Location and climate factors governing morphological features of ice wedge polygons in arctic zone Abstract This thesis reports the geometry of active soil and ice-wedge polygonal network located along the Canadian Arctic and in Alaska. This High Arctic periglacial environment was chosen to ensure active thermal-contraction cracking of permafrost in Holocene allowing comparison of observed ice-wedge polygons with existing climatic data. Geoinformatic software (Google Earth, ArcGIS) was used to obtain and digitalize satellite images of polygonal networks located around Eureka, Mould Bay, Churchill, Rankin Inlet, Inuvik, and Kotzebue. Defined polygonal networks were statistically analyzed in order to define predominant environmental factors controlling morphological parameters of these polygonal networks. Polygon size (overall influence computed on the basis of coefficient of determination) is determined mostly by the duration of development (18 %), frequency of cyclonic passage (17.8 %) and winter air temperature (16.1 %). Conversely, polygon regularity results mainly from nature of the substrate (21.8 %), winter wind speed (15.1 %) and snow cover thickness (12.2 %). Dominant polygon elongation in the polygonal network follows closely the winter wind direction (3/4 of all networks) as the result of snow...

Recognition and classification of patterned ground polygons from remote sensing data Abstract The main objective of this thesis has been to prove the possibility of using object based image analysis classification for identification of the ice-wedge polygons and to find general method for their classification. The thesis contains a comparison of the object based and pixel based classification of the subject. The three classification rulesets for OBIA were developed on three test sites on Mars captured by HiRISE sensor. As a result, the general classification approach is suggested. The manually collected datasets, which are common in geomorphological research, were used as the reference sample. The OBIA classification provided better results in all three cases, whereas the pixel classification was valid in only one case. Another objective has been the automatization of the process of gaining information about morphometric characteristics of the ice-wedge polygons and the subsequent classification of the polygons. Within the scope of the process were developed methods for creating polygonal network and specified parameters of those methods. Several toolboxes for the ArcGIS software were prepared and they are part of the results of the thesis. Keywords: patterned ground, ice-wedge polygons, remote sensing,...

The stratified flow of the lower Mississippi River due to density gradients is a well documented phenomenon. This stratification of fresh and saline water manifests itself as a heavier wedge of saline water that extends upriver and a buoyant fresh water plume extending into the Gulf of Mexico past the Southwest Pass jetties. The maximum absolute distance of saltwater intrusion observed anywhere in the world occurred on the Mississippi River in 1939 and 1940 when saltwater was observed approximately 225 km upstream from the mouth of Southwest Pass. The U. S. Army Corps of Engineers now prevents the wedge from migrating upstream by constructing a subaqueous barrier in the river channel. A curvilinear grid was constructed representative of the modern Mississippi River delta. Boundary conditions were developed for the drought year of 2012 and the grid was tested in order to evaluate the salinity intrusion and sediment transport abilities of the Cartesian Z-coordinate Delft3D code. The Z-model proved to have the ability to propagate the saline density current as observed in the prototype. The effect of salinity on fine sediment transport is evaluated by manipulation of the settling velocity through a cosine function provided in the model code. Manipulation of the fine sediment fall velocity through the cosine function was an effective means to simulate the re-circulation of flocculated sediments in the saline wedge turbidity maxima. In addition, the Z-model capably reproduced the fine sediment concentration profiles in a fully turbulent shear flow environment. With the ability to reproduce the seasonal saline density current and its effect on sedimentation within the turbidity maxima as well as sedimentation characteristics in a fully turbulent shear flow, a model capable of analyzing all of the major processes affecting fine sediment transport within the Mississippi River salt wedge estuary has been developed.

