Collapsing supra-massive magnetars: FRBs,the repeating FRB121102 and GRBs     

Patrick Das Gupta  Nidhi Saini 《Journal of Astrophysics and Astronomy》2018,39(1):14

Fast Radio Bursts (FRBs) last for \(\sim \) few milli-seconds and, hence, are likely to arise from the gravitational collapse of supra-massive, spinning neutron stars after they lose the centrifugal support (Falcke & Rezzolla 2014). In this paper, we provide arguments to show that the repeating burst, FRB 121102, can also be modeled in the collapse framework provided the supra-massive object implodes either into a Kerr black hole surrounded by highly magnetized plasma or into a strange quark star. Since the estimated rates of FRBs and SN Ib/c are comparable, we put forward a common progenitor scenario for FRBs and long GRBs in which only those compact remnants entail prompt \(\gamma \)-emission whose kick velocities are almost aligned or anti-aligned with the stellar spin axes. In such a scenario, emission of detectable gravitational radiation and, possibly, of neutrinos are expected to occur during the SN Ib/c explosion as well as, later, at the time of magnetar implosion.  相似文献   

Perceptive of the pyroxene-bearing micrometeorites and their relation to chondrites     

N. G. Rudraswami  D. Fernandes  Agnelo De Araujo  M. Shyam Prasad  S. Taylor 《Meteoritics & planetary science》2018,53(10):2035-2050

We studied 149 pyroxenes from 69 pyroxene-bearing micrometeorites collected from deep-sea sediments of the Indian Ocean and South Pole Water Well at Antarctica, Amundsen-Scott South Pole station. The minor elements in pyroxenes from micrometeorites are present in the ranges as follows: MnO ~0.0–0.4 wt%, Al₂O₃ ~0.0–1.5 wt%, CaO ~0.0–1.0 wt%, Cr₂O₃ ~0.3–0.9 wt%, and FeO ~0.5–4 wt%. Their chemical compositions suggest that pyroxene-bearing micrometeorites are mostly related to precursors from carbonaceous chondrites rather than ordinary chondrites. The Fe/(Fe+Mg) ratio of the pyroxenes and olivines in micrometeorites shows similarities to carbonaceous chondrites with values lying between 0 and 0.2, and those with values beyond this range are dominated by ordinary chondrites. Atmospheric entry of the pyroxene-bearing micrometeorites is expected to have a relatively low entry velocity of <16 km s⁻¹ and high zenith angle (70–90°) to preserve their chemical compositions. In addition, similarities in the pyroxene and olivine mineralogical compositions between carbonaceous chondrites and cometary particles suggest that dust in the solar system is populated by materials from different sources that are chemically similar to each other. Our results on pyroxene chemical compositions reveal significant differences with those from ordinary chondrites. The narrow range in olivine and pyroxene chemical compositions are similar to those from carbonaceous chondrites, and a small proportion to ordinary chondrites indicates that dust is largely sourced from carbonaceous chondrite-type bodies.  相似文献   

Distribution and possible sources of organochlorine residues in sediments of a large urban estuary,Port Jackson,Sydney     

G. F. Birch  S. E. Taylor 《Australian Journal of Earth Sciences》2013,60(4):749-756

Sydney Harbour is surrounded by a large capital city of about four million people and its highly urbanised (86%) catchment supports a substantial industrial base and an extensive transport infrastructure. Large commercial and naval ports occupy the waterway and the harbour is an important recreational area. Surficial sediment in Sydney Harbour contains high concentrations of PCBs, HCB, total chlordane, total DDT, aldrin, dieldrin, heptachlor and heptachlor‐epoxide, but low concentrations of lindane. PCBs, total chlordane, and to a lesser extent dieldrin, are most elevated in sediment in creeks on the southern shores of the harbour suggesting sources within older, highly urbanised/industrialised catchments of western‐central Sydney. There are high concentrations of total DDT and HCB in sediments of the upper harbour and Homebush Bay suggesting that chemical industries on the shores of the estuary in this area are sources of these contaminants. Although no sediment quality guidelines apply in Australia, empirically derived biological effects criteria suggest that sediment over extensive areas of Sydney Harbour may have an adverse impact on biota. Especially of concern are sediments containing high concentrations of chlordane and DDT.  相似文献   

Better air for better health: Forging synergies in policies for energy access,climate change and air pollution     

Shilpa Rao  Shonali Pachauri  Frank Dentener  Patrick Kinney  Zbigniew Klimont  Keywan Riahi  Wolfgang Schoepp 《Global Environmental Change》2013,23(5):1122-1130

