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Teaching Grit: Examining the Effects of a School-Based Intervention to Foster Grit
No full textNon-cognitive skills, such as grit—defined as perseverance and consistency in pursuing long-term goals—have garnered increasing attention in education research. The current study explored grit’s relevance in the German educational context, addressing gaps in understanding its role, malleability, and potential to reduce achievement gaps for disadvantaged students. Using brief, web-based interventions tailored for secondary school students in Germany, the research aimed to foster grit and improve academic outcomes. Interventions targeted grit’s proposed psychological antecedents, namely academic mindsets and learning skills and strategies. Dependent variables included GPA, teacher evaluations of students’ progress, personal and school goal achievement, and educational attainment over five years.
The study employed a mixed-methods sequential explanatory design, combining the strengths of quantitative and qualitative approaches. The quantitative strand, prioritized in this design, included a cross-sectional pre-intervention study to examine the relationships between grit, its correlates, and school performance, followed by a cluster-randomized controlled longitudinal field quasi-experiment to evaluate the effects of grit interventions. Findings from the cross-sectional study revealed that school-specific grit uniquely predicted GPA, particularly for students with lower socio-educational advantage (SEA) and academic ability, with behavioral school engagement fully mediating this relationship. The longitudinal study revealed significant GPA improvements in the intervention groups, primarily for socially and academically disadvantaged students. Moreover, the grit interventions positively influenced the achievement of self-selected school goals and maintained GPA levels for advantaged, high-performing students, preventing the declines seen in the control group. The follow-up qualitative strand included focus groups with students grouped by academic progress post-intervention (improved vs. stagnated / declined), exploring their subjective experiences, the resonance of intervention content, and the potential behavioral mechanisms behind intervention success or failure. This integration of quantitative and qualitative findings deepened insights into grit’s impact on academic performance and intervention efficacy.
This research makes significant contributions to grit theory, methodology, and practice. It advances understanding of grit’s psychological antecedents, domain specificity, and mindsets and behaviors linking grit to academic outcomes. Methodologically, it employs a user-centered design process and a comprehensive, longitudinal evaluation, offering a model for scalable interventions. Practically, it provides schools with actionable tools to support students achieve better academic outcomes. These contributions emphasize the relevance of grit-focused strategies for educational policy and practice in Germany and beyond
Assessment of macroalgal biodiversity and habitat change in the European Arctic
No full textGlobal warming is a major driver for change across European Arctic fjord systems. Macroalgae are important foundation species along the rocky Arctic coastline and their community structure, horizontal and vertical distribution and species richness serves as a sensitive indicator of changing environmental conditions. In this doctoral thesis, I use a combination of in situ field data (quantitative and semi-quantitative sampling of species) and molecular biodiversity assessments (DNA barcoding and eDNA metabarcoding) to characterize the macroalgal communities of two Arctic fjord systems at different stages of deglaciation. High-Arctic Kongsfjorden on Svalbard is surrounded by melting glaciers and is currently under transition from Arctic to cold-temperate conditions as a consequence of atlantification. Low-Arctic Porsangerfjorden in northern Norway is already largely ice-free and, although it is located north of the Arctic Circle (66°N), cold-temperate conditions prevail. The aim of this study was to improve our knowledge of the current status of subtidal and intertidal macroalgal community structure and their biodiversity at these two key locations in the European Arctic.
In a time-for-time approach (Publication 1), I showed that over the course of 25 years the subtidal community structure and kelp demography at the study site Hansneset in high-Arctic Kongsfjorden has changed considerably. The kelp forest and consequently the overall macroalgal biomass maximum had shifted upwards by several meters to the shallow subtidal. Furthermore, the kelp forest structure and demography has shifted as ‘Digitate Kelps’ and Saccharina latissima retreated to the uppermost depth level and Alaria esculenta became the dominant and only kelp species still reaching down to deeper levels. These alterations in species dominance over time are associated with a functional shift of the kelp forest as I showed that each kelp exhibits a species-specific strategy in biomass accretion and thereby carbon allocation. The main driver shaping Arctic macroalgal communities currently appears to be the decrease in water transparency as a consequence of melting glaciers and resulting sediment plumes, which was confirmed by in situ decreasing PAR and increasing turbidity data.
