Fakultät 2 Mathematik und Naturwissenschaften

1761 Items

Recent Submissions
Physical minimal models of amoeboid cell motility

Kulawiak, Dirk Alexander (2017)

Cell locomotion plays an important role in many biological processes such as the immune system, embryonic development, or cancer metastasis. In these examples, cells interact with their environments or coordinate their movements with other cells, creating collective behavior. In this thesis, we utilize minimal modeling to investigate single and collective cell motility in three different settin...

Comparative venomics of the Vipera ammodytes transcaucasiana and Vipera ammodytes montandoni from Turkey provides insights into kinship

Hempel, Benjamin-Florian ; Damm, Maik ; Göçmen, Bayram ; Karis, Mert ; Oguz, Mehmet Anıl ; Nalbantsoy, Ayse ; Süssmuth, Roderich D. (2018)

The Nose-horned Viper (Vipera ammodytes) is one of the most widespread and venomous snakes in Europe, which causes high frequent snakebite accidents. The first comprehensive venom characterization of the regional endemic Transcaucasian Nose-horned Viper (Vipera ammodytes transcaucasiana) and the Transdanubian Sand Viper (Vipera ammodytes montandoni) is reported employing a combination of intact...

Accessing the dark exciton spin in deterministic quantum-dot microlenses

Heindel, Tobias ; Thoma, Alexander ; Schwartz, Ido ; Schmidgall, Emma R. ; Gantz, Liron ; Cogan, Dan ; Strauß, Max ; Schnauber, Peter ; Gschrey, Manuel ; Schulze, Jan-Hindrik ; Strittmatter, Andre ; Rodt, Sven ; Gershoni, David ; Reitzenstein, Stephan (2017)

The dark exciton state in semiconductor quantum dots (QDs) constitutes a long-lived solid-state qubit which has the potential to play an important role in implementations of solid-state-based quantum information architectures. In this work, we exploit deterministically fabricated QD microlenses which promise enhanced photon extraction, to optically prepare and read out the dark exciton spin and...

IR spectro-electrochemistry of an adsorbed oxygen-tolerant [NiFe] hydrogenase on conductive surfaces

Heidary, Nina (2017)

Hydrogenases are metalloenzymes, catalyzing the reversible oxidation of molecular hydrogen into two protons and two electrons. The 'Knallgasbacterium' Ralstonia eutropha H16 (Re) is one of the few examples, harboring several [NiFe] hydrogenases that established mechanisms to enable catalytic conversion of H2 in the presence of O2. In order to exploit the catalytic potential of these oxygen-tole...

P1-Nonconforming finite elements on triangulations into triangles and quadrilaterals

Altmann, Robert ; Carstensen, C. (2012)

The P1-nonconforming finite element is introduced for arbitrary triangulations into quadrilaterals and triangles of multiple connected Lipschitz domains. An explicit a priori analysis for the combination of the Park–Sheen and the Crouzeix–Raviart nonconforming finite element methods is given for second-order elliptic PDEs with inhomogeneous Dirichlet boundary conditions.

Quantum light driven many level systems in the weak and strong coupling limits

Chatraee Azizabadi, Shahabedin (2017)

We propose a possibility to study the quantum light excitation of atomic systems. To confine our study, we limit the configuration to two and four level emitters as target systems. Source and target are coupled via unidirectional waveguide. We numerically implement the cascaded formalism and use the source-target approach. Herein, we focus on continuous excitation scenarios where the source s...

Ultrafast dynamics of nanoparticles in highly intense X-Ray pulses

Bucher, Maximilian Jakob (2017)

With the advent of X-ray free electron laser, such as the Linac Coherent Light Source (LCLS), structural studies on non-repetitive and non-reproducible nanoparticles, such as single bio-molecules appear imminent. A key challenge to increasing the resolution of single particle imaging is radiation damage. Only a sound understanding of the underlying damage processes, such as the nanoplasma expan...

Beiträge zur bioinspirierten Katalyse

Lindenmaier, Nils (2017)

In dieser Arbeit wurden einkernige Ni- und heterodimere [NiFe]-Komplexe im Kontext der von [NiFe]-H2ase und -CODH „bioinspirierten” Katalyse synthetisiert und untersucht. Im ersten Teil der Arbeit wurde ein neuartiger Silylen-Pyridin-Hybridligand für die Koordination von Nickel(II)- und Nickel(0)-Spezies entwickelt und auf seine σ-Donor- und π-Akzeptoreigenschaften hin analysiert. Der zweite Te...

Matroidal subdivisions, Dressians and tropical Grassmannians

Schröter, Benjamin (2018)

In dieser Arbeit untersuchen wir verschiedene Aspekte von tropischen linearen Räumen und deren Modulräumen, den tropischen Grassmannschen und Dressschen. Tropische lineare Räume sind dual zu Matroidunterteilungen. Motiviert durch das Konzept der Splits, dem einfachsten Fall einer polytopalen Unterteilung, wird eine neue Klasse von Matroiden eingeführt, die mit Techniken der polyedrischen Geomet...

Scattering techniques for nanoparticle analysis

Breßler, Ingo (2017)

This work presents three program packages implementing different methods for nanoparticle analysis, focusing on the quantitative determination of particle size distributions required in standardization of nanoparticle reference materials. In part one, classical curve fitting is discussed. It finds optimal parameters of a scattering model composed of analytical expressions. The classical curve ...

