We present measurements of the evolutionary timescales of speckles around adaptive optics-corrected PSFs. We placed a SELEX SAPHIRA HgCdTe detector behind the SCExA0 instrument at Subaru Telescope. We analyzed the behavior of speckles at radial distances of 2-8 A/D away from the diffraction-limited PSF in H-band (-1.6 m) images collected at 1 kHz framerates. Speckles evolve with a variety of timescales, and these have not previously been studied at near-infrared wavelengths. Ultimately we would like to image reflected-light exoplanets, which necessitates a fast speckle control loop. Based on our measurements, we calculate the parameters of an optimized control loop that would enable such observations.

La microcirculation cutanée a été proposée comme modèle d’étude de la dysfonction microvasculaire globale dans les maladies cardiovasculaires. Par ailleurs, elle est spécifiquement atteinte dans la sclérodermie systémique (SSc), qui est une maladie dysimmunitaire rare, particulièrement invalidante, caractérisée par une fibrose cutanée et viscérale associée à une atteinte microvasculaire diffuse et la présence d’auto anticorps dirigés contre des antigènes cellulaires. L’exploration de la fonction microvasculaire cutanée suscite donc un réel intérêt, même s’il n’existe pas de technique standardisée pour l’étude de la fonction microvasculaire, en particulier endothéliale.La première partie de ce travail a porté sur l’étude physiologique de la microcirculation cutanée chez le volontaire sain, en utilisant les méthodes les plus récentes adaptées à l’étude fonctionnelle de la microcirculation (tests de réactivité vasculaire couplés à l’enregistrement du flux sanguin cutané par laser speckle contrast imaging). Dans une seconde partie, nous avons étudié la pathologie de la microcirculation cutanée dans la sclérodermie systémique, en utilisant les mêmes d’étude fonctionnelle de la microcirculation. La dernière partie de cette thèse a été consacrée à l’étude d’une nouvelle approche pharmacologique et thérapeutique dans la prise en charge des manifestations vasculaires cutanées périphériques identifiées chez les patients. Nous avons évalué l’effet vasodilatateur du tréprostinil, analogue de la prostacycline, sur le flux sanguin cutané de divers zones anatomiques, chez le volontaire sain, le patient atteint de SSc, le patient diabétique et lors d’un refroidissement local dans la SSc. / Cutaneous microcirculation has been proposed as a model to study the global microvascular dysfunction occurring in cardiovascular diseases. Furthermore, it is specifically impaired in systemic sclerosis (SSc), which is a rare and particularly invalidating auto-immune disease, characterized by a cutaneous and visceral fibrosis, associated with a diffuse microvascular impairment and auto-antibodies targeting some cellular antigens. The study of cutaneous microvascular function provides a real interest despite the lack of available standardized techniques, particularly to explore endothelial microvascular function.In the first part of this work, we aimed to study the physiology of cutaneous microcirculation in healthy volunteers, using the more recent methods in this field, adapted to functional study of microcirculation (vascular reactivity tests coupled with cutaneous blood flow recording by laser speckle contrast imaging). The second part of our work aimed to study the pathology of cutaneous microcirculation in SSc volunteers, by using the same functional exploration methods. The last part of this work has been dedicated to a new pharmacologic and therapeutic approach for the management of peripheral cutaneous vascular manifestations in patients, using innovating technics as cutaneous iontophoresis. We studied the vasodilator effect of treprostinil, a prostacycline analogue, on cutaneous blood flow in several anatomic regions in healthy subject, SSc patient and diabetic patient, and also during a local cooling in SSc.

