery-Smith, Timothy W. Randolph

Mathematics and Statistics Faculty Research & Creative Works

We study evolutionary semigroups generated by a strongly continuous semi-cocycle over a locally compact metric space acting on Banach fibers. This setting simultaneously covers evolutionary semigroups arising from non-autonomous abstract Cauchy problems and C0-semigroups, and linear skew-product flows. The spectral mapping theorem for these semigroups is proved. The hyperbolicity of the semigroup is related to the exponential dichotomy of the corresponding linear skew-product flow. To this end a Banach algebra of weighted composition operators is studied. The results are applied in the study of: "roughness" of the dichotomy, dichotomy and solutions of nonhomogeneous equations, Green's function for a linear skew-product …

Main Sequence Masses And Radii From Gravitational Redshifts, Ted Von Hippel

Publications

Modern instrumentation makes it possible to measure the mass to radius ratio for main sequence stars in open clusters from gravitational redshifts. For stars where independent information is available for either the mass or the radius, this application of general relativity directly determines the other quantity. Applicable examples are: 1) measuring the radii of solar metallicity main sequence stars for which the mass - luminosity relation is well known, 2) measuring the radii for stars where model atmospheres can be used to determine the surface gravity (the mass to radius squared ratio), 3) refining the mass - radius relation for …

Lake Whatcom Monitoring Project 1994/1995 Report, Robin A. Matthews, Michael Hilles, Geoffrey B. Matthews

Lake Whatcom Annual Reports

This report is part of an on-going series of annual reports and special project reports that document the Lake Whatcom monitoring program.

This work is conducted by the Institute for Watershed Studies and other departments at Western Washington University. The major objective of this program is to provide long-term baseline water quality monitoring in Lake Whatcom and selected tributaries. Each section contains brief explanations about the water quality data, along with discussions of patterns observed in Lake Whatcom.

Multifragment Production In Au+Au At 35 Mev/U, M. D'Agostino, P. F. Mastinu, P. M. Milazzo, M. Bruno, D. R. Bowman, P. Buttazzo, L. Celano, N. Colonna, J. D. Dinius, A. Ferrero, M. L. Fiandri, C. K. Gelbke, T. Glasmacher, F. Gramegna, D. O. Handzy, D. Horn, W. C. Hsi, M. Huang, I. Iori, G. J. Kunde, M. A. Lisa, W. G. Lynch, L. Manduci, G. V. Margagliotti, C. P. Montoya, A. Moroni, Graham F. Peaslee, F. Petruzzelli, L. Phair, R. Rui, C. Schwarz, M. B. Tsang, G. Vannini, C. Williams

Faculty Publications

Multifragment disintegration has been measured with a high efficiency detection system for the reaction Au + Au at E/A = 35 MeV. From the event shape analysis and the comparison with the predictions of a many-body trajectories calculation the data, for central collisions, are compatible with a fast emission from a unique fragment source.

Evidence Favoring Molybdenum−Carbon Bond Formation In Xanthine Oxidase Action: 17O- And 13C-Endor And Kinetic Studies, Barry D. Howes, Robert C. Bray, Raymond L. Richards, Nigel A. Turner, Brian Bennett, David J. Lowe

Physics Faculty Research and Publications

The reaction mechanism of the molybdoenzyme xanthine oxidase has been further investigated by ¹³C and ¹⁷O ENDOR of molybdenum(V) species and by kinetic studies of exchange of oxygen isotopes. Three EPR signal-giving species were studied:  (i) Very Rapid, a transient intermediate in substrate turnover, (ii) Inhibited, the product of an inhibitory side reaction with aldehyde substrates, and (iii) Alloxanthine, a species formed by reaction of reduced enzyme with the inhibitor, alloxanthine. The Very Rapid signal was developed either with [8-¹³C]xanthine or with 2-oxo-6-methylpurine using enzyme equilibrated with [¹⁷O]H₂O. The Inhibited signal was …

A Trust For Whom?: Managing Colorado's 3 Million Acres Of State Land, John M. Evans, Reeves Brown, Mark A. E. Burget, University Of Colorado Boulder. Natural Resources Law Center

A Trust for Whom?: Managing Colorado's 3 Million Acres of State Land: A Critique of the Constitutional Amendment (February 5)

14 pages.

Includes biographical information for John M. Evans, Reeves Brown, and Mark A. E. Burget.

State Land Board Commissioner Maxine Stewart was also a speaker for this program, but did not submit any written materials.

Contents:

A trust for whom? managing Colorado's 3 million acres of state land : a critique of the constitutional amendment / prepared by John Evans -- A cattlemen's [sic] perspective of state land management / presented by Reeves Brown -- Remarks outline / Mark A. E. Burget

Program was presented on Monday, February 5, 1996 at the offices of Holland & Hart in Denver, …

Paleolimnological Records Of Climatic Change In North America, Sherilyn C. Fritz

Department of Earth and Atmospheric Sciences: Faculty Publications

Lacustrine fossil records provide long time series of data on limnological and climatic conditions; these data are useful for establishing natural patterns of climate variability and for generating testable hypotheses about atmospheric circulation and climate-ecosystem linkages. Shoreline features can indicate past lake-level fluctuations that may reflect changes in moisture balance, but often these records are discontinuous and are evidence of only extreme conditions. The organisms, geochemistry, and sedimentology of lake sediments may provide a more continuous sequence of direct and indirect lake-climate interactions in the past. The most clearly interpretable paleolimnnological records of climatic change are those that use several …

Effects Of Water Stress On Soybean Productivity In Central India, Ajay K. Srivastava, Diwakar Naidu, A. S. R. A. S. Sastri, J. S. Urkurkar, B. Das Gupta

Drought Network News (1994-2001)

In the Chhattisgarh plains in the agroclimatic region of central India (Figure 1), farms may be characterized by one of the following: unbunded lathyritic soils, bunded rice fields (rainfed), bunded rice fields (irrigated), unbunded black soils, or rice bunds. Under these five farming situations, different crop sequences have been in vogue. New crops and crop sequences are recommended by the Agricultural University from time to time based on experimental results.

