@phdthesis{Kolk2019,
  author    = {Kolk, Jens},
  title     = {The long-term legacy of historical land cover changes},
  doi       = {10.25932/publishup-43939},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-439398},
  school      = {Universit{\"a}t Potsdam},
  pages     = {196},
  year      = {2019},
  abstract  = {Over the last years there is an increasing awareness that historical land cover changes and associated land use legacies may be important drivers for present-day species richness and biodiversity due to time-delayed extinctions or colonizations in response to historical environmental changes. Historically altered habitat patches may therefore exhibit an extinction debt or colonization credit and can be expected to lose or gain species in the future. However, extinction debts and colonization credits are difficult to detect and their actual magnitudes or payments have rarely been quantified because species richness patterns and dynamics are also shaped by recent environmental conditions and recent environmental changes. In this thesis we aimed to determine patterns of herb-layer species richness and recent species richness dynamics of forest herb layer plants and link those patterns and dynamics to historical land cover changes and associated land use legacies. The study was conducted in the Prignitz, NE-Germany, where the forest distribution remained stable for the last ca. 100 years but where a) the deciduous forest area had declined by more than 90 per cent (leaving only remnants of "ancient forests"), b) small new forests had been established on former agricultural land ("post-agricultural forests"). Here, we analyzed the relative importance of land use history and associated historical land cover changes for herb layer species richness compared to recent environmental factors and determined magnitudes of extinction debt and colonization credit and their payment in ancient and post-agricultural forests, respectively. We showed that present-day species richness patterns were still shaped by historical land cover changes that ranged back to more than a century. Although recent environmental conditions were largely comparable we found significantly more forest specialists, species with short-distance dispersal capabilities and clonals in ancient forests than in post-agricultural forests. Those species richness differences were largely contingent to a colonization credit in post-agricultural forests that ranged up to 9 species (average 4.7), while the extinction debt in ancient forests had almost completely been paid. Environmental legacies from historical agricultural land use played a minor role for species richness differences. Instead, patch connectivity was most important. Species richness in ancient forests was still dependent on historical connectivity, indicating a last glimpse of an extinction debt, and the colonization credit was highest in isolated post-agricultural forests. In post-agricultural forests that were better connected or directly adjacent to ancient forest patches the colonization credit was way smaller and we were able to verify a gradual payment of the colonization credit from 2.7 species to 1.5 species over the last six decades.},
  language  = {en}
}
@phdthesis{Trautmann2022,
  author    = {Trautmann, Tina},
  title     = {Understanding global water storage variations using model-data integration},
  doi       = {10.25932/publishup-56595},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-565954},
  school      = {Universit{\"a}t Potsdam},
  pages     = {VIII, 141},
  year      = {2022},
  abstract  = {Climate change is one of the greatest challenges to humanity in this century, and most noticeable consequences are expected to be impacts on the water cycle - in particular the distribution and availability of water, which is fundamental for all life on Earth. In this context, it is essential to better understand where and when water is available and what processes influence variations in water storages. While estimates of the overall terrestrial water storage (TWS) variations are available from the GRACE satellites, these represent the vertically integrated signal over all water stored in ice, snow, soil moisture, groundwater and surface water bodies. Therefore, complementary observational data and hydrological models are still required to determine the partitioning of the measured signal among different water storages and to understand the underlying processes. However, the application of large-scale observational data is limited by their specific uncertainties and the incapacity to measure certain water fluxes and storages. Hydrological models, on the other hand, vary widely in their structure and process-representation, and rarely incorporate additional observational data to minimize uncertainties that arise from their simplified representation of the complex hydrologic cycle. In this context, this thesis aims to contribute to improving the understanding of global water storage variability by combining simple hydrological models with a variety of complementary Earth observation-based data. To this end, a model-data integration approach is developed, in which the parameters of a parsimonious hydrological