abstract: Nitride semiconductors have wide applications in electronics and optoelectronics technologies. Understanding the nature of the optical recombination process and its effects on luminescence efficiency is important for the development of novel devices. This dissertation deals with the optical properties of nitride semiconductors, including GaN epitaxial layers and more complex heterostructures. The emission characteristics are examined by cathodoluminescence spectroscopy and imaging, and are correlated with the structural and electrical properties studied by transmission electron microscopy and electron holography. Four major areas are covered in this dissertation, which are described next. The effect of strain on the emission characteristics in wurtzite GaN has been studied. The values of the residual strain in GaN epilayers with different dislocation densities are determined by x-ray diffraction, and the relationship between exciton emission energy and the in-plane residual strain is demonstrated. It shows that the emission energy increases withthe magnitude of the in-plane compressive strain. The temperature dependence of the emission characteristics in cubic GaN has been studied. It is observed that the exciton emission and donor-acceptor pair recombination behave differently with temperature. The donor-bound exciton binding energy has been measured to be 13 meV from the temperature dependence of the emission spectrum. It is also found that the ionization energies for both acceptors and donors are smaller in cubic compared with hexagonal structures, which should contribute to higher doping efficiencies. A comprehensive study on the structural and optical properties is presented for InGaN/GaN quantum wells emitting in the blue, green, and yellow regions of the electromagnetic spectrum. Transmission electron microscopy images indicate the presence of indium inhomogeneties which should be responsible for carrier localization. The temperature dependence of emission luminescence shows that the carrier localization effects become more significant with increasing emission wavelength. On the other hand, the effect of non-radiative recombination on luminescence efficiency also varies with the emission wavelength. The fast increase of the non-radiative recombination rate with temperature in the green emitting QWs contributes to the lower efficiency compared with the blue emitting QWs. The possible saturation of non-radiative recombination above 100 K may explain the unexpected high emission efficiency for the yellow emitting QWs Finally, the effects of InGaN underlayers on the electronic and optical properties of InGaN/GaN quantum wells emitting in visible spectral regions have been studied. A significant improvement of the emission efficiency is observed, which is associated with a blue shift in the emission energy, a reduced recombination lifetime, an increased spatial homogeneity in the luminescence, and a weaker internal field across the quantum wells. These are explained by a partial strain relaxation introduced by the InGaN underlayer, which is measured by reciprocal space mapping of the x-ray diffraction intensity. / Dissertation/Thesis / Ph.D. Physics 2012

