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Differences between persistent and episodic depression in processing novel positive information
Get PDFBackground.
Research has pointed to important psychopathological differences between persistent and episodic depressive disorders. Here, we tested the hypothesis that people with persistent rather than episodic depression have difficulty revising established expectations in response to novel positive information. In terms of underlying mechanisms, we predicted that these differences between the two subtypes would be related to the engagement in cognitive immunization (i.e. devaluing expectation-disconfirming positive information).
Methods.
Prior to their psychotherapeutic treatment, 54 outpatients with persistent depressive disorder and 102 outpatients with episodic major depressive disorder completed an experimental task. In this task, participants watched other patients’ reports of positive effects of psychotherapy. Our primary outcome was change in treatment expectations from before to after watching the positive reports.
Results.
Overall, people with persistent depression had lower treatment expectations than people with episodic depression. In addition, they changed their treatment expectations less in response to other patients’ positive reports. This effect was greater for psychotherapy outcome expectations than for role expectations. The lack of expectation change in persistent depression relative to episodic depression was particularly pronounced in a cognitive immunizationpromoting experimental condition.
Conclusions.
The results indicate that people with persistent depression have difficulty adjusting their treatment expectations in response to positive information on psychotherapy. This may be a risk factor for poor treatment outcome. The results regarding cognitive immunization suggest that for people with persistent depression, slight doubts about the value of information on the positive effects of psychotherapy may be sufficient to prevent them from integrating this information
Methoden für einen intelligenten Einklemmschutz auf Basis lernfähiger nichtlinearer Beobachtung sowie kapazitiver und optischer Messverfahren
Get PDFIm Bereich des automobilen Einklemmschutzes werden Methoden zur robusten und immer sensitiveren Detektion von Einklemmobjekten gesucht, um die Sicherheit zu erhöhen und Risiken des vollautonomen Betriebs zu minimieren. Die weit verbreiteten indirekten Detektionsverfahren erfordern eine präzise Prädiktion zeitvarianter, nichtlinearer Aktuatorlastprofile. In dieser Arbeit werden drei Detektionsansätze vorgestellt, die auf unterschiedlichen Sensorkonzepten basieren. Der erste Ansatz umfasst eine Lastprofilidentifikation anhand von lernfähiger Beobachtung, indem Unscented Kalman Filter mit neuronaler Reibungsidentifikation kombiniert werden. Die kalmanfilterbasierte Lastprofilidentifikation wird anschließend zu einem sensorlosen, beobachterfehlerbasierten Einklemmschutz erweitert. In einem zweiten Ansatz wird ein elektrostatischer Einklemmschutzprototyp auf Basis von Eigenkapazitätsänderungen vorgestellt. Mit einer mehrstufigen Validierung und dem Einsatz von seriennahen Dichtungsprototypen wird die Konzepttauglichkeit unter Randbedingungen geschlussfolgert. Der dritte Ansatz besteht in einem kamerabasierten Einklemmschutz zur berührungslosen Detektion und Klassifikation von Einklemmobjekten und -situationen. Mittels Prüfstandsvalidierung und Robustheitsanalysen werden Reaktionszeiten und Zuverlässigkeiten identifiziert, welche Rückschlüsse auf Hardware und Trainingsaufwände liefern. Mit diesen drei Ansätzen werden durch die Schaffung von Rechen- und Sensorsynergien neue Möglichkeiten für derzeitige und zukünftige Fahrzeugarchitekturen aufgezeigt.In the area of automotive pinch protection, methods for robust and increasingly sensitive detection of pinch objects are sought in order to increase safety and minimize the risks of autonomous driving. The widely used indirect detection methods require a precise prediction of time-variant, non-linear actuator load profiles. In this thesis, three different approaches that are based on different sensor solutions are presented. The first approach consists of load profile identification that utilizes intelligent observers by combining Unscented Kalman filters with neuronal friction identification. This Kalman-filter-based approach is then subsequently extended towards a sensorless anti-pinch detection logic that is fully based on the observer error. In a second approach, an electrostatic anti-pinch protection is presented that utilizes self-capacitance changes. The proof of concept under target conditions was concluded with a multistep validation procedure and the use of series conform sealing prototypes. The third approach consists of a camera-based pinch protection that allows touchless detection and classification of pinch objects and situations. As part of the test bench validations, reaction times and overall computation time are evaluated, which serve as indication for computational requirements. The results show compliance with functional requirements, which is evaluated as part of a robustness analysis. The three proposed approaches showcase new options that can be suitable for current and future car architectures by utilizing computational- and sensorical synergies
Development of Analytical Methods to Quantify Thyroid Hormones (TH) in Multiple Biological Matrices to Facilitate the Prediction of Endocrine Disruption in the Testing and Assessment of Chemicals