model are calibrated against several observational constraints, inducing GRACE TWS, simultaneously, while taking into account each data's specific strengths and uncertainties. This approach is used to investigate 3 specific aspects that are relevant for modelling and understanding the composition of large-scale TWS variations. The first study focusses on Northern latitudes, where snow and cold-region processes define the hydrological cycle. While the study confirms previous findings that seasonal dynamics of TWS are dominated by the cyclic accumulation and melt of snow, it reveals that inter-annual TWS variations on the contrary, are determined by variations in liquid water storages. Additionally, it is found to be important to consider the impact of compensatory effects of spatially heterogeneous hydrological variables when aggregating the contribution of different storage components over large areas. Hence, the determinants of TWS variations are scale-dependent and underlying driving mechanism cannot be simply transferred between spatial and temporal scales. These findings are supported by the second study for the global land areas beyond the Northern latitudes as well. This second study further identifies the considerable impact of how vegetation is represented in hydrological models on the partitioning of TWS variations. Using spatio-temporal varying fields of Earth observation-based data to parameterize vegetation activity not only significantly improves model performance, but also reduces parameter equifinality and process uncertainties. Moreover, the representation of vegetation drastically changes the contribution of different water storages to overall TWS variability, emphasizing the key role of vegetation for water allocation, especially between sub-surface and delayed water storages. However, the study also identifies parameter equifinality regarding the decay of sub-surface and delayed water storages by either evapotranspiration or runoff, and thus emphasizes the need for further constraints hereof. The third study focuses on the role of river water storage, in particular whether it is necessary to include computationally expensive river routing for model calibration and validation against the integrated GRACE TWS. The results suggest that river routing is not required for model calibration in such a global model-data integration approach, due to the larger influence other observational constraints, and the determinability of certain model parameters and associated processes are identified as issues of greater relevance. In contrast to model calibration, considering river water storage derived from routing schemes can already significantly improve modelled TWS compared to GRACE observations, and thus should be considered for model evaluation against GRACE data. Beyond these specific findings that contribute to improved understanding and modelling of large-scale TWS variations, this thesis demonstrates the potential of combining simple modeling approaches with diverse Earth observational data to improve model simulations, overcome inconsistencies of different observational data sets, and identify areas that require further research. These findings encourage future efforts to take advantage of the increasing number of diverse global observational data.},
  language  = {en}
}
@phdthesis{Brenner2022,
  author    = {Brenner, Andri Caspar},
  title     = {Sustainable urban growth},
  doi       = {10.25932/publishup-55522},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-555223},
  school      = {Universit{\"a}t Potsdam},
  pages     = {231},
  year      = {2022},
  abstract  = {This dissertation explores the determinants for sustainable and socially optimalgrowth in a city. Two general equilibrium models establish the base for this evaluation, each adding its puzzle piece to the urban sustainability discourse and examining the role of non-market-based and market-based policies for balanced growth and welfare improvements in different theory settings. Sustainable urban growth either calls for policy actions or a green energy transition. Further, R\&D market failures can pose severe challenges to the sustainability of urban growth and the social optimality of decentralized allocation decisions. Still, a careful (holistic) combination of policy instruments can achieve sustainable growth and even be first best.},
  language  = {en}
}
@phdthesis{Neuendorf2022,
  author    = {Neuendorf, Claudia},
  title     = {Leistungsstarke Sch{\"u}lerinnen und Sch{\"u}ler in Deutschland},
  doi       = {10.25932/publishup-56470},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-564702},
  school      = {Universit{\"a}t Potsdam},
  pages     = {203},
  year      = {2022},
