Thesis (Master of Science)--Miami University, Dept. of Physics, 2005. / Title from first page of PDF document. Document formatted into pages; contains [1], ???, ??? p. : ill. Includes bibliographical references (p. Xx-Xx).

No description available.

Thesis (Ph. D.)--University of Texas at Austin, 2004. / Supervisors: Konstantin Sokolov and Mark Raizen. Vita. Includes bibliographical references. Also available from UMI.

Thesis (M.S.)--Florida State University, 2003. / Advisor: Dr. Timothy A. Cross, Florida State University, College of Arts and Sciences, Dept. of Chemistry and Biochemistry. Title and description from dissertation home page (viewed Mar. 4, 2004). Includes bibliographical references.

Thesis (M.Ch.E.)--University of Delaware, 2009. / Principal faculty advisor: Jochen A. Lauterbach, Dept. of Chemical Engineering. Includes bibliographical references.

A unique Raman spectroscopic investigation combining a number of different techniques has been conducted in situ on the composition of the passive film on iron, both during its growth in 0.05 M NaOH by potentiodynamic polarization and during localized breakdown by pitting after addition of 0.05 M NaCl. There are differing theories for the mechanism of pit initiation and formation in the passive film on iron, and while these are in part due to different environmental factors, they are also influenced by differing theories for the nature of the passive film. The detailed information obtained in this study corroborate the two layer model for the passive film on iron, with γ-Fe2O3 forming the inner layer and the outer layer consisting of δ-FeOOH, α-FeOOH, γ-FeOOH, other components such as Fe(OH)2 and other intermediates. In the passive region of anodic polarization the film became increasingly hydrated with increasing anodic potential and with increased cycles became amorphous, comparing well with the Hydrated Polymeric Oxide model. Pre-resonance enhancement of the Raman bands of iron oxides and particularly iron oxy-hydroxides was afforded by excitation at 636.4 nm, and particularly at low wavenumbers. The use of Multivariate Curve Resolution with Alternating Least Squares (MCR-ALS) enabled determination of the relative amounts of the iron oxide and oxy-hydroxide components from the complex spectra recorded during potentiodynamic polarization. The amount of water incorporated in the passive film under the same conditions was also monitored in situ at similar potentials using excitation at 514.5 nm. Addition of chloride ions resulted in an increase in hydration and a change of the composition of the passive film to comprise mainly β-FeOOH and Green complex with some γ-Fe2O3 and γ-FeOOH. At the pitting potential significant changes in the composition occurred along with reduction in hydration, so that re-passivation could no longer be maintained at the same rate as dissolution by the chloride ions, enabling stable pitting. These observations indicate that water plays a protective role in the passive film and reinforce the mechanisms for pit initiation based on the De-passivation–Re-passivation theory and Chemical Dissolution theory.

Not available / text

Thesis (M.S.)--Miami University, Dept. of Physics, 2008. / Title from first page of PDF document. Includes bibliographical references (p. 36-37).

No description available.

