TY - JOUR A1 - Nitzbon, Jan A1 - Gadylyaev, Damir A1 - Schlüter, Steffen A1 - Köhne, John Maximilian A1 - Grosse, Guido A1 - Boike, Julia T1 - Brief communication: Unravelling the composition and microstructure of a permafrost core using X-ray computed tomography JF - The Cryosphere : TC ; an interactive open access journal of the European Geosciences Union N2 - The microstructure of permafrost ground contains clues to its formation and hence its preconditioning to future change. We applied X-ray computed microtomography (CT) to obtain high-resolution data (Delta x = 50 mu m) of the composition of a 164 cm long permafrost core drilled in a Yedoma upland in north-eastern Siberia. The CT analysis allowed the microstructures to be directly mapped and volumetric contents of excess ice, gas inclusions, and two distinct sediment types to be quantified. Using laboratory measurements of coarsely resolved core samples, we statistically estimated the composition of the sediment types and used it to indirectly quantify volumetric contents of pore ice, organic matter, and mineral material along the core. We conclude that CT is a promising method for obtaining physical properties of permafrost cores which opens novel research potentials. Y1 - 2022 U6 - https://doi.org/10.5194/tc-16-3507-2022 SN - 1994-0416 SN - 1994-0424 VL - 16 IS - 9 SP - 3507 EP - 3515 PB - Copernicus CY - Göttingen ER - TY - JOUR A1 - Wang, Ningzhen A1 - van Turnhout, Jan A1 - Daniels, Robert A1 - Wu, Chao A1 - Huo, Jindong A1 - Gerhard, Reimund A1 - Sotzing, Gregory A1 - Cao, Yang T1 - Ion-boosting the charge density and piezoelectric response of ferroelectrets to significantly high levels JF - ACS applied materials & interfaces N2 - In contrast to molecular-dipole polymers, such as PVDF, ferroelectrets are a new class of flexible spatially heterogeneous piezoelectric polymers with dosed or open voids that act as deformable macro-dipoles after charging. With a spectrum of manufacturing processes being developed to engineer the heterogeneous structures, ferroelectrets are made with attractive piezoelectric properties well-suited for applications, such as pressure sensors, acoustic transducers, etc. However, the sources of the macro-dipole charges have usually been the same, microscopic dielectric barrier discharges within the voids, induced when the ferroelectrets are poled under a large electric field typically via a so-called corona poling, resulting in the separation and trapping of opposite charges into the interior walls of the voids. Such a process is inherently self-limiting, as the reverse internal field from the macro-dipoles eventually extinguishes the microdischarges, resulting in limited density of ions and not too high overall piezoelectric performance. Here, a new method to form ferroelectrets with gigantic electroactivity is proposed and demonstrated with the aid of an external ion booster. A laminate consisting of expanded polytetrafluoroethylene (ePTFE) and fluorinated-ethylene-propylene (FEP) was prefilled with bipolar ions produced externally by an ionizer and sequentially poled to force the separation of positive and negative ions into the open fibrous structure, rendering an impressive piezoelectric d(33)( )coefficient of 1600 pC/N-an improvement by a factor of 4 in comparison with the d(33) of a similar sandwich poled with nonenhanced corona poling. The (pre)filling dearly increases the ion density in the open voids significantly. The charges stored in the open-cell structure stays at a high level for at least 4 months. In addition, an all-organic nanogenerator was made from an ePTFE-based ferroelectret, with conducting poly(3,4-ethylene dioxythiophene): poly(styrenesulfonate) (PEDOT: PSS) coated fabric electrodes. When poled with this ion-boosting process, it yielded an output power twice that of a similar sample poled in a conventional corona-only process. The doubling in output power is mainly brought about by the significantly higher charge density achieved with the aid of external booster. Furthermore, aside from the bipolar ions, extra monopolar ions can during the corona poling be blown into the open pores by using for instance a negative ionic hair dryer to produce a unipolar ePTFE-based ferroelectret with its d(33) coefficient enhanced by a factor of 3. Ion-boosting poling thus unleashes a new route to produce bipolar or unipolar open-cell ferroelectrets with highly enhanced piezoelectric response. KW - ePTFE ferroelectret KW - corona charging KW - ion boost KW - bipolar and unipolar charging KW - piezoelectric response KW - wearable energy harvester Y1 - 2022 U6 - https://doi.org/10.1021/acsami.2c12185 SN - 1944-8244 SN - 1944-8252 VL - 14 IS - 37 SP - 42705 EP - 42712 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Steinhoff, Julia S. A1 - Wagner, Carina A1 - Taschler, Ulrike A1 - Wulff, Sascha A1 - Kiefer, Marie F. A1 - Petricek, Konstantin M. A1 - Wowro, Sylvia J. A1 - Oster, Moritz A1 - Flores, Roberto E. A1 - Yang, Na A1 - Li, Chen A1 - Meng, Yueming A1 - Sommerfeld, Manuela A1 - Weger, Stefan A1 - Henze, Andrea A1 - Raila, Jens A1 - Lass, Achim A1 - Schupp, Michael T1 - Acute retinol mobilization by retinol-binding protein 4 in mouse liver induces fibroblast growth factor 21 expression JF - Journal of lipid research N2 - Hepatocytes secrete retinol-binding pro-tein 4 (RBP4) into circulation, thereby mobilizing vitamin A from the liver to provide retinol for extrahepatic tissues. Obesity and insulin resistance are associated with elevated RBP4 levels in the blood. However, in a previous study, we observed that chronically increased RBP4 by forced Rbp4 expres-sion in the liver does not impair glucose homeostasis in mice. Here, we investigated the effects of an acute mobilization of hepatic vitamin A stores by hepatic overexpression of RBP4 in mice. We show that he-patic retinol mobilization decreases body fat content and enhances fat turnover. Mechanistically, we found that acute retinol mobilization increases hepatic expression and serum levels of fibroblast growth factor 21 (FGF21), which is regulated by retinol mobilization and retinoic acid in primary hepato-cytes. Moreover, we provide evidence that the insulin-sensitizing effect of FGF21 is associated with organ-specific adaptations in retinoid homeostasis. Taken together, our findings identify a novel cross-talk between retinoid homeostasis and FGF21 in mice with acute RBP4-mediated retinol mobilization from the liver. KW - vitamin A KW - retinoids KW - glucose KW - hepatic retinol mobilization KW - retinyl ester storage KW - obesity KW - hepatocyte KW - retinoid homeostasis KW - insulin resistance Y1 - 2022 U6 - https://doi.org/10.1016/j.jlr.2022.100268 SN - 0022-2275 SN - 1539-7262 VL - 63 IS - 10 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Metzler, Ralf A1 - Rajyaguru, Ashish A1 - Berkowitz, Brian T1 - Modelling anomalous diffusion in semi-infinite disordered systems and porous media JF - New journal of physics : the open-access journal for physics N2 - For an effectively one-dimensional, semi-infinite disordered system connected to a reservoir of tracer particles kept at constant concentration, we provide the dynamics of the concentration profile. Technically, we start with the Montroll-Weiss equation of a continuous time random walk with a scale-free waiting time density. From this we pass to a formulation in terms of the fractional diffusion equation for the concentration profile C(x, t) in a semi-infinite space for the boundary condition C(0, t) = C-0, using a subordination approach. From this we deduce the tracer flux and the so-called breakthrough curve (BTC) at a given distance from the tracer source. In particular, BTCs are routinely measured in geophysical contexts but are also of interest in single-particle tracking experiments. For the "residual' BTCs, given by 1- P(x, t), we demonstrate a long-time power-law behaviour that can be compared conveniently to experimental measurements. For completeness we also derive expressions for the moments in this constant-concentration boundary condition. KW - diffusion KW - anomalous diffusion KW - breakthrough curves KW - constant boundary concentration Y1 - 2022 U6 - https://doi.org/10.1088/1367-2630/aca70c SN - 1367-2630 VL - 24 IS - 12 PB - IOP Publ. Ltd. CY - London ER - TY - THES A1 - Satanowski, Jerome Ari T1 - Design and in vivo implementation of metabolic modules for synthetic carbon fixation N2 - Climate change, driven by increasing atmospheric levels of carbon dioxide (CO2), presents a significant societal challenge for the 21st century. Biotechnological approaches for microbial production of commodity chemicals and fuels offer possible solutions to re-fix CO2 from the atmosphere, thereby mitigating carbon emissions and contributing to a sustainable carbon-economy in the future. Biological CO2 fixation is also at the heart of agricultural productivity, where photosynthesis and the Calvin-Benson-Bassham cycle present promising biotechnological targets for crop improvement. Synthetic biology allows testing metabolic solutions not known to exist in nature, which may exceed their natural counterparts in terms of efficiency. In this thesis, I explore the design of such new-to-nature metabolic pathways for biological CO2 utilization and their implementation in living cells (in vivo). In the first