Fak. 2 Mathematik und Naturwissenschaften

2045 Items

Recent Submissions
Chromophore binding to two cysteines increases quantum yield of near-infrared fluorescent proteins

Buhrke, David ; Tavraz, Neslihan N. ; Shcherbakova, Daria M. ; Sauthof, Luisa ; Moldenhauer, Marcus ; Vélazquez Escobar, Francisco ; Verkhusha, Vladislav V. ; Hildebrandt, Peter ; Friedrich, Thomas (2019-02-12)

Phytochromes are red/far-red light sensing photoreceptors employing linear tetrapyrroles as chromophores, which are covalently bound to a cysteine (Cys) residue in the chromophore-binding domain (CBD, composed of a PAS and a GAF domain). Recently, near-infrared (NIR) fluorescent proteins (FPs) engineered from bacterial phytochromes binding biliverdin IXα (BV), such as the iRFP series, have beco...

Dynamics of metal catalysts under reactive conditions studied by ESEM

Cao, Jing (2019)

Solid surfaces are extremely important in heterogeneous catalysis. They represent the boundary between lid catalyst and surrounding gaseous or liquid environment, and heavily influence chemisorption, surface diffusion, reaction and desorption processes involved in the catalytic cycle. All of these key steps critically depend on the surface composition, structure and morphology. In many cases, c...

In situ studies of Pt nanoparticles on different supports for corrosion stable PEM fuel cell cathodes

Schmies, Henrike (2019)

Wasserstoffbrennstoffzellen bieten als elektrochemische Energiewandler die Möglichkeit, Wasserstoff aus erneuerbaren Resourcen als saubere und emissionsarme Energiequelle für elektrische Verbraucher, wie Elektromotoren, zu nutzen. Um eine konkurrenzfähige Alternative zu heutigen Verbrennungsmotoren in der Automobilindustrie darstellen zu können, müssen aber noch verschiedenste Hindernisse überw...

Out-of-equilibrium dynamics of open quantum many-body systems

Droenner, Leon Janek (2019)

Many-body localization, which prevents a many-body quantum systems from reaching thermal equilibrium has opened the possibility to study out-of-equilibrium dynamics of isolated quantum systems, leading to new phases of matter such as the discrete time crystal. However, little is known about these effects when the quantum many-body system is coupled to an external environment. An intuitive assum...

A new inductive-annealing dual electrochemical cell for crystal alloy and thin-film electrode voltammetry

Özer, Ebru (2019)

Proton exchange membrane (PEM) electrolyzers are considered as the most promising candidates for the supply of high purity hydrogen through water electrolysis. As a non polluting technology these electrolyzers enable to store surplus electricity of intermittent renewable power sources. In the highly acidic corrosive media of PEM electrolyzers, noble metal materials and their oxides represent th...

Development and investigation of photoswitchable DTE(OMe)-fluorophore conjugates

Ziebart, Nandor (2019)

Photoswitchable modulation of fluorescence became a field of high interest for different applications, as optical devices. The detailed nature of energy and electron transfer in conjugates on semiconductor surfaces could lead to a better understanding and future applications in sensors or optoelectronics. Former work group projects showed efficient on off energy transfer in photoswitchable DTE...

Stability analysis in the inverse Robin transmission problem

Meftahi, Houcine (2016)

In this paper, we consider the conductivity problem with piecewise‐constant conductivity and Robin‐type boundary condition on the interface of discontinuity. When the quantity of interest is the jump of the conductivity, we perform a local stability estimate for a parameterized non‐monotone family of domains. We give also a quantitative stability result of local optimal solution with respect to...

Spectral properties of the random conductance model

Flegel, Franziska (2019)

Charge and exciton transport in disordered media plays an essential role in modern technologies. Classical examples are amorphous and organic semiconductors where the disorder can give rise to localized electron states. These localized electrons effectively behave like discrete particles hopping between discrete sites in an inhomogeneous environment. A popular model for such a hopping process ...

A stable, polynomial-time algorithm for the eigenpair problem

Armentano, Diego ; Beltrán, Carlos ; Bürgisser, Peter ; Cucker, Felipe ; Shub, Michael (2018)

We describe algorithms for computing eigenpairs (eigenvalue-eigenvector pairs) of a complex n×n matrix A. These algorithms are numerically stable, strongly accurate, and theoretically efficient (i.e., polynomial-time). We do not believe they outperform in practice the algorithms currently used for this computational problem. The merit of our paper is to give a positive answer to a long-standing...

The Loewner equation and Lipschitz graphs

Rohde, Steffen ; Tran, Huy ; Zinsmeister, Michel (2018)

The proofs of continuity of Loewner traces in the stochastic and in the deterministic settings employ different techniques. In the former setting of the Schramm–Loewner evolution SLE, Hölder continuity of the conformal maps is shown by estimating the derivatives, whereas the latter setting uses the theory of quasiconformal maps. In this note, we adopt the former method to the deterministic sett...

