KLUEDO Dokumente/documents https://kluedo.ub.rptu.de/index/index/ Fri, 13 Mar 2026 09:23:12 +0100 Fri, 13 Mar 2026 09:23:12 +0100 https://kluedo.ub.rptu.de/frontdoor/index/index/docId/9705 This thesis investigates two distinct but computationally intensive problems in algebraic and tropical geometry. The first part addresses the automation of generating sets for automorphism groups of K3 surfaces, along with their associated rational curves and fundamental domains. By analyzing a computational framework in detail, this work clarifies the theoretical foundations and enables systematic verification of these groups, highlighting the complexity of their structure. Existing methods from the literature were independently assessed to ensure the soundness and reliability of the underlying approach rather than its numerical implementation. This combined focus on methodological scrutiny and automation provides a more robust basis for further study of K3 surface automorphisms. Ultimately, the investigation confirms the theoretical robustness of the framework, while demonstrating that practical computational feasibility remains a nontrivial challenge. The second part of this thesis focuses on computing 𝔸¹-multiplicities for the bitangent classes of smooth generic tropical quartic curves and leveraging these computations to analyze the structure of the associated secondary fan. By systematically determining these multiplicities, the study quantifies the proportion of the secondary fan corresponding to the invariant 14ℍ, providing a refined perspective on the geometric distribution of bitangent shapes. I employ a hierarchical Bayesian framework for this analysis, which not only integrates prior geometric knowledge but also models variability at multiple levels, both globally across the entire fan and locally within specific secondary cones and their subcones. This hierarchical structure allows for more nuanced inference, especially in the presence of sparse or unevenly distributed data, and enables us to borrow statistical strength across related regions of the secondary fan. As a result, the analysis yields more stable posterior estimates of multiplicity frequencies and offers deeper insight into the geometry of the parametric space for smooth tropical quartics. Firoozeh Dastur doctoralthesis https://kluedo.ub.rptu.de/frontdoor/index/index/docId/9705 Fri, 13 Mar 2026 09:23:12 +0100 https://kluedo.ub.rptu.de/frontdoor/index/index/docId/9707 Im Bereich der kuchenbildenden Fest-Flüssig-Trennung wird seit langem die Realisierung einer gasdurchsatzlosen Kuchenfiltration erforscht, da eine Kuchenfiltration ohne Gasdurchsatz bei der Entfeuchtung zu erheblichen Energieeinsparungen führen würde und ebenso zur Reduzierung der mechanisch erreichbaren Restfeuchte in Filterkuchen beitragen könnte. Im Rahmen dieses Projekts wurden daher umfangreiche experimentelle Untersuchungen durchgeführt, welche insbesondere von KMU nicht zu leisten sind, um die Tauglichkeit von Membran-Gewebe-Kompositen für diesen Einsatzzweck zu zeigen. Es wurden insgesamt drei unterschiedliche Fügeverfahren zur Verbindung der Membran auf dem Gewebe untersucht: Die flächige Verschweißung, die punktuelle Verschweißung und die punktuelle Klebung. Hierbei hat sich gezeigt, dass eine Verschweißung der beiden Materialien miteinander höhere Verbindungsfestigkeiten zwischen Membran und Gewebe zur Folge hatte, als dies bei einer Verklebung der Fall war. Jedoch liegt die Herausforderung bei der Verschweißung nach wie vor in der gasdichten Fügung. Durch das Aufschmelzen der Membran wird diese beschädigt, sodass durch offene Stellen erneut Gas durch das Komposit-Material hindurchtreten kann. Daher wird mit Abschluss des Projekts eine Herstellung der Membran-Gewebe-Komposite mittels Punktverklebung favorisiert. Dieses Herstellungsverfahren wird bereits großindustriell von KMU eingesetzt, weshalb ein Übergang zu größeren Maßstäben unproblematisch erscheint und für KMU am einfachsten umzusetzen ist. Anhand von diversen Filtrationsversuchen und μCT-Aufnahmen wurde innerhalb des Projekts die Eignung eines solchen geklebten Membran-Gewebe-Komposits nachgewiesen. Es konnte genauer gezeigt werden, dass der Filtermittelwiderstand nicht signifikant erhöht wird, solange die Klebepunkte auf denen nach obenstehenden Gewebefasern platziert werden. Die Forschungsergebnisse des Projekts sind in zwei Publikationen bereits veröffentlicht worden und stehen somit KMU zur Verfügung, um Ihre eigenen Produkte weiterzuentwickeln und konkurrenzfähig bleiben zu können. Nikolai Benz; Sergiy Antonyuk report https://kluedo.ub.rptu.de/frontdoor/index/index/docId/9707 Thu, 12 Mar 2026 10:14:57 +0100 https://kluedo.ub.rptu.de/frontdoor/index/index/docId/9706 The continuous development of new products in pharmaceutical and biotechnology industries requires efficient and scalable separation processes. Standardized laboratory tests for hydraulic resistance of filtration membrane typically demand large membrane areas and substantial suspension volumes. Analytical photo-centrifugal filtration (ACF) offers a novel approach for high-throughput membrane characterization using minimal sample volumes. Based on continuous in-situ measurement of space- and time-resolved light transmission, ACF determines filtrate volume via STEP-Technology®. Unlike conventional pressure-driven methods, ACF operates without external pressure and requires minimal cleaning. Its flexible design allows parameter adjustments by varying rotor speeds or temperature profiles within a single experiment. In contrast to the conventional method (VDI 2762), several samples can be measured at once. This study presents an improved filtration cell for ACF and demonstrates the comparability of membrane resistances measured by ACF and VDI 2762. A polypropylene membrane with a nominal pore size of approximately 0.1 μm was used. Challenges and future opportunities are also discussed. Philipp Lösch; André Lier; Nikolai Benz; Sebastian Boldt; Dietmar Lerche; Sergiy Antonyuk article https://kluedo.ub.rptu.de/frontdoor/index/index/docId/9706 Thu, 12 Mar 2026 10:04:30 +0100 https://kluedo.ub.rptu.de/frontdoor/index/index/docId/9703 Automatic differentiation (AD) provides accurate derivatives of computer programs in an efficient manner. With extensions to handle programs that are parallelized with MPI or OpenMP, it can also be applied at large scale. The reverse mode of AD is particularly suitable for applications with low-dimensional output and high-dimensional input, as is typical in optimization contexts. However, it requires reversal of the entire computational graph, which can consume substantial amounts of memory. Several techniques exist to make applications of the reverse mode of AD feasible, one of which is preaccumulation, where Jacobians of parts of the computational graph are already assembled as the graph is recorded. If multiple threads share global derivative variables, simultaneous thread-local preaccumulations with shared input variables introduce data races. We address these