Thesis advisor: Larry W. McLaughlin / The ability to control gene expression has traditionally been pursued at the protein level, using drugs designed to mimic a natural substrate or to disrupt a protein's active site. Traditional drug targeting by competitive and non-competitive inhibitors, however, requires a fairly detailed knowledge of the target protein's three-dimensional structure. More recently, focus has broadened to include alternative methods of genetic control, including the use of single-stranded DNA or RNA probe sequences which control gene expression by targeting the genes themselves. Within the last two decades, peptide nucleic acids (PNAs) – DNA mimics possessing natural bases linked to an N-(2-aminoethyl)-glycine (AEG) backbone – have proven as effective in gene-targeting as traditional synthetic DNA or RNA with the added advantages of tighter binding and greater specificity. Additionally, PNAs are not easily recognized by nucleases, proteases, and peptidases giving them greater resistance to enzyme degradation and making them even more favorable for gene targeting in vivo. Traditional PNA triplexes are composed of two polypyrmidine PNA strands bound to the Watson-Crick and Hoogsteen faces, respectively, of the polypurine strand of target DNA after displacing the polypyrimidine strand of the original DNA duplex. Janus Wedge (JW) residues, on the other hand, utilize unnatural bases linked to the AEG backbone, which are capable of hydrogen bonding to the Watson-Crick faces of both strands of a target DNA duplex. JW triplex formation, then, has a DNA2-PNA stoichiometry, and no Hoogsteen face interactions. The generalization of the DNA duplex targeting strategy by peptide oligomers requires substantial discoveries in the field of PNA research, including an understanding of the three-dimensional structure and folding pattern of these triple-stranded molecules. This report details the crystallization efforts on JW DNA-peptide-DNA triplexes using 11dC811-11T811 target sequences – with and without single base overhangs – and synthetic W8K peptide. Hanging drop vapor diffusion methods showed that while crystal formation was extremely elusive, in narrowing the optimal buffer conditions, 25% PEG concentration was consistently correlated with the most promising crystallization efforts for both the overhanged and non-overhanged sequences. / Thesis (BS) — Boston College, 2005. / Submitted to: Boston College. College of Arts and Sciences. / Discipline: Chemistry. / Discipline: College Honors Program.

Thesis advisor: Sanjay K. Chugh / Thesis advisor: Fabio Schiantarelli / My doctoral research focuses on the role of labor market frictions in shaping macroeconomic outcomes. I am currently pursuing three main lines of research that constitute the three chapters of this dissertation. The first chapter focuses on involuntary part-time employment as an additional margin used by firms to adjust to business cycle fluctuations. The chapter documents empirical regularities of involuntary part-time employment in the U.S. and furnishes a tractable analytical framework for studying this phenomenon that has gained so much attention in the years that followed the Great Recession. In the second chapter, which is joint work with Sanjay Chugh, Ryan Chahrour and Alan Finkelstein-Shapiro, we study the labor market wedge in the context of a search and matching model to understand how static and dynamic inefficiencies change over the business cycle. Measuring the labor market wedge and understanding its sources of movement is of great importance from a macroeconomic point of view, as existing research shows it holds a prominent place in explaining fluctuations in aggregate output. Finally, in the third chapter I study empirically the determinants of the job finding probability, a key object in the context of frictional labor markets. More specifically, I analyze how decisions on time allocation by the unemployed affect their chances of finding a job, and identify the activities that make more likely for an unemployed individual to receive and accept a job offer. Chapter 1. In recent years researchers and policymakers have shown renewed interest in involuntary part-time employment as a crucial indicator of labor market health. The fact that individuals have part-time jobs even though they would be willing to work more hours is evidence that resources in the economy are not employed at full capacity. This group represents almost 40 percent of total underemployment. Despite its large size and importance to policy-makers, surprisingly little literature addresses the empirical regularities or economic role this margin plays in determining labor market outcomes. In "Underemployment and the Business Cycle" I address several questions regarding involuntary part-time employment. First, how does involuntary part-time employment differ from the standard extensive and intensive margins? Second, what factors influence the choice of firms to use involuntary part-time workers? Third, how might economic policy contribute to the existence of involuntary part-time employment in the economy? And, fourth, have there been any changes over time in the response of involuntary part-time employment to changes in aggregate economic conditions and, if so, what explains them? To describe the empirical regularities of involuntary part-time employment, I use detailed micro-level data from longitudinally-linked monthly files of the Current Population Survey. A novel finding that emerges from the analysis of this dataset is that wages of involuntary part-time workers display higher volatility and lower persistence than