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On Postcritically Minimal Newton Maps
No full textThe Newton map of an entire map f is defined by N_f(z):=z-f(z)/f'(z). For f(z)=p(z)e^q(z), where p and q are polynomials, its Newton map N_pe^q=z-p(z)/(p'(z)+p(z) q'(z)}) is a rational function. For a Newton map N_pe^q the finite fixed points are (super)attracting and are roots of p. The point at infinity is a parabolic fixed point with deg(q) petals for a Newton map N_pe^q. For fixed integers d>=3 and 1<=n<=d, let deg(p)=d-n with p having only simple roots and deg(q)=n, then we have deg(N_pe^q)=d. The parameter plane (parametrized by coefficients of p and q) of Newton maps satisfying properties above is of complex dimension d-2. Due to existence of the parabolic fixed point for these Newton maps, we can not have post-critically finiteness condition in this family. But there exists an analogous notion, that we call it ``post-critically minimal", to the notion of post-critically finite.
The properties of post-critically minimal Newton maps are also similar to those of post-critically finite Newton maps of polynomials. Using surgery tools developed by P. Haissinsky and G. Cui we give a full classification of post-critically minimal Newton maps in terms of post-critically finite Newton maps of polynomials. The latter was recently classified by Y. Mikulich, R. Lodge and D. Schleicher
Unpacking the Political Resource Curse: How Oil Fuels Personalism and Undermines Democratization
No full textOil wealth is often associated with prolonged authoritarian rule, poor governance and other institutional pathologies. These unusual effects of petroleum have been variously described as the 'Paradox of Plenty' (Karl 1997), 'Natural Resource Trap' (Collier 2007), and the 'Oil Curse' (Ross 2012), and an increasing number of studies have examined the causes and effects of the oil curse (Humphreys et al. 2007). However, the prevailing assumption in most studies has been that oil will have an equally strong anti-democratic effect across authoritarian regime types (Ross 2001; 2012; Jensen and Wantchekon 2004; Haber and Menaldo 2011). Theoretical and empirical studies on the resource curse have ignored institutional differences in authoritarian rule emphasized by scholars of authoritarian politics (Linz and Stepan 1996; Geddes 1999; Schedler 2009; Geddes, Wright and Frantz 2014). In this study, I combine these two strands of literature and show that oil has a particularly dire effect on the democratization prospects of a particular subtype of authoritarianism, namely, personalist autocracies. The analysis of regime development patterns across oil and non-oil producing states presented in this study shows that oil wealth particularly strongly harmed democratization prospects in the personalist sub-set of authoritarianism. Using three country-case studies of Azerbaijan, Cameroon, and Venezuela, I illustrate the ways in which oil can reinforce personalism and undermine the democratization processes and suggest that the causal channels linking oil and regime outcomes (authoritarian durability and democratic transitions) depend on the composition of authoritarian rule in place, and may not be uniform across regime types. The case of Venezuela under Chávez also indicates that in democratic regimes with a long history of oil-induced elite corruption, oil wealth may contribute to the personalization of power in a failing democracy
Differential Transport of Murine MHC Class I Molecules from the Endoplasmic Reticulum to the Golgi Apparatus
No full textMajor Histocompatibility Complex (MHC) class I molecules are cell surface glycoprotein complexes that present endogenous peptides to cytotoxic T cells of the immune system. The trimeric MHC class I molecules (heavy chain, light chain, and peptide) are assembled in the early secretory pathway - the endoplasmic reticulum (ER), the ER-Golgi intermediate compartment (ERGIC), and the cis side of the Golgi apparatus. MHC class I molecules then progress to the medial Golgi and follow the secretory pathway to the cell surface.
