http://www.sciencedirect.com/science/article/pii/S1674987114000905     

Petar Gliovi  Alessandro M.Forte 《地学前缘(英文版)》2015,6(1):3-22

Although there has been significant progress in the seismic imaging of mantle heterogeneity,the outstanding issue that remains to be resolved is the unknown distribution of mantle temperature anomalies in the distant geological past that give rise to the present-day anomalies inferred by global tomography models.To address this question,we present 3-D convection models in compressible and self-gravitating mantle initialised by different hypothetical temperature patterns.A notable feature of our forward convection modelling is the use of self-consistent coupling of the motion of surface tectonic plates to the underlying mantle flow,without imposing prescribed surface velocities(i.e.,plate-like boundary condition).As an approximation for the surface mechanical conditions before plate tectonics began to operate we employ the no-slip(rigid) boundary condition.A rigid boundary condition demonstrates that the initial thermally-dominated structure is preserved,and its geographical location is fixed during the evolution of mantle flow.Considering the impact of different assumed surface boundary conditions(rigid and plate-like) on the evolution of thermal heterogeneity in the mantle we suggest that the intrinsic buoyancy of seven superplumes is most-likely resolved in the tomographic images of present-day mantle thermal structure.Our convection simulations with a plate-like boundary condition reveal that the evolution of an initial cold anomaly beneath the Java-Indonesian trench system yields a long-term,stable pattern of thermal heterogeneity in the lowermost mantle that resembles the presentday Large Low Shear Velocity Provinces(LLSVPs),especially below the Pacific.The evolution of subduction zones may be,however,influenced by the mantle-wide flow driven by deeply-rooted and longlived superplumes since Archean times.These convection models also detect the intrinsic buoyancy of the Perm Anomaly that has been identified as a unique slow feature distinct from the two principal LLSVPs.We find there is no need for dense chemical ’piles’ in the lower mantle to generate a stable distribution of temperature anomalies that are correlated to the LLSVPs and the Perm Anomaly.Our tomography-based convection simulations also demonstrate that intraplate volcanism in the south-east Pacific may be interpreted in terms of shallow small-scale convection triggered by a superplume beneath the East Pacific Rise.  相似文献   

Excavation works in stiff jointed clay material: examples from the Trubi formation,southern Italy     

David Segato  Giuseppe Scarpelli  Viviene M. E. Fruzzetti  Paolo Ruggeri  Alessandro Vita  Alessandra Paternesi 《Landslides》2015,12(4):721-730

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Assessing the influence of climate model uncertainty on EU-wide climate change impact indicators     

Tobias Lung  Alessandro Dosio  William Becker  Carlo Lavalle  Laurens M. Bouwer 《Climatic change》2013,120(1-2):211-227

Despite an increasing understanding of potential climate change impacts in Europe, the associated uncertainties remain a key challenge. In many impact studies, the assessment of uncertainties is underemphasised, or is not performed quantitatively. A key source of uncertainty is the variability of climate change projections across different regional climate models (RCMs) forced by different global circulation models (GCMs). This study builds upon an indicator-based NUTS-2 level assessment that quantified potential changes for three climate-related hazards: heat stress, river flood risk, and forest fire risk, based on five GCM/RCM combinations, and non-climatic factors. First, a sensitivity analysis is performed to determine the fractional contribution of each single input factor to the spatial variance of the hazard indicators, followed by an evaluation of uncertainties in terms of spread in hazard indicator values due to inter-model climate variability, with respect to (changes in) impacts for the period 2041–70. The results show that different GCM/RCM combinations lead to substantially varying impact indicators across all three hazards. Furthermore, a strong influence of inter-model variability on the spatial patterns of uncertainties is revealed. For instance, for river flood risk, uncertainties appear to be particularly high in the Mediterranean, whereas model agreement is higher for central Europe. The findings allow for a hazard-specific identification of areas with low vs. high model agreement (and thus confidence of projected impacts) within Europe, which is of key importance for decision makers when prioritising adaptation options.  相似文献   

The special climate change fund: origins and prioritisation assessment     

Valentina Bosetti  Marzio Galeotti  Alessandro Lanza 《Climate Policy》2013,13(3):295-312

Abstract

A central issue in tackling climate change is to understand to what extent different short-term mitigation strategies are consistent with long-term stabilization targets. The present article aims at cross-comparing emission paths derived by plausible short-term policies against those implied by long-term climate targets, comparing, for example, differences in peak periods. Short-term policies considered are, for instance, Kyoto-type targets with or without participation by the USA and/or by developing countries. Long-term targets focus instead on stabilization of CO₂ concentrations, radiative forcing and the increase in atmospheric temperature relative to pre-industrial levels. In order to account for the uncertainty surrounding the climate cycle, for each long-term goal multiple paths of emission—the most probable, the optimistic and the pessimistic projections—are considered in the comparison exercise. Comparative analysis is performed using the FEEM-RICE model, a regional economy—climate model. The results suggest that some early policy action should take place for short-term emissions to be compatible with long-term targets. In particular, the Kyoto-type regimes appear to be on a compatible emission path, at least up to the second commitment period. However, this is no longer the case when assuming a pessimistic realization of the uncertain climate parameters.  相似文献   

Highly reproducible quasi-mosaic crystals as optical components for a Laue lens     

Riccardo Camattari  Alessandro Battelli  Valerio Bellucci  Vincenzo Guidi 《Experimental Astronomy》2014,37(1):1-10

