Physical Sciences and Mathematics Commons^™

Low-Energy Electrons And Their Dynamical Correlation With Recoil Ions For Single Ionization Of Helium By Fast, Heavy-Ion Impact, R. Moshammer, J. Ullrich, M. Unverzagt, W. Schmidt, P. Jardin, Ronald E. Olson, R. Mann, R. Dörner, V. Mergel, U. Buck, H. Schmidt-Böcking

Physics Faculty Research & Creative Works

Helium single ionization by 3.6 me V/u Ni24+ impact was explored in a kinematically complete experiment by combining a high-resolution recoil-ion momentum spectrometer with a novel 4 low-energy electron analyzer. More than 90% of the "soft electrons" (Ee50 eV) are ejected in the forward direction in agreement with classical-trajectory Monte Carlo predictions. The electron longitudinal momentum is not balanced by the longitudinal momentum change of the projectile but mainly by the backwards recoiling He1+ ion. Energy losses of the 0.2 GeV projectiles as small as EPEP=3.4x10-7 are observable. © 1994 The American Physical Society.

Clean Ultrahigh Vacuum System With Single-Structure Diffusion Pumps, Timothy J. Gay, M. C. Fritts, E. R. Mell, M. T. Sieger

Physics Faculty Research & Creative Works

A practical example of the use of single-structure diffusion pumping groups in an experiment requiring hydrocarbon-free, ultrahigh vacuum is presented. With the use of proper vacuum procedures and careful foreline design and operation, but with no exotic hardware or liquid nitrogen, we have demonstrated that such a pump could provide vacuum that was "clean," i.e., which had no residual pump-oil contamination to a partial pressure below 10 -8 mbar. Their use is thus compatible, at least in peripheral vacuum chambers, with standard "UHV-surface science" processes. We discuss our vacuum system in detail, and present a review of the literature on …

Superelastic And Inelastic He2++He State-Selective Electron Capture, V. D. Irby, Timothy James Gay, John T. Park, S. W. Bross, A. D. Gaus

Physics Faculty Research & Creative Works

Experimental studies have been made of super elastic and inelastic collision processes involved in the state-selective single-electron capture reaction He2+3+He (1 1S)3He+(n)+He+(n), where n and n are the final principal quantum-number states of the collision products. Total cross sections have been measured at projectile energies of 15, 30, and 45 keV/u, by examining the energy loss-gain of the fast He+3 product ions, for the super elastic n=n=1 channel, and for the sum of the inelastic n=2, n=1 and n=1, n=2 states. Measurements are also presented for Ne and Ar targets. © 1994 The American Physical Society.

Electron-Electron Interaction In Projectile Ionization Investigated By High Resolution Recoil Ion Momentum Spectroscopy, R. Dörner, V. Mergel, R. Ali, U. Buck, C. L. Cocke, K. Froschauer, O. Jagutzki, S. Lencinas, W. E. Meyerhof, S. Nüttgens, Ronald E. Olson, H. Schmidt-Böcking, L. Spielberger, K. Tökesi, J. Ullrich

Physics Faculty Research & Creative Works

Contributions of the electron-electron and the nuclear-electron interactions to projectile electron loss in He+ on helium collisions have been clearly separated kinematically for the first time by measuring the longitudinal and transverse momenta of the recoiling target ion with precision of better than ±0.15 a.u. The longitudinal and transverse momentum distributions are in general agreement with two-center n-body classical trajectory Monte Carlo calculations. © 1994 The American Physical Society.

Anisotropy Effects In Electron Capture By O6+ From Aligned Na*(3p), S. Schippers, A. R. Schlatmann, W. P. Wiersema, R. Hoekstra, R. Morgenstern, Ronald E. Olson, J. Pascale

Physics Faculty Research & Creative Works

We report results of one electron capture by highly charged ions colliding with laser excited aligned Na*(3p). The O vi(10→8) photon emission cross section after electron capture by the O6+ projectile is measured in the collision energy range 2-8 keV/amu. Effects of the Na*(3p) orbital alignment on the) O vi(10→8) emission are observed and found to be "reversed" as compared to the He2+→Na*(3p) collision system. Classical trajectory Monte Carlo calculations agree with the measured data and indicate that capture to states with n>10, contributing to the O vi(10→8) emission via cascades, plays a crucial role in the alignment cross …