those of their full-time counterparts, thus indicating a higher degree of flexibility. In addition, I find that changes in involuntary part-time employment are mostly explained by reallocation of workers from full-time to part-time positions within the firm, which involves more than just a mere reduction in hours worked. I then aggregate the data and compute business cycle statistics. Surprisingly, I find that the behavior of involuntary part-time employment resembles the behavior of unemployment more than the one of full-time employment. In fact, the results indicate that involuntary part-time employment is very volatile and strongly countercyclical. To understand the evidence I find at the micro and macro levels, I build an augmented search and matching model of the labor market featuring full-time and part-time employment, and a production function that combines both types of workers. The decision of whether a worker is full-time or part-time is made entirely by the firm, depending on the realizations of both aggregate and idiosyncratic productivity processes. The model is able to deliver the countercyclicality of involuntary part-time employment found in the data. The key mechanism to obtain this result is the relatively higher flexibility of part-time contracts that makes it more profitable for the firm to reallocate workers from full-time to part-time arrangements during recessions. Based on the model that captures key empirical facts, I conduct policy analysis to evaluate the effect of an increase in the cost of health insurance on involuntary part-time employment. The policy experiment predicts that an increase in the cost of health insurance provided by the firm to its full-time workers, such that their share in average full-time wages goes up by 1 percentage point, leads to an increase of steady state involuntary part-time employment by 10 percent, which nowadays would be equivalent to half a million additional involuntary part-time workers. I find evidence that involuntary part-time employment has become more volatile and persistent in the last 25 years. I study the impact that innovation in workforce management practices, a process that started in the 1990s and that has increased the degree of substitutability between full-time and part-time workers, may have had in changing the response over time of involuntary part-time employment to business cycle fluctuations. Impulse response analysis from the model indicates that an increase in the degree of substitutability makes involuntary part-time employment more sensitive to aggregate productivity shocks. Chapter 2. In "The Labor Wedge: A Search and Matching Perspective" we define and quantify static and dynamic labor market wedges in a search and matching model with endogenous labor force participation. Existing literature has generally centered on Walrasian labor markets in characterizing the inefficiencies, or ``gaps'', between labor demand and labor supply. However, given the conventional view in the profession that the matching process plays an important role in the labor market, the neoclassically-measured labor wedge suffers from a misspecification problem as it ignores the role of long-lasting relationships in explaining the cyclical pattern of the labor wedge. To construct the wedge we use a rigorously defined transformation function of the economy, which contains both the matching technology and the neoclassical production technology. Both technologies are primitives of the economy in the sense that a Social Planner must respect both processes. Given the model-appropriate transformation frontier and the household's static and dynamic marginal rates of substitution, we use data on the labor force participation rate, the employment rate, the vacancy rate, real consumption, real government spending, and real GDP to construct static and dynamic labor wedges. We find that, in a version of the model where all employment relationships turn over every period, the static labor wedge is countercyclical, a result that is consistent with existing literature. Once we consider long-lasting employment relationships, we can measure both static and dynamic wedges separately. We then find that, while the static wedge continues to be countercyclical, the dynamic (or intertemporal) wedge is procyclical. Since the latter is associated with the vacancy-posting decision of the firm, this result suggests that understanding the behavior of labor demand may be crucial to explaining the dynamic wedge. Our focus so far has been on obtaining a quantitative measure of both the static and dynamic wedges, and on analyzing their business cycle properties. Now we are working on extending this framework to provide a micro-founded explanation of the forces that could be driving the cyclical movements of the wedges. Chapter 3. Recent research has found that individuals who become unemployed allocate most of their forgone working hours into leisure rather than increasing the time devoted to job search activities. What is the rationale behind this decision? There are many factors that may affect the job search behavior of the unemployed. However, in this study I focus on a particular channel: the decision on how unemployed individuals allocate their time could be biased towards activities that increase their probability of finding a job. They might find more valuable to increase their social activities rather than looking formally for a job because this enhances their network, which could increase their chances of finding a job, even with less search effort. In "The Time Use Decisions of the Unemployed: A Survival Analysis", I conduct a