Thèses sur le sujet « Imagerie fUS »

Les épilepsies sont des hyperactivités neuronales pathologiques largement distribuées au sein du système nerveux. Aborder la question de l'organisation spatiotemporelle de ces crises est un premier pas crucial vers la dissection des mécanismes qui les sous-tendent. Alors qu'il existe de nombreux modèles d'hyperactivité épileptiforme, il est plus difficile d'étudier les crises spontanées, qui sont altérées par la sédation. Dans cette thèse, j'ai développé une approche combinant l'électroencéphalogramme (EEG) avec l'imagerie fonctionnelle ultrasonore (fUS), sur le rat mobile. Ainsi, sur un modèle d'épilepsie absence, j'ai pu enregistrer simultanément la survenue des crises et les variations hémodynamiques, marqueurs du métabolisme cellulaire. Le suivi additionnel de l'activité hémodynamique n'avait pas d'effet en soi sur l'occurrence et la durée des crises épileptiques. L'analyse des enregistrements a permis de mettre en évidence des corrélations entre les activités électriques et vasculaires durant les crises. Tandis que le thalamus présentait des zones d'hyperperfusion pendant les crises, le cortex présentait des corrélats variables suivant les aires, avec une hyperémie des aires somato-sensorielles accompagnée parfois d'une baisse de perfusion des tissus adjacents. La sensibilité du fUS a révélé, à partir d'événements uniques, qu'une série de pointe-ondes observée par une électrode EEG ne s'accompagne pas toujours d'une hyperactivité vasculaire au même endroit. Ainsi, cette approche permet de délimiter le contour des aires présentant une activité vasculaire pendant les crises et montre une dichotomie partielle entre les composantes électriques et vasculaires des crises
Epilepsies consist in neuronal hyperactivities distributed across the nervous system that need first to be located in order to later decipher the mechanisms of these pathologies. While there are many models of epileptiform hyperactivity, it is more difficult to study spontaneous seizures, which are altered by sedation. In this thesis, I developed an approach that combines electroencephalography (EEG) and functional ultrasound imaging (fUS), on the mobile rat. Thus, on a model of absence epilepsy, I could record simultaneously the occurrence of seizures and the hemodynamic variations, which reflect cellular metabolism. Seizures were unaltered by the recording protocol, compared to rats with EEG alone. Correlations were observed between electric and vascular activities. The thalamus showed areas of hyperperfusion during seizures. The cortex exhibited different correlates in distinct areas, with hyperaemia in somato-sensory areas, occasionally associated with a decrease in perfusion in adjacent tissue. The sensitivity of fUS, which could resolve blood changes from single occurrences, revealed that series of spike-wave discharges recorded from an EEG electrode were not always associated with vascular hyperactivity in the same region. Thus, this approach can delimit the contour of areas presenting vascular activity during seizures and shows a partial dichotomy between the electric and vascular components of seizures

La douleur neuropathique est une sensation de douleur anormale qui persiste au-delà du cours temporel de la guérison naturelle. Elle interfère avec la qualité de vie du patient et est associée à plusieurs comorbidités telles que l'anxiété et la dépression. Des études antérieures ont suggéré que la douleur chronique pourrait résulter d’une plasticité neuronale anormale et inadaptée dans les structures connues pour être impliquées dans la perception de la douleur (Bliss et al. 2016). Cela signifie qu'une lésion nerveuse déclencherait une potentialisation à long terme de la transmission synaptique dans les aires cérébrales liées à la douleur (Zhuo et al. 2014). Comme ces régions sont également impliquées dans les aspects émotionnels de la douleur, notre hypothèse est que la plasticité inadaptée susmentionnée dans ces zones cérébrales pourrait constituer un mécanisme clé pour le développement de comorbidités, telles que l'anxiété et la dépression.Au cours de ma thèse, nous avons choisi de tester cette hypothèse de travail par l’étude des altérations de la connectivité fonctionnelle (CF) intrinsèque des réseaux cérébraux par imagerie fonctionnelle ultrasonore (fUS) dans un modèle murin de douleur neuropathique. Cette technique de neuro-imagerie relativement récente a permis de nombreuses avancées en neurosciences, grâce à sa haute résolution spatio-temporelle, à sa sensibilité, mais aussi son adaptabilité, permettant des études chez l’animal anesthésié ou éveillé.Dans une première étude, j’ai mis au point un protocole expérimental permettant d’imager le cerveau des souris éveillées de façon reproductible et avec un minimum de stress et d artefacts de mouvements et ai également été impliquée dans le développement d’un nouvel algorithme d’analyse des signaux générées par ces acquisitions. Cette première approche étant réalisée avec une sonde linéaire en mouvement qui ne permet pas de visualiser l’entièreté du cerveau, dans une seconde étude, j’ai participe au développement d’une nouvelle technologie de sonde compilées et motorisée.Fort de ces développements technologiques, j’ai alors utilisé ces nouvelles approches pour tester mon hypothèse neurobiologique. J’ai entrepris deux études en parallèle chez des animaux anesthésiés pour l’une et éveillés pour la seconde, chez lesquelles nous avons étudié le lien temporel entre les altérations de la CF cérébrale et le développement de la douleur neuropathique et/ou des comorbidités associées. Pour cela, nous avons mesuré la CF (en période de repos) chez des souris atteintes de douleur neuropathique, à trois moments différents : I) 2 semaines après l’induction de la douleur neuropathique (manchon autour du nerf sciatique) II) à 8 semaines post-induction, lorsque l'anxiété émerge et III) à 12 semaines post-induction, lorsque la dépression apparait (12W). Ce suivi longitudinal a également été réalisé en parallèle sur un groupe d’animaux contrôles.Nos résultats indiquent des changements significatifs de la CF dans les principales régions cérébrales impliquées dans la transmission ou la modulation de la sensibilité ou de la douleur, suggérant la mise en place d’une plasticité inadaptée du réseau de la douleur, suite à la lésion nerveuse. De plus, nous observons une évolution temporelle de ces altérations, potentiellement corrélée à l'apparition des comorbidités associées. Ainsi, ces mécanismes pourraient participer à la chronicisation de la douleur
Neuropathic pain is an abnormal pain sensation that persists longer than the temporal course of natural healing. It interferes with the patient’s quality of life and leads to several comorbidities, such as anxiety and depression. It has been suggested that chronic pain may result from abnormal and maladaptive neuronal plasticity in the structures known to be involved in pain perception (Bliss et al. 2016). This means that nerve injury would trigger long-term potentiation of synaptic transmission in pain-related areas (Zhuo et al. 2014). Since these regions are also involved in the emotional aspects of pain, our hypothesis is that the aforementioned maladaptive plasticity in these brain areas could constitute a key mechanism for the development of comorbidities such as anxiety and depression.My PhD aimed at testing this working hypothesis, through the study of brain resting state functional connectivity (FC) using functional ultrasound imaging (fUS) in a mouse model of neuropathic pain. FUS is a relatively recent neuroimaging technique that enabled numerous advances in neuroscience, thanks to its high spatio-temporal resolution, its sensitivity, but also its adaptability, allowing studies in anesthetized or awake animals.In a first study, I developed an experimental protocol allowing the brains of awake mice to be imaged in a reproducible manner and with minimal stress and movement artifacts and was also involved in the development of a new algorithm for the analysis of the signals generated by these acquisitions. As this first approach was carried out with a moving linear probe which does not allow the entire brain to be visualized, in a second study, I participated in the development of a new compiled and motorized probe technology.Building on these technological developments, I then used these new approaches to test my neurobiological hypothesis. I undertook two parallel studies in animals anesthetized for one and awake for the second, in which we studied the temporal link between alterations in cerebral FC and the development of neuropathic pain and/or associated comorbidities. To do this, we measured the resting-state functional connectivity (FC) in anesthetized and in awake head-fixed mice, at three time points: I) 2 weeks after induction of neuropathic pain (cuff around the sciatic nerve), II) at 8 weeks post-induction during the emergence of anxiety (8W) and III) at 12 weeks post-induction during the emergence of depression. This longitudinal follow-up has been conducted concurrently on a control group.Our results show significant changes in FC in major pain-related brain regions in accordance with the development of neuropathic pain symptoms. These findings suggest that the pain network undergoes maladaptive plasticity following nerve injury which could contribute to pain chronification. Moreover, the time course of these connectivity alterations between regions of the pain network could be correlated with the subsequent apparition of associated comorbidities

