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1997

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Articles 541 - 570 of 2472

Full-Text Articles in Physical Sciences and Mathematics

Spectroscopically Distinct Cobalt(Ii) Sites In Heterodimetallic Forms Of The Aminopeptidase From Aeromonas Proteolytica:  Characterization Of Substrate Binding, Brian Bennett, Richard C. Holz Aug 1997

Spectroscopically Distinct Cobalt(Ii) Sites In Heterodimetallic Forms Of The Aminopeptidase From Aeromonas Proteolytica:  Characterization Of Substrate Binding, Brian Bennett, Richard C. Holz

Physics Faculty Research and Publications

The Co(II)Zn(II)- and Zn(II)Co(II)-substituted derivatives of the aminopeptidase from Aeromonas proteolytica (AAP) were probed by EPR spectroscopy. EPR spectra of the high-spin S = 3/2 Co(II) ions in [CoZn(AAP)] and [ZnCo(AAP)] indicated that each metal binding site provides a spectroscopically distinct signature. For [CoZn(AAP)], subtraction of EPR spectra recorded at pH 7.5 and 10 revealed that two species were present and that the relative contributions to each of the experimental spectra were pH-dependent. The first EPR species, predominant at lower pH values, was simulated as a relatively featureless axial signal with geff values of 2.20, 3.92, and …

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Co J = 3-2 Emission In The Radio Galaxy 53w002 At Z = 2.394, N Z. Scoville, Min S. Yun, R A. Windhorst, W C. Keel, L Armus Aug 1997

Co J = 3-2 Emission In The Radio Galaxy 53w002 At Z = 2.394, N Z. Scoville, Min S. Yun, R A. Windhorst, W C. Keel, L Armus

Min S. Yun

We report a sensitive search for redshifted CO J = 3-2 emission from the weak radio galaxy 53W002 at z = 2.394. Maps at resolutions of 3'' and 235 km s-1 show a significant emission peak within 0farcs5 of the optical and radio continuum peaks. The measured narrowband flux is approximately 10 times the extrapolated centimeter-wavelength nonthermal radio continuum expected at 101.9 GHz and exhibits a spectral profile implying a 540 km s-1 width (FWHM) at a systemic redshift z = 2.394 ± 0.001 for CO (3-2). This emission has a total integrated flux of 1.51 ± 0.2 Jy km …

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Scanning Motions Of An Atomic Force Microscope Tip In Water, Kenichiro Koga, Xiao Cheng Zeng Aug 1997

Scanning Motions Of An Atomic Force Microscope Tip In Water, Kenichiro Koga, Xiao Cheng Zeng

Xiao Cheng Zeng Publications

Integral equation techniques are used to study scanning motions of a single-atom tip of the atomic force microscope (AFM) over a rigid, hydrophobic monolayer substrate in water. The calculated force curve is found to be oscillatory, in agreement with recent AFM experiments, which can lead to multiple scanning trajectories for the tip under a constant load. The unique trajectory along which the system is thermodynamically stable is revealed. This study shows that the tip may take a hopping motion over a defect-free substrate due to layering of water molecules between the tip and substrate.

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Search For The Decays B0 → D (*)+D (*)-, D. M. Asner, Kenneth A. Bloom, Cleo Collaboration Aug 1997

Search For The Decays B0 → D (*)+D (*)-, D. M. Asner, Kenneth A. Bloom, Cleo Collaboration

Kenneth Bloom Publications

Using the CLEO-II data set we have searched for the decays B0 → D(*)+D(*)-. We observe one candidate signal event for the decay B0 → D*+D*- with an expected background of 0.022 ± 0.011 events. This yield corresponds to a branching fraction of B(B0 → D*+D*-) = [5.317-3.7+7.1(stat) ± 1.0(syst)] x 10-4 and an upper limit of B(B0 → D*+D*-) < 2.2 X 10-3 at the 90% C.L. We see no significant excess of signal above …

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39th Rocky Mountain Conference On Analytical Chemistry Aug 1997

39th Rocky Mountain Conference On Analytical Chemistry

Rocky Mountain Conference on Magnetic Resonance

Preliminary program and registration information for the 39th annual meeting of the Rocky Mountain Conference on Analytical Chemistry, co-sponsored by the Colorado Section of the American Chemical Society and the Rocky Mountain Section of the Society for Applied Spectroscopy. Held in Denver, Colorado, August 3-7, 1997.

