Physical Sciences and Mathematics Commons^™

Design And Characterization Of A Synthetic Electron-Transfer Protein, Anna Y. Kornilova, James F. Wishart, Wenzhong Xiao, Robin C. Lasey, Anna Fedorova, Yeon-Kyun Shin, Michael Y. Ogawa

Chemistry Faculty Publications

A 30-residue polypeptide [H21(30-mer)] with the sequence Ac-K(IEALEGK)(2)(IEALEHK)-(IEALEGK)G-NH2 was synthesized. The circular dichroism (CD) spectrum of the peptide shows minima at 208 and 222 nm and theta(222)/theta(208) = 1.06, which indicates the formation of a self-assembled coiled-coil when dissolved in aqueous solution. The concentration dependence of the CD data can be fit to an expression that describes a two-state monomer-dimer equilibrium for the apopeptide (K-d = 1.5 +/- 0.4 mu M and theta(max) = -23 800 +/- 130 deg cm(2) dmol(-1)), showing that it has a maximum helicity of 69%. A [MTSL-C21(30-mer)] dimer was also prepared in which MTSL is …

The Narrow-Line Region In The Seyfert 2 Galaxy Ngc 3393, Andrew J. Cooke, J. A. Baldwin, Gary J. Ferland, Hagai Netzer, Andrew S. Wilson

Physics and Astronomy Faculty Publications

The narrow-line region (NLR) of the Seyfert 2 galaxy NGC 3393 is dominated by a symmetric structure which appears as S-shaped arms in Hubble Space Telescope (HST) images. These arms, which occupy the central few arcseconds of the nucleus, border a linear, triple-lobed radio source. We use HST imaging and spectra, ground-based optical images, long-slit spectra, Fabry-Perot imaging spectroscopy, and VLA radio data to perform a detailed investigation of the kinematics and ionization of the line-emitting gas in NGC 3393 and of its relationship with the relativistic gas responsible for the radio emission. The excitation map [O III] …

Release Of No(X) From Sunlight-Irradiated Midlatitude Snow, R E. Honrath, Matthew C. Peterson, M P. Dziobak, Jack E. Dibb, Matthew Arsenault, S A. Green

Earth Sciences

Photochemical production and release of gas-phase NO(x) (NO + NO2) from the natural snowpack at a remote site in northern Michigan were investigated during the Snow Nitrogen and Oxidants in Winter study in January 1999. Snow was collected in an open 34 L chamber, which was then sealed with a transparent Teflon cover and used as an outdoor flow and reaction chamber. Significant increases in NO(x) mixing ratio were observed in synthetic and ambient air pulled through the sunlit chamber. [NO(x)] enhancements were correlated to ultraviolet sunlight intensity, reaching ~300 pptv under partially overcast midday, mid-winter conditions. These findings are …

The Application And Performance Of A Generic Task Routine Decision Making Algorithm To Recipe Selection In Meal Planning, Michelle M. Cox

Theses and Dissertations - UTB/UTPA

A nutritional meal planning system was implemented to test the effectiveness of a previously developed routine decision making algorithm. The combinatorics involved in ordering recipes in all possible combinations to produce variability in a meal plan and provide sufficient nutrition is conceptually intensive. Meal planning involves selection of food to eat to fulfill a person's nutritional and personal preferences. This thesis demonstrates meal planning as a decision making problem and demonstrates the utility of the routine decision making algorithm by solving this problem. Generic Tasks, identified through artificial intelligence research, provides the basis for this algorithm. It uses user preferences …

Studies Of Sulfur Reduction Of Taurine And Taurine-Conjugated Bile Acids By Bile Acid 7Α-Dehydroxylating Bacteria, Jiang Qian

Masters Theses & Specialist Projects

Bile acids are C24 steroids that are derived in the liver from cholesterol and secreted into the intestinal lumen to aid in emulsification of dietary lipids and lipid-soluble vitamins. The indigenous intestinal microflora modify bile acids, producing up to 20 unique bile acid metabolites. The 7α-dehydroxylation of the bile acids is the most physiologically important bile acid biotransformation. All known intestinal bacteria capable of bile acid 7α-dehydroxylation are anaerobic, gram-positive rods of the genera Clostridium and Eubcicterium. Bile acid 7α-dehydroxylating bacteria often contain bile salt hydrolase, which hydrolyzes the peptide bond in taurine-conjugated bile acids to yield a free bile …