In a space-for-time substitution (Publication 2), I revealed that at present the intertidal and subtidal macroalgal communities in high-Arctic Kongsfjorden differ to a great extent from those of low-Arctic Porsangerfjorden. Kongsfjorden displayed an emerging intertidal macroalgal community primarily dominated by Fucus distichus, whereas Porsangerfjorden featured assemblages dominated by six species of Fucales, characterized by significantly higher biomass. However, the macroalgal biomass at the subtidal fringe level was similar between the fjords, although the species contributions varied. In contrast to the shallow kelp forests dominated by Alaria esculenta observed in Kongsfjorden (Publication 1), Saccharina latissima was the dominant species in Porsangerfjorden, where the kelp forests extended to considerable depths. I conclude, that the presence of flourishing intertidal macroalgal communities in the Arctic is supported by retreating sea ice and warmer water temperatures, while the extension of subtidal kelp forests is largely dependent on the underwater light conditions and hindered by increased water turbidity. As Arctic warming continues and biogeographical regions shift, cold-temperate Atlantic species are expected to expand their distribution northward. Ultimately, this expansion is likely to transform the high-Arctic macroalgal community in Kongsfjorden into a composition similar to that found in Porsangerfjorden in the future.
The quantitative field surveys in Publications 1 and 2 were complemented by a comprehensive molecular biodiversity assessment in Publications 3 and 4, which represent a novel macroalgal sequence database for the Arctic. A total of 604 new DNA barcodes were generated using the best practice collection scheme and will serve as reliable reference DNA barcodes for the assessment of future species inventories with molecular methods. I found that a large part of the molecular macroalgal biodiversity in both Kongsfjorden (Publication 3) and Porsangerfjorden (Publication 4) was not represented in previous species lists based purely on identification via morphological characters. Using DNA barcoding I could confirm 51 morphological species across both fjords, of which 20 were hitherto overlooked species or misidentified. Additionally, I identified 13 genetic macroalgae species with no assigned morphological species concept and seven previously unsequenced taxa, all of which require further taxonomic work. Ulvophyceae metabarcoding conducted on surface water samples additionally revealed that 18 more Ulvophyceae species might be present in the European Arctic which were missed by my DNA barcode survey. My results highlight the power of molecular biodiversity assessments and the need to connect them with classical taxonomy to utilize their full potential. We are currently noticeably underestimating the biodiversity of Arctic fjord systems due to species misidentifications and resulting incomplete biogeographic information. It is therefore of utmost importance to implement regular monitoring efforts in the European Arctic in order to truly assess the biodiversity present in these habitats especially impacted by climate change and to establish molecularly verified species lists to detect future shifts in species distribution ranges. This may be important not only for detecting, but also for conserving macroalgal species at a time when the socio-economic situation in the Arctic is changing and effective coastal zone management concepts based on solid biodiversity data is needed to preserve local heritage.
In conclusion, my findings clearly demonstrated substantial differences in macroalgal communities between two fjord systems in the European Arctic located at different latitudes, and facing contrasting temperature regimes and stages of cryosphere loss. I set newly collected quantitative and molecular datasets in perspective to historical observations which allowed for well-founded predictions about the future of macroalgae in warming high-arctic fjords after deglaciation. Furthermore, my research has established a comprehensive baseline for the current community composition and biodiversity of intertidal and subtidal macroalgae in the European Arctic. My doctoral thesis intends to facilitate future monitoring efforts on expected shifts in macroalgal community structure and biodiversity resulting from climate change related changes in environmental conditions
Healthy eating in the context of social inequalities: The influence of socioeconomic factors on attitudes and dietary behavior
No full textSoziale Ungleichheiten im Ernährungsverhalten sind eine wesentliche Ursache gesundheitlicher Ungleichheiten. Einstellungen zur gesunden Ernährung beeinflussen das Ernährungsverhalten, wobei sozioökonomische Unterschiede bestehen. Ein besseres Verständnis dieser Zusammenhänge ist entscheidend für gezielte Interventionen. Diese kumultative Dissertation untersucht Einstellungen zur gesunden Ernährung, ihren Einfluss auf das Ernährungsverhalten und die Rolle sozioökonomischer Faktoren anhand eines systematischen Reviews und zweier Sekundäranalysen bevölkerungsbasierter Daten aus Deutschland und Europa.
