Les études astrochimiques de la formation stellaire sont particulièrement importantes pour la compréhension de l'évolution de l'Univers, du milieu interstellaire diffus à la formation des systèmes stellaires. Les récentes avancées en matière de modélisation chimique permettent d'apporter de nouveaux résultats sur le processus de formation stellaire et les structures mises en jeu. L'objectif de ma thèse était donc d'apporter un regard neuf sur la chimie de la formation stellaire en utilisant les récentes avancées sur le modèle chimique Nautilus. J'ai pour cela étudié l'évolution de la chimie du soufre durant la formation stellaire pour tenter d'apporter de nouvelles réponses au problème de déplétion du soufre. J'ai d'abord effectué une révision du réseau chimique soufré et étudié son effet sur la modélisation du soufre dans les nuages denses. En comparant aux observations, j'ai montré que le modèle textsc{Nautilus} était capable de reproduire les abondances des espèces soufrées dans les nuages denses en utilisant comme abondance élémentaire de soufre son abondance cosmique. Ce résultat m'a permis d'apporter de nouveaux indices sur les reservoirs de soufre dans ces objets. Puis j'ai effectué une étude complète de la chimie du souffre dans les coeurs chauds en me concentrant sur les effets sur la chimie de la composition pre-effondrement. J'ai également étudié les conséquences des différentes simplifications couramment faites pour la modélisation des coeurs chauds. Mes résultats montrent que la composition pre-effondrement est un paramètre majeur de l'évolution chimique des coeurs chauds, fournissant de nouveaux indices pour expliquer la variété de compositions en espèces soufrées observée dans ces objets. De plus, ma recherche a mis en évidence la nécessité d'uniformiser les modèles de chimie utilisés pour les coeurs chauds. Enfin, j'ai développé une méthode efficace pour inverser les paramètres initiaux d'effondrement de nuages denses en me basant sur une base de données de modèles physico-chimiques d'effondrement, ainsi que sur l'observation d'enveloppes de protoétoiles de Classe 0. A partir d'un échantillon de 12 sources, j'ai pu en déduire des probabilités concernant les possibles paramètres initiaux d'effondrement de la formation d'étoiles de faible masse. / Astrochemical studies of star formation are of particular interest because they provide a better understanding of how the chemical composition of the Universe has evolved, from the diffuse interstellar medium to the formation of stellar systems and the life they can shelter. Recent advances in chemical modeling, and particularly a better understanding of grains chemistry, now allow to bring new hints on the chemistry of the star formation process, as well as the structures it involves. In that context, the objective of my thesis was to give a new look at the chemistry of star formation using the recent enhancements of the Nautilus chemical model. To that aim, I focused on the sulphur chemistry throughout star formation, from its evolution in dark clouds to hot cores and corinos, attempting to tackle the sulphur depletion problem. I first carried out a review of the sulphur chemical network before studying its effects on the modeling of sulphur in dark clouds. By comparison with observations, I showed that the textsc{Nautilus} chemical model was the first able to reproduce the abundances of S-bearing species in dark clouds using as elemental abundance of sulphur its cosmic one. This result allowed me to bring new insights on the reservoirs of sulphur in dark clouds. I then conducted an extensive study of sulphur chemistry in hot cores and corinos, focusing on the effects of their pre-collapse compositions on the evolution of their chemistries. I also studied the consequences of the use of the common simplifications made on hot core models. My results show that the pre-collapse composition is a key parameter for the evolution of hot cores which could explain the variety of sulphur composition observed in such objects. Moreover, I highlighted the importance of standardizing the chemical modeling of hot cores in astrochemical studies. For my last study, I developed an efficient method for the derivation of the initial parameters of collapse of dark clouds via the use of a physico-chemical database of collapse models, and comparison with observations of Class 0 protostars. From this method, and based on a sample of 12 sources, I was able to derive probabilities on the possible initial parameters of collapse of low-mass star formation.

