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2001

Faculty Publications

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Tailoring Harmonic Radiation To Different Applications Using A Genetic Algorithm, L. Roos, M. B. Gaarde, A. L'Huillier Dec 2001

Tailoring Harmonic Radiation To Different Applications Using A Genetic Algorithm, L. Roos, M. B. Gaarde, A. L'Huillier

Faculty Publications

We use a genetic algorithm to theoretically optimize several properties of extreme ultraviolet (XUV) radiation, generated as high-order harmonics in xenon and argon. We maximize the harmonic pulse energy, minimize the pulse duration or optimize the temporal coherence by varying at the same time two or three parameters that are easily accessible in experiments, related to the characteristics of the laser beam and the nonlinear medium. For the 15th and 29th harmonics in argon, we find up to 109 photons per pulse, and pulse durations as short as 6 fs generated by a 50 fs laser pulse. We can also …

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Localization Of Carriers And Polarization Effects In Quaternary Alingan Multiple Quantum Wells, E. Kuokstis, J. Zhang, M.-Y. Ryu, J. W. Yang, Grigory Simin, M. Asif Khan, R. Gaska, M. S. Shur Dec 2001

Localization Of Carriers And Polarization Effects In Quaternary Alingan Multiple Quantum Wells, E. Kuokstis, J. Zhang, M.-Y. Ryu, J. W. Yang, Grigory Simin, M. Asif Khan, R. Gaska, M. S. Shur

Faculty Publications

We report on observing a long-wavelength band in low-temperature photoluminescence(PL)spectrum of quaternary Al0.22In0.02Ga0.76N/Al0.38In0.01Ga0.61N multiple quantum wells(MQWs), which were grown over sapphire substrates by a pulsed atomic-layer epitaxy technique. By comparing the excitation-power density and temperature dependence of the PLspectra of MQWs and bulk quaternary AlInGaN layers, we show this emission band to arise from the carrier and/or exciton localization at the quantum well interface disorders. PL data for other radiative transitions in MQWs indicate that excitation-dependent spectra position is determined by screening of the built-in electric field.

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Spatial Patterns Of Morphological Diversity Across The Indo-Pacific: Analyses Using Strombid Gastropods, Kaustuv Roy, Deborah P. Balch, Michael E. Hellberg Dec 2001

Spatial Patterns Of Morphological Diversity Across The Indo-Pacific: Analyses Using Strombid Gastropods, Kaustuv Roy, Deborah P. Balch, Michael E. Hellberg

Faculty Publications

Biological diversity can be measured using various metrics, but existing knowledge of spatial patterns of diversity is largely based on species counts. There is increasing evidence that trends in species richness might not match trends in other biodiversity metrics, such as morphological diversity. Here, we use data from a large group of Indo-Pacific gastropods (family Strombidae) to show that the species richness of a region is a poor predictor of the morphological diversity present there. Areas with only a few species can harbour an impressive array of morphologies and, conversely, morphological diversity in the most species-rich regions is no higher …

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“[Cu(Pyrazine-2-Carboxylate)2]2Cd4I8: Unprecedented 1-D Serpentine Chains And Regular 2-D Regular Metal-Organic Square Grids In A 3-D Framework., Delia M. Ciurtin, Mark D. Smith, Hans Conrad Zur Loye Dec 2001

“[Cu(Pyrazine-2-Carboxylate)2]2Cd4I8: Unprecedented 1-D Serpentine Chains And Regular 2-D Regular Metal-Organic Square Grids In A 3-D Framework., Delia M. Ciurtin, Mark D. Smith, Hans Conrad Zur Loye

Faculty Publications

A novel three-dimensional coordination polymer containing
an unprecedented one-dimensional serpentine motif conjoined
with a two-dimensional square grid motif is presented.

