The possibility of combining different functionalities in a single device is of great relevance for further development of organic electronics in integrated components and circuitry. Organic light-emitting transistors (OLETs) have been demonstrated to be able to combine in a single device the electrical switching functionality of a field-effect transistor and the capability of light generation. A novel strategy in OLET realization is the tri-layer vertical hetero-junction. This configuration is similar to the bi-layer except for the presence of a new middle layer between the two transport layers. This “recombination” layer presents high emission quantum efficiency and OLED-like (Organic Light-Emitting Diode) vertical bulk mobility value. The key idea of the vertical tri-layer hetero-junction approach in realizing OLETs is that each layer has to be optimized according to its specific function (charge transport, energy transfer, radiative exciton recombination). Clearly, matching the overall device characteristics with the functional properties of the single materials composing the active region of the OFET, is a great challenge that requires a deep investigation of the morphological, optical and electrical features of the system. As in the case of the bi-layer based OLETs, it is clear that the interfaces between the dielectric and the bottom transport layer and between the recombination and the top transport layer are crucial for guaranteeing good ambipolar field-effect electrical characteristics. Moreover interfaces between the bottom transport and the recombination layer and between the recombination and the top transport layer should provide the favourable conditions for the charge percolation to happen in the recombination layer and form excitons. Organic light emitting transistor based on the tri-layer approach with external quantum efficiency out-performing the OLED state of the art has been recently demonstrated [Capelli et al., Nat. Mater. 9 (2010) 496-503] widening the scientific and technological interest in this field of research.

Many studies on the morphology, molecular orientation, device performance, substrate nature and growth parameter dependence have been carried out since the proposal of Sexithiophene (6T) for organic electronics [ ] However, these studies were mostly performed on films thicker than 20nm and without specifically addressing the relationship between morphology and molecular orientation within the nano and micro structures of ultrathin films of 0-3 monolayers. In 2004, the observation that in OFETs only the first few monolayers at the interface in contact with the gate insulator contribute to the charge transport [ ], underlined the importance to study submonolayer films and their evolution up to a few monolayers of thickness with appropriate experimental techniques. We present here a detailed Non-contact Atomic Force Microscopy and Scanning Tunneling Microscopy study on various substrates aiming at the investigation of growth mechanisms. Most reported similar studies are performed on ideal metals in UHV. However it is important to investigate the details of organic film growth on less ideal and even technological surfaces and device testpatterns. The present work addresses the growth of ultra thin organic films in-situ and quasi real-time by NC-AFM. An organic effusion cell is installed to evaporate the organic material directly onto the SPM sample scanning stage.

During the last decade advances in the field of sensor design and improved base materials have pushed the radiation hardness of the current silicon detector technology to impressive performance. It should allow operation of the tracking systems of the Large Hadron Collider (LHC) experiments at nominal luminosity (1034 cm-2s-1) for about 10 years. The current silicon detectors are unable to cope with such an environment. Silicon carbide (SiC), which has recently been recognized as potentially radiation hard, is now studied. In this work it was analyzed the effect of high energy neutron irradiation on 4H-SiC particle detectors. Schottky and junction particle detectors were irradiated with 1 MeV neutrons up to fluence of 1016 cm-2. It is well known that the degradation of the detectors with irradiation, independently of the structure used for their realization, is caused by lattice defects, like creation of point-like defect, dopant deactivation and dead layer formation and that a crucial aspect for the understanding of the defect kinetics at a microscopic level is the correct identification of the crystal defects in terms of their electrical activity. In order to clarify the defect kinetic it were carried out a thermal transient spectroscopy (DLTS and PICTS) analysis of different samples irradiated at increasing fluences. The defect evolution was correlated with the transport properties of the irradiated detector, always comparing with the un-irradiated one. The charge collection efficiency degradation of Schottky detectors induced by neutron irradiation was related to the increasing concentration of defects as function of the neutron fluence.

The main objective of this research is to improve the comprehension of the processes controlling the formation of caves and karst-like morphologies in quartz-rich lithologies (more than 90% quartz), like quartz-sandstones and metamorphic quartzites. In the scientific community the processes actually most retained to be responsible of these formations are explained in the “Arenisation Theory”. This implies a slow but pervasive dissolution of the quartz grain/mineral boundaries increasing the general porosity until the rock becomes incohesive and can be easily eroded by running waters. The loose sands produced by the weathering processes are then evacuated to the surface through processes of piping due to the infiltration of waters from the fracture network or the bedding planes. To deal with these problems we adopted a multidisciplinary approach through the exploration and the study of several cave systems in different tepuis. The first step was to build a theoretical model of the arenisation process, considering the most recent knowledge about the dissolution kinetics of quartz, the intergranular/grain boundaries diffusion processes, the primary diffusion porosity, in the simplified conditions of an open fracture crossed by a continuous flow of undersatured water. The results of the model were then compared with the world’s widest dataset (more than 150 analyses) of water geochemistry collected till now on the tepui, in superficial and cave settings. All these studies allowed verifying the importance and the effectiveness of the arenisation process that is confirmed to be the main process responsible of the primary formation of these caves and of the karst-like superficial morphologies. The numerical modelling and the field observations allowed evaluating a possible age of the cave systems around 20-30 million of years.