Get PDFThe thyroid hormone (TH) synthesis is regulated by negative feedback mechanism involving the hypothalamus, pituitary gland and thyroid gland which is called the hypothalamic-pituitary-thyroid (HPT)-axis. This HPT-axis flexible adjusts to the T4 and T3 concentrations in blood to either stimulate or repress TH synthesis. THs are important regulators for various processes such as metabolic rate and thermogenesis but also play an important role during development in particular of the neuronal system. Within this TH homeostasis TH-related disruption might occur through various mode of actions (MOAs) by e.g. industrial chemicals, drugs, or pesticides. The effect on TH concentrations in rat plasma as well as brain by different TH-related MOAs caused by representative substances were investigated during the scope of this project. To assess these alterations, first method development was conducted to detect THs (T4, T3, rT3, T2, and T1) in the given matrices using an online-SPE-LC-MS/MS system. The investigated MOAs were divided by either directly interfering with the TH system through e.g. inhibition of the thyroid peroxidase (TPO) directly affecting TH synthesis or indirectly such as by competitively binding to plasma TH-binding proteins. The shown results indicated the strongest decline of TH concentrations after exposure to substances directly interfering with the TH synthesis which was evident in most of the analyses investigated. Additionally, the free fraction of TH in blood was assessed for which first different technical devices were tested from which one was further methodically improved. As a final step the free fraction in plasma samples from rats exposed to different TH disrupting substances were determined. TH analysis in rat plasma was further expanded to TH detection in rat whole brain as well as in specific brain regions. In rat plasma and rat brain the course of TH concentration with increasing age (post-natal day (PND) 4, 21, and 97-99 day-old) was investigated and contrasted between the matrices. This revealed for example peak concentrations of analyte T3 in both matrices and of T2 in brain on PND21. Moreover, in-vitro analysis of rT3 to T2 conversion was assessed in human liver microsomes via online-SPE-LC-MS/MS analysis. The potential interference by exemplary substances with the responsible deiodinase enzyme (DIO1) was evaluated by calculating the concentration at which half of the enzyme is inhibited (IC50). These results were compared to the initial method evaluating the release of Iodide by a colorimetric reaction. The assessment of rT3 and T2 concentrations by online-SPE-LC-MS/MS analysis was advantageous especially when assessing the influence of substances structurally containing Iodide. Furthermore, it has been identified that T2 concentrations were a superior readout parameter than rT3 because it demonstrated to be independent of handling errors that were visible in rT3 concentrations.
Besides TH analysis in rats, the developed method was further adjusted to assess TH whole embryo content in zebrafish (Danio rerio). Zebrafish embryos are alternative models because below 120 hours post fertilization (hpf), they do not account to animal welfare regulations and current research showed that until this age they seem to be a suitable model to assess thyroid disruption. Thus, after primarily analyzing THs in control zebrafish samples to determine the number of embryos needed as well as secondly to assess the course of TH concentrations over time. An exemplary study was performed exposing the embryos to the positive substance 6-Propy-2-thiouracil (PTU) which is a thyreostatic drug directly inhibiting TPO demonstrated reduced T4 and T3 concentrations even after beginning of TH synthesis (~ 70 to 80 hpf).
All in all, an easily adjustable online-SPE-LC-MS/MS method was developed which was easily modified for TH analysis of various tissues in-vivo and in-vitro. This expansion to various matrices of different origin enables a TH modality assessment of various MOAs within the TH system
Ultrasonic modification of metals - influence of ultrasound on the density of geometrically necessary dislocations
Get PDFUltrasonic processes are typically energy time and cost efficient and recently of high interest, especially for joining. However, the sonication of materials is often associated with phenomena that remain largely unresolved to date, such as increased ductility during sonication and microstructural changes. To gain a deeper understanding of the elementary processes contributing to increased ductility through ultrasonic sonication, this study investigates the modification of metal by ultrasound and its impact on the density of geometrically necessary dislocations (GNDs). The presence of a large grain structure in IN617 allowed the effect of ultrasound to be more easily observed and analysed. Therefore, samples of IN617 were used for study. The effect of ultrasonic treatment on the density of GNDs in IN617 was analysed using Electron Backscatter Diffraction (EBSD) measurements. Additionally, an E–m model and finite element modelling (FEM) were employed to gain deeper insights into grain behaviour. The FEM model was successfully applied by correlating the mechanical behaviour predicted by the E–m model based on Young’s modulus and the Schmid factor with experimental observations. A combination of experimental data and computational modelling was used to analyse the effect of ultrasonic treatment on dislocation dynamics. EBSD data from three different samples were used to simulate the material’s response to various mechanical and ultrasonic loading conditions. The analysis revealed distinct variations in GND density across the samples. Many grains exhibited a unique response under different loading conditions, as observed through Young’s modulus, Schmid factor, resolved shear stress, and plastic strain. The results indicate that ultrasonic treatment influences dislocation behaviour by either promoting stress relaxation or increasing local hardness.
