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Lev B, Chennath M, Cranfield CG, Cornelius F, Allen TW, Clarke RJ. Involvement of the alpha-subunit N-terminus in the mechanism of the Na +,K +-ATPase. Biochim Biophys Acta Mol Cell Res 2023; 1870:119539. [PMID: 37479188 DOI: 10.1016/j.bbamcr.2023.119539] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/11/2023] [Revised: 06/26/2023] [Accepted: 07/10/2023] [Indexed: 07/23/2023]
Abstract
Previous studies have shown that cytoplasmic K+ release and the associated E2 → E1 conformational change of the Na+,K+-ATPase is a major rate-determining step of the enzyme's ion pumping cycle and hence a prime site of acute regulatory intervention. From the ionic strength dependence of the enzyme's distribution between the E2 and E1 states, it has also been found that E2 is stabilized by an electrostatic attraction. Any disruption of this electrostatic attraction would, thus, have profound effects on the rate of ion pumping. The aim of this paper is to identify the location of this interaction. Using enhanced-sampling molecular dynamics simulations with a predicted N-terminal structure added to the X-ray crystal structure of the Na+,K+-ATPase, a previously postulated salt bridge between Lys32 and Glu233 (rat sequence numbering) of the enzyme's α-subunit can be excluded. The residues never approach closely enough to form a salt bridge. In contrast, strong interactions with anionic lipid head groups were seen. To investigate the possibility of a protein-lipid interaction experimentally, the surface charge density of Na+,K+-ATPase-containing membrane fragments was estimated from zeta potential measurements to be 0.019 (± 0.001) C m-2. This is in good agreement with the charge density previously determined to be responsible for stabilization of the E2 state of 0.023 (± 0.009) C m-2 and the membrane charge density estimated here from published electron-microscopic images of 0.018C m-2. The results are, therefore, consistent with an interaction of the Na+,K+-ATPase α-subunit N-terminus with negatively-charged lipid head groups of the neighbouring cytoplasmic membrane surface as the origin of the electrostatic interaction stabilising the E2 state.
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Affiliation(s)
- B Lev
- School of Science, RMIT University, Melbourne, Vic, 3001, Australia
| | - M Chennath
- School of Life Sciences, University of Technology Sydney, Ultimo, NSW 2007, Australia
| | - C G Cranfield
- School of Life Sciences, University of Technology Sydney, Ultimo, NSW 2007, Australia
| | - F Cornelius
- Department of Biomedicine, University of Aarhus, DK-8000 Aarhus, C, Denmark
| | - T W Allen
- School of Science, RMIT University, Melbourne, Vic, 3001, Australia
| | - R J Clarke
- School of Chemistry, University of Sydney, Sydney, NSW 2006, Australia; The University of Sydney Nano Institute, Sydney, NSW 2006, Australia.
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Jimenez Madrid AM, Allen TW, Vargas A, Connor A, Wilkerson TH. First Report of Curvularia Leaf Spot of Field Corn, Caused by Curvularia lunata, in Mississippi. Plant Dis 2022; 106:PDIS10212189PDN. [PMID: 34978873 DOI: 10.1094/pdis-10-21-2189-pdn] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Affiliation(s)
| | - T W Allen
- Delta Research and Extension Center, Stoneville, MS 38776
| | - A Vargas
- Delta Research and Extension Center, Stoneville, MS 38776
| | - A Connor
- Delta Research and Extension Center, Stoneville, MS 38776
| | - T H Wilkerson
- Delta Research and Extension Center, Stoneville, MS 38776
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Mehl HL, Dufault NS, Allen TW, Hagan AK, Price P, Kemerait RC, Kelly H, Mulvaney MJ, Nichols RL. Multiyear Regional Evaluation of Foliar Fungicide Applications for Cotton Target Spot Management in the Southeastern United States. Plant Dis 2020; 104:438-447. [PMID: 31821101 DOI: 10.1094/pdis-06-19-1150-re] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Fungicide programs for managing target spot of cotton caused by Corynespora cassiicola were evaluated over 15 site-years in the southeastern United States between 2014 and 2016. Two cultivars, hypothesized to vary in target spot susceptibility, PhytoGen 499WRF (PHY499) and Deltapine 1137B2RF (DPL1137), and four fungicides (azoxystrobin, flutriafol, pyraclostrobin, pyraclostrobin + fluxapyroxad) plus nontreated control, were compared. Fungicide programs consisted of 1) a single application at first flower or disease onset and 2) the first application followed by a second 14 days later. Treatments were applied in a factorial, randomized complete block design. Target spot onset and severity varied among site-years. Except when severity was low, target spot-associated defoliation was greater on PHY499 than on DP1137. Fungicides delayed disease development and defoliation, but application number had little impact. Based on a meta-analysis of 15 site-years, pyraclostrobin-based applications resulted in a 4 to 6% yield preservation, and yield preservation was greater at site-years with early disease onset and >40% target spot associated defoliation. Results suggest a single well-timed application of a pyraclostrobin-based fungicide reduces defoliation and protects cotton yield at locations with high target spot severity. Additional research is needed to identify risk factors for target spot-associated yield losses in cotton production systems.
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Affiliation(s)
- H L Mehl
- Virginia Tech Tidewater Agricultural Research and Extension Center, Suffolk, VA 23437
| | - N S Dufault
- Department of Plant Pathology, University of Florida, Gainesville, FL 32611
| | - T W Allen
- Mississippi State University, Delta Research and Extension Center, Stoneville, MS 38776
| | - A K Hagan
- Department of Entomology and Plant Pathology, Auburn University, AL 36849
| | - P Price
- Macon Ridge Research Station, Louisiana State University Agricultural Center, Winnsboro, LA 71295
| | - R C Kemerait
- Department of Plant Pathology, University of Georgia, Tifton, GA 31793
| | - H Kelly
- Department of Entomology and Plant Pathology, The University of Tennessee, Jackson, TN 37996
| | - M J Mulvaney
- Agronomy Department, University of Florida, Institute of Food and Agricultural Sciences, Jay, FL 32565
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Abstract
Sodium channels are chief proteins involved in electrical signaling in the nervous system, enabling critical functions like heartbeat and brain activity. New high-resolution X-ray structures for bacterial sodium channels have created an opportunity to see how these proteins operate at the molecular level. An important challenge to overcome is establishing relationships between the structures and functions of mammalian and bacterial channels. Bacterial sodium channels are known to exhibit the main structural features of their mammalian counterparts, as well as several key functional characteristics, including selective ion conduction, voltage-dependent gating, pore-based inactivation and modulation by local anesthetic, antiarrhythmic and antiepileptic drugs. Simulations have begun to shed light on each of these features in the past few years. Despite deviations in selectivity signatures for bacterial and mammalian channels, simulations have uncovered the nature of the multiion conduction mechanism associated with Na(+) binding to a high-field strength site established by charged glutamate side chains. Simulations demonstrated a surprising level of flexibility of the protein, showing that these side chains are active participants in the permeation process. They have also uncovered changes in protein structure, leading to asymmetrical collapses of the activation gate that have been proposed to correspond to inactivated structures. These observations offer the potential to examine the mechanisms of state-dependent drug activity, focusing on pore-blocking and pore-based slow inactivation in bacterial channels, without the complexities of inactivation on multiple timescales seen in eukaryotic channels. Simulations have provided molecular views of the interactions of drugs, consistent with sites predicted in mammalian channels, as well as a wealth of other sites as potential new drug targets. In this chapter, we survey the new insights into sodium channel function that have emerged from studies of simpler bacterial channels, which provide an excellent learning platform, and promising avenues for mechanistic discovery and pharmacological development.