Electrical Properties Of Boron-Doped P-Sigec Grown On N(-)-Si Substrate, M. Ahoujja, Y. K. Yeo, R. L. Hengehold, G. S. Pomrenke, David C. Look, J. Huffman

Physics Faculty Publications

Electrical properties of fully strained boron-doped Si_0.90−yGe_0.10C_y/n⁻–Si grown by low pressure chemical vapor deposition have been investigated as a function of carbon content (0.2%–1.5%), using the variable temperature (25–650 K) Hall-effect technique. The results of Hall-effect measurements show that the Si substrate and the SiGeC/Si interfacial layer affect significantly the electrical properties of the SiGeC epitaxial layer. Thus, a three-layer conducting model has been used to extract the carrier concentration and mobility of the SiGeC layer alone. At room temperature, the hole carrier concentration decreases from 6.8×10¹⁷ to 2.4×10 …

Time-Resolved Photoluminescence Lifetime Measurements Of The Gamma(5) And Gamma(6) Free Excitons In Zno, D. C. Reynolds, David C. Look, B. Jogai, J. E. Hoelscher, R. E. Sherriff, M. T. Harris, M. J. Callahan

Physics Faculty Publications

Time-resolved photoluminescence spectroscopy at 2 K was used to measure the radiative recombination lifetime of the allowed (Γ₅) and forbidden (Γ₆) free excitons in ZnO. The measurements were made on a sample containing internal strain, which altered the sample symmetry, and resulted in relaxed selection rules, allowing the Γ₆ exciton to be observed. A radiative recombination lifetime of 259 ps was measured for the Γ₅ exciton and 245 ps for the Γ₆ exciton. The decay of the free excitons was of single-exponential form, and the decay times were obtained using a least-squares fit …

Properties Of Semi‐Insulating Gaas:Fe Grown By Hydride Vapor Phase Epitaxy, E. Rodríguez Messmer, D. Söderström, P. Hult, S. Marcinkevicius, S. Lourdudoss, David C. Look

Physics Faculty Publications

In this paper we analyze GaAs grown by hydride vapor phase epitaxy (HVPE) and doped with four different iron concentrations between and . From temperature dependent current‐voltage measurements we observed the highest resistivity in the lowest doped sample. We also quantified the activation energy. These results together with those of time resolved photoluminescence measurements indicate that in the sample with the lowest Fe concentration, EL2 may be dominant. From the analysis of the time resolved photoluminescence measurements, the intrinsic EL2 concentration and the electron and hole capture cross sections of Fe in GaAs were estimated. © 2000 The Electrochemical Society. …

Photophysical Study Of Linked 1,4,7-Triazacyclonane Cr (Iii) Complexes, Weizhen Tu

Masters Theses

A series of mono and bimetallic Cr(III) complexes based on the 1,4,7- triazacyclonoane(TACN) were prepared. Complexes of the Cr(TACN)X₃ , and Cr₂(DTNE)X₆ demonstrated marked difference of photophysical properties on the nature of X. In cases where X is more easily oxidized, enhanced extinction coefficient in the ⁴A₂ ➔ ²T, absorption and larger quantum yield of emission at 77K were observed in the dimer complexes. Shorter lifetime and enhanced decay rate were also found in the dimer complexes suggests that there might exists weak coupling behavior between the two Cr(III) metal cents in the …

Reducing Mass Degeneracy In Sar By Ms By Stable Isotopic Labeling, Chris Bailey-Kellogg, John J. Kelley Iii, Cliff Stein, Bruce Randall Donald