A geometrically necessary dislocation (GND) analysis was conducted to explore the effect of plastic deformation on three different samples (N1, N2, and N3) of IN617 alloy after sonication was applied. Several software tools, including MATLAB, MTEX tool box, Origin, GMSH, Python and Dassault Abaqus were employed to assist in the analysis. Three samples were analysed under different conditions: in the first case, the initial sample was examined; for the second case, the sample was subjected to a force of 400 N; for the third case, a force ranging from 100 to 200 N was applied over a period of 50 milliseconds; and for the fourth case, the same force was applied for a period of 5000 milliseconds. The GND analysis of all these cases was carried out using Electron Backscatter Diffraction (EBSD). Additionally, various plots, such as plastic strain, resulting shear stress, von Mises stress, and maximum principal stress,
were generated using ABAQUS. Other important data, including Young’s modulus (E), Schmid factor (m), and the product of Young’s modulus and Schmid factor (.), were also plotted. These graphs were compared, and a comprehensive study was conducted to understand the likelihood of plastic deformation under different conditions. By conducting the aforementioned analysis and detailed study, a comprehensive understanding of the influence of ultrasound on the density of geometrically necessary dislocations (GNDs) in the nickel-based super-alloy IN617 was achieved
Specifying and Fuzzing Machine-Learning Models
Get PDFMachine Learning (ML) models are increasingly prevalent in safety critical systems, from self-driving cars to aviation, where failures can result in catastrophic outcomes. While researchers have addressed specific properties like robustness and fairness, specifying and checking general functional-correctness expectations from ML models remains challenging. This thesis introduces novel tools and approaches inspired by software testing concepts to specify and fuzz ML artifacts for their functional correctness. Software testing identifies bugs by running programs with given inputs, facing two main challenges: generating test inputs and finding test oracles. Fuzzing is a widely adopted method for generating test inputs, while specifications address the oracle problem. These techniques and concepts have proven effective and crucial for validating software reliability. We tailor these methods to assess ML model reliability. One of the biggest recent advancements in machine learning has been in solving sequential decision-making problems where agents learn action policies. In this thesis, we devise techniques to test action policies’ reliability. Beyond checking if policies lead to undesirable outcomes, we address: how can we identify undesirable yet avoidable outcomes? We present novel test oracles based on metamorphic relations and develop the fuzz framework to identify bugs in action policies. Next, we formalize metamorphic relations as k safety properties, or hyperproperties, describing relationships between multiple input-output pairs. We show hyperproperties can specify functional correctness across various ML domains. To express these, we create NOMOS, a declarative, domain-agnostic specification language with an automated testing framework. We demonstrate its effectiveness in finding bugs across various domains including image classification, sentiment analysis, and speech recognition. We also extend NOMOS to accommodate code translation models. Overall, this thesis contributes to the field by providing a specification language and novel automated testing frameworks to validate the reliability and safety of ML models which are now prevalent in our daily lives
Contributions to the Design and Application of Integrated Spiking Multi-Sensor Electronics with Self-X Properties for Future Robust Integrated Intelligent Systems
Get PDFThe rapid evolution of micro and nano-scale technologies has propelled advancements
in sensory systems, driving their adoption across IoT, Industry 4.0, autonomous vehicles,
healthcare, and robotics. However, conventional amplitude-based sensory systems
struggle with adaptability, energy efficiency, and reliable performance under fluctuating
environmental and operational conditions. This thesis introduces a Neuromorphic Adaptive
Spiking Analog-Front-End with Self-X Capabilities for Sensors (SAFEX), offering a
novel and comprehensive design inspired by neuromorphic principles to overcome these
limitations.
The proposed system combines two key components: the Adaptive Sensor Signal-to-
Spike Converter (ASSC) and the Self-Adaptive Spike-to-Digital Converter (SA-SDC),
working in tandem to deliver a highly flexible and efficient sensory interface. The ASSC
transforms analog signals into spike timings, employing adjustable synaptic weights
to ensure alignment of the sensor’s input span with subsequent processing stages. This
design eliminates the need for external level-shifting and amplification circuits, streamlining
the signal-conditioning process. By leveraging the time domain for signal processing,
the ASSC achieves a compact and adaptive implementation suitable for a variety of operating
conditions. The transfer function of the ASSC was obtained using measurement
processes for various gains. Adjustments in gain extended the duration of the ASSC,
increasing the number of bits resolved by the SA-SDC to 11.98 bits. An offset of 77.6
LSB was observed in the transfer function due to specific synapse weights, which was
rectified through synaptic weight adjustments.
Benchmarking against SoA sensory systems, the Neuromorphic Spiking Sensory System
demonstrates superior adaptability and resource efficiency. Initial tests showed
that the automatic adaptation mechanism reduced Differential Non-Linearity (DNL)
from 0.6 to 0.34 LSB (a 43% improvement) and Integral Non-Linearity (INL) from 2.07
to 0.53 LSB (a 74% improvement) at nominal conditions. Under reduced power supply
(from 3.3 V to 2.4 V), the system corrected eight missing codes, improving DNL from
1.53 to 0.4 LSB (a 74% reduction) and INL from 4.4 to 0.46 LSB (a 90% reduction).
