Orientador: Mônica Alonso Cotta / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin / Made available in DSpace on 2018-08-17T12:15:05Z (GMT). No. of bitstreams: 1 Moreau_AlbertoLuisDario_D.pdf: 4972430 bytes, checksum: 23390541e98ea8174b689428392b8457 (MD5) Previous issue date: 2011 / Resumo: Na primeira parte deste trabalho, nós investigamos o processo de crescimento de um biofilme de bactérias (Xylella fastidiosa) inoculadas sobre lamínulas de vidro. O tamanho e a distância entre os biofilmes foram estudados por imagens de microscopia óptica; e uma análise fractal foi realizada usando conceitos de escala e imagens de AFM. Observamos que biofilmes diferentes mostram características fractais semelhantes, embora as variações na morfologia possam ser identificadas para diferentes estádios de crescimento do biofilme. Dois tipos de padrões estruturais são identificados através da dimensão fractal (Df) sugerindo que o crescimento do biofilme pode ser entendido como o modelo de Eden nos estágios de formação e no final, enquanto para o estágio de maturação aparecem evidências do modelo DLA (diffusion-limited aggregation). Estes resultados foram correlacionados à formação da matriz do biofilme que pode dificultar a difusão dos nutrientes e por isso criar condições para um crescimento DLA. Ainda com o AFM, fizemos medidas de espectroscopia de força para estudar a interação específica entre antígeno-anticorpo relacionados ao vírus CTV (citrus tristeza virus). Para tanto foi realizado o estudo da imobilização deste material biológico nas superfícies da ponta do AFM, e nos substratos planos de Si e InP. Usamos para isto imagens topográficas de AFM, imagens de microscopia eletrônica e ensaios imunoquímicos de ELISA; com isso pudemos confirmar que tanto o antígeno quanto o anticorpo foram imobilizados e que eles continuavam em seus estados nativos. Com as medidas de espectroscopia de força, detectamos que a diferença de força entre as interações específicas (antígeno-anticorpo) e não-específicas (antígeno-antígeno) foi de aproximadamente 60%. Utilizamos a mesma rotina de preparação em substrato de InP para o desenvolvimento de um biossensor baseado no funcionamento de um transistor FET (field-effect transistor). Os anticorpos foram imobilizados na superfície do semicondutor, enquanto doses de antígenos livres eram adicionadas a uma célula líquida que mantinha contato com esta superfície. Com curvas de corrente vs tensão em regiões lineares do dispositivo, estudamos a resposta, a sensibilidade e a especificidade do sensor, obtendo resultados promissores indicando viabilidade no desenvolvimento e no uso do mesmo. Por fim, estudamos a durabilidade de pontas de AFM com CNT (carbon nanotube) encapsulados com carbono amorfo numa amostra padrão semicondutora de pontos quânticos, além de estudar a sua estabilidade em meio líquido. Duas pontas foram estudadas, uma fabricada pelo nosso grupo e outra comercial, fornecida pela empresa americana CDI (Carbon Design Inovation). Utilizamos ferramenta de FT (fourier transform) para o estudo da resolução das pontas em imagens topográficas de AFM, e verificamos que ambas as pontas duraram mais de 400 imagens tendo uma perda da resolução de ~ 7% no ar e de ~ 5% ¿ em relação às medidas a seco ¿ em meio líquido, mostrando a viabilidade de seu uso no estudo de amostras biológicas / Abstract: We have investigated the growth process of Xylella fastidiosa biofilms inoculated on glass. The size and the distance between biofilms were analyzed by optical microscopy images; a fractal analysis was carried out using scaling concepts and Atomic Force Microscopy (AFM) images. We observed that different biofilms show similar fractal characteristics, although morphological variations can be identified for the different biofilm stages. Two types of structural patterns are suggested from the observed fractal dimensions Df: and suggest that the biofilm growth can be understood as an Eden model in the initial and final stages, while diffusion-limited aggregation (DLA) seems to dominate the maturation stage. Changes in the correlation length parallel to the surface were also observed; these results were correlated to the biofilm matrix formation which can hinder nutrient diffusion and thus create conditions to drive DLA growth. Atomic force spectroscopy was used as a method to investigate the specific antibody-antigen binding using proteins of the CTV (citrus tristeza virus). Subsequently, the chemical processes of covalent immobilization of the used biomolecules to different solid supports ¿ Si3N4 AFM Tips, Si and InP plane substrates ¿ was developed and characterized. The verification of the chemical binding process by different methods like AFM topography experiments, electron microscopy and ELISA immunochemical assays showed a successful immobilization of the biomolecules and that they were still in their native state. The analysis of the spectroscopic force data showed a significant difference in binding force between the specific antibody-antigen complexes and the non-specific controls (approximately 60%). The same chemical immobilization process was used to bind biomolecules