2,579 research outputs found

    Analytical assessment of mine water rebound. Case study Ruhr coal basin

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    This study aims to assess key factors that influence mine water rebound on the example of a large amount of hard coal mines flooded or being flooded in Europe. Three German mines have been selected for a detailed study. A mathematical model based on analytical formulae of seepage theory has been employed to calculate time-dependent radial inflow to the shaft simulated as a big well in vertically heterogeneous rocks. The results of modelling showed good conformity with measurements for all studied mines. Besides, we evaluated the sensitivity of the model output to parameter variations for mine water level and initial inflow to the mine

    Mechanical effect of van der Waals interactions observed in real time in an ultracold Rydberg gas

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    We present time-resolved spectroscopic measurements of Rydberg-Rydberg interactions in an ultracold gas, revealing the pair dynamics induced by long-range van der Waals interactions between the atoms. By detuning the excitation laser, a specific pair distribution is prepared. Penning ionization on a microsecond timescale serves as a probe for the pair dynamics under the influence of the attractive long-range forces. Comparison with a Monte Carlo model not only explains all spectroscopic features but also gives quantitative information about the interaction potentials. The results imply that the interaction-induced ionization rate can be influenced by the excitation laser. Surprisingly, interaction-induced ionization is also observed for Rydberg states with purely repulsive interactions

    Precis of neuroconstructivism: how the brain constructs cognition

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    Neuroconstructivism: How the Brain Constructs Cognition proposes a unifying framework for the study of cognitive development that brings together (1) constructivism (which views development as the progressive elaboration of increasingly complex structures), (2) cognitive neuroscience (which aims to understand the neural mechanisms underlying behavior), and (3) computational modeling (which proposes formal and explicit specifications of information processing). The guiding principle of our approach is context dependence, within and (in contrast to Marr [1982]) between levels of organization. We propose that three mechanisms guide the emergence of representations: competition, cooperation, and chronotopy; which themselves allow for two central processes: proactivity and progressive specialization. We suggest that the main outcome of development is partial representations, distributed across distinct functional circuits. This framework is derived by examining development at the level of single neurons, brain systems, and whole organisms. We use the terms encellment, embrainment, and embodiment to describe the higher-level contextual influences that act at each of these levels of organization. To illustrate these mechanisms in operation we provide case studies in early visual perception, infant habituation, phonological development, and object representations in infancy. Three further case studies are concerned with interactions between levels of explanation: social development, atypical development and within that, developmental dyslexia. We conclude that cognitive development arises from a dynamic, contextual change in embodied neural structures leading to partial representations across multiple brain regions and timescales, in response to proactively specified physical and social environment

    3D ultrastructural organization of whole Chlamydomonas reinhardtii cells studied by nanoscale soft x-ray tomography

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    The complex architecture of their structural elements and compartments is a hallmark of eukaryotic cells. The creation of high resolution models of whole cells has been limited by the relatively low resolution of conventional light microscopes and the requirement for ultrathin sections in transmission electron microscopy. We used soft x-ray tomography to study the 3D ultrastructural organization of whole cells of the unicellular green alga Chlamydomonas reinhardtii at unprecedented spatial resolution. Intact frozen hydrated cells were imaged using the natural x-ray absorption contrast of the sample without any staining. We applied different fiducial-based and fiducial-less alignment procedures for the 3D reconstructions. The reconstructed 3D volumes of the cells show features down to 30 nm in size. The whole cell tomograms reveal ultrastructural details such as nuclear envelope membranes, thylakoids, basal apparatus, and flagellar microtubule doublets. In addition, the x-ray tomograms provide quantitative data from the cell architecture. Therefore, nanoscale soft x-ray tomography is a new valuable tool for numerous qualitative and quantitative applications in plant cell biology

    Natural Selection and Morphological Variability: The Case of Europe From Neolithic to Modern Times [Comment]

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    https://www.journals.uchicago.edu/doi/abs/10.1086/20200

