Open Access. Powered by Scholars. Published by Universities.®

Physical Sciences and Mathematics Commons™

Open Access. Powered by Scholars. Published by Universities.®

2009

Discipline
Institution
Keyword
Publication
Publication Type
File Type

Articles 4051 - 4080 of 7616

Full-Text Articles in Physical Sciences and Mathematics

Assessing Time-Dependent Association Between Scalp Eeg And Muscle Activation: A Functional Random-Effects Model Approach, Xiao-Feng Wang, Qi Yang, Zhaozhi Fan, Chang-Kai Sun, Guang H. Yue Feb 2009

Assessing Time-Dependent Association Between Scalp Eeg And Muscle Activation: A Functional Random-Effects Model Approach, Xiao-Feng Wang, Qi Yang, Zhaozhi Fan, Chang-Kai Sun, Guang H. Yue

Xiaofeng Wang

This study investigates time-dependent associations between source strength estimated from high-density scalp electroencephalogram (EEG) and force of voluntary handgrip contraction at different intensity levels. We first estimate source strength from raw EEG signals collected during voluntary muscle contractions at different levels and then propose a functional random-effects model approach in which both functional fixed effects and functional random-effects are considered for the data. Two estimation procedures for the functional model are discussed. The first estimation procedure is a two-step method which involves no iterations. It can flexibly use different smoothing methods and smoothing parameters. The second estimation procedure benefits from …

Go to article

Exploring Persistence In The Forward Rate Series, Derek Bond Feb 2009

Exploring Persistence In The Forward Rate Series, Derek Bond

Derek Bond

This presentation reviews the use of tests for non-linearity based on semi-parametric estimates of the fractional difference parameter

Go to article

A Comparison Of Turbulent Thermal Convection Between Conditions Of Constant Temperature And Constant Flux, Hans Johnston, Charles R. Doering Feb 2009

A Comparison Of Turbulent Thermal Convection Between Conditions Of Constant Temperature And Constant Flux, Hans Johnston, Charles R. Doering

Hans Johnston

We report the results of high-resolution direct numerical simulations of two-dimensional Rayleigh-Bénard convection for Rayleigh numbers up to Ra=1010 in order to study the influence of temperature boundary conditions on turbulent heat transport. Specifically, we considered the extreme cases of fixed heat flux (where the top and bottom boundaries are poor thermal conductors) and fixed temperature (perfectly conducting boundaries). Both cases display identical heat transport at high Rayleigh numbers fitting a power law Nu≈0.138×Ra0.285 with a scaling exponent indistinguishable from 2/7=0.2857… above Ra=107. The overall flow dynamics for both scenarios, in particular, the time averaged temperature profiles, are also indistinguishable …

Go to article

A Comparison Of Turbulent Thermal Convection Between Conditions Of Constant Temperature And Constant Flux, Hans Johnston, Charles R. Doering Feb 2009

A Comparison Of Turbulent Thermal Convection Between Conditions Of Constant Temperature And Constant Flux, Hans Johnston, Charles R. Doering

Hans Johnston

We report the results of high-resolution direct numerical simulations of two-dimensional Rayleigh-Bénard convection for Rayleigh numbers up to Ra=1010 in order to study the influence of temperature boundary conditions on turbulent heat transport. Specifically, we considered the extreme cases of fixed heat flux (where the top and bottom boundaries are poor thermal conductors) and fixed temperature (perfectly conducting boundaries). Both cases display identical heat transport at high Rayleigh numbers fitting a power law Nu≈0.138×Ra0.285 with a scaling exponent indistinguishable from 2/7=0.2857… above Ra=107. The overall flow dynamics for both scenarios, in particular, the time averaged temperature profiles, are also indistinguishable …

Go to article

The Mechanical Properties Of Individual, Electrospun Fibrinogen Fibers, Christine C. Helms, Corentin Coulais, Manoj Namboothiry, David L. Carroll, Roy R. Hantgan, Martin Guthold Feb 2009

