The goal of this research was to devise a new analytical technique, using Accelerator Mass Spectrometry (AMS), to measure Platinum Group Element (PGE) concentrations to the sup-ppb levels in natural, insulating, samples. The challenges were threefold. First, a method of sputtering an insulating sample to successfully produce a stable beam of anions needed to be devised. Second, a suitable standard of known PGE concentrations had to be found and third, spectral analysis of the beam had to verify any claims of PGE abundance. The first challenge was met by employing a modified high intensity negative ion source flooded with neutral caesium that successfully sputtered insulators to produce a beam of negative ions. The second challenge, that of finding a suitable standard, was fraught with difficulties, as no synthesized standards available were found to be appropriate for this work. As a result, direction is provided for future production of standards by ion implantation. The third challenge, successful spectral analysis, was accomplished using a newly designed gas ionization detector which allowed for resolution of the interfering molecular fragment from the PGE ions. Coupled with the use of the SRIM computer programme, positive identification of all peaks in the spectra of the analyzed samples was accomplished. The success of the first and third challenges lead to the qualitative analyses of geological samples for sub-ppb levels of PGE by AMS. Quantitative analyses await only for the appropriate standards and with those will come a whole new range of research possibilities for measuring sub-ppb levels of PGE in insulating samples by AMS.

A controlled and efficient coordination of gene expression is the key for normal development of an organism. In mammals, a subset of autosomal genes is expressed monoallelically depending on the sex of the transmitting parent, a phenomenon known as genomic imprinting. The imprinted state of the H19 and Igf2 genes is controlled by a short stretch of sequences upstream of H19 known as the imprinting control region (ICR). This region is differentially methylated and is responsible for the repression of the maternally inherited Igf2 allele. It harbors hypersensitive sites on the unmethylated maternal allele and functions as an insulator that binds a chromatin insulator protein CTCF. Hence the H19 ICR, which plays an important role in maintaining the imprinting status of H19 and Igf2, was shown to lose the insulator property upon CpG methylation. Another ICR in the Kcnq1 locus regulates long-range repression of p57Kip2 and Kcnq1 on the paternal allele, and is located on the neighboring subdomain of the imprinted gene cluster containing H19 and Igf2, on the distal end of mouse chromosome 7. Similarly to the H19 ICR, the Kcnq1 ICR appears to possess a unidirectional and methylation-sensitive chromatin insulator property in two different somatic cell types. Hence, methylation dependent insulator activity emerges as a common feature of imprinting control regions. The protein CTCF is required for the interpretation and propagation of the differentially methylated status of the H19 ICR. Work in this thesis shows that this feature applies genomewide. The mapping of CTCF target sites demonstrated not only a strong link between CTCF, formation of insulator complexes and maintaining methylation-free domains, but also a network of target sites that are involved in pivotal functions. The pattern of CTCF in vivo occupancy varies in a lineage-specific manner, although a small group of target sites show constitutive binding. In conclusion, the work of this thesis shows that epigenetic marks play an important role in regulating the insulator property. The studies also confirm the importance of CTCF in maintaining methylation-free domains and its role in insulator function. Our study unravels a new range of target sites for CTCF involved in divergent functions and their developmental control.

