Scientific publications of the Saarland University
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Equations in wreath products
Get PDFWe survey solvability of equations in wreath products of groups, and prove that the quadratic diophantine problem is solvable in wreath products of Abelian groups. We consider the related question of determining commutator width, and prove that the quadratic diophantine problem is also solvable in Baumslag’s finitely presented metabelian group. This text is a short version of an extensive article by the first-named authors
Interpretable and explainable machine learning methods for predictive process monitoring: a systematic literature review
Get PDFThis study presents a systematic literature review on the explainability and interpretability
of machine learning models within the context of predictive process monitoring. Given the
rapid advancement and increasing opacity of artificial intelligence systems, understanding
the "black-box" nature of these technologies has become critical, particularly for models
trained on complex operational and business process data. Using the PRISMA framework,
this review systematically analyzes and synthesizes the literature of the past decade, in cluding recent and forthcoming works from 2025, to provide a timely and comprehen sive overview of the field. We differentiate between intrinsically interpretable models and
more complex systems that require post-hoc explanation techniques, offering a structured
panorama of current methodologies and their real-world applications. Through this rig orous bibliographic analysis, our research provides a detailed synthesis of the state of
explainability in predictive process mining, identifying key trends, persistent challenges
and a clear agenda for future research. Ultimately, our findings aim to equip researchers
and practitioners with a deeper understanding of how to develop and implement more
trustworthy, transparent and effective intelligent systems for predictive process analytics
Vergleich zweier Point of Care-Geräte zur Gerinnungsdiagnostik: Multiplate® und Verify Now®
Get PDFZusammenfassung
Zielsetzung: Diese Studie ist eine kontrollierte, unverblindete monozentrische Studie zum
Vergleich der beiden Point-of-Care Geräte zur Gerinnungsdiagnostik Multiplate® Analyzer und
Verify Now®. Hierfür wurden zwischen August 2022 und Juli 2023 insgesamt 75
kardiochirurgische Patienten in die Studie eingeschlossen. Ziel der Arbeit ist es, die
Messergebnisse beider Geräte bei Patienten, die sich einem herzchirurgischen Eingriff unter
Einsatz der Herz-Lungen-Maschine unterziehen, zu erfassen und zu vergleichen. Untersucht
werden soll, ob die Störung der Thrombozytenfunktion im Verify Now® ebenfalls detektiert
werden kann.
Methodik: Insgesamt 75 kardiochirurgische Patienten wurden innerhalb eines Zeitraums von
12 Monaten in die Studie eingeschlossen. Präoperativ wurden routinemäßige Laborparameter
sowie die Thrombozytenfunktion mittels beider Point-of-Care Geräte erfasst. Nach erfolgter
extrakorporaler Zirkulation wurden erneut die Gerinnungsparameter im Routinelabor erfasst
und die Thrombozytenfunktion bestimmt. Es erfolgten Korrelationsanalysen zwischen den
Messwerten beider Geräte.
Ergebnisse: Mittels beider Testverfahren konnte eine Einschränkung der
Thrombozytenfunktion dargestellt werden, es zeigte sich ein signifikanter Abfall der Werte
nach extrakorporaler Zirkulation sowohl im Verify Now®, als auch im Multiplate® Analyzer
(prä-EKZ vs. post-EKZ: ADP (AUC) 51,9 ± 28,31 vs. 36,9 ± 24,96, p<0,001; ASPI (AUC) 67,1
± 33,55 vs. 42,0 ± 32,52, p<0,001; PRU 276,8 ± 45,31 vs. 301,6 ± 44,40, p<0,001; ARU 612,3
± 80,35 vs. 560,5 ± 60,54, p<0,01). In den Korrelationsanalysen zeigte sich eine signifikante
Korrelation zwischen der Thrombozytenzahl und der Thrombozytenfunktion gemessen mittels
Multiplate® Analyzer sowohl für die Werte prä-EKZ als auch post-EKZ. Die
Korrelationsanalysen zwischen den jeweiligen Messwerten von VerifyNow® und Multiplate®
Analyzer zeigten heterogene Ergebnisse.
