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The computational analysis and the optimization of transport and mixing processes in fluid flows are of ongoing scientific interest. Transfer operator methods are powerful tools for the study of these processes in dynamical systems. The focus in this context has been mostly on closed dynamical systems and the main applications have been geophysical flows. In this thesis, the authors consider transport and mixing in closed flow systems and in open flow systems that mimic technical mixing devices. Via transfer operator methods, They study the coherent behavior in closed example systems including a turbulent Rayleigh-Bénard convection flow and consider the finite-time mixing of two fluids. They extend the transfer operator framework to specific open flows. In particular, they study time-periodic open flow systems with constant inflow and outflow of fluid particles and consider several example systems. In this case, the transfer operator is represented by a transition matrix of a time-homogeneous absorbing Markov chain restricted to finite transient states. The chaotic saddle and its stable and unstable manifolds organize the transport processes in open systems. The authors extract these structures directly from leading eigenvectors of the transition matrix. For a constant source of two fluids in different colors, the mass distribution in the mixer and its outlet region converges to an invariant mixing pattern. In parameter studies, they quantify the degree of mixing of the resulting patterns by several mixing measures. More recently, network-based methods that construct graphs on trajectories of fluid particles have been developed to study coherent behavior in fluid flow. They use a method based on diffusion maps to extract organizing structures in open example systems directly from trajectories of fluid particles and extend this method to describe the mixing of two types of fluids.
This thesis aims to contribute to a better understanding of the actual implementation of transdisciplinary research in sustainability science. Following three aims, this work likes to (1) contribute to the measurability of transdisciplinary research processes as well as their societal and academic outputs and impacts, to (2) demarcate transdisciplinary research from other modes of research in sustainability science and to (3) identify and examine the determinants that shape the contribution of transdisciplinary research to societal action for sustainable development and to scientific knowledge production. To serve these aims a mixed methods approach is applied that combines strong quantitative elements with in-depth qualitative analyses that integrate the perspectives of practitioners. This thesis provides a broad set of indicators to describe and assess transdisciplinary research that translate theoretical concepts form transdisciplinarity theory into observable variables. The indicators offer a holistic perspective on transdisciplinary research by representing research mode characteristics, societal as well as scientific outcomes of research projects and their specific context. To theoretically demarcate transdisciplinary research from other forms of research, a narrative literature review first elaborates the differences between "normal science", political use of scientific knowledge and transdisciplinarity in their underlying logics of problem definition, knowledge production and research utilization. Subsequently, these concepts were compared with perspectives and expectations of practitioners in the forest sector on integrative research settings. Moreover, a cluster analysis of data from 59 research projects identified five research modes that empirically demarcate ideal-typical transdisciplinary research from other research modes within sustainability science: (1) purely academic research, (2) practice consultation, (3) selective practitioner involvement, (4) ideal-typical transdisciplinary research and (5) practice-oriented research. Based on this finding, transdisciplinary research can be characterized as an intensive, but balanced involvement of practitioners. It incorporates not only the needs and goals of the practitioners but also their norms and values. Ideal-typical transdisciplinary research goes beyond mere consultatory research approaches and must be distinguished from what is conceptualized as applied research. Regression analysis of 81 research projects and statistical group comparisons of the five research mode clusters show that societal and academic outputs and impacts vary with specific project characteristics and combinations of project characteristics defined as research modes. The findings indicate that more interactive research modes reach more societal impacts. In particular, the involvement of practitioners in early project phases and the targeted dissemination of the research results positively affect societal impacts. This finding also aligns with practitioner expectations on integrative research and research utilization, provided by qualitative analysis. Moreover, the quantitative results show that scientific outputs and impacts decrease with the intensity of interactions, indicating a trade-off between societal and scientific outcomes and impacts. Overall, the empirical results of this thesis support the claimed effectiveness of transdisciplinary research in providing societally relevant, applicable knowledge and encourage further funding of transdisciplinary research by funding agencies.