  abstract  = {Die vorliegende kumulative Promotionsarbeit besch{\"a}ftigt sich mit leistungsstarken Sch{\"u}lerinnen und Sch{\"u}lern, die seit 2015 in der deutschen Bildungspolitik, zum Beispiel im Rahmen von F{\"o}rderprogrammen wieder mehr Raum einnehmen, nachdem in Folge des „PISA-Schocks" im Jahr 2000 zun{\"a}chst der Fokus st{\"a}rker auf den Risikogruppen lag. W{\"a}hrend leistungsst{\"a}rkere Sch{\"u}lerinnen und Sch{\"u}ler in der {\"o}ffentlichen Wahrnehmung h{\"a}ufig mit „(Hoch-)Begabten" identifiziert werden, geht die Arbeit {\"u}ber die traditionelle Begabungsforschung, die eine generelle Intelligenz als Grundlage f{\"u}r Leistungsf{\"a}higkeit von Sch{\"u}lerinnen und Sch{\"u}lern begreift und beforscht, hinaus. Stattdessen l{\"a}sst sich eher in den Bereich der Talentforschung einordnen, die den Fokus weg von allgemeinen Begabungen auf spezifische Pr{\"a}diktoren und Outcomes im individuellen Entwicklungsverlauf legt. Der Fokus der Arbeit liegt daher nicht auf Intelligenz als Potenzial, sondern auf der aktuellen schulischen Leistung, die als Ergebnis und Ausgangspunkt von Entwicklungsprozessen in einer Leistungsdom{\"a}ne doppelte Bedeutung erh{\"a}lt. Die Arbeit erkennt die Vielgestaltigkeit des Leistungsbegriffs an und ist bestrebt, neue Anl{\"a}sse zu schaffen, {\"u}ber den Leistungsbegriff und seine Operationalisierung in der Forschung zu diskutieren. Hierf{\"u}r wird im ersten Teil ein systematisches Review zur Operationalisierung von Leistungsst{\"a}rke durchgef{\"u}hrt (Artikel I). Es werden Faktoren herausgearbeitet, auf welchen sich die Operationalisierungen unterscheiden k{\"o}nnen. Weiterhin wird ein {\"U}berblick gegeben, wie Studien zu Leistungsstarken sich seit dem Jahr 2000 auf diesen Dimensionen verorten lassen. Es zeigt sich, dass eindeutige Konventionen zur Definition schulischer Leistungsst{\"a}rke noch nicht existieren, woraus folgt, dass Ergebnisse aus Studien, die sich mit leistungsstarken Sch{\"u}lerinnen und Sch{\"u}lern besch{\"a}ftigen, nur bedingt miteinander vergleichbar sind. Im zweiten Teil der Arbeit wird im Rahmen zwei weiterer Artikel, welche sich mit der Leistungsentwicklung (Artikel II) und der sozialen Einbindung (Artikel III) von leistungsstarken Sch{\"u}lerinnen und Sch{\"u}lern befassen, darauf aufbauend der Ansatz verfolgt, die Variabilit{\"a}t von Ergebnissen {\"u}ber verschiedene Operationalisierungen von Leistungsst{\"a}rke deutlich zu machen. Damit wird unter anderem auch die k{\"u}nftige Vergleichbarkeit mit anderen Studien erleichtert. Genutzt wird dabei das Konzept der Multiversumsanalyse (Steegen et al., 2016), bei welcher viele parallele Spezifikationen, die zugleich sinnvolle Alternativen f{\"u}r die Operationalisierung darstellen, nebeneinandergestellt und in ihrem Effekt verglichen werden (Jansen et al., 2021). Die Multiversumsanalyse kn{\"u}pft konzeptuell an das bereits vor l{\"a}ngerem entwickelte Forschungsprogramm des kritischen Multiplismus an (Patry, 2013; Shadish, 1986, 1993), erh{\"a}lt aber als spezifische Methode aktuell im Rahmen der Replizierbarkeitskrise in der Psychologie eine besondere Bedeutung. Dabei st{\"u}tzt sich die vorliegende Arbeit auf die Sekund{\"a}ranalyse großangelegter Schulleistungsstudien, welche den Vorteil besitzen, dass eine große Zahl an Datenpunkten (Variablen und Personen) zur Verf{\"u}gung steht, um Effekte unterschiedlicher Operationalisierungen zu vergleichen. Inhaltlich greifen Artikel II und III Themen auf, die in der wissenschaftlichen und gesellschaftlichen Diskussion zu Leistungsstarken und ihrer Wahrnehmung in der {\"O}ffentlichkeit immer wieder aufscheinen: In Artikel II wird zun{\"a}chst die Frage gestellt, ob Leistungsstarke bereits im aktuellen Regelunterricht einen kumulativen Vorteil gegen{\"u}ber ihren weniger leistungsstarken Mitsch{\"u}lerinnen und Mitsch{\"u}lern haben (Matth{\"a}us-Effekt). Die Ergebnisse zeigen, dass an Gymnasien keineswegs von sich vergr{\"o}ßernden Unterschieden gesprochen werden kann. Im Gegenteil, es verringerte sich im Laufe der Sekundarstufe der Abstand zwischen den Gruppen, indem die Lernraten bei leistungsschw{\"a}cheren Sch{\"u}lerinnen und Sch{\"u}lern h{\"o}her waren. Artikel III hingegen betrifft die soziale Wahrnehmung von leistungsstarken Sch{\"u}lerinnen und Sch{\"u}lern. Auch hier h{\"a}lt sich in der {\"o}ffentlichen Diskussion die Annahme, dass h{\"o}here Leistungen mit Nachteilen in der sozialen Integration einhergehen k{\"o}nnten, was sich auch in Studien widerspiegelt, die sich mit Geschlechterstereotypen Jugendlicher in Bezug auf Schulleistung besch{\"a}ftigen. In Artikel III wird unter anderem erneut das Potenzial der Multiversumsanalyse genutzt, um die Variation des Zusammenhangs {\"u}ber Operationalisierungen von Leistungsst{\"a}rke zu beschreiben. Es zeigt sich unter unterschiedlichen Operationalisierungen von Leistungsst{\"a}rke und {\"u}ber verschiedene Facetten sozialer Integration hinweg, dass die Zusammenh{\"a}nge zwischen Leistung und sozialer Integration insgesamt leicht positiv ausfallen. Annahmen, die auf differenzielle Effekte f{\"u}r Jungen und M{\"a}dchen oder f{\"u}r unterschiedliche F{\"a}cher abzielen, finden in diesen Analysen keine Best{\"a}tigung. Die Dissertation zeigt, dass der Vergleich unterschiedlicher Ans{\"a}tze zur Operationalisierung von Leistungsst{\"a}rke — eingesetzt im Rahmen eines kritischen Multiplismus — das Verst{\"a}ndnis von Ph{\"a}nomenen vertiefen kann und auch das Potenzial hat, Theorieentwicklung voranzubringen.},
  language  = {de}
}
@phdthesis{Forster2021,
  author    = {Forster, Florian},
  title     = {Continuous microgravity monitoring of the Þeistareykir geothermal field (North Iceland)},