nÃo hà / As taxas de morbimortalidade se elevam quando a diarreia està associada à desnutriÃÃo. Entretanto, os mecanismos pelos quais as deficiÃncias nutricionais afetam o intestino sÃo em grande parte desconhecidos. O objetivo desse trabalho foi avaliar alteraÃÃes morfomÃtricas, nas proteÃnas transportadoras de substratos e no transporte intestinal de eletrÃlitos e Ãgua em modelo de desnutriÃÃo em camundongos. Objetivamos ainda, analisar o efeito da toxina do cÃlera (TC) associada ou nÃo à desnutriÃÃo, sobre as proteÃnas transportadoras de substratos, sobre o transporte hidroeletrolÃtico em camundongos e por fim, avaliamos os efeitos de soluÃÃes de reidrataÃÃo oral (SRO) da OMS (SGli) e modificadas com glutamina (SGln), alanil-glutamina(SAla-Gln) e arginina (SArg) nesse transporte. Camundongos (n=20) receberam por 7 dias uma raÃÃo deficiente em proteÃnas, gorduras e minerais (DBR). Segmentos de Ãleo foram obtidos antes e no 7 dia da dieta, para estudos de morfometria, imunohistoquÃmica para as proteÃnas: SGTL-1, PepT-1, CAT-1 e SN-2 e avaliaÃÃo por RT-qPCR da expressÃo RNAm dessas proteÃnas transportadoras. O modelo de perfusÃo intestinal por 75 min em camundongos (n=6) foi utilizado para avaliar o transporte intestinal de Ãgua e eletrÃlitos e para avaliar o papel de soluÃÃes de reidrataÃÃo oral em camundongos nutridos e desnutridos expostos ou nÃo à toxina do cÃlera (1Âg/ml). Animais desnutridos apresentaram perda ponderal, atrofia dos vilos e reduÃÃo na expressÃo por imunofluorescÃncia da SGTL-1. A desnutriÃÃo causou ainda reduÃÃo na expressÃo do RNAm da SGTL-1 e PEPT-1 e aumento na expressÃo do RNAm para o SN-2 no ileo de camundongos. No modelo de perfusÃo intestinal, a desnutriÃÃo aguda aumentou a secreÃÃo intestinal de eletrÃlitos e Ãgua. A TC aumentou a secreÃÃo de eletrÃlitos e Ãgua em modelo de perfusÃo intestinal de camundongos. A TC aumentou a transcriÃÃo para o RNAm dos transportadores intestinais SGTL-1, PEPT-1 e CAT-1, mas nÃo aumentou a transcriÃÃo para o SN-2. As soluÃÃes de reidrataÃÃo com glicose (SGli), glutamina (SGln), alanil-glutamina (SAla-Gln) e arginina (SArg) diminuÃram a secreÃÃo de eletrÃlitos induzida pela TC. Apenas a SGln nÃo conseguiu diminuir significativamente a secreÃÃo de Ãgua induzida pela TC. Apenas a SGli reduziu a secreÃÃo de Ãgua induzida pela TC. SGli, SAla-Gln e SArg, mas nÃo SGln, diminuÃram a secreÃÃo de sÃdio e cloreto induzida pela TC. A desnutriÃÃo associada à diarreia pela TC causou reduÃÃo na transcriÃÃo para o RNAm dos transportadores intestinais SGTL-1, PEPT-1, CAT-1 e SN-2. A desnutriÃÃo associada à TC aumentou a secreÃÃo de Ãgua quando comparado ao grupo nutrido exposto à TC. SGli, SAla-Gln e SArg, mas nÃo SGln, diminuÃram a secreÃÃo de Ãgua induzida pela desnutriÃÃo associada à TC. Todas as soluÃÃes diminuÃram a secreÃÃo de sÃdio e cloreto induzida pela desnutriÃÃo associada à TC. / The morbidity and mortality rates rise when diarrhea is associated with malnutrition. However, the mechanisms by which nutritional deficiencies affect the gut are largely unknown. The aim of this study was to evaluate morphological changes in transport proteins and substrates in intestinal transport of electrolytes and water in malnutrition model in mice. We aim to further analyze the effect of cholera toxin (CT) with or without malnutrition on the carrier proteins substrates on electrolyte transport in mice and finally, we evaluate the effects of oral rehydration solutions (ORS) of OMS (SGli) e modified with glutamine (SGln), alanyl-glutamine (SAla-Gln) and arginine (SArg) in this transport. Mice (n=20) received for 7 days a diet deficient in protein, fat and minerals (DBR). Segments of ileum were obtained before and on day 7 of the diet, for studies of morphology, immunohistochemistry for proteins: SGTL-1, PEPT-1, CAT-1 and SN-2 and evaluated by RT-qPCR of mRNA expression of these transport proteins. The model of intestinal perfusion for 75 min in mice (n=6) was used to evaluate the intestinal transport of water and electrolytes and to evaluate the role of oral rehydration solutions in mice exposed nourished and malnourished or without cholera toxin (1Âg/ml). Malnourished animals showed weight loss, atrophy of the villi and reduced expression by immunofluorescence of SGTL-1. Malnutrition also caused a reduction in mRNA expression SGTL-1 and PEPT-1 and increased mRNA expression for SN-2 in mice ileum. In the model of intestinal perfusion, acute malnutrition increased intestinal secretion of electrolytes and water. CT increased the secretion of electrolytes and water into the intestinal perfusion model mice. SGli, SGln, SAla-Gln and SArg decreased secretion of electrolytes induced by CT. Just SGln failed to significantly decrease water secretion induced by CT. CT increased mRNA transcription for intestinal transporters SGTL-1, PEPT-1 and CAT-1 but not to increased transcription SN -2. Only SGli reduced water secretion induced by CT. SGli, SAla-Gln and SArg, but not SGln , decreased secretion of sodium and chloride induced by CT. The malnutrition associated with diarrhea caused by TC reduction in the transcription of mRNA for intestinal transporters SGT -1, PEPT-1, CAT-1 and SN-2. Malnutrition associated with CT increased the secretion of water when compared to the group fed exposed to TC. SGli , SAla-Gln and SArg, but not SGln, decreased water secretion induced by malnutrition associated with TC. All solutions decreased secretion of sodium and chlorid induced malnutrition associated with TC.

