100 research outputs found

    Likelihood-free inference of experimental Neutrino Oscillations using Neural Spline Flows

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    In machine learning, likelihood-free inference refers to the task of performing an analysis driven by data instead of an analytical expression. We discuss the application of Neural Spline Flows, a neural density estimation algorithm, to the likelihood-free inference problem of the measurement of neutrino oscillation parameters in Long Baseline neutrino experiments. A method adapted to physics parameter inference is developed and applied to the case of the disappearance muon neutrino analysis at the T2K experiment.Comment: 10 pages, 3 figure

    Junction formation by Zn(O,S) sputtering yields CIGSe-based cells with efficiencies exceeding 18%

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    In an effort to reduce the complexity and associated production costs of Cu(In,Ga)Se2 (CIGSe)-based solar cells, the commonly used sputtered undoped ZnO layer has been modified to eliminate the requirement for a dedicated buffer layer. After replacing the ZnO target with a mixed ZnO/ZnS target, efficient solar cells could be prepared by sputtering directly onto the as- grown CIGSe surface. This approach has now been tested with high-quality lab- scale glass/Mo/CIGSe substrates. An efficiency of 18.3% has been independently confirmed without any post-deposition annealing or light soaking

    Auswirkung differenzierter mechanischer Bodenbelastungen auf die Erträge von Erbse, Hafer und Erbse-Hafer-Gemenge

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    Die nachhaltige Erhaltung und Steigerung der Bodenfruchtbarkeit ist für ökologisch wirtschaftende Betriebe von höchster Bedeutung. Im Ökologischen Landbau hängt das Niveau der Bodenfruchtbarkeit – abgesehen von den kaum zu beeinflussenden standörtlichen Gegebenheiten – sehr von der Leistungsfähigkeit der Leguminosen ab. Vor allem durch ihre Fähigkeit, Luftstickstoff zu binden und diesen für ihr eigenes Wachstum sowie für die Folgekulturen verfügbar zu machen, bilden Leguminosen die Grundlage der Bodenfruchtbarkeit im Ökologischen Landbau. In der Konsequenz bedeutet dies, dass Beeinträchtigungen der Leistungsfähigkeit der Leguminosen nicht nur deren eigenen Ertrag sondern auch die Leistungsfähigkeit der gesamten Fruchtfolge am Standort begrenzen. Speziell für vieharme oder viehlose Öko-Betriebe könnte es gewinnbringend sein, großkörnige Leguminosen (Erbse, Ackerbohne) ergänzend zu Kleegras zur Erhaltung der Bodenfruchtbarkeit in die Fruchtfolge zu integrieren. Andererseits reagieren aber gerade Körnerleguminosen besonders empfindlich auf Beeinträchtigungen, sei es durch geringe Verfügbarkeit von Nährstoffen wie Phosphor und Kali, durch das Vorhandensein von boden- oder samenbürtigen Pathogenen oder durch Verdichtungen im Wurzelraum. Die Bodenbearbeitung im Öko-Anbau ist vergleichsweise intensiv, und das Risiko für Bodenverdichtungen daher hoch. Ziel ist es, Aussagen über den Einfluss von Bodenverdichtungen auf den Ertrag von Erbsen machen zu können. Zusätzlich soll geklärt werden, welchen Einfluss mechanische Bodenbeanspruchung auf die Bestandsentwicklung, das Auftreten von Wurzel- und Sprosskrankheiten und den Schädlingsbefall von Erbsen, Erbsen-Hafer-Gemenge und Hafer hat. Dazu wurden an vier Standorten in Deutschland im Rahmen eines von der Bundesanstalt für Landwirtschaft und Ernährung geförderten Verbundprojektes „Belastungsversuche“ angelegt

    Reliable wet-chemical cleaning of natively oxidized high-efficiency Cu(In,Ga)Se2 thin-film solar cell absorbers