data races by using thread-local derivative variables instead. We evaluate different vector- and map-based implementations with respect to memory consumption, memory allocation, and memory access times. We implement these alternatives in the AD tool CoDiPack and benchmark them in the multiphysics simulation suite SU2, which is differentiated with CoDiPack together with the add-ons OpDiLib for AD of OpenMP and MeDiPack for AD of MPI. Johannes Blühdorn; Nicolas R. Gauger conferenceobject https://kluedo.ub.rptu.de/frontdoor/index/index/docId/9703 Thu, 12 Mar 2026 09:12:11 +0100 https://kluedo.ub.rptu.de/frontdoor/index/index/docId/9702 In computational engineering, accompanying derivatives help to assess and further process primal simulation results, for example for sensitivity analysis, design optimization, or uncertainty quantification. Discrete adjoint approaches, specifically, compute derivatives that are consistent with the solution procedure of discretized problems, and automatic differentiation (AD) may serve as a key ingredient for their implementation. Discrete adjoints in the open-source multiphysics simulation suite SU2 are based on the operator overloading AD tool CoDiPack, coupled with the MeDiPack add-on for the differentiation of MPI parallelism. With a view on scalability, an additional layer of OpenMP parallelism has recently been added to SU2's primal solvers. To extend this to discrete adjoint solvers, we couple SU2 together with the already applied AD tools with the OpDiLib add-on that introduces operator overloading AD support for OpenMP parallelism. We discuss the impact on SU2's AD workflow, identify differences to pure MPI in terms of AD, and study and improve the parallel discrete adjoint performance on test cases from external aerodynamics. Johannes Blühdorn; Nicolas R. Gauger conferenceobject https://kluedo.ub.rptu.de/frontdoor/index/index/docId/9702 Thu, 12 Mar 2026 09:09:33 +0100 https://kluedo.ub.rptu.de/frontdoor/index/index/docId/9700 In this thesis, two topics are being discussed: the investigation of the reactivity of \(Cu-H_2dmg\) complexes and the synthesis and characterization of photoswitchable dinuclear copper complexes with azobenzene-based ligands. In the first chapter, the formation and reactivity of various mono- and dinuclear copper dimethylglyoxime complexes is studied. It was determined that the pH value strongly influences the nuclearity of the complexes formed: under basic conditions the mononuclear complex \([Cu(Hdmg)_2]\) is favored, while neutral and slightly acidic conditions yield the dinuclear complex \([Cu_2(H_2dmg)(Hdmg)(dmg)]X (X = ClO_4^-, BF_4^-, OTf^-)\). However, for the conversion between these two species an adjustment of the pH value as well as addition of extra ligand is needed. Additionally, changing the copper salts used affect the complex formation: the slightly basic \(Cu(OAc)_2\) leads to \([Cu(Hdmg)_2]\), \(CuCl_2·2H_2O\) yields \([Cu(H_2dmg)Cl_2]\), while \(Cu(ClO_4)_2·6H_2O\), \(Cu(BF_4)_2·6H_2O\), and \(Cu(OTf)_2\) form dinuclear complexes of the type \([Cu_2(H_2dmg)(Hdmg)(dmg)]X (X = ClO_4^-, BF_4^-, OTf^-)\). Interestingly, starting from \(Cu(BF_4)_2·6H_2O\) additionally forms O-O-bidentate \(BF_2\)-bridged complexes, such as \([Cu_2(dmg ⋅ BF_2)(Hdmg)(H_2dmg)]BF_4\), \([Cu(dmg ⋅ BF_2)_2(MeCN)]\), and \([Cu(dmg ⋅ BF_2)(Hdmg)]\) via the decomposition of \(BF_4^-\). This provides a facile synthetic route for these types of complexes without the usage of the highly toxic \(BF_3·Et_2O\). Attempts to use the resulting fluoride ions for the fluorination of organic substrates were not successful. The solvent-dependent reactivity of \([Cu_2(H_2dmg)(Hdmg)(dmg)]ClO_4\) was also examined. Unlike its mononuclear analogue, it is sensitive towards \(H_2O\), leading to the hydrolysis of \(H_2dmg\) forming 2,3-butanedione monoxime and hydroxylamine \((NH_2OH)\). This reaction is enabled by cooperative effects of the two copper centers, which increase the electrophilicity of the \(µ_2-O-N=C\) group. Depending on the solvent, \(NH_2OH\) is either reduced to \(NH_4^+\) (in ethanol) or oxidized to \(N_2O\) (in acetonitrile). The latter reaction yields \([Cu(MeCN)_4]X (X = ClO_4^-, BF_4^-, OTf^-)\), providing a simple method to prepare Cu(I) salts. Overall, the reactivity of \([Cu_2(H_2dmg)(Hdmg)(dmg)]X (X = ClO_4^-, BF_4^-, OTf^-)\) exemplifies functional, enthalpic, and entropic cooperativity. In the second, chapter the synthesis and characterization of the new azobenzene and azoxybenzene based ligands \(3,3'-Azobenz(metPA)_2\) and \(3,3'-Azoxybenz(metPA)_2\) as well as their (macro-)cyclic dinuclear Cu(I) complexes are described. \(3,3'-Azobenz(metPA)_2\) was synthesized in a three-step synthesis starting from 3-nitrobenzyl alcohol and exhibits reversible photoisomerization, as confirmed by spectroscopic studies and quantum-chemical calculations. The complex \([Cu_2(3,3'-Azobenz(metPA)_2)_2](BF_4)_2\) also remains reversibly photoswitchable – representing the first known reversibly photoswitchable (3d-)metallocycle. This photoswitchable copper complex offers promising potential for light-controlled host guest systems and electron transfer applications, as isomerization alters the cavity size and the coordination geometry of the Cu(I)-center. Geometry optimizations suggest a shift toward a more tetrahedrally distorted Cu(I) coordination \((τ_4 = 0.59–0.68)\), potentially facilitating reversible Cu(I)/Cu(II) interconversion - an entatic state-like behavior. The photoreactivity of the azoxybenzene analogue of the ligand, \(3,3'-Azoxybenz(metPA)_2\), depends on the wavelength used: 365 nm induces a Wallach rearrangement to a 2-hydroxyazobenzene derivative instead of E-Z isomerization, thus, hindering the subsequent Z–E isomerization, while irradiation at 310 nm favors E–Z isomerization. However, re-isomerization using 448 nm causes small parts of the compound to undergo a Wallach rearrangement, which limits photoisomerization as with high numbers of cycles the corresponding 2-hydroxyazobenzole derivative is enriched. Additionally, the corresponding Cu(I) complex \([Cu_2(3,3'-Azoxybenz(metPA)_2](BF_4)_2\) could be synthesized. However, due to the observed Wallach rearrangement, it was not investigated towards its photophysical properties. Raphael Immanuel Petrikat doctoralthesis https://kluedo.ub.rptu.de/frontdoor/index/index/docId/9700 Wed, 11 Mar 2026 07:36:27 +0100 https://kluedo.ub.rptu.de/frontdoor/index/index/docId/9695 In dem vorliegenden Dissertationsdokument werden die Forschungsresultate zur Anwendung von Magnetpartikeln in biopharmazeutischen und lebensmitteltechnischen Prozessen vorgestellt. Durch das hohe Oberflächen-Volumen-Verhältnis von sphärischen Magnetpartikeln sind diese als Mikrosorbentien und als Trägerpartikel für Enzyme geeignet. Nach einer Oberflächenfunktionalisierung mit Affinitätsliganden lassen sich Biomoleküle spezifisch als Wertprodukte aus komplexen Systemen isolieren. Bei einem Einsatz als Trägerpartikel für immobilisierte Enzyme ist ihre Wiederverwendung im