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41.
The Induced Gravitational Collapse (IGC) paradigm points to a binary origin for the longduration gamma-ray burst (GRBs) associated with supernovae (SN). In this one, a carbon-oxygen core (COcore) explodes in a Type Ib/c SN in presence of a close neutron star (NS) companion. The SN triggers a hypercritical accretion into the NS and depending on the initial binary parameters, two outcomes are possible givimg place to two family of long GRBs: binary-driven hypernova (BdHNe), where the NS reaches its critical mass, and collapses to a black hole (BH), emitting a GRB; and x-ray flashes (XRFs) where the hypercritical accretion onto the NS is not sufficient to induce its gravitational collapse. We perform 3-dimensional (3D) numerical simulations of the IGC paradigm with the smoothed particle hydrodynamics (SPH) technique. We determine whether the star gravitational collapse is possible and assess if the binary holds gravitationally bound or it becomes unbound by the SN explosion. 相似文献
42.
P.M. Chittaro P. Usseglio B.J. Fryer P.F. Sale 《Estuarine, Coastal and Shelf Science》2006,67(4):673-680
Lutjanus apodus (Schoolmaster) were collected from several mangroves and coral reefs at Turneffe Atoll, Belize, in order to investigate whether elemental concentrations from the otolith edge could be used as a means to identify the habitat (mangrove or coral reef) and site (9 mangrove sites and 6 reef sites) from which they were collected. Results of a two factor nested MANOVA (sites nested within habitat) indicated significant differences in elemental concentrations between habitats (i.e., mangrove versus reef) as well as among sites. When separate Linear Discriminant Function Analyses (LDFA) were used to assess whether the spatial variability in otolith chemistry was sufficient to differentiate individuals to their respective habitats or sites, the results indicated that fish were classified (jackknife procedure) with a moderate to poor degree of accuracy (i.e., on average, 67% and 40% of the individuals were correctly classified to the habitat and site from which they were collected, respectively). Using a partial Mantel test we did not find a significant correlation between the differences in otolith elemental concentrations between sites and the distance between sites, while controlling the effect of habitat type (mangrove or reef). This suggests that for mangrove and reef sites at Turneffe Atoll, Belize, the overlap in terms of L. apodus otolith elemental concentrations is too high for investigations of fish movement. Finally, by comparing previously published Haemulon flavolineatum otolith chemistry to that of L. apodus we assessed whether these species showed similar habitat and/or site specific patterns in their otolith chemistry. Although both species were collected from the same sites our results indicated little similarity in their elemental concentrations, thus suggesting that habitat and site elemental signatures are species specific. 相似文献
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44.
C.G. Weisener J.W. Guthrie C.M. Smeaton D. Paktunc B.J. Fryer 《Journal of Geochemical Exploration》2011
Globally arsenic (As) is a ubiquitous trace element derived from the natural weathering of As-bearing rock. With the onset of reducing conditions, the prevalence of aqueous As(III) may be intensified through biotic and abiotic processes. Here we evaluate the stability of arsenic bearing Ca–Fe hydroxide phases collected from exposed tailings at Ketza River mine, Yukon, Canada, during the reductive dissolution of both acid treated and untreated samples by Shewanella putrefaciens 200R and Shewanella sp. ANA-3. Samples were acid treated in order to remove Ca–Fe oxide coatings and evaluate the influence of these coatings on the rates of microbial Fe(III) and As(V) reduction. Environmental scanning electron microscope (ESEM) micrographs of the solid phase show significant differences in the chemistry and physical morphology of the material by the bacteria over time and are especially evident in the acid treated samples. Moreover, while solution chemistry showed similar As(III) respiration rates of the inoculated acid treated samples for both ANA3 and 200R at ~ 1.1 × 10−6 μM·s− 1·m− 2, the Fe(II) respiration rates differed at 1.4 × 10− 7 and 9.5 × 10− 8 μM·s− 1·m−2 respectively, thus suggesting strain specific metal reduction metabolic pathways Additionally, the enhanced metal reduction observed in the acid treated inoculated samples suggests that the presence of the Ca–Fe hydroxide phase in the untreated samples acted as a barrier, inhibiting the bacteria from accessing the metals. This has implications for increased mobilization of metals by metal reducing bacteria within areas of increased acidity, such as acid mine drainage sites and industrial tailings ponds that can come into contact with surface and ground water sources. 相似文献
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Nelson?O.?Campos-AlvarezEmail author Iain?M.?Samson Brian?J.?Fryer 《Mineralium Deposita》2012,47(4):441-465
The Ferguson Lake Ni–Cu–Co–platinum-group element (PGE) deposit in Nunavut, Canada, occurs near the structural hanging wall
of a metamorphosed gabbroic sill that is concordant with the enclosing country rock gneisses and amphibolites. Massive to
semi-massive sulfide occurs toward the structural hanging wall of the metagabbro, and a low-sulfide, high-PGE style of mineralization
