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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Marine biology 34 (1976), S. 59-66 
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Using a light trap, zooplankton was sampled at three stations at Heron Reef, Great Barrier Reef: (a) a typical patch reef in the Heron lagoon, (b) a site in 8 m water on the southern slope of Heron reef, and (c) a station approximately 300 m south of (b), in the open water of the channel between Heron and Wistari reefs. Samples were taken at the surface and on the substratum at the lagoon and reef-slope stations, and at 3 to 6 m depth at the open-water station. A total of 114 taxa, many recognized as species, were distinguished in the samples. Pronounced differences existed in abundance, diversity, and taxonomic composition of the samples obtained at different stations. Less pronounced differences existed between surface and substratum samples from the same station. Near-reef samples were more similar to one another than to open-water samples. Decapod larvae, amphipods, and cumaceans were all abundant in near-reef samples and very rare in open-water samples. Forams, isopods, mysids and polychaetes were common in near-reef samples, and rare or absent in open-water samples. Copepods were abundant in all samples but the near-reef samples contained predominantly different species than did samples from the open water. The near-reef fauna included 66 taxa which did not occur in open-water samples. Many of these were epibenthic rather than strictly planktonic in behaviour.
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  • 2
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Reproduction ofHeliocidaris erythrogramma (Valenciennes) andH. tuberculata (Lamarck) was compared through examination of oogenesis, spermatogenesis and monthly measurement of the gonad index. These species occur sympatrically in the Sydney region. Their reproduction was examined at two sites near Botany Bay, New South Wales, Australia, from February 1989 through January 1990.H. erythrogramma produces buoyant, 450µm-diam eggs and the sperm have a head region 10µm in length. By contrast,H. tuberculata produces negatively-buoyant, 95µm-diam eggs and the sperm have a head region 4µm in length. Histochemical examination of the gonads revealed that periodic acid Schiff-positive (PAS +) material stored in the nutritive phagocytes appears to support vitellogenesis in both species. InH. tuberculata this material is utilized in the formation of PAS + yolk oligolecithal eggs, whereas inH. erythrogramma the PAS + material appears to be converted to lipid yolk in macrolecithal eggs.H. erythrogramma had a seasonal reproductive pattern with a 3 mo summer spawning period, whereas both populations ofH. tuberculata had a 9 mo breeding period characterized by the continual presence of nutrient reserves and vitellogenic oocytes which rapidly replaced spawned ova. Spawning ceased only for 3 mo over the summer. Due to the 9 mo spawning ofH. tuberculata it is not clear what factors serve to cue reproduction in this species.
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  • 3
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Samples of zooplankton were collected using a light trap at 5 sites in 3 locations on Heron Reef: (a) near the surface of open water 300 m south of the reef crest; (b) near the surface and at the substratum on the upper reef slope; (c) near the surface and at the substratum on a patch reef in the Heron lagoon. The collections made were analysed with respect to: (a) distribution and abundance of the taxa present; (b) faunistic relationships among samples from the 5 sites; (c) seasonal changes in both of these factors. A total of 181 taxa were recognised, many of which are identified to species, and many of which are demersal or epi-benthic in habits. At all sites, the abundance of animals increases from May to November, and faunal similarity between sites also changes. In May, reef collections are generally similar to one another and, with the exception of the slope surface collection, distinct from the open water collection. In September this pattern is enhanced, but in November slope collections more closely resemble the open water collection, while the lagoon collections are quite distinct from slope and open water collections. Lagoon surface and substratum collections also differ considerably from each other at this time. A MULTCLAS cluster analysis of the samples confirms the pattern of change in faunal relationships seen from examination of the collections. Dark-trap samples were used to assess the bias introduced by using a light to attract the animals, as well as to estimate the density of the fauna sampled. Lighttrap samples over-represent calanoid and harpacticoid copepods and gammarid amphipods, but the bias is minor and does not prevent use of a light trap as an efficient sampling tool for near-reef plankton. The density of the fauna is approximately 700 animals m-3 at all sites. This may be a lower density than in more tropical regions. Pronounced seasonal changes occur in faunal composition of collections from open water and from surface sites. The substratum collections show more constant faunas throughout the year. Major changes are primarily in the proportions of copepods and cumaceans present. Changes in amphipod numbers are also important at lagoon sites.
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  • 4
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 190 (1961), S. 560-561 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Methods for maintaining breeding stocks of D. tryoni in the laboratory are described by Bateman*. Development of the eggs, an account of which will be published in due course, follows the typical dipteran pattern, with cleavage leading to the formation of a blastoderm by 7J hr. at 25 C. and ...