Rahmen der Biotransformation möglich. Bevor jedoch das Wertprodukt von den Magnetpartikeln desorbiert werden kann bzw. die Enzym-Magnetpartikel recycliert werden, ist eine Magnetseparation erforderlich. Durch die super-paramagnetischen Eigenschaften der Partikel können diese mittels Hochgradienten-Magnetseparation (HGMS) selektiv aus strömenden Mehrkomponenten-Suspensionen abgetrennt werden. In dieser Arbeit wurden HGMS-Abscheidekammern für den Einmalgebrauch entwickelt. Dabei wurde hinsichtlich der Wirtschaftlichkeit eines Magnetpartikel-basierten Prozesses ein hoher Partikelrückhalt sowie die möglichst verlustfreie Partikelrückgewinnung angestrebt. Die Konstruktion der verschiedenen Abscheidegeometrien erfolgte in der Computer-Aided-Design-Software Siemens NX 12 (Siemens PLM, Plano, USA). Zur Bewertung der Designs wurden Magnetfeld- und Strömungssimulationen durchgeführt. Die HGMS-Abscheidekammern wurden zudem so ausgelegt, dass sie im Rahmen des Rapid Prototypings mittels 3D-Druck aus einem pharmazertifizierten Harz (USP Class VI) gefertigt werden können. Um dem strengregulierten pharmazeutischen Umfeld Rechnung zu tragen, wurden dabei alle produktberührenden Oberflächen in der HGMSAbscheidekammern aus diesem Kunststoff gebildet. Die HGMS-Abscheidematrix war damit umhüllt und somit von den Prozessfluiden isoliert. Um eine optische Prozesskontrolle zu ermöglichen und die Partikelrückgewinnung zu beurteilen, wurde ein Verfahren zur Steigerung der Transparenz von Bauteilen entwickelt. Durch dieses konnte der Mittenrauwert von 0,52 µm auf 0,31 µm gesenkt werden, was den Anforderungen eines Hygienic Designs entgegenkommt. Zur Charakterisierung der HGMS-Abscheidekammern wurden diese mit anwendungsspezifischen Magnetpartikel-Suspensionen beaufschlagt und Versuchsparameter variiert. Bevorzugt wurde ein Volumenstrom von 100 mL⸱min-1 gewählt, der geometriekorreliert zu Verweilzeiten von 9,3 - 29,3 s führte. Die Quantifizierung von Partikelverlusten erfolgte über UV/Vis-Messungen. Zu den experimentell beleuchteten Teilgebieten zählte die mRNA-Aufreinigung im Kontext der Impfstoffherstellung über Magnetpartikel und die Verwendung von Enzym-Magnetpartikeln mit ß-Glucosidase-Aktivität für die Veredlung von Craft-Bier. Im Rahmen einer holistischen Betrachtung von der Funktionalisierung der Partikel bis zu ihrem Recycling wurde der Partikelgrößenverteilung besondere Bedeutung zugeschrieben. Agglomerierte Partikel verfügen über ein reduziertes Oberflächen-Volumen-Verhältnis und sind daher in jedem Anwendungsgebiet unerwünscht. Um die ursprüngliche Partikelgrößenverteilung wieder herzustellen, wurde Ultraschall als Methode zur De-Agglomeration untersucht. Lars Wommer doctoralthesis https://kluedo.ub.rptu.de/frontdoor/index/index/docId/9695 Tue, 10 Mar 2026 12:00:18 +0100 https://kluedo.ub.rptu.de/frontdoor/index/index/docId/9696 Das vom BMBF geförderte Verbundforschungsprojekt CyberTech adressiert die wachsende Komplexität moderner Produktentwicklungsprozesse, die durch steigende Softwareanteile, zunehmende Vernetzung und verkürzte Innovationszyklen geprägt sind. Ziel des Projekts war die Entwicklung und Erprobung eines integrativen Ansatzes für Advanced Systems Engineering (ASE), der die Dimensionen Mensch, Technik und Organisation nach dem MTO-Prinzip ganzheitlich verbindet. Im Mittelpunkt stand die Frage, wie cyber-technische Systeme künftig effizient, nachvollziehbar und menschzentriert entwickelt werden können. Innerhalb der Säule Mensch wurden ein ASE-spezifisches Kompetenzmodell, Maßnahmen zur Förderung agiler Lernkulturen sowie moderne Lernformate einschließlich eines universitären Lehr- und Lernlabors entwickelt. Die Säule Technik fokussierte die Gestaltung digitaler Zwillinge, die Integration von Sensordaten in Simulationsmodelle, ein ASE-Reifegradmodell sowie Methoden zur domänenübergreifenden Interoperabilität und Traceability. In der Säule Organisation entstanden ein agiles Vorgehensmodell für MBSE, ein generisches Informationsmodell zur Gestaltung durchgängiger Digital Threads sowie Ansätze für KI-basierte Entwicklungsassistenz zur Unterstützung der Systemmodellierung und Normkonformitätsprüfung. Der Abschlussbericht fasst die genannten Ergebnisse zusammen und bietet somit einen Leitfaden zur Einführung von ASE in der industriellen Praxis und skizziert zugleich künftige Forschungsbedarfe für resiliente, vernetzte und menschorientierte Engineering-Prozesse. Benjamin Schleich; Reiner Anderl; Benjamin Röhm; Tanja Steinbach; Oliwia Karasek; Yusuf Arslanparcasi; Mohammad Chami; Ibrahim Ghanawi; Albrecht Urbaszek; Günter Eßl; Marko Ćorić report https://kluedo.ub.rptu.de/frontdoor/index/index/docId/9696 Tue, 10 Mar 2026 10:08:04 +0100 https://kluedo.ub.rptu.de/frontdoor/index/index/docId/9683 The increasing reliance on vision-based deep learning for automated quality inspection in manufacturing emphasizes the need for collaborative model development across distributed production sites. Also, legal, privacy, and proprietary constraints often prevent centralized aggregation of such industrial data. This thesis investigates the use of Federated Learning (FL) as a decentralized framework for training high performance computer vision models without sharing raw data. A modular and scalable FL architecture is proposed, supporting both image classification and object detection under non-Identically and Independent Distributed (non-IID) client distributions, and leveraging lightweight, high-accuracy deep learning models suitable for industrial deployment. The experimental validation covers diverse industrial scenarios, including USB port and cabin windshield classification, as well as YOLO-based object detection for localizing quality-relevant components. The framework is further extended to hybrid setups that incorporate synthetic and real clients to address data scarcity, and validated through live inference across heterogeneous domains. In addition, a novel Federated Ensemble (FedEnsemble) strategy is introduced, in which a centralized dataset is partitioned into clients for federated training, yielding models that outperform conventional centralized baselines under domain shift. The main contributions of this thesis are: (i) a validated FL framework tailored for privacy-preserving quality inspection in industrial environments, (ii) empirical insights into training dynamics with a small number of heterogeneous clients, (iii) evidence of robust cross-domain generalization through hybrid federated setups combining real and synthetic data, and (iv) the introduction of FedEnsemble as a practical extension of FL that improves detection robustness in deployment. Together, these findings establish FL as a viable foundation for building distributed, scalable, and secure AI systems in smart manufacturing, enabling the development of robust and generalizable quality inspection models. Vinit Vikas Hegiste doctoralthesis https://kluedo.ub.rptu.de/frontdoor/index/index/docId/9683 Tue, 10 Mar 2026 09:19:51 +0100 https://kluedo.ub.rptu.de/frontdoor/index/index/docId/9694 