  doi       = {10.25932/publishup-54851},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-548517},
  school      = {Universit{\"a}t Potsdam},
  pages     = {XVII, 164},
  year      = {2021},
  abstract  = {In my doctoral thesis, I examine continuous gravity measurements for monitoring of the geothermal site at Þeistareykir in North Iceland. With the help of high-precision superconducting gravity meters (iGravs), I investigate underground mass changes that are caused by operation of the geothermal power plant (i.e. by extraction of hot water and reinjection of cold water). The overall goal of this research project is to make a statement about the sustainable use of the geothermal reservoir, from which also the Icelandic energy supplier and power plant operator Landsvirkjun should benefit. As a first step, for investigating the performance and measurement stability of the gravity meters, in summer 2017, I performed comparative measurements at the gravimetric observatory J9 in Strasbourg. From the three-month gravity time series, I examined calibration, noise and drift behaviour of the iGravs in comparison to stable long-term time series of the observatory superconducting gravity meters. After preparatory work in Iceland (setup of gravity stations, additional measuring equipment and infrastructure, discussions with Landsvirkjun and meetings with the Icelandic partner institute ISOR), gravity monitoring at Þeistareykir was started in December 2017. With the help of the iGrav records of the initial 18 months after start of measurements, I carried out the same investigations (on calibration, noise and drift behaviour) as in J9 to understand how the transport of the superconducting gravity meters to Iceland may influence instrumental parameters. In the further course of this work, I focus on modelling and reduction of local gravity contributions at Þeistareykir. These comprise additional mass changes due to rain, snowfall and vertical surface displacements that superimpose onto the geothermal signal of the gravity measurements. For this purpose, I used data sets from additional monitoring sensors that are installed at each gravity station and adapted scripts for hydro-gravitational modelling. The third part of my thesis targets geothermal signals in the gravity measurements. Together with my PhD colleague Nolwenn Portier from France, I carried out additional gravity measurements with a Scintrex CG5 gravity meter at 26 measuring points within the geothermal field in the summers of 2017, 2018 and 2019. These annual time-lapse gravity measurements are intended to increase the spatial coverage of gravity data from the three continuous monitoring stations to the entire geothermal field. The combination of CG5 and iGrav observations, as well as annual reference measurements with an FG5 absolute gravity meter represent the hybrid gravimetric monitoring method for Þeistareykir. Comparison of the gravimetric data to local borehole measurements (of groundwater levels, geothermal extraction and injection rates) is used to relate the observed gravity changes to the actually extracted (and reinjected) geothermal fluids. An approach to explain the observed gravity signals by means of forward modelling of the geothermal production rate is presented at the end of the third (hybrid gravimetric) study. Further modelling with the help of the processed gravity data is planned by Landsvirkjun. In addition, the experience from time-lapse and continuous gravity monitoring will be used for future gravity measurements at the Krafla geothermal field 22 km south-east of Þeistareykir.},
  language  = {en}
}
@phdthesis{Farkas2022,
  author    = {Farkas, Marton Pal},
  title     = {Hydraulic fracturing in hard rock - numerical studies from laboratory to reservoir scale},
  doi       = {10.25932/publishup-54934},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-549343},
  school      = {Universit{\"a}t Potsdam},
  pages     = {155},
  year      = {2022},
  abstract  = {Hydraulic-driven fractures play a key role in subsurface energy technologies across several scales. By injecting fluid at high hydraulic pressure into rock with intrinsic low permeability, in-situ stress field and fracture development pattern can be characterised as well as rock permeability can be enhanced. Hydraulic fracturing is a commercial standard procedure for enhanced oil and gas production of rock reservoirs with low permeability in petroleum industry. However, in EGS utilization, a major geological concern is the unsolicited generation of earthquakes due to fault reactivation, referred to as induced seismicity, with a magnitude large enough to be felt on the surface or to damage facilities and buildings. Furthermore, reliable interpretation of hydraulic fracturing tests for stress measurement is a great challenge for the energy technologies. Therefore, in this cumulative doctoral thesis the following research questions are investigated. (1): How do hydraulic fractures grow in hard rock at various scales?; (2): Which parameters control hydraulic fracturing and hydro-mechanical coupling?; and (3): How can hydraulic fracturing in hard rock be modelled? In the laboratory scale study, several laboratory hydraulic fracturing