Dissertationen zum Thema „Radula (plantes)“

La radulanine A est une substance naturelle identifiée dans les années 1970 chez des hépatiques du genre Radula et dont l’activité phytotoxique a été récemment mise en évidence. L’objectif de la thèse a été de déterminer le mode d’action de cette substance en utilisant Arabidopsis thaliana comme plante modèle. La mise au point d’une voie de synthèse totale en 5 étapes a permis de synthétiser la radulanine A ainsi que des analogues structuraux en quantité suffisante pour réaliser l’étude biologique. Cette nouvelle voie de synthèse utilise une étape finale d’extension de cycle par photochimie en flux à partir d’un chromène désigné « Radula chromène » dans le manuscrit. Ce composé, ainsi que les autres intermédiaires de cette voie de synthèse, sont des molécules naturelles également présentes chez des hépatiques du genre Radula. Parmi ces analogues, le Radula chromène et la tylimanthine B présentent une phytotoxicité similaire à celle de la radulanine A. En revanche, l’analogue O-méthylé du Radula chromène apparait biologiquement inactif, suggérant que le groupement phénolique est indispensable à l’activité phytotoxique des composés étudiés. L’étude de la phytotoxicité des analogues a ainsi permis d’apporter les premiers éléments reliant structure et activité phytotoxique de la radulanine A et de ses analogues naturels. L’impact de ces différentes molécules sur le fonctionnement de la chaîne de transfert d'électron photosynthétique a été finement étudié via des analyses de fluorescence des chlorophylles. Les données obtenues indiquent que les analogues bioactifs inhibent le rendement de la chaîne de transfert d’électron photosynthétique au sein des plantules traités. Les analyses de thermoluminescence menées sur des photosystèmes II isolés indiquent que la radulanine A et le Radula chromène, mais pas l’analogue chromène O-méthylé, inhibent la fonctionnalité du site QB du photosystème II. Cette étude établit donc une corrélation forte entre inhibition de la phase photochimique de la photosynthèse et phytotoxicité de la Radulanine A et de ses analogues bioactifs. La Radulanine A est ainsi la première molécule à structure dihydrooxépine identifiée comme inhibitrice de ce site. En parallèle, l’effet du Radula chromène sur le métabolisme de plantules d’Arabidopsis a été étudié via une approche métabolomique par GC-MS. Les quatre-vingt-dix-huit métabolites détectés et quantifiés dans les plantules au cours de cette étude sont majoritairement issus du métabolisme primaire (sucres, acides aminés, acides organiques, purines). Quatre-vingt-deux métabolites présentent une différence significative d’abondance après traitement par le Radula chromène. Les variations sont rapides, et essentiellement observées en réponse à la plus forte dose (400 µM) appliquée. L’application du Radula chromène induit une réduction de la quantité de la plupart des métabolites détectés, suggérant un impact sur la globalité du métabolisme primaire des plantules. Des expériences préliminaires ont été réalisées pour établir un lien fonctionnel entre l’effet du Radula chromène sur le métabolisme et sa phytotoxicité. Dans l'ensemble, l’élaboration d’une nouvelle synthèse totale courte de la radulanine A a permis de définir le potentiel d’inhibition de la photosynthèse par la radulanine A et certains analogues structuraux. Des études supplémentaires ont permis d’identifier la radulanine A, ainsi que le Radula chromène, comme inhibiteurs du photosystème II au sein du site QB. L’étude de l’impact du Radula chromène sur le métabolome primaire des plantules suggère que l’inhibition de la photosynthèse ne serait pas le seul mode d’action responsable de la phytotoxicité. Des analyses complémentaires à l’étude métabolomique telle qu’une étude lipidomique permettrait la vérification de cette hypothèse
Radulanin A is a natural substance identified in the 1970s in liverworts of the Radula genus, and recently shown to have phytotoxic activity. The purpose of this PhD project was to determine the mode of action of this substance, using Arabidopsis thaliana as a model plant. The development of a 5-step total synthesis route made it possible to synthesize radulanine A and structural analogues in sufficient quantity to carry out biological studies. This new synthetic route employs a final cycle-extension step by flow photochemistry starting from a chromene designated "Radula chromene" in the manuscript. This compound, as well as the other intermediates of this synthetic route, are natural molecules also found in liverworts of the Radula genus. Of these analogues, Radula chromene and tylimanthin B exhibit phytotoxicity similar to that of radulanin A. In contrast, the O-methylated analog of Radula chromene appeared biologically inactive, suggesting that the phenolic group is essential for the phytotoxic activity of the studied compounds. The study of the phytotoxicity of the analogues thus provided the first evidence linking the structure and phytotoxic activity of radulanine A and its natural analogues. The impact of these different molecules on the photosynthetic electron transfer chain was studied in detail using chlorophyll fluorescence analyses. The data obtained indicate that the bioactive analogues inhibit the performance of the photosynthetic electron transfer chain in treated seedlings. Thermoluminescence analyses carried out on isolated photosystems II indicate that radulanin A and Radula chromene, but not the O-methylated chromene analog, inhibit the activity of the QB site of photosystem II. This study therefore establishes a strong correlation between inhibition of the photochemical phase of photosynthesis and phytotoxicity of radulanine A and its bioactive analogues. Radulanin A is thus the first molecule with a dihydrooxepin structure to be identified as an inhibitor of this site. In parallel, the effect of Radula chromene on the metabolism of Arabidopsis seedlings was studied using a GC-MS metabolomics approach. The ninety-eight metabolites detected and quantified in the seedlings during this study were mainly derived from primary metabolism (sugars, amino acids, organic acids, purines). Eighty-two metabolites showed a significant difference in abundance after treatment with Radula chromene. Variations are fast, and mainly observed in response to the highest dose (400 µM) applied. The application of Radula chromene induced a reduction in the quantity of most of the metabolites detected, suggesting an impact on the overall primary metabolism of the seedlings. Preliminary experiments were carried out to establish a functional link between the effect of Radula chromene on metabolism and its phytotoxicity. Overall, the development of a new short total synthesis of radulanin A defined the potential for inhibition of photosynthesis by radulanin A and certain structural analogues. Further studies identified radulanine A and Radula chromene as photosystem II inhibitors within the QB site. Investigation of the impact of Radula chromene on the seedling primary metabolome suggests that inhibition of photosynthesis may not be the only mode of action responsible for phytotoxicity. Complementary analyses to the metabolomic study, such as a lipidomic study, would enable this hypothesis to be verified

Context. For over 12 yr, we have carried out a precise radial velocity (RV) survey of a sample of 373 G- and K-giant stars using the Hamilton Echelle Spectrograph at the Lick Observatory. There are, among others, a number of multiple planetary systems in our sample as well as several planetary candidates in stellar binaries. Aims. We aim at detecting and characterizing substellar and stellar companions to the giant star HD 59686 A (HR 2877, HIP 36616). Methods. We obtained high-precision RV measurements of the star HD 59686 A. By fitting a Keplerian model to the periodic changes in the RVs, we can assess the nature of companions in the system. To distinguish between RV variations that are due to non-radial pulsation or stellar spots, we used infrared RVs taken with the CRIRES spectrograph at the Very Large Telescope. Additionally, to characterize the system in more detail, we obtained high-resolution images with LMIRCam at the Large Binocular Telescope. Results. We report the probable discovery of a giant planet with a mass of m(p) sin i = 6.92(-0.24)(+0.18) M-Jup orbiting at a(p) = 1.0860(-0.0007)(+0.0006) aufrom the giant star HD 59686 A. In addition to the planetary signal, we discovered an eccentric (e(B) = 0.729(-0.003)(+0.004)) binary companionwith a mass of m(B) sin i = 0.5296(-0.0008)(+0.0011) M-circle dot orbiting at a close separation from the giant primary with a semi-major axis of a(B) = 13.56(-0.14)(+0.18) au. Conclusions. The existence of the planet HD 59686 Ab in a tight eccentric binary system severely challenges standard giant planet formation theories and requires substantial improvements to such theories in tight binaries. Otherwise, alternative planet formation scenarios such as second-generation planets or dynamical interactions in an early phase of the system's lifetime need to be seriously considered to better understand the origin of this enigmatic planet.

This Ph.D. Thesis has as general subject the study of extrasolar planets using the radial velocity technique from both, instrumental and observative, points of view. Two main parts compose the work: the upgrade of the spectrograph FOCES, a high resolution spectrograph that will be installed next year at the Wendelstein Observatory, and the search of giant planets around stars in the open cluster Messier-67 (M67).
Die vorliegende Dissertation behandelt die Suche von extra-solaren Planeten mit der Radialgeschwindigkeits Methode und zwar sowohl in Bezug auf die dafür notwendige Instrumentierung als auch auf die Beobachtung. Die Arbeit ist in zwei Teile gegliedert. Im ersten Teil werden die vorgenommenen Verbesserungen des hochauflösenden Spektrographen FOCES beschrieben, der im kommenden Jahr am Wendelstein Observatorium installiert werden wird. Der zweite Teil handelt von der Suche nach Gasplaneten im offenen Sternhaufen M67.

The detection of low-mass extra-solar planets through radial-velocity searches is currently limited by the intrinsic magnetic activity of the host stars. The correlated noise that arises from their natural radial-velocity variability can easily mimic or conceal the orbital signals of super-Earth and Earth-mass extra-solar planets. I developed an intuitive and robust data analysis framework in which the activity-induced variations are modelled with a Gaussian process that has the frequency structure of the photometric variations of the star, thus allowing me to determine precise and reliable planetary masses. I applied this technique to three recently discovered planetary systems: CoRoT-7, Kepler-78 and Kepler-10. I determined the masses of the transiting super-Earth CoRoT-7b and the small Neptune CoRoT-7c to be 4.73 ± 0.95 M⊕ and 13.56 ± 1.08 M⊕, respectively. The density of CoRoT-7b is 6.61 ± 1.72 g.cm⁻³, which is compatible with a rocky composition. I carried out Bayesian model selection to assess the nature of a previously identified signal at 9 days, and found that it is best interpreted as stellar activity. Despite the high levels of activity of its host star, I determined the mass of the Earth-sized planet Kepler-78b to be 1.76 ± 0.18 M⊕. With a density of 6.2(+1.8:-1.4) g.cm⁻³, it is also a rocky planet. I found the masses of Kepler-10b and Kepler-10c to be 3.31 ± 0.32 M⊕ and 16.25 ± 3.66 M⊕, respectively. Their densities, of 6.4(+1.1:-0.7) g.cm⁻³ and 8.1 ± 1.8 g.cm⁻³, imply that they are both of rocky composition – even the 2 Earth-radius planet Kepler-10c! In parallel, I deepened our understanding of the physical origin of stellar radial-velocity variability through the study of the Sun, which is the only star whose surface can be imaged at high resolution. I found that the full-disc magnetic flux is an excellent proxy for activity-induced radial-velocity variations; this result may become key to breaking the activity barrier in coming years. I also found that in the case of CoRoT-7, the suppression of convective blueshift leads to radial-velocity variations with an rms of 1.82 m.s⁻¹, while the modulation induced by the presence of dark spots on the rotating stellar disc has an rms of 0.46 m.s⁻¹. For the Sun, I found these contributions to be 2.22 m.s⁻¹ and 0.14 m.s⁻¹, respectively. These results suggest that for slowly rotating stars, the suppression of convective blueshift is the dominant contributor to the activity-modulated radial-velocity signal, rather than the rotational Doppler shift of the flux blocked by starspots.

