Devido as frequentes dúvidas dos usuários das câmaras de ionização do tipo lápis calibradas no Laboratório de Calibração de Instrumentos do IPEN (LCI IPEN), em como aplicar corretamente os fatores indicados em seus certificados de calibração, foi elaborado um guia orientativo para dosimetria em tomografia computadorizada. O guia orientativo inclui o conhecimento prévio da Camada Semirredutora (CSR), já que é necessário conhecer a energia efetiva do feixe para aplicação do fator de correção para qualidade (kq). A avaliação da CSR em tomógrafos torna-se uma difícil tarefa devido à geometria do sistema e por essa razão foi realizado um levantamento das metodologias existentes para a determinação da CSR em feixes clínicos de Tomografia Computadorizada (TC), levando em consideração fatores técnicos, práticos e econômicos. Neste trabalho, optou-se em testar um Sistema Tandem composto por capas absorvedoras confeccionado na oficina do IPEN, baseado em estudos preliminares devido ao baixo custo e boa reposta. O Sistema Tandem é composto por 5 capas absorvedoras cilíndricas de 1 mm, 3 mm, 5 mm, 7 mm, e 10 mm de alumínio e por 3 capas absorvedoras cilíndricas de 15 mm, 25 mm e 35 mm de acrílico (PMMA) acopladas à câmara de ionização do tipo lápis comercial amplamente utilizada em testes de controle de qualidade na dosimetria em feixes clínicos de Tomografia Computadorizada. Através das curvas Tandem, foi possível avaliar os valores de CSR e, através da curva de calibração da câmara de ionização do tipo lápis, encontrar o Kq adequado ao feixe. O Guia elaborado traz informações de como construir a curva de calibração em função da CSR, para encontrar o Kq, bem como informações para construção da curva Tandem, para encontrar valores próximos de CSR. / Due to frequent questions from users of ionization chambers pencil type calibrated in the Instrument Calibration Laboratory of the Institute of Energy and Nuclear Research (LCI - IPEN), on how to properly apply the factors indicated in their calibration certificates, a guide was prepared guidance for dosimetry in computed tomography. The guide includes guidance prior knowledge of half value layer (HVL), as it is necessary to know the effective beam energy for application quality for correction factor (kq). The evaluation of HVL in TC scanners becomes a difficult task due to system geometry and therefore a survey was conducted of existing methodologies for the determination of HVL in clinical beams Computed Tomography, taking into account technical, practical and economic factors. In this work it was decided to test a Tandem System consists of absorbing covers made in the workshop of IPEN, based on preliminary studies due to low cost and good response. The Tandem system consists of five cylindrical absorbing layers of 1mm, 3mm, 5mm, 7mm and 10mm aluminum and 3 cylindrical absorbing covers 15mm, 25mm and acrylic 35mm (PMMA) coupled to the ionization chamber of commercial pencil type widely used in quality control tests in dosimetry in clinical beams Computed tomography. Through Tandem curves it was possible to assess HVL values and from the standard curve pencil-type ionization chamber, Kq find the appropriate beam. The elaborate Guide provides information on how to build the calibration curve on the basis of CSR, to find the Kq and information for construction Tandem curve, to find values close to CSR.