Dartmouth Scholarship

Mass spectrometry (MS) promises to be an invaluable tool for functional genomics, by supporting low-cost, high-throughput experiments. However, large-scale MS faces the potential problem of mass degeneracy -- indistinguishable masses for multiple biopolymer fragments (e.g. from a limited proteolytic digest). This paper studies the tasks of planning and interpreting MS experiments that use selective isotopic labeling, thereby substantially reducing potential mass degeneracy. Our algorithms support an experimental-computational protocol called Structure-Activity Relation by Mass Spectrometry (SAR by MS), for elucidating the function of protein-DNA and protein-protein complexes. SAR by MS enzymatically cleaves a crosslinked complex and analyzes the resulting mass spectrum …

Two-Level Atom In An Optical Parametric Oscillator: Spectra Of Transmitted And Fluorescent Fields In The Weak Driving Field Limit, James P. Clemens, Perry R. Rice, Pranaw Kumar Rungta, Robert J. Brecha

Physics Faculty Publications

We consider the interaction of a two-level atom inside an optical parametric oscillator. In the weak-driving-field limit, we essentially have an atom-cavity system driven by the occasional pair of correlated photons, or weakly squeezed light. We find that we may have holes, or dips, in the spectrum of the fluorescent and transmitted light. This occurs even in the strong-coupling limit when we find holes in the vacuum-Rabi doublet. Also, spectra with a subnatural linewidth may occur. These effects disappear for larger driving fields, unlike the spectral narrowing obtained in resonance fluorescence in a squeezed vacuum; here it is important that …

H-1 Nuclear Magnetic Resonance Spin-Lattice Relaxation, C-13 Magic-Angle-Spinning Nuclear Magnetic Resonance Spectroscopy, Differential Scanning Calorimetry, And X-Ray Diffraction Of Two Polymorphs Of 2,6-Di-Tert-Butylnaphthalene, Peter A. Beckmann, Kendra S. Burbank, Katharine M. Clemo, Erin N. Slonaker, Kristin Averill, Cecil Dybowski, Joshua S. Figueroa, Alicia Glatfelter, Stephanie Koch, Louise M. Liable-Sands, Arnold L. Rheingold

Physics Faculty Research and Scholarship

Polymorphism, the presence of structurally distinct solid phases of the same chemical species, affords a unique opportunity to evaluate the structural consequences of intermolecular forces. The study of two polymorphs of 2,6-di-tert-butylnaphthalene by single-crystal x-ray diffraction, differential scanning calorimetry (DSC), C-13 magic-angle-spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy, and H-1 NMR spin-lattice relaxation provides a picture of the differences in structure and dynamics in these materials. The subtle differences in structure, observed with x-ray diffraction and chemical shifts, strikingly affect the dynamics, as reflected in the relaxation measurements. We analyze the dynamics in terms of both discrete sums and continuous …

Oslo Summer Workshop On Stochastic Analysis, Salah-Eldin A. Mohammed

Miscellaneous (presentations, translations, interviews, etc)

No abstract provided.

Water Current, Volume 32, No. 4, August 2000

Water Current Newsletter

New Method for Detecting Trace Amounts of MTBE and Ethanol at Heart of UNL Contamination Research
From the Director: New Director, New Directions, New Challenges
Lawn and Garden Drought and Climate Tolerance Are Focus of Festival of Color
Summer 2000 Water and Natural Resources Tour
Re-Cap of Water Management Issues Available Free
See You at Husker Harvest Days
NDEQ Water Quality Monitoring
Center-Pivot Map Available

Computational Geometry Column 39, Joseph O'Rourke

Computer Science: Faculty Publications

The resolution of a decades-old open problem is described: polygonal chains cannot lock in the plane.

Strain Variation With Sample Thickness In Gan Grown By Hydride Vapor Phase Epitaxy, D. C. Reynolds, David C. Look, B. Jogai, J. E. Hoelscher, R. E. Sherriff, Richard J. Molnar

Physics Faculty Publications

High quality GaN crystals can be grown on sapphire by hydride vapor phase epitaxy. The thermal expansion mismatch between sapphire and GaN produces strain in the GaN crystal as it is cooled from the growth temperature to room temperature. The strain is evidenced by shifts in the photoluminescence and reflectance line positions. By analyzing the surface strain as the crystal thickness is increased, the thickness required to obtain zero surface strain can be estimated. This structure might provide a lattice matched and thermally matched substrate for further epitaxial growth of GaN.