(sulfide veins and disseminations) locally occurs ~30–50 m below the main massive sulfide. Water–rock interaction in the Ferguson
Lake Ni–Cu–Co–PGE deposit is manifested mostly as widespread, post-metamorphic, epidote–chlorite–calcite veins, and replacement
assemblages that contain variable amounts of sulfides and platinum-group minerals (PGM). PGM occur as inclusions in magmatic
pyrrhotite and chalcopyrite in both the massive sulfide and high-PGE zones, at the contact between sulfides and hornblende
or magnetite inclusions in the massive sulfide, in undeformed sulfide veins and adjacent chlorite and/or epidote halos, in
hornblende adjacent to hydrothermal veins, and in plagioclase–chlorite aggregates replacing garnet cemented by sulfide. The
PGM are mostly represented by the kotulskite (PdTe)–sobolevskite (PdBi) solid solution but also include michenerite (PdBiTe),
froodite (PdBi2), merenskyite (PdTe2), mertieite II (Pd8[Sb,As]3), and sperrylite (PtAs2) and occur in variety of textural settings. Those that occur in massive and interstitial sulfides, interpreted to be of magmatic
origin and formed through exsolution from base metal sulfides at temperatures <600°C, are dominantly Bi rich (i.e., Te-bearing
sobolevskite), whereas those that occur in late-stage hydrothermal sulfide/silicate veins and their epidote–chlorite alteration
halos tend to be more Te rich (i.e., Bi-bearing kotulskite). The chemistry and textural setting of the various PGM supports
a genetic model that links the magmatic and hydrothermal end-members of the sulfide–PGM mineralization. The association of
PGM with magmatic sulfides in the massive sulfide and high-PGE zones has been interpreted to indicate that PGE mineralization
was initially formed through exsolution from base metal sulfides which formed by magmatic sulfide liquid segregation and crystallization.
However, the occurrence of PGM in undeformed sulfide-bearing veins and in their chlorite–epidote halos and differences in
PGM chemistry indicate that hydrothermal fluids were responsible for post-metamorphic redistribution and dispersion of PGE. 相似文献
48.
Sheldon R. Huelin Henry P. Longerich Derek H.C. Wilton Brian J. Fryer 《Journal of Geochemical Exploration》2006,91(1-3):110-124
Iron–manganese oxide coatings form on a wide range of geologic samples where they have the ability to adsorb elements and potentially act as a mineral exploration/environmental monitoring tool. In this study, Fe–Mn oxide coatings on stream pebbles were collected from streams in four study areas located across the province of Newfoundland and Labrador, Canada. The study locations were in areas of former copper mines (Tilt Cove and Betts Cove), carbonate geology (Robinsons River), and a metropolitan area (Rennies River). Collected pebbles underwent a simple sample preparation procedure and were then analyzed for a wide range of elements by LA-ICP-MS after optimization of the operating conditions. Water samples accompanied the pebbles, and these were analyzed for pH, dissolved oxygen, conductivity, and a large selection of elements by ICP-MS. Multivariate statistics, in the form of Principal Component Factor Analysis (PCFA) was performed on both data sets. Graphs of the factor scores from the PCFA produced groupings of the samples that were related to geologic/environmental inputs. The loading of variables in each factor was related to the adsorption of the element either to the MnO2 or Fe2O3 phase with most elements except Cr and Cu displaying preferential adsorption to MnO2. Elemental Fe–Mn oxide coating concentrations were a result of the element's affinity (chalcophile, lithophile, or siderophile), pH of the environment, stream water concentration, and amount of each oxide phase present. Even with these complications, LA-ICP-MS analysis of Fe–Mn oxides was able to identify areas of heavy metal pollution and locate geologic inputs. 相似文献
49.
Gerard J. Fryer 《Geophysical Journal International》1980,63(3):747-758
b
Of the many schemes available for computing synthetic seismograms, the reflectivity method is probably the most widely used because of its ability to provide complete solutions. The method does, however, suffer the disadvantage that intermediate results are quite difficult to interpret. A new reflectivity technique, here called reflectivity-slowness, results if the original method is reformulated using a slowness rather than a spectral approach. The new procedure bears a strong similarity to the WKBJ method, but retains the ability to give complete solutions. The reflectivity-slowness and WKBJ methods share the property that intermediate results are readily interpreted; this feature may eventually be exploited in the solution of the inverse problem. 相似文献
Of the many schemes available for computing synthetic seismograms, the reflectivity method is probably the most widely used because of its ability to provide complete solutions. The method does, however, suffer the disadvantage that intermediate results are quite difficult to interpret. A new reflectivity technique, here called reflectivity-slowness, results if the original method is reformulated using a slowness rather than a spectral approach. The new procedure bears a strong similarity to the WKBJ method, but retains the ability to give complete solutions. The reflectivity-slowness and WKBJ methods share the property that intermediate results are readily interpreted; this feature may eventually be exploited in the solution of the inverse problem. 相似文献
50.