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Redshifts And Luminosities For 112 Gamma-Ray Bursts, Bradley E. Schaefer, Ming Deng, David L. Band Dec 2001

Redshifts And Luminosities For 112 Gamma-Ray Bursts, Bradley E. Schaefer, Ming Deng, David L. Band

Faculty Publications

Two different luminosity indicators have recently been proposed for gamma-ray bursts that use gamma-ray observations alone. They relate the burst luminosity (L) with the time lag between peaks in hard and soft energies (τlag) and the spikiness or variability of the burst's light curve (V). These relations are currently justified and calibrated with only six or seven bursts with known redshifts. We have examined BATSE data for τlag and V for 112 bursts. (1) A strong correlation between τlag and V exists, and it is exactly as predicted from the two proposed relations. This is proof that both luminosity indicators …

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Magnetic Field Effects On Neutron Diffraction In The Antiferromagnetic Phase Of Upt3, Juana Moreno, J. A. Sauls Dec 2001

Magnetic Field Effects On Neutron Diffraction In The Antiferromagnetic Phase Of Upt3, Juana Moreno, J. A. Sauls

Faculty Publications

We discuss possible magnetic structures in UPt3 based on our analysis of elastic neutron-scattering experiments in high magnetic fields at temperatures T < TN. The existing experimental data are compatible with a true antiferromagnetic order displaying a single-q antiferromagnetic structure with three independent domains. For modest in-plane spin-orbit interactions, the Zeeman coupling between the antiferromagnetic order parameter and the magnetic field induces a rotation of the magnetic moments, but not an adjustment of the propagation vector of the magnetic order. A triple-q magnetic structure is also consistent with neutron experiments, but in general leads to a nonuniform magnetization in the crystal. New experiments involving higher fields and polarized neutrons could decide between these structures. © 2000 The American Physical Society.

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Development Of Cfl-Free, Explicit Schemes For Multidimensional Advection-Reaction Equations, Hong Wang, Jiangguo Liu Dec 2001

Development Of Cfl-Free, Explicit Schemes For Multidimensional Advection-Reaction Equations, Hong Wang, Jiangguo Liu

Faculty Publications

We combine an Eulerian–Lagrangian approach and multiresolution analysis to develop unconditionally stable, explicit, multilevel methods for multidimensional linear hyperbolic equations. The derived schemes generate accurate numerical solutions even if large time steps are used. Furthermore, these schemes have the capability of carrying out adaptive compression without introducing mass balance error. Computational results are presented to show the strong potential of the numerical methods developed.

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Manipulation Of Prenatal Hormones And Dietary Phytoestrogens During Adulthood Alter The Sexually Dimorphic Expression Of Visual Spatial Memory, Edwin D. Lephart, Trent D. Lund Dec 2001

Manipulation Of Prenatal Hormones And Dietary Phytoestrogens During Adulthood Alter The Sexually Dimorphic Expression Of Visual Spatial Memory, Edwin D. Lephart, Trent D. Lund

Faculty Publications

In learning and memory tasks, requiring visual spatial memory (VSM), males exhibit higher performance levels compared to females (a difference attributed to sex steroid hormonal influences). Based upon the results from our companion investigation, this study examined the influence of prenatal sex steroid hormone manipulations on VSM in adulthood, as assessed in the radial arm maze. Additionally, the influence of dietary soy phytoestrogens (i.e., the presence of high or low estrogen-like compounds present in the animal's diet) on VSM was examined in combination with the prenatal hormonal manipulations. Results: Radial arm maze performance on a phytoestrogen-rich diet: 1) females treated …

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Glycoprotein K Specified By Herpes Simplex Virus Type 1 Is Expressed On Virions As A Golgi Complex-Dependent Glycosylated Species And Functions In Virion Entry, T. P. Foster, G. V. Rybachuk, K. G. Kousoulas Dec 2001

Glycoprotein K Specified By Herpes Simplex Virus Type 1 Is Expressed On Virions As A Golgi Complex-Dependent Glycosylated Species And Functions In Virion Entry, T. P. Foster, G. V. Rybachuk, K. G. Kousoulas