The many known human and murine allotypes of MHC class I differ in their rates of cell surface transport. This difference might be caused by allotype-specific protein folding and assembly, transport to ER exit sites (ERES), recruitment into ER-to-Golgi transport carriers, or retrieval processes from the ERGIC or the cis-Golgi to the ER. In this work, I have evaluated the contribution of each of these processes to MHC class I cell surface transport with two murine allotypes as model proteins, H-2Db (slow transport) and H-2Kb (fast transport), using radioactive pulse-chase experiments, in vitro generation of ER-to-Golgi transport carriers, and protein folding assays. From the results, I conclude that both proteins are recruited to ER-to-Golgi transport carriers with the same efficiency, but that a novel pre-ER exit step delays their access to ERES. This step is mediated by proteins of the ER matrix, and it acts on the peptide-bound lumenal domain of MHC class I.
I have also analyzed the ER exit of proteins that participate in MHC class I assembly: the peptide transporter TAP, the chaperone tapasin, and the lectin calreticulin. In my experiments, these proteins leave the ER and may promote MHC class I assembly in post-ER compartments, though only to a minor extent.
My data support a model, in which MHC class I protein complexes are predominantly assembled in the ER. I propose that the cell surface transport rate for MHC class I molecules is determined by the rates of protein folding and unfolding, the affinity of all MHC class I folding intermediates to proteins of the ER matrix, and the proteostasis in the ER and the secretory pathway
Distributive Cooperative 3D Exploration under Range Communication Constraints
No full textExploration can be termed as the process of autonomously navigating in an environment in order to build a map. This is one of the core components for autonomous robots. Mobile robots are increasingly being used in areas where human interaction is not present or extremely limited. These include realms such as surfaces of planets and moons, underwater sites, nuclear power plants etc. In such situations, robots need to navigate the environment without human intervention. They need to decide the next goal points to reach in order to increase their knowledge of the environment, using just the information collected so far.
With great advances being made in the field of single robot mapping and exploration, the next step is to use multiple robots. The obvious advantage is the speed up of exploration time by distributing the exploration task among multiple robots. Furthermore, the use of multiple robots ensures that there is no single point of failure, increasing redundancy, allowing for increased robustness. Also, multiple robots may help in localisation by detecting each other, or the same feature from multiple locations.
Most of the work done till now has focused on 2D exploration. This thesis proposes an exploration method which performs true 3D exploration, with robots navigating in a 3D environment to produce a 3D map. Furthermore, the members of the robot team stay within communication range of each other, thereby always being able to communicate, and hence being able to cooperate in the exploration process.
Also, multi-robot exploration has a very large search space. This means that it is not possible to arrive at an optimal solution in a reasonable amount of time. This requires sampling the search space to reach a solution. The random nature of the algorithm often leads to suboptimal solutions. In this thesis, the random sampling is augmented by a heuristic which improves the exploration time by preventing unnecessary steps during the exploration process.
The algorithm is tested in a high-fidelity simulator which was developed during the course of the project which takes into account the dynamics of the robot, thereby allowing a seamless transition to real life systems
Engineering filamentous fungi to improve bio-reaction performance in fermentation systems: application to the production of food/technical enzymes : Genetic engineering of fungi for food industrial applications
No full textSolid-state fermentation (SSF) processes with the filamentous fungus Aspergillus sojae ATCC 20235 (A. sojae) are known to yield good levels of pectinolytic enzymes which are valuable biocatalysts in the food industry. However, in fungal-based SSF systems there is a poor availability of oxygen in inner regions of the fermented mass, leading to limited cell growth and protein production. Previous studies showed that the heterologous expression of the bacterial Vitreoscilla hemoglobin (VHb) –commonly referred to as the “vgb/VHb technology”- can favor respiratory metabolism and cell growth of prokaryotes and eukaryotes under oxygen-limited conditions. The main purpose of this thesis was to genetically engineer A. sojae with VHb aiming to enhance its cell growth and protein production under conditions of SSF.