Transmission electron microscopy (TEM) is a powerful tool for studying solidstate crystalline systems. With the advances in aberration correction, monochromation, and in situ capabilities, these microscopes are now more useful for addressing fundamental materials chemistry problems than ever before. This dissertation will illustrate the ways in which I have been using high-resolution imaging and in situ heating in the TEM during my Ph.D. research to investigate unique solid state chemistry questions. This dissertation will focus on four unique crystal systems: thermoelectric skutterudite crystals, vapor-liquid-solid (VLS) grown nanowires, and hafnium dioxide nanorods. Although these systems are very different from one another, high resolution and/or in situ heating in TEM is an integral part of each study. Through these techniques, we gain insight and knowledge of these systems that may have gone unknown through different analysis techniques. The experiments I will describe in some cases provide surprising and unexpected results that arise from the nanoscale nature of the materials and would be difficult to observe through bulk analytical methods. The work presented here helps to demonstrate the strength and versatility of TEM to address solid state chemistry questions.

Transition disks, protoplanetary disks with inner clearings, are promising objects in which to directly image forming planets. The high contrast imaging technique of non-redundant masking is well posed to detect planetary mass companions at several to tens of AU in nearby transition disks. We present non-redundant masking observations of the T Cha and LkCa 15 transition disks, both of which host posited sub-stellar mass companions. However, due to a loss of information intrinsic to the technique, observations of extended sources (e.g. scattered light from disks) can be misinterpreted as moving companions. We discuss tests to distinguish between these two scenarios, with applications to the T Cha and LkCa 15 observations. We argue that a static, forward-scattering disk can explain the T Cha data, while LkCa 15 is best explained by multiple orbiting companions.

Submitted by Luciana Ferreira (lucgeral@gmail.com) on 2016-03-03T14:19:21Z No. of bitstreams: 2 Dissertação - Jonas Francisco Scopel - 2015.pdf: 1854226 bytes, checksum: 9d48662eb3f8662b36ce1a088c29ac1c (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2016-03-03T14:22:35Z (GMT) No. of bitstreams: 2 Dissertação - Jonas Francisco Scopel - 2015.pdf: 1854226 bytes, checksum: 9d48662eb3f8662b36ce1a088c29ac1c (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Made available in DSpace on 2016-03-03T14:22:35Z (GMT). No. of bitstreams: 2 Dissertação - Jonas Francisco Scopel - 2015.pdf: 1854226 bytes, checksum: 9d48662eb3f8662b36ce1a088c29ac1c (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) Previous issue date: 2015-02-20 / Diagnostic imaging techniques play an important role in assessing the exact location, cause, and extent of a nerve lesion, thus allowing clinicians to diagnose and manage more effectively a variety of pathological conditions such as entrapment syndromes, traumatic injuries, and space-occupying lesions. Ultrasound and nuclear magnetic resonance imaging are becoming useful methods for this purpose, but they still lack spatial resolution. In this regard, recent phase contrast x-ray imaging experiments of peripheral nerve allowed the visualization of each nerve fiber surrounded by its myelin sheath as clearly as optical microscopy. In the present study, we attempted to produce high-resolution x-ray phase contrast images of a human sciatic nerve by using synchrotron radiation propagation-based imaging (PBI). The PBIs showed high contrast and high spatial resolution, allowing clear identification of each fascicle structure and surrounding connective tissue. The outstanding result is the detection of such structures by phase contrast x-ray tomography of a thick human sciatic nerve section. This may further enable the identification of diverse pathological patterns, such as Wallerian degeneration, inflammatory infiltration and amyloid deposits. To the best of our knowledge, this is the first successful phase contrast x-ray imaging experiment of a human peripheral nerve sample. Our long-term goal is to develop peripheral nerve imaging methods that could supersede biopsy procedures. / As técnicas de diagnóstico por imagem desempenham um importante papel na determinação da localização exata, causa, e extensão de lesões de nervos periféricos, permitindo que o diagnóstico e manejo sejam mais eficazes em uma série de condições patológicas, como síndromes de encarceramento, e lesões traumáticas e expansivas. A Ressonância Nuclear Magnética e a Ultrassonografia têm se mostrado úteis neste propósito, porém possuem resolução espacial relativamente baixa. Neste sentido, experimentos recentes utilizando Radiografia por Contraste de Fase permitiram observar fibras nervosas individuais recobertas por suas bainhas de mielina de forma tão detalhada quanto a microscopia óptica. No presente estudo, procuramos obter imagens de alta resolução de nervo ciático humano, utilizando método de Imagem Realçada por Refração. As imagens demonstraram alto contraste e resolução espacial, permitindo a identificação de cada fascículo nervoso e suas respectivas bainhas conjuntivas. Resultados promissores foram obtidos através de Tomografia por Contraste de Fase de um espesso fragmento de nervo ciático humano, onde tais estruturas foram igualmente identificadas. Tais resultados poderiam possibilitar a detecção de diversas alterações patológicas, como degeneração Walleriana, infiltrado inflamatório e depósitos de amiloide. Ao nosso conhecimento, este é o primeiro experimento bem sucedido de Imagem por Contraste de Fase de nervos periféricos humanos. Nosso objetivo a longo prazo é desenvolver métodos de diagnóstico por imagem que possam substituir procedimentos de biópsia.