O poli(ε-caprolactona) (PCL) é um polímero biocompatível e biodegradável, aprovado pelo Food and Drug Administration (FDA) para ser usado como biomaterial. Diversos estudos utilizando sua forma linear ou ramificada têm demonstrado resultados promissores para seu uso no desenvolvimento de dispositivos médicos e em aplicações na área farmacêutica. O objetivo deste trabalho foi utilizar o PCL com estrutura estrelada (PCLE) para obter microesferas biorreabsorvíveis. Primeiramente realizou-se a avaliação das propriedades físico-químicas do PCLE por meio da cromatografia de permeação em gel (GPC), ressonância magnética de prótons (1H-RMN) e carbono (13C-RMN), calorimetria exploratória diferencial (DSC) e espectrometria por infravermelho com transformada de Fourier (FT-IR). A avaliação toxicológica do PCLE foi obtida por meio do ensaio de citotoxicidade utilizando células CHO-K1 e o corante vital 5-(3-carboximethoxifenil)-2-(4,5-dimetiltiazolil)-3-(4-sulfofenil) tetrazolium e do acoplador de elétrons fenazine metilssulfato (MTS/PMS). O ensaio de biodegradação foi conduzido em pH 7,4 na presença de lipase a 37 ºC. Após essas análises o PCLE foi utilizado para preparação de esferas por meio de emulsão complexa A/O/A. O PCLE foi caracterizado como um polímero de baixa massa molar, com dispersão de tamanho unimodal e cerca de 68,8 % de suas moléculas apresentaram estrutura estrelada com três braços. Em relação às propriedades térmicas o PCLE apresentou temperatura de fusão de 57,3 ºC e temperatura de transição vítrea de -54,3 ºC. A avaliação da citotoxicidade mostrou que o extrato de PCLE é compatível com o metabolismo celular. As microesferas obtidas a partir do PCLE, por emulsão A/O/A apresentaram polidispersão de tamanho. / The poly(ε-caprolactone) (PCL) is a biocompatible and biodegradable polymer which has been approved by Food and Drug Administration (FDA). Many studies that are using its linear or branched form have showed promising results for medical devices and controlled drug delivery applications. The aim of this research was the use of star-shaped PCL (PCLE) to prepare bioreabsorbable microspheres. At first, the physical-chemical properties were characterized by Gel Permeation Chromatography (GPC), Protons Resonance Magnetic Nuclear (1H-RMN), Carbon Resonance Magnetic Nuclear (13C-RMN), Differential Scanning Calorimetry (DSC) and Fourier Transformed Infrared Spectroscopy (FT-IR). The toxicological property was investigated by colorimetric assay using CHO-K1 cells and the vital dye (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium) (MTS) and the electron acceptor phenazine methosulfate (PMS). The biodegradation behavior was evaluated in the presence of lipase at 37 ºC and pH 7.4. The microspheres were prepared by complex emulsion W/O/W. The PCLE was characterized as low molecular weight polymer with monomodal distribution and about 68,8 % of the molecules were three-arm branched. The melting and glass transition temperatures were 57.3 ºC and -54.3 ºC, respectively. The cytotoxicity evaluation showed that PCLE extract was cell compatible. The obtained microspheres showed diameter polydispersity.

Nesta tese é apresentado um catálogo fotométrico no infravermelho próximo de 35 Regiões HII, todas pertencentes ao disco Galáctico. Esta faixa espectral é útil uma vez que os comprimentos de onda são grandes o suficiente para se ter uma baixa extinção interestelar comparada ao visível, e são pequenos o suficiente para diagnosticar as fotosferas estelares. Foram obtidas imagens nas bandas J, H e K e imagens do Spitzer nos canais de 3,5, 5,8 e 8,0 m. Após a fotometria nas imagens JHK, foi possível construir diagramas cor-cor e cor-magnitude. Foram utilizadas imagens coloridas, compostas de uma combinação RGB das imagens nas três bandas, tanto para as imagens JHK quanto para as imagens do Spitzer. Estas imagens, junto com os diagramas, foram utilizadas para levantar candidatos a fontes ionizantes das regiões HII, assim como objetos ainda em estágios primordiais de evolução (CTTs e MYSOs). Estes dados também foram utilizados para associar à cada região HII um estágio evolutivo (de A até D, da região mais jovem à mais evoluída). Baseado na posição da Sequência Principal em diagramas cor-magnitude, foi possível comparar as distâncias cinemáticas com nossos dados. Além disso, quando possível, foram