The relationship between the optical Hα filaments and the X-ray emission in the core of the Perseus cluster     

A. C. Fabian  J. S. Sanders  C. S. Crawford  C. J. Conselice  J. S. Gallagher  III    R. F. G. Wyse 《Monthly notices of the Royal Astronomical Society》2003,344(3):L48-L52

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Pyritization of trace metals in mangrove sediments     

R. A. Andrade  C. J. Sanders  G. Boaventura  S. R. Patchineelam 《Environmental Earth Sciences》2012,67(6):1757-1762

The present study investigates the levels of Mn, Zn, Ni, and Co pyritization in mangrove sediments along distinct sedimentary zones in Enseada das Gra?as, a lagoon-type estuary located on the southeastern coast of Brazil. The coastal geology is characterized by intense interactions of trace metals, forming pyrite minerals. Specific orders of DOP (degree of pyritization) and DTMP (degree of trace-metal pyritization) are shown: supratidal flat?<?mangrove forest?<?mud flat. Distinct changes in content along the sediment profiles are noted, where a supratidal flat presented low levels of DOP and DTMP with little variance along the sedimentary depths. The mangrove forest showed relatively high values of DOP and DTMP in the lower depths, while the mud flat showed the highest levels of DOP and DTMP.  相似文献   

Comparison of the growth rates of two stocks ot snapper (Chrysophrys auratus) in south‐east Australian waters using capture‐recapture data     

M. J. Sanders  D. G. M. Powell 《新西兰海洋与淡水研究杂志》2013,47(2):279-284

Between 1957 and 1962, 4155 snapper, Chrysophrys auratus (Bloch & Schneider), were tagged and released at a number of sites in Victoria. By the end of June 1972, 210 had been recaptured, and knowing their lengths at release and recapture and the periods at liberty, we determined the von Bertalanffy growth parameters K and L ₈ ^. The values (with 95% confidence limits) were: eastern stock ‐ K = 0.071 ± 0.040, L₈ = 968 ± 325 mm; western stock ‐ K = 0.068 ± 0.023, L₈ = 1079 ± 209 mm; combined stocks ‐ K = 0.062 ± 0.019, L ₈ = 1119 ± 215 mm. No difference between the stocks was apparent when we compared the estimates of K and L ₈ separately; however, when the estimates of K and L ₈ were compared together, a Wilcoxon's test gave a significance probability of 1.5%, indicating a difference in growth rate between the stocks. For the range of lengths of snapper recaptured, this difference was evidently caused by faster growth of snapper from the western stock.  相似文献   

Tagging indicates at least two stocks of snapper Chrysophrys auratus in south‐east australian waters     

M. J. Sanders 《新西兰海洋与淡水研究杂志》2013,47(2):371-374

During 1957 to 1962, 4 155 snapper Chrysophrys auratus (Bloch & Schneider) were tagged and released at a number of sites in Victoria. From 1957 until 31 June 1972, 210 of these fish have been reported, and the relationship between the release and recapture sites indicates the existence of at least two stocks: One stock extends from central Victoria to eastern South Australia, and the other extends from eastern Victoria to northern New South Wales.  相似文献   

Implications of the carbonaceous chondrite Mn-Cr isochron for the formation of early refractory planetesimals and chondrules     

Edward R.D. Scott  Ian S. Sanders 《Geochimica et cosmochimica acta》2009,73(17):5137-5149

An excellent ⁵³Mn-⁵³Cr isochron for bulk CI, CM, CO, CV, CB, and ungrouped C3 chondrites seems to suggest that each carbonaceous chondrite group acquired its Mn/Cr ratio 4568 ± 1 Myr ago. This age is indistinguishable from the age of Ca-Al-rich inclusions (CAIs), which is considered to be the start of the solar system (t₀). However, carbonaceous chondrites were not assembled until at least 1.5-5 Myr after t₀, to judge by the ²⁰⁷Pb-²⁰⁶Pb and ²⁶Al-²⁶Mg ages of the chondrules within them, and by the fact that they were not melted by heat from the decay of ²⁶Al. Presumably, therefore, these meteorites inherited their bulk Mn-Cr isochron from precursor materials which experienced Mn-Cr fractionation at t₀. As a possible physical mechanism for how the isochron was established initially, and later inherited by the carbonaceous chondrites, we propose the rapid formation at t₀ of planetesimals that were variably depleted in moderately volatile elements, and hence had variably low Mn/Cr. The planetesimals and the undepleted (high Mn/Cr) primitive dust from which they were made shared the same initial ε⁵³Cr, and therefore evolved on an isochron. We suggest that later impact-disruption of the planetesimals produced dusty debris, which became mixed, in various proportions, with unprocessed (high Mn/Cr) dust before accreting to the carbonaceous chondrite parent bodies. With mixing in a closed system, the isochron was unchanged. We infer that some debris-rich material was converted to chondrules prior to accretion. The chondrules could have been formed by flash melting of the mixed dust, or could instead have been made directly by the impact splashing of molten planetesimals, or by condensation from impact-generated vapor plumes.  相似文献   