An Agrobacterium tumefaciens-mediated transformation procedure was established to successively integrate the VHb gene (vgb) into the genome of A. sojae. The transformed A. sojae strain harboring vgb (A. sojae vgb+) yielded more biomass and enzymatic units of exo-pectinases and protease in comparison to its parental strain (A. sojae wt) in solid-state cultures in Erlenmeyer flasks. Fermentations were up-scaled (100 times) in a drum-type reactor and the recombinant fungus produced up to 38% more pectinases and 33% more proteases in comparison to its wild-type. Furthermore, enzymatic extracts of A. sojae vgb+ clarified apple juice and blood orange juice with up to 37% and 50% more efficiency, respectively in comparison to the enzymatic extracts of A. sojae wt.
Overall, the results of this dissertation show that the vgb/VHb technology can improve cell growth and protein production of A. sojae in SSF and that the protein complex of the recombinant A. sojae vgb+ was substantially more efficient in the clarification of fruit-based beverages compared to A. sojae wt
Role of variability in spatiotemporal pattern formation
No full textThis thesis explores the effects of variability on spatiotemporal pattern formation. Using a variety of mathematical models, but mainly focussing on the FitzHugh-Nagumo model, we explore the ways in which variability in the properties of a group of diffusively coupled elements can determine the resulting pattern. We devise a series of distinct developmental paths, i.e. time-dependent changes of element properties, in lattices of FitzHugh-Nagumo oscillators. Our paths are modelled after the developmental paths created in previous works to explain spiral waves of cyclic adenosine monophosphate which lead to aggregation in populations of the slime mould Dictyostelium discoideum. These differ in the amount of element-to-element desycnhronisation in a specific parameter value, which varies as a function of time, as well as the rate of change of this property. The resulting paths display distinctions in the events which occur, the spiral and target wave numbers, and the relationships between the event locations and the element properties. We establish a general notion of diversity-induced resonance in the FitzHugh- Nagumo model in terms of the spiral tip and target wave numbers, using the standard deviation of an element property over the lattice of coupled elements as our measure of diversity. Exploring the mechanisms underlying this resonance, we observe that target-spiral competition appears to drive the resonance in these patterns. However, we find that the frequency of wave events, which in turn depends on the properties of the individual elements, is not sufficient in itself to determine the type of wave pattern which will eventually dominate the lattice of elements. Complex inter-wave interactions must be taken into account to arrive at more accurate predictions of the lattice state, while the number of elements in the oscillatory regime but close to the excitable border proved to accurately predict the values of diversity at which maximum spiral numbers were observed in simulated experiments.
Based on the importance of understanding events occurring en route to spatiotemporal pattern formation in the discrimination of different pattern formation strategies, we advocate an event-based view of pattern formation. This view reflects the additional quantitative and qualitative information that can be obtained by exploring these pattern events, and could potentially allow the development of insights into mathematical models and real biological systems based on the observable properties of their specific pattern event sequences. In general, our results elucidate some of the mechanisms and diverse interactions which characterise the influence of variability on pattern formation in excitable systems
Trap limited charge transport analysis in Poly(3-hexylthiophene)
No full textCharge transport in organic thin films is analyzed through different measurements techniques. In the first place, temperature and charge carrier dependence of the mobility is used to determine a model describing charge transport in the accumulation layer of a poly(hexyl-thiophene) based organic field effect transistors. A model based on a two-dimensional charge transport and the Vissenberg and Matters model is elaborated and is found to closely match the experimental data.
Impedance and transient current measurements on a metal-insulator-semiconductor (MIS) capacitor are used as tools to thoroughly investigate the bulk and interface electronic transport properties of semiconducting polymers, i.e. poly(3-hexylthiophene). Both interfaces, i.e. metal-semiconductor and semiconductor-insulator show distinct features. The results revealed a dispersive transport in the bulk due to the band tail of the localized states, presence of interface states at the interface between the insulator and the semiconductor and formation of a less conductive small layer at the interface semiconductor-metal contact due to intrusions of sputtered Au particles. Effects of self-assembled monolayers (SAMs) treatments of the gate insulating dielectric were investigated showing that treating the gate dielectric with either ozone or hexamethyldisilazane (HMDS) or octyltrichlorosilane (OTS) alter not only the interface semiconductor-insulator but the bulk properties as well. An exponential density of states with a width parameter of 38 to 58 meV depending on the surface treatment was found to be representative of the band tail of poly(3-hexylthiophene) (P3HT). Though both OTS and HMDS treatments slightly increase the density of interface states, only OTS treated samples showed a decrease in disorder parameter of the bulk. The latter fact can be attributed to an increase of the grain size due to a favored π-π stacking film growth, an outcome explaining the already reported increase of the lateral mobility and decrease of the vertical mobility observed upon OTS treatment of the gate insulating dielectric in poly(3-hexylthiophene) based devices.