The Mechanical Properties Of Individual, Electrospun Fibrinogen Fibers, Christine C. Helms, Corentin Coulais, Manoj Namboothiry, David L. Carroll, Roy R. Hantgan, Martin Guthold

Physics Faculty Publications

We used a combined atomic force microscope (AFM)/fluorescence microscope technique to study the mechanical properties of individual, electrospun fibrinogen fibers in aqueous buffer. Fibers (average diameter 208 nm) were suspended over 12 μm-wide grooves in a striated, transparent substrate. The AFM, situated above the sample, was used to laterally stretch the fibers and to measure the applied force. The fluorescence microscope, situated below the sample, was used to visualize the stretching process. The fibers could be stretched to 2.3 times their original length before breaking; the breaking stress was 22·106 Pa. We collected incremental stress-strain curves to determine the …

Go to article

Indiana Wildlife Disease News, Volume 4, Issue 1 – February 2009 Feb 2009

Indiana Wildlife Disease News, Volume 4, Issue 1 – February 2009

Indiana Wildlife Disease News

Inside this issue:
• Starvation and malnutrition in deer
• New test at ADDL can test for starvation and/or malnutrition in wildlife
• Avian Influenza symposium at the University of Georgia
• White-nose syndrome update
• WBII Information Node
• New Test at ADDL
• Int. Symposium on AI
• Steve Hooser Bio
• Upcoming Wildlife Disease Conf.
• NBII Information Node
• Midwest Wildlife Disease Update

Go to article

A Combined Routing Method For Ad Hoc Wireless Networks, Soumendra Nanda, Zhenhui Jiang, David Kotz Feb 2009

A Combined Routing Method For Ad Hoc Wireless Networks, Soumendra Nanda, Zhenhui Jiang, David Kotz

Computer Science Technical Reports

Several simulation and real world studies show that certain ad hoc routing protocols perform better than others under specific mobility and traffic patterns. In order to exploit this phenomena, we propose a novel approach to adapt a network to changing conditions; we introduce "a combined routing method" that allows the network to seamlessly swap from one routing protocol to another protocol dynamically, while routing continues uninterrupted. By creating a thin new virtual layer, we enable each node in the ad hoc wireless network notify each other about the protocol swap and we do not make any changes to existing routing …

Go to article

Louisiana Barrier Island Comprehensive Monitoring Program (Bicm) Volume 5: Chenier Plain, South-Central Louisiana And Chandeleur Islands, Habitat Mapping And Change Analysis 1996 To 2005 Part 2: Habitat, Habitat Change, Land Loss, And Mosaic Maps, Sarah Fearnley, Lynn F. Brien, Luis Martinez, Michael Miner, Mark Kulp, Shea Penland Feb 2009

Louisiana Barrier Island Comprehensive Monitoring Program (Bicm) Volume 5: Chenier Plain, South-Central Louisiana And Chandeleur Islands, Habitat Mapping And Change Analysis 1996 To 2005 Part 2: Habitat, Habitat Change, Land Loss, And Mosaic Maps, Sarah Fearnley, Lynn F. Brien, Luis Martinez, Michael Miner, Mark Kulp, Shea Penland

Pontchartrain Institute Reports and Studies

No abstract provided.

Go to article

Louisiana Barrier Island Comprehensive Monitoring Program (Bicm) Volume 5: Chenier Plain, South-Central Louisiana, And Chandeleur Islands, Habitat Mapping And Change Analysis 1996-2005 Part 1: Methods For Habitat Mapping And Change Analysis 1995 To 2005, Sarah Fearnley, Lynn F. Brien, Luis Martinez, Michael Miner, Mark Kulp, Shea Penland Feb 2009

Louisiana Barrier Island Comprehensive Monitoring Program (Bicm) Volume 5: Chenier Plain, South-Central Louisiana, And Chandeleur Islands, Habitat Mapping And Change Analysis 1996-2005 Part 1: Methods For Habitat Mapping And Change Analysis 1995 To 2005, Sarah Fearnley, Lynn F. Brien, Luis Martinez, Michael Miner, Mark Kulp, Shea Penland

Pontchartrain Institute Reports and Studies

No abstract provided.

