Biomasseabschätzung im ökologischen Feldfutterbau mittels drohnengestützten RGB-Aufnahmen

Monitoringansätze im ökologischen Futterbau, die den Biomasseertrag über den gesamten Betrieb abschätzen, ermöglichen es dem Landwirt, standortspezifische Managemententscheidungen zu treffen. Die pflanzliche Biomasse und ihre Höhe korrelieren miteinander, wodurch die Höhe des Bestandes zur Ertragsprognose verwendet werden kann. Fernerkundliche Messmethoden sind nützlich, um räumliche Informationen über die Pflanzenhöhe auch über größere Flächen zu erhalten. In dieser Studie wurde eine RGB-Kamera (rot, grün, blau), die an einem kleinen unbemannten Luftfahrzeug (Drohne) angebracht war, zur Ertragsabschätzung in einem ökologischen Futterbauexperiment verwendet. Das Experiment wurde 2016 mit zwei Leguminosen-Grasmischungen (Klee- und Luzernegras) sowie mit ihren reinen Leguminosen und Gräsern angelegt. In der Vegetationsperiode des nächsten Jahres wurden jede zweite Woche RGB-Aufnahmen durchgeführt. Parallel dazu wurden Referenzdaten für die Biomasseerträge und manuelle Höhenmessungen erstellt. 3D-Modelle, die aus den RGB-Aufnahmen erzeugt wurden, wurden zur Berechnung der Bestandeshöhe verwendet. Der Biomasseertrag wurde mit zufriedenstellenden Ergebnissen vorhergesagt

Real-time evolution of quenched quantum systems

The study of the interplay between interaction-induced correlations and nonequilibrium initial conditions in many-body systems has recently attracted a lot of attention. New experimental techniques provide high control over many-body systems and systematic access to their nonequilibrium regime. In many systems the nonequilibrium properties of a Fermi liquid can be relevant. A first approach to their understanding is the main content of this thesis. At the beginning, nonequilibrium phenomena, Landau's theory of a Fermi liquid, the Hubbard model, time evolution in quantum mechanics, related experiments, and the flow equation method are reviewed. The key observation of this thesis, namely a characteristic mismatch of expectation values in equilibrium and nonequilibrium, is first illustrated for the squeezed oscillator. For this one-particle model Hamiltonian the perturbative approach can be compared with the exact solution and it is shown that the mismatch holds even beyond perturbation theory. Afterwards these observations are generalized to a larger class of one-particle models. Then the nonequilibrium behavior of a Fermi liquid is examined by analyzing the Fermi liquid phase of the Hubbard model in more than one dimension. After a sudden switch-on of a weak two-particle interaction to the noninteracting Fermi gas the relaxation of the many-body system is observed. For this purpose, the flow equation transformation is implemented for the Hubbard Hamiltonian. Then the discussion of the momentum distribution function and of the kinetic energy displays a three-step relaxation behavior of the Fermi liquid from the initial perturbation until thermalization is reached. Firstly, the sudden switch inserts excitation energy into the system which drives the following dynamics. Then a rapid initial build-up of correlations is caused by initial dephasing and leads to the establishment of a quasiparticle picture. By that the system enters into a quasi-stationary state which can be long-lasting for weak interaction. This state shows prethermalization of the kinetic energy which already has relaxed to its final values. However, the momentum distribution still resembles a zero temperature Fermi liquid. Its later relaxation on a second time scale is caused by a residual two-particle interaction which allows for scattering processes and can be described by a quantum Boltzmann equation. The physical origin of this delayed relaxation can be traced back to an interplay of translational invariance of the Hubbard model and the Pauli principle for fermions; together they restrict the phase space for scattering events. Comparing with similar work I conjecture on the generic nature of the findings made for the quenched Fermi liquid in other many-body systems. Finally I point out to the potential relevance of the delayed relaxation for the observation of further nonequilibrium phenomena, for instance in BCS systems. In order to extend the study of sudden switching to arbitrary switching processes the calculation is repeated using the Keldysh perturbation theory. First evaluations for a linear increase of the interaction strength are given. Extensions of this work are suggested and may motivate further research

