Numerics of photonic and plasmonic nanostructures with advanced material models

In dieser Arbeit untersuchen wir mehrere Anwendungen von photonischen und plasmonischen Nanostrukturen unter Verwendung zweier verschiedener numerischer Methoden: die Fourier-Moden-Methode (FMM) und ein unstetiges Galerkin-Zeitraumverfahren (discontinuous Galerkin time-domain method, DGTD method). Die Methoden werden für vier verschiedene Anwendungen eingesetzt, die alle eine Materialmodellerweiterung in der Implementierung der Methoden erfordern. Diese Anwendungen beinhalten die Untersuchung von dünnen, freistehenden, periodisch perforierten Goldfilmen. Wir charakterisieren die auftretenden Oberflächenplasmonenpolaritonen durch die Berechnung von Transmissions- und Elektronenenergieverlustspektren, die mit experimentellen Messungen verglichen werden. Dazu stellen wir eine Erweiterung der DGTD-Methode zur Verfügung, die sowohl absorbierende, impedanzangepasste Randschichten als auch Anregung mit geglätteter Ladungsverteilung für materialdurchdringende Elektronenstrahlen beinhaltet. Darüber hinaus wird eine Erweiterung auf nicht-dispersive anisotrope Materialien für eine Formoptimierung einer volldielektrischen magneto-optischen Metaoberfläche verwendet. Diese Optimierung ermöglicht eine verstärkte Faraday-Rotation zusammen mit einer hohen Transmission. Zusätzlich untersuchen wir abstimmbare hyperbolische Metamaterialresonatoren im nahen Infrarot mit Hilfe der FMM. Wir berechnen deren Resonanzen und vergleichen sie mit dem Experiment. Zum Schluss wird die Implementierung eines nichtlinearen Vier-Niveau-System-Materialmodells in der DGTD-Methode verwendet, um die Laserschwellen eines Mikroresonators mit Bragg-Spiegeln zu berechnen. Bei Einführung eines Silbergitters mit variablen Spaltgrößen wird eine defektinduzierte Kontrolle der Laserschwellen ermöglicht. Die Berechnung der vollständigen, zeitaufgelösten Felddynamik innerhalb des Resonator gibt dabei Aufschluss über die beteiligten Lasermoden.In this thesis, we study several applications of photonic and plasmonic nanostructures by employing two different numerical methods: the Fourier modal method (FMM) and discontinuous Galerkin time-domain (DGTD) method. The methods are used for four different applications, all of which require a material model extension for the implementation of the methods. These applications include the investigation of thin, free-standing periodically perforated gold films. We characterize the emerging surface plasmon polaritons by computing both transmittance and electron energy loss spectra, which are compared to experimental measurements. To this end, we provide an extension of the DGTD method, including absorbing stretched coordinate perfectly matched layers as well as excitations with smoothed charge distribution for material-penetrating electron beams. Furthermore, an extension to non-dispersive anisotropic materials is used for shape optimization of an all-dielectric magneto-optic metasurface. This optimization enables an enhanced Faraday rotation along with high transmittance. Additionally, we study tuneable near-infrared hyperbolic metamaterial cavities with the help of the FMM. We compute the cavity resonances and compare them to the experiment. Finally, the implementation of a non-linear four-level system material model in the DGTD method is used to compute lasing thresholds of a distributed Bragg reflector microcavity. Introducing a silver grating with variable gap sizes allows for a defect-induced lasing threshold control. The computation of the full time-resolved field dynamics of the cavity provides information on the involved lasing modes

An integrated model for the probabilistic prediction of yield strength in electron-beam additively manufactured Ti-6Al-4V

