Scattering Dynamics of Driven Closed Billiards

We investigate the classical scattering dynamics of the driven elliptical billiard. Two fundamental scattering mechanisms are identified and employed to understand the rich behavior of the escape rate. A long-time algebraic decay which can be tuned by varying the driving amplitude is established. Pulsed escape rates and decelerated escaping particles are generic properties of the harmonically breathing billiard. This suggests time-dependent billiards as prototype systems to study the nonequilibrium evolution of classical ensembles encountering a multitude of scattering processes off driven targets.Comment: 12 pages, 4 figure

Patterned Deposition of Particles in Spatio-temporally Driven Lattices

We present and analyze mechanisms for the patterned deposition of particles in a spatio-temporally driven lattice. The working principle is based on the breaking of the spatio-temporal translation symmetry, which is responsible for the equivalence of all lattice sites, by applying modulated phase shifts to the lattice sites. The patterned trapping of the particles occurs in confined chaotic seas, created via the ramping of the height of the lattice potential. Complex density profiles on the length scale of the complete lattice can be obtained by a quasi-continuous, spatial deformation of the chaotic sea in a frequency modulated lattice.Comment: 5 pages, 4 figure

Dynamical trapping and chaotic scattering of the harmonically driven barrier

A detailed analysis of the classical nonlinear dynamics of a single driven square potential barrier with harmonically oscillating position is performed. The system exhibits dynamical trapping which is associated with the existence of a stable island in phase space. Due to the unstable periodic orbits of the KAM-structure, the driven barrier is a chaotic scatterer and shows stickiness of scattering trajectories in the vicinity of the stable island. The transmission function of a suitably prepared ensemble yields results which are very similar to tunneling resonances in the quantum mechanical regime. However, the origin of these resonances is different in the classical regime.Comment: 14 page

In vitro-Untersuchungen zum Einfluss des SGLT2-Inhibitors Empagliflozin auf LPS-aktivierte Mikroglia vor dem Hintergrund des Morbus Parkinson

Für Mikroglia wurde im Zusammenhang mit dem M. Parkinson eine dauerhafte proinflammatorische Aktivierung nachgewiesen, die sich in der stark erhöhten Expression und Freisetzung proinflammatorischer Mediatoren wie u. a. IL-6, TNF-α, IL-1β und NO darstellt. Die daraus resultierende Neurotoxizität wird für die weitere Progression der Erkrankung mitverantwortlich gemacht. Als mögliche Therapiestrategie gilt daher, den proinflammatorischen Mikroglia-Phänotyp in Richtung eines neuroregenerativen Phänotyps zu modifizieren, welcher sich durch vermehrte Produktion und Freisetzung antiinflammatorischer Moleküle, wie z.B. IL-10, und Wachstumsfaktoren auszeichnet. Im Rahmen dieser Arbeit wurde in vitro untersucht, ob der SGLT2-Inhibitor Empagliflozin die Mikroglia auf diese Weise beeinflussen kann. Die Mikroglia wurden dabei durch eine Behandlung mit LPS in einen ähnlichen Aktivitätszustand wie beim M. Parkinson versetzt. Empagliflozin konnte die durch LPS erhöhte Expression und Freisetzung aller untersuchten Mediatoren signifikant reduzieren, ebenso wurde die Freisetzung des entzündungshemmenden IL-10 signifikant gemindert. Weiterhin wurden Signalwege der Neuroinflammation (in dieser Arbeit untersucht: ERK- und NFκB-Kaskade) in ihrer Aktivität herabreguliert. Viele der in dieser Arbeit gezeigten Effekte waren allerdings erst bei der Kombination hoher Empagliflozin-Konzentrationen und langer Stimulationsdauer sichtbar. Insgesamt konnte Empaglilozin die LPS-induzierte mikrogliale Inflammation signifikant vermindern, insbesondere bei hohen Empagliflozin-Konzentrationen. Allerdings deutet die ebenfalls reduzierte IL-10-Freisetzung nicht darauf hin, dass Empagliflozin eine Phänotypen-Modulation hin zu einem neuroprotektiven Mikroglia-Phänotyp vornehmen konnte