Choy, Man Fai. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2008. / Includes bibliographical references (leaves 120-123). / Abstracts in English and Chinese. / Title Page --- p.1 / Abstract (English) --- p.2 / Abstract (Chinese) --- p.3 / Acknowledgement --- p.4 / Declaration --- p.5 / Table of Content --- p.6 / Lists of Figures --- p.9 / Lists of Tables --- p.12 / List of Schemes --- p.13 / Chapter Chapter One --- Introduction / Historical perspective and overview of tandem mass spectrometry for structural biochemistry --- p.14 / Electrospray ionization (ESI) --- p.15 / Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) --- p.18 / Chapter 1.3.1 --- History of FTICR --- p.18 / Chapter 1.3.2 --- Theory of FTICR --- p.21 / Chapter 1.4 --- Sequencing of DNA fragments --- p.26 / Chapter 1.4.1 --- Conventional and mass spectrometric sequencing techniques --- p.26 / Chapter 1.4.2 --- Fragment-ion nomenclature --- p.27 / Chapter 1.4.3 --- Tandem mass spectrometry of oligonucleotide ions --- p.29 / Chapter 1.4.4 --- Electron capture dissociation of oligonucleotide ions --- p.31 / Chapter 1.5 --- Outline of the present work --- p.32 / Chapter Chapter Two --- Instrument and Experimental / Chapter 2.1 --- Instrumentation --- p.35 / Chapter 2.1.1 --- Fourier-transform ion cyclotron resonance mass spectrometer --- p.35 / Chapter 2.1.2 --- Vacuum system --- p.35 / Chapter 2.1.3 --- Nanospray ion source --- p.39 / Chapter 2.1.4 --- Ion Transfer system --- p.41 / Chapter 2.1.5 --- Infinity cell --- p.43 / Chapter 2.1.6 --- Electron emission source --- p.44 / Chapter 2.2 --- Experimental section --- p.47 / Chapter 2.2.1 --- Simple acquisition pulse program --- p.47 / Chapter 2.2.2 --- ECD pulse program --- p.49 / Chapter Chapter Three --- Production of Doubly-prontonated Oligonucleotide ions using Nanospray Ionization / Chapter 3.1 --- Introduction --- p.52 / Chapter 3.2 --- Experimental and instrumental section --- p.53 / Chapter 3.2.1 --- Materials --- p.53 / Chapter 3.2.2 --- Sample preparation --- p.53 / Chapter 3.2.3 --- Instrumentation --- p.54 / Chapter 3.3 --- Results and discussion --- p.54 / Chapter 3.3.1 --- Effect of the concentration of ammonium formate --- p.54 / Chapter 3.3.2 --- Effects of the anionic pair of the ammonium salts --- p.57 / Chapter 3.3.3 --- Effects of solvent composition --- p.64 / Chapter 3.3.4 --- Effects of analyte concentration --- p.66 / Chapter 3.4 --- Conclusion --- p.68 / Chapter Chapter Four --- Electron Capture Dissociation of Model Oligonucleotides / Chapter 4.1 --- Introduction --- p.69 / Chapter 4.2 --- Experimental and instrumental section --- p.70 / Chapter 4.2.1 --- Materials --- p.70 / Chapter 4.2.2 --- Sample preparation --- p.70 / Chapter 4.2.3 --- Instrumentation --- p.71 / Chapter 4.2.4 --- Method of calculations --- p.71 / Chapter 4.3 --- Results and discussion --- p.72 / Chapter 4.3.1 --- "ECD of d(CCCCC), d(CCAAC), d(CCTTC) and d(CCGGC)" --- p.72 / Chapter 4.3.1.1 --- General features --- p.72 / Chapter 4.3.1.2 --- Protonated nucleobases and nucleoside-like fragments --- p.73 / Chapter 4.3.1.3 --- Doubly-charged fragment ions --- p.79 / Chapter 4.3.2 --- Theoretical calculation of electron capture affinities of common functionalities in oligonucleotides --- p.80 / Chapter 4.3.3 --- Electron capture dissociation of C/T binary-based oligonucleotides --- p.81 / Chapter 4.3.3.1 --- "ECD of d(CTCTC), d(TCCCT) and d(CTTTC)" --- p.84 / Chapter 4.3.3.2 --- ECD of d(CCCCT) and d(TCCCC) --- p.84 / Chapter 4.3.4 --- Mechanistic implications --- p.89 / Chapter 4.4 --- Conclusion --- p.99 / Chapter Chapter Five --- Electron Capture Dissociation of a Series of G/T Binary Base of Oligonucleotides / Chapter 5.1 --- Introduction --- p.100 / Chapter 5.2 --- Experimental and instrumental section --- p.100 / Chapter 5.2.1 --- Materials --- p.100 / Chapter 