The hyperbolic geometry of Markov’s theorem on Diophantine approximation and quadratic forms

Springborn, Boris (2017)

Markov’s theorem classifies the worst irrational numbers with respect to rational approximation and the indefinite binary quadratic forms whose values for integer arguments stay farthest away from zero. The main purpose of this paper is to present a new proof of Markov’s theorem using hyperbolic geometry. The main ingredients are a dictionary to translate between hyperbolic geometry and algebra...

Moments of quantum Lévy areas using sticky shuffle Hopf algebras

Hudson, Robin ; Schauz, Uwe ; Wu, Yue (2018)

We study a family of quantum analogs of Lévy's stochastic area for planar Brownian motion depending on a variance parameter σ ≥ 1 which deform to the classical Lévy area as σ → ∞. They are defined as second rank iterated stochastic integrals against the components of planar Brownian motion, which are one-dimensional Brownian motions satisfying Heisenberg-type commutation relations. Such iterate...

A coupling approach to Doob’s theorem

Kulik, Alexei ; Scheutzow, Michael (2015)

We provide a coupling proof of Doob’s theorem which says that the transition probabilities of a regular Markov process which has an invariant probability measure μ converge to μ in the total variation distance. In addition we show that non-singularity (rather than equivalence) of the transition probabilities suffices to ensure convergence of the transition probabilities for μ-almost all initial...

Überprüfung der katalytischen Aktivität von keramischen Wabenkörpern an einem Modellgas und einem thermisch regenerativen Nachverbrennungsprozess

Knoll, Manuela (2019)

Durch Untersuchungen zum Abbauverhalten des Modellgases Propan an keramischen Wabenkörpern, die als katalytisch inaktiv vermarktet werden, konnten Aktivitätsunterschiede in einer Modell-Anlage festgestellt werden. Dabei wurden aus den 27 untersuchten Wabenkörpern die vier aktivsten ermittelt. Die Bewertung der Wabenkörper erfolgt unter anderem aus dem Vergleich der Umsatzgradkurven von Propan ü...

Planar graphs and face areas: Area-Universality

Kleist, Linda (2018)

In this work, we study planar graphs with prescribed face areas. This field is inspired by cartograms. A 'cartogram' is a distorted map where the size of the regions are proportional to some statistical parameter such as the population, the total birth, the gross national product, or some other special property. As a mathematical abstraction we are interested in straight-line drawings of plane...

A bilevel shape optimization problem for the exterior Bernoulli free boundary value problem

Kasumba, Henry ; Kunisch, Karl ; Laurain, Antoine (2014)

A bilevel shape optimization problem with the exterior Bernoulli free boundary problem as lowerlevel problem and the control of the free boundary as the upper-level problem is considered. Using the shape of the inner boundary as the control, we aim at reaching a specific shape for the free boundary. A rigorous sensitivity analysis of the bilevel shape optimization in the infinite-dimensional se...

Anisotropic surface energy formulations and their effect on stability of a growing thin film

Korzec, Maciek D. ; Münch, Andreas ; Wagner, Barbara (2012)

In this paper we revisit models for the description of the evolution of crystalline films with anisotropic surface energies.We prove equivalences of symmetry properties of anisotropic surface energy models commonly used in the literature. Then we systematically develop a framework for the derivation of surface diffusion models for the self-assembly of quantum dots during Stranski-Krastanov grow...

Pinning of interfaces in random media

Dirr, Nicolas ; Dondl, Patrick W. ; Scheutzow, Michael (2011)

For a model for the propagation of a curvature sensitive interface in a time independent random medium, as well as for a linearized version which is commonly referred to as Quenched Edwards– Wilkinson equation, we prove existence of a stationary positive supersolution at non-vanishing applied load. This leads to the emergence of a hysteresis that does not vanish for slow loading, even though th...

Application of a Rapid and Integrated Analysis System (RIAS) as a High-Throughput Processing Tool for In Vitro ADME Samples by Liquid Chromatography/Tandem Mass Spectrometry

Luippold, Andreas H. ; Arnhold, Thomas ; Jörg, Wolfgang ; Krüger, Beate ; Süßmuth, Roderich D. (2011)

Over the past decade, drug discovery programs have started to address the optimization of key ADME properties already at an early stage of the process. Hence, analytical chemists have been confronted with tremendously rising sample numbers and have had to develop methodologies accelerating quantitative liquid chromatography/tandem mass spectrometry (LC/MS/MS). This article focuses on the applic...

Analysis and Numerical Approximation of an Integro-differential Equation Modeling Non-local Effects in Linear Elasticity

Emmrich, Etienne ; Weckner, Olaf (2007)

Long-range interactions for linearly elastic media resulting in nonlinear dispersion relations are modeled by an initial-value problem for an integro-differential equation (IDE) that incorporates non-local effects. Interpreting this IDE as an evolutionary equation of second order, well-posedness in L ∞(ℝ) as well as jump relations are proved. Moreover, the construction of the micromodulus funct...