A transient current measurement technique which does not need light stimulus is developed. This illumination-free transient current (IFTC) technique offers insights on trapping states characteristics such as the capture time of the trapping states, their density of states (DOS) and the attempt-to-escape frequency of trapped carriers. For the analysis of IFTC measurements carried out on metal-insulator-semiconductor (MIS) capacitors, numerical simulation of the transient current were performed as a way around usual assumptions of negligible transit times which can considerably distort the values from transient current measurements. A combination of experimental data and simulations revealed the need to take into account retrapping events in order to extract the correct band tail density of states and corresponding characteristic parameters. An exponential density of states with a total density of 4•10²³ /m³ and an exponential width parameter of 50 meV was found to be representative of the band tail of spin-coated poly(3-hexlythiophene) (P3HT). A broader exponential distribution with a width parameter of 83 meV is extracted for the interface states towards SiO₂. Using a multiple trap and release model, the capturing time for a reference carrier concentration of 7•10²³ /m³ and the attempt-to-escape frequency of the band tail states were found to be 1/10 ns and 10⁸/s , respectively. With this technique, we are able to also pinpoint the energy position of the Fermi level relative to the transport energy level.
Finally, Organic field effect transistors with lower threshold voltage and lower off-current upon embedding Au particles in the bulk of the semiconductor are demonstrated. With this technique, the threshold voltage can be tuned in the range of 5 V and the off-current can be decreased by a factor of 4
From good intentions to healthy behaviour: Strategies and resources in bridging the intention-behaviour gap
No full textNoncommunicable diseases often have their roots in insufficient health behaviour and could be prevented or managed by health behaviour change. Although many people are aware of this, too many are not sufficiently performing regular physical activity and healthy nutrition. In other words, even in the face of good intentions behaviour change can become a challenging task that requires a high amount of self-regulation, by attempting to overcome established behavioural patterns. Research has shown that intentions are a crucial factor in the phase of health behaviour initiation, however, until now, it is not clear which mechanisms can bridge the intention-behaviour gap most effectively with regard to long-term behaviour maintenance. Therefore, the aim of this thesis was to broaden the understanding of motivational and volitional processes involved in single and multiple health behaviour change. Determinants of successful lifestyle management must be unveiled, in order to enable further examination of social-cognitive and behavioural mechanisms in individuals. Specific research questions were outlined and examined in three observational studies, in clinical and nonclinical samples, across the lifestyle factors of physical activity and diet. Results from the studies in this dissertation indicate that personal and social resources (self-determination, social support, intergoal facilitation) as well as self-regulatory strategies (planning, self-efficacy, selective optimization with compensation) foster behaviour change in the domains of physical activity and healthy nutrition. The findings provide a solid basis for intervention design to empower individuals to sustainable health behaviour change: Self-regulatory strategies, such as planning and selective optimization with compensation, should be taken into account to achieve long-term adaptation to a healthy lifestyle, in particular with regard to multiple health behaviour change.Viele chronisch degenerative Erkrankungen haben ihre Wurzeln in unzureichenden Gesundheitsverhaltensweisen und könnten durch Verhaltensänderungen verhindert werden. Ein nachhaltiger Nutzen für die Gesundheit wird insbesondere durch körperliche Aktivität und eine gesunde Ernährung erreicht. Aber auch bei einer hohen Motivation kann dies für den Einzelnen eine große Herausforderung darstellen, die ein hohes Maß an Selbstregulation erfordert, um