Die Ergebnisse zeigen, dass i) die Allgemeinbevölkerung unterschiedliche Perspektiven zur (gesunden) Ernährung hat, ii) sozioökonomische Unterschiede in diesen Bedeutungen bestehen, iii) niedrigere sozioökonomische Gruppen ungünstigere Ernährungsverhaltensweisen zeigen, iv) positive ernährungsbezogene Einstellungen die Ernährungsqualität verbessern und v) diese Einstellungen als vermittelnder Faktor zwischen sozioökonomischem Status und Ernährungsverhalten wirken. Damit bestätigen die Ergebnisse sozial-kognitive Verhaltenstheorien, wonach Einstellungen das Ernährungsverhalten maßgeblich beeinflussen.
Für Forschung und Praxis ergeben sich daraus wichtige Implikationen. Zukünftige Studien sollten intersektionale Perspektiven einbeziehen, um Gruppen mit besonderem Bedarf an Ernährungsinterventionen zu identifizieren. Zudem ist eine einheitliche Erfassung ernährungsbezogener Einstellungen im Zusammenhang mit sozioökonomischen Faktoren entscheidend. Um soziale Unterschiede im Ernährungsverhalten besser zu verstehen, sollten weitere Mediatoren untersucht werden. Die Ergebnisse verdeutlichen den Bedarf an Interventionen, die Ernährungswissen und -kompetenzen fördern sowie eine positive Wahrnehmung gesunder Ernährung stärken. Besondere Berücksichtigung sollten die Bedürfnisse sozioökonomisch benachteiligter Gruppen finden, um Ungleichheiten zu reduzieren
Ökologische Nachhaltigkeit und Lebenszyklusanalyse im Gesundheitswesen
No full textDie Bemühungen, das Gesundheitssystem hin zu umweltfreundlicheren Praktiken zu transformieren, nehmen auf vielen Ebenen zu. Initiativen wie die Verpflichtungen im Rahmen der Alliance for Transformative Action on Climate and Health, die Budapest Declaration sowie die Beschlüsse des 125. Deutschen Ärztetages unterstreichen die Bestrebungen in Deutschland, diese Transformation voranzutreiben.
Um jedoch ein effektives Umweltmanagement für die Transformation umzusetzen, besteht weiterhin ein Bedarf an umfassenden Erkenntnissen über Emissionsquellen innerhalb des Systems, Methoden zur Messung der Umweltauswirkungen – insbesondere der Treibhausgasemissionen – durch Gesundheitsorganisationen sowie an Evidenz zu möglichen Reduktionsmaßnahmen.
Diese Dissertation widmet sich diesen Themen anhand von vier Forschungsfragen und fünf Modulen:
Forschungsfrage 1 (RQ1) und Modul 1 (M1) skizzieren, wie die Lebenszyklusanalyse auf verschiedenen Ebenen im Gesundheitssektor effektiv implementiert werden kann, um dessen Treibhausgasemissionen zu minimieren. Forschungsfrage 2 (RQ2) und Modul 2 (M2) untersuchen die Evidenz zu Emissionsquellen innerhalb nationaler Gesundheitssysteme. Forschungsfrage 3 (RQ3) beinhaltet empirische Arbeiten im Rahmen dieser Dissertation, bei denen die Emissionsquellen eines deutschen Krankenhauses und eines ambulanten Pflegedienstes als Fallstudien für die Anwendung der organisatorischen Lebenszyklusanalyse im Gesundheitswesen detailliert analysiert werden (Module M3 und M4). Die abschließende Forschungsfrage (RQ4) umfasst Erkenntnisse zu einzelnen Reduktionsmaßnahmen und deren Wirksamkeit, behandelt in den Modulen M4 und M5.