Mes travaux de thèse portent sur l’application de l’imagerie fUS (functional ultrasound imaging) à l’imagerie cérébrale préclinique chez le petit animal. Le but était de transformer cette technique d’imagerie cérébrale récente en un véritable outil de quantification de l’état cérébral. Les objectifs principaux ont été de démontrer la faisabilité de l’imagerie fUS chez le petit animal non anesthésié ainsi que de passer du modèle rat au modèle souris - modèle de choix en imagerie préclinique en neurosciences - de surcroît de façon non invasive. J’ai tout d’abord mis au point une nouvelle séquence d’imagerie ultrasonore ultrarapide (Multiplane Wave imaging), permettant d’améliorer le rapport signal-à-bruit des images grâce à l’augmentation virtuelle de l’amplitude du signal émis, sans diminuer la cadence ultrarapide d’acquisition. Dans un deuxième temps j’ai démontré la possibilité d’imager le cerveau de la souris et du jeune rat anesthésiés par échographie Doppler ultrarapide, de manière transcrânienne et complètement non invasive, sans chirurgie ni injection d’agents de contraste. J’ai ensuite mis au point un montage expérimental, une séquence ultrasonore et un protocole expérimental permettant de réaliser de l’imagerie fUS de manière minimalement invasive chez des souris éveillées et libres de leurs mouvements. Enfin, j’ai démontré la possibilité d’utiliser le fUS pour étudier la connectivité fonctionnelle du cerveau au repos (sans stimulus) chez des souris éveillées ou sédatées. L’imagerie fUS et la combinaison « modèle souris » + « minimalement invasif » + « animal éveillé » + « connectivité fonctionnelle » constituent un outil précieux pour la communauté des neuroscientifiques travaillant sur des modèles animaux pathologiques ou de nouvelles molécules pharmacologiques
My work focuses on the application of fUS (functional ultrasound) imaging to preclinical brain imaging in small animals. The goal of my thesis was to turn this recent vascular brain imaging technique into a quantifying tool for cerebral state. The main objectives were to demonstrate the feasibility of fUS imaging in the non-anaesthetized small rodents and to move from rat model imaging to mouse model imaging –most used model for preclinical studies in neuroscience-, while developing the least invasive imaging protocols. First, I have developed a new ultrafast ultrasonic imaging sequence (Multiplane Wave imaging), improving the image signal-to-noise ratio by virtually increasing emitted signal amplitude, without reducing the ultrafast framerate. Then, I have demonstrated the possibility to use ultrafast Doppler ultrasound imaging to image both the mouse brain and the young rat brain, non-invasively and through the intact skull, without surgery or contrast agents injection. Next, I have developed an experimental setup, an ultrasound sequence and an experimental protocol to perform minimally invasive fUS imaging in awake and freely-moving mice. Finally, I have demonstrated the possibility to use fUS imaging to study the functional connectivity of the brain in a resting state in awake or sedated mice, still in a transcranial and minimally invasive way. fUS imaging and the combination of "mouse model" + "minimally invasive" + "awake animal" + "functional connectivity" represent a very promising tool for the neuroscientist community working on pathological animal models or new pharmacological molecules

The work in this thesis has been centred on the light emitting properties of silicon nanocrystals and the possible applications of this particular material platform to various topics ranging from bio-imaging to erbium ion sensitization. Silicon nanocrystals as bio-imaging agent have been investigated by employing colloidal dispersion of individual silicon nanocrystals where surface properties could be controlled to a great extent. By using a suitable functionalization scheme, high quality hydrophilic luminescent nanoparticles were produced. Using the improvements in the physical coating, bio-imaging on living cells (in vitro) was demonstrated showing that silicon nanocrystals have a great potential in bio-imaging and offer a promising alternative to commonly used fluorescence dyes. A part from being good light emitters, silicon nanocrystals could also amplify the light. This is a reason why the part of the work in this thesis has been dedicated to the investigation of silicon nanocrystals as a gain material. While most of the studies on this topic are concentrated on the nanocrystal surface as a driving mechanism behind the optical amplification, the work presented in this thesis concerns the study of a zero phonon (direct) optical transition as a possible source of optical amplification in this material system. To this scope, investigation of the dynamics of the system on a nanosecond time-scale and under high excitation conditions has been employed. Additional insight on ultrafast dynamics has been obtained by using optical cavities in the form of optically active free-standing micro-disk resonators. Finally, in the last part of this thesis a study of Er3+-doped Silicon-Rich-Oxide (SRO) materials and Er3+-doped SRO based devices is presented. This part of the work differs from the rest of the work reported in this thesis as is not focused on the light emitting properties of silicon nanocrystals but mostly on their non-radiative process engineering (energy transfer to erbium ions). Er3+ doped SRO opens the route towards compact waveguide amplifiers and lasers and allows for the possibility of electrical injection schemes, which are not realizable in standard erbium amplifiers used in EDFA for telecom applications. To that end, novel opto-electronic structures were proposed, modeled and manufactured and preliminary results of their performance were presented. The sensitization mechanism between silicon nanoparticles and erbium ions was studied and its complex nature was illustrated. Although, the acquired knowledge of physics involved was not sufficient for formulation of a complete working theory of the energy transfer process, some important physical aspects of this process have been elucidated paving the way towards its complete understanding.