Dilaton Black Holes With Electric Charge, Malik Rakhmanov

Physics and Astronomy Faculty Publications and Presentations

New static spherically symmetric solutions of the Einstein-Maxwell gravity with the dilaton field are found. The solutions correspond to black holes and naked singularities. In addition to mass and electric charge these solutions are labeled by a new parameter, the dilaton charge of the black hole. Depending on the values of electric and dilaton charges there are different types of solutions. The solutions exhibit a new type of a symmetry. Namely one solution transforms into another when the mass and the dilaton charge are interchanged. We also found that there is a finite interval of values of electric charge for …

A Greedy Hypercube-Labeling Algorithm, D. Bhagavathi, C. E. Grosch, S. Olariu

Computer Science Faculty Publications

Due to its attractive topological properties, the hypercube multiprocessor has emerged as one of the architectures of choice when it comes to implementing a large number of computational problems. In many such applications, Gray-code labelings of the hypercube are a crucial prerequisite for obtaining efficient algorithms. We propose a greedy algorithm that, given an n-dimensional hypercube H with N=2² nodes, returns a Gray-code labeling of H, that is, a labeling of the nodes with binary strings of length n such that two nodes are neighbors in the hypercube if, and only if, their labels differ in exactly …

The World Wide Web And Technology Transfer At Nasa Langley Research Center, Michael L. Nelson, David J. Bianco

Computer Science Faculty Publications

NASA Langley Research Center (LaRC) began using the World Wide Web (WWW) in the summer of 1993, becoming the first NASA installation to provide a Center-wide home page. This coincided with a reorganization of LaRC to provide a more concentrated focus on technology transfer to both aerospace and non-aerospace industry. Use of the WWW and NCSA Mosaic not only provides automated information dissemination, but also allows for the implementation, evolution and integration of many technology transfer applications. This paper describes several of these innovative applications, including the on-line presentation of the entire Technology Opportunities Showcase (TOPS), an industrial partnering showcase …

World Wide Web Implementation Of The Langley Technical Report Server, Michael L. Nelson, Gretchen L. Gottlich, David J. Bianco

Computer Science Faculty Publications

On January 14, 1993, NASA Langley Research Center (LaRC) made approximately 130 formal, 'unclassified, unlimited' technical reports available via the anonymous FTP Langley Technical Report Server (LTRS). LaRC was the first organization to provide a significant number of aerospace technical reports for open electronic dissemination. LTRS has been successful in its first 18 months of operation, with over 11,000 reports distributed and has helped lay the foundation for electronic document distribution for NASA. The availability of World Wide Web (WWW) technology has revolutionized the Internet-based information community. This paper describes the transition of LTRS from a centralized FTP site to …

A Strategy For Electronic Dissemination Of Nasa Langley Technical Publications, Donna G. Roper, Mary K. Mccaskill, Scott D. Holland, Joanne L. Walsh, Michael L. Nelson, Susan L. Adkins, Manjula Y. Ambur, Bryan A. Campbell

Computer Science Faculty Publications

To demonstrate NASA Langley Research Center's relevance and to transfer technology to external customers in a timely and efficient manner, Langley has formed a working group to study and recommend a course of action for the electronic dissemination of technical reports (EDTR). The working group identified electronic report requirements (e.g., accessibility, file format, search requirements) of customers in U.S. industry through numerous site visits and personal contacts. Internal surveys were also used to determine commonalities in document preparation methods. From these surveys, a set of requirements for an electronic dissemination system was developed. Two candidate systems were identified and evaluated …

Invariant Manifolds Of A Toy Climate Model, Michael Toner

Mathematics & Statistics Theses & Dissertations

According to astronomical theory, ice ages are caused by variations in the Earth's orbit. However, ice core data shows strong fluctuations in ice volume at a low frequency not significantly present in orbital variations. To understand how this might occur, the dynamics of a two dimensional nonlinear differential equation representing glacier/temperature interaction of an idealized climate was studied. Self sustained oscillation of the autonomous equation was used to model the internal mechanisms that could produce these fluctuations. Periodic parametric modulation of a damped internal oscillation was used to model periodic climate response at double the external modulation period. Both phenomena …

Invariance Properties Of Statistical Tests For Dependent Observations, Akhil K. Vaish

Mathematics & Statistics Theses & Dissertations

In this dissertation we assume that the observations are from normal populations but are correlated and study the problem of characterizing the class of covariance structures such that the distributions of the popular test statistics remain invariant, that is, they remain the same except for a constant factor. We first obtain some simple extensions and variations of the well known Cauchy-Schwarz inequality. Incidentally, several inequalities that are useful in the detection of outliers can be deduced from our results.