utilizadas distâncias de regiões HII determinadas por paralaxe espectrofotométrica (disponíveis na literatura) e utilizando duas leis de extinção interestelar extremas mostrou-se que estas distâncias são menores que suas contrapartidas cinemáticas, e estão em acordo com distâncias determinadas por outros métodos, como por paralaxe trigonométrica. Sabendo que estas regiões de formação estelar seguem a dinâmica do gás, o mapeamento da distribuição destas regiões permite checar a estrutura espiral da Via Láctea. / In this work, a near infrared photometric catalog of 35 HII regions that belongs to the Galactic plane is presented. This spectral range is useful since the wavelengths are long enough to have less influence of the interstellar extinction compared to the visible domain, and they are small enough to still show stellar photospheric features. Images of these HII regions in the J, H and K-band together with IRAC-Spitzer images (channels 4.5, 5.8 and 8.0 m) were used. After the photometry in the JHK images, color-color and color-magnitude diagrams were constructed. These two group of images (JHK and 4.5, 5.8 and 8.0 m) colored in a RGB combination were used, together with the diagrams, to identify the ionizing sources candidates, as well as objects still embedded in their natal cocoon (CTTs and MYSOs). An evolutionary stage to these regions (from A to D, from the younger region to the more evolved) was inferred based on the images and diagrams. These diagrams were also used to infer if the kinematic distance is correct, based on the Main Sequence location. Non-kinematic distances to several HII regions, when it was possible, were collected from the literature. Using two extreme interstellar extinction laws, it was possible to compare these distances with the kinematic results. These non-kinematic distances are lower than that from kinematic techniques. Also, these distance discrepancies are in agreement with distances derived by others methodologies, as trigonometric parallax. Since these star forming regions follow the gas dynamics, mapping their distribution along the Galaxy allows to check the spiral pattern of the Milky Way.

The era of Big Data is here: the combination of unprecedented amounts of data collected every day with the promotion of open source solutions for massively parallel processing has shifted the industry in the direction of data-driven solutions. From recommendation systems that help you find your next significant one to the dawn of self-driving cars, Cloud Computing has enabled companies of all sizes and areas to achieve their full potential with minimal overhead. In particular, the use of these technologies for Data Warehousing applications has decreased costs greatly and provided remarkable scalability, empowering business-oriented applications such as Online Analytical Processing (OLAP). One of the most essential primitives in Data Warehouses are the Star Joins, i.e. joins of a central table with satellite dimensions. As the volume of the database scales, Star Joins become unpractical and may seriously limit applications. In this thesis, we proposed specialized solutions to optimize the processing of Star Joins. To achieve this, we used the Hadoop software family on a cluster of 21 nodes. We showed that the primary bottleneck in the computation of Star Joins on Hadoop lies in the excessive disk spill and overhead due to network communication. To mitigate these negative effects, we proposed two solutions based on a combination of the Spark framework with either Bloom filters or the Broadcast technique. This reduced the computation time by at least 38%. Furthermore, we showed that the use of full scan may significantly hinder the performance of queries with low selectivity. Thus, we proposed a distributed Bitmap Join Index that can be processed as a secondary index with loose-binding and can be used with random access in the Hadoop Distributed File System (HDFS). We also implemented three versions (one in MapReduce and two in Spark) of our processing algorithm that uses the distributed index, which reduced the total computation time up to 88% for Star Joins with low selectivity from the Star Schema Benchmark (SSB). Because, ideally, the system should be able to perform both random access and full scan, our solution was designed to rely on a two-layer architecture that is