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Affiliation(s)
- C Boiteux
- RMIT University, Melbourne, VIC, Australia
| | - T W Allen
- RMIT University, Melbourne, VIC, Australia; University of California Davis, Davis, CA, United States
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Melnyk A, Potts CA, Allen TW, DeCorby RG. Visible-range hollow waveguides by guided buckling of Ta 2O 5/SiO 2 multilayers. Appl Opt 2016; 55:3645-3649. [PMID: 27140383 DOI: 10.1364/ao.55.003645] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Hollow waveguides operating near 550 nm wavelength were fabricated by guided formation of delamination buckles within Ta2O5/SiO2 multilayers. The fabrication process employed a pair of sequentially deposited 10-period Bragg mirrors separated by a patterned, low-adhesion fluorocarbon layer. Propagation loss as low as a few dB/cm was measured, consistent with theoretical predictions.
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Melnyk A, Bitarafan MH, Allen TW, DeCorby RG. Air gap resonant tunneling bandpass filter and polarizer. Opt Lett 2016; 41:1845-1848. [PMID: 27082360 DOI: 10.1364/ol.41.001845] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We describe a bandpass filter based on resonant tunneling through an air layer in the frustrated total internal reflection regime, and show that the concept of induced transmission can be applied to the design of thin film matching stacks. Experimental results are reported for Si/SiO2-based devices exhibiting a polarization-dependent passband, with bandwidth on the order of 10 nm in the 1550 nm wavelength range, peak transmittance on the order of 80%, and optical density greater than 5 over most of the near infrared region.
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Bitarafan MH, Ramp H, Potts C, Allen TW, Davis JP, DeCorby RG. Bistability in buckled dome microcavities. Opt Lett 2015; 40:5375-5378. [PMID: 26565878 DOI: 10.1364/ol.40.005375] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We describe optical bistability in monolithically integrated, curved-mirror Fabry-Perot microcavities. The cavities were fabricated by controlled formation of circular delamination buckles within sputtered Si/SiO(2) multilayers. The dominant source of the bistability is heating due to residual absorption in the mirror layers, which leads to out-of-plane deflection of the buckled mirror. Hysteresis occurs for submilliwatt input powers.
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Standish JR, Tomaso-Peterson M, Allen TW, Sabanadzovic S, Aboughanem-Sabanadzovic N. Occurrence of QoI Fungicide Resistance in Cercospora sojina from Mississippi Soybean. Plant Dis 2015; 99:1347-1352. [PMID: 30690983 DOI: 10.1094/pdis-02-15-0157-re] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Frogeye leaf spot, caused by Cercospora sojina Hara, is a foliar disease affecting soybean (Glycine max (L.) Merr.), often managed by applications of quinone outside inhibitor (QoI) fungicides. In 2013 and 2014, 634 C. sojina monoconidial isolates were collected from soybean fields throughout Mississippi. Initially, in vitro bioassays were performed to evaluate the sensitivity of 14 of 634 isolates plus a baseline. Resistant and sensitive isolates were characterized by determining the effective fungicide concentrations at which 50% of conidial germination was inhibited (EC50). The molecular mechanism of resistance was determined for all 634 isolates, using a PCR-RFLP method and comparing nucleotide sequences of the cytochrome b gene. The state of Mississippi was divided into five distinct geographical regions (the Hills, Delta, Pines, Capital, and Coast) based on estimates of total soybean hectares. The greatest proportion (16.7%) of QoI-sensitive isolates was collected in the Hills while the Coast had no QoI-sensitive isolates. QoI-sensitive isolates from the Pines, Capital, and Delta ranged from 1.6 to 7.0%. Results of this study determined that more than 93% of C. sojina isolates collected in Mississippi carried the G143A amino acid substitution, indicating a shift to a QoI-resistant population throughout Mississippi soybean fields.
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Affiliation(s)
- J R Standish
- Department of Biochemistry, Molecular Biology, Entomology and Plant Pathology, Mississippi State University, Mississippi State 39762
| | - M Tomaso-Peterson
- Department of Biochemistry, Molecular Biology, Entomology and Plant Pathology, Mississippi State University, Mississippi State 39762
| | - T W Allen
- Delta Research and Extension Center, Mississippi State University, Stoneville 38776
| | - S Sabanadzovic
- Department of Biochemistry, Molecular Biology, Entomology and Plant Pathology, Mississippi State University, Mississippi State 39762
| | - N Aboughanem-Sabanadzovic
- Institute for Genomics, Biocomputing and Biotechnology, Mississippi State University, Mississippi State 39762
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Aboughanem-Sabanadzovic N, Allen TW, Broome M, Lawrence A, Moore WF, Sabanadzovic S. First Report of Kudzu (Pueraria montana) Infections by Tobacco ringspot virus in Mississippi. Plant Dis 2014; 98:1746. [PMID: 30703908 DOI: 10.1094/pdis-12-13-1249-pdn] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Virus-like symptoms were observed in several kudzu patches in Mississippi during a survey of viruses infecting soybean carried out in late summer/fall of 2013 as a part of a project funded by the Mississippi Soybean Promotion Board. Symptomatology consisted of chlorotic mottle and ringspots, vein-associated feathering, necrosis, and leaf deformation, which were often observed in combination on the same plant. In order to identify the virus(es) involved in the disease, young leaves from a symptomatic kudzu sample collected in Kemper County were crushed in 10 volumes of 0.1 M phosphate buffer (pH 7.2) and mechanically inoculated onto celite-dusted leaves of two soybean varieties (Asgrow AG4605 and AG4730), each represented by 10 plants. Sap from an asymptomatic kudzu sample from Oktibbeha County was used as a control. Both varieties reacted by systemic mottle, stunting, and apical leaf necrosis approximately 2 weeks after inoculation, while no symptoms could be observed in controls. Partially purified preparations from both symptomatic soybean cultivars exhibited the presence of putative intact and empty spherical virus particles ~30 nm in diameter. ELISA tests with antisera to several soybean viruses were performed on the original kudzu sample and inoculated AG4605 and AG4730 soybean plants. These tests revealed the presence of Tobacco ringspot virus (TRSV) in all symptomatic samples. In order to better understand the incidence of this virus in kudzu in Mississippi, a total of 127 samples from 28 counties were collected during October 2013 and tested using ELISA. A total of 11 samples collected in 8 different counties were positive for TRSV. To further confirm these results, one step RT-PCR test was performed on total nucleic extracts from all ELISA-positive and four negative kudzu samples using TRSV-specific primers (3). A specific PCR product of 766 bp was present in all ELISA-positive samples and positive controls, whereas no visible bands were present in negative samples. PCR products generated from samples, collected in Kemper, Tippah, and Jefferson Davis counties, were cloned and custom sequenced. Pair-wise comparisons indicated conserved nucleotide (95 to 98%) and amino acid (98 to 99%) contents among sequenced products. Kudzu isolates from Mississippi shared 91 to 96% and 98 to 99% conserved nucleotides and amino acids, with TRSV sequences currently available in the NCBI/GenBank database. This is the first report of TRSV infection of kudzu in Mississippi. The possible implications to the soybean industry are yet to be determined since kudzu occupies approximately 202,000 ha in Mississippi and TRSV has historically been reported associated with bud blight in soybean (1). Nonetheless, results of our study, along with the recent report from Louisiana (2), strongly suggest that kudzu, due to its widespread distribution in the region, may represent a major reservoir of TRSV in the southeastern United States. References: (1) G. L. Hartman et al. Compendium of Soybean Diseases. American Phytopathological Society, St. Paul, MN, 1999. (2) Khankhum et al. Plant Dis. 97:561, 2013. (3) S. Sabanadzovic et al. Plant Dis. 94:126, 2010.