In the unbunded black soils, farmers usually plant small millets and pigeon pea. However, based on experimental results, the University has recommended soybean followed by chickpea crop sequence under rainfed …

Water Current, Volume 28, No. 1, February 1996

Water Current Newsletter

Teachers Downlink Water Lessons
From the Director: Missouri, Platte Rivers Focus of Spring Events
Two Best Management Practices May Be More Practical and Effective Than a Current Label Requirement
Zhang Stretches Potential of Tiny Organisms
Nebraska Water News
Kamble Receives National Award
Conference Flier Mailed to Readers
Program Pays to Enroll Pivot Corners for Habitat
Pesticides Plentiful in Gardening, Lawn Care
Nebraska Field Days Influence Participants
WEF Announces Speciality Conference
Research, Teaching Intersect as Student Design Sampler

An Existence Result For Linear Partial Differential Equations With C∞ Coefficients In An Algebra Of Generalized Functions, Todor D. Todorov

Mathematics

We prove the existence of solutions for essentially all linear partial differential equations with C^∞-coefficients in an algebra of generalized functions, defined in the paper. In particular, we show that H. Lewy’s equation has solutions whenever its right-hand side is a classical C^∞-function.

Drought Preparedness And Management Training Seminar Conducted For West Africa

Drought Network News (1994-2001)

All of the World Meteorological Organization (WMO) member countries of western Africa were represented at a seminar conducted in Banjul, The Gambia, 4–9 September 1995. The Training Seminar on Drought Preparedness and Management for Western Africa was conducted to improve awareness of drought and appropriate mitigation and preparedness technologies to reduce impacts. The seminar was organized by WMO and sponsored by WMO and the UN Sudano-Sahelian Office.

Century-Scale Paleoclimatic Reconstruction From Moon Lake, A Closed-Basin Lake In The Northern Great Plains, Kathleen R. Laird, Sherilyn C. Fritz, Eric C. Grimm, Pietra G. Mueller

Department of Earth and Atmospheric Sciences: Faculty Publications

Estimates of past lake-water salinity from fossil diatom assemblages were used to infer past climatic conditions at Moon Lake, a climatically sensitive site in the northern Great Plains. A good correspondence between diatom-inferred salinity and historical records of mean annual precipitation minus evapotranspiration (P - ET) strongly suggests that the sedimentary record from Moon Lake can be used to reconstruct past climatic conditions. Century-scale analysis of the Holocene diatom record indicates four major hydrological periods: an early Holocene transition from an open freshwater system to a closed saline system by 7300 B.P., which corresponds with a transition from spruce forest …

Search For Gamma-Ray Emission From The Lagrangian Points Of Psr 1957+20, R Buccheri, V. Salamone, K Bennett, M Busetta, L Kuiper, W Hermsen, Mark L. Mcconnell, R Much, James M. Ryan, H Steinle, V. Schonfelder

Physics & Astronomy

Compton Gamma Ray Observatory data of the COMPTEL and EGRET telescopes from 3 viewing periods have been used to search for gamma-ray emission from the Lagrangian points L_4_ and L_5_ of the binary system including the eclipsing pulsar PSR1957+20. The result was negative and the upper limits derived remain significantly below detections reported earlier.

Heat-Capacity And Magnetic Measurements On The Y(Ni2-XCoX)B2C System, C. C. Hoellwarth, P. Klavins, R. N. Shelton

Physics

We have performed field-and temperature-dependent magnetization, resistivity, and heat-capacity measurements on polycrystalline samples of the Y(Ni_2-xCo_x)B₂C system with 0.0≤x≤0.4. Values of T_c ,x₀,H_c2,Θ_D,λ and N(E_d) were determined for various samples. We observe that Θ_D increases with x, while all the other parameters decrease with x. The T_c vs x data can be described using the BCS theory and the measured values of N(E_f)and Θ_D. The results suggest that the decrease in T_c is due to the decrease in …

Low Energy Electron Scattering From Ch3Cl, X. Shi, V.K. Chan, Gordon A. Gallup, Paul Burrow

Paul Burrow Publications

Differential cross section measurements for the elastic scattering of electrons from CH₃Cl at energies from 0.5 to 9.5 eV are reported for scattering angles of 30° and 100°. The angular scattering dependence is determined at selected energies over this range. At energies below 1.0 eV, the cross sections are in excellent agreement with calculations using the Born dipole approximation. At large angles and higher energies, the scattering is dominated by a ²A₁ temporary negative ion state near 3.5 eV. Energy loss data at 3.5, 5.0, and 8.5 eV are reported and the relative contributions of various …

Fast Compression Of Transportable Tcl Scripts, Robert S. Gray

Computer Science Technical Reports

An information agent is charged with the task of searching a collection of electronic resources for information that is relevant to the user's current needs. These resources are often distributed across a network and can contain tremendous quantities of data. One of the paradigms that has been suggested for allowing efficient access to such resources is transportable agents -- the agent is sent to the machine that maintains the information resource; the agent executes on this remote machine and then returns its results to the local machine. We have implemented a transportable agent system that uses the Tool Command Language …

Graphics For Macromolecular Crystallography And Electron Microscopy, Ioana Maria Martin, Dan C. Marinescu

Department of Computer Science Technical Reports

No abstract provided.

Bond- A Parallel Virtual Environment, Mihai G. Sirbu, Dan C. Marinescu

Department of Computer Science Technical Reports

No abstract provided.