framework-agnostic and enables the use of a query optimizer to select which approaches should be used as a function of the query. Due to the ubiquity of joins as primitive queries, our solutions are likely to fit a broad range of applications. Our contributions not only leverage the strengths of massively parallel frameworks but also exploit more efficient access methods to provide scalable and robust solutions to Star Joins with a significant drop in total computation time. / A era do Big Data chegou: a combinação entre o volume dados coletados diarimente com o surgimento de soluções de código aberto para o processamento massivo de dados mudou para sempre a indústria. De sistemas de recomendação que assistem às pessoas a encontrarem seus pares românticos à criação de carros auto-dirigidos, a Computação em Nuvem permitiu que empresas de todos os tamanhos e áreas alcançassem o seu pleno potencial com custos reduzidos. Em particular, o uso dessas tecnologias em aplicações de Data Warehousing reduziu custos e proporcionou alta escalabilidade para aplicações orientadas a negócios, como em processamento on-line analítico (Online Analytical Processing- OLAP). Junções Estrelas são das primitivas mais essenciais em Data Warehouses, ou seja, consultas que realizam a junções de tabelas de fato com tabelas de dimensões. Conforme o volume de dados aumenta, Junções Estrela tornam-se custosas e podem limitar o desempenho das aplicações. Nesta tese são propostas soluções especializadas para otimizar o processamento de Junções Estrela. Para isso, utilizamos a família de software Hadoop em um cluster de 21 nós. Nós mostramos que o gargalo primário na computação de Junções Estrelas no Hadoop reside no excesso de operações escrita do disco (disk spill) e na sobrecarga da rede devido a comunicação excessiva entre os nós. Para reduzir estes efeitos negativos, são propostas duas soluções em Spark baseadas nas técnicas Bloom filters ou Broadcast, reduzindo o tempo total de computação em pelo menos 38%. Além disso, mostramos que a realização de uma leitura completa das tables (full table scan) pode prejudicar significativamente o desempenho de consultas com baixa seletividade. Assim, nós propomos um Índice Bitmap de Junção distribuído que é implementado como um índice secundário que pode ser combinado com acesso aleatório no Hadoop Distributed File System (HDFS). Nós implementamos três versões (uma em MapReduce e duas em Spark) do nosso algoritmo de processamento baseado nesse índice distribuído, os quais reduziram o tempo de computação em até 77% para Junções Estrelas de baixa seletividade do Star Schema Benchmark (SSB). Como idealmente o sistema deve ser capaz de executar tanto acesso aleatório quanto full scan, nós também propusemos uma arquitetura genérica que permite a inserção de um otimizador de consultas capaz de selecionar quais abordagens devem ser usadas dependendo da consulta. Devido ao fato de consultas de junção serem frequentes, nossas soluções são pertinentes a uma ampla gama de aplicações. A contribuições desta tese não só fortalecem o uso de frameworks de processamento de código aberto, como também exploram métodos mais eficientes de acesso aos dados para promover uma melhora significativa no desempenho Junções Estrela.

Mon travail de thèse présente deux types de structures denses : des sources froides compactes détectées par Planck et des condensations denses dans une région de photodissociation (PDR), à savoir la Barre d’Orion. Les deux types de structures sont étroitement liées à la formation des étoiles. Les sources froides sont étudiées comme objets potentiellement gravitationnellement liés, c’est-à-dire comme objets préstellaires. La Barre d’Orion est intéressante en tant que PDR à fort champ UV (G0 ∼104) prototypique, avec plusieurs disques protoplanétaires connus, éclairés par les jeunes étoiles du Trapèze.D’abord, je présente un article publié dans A&A: The Physical state of selected cold clumps. Dans cet article, nous avons comparé les observations du continuum de la poussière par Herschel provenant de l’open time key program Galactic Cold Cores (Herschel) aux observations de raies moléculaires par le radiotélescope de 20-m de l’Onsala Space Observatory en Suède. Les objets ont été sélectionnés en fonction de leur luminosités et faibles températures de couleur des poussières (T∼10−15 K). Nous avons