Publikationen im Open Access gefördert durch die UB

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Auflistung Publikationen im Open Access gefördert durch die UB nach Auflistung nach Fachbereich/Einrichtung "FB 07 - Mathematik und Informatik, Physik, Geographie"

Gerade angezeigt 1 - 20 von 139
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    3D micro printed capillary electrospray thruster with a fully modular integrated extraction electrode
    (2024) Kunze, Fynn L.; Henning, Torsten; Klar, Peter J.
    An internally wetted capillary-type electrospray thruster design is presented. The capillary emitters are optimized for fabrication using 3D micro lithography and can achieve sub 10-micrometer capillary diameters with an aspect ratio of over 20. Also provided is a design for a completely modular integrated extraction electrode that comprises an electrode carrier produced by 3D micro lithography and a thin metal film. The electrode orifices, distance to emitters, and size are all customizable thanks to the modularity of the design, which is compatible with any electrospray thruster type. The design provides alignment precision within 5 micrometers of the emitter tip and electrode orifice. While our new electrode achieved reproducible extraction, instability is still present. The data on emission from these emitter-electrode stacks is presented, as well as in situ microscopic optical observation of individual emitters. The images demonstrate emission in multiple extraction modes, microfluidic behaviour of the capillaries in space-like conditions, and interactions of the emission modes with the integrated electrode.
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    A biologically inspired repair mechanism for neuronal reconstructions with a focus on human dendrites
    (2024) Groden, Moritz; Moessinger, Hannah M.; Schaffran, Barbara; DeFelipe, Javier; Benavides-Piccione, Ruth; Cuntz, Hermann; Jedlicka, Peter
    Investigating and modelling the functionality of human neurons remains challenging due to the technical limitations, resulting in scarce and incomplete 3D anatomical reconstructions. Here we used a morphological modelling approach based on optimal wiring to repair the parts of a dendritic morphology that were lost due to incomplete tissue samples. In Drosophila, where dendritic regrowth has been studied experimentally using laser ablation, we found that modelling the regrowth reproduced a bimodal distribution between regeneration of cut branches and invasion by neighbouring branches. Interestingly, our repair model followed growth rules similar to those for the generation of a new dendritic tree. To generalise the repair algorithm from Drosophila to mammalian neurons, we artificially sectioned reconstructed dendrites from mouse and human hippocampal pyramidal cell morphologies, and showed that the regrown dendrites were morphologically similar to the original ones. Furthermore, we were able to restore their electrophysiological functionality, as evidenced by the recovery of their firing behaviour. Importantly, we show that such repairs also apply to other neuron types including hippocampal granule cells and cerebellar Purkinje cells. We then extrapolated the repair to incomplete human CA1 pyramidal neurons, where the anatomical boundaries of the particular brain areas innervated by the neurons in question were known. Interestingly, the repair of incomplete human dendrites helped to simulate the recently observed increased synaptic thresholds for dendritic NMDA spikes in human versus mouse dendrites. To make the repair tool available to the neuroscience community, we have developed an intuitive and simple graphical user interface (GUI), which is available in the TREES toolbox (www.treestoolbox.org).
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    A Dry-Processed Al2O3/LiAlO2 Coating for Stabilizing the Cathode/Electrolyte Interface in High-Ni NCM-Based All-Solid-State Batteries
    (2022) Negi, Rajendra S.; Yusim, Yuriy; Pan, Ruijun; Ahmed, Shamail; Volz, Kerstin; Takata, Ryo; Schmidt, Franz; Henss, Anja; Elm, Matthias T.