chapter, I describe the development of a metabolic pathway that enables intracellular conversion of CO2 to formate, giving access to highly efficient carbon fixation routes. In nature, CO2-reduction remains restricted to anaerobic organisms and low redox potentials. Here, we introduce the “CORE cycle”, a synthetic metabolic pathway that converts CO2 to formate under fully aerobic conditions and ambient CO2 levels, using only NADPH as a reductant. We leverage this synthetic, ATP-energized pathway to overcome the thermodynamic and kinetic barriers associated with CO2-reduction. Applying rational metabolic engineering and adaptive evolution, this work demonstrates that Escherichia coli can utilize ambient CO2 as the sole source of one-carbon units and serine, achieving a first step towards novel modes of synthetic autotrophy. We further apply computational modeling to showcase the potential of the CORE cycle as a photorespiratory bypass for enhancing photosynthesis. In the second chapter, I describe the development of the “LCM module”, a novel metabolic route for CO2-incorporating conversion of acetyl-CoA to pyruvate. This route relies on the newly uncovered, promiscuous activity of an adenosylcobalamin (B12)-dependent enzyme, which we significantly optimize through targeted hypermutation and in vivo selection strategies. The LCM module provides a shorter and more efficient pathway for acetyl-CoA assimilation compared to natural routes, offering novel opportunities for synthetic CO2 fixation. Overall, through theoretical pathway analysis, enzyme bioprospecting, and modular metabolic engineering in E. coli, this thesis expands the solution space for biological CO2 fixation. KW - synthetic biology KW - metabolic engineering KW - carbon fixation KW - photosynthesis KW - enzyme KW - CO2 assimilation KW - auxotrophy Y1 - 2024 ER - TY - JOUR A1 - Wörner, Salome A1 - Becker, Sebastian A1 - Küchemann, Stefan A1 - Scheiter, Katharina A1 - Kuhn, Jochen T1 - Development and validation of the ray optics in converging lenses concept inventory JF - Physical Review Physics Education Research (PRPECZ) N2 - Optics is a core field in the curricula of secondary physics education. In this study, we present the development and validation of a test instrument in the field of optics, the ray optics in converging lenses concept inventory (ROC-CI). It was developed for and validated with middle school students, but can also be adapted for the use in higher levels of physics education. The ROC-CI can be used as a formative or a summative assessment of students' conceptual understanding of image formation by converging lenses, assessing the following: (i) the overall understanding of fundamental concepts related to converging lenses, (ii) the understanding of specific concepts, and (iii) students' propensity for difficulties within this topic. The initial ROC-CI consists of 16 multiple-choice items; however, one item was removed based on various quality checks. We validated the ROC-CI thoroughly with distractor analyses, classical test theory, item response theory, structural analyses, and analyses of students' total scores at different measurement points as quantitative approaches, as well as student interviews and an expert survey as qualitative approaches. The quantitative analyses are mostly based on a dataset of N 1/4 318 middle school students who took the ROC-CI as a post-test. The student interviews were conducted with seven middle school students after they were taught the concepts of converging lenses. The expert survey included five experts who evaluated both individual items and the test as a whole. The analyses showed good to excellent results for the test instrument, corroborating the 15-item ROC-CI's validity and its compliance with the three foci outlined above. Y1 - 2022 U6 - https://doi.org/10.1103/PhysRevPhysEducRes.18.020131 SN - 2469-9896 VL - 18 IS - 2 PB - American Physical Society CY - College Park ER - TY - THES A1 - Lagarde, Sophie T1 - Seismic imprint of natural and anthropogenic processes on the Earth surface T1 - Seismische Merkmale natürlicher und anthropogener Prozesse auf der Erdoberfläche N2 - Terrestrial landscape dynamics are dominated by the production, mobilisation, transfer and deposition of sediment. Numerous chemical elements are carried by sediments, making them a key component for ecological processes, as soil constitution and thus plants and animal ecosystems depends on them, and by extension the human species. They are also essential for climate evolution and regulation as marine sedimentation acts as a carbon sink. However, the processes at the origin of their production, mobilisation, transfer