Tropical ecosystems are critical for biodiversity conservation and local people’s livelihood sustenance. However, these ecosystems are under high pressure from land-use and land cover (LULC) change, which is further projected to intensify and increase rapidly, thereby affecting biodiversity and the provisioning of vital ecosystem services (ES). It is thus important to understand how LULC might change in the future and how such changes could affect biodiversity and ES provisioning in a given landscape of tropical ecosystems. Scenario planning has become an increasingly popular tool and technique to produce narrative scenarios of the future landscape change. Thus, quantifying changes under different land-use scenarios could be a means to elucidate the synergies and trade-offs within the scenarios. In this dissertation, the author examines the future of biodiversity and ES provisioning for different plausible land-use scenarios in southwestern Ethiopia. First, he translates four future plausible narrative social-ecological land-use scenarios ("Gain over grain", "Coffee and conservation", "Mining green gold" and "Food first") developed for southwestern Ethiopia by participatory scenario planning into spatially explicit LULC scenario maps. Results showed distinct LULC changes under each scenario. Second, the author investigates the impact of these land-use scenarios on biodiversity by specifically modelling woody plant species richness in farmland and forest. Both indicators of human disturbance and environmental conditions were used. Third, he also investigates the effect of these land-use scenarios on woody plant-based ES provisioning by combining woody plant species with household surveys on how woody plants were used by the local community. He models and predicts the current and future availability of woody plant-based ES under the four scenarios of landscape change. Overall, the findings of this dissertation show the importance of integrating future land-use mapping with participatory, narrative-based scenarios to assess the social-ecological outcomes of alternative futures. The spatially explicit maps of LULC change, biodiversity and ES (at different scales) could be used as a valuable input to support stakeholders and decision-makers to weigh the advantages and disadvantages of different development trajectories on ecosystems and human well-being and to avoid or minimize future undesirable consequences. To this end, apart from the benefits of coffee production under "Mining green gold" and crop production under "Food first" scenarios, the findings under these scenarios of large-scale agricultural intensification point to a potentially high loss of biodiversity and ES. These two scenarios could have a negative long-term impact on ecosystems and human well-being. Finally, the "Coffee and conservation" scenario, which involves the creation of a new biosphere reserve, appears to be the most sustainable scenario. This scenario could result in a sustainably managed, diversified landscape which could make major contributions to biodiversity conservation and human well-being in the region and beyond.
Protected areas are an essential tool for conserving biodiversity. However, their ecological effectiveness is contested and their capacity to resist human pressures differ. This dissertation aimed to assess the ecological effectiveness of different protection levels (from strict to less strictly protected: national park, game reserve, forest reserve, game-controlled area, and unprotected areas) in biodiversity (both mega diverse butterflies and mammals), maintaining habitat connectivity, and reducing anthropogenic threats at the wider landscape in the Katavi-Rukwa Ecosystem of southwestern Tanzania. To achieve this overarching goal, the researcher employed an interdisciplinary approach. First, he analyzed butterfly diversity and community composition patterns across protection levels in the Katavi-Rukwa Ecosystem. He found that species richness and abundance were highest in the game reserves and game-controlled areas, intermediate in the forest reserves, national park and unprotected areas. Species composition differed significantly among protection levels. Landscape heterogeneity, forest cover, and primary productivity influenced species composition. Land-use, burned areas, forest cover, and primary productivity explained the richness of species and functional traits. Game reserves hosted most indicator species. Second, the author modelled the spatial distribution of six large mammal target species (buffalo Syncerus caffer, elephant Loxodonta africana, giraffe Giraffa camelopardalis, hartebeest Alcelaphus buselaphus, topi Damaliscus korrigum, and zebra Equus burchellii) across environmental and protection gradients in the Katavi-Rukwa Ecosystem. Based on species-specific density surface models, he found relatively consistent effects of protection level and land-use variables on the spatial distribution of the target mammal species: relative densities were highest in the national park and game reserves, intermediate in forest reserves and game-controlled areas and lowest in un-protected areas. Beyond species-specific environmental predictors for relative densities, the results highlight consistent negative associations between relative densities of the target species and distance to cropland and avoidance of areas in proximity to houses. Third, the author examined temporal changes in land-use, population densities and distribution of six large mammal target species across protection levels between 1991 and 2018. During the surveyed period, cropland increased. Wildlife densities of most, but not all target species declined across the entire landscape. Based on logistic regression models, target species preferred the national park over less strictly protection levels and areas distant to cropland. Fourth, he quantified land-use changes, modelled habitat suitability and connectivity of elephant over time across a large protected area network in southwestern Tanzania. Based on analyses of remotely-sensed data, cropland increased from 7% in 2000 to 13% in 2019. Based on ensemble models, distance from cropland influenced survey-specific habitat suitability for elephant the most. Despite cropland expansion, the locations of the modelled elephant corridors (n=10) remained similar throughout the survey period. Based on circuit theory, the author prioritizes three corridors for protected area connectivity. Key indicators of corridor quality varied over time, whereas elephant movement through some corridors appears to have increased over time. Overall, this dissertation underpins differences in ecological effectiveness of protected areas within one ecosystem. It highlights the need to utilize a landscape conservation approach to guide effective conservation across the entire protection gradient. It also suggests the need to enforcing land use plans and having alternative and sustainable forms for generating income from the land without impairing wildlife habitat.
