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2003

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Articles 3181 - 3210 of 3345

Full-Text Articles in Physical Sciences and Mathematics

Long-Lived Pluvial Episodes During Deposition Of The Navajo Sandstone, David B. Loope, Clinton M. Rowe Jan 2003

Long-Lived Pluvial Episodes During Deposition Of The Navajo Sandstone, David B. Loope, Clinton M. Rowe

Department of Earth and Atmospheric Sciences: Faculty Publications

The Navajo Sandstone of the American Southwest was deposited at approximately 190 Ma in a giant, subtropical dune field near the western margin of Pangea. From this unit, we report thick intervals of dune cross-strata that were churned by insects and trampled by reptiles. Although dunes continued to migrate freely, the distribution of trace fossils shows that plant life in wet interdune areas sustained high levels of animal activity on the dunes for many thousands of years. We interpret this suite of structures as the record of a pluvial episode climatologically similar to the period of “greening” in the Sahara …

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Where Are The Women Geoscience Professors?, Mary Anne Holmes, Suzanne O'Connel Jan 2003

Where Are The Women Geoscience Professors?, Mary Anne Holmes, Suzanne O'Connel

Department of Earth and Atmospheric Sciences: Faculty Publications

Compiles an extensive set of data on the status of women in the geosciences, identifying successful strategies for increasing diversity as well as obstacles that hinder efforts. The lessons learned and best practices that arise from this report will help geoscientists continue to increase the gender diversity of their community. Some of these lessons also provide insight into ways to improve the racial and ethnic diversity of the geosciences.

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2mass J0516288+260738: Discovery Of The First Eclipsing Late K + Brown Dwarf Binary System?, Sonja L. Schüh, Matt A. Wood Jan 2003

2mass J0516288+260738: Discovery Of The First Eclipsing Late K + Brown Dwarf Binary System?, Sonja L. Schüh, Matt A. Wood

Aerospace, Physics, and Space Science Faculty Publications

We report the discovery of a new eclipsing system less than one arcminute south of the pulsating DB white dwarf KUV 05134+2605 . The object could be identified with the point source 2MASS J0516288+260738 published by the Two Micron All Sky Survey. We present and discuss the first light curves as well as some additional colour and spectral information. The eclipse period of the system is 1.29 d, and, assuming this to be identical to the orbital period, the best light curve solution yields a mass ratio of m₂/m₁=0.11, a radius ratio of r₂/r₁ ≈ 1 and an inclination of …

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The Everchanging Pulsating White Dwarf Gd358, Souza Oliveira Kepler, Matt A. Wood, Nicole M. Silvestri, Thomas J. Ahrens Jan 2003

The Everchanging Pulsating White Dwarf Gd358, Souza Oliveira Kepler, Matt A. Wood, Nicole M. Silvestri, Thomas J. Ahrens

Aerospace, Physics, and Space Science Faculty Publications

We report 323 hours of nearly uninterrupted time series photometric observations of the DBV star GD 358 acquired with the Whole Earth Telescope (WET) during May 23rd to June 8th, 2000. We acquired more than 232 000 independent measurements. We also report on 48 hours of time-series photometric observations in Aug 1996. We detected the non-radial g-modes consistent with degree ℓ = 1 and radial order 8 to 20 and their linear combinations up to 6th order. We also detect, for the first time, a high amplitude ℓ = 2 mode, with a period of 796 s. In the 2000 …

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Multisite Observations Of The Pms Δ Scuti Star V351 Ori, Vincenzo Ripepi, T D. Oswalt, Mark J. Rudkin, Kyle B. Johnston Jan 2003

Multisite Observations Of The Pms Δ Scuti Star V351 Ori, Vincenzo Ripepi, T D. Oswalt, Mark J. Rudkin, Kyle B. Johnston

Aerospace, Physics, and Space Science Faculty Publications

We present the results of multisite observations spanning two years on the pre-main-sequence (PMS) star V351 Ori. A total of around 180 hours of observations over 29 nights have been collected, allowing us to measure five different periodicities, most likely related to the δ Scuti variability of V351 Ori. Comparison with the predictions of linear nonadiabatic radial pulsation models put stringent constraints on the stellar parameters and indicate that the distance to V351 Ori is intermediate between the lower limit measured by Hipparcos (210 pc) and that of the Orion Nebula (450 pc). However, radial pulsation models are unable to …

