Thesis (MSc)--University of Stellenbosch, 2005. / Bibliography. Also available via the Internet.

The hypertoric variety M_A defined by an arrangement A of affine hyperplanes admits a natural tropicalization, induced by its embedding in a Lawrence toric variety. In this thesis, we explicitly describe the polyhedral structure of this tropicalization and calculate the fibers of the tropicalization map. Using a recent result of Gubler, Rabinoff, and Werner, we prove that there is a continuous section of the tropicalization map.

Made available in DSpace on 2015-04-09T12:28:21Z (GMT). No. of bitstreams: 0 Previous issue date: 2014-02-28Bitstream added on 2015-04-09T12:48:18Z : No. of bitstreams: 1 000810685.pdf: 423114 bytes, checksum: d115e8de0825c2a98f8531e8d0a39ce2 (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / A fibração de Milnor aparece como a principal ferramenta no estudo local da topologia das singularidades analíticas reais e complexas. Neste trabalho estudaremos o Teorema de Fibração de Milnor e o surpreendente comportamento topológico das Fibras de Milnor. Para tais objetivos, usaremos algumas ferramentas da Geometria Algébrica, Análise Complexa em várias variáeis e um pouco da Teoria de Morse / The Milnor bration appears as the main tool in the topological local study of real and complex analytic singularities. In this work we study the famous Milnor Fibration Theorem, and the surprising topological behavior of the Milnor bres. To reach these objectives we use some tools of classical Algebraic Geometry, Complex Analysis of several variables and also some aspects of Morse Theory

Made available in DSpace on 2014-06-11T19:24:44Z (GMT). No. of bitstreams: 0 Previous issue date: 2013-07-22Bitstream added on 2014-06-13T20:12:55Z : No. of bitstreams: 1 garcia_el_me_botfca.pdf: 913637 bytes, checksum: ba7a54ec3c0db0e89c7d86fe40d4d7b5 (MD5) / O mercado de amido vem crescendo e se aperfeiçoando nos últimos anos, levando à busca de produtos com características específicas que atendam as exigências industriais. No presente trabalho objetivou-se avaliar a composição físico-química de tubérculos de batata e suas potencialidades industriais. Foram avaliadas oito cultivares: Beacon Chipper, BRS Ana, Colorado, Harley Beckhell, Marcy, Marlen, Pirassu e Snowden, cultivadas no município de Pouso Alegre/MG safra 2011. Os tubérculos foram caracterizados segundo os valores encontrados para teor de umidade, cinzas, proteína, fibra, matéria graxa, açúcares, amido, pH, acidez titulável e cor da casca e da polpa. Após a caracterização dos tubérculos, realizou-se a extração do amido e este foi avaliado quanto a composição centesimal, propriedades de pasta, propriedades térmicas, teor de minerais (P, K, Ca e Mg), teor de amilose aparente, pH e acidez titulável. Na caracterização da coloração dos tubérculos a cultivar Beacon Chipper apresentou maior brilho e maior intensidade do componente de cor amarela (b* positivo), as cultivares BRS Ana e Pirassu apresentaram os maiores valores para o componente de cor vermelha (a* positivo). As cultivares BRS Ana e Harley Beckhell apresentaram o maior teor de matéria seca. O maior e menor rendimento de extração de amido foi obtido com a cultivar Harley Beckhell e Colorado, respectivamente. O amido extraído dos tubérculos apresentou alto grau de pureza e a cultivar Beacon Chipper apresentou o menor teor de amilose aparente. O teor de fósforo foi elevado para as cultivares Marcy e Harley Beckhell, já para as cultivares BRS Ana e Pirassu o teor desse mineral foi menor. Nas propriedades de pasta a cultivar Marcy apresentou valores elevados para viscosidade máxima, quebra de viscosidade e tendência a retrogradação, que são... / The starch market has been growing and improving in recent years, leading to a search for products with specific characteristics that meet the industrial requirements. This work aimed to evaluate the physical and chemical composition of potato tubers (Solanum tuberosum L.) and its industrial potential. Eight cultivars were evaluated: Snowden, Harley Beckhell, Marlen, Colorado, BRS Ana, Pirassu, Beacon Chipper and Marcy grown in Pouso Alegre, Minas Gerais state, in 2011. Tubers were characterized to the moisture, ash, protein, fiber, lipids, sugars, starch, pH, titratable acidity and color of the peel and pulp. After characterization of the tubers, held the extraction of starch and this was evaluated for proximate composition, pasting properties, thermal properties, mineral content (P, K, Ca and Mg), content of apparent amylose, pH and titratable acidity . In characterizing the color of the tubers to cultivar Beacon Chipper showed higher brightness and greater intensity of the yellow color component (b* positive), the cultivars BRS Ana and Pirassu showed the highest values for the red color component (a* positive). The cultivars BRS Ana and Harley Beckhell showed the highest dry matter content. The highest and lowest... (Complete abstract click electronic access below)

