q-deformed Hermite Polynomials in q-Quantum Mechanics

The q-special functions appear naturally in q-deformed quantum mechanics and both sides profit from this fact. Here we study the relation between the q-deformed harmonic oscillator and the q-Hermite polynomials. We discuss: recursion formula, generating function, Christoffel-Darboux identity, orthogonality relations and the moment functional.Comment: latex, 8 pages, no figures. accepted for publication in European Journal of Physics

A Calculus Based on a q-deformed Heisenberg Algebra

We show how one can construct a differential calculus over an algebra where position variables x and momentum variables p have be defined. As the simplest example we consider the one-dimensional q-deformed Heisenberg algebra. This algebra has a subalgebra generated by x and its inverse which we call the coordinate algebra. A physical field is considered to be an element of the completion of this algebra. We can construct a derivative which leaves invariant the coordinate algebra and so takes physical fields into physical fields. A generalized Leibniz rule for this algebra can be found. Based on this derivative differential forms and an exterior differential calculus can be constructed.Comment: latex-file, 23 page

The Geometry of a qq-Deformed Phase Space

The geometry of the $q$-deformed line is studied. A real differential calculus is introduced and the associated algebra of forms represented on a Hilbert space. It is found that there is a natural metric with an associated linear connection which is of zero curvature. The metric, which is formally defined in terms of differential forms, is in this simple case identifiable as an observable.Comment: latex file, 26 pp, a typing error correcte

Ant colony optimisation and local search for bin-packing and cutting stock problems

The Bin Packing Problem and the Cutting Stock Problem are two related classes of NP-hard combinatorial optimization problems. Exact solution methods can only be used for very small instances, so for real-world problems, we have to rely on heuristic methods. In recent years, researchers have started to apply evolutionary approaches to these problems, including Genetic Algorithms and Evolutionary Programming. In the work presented here, we used an ant colony optimization (ACO) approach to solve both Bin Packing and Cutting Stock Problems. We present a pure ACO approach, as well as an ACO approach augmented with a simple but very effective local search algorithm. It is shown that the pure ACO approach can compete with existing evolutionary methods, whereas the hybrid approach can outperform the best-known hybrid evolutionary solution methods for certain problem classes. The hybrid ACO approach is also shown to require different parameter values from the pure ACO approach and to give a more robust performance across different problems with a single set of parameter values. The local search algorithm is also run with random restarts and shown to perform significantly worse than when combined with ACO

Classical and quantum q-deformed physical systems

On the basis of the non-commutative q-calculus, we investigate a q-deformation of the classical Poisson bracket in order to formulate a generalized q-deformed dynamics in the classical regime. The obtained q-deformed Poisson bracket appears invariant under the action of the q-symplectic group of transformations. In this framework we introduce the q-deformed Hamilton's equations and we derive the evolution equation for some simple q-deformed mechanical systems governed by a scalar potential dependent only on the coordinate variable. It appears that the q-deformed Hamiltonian, which is the generator of the equation of motion, is generally not conserved in time but, in correspondence, a new constant of motion is generated. Finally, by following the standard canonical quantization rule, we compare the well known q-deformed Heisenberg algebra with the algebra generated by the q-deformed Poisson bracket.Comment: 9 pages, accepted for publication in "The European Physical Journal C

Physico-Chemical development of oxide-based ceramics for thermoelectric energy harvesting