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Ulysses Cospin Observations Of Cosmic Rays And Solar Energetic Particles From The South Pole To The North Pole Of The Sun During Solar Maximum, Robert Bruce Mckibben, Ming Zhang Jan 2003

Ulysses Cospin Observations Of Cosmic Rays And Solar Energetic Particles From The South Pole To The North Pole Of The Sun During Solar Maximum, Robert Bruce Mckibben, Ming Zhang

Aerospace, Physics, and Space Science Faculty Publications

In 2000–2001 Ulysses passed from the south to the north polar regions of the Sun in the inner heliosphere, providing a snapshot of the latitudinal structure of cosmic ray modulation and solar energetic particle populations during a period near solar maximum. Observations from the COSPIN suite of energetic charged particle telescopes show that latitude variations in the cosmic ray intensity in the inner heliosphere are nearly non-existent near solar maximum, whereas small but clear latitude gradients were observed during the similar phase of Ulysses’ orbit near the 1994–95 solar minimum. At proton energies above ∼10 MeV and extending up to …

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Absorption Spectroscopy Of Colored Dissolved Organic Carbon In Georgia (Usa) Rivers: The Impact Of Molecular Size Distribution, Yosef Z. Yacobi, James J. Alberts, Monika Takacs, Michelle Mcelvaine Jan 2003

Absorption Spectroscopy Of Colored Dissolved Organic Carbon In Georgia (Usa) Rivers: The Impact Of Molecular Size Distribution, Yosef Z. Yacobi, James J. Alberts, Monika Takacs, Michelle Mcelvaine

Ocean Engineering and Marine Sciences Faculty Publications

Dissolved organic carbon (DOC) was collected in six rivers that transect the coastal plain of Georgia in July 1999 and February 2000. DOC concentrations ranged from 4.9 to 40.7 g m-3 and from 7.1 to 40.5 g m-3, respectively. The absorption coefficient at 440 nm was highly correlated with DOC concentration, suggesting that the optical parameter may be utilized for rapid estimation of DOC in these waters. The isolated DOC was separated into fractions of operationally defined molecular size, using an ultrafiltration technique that yielded three fractions: <10 ("small"), 10-50 ("medium") and >50 ("large") kilodalton. The smallest fraction was the most abundant (>50%) in …

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The Ceres-Rice Model-Based Estimates Of Potential Monsoon Season Rainfed Rice Productivity In Bangladesh, Rezaul Mahmood, Mark Meo, David R. Legates, Mark L. Morrissey Jan 2003

The Ceres-Rice Model-Based Estimates Of Potential Monsoon Season Rainfed Rice Productivity In Bangladesh, Rezaul Mahmood, Mark Meo, David R. Legates, Mark L. Morrissey

School of Natural Resources: Faculty Publications

Agricultural practices in Bangladesh are largely dependent on the monsoonal rainfall. Historically, Bangladesh often experiences severe droughts and floods during the monsoon months, with significant crop losses during both extreme conditions. This article provides a quantitative assessment of potential monsoon-season aman rice for four transplanting dates: 1 June, 1 July, 15 July, and 15 August. A crop-growth simulation model, the CERES-Rice, is applied to sixteen locations representing major rice-growing regions of Bangladesh to determine baseline yield estimates for four transplanting dates. The applications were conducted for 1975 through 1987. Average potential yield in Bangladesh is 6,907, 5,039, 3,637, and 1,762 …

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Integral Transforms Of Functionals In L2(C0[0, T]), Byoung Soo Kim, David Skough Jan 2003

Integral Transforms Of Functionals In L2(C0[0, T]), Byoung Soo Kim, David Skough

Department of Mathematics: Faculty Publications

In this paper we give a necessary and sufficient condition that a functional F(x) in L2(C0[0, T]) has an integral transform Fα,βF(x) which also belongs to L2(C0[0, T]).