calculé les masses du viriel et de Bonnor-Ebert et les avons comparées aux masses déduites à partir des observations. Les résultats indiquent que la plupart des objets froids observés ne sont pas nécessairement préstellaires.Dans mon étude de la Barre d’Orion, j’utilise des observations de l’instrumentPACS d’Herschel du programme Unveiling the origin and excitation mechanisms of the warm CO, OH and CH+ . Je présente des cartes de 110” ×110” du cation méthylidyne (CH+ J=3-2), des doublets de OH à 84 μm, et des raies de CO á hauts J (J=19-18). C’est la première fois que ces traceurs des PDR ont présentés avec une telle résolution spatiale et un tel rapport signal-sur-bruit.La répartition spatiale de CH+ et OH montre la même structure de la Barre qui a été vue dans d’autres observations. La morphologie du CH+ et H2 confirme que la formation et l’excitation de CH+ est fortement dépendante du H2 excité vibrationnellement. Le maximum d’émission de OH84 μm correspond à un objet brillant jeune, identifié comme le disque protoplanetaire 244-440.Je présente également des transitions rotationnelles de CO de moyenne (∼20 K) et haute (∼1000 K) énergie. La morphologie de l’émission du CO rotationnellement excité est corrélée avec la présence des petites structures denses irradiées. Nous établissons le lien entre le coeur de ces structures, tracé en CS J=2-1 par Lee et al. (2013) et H 13 CN par Lis and Schilke (2003) et le bord de la PDR, tracé en CO J=19-18 et le H 2 vibrationnellement excitée. Nous montrons également que le CO est principalement excité par le chauffage UV. / In this thesis I present a study of two kinds of dense ISM structures: compact cold sources detected by Planck and dense condensations in a photodissociation region (PDR), namely the Orion Bar detected by ground-based and Herschel telescopes. Both kinds of structures are closely related to star formation. The cold sources are investigated as potentially gravitationally bound, prestellar, objects. The Orion Bar is a highly FUV-illuminated (G0=104) prototypical PDR, with several known protoplanetary disks, illuminated by the young Trapezium stars.First I introduce a paper published in A&A: The Physical state of selected cold clumps. In this paper we compared the Herschel dust continuum observations from the open time key program Galactic Cold Cores to ground based molecular line observations from the 20-m radio telescope of the Onsala Space Observatory in Sweden. The clumps were selected based on their brightness and low dust color temperatures (T=10-15 K). We calculated the virial and Bonnor-Ebert masses and compared them to the masses calculated from the observations. The results indicate that most of the observed cold clumps are not necessarily prestellar.Then I move on to the warm and dense condensations of the ISM. In my study of the Orion Bar, I use observations from PACS instrument on board Herschel from the open time program Unveiling the origin and excitation mechanisms of the warm CO, OH and CH+. I present maps of 110”x110” of the methylidyne cation (CH+ J=3-2), OH doublets at 84 µm, and high-J CO (J=19-18). This is the first time that these PDR tracers are presented in such a high spatial resolution and high signal-to-noise ratio. The CH+ and OH have critical densities (1010 cm-3) and upper level energy temperatures (250 K). In addition the endothermicity of the CH+ + H2 reaction (4300 K) that forms CH+ is comparable to the activation barrier of the O + H2 reaction (4800 K) forming OH. Given these similarities it is interesting to compare their emission. The spatial distribution of CH+ and OH shows the same clumpy structure of the Bar that has been seen in other observations. The morphology of CH+ and H2 confirms that CH+ formation and excitation is strongly dependent on the vibrationally excited H2, while OH is not. The peak in the OH 84 µm emission corresponds to a bright young object, identified as the externally illuminated protoplanetary disk 244-440.Finally, I study the high-J CO in the Orion Bar. I also introduce low- and mid-J CO observations of the area. The high-J CO morphology shows a clumpy structure in the Bar and we establish a link between the dense core of the clumps, traced in CS J=2-1 by Lee et al. (2013) and in H13CN by Lis and Schilke (2003). We also show that the high-J CO is mainly excited by the UV heating.