The work in this thesis has been centred on the light emitting properties of silicon nanocrystals and the possible applications of this particular material platform to various topics ranging from bio-imaging to erbium ion sensitization. Silicon nanocrystals as bio-imaging agent have been investigated by employing colloidal dispersion of individual silicon nanocrystals where surface properties could be controlled to a great extent. By using a suitable functionalization scheme, high quality hydrophilic luminescent nanoparticles were produced. Using the improvements in the physical coating, bio-imaging on living cells (in vitro) was demonstrated showing that silicon nanocrystals have a great potential in bio-imaging and offer a promising alternative to commonly used fluorescence dyes. A part from being good light emitters, silicon nanocrystals could also amplify the light. This is a reason why the part of the work in this thesis has been dedicated to the investigation of silicon nanocrystals as a gain material. While most of the studies on this topic are concentrated on the nanocrystal surface as a driving mechanism behind the optical amplification, the work presented in this thesis concerns the study of a zero phonon (direct) optical transition as a possible source of optical amplification in this material system. To this scope, investigation of the dynamics of the system on a nanosecond time-scale and under high excitation conditions has been employed. Additional insight on ultrafast dynamics has been obtained by using optical cavities in the form of optically active free-standing micro-disk resonators. Finally, in the last part of this thesis a study of Er3+-doped Silicon-Rich-Oxide (SRO) materials and Er3+-doped SRO based devices is presented. This part of the work differs from the rest of the work reported in this thesis as is not focused on the light emitting properties of silicon nanocrystals but mostly on their non-radiative process engineering (energy transfer to erbium ions). Er3+ doped SRO opens the route towards compact waveguide amplifiers and lasers and allows for the possibility of electrical injection schemes, which are not realizable in standard erbium amplifiers used in EDFA for telecom applications. To that end, novel opto-electronic structures were proposed, modeled and manufactured and preliminary results of their performance were presented. The sensitization mechanism between silicon nanoparticles and erbium ions was studied and its complex nature was illustrated. Although, the acquired knowledge of physics involved was not sufficient for formulation of a complete working theory of the energy transfer process, some important physical aspects of this process have been elucidated paving the way towards its complete understanding.