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Affiliation(s)
- N Aboughanem-Sabanadzovic
- Institute for Genomics, Biocomputing and Biotechnology, Mississippi State University, Mississippi State 39762
| | - T W Allen
- Delta Research and Extension Center, Mississippi State University, Stoneville 38776
| | - M Broome
- Delta Research and Extension Center, Mississippi State University, Stoneville 38776
| | - A Lawrence
- Institute for Imaging and Analytical Technologies, Mississippi State University, Mississippi State 39762
| | - W F Moore
- Department of Biochemistry, Molecular Biology, Entomology and Plant Pathology, Mississippi State University, Mississippi State 39762
| | - S Sabanadzovic
- Department of Biochemistry, Molecular Biology, Entomology and Plant Pathology, Mississippi State University, Mississippi State 39762
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Potts C, Allen TW, Azar A, Melnyk A, Dennison CR, DeCorby RG. Wavelength interrogation of fiber Bragg grating sensors using tapered hollow Bragg waveguides. Opt Lett 2014; 39:5941-5944. [PMID: 25361125 DOI: 10.1364/ol.39.005941] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We describe an integrated system for wavelength interrogation, which uses tapered hollow Bragg waveguides coupled to an image sensor. Spectral shifts are extracted from the wavelength dependence of the light radiated at mode cutoff. Wavelength shifts as small as ~10 pm were resolved by employing a simple peak detection algorithm. Si/SiO₂-based cladding mirrors enable a potential operational range of several hundred nanometers in the 1550 nm wavelength region for a taper length of ~1 mm. Interrogation of a strain-tuned grating was accomplished using a broadband amplified spontaneous emission (ASE) source, and potential for single-chip interrogation of multiplexed sensor arrays is demonstrated.
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Sikora EJ, Allen TW, Wise KA, Bergstrom G, Bradley CA, Bond J, Brown-Rytlewski D, Chilvers M, Damicone J, DeWolf E, Dorrance A, Dufault N, Esker P, Faske TR, Giesler L, Goldberg N, Golod J, Gómez IRG, Grau C, Grybauskas A, Franc G, Hammerschmidt R, Hartman GL, Henn RA, Hershman D, Hollier C, Isakeit T, Isard S, Jacobsen B, Jardine D, Kemerait R, Koenning S, Langham M, Malvick D, Markell S, Marois JJ, Monfort S, Mueller D, Mueller J, Mulrooney R, Newman M, Osborne L, Padgett GB, Ruden BE, Rupe J, Schneider R, Schwartz H, Shaner G, Singh S, Stromberg E, Sweets L, Tenuta A, Vaiciunas S, Yang XB, Young-Kelly H, Zidek J. A Coordinated Effort to Manage Soybean Rust in North America: A Success Story in Soybean Disease Monitoring. Plant Dis 2014; 98:864-875. [PMID: 30708845 DOI: 10.1094/pdis-02-14-0121-fe] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Existing crop monitoring programs determine the incidence and distribution of plant diseases and pathogens and assess the damage caused within a crop production region. These programs have traditionally used observed or predicted disease and pathogen data and environmental information to prescribe management practices that minimize crop loss. Monitoring programs are especially important for crops with broad geographic distribution or for diseases that can cause rapid and great economic losses. Successful monitoring programs have been developed for several plant diseases, including downy mildew of cucurbits, Fusarium head blight of wheat, potato late blight, and rusts of cereal crops. A recent example of a successful disease-monitoring program for an economically important crop is the soybean rust (SBR) monitoring effort within North America. SBR, caused by the fungus Phakopsora pachyrhizi, was first identified in the continental United States in November 2004. SBR causes moderate to severe yield losses globally. The fungus produces foliar lesions on soybean (Glycine max) and other legume hosts. P. pachyrhizi diverts nutrients from the host to its own growth and reproduction. The lesions also reduce photosynthetic area. Uredinia rupture the host epidermis and diminish stomatal regulation of transpiration to cause tissue desiccation and premature defoliation. Severe soybean yield losses can occur if plants defoliate during the mid-reproductive growth stages. The rapid response to the threat of SBR in North America resulted in an unprecedented amount of information dissemination and the development of a real-time, publicly available monitoring and prediction system known as the Soybean Rust-Pest Information Platform for Extension and Education (SBR-PIPE). The objectives of this article are (i) to highlight the successful response effort to SBR in North America, and (ii) to introduce researchers to the quantity and type of data generated by SBR-PIPE. Data from this system may now be used to answer questions about the biology, ecology, and epidemiology of an important pathogen and disease of soybean.