can occur suddenly with high-energy content – such as volcanic eruption, mass wasting or flooding events and wildfires – shaking ecosystems and shaping landforms. Besides, in the last era, the human species has shown its ability to disturb landscape dynamics and change sediments cycles. Thus, there is a need for predictive understanding of the processes involved. This relies on un-derstanding of the mechanisms of key processes and their controls, and knowledge of the state and evolution of the Earth’s surface. Classic approaches to these challenges include empirical observations and numerical modeling of geochemical fluxes and surface processes, as well as the study of terrestrial sedimentary archives to better understand the parameters at stake in landscape dynamics and climate changes and the different actions and retroactions between the production, mobilisation, transfer and deposition of sediments which ultimately shape landscapes. Environmental seismology complements these approaches. Environmental seismology is the science topic investigating the source functions and propagation properties of seismic vibrations triggered by processes happening at or near the Earth’s surface, below and above it - cryosphere, hydrosphere, atmosphere, human habitat, biosphere, etc., to obtain insight into all these physical processes. Indeed, from mass wasting event to rivers, from wild species to hu-man, all these processes are generating seismic waves. Environmental seismology is a rather recent field, with new branches rapidly expanding and at various stages of scientific progress. This thesis is motivated by the goal of learning more on two major natural process hazards (river bedload transport and mass wasting) as well as on human-generated acoustic hazard, while covering the axis of funda-mental research progression, from data exploration and method and theory development to proof of concept, with the twin aims of developing a better understanding of the operation of these specific processes, and of advancing the methods we have at our disposal to study them. First, I provide a benchmark for assessment of the reliability of existing seismic bedload model inver-sion to retrieve bedload flux from seismic data. Bedload flux measurements are essential to better understand river dynamics, and this can be achieved with environmental seismology. However, due to a lack of well-constrained validation data, the accuracy of the resulting inversions is unknown. I address this gap in Chapter 2.2, reporting a seismic field experiment, and comparing the results to high-quality independent bedload measurements to constrain a seismic bedload model. The study shows that the quality of bedload flux estimates from seismic data strongly depends on the quality of the input data for the model. Direct measurements of relevant parameters, chiefly seismic ground proper-ties needed for the Green's function and the grain size distribution of the moving bedload, considerably improve the model quality over generic approaches using empirical or theoretical functions. I also pro-vide a numerical tool to facilitate the use of water turbulence and bedload seismic inversion models: seismic models for bedload flux and water turbulence require painstaking work to constrain parame-ters describing the ground properties by active seismic study or analysis of passive seismic data, and the grain size distribution via independent measurements. Reasonable predictions can be achieved by using a Monte Carlo approach to optimize the free parameters with respect to the target parameters. The validation of the tool, in Chapter 2.3, with independent measurements of water depth and bedload flux at a study site on the Eshtemoa river in Israël makes it available for reliable use at other sites. The work reported in this chapter has been published in Lagarde et al. 2021 and Dietze et al. 2019b. In a second study, reported in Chapter 3, I investigate the formation of a failure plane prior to a rock-slide. A better understanding of the dynamics of the preparation phase is essential to determine the timing, volume and mobilization mechanism of a rock slope failure, and this can be achieved with envi-ronmental seismology. I take advantage of a network of seismic stations close to an instable slope recording cracking signals prior to the slope failure, and use a machine learning technique based on hidden Markov models to isolate these signals from the seismic data, retrieving the cumulative number of cracking events in a period of 20 days prior to a large rockslide and 10 days after. The trajectory of the cumulative number of cracks shifts from a rather linear shape in the