Probabilistic seismic hazard analysis for spatially distributed infrastructure

Two key issues distinguish probabilistic seismic risk analysis of a lifeline or portfolio of structures from that of a single structure. Regional analysis must consider the correlation among lifeline components or structures in the portfolio, and the larger scope makes it much more computationally demanding. In this paper, we systematically identify and compare alternative methods for regional hazard analysis that can be used as the first part of a computationally efficient regional probabilistic seismic risk analysis that properly considers spatial correlation. Specifically, each method results in a set of probabilistic ground motion maps with associated hazard‐consistent annual occurrence probabilities that together represent the regional hazard. The methods are compared according to how replicable and computationally tractable they are and the extent to which the resulting maps are physically realistic, consistent with the regional hazard and regional spatial correlation, and few in number. On the basis of a conceptual comparison and an empirical comparison for Los Angeles, we recommend a combination of simulation and optimization approaches: (i) Monte Carlo simulation with importance sampling of the earthquake magnitudes to generate a set of probabilistic earthquake scenarios (defined by source and magnitude); (ii) the optimization‐based probabilistic scenario method, a mixed‐integer linear program, to reduce the size of that set; (iii) Monte Carlo simulation to generate a set of probabilistic ground motion maps, varying the number of maps sampled from each earthquake scenario so as to minimize the sampling variance; and (iv) the optimization‐based probabilistic scenario again to reduce the set of probabilistic ground motion maps. Copyright © 2012 John Wiley & Sons, Ltd.     

Synthesis of zinc oxide–montmorillonite composite and its effect on the removal of aqueous lead ions

Acta Geochimica - Lead adsorption of zinc oxide-coated ACOR montmorillonite was investigated in batches and under reducing conditions at ambient temperature. The presence of zinc oxide coating...     

Variationally adjusted surface winds

This paper describes a one-level variational adjustment process for producing mass-consistent surface winds in the Barrow Strait area, N.W.T. To achieve this result, the continuity equation is employed as a physical constraint. The variational technique adjusts mean winds (vertically averaged through the planetary boundary layer); therefore, a relationship is required between surface and mean winds. Use is made of existing velocity profiles, but interpolation may be used between surface and geostrophic winds. The model was found to be strongly dependent upon specification of boundary-layer height. Channeling effects are not readily seen until topography begins to protrude through the boundary layer. The model might thus be better suited to areas where shallow inversion layers are well defined. By application of the variational adjustment, errors in continuity are reduced by six orders of magnitude. Upon comparison of the variational technique with a diagnostic, one-level, primitive equation model, median errors between computed and observed surface winds were found to be comparable.     

Production of bioavailable and refractory dissolved organic matter by coastal heterotrophic microbial populations

Production of dissolved organic matter (DOM) by heterotrophic microbial communities isolated from Loch Creran (Scotland) was studied in time course incubations in which cells were re-suspended in artificial seawater amended with variable proportions of glucose, ammonium and phosphate. The incubation experiments demonstrated that microheterotrophs released part of the substrate as new DOM, with a production efficiency of 11 ± 1% for DOC, 18 ± 2% for DON and 17 ± 2% for DOP. Estimating the impact of this production in Loch Creran, showed that from 3 ± 1% (DOC) to 72 ± 16% (DOP) of DOM could originate from the heterotrophic microbial community. The produced DOM (PDOM) was both bioavailable (BDOM) and refractory (RDOM). Bioavailability as assessed by the difference between the maximum and the end DOM concentration, was generally higher than found in natural systems, with DOP (73 ± 15%, average ± SD) more bioavailable than DON (70 ± 15%), and DON than DOC (34 ± 13%).The stoichiometry of PDOM was linked to both nutrient uptake and BDOM ratios. Absorption and fluorescence of DOM increased significantly during the incubation time, indicating that microheterotrophs were also a source of coloured DOM (CDOM) and that they produce both bioavailable protein-like and refractory humic-like fluorophores.     

Measuring the level of interstellar inheritance in the solar protoplanetary disk

The timing and extent to which the initial interstellar material was thermally processed provide fundamental constraints for models of the formation and early evolution of the solar protoplanetary disk. We argue that the nonsolar (solar Δ¹⁷O ≈ ?29‰) and near‐terrestrial (Δ¹⁷O ≈ 0‰) O‐isotopic compositions of the Earth and most extraterrestrial materials (Moon, Mars, asteroids, and comet dust) were established very early by heating of regions of the disk that were modestly enriched (dust/gas ≥ 5–10 times solar) in primordial silicates (Δ¹⁷O ≈ ?29‰) and water‐dominated ice (Δ¹⁷O ≈ 24‰) relative to the gas. Such modest enrichments could be achieved by grain growth and settling of dust to the midplane in regions where the levels of turbulence were modest. The episodic heating of the disk associated with FU Orionis outbursts were the likely causes of this early thermal processing of dust. We also estimate that at the time of accretion the CI chondrite and interplanetary dust particle parent bodies were composed of ~5–10% of pristine interstellar material. The matrices of all chondrites included roughly similar interstellar fractions. Whether this interstellar material avoided the thermal processing experienced by most dust during FU Orionis outbursts or was accreted by the disk after the outbursts ceased to be important remains to be established.     

Developing institutions for the clean development mechanism (CDM): African perspectives

Abstract

The clean development mechanism (CDM) requires developing countries to set up designated national authorities (DNAs). The DNA should be designed to both attract investment and to establish an effective regulatory framework for project approval—including assessment to ensure that CDM projects contribute to national sustainable development objectives. Since CDM investment flows to Africa are uncertain, however, countries cannot risk large investments in institutional infrastructure and need to build on existing institutions. This article examines the critical functions that a DNA has to fulfil, and outlines several institutional models. It concludes that models that minimize institutional cost by drawing on existing institutions for environmental impact assessment and promotion of foreign direct investment are likely to be the best starting-point for DNAs in many African countries.     

The temperature dependent,infrared absorption cross-sections for the chlorofluorocarbons: CFC-11, CFC-12, CFC-13, CFC-14, CFC-22, CFC-113, CFC-114, and CFC-115

The infrared absorption cross-sections for eight commonly used halogenated methanes and ethanes have been measured as a function of temperature from 203 to 293 K. High resolution spectra (0.03 cm^-1) have been used to derive integrated band strengths and peak cross-sections associated with the spectral features in the infrared region from 600 to 1500 cm^-2. The values obtained in this study are compared to those from previous reports, and recommendations are made for uses in atmospheric sensing and radiative energy transfer models. The observed temperature dependence in the spectral features is also discussed.     

The use of oxygen isotope geothermometry on the granulites and related intrusives,Musgrave Ranges,central Australia

Oxygen isotope equilibration involving quartz, feldspar and magnetite has taken place within the granulites of the metamorphic aureole of the intrusive charnockitic Ernabella Adamellite, and a temperature of approximately 550° C is indicated by ¹⁸O/¹⁶O values from quartz-magnetite and plagioclase-magnetite pairs. Pyroxene-magnetite fractionations are larger than equilibrium fractionations at this temperature, and demonstrate that caution is necessary in assigning estimates of temperature to highly metamorphosed rocks.The intrusive adamellite and related fine-grained and pegmatitic phases appear to have attained oxygen isotope equilibrium with the granulites at a similar temperature (approx. 550° C) which is here regarded as a late metamorphic equilibration temperature rather than the maximum temperature (estimated to be about 780° C) reached within the aureole.Oxygen was extracted from the minerals by means of bromine pentafluoride, and the isotopes were successfully measured without the normal prior conversion of oxygen to carbon dioxide.