University of Kaiserslautern
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The function of Mak16 in ribosome biogenesis depends on its [4Fe-4S] cluster
Get PDFMak16 and its interacting partner Rpf1 play a critical role at an early step in the maturation of the ribosomal 60S subunit of eukaryotes, as revealed by cryoelectron microscopy structures. While these studies suggested no metal participation or the presence of a Zn2+ ion in Mak16, we identify a previously unexplored iron–sulfur
(Fe/S) cluster in yeast Mak16 through both in vivo and in vitro methods. We demonstrate a functional link between mitochondrial and cytosolic Fe/S protein biogenesis and ribosome assembly, highlighting an overlooked aspect of 60S ribosomal biogenesis.
Characterization of human and yeast Mak16 revealed a redox-active
[4Fe-4S] 2+/1+ cluster with a midpoint potential below –500 mV. Oxidative stress destabilizes Mak16 and disrupts its interaction with Rpf1 in vivo, while in vitro H2O2 causes [3Fe-4S] 1+ cluster formation. Our findings also reveal that upon binding to rRNA expansion segment 7 the redox properties of the nearby Fe/S cluster largely remain unchanged. However, disruption of Fe/S cluster coordination destabilized Mak16, impaired the Mak16–Rpf1 complex formation and decreased the 25S rRNA level. The critical role
of Fe/S proteins in eukaryotic DNA replication and repair, mitoribosomal function, and maturation has now been extended to nuclear ribosomal assembly. Relying on a vulnerable cofactor comes at a cost, as cluster loss can severely disrupt essential cellular processes. The inherent biosynthetic complexity and instability of the Fe/S cluster of Mak16 allows it to function as sensor for redox imbalance, creating the possibility to regulate cellular homeostasis under stress
Kunsthandel: Markt oder Hierarchie? Eine Analyse der strukturellen Eigenschaften und ihrer Implikationen für das Kulturmanagement
Get PDFDer zeitgenössische Kunsthandel wird häufig als Markt beschrieben, folgt jedoch nur begrenzt den Logiken anonymer Preisbildung. Vielmehr ist er wesentlich durch hierarchische, relationale und hybride Koordinationsformen geprägt, in denen Beziehungsnetzwerke, symbolisches Kapital und informelle Steuerungsmechanismen eine zentrale Rolle spielen. Die vorliegende Arbeit argumentiert, dass Markt und Hierarchie im Kunsthandel nicht als Gegensätze, sondern als komplementäre Koordinationsformen zu verstehen sind, deren Ausprägung kontextabhängig variiert.
Anhand ausgewählter Fallbeispiele werden strukturelle Defizite wie Intransparenz, fehlende Regulierung und erhöhte Risiken im internationalen Kunsthandel aufgezeigt, die Praktiken in rechtlichen Grauzonen begünstigen. Vor diesem Hintergrund untersucht die Arbeit die Frage, inwieweit der Kunstmarkt mit klassischen Marktmodellen der Wirtschaftstheorie erklärbar ist oder ob er, im Sinne der Transaktionskostentheorie nach Williamson, stärker durch hierarchische, netzwerkartige und institutionelle Strukturen bestimmt wird. Ziel ist es, ein theoretisch fundiertes und zugleich praxisrelevantes Verständnis der Koordinationslogiken des Kunsthandels zu entwickeln.Contemporary art dealing is commonly described as a market, yet it operates only to a limited extent according to mechanisms of anonymous price formation. Instead, it is largely shaped by hierarchical, relational, and hybrid forms of coordination in which networks, symbolic capital, and informal governance mechanisms play a central role. This study argues that market and hierarchy in the art trade should not be understood as opposing principles but as complementary modes of coordination whose relevance varies according to context.