Faculty Publications

To facilitate detection of glycoprotein K (gK) specified by herpes simplex virus, a 12-amino-acid epitope tag was inserted within gK domain III. Recombinant virus gKprotC-DIII, expressing the tagged gK, was isolated. This virus formed wild-type plaques and replicated as efficiently as the wild-type KOS virus in Vero cells. Anti-protein C MAb detected high-mannose and Golgi complex-dependent glycosylated gK within cells as well as on purified virions. The gK-null virus ΔgK (gK-/-) entered Vero cells substantially more slowly than the wild-type KOS (gK+/+), while ΔgK virus grown in complementing VK302 cells (gK-/+) entered with entry kinetics similar to those of the …

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Ultraviolet Light-Emitting Diodes At 340 Nm Using Quaternary Alingan Multiple Quantum Wells, V. Adivarahan, A. Chitnis, J. P. Zhang, M. Shatalov, J. W. Yang, Grigory Simin, M. Asif Khan, R. Gaska, M. S. Shur Dec 2001

Ultraviolet Light-Emitting Diodes At 340 Nm Using Quaternary Alingan Multiple Quantum Wells, V. Adivarahan, A. Chitnis, J. P. Zhang, M. Shatalov, J. W. Yang, Grigory Simin, M. Asif Khan, R. Gaska, M. S. Shur

Faculty Publications

An ultraviolet light-emitting diode with peak emission wavelength at 340 nm is reported. The active layers of the device were comprised of quaternary AlInGaN/AlInGaN multiple quantum wells, which were deposited over sapphire substrates using a pulsed atomic-layer epitaxy process that allows precise control of the composition and thickness. A comparative study of devices over sapphire and SiC substrates was done to determine the influence of the epilayer design on the performance parameters and the role of substrate absorption.

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Visual Spatial Memory Is Enhanced In Female Rats (But Inhibited In Males) By Dietary Soy Phytoestrogens, Edwin D. Lephart, Trent D. Lund, Timothy W. West, Lilyan Y. Tian, Lihong H. Bu, Daniel L. Simmons, Kenneth Setchell, Herman Adlercreutz Dec 2001

Visual Spatial Memory Is Enhanced In Female Rats (But Inhibited In Males) By Dietary Soy Phytoestrogens, Edwin D. Lephart, Trent D. Lund, Timothy W. West, Lilyan Y. Tian, Lihong H. Bu, Daniel L. Simmons, Kenneth Setchell, Herman Adlercreutz

Faculty Publications

In learning and memory tasks, requiring visual spatial memory (VSM), males exhibit superior performance to females (a difference attributed to the hormonal influence of estrogen). This study examined the influence of phytoestrogens (estrogen-like plant compounds) on VSM, utilizing radial arm-maze methods to examine varying aspects of memory. Additionally, brain phytoestrogen, calbindin (CALB), and cyclooxygenase-2 (COX-2) levels were determined. Results: Female rats receiving lifelong exposure to a high-phytoestrogen containing diet (Phyto-600) acquired the maze faster than females fed a phytoestrogen-free diet (Phyto-free); in males the opposite diet effect was identified. In a separate experiment, at 80 days-of-age, animals fed the Phyto-600 …

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Origins Of Nonstoichiometry And Vacancy Ordering In Sc1-X□Xs, Gus L. W. Hart, Alex Zunger Dec 2001

Origins Of Nonstoichiometry And Vacancy Ordering In Sc1-X□Xs, Gus L. W. Hart, Alex Zunger

Faculty Publications

Whereas nearly all compounds AnBm obey Dalton's rule of integer stoichiometry (n:m, both integer), there is a class of systems, exemplified by the rocksalt structure Sc1-x□xS, that exhibits large deviations from stoichiometry via vacancies, even at low temperatures. By combining first-principles total energy calculations with lattice statistical mechanics, we scan an astronomical number of possible structures, identifying the stable ground states. Surprisingly, all have the same motifs: (111) planes with (112) vacancy rows arranged in (110) columns. Electronic structure calculations of the ground states (identified out of ~3 × 10^6 structures) reveal the remarkable origins of nonstoichiometry.