PHA sind mikrobiologisch abbaubare Polymere und können aus Sekundärrohstoffen hergestellt werden. Schwarzwasser aus Vakuumtoiletten und Küchenabfälle sind aufgrund ihres Kohlenstoffgehalts potenziell geeignete Substrate. Hohe Nährstoffgehalte und eine komplexe Substratmatrix stellen jedoch Hürden dar, da diese nach der Literatur die PHA-Produktion inhibieren. Die Kombination mit Verfahren zur Nährstoffrückgewinnung ist eine vielversprechende Technologie, um diesem Problem zu begegnen. In dieser Dissertation wurden sowohl nährstoffreiche als auch nährstoffreduzierte Substrate in einem dreistufigen Prozess aus anaerober Versäuerung, Biomasseslektion und PHA-Akkumulation unter-sucht. Dabei war das Ziel herauszufinden unter welchen Betriebsbedingungen eine PHA-Produktion aus Schwarzwasser und Küchenabfällen möglich ist. In der anaeroben Versäuerung werden komplexe organische Moleküle bakteriell zu organischen Säuren umgewandelt, die als Substrat für die PHA-Produktion dienen. In Batchversuchen mit Schwarzwasser und Küchenabfällen wurden der pH-Wert, die Temperatur und die Konzentration der Küchenabfälle variiert, um die geeigneten Betriebsparameter für hohe Versäuerungsgrade und eine Beeinflussung des Produktspektrums zu finden. Die höchsten Versäuerungsgrade von 53% konnten bei Konzentrationen der Küchenabfälle von 62,5 g/L im mesophilen und pH-ungeregelten Betrieb erzielt werden. Essigsäure war in allen Versuchen dominierend, durch den pH-Wert konnte das weitere Produktspektrum jedoch beeinflusst werden. Bei pH 5 fand eine Lösungsmittelgärung statt, bei pH 6 eine Buttersäuregärung und bei pH 8 eine Propionsäuregärung. Dadurch können die produzierten PHA bereits teilweise in der Versäuerung beeinflusst werden. Die Selektion einer Bioasse, die reich an PHA-produzierenden Bakterien ist, kann durch ein Feast-Famine-Regime erreicht werden. Während eines zeitlich begrenzten Substratüberschusses können diese Bakterien Energie als PHA speichern und haben während des darauffolgenden längeren Substratmangels einen Selektionsvorteil. Als Substrat kamen hier sowohl nährstoffreiche als auch nährstoffreduzierte Substrate zum Einsatz. Mit beiden Substraten konnte erfolgreich eine PHA-produzierende Biomasse selektiert werden. Mit nährstoffreduzierten Substraten gelang es im besten Fall innerhalb von 8 Tagen 71% PHA-Produzenten mit PHA-Zellgehalten von bis zu 67% zu erreichen, im Gegensatz zu 38% Zellgehalt mit nährstoffreichem Substrat. Eine vorausgehende Nährstoffrückgewinnung ist für die Biomasseselektion somit von Vorteil, auch wenn gezeigt werden konnte, dass hohe Nährstoffkonzentrationen der PHA-Produktion nicht entgegenstehen. In der PHA-Akkumulation erfolgt ein dauerhafter Substratüberschuss, der die selektierten Bakterien zur PHA-Produktion anregt. In zahlreichen Versuchen kamen nährstoffreiche, nährstoffreduzierte und nährstofffreie reale und synthetische Substrate aus Schwarzwasser und Küchenabfällen zum Einsatz. Die Nutzung des gleichen Substrats wie in der Biomasselektion führte zu PHA-Zellgehalten von bestenfalls 45% und PHA-Konzentrationen von 449 mg/L. Durch ein phosphorfreies Substrat konnte der PHA-Zellgehalt weiter auf 60% gesteigert werden. Die PHA-Konzentration war mit 1.085 mg/L jedoch in einem zwar stickstoffreduzierten jedoch phosphorreichen Substrat am höchsten. Die Skalierung des Prozesses auf einen halbtechnischen Maßstab war mit 47% PHA-Zellgehalt ebenfalls erfolgreich. Florian Ye doctoralthesis https://kluedo.ub.rptu.de/frontdoor/index/index/docId/9694 Mon, 09 Mar 2026 14:06:37 +0100 https://kluedo.ub.rptu.de/frontdoor/index/index/docId/9692 In industry, automatic visual surface inspection is a common technique for quality control. Machine learning methods provide promising results for automated defect detection. Data in sufficient quantity and quality is needed to train robust models. Real image data, especially of defective surfaces, is commonly not available in the needed amount. For rarely produced objects, not all critical defect types may be included in the data set. In addition, real data has to be annotated manually. Synthetic data offers a suitable alternative. Therefore, the imaging environment including the camera, the light source and the object to be inspected as well as the imaging method have to be simulated. In this thesis we consider the details of the digital twin of the object to be inspected. We focus on metallic objects which are strongly reflective. Therefore, the visibility of surface defects highly depends on the surface texture. Hence, part one of this thesis deals with the simulation of two different surface textures resulting from the following surface processing methods: sandblasting and linear/spiral milling. Two different models have been developed based on real topography measurements. To model sandblasted surfaces, two steps are needed. To generate textures that cover the entire object surface, small patches are created first using the random phase noise (RPN). Then, those are stitched using an adaptation of the method from Efros and Freeman. Textures of milled surfaces are modeled by a multi-step model, considering the milling pattern, the movement of the milling head and the overlap of neighboring milling paths. Real parameters are included into the model. Part two of this thesis deals with the simulation of synthetic 3d defect geometries which can then be added to an object geometry. We restrict to common defect types that appear for cast objects, for example cracks, rat tails or lift-offs of the surface top layer. Parametric, defect-specific models are developed. In general, 2d Voronoi tessellations build the basis for the models since they reflect the poly-crystalline micro-structure of metal. The tessellations are used to model defects on different scales and to ensure variability also when using the same parameter configuration due to the underlying random point processes. The diversity of defect geometries within a defect class is obtained by different parameter configurations. Natascha Jeziorski doctoralthesis https://kluedo.ub.rptu.de/frontdoor/index/index/docId/9692 Mon, 09 Mar 2026 12:45:41 +0100 https://kluedo.ub.rptu.de/frontdoor/index/index/docId/9679 Recent reports warn of the imminent surpassing of a tipping point that will transform the Amazon rainforest into a savannah. In the transboundary region shared by Bolivia, Brazil, and Peru (named the MAP region, an acronym for the states of Madre de Dios, Peru; Acre, Brazil; and Pando, Bolivia), this land-use conversion has been triggered by logging and farming, and recently intensified by the construction of a transcontinental highway. As economic incentives grow, so does social and environmental harm. We devised a participatory systems approach to evaluate and characterize the social-ecological system in a site in each of the three countries, and to identify the factors that may lead to the systems’ loss of resilience and eventual trespassing of tipping points. Methodologically, the approach combines stakeholder analysis, network