Sedimentpetrographische Untersuchungen der Calvörde- Formation (Unterer Buntsandstein, Untertrias)

Die gemischt siliziklastischen Kalke des 3. und 4. Kleinzyklus der Calvörde-Formation, Unterer Buntsandstein, werden im Aufschluss (Südbahneinschnitt Thale) und in der Bohrung (Remlingen 5) sedimentpetrographisch analysiert und verglichen. In den überwiegend Ton- und Siltsteinen sind feinsandige Bänke und oolithische Lagen zwischengeschaltet. Die oolithischen Lagen werden drei Lithofazies-Typen zugeordnet: (1) oolithischer Kalkstein (quarzführende Wacke- bis Grainstones), (2) oolithischer Sandstein (quarz- und ooidreiche Sandsteine) und (3) karbonatischer Sandstein (Ooidgehalte < 10 %). Alle drei oolithischen Lithofazies sind durch wechselnde Anteile von radial-konzentrischen, radialstrahligen und mikritischen Ooiden gekennzeichnet. Die detaillierte petrographische Beschreibung erfolgt an 25 Dünnschliffen und zahlreichen polierten Handstücken, ergänzt durch μ-XRF-Daten ausgewählter oolithischer Kalksteine. Die vertikalen Lithofazies-Abfolgen belegen zyklische base level-Schwankungen, die mit Änderungen des relativen Seespiegelstandes im astrochronologischen Kontext diskutiert werden. Die oolithischen Lagen werden mit hohen Seespiegelständen assoziiert, währenddie Ton- und Siltsteine mit eingeschalteten Sandsteinlagen niedrige Seespiegelstände mit distalen fluviatilen Einschwemmungen widerspiegeln. Die untersuchten Profile lagen am Rande eines flachen, endorheischen Playa-Sees im Mitteleuropäischen Becken, geprägt durch hochenergetische Sandbänke (Ooid-Barren) bzw. spill-over lobes (Verteilungsloben). Die strukturellen Merkmale der Ooide der Calvörde-Formation lassen sich gut mit rezenten Ooiden des hypersalinen Great Salt Lake (Utah, USA) vergleichen.A petrographic study is carried out on mixed siliciclastic carbonates of cycles 3 and 4 of the Calvörde Formation (Lower Buntsandstein subgroup) of two sections: outcrop Thale (railway cut) and core Remlingen 5, both in Central Germany (approx. 50 km lateral distance). They are mainly composed of clay- and siltstones with intercalated oolitic beds and fine-grained sandstone beds. The oolitic beds are subdivided into three lithofacies types, namely (1) oolitic limestone (quartz-bearing wacke- or grainstones), (2) oolitic sandstone (ooid-bearing sandstones) and (3) carbonatic sandstone (ooid content <10 %). All three oolitic lithofacies show variable contents of ooids with radial-concentric, radial and micritic fabrics. 25 thin sections and additional polished rock samples are studied by optical microscopy. μ-XRF analysis is carried out on selected oolitic limestones to further characterize the mineralogy. Vertical cyclic changes of the lithofacies indicate base-level fluctuations that are discussed with changes of the lake level and in context with astrochronologic cycles. Oolitic beds are associated with high lake levels, while clay- and siltstones with sandstone streaks indicate low lake levels. Our results indicate nearshore deposition in a shallow, endorheic playa lake, situated within the Central European Basin. Oolitic limestones accumulated in distinct high-energy ooid shoals, while oolitic sandstones and carbonatic sandstones are interpreted as storm-induced, reworked spill-over deposits. Fossil ooids of the oolitic limestones share many structural features with modern ooids of the hypersaline Great Salt Lake (Utah, USA)

The Digital Bee Brain: Integrating and Managing Neurons in a Common 3D Reference System

The honeybee standard brain (HSB) serves as an interactive tool for relating morphologies of bee brain neurons and provides a reference system for functional and bibliographical properties (http://www.neurobiologie.fu-berlin.de/beebrain/). The ultimate goal is to document not only the morphological network properties of neurons collected from separate brains, but also to establish a graphical user interface for a neuron-related data base. Here, we review the current methods and protocols used to incorporate neuronal reconstructions into the HSB. Our registration protocol consists of two separate steps applied to imaging data from two-channel confocal microscopy scans: (1) The reconstruction of the neuron, facilitated by an automatic extraction of the neuron's skeleton based on threshold segmentation, and (2) the semi-automatic 3D segmentation of the neuropils and their registration with the HSB. The integration of neurons in the HSB is performed by applying the transformation computed in step (2) to the reconstructed neurons of step (1). The most critical issue of this protocol in terms of user interaction time – the segmentation process – is drastically improved by the use of a model-based segmentation process. Furthermore, the underlying statistical shape models (SSM) allow the visualization and analysis of characteristic variations in large sets of bee brain data. The anatomy of neural networks composed of multiple neurons that are registered into the HSB are visualized by depicting the 3D reconstructions together with semantic information with the objective to integrate data from multiple sources (electrophysiology, imaging, immunocytochemistry, molecular biology). Ultimately, this will allow the user to specify cell types and retrieve their morphologies along with physiological characterizations

Fermi Large Area Telescope Constraints on the Gamma-ray Opacity of the Universe

The Extragalactic Background Light (EBL) includes photons with wavelengths from ultraviolet to infrared, which are effective at attenuating gamma rays with energy above ~10 GeV during propagation from sources at cosmological distances. This results in a redshift- and energy-dependent attenuation of the gamma-ray flux of extragalactic sources such as blazars and Gamma-Ray Bursts (GRBs). The Large Area Telescope onboard Fermi detects a sample of gamma-ray blazars with redshift up to z~3, and GRBs with redshift up to z~4.3. Using photons above 10 GeV collected by Fermi over more than one year of observations for these sources, we investigate the effect of gamma-ray flux attenuation by the EBL. We place upper limits on the gamma-ray opacity of the Universe at various energies and redshifts, and compare this with predictions from well-known EBL models. We find that an EBL intensity in the optical-ultraviolet wavelengths as great as predicted by the "baseline" model of Stecker et al. (2006) can be ruled out with high confidence.Comment: 42 pages, 12 figures, accepted version (24 Aug.2010) for publication in ApJ; Contact authors: A. Bouvier, A. Chen, S. Raino, S. Razzaque, A. Reimer, L.C. Reye

Microfacies studies of carbonate rocks from Jurassic outcrops in the north of Faro, Southern Portugal

The Middle and Upper Jurassique limestones investigated were sub-divided into nine microfacies (MF) types. The firsts four represent Bathonian sediments with shallow water characteristics typical for carbonate platforms. They are comparable with Wilson's facies zones 6 to 8. Reef and reef debris, near-shore clastic-dominated limestones are not present. These MF-types are reiterated several times without cyclicity. The vertical development of the differentiated facies units indicates a close interfingering. The microfacies data are typical of inter to shallow subtidal environments; both authigenous quartz and low faunal and floral diversity of several layers point to temporary restricted conditions. The occurrence of Dictyoconus cayeuxi LUCAS and Callovian ammonites from the above lying strata argue for a Bathonian age. The MF-types 5-9 (Oxfordian-Kimmeridgian) show completely different sedimentation conditions. Fully marine nearshore recifal limestones alternate with pelagic sediments formed at deeper shelf areas. The pelagic micritic limestones of Oxfordian age are characterized by allodapic intercalations whereas the Oxfordian/Kimmeridgian limestones with tuberolithic fabrics often show intensive silifications. Only initial patch reef growth-stages were reached during the development of the Oxfordian and Kimmeridgian shallow water limestones