Cluster cross-sections for strong lensing: analytic and numerical lens models     

Massimo Meneghetti  Matthias Bartelmann  Lauro Moscardini † 《Monthly notices of the Royal Astronomical Society》2003,340(1):105-114

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Quantitative methods in the earth sciences     

A. F?rster  D. F. Merriarn 《Mathematical Geology》1997,29(5):727

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The X-ray and extreme-ultraviolet flux evolution of SS Cygni throughout outburst     

Peter J. Wheatley  Christopher W. Mauche  Janet A. Mattei 《Monthly notices of the Royal Astronomical Society》2003,345(1):49-61

We present the most complete multiwavelength coverage of any dwarf nova outburst: simultaneous optical, Extreme Ultraviolet Explorer and Rossi X-ray Timing Explorer observations of SS Cygni throughout a narrow asymmetric outburst. Our data show that the high-energy outburst begins in the X-ray waveband 0.9–1.4 d after the beginning of the optical rise and 0.6 d before the extreme-ultraviolet rise. The X-ray flux drops suddenly, immediately before the extreme-ultraviolet flux rise, supporting the view that both components arise in the boundary layer between the accretion disc and white dwarf surface. The early rise of the X-ray flux shows that the propagation time of the outburst heating wave may have been previously overestimated.
The transitions between X-ray and extreme-ultraviolet dominated emission are accompanied by intense variability in the X-ray flux, with time-scales of minutes. As detailed by Mauche & Robinson, dwarf nova oscillations are detected throughout the extreme-ultraviolet outburst, but we find they are absent from the X-ray light curve.
X-ray and extreme-ultraviolet luminosities imply accretion rates of  3 × 10¹⁵ g s⁻¹  in quiescence,  1 × 10¹⁶ g s⁻¹  when the boundary layer becomes optically thick, and  ∼10¹⁸ g s⁻¹  at the peak of the outburst. The quiescent accretion rate is two and a half orders of magnitude higher than predicted by the standard disc instability model, and we suggest this may be because the inner accretion disc in SS Cyg is in a permanent outburst state.  相似文献   

Laser Interferometer Space Antenna double black holes: dynamics in gaseous nuclear discs     

Massimo Dotti  Monica Colpi  Francesco Haardt 《Monthly notices of the Royal Astronomical Society》2006,367(1):103-112

We study the inspiral of double black holes, with masses in the Laser Interferometer Space Antenna ( LISA ) window of detectability, orbiting inside a massive circumnuclear, rotationally supported gaseous disc. Using high-resolution smoothed particle hydrodynamics simulations, we follow the black hole dynamics in the early phase when gas-dynamical friction acts on the black holes individually, and continue our simulation until they form a close binary. We find that in the early sinking the black holes lose memory of their initial orbital eccentricity if they corotate with the gaseous disc. As a consequence, the massive black holes bind forming a binary with a low eccentricity, consistent with zero within our numerical resolution limit. The cause of circularization resides in the rotation present in the gaseous background where dynamical friction operates. Circularization may hinder gravitational waves from taking over and leading the binary to coalescence. In the case of counter-rotating orbits, the initial eccentricity (if present) does not decrease, and the black holes may bind forming an eccentric binary. When dynamical friction has subsided, for equal mass black holes and regardless their initial eccentricity, angular momentum loss, driven by the gravitational torque exerted on the binary by surrounding gas, is nevertheless observable down to the smallest scale probed (≃1 pc). In the case of unequal masses, dynamical friction remains efficient down to our resolution limit, and there is no sign of formation of any ellipsoidal gas distribution that may further harden the binary. During inspiral, gravitational capture of gas by the black holes occurs mainly along circular orbits; eccentric orbits imply high relative velocities and weak gravitational focusing. Thus, the active galactic nucleus activity may be excited during the black hole pairing process and double active nuclei may form when circularization is completed, on distance scales of tens of parsecs.  相似文献   

Lead isotope systematics of Late Cretaceous – Tertiary Andean arc magmas and associated ores between 8°N and 40°S: evidence for latitudinal mantle heterogeneity beneath the Andes     

