34,432 research outputs found
Estimation of Standardized Effort in the Heterogeneous Gulf of Mexico Shrimp Fleet
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.
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
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 A 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
1.4 10cm and the sample temperature of 3K, the
lattice displacement of the coherent phonon mode is estimated to be as high as
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 10 cm, 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)
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
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
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
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
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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