No description available.

Local inhibitory microcircuit of amygdala is an active component in processing emotional information. Despite prominent evidence of its importance, our understanding of GABAergic cell types, their connectivity and role in amygdala network is limited. The aim of this thesis is to understand connectivity and physiology of two specific components of GABAergic microcircuit of amygdala: so-called intercalated cells and neuropeptide Y (NPY) expressing interneurons. Intercalated cells (ITCs) of the amygdala are clusters of GABAergic neurons that surround the basolateral complex of amygdala (BLA). There is growing evidence suggesting that ITCs are required for the expression of fear extinction. The main intercalated nucleus (Im) is the largest of the ITC clusters and could be also important for emotional processing. Using patch-clamp whole-cell recordings paired with subsequent anatomical analysis I described basic physiology and anatomy of neurons within the Im. I found that these neurons share common characteristics to earlier described neurons within the medial ITC cluster, yet they can be divided into three distinct groups. Next, I provided anatomical and functional evidence that Im neurons project to central and basal nucleus of amygdala and that they are reciprocally connected with medial and lateral ITCs clusters. I found that Im neurons receive excitatory inputs from BLA as well as cortex; next I verified that heterogeneous inputs do not interact with each other. I have shown that the Im neurons express both AMPA and NMDA receptors, suggesting that they may undergo NMDA-dependent plasticity. I have reported that dopamine hyperpolarizes Im neurons via dopamine receptor 1, therefore providing a cellular substrate for disinhibition of the amygdala at the systemic level. Thus, the Im is likely to be an additional site of integration of the distributed network underlying acquisition, expression and extinction of conditioned fear. In another project, I report novel interneuron type of the BLA and call it neurogliaform cell (NGFC) of amygdala. I used a mouse line expressing green fluorescent protein (GFP) under NPY promoter and patch clamp technique combined with pharmacology and electron microscope analysis. I performed paired recordings between presynaptic NPY-GFP positive (+) cells and postsynaptic principal neurons (PNs). Presynaptic NPY-GFP+ neurons display small soma and short dendrites embedded in a cloud of highly arborized axon. I showed that NPY-GFP+ cells are source of GABAA receptor-mediated slow inhibitory postsynaptic currents (IPSCs, decay time constant > 30 ms) evoked in PNs and in themselves (autapses). These slow IPSCs are known in literature as GABAA,slow. My results indicate that the slow kinetics of these IPSCs was likely caused by the low concentration and spillover of extracellular GABA. Physiologically-relevant in vivo firing re-played in NPY+-NGFCs in vitro evoked a transient depression of the IPSCs. Presynaptic GABAB receptors controlled the strength of this short-term plasticity. Interestingly, synaptic contacts made by NGFCs showed close appositions, without identifiable classical synaptic structures, between presynaptic boutons of the recorded cells and postsynaptic profiles. Thus, volume transmission of GABA is likely to be generated by this interneuron of the amygdala. NPY+-NGFC is a novel interneuron type of the BLA. The peculiar functional mode of NGFCs makes them unique amongst all GABAergic cell types of the amygdala identified so far.

This thesis is submitted in a format of published papers by the candidate. Advanced methods of electron microscopy and X-ray spectroscopy have been used to study the relationship between the pillars and the silicate structure ranging from Al13 and Ga13 complexes to the final products Al- and Ga-pillared clays. The Al13 and Ga13 pillared montmorillonites have been prepared by conventional and ultrasonic methods. The ultrasonic method has been proven to be effective and showed very good catalytically activity. Transmission electron microscopy combined with elemental mapping by EDS showed the distribution of the Ga and Al pillars in the clay structure. The use of gallium allowed the independent observation of the Ga pillar distribution from the Al distribution in the clay structure. XPS spectra of the Ga13 pillared montmorillonites showed that the pillars has been changed from the original Keggin structure with a 7+ charge to something more stable with a lower charge upon intercalation. No direct evidence of the inverted silicon tetrahedron structure bonding to the pillar structure, as suggested by Plee in his original thesis, was observed. For comparative reasons the major aluminium hydroxide minerals in bauxite (gibbsite, bayerite and (pseudo-) boehmite) were studied. Detailed information about the Al13 structure was obtained by studying the basic sulphate and nitrate salts with XPS. The XPS results of a set of starting clays in comparison to the pillared clays indicated that small changes in the binding energy could explain the changes in the pillar structure and the formation of chemical bonds to the clay tetrahedral sheets during the calcination leading to the final products.