Topological insulators (TIs) are recently predicted, and much studied, new quantum materials. These materials are characterised by their unique surface electronic properties; namely, behaving as band insulators within their bulk, but with spin-momentum locked surface or edge states at their interface. These surface/edge crossing states are protected by the underlying time-reversal symmetry (TRS) of the bulk band structure, leading to a robust topological surface state (TSS) that is resistant to scattering from impurities which do not break TRS. Their surface band dispersion has a characteristic crossing at time reversal invariant momenta (TRIM) called a Dirac cone. It has been predicted that the introduction of a TRS breaking effect, through ferromagnetic order for instance, will open a band-gap in this Dirac cone. It can be seen that magnetic fields are not time reversal invariant by considering a solenoid. If time is reversed, the current will also reverse in the solenoid and so the magnetic field will also be reversed. So it can be seen that magnetic fields transform as odd under time reversal, the same will be true of internal magnetisation. By manipulating this gapped surface state a wide range of new physical phenomena are predicted, or in some cases, already experimentally observed. Of particular interest is the recently observed quantum anomalous Hall effect (QAHE) as well as, e.g., topological magneto-electric effect, surface Majorana Fermions and image magnetic monopoles. Building on these novel physical effects, it is hoped to open new pathways and device applications within the emerging fields of spintronics and quantum computation. This thesis presents an investigation of the nature of magnetic doping of the chalcogenide TIs Bi₂Se₃ and Bi₂Te₃ using 3d transition-metal dopants (Mn and Cr). Samples were grown by molecular beam epitaxy (MBE), an ideal growth method for the creation of high-quality thin film TI samples with very low defect densities. The grown films were investigated using a range of complementary lab-based and synchrotron-based techniques to fully resolve their physical structure, as well as their magnetic and electronic properties. The ultimate aim being to form a ferromagnetic ground state in the insulating material, which may be expanded into device applications. Samples of bulk Mn-doped Bi₂Te₃ are presented and it is shown that a ferromagnetic ground state is formed below a measured T_C of 9-13 K as determined by a range of experimental methodologies. These samples are found to have significant inhomogeneities within the crystal, a problem that is reduced in MBE-grown crystals. Mn-doped Bi₂Se₃ thin films were grown by MBE and their magnetic properties investigated by superconducting quantum interference device (SQUID) magnetometry and x-ray magnetic circular dichroism (XMCD). These reveal a saturation magnetisation of 5.1 μ_B/Mn and show the formation of short-range magnetic order at 2.5 K (from XMCD) with indication of a ferromagnetic ground state forming below 1.5 K. Thin films of Cr-doped Bi₂Se₃ were grown by MBE, driven by the recent observation of the QAHE in Cr-doped (Bi_1−xSb_x)₂Te₃. Investigation by SQUID shows a ferromagnetic ground state below 8.5 K with a saturation magnetisation of 2.1 μ_B/Cr. Polarised neutron reflectometry shows a uniform magnetisation profile with no indication of surface enhancement or of a magnetic dead layer. Further studies by extended x-ray absorption fine structure (EXAFS) and XMCD elucidate the electronic nature of the magnetic ground state of these materials. It is found that hybridisation between the Cr d and Se p orbitals leads to the Cr being divalent when doping on the Bi^3+ site. This covalent character to the electronic structure runs counter to the previously held belief that divalent Cr would originate from Cr clusters within the van der Waals gap of this material. The work overall demonstrates the formation of a ferromagnetic ground state for both Cr and Mn doped material. The transition temperature, below which ferromagnetic order is achieved, is currently too low for usable device applications. However, these materials provide a promising test bed for new physics and prototype devices.

