Conceptualizing catchment storage dynamics and nonlinearities          下载免费PDF全文

Marco P. Maneta  Chris Soulsby  Sylvain Kuppel  Doerthe Tetzlaff 《水文研究》2018,32(21):3299-3303

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Interplay between erosion and tectonics in the Western Alps     

Marco G. Malus  Giovanni Vezzoli 《地学学报》2006,18(2):104-108

Bedrock fission‐track analysis, high‐resolution petrography and heavy mineral analyses of sediments are used to investigate the relationships between erosion and tectonics in the Western Alps. Along the Aosta Valley cross‐section, exhumation rates based on fission‐track data are higher in the fault‐bounded western block than in the eastern block (0.4–1.5 vs. 0.1–0.3 mm yr⁻¹). Erosion rates based on the analysis of bed‐load in the Dora Baltea drainage display the same pattern and have similar magnitudes in the relative sub‐basins (0.4–0.7 vs. 0.04–0.08 mm yr⁻¹). Results highlight that climate, relief and lithology are not the controlling factors of erosion in the Western Alps. The main driving force behind erosion is instead tectonics that causes the differential upward motion of crustal blocks.  相似文献   

Abundances of [WC] central stars and their planetary nebulaee     

O. De Marco  M. J. Barlow 《Astrophysics and Space Science》2001,275(1-2):53-66

We review elemental abundances derived for planetary nebula (PN) WCcentral stars and for their nebulae. Uncertainties in the abundances of[WC] stars are still too large to enable an abundance sequenceto be constructed. In particular it is not clear why the hotter [WCE]stars have C and O abundances which are systematically lower than those oftheir supposed precursors, the [WCL] stars. This abundance differencecould be real or it may be due to unaccounted-for systematic effects inthe analyses. Hydrogen might not be present in [WC] star winds asoriginallysuggested, since broad pedestals observed at the base of nebular lines canplausibly be attributed to high velocity nebular components. It isrecommended that stellar abundance analyses should be carried out withnon-LTE model codes, although recombination line analyses can provideuseful insights. In particular, C II dielectronic recombinationlines provide a unique means to determine electron temperatures in cool[WC] star winds. We then compare the abundances found for PNe which have [WC] central starswith those that do not. Numerous abundance analyses of PNe have beenpublished, but comparisons based on non-uniform samples and methods arelikely to lack reliability. Nebular C/H ratios, which might be expected todistinguish between PNe around H-poor and H-rich stars, are rather similarfor the two groups, with only a small tendency towards larger values fornebulae around H-deficient stars. Nebular abundances should be obtainedwith photoionization models using the best-fitting non-LTE modelatmosphere for the central star as the input. Heavy-metal line blanketingstill needs to be taken into consideration when modeling the central star,as its omission can significantly affect the ionizing fluxes as well asthe abundance determinations. We discuss the discrepancies between nebularabundances derived from collisionally excited lines and thosederived from optical recombination lines, a phenomenon that may havelinks with the presence of H-deficient central stars.  相似文献   

Keck observations of near-Earth asteroids in the thermal infrared     

Marco Delbó  Alan W. Harris  Richard P. Binzel  John K. Davies 《Icarus》2003,166(1):116-130

We present the results of thermal-infrared observations of 20 near-Earth asteroids (NEAs) obtained in the period March 2000-February 2002 with the 10-m Keck-I telescope on Mauna Kea, Hawaii. The measured fluxes have been fitted with thermal-model emission continua to determine sizes and albedos. This work increases the number of NEAs having measured albedos by 35%. The spread of albedos derived is very large (p_v=0.02−0.55); the mean value is 0.25, which is much higher than that of observed main-belt asteroids. In most cases the albedos are in the ranges expected for the spectral types, although some exceptions are evident. Our results are consistent with a trend of increasing albedo with decreasing size for S-type asteroids with diameters below 20 km. A number of objects are found to have unexpectedly low apparent color temperatures, which may reflect unusual thermal properties. However, the results from our limited sample suggest that high thermal-inertia, regolith-free objects may be uncommon, even amongst NEAs with diameters of less than 1 km. We discuss the significance of our results in the light of information on these NEAs taken from the literature and the uncertainties inherent in applying thermal models to near-Earth asteroids.  相似文献   

A non-coherent surface backscattering model for radar observation of planetary bodies and its application to Cassini radar altimeter     

E. Montefredini  F. Morelli  G. Picardi  R. Seu 《Planetary and Space Science》1995,43(12)

Mission and hardware constraints make the Cassini radar altimeter working in the beam limited or pulse limited mode dependent on the radar operative mode (Low and High Resolution, respectively), but never allows work in a condition such that the pulsewidth limited circle is much smaller than the beamwidth limited circle. Unfortunately this latter condition is vital for the application of the so-called Brown model widely and successfully used in Earth (ocean) observation missions where the quoted condition is really met. In the paper a new model is discussed which is based on the same general hypotheses of the Brown model but is worked out by means of a different approach which makes it more general and independent of the specific operative conditions. An extension of the new model to take into account large mispointing angles is considered as well based on a series expansion of the Bessel function and on the analysis of the truncation error. Finally a comparison with the classical Brown model is discussed too.  相似文献   

CO-Observations of post-starburst galaxies     

Marco Barden  Linda J. Tacconi  Matthew D. Lehnert  Dimitra Rigopoulou 《Astrophysics and Space Science》2001,277(1):95-95

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Holocene activity of the Scilla Fault, Southern Calabria: Insights from coastal morphological and structural investigations     