analysis, and systems analysis, and includes transboundary research and locals’ participation as overarching premises adding plausibility and legitimacy to the findings. Results show that the three country-sites, despite their similarities, have evolved divergently into archetypal social-ecological systems, each confronting specific challenges, i.e., in Bolivia, dependence on the volatile commodity Brazil nut, and unstable politics, has weakened a previously stable and functional institutional landscape. In Brazil, the conversion of forests into pastures for cattle ranching remains the major peril, fueled by a steady market demand and, regardless of the party in power, insufficient restraining measures. In Peru, economic diversification has increased the system’s resilience as a whole, however authorities struggle to exert control over the economic activities, some of which are illegal. Daniel Callo-Concha; Oliver Frör article https://kluedo.ub.rptu.de/frontdoor/index/index/docId/9679 Wed, 04 Mar 2026 10:25:42 +0100 https://kluedo.ub.rptu.de/frontdoor/index/index/docId/9678 The hydraulic performance and operational stability of centrifugal pumps are closely governed by the internal flow characteristics of the impeller. Under off-design conditions, conventional impellers tend to experience flow separation, vortex-induced energy loss, and intensified pressure pulsations, which impair performance and induce vibration. To improve these limitations, this study introduces a tandem-blade impeller configuration, where the front and rear blades cooperate to redistribute aerodynamic loading and enhance energy transfer. Performance tests and high-fidelity numerical simulations analyses were conducted on conventional and tandem impellers with varying blade numbers to evaluate hydraulic performance, vortex evolution and unsteady excitation forces. The results show that the tandem impeller realizes a notable head increase of approximately 1-2m, particularly evident at moderate and high flow rates. This improvement arises from more progressive pressure loading along the blade passages and a more uniform exit velocity field. Furthermore, the tandem impeller achieves two-stage pressure rise, which weakens abrupt loading zones and alleviates mid-span flow separation typically observed in conventional impellers. Vortex identification based on the Ω-criterion reveals that the tandem impeller induces stronger suction surface separation vortex within the gap. The development of these vortices is dominated by vortex stretching and rotational inertia effects, leading to enhanced vortex intensity and broader spatial distribution. These flow structures significantly modify the unsteady pressure field, as confirmed by FFT and continuous wavelet transform analysis, where the tandem impeller exhibits higher amplitude low-frequency components and more pronounced time-varying spectral energy, particularly under part-load conditions. In terms of force response, the tandem impeller shows improved radial force and axial force balance near the design and overload conditions. However, under part-load conditions, the enhanced low-frequency excitation leads to larger radial and axial force fluctuations, which may negatively impact mechanical stability. Overall, the tandem impeller demonstrates clear advantages in improving hydraulic head and outlet flow uniformity, but its gap-induced unsteady flow behavior requires further optimization, especially for stable operation under part-load conditions. Gang Yang doctoralthesis https://kluedo.ub.rptu.de/frontdoor/index/index/docId/9678 Wed, 04 Mar 2026 08:43:10 +0100 https://kluedo.ub.rptu.de/frontdoor/index/index/docId/9674 In this PhD thesis, we investigate the application of neural networks for simulating daily spot and equity European option markets to facilitate the automation of hedging a portfolio of derivatives by reinforcement learning algorithms such as Deep Hedging. The simulation of such markets poses several challenges: handling of high-dimensional option data, no-arbitrage constraints and estimating the market's transition dynamic from limited real-world datasets. Among these challenges, we first focus on maintaining the arbitrage-free constraints in the generated call prices. Though arbitrage opportunities exist on the equities market, they are spurious, fleeting and often non-tradeable due to market frictions such as liquidity constraints and transaction costs. Furthermore, any arbitrage opportunity would be completely exploited by a downstream algorithm, making the approximated hedging strategy useless in practice. To ensure the absence of arbitrage in the generated call prices, we leverage an arbitrage-free parameterization through Discrete Local Volatilities. This parameterization simplifies the no arbitrage constraints of European call options to a positivity requirement and facilitates an efficient conversion to the original price space through a large-step implicit finite difference scheme. Options are observed at various strikes and maturities and create an extremely high-dimensional space, making it particularly challenging to calibrate a conditional density that models the transition dynamic from the current to the next day's state due to the curse of dimensionality. We address this by using autoencoders that compress equivalent arbitrage-free option representation, the Discrete Local Volatility lattice, to an efficient low-dimensional non-linear embedding. This embedding, combined with the spot return is then used to define the market state from which we estimate transition dynamics. Having obtained a low-dimensional arbitrage-free compressed representation, we next develop a model to estimate the conditional dynamic under the real-world measure \(\mathbb{P}\) for a single asset. For this purpose we introduce the neural spline flow - a highly versatile model defined by a collection of conditional cumulative distribution functions that characterize the conditional joint distribution through a neural network-based spline construction. We further extend the neural spline flow using path signatures from rough path theory and establish theoretical foundations that demonstrate practical advantages such as convexity in the model's parameters during calibration, mitigating the presence of local minima in the optimization function. Since real-world hedging applications involve portfolios consisting of multiple underlyings or more complex options (such as basket, rainbow or spread options), we consider constructing a multi-asset market simulator. To address scalability challenges, we propose static and dynamic Gaussian copulas that are conditional on the market state to correlate already calibrated single-asset market simulators. While we ensure in our real-world simulator that the spot process is a martingale and the call prices do not admit static arbitrage, the real-world simulator still admits statistical arbitrage, that is arbitrage in expectation, which is a weaker form of arbitrage. For this purpose, we propose to