Cette thèse poursuit deux directions dans le domaine des isolants et supraconducteurs topologiques.Dans la première partie de la thèse nous étudions des isolants en deux dimensions sur réseau, présentant un effet Hall quantique anormal (c'est-à-dire en l'absence d'un champ magnétique externe), induit par la présence d'un flux magnétique inhomogène dans la maille. Le système possède des phase isolantes caractérisés par un invariant topologique, le nombre de Chern, qui est lié à la conductance portée par le bord états. Nous montrons que les modèles à deux bandes admettent des phase à nombre de Chern arbitraire, ou, de façon équivalente, un nombre arbitraire d'états de bord, quand on augmente la portée des couplages sur réseau. Cette compréhension est rendue possible grâce à la démonstration d'une formule montrant que le nombre de Chern d'une bande dépend de certains propriétés d'un ensemble discret de points dans la zone de Brillouin, les points de Dirac en l'absence du gap. Ces idées sont rendues plus concrètes dans l'étude du modèle de Haldane et dans la création d'un modèle artificiel avec cinq phases de Chern dont les états de bord sont déterminés en détail. La deuxième partie de la thèse porte sur les supraconducteurs topologiques unidimensionnels qui exhibent des états exotiques d'énergie zéro: les états liés de Majorana. Nous étudions ici la présence de fermions de Majorana dans des fils de semiconducteurs à fort couplage spin-orbite sous l’effet de proximité d'un supraconducteur d'onde s. Nous montrons que la polarisation de spin des degrés de liberté électroniques dans la fonction d'onde Majorana dépend du poids relatif du couplage spin-orbite Dresselhaus et Rashba. Nous étudions également les fermions de Majorana dans des jonctions linéaires longues supraconducteur-normal et supraconducteur-normal-supraconducteur (SNS) où ils apparaissent comme des états étendus dans la jonction normale. En outre, la géométrie d'anneaux peut être mise en correspondance avec une jonction SNS, et, sous l'action de gradients dans la phase supraconductrice, des fermions Majorana étendus se forment encore à l'intérieur du fil normal. Enfin, un modèle à deux bandes avec des fermions de Majorana multiples est traité. Nous démontrons que les jonctions Josephson construites à partir de ce modèle maintiennent l'une des signatures remarquables des fermions de Majorana, à savoir la périodicité 4π de l'effet Josephson fractionnaire. / This thesis follows two threads in the field of topological insulators and superconductors. The first part of the thesis is devoted to the study of two-dimensional quantum anomalous Hall insulators on a lattice, in the absence of an external magnetic flux, but induced by an inhomogeneous flux in the unit cell. The system possesses several gapped phases characterized by a topological invariant, the Chern number, that is related to the conductance carried by the edge states. Here we show that two-band models admit an arbitrary large number of Chern phases or, equivalently, an arbitrary number of edge states, by adding hopping between distant neighbor sites. This result is based on a formula proving that the Chern number of a band depends on certain properties of a finite set of points in the Brillouin zone, i.e. the Dirac points for the gapless system. These ideas are made more concrete in the study of a modified Haldane model, and also by creating an artificial model with five Chern phases, whose edge states are determined in detail. The second part of the thesis focuses on one-dimensional topological superconductors with exotic zero-energy edge states: the Majorana bound states. Here we investigate the presence of Majorana fermions in spin-orbit coupled semiconducting wire in proximity to an s-wave superconductor. We show that the spin-polarization of the electronic degrees of freedom in the Majorana wave function depends on the relative weight of Dresselhaus and Rashba spin-orbit couplings. We also investigate Majorana fermions in linear superconductor-normal and long superconductor-normal-superconductor (SNS) junctions where they appear as extended states in the normal junction. Furthermore, ring geometries can be mapped to an SNS junction, and, we have shown that under the action of superconducting phases gradients, extended Majorana fermions can form again inside the normal wire. Finally a two-band model with multiple Majorana fermions is treated and we show that Josephson junctions built from this model maintain the 4π periodicity for the fractional Josephson effect, one of Majorana fermions signatures.

Nessa tese de doutorado apresentamos um estudo da estrutura eletronica de materiais isolantes topologicos. A teoria fundamental dos isolantes topologicos foi abordada atraves de invariantes topologicos Z2, assim como os seus metodos para o calculo desses invariantes topologicos e as consequencias da topologia de bandas nao-trivial. Assim como as propriedades atomisticas e energeticas, as propriedades eletronicas de alguns isolantes topologicos foram calculadas atraves de metodos de primeiros principios baseados na Teoria do Funcional da Densidade. Apresentamos nessa tese o estudo de quatro sistemas de interesse fisico: (1) Em isolantes topologicos do tipo Bi2Se3 e Bi2Te3 com falhas de empilhamentos, encontramos que o Bi2Te3 com falhas de empilhamentos apresentam estados metalicos na regiao do