As the world strives to adapt to the increasing demand for electrical power, sustainable energy sources are attracting significant interest. Around 60% of energy utilized in the world is wasted as heat. Different industrial processes, home heating, and exhausts in cars, all generate a huge amount of unused waste heat. With such a huge potential, there is also significant interest in discovering inexpensive technologies for power generation from waste heat. As a result, thermoelectric materials have become important for many renewable energy research programs. While significant advancements have been done in improving the thermoelectric properties of the conventional heavy-element based materials (such as Bi2Te3 and PbTe), high-temperature applications of thermoelectrics are still limited to one materials system, namely SiGe, since the traditional thermoelectric materials degrade and oxidize at high temperature. Therefore, oxide thermoelectrics emerge as a promising class of materials since they can operate athigher temperatures and in harsher environments compared to non-oxide thermoelectrics. Furthermore, oxides are abundant and friendly to the environment. Among oxides, crystalline SrTiO3 and ZnO are promising thermoelectric materials. The main objective of this work is therefore to pursue focused investigations of SrTiO3 and ZnO thin films and superlattices grown by pulsed laser deposition (PLD), with the goal of optimizing their thermoelectric properties by following different strategies. First, the effect of laser fluence on the thermoelectric properties of La doped epitaxial SrTiO3 films is discussed. Films grown at higher laser fluences exhibit better thermoelectric performance. Second, the role of crystal orientation in determining the thermoelectric properties of epitaxial Al doped ZnO (AZO) films is explained. Vertically aligned (c-axis) AZO films have superior thermoelectric properties compared to other films with different crystal orientations. Third, additional B-site doping of A-site doped SrTiO3 films leads to a prominent reduction in the lattice thermal conductivity without limiting the electrical transport, and hence an improvement in the figure of merit is noticed. Fourth and last, the enhancement of thermoelectric properties of thermally robust, high quality SrTiO3-based superlattices is discussed. Beside the randomly distributed oxygen vacancies and extrinsic dopants, the structure of SrTiO3-based superlattices increases the scattering of phonons at the interfaces between the alternative layers, and hence reducing the thermal conductivity, which leads to a notable enhancement in the figure of merit.

No description available.

