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441.
We assess the ability of multivariate statistical analyses applied to event hydrographs parameters, to characterize a catchment hydrological behaviour. Motivation for such an approach lies in the fact that streamflow records have yet to be exploited to their full potential towards hydrological interpretation and can be used to infer a catchment state of connectivity from a qualitative standpoint. We have therefore processed 96 event hydrographs from a small headwater temperate humid forested catchment using principal component analysis, variation partitioning and classification tree analysis. These techniques prove to be promising in discriminating contrasted types of hydrologic responses (e.g. low‐ vs high‐magnitude events, slow vs quick timing events), identifying the main hydro‐meteorological variables that control these responses and determining thresholds values of the hydro‐meteorological variables leading to a switch between catchment response types. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
442.
443.
Florent Renaud Michel Warnau François Oberhänsli Jean-Louis Teyssié Ali Temara Claude Rouleau Marc Metian 《Marine pollution bulletin》2014
Uptake and depuration kinetics of dissolved [14C]C12-6-linear alkylbenzene sulfonate (LAS) were determined in the shrimp Palaemonetes varians using environmentally relevant exposure concentration. The shrimp concentrated LAS from seawater with a mean BCF value of 120 L kg−1 after a 7-day exposure. Uptake biokinetics were best described by a saturation model, with an estimated BCFss, of 159 ± 34 L kg−1, reached after 11.5 days. Shrimp weight influenced significantly BCF value with smaller individuals presenting higher affinity to LAS. To the light of a whole body autoradiography, major accumulation of LAS occurred in the cephalothorax circulatory system (gills, heart, hepatopancreas) and ocular peduncle, but not in the flesh, limiting potential transfer to human consumers. LAS depuration rate constant value of the shrimp was 1.18 ± 0.08 d−1 leading to less than 1% of remaining LAS in its tissues after 8 days of depuration. 相似文献
444.
Bernard Gelly Claude Le Men Arturo López Ariste Cyril Delaigue Ruyman Gónzalez Perez 《Experimental Astronomy》2008,22(1-2):67-85
An image stabilizer has been inserted into the optical path of the THEMIS solar telescope. THEMIS is a Ritchey–Chretien reflector telescope using an altazimuthal mount and closely tied to its spectrograph. The optical and mechanical design, implementation and system tests are described, and emphasis is put on the complexity of situations that this stabilizer must accept, including the scanning of the solar surface while stabilizing. The current closed-loop crossover frequency of the device is 65 Hz at ??3 dB on all typical solar scenes. 相似文献
445.
Bernard Barnier Gurvan Madec Thierry Penduff Jean-Marc Molines Anne-Marie Treguier Julien Le Sommer Aike Beckmann Arne Biastoch Claus Böning Joachim Dengg Corine Derval Edmée Durand Sergei Gulev Elizabeth Remy Claude Talandier Sébastien Theetten Mathew Maltrud Julie McClean Beverly De Cuevas 《Ocean Dynamics》2009,59(3):537-537
446.
Jorge?Plá Cid Lauro?Valentim?Stoll?NardiEmail author Pere?Enrique?Gisbert Claude?Merlet Bernard?Boyer 《Contributions to Mineralogy and Petrology》2005,148(6):675-688
Trace and rare earth element contents were determined by SIMS technique in clinopyroxene and mica crystals from minette lamprophyric enclaves in a potassic syenite host. This co-mingled system was crystallized at high pressures, which varied about 3–5 GPa, as indicated by the presence of K-clinopyroxenes and pyrope-rich garnet with measurable amounts of K2O and Na2O, among the near-liquidus phases. Major and trace element composition of these lamprophyric enclaves is quite similar to those observed in silica-rich lamproites, suggesting that similar sources were involved in their origin. In a general view, the concentrations of most trace and rare earth elements in clinopyroxene of the studied enclaves are higher than those referred to by other authors. Clinopyroxene/melt partition coefficient for most trace elements are close to determinations in alkali-basalts and lamproites from Leucite Hills, with considerable differences relative to Gaussberg lamproites. Furthermore, these partition data are completely different from those determined for potassic lavas crystallized under crustal pressures. Spidergrams for clinopyroxenes exhibit negative-Sr anomalies relative to LREE, which have been associated by most authors to crystallization under low-pressures, out of garnet stability field. The presence of pyrope together with K-clinopyroxene excludes such hypotheses for the studied enclaves. Y and HREE are concentrated in clinopyroxene, whilst the other trace elements have Kd<1. LIL elements, except Rb, have incompatible (Kd<1) behavior in phlogopite. The high partition coefficient for Nb (Kd>3) determined in the studied phlogopite is unusual in lamproites, lamprophyres, and basalts, but frequently observed in phlogopite from metasomatic mantle samples, as well as in acid magmas. This partition value may indicate the lack of other mineral phase with high partition for this element during crystallization, and may be enhanced by the liquid composition progressively closer to alkali feldspar, an unsuitable structure for six-coordinated cations. Ce/Yb, Rb/Sr, and Zr/Hf ratios in clinopyroxene and mica suggest that the minettic magma could produce the host Piquiri potassic syenite by fractional crystallization. This hypothesis is not consistent with Ba concentrations in clinopyroxene and mica, which suggest that a Ba-bearing phase (e.g. alkali feldspar) should be among the fractionated phases in order to produce the potassic syenites. 相似文献
447.