to solid InP supports to develop a biosensor based on the field-effect transistor (FET) principle. The same antibodies, as used in atomic force experiments, were immobilized covalently to the semiconductor surface. The antibody-antigen complexation by adding the specific antigens to the functionalized surface was detected through changes in the current vs tension curves of semiconductor sample. The characterization of the electrochemical response, the molecular sensibility and the specificity of this biosensor showed a suitable method to detect specific molecular binding events. Further, the durability and stability of AFM tips with bonded carbon nanotubes with encapsulated amorphous carbon was studied on a standard semiconductor sample with quantum dots in air and liquid environment. Two different CNT AFM-tips were studied within this study in acoustic mode. One was assembled in our group and the other tip was provided by the american CDI (Carbon Design Innovation) company. The topographic AFM images were analyzed via FT (Fourier Transform) to study the spatial resolution of these tips. In air, both types of CNT tips showed a minor resolution decrease of approximately 6% after 400 topographic scans. In liquid environment an overall 10% lower spatial resolution of the tips was observed compared to the resolution in air which nevertheless makes these CNT AFM-tips suitable for experiments with native biological samples / Doutorado / Biofísica / Doutor em Ciências

Orientador: Mônica Alonso Cotta / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin / Made available in DSpace on 2018-08-17T22:17:37Z (GMT). No. of bitstreams: 1 NietoGonzalez_Luis_D.pdf: 3428571 bytes, checksum: 13775c720d8ebcf8c855b532ae715b49 (MD5) Previous issue date: 2007 / Resumo: Neste trabalho estudamos os mecanismos de crescimento durante a epitaxia por feixe químico de nanoestruturas III-V baseadas no sistema InAs/InP. Particularmente, foram estudados nanofios e ilhas de InAs sobre uma camada buffer InP(001) e nanofios de InAs sobre uma matriz de InGaAs/InP (com mesmo parâmetro de rede). Apresentaremos, nesta tese, as diferenças e similaridades destes sistemas quanto a condições de crescimento, distribuição de tamanho, forma e os efeitos de volume da camada de InGaAs sobre as nanoestruturas de InAs quando comparadas ao sistema InAs/InP. Nossa escolha do InGaAs/InP como camada buffer para a nucleação dos fios de InAs, foi feita porque facilitaria a utilização deste sistema em diversas aplicações, proporcionando maior flexibilidade no desenho dos dispositivos. Por outro lado, este material abre a possibilidade de controlar as características das nanoestruturas através das propriedades de bulk e superficiais da liga ternária InGaAs. Além disso, ligas ternárias podem exibir efeitos de volume que afetam suas propriedades superficiais. Estes fenômenos podem afetar a nucleação dos fios quânticos e por isso foram objeto de nosso estudo. Para isso utilizamos e correlacionamos medidas in situ de difração de elétrons de alta energia (RHEED), microscopia de força atômica (AFM) e eletrônica de transmissão (TEM), com os resultados obtidos por difração de raios X com incidência rasante (GIXD). Verificamos, deste modo, tanto a influência das condições de crescimento, como o comportamento da relaxação da energia elástica nas nanoestruturas. Com todos estes resultados mostramos como acontece a evolução da deformação nos nanofios e pontos quânticos de InAs/InP e como acontecem as transições de forma entre estes dois tipos de nanoestruturas, em função das condições de crescimento e tipo de superfície do substrato utilizado. Mostramos, também que a introdução de um composto ternário (InGaAs) entre o InAs e o InP não afeta significativamente a forma e tamanho das nanoestruturas quando comparadas ao caso InAs/InP. Em particular, a interdifusão gerada por variações locais da composição na camada buffer em nanofios de InAs pode ser minimizada através de mudanças nas condições de crescimento do InGaAs / Abstract: In this work we study the growth mechanisms of III-V nanostructures by chemical beam epitaxy (CBE) based on the InAs/InP materials system. Particularly, nanowires and nanodots of InAs on InP (001) and InAs nanowires on InGaAs/InP (lattice matched) buffer layers were studied. The differences and similarities of these systems are presented in this text, as a function of growth conditions, size distribution, as well as the bulk effects of the InGaAs layer on InAs nanostructures when compared to the InAs/InP system. Our choice of InGaAs/InP buffer layer for InAs nanowire nucleation was due to the possible use of this system in many applications, providing greater flexibility in device design. Furthermore, this material opens up the possibility of controlling nanostructures characteristics through bulk and surface properties of the InGaAs ternary alloy. In other hand, ternary alloys may present volume effects that affect their surface properties. These phenomena can affect quantum wires nucleation and thus became one of the subjects of our study. With these goals in mind, we have correlated in situ high-energy electrons