approximate a network-based measure change to obtain an approximation of the minimal entropy martingale measure - that is the martingale measure \(\mathbb{Q}\) that is minimal with respect to the Kullback-Leibler divergence. Using the approximate near-martingale measure, we calibrate a new market simulator, that as evidenced through numerical findings, admits less statistical arbitrage. All research presented in this thesis is accompanied by comprehensive numerical benchmarks that validate and demonstrate the effectiveness our approach. Wiese Magnus doctoralthesis https://kluedo.ub.rptu.de/frontdoor/index/index/docId/9674 Wed, 04 Mar 2026 08:35:12 +0100 https://kluedo.ub.rptu.de/frontdoor/index/index/docId/9675 Agricultural intensification and climate change increase pressure on biodiversity, with pesticides dispersing beyond treated fields into non-target areas. This thesis investigated three major stressors relevant to aquatic-terrestrial ecosystems: pesticide contamination, altered hydrological regimes, and the mosquito control agent Bacillus thuringiensis israelensis (Bti). It addresses the lack of data on the environmental presence and spatio-temporal dynamics of pesticide contamination and on how different environmental stressors influence trait development in aquatic-terrestrial organisms, with potential consequences for reproduction and higher trophic levels. This thesis combines multi-scale mapping of pesticide residues with computer-vision analysis of morphological traits of a damselfly under controlled exposures to each stressor. It uses a tiered approach linking field observations, experiments, and validation across scales for mechanistic and ecological insight. Large-scale pesticide monitoring across the Upper Rhine Valley in Germany revealed pronounced spatial gradients and pervasive background contamination. Prediction maps identified regional hotspots of mixture complexity, and contamination of conservation areas far from agricultural land. Temporal monitoring demonstrated chronic contamination in soils and seasonal peaks in vegetation during periods of high biological activity. At finer scales, riparian non-target buffer zone assessment showed high contamination regardless of buffer width, challenging their function as effective buffers or refuges for non-target organisms. Together, these studies showed pesticide mixtures to be a widespread and persistent characteristic in non-target habitats. Experimental exposures of damselfly larvae to an insecticide, Bti, and altered hydrology produced distinct trait signatures in wing morphology, including size, structure and asymmetry indicating changes in developmental stability. In two damselfly populations, morphological predictors of short-term mating success varied between sites, indicating that trait-fitness relationships are environmentally mediated. Furthermore, changes in emerging insect prey quality influenced higher trophic levels by affecting the developmental stability in riparian spiders. This research reveals that environmental stressors can alter morphological traits in aquatic organisms that are linked to important terrestrial processes such as mating success and predator-prey interactions. The widespread detection of pesticide mixtures in non-target areas suggests exposure pathways that current regulatory frameworks may not adequately address. The findings also emphasize the need for integrated management approaches that consider cross-ecosystem connectivity when assessing the ecological implications of micropollutants and climate change. Ken Maximilian Mauser doctoralthesis https://kluedo.ub.rptu.de/frontdoor/index/index/docId/9675 Mon, 02 Mar 2026 16:31:59 +0100 https://kluedo.ub.rptu.de/frontdoor/index/index/docId/9667 Bildung für nachhaltige Entwicklung (BNE) richtet sich heute mit vielfältigen Projekten und Bildungsangeboten an unterschiedliche Zielgruppen; seit 2015 werden auch zugewanderte Erwachsene verstärkt adressiert. Der Beitrag setzt an diesem Punkt an und untersucht die BNE-Verständnisse und pädagogischen Ansatzpunkte ausgewählter BNE-Angebote. Dazu wurden mit der Dokumentarischen Diskursinterpretation BNE-relevante Kapitel von fünf Orientierungskursbüchern sowie öffentlich zugängliche Informationen wie Webseiten, Videos, Flyer, Presseinterviews, Projektzusammenfassungen und Handreichungen von zehn BNE-Angeboten ausgewertet. Aus den untersuchten Materialien konnten fünf Diskursstränge rekonstruiert werden, die in diesem Beitrag anhand von fünf Bildungsangeboten, die diese Diskurse repräsentieren, dargestellt werden. Mit Blick auf die verfolgten pädagogischen Konzepte zeigen die Rekonstruktionen, dass die untersuchten BNE-Angebote vor allem ältere pädagogische Ansätze aufgreifen, wodurch neuere Perspektiven auf Bildung und Erziehung in der Migrationsgesellschaft in diesen Bildungsangeboten weitgehend unberücksichtigt bleiben. Auch die BNE-Verständnisse, die den untersuchten BNE-Angeboten zugrunde liegen, divergieren stark und reichen von Umweltverständnissen, die sich auf Mülltrennung und Sauberhaltung der unmittelbaren Umwelt beschränken, bis hin zu umfassenden Auseinandersetzungen mit Nachhaltigkeit, die einem BNE-Verständnis gerecht werden, das auf ergebnisoffene Reflexions‑, Lern- und Bildungsprozesse abzielt und BNE als facettenreiches, mehrdimensionales Lernfeld versteht. Barbara Pusch article https://kluedo.ub.rptu.de/frontdoor/index/index/docId/9667 Thu, 26 Feb 2026 19:34:53 +0100 https://kluedo.ub.rptu.de/frontdoor/index/index/docId/9665 Exposure to synthetic chemicals, such as pesticides and pharmaceuticals, affects freshwater communities at broad spatial scales. This risk is commonly managed in a prospective environmental risk assessment (ERA). Relying on generic methods, a few standard test organisms, and safety factors to account for uncertainty, ERA determines concentrations that are assumed to pose low risks to ecosystems. Currently, this procedure neglects potential variation in assemblage sensitivity among ecosystem types and recommends a single low-risk concentration for each compound. Whether systematic differences in assemblage sensitivity among ecosystem types exist or their size, are currently unknown. Elucidating spatial patterns in sensitivity to chemicals could therefore enhance ERA precision and narrow a fundamental knowledge gap in ecology, the Hutchinsonian shortfall. We analyzed whether taxonomic turnover between field-sampled macroinvertebrate assemblages of different broad river types across Europe results in systematic differences in assemblage sensitivity to copper and imidacloprid. We used an extensive database of macroinvertebrate assemblage compositions throughout Europe and employed a hierarchical species sensitivity distribution model to predict the concentration that would be harmful to 5% of taxa (HC5) in each assemblage. Predicted HC5 values varied over several orders of magnitude. However, variation within the 95% highest density intervals remained within one order of magnitude. Differences between the river types