two weeks prior to the rock-slide to an S-shaped development in the last 27 h before failure. I interpret this change as a switch from initial distributed cracking to localised damage accumulation in the hours prior to the failure. I develop a simple physical model to explain the temporal evolution of crack activity during the S-shape phase, revealing the importance of an internal parameter, the total crack boundary length as the dominant control parameter of failure plane evolution. This study has been published as Lagarde et al. 2023. Third, I develop a model converting acoustic signals to seismic signals. A part of the acoustic vibrations generated on the Earth’s surface is converted to seismic signals at the ground interface. Consequently, noise pollution may be translated to slope fatigue and rock micro (or macro) fracturing resulting in a degrading effect on landforms. Moreover, this pollution can have negative impacts, such as physical, physiological as well as psychological effects on animal species. At present, the impact of seismic pol-lution generated by acoustic sources is difficult to evaluate. In Chapter 4, I improve and implement a model converting the acoustic pressure generated by a source in the atmosphere to the corresponding seismic signal for a receiver within the ground. The ground is considered to be a porous elastic medium in which wave behaviour can be approximated by the Biot-Stoll model. The model is extended for use of a temporal pressure pulse as an input, and to produce output on a plan 2D map, where the wind effect on the acoustic to seismic coupling can be reproduced. I invest extensive effort in making the model user-friendly, as the project aims at reaching a large audience, comprising, for example, geo-morphologists, biologists and sociologists. Finally, the model is subjected to synthetic testing as well as a qualitative comparison of the predicted ground particle velocity and the seismic signal of a real heli-copter flight as a source of acoustic input. These studies advance understanding of the operation of specific natural processes in channels and on hillslopes, and bring us closer to designing functioning early warning systems for mass-wasting and flood events. This thesis also raises questions that have not been considered before, such as the con-tribution of human acoustic pollution to the seismic hum and its impact on the natural environment, or the importance of cracks in the self-development of the failure plane prior to slope. Together, these studies question general assumptions usually made regarding the triggering of mass wasting or the hillslope-channel connectivity. Beyond this, the thesis covers the axis of fundamental research progres-sion, from data exploration and method and theory development to proof of concept, and shows how in the rapidly developing field of environmental seismology, an active awareness of progress can help strengthen and accelerate general advances. N2 - Die Dynamik terrestrischer Landschaften wird von der Produktion, Mobilisierung, Übertragung und Ablagerung von Sedimenten dominiert. In Sedimenten sind zahlreiche chemische Elemente enthalten, die sie zu einer Schlüsselkomponente für ökologische Prozesse machen, da von ihnen die Bodenbe-schaffenheit und damit die Ökosysteme von Pflanzen und Tieren und damit auch das menschliche Wohlergehen abhängen. Sie sind auch für die Entwicklung und Regulierung des Klimas von wesentlicher Bedeutung, da Sedimentation im Meer als Kohlenstoffsenke fungieren kann. Allerdings können die Pro-zesse, die ihrer Produktion, Mobilisierung und Übertragung zugrunde liegen, bei hohem Energiegehalt plötzlich auftreten – wie Vulkanausbrüche, gravitative Massenbewegungen, Überschwemmungen und Waldbrände – und Ökosysteme erschüttern und Landschaften formen. Darüber hinaus hat die mensch-liche Spezies immer wieder gezeigt, dass sie die Landschaftsdynamik stören und Sedimentzyklen verän-dern kann. Daher besteht Bedarf, die beteiligten Prozesse auf eine Weise zu verstehen, die quantitative Vorhersagen erlaubt. Dies erfordert ein Verständnis der Physik wichtiger Prozesse, der Parameter, die sie bedingen, sowie Kenntnisse über den Zustand und die Entwicklung der Erdoberfläche. Zu den klassi-schen Ansätzen zur Bewältigung dieser Herausforderungen gehören empirische Beobachtungen und numerische Modellierung geochemischer Stoffflüsse und Oberflächenprozesse sowie die Untersuchung terrestrischer Sedimentarchive, um die Parameter, die bei Landschaftsdynamik und Klimaveränderun-gen eine Rolle spielen, sowie die unterschiedlichen Aktionen und Rückwirkungen zwischen Produktion, Mobilisierung, Transfer und Ablagerung von