34,017 research outputs found

    Estimation of Standardized Effort in the Heterogeneous Gulf of Mexico Shrimp Fleet

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    In this paper we estimate nominal and standardized shrimping effort in the Gulf of Mexico for the years 1965 through 1993. We accomplish this by first developing a standardization method (model) and then an expansion method (model). The expansion model estimates nominal days fished for noninterview landings data. The standardization model converts nominal days fished to standard days fished. We then characterize the historical trends of the penaeid shrimp fishery byvessel configuration, relative fishing power, and nominal and standardized effort. Wherever possible, we provide comparison with previous estimates by the National Marine Fisheries Service, NOAA

    Pedaling out of poverty: Social impact of a manual irrigation technology in South Asia.

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    Irrigation management / Treadle pump / Treadle pump technology / Technology transfer / Manual pumps / Water lifting / Low lift pumps / Aquifers / Poverty / Irrigated farming / Social impact / Income / Marketing / Pricing / South Asia / India / Bangladesh / Nepal

    Large-amplitude chirped coherent phonons in tellurium mediated by ultrafast photoexcited carrier diffusion

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    We report femtosecond time-resolved reflectivity measurements of coherent phonons in tellurium performed over a wide range of temperatures (3K to 296K) and pump laser intensities. A totally symmetric A1_{1} coherent phonon at 3.6 THz responsible for the oscillations in the reflectivity data is observed to be strongly positively chirped (i.e, phonon time period decreases at longer pump-probe delay times) with increasing photoexcited carrier density, more so at lower temperatures. We show for the first time that the temperature dependence of the coherent phonon frequency is anomalous (i.e, increasing with increasing temperature) at high photoexcited carrier density due to electron-phonon interaction. At the highest photoexcited carrier density of \sim 1.4 ×\times 1021^{21}cm3^{-3} and the sample temperature of 3K, the lattice displacement of the coherent phonon mode is estimated to be as high as \sim 0.24 \AA. Numerical simulations based on coupled effects of optical absorption and carrier diffusion reveal that the diffusion of carriers dominates the non-oscillatory electronic part of the time-resolved reflectivity. Finally, using the pump-probe experiments at low carrier density of 6 ×\times 1018^{18} cm3^{-3}, we separate the phonon anharmonicity to obtain the electron-phonon coupling contribution to the phonon frequency and linewidth.Comment: 22 pages, 6 figures, submitted to PR

    Cholinesterase inhibitors from heartwood of artocarpus fulvicortex F. M. Jarret (Moraceae)

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    Cholinesterase inhibition activities were screened on crude extracts and isolated compounds of the heartwood of Artocarpus fulvicortex. Phytochemical studies on the heartwood of A. fulvicortex have resulted in the isolation of one flavonoid, one stilbenoid and two triterpenes. Their structures were determined by spectroscopic analysis as catechin (1), oxyresveratrol (2), lupeol-3-acetate (3) and friedelin (4). All isolates were evaluated for the first time for anti-cholinesterase activity. Inhibition of acetylcholinesterase (AChE), tested by Ellman’s method and modified TLC bioautographic assay showed catechin (1) and oxyresvetratrol (2) were active agents with detection limit of 2 mM. The microplate assay was carried out using butyrylcholinesterase (BChe) to further confirmed that catechin (1) and oxyresvetratrol (2) displayed positive cholinesterase activity with IC50 values 50.0 mM and 6.25 mM respectively in dose dependent manner

    Geochemistry and provenance of the Lower Siwaliks from southwestern Kohat, western Himalayan Foreland Basin, NW Pakistan

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    Equivalent to the Lower Siwalik Group, the Late Miocene Chinji Formation in Pakistan consists of interbedded in-channel sandstone (SSt) and overbank mudstone (MSt) sequences. Twelve sandstone and sixteen mudstone samples from three different sections of the formation in southwestern Kohat, NW Pakistan were analyzed for major elements and selected trace elements. The Chinji sandstones are feldspathic and lithic arenites. They are mostly matrix-supported, moderately to well sorted, and contain angular to rounded framework grains. Authigenic carbonate makes up most of the matrix. The framework grains consist of abundant monocrystalline quartz, alkali feldspar, and lithic fragments with subordinate mica and trace to accessory amounts of heavy minerals including epidote, monazite, apatite, garnet, rutile, and brown hornblende. The lithic fragments consist of sedimentary, volcanic, and low-grade metamorphic rocks.The average concentration of Zr, Nb and Y, and the Ba/Sc and Ba/Co ratios in the studied samples are lower than the corresponding values for the upper continental crust (UCC) and Post-Archean Australian Shale (PAAS) indicating the presence of mafic phases in the source area(s). The high average Cr/Zr and Cr/V ratios of the investigated samples relative to UCC and PASS also support the presence of mafic lihtologies, possibly chromite and ultramafic rocks in the source region. The La/Sc and Th/Sc ratios of the Chingi samples are more like the UCC while the Th/Co and Cr/Th ratios suggest a major contribution from mafic rocks. The average percent differences of the Chinji samples from both the UCC and PAAS in terms of critical silicic to basic trace element ratios (Ba/Co, Ba/Sc, La/Co, La/Sc, Th/Co, Th/Sc, Zr/Cr, and Zr/Sc) suggest a mafic contribution of 23 to 47% (mudstone) and 56 to 69% (sandstone). The lower Th/U, Rb/Sr and Zr/Sc ratios in the studied samples than the corresponding values of the UCC and PAAS suggest negligible recycling for the sediments of the Chinji Formation. Petrographic point count data on the Chinji sandstone indicate sediment derivation from a dissected arc, suture belt, and recycled orogen corresponding to the Kohistan-Ladakh Arc, the Indus Suture Zone, and the Himalayan Tectonic units, respectively. The different source rocks identified on the basis of various petrographic and geochemical parameters occur as part of the mentioned tectonic domains