La recherche des exoplanètes traverse aujourd'hui une période décisive. D'un côté, notre connaissance des planètes géantes gazeuses s'est considérablement développée, et l'objectif de la recherche est maintenant de caractériser leurs propriétés physiques et de mieux comprendre leurs mécanismes de formation et d'évolution. D'un autre côté, la précision et la stabilité des instruments ont atteint un niveau qui rend techniquement possible la détection de planètes telluriques situées dans la zone habitable de leur étoile. Cependant, les perturbations du signal dues à l'étoile elle-même constituent un obstacle important à cette avancée. Mon travail de thèse se situe à la rencontre de ces problématiques. Il a consisté d'une part en l'analyse de deux relevés de vitesses radiales visant des étoiles relativement exotiques pour la recherche d'exoplanètes: les étoiles naines de type AF massives. Ce travail a donné lieu à la première caractérisation de la population de planètes géantes autour de ces étoiles et a montré que les mécanismes de migration planétaire étaient au moins partiellement inhibés autour de ces étoiles par rapport aux étoiles de type FGKM. Dans un second temps, j'ai conduit les observations et l'analyse des premiers résultats de deux grands relevés de vitesses radiales débutés pendant ma thèse et visant à détecter des planètes géantes en orbite autour d'étoiles jeunes et proches. Ces étoiles jeunes sont les seules sources pour lesquelles une exploration complète des planètes géantes à toutes les séparations devient possible, par combinaison des techniques de vitesses radiales et de l'imagerie. Cette combinaison permettra de tester de manière unique les modèles de formation et d'évolution planétaire. Les résultats provisoires de ces relevés indiquent une absence de planètes géantes à très courte séparation (Jupiters chauds) autour de nos cibles. Un autre résultat intéressant est la découverte d'une binaire spectroscopique eccentrique au centre d'un système planétaire imagé à grande séparation. Pour compléter cette approche observationnelle et mieux évaluer la détectabilité des exoplanètes semblables à la Terre, j'ai étalonné et caractérisé un modèle entièrement paramétré de l'activité d'une étoile semblable au Soleil et de son impact sur les vitesses radiales. Je l'ai dans un premier temps étalonné en comparant ses résultats à ceux obtenus à partir d'observations des zones actives du Soleil, puis je l'ai utilisé pour caractériser l'impact de l'inclinaison de l'étoile sur le signal induit par l'activité. Ce modèle paramétré ouvre de très nombreuses possibilités, étant en effet potentiellement adaptable à des types d'étoiles et d'activité différents. Il permettrait ainsi de caractériser les perturbations en vitesses radiales attendues pour chaque cas testé, et donc à la fois de déterminer quelles étoiles et quels types d'activité sont les plus favorables pour la détection de planètes de masse terrestre dans la zone habitable. En explorant ces trois problématiques en apparence très diverses mais complémentaires, j'y ai retrouvé un motif commun, celui de l'importance des étoiles elles-mêmes et de la physique stellaire pour la recherche d'exoplanètes
The search for exoplanets has reached a decisive moment. On the one hand, our knowledge of giant gaseous planets has significantly developed, and the aim of the research is now to characterize their physical properties and to better understand the formation and evolution processes. On the other hand, the instrumental precision and stability have reached a level that makes it technically possible to detect telluric planets in the habitable zone of their host star. However, the signal alterations induced by the star itself definitely challenge this breakthrough. My PhD stands at the crossroads of these problems. It consisted first in the analysis of two radial velocity surveys dedicated to stars somewhat exotic to exoplanet searches: the massive AF dwarf stars. This work has led to the first characterization of the giant planet population found around these stars and has showed that the planetary migration mechanisms were at least partially inhibited around these stars compared to FGKM stars. I then made the observations and the first analysis of two radial velocity surveys dedicated to the search for giant planets around young, nearby stars. Young stars are the only sources for which a full exploration of the giant planets at all separations can be reached, through the combination of radial velocities techniques and direct imaging. Such a combination will allow to test uniquely the planetary formation and evolution processes. The first results of these surveys show an absence of giant planets at very short separations (Hot Jupiters) around our targets. Another interesting result is the detection of an eccentric spectroscopic binary at the center of a planetary system imaged at a wide separation. To complete this observational approach and better estimate the detectability of Earth-like planets, I calibrated and characterized a fully parameterized model of the activity pattern of a Sun-like star and its impact on the radial velocities. I first calibrated it by comparing it to the results obtained with observations of the solar active structures, and then characterized the impact of stellar inclination on the activity-induced signal. Such a fully parameterized model is potentially adaptable to different types of stars and of activity and would thus allow to characterize the expected radial velocity jitter for each tested case, and then allow both to determine which types of stars and of activity patterns are the most favorable for detecting Earth-like planets in the habitable zone. While investigating these three seemingly different but complementary topics, I found that they shared a basic feature, namely the importance of the stars themselves and of stellar physics in exoplanet searches

Neste trabalho estudamos a questão de simetria de soluções positivas de equações e sistemas de equações diferenciais parciais. Descrevemos em detalhe a demonstração de dois resultados sobre simetria radial, um para equações em domínios limitados e outro para sistemas de equações no espaço todo. Ambas as demonstrações baseiam-se no método dos moving planes. Em seguida aplicamos um dos resultados mencionados acima para a equação de Choquard.
In this work we study the question of symmetry for positive solutions of equations and systems of partial differential equations. We describe in detail the proof of two results on radial symmetry, one for equations in bounded domains and the other for systems of equations in the whole space. Both proofs are based on the method of moving planes. We apply one of the results mentioned above for the Choquards equation.

Extrasolar planetary surveys have discovered about 780 extrasolar planets and more than 100 multiple planetary systems to date, with the largest fraction of them being confirmed by the radial velocity detection method. Multiple planetary systems, especially those contain pairs of planets in mean-motion resonances, are particularly interesting because their current orbital architectures provide constraints for orbital evolution of planetary systems. Precisely determining the orbital and dynamical state of multiple planetary systems with radial velocity measurements is important. New results from an analysis of radial velocity data of the HD 82943 planetary system based on 10 years of measurements obtained with the Keck telescope is presented in this thesis. Previous studies have shown that the HD 82943 system has two planets that are likely in 2:1 MMR, with the orbital periods about 220 and 440 days (Lee et al. 2006). However, alternative fits that are qualitatively different have also been suggested, with the two planets in 1:1 resonance or the addition of a third planet possibly in a Laplace 4:2:1 resonance with the other two (Goździewski & Konacki 2006; Beaugé et al. 2008). Here based on the X^2 minimization method combined with parameter grid search, the orbital parameters and dynamical states of the qualitatively different types of fits have been investigated. The results support the coplanar 2:1 MMR configuration for this system and fits of the 1:1 resonance and the 3-planet Laplace resonance are ruled out according to X^2 statistic and dynamical instability. The inclination of the HD 82943 system is well constrained at about 20°C. The system contains two planets with masses of about 4.64 MJ and 4.66 MJ and orbital periods of about 219 and 442 days for the inner and outer planet, respectively. The best fit is dynamically stable with two resonance angles θ 1 = λ1 - 2λ2 + ϖ1 and θ 2 = λ1 - 2λ2 + ϖ 2 librating around 0°. Based on the best fit, the origin of the 2:1 MMR of the HD 82943 planetary system has been explored by N-body simulations with forced inward migration of the outer planet. This research has demonstrated the importance of dynamical fitting for multiple planetary systems with radial velocity measurements. It also fulfills the cases of planetary systems in mean-motion resonances such that more generic understanding of the orbital evolution of planetary systems can be obtained.
published_or_final_version
Earth Sciences
Master
Master of Philosophy

This thesis concerns the cataloguing and characterisation of extrasolar planets, an important topic given its potential to inform theories of planet formation and evolution, and its relevance for future studies defining and assessing the habitability of other worlds. The first aspect of the study is the calculation of orbits, using radial velocity measurements coupled with Bayesian and Markov chain Monte Carlo methods, to produce a catalogue of orbital elements for a sizeable sample of planets. This constitutes a self-consistent, uniformly-derived catalogue, useful for statistical planetary population and formation studies, to be contrasted with other databases of planetary parameters, which are in general compilations of measurements from different sources and using various techniques. The orbital elements determine important star-on-planet forcings (for example ultra-violet irradiation, which has significant impacts on planetary (photo)chemistry and dynamics), and this study also looks at characterising planets explicitly in terms of their atmospheres. A 1D radiative transfer model for planetary transmission spectroscopy has been produced, and made freely-available for use by the community. This method is particularly useful since it allows the retrieval of first-order abundances of trace atmospheric molecules, which in turn can be used to estimate parameters such as the C/O ratio, potentially providing further constraints on planetary formation processes. The code in question has been validated by comparison to models in the literature, and applied to several real planetary atmospheres. It has also been extended by incorporating a method to estimate the opacity due to scattering particles in clouds and haze layers. If present in an atmosphere such phenomena can lead to the persistence of various parameter degeneracies, and limit the extent to which inferences can be drawn from spectra (leading to potentially order-of-magnitude errors in estimates of molecular abundances). Future extensions to this work could include the development of an automated inversion framework, utilising joint Bayesian/Markov chain Monte Carlo techniques to explore the parameter space of all relevant atmospheric quantities in order to retrieve a complete solution that is consistent with observations.

Flows, instabilities, and magnetism play significant roles in the internal and atmospheric dynamics of objects ranging from the smallest exoplanets to the largest stars. These phenomena are governed by the equations of magnetohydrodynamics (MHD), which link the flows and magnetic fields, and from which the operational parameters and growth rates of instabilities can be recovered. Here we present an overview of interesting phenomena (such as the internal dynamics of stellar and planetary objects, as well as instabilities which might operate within these environs), as well as computational techniques by which these phenomena might both be understood and analysed (through both ‘simplifications’ of the MHD equations and different numerical/computational approaches). We first present an investigation into the Heat-Flux-Driven Buoyancy Instability (HBI) within stellar and planetary atmospheres, considering both the parameter space it might operate within as well as its non-linear effects during said operation. We find that whilst the HBI may be able to play a role in Solar, stellar and planetary atmospheres, it is likely to be quite limited in scope, only operating within small regions. However, its dramatic consequences for heat transport in the non-linearly evolved state, and the prospects that it may operate outside the narrow regimes that our analytical analysis suggested, suggest that it may merit further study. This is followed with a discussion of a method by which the surface flows of exoplanets might be measured: The Rossiter-Mclaughlin Effect at Secondary Eclipse (RMse). We formulate the effect, showing that the formalism is identical to the traditional Rossiter-Mclaughlin effect, albeit in a different frame (a planet transiting a star becomes a star transiting a planet), and consider its observational implications: the effect should be observable for the brightest planet hosting stars using upcoming 40m-class telescopes (i.e.E-ELT). We finish with a series of 3D anelastic simulations of fully convective stars, designed to investigate how the internal flows are affected by varying stellar parameters, as well as a possible link between residual entropy and differential rotation contours, and a method by which this link can be used (via the thermal wind equation - TWE) to extrapolate the internal rotation. We find a clear transition between ‘solar-like’ and ‘anti-solar’ internal dynamics, characterised in the meridional circulation, differential rotation, residual entropy, and angular momentum flux profiles. Furthermore we find that, whilst the alignment between residual entropy and differential rotation contours is somewhat varied, the resultant extrapolation, via the TWE, produces a generally good fit to the differential rotation contours, suggesting a general robustness to the theory.