Classical and quantum dynamics of driven elliptical billiards

Subject of this thesis is the investigation of the classical dynamics of the driven elliptical billiard and the development of a numerical method allowing the propagation of arbitrary initial states in the quantum version of the system. In the classical case, we demonstrate that there is Fermi acceleration in the driven billiard. The corresponding transport process in momentum space shows a surprising crossover from sub- to normal diffusion. This crossover is not parameter induced, but rather occurs dynamically in the evolution of the ensemble. The four-dimensional phase space is analyzed in depth, especially how its composition changes in different velocity regimes. We will show that the stickiness properties, which eventually determine the diffusion, are intimately connected with this change of the composition of the phase space with respect to velocity. In the course of the evolution, the accelerating ensemble thus explores regions of varying stickiness, leading to the mentioned crossover in the diffusion. In the quantum case, a series of transformations tailored to the elliptical billiard is applied to circumvent the time-dependent Dirichlet boundary conditions. By means of an expansion ansatz, this eventually yields a large system of coupled ordinary differential equations, which can be solved by standard techniques

Directed transport and localization in phase-modulated driven lattices

We explore the dynamics of non-interacting particles loaded into a phase-modulated one-dimensional lattice formed by laterally oscillating square barriers. Tuning the parameters of the driven unit cell of the lattice selected parts of the classical phase space can be manipulated in a controllable manner. We find superdiffusion in position space for all parameters regimes. A directed current of an ensemble of particles can be created through locally breaking the spatiotemporal symmetries of the time-driven potential. Magnitude and direction of the current are tunable. Several mechanisms for transient localization and trapping of particles in different wells of the driven unit cell are presented and analyzed

A SAM analogue-utilizing ribozyme for site-specific RNA alkylation in living cells

Post-transcriptional RNA modification methods are in high demand for site-specific RNA labelling and analysis of RNA functions. In vitro-selected ribozymes are attractive tools for RNA research and have the potential to overcome some of the limitations of chemoenzymatic approaches with repurposed methyltransferases. Here we report an alkyltransferase ribozyme that uses a synthetic, stabilized S-adenosylmethionine (SAM) analogue and catalyses the transfer of a propargyl group to a specific adenosine in the target RNA. Almost quantitative conversion was achieved within 1 h under a wide range of reaction conditions in vitro, including physiological magnesium ion concentrations. A genetically encoded version of the SAM analogue-utilizing ribozyme (SAMURI) was expressed in HEK293T cells, and intracellular propargylation of the target adenosine was confirmed by specific fluorescent labelling. SAMURI is a general tool for the site-specific installation of the smallest tag for azide-alkyne click chemistry, which can be further functionalized with fluorophores, affinity tags or other functional probes

Anti-Inflammatory Properties of the SGLT2 Inhibitor Empagliflozin in Activated Primary Microglia

Sodium-glucose cotransporter 2 (SGLT2) inhibitors, including empagliflozin, are routinely used as antidiabetic drugs. Recent studies indicate that beside its beneficial effects on blood glucose level, empagliflozin may also exert vascular anti-inflammatory and neuroprotective properties. In the brain, microglia are crucial mediators of inflammation, and neuroinflammation plays a key role in neurodegenerative disorders. Dampening microglia-mediated inflammation may slow down disease progression. In this context, we investigated the immunomodulatory effect of empagliflozin on activated primary microglia. As a validated experimental model, rat primary microglial cells were activated into a pro-inflammatory state by stimulation with LPS. The influence of empagliflozin on the expression of pro-inflammatory mediators (NO, Nos2, IL6, TNF, IL1B) and on the anti-inflammatory mediator IL10 was assessed using quantitative PCR and ELISA. Further, we investigated changes in the activation of the ERK1/2 cascade by Western blot and NFkB translocation by immunostaining. We observed that empagliflozin reduces the expression of pro- and anti-inflammatory mediators in LPS-activated primary microglia. These effects might be mediated by NHE-1, rather than by SGLT2, and by the further inhibition of the ERK1/2 and NFkB pathways. Our results support putative anti-inflammatory effects of empagliflozin on microglia and suggest that SGLT2 inhibitors may exert beneficial effects in neurodegenerative disorders