Submitted by Jadson Francisco de Jesus SILVA (jadson@uefs.br) on 2018-07-12T22:44:48Z No. of bitstreams: 1 Disserta??o Andr? VErs?o Final + Ficha Catalogr?fica (1).pdf: 5597865 bytes, checksum: 47b14bdb3b0cc0a2e5b68f0252c589ff (MD5) / Made available in DSpace on 2018-07-12T22:44:48Z (GMT). No. of bitstreams: 1 Disserta??o Andr? VErs?o Final + Ficha Catalogr?fica (1).pdf: 5597865 bytes, checksum: 47b14bdb3b0cc0a2e5b68f0252c589ff (MD5) Previous issue date: 2017-12-20 / Funda??o de Amparo ? Pesquisa do Estado da Bahia - FAPEB / In this dissertation we present as proposal the teaching of Star Evolution in the discipline sciences for students of the 9th year of elementary school. From this series, students have their first contact with study of the atomic structure, periodic table, chemical reactions, among other topics of physics and chemistry. Using Stellar Evolution, in an interdisciplinary way, we were able to discuss these obligatory contents and, in addition, we present new knowledge such as: the synthesis of chemical elements, nuclear reactions and other topics of Astronomy and Astrophysics. This approach allows students to gain access to modern physics content guided by NCPs, which in turn has been neglected in school curricula. Based on Chevallard's Didactic Transposition Theory, we analyze the aspects that make it possible to adapt the Wise Knowledge, Star Evolution, to the reality of basic education. To do so, we did initially a quantitative survey in textbooks, evaluating how the knowledge related to Astronomy has been presented. The second step was to perform a pre-test to evaluate students' prior knowledge, and then compare them with a post-test. The transposition of these contents indicated that the Star Evolution in conjunction with the science discipline makes learning more playful and meaningful, being a perfectly feasible proposal, as well as showing the results. In addition, we constructed a didactic game, an educational product that can be used as a tool that helps students learn the evolutionary processes of the stars. / Nesta disserta??o apresentamos como proposta o ensino de Evolu??o Estelar na disciplina ci?ncias para alunos do 9? ano do ensino fundamental. A partir desta s?rie, os alunos tem seu primeiro contato com estudo da estrutura at?mica, tabela peri?dica, rea??es qu?micas, entre outros t?picos de f?sica e qu?mica. Usando a Evolu??o Estelar, de um modo interdisciplinar, pudemos discutir estes conte?dos obrigat?rios e, al?m disso, apresentamos novos conhecimentos como: a s?ntese dos elementos qu?micos, rea??es nucleares e outros temas de Astronomia e Astrof?sica. Esta abordagem permite que os alunos tenham acesso a conte?dos de f?sica moderna orientados pelos PCN, que por sua vez, tem sido ainda negligenciado nos curr?culos escolares. Com base na Teoria da Transposi??o Did?tica de Chevallard, analisamos os aspectos que tornam poss?vel adequar o Saber S?bio e a Evolu??o Estelar, ? realidade do ensino b?sico. Para tanto, fizemos inicialmente um levantamento quantitativo em livros did?ticos, avaliando como os Saberes ligados a Astronomia tem sido apresentados. O segundo passo foi a realiza??o de um pr?-teste para avaliarmos o conhecimento pr?vio dos estudantes, e posteriormente compar?-los com um p?s-teste. A transposi??o destes conte?dos indicou que a Evolu??o Estelar em conjunto com a disciplina ci?ncias torna o aprendizado mais l?dico e significativo, sendo uma proposta perfeitamente vi?vel, assim como mostram os resultados. Ademais, constru?mos um jogo did?tico, produto educacional que pode ser usado como ferramenta que auxilie os estudantes no aprendizado dos processos evolutivos das estrelas.

O poli(ε-caprolactona) (PCL) é um polímero biocompatível e biodegradável, aprovado pelo Food and Drug Administration (FDA) para ser usado como biomaterial. Diversos estudos utilizando sua forma linear ou ramificada têm demonstrado resultados promissores para seu uso no desenvolvimento de dispositivos médicos e em aplicações na área farmacêutica. O objetivo deste trabalho foi utilizar o PCL com estrutura estrelada (PCLE) para obter microesferas biorreabsorvíveis. Primeiramente realizou-se a avaliação das propriedades físico-químicas do PCLE por meio da cromatografia de permeação em gel (GPC), ressonância magnética de prótons (1H-RMN) e carbono (13C-RMN), calorimetria exploratória diferencial (DSC) e espectrometria por infravermelho com transformada de Fourier (FT-IR). A avaliação toxicológica do PCLE foi obtida por meio do ensaio de citotoxicidade utilizando células CHO-K1 e o corante vital 5-(3-carboximethoxifenil)-2-(4,5-dimetiltiazolil)-3-(4-sulfofenil) tetrazolium e do acoplador de elétrons fenazine metilssulfato (MTS/PMS). O ensaio de biodegradação foi conduzido em pH 7,4 na presença de lipase a 37 ºC. Após essas análises o PCLE foi utilizado para preparação de esferas por meio de emulsão complexa A/O/A. O PCLE foi caracterizado como um polímero de baixa massa molar, com dispersão de tamanho unimodal e cerca de 68,8 % de suas moléculas apresentaram estrutura estrelada com três braços. Em relação às propriedades térmicas o PCLE apresentou temperatura de fusão de 57,3 ºC e temperatura de transição vítrea de -54,3 ºC. A avaliação da citotoxicidade mostrou que o extrato de PCLE é compatível