Several projects in astronomy require detectors with a high number of resolution elements on the sky. For this reason, many observatories equipped their telescopes with a particular kind of detectors, the so-called wide-field imagers, that fulfil this requirement. In this thesis we show that, with a careful data analysis based on an accurate point-spread-function (PSF) modelling and geometric-distortion correction, it is possible to obtain high astrometric and photometric accuracy over wide field of views (FoVs). The prescriptions discussed in the thesis can be extended to the most of the detectors that are or will be placed at ground and space observatories. In the first part of the thesis, we mainly focus on detectors working in the near-infrared (NIR) regime. We want to concentrate on NIR imaging because of the increasing interest of the astronomical community for this wavelength range, which will be the baseline for JWST. In the second part of the thesis we also present a couple of applications to optical wide-field imagers (LBC@LBT and the CCD mounted at the Asiago Schmidt telescope). We start by investigating the astrometric and photometric performance of the NIR wide-field imager HAWK-I@VLT. We adapt to HAWK-I the techniques originally developed for the Hubble Space Telescope (HST) imagers to obtain high-precision astrometry and photometry, and then adapted to the ground-based, wide-field imager mounted at the 2.2-m MPI/ESO telescope. We accurately model HAWK-I PSFs and solve for the geometric distortion of the detector. With this careful data reduction, we are able to reach an astrometric accuracy of a few milliarcsec (mas) over the entire FoV of the instrument. Together with the distortion-correction package, we also create astro-photometric catalogues of seven fields (four stellar clusters, two extragalactic fields and one region toward the Galactic centre). Furthermore, to test the reached astrometric accuracy, we compute relative proper motions for stars in two globular clusters (M 22 and M 4) and successfully separate cluster members from background/foreground objects. Proper-motion-selected colour-magnitude diagrams of the globular cluster M 22 allow us to study its multiple stellar populations, finding that the two stellar populations hosted in the sub-giant branches of M 22 have the same radial distribution from the cluster centre out to 9 arcmin, within our uncertainty. We then move to the wide-field imager VIRCAM@VISTA. Again, we export the tools made for HAWK-I to this imager and solve for the distortion of the detector. The geometric-distortion correction of VIRCAM is quite challenging because the tangential-plane projection effects are not negligible over a FoV larger than 1 sq. deg on the sky. We start by using the 2MASS catalogue as reference frame, and then we auto-calibrate the geometric distortion as done for the HAWK-I detector. This way, we are able to correct the geometric distortion of VIRCAM to an astrometric accuracy of about 8 mas. Finally, we use the `VISTA Variables in the Vía Láctea' (VVV) data to compute M 22 globular-cluster relative proper motions. VVV observations are not designed to such high-astrometric-accuracy purposes, but, with our tools, we are able to reach a proper-motion precision of ~1.4 mas/yr and separate cluster and field stars, as well as to measure the motion difference between Galactic bulge and disc stars toward the direction of M 22. In the last part of the thesis we describe our new project, focused to exploit the data coming from the planet-hunting K2 mission, the re-designed Kepler mission after the problems that occurred to its spacecraft. The analysis of crowded environments using K2 data can be very complex with classical (aperture-based) photometric approaches. Our method is instead specifically developed to deal with these particular regions (stellar clusters and toward the Galactic centre) and its key ingredients are PSF astrometry and photometry, high-angular-resolution input catalogues and PSF-based neighbour subtraction. We first address the problem of the K2 undersampled PSFs which fine structures, if not properly modelled, can introduce systematic errors that worsen both astrometry and photometry. To this aim, we follow the iterative method made to model HST undersampled PSFs. We then use a high-angular-resolution, ground-based catalogue to identify all detectable objects in the field and, for each of them, we measure their flux after we subtract all close-by neighbours. This way, we increase the number of measurable sources in the field and obtain a more reliable estimate of their flux. Most importantly, for variable stars, eclipsing binaries and exoplanet candidates, this method leads to a more reliable value of the true amplitude or eclipse/transit depth of their light curves because we reduce light-dilution effects. This is particularly interesting for exoplanets, as the true radius of the transiting objects would be otherwise under-estimated. We apply this method to the first K2 Campaign that covered two open clusters (M 35 and NGC 2158) and extract about 50000 light curves from only one channel of K2. This number is more than two times the total number of sources usually analysed over the entire FoV (76 channels) in a typical K2 Campaign. For bright stars, we reach a photometric precision of ~30 parts per million, comparable with other works in the literature focused on isolated stars. At the faint end, we measure objects down to 5 magnitudes fainter than in any published work with K2 data so far, and show that the PSF photometry performs better than aperture photometry in this magnitude regime. The improvement here described is more significant in crowded regions. Within the field of these two clusters we also find more than 2000 variable stars. All the projects developed during this thesis have also interesting long-term perspectives, since they can be seen as complementary or in preparation to future space-based missions like TESS and PLATO. Candidate exoplanets from Kepler/K2 (but also from the forthcoming TESS) observations can potentially be interesting targets for JWST, and then E-ELT
Diversi progetti in astronomia richiedono rivelatori con un elevato numero di elementi risolutivi in cielo. Per questo motivo, molti osservatori hanno equipaggiato i loro telescopi con un particolare tipo di rivelatori, i cosiddetti rivelatori a grande campo, che soddisfano tale requisito. In questa tesi mostriamo come sia possibile ottenere astrometria e fotometria di elevata accuratezza su grandi campi con un'attenta analisi dei dati basata sul modellare accuratamente le funzioni di sorgenti puntiformi (dall'inglese point-spread functions, o PSFs) e sulla correzione della distorsione geometrica. Le metodologie di lavoro discusse in questa tesi possono essere estese alla maggior parte dei rivelatori che sono o verranno collocati in osservatori da terra e da spazio. Nella prima parte della tesi ci focalizziamo principalmente sui rivelatori che lavorano nel regime del vicino infrarosso. Vogliamo concentrarci su tali camere infrarosse a causa del crescente interesse della comunità astronomica a queste lunghezze d'onda, che saranno alla base di JWST. Tuttavia nella seconda parte della tesi presentiamo anche alcuni esempi di applicazioni con rivelatori a grande campo che lavorano nella parte ottica dello spettro elettromagnetico (la camera LBC montata al telescopio LBT e il rivelatore montato al telescopio Schmidt di Asiago). Inizialmente esaminiamo le prestazioni astrometriche e fotometriche del rivelatore infrarosso a grande campo HAWK-I montato al VLT. Adattiamo per i dati HAWK-I le tecniche originariamente sviluppate per ottenere astrometria e fotometria di alta precisione con le camere di Hubble Space Telescope (HST), e successivamente estese alla camera a grande campo posta al telescopio da terra di 2.2 m dell'ESO/MPI. Modelliamo accuratamente le PSFs e correggiamo la distorsione geometrica di HAWK-I. Con questa attenta analisi dei dati, riusciamo a raggiungere un'accuratezza astrometrica di qualche millesimo di arcosecondo (mas) su tutto il campo di vista dello strumento. Oltre alla correzione della distorsione, costruiamo anche cataloghi astro-fotometrici di sette campi (quattro ammassi stellari, due campi extragalattici e un campo in direzione del centro Galattico). Inoltre, per testare l'accuratezza astrometrica raggiunta, calcoliamo i moti propri relativi delle stelle in due ammassi globulari (M 22 e M 4) e separiamo con successo i membri di ammasso da quelli di campo. Diagrammi colore-magnitudine decontaminati dalle stelle di campo grazie ai moti propri ci permettono di studiare le popolazioni stellari multiple dell'ammasso M 22, e di trovare che le due popolazioni visibili nei rami delle sub-giganti di M 22 hanno, entro gli errori delle nostre misure, la stessa distribuzione radiale dal centro dell'ammasso fino a 9 arcominuti. Successivamente ci spostiamo sul rivelatore VIRCAM montato al telescopio VISTA. Adattiamo nuovamente per questa camera i programmi sviluppati per HAWK-I e correggiamo la distorsione geometrica. La correzione della distorsione si è rivelata ardua perché su campi di vista estesi più di un 1 grado quadrato in cielo gli effetti dovuti alla proiezione della sfera celeste sul piano tangente di un'immagine non sono trascurabili. Per questo motivo, usiamo inizialmente come riferimento il catalogo 2MASS e poi auto-calibriamo la distorsione come fatto per HAWK-I. In questo modo siamo in grado di correggere la distorsione di VIRCAM e di raggiungere un'accuratezza astrometrica di circa 8 mas. Infine usiamo i dati provenienti dalle osservazioni di `VISTA Variables in the Vía Láctea' (VVV) per calcolare i moti propri delle stelle dell'ammasso globulare M 22. Le osservazioni di VVV non sono concepite per conseguire progetti basati su un'elevata accuratezza astrometrica, ma con i nostri strumenti raggiungiamo una precisione nei moti propri dell'ordine di 1.4 mas/yr, separiamo le stelle di campo da quelle di ammasso, ed inoltre misuriamo la differenza tra il moto proprio delle stelle del Bulge e del Disco della nostra Galassia nella direzione di M 22. Nell'ultima parte della tesi descriviamo il progetto focalizzato nello sfruttare i dati dal cacciatore di pianeti K2, il successore della missione Kepler, ridisegnata dopo i vari problemi in cui è incorsa. L'analisi di ambienti ad alta densità stellare usando i dati K2 può risultare molto complessa con le classiche tecniche fotometriche (basate sulla fotometria di apertura). Il nostro metodo invece è stato specificatamente elaborato per analizzare queste regioni (ammassi stellari e nella direzione del centro Galattico) e i suoi elementi chiave sono astrometria e fotometria di PSF, cataloghi ad alta risoluzione angolare e sottrazione delle stelle vicine tramite l'utilizzo della PSF. Inizialmente affrontiamo il problema delle PSFs sottocampionate di K2 le cui strutture su piccola scala, se non correttamente modellate, possono introdurre errori sistematici che peggiorano l'astrometria e la fotometria. Per questo scopo, seguiamo il metodo iterativo progettato per modellare le PSFs sottocampionate di HST. Successivamente utilizziamo un catalogo ad alta risoluzione angolare, ottenuto con telescopi da terra, per identificare tutte le sorgenti rilevabili nel campo e, per ciascuna di esse, misuriamo il flusso dopo aver sottratto tutte le stelle vicine. In questo modo aumentiamo il numero di sorgenti analizzabili nel campo e otteniamo una stima più veritiera del loro flusso. In particolare per stelle variabili, binarie ad eclissi ed esopianeti questo metodo permette di ottenere un valore più realistico della vera ampiezza o profondità dell'eclissi/transito della loro curva di luce poiché diminuiamo gli effetti di diluizione della luce. Questo risvolto è particolarmente importante per gli esopianeti perché altrimenti il vero raggio del pianeta verrebbe sottostimato. Applichiamo questo metodo alla prima campagna osservativa della missione K2 in cui sono stati osservati due ammassi aperti (M 35 e NGC 2158) ed estraiamo le curve di luce di più di 50000 oggetti da un solo canale di lettura di una delle camere K2. Questo numero è più del doppio del numero di oggetti normalmente analizzati in tutto il campo di vista di K2 (76 canali) in una data campagna osservativa. Per le stelle brillanti raggiungiamo una precisione fotometrica di circa 30 parti per milione, un valore confrontabile con quanto si può trovare in altri lavori in letteratura su stelle isolate. Inoltre riusciamo ad estendere la nostra analisi a stelle fino a 5 magnitudini più deboli di quanto studiato in lavori già pubblicati, e mostriamo che per questi oggetti deboli la fotometria di PSF è migliore di quella di apertura. Tale miglioramento è maggiori nei campi a più alta densità stellare. Infine troviamo più di 2000 stelle variabili in questi due ammassi. Tutti i progetti sviluppati in questa tesi hanno anche interessanti prospettive a lungo termine in quanto possono essere visti come complementari o in preparazione a missioni da spazio future come TESS e PLATO. I candidati pianeti trovati con le osservazioni di Kepler/K2 (ma anche dell'imminente TESS) possono potenzialmente essere target interessanti per JWST, e successivamente per E-ELT