experiments are investigated numerically using Irazu2D that were performed on intact cubic Pocheon granite samples from South Korea applying different injection protocols. The goal of the laboratory experiments is to test the concept of cyclic soft stimulation which may enable sustainable permeability enhancement (Publication 1). In the borehole scale study, hydraulic fracturing tests are reported that were performed in boreholes located in central Hungary to determine the in-situ stress for a geological site investigation. At depth of about 540 m, the recorded pressure versus time curves in mica schist with low dip angle foliation show atypical evolution. In order to provide explanation for this observation, a series of discrete element computations using Particle Flow Code 2D are performed (Publication 2). In the reservoir scale study, the hydro-mechanical behaviour of fractured crystalline rock due to one of the five hydraulic stimulations at the Pohang Enhanced Geothermal site in South Korea is studied. Fluid pressure perturbation at faults of several hundred-meter lengths during hydraulic stimulation is simulated using FracMan (Publication 3). The doctoral research shows that the resulting hydraulic fracturing geometry will depend "locally", i.e. at the length scale of representative elementary volume (REV) and below that (sub-REV), on the geometry and strength of natural fractures, and "globally", i.e. at super-REV domain volume, on far-field stresses. Regarding hydro-mechanical coupling, it is suggested to define separate coupling relationship for intact rock mass and natural fractures. Furthermore, the relative importance of parameters affecting the magnitude of formation breakdown pressure, a parameter characterising hydro-mechanical coupling, is defined. It can be also concluded that there is a clear gap between the capacity of the simulation software and the complexity of the studied problems. Therefore, the computational time of the simulation of complex hydraulic fracture geometries must be reduced while maintaining high fidelity simulation results. This can be achieved either by extending the computational resources via parallelization techniques or using time scaling techniques. The ongoing development of used numerical models focuses on tackling these methodological challenges.},
  language  = {en}
}
@phdthesis{MbayaMani2017,
  author    = {Mbaya Mani, Christian},
  title     = {Functional nanoporous carbon-based materials derived from oxocarbon-metal coordination complexes},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-407866},
  school      = {Universit{\"a}t Potsdam},
  pages     = {IV, 135},
  year      = {2017},
  abstract  = {Nanoporous carbon based materials are of particular interest for both science and industry due to their exceptional properties such as a large surface area, high pore volume, high electroconductivity as well as high chemical and thermal stability. Benefiting from these advantageous properties, nanoporous carbons proved to be useful in various energy and environment related applications including energy storage and conversion, catalysis, gas sorption and separation technologies. The synthesis of nanoporous carbons classically involves thermal carbonization of the carbon precursors (e.g. phenolic resins, polyacrylonitrile, poly(vinyl alcohol) etc.) followed by an activation step and/or it makes use of classical hard or soft templates to obtain well-defined porous structures. However, these synthesis strategies are complicated and costly; and make use of hazardous chemicals, hindering their application for large-scale production. Furthermore, control over the carbon materials properties is challenging owing to the relatively unpredictable processes at the high carbonization temperatures. In the present thesis, nanoporous carbon based materials are prepared by the direct heat treatment of crystalline precursor materials with pre-defined properties. This synthesis strategy does not require any additional carbon sources or classical hard- or soft templates. The highly stable and porous crystalline precursors are based on coordination compounds of the squarate and croconate ions with various divalent metal ions including Zn2+, Cu2+, Ni2+, and Co2+, respectively. Here, the structural properties of the crystals can be controlled by the choice of appropriate synthesis conditions such as the crystal aging temperature, the ligand/metal molar ratio, the metal ion, and the organic ligand system. In this context, the coordination of the squarate ions to Zn2+ yields porous 3D cube crystalline particles. The morphology of the cubes can be tuned from densely packed cubes with a smooth surface to cubes with intriguing micrometer-sized openings and voids which evolve on the centers of the low index faces as the crystal aging temperature is raised. By varying the molar ratio, the particle shape can be changed from truncated cubes to perfect cubes with right-angled edges. These crystalline precursors can be easily transformed into the respective carbon based materials by heat treatment at elevated temperatures in a nitrogen atmosphere followed by a facile washing step. The resulting carbons are obtained in good yields