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    A fundamental problem of hypothesis testing with finite inventory in e-commerce
    (2020) Bohle, Dennis; Marynych, Alexander; Meiners, Matthias
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    A Sensitivity Assessment of COSMO-CLM to Different Land Cover Schemes in Convection-Permitting Climate Simulations over Europe
    (2021) Zhang, Mingyue; Tölle, Merja H.; Hartmann, Eva; Xoplaki, Eleni; Luterbacher, Jürg
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    Ab initio calculations of conduction band effective mass parameters of thermoelectric Mg2X1-xYx (X, Y = Si, Ge, Sn) alloys
    (2020) Guerra-Castro, Juan Manuel; Mahr, Carsten; Giar, Marcel; Czerner, Michael; Heiliger, Christian
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    Ab initio description of disorder effects in layered cathode active materials by the coherent potential approximation
    (2022) Eckhardt, Janis K; Risius, Philipp E; Czerner, Michael; Heiliger, Christian
    Disorder effects in alloys are usually modeled by averaging various supercell calculations considering different positions of the alloy atoms. This approach, however, is only possible as long as the portion of the individual components of the alloy is sufficiently large. Herein, we present an ab initio study considering the lithium insertion material Li1−x[Ni0.33Co0.33Mn0.33]O2 as model system to demonstrate the power of the coherent potential approximation within the Korringa–Kohn–Rostoker Green's function method. This approach enables the description of disorder effects within alloy systems of any composition. It is applied in this study to describe the (de-)intercalation of arbitrary amounts of lithium from the cathode active material. Moreover, we highlight that using either fully optimized structures or experimental lattice parameters and atomic positions both lead to comparable results. Our findings suggest that this approach is also suitable for modeling the electronic structure of state-of-the-art materials such as high-nickel alloys.
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    Adsorption dynamics of bifunctional molecules: Allyl methyl ether on Si(001)
    (2021) Bohamud, Tamam; Höfer, Ulrich; Dürr, Michael
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    Advantageous optical characteristics of tantalum vanadium oxide as counter electrode in electrochromic devices
    (2022) Gies, Mario; Rempel, Thomas; Becker, Martin; Polity, Angelika
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    Analysis of the radiated emission of an ECR thruster with magnetic nozzle in terms of its EMC
    (2024) Kiefer, Felix; Keil, K.; Holste, Kristof; Klar, Peter J.; Thüringer, Rainer
    The demand for space propulsion systems is increasing due to the rising number of satellite launches. Electric thrusters gain considerable importance as highly efficient systems in space. As the thrust generation process involves electrically charged particles in motion, ion and plasma thrusters can cause electromagnetic noise, which may interfere with satellite electronics or radio communication. Our objectives are to quantify such emissions and to better understand their origin. We use two facilities to achieve this goal: a semi-anechoic chamber (SAC) with a dedicated vacuum chamber and a mode-tuned vacuum chamber, also known as a reverberation chamber (RVC). Here, we conduct measurements in both facilities on an electron-cyclotron resonance (ECR) thruster with a magnetic nozzle in order to assess its electromagnetic compatibility (EMC). This thruster emits a quasi-neutral plasma plume without requiring an additional neutralizer, thus, is especially suitable for conducting our studies. The thruster in operation acts as an electromagnetic noise source contributing to different frequency ranges. In addition to the excitation frequency band, the data reveals emissions occurring approximately one decade lower in frequency. These emissions depend on propellant mass flow, background pressure and excitation power, i.e., vary with the electron density of the plasma generated inside the ECR thruster. The thruster was characterized following primarily MIL-STD-461G and further ECSS-E-ST-20-07C.
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    Assigning the absolute configuration of single aliphatic molecules by visual inspection
    (2018) Ebeling, Daniel; ekutor, Marina; Stiefermann, Marvin; Tschakert, Jalmar; Dahl, Jeremy E. P.; Carlson, Robert M. K.; Schirmeisen, André; Schreiner, Peter R.
    Deciphering absolute configuration of a single molecule by direct visual inspection is the next step in compound identification, with far-reaching implications for medicinal chemistry, pharmacology, and natural product synthesis. We demonstrate the feasibility of this approach utilizing low temperature atomic force microscopy (AFM) with a CO-functionalized tip to determine the absolute configuration and orientation of a single, adsorbed [123]tetramantane molecule, the smallest chiral diamondoid. We differentiate between single enantiomers on Cu(111) by direct visual inspection, and furthermore identify molecular dimers and molecular clusters. The experimental results are confirmed by a computational study that allowed quantification of the corresponding intermolecular interactions. The unique toolset of absolute configuration determination combined with AFM tip manipulation opens a route for studying molecular nucleation, including chirality-driven assembly or reaction mechanisms.
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    Bond-specific fragmentation of oligopeptides via electronic stopping of swift heavy ions in molecular films
    (2022) Schneider, P.; Keller, P.; Schubert, I.; Bender, M.; Trautmann, C.; Dürr, M.