Companies are invited to contribute to the United Nations' 17 Sustainable Development Goals (SDGs) and sustainability management accounting (SMA) has an important role to play in achieving them. However, if companies are to address the SDGs and linkages beyond organizational boundaries, SMA needs a broader scope than is conventionally assumed. Therefore, the author advances a multi-level framework that addresses context, action-formation, and transformative contributions (CAT) in the following directions: first, an innovative systematic method that allows screening company-related SDGs and assessing corporate contributions to selected SDGs is introduced; second, management control systems are integrated to support managers in guiding employee behavior to make contributions to the SDGs; and, third, self-reinforcing mechanisms of the path-dependence theory are incorporated to serve as a guide to identifying barriers to individuals and groups becoming involved in SMA. This advanced CAT framework contributes to corporate practice and research by providing a multilevel framework that offers concrete management guidance for SMA to address the SDGs. It also facilitates analysis of both enabling and inhibiting factors at the organizational level. The advanced CAT framework has several implications for SMA: it promotes backcasting from the SDGs for benchmarking purposes, integrates different social, environmental, and economic issues, facilitates future-oriented action and transformation planning, addresses different layers such as the company as well as individuals and groups within it and enables to identify barriers hindering individuals and groups from becoming involved in SMA.
This cumulative dissertation presents how commercial banks in Germany communicate their ambitions and commitment regarding corporate responsibility - i.e., CSR. The results of the first article show that the quality of mandatory non-financial reporting needs to be improved and that certain characteristics (e.g., previous reporting experience, reporting format and standard) have a positive influence on reporting quality. The second article shows that the CSR reporting scope on bank websites also has room for improvement and that various banking characteristics such as size, capital market orientation, media visibility or public ownership have an influence on communication. The third article illustrates that credit institutions in Germany are increasingly using social media for CSR communication, but that CSR communication strategies differ (Facebook vs. Twitter). The fourth article discusses CSR communication using advertisements and shows that the conceptual design of advertisements should be in line with the credit institution's business model and is therefore beneficial.
The research described in this dissertation focuses on developing a process to remove oligomers and suppress their formation by intercepting the aging procedure's precursors using adsorbents when biodiesel and its blends are used as fuel. So far, there has been no attempt to cause the stabilization of biodiesel and its blends using adsorbents from open literature. This investigation is one of the first studies on the use of adsorbents to mitigate biodiesel and diesel fuel's stability behavior–biodiesel blends and the removal of oligomers or suppressing the formation of high molecular mass species in aging oil. This study's primary aim has been achieved by several experimental measurements that provided results on adsorbents' effecton fuel oxidative stability, especially ester-based fuel like biodiesel and its blends. The chemical composition and some critical rheological analyses of the samples have been measured to understand their role in the oxidation of the sample by comparing the presence and absence of the adsorbents during the aging process. Furthermore, it aims to use adsorbents to suppress oligomers' formation and remove them in aging oil due to the influence of biodiesel and its blends. The research project also seeks to stabilize fuel, especially ester-based fuel like biodiesel, and its blends using the adsorbents. The adsorbents' application will enhance biodiesel's oxidative stability and its blends during long-term storage or application, focusing on its use in plug-in hybrid vehicles, emergency power plants,and generators. The combustion engine only starts in plug-in hybrid vehicles if the battery cannot supply energy on longer journeys. As a result, the fuel remains longer in plug-in hybrid vehicles. Fuels that are exposed to heat and oxygen over anextendedperiod can form aging products. These aging products lead to the formation of deposits, especially in the case of diesel fuels mixed with biodiesel content,and can, therefore, endanger the operational safety of the vehicle in critical components such as injectors or filter units.