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Affiliation(s)
- E J Sikora
- Department of Entomology and Plant Pathology, Auburn University, Auburn 36849
| | - T W Allen
- Department of Biochemistry, Molecular Biology, Entomology and Plant Pathology, Delta Research and Extension Center, Mississippi State University, Stoneville 38776
| | - K A Wise
- Department of Botany and Plant Pathology, Purdue University, West Lafayette 47907
| | - G Bergstrom
- Department of Plant Pathology and Plant-Microbe Biology, Cornell University, Ithaca 14853
| | - C A Bradley
- Department of Crop Sciences, University of Illinois, Urbana 61801
| | - J Bond
- Department of Plant, Soil, and Agricultural Systems, Southern Illinois University, Carbondale 62901
| | - D Brown-Rytlewski
- Department of Plant, Soil, and Microbial Sciences, Michigan State University, East Lansing 48824
| | - M Chilvers
- Department of Plant, Soil, and Microbial Sciences, Michigan State University, East Lansing 48824
| | - J Damicone
- Department of Entomology and Plant Pathology, Oklahoma State University, Stillwater 74078
| | - E DeWolf
- Department of Plant Pathology, Kansas State University, Manhattan 66506
| | - A Dorrance
- Department of Plant Pathology, The Ohio State University, Wooster 44691
| | - N Dufault
- Department of Plant Pathology, University of Florida, Gainesville 32611
| | - P Esker
- Escuela de Agronomia, Universidad de Costa Rica, San José, Costa Rica 10111
| | - T R Faske
- Department of Plant Pathology, University of Arkansas Lonoke Research and Extension Center, Lonoke 72086
| | - L Giesler
- Department of Plant Pathology, University of Nebraska-Lincoln, Lincoln 68508
| | - N Goldberg
- Department of Plant Sciences, New Mexico State University, Las Cruces 88003
| | - J Golod
- Department of Plant Pathology and Environmental Microbiology, Pennsylvania State University, University Park 16802
| | - I R G Gómez
- Sistema Nacional de Vigilancia Epidemiologica Fitosanitaria, Centro Nacional de Referenceia Fitosanitaria, Col. Del Carmen, Coyoacan, Mexico
| | - C Grau
- Department of Plant Pathology, University of Wisconsin, Madison 53706
| | - A Grybauskas
- Department of Plant Science and Landscape Management, University of Maryland, College Park 20742
| | | | - R Hammerschmidt
- Department of Plant, Soil, and Microbial Sciences, Michigan State University, East Lansing 48824
| | - G L Hartman
- United States Department of Agriculture/Agricultural Research Service, Urbana 61801
| | - R A Henn
- Department of Biochemistry, Molecular Biology, Entomology, and Plant Pathology, Mississippi State 39762
| | - D Hershman
- Department of Plant Pathology, University of Kentucky Research and Education Center, Princeton 42445
| | - C Hollier
- Department of Plant Pathology and Crop Physiology, Louisiana State University Agricultural Center, Baton Rouge 70803
| | - T Isakeit
- Department of Plant Pathology & Microbiology, Texas A&M University, College Station 77843
| | - S Isard
- Department of Plant Pathology and Environmental Microbiology, Pennsylvania State University, University Park 16802
| | - B Jacobsen
- Department of Plant Sciences and Plant Pathology, Montana State University, Bozeman 59717
| | - D Jardine
- Department of Plant Pathology, Kansas State University, Manhattan 66506
| | - R Kemerait
- Department of Plant Pathology, University of Georgia, Tifton 31793
| | - S Koenning
- Department of Plant Pathology, North Carolina State University, Raleigh 27695
| | - M Langham
- Department of Plant Science, South Dakota State University, Brookings 57007
| | - D Malvick
- Department of Plant Pathology, University of Minnesota, St. Paul 55108
| | - S Markell
- Department of Plant Pathology, North Dakota State University, Fargo 58108
| | - J J Marois
- Department of Plant Pathology, University of Florida, Gainesville 32611
| | - S Monfort
- Edisto Research and Education Center, Clemson University, Blackville 29817
| | - D Mueller
- Department of Plant Pathology and Microbiology, Iowa State University, Ames 50011
| | - J Mueller
- Edisto Research and Education Center, Clemson University, Blackville 29817
| | - R Mulrooney
- Department of Plant and Soil Science, University of Delaware, Newark 19716
| | - M Newman
- BASF Corporation, Jackson, TN 38301
| | | | - G B Padgett
- Department of Plant Pathology and Crop Physiology, Louisiana State University Agricultural Center, Baton Rouge 70803
| | - B E Ruden
- South Dakota Wheat Growers Association, Aberdeen 57401
| | - J Rupe
- Department of Plant Pathology, University of Arkansas, Fayetteville 72701
| | - R Schneider
- Department of Plant Pathology and Crop Physiology, Louisiana State University Agricultural Center, Baton Rouge 70803
| | - H Schwartz
- Department of Bioagricultural Sciences and Pest Management, Colorado State University, Fort Collins 80523
| | - G Shaner
- Department of Botany and Plant Pathology, Purdue University, West Lafayette 47907
| | - S Singh
- Department of Plant, Soil and Entomological Sciences, University of Idaho, Kimberly 83341
| | - E Stromberg
- Department of Plant Pathology, Physiology, and Weed Science, Virginia Polytechnic Institute and State University, Blacksburg 24061
| | - L Sweets
- Division of Plant Sciences, University of Missouri, Columbia 65211
| | - A Tenuta
- Ontario Ministry of Agriculture and Food, and Ministry of Rural Affairs, Ridgetown, Ontario, Canada, NOP2CO
| | - S Vaiciunas
- New Jersey Department of Agriculture, Trenton 08625
| | - X B Yang
- Department of Plant Pathology and Microbiology, Iowa State University, Ames 50011
| | - H Young-Kelly
- Department of Entomology and Plant Pathology, University of Tennessee West Tennessee Research and Education Center, Jackson 38301
| | - J Zidek
- ZedX Incorporated, Bellefonte, PA 16823
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Zhang MC, Allen TW, Drobot B, McFarlane S, Meldrum A, DeCorby RG. Transparency and stability of Ag-based metal-dielectric multilayers. Appl Opt 2013; 52:7479-7485. [PMID: 24216646 DOI: 10.1364/ao.52.007479] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/25/2013] [Accepted: 09/26/2013] [Indexed: 06/02/2023]
Abstract
We fabricated and tested periodic metal (Ag)-dielectric (SiO2 or TiO2) multilayers with transparency bands in the visible range. For samples with Ag-TiO2 interfaces, the optical properties exhibited relatively poor predictability, likely due to oxidation of the Ag layers. Ag/SiO2-based multilayers were found to be more predictable and stable, but the relatively low refractive index of SiO2 limits their inherent transparency and pass-band bandwidth. We show that termination of the multilayer with a single high-index layer reduces the admittance mismatch with the ambient media, and thus improves the properties of the transparency band.
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Allen TW, DeCorby RG. Conditions for admittance-matched tunneling through symmetric metal-dielectric stacks. Opt Express 2012; 20 Suppl 5:A578-A588. [PMID: 23037525 DOI: 10.1364/oe.20.00a578] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
We used the theory of potential transmittance to derive a general expression for reflection-less tunneling through a periodic stack with a dielectric-metal-dielectric unit cell. For normal-incidence from air, the theory shows that only a specific (and typically impractically large) dielectric index can enable a perfect admittance match. For off-normal incidence of TE-polarized light, an admittance match is possible at a specific angle that depends on the index of the ambient and dielectric media and the thickness and index of the metal. For TM-polarized light, admittance matching is possible within the evanescent-wave range (i.e. for tunneling mediated by surface plasmons). The results provide insight for research on transparent metals and superlenses.
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Affiliation(s)
- T W Allen
- ECE Department, University of Alberta, 9107-116 St. NW, Edmonton, Alberts, Canada.
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Allen TW, Silverstone J, Ponnampalam N, Olsen T, Meldrum A, DeCorby RG. High-finesse cavities fabricated by buckling self-assembly of a-Si/SiO2 multilayers. Opt Express 2011; 19:18903-18909. [PMID: 21996832 DOI: 10.1364/oe.19.018903] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Arrays of half-symmetric Fabry-Perot micro-cavities were fabricated by controlled formation of circular delamination buckles within a-Si/SiO(2) multilayers. Cavity height scales approximately linearly with diameter, in reasonable agreement with predictions based on elastic buckling theory. The measured finesse (F > 10(3)) and quality factors (Q > 10(4) in the 1550 nm range) are close to reflectance limited predictions, indicating that the cavities have low roughness and few defects. Degenerate Hermite-Gaussian and Laguerre-Gaussian modes were observed, suggesting a high degree of cylindrical symmetry. Given their silicon-based fabrication, these cavities hold promise as building blocks for integrated optical sensing systems.