Diese Dissertation hebt die Bedeutung zentraler Organisationen, wie Krankenhäuser, als Emissionsquellen im Gesundheitssektor hervor. Zudem wird eine allgemeine Berechnungsmethode für organisatorische Lebenszyklusanalysen auf Gesundheitsorganisationen angewendet und methodisch angepasst. Schließlich wurden einzelne Reduktionsmaßnahmen hinsichtlich ihrer Wirksamkeit untersucht. Die Ergebnisse dieser Dissertation sind durch die Kontextabhängigkeit des Entscheidungsprozesses bei der Anwendung von Lebenszyklusanalyse-Methoden, die fehlende Untersuchung von Ergebnisunsicherheiten sowie die eingeschränkte Repräsentativität der Resultate für den breiteren deutschen Kontext limitiert.
Trotz dieser Einschränkungen können die in der Dissertation vorgestellten Erkenntnisse Praktikerinnen und Praktikern, einschließlich politischer Entscheidungsträger, die Finanzierungsstrukturen gestalten und Ressourcen zuteilen, sowie Entscheidern innerhalb des Gesundheitswesens helfen. Diese Einsichten unterstützen sie dabei, relevante Emissionsquellen zu identifizieren und wirksame Maßnahmen zur Reduktion dieser Emissionen zu ergreifen. Zukünftige Forschung kann sich den diskutierten Limitationen widmen und die Methodik weiterentwickeln. Dadurch wird es Organisationen ermöglicht, schnell und unkompliziert eine robuste Methode zur Berechnung ihrer Treibhausgasemissionen zu übernehmen
Modelling two decades of change and future developments in the Gulf of Nicoya (Costa Rica) ecosystem using the Ecopath with Ecosim toolbox
No full textThe Gulf of Nicoya is a highly productive estuary located on the Pacific coast of Costa Rica and accounts for the country’s primary fish production. It is increasingly impacted by its fisheries and climate variations, urbanization, tourism developments, the input of pollutants from urban centres, and agriculture activities in the catchment areas of large rivers entering the gulf. Thus, our study intensively assesses the Gulf of Nicoya’s past, present, and future states and the main driver of ecosystem change. The state of the ecosystem, food-web dynamics, detectable patterns in fishing efforts, and the external drivers’ influence on the system were analyzed. Also, the economic impacts of fishing effort regulations were simulated to test and propose possible management plans. A spatial model was also built to test the effect of a temporary fishing closure on the stock recovery of target species in the Gulf of Nicoya and to propose management alternatives.
In the early 1990s, ecological and fishery data from the Gulf of Nicoya were holistically analyzed, and a trophic model was constructed using the Ecopath modelling approach. The results indicated that this tropical estuary, a hotspot for Costa Rican fisheries, was already overexploited by shrimp trawlers and longline fleets, and recent observations suggest further deterioration in this system. To evaluate the ecosystem and socio-economic changes in the Gulf of Nicoya over the last 20 years, the 1993 model was reconstructed with data from 2013 to compare both system states. Although the summary statistics of both states (i.e., 1993 and 2013) suggest that the system maintained its general functionality and even enabled the total harvest to increase by approximately 20%, a more detailed analysis of the levels of the functional groups led to the conclusion that the system was further degraded, causing a tremendous economic loss of approximately 50%. Like other coastal ecosystems, the Gulf of Nicoya is impacted by its fisheries, anthropogenic activities, and pollution from the large rivers entering the gulf. Thus, the gulf is particularly sensitive to short- and long-term changes in the climate, especially during extreme conditions in El Niño periods. For further analysis, we used a holistic approach to examine the impacts of fishing and environmental changes to identify the main drivers in the observed changes in the Gulf of Nicoya ecosystem. While the model simulations indicate that fisheries’ exploitation rates mainly drive variations in the catchment, several species are also substantially affected by climate variations. This factor must be considered alongside implementing fishing regulations to form and develop appropriate management strategies. This dissertation tested the effectiveness of different management scenarios applied to the Gulf of Nicoya, including top-down and participatory fishing policies. Besides testing the current policy (which bans shrimp trawling), we used the automated fishing policy search tool of the EwE software to explore an alternative, optimized management scenario. The analysis indicates that the ban on trawling is important for the ecosystem’s recovery. However, additional measures might be needed, such as reducing fishing efforts by semi-industrial purse seine fleets and artisanal longline fleets. We present two possible alternative management scenarios with different balances of ecosystem conservation and economic losses. We complement our extensive analysis by adding a spatial component using the Ecospace tool, which can simulate species’ spatial distribution and fishing fleet effort over time. One obvious application is the assessment of the efficiency of existing and potential locations of MPAs to explore spatial management options and address various research questions, including the regional consequences of climate change. The approach was used to test the effectiveness of the existing annual seasonal fishing closure in the gulf (known as “Veda” in Spanish) and to tackle further questions. For example, is excluding all fleets from the gulf necessary during fishing closure? Would a seasonal closure covering the entire area of the Gulf of Nicoya be more efficient?