A complete model for the prediction of the yield strength of Titanium 6Al-4V in an additively manufactured component is presented herein. A thermal model is presented utilizing the ABAQUS simulation software to provide the process leg of the materials tetrahedron. The thermal model is fed into an implementation of the Langmuir equation that has been adapted for use in the simulation of the Electron-Beam Additive Manufacturing (EBAM) process. The predicted chemistry provided by the Langmuir equation for the Ti-6Al-4V alloy is then used in a phenomenological equation for the prediction of yield strength; a design probability curve is generated through random sampling of the thermal model. Using Weibull probability distributions, the model is verified against a rich mechanical and chemical database built from an actual EBAM build used in previous research

A near-field study on the transition from localized to propagating plasmons on 2D nano-wedges

In this manuscript we report on a near-feld study of two-dimensional plasmonic gold nano-wedges using electron energy loss spectroscopy in combination with scanning transmission electron microscopy, as well as discontinuous Galerkin time-domain computations. With increasing nano-wedge size, we observe a transition from localized surface plasmons on small nano-wedges to non-resonant propagating surface plasmon polaritons on large nano-wedges. Furthermore we demonstrate that nano-wedges with a groove cut can support localized as well as propagating plasmons in the same energy range

Dissolution, Reactor, and Environmental Behavior of ZrO2-MgO Inert Fuel Matrix: Quarterly Report, January 2006 to March 2006

This project will examine inert matrix fuels containing ZrO2 and MgO as the inert matrix, with the relative amount of MgO varied from 30% to 70% in ZrO2. Reactor physics calculations will be used to examine suitable quantities of burnable poisons from the candidate elements Gd, Er, or Hf with reactor grade Pu providing the fissile component, with up to 10% of 239Pu. Ceramics will be synthesized and characterized based on the reactor physics results. The solubility of the fuel ceramics, in reactor conditions, reprocessing conditions, and repository conditions, will be investigated in a manner to provide thermodynamic data necessary for modeling. The fuel matrix will be designed based on neutronic properties, repository behavior, and reprocessing characteristics. The matrix should be as neutron transparent as possible. Burnable poisons will be used to maintain constant reactivity. The matrix should also act as a suitable host form for fission products and actinides in a repository environment. Finally, the matrix should be compatible with reprocessing schemes under development in the advanced fuel cycle. Work accomplished last quarter: The synthesis of the entire range of Zr to Mg, with Ce and Er concentrations being held at 5% and 2.5% respectively, has been completed with enough material for characterization and solubility studies. X-ray fluorescence has been performed on all ten batches to verify concentrations. X-ray diffraction has shown the range of Mg required for a single phase solid solution of cubic zirconia to be 10% to 28% Mg at current concentrations of Ce and Er. Pressure vessel experiments have begun. Acid dissolution studies suggest that it could be possible to leach uranium out of the ceramic without dissolving it. Therefore, these studies will be performed with uranium samples once they are prepared. The soxhlet studies have yielded quantitative data on water absorption, magnesium hydration, and corrosion of the ceramic. Calculations were performed on 3 dimensional full core neutronic modeling of MgO-ZrO2 fertile free fuel with previously selected most promising burnable poison designs. Work performed this quarter: Optical Microscopy and SEM (scanning electron microscopy) where used to image the ceramic material. Elemental scanning by microprobe showed CeO2 to be the least soluble in the 2 ZrO2. Microprobe analysis showed the periclase phase to be pure MgO and gave stoichiometric data on the ZrO2 phase. The entire range of ZrO2 to MgO was synthesized replacing CeO2 with UO2 as the plutonium analog. XAFS (X-ray absorption fine structure) and XANES (X-ray absorption near edge spectroscopy) were performed at Argonne National Lab. Pressure vessel dissolution studies showed that although the pellet could be physically destroyed, nothing was dissolved in the water. Sulfuric acid was successful in dissolving sintered material and may therefore be a possible head-in to a reprocessing scheme. The Soxhlet apparatus shows increasing corrosion rates with increasing MgO concentration

