Chaos und Turbulenz in der Belousov-Zhabotinsky-Reaktion

In dieser Arbeit werden verschiedene Aspekte einer oszillierenden chemischen Reaktion, der sogenannten Belousov-Zhabotinsky-Reaktion untersucht.Das Thema des ersten Kapitels sind riddled basins-ähnliche Einzugsgebiete. Es werden Systeme betrachtet, die zwei koexistierende Attraktoren besitzen, von denen jedoch einer durch eine sog. Krise transientes Verhalten zeigt. Durch endliche Iterations- bzw. Integrationszeiten werden Anfangsbedingungen dem transienten Attraktor zugeordnet, wodurch die berechneten Einzugsgebiete riddled basins gleichen. Die zur Quantifizierung von riddled basins benutzte Funktion f (e) wird mit Hilfe der logistischen Gleichung analytisch hergeleitet. Die Ergebnisse sind auf ein Modell für die räumlich homogene Belousov-Zhabotinsky- Reaktion anwendbar. Im zweiten Teil dieser Arbeit wird der Einfluss von Methanol auf die Belousov-Zhabotinsky-Reaktion untersucht. In einem ständig gerührten, also räumlich homogenen System findet bei Erhöhung der Methanolkonzentration [Me] über einen kritischen Wert [Me]crit hinaus ein Übergang von einem anfangs anregbaren zu oszillatorischem Verhalten statt. Die Schwingungsperiode nimmt im oszillatorischen Bereich bei steigender Methanolkonzentration ab. Mit Hilfe eines Modells kann die im Experiment gefundenen Systemdynamik quantitativ beschrieben werden. In einem raumzeitlichen geschlossenen Gel-Lösungs-System führt eine Methanolzugabe zur Ausbildung eines vertikalen Methanolgradienten. Die Dynamik von Spiralwellen ändert sich daher in Abhängigkeit der Höhe. Das Systemverhalten bei drei unterschiedlichen Gradienten wird vorgestellt: 1.) bei geringer Methanolkonzentration ([Me] = 0.1 M) erhöht sich die Umdrehungsperiode einer Spiralwelle, wobei gleichzeitig die Wellenlänge reduziert wird. 2.) Bei mittlerer Methanolkonzentration ([Me] = 0.15 M) beginnt im Spiralzentrum ein komplexer Kollisionsprozess, welcher letztendlich zur Turbulenz des gesamten Mediums führt. 3.) Durch Erhöhung auf ([Me] = 0.2 M) findet zunächst eine (evtl. mehrfache) Aufspaltung der Spiralwellen statt. Viele oszillierende und miteinander kollidierende Wellenfronten erzeugen in kurzer Zeit eine turbulente Struktur. Simulationen mit partiellen Differentialgleichungen liefern Erklärungen für die experimentell beobachteten Strukturen. Turbulenzlöschung mit Hilfe eines Lichtpulses ist Thema des dritten Teils der Arbeit. Es werden zwei verschiedenen experimentellen Aufbauten betrachtet, in denen das BZ-Medium aufgrund unterschiedlicher Mechanismen turbulentes Verhalten aufweist: 1.) durch den Einfluss von Methanol und 2.) durch Verwendung eines grobkörnigen Mediums. Alle beobachteten Turbulenzen zeichnen sich durch unregelmäßig umherwandernde Wellenbruchstücke aus. Ein geeigneter Lichtpuls kann Erregungswellen in zwei in entgegengesetzte Richtungen laufende Fronten aufspalten. Es wird gezeigt, dass eine endliche Anzahl solcher Pulse die turbulenten Strukturen auslöschen kann. Numerische Integration von auf dem Bär-Eiswirth-Modell basierenden Differentialgleichungen untermauern die experimentellen Ergebnisse

Factor graph-based receivers for multi-carrier transmission in two-way relaying and massive machine type communications

