Observation of extrasolar planets at various ages

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

BID and the α-bisabolol-triggered cell death program: converging on mitochondria and lysosomes

\u3b1-Bisabolol (BSB) is a plant-derived sesquiterpene alcohol able to trigger regulated cell death in transformed cells, while deprived of the general toxicity in several mouse models. Here, we investigated the involvement of lysosomal and mitochondrial compartments in the cytotoxic effects of BSB, with a specific focus on the BH3-only activator protein BID. We found that BSB particularly accumulated in cancer cell lines, displaying a higher amount of lipid rafts as compared to normal blood cells. By means of western blotting and microscopy techniques, we documented rapid BSB-induced BID translocation to lysosomes and mitochondria, both of them becoming dysfunctional. Lysosomal membranes were permeabilized, thus blocking the cytoprotective autophagic flux and provoking cathepsin B leakage into the cytosol. Multiple flow cytometry-based experiments demonstrated the loss of mitochondrial membrane potential due to pore formation across the lipid bilayer. These parallel events converged on neoplastic cell death, an outcome significantly prevented by BID knockdown. Therefore, BSB promoted BID redistribution to the cell death executioner organelles, which in turn activated anti-autophagic and proapoptotic mechanisms. This is an example of how xenohormesis can be exploited to modulate basic cellular programs in cancer

estudos artísticos

info:eu-repo/semantics/publishedVersio

Observation of extrasolar planets at various ages

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

In Vitro Evaluation of Curcumin- and Quercetin-Loaded Nanoemulsions for Intranasal Administration: Effect of Surface Charge and Viscosity

The nose-to-brain delivery of neuroprotective natural compounds is an appealing approach for the treatment of neurodegenerative diseases. Nanoemulsions containing curcumin (CUR) and quercetin (QU) were prepared by high-pressure homogenization and characterized physicochemically and structurally. A negative (CQ_NE−), a positive (CQ_NE+), and a gel (CQ_NEgel) formulation were developed. The mean particle size of the CQ_NE− and CQ_NE+ was below 120 nm, while this increased to 240 nm for the CQ_NEgel. The formulations showed high encapsulation efficiency and protected the CUR/QU from biological/chemical degradation. Electron paramagnetic resonance spectroscopy showed that the CUR/QU were located at the interface of the oil phase in the proximity of the surfactant layer. The cytotoxicity studies showed that the formulations containing CUR/QU protected human nasal cells from the toxicity evidenced for blank NEs. No permeation across an in vitro model nasal epithelium was evidenced for CUR/QU, probably due to their poor water-solubility and instability in physiological buffers. However, the nasal cells’ drug uptake showed that the total amount of CUR/QU in the cells was related to the NE characteristics (CQ_NE− > CQ_NE+ > CQ_NEgel). The method used allowed the obtainment of nanocarriers of an appropriate size for nasal administration. The treatment of the cells showed the protection of cellular viability, holding promise as an anti-inflammatory treatment able to prevent neurodegenerative diseases

Solid state solvation: a fresh view

The design of efficient organic electronic devices, including OLEDs, OPVs, luminescent solar concentrators, etc., relies on the optimization of relevant materials, often constituted by an active (functional) dye embedded in a matrix. Understanding solid state solvation (SSS), i.e. how the properties of the active dye are affected by the matrix, is therefore an issue of fundamental and technological relevance. Here an extensive experimental and theoretical investigation is presented shedding light on this, somewhat controversial, topic. The spectral properties of the dye at equilibrium, i.e. absorption and Raman spectra, are not affected by the matrix dynamics. Reliable estimates of the matrix polarity are then obtained from an analysis of the micro-Raman spectra of polar dyes. Specifically, to establish a reliable polarity scale, the spectra of DCM or NR dispersed in amorphous matrices are compared with the spectra of the same dyes in liquid solvents with known polarity. On the other hand, steady-state emission spectra obtained in solid matrices depend in a highly non-trivial way on the matrix polarity and its dynamics. An extensive experimental and theoretical analysis of the time-resolved emission spectra of NR in a very large time window (15 fs-15 ns) allows us to validate this dye as a good probe of the dielectric dynamics of the surrounding medium. We provide a first assessment of the relaxation dynamics of two matrices (mCBPCN and DPEPO) of interest for OLED application, unambiguously demonstrating that the matrix readjusts for at least 15 ns after the dye photoexcitation

First science with SPHERE

The Spectro-Polarimetric High-contrast Exoplanet Research (SPHERE) facility mounted at ESO-VLT aims at discovering giant extrasolar planets in the proximity of bright stars and characterising them through spectroscopic and polarimetric observations. SPHERE is a complete system with a core made of an extreme-Adaptive Optics (XAO) turbulence correction, a pupil tracker and NIR and Visible coronagraph devices. At its back end, a differential dual imaging camera (IRDIS) and an integral field spectrograph (IFS) work in the Near Infrared (NIR) (0.95 < lambda < 2.32 μm) while a high resolution polarization camera covers the visible domain (0.6 < lambda < 0.9 μm). The IFS is a low resolution spectrograph (R̃50) that operates in the near IR (0.95< lambda < 1.6 μm), an optimal wavelength range for the detection of planetary features, over a field of view of about 1.7 × 1.7 square arcsecs. From spectra it is possible to reconstruct monochromatic images with high contrast (10[SUP]-6[/SUP] at 0.5 arcsec) and high spatial resolution, well inside the star PSF. The commissioning of the instrument ended in October 2014 and ESO has already offered SPHERE to the community. In this paper several results obtained during the commissioning and science verification phase are described. <P /

First resolved observations of a highly asymmetric debris disc around HD 160305 with VLT/SPHERE★★★

International audienceContext. Direct imaging of debris discs gives important information about their nature, their global morphology, and allows us to identify specific structures possibly in connection with the presence of gravitational perturbers. It is the most straightforward technique to observe planetary systems as a whole.Aims. We present the first resolved images of the debris disc around the young F-type star HD 160305, detected in scattered light using the VLT/SPHERE instrument in the near infrared.Methods. We used a post-processing method based on angular differential imaging and synthetic images of debris discs produced with a disc modelling code (GRaTer) to constrain the main characteristics of the disc around HD 160305. All of the point sources in the field of the IRDIS camera were analysed with an astrometric tool to determine whether they are bound objects or background stars.Results. We detect a very inclined (~82°) ring-like debris disc located at a stellocentric distance of about 86 au (deprojected width ~27 au). The disc displays a brightness asymmetry between the two sides of the major axis, as can be expected from scattering properties of dust grains. We derive an anisotropic scattering factor g > 0.5. A second right-left asymmetry is also observed with respect to the minor axis. We measure a surface brightness ratio of 0.73 ± 0.18 between the bright and the faint sides. Because of the low signal-to-noise ratio (S/N) of the images we cannot easily discriminate between several possible explanations for this left-right asymmetry, such as perturbations by an unseen planet, the aftermath of the breakup of a massive planetesimal, or the pericenter glow effect due to an eccentric ring. Two epochs of observations allow us to reject the companionship hypothesis for the 15 point sources present in the field