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Faculty Publications

2006

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Articles 61 - 84 of 84

Full-Text Articles in Physical Sciences and Mathematics

The Structure Of Β-Carbonic Anhydrase From The Carboxysomal Shell Reveals A Distinct Subclass With One Active Site For The Price Of Two, Michael R. Sawaya, Gordon C. Cannon, Sabine Heinhorst, Shiho Tanaka, Eric B. Williams, Todd O. Yeates, Cheryl A. Kerfeld Mar 2006

The Structure Of Β-Carbonic Anhydrase From The Carboxysomal Shell Reveals A Distinct Subclass With One Active Site For The Price Of Two, Michael R. Sawaya, Gordon C. Cannon, Sabine Heinhorst, Shiho Tanaka, Eric B. Williams, Todd O. Yeates, Cheryl A. Kerfeld

Faculty Publications

CsoSCA (formerly CsoS3) is a bacterial carbonic anhydrase localized in the shell of a cellular microcompartment called the carboxysome, where it converts HCO-3 to CO2 for use in carbon fixation by ribulose-bisphosphate carboxylase/oxygenase (RuBisCO). CsoSCA lacks significant sequence similarity to any of the four known classes of carbonic anhydrase (α, β, γ, or δ), and so it was initially classified as belonging to a new class, ϵ. The crystal structure of CsoSCA from Halothiobacillus neapolitanus reveals that it is actually a representative member of a new subclass of β-carbonic anhydrases, distinguished by a lack of active site …

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A General Theory Of Almost Convex Functions, S J. Dilworth, Ralph Howard, James W. Roberts Mar 2006

A General Theory Of Almost Convex Functions, S J. Dilworth, Ralph Howard, James W. Roberts

Faculty Publications

No abstract provided.

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Learning Real-Time A* Path Planner For Unmanned Air Vehicle Target Sensing, Jason K. Howlett, Timothy W. Mclain, Michael A. Goodrich Mar 2006

Learning Real-Time A* Path Planner For Unmanned Air Vehicle Target Sensing, Jason K. Howlett, Timothy W. Mclain, Michael A. Goodrich

Faculty Publications

This paper presents a path planner for sensing closely-spaced targets from a fixed-wing unmanned air vehicle (UAV) having a specified sensor footprint. The planner is based on the learning real-time A* (LRTA*) search algorithm and produces dynamically feasible paths that accomplish the sensing objectives in the shortest possible distance. A tree of candidate paths that span the area of interest is created by assembling primitive turn and straight sections of a specified step size in a sequential fashion from the starting position of the UAV. An LRTA* search of the tree produces feasible paths any time during its execution and …

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Compact Solid-State Laser Source For 1s-2s Spectroscopy In Atomic Hydrogen, Scott D. Bergeson, N. Kolachevsky, J. Alnis, T. W. Hansch Feb 2006

Compact Solid-State Laser Source For 1s-2s Spectroscopy In Atomic Hydrogen, Scott D. Bergeson, N. Kolachevsky, J. Alnis, T. W. Hansch

Faculty Publications

We demonstrate a compact solid-state laser source for high-resolution two-photon spectroscopy of the 1S-2S transition in atomic hydrogen. The source emits up to 20 mW at 243 nm and consists of a 972 nm diode laser, a tapered amplifier, and two doubling stages. The diode laser is actively stabilized to a high-finesse cavity. We compare the new source to the stable 486 nm dye laser used in previous experiments and record 1S-2S spectra using both systems. With the solid-state laser system, we demonstrate a resolution of the hydrogen spectrometer of 6×10^11, which is promising for a number of high-precision measurements …

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Finding The Radial Parallel Temperature Profile In A Non-Neutral Plasma Using Equilibrium Calculations On Experimental Data, Grant W. Hart, Bryan G. Peterson Feb 2006

Finding The Radial Parallel Temperature Profile In A Non-Neutral Plasma Using Equilibrium Calculations On Experimental Data, Grant W. Hart, Bryan G. Peterson

Faculty Publications

In 1992, Eggleston et al. [D. L. Eggleston et al., Phys. Fluids B 4, 3432 (1992)] reported on a technique for measuring the radial temperature profile in a pure-electron plasma confined in a Malmberg-Penning trap by partially dumping the plasma onto a charge collector at the end of the trap. For short plasmas and short confining rings, the assumptions in their paper are violated and a more general calculation is needed. This paper presents a variation of the standard equilibrium calculation to find the temperature profile of a pure-electron plasma. Eggleston's shortcut "evaporation" temperature method is found to require a …