This intensive assessment of the state of the Gulf of Nicoya ecosystem leads to the conclusion that a drastic decrease in fishing effort, especially of semi-industrial fleets, is needed to maintain the ecosystem’s functionality, rebuild the biomass of target species, and strengthen its resilience to environmental change. In this process, the enforcement of the fishing closure will play an important role
Complementary Funding: How Location Links Crowdfunding and Venture Capital
No full textWhile Equity Crowdfunding (ECF) platforms are a virtual space for raising funds, geography remains relevant. To determine how location matters for entrepreneurs using equity crowdfunding (ECF), we analyze the spatial distribution of successful ECF campaigns and the spatial relationship between ECF campaigns and traditional investors, such as banks and venture capitalists (VCs). Using data from the two leading German platforms – Companisto and Seedmacht – we employ spatial eigenvalue filtering and negative binomial estimations. In addition, we introduce an event study based on the implementation of the Small Investor Protection Act in Germany allowing us to obtain causal evidence. Our combined analysis reveals a significant geographic concentration of successful ECF campaigns in some, but not all, dense areas. ECF campaigns tend to cluster in dense areas with VC activity, while they are less prevalent in dense areas with high banking activity, and are rarely found in rural areas. Thus, rather than closing the so-called regional funding gap, our results suggest that, from a spatial perspective, ECF fills the gap when firms in dense areas seek external financing below the minimum equity threshold offered by VCs and when there are few banks offering loans.250
Relative localization and multi-robot SLAM for autonomous systems
No full textAutonomous systems that navigate or interact with their environment must accurately
estimate their own motion and understand their surroundings in order to operate safely
and effectively. This cumulative thesis primarily presents scientific contributions in two
closely related domains: relative localization and multi-robot simultaneous localization
and mapping (SLAM).
Relative localization estimates a platform’s motion from arbitrary coordinate frames
and forms the foundation of SLAM. SLAM builds on these motion estimates by incorpo-
rating exteroceptive sensor data to incrementally construct a model of the environment.
SLAM achieves a consistent representation of the surroundings through loop closures,
which associate observations from different times and places to reduce accumulated drift.
This thesis begins by laying the theoretical and algorithmic foundations of relative lo-
calization and SLAM. It introduces key sensors, particularly cameras, light detection and
ranging (lidar), and inertial measurement units (IMUs). Mathematical frameworks for
state estimation using Kalman filters and graph-based optimization are presented, with
a focus on the handling of 3D orientations via the ⊞-operator, which enables state esti-
mation on manifolds. Quantitative performance evaluation methods, including absolute
and relative trajectory error metrics, are also introduced.
The thesis places an emphasis on visual-inertial odometry (VIO) which fuses data from
cameras and IMUs for relative localization. In particular, two algorithms designed for the
domain of highly automated driving are presented, which additionally use vehicle-related
quantities, such as vehicle speed and steering angle information. Inertial state kinemat-
ics, which are the backbone of VIO systems, are highlighted and 3D scene projection
from camera data is discussed. Further insights into the performance of a contributed
VIO algorithm are presented using two IMUs with different performance characteristics.
In the domain of multi-robot SLAM, a decentralized graph-based system is proposed
that supports various collaborative exploration strategies. The system primarily relies
on lidar and integrates robot poses as graph nodes, with spatial constraints encoded as
odometry or loop closure edges. The design of the graph structure allows for the flexible
integration of sensor data from various sources, which makes it particularly suitable for
the cooperation of multiple robotic systems. Further enhancements beyond the orig-
inal method are presented, including an offline static map provider, edge removal for
erroneous loop closures, and the integration of radio-based distance constraints between
mobile robots and stationary beacons.