These performance enhancements surpass those reported in recent SoA designs, which
often struggle to mitigate errors without extensive manual recalibration or complex error correction algorithms. Furthermore, the system’s intrinsic self-adaptation at the hardware
level directly contributes to yield improvement by automatically compensating for
process variations, ensuring that each instance of the SAFEX system continuously selfoptimizes
without any supervision or external handling. This eliminates the need for
manual recalibration and post-fabrication calibration, effectively lowering production
costs.
Real-world validation using Tunnel Magnetoresistance (TMR) sensors for angle measurements
further emphasized the system’s robustness. When the TMR sensor’s output
decreased from 0.225 Vp-p to 0.104 Vp-p due to repositioning from 4 mm to 7 mm, the
ASSC adapted by adjusting synapse weights, reducing the angle error from 24.95° to
12.72° a 49% improvement. This level of autonomous correction sets the system apart
from traditional sensory interfaces, which lack adaptability and require manual recalibration.
In summary, this thesis introduces a transformative Neuromorphic Spiking Sensory
System, bridging analog signal processing and time-domain techniques with self-X capabilities
self-calibration, self-compensation, self-optimization, and self-repair. The design
not only addresses the core technical and industrial challenges faced by existing sensory
systems but also establishes a scalable, energy-efficient framework tailored to modern
applications. This work takes a step towards dynamic adaptability, robust performance,
and yield improvement through hardware-level self-adaptation, building on existing
developments in neuromorphic engineering and sensory technology.
Future research will focus on extending system resolution, broadening application domains,
and integrating higher-level self-X functionalities. With these advancements, the
Neuromorphic Spiking Sensory System is well-positioned to meet the evolving demands
of edge computing and intelligent, resource-constrained environments
Einfluss des Reifefortschritts von Weintrauben auf die phenolchemische Zusammensetzung und die sensorischen Eigenschaften von Rotwein
Get PDFSuccessful cultivation of grapevine depends on various environmental factors, because grapevine are very sensitive to changes in weather and climate. Global warming and related increases in growing degree days (GDD) have been shown to trigger advanced and/or accelerated ripening of grapes. Previous studies suggest that with progressing climate change, the ripening kinetics of different grape constituents, such as sugar and anthocyanin accumulation might decouple. Therefore, traditional indicators for grape maturity such as potential alcohol or the ratio of total soluble solids to titratable acidity might no longer provide accurate information about the maturity of other grape constituents. Phenolic maturity is a well-known, but vaguely defined concept for red grape varieties to identify optimal maturity focusing on the content and extractability of phenolics from grapes. In this thesis, the influence of the ripening progress of two red varieties of international importance (Pinot noir and Cabernet Sauvignon) on the phenolic composition and sensory properties of wine was investigated in the European winegrowing zone A (cool climate). It was further shown how phenolic maturity is reflected in wine and indicators for phenolic maturity perceived in wine were identified. Anthocyanins and non-precipitable polymeric pigments were positively correlated with progressing grape maturity and were independent of potential alcohol enhancement and winemaking procedures, making them suitable indicators for phenolic maturity if sugar accumulation is decoupled from the ripening kinetics of other grape constituents. Varietal differences were observed, suggesting that varieties with low phenolic contents such as Pinot noir should focus on anthocyanins, whereas varieties with high phenolic contents such as Cabernet Sauvignon should focus on non-precipitable polymeric pigments. An experimental model using phenol and sensory data from Pinot noir and Cabernet Sauvignon of two consecutive vintages was developed to determine the extent to which the potential alcohol acts as a solvent modulating the extraction of phenolic compounds during winemaking. The effect of potential alcohol enhancement was shown to be different for individual polyphenols. However, the results presented in this thesis suggest that neither potential alcohol enhancement nor winemaking techniques such as extended maceration time can manipulate the sensory characteristics of wine produced from immature grapes towards the characteristics of late harvest wines. The influence of potential alcohol or maceration time on the phenolic composition of red wine was different from the influence of grape maturity. Viticultural strategies such as leaf removal and timing of harvest