Real-time evolution of quenched quantum systems

The study of the interplay between interaction-induced correlations and nonequilibrium initial conditions in many-body systems has recently attracted a lot of attention. New experimental techniques provide high control over many-body systems and systematic access to their nonequilibrium regime. In many systems the nonequilibrium properties of a Fermi liquid can be relevant. A first approach to their understanding is the main content of this thesis. At the beginning, nonequilibrium phenomena, Landau's theory of a Fermi liquid, the Hubbard model, time evolution in quantum mechanics, related experiments, and the flow equation method are reviewed. The key observation of this thesis, namely a characteristic mismatch of expectation values in equilibrium and nonequilibrium, is first illustrated for the squeezed oscillator. For this one-particle model Hamiltonian the perturbative approach can be compared with the exact solution and it is shown that the mismatch holds even beyond perturbation theory. Afterwards these observations are generalized to a larger class of one-particle models. Then the nonequilibrium behavior of a Fermi liquid is examined by analyzing the Fermi liquid phase of the Hubbard model in more than one dimension. After a sudden switch-on of a weak two-particle interaction to the noninteracting Fermi gas the relaxation of the many-body system is observed. For this purpose, the flow equation transformation is implemented for the Hubbard Hamiltonian. Then the discussion of the momentum distribution function and of the kinetic energy displays a three-step relaxation behavior of the Fermi liquid from the initial perturbation until thermalization is reached. Firstly, the sudden switch inserts excitation energy into the system which drives the following dynamics. Then a rapid initial build-up of correlations is caused by initial dephasing and leads to the establishment of a quasiparticle picture. By that the system enters into a quasi-stationary state which can be long-lasting for weak interaction. This state shows prethermalization of the kinetic energy which already has relaxed to its final values. However, the momentum distribution still resembles a zero temperature Fermi liquid. Its later relaxation on a second time scale is caused by a residual two-particle interaction which allows for scattering processes and can be described by a quantum Boltzmann equation. The physical origin of this delayed relaxation can be traced back to an interplay of translational invariance of the Hubbard model and the Pauli principle for fermions; together they restrict the phase space for scattering events. Comparing with similar work I conjecture on the generic nature of the findings made for the quenched Fermi liquid in other many-body systems. Finally I point out to the potential relevance of the delayed relaxation for the observation of further nonequilibrium phenomena, for instance in BCS systems. In order to extend the study of sudden switching to arbitrary switching processes the calculation is repeated using the Keldysh perturbation theory. First evaluations for a linear increase of the interaction strength are given. Extensions of this work are suggested and may motivate further research

Methoden zur lasergestützten Abschätzung extensiver Grünlandbestände

In der Forstwirtschaft ist die lasergestützte Holzertragsabschätzung bereits eine etablierte Technik. In Graslandökosystemen hingegen fand diese Technik bisher weniger Aufmerksamkeit. Deshalb ist die Abschätzung extensiver Grünlandbestände mittels eines terrestrischen Laserscanners (TLS) noch wenig erforscht. Der Einsatz fernerkundlicher Methoden zur Erfassung qualitativer und quantitativer Parameter von extensiven Grünlandbeständen kann Managementstrategien zum Erhalt schützenswerter Ökosysteme unterstützen. Die Versuchsflächen befanden sich im „UNESCO Biosphärenreservat Rhön“ und wurden zu drei Terminen im Jahr mittels eines terrestrischen Laserscanners (Leica P30) gemessen. Vier Methoden zur Biomassebestimmung aus dreidimensionalen Punktwolken wurden auf die Datensätze angewendet: Die Methode der Vegetationshöhe, der Summe der Voxel, der mittleren 3d-Raster Höhe und das Volumen der konvexen Hülle. Die Methoden wurden teilweise modifiziert in Bezug auf einzelne funktionale Parameter, um die Modellstabilität und Modellstärke zu optimieren. Die Methoden wurden verglichen hinsichtlich ihrer Modellstärke, der Kalkulationsdauer und hinsichtlich der Anzahl an Scans, die in jede Punktwolke einfließen. Die Methoden wurden erfolgreich angewendet und die jeweils optimalen Parametereinstellungen wurden identifiziert. Die beste Modellstärke lieferte die Methode der Vegetationshöhe gemittelt aus den oberen 5 % aller Vegetationshöhenwerte (angepasstes R² 0,72). Die Korrelationen der Modelle mit dem gemessenen Frischmasseertrag fielen durchweg besser aus im Vergleich zum Trockenmasseertrag. Modelle der Vegetationshöhe, beruhend auf Punktwolken aus zwei Scans, erzielten die höchste Schätzgenauigkeit für Frisch- und Trockenmasseertrag (angepasstes R² 0,73 und 0,58)