Air pollution and its related health impacts are a global concern. This paper addresses how current policies on air pollution, climate change and access to clean cooking fuels can effectively reduce both outdoor and household air pollution and improve human health. A state of the art modeling framework is used that combines an integrated assessment model and an atmospheric model to estimate the spatial extent and distribution of outdoor air pollution exposures. Estimates of household energy access and use are modeled by accounting for heterogeneous household energy choices and affordability constraints for rural and urban populations spanning the entire income distribution. Results are presented for 2030 for a set of policy scenarios on air pollution, climate change and energy access and include spatially explicit emissions of air pollutants; ambient concentrations of PM2.5; and health impacts in terms of disability adjusted life years (DALYs) from both ambient and household air pollution. The results stress the importance of enforcing current worldwide air quality legislation in addressing the impacts of outdoor air pollution. A combination of stringent policies on outdoor air pollution, climate change and access to clean cooking fuels is found to be effective in achieving reductions in average ambient PM2.5 exposures to below World Health Organization recommended levels for a majority of the world's population and results in a significant decline in the global burden of disease from both outdoor and household air pollution.  相似文献   

Seismic stability analysis of piled embankments: A multiphase approach     

Quang Thai Son  Ghazi Hassen  Patrick de Buhan 《国际地质力学数值与分析法杂志》2010,34(1):91-110

The seismic stability analysis of an embankment lying over a soft foundation soil reinforced by a group of vertical piles is performed within the framework of the upper bound kinematic approach of yield design. The analysis is based on a previously developed ‘multiphase’ model of the reinforced ground, which explicitly accounts for the shear and bending resistances of the piles. Making use of appropriate failure mechanisms involving shear zones across which the reinforcements are continuously deforming, along with ‘plastic hinge’ surfaces, upper bound estimates to the critical seismic coefficient of the structure are derived. The results, which are confirmed by the simulations obtained from a finite element elastoplastic code, give clear evidence of the key role played by the bending strength capacities of the piles in ensuring the stability of the pile reinforced embankment. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

Calderas,landslides and paleo-canyons on Piton de la Fournaise volcano (La Réunion Island,Indian Ocean)     

Olivier Merle  Philippe Mairine  Laurent Michon  Patrick Bachèlery  Magali Smietana 《Journal of Volcanology and Geothermal Research》2010,189(1-2):131-142

Based upon a re-interpretation of previous data and a new field campaign, a structural evolution is proposed for the early history of Piton de la Fournaise volcano from 500,000 to 50,000 years. Conceptually, it is shown that the formation of a caldera in which lava flows are contained inside the caldera depression, gives time for erosion to excavate deep canyons on the external slopes of the volcano, for example, the Rivière des Remparts, the Rivière Langevin and the Rivière de l'Est canyons on Piton de la Fournaise volcano. These canyons are infilled when lavas, filling the caldera and overflowing its rim, are able again to flow on the external slopes of the volcano. In the past, this excavating/infilling process has occurred twice following the formation of the Rivière des Remparts and Morne Langevin calderas. The formation of the third caldera, the Plaine des Sables caldera, was followed by the excavation of the current canyons. In addition to this process, two large landslides have been documented in the field. The first, which happened about 300,000 years ago, is apparently the first episode of the break up of Piton de la Fournaise volcano, predating the formation of the four large calderas. The second landslide, which occurred 150,000 years ago and is considered to be less extensive, has carried away the entire southern flank of the Rivière des Remparts caldera.  相似文献   

A strontium,neodymium and oxygen isotope study of hydrothermal metamorphism and crustal anatexis in the Trois Seigneurs Massif,Pyrenees, France     

M. J. Bickle  S. M. Wickham  H. J. Chapman  H. P. Taylor Jr. 《Contributions to Mineralogy and Petrology》1988,100(4):399-417