and possess a hierarchical pore structure with well-organized and interconnected micro-, meso- and macropores. Moreover, high surface areas and large pore volumes of up to 1957 m2 g-1 and 2.31 cm3 g-1 are achieved, respectively, whereby the macroscopic structure of the precursors is preserved throughout the whole synthesis procedure. Owing to these advantageous properties, the resulting carbon based materials represent promising supercapacitor electrode materials for energy storage applications. This is exemplarily demonstrated by employing the 3D hierarchical porous carbon cubes derived from squarate-zinc coordination compounds as electrode material showing a specific capacitance of 133 F g-1 in H2SO4 at a scan rate of 5 mV s-1 and retaining 67\% of this specific capacitance when the scan rate is increased to 200 mV s-1. In a further application, the porous carbon cubes derived from squarate-zinc coordination compounds are used as high surface area support material and decorated with nickel nanoparticles via an incipient wetness impregnation. The resulting composite material combines a high surface area, a hierarchical pore structure with high functionality and well-accessible pores. Moreover, owing to their regular micro-cube shape, they allow for a good packing of a fixed-bed flow reactor along with high column efficiency and a minimized pressure drop throughout the packed reactor. Therefore, the composite is employed as heterogeneous catalyst in the selective hydrogenation of 5-hydroxymethylfurfural to 2,5-dimethylfuran showing good catalytic performance and overcoming the conventional problem of column blocking. Thinking about the rational design of 3D carbon geometries, the functions and properties of the resulting carbon-based materials can be further expanded by the rational introduction of heteroatoms (e.g. N, B, S, P, etc.) into the carbon structures in order to alter properties such as wettability, surface polarity as well as the electrochemical landscape. In this context, the use of crystalline materials based on oxocarbon-metal ion complexes can open a platform of highly functional materials for all processes that involve surface processes.},
  language  = {en}
}
@phdthesis{Schmitz2023,
  author    = {Schmitz, Se{\´a}n},
  title     = {Using low-cost sensors to gather high resolution measurements of air quality in urban environments and inform mobility policy},
  doi       = {10.25932/publishup-60105},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-601053},
  school      = {Universit{\"a}t Potsdam},
  pages     = {180},
  year      = {2023},
  abstract  = {Air pollution has been a persistent global problem in the past several hundred years. While some industrialized nations have shown improvements in their air quality through stricter regulation, others have experienced declines as they rapidly industrialize. The WHO's 2021 update of their recommended air pollution limit values reflects the substantial impacts on human health of pollutants such as NO2 and O3, as recent epidemiological evidence suggests substantial long-term health impacts of air pollution even at low concentrations. Alongside developments in our understanding of air pollution's health impacts, the new technology of low-cost sensors (LCS) has been taken up by both academia and industry as a new method for measuring air pollution. Due primarily to their lower cost and smaller size, they can be used in a variety of different applications, including in the development of higher resolution measurement networks, in source identification, and in measurements of air pollution exposure. While significant efforts have been made to accurately calibrate LCS with reference instrumentation and various statistical models, accuracy and precision remain limited by variable sensor sensitivity. Furthermore, standard procedures for calibration still do not exist and most proprietary calibration algorithms are black-box, inaccessible to the public. This work seeks to expand the knowledge base on LCS in several different ways: 1) by developing an open-source calibration methodology; 2) by deploying LCS at high spatial resolution in urban environments to test their capability in measuring microscale changes in urban air pollution; 3) by connecting LCS deployments with the implementation of local mobility policies to provide policy advice on resultant changes in air quality. In a first step, it was found that LCS can be consistently calibrated with good performance against reference instrumentation using seven general steps: 1) assessing raw data distribution, 2) cleaning data, 3) flagging data, 4) model selection and tuning, 5) model validation, 6) exporting final predictions, and 7) calculating associated uncertainty. By emphasizing the need for consistent reporting of details at each step, most crucially on model selection, validation, and performance, this work pushed forward with the effort towards standardization of calibration methodologies. In addition, with the open-source publication of code and data for the seven-step methodology, advances were made towards reforming the largely black-box nature of LCS calibrations. With a transparent and reliable calibration methodology