Efficacy in German Teacher Education

At the present time German teacher training is confronted with a great political will to bring about change. International comparative studies of recent years have shown a dissatisfying learning outcome. The most dramatic result is a strong interdependence of school success and social background. German teachers experience their profession as problematic. At present only 35% work until the normal pension age. The article discusses structural differences in teacher training compared to other countries and analyses motivation for the choice of study, perceived self-efficacy, experience of stress, patterns of uncertainty avoidance and previous experience in a sample of 1358 students starting teacher training.Key words: Teacher training; Career choice motivation; Self-efficacy; Experience of stress; Uncertainty avoidanc

Comparison of XCO abundances from the Total Carbon Column Observing Network and the Network for the Detection of Atmospheric Composition Change measured in Karlsruhe

We present a comparison of Karlsruhe XCO records (April 2010–December 2014) from the Total Carbon Column Observing Network (TCCON) and from the spectral region covered by the Network for the Detection of Atmospheric Composition Change (NDACC). The Karlsruhe TCCON Fourier transform infrared (FTIR) spectrometer allows us to record spectra in the mid-infrared (MIR) and near-infrared (NIR) spectral region simultaneously, which makes Karlsruhe a favourable FTIR site to directly compare measurements from both spectral regions. We compare XCO retrieved from the fundamental absorption band at 4.7 µm (as used by NDACC) and first overtone absorption band at 2.3 µm (TCCON-style measurements). We observe a bias of (4.47 ± 0.17) ppb between both data sets with a standard deviation of 2.39 ppb in seasonal variation. This corresponds to a relative bias of (4.76 ± 0.18) % and a standard deviation of 2.28 %. We identify different sources which contribute to the observed bias (air-mass-independent correction factor, air-mass-dependent correction factor, isotopic identities, differing a priori volume mixing ratio profiles) and quantify their contributions. We show that the seasonality in the residual of NDACC and TCCON XCO can be largely explained by the smoothing effect caused by differing averaging kernel sensitivities between the MIR and NIR spectral region. This study aims to improve the comparability of NDACC and TCCON XCO validation data sets as desired for potential future satellite missions and model studies

“I’ve been manipulated!”: Designing Second Screen Experiences for Critical Viewing of Reality TV

The recent proliferation of a reality TV genre that focusses on welfare recipients has led to concerns that prime-time media experiences are exacerbating misconceptions, and stifling critical debate, around major societal issues such as welfare reform and poverty. Motivated by arguments that ‘second screening’ practices offer opportunities to engage viewers with issues of political concern, we describe the design and evaluation of two smartphone apps that facilitate and promote more critical live-viewing of reality TV. Our apps, Spotting Guide and Moral Compass, encourage users to identify, categorise, tag and filter patterns and tropes within reality TV, as well as reinterpret social media posts associated with their broadcast. We show that such interactions encourage critical thinking around typical editing and production techniques and foster co-discussion and reflection amongst viewers. We discuss, more broadly, how these interactions encourage users to identify the wider consequences and framings of reality TV, and offer implications and considerations for design that provokes criticality and reflection in second screening contexts

A Circulating MicroRNA Profile in a Laser-Induced Mouse Model of Choroidal Neovascularization

Funding: This research was funded by the Deutsche Forschungsgemeinschaft (GR5065/1-1). Author Contributions: Conceptualization, F.G. and B.H.F.W.; Data curation, T.S.; Formal analysis, P.B., M.K., A.A., and T.S.; Funding acquisition, C.K. and F.G.; Investigation, M.K. and B.H.F.W.; Methodology, C.K. and A.A.;Project administration, B.H.F.W.; Resources, M.K., A.A., T.L., and F.G.; Software, C.K. and T.S.; Supervision, T.L., F.G., and B.H.F.W.; Validation, P.B.; Visualization, C.K.; Writing—original draft, C.K. and P.B.; Writing—review & editing, B.H.F.W. All authors have read and agreed to the published version of the manuscript.Peer reviewedPublisher PD