Nonlinear pulses at the interface and its relation to state and temperature See

Environmental temperature has a well-conserved effect on the pulse velocity and excitability of excitable biological systems. The consistency suggests that the cause originates from a fundamental principle. A physical (hydrodynamic) approach has proposed that the thermodynamic state of the hydrated interface (e.g., plasma membrane) determines the pulse behavior. This implies that the temperature effect happens because the environmental temperature affects the state of the interface in any giv...

A selection framework for LHCb’s upgrade trigger See

Das LHCb Experiment am Large Hadron Collier am CERN wird momentan für die nächste Datennahme verändert und modernisiert. Die instantane Luminosität wird um einen Faktor fünf erhöht, damit mehr Daten in kürzerer Zeit aufgenommen werden können. Die erste Stufe der Datennahme, der Hardwaretrigger, wird entfernt. LHCb muss nun eine Kollisionsrate von 30MHz in Echtzeit verarbeiten. In dieser Arbeit werden drei Projekte vorgestellt,die signifikant zu der Entwicklung eines schnellen und effizienten...

Bad moon rising? See

This dissertation presents a study on the influence of the night sky background (NSB) on the performance of the First G-APD Cherenkov Telescope (FACT), which is the first imaging atmospheric Cherenkov telescope (IACT) with a silicon photomultiplier (SiPM) camera. The up till now state-of-the-art, photomultiplier tubes (PMTs), can be easily and severely damaged by bright moonlight. SiPMs are an alternative robust photon detector for IACTs allowing for maximization of observation time by extend...

Stark korrelierte Quantenstörstellensysteme: der Übergang von einer einzelnen Störstelle zu einem periodischen Gitter See

In dieser Arbeit werden verschiedene Quantenstörstellensysteme mithilfe der numerischen Renormierungsgruppe (NRG) behandelt. Die betrachteten Modelle unterscheiden sich dabei vor allem durch die Anzahl der berücksichtigten Störstellen. Eine Kombination der NRG und der Dichtefunktionaltheorie (DFT) wird dazu verwendet, die Spektralfunktionen eines Metall-Molekül-Komplexes, bestehend aus einem Naphthalin-tetracarbonsäure-dianhydrid (NTCDA) Molekül auf einer Silber Ag(111)-Oberfläche, zu bere...

Investigations of planar n+-in-n ATLAS silicon sensors with modified pixel implantations See

In hoch energetischen Physikexperimenten werden kontinuierlich verbesserte Sensoren und Module benötigt, um neuen Anforderungen gerecht zu werden. Die REINER-Pixelmodule weisen verschiedene Pixelvariationen auf, um die Sensoreigenschaften, vor allem nach Bestrahlung, zu untersuchen. In dieser Arbeit werden die Labor- und Teststrahlergebnisse von mehreren REINER- Pixelmodulen präsentiert. Insgesamt wurden dazu neun Module mit Protonen und Neutronen in Bestrahlungseinrichtungen bestrahlt, um d...

Strong magnon-phonon coupling in a ferromagnetic nanograting See

The aim of this work is the development of a method to operate elementary spin excitations (magnons) in a ferromagnetic metal by means of elementary vibrational excitations of the lattice (phonons). The utilized magnon-phonon coupling was confirmed more than 50 years ago, but only recently the experimental approaches of ultrafast acoustics have made available the excitation and time-resolved detection of coherent phonons in the sub-THz frequency range. The most intriguing regime of the magnon...

First evidence of standard model pp → tttt production and performance studies of the ATLAS tile calorimeter for HL-LHC See

In diesem Dokument werden zwei Analysen auf dem Gebiet der Teilchenphysik vorgestellt. Erstens, Studien über die Performanz der Rekonstruktion von Myonen unter Verwendung von Kalorimeterinformationen während der HL-LHC Phase des ATLAS Detektors. Zweitens, die Suche nach der simultanen Produktion von vier Top-Quarks, wie vom Standard Modell (SM) prognostiziert, unter Verwendung des vollständigen Run-II-Datensatzes, der von ATLAS aufgenommen wurde. Dieser Datensatz entspricht einer integrierten...

Influence of viral fusion peptides, cellular solutes and cholesterol on the structure of lipid membranes See

Lipid membranes are crucial components of living cells. They constitute the outer shell and separate intracellular compartments and organelles. To regulate the mass transfer between the separated regions, they undergo remodeling processes like fusion and budding. In the framework of this thesis, it was examined how viral fusion peptides, cellular solutes and cholesterol modulate the behavior of lipid structures. In a small angle X-ray scattering study on monoolein mesophases, it was explored ...

Spin dynamics in indirect band-gap quantum wells and quantum dots See

In this thesis, semiconductor quantum wells (QWs) and quantum dots (QDs) with an indirect band gap in momentum space are investigated with regard to their fine structure and the related spin dynamics. Indirect nanostructures are being developed because of their very long recombination times, which make them interesting for spintronic applications. Here, the focus is on a fascinating but barley studied, quantum mechanical property: The absence of exchange interaction, which, despite the spatia...