were minor for imidacloprid and only slightly higher for copper. The largest difference between river-type-specific median HC5 values was a factor of 3.1. This level of variation is below the assessment factors recommended by the European Food Safety Authority and therefore would be captured in the current ERA for plant protection products. We conclude that the differences in taxonomic composition between broad river types translate into relatively small differences in macroinvertebrate assemblage sensitivity toward the evaluated chemicals at the European scale. However, systematic differences in bioavailability and multi-stressor context were not evaluated and might exacerbate the differences in the ecological effects of chemicals among broad river types in real-world ecosystems. Jonathan F. Jupke; Thomas Sinclair; Lorraine Maltby; Jukka Aroviita; Libuše Barešová; Núria Bonada; Emília Mišíková Elexová; M. Teresa Ferreira; Maria Lazaridou; Margita Lešťáková; Piotr Panek; Petr Pařil; Edwin T. H. M. Peeters; Marek Polášek; Leonard Sandin; Dénes Schmera; Michal Straka; Ralf B. Schäfer article https://kluedo.ub.rptu.de/frontdoor/index/index/docId/9665 Thu, 26 Feb 2026 18:44:55 +0100 https://kluedo.ub.rptu.de/frontdoor/index/index/docId/9664 Biodiversity is declining worldwide as ecosystems are increasingly threatened by multiple stressors associated with anthropogenic global change. Stressors frequently co-occur across scales spatially and temporally, resulting in joint effects that are additive or non-additive, i.e., antagonism or synergism. Forecasting and counteracting threats from intensifying stressors requires improved mechanistic understanding of joint effects, which is currently relatively low. To date, research on multiple stressors has been biased toward simplified scenarios, emphasized classification of interactions over realized joint effects, and mostly ignored adaptation (i.e., phenotypic plasticity or evolving life-history traits) of organisms. To investigate if more a realistic scenarios design incorporating complex spatiotemporal stressor profiles and adaption change joint effects and interactions of multiple stressors compared to simplified scenarios, we modified a spatially explicit meta-population model for a generic freshwater insect. We used the model to simulate different, hypothetical spatiotemporal profiles of a continuous and a discrete stressor and evaluated their joint effects and interactions. Agricultural land use represented the continuous stressor impacting meta-population patch quality and network connectivity and related scenarios implied different trajectories. Climatic events represented the discrete stressor impacting all patches simultaneously by temporary mortality events, with related scenarios implying different event severity. Adaptation mitigated the effects of climatic events based on previous events. Lucas Streib; Jürg W. Spaak; Marius Kloft; Ralf B. Schäfer article https://kluedo.ub.rptu.de/frontdoor/index/index/docId/9664 Thu, 26 Feb 2026 18:28:32 +0100 https://kluedo.ub.rptu.de/frontdoor/index/index/docId/9663 Methane (CH4) emissions from natural systems are rising in a concerning manner with an incomplete understanding of its drivers. Recently, chemical stressors such as antibiotics have been suggested as a thus far overlooked factor increasing methanogenesis in freshwaters. Since usage and toxicological impact of antibiotics could increase in a warming climate, we assessed the temperature-dependence of antibiotic effects on methanogenesis. In this light, we conducted anaerobic incubations with freshwater sediment at 10, 15, and 20 °C in presence of a mixture of five antibiotics at field-relevant concentrations. Weekly measurements of CH4 showed a strong temperature dependence of antibiotic effects by changing effect sizes, directions and dynamics. While antibiotics reduced CH4 production at 10 °C, methanogenesis was elevated at 15 °C with the most pronounced increase occurring at 20 °C. Furthermore, antibiotics changed the prokaryotic assemblage at all temperatures and effect patterns of CH4 producing Methanomicrobia strongly followed the patterns observed for methanogenesis. While analyses of compound-specific stable isotopes and the metatranscriptome suggest the acetoclastic pathway as most relevant, linking prokaryotic structure to function remains one of the most significant research challenges. Nevertheless, the evidence provided by this study suggests a positive relationship between temperature and the stimulating effects of antibiotics on CH4 production. Eric Bollinger; Paul Schwilden; Foon Yin Lai; Ralf Schulz; Mirco Bundschuh; Sabine Filker article https://kluedo.ub.rptu.de/frontdoor/index/index/docId/9663 Thu, 26 Feb 2026 17:51:34 +0100 https://kluedo.ub.rptu.de/frontdoor/index/index/docId/9666 Microbiologically Induced Calcium Carbonate Precipitation (MICP) is a technology for improving soil characteristics, especially strength, that has been gaining increasing interest in literature during the last few years. Although a lot of influencing factors on the result of MICP are known, particle size and shape of the particles remain poorly understood. While destructive measuring of compressive strength or calcium carbonate content are important for the characterization of samples these methods give no insight into the internal structures and pore networks of the samples. X-ray microcomputed tomography (micro-CT) is a technique that is used to characterize the internals of rocks and to a certain degree MICP-treated soils. However, the impact of filtering and image processing of micro-CT Data depending on the type of MICP sample is poorly described in the literature. In this study, single fractions of local quarry were treated with MICP through the ureolytic microorganism Sporosarcina pasteurii to investigate the influence of particle size distribution on calcium carbonate content, unconfined compressive strength and the reduction of water permeability. Additionally, micro-CT was conducted to obtain insights into the resulting pore system. The impact of the Gauss filter und Non-local means filter on the resulting images and data on the pore network are discussed. The results show that particle size has a significant impact on the result of all tested parameters of biosandstone with lower particle size leading to higher strength and generally higher calcium carbonate content. Micro-CT data showed that the technology is feasible to gain valuable insights into the internal structures of biosandstone but the resolution and signal-to-noise ratio remain challenging, especially for samples with particle sizes smaller than 125 µm. Niklas Erdmann; Susanne Schaefer; Torben Simon; Andreas Becker; Ulrich Bröckel; Dorina Strieth article https://kluedo.ub.rptu.de/frontdoor/index/index/docId/9666 Thu, 26 Feb 2026 10:20:30 +0100 https://kluedo.ub.rptu.de/frontdoor/index/index/docId/9662 The microscopic pair structure of superfluids has profound consequences on their properties. Delocalized pairs are predicted