Peripheral arterial disease (PAD) affects approximately 200 million individuals worldwide. It is characterized by a reduction in blood flow to the lower extremities due to atherosclerosis. This can result in leg pain, tissue loss, and ultimately amputation. Revascularization procedures aim to restore blood flow, but up to 50% of patients require another intervention within a year. Revascularization monitoring and early detection of failure are crucial in preventing limb loss and adverse cardiovascular events. However, current evaluation methods do not directly measure perfusion and are limited in a significant segment of PAD patients, such as those with diabetes and renal insufficiency. Diffuse optical imaging (DOI) techniques are promising tools to overcome these limitations. Employing near-infrared light, they are non-invasive, non-ionizing, contrast-free, and cost-effective methods that are sensitive to hemodynamic parameters such as changes in oxy-, deoxy-, and total hemoglobin concentration, making DOI ideal for revascularization monitoring. In this dissertation, I investigate and develop DOI systems for the purpose of monitoring lower extremity revascularization procedures in PAD patients. We utilize a contact-based diffuse optical spectroscopy (DOS) system to monitor localized foot perfusion in an ongoing clinical study of 100 patients undergoing lower extremity angiography. I demonstrate the utility of DOS measurements to provide valuable insights into revascularization related hemodynamic remodeling and to predict revascularization success. Furthermore, I also develop a clinic friendly contact-free diffuse optical tomography (DOT) system that is better-suited for PAD patients with ulcers. I show that this system can provide spatial maps of perfusion within the foot. Collectively, this work establishes diffuse optical imaging as a valuable imaging modality for the evaluation of lower extremity perfusion.

Dans le cadre de ma thèse, j’ai étudié des supraconducteurs par une nouvelle  technique de spectroscopie optique. Cette technique, inspirée de détecteurs de photons utilisés en astrophysique, permet de faire des mesures de 0 à 300 GHz, avec une résolution de ~1 GHz, à une température de ~100 mK. Les supraconducteurs étudiés sont lithographiés sous la forme de résonateurs pour devenir des détecteurs de photons dont leur fréquence de résonance varie en fonction de leur densité superfluide.  Au cours de cette thèse, j’ai fabriqué et étudié des résonateurs à partir de différents matériaux supraconducteurs (en couches minces). La dimensionnalité joue un rôle essentiel dans la supraconductivité. A priori, en deux dimensions un système ne devrait pas être supraconducteur mais il existe de nombreux contre-exemples (monocouche de FeSe, interface d’oxydes,…). Dans ce contexte l’aluminium est particulièrement intéressant car le mécanisme supraconducteur est conventionnel (couplage électron-phonon) et que l’on peut faire varier son épaisseur (couches minces) et sa microstructure (aluminium granulaire) relativement facilement. La thèse se compose de deux parties.Dans une première partie je me suis intéressé à l’influence de l’épaisseur sur la supraconductivité de couches minces d’aluminium (de 15nm à 200nm). Dans la majorité des matériaux supraconducteurs, la température critique diminue avec l’épaisseur alors que dans certains matériaux, comme dans l’aluminium, elle augmente. Différentes théories existent pour expliquer ce phénomène mais il n’existe actuellement aucun consensus. Par des techniques combinées de spectroscopie à forte résolution et de résistivité, j’essaye d’apporter un éclairage nouveau à l’augmentation de la température critique dans l’aluminium lors de la diminution de l’épaisseur. J’interprète ce phénomène comme étant lié à un durcissement des phonons, ce qui ne constitue pas une explication habituellement citée.Dans une deuxième partie, on présente des supraconducteurs désordonnés, à savoir l’oxyde d’indium (InOx) et l’aluminium granulaire (GrAl). Dans ces matériaux, on a mis en évidence des excitations sous le gap supraconducteur par des mesures de spectroscopie optique. Ces excitations, dont l’origine est discutée, sont a priori inattendues dans les supraconducteurs conventionnels.Ainsi, on a mis en évidence dans des résonateurs d’oxyde d’indium la détection très sélective en énergie de photons ayant une énergie très inférieure au gap supraconducteur. On explique le mécanisme de détection en démontrant qu’il est lié à l’excitation des modes de résonance d’ordre supérieur, associée à la non linéarité de l’inductance cinétique avec le courant circulant dans le résonateur.Dans l’aluminium granulaire, on a étudié certaines excitations sous le gap supraconducteur dans deux échantillons de résistivité différente. Une antenne radio-fréquences placée devant le cryostat illumine les résonateurs. On choisit un résonateur quelconque et on sélectionne la fréquence des photons délivrés par l'antenne de telle sorte qu'elle corresponde aux différentes excitations que l'on souhaite étudier. On s'intéresse alors à l'influence de la puissance des photons incidents sur l’évolution de la résonance. On met en évidence des comportements non standards de la fréquence de résonance ainsi que du facteur de qualité, selon les excitations étudiées. / During my PhD-thesis, I studied superconductors thanks to a new optical spectroscopy measurements technique, based on photon detectors for astrophysics. This technique enables measurements ranging from 0 to 300 GHz with a resolution of ~1 GHz at a temperature of ~100 mK. The superconductors are lithographed into resonators whose resonance frequency depends on the superfluid density. During this thesis, I made and studied resonators from different superconducting materials in thin films.Dimensionality plays a fundamental role in superconductors. In principle, in two dimensions a system should not be superconducting but there are a lot of counterexamples like single layer of FeSe or oxide interfaces. In this context, aluminum is particularly interesting for mainly two reasons. First, the superconducting mechanism is conventional : it consists in an electron-phonon coupling. Then, it is pretty easy to modify its thickness (thin films) and its microstructure (granular aluminum).The manuscript is composed of two parts.In the first part, I studied the role played by the thickness on the superconductivity of aluminum thin films, ranging from 15 nm to 200 nm. In most superconductors, the critical temperature decreases with thickness, whereas in some materials like aluminum, it increases. Several theories may explain this phenomenon but there is currently no consensus. Thanks to combined techniques of high resolution optical spectroscopy and of resistivity measurements, I suggest that the origin of the critical temperature increase in aluminum thin films would be phonon hardening. This explanation is not among the popular ones.In the second part, we present disordered superconductors, namely indium oxide (InOx) and granular aluminum (GrAl). In these materials, we evidenced sub-gap optical absorptions. In principle, these absorptions are unexpected in superconductors. We show that they are caused by higher order resonance mode excitations combined with kinetic inductance non-linearity with the current circulating in the resonator.In granular aluminum, we studied some sub-gap excitations in two samples with a different room temperature resistivity. A radio-frequency antenna situated in front of the dilution refrigerator illuminates the resonators. We choose a resonator and we select the photon frequency in such a way that it matches with the different studied excitations. We observe the influence of the incident photon power on the resonance. We evidence non standard behaviors of resonance frequency and quality factor, according to the studied excitations.