L. Ferranti  C. Monaco  D. Morelli  F. Antonioli  L. Maschio 《Tectonophysics》2008,453(1-4):74

Integration of on-land and offshore geomorphological and structural investigations coupled to extensive radiometric dating of co-seismically uplifted Holocene beaches allows characterization of the geometry, kinematics and seismotectonics of the Scilla Fault, which borders the eastern side of the Messina Strait in Calabria, Southern Italy. This region has been struck by destructive historical earthquakes, but knowledge of geologically-based source parameters for active faults is relatively poor, particularly for those running mostly offshore, as the Scilla Fault does. The  30 km-long normal fault may be divided into three segments of  10 km individual length, with the central and southern segments split in at least two strands. The central and northern segments are submerged, and in this area marine geophysical data indicate a youthful morphology and locally evidence for active faulting. The on-land strand of the western segment displaces marine terraces of the last interglacial (124 to 83 ka), but seismic reflection profiles suggest a full Quaternary activity. Structural data collected on bedrock faults exposed along the on-land segment provide evidence for normal slip and  NW-SE extension, which is consistent with focal mechanisms of large earthquakes and GPS velocity fields in the region. Detailed mapping of raised Holocene marine deposits exposed at the coastline straddling of the northern and central segments supplies evidence for two co-seismic displacements at  1.9 and  3.5 ka, and a possible previous event at  5 ka. Co-seismic displacements show a consistent site value and pattern of along-strike variation, suggestive of characteristic-type behaviour for the fault. The  1.5–2.0 m average co-seismic slips during these events document M_e  6.9–7.0 earthquakes with  1.6–1.7 ka recurrence time. Because hanging-wall subsidence cannot be included into slip magnitude computation, these slips reflect footwall uplift, and represent minimum average estimates. The palaeoseismological record based on the palaeo-shorelines suggests that the last rupture on the Scilla Fault during the February 6, 1783 M_w = 5.9–6.3 earthquake was at the expected time but it may have not entirely released the loaded stress since the last great event at  1.9 ka. Comparison of the estimated co-seismic extension rate based on the Holocene shoreline record with available GPS velocities indicates that the Scilla Fault accounts for at least  15–20% of the contemporary geodetic extension across the Messina Strait.  相似文献   

Risk assessment strategies for the reactivation of earth flows in the Northern Apennines (Italy)     

Giovanni Bertolini  Marco Pizziolo 《Engineering Geology》2008,102(3-4):178

The aim of this paper is to analyze the reactivation mechanism of ancient earth flows, with a view to gleaning information that can subsequently be utilized to formulate a risk-reduction strategy. All considerations made herein are the result of direct experience and observation of actual events which have occurred over the past few decades in the Northern Apennines. Particular attention has been paid to the analysis of the evolution of landslides during actual reactivation, acknowledging a typical, recurring succession of events that precede the failure of the slope. The hazard assessment of these large landslide bodies, which are of slope scale, constitutes a thorny problem, especially in view of the inapplicability of traditional deterministic models such as limit equilibrium stability analysis. Nevertheless, a site-specific assessment of probability of reactivation of these large and ancient earth flows is fundamental to effective land-use planning.  相似文献   

The passivation of calcite by acid mine water. Column experiments with ferric sulfate and ferric chloride solutions at pH 2   总被引：2，自引：1，他引：1  

Josep M. Soler  Marco Boi  Jos Luis Mogolln  Jordi Cama  Carlos Ayora  Peter S. Nico  Nobumichi Tamura  Martin Kunz 《Applied Geochemistry》2008,23(12):3579-3588

Column experiments, simulating the behavior of passive treatment systems for acid mine drainage, have been performed. Acid solutions (HCl or H₂SO₄, pH 2), with initial concentrations of Fe(III) ranging from 250 to 1500 mg L⁻¹, were injected into column reactors packed with calcite grains at a constant flow rate. The composition of the solutions was monitored during the experiments. At the end of the experiments (passivation of the columns), the composition and structure of the solids were measured. The dissolution of calcite in the columns caused an increase in pH and the release of Ca into the solution, leading to the precipitation of gypsum and Fe–oxyhydroxysulfates (Fe(III)–SO₄–H⁺ solutions) or Fe–oxyhydroxychlorides (Fe(III)–Cl–H⁺ solutions). The columns worked as an efficient barrier for some time, increasing the pH of the circulating solutions from 2 to 6–7 and removing its metal content. However, after some time (several weeks, depending on the conditions), the columns became chemically inert. The results showed that passivation time increased with decreasing anion and metal content of the solutions. Gypsum was the phase responsible for the passivation of calcite in the experiments with Fe(III)–SO₄–H⁺ solutions. Schwertmannite and goethite appeared as the Fe(III) secondary phases in those experiments. Akaganeite was the phase responsible for the passivation of the system in the experiments with Fe(III)–Cl–H⁺ solutions.  相似文献   

How a court, a commissioner and a lobby group brought European transport policy to life in 1985     

Marco te Brömmelstroet  Tobias Nowak 《GeoJournal》2008,72(1-2):33-44

Until the mid-1980s, transport policy was considered by many as one of the least successful domains of the European integration project. However, from the early 1990s onwards, there are clear signs of a single European transport policy, along with the accompanying implementation of infrastructure projects. What is the explanation for such a change in pace? This paper aims to offer insight in these processes by looking at the mechanisms which form and transform this policy domain. To understand the state of a policy domain and its dynamics over time an institutional approach is taken. Two concepts in political science, ‘policy arrangements’ and ‘supranational governance’ are combined and used as a framework to analyse the European transport policy domain. This analysis describes the development of several elements: organisations, rules, the transnational society, power, resources, and the central transport discourse. It demonstrates that all of these elements have developed from an intergovernmental setting towards a more supranational one. This development was slow in the first decennia when European transport policy was rather passive, but it picked up speed in the 1980s and 1990s. In the pivotal year of 1985, pressure from the transnational society resulted in a rapid change of the rules, the resources and the discourse.  相似文献