A partir de considerações sobre a atividade de transporte rodoviário de cargas, e tendo em vista os elevados custos que envolvem as operações de transporte, este trabalho apresenta uma sistemática que pode ser adotada por uma empresa de transporte rodoviário de cargas fracionadas, com ênfase na análise e na descrição da terceirização, através de etapas que envolvem o planejamento e as atividades a serem desempenhadas por agentes terceirizados nas operações de transporte. A adoção de tal sistemática visa tornar a empresa de transporte mais competitiva, criando diferenciais para melhor atender os graus de exigência cada vez maiores por parte dos clientes, agregando valor à atividade de transporte. / From some consideration of the road carrier activity, and having in mind the high costs involved in such operations, this work presents a system which can be adopted by a road carrier company (of fractional cargo), with emphasis on the analysis and description of outsourcing, through the steps involved in planning, and the tasks to be performed by outsourced agents in the transport operations. The adoption of such system aims to turn the transport company into a more competitive business, generating competitive edge to better meet the increasing demands of clients, providing added value to the transport activity.

Made available in DSpace on 2014-10-09T12:29:21Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:00:44Z (GMT). No. of bitstreams: 1 01240.pdf: 3735807 bytes, checksum: 0e9709821f36bbfb1be6ca3ed86a7d0f (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

A bixina é o principal carotenoide encontrado na superfície externa das sementes de Bixa orellana L., conhecida popularmente como urucum. Os extratos das sementes são largamente utilizados, tradicionalmente como condimento e no preparo de \"remédios\" caseiros para diversos tipos de doenças e sintomas. Industrialmente, é empregado em formulações farmacêuticas, cosméticos e alimentos como corante de origem natural. Contudo, o uso da bixina ainda é limitado pela sua baixa solubilidade em água. Foi observado que a bixina pode ser dispersa em água, por meio de técnica já patenteada pelo nosso grupo, sem uso de suportes e adjuvantes. O presente projeto teve por objetivo obter a bixina purificada de um extrato comercial de semente de urucum, preparar e caracterizar a dispersão de bixina em água e aplicá-la como um carreador de fármacos, utilizando daunorrubicina como modelo e que é utilizada no tratamento de tumores. Bixina foi obtida com 95% de pureza, a partir do extrato de semente de urucum e dispersões a partir deste composto foram preparadas em soluções aquosas e estabilizadas em cerca de duas horas. Foi determinado que a dispersão em água é constituída por partículas esféricas, com diâmetro médio variando de 20 a 150 nm e potencial Zeta de -24,7 mV. A dispersão manteve-se estável quando submetida a concentrações de NaCl de até 50 mmol/L e resistente em pH ácido. Porém, a partir de pH=10, ocorreu hidrólise do éster metílico da bixina, convertendo-a em norbixina. As partículas de bixina foram capazes de incorporar o fármaco daunorrubicina, em proporção molar máxima de bixina/daunorrubicina de 2:1. Nas concentrações testadas, a incorporação da daunorrubicina à dispersão de bixina causou aumento na atividade antiproliferativa, sendo até 60% mais ativa do que a daunorrubicina livre, na concentração de 1 µg/mL. A dispersão de bixina apresentou tolerância a variações em pH e concentração salina e capacidade de incorporar e aumentar a atividade do fármaco daunorrubicina. Sendo assim, constitui-se em um potencial sistema carreador de fármaco derivado de um produto natural. / Bixin is a carotenoid found on surface of Bixa orellana L. seeds, known as annatto. Annatto seeds extracts are popularly used as a condiment for foods and remedy for several diseases and symptoms. It is also applied in pharmaceutical products, cosmetics and food industry as a natural colorant. Nevertheless, the use of bixin is still limited by its poor solubility in water. Our research group has developed and patented a technique to disperse bixin in water, with no use of stabilizers or scaffolds. In this project, we aimed to obtain purified bixin from commercial annatto seeds extracts, prepare and characterize a dispersion of bixin in water and to employ it as a drug delivery system. Daunorubicin was chosen as a drug model to be delivered by bixin dispersion. Bixin was isolated from extracts in 95% purity. Aqueous dispersions of bixin demonstrated to be stable two hours after preparation. Bixin formed spherical particles with mean diameter ranging from 20 to 150 nm and Zeta potential of -24,7 mV. The dispersion was stable in NaCl solution up to 50 mMol/L and resistant to acidic medium. However, above pH=10, hydrolysis of ester termination begins to occur, converting bixin into to norbixin and since norbixin is water-soluble, the particles dissolved in water. Bixin dispersion was able to incorporate daunorubicin, in a bixin:daunorubicin molar proportion of 2:1. In all tested concentrations, daunorubicin delivered by bixin showed higher antiproliferative activity compared to free drug, reaching 60% more acitivity at 1 µg/mL In conclusion, bixin dispersion showed good stability in large range of pH and salt concentrations, ability to incorporate daunorubicin and enhanced the antitumoral activity. Thus, it can be considered a potential drug delivery system derived from a natural product.