In this thesis I studied La0.7Sr0.3MnO3/Alq3/AlOx/Co organic spin valves, which are multifunctional devices showing an interesting interplay between magnetoresistive effects and memristive switching. In particular this work aims at elucidating the elusive mechanisms for spin injection and transport in this archetypal structure. While spin injection in organic materials was demonstrated by different spectroscopic techniques, the origin of magnetoresistive effect in organic spin valves is still debated. In fact, the Hanle effect, considered to be the only reliable proof for spin transport across the organic spacer layer, has not been observed in such a device, yet. I investigated the thickness and temperature dependence of charge transport and magnetoresistive properties, and demonstrated the absence of the Hanle effect. Moreover I studied how the resistance and magnetoresistance of our devices were affected by memristive switching, which turned out to be a fundamental tool to enlighten the comprehensive picture. Two clearly distinguishable conduction regimes have been found for non magnetoresistive and magnetoresistive devices. The former is compatible with models for charge transport in organic materials, the latter can be described by an equivalent circuit where metallic paths and hopping channels act in parallel. In the framework of this model, a coherent description for the interplay between MR and memristive switching can be given. SV signals can be explained as tunnel magnetoresistance (TMR) or ballistic magnetoresistance (BMR) occurring across shortened regions of the organic bulk, which is an explanation compatible with the absence of Hanle effect. This work demonstrates that SV signals can be explained without resorting to spin injection and transport into the organic layer.

Orientador: Bruto Max Pimentel Escobar. / Mestre

Resumo: O objetivo deste estudo foi de analisar a influência de um programa de exercício físico generalizado na memória e nas funções executivas de pessoas com doença de Parkinson. A amostra inicial foi composta por 69 participantes de ambos os gêneros (n=23 - grupo controle (GC), sem doenças neurodegenerativas; n=23 - grupo controle com doença de Parkinson (GCP), não participaram de programa de exercício físico; e n=23 - grupo de treinamento (GT) participaram de um programa de exercício físico durante seis meses). Em todos os grupos, pré-intervenção, avaliouse: estágio da doença pela Escala de Hoehn-Yahr modificada; rastreio cognitivo pelo Mini-Exame do Estado Mental; nível de atividade física pelo Questionário Baecke Modificado para Idosos; memória declarativa episódica e capacidade de evocação pelos sub-testes Memória Lógica I e II; memória de curto prazo, memória declarativa episódica, aprendizagem, capacidade de evocação e funções executivas pelo subteste Pares Verbais Associados; memória visuo-espacial pelo sub-teste Blocos de Corsi; memória de curto prazo e memória operacional pelo sub-teste Dígitos; memória operacional pelo sub-teste Sequência de Números e Letras; funções executivas pelo Teste Wisconsin de Classificação de Cartões; atenção concentrada pelo sub-teste Procurar Símbolos; sintomas de ansiedade pelo Inventário de Ansiedade Traço-Estado; sintomas depressivos pela Escala Hospitalar de Ansiedade e Depressão; e sintomas de estresse pelo Inventário de Sintomas de Stress para adultos de Lipp. Após seis meses de intervenção, 56 participantes (n=20 GC; n=20 GCP; n=16 GT) foram reavaliados pelos mesmos testes. Para a análise dos dados foi utilizada estatística descritiva (média e desvio-padrão) e ANOVA two-way para medidas repetidas em todas as variáveis com nível de significância... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The purpose of this study was to analyze the influence of a generalized physical exercise program on memory and executive functions in people with Parkinson's disease. The initial sample was composed by 69 participants of both gender (n=23 - control group (CG), without neurodegenerative diseases; n=23 - control group with Parkinson's disease (CGP), no participated in program of physical exercise; and n=23 - training group (TG), participated in program of physical exercíse for six months). In all of the groups, pre-intervention, was evaluated: severity of disease by Hoehn-Yahr Scale; cognitive screening by Mini-Mental State Examination; level of physical activity by Questionnaires Baecke Modified for the Elderly; episodic memory and recall memory by sub-tests Logic Memory I and II; short-term memory, episodic memory, learning, recall memory and executive functions by sub-test Paired Associated Learning; visuo-spatial memory by sub-test Corsi's Block-tapping test; short-term memory and working memory by sub-test Digits span; working memory by sub-test Letter Number Sequencing; executive functions by the Wisconsin Card Sorting Test; concentrated attention by sub-test Symbol Search; anxiety symptoms by State-Trait Anxiety Inventory; depressive symptoms by the Hospital Anxiety and Depression Scale; and stress symptoms by Lipp's Stress Symptoms Inventory for Adults. After six months of intervention, 56 participants (n=20 CG; n=20 CGP; n=16 TG) were revalued by the same tests. For the analysis of the data it was used descriptive statistics (mean and standard deviation) and two-way ANOVA for repeated measurements of all variables. The level of significance adopted was p<0.05. The results pointed significant interactions (p<0.05) in episodic memory, recall memory, learning, visuo-spatial memory, working memory and executive... (Complete abstract click electronic access below) / Orientador: Sebastião Gobbi / Coorientador: Ruth Ferreira Santos / Banca: José Carlos Fernandes Galduróz / Banca: Florindo Stella / Mestre

