23 research outputs found

    Constructive approach to limiting periodic orbits with exponential and power law dynamics

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    In dynamical systems limit cycles arise as a result of a Hopf bifurcation, after a control parameter has crossed its critical value. In this study we present a constructive method to produce dissipative dynamics which lead to stable periodic orbits as time grows, with predesigned transient dynamics. Depending on the construction method a) the limiting orbit can be a regular circle, an ellipse or a more complex closed orbit and b) the approach to the limiting orbit can follow an exponential law or a power law. This technique allows to design nonlinear models of dynamical systems with desired (exponential or power law) relaxation properties.Comment: 17 pages, 6 figure

    KoKoN – Ein Expertenwalkthrough zu digitalen Lehr-Kooperationen im Kontext der Nationalen Bildungsplattform

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    ... Für die erfolgreiche Umsetzung digitalgestützter Lehre nehmen sowohl hochschulinterne als auch -übergreifende Kooperationen einen immer höheren ... Stellenwert ein. Die damit einhergehende Vernetzung und das Zusammenwirken verschiedener Bildungsanbieter bilden die Grundlage des lebenslangen Lernens sowie der bildungsbereichübergreifenden Gestaltung von individuellen Bildungsbiografien (vgl. Schleifenbaum, & Walther, 2015). Die Anbahnung und Durchführung von insbesondere digitalen Lehr-Kooperationen erfordern über reine IT-Kenntnisse hinausgehende Kompetenzen seitens der Lehrenden. Für gelingende Kooperationsprozesse zwischen Lehrenden sind daher weitere Facetten digitaler Kompetenz erforderlich, wie bspw. bzgl. der Durchführung von Kommunikationsund Kooperationsprozessen im digitalen Raum, des Aufbaus einer eigenen digitalen Lehr- und Forscher:innen-Identität sowie der Reflexion des eigenen digitalen Lehr-Handelns (Eichhorn, Müller, & Tillmann, 2017; Eichhorn, 2020). [Aus: Herausforderungen für die digitalgestützte Hochschullehre

    Entwicklung und Evaluation digitaler Lernspiele: Wissenschaftliche Befunde jenseits des Entertainment

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    Ziel des Beitrages ist es, eigene wissenschaftliche Befunde aus vier Jahren Forschung zur Konzeption, Entwicklung und Evaluation digitaler Lernspiele1 für die betriebliche Aus- und Weiterbildung im sozialen Dienstleistungssektor vorzustellen. Die Darstellung der Ergebnisse erfolgt anhand von zwei aktuellen Projekten am Medienzentrum der Technischen Universität Dresden. In beiden Projekten wurden bzw. werden Serious Games für Führungskräfte im sozialen Dienstleistungssektor entwickelt, in welchen der Ansatz des spielerischen Lernens (vgl. Mangold, 2004) zur Vermittlung gesundheitsbezogener Themen herangezogen wird. Methodisch werden die Befunde entlang der Prozessschritte des Learning Experience Design (LXD) (vgl. Ahn, 2018) präsentiert

    Entwicklung und Evaluation digitaler Lernspiele: Wissenschaftliche Befunde jenseits des Entertainment

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    Ziel des Beitrages ist es, eigene wissenschaftliche Befunde aus vier Jahren Forschung zur Konzeption, Entwicklung und Evaluation digitaler Lernspiele1 für die betriebliche Aus- und Weiterbildung im sozialen Dienstleistungssektor vorzustellen. Die Darstellung der Ergebnisse erfolgt anhand von zwei aktuellen Projekten am Medienzentrum der Technischen Universität Dresden. In beiden Projekten wurden bzw. werden Serious Games für Führungskräfte im sozialen Dienstleistungssektor entwickelt, in welchen der Ansatz des spielerischen Lernens (vgl. Mangold, 2004) zur Vermittlung gesundheitsbezogener Themen herangezogen wird. Methodisch werden die Befunde entlang der Prozessschritte des Learning Experience Design (LXD) (vgl. Ahn, 2018) präsentiert

