Fak. 2 Mathematik und Naturwissenschaften

2069 Items

Recent Submissions
Untersuchungen zur Biosynthese von Omphalotin

Ramm, Sascha (2019)

Originally discovered in 1987, Omphalotin is an undodecapeptide (which is) synthesized by the basidiomycete Omphalotus olearius. The fungal secondary metabolite shows a strong nematicide and selective activity against the plant parasite Meloidogyne incognita. Structurally, it bears various remarkable characteristics, as for example nine methylations of the α-nitrogen atoms in the peptide backbo...

Symmetry-Breaking bifurcations and reservoir computing in regular oscillator networks

Röhm, André (2019)

The focus of this thesis is the investigation of regular oscillator networks with numerical and analytical tools. Such systems are ubiquitous in nature and can emerge in the shape of vastly different processes. Among others, they can be mathematically derived as discrete approximations of continuous wave equations or as a local approximation of coupled dynamical systems. In the most basic meani...

Commensurate Nb2Zr5O15: Accessible Within the Field Nb2ZrxO2x+5 After All

Wiedemann, Dennis ; Orthmann, Steven ; Mühlbauer, Martin J. ; Lerch, Martin (2019-04-04)

Doped niobium zirconium oxides are applied in field-effect transistors and as special-purpose coatings. Whereas their material properties are sufficiently known, their crystal structures remain widely uncharacterized. Herein, we report on the comparably mild sol–gel synthesis of Nb2Zr5O15 and the elucidation of its commensurately modulated structure via neutron diffraction. We describe the stru...

Structure–Thermodynamic‐Property Relationships in Cyanovinyl‐Based Microporous Polymer Networks for the Future Design of Advanced Carbon Capture Materials

Yassin, Ali ; Trunk, Matthias Georg ; Czerny, Frank ; Fayon, Pierre ; Trewin, Abbie ; Schmidt, Johannes ; Thomas, Arne (2017)

Nitrogen‐rich solid absorbents, which have been immensely tested for carbon dioxide capture, seem until this date to be without decisive molecular engineering or design rules. Here, a family of cyanovinylene‐based microporous polymers synthesized under metal‐catalyzed conditions is reported as a promising candidate for advanced carbon capture materials. These networks reveal that isosteric heat...

Room-Temperature Activation of Hydrogen by Semi-immobilized Frustrated Lewis Pairs in Microporous Polymer Networks

Trunk, Matthias Georg ; Teichert, Johannes F. ; Thomas, Arne (2017)

Porous polymer networks based on sterically encumbered triphenylphosphine motifs, mimicking the basic sites employed in frustrated Lewis pair (FLP) chemistry, were synthesized via Yamamoto polymerization and their interactions with the strong Lewis acid B(C6F5)3 probed. The combinations yield semi-immobilized FLPs, which are able to cleave dihydrogen heterolytically at ambient temperature and l...

Subspace concentration of geometric measures

Pollehn, Hannes (2019)

In this work we study geometric measures in two different extensions of the Brunn-Minkowski theory. The first part of this thesis is concerned with problems in Lp Brunn-Minkowski theory, that is based on the concept of p-addition of convex bodies, which was first introduced by Firey for p = 1 and later considered for all real p by Lutwak et al. The interplay of the volume and other functionals ...

Electric fields at biomimetic interfaces

Staffa, Jana Katharina (2019)

Electric fields and electrostatic interactions can essentially influence biological processes. This is particularly true for membrane proteins since their activities may be controlled by changes of the transmembrane potential. To elucidate such processes requires appropriate biomimetic membranes, preferentially on electrodes to allow variations of the potential across a bilayer. Particular conv...

Dynamics of collective attention

Lorenz-Spreen, Philipp Gert Josef (2019)

This dissertation aims to capture and understand the macroscopic ebbs and flows of public interest and popular topics. Operationalized as e.g. usage volume of hashtags, movie ticket sales or the counts of comments on online forums, we measure the dynamics of `public attention' for various cultural items in large online data sets. These trajectories of public attention became accessible since th...

Surface functionalised and nanostructured transparent conductive oxides

Harris, Tomos Gwilym Ab Alun (2019)

Storage of (renewable) energy in the form of chemical bonds in electrofuels, their later conversion back to electricity, or the generation of renewable chemical feedstocks from CO2, N2 etc. all require the use of stable and efficient catalysts. In particular, there is urgent need for the development of efficient, precious-metal free catalysts. Enzymes and inorganic (e.g. biomimetic) molecular c...

Nanostructured porous carbon synthesized from metal-organic precursors as efficient electrochemical catalysts

Li, Shuang (2019)

The development of electrocatalysts for the oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER) is of crucial importance to address the global demand for sustainable energy conversion devices with high efficiency, such as fuel cells and metal–air batteries, and the production of hydrogen by electrolysis of water. Nanostructured carbons are pro...