L’imagerie de la dynamique d’émission de fluorescence biphotonique est un développement technologique particulièrement attractif dans le domaine de la biophotonique. En particulier, les techniques de FLIM et FCS permettent l’imagerie cellulaire avec le suivi en temps réel des phénomènes biologiques mis en jeu, tandis que leur couplage à une excitation multiphotonique offre de plus grandes performances en termes de résolution spatiale, de profondeur de pénétration, d’innocuité vis-à-vis des systèmes biologiques. Les mesures FLIM par excitation biphotonique ont été utilisées pour l’étude in vitro et ex vivo d'un anti-intégrase du VIH-1, la 2-styrylquinoline Fz41. L’étude en solution de la dynamique réactionnelle de ce composé a permis de préciser sa spécificité de reconnaissance avec l’intégrase. Ces données ont été confrontées à des mesures au sein de cellules HeLa transduites par un vecteur lentiviral. C’est grâce à la durée de vie de fluorescence utilisée comme facteur de contraste qu’il a été permis de décrire l’activité intracellulaire de Fz41. La FCS a été utilisée pour étudier la diffusion-réaction de bactériophages c2 au sein de biofilms (communauté microbienne contenue dans une matrice de polymères organiques) sensibles ou non à cette entité biologique. Les résultats expérimentaux ont permis de conclure que la diffusion des particules virales au sein des biofilms est contrôlée par la structure de la matrice d’exopolymères. Dans ce travail, pour la première fois, la méthode FCS a permis de « visualiser » in situ l’interaction des bactériophages avec les bactéries possédant sur leur membrane le site de reconnaissance spécifique
The imaging of the biphotonic fluorescence emission dynamics is a technological development especially attractive in biophotonic. In particular, the FLIM and FCS techniques make cell imaging possible with a real-time follow-up of the occurring biological phenomena. Furthermore, their combination to a multiphotonic excitation increases their performance in terms of spatial resolution, penetration depth and harmlessness to biological systems. FLIM with two-photon excitation was used for the in-vitro and ex-vivo study of the 2-styrylquinoline Fz41 VIH-1 anti-integrase. The reaction dynamic study in solution of this component enabled us to check its specific recognition of the integrase. These data were compared with measurements performed in HeLa cells transduced with a lentiviral vector. By using the fluorescence lifetime as a contrast factor, the Fz41 intracellular activity could be described. The FCS was used to study the diffusion-reaction of c2 bacteriophages in biofilms (microbial community in an organic matrix) sensitive or not to this biological entity. The experimental results enabled us to conclude that the viral particle diffusion into biofilms is controlled by the exopolymeric matrix. In this study, for the first time, with the FCS technique, it was possible to visualise in situ the interaction of bacterophages with the bacteria whose membrane contained the specific recognition site

Depuis le milieu du XXème siècle, les techniques d’imagerie fonctionnelles ont un rôle grandissant dans notre compréhension sur les fonctions du cerveau en conditions physiologique et pathologique. Bien que l’IRMf fasse partie des techniques les plus communément utilisées pour l’imagerie du cerveau complet lors d’études préclinique et clinique, cette modalité souffre de sa résolution spatiotemporelle et sa sensibilité pour enregistrer finement les fonctions et activités cérébrales. Récemment l’imagerie fonctionnelle par ultrason (ifUS) a subi des développements permettant d’être complémentaires à l’IRMf ainsi qu’aux autres techniques d’imagerie cérébrales classiquement employées. Contrairement aux ultrasons focalisés conventionnels, l’imagerie hémodynamique proposé par l’ifUS repose sur une illumination ultrasonore plane permettant la détection des globules rouges en mouvement et la mesure de leur vitesse dans les micro-vaisseaux cérébraux. De ce fait, l’ifUS est indirectement lié à l’activité cérébrale d’où l’importance d’une meilleure compréhension des mécanismes du couplage neuro-vasculaire liant l’activité neuronale et les variations cérébrales d’apport en sang. De plus, cette technique a le potentiel pour fournir des informations précises sur les processus de certaines pathologies à la fois sur des modèles précliniques et chez l’homme. Dans un premier temps, j’exposerais mes travaux sur les récents développements techniques permettant l’ifUS in vivo (i) en condition chronique, (ii) sur l’animal éveillé, libre de mouvement et effectuant une tache comportementale et (iii) des vaisseaux capillaires chez le rongeur et l’homme. Dans un second temps, je démontrerais que l’ifUS in vivo peut fournir des informations nouvelles sur des pathologies telles que l’accident vasculaire cérébrale
Since the middle of the 20th century, functional imaging technologies are making an increasing impact on our understanding on brain functions in both physiological and pathological conditions. Even if fMRI is nowadays one of the most used tool for whole brain imaging in pre-clinical and clinical studies, it lacks sufficient spatiotemporal resolution and sensitivity to assess fine brain function and activity. Functional ultrasound imaging (fUSi) has been recently developed and presents a potential to complement fMRI and other existing brain imaging modalities. Contrary to conventional ultrasound using focus beams, fUSi relies on hemodynamic imaging based on ultrasound plane-wave illumination to detect red blood cells movement and velocity in brain micro-vessels. Consequently, the fUSi signal is indirectly related to brain activity and it is therefore important to better understand the mechanisms of the neurovascular coupling linking neural activity and cerebral blood changes. Here again, fUSi may provide relevant information about disease processes in preclinical models but also in humans. First, I will present recent technical developments allowing in vivo fUSi (i) in chronic condition, (ii) in freely moving and behaving rats and (iii) in rodents and human brain capillaries. Second, I will demonstrate how fUSi could provide new insights in brain pathologies such as stroke