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Biology Of Shovelnose Sturgeon, Scaphirhynchus Platorynchus, In The Lower Platte River, Nebraska, Robin L. Hofpar Aug 1997

Biology Of Shovelnose Sturgeon, Scaphirhynchus Platorynchus, In The Lower Platte River, Nebraska, Robin L. Hofpar

School of Natural Resources: Dissertations, Theses, and Student Research

No abstract provided.

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Water Current, Volume 29, No. 4, August 1997 Aug 1997

Water Current, Volume 29, No. 4, August 1997

Water Current Newsletter

Fifth Annual Festival of Color Highlights Landscaping, Youth Activities Near Mead
From the Director: Retirement, New Staff Welcomed, USGS Funds Nebraska Proposals
Unicameral Moves Quickly on Changes to Instream Appropriations Process with LB877
Schulze One of Three Extension Staff Honored
Native Plants Help Clean-Up Toxins
Spalding Recognized for EPA Superfund Cleanup Technique
Education and Action Join Forces
Water News Briefs
42nd Annual Midwest Groundwater Conference
Symposium Focused on Water Act and Groundwater
Nineteen Attend Groundwater U
Environment97
AWWA Research RFPs
Ground Water Protection Council Annual Forum in Cleveland, Ohio
National Drought Planning Center Headquarters at UNL

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A Generalized Mahonian Statistic On Absorption Ring Mappings, Don Rawlings Aug 1997

A Generalized Mahonian Statistic On Absorption Ring Mappings, Don Rawlings

Mathematics

Based on a coin-tossing scheme, a generalized Mahonian statistic is defined on absorption ring mappings and applied in obtaining combinatorial interpretations of the coefficient ofqjin the expansion of ∏ki=1 (1+q+q2+…+qmi). In the permutation case, the statistic coincides with one studied by Han that specializes many known Mahonian statistics.

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Ar-40/Ar-39 Evidence For Middle Proterozoic (1300-1500 Ma) Slow Cooling Of The Southern Black Hills, South Dakota, Midcontinent, North America: Implications For Early Proterozoic P-T Evolution And Posttectonic Magmatism, Daniel K. Holm, Peter S. Dahl, Daniel R. Lux Aug 1997

Ar-40/Ar-39 Evidence For Middle Proterozoic (1300-1500 Ma) Slow Cooling Of The Southern Black Hills, South Dakota, Midcontinent, North America: Implications For Early Proterozoic P-T Evolution And Posttectonic Magmatism, Daniel K. Holm, Peter S. Dahl, Daniel R. Lux

Earth Science Faculty Scholarship

Ar-40/Ar-39 total gas and plateau dates from muscovite and biotite in the southern Black Hills, South Dakota, provide evidence for a period of Middle Proterozoic slow cooling. Early Proterozoic (1600-1650 Ma) mica dates were obtained from metasedimentary rocks located in a synformal structure between the Harney Peak and Bear Mountain domes and also south of Bear Mountain. Metamorphic rocks from the dome areas and undeformed samples of the similar to 1710 Ma Harney Peak Granite (HPG) yield Middle Proterozoic mica dates (similar to 1270-1500 Ma). Two samples collected between the synform and Bear Mountain dome yield intermediate total gas mica …

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Glaciochemistry Of Polar Ice Cores: A Review, Michel Legrand, Paul Andrew Mayewski Aug 1997

Glaciochemistry Of Polar Ice Cores: A Review, Michel Legrand, Paul Andrew Mayewski