Drawing on selected case studies, the paper highlights structural deficits such as opacity, insufficient regulation, and heightened risk in the international art trade, which systematically facilitate practices situated in legal grey areas. Against this backdrop, the study examines whether the art market can be adequately described by classical economic market models or whether, following Williamson’s transaction cost theory, it is more accurately understood as being governed by hierarchical, network-based, and institutional structures. The aim is to develop a theoretically grounded yet practice-oriented understanding of the coordination mechanisms underlying the contemporary art trade
Projection optimization method for open-dissipative quantum fluids and its application to a single vortex in a photon Bose-Einstein condensate
Get PDFOpen dissipative systems of quantum fluids have been well studied numerically. In view of a complementary analytical description, we extend here the variational optimization method for Bose-Einstein condensates of closed systems to open-dissipative condensates. The resulting projection optimization method is applied to a complex Gross-Pitaevskii equation, which models a photon Bose Einstein condensate. Together with known methods from hydrodynamics, we obtain an approximate vortex solution, which depends on the respective open system parameters and has the same properties as obtained numerically in the literature
Amtliche Bekanntmachung der RPTU Kaiserslautern-Landau 2025.06
Get PDFAmtliche Bekanntmachung der RPTU Nr. 6/14.07.202
Adaptive Strategies for Exponential Shape Functions in Fracture Phase Field Models
Get PDFThe phase field approach is a powerful tool that can approximate different physical phenomena, including the presented fracture propagation. Even though a static discretization can be used for its computation, intense resources are required to achieve sufficient solutions. Therefore, a new element formulation with exponential functions is implemented to describe the steep curvatures of the fracture phase field crack surfaces more accurately. Unfortunately, an adaptive algorithm is necessary to circumvent their missing symmetry to approximate crack surfaces similarly. Additionally, the numerical integration for these special shape functions is investigated to improve the accuracy
Die Gewährung von Auskunfts- und Auditrechten aus vertraglichen Verpflichtungen im Sinne von § 6 Abs. 4 Nr. 2 und Nr. 4 LkSG aus Sicht eines mittelständischen Lieferanten des produzierenden Gewerbes, insbesondere aus der chemischen Industrie – Probleme im Hinblick auf den Schutz von Geschäftsgeheimnissen und den Schutz personenbezogener Daten
Get PDFDie Masterarbeit untersucht die Frage, inwiefern vertraglich auf Grund von § 6 Abs. 4 Nr. 2 und Nr. 4 LkSG Auskunfts- und Auditrechte, wirksam sind und wie Kollisionen mit dem Schutz von Geschäftsgeheimnissen und personenbezogenen Daten begegnet werden kann. Hierbei wird die Konstellation betrachtet, in der ein aus § 1 LkSG verpflichtetes Unternehmen sich gegenüber einem nicht verpflichteten Unternehmen Auskunfts- und Auditrechte vertraglich einräumen lassen will
Shifting Risk Assessment from Design Time to Runtime for Highly Automated Vehicles
Get PDFEnsuring safety of Highly Automated Vehicles (HAVs) presents substantial challenges to the prevailing safety assurance approaches within the automotive industry. The current state-of-the-art automotive Hazard Analysis and Risk Assessment (HARA) process relies on worst-case operational assumptions. This results in a robust system design guaranteeing safety, but at the cost of reduced performance and availability, a high reliance on the human driver for control takeover, and a static representation of the environment. As driving automation increases, the involvement of the human driver in driving-related tasks decreases, shifting the responsibility for driving and safety from the human to the system. Consequently, it becomes crucial for the system to be aware of its own functional
capabilities and the current operational situation. This can be achieved by shifting certain aspects of safety assurance, such as risk assessment, to runtime.
To this end, we present a novel framework, Safety-rules-based Runtime Risk Assessment for Automated Vehicles (STATUS), that demonstrates and implements the shift of risk assessment from design time to runtime. We introduce a systematic approach to elaborated-HARA (elHARA) that incorporates the dynamic entities of the environment during the analysis of hazardous events. Subsequently, we use ontology formalism to represent the information obtained from elHARA and create a corresponding set of safety rules. These ontologies and rules enable the creation of a knowledge base containing risk-relevant entities used for risk inference at runtime.
