Advanced schemes for surface plasmon resonance and plasmon-enhanced fluorescence biosensors

Advanced optical biosensor platforms exploiting long range surface plasmons (LRSPs) and responsive N-isopropylacrylamide (NIPAAm) hydrogel binding matrix for the detection of protein and bacterial pathogen analytes were carried out. LRSPs are optical waves that originate from coupling of surface plasmons on the opposite sites of a thin metallic film embedded between two dielectrics with similar refractive indices. LRSPs exhibit orders of magnitude lower damping and more extended profile of field compared to regular surface plasmons (SPs). Their excitation is accompanied with narrow resonance and provides stronger enhancement of electromagnetic field intensity that can advance the sensitivity of surface plasmon resonance (SPR) and surface plasmon-enhanced fluorescence spectroscopy (SPFS) biosensors. Firstly, we investigated thin gold layers deposited on fluoropolymer surface for the excitation of LRSPs. The study indicates that the morphological, optical and electrical properties of gold film can be changed by the surface energy of fluoropolymer and affect the performance of a SPFS biosensor. A photo-crosslinkable NIPAAm hydrogel was grafted to the sensor surface in order to serve as a binding matrix. It was modified with bio-recognition elements (BREs) via amine coupling chemistry and offered the advantage of large binding capacity, stimuli responsive properties and good biocompatibility. Through experimental observations supported by numerical simulations describing diffusion mass transfer and affinity binding of target molecules in the hydrogel, the hydrogel binding matrix thickness, concentration of BREs and the profile of the probing evanescent field was optimized. Hydrogel with a up to micrometer thickness was shown to support additional hydrogel optical waveguide (HOW) mode which was employed for probing affinity binding events in the gel by means of refractometric and fluorescence measurements. These schemes allow to reach limits of detection (LODs) at picomolar and femtomolar levels, respectively. Besides hydrogel based experiments for detection of molecular analytes, long range surface plasmon-enhanced fluorescence spectroscopy (LRSP-FS) was employed for detection of bacterial pathogens. The influence of capture efficiency of bacteria on surfaces and the profile of the probing field on sensor response were investigated. The potential of LRSP-FS with extended evanescent field is demonstrated for detection of pathogenic E. coli O157:H7 on sandwich immunoassays . LOD as low as 6 cfu mL-1 with a detection time of 40 minutes was achieved.rn

Quantum Einstein gravity - advancements of heat kernel-based renormalization group studies

The asymptotic safety scenario allows to define a consistent theory of quantized gravity within the framework of quantum field theory. The central conjecture of this scenario is the existence of a non-Gaussian fixed point of the theory's renormalization group flow, that allows to formulate renormalization conditions that render the theory fully predictive. Investigations of this possibility use an exact functional renormalization group equation as a primary non-perturbative tool. This equation implements Wilsonian renormalization group transformations, and is demonstrated to represent a reformulation of the functional integral approach to quantum field theory.rnAs its main result, this thesis develops an algebraic algorithm which allows to systematically construct the renormalization group flow of gauge theories as well as gravity in arbitrary expansion schemes. In particular, it uses off-diagonal heat kernel techniques to efficiently handle the non-minimal differential operators which appear due to gauge symmetries. The central virtue of the algorithm is that no additional simplifications need to be employed, opening the possibility for more systematic investigations of the emergence of non-perturbative phenomena. As a by-product several novel results on the heat kernel expansion of the Laplace operator acting on general gauge bundles are obtained.rnThe constructed algorithm is used to re-derive the renormalization group flow of gravity in the Einstein-Hilbert truncation, showing the manifest background independence of the results. The well-studied Einstein-Hilbert case is further advanced by taking the effect of a running ghost field renormalization on the gravitational coupling constants into account. A detailed numerical analysis reveals a further stabilization of the found non-Gaussian fixed point.rnFinally, the proposed algorithm is applied to the case of higher derivative gravity including all curvature squared interactions. This establishes an improvement of existing computations, taking the independent running of the Euler topological term into account. Known perturbative results are reproduced in this case from the renormalization group equation, identifying however a unique non-Gaussian fixed point.rn

LoneStar : Design and evaluation of an energy-efficient, disk-based archival storage system

Bandlaufwerke waren bisher die vorherrschende Technologie, um die anfallenden Datenmengen in Archivsystemen zu speichern. Mit Zugriffsmustern, die immer aktiver werden, und Speichermedien wie Festplatten die kostenmäßig aufholen, muss die Architektur vor Speichersystemen zur Archivierung neu überdacht werden. Zuverlässigkeit, Integrität und Haltbarkeit sind die Haupteigenschaften der digitalen Archivierung. Allerdings nimmt auch die Zugriffsgeschwindigkeit einen erhöhten Stellenwert ein, wenn aktive Archive ihre gesamten Inhalte für den direkten Zugriff bereitstellen. Ein band-basiertes System kann die hierfür benötigte Parallelität, Latenz und Durchsatz nicht liefern, was in der Regel durch festplattenbasierte Systeme als Zwischenspeicher kompensiert wird.rnIn dieser Arbeit untersuchen wir die Herausforderungen und Möglichkeiten ein festplattenbasiertes Speichersystem zu entwickeln, das auf eine hohe Zuverlässigkeit und Energieeffizienz zielt und das sich sowohl für aktive als auch für kalte Archivumgebungen eignet. Zuerst analysieren wir die Speichersysteme und Zugriffsmuster eines großen digitalen Archivs und präsentieren damit ein mögliches Einsatzgebiet für unsere Architektur. Daraufhin stellen wir Mechanismen vor um die Zuverlässigkeit einer einzelnen Festplatte zu verbessern und präsentieren sowie evaluieren einen neuen, energieeffizienten, zwei- dimensionalen RAID Ansatz der für „Schreibe ein Mal, lese mehrfach“ Zugriffe optimiert ist. Letztlich stellen wir Protokollierungs- und Zwischenspeichermechanismen vor, die die zugrundeliegenden Ziele unterstützen und evaluieren das RAID System in einer Dateisystemumgebung.