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Full Shot Noise In Mesoscopic Tunnel Barriers, Yuanzhen Chen, Richard A. Webb Jan 2006

Full Shot Noise In Mesoscopic Tunnel Barriers, Yuanzhen Chen, Richard A. Webb

Faculty Publications

We report shot noise measurements performed in mesoscopic tunnel barriers fabricated in a GaAs∕AlGaAs heterostructure. Two sets of tunnel barriers of different size are used in the study. All large size samples and some of the small size samples show a nonlinear dependence of shot noise on tunneling current due to localized states inside the barriers. Both suppression and enhancement of shot noise have been observed. Some small size barriers, however, exhibit the shot noise behavior of an ideal tunnel barrier over a wide range of barrier transmission coefficients, tunneling currents, and bias voltages.

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Forward Jet Production In Deep Inelastic Ep Scattering And Low-X Parton Dynamics At Hera, S. Chekanov, M. Derrick, S. Magill, S. Miglioranzi, B. Musgrave, J. Repond, R. Yoshida, Margarita C. K. Mattingly, N. Pavel, A. G. Yagües Molina, P. Antonioli, G. Bari, M. Basile, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, G. Cara Romeo, L. Cifarelli, F. Cindolo, A. Contin, M. Corradi, S. De Pasquale, P. Giusti, G. Iacobucci, A. Margotti, A. Montanari, R. Nania, F. Palmonari, A. Pesci, A. Polini Jan 2006

Forward Jet Production In Deep Inelastic Ep Scattering And Low-X Parton Dynamics At Hera, S. Chekanov, M. Derrick, S. Magill, S. Miglioranzi, B. Musgrave, J. Repond, R. Yoshida, Margarita C. K. Mattingly, N. Pavel, A. G. Yagües Molina, P. Antonioli, G. Bari, M. Basile, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, G. Cara Romeo, L. Cifarelli, F. Cindolo, A. Contin, M. Corradi, S. De Pasquale, P. Giusti, G. Iacobucci, A. Margotti, A. Montanari, R. Nania, F. Palmonari, A. Pesci, A. Polini

Faculty Publications

Differential inclusive jet cross sections in neutral current deep inelastic ep scattering have been measured with the ZEUS detector using an integrated luminosity of 38.7 pb-1. The jets have been identified using the kT cluster algorithm in the longitudinally invariant inclusive mode in the laboratory frame; they have been selected with jet transverse energy, ETjet above 6 GeV and jet pseudorapidity, ηjet, between -1 and 3. Measurements of cross sections as functions of ETjet, Björken x and the photon virtuality, Q2, are presented. Three phase-space regions have been selected in order to study parton dynamics from the most global to …

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Maldi-Tof Baseline Drift Removal Using Stochastic Bernstein Approximation, Joseph Kolibal, Daniel Howard Jan 2006

Maldi-Tof Baseline Drift Removal Using Stochastic Bernstein Approximation, Joseph Kolibal, Daniel Howard

Faculty Publications

Stochastic Bernstein (SB) approximation can tackle the problem of baseline drift correction of instrumentation data. This is demonstrated for spectral data: matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF) data. Two SB schemes for removing the baseline drift are presented: iterative and direct. Following an explanation of the origin of the MALDI-TOF baseline drift that sheds light on the inherent difficulty of its removal by chemical means, SB baseline drift removal is illustrated for both proteomics and genomics MALDI-TOF data sets. SB is an elegant signal processing method to obtain a numerically straightforward baseline shift removal method as it includes a …

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Oxygen Depletion In The Gulf Of Mexico Adjacent To The Mississippi River, Nancy N. Rabalais, R. Eugene Turner Jan 2006

Oxygen Depletion In The Gulf Of Mexico Adjacent To The Mississippi River, Nancy N. Rabalais, R. Eugene Turner

Faculty Publications

The seasonal formation of a bottom water layer severely depleted in dissolved oxygen has become a perennial occurrence on the Louisiana continental shelf adjacent to the Mississippi River system. Dramatic changes have occurred in this coastal ecosystem in the last half of the 20th century as the loads of dissolved inorganic nitrogen tripled. There are increases in primary production, shifts in phytoplankton community composition, changes in trophic interactions, and worsening severity of hypoxia. The hypoxic conditions (dissolved oxygen less than 2 mg l-1) cover up to 22,000 km2 of the seabed in mid-summer. Dissolved oxygen concentrations seldom decrease to anoxia, …