defeito; (2) Na interface Bi2Se3/GaAs com tratamento de Se na regiao do GaAs, encontramos que a interacao entre o cone de Dirac do Bi2Se3 com a banda de valencia do GaAs abre um gap de energia no ponto ; (3) Em nanoestradas de germaneno imersas em germanano com interfaces zigzag, encontramos que a partir de uma largura critica podemos observar o efeito Hall quantico de spin; e (4) nas ligas desordenadas hexagonais de SixGe1-x em duas dimensoes, o sistema desordenado compartilha a mesma topologia de bandas do siliceno e do germaneno, enquanto que a liga ordenada Si0.5Ge0.5 e um isolante trivial. As estruturas eletronicas desses sistemas foram investigadas no intuito de entender as consequencias fisicas da topologia de bandas nao-trivial nos estados de Bloch de bulk e de superficies/interfaces. / In this doctoral thesis we present a study of the electronic structure of topological insulators materials. The fundamental theory of topological insulators was addressed through the Z2 topological invariants, as well as their methods to calculate these topological invariants and the consequences of non-trivial band topology. Just as atomistic and energetic properties, the electronic properties of some topological insulators were calculated using first-principles methods based upon Density Functional Theory. We present in this thesis the study of four systems of physical interest: (1) In topological insulators like Bi2Se3 and Bi2Te3 with stacking faults, we found that the Bi2Te3 with stacking faults presents metallic states in the region of the defect; (2) For Bi2Se3/GaAs interface with Se-treatment in the GaAs region, we found that the interaction between the Dirac cone of the Bi2Se3 and the valence band of the GaAs opens a bandgap at the -point; (3) In germanene nanoroads embedded on germanane with zigzag interfaces/edge, we found that from a critical width we can observe the quantum spin Hall effect; and (4) For SixGe1x two-dimensional hexagonal disordered alloy, the system shares the same non-trivial band topology of the silicene and germanene, while the ordered alloy Si0.5Ge0.5 is a trivial insulator. The electronic structures of these systems were investigated in order to understand the physical consequences of non-trivial band topology in the bulk and surfaces/interfaces Bloch states.

Neste trabalho estudamos uma rede hexagonal com uma cadeia de impurezas nas bordas e com supercondutividade induzida, de forma a mostrar a existência de fases com férmions de Majorana. Para tal, começamos introduzindo invariantes topológicos, número de Chern e Z2 e mostramos dois modelos para rede hexagonal. O primeiro, modelo de Haldane, fazemos como motivação histórica. O segundo, modelo de Kane-Mele, é usado como base para todo o trabalho. Seguimos introduzindo supercondutividade e como ela ocorre quando aplicada junto do Modelo de Kane-Mele, o método auto-consistente e quais as condições necessárias para termos supercondutividade apenas nas bordas. Continuamos com efeitos de impurezas magnéticas nas bordas e introduzimos férmions de Majorana que são os alvos principais dos resultados. Mostramos então, que existe fases topológicas em cadeias de impureza magnética, com momentos em espiral, contudo o diagrama de fase depende de várias condições. Por fim, mostramos que a variação da fase topológica se deve a oscilações nos níveis de energia em que o invariante topológico também varia, contrariando resultados obtidos para a rede quadrada. Concluímos esse trabalho com implicações experimentais desse resultado e possíveis caminhos que podem ser seguidos. / In this work, we study a honeycomb lattice with induced superconductivity and edge impurity in order to show the existence of a phase that host Majorana bound state. To do so, we start introducing topological invariants, Chern number and Z2, and we show two models for honeycomb lattice. The first, Haldane\'s Model, due its historical importance. The second, Kane-Mele model, because it will be used during all this work. Then we review superconductivity, showing the self-consistent method, and we apply it to Kane-Mele model, in which we find some necessary conditions to induce superconductivity only at the edges. From this point, we study the effect of magnetic impurities at the edges, and we introduce Majorana bound state, that will be the main objective of our results. In our results, we show the existence of topological non-trivial phases for spiral magnetic chain in the zigzag edge. With this we make a phase diagram. We also find oscillation in the energy spectrum and the topological phase changes with the oscillation, this is different from square lattice in which we should not have a change in the topological phase. We conclude this work with experimental implications of our result and possible developments.