Biomasseertrag, Lupinenanteil und Alkaloidgehalte in Bergmähwiesen in Abhängigkeit des Erntezeitpunktes

Die invasive Leguminose Lupinus polyphyllus (Vielblättrige Lupine) breitet sich in artenreichen Borstgrasrasen und Bergmähwiesen aus. Dort verdrängt sie gefährdete Rote-Liste Arten und verändert die Artenzusammensetzung. Wir führten ein Experiment durch um den Biomasseertrag und den Lupinenanteil an der Biomasse zu unterschiedlichen Nutzungszeitpunkten zu untersuchen. Zusätzlich wurde der Alkaloidgehalt der Lupinen ermittelt, da dieser einen Einsatz der Biomasse in der Tierernährung verhindern kann. Die Ergebnisse zeigten Bioamsseerträge vo 3,6 bis 3,9 t Trockenmasse pro Hektar und Lupinenanteile von ca. 30% im Mittel. Der Alkaloidgehalt in den Lupinen wies eine Spannweite zwischen 0,7 und 2,5% in der Trockenmasse auf und war signifikant abhängig vom untersuchten Pflanzenorgan. Die Samen und Blätter hatten signifikant höhere Alkaloidgehalte als die Stängel und Blüten

Crossover from adiabatic to sudden interaction quenches in the Hubbard model: Prethermalization and nonequilibrium dynamics

The recent experimental implementation of condensed matter models in optical lattices has motivated research on their nonequilibrium behavior. Predictions on the dynamics of superconductors following a sudden quench of the pairing interaction have been made based on the effective BCS Hamiltonian; however, their experimental verification requires the preparation of a suitable excited state of the Hubbard model along a twofold constraint: (i) a sufficiently nonadiabatic ramping scheme is essential to excite the nonequilibrium dynamics, and (ii) overheating beyond the critical temperature of superconductivity must be avoided. For commonly discussed interaction ramps there is no clear separation of the corresponding energy scales. Here we show that the matching of both conditions is simplified by the intrinsic relaxation behavior of ultracold fermionic systems: For the particular example of a linear ramp we examine the transient regime of prethermalization [M. Moeckel and S. Kehrein, Phys. Rev. Lett. 100, 175702 (2008)] under the crossover from sudden to adiabatic switching using Keldysh perturbation theory. A real-time analysis of the momentum distribution exhibits a temporal separation of an early energy relaxation and its later thermalization by scattering events. For long but finite ramping times this separation can be large. In the prethermalization regime the momentum distribution resembles a zero temperature Fermi liquid as the energy inserted by the ramp remains located in high energy modes. Thus ultracold fermions prove robust to heating which simplifies the observation of nonequilibrium BCS dynamics in optical lattices.Comment: 27 pages, 8 figures Second version with small modifications in section

Konzepte der Elektromobilität. Ihre Bedeutung für Wirtschaft, Gesellschaft und Umwelt