Schlussfolgerung: Dies ist die erste Arbeit, die die Messergebnisse zwischen den beiden
Point-of-Care Geräten VerifyNow® und Multiplate® Analyzer bei Patienten verglichen hat, die
sich einem kardiochirurgischen Eingriff unter Einsatz einer Herz-Lungen-Maschine unterzogen
haben. Mittels beider Testverfahren konnte eine Einschränkung der Thrombozytenfunktion
dargestellt werden. Die Korrelationsanalysen zwischen den jeweiligen Messwerten von
VerifyNow® und Multiplate® Analyzer zeigten heterogene Ergebnisse.Abstract
Background: This study is a controlled, unblinded, single-center study comparing the two point-of-care coagulation diagnostic devices Multiplate® Analyzer and Verify Now®. A total of 75 cardiac surgery patients were included in the study between August 2022 and July 2023. The aim of the study is to record and compare the measured results of both devices in patients undergoing cardiac surgery using the heart-lung machine. The aim is to investigate whether the disruption of platelet function can also be detected in Verify Now®.
Methods: A total of 75 cardiac surgery patients were included in the study over a period of 12 months. Preoperatively, routine laboratory parameters and platelet function were recorded using both point-of-care devices. After extracorporeal circulation, coagulation parameters were recorded again in the routine laboratory and platelet function was determined. Correlation analyses were carried out between the measured values of both devices.
Results: Using both test methods, a reduction in platelet function could be shown, with a significant drop in values after extracorporeal circulation in both the VerifyNow® and the Multiplate® Analyzer (pre-ECC vs. post-ECC: ADP (AUC) 51.9 ± 28.31 vs. 36.9 ± 24.96, p<0.001; ASPI (AUC) 67.1 ± 33.55 vs. 42.0 ± 32.52, p<0.001; PRU 276.8 ± 45.31 vs. 301.6 ± 44.40, p<0.001; ARU 612.3 ± 80.35 vs. 560.5 ± 60.54, p<0.01). The correlation analyses showed a significant correlation between the platelet count and platelet function measured by the Multiplate® Analyzer for both the pre-ECC and post-ECC values. The correlation analyses between the respective measured values of VerifyNow® and Multiplate® Analyzer showed heterogeneous results.
Conclusion: This is the first study to compare the measurement results between the two point-of-care devices Verify Now® and Multiplate® Analyzer in patients who have undergone cardiac surgery using a heart-lung machine. Both test methods were able to show a reduction in platelet function. The correlation analyses between the respective measured values of VerifyNow® and Multiplate® Analyzer showed heterogeneous results
An expanded view on electronic monitoring: Testing moderating effects of participation and perceived purposes of electronic monitoring
Get PDFElectronic monitoring has become a widespread method to record and analyze the behavior of employees. The current study investigated how developmental and controlling purposes of electronic monitoring, as well as participation, moderate the effects of electronic monitoring on employees’ well-being. Based on social information processing theory, developmental and controlling purposes were assumed to buffer or strengthen the relationship of monitoring with work satisfaction, engagement, and stress. In addition, participative decision making by team-leaders and works councils were expected to weaken this relationship. To examine our hypotheses, we surveyed 365 blue-collar workers from 29 organizations in Germany. To provide the best fit to the data, a Bayesian multivariate and multilevel approach was applied. We found detrimental effects of electronic monitoring on worker stress. However, we could not find the proposed moderator effects. We discuss several theoretical and methodological aspects that may have led to these findings. Future research on electronic monitoring should consider additional explaining factors rather than solely focusing on electronic monitoring
Production of fluorine-doped silica bodies using the optimized Vi-Si-HIP manufacturing process from the combination of viscous sintering and gas phase fluorination with subsequent hot isostatic pressing
Get PDFA new manufacturing process aims to optimize the production of fluorine-doped glass in terms of energy efficiency. The green bodies are produced from nanoscale powders in a wet-chemical process and sintered at low temperatures in a fluorine-containing atmosphere. The green body composition and the sintering parameters such as gas atmosphere, temperature and feed rate are important for the resulting fluorine concentration and glass formation. The subsequent hot isostatic pressing leads to complete compaction of the sintered bodies and the associated increased transmission. By recompressing the samples, the sintering temperature can be lowered, thereby reducing the defluorination process at high sintering temperatures