Our main result is a characterization of the class of all nonnegative definite solutions W to the matrix equation AWA = …

Isostatic Rebound In The Lake Agassiz Basin Since The Late Wisconsinan, Eric C. Brevik

Theses and Dissertations

This study addressed three main questions: I) how thick was the ice that covered the southern Lake Agassiz basin during the Wisconsinan and how much that ice depressed the crust, 2) how much rebound has occurred since deglaciation and whether or not rebound is complete, and 3) what were the effects of this rebound on the basin.

The most direct method of measuring rebound in the Lake Agassiz basin is from strandlines left by glacial Lake Agassiz. The oldest complete strandline, the Herman, presumably rebounded, with the northern end rebounding more because the ice was thicker there and had melted …

Multigrid Acceleration Of Time-Dependent Solutions Of Navier-Stokes Equations, Sarafa Oladele Ibraheem

Mechanical & Aerospace Engineering Theses & Dissertations

Recent progress in Computational Fluid Dynamics is encouraging scientists to look at fine details of flow physics of problems in which natural unsteady phenomena have hitherto been neglected. The acceleration methods that have proven very successful in steady state computations can be explored for time dependent computations. In this work, an efficient multigrid methods is developed to solve the time-dependent Euler and Navier-Stokes equations. The Beam-Warming ADI method is used as the base algorithm for time stepping calculations. Application of the developed algorithm proved very efficient in selected steady and unsteady test problems. For instance, the inherent unsteadiness present in …

The Dinoflagellate Flora Of The Late Oligocene - Early Miocene Old Church Formation Mid-Atlantic Coastal Plain, Alan P. Hoffmeister

OES Theses and Dissertations

The Old Church Formation contains the only presently known exposed Oligocene sediments in the North American mid-Atlantic Coastal Plain. Some ambiguity concerning the exact age of the Old Church Formation exists because it may include both Oligocene and Miocene sediments. Two outcrops and four cores containing the Old Church Formation were examined for dinoflagellates to determine the composition of the dinoflagellate flora in the Old Church Formation, the age of the Old Church Formation as indicated by this flora, general depositional environment of the Old Church Formation and correlative relationships of the Old Church Formation with other Coastal Plain units. …

Materials Recovery Facilities In The United States Virgin Islands: A Regional Facilities Location Model Study, Lloyd O. Prince Jr.

Engineering Management & Systems Engineering Theses & Dissertations

Continental municipalities have derived many benefits from the economies of scale associated with a regional approach to facilities location and management planning. Centralized solid waste processing facilities is an example. Island communities, however, surrounded by miles of ocean, are constrained to a fragmented approach to the facilities location solution. This research was conducted to determine if the regional paradigm suggested in the literature is applicable to a set of island communities connected by an ocean transportation infrastructure. A linear programming (LP) model, constraints and data requirements were developed and applied to a network of islands. A series of hypothetical material …

Pitfalls In Designing Substitution Boxes, Jennifer Seberry, Xian-Mo Zhang, Yuliang Zheng

Faculty of Informatics - Papers (Archive)

Two significant recent advances in cryptanalysis, namely the differential attack put forward by Biham and Shamir [3] and the linear attack by Matsui [7, 8] have had devastating impact on data encryption algorithms. An eminent problem that researchers are facing is to design S-boxes or substitution boxes so that an encryption algorithm that employs the S-boxes is immune to the attacks. In this paper we present evidence indicating that there are many pitfalls on the road to achieve the goal. In particular, we show that certain types of S-boxes which are seemly very appealing do not exist. We also show …

Quaternary Seismic Stratigraphy Of The Inner Shelf And Coastal Zone, Southern Delmarva Peninsula, Virginia, Anthony M. Foyle

OES Theses and Dissertations

The Pleistocene stratigraphic record beneath the Virginia inner shelf is largely unknown. On the adjacent lower Atlantic Coastal Plain of southeastern Virginia, the Pleistocene record consists of seven stacked transgressive sequences, while on the southern Delmarva Peninsula, a series of three transgressive to highstand sequences are developed. Reconstruction of the mid-Atlantic basin margin response to high-frequency Quaternary glacioeustasy is limited by this sparse record of late transgressive through early regressive deposition. Knowledge of high-frequency depositional sequence architecture, developed under conditions of low subsidence (to net uplift) and low sediment input, is also incomplete. The Atlantic inner shelf and coastal zone, …

Production And Extraction Of Polarized Electrons From An Optically Pumped Helium Discharge, Raymond James Vandiver

Doctoral Dissertations

"Polarized electron sources are needed to study the spin dependent processes in atomic and molecular systems. This area of physics has enjoyed much success in the past decade due to the development of polarized electron sources of high electron polarization and current. We have investigated the production and extraction of polarized electrons from an optically pumped helium discharge.