duration analysis to estimate the effect of different time use allocations on the unemployment hazard rate using time use data from the Survey of Unemployed Workers in New Jersey. Defining "finding a job" as a failure, I estimate a single-spell, discrete-time duration model of unemployment with time-varying covariates using semi-parametric techniques. Given that I work with interval-censored data, I conduct the analysis using discrete time survival analysis techniques. The results indicate that education/training activities have a significant and positive impact on the hazard rate, i.e. they increase the probability that an unemployed worker finds a job, while leisure has the opposite effect. Furthermore, neither job-search nor networking have a significant effect on the hazard rate in the baseline specification. However, this result changes when incorporating into the regression interaction terms of these variables with a dummy that takes the value one if the individual is a long-term unemployed and zero otherwise. In this case, the coefficient associated with networking becomes positive and significant, while the coefficient of the interaction term is negative. This implies that networking has a positive effect on the hazard rate for short unemployment spells, but this effect weakens if the individual has been unemployed for a longer period. On the other hand, even after incorporating the interaction term, job search remains insignificant. These findings shed light on why individuals may not want to devote additional time to formal job search: it does not pay off with a higher likelihood of receiving a job offer, regardless of the length of the unemployment spell. On the other hand, other activities, such as investing in education or networking, are positively related to the probability of finding a job -- at least for short unemployment spells -- and thus it makes more sense for these individuals to devote more time to them.

Refratários são materiais com microestrutura heterogênea constituída de uma fração grosseira, os agregados, e de uma fração mais fina, a matriz, em que ambas exercem papéis fundamentais nas propriedades dos refratários, sendo a resistência ao dano por choque térmico, uma das mais importantes. Para avaliar essa questão crítica dos refratários há necessidade de se conhecer bem seu comportamento à propagação de trinca, principalmente quando submetido a uma tensão. Porém, devido à complexidade da estrutura desses materiais, o comportamento das regiões à frente e atrás da ponta da trinca sempre foi muito discutido, só que essa discussão sempre fez uso de modelos e simulações computacionais, já que é prevista uma zona de processo, em que diferentes mecanismos podem absorver energia aumentando a resistência à propagação da trinca principal. Nesta tese foi proposto o estudo experimental do comportamento da propagação de trinca em refratários, visando entender os mecanismos de resistência à propagação de trinca e o caminho das trincas propagantes, utilizando o método da cunha para propagação estável da trinca, que é o mais adequado para essa classe de materiais. Para isso foram utilizados, dois refratários distintos: tijolo e concreto, ambos de alta alumina. No tijolo, para visualização do caminho da trinca propagante após o ensaio, o caminho da trinca foi infiltrado com cola instantânea para garantir a integridade da mesma, a fim que amostras pudessem ser preparadas para análise de imagens em microscópio eletrônico de varredura. Devido à dificuldade dessa preparação, e de só ser possível observar a trinca após a propagação, um microscópio digital passou a ser utilizado in loco ao ensaio. Esse estudo foi realizado com o concreto, sendo possível associar o comprimento da trinca com a curva carga-deslocamento. A fim de complementar o estudo do processo de fratura, a técnica de emissão acústica (EA) passou a ser utilizada nos ensaios de propagação de trinca, já que quando um material é submetido a uma carga e as trincas se desenvolvem, há liberação de energia de deformação do material, sendo possível capturar os dados de energia dos sinais gerados pela propagação. Sendo assim foi possível correlacionar resultados de energia de fratura, início e tamanho de trinca com as curvas carga-deslocamento, carga-tempo, e inclusive, com a contagem de sinais acumulada-tempo, que foi complementar na estimativa da zona de processo completa, ou seja, os fenômenos produzidos atingiram o estado estacionário. A região em que se encontra o final da zona de processo coincide com o fim do regime estacionário, que é onde a trinca atravessa o corpo de prova. Dessa forma, mostra-se com essa tese, que o corpo de prova utilizado para a propagação estável de trinca pelo método da cunha, nas dimensões atuais, são suficientes para o desenvolvimento de todos os mecanismos de resistência à propagação de trinca em refratários. / Refractories are materials with heterogeneous microstructure, consisting of a coarse fraction, aggregates, and a finer fraction, the matrix, in which both play key roles in the properties of the refractory, and the resistance to thermal shock damage, one of the most important. To examine this critical issue of the refractory is no need to be familiar with their behavior to crack propagation, especially when subjected to a stress. The behavior of the regions ahead of and behind the crack tip has been discussed exhaustively, because a process zone was envisaged in which different mechanisms could absorb energy, thus increasing the propagation resistance of the main crack. However, this discussion has always been based on the use of models and computer simulations. The