were shown to influence the phenolic composition of Pinot noir wine, however these strategies only had a marginal effect on the berry size distribution in the vineyard. Berry size significantly influenced the phenolic composition of Pinot noir wine. Small berries produced wines with the highest phenolic content. This thesis shows that grape ripening significantly influences the phenolic composition and extraction in red wine as well as the sensory properties. The results also show that grape maturity outweighs the influence of winemaking techniques.Ob der Anbau von Weinreben erfolgreich ist, hängt von verschiedenen Umweltfaktoren ab, da Weinreben sehr empfindlich auf Wetter- und Klimaveränderungen reagieren. Es hat sich gezeigt, dass die globale Erwärmung und der damit verbundene Anstieg der Wachstumsgradtage (GDD) eine fortgeschrittene und/oder beschleunigte Reifung von Weintrauben auslösen. Frühere Studien deuten darauf hin, dass sich mit fortschreitendem Klimawandel die Reifekinetik verschiedener Traubenbestandteile, wie z. B. die Akkumulation von Zuckern und Anthocyanen, entkoppeln könnte. Daher könnten herkömmliche Indikatoren für die Traubenreife wie der potenzielle Alkoholgehalt oder das Verhältnis von Zucker zu Säure möglicherweise keine konkreten Informationen mehr über die Reife anderer Traubenbestand-teile liefern. Die Phenolische Reife ist ein bekanntes, aber nur vage definiertes Konzept für rote Rebsorten, um den optimalen Reifegrad zu ermitteln, wobei der Gehalt und die Extrahierbarkeit von Phenolen aus Trauben im Mittelpunkt stehen. In dieser Arbeit wurde der Einfluss des Reifegrads zweier roter Rebsorten von internationaler Bedeutung (Pinot noir und Cabernet Sauvignon) auf die phenolchemische Zusammensetzung und die sensorischen Eigenschaften von Wein in der Europäischen Weinbauzone A (cool climate) untersucht. Es wurde ferner gezeigt, wie sich die phenolische Reife im Wein widerspiegelt, und es wurden Indikatoren für die im Wein wahrgenommene phenolische Reife ermittelt. Anthocyane und nicht präzipitierbare polymere Pigmente korrelierten positiv mit der fortschreitenden Traubenreife und waren unabhängig von einer möglichen Alkoholanreicherung und den Weinbereitungsverfahren, was sie zu geeigneten Indikatoren für die phenolische Reife macht, wenn die Zuckerakkumulation von der Reifungskinetik anderer Traubenbestandteile entkoppelt wird. Es wurden Sortenunterschiede festgestellt, die darauf hindeuten, dass bei Sorten mit niedrigem Gesamtphenolgehalt wie Pinot noir die Anthocyane berücksichtigt werden sollten, während bei Sorten mit hohem Gesamtphenolgehalt wie Cabernet Sauvignon die nicht präzipitierbaren polymeren Pigmente im Vordergrund stehen sollten. Es wurde ein experimentelles Modell entwickelt, bei dem phenolchemische und sensorische Daten von Pinot noir und Cabernet Sauvignon aus zwei aufeinanderfolgenden Jahrgängen verwendet wurden, um festzustellen, inwieweit der potenzielle Alkohol als Lösungsmittel fungiert, das die Extraktion der phenolischen Verbindungen während der Weinbereitung moduliert. Es zeigte sich, dass die Wirkung des potenziellen Alkohols auf die einzelnen Polyphenole unterschiedlich ist. Die in dieser Arbeit vorgestellten Ergebnisse deuten jedoch darauf hin, dass weder eine Erhöhung des potenziellen Alkoholgehalts noch Weinbereitungsverfahren wie eine verlängerte Mazerationszeit die sensorischen Eigenschaften von Wein aus unreifen Trauben in Richtung der Eigenschaften von Weinen der Spätlese manipulieren können. Der Einfluss des potenziellen Alkohols oder der Mazerationszeit auf die phenolchemische Zusammensetzung des Rotweins unterschied sich vom Einfluss der Traubenreife. Es wurde nachgewiesen, dass weinbauliche Strategien wie Entlaubung und Erntezeitpunkt die phenolische Zusammensetzung von Pinot noir beeinflussen, jedoch hatten diese Strategien nur einen geringen Einfluss auf die Beerengrößenverteilung im Weinberg. Die Beerengröße hatte einen signifikanten Einfluss auf das Polyphenolprofil von Pinot noir Wein. Kleine Beeren erzeugten Weine mit dem höchsten Gesamtphenolgehalt. Diese Arbeit zeigt, dass der Reifefortschritt von Weintrauben die phenolchemische Zusammensetzung und Extraktion in Rotwein sowie die sensorischen Eigenschaften erheblich beeinflusst. Die Ergebnisse zeigen auch, dass die Traubenreife den Einfluss der Weinbereitungsmethoden überwiegt
Dynamik der mikrobiellen Mischbiozönose und der PHA-Produktion aus Restströmen unter variierenden Betriebsstrategien