Multidimensional high harmonic spectroscopy

Serbinenko, Valeriya (2017)

Multidimensional high harmonic spectroscopy is a cutting-edge technique for studying the effect of the intense low-frequency laser fields on atoms and molecules. The high energy photons, emitted by a particle as a result of the interaction with the strong laser field, carry the information about the processes in atoms and molecules, which lead to the emission. Multidimensional character of the te...

Quantum control of light and matter fields in the nonlinear regime

Naumann, Nicolas Ludwig (2017)

In this thesis three different approaches to control the quantum statistics in nanoscopic devices are investigated. In the first part of the thesis, mechanical oscillations in solid state devices are manipulated by an external laser to show bistabilities, coherent amplification, and enhanced damping. The dynamics is controlled by the frequency of the external laser. This study is performed in a...

Advanced X-ray analytical methods for the characterization of buried interfaces with relevance for energy conversion devices

Baumann, Jonas (2017)

The efficiency of devices for novel renewable energy sources, like solar cells and thermoelectric generators (TEGs), is strongly increasing since the advent of nanotechnology. Synchrotron radiation-based advanced X-ray fluorescence (XRF) techniques, like grazing emission (GE-) or grazing incidence (GI-) XRF, offer non-destructive and quantitative access to elemental depth profiles in the nanome...

Multinary metal oxides for solar water splitting

Wang, Fuxian (2017)

The world has experienced an exponential increase in the demand for energy primarily coming from the consumption of fossil fuels, which is accompanied by the inevitable emission of carbon dioxide, causing global warming. Developing renewable and carbon-free sources is essential to reduce carbon dioxide emission and mitigate global warming. Among the renewable energy sources, solar energy has th...

Elucidating the mechanism of action of antimicrobial peptides by means of computational approaches

de Miguel Catalina, Alejandra (2017)

Microorganism such as bacteria, viruses, fungi and some parasites, possess the inherent ability to cease the activity of an antimicrobial -for instance antibiotics, antivirals and antimalarials- against it. This property is known as antimicrobial resistance (AMR) and causes with time the ineffectiveness of standard treatments, helping infections persist and spread to other hosts. AMR is one of ...

HP-MoO2: A High-Pressure Polymorph of Molybdenum Dioxide

Lüdtke, Tobias Clemens ; Wiedemann, Dennis ; Efthimiopoulos, Ilias ; Becker, Nils ; Seidel, Stefan ; Janka, Oliver ; Pöttgen, Rainer ; Dronskowski, Richard ; Koch-Müller, Monika ; Lerch, Martin (2017)

High-pressure molybdenum dioxide (HP-MoO2) was synthesized using a multianvil press at 18 GPa and 1073 K, as motivated by previous first-principles calculations. The crystal structure was determined by single-crystal X-ray diffraction. The new polymorph crystallizes isotypically to HP-WO2 in the orthorhombic crystal system in space group Pnma and was found to be diamagnetic. Theoretical investi...

Synthesis and crystal structure of δ-TaON, a metastable polymorph of tantalum oxide nitride

Lüdtke, Tobias Clemens ; Schmidt, Alexander ; Göbel, Caren ; Fischer, Anna ; Becker, Nils ; Reimann, Christoph ; Bredow, Thomas ; Dronskowski, Richard ; Lerch, Martin (2014)

δ-TaON was prepared by reaction of gaseous ammonia with an amorphous tantalum oxide precursor. As a representative of the anatase structure (aristotype) it crystallizes in the tetragonal crystal system with lattice parameters a = 391.954(16) pm and c = 1011.32(5) pm. At temperatures between 800 and 850 °C an irreversible phase transformation to baddeleyite-type β-TaON is observed. While quantum...

Bixbyite-type phases in the system Ta-Zr-O-N

Lüdtke, Tobias Clemens ; Orthmann, Steven ; Lerch, Martin (2017)

Phase-pure tantalum/zirconium oxide nitrides and nitrides were synthesized by the ammonolysis of amorphous oxide precursors. The nitrogen-rich oxide nitrides with variable anion composition and the nitride TaZrN3 crystallize in the cubic bixbyite-type structure (space group Ia3̅). The nitrogen content of these compounds has a significant influence on the cell parameters, the atomic positions, a...

A density-functional theory approach to the existence and stability of molybdenum and tungsten sesquioxide polymorphs

Becker, Nils ; Reimann, Christoph ; Weber, Dominik ; Lüdtke, Tobias Clemens ; Lerch, Martin ; Bredow, Thomas ; Dronskowski, Richard (2016)

The sesquioxides of molybdenum and tungsten have been reported as thin films or on surfaces as early as 1971, but the preparation of bulk materials and their crystal structures are still unknown up to the present day. We present a systematic ab initio approach to their possible syntheses and crystal structures applying complementary methods and basis-set types. For both compounds, the corundum ...

Computable convergence bounds for GMRES

Liesen, Jörg (2006)

The purpose of this paper is to derive new computable convergence bounds for GMRES. The new bounds depend on the initial guess and are thus conceptually different from standard "worst-case" bounds. Most importantly, approximations to the new bounds can be computed from information generated during the run of a certain GMRES implementation. The approximations allow predictions of how the algorit...