established, LCS were then deployed in various street canyons between 2017 and 2020. Using two types of LCS, metal oxide (MOS) and electrochemical (EC), their performance in capturing expected patterns of urban NO2 and O3 pollution was evaluated. Results showed that calibrated concentrations from MOS and EC sensors matched general diurnal patterns in NO2 and O3 pollution measured using reference instruments. While MOS proved to be unreliable for discerning differences among measured locations within the urban environment, the concentrations measured with calibrated EC sensors matched expectations from modelling studies on NO2 and O3 pollution distribution in street canyons. As such, it was concluded that LCS are appropriate for measuring urban air quality, including for assisting urban-scale air pollution model development, and can reveal new insights into air pollution in urban environments. To achieve the last goal of this work, two measurement campaigns were conducted in connection with the implementation of three mobility policies in Berlin. The first involved the construction of a pop-up bike lane on Kottbusser Damm in response to the COVID-19 pandemic, the second surrounded the temporary implementation of a community space on B{\"o}ckhstrasse, and the last was focused on the closure of a portion of Friedrichstrasse to all motorized traffic. In all cases, measurements of NO2 were collected before and after the measure was implemented to assess changes in air quality resultant from these policies. Results from the Kottbusser Damm experiment showed that the bike-lane reduced NO2 concentrations that cyclists were exposed to by 22 ± 19\%. On Friedrichstrasse, the street closure reduced NO2 concentrations to the level of the urban background without worsening the air quality on side streets. These valuable results were communicated swiftly to partners in the city administration responsible for evaluating the policies' success and future, highlighting the ability of LCS to provide policy-relevant results. As a new technology, much is still to be learned about LCS and their value to academic research in the atmospheric sciences. Nevertheless, this work has advanced the state of the art in several ways. First, it contributed a novel open-source calibration methodology that can be used by a LCS end-users for various air pollutants. Second, it strengthened the evidence base on the reliability of LCS for measuring urban air quality, finding through novel deployments in street canyons that LCS can be used at high spatial resolution to understand microscale air pollution dynamics. Last, it is the first of its kind to connect LCS measurements directly with mobility policies to understand their influences on local air quality, resulting in policy-relevant findings valuable for decisionmakers. It serves as an example of the potential for LCS to expand our understanding of air pollution at various scales, as well as their ability to serve as valuable tools in transdisciplinary research.},
  language  = {en}
}
@phdthesis{Behm2019,
  author    = {Behm, Laura Vera Johanna},
  title     = {Thermoresponsive Zellkultursubstrate f{\"u}r zeitlich-r{\"a}umlich gesteuertes Auswachsen neuronaler Zellen},
  doi       = {10.25932/publishup-43619},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-436196},
  school      = {Universit{\"a}t Potsdam},
  pages     = {VII, 105},
  year      = {2019},
  abstract  = {Ein wichtiges Ziel der Neurowissenschaften ist das Verst{\"a}ndnis der komplexen und zugleich faszinierenden, hochgeordneten Vernetzung der Neurone im Gehirn, welche neuronalen Prozessen, wie zum Beispiel dem Wahrnehmen oder Lernen wie auch Neuropathologien zu Grunde liegt. F{\"u}r verbesserte neuronale Zellkulturmodelle zur detaillierten Untersuchung dieser Prozesse ist daher die Rekonstruktion von geordneten neuronalen Verbindungen dringend erforderlich. Mit Oberfl{\"a}chenstrukturen aus zellattraktiven und zellabweisenden Beschichtungen k{\"o}nnen neuronale Zellen und ihre Neuriten in vitro strukturiert werden. Zur Kontrolle der neuronalen Verbindungsrichtung muss das Auswachsen der Axone zu benachbarten Zellen dynamisch gesteuert werden, zum Beispiel {\"u}ber eine ver{\"a}nderliche Zug{\"a}nglichkeit der Oberfl{\"a}che. In dieser Arbeit wurde untersucht, ob mit thermoresponsiven Polymeren (TRP) beschichtete Zellkultursubstrate f{\"u}r eine dynamische Kontrolle des Auswachsens neuronaler Zellen geeignet sind. TRP k{\"o}nnen {\"u}ber die Temperatur von einem zellabweisenden in einen zellattraktiven Zustand geschaltet werden, womit die Zug{\"a}nglichkeit der Oberfl{\"a}che f{\"u}r Zellen dynamisch gesteuert werden kann. Die TRP-Beschichtung wurde mikrostrukturiert, um einzelne oder wenige neuronale Zellen zun{\"a}chst auf der Oberfl{\"a}che anzuordnen und das Auswachsen der Zellen und Neuriten {\"u}ber definierte TRP-Bereiche in Abh{\"a}ngigkeit der Temperatur zeitlich und r{\"a}umlich zu kontrollieren. Das Protokoll wurde mit der neuronalen Zelllinie SH-SY5Y etabliert und auf humane induzierte Neurone {\"u}bertragen. Die Anordnung der Zellen konnte bei Kultivierung im zellabweisenden Zustand des TRPs f{\"u}r bis zu 7 Tage aufrecht erhalten werden. Durch Schalten