Respirable coal mine dust (RCMD) still poses serious occupational health hazards to coal miners and can lead to incurable lung diseases such as coal workers' pneumoconiosis (CWP, also referred to as "black lung"). Further, CWP can develop into a more severe form known as progressive massive fibrosis (PMF). There has been a resurgence of PMF since the late 1990s. Coal miners are also exposed to crystalline silica, which can lead to a lung disease known as silicosis. While coal mining related disease is on the rise, the historic dust monitoring data does not indicate such a striking resurgence. As a result, there has been an increased interest in research surrounding RCMD to understand exposure as well as prevent health effects. Scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX) is a powerful tool that can analyze RCMD on a particle-level. The images produced by the SEM can size and characterize morphology of micron and submicron-sized particles. In addition, the EDX can determine elemental content, which can be used to infer mineralogy. However, particle classification can be impacted by interferences due to particle loading density (PLD) and agglomeration. PLD refers to the number of particles per unit area of substrate, while agglomeration describes clustered or overlapping particles. This thesis includes two studies aimed at exploring the effects of both PLD and agglomeration on SEM-EDX analysis. Study 1 includes an investigation into the effect of PLD on RCMD classification by SEM-EDX analysis. Dust recovered from the sample parent filters under low and high PLD conditions were used to isolate the effect of PLD. The comparison between the low and high PLD filters was then used to establish modified classification criteria to correct for high PLD. When the modified criteria were then applied to RCMD particles analyzed direct-on-filter, minimal change was observed in the apparent mineralogy distributions for most samples. These results suggest that particle agglomeration may have substantial effects on the particle classification of respirable dust analyzed direct-on-filter. Study 2 includes an investigation into the effect of particle agglomeration on RCMD by SEM-EDX analysis. Automated and manual SEM-EDX analysis was performed on paired filters collected from a parent filter. The manual analysis targeted respirable silica containing agglomerates. Each pair consisted of a filter analyzed directly and a filter that underwent a recovery process to deposit dust particles onto a new filter. The mineralogy distributions from the automated analysis suggest that agglomeration affects sizing and particle classification. Based on the manual analysis, there was an apparent increase in independent silica and a decrease in respirable silica-containing agglomerates after the recovery process. A limited collection of passive samples revealed more agglomerates than on the filters that were collected using a pump and size-selector cyclone. The work in this thesis is relevant to the research efforts aimed at the resurgence of coal mining related lung diseases, as the use of SEM-EDX can characterize RCMD by geographic region, geology, and location within a mine. Future work in this area of study might look at methods to estimate PLD in the field, other dust recovery methods, and a comparison of sampling methods. / Master of Science / Respirable coal mine dust (RCMD) still poses serious occupational health hazards to coal miners and can lead to incurable lung diseases such as coal workers' pneumoconiosis (CWP, also referred to as "black lung"). Further, CWP can develop into a more severe form known as progressive massive fibrosis (PMF). There has been a resurgence of PMF since the late 1990s. Coal miners are also exposed to crystalline silica, which can lead to a lung disease known as silicosis. While coal mining related disease is on the rise, the historic dust monitoring data does not indicate such a striking resurgence. As a result, there has been an increased interest in research surrounding RCMD to understand exposure as well as prevent health effects. Scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX) is a powerful tool that can analyze RCMD on a particle-level. SEM-EDX analysis can provide data on the size and elemental content of individual particles. The elemental content of each particle can be used to infer the mineralogy. However, the effectiveness of SEM-EDX analysis is dependent on sample conditions. Interference can occur if the samples are loaded with too many particles close together or clustered particles. In Study 1, a modified classification criteria to correct for overloading was created by using a dataset that consisted of paired filters with ideal loading and overloading. The modified criteria were applied to a second dataset, resulting in minimal change on the filters analyzed directly indicating that clustered particles may be present. Study 2 utilized automated and manual SEM-EDX analysis on paired filters, one filter was analyzed directly, and the other filter was dispersed using a recovery method. The automated results suggest that clustered particles can affect the sizing and particle classification. The manual analysis, which looked at clusters containing silica, revealed that less clusters were present on the filters that underwent the recovery process. A collection of passive samples exhibited more clustered particles compared to direct filters collected using a pump and size-selector. These findings are relevant to the research efforts aimed at the resurgence of coal mining related lung diseases, as the use of SEM-EDX analysis can characterize RCMD by geographic region, geology, and location within a mine.

The layered honeycomb lattice iridate Na2IrO3 is a novel candidate material for either a topological insulator or spin liquid. These states of matter are one possible starting point for the future realization of scalable quantum computation, but may also find application in magnetic memory or low-power electronic devices. This thesis reports on the pulsed laser deposition of high-quality heteroepitaxial (001)-oriented Na2IrO3 thin films with well-defined in-plane epitaxial relationship on 5-by-5 and 10-by-10 square millimeter single-crystalline sapphire, YAlO3 and zinc oxide substrates. Three-dimensional Mott variable range hopping is the dominant conduction mechanism between 40 and 300 K. Moreover, a signature of the proposed topological insulator phase is found in magnetoresistance by observation of the weak antilocalization effect that is associated with topological surafce states. Compared to single crystals, a smaller, 200-meV optical gap in Na2IrO3 thin films is found by Fourier-transform infrared transmission spectroscopy.