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A Multilevel Discontinuous Galerkin Method, Jay Gopalakrishnan, Guido Kanschat Jan 2003

A Multilevel Discontinuous Galerkin Method, Jay Gopalakrishnan, Guido Kanschat

Mathematics and Statistics Faculty Publications and Presentations

A variable V-cycle preconditioner for an interior penalty finite element discretization for elliptic problems is presented. An analysis under a mild regularity assumption shows that the preconditioner is uniform. The interior penalty method is then combined with a discontinuous Galerkin scheme to arrive at a discretization scheme for an advection-diffusion problem, for which an error estimate is proved. A multigrid algorithm for this method is presented, and numerical experiments indicating its robustness with respect to diffusion coefficient are reported.

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A Schwarz Preconditioner For A Hybridized Mixed Method, Jay Gopalakrishnan Jan 2003

A Schwarz Preconditioner For A Hybridized Mixed Method, Jay Gopalakrishnan

Mathematics and Statistics Faculty Publications and Presentations

In this paper, we provide a Schwarz preconditioner for the hybridized versions of the Raviart-Thomas and Brezzi-Douglas-Marini mixed methods. The preconditioner is for the linear equation for Lagrange multipliers arrived at by eliminating the ux as well as the primal variable. We also prove a condition number estimate for this equation when no preconditioner is used. Although preconditioners for the lowest order case of the Raviart-Thomas method have been constructed previously by exploiting its connection with a nonconforming method, our approach is different, in that we use a new variational characterization of the Lagrange multiplier equation. This allows us to …

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Monte Carlo Analysis Of Gan-Based Gunn Oscillators For Microwave Power Generation, R. P. Joshi, V. Sridhara, P. Shah, R. D. Del Rosario Jan 2003

Monte Carlo Analysis Of Gan-Based Gunn Oscillators For Microwave Power Generation, R. P. Joshi, V. Sridhara, P. Shah, R. D. Del Rosario

Electrical & Computer Engineering Faculty Publications

Monte Carlo studies of transferred electron oscillators based on bulk wurtzite GaN are presented. Two structures have been examined: (i) devices with the conventional single notch structure, and (ii) repetitive structures with serial segments to fashion a "multiple domain" device. Wurtzite material has been chosen because of the higher drift velocity and because analytical expressions for the band structure have recently become available. Performance parameters of interest such as the operating frequency, output power, and conversion efficiency are calculated. Variations due to changes in temperature, biasing voltage, and device length are also included. It is shown that multidomain Gunn diodes …

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Neuro Emission Controller For Minimizing Cyclic Dispersion In Spark Ignition Engines, Pingan He, Jagannathan Sarangapani Jan 2003

Neuro Emission Controller For Minimizing Cyclic Dispersion In Spark Ignition Engines, Pingan He, Jagannathan Sarangapani

Electrical and Computer Engineering Faculty Research & Creative Works

A novel neural network (NN) controller is developed to control spark ignition (SI) engines at extreme lean conditions. The purpose of neurocontroller is to reduce the cyclic dispersion at lean operation even when the engine dynamics are unknown. The stability analysis of the closed-loop control system is given and the boundedness of all signals is ensured. Results demonstrate that the cyclic dispersion is reduced significantly using the proposed controller. The neuro controller can also be extended to minimize engine emissions with high EGR levels, where similar complex cyclic dynamics are observed. Further, the proposed approach can be applied to control …

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Rate-Based End-To-End Congestion Control Of Multimedia Traffic In Packet Switched Networks, Mingsheng Peng, S. R. Subramanya, Jagannathan Sarangapani Jan 2003

Rate-Based End-To-End Congestion Control Of Multimedia Traffic In Packet Switched Networks, Mingsheng Peng, S. R. Subramanya, Jagannathan Sarangapani

Electrical and Computer Engineering Faculty Research & Creative Works

This paper proposes an explicit rate-based end-to-end congestion control mechanism to alleviate congestion of multimedia traffic in packet switched networks such as the Internet. The congestion is controlled by adjusting the transmission rates of the sources in response to the feedback information from destination such as the buffer occupancy, packet arrival rate and service rate at the outgoing link, so that a desired quality of service (QoS) can be met. The QoS is defined in terms of packet loss ratio, transmission delay, power, and network utilization. Comparison studies demonstrate the effectiveness of the proposed scheme over New-Reno TCP (a variant …