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Affiliation(s)
- T W Allen
- ECE Department, University of Alberta, 2nd Floor, 9107-116 St. NW, Edmonton, AB, T6G 2V4, Canada
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Paul PA, Madden LV, Bradley CA, Robertson AE, Munkvold GP, Shaner G, Wise KA, Malvick DK, Allen TW, Grybauskas A, Vincelli P, Esker P. Meta-analysis of yield response of hybrid field corn to foliar fungicides in the U.S. Corn Belt. Phytopathology 2011; 101:1122-32. [PMID: 21554185 DOI: 10.1094/phyto-03-11-0091] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
The use of foliar fungicides on field corn has increased greatly over the past 5 years in the United States in an attempt to increase yields, despite limited evidence that use of the fungicides is consistently profitable. To assess the value of using fungicides in grain corn production, random-effects meta-analyses were performed on results from foliar fungicide experiments conducted during 2002 to 2009 in 14 states across the United States to determine the mean yield response to the fungicides azoxystrobin, pyraclostrobin, propiconazole + trifloxystrobin, and propiconazole + azoxystrobin. For all fungicides, the yield difference between treated and nontreated plots was highly variable among studies. All four fungicides resulted in a significant mean yield increase relative to the nontreated plots (P < 0.05). Mean yield difference was highest for propiconazole + trifloxystrobin (390 kg/ha), followed by propiconazole + azoxystrobin (331 kg/ha) and pyraclostrobin (256 kg/ha), and lowest for azoxystrobin (230 kg/ha). Baseline yield (mean yield in the nontreated plots) had a significant effect on yield for propiconazole + azoxystrobin (P < 0.05), whereas baseline foliar disease severity (mean severity in the nontreated plots) significantly affected the yield response to pyraclostrobin, propiconazole + trifloxystrobin, and propiconazole + azoxystrobin but not to azoxystrobin. Mean yield difference was generally higher in the lowest yield and higher disease severity categories than in the highest yield and lower disease categories. The probability of failing to recover the fungicide application cost (p(loss)) also was estimated for a range of grain corn prices and application costs. At the 10-year average corn grain price of $0.12/kg ($2.97/bushel) and application costs of $40 to 95/ha, p(loss) for disease severity <5% was 0.55 to 0.98 for pyraclostrobin, 0.62 to 0.93 for propiconazole + trifloxystrobin, 0.58 to 0.89 for propiconazole + azoxystrobin, and 0.91 to 0.99 for azoxystrobin. When disease severity was >5%, the corresponding probabilities were 0.36 to 95, 0.25 to 0.69, 0.25 to 0.64, and 0.37 to 0.98 for the four fungicides. In conclusion, the high p(loss) values found in most scenarios suggest that the use of these foliar fungicides is unlikely to be profitable when foliar disease severity is low and yield expectation is high.
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Affiliation(s)
- P A Paul
- Department of Plant Pathology, The Ohio State University, OH, USA.
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Allen TW, Jones DC, Boratynski TN, Ykema RE, Rush CM. Application of the Humid Thermal Index for Relating Bunted Kernel Incidence to Soilborne Tilletia indica Teliospores in an Arizona Durum Wheat Field. Plant Dis 2009; 93:713-719. [PMID: 30764364 DOI: 10.1094/pdis-93-7-0713] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
A study was conducted to determine the relationship between soilborne Tilletia indica teliospore density and Karnal bunt incidence in an Arizona durum wheat field in 2005 and 2006. Soil samples were collected from 507 sample points according to a grid marked in a 7.7-ha field. Approximately 500 g of soil from the top 5 cm was collected from each sample point, and teliospores were recovered from 25-g aliquots by a modified size-selective sieving, sucrose centrifugation procedure. Twenty-five and 50 wheat heads were collected from a 1-m2 area around each sample point in May 2005 and June 2006, respectively. Wheat head samples from each sample point were bulked, threshed, and examined for the presence of bunted kernels. Additionally, data for soilborne teliospores and percent bunted kernels from 70 sample points in 2005 and 2006 that corresponded to sample points from a 2004 bunted kernel survey conducted by the USDA and Arizona Department of Agriculture were analyzed. Soilborne teliospore numbers ranged from 6 to 1,000 per 25-g soil sample in the 2-year study. No bunted kernels were recovered in 2005; however, two sample points yielded bunted kernels in 2006. Weather data from three time periods in 2004, 2005, and 2006 were applied to the humid thermal index model and suggested that a conducive environment for disease development existed in 2005. Based on the data from this research, we concluded that even though high numbers of soilborne teliospores were present in the field, and although a conducive environment was present for disease to develop on only one occasion, a direct relationship between soilborne teliospores and disease incidence may not exist.
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Affiliation(s)
- T W Allen
- Texas AgriLife Research, 2301 Experiment Station Road, Bushland 79012-0010
| | - D C Jones
- Texas AgriLife Research, 2301 Experiment Station Road, Bushland 79012-0010
| | | | - R E Ykema
- Arizona Department of Agriculture, Phoenix 85009-2701
| | - C M Rush
- Texas AgriLife Research, 2301 Experiment Station Road, Bushland 79012-0010
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Bonde MR, Nester SE, Moore WF, Allen TW. Comparative Susceptibility of Kudzu Accessions from the Southeastern United States to Infection by Phakopsora pachyrhizi. Plant Dis 2009; 93:593-598. [PMID: 30764392 DOI: 10.1094/pdis-93-6-0593] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Soybean rust, caused by Phakopsora pachyrhizi, was first discovered in the continental United States in the fall of 2004. The potential for economic loss in the United States hinges largely on whether or not the pathogen can survive winters in the absence of soybean. Kudzu (Pueraria lobata) is known to be a host for P. pachyrhizi in Asia and South America and is widely distributed in the southern United States. This study examined reactions of kudzu collected from several areas of the southeastern United States to three isolates of P. pachyrhizi, one each from Alabama, Louisiana, and Brazil. Susceptible tan (TAN) lesions, resistant reddish-brown (RB) lesions, and immune (IM) response, previously described on soybean, were produced on kudzu based on the evaluation of 125 plants. However, in contrast to soybean, the RB response on kudzu was common, with approximately 50% frequency. IM responses to at least one isolate were observed on five individual plants, and two plants were immune to all three pathogen isolates used in the test. TAN lesions averaged 3.2 uredinia per lesion with an average diameter per uredinium of 121 μm. In contrast, RB lesions had an average of 0.3 uredinia per lesion with an average uredinial diameter of 77 μm. In 25 of 39 (64%) instances in which multiple plants were tested from a site, each reacted the same to the individual pathogen isolates. This suggested a tendency for plants at specific sites to be genetically identical with respect to rust reaction. Only 19 of 125 (15%) individual plants produced a different reaction to one isolate than to the other two isolates. When four kudzu plants previously shown to produce only TAN lesions to P. pachyrhizi isolates Alabama 04-1, Brazil 01-1, and Louisiana 04-1 were inoculated with eight additional isolates from several areas of the world, all 11 isolates produced only TAN lesions. Likewise, when five other plants previously shown to produce only RB lesions when inoculated with the three isolates were inoculated with the 11 isolates, all produced only RB lesions. These results suggest that susceptibility or resistance to P. pachyrhizi in individual kudzu plants often is broad, extending over a wide range of P. pachyrhizi isolates.