O protótipo de um detector de nêutrons térmicos portátil foi desenvolvido no Instituto de Pesquisa Energéticas e Nucleares (IPEN-CNEN/SP), utilizando um fotodiodo de Si do tipo PIN associado a um filme de boro enriquecido. O filme de boro foi fabricado por meio da técnica de Deposição a Laser Pulsado, considerando duas possibilidades para depositar o boro: deposição direta do boro na face do fotodiodo e deposição na lâmina de vidro. Foram desenvolvidos dois protótipos, no primeiro foi possível ler apenas o sinal elétrico do sistema fotodiodo-boro no qual o filme está depositado na lâmina de vidro. Para aprimorar a resposta do sistema de detecção, outro circuito foi desenvolvido e permitiu contar nêutrons em ambas as situações tanto do filme na lamínula quanto do filme direto no fotodiodo. A caracterização dos protótipos foi feita via irradiação de feixes de nêutrons predominantemente térmicos e frios, por meio de quatro experimentos principais: reposta do sistema ao fluxo de nêutrons, teste de linearidade, resposta angular e o teste de reprodutibilidade. Os protótipos apresentaram uma resposta linear à variação do fluxo, reprodutibilidade, e a resposta angular não foi isotrópica. A eficiência intrínseca em porcentagem do protótipo 1 para um espectro de nêutrons predominantemente térmicos e frios foi (1,17 ± 0,01) % e (1,37 ± 0,01) %, respectivamente. No protótipo 2 foram feitas medições de nêutrons com os dois sistemas fotodiodo-boro (lâmina de vidro, direto no fotodiodo), porém nas medidas com o boro direto no sensor houve um aumento significativo no ruído eletrônico. A eficiência intrínseca do protótipo 2 para os nêutrons frios foi de (5,2 ± 0,4) %. / A portable thermal neutron detector prototype, using a silicon photodiode type PIN coupled to a boron converter, was developed at Nuclear and Energy Research Institute (IPEN-CNEN/SP). The boron layers were made by Pulsed Laser Deposition method using two configurations: directly deposited on the surface of photodiode and at a glass surface. Two prototypes were made in this study using two different associated electronics, in the first prototype is only possible reads signs from the photodiode coupled to boron film and in the second one reads both types of configurations (directly on the photodiode, boron glass). The prototypes were characterized using thermal and cold neutron beam. Four experiments were performed: response of the detection system at neutron beam, linearity test, angular response and repetitive test. The prototypes present a linear behavior, were reproducible and the angular response of the prototypes was not isotropic. The values of intrinsic efficiency from the prototype 1 for thermal and cold neutron were respectively: (1.17 ± 0.01) % e (1.37 ± 0.01) %. In the prototype 2 it was performed an experiment for compare the read out in the detection system for the two possible configuration of system photodiode-boron, in the situation that the boron is part integrant of the system there was an significant increase in the electronic noise, therefore the characterization of this prototype were made using the boron film coupled to the photodiode, and intrinsic efficiency for cold neutron beam was (5.2 ± 0.4) %.

Les phospholipases D (PLD, EC 3.1.4.4) sont des enzymes ubiquitaires retrouvées aussi bien chez les procaryotes (bactéries) que chez les eucaryotes (plantes, animaux et champignons). Les PLD catalysent l'hydrolyse des glycérophospholipides au niveau distal de la liaison phosphodiester pour former de l'acide phosphatidique, un important messager cellulaire impliqué dans de nombreuses voies telles que la prolifération cellulaire, la formation et le trafic vésiculaire, mais aussi la transcription et la survie cellulaire. Les PLD appartiennent à une superfamille de protéines (superfamille des PLD) qui ont en commun un site catalytique HXKX4D, X étant un acide aminé quelconque, contenant les résidus H (Histidyl), K (Lysyl) et D (Aspartyl). Ce site est nommé séquence consensus "HKD" et est dupliqué dans la plupart des membres de la superfamille des PLD. L'étude des PLD de plante est le moyen le plus sûr d'étudier cette famille d'enzyme car ce sont les seules PLD eucaryotiques purifiées à homogénéité et en grande quantité à ce jour. Ces travaux proposent une caractérisation fonctionnelle des résidus conservés au sein des PLD végétales menant à une caractérisation structurale avec la cristallisation de cette protéine. Dans un second temps l'activité de l'enzyme est modulée avec l'étude du domaine minimum, de la maturation post-traductionnelle de l'enzyme et le recherche d'un nouvel inhibiteur. Enfin, nous proposons le clonage d'une nouvelle PLD et la mise au point d'un système de détection in vivo de l'activité PLD / Phospholipases D (PLD, EC 3.1.4.4) are ubiquitary enzymes found in prokaryotes (bacteria) as well as in eukaryotes (plant, animals and fungi). PLD catalyzes the hydrolysis of the distal phosphoester bound of phospholipids thus forming phosphatidic acid, an important cell signaling messenger implicated in numerous pathways such as cell proliferation, vesicular formation and trafficking but also transcription and cell survival. PLDs belong to a superfamily of protein which share a common catalytic site called “HKD” for HXKX4D, X is a random amino acid, containing H (Histidyl), K (lysyl) and D (aspartyl) residues. This consensus sequence is duplicated in most of the PLD superfamily members. The study of plant PLD is the best way to understand this family of proteins as they are the sole eukaryotic PLDs to be purified to homogeneity so far. This work provides a functional characterization of the most conserved residues in plant PLDs leading to a structural characterization with the crystallization of this enzyme. A second part of this work proposes the modulation of the enzyme hydrolysis activity by studying the minimal domain necessary for the activity and post-translational maturation undergone by plant PLDs. Also, we look for a new specific inhibitory molecule. Finally, we propose the cloning of a new plant PLD and the development of a new way to detect in vivo PLD activity

No description available.