com o metabolismo celular. As microesferas obtidas a partir do PCLE, por emulsão A/O/A apresentaram polidispersão de tamanho. / The poly(ε-caprolactone) (PCL) is a biocompatible and biodegradable polymer which has been approved by Food and Drug Administration (FDA). Many studies that are using its linear or branched form have showed promising results for medical devices and controlled drug delivery applications. The aim of this research was the use of star-shaped PCL (PCLE) to prepare bioreabsorbable microspheres. At first, the physical-chemical properties were characterized by Gel Permeation Chromatography (GPC), Protons Resonance Magnetic Nuclear (1H-RMN), Carbon Resonance Magnetic Nuclear (13C-RMN), Differential Scanning Calorimetry (DSC) and Fourier Transformed Infrared Spectroscopy (FT-IR). The toxicological property was investigated by colorimetric assay using CHO-K1 cells and the vital dye (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium) (MTS) and the electron acceptor phenazine methosulfate (PMS). The biodegradation behavior was evaluated in the presence of lipase at 37 ºC and pH 7.4. The microspheres were prepared by complex emulsion W/O/W. The PCLE was characterized as low molecular weight polymer with monomodal distribution and about 68,8 % of the molecules were three-arm branched. The melting and glass transition temperatures were 57.3 ºC and -54.3 ºC, respectively. The cytotoxicity evaluation showed that PCLE extract was cell compatible. The obtained microspheres showed diameter polydispersity.

O mecanismo de formação de estrelas de alta massa é um dos problemas fundamentais em Astrofísica e um dos menos compreendidos. Duas teorias predizem a formação destes objetos, que se formariam via i) colisão de estrelas de baixa massa, ou ii) acreção por disco circunstelar. Atualmente, ambas as teorias carecem de testes observacionais críticos. Não obstante, o número de estrelas de alta massa jovens já identificadas na Galáxia corresponde a uma fração muito menor do que o esperado pela função de massa inicial. Este trabalho apresenta um estudo observacional de candidatos a MYSOs, selecionados a partir do levantamento Red MSX Source. Observações de 376 objetos nos filtros estreitos do H2 em 2.12 mícrons e num contínuo adjacente foram realizadas para identificar jatos moleculares colimados e 296 delas são apresentadas nesse trabalho. As observações do hemisfério Norte foram realizadas com o telescópio CFHT (Havaí) enquanto os objetos do hemisfério Sul, foram observados com o telescópio SOAR (Chile). A análise dos mapas de emissão em H2 permitiu concluir que 150 dos 296 objetos (51%) estão associados a emissões extensas em H2, e 62 delas foram classificadas como emissões polares. A análise da razão de aspecto das estruturas identificadas mostra que as emissões associadas a fontes com maior luminosidade apresentam baixo grau de colimação, tal como sugere o cenário de geração dos jatos a partir de ventos emanados pela pressão de radiação do disco circunstelar. A baixa fração de emissões polares (apenas 21% da amostra) indica que o tempo de vida dessas estruturas devem ser curtos. As evidências observacionais encontradas nesse trabalho corroboram o cenário de acreção via disco circunstelar e invalidam o modelo formação via coalescência de estrelas de baixa massa, que requer ambientes relativamente densos e não é capaz de produzir jatos colimados. / Very few massive stars in early formation stages were clearly identified in our Galaxy. The formation process of these objects is still unclear and two theories predict the formation of massive stars: i) by merging of low mass stars or ii) by an accretion disk. There are no critical observational evidences to choose between them. The lack of observational evidences combined with the small number of known massive stars in formation in our Galaxy does not allow us to choose between these scenarios. We present a near-infrared survey of MYSOs candidates selected from the Red MSX Source survey. Such catalog is based on an accurate revision of distances and luminosities, overcoming the limitations and failures in previous searches of this kind. 376 targets were observed through the H2 narrow-band filter at 2.12 microns and in the continuum to identify collimated molecular jets. 296 targets were successfully processed using the THELI pipeline and are presented. Observations in the Northern Hemisphere were carried at the CFHT telescope (Hawaii) while the Southern targets were observed with the Soar Telescope (Chile). The results show that 150 of the 296 sources display extended H2 emission and 62 of them are polar. The analysis of the aspect ratio of the structures indicates that emissions associated with higher luminosity sources have low degree of collimation. This is in agreement with the scenario of the radiation pressure-driven outflows from the circunstellar discs. The low fraction of sources associated with polar jets (21%) indicates a short timescale of such structures. The observational evidences found on this work support the accretion scenario and show that coalescence of low-mass stars (which may require relatively dense environments and is not expected to produce jet-like structures) is not likely to explain most of the studied MYSOs candidates.

