Search results for "Rust"
showing 10 items of 1659 documents
Thermal entanglement of a spin-1/2 Ising–Heisenberg model on a symmetrical diamond chain
2011
International audience; The entanglement quantum properties of a spin-1/2 Ising-Heisenberg model on a symmetrical diamond chain were analyzed. Due to the separable nature of the Ising-type exchange interactions between neighboring Heisenberg dimers, calculation of the entanglement can be performed exactly for each individual dimer. Pairwise thermal entanglement was studied in terms of the isotropic Ising-Heisenberg model and analytical expressions for the concurrence (as a measure of bipartite entanglement) were obtained. The effects of external magnetic field H and next-nearest neighbor interaction J(m) between nodal Ising sites were considered. The ground state structure and entanglement …
Acute Toxicity Tests with Cadmium, Lead, Sodium Dodecyl Sulfate, and Bacillus thuringiensis on a Temporary Pond Ostracod
2012
A complete assessment of effects of pollutants in the environment requires the use of a wide assemblage of test organisms. Crustaceans have been widely used in aquatic environments, but within this group, ostracods have been overlooked, even though they are one of the commonest groups of animals in temporary waters. Within this framework, static acute toxicity bioassays were conducted with heavy metals Cd and Pb, the surfactant SDS and spores of the bacteria Bacillus thuringiensis var. israeliensis using adult parthenogenetic females of the temporary pond ostracod Heterocypris bosniaca. Experiments were run at 20 °C and in a 12 by 12 h photoperiod. The toxicity tests results are expressed a…
Ability of soil bacterial composition as an indicator of levels of soil erosion in a badland
2022
Calanchi (plural of calanco) are typical Italian badlands created by a combination of morphogenetic processes (rill and interrill erosion, gullying, piping, and mass movements) mainly originated by the effect of water. Calanchi are characterized by the sparse and patchy distribution of vegetation, and, in interplant areas, the soil surface is colonized by an association of organisms known as biological soil crust (BSC). A morphometric analysis of 45 basins in the studied calanchi area, based on a high-resolution digital elevation model, showed those basins are sediment removal systems characterized by rapid and relevant erosion processes. The goal of the current research is to evaluate the …
High-resolution analysis of trace elements in crustose coralline algae from the North Atlantic and North Pacific by laser ablation ICP-MS
2011
We have investigated the trace elemental composition in the skeleta of two specimens of attached-living coralline algae of the species Clathromorphum compactum from the North Atlantic (Newfoundland) and Clathromorphum nereostratum from the North Pacific/Bering Sea region (Amchitka Island, Aleutians). Samples were analyzed using Laser Ablation-Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) yielding for the first time continuous individual trace elemental records of up to 69 years in length. The resulting algal Mg/Ca, Sr/Ca, U/Ca, and Ba/Ca ratios are reproducible within individual sample specimens. Algal Mg/Ca ratios were additionally validated by electron microprobe analyses (Amch…
Spherulites in Calcrete Laminar Crusts: Biogenic CACO3 Precipitation as a Major Contributor to Crust Formation
1995
ABSTRACT Spherulites (calcitic fibro-radial spherulitic polycrystals) are a major component of calcite layers in Quaternary calcrete laminar crusts. To explain the formation of spherulites, petrographic and chemical studies were performed on Pleistocene calcrete laminar crusts, Holocene biological crusts, and laboratory (in vitro) cultures of cyanobacterial strains. Spherulites were found to be formed of acicular and radiating crystals, either smooth and regular-edged, or twisted and irregular-edged. Spherulites were composed of low-Mg calcite, the concentration of Mg in the spherulites increasing from nucleus to periphery. The shape and chemistry of the in vitro spherulites and laminar cru…
Empirical calibration of shell chemistry of Cyprideis torosa (Jones, 1850) (Crustacea: Ostracoda)
2012
Abstract Cyprideis torosa is a species of ostracode that inhabits a wide range of aquatic habitats in which its low Alk/Ca requirement is met. Its fossil remains are widely used in palaeoecological studies of coastal environments and inland salt lakes. We collected C. torosa from 20 water bodies near Valencia, Spain. Temperature, chlorophyll a concentration, electrical conductivity, and the concentration of major ions and oxygen isotopes were measured at each site. Between 2 and 20 live individuals of C. torosa were collected per site, their instar stage and sex determined and their shell chemistry (Mg/Ca, Sr/Ca and carbon and oxygen isotope composition) analyzed. Three of these sites were …
Bulk composition of northern African dust and its source sediments — A compilation
2013
Abstract This paper presents a review of bulk compositional data of northern African dust and its potential source sediments and includes elemental, isotope and mineralogical data. Northern African dust represents about one half of the total global atmospheric mineral dust burden, and its uplift, transport and deposition have strong impacts on climate and various terrestrial and marine ecosystems. The chemical data set shows, that an ‘average northern African dust’ exhibits comparable Si, Fe and Mn contents with respect to the average composition of the upper continental crust, is slightly depleted in the alkali metals K and Na, and enriched in Ti and P. However, the complete data set yield…
The role of trapped fluids during the development and deformation of a carbonate/shale intra-wedge tectonic mélange (Mt. Massico, Southern Apennines,…
2020
Abstract Numerous studies exist on exhumed tectonic melanges along subduction channels whereas, in accretionary wedge interiors, deformation mechanisms and related fluid circulation in tectonic melanges are still underexplored. We combine structural and microstructural observations with geochemical (stable and clumped isotopes and isotope composition of noble gases in fluid inclusions of calcite veins) and U-Pb geochronological data to define deformation mechanisms and syn-tectonic fluid circulation within the Mt. Massico intra-wedge tectonic melange, located in the inner part of the central-southern Apennines accretionary wedge, Italy. This melange developed by shear deformation at the bas…
Calcitic radial palisadic fabric in freshwater stromatolites: diagenetic and recrystallized feature or physicochemical sinter crust?
1999
Abstract When favorable conditions occur for carbonate precipitation (physicochemical processes) in tufas and travertines, organisms intervene either directly (the framework created by organisms acts as a crystal support) or indirectly (organic products influencing the mineralogy, nucleation, growth and habit of primary crystals). In the literature, fluvial and travertine crystalline sparite crusts with palisadic or prismatic crystals are generally interpreted as the result of early recrystallization of micrite in algal buildups (mostly composed of Schizothrix). Therefore, biological mediation is essential for the construction of continental bioherms and biostromes, even if organic remains …
Recycled crustal carbon in the depleted mantle source of El Hierro volcano, Canary Islands
2021
The Canary Islands, in the eastern Atlantic, are among the most enigmatic Oceanic Island provinces on Earth, as the mantle source feeding its volcanism exhibits wide spatial heterogeneity and a multiplicity of sources. Multi-isotope whole-rock studies have long revealed the presence of a recycled oceanic crust/lithosphere component in the mantle source. However, noble gas systematics have been more challenging to interpret, and the available carbon isotope data is limited and cannot support/dismiss this interpretation. Here, we present the very first isotopic characterisation of CO2 and noble gases (He-Ne-Ar) in fluid inclusions (FI) in minerals hosted in mantle xenoliths from El Hierro, th…