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Microscale Patchiness Of Bacterioplankton Assemblage Richness In Seawater, Richard A. Long, Farooq Azam Dec 2001

Microscale Patchiness Of Bacterioplankton Assemblage Richness In Seawater, Richard A. Long, Farooq Azam

Faculty Publications

We sought to test the hypothesis that bacterial species richness and composition vary at the millimeter scale in the marine pelagic environment, in response to the heterogeneous distribution of organic matter. To test this hypothesis, it was necessary to design and test a protocol to sample, lyse and analyze (by polymerase chain reaction/denaturing gradient gel electrophoresis [PCR-DGGE]) bacterioplankton species richness in a single microliter of seawater. Significant variation in bacterial species richness was found amongst 1 μl samples. Greater species richness was seen when seawater was enriched with diatom detritus. Examination of species richness at 2 mm intervals over a …

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Three Unique Coordination Geometries Involving 1,2-Dimethoxy-4,5-Bis(2-Pyridylethynyl)Benzene, Jeffrey E. Fiscus, Sandra Shotwell, Ralph C. Layland, Mark D. Smith, Hans Conrad Zur Loye, Uwe H. F. Bunz Dec 2001

Three Unique Coordination Geometries Involving 1,2-Dimethoxy-4,5-Bis(2-Pyridylethynyl)Benzene, Jeffrey E. Fiscus, Sandra Shotwell, Ralph C. Layland, Mark D. Smith, Hans Conrad Zur Loye, Uwe H. F. Bunz

Faculty Publications

Reaction of the new ligand 1,2-dimethoxy-4,5-bis(2-pyridylethynyl) benzene with different metal centers under similar reaction conditions led to three distinct structure formation processes: molecular ring closure, dimerization, and polymer formation.

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Precise Measurement Of Dimuon Production Cross Sections In Νμfe And Ν̄Μfe Deep Inelastic Scattering At The Fermilab Tevatron, M. Goncharov, T. Adams, A. Alton, T. Bolton, J. Goldman, P. Spentzouris, J. Conrad, B. T. Fleming, J. Formaggio, S. Koutsoliotas, J. H. Kim, C. Mcnulty, A. Romosan, M. H. Shaevitz, E. G. Stern, A. Vaitaitis, E. D. Zimmerman, R. A. Johnson, M. Vakili, N. Suwonjandee, R. H. Bernstein, L. Bugel, M. J. Lamm, W. Marsh, P. Nienaber, J. Yu, L. De Barbaro, D. Buchholz, H. Schellman, G. P. Zeller, J. Brau, R. B. Drucker, R. Frey Dec 2001

Precise Measurement Of Dimuon Production Cross Sections In Νμfe And Ν̄Μfe Deep Inelastic Scattering At The Fermilab Tevatron, M. Goncharov, T. Adams, A. Alton, T. Bolton, J. Goldman, P. Spentzouris, J. Conrad, B. T. Fleming, J. Formaggio, S. Koutsoliotas, J. H. Kim, C. Mcnulty, A. Romosan, M. H. Shaevitz, E. G. Stern, A. Vaitaitis, E. D. Zimmerman, R. A. Johnson, M. Vakili, N. Suwonjandee, R. H. Bernstein, L. Bugel, M. J. Lamm, W. Marsh, P. Nienaber, J. Yu, L. De Barbaro, D. Buchholz, H. Schellman, G. P. Zeller, J. Brau, R. B. Drucker, R. Frey

Faculty Publications

We present measurements of the semi-inclusive cross sections for νμ- and ν̄μ-nucleon deep inelastic scattering interactions with two oppositely charged muons in the final state. These events dominantly arise from the production of a charm quark during the scattering process. The measurement was obtained from the analysis of 5102 νμ-induced and 1458 ν̄μ-induced events collected with the NuTeV detector exposed to a sign-selected beam at the Fermilab Tevatron. We also extract a cross-section measurement from a reanalysis of 5030 νμ-induced and 1060 ν̄μ-induced events collected from the exposure of the same detector to a quad-triplet beam by the Chicago Columbia …

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Swst 1: An O-Rich Planetary Nebula Around A C-Rich Central Star, Orsola De Marco, P. A. Crowther, M. J. Barlow, Geoffrey C. Clayton, A. De Koter Dec 2001