5.2.2 --- Sample preparation --- p.100 / Chapter 5.2.3 --- Instrumentation --- p.101 / Chapter 5.3 --- Results and discussion --- p.101 / Chapter 5.3.1 --- Electron capture dissociation of d(GGGGG) --- p.101 / Chapter 5.3.2 --- Electron capture dissociation of G/T binary-based oligonucleotides --- p.104 / Chapter 5.3.2.1 --- "ECD of d(GTGTG), d(GTTTG) and d(TGGGT)" --- p.104 / Chapter 5.3.2.2 --- ECD of d(GGGGT) and d(TGGGG) --- p.107 / Chapter 5.3.3 --- Mechanistic implications --- p.110 / Chapter 5.4 --- Conclusion --- p.117 / Chapter Chapter Six --- Conclusion Remarks --- p.118 / References --- p.120 / Appendix A --- p.124 / Appendix B --- p.127

Until first half of the XX century, sickle cell disease was practically limited to the malaria endemic areas and countries having known an important surge of African slaves. Today, migratory flows and progress of medicine have modified considerably the distribution of sickle cell disease which is from now on a frequent affection in Western Europe. The preventive implementation of medical care makes it possible to reduce morbidity and mortality associated with this pathology. Stake of a medical policy and economic interests, neonatal screening for hemoglobin disorders justifies then fully the implementation of powerful and adapted means. In order to initiate a newborn screening programme in our centre, we developed various immunological tests allowing to identify the sickle hemoglobin. We first of all developed an indirect immunoassay and led a population study on 46082 Belgian newborns and 1825 neonates from Central Africa. The performances of this assay were improved thereafter by conceiving a competitive test. Next, for reasons independent of our will, we had unfortunately to abandon the immunological approach. This methodology was thus supplanted in our center by an innovative method for this indication: the mass spectrometry. Our promising results currently authorize us to perennialize our policy in the neonatal screening for sickle cell disease and open the way for new developments in other fields. / Jusquà la première moitié du XXe siècle, la drépanocytose se limitait pratiquement aux zones dendémie palustre et aux pays ayant connu un important afflux desclaves dorigine africaine. Aujourdhui, les flux migratoires et les progrès de la médecine ont considérablement modifié la distribution de cette maladie qui est désormais une affection fréquente en Europe occidentale. La prise en charge précoce permet de réduire la morbidité et la mortalité associées à cette maladie. Enjeu dune politique sanitaire et dintérêts économiques, le dépistage néonatal de la drépanocytose justifie donc ainsi pleinement la mise en uvre de moyens performants et adaptés. Afin dinitier un programme de dépistage au sein de notre centre, nous avons initialement développé divers tests immunologiques permettant didentifier lhémoglobine anormale. Nous avons tout dabord mis au point un immunoessai indirect et conduit une étude de population sur 46082 nouveau-nés belges et 1825 bébés originaires dAfrique centrale. Les performances de lessai ont par la suite été améliorées en concevant un test compétitif. Lapprovisionnement laborieux danticorps nécessaires aux tests de détection a par la suite entravé notre programme. En effet, la commercialisation en a été interrompue et la production danticorps monoclonaux par nos moyens propres na pas été couronnée du succès escompté. Lapproche immunologique du dépistage néonatal de la drépanocytose a ainsi été supplantée dans notre centre par une méthode novatrice pour cette indication : la spectrométrie de masse. Nos résultats prometteurs nous autorisent actuellement à pérenniser notre nouvelle façon de faire dans le dépistage néonatal de la drépanocytose et ouvre la voie pour de nouveaux développements dans dautres domaines.