Massimo Chiaradia  Lluís Fontboté 《地学学报》2002,14(5):337-342

ABSTRACT Lead isotope variability of magmatic arc rocks and associated mineralization of the Central Andes is usually considered to be the result of mixing between a homogeneous mantle and heterogeneous continental crust. About 230 new lead isotope data on the Northern and Central Andes allow us to compare for the first time lead isotope systematics of the Late Cretaceous – Tertiary arc magmatism and associated mineralization along the Andean chain between 8°N and 40°S. Lead isotope compositions indicate mixing between mantle and upper crustal rocks along the whole Andean chain. Additionally, we have found that mantle end-members of the Late Cretaceous – Tertiary magmatism are heterogeneous and systematically shifted towards less radiogenic ²⁰⁶Pb/²⁰⁴Pb compositions from north to south along the Andes. This heterogeneity most likely results from mixing between a low radiogenic mantle, possibly carrying a DMM or EM I component, and a more radiogenic mantle, possibly carrying an HIMU component. Thus, our results imply that lead isotope variability of Andean magmas at the continental scale is caused not only by crustal but also by mantle heterogeneity.  相似文献   

Stable isotope geochemistry and structural elements of the Sabina region (Central Apennines, Italy)     

A. Maiorani† †  R. Funiciello  M. Mattei  B. Turi 《地学学报》1992,4(4):484-488

Various tectonic features are present in the Meso-Cenozoic basin units of the Sabina region (Central Apennines, Italy): Mio-Pliocene northeasterly verging thrusts are followed by Plio-Pleistocene, N-S oriented right-lateral strike-slip faults. Stable isotope geochemistry and examination of meso- and microstructures show that strain conditions differed through the course of tectonic history. Carbon and oxygen isotope analyses of the calate-filled extensional fractures, the sigmoidal veins present between stylolitic cleavage surfaces, and fault plane surfaces with differing motion, demonstrate those different geneses.
The "C/'" C of the older calcite-filling fractures (present both in the thrust and the strike-slip systems) suggests a deposition from shallow, fresh water circulation. Furthermore, the calcite fill of en echelon systems, that occur in the southernmost Plio-Pleistocene units, is clearly the result of a more recent, right-lateral strike-slip movement, connected with shallow water circulation within Mesozoic limestones.
The sigmoidal vein fills are derived from solid-state pressure solution processes which were the result of strike-slip movement. The deformation pattern related to the older thrust system is similar, but less intense; this also demonstrates general recrystallization processes in a closed system.
This suggests that the total shortening of the deformed sections is lower than that obtained on the basis of solution on stylolitic planes, because a sigruficant volume of dissolved carbonates remained in the system.
Stable isotope analysis also confirms that the deformational history of strongly cleaved rocks in the Sabina region took place in two phases and that extensional fractures formed before stylolithic planes, as suggested by structural and field observations.  相似文献   

An Example of Island-Arc Petrogenesis: Geochemistry and Petrology of the Southern Luzon Arc, Philippines   总被引：7，自引：1，他引：6  

DEFANT  MARC J.; MAURY  REN? C.; RIPLEY  EDWARD M.; FEIGENSON  MARK D.; JACQUES  DARIO 《Journal of Petrology》1991,32(3):455-500

Volcanism throughout the Luzon arc is associated with eastwardsubduction of the South China Sea floor along the Manila Trench.The southern section of the arc, the focus of this study, extendsfrom the Lingayen-Dingalan fault to the small islands just southof Luzon. Two segments appear to exist along this section ofthe arc the northern Bataan and southern Mindoro segments whichare separated by the Macolod Corridor. The volcanic rocks have typical arc phenocryst mineralogies:olivine, clinopyroxene, plagioclase, and titanomagnetite inthe most mafic rocks and clinopyroxene, plagioclase, orthopyroxene,titanomagnetite, ? amphibole in the more felsic samples. Complexzoning, sieve textures, and decoupling of incompatible traceelements suggest that processes such as assimilation have takenplace. The rocks from the study area range from basalts to rhyolitesand show typical calc-alkaline features. The rocks of the MacolodCorridor and Mindoro segment are particularly enriched in largeion lithophile elements (LILE), light rare earth elements (LREE),and radiogenic Sr compared with the Bataan segment. The datafall within the mantle array on Sr-Nd isotopic diagrams andgrade toward higher Sr and lower Nd isotopic values from northto south. A likely source for the volcanics of this study is either amid-ocean ridge basalt (MORB)-type mantle that undergoes higherdegrees of partial melting than regions involved in MORB generationor a previously depleted source. We suggest that the high fieldstrength element (HFSE) anomalies have been derived throughdifferential element partitioning during fluid transport fromthe subducted lithosphere to the mantle wedge. Continental crustal material seems to play a significant roleparticularly in the Macolod Corridor and the Mindoro segment,based on the high LILE, La/Sm ratios, radiogenic Sr isotopes,and ¹⁸O values. The Macolod Corridor and the Mindoro segmenthave undergone source contamination by crustal material fromthe North Palawan-Mindoro crustal block either during the collisionof this block with the Manila Trench or by subduction of sedimentsrich in this crustal material. A similar component has alsobeen detected in the Bataan segment but in minor amounts. Thetrace element and isotopic differences between the northernand southern sections of the arc are interpreted in terms ofvariable composition (i. e., variable amounts of a crustal componentintroduced from the Palawan-Mindoro crustal terrain) of themetasomatic fluids released into the source.  相似文献   