Gesellschaft und Politik knüpfen große Hoffnung an die Elektromobilität. Allerdings wird sehr kontrovers diskutiert, ob und wie eine umfassende und nachhaltige Verbreitung von Elektrofahrzeugen erreichbar ist. Für die Fortsetzung dieser Debatte ist es wichtig, die Ergebnisse aus der Vielzahl von Förderprogrammen und Studien, die in den letzten Jahren mit unterschiedlichen Fragestellungen und Perspektiven angestoßen wurden, in einem umfassenden Überblick zusammenzuführen – dieser Aufgabe unterziehen sich die Autor/inn/en dieses Bandes. Sie präsentieren hier eine mit zahlreichen Fakten und Daten untermauerte Gesamtschau über den technischen Entwicklungsstand, aussichtsreiche Erstmärkte, Markthochlaufszenarien sowie politische Aktivitäten und veranschaulichen im Rahmen einer ganzheitlichen Bewertung die ökologische, ökonomische und soziale Dimension der Integration von Elektrofahrzeugen in die heutigen Verkehrs- und Energiesysteme. Auf dieser Basis diskutieren sie Handlungsoptionen und liefern die Grundlage für politische Entscheidungen über Ziele und Maßnahmen. Als Baustein einer nachhaltigen Entwicklung hat die Elektromobilität großes Potenzial, dessen Entfaltung freilich Zeit und geeignete Rahmenbedingungen erfordert. Das Buch basiert auf dem TAB-Arbeitsbericht Nr. 153 »Konzepte der Elektromobilität und deren Bedeutung für Wirtschaft, Gesellschaft und Umwelt

Erfahrungen, Herausforderungen und Lösungsansätze aus der Extraktion pseudonymer Daten für das Projekt INDEED

Background: In Germany there is currently no health reporting on cross-sectoral care patterns in the context of an emergency department care treatment. The INDEED project (Utilization and trans-sectoral patterns of care for patients admitted to emergency departments in Germany) collects routine data from 16 emergency departments, which are later merged with outpatient billing data from 2014 to 2017 on an individual level. Aim: The methodological challenges in planning of the internal merging of routine clinical and administrative data from emergency departments in Germany up to the final data extraction are presented together with possible solution approaches. Methods: Data were selected in an iterative process according to the research questions, medical relevance, and assumed data availability. After a preparatory phase to clarify formalities (including data protection, ethics), review test data and correct if necessary, the encrypted and pseudonymous data extraction was performed. Results: Data from the 16 cooperating emergency departments came mostly from the emergency department and hospital information systems. There was considerable heterogeneity in the data. Not all variables were available in every emergency department because, for example, they were not standardized and digitally available or the extraction effort was judged to be too high. Conclusion: Relevant data from emergency departments are stored in different structures and in several IT systems. Thus, the creation of a harmonized data set requires considerable resources on the part of the hospital as well as the data processing unit. This needs to be generously calculated for future projects

Clinical and virological characteristics of hospitalised COVID-19 patients in a German tertiary care centre during the first wave of the SARS-CoV-2 pandemic: a prospective observational study

Purpose: Adequate patient allocation is pivotal for optimal resource management in strained healthcare systems, and requires detailed knowledge of clinical and virological disease trajectories. The purpose of this work was to identify risk factors associated with need for invasive mechanical ventilation (IMV), to analyse viral kinetics in patients with and without IMV and to provide a comprehensive description of clinical course. Methods: A cohort of 168 hospitalised adult COVID-19 patients enrolled in a prospective observational study at a large European tertiary care centre was analysed. Results: Forty-four per cent (71/161) of patients required invasive mechanical ventilation (IMV). Shorter duration of symptoms before admission (aOR 1.22 per day less, 95% CI 1.10-1.37, p < 0.01) and history of hypertension (aOR 5.55, 95% CI 2.00-16.82, p < 0.01) were associated with need for IMV. Patients on IMV had higher maximal concentrations, slower decline rates, and longer shedding of SARS-CoV-2 than non-IMV patients (33 days, IQR 26-46.75, vs 18 days, IQR 16-46.75, respectively, p < 0.01). Median duration of hospitalisation was 9 days (IQR 6-15.5) for non-IMV and 49.5 days (IQR 36.8-82.5) for IMV patients. Conclusions: Our results indicate a short duration of symptoms before admission as a risk factor for severe disease that merits further investigation and different viral load kinetics in severely affected patients. Median duration of hospitalisation of IMV patients was longer than described for acute respiratory distress syndrome unrelated to COVID-19