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Exploring the categorical nature of colour perception : insights from artificial networks
(2025) Akbarinia, Arash
The electromagnetic spectrum of light from a rainbow is a continuous signal, yet we perceive it vividly in several distinct colour categories. The origins and underlying mechanisms of this phenomenon remain partly unexplained. We investigate categorical colour perception in artificial neural networks (ANNs) using the odd-one-out paradigm. In the first experiment, we compared unimodal vision networks (e.g., ImageNet object recognition) to multimodal vision-language models (e.g., CLIP text-image matching). Our results show that vision networks predict a significant portion of human data (approximately 80%), while vision-language models account for the remaining unexplained data, even in non-linguistic experiments. These findings suggest that categorical colour perception is a language-independent representation, though it is partly shaped by linguistic colour terms during its development. In the second experiment, we explored how the visual task influences the colour categories of an ANN by examining twenty-four Taskonomy networks. Our results indicate that human-like colour categories are task-dependent, predominantly emerging in semantic and 3D tasks, with a notable absence in low-level tasks. To explain this difference, we analysed kernel responses before the winner-takes-all stage, observing that networks with mismatching colour categories may still align in underlying continuous representations. Our findings quantify the dual influence of visual signals and linguistic factors in categorical colour perception and demonstrate the task-dependent nature of this phenomenon, suggesting that categorical colour perception emerges to facilitate certain visual tasks.
Natural Product Discovery at the Intersection of Genomics and Synthetic Biology: Insights from Bacteroidota and Acidobacteriota
(2025) Zumkeller, Celine Mara
Microbial natural products remain a valuable source of bioactive compounds, such as antibiotics; however, discovery pipelines often encounter issues such as rediscovery, culture bias, and natural product (NP)-encoding but silent biosynthetic gene clusters (BGCs). This dissertation connects and applies an omics-guided, cultivation-dependent workflow for underexplored Bacteroidota and Acidobacteriota. It also establishes a heterologous expression toolkit for optimising the expression of silent biosynthetic gene clusters by applying synthetic biology principles. The section “Genome Mining of Bacteroidota” employed genome mining tools, including quality control, taxonomy, BGC prediction, and similarity networking, to profile and describe newly isolated marine Bacteroidota. These expanded genomic reference resources support future rational strain prioritisation for natural product discovery. Thus, the work establishes a foundation for systematic genomics documentation and reporting, enabling portfolio-style reporting of novel strains that are being included in the Fraunhofer (FHG) strain collection. A genus-wide analysis of the Pedobacter (phylum Bacteroidota) identified a branch genetically enriched in multimodular non-ribosomal peptide BGCs. Genetic validation connected one NRP cluster of interest to the novel cryopeptin lipopeptide family, positioning this clade as a genetically tractable hotspot for novel scaffolds. The section “Profiling of Novel Acidobacteriota” investigates the biosynthetic potential of the Acidobacteriota. High-throughput selective cultivation yielded novel representatives of the Acidobacteriaceae, which were profiled for their BGC composition in a comparative study of curated public Acidobacteriota genomes. Metabolomics revealed the production of the phytohormones indole-3-acetic acid (IAA) and the cytokinin N6-(Δ2-isopentenyl)adenine (iP). Subsequent tryptophan supplementation drove a global metabolic shift, also increasing IAA production while generally decreasing iP. Absolute quantification of phytohormones placed amounts within functionally relevant ranges, but crude-extract testing did not increase barley seedling biomass under the tested conditions. Furthermore, tryptophan-driven metabolic reprogramming induced the production of indole-derived antifungal metabolites that inhibited the growth of the phytopathogen Septoria tritici. These results refine the ecological and functional potential of Acidobacteriota and map the distributions of plant growth-promoting traits (PGPTs) across families. The last section presents HEL, a modular, heterologous expression and library-style cloning platform that retrofits BGC clones with reusable, exchangeable expression cassettes (e.g., promoter libraries) and optional host-specific compatibility cassettes for broad chassis transfer. By doing so, HEL enables the tuning of expression by linking a prioritised BGC to standard, library-style phenotypes using modular cloning (MoClo), a Golden Gate-like cloning method. Collectively, this dissertation provides a reproducible genomic workflow for underexplored phyla and the FHG strain collection (i); new genomic resources, genetic prioritisation, and tractability in Pedobacter (ii); integrated genomic–metabolomic insights into tryptophan-induced metabolic dynamics, phytohormone biology, and PGPT architecture in Acidobacteriaceae, and (iii) a flexible genetic toolkit (HEL) to induce activation or accelerate the expression of prioritised BGCs across different heterologous hosts.