To evaluate the effectiveness of the proposed framework, we apply it to an exemplary Highway Pilot Assist function for a set of simulated highway scenarios. We show how elHARA is performed and facilitates comprehensive situation analysis, resulting in the determination of suitable safety integrity values. Furthermore, we demonstrate how the knowledge base, created using the ontology models and predefined safety rules, enables the system to reason about and infer risk at runtime
Generating Representations for Human Activity Recognition
Get PDFHuman activity recognition (HAR) using wearable sensors has benefited much less from recent advances in Deep Learning than fields such as computer vision and natural language processing. This is, to a large extent, due to the lack of large scale (as compared to computer vision) repositories of labelled training data for sensor based HAR tasks. While more and more people are wearing sensor enabled devices (e.g. fitness trackers) and often uploading to respective platforms this data cannot be labelled using crowdsourcing services such as Amazon Mechanical Turk (this is how most ImageNet images were labelled), by leveraging captions, or known topics of image collections. By contrast, labelling sensor data is much more difficult, as interpreting raw sensor data can be challenging even for experts. Recently, several approaches have been proposed to improve HAR by leveraging unlabelled data, cross-modality information and even online repositories.
This dissertation investigates many of those approaches to bridge the label gap Those include producing more labelled IMU data using YouTube videos by applying pose estimation,
but also techniques aimed at improving HAR representations. In this direction several scenarios were explored. For example, learning better representations for target sensors by leveraging sensors (or modalitites) that exist only at training time or learning user-independent representations using generative adversarial neural networks. I also explored adding new sensors to existing systems by leveraging unlabelled data that includes both sensors. Finally, regarding unlabelled data I also explored self-supervised learning techniques, evaluating different training procedures
Mathematical models for cell triggered tissue regeneration and wound formation
Get PDFThis thesis explores the mathematical modelling of tissue dynamics, focusing on processes
such as tissue regeneration and degradation, influenced by cell migration and proliferation.
The first chapter examines meniscus cartilage regeneration. Utilising kinetic transport
equations, we apply an upscaling technique to the lower-scale dynamics of stem cells
and chondrocytes, deriving a macroscopic system of reaction-diffusion-(taxis) equations
(RD(T)Es) coupled with an ordinary differential equation (ODE) for hyaluron. Analysis
of pattern formation in a simplified version of this system highlights the critical role of the
taxis coefficient. Numerical simulations complement this analysis, demonstrating pattern
formation and system stability for varying taxis coefficient values.
The second chapter investigates wound formation and spread in Buruli ulcer, caused
by bacteria named Mycobacterium ulcerans. Starting from kinetic transport equations
(KTEs) and using parabolic scaling, we derive a macroscopic reaction-diffusion-taxis equation
for bacteria, incorporating multiple taxis. An RDTE-RDE-ODE system is developed
to model interactions among bacteria, the toxin mycolactone, normal tissue, and necrotic
matter. We provide an analysis proving the existence of classical solution. Numerical
simulations explore five scenarios with different taxis sensitivity parameters and initial
conditions, revealing distinct dynamics for each solution component.
The final chapter incorporates microscopic-level bacterial dynamics through a random
jump approach, resulting in a RDTE for bacteria. We analyse an RDTE-RDE-ODE system
modelling bacteria, toxin, normal tissue, and necrotic matter, demonstrating solution
existence in classical sense. Simulations offer deeper insights into the underlying biological
processes. We conclude with a numerical simulation that highlights the differences
in dynamics between the system derived from the random jump approach and the model
based on kinetic transport equations.
