Complex polynomials for the computation of 2D gravity anomalies

We present an efficient algorithm using a complex variables formulation for the computation of the gravity effect of 2D polygonal bodies having densities varying both laterally and with depth. The first derivatives of the gravity effect are also provided in order to enable the computation of the Jacobian matrix, which is necessary for linear inverse gravity problems. A geophysical example based on numerical assumptions about the density contrast on a well-studied basin area shows the applicability of the algorithm.     

The Crati Submarine Fan,Ionian Sea

The Crati Fan is located in the tectonically active submerged extension of the Apennines chain and foretrough. The small fan system is growing in a relatively shallow (200 to 450 m), elongate nearshore basin receiving abundant input from the Crati River. The fan is characterized by a short, steep, channelized section (inner or upper fan) and a smooth, slightly bulging distal section (outer or lower fan). The numerous subparallel channels head in the shelf or littoral zone and do not form branching distributary patterns. Sand and mud depositional lobes of the outer fan stretch over more than 60% of fan length.     

Impacts from decommissioning of hydroelectric dams: a life cycle perspective

Greenhouse gas (GHG) emissions from hydroelectric dams are often portrayed as nonexistent by the hydropower industry and have been largely ignored in global comparisons of different sources of electricity. However, the life cycle assessment (LCA) of any hydroelectric plant shows that GHG emissions occur at different phases of the power plant’s life. This work examines the role of decommissioning hydroelectric dams in greenhouse gas emissions. Accumulated sediments in reservoirs contain noticeable levels of carbon, which may be released to the atmosphere upon decommissioning of the dam. The rate of sediment accumulation and the sediment volume for six of the ten largest United States hydroelectric power plants is surveyed. The amount of sediments and the respective carbon content at the moment of dam decommissioning (100 years after construction) was estimated. The released carbon is partitioned into CO₂ and CH₄ emissions and converted to CO₂ equivalent emissions using the global warming potential (GWP) method. The global warming effect (GWE) due to dam decommissioning is normalized to the total electricity produced over the lifetime of each power plant. The estimated GWE of the power plants range from 128–380 g of CO₂eq./kWh when 11% of the total available sediment organic carbon (SOC) is mineralized and between 35 and 104 g of CO₂eq./kWh when 3% of the total SOC is mineralized. Though these values are below emission factors for coal power plants (890 g of CO₂eq./kWh), the amount of greenhouse gases emitted by the sediments upon dam decommissioning is a notable amount that should not be ignored and must be taken into account when considering construction and relicensing of hydroelectric dams.     

Sulphidizing reactions in the flotation of oxidized copper minerals,I. Chemical factors in the sulphidization of copper oxide

The rate and extent of the heterogeneous reaction that takes place between dissolved sodium sulphide and synthetic tenorite is studied for a wide range of sodium sulphide to copper oxide ratios. Besides the sulphidization with the formation of a copper-sulphide layer, a substantial oxidation of sulphide ions takes place at the surface of the solid. The extent of both types of reactions is quantitized by combining specific analytical methods.The results are discussed in terms of possible mechanisms and of their implications in the sulphidization process applied in the flotation of oxidized copper ores.     

Sulphidizing reactions in the flotation of oxidized copper minerals,II. Role of the adsorption and oxidation of sodium sulphide in the flotation of chrysocolla and malachite

The rate of consumption of sulphide in the sulphidizing reactions of malachite and chrysocolla has been measured. The oxidation of sulphide ions at the surface of sulphidized chrysocolla was shown to take place. The influence of thiosulphate anions on the xanthate flotation of sulphidized malachite and chrysocolla was investigated and it was shown to depress the flotation of chrysocolla strongly.The result suggest, that the presence of thiosulphate as a product of simultaneous oxidation can be one of the reasons for the more difficult flotation of sulphidized chrysocolla.     

Convergence in a thermally softened thick crust: Variscan intracontinental tectonics in Iberian plate rocks

The subduction phase in the development of the Variscan Orogen in SW Europe was followed by an extended period of ‘intracontinental’ tectonics. The progressive temperature rise in the hinterland during plate convergence was accompanied by widespread partial melting in the lower crust and the nucleation of kilometric buckle folds and crustal‐scale shear zones in the stronger upper crust. Thermal mechanical weakening in the core of the orogen was contemporaneous with shortening and thickening in the foreland fold‐and‐thrust belt. We evaluate lithospheric strength profiles in the hinterland and foreland based on the metamorphic and structural record for three tectonic stages. We find that lower crustal strength varied in space as well as in time during orogenesis. Strength contrasts between the foreland and the hot hinterland during convergence may have led to the additional indentation of the foreland into the hinterland of the Ibero‐Armorican Arc.     

Optimization for performance-based design under seismic demands,including social costs

Performance-based design in earthquake engineering is a structural optimization problem that has, as the objective, the determination of design parameters for the minimization of total costs, while at the same time satisfying minimum reliability levels for the specifi ed performance criteria. Total costs include those for construction and structural damage repairs, those associated with non-structural components and the social costs of economic losses, injuries and fatalities. This paper presents a general framework to approach this problem, using a numerical optimization strategy and incorporating the use of neural networks for the evaluation of dynamic responses and the reliability levels achieved for a given set of design parameters. The strategy is applied to an example of a three-story offi ce building. The results show the importance of considering the social costs, and the optimum failure probabilities when minimum reliability constraints are not taken into account.     

Effect of coastal urbanization on sandy beach coleoptera Phaleria maculata (Kulzer, 1959) in northern Chile

The beetle Phaleria maculata is a common inhabitant of the upper intertidal fringe of Chilean beaches. Anthropogenic intervention in coastal areas has increased intensely, leading to changes in the flora and fauna of sandy beaches. To examine the impact of human activities on P. maculata, we studied several beaches along the northern Chilean coast. Beaches were characterized based on morphodynamics and the level of intervention, leading to the estimation of an “Urbanization Index” based on various indicators. The analysis showed a significant inverse correlation between the rate of urbanization and night sky quality. Larval and adult beetles were almost absent on beaches with high levels of urbanization. The results of simple and multiple correlations based on nMDS ordination showed an inverse relationship between increases in urbanization and the abundance of beetles. Because darkling beetles are very sensitive to human interventions on sandy beaches, we suggest that they are ideal indicator organisms for the health of these environments.