1,958 research outputs found

    The Assessment of Commercial Fishing Effort in Virginia 1987

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    This report summarizes the assessment of commercial fishing effort in Chesapeake Bay and its Virginia tributaries during the period January 1, 1987 through December 31, 1987. Objectives of this study were: 1) to assess pound net fishing effort in Chesapeake Bay, and in the James, York and Rappahannock rivers; and 2) to assess anchor, drift, and stake gill net fishing effort in the James, York and Rappahannock rivers. The study period covered the calendar year which represents a natural break in fishing effort in Virginia. Data for fyke net and haul seine fisheries, when available, have also been included

    The assessment of commercial fishing effort in Virginia Annual Report 1986

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    This report summarizes the assessment of commercial fishing effort in Chesapeake Bay and its Virginia tributaries during the period October 1, 1985 through December 31, 1986. Objectives of this study were: 1. to assess pound net fishing effort in Chesapeake Bay, and in the James, York and Rappahannock rivers; and 2. to assess anchor, drift, and stake gill net fishing effort in the James, York and Rappahannock rivers. Additionally, two months of data for pound nets and anchor, drift, and stake gill nets have been included in order that the cessation of the study period would occur at a natural break in fishing effort in Virginia. Data for fyke net and haul seine fisheries have also been included

    Detecting Stress in Glasshouse Plants Using Color Infrared Imagery: A Potential New Application for Remote Sensing

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    English: Studies were conducted to evaluate the effectiveness of color infrared (CIR) film for detecting physiological stress in plants located within glasshouse structures. Spectroradiometer measurements obtained within and outside of a structure constructed of polycarbonate plastic indicated no significant attenuation or disruption of visible and near-infrared radiation entering the structure. CIR photographs of cucumber seedlings (Cucumis sativus) obtained within the greenhouse were comparable in quality to those obtained outside the structure, and clearly distinguished between foliage of healthy plants and those subjected to a moderate level of nitrogen stress. In CIR imagery of a trifoliate orange tree (Poncirus trifoliata (L.) Raf.) obtained within a greenhouse constructed of yellow fiberglass panels, leaves damaged by citrus red mites (Panonychus citri [McGregor]) were distinguishable from healthy foliage, and the distribution of damaged leaves on the tree itself was clearly evident. These results suggest that remote sensing techniques which have been used successfully to monitor conventional field crops are readily extendable to the commercial glasshouse environment with certain modifications. Spanish: Se condujeron estudios para evaluar la eficacia de la película infrarroja de color (CIR) para detectar el estrés fisiológico en las plantas situadas dentro de un invernadero. Las mediciones del spectroradiómetro obtenidas dentro y fuera de un invernadero construido con plástico de policarbonato no indicaron ninguna atenuación o interrupción significativa de la radiación visible y del cercano infrarrojo que penetraba al invernadero. Las fotografías con CIR de las plantas de semillero de pepino (Cucumis sativus) obtenidas dentro del invernadero fueron comparables en calidad a aquellas obtenidas fuera de este, y distinguieron claramente entre el follaje de plantas sanas y de aquellas sometidas a un nivel moderado de estrés de nitrógeno. En imágenes de CIR de un naranjo trifoliado (Poncirus trifoliata (L.) Raf.) obtenidas dentro de un invernadero construido de paneles amarillos de fibra de vidrio, las hojas dañadas por el ácaro rojo de los cítricos (Panonychus citri [McGregor]) se distinguieron del follaje sano, y la distribución de hojas dañadas en el árbol mismo fueron claramente evidentes. Estos resultados sugieren que las técnicas de detección a distancia que se han utilizado con éxito para supervisar campos de cultivo convencionales, también pueden usarse fácilmente, con algunas modificaciones, en cultivos comerciales en invernadero

    Five High-Redshift Quasars Discovered in Commissioning Imaging Data of the Sloan Digital Sky Survey

