Interpolation using a generalized Green's function for a spherical surface spline in tension

A variety of methods exist for interpolating Cartesian or spherical surface data onto an equidistant lattice in a procedure known as gridding. Methods based on Green's functions are particularly simple to implement. In such methods, the Green's function for the gridding operator is determined and the resulting gridding solution is composed of the superposition of contributions from each data constraint, weighted by the Green's function evaluated for all output–input point separations. The Green's function method allows for considerable flexibility, such as complete freedom in specifying where the solution will be evaluated (it does not have to be on a lattice) and the ability to include both surface heights and surface gradients as data constraints. Green's function solutions for Cartesian data in 1-, 2- and 3-D spaces are well known, as is the dilogarithm solution for minimum curvature spline on a spherical surface. Here, the spherical surface case is extended to include tension and the new generalized Green's function is derived. It is shown that the new function reduces to the dilogarithm solution in the limit of zero tension. Properties of the new function are examined and the new gridding method is implemented in Matlab® and demonstrated on three geophysical data sets.     

Environmental Radioxenon Levels in Europe: a Comprehensive Overview

Activity concentration data from ambient radioxenon measurements in ground level air, which were carried out in Europe in the framework of the International Noble Gas Experiment (INGE) in support of the development and build-up of a radioxenon monitoring network for the Comprehensive Nuclear-Test-Ban Treaty verification regime are presented and discussed. Six measurement stations provided data from 5 years of measurements performed between 2003 and 2008: Longyearbyen (Spitsbergen, Norway), Stockholm (Sweden), Dubna (Russian Federation), Schauinsland Mountain (Germany), Bruyères-le-Châtel and Marseille (both France). The noble gas systems used within the INGE are designed to continuously measure low concentrations of the four radioxenon isotopes which are most relevant for detection of nuclear explosions: ^131mXe, ^133mXe, ¹³³Xe and ¹³⁵Xe with a time resolution less than or equal to 24 h and a minimum detectable concentration of ¹³³Xe less than 1 mBq/m³. This European cluster of six stations is particularly interesting because it is highly influenced by a high density of nuclear power reactors and some radiopharmaceutical production facilities. The activity concentrations at the European INGE stations are studied to characterise the influence of civilian releases, to be able to distinguish them from possible nuclear explosions. It was found that the mean activity concentration of the most frequently detected isotope, ¹³³Xe, was 5–20 mBq/m³ within Central Europe where most nuclear installations are situated (Bruyères-le-Châtel and Schauinsland), 1.4–2.4 mBq/m³ just outside that region (Stockholm, Dubna and Marseille) and 0.2 mBq/m³ in the remote polar station of Spitsbergen. No seasonal trends could be observed from the data. Two interesting events have been examined and their source regions have been identified using atmospheric backtracking methods that deploy Lagrangian particle dispersion modelling and inversion techniques. The results are consistent with known releases of a radiopharmaceutical facility.     

Negotiating on location, timing, duration, and participant in agent-mediated joint activity-travel scheduling

Agent-based simulation has become an important modeling approach in activity-travel analysis. Social activities account for a large amount of travel and have an important effect on activity-travel scheduling. Participants in joint activities usually have various options regarding location, participants, and timing and take different approaches to make their decisions. In this context, joint activity participation requires negotiation among agents involved, so that conflicts among the agents can be addressed. Existing mechanisms do not fully provide a solution when utility functions of agents are nonlinear and non-monotonic. Considering activity-travel scheduling in time and space as an application, we propose a novel negotiation approach, which takes into account these properties, such as continuous and discrete issues, and nonlinear and non-monotonic utility functions, by defining a concession strategy and a search mechanism. The results of experiments show that agents having these properties can negotiate efficiently. Furthermore, the negotiation procedure affects individuals’ choices of location, timing, duration, and participants.     

Analyses of pre-injection reservoir data for stable carbon isotope trend predictions in CO2 monitoring: preparing for CO2 injection

Baseline monitoring at the proposed enhanced gas recovery site in Altmark (Germany) was carried out in combination with theoretical and laboratory investigations to describe and predict the principles of expected stable carbon isotope and dissolved inorganic carbon (DIC) trends during CO₂ injection in reservoirs. This provides fundamental data for site-specific characterisation for monitoring purposes. Baseline ??¹³C values at the Altmark site ranged between ?1.8 and ?11.5??? and DIC values were about 2?mmol?L^?1. These baseline values form the basis for a theoretical study on the influences of the ambient reservoir conditions on the state of geochemical and isotope equilibrium of the reservoir fluids. Transferring this theoretical study to the Altmark site enables predictions on geochemical trends during potential injection. Assuming that CO₂ would be injected at the Altmark site to pCO₂?=?100?bar and with a ??¹³C of ?30???, at isotopic and geochemical equilibrium, ??¹³C_DIC values would approach this end-member, and DIC concentrations of 1,000?mmol L^?1 would be expected. Laboratory experiments were conducted at low pCO₂ levels (4?C35?bars) to mimic the approach of a CO₂ plume at a monitoring well. These results support field investigations from other sites: that ??¹³C_DIC is a sensitive tool for monitoring CO₂ migration in the subsurface and simultaneously allows quantification of geochemical trapping of CO₂.     