Depuis la première détection d'une planète extrasolaire autour d'une étoile de type solaire par Mayor et Queloz (1995), plus de 1500 planètes ont été découverts. Actuellement il existe un énorme intérêt à découvrir et caractériser des planètes semblables à la Terre, en particulier celles situées dans la zone habitable de leur étoile hôte (définie comme la distance à l'étoile hôte où la température de la planète permet l'existence d'eau liquide à la surface). La détection de planètes de type terrestre, et la recherche de biomarqueurs dans leurs atmosphères sont parmi les principaux objectifs de l'astronomie du vingt et unième siècle. La méthode des vitesses radiales (VR), consistant à mesurer le mouvement réflexe de l'étoile induit par des planètes en orbite, est une remarquable technique pour atteindre cet objectif.Pour atteindre les précisions nécessaire à la detection de telles planètes il est absolument nécessaire de concevoir des spectrographes extrêmement stables, d'avoir une très bonne compréhension de l'activité stellaire (qui peut mimer l'effet d'une planète), d'effectuer un traitement soigneux de l'atmosphère terrestre (laquelle inévitablement laisse des empreintes dans les spectres acquis depuis le sol), et de disposer d'une puissante technique pour extraire, à partir des spectres, autant d'information Doppler que possible. La recherche de planètes orbitant autour des étoiles de très faible masse, plutôt qu'autour des étoiles de type solaire, permet d'aborder dès maintenant la détection de planètes de faible masse dans la zone habitable. En effet, en gardant tout les autres paramètres égaux, le mouvement réflexe (et donc l'amplitude de la variation VR) sera plus grande si l'étoile centrale est de très faible masse. De plus les naines M ont une plus faible luminosité que les étoiles de type solaire, il en resulte des périodes orbitales courtes des planètes dans la zone habitable (~50 jours pour les naines M contre ~360 jours pour des étoiles de type solaire), entraînant à nouveau en une plus grande amplitude des VR. Une précision de ~1 m/s en VR permet la détection d'une planète dans la zone habitable d'une naine M, alors que ~0.1 m/s sont nécessaire dans le cas d'une étoile de type solaire.Cette thèse vise à optimiser l'extraction de VR des spectres des naines M à haute résolution acquis avec le spectrographe HARPS (avec une possibilité d'applications futures sur d'autres instruments comme SOPHIE, HARPS-N et le prochain spectrographe infrarouge SPIRou - prochainement mis en service au CFHT). Les effets de l'activité stellaire des naines M seront également analysées, dans le contexte de la technique des VR. Divers traceurs d'activité stellaire sont utilisés pour rejeter des fausses détections ou pour étudier les relations entre l'activité magnétique et la rotation. Dans cette thèse (Chap. 3) je calibre pour la première fois le flux dans les raies H et K du Calcium en fonction de la luminosité bolométrique et je détermine la relation entre cet estimateur R'HK et la période de rotation des naines M. Dans le chapitre 4 je décris l'implémentation d'une méthode d'extraction de VR par une minimisation du Chi-deux entre un template spectral et les spectres observés. Je démontre que cette méthode est plus précise que celle classiquement utilisée. Les raies telluriques qui affectent les mesures VR sont prises en compte dans les procédures d'analyse. Ces méthodes sont testées sur des systèmes avec des candidats planétaires, je discuterais l'analyse de certains de ces systèmes
Since the first detection of an extrasolar planet orbiting a Sun-like star by Mayor and Queloz (1995), more than 1500 have been discovered. Enormous interest is currently focused on finding and characterising Earth-like planets, in particular those located in the habitable zone of their host star (defined as the distance from the host star where the planet temperature allows liquid water to flow on its surface). Both the detection of Earth-like planets, and the search for biomarkers in their atmospheres are among the main objectives of the twenty-first century's astronomy. The method known as radial velocities (RV), that consists in the measure of the star's reflex motion induced by orbiting planets, is a promising technique to achieve that quest.The main difficulties with the RV technique are the needs of an extremely stable spectrograph, a correct understanding of stellar activity (which can mimic the effect of a planet), a careful treatment of our Earth's atmosphere (which inevitable imprints spectra taken from the ground), and the need to dispose of a powerful algorithm to extract as much Doppler information as possible from the recorded spectra. Search for planets orbiting very low-mass stars (M dwarfs) can more easily reach the goal of detecting low-mass planets in the habitable zone of their parent star, compared to solar-type stars. Indeed, everything else being equal, a lower mass of the host star implies a larger reflex motion, and thus a larger RV amplitude. Moreover, the lower luminosity of M dwarfs compared to Sun-like stars, implies shorter orbital periods from planets in the habitable zone (~50 days against ~360 days, for M dwarfs compared to solar-type stars, respectively), resulting again in a larger RV amplitude. A RV precision of ~1 m/s allows a planet detection in the habitable zone of an M dwarf, whereas ~0.1 m/s is required in the case of a solar-type stars.This thesis aims to optimise the RV extraction from HARPS high-resolution spectra (and to open similar analysis on other instruments like SOPHIE, HARPS-N and the upcoming infrared spectrograph SPIRou -- to be commissioned to the 3.6-m CFH-Telescope). The effects of stellar activity will also be analysed, and contextualised in the RV technique. Stellar activity tracers are used to reject false detections or to study the relationships between the stellar magnetic activity and rotation. In this thesis (Chap.ref{chap:mag_activity}) I calibrate for the first time the ratio between the Ca textrm{small II} Htextrm{small &}K chromospheric lines and the bolometric luminosity for M dwarfs. I determine a relationship between the R^prime_{HK}-index and the rotation period of M dwarfs. In chapter~ref{chap:template_matching} I describe my algorithm to extract RVs through a chi^2-minimisation between a stellar template and the observed spectra. I demonstrate the improved accuracy of this method. Telluric spectral lines also affect the measurements of RV and are taken into account in the analysis procedures. I tested these methods on systems with planetary candidates, and for some systems, I took in charge the Keplerian analysis

Les plants d'une solanee tropicale (solanum gilo) sont atteints d'une maladie foliaire dite des taches anguleuses provoquee par un agent pathogene fongique (stemphylium floridanum). Les symptomes necrotiques sont d'autant plus importants que les feuilles sont plus agees, les plus jeunes manifestant un niveau eleve de resistance. L'emploi d'un fongicide, le thirame, assure une excellente protection des cultures. In vitro, le developpement du champignon sur les milieux de culture usuels est marque par une grande variabilite morphologique. Seule la culture sur v8 dans des conditions d'eclairement et de temperature determinees stabilise les caracteres morphologiques et facilite la diagnose. A la suite de l'inoculation experimentale, l'attaque parasitaire debute par la penetration stomatique suivie de profondes modifications ultrastructurales des tissus foliaires. La culture du champ en presence de broyats foliaires s'accompagne de l'excretion d'enzymes hydrolytiques dans le milieu de culture. La production de cellulase est faible, celle des proteases et des pectinases est precoce, abondante et croit avec l'age des feuilles. En relation avec la resistance foliaire, la presence preponderante de l'acide chlorogenique parmi celle d'autres composes phenoliques a ete observee: soit par un taux constitutif eleve, soit par une synthese abondante et rapide induite par des eliciteurs fongiques. L'ensemble des resultats suggere que la fongitoxicite des composes phenoliques foliaires, particulierement celle de l'acide chlorogenique sur les activites enzymatiques serait en correlation avec les differentes capacites de resistance foliaire

La scoperta di pianeti che orbitano intorno ad altre stelle è uno degli eventi più importanti nell'astrofisica galattica degli ultimi due decenni. Dalla scoperta del primo esopianeta nel 1995, il numero di esopianeti scoperti è cresciuto sempre più in fretta e attualmente conosciamo più di 4,000 pianeti, molto diversi per dimensioni e distanza dalla stella ospite e anche in fattori come temperatura, massa, densità. La diversità degli esopianeti è un fattore chiave per comprendere la formazione dei sistemi planetari e in particolare la formazione del Sistema Solare e del nostro pianeta, la Terra. Questo è il motivo per cui la scienza osservativa degli esopianeti si sta concentrando su due diversi obiettivi: i) la caratterizzazione degli esopianeti, nel tentativo di determinare il raggio, la massa, la densità e la composizione degli oggetti osservati e ii) la caratterizzazione delle loro atmosfere, stabilendo gli elementi che l'atmosfera di un pianeta può supportare e i meccanismi che guidano i processi atmosferici. Caratterizzazione degli Esopianeti La fotometria, con il metodo dei transiti si è rivelato senza dubbio il metodo di scoperta di esopianeti con il maggior successo. La forza di questo metodo è il numero di parametri che possono essere ottenuti osservando il transito dei pianeti, soprattutto in combinazione con le osservazioni di velocità radiale (VR). In questo contesto, uno dei gruppi più prolifici è il Consorzio GTO di HARPS-N, che sfrutta l'alta risoluzione e l'estrema stabilità dello spettrografo HARPS-N, installato al Telescopio Nazionale Galileo, per caratterizzare e scoprire esopianeti combinando il metodo dei transiti e quello delle velocità radiali. Come collaboratore di questo gruppo, ho studiato un pianeta candidato scoperto dalla Campagna 16 della missione K2, HD 80653 b, una super-Terra che transita davanti alla sua stella con un periodo orbitale molto breve, e ho usato le VR HARPS-N per caratterizzarlo, ottenendo la sua massa e definendone la densità. Il pianeta appartiene ad una particolare classe di esopianeti: i pianeti a periodo ultra-corto, oggetti che orbitano intorno alle loro stelle con periodi estremamente brevi, più piccoli di due raggi terrestri e con composizioni simili a quella terrestre. Caratterizzazione di Atmosfere I gioviani ultra-caldi sono laboratori eccellenti per lo studio delle atmosfere esoplanetarie. Il sodio, per la sua grande sezione d'urto e per il fatto che le sue righe spettrali principali si trovano nel range spettrale della maggior parte degli spettrografi, è l'elemento più studiato, ma lo studio di nuove righe spettrali è cominciato. Righe del ferro, del titanio, del magnesio, ma anche tracce di cromo, scandio e ittrio sono state trovate negli spettri di trasmissione ad alta risoluzione dei pianeti più caldi. I due gioviani ultra-caldi KELT-9 b e KELT-20 b sono stati osservati dal programma atmosfere del gruppo italiano Global architecture of Planetary Systems (GAPS). Come membro del gruppo ho potuto esplorare più in dettaglio il metodo della spettroscopia in transito, creando due diverse routine per la caratterizzazione delle atmosfere. Il primo metodo segue approcci già utilizzati in precedenza, ma è in grado di rilevare righe spettrali deboli come quelle del magnesio, sommandole nello spazio delle velocità. Usando questo approccio ho analizzato gli spettri ad alta risoluzione di KELT-9 b e KELT-20 b e ho ottenuto i loro spettri di trasmissione, rilevando un assorbimento significativo per Na, H, Fe e Mg I. Il secondo metodo estrae gli spettri di trasmissione ad alta risoluzione e li cross-correla con modelli teorici di spettri di trasmissione. Analizzando gli spettri di KELT-20 b e utilizzando la cross-correlazione ho potuto confermare la presenza di Fe I, Fe II e Na I, trovate da analisi precedenti di altri gruppi di ricerca.
The discovery of planets orbiting around stars other than the Sun is by far the most relevant event in the galactic astrophysics of the last two decades. Since the discovery of the first exoplanet in 1995, the number of exoplanets discovered grew fast and we currently know more than 4,000 exoplanets, very diverse in dimension and distance from parent stars and also in factors as temperature, mass, density. The diversity of exoplanets is a key factor to understand more about the formation of planetary systems and in particular the formation of the Solar System and our planet, the Earth. This is the reason why observational exoplanetary science is currently focusing on two different fields: i) the characterization of exoplanets, trying to determine the radius, the mass, the density and the bulk composition of the objects observed, and ii) the characterization of their atmospheres, establishing the elements that the atmosphere of a planet supports and the mechanisms that drive the atmospheric processes. Characterization of Exoplanets Photometry with the transit method has arguably been the most successful exoplanet discovery method to date. The method’s strength is the rich set of parameters that can be obtained from transiting planets, in particular in combination with RV observations. In this framework, one of the most prolific groups is the HARPS-N Guaranteed Time Observations (GTO) Consortium, that makes use of the high resolution (R = 115,000) and extreme stability of the HARPS-N spectrograph, installed on the Telescopio Nazionale Galileo (TNG), to characterize and discover exoplanets by combining transits and RV methods. As a collaborator of this group, I studied a candidate planet discovered by K2 Campaign 16, HD 80653 b, a super-Earth planet transiting the star on a short period orbit, and used HARPS-N RV data to characterize it, finding its mass and defining its bulk density. It belongs to a peculiar class of exoplanets: the Ultra-Short Period (USP) planets, objects that orbit their stars with extremely short periods, smaller than about 2 Earth Radii and compositions similar to that of the Earth. Characterization of Atmospheres Ultra-hot Jupiters are excellent laboratories for the study of exoplanetary atmospheres. Sodium, due to its large cross-section and to the fact it is in the wavelength range of most optical spectrographs, is the most studied element, but new interesting features begin to be analyzed. Lines of iron, titanium, magnesium, but also chromium, scandium and yttrium have been found in the high resolution transmission spectra of the hottest planets. The two ultra-hot Jupiters KELT-9 b and KELT-20 b were observed in the framework of the Global architecture of Planetary Systems (GAPS) Atmosphere program. I explored more in detail the transit spectroscopy method, creating two different routines for atmosphere characterization. The first routine follows previous approaches for high-resolution spectroscopy, but is able to detect weak spectral lines such as those of magnesium, by co-adding the lines in the velocities space. Using this procedure, I analyzed the high-resolution spectra of KELT-9 b and KELT-20 b, obtaining their transmission spectra and detecting significant absorption for Na, H, Fe and Mg I. The second routine extracts the high-resolution transmission spectra of exoplanets and cross-correlates them with theoretical transmission spectra models. I analyzed the high-resolution spectra of KELT-20 b and with the cross-correlation technique I confirmed previous detections of Fe I, Fe II, and Na I.