    Biostratigraphy of the upper Bajocian-middle Callovian (Middle Jurassic), South America

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    The biostratigraphic division of the upper Bajocian-middle Callovian of South America is based on ammonites from different sections of the following provinces and regions: Neuquén, Mendoza, and San Juan in Argentina; Malleco, Linares, Talca, Atacama, Antofagasta, and Tarapacá in Chile. The complete upper Bajocian-middle Callovian succession includes the following biostratigraphic units: the Megasphaeroceras magnum assemblage zone, lowermost upper Bajocian; the Cadomites-Tulitidae mixed assemblage, (?lower) middle and upper Bathonian; the Steinmanni zone, index Lilloettia steinmanni (Spath), uppermost Bathonian, with two local horizons — Stehnocephalites gerthi horizon (Argentina) and Choffatia jupiter horizon (northern Chile); the Vergarensis zone, index Eur y cep halites vergarensis (Burck.), near the Bathonian-Callovian boundary; the Bodenbenderi zone, index Neuquenicerás (Frickites) bodenbenderi (Tornq.), lower Callovian; the Proximum zone, index Hecticoceras proximum Elmi, uppermost lower Callovian; and the Rehmannia (Loczyceras) patagoniensis horizon, middle Callovian.La división bioestratigráfica del Bajociano superior-Caloviano inferior de América del Sur esté basada en la fauna de amonites proveniente de diferentes secciones de las provincias/regiones de Neuquén, Mendoza, San Juan (Argentina), Malleco, Linares, Talca, Atacama, Antofagasta, y Tarapacá (Chile). La sucesión del Bajociano superior-Caloviano medio incluye las siguientes unidades bioestratigráfícas: zona de asociación de Megasphaeroceras magnum, Bajociano superior bajo; asociación de mezcla de Cadomites- Tulitidae, Bathoniano (?inferior) medio y superior; zona de Steinmanni, fósil guía Lilloettia steinmanni (Spath), Bathoniano superior alto, con dos horizontes locales — horizonte con Stehnocephalites gerthi (Argentina) y horizonte con Choffatia jupiter (norte de Chile); zona de Vergarensis, fósil guía Eurycephalites vergarensis (Burck.), aproximadamente límite Bathoniano-Caloviano; zona de Bodenbenderi, fósil guía Neuquenicerás (Frickites) bodenbenderi (Tornq.), Caloviano inferior; zona de Proximum, fósil guía Hecticoceras proximum Elmi, Caloviano inferior alto; horizonte con Rehmannia (Loczyceras) patagoniensis, Caloviano medio.Facultad de Ciencias Naturales y Muse

    Biostratigraphy of the upper Bajocian-middle Callovian (Middle Jurassic), South America