Ziel dieser Arbeit war die Untersuchung des Einflusses epitaktischer Verspannung auf die Eigenschaften von dünnen Schichten eisenbasierter Supraleiter. Dafür wurden erstmalig epitaktische Schichten des Materials Ba(Fe1−xNix)2As2 mit unterschiedlichem Nickelgehalt mithilfe der gepulsten Laserdeposition hergestellt und ihre strukturellen und elektrischen Transporteigenschaften charakterisiert. Die Ergebnisse wurden mit Massivproben, sowie mit Dünnschichten des verwandten Systems Ba(Fe1−xCox)2As2 verglichen. Dabei wurde ein maximales Tc von 21,6K gemessen, was die entsprechenden Werte für Massivproben dieses Materials übersteigt. Je nach verwendetem Substrat führt die induzierte stauchende oder dehnende mechanische Verspannung zu einer Verschiebung des elektronischen Phasendiagrammes. Die Wechselwirkung mit magnetischen Fluktuationen nahe des antiferromagnetischen Phasenübergangs führt zudem in Dünnschichten zu einer starken Erhöhung des Anstieges des oberen kritischen Magnetfeldes nahe der Sprungtemperatur. Untersuchungen des magnetischen Phasendiagrammes in hohen Magnetfeldern zeigen für Ba(Fe1−xNix)2As2 ein ähnliches Verhalten wie im Co-dotierten System. Die Messungen ergaben bei niedrigen Temperaturen eine geringe Anisotropie des oberen kritischen Feldes, während die Anisotropie des Irreversibilitätsfeldes aufgrund der vorherrschenden Defektstruktur erhöht ist. Des Weiteren wurden epitaktische Dünnschichten des Supraleiters FeSe1−xTex erstmalig auf dem Halbleitersubstrat GaAs abgeschieden. Dabei wurden Sprungtemperaturen von bis zu 17,4K erreicht. Das Wachstum auf speziellen mehrlagigen GaAs-Architekturen ermöglichte zudem die Realisierung dreidimensionaler Mikroobjekte, bei denen sich die Dünnschicht aufgrund von Relaxation epitaktischer Verspannung des Substrates zu Helices aufrollt. Mechanische Defekte führten jedoch dazu, dass keine supraleitenden Eigenschaften gemessen werden konnten. In diesem Fall ist eine weitere Optimierung der Mikrostrukturierungsprozesse notwendig. / In this work, we studied the influence of epitaxial strain on the properties of iron based superconducting thin films grown by pulsed laser deposition. Epitaxial films of Ba(Fe1-xNix)2As2 have been realised for the first time using different nickel doping contents. Afterwards their structural and superconducting properties have been characterised. The results were compared to bulk samples as well as to thin films of the related compound Ba(Fe1-xCox)2As2. A maximum Tc of 21,6 K was measured, which exeeds the highest reported values of bulk samples. Depending on the used substrate, the phase diagram is shifted due to the induced tensile or compressive strain in the films. Compared to bulk samples, the slope of the upper critical field is strongly enhanced near the critical temperature due to antiferromagnetic fluctuations. The magnetic phase diagram measured in high fields shows simularities with the isostructural Co-doped system. The measurements reveal a small anisotropy of the upper critical field for low temperatures, while the anisotropy of the irreversibility field is increased due to the defect structure in the film. Furthermore, epitaxial thin FeSe1-xTex films have been deposited on GaAs as a new substrate material for iron based superconducting thin films achieving a critical temperature of up to 17,4 K. The self-organised formation of threedimensional micro helices by strain relaxation was realised by the preparation of epitaxial films on customized GaAs-based multilayer achitectures. However, mechanical defects prevented the superconducting characterisation. Therefore, a further improvement of the involved processes for microstructuring is necessary.