Metabolically engineered Corynebacterium glutamicum with biosensing and drug delivering properties for living therapeutic material applications
No full textLiving therapeutic materials are biomaterials that incorporate living cells as an integral part of their structure and function, enabling them to serve as versatile therapeutic devices and perform tasks difficult to achieve with traditional therapies. Hydration-regulating living therapeutic materials represent promising therapeutic options, as changes in cellular hydration can disrupt homeostasis and contribute to dry eye and skin conditions. In this work a remarkable hydration property of ectoine, a compatible solute found in extreme environments, were explored. The gram-positive soil bacterium Corynebacterium glutamicum serves as an excellent platform for ectoine production. This strain was engineered into a versatile cellular platform with therapeutic, fluorescence, and biosensing capabilities. The encapsulation of generated strain mutants was achieved through bacterial patches and hydrogels to enhance safety and controlled release. Within this thesis, prototypes with prolonged, sustained ectoine release were developed, offering a potential alternative to high-dose ectoine drops and enabling more user-friendly application options. This work represents a step toward the goal of "living therapeutic materials" as the next pillar of therapeutics.Living therapeutic materials are biomaterials that incorporate living cells as an integral part of their structure and function, enabling them to serve as versatile therapeutic devices and perform tasks difficult to achieve with traditional therapies. Hydration-regulating living therapeutic materials represent promising therapeutic options, as changes in cellular hydration can disrupt homeostasis and contribute to dry eye and skin conditions. In this work a remarkable hydration property of ectoine, a compatible solute found in extreme environments, were explored. The gram-positive soil bacterium Corynebacterium glutamicum serves as an excellent platform for ectoine production. This strain was engineered into a versatile cellular platform with therapeutic, fluorescence, and biosensing capabilities. The encapsulation of generated strain mutants was achieved through bacterial patches and hydrogels to enhance safety and controlled release. Within this thesis, prototypes with prolonged, sustained ectoine release were developed, offering a potential alternative to high-dose ectoine drops and enabling more user-friendly application options. This work represents a step toward the goal of "living therapeutic materials" as the next pillar of therapeutics.Lebende therapeutische Materialien sind Biomaterialien, die lebende Zellen als integralen Bestandteil ihrer Struktur und Funktion enthalten. Dadurch können sie als vielseitige therapeutische Hilfsmittel dienen und Aufgaben erfüllen, die mit herkömmlichen Therapien nur schwer zu erreichen sind. Hydratationsregulierende lebende therapeutische Materialien stellen vielversprechende therapeutische Optionen dar, da Veränderungen der zellulären Hydratation die Homöostase stören und zu trockenen Augen und Hauterkrankungen beitragen können. In dieser Arbeit wurde die bemerkenswerte Hydratationseigenschaft von Ectoin, einem kompatiblen Soluten aus extremen Umgebungen, untersucht. Das grampositive Bodenbakterium Corynebacterium glutamicum dient als Plattform für die Ectoinproduktion. Dieser Stamm wurde in eine vielseitige zelluläre Plattform mit therapeutischen, Fluoreszenz-und Biosensor-Fähigkeiten umgewandelt. Die Verkapselung der erzeugten Stammmutanten wurde durch bakterielle Pflaster und Hydrogele erreicht, um Sicherheit und kontrollierte Freisetzung von Ectoin zu verbessern. Im Rahmen dieser Arbeit wurden Prototypen mit verlängerter, kontinuierlicher Ectoin-Freisetzung entwickelt, die eine potenzielle Alternative zu hochdosierten Ectoin-Tropfen darstellen und anwenderfreundlichere Anwendungsmöglichkeiten bieten. Diese Arbeit stellt damit einen Schritt in Richtung des Ziels „Lebender Therapeutischer Materialien“ als nächste Säule für Therapeutika dar.Lebende therapeutische Materialien sind Biomaterialien, die lebende Zellen als integralen Bestandteil ihrer Struktur und Funktion enthalten. Dadurch können sie als vielseitige therapeutische Hilfsmittel dienen und Aufgaben erfüllen, die mit herkömmlichen Therapien nur schwer zu erreichen sind. Hydratationsregulierende lebende therapeutische Materialien