Complementary research efforts are also presented. A high-precision trajectory evalu-
ation was performed for an autonomous lawn mower, achieving sub-centimeter accuracy
using lidar and an infrared tracking system. This precision was necessary due to the
centimeter-level accuracy already provided by global navigation satellite system (GNSS)
and real-time kinematic (RTK) localization. Another contribution involves a radar- and
lidar-based object tracking framework for highly automated driving applications. Traffic
participants, including pedestrians, cyclists, and vehicles, are treated as objects to be
relatively localized with respect to the ego vehicle. Special attention is given to the
design of an efficient data association method.
Overall, this thesis presents both theoretical and practical contributions across multi-
ple platforms, including vehicles, autonomous lawn mowers, and ground rovers, advanc-
ing the state of the art in optically aided relative localization and SLAM for autonomous
systems
Sozialer Zusammenhalt in Zeiten von Krisen: Erkenntnisse zum gesellschaftlichen Zusammenhalt in Europa
No full textIt seems reasonable that once a crisis or challenge is ongoing, people’s lives will be affected or disrupted in various aspects. European societies, in particular, are currently facing numerous challenges and a rapidly changing environment, which requires a high level of adaptability, a strong democracy, and a committed, cohesive civil society. This dissertation aims to shed light on the role of social cohesion during European crises. It assumes that a cohesive society not only benefits from collective well-being but can also support individuals in coping with challenges and crises. This dissertation aims to contribute to the discourse on social cohesion by continuing the European leg of Bertelsmann’s Social Cohesion Radar (SCR), a concept for assessing and monitoring social cohesion over time and across countries. This takes into account the need for up-to-date, cross-nationally comparable assessments. At the same time, it examines how social cohesion has developed during the current crises and postmodern challenges and provides insights into the changing dynamics within European societies. Additionally, the dissertation will present two examples of cases that highlight the role of social cohesion during significant contemporary issues: the COVID-19 pandemic and the increase of conspiracy beliefs.
First and foremost, the dissertation will contribute to the continuation of a comparable social cohesion monitoring system across countries and examine recent trends in social cohesion in Europe. The continuation of the Social Cohesion Radar (2013 – 2020) provides a comprehensive overview of social cohesion trends, revealing relative stability over the past decade with high levels of civic participation, trust, and acceptance of diversity, particularly in Nordic and Northwestern European countries. It continues the countries’ comparability with their established social cohesion baseline and highlights the importance of consistent measurement in understanding changes over time.
In light of the current state of cohesion in European countries, it is essential to explore and understand how social cohesion can play a role in addressing current crises and postmodern challenges. To answer that research question, the dissertation focuses on two further explanatory perspectives: firstly, whether social cohesion can act as a buffer during the COVID pandemic, using Germany as an example. Based on Bertelsmann data from Baden-Württemberg, the chapter explores how social cohesion interacts with the subjective and objective strain brought about by the COVID-19 pandemic. The findings demonstrate that while social cohesion only modestly moderates the relationship between pandemic-induced strain and future optimism, individuals affected by COVID-19 exhibit a resilient, optimistic outlook. This suggests that social cohesion might play a subtle yet vital role in fostering resilience during crises.
Based on data from the Visegrad countries, the dissertation furthermore explores the significance of social cohesion in the context of rising conspiracy beliefs and right-wing political shifts. It finds that strong social cohesion can alleviate feelings of uncertainty and anomia, thereby reducing the propensity for conspiracy mentalities, particularly in countries like Germany, where social cohesion is robust. However, this mitigating effect is less pronounced in countries with weaker social cohesion, like Poland. Taken together, these chapters illustrate the critical role of social cohesion in shaping societal responses to crises and uncertainties, highlighting both its stabilizing influence and the complexities of its impact across different contexts and issues
Understanding change and continuity in Polish politics - political elites, the party politics of higher education and the impact of right-wing populism (1989-2021)
No full textThis cumulative dissertation expands our knowledge of parties, political elites, and parliamentary debates in Poland since the onset of the post-socialist transformation to 2021. The single-country study comprises four case studies on the recruitment of post-socialist political elites, parliamentary debates, and the respective impact of populist right parties. To better understand processes linked to elite recruitment, the thesis focuses on the policy field of higher education, which enjoyed a particularly high salience in Poland’s process of “catching up with the West”.