Les travaux menés dans cette thèse s’inscrivent dans une démarche ethno-pharmacologique visant à valoriser des plantes utilisées traditionnellement en médecine au Mozambique. Cette étude a comme but principal d’apporter des éléments chimio taxonomiques concernant des espèces végétales peu décrites et de préciser la composition métabolique de parties de plante utilisées en médecine traditionnelle, pour aboutir potentiellement à de nouvelles molécules utilisables en thérapeutique. Le travail est ainsi découpé en trois parties distinctes, chacune portant sur une plante différente.La Partie 1présente l’étude phyto-chimique des racines sèches de Ptaeroxylon obliquum Radlk (Rutaceae). L’étude phyto-chimique de l’extrait chloroformique des racines de P.obliquum a permis l’isolement de cinq composés appartenant à la famille des coumarines ou de chromones dont un totalement original : un meroterpène de type chromone, le Ptaerobliquol. Les structures de ces composés ont été élucidées par différentes techniques analytiques de pointes (RMN, Spectrométrie de masse) et diffraction des rayons X.La Partie 2 porte sur l’étude phyto-chimique des écorces de tubercules de Pyrenacantha kaurabassana (Icacinaceae). Cette plante n’a été que très peu étudiée d’un point de vue phytochimique. Un criblage des métabolites présents a été réalisé, montrant la présence prépondérente de composés de la famille des quinones et des flavonoïdes. Le fractionnement de l’extrait acétate d’éthyle des écorces de tubercule a abouti à l’isolement et l’identification de 4 métabolites, dont 2 totalement originaux, appartenant à la famille des xanthones.Enfin la Partie 3 porte sur l’étude phytochimique des tiges de Monadenium lugardiae ou Euphorbia lugardiae (Euphorbiaceae). Le fractionnement de l’extrait chloroformique des tiges a permis l’isolement et l’identification de deux métabolites jamais décrits dans cette plante, le jolkinolide B, l’Hélioscopinolide F, conjointement avec la scopoletine
This PhD work is part of an ethno-pharmacological approach to enhance plant used in traditional medicine in Mozambique. The aim of this work is to elucidate major metabolites through a chemo-taxonomic approach and clarify the phytochemical composition of plant used in traditional medicine, leading potentially to new molecules of therapeutical interest.The work is thus cut into three parts, each focusing on a different plant.The Part 1describes the phytochemical study of dry roots of Ptaeroxylon obliquum Radlk (Rutaceae). The phytochemical study of the chloroform extract of the roots of P. obliquum resulting in the isolation of five compounds belonging to coumarin or chromone. A totally original meroterpenoid chromone was then isolated and elucidated: the Ptaerobliquol. Structures of these metabolites were elucidated by various analytical techniques (NMR, mass spectrometry) and X-ray diffraction.Part 2 focuses on the phyto-chemical study of bark tubers of Pyrenacantha kaurabassana (Icacinaceae). Few phytochemical data were available about this plant in the litterature. Screening of metabolites was so carried out, showing the preponderant presence of compounds belonging to the family of quinones and flavonoids. The study of the ethyl acetate extract of the bark of tuber resulted in the isolation and identification of four metabolites, including two totally original, belonging to the family of xanthones.Finally, Part 3 focuses on the phytochemical study of stems of Monadenium lugardiae or Euphorbia lugardiae (Euphorbiaceae). Fractionnation of the chloroform extract of the stemshas led to the isolation and identification of two metabolites never described in this plant, jolkinolide B, the Hélioscopinolide F, together with scopoletin

Since the discovery of the first planetary mass companion around a pulsar star (Wolszczan and Frail 1992) and shortly after around a star similar to our Sun (51 Peg Mayor and Queloz 1995), many steps have been done in exoplanet science. This led to a rapidly growing sample of detected planets: the minimum mass of the companions is decreasing fast, and is now close to the Earth mass. New and more precise instruments have been built and many others are planned. The final goal is the discovery of Earth twins and, ultimately, traces of extrasolar life. As learnt with the discovery of 51 Peg, about fifteen years ago, observations often open new questions about how the discovered planets can form and survive, ending in the needs of more sophisticated theories to address these items. Many statistical studies have been done using information coming from more than a decade of extensive searches for exoplanets, trying to answer questions either related to the distribution of the properties of those objects, such as the mass, orbital period and eccentricity (Lineweaver and Grether 2003; Cumming et al. 2008) as well as about the relevance of the host star characteristics (mass, metallicity) on the final frequency and distribution of planetary systems (see Fischer and Valenti 2005; Santos et al. 2004b; Johnson et al. 2007; Bonavita and Desidera 2007; Valenti and Fischer 2008; Kennedy and Kenyon 2008; Bonavita et al. 2010). Since the most successful techniques (radial velocity and transit) have focused on the inner (< 5 UA) environment of main sequence solar-type stars, most of the available informations on the frequency of planets concern this kind of targets. In this context it is useful and crucial to learn as much as possible from the available data. In addition it is also very important to determine the frequency of planets in binaries. This is an important issue in the field of extrasolar planets studies, because of its relevance for an estimate of the global planet population of our Galaxy (more than half of solar type stars are in binary or multiple systems as reported in Duquennoy and Mayor 1991) and the clues it can give to our understanding of planet formation and evolution. The study of the properties of planets in binaries, and any difference to those of the planets orbiting single stars, would shed light on the effects caused by the presence of the companions. The SARG survey (Desidera et al. 2010) searches for planets in binary stars, an environment usually excluded from the RV surveys. Another peculiarity of the survey stars is their activity level, because the sample has many stars relatively active, which makes the distinction of any signal due to a planet very tricky. In this thesis we present the results on the discovered planet, the method we used to detect it, the error analysis, the stellar activity analysis and finally the study on the frequency of planet in the binary system. In the Chapter 1 I will try to put our work in context, by summarizing the status of the art of the extrasolar planet research and knowledge, both on the theoretical and observational side, in particular in binary star systems. First I will present an overview of the techniques for detecting extrasolar planets and of the planet formation theories. Then I will summarize the properties of the exoplanets as they come from the observational results, finally focusing on the properties and formation of the planet in binary system. Chapter 2 reviews the SARG survey, the instrument used for observations, the aims of this project and the sample observed. Chapter 3 includes the description of the data reduction technique and a detailed overview on the data analysis code. In the Chapter 4 I will present a detailed description of the analysis of the survey. We started with a thorough error analysis to distinguish the “noise” contributions from the planet signal. We performed also a detailed jitter study for the whole stars sample for monitoring the most important contribution to the errors. After this analysis, I will go into detail with the presentation of the trend study on the survey and the search for planet candidates using an IDL code that I personally wrote. This code includes the study of the periodogram for each RV data set, and the Keplerian orbit modeling due to the presence of the possible companion of the observed star. Statistical tests on significativity of the periodicity and the computation of the orbital parameter error bars were performed for a more complete analysis. In the Chapter 5 the discovered planet is presented. I personally dealt with the computation of the orbital parameters of the planet, and also contributed to the jitter analysis of the stars and to obtain the contrast limit on companion masses of the A component. Chapter 6 analyzes how we investigated on a peculiar stellar activity case in the survey. I personally dealt with the computation of the activity index to prove the relation between the RV variations and the stellar activity cycle. In the Chapter 7 I will include the results on a planet which was discovered by other authors, but, that we could find with more observations. I will present the periodogram and Keplerian orbit analysis compared to the results of the other researchers group. Chapter 8 gives a brief overview of the current knowledge on the frequency of planets, and a detailed description on the results came from the Monte Carlo simulation for the SARG survey. In the Chapter 9 I finally summarizes the conclusions and future perspectives of the work.
Dalla scoperta del primo compagno di massa planetaria attorno a una stella pulsar (Wolszczan and Frail 1992) e da quella, di poco successiva, attorno ad una stella simile al nostro Sole (51 Peg Mayor and Queloz 1995), si sono compiuti numerosi progressi nella scienza che si occupa degli esopianeti. Sono stati costruiti strumenti nuovi e sempre più precisi e molti altri sono in fase di studio e realizzazione. Ciò ha portato ad un campione rapidamente crescente di pianeti rivelati, inoltre la massa minima dei pianeti extrasolari si è ridotta velocemente ed ora è vicina a quella della Terra. Lo scopo finale è quello della scoperta di pianeti il più possibilmente simili alla Terra ed, infine, di tracce di vita extrasolare. Con la scoperta di 51 Peg, circa quindici anni fa, si è imparato come le osservazioni sollevino spesso nuovi dubbi riguardo le teorie di formazione ed evoluzione, concludendosi con la necessità di sviluppare teorie più sofisticate per affrontare tali questioni. Grazie alle informazioni provenienti da più di un decennio di ricerca di pianeti extrasolari, sono stati eseguiti numerosi studi statistici per cercare di rispondere a domande correlate alla distribuzione delle proprietà di questi oggetti, come massa, periodo orbitale ed eccentricità (Lineweaver and Grether 2003; Cumming et al. 2008), come pure a quelle riguardanti le caratteristiche delle stelle ospitanti (massa, metallicità) sulla frequenza e distribuzione finale dei sistemi planetari (consultare Fischer and Valenti 2005; Santos et al. 2004b; Johnson et al. 2007; Bonavita and Desidera 2007; Valenti and Fischer 2008; Kennedy and Kenyon 2008; Bonavita et al. 2010). Poichè le tecniche di maggior successo (velocità radiali e transiti) si sono focalizzate sull’ambiente interno (< 5UA) per stelle di tipo solare di sequenza principale, gran parte delle informazioni disponibili sulla frequenza di pianeti riguardano questo tipo di target. In questo contesto è, quindi, fondamentale analizzare quanto possibile i dati osservativi. Inoltre, studiare la frequenza di pianeti in stelle binarie è di grande interesse, in quanto più della metà delle stelle di tipo solare si trova in sistemi binari o multipli (Duquennoy and Mayor 1991), e quindi una tale informazione può fornire indicazioni sulla formazione ed evoluzione dei pianeti. Lo studio delle proprietà dei pianeti in stelle binarie, confrontato con le peculiarità dei pianeti ospiti di stelle singole, può chiarire quali possano essere gli effetti causati dalla presenza dei compagni planetari. La survey SARG (Desidera et al. 2010) è dedicata a ricercare pianeti in stelle binarie, un ambiente di solito non preso in considerazione dalla maggior parte delle survey che si basano sulla misurazione delle velocità radiali delle stelle. Questo è dovuto principalmente alla difficoltà di isolare le componenti vicine nella fenditura e, quindi, ad evitare di andare incontro a problemi di contaminazione. Un’altra peculiarità delle stelle del nostro campione è il loro livello di attività. Molti oggetti sono relativamente attivi, il che rende la distinzione del segnale planetario molto delicata, ma allo stesso tempo molto interessante da analizzare. In questa tesi si presentano i risultati dell’unico pianeta scoperto, il metodo che è stato utilizzato per rilevarlo, l’analisi degli errori effettuata per l’intero campione, includendo anche la trattazione sull’attività stellare, e si conclude con uno studio sulla frequenza dei pianeti in sistemi binari che risulta dall’analisi della survey. Nel Capitolo 1 si contestualizzerà il lavoro, riassumendo lo stato dell’arte della ricerca dei pianeti extrasolari e la conoscenza in particolare, sia dal punto di vista teorico, sia osservativo, dei pianeti scoperti in sistemi stellari binari. Per prima cosa si presenterà una panoramica delle tecniche per la rilevazione di pianeti extrasolari e delle teorie della formazione dei pianeti. In seguito verranno riassunte le proprietà dei pianeti extrasolari che provengono dai risultati osservativi e, per concludere, ci si focalizzerà sulle proprietà della formazione dei pianeti in sistemi binari. Nel Capitolo 2 si presenterà la survey SARG, a partire dalla descrizione dello strumento utilizzato per le osservazioni e si proseguirà con l’esposizione degli obiettivi di questo progetto, la presentazione del campione di stelle osservato e lo stato del programma. Il Capitolo 3 descriverà la tecnica di riduzione dei dati ed include una panoramica dettagliata sul codice di analisi dei dati. Nel Capitolo 4 presenterò una descrizione dettagliata delle analisi delle stelle del campione. Illustrerò come per prima cosa sia stata effettuata un’analisi approfondita degli errori per distinguere il contributo “ rumoroso” dall’eventuale segnale planetario e, successivamente, sia stato eseguito uno studio dettagliato sul jitter per l’intero campione di stelle, in quanto il suo contributo è molto importante nell’analisi delle piccole variazioni delle velocità radiali. Dopo questa analisi entrerò in dettaglio presentando lo studio sui trend del campione e la ricerca dei pianeti candidati utilizzando un codice che ho personalmente implementato. Questo programma comprende lo studio del periodogramma per ogni set di dati e la modellizzazione dell’orbita Kepleriana dovuta all’eventuale presenza di un compagno planetario o stellare della stella osservata. Presenterò, infine, i test statistici eseguiti sulla significatività della periodicità ed il calcolo delle barre d’errore nei parametri orbitali, al fine di ottenere un’analisi solida e completa. Nel Capitolo 5 verrà presentato il pianeta rivelato. Ho contribuito personalmente al calcolo dei parametri orbitali del pianeta, utilizzando il codice descritto nel capitolo precedente e mi sono, inoltre, occupata dell’analisi del jitter delle stelle e di ricavare il limite di massa della compagna della componente primaria, dal contrasto in banda K. Nel Capitolo 6 si analizzerà un caso peculiare di attività stellare all’interno del nostro campione. Ho personalmente calcolato un indice di attività misurato su una riga degli spettri, per verificare la relazione tra le variazioni delle velocità radiali e il ciclo di attività stellare. Nel Capitolo 7 saranno presentati i risultati su un pianeta ospite di una stella del nostro campione, ma rivelato da altri autori. Riporterò l’analisi del periodogramma e l’analisi dell’orbita Kepleriana, al fine di confrontare i nostri risultati con quelli ottenuti dagli scopritori. Il Capitolo 8 fornirà una breve panoramica delle attuali conoscenze sulla frequenza dei pianeti, e una descrizione dettagliata dei risultati ottenuti dall’analisi statistica della survey SARG. Nel Capitolo 9 riassumerò, infine, le conclusioni e le prospettive future.