Abstract : A lossless compression algorithm often applies the same coding scheme on the whole sequence to be compressed. Therefore, some factors of the sequence are shortened while others are lengthened. In this work, we propose an optimization algorithm of compression methods which breaks off the coding where it is not profitable, so that some segments of the initial sequence are copied as they are instead of being coded. The achieved compression is said modular, meaning that the compressed sequence is a sequel of compressed segments and copied segments. Under specific hypotheses, our algorithm computes an optimal modular compression in time O(n log n) where n is the length of the sequence. We show that our optimization method can be advantageously used to analyze data, and particularly genetic sequences. The Kolmogorov complexity theory brings to light the usefulness of compression when analyzing sequences. The work consists of three parts. The first one introduces the classical concepts of compression and coding, as well as the new concept of ICL codes for the integers. The second one presents the compression optimization algorithm by liftings that uses ICL codes. Finally, the third part presents applications of the compression optimization by liftings, especially in the context of genetic sequence analysis. With the specific problem of the localization of approximate tandem repeats, we show how the compression optimization algorithm by liftings can be used to localize regular segments and irregular segments of a sequence in a precise and optimal way. This comeback to experimentation makes it possible to analyze sequences that contain several thousands of symbols within the space of a few seconds. /Résumé : Une méthode de compression sans perte d'informations applique souvent le même schéma de codage d'un bout à l'autre de la séquence à comprimer. Certains facteurs de la séquence sont ainsi raccourcis mais malheureusement d'autres sont rallongés. Dans ce travail, nous proposons un algorithme d'optimisation de compression qui rompt le codage là ou il n'est pas intéressant en recopiant des morceaux de la séquence initiale. La compression obtenue est dite modulaire : la séquence comprimée est une succession de morceaux comprimés et de morceaux recopiés tels quels. Sous certaines hypothèses, notre algorithme fournit une compression modulaire optimale en temps O(n log n) où n est la longueur de la séquence. Nous montrons que notre méthode de compression peut avantageusement être utilisée pour analyser des données et plus particulièrement des séquences génétiques. La théorie de la complexité de Kolmogorov éclaire l'idée d'analyse de séquences par compression. Le travail comporte trois parties. La première introduit les concepts classiques de compression et de codage, ainsi que le concept nouveau de codage ICL d'entiers. La seconde développe l'algorithme d'optimisation de compression par liftings qui utilise les codes ICL. La dernière partie présente des applications de l'optimisation de compression par liftings, plus particulièrement dans le domaine de l'analyse de séquences génétiques. Nous montrons, à l'aide du problème spécifique de localisation de répétitions en tandem approximatives, comment l'algorithme d'optimisation par liftings peut être utilisé pour localiser précisément et de manière optimale les segments réguliers et les segments non réguliers des séquences. Il s'agit d'un retour à l'expérience qui permet l'analyse de séquences de plusieurs centaines de milliers de bases en quelques secondes.

Submitted by Ana Maria Fiscina Sampaio (fiscina@bahia.fiocruz.br) on 2012-07-16T21:36:49Z No. of bitstreams: 1 Enio Paulo Estimativa de mistura étnica avaliada por Marcadores Informativos de.pdf: 352598 bytes, checksum: 7d448dc54afe1ec271f59fc912275f41 (MD5) / Made available in DSpace on 2012-07-16T21:36:49Z (GMT). No. of bitstreams: 1 Enio Paulo Estimativa de mistura étnica avaliada por Marcadores Informativos de.pdf: 352598 bytes, checksum: 7d448dc54afe1ec271f59fc912275f41 (MD5) Previous issue date: 2010 / Fundação Oswaldo Cruz. Centro de Pesquisas Gonçalo Moniz. Salvador, Bahia, Brasil / A miscigenação entre os três principais grupos étnicos (ameríndios, europeus e africanos) originou a alta diversidade genética da população brasileira. Na Bahia a proporção de afrodescendentes é de 77,5%, sendo que em Salvador 79,8% se auto-denominam negros ou pardos. Poucos estudos descrevem a diversidade genética da população baiana e a contribuição de cada grupo étnico na sua formação. Diversos marcadores de DNA são atualmente utilizados para estimar mistura étnica em populações miscigenadas. Estes marcadores são denominados alelos específicos de população (PSAs) ou marcadores