The Relationship Of Small Mammal Species To Habitat Variables In West-Central Georgia And East-Central Alabama, Patricia Maureen Kosky

Theses and Dissertations

The objective of this investigation was to assess the impact of environmental variables upon small mammal species distribution in 60 plots on Fort Benning, Muscogee and Chattahoochee Counties, Georgia and Russell County, Alabama. The small mammal fieldwork was carried out in December of 1994 through January of 1995. The vegetation was inventoried in June through October of 1995. During this period, 235 small mammals were trapped in a total of 5950 trap nights. A total of 10 small mammal species and 234 plant species were identified. The small mammal species abundance's were determined by using snap trapping along the plot …

Theoretical Basis For The Ce-Qual-W2 River Basin Model, Scott A. Wells, Thomas M. Cole

Civil and Environmental Engineering Faculty Publications and Presentations

The primary objective of this research is to integrate a riverine model into the existing W2 code that would provide the capability for modeling entire watersheds. This task was accomplished by the following steps:

• Formal derivation of governing equations and solution algorithm with general channel slope

• Detailed analysis of algorithm for linking branches and smooth implementation of boundary conditions between branches

• Algorithm development and changes to basic model code (including branch definitions with slope, slope correction to solution algorithm, transfer of momentum between internal branches)

These tasks were performed with the following constraints and initiatives:

• Utilize …

Masses For Galactic Beat Cepheids, Noella L. D'Cruz, Siobahn M. Morgan, Erika Böhm-Vitense

Faculty Publications

Accurate mass determinations for Cepheids may be used to determine the degree of excess mixing in the interiors of their main-sequence progenitors : the larger the excess mixing, the larger the luminosity of the Cepheid of a given mass, or the smaller the mass of a Cepheid with given luminosity. Dynamical masses determined recently for a few Cepheid binaries indicate excess mixing somewhat stronger than that corresponding to the convective overshoot models by Schaller et al. Beat Cepheids can be used similarly to test main-sequence mixing in stellar interiors. The period ratios for beat Cepheids depend on luminosity, heavy element …

Performance Analysis Of Mobile Agents For Filtering Data Streams On Wireless Networks, David Kotz, Guofei Jiang, Robert Gray, George Cybenko, Ronald A. Peterson

Dartmouth Scholarship

Wireless networks are an ideal environment for mobile agents, because their mobility allows them to move across an unreliable link to reside on a wired host, next to or closer to the resources they need to use. Furthermore, client-specific data transformations can be moved across the wireless link, and run on a wired gateway server, with the goal of reducing bandwidth demands. In this paper we examine the tradeoffs faced when deciding whether to use mobile agents to support a data-filtering application, in which numerous wireless clients filter information from a large data stream arriving across the wired network. We …

On The Effectiveness Of Probabilistic Packet Marking For Ip Traceback Under Denial Of Service Attack, Kihong Park, Heejo Lee

Department of Computer Science Technical Reports

No abstract provided.

Computer-Aided Synthesis Of Higher Pairs Via Configuration Space Manupulation, Min-Ho Kyung, Elisha Sacks

Department of Computer Science Technical Reports

No abstract provided.

Rosat Hri And Asca Observations Of The Spiral Galaxy Ngc 6946 And Its Northeast Complex Of Luminous Supernova Remnants, Eric M. Schlegel, William P. Blair, Robert A. Fesen

Dartmouth Scholarship

Analysis of 80 ks ASCA and 60 ks ROSAT HRI observations of the face-on spiral galaxy NGC 6946 are presented. The ASCA image is the first observation of this galaxy above ~2 keV. Diffuse emission may be present in the inner ~4' extending to energies above ~2–3 keV. In the HRI data, 14 pointlike sources are detected, the brightest two being a source very close to the nucleus and a source to the northeast that corresponds to a luminous complex of interacting supernova remnants (SNRs). We detect a point source that lies ~30'' west of the SNR complex but with …

High Efficiency Separation Of Microbial Aggregates Using Capillary Electrophoresis, J. M. Schneiderheinze, Daniel W. Armstrong, G. Schulte, David J. Westenberg