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    We report the discovery of five quasars with redshifts of 4.67 - 5.27 and z'-band magnitudes of 19.5-20.7 M_B ~ -27. All were originally selected as distant quasar candidates in optical/near-infrared photometry from the Sloan Digital Sky Survey (SDSS), and most were confirmed as probable high-redshift quasars by supplementing the SDSS data with J and K measurements. The quasars possess strong, broad Lyman-alpha emission lines, with the characteristic sharp cutoff on the blue side produced by Lyman-alpha forest absorption. Three quasars contain strong, broad absorption features, and one of them exhibits very strong N V emission. The amount of absorption produced by the Lyman-alpha forest increases toward higher redshift, and that in the z=5.27 object (D_A ~ 0.7) is consistent with a smooth extrapolation of the absorption seen in lower redshift quasars. The high luminosity of these objects relative to most other known objects at z >~ 5 makes them potentially valuable as probes of early quasar properties and of the intervening intergalactic medium.Comment: 13 pages in LaTex format, two postscirpt figures. Submitted to the Astronomical Journa

    High-Redshift Quasars Found in Sloan Digital Sky Survey Commissioning Data IV: Luminosity Function from the Fall Equatorial Stripe Sampl

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    This is the fourth paper in a series aimed at finding high-redshift quasars from five-color imaging data taken along the Celestial Equator by the SDSS. during its commissioning phase. In this paper, we use the color-selected sample of 39 luminous high-redshift quasars presented in Paper III to derive the evolution of the quasar luminosity function over the range of 3.6<z<5.0, and -27.5<M_1450<-25.5 (Omega=1, H_0=50 km s^-1 Mpc^-1). We use the selection function derived in Paper III to correct for sample incompleteness. The luminosity function is estimated using three different methods: (1) the 1/V_a estimator; (2) a maximum likelihood solution, assuming that the density of quasars depends exponentially on redshift and as a power law in luminosity and (3) Lynden-Bell's non-parametric C^- estimator. All three methods give consistent results. The luminous quasar density decreases by a factor of ~ 6 from z=3.5 to z=5.0, consistent with the decline seen from several previous optical surveys at z<4.5. The luminosity function follows psi(L) ~ L^{-2.5} for z~4 at the bright end, significantly flatter than the bright end luminosity function psi(L) \propto L^{-3.5} found in previous studies for z<3, suggesting that the shape of the quasar luminosity function evolves with redshift as well, and that the quasar evolution from z=2 to 5 cannot be described as pure luminosity evolution. Possible selection biases and the effect of dust extinction on the redshift evolution of the quasar density are also discussed.Comment: AJ accepted, with minor change

    Genetic Interactions between Chromosomes 11 and 18 Contribute to Airway Hyperresponsiveness in Mice

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    We used two-dimensional quantitative trait locus analysis to identify interacting genetic loci that contribute to the native airway constrictor hyperresponsiveness to methacholine that characterizes A/J mice, relative to C57BL/6J mice. We quantified airway responsiveness to intravenous methacholine boluses in eighty-eight (C57BL/6J X A/J) F2 and twenty-seven (A/J X C57BL/6J) F2 mice as well as ten A/J mice and six C57BL/6J mice; all studies were performed in male mice. Mice were genotyped at 384 SNP markers, and from these data two-QTL analyses disclosed one pair of interacting loci on chromosomes 11 and 18; the homozygous A/J genotype at each locus constituted the genetic interaction linked to the hyperresponsive A/J phenotype. Bioinformatic network analysis of potential interactions among proteins encoded by genes in the linked regions disclosed two high priority subnetworks - Myl7, Rock1, Limk2; and Npc1, Npc1l1. Evidence in the literature supports the possibility that either or both networks could contribute to the regulation of airway constrictor responsiveness. Together, these results should stimulate evaluation of the genetic contribution of these networks in the regulation of airway responsiveness in humans

    Complete chloroplast genome sequence of Holoparasite Cistanche Deserticola (Orobanchaceae) reveals gene loss and horizontal gene transfer from Its host Haloxylon Ammodendron (Chenopodiaceae)

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    The central function of chloroplasts is to carry out photosynthesis, and its gene content and structure are highly conserved across land plants. Parasitic plants, which have reduced photosynthetic ability, suffer gene losses from the chloroplast (cp) genome accompanied by the relaxation of selective constraints. Compared with the rapid rise in the number of cp genome sequences of photosynthetic organisms, there are limited data sets from parasitic plants. The authors report the complete sequence of the cp genome of Cistanche deserticola, a holoparasitic desert species belonging to the family Orobanchaceae
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