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Study Of A Growth Instability Of Γ-In[Sub 2]Se[Sub 3], C. Amory, J. C. Bernede, S. Marsillac Jan 2003

Study Of A Growth Instability Of Γ-In[Sub 2]Se[Sub 3], C. Amory, J. C. Bernede, S. Marsillac

Electrical & Computer Engineering Faculty Publications

γ-In[sub 2]Se[sub 3] thin film are deposited for various substrate temperatures in the range of 523–673 K. This study shows that at 573 and 673 K the thin films are well crystallized with grains aligned along the c axis. Between these temperatures, a domain of instability appears where the γ-In[sub 2]Se[sub 3] thin films have a randomly orientation and the c-lattice parameter increases. The presence of the metastable phase κ-In[sub 2]Se[sub 3], during the growth, can explain the existence of this domain of instability. The insertion of Zn during the preparation process allows us to stabilize the phase κ at …

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Electron Bernstein Wave-X-O Mode Conversion And Electron Cyclotron Emission In Mast, Josef Preinhaelter, Pavol Pavlo, Vladimir Shevchenko, Martin Valovic, Linda L. Vahala, George Vahala Jan 2003

Electron Bernstein Wave-X-O Mode Conversion And Electron Cyclotron Emission In Mast, Josef Preinhaelter, Pavol Pavlo, Vladimir Shevchenko, Martin Valovic, Linda L. Vahala, George Vahala

Electrical & Computer Engineering Faculty Publications

Electron cyclotron emission (ECE) from overdense plasmas can only occur due to electron Bernstein waves (EBW) mode converting near the upper hybrid region to an electromagnetic wave. Experimental data of ECE observations on MAST are studied and compared with EBW-X-O mode conversion modeling results.

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Million City Traveling Salesman Problem Solution By Divide And Conquer Clustering With Adaptive Resonance Neural Networks, Samuel A. Mulder, Donald C. Wunsch Jan 2003

Million City Traveling Salesman Problem Solution By Divide And Conquer Clustering With Adaptive Resonance Neural Networks, Samuel A. Mulder, Donald C. Wunsch

Electrical and Computer Engineering Faculty Research & Creative Works

The Traveling Salesman Problem (TSP) is a very hard optimization problem in the field of operations research. It has been shown to be NP-complete and is an often-used benchmark for new optimization techniques. One of the main challenges with this problem is that standard, non-AI heuristic approaches such as the Lin-Kernighan algorithm (LK) and the chained LK variant are currently very effective and in wide use for the common fully connected, Euclidean variant that is considered here. This paper presents an algorithm that uses adaptive resonance theory (ART) in combination with a variation of the Lin-Kernighan local optimization algorithm to …

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Experimental Investigation Of Elemental Incorporation In The Otoliths Of Larval And Juvenile Fish: Implications For Use As Environmental Recorders, Gretchen Bath Martin Jan 2003

Experimental Investigation Of Elemental Incorporation In The Otoliths Of Larval And Juvenile Fish: Implications For Use As Environmental Recorders, Gretchen Bath Martin

Biological Sciences Theses & Dissertations

Innovative techniques for discerning fish stocks, identifying nursery habitats, locating spawning sites, tracing larval transport pathways, and quantifying the degree of population connectivity are required to meet the goals of sustainable management of marine capture fisheries. One of the most promising techniques is the use of elemental signatures in fish otoliths (ear stones), which record valuable life history data and serve as the link between fish and their environment. To validate the assumption that otolith elemental composition is a function of water elemental concentrations, and to address the possible effects of external variables such as temperature and salinity, the composition …

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Recognizing Toxic Species In Aquatic Habitats: A Potential Concern In Lake Management, Mikolaj Kokocinski, Harold G. Marshall Jan 2003

Recognizing Toxic Species In Aquatic Habitats: A Potential Concern In Lake Management, Mikolaj Kokocinski, Harold G. Marshall