Get PDFDie globale Plastikverschmutzung stellt ein zunehmendes Problem dar, das unsere Umwelt und unsere Gesundheit gefährdet. Daher wäre der Ersatz von konventionellem Plastik durch Bioplastik ein wichtiger Schritt zur Minimierung der Folgen. Ein biologisch abbaubares Plastik ist PHA (Polyhydroxyalkanoat), welches durch verschiedene Mikroorganismen als Speicherstoff hergestellt werden kann. Die bisherige kommerzielle Herstellung dieses Polymers erfolgt unter sterilen Arbeitsbedingungen mithilfe von Reinkulturen und teuren Substraten, wodurch das Plastik teuer und wenig konkurrenzfähig auf dem Markt ist. Zur Verbesserung der Konkurrenzfähigkeit und Senkung des Preises, kann eine Herstellung mittels Bakterienmischkulturen und Restströmen über ein mehrstufiges Verfahren eingesetzt werden. Allerdings gibt es zurzeit noch einige Hindernisse zu überwinden, um das Verfahren im industriellen Maßstab umsetzen zu können. Probleme dabei stellen beispielsweise die schwankende Quantität und Qualität des produzierten Polymers unter realen Betriebsbedingungen mit schwankenden Reststromeigenschaften dar. Zum Überwinden dieser Problematik ist ein besseres Verständnis der PHA-produzierenden Bakterienmischbiozönose und deren Reaktion auf bestimmte Betriebsweisen notwendig. Daher sollten in dieser Arbeit i) der Einfluss unterschiedlicher Betriebsparameter in der Selektion auf die Mischbiozönose und die PHA-Produktion untersucht werden und die Identifizierung von Kernorganismen stattfinden, ii) mit einer Auswahl der Betriebsparameter eine Langzeit-Selektion durchgeführt und die Stabilität der PHA-Produktion und Zusammensetzung der Biozönose untersucht werden, iii) der Einfluss unterschiedlicher Substrate in der Akkumulationsphase auf die PHA-Produktion in Verbindung mit der Zusammensetzung der Biozönose analysiert werden. Hierzu wurde ein aufeinander aufbauendes Versuchsdesign entwickelt, in welchem zunächst verschiedene Betriebsparameter in der Selektion miteinander verglichen wurden und die beste Variation für den nächsten Versuch ausgewählt wurde. Mit der Auswahl der am besten geeigneten Parameterkombination, erfolgte eine Langzeit-Selektion, in welcher zudem ein Substratwechsel stattfand. In den Selektionsversuchen wurden regelmäßige Akkumulationen zur Evaluierung der PHA-Produktionsperformance und dessen Eigenschaften durchgeführt und Proben zur Analyse der mikrobiellen Zusammensetzung genommen. Die Analyse erfolgte mittels Amplifizierung und Illumina-Sequenzierung der V3-V4-Region der bakteriellen 16S rDNA. Mit der selektierten Biomasse des Langzeitversuches wurden zusätzliche Akkumulationen mit variierendem Substrat durchgeführt. Die Ergebnisse zeigten, dass unter Verwendung der gleichen Betriebsweise eine Selektion unterschiedlicher Inokula zu ähnlich zusammengesetzten Biozönosen mit vergleichbarer PHA-Produktionsperformance führt. Die Selektionsphase führte zudem zu einer effektiven Anreicherung potenzieller PHA-Produzenten und zur Steigerung der PHA-Produktion. Dabei wurden größtenteils bereits nach 7 bis 14 Tagen hohe PHA-Gehalte und Anteile potenzieller PHA-Produzenten erreicht. Eine weitere Steigerung war jedoch in der Langzeit-Selektion bis Tag 56 erkennbar. Unter Nutzung eines Belebtschlammes einer Brauerei, eines Schlammalters von 4 d, einer Zyklusdauer von 6 h und einer Raumbelastung von ca. 1 gCSBVFA/(L*d) konnte mit versäuertem Brauereiabwasser als Substrat ein maximaler PHA-Gehalt von ca. 48 %oTS erzielt werden. Das gleiche Inokulum entwickelte sich unter Nutzung unterschiedlicher Betriebsparameter in der Selektion teils unterschiedlich, allerdings waren Überschneidungen in den dominantesten Organismen erkennbar. Zu den wichtigsten potenziellen PHA-Produzenten zählten die Gattungen Pseudomonas, Acinetobacter, Paracoccus, Comamonas, Flavobacterium, Zoogloea, Rhodobacter, Leadbetterella und Hydrogenophaga. Die Nutzung hoher Raumbelastungen (6 und 10 gCSBVFA/(L*d)) führte jedoch zu großen Unterschieden in der mikrobiellen Zusammensetzung und zu einer schlechten PHA-Produktionsperformance. Während der Langzeit-Selektion konnten kontinuierliche Veränderungen der Biozönose über die Zeit und zwischen dem Substratwechsel festgestellt werden, wobei der PHA-Gehalt jedoch vergleichbar blieb. In den anderen Selektionsversuchen konnten ebenfalls Wechsel der dominanten Organismen über die Zeit mit teils unveränderter PHA-Produktion festgestellt werden. Dies spricht für eine funktionelle Redundanz und Stabilität des Systems trotz des Einflusses stochastischer Prozesse auf die Biozönose. Die PHA-Zusammensetzung entwickelte sich zumeist über die Zeit in eine ähnliche Richtung der, durch die Substratzusammensetzung zu erwartenden, theoretischen, Zusammensetzung. Dies deutet auf eine metabolische Anpassung der Biozönose hin. Während der Akkumulationsversuche mit unterschiedlichem Substrat konnten Unterschiede im Gehalt und der Zusammensetzung an produziertem PHA, aber nicht in der bakteriellen Zusammensetzung festgestellt werden. Substrate mit Eigenschaften ähnlich denen, des in der Selektion verwendeten, führten zu höheren PHA-Gehalten oder vorhersagbareren PHA-Zusammensetzungen. Daher hängen die PHA-Produktionseigenschaften offenbar mit der metabolischen Adaption der Mischbiozönose in der Selektionsphase zusammen. Eine Erhöhung der Substratkonzentration führte zudem nur bis zu einem gewissen Grad zur Erhöhung der PHA-Produktion und eine Nährstoffzugabe hatte keinen Einfluss auf diese, es sei denn Stickstoff und Phosphor wurden zusammen zugegeben. Die