In this thesis investigations into chemically modified graphene structures are presented. Chemical functionalization of graphene is the chemical attachment of molecules or atoms to the graphene surface via covalent or Van der Waals bonds, this process offers a unique way to tailor the properties of graphene to make it useful for a wide range of device applications. One type of chemical functionalization presented in this thesis is fluorination of graphene which is the covalent attachment of fluorine to the carbon atoms of graphene and the resultant material is fluorographene which is a wide band-gap semiconductor. For low fluorine coverage the low temperature electron transport is through localized states due to the presence of disorder induced sub-gap states. For high fluorine coverage the electron transport can be explained by a lightly doped semiconductor model where transport is through thermal activation across an energy gap between an impurity and conduction bands. On the other hand, at low temperatures the disorder induced sub-gap density of states dominates the electrical properties, and the conduction takes place via hopping through these localized states. In this thesis it is also shown that electron beam irradiation can be used to tune the coverage of fluorine adatoms and therefore control energy gap between the impurity and conduction bands. Futhermore, electron beam irradiation also offers a valuable way to pattern conductive structures in fluorinated graphene \textit{via} the irradiation-induced dissociation of fluorine from the fluorinated graphene. This technique can be extended to the patterning of semiconducting nano-ribbons in fluorinated graphene where the spatial localization of electrons is just a few nm. The second type of chemical functionalization presented in this thesis is the intercalation of few layer graphene with ferric chloride which greatly enhances the electrical conductivity of few layer graphene materials making them the best known transparent conductors.

No description available.

Mimicking nature gives rise to many important facets of biomaterials. This study is inspired by nature and reports on the fabrication of an intercalated polymer-NiTi nanocomposite that mimics the structural order of urethral tissue performing micturition. PTFE is chosen due to its hydrophobicity, low surface energy, and thermal and chemical stability. NiTi has been selected as a prime candidate for this research due to its excellent mechanical stability, corrosion resistance, energy absorbance, shape memory and biocompatibility. Nanoscale engineering of intercalated nanocomposites is done by PVD sputtering PTFE and NiTi. FTIR spectroscopy confirms that PTFE reforms as polymer chains after sputtering. Suitable PVD sputtering parameters were selected by investigating their influence on deposition rates, microstructure and properties of PTFE and NiTi thin films. PTFE forms stable nanocomposite coatings with NiTi and displays favourable surface interactions, known as ‘intercalation’. Intercalated PTFE-NiTi films were fabricated as layered and co-sputtered thin films. Co-sputtered nanocomposites contained nearly one-third vacant sites within its internal microstructure because of intercalation while intercalation introduced minute pits in fibrous NiTi columns of layered nanocomposites. These pits allow PTFE to extend their chains and crosslinks, resulting in microstructural and functional changes in the thin films. Intercalated PTFE-NiTi nanocomposites offer a close match to the natural tissue in terms of responding to the fluid contact (wetting angle modifications), and allow the soft and hard matter to incorporate in one framework without any chemical reactions (intercalation). An intercalated microstructure in co-sputtered and layered nanocomposites was verified by EDS-SEM and EDS-TEM techniques. The functional responses were witnessed by changes in water contact angle (WCA) and coefficient of friction (CoF) values measured on the film surface. The WCA (99°) and CoF (0.1 – 0.2) of the intercalated nanocomposite (sample PNT12) were different to the NiTi (top layer). WCA and CoF indicate the internal microstructural interactions because of intercalation. Although the pseudoelastic behaviour of NiTi can provide additional fluid response but the difficulty is an absence of crystallinity in as-deposited NiTi, and the heat treatment that melts PTFE. However, DSC and XRD techniques were employed to find the optimum NiTi composition and transition temperatures for phase transformation related to pseudoelasticity. This study provides the basis to incorporate the shape memory (pseudoelasticity or thermal shape memory effect (shape memory effect)) features of NiTi into the intercalated nanocomposite in future. The intercalated PTFE-NiTi nanocomposite reveals a fascinating research precinct, having the response generating characteristics similar to that of natural tissue.