This Thesis describes the development of an electron-impact microfocus x-ray source and its application for phase-contrast imaging. The source is based on a novel, liquid-jet target concept. Stable and continuous operation can be achieved at substantially higher electron-beam power densities than conventional solid target based systems. The maximum x-ray brightness can potentially be increased by a factor of 10-1000, which would provide significantly improved performance in applications such as imaging. In order to reach the high x-ray brightness, comparable performance from the electron gun is needed. A LaB6-cathode-based electron gun is analyzed in terms of achievable e-beam brightness and beam quality and is found capable to deliver power densities in the 10-100 MW/mm2 range using optimized electro-optics. A proof-of-principle microfocus source has been developed. Experiments show that the liquid-metal-jet target can be operated at more than an order of magnitude higher e-beam power densities than modern solid-metal targets. This brightness enhancement has been utilized to acquire in-line phase-contrast images of weakly absorbing objects. The source potentially enables the application of high-resolution phase-contrast x-ray imaging with short exposure times in clinics and laboratories. Different liquid-jet-target materials have been tested. The Sn-jet (Ka=25.3 keV) could be suitable for mammography, whereas the Ga-jet ((Ka=9.2 keV) may be utilized for x-ray diffraction studies. In addition, a non-metallic methanol jet has been the demonstrated in stable x-ray operation. All materials and compounds found in liquid form can, thus, potentially be used for electron-impact liquid-jet-target x-ray generation. Scaling to higher e-beam power density and x-ray brightness levels is discussed and is determined to be feasible. Potential difficulties, such as debris emission and instabilities of the x-ray emission spot, are investigated in some detail. Larger and/or faster jets could overcome the present limitations because of their inherently higher heat load capacities. Dynamic-similarity experiments show that liquid jets can in principle be operated in a stable manner at much higher speeds than previously shown. / QC 20100915

Magnetic resonance imaging (MRI) is an useful technique that provides a noninvasive method in clinical applications. For the patient of tetralogy of Fallot (TOF) after repaired, turbulence and regurgitation in blood flow may appear in pulmonary arteries. In this study, phase contrast MR imaging was applied and vortical flow patterns in the pulmonary arteries of patients after repair of TOF has been investigated. There are two major part of this study. Firstly we simulated vortical flow patterns of star, focus, and saddle which are most frequently appeared in blood flow. Quadrant index has been proposed for pattern analysis. In the second part we applied these parameters to in vivo data of repaired TOF patients, and compared with other parameters such as vorticity, coefficient of variance (CV), and regurgitant fraction (RF). Our result shows that the linear correlation between the mean of CV of velocity and mean of CV of vorticity in right pulmonary artery (RPA) as well as pulmonary trunk (PT) is larger than that in left pulmonary artery (LPA). This study shows that vorticity may provide some useful information of flow patterns and therefore helps doctors in clinical diagnosis

