Hydrograph separation using isotopic, chemical and hydrological approaches (Strengbach catchment, France)

The streamflow components were determined in a small catchment located in Eastern France for a 40 mm rain event using isotopic and chemical tracing with particular focus on the spatial and temporal variations of catchment sources. Precipitation, soil solution, springwater and streamwaters were sampled and analysed for stable water isotopes (18O and 2H), major chemical parameters (SO4, NO3, Cl2, Na1, K1, Ca21, Mg21, NH4, H1, H4SiO4, alkalinity and conductivity), dissolved organic carbon (DOC) and trace elements (Al, Rb, Sr, Ba, Pb and U). 18O, Si, DOC, Ba and U were finally selected to assess the different contributing sources using mass balance equations and end-member mixing diagrams. Isotopic hydrograph separation shows that the pre-event water only contributes to 2% at the beginning of the stormflow to 13% at the main peak flow. DOC associated to Si and U to Ba allow to identify the different contributing areas (upper layers of the saturated areas, deep layers of the hillslope and rainwater). The streamflow (70%) originates from the deep layers of the hillslope, the remaining being supplied by the small saturated areas. The combination of chemical (both trace and major elements) and isotopic tracers allows to identify the origin of water pathways. During the first stage of the storm event, a significant part of the runoff (30±39%) comes from the small extended saturated areas located down part of the basin (overland runoff then groundwater ridging). During the second stage, the contribution of waters from the deep layers of the hillslope in the upper subcatchment becomes more significant. The final state is characterised by a balanced contribution between aquifers located in moraine and downslopes. Indeed, this study demonstrates the interest of combining a variety of hydrometric data, geochemical and isotopic tracers to identify the components of the streamwater in such conditions

Nuclear bars and blue nuclei within barred spiral galaxies

Multicolour near IR photometry for a sample of 32 large barred spiral galaxies is presented. By applying ellipse fitting techniques, we identify significant isophote twists with respect to the primary bar axis in the nuclear regions of $\sim$70 \%\ of the sample. These twists are identified in galaxies as late as SBbc and are clearly distinguishable from spiral arm morphology. At most seven of the galaxies with isophote twists are inferred to possess secondary (nuclear) bars, the axis ratios of which appear to correlate with morphological type. The remainder may result from triaxial bulges, or from oblate bulges misaligned with the primary bar. The near IR colour distributions in these data show evidence for (red) circumnuclear star forming rings in 4 galaxies. The majority of the sample (19) also possess striking blue nuclear regions, bluer than typical old stellar populations by $\sim$0.3 mag. in (J--H) and $\sim$0.23 mag. in (H--K). Such blue colours do not appear to correlate with the presence of nuclear rings or pseudo--rings, nor with the activity of the host galaxy (as determined from emission--line spectroscopic characteristics). Several mechanisms to explain this blue colour are considered.Comment: 24 pages plain LaTex( including table captions), 5 tables and 18 figures. Accepted for publication in MNRAS. Paper and tables available via anonymous ftp://143.167.4.101/pub/papers as sqiid-paper.tex and table1,2,3.tex, table4.ps, table5.ps. Figures available as postcript upon request to first Autho

A uniform isotopic and chemical signature of dust exported from Patagonia: Rock sources and occurrence in southern environments

Patagonia is considered to be the most important source of dust from South America that is deposited in surrounding areas, and we present here a systematic Sr and Nd isotopic study of sediment currently being exported. Eolian and suspended riverine sediments from Patagonia have a homogeneous chemical and isotopic composition that results from the mixing of by-products from explosive Andean volcanism, derived from the extensive Jurassic silicic Province of Chon Aike and pyroclastic materials from the basic to intermediate southern Andean Quaternary arc, which are easily denudated and dispersed. The main Andean uplift and the glaciations that began in the Late Tertiary account for the extensive distribution of these sediments in the extra-Andean region. The present geochemical signature of Patagonian sediments was produced during the Pleistocene, along with the onset of the southern Andean explosive arc volcanism. Previously published compositions of sediments from other southern South American source regions, assumed to be representative of Patagonia, are distinct from our data. Considering the alleged importance of Patagonia as a dust source for different depositional environments in southern latitudes, it is surprising to verify that the chemical and isotopic signatures of Patagonian-sourced sediments are different from those of sediments from the Southern Ocean, the Pampean Region or the Antarctic ice. Sediments from these areas have a crustal-like geochemical signature reflecting a mixed origin with sediment from other southern South American sources, whereas Patagonian sediments likely represent the basic to intermediate end-member composition

The signature of river- and wind-borne materials exported from Patagonia to the southern latitudes: a view from REEs and implications for paleoclimatic interpretations

Riverine and wind-borne materials transferred from Patagonia to the SW Atlantic exhibit a homogeneous rare earth element (REE) signature. They match well with the REE composition of Recent tephra from the Hudson volcano,and hence this implies a dominance of material supplied by this source and other similar Andean volcanoes. Due to the trapping effect of proglacial and reservoir lakes,the larger Patagonian rivers deliver to the ocean a suspended load with a slightly modified Andean signature,that shows a REE composition depleted in heavy REEs. In this paper we redefine Patagonia as a source of sediments,which is in contrast with other sources located in southern South America. Quaternary sediments deposited in the northern and,to a lesser extent, in the southern Scotia Sea, and most of the dust in ice cores of east Antarctica have REE compositions very similar to the loess from Buenos Aires Province and to Patagonian eolian dust. However,we rule out Buenos Aires province as a Holocene major source of sediments. Similarly to Buenos Aires loess (a proximal facies),it is likely that the REE compositions of most sediment cores of the Scotia Sea and Antarctica reflect a distal transport of dust with an admixed composition from two main sources: a major contribution from Patagonia,and a minor proportion from source areas containing sediments with a clear upper crustal signature (e.g.,western Argentina) or from Bolivia’s Altiplano. Evidence indicates that only during the Last Glacial Maximum,Patagonian materials were the predominant sediment source to the southern latitudes