stellen vielversprechende therapeutische Optionen dar, da Veränderungen der zellulären Hydratation die Homöostase stören und zu trockenen Augen und Hauterkrankungen beitragen können. In dieser Arbeit wurde die bemerkenswerte Hydratationseigenschaft von Ectoin, einem kompatiblen Soluten aus extremen Umgebungen, untersucht. Das grampositive Bodenbakterium Corynebacterium glutamicum dient als Plattform für die Ectoinproduktion. Dieser Stamm wurde in eine vielseitige zelluläre Plattform mit therapeutischen, Fluoreszenz-und Biosensor-Fähigkeiten umgewandelt. Die Verkapselung der erzeugten Stammmutanten wurde durch bakterielle Pflaster und Hydrogele erreicht, um Sicherheit und kontrollierte Freisetzung von Ectoin zu verbessern. Im Rahmen dieser Arbeit wurden Prototypen mit verlängerter, kontinuierlicher Ectoin-Freisetzung entwickelt, die eine potenzielle Alternative zu hochdosierten Ectoin-Tropfen darstellen und anwenderfreundlichere Anwendungsmöglichkeiten bieten. Diese Arbeit stellt damit einen Schritt in Richtung des Ziels „Lebender Therapeutischer Materialien“ als nächste Säule für Therapeutika dar
Endothelial Effects in the Elderly: Fibroblast Regulation in Soft Tissue Healing
Get PDFTwo main influencing factors of human soft tissue healing are concomitant diseases and cellular senescence, both accumulating with increasing age. Due to the raising population of the elderly in western countries, it is essential to enhance the level of knowledge concerning the function of senescence in a granulation tissue during repair. The present study was intended to verify classic markers of senescence, like senescence-associated ß-galactosidase and the development of a senescence-associated secretory phenotype among fibroblasts during emerging senescence. The application of an in vitro model using serial passaging as inducer of replicative senescence revealed specific differences of a non-senescent and a pre-senescent fibroblast phenotype in mono-cultures, representing the basis for a detailed examination of the phenotypes in their interaction with microvascular endothelial cells in co-cultures. The results deliver new insights into the age dependent process of tissue repair. Characteristics of pre-senescent fibroblasts in terms of modified proliferation, cell morphology, cell cycle regulation, myofibroblastoid differentiation and cytokine release indicate a strong responsibility of this phenotype for the composition and function of a granulation tissue at different locations, including vascular sites. In its entirety, the results support the assumption, that a missing clearance of the senescence phenotype in late stages of tissue repair is one of the main reasons for healing failure
Reduced false memory effects for predictable words in L2 speakers of German: evidence from self-paced reading and recognition memory
Get PDFPrevious research has demonstrated that predictable words that are not presented linger in
memory and lead to false recognition in subsequent memory tests. However, little is known
about these effects among second language learners, a population that is known for
engaging less in prediction. Here, we used a self-paced reading and word recognition
memory test to examine encoding differences and subsequent memory effects in groups of
L1 and L2 speakers of German. For initial reading, results showed no group differences in
the size of the predictability effect, possibly because group differences in attention
allocation during reading masked predictability effects. For recognition memory, L2
learners showed reduced rates of false remembering for predictable words (after correcting
for response bias), and they were also less likely to false-alarm to predictable words with
high subjective memory confidence, similar to L1 speakers. In addition, L2 learners showed
reduced recognition memory for previously presented words. Taken together, these results
are consistent with models arguing that lexical-semantic entries are less firmly represented
in the L2 lexicon, which in turn lowers pre-activation of predictable referents during L2
sentence processing and leads to the formation of less distinct memory representations for
previously encoded information
Competing ion effects and electrolyte optimization for electrochemical lithium extraction from spent lithium iron phosphate battery cathodes