This is a spectroscopic and photometric study of suspected close binary systems among the massive stars. The stars studied here include stars with temperatures ranging from 45,000 Kelvin (K) to 15,000 K, corresponding to spectral types ranging from O3 V to B5 III, masses between 47 Solar Masses and 5 Solar Masses, and absolute V magnitudes from -6.28 to -2.0. I categorize 30 targets according to my spectroscopic observations into groups with no radial velocity variability, single-lined, and double-lined variability. My analysis of the 18 constant velocity stars results in estimates of stellar effective temperature, Teff, gravity, log g, projected rotational velocity, v sin i, and spectral classification. Analyzing single-lined systems, I find the same stellar parameters for five more systems, and also present the first orbits for these systems. I also explore the probable characteristics of the unseen companions in these systems. Three double-lined systems, two eclipsing and one with an ellipsoidal variation in the light curve, are fully analyzed, and I present important astrophysical parameters for each of these systems, including stellar masses, radii, ages, and distances to each system. The masses are accurate to 4.3% and 3.6% for the primary and secondary for LH 54-425, 2.1% and 1.6% for HI Mon, and 1.1% and 0.6% for HD 42401. Two more double-lined systems are studied, and preliminary results are presented. Photometric observations are analyzed for 56 targets from the All Sky Automated Survey in order to facilitate spectroscopic observations at key points in the binary orbit where spectral features of both components will be well separated. New spectroscopic observations of these eclipsing binaries with my computed ephemerides will allow us to obtain double-lined orbital elements and determine their masses, radii, ages, and distances. These computed parameters will then allow for comparison with theoretical stellar models, and a better understanding of the evolution of massive stars.

Kyoto University (京都大学) / 0048 / 新制・課程博士 / 博士(エネルギー科学) / 甲第19096号 / エネ博第320号 / 新制||エネ||65 / 32047 / 京都大学大学院エネルギー科学研究科エネルギー応用科学専攻 / (主査)教授 松田 一成, 教授 岸本 泰明, 教授 大垣 英明 / 学位規則第4条第1項該当

Dissertation (Ph.D.)--Auburn University, 2006. / Abstract. Includes bibliographic references.

Thesis (doctoral)--Göteborg University, 2007. / Original thesis t.p. with abstract (2 p.) inserted. Includes bibliographical references.

Thesis (Ph. D.)--University of Texas at El Paso, 2009. / Title from title screen. Vita. CD-ROM. Includes bibliographical references. Also available online.

Thesis (Ph. D.)--Duke University, 2007. / Includes bibliographical references.

We present a time-dependent mixed quantum/semiclassical approach to calculating linear absorption spectra. Applying Variational Fixed Vibrational Basis/Gaussian Bath theory (FVB/GB) to the treatment of small molecules isolated in an extended cryogenic medium, an assumed time-scale separation between the few rapid, largely intramolecular modes of the guest and the several slower extended modes of the medium is utilized to partition a system from the surrounding bath. The system dynamics are handled with basis set methods, while the bath degrees of freedom are subject to a semiclasscial thawed Gaussian ansatz. The linear absorption spectrum for a realistic model system is calculated using FVB/GB results and then compared with a numerically exact calculation. Also contained in this dissertation are previously published theoretical works on Transient Absorption and Femtosecond Stimulated Raman Spectroscopy. Both encompass a rebuilding of the theory and elucidate the information content of the respective spectroscopic signals. This dissertation includes previously published co-authored material.

Understanding the properties of electronically interacting molecular chromophores, which involve internally coupled electronic-vibrational motions, is important to the spectroscopy of many biological systems. Here we apply linear absorption, circular dichroism, and two-dimensional fluorescence spectroscopy to study the local structure and excited state dynamics of excitonically coupled cyanine dimers that are rigidly positioned within the sugar-phosphate backbones of the DNA. Dimer probes were positioned within the double-stranded DNA duplex and at the single-strand/double-stranded DNA junction to examine the positional dependence of the structural variation and fluctuations. We interpret spectroscopic measurements in terms of the Holstein vibronic dimer model, from which we obtain information about the local conformation of the dimer probe locally within their respective DNA environments. We show that the exciton-coupling strength of the dimer-DNA construct can be systematically varied with temperature below the double-stranded – single-strand DNA denaturation transition. Using time-resolve 2DFS measurements we observed long lived vibronic coherences in the system. The properties of the cyanine DNA construct we determine suggest that it may be employed as a useful model system to test fundamental concepts of protein DNA interactions and the role of electronic-vibrational coherence in electronic energy migration within exciton-coupled biomolecular arrays. This dissertation contains previously published and unpublished co-authored material.