informativos de ancestralidade (AIMs) e apresentam alelos com grandes diferenciais de freqüência, superiores a 30%, entre populações geográfica ou etnicamente definidas. Os microssatélites (STRs) são variantes genéticos úteis no mapeamento genético de espécies, na identificação de pessoas, mapeamento genético e análise de populações. Alguns STRs apresentam alelos com freqüências marcantes em determinados grupos populacionais. Com objetivo de comparar a ancestralidade genomica avaliada com dois tipos de marcadores, foram estudados 8 microssatélites STRs autossômicos (TH01, vWA31, D18S51, FGA, TPOX, D7S820, D3S1358, D8S1179) e 9 AIMs (FY-Null, LPL, AT3-I/D, Sb19.3, APO, PV92, CYP3A4, CKMM, GC-1F e GC-1S), em 203 indivíduos miscigenados da Bahia. A genotipagem foi realizada por PCR (Polimerase Chain Reaction), para deleções, inserções e para os microssatélites e PCR quantitativo em tempo real para mutações pontuais. As contribuições africana, européia e ameríndia observadas foram respectivamente 33,5%, 58,6% e 7,9% para os STRs e 45,08%, 45,16% e 9,75% para os AIMs, comprovando a miscigenação da população. O Índice Kappa, mostrou que a concordância entre as estimativas de ancestralidade utilizando os dois tipos de marcadores (AIMs e STRs), foi muito baixa (kappa = 0,12). Foi observada associação entre sobrenome de conotação religiosa e ancestralidade africana / The mixing between the three main ethnic groups (Amerindians, Europeans and Africans) produced a high genetic diversity of the braziliam population. In Bahia, the proportion of African descent that call themselves black or brown is 77.5% and 79.8% in Salvador. Few studies describe the genetic diversity of the population of Bahia and the contribution of each ethnic group in its formation. Several DNA markers are currently used to estimate ethnic mix in admixed populations. These markers are called alleles specific population (PSAs) or ancestry informative markers (AIMs) and carry alleles with large differences in frequency above 30% between populations geographically or ethnically defined. Microsatellites (STRs) are useful genetic variants in the genetic mapping of species, identification of persons, genetic mapping and analysis of populations. Some STRs have alleles with frequencies marked in certain population groups. To compare the ancestry genomica evaluated with two types of markers were studied 8 microsatellite autosomal STRs (TH01, vWA31, D18S51, FGA, TPOX, D7S820, D3S1358, D8S1179) and 9 AIMs (FY-Null, LPL, AT3-I /D, Sb19.3, APO, PV92, CYP3A4, CK-MM, GC and GC-1F-1S) in 203 subjects with mixed Bahia. Genotyping was performed by PCR (Polymerase Chain Reaction), for deletions, insertions and for microsatellite and quantitative PCR in real time for mutations. The contributions of African, European and Amerindian observed were respectively 33.5%, 58.6% and 7.9% for the STRs and 45.08%, 45.16% and 9.75% for the AIMs, proving the mixing of population. The Kappa index showed that the correlation between the estimates of ancestry using both types of markers (AIMs and STRs), was very low (kappa = 0.12). Association was found between devotional surnames and African ancestry.

Made available in DSpace on 2014-06-11T19:35:08Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-04-23Bitstream added on 2014-06-13T18:46:23Z : No. of bitstreams: 1 pivatto_m_dr_araiq.pdf: 3895401 bytes, checksum: 8f00934510e296fa101a80060a9db12a (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / O presente trabalho teve como objetivo o estudo das vias biossintéticas dos alcalóides piperidínicos presentes em Senna spectabilis, motivado pela potente atividade anticolinesterásica e baixa toxicidade observada no derivado (–)-3-O-acetil-espectalina (15), eleito como composto líder para o desenvolvimento de fármacos anti-Alzheimer que estão em fase de estudos pré-clínicos. Por outro lado, o interesse acadêmico no conhecimento das vias metabólicas, pode levar a estudos futuros de engenharia genética para potencializar a produção desses metabólitos uma vez que a síntese é extremamente complexa em função da presença de três centros estereogênicos. Tendo isso em vista, foram selecionadas seis espécies de Senna e Cassia para avaliar a presença dos alcalóides e selecionar aquela que os produz em maior quantidade. Foram estudadas as flores de S. spectabilis, S. multijuga, S. macranthera, S. velutina, C. fistula, C. leptophylla, sendo que só foram detectados alcalóides piperidínicos e piridínicos em S. spectabilis e S. multijuga, respectivamente, utilizando a espectrometria de massas tandem. Embora sejam de classes diferentes, esses metabólitos têm padrão de substituição similar, porém, apresentaram atividade anticolinesterásica diferenciada. De S. spectabilis