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    Currently, Cu-containing chalcopyrite-based solar cells provide the highest conversion efficiencies among all thin-film photovoltaic (PV) technologies. They have reached efficiency values above 20%, the same performance level as multi-crystalline silicon-wafer technology that dominates the commercial PV market. Chalcopyrite thin-film heterostructures consist of a layer stack with a variety of interfaces between different materials. It is the chalcopyrite/buffer region (forming the p-n junction), which is of crucial importance and therefore frequently investigated using surface and interface science tools, such as photoelectron spectroscopy and scanning probe microscopy. To ensure comparability and validity of the results, a general preparation guide for “realistic” surfaces of polycrystalline chalcopyrite thin films is highly desirable. We present results on wet-chemical cleaning procedures of polycrystalline Cu(In1-xGax)Se2 thin films with an average x = [Ga]/([In] + [Ga]) = 0.29, which were exposed to ambient conditions for different times. The hence natively oxidized sample surfaces were etched in KCN- or NH3-based aqueous solutions. By x-ray photoelectron spectroscopy, we find that the KCN treatment results in a chemical surface structure which is – apart from a slight change in surface composition – identical to a pristine as-received sample surface. Additionally, we discover a different oxidation behavior of In and Ga, in agreement with thermodynamic reference data, and we find indications for the segregation and removal of copper selenide surface phases from the polycrystalline material

    The first synapse in vision in the aging mouse retina

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    Vision is our primary sense, and maintaining it throughout our lifespan is crucial for our well-being. However, the retina, which initiates vision, suffers from an age-related, irreversible functional decline. What causes this functional decline, and how it might be treated, is still unclear. Synapses are the functional hub for signal transmission between neurons, and studies have shown that aging is widely associated with synaptic dysfunction. In this study, we examined the first synapse of the visual system – the rod and cone photoreceptor ribbon synapse – in the mouse retina using light and electron microscopy at 2–3 months, ~1 year, and >2 years of age. We asked, whether age-related changes in key synaptic components might be a driver of synaptic dysfunction and ultimately age-related functional decline during normal aging. We found sprouting of horizontal and bipolar cells, formation of ectopic photoreceptor ribbon synapses, and a decrease in the number of rod photoreceptors and photoreceptor ribbon synapses in the aged retina. However, the majority of the photoreceptors did not show obvious changes in the structural components and protein composition of their ribbon synapses. Noteworthy is the increase in mitochondrial size in rod photoreceptor terminals in the aged retina

    Graph neural network for 3D classification of ambiguities and optical crosstalk in scintillator-based neutrino detectors

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    Deep learning tools are being used extensively in high energy physics and are becoming central in the reconstruction of neutrino interactions in particle detectors. In this work, we report on the performance of a graph neural network in assisting with particle flow event reconstruction. The three-dimensional reconstruction of particle tracks produced in neutrino interactions can be subject to ambiguities due to high multiplicity signatures in the detector or leakage of signal between neighboring active detector volumes. Graph neural networks potentially have the capability of identifying all these features to boost the reconstruction performance. As an example case study, we tested a graph neural network, inspired by the GraphSAGE algorithm, on a novel 3D-granular plastic-scintillator detector, that will be used to upgrade the near detector of the T2K experiment. The developed neural network has been trained and tested on diverse neutrino interaction samples, showing very promising results: the classification of particle track voxels produced in the detector can be done with efficiencies and purities of 94-96% per event and most of the ambiguities can be identified and rejected, while being robust against systematic effects

    Bathymetric Mapping Of The Seafloor - A German Contribution To Completing The Map By 2030, Cruise No. MSM88/1 + MSM88/2, November 28, 2019 - January 14, 2020, Mindelo (Cabo Verde) - Mindelo (Cabo Verde) - Bridgetown (Barbados)

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    Despite over 100 years of acoustic seabed mapping, only around 15% of the seafloor has ever been directly mapped and little of the mapping performed has been systematic or over larger areas. The result is that our knowledge of seafloor structure is rudimentary and our understanding of the processes which form them has, in principle, advanced little since the advent of plate tectonics. Societally, the seafloor plays a vital role in humanity’s "life support system", for example providing habitat for marine organisms, stimulating mixing of ocean water as part of the overturning circulation system and increasingly being the site of industrial installations. It is scientifically and societally imperative that we bring the level of knowledge of the surface of our planet up to that of bodies like Moon and Mars that are mapped with a resolution better than 100 m per pixel. It is also essential that the data are made freely available to all to support research and conservation. The aim of this cruise was to map previously uncharted part of the tropical Atlantic using the ship’s multibeam system and to provide the data to global open databases as well as to acquire magnetic gradient data along the same tracks. Magnetic anomalies from so-called Oceanic Core Complexes challenged the conventional view that marine magnetic anomalies arose in the upper, extrusive layer of the oceanic crust, because the crust has been stripped away at these complexes. We therefore collected magnetic data simultaneously to the multibeam data in order to constrain the interpretation of the observed seabed morphology