Earth Science Faculty Scholarship

Human activities have already modified the chemical composition of the natural atmosphere even in very remote regions of the world. The study of chemical parameters stored in solid precipitation and accumulated on polar ice sheets over the last several hundred thousand years provides a unique tool for obtaining information on the composition of the preindustrial atmosphere and its natural variability over the past. This paper deals with the chemistry of polar ice focused on the soluble mineral (Na+, NH4+, K+, Ca++, Mg++, H+, F−, Cl …

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Magneto-Aerotaxis In Marine Coccoid Bacteria, Richard B. Frankel, Dennis A. Bazylinski, Mark S. Johnson, Barry L. Taylor Aug 1997

Magneto-Aerotaxis In Marine Coccoid Bacteria, Richard B. Frankel, Dennis A. Bazylinski, Mark S. Johnson, Barry L. Taylor

Physics

Magnetotactic cocci swim persistently along local magnetic field lines in a preferred direction that corresponds to downward migration along geomagnetic field lines. Recently, high cell concentrations of magnetotactic cocci have been found in the water columns of chemically stratified, marine and brackish habitats, and not always in the sediments, as would be expected for persistent, downward-migrating bacteria. Here we report that cells of a pure culture of a marine magnetotactic coccus, designated strain MC-1, formed microaerophilic bands in capillary tubes and used aerotaxis to migrate to a preferred oxygen concentration in an oxygen gradient. Cells were able to swim in …

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The Probe, Issue 179 - August 1997 Aug 1997

The Probe, Issue 179 - August 1997

The Probe: Newsletter of the National Animal Damage Control Association

Contents:
The Uneasy Conscience of the Animal Rights Movement
Calendar of Upcoming Events
NADCA Officers' Nominations Needed
Berryman Institute Announces Fellows
Reviews of the Video: “Balancing Nature – Trapping in Today’s World”
New Product Available: “Scarecrow” by Contech Deters Mammals, Birds
Garlic Repellent Device for Deer, Rabbits

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Spurious Electrons In Electron Spectrometers And Their Effect On Differential Electron Impact Ionization Cross-Section Measurements, M. Eugene Rudd Aug 1997

Spurious Electrons In Electron Spectrometers And Their Effect On Differential Electron Impact Ionization Cross-Section Measurements, M. Eugene Rudd

M. Eugene Rudd Publications

The effect of the nonideal response characteristics of electrostatic analyzers is described and equations are derived, which allow a calculation of the distortion that this causes in measurements of angular and energy distributions of electrons from atomic collisions, especially in electron impact. Examples are given that show how a contamination as small as 10-5 from spurious electrons generated inside an analyzer can explain the peak seen at zero angle in some angular distribution measurements and the filling in of the minimum in the energy distributions in others.

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Infinite-Dimensional Hamilton-Jacobi-Bellman Equations In Gauss-Sobolev Spaces, Pao-Liu Chow, Jose-Luis Menaldi Aug 1997

Infinite-Dimensional Hamilton-Jacobi-Bellman Equations In Gauss-Sobolev Spaces, Pao-Liu Chow, Jose-Luis Menaldi

Mathematics Faculty Research Publications

We consider the strong solution of a semi linear HJB equation associated with a stochastic optimal control in a Hilbert space H: By strong solution we mean a solution in a L2(μ,H)-Sobolev space setting. Within this framework, the present problem can be treated in a similar fashion to that of a finite-dimensional case. Of independent interest, a related linear problem with unbounded coefficient is studied and an application to the stochastic control of a reaction-diffusion equation will be given.

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Arcsecond Imaging Of Co Emission In The Nucleus Of Arp 220, N Z. Scoville, Min S. Yun, P M. Bryant Aug 1997

Arcsecond Imaging Of Co Emission In The Nucleus Of Arp 220, N Z. Scoville, Min S. Yun, P M. Bryant

Min S. Yun

We report high-resolution (1A) imaging of CO (2È1) and dust continuum emission in the ultraluminous galaxy Arp 220. The CO (1È0) line was also imaged at 2A resolution for comparison. Both data sets recover essentially all of the observed single-dish line emission. Our aperture synthesis maps reveal for the Ðrst time, multiple components in the dense gas: peaks corresponding to each of the double nuclei (separated by 0A.95 at P.A.\101¡) seen in the near infrared and radio continuum and a more extended disklike structure at P.A.\53¡, similar to the dust lane seen in optical images. Approximately two-thirds of the total …

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38. Hiromichi Kawai, Otto Vogl, Takeji Hashimoto Aug 1997

38. Hiromichi Kawai, Otto Vogl, Takeji Hashimoto

Otto Vogl

No abstract provided.