to be less affected by static disorder than localized pairs. Ultracold gases allow tuning the pair size via interactions, where for resonant interaction superfluids show largest critical velocity, i.e., stability against perturbations. The sensitivity of such fluids to strong, time-dependent disorder is less explored. Here, we investigate ultracold, interacting Fermi gases across various interaction regimes after rapid switching optical disorder potentials. We record the ability for quantum hydrodynamic expansion of the gas to quantify its long-range phase coherence. Contrary to static expectations, the Bose-Einstein condensate (BEC) exhibits significant resilience against disorder quenches, while the resonantly interacting Fermi gas permanently loses quantum hydrodynamics. Our findings suggest an additional absorption channel perturbing the resonantly interacting gas as pairs can be directly affected by the disorder quench. Jennifer Koch; Sian Barbosa; Felix Lang; Artur Widera article https://kluedo.ub.rptu.de/frontdoor/index/index/docId/9662 Thu, 26 Feb 2026 10:19:47 +0100 https://kluedo.ub.rptu.de/frontdoor/index/index/docId/9661 Tetrapyrroles such as heme, chlorophyll, and vitamin B12 are essential for various metabolic pathways. They derive from 5-aminolevulinic acid (5-ALA), which can be synthesized by a single enzyme (5-ALA synthase or AlaS, Shemin pathway) or by a two-enzyme pathway. The genomes of some bacteriophages from aquatic environments carry various tetrapyrrole biosynthesis genes. Here, we analyze available metagenomic datasets and identify alaS homologs (viral alaS, or valaS) in sequences corresponding to marine and freshwater phages. The genes are found individually or as part of complete or truncated three-gene loci encoding heme-catabolizing enzymes. Amino-acid sequence alignments and three-dimensional structure prediction support that the valaS sequences likely encode functional enzymes. Indeed, we demonstrate that is the case for a freshwater phage valaS sequence, as it can complement an Escherichia coli 5-ALA auxotroph, and an E. coli strain overexpressing the gene converts the typical AlaS substrates glycine and succinyl-CoA into 5-ALA. Thus, our work identifies valaS as an auxiliary metabolic gene in phage sequences from aquatic environments, further supporting the importance of tetrapyrrole metabolism in bacteriophage biology. Helen Wegner; Sheila Roitman; Anne Kupczok; Vanessa Braun; Jason Nicholas Woodhouse; Hans-Peter Grossart; Susanne Zehner; Oded Béjà; Nicole Frankenberg-Dinkel article https://kluedo.ub.rptu.de/frontdoor/index/index/docId/9661 Thu, 26 Feb 2026 09:16:08 +0100 https://kluedo.ub.rptu.de/frontdoor/index/index/docId/9660 The magnetic properties of Ni nanoparticles (NPs) with diameter D are investigated using spin-lattice dynamics (SLD) simulations. Using exchange interactions fitted to ab-initio results we obtain a Curie temperature, Tc, similar, but lower, than experiments. In order to reproduce quantitatively the bulk Curie temperature and the experimental results, the exchange energy has to be increased by 25% compared to the ab-initio value. During the simulated time, Ni NPs remain ferromagnetic down to the smallest sizes investigated here, containing around 500 atoms. The average magnetic moment of the NPs is slightly smaller than that determined experimentally. By considering a core-shell model for NPs, in which the shell atoms are assigned a larger magnetic moment, this discrepancy can be removed. Tc is lower for a moving lattice than for a frozen lattice, as expected, but this difference decreases with NP size because smaller NPs include higher surface disorder which dominates the transition. For NPs, Tc decreases with the NP diameter D by at most 10% at D = 2 nm, in agreement with several experiments, and unlike some modeling or theoretical scaling results which predict a considerably larger decrease. The decrease of Tc is well described by finite-size scaling models, with a critical exponent that depends on the SLD settings for a frozen or moving lattice, and also depends on the procedure for determining Tc. Extrapolating the inverse of the magnetization as function of temperature near Tc gives a lower Tc than the maximum of the susceptibility. Gonzalo dos Santos; Herbert M. Urbassek; Eduardo M. Bringa article https://kluedo.ub.rptu.de/frontdoor/index/index/docId/9660 Thu, 26 Feb 2026 09:14:44 +0100 https://kluedo.ub.rptu.de/frontdoor/index/index/docId/9659 We study the effects of the chemical short-range order (SRO) on the thermal conductivity of the refractory high-entropy alloy HfNbTaTiZr using atomistic simulation. Samples with different degrees of chemical SRO are prepared by a Monte Carlo scheme. With increasing SRO, a tendency of forming HfTi and TiZr clusters is found. The phonon density of states is determined from the velocity auto-correlation function and chemical SRO modifies the high-frequency part of the phonon density of states. Lattice heat conductivity is calculated by non-equilibrium molecular dynamics simulations. The heat conductivity of the random alloy is lower than that of the segregated binary alloys. Phonon scattering by SRO precipitates might be expected to reduce scattering times and, therefore, decrease thermal conductivity. We find that, in contrast, due to the increase of the conductivity alongside SRO cluster percolation pathways, SRO increases the lattice heat conductivity by around 12 %. This is expected to be a general result, extending to other HEAs. Geraudys Mora-Barzaga; Herbert M. Urbassek; Orlando R. Deluigi; Marcelo Pasinetti; Eduardo M. Bringa article https://kluedo.ub.rptu.de/frontdoor/index/index/docId/9659 Thu, 26 Feb 2026 09:13:33 +0100 https://kluedo.ub.rptu.de/frontdoor/index/index/docId/9658 Permaculture is proposed as a tool to design and manage agroecological systems in response to the pressing environmental challenges of soil degradation, climate change and biodiversity loss. However, scientific evidence on the effects of permaculture is still scarce. In this comprehensive study on a wide range of soil and biodiversity indicators, we examined nine farms utilizing permaculture and paired control fields with locally predominant agriculture in Central Europe. We found 27% higher soil carbon stocks on permaculture sites than on control fields, while soil bulk density was 20% lower and earthworm abundance was 201% higher. Moreover, concentrations of various soil macro- and micronutrients were higher on permaculture sites indicating better conditions for crop production. Species richness of vascular plants, earthworms and birds was 457%, 77% and 197% higher on permaculture sites, respectively. Our results suggest permaculture as effective tool for the redesign of farming systems towards environmental sustainability. Julius Reiff; Hermann F. Jungkunst; Ken M. Mauser; Sophie Kampel; Sophie Regending; Verena Rösch; Johann G. Zaller; Martin H. Entling article https://kluedo.ub.rptu.de/frontdoor/index/index/docId/9658 Thu, 26 Feb 2026 09:12:29 +0100