Go to article

Louisiana Barrier Island Comprehensive Monitoring Program (Bicm) Volume 5: Chenier Plain, South-Central Louisiana, And Chandeleur Islands, Habitat Mapping And Change Analysis 1996 To 2005 Part 4: Results, Sarah Fearnley, Lynn F. Brien, Luis Martinez, Michael Miner, Mark Kulp, Shea Penland Feb 2009

Louisiana Barrier Island Comprehensive Monitoring Program (Bicm) Volume 5: Chenier Plain, South-Central Louisiana, And Chandeleur Islands, Habitat Mapping And Change Analysis 1996 To 2005 Part 4: Results, Sarah Fearnley, Lynn F. Brien, Luis Martinez, Michael Miner, Mark Kulp, Shea Penland

Pontchartrain Institute Reports and Studies

No abstract provided.

Go to article

Louisiana Barrier Island Comprehensive Monitoring Program (Bicm) Volume 5: Chenier Plain, South-Central Louisiana, And Chandeleur Islands, Habitat Mapping And Change Analysis 1996 To 2005 Part 3: Habitat Class Tables, Habitat Change Tables, And Final Statistics 1996 To 2005, Sarah Fearnley, Lynn F. Brien, Luis Martinez, Michael Miner, Mark Kulp, Shea Penland Feb 2009

Louisiana Barrier Island Comprehensive Monitoring Program (Bicm) Volume 5: Chenier Plain, South-Central Louisiana, And Chandeleur Islands, Habitat Mapping And Change Analysis 1996 To 2005 Part 3: Habitat Class Tables, Habitat Change Tables, And Final Statistics 1996 To 2005, Sarah Fearnley, Lynn F. Brien, Luis Martinez, Michael Miner, Mark Kulp, Shea Penland

Pontchartrain Institute Reports and Studies

No abstract provided.

Go to article

Louisiana Barrier Island Comprehensive Monitoring Program (Bicm) Volume 3: Bathymetry And Historical Seafloor Change 1869-2007 Part 3: Southern Chandeleur Islands And Western Chenier Beaches, Bathymetery Maps, Michael Miner, Mark Kulp, Jeffrey P. Motti, Phil Mccarty, Michael Brown, Julie Torres, Luis Martinez, James G. Flocks, Nancy Dewitt, B J. Reynolds, David Twichell, Wayne Baldwin, Bill Danforth, Chuck Worley, Emile Bergeron Feb 2009

Louisiana Barrier Island Comprehensive Monitoring Program (Bicm) Volume 3: Bathymetry And Historical Seafloor Change 1869-2007 Part 3: Southern Chandeleur Islands And Western Chenier Beaches, Bathymetery Maps, Michael Miner, Mark Kulp, Jeffrey P. Motti, Phil Mccarty, Michael Brown, Julie Torres, Luis Martinez, James G. Flocks, Nancy Dewitt, B J. Reynolds, David Twichell, Wayne Baldwin, Bill Danforth, Chuck Worley, Emile Bergeron

Pontchartrain Institute Reports and Studies

No abstract provided.

Go to article

Louisiana Barrier Island Comprehensive Monitoring Program (Bicm) Volume 3: Bathymetry And Historical Seafloor Change 1869-2007 Part 2: South Central Louisiana And Northern Chandeleur Islands, Bathymetry Maps, Michael Miner, Mark Kulp, Jeffrey P. Motti, Dallon Weathers, Phil Mccarty, Michael Brown, Julie Torres, Luis Martinez, James G. Flocks, Nancy Dewitt, Nick Ferina, B J. Reynolds, David Twichell, Wayne Baldwin, Bill Danforth, Chuck Worley, Emile Bergeron Feb 2009