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    The biostratigraphic division of the upper Bajocian-middle Callovian of South America is based on ammonites from different sections of the following provinces and regions: Neuquén, Mendoza, and San Juan in Argentina; Malleco, Linares, Talca, Atacama, Antofagasta, and Tarapacá in Chile. The complete upper Bajocian-middle Callovian succession includes the following biostratigraphic units: the Megasphaeroceras magnum assemblage zone, lowermost upper Bajocian; the Cadomites-Tulitidae mixed assemblage, (?lower) middle and upper Bathonian; the Steinmanni zone, index Lilloettia steinmanni (Spath), uppermost Bathonian, with two local horizons — Stehnocephalites gerthi horizon (Argentina) and Choffatia jupiter horizon (northern Chile); the Vergarensis zone, index Eur y cep halites vergarensis (Burck.), near the Bathonian-Callovian boundary; the Bodenbenderi zone, index Neuquenicerás (Frickites) bodenbenderi (Tornq.), lower Callovian; the Proximum zone, index Hecticoceras proximum Elmi, uppermost lower Callovian; and the Rehmannia (Loczyceras) patagoniensis horizon, middle Callovian.La división bioestratigráfica del Bajociano superior-Caloviano inferior de América del Sur esté basada en la fauna de amonites proveniente de diferentes secciones de las provincias/regiones de Neuquén, Mendoza, San Juan (Argentina), Malleco, Linares, Talca, Atacama, Antofagasta, y Tarapacá (Chile). La sucesión del Bajociano superior-Caloviano medio incluye las siguientes unidades bioestratigráfícas: zona de asociación de Megasphaeroceras magnum, Bajociano superior bajo; asociación de mezcla de Cadomites- Tulitidae, Bathoniano (?inferior) medio y superior; zona de Steinmanni, fósil guía Lilloettia steinmanni (Spath), Bathoniano superior alto, con dos horizontes locales — horizonte con Stehnocephalites gerthi (Argentina) y horizonte con Choffatia jupiter (norte de Chile); zona de Vergarensis, fósil guía Eurycephalites vergarensis (Burck.), aproximadamente límite Bathoniano-Caloviano; zona de Bodenbenderi, fósil guía Neuquenicerás (Frickites) bodenbenderi (Tornq.), Caloviano inferior; zona de Proximum, fósil guía Hecticoceras proximum Elmi, Caloviano inferior alto; horizonte con Rehmannia (Loczyceras) patagoniensis, Caloviano medio.Facultad de Ciencias Naturales y Muse

    Biostratigraphy of the upper Bajocian-middle Callovian (Middle Jurassic), South America

    Get PDF
    The biostratigraphic division of the upper Bajocian-middle Callovian of South America is based on ammonites from different sections of the following provinces and regions: Neuquén, Mendoza, and San Juan in Argentina; Malleco, Linares, Talca, Atacama, Antofagasta, and Tarapacá in Chile. The complete upper Bajocian-middle Callovian succession includes the following biostratigraphic units: the Megasphaeroceras magnum assemblage zone, lowermost upper Bajocian; the Cadomites-Tulitidae mixed assemblage, (?lower) middle and upper Bathonian; the Steinmanni zone, index Lilloettia steinmanni (Spath), uppermost Bathonian, with two local horizons — Stehnocephalites gerthi horizon (Argentina) and Choffatia jupiter horizon (northern Chile); the Vergarensis zone, index Eur y cep halites vergarensis (Burck.), near the Bathonian-Callovian boundary; the Bodenbenderi zone, index Neuquenicerás (Frickites) bodenbenderi (Tornq.), lower Callovian; the Proximum zone, index Hecticoceras proximum Elmi, uppermost lower Callovian; and the Rehmannia (Loczyceras) patagoniensis horizon, middle Callovian.La división bioestratigráfica del Bajociano superior-Caloviano inferior de América del Sur esté basada en la fauna de amonites proveniente de diferentes secciones de las provincias/regiones de Neuquén, Mendoza, San Juan (Argentina), Malleco, Linares, Talca, Atacama, Antofagasta, y Tarapacá (Chile). La sucesión del Bajociano superior-Caloviano medio incluye las siguientes unidades bioestratigráfícas: zona de asociación de Megasphaeroceras magnum, Bajociano superior bajo; asociación de mezcla de Cadomites- Tulitidae, Bathoniano (?inferior) medio y superior; zona de Steinmanni, fósil guía Lilloettia steinmanni (Spath), Bathoniano superior alto, con dos horizontes locales — horizonte con Stehnocephalites gerthi (Argentina) y horizonte con Choffatia jupiter (norte de Chile); zona de Vergarensis, fósil guía Eurycephalites vergarensis (Burck.), aproximadamente límite Bathoniano-Caloviano; zona de Bodenbenderi, fósil guía Neuquenicerás (Frickites) bodenbenderi (Tornq.), Caloviano inferior; zona de Proximum, fósil guía Hecticoceras proximum Elmi, Caloviano inferior alto; horizonte con Rehmannia (Loczyceras) patagoniensis, Caloviano medio.Facultad de Ciencias Naturales y Muse
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