Cette recherche porte sur les influences du « printemps arabe » sur le discours touristique que nous abordons sous deux modalités argumentatives : la publicité touristique et la promotion touristique. Pour traiter cette problématique, nous avons collecté un corpus iconotextuel (texte + image) parmi des ressources médiatiques très variées diffusées entre 2011 et 2015 par deux pays représentatifs pour l’ampleur de leur activité touristique (Égypte et Tunisie). L’analyse de ce corpus part de l’hypothèse que les genres variés de notre corpus reposent sur une conception linguistique et visuelle relativement différente de l’information en fonction du genre et de la cible d’une part, et en fonction du soubassement culturel et psychosocial d’une image idéologique virtuelle complexe en adéquation avec la post-crise d’autre part. Le cadre théorique met en avant cette image virtuelle complexe sous la forme de « l’imagerie », concept psychosocial central dans la publicité et la promotion touristique grâce à sa capacité d’associer l’héritage culturel de représentations du passé avec les attentes, les rêves et les souhaits suscités par la future aventure touristique mise en promotion, esquissés dans cette imagerie. Le cadre théorique ancre l’imagerie dans différents genres de discours à partir de leurs dimensions constitutives comme les dimensions textuelle, sociopragmatique et matérielle, afin de dégager le processus linguistique mis en œuvre par le genre de discours responsable du contrat de lecture avec le destinataire et de la mobilisation du contenu culturel.La Tunisie et l’Égypte n’ont pas réagi de la même manière à l’impact du nouveau contexte post-crise problématique au niveau politique et sécuritaire. En effet, alors que l’Égypte s’est contentée de la reproduction classique de l’imagerie touristique fondée sur la variété de son héritage pharaonique, en écartant l’enjeu de l’évolution géopolitique du printemps en post-crise dans ses imageries, la Tunisie, pour sa part, a recouru à l’alliance de l’argumentation discursive et visuelle fondant une imagerie qui conjugue non seulement tradition et architecture mais aussi sécurité et modernité d’expériences touristiques intenses.De plus, le corpus tunisien s’est montré davantage ouvert à la créativité, par rapport au corpus égyptien, grâce à l’intégration de nouveaux genres très variés comme les articles d’actualités économique ou politique, la chronique littéraire, etc. dans sa promotion touristique non publicitaire. L’adaptation du contenu à la post-crise dans un éventail élargi de genres de discours, dont nous avons pu dégager les caractéristiques sémiolinguistiques grâce à une analyse menée à partir d’une grille conçue spécifiquement, a ensuite trouvé sa traduction didactique dans la proposition d’un module de Français sur Objectif spécifique (FOS) qui vise l’acquisition des compétences professionnelles particulières pour les futurs professionnels du tourisme de certains pays du Moyen-Orient dont le contexte sociolinguistique du français est similaire au contexte égyptien
This research focuses on the influences of the "Arab Spring" on the tourist discourse that we approach under two argumentative modalities: tourism advertising and tourism promotion. To deal with this issue, we have collected an iconotexual corpus (text + image) among media resources very varied, distributed between 2011 and 2015 by two representative countries for the scale of their tourism activity (Egypt and Tunisia).The analysis of this corpus is based on the assumption that the various speech genres of our corpus are based on a linguistic and visual conception that is relatively different from the information according to the speech genre and the target on the one hand, and according to the cultural underpinning and psychosocial of a complex virtual ideological image in adequacy with the post-crisis on the other hand. The theoretical framework puts forward this complex virtual image in the form of "imagery", a central psychosocial concept in advertising and tourism promotion thanks to its ability to associate the cultural heritage of representations of the past with expectations, dreams and the wishes aroused by the future tourist adventure put on display in this imagery. The theoretical framework anchors the imagery in different speech genres from their constituent dimensions as the textual, socio-physical and material dimensions in order to identify the linguistic process implemented by the speech genre responsible for the reading contract with the recipient and the mobilization of cultural content.Tunisia and Egypt have not responded in the same way to the impact of the new post-crisis political and security context. Indeed, while Egypt has been content with the classic reproduction of tourist imagery based on the variety of its pharaonic heritage by removing the issue of the geopolitical evolution of spring in post-crisis in its imagery, Tunisia, for its part, has resorted to the combination of discursive and visual argumentation founding an imagery that combines not only tradition and architecture but also the security and modernity of intense tourist experiences.In addition, the Tunisian corpus has been more open to creativity, compared to the Egyptian corpus, through the integration of new very varied genres such as economic or political news articles, literary chronicles, etc. The post-crisis adaptation of the content in a wider range of speech genres from which we have been able to identify the semiolinguistic characteristics through an analysis conducted from a specifically designed grid which has subsequently been translated into didactic translation in the proposal for a French module for Specific Objective (FSO) aimed at acquiring specific professional skills for future tourism professionals in certain Middle Eastern countries whose socio-linguistic context of French is similar to the Egyptian context

La navigation spatiale est une fonction complexe qui nécessite de combiner des informations sur l’environnement et notre mouvement propre pour construire une représentation du monde et trouver le chemin le plus direct vers notre but. Cette intégration multimodale suggère qu’un large réseau de structures corticales et sous-corticales interagit avec l’hippocampe, structure clé de la navigation. Je me suis concentrée chez la souris sur la navigation de type séquence (ou stratégie égocentrique séquentielle) qui repose sur l’organisation temporelle de mouvements associés à des points de choix spatialement distincts. Après avoir montré que l’apprentissage de cette navigation de type séquence nécessitait l’hippocampe et le striatum dorso-médian, nous avons caractérisé le réseau fonctionnel la sous-tendant en combinant de l’imagerie Fos, de l’analyse de connectivité fonctionnelle et une approche computationnelle. Les réseaux fonctionnels changent au cours de l’apprentissage. Lors de la phase précoce, le réseau impliqué comprend un ensemble de régions cortico-striatales fortement corrélées. L’hippocampe était activé ainsi que des structures impliquées dans le traitement d’informations de mouvement propre (cervelet), dans la manipulation de représentations mentales de l’espace (cortex rétrosplénial, pariétal, entorhinal) et dans la planification de trajectoires dirigées vers un but (boucle cortex préfrontal-ganglions de la base). Le réseau de la phase tardive est caractérisé par l’apparition d’activations coordonnées de l’hippocampe et du cervelet avec le reste du réseau. Parallèlement, nous avons testé si l’intégration de chemin, de l’apprentissage par renforcement basé modèle ou non-basé modèle pouvaient reproduire le comportement des souris. Seul un apprentissage par renforcement non-basé modèle auquel une mémoire rétrospective était ajoutée pouvait reproduire les dynamiques d’apprentissage à l’échelle du groupe ainsi que la variabilité individuelle. Ces résultats suggèrent qu’un modèle d’apprentissage par renforcement suffit à l’apprentissage de la navigation de type séquence et que l’ensemble des structures que cet apprentissage requiert adaptent leurs interactions fonctionnelles au cours de l’apprentissage
Spatial navigation is a complex function requiring the combination of external and self-motion cues to build a coherent representation of the external world and drive optimal behaviour directed towards a goal. This multimodal integration suggests that a large network of cortical and subcortical structures interacts with the hippocampus, a key structure in navigation. I have studied navigation in mice through this global approach and have focused on one particular type of navigation, which consists in remembering a sequence of turns, named sequence-based navigation or sequential egocentric strategy. This navigation specifically relies on the temporal organization of movements at spatially distinct choice points. We first showed that sequence-based navigation learning required the hippocampus and the dorsomedial striatum. Our aim was to identify the functional network underlying sequence-based navigation using Fos imaging and computational approaches. The functional networks dynamically changed across early and late learning stages. The early stage network was dominated by a highly inter-connected cortico-striatal cluster. The hippocampus was activated alongside structures known to be involved in self-motion processing (cerebellar cortices), in mental representation of space manipulations (retrosplenial, parietal, entorhinal cortices) and in goal-directed path planning (prefrontal-basal ganglia loop). The late stage was characterized by the emergence of correlated activity between the hippocampus, the cerebellum and the cortico-striatal structures. Conjointly, we explored whether path integration, model-based or model-free reinforcement learning algorithms could explain mice’s learning dynamics. Only the model-free system, as long as a retrospective memory component was added to it, was able to reproduce both the group learning dynamics and the individual variability observed in the mice. These results suggest that a unique model-free reinforcement learning algorithm was sufficient to learn sequence-based navigation and that the multiple structures this learning required adapted their functional interactions across learning