The circumnuclear material in the Galactic Centre: a clue to the accretion process     

Sanders 《Monthly notices of the Royal Astronomical Society》1998,294(1):35-46

On the basis of 'sticky particle' calculations, it is argued that the gas features observed within 10 pc of the Galactic Centre — the circumnuclear disc (CND) and the ionized gas filaments — as well as the newly formed stars in the inner 1 pc can be understood in terms of tidal capture and disruption of gas clouds on low angular momentum orbits in a potential containing a point mass. The calculations demonstrate that a dissipative component forms a 'dispersion ring', an asymmetric elliptical torus precessing counter to the direction of rotation, and that this shape can be maintained for many orbital periods. For a range of plausible initial conditions, such a structure can explain the morphology and kinematics of the CND and of the most conspicuous ionized filament. While forming the dispersion ring, a small cloud with low specific angular momentum is drawn into a long filament which repeatedly collides with itself at high velocity. The compression in strong shocks is likely to lead to star formation even in the near tidal field of the point mass. This process may have general relevance to accretion on to massive black holes in normal and active galactic nuclei.  相似文献   

X-ray active galactic nuclei in the core of the Perseus cluster     

S. Santra  J. S. Sanders  A. C. Fabian 《Monthly notices of the Royal Astronomical Society》2007,382(2):895-902

We present a study of the X-ray emission from the nuclei of galaxies observed in the core of the Perseus cluster in a deep exposure with Chandra . Point sources are found coincident with the nuclei of 13 early-type galaxies, as well as the central galaxy NGC 1275. This corresponds to all galaxies brighter than M _B > −18 in the Chandra field. All of these sources have a steep power-law spectral component and four have an additional thermal component. The unabsorbed power-law luminosities in the 0.5–7.0 keV band range from 8 × 10³⁸ to 5 × 10⁴⁰ erg s⁻¹. We find no simple correlations between the K -band luminosity, or the FUV and NUV AB magnitudes of these galaxies and their X-ray properties. We have estimated the black hole masses of the nuclei using the K -band   M _BH– L _{K bol}  relation and again find no correlation between black hole mass and the X-ray luminosity. Bondi accretion on to the black holes in the galaxies with minihaloes should make them much more luminous than observed.  相似文献   

Confrontation of MOdified Newtonian Dynamics with the rotation curves of early-type disc galaxies     

R. H. Sanders  E. Noordermeer 《Monthly notices of the Royal Astronomical Society》2007,379(2):702-710

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Temporal and spatial variations of trace metal concentrations in oysters from the Patuxent River, Maryland     

Gerhardt F. Riedel  George R. Abbe  James G. Sanders 《Estuaries and Coasts》1998,21(3):423-434

Concentrations of copper (Cu), silver (Ag), and cadmium (Cd) in eastern oysters (Crassostrea virginica) from the upper Patuxent River estuary analyzed since 1986 (Cd since 1991) were high relative to concentrations in other sites in the United States analyzed by the National Oceanic and Atmospheric Administration National Status and Trends program. Patuxent River oysters had above average concentrations of Ag and Cu, and unusually high concentrations of Cd. Metal concentrations were highest in summer, a period in which oyster meat condition index was relatively low. Copper values were highest in 1986–1987, likely elevated by erosion from Cu-Ni alloy condensers at a local power plant. Silver and Cd values exhibited more year-to-year variation. A number of factors were examined as candidates to explain the interannual differences, including river flow, salinity, and oyster condition, but none was able to explain the high and low years. Samples collected in spring and late summer of 1996 at a number of oyster bars located along the length of the Patuxent River showed that concentrations of all three metals increased with distance up-river. For Cd, the upstream increase was linear with distance, while for Ag and Cu, there was a secondary maximum near river km 16. A close correlation was observed between Ag and Cu for individuals at each site, with a poorer correlation between Cd and either Ag or Cu.  相似文献   

A Method of Directly Estimating Natural Mortality and Initial Tagging Mortality Applicable to Certain Exploited Mollusc Populations     

Sanders  M. J. 《ICES Journal of Marine Science》1969,32(3):416-418

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