Fermi surface, the locus in momentum space of gapless low-energy excitations, is a concept of fundamental importance in solid state physics. Electronic properties of a material are determined by the long-lived low-energy excitations near the Fermi surface. Conventionally, Fermi surface is understood as a property exclusive to a metallic state, contoured by electronic bands crossed by the Fermi level, although there has been a continuing effort in searching for Fermi surface outside the conventional description. In this thesis, techniques developed to prepare high-quality single crystals of SmB$_6$ and YBa$_2$Cu$_3$O$_{6+x}$ (abbreviated as YBCO$_{6+x}$ hereinafter) are described. By utilising measurement techniques of exceptional sensitivity and exploring a wide range of temperatures, magnetic fields, and electrical currents, we found signatures of unconventional Fermi surfaces beyond the traditional description in these strongly correlated electronic systems. SmB$_6$ is a classic example of Kondo insulators whose insulating behaviour arises due to strong correlation between the itinerant $d$-electrons and localised $f$-electrons. The peculiar resistivity plateau onsets below 4 K has been a decades-long puzzle whose origin has been recently proposed as the manifestation of topological conducting surface states. We found that the insulating behaviour in electrical transport is robust against magnetic fields up to 45 T, while prominent quantum oscillations in magnetisation are observed above 10 T. Angular dependence of the quantum oscillations revealed a three-dimensional characteristics with an absolute amplitude consistent with a bulk origin, and temperature dependence showed a surprising departure from the conventional Lifshitz-Kosevich formalism. Complementary thermodynamic measurements showed results consistent with a Fermi surface originating from neutral itinerant low-energy excitations at low temperatures. Theoretical proposals of the unconventional ground state uncovered by our measurements in SmB$_6$ are discussed. YBCO$_{6+x}$ is a high-temperature superconductor with a maximum $T_{\rm c}$ of 93.5 K and the cleanest member in the family of copper-oxide, or {\it cuprate}, superconductors. The correct description of electronic ground state in the enigmatic pseudogap regime, where the antinodal density of states are suppressed below a characteristic temperature $T^*$ above $T_{\rm c}$, has been a subject of active debates. While the quantum oscillations observed in underdoped YBCO$_{6+x}$ have been predominately interpreted as a property of the normal state where the superconducting parameter is completely suppressed at $\approx$ 23 T, we made the discovery that YBCO$_{6.55}$ exhibits zero resistivity up to 45 T when a low electrical current is used, consistent with the observation of a hysteresis loop in magnetisation. Quantum oscillations in the underdoped YBCO$_{6+x}$ are thus seen to coexist with $d$-wave superconductivity. Characteristics of the quantum oscillations are consistent with an isolated Fermi pocket reconstructed by a charge density wave order parameter and unaccompanied by significant background density of states, suggesting the antinodal density of states is completely gapped out by a strong order parameter involving pairing correlations, potentially in addition to the other order parameters. Transport measurements performed over a wide doping range show signatures consistent with pairing correlations that persist up to the pseudogap temperature $T^*$. The surprising observation of quantum oscillations in insulating SmB$_6$ and superconducting YBCO$_{6+x}$ demonstrates a possible new paradigm of a Fermi surface without a conventional Fermi liquid. A new theoretical framework outside the realm of Fermi liquid theory may be needed to discuss the physics in these strongly correlated materials with enticing electronic properties.

The following dissertation presents a comprehensive study of the interaction between Dirac fermion quasiparticles (DFQs) and surface phonons on the surfaces of the topological insulators Bi2Se3 and Bi2Te3. Inelastic helium atom surface scattering (HASS) spectroscopy and time of flight (TOF) techniques were used to measure the surface phonon dispersion of these materials along the two high-symmetry directions of the surface Brillouin zone (SBZ). Two anomalies common to both materials are exhibited in the experimental data. First, there is an absence of Rayleigh acoustic waves on the surface of these materials, pointing to weak coupling between the surface charge density and the surface acoustic phonon modes and potential applications for soundproofing technologies. Secondly, both materials exhibit an out-of-plane polarized optical phonon mode beginning at the SBZ center and dispersing to lower energy with increasing wave vector along both high-symmetry directions of the SBZ. This trend terminates in a V-shaped minimum at a wave vector corresponding to 2kF for each material, after which the dispersion resumes its upward trend. This phenomenon constitutes a strong Kohn anomaly and can be attributed to the interaction between the surface phonons and DFQs. To quantify the coupling between the optical phonons experiencing strong renormalization and the DFQs at the surface, a phenomenological model was constructed based within the random phase approximation. Fitting the theoretical model to the experimental data allowed for the extraction of the matrix elements of the coupling Hamiltonian and the modifications to the surface phonon propagator encoded in the phonon self energy. This allowed, for the first time, calculation of phonon mode-specific quasiparticle-phonon coupling λⱱ(q) from experimental data. Additionally, an averaged coupling parameter was determined for both materials yielding ¯λ^Te ≈ 2 and ¯λ^Se ≈ 0.7. These values are significantly higher than those of typical metals, underscoring the strong coupling between optical surface phonons and DFQs in topological insulators. In an effort to connect experimental results obtained from phonon and photoemission spectroscopies, a computational process for taking coupling information from the phonon perspective and translating it to the DFQ perspective was derived. The procedure involves using information obtained from HASS measurements (namely the coupling matrix elements and optical phonon dispersion) as input to a Matsubara Green function formalism, from which one can obtain the real and imaginary parts of the DFQ self energy. With these at hand it is possible to calculate the DFQ spectral function and density of states, allowing for comparison with photoemission and scanning tunneling spectroscopies. The results set the necessary energy resolution and extraction methodology for calculating ¯λ from the DFQ perspective. Additionally, determining ¯λ from the calculated spectral functions yields results identical to those obtained from HASS, proving the self-consistency of the approach.