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Impacts Of A Manure Composting Program On Stream Water Quality, A. Bekele, A. M.S. Mcfarland, A. J. Whisenant Jan 2006

Impacts Of A Manure Composting Program On Stream Water Quality, A. Bekele, A. M.S. Mcfarland, A. J. Whisenant

Faculty Publications

In February 2001, the Texas Commission on Environmental Quality (TCEQ) adopted a Total Maximum Daily Load (TMDL) for soluble reactive phosphorus (SRP) along the North Bosque River. Within this TMDL, dairy waste application fields were identified as the major nonpoint-source contribution of nutrients. In September 2000, a manure composting program was initiated that resulted in about 500,000 metric tons of dairy manure being hauled to composting facilities and exported from the watershed through December 2004. To evaluate the impact of the manure composting program on stream water quality, storm event mean concentrations of nutrients and total suspended solids were compared …

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Structure And Vibrational Spectra Of Mononitrated Benzo [A] Pyrenes., Kefa Karimu Onchoke, Christopher M. Hadad, Prabir K. Dutta Jan 2006

Structure And Vibrational Spectra Of Mononitrated Benzo [A] Pyrenes., Kefa Karimu Onchoke, Christopher M. Hadad, Prabir K. Dutta

Faculty Publications

The molecules benzo[a]pyrene (BaP) and 1-, 3-, and 6-nitrobenzo[a]pyrene (1-NBaP, 3-NBaP, 6-NBaP) are currently of significant interest due to their presence in respirable combustion exhaust particulates and their mutagenic and carcinogenic properties. Structure−function correlations as well as spectroscopic signatures for trace analysis are necessary for these benzo[a]pyrene derivatives. In this paper, detailed infrared and Raman spectroscopic data of BaP and its three mononitrated isomers are provided for the first time. By utilizing density functional theory (DFT, B3LYP method with 6-311+G** basis set), the molecular geometries and the vibrational spectra are calculated. Good agreement is …

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Subspaces Of Ωω That Are Paracompact In Some Forcing Extension, Akira Iwasa Jan 2006

Subspaces Of Ωω That Are Paracompact In Some Forcing Extension, Akira Iwasa

Faculty Publications

We discuss when a subspace of ωω is paracompact in some forcing extension.

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Introducing Semantics In Web Personalization: The Role Of Ontologies, Magdalini Eirinaki, Dimitrios Mavroeidis, George Tsatsaronis, Michalis Vazirgiannis Jan 2006

Introducing Semantics In Web Personalization: The Role Of Ontologies, Magdalini Eirinaki, Dimitrios Mavroeidis, George Tsatsaronis, Michalis Vazirgiannis

Faculty Publications

Web personalization is the process of customizing a web site to the needs of each specific user or set of users. Personalization of a web site may be performed by the provision of recommendations to the users, high-lighting/adding links, creation of index pages, etc. The web personalization systems are mainly based on the exploitation of the navigational patterns of the web site’s visitors. When a personalization system relies solely on usage-based results, however, valuable information conceptually related to what is finally recommended may be missed. The exploitation of the web pages’ semantics can considerably improve the results of web usage …

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Hydrodynamic Description Of The Adiabatic Piston, Alejandro Garcia, M. M. Mansour Jan 2006

Hydrodynamic Description Of The Adiabatic Piston, Alejandro Garcia, M. M. Mansour

Faculty Publications

A closed macroscopic equation for the motion of the two-dimensional adiabatic piston is derived from standard hydrodynamics. It predicts a damped oscillatory motion of the piston towards a final rest position, which depends on the initial state. In the limit of large piston mass, the solution of this equation is in quantitative agreement with the results obtained from both hard disk molecular dynamics and hydrodynamics. The explicit forms of the basic characteristics of the piston’s dynamics, such as the period of oscillations and the relaxation time, are derived. The limitations of the theory’s validity, in terms of the main system …

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Estimating Hydrodynamic Quantities In The Presence Of Microscopic Fluctuations, Alejandro Garcia Jan 2006

Estimating Hydrodynamic Quantities In The Presence Of Microscopic Fluctuations, Alejandro Garcia