die bestehenden Verhaltensmuster zu überwinden. Bisherige Forschung konnte zeigen, dass Intentionen eine entscheidende Rolle in der Phase der Handlungsaufnahme darstellen, doch bisher ist unklar, welche Mechanismen die Intentions-Verhaltenslücke in Hinblick auf die langfristige Ausübung des Gesundheitsverhaltens nachhaltig schließen. Daher war es das Ziel dieser Arbeit, die motivationalen und volitionalen Prozesse in der Veränderung einzelner oder mehrerer Gesundheitsverhaltensweisen genauer zu beleuchten. Entscheidende Faktoren in der erfolgreichen Lebensstiländerung müssen identifiziert werden, um die weitere Untersuchung sozial-kognitiver und verhaltensbasierter Mechanismen zu ermöglichen. Entsprechend wurden Forschungsfragen formuliert und in drei Beobachtungsstudien zu körperlicher Aktivität und gesunder Ernährung untersucht, sowohl im klinischen als auch im nicht-klinischen Kontext. Die Ergebnisse der Studien in dieser Dissertation zeigen, das neben personalen und sozialen Ressourcen (Selbstdetermination, soziale Unterstützung, Zielkohärenz) insbesondere selbstregulative Strategien (Planung, Selbstwirksamkeit, selektive Optimierung und Kompensation) in der Verhaltensänderung von körperlicher Aktivität und gesunder Ernährung wirksam sind. Die Befunde liefern eine solide Basis für die Gestaltung von Interventionen, die den Einzelnen zur nachhaltigen Veränderung der eigenen Gesundheitsverhaltensweisen befähigen und in der Verwirklichung seiner Ziele bestärken
Migrating Imageries : zoomorphic depictions of immigrants in American illustrations
No full textIn the seven chapters which comprise this work, the movement of zoomorphic or animalistic imagery is shown to be present throughout the waves of immigration to the United States as it is evidenced in illustrations taken from the respective waves. In this aim, the zoomorphic imagery is shown to be consistently present in illustrations, not only pictorially but also in regards to the language used in the accompanying texts and titles attached to the illustrations. Furthermore, in order to support the drawn conclusions from each wave which prove the migration of zoomorphic imagery throughout the various waves, a historic review is offered for each major chapter containing relevant information on depicted events and immigrant groups.
Overall methodologies used herein include, Panofsky’s iconographic analysis in which a three-tiered reading of images is undertaken in order to isolate icons which transport meaning to the viewer, both contemporarily and contemporaneously, via their careful placement in relation to the scopic regimes at the time of creation and also currently. Additionally, the use of language both as text to be read regarding the illustrations and text included in the illustrations themselves in the forms of captions, titles, etc., will be subjected to discourse analysis and the degree to which the images and texts work together to create a unique imagery that is observable throughout the historic taxonomies is determined. The work then proves that considering historic events, the interpretive elements of the imagery are not contemporary reimaginings but relate closely to contemporaneous scopic regime interpretations that are traceable up until and including the continuing debate on immigration.
The discourse analyses follow those guidelines developed by Foucault and Gee and especially poignant here is the notion of the discursive formation and the undefined ‘more’ that result from formative aspects of discourse at its inception. Discourse thereby contributes to the tracing of the imagery as it is possible to track also the phraseology used in relationship to immigrants during varying timeframes in the United States’ immigration history and to review how, and to which degree, that language has morphed in relation to its inclusion of animalistic elements. It is also in the discourse analyses in which the zoomorphic imagery supersedes the level of visuality and enters concretely into imagery. That concretization is explored here as a discursive formation, and yet this work proves that this does not involve a stagnation of imagery as there is a driving force which is recognizable in the successive waves. The zoomorphic aspects are examined insomuch as the imagery is compared to animal imagery, anatomy and behavior.