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Affiliation(s)
- M R Bonde
- USDA, ARS, Foreign Disease-Weed Science Research Unit, 1301 Ditto Ave., Fort Detrick, MD 21702
| | - S E Nester
- USDA, ARS, Foreign Disease-Weed Science Research Unit, 1301 Ditto Ave., Fort Detrick, MD 21702
| | - W F Moore
- Department of Entomology and Plant Pathology, Box 9655, Dorman Hall, Mississippi State University, Mississippi State 39762
| | - T W Allen
- Delta Research and Extension Center, Mississippi State University, 82 Stoneville Road, Stoneville 38776
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Allen TW, Maples HW, Workneh F, Stein JM, Rush CM. Distribution and Recovery of Tilletia indica Teliospores from Regulated Wheat Fields in Texas. Plant Dis 2008; 92:344-350. [PMID: 30769673 DOI: 10.1094/pdis-92-3-0344] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Eight wheat fields from the Karnal bunt-regulated regions within Texas were grid sampled to gain a better understanding of the ecology and epidemiology of teliospores produced by the causal agent, Tilletia indica. Teliospores from 25-g aliquots of soil from each grid point were extracted using a size-selective sieving sucrose-centrifugation procedure. Teliospores were recovered from all eight fields and, in some cases, from every grid point within a field. Total teliospore numbers ranged from 0 to 1,305 per 25 g of soil. Over 70% of the total grid sampled points contained one or more teliospores. The relation between soil chemical and physical characteristics and teliospore numbers from each field was evaluated. In general, no consistent, significant trend could be made between soil factors and teliospore numbers. Geostatistics were used to analyze data from grid points and create contour maps. Teliospore distribution was aggregated in four of the fields, random in three of the fields, and discontinuous (neither random nor aggregated) in a single field. This is the first report of widespread distribution and high teliospore numbers from wheat field soils in the United States.
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Affiliation(s)
- T W Allen
- Texas Agricultural Experiment Station, Bushland 79012-0010
| | - H W Maples
- Texas Agricultural Experiment Station, Bushland 79012-0010
| | - F Workneh
- Texas Agricultural Experiment Station, Bushland 79012-0010
| | - J M Stein
- Plant Science Department, South Dakota State University, Brookings 57007
| | - C M Rush
- Texas Agricultural Experiment Station, Bushland
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Allen TW, Workneh F, Steddom KC, Peterson GL, Rush CM. The Influence of Tillage on Dispersal of Tilletia indica Teliospores from a Concentrated Point Source. Plant Dis 2008; 92:351-356. [PMID: 30769674 DOI: 10.1094/pdis-92-3-0351] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
A study was conducted to determine the impact of tillage on dispersal of Tilletia indica teliospores from a concentrated point source in Arizona. The infested source was created using a 300-ml teliospore suspension, containing approximately 9.0 × 104 teliospores/ml, sprayed onto a 1-by-3-m soil area. Approximately 400 g of soil was collected before tillage treatments, representing the teliospore baseline, and after each of five disk passes, to an approximate depth of 20 cm, through the infestation source (n = 597). Soil samples were collected along three parallel lines extending from the infested area at increments of 1, 3, or 10 m to a total distance of 10, 30, and 50 m, respectively. Teliospores were recovered from soil samples by a combined size-selective sieving sucrose-centrifugation technique. Immediately following teliospore infestation, an average of 3.6 × 103 teliospores per 25 g of soil sample were recovered from the infestation area. Two different trends in recoverable teliospores occurred at 0- to 10-m sampling distances following five plow passes: either a decrease in the number of teliospores recovered, represented at points 0, 1, and 2 m, or an increase in recoverable teliospores found at points 3 to 10 m. The study was repeated twice for a total of three experiments, and teliospores were recovered to a maximum distance of 24 m. However, the numbers recovered from distances beyond 10 m were sporadic. Based on data from this research, we conclude that teliospores are not distributed in large quantities to great distances by tillage and, therefore, tillage cannot account for the spatial distribution of teliospores in many infested wheat fields.
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Affiliation(s)
- T W Allen
- Texas Agricultural Experiment Station, Bushland 79012-0010
| | - F Workneh
- Texas Agricultural Experiment Station, Bushland 79012-0010
| | - K C Steddom
- Texas Agricultural Experiment Station, Overton 75684
| | - G L Peterson
- United States Department of Agriculture-Agricultural Research Service, Foreign Disease-Weed Science Research Unit, Fort Detrick, MD 21702-5023
| | - C M Rush
- Texas Agricultural Experiment Station, Bushland
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Workneh F, Allen TW, Nash GH, Narasimhan B, Srinivasan R, Rush CM. Rainfall and temperature distinguish between Karnal bunt positive and negative years in wheat fields in Texas. Phytopathology 2008; 98:95-100. [PMID: 18943243 DOI: 10.1094/phyto-98-1-0095] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Karnal bunt of wheat, caused by the fungus Tilletia indica, is an internationally regulated disease. Since its first detection in central Texas in 1997, regions in which the disease was detected have been under strict federal quarantine regulations resulting in significant economic losses. A study was conducted to determine the effect of weather factors on incidence of the disease since its first detection in Texas. Weather variables (temperature and rainfall amount and frequency) were collected and used as predictors in discriminant analysis for classifying bunt-positive and -negative fields using incidence data for 1997 and 2000 to 2003 in San Saba County. Rainfall amount and frequency were obtained from radar (Doppler radar) measurements. The three weather variables correctly classified 100% of the cases into bunt-positive or -negative fields during the specific period overlapping the stage of wheat susceptibility (boot to soft dough) in the region. A linear discriminant-function model then was developed for use in classification of new weather variables into the bunt occurrence groups (+ or -). The model was evaluated using weather data for 2004 to 2006 for San Saba area (central Texas), and data for 2001 and 2002 for Olney area (north-central Texas). The model correctly predicted bunt occurrence in all cases except for the year 2004. The model was also evaluated for site-specific prediction of the disease using radar rainfall data and in most cases provided similar results as the regional level evaluation. The humid thermal index (HTI) model (widely used for assessing risk of Karnal bunt) agreed with our model in all cases in the regional level evaluation, including the year 2004 for the San Saba area, except for the Olney area where it incorrectly predicted weather conditions in 2001 as unfavorable. The current model has a potential to be used in a spray advisory program in regulated wheat fields.
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Affiliation(s)
- F Workneh
- Texas Agricultural Experiment Station, Bushland 79012, USA.
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Clement TJ, Decorby RG, Ponnampalam N, Allen TW, Hryciw A, Meldrum A. Nanocluster sensitized erbium-doped silicon monoxide waveguides. Opt Express 2006; 14:12151-12162. [PMID: 19529642 DOI: 10.1364/oe.14.012151] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
We describe the fabrication and characterization of micron-scale buried strip waveguides with erbium-doped (~ 1 at. %) silicon monoxide (SiO) cores and SiO(2) and polymer claddings. In spite of large core-cladding index offset (Deltan~0.4), propagation loss is as low as ~ 1 dB/cm. The cross-section for the (4)I(13/2) to (4)I(15/2) erbium transition was estimated as ~10(-20) cm(2), a factor of 2 to 3 higher than in silica glass. The annealed core material contains a high density of amorphous silicon nanoclusters, which act as efficient broadband sensitizers for erbium. Both a traditional co-propagating pump (980 nm wavelength) configuration and a transverse pump (532 nm wavelength, < 10 W/cm(2)) configuration were tested. In either case, free carrier absorption loss is the dominant pump-induced mechanism and approximately 15-20 % of the erbium population is invertible.