A dual channel polarimeter was incorporated into the Hokupa'a adaptive optics system mounted on the Gemini North telescope to enhance sensitivity to detecting the light scattered by circumstellar material. The technique suppressed noise introduced by non-repeatable variations of the point spread function which limit the sensitivity of non-simultaneous adaptive optics imaging. Polarimetric images of the classical T-Tauri star environments around GG Tauri Aab, TW Hydrae, LkCa 15, LkHα 242, GM Aurigae, and SR24 N/S were observed to establish the instrument's sensitivity. A survey of nearby ( d < 25 pc), young ( age < 1 Gyr), solar-analog stars was undertaken with the polarimeter to search for collisionally active debris disks analogous to our young solar system. Of the 24 stars sampled, none were found to have obvious scattered light signatures. Isotropic and Mie scattering model images of debris disks were used to constrain the amount of material around the survey stars to no more than M dust ∼ 10 -2 M Moon of 1-10μ m sized dust contained between 5-50 AU from the sample stars. Particle lifetimes under the influence of the Poynting Robertson Drag, radiation pressure, and solar wind drag are calculated as a function of central star spectral type. The corpuscular drag from stellar winds shorten dust lifetimes by an amount inversely proportional to the stellar wind mass-loss rate. This translates into dust lifetimes 100-1000 times shorter around young solar analog stars compared to the present day. This effect, cam significantly reduce the near-IR detectability of debris disks around these chromospherically active stars.

For decades, astronomers have used observations of mature planetary systems to constrain planet formation theories, beginning with our own solar system and now the thousands of known exoplanets. Recent advances in instrumentation have given us a direct view of some steps in the planet formation process, such as large-scale protostar and protoplanetary disk features and evolution. However, understanding the details of how planets accrete and interact with their environment requires direct observations of protoplanets themselves. Transition disks, protoplanetary disks with inner clearings that may be caused by forming planets, are the best targets for these studies. Their large distances, compared to the stars normally targeted for direct imaging of exoplanets, make protoplanet detection difficult and necessitate novel imaging techniques. In this dissertation, I describe the results of using non-redundant masking (NRM) to search for forming planets in transition disk clearings. I first present a data reduction pipeline that I wrote to this end, using example datasets and simulations to demonstrate reduction and imaging optimizations. I discuss two transition disk NRM case studies: T Cha and LkCa 15. In the case of T Cha, while we detect significant asymmetries, the data cannot be explained by orbiting companions. The fluxes and orbital motion of the LkCa 15 companion signals, however, can be naturally explained by protoplanets in the disk clearing. I use these datasets and simulated observations to illustrate the effects of scattered light from transition disk material on NRM protoplanet searches. I then demonstrate the utility of the dual-aperture Large Binocular Telescope Interferometer's NRM mode on the bright B[e] star MWC 349A. I discuss the implications of this work for planet formation studies as well as future prospects for NRM and related techniques on next generation instruments.

On March 2015 an L'-band vortex coronagraph based on an Annular Groove Phase Mask made up of a diamond sub-wavelength grating was installed on NIRC2 as a demonstration project. This vortex coronagraph operates in the L' band not only in order to take advantage from the favorable star/planet contrast ratio when observing beyond the K band, but also to exploit the fact that the Keck II Adaptive Optics (AO) system delivers nearly extreme adaptive optics image quality (Strehl ratios values near 90%) at 3.7 mu m. We describe the hardware installation of the vortex phase mask during a routine NIRC2 service mission. The success of the project depends on extensive software development which has allowed the achievement of exquisite real-time pointing control as well as further contrast improvements by using speckle nulling to mitigate the effect of static speckles. First light of the new coronagraphic mode was on June 2015 with already very good initial results. Subsequent commissioning nights were interlaced with science nights by members of the VORTEX team with their respective scientific programs. The new capability and excellent results so far have motivated the VORTEX team and the Keck Science Steering Committee (KSSC) to offer the new mode in shared risk mode for 2016B.