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  • 5
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The leading terms of the magnetic field spectrum for the Helically Symmetric Experiment [Fusion Technol. 27, 273 (1995)] at low magnetic field are determined by analyzing the orbits of passing particles. The images produced by the intersection of electron orbits with a fluorescent mesh are recorded with a charge coupled device and transformed into magnetic coordinates using a neural network. To obtain the spectral components, the transformed orbits are then fit to an analytic expression that models the drift orbits of the electrons. The results confirm for the first time that quasihelical stellarators have a large effective transform that results in small excursions of particles from a magnetic surface. The drift orbits are also consistent with a very small toroidal curvature component in the spectrum. An external magnetic perturbation, nearly resonant with the transform, is shown to induce a large excursion of the particle orbit off a flux surface. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Entomology 11 (1966), S. 23-46 
    ISSN: 0066-4170
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 5 (1993), S. 4061-4071 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Probe measurements over the two-dimensional plasma cross section of the average and fluctuating density, electron temperature, and potential, as well as the Reynolds stress, have been made in the Interchangeable Module Stellarator (IMS) [D. T. Anderson, J. A. Derr, and J. L. Shohet, IEEE Trans. Plasma Sci. PS-9, 212 (1981)]. These measurements were performed at two magnetic field strengths, and also when a positively biased electrode induces a poloidal plasma flow. The data shows the fluctuation-induced transport to be poloidally asymmetric and dependent upon the location of the electron cyclotron resonance position, and upon the electrode biasing. The induced poloidal plasma flow changes the nominally outward fluctuation-induced particle transport to be inward (negative radial transport) by changing the phase relationship of the density and potential oscillations. The amplitude of the density and potential fluctuations are, in general, not reduced by the sheared poloidal flow. Calculations are presented comparing the computed Reynolds stress induced poloidal plasma flows with the flow calculated from momentum balance.
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  • 8
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Recent experiments in the Advanced Toroidal Facility (ATF) torsatron [Plasma Physics and Controlled Nuclear Fusion Research 1990 (IAEA, Vienna, in press)] have emphasized the role of magnetic configuration control in transport studies. Long-pulse plasma operation up to 20 sec has been achieved with electron cyclotron heating (ECH). With neutral beam injection (NBI) power of ≥1 MW, global energy confinement times of 30 msec have been obtained with line-average densities up to 1.3×1020 m−3. The energy confinement and the operational space in ATF are roughly the same as those in tokamaks of similar size and field. The empirical scaling observed is similar to gyro-reduced Bohm scaling with favorable dependences on density and field offsetting an unfavorable power dependence. The toroidal current measured during ECH is identified as the bootstrap current. The observed currents agree well with predictions of neoclassical theory in magnitude and in parametric dependence. Variations of the magnetic configuration in discharges heated by ECH alone and by NBI change plasma transport and plasma profiles. Magnetic fluctuations respond to the concomitant pressure profile variations. Comparative studies of edge fluctuations in the Texas experimental tokamak (TEXT) [Plasma Physics and Controlled Nuclear Fusion Research 1990 (IAEA, Vienna, in press)] and the ATF stellarator showed remarkable similarity in the levels of fluctuations and the existence of a velocity shear layer.
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  • 9
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 29 (1986), S. 3807-3812 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The numerically predicted magnetic surface structure within the separatrix of the interchangeable module stellarator (IMS) [IEEE Trans. Plasma Sci. PS-9, 212 (1981)] has been measured experimentally with the use of an electron beam. The results show nested, well-formed surfaces with a rotational transform profile corresponding to the predicted profile. In the area outside the separatrix, regions of localized magnetic flux emergence from the coil volume (modular divertors) have been seen using an electron beam as well as during plasma operation, and correspond to regions of localized particle flux emergence from between the modular coils.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 2599-2606 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A Mach probe is used to measure poloidal and toroidal flows induced by a biased electrode in IMS. Mach probe theories are reviewed and classified as either magnetized or unmagnetized. A simple geometric model of the IMS Mach probe shows that the variation of the effective probe area as a function of the probe orientation with respect to the magnetic field is 20%–25%, predicting the probe to be only slightly magnetized. Measurements of the variation in the total ion saturation current collected by the probe, as the angle with respect to the magnetic field is varied, demonstrate this level of magnetization only at low neutral pressure at large minor radius, while in other cases the variation in the total collected current is negligible. Based on this result an unmagnetized model [M. Hudis and L. M. Lidsky, J. Appl. Phys. 41, 5011 (1970)] is chosen to analyze the IMS Mach probe data. Comparison of Mach probe poloidal flow measurements as a function of minor radius to calculations of the E×B drift velocity and the ion diamagnetic drift velocity from radial profiles of floating potential and ion saturation current, respectively, shows agreement to within 15%.
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