The way of communication has evolved in recent years from purely human-driven communication - with the need for voice calls and simple data packets such as SMS - to a mixture of fast human-driven communication and machine-driven communication, leading to networks that support a growing number of services with different quality of service requirements and an increasing number of devices. This development is at the expense of a wide range of different service needs that have serious implications for the architecture of mobile communications systems. Some forecasts predict an explosion of connected devices in the near future. This extremely high demands on today's communication systems are constantly increasing as very broad requirements such as coverage, short latency times and simple transmitter design are made. In particular, the latter leads to cheap and therefore imprecise hardware implementations, leading to higher detection processing at a receiver. The aim of this thesis is to analyze such scenarios using a framework of robust multicarrier transmission systems and factor graphics-based detection schemes. Overall, this work gives a deeper insight to multi-carrier schemes applying well-localized waveforms and its applications in Two Way Relaying and massive machine type communication. Furthermore, for massive machine type communication a multi-carrier narrow band system that addresses key aspects in this type of communication, which takes advantage of compressive sensing multi-user detection has been introduced. Especially, for these scenarios the framework of well-localized waveforms and factor graphs, utilizing the knowledge of the waveforms, lead to flexible and controllable design of factor graph-based equalizers. The results of these analyses yield the statement that multi-carrier concepts with well-localized waveform can improve the robustness in multiple access schemes, as shown by performance investigations with time and frequency offsets in future mobile radio systems

Turbulence control by wave splitting in excitable media

Erratic wave break-ups can cause spatiotemporal disorder (often called 'turbulence') in excitable media, Using different experimental setups of the Belousov-Zhabotinsky reaction, as well as simulations, we show that a finite number of pulses, each of which causes backfiring (splitting) of the waves, completely annihilates the disordered waves. Considering formal analogies, one may similarly control cardiac fibrillation. (C) 2002 Elsevier Science B.V. All rights reserved

Performance of HARQ with Reduced Size Retransmissions using Network Coding Principles

Abstract—This paper discusses retransmission approaches to improve the throughput performance of Hybrid-ARQ (HARQ) schemes in a point-to-point single user 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) uplink system. One goal of communication systems is to achieve a reliable transmission with a throughput performance as close as possible to channel capacity. For that, reducing the channel utilization will improve the throughput performance. Instead of sending two retransmission packets for two HARQ processes of one users, a previously published HARQ scheme uses the XOR combining of these packets to get only one retransmission packet with the same size. Similar to this idea, a new varied scheme performs XOR combining of parts of one conventional full retransmission to generate a smaller retransmission packet. Both approaches will reduce the channel utilization. They will be compared with a HARQ system in LTE uplink using a full size retransmission and a half size retransmission. The main focus of this work is the throughput performance evaluation of these schemes in an LTE link-level simulator. Index Terms—Network coding, HARQ, In-Packet, LTE uplink. I

The sterlet sturgeon genome sequence and the mechanisms of segmental rediploidization

Sturgeons seem to be frozen in time. The archaic characteristics of this ancient fish lineage place it in a key phylogenetic position at the base of the ~30,000 modern teleost fish species. Moreover, sturgeons are notoriously polyploid, providing unique opportunities to investigate the evolution of polyploid genomes. We assembled a high-quality chromosome-level reference genome for the sterlet, Acipenser ruthenus. Our analysis revealed a very low protein evolution rate that is at least as slow as in other deep branches of the vertebrate tree, such as that of the coelacanth. We uncovered a whole-genome duplication that occurred in the Jurassic, early in the evolution of the entire sturgeon lineage. Following this polyploidization, the rediploidization of the genome included the loss of whole chromosomes in a segmental deduplication process. While known adaptive processes helped conserve a high degree of structural and functional tetraploidy over more than 180 million years, the reduction of redundancy of the polyploid genome seems to have been remarkably random.publishe

The broad-leaf herbicide 2,4-dichlorophenoxyacetic acid turns rice into a living trap for a major insect pest and a parasitic wasp

Synthetic chemical elicitors of plant defense have been touted as a powerful means for sustainable crop protection. Yet, they have never been successfully applied to control insect pests in the field. We developed a high-throughput chemical genetics screening system based on a herbivore-induced linalool synthase promoter fused to a β-glucuronidase (GUS) reporter construct to test synthetic compounds for their potential to induce rice defenses. We identified 2,4-dichlorophenoxyacetic acid (2,4-D), an auxin homolog and widely used herbicide in monocotyledonous crops, as a potent elicitor of rice defenses. Low doses of 2,4-D induced a strong defensive reaction upstream of the jasmonic acid and ethylene pathways, resulting in a marked increase in trypsin proteinase inhibitor activity and volatile production. Induced plants were more resistant to the striped stem borer Chilo suppressalis, but became highly attractive to the brown planthopper Nilaparvata lugens and its main egg parasitoid Anagrus nilaparvatae. In a field experiment, 2,4-D application turned rice plants into living traps for N. lugens by attracting parasitoids. • Our findings demonstrate the potential of auxin homologs as defensive signals and show the potential of the herbicide to turn rice into a selective catch crop for an economically important pest