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101.
A. Bajat O. Godet J.-L. Atteia S. Maestre D. Rambaud V. Waegebaert C. Amoros S. Bordon S. Delaigue M. Galliano B. Houret K. Lacombe P. Mandrou W. Marty R. Pons P. Ramon 《Experimental Astronomy》2018,46(2):337-356
French (CNES) and Chinese (CNSA) space agencies collaborate to build the SVOM (Space-based multi-band Variable Object Monitor) mission due to be launched in 2021 to study gamma-ray bursts and high-energy transients. The SVOM prime instrument, ECLAIRs, will detect and localize GRBs autonomously as well as provide a spectral and temporal characterization of the GRB prompt emission. ECLAIRs is expected to detect around 200 GRBs during the 3 year nominal lifetime of the mission. ECLAIRs is a wide-field (\(\sim 2 \text {sr}\)) coded mask camera with a detection plane made of 8 independent sectors of 800 Schottky CdTe detectors working in the 4-150 keV energy range. Each sector is connected to independent readout electronics. In this paper, we focus on the study of the temporal performance and we estimate how dead time will affect bright transient lightcurves. We discuss the analytical model based on simulations over a large range of source count rates on a dedicated test bench. We show that dead time will not significantly affect ECLAIRs data, even for the brightest GRBs (3.7% of lost counts for a count rate of 105 counts.s??1 over the detection plane in the energy range 4?150 keV) and our model can nicely correct the parts of the lightcurves which are the most affected by dead time effects for very bright GRBs. 相似文献
102.
Data conflicts in fishery models: incorporating hydroacoustic data into the Prince William Sound Pacific herring assessment model 总被引:2,自引:0,他引:2
103.
104.
We use the results of elevated pressure melting experiments to constrain the role of melt/mantle reaction in the formation
of tholeiitic magma from Kilauea volcano, Hawaii. Trace element abundance data is commonly interpreted as evidence that Kilauea
tholeiite is produced by partial melting of garnet lherzolite. We experimentally determine the liquidus relations of a tightly
constrained estimate of primary tholeiite composition, and find that it is not in equilibrium on its liquidus with a garnet
lherzolite assemblage at any pressure. The composition is, however, cosaturated on its liquidus with olivine and orthopyroxene
at 1.4 GPa and 1425 °C, from which we infer that primary tholeiite is in equilibrium with harzburgite at lithospheric depths
beneath Kilauea. These results are consistent with our observation that tholeiite primary magmas have higher normative silica
contents than experimentally produced melts of garnet lherzolite. A model is presented whereby primary tholeiite forms via
a two-stage process. In the first stage, magmas are generated by melting of garnet lherzolite in a mantle plume. In the second
stage, the ascent and decompression of magmas causes them to react with harzburgite in the mantle by assimilating orthopyroxene
and crystallizing olivine. This reaction can produce typical tholeiite primary magmas from significantly less siliceous garnet
lherzolite melts, and is consistent with the shift in liquidus boundaries that accompanies decompression of an ascending magma.
We determine the proportion of reactants by major element mass balance. The ratio of mass assimilated to mass crystallized
(Ma/Mc) varies from 2.7 to 1.4, depending on the primary magma composition. We use an AFC calculation to model the effect of melt/harzburgite
reaction on melt rare earth and high field strength element abundances, and find that reaction dilutes, but does not significantly
fractionate, the abundances of these elements. Assuming olivine and orthopyroxene have similar heats of fusion, the Ma/Mc ratio indicates that reaction is endothermic. The additional thermal energy is supplied by the melt, which becomes superheated
during adiabatic ascent and can provide more thermal energy than required. Melt/harzburgite reaction likely occurs over a
range of depths, and we infer a mean depth of 42 km from our experimental results. This depth is well within the lithosphere
beneath Kilauea. Since geochemical evidence indicates that melt/harzburgite reaction likely occurs in the top of the Hawaiian
plume, the plume must be able to thin a significant portion of the lithosphere.
Received: 4 February 1997 / Accepted: 27 August 1997 相似文献
105.