Faculty Publications

This paper discusses the evaluation of hydrodynamic variables in the presence of spontaneous fluctuations, such as in molecular simulations of fluid flows. The principal point is that hydrodynamic variables such as fluid velocity and temperature must be defined in terms of mechanical variables such as momentum and energy density). Because these relations are nonlinear and because fluctuations of mechanical variables are correlated, care must be taken to avoid introducing a bias when evaluating means, variances, and correlations of hydrodynamic variables. The unbiased estimates are formulated; some alternative, incorrect approaches are presented as cautionary warnings. The expressions are verified by numerical …

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A Deep Kinematic Survey Of Planetary Nebulae In The Andromeda Galaxy Using The Planetary Nebula Spectrograph, H. R. Merrett, M. R. Merrifield, N. G. Douglas, K. Kuijken, Aaron J. Romanowsky, N. R. Napolitano, M. Arnaboldi, M. Capaccioli, K. C. Freeman, O. Gerhard, L. Coccato, D. Carter, N. W. Evans, M. I. Wilkinson, C. Halliday, T. J. Bridges Jan 2006

A Deep Kinematic Survey Of Planetary Nebulae In The Andromeda Galaxy Using The Planetary Nebula Spectrograph, H. R. Merrett, M. R. Merrifield, N. G. Douglas, K. Kuijken, Aaron J. Romanowsky, N. R. Napolitano, M. Arnaboldi, M. Capaccioli, K. C. Freeman, O. Gerhard, L. Coccato, D. Carter, N. W. Evans, M. I. Wilkinson, C. Halliday, T. J. Bridges

Faculty Publications

We present a catalogue of positions, magnitudes and velocities for 3300 emission-line objects found by the Planetary Nebula Spectrograph in a survey of the Andromeda galaxy, M31. Of these objects, 2615 are found likely to be planetary nebulae (PNe) associated with M31. The survey area covers the whole of M31's disc out to a radius of Graphic. Beyond this radius, observations have been made along the major and minor axes, and the Northern Spur and Southern Stream regions. The calibrated data have been checked for internal consistency and compared with other catalogues. With the exception of the very central, high …

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Planetary Nebula Velocities In The Disc And Bulge Of M31, C. Halliday, D. Carter, T. J. Bridges, Z. C. Jackson, M. I. Wilkinson, D. P. Quinn, N. W. Evans, N. G. Douglas, H. R. Merrett, Aaron J. Romanowsky, K. Kuijken, M. J. Irwin Jan 2006

Planetary Nebula Velocities In The Disc And Bulge Of M31, C. Halliday, D. Carter, T. J. Bridges, Z. C. Jackson, M. I. Wilkinson, D. P. Quinn, N. W. Evans, N. G. Douglas, H. R. Merrett, Aaron J. Romanowsky, K. Kuijken, M. J. Irwin

Faculty Publications

We present radial velocities for a sample of 723 planetary nebulae in the disc and bulge of M31, measured using the WYFFOS fibre spectrograph on the William Herschel Telescope. Velocities are determined using the [O III] λ5007 emission line. Rotation and velocity dispersion are measured to a radius of 50 arcmin (11.5 kpc), the first stellar rotation curve and velocity dispersion profile for M31 to such a radius. Our kinematics are consistent with rotational support at radii well beyond the bulge effective radius of 1.4 kpc, although our data beyond a radius of 5 kpc are limited. We present tentative …

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Wide-Field Kinematics Of Globular Clusters In The Leo I Group, G. Bergond, S. E. Zepf, Aaron J. Romanowsky, R. M. Sharples, K. L. Rhode Jan 2006

Wide-Field Kinematics Of Globular Clusters In The Leo I Group, G. Bergond, S. E. Zepf, Aaron J. Romanowsky, R. M. Sharples, K. L. Rhode

Faculty Publications

We present wide-field spectroscopy of globular clusters around the Leo I group galaxies NGC 3379 and NGC 3384 using the FLAMES multi-fibre instrument at the VLT. We obtain accurate radial velocities for 42 globular clusters (GCs) in total, 30 for GCs around the elliptical NGC 3379, eight around the lenticular NGC 3384, and four which may be associated with either galaxy. These data are notable for their large radial range extending from 0$\farcm$7 to 14$\farcm$5 (2 to 42 kpc) from the centre of NGC 3379, and small velocity uncertainties of about 10 km s-1. We combine our sample of 30 …

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The Araucaria Project. An Accurate Distance To Ngc 6822 From Near-Infrared Photometry Of Cepheid Variables, W. Gieren, G. Pietrzyński, K. Nalewajko, I. Soszyński, F. Bresolin, R.-P. Kudritzki, D. Minniti, Aaron J. Romanowsky Jan 2006