O principal problema no desenvolvimento de vacinas de segunda geração é a baixa resposta contra os antígenos, geralmente extremamente purificados. Isto tem levado à busca de novos adjuvantes que sejam mais eficientes e menos tóxicos. Este trabalho objetivava o estudo de uma proteína de choque térmico de Mycobacterium leprae - 18kDa-hsp - recombinante, produzida em levedura, veiculada em lipossomos, como modelo de proteína carregadora para antígenos fracos. Além de um estudo de estabilização de lipossomos por liofilização. A 18kDa-hsp apresenta certas características peculiares que levaram ao desenvolvimento de um método de dosagem próprio e extensível a outras proteínas com baixo teor em aminoácido cromóforos. Tendo uso potencial como proteína carregadora, a 18kDa-hsp é estável, suportando bem aquecimento, liofilização, acilação e associação com lipossomos de fosfolípides, sem perda significativa de sua atividade. Estudos paralelos de estabilização de lipossomos unilamelares mostraram que se pode usar trealose como crioprotetora no processo de liofilização-reidratação, sem perdas significativas do conteúdo dos lipossomos e com manutenção das estruturas das vesículas. Finalmente, o sistema lipossomos-18kDa-hsp mostra-se promissor como um sistema estável para veiculação de imunógenos fracos. / The major problem on development of second generation vaccines is the poor response against some immunogens. It has leading an intense research to find other substances non toxic and more efficient on enhancement of the immunological response. The aim of this work was the study of a heat-shock protein from Mycobacterium leprae - 18kDa-hsp - produced in yeast and vehiculated in liposomes, as a protein carrier model for weak immunogens. Furthermore, there was a study on stabilization of liposomes by lyophilization. The peculiar protperties of the 18kDa-hsp lead us to develop a new method for quantification that can be extended to other proteins with low chromophore content. Potentially a carrier protein, the 18kDa-hsp is very stab1e: it has no significant loss of its antigenic reactivity when heated, lyophilized, acylated and associated to liposomes. Parallel studies on liposomes stabilisation show trehalose as a good cryoprotector. The sugar can avoid the leakage of the entrapped marker (protein) and maintain the vesicles structures on the lyophilisation-rehydration processo Finally, the system liposomes-18kDa-hsp is promising for vehiculation of weak immunogens.

M.Ing. (Electrical And Electronic Engineering) / In-vehicle Power Line Communication (PLC) is an emerging technology that can easily bene t the automotive industry by reducing the amount of wires (and hence cost, weight and complexity) for vehicle wire harnesses. The reduction in weight would also lead to less fuel consumption. This dissertation aims at taking the research of this technology a step towards fully understanding the vehicle's power line as a communication medium. We investigate the bit error characteristics of a readily available transceiver on the vehicle's power bus. To do so, we develop and perform bit error recording over the medium to get experimental results with the battery line under di ferent operating conditions. Using the rst set of these results, we parametrise di erent kinds of Markov models to see which one simulates the channel best. Using the preferred model, we then model the rest of the sets of results so that we can simulate the channel's bit error characteristics under these di erent conditions. Using these models, we demonstrate how these simulations can be used to evaluate the performance of di erent error detection and correction techniques. In particular, we evaluate the error detection mechanisms used in the popular in-vehicle Local Intercon- nect Network (LIN) protocol, in addition to some simple error correction techniques.