Swst 1: An O-Rich Planetary Nebula Around A C-Rich Central Star, Orsola De Marco, P. A. Crowther, M. J. Barlow, Geoffrey C. Clayton, A. De Koter

Faculty Publications

The hydrogen-deficient [WCL] type central star HD 167362 and its planetary nebula (PN) SwSt 1 are investigated. The central star has a carbon-rich emission-line spectrum, and yet the nebula exhibits a 10-μm emission feature from warm silicate dust, perhaps indicating a recent origin for the carbon-rich stellar spectrum. Its stellar and nebular properties might therefore provide further understanding as to the origin of the [WCL] central star class. The central star optical and UV spectra are modelled with state-of-the art non-LTE codes for expanding atmospheres, from which the stellar parameters are determined. Using the Sobolev approximation code ISA-Wind, we find …

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Evidence For Neutrino Oscillations From The Observation Of Ν̄E Appearance In A Ν̄Μ Beam, A. Aguilar, L. B. Auerbach, R. L. Burman, D. O. Caldwell, E. D. Church, A. K. Cochran, J. B. Donahue, A. Fazely, G. T. Garvey, R. M. Gunasingha, R. Imlay, W. C. Louis, R. Majkic, A. Malik, W. Metcalf, G. B. Mills, V. Sandberg, D. Smith, I. Stancu, M. Sung, R. Tayloe, G. J. Vandalen, W. Vernon, N. Wadia, D. H. White, S. Yellin Dec 2001

Evidence For Neutrino Oscillations From The Observation Of Ν̄E Appearance In A Ν̄Μ Beam, A. Aguilar, L. B. Auerbach, R. L. Burman, D. O. Caldwell, E. D. Church, A. K. Cochran, J. B. Donahue, A. Fazely, G. T. Garvey, R. M. Gunasingha, R. Imlay, W. C. Louis, R. Majkic, A. Malik, W. Metcalf, G. B. Mills, V. Sandberg, D. Smith, I. Stancu, M. Sung, R. Tayloe, G. J. Vandalen, W. Vernon, N. Wadia, D. H. White, S. Yellin

Faculty Publications

A search for ν̄μ→ν̄e oscillations was conducted by the Liquid Scintillator Neutrino Detector at the Los Alamos Neutron Science Center using ν̄μ from μ+ decay at rest. A total excess of 87.9±22.4±6.0 events consistent with ν̄ep→e+n scattering was observed above the expected background. This excess corresponds to an oscillation probability of (0.264±0.067±0.045)%, which is consistent with an earlier analysis. In conjunction with other known limits on neutrino oscillations, the LSND data suggest that neutrino oscillations occur in the 0.2-10 eV2/c4 Δm2 range, indicating a neutrino mass greater than 0.4 eV/c2. ©2001 The American Physical Society.

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Probing D-Wave Pairing Correlations In The Pseudogap Regime Of The Cuprate Superconductors Via Low-Energy States Near Impurities, Daniel E. Sheehy, A. Adagideli, Paul M. Goldbart, Ali Yazdani Dec 2001

Probing D-Wave Pairing Correlations In The Pseudogap Regime Of The Cuprate Superconductors Via Low-Energy States Near Impurities, Daniel E. Sheehy, A. Adagideli, Paul M. Goldbart, Ali Yazdani

Faculty Publications

The issue of probing the pseudogap regime of the cuprate superconductors, specifically with regard to the existence and nature of superconducting pairing correlations of d-wave symmetry, is explored theoretically. It is shown that if the d-wave correlations believed to describe the superconducting state persist into the pseudogap regime, but with pair-potential phase fluctuations that destroy their long-range nature, then the low-energy quasiparticle states observed near extended impurities in the truly superconducting state should also persist as resonances in the pseudogap regime. The scattering of quasiparticles by these phase-fluctuations broadens what was (in the superconducting state) a sharp peak in the …

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Fusobacteriosis In Captive Wild-Caught Pronghorns (Antilocapra Americana), J. F. Edwards, D. S. Davis, T. J. Roffe, F. Ramiro-Ibañez, P. H. Elzer Dec 2001