Thermal infrared (IR, 10.5 – 12.5 m) images from the Meteosat Visible and Infrared Imager (MVIRI) of cold cloud episodes (cloud top brightness temperature < 241 K) are used as a proxy of precipitating clouds to derive a warm season (May-August) climatology of their coherency, duration, span, and speed over Europe and the Mediterranean. The analysis focuses over the 30°-54°N, 15°W-40°E domain in May-August 1996-2005. Harmonic analysis using discrete Fourier transforms is applied together with a statistical analysis and an investigation of the diurnal cycle. This study has the objective to make available a set of results on the propagation dynamics of the cloud systems with the aim of assist numerical modellers in improving summer convection parameterization. The zonal propagation of cold cloud systems is accompanied by a weak meridional component confined to narrow latitude belts. The persistence of cold clouds over the area evidences the role of orography, the Pyrenees, the Alps, the Balkans and Anatolia. A diurnal oscillation is found with a maximum marking the initiation of convection in the lee of the mountains and shifting from about 1400 UTC at 40°E to 1800 UTC at 0°. A moderate eastward propagation of the frequency maximum from all mountain chains across the domain exists and the diurnal maxima are completely suppressed west of 5°W. The mean power spectrum of the cold cloud frequency distribution evidences a period of one day all over Europe disappearing over the ocean (west of 10°W). Other maxima are found in correspondence of 6 to 10 days in the longitudes from 15° W to 0° and indicate the activity of the westerlies with frontal passage over the continent. Longer periods activities (from 15 up to 30 days) were stronger around 10° W and from 5° W to 15° E and are likely related to the Madden Julian Oscillation influence. The maxima of the diurnal signal are in phase with the presence of elevated terrain and with land masses. A median zonal phase speed of 16.1 ms-1 is found for all events ≥ 1000 km and ≥ 20 h and a full set of results divided by years and recurrence categories is also presented.

Thermal infrared (IR, 10.5 – 12.5 m) images from the Meteosat Visible and Infrared Imager (MVIRI) of cold cloud episodes (cloud top brightness temperature < 241 K) are used as a proxy of precipitating clouds to derive a warm season (May-August) climatology of their coherency, duration, span, and speed over Europe and the Mediterranean. The analysis focuses over the 30°-54°N, 15°W-40°E domain in May-August 1996-2005. Harmonic analysis using discrete Fourier transforms is applied together with a statistical analysis and an investigation of the diurnal cycle. This study has the objective to make available a set of results on the propagation dynamics of the cloud systems with the aim of assist numerical modellers in improving summer convection parameterization. The zonal propagation of cold cloud systems is accompanied by a weak meridional component confined to narrow latitude belts. The persistence of cold clouds over the area evidences the role of orography, the Pyrenees, the Alps, the Balkans and Anatolia. A diurnal oscillation is found with a maximum marking the initiation of convection in the lee of the mountains and shifting from about 1400 UTC at 40°E to 1800 UTC at 0°. A moderate eastward propagation of the frequency maximum from all mountain chains across the domain exists and the diurnal maxima are completely suppressed west of 5°W. The mean power spectrum of the cold cloud frequency distribution evidences a period of one day all over Europe disappearing over the ocean (west of 10°W). Other maxima are found in correspondence of 6 to 10 days in the longitudes from 15° W to 0° and indicate the activity of the westerlies with frontal passage over the continent. Longer periods activities (from 15 up to 30 days) were stronger around 10° W and from 5° W to 15° E and are likely related to the Madden Julian Oscillation influence. The maxima of the diurnal signal are in phase with the presence of elevated terrain and with land masses. A median zonal phase speed of 16.1 ms-1 is found for all events ≥ 1000 km and ≥ 20 h and a full set of results divided by years and recurrence categories is also presented.

SHARK-NIR is the second-generation high-contrast coronagraphic imager for the Large Binocular Telescope (LBT). In my Ph.D. project I have been involved in the conceptual and final design phase of the instrument. In specific, I developed a simulator in IDL language that operated as a virtual test bench to make a comparative study of several coronagraphic techniques identified as suitable candidates for implementation in the instrument. The simulator is based on physical optics propagation and adopts an end-to-end approach to generate images in presence of several sources of optical aberrations, from atmospheric residuals to telescope vibrations and non common path aberrations (NCPA). In particular, a big effort has been devoted to the optimization of the software efficiency through a dedicated parallelization scheme, to modelling of NCPA spatial and temporal properties, to the investigation of the effects of telescope vibrations and of the impact of the forthcoming upgrade of LBT Adaptive Optics system. I explored the coronagraphic performance in a wide range of observing conditions and characterized the coronagraphs sensitivity to aberrations, misalignments of optical components and chromatism. I also helped developing a data reduction pipeline to process simulated data adopting several algorithms. Simulations results have been used to define a final set of coronagrahic solutions that allow to fulfill the top-level scientific requirements.\\Finally, I validated with simulations the phase diversity approach as a strategy for on-line sensing of NCPA. Simulations contributed to the final choice of the internal DM for both NCPA and fast tip-tilt correction.
SHARK-NIR è l'imager ad alto contrasto di seconda generazione per il Large Binocular Telescope. Durante il mio Ph.D. sono stato coinvolto nella fasi di design concettuale e finale dello strumento. In specifico, ho sviluppato un simulatore in IDL che è stato utilizzato come banco di test virtuale per realizzare uno studio comparativo di diverse tecniche coronografiche identificate come possibili candidate a essere implementate nello strumento. Il simulatore è basato sulla propagazione di fronti d'onda e utilizza un approccio end-to-end per generare immagini in presenza di svariate sorgenti di aberrazioni ottiche, da residui atmosferici a vibrazioni e aberrazioni di non-common path (NCPA). Un'attenzione particolare è stata rivolta all'ottimizzazione del software attraverso specifici schemi di parallelizzazione, alla modellizzazione delle proprietà temporali e spaziali delle NCPA e allo studio dell'impatto del prossimo upgrade dei sistema di Ottica Adattiva di LBT. Ho esplorato le performance di diversi coronografi in un ampio range di condizioni osservative e caratterizzato la loro sensibilità ad aberrazioni, disallineamenti e cromatismo. Ho anche contribuito allo sviluppo di una pipeline di riduzione dati rivolta a processare le immagini simulate adottando diversi algoritmi. I risultati delle simulazioni sono stati utilizzati per effettuare una selezione di tecniche coronografiche in grado di soddisfare i requisiti scientifici dello strumento. Infine, ho validato attraverso simulazioni un approccio denominato Phase Diversity il cui fine è misurare on-line le NCPA. Le simulazioni hanno contribuito alla scelta di implementare uno specchio deformabile interno per la correzione simultanea di NCPA e vibrazioni residue ad alta frequenza.