Sedimenten, die letztendlich Landschaften formen. Die Umweltseismologie ergänzt diese Ansätze. Umweltseismologie ist das wissenschaftliche Fachgebiet, das die Quellfunktionen und Ausbreitungsei-genschaften seismischer Schwingungen untersucht, die durch Prozesse an oder in der Nähe der Erd-oberfläche, darunter und darüber ausgelöst werden – zum Beispiel in der Kryosphäre, Hydrosphäre, Atmosphäre, dem menschlichen Lebensraum, der Biosphäre usw. –, um Einblicke in deren physikalische Prozesse zu gewinnen. All diese Prozesse erzeugen seismische Wellen, von Massenbewegungen bis hin zu Flüssen, von wild lebenden Tierarten bis hin zum Menschen. Die Umweltseismologie ist ein recht junges, schnell wachsendes Fachgebiet, mit Zweigen, die sich in unterschiedlichen Stadien des wissen-schaftlichen Fortschritts befinden. Ziel dieser Arbeit ist es, zwei große Naturgefahrenprozesse, Ge-schiebetransport in Flüssen und gravitative Massenbewegung, sowie über vom Menschen verursachte akustische Gefahren zu untersuchen. Gleichzeitig soll die Achse des grundlegenden Forschungsfort-schritts von der Datenexploration bis zur Methode und von der Theorieentwicklung bis zum Proof of Concept abgedeckt werden, mit dem doppelten Ziel ein besseres Verständnis für die Funktionsweise dieser spezifischen Prozesse zu entwickeln und die uns zur Verfügung stehenden Methoden zu ihrer Untersuchung weiterzuentwickeln. Zunächst stelle ich einen Maßstab für die Bewertung der Zuverlässigkeit der bestehenden seismischen Geschiebemodellinversion vor, um den Geschiebetrieb aus seismischen Daten abzuleiten. Messungen des Geschiebetriebs sind für ein besseres Verständnis der Flussdynamik unerlässlich, und dies kann mit der Umweltseismologie erreicht werden. Aufgrund des Mangels an streng eingeschränkten Validie-rungsdaten ist die Genauigkeit der resultierenden Inversionen jedoch unbekannt. Auf diese Lücke gehe ich in Kapitel 2.2 ein, wo ich über ein seismisches Feldexperiment berichte und die Ergebnisse mit hochwertigen unabhängigen Geschiebemessungen vergleiche, um ein seismisches Geschiebemodell einzugrenzen. Die Studie zeigt, dass die Qualität der Berechnungen der Geschiebetransportraten aus seismischen Daten stark von der Qualität der Eingabedaten für das Modell abhängt. Direkte Messungen relevanter Parameter, vor allem seismischer Bodeneigenschaften, die für die Green-Funktion benötigt werden, und der Korngrößenverteilung des bewegten Geschiebes, verbessern die Modellqualität erheb-lich gegenüber generischen Ansätzen, die empirische oder theoretische Funktionen verwenden. Ich stelle auch ein numerisches Werkzeug zur Verfügung, um die Verwendung von Modellen für Was-serturbulenzen und seismische Geschiebeinversion zu erleichtern: Seismische Modelle für Geschiebe-fluss und Wasserturbulenzen erfordern Sorgfalt, um Parameter, die die Bodeneigenschaften beschrei-ben, durch aktive seismische Untersuchungen oder passive seismische Analysen einzuschränken Daten und die Korngrößenverteilung über unabhängige Messungen. Vernünftige Vorhersagen können durch die Verwendung eines Monte-Carlo-Ansatzes zur Optimierung der freien Parameter im Hinblick auf die Zielparameter erzielt werden. Die Validierung des Werkzeugs in Kapitel 2.3 mit unabhängigen Messun-gen der Wassertiefe und des Geschiebeflusses an einem Untersuchungsstandort am Eshtemoa in Israel macht es für den zuverlässigen Einsatz an anderen Standorten verfügbar. Die in diesem Kapitel be-schriebene Arbeit wurde in Lagarde et al. 2021 und Dietze et al. 2019b veröffentlicht. In einer zweiten Studie, über die in Kapitel 3 berichtet wird, untersuche ich die Bildung einer Bruchflä-che vor einem Steinschlag. Ein besseres Verständnis der Dynamik der Vorbereitungsphase ist für die Bestimmung des Zeitpunkts, des Volumens und des Mobilisierungsmechanismus eines Felshangbruchs von entscheidender Bedeutung. Dies kann mit der Umweltseismologie erreicht werden. Ich nutze ein Netzwerk von seismischen Stationen in der Nähe eines instabilen Hangs, um die Signale von Rissen im Gestein vor dem Hangversagen aufzeichnen. Mittels einer auf Hidden-Markov-Modellen basierenden Technik des maschinellen Lernens werden diese Signale aus den seismischen Daten isoliert und so die kumulative Anzahl der Rissereignisse in den 20 Tagen vor einem großen Felssturz und den 10 Tagen danach aufgezeichnet. Der Verlauf der kumulierten Anzahl von Rissen verschiebt sich von einer eher linearen Form in den zwei Wochen vor dem Felssturz zu einer S-förmigen Entwicklung in den letzten 27 Stunden vor dem Versagen. Ich interpretiere diese Veränderung als einen Wechsel von anfänglicher verteilter Rissbildung zu lokalisierter Schadensakkumulation in den Stunden vor