Fusobacteriosis In Captive Wild-Caught Pronghorns (Antilocapra Americana), J. F. Edwards, D. S. Davis, T. J. Roffe, F. Ramiro-Ibañez, P. H. Elzer

Faculty Publications

An outbreak of Fusobacterium necrophorum-induced septicemia occurred in a group of 40 captive wild-caught pronghorns (Antilocapra americana). Primary pododermatitis or necrotic stomatitis progressed to produce fatal septicemia with metastatic lesions in the forestomachs, lung, liver, and cecum in 38 of the animals. Two remaining animals were euthanatized because of chronic pododermatitis. Housing the animals in a pasture previously used by bovids and heavy rains with persistence of ground water pools in the pasture were contributing factors in the pathogenesis of this outbreak.

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Watts Towers, Jo Farb Hernandez Dec 2001

Watts Towers, Jo Farb Hernandez

Faculty Publications

No abstract provided.

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Powwows And Identity On The Piedmont And Coastal Plains Of North Carolina, Chris J. Goertzen Dec 2001

Powwows And Identity On The Piedmont And Coastal Plains Of North Carolina, Chris J. Goertzen

Faculty Publications

No abstract provided.

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Greenland Snow Accumulation Estimates From Satellite Radar Scatterometer Data, Mark R. Drinkwater, David G. Long, Andrew W. Bingham Dec 2001

Greenland Snow Accumulation Estimates From Satellite Radar Scatterometer Data, Mark R. Drinkwater, David G. Long, Andrew W. Bingham

Faculty Publications

Data collected by the C band ERS-2 wind scatterometer (EScat), the Ku band ADEOS-1 NASA scatterometer (NSCAT), and the Ku band SeaWinds on QuikScat (QSCAT) satellite instruments are used to illustrate spatiotemporal variability in snow accumulation on the Greenland ice sheet. Microwave radar backscatter images of Greenland are derived using the scatterometer image reconstruction (SIR) method at 3-day intervals over the periods 1991–1998 and 1996–1997 for EScat and NSCAT, respectively. The backscatter coefficient σ° normalized to 40° incidence, A, and gradient in backscatter, B, in the range 20°–60° are compared with historical snow accumulation data and recent measurements …

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Image Magnification Using Level-Set Reconstruction, Bryan S. Morse, Duane Schwartzwald Dec 2001

Image Magnification Using Level-Set Reconstruction, Bryan S. Morse, Duane Schwartzwald

Faculty Publications

Image magnification is a common problem in imaging applications, requiring interpolation to “read between the pixels”. Although many magnification/interpolation algorithms have been proposed in the literature, all methods must suffer to some degree the effects of impefect reconstruction―false high-frequency content introduced by the underlying original sampling. Most often, these effects manifest themselves as jagged contours in the image. This paper presents a method for constrained smoothing of such artifacts that attempts to produce smooth reconstructions of the image’s level curves while still maintaining image fidelity. This is similar to other iterative reconstruction algorithms and to Bayesian restoration techniques, but instead …

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Fast Focal Length Solution In Partial Panoramic Image Stitching, William A. Barrett, Kirk L. Duffin Dec 2001

Fast Focal Length Solution In Partial Panoramic Image Stitching, William A. Barrett, Kirk L. Duffin

Faculty Publications

Accurate estimation of effective camera focal length is crucial to the success of panoramic image stitching. Fast techniques for estimating the focal length exist, but are dependent upon a close initial approximation or the existence of a full circle panoramic image sequence. Numerical solutions of the focal length demonstrate strong coupling between the focal length and the angles used to position each component image about the common spherical center. This paper demonstrates that parameterizing panoramic image positions using spherical arc length instead of angles effectively decouples the focal length Ji.om the image position. This new parameterization does not require an …

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Houghing The Hough: Peak Collection For Detection Of Corners, Junctions And Line Intersections, William A. Barrett, Kevin D. Petersen Dec 2001

Houghing The Hough: Peak Collection For Detection Of Corners, Junctions And Line Intersections, William A. Barrett, Kevin D. Petersen