Abstract In this report I present a study of possible age gradients in the Green Pea galaxy J145735.13+223201.8 to be able to conclude if there is an extended star forming history in such a galaxy. Data are coming from two different sources, highly resolved images in four different wavelengths of stars in the galaxy, and of nebular gas in a narrow band Ha Balmer line filter, from the Hubble Space Telescope (HST), as well as spectral line information from the Sloan Digital Sky Survey (SDSS). I compare the observations with stellar population models from two different libraries, Yggdrasil and Starburst99. Due to the highly resolved images from HST this is one of the first studies of spatially resolved stellar populations in a Green Pea galaxy. With the help from these spatially resolved images it was possible to study star clumps independently from each other. This would not be possible when using only data from SDSS. In this way it was possible to conclude an age difference between the centre of the galaxy and its outskirts. I found that the galaxy has an age gradient at a confidence level greater than 95%.

Des nuages moléculaires aux étoiles, l'ensemble des stades d'évolution des étoiles jeunes peuvent être observés dans le domaine submillimétrique. A cette fin, le télescope Herschel a observé, dans le cadre d'un relevé de la Ceinture de Gould, plusieurs nuages moléculaires. Lorsque ces nuages se fragmentent, des coeurs denses, accumulant de la poussière et du gaz, se forment et se contractent. Nous avons effectué un relevé exhaustif des coeurs denses préstellaires dans le nuage moléculaire d'Ophiuchus qui apparaissent couplés avec des structures filamentaires dans le cadre du paradigme de la formation d'étoiles au sein de filaments interstellaires. La région n'était pas connue pour être filamentaire, malgré des alignements de protoétoiles observables. Ce nuage moléculaire présente la particularité d'être soumis à une rétroaction importante venant d'étoiles actives à proximité, visible dans la structure du nuage moléculaire. Oph B-11, mise en évidence par des observations interférométriques, est un précurseur de naine brune, de masse finale trop faible pour que l'étoile produite brûle de l'hydrogène. Leur mécanisme de formation est mal connu. Il faut caractériser et observer un premier candidat pré-naine brune. Oph B-11 a été détectée à proximité d'un choc proche, que nous avons caractérisé chimiquement. De plus, à plus haute résolution avec ALMA, nous avons montré l'environnement moléculaire structuré, contraint le mécanisme de formation de ce type d'objet. Ces observations dévoilent une série de chocs dans plusieurs traceurs, coïncidant avec la détection de la pré-naine brune, favorisant le scénario gravo-turbulent pour la formation des naines brunes. / From molecular clouds to stars, every step of the evolution of young stars can be observed in the submillimetric range. The Herschel Space Telescope observed, as part of the Herschel Gould Belt Survey, many molecular clouds.When these molecular clouds are fragmenting, dense prestellar cores accumulating dust and gaz are forming and contracting. We performed a census of prestellar dense cores in the Ophiuchus Molecular Cloud, which appear to be coupled with filamentary structures, as part of the paradigm of star-formation inside insterstellar filaments. The region was not previously known as filamentary, despite the observation of protostellar alignments.This molecular could is under the heavy feedback of active stars nearby seen in the structure of the molecular cloud.Oph B-11, detected with interferometric observations, is a brown dwarf precursor, which final mass will not be important enough for the final star to burn hydrogen. Their formation mechanism is not well constrained, we must find and characterize a first candidate pre-brown dwarf.Oph B-11 was detected along a nearby shock, we characterize chemically. Moreover, higher resolution studies with ALMA show a structured molecular environment, and help us constrain the mechanism of formation of this kind of objects. These observations show a series of shocks in differents tracers, spatially coincident with the detected position of the pre-brown dwarf, in favor of the gravo-turbulent scenario for the formation of brown dwarfs.