Orientador: João Carlos Ferreira Costa / Banca: Ana Claudia Nabarro / Banca: Luciana de Fátima Martins / Resumo: A fibração de Milnor aparece como a principal ferramenta no estudo local da topologia das singularidades analíticas reais e complexas. Neste trabalho estudaremos o Teorema de "Fibração" de Milnor e o surpreendente comportamento topológico das Fibras de Milnor. Para tais objetivos, usaremos algumas ferramentas da Geometria Algébrica, Análise Complexa em várias variáeis e um pouco da Teoria de Morse / Abstract: The Milnor bration appears as the main tool in the topological local study of real and complex analytic singularities. In this work we study the famous Milnor Fibration Theorem, and the surprising topological behavior of the Milnor bres. To reach these objectives we use some tools of classical Algebraic Geometry, Complex Analysis of several variables and also some aspects of Morse Theory / Mestre

Orientador: Magali Leonel / Banca: Glauber José de Castro Gava / Banca: Regina Marta Evangelista / Resumo: O mercado de amido vem crescendo e se aperfeiçoando nos últimos anos, levando à busca de produtos com características específicas que atendam as exigências industriais. No presente trabalho objetivou-se avaliar a composição físico-química de tubérculos de batata e suas potencialidades industriais. Foram avaliadas oito cultivares: Beacon Chipper, BRS Ana, Colorado, Harley Beckhell, Marcy, Marlen, Pirassu e Snowden, cultivadas no município de Pouso Alegre/MG safra 2011. Os tubérculos foram caracterizados segundo os valores encontrados para teor de umidade, cinzas, proteína, fibra, matéria graxa, açúcares, amido, pH, acidez titulável e cor da casca e da polpa. Após a caracterização dos tubérculos, realizou-se a extração do amido e este foi avaliado quanto a composição centesimal, propriedades de pasta, propriedades térmicas, teor de minerais (P, K, Ca e Mg), teor de amilose aparente, pH e acidez titulável. Na caracterização da coloração dos tubérculos a cultivar Beacon Chipper apresentou maior brilho e maior intensidade do componente de cor amarela (b* positivo), as cultivares BRS Ana e Pirassu apresentaram os maiores valores para o componente de cor vermelha (a* positivo). As cultivares BRS Ana e Harley Beckhell apresentaram o maior teor de matéria seca. O maior e menor rendimento de extração de amido foi obtido com a cultivar Harley Beckhell e Colorado, respectivamente. O amido extraído dos tubérculos apresentou alto grau de pureza e a cultivar Beacon Chipper apresentou o menor teor de amilose aparente. O teor de fósforo foi elevado para as cultivares Marcy e Harley Beckhell, já para as cultivares BRS Ana e Pirassu o teor desse mineral foi menor. Nas propriedades de pasta a cultivar Marcy apresentou valores elevados para viscosidade máxima, quebra de viscosidade e tendência a retrogradação, que são... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The starch market has been growing and improving in recent years, leading to a search for products with specific characteristics that meet the industrial requirements. This work aimed to evaluate the physical and chemical composition of potato tubers (Solanum tuberosum L.) and its industrial potential. Eight cultivars were evaluated: Snowden, Harley Beckhell, Marlen, Colorado, BRS Ana, Pirassu, Beacon Chipper and Marcy grown in Pouso Alegre, Minas Gerais state, in 2011. Tubers were characterized to the moisture, ash, protein, fiber, lipids, sugars, starch, pH, titratable acidity and color of the peel and pulp. After characterization of the tubers, held the extraction of starch and this was evaluated for proximate composition, pasting properties, thermal properties, mineral content (P, K, Ca and Mg), content of apparent amylose, pH and titratable acidity . In characterizing the color of the tubers to cultivar Beacon Chipper showed higher brightness and greater intensity of the yellow color component (b* positive), the cultivars BRS Ana and Pirassu showed the highest values for the red color component (a* positive). The cultivars BRS Ana and Harley Beckhell showed the highest dry matter content. The highest and lowest... (Complete abstract click electronic access below) / Mestre