thesis presented here proposes an experimental study of the behavior of crack propagation in refractories, aiming to understand the mechanisms of crack propagation resistance and the crack propagation path, using the wedge splitting method to achieve stable crack propagation. To this end, two different refractory materials were used: brick and concrete, both high alumina. Based on the stable crack propagation test by the wedge method, techniques were sought that would aid in the visualization of crack propagation. In brick, the crack path was infiltrated with instant glue and infiltrated samples were examined by scanning electron microscopy (SEM); however, in addition to proving laborious, the crack was only visible after its propagation. In the case of concrete, this study was performed in loco during the test, using a digital microscope in combination with the acoustic emission (AE) technique. AE is defined as the generation of stress waves stored energy is suddenly released from localized sources within a material subjected to external loads. By means of the fracture energy data and the AE signals, it was possible to observe the entire fracture process and to correlate the results of fracture energy and crack onset and size with the load-displacement and load-time curves, and even the count of signals accumulated over time. This information was complementary to estimate the complete process zone, i.e., the phenomena produced reached the steady state. This study demonstrated that the dimensions of the test specimen used for stable crack propagation by the wedge splitting method suffice for the development of all the mechanisms of crack propagation resistance in refractories.

Os concretos refratários são materiais que apresentam estrutura complexa contendo uma fração de partículas finas (D < 100?m) chamada de matriz e outra mais grosseira da ordem de até centímetros compostas por agregados. Dentre as propriedades importantes durante a aplicação dos concretos refratários, este trabalho aborda principalmente a energia de fratura e a resistência à erosão. Para a avaliação dessas propriedades vários estudos vêm sendo desenvolvidos nos últimos anos. A introdução do método da cunha para propagação estável da trinca é um exemplo, pois este método é utilizado para materiais com estrutura grosseira, como é o caso dos concretos. Já em se tratando de resistência a erosão, pouco se encontra na literatura a respeito desse assunto para concretos refratários. Tendo em vista a aplicação destes materiais, foi avaliado o comportamento da energia de fratura e resistência à erosão de concretos refratário aluminoso convencional antierosivo utilizado na indústria petroquímica com o objetivo de correlacionar os resultados de energia de fratura e a resistência à erosão. Para o desenvolvimento do trabalho foram usados dois concretos a com mesma composição química, variando somente o tamanho de agregado. Foram avaliadas além da energia de fratura e da resistência à erosão outras propriedades foram avaliadas como: os módulos elástico e de ruptura, porosidade aparente, fases cristalinas e microestrutura, e ainda foi realizado um estudo da matriz do concreto. Os resultados mostraram que a energia de fratura aumenta com o aumento do tamanho de agregado para o concreto estudado e a resistência a erosão aumenta com a temperatura de tratamento térmico devido a ceramização da matriz, conforme análise das imagens. Em função dos resultados, pode-se concluir que não foi observada uma boa correlação entre energia de fratura e resistência à erosão. Mas esta correlação de energia de fratura e de resistência à erosão pode ter o mesmo comportamento que a correlação entre comprimento característico e resistência á erosão para faixas específicas de tamanho de agregado. / Castables materials are known to be formed by a complex microstructure containing a fine fraction known as matrix (D<100?m) and another one known as aggregate containing thicker particles up to centimeters in size. Among its most notable properties regarding application, this research primarily addresses to the fracture energy and its erosion resistance. In recent years, some studies have been performed concerning such assessments. As an example, the wedge splitting procedure has been applied in the stable crack propagation method used for some thicker structured materials evaluation such the castables ones. On the other hand, a few data have been gathered concerning castable\'s erosion resistance. Facing such applications the main goal was the study of conventional aluminous anti erosive castables once it has been used in the petrochemical industry in order to correlate fracture energy and erosion resistance results. On this research, two castables samples with the same chemical composition were tested differing only its aggregate particle grain sizes. Besides fracture energy and erosion resistance, other important properties were evaluated as following: elastic modulus, rupture modulus, apparent porosity, crystalline phases and a castable matrix study was also carried out. The results demonstrate an increase on fracture energy as the studied castable aggregate size also increases and according to images studied, the erosion resistance suffers another increment regarding the thermal treatment temperature increase due matrix ceramization. Based on the obtained results, it can be concluded that no observation was made regarding the fracture energy and erosion resistance but it may exist an energy correlation between them once there is some observed between the characteristic length and the erosion resistance concerning the aggregate size range.