Este trabalho tem como objetivo propor uma metodologia para a classificação da hidrofobicidade (HC) em isoladores elétricos poliméricos de alta tensão. Atualmente a HC esta baseada no guia da STRI (Swedish Transmission Research Institute) elaborado em 1992. Porém neste guia a hidrofobicidade das superfícies de isoladores e classificada de acordo com o angulo de contato e/ou a quantidade de superfície molhada com água de forma subjetiva, através de um operador dependurado em uma torre de transmissão. Desta forma, este trabalho contribuiu na classificação da hidrofobicidade de forma objetiva, onde a analise foi realizada através de processamento digital de imagens. Na metodologia proposta, a HC foi determinada utilizando a analise da textura de imagens obtidas para materiais de isoladores elétricos poliméricos. Essas análises foram avaliadas com base na morfologia matemática, dimensão fractal, entropia, energia, variância e homogeneidade. Foram simuladas imagens (imagens sintéticas) da textura das superfícies dos isoladores utilizando uma placa de silicone e soluções de álcool isopropílico e água destilada (AIA) em proporções que variaram de 0 ate 100% em volume de álcool. A partir destas soluções foram obtidas imagens de gotas sobre as superfícies, para determinação do angulo de contato, e imagens da superfície para a obtenção dos padrões das texturas, que serviriam de base para a aplicação dos métodos estudados. Na tentativa de analisar as imagens independentes do padrao de iluminação, inerente as condições ambientais, foi aplicado o equalização de histograma (EQU) e/ ou implementado um filtro do tipo White Top-Hat (WTH). Este filtro funciona como um passa-alta, reduzindo o gradiente de iluminação das imagens obtidas em condições naturais. Outro método analisado de forma a eliminar o efeito do gradiente de iluminação, foi através da segmentação usando detecção de borda. Os cálculos da dimensão fractal das imagens em escala de cinza foram realizados através do método do box-counting, com tamanho do cubo variando de 3 até 11. A morfologia matemática foi utilizada de forma a qualificar as formas presentes nas imagens. Foram analisadas as derivadas das curvas do volume das imagens de abertura, de forma a identificar o tamanho dos elementos presentes na imagem. Na classificação das texturas das imagens através dos descritores de textura, os valores obtidos com a entropia apresentaram menor dispersão dentre os resultados, alem de baixo tempo de processamento, se apresentando como uma metodologia apropriada para a classificação da hidrofobicidade. Alteração nos valores de gama das imagens foi feito de forma a observar a modificação dos valores de entropia em função do efeito da iluminação das imagens. Os valores apresentaram pouca variação deste parâmetro nos resultados. Como forma de avaliar a qualidade da imagem em termos de tamanho, aumento e resolução, diversas imagens foram geradas visando a modificação destes parâmetros e analisando sua influencia nos valores de entropia. A partir dos resultados obtidos foi possível obter uma relação matemática entre as ferramentas aplicadas e as imagens, sendo possível definir a HC. Utilizando estas técnicas foi determinado o desvio dos resultados e o tempo de processamento, visando a aplicação em dispositivos moveis, como por exemplo, celulares. Assim, foi elaborado um aplicativo embarcado em um smartphone para analisar uma imagem em campo de um isolador, mostrando ao operador o valor da classificação da hidrofobicidade em aproximadamente um minuto. / The aim of this study is to propose a new method to classify the hydrophobicity (HC) in high voltage polymer insulators. Currently the HC is based on the STRI guide (Swedish Transmission Research Institute) published in 1992, where the hydrophobicity is classified by contact angle and/or amount of wet surface. In the proposed method, the HC was analyzed by digital image processing using the textures of the images obtained from electric insulators polymeric materials. These analysis were evaluated using mathematical morphology, fractal dimension, entropy, energy, variance and homogeneity. Simulated texture images (synthetic Images) about the surfaces of the insulators were created using a silicon plate and isopropyl alcohol and distilled water solutions in proportions from 0 to 100% in