des TRPs in den zellattraktiven Zustand konnte das Auswachsen der Neuriten und Zellen zeitlich und r{\"a}umlich induziert werden. Immunozytochemische F{\"a}rbungen und Patch-Clamp-Ableitungen der Neurone demonstrierten die einfache Anwendbarkeit und Zellkompatibilit{\"a}t der TRP-Substrate. Eine pr{\"a}zisere r{\"a}umliche Kontrolle des Auswachsens der Zellen sollte durch lokales Schalten der TRP-Beschichtung erreicht werden. Daf{\"u}r wurden Mikroheizchips mit Mikroelektroden zur lokalen Jouleschen Erw{\"a}rmung der Substratoberfl{\"a}che entwickelt. Zur Evaluierung der generierten Temperaturprofile wurde eine Temperaturmessmethode entwickelt und die erhobenen Messwerte mit numerisch simulierten Werten abgeglichen. Die Temperaturmessmethode basiert auf einfach zu applizierenden Sol-Gel-Schichten, die den temperatursensitiven Fluoreszenzfarbstoff Rhodamin B enthalten. Sie erm{\"o}glicht oberfl{\"a}chennahe Temperaturmessungen in trockener und w{\"a}ssriger Umgebung mit hoher Orts- und Temperaturaufl{\"o}sung. Numerische Simulationen der Temperaturprofile korrelierten gut mit den experimentellen Daten. Auf dieser Basis konnten Geometrie und Material der Mikroelektroden hinsichtlich einer lokal stark begrenzten Temperierung optimiert werden. Ferner wurden f{\"u}r die Kultvierung der Zellen auf den Mikroheizchips eine Zellkulturkammer und Kontaktboard f{\"u}r die elektrische Kontaktierung der Mikroelektroden geschaffen. Die vorgestellten Ergebnisse demonstrieren erstmalig das enorme Potential thermoresponsiver Zellkultursubstrate f{\"u}r die zeitlich und r{\"a}umlich gesteuerte Formation geordneter neuronaler Verbindungen in vitro. Zuk{\"u}nftig k{\"o}nnte dies detaillierte Studien zur neuronalen Informationsverarbeitung oder zu Neuropathologien an relevanten, humanen Zellmodellen erm{\"o}glichen.},
  language  = {de}
}
@phdthesis{Paganini2018,
  author    = {Paganini, Claudio Francesco},
  title     = {The role of trapping in black hole spacetimes},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-414686},
  school      = {Universit{\"a}t Potsdam},
  pages     = {v, 138},
  year      = {2018},
  abstract  = {In the here presented work we discuss a series of results that are all in one way or another connected to the phenomenon of trapping in black hole spacetimes. First we present a comprehensive review of the Kerr-Newman-Taub-NUT-de-Sitter family of black hole spacetimes and their most important properties. From there we go into a detailed analysis of the bahaviour of null geodesics in the exterior region of a sub-extremal Kerr spacetime. We show that most well known fundamental properties of null geodesics can be represented in one plot. In particular, one can see immediately that the ergoregion and trapping are separated in phase space. We then consider the sets of future/past trapped null geodesics in the exterior region of a sub-extremal Kerr-Newman-Taub-NUT spacetime. We show that from the point of view of any timelike observer outside of such a black hole, trapping can be understood as two smooth sets of spacelike directions on the celestial sphere of the observer. Therefore the topological structure of the trapped set on the celestial sphere of any observer is identical to that in Schwarzschild. We discuss how this is relevant to the black hole stability problem. In a further development of these observations we introduce the notion of what it means for the shadow of two observers to be degenerate. We show that, away from the axis of symmetry, no continuous degeneration exists between the shadows of observers at any point in the exterior region of any Kerr-Newman black hole spacetime of unit mass. Therefore, except possibly for discrete changes, an observer can, by measuring the black holes shadow, determine the angular momentum and the charge of the black hole under observation, as well as the observer's radial position and angle of elevation above the equatorial plane. Furthermore, his/her relative velocity compared to a standard observer can also be measured. On the other hand, the black hole shadow does not allow for a full parameter resolution in the case of a Kerr-Newman-Taub-NUT black hole, as a continuous degeneration relating specific angular momentum, electric charge, NUT charge and elevation angle exists in this case. We then use the celestial sphere to show that trapping is a generic feature of any black hole spacetime. In the last chapter we then prove a generalization of the mode stability result of Whiting (1989) for the Teukolsky equation for the case of real frequencies. The main result of the last chapter states that a separated solution of the Teukolsky equation governing massless test fields on the Kerr spacetime, which is purely outgoing at infinity, and purely ingoing at the horizon, must vanish. This has the consequence, that for real frequencies, there are linearly independent fundamental solutions of the radial Teukolsky equation which are purely ingoing at the horizon, and purely outgoing at infinity, respectively. This fact yields a representation formula for solutions of the inhomogenous Teukolsky equation, and was recently used by Shlapentokh-Rothman (2015) for the scalar wave equation.},
  language  = {en}
}