dem Ausfall. Ich ent-wickle ein einfaches physikalisches Modell, um die zeitliche Entwicklung der Rissaktivität während der S-Form-Phase zu erklären und die Bedeutung eines internen Parameters, der gesamten Rissgrenzenlän-ge, als dominanten Kontrollparameter für die Entwicklung der Versagensebene aufzuzeigen. Diese Stu-die wurde als Lagarde et al. 2023 veröffentlicht. Drittens entwickle ich ein Modell, das akustische Signale in seismische Signale umwandelt. Ein Teil der auf der Erdoberfläche erzeugten akustischen Schwingungen wird an der Erdoberfläche in seismische Signale umgewandelt. Infolgedessen kann die Lärmbelästigung zu Hangermüdung und Mikro- (oder Makro-)Brüchen des Gesteins führen, was zu Schäden an Landschaftsformen führen kann. Darüber hinaus kann diese Verschmutzung negative Auswirkungen haben, beispielsweise physische, physiologi-sche und psychologische Auswirkungen auf Tierarten. Derzeit ist es schwierig, die Auswirkungen seismi-scher Verschmutzung durch akustische Quellen abzuschätzen. In Kapitel 4 implementierte und verbes-sere ich ein Modell, das den von einer Quelle in der Atmosphäre erzeugten Schalldruck in das entspre-chende seismische Signal für einen Empfänger im Boden umwandelt. Der Boden gilt als poröses elasti-sches Medium, in dem das Wellenverhalten durch das Biot-Stoll-Modell angenähert werden kann. Das Modell wird erweitert, um einen zeitlichen Druckimpuls als Eingabe zu verwenden und eine Ausgabe auf einer planaren 2D-Karte zu erzeugen, auf der der Windeffekt auf die akustische und seismische Kopp-lung reproduziert werden kann. Ich investiere große Anstrengungen, um das Modell benutzerfreundlich zu gestalten, da das Projekt darauf abzielt, ein großes Publikum zu erreichen, das beispielsweise aus Geomorphologen, Biologen und Soziologen besteht. Abschließend wird das Modell einer synthetischen Prüfung sowie einem qualitativen Vergleich der vorhergesagten Bodenpartikelgeschwindigkeit und dem seismischen Signal eines realen Hubschrauberfluges als Quelle akustischer Eingaben unterzogen. Diese Studien verbessern das Verständnis der Funktionsweise spezifischer natürlicher Prozesse in Gerinnen und an Berghängen und bringen uns der Entwicklung funktionierender Frühwarnsysteme für Massenbewegungen und Überschwemmungen näher. Diese Arbeit wirft auch Fragen auf, die bisher nicht berücksichtigt wurden, wie zum Beispiel den Beitrag menschlicher Schallverschmutzung zum seismischen Brummen und seine Auswirkungen auf die natürliche Umwelt oder die Bedeutung von Ris-sen bei der Selbstentwicklung einer Versagensebene. Zusammengenommen stellen diese Studien all-gemeine Annahmen in Frage, die üblicherweise hinsichtlich der Auslösung von Massenverschwenbewe-gungen oder der Verbindung zwischen Hang und Gerinne gemacht werden. Darüber hinaus deckt die Dissertation die Achse des Fortschritts der Grundlagenforschung ab, von der Datenexploration über die Methoden- und Theorieentwicklung bis hin zum Proof of Concept, und zeigt, wie im sich schnell entwi-ckelnden Bereich der Umweltseismologie ein aktives Bewusstsein für den Fortschritt dazu beitragen kann, diesen zu stärken und den Fortschritt zu beschleunigen. KW - environmental seismology KW - bedload flux KW - mass wasting preparation phase KW - acoustic to seismic field KW - akustische zu seismischen Wellen KW - Geschiebetrieb KW - Umweltseismologie KW - Vorboten für Massenbewegungen Y1 - 2024 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-649136 ER - TY - JOUR A1 - Picozzi, Matteo A1 - Bindi, Dino A1 - Festa, Gaetano A1 - Cotton, Fabrice Pierre A1 - Scala, Antonio A1 - D'Agostino, Nicola T1 - Spatiotemporal evolution of microseismicity seismic source properties at the Irpinia Near-Fault Observatory, Southern Italy JF - Bulletin of the Seismological Society of America N2 - We estimate the source parameters of small-magnitude earthquakes that occurred during 2008-2020 in the Irpinia faults area (southern Italy). We apply a spectral decomposition approach to isolate the source contribution from propagation and site effects for similar to 3000 earthquakes in the local magnitude range between M-L 0 and 4.2. We develop our analyses in three steps. First, we fit the Brune (1970) model to the nonparametric source spectra to estimate corner frequency and seismic moment, and we map the spatial distribution of stress drop across the Irpinia area. We found stress drops in the range 0.4-8.1 MPa, with earthquakes deeper than 7 km characterized by higher average stress drop (i.e., 3.2 MPa). Second, assuming a simple stress-release model (kanamori and Heaton, 2000), we derive fracture energy and critical slip-weakening distance. The spatial variability of stress