volume of alcohol (AIA). From these solutions, images of drops on the insulator surfaces were obtained to measure the contact angle; and surfaces images using the AIA solutions were obtained and then employed in the analysis of the texture patterns, which were used as basis for the analyzed methods. To analyze the images regardless the illumination conditions, which is a serious problem in natural weather, histogram equalization (EQU) and/or a White Top-Hat filter (WTH) was applied. This filter works as a high-pass filter, reducing the illumination gradient from the images obtained in natural conditions. Another way to avoid the gradient illumination was the segmentation technique by edge detection. The fractal dimension calculations in grayscale images were performed by the box-count method, with box size ranging from 3 to 11. Mathematical morphology was used to quantify the shapes in the images. The derivate of the volume from the opening images was analyzed to identify the elements in the image. The classification of the image texture by the entropy revealed not only the lowest dispersion of the results, but also the shortest time processing, presenting as an appropriated method to classify the hydrophobicity. Gama alterations in the images was done to observe the entropy values modifications as a function of the illumination effects in the images. The values shown the low influence of this parameter in the results. To evaluate the image quality regarding to size, zoom and resolution, different images were produced to observe the modification of these parameters and analyze its influence in the entropy values. From this study was possible to propose a mathematical function which relates the surface hidrophobicity and the texture patterns obtained by the AIA images. Hence, the hidrophobicity classification could be embedded in mobile devices, as example, cell phones, and performed in loco. A smartphone software was then developed to analyze the surface image of an insulator, producing the hidrophobicity classification value in about one minute.

Higher-order regulatory interactions between enhancer elements and target gene promoters have been implicated in the coordination and regulation of transcription in a spatio-temporal manner. Within development, the graded activity of enhancers controls transcriptional programs necessary to establish cell fates and tissue patterning. How enhancer promoter interactions form and dynamically change throughout development remains largely unknown. The aim of this thesis is to further characterise BMP enhancers during development. Using ChIP data, an enrichment of architectural binding proteins (ABPs) with enhancers regulated by the BMP pathway was identified. Analysis of chromatin signatures revealed a correlation with the active histone marks, H3K27ac and H3K36me3, over BMP enhancers enriched for the ABP BEAF32. BEAF32 mutants show disrupted expression of BMP target genes and altered tissue fates defined by the BMP pathway. Consequently, the role of BEAF32 genome-wide was considered, revealing interactions with factors associated with enhancers and promoters, in addition to a correlation with RNA Polymerase II (RNAPII) pausing at promoter regions. This suggests a possible role for BEAF32 in bridging enhancer promoter interactions and releasing paused RNAPII. Based on the prevalence of BEAF32 at some enhancer sites and interaction with CBP, eRNAs were identified within the Drosophila embryo, utilising available GRO-seq data and GroHMM. eRNA expression correlates to accessible enhancer states regardless of chromatin composition, with transcribed enhancers revealing interactions with active promoters, supporting correlations to transcriptional activation. Chromatin architecture of BMP targets were lastly considered using Capture-C against BMP regulated promoters, revealing multiple regulatory interactions including contacts with enhancers regulated along the Dorso-ventral (DV) axis and additional BMP promoters, with dynamic interactions between enhancers and promoters. Overall the presented data suggest that BMP promoters are dynamically regulated by distal enhancers, with a plausible role for BEAF32 in mediating enhancer promoter interactions, to co-ordinate transcription programs used to pattern dorsal tissues in the Drosophila embryo.