    Geochemistry and provenance of the Lower Siwaliks from southwestern Kohat, western Himalayan Foreland Basin, NW Pakistan

    Get PDF
    Equivalent to the Lower Siwalik Group, the Late Miocene Chinji Formation in Pakistan consists of interbedded in-channel sandstone (SSt) and overbank mudstone (MSt) sequences. Twelve sandstone and sixteen mudstone samples from three different sections of the formation in southwestern Kohat, NW Pakistan were analyzed for major elements and selected trace elements. The Chinji sandstones are feldspathic and lithic arenites. They are mostly matrix-supported, moderately to well sorted, and contain angular to rounded framework grains. Authigenic carbonate makes up most of the matrix. The framework grains consist of abundant monocrystalline quartz, alkali feldspar, and lithic fragments with subordinate mica and trace to accessory amounts of heavy minerals including epidote, monazite, apatite, garnet, rutile, and brown hornblende. The lithic fragments consist of sedimentary, volcanic, and low-grade metamorphic rocks.The average concentration of Zr, Nb and Y, and the Ba/Sc and Ba/Co ratios in the studied samples are lower than the corresponding values for the upper continental crust (UCC) and Post-Archean Australian Shale (PAAS) indicating the presence of mafic phases in the source area(s). The high average Cr/Zr and Cr/V ratios of the investigated samples relative to UCC and PASS also support the presence of mafic lihtologies, possibly chromite and ultramafic rocks in the source region. The La/Sc and Th/Sc ratios of the Chingi samples are more like the UCC while the Th/Co and Cr/Th ratios suggest a major contribution from mafic rocks. The average percent differences of the Chinji samples from both the UCC and PAAS in terms of critical silicic to basic trace element ratios (Ba/Co, Ba/Sc, La/Co, La/Sc, Th/Co, Th/Sc, Zr/Cr, and Zr/Sc) suggest a mafic contribution of 23 to 47% (mudstone) and 56 to 69% (sandstone). The lower Th/U, Rb/Sr and Zr/Sc ratios in the studied samples than the corresponding values of the UCC and PAAS suggest negligible recycling for the sediments of the Chinji Formation. Petrographic point count data on the Chinji sandstone indicate sediment derivation from a dissected arc, suture belt, and recycled orogen corresponding to the Kohistan-Ladakh Arc, the Indus Suture Zone, and the Himalayan Tectonic units, respectively. The different source rocks identified on the basis of various petrographic and geochemical parameters occur as part of the mentioned tectonic domains

    Hydraulic simulations to evaluate and predict design and operation of the Chashma Right Bank Canal

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    Irrigation systems / Irrigation canals / Flow control / Velocity / Canal regulation techniques / Hydraulics / Simulation models / Design / Operations / Crop-based irrigation / Distributary canals / Water delivery / Policy / Protective irrigation / Water allocation / Water requirements / Sedimentation / Water distribution / Equity / Water conveyance / Pakistan / Chashma Right Bank Canal

    Localizing gravitational wave sources with optical telescopes and combining electromagnetic and gravitational wave data

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    Neutron star binaries, which are among the most promising sources for the direct detection of gravitational waves (GW) by ground based detectors, are also potential electromagnetic (EM) emitters. Gravitational waves will provide a new window to observe these events and hopefully give us glimpses of new astrophysics. In this paper, we discuss how EM information of these events can considerably improve GW parameter estimation both in terms of accuracy and computational power requirement. And then in return how GW sky localization can help EM astronomers in follow-up studies of sources which did not yield any prompt emission. We discuss how both EM source information and GW source localization can be used in a framework of multi-messenger astronomy. We illustrate how the large error regions in GW sky localizations can be handled in conducting optical astronomy in the advance detector era. We show some preliminary results in the context of an array of optical telescopes called BlackGEM, dedicated for optical follow-up of GW triggers, that is being constructed in La Silla, Chile and is expected to operate concurrent to the advanced GW detectors.Comment: 8 pages, 8 figures, Proceeding for Sant Cugat Forum for Astrophysic
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