J. Tzanopoulos R. Mouttet A. Letourneau I.N. Vogiatzakis S.G. Potts K. Henle R. Mathevet P. Marty 《Global Environmental Change》2013,23(1):167-178
The development of effective environmental management plans and policies requires a sound understanding of the driving forces involved in shaping and altering the structure and function of ecosystems. However, driving forces, especially anthropogenic ones, are defined and operate at multiple administrative levels, which do not always match ecological scales. This paper presents an innovative methodology of analysing drivers of change by developing a typology of scale sensitivity of drivers that classifies and describes the way they operate across multiple administrative levels. Scale sensitivity varies considerably among drivers, which can be classified into five broad categories depending on the response of ‘evenness’ and ‘intensity change’ when moving across administrative levels. Indirect drivers tend to show low scale sensitivity, whereas direct drivers show high scale sensitivity, as they operate in a non-linear way across the administrative scale. Thus policies addressing direct drivers of change, in particular, need to take scale into consideration during their formulation. Moreover, such policies must have a strong spatial focus, which can be achieved either by encouraging local–regional policy making or by introducing high flexibility in (inter)national policies to accommodate increased differentiation at lower administrative levels. High quality data is available for several drivers, however, the availability of consistent data at all levels for non-anthropogenic drivers is a major constraint to mapping and assessing their scale sensitivity. This lack of data may hinder effective policy making for environmental management, since it restricts the ability to fully account for scale sensitivity of natural drivers in policy design. 相似文献
106.
The beginnings of hydrous mantle wedge melting 总被引:5,自引:3,他引:2
Christy?B.?TillEmail author Timothy?L.?Grove Anthony?C.?Withers 《Contributions to Mineralogy and Petrology》2012,163(4):669-688
This study presents new phase equilibrium data on primitive mantle peridotite (0.33 wt% Na2O, 0.03 wt% K2O) in the presence of excess H2O (14.5 wt% H2O) from 740 to 1,200°C at 3.2–6 GPa. Based on textural and chemical evidence, we find that the H2O-saturated peridotite solidus remains isothermal between 800 and 820°C at 3–6 GPa. We identify both quenched solute from
the H2O-rich fluid phase and quenched silicate melt in supersolidus experiments. Chlorite is stable on and above the H2O-saturated solidus from 2 to 3.6 GPa, and chlorite peridotite melting experiments (containing ~6 wt% chlorite) show that
melting occurs at the chlorite-out boundary over this pressure range, which is within 20°C of the H2O-saturated melting curve. Chlorite can therefore provide sufficient H2O upon breakdown to trigger dehydration melting in the mantle wedge or perpetuate ongoing H2O-saturated melting. Constraints from recent geodynamic models of hot subduction zones like Cascadia suggest that significantly
more H2O is fluxed from the subducting slab near 100 km depth than can be bound in a layer of chloritized peridotite ~ 1 km thick
at the base of the mantle wedge. Therefore, the dehydration of serpentinized mantle in the subducted lithosphere supplies
free H2O to trigger melting at the H2O-saturated solidus in the lowermost mantle wedge. Alternatively, in cool subduction zones like the Northern Marianas, a layer
of chloritized peridotite up to 1.5 km thick could contain all the H2O fluxed from the slab every million years near 100 km depth, which suggests that the dominant form of melting below arcs
in cool subduction zones is chlorite dehydration melting. Slab P–T paths from recent geodynamic models also allow for melts of subducted sediment, oceanic crust, and/or sediment diapirs to
interact with hydrous mantle melts within the mantle wedge at intermediate to hot subduction zones. 相似文献
107.
Christy B. Till Timothy L. Grove Anthony C. Withers 《Contributions to Mineralogy and Petrology》2012,164(6):1073-1076
The comment of Stalder raises three main concerns regarding the interpretation of the experiments presented by Till et al. (2012): (1) our inability to uniquely distinguish between high-pressure hydrous silicate melt and solute-rich aqueous fluid leads to the incorrect interpretation of phase relations, (2) the temperature interval over which hydrous melting takes places is inordinately large and contrary to expectations, and/or (3) the possibility that the system may be above the second critical end point (SCEP) in this H2O-rich silicate system has been insufficiently discussed. In this reply, we provide clarification on these concerns and argue that with the extent of knowledge available today, the chemical characteristics of our experimental products at 3.2 and 4?GPa evince the presence of a silicate melt at temperatures <1,000?°C and we are below the SCEP in the peridotite–H2O system at the P–T conditions of our experiments. If in fact the quench observed in our experiments does represent that of a supercritical (SC) fluid, then our data suggest Mg and Fe are highly soluble in SC fluids at the P–T conditions of the base of the mantle wedge below arc volcanoes. Therefore, our results would require a significant change in thinking about the chemical compositional characteristics of SC fluids. 相似文献
108.