Nd, Sr, and O isotope analyses have been made on metamorphic and igneous rocks and minerals from a 310–340 Ma Hercynian-age metamorphic terrane in the Pyrenees, France. Lower Paleozoic shales and phyllites have ⁸⁷Sr/⁸⁶Sr values of 0.707–0.717 at 310 Ma, but model values at 310 Ma of 0.709–0.736 (based on assumed depositional age of 450 Ma and an initial ⁸⁷Sr/⁸⁶Sr=0.707). On a regional scale, ⁸⁷Sr/⁸⁶Sr was homogenized to about 0.713 to 0.717 in the higher-grade pelitic schists during metamorphism. Much of this ⁸⁷Sr/⁸⁶Sr exchange occurred at very low grades (below the biotite isograd), but significant changes also accompanied the δ ¹⁸O lowering of the phyllites (+13 to +16) during their transformation to andalusite- and sillimanite-grade schists (δ ¹⁸O=+11 to +12); all of these effects are attributed to pervasive interactions with hydrothermal fluids (Wickham and Taylor 1985). The data also show that a syn-metamorphic plutonic complex, dominated by a biotite granite body, was derived by mixing of a relatively mafic magmatic end-member (⁸⁷Sr/⁸⁶Sr～ 0.7025–0.7050 and δ ¹⁸O～ +7.5 to +8.0) with two metasedimentary sources, both having ⁸⁷Sr/⁸⁶Sr～0.715 and δ ¹⁸O～ +10.0 to +12.0, but with one being more homogeneous than the other. The more homogeneous component and the (mantle-derived?) magmatic end-member dominate at low structural levels within the complex. The less homogeneous end-member that dominates at high levels is clearly derived from the local Paleozoic pelitic schists. A Rb-Sr age of 330±20 Ma was obtained on hornblende from a deep level within the complex, which fixes this age for the regional metamorphism, as well. Although a post-metamorphic granodiorite magma body at Trois Seigneurs also displays heterogeneities in δ ¹⁸O and ⁸⁷Sr/⁸⁶Sr (and thus does not give a clear-cut Rb-Sr isochron), the data are consistent with an emplacement age between 260 and 310 Ma, similar to ages of other late granodiorites in the Pyrenees. ¹⁴³Nd/ ¹⁴⁴Nd is very uniform within the Hercynian crust, both at Trois Seigneurs (? _Nd=?3 to ?7) and elsewhere in the Pyrenees; almost all igneous lithologies have depleted-mantle, mid-Proterozoic model ages, consistent with efficient recycling of crustal material following original crustal accretion in this area at about 1600 Ma or earlier. Rb-Sr mineral ages exhibit a complex cooling history reflecting late Hercynian and Mesozoic thermal events. Our results show that profound homogenization of the ⁸⁷Sr/⁸⁶Sr and ¹⁸O/¹⁶O ratios of large volumes of the crust can occur during regional metamorphism and crustal anatexis, particularly in regions undergoing extensional tectonics. Such processes can significantly modify the isotopic compositions of the protoliths of granitic magmas; this may explain why many peraluminous Hercynian granitoids of Western Europe have anomalously low (⁸⁷Sr/⁸⁶Sr) initial values compared to their probable sedimentary parent rocks.  相似文献   

Major's Creek,N.S.W., Australia — A Devonian epithermal gold deposit     

B. A. Wake  G. R. Taylor 《Mineralium Deposita》1988,23(4):239-246

Mineralized veins at Major's Creek consist of preponderant quartz and carbonate gangue with gold, Au-Ag tellurides and base metal sulphides within silicified and sericitized dykes or granodiorite of the Braidwood Granite. Fluid inclusion studies indicate deposition throughout the range 350–80°C by low salinity fluids. Significant Au-Ag telluride mineralization took place at a temperature of about 155°C. Mineral deposition was due to the separation of a liquid CO₂ phase from an originally CO₂-rich aqueous fluid. Observed argillic alteration is a consequence of acid leaching above the boiling zone. Mineralization is epithermal in character and probably formed during the existence of a hydrothermal convective system. A relationship with similar epithermal gold deposits in the adjacent Eden-Yalwal Rift zone is inferred.  相似文献   

On the inner-layer scale height of boundary-layer flow over low hills     

Anton C. M. Beljaars  Peter A. Taylor 《Boundary-Layer Meteorology》1989,49(4):433-438

The scaling properties of the depth of the inner-layer of flow over low hills are studied by means of numerical solution of the equations. Two closure schemes are applied: the mixing-length model and the E- formulation. It is shown that the scale relation for the inner-layer depth lies between two formulations proposed in literature. It is also shown that the scale relation depends on the closure scheme.Presently at the European Centre for Medium-Range Weather Forecasts, Shinficld Park, Reading, Berkshire RG2 9AX, England.  相似文献   

Partitioning data pertaining to Fe-Mg ordering around trace cations in olivine and low-Ca pyroxene     

R. O. Colson  G. A. McKay  L. A. Taylor 《Contributions to Mineralogy and Petrology》1989,102(2):242-246

We have used trace element partitioning data available in the literature to investigate nonideality of the cations of Yb, Sm, Gd, Ca, Mn, Sc, Ni, and Al in silicate melt, olivine, and low-Ca pyroxene. Results are consistent with ordering of Mg and Fe around trace cations in olivine and pyroxene. On the basis of these data, we suggest there is an increasing tendency for Fe to congregate in the vincinity of the trace cation as the size of the trace cation increases. These results are important both in achieving a better understanding of trace element behavior in crystals and in constraining the temperature and compositional dependence of trace element partitioning.  相似文献