Submitted by Gustavo Caixeta (gucaixeta@gmail.com) on 2017-02-16T10:41:56Z No. of bitstreams: 1 texto compĺeto.pdf: 927308 bytes, checksum: 87f5c56a4b88cc4b7ab4bed346550ec1 (MD5) / Made available in DSpace on 2017-02-16T10:41:56Z (GMT). No. of bitstreams: 1 texto compĺeto.pdf: 927308 bytes, checksum: 87f5c56a4b88cc4b7ab4bed346550ec1 (MD5) Previous issue date: 2003-12-05 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior, CAPES, Brasil / Este trabalho faz uma breve revisão das técnicas de crescimento de cristais, tanto volumétricas, quanto em camadas. São abordadas as técnicas Czocrhalski, Bridgman, Epitaxia por Fase Líquida, por Fluxo Molecular e de Paredes Quentes. Esta última técnica é utilizada no crescimento de filmes de CdTe sobre substratos de Si. A caracterização das amostras produzidas é feita por microscopia de força atômica, técnica que é descrita em detalhes. Finalmente são apresentados os resultados do estudo sobre o processo de nucleação do CdTe sobre Si e discutida a possibilidade de utilização deste processo na fabricação de pontos quânticos auto-formados. / This work makes a brief revision of crystal growth techniques. It describes the techniques Czocrhalski and Bridgman, used for bulk crystal growth, and also Liquid Phase Epitaxy, Molecular Beam Epitaxy and Hot Wall Epitaxy, which are used for the growth of thin layers. The last technique (HWE) is used in the experimental part of this work for the growth of CdTe films on Si(111) substrates. The characterization of the produced samples is done by Atomic Force Microscopy. The results obtained about the nucleation process of CdTe on Si(111) are presented and the possibility of the use of this technique in the production of self-assembled quantum dots is discussed.

Made available in DSpace on 2015-03-26T13:35:12Z (GMT). No. of bitstreams: 1 texto completo.pdf: 4918198 bytes, checksum: d8295a3e9f68661e7fe4f267ae5aa01d (MD5) Previous issue date: 2010-04-30 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The presence of nuclear radiation detectors is extremily important in various industries such as medical, astronomy and of national security. There are many types of detectors. However, the detector constructed with CdTe and CdZnTe semiconductor films has become very popular due to some characteristics as convenience, density, energy resolution and for having the possibility of operating at room temperature. In this work, a review of nuclear radiation detectors is made, especially those built with semiconductor. Here are also presented structural, superficial and electric characterization methods to inform which type of sample is the most viable for such purpose. We also present in this work the results of the of CdTe films growth using HotWall Epitaxy technique (HWE) in temperatures from 150 C and 250 C over Si (111), simple glass and glass covered with tin oxide with fluorine . It is also presented the results ofcharacterization of CdTe films by x-ray diffraction and electrical characterization by curves I x V. / A presença de detectores de radiação nuclear é de extrema importância em várias indústrias como, por exemplo, a médica, a astronômica e de segurança nacional. Existem inúmeros tipos de detectores. Um deles, o detector construído com ligas semicondutoras de CdTe e CdZnTe, tem se tornado bastante popular devido às características peculiares como: praticidade, densidade, resolução energética e pela possibilidade de operarem a temperatura ambiente. Neste trabalho, faremos uma revisão de detectores de radiação nuclear, especialmente dos construídos com semicondutores. Apresentamos também métodos de caracterização estrutural, superficial e elétrica de amostras a fim de informar qual tipo de amostra é a mais viável para tal finalidade. Mostramos os resultados do crescimento de filmes espessos de CdTe, utilizando a técnica de Epitaxia de Paredes Quentes (HWE) nas temperaturas de 150 C e 250 C sobre Si (111), vidro simples e vidro coberto com óxido de estanho dopado com flúor. São também apresentados os resultados de caracterização dos filmes de CdTe por difração de raios-X e caracterização elétrica através de curvas I x V do filme.

Rhizobium leguminosarum is a Gram negative, motile, nitrogen-fixing soil bacterium. Due to the scarcity of iron in the soil bacteria have developed a wide range of iron scavenging systems. The two types of iron scavenging systems used are indirect and direct. In-silico analysis of the genome identified a unique direct iron scavenging system the Hmu operon. This system has been identified in other closely related rhizobium species and is believed to be involved in utilizing heme compounds as a sole source of iron. We have attempted to characterize the role of the Hmu operon in iron utilization by monitoring the growth of R. leguminosarum ATCC 14479 in hemin supplemented media. Growth curves show that it is capable of using hemin as a sole source of iron. The outer membrane profiles were analyzed for the presence of hemin binding proteins.

No description available.

Στην παρούσα διατριβή παρουσιάζεται μια νέα μεθοδολογία σύνθεσης μη-πρωτεϊνικών αμινοξέων (ΜΠΑ) κατάλληλων για εφαρμογές στην πεπτιδική σύνθεση με χρήση του ασπαραγινικού οξέος ως χειρόμορφου εκμαγείου. Η μεθοδολογία αυτή βασίζεται στην επιτυχή και σε καλές αποδόσεις σύνθεση της β-αλδεΰδης του Ν-τριτυλοασπαραγινικού τριτ-βουτυλεστέρα, η οποία αποτελεί την ένωση «κλειδί». Αυτή στη συνέχεια έδωσε μια ποικιλία νέων ΜΠΑ μέσω αντιδράσεων Wittig, Horner-Emmons ή με επίδραση οργανοψευδραργυρικών αντιδραστηρίων. Ανάλογες μελέτες με σκοπό την σύνθεση των αντίστοιχων ομολόγων τους με έναν άνθρακα λιγότερο ή περισσότερο στην πλευρική αλυσίδα, ξεκινώντας από σερίνη ή γλουταμινικό οξύ δεν απέδωσαν τα αναμενόμενα αποτελέσματα ή ήταν ανεπιτυχείς. / In the present dissertation a new methodology is reported for the synthesis of novel non-proteinogenic amino acids (NPAAs) suitable for applications in solid phase peptide synthesis. This methodology involves aspartic acid as chiral template and relies on the successful and in good yields pepraration of the key N-tritylaspartic tert-butyl ester’s β-aldehyde, which when followed by Wittig, Horner-Emmons or Grignard type reactions may result in a variety of new NPAAs. Furthermore unsuccessful attempts towards the application of the present methodology for the synthesis of NPAA homologues bearing one carbon atom less or more in the side chain by using as chiral templates serine or glutamic acid, respectively, are also reported.