1-Year Outcomes of Transcatheter Aortic Valve Replacement Using a Self-Expanding vs Balloon-Expandable Transcatheter Aortic Valve
(2025) Kim, Won-Keun; Pellegrini, Costanza; Eckel, Clemens; Renker, Matthias; Grothusen, Christina; Choi, Yeong-Hoon; Charitos, Efstratios I.; Duesmann, Charlotte; Blumenstein, Johannes; Rheude, Tobias; Sossalla, Samuel Tobiasubgi3; Joner, Michael; Möllmann, Helge
Background: Mid-term comparative data for the self-expanding ACURATE neo2 transcatheter heart valve and the balloon-expandable SAPIEN 3 Ultra are lacking. Objectives: The aim of this study was to compare 1-year outcomes after transcatheter aortic valve replacement of these 2 valves. Methods: A total of 2,106 patients from 3 centers (neo2, n = 1,166; Ultra, n = 940) undergoing transfemoral transcatheter aortic valve replacement were analyzed retrospectively. The primary endpoint was the composite of all-cause mortality, stroke, and rehospitalization at 1 year. Secondary endpoints were the individual components of the primary endpoint at 1 year. To adjust for baseline differences, nearest neighbor propensity score matching was used. Results: After matching (702 pairs), baseline characteristics were similar between groups. Device success was more common in the neo2 group (87.5% vs 82.3%; P = 0.007), irrespective of matching. DP mean after the procedure was higher for Ultra (13 mm Hg [Q1-Q3: 10-15 mm Hg] vs 8 mm Hg [Q1-Q3: 6-11] mm Hg; P < 0.001). Rates of paravalvular leakage, device embolization, and multiple valve implantations were more common in the neo2 arm, whereas major cardiac structural complications and major vascular complications occurred more frequently in the Ultra group. All other in-hospital complication rates were similar between the 2 groups. At 1 year, the cumulative incidence of the primary endpoint (14.1% for neo2 vs 14.5% for Ultra; P = 0.819) was similar between the groups. Likewise, the individual components showed no difference between the groups. Conclusions: Despite differing immediate results, the outcomes at 1 year, including the composite of all-cause mortality, stroke, or hospitalization, were similar for neo2 and Ultra transcatheter heart valves.
Opening up food sovereignty and Community Supported Agriculture with organizational perspectives: zooming into the diversity of economic actors that are striving for food sovereignty
(2025) Middendorf, Matthias
Agri-food systems face multiple interlinked crises, including accelerating climate change, biodiversity loss, entrenched social inequalities, and pressures on democratic institutions. Food sovereignty has emerged as a prominent pathway for transforming agri-food systems toward greater justice and sustainability, understood as peoples’ right to healthy, culturally appropriate food produced sustainably and to define their own agri-food systems. It is articulated as both a social movement and an alternative food concept and is addressed in movement strategies, policy debates, and research at international, national, and regional levels. Yet most analyses remain concentrated at the macro-/system-level, while actors and organizational phenomena receive limited analytical attention. In particular, actors engaged in economic activities (e.g., production, processing, distribution) are not consistently named in the food sovereignty discourse as ‘economic actors’ and are often overlooked. This stands in tension with the movement’s explicit calls to build an alternative economic model. Shaped by critiques of the corporate agri-food system, such terminological caution fosters generalization and limits differentiation among actors, thereby sidelining analysis at the organizational level. As a result, the organizational configurations through which economic actors operate (understood as combinations of organizational characteristics such as decision-making, property, and labor) are seldom examined. This conceptual flattening marginalizes organizational perspectives in the food sovereignty discourse and underrepresents the diversity of economic actors, their configurations, and challenges, thereby limiting opportunities for their support. The functioning and stability of economic actors are essential for shaping transformations. Accordingly, organizational configurations must be analyzed alongside economic activities. Community Supported Agriculture (CSA) organizations, often cited as an expression of food sovereignty, illustrate this gap, as they are rarely differentiated or subjected to organizational analysis. The overall aim of this dissertation is to open up, broaden, and deepen the discourse on food sovereignty and CSA by approaching food sovereignty not only as a movement and concept but also as an organizational phenomenon. It uses organizational perspectives as a heuristic lens to render the organizational configurations of economic actors analytically visible. Adopting an actor-centered perspective at the organizational level, the dissertation conceptualizes the diversity of economic actors striving for food sovereignty (EAFS) and differentiates their organizational configurations in general and for CSAs in particular. The first paper develops a conceptual framework based on an integrative literature review and thematic analysis of 108 publications on food sovereignty, including gray literature. It conceptualizes organizational diversity within EAFS by identifying general patterns across Global North and Global South contexts and differentiates EAFS at the organizational level. The second transdisciplinary paper develops a CSA Framework in partnership with the German CSA Network and applies a mixed-methods design to CSAs in Germany. It uses a survey of 70 CSAs to test the framework, documents organizational heterogeneity, demonstrates that configurations differ by governance type (producer-led, consumer-led, integrated), and confirms the diversity and complexity of CSA organizations. Synthesizing the findings of both studies yields the Synthesized EAFS Framework, which provides a more differentiated organizational perspective on EAFS. This framework distinguishes three domains comprising 12 characteristics: Conditions that shape EAFS (Motives, Transformative approach, Intersectionality), Organizational-related characteristics (Organizational governance types, Founding impulse and establishing paths, Ownership/Property and legal forms, Work/Labor, Participation, Non-economic partnerships and cooperation), and Economic-related characteristics (Production practices and services, Scope of supply chains, Economic partnerships and cooperation). The framework defines Size as a cross-cutting