Tese (doutorado)—Universidade de Brasília, Faculdade de Ciências da Saúde, 2006.
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A utilização de plantas com fins terapêuticos é uma das mais antigas formas de prática medicinal da humanidade. Produtos naturais, incluindo derivados de plantas, têm contribuído grandemente para o desenvolvimento de modernos fármacos. O Brasil possui uma grande tradição no uso de plantas com fins terapêuticos, com pouca ou nenhuma comprovação de suas propriedades farmacológicas. O principal objetivo dos estudos aqui apresentados foi o de aumentar o conhecimento científico sobre a ação de espécies vegetais de nossa flora utilizadas com finalidade terapêutica. Essas informações pretendem contribuir, não somente para o descobrimento de novos ligantes para receptores nucleares, como também para o descobrimento de novos fármacos que tenham sua ação modulada pelos receptores de estrogênio e de glicocorticóide. As espécies aqui estudadas, Morus nigra, Pouteria torta, Plectranthus ornatus e Ipomoea cairica têm uso comum na medicina popular do Brasil e suas ações ainda não são adequadamente conhecidas em receptores nucleares. Utilizando-se ensaio de gene repórter e transfecção em cultura de células U937, foram pesquisadas as ações de extratos e de substâncias isoladas das espécies já citadas nos receptores de estrogênios (ERa e ERb) e de glicocorticóide (GR). Nas condições experimentais o extrato etanólico de Morus nigra apresentou toxicidade para as células U937; os extratos aquoso e o hexânico não apresentaram ação agonista ou antagonista em ERa e ERb. O extrato hexânico de Pouteria torta apresentou atividade antagonista (não competitiva) em ERb e nenhuma atividade em ERa. O extrato etanólico de Ipomoea cairica apresentou efeito antagonista em ERa e nenhuma ação sobre o ERb. Com relação aos fitoconstituintes de Ipomoea cairica, o glicosídeo de arctigenina, o glicosídeo de traquelogenina, o ácido 4,5-di-O-cafeoilquínico e o ácido 3,5-di-O-cafeoilquínico ativaram a transcrição do ERa. Essa ativação foi menor do que a ativação promovida pelo estradiol. O glicosídeo de traquelogenina e o ácido 4,5-di-O-cafeoilquínico, na presença de estradiol, intensificaram a atividade transcricional do ERb. O extrato hexânico de Plectranthus ornatus aumentou a atividade transcricional do GR com intensidade igual à da dexametasona. Quando adicionados conjuntamente, o extrato hexânico de P. ornatus e dexametasona, a atividade transcricional do GR foi intensificada. Os diterpenos ácido 11R*-acetoxicolavênico, 1a,6b,7b-triacetoxi-8,13R*-epoxi-14-labden-11-ona e 1a,6b,7b-triacetoxi-9-hidroxi-8,13R*-epoxi-14-labden-11-ona, isolados do extrato hexânico de P. ornatus, não tiveram qualquer ação sobre o receptor do GR. ________________________________________________________________________________________ ABSTRACT
The use of plants for treatment and prevention of diseases is one the oldest medicinal practices. However, for several of these plants, few or none scientific evidence of their pharmacological properties are known. Natural products, including plant derivatives, have contributed to the development of new drugs. The aim of this study is evaluate four species widely used in Brazilian folk medicine, Morus nigra, Pouteria torta, Plectranthus ornatus, and Ipomoea cairica, in relation to their activities on estrogen (ERa and ERb) and glucocorticoid (GR) receptors. In the experimental conditions the ethanol extract of Morus nigra showed to be toxic for the U937 cells, the aqueous and hexane extracts did not present either an agonist or an antagonist action on ERa and ERb. The hexane extract of Pouteria torta presented non-competitive antagonist activity on ERb and no action on ERa. Ipomoea cairica hexane extract showed an antagonist effect on ERa and no action on ERβ. The compounds isolated from Ipomoea cairica, arctigenin glucoside, trachelogenin glucoside, 3,5-di-O-caffeoylquinic acid and 4,5-di-O-caffeoylquinic acid activated the transcription of ERa. This activation was lower than the activation obtained with estradiol. The trachelogenin glucoside and the 4,5-di-O-caffeoylquinic acid, in presence of estradiol, enhanced the ERb transcriptional activity. The hexane extract of Plectranthus ornatus increased the GR transcriptional activity as well as dexametasone. When were togheter, the hexane extract of Plectranthus ornatus and dexametasone, the GR transcriptional activity was enhanced. Diterpenes 11R*-acetoxykolavenic acid, 1a,6b,7b-triacetoxy-8,13R*-epoxy-14-labden-11-one, 1a,6b,7b-triacetoxy-9-hydroxy-8,13R*-epoxy-14-labden-11-one, isolated from the hexane extract of P. ornatus did not showed effects on the GR receptor. The use of plants for treatment and prevention of diseases is one the oldest medicinal practices. However, for several of these plants, few or none scientific evidence of their pharmacological properties are known. Natural products, including plant derivatives, have contributed to the development of new drugs. The aim of this study is evaluate four species widely used in Brazilian folk medicine, Morus nigra, Pouteria torta, Plectranthus ornatus, and Ipomoea cairica, in relation to their activities on estrogen (ERa and ERb) and glucocorticoid (GR) receptors. In the experimental conditions the ethanol extract of Morus nigra showed to be toxic for the U937 cells, the aqueous and hexane extracts did not present either an agonist or an antagonist action on ERa and ERb. The hexane extract of Pouteria torta presented non-competitive antagonist activity on ERb and no action on ERa. Ipomoea cairica hexane extract showed an antagonist effect on ERa and no action on ERβ. The compounds isolated from Ipomoea cairica, arctigenin glucoside, trachelogenin glucoside, 3,5-di-O-caffeoylquinic acid and 4,5-di-O-caffeoylquinic acid activated the transcription of ERa. This activation was lower than the activation obtained with estradiol. The trachelogenin glucoside and the 4,5-di-O-caffeoylquinic acid, in presence of estradiol, enhanced the ERb transcriptional activity. The hexane extract of Plectranthus ornatus increased the GR transcriptional activity as well as dexametasone. When were togheter, the hexane extract of Plectranthus ornatus and dexametasone, the GR transcriptional activity was enhanced. Diterpenes 11R*-acetoxykolavenic acid, 1a,6b,7b-triacetoxy-8,13R*-epoxy-14-labden-11-one, 1a,6b,7b-triacetoxy-9-hydroxy-8,13R*-epoxy-14-labden-11-one, isolated from the hexane extract of P. ornatus did not showed effects on the GR receptor.

The search and characterization of extrasolar planets is one of the main topics of current astronomy, with the ultimate goals of understanding the formation and evolution of planetary systems, the general conditions for the formation of life-friendly environments, and possibly detecting signature of extra-solar life. In the last decades the research of extrasolar planets underwent a steep increase of interest and different methods of detection were developed. Each of them has its own merit and lack in studying the extrasolar system architecture and the characteristics of extrasolar planets. Stars and their planetary entourage form and grow together, at least in most cases, tied by the circumstellar disk. A unique theory that can describe all the processes that happen between the protostellar cloud collapse and the final system stabilization is not available at the moment. Indirect methods are very useful to study more evolved systems, where the protoplanetary disk contribution is negligible, in their innermost regions. On the other hand, direct imaging with high-contrast instruments offers the possibility to study the early phases of the planet formation, that are not accessible to other indirect methods of planets detection, and plays a key role in current planet formation theories. This thesis focuses on the capabilities of direct imaging with SPHERE, the new high-contrast imager of VLT, in detecting planets at different stages of their evolution, coupled with radial velocities observations of old systems obtained from SARG, the old TNG echelle spectrograph. Chapter 1 briefly introduces the planet formation and evolution theories with the most important exoplanets research methods. Chapter 2 describes the SPHERE instrument used for the majority of the results presented in this thesis. In Chapter 3 I present the case of four young objects. I exploit the SPHERE visible channel to study Z CMa jets, and the near-IR channel for HD 100546 and T Cha, looking for the presence of planets. At the same time, I was able to study in detail the circumplanetary disk of HD 100546 in a quite wide spectral range: in the dedicated Section I show that the system brightest structures suggest the presence of at least three gaps in the inner regions of the disk, coupled with other structures, such as spiral arms. I detected a diffuse source at the location of the claimed planet HD 100546 b, but the nature of this emission is, however, still unknown. Lastly, LkCa15 was studied both in the visible and in the near-IR of SPHERE. In Chapter 4 I present the study of the accretion signature in a few objects. GQ Lup b accretion was observed both in H_alpha and in Paschen beta, exploiting all three SPHERE subsystems. Two systems that have already cleaned out their surroundings from gas and dust are presented in Chapter 5: HIP 80591 and HD 65426. In the latter, I first found out that one companion candidate had high probability to be bound to the star due to its position and it spectral features. These findings were later confirmed by a deeper analysis and follow up observations that demonstrate HD 65426 b, the companion I studied, is a warm Jupiter-like planet with mass between 6 and 12 M_J. In Chapter 6, I study the chromospheric activity in older binary stars in order to detect a radial velocity signal hidden by the Doppler shift induced by the activity. I found out that Ha-excess, an index based on the Halpha line, is a good indicator of the star activity when the log_RHK' index is not available and can be used also to infer stellar ages in case of stars younger then 1.5 Gyr. Moreover, HD 76073 B shows a high radial velocities scatter that can be explained by the presence of a low-mass companion (Sissa et al. 2016). Finally, in Chapter 7 I give the conclusions and explain future prospects. Appendixes are dedicated to the more technical aspects of my work, that were needed to improve instrument capabilities and data reduction, and to better defining the instrument set-ups needed to achieve different scientific aims.
La ricerca e la caratterizzazione dei pianeti extrasolari è uno dei maggiori campi di ricerca dell’astronomia attuale, con lo scopo ultimo di capire i meccanismi di formazione e di evoluzione dei sistemi planetari, le condizioni che permettono la formazione di ambienti adatti alla vita, e di trovare le prove di vita extra-solare. Negli ultimi decenni, la ricerca dei pianeti extrasolari ha visto un rapido aumento di interesse, e sono state cosí sviluppate nuove metodologie di ricerca. Ognuna di esse ha aspetti positivi e negativi per lo studio dell’architettura dei sistemi extrasolari e la caratterizzazione dei pianeti. Le stelle e il loro entourage planetario si formano e crescono assieme, per lo meno nella maggioranza dei casi, legate dal disco circumstellare. Al momento manca una teoria universale che possa descrivere tutti i processi che accadono tra le fasi del collasso della nube protostellare e la stabilizzazione finale del sistema. I metodi indiretti sono molto utili per studiare le zone interne dei sistemi più evoluti, nei quali il contributo del disco protoplanetario è trascurabile. Dall’altro lato, la tecnica dell’imaging diretto con strumenti ad alto contrasto offre la possibilità di studiare le prime fasi della formazione planetaria, non accessibili con altri metodi indiretti, e gioca un ruolo fondamentale per le attuali teorie di formazione planetaria. Questa tesi si focalizza sulle capacità dell’imaging diretto ottenuto con SPHERE, il nuovo strumento ad alto contrasto del VLT, nel rivelare pianeti in diversi stadi della loro evoluzione, e presenta uno studio complementare di sistemi vecchi basato sulle osservazioni delle velocità radiali con SARG, il vecchio spettrografo echelle del TNG. Il Capitolo 1 introduce brevemente le teorie di formazione ed evoluzione dei pianeti con i più importanti metodi di ricerca. Il Capitolo \ref{sec:sphere} descrive SPHERE, lo strumento usato per la maggior parte dei risultati presentati in questa tesi. Nel Capitolo 3 presento il caso di quattro oggetti giovani. Ho sfruttato il canale visibile di SPHERE per studiare i jet di Z CMa, e il canale nel vicino infrarosso per HD 100546 e T Cha, cercando segnali della presenza di pianeti. Allo stesso tempo, ho potuto studiare in dettaglio il disco circumstellare di HD 100546 in un intervallo spettrale relativamente ampio: nella sezione ad esso dedicata mostra che le strutture più brillanti del sistema suggeriscono la presenza di almeno tre regioni vuote nelle zone interne del disco, assieme ad altre strutture, come ad esempio bracci a spirale. Ho anche rilevato la presenza di una sorgente diffusa nella posizione attesa per il potenziale pianeta b, ma la natura di questa emissione è, tuttavia, ancora sconosciuta. Infine, LkCa 15 è stato studiato sia nel canale visibile che in quello del vicino infrarosso di SPHERE. Nel Capitolo 4 presento lo studio dei segni distintivi di accrescimento in un gruppo di oggetti. L’accrescimento di GQ Lup b è stato osservato sia in H_alpha che il Paschen beta, sfruttando tutti e tre i sottosistemi di SPHERE. Due sistemi i cui dintorni sono già stati ripuliti dal gas e dalla polvere sono presentati nel Capitolo 5: HIP 80591 e HIP 65426. In quest’ultimo, ho scoperto che uno dei candidati compagni aveva un’alta probabilità di essere legato alla stella a causa della sua posizione e delle sue caratteristiche spettrali. Queste conclusioni sono state poi confermate da un’analisi approfondita e da ulteriori osservazioni che hanno dimostrato che quel compagno, HD 65426 b, è un pianeta gioviano caldo con massa compresa tra 6 e 12 M_J. Nel Capitolo 6, studio l’attività cromosferica in stelle binarie vecchie allo scopo di identificare un segnale nelle velocità radiali nascosto dallo spostamento Doppler indotto dall’attività. Ho scoperto che Ha-excess, un indice basato sulla riga \Ha, è un buon indicatore dell’attività stellare quando l’indice \RHK\ non è disponibile e può essere anche usato per derivare l’età delle stelle nel caso siano più giovani di 1.5 Gyr. Inoltre, HD 76037 B mostra una variazione elevata delle velocità radiali che puo’ essere spiegata con la presenza di un compagno di piccola massa (Sissa et al. 2017) Infine, nel Capitolo 7 fornisco le conclusioni del lavoro ed espongo sviluppi futuri. Le appendici sono dedicate agli aspetti più tecnici del mio lavoro, che sono stati necessari per migliorare le capacità dello strumento e la riduzione dei dati, e per definire al meglio i set-up necessari allo strumento per raggiungere i differenti scopi scientifici.

