Extended particle-in-cell schemes for physics in ultrastrong laser fields: Review and developments.

We review common extensions of particle-in-cell (PIC) schemes which account for strong field phenomena in laser-plasma interactions. After describing the physical processes of interest and their numerical implementation, we provide solutions for several associated methodological and algorithmic problems. We propose a modified event generator that precisely models the entire spectrum of incoherent particle emission without any low-energy cutoff, and which imposes close to the weakest possible demands on the numerical time step. Based on this, we also develop an adaptive event generator that subdivides the time step for locally resolving QED events, allowing for efficient simulation of cascades. Further, we present a unified technical interface for including the processes of interest in different PIC implementations. Two PIC codes which support this interface, PICADOR and ELMIS, are also briefly reviewed

Groundwater geochemistry, hydrogeology and potash mineral potential of the Lake Woods region, Northern Territory, Australia

We collected 38 groundwater and two surface-water samples in the semi-arid Lake Woods region of the Northern Territory to better understand the hydrogeochemistry of this system, which straddles the Wiso, Tennant Creek and Georgina geological regions. Lake Woods is presently a losing waterbody feeding the underlying groundwater system. The main aquifers comprise mainly carbonate (limestone and dolostone), siliciclastic (sandstone and siltstone) and evaporitic units. The water composition was determined in terms of bulk properties (pH, electrical conductivity, temperature, dissolved oxygen, redox potential), 40 major, minor and trace elements, and six isotopes (δ18Owater, δ2Hwater, δ13CDIC, δ34SSO42–, δ18OSO42–, 87Sr/86Sr). The groundwater is recharged through infiltration in the catchment from monsoonal rainfall (annual average rainfall ∼600 mm) and runoff. It evolves geochemically mainly through evapotranspiration and water–mineral interaction (dissolution of carbonates, silicates and to a lesser extent sulfates). The two surface waters (one from the main creek feeding the lake, the other from the lake itself) are extraordinarily enriched in 18O and 2H isotopes (δ18O of +10.9 and +16.4‰ VSMOW, and δ2H of +41 and +93‰ VSMOW, respectively), which is interpreted to reflect evaporation during the dry season (annual average evaporation ∼3000 mm) under low humidity conditions (annual average relative humidity ∼40%). This interpretation is supported by modelling results. The potassium (K) relative enrichment (K/Cl– mass ratio over 50 times that of sea water) is similar to that observed in salt-lake systems worldwide that are prospective for potash resources. Potassium enrichment is believed to derive partly from dust during atmospheric transport/deposition, but mostly from weathering of K-silicates in the aquifer materials (and possibly underlying formations). Further studies of Australian salt-lake systems are required to reach evidence-based conclusions on their mineral potential for potash, lithium, boron and other low-temperature mineral system commodities such as uranium.This project was undertaken as part of the salt-lake mineral prospectivity project at Geoscience Australia during 2012–2013, which was supported by appropriation funding from the Commonwealth of Australi

Deep groundwater resources of the Ti-Tree Basin

Made available by the Northern Territory Library via the Publications (Legal Deposit) Act 2004 (NT).This report is the summation of the main activities, findings, achievements and recommendations of the work program conducted in the Ti-Tree region of the Northern Territory for the Raising National Water Standards project: 'Water for Australia's arid zone - identifying and assessing Australia's palaeovalley groundwater resources'. The aim of the Palaeovalley Groundwater Project was to deliver an innovative and integrated national-scale approach for better understanding the capacity, quality, quantity and dynamics of groundwater systems in palaeovalley aquifers, thereby enabling improved management of these important groundwater resources.Executive summary -- 1. Introduction -- 1.1. The Palaeovalley Groundwater Project -- 1.2. Project operations in the Ti-Tree Basin -- 1.3. Overview of the Ti-Tree Basin -- 2. Geological and geophysical setting -- 2.1. Geology -- 2.2. Regolith -- 2.3. Geophysics -- 2.4. Palynology -- 3. Hydrogeological setting -- 3.1. Introduction -- 3.2. Groundwater flow in the shallow aquifer -- 3.3 Recharge -- 3.4. Groundwater chemistry of the shallow aquifer -- 3.5. Potential for groundwater resources in deep aquifers -- 3.6. Summary -- 4. Investigation of deep groundwater systems in the T-Tree Basin -- 4.1. Gravity -- 4.2. Drilling -- 4.3. Stratigraphic analysis -- 4.4. Palynostratigraphic analysis -- 4.5. Hydrogeologic analysis -- 5. Revised hydrostratigraphic model of the T-Tree Basin -- 5.1. Introduction -- 5.2. Regional cross-sections -- 5.3. Hydrogeology -- 5.4. Stratigraphic correlations and comparisons with other arid zone palaeovalleys -- 5.5 Conclusions -- 6. Conclusions and recommendations -- 9. References -- Appendix 1. Deep investigative drillhole logs. Drilling report log for RN18356 (T-Tree Station). Drilling report log for RN18594.This project was funded by the Australian Government through the National Water Commission?s Raising National Water Standards Program

Comparing results from two continental geochemical surveys to world soil composition and deriving Predicted Empirical Global Soil (PEGS2) reference values

Available online 21 January 2012Analytical data for 10 major oxides (Al₂O₃, CaO, Fe₂O₃, K₂O, MgO, MnO, Na₂O, P₂O₅, SiO₂ and TiO₂), 16 total trace elements (As, Ba, Ce, Co, Cr, Ga, Nb, Ni, Pb, Rb, Sr, Th, V, Y, Zn and Zr), 14 aqua regia extracted elements (Ag, As, Bi, Cd, Ce, Co, Cs, Cu, Fe, La, Li, Mn, Mo and Pb), Loss On Ignition (LOI) and pH from 3526 soil samples from two continents (Australia and Europe) are presented and compared to (1) the composition of the upper continental crust, (2) published world soil average values, and (3) data from other continental-scale soil surveys. It can be demonstrated that average upper continental crust values do not provide reliable estimates for natural concentrations of elements in soils. For many elements there exist substantial differences between published world soil averages and the median concentrations observed on two continents. Direct comparison with other continental datasets is hampered by the fact that often mean, instead of the statistically more robust median, is reported. Using a database of the worldwide distribution of lithological units, it can be demonstrated that lithology is a poor predictor of soil chemistry. Climate-related processes such as glaciation and weathering are strong modifiers of the geochemical signature inherited from bedrock during pedogenesis. To overcome existing shortcomings of predicted global or world soil geochemical reference values, we propose Preliminary Empirical Global Soil reference values based on analytical results of a representative number of soil samples from two continents (PEGS2).Patrice de Caritat, Clemens Reimann, NGSA Project Team and GEMAS Project Team (M. McLaughlin part of the GEMAS Project Team