CoordenaÃÃo de AperfeiÃoamento de NÃvel Superior / Neste trabalho um modelo atmosfÃrico de resoluÃÃo de nuvens e um modelo da camada superior do oceano sÃo usados, isolados e acoplados, com a finalidade de se estudar, em duas dimensÃes (plano xz) a circulaÃÃo de Walker. As simulaÃÃes com o modelo oceÃnico, forÃadas por ventos zonais sÃo utilizadas para imitar o perfil climatolÃgico das temperaturas no Oceano PacÃfico Equatorial e obter a influÃncia da convecÃÃo sobre a temperatura da superfÃcie do oceano na parte equatorial oeste do PacÃfico. No modelo atmosfÃrico, a convecÃÃo atmosfÃrica Ãmida e o fluxo de grande-escala sÃo impulsionados por um gradiente linear de grande-escala da temperatura da superfÃcie do mar. As caracterÃsticas bÃsicas da circulaÃÃo de Walker e a realimentaÃÃo de ondas curtas das nuvens sobre a temperatura da superfÃcie sÃo estudadas. O acoplamento entre os modelos oceÃnico e atmosfÃrico à forÃado somente pelo perfil de temperatura das Ãguas mais quentes na parte oeste e Ãguas frias na parte leste da bacia oceÃnica. Algumas caracterÃsticas reais de processos fÃsicos de grande e de pequena-escala, tal como a correlaÃÃo entre salinidade e temperatura, sÃo relativamente bem reproduzi das em um modelo bidimensional acoplado.

Submitted by Cleide Dantas (cleidedantas@ufpa.br) on 2014-04-16T18:07:40Z No. of bitstreams: 2 license_rdf: 23898 bytes, checksum: e363e809996cf46ada20da1accfcd9c7 (MD5) Dissertacao_EfeitosTemperaturaPotencial.pdf: 344094 bytes, checksum: 23f60186b02599bfee5680a55f01848b (MD5) / Approved for entry into archive by Ana Rosa Silva (arosa@ufpa.br) on 2014-06-13T13:36:30Z (GMT) No. of bitstreams: 2 license_rdf: 23898 bytes, checksum: e363e809996cf46ada20da1accfcd9c7 (MD5) Dissertacao_EfeitosTemperaturaPotencial.pdf: 344094 bytes, checksum: 23f60186b02599bfee5680a55f01848b (MD5) / Made available in DSpace on 2014-06-13T13:36:30Z (GMT). No. of bitstreams: 2 license_rdf: 23898 bytes, checksum: e363e809996cf46ada20da1accfcd9c7 (MD5) Dissertacao_EfeitosTemperaturaPotencial.pdf: 344094 bytes, checksum: 23f60186b02599bfee5680a55f01848b (MD5) Previous issue date: 2009 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Neste trabalho iremos estudar os efeitos do potencial químico em (1 + 1) dimensões em modelos de teoria de campos a temperatura finita. Em particular, consideraremos férmions não massivos em um campo de fundo de calibre abeliano e calcularemos a ação efetiva por meio da função de n-pontos. Escreveremos a estrutura das amplitudes correspondentes e generalizaremos cálculos já existentes na literatura sem o potencial químico. Mostraremos através dos cálculos que a anomalia quiral não e afetada pela presença do potencial químico a temperatura finita. Entretanto, na ausência desse potencial as funções ímpares são nulas. Já na presença dele a temperatura finita, a função tem contribuições pares e ímpares. Mostraremos que a origem da estrutura das amplitudes e melhor vista a partir da formulação alternativa da teoria em termos dos espinores left- e right-handed. Os cálculos são também mais simples nessa formalação e alguns aspectos da teoria ficam mais claros. / In this work we study the e ects of a nonzero chemical potential in (1 + 1) dimensions quantum eld models at nite temperature. We particularly consider massless fermions in an abelian gauge eld background and calculate the e ective action by evaluating the n-point functions. We nd that the structure of the amplitudes corresponds to a generalization of the structure noted earlier in a calculation found in the literature without a chemical potential (the associated integrals carry the dependence on the chemical potential). Our calculation shows that the chiral anomaly is una ected by the presence of a chemical potential at nite temperature. However, unlike in the absence of a chemical potential, odd point functions do not vanish. In fact, we nd that all the even point functions are even functions of while the odd point functions are odd functions of . We show that the origin of the structure of the amplitudes is best seen from a formulation of the theory in terms of left and right handed spinors. The calculations are also much simpler in this formulation and it clari es many other aspects of the theory.

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