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This paper describes the development of methodology for capillary electrophoresis with UV detection for the determination of 14 polyphenolic antioxidants in extracts of Connarus perrottetii var. angustifolius Radlk, a native plant of the Amazon forest. The method using capillary zone electrophoresis (CZE) allows simultaneous determination of 3-acetyilcoumarine, resveratrol, 6-hydroxycoumarin, catechin, rutin, ferulic acid, quercitrin, kaempferol, fisetin, myricetin, quercetin, caffeic acid, gallic acid and 4 hydroxicinnamic acid in the optimized conditions: borate buffer 20 mmol L-1 (pH 9.2) as work electrolyte containing 15% methanol (v /v), -20 kV potential separation, temperature 25 °C; hydrodynamic injection gravity 20 cm for 60 s. The method was validated on parameters of linearity, limit of detection, quantification limit, precision and accuracy, and was used in the analysis of aqueous infusion and ethanol, butanol and ethyl acetate plant fractions. The method was capable of identifying the antioxidants present in samples with high selectivity and sensitivity. In infusion and in ethanol and butanol fractions was found the presence of catechin and rutin as major compounds, which makes up about 0.5% of the total mass of medicinal plant. The obtained dry extracts (ethanol and butanol) allowed the concentration of rutin and catechin around 20 times compared to the dry plant. In addition, tests were performed to measure the antioxidant activity of the extracts against DPPH radical, superoxide anion radical, hydroxyl and peroxyl. A sample of aqueous infusion of 10% showed the highest activity against most free radicals. It corroborates the results of characterization by capillary electrophoresis, where catechin and rutin were determined in relatively high concentrations in the aqueous infusion. But all treatments of the samples showed good antiradicalar behavior with the methodologies applied. Against DPPH, for example, the ethyl acetate fraction showed a potential of 94,43%. Against superoxide and hydroxyl radicals, the butanol fraction showed the best performance: 64,23% and 74,97%, respectively.
Este trabalho descreve o desenvolvimento de metodologia em eletroforese capilar com detecção UV para a determinação de 14 antioxidantes polifenólicos em extratos de Connarus perrottetii var. angustifolius Radlk, planta nativa da Amazônia brasileira. O método empregando eletroforese capilar de zona (CZE) permite a determinação simultânea de 3-acetilcumarina, resveratrol, 6-hidroxicumarina, catequina, rutina, ácido ferúlico, quercitrina, canferol, fisetina, miricetina, quercetina, ácido cafeico, ácido gálico e ácido 4-hidroxicinâmco nas condições otimizadas: eletrólito de trabalho tampão borato 20 mmol L-1 (pH 9,2) contendo metanol 15% (v/v), potencial de separação -20 Kv, temperatura 25 °C; injeção hidrodinâmica por gravidade em 20 cm durante 60 s. O método foi validado nos parâmetros de linearidade, limite de detecção, limite de quantificação, precisão e exatidão e foi aplicado na análise da infusão aquosa e frações etanólica, butanólica e acetato de etila da planta. O método foi capaz de identificar os antioxidantes presentes nas amostras com alta seletividade e sensibilidade. Na infusão e nas frações etanólica e butanólica foi encontrada a presença de catequina e rutina como compostos majoritários, os quais compõe cerca de 0,5% da massa total de planta medicinal. Os extratos secos obtidos (etanólico e butanólico) possibilitaram a concentração de rutina e catequina em torno de 20 vezes em relação à planta seca. Além disso, foram realizados testes para mensurar a atividade antioxidante dos extratos frente aos radicais DPPH, ânion radical superóxido, hidroxila e peroxila. A amostra de infusão aquosa a 10% foi a que apresentou maior atividade frente à maioria dos radicais livres. Esse resultado corrobora os resultados de caracterização por eletroforese capilar, onde catequina e rutina foram determinadas em concentrações relativamente altas na infusão aquosa. Porém, todos os tratamentos das amostras apresentaram bom comportamento anti-radicalar com as metodologias aplicadas. Frente ao radical DPPH, por exemplo, a fração acetato de etila demonstrou um potencial de 94,43%. Frente aos radicais superóxido e hidroxila, a fração butanólica apresentou o melhor desempenho: 64,23% e 74,97%, respectivamente.

Trees are considered one of the most sensitive indicators of the environmental condition from all life forms. They are most suitable for the evaluation of the environmental changes. Due to the structure of crown trees have better contact with the atmosphere, so they filter the flowing air mass better than other vegetation forms, determine the processes in the ecosphere and react sensitively to the anthropogenic factors and consequently indicate the condition of the forest ecosystems by anatomical and morphological symptoms. Tree rings, their width and structure integrally reflect the complex impact of environmental factors. Therefore the role of tree rings, as the indicator of environmental conditions, is important for the evaluation of environmental changes. Forest ecosystems growing close to the pollution sources suffer the greatest impact because the concentration of harmful materials in the local pollution zone often exceeds permissible amounts. The objective of the research was to analyse the changes of annual radial increment of pine stands (Pinus sylvestris L.) in the zones of local alkalizing, acidifying and eutrophying pollution and to determine the regularities of radial increment recovery after the decrease of pollution. First time in Lithuania a comprehensive dendrochronological research on the impact of climatic factors and industrial pollution on the radial increment of Scots pine (Pinus sylvestris L.) has been carried out in the surroundings of “Akmenės... [to full text]
Medžiai yra vieni jautriausių aplinkos būklės indikatorių, iš visų gyvybės formų labiausiai tinkamų aplinkos pokyčiams vertinti. Dėl lajų struktūros ypatumų jie glaudžiau kontaktuoja su atmosfera ir daugiau negu kitos augalijos formos filtruoja pernešamo oro masę, lemia ekosferoje vykstančius procesus bei jautriai reaguoja į antropogeninius veiksnius, anatominiais ir morfologiniais požymiais indikuoja miško ekosistemų būklę. Medžių metinių rievių dinamika suteikia informaciją apie ekologines bei klimatines vietovės sąlygas, aplinkoje vykstančius reiškinius, o jų plotis ir struktūra integraliai atspindi kompleksinį aplinkos veiksnių poveikį. Labiausiai nukenčia arti taršos šaltinių augančios miško ekosistemos, kadangi vietinės taršos zonoje kenksmingų medžiagų koncentracija dažnai viršija ribines leistinas normas. Darbo tikslas – ištirti paprastosios pušies (Pinus sylvestris L.) medynų metinio radialiojo prieaugio pokyčius vietinės šarminančios, rūgštinančios ir eutrofizuojančios taršos poveikio zonose bei radialiojo prieaugio atsikūrimo dėsningumus sumažėjus taršos poveikiui. Pirmą kartą Lietuvoje atlikti išsamūs dendrochronologiniai klimato veiksnių ir pramonės taršos poveikio paprastosios pušies (Pinus sylvestris L.) metiniam radialiajam prieaugiui tyrimai „Akmenės cemento“ poveikio zonoje. Darbe taip pat analizuotas cemento dulkių poveikis paprastosios pušies metiniam radialiajam prieaugiui; įvertinti antropogeniniai radialiojo prieaugio pokyčiai „Akmenės cemento“ ir... [toliau žr. visą tekstą]

Dissertação (mestrado)—Universidade de Brasília, Faculdade de Ciências da Saúde, Programa de Pós-Graduação em Ciências da Saúde, 2015.
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Pouteria ramiflora (Mart.) Radlk., espécie comumente encontrada no Cerrado é popularmente conhecida como, “curriola” (“curiola”), “brasa-viva”, “figo-do-cerrado” entre outros. Essa planta produz frutos comestíveis e é usada na medicina popular contra hiperlipidemias e para tratar vermes, disenteria, dor e inflamação. Extratos dessa espécie apresentam atividades alelopática, anti-inflamatória, antinociceptiva, antimicrobiana, antioxidante, citotóxica, mutagênica, neuroprotetora, sendo útil no controle glicêmico e de peso. Pouteria ramiflora apresenta ainda inibição das enzimas α-amilase e α-glicosidase motivo pelo qual foi escolhida para ser estudada visando a descoberta de novos inibidores da α-amilase. A inibição dessa enzima está relacionada ao controle glicêmico em pacientes com diabetes mellitus tipo 2, uma desordem metabólica que implica em várias complicações secundárias e atinge pessoas no mundo todo. Neste trabalho foi realizado o estudo químico e o biomonitoramento da atividade inibitória da enzima α-amilase por extratos de folhas de Pouteria ramiflora. A α-amilase foi exposta aos extratos brutos, aquoso, hexânico e etanólico e a atividade da enzima foi avaliada na presença e na ausência do possível inibidor pelo método colorimétrico descrito por Bernfeld (1955), com modificações. O extrato mais ativo foi definido com a obtenção do valor de CI50 em comparação ao padrão acarbose. Esse extrato foi fracionado com o objetivo de isolar o composto ativo. Os compostos foram isolados e identificados por técnicas cromatográficas e espectrométricas como CCD, CC, CLAE-DAD, IV, CG-EM e RMN de 1H e 13C e identificados. O extrato aquoso (CI50 = 9,51 μg/mL) e a fração aquosa (CI50 = 9,71 μg/mL) desse extrato foram os mais ativos contra a enzima avaliada com valores de IC50 próximos ao padrão acaborse (CI50 = 4,2 μg/mL). Os triterpenos epifriedelanol, friedelina e taraxerol foram identificados e/ou isolados a partir do extrato hexânico e o flavonoide miricitrina, marcador do gênero, foi isolado e identificado a partir do extrato aquoso de P. ramiflora. Até onde vai o nosso conhecimento, este é o primeiro relato da identificação de epi-friedelanol, friedelina, taraxerol e do isolamento miricitrina em P. ramiflora. A presença desses compostos pode justificar, pelo menos em parte, a atividade observada nos extratos desta planta. ______________________________________________________________________________________________ ABSTRACT
Pouteria ramiflora (Mart.) Radlk., a species commonly found in Cerrado and populary known as curriola (curiola), brasa-viva, figo-do-cerrado among others. This plant produces edible fruits and is used in folk medicine as hyperlipaedemic and to treat worms, dysentery, pain and inflammation. Extracts of this species exhibit allelopathic, antiinflammatory, antinociceptive, antimicrobial, antioxidant, cytotoxic, mutagenic, neuroprotective activities and also is useful in glycemic and weight control. Because Pouteria ramiflora extracts present α-amylase and α-glucosidase inhibition, this species was chosen in this study toward the potential discovery of new α-amylase inhibitors. Inhibition of this enzyme is related to glycemic control in patients with diabetes mellitus type 2, a metabolic disorder that involves multiple secondary complications and affects people worldwide. In this work we performed the chemical and biomonitoring studies of the in vitro inhibition activity of extracts from Pouteria ramiflora against α-amylase enzyme. The aqueous, hexane and ethanol crude extracts were evaluated against α-amilase; and the enzyme activity was tested in the presence and absence of possible inhibitors by the colorimetric method described by Bernfeld (1955) with modifications. The IC50 was obtained and the most active extract was defined and compared to acarbose standard. This extract was fractionated with the purpose of isolating the active compound. The compounds were isolated and identified for chromatographic and spectrometric techniques such as TLC, CC, HPLC-DAD, IR, GC-MS and 1H NMR and 13C NMR and identified. Aqueous extracts ((IC50 = 9,51 μg/mL) and its aqueous fraction (IC50 = 9,51 μg/mL) were the most active against the α-amilase with the IC50 value similar to the standard acarbose (IC50 = 4,2 μg/mL). The triterpenes epi-friedelanol, friedelin and taraxerol were identified from the hexane extract and the myricitrin flavonoid, chemical marker of the genus Pouteria, was isolated and identified from the P. ramiflora aqueous extract. As far as know, this is the first report of the identification of epi-friedelanol, friedelin, taraxerol and the isolation of myricitrin from P. ramiflora. The presence of these compounds may help to clarify at least in part the reported biological activity for this species.