These seven chapters prove that there is indeed an ever-present zoomorphic imagery throughout the waves of immigration to the United States and such an endeavor has not yet been undertaken in an academic context. The comprehensive work of Roger Daniels offers much of the backbone to the historic methodology used, and the contribution of his corpus is reviewed in the literary review chapter which gives an up-to-date account of the state of research in regards to this particular enquiry. As there is very little research combining these multiple analyses in regards to American immigrant imagery, scholarly material has been used from the field of Human-Animal Studies as this growing discipline encompasses similar approaches to the examination and appropriation of animals in human civilization even if not exactly matching to the research aims and findings of this work.
An introduction, outlining the target questions and the basic approach of the text is followed by a literature review and a methodology section wherein the various methods that are used to trace the imagery are outlined and the reasons for their selection as integral are stated. Next, there are three major chapters which are based on the time period that each wave covers (a taxonomy which is explained in the methodology chapter), with each chapter containing an introduction to the illustrations, the historic background on them, the pictorial analyses and the discourse analysis of the wave. For each chapter there is also a conclusion which presents the findings of that particular chapter and leads into the next. Finally, at the end an overall conclusion is given which functions to not only summarize the work as a whole but also to reiterate the proof of the use of zoomorphic imagery throughout the immigration waves. Also, the conclusion contains markers which might direct further scholarly research on this research topic and poses questions which have sprung out of the research contained herein.
Overall, Migrating Imageries: zoomorphic depictions of immigrants in American illustrations serves as a springboard from which the relationship between zoomorphic imagery and the depiction of the immigrant in American illustrations (and also in the general visuality) can be based, which could consequently lead to furthered academic research in this area. This work joins the ongoing development of the academic field of Human-Animal Studies and contributes to the larger study of American visual culture
Comparative Study of Time-Dependent Theories applied to Charge Transport through Molecular Junctions
No full textThis thesis deals with numerical investigations of charge transport through molecular junctions, where the latter are to be understood as single molecules sandwiched between two leads, acting as active circuit elements. The model used to describe such a device is a linear chain of tight-binding sites coupled to external fermionic leads, where the mentioned sites mimic those molecular orbitals relevant to charge transport. To this end, we discuss several techniques for describing quantum systems coupled to fermionic reservoirs. Specifically, we deal with three different formalisms: quantum master equations, derived in a perturbative manner with respect to coupling to reservoirs, the hierarchical equations of motion approach and a scheme based on timedependent nonequilibrium Green's functions. These theories are all suited to describe time-dependent effects in molecular junctions and deliver the occupation-number dynamics of molecular sites as well as the time-dependent electron current through the device.
Our contribution on the theoretical side is twofold. First, we treat the derivation of master equations in great
detail. This allows us to achieve a good understanding of the abstract quantities involved and also to shed light on the strengths and limitations of this approach. Second, we write the final equations of the aforementioned methods in a unified notation, which allows to better grasp similarities and further ignites a comparative discussion with the goal of choosing the most suited scheme for our envisaged numerical simulations.
On the numerical side, the three schemes mentioned above were implemented in computer programs. We performed a direct comparison of the methods for the single resonant level (e.g. the ground state of a molecule or a quantum dot), where we showed the limitations of the quantum master equations, due to their intrinsic perturbative nature. For this system our findings are in agreement with other works in the literature. The key point of this thesis is represented by numerical simulations performed for a rather realistic system. In effect, the set-up is given by a molecule contacted by external leads and placed in an aqueous environment, thus being subject to the fluctuations of the solvent molecules. These external fluctuations lead to incoherent effects and influence the electron transport properties. Speciffically, we deal with a double-stranded DNA heptamer. By means of classical molecular dynamics simulations followed by quantum chemistry calculations one obtains time series of on-site energies and effective inter-site couplings. We use these trajectories to compute the electric current through the molecular junction, adopting the above mentioned Green's functions method. Its outcomes are compared with the yields of the snapshot-averaged Landauer-Büttiker approach, which is often used in related studies. Among other findings, we show that for scenarios with rapidly fluctuating system parameters (e.g. in the femtosecond range)the dominant transfer mechanism is sequential transport, since on such a time scale the system is usually not able to reach the steady state