Refratários são materiais com microestrutura heterogênea constituída de uma fração grosseira, os agregados, e de uma fração mais fina, a matriz, em que ambas exercem papéis fundamentais nas propriedades dos refratários, sendo a resistência ao dano por choque térmico, uma das mais importantes. Para avaliar essa questão crítica dos refratários há necessidade de se conhecer bem seu comportamento à propagação de trinca, principalmente quando submetido a uma tensão. Porém, devido à complexidade da estrutura desses materiais, o comportamento das regiões à frente e atrás da ponta da trinca sempre foi muito discutido, só que essa discussão sempre fez uso de modelos e simulações computacionais, já que é prevista uma zona de processo, em que diferentes mecanismos podem absorver energia aumentando a resistência à propagação da trinca principal. Nesta tese foi proposto o estudo experimental do comportamento da propagação de trinca em refratários, visando entender os mecanismos de resistência à propagação de trinca e o caminho das trincas propagantes, utilizando o método da cunha para propagação estável da trinca, que é o mais adequado para essa classe de materiais. Para isso foram utilizados, dois refratários distintos: tijolo e concreto, ambos de alta alumina. No tijolo, para visualização do caminho da trinca propagante após o ensaio, o caminho da trinca foi infiltrado com cola instantânea para garantir a integridade da mesma, a fim que amostras pudessem ser preparadas para análise de imagens em microscópio eletrônico de varredura. Devido à dificuldade dessa preparação, e de só ser possível observar a trinca após a propagação, um microscópio digital passou a ser utilizado in loco ao ensaio. Esse estudo foi realizado com o concreto, sendo possível associar o comprimento da trinca com a curva carga-deslocamento. A fim de complementar o estudo do processo de fratura, a técnica de emissão acústica (EA) passou a ser utilizada nos ensaios de propagação de trinca, já que quando um material é submetido a uma carga e as trincas se desenvolvem, há liberação de energia de deformação do material, sendo possível capturar os dados de energia dos sinais gerados pela propagação. Sendo assim foi possível correlacionar resultados de energia de fratura, início e tamanho de trinca com as curvas carga-deslocamento, carga-tempo, e inclusive, com a contagem de sinais acumulada-tempo, que foi complementar na estimativa da zona de processo completa, ou seja, os fenômenos produzidos atingiram o estado estacionário. A região em que se encontra o final da zona de processo coincide com o fim do regime estacionário, que é onde a trinca atravessa o corpo de prova. Dessa forma, mostra-se com essa tese, que o corpo de prova utilizado para a propagação estável de trinca pelo método da cunha, nas dimensões atuais, são suficientes para o desenvolvimento de todos os mecanismos de resistência à propagação de trinca em refratários. / Refractories are materials with heterogeneous microstructure, consisting of a coarse fraction, aggregates, and a finer fraction, the matrix, in which both play key roles in the properties of the refractory, and the resistance to thermal shock damage, one of the most important. To examine this critical issue of the refractory is no need to be familiar with their behavior to crack propagation, especially when subjected to a stress. The behavior of the regions ahead of and behind the crack tip has been discussed exhaustively, because a process zone was envisaged in which different mechanisms could absorb energy, thus increasing the propagation resistance of the main crack. However, this discussion has always been based on the use of models and computer simulations. The thesis presented here proposes an experimental study of the behavior of crack propagation in refractories, aiming to understand the mechanisms of crack propagation resistance and the crack propagation path, using the wedge splitting method to achieve stable crack propagation. To this end, two different refractory materials were used: brick and concrete, both high alumina. Based on the stable crack propagation test by the wedge method, techniques were