In sum, this thesis contributes to developing and analysing multiscale mathematical models
that enhance our understanding of tissue dynamics, with possible applications to tissue
regeneration and wound formation
Investigating the sustainability of high-speed laser directed energy deposition – a model for predicting specific environmental impacts
Get PDFDas Hochgeschwindigkeits-Laserauftragschweißen (HS DED-LB) ist ein Verfahren der additiven Fertigung, bei dem Metallpulver durch einen Laserstrahl oberhalb der Substratoberfläche aufgeschmolzen und somit im flüssigen Aggregatszustand zum Geometrieaufbau aufgetragen wird. Aufgrund der zunehmenden Relevanz und Notwendigkeit von nachhaltigen Fertigungsverfahren gilt es, insbesondere junge Technologien hinsichtlich ihrer Umweltauswirkungen zu analysieren, um Verbesserungspotenziale zu identifizieren und eine Möglichkeit zur Einbeziehung der Umweltauswirkungen als Entscheidungsfaktor zur Prozessgestaltung zu schaffen. Ziel ist somit, die Umweltauswirkungen der Bauteilherstellung mittels HS DED-LB transparent zu machen, indem die individuelle Prognose des resultierenden kumulierten Energieaufwands (KEA) und Treibhausgaspotenzials (GWP) der Herstellung eines Bauteils von der Rohstoffgewinnung bis zum fertigen Produkt ermöglicht wird. Hierfür wird, ausgehend von einer energetischen Analyse des HS DED-LB-Fertigungssystems und -prozesses, zunächst ein Modell zur Prognose des Energiebedarfs, der während der Fertigung mittels HS DED-LB benötigt wird, entwickelt. Dieses Prognosemodell wird anschließend um die Stoffflüsse sowie um die dem HS DED-LB-Prozess vor- und nachgelagerten Prozessschritte der Rohmaterial- und Pulverherstellung sowie der Nachbearbeitung erweitert und mit Charakterisierungsfaktoren verknüpft, die nach der Methode der Ökobilanzierung erstellt werden. Hierdurch ist nun die prognostische Bestimmung des KEA sowie des GWP eines Bauteils, das mittels HS DED-LB gefertigt wird, entlang der gesamten Herstellungskette möglich. Die Analyse des KEA und des GWP der gesamten Prozesskette zeigen, dass in Abhängigkeit von der individuellen Prozessgestaltung alle vier Prozessschritte einen signifikanten Einfluss auf die betrachteten Wirkungskategorien aufweisen. Welcher Prozessschritt hierbei die größten Auswirkungen hat, ist individuell, sodass die Vernachlässigung eines oder mehrerer Prozessschritte zu einer unzureichenden Abbildung der resultierenden Umweltauswirkungen führen kann.High-Speed Laser Directed Energy Deposition (HS DED-LB) is an additive manufacturing process in which metal powder is melted by a laser beam above the substrate surface and deposited in a liquid state to create the part. Due to the increasing relevance and necessity of sustainable manufacturing processes, it is particularly important to analyze new technologies with regard to their environmental impact in order to identify potential for improvement and to create an opportunity to include environmental impact as a decision-making factor in process design. Thus, the aim of this work is to provide transparency on the environmental im-pact of the production of parts using HS DED-LB by allowing the individual prediction of the Cumulative Energy Demand (CED) and Global Warming Potential (GWP) of the manufacturing of a part from raw material extraction to the finished product. For this purpose, first a model is developed to predict the energy required during production using HS DED-LB, based on an energy analysis of the HS DED-LB manufacturing system and process. This predictive model is then extended to include the material flows and process steps upstream and downstream of the HS DED-LB process, including raw material production, powder production, and post-processing. They are then linked to characterization models developed using the Life Cycle Assessment method. This allows the predictive determination of the CED and GWP of a part manufactured using HS DED-LB along the entire process chain. The analysis of CED and GWP along the process chain shows that, depending on the individual process design and the part, all four process steps can have a significant influence on the impact categories analyzed. Which process step has the greatest impact depends on the individual case, so that neglecting one or more process steps leads to an inadequate representation of the resulting environmental impact