Ergebnisse liefern Implikationen für weitere Untersuchungen wichtiger PHA-Produzenten zur Entwicklung von Monitoring-Strategien und zur Anpassung der Betriebsstrategien in der Selektion. Zudem liefern sie Einblicke in den Einfluss von Substratschwankungen im Verfahren und zu den Vor- und Nachteilen einer Langzeit- oder Kurzzeitselektion.Global plastic pollution is an increasing problem, which threatens our environment and health. Replacing conventional plastic with bioplastics would be an important step in minimizing the effects of this pollution. PHA (Polyhydroxyalkanoate) is a biodegradable polymer which can be produced by a variety of microorganisms for energy storage. The commercial PHA production is executed with the use of pure cultures and expensive feed stocks under sterile conditions. This results in a high market price of PHA and leads to lower competitiveness compared to conventional plastic. The production of PHA with mixed microbial cultures and residual streams in a multi-stage process can be used to reduce the price and to improve the competitiveness on the market. However, there are still some obstacles to overcome before the process can be implemented on an industrial scale. Problems include the fluctuating quantity and quality of the polymer produced under real operating conditions with varying residual stream properties. To overcome this, a better understanding of the PHA-producing microbial community and the reaction of the community to varying process parameters is needed. Therefore, in this work i) the influence of different operating parameters in the selection on the mixed microbial culture and the PHA production should be investigated and core organisms should be identified, ii) with the chosen operating parameters, a long-term selection should be performed and the stability of the PHA production and composition of the microbial culture should be investigated, iii) the influence of different substrates in the accumulation phase on the PHA production and the composition of the mixed microbial culture should be analyzed. A consecutive test design was developed in which different operating parameters in the selection phase were compared and the best variation was chosen for the next experiment. Once the most suitable combination of parameters had been selected, a long-term selection was performed, in which a substrate change was realized. During the selection experiments, regular accumulations were conducted to evaluate the PHA production performance and its properties. Samples for microbial composition analysis were regularly taken. For this analysis, the V3-V4 region of the bacterial 16S rDNA was amplified and sequenced via Illumina-Sequencing. Additional accumulation experiments using different substrates were conducted with the selected biomass from the long-term selection. Results showed that, using the same operating conditions, a similarly composed mixed microbial culture with a comparable PHA production capacity can be selected with inocula of different origin. The selection phase also led to an effective enrichment of potential PHA producers and to an increase in PHA production. High PHA contents and relative abundances of potential PHA producers were frequently achieved after 7 to 14 days. However, a further increase could be recognized in the long-term selection up to day 56. A maximum PHA content of approximately 48 %VSS could be achieved with activated sludge taken from a brewery, a sludge retention time of 4 d, a cycle length of 6 h and an organic loading rate of ca. 1 gCODVFA/(L*d) using a fermented brewery residual stream. Partially, the same inoculum developed differently under the use of different operating parameters in the selection phase although intersections between the dominant organisms could be observed. The genera Pseudomonas, Acinetobacter, Paracoccus, Comamonas, Flavobacterium, Zoogloea, Rhodobacter, Leadbetterella und Hydrogenophaga were among the most important potential PHA producers. However, the use of high organic loading rates (6 and 10 gCODVFA/(L*d)) resulted in more pronounced differences in microbial composition and in deteriorated PHA production performances. During long-term selection, continuous variations in mixed microbial composition could be observed over time and between substrates used. Nevertheless, the PHA production remained comparable. In the selection experiments on different operating conditions, changes in the dominant organisms over time with oftentimes unchanged PHA production were also observed. This indicates a functional redundancy and stability of the system despite the influence of stochastic processes on the microbial culture. The PHA composition usually developed in a similar direction to the theoretical composition to be expected from the substrate composition over time. This indicates a metabolic adaptation of the mixed microbial culture. During the accumulation experiments with different substrates, differences in the content and