Chemistry Faculty Research & Creative Works

Recent advances in the technique of capillary electrophoresis have demonstrated fast, highly efficient separation of mixtures of intact microbes. This paper describes the application of this technique for the separation of microbial aggregates of Micrococcus luteus, Saccharomyces cerevisiae, or Alcaligenes faecalis. The aggregates of these microbes were resolved into several highly efficient peaks with analysis times under 10 min and efficiencies approaching 1 000 000 plates m-1 in some cases. A reproducible relationship was found between the electrophoretic mobility and the aggregation number or size of the cluster under a given set of experimental conditions. Often, cellular aggregation was reversible …

Cyclodextrin Inclusion Complexes Of Betamethasone-Related Steroids Studied Using Hplc, Keith Gerald Flood

Seton Hall University Dissertations and Theses (ETDs)

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Alteration Processes Of Alkenones And Related Lipids In Water Columns And Sediments, H. Rodger Harvey

OES Faculty Publications

Alkenones produced by the haptophyte algae are currently being used as indices of sea surface temperature in recent and past ocean environments, but limited information is available concerning the impact of biotic and abiotic processes on the integrity of these long chain lipids. This synthesis provides selected background information on major alteration processes that must be considered before such indices can be used with confidence. A number of processes in the water column and surface sediments have the potential to impact the structural integrity of alkenones and compromise their ability as temperature markers. Processes discussed include the alteration of alkenone …

Kinetic Studies On The Reaction Of Hydroxyl Radicals With Aromatic Compounds, Paul Chadwick

Masters

No abstract provided

Observation Of Stratospheric Ozone Depletion Associated With Delta Ii Rocket Emissions, Martin N. Ross, Darin W. Toohey, W. T. Rawlins, E. C. Richard, K. K. Kelly, A. F. Tuck, M. H. Proffitt, Donald E. Hagen, Alfred R. Hopkins, Philip D. Whitefield, J. R. Benbrook, W. R. Sheldon

Physics Faculty Research & Creative Works

Ozone, chlorine monoxide, methane, and submicron particulate concentrations were measured in the stratospheric plume wake of a Delta II rocket powered by a combination of solid (NH₄ClO₄/Al) and liquid (LOX/kerosene) propulsion systems. We apply a simple kinetics model describing the main features of gas-phase chlorine reactions in solid propellant exhaust plumes to derive the abundance of total reactive chlorine in the plume and estimate the associated cumulative ozone loss. Measured ozone loss during two plume encounters (12 and 39 minutes after launch) exceeded the estimate by about a factor of about two. Insofar as only the …

Molecular-Dynamics Study Of Phase Transitions In Alkali Thiocyanates, M. M. Ossowski, John R. Hardy, R. W. Smith

John R. Hardy Papers

An account is presented of our studies of the order-disorder phase transitions in KSCN, RbSCN, and CsSCN. These are based on parameter-free interionic potentials based on the Gordon-Kim modified electron gas formalism extended to molecular ions. We performed static structural relaxations and supercell molecular dynamics and predicted with reasonable accuracy the temperatures for the onset of the transitions. In particular, we address the question of how the SCN^- ions disorder to yield subsequent structural transformations. We found high-temperature phases of average Fm3m symmetry for both KSCN and RbSCN. We argue that in reality the full appearance of …

Effect Of Disorder On Perpendicular Magnetotransport In Co/Cu Multilayers, Evgeny Y. Tsymbal

Evgeny Tsymbal Publications

We investigate the spin-dependent conductance of the Co/Cu multilayers in the current-perpendicular-tothe- plane (CPP) geometry. Using a realistic tight-binding model for the electronic band structure of the multilayer, and introducing disorder in the on-site atomic energies we calculate the conductance and giant magnetoresistance (GMR) within the quantum-mechanical linear response theory by performing averaging over random disorder configurations. By varying the thickness and the number of individual layers and the degree of disorder in the multilayers, we analyze factors influencing the CPP GMR. In particular, we show the importance of the thickness-dependent interface resistance, which depends on the mean free path …