Wavelength predictions for the 1s 22s-1s2s3p satellite transitions     

Massimo Mazzoni 《Solar physics》1986,103(2):231-234

The experimentally known energies of the 1s ²2s 1s2s(¹ S, ³ S)3p transitions are considered for lithium to calcium. Their differences from the corresponding He-like resonances are fitted to the atomic number by means of a polynomial function and, through interpolation, the wavelengths for nitrogen to sodium are calculated.  相似文献   

Modeling of water–rock interactions in an aquitard of sandy clay in the coastal area near Beihai,China     

Zhou?XunEmail author  Yao?Jinmei  Zhang?Hua  Li?Rui  Xu?Fang 《Environmental Geology》2008,56(1):183-188

Unconsolidated sand, gravel and clay deposits near Beihai and in the Leizhou Peninsula in southern China form an unconfined aquifer, aquitard and a confined aquifer. Water and soil samples were collected from the two aquifers in the coastal Beihai area for the determination of chemical compositions, minerals and soluble ions. Hydrogeochemical modeling of three flow paths through the aquitard are carried out using PHREEQC to determine water–rock interactions along the flow paths. The results indicate that the dissolution of anorthite, fluorite, halite, rhodochrosite and CO₂, and precipitation of potash feldspar and kaolinite may be occurring when groundwater leaks through the aquitard from the unconfined aquifer to the confined aquifer. Cation exchanges between Na and Ca can also happen along the flow paths.  相似文献   

Petrology and U-Pb Zircon Geochronology of Amphibole-rich Cumulates with Sanukitic Affinity from Husky Ridge (Northern Victoria Land, Antarctica): Insights into the Role of Amphibole in the Petrogenesis of Subduction-related Magmas     

Tiepolo  Massimo; Tribuzio  Riccardo 《Journal of Petrology》2008,49(5):937-970

A microanalytical trace element and geochronological study wascarried out on mafic amphibole-rich cumulates (quartz diorites)cropping out in northern Victoria Land (Antarctica). Associatedtonalites and basement rocks were also investigated. Rock texturesand major and trace element mineral compositions reveal thepresence in quartz diorites of two mineral assemblages: (1)clinopyroxene-I + brown amphibole ± dark mica; (2) clinopyroxene-II+ green amphibole + plagioclase + quartz. Both mineral assemblagescontain mafic phases with elevated Mg-number, but their traceelement signatures differ significantly. In situ U–Pbzircon geochronology was carried out to support petrogeneticand geological interpretations. Quartz diorites were emplacedin the mid-crust probably at 516 ± 3 Ma. Parental meltsof quartz diorites were computed by applying solid/liquid partitioncoefficients. The melt in equilibrium with the first mineralassemblage (melt-I) is extremely depleted in heavy rare earthelements (HREE), Y, Ti, Zr and Hf (at about 0·2 timesnormal mid-ocean ridge basalt) and enriched in B, Th, U, thelarge ion lithophile elements and light REE (LREE). It sharesmany similarities with sanukitic melts (e.g. Setouchi andesites),which originated by equilibration of subduction-derived sedimentmelts with a refractory mantle. The melt in equilibrium withthe second mineral assemblage (melt-II) is characterized bya steep LREE enrichment (La_N/Yb_N up to 39), a U-shaped HREEpattern and low Ti, which is depleted relative to HREE. Thetrace element signature of melt-II can be acquired through amphibolecrystallization starting from a sanukitic melt similar to melt-I,probably in a deeper magma chamber. Our results allow us toconstrain that melts from the subducted slab were produced ona regional scale, in accordance with literature data, belowa large sector of the east Gondwana margin during the mid-Cambrian.Implications for the role of amphibole in petrogenesis of subduction-relatedmagmas are also discussed. KEY WORDS: amphibole; sanukite; high-Mg andesites; Ross Orogeny; Antarctica  相似文献