    Highly bond-specific fragmentation of oligopeptides induced by swift heavy ion (SHI) irradiation was investigated by means of mass spectrometry. In pronounced contrast to measurements of samples irradiated with keV ions, oligopeptides which were exposed to 946 MeV Au ions show a high abundance of specific fragments. The highly bond-specific nature of SHI-induced fragmentation is attributed to electronic stopping as the most relevant energy loss mechanism for SHI in the oligopeptide samples in combination with the subsequent coupling between the excited electronic and the atomic subsystem. Fragmentation induced by SHI is observed to be further influenced by the structure of the oligopeptides, suggesting that electronic excitation and/or the electronic-vibrational coupling depend on the details of the molecular structure.
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    Characterization of Vegard strain related to exceptionally fast Cu-chemical diffusion in Cu2Mo6S8 by an advanced electrochemical strain microscopy method
    (2021) Badur, Sebastian; Renz, Diemo; Cronau, Marvin; Göddenhenrich, Thomas; Dietzel, Dirk; Roling, Bernhard; Schirmeisen, André
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    Click Chemistry in Ultra-high Vacuum – Tetrazine Coupling with Methyl Enol Ether Covalently Linked to Si(001)
    (2021) Glaser, Timo; Meinecke, Jannick; Freund, Lukas; Länger, Christian; Luy, Jan-Niclas; Tonner, Ralf; Koert, Ulrich; Dürr, Michael
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    Combination of optical emission spectroscopy and multivariate data analysis techniques as a versatile non-invasive tool for characterizing xenon\/krypton mixed gas plasma inside operating ion thrusters
    (2022) Nauschütt, Benny; Chen, Limei; Holste, Kristof; Klar, Peter J.
    Non-invasive assessment of the plasma parameters is a useful tool for a reliable characterization of many electric thrusters for space applications. Due to high costs, limited availability, and growing use of electric propulsion in spaceflight, alternatives to Xe as a propellant are becoming increasingly important. One option is to use the lighter noble gas krypton or xenon/krypton gas mixtures as a propellant. We propose a versatile analytical approach for establishing empirical correlations between plasma parameters and optical emission (OE) spectroscopy utilizing principal component analysis (PCA). Our approach allows us to establish a surjective mapping of individual OE spectra via their PCA scores onto the corresponding plasma parameters. We prove the feasibility of this approach for Xe, Kr, and Xe/Kr mixed plasmas demonstrating that it is applicable for a wide range of propellant candidates. A major advantage is that the approach does not rely on any microscopic modeling of the OE spectra of the plasma. After having established corresponding reference mappings, the approach can be explored for determining non-invasively and spatially resolved plasma parameters of the propellant plasma of various kinds of operating ion thrusters, which operate in the same plasma regime as the reference plasma. Thus, this method may contribute to shorter qualification and testing times of ion thrusters.
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    Combination of Thin-Layer Chromatography and Mass Spectrometry Using Cluster-Induced Desorption/Ionization.
    (2019) Heep, Julian; Tuchecker, Paul H. K.; Gebhardt, Christoph R.; Dürr, Michael
    Desorption/ionization induced by neutral clusters (DINeC) was employed for mass spectrometry (MS) of oligopeptides and lipids after separation by means of thin-layer chromatography (TLC). Clear and fragmentation-free spectra were obtained from the TLC plates without any further sample treatment. Mass-resolved chromatograms were deduced when scanning the TLC plates with the cluster beam along the direction of solvent movement. Using vancomycin and noncovalently bound complexes, the soft nature of DINeC was demonstrated also when used in combination with TLC. As a test application, TLC and DINeC-MS were employed to separate and detect different phospholipids obtained from egg yolk.
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    Combined XPS and DFT investigation of the adsorption modes of methyl enol ether functionalized cyclooctyne on Si(001)
    (2021) Glaser, Timo; Meinecke, Jannick; Länger, Christian; Luy, Jan-Niclas; Tonner, Ralf; Koert, Ulrich; Dürr, Michael
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    Comparison of carrier-recombination in Ga(As,Bi)/Ga(N,As)-type-II quantum wells and W-type heterostructures
    (2021) Veletas, Julian; Hepp, Thilo; Dobener, Florian; Volz, Kerstin; Chatterjee, Sangam