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  • 1
    ISSN: 1573-5117
    Keywords: Macroinvertebrates ; wetlands ; seasonal ; nutrients ; Western Australia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Physicochemical attributes were measured and aquatic macroinvertebrates were collected from six wetlands near Perth, Western Australia at three weekly intervals over a 13 month period from August 1988 to September 1989. The six wetlands encompassed a range of depths, pH, concuctivities, nutrient concentrations and colours. Temporal changes in the macroinvertebrate communities appeared to be related to seasonal changes in the physical and chemical characteristics of the wetlands. Community composition differed more between the less enriched wetlands then the higly enriched wetlands where communities were generally similar. High species richness was associated with seasonal drying. High macro invertebrate abundance appeared to be associated with the presence of either green algal or cyanobacterial blooms in the enriched wetlands. The highest macroinvertebrate biomass was recorded in wetlands with both cyanobacterial blooms and abundant macrophytes present.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-5117
    Keywords: macroinvertebrates ; sampling methods ; wetlands ; classification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Macroinvertebrate communities sampled by a corer, plankton net and sweep net from five wetlands on the Swan Coastal Plain were compared. The composition of the fauna collected in sweeps and tows was generally similar and differed from that collected in the cores. Cores caught fewer species than tows and sweeps at all wetlands and did not capture fast swimming hemipterans or less abundant taxa. The highest species richness was recorded in sweep samples in four out of the five wetlands. Classification (TWIN-SPAN) and ordination (SSH) of the samples collected in sweeps and tows gave good separation of the wetlands, whereas classification of core samples did not. Coring appeared to be the least suitable sampling method for describing the major components of the macroinvertebrate communities of these wetlands. Plankton tows were useful if the time available for sorting was limited as these samples were free of sediments and generally gave similar results to those obtained with sweeps. Sweeps appeared to be the most useful method for a large classification study as they collected more species and resulted in the best discrimination amongst wetlands.
    Type of Medium: Electronic Resource
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  • 3
    Publication Date: 2019-07-13
    Description: The distribution of dust in the ecliptic plane between 0.96 and 1.04 au has been inferred from impacts on the two Solar Terrestrial Relations Observatory (STEREO) spacecraft through observation of secondary particle trails and unexpected off-points in the heliospheric imager (HI) cameras. This study made use of analysis carried out by members of a distributed webbased citizen science project Solar Stormwatch. A comparison between observations of the brightest particle trails and a survey of fainter trails shows consistent distributions. While there is no obvious correlation between this distribution and the occurrence of individual meteor streams at Earth, there are some broad longitudinal features in these distributions that are also observed in sources of the sporadic meteor population. The different position of the HI instrument on the two STEREO spacecraft leads to each sampling different populations of dust particles. The asymmetry in the number of trails seen by each spacecraft and the fact that there are many more unexpected off-points in the HI-B than in HI-A indicates that the majority of impacts are coming from the apex direction. For impacts causing off-points in the HI-B camera, these dust particles are estimated to have masses in excess of 10 (exp17) kg with radii exceeding 0.1 m. For off-points observed in the HI-A images, which can only have been caused by particles travelling from the anti-apex direction, the distribution is consistent with that of secondary 'storm' trails observed by HI-B, providing evidence that these trails also result from impacts with primary particles from an anti-apex source. Investigating the mass distribution for the off-points of both HI-A and HI-B, it is apparent that the differential mass index of particles from the apex direction (causing off-points in HI-B) is consistently above 2. This indicates that the majority of the mass is within the smaller particles of this population. In contrast, the differential mass index of particles from the anti-apex direction (causing off-points in HI-A) is consistently below 2, indicating that the majority of the mass is to be found in larger particles of this distribution.
    Keywords: Astronomy
    Type: GSFC-E-DAA-TN9123 , Monthly Notices of the Royal Astronomical Society (MNRAS); 420; 2; 1355-1366
    Format: application/pdf
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  • 4
    Publication Date: 2019-07-13
    Description: A series of large scale wind tunnel experiments were conducted on a gimbal mounted Cassegrainian telescope enclosed in a shroud with various aerodynamic fairings. The optical aperture was open to the airstream, resulting in acoustic inputs to the telescope. Resonance was shown to be dependent on free stream Mach number, internal cavity and external fairing geometry, and the angle of the plane of the opening relative to the free stream direction. Configurations were found which caused low noise and low unsteady internal loads at the expense of decreased view angle. Air injection over the cavity aided in reducing acoustic resonance.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 74-195 , Aerospace Sciences Meeting; Jan 30, 1974 - Feb 01, 1974; Washington, DC
    Format: text
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  • 5
    Publication Date: 2019-07-13
    Description: Transonic testing of an NACA 64A010 airfoil at the Ohio State University Aero-Astro Research Laboratory is described, and results of fixed angle of attack and pitch oscillation experiments are discussed. The operating range was Mach 0.20 to 1.07 with available total pressures of 140,000 N/m2 to 620,000 N/m2. The airfoil model was mounted on roller bearings installed in the solid sidewalls of the tunnel test section. The equipment included transducers to measure unsteady pressures, and static pressure taps obtaining steady-state data. The data gathered at Mach 0.8 gave an indication of the influence of the natural shock instability and shock-induced flow separation on the unsteady pressures, with the location of the peak disturbance level shifting forward in the comparison of 0 to 2 deg pitch angle data. The oscillating airfoil data is examined in terms of harmonic content and the in-phase and out-of-phase components. It is concluded that the experimental data has good qualitative comparison with methods accounting for shock interaction.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 79-0330 , American Institute of Aeronautics and Astronautics, Aerospace Sciences Meeting; Jan 15, 1979 - Jan 17, 1979; New Orleans, LA
    Format: text
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