foram isolados os alcalóides piperidínicos: (–)-cassina (1), (–)-espectalina (9), (–)-3-O-acetil-espectalina (15), (–)-3-O-acetil-cassina (16) e identificados 7-hidroxi-carnavalina (71), 7-hidroxi-cassina (18) e/ou espicigerina (42) utilizando a EM. De S. multijuga foram isolados os alcalóides piridínicos: 7'-multijuguinona (67) e 12'-hidroxi-7'-multijuguinona (69) e identificados 7'-multijuguinol (68) e 12'-hidroxi-7'- multijuguinol (70). Para os estudos biossintéticos dos alcalóides piperidínicos foi inicialmente proposta a biogênese onde lisina e acetato foram eleitos potenciais... / The following work encompass as main goal the study of biosynthetic pathways to produce piperidine alkaloids using Senna spectabilis as natural matrix. Such research was instigated due to the high acetylcholinesterase activity and low toxicity showed by the derivative (–)-3-O-acetyl-spectaline (15), selected as a lead compound against Alzheimer’s disease and currently under pre-clinical trials. Still yet, the academic interest on researching metabolic pathways that may lead to further genetic engineering studies to enhance the production of these metabolites is of extremely importance, due to the inability of producing any commercially viable synthetic strategy for their stereogenic centers. We selected six Senna and Cassia species to evaluate the presence of these metabolites aiming to select which matrix will produce them the most. We studied flowers from S. spectabilis, S. multijuga, S. macranthera, S. velutina, C. fistula and C. leptophylla. From those, we were able to detect piperidine and pyridine alkaloids only in S. spectabilis and S. multijuga, respectively, using tandem mass spectrometry. Regardless of the different structural nature towards 15, those metabolites have similar substitution patterns and showed differential acetylcholinesterase activity. From S. spectabilis were isolated the piperidine alkaloids: (–)-cassine (1), (–)-spectaline (9), (–)-3-O-acetyl-spectaline (15), (–)-3-O-acetyl-cassine (16), and identified 7-hidroxy- carnavaline (71), 7-hidroxy-cassine (18) and/or spicigerine (42) by tandem mass spectrometry and from S. multijuga were isolated the pyridine alkaloids: 7'-multijuguinone (67), 12'-hydroxy-7'-multijuguinone (69) and, identified by MS: 7'-multijuguinol (68) and 12'-hydroxy-7'-multijuguinol (70). We initially proposed the incorporation of lysine and acetate as main precursors of the piperidine alkaloids biosynthetic pathway and thus... (Complete abstract click electronic access below)

Cette thèse étudie les différentes formes d'étayage que les étudiants mettent en place dans un tandem par visiocoférence poste à poste afin de s'entraider dans leurs apprentissages des langues française et chinoise. Nous passons en revue différentes études s'étant penchées sur les questions de l'apprentissage, l'interaction, l'apprentissage des langues dans l'interaction, la compétence communicative, la multimodalité de la communication médiatisée par ordinateur. Pour les fins de notre recherche, nous avons compilé un corpus de vingt heures environ d'interactions télétandem. En adoptant un positionnement épistémologique constructiviste, complexe, transdisciplinaire et compréhensif, nous élaborons une perspective interactionniste et écologique dégageant plusieurs niveaux d'analyse, analysés avant tout séparément, ensuite en les reliant. Ainsi, nous étudions les positionnements discursifs d'expertise et différentes formes de séquences latérales d'étayage langagier. A l'aide de statistiques descriptives, nous dégageons les configurations et les attracteurs du système binôme télétandem et en analysons les potentialités pour le développement de la compétence communicative. / This thesis studies different forms of scaffolding that students provide in a tandem through desktop videoconference in order to help one another in learning French and Chines as foreign languages. I review studies on learning, interaction, language learning in interaction, communicative competence, the multimodality of computer-mediated communication.For my research, I compiled a corpus of about twenty hours of teletandem interactions. I adopt an epistemological posture which is constructivist, complex, transdisciplinary and comprehensive. I elaborate an interactionist and ecological perspective bringing out different levels of analysis, analyzed separately at first, then together. In this way, I study discursive positioning of expertise and different forms of scaffolding side sequences for language learning. Using descriptive statistics tools, I identify the configurations and attractors of the teletandem pair system and I discuss their potential for the development of communicative competence.