This thesis investigates the IEEE 802.11b standard that describes radio communication for networks. The standard is carefully explained and the limitations of the standard are presented. To put the system in its context and to study the effects from the frequency translation, surrounding areas such as radio propagation and networks in general are presented. For radio communications the carrier frequency gives the basic properties for the application, long distance communication uses low frequencies and the opposite for short-range communication. The report investigates the possibilities to translate the frequency for an IEEE 802.11b system to move the limits of IEEE 802.11b Three alternative solutions are compared. A final solution evolves from one of them. The resulting solution is based on existing hardware and is ready for testing. One major conclusion is that 802.11b is a well developed standard where the development of the hardware is focussed on the physical size. This miniaturization makes alteration more complex. Finally other interesting wireless techniques that could give the desired properties and other possible further work are presented.

Les polymères synthétiques tels que les dendrons ou les dendrimères possèdent des propriétés structurales intéressantes. Leur monodispersité et leur synthèse étape par étape permet de contrôler et de caractériser totalement leur structure. De plus, la multivalence offre aux vecteurs une meilleure affinité d’interactions entre plusieurs copies d’un ligand lié au dendron/dendrimère et le récepteur désiré en comparaison au ligand seul. L’adamantane est une molécule rigide et stable dont plusieurs dérivés ont été commercialisés pour des applications thérapeutiques, principalement comme agents antiviraux. De plus, il est possible de le fonctionnaliser sur 4 positions symétriques via des synthèses organiques. Sa conformation 3D permet d’amoindrir les encombrements stériques entre les groupements fonctionnels. Nous avons alors choisi de combiner les propriétés de l’adamantane et des dendrons afin de construire de nouveaux vecteurs synthétiques. Leurs synthèses s’effectuent avec de hauts rendements et chaque nouveau composé a été totalement caractérisé par les différentes techniques d’analyses chimiques et structurales. Les dendrons à base d’adamantane polycationiques non cytotoxiques ont révélé une forte pénétration cellulaire permettant de mieux comprendre les mécanismes d’internalisation des dendrons. Ils ont également été évalués pour la formation de complexes avec un plasmide d’ADN. Des modifications sur leurs structures ont amélioré leur capacité à interagir avec l’acide nucléique grâce à la modification du point focal. Enfin, un peptide thérapeutique aux propriétés protectrices dans le lupus érythémateux disséminé, P140, a été couplé à un dendron à base d’adamantane à 3 branches et nous avons analysé les effets biologiques du trimère en comparaison avec le monomère. / Dendrons (wedge-shaped dendrimer sections) have been investigated as ideal nanoscale carrier molecules for the delivery of bioactive materials into the cells. Molecular engineering of these hyperbranched, monodisperse, well-defined structures can be easily performed using simple organic synthesis. Multivalency constituted by the multiple surface groups at the periphery of a dendron promotes higher binding affinity for ligand/receptor interactions. Adamantane molecule is a rigid structure consisting of four cyclohexane rings fused in chair conformation. The well-defined 3D conformation, the hydrophobicity and the lipophilicity provide to adamantane-based compounds favorable properties for their transport through biological membranes. In this context, the first part of this work was focused on the design and the synthesis of a novel type of polycationic dendrons based on adamantane, which are able to penetrate into cells without triggering cytotoxic effects. The next study of this Thesis concerned the investigation of our polycationic adamantane-based dendrons for gene delivery. We evaluated the capacity of the dendrons to complex a plasmid DNA. Hydrophobic compounds (biotin and cholesterol) were covalently bound to the focal point of the dendrons via “click” chemistry and the effects of the dendron generation, the peripheral cationic groups, and the hydrophobic modifications on the formation and stability of the complexes were studied. Finally, the dendrons constituted of an adamantane core, a focal point and three arms, were synthetized starting from a multifunctional adamantane derivative. We have coupled P140, a therapeutic peptide with protective properties in systemic lupus erythematosus, to an adamantane-based dendron and we have analyzed the biological effects of the resulting trimer compared to the monomer.

No description available.