composition of PHA produced were observed, but not in the bacterial composition. Substrates with properties similar to those used in the selection resulted in higher PHA contents or more predictable PHA compositions. Therefore, PHA production characteristics may be related to the metabolic adaptation of the mixed microbial culture during selection. Furthermore, increasing the substrate concentration only led to an increase in PHA production to a certain extent and adding nutrients had no effect on this, unless nitrogen and phosphorus were added together. The results provide implications for further investigations on important PHA producers for the development of monitoring strategies and for the adaptation of operating strategies in the selection phase. They also provide insights into the influence of substrate fluctuations on the process and into the advantages and disadvantages of a long-term or short-term selection phase
Amtliche Bekanntmachung der RPTU Kaiserslautern-Landau 2025.01
Get PDFAmtliche Bekanntmachung der RPTU Nr. 1/22.01.202
Analyse zum Kühlschmierstoffeinsatz beim Mikrofräsen von cp-Titan
Get PDFDie Entwicklung von Mikrobearbeitungsverfahren wie dem Mikrofräsen wurde durch die fortschreitende Miniaturisierung von Bauteilen und die Nachfrage nach funktionalisierten Bauteiloberflächen vorangetrieben. Hohe Flexibilität, ein breites Spektrum an bearbeitbaren Werkstoffen und eine große Vielfalt an herstellbaren Geometrien zeichnen das Mikrofräsen aus. Nachteilig ist jedoch die prozessbedingt hohe Reibung, die wiederum zu hohem Werkzeugverschleiß und reduzierter Oberflächenqualität führt. Eine Möglichkeit zur Reduzierung des Verschleißes und damit zur Erhöhung der Standzeit der Werkzeuge und der Qualität der erzeugten Oberflächen ist der Einsatz von Kühlschmierstoffen. Im Unterschied zum konventionellen Fräsen werden Kühlschmierstoffe beim Mikrofräsen bislang nur vereinzelt eingesetzt. Aufgrund von Größeneffekten können die Kenntnisse der konventionellen Zerspanung nicht direkt auf das Mikrofräsen übertragen werden. Deshalb sind grundlegende Untersuchungen zum Einsatz von Kühlschmierstoffen beim Mikrofräsen erforderlich. In dieser Arbeit wurde eine Analyse zum Kühlschmierstoffeinsatz beim Mikrofräsen von cp-Titan mit Mikrofräsern mit einem Durchmesser von 50 μm durchgeführt. Hierzu wurden Kühlschmiersysteme zum Einsatz beim Mikrofräsen entwickelt und ausgelegt und der Einsatz verschiedener Kühlschmierstrategien beim Mikrofräsen von cp-Titan untersucht. Dabei wurden die Kühlschmierstrategien Trockenbearbeitung, Nassbearbeitung, Minimalmengenschmierung und indirekte Werkstückkühlung betrachtet. Darüber hinaus wurde der Einfluss unterschiedlicher Kühlschmierstoffe und Drehzahlen auf die Prozess- und Prozessergebnisgrößen untersucht. Die Ergebnisse zeigen, dass die gewählte Kühlschmierstrategie, der Kühlschmierstoff bzw. die Kühltemperatur und die Drehzahl den Werkzeugverschleiß und die Oberflächenqualität maßgeblich beeinflussen. Durch die geeignete Wahl der Kühlschmierung wird das Prozessergebnis verbessert und gleichzeitig die Prozesseffizienz erhöht.The development of micromachining processes such as micro milling was driven by the ongoing miniaturisation of components and the demand for functionalised component surfaces. Micro milling is characterised by high flexibility, a wide range of materials that can be machined, and a large variety of geometries that can be produced. However, the process-related high friction is a disadvantage, which in turn leads to high tool wear and reduced surface quality. One way to reduce wear and thus increase the tool life and the quality of the manufactured surfaces is to use metalworking fluids. In contrast to conventional milling, metalworking fluids have only been used sporadically in micro milling and, due to size effects, the knowledge of conventional machining cannot be directly transferred to micro milling. Therefore, fundamental studies on the application of metalworking fluids in micro milling are necessary. In this thesis, an analysis was carried out on the application of metalworking fluids in micro milling of cp-titanium with micro end mills with a diameter of 50 μm. Within this research, cooling lubrication systems for use in micro milling were designed and developed and the use of different cooling lubrication strategies for micro milling of cp-titanium were investigated. The cooling lubrication strategies dry machining, wet machining, minimum quantity lubrication and indirect workpiece cooling were considered. In addition, the influence of different metalworking fluids and spindle speeds on the process and process results were investigated. The results show that the selected cooling lubrication strategy, the metalworking fluid and the cooling temperature, and the spindle speed have a significant influence on tool wear and surface quality. The appropriate choice of cooling lubrication improves the process result and at the same time increases the process efficiency