Using FTIR spectroscopy to characterise the soil mineralogy and geochemistry of cryoconite from Aldegondabreen glacier,Svalbard

Mineralogical and geochemical diversity in cryoconite granules from Aldegondabreen glacier was investigated using FTIR spectroscopy. Results suggest that the technique is an effective tool for investigating mineralogy and identifying spatial differences in geochemistry, based upon characteristic spectral signatures.     

Sulfide Oxidation across Diffuse Flow Zones of Hydrothermal Vents

The sulfide (H₂S/HS^?) that is emitted from hydrothermal vents begins to oxidize abiotically with oxygen upon contact with ambient bottom water, but the reaction kinetics are slow. Here, using in situ voltammetry, we report detection of the intermediate sulfur oxidation products polysulfides [ $ {\text{S}}_{\text{x}}^{2 - } $ ] and thiosulfate [ $ {\text{S}}_{ 2} {\text{O}}_{ 3}^{ 2- } $ ], along with contextual data on sulfide, oxygen, and temperature. At Lau Basin in 2006, thiosulfate was identified in less than one percent of approximately 10,500 scans and no polysulfides were detected. Only five percent of 11,000 voltammetric scans taken at four vent sites at Lau Basin in May 2009 show either thiosulfate or polysulfides. These in situ data indicate that abiotic sulfide oxidation does not readily occur as H₂S contacts oxic bottom waters. Calculated abiotic potential sulfide oxidation rates are <10^?3 ??M/min and are consistent with slow oxidation and the observed lack of sulfur oxidation intermediates. It is known that the thermodynamics for the first electron transfer step for sulfide and oxygen during sulfide oxidation in these systems are unfavorable, and that the kinetics for two electron transfers are not rapid. Here, we suggest that different metal catalyzed and/or biotic reaction pathways can readily produce sulfur oxidation intermediates. Via shipboard high-pressure incubation experiments, we show that snails with chemosynthetic endosymbionts do release polysulfides and may be responsible for our field observations of polysulfides.     

In situ laser ablation ICP‐MS analyses of dimict diogenites: Further evidence for harzburgitic and orthopyroxenitic lithologies

Trace element concentrations in pyroxene, plagioclase, and olivine were measured in five diogenite breccias previously identified as containing distinct harzburgitic (ol+opx) and orthopyroxenitic (opx) lithologies (dimict). Three samples show two distinct populations of pyroxene trace element abundances, supporting their classification as dimict. These three meteorites show increases in Y, Yb, and HREE concentrations from harzburgitic to orthopyroxenitic pyroxenes, supporting the hypothesis that the lithologies are related through fractional crystallization whereby harzburgite olivine and pyroxene crystallized from the magma first followed by orthopyroxenite pyroxene. Depletions in LREE and Eu concentrations in the orthopyroxenitic lithology are most likely due to equilibration with LREE and Eu‐rich phases, likely plagioclase, which is found primarily in that lithology. Two samples do not show evidence supporting a dimict classification. Large pyroxene trace element variation in one sample indicates that it is polymict, while uniform trace element distribution in the other suggests that it may be a monomict breccia.     

Re-assessment of foundation settlements for the Burj Khalifa, Dubai

This paper deals with the re-assessment of foundation settlements for the Burj Khalifa Tower in Dubai. The foundation system for the tower is a piled raft, founded on deep deposits of calcareous rocks. Two computer programs, Geotechnical Analysis of Raft with Piles (GARP) and Non-linear Analysis of Piled Rafts (NAPRA) have been used for the settlement analyses, and the paper outlines the procedure adopted to re-assess the foundation settlements based on a careful interpretation of load tests on trial piles in which the interaction effects of the pile test set-up are allowed for. The paper then examines the influence of a series of factors on the computed settlements. In order to obtain reasonable estimates of differential settlements within the system, it is found desirable to incorporate the effects of the superstructure stiffness which act to increase the stiffness of the overall foundation system. Values of average and differential settlements for the piled raft calculated with GARP and NAPRA were found to be in reasonable agreement with measured data on settlements taken near the end of construction of the tower.