drop and fracture energy allows us to image the present stress conditions of fault segments activated during the 23 November 1980 M-s 6.9 earthquake. The variability of the source parameters shows clear patterns of the fault mechanical properties, suggesting that the Irpinia fault system can be divided into three main sectors, with the northern and southern ones showing different properties from the central one. Our results agree with previous studies indicating the presence of fluids with different composition in the different sectors of the Irpinia fault system. In the third step, we compare the time evolution of source parameters with a time series of geodetic displacement recorded near the fault system. Temporal trends in the correlation between geodetic displacement and different source parameters indicate that the poroelastic deformation perturbation generated by the karst aquifer recharge is modulating not only the occurrence rate of micro-seismicity ( D' Agostino et al., 2018) but may lead to rupture asperities with different sizes and characteristics. Y1 - 2021 U6 - https://doi.org/10.1785/0120210064 SN - 0037-1106 SN - 1943-3573 VL - 112 IS - 1 SP - 226 EP - 242 PB - Seismological Society of America CY - El Cerito, Calif. ER - TY - JOUR A1 - Eickenscheidt, Alice A1 - Lavaux, Valentine A1 - Paschke, Stefan A1 - Martinez Guajardo, Alejandro A1 - Schönemann, Eric A1 - Laschewsky, Andre A1 - Lienkamp, Karen A1 - Staszewski, Ori T1 - Effect of poly(oxanorbonene)- and poly(methacrylate)-based polyzwitterionic surface coatings on cell adhesion and gene expression of human keratinocytes JF - Macromolecular bioscience N2 - Polyzwitterions are generally known for their anti-adhesive properties, including resistance to protein and cell adhesion, and overall high bio-inertness. Yet there are a few polyzwitterions to which mammalian cells do adhere. To understand the structural features of this behavior, a panel of polyzwitterions with different functional groups and overall degrees of hydrophobicity is analyzed here, and their physical and biological properties are correlated to these structural differences. Cell adhesion is focused on, which is the basic requirement for cell viability, proliferation, and growth. With the here presented polyzwitterion panel, three different types of cell-surface interactions are observed: adhesion, slight attachment, and cell repellency. Using immunofluorescence methods, it is found that human keratinocytes (HaCaT) form focal adhesions on the cell-adhesive polyzwitterions, but not on the sample that has only slight cell attachment. Gene expression analysis indicates that HaCaT cells cultivated in the presence of a non-adhesive polyzwitterion have up-regulated inflammatory and apoptosis-related cell signaling pathways, while the gene expression of HaCaT cells grown on a cell-adhesive polyzwitterion does not differ from the gene expression of the growth control, and thus can be defined as fully cell-compatible. KW - cell compatibility KW - focal adhesion KW - gene expression KW - immune response KW - polyzwitterions Y1 - 2022 U6 - https://doi.org/10.1002/mabi.202200225 SN - 1616-5187 SN - 1616-5195 VL - 22 IS - 11 PB - Wiley-VCH CY - Weinheim ER - TY - GEN A1 - Ebers, Martin A1 - Hoch, Veronica R. S. A1 - Rosenkranz, Frank A1 - Ruschemeier, Hannah A1 - Steinrötter, Björn T1 - The European Commission’s proposal for an Artificial Intelligence Act BT - A critical assessment by members of the Robotics and AI Law Society (RAILS) T2 - Zweitveröffentlichungen der Universität Potsdam : Rechtswissenschaftliche Reihe N2 - On 21 April 2021, the European Commission presented its long-awaited proposal for a Regulation “laying down harmonized rules on Artificial Intelligence”, the so-called “Artificial Intelligence Act” (AIA). This article takes a critical look at the proposed regulation. After an introduction (1), the paper analyzes the unclear preemptive effect of the AIA and EU competences (2), the scope of application (3), the prohibited uses of Artificial Intelligence (AI) (4), the provisions on high-risk AI systems (5), the obligations of providers and users (6), the requirements for AI systems with limited risks (7), the enforcement system (8), the relationship of the AIA with the existing legal framework (9), and the regulatory gaps (10). The last section draws some final conclusions (11). T3 - Zweitveröffentlichungen der Universität Potsdam : Rechtswissenschaftliche Reihe - 8 KW - artificial intelligence KW - machine learning KW - European Union KW - regulation KW - harmonization KW - Artificial Intelligence Act Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-596824 IS - 8 ER -