We have directly extracted electrons with polarizations between 6% and 7% at currents greater than 200 µA from a helium DC discharge where the helium 2³S₁ metastable atoms are optically pumped to nearly 100% polarization. These high metastable polarizations …

Predation On Juvenile Blue Crabs, Callinectes Sapidus Rathbun, In Lower Chesapeake Bay: Patterns, Predators, And Potential Impacts, Kirt E. Moody

Dissertations, Theses, and Masters Projects

Various investigations of the population dynamics of blue crabs in Chesapeake Bay indicate that predator-induced mortality in the juvenile phase may determine year-class strength. In a tethering study, which spanned three seasons in shallow-water habitats of the lower York River, daily mortality rates of juvenile crabs were measured across three variables: crab size (30-70 mm carapace width), habitat type (seagrass, mud, and sand), and month (May-November). Vulnerability to predation was consistently lower for larger crabs, approaching a size refuge from predation at approximately 90 mm carapace width. Predation was most intense in unvegetated sand habitats, and significantly lower in seagrass …

The Synthesis Of 5-Benzoyl-1,3-Benzendediacids For The Double-Capping Of Beta-Cyclodextrin, Daniel Macdougall Williams

Dissertations, Theses, and Masters Projects

No abstract provided.

Nebraska Mineral Operations Review, 1993, Raymond R. Burchett, Duane A. Eversoll

Conservation and Survey Division

No abstract provided.

Groundwater-Level Changes In Nebraska, 1992, Gregory V. Steele, Perry B. Wigley

Conservation and Survey Division

No abstract provided.

Cass County Test Hole Logs, Raymond R. Burchett, Frank A. Smith

Conservation and Survey Division

No abstract provided.

Clay County Test Hole Logs, Raymond R. Burchett

Conservation and Survey Division

No abstract provided.

Resource News-Summer 1994

Conservation and Survey Division

No abstract provided.

Location Of Registered Irrigation Wells In Nebraska As Of 1994

Conservation and Survey Division

No abstract provided.

Operator Equations And Invariant Subspaces, Valentin Matache

Mathematics Faculty Publications

Banach space operators acting on some fixed space X are considered. If two such operators A and B verify the condition A² = B² and if A has non-trivial hyperinvariant subspaces, then B has nontrivial invariant subspaces. If A and B commute and satisfy a special type of functional equation, and if A is not a scalar multiple of the identity, the author proves that if A has nontrivial invariant subspaces, then so does B.

Winter Diet And Nutritional Condition Of White-Tailed Deer In The Northern Black Hills, South Dakota, Robert G. Osborn

Electronic Theses and Dissertations

Habitat deterioration in the northern Black Hills (NBH) of South Dakota may be responsible for declining white-tailed deer (Odocoileus virginianus) population levels (Griffin et al. 1992). Because of the relationship between habitat and nutrition, a two-year research project was initiated in January 1992 to evaluate the physical and nutritional condition of white-tailed deer inhabiting five NBH winter subranges. Habitat variables were measured at 100 random locations on each study area. Pellet groups were collected throughout each study area at two-week intervals during January, February, and March 1992 and 1993. Five female white-tailed deer were collected from each study area in …

Winter/Spring Population Characteristics Of White-Tailed Deer In An Agricultural/Wetland Complex In Northeastern South Dakota, Brian J. Kernohan

Electronic Theses and Dissertations

Habitat preference, cover characteristics of corn, movements, and sexual segregation patterns of white-tailed deer (Odocoileus virginianus) were evaluated at Sand Lake National Wildlife Refuge (SLNWR) in winter (January - March) and spring (April - June), 1993 and 1994. An average of 20 radio-collared deer were monitored per season, which resulted in 4, 058 relocations. Habitat preference was assessed using 95 and 50% home range contours that were estimated using an adaptive kernel method. Agricultural crops (i.e., corn [Zea mays], row crops other than corn [e.g., soybeans [Glycine max]], small grains [e. g., wheat [Triticum aestivum]], and alfalfa [Medicago sativa]) were …