Linda T. Elkins‐Tanton Nilanjan Chatterjee Timothy L. Grove 《Meteoritics & planetary science》2003,38(4):515-527
Abstract— Phase equilibrium experiments on the most magnesian Apollo 15C green picritic glass composition indicate a multiple saturation point with olivine and orthopyroxene at 1520°C and 1.3 GPa (about 260 km depth in the moon). This composition has the highest Mg# of any lunar picritic glass and the shallowest multiple saturation point. Experiments on an Apollo 15A composition indicate a multiple saturation point with olivine and orthopyroxene at 1520°C and 2.2 GPa (about 440 km depth in the moon). The importance of the distinctive compositional trends of the Apollo 15 groups A, B, and C picritic glasses merits the reanalysis of NASA slide 15426,72 with modern electron microprobe techniques. We confirm the compositional trends reported by Delano (1979, 1986) in the major element oxides SiO2, TiO2, Al2O3, Cr2O3, FeO, MnO, MgO, and CaO, and we also obtained data for the trace elements P2O5, K2O, Na2O, NiO, S, Cu, Cl, Zn, and F. Petrogenetic modeling demonstrates that the Apollo 15 A‐B‐C glass trends could not have been formed by fractional crystallization or any continuous assimilation/fractional crystallization (AFC) process. The B and C glass compositional trends could not have been formed by batch or incremental melting of an olivine + orthopyroxene source or any other homogeneous source, though the A glasses may have been formed by congruent melting over a small pressure range at depth. The B compositional trend is well modeled by starting with an intermediate A composition and assimilating a shallower, melted cumulate, and the C compositional trend is well modeled by a second assimilation event. The assimilation process envisioned is one in which heat and mass transfer were separated in space and time. In an initial intrusive event, a picritic magma crystallized and provided heat to melt magma ocean cumulates. In a later replenishment event, the picritic magma incrementally mixed with the melted cumulate (creating the compositional trends in the green glass data set), ascended to the lunar surface, and erupted as a fire fountain. A barometer created from multiple saturation points provides a depth estimate of other glasses in the A‐B‐C trend and of the depths of assimilation. This barometer demonstrates that the Apollo 15 A‐B‐C trend originated over a depth range of ?460 km to ?260 km within the moon. 相似文献
109.
Y. Ueda K. Yamaoka J.E. Grove M. McCollough P. Durouchoux J. Rodriguez F. Mirabel J. Swank M. Feroci P. Casella A.J. Castro-Tirado C. Sánchez-Fernández S. Chaty H. Castaneda K. Kohno V. Dhawan S.A. Trushkin K. Ebisawa T. Kotani H. Inoue 《Astrophysics and Space Science》2001,276(1):25-28
We report results from multiwavelength observations of the microquasarGRS 1915+105 performed during the 2000 April campaign. This is one ofthe biggest campaigns ever made for this source covering the broadband from radio to γ-rays. Multiwavelength light curves compiledfrom all the data reduced up to date and broad band spectra obtainedwith ASCA and RXTE are presented. 相似文献
110.
We report the oxygen isotope composition of olivine and orthopyroxene phenocrysts in lavas from the main magma types at Mt
Shasta and Medicine Lake Volcanoes: primitive high-alumina olivine tholeiite (HAOT), basaltic andesites (BA), primitive magnesian
andesites (PMA), and dacites. The most primitive HAOT (MgO > 9 wt%) from Mt. Shasta has olivine δ18O (δ18OOl) values of 5.9–6.1‰, which are about 1‰ higher than those observed in olivine from normal mantle-derived magmas. In contrast,
HAOT lavas from Medicine Lake have δ18OOl values ranging from 4.7 to 5.5‰, which are similar to or lower than values for olivine in equilibrium with mantle-derived
magmas. Other magma types from both volcanoes show intermediate δ18OOl values. The oxygen isotope composition of the most magnesian lavas cannot be explained by crustal contamination and the trace
element composition of olivine phenocrysts precludes a pyroxenitic mantle source. Therefore, the high and variable δ18OOl signature of the most magnesian samples studied (HAOT and BA) comes from the peridotitic mantle wedge itself. As HAOT magma
is generated by anhydrous adiabatic partial melting of the shallow mantle, its 1.4‰ range in δ18OOl reflects a heterogeneous composition of the shallow mantle source that has been influenced by subduction fluids and/or melts
sometime in the past. Magmas generated in the mantle wedge by flux melting due to modern subduction fluids, as exemplified
by BA and probably PMA, display more homogeneous composition with only 0.5‰ variation. The high-δ18O values observed in magnesian lavas, and principally in the HAOT, are difficult to explain by a single-stage flux-melting
process in the mantle wedge above the modern subduction zone and require a mantle source enriched in 18O. It is here explained by flow of older, pre-enriched portions of the mantle through the slab window beneath the South Cascades. 相似文献