sought that would aid in the visualization of crack propagation. In brick, the crack path was infiltrated with instant glue and infiltrated samples were examined by scanning electron microscopy (SEM); however, in addition to proving laborious, the crack was only visible after its propagation. In the case of concrete, this study was performed in loco during the test, using a digital microscope in combination with the acoustic emission (AE) technique. AE is defined as the generation of stress waves stored energy is suddenly released from localized sources within a material subjected to external loads. By means of the fracture energy data and the AE signals, it was possible to observe the entire fracture process and to correlate the results of fracture energy and crack onset and size with the load-displacement and load-time curves, and even the count of signals accumulated over time. This information was complementary to estimate the complete process zone, i.e., the phenomena produced reached the steady state. This study demonstrated that the dimensions of the test specimen used for stable crack propagation by the wedge splitting method suffice for the development of all the mechanisms of crack propagation resistance in refractories.

In the Romantic period, expanded tonality offers a creative challenge to composers as they explore new ways of establishing the hierarchy of pitches and utilizing the chromatic and diatonic resources. Prominent compositional techniques of this period include the use of linear harmony with less clearly defined root movements, the structural placement of dominant function, new approaches that redefine tonal stability, motivic treatment that generates harmony and form, flexible treatment of rhythm and meter, and functional treatment of chromatic pitches. This study explores the ways in which characteristics of the Romantic period are influenced by the upper/lower leading tone and the effects of compositional treatment on the expansion of tonality. In addition, this study includes two supportive concepts: (1) the wedge and toggle switch by David Witten and (2) The Neapolitan Complex by Christopher Wintle. In describing techniques in expanded tonality, excerpts from compositions by Robert Schumann and Johannes Brahms (both prominent composers of the Romantic period) are used to establish the significance of these techniques. In the fourth movement of Sonata in E minor "Undine," by Carl Reinecke, the structural treatment of the upper/lower leading tones to tonic and dominant are very prominent features that contribute significantly to the development of the concepts in this study.

This dissertation is concerned with extensions and wedge products of positive currents. Our study can be considered as a generalization for classical works done earlier in this field. Paper I deals with the extension of positive currents across different types of sets. For closed complete pluripolar obstacles, we show the existence of such extensions. To do so, further Hausdorff dimension conditions are required. Moreover, we study the case when these obstacles are zero sets of strictly k-convex functions. In Paper II, we discuss the wedge product of positive pluriharmonic (resp. plurisubharmonic) current of bidimension (p,p) with the Monge-Ampère operator of plurisubharmonic function. In the first part of the paper, we define this product when the locus points of the plurisubharmonic function are located in a (2p-2)-dimensional closed set (resp. (2p-4)-dimensional sets), in the sense of Hartogs. The second part treats the case when these locus points are contained in a compact complete pluripolar sets and p≥2 (resp. p≥3). Paper III studies the extendability of negative S-plurisubharmonic current of bidimension (p,p) across a (2p-2)-dimensional closed set. Using only the positivity of S, we show that such extensions exist in the case when these obstacles are complete pluripolar, as well as zero sets of C2-plurisubharmoinc functions. / At the time of doctoral defense, the following papers were unpublished and had a status as follows: Paper 1: Accepted. Paper 2: Manuscript. Paper 3: Manuscript.