11,684 research outputs found
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Changes in fish populations in the Lower Canyons of the Rio Grande
The Lower Canyons of the Rio Grande suffer from environmental degradation that has negatively impacted native fish populations and their distributions. Macrhybopsis aestivalis (speckled chub), Notropis jemezanus (Rio Grande shiner), Rhinichthys cataractae (longnose dace) and Cycleptus elongatus (blue sucker) populations appear to have suffered recent declines. Although diminished water quantity is likely an important factor in these declines, related changes in channel morphology precipitated by massive stands of Arundo donax (giant reed) and Tamarix sp. (salt cedar) may also be responsible. These invasive exotics have essentially channelized the river, disrupted normal sediment distribution and reduced shallow, low-velocity habitats. Much of the Lower Canyons of the Rio Grande are devoid of sandy sediment and most riffles are now composed of gravel and cobble.Integrative Biolog
Microminiature thermocouple monitors own installation
Microminiature thermocouple makes precision gas sidewall temperature readings inside large thrust chambers. It is installed by a technique whereby the sensor monitors its own installation to insure against thermal damage to the thermocouple and ensure minimum disturbance to chamber surfaces
Comparative analyses of space-to-space central power stations
The technological and economical impact of a large central power station in Earth orbit on the performance and cost of future spacecraft and their orbital transfer systems are examined. It is shown that beaming power to remote users cannot be cost effective if the central power station uses the same power generation system that is readily available for provision of onboard power and microwave transmission and reception of power through space for use in space is not cost competitive with onboard power or propulsion systems. Laser and receivers are required to make central power stations feasible. Remote power transmission for propulsion of orbital transfer vehicles promises major cost benefits. Direct nuclear pumped or solar pumped laser power station concepts are attractive with laser thermal and laser electric propulsion systems. These power stations are also competitive, on a mass and cost basis, with a photovoltaic power station
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An Annotated Checklist of the Freshwater Fishes of Texas, with Keys to Identification of Species
Forty-five families and 247 species of fishes are known to inhabit the freshwaters of Texas. We report on the distribution and status of these fishes and provide a key to their identification. Of the native fishes originally found in Texas, five taxa, Notropis orca (phantom shiner), Notropis simus simus (Rio Grande bluntnose shiner), Cyprinella lutrensis blairi (Maravillas red shiner), Gambusia amistadensis (Amistad gambusia) and Gambusia georgei (San Marcos gambusia) are apparently extinct, and three, Oncorhynchus clarki virginalis (Rio Grande cutthroat trout), Hybognathus amarus (Rio Grande silvery minnow) and Gambusia senilis (blotched gambusia) appear to be extirpated from the state. More than 20 percent of the remaining primary freshwater species appear to be in some need of protection.Integrative Biolog
Gravitationally lensed radio emission associated with SMM J16359+6612, a multiply imaged submillimeter galaxy behind A2218
We report the detection of discrete, lensed radio emission from the multiply
imaged, z=2.516 submillimetre selected galaxy, SMM J16359+6612. All three
images are detected in deep WSRT 1.4 GHz and VLA 8.2 GHz observations, and the
radio positions are coincident with previous sub-mm SCUBA observations of this
system. This is the widest separation lens system to be detected in the radio
so far, and the first time that multiply imaged lensed radio emission has been
detected from a star forming galaxy -- all previous multiply-lensed radio
systems being associated with radio-loud AGN. Taking into account the total
magnification of ~45, the WSRT 1.4 GHz observations suggest a star formation
rate of 500 Solar mass/yr. The source has a steep radio spectrum (alpha -0.7)
and an intrinsic flux density of just 3 microJy at 8.2 GHz. Three other SCUBA
sources in the field are also detected by the WSRT, including SMMJ16359+66118,
a singly imaged (and magnified) arclet at z=1.034. Higher resolution radio
observations of SMMJ16359+6612 (and other highly magnified star forming
galaxies) provide a unique opportunity to study the general properties and
radio morphology of intrinsically faint, distant and obscured star forming
galaxies. They can also help to constrain the technical specification of next
generation radio telescopes, such as the Square Kilometre Array.Comment: 5 pages, 2 figures, to appear in A&A letter
International and U.S. Inland Navigation Rules and LNG Transport
Involved in the extensive research that was required by this study included; a research of publications dealing with the engineering and construction of LNG vessels, review of tests conducted by the U.S. Coast guard and the U.S. Bureau of Mines dealing with the possible spill of LNG, establishment of the dangers of LNG, establishment of the U.S. Coast Guard Inland and International Rules of Navigation and how they relate to the safe navigation of LNG vessels, and recommendations for amendments and/or changes to the navigation rules to better ensure the safe navigation of LNG vessels
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