Louisiana Barrier Island Comprehensive Monitoring Program (Bicm) Volume 3: Bathymetry And Historical Seafloor Change 1869-2007 Part 2: South Central Louisiana And Northern Chandeleur Islands, Bathymetry Maps, Michael Miner, Mark Kulp, Jeffrey P. Motti, Dallon Weathers, Phil Mccarty, Michael Brown, Julie Torres, Luis Martinez, James G. Flocks, Nancy Dewitt, Nick Ferina, B J. Reynolds, David Twichell, Wayne Baldwin, Bill Danforth, Chuck Worley, Emile Bergeron

Pontchartrain Institute Reports and Studies

No abstract provided.

Go to article

A Berry-Esseen Theorem For Sample Quantiles Under Weak Dependence, S. N. Lahiri, Shuxia Sun Feb 2009

A Berry-Esseen Theorem For Sample Quantiles Under Weak Dependence, S. N. Lahiri, Shuxia Sun

Mathematics and Statistics Faculty Publications

This paper proves a Berry-Esseen theorem for sample quantiles of strongly-mixing random variables under a polynomial mixing rate. The rate of normal approximation is shown to be O(n-1/2) as n -> infinity, where n denotes the sample size. This result is in sharp contrast to the case of the sample mean of strongly-mixing random variables where the rate O(n-1/2) is not known even under an exponential strong mixing rate. The main result of the paper has applications in finance and econometrics as financial time series important data often are heavy-tailed and quantile …

Go to article

Right Whale Ais Project (Rap): Acoustic Detections In The Boston Approaches, Kurt Schwehr, Lee Alexander Feb 2009

Right Whale Ais Project (Rap): Acoustic Detections In The Boston Approaches, Kurt Schwehr, Lee Alexander

Center for Coastal and Ocean Mapping

No abstract provided.

Go to article

Accumulation Of Dna Damage In Antarctic Mosses: Correlations With Ultraviolet-B Radiation, Temperature And Turf Water Content Vary Amongst Species, J. D. Turnbull, Sharon A. Robinson Feb 2009

Accumulation Of Dna Damage In Antarctic Mosses: Correlations With Ultraviolet-B Radiation, Temperature And Turf Water Content Vary Amongst Species, J. D. Turnbull, Sharon A. Robinson

Faculty of Science - Papers (Archive)

The susceptibility of three East Antarctic moss species to UV-B radiation was examined by measuring accumulation of cyclobutane pyrimidine dimers under natural sunlight during the austral summer season of 2002/03. The 2002/03 season was characterised by unusually low springtime ozone depletion and as such our results likely underestimate the DNA damage possible in a more typical UV-B radiation season. Despite this all three species accumulated significant DNA photoproducts. We also found a positive association between photoproduct accumulation and incident UV-B radiation in the two cosmopolitan species, Bryum pseudotriquetrum and Ceratodon purpureus, with more DNA damage in samples collected early …

Go to article

Trace Forms Over Finite Fields Of Characteristic 2 With Prescribed Invariants, Robert W. Fitzgerald Feb 2009

Trace Forms Over Finite Fields Of Characteristic 2 With Prescribed Invariants, Robert W. Fitzgerald

Articles and Preprints

No abstract provided.

Go to article

Arts And Sciences Newsletter, Volume 13, Issue 2, College Of Arts & Sciences Feb 2009

Arts And Sciences Newsletter, Volume 13, Issue 2, College Of Arts & Sciences

Arts and Sciences Newsletters

No abstract provided.