Thanks to a range of discovery methods that are sensitive to different regions of parameter space, we now know of over 900 planets in over 700 planetary systems. This large population has allowed exoplanetary scientists to move away from a focus on simple discovery, and towards efforts to study the bigger pictures of planetary system formation and evolution. The interactions between planets and their host stars have proven to be varied in both mechanisms and scope. In particular, tidal interactions seem to affect both the physical and dynamical properties of planetary systems, but characterising the broader implications of this has proven challenging. In this thesis I present work that investigates different aspects of tidal interactions, in order to uncover the scope of their influence of planetary system evolution. I compare two different age calculation methods using a large sample of exoplanet and brown dwarf host stars, and find a tendency for stellar model fitting to supply older age estimates than gyrochronology, the evaluation of a star's age through its rotation (Barnes 2007). Investigating possible sources of this discrepancy suggests that angular momentum exchange through the action of tidal forces might be the cause. I then select two systems from my sample, and investigate the effect of tidal interactions on their planetary orbits and stellar spin using a forward integration scheme. By fitting the resulting evolutionary tracks to the observed eccentricity, semi-major axis and stellar rotation rate, and to the stellar age derived from isochronal fitting, I am able to place constraints on tidal dissipation in these systems. I find that the majority of evolutionary histories consistent with my results imply that the stars have been spun up through tidal interactions as the planets spiral towards their Roche limits. I also consider the influence of tidal interactions on the alignment between planetary orbits and stellar spin, presenting new measurements of the projected spin-orbit alignment angle, λ, for six hot Jupiters. I consider my results in the context of the full ensemble of measurements, and find that they support a previously identified trend in alignment angle with tidal timescale, implying that tidal realignment might be responsible for patterns observed in the λ distribution.

Les Jupiters chauds sont des exoplanètes si proches de leur étoile que leur atmosphère peut perdre du gaz par échappement hydrodynamique. Les géantes gazeuses qui transitent sont un excellent moyen de comprendre ce processus, mais il faut étudier d'autres types de planètes pour déterminer son impact sur la population exoplanétaire. Cette thèse propose d'utiliser la spectroscopie du transit pour observer l'atmosphère de plusieurs planètes, étudier leurs propriétés et caractériser l'échappement hydrodynamique. Des raies de l'ultraviolet observées avec le télescope Hubble sont analysées avec le modèle numérique de la haute atmosphère que nous avons développé. Grâce à la raie Ly-? nous mettons en évidence les interactions énergétiques et dynamiques entre l'atmosphère des Jupiters chauds HD209458b et HD189733b et leurs étoiles. Nous étudions la dépendance de l'échappement à l'environnement d'une planète et à ses propriétés physiques, en observant une super-Terre et un Jupiter tiède dans le système 55Cnc. Grâce à des observations de HD209458b nous montrons que les raies du magnésium permettent de sonder la région de formation de l'échappement. Nous étudions le potentiel de la spectroscopie du transit dans le proche UV pour détecter de nouveaux cas d'échappement. Ce mécanisme est favorisé par la proximité d'une planète à son étoile, ce qui rend d'autant plus important la compréhension des processus de formation et de migration, qui peuvent être étudiés par l'alignement d'un système planétaire. Grâce à des mesures des spectrographes HARPS-N et SOPHIE nous étudions les alignements de 55Cnc e et du candidat Kepler KOI-12.01, dont nous cherchons aussi à valider la nature planétaire.

An ethnobotanical survey of plants used for the treatment of eye infections was carried out in the Eastern Cape Province of South Africa. The study revealed that 12 plant species are commonly used with Hippobromus pauciflorus (L.f) Radlk being the most frequent. The crude extracts of the leaves, stem bark and roots of the plant were investigated for antimicrobial activity against 10 bacterial and four fungal strains. The methanol extracts of the plant parts were the most active and showed appreciable activity against Gram-positive and Gram-negative bacteria. The methanol extracts of the leaves and stem bark inhibited the growth of fungi with activities ranging from 78.70 percent to 100 percent on Aspergillus niger and Penicillium notatum. The acetone extracts of the leaves and stem bark were active against A. niger (51.76 percent) and P. notatum (77.22 percent). The aqueous extract of Hippobromus pauciflorus leaves at 50, 100 and 200 mg/kg body weight doses were evaluated for anti-inflammatory, analgesic and antipyretic activities in male Wistar rats. Anti-inflammatory activity was studied by using carrageenan-and histamine induced oedema right hind paw volume while the analgesic effect was evaluated using formalin-induced pain and tail flick nociception response. The brewer’s yeast-induced pyrexia model was used for the antipyretic investigation. The extract at all the doses used significantly inhibited both the carrageenan- and histamine-induced inflammation in a manner that was not dose dependent. The extract reduced the formalin-induced pain licking as well as prolonged the reaction time in the tail flick-induced pain. The effects of the aqueous extract of the plant leaves at 50, 100 and 200 mg/kg body weight doses were investigated for 14 days on some biochemical parameters of male Wistar rats. The extract at all the doses tested did not significantly alter the levels of white blood cells, red blood cells, mean corpuscular volume, platelets, neutrophils, monocytes, lymphocytes and large unstained cells. While the levels of haemoglobin, packed cell volume and basophils increased at specific doses, those of mean corpuscular haemoglobin, mean corpuscular haemoglobin concentration and eosinophils decreased. In vitro antiviral activities of the plant against herpes simplex virus type 1(HSV-1) and coxsakie virus B6 were investigated. Cytotoxicity was evaluated by MTT assay in Vero cells. At concentrations ranging from 165-270/μg/ml there was significant antiviral activity against HSV-1, but toxicity was also noted. There was no antiviral activity against coxsakie virus B6. Bioactivity-guided fractionation of the leaves of H. pauciflorus yielded three known compounds. From the ethyl acetate fraction, two compounds were isolated (epicatechin and -sitosterol ) and from the n- hexane fractions, one compound (lupeol) was isolated. They were isolated and identified using various techniques. The antimicrobial, anti-inflammatory, analgesic and anti-pyretic activity of these compounds have been reported in literature. The structure and distribution of foliar appendages on the leaves of H. pauciflorus were examined by scanning electron microscope. The leaves have long unicellular nonglandular trichomes which were distributed over the mid rib and densely populated at the edges of the adaxial and abaxial surfaces. In general, the experiments and tests conducted in this study appear to have justified the use of Hippobromus pauciflorus for the treatment of eye infections and make a substantial contribution to the knowledge base of the use of herbal medicine for the treatment of the eye infections.

ν Octantis is a spectroscopic binary with a semi-major axis and period of 2.55 AU and 2.9 years, respectively. Ramm et al. (2009) discovered a 52 ms^(-1) radial-velocity (RV) perturbation with a period of 417 days in this system. All evidence, both photometric and spectroscopic, suggests the perturbation is the result of a 2.5 MJ planet orbiting the primary star. However, when assuming a “normal” prograde coplanar orbit, celestial mechanics predicts this orbit is unstable, contradicting the observed stability. Simulations by Eberle and Cuntz (2010) showed a retrograde orbit for the planet to be stable for at least 10^7 years. In this thesis, we performed a 10^8 -yr simulation of the retrograde orbit, and found it remained stable. Simulations over a range of planetary semi-major axes, eccentricities, and primary/secondary masses showed that stable retrograde orbits are not possible past a semi-major axis of 1.315 +/- 0.092 AU . Therefore, planetary retrograde orbits are most likely inherently more stable than prograde orbits owing to the absence of stability at known mean-motion resonances. Eccentricity simulations showed that the period of the planet's dominant eccentricity variation is related to the planet's semi-major axis by a second order exponential. However, retrograde orbits tend to have longer eccentricity periods than prograde orbits at the same semi-major axis. There is also evidence that this eccentricity period is connected to the orbital stability. By fitting a keplerian to both Ramm et al. (2009) and current radial velocities, the period of the ν Octantis binary was determined to be 1050.04 +/- 0.02 days with an eccentricity of 0.2359 +/- 0.001 . The planetary orbital solution for just the data reduced in this thesis gave a period of 416.9 +/- 2.1 days and an eccentricity of 0.099 +/- 0.015 , with an RMS scatter of 9.6 ms^(-1). Therefore, the orbital elements are within 1σ of the Ramm et al. (2009) elements. Assuming a retrograde coplanar orbit about the primary star then the planet has a mass of M_pl = 2.3 M_J and a semi-major axis of a_pl = 1.21 +/- 0.09 AU.