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Performing Out-Of-Core Ffts On Parallel Disk Systems, Thomas H. Cormen, David M. Nicol Aug 1997

Performing Out-Of-Core Ffts On Parallel Disk Systems, Thomas H. Cormen, David M. Nicol

Computer Science Technical Reports

The Fast Fourier Transform (FFT) plays a key role in many areas of computational science and engineering. Although most one-dimensional FFT problems can be solved entirely in main memory, some important classes of applications require out-of-core techniques. For these, use of parallel I/O systems can improve performance considerably. This paper shows how to perform one-dimensional FFTs using a parallel disk system with independent disk accesses. We present both analytical and experimental results for performing out-of-core FFTs in two ways: using traditional virtual memory with demand paging, and using a provably asymptotically optimal algorithm for the Parallel Disk Model (PDM) of …

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Generating, Visualizing And Evaluating High Quality Clusters For Information Organization, Javed Aslam, Katya Pelekhov, Daniela Rus Aug 1997

Generating, Visualizing And Evaluating High Quality Clusters For Information Organization, Javed Aslam, Katya Pelekhov, Daniela Rus

Computer Science Technical Reports

We present and analyze the star clustering algorithm. We discuss an implementation of this algorithm that supports browsing and document retrieval through information organization. We define three parameters for evaluating a clustering algorithm to measure the topic separation and topic aggregation achieved by the algorithm. In the absence of benchmarks, we present a method for randomly generating clustering data. Data from our user study shows evidence that the star algorithm is effective for organizing information.

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Hypersurfaces In R-D And The Variance Of Exit Times For Brownian Motion, Kimberly Kinateder, Patrick Mcdonald Aug 1997

Hypersurfaces In R-D And The Variance Of Exit Times For Brownian Motion, Kimberly Kinateder, Patrick Mcdonald

Mathematics and Statistics Faculty Publications

Using the first exit time for Brownian motion from a smoothly bounded domain in Euclidean space, we define two natural functionals on the space of embedded, compact, oriented, unparametrized hypersurfaces in Euclidean space. We develop explicit formulas for the first variation of each of the functionals and characterize the critical points.

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The Eclipsing Double-Lined Spectroscopic Binary System V505 Persei, Laurence A. Marschall, Robert P. Stefanik, Claud H. Lacy, Guillermo Torres, David B. Williams, Franz Agerer Aug 1997

The Eclipsing Double-Lined Spectroscopic Binary System V505 Persei, Laurence A. Marschall, Robert P. Stefanik, Claud H. Lacy, Guillermo Torres, David B. Williams, Franz Agerer

Physics and Astronomy Faculty Publications

The recently-discovered eclipsing double-lined spectroscopic binary V505 Persei (SAO 23229) consists of two nearly identical F5 main sequence stars in a 4.2 day orbit. We have obtained both spectroscopic and photometric observations of the binary that densely sample the complete cycle of radial velocity and light variations. These observations have been used to determine the elements of the orbit, to determine individual masses of the stars in the system to a precision of better than 1%, and to estimate an age for the system. The derived properties agree well with current stellar structure models and provide fundamental data for tests …

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A Bayesian Nonlinear Inversion Of Seismic Body-Wave Attenuation Factors, Stephen S. Gao Aug 1997

A Bayesian Nonlinear Inversion Of Seismic Body-Wave Attenuation Factors, Stephen S. Gao

Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works

It is a well-known fact that the uncertainties in measuring relative attenuation factors within a local or regional seismic network are usually high, due to noise of different kinds and unrealistic assumptions. Numerical experiments using nine synthetic seismograms, created using t* values ranging from 0.1 to 0.9 sec, reveal that the commonly used spectral ratio method is strongly affected by the selection of data processing parameters such as width of the spectral smoothing window, reference station, and so on. The numerical experiments demonstrate that a Bayesian nonlinear inversion approach that directly matches the spectra is better at finding the correct …

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Parallel 3d Reconstruction Of Spherical Virus Particles From Digitized Images Of Entire Electron Micrographs Using Cartesian Coordinates And Fourier Analysis, Robert E. Lynch, Dan C. Marinescu Aug 1997

Parallel 3d Reconstruction Of Spherical Virus Particles From Digitized Images Of Entire Electron Micrographs Using Cartesian Coordinates And Fourier Analysis, Robert E. Lynch, Dan C. Marinescu

Department of Computer Science Technical Reports

No abstract provided.

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Magnetism In One Dimension: Fe On Cu(111), J. Shen, Ralph Skomski, M. Klaua, H. Jenniches, S. Sundar Manoharan, J. Kirschner Aug 1997

Magnetism In One Dimension: Fe On Cu(111), J. Shen, Ralph Skomski, M. Klaua, H. Jenniches, S. Sundar Manoharan, J. Kirschner

Ralph Skomski Publications

The magnetism and the morphology of one-dimensional Fe stripes on a Cu(111) vicinal surface with perpendicular magnetization are investigated. Scanning tunneling microscopy shows that the Fe stripes have nanometer width and are aligned in parallel along the [011] direction. From the magnetization curves it is inferred that the stripes exhibit a ferromagnetic behavior well below the nominal thickness of one monolayer. In contrast to two-dimensional films, the magnetization of the stripes is not only temperature but also time dependent. The dynamics of the stripes have been described by a micromagnetic Ising model with Glauber dynamics, yielding an effective anisotropy constant …

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Seasonal Adjustment Of Naira Exchange Rate Statistics 1970-1995, O M. Akinuli Aug 1997

Seasonal Adjustment Of Naira Exchange Rate Statistics 1970-1995, O M. Akinuli

CBN Occasional Papers

This paper uses a current statistical approach to examine and adjust the seasonalities in the Naira exchange rate statistics, vis-a-vis the U.S. Dollar and the pound sterling for a period of twenty-five (25) years. Such study is necessary as it helps to understand the behavioural pattern of a trend in an attempt to predict the future. An investigation like this also helps to expose both the short and long run tendencies of a series which may require urgent or new policy measures to be taken sooner than expected. This paper reviews the regimes of exchange rate under the period, the …

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Quasi-Steady Monopole And Tripole Attractors In Relaxing Vortices, Louis F. Rossi, Joseph F. Lingevitch, Andrew J. Bernoff Aug 1997

Quasi-Steady Monopole And Tripole Attractors In Relaxing Vortices, Louis F. Rossi, Joseph F. Lingevitch, Andrew J. Bernoff

All HMC Faculty Publications and Research

Using fully nonlinear simulations of the two-dimensional Navier–Stokes equations at large Reynolds number (Re), we bracket a threshold amplitude above which a perturbed Gaussian monopole will relax to a quasi-steady, rotating tripole, and below which will relax to an axisymmetric monopole. The resulting quasi-steady structures are robust to small perturbations. We propose a means of measuring the decay rate of disturbances to asymptotic vortical structures wherein streamlines and lines of constant vorticity correspond in some rotating or translating frame. These experiments support the hypothesis that small or moderate deviations from asymptotic structures decay through inviscid and viscous mixing.