Biological Sciences Faculty Publications

The importance of distinguishing toxic and non-toxic algal species is becoming a more common problem for management decisions associated with various freshwater and estuarine habitats. An example is given where two dinoflagellates, originally unidentified as closely resembling the toxin producing Pfiesteria spp., have been compared to these species. In order to clarify any relationship to Pfiesteria spp., scanning electron microscopy was used to determine the plate tabulation patterns of these dinoflagellates and make comparisons to the tabulation present in Pfiesteria spp. The results indicated significant differences in the plate tabulations of these taxa to distinguish them from Pfiesteria …

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Extracellular Enzyme Activity And Uptake Of Carbon And Nitrogen Along An Estuarine Salinity And Nutrient Gradient, Margaret R. Mulholland, Cindy Lee, Patricia M. Gilbert Jan 2003

Extracellular Enzyme Activity And Uptake Of Carbon And Nitrogen Along An Estuarine Salinity And Nutrient Gradient, Margaret R. Mulholland, Cindy Lee, Patricia M. Gilbert

OES Faculty Publications

Amino acid oxidation (AAO) and peptide hydrolysis (PH) are processes affecting the recycling of organic material and nutrients. We compared extracellular AAO and PH rates to C and N uptake rates along estuarine gradients of salinity, nutrients and productivity in the Pocomoke River, a subestuary of the Chesapeake Bay. This estuary is seasonally depleted in inorganic N, and rich in dissolved organic material (DOM) throughout the year. AAO, PH, and N uptake rates measured in 1999 and 2000 were not limited to particular size fractions measured, or to auto- or heterotrophic groups of organisms. At a station near the turbidity …

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Sources Of Sediment Found In Sea Ice From The Western Arctic Ocean, New Insights Into Processes Of Entrainment And Drift Patterns, Dennis A. Darby Jan 2003

Sources Of Sediment Found In Sea Ice From The Western Arctic Ocean, New Insights Into Processes Of Entrainment And Drift Patterns, Dennis A. Darby

OES Faculty Publications

The geochemical fingerprint of entrained Fe oxide mineral grains in Arctic Ocean sea ice is used to determine precise sources of this sediment. This approach substantiates the importance of the Laptev Sea as a source of sea ice and even the presence of Russian ice in the Beaufort Sea off Alaska. Fe oxide grains from the Laptev Sea were found in floes in the Beaufort Sea, Chukchi Borderland, and central Arctic Ocean, demonstrating the importance of sea ice in distributing itself throughout the Arctic Ocean and the potential of transporting sediment from Russian rivers to North American shelves. Banks Island …

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Effects Of Epiphyte Load On Optical Properties And Photosynthetic Potential Of The Seagrasses Thalassia Testudinum Banks Ex König And Zostera Marina L, Lisa A. Drake, Fred C. Dobbs, Richard C. Zimmerman Jan 2003

Effects Of Epiphyte Load On Optical Properties And Photosynthetic Potential Of The Seagrasses Thalassia Testudinum Banks Ex König And Zostera Marina L, Lisa A. Drake, Fred C. Dobbs, Richard C. Zimmerman

OES Faculty Publications

The biomass and optical properties of seagrass leaf epiphytes were measured to evaluate their potential impact on the photosynthetic performance of the seagrasses Thalassia testudinum Banks ex König (turtlegrass) and Zostera marina L. (eelgrass). Turtlegrass was obtained from oligotrophic waters near Lee Stocking Island, Bahamas; eelgrass was collected from a eutrophic environment in Monterey Bay, California. Leaf–epiphyte loads were characterized visually and quantified using measurements of their phospholipid biomass. Light absorption and reflectance of the intact epiphyte layer were determined spectrophotometrically. Turtlegrass epiphytes from the oligotrophic site absorbed a maximum of 36% of incident light in peak chlorophyll absorption …

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Urer, The Transcriptional Activator Of The Proteus Mirabilis Urease Gene Cluster, Is Required For Urease Activity And Virulence In Experimental Urinary Tract Infections, Jonathan D. Dattelbaum, C. Virginia Lockatell, David E. Johnson, Harry L.T. Mobley Jan 2003