Go to article

Extensive Phylogenetic Analysis Of A Soil Bacterial Community Illustrates Extreme Taxon Evenness And The Effects Of Amplicon Length, Degree Of Coverage, And Dna Fractionation On Classification And Ecological Parameters, Sergio E. Morales, Theodore F. Cosart, Jesse Johnson, William Holben Feb 2009

Extensive Phylogenetic Analysis Of A Soil Bacterial Community Illustrates Extreme Taxon Evenness And The Effects Of Amplicon Length, Degree Of Coverage, And Dna Fractionation On Classification And Ecological Parameters, Sergio E. Morales, Theodore F. Cosart, Jesse Johnson, William Holben

Computer Science Faculty Publications

To thoroughly investigate the bacterial community diversity present in a single composite sample from an agricultural soil and to examine potential biases resulting from data acquisition and analytical approaches, we examined the effects of percent G+C DNA fractionation, sequence length, and degree of coverage of bacterial diversity on several commonly used ecological parameters (species estimation, diversity indices, and evenness). We also examined variation in phylogenetic placement based on multiple commonly used approaches (ARB alignments and multiple RDP tools). The results demonstrate that this soil bacterial community is highly diverse, with 1,714 operational taxonomic units demonstrated and 3,555 estimated (based on …

Go to article

Ga-Related Photoluminescence Lines In Ga-Doped Zno Grown By Plasma-Assisted Molecular-Beam Epitaxy, Z. Yang, David C. Look, J. L. Liu Feb 2009

Ga-Related Photoluminescence Lines In Ga-Doped Zno Grown By Plasma-Assisted Molecular-Beam Epitaxy, Z. Yang, David C. Look, J. L. Liu

Physics Faculty Publications

Low-temperature photoluminescence (PL) and temperature-dependent Hall-effect (T-Hall) measurements were carried out in undoped and Ga-doped ZnO thin films grown by molecular-beam epitaxy. As the carrier concentration increases from 1.8×1018 to 1.8×1020 cm−3, the dominant PL line at 9 K changes from I1 (3.368–3.371 eV) to IDA (3.317–3.321 eV), and finally to I8 (3.359 eV). The dominance of I1, due to ionized-donor bound excitons, is unexpected in n-type samples but is shown to be consistent with the T-Hall results. We also show that IDA has characteristics of …

Go to article

Northern Fur Seal Rookery Photo Archive: Aerial And Ground-Level Photos, Pribilof Islands, Alaska, 1895 - 2006, Kymberly M. Yano, Jessica Y. Tingg, Charles W. Fowler Feb 2009

Northern Fur Seal Rookery Photo Archive: Aerial And Ground-Level Photos, Pribilof Islands, Alaska, 1895 - 2006, Kymberly M. Yano, Jessica Y. Tingg, Charles W. Fowler

United States Department of Commerce: Staff Publications

The northern fur seal (Callorhinus ursinus) has been the subject of recorded history for more than two centuries (Scheffer et al. 1984, Scott et al. 2006). It has a long history of being commercially harvested for its valuable pelts (Roppel 1984). Recently, however, fur seals are being seen as one of many species reflecting the conditions of their environment, especially an environment increasingly altered by human influence. The Pribilof Islands fur seal population is currently listed as depleted under terms of the U.S. Marine Mammal Protection Act owing to numbers greatly reduced from those observed historically (National Marine …

Go to article

Development And Validation Of An Empirical Free Energy Function For Calculating Protein–Protein Binding Free Energy Surfaces, Joseph Audie Feb 2009

Development And Validation Of An Empirical Free Energy Function For Calculating Protein–Protein Binding Free Energy Surfaces, Joseph Audie

Chemistry & Physics Faculty Publications

In a previous paper, we described a novel empirical free energy function that was used to accurately predict experimental binding free energies for a diverse test set of 31 protein–protein complexes to within ≈1.0 kcal. Here, we extend that work and show that an updated version of the function can be used to (1) accurately predict native binding free energies and (2) rank crystallographic, native-like and non-native binding modes in a physically realistic manner. The modified function includes terms designed to capture some of the unfavorable interactions that characterize non-native interfaces. The function was used to calculate one-dimensional binding free …

Go to article

Virtual Resonant States In Two-Photon Decay Processes: Lower-Order Terms, Subtractions, And Physical Interpretations, Ulrich D. Jentschura Feb 2009

Virtual Resonant States In Two-Photon Decay Processes: Lower-Order Terms, Subtractions, And Physical Interpretations, Ulrich D. Jentschura