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Allen TW, Han DY, Bowen KL. Effect of environmental characteristics on Pythium and Mesocriconema spp. in golf course greens in Alabama. Can J Microbiol 2005; 51:287-93. [PMID: 15980890 DOI: 10.1139/w05-005] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The role the environment has on populations of Pythium and Mesocriconema spp. was investigated at 5 golf course locations in east central Alabama. Every 4 to 5 weeks soil samples were collected from 3 golf greens on each of the 5 golf courses. Environmental data, including air and soil temperature, pH and relative humidity, were also collected. Dilution plating and a combined sieving and sugar flotation procedure were conducted to determine the populations of Pythium and Mesocriconema spp. for each month. Isolates of Pythium from 4 months were also identified. Pythium spp. populations increased as soil temperature and ambient air temperature prior to sampling decreased (P < 0.05). Pythium spp. populations were highest in the winter and lowest in the spring. At some locations, populations of Mesocriconema spp. increased as soil acidity and populations of Pythium spp. decreased (P < 0.05) and as ambient air temperature prior to sampling increased (P < 0.05). Eight species of Pythium were isolated from 4 months, with Pythium rostratum being the most commonly isolated. Results suggest that Pythium and Mesocriconema spp. prefer different soil environments.
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Affiliation(s)
- T W Allen
- Department of Entomology and Plant Pathology, Auburn University, 209 Life Sciences Building, Auburn, AL 36849, USA.
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Allen TW, Prasad V, Prasad GS, Hoffman RM, Ramaswamy S. Crystal structure of L-homocysteine γ-lyase at 1.8 Å. Acta Crystallogr A 2002. [DOI: 10.1107/s0108767302088815] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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Abstract
Three-dimensional Brownian dynamics simulations are used to study conductance of the KcsA potassium channel using the known crystallographic structure. Employing an open-state channel created by molecular dynamics simulations, current-voltage and current-concentration curves broadly consistent with experimental measurements are obtained. In the absence of an applied potential, the channel houses three potassium ions at positions that are in close agreement with X-ray diffraction maps.
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Affiliation(s)
- T W Allen
- Department of Physics, Australian National University, 0200, Canberra, ACT, Australia
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Liang MT, Allen TW, McKeigue ME, Kotis A, Gierke LW. Effect of cooling on muscular health prior to running a marathon. J Am Osteopath Assoc 2001; 101:219-25. [PMID: 11370546] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 04/16/2023]
Abstract
To examine the effects of a prerace whole-body cold shower on muscle soreness (MS) and on serum creatine kinase (CK) and creatine kinase MB (CK-MB) isoenzyme activities, 16 experienced distance runners were randomly assigned to one of two treatment categories prior to running a marathon: cold shower (n = 8) or without cold shower (n = 8). Venous blood samples were drawn 3 days before the race, 10 minutes before the race, immediately (within 3 minutes) after the race, and at 1, 24, 48, and 96 hours postrace. Nine muscle sites were evaluated for soreness 10 minutes before the race, immediately after the race, and at 24, 48, and 96 hours postrace. The results showed a marked (P < .05) difference between the cold shower group and the group without cold showers for CK-MB/CK ratio, and no difference for CK, CK-MB, and MS. Both CK and CK-MB values peaked at 24 hours postrace. MS occurred most frequently immediately after the race and at 24 hours postrace. The MS was completely resolved in all subjects by 96 hours postrace. The most frequently reported sites of MS were the quadriceps, followed by the gastrocnemius, the soleus, and the tibialis anterior. Severe MS was rated highest at the quadriceps and the soleus, and the least at the gastrocnemius and the tibialis anterior. The data suggest that prerace whole-body cold showers neither prevented the production of serum CK and its MB fraction, nor attenuated MS after a marathon. Peak serum CK and CK-MB activity was not associated with the onset of MS.
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Affiliation(s)
- M T Liang
- Department of Kinesiology and Health Promotion, California State Polytechnic University, 3801 West Temple Ave., Pomona, CA 91768, USA.
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Abstract
The mechanisms underlying ion transport and selectivity in calcium channels are examined using electrostatic calculations and Brownian dynamics simulations. We model the channel as a rigid structure with fixed charges in the walls, representing glutamate residues thought to be responsible for ion selectivity. Potential energy profiles obtained from multi-ion electrostatic calculations provide insights into ion permeation and many other observed features of L-type calcium channels. These qualitative explanations are confirmed by the results of Brownian dynamics simulations, which closely reproduce several experimental observations. These include the current-voltage curves, current-concentration relationship, block of monovalent currents by divalent ions, the anomalous mole fraction effect between sodium and calcium ions, attenuation of calcium current by external sodium ions, and the effects of mutating glutamate residues in the amino acid sequence.
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Affiliation(s)
- B Corry
- Protein Dynamics Unit, Department of Chemistry, Australian National University, Canberra, Australian Capital Territory
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Abstract
We propose a model of calcium channels that can explain most of their observed properties, including the anomalous mole fraction effect and mutation of the glutamate residues. The structure grossly resembles that of the KcsA potassium channel except for the presence of an extracellular vestibule and a shorter selectivity filter containing four glutamate residues. Using this model in electrostatic calculations and Brownian dynamics simulations, we study mechanisms of ion permeation and selectivity in the channel. Potential energy profiles calculated for multiple ions in the channel provide explanations of ion permeation, the block of Na(+) currents by Ca(2+) ions, and many other observed properties. Brownian dynamics simulations provide quantitative predictions for the channel currents which reproduce available experimental data.
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Affiliation(s)
- B Corry
- Protein Dynamics Unit, Department of Chemistry, Research School of Physical Sciences, Australian National University, Canberra
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Abstract
Molecular dynamics simulations are carried out to obtain estimates of diffusion coefficients of biologically important Na+, K+, Ca2+ and Cl- ions in hydrophobic cylindrical channels with varying radii and large reservoirs. Calculations for the cylindrical channels are compared to those for the KcsA potassium channel, for which the protein structure has recently been determined from X-ray diffraction experiments. Our results show that ion diffusion is maintained at reasonably high levels even within narrow channels, and does not support the very small diffusion coefficients used in some continuum models in order to fit experimental data. The present estimates of ion diffusion coefficients are useful in the calculation of channel conductance using the Poisson-Nernst-Planck theory, or Brownian dynamics.
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Affiliation(s)
- T W Allen
- Department of Chemistry, Australian National University, Canberra, ACT, Australia.
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Abstract
The structural, dynamical, and thermodynamic properties of a model potassium channel are studied using molecular dynamics simulations. We use the recently unveiled protein structure for the KcsA potassium channel from Streptomyces lividans. Total and free energy profiles of potassium and sodium ions reveal a considerable preference for the larger potassium ions. The selectivity of the channel arises from its ability to completely solvate the potassium ions, but not the smaller sodium ions. Self-diffusion of water within the narrow selectivity filter is found to be reduced by an order of magnitude from bulk levels, whereas the wider hydrophobic section of the pore maintains near-bulk self-diffusion. Simulations examining multiple ion configurations suggest a two-ion channel. Ion diffusion is found to be reduced to approximately 1/3 of bulk diffusion within the selectivity filter. The reduced ion mobility does not hinder the passage of ions, as permeation appears to be driven by Coulomb repulsion within this multiple ion channel.