Lead-based piezoelectric materials, such as PbZrxTi1-xO3 (PZT), have attracted considerable attention and have been widely used in actuators, sensors and transducers due to their excellent electric properties. However, considering the toxicity of lead and its oxides, environmentally friendly lead-free piezoelectric materials are attracting more attention as potential replacements for PZT. Among them, Bi0.5Na0.5TiO3 (BNT)-based materials exhibit good electrical properties and electromechanical coupling response. In this work, the 0.97Bi0.5Na0.5TiO3-0.03BiAlO3 (BNTBA) thin films (~120 nm thickness) were successfully prepared using the pulsed laser deposition (PLD) method on Pt/TiO2/SiO2/Si substrates. The effects of substrate temperature, oxygen pressure, laser repetition rate, and post-annealing treatment were investigated. X-ray diffraction (XRD) and scanning electron microscope (SEM) are used to study the structure of the films and the ferroelectric and dielectric properties are measured. The results show that it is necessary to introduce excess sodium and bismuth to compensate for their evaporation in further thermal treatment. The values of remnant polarization increase from 8.7 μC/cm2 to 12.3 μC/cm2 with the introduction BiAlO3. The dielectric constant increases from 600-550 to 710-600 and the dielectric loss increases from 4.2% to 6.7% at higher frequency when the oxygen pressure increases from 20 Pa to 30 Pa. / Blybaserade piezoelektriska material, såsom PbZrxTi1-xO3 (PZT), har väckt stor uppmärksamhet och har använts i stor utsträckning på grund av deras utmärkta elektriska egenskaper. Men med tanke på toxiciteten hos bly och dess oxider lockar miljövänliga blyfria piezoelektriska material mer uppmärksamhet från forskare som potentiella utbyten för PZT. Bland dem uppvisar Bi0.5Na0.5TiO3 (BNT) -baserade material bra elektriska egenskaper och elektromekanisk kopplingssvar. I detta arbete framställdes 0,97Bi0.5Na0.5TiO3-0.03BiAlO3 (BNTBA) tunna filmer (~ 120 nm tjocklek) med användning av pulserad laseravsättningsmetod på Pt / TiO2 / SiO2 / Si-substrat. Effekterna av substrattemperatur, syretryck, laserrepetitionshastighet och efterglödande behandling undersöktes. Röntgendiffraktions (XRD) och skanningelektronmikroskop (SEM) används för att studera filmens struktur och de ferroelektriska och dielektriska egenskaperna mäts. Resultaten visar att det är nödvändigt att införa överskott av natrium och vismut för att kompensera för deras avdunstning vid vidare termisk behandling. Värdena för återstående polarisation ökar från 8,7 μC / cm2 till 12,3 μC / cm2 med introduktionen BiAlO3. Den dielektriska konstanten ökar från 600-550 till 710-600 och den dielektriska förlusten ökar från 4,2% till 6,7% vid högre frekvens när syretrycket ökar från 20 Pa till 30 Pa.

[pt] O atual panorama do mercado energético no Brasil permite aos produtores de energia realizar operações de swap de preços, o que diminui os riscos intrínsecos da operação, além de garantir, ocasionalmente, melhores lucros. Devido à diferenças existentes entre as demandas dos diversos submercados de energia, pode-se arbitrar os preços, de modo a minimizar as perdas. Tendo por objetivo encontrar melhores formas de realizar este swap e utilizando-se de duas mil séries dos preços projetados de liquidação das diferenças (PLD), dos anos de 2016, 2017 e 2018, analisou-se a magnitude dos riscos considerando-se o hedge especificamente para parques eólicos no nordeste com venda no sudeste. Os resultados encontrados indicam que apesar da magnitude do risco ser grande, os swaps de energia são bastante eficazes em sua mitigação. / [en] The panorama of the energy market in Brazil allows energy producers to make swap operations with prices, decreasing the intrinsic risks of operation, besides ensuring, occasionally, better profits. Due to the difference between the demands of the various energy submarkets, they may arbitrage the prices to minimize their losses. With the objective to find better ways to make this swap, and working on two thousand series of the settlement price of differences, from the years of 2016, 2017 and 2018, it was possible to analyze the magnitude of the risks, considering the hedge. Despite the results, the Brazilian energy infrastructure is highly dependent on rainfall patterns, showing clear weakness in drought periods. A higher investment in the sustainable energy sector, is necessary in or-der to ensure a more continuous supply, taking into account the experience of other countries.