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Simulation Of A Microdosimetry Problem: Behavior Of A Pseudorandom Series At A Low Probability, P. Meyer, J. E. Groetz, Robert Katz, M. Fromm, A. Chambaudet Aug 1997

Simulation Of A Microdosimetry Problem: Behavior Of A Pseudorandom Series At A Low Probability, P. Meyer, J. E. Groetz, Robert Katz, M. Fromm, A. Chambaudet

Robert Katz Publications

The carcinogenic effects for low dose irradiations are not very well known. Estimations usually are made based on the effects observed at high doses that are then extrapolated to low doses. To estimate low dose effects, the ICRP (International Commission on Radiological Protection) uses a linear extrapolation matched with a dose-rate reduction factor equal to two. This proportionality of the effect and dose, even for the lowest doses and dose-rates, leads to two assumptions which must be questioned :
1. the efficiency of DNA repair in cells does not vary with the dose and the dose-rate,
2. when one single …

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Time-Efficient Maze Routing Algorithms On Reconfigurable Mesh Architectures, Fikret Ercal, H. C. Lee Aug 1997

Time-Efficient Maze Routing Algorithms On Reconfigurable Mesh Architectures, Fikret Ercal, H. C. Lee

Computer Science Faculty Research & Creative Works

The routing problem is one of the most widely studied problems in VLSI design. Maze-routing algorithms are used in VLSI routing and robot path planning. Efficiency of the parallel maze routing algorithms which were mostly based on C. Y. Lee's algorithm8is poor. In this paper, we propose time-efficient algorithms to solve the maze-routing problem on a reconfigurable mesh architecture. The constant-time algorithms presented include: (i) testing the existence of specific types of paths between two terminals, and (ii) finding an absolute shortest path (ASP) and a shortest duplex-path (SDP). In addition, a fast algorithm to find the single shortest path …

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Optical Components For Wdm Lightwave Networks, Michael S. Borella, Jason P. Jue, Dhritiman Banerjee, Byrav Ramamurthy, Biswanath Mukherjee Aug 1997

Optical Components For Wdm Lightwave Networks, Michael S. Borella, Jason P. Jue, Dhritiman Banerjee, Byrav Ramamurthy, Biswanath Mukherjee

School of Computing: Faculty Publications

Recently, there has been growing interest in developing optical fiber networks to support the increasing bandwidth demands of multimedia applications, such as video conferencing and World Wide Web browsing. One technique for accessing the huge bandwidth available in an optical fiber is wavelength-division multiplexing (WDM). Under WDM, the optical fiber bandwidth is divided into a number of nonoverlapping wavelength bands, each of which may be accessed at peak electronic rates by an end user. By utilizing WDM in optical networks, we can achieve link capacities on the order of 50 THz. The success of WDM networks depends heavily on the …

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White Dwarfs In Globular Clusters: Hubble Space Telescope Observations Of M4, Harvey B. Richer, Matt A. Wood Aug 1997

White Dwarfs In Globular Clusters: Hubble Space Telescope Observations Of M4, Harvey B. Richer, Matt A. Wood

Aerospace, Physics, and Space Science Faculty Publications

Using WFPC2 on the Hubble Space Telescope, we have isolated a sample of 258 white dwarfs (WDs) in the Galactic globular cluster M4. Fields at three radial distances from the cluster center were observed, and sizable WD populations were found in all three. The location of these WDs in the color-magnitude diagram, their mean mass of 0.51(±0.03) M⊙, and their luminosity function confirm basic tenets of stellar evolution theory and support the results from current WD cooling theory. The WDs are used to extend the cluster main-sequence mass function upward to stars that have already completed their nuclear evolution. The …

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Lyapunov Exponents, Singularities, And A Riddling Bifurcation, Lora Billings, James H. Curry, Eric Phipps Aug 1997

Lyapunov Exponents, Singularities, And A Riddling Bifurcation, Lora Billings, James H. Curry, Eric Phipps

Department of Mathematics Facuty Scholarship and Creative Works

There are few examples in dynamical systems theory which lend themselves to exact computations of macroscopic variables of interest. One such variable is the Lyapunov exponent which measures the average attraction of an invariant set. This article presents .a family of noninvertible transformations of the plane for which such computations are possible. This model sheds additional insight into the notion of what it can mean for an attracting invariant set to have a riddled basin of attraction.

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