This dissertation evaluated the efficacy of three different internet-based interventions that can be regarded as indirect interventions to reduce depression since they primarily targeted risk factors for depression. For this purpose three registered randomized controlled trials were conducted. In addition to assessing the efficacy of the interventions regarding the primary outcomes, the efficacy to reduce depression and further secondary outcomes was studied. In Study I (N=200) the efficacy of an internet-based stress management intervention (iSMI), which was adapted and tailored to career starting teachers, was compared to a waitlist control group (WLG). The participants of the intervention group (IG) reported significant reductions on the primary outcome perceived stress at post-intervention (T2) and three month follow-up (3-MFU). Furthermore, it was shown that the intervention indirectly also reduced depression at T2 and 3-MFU. The effects were sustained at an extended 6-MFU. Besides efficacy, the feasibility to complement the iSMI with a newly developed internet-based classroom management training was shown. Moreover, mediation analyses corroborated the role of problem- and emotion-focused coping skills in the intervention's effect on stress and the indirect effect of the intervention on depression through stress. Study II (N=262) demonstrated the efficacy of an internet- and app-based gratitude intervention on the reduction of primary assessed repetitive negative thoughts at T2 and 3-MFU, as compared to a WLG. The participants of the IG also reported significantly reduced depressive symptoms at T2, and 3-MFU, with significant clinically meaningful effects. The effects were sustained at an extended 6-MFU. Besides efficacy, mediation analyses showed that repetitive negative thinking mediated the gratitude intervention's effect on depression. Finally, Study III N(=351) showed that an internet-based intervention, tackling worries at the beginning of the COVID-19 pandemic, was effective as compared to an active mental health advice group. At T2, two weeks after randomization, the IG reported significantly reduced levels on the primary outcome worry as compared to controls. Participants of the IG also reported significantly reduced levels of depression at T2, with significant clinically meaningful reductions. The extended follow-ups in the IG indicated that the improvements from baseline were sustained until the 2-MFU and the 6-MFU. In a mediation analysis, worry was shown to mediate the intervention's effect on depression. Across all three studies a reliable deterioration of depression was occasionally observed. In summary, the studies in this dissertation demonstrated the efficacy of various indirect interventions focusing on rather common psychological problems to indirectly reduce depressive symptoms. The extent to which depression severity could be reduced is comparable to reductions found within participants with comparable baseline depression severity, in internet-based interventions directly addressing depressive symptoms. Indirect interventions are suggested to increase the uptake of interventions that reduce depressive symptoms, since they might be perceived as less stigmatizing and might broaden the range of interventions to choose from.
Environmental governance beyond borders: Governing telecoupled systems towards sustainability
(2023)
This doctoral dissertation analyses the environmental governance of long-distance social-ecological interactions in telecoupled systems in two issue domains: global commodity chains and infrastructure projects as part of China’s Belt and Road Initiative (BRI). Although both domains involve different governance actors, institutions and processes, they both concern the question of how the involved actors develop governance structures and institutional responses to telecoupling. This dissertation aims to contribute to a deeper understanding of how to govern environmental problems that are associated with global flows. Since many multilateral environmental governance initiatives have not yet produced the desired solutions to global problems, particular attention is directed at unilateral state-led governance approaches. This dissertation addresses the questions of (1) how to achieve a spatial fit between the scale of telecoupled systems and the scale of governance institutions, (2) how governance actors exercise agency in governing telecoupled systems, and (3) how state actors can govern the domestic and foreign environmental effects of telecoupled flows. The results show that creating a spatial fit in the governance of global commodity flows is challenging because boundary and resolution mismatches can emerge. Boundary mismatches denote situations where social-ecological problems transcend established jurisdictional boundaries, whereas resolution mismatches refer to governance institutions that have too coarse a spatial resolution to allow them to address the specific aspects of social-ecological problems effectively. No single governance institution is likely to avoid all mismatches, which highlights the need to align multiple governance approaches to effectively govern telecoupled systems.
This dissertation comprises three stand-alone research papers dealing with different aspects of labor market characteristics: bonus payments and the gender pay gap; second job holding; and workers un-covered by collective bargaining. The first paper investigates whether and how non-base compensation in the form of bonus payments, overtime pay, and shift premia contributes to the gender pay gap. Unionization along with collective bargaining coverage has been on the decline on recent decades. Using German administrative data, the second paper examines which workers in firms covered by col-lective bargaining agreements still individually benefit from these union agreements, which workers are not covered anymore and what this means for their wages. The third paper studies the development and persistence of second job holding in Germany after a legislative change in the year 2003 allowed the extensive dispensation of marginal second jobs from taxes and social security contributions. Using data from the German Socio-Economic Panel, the author documents a substantial increase in second job holding in Germany since 2003 and finds in a dynamic panel model setting that there is true state dependence in second job holding.