Urer, The Transcriptional Activator Of The Proteus Mirabilis Urease Gene Cluster, Is Required For Urease Activity And Virulence In Experimental Urinary Tract Infections, Jonathan D. Dattelbaum, C. Virginia Lockatell, David E. Johnson, Harry L.T. Mobley

Chemistry Faculty Publications

Proteus mirabilis, a cause of complicated urinary tract infection, produces urease, an essential virulence factor for this species. UreR, a member of the AraC/XylS family of transcriptional regulators, positively activates expression of the ure gene cluster in the presence of urea. To specifically evaluate the contribution of UreR to urease activity and virulence in the urinary tract, a ureR mutation was introduced into P. mirabilis HI4320 by homologous recombination. The isogenic ureR::aphA mutant, deficient in UreR production, lacked measurable urease activity. Expression was not detected in the UreR-deficient strain by Western blotting with monoclonal antibodies raised against UreD. Urease …

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Simulations Of Quantized Double Layer Charging Voltammetry Of Poly Disperse And Mono-Disperse Monolayer Protected Clusters, Deon T. Miles, Michael C. Leopold, Jocelyn F. Hicks, Royce W. Murray Jan 2003

Simulations Of Quantized Double Layer Charging Voltammetry Of Poly Disperse And Mono-Disperse Monolayer Protected Clusters, Deon T. Miles, Michael C. Leopold, Jocelyn F. Hicks, Royce W. Murray

Chemistry Faculty Publications

This paper describes simulated differential pulse voltammetry (DPV) of quantized double-layer charging (QDL) in poly-disperse monolayer-protected gold cluster (MPC) solutions. The simulation accounts for the voltage spacing between QDL peaks with a concentric sphere capacitor model, in which core sizes, and the relative proportion of each size, are input using transmission electron microscopy (TEM) data. MPC diffusion coefficients are estimated from hydrodynamic radii, and peaks are broadened to account for DPV pulse height effects. The smallest MPCs are omitted from the simulation because electrochemical HOMO/LUMO gap information is uncertain. The largest ones are shown to produce the underlying DPV current …

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Near-Real-Time Measurement Of Sea-Salt Aerosol During The Seas Campaign: Comparison Of Emission-Based Sodium Detection With An Aerosol Volatility Technique, P. Campuzano-Jost, Catherine D. Clark, H. Maring, D. S. Covert, S. Howell, V. Kapustin, K. A. Clarke, E. S. Saltzman, A. J. Hynes Jan 2003

Near-Real-Time Measurement Of Sea-Salt Aerosol During The Seas Campaign: Comparison Of Emission-Based Sodium Detection With An Aerosol Volatility Technique, P. Campuzano-Jost, Catherine D. Clark, H. Maring, D. S. Covert, S. Howell, V. Kapustin, K. A. Clarke, E. S. Saltzman, A. J. Hynes

Biology, Chemistry, and Environmental Sciences Faculty Articles and Research

The first deployment of an emission-based aerosol sodium detector (ASD), designed to chemically characterize marine aerosols on a near-real-time basis, is reported. Deployment occurred as part of the Shoreline Environment Aerosol Study ( SEAS) from 16 April to 1 May 2000 at Bellows Air Force Base on the east side of Oahu, where the University of Hawaii's Department of Oceanography maintains a tower for aerosol measurements. The instrument was operated in size-unsegregated mode and measurements were made that included two extended continuous sampling periods, each of which lasted for 24 h. During this time, the ASD was compared with measurements …

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An Open Singularity-Free Cosmological Model With Inflation, Koray Karaca, Selçuk Bayin Jan 2003

An Open Singularity-Free Cosmological Model With Inflation, Koray Karaca, Selçuk Bayin