The master thesis deals with the design of a light tandem roller with an electric drive. The final design of the machine is designed in regard to the knowledge from design and technical analysis and the shortcomings of current rollers. The purpose of this work is to design a tandem roller which will respect the ergonomic requirements of the operator.

La limite théorique d’efficacité d’une cellule solaire simple jonction est de ~29 %. Afin de dépasser cette limite, une des moyens les plus prometteurs est de combiner le silicium avec des matériaux III-V. Alors que la plupart des solutions proposées dans la littérature proposent de faire croître directement le matériau III-V sur substrat silicium, ce travail présente une approche innovante de fabriquer ces cellules solaires tandem. Nous proposons une approche inverse métamorphique, où le silicium cristallin ou SiGe est cru directement sur le matériau III-V par PECVD. La faible température de dépôt (< 200 °C) diminue les problèmes de différence de dilatation thermique, et le fait de croître le matériau IV sur le matériau III-V élimine les problèmes de polarité.La réalisation de la cellule tandem finale en SiGe/AlGaAs passe par le développement et l’optimisation de plusieurs briques technologiques. Tout d’abord, nous développons l’épitaxie à 175 °C de Si(Ge) sur des substrats de Si (100) dans un réacteur de RF-PECVD industriel. La réalisation de cellules solaires à hétérojonction à partir de ce matériau Si(Ge) crû par PECVD montre que ses performances électriques s’avèrent prometteuses. Nous obtenons pour un absorbeur de 1.5 µm des Voc qui atteignent 0.57 V. L’incorporation de Ge permet d’augmenter le JSC de 15.4 % jusqu’à 16.6 A/cm2 pour Si0.72Ge0.28.En parallèle, la croissance de cellules solaires AlGaAs a été développée, ainsi que sa fabrication technologique. Nous obtenons une efficacité de 17.6 % pour une cellule simple en Al0.22Ga0.78As. Nous développons aussi des jonctions tunnel, parties essentielles d’une cellule tandem dans une configuration à deux terminaux. Nous développons notamment le dopage n du GaAs en utilisant le précurseur DIPTe, et obtenons des jonctions tunnel ayant des courants pic atteignant jusqu’à 3000 A/cm2, rejoignant ainsi les résultats de l’état de l’art.Ensuite, nous étudions l’hétéro-épitaxie de Si sur GaAs par PECVD. Le c-Si montre d’excellentes propriétés structurales. Les premiers stades de croissance sont étudiés par diffraction des rayons X avec rayonnement synchrotron. Nous trouvons un comportement inattendu : le Si est relâché dès les premiers nanomètres, mais sa maille est tétragonale. Alors que le GaAs a un paramètre de maille plus grand que le Si, le paramètre hors du plan (a⏊) du Si est plus élevé que son paramètre dans le plan (a//). Nous trouvons une forte corrélation entre cette tétragonalité et la présence d’hydrogène dans la couche de silicium. D’autre part, nous montrons que le plasma d’hydrogène présent lors du dépôt PECVD affecte les propriétés du GaAs : son dopage diminue d’environ un ordre de grandeur lorsque le GaAs est exposé au plasma H2, dû à la formation de complexes entre le H et le dopant (C, Te ou Si). Le dopage initial peut être retrouvé après un recuit à 350 °C.Enfin, nous étudions la dernière étape de fabrication de la cellule tandem : le collage. Nous avons pu reporter une cellule simple inversée en AlGaAs sur un substrat hôte (en Si), retirer le substrat GaAs et effectuer les étapes de microfabrication sur un substrat 2 pouces. Des couches épaisses de Si (>1 µm) ont été crues avec succès sur une cellule AlGaAs inversée suivie d’une jonction tunnel. Le collage de cette cellule tandem, et la processus de fabrication technologique du dispositif final sont ensuite étudiés, afin de pouvoir caractériser électriquement la première cellule solaire tandem fabriquée par croissance inverse métamorphique de Si sur III-V. / Combining Silicon with III-V materials represents a promising pathway to overcome the ≈29% efficiency limit of a single c-Si solar cell. While the standard approach is to grow III-V materials on Si, this work deals with an innovative way of fabricating tandem solar cells. We use an inverted metamorphic approach in which crystalline silicon or SiGe is directly grown on III-V materials by PECVD. The low temperature of this process (<200 °C) reduces the usual thermal expansion problems, and growing the group IV material on the III-V prevents polarity