Im Rahmen dieser Arbeit wurden zwei humane Varianten des von Wang et al., 1999, erstmals beschriebenen muskelspezifischen Proteins Xin (Huhn und Maus) über Sequenzanalyse, Immunofluoreszenzmikroskopie, Transfektionsstudien und biochemischer Analyse näher charakterisiert. <br /> Die Proteine wurden mit human Xin related proteins 1 und 2 – hXirp1 und 2 –bezeichnet. Die Xin-Proteine enthielten bisher unbekannte, sowie spezifische, repetitive Motive, die aus jeweils mindestens 16 Aminosäuren bestanden. Ihre Aminosäuresequenz, mit einer Vielzahl weiterer putativer Motivsequenzen, verwies auf eine potentielle Funktion von hXirp als Adapterprotein in Muskelzellen. Das hier näher untersuchte hXirp1 lokalisierte an den Zell-Matrix-Verbindungen der Muskel-Sehnen-Übergangszone im Skelettmuskel, sowie an den Zell-Zell-Verbindungen der Glanzstreifen im Herzmuskel. Während der Muskelentwicklung zeigte hXirp1 eine sehr frühe Expression, zusammen mit einer prägnanten Lokalisation an den Prämyofibrillen und deren Verankerungsstrukturen, die auf eine Funktion des Proteins in der Myofibrillogenese deuten. Ektopische Expressionen von hXirp1 in einer Vielzahl von Nichtmuskel-Kulturzellen zeigten wiederum eine Lokalisation des Proteins an den Zell-Matrix-Kontakten dieser Zellen. Am Beispiel von hXirp1 und 2 wurde stellvertretend für die Familie der Xin-Proteine gezeigt, daß es sich bei den repetitiven Motiven um neuartige, F-Aktin bindende Sequenzmotive handelte. Die Xin-Proteine können somit als muskelspezifische, aktinbindende, potentielle Adapterproteine bezeichnet werden, denen eine strukturelle und funktionelle Beteiligung an der Verankerung der Myofibrillen im adulten Muskel, wie auch während der Myofibrillogenese zukommt. / The scope of this work was a further characterization of two human variants of the protein Xin which was reported for chicken and mouse in 1999 by Wang et al. Therefor sequence analysis, immunofluorescence microscopy, transfection studies and biochemical approaches were utilized.<br /> The proteins were named human Xin related proteins 1 und 2 – hXirp1 und 2. Xin-proteins possess specific repetitive motives consisting of a minimum of 16 amino acids each. Concerning further putative motive sequences hXirp is a potential adapter protein in the muscle cell. hXirp1 localized within the cell-matrix-contacts of the myotendinous junction in skeletal muscle as well as within the cell-cell-contacts of the intercalated disc in the cardiac muscle. During the development of muscle cells hXirp1 showed early expression as well as concise localization to premyofibrils and their anchorage structures indicating a potential role for this protein in myofibrillogenesis. Ectopic expression of hXirp1 in several non-muscle cells again revealed localization of this protein to cell-matrix contacts. Considering hXirp1 and 2 as an example for all Xin-proteins it was shown that the repetitive motives are new actin binding motives. The data indicated the Xin-proteins as muscle specific, actin binding and potential adapter proteins with implications in structure and function of anchorage of myofibrils in adult muscle and myofibrillogenesis.

The assembly, form, and function of the heart is regulated by complex mechanical signals originating from intrinsic and extrinsic sources, such as the cytoskeleton and the extracellular matrix. During development, mechanical forces influence the self-assembly of highly organized ventricular myocardium. However, mechanical overload induces maladaptive remodeling of tissue structure and eventual failure. Thus, mechanical forces potentiate physiological or pathological remodeling, depending on factors such as frequency and magnitude. We hypothesized that mechanical stimuli in the form of microenvironmental stiffness, cytoskeletal architecture, or cyclic stretch regulate cell-cell junction formation and cytoskeletal remodeling during development and disease. To test this, we engineered cardiac tissues in vitro and quantified structural and functional remodeling over multiple spatial scales in response to diverse mechanical perturbations mimicking development and disease. We first asked if the mechanical microenvironment impacts tissue assembly. To investigate this, we cultured two-cell cardiac µtissues on flexible substrates with tunable stiffness and monitored cell-cell junction formation over time. As myocytes transitioned from isolated cells to interconnected µtissues, focal adhesions disassembled near cell-cell interfaces and mechanical forces were transmitted almost completely through cell-cell junctions. However, µtissues cultured on stiff substrates mimicking fibrotic microenvironments retained focal adhesions near the cell-cell interface, potentially to reinforce the cell-cell junction in response to excessive forces generated by myofibrils in stiff microenvironments. Intercellular electrical conductance between myocytes was measured as a function of connexin 43 immunosignal and the length-to-width ratio of cell pairs. We observed that conductance was correlated to connexin 43 immunosignal and cell pair length-to-width ratio, indicating that tissue architecture can affect electrical coupling. The impact of mechanical overload was also determined by applying chronic cyclic stretch to engineered cardiac tissues. Stretch activated gene expression patterns characteristic of pathological remodeling, including up-regulation of focal adhesion genes, and impacted sarcomere alignment and myocyte shape. Furthermore, chronic cyclic stretch altered intracellular calcium cycling in a manner similar to heart failure and decreased contractile stress generation, suggestive of maladaptive remodeling. In summary, we show that the assembly, form, and function of cardiac tissue is sensitive to a wide range of mechanical cues that emerge during physiological and pathological growth. / Engineering and Applied Sciences

In this thesis the properties of graphene and its few-layers are engineered to make them highly conductive. Two different approaches were implemented to achieve this goal. One approach was to increase the concentration of charge carriers by intercalation of acceptor FeCl3 molecules between graphene planes. This resulted in a highly conductive yet transparent material which can be useful for applications. Another approach was to increase the mobility of carriers by means of removing surface contamination in the current annealing process. Optimal annealing parameters were found and a reproducible cleaning method was suggested.

CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / O presente trabalho apresenta o desenvolvimento de uma metodologia de sÃntese e caracterizaÃÃo de caulins modificados quimicamente, partindo de caulins naturais da regiÃo nordeste do Brasil. Os caulins foram modificados atravÃs de procedimentos de remoÃÃo da matÃria orgÃnica, obtenÃÃo de forma sÃdica, obtenÃÃo de forma amoniacal, obtenÃÃo da forma Ãcida e intercalaÃÃo com dimetilsulfÃxido. Para caracterizaÃÃo dos caulins obtidos apÃs toda a modificaÃÃo, foram realizadas tÃcnicas de difraÃÃo de raios â X (DRX), anÃlise quÃmica (absorÃÃo atÃmica), termogravimetria (TG), calorimetria diferencial exploratÃria (DSC) e espectroscopia na regiÃo do infravermelho (FT-IR). Os resultados obtidos atravÃs da anÃlise quÃmica e de difraÃÃo de raios â X confirmaram que a composiÃÃo dos caulins era basicamente caulinita e algumas impurezas, tais como, a Mica presente como argilomineral agregado no caulim cinza. AtravÃs dos resultados obtidos de capacidade de troca catiÃnica (CTC), foi possÃvel avaliar e adaptar as metodologias para a obtenÃÃo de melhores resultados. A avaliaÃÃo da estabilidade termodinÃmica do dimetilsulfÃxido intercalado nas estruturas dos caulins foi realizada atravÃs de termogravimetria, tendo como base o mÃtodo de Ozawa, onde a partir das curvas TG nas razÃes de aquecimento 2, 5, 7 e 10oC.min-1, obteve-se o grÃfico da razÃo de aquecimento pelo recÃproco da temperatura, depois realizou-se regressÃo linear, em seguida obteve-se o coeficiente angular(B), que quando substituÃdo na expressÃo: ?E = -18,2045.B, obtÃm-se a energia de ativaÃÃo, sendo esta um parÃmetro termodinÃmico fundamental na avaliaÃÃo da estabilidade. O dimetilsulfÃxido intercalado na estrutura do caulim branco demonstrou valores mais expressivos de energia de ativaÃÃo (Ea) em relaÃÃo ao intercalado no caulim cinza, denotando assim uma maior estabilidade termodinÃmica, podendo dessa forma ser considerado um melhor material de partida na obtenÃÃo de adsorventes de maior eficiÃncia. / The present work presents the development of a synthesis methodology and characterization of kaolins modified chemically, leaving of natural kaolins of the northeast area of Brazil. The kaolins were modified through procedures of removal organic matter, obtaining in a sodic way, obtaining of form amoniacal, obtaining in the acid way and collation with dimethylsulfoxide. For characterization of the kaolins obtained after all the modification, techniques of XâRay diffraction (DRX), chemical analysis (atomic absorption), thermogravimetry (TG), differential scanning calorimetry (DSC) and infrared absorption spectroscopy (FT-IR). The results obtained through the chemical analysis and of XâRay diffraction confirmed that the composition of the kaolins was basically kaolinite and some sludges, such as, present Mica as clay mineral joined in the gray kaolin. Through the obtained results of capacity of change cationic (CTC), it was possible to evaluate and to adapt the methodologies for the obtaining of better results. The evaluation of the thermodynamic stability of the dimethylsulfoxide inserted in the structures of the kaolins it was accomplished through thermogravimetry, tends as base the method of Ozawa, where starting from the curves TG in the reasons of heating 2, 5, 7 and 10oC.min-1, it was obtained the graph of the heating reason by the reciprocal of the temperature, later he/she took place lineal regression, soon after it was obtained the coefficient angular(B), that when substituted in the expression: ? E = -18,2045.B, it is obtained the activation energy, being this a fundamental thermodynamic parameter in the evaluation of the stability. The dimethilsulfoxide inserted in the structure of the white kaolin it demonstrated more expressive values of activation energy (Ea) in relation to the inserted in the gray kaolin, denoting like this a larger thermodynamic stability, being able to in that way a better departure material to be considered in the obtaining of adsorventes of larger efficiency.