Turkish Journal of Physics

In the light of recent observations which point to an open universe (\Omega _{0} < 1), we reconsider singularity-free models, originally constructed for closed universes. Our model starts from a nonsingular state called prematter, governed by an inflationary equation of state P=( \gamma _{p}-1) \rho , where \gamma _{p} is a small positive parameter representing the initial vacuum dominance of the universe. Unlike the closed models, an open universe cannot be initially static hence, starts with an initial expansion rate represented by the initial value of the Hubble constant H(0). Therefore, our model is a two-parameter universe model (\gamma _{p},H(0)). During the prematter phase, due to the unusual characteristic of the equation of state, the universe heats up even though it expands. When the temperature in the universe reaches the Planck temperature T_{pl}, which is taken as the maximum attainable physical temperature, a first order phase transition carries the universe into the radiation era. Then the universe starts to behave as predicted in the standard model. The model proposed in this work predicts a value between 60 and 80 Km\cdot \sec ^{-1}\cdot Mpc^{-1} for the present value of the Hubble constant H_{0}, and the predicted value of \Omega _{0} lies between 0.3 and 0.6. Comparing the predictions of this model for the present properties of the universe with the recent observational results, we argue that the model constructed in this paper could be used as a realistic universe model.

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Inflation In A Flat Universe, Koray Karaca, Selçuk Bayin Jan 2003

Inflation In A Flat Universe, Koray Karaca, Selçuk Bayin

Turkish Journal of Physics

We started the evolution of a flat universe from a nonsingular state called prematter which is governed by an inflationary equation of state P=(\gamma -1)\rho , where \gamma represents the initial vacuum dominance of the universe. The evolution of the universe-except in the prematter era-is affected neither by the initial vacuum dominance nor by the initial expansion rate of the universe. On the other hand, present properties of the universe, such as the Hubble constant, age and density, are sensitive to the value of the temperature at the decoupling ( T_{m}) . Over a range between 3\cdot 10^{4}and 5\cdot 10^{4} …

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The Motion Of Cosmic Strings In The Schwarzschild Black Hole Spacetime, Sergey Roshchupkin, Yevgeniy Zinchenko Jan 2003

The Motion Of Cosmic Strings In The Schwarzschild Black Hole Spacetime, Sergey Roshchupkin, Yevgeniy Zinchenko

Turkish Journal of Physics

We study the classical dynamics of a bosonic string in the Schwarzschild spacetime using a perturbative scheme which is based on the assumption of a small value of a rescaled string tension parameter. The proposed approximation selfconsistently describes the string dynamics on the scale of large values for the worldsheet time in a fixed gauge.

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Multiply Charged Ions Produced After Deexcitation Processes For Important Elements In Astrophysics, Adel M. El-Shime, Adel A. Ghoneim, Yehia A. Lotfy Jan 2003

Multiply Charged Ions Produced After Deexcitation Processes For Important Elements In Astrophysics, Adel M. El-Shime, Adel A. Ghoneim, Yehia A. Lotfy

Turkish Journal of Physics

Selection random number method (Monte Carlo technique) is used to calculate the ion charge state distributions (CSD) and mean ion charge \bar{q} after K-, L_{I}, L_{III}- and M_{I}- shell ionization in neutral atoms and their q-fold ground state ions (q = 0 to 10) from C to Fe elements. Atomic data for radiative and non-radiative transitions and electron shake off process, which is used in the modeling vacancy cascade program, are computed with relativistic wave functions. Use of atomic data is important to accurately model vacancy cascades. To enhance the agreement between calculated and experimental values, the electron shake-off processes …

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Modeling Of Infrared Radiation For All Skies From Easy-To-Measure Meteorological Parameters At Tropical Location: Ilorin, Nigeria, Sunday O. Udo Jan 2003

Modeling Of Infrared Radiation For All Skies From Easy-To-Measure Meteorological Parameters At Tropical Location: Ilorin, Nigeria, Sunday O. Udo

Turkish Journal of Physics

Downward infrared radiation (L) and some easy-to-measure meteorological variables (relative humidity, clearness index and vapour pressure) were collected for a period of two years at Ilorin. Downward infrared radiation data were obtained using a pyrgeometer (Eppley-PIR), while data for relative humidity and vapour pressure for Ilorin were obtained from the Nigerian Meteorological Services, Lagos. Based on these data, using statistical regression analysis, empirical models (seven one-variable and nine two-variable) for predicting daily mean infrared radiation, from both clear and cloudy skies, were tested. Their advantage is that they only make use of easily measured meteorological parameters. The best one-variable model …

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