Physics Faculty Research & Creative Works

We investigate the two-photon decay rate of a highly excited atomic state which can decay to bound states of lower energy via cascade processes. We show that a naïve treatment of the process, based on the introduction of phenomenological decay rates for the intermediate, resonant states, leads to lower-order terms which need to be subtracted in order to obtain the coherent two-photon correction to the decay rate. The sum of the lower-order terms is exactly equal to the one-photon decay rate of the initial state, provided the naïve two-photon decay rates are summed over all available two-photon channels. A quantum …

Go to article

Haloform Adsorption On Crystalline Copolymer Films Of Vinylidene Fluoride With Trifluoroethylene, Jie Xiao, Carolina C. Ilie, Ning Wu, Keisuke Fukutani, Peter A. Dowben Feb 2009

Haloform Adsorption On Crystalline Copolymer Films Of Vinylidene Fluoride With Trifluoroethylene, Jie Xiao, Carolina C. Ilie, Ning Wu, Keisuke Fukutani, Peter A. Dowben

Peter Dowben Publications

Reversible bromoform adsorption on crystalline polyvinylidene fluoride with 30% of trifluoroethylene, P(VDF–TrFE 70:30) was examined by photoemission and inverse photoemission spectroscopies. The adsorption of bromoform on this polymer surface is associative and reversible. Molecular bromoform adsorption appears to be an activated process at 120 K with enhanced adsorption following the initial adsorption of bromoform. Strong intermolecular interactions are also implicated in the presence of a weak shake off or screened photoemission final state, whose intensity scales with the unscreened photoemission final state.

Go to article

Weighting And Prediction In Sample Surveys, Rod Little Feb 2009

Weighting And Prediction In Sample Surveys, Rod Little

The University of Michigan Department of Biostatistics Working Paper Series

A fundamental technique in survey sampling is to weight included units by the inverse of their probability of inclusion, which may be known (as in the case of sampling weights) or estimated (as in the case of nonresponse weights). The technique is closely associated with the design-based approach to survey inference, with the idea that units in the sample are representing a certain number of units in the population. I discuss weighting from a modeling perspective. Some common misconceptions of weighting will be addressed, including the idea that modelers can ignore the sampling weights, or that weighting necessarily reduces bias …

Go to article

Node Isolation Model And Age-Based Neighbor Selection In Unstructured P2p Networks, Zhongmei Yao, Derek Leonard, Dmitri Loguinov Feb 2009

Node Isolation Model And Age-Based Neighbor Selection In Unstructured P2p Networks, Zhongmei Yao, Derek Leonard, Dmitri Loguinov

Computer Science Faculty Publications

Previous analytical studies of unstructured P2P resilience have assumed exponential user lifetimes and only considered age-independent neighbor replacement. In this paper, we overcome these limitations by introducing a general node-isolation model for heavy-tailed user lifetimes and arbitrary neighbor-selection algorithms. Using this model, we analyze two age-biased neighbor-selection strategies and show that they significantly improve the residual lifetimes of chosen users, which dramatically reduces the probability of user isolation and graph partitioning compared with uniform selection of neighbors. In fact, the second strategy based on random walks on age-proportional graphs demonstrates that, for lifetimes with infinite variance, the system monotonically increases …

Go to article

Bmq-Processor: A High-Performance Border Crossing Event Detection Framework For Large-Scale Monitoring Applications, Jinwon Lee, Seungwoo Kang, Youngki Lee, Sangjeong Lee, Junehwa Song Feb 2009

Bmq-Processor: A High-Performance Border Crossing Event Detection Framework For Large-Scale Monitoring Applications, Jinwon Lee, Seungwoo Kang, Youngki Lee, Sangjeong Lee, Junehwa Song

