2,250 research outputs found

    Magnetostratigraphy of the Miocene continental deposits of the Montes de Castejón (central Ebro basin, Spain): geochronological and paleoenvironmental implications

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    A detailed magnetostratigraphic study has been carried out in the early to middle Miocene distal alluvial and lacustrine sediments of the Montes de Castejón (central Ebro Basin). The study was based on the analysis of 196 magnetostratigraphic sites sampled along a stratigraphic interval of about 240 meters. Local magnetostratigraphy yielded a sequence of 12 magnetozones (6 normal and 6 reverse) which could be correlated with the Geomagnetic Polarity Time Scale (GPTS) interval C5Cr to C5AD (between 17 and 14.3 Ma.). The sampled sedimentary sequences include the boundary between two tectosedimentary units (TSU, T5 and T6) already defined in the Ebro Basin. The magnetostratigraphy of the Montes de Castejón allows to date the T5/T6 TSU boundary at 16.14 Ma, within chron C5Cn.1n. This magnetostratigraphy also allows us to analyse in detail as well as to discuss the variations in sedimentation rates through space and time between different lacustrine environments: Outer carbonate lacustrine fringes and distal alluvial plains (Montes de Castejón sections) show higher sedimentation rates than offshore lacustrine areas (San Caprasio section, 50 km east of Montes de Castejón)

    Transfinite order dimension

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    We give two different transfinite extensions of the covering dimension based on the Borst's order of certain families of boundaries of basic open sets. We compare them and we study their main properties

    Dimension, inverse limits and GF-spaces

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    In this paper we characterize (covering) dimension in metrizable spaces in terms of fractal structures. We will also study dimension for compact metric spaces, giving a theorem relating dimension and a certain class of inverse limits, similar to that of Freudenthal

    Metastable anisotropy orientation of nematic quantum Hall fluids

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    We analyze the experimental observation of metastable anisotropy resistance orientation at half filled quantum Hall fluids by means of a model of a quantum nematic liquid in an explicit symmetry breaking potential. We interpret the observed ``rotation'' of the anisotropy axis as a process of nucleation of nematic domains and compute the nucleation rate within this model. By comparing with experiment, we are able to predict the critical radius of nematic bubbles, Rc2.6μmR_c\sim 2.6 \mu m . Each domain contains about 10410^4 electrons.Comment: 10 pages, 8 figures, final version as will appear in PR

    Are bullying behaviors tolerated in some cultures? Evidence for a curvilinear relationship between workplace bullying and job satisfaction among Italian workers

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    Since the early 1990s, increasing attention has been paid to the impact of workplace bullying on employees’ well-being and job attitudes. However, the relationship between workplace bullying and job satisfaction remains unclear. This study aims to shed light on the nature of the bullying-job satisfaction relationship in the Italian context (n = 1,393 employees from different organizations). As expected, the results revealed a U-shape curvilinear relationship between workplace bullying and job satisfaction after controlling for demographic variables. In contrast to the curvilinear model, the results support a negative linear relationship between workplace bullying and psychological well-being, in which higher exposure to negative acts at work is associated with diminished well-being. In addition, gender and job position significantly predicted mental health scores where men and managers reported a better psychological well-being than women, blue-collar, and white-collar employees. Practical and theoretical implications are discussed according to these results.info:eu-repo/semantics/acceptedVersio

    Magnetite: Raman study of the high-pressure and low-temperature effects

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    We report the results of a low-temperature (300K-15K) high-pressure (up to 22GPa) Raman study of the Verwey transition in magnetite (Fe3O4). We use additional Raman modes observed below the Verwey transition to determine how the transition temperature changes with the quasihydrostatic pressure. Increase of the pressure results in the linear decrease of the Verwey transition temperature, with no discontinuity. The corresponding pressure coefficient dTV/dP is found to be ~ -5.2 K/GPa. Such a decrease is substantially larger than the one predicted by the mean-field Coulomb interaction model of the transition

    Sedimentology and depositional architecture of tufas deposited in stepped fluvial systems of changing slope: Lessons from the quaternary añamaza valley (Iberian Range, Spain)

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    The Pleistocene and Holocene tufas of the Añamaza valley (stepped build-ups, up to 70 m thick, along the valley) consist of several depositional stages separated by erosional surfaces. Eight associations of tufa and related carbonate facies, plus minor polygenic detrital facies, represent the processes that occurred in different fluvial and related environments. The bedrock lithology and structure controlled the location of the knickpoints along the valley and allowed separation of two stepped stretches with distinct conceptual facies models. The moderate-slope model includes extensive standing-water areas dammed by barrage-cascades. In the lakes, bioclastic silts, sands and limestones along with phytoclastic and marly, at places peaty, sediments formed. Abundant stem phytoherms account for extensive palustrine areas. The high-slope model consists of smaller dammed areas between close-up cascades and barrage-cascades, which were composed primarily of moss phytoherms and phytoclastic tufas. An outstanding feature is the extensive steep reach with phytoclastic and polygenic detrital sediments, and stepped cascades consisting of stromatolitic and moss phytoherms. There, the steep slope limited the preservation of stem phytoherms and favoured erosion. The geometry and thickness of the sedimentary fill (wedge-shaped units composed of cascade and barrage-cascade deposits downstream, and dammed and gentle-sloped channel deposits upstream) are therefore different for each model. Multi-storey wedges are a distinctive feature of the high-slope model. The initial knickpoint geometry and the tufa aggradation/progradation ratio on such steep surfaces (for example, related to changes in discharge) controlled the growth style of the cascades or barrage-cascades and, hence, the extent, thickness and vertical evolution of the upstream deposits. The sedimentological attributes and stable-isotope composition of the carbonate facies suggest a higher and more variable precipitation/evaporation ratio during the Pleistocene than during the Holocene, consistent with an overall decrease in the river discharge. This evolution was coupled with warm conditions, which prevailed during the stages of tufa formation. These results may help to assess architectural patterns in interpreting other basins, and underscore the significance of tufas as records of past hydrology and climate
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