Ultraschnelle Energietransferprozesse zwischen den Anregungszuständen organischer Pigmentmoleküle in photosynthetischen Lichtsammelkomplexen gehören zu den schnellsten bisher untersuchten biologischen Ereignissen. Diese Vorgänge wurden insbesondere auch für den Haupt-Antennenkomplex der höheren Pflanzen (LHCII) beobachtet, der mehr als die Hälfte des pflanzlichen Chlorophylls (Chl) bindet (5 Chl b und 7 Chl a pro Monomer). Offenbar ist dieser Pigment-Protein-Komplex entscheidend für Regulationsmechanismen verantwortlich, die eine schnelle Adaptation des Photosyntheseapparats an wechselnde Licht- bedingungen ermöglichen. Die Struktur von LHCII ist mit einer Auflösung von 3.4 Å bekannt und erlaubt (im Prinzip) die Berechnung des Anregungsenergietransfers auf Basis eines Förster-Mechanismus. In diesem Zusammenhang gibt es jedoch noch zahlreiche ungeklärte Fragen, die vor allem die Orientierung der Pigmente zueinander sowie deren mögliche starke (exzitonische) Wechselwirkung betreffen. Allerdings sind konventionelle spektroskopische Methoden nicht geeignet, diese Merkmale ausreichend aufzuklären. Aus diesem Grund wird in dieser Arbeit untersucht, inwieweit neuere laserspektroskopische Methoden wie die nichtlineare Polarisationsspektroskopie in der Frequenzdomäne (NLPF) zur Ermittlung unbekannter Parameter beitragen können. Anfänglich ergaben sich besonders Fragen der Anwendbarkeit der NLPF auf solche hoch- komplexen Untersuchungsobjekte sowie der Signifikanz eventuell erzielbarer Ergebnisse. Aufbauend auf einer parallel verfaßten Dissertation zu theoretischen Aspekten der NLPF- Methode [1] wurde daher ein vereinfachtes System modelliert, das die Heterogenität der individuellen Chl(e) im LHCII widerspiegelt. Die gewonnenen Resultate ließen vermuten, daß die reine Simulation von NLPF-Spektren nicht ausreicht, um eindeutige Aussagen über die Molekülparameter zu gewinnen. Um den benötigten zusätzlichen Erkenntnisgewinn zu erreichen, wurden daher Paralleluntersuchungen mit anderen laserspektroskopischen Methoden (nichtlineare Absorption mit fs-Pulsen, intensitätsabhängige NLPF, Einzelmolekülspektroskopie, Tieftemperatur-NLPF) sowie mit in vitro rekonstituierten Protein-Mutanten durchgeführt. Als Ergebnis konnte die Subbstruktur der Qy- Absorptionsbande der ersten angeregten Zustände der Chl(e) für LHCII ausreichend beschrieben werden. Darüber hinaus ergaben sich Aussagen zu exzitonischen Wechselwirkungen zwischen bestimmten Chl(en), die unter anderem Einfluß auf das Energie- transferverhalten haben. Diese zusätzlichen Untersuchungen erlaubten letztendlich eine Modellierung der bei Raum- temperatur an LHCII gemessenen NLPF-Spektren. Neben dem dabei implizit gewonnenen Verständnis der nichtlinearen optischen Eigenschaften im Bereich der Qy-Absorption ließen sich so Aussagen über bestimmte Modellparameter, besonders über die Orientierung von Übergangsdipolmomenten, ableiten. Abschließend wurde die Auswirkung der Erkenntnisse auf das Verständnis der Struktur-Funktionsbeziehungen für intra- und inter-komplexen Energietransfer erläutert. / Ultra-fast excitation energy transfer (EET) between excited states of organic pigment molecules in photosynthetic antenna complexes belongs to the fastest observed biological processes. Such EET phenomena has been studied to a large extent for the main light- harvesting complex of the higher plants (LHCII), which appears to play an exceptional role for the regulatory function (i.e. light adaptation) of the plant photosynthetic apparatus. The structure of this pigment-protein complex harboring more than 50 % of the total chlorophyll (Chl) content is known with 3.4 Å resolution and reveals the binding sites of 5 Chl b and 7 Chl a per monomeric unit. Based on this structure analysis, EET calculations are (in principle) available on the molecular level under the assumption of Förster-type transfer. However, several molecular features like mutual pigment orientations and electronic interactions between their transition dipoles are still rather uncertain. Since conventional spectroscopic techniques can hardly reveal the corresponding parameters, this work was aimed at the evaluation of newly introduced laser spectroscopic techniques with respect to these questions. In the beginning, suitability and significance of the method when applied to highly complicated structures like pigment-protein complexes were studied by modeling heterogeneous, LHCII-like absorption systems in NLPF experiments. Based on recent improvements in the NLPF theory by a parallel theoretical investigation [1], these simulations clarified the sensitivity of the NLPF method on numerous physical parameters. As a major consequence, unambiguous evaluations of NLPF measurements appear to require substantial additional information about the investigated system. Accordingly, several supplementary methods like nonlinear absorption (using fs-pulses), intensity-dependent NLPF, single- molecule spectroscopy, and NLPF at low temperatures were employed. These investigations revealed unique information about excitonic interaction between certain Chl(s), including implications for the overall EET scheme. The sub-structure model for the Qy-absorption region of LHCII was further essentially improved by the analysis of reconstituted proteins with selectively modified Chl binding residues in the amino-acid sequence. The sum of all complementary investigations allowed finally the evaluation of room temperature NLPF measurements of trimeric LHCII. Due to the unique selectivity of the spectra to individual transition-dipole directions, several orientation parameters have been obtained. Under this point of view, the NLPF method has indeed revealed a high potential as compared to conventional techniques like circular dichroism spectroscopy. Moreover, the understanding of nonlinear phenomena in the Qy-absorption region of LHCII as a consequence of molecular interaction provides further knowledge for the application of other nonlinear optical experiments. Concluding, implications of the obtained results for the structure-function relationship of intra- and inter-complex EET were elucidated.