structural factor. Conditions guide configuration choices across these characteristics. The framework also embeds the governance typology from the second study as a key lever for allocating decision rights. In doing so, the framework provides an actor-centered language for systematic comparison that moves beyond overly abstract descriptions. Finally, the dissertation aligns the Synthesized EAFS Framework with the six food sovereignty pillars established at the 1st Global Nyéléni Forum. This alignment makes configurations of EAFS at the organizational level analytically visible and grounds the framework in widely recognized movement principles. This supports the view that food sovereignty is also an organizational phenomenon and frames EAFS as a configuration space in which mixed forms are common. Accordingly, the findings reject simplistic binaries and show the prevalence of mixed forms: depending on the configuration, EAFS can combine conventional logics (e.g., market participation, revenue generation) with alternative approaches (e.g., solidarity-based practices, community ownership, collective governance, shared economic risk). This perspective centers on differentiated organizational configurations rather than generalized forms. Taken together, the dissertation makes several key contributions. Conceptually, it first makes the diversity of EAFS along the agri-food supply chain visible. Second, it develops an integrative, actor-centered organizational language and a novel framework that links food sovereignty goals to organizational phenomena and enables application across contexts as well as the analysis of EAFS configurations. Empirically, it documents organizational heterogeneity among CSAs in Germany, a prominent EAFS case, and shows how governance types and characteristics are distributed. Methodologically, it offers an analytical lens for comparing EAFS in different settings by making organizational configurations analytically visible. In practice, it guides context-sensitive configurations for practitioners and movement educators and supports alliance-building among EAFS. It enables the identification of organizational challenges (e.g., unclear decision rights and roles, resource constraints, power asymmetries) that provide a basis for strengthening organizational stability and adaptability. For policy and support systems, it points to the importance of aligning instruments with actual configuration options and addressing organizational challenges where relevant. Future research should refine and extend the Synthesized EAFS Framework beyond CSA to other EAFS (e.g., food hubs or food processing actors) and apply it across contexts, including in the Global South. It should examine decision-making, participation, and power within governance types to determine who benefits and who is excluded. It should also analyze how organizational stability and adaptability relate to governance and ownership/property under operational constraints. Overall, these directions shift the discourse from whether EAFS matter to how specific configurations function, for whom, and under what conditions, while supporting practice-research transfer within the contemporary food sovereignty discourse.
Mass spectrometric analysis of particulate matter in remote regions and highly polluted Chinese and Iranian megacities
(2025) Barth, Christof
The investigations in the present work are intended to contribute to the understanding of the health and environmental impacts of aerosol pollution, both in remote regions and in strongly polluted megacities. This was achieved by a combination of different instrumental and methodological approaches. First, in-situ single-particle analysis and its evaluation, based on multivariate statistical methods, was methodologically advanced using the example of a comparative measurement of standard samples in the laboratory and of online measurements on the Jungfraujoch high altitude research station at 3580 m asl in the Swiss Alps. In order to rationalize single-particle data, weather conditions, wind speed and wind direction as well as the geographical position during the measurement were taken into account. It was found that during the field measurements at the Jungfraujoch site, Sahara desert storm events were a major source for less aged iron- and silicon-rich mineral particles. Between those events the particle population was dominated by inorganic carbonaceous compounds. Both types of particles increase the local temperature and accelerate snowmelt, either by reducing snow albedo or by absorbing light over a broad spectral range. Secondly, in order to be able to address the environmental and health related factors in greater detail, particles from two heavily polluted megacities in Hangzhou, China and Tehran, Iran were extensively characterized. Filter samples were collected and measured by high-resolution mass spectrometry imaging to assign organic hydrocarbons and more complex inorganic compounds. This enabled analysis of intact organic molecules with high mass resolution and high mass accuracy. The novel methodological approach, in which the surface of particle quartz filter samples was scanned under atmospheric pressure using a 343 nm (Yb:YAG) laser (lateral resolution about 50 µm), enabled spatially resolved determination of the molecular particle composition. More than 3200 inorganic and organic compounds were specifically assigned to individual particles based on their exact mass and location on the filter surface. Particle sources could be easily distinguished from each other by means of characteristic mass spectrometric patterns using statistical clustering methods. Standard addition methods were also used to quantify polyaromatic hydrocarbons (PAHs) on the surface of the filters. By correlating the quantitative data with the spatially resolved particle measurements, it was possible to make well-founded statements about the respective particle pollution and its causes on site. Levels of heavy metals and harmful organic compounds, primarily from anthropogenic sources, were significant in both cities. However, higher concentrations of PAHs and a greater number of heavy metal compounds were found in the samples from Tehran. Since total particle pollution in Tehran during sampling was lower than in Hangzhou, these values are extremely alarming and demonstrate the non-compliance with and the lack of air pollution control strategies in the eastern Mediterranean region. Finally, it was shown that both methods require little or no sample preparation and provide excellent results in terms of speed, accuracy and selectivity.