Frequency analysis of the stability of asteroids in the framework of the restricted three-body problem 总被引:1,自引:1,他引:0
Alessandra?CellettiEmail author Claude?Froeschlé Elena?Lega 《Celestial Mechanics and Dynamical Astronomy》2004,90(3-4):245-266
The stability of some asteroids, in the framework of the restricted three-body problem, has been recently proved in (Celletti
and Chierchia, 2003), by developing an isoenergetic KAM theorem. More precisely, having fixed a level of energy related to
the motion of the asteroid, the stability can be obtained by showing the existence of nearby trapping invariant tori existing
at the same energy level. The analytical results are compatible with the astronomical observations, since the theorem is valid
for the realistic mass-ratio of the primaries.
The model adopted in (Celletti and Chierchia, 2003), is the planar, circular, restricted three-body model, in which only the
most significant contributions of the Fourier development of the perturbation are retained. In this paper we investigate numerically
the stability of the same asteroids considered in (Celletti and Chierchia, 2003), (namely, Iris, Victoria and Renzia). In
particular, we implement the nowadays standard method of frequency-map analysis and we compare our investigation with the
analytical results on the planar, circular model with the truncated perturbing function. By means of frequency analysis, we
study the behaviour of the bounding tori and henceforth we infer stability properties on the dynamics of the asteroids. In
order to test the validity of the truncated Hamiltonian, we consider also the complete expression of the perturbing function
on which we perform again frequency analysis. We investigate also more realistic models, taking into account the eccentricity
of the trajectory of Jupiter (planar-elliptic problem) or the relative inclination of the orbits (circular-inclined model).
We did not find a relevant discrepancy among the different models. 相似文献
448.
At Santa Maria Volcano (New Hebrides island arc), extensive ash and scoria flow deposits overlie the mainly effusive, pre-caldera cone. Hydromagmatic features characterize these deposits, the composition of juvenile clasts ranges from basalt to acid andesite/dacite (SiO2 = 51–63.6%) with a dominant basaltic composition. The stratigraphic position of this pyroclastic series and its spatial distribution around a 8.5 km × 6 km wide caldera provide evidence of a relationship between this series and the caldera formation. In addition, these pyroclastic deposits are co-genetic to parasitic cones and lava flows developed along faults concentric to the caldera. Both series result from a compositionally layered magma reservoir, the subordinate differentiated magmas being the result of fractional crystallization from the basalts. A model of caldera formation which implies a large hydromagmatic eruption at the central vent and minor magma withdrawal by flank eruptions is proposed. This model emphasizes the importance of mafic hydroclastic eruptions in the caldera forming event and contradicts a model implying only quiet subsidence, a process often proposed for the formation of calderas in island are volcanoes of mainly mafic composition. 相似文献
449.
Different methods are proposed and tested for transforming a nonlinear differential system, and more particularly a hamiltonian one, into a map without having to integrate the whole orbit as in the well known Poincaré map technique. We construct piecewise polynomial maps by coarse-graining the phase surface of section into parallelograms using values of the Poincaré maps at the vertices to define a polynomial approximation within each cell. The numerical experiments are in good agreement with the standard map taken as a model problem. The agreement is better when the number of vertices and the order of the polynomial fit increase. The synthetic mapping obtained is not symplectic even if at vertices there is an exact interpolation. We introduce a second new method based on a global fitting . The polynomials are obtained using at once all the vertices and fitting by least square polynomes but in such a way that the symplectic character is not lost. 相似文献
450.
Claude R. Canizares 《Astrophysics and Space Science》1976,42(1):111-122
A variety of transient X-ray phenomena have been studied by the M.I.T. X-ray Astronomy Group. Data from the OSO-7 satellite reveal both long and short time-scale transients. Extensive observations have been made of the Lupus X-ray Nova (3U1543-47) and of GX339-4 (MX1658-48) which may represent a very different type of transient source A unique, intense X-ray flare lasting ten minutes was also recorded, and the X-ray emission from the active galaxy Cen A was found to vary significantly over a period of several days. In a recent ballon flight the Crab, pulsar, NP0532, was observed to exhibit a transient pulsed component distinct from the usual main pulse and interpulse. A sounding-rocket experiment detected an ultrasoft transient X-ray source tentatively associated with SS Cygni, and preliminary results from SAS-3 show a very hard spectrum for the new source A0535+26. On the other hand, extensive OSO-7 null observations of both Type I and II supernovae and of the flaring radio star Algol make it unlikely that these types of objects are potent transient X-ray emitters.Supported in part by the National Aeronautics and Space Administration under contracts NGL 22-009-015, NSR 22-009-654 and grant NGL 22-099-730 and by the National Science Foundation under grant GP-31378.Paper presented, at the COSPAR Symposium on Fast Transients in X- and Gamma-Rays, held at Varna, Bulgaria, 29–31 May, 1975. 相似文献