Let G be a split semisimple algebraic group over a field k. Our main objects of interest are twisted forms of projective homogeneous G-varieties. These varieties have been important objects of research in algebraic geometry since the 1960's. The theory of Chow motives and their decompositions is a powerful tool for studying twisted forms of projective homogeneous varieties. Motivic decompositions were discussed in the works of Rost, Karpenko, Merkurjev, Chernousov, Calmes, Petrov, Semenov, Zainoulline, Gille and other researchers. The main goal of the present thesis is to connect motivic decompositions of twisted homogeneous varieties to decompositions of certain modules over Hecke-type algebras that allow purely combinatorial description. We work in a slightly more general situation than Chow motives, namely we consider the category of h-motives for an oriented cohomology theory h. Examples of h include Chow groups, Grothendieck K_0, algebraic cobordism of Levine-Morel, Morava K-theory and many other examples. For a group G there is the notion of a versal torsor such that any G-torsor over an infinite field can be obtained as a specialization of a versal torsor. We restrict our attention to the case of twisted homogeneous spaces of the form E/P where P is a special parabolic subgroup of G. The main result of this thesis states that there is a one-to-one correspondence between h-motivic decompositions of the variety E/P and direct sum decompositions of modules DFP* over the graded formal affine Demazure algebra DF. This algebra was defined by Hoffnung, Malagon-Lopez, Savage and Zainoulline combinatorially in terms of the character lattice, the Weyl group and the formal group law of the cohomology theory h. In the classical case h=CH the graded formal affine Demazure algebra DF coincides with the nil Hecke ring, introduced by Kostant and Kumar in 1986. So the Chow motivic decompositions of versal homogeneous spaces correspond to decompositions of certain modules over the nil Hecke ring. As an application, we give a purely combinatorial proof of the indecomposability of the Chow motive of generic Severi-Brauer varieties and the versal twisted form of HSpin8/P1.

Nilpotent Hessenberg varieties are a family of subvarieties of the flag variety, which include the Springer varieties, the Peterson variety, and the whole flag variety. In this thesis I give a geometric proof that the cohomology of the flag variety surjects onto the cohomology of the Peterson variety; I provide a combinatorial criterion for determing the singular loci of a large family of regular nilpotent Hessenberg varieties; and I describe the equivariant cohomology of any regular nilpotent Hessenberg variety whose cohomology is generated by its degree two classes.

No description available.

Okra (Abelmoschus esculentus) is a traditional crop commercially cultivated in many parts of the world. Fresh okra has a high nutritional value and grows very quickly with high temperatures, which lends its production to more tropical areas. This study was implemented to evaluate different varieties of okra and determine the optimum density for production in Massachusetts. Two experiments were carried out between May and September of 2009 and 2010 at the UMass Research Farm in South Deerfield, MA. For the variety trial in 2009: Annie Oakley, Baby Bubba, Cajun Delight, Chifre de Veado, Clemson Spineless, Millionaire, North & South and Santa Cruz 47. The immature pods were harvested when reached 70 mm in length (size desired by the market in the USA) and in another plot for Chifre de Veado and Santa Cruz 47 the pods were harvested when reached 100 mm (market in Brazil). The density trial was set in a randomized complete block design with seven different plant spacings (7.5, 15.0, 22.5, 30.0, 38.5, 45.0 and 52.5 cm) in double row of plants of Cajun Delight. The pods were harvested three times a week, counted and weighted. Analyses of variance were performed by SAS, and means were compared using Duncan’s new multiple range test (P = 0.05) and orthogonal polynomial comparisons. In 2010, Santa Cruz 47 harvested based on Brazilian market size had the best performance over the season with the yield of 17.86 ton.ha-1 and similar statistic results comparing to North and South (15.99 ton.ha-1) and Annie Oakley (15.24 ton.ha-1). The differences among the plant spacings in 2010, were represented by a quadratic relationship, where the greater plant spacing for yield was ‘52.5 cm’ with the total yield of 14.91 ton.ha-1. Both trials in 2009 were negatively affected by the soil-borne fungus Verticillium spp., which, combined with the cold and wet weather, became very aggressive, especially in the end of the season. The results show that the varieties: North and South, Annie Oakley, Cajun Delight, Millionaire, Clemson Spineless, Santa Cruz 47 can be commercially grown in Massachusetts and the recommended plant spacing of okra is 52.5 cm.