Iron and other transition metals in Patagonian riverborne and windborne materials: Geochemical control and transport to the southern South Atlantic Ocean

The bulk of particulate transition metals transported by Patagonian rivers shows an upper crustal composition. Riverine particulate 0.5 N HCl leachable trace metal concentrations are mainly controlled by Fe-oxides. Complexation of Fe by dissolved organic carbon (DOC) appears to be an important determinant of the phases transporting trace metals in Patagonian rivers. In contrast, aeolian trace elements have a combined crustal and anthropogenic origin. Aeolian materials have Fe, Mn, and Al contents similar to that found in regional topsoils. However, seasonal concentrations of some metals (e.g., Co, Pb, Cu, and Zn) are much higher than expected from normal crustal weathering and are likely pollutant derived. We estimate that Patagonian sediments are supplied to the South Atlantic shelf in approximately equivalent amounts from the atmosphere (30 106 T yr1) and coastal erosion (40 106 T yr1) with much less coming from the rivers (2.0 106 T yr1). Low trace metal riverine fluxes are linked to the low suspended particulate load of Patagonian rivers, inasmuch most of it is retained in pro-glacial lakes as well as in downstream reservoirs. Based on our estimation of aeolian dust fluxes at the Patagonian coastline, the high nutrient-low chlorophyll sub Antarctic South Atlantic could receive 1.0 to 4.0 mg m2 yr1 of leachable (0.5 N HCl) Fe. Past and present volcanic activity in the southern Andes—through the ejection of tephra—must be highlighted as another important source of Fe to the South Atlantic Ocean. Based on the 1991 Hudson volcano eruption, it appears that volcanic events can contribute several thousand-fold the mass of “leachable” Fe to the ocean as is introduced by annual Patagonian dust fallout

Anisotropic electrical resistivity of LaFeAsO: evidence for electronic nematicity

Single crystals of LaFeAsO were successfully grown out of KI flux. Temperature dependent electrical resistivity was measured with current flow along the basal plane, \rho_perpend(T), as well as with current flow along the crystallographic c-axis, \rho_parallel(T), the latter one utilizing electron beam lithography and argon ion beam milling. The anisotropy ratio was found to lie between \rho_parallel/\rho_perpend = 20 - 200. The measurement of \rho_perpend(T) was performed with current flow along the tetragonal [1 0 0] direction and along the [1 1 0] direction and revealed a clear in-plane anisotropy already at T \leq 175 K. This is significantly above the orthorhombic distortion at T_0 = 147 K and indicates the formation of an electron nematic phase. Magnetic susceptibility and electrical resistivity give evidence for a change of the magnetic structure of the iron atoms from antiferromagnetic to ferromagnetic arrangement along the c-axis at T^\ast = 11 K.Comment: 10 pages, 6 figures, minor change

Towards formal analysis of insider threats for auctions

This paper brings together the world of insider threats and auctions. For online-auction systems, like eBay, but also for high-value one-off auction algorithms as they are used for selling radio wave frequencies, the use of rigorous machine supported modelling and verification techniques is meaningful to prove correctness and scrutinize vulnerability to security and privacy attacks. Surveying the threats in auctions and insider collusions, we present an approach to model and analyze auction protocols for insider threats using the interactive theorem prover Isabelle. As a case study, we use the cocaine auction protocol that represents a nice combination of cryptographic techniques, protocols, and privacy goals suitable for highlighting insider threats for auctions

Riverine transfer of heavy metals from Patagonia to the southwestern Atlantic Ocean

The occurrence and geochemical behaviour of Fe, Mn, Pb, Cu, Ni, Cr, Zn and Co are studied in riverine detrital materials transported by Patagonian rivers. Their riverine inputs have been estimated and the nature of these inputs to the Atlantic Ocean is discussed. Most of the metals are transported to the ocean via the suspended load; there is evidence that Fe oxides and organic matter are important phases controlling their distribution in the detrital non-residual fraction. Most heavy metal concentrations found in bed sediments, in suspended matter, and in the dissolved load of Patagonian rivers were comparable to those reported for non-polluted rivers. There is indication that human activity is altering riverine metal inputs to the ocean. In the northern basins – and indicatinganthropogenic effects – heavy metals distribution in the suspended load is very different from that found in bed sediments. The use of pesticides in the Negro River valley seems correlated with increased riverine input of Cu, mostly bound to the suspended load. The Deseado and Chico Rivers exhibit increased specific yield of metals as a consequence of extended erosion within their respective basins. The Santa Cruz is the drainage basin least affected by human activity and its metal-exporting capacity should be taken as an example of a relatively unaffected large hydrological system. In contrast, coal mining modifies the transport pattern of heavy metals in the Gallegos River, inasmuch as they are exported to the coastal zone mainly as dissolved load