The Araucaria Project. An Accurate Distance To Ngc 6822 From Near-Infrared Photometry Of Cepheid Variables, W. Gieren, G. Pietrzyński, K. Nalewajko, I. Soszyński, F. Bresolin, R.-P. Kudritzki, D. Minniti, Aaron J. Romanowsky

Faculty Publications

We have measured near-infrared magnitudes in the J and K bands for 56 Cepheid variables in the Local Group galaxy NGC 6822 with well-determined periods and optical light curves in the V and I bands. Using the template light-curve approach of Soszyński and coworkers, accurate mean magnitudes were obtained from these data, which allowed us to determine with unprecedented accuracy the distance to NGC 6822 from a multiwavelength period-luminosity solution in the VIJK bands. From our data, we obtain a distance to NGC 6822 of (m - M)0 = 23.312 ± 0.021 (random error) mag, with an additional systematic uncertainty …

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New Orleans, The Chesapeake, And The Future Of Environmental Assessment: Overcoming The Natural Resources Law Of Unintended Consequences, Erin Ryan Jan 2006

New Orleans, The Chesapeake, And The Future Of Environmental Assessment: Overcoming The Natural Resources Law Of Unintended Consequences, Erin Ryan

Faculty Publications

No abstract provided.

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Counting Coffee Combinations: An Example Of The Fundamental Principle Of Counting, David R. Duncan, Bonnie H. Litwiller Jan 2006

Counting Coffee Combinations: An Example Of The Fundamental Principle Of Counting, David R. Duncan, Bonnie H. Litwiller

Faculty Publications

Teachers in courses which involve probability and statistics are always looking for situations in which the Fundamental Principle of Counting (FPC) can be exemplified. We shall present an example involving a coffee vending machine at a highway rest stop.

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Mathematically Modeling The Effects Of Counting Factor (Cf) In Dictyostelium Discoideum, J. C. Dallon, W. Jang, R. H. Gomer Jan 2006

Mathematically Modeling The Effects Of Counting Factor (Cf) In Dictyostelium Discoideum, J. C. Dallon, W. Jang, R. H. Gomer

Faculty Publications

Size regulation is a crucial feature in many biological systems, with misregulation leading to dysplasia or hyperplasia. The recent discovery of counting factor (CF) in Dictyostelium discoideum will lead to a greater understanding of how the system regulates the size of a group of cells. In this paper we mathematically model the known effects of CF using two different models: a cellular automata model and a discrete continuum hybrid model. With the use of these models we are able to understand how modulation of adhesion and motile forces by CF can facilitate stream breakup. In addition, the modelling suggests a …

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The "Fair" Triathlon: Equating Standard Deviations Using Bayesian Nonlinear Models, Gilbert W. Fellingham, C. Shane Reese, S. Mckay Curtis Jan 2006

The "Fair" Triathlon: Equating Standard Deviations Using Bayesian Nonlinear Models, Gilbert W. Fellingham, C. Shane Reese, S. Mckay Curtis

Faculty Publications

The Ironman triathlon was created in 1978 by combining events with the longest distances for races then contested in Hawaii in swimming, cycling, and running. The Half Ironman triathlon was formed using half the distances of each of the events in the Ironman. The Olympic distance triathlon was created by combining events with the longest distances for races sanctioned by the major federations for swimming, cycling, and running. The relative importance of each event in overall race outcome was not given consideration when determining the distances of each of the races in modern triathlons. Thus, there is a general belief …

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Adaptive Finite Element Methods For Elliptic Pdes Based On Conforming Centroidal Voronoi-Delaunay Triangulations, Lili Ju, Max Gunzburger, Weidong Zhao Jan 2006

Adaptive Finite Element Methods For Elliptic Pdes Based On Conforming Centroidal Voronoi-Delaunay Triangulations, Lili Ju, Max Gunzburger, Weidong Zhao

Faculty Publications

A new triangular mesh adaptivity algorithm for elliptic PDEs that combines a posteriori error estimation with centroidal Voronoi–Delaunay tessellations of domains in two dimensions is proposed and tested. The ability of the first ingredient to detect local regions of large error and the ability of the second ingredient to generate superior unstructured grids result in a mesh adaptivity algorithm that has several very desirable features, including the following. Errors are very well equidistributed over the triangles; at all levels of refinement, the triangles remain very well shaped, even if the grid size at any particular refinement level, when viewed globally, …

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