Les biofilms sont des communautés de microorganismes emprisonnés dans une matrice de polymères organiques extracellulaires (EPS) permettant de stabiliser ces édifices tridimensionnels. La cohésion des EPS polyanioniques dans un environnement hydraté est assurée par des microdomaines hydrophobes. La localisation de ces sites hydrophobes est très importante pour comprendre la variabilité ainsi que la réactivité des EPS. Notre travail vise la synthèse de nouvelles sondes fluorescentes hydrophiles ou amphiphiles capables de marquer les EPS. Dans ce but, nous avons synthétisé une série de nanocristaux fluorescents à coeur CdSe, appelés Quantum Dots (QDs), modifiés à leur périphérie par des ligands hydrophiles (acide 3-mercaptopropionic) ou amphiphiles (acide dihydrolipoique couplé à des acides aminés hydrophobes tels que la Leucine ou la Phénylalanine). Par microscopie confocale de fluorescence et spectroscopie de corrélation de fluorescence (FCS), nous avons montré que les QDs fonctionnalisés s'associaient fortement aux EPS des biofilms de la bactérie S. oneidensis. La distribution de ces nanoparticules dans les EPS est dépendante de la structure du ligand et de sa densité à la périphérie des QDs. Une dispersion homogène des QDs hydrophiles dans l'ensemble du biofilm et une clusterisation des QDs amphiphiles dans des microdomaines hydrophobes ont notamment été observés. Les nouvelles sondes fluorescentes développées dans ce travail permettront de suivre le développement ainsi que la réorganisation de matrices biologiques complexes telles que les biofilms
Microorganisms predominantly live in communities, such as biofilms, in which extracellular polymeric substances (EPS) form the matrix and stabilize the three-dimensional structure. Hydrophobic microdomains allow the cohesiveness of these hydrophilic, polyanionic systems. The localization of these hydrophobic sites is very important to understand the variability and the reactivity of the EPS. The objective of our work was to engineer new fluorescent probes with amphiphilic or hydrophilic properties able to label the EPS. For that purpose, we have synthesized a series of fluorescent CdSe-core nanocrystals, also called Quantum Dots (QDs), modified at their periphery with hydrophilic (3-mercaptopropionic acid) or amphiphilic ligands (dihydrolipoic acid coupled to hydrophobic aminoacids like Leucine or Phenylalanine). Using confocal fluorescence microscopy and fluorescence correlation spectroscopy (FCS), we demonstrated that the functionalized QDs strongly associated with the EPS of S. oneidensis biofilms and allow imaging of these microbial communities. The location of these probes within the EPS was dependent on the surface ligand structure and on its density at the periphery of QDs. A homogeneous dispersion of hydrophilic QDs in the whole biofilm was observed, while amphiphilic QDs clusterized in the small hydrophobic domains. These new fluorescent probes will be of great use to understand the development and the reorganization of complex biological matrix like biofilms

In the year of the 20th anniversary of the discovery of the first extrasolar planet we can count more than 1800 companions found with different techniques. The majority of them are indirect methods that infer the presence of an orbiting body by observing the parent star (radial velocity, transits, astrometry). In this work we explore the technique that permits to directly observe planets and retrieve their spectra, under the conditions that they are bright and far enough from their host star. Direct imaging is a new technique became possible thanks to a new generation of extreme adaptive optics instruments mounted on 8m class telescopes. On the Very Large Telescope two instruments dedicated to the research for exoplanets with direct imaging are now operative: NACO and SPHERE. This thesis will describe the development and results of SPHERE from its predecessor NACO to its integration in laboratory and the final on sky results. Chapter 1 gives a presentation of the exoplanet research, the formation mechanisms, and the characterization of planet atmospheres. Chapter 2 gives a general frame of the two instruments used for the results presented in this thesis: NACO and SPHERE. In Chapter 3 I describe an example of a false positive in the direct imaging technique, found during the survey NACO-Large Program. This work have been published in Zurlo et al. 2013. In Chapter 4 I present the performance of SPHERE, in particular of the subsystems IRDIS and IFS, deeply tested in the laboratory before the shipping to Paranal. This work has been published in Zurlo et al. 2014. Chapter 5 presents a work done to find special targets for the NIRSUR survey, these object are radial velocity long period planets which are observable with SPHERE. In Chapter 6 I present one of the first on sky result, the observations and analysis of the multi-planetary system HR\,8799. In Chapter 7 I give the conclusions and future prospects.
Al giorno d'oggi più di 1800 pianeti sono stati scoperti orbitare attorno a stelle al di fuori del sistema solare. Le tecniche utilizzate per la ricerca di pianeti extrasolari sono molteplici: alcune, dette metodi indiretti, si basano sull'osservazione della perturbazione indotta dal pianeta orbitante sulla stella ospite, mentre altre si basano sull'osservazione diretta del pianeta stesso. La maggior parte dei pianeti scoperti attualmente é stata rivelata grazie ai primi. Specialmente il metodo delle velocità radiali e dei transiti hanno fornito il più alto numero si scoperte. Lo svantaggio di questo tipo di tecniche é che la caratterizzazione del pianeta non può essere completa a meno che non vengano usate simultaneamente più tecniche. Inoltre, per ottenere lo spettro del pianeta, quest'ultimo deve transitare e anche in questo caso il segnale é difficilmente estrapolabile. L'osservazione diretta di questi oggetti, detta “direct imaging”, é oggi possibile grazie ad avanzati sistemi di ottica adattiva installati su telescopi della classe 8m. Il direct imaging permette l'osservazione diretta di pianeti sufficientemente luminosi e distanti dalla stella ospite grazie ad una maschera che oscura la luce di quest'ultima. Questa tecnica quindi é particolarmente efficiente su sistemi giovani e vicini, dato che la luminosità intrinseca del pianeta diminuisce con l'età e che la separazione effettiva del pianeta dipende dalla distanza del sistema stesso. Sul Very Large Telescope a Paranal (Chile) due strumenti sono dedicati a questo tipo di ricerca: NACO e SPHERE. NACO é stato pensato come predecessore e prototipo di SPHERE, ma viene mantenuto grazie alle sue performance ancora competitive ed ad alcune caratteristiche che non sono presenti in SPHERE. SPHERE ha visto la sua prima luce in Maggio 2014 ed é ora pronto per cominciare una survey dedicata alla scoperta di pianeti attorno a sistemi giovani e vicini, NISUR. Questo strumento é composto da tre sottosistemi: IRDIS, IFS e ZIMPOL. IRDIS é una camera infrarossa cui detector é suddiviso in due porzioni uguali per sfruttare l'immagine simultanea del target in due filtri adiacenti. IFS é lo spettrografo di SPHERE, permette di estrarre lo spettro del pianeta con risoluzioni di 30 e 50 a seconda della banda spettrale utilizzata. ZIMPOL é l'unico sottosistema che lavora nel visibile, viene utilizzato per osservare la polarizzazione dei sistemi planetari. In questo lavoro viene presentato lo strumento SPHERE e il suo predecessore NACO, focalizzando sui risultati e sulle performance nella caratterizzazione dei sistemi planetari.

碩士
中國文化大學
美術學系
107
Lotus enriches the landscape and provides continuous nutrient to the world, brightens human civilization, and further enhances the spiritual level that human beings pursue. Poets and artists create poem and art work through the beauty of lotus thus enrich human being’s aesthetic culture.Paintings and poemsare Imagery artistic expressions of human’s emotions and thoughts. Even though the forms of presentation are different, there is common aesthetic appreciation between poem and painting. Therefore, the study uses the imagery of spiritual inspiration given by lotus poems as the motivation of painting creation to combine literature with painting to complete the research for the art creationof painting. 　　The structure of the study starts with the explanation of research motivation, purpose, scope and method before introducing the cultural and esthetics connotation of lotus. In chapter three, it explores the presentation of lotus in art; in chapter four, the author analyzes the concept of painting and the artwork of the “imagery of lotus” for the poetic lotus done by the author; chapter five is the conclusion of the creation and research experience as well as the self-expectation and outlook for the extended creation in the future.