The realization of a Laue lens for astronomical purposes involves the mass production of a series of crystalline tiles as optical components, allowing high-efficiency diffraction and high-resolution focusing of photons. Crystals with self-standing curved diffraction planes is a valid and promising solution. Exploiting the quasi-mosaic effect, it turns out to be possible to diffract radiation at higher resolution. In this paper we present the realization of 150 quasi-mosaic Ge samples, bent by grooving one of their largest surface. We show that grooving method is a viable technique to manufacture such crystals in a simple and very reproducible way, thus compatible with mass production. Realized samples present very homogenous curvature. Furthermore, with a specific chemical etch, it is possible to fine adjust one by one the radius of curvature of the grooved samples. Realized crystals was selected for the ASI’s Laue project, that involves the implementation of a prototype of a Laue lens for hard X- and soft γ-ray astronomy.  相似文献   

3. Solar System Formation and Early Evolution: the First 100 Million Years     

Thierry Montmerle  Jean-Charles Augereau  Marc Chaussidon  Mathieu Gounelle  Bernard Marty  Alessandro Morbidelli 《Earth, Moon, and Planets》2006,98(1-4):39-95

The solar system, as we know it today, is about 4.5 billion years old. It is widely believed that it was essentially completed 100 million years after the formation of the Sun, which itself took less than 1 million years, although the exact chronology remains highly uncertain. For instance: which, of the giant planets or the terrestrial planets, formed first, and how? How did they acquire their mass? What was the early evolution of the “primitive solar nebula” (solar nebula for short)? What is its relation with the circumstellar disks that are ubiquitous around young low-mass stars today? Is it possible to define a “time zero” (t ₀), the epoch of the formation of the solar system? Is the solar system exceptional or common? This astronomical chapter focuses on the early stages, which determine in large part the subsequent evolution of the proto-solar system. This evolution is logarithmic, being very fast initially, then gradually slowing down. The chapter is thus divided in three parts: (1) The first million years: the stellar era. The dominant phase is the formation of the Sun in a stellar cluster, via accretion of material from a circumstellar disk, itself fed by a progressively vanishing circumstellar envelope. (2) The first 10 million years: the disk era. The dominant phase is the evolution and progressive disappearance of circumstellar disks around evolved young stars; planets will start to form at this stage. Important constraints on the solar nebula and on planet formation are drawn from the most primitive objects in the solar system, i.e., meteorites. (3) The first 100 million years: the “telluric” era. This phase is dominated by terrestrial (rocky) planet formation and differentiation, and the appearance of oceans and atmospheres.  相似文献   

Systematic conservation planning in the Mediterranean: a flexible tool for the identification of no-take marine protected areas     

Maiorano  Luigi; Bartolino  Valerio; Colloca  Francesco; Abella  Alvaro; Belluscio  Andrea; Carpentieri  Paolo; Criscoli  Alessandro; Jona Lasinio  Giovanna; Mannini  Alessandro; Pranovi  Fabio; Reale  Bruno; Relini  Giulio; Viva  Claudio; Ardizzone  Gian Domenico 《ICES Journal of Marine Science》2009,66(1):137-146

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Mapping and monitoring carbon stocks with satellite observations: a comparison of methods     

Scott J Goetz  Alessandro Baccini  Nadine T Laporte  Tracy Johns  Wayne Walker  Josef Kellndorfer  Richard A Houghton  Mindy Sun 《Carbon balance and management》2009,4(1):2-7

Mapping and monitoring carbon stocks in forested regions of the world, particularly the tropics, has attracted a great deal of attention in recent years as deforestation and forest degradation account for up to 30% of anthropogenic carbon emissions, and are now included in climate change negotiations. We review the potential for satellites to measure carbon stocks, specifically aboveground biomass (AGB), and provide an overview of a range of approaches that have been developed and used to map AGB across a diverse set of conditions and geographic areas. We provide a summary of types of remote sensing measurements relevant to mapping AGB, and assess the relative merits and limitations of each. We then provide an overview of traditional techniques of mapping AGB based on ascribing field measurements to vegetation or land cover type classes, and describe the merits and limitations of those relative to recent data mining algorithms used in the context of an approach based on direct utilization of remote sensing measurements, whether optical or lidar reflectance, or radar backscatter. We conclude that while satellite remote sensing has often been discounted as inadequate for the task, attempts to map AGB without satellite imagery are insufficient. Moreover, the direct remote sensing approach provided more coherent maps of AGB relative to traditional approaches. We demonstrate this with a case study focused on continental Africa and discuss the work in the context of reducing uncertainty for carbon monitoring and markets.  相似文献   

Extragalactic Astronomy with the VLTI: a new window on the Universe     

Alessandro Marconi  Roberto Maiolino  Romain G. Petrov 《Astrophysics and Space Science》2003,286(1-2):245-254

Interferometry in the optical and near infrared has so far played a marginal role in Extragalactic Astronomy. Active Galactic Nuclei are the brightest and most compact extragalactic sources, nonetheless only a very limited number could be studied with speckle interferometry and none with long baseline interferometry. The VLTI will allow the study of moderately faint extragalactic objects with very high spatial resolution thus opening a new window on the universe. With this paper we focus on three scientific cases to show how AMBER and MIDI can be used to tackle open issues in extragalactic astronomy. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

The gaseous Halo of the Virgo Cluster Galaxy 45     

Gerhard Hensler  Daniel Tschöke  Dominik Bomans  Alessandro Boselli 《Astrophysics and Space Science》2003,284(2):467-470

Observations of the Virgo Cluster galaxy NGC 4569 in soft X-rays and in Hα reveal both an asymmetrically distributed hot gaseous halo and a giant filament of diffuse emission, respectively, extending from the same side of the disk, the latter one to at least 8.8 kpc. A deep longslit spectrum along the filament shows velocities systematically different from the systemic velocity of NGC 4569. With the inclination of the disk one can determine the Hα spur as a giant outflow in NGC 4569. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献