Research Collection School Of Computing and Information Systems

In this paper, we present BMQ-Processor, a high-performance Border-Crossing Event (BCE) detection framework for large-scale monitoring applications. We first characterize a new query semantics, namely, Border Monitoring Query (BMQ), which is useful for BCE detection in many monitoring applications. It monitors the values of data streams and reports them only when data streams cross the borders of its range. We then propose BMQ-Processor to efficiently handle a large number of BMQs over a high volume of data streams. BMQ-Processor efficiently processes BMQs in a shared and incremental manner. It develops and operates over a novel stateful query index, achieving a …

Go to article

Effect Of Bacterial Adsorption On Low Frequency Electrical Properties Of Clean Quartz Sands And Iron-Oxide Coated Sands, Gamal Z. Abdel Aal, Estella A. Atekwana, Sylvia Radzikowski, Silvia Rossbach Feb 2009

Effect Of Bacterial Adsorption On Low Frequency Electrical Properties Of Clean Quartz Sands And Iron-Oxide Coated Sands, Gamal Z. Abdel Aal, Estella A. Atekwana, Sylvia Radzikowski, Silvia Rossbach

Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works

Low frequency electrical measurements (0.1-1000 Hz) were conducted to investigate the adsorption effect of Pseudomonas aeruginosa cells onto clean quartz sands and iron-oxide coated sands. The clean quartz sands showed a gradual increase in the microbial adsorption to mineral grains, concurrent with an increase of 13% in the imaginary conductivity component (σ″). However, iron-oxide coated sands (20-100% by weight) showed a rapid increase in microbial adsorption with σ″ reaching a maximum of 37% for the 80-100% iron coated sands. No significant changes were observed in the real conductivity component (σ′) due to microbial adsorption. A power law dependency was observed …

Go to article

Changes In Water Levels And Storage In The High Plains Aquifer, Predevelopment To 2007, V. L. Mcguire Feb 2009

Changes In Water Levels And Storage In The High Plains Aquifer, Predevelopment To 2007, V. L. Mcguire

United States Geological Survey: Publications

The High Plains aquifer underlies 111.6 mil¬lion acres (174,000 square miles) in parts of eight States—Colorado, Kansas, Nebraska, New Mexico, Oklahoma, South Dakota, Texas, and Wyoming. The area overlying the High Plains aquifer is one of the primary agricultural regions in the Nation. Water-level declines began in parts of the High Plains aquifer soon after the beginning of substantial irrigation with ground water in the aquifer area. By 1980, water levels in the High Plains aquifer in parts of Texas, Oklahoma, and southwestern Kansas had declined more than 100 feet (Luckey and others, 1981). In response to these water-level declines, …

Go to article

Influence Of The Rare-Earth Element On The Effects Of The Structural And Magnetic Phase Transitions In Cefeaso, Prfeaso And Ndfeaso, Michael A. Mcguire, Raphäel P. Hermann, Athena S. Sefat, Brian C. Sales, Rongying Jin, David Mandrus, Fernande Grandjean, Gary J. Long Feb 2009

Influence Of The Rare-Earth Element On The Effects Of The Structural And Magnetic Phase Transitions In Cefeaso, Prfeaso And Ndfeaso, Michael A. Mcguire, Raphäel P. Hermann, Athena S. Sefat, Brian C. Sales, Rongying Jin, David Mandrus, Fernande Grandjean, Gary J. Long

Chemistry Faculty Research & Creative Works

We present results of transport and magnetic properties and heat capacity measurements on polycrystalline CeFeAsO, PrFeAsO and NdFeAsO. These materials undergo structural phase transitions, spin density wave-like magnetic ordering of small moments on iron and antiferromagnetic ordering of rare-earth moments. The temperature dependence of the electrical resistivity, Seebeck coefficient, thermal conductivity, Hall coefficient and magnetoresistance are reported. The magnetic behavior of the materials have been investigated using Mössbauer spectroscopy and magnetization measurements. Transport and magnetic properties are affected strongly by the structural and magnetic transitions, suggesting significant changes in the band structure and/or carrier mobilities occur, and phonon-phonon scattering is …

Go to article

First Prev Next Last