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Affiliation(s)
- T W Allen
- Protein Dynamics Unit, Department of Chemistry, Research School of Physical Sciences, Australian National University, Canberra, ACT 0200, Australia.
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Allen TW, Kuyucak S, Chung SH. The effect of hydrophobic and hydrophilic channel walls on the structure and diffusion of water and ions. J Chem Phys 1999. [DOI: 10.1063/1.480132] [Citation(s) in RCA: 79] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Abstract
The physical mechanisms underlying the transport of ions across a model potassium channel are described. The shape of the model channel corresponds closely to that deduced from crystallography. From electrostatic calculations, we show that an ion permeating the channel, in the absence of any residual charges, encounters an insurmountable energy barrier arising from induced surface charges. Carbonyl groups along the selectivity filter, helix dipoles near the oval chamber, and mouth dipoles near the channel entrances together transform the energy barrier into a deep energy well. Two ions are attracted to this well, and their presence in the channel permits ions to diffuse across it under the influence of an electric field. Using Brownian dynamics simulations, we determine the magnitude of currents flowing across the channel under various conditions. The conductance increases with increasing dipole strength and reaches its maximum rapidly; a further increase in dipole strength causes a steady decrease in the channel conductance. The current also decreases systematically when the effective dielectric constant of the channel is lowered. The conductance with the optimal choice of dipoles reproduces the experimental value when the dielectric constant of the channel is assumed to be 60. The current-voltage relationship obtained with symmetrical solutions is linear when the applied potential is less than approximately 100 mV but deviates from Ohm's law at a higher applied potential. The reversal potentials obtained with asymmetrical solutions are in agreement with those predicted by the Nernst equation. The conductance exhibits the saturation property observed experimentally. We discuss the implications of these findings for the transport of ions across the potassium channels and membrane channels in general.
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Affiliation(s)
- S H Chung
- Protein Dynamics Unit, Department of Chemistry, Research School of Physical Sciences, Australian National University, Canberra, ACT 0200, Australia.
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Allen TW. Coming full circle: osteopathic manipulative treatment and immunity. J Am Osteopath Assoc 1998; 98:204. [PMID: 9594483] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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Allen TW. Will failure to use OMT be grounds for malpractice? J Am Osteopath Assoc 1997; 97:268. [PMID: 9195787 DOI: 10.7556/jaoa.1997.97.5.268] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
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Washowich TL, Williams SC, Richardson LA, Simmons GE, Dao NV, Allen TW, Hammet GC, Morris MJ. Detection of interstitial lung abnormalities on picture archive and communication system video monitors. J Digit Imaging 1997; 10:34-9. [PMID: 9147526 PMCID: PMC3453189 DOI: 10.1007/bf03168548] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
The purpose of this study was to compare the detection of interstitial lung abnormalities on video display workstation monitors between radiologists experienced with video image interpretation and radiologists who lack this experience. Twenty-four patients with interstitial lung abnormalities documented by high-resolution computed tomography (HRCT) and lung biopsy, and 26 control patients with no history of pulmonary disease or a normal HRCT and normal chest radiographs were studied. Images were acquired using storage phosphor digital radiography and displayed on 1,640 x 2,048 pixel resolution video monitors. Five board-certified radiologists evaluated the images in a blinded and randomized manner by using a six-point presence of abnormality grading scale. Three radiologists were from 1 to 4 years out of residency and considered to be experienced workstation monitor readers with between 1 to 3 years of video monitor image interpretation. For the inexperienced readers, one radiologist had no prior experience with reading images from a video monitor and was direct out of residency, and the other radiologist had less than 4 months of intermittent exposure and was 1 year out of residency. Sensitivity and specificity were determined for individual readers. Positive predictive values, negative predictive values, accuracy, and receiver-operating curves were also generated. A comparison was made between experienced and inexperienced readers. For readers experienced with video monitor image interpretation, the sensitivity ranged from 87.5% to 92%, specificity from 69% to 92%, positive predictive value (PPV) from 73% to 87.5%, negative predictive value (NPV) from 87% to 90%, and accuracy from 80% to 88%. For inexperienced readers, these values were sensitivity 58%, specificity 50% to 65%, PPV 52% to 61%, NPV 56.5% to 63%, and accuracy 54% to 62%. Comparing image interpretation between experienced and inexperienced readers, there were statistically significant differences for sensitivity (P < .01), specificity (P < .01), PPV (P < .05), NPV (P < .05), accuracy (P < .05), and area under the receiver operator curve (Az) (P < .01). Within the respective experienced and inexperienced groups, no statistical significant differences were present. Our results show that digitally acquired chest radiographs displayed on high-resolution workstation monitors are adequate for the detection of interstitial lung abnormalities when the images are interpreted by radiologists experienced with video image interpretation. Radiologists inexperienced with video monitor image interpretation, however, cannot reliably interpret images for the detection of interstitial lung abnormalities.
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Affiliation(s)
- T L Washowich
- Department of Radiology, Brooke Army Medical Center, Fort Sam Houston, TX 78234, USA
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Allen TW. 'Active ingredient' for a healthy life. J Am Osteopath Assoc 1996; 96:722. [PMID: 9111773] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
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Allen TW, Burden CJ. Erratum: Positronium states in three-dimensional QED. Phys Rev D Part Fields 1996; 54:6567. [PMID: 10020663 DOI: 10.1103/physrevd.54.6567] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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Allen TW. Smoking cessation is not an oxymoron. J Am Osteopath Assoc 1996; 96:460. [PMID: 8810155] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
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Allen TW. Cigarette smoking still smolders after all these years. J Am Osteopath Assoc 1995; 95:636. [PMID: 8575945] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
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Allen TW. Synergism strengthens osteopathic medical education programs. J Am Osteopath Assoc 1995; 95:586. [PMID: 8557546] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
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Allen TW. Federal guidelines endorse OMT for acute low back pain. J Am Osteopath Assoc 1995; 95:160. [PMID: 7751166] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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Allen TW. Family physicians key partners in preventing suicide among youth. J Am Osteopath Assoc 1994; 94:699-700. [PMID: 7995733] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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Allen TW. Cohesive social systems key to breaking cycle of family violence. J Am Osteopath Assoc 1994; 94:535-6. [PMID: 8083063] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
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Allen TW. DOs encouraged to participate in pharmaceutical, clinical trials. J Am Osteopath Assoc 1994; 94:378. [PMID: 8056625] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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Allen TW. Exercise: the antiaging antidote? J Am Osteopath Assoc 1994; 94:378, 380. [PMID: 8056626] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
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Allen TW. An apple a day may keep cardiovascular disease at bay. J Am Osteopath Assoc 1994; 94:292. [PMID: 8026996] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
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Allen TW. Cigarette smoking still smolders after all these years. J Am Osteopath Assoc 1994; 94:205. [PMID: 8200822] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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Allen TW. Elderly abuse: the silent violation. J Am Osteopath Assoc 1994; 94:131-2. [PMID: 8200817] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
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