issues.The realization of the final tandem solar cell made of SiGe/AlGaAs requires the development and optimization of various building blocks. First, we develop the epitaxy at 175°C of Si(Ge) on (100) Si substrates in an industrial standard RF-PECVD reactor. We prove the promising electrical performances of such grown Si(Ge) by realizing PIN heterojunction solar cells with 1.5µm epitaxial absorber leading to a Voc up to 0.57 V. We show that the incorporation of Ge in the layer increases the Jsc from 15.4 up to 16.6 A/cm2 (SiGe28%).Meanwhile, we develop the growth of AlGaAs solar cells by MOVPE and its process flow. We reach an efficiency of 17.6 % for a single Al0.22GaAs solar cell. We then develop the tunnel junction (TJ), essential part of a tandem solar cell with 2-terminal integration. We develop the growth of n-doped GaAs with DIPTe precursor to fabricate TJs with peak tunneling currents up to 3000 A/cm2, reaching state-of-the art TJs.Then, the hetero-epitaxy of Si on GaAs by PECVD is studied. c-Si exhibits excellent structural properties, and the first stages of the growth are investigated by X-ray diffraction with synchrotron beam. We find an unexpected behavior: the grown Si is fully relaxed, but tetragonal. While the GaAs lattice parameter is higher than silicon one, we find a higher out-of-plane Si parameter (a⏊) than in-plane (a//), contradicting the common rules of hetero-epitaxy. We find a strong correlation between this tetragonal behavior and the presence of hydrogen in the Si layer. We furthermore show that hydrogen also plays a strong role in GaAs: the doping level of GaAs is decreased by one order of magnitude when exposed to a H2 plasma, due to the formation of complexes between H and the dopants (C, Te, Si). This behavior can be recovered after annealing at 350°C.Finally, the last step of device fabrication is studied: the bonding. We successfully bonded an inverted AlGaAs cell, removed it from its substrate, and processed a full 2” wafer. We succeeded in growing our first tandem solar cells by growing thick layers (>1 µm) of Si on an inverted AlGaAs solar cells followed by a TJ. The bonding and process of this final device is then performed, leading, as a next step, to the electrical measurement of the very first tandem solar cell grown by inverted metamorphic growth of Si on III-V.

The tandem airfoil has potential to do more work as a compressor blade than a single airfoil without incurring significantly higher losses. Although tandem blades are sometimes employed as stators, they have not been used in any known commercial rotors. The goal of this work is to evaluate the aerodynamic feasibility of using a tandem rotor in the rear stages of a core compressor. As such, the results are constrained to shock-free, fully turbulent flow. The work is divided into 2-D and 3-D simulations. The 3-D results are subject to an additional constraint: thick endwall boundary layers at the inlet. Existing literature data on tandem airfoils in 2-D rectilinear cascades have been compiled and presented in a Lieblein loss versus loading correlation. Large scatter in the data gave motivation to conduct an extensive 2-D CFD study evaluating the overall performance as a function of the relative positions of the forward and aft airfoils. CFD results were consistent with trends in the open literature, both of which indicate that a properly designed tandem airfoil can outperform a comparable single airfoil on- and off-design. The general agreement of the CFD and literature data serves as a validation for the computational approach. A high hub-to-tip ratio 3-D blade geometry was developed based upon the best-case tandem airfoil configuration from the 2-D study. The 3-D tandem rotor was simulated in isolation in order to scrutinize the fluid mechanisms of the rotor, which had not previously been well documented. A geometrically similar single blade rotor was also simulated under the same conditions for a baseline comparison. The tandem rotor was found to outperform its single blade counterpart by attaining a higher work coefficient, polytropic efficiency and numerical stall margin. An examination of the tandem rotor fluid mechanics revealed that the forward blade acts in a similar manner to a conventional rotor. The aft blade is strongly dependent upon the flow it receives from the forward blade, and tends to be more three-dimensional and non-uniform than the forward blade. / Ph. D.