The dissertation finds an increasing salience of higher education policies among political elites in party manifestos, parliamentary debates, and reforms, which is comparable to trends observed in Western Europe. The qualitative content analysis of 41 party manifestos highlights the unique character of partisan debates in Poland, making Polish parties clearly distinguishable from their West European counterparts. While the parties align in their positioning regarding the question of how universities should be steered, there are clear differences regarding redistributive questions. The key results for the positioning of populist right parties can be summarized as follows: the more established these parties are, the more interest they exhibit in their party manifestos and the more they engage in debates in this policy field beyond their typical core themes. Furthermore, since the emergence of populist right parties in Poland in the early 2000s, there has been a deterioration in the culture of parliamentary debate, a growing government-opposition divide in votes, and more fundamental criticism in the rhetoric of the Polish parliament.
In contrast to these parties’ frequent calls for lustration and an exchange of elites, the three governments led by the populist right party Law and Justice have had only a limited impact on the composition of Polish political elites. Two studies on political elites in post-socialist Eastern Europe show a sociodemographic homogeneity of elites for the period from 1990 to 2020. Poland exhibits comparatively strong continuities of former supporters of the socialist regime as well as of the opposition among contemporary political elites. A comparison with the former GDR points to country-specific recruitment patterns with regard to the previous role in socialism and the female share of elites.
The long-term research period from 1989 to 2021 allows for a better understanding of the path dependencies, reverberations, and legacies from socialism, as well as helps to contribute to explaining the evolution of Polish politics. As Poland converges with other OECD countries in terms of economic and political development, the study offers promising avenues to situate Poland more as a focus of comparative political science
Verbesserung der Zerstäubungseffizienz in innenmischenden Y-Jet-Düsen unter Verwendung unterschiedlicher Dispergiermedien
No full textOil refining produces various petrochemical products, including ethylene, butane, diesel, jet fuel, and gasoline. These brands are generated through crude oil's fluid catalytic cracking (FCC) within reactors. Heavy fuel oil atomization is critical to this process and is responsible for forming fine sprays to enhance transfer phenomena during catalytic reactions. Oil dispersion is typically achieved in FCC units using internal-mixing nozzles, with steam as the dispersing phase.
Despite ongoing rapid advances to transition towards renewable energy sources, fossil fuels and combustion processes will contribute to the global energy matrix for decades, posing significant environmental challenges. Therefore, optimizing existing processes to improve efficiency is essential. Due to its high demand and production loads, even slight improvements in oil refinery operations can substantially impact this industry's economic and environmental aspects by having larger productivity and reducing raw material consumption.
Effective catalytic cracking depends heavily on adequate oil atomization, as the oil dispersion fluid dynamics directly influence subsequent reactions. However, steam-assisted atomization studies usually employ external-mixing nozzles and typically focus on flue gas analyses, neglecting the detailed fluid dynamics of the atomization process. Additionally, the mixing state using internal-mixing nozzles requires further understanding, mainly how the internal geometry affects the fluid interaction and contributes to a finer spray.
Accordingly, the most applied Y-jet nozzle geometry is examined considering key geometric features. The internal flow and the external spray characteristics are explored, with correlations established to identify parameters that produce a fine spray. The aim is to investigate the effect of nozzle geometry on spray fluid dynamics and ultimately increase nozzle atomization efficiency, particularly in the steam-assisted atomization scenario.
The relevance of this work for both the industry and spray research field concerns the experimental conditions approximation to industrial cases by matching dimensionless numbers, especially the Reynolds number and the Weber number of the liquid and gas. The analysis combines numerical and experimental investigations of the flow inside the nozzle, and the results are correlated with the external spray characteristics, such as the droplet sizes and velocities, spray boundary fluctuations, and mass flux distributions. The experiments use air or steam as the dispersing medium. In the latter case, the spray fluid dynamic investigation provides essential conditions for effective atomization.
The primary outcome of this work concerns advancing the understanding of gas-assisted internal-mixing atomization processes and shedding some light on the liquid breakup mechanisms in the nozzle cavity. By optimizing the nozzle geometry and investigating the spray dynamics, the research contributes to enhancing atomization performance and efficiency in the petrochemical industry