Dark matter models: the neutrino and flavor portals See

In this thesis, we analyze several standard model extensions involving one or multiple dark matter candidates and link the dark matter problem to different other standard model shortcomings such as neutrino mass generation and flavor anomalies. First we discuss the leptonic flavor structure of an extra dimensional seesaw mechanism, which does not include a dark matter candidate. However, the mechanism suppresses couplings to the new right-handed neutrino state. This serves as a motivation to ...

Measurement of the modulation transfer function with an edge phantom at megavoltage energies See

The quality of a medical imaging system is determined by how well it transfers diagnostically important information. In terms of spatial resolution, the performance of a system can be objectively characterized by the modulation transfer function (MTF), which describes the transfer of image structures as a function of spatial frequency. MTF measurements at MV energies have previously been conducted with a wide variety of phantoms. The partly contradictory reports raise the question whether...

Beautiful leptons - setting limits to New Physics with the LHCb experiment See

In this thesis, searches for physics effects beyond the Standard Model are performed by studying purely leptonic and lepton-flavour violating B-meson decays with the LHCb experiment. Advanced statistical tools to interpret nulltests are implemented and used in the analysis of the very rare decays discussed in this thesis. A search for lepton-flavour violating B+→K+µ±e∓ decays is performed based on the LHCb Run 1 sample as the first analysis of these transitions with LHCb data. Upper limits...

Wechselwirkung von Nichtgleichgewichtsplasmen mit kontrollierter Atmosphäre zur effizienten Ionisierung molekularer Analyten See

Die Ionisierung von Analyten ist ein wesentlicher Bestandteil der Massenspektrometrie. Die vorliegende Arbeit erforscht im Wesentlichen zwei Plasmaquellen im Hinblick auf die vorliegenden Mechanismen zur Ionisierung von Analyten für die Massenspektrometrie. Dabei handelt es sich zum einen um die dielektrisch behinderte Entladung (DBDI) und zum anderen um die flexible Mikrokapillarentladung (FµTP). Um die Mechanismen systematisch zu untersuchen wurde für beide Entladungen ein experimenteller A...

Level anti-crossings of a nitrogen-vacancy center in diamond: decoherence-free subspaces and 3D sensors of microwave magnetic fields See

Nitrogen-vacancy (NV) centers in diamond have become an important tool for quantumtechnologies. All of these applications rely on long coherence times of electron and nuclear spinsassociated with these centers. Here, we study the energy level anti-crossings of an NV center indiamond coupled to a first-shell13C nuclear spin in a small static magnetic field. These levelanti-crossings (LACs) occur for specific orientations of the static magnetic field due to the strongnon-secular components of t...

Strongly interacting Rydberg excitons in Cu2O See

Excitons are fundamental electronic excitations in a semiconductor. They are bound states consisting of an electron in the conduction band and a positively charged hole in the valence band. They have hydrogen-like properties and are therefore referred to as the hydrogen analogues in solid states. In the semiconductor Cuprous Oxide, Cu2O, highly excited states of excitons can be observed with principal quantum numbers up to n = 25. These states are called Rydberg excitons in analogy to th...

Searches for vector-like quarks with 13 TeV at the ATLAS experiment and development of a boosted-object tagger using a deep neural network See

In this thesis, two searches for the pair production of vector-like top (VLT) and vector-like bottom (VLB) quarks are presented using 36.1 fb⁻¹ and 139 fb⁻¹ of data. The data was taken at √s = 13 TeV in proton-proton collisions with the ATLAS detector, which is one of the major experiments at the Large Hadron Collider at CERN. The decay signature of this search for TT and BB production is characterized by the presence of a Z-boson, which is reconstructed from two opposite-charge same-flavor l...

Detection and identification of electrons and photons See

It is important to exploit particle detectors for the detection and identification of electrons and photons in the best possible way, as it is adressed in this thesis by discussing three different application examples of precisely measuring electrons and photons at high-energy physics and test beam experiments. Firstly, the optimization of the photon identification within the ATLAS detector at the LHC is investigated. Appropriate selection criteria are needed to efficiently discriminate pr...

Exchange-mediated magnetic blue-shift of the band-gap energy in the antiferromagnetic semiconductor MnTe See

In magnetic semiconductors the optical spectrum and, in particular, the absorption edge representing the band-gap are strongly affected by the onset of the magnetic order. This contribution to the band-gap energy has hitherto been described theoretically in terms of a Heisenberg Hamiltonian, in which a delocalized conduction carrier is coupled to the localized magnetic moments by the exchange interaction. Such models, however, do not take into account the strong correlations displayed in a wi...

In-situ analysis of the influence of gases and ions on biological interfaces See

In dieser Arbeit wurde das Adsorptionsverhalten verschiedener Substanzen aus der Gas- oder Flüssigphase an Modellmembranen untersucht. Lipidmembranen spielen in lebenden Organismen eine wesentliche Rolle. In Form von Doppelschichten organisieren sie die Abgrenzung der Zelle und der intrazellulären Kompartimente. In der Lunge reguliert eine komplexe Lipid-Protein Monolage, das sogenannte pulmonale Surfactant, den störungsfreien Gasaustausch. Heutzutage ist die menschliche Lunge vielen potenzie...