The thermoelectric effect describes the conversion of heat into electrical energy and it is the pivotal element for the utilization of waste heat via Energy Harvesting. Especially high-temperature applications in industrially relevant areas such as basic materials production or transportation hold enormous potential for unused energy. Proper thermoelectric materials for these high-temperature applications are mandatory to ensure high conversion efficiency and high electrical power output. Oxides are auspicious candidates for this task as they exhibit high thermal stability under air and are less toxic than most alternatives. Therefore, it is expedient to investigate the electrical performance and the energy conversion efficiency of these promising high-temperature materials more intensively. The currently best performing oxide material is Ca3Co4O9 (CCO), so improving its thermoelectric properties was the main research focus of this thesis. Novel composite materials based on CCO in combination with other oxides such as La2NiO4 (LNO), Na2Ca2Nb4O13 (NCNO), NaxCoO2 (NCO) and Bi2Ca2Co2O9 (BCCO) as well as the oxyselenide BiCuSeO (BCSO) were synthesized and thoroughly investigated regarding synergistic effects. Close attention was given to the microstructure and elemental composition, which were investigated by various methods such as electron microscopy as well as electron or X-ray diffraction. Further analyses regarding the thermoelectric performance were made by measuring the Seebeck coefficient, the electrical conductivity and the thermal conductivity. All investigated materials exhibit layered crystal structures and hence anisotropic transport properties. Preferred crystal orientations within the composite ceramics were observed due to uniaxial pressing during processing. In case of LNO or NCNO, the orientation was influenced by using large plate-like particles synthesized by molten-flux synthesis. Sintering resulted in advantageous reactions between the mixing partners. Regarding LNO or NCNO, heavily doped perovskite phases La(Co,Ni)O3 and Ca(Nb,Co)O3 were ascertained with beneficial impact on the thermoelectric properties. Especially the power factor was positively influenced, either by an enhanced electrical conductivity or by a higher Seebeck coefficient. Approaches in the nanodimension were realized by a triple-phase ceramic including NCO and BCCO as two-dimensional nanostructures within a CCO matrix or by using BCSO nanosheets as a mixing partner. In both cases, the electrical conductivity and the Seebeck coefficient were increased simultaneously as a result of doping and emerged phases. While the large particles could increase either the average or even the maximum figure-of-merit compared to CCO, the nanodimensional strategy led to a significantly enhanced power factor.Der thermoelektrische Effekt beschreibt die Umwandlung von Wärme in elektrische Energie und ist das zentrale Element für die Ausnutzung von Verlustwärme durch "Energy Harvesting". Besonders Hochtemperatur-Anwendungen in industriell relevanten Sektoren, wie der Herstellung von Basismaterialien oder des Transportwesens, umfassen große Potentiale von ungenutzter Energie. Um eine hohe Effizienz beim Umwandeln der Energieformen und eine hohe elektrische Leistungsabgabe zu erreichen, sind für diese Hochtemperatur-Anwendungen geeignete thermoelektrische Materialien erforderlich. Oxide sind vielversprechende Kandidaten, da sie eine hohe Temperaturstabilität und eine geringere Toxizität als die meisten Alternativen aufweisen. Es ist daher zielführend, die elektrische Leistungsfähigkeit und die Effizienz der Energieumwandlung dieser vielversprechenden Hochtemperatur-Materialien intensiver zu untersuchen. Momentan stellt Ca3Co4O9 (CCO) das leistungsstärkste oxidische Material dar, weshalb die Verbesserung seiner thermoelektrischen Eigenschaften den Hauptaspekt der vorliegenden Dissertation darstellt. Hierzu wurden neuartige Kompositmaterialien basierend auf CCO in Kombination mit anderen Oxiden wie La2NiO4 (LNO), Na2Ca2Nb4O13 (NCNO), NaxCoO2 (NCO) und Bi2Ca2Co2O9 (BCCO) oder dem Oxyselenid BiCuSeO (BCSO) hergestellt und ausgiebig hinsichtlich synergistischer Effekte untersucht. Ein besonderes Augenmerk lag auf der Mikrostruktur und der elementaren Zusammensetzung, welche mittels zahlreicher Analysemethoden wie etwa der Elektronenmikroskopie oder der Elektronen- und Röntgen-Beugung untersucht wurden. Weitere Analysen bezüglich des thermoelektrischen Verhaltens erfolgten durch Messung des Seebeck-Koeffizienten, der elektrischen sowie der thermischen Leitfähigkeit. Alle untersuchten Materialien weisen geschichtete Kristallstrukturen und damit anisotrope Transporteigenschaften auf. Durch das uniaxiale Pressen während der Prozessierung konnten innerhalb der Komposit-Keramiken bevorzugte Kristall-Orientierungen erzeugt werden. Im Falle von LNO und NCNO wurde die Orientierung durch den Einsatz großer plättchenförmiger Partikel, welche durch Schmelzfluss-Synthese gewonnen wurden, beeinflusst. Das Sintern resultierte in vorteilhaften Reaktionen zwischen den jeweilig gemischten Komponenten. Unter Einsatz von LNO oder NCNO konnten die hochdotierten Perowskit-Phasen La(Co,Ni)O3 und Ca(Nb,Co)O3 mit vorteilhaften Auswirkungen für die thermoelektrischen Eigenschaften identifiziert werden. Insbesondere der Leistungsfaktor wurde positiv beeinflusst, entweder durch eine erhöhte elektrische Leitfähigkeit oder durch einen größeren Seebeck-Koeffizienten. Eine auf Nanodimensionalität beruhende Strategie wurde durch eine dreiphasige Keramik mit NCO und BCCO als zweidimensionale Nanostrukturen innerhalb einer CCO Matrix oder durch den Einsatz von BCSO als Mischungspartner realisiert. In beiden Fällen konnten mittels Dotierung und neu entstandener Phasen die elektrische Leitfähigkeit und der Seebeck Koeffizient simultan erhöht werden. Während die großen Partikel den Durchschnittswert oder sogar den Maximalwert der Gütezahl gegenüber CCO erhöhen konnten, führte der nanodimensionale Ansatz zu einer signifikanten Erhöhung des Leistungsfaktors

The MAPK/ERK signalling pathway: functional characterisation of rare human genetic variants associated with longevity