Copper‐Free Sonogashira Coupling for High‐Surface‐Area Conjugated Microporous Poly(aryleneethynylene) Networks

Trunk, Matthias Georg ; Herrmann, Anna ; Bildirir, Hakan ; Yassin, Ali ; Schmidt, Johannes ; Thomas, Arne (2016)

A modified one‐pot Sonogashira cross‐coupling reaction based on a copper‐free methodology has been applied for the synthesis of conjugated microporous poly(aryleneethynylene) networks (CMPs) from readily available iodoarylenes and 1,3,5‐triethynylbenzene. The polymerization reactions were carried out by using equimolar amounts of halogen and terminal alkyne moieties with extremely small loading...

Simulation of building blocks for silicon photonic integrated circuits

Atif, Muhammad (2019)

This study focusses upon simulation of building blocks for silicon photonic integrated circuits. The two necessary steps for the simulation are control of temperature in the integrated Mach-Zehnder Interferometer (MZI) or modulators (MZM), and stabilization and tuning of optical modulated spectrum in node-matched-diode (NMD) Fabry-Pérot (FP) resonator or modulators. Hence the thesis consists of...

Controlling the formation of vesicle structures and their fixation by polymerization

Yalcinkaya, Hacer (2019)

In recent years, nanostructures have drawn much interest due to their potential applications in biomedicine, energy conversion, detergency or electronics. Controlling their formation and stability is one of the key issues to obtain such versatile structures with enhanced morphological properties. Especially vesicles are interesting nanostructures with their hollow spherical geometry, allowing e...

SEIRA optofluidics of sub-monolayers of biomolecules in nL-volumes

Kratz, Christoph Andreas (2019)

Optofluidics enables one to analyze minute amount of samples and facilitates new ways in the analysis of biological samples which are often only available in small amounts and should be used as economically as possible. The integration of in situ IR spectroscopy for the detection in optofluidics however is in a very early stage. In particular integration of SEIRA spectroscopy with metal island ...

Computational and analytical approaches towards epidemic spread containment of temporal animal trade networks

Bassett, George Jason (2019)

In this thesis a threefold approach to assess the risk of epidemic spread on animal trade networks and pinpoint strategies to contain it is presented. Firstly, an exhaustive description of a stochastic, event-driven, hierarchical agent-based model designed to reproduce the infectious state of the cattle disease called Bovine Viral Diarrhea (BVD) on the German trade network is outlined. It takes...

Connectedness of random set attractors

Scheutzow, Michael ; Vorkastner, Isabell (2018-12-28)

We examine the question whether random set attractors for continuous-time random dynamical systems on a connected state space are connected. In the deterministic case, these attractors are known to be connected. In the probabilistic setup, however, connectedness has only been shown under stronger connectedness assumptions on the state space. Under a weak continuity condition on the random dynam...

Low rank tensor decompositions for high dimensional data approximation, recovery and prediction

Wolf, Alexander Sebastian Johannes Wolf (2019)

In this thesis, we examine different approaches for efficient high dimensional data acquisition and reconstruction using low rank tensor decomposition techniques. High dimensional here refers to the order of the ambient tensor space in which the data is contained. Examples of such data include tomographic videos, solutions to parametric differential equations and quantum states of many particle...

Heat flow due to time-delayed feedback

Loos, Sarah A. M. ; Klapp, Sabine H. L. (2019-02-21)

Many stochastic systems in biology, physics and technology involve discrete time delays in the underlying equations of motion, stemming, e. g., from finite signal transmission times, or a time lag between signal detection and adaption of an apparatus. From a mathematical perspective, delayed systems represent a special class of non-Markovian processes with delta-peaked memory kernels. It is wel...

Phononen-assistierte Anregungsprozesse und Hochanregungseffekte in positionierten einzelnen Quantenpunkten

Hitzemann, Ole (2019)

Mit steigender Leistung moderner Rechner und der möglichen Entwicklung verbesserter Algorithmen sowie neuer Technologien wie dem Quantencomputer sind herkömmliche Kryptographieverfahren langfristig nicht mehr sicher. Abhilfe könnte die Quantenkommunikation schaffen, die physikalisch nachweisbar mathematisch sichere Schlüssel übertragen kann. Um nachweislich abhörsicher und mit hoher Effizienz Q...

Eigenschaften ultradünner Galliumnitrid- und -Oxidschichten über InGaN-Quantenfilmen für sensorische Anwendungen

Alamé, Sabine Hildegard Vera (2019)

Die technologische Entwicklung der heutigen Zeit befasst sich zunehmend mit der Kombination traditionell verwendeter Materialien mit organischen Verbindungen. Dadurch ergeben sich eine Vielzahl neuer Anwendungsgebiete und oft einfachere und kostengünstige Bauelemente. In dieser Arbeit wurde untersucht, wie sich das bereits in der Halbleitertechnologie weit verbreitete Materialsystem InGaN und...