diffraction (RHEED) measurements, atomic force microscopy (AFM) and transmission electron microscopy (TEM) images with the results obtained by grazing incidence X-ray diffraction (GIXD). We report here the influence of the growth conditions on nanostructure shape as well as the behavior of elastic energy relaxation within the nanostructures. Our results show how the evolution of deformation within InAs/InP nanowires and quantum dots occur and how the shape transition between these two types of nanostructures depend on the growth conditions and the substrate surface type used. We also show that the introduction of a ternary compound (InGaAs) between InAs and InP does not significantly affect the shape and size of nanostructures as compared to the InAs / InP case. In particular, the interdifusion generated in InAs nanowires by local variations in the buffer layer composition can be minimized through changes in InGaAs growth conditions / Doutorado / Estrutura de Líquidos e Sólidos; Cristalografia / Doutor em Ciências

Given the lack of effective vaccine or medicine, changing an individual's risk behaviours has been crucial in preventing the spread of HIV. Consistent and correct condom use has been considered as the most effective form of HIV prevention among female sex workers. Despite coordinated national level interventions over the last decade, a consistent decline in condom use among female sex workers has been evidenced in the Ethiopian context, particularly with non-paying partners. Thus far, no study has been produced that has illustrated major determinants of consistent condom use among female sex workers which would help in developing effective intervention strategies for the prevention of HIV spread in the country. In other countries, the Information, Motivation and Behaviour (IMB) model has been used to identify individual level determents of condom use. However, the researcher postulated that behaviour emanating from the personality structure of individuals could be the fundamental individual level determents of adherence to condom use and chose to investigate this using the Enneagram theory of personality, which was acknowledged for its heuristic value in explaining and enhancing self-development of at-risk individuals. This cross-sectional study was conducted in Addis Ababa. With the Without Finite Population Correction of the Sample Size Estimation Formula, the sample size of 350 was set and participants were recruited using Respondent-Driven Sampling (RDS). Using trained female sex workers, the Essential Enneagram Test (EET) and an Information-Motivation-Behaviour (IMB) questionnaire were administered to collect data. General Linear Modeling (GLM) Multivariate analysis was carried out to assess the correlation between personality style and consistent condom use among participants in the last seven days before the interview. The finding of this study revealed that personality type, measured by the Essential Enneagram Test (EET), is able to predict adherence to condom use among female sex workers and provided a new dimension for policy makers and practitioners in behavioural intervention programmes, such as Information-Education-Communication, peer-to-peer approaches, as well as health and rehabilitation services by using the Enneagram principles and universal growth process. / Psychology / D. Litt. et Phil. (Psychology)

Given the lack of effective vaccine or medicine, changing an individual's risk behaviours has been crucial in preventing the spread of HIV. Consistent and correct condom use has been considered as the most effective form of HIV prevention among female sex workers. Despite coordinated national level interventions over the last decade, a consistent decline in condom use among female sex workers has been evidenced in the Ethiopian context, particularly with non-paying partners. Thus far, no study has been produced that has illustrated major determinants of consistent condom use among female sex workers which would help in developing effective intervention strategies for the prevention of HIV spread in the country. In other countries, the Information, Motivation and Behaviour (IMB) model has been used to identify individual level determents of condom use. However, the researcher postulated that behaviour emanating from the personality structure of individuals could be the fundamental individual level determents of adherence to condom use and chose to investigate this using the Enneagram theory of personality, which was acknowledged for its heuristic value in explaining and enhancing self-development of at-risk individuals. This cross-sectional study was conducted in Addis Ababa. With the Without Finite Population Correction of the Sample Size Estimation Formula, the sample size of 350 was set and participants were recruited using Respondent-Driven Sampling (RDS). Using trained female sex workers, the Essential Enneagram Test (EET) and an Information-Motivation-Behaviour (IMB) questionnaire were administered to collect data. General Linear Modeling (GLM) Multivariate analysis was carried out to assess the correlation between personality style and consistent condom use among participants in the last seven days before the interview. The finding of this study revealed that personality type, measured by the Essential Enneagram Test (EET), is able to predict adherence to condom use among female sex workers and provided a new dimension for policy makers and practitioners in behavioural intervention programmes, such as Information-Education-Communication, peer-to-peer approaches, as well as health and rehabilitation services by using the Enneagram principles and universal growth process. / Psychology / D. Litt. et Phil. (Psychology)