No full textWith rising demand for lithium-ion batteries, efficient recycling is crucial. While conventional methods face cost and environmental challenges, electrochemical recovery offers a sustainable and energy-efficient alternative. In this study, we investigate the electrochemical recovery of lithium-ions from spent lithium iron phosphate batteries using carbon-coated lithium iron phosphate electrodes, with a focus on the influence of pH adjustment and competing ion effects. Our results demonstrate that NaOH-adjusted electrolytes provide the highest lithium-ion recovery efficiency, with an average removal capacity of 18 mgLi gLFP−1 over 50 cycles. However, prolonged cycling leads to capacity fading, particularly in the presence of competing cations such as Na+ and K+, which impact lithium selectivity and electrode stability. These findings underscore the importance of optimizing electrolyte conditions and electrode materials to enhance long-term performance. Future research should explore alternative pH control strategies and scalable process designs to facilitate industrial implementation. Advancing electrochemical lithium-ion recovery aligns with broader sustainability goals, offering a viable route toward circular battery recycling and reduced environmental impact
Quantum symmetries of combinatorial structures: A computer assisted approach
No full textIn this thesis, we study the quantum symmetries of various combinatorial objects. More precisely, we investigate the quantum automorphism groups of vertex- transitive graphs, which were first defined by Banica and Bichon in [4], [13], and introduce the new notions of quantum switching isomorphisms of signed graphs and quantum automorphism groups of matroids. The results include a complete determination of the existence of quantum symmetries of all vertex-transitive graphs on 12 vertices, extending work done in [6], [22], [23], and the computation of the quantum automorphism groups of two of these graphs aided by a Gröbner basis computation. Inspired by the graph isomorphism game introduced in [2], we moreover constructed a switching isomorphism game for signed graphs. Analogously to the study of the graph isomorphism game in [51], we find that there is a strong connection between the perfect quantum strategies for the switching isomorphism game and the hyperoctahedral quantum group. However, we also find that for connected signed graphs, any true quantum switching isomorphism always implies the existence of a true quantum isomorphism of the underlying graphs. Lastly, we define several quantum automorphism groups for matroids. It turns out that unlike the classical automorphism groups of matroids, the quantum automorphism groups depend on the axiom system chosen for the matroid. We then study the quantum automorphism groups of several matroids, using amongst others Gröbner basis computations. This work is based in parts on the research articles [26], [73] of which the author of the thesis was the author and a coauthor respectively.In dieser Arbeit untersuchen wir die Quantensymmetrien verschiedener kombinatorischer Objekte. Um genauer zu sein, befassen wir uns mit den Quantenautomorphismengruppen von vertextransitiven Graphen, die zuerst von Banica und Bichon in [4], [13] definiert wurden, und führen die neuen Begriffe der Quantenswitchingisomorphie von signierten Graphen und der Quantenautomorphismengruppen von Matroiden ein. Unter den Ergebnissen ist eine vollständige Bestimmung der Existenz von Quantensymmetrien von allen vertextransitiven Graphen auf 12 Punkten. Dies erweitert die Arbeit aus [6], [22], [23]. Weiterhin berechnen wir die Quantenautomorphismen- gruppen von zwei dieser Graphen, wobei teilweise auf Gröbnerbasisberechnungen zurückgegriffen wird. Außerdem konstruieren wir ein Switching-Isomorphie-Spiel für signierte Graphen nach dem Vorbild des Graph-Isomorphie-Spiels aus [2]. Analog zur Analyse des Graph-Isomorphie-Spiels in [51] können wir zeigen, dass es eine starke Verbindung zwischen perfekten Quantenstrategien für das Switching-Isomorphie-Spiel und der hyperoktaedrische Quantengruppe. Wir können allerdings auch zeigen, dass für zusammenhängende signierte Graphen jeder wahre Quantenswitchingisomorphismus schon die Existenz eines wahren Quantenswitchingisomorphismus der zugrunde liegenden Graphen impliziert. Schließlich definieren wir verschiedene Quantenautomorphismengruppen für Matroide. Es stellt sich heraus, dass – anders als die klassische Automorphismengruppen von Matroiden – die Quantenautomorphismengruppen von dem Axiomsystem abhängt, welches man wählt um den Matroid zu beschreiben. Wir untersuchen die Quantenautomorphismengruppen von verschiedenen Matroiden, unter anderem mithilfe von Gröbnerbasisberechnungen. Diese Arbeit basiert teilweise auf den Forschungsartikeln [26], [73], welche der Autor der Dissertation verfasst bzw. mitverfasst hat.This PhD thesis has been supported by the SFB-TRR 195 Symbolic Tools in Mathematics and their Application of the German Research Foundation (DFG)