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Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior
This work aims to show how the application of frequency selective surfaces (FSS) in planar antenna arrays become an alternative to obtain desired radiation characteristics from changes in radiation parameters of the arrays, such as bandwidth, gain and directivity. In addition to analyzing these parameters is also made a study of the mutual coupling between the elements of the array. To accomplish this study, were designed a microstrip antenna array with two patch elements, fed by a network feed. Another change made in the array was the use of the truncated ground plane, with the objective of increasing the bandwidth and miniaturize the elements of the array. In order to study the behavior of frequency selective surfaces applied in antenna arrays, three different layouts were proposed. The first layout uses the FSS as a superstrate (above the array). The second layout uses the FSS as reflector element (below the array). The third layout is placed between two FSS. Numerical and experimental results for each of the proposed configurations are presented in order to validate the research
Este trabalho tem como objetivo apresentar como a aplica??o de superf?cies seletivas em frequ?ncia (FSS) em arranjos de antenas planares se torna uma alternativa interessante para se obter caracter?sticas de radia??o desejadas, a partir de altera??es em par?metros de radia??o dos arranjos, tais como largura de banda, ganho e diretividade. Al?m de analisar esses par?metros, tamb?m ? feito o estudo do acoplamento m?tuo entre os elementos do arranjo. Para realizar tal estudo, foi projetado um arranjo de antenas de microfita, com dois elementos do tipo patch, alimentado por uma rede de alimenta??o. Outra modifica??o feita no arranjo foi a utiliza??o do plano de terra truncado, com o objetivo de aumentar a largura de banda e miniaturizar os elementos do arranjo. Para poder estudar o comportamento das superf?cies seletivas em frequ?ncia aplicadas em arranjos de antenas, foram propostos tr?s layouts diferentes. O primeiro layout consiste em utilizar a FSS como superstrato (acima do arranjo). O segundo consiste em utilizar a FSS como elemento refletor (abaixo do arranjo). O terceiro layout consiste em colocar o arranjo entre duas camadas de FSS, tanto em cima quanto abaixo. Resultados num?ricos e experimentais para cada uma das configura??es propostas s?o apresentados

La mitochondrie et le chloroplaste possèdent un génome dont l’expression et la maintenance dépendent de facteurs codés par le génome nucléaire. L’ADN mitochondrial des plantes (ADNmt) est caractérisé par d’importantes activités de recombinaison qui modulent sa structure et contribuent à son évolution. Au cours de ma thèse, j’ai caractérisé l’hélicase RADA qui est impliquée dans les étapes tardives de la recombinaison homologue organellaire. RADA possède des fonctions similaires à son homologue bactérien (RadA), mais semble jouer un rôle plus important dans les organelles de plantes. L’expression du génome chloroplastique (ADNcp) repose sur deux types d’ARN polymérases : la NEP, codés par le génome nucléaire et la PEP, codés par l’ADNcp. Durant ma thèse, j’ai également étudié le rôle de TRCF, homologue du facteur Mfd et adressé aux chloroplastes. Chez les bactéries, Mfd est impliqué dans le dégagement des ARN polymérases bloquées par des lésions et le recrutement de facteurs de réparation. Chez Arabidopsis, TRCF n’est plus impliqué dans la réparation, mais semble jouer un rôle dans la régulation de l’expression des gènes chloroplastiques
The mitochondria and chloroplasts have their own genomes whose expression and maintenance depend on factors encoded by the nuclear genome. The plant mitochondrial DNA (mtDNA) is characterized by important recombination activities that modulate its structure and contribute to its evolution. During my thesis, I characterized the RADA helicase that is involved in the late stages of organelle homologous recombination. RADA has similar functions to its bacterial homolog (RadA), but seems to play a more important role in plant organelles. The expression of the chloroplast genome (cpDNA) relies on two types of RNA polymerases: NEP encoded by the nuclear genome and PEP encoded by the cpDNA. During my thesis, I also studied the role of TRCF, an homolog of the Mfd factor which is addressed to chloroplasts. In bacteria, Mfd is involved in the release of stalled RNA polymerases by lesions and the recruitment of repair factors. In Arabidopsis, TRCF is no longer involved in repair but appears to play a role in the regulation of chloroplast gene expression

The central aim for the research undertaken in this PhD thesis is the development of a model for simulating water droplet movement on a leaf surface and to compare the model behavior with experimental observations. A series of five papers has been presented to explain systematically the way in which this droplet modelling work has been realised. Knowing the path of the droplet on the leaf surface is important for understanding how a droplet of water, pesticide, or nutrient will be absorbed through the leaf surface. An important aspect of the research is the generation of a leaf surface representation that acts as the foundation of the droplet model. Initially a laser scanner is used to capture the surface characteristics for two types of leaves in the form of a large scattered data set. After the identification of the leaf surface boundary, a set of internal points is chosen over which a triangulation of the surface is constructed. We present a novel hybrid approach for leaf surface fitting on this triangulation that combines Clough-Tocher (CT) and radial basis function (RBF) methods to achieve a surface with a continuously turning normal. The accuracy of the hybrid technique is assessed using numerical experimentation. The hybrid CT-RBF method is shown to give good representations of Frangipani and Anthurium leaves. Such leaf models facilitate an understanding of plant development and permit the modelling of the interaction of plants with their environment. The motion of a droplet traversing this virtual leaf surface is affected by various forces including gravity, friction and resistance between the surface and the droplet. The innovation of our model is the use of thin-film theory in the context of droplet movement to determine the thickness of the droplet as it moves on the surface. Experimental verification shows that the droplet model captures reality quite well and produces realistic droplet motion on the leaf surface. Most importantly, we observed that the simulated droplet motion follows the contours of the surface and spreads as a thin film. In the future, the model may be applied to determine the path of a droplet of pesticide along a leaf surface before it falls from or comes to a standstill on the surface. It will also be used to study the paths of many droplets of water or pesticide moving and colliding on the surface.

The central aim for the research undertaken in this PhD thesis is the development of a model for simulating water droplet movement on a leaf surface and to compare the model behavior with experimental observations. A series of five papers has been presented to explain systematically the way in which this droplet modelling work has been realised. Knowing the path of the droplet on the leaf surface is important for understanding how a droplet of water, pesticide, or nutrient will be absorbed through the leaf surface. An important aspect of the research is the generation of a leaf surface representation that acts as the foundation of the droplet model. Initially a laser scanner is used to capture the surface characteristics for two types of leaves in the form of a large scattered data set. After the identification of the leaf surface boundary, a set of internal points is chosen over which a triangulation of the surface is constructed. We present a novel hybrid approach for leaf surface fitting on this triangulation that combines Clough-Tocher (CT) and radial basis function (RBF) methods to achieve a surface with a continuously turning normal. The accuracy of the hybrid technique is assessed using numerical experimentation. The hybrid CT-RBF method is shown to give good representations of Frangipani and Anthurium leaves. Such leaf models facilitate an understanding of plant development and permit the modelling of the interaction of plants with their environment. The motion of a droplet traversing this virtual leaf surface is affected by various forces including gravity, friction and resistance between the surface and the droplet. The innovation of our model is the use of thin-film theory in the context of droplet movement to determine the thickness of the droplet as it moves on the surface. Experimental verification shows that the droplet model captures reality quite well and produces realistic droplet motion on the leaf surface. Most importantly, we observed that the simulated droplet motion follows the contours of the surface and spreads as a thin film. In the future, the model may be applied to determine the path of a droplet of pesticide along a leaf surface before it falls from or comes to a standstill on the surface. It will also be used to study the paths of many droplets of water or pesticide moving and colliding on the surface.

The axial compressors of power-generation gas turbines have a high stage count, blades with low aspect ratios and relatively large clearances in the rear section. These features tend to promote the development of intense secondary flows that, coupled with the severe diffusion characterizing these machines, make the CFD modelling of axial compressors a great challenge. The focus of this thesis is on the use and tuning of modern CFD methods able to assess a reliable numerical setup to be used by the industry as a base for the design of efficient and high-performing multi-stage axial compressors. The first part of the work includes the details about the development and implementation of a highly conservative non-reflecting mixing plane model in the in-house CFD code TRAF, able to handle both the perfect and the real gas case. Later, the numerical setup for steady-state multi-stage compressor simulations is presented, providing also details about some crucial aspects of the compressor modelling, namely shroud leakages and clearances. The setup has been validated against experimental data on a GT compressor designed by Ansaldo Energia. To determine the influence of mixing plane models on performance prediction, unsteady full-annulus simulations have been performed at two different operating conditions: design point and near-stall. Finally, the last part of the thesis is dedicated to well-known phenomenon of radial mixing in axial compressors. The physical causes of radial mixing are discussed in depth, leading to the conclusion that a state-of-the-art, unsteady calculation of the full compressor is able to provide very strong evidence of radial mixing. A special attention is devoted to the evaluation of what is lost in the compressor modelling due to the assumption of a steady-state picture of the flow. In order to do this, the high-pressure section of a heavy-duty axial compressor of the Ansaldo Energia fleet, characterized by really high clearances, is considered. The results of steady and unsteady RANS simulations are compared with experimental data, showing that only adopting an unsteady approach, the enhanced radial mixing of this peculiar application can be properly captured. On the contrary, the steady-state modelling leads to a strong underestimation of the radial transport phenomenon. A possible explanation for this is provided after examining what occurs across the inter-row interfaces for RANS and URANS solutions: the stream-wise vorticity associated with clearance flows is one of the main drivers of radial mixing and restraining it by pitch-averaging the flow at mixing planes is the reason why the RANS approach is not able to properly predict the radial transport of fluid properties in the rear part of the axial compressor.

As part of the McDonald Observatory M dwarf planet search program, we present the results and detection limits for our high-precision radial velocity survey of 99 M dwarf stars. We also detail our efforts to improve the precision of our RV measurements as well as our frequency analysis methods. For any RV program, it is essential to obtain as high a precision as possible; increasing sensitivity can realistically reveal terrestrial-mass planets with our data. M dwarfs provide a unique opportunity to study these lower-mass planets (the so-called "super-Earths") from ground-based facilities; such planets are mostly undetectable around FGK stars, whose larger masses result in much smaller RV amplitudes. However, the low intrinsic luminosities of the M spectral type make it difficult to obtain high S/N measurements for a statistically significant sample, making our analysis improvements especially critical. Finally, we conduct a statistical analysis of the 21 known M dwarf planets. In particular, we use the photometric metallicity calibration for M dwarfs described in Johnson and Apps (2009) to further explore the frequency of planetary systems as a function of stellar metallicity. Our analysis confirms the correlation between stellar mass and the presence of giant planets, but also reveals a significant metallicity dependence on the presence of high-mass planets for M dwarfs. We show that the metallicities of our target sample are evenly distributed around solar [M/H], eliminating the possibility that the results of our survey will be biased due to metallicity effects. The frequency and characteristics of planets around M stars provides important insight into planet formation theories, especially for giant planets, which appear to form less easily around low-mass primaries. While previous results suggesting a dearth of short-period Jovian planets around M stars still holds, there is now a long enough observational time baseline to begin to characterize the frequency of planets with lower masses and larger orbital separations around these stars as opposed to other main sequence stars.
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Thesis (M.Sc. (Biochemistry) -- University of Limpopo, 2018
Dicerocaryum senecioides is a plant widely used as a nutritional source. It is used also for treatment of measles, wounds and to facilitate birth in domestic animal and humans in many parts of southern Africa (Mampuru et al., 2012). Findings in our laboratory have shown that a dichloromethane fraction of D. senecioides possesses antiinflammatory properties in human t-lymphocytes (Madiga, 2009), while the methanol crude extract possesses anti-proliferative and proapoptotic properties against Jurkat T cancer cells (Mphahlele, 2008). In this study, the probable anti-cancer effect of D. senecioides crude methanol leaf extract was investigated on cervical HeLa cancer cells. Dried powdered leaves of D. senecioides were extracted with absolute methanol to obtain a crude extract. To assess the cytotoxicity effect of the extract, KMST-6 and HeLa cell cultures were exposed to various extract concentrations (0 to 600 µg/ml) for 24 and 48 hours and subjected to the MTT assay. The results showed the extract to have no significant increase in the viability inhibition of HeLa cells at all tested concentrations after 24 hours of treatment. However, treatment with 400, 500 and 600 µg/ml of the extract for 48 hours revealed significantly increased HeLa cell viability inhibition. Furthermore, the extract showed to have no effect on the viability of normal human fibroblast KMST-6 cells at concentrations below 600 µg/ml, after 24 and 48 hours of treatment, thus showing selective cytotoxicity of the extract. To determine the mode of cell death associated with the increase in HeLa cell viability inhibition, the Hoechst 33258 nuclear staining assay and inverted light microscopy were employed. The data proposed apoptosis as the mode of cell death associated with the inhibition of HeLa cell viability. This was evidenced by changes in cell morphology such as the loss of HeLa cell radial extensions, cell shrinkage, as well as nuclear morphological features such as chromatin condensation. Apoptosis induction was further confirmed by the annexin-V/PI and multicaspase assays, using flow cytometry. The results showed an increase in the percentage of cells stained with annexin-V/PI, as well as increased caspase activity in extract-treated HeLa cells. To elucidate proapoptotic mechanisms of the extract, Western blotting analysis as well as the human apoptosis antibody array kit were used. This was to measure the expression profile of a number of apoptosis regulatory proteins. The results demonstrated modulation of some anti- and pro-apoptotic proteins, as well as the release of mitochondrial proteins required xiii for initiation of apoptosis, in the cytoplasm. The D. senecioides extract showed to have no effect on the cell division cycle of HeLa cells as determined by the PI staining assay. In conclusion, D. senecioides crude methanol leaf extract induced some degree of apoptosis in cervical HeLa cancer cells via the intrinsic apoptosis pathway. This was by modulating some of the members of the Bcl-2 family of proteins, which, facilitated the release of cytochrome C and activation of a caspase cascade.
South African Medical Research Council (SAMRC)

The aim of this thesis is to create collections of examples for the subject Astronomy taught for students of pedagogical faculties, studying this discipline as a part of physics courses. Due to very different mathematical knowledge of students I have chosen typical and not much difficult examples oriented to several branches of astronomy. Each part of examples begins with a self-contained theoretical introduction. The difficulty rises gradually from trivial to more complicated examples. The examples are mainly focused on motions in radial gravitational fields.