    Microbial rock inhabitants survive hypervelocity impacts on Mars-like host planets: first phase of lithopanspermia experimentally tested

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    The scenario of lithopanspermia describes the viable transport of microorganisms via meteorites. To test the first step of lithopanspermia, i.e., the impact ejection from a planet, systematic shock recovery experiments within a pressure range observed in martian meteorites (5–50 GPa) were performed with dry layers of microorganisms (spores of Bacillus subtilis, cells of the endolithic cyanobacterium Chroococcidiopsis, and thalli and ascocarps of the lichen Xanthoria elegans) sandwiched between gabbro discs (martian analogue rock). Actual shock pressures were determined by refractive index measurements and Raman spectroscopy, and shock temperature profiles were calculated. Pressure-effect curves were constructed for survival of B. subtilis spores and Chroococcidiopsis cells from the number of colony-forming units, and for vitality of the photobiont and mycobiont of Xanthoria elegans from confocal laser scanning microscopy after live/dead staining (FUN-I). A vital launch window for the transport of rock-colonizing microorganisms from a Mars-like planet was inferred, which encompasses shock pressures in the range of 5 to about 40 GPa for the bacterial endospores and the lichens, and a more limited shock pressure range for the cyanobacterium (from 5–10 GPa). The results support concepts of viable impact ejections from Mars-like planets and the possibility of reseeding early Earth after asteroid cataclysms

    Magnetic Nanoparticle Based Nonviral MicroRNA Delivery into Freshly Isolated CD105 +

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    Genetic modifications of bone marrow derived human mesenchymal stem cells (hMSCs) using microRNAs (miRs) may be used to improve their therapeutic potential and enable innovative strategies in tissue regeneration. However, most of the studies use cultured hMSCs, although these can lose their stem cell characteristics during expansion. Therefore, we aimed to develop a nonviral miR carrier based on polyethylenimine (PEI) bound to magnetic nanoparticles (MNPs) for efficient miR delivery in freshly isolated hMSCs. MNP based transfection is preferable for genetic modifications in vivo due to improved selectivity, safety of delivery, and reduced side effects. Thus, in this study different miR/PEI and miR/PEI/MNP complex formulations were tested in vitro for uptake efficiency and cytotoxicity with respect to the influence of an external magnetic field. Afterwards, optimized magnetic complexes were selected and compared to commercially available magnetic vectors (Magnetofectamine, CombiMag). We found that all tested transfection reagents had high miR uptake rates (yielded over 60%) and no significant cytotoxic effects. Our work may become crucial for virus-free introduction of therapeutic miRs as well as other nucleic acids in vivo. Moreover, in the field of targeted stem cell therapy nucleic acid delivery prior to transplantation may allowfor initial cell modulation in vitro

    Magnetic Nanoparticle Based Nonviral MicroRNA Delivery into Freshly Isolated CD105+ hMSCs

    No full text
    Genetic modifications of bone marrow derived human mesenchymal stem cells (hMSCs) using microRNAs (miRs) may be used to improve their therapeutic potential and enable innovative strategies in tissue regeneration. However, most of the studies use cultured hMSCs, although these can lose their stem cell characteristics during expansion. Therefore, we aimed to develop a nonviral miR carrier based on polyethylenimine (PEI) bound to magnetic nanoparticles (MNPs) for efficient miR delivery in freshly isolated hMSCs. MNP based transfection is preferable for genetic modifications in vivo due to improved selectivity, safety of delivery, and reduced side effects. Thus, in this study different miR/PEI and miR/PEI/MNP complex formulations were tested in vitro for uptake efficiency and cytotoxicity with respect to the influence of an external magnetic field. Afterwards, optimized magnetic complexes were selected and compared to commercially available magnetic vectors (Magnetofectamine, CombiMag). We found that all tested transfection reagents had high miR uptake rates (yielded over 60%) and no significant cytotoxic effects. Our work may become crucial for virus-free introduction of therapeutic miRs as well as other nucleic acids in vivo. Moreover, in the field of targeted stem cell therapy nucleic acid delivery prior to transplantation may allowfor initial cell modulation in vitro
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