Abstract This study aims to clarify the early development stages of technology intensive companies. The current literature does not offer an extensive review of stage perspectives for company growth – the overall picture of the field is somewhat vague. The evolution of this field remains unclear as well as the current state. Further, recent empirical stage models focusing on technology intensive companies have not been delineated. As companies move through their early stages, they face events which contribute to or detract from their aim. A study focusing on these events may provide fresh viewpoints for understanding the management processes. This study seeks to clarify how the literature describes the early stages of technology intensive companies, and what viewpoints are highlighted by the management as a company progresses through these sequences. This retrospective multiple case study clarifies the topic with two meta-analyses and a sequential incident study carried out in ten young technology intensive companies in Finland and Thailand. First, well covered areas, trends, and ideas for fresh approaches are studied through a meta-analysis of the past 60 years of literature focusing on stages of development. Based on recent empirical studies, a sequential self assessment framework is formed. Second, it is studied whether the case study methodology could be utilised to further clarify the early stages of technology intensive companies. Third, the experiences of ten case companies are reflected through the framework in order to test the framework, and to study what viewpoints these cases reveal about the early stages of technology intensive companies. This study provided an extensive review of the research focusing on the stages of development. A four-stage framework was found applicable for a self-assessment of the early stages in technology intensive companies, while ten case studies and cross case analysis provided partial support for the framework. In addition, this study provided many potential fresh viewpoints for a theory related to the early stages of technology intensive companies. These viewpoints are considered here as starting points for further research, which is expected to provide sufficient evidence for further modification of the framework. / Tiivistelmä Tämän tutkimuksen tavoitteena on selkeyttää teknologiaintensiivisten yritysten varhaisia kehitysvaiheita. Kirjallisuus ei tarjoa kattavaa katsausta yrityksen kehitysvaiheita käsittelevästä tutkimuksesta – kokonaiskuva aiheesta jää jokseenkin epämääräiseksi samoin kuin alan kehitys ja nykytila. Lisäksi viimeaikaisten empiiristä aineistoa sisältävien vaihemallien tuloksia ei ole koottu yhteen. Varhaisissa kehitysvaiheissaan yritykset kohtaavat sekä tavoitteitaan edistäviä että estäviä tapahtumia. Tapahtumia tutkimalla on mahdollista nostaa esille tuoreita näkökulmia varhaisiin vaiheisiin liittyviin johtamisprosesseihin. Tämä tutkimus pyrkii selvittämään, kuinka teknologiayrityksen varhaiset kehitysvaiheet on kuvattu kirjallisuudessa ja mitä näkökulmia varhaisen kehityksen läpi käyneiden yritysten johto korostaa. Tämä takautuva monitapaustutkimus analysoi aihetta kahden meta-analyysin ja vaiheittain toteutetun kriittiset tapahtumat -menetelmän avulla. Tapaustutkimus suoritettiin kymmenessä suomalaisessa ja thaimaalaisessa yrityksessä. Ensiksi 60 edeltävää vuotta käsittävässä meta-analyysissä analysoitiin vaihemallien historia ja nykytila, trendit ja potentiaaliset ideat uusille lähestymistavoille. Viimeaikaisten empiiristen tutkimusten perusteella muodostettiin synteesi varhaisten kehitysvaiheiden itsearviointikehykseksi. Toiseksi tutkittiin voidaanko tapaustutkimusta hyödyntämällä edelleen selventää teknologiaintensiivisten yritysten varhaisia kehitysvaiheita. Kolmanneksi kymmenen tapausyrityksen kokemuksia peilattiin itsearviointikehykseen tarkoituksena testata kehystä ja analysoida mitä näkökulmia tapaukset paljastavat teknologiaintensiivisten yritysten varhaisista vaiheista. Tutkimus tarjosi laajan katsauksen yrityksen kehitysvaiheisiin keskittyvään tutkimuskenttään. Nelivaiheinen kehys todettiin soveltuvaksi varhaisten kehitysvaiheiden itsearviointiin teknologiaintensiivisissä yrityksissä – kymmenen tapausta ja näiden vertailu antoi osittaisen tuen tälle. Lisäksi tutkimus tarjosi useita uusia näkökulmia teknologiaintensiivisten yritysten varhaisia kehitysvaiheita käsittelevään teoriaan. Nämä näkökulmat toimivat lähtökohtana jatkotutkimuksille, joiden oletetaan tuovan riittävästi todistusaineistoa itsearviointikehyksen edelleenkehittämiseksi.