Observational and experimental studies have revealed that ageing is malleable. Research in different organisms has shown that dietary, pharmacological and genetic interventions can extend health- and lifespan. Similarly in humans, diet and other lifestyle factors such as exercise, have been shown to slow the ageing process, however, the role of genetics is less clear. For human lifespan, the heritability is somewhere in the range of 12-25%, but for longevity, i.e. belonging to the top 10% longest-lived, the heritability remains elusive. Investigations in this field have, thus far, identified a limited number of common longevity-associated variants, suggesting that rare genetic variants may play a role in human longevity. Ageing research in model organisms has implicated the insulin/insulin-like growth factor signalling (IIS) network in lifespan and longevity. A mild reduction in activity through genetic and pharmacological interventions in the IIS network, e.g. with rapamycin, have been shown to robustly extend lifespan. The mitogen-activated protein kinase/extracellular signal-regulated kinase (MAPK/ERK) signalling pathway is one branch of the IIS network and has been implicated in lifespan in yeast, worms, flies and mice, through its genetic and pharmacological manipulation, e.g. with trametinib. Whether it also plays a role in human lifespan and longevity, remains unknown. My PhD thesis first explores the role of rare genetic variants in the MAPK/ERK signalling pathway observed in long-lived individuals belonging to the Leiden Longevity Study. After their identification using a bioinformatic pipeline, I aimed to functionally characterise these genetic variants in vitro and in vivo to determine their possible role in human longevity. Second, I investigated the geroprotective potential of a dual MAPK/ERK and PI3K/AKT/mTOR signalling pathway inhibitor, Rigosertib, in promoting healthy ageing in the fruit fly. Chapter 3 of this thesis entails a novel pipeline to functionally characterise genetic variants in cells and different model organisms. For this purpose, I generated cells, flies and mice harbouring longevity-associated human variants and assessed their effect on cellular phenotypes, such as pathway activity and stress resistance. Two variants, Nf1Phe1112Leu and Raf1Asp633Tyr, showed opposing effects on MAPK/ERK signalling pathway activity and resulted in extensive rewiring of the MAPK/ERK related proteome and metabolome in cells. The one variant that I introduced in the fly, Nf1Phe1148Leu, led to shortened lifespan in the homozygous state, while it did not seem to affect lifespan in flies in the heterozygous state (in which it was detected in the long-lived individuals). For the other variant, however, Raf1Asp633Tyr, I was able to show an improved stress response, which was conserved in mouse embryonic fibroblasts, suggesting that this variant may have contributed to human longevity through improved stress resistance mechanisms. In Chapter 4 of this thesis, I investigated the effects of Rigosertib treatment on health- and lifespan in the fruit fly. I could show that Rigosertib robustly extends lifespan in female and male flies. Somewhat surprisingly, the MAPK/ERK signalling pathway activity appeared downregulated in vitro and upregulated in vivo, highlighting context specific regulation of this signalling pathway. Furthermore, in order to understand how the drug extends lifespan in both sexes, I investigated gut health of Rigosertib-fed flies. I could demonstrate that Rigosertib treatment ameliorated age-related decline in gut homeostasis, suggesting that this at least partially contributes to improved health- and lifespan in flies

Studienwahl als Selbstbehandlungsprozess – Eine tiefenpsychologische Analyse der Gründe für die Auswahl der Wirtschaftspsychologie als Bachelorstudiengang

Die vorliegende Arbeit ist eine psychologische Analyse der Studienwahlmotive von Bachelorstudierenden, die sich für das Studienfach ‚Wirtschaftspsychologie‘ eingeschrieben haben. In der Analyse der Motive werden sowohl bewusste als auch unbewusste Einflussgrößen herausgearbeitet und vorgestellt. Die Untersuchung zeigt, dass die Auswahl des Studiums mit einem großen Entwicklungsanspruch einhergeht, der sich darum bemüht, die Summe aller Möglichkeiten auf ein Bild zu bringen. Durch die Wahl des Studienfaches wird versucht, Entwicklung entschieden und zugleich offen zu halten. Dieser Balanceakt belastet, da er sich darum bemüht, Entwicklung in einem Provisorium zu halten, indem er Entschiedenheit auflösen will. Die Analyse stützt sich dabei auf 37 tiefenpsychologische Interviews, die vorwiegend mit Bachelorstudierenden des ersten Semesters in der Wirtschaftspsychologie geführt und mithilfe des morphologischen Versionengangs ausgewertet wurden. Der Forschungsstand der Arbeit eröffnet den Blick auf die gängigen Berufs- und Studienwahlmodelle und gibt ein Beispiel dafür, dass sich die Morphologische Psychologie sehr gut für die Analyse von Auswahlmotiven in der Berufs- und Studienwahl eignet, weil sie auch unbewussten Einflüsse der Studienwahl sichtbar machen kann. In einer abschließenden Diskussion werden die Ergebnisse in Abgleich mit den Befunden der aktuellen Berufs- und Studienwahlforschung gebracht und Handlungsempfehlungen für Berufsberatungen, Hochschulen und Eltern formuliert. Stichworte: Studienwahl, Wirtschaftspsychologie, Studienwahlmotive, Bachelorstudium, Auswahlprozess, qualitative Berufs- und Studienwahlforschung, Studienberatung, Psychologische Studienwahlforschung, Subjektorientierte Studienwahl, Morphologie, Multioptionalität