Faculty Publications

We exploit the Accumulator Array of the Hough Transform by finding collections of (2 or more) peaks through which a given sinusoid will pass. Such sinusoids identify points in the original image where lines intersect. Peak collection (or line aggregation) is performed by making a second pass through the edge map, but instead of laying points down in the accumulator array (as with the original Hough Transform), we compute the line integral over each sinusoid that corresponds to the current edge point. If a sinusoid passes through greater than or equal to 2 peaks, we deposit that sum/integral into a …

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Hot Topics: 3d Imaging, Samantha K. Hastings Dec 2001

Hot Topics: 3d Imaging, Samantha K. Hastings

Faculty Publications

No abstract provided.

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The Flexible Firm: Capability Management In Network Organizations, C. Annique Un Dec 2001

The Flexible Firm: Capability Management In Network Organizations, C. Annique Un

Faculty Publications

The article reviews the book "The Flexible Firm: Capability Management in Network Organizations," edited by Julian Birkinshaw and Peter Hagström.

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A Confidence Measure For Boundary Detection And Object Selection, William A. Barrett, Eric N. Mortensen Dec 2001

A Confidence Measure For Boundary Detection And Object Selection, William A. Barrett, Eric N. Mortensen

Faculty Publications

We introduce a confidence measure that estimates the assurance that a graph arc (or edge) corresponds to an object boundary in an image. A weighted, planar graph is imposed onto the watershed lines of a gradient magnitude image and the confidence measure is a function of the cost of fixed-length paths emanating from and extending to each end of a graph arc. The confidence measure is applied to automate the detection of object boundaries and thereby reduces (often greatly) the time and effort required for object boundary definition within a user-guided image segmentation environment.

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Accumulation Of A Polyisoprene-Linked Amino Sugar In Polymyxin-Resistant Salmonella Typhimurium And Escherichia Coli: Structural Characterization And Transfer To Lipid A In The Periplasm, M. Stephen Trent, Anthony A. Ribeiro, William T. Doerrler, Shanhua Lin, Robert J. Cotter, Christian R.H. Raetz Nov 2001

Accumulation Of A Polyisoprene-Linked Amino Sugar In Polymyxin-Resistant Salmonella Typhimurium And Escherichia Coli: Structural Characterization And Transfer To Lipid A In The Periplasm, M. Stephen Trent, Anthony A. Ribeiro, William T. Doerrler, Shanhua Lin, Robert J. Cotter, Christian R.H. Raetz

Faculty Publications

Polymyxin-resistant mutants of Escherichia coli and Salmonella typhimurium accumulate a novel minor lipid that can donate 4-amino-4-deoxy-L-arabinose units (L-Ara4N) to lipid A. We now report the purification of this lipid from a pss- pmrAC mutant of E. coli and assign its structure as undecaprenyl phosphate-α-L-Ara4N. Approximately 0.2 mg of homogeneous material was isolated from an 8-liter culture by solvent extraction, followed by chromatography on DEAE-cellulose, C18 reverse phase resin, and silicic acid. Matrix-assisted laser desorption ionization/time of flight mass spectrometry in the negative mode yielded a single species [M - H]- at m/z 977.5, consistent with undecaprenyl phosphate-α-L-Ara4N (Mr = …

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Concentration Gradient, Diffusion, And Flow Through Open Porous Medium Near Percolation Threshold Via Computer Simulations, Ras B. Pandey, J.F. Gettrust, D. Stauffer Nov 2001

Concentration Gradient, Diffusion, And Flow Through Open Porous Medium Near Percolation Threshold Via Computer Simulations, Ras B. Pandey, J.F. Gettrust, D. Stauffer

Faculty Publications

The interacting lattice gas model is used to simulate fluid flow through an open percolating porous medium with the fluid entering at the source-end and leaving from the opposite end. The shape of the steady-state concentration profile and therefore the gradient field depends on the porosity (p). The root mean square (rms) displacements of fluid and its constituents (tracers) show a drift power-law behavior, R∝t in the asymptotic regime (t→∞). The flux current density (j) is found to scale with the porosity according to, j∝(Δp)β with Δp …

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