O teorema de Hilbert-Burch fornece uma boa descrição de variedades determinantais de codi- mensão dois e de suas deformações em termos da matriz de representação. Neste trabalho, usamos esta correspondência para estudar propriedades de tais variedades usando métodos da teoria de singularidades. Na primeira parte da tese, estabelecemos a teoria de singularidades de matrizes n X p, generalizando os resultados obtidos por J. W. Bruce and F. Tari em [5], para ma- trizes quadradas, e por A. Frühbis-Krüger em [16], para matrizes n X (n+1). Na segunda parte, nos concentramos em variedades determinantais de codimensão 2, com singularidade isolada na origem. Para estas variedades, podemos mostrar a existência e a unicidade de suavizações, o que possibilita definir seu número de Milnor como o número de Betti na dimensão média de sua fibra genérica. Para superfícies em \'C POT. 4\', obtemos uma fórmula Lê-Greuel expressando o número de Milnor da superfície em termos da segunda multiplicidade polar e do número de Milnor de uma seção genérica / The theorem of Hilbert- Burch provides a good description of codimension two determinantal varieties and their deformations in terms of their presentation matrices. In this work we use this correspondence to study properties of determinantal varieties, based on methods of singularity theory of their presentation matrices. In the first part of the thesis we establish the theory of singularities for n X p matrices extending previous results of J. W. Bruce and F. Tari in [5], for classes of square matrices, and A. Frühbis-Krüger for n X (n+1) matrices in [16]. In the second part we concentrate on codimension two determinantal varieties with isolated singularities. These singularities admit a unique smoothing, thus we can define their Milnor number as the middle Betti number of their generic fiber. For surfaces in \'C POT. 4\' , we obtain a Lê-Greuel formula expressing the Milnor number of the surface in terms of the second polar multiplicity and the Milnor number of the generic section

Bast fibrous renewable materials, as commercial crops for the manufacture of textile based and other products, have been used for thousands of years to satisfy certain human needs, such as for shelter, clothing, source of energy and tools, and to sustain the livelihood of many communities in countries, such as in Asia, Europe and Africa. Concern for the environment has led to a number of global initiatives that favour the use of natural fibres. It is forecast that the global fibre demand by 2050 will be 130 million tonnes, which the cotton and synthetic fibre production will not be able to meet. Other than the environmental concerns, the renewed global interest in natural fibres, such as flax and hemp, forms part of a strategy to satisfy the fibre demand. South Africa, notwithstanding the fact that the flax and hemp industries have long been established for thousands of years in Europe, Asia and Egypt (Africa), has no history of the breeding, growing, processing and production of these cash crops. The renewed global interest in these crops has also stimulated interest from South Africa with respect to the development of a flax and hemp fibre industry so as to address some of the socio-economic challenges confronting the country today in its attempts to bring about real development in the rural areas through the cultivation and complete beneficiation of these fibre crops. In this regard, the relevant stakeholders, namely government, research councils, tertiary education institutions, farmers and communities worked together to investigate whether South Africa has the agronomic and climatic conditions, technical expertise as well as the necessary processing and production infrastructure to support the development of a local flax and hemp agro-industry. The purpose of this study was firstly to evaluate the performance of EU flax and hemp cultivars grown under different agronomic conditions in South Africa, and their effect on straw biomass yield, fibre yield and total fibre yield per hectare as well as associated fibre properties, and secondly to undertake mechanical fibre modification trials aimed at producing flax and hemp fibres with fibre diameters close to those of cotton. The minimum fibre diameter targeted being 20μm. In accordance with the project objectives and work plan, selected dew retted flax and hemp straw samples from the various planting sites selected by the Agriculture Research Council – Institute for Industrial Crops, representing all the agronomic conditions under investigation, were taken to the CSIR for fibre extraction and testing. A relatively inexpensive and easy to operate Russian designed and manufactured machine, the CMT-200M breaker-cum-scutcher, was used for fibre extraction and the resultant extracted fibre bundles were further refined, using a steel comb, to obtain optimal fibre separation before their physical and chemical properties were evaluated. Results obtained in this research study proved that the climatic and agronomic conditions in South Africa were suitable for the cultivation of flax and hemp, notwithstanding the fact that the fibre yields achieved for hemp were lower than the minimum criteria of 23 percent, and that for flax only just exceeded the 25 percent minimum. The lack of local technical expertise on the growing and retting of flax and hemp, contributed to the low fibre yields. The planting parameters which were found to produce good results for the cultivation of hemp were the October planting date, using a row spacing of between 12.5 to 25 cm, with a seeding density of between 80 – 100kg, and the application of 50 – 100kg nitrogen fertiliser. The use of extra artificial lighting and herbicide treatment did not appear to beneficially improve the hemp fibre yields. Similar considerations for flax cultivation in the Southern Cape region, particularly Oudtshoorn and Outeniqua, indicated that May to July planting dates, using inter-row spacing of 25cm and sowing density of 63kg seed.haˉ¹, produced a fibre yield and total fibre yield per hectare above the minimum values of 25 percent and 0,8 tonnes per hectare, respectively, quoted in the literature.

Many English teachers see British English as the standard variety and teach this variety in the classroom. Their students are, however, also exposed to a great deal of American English in today’s media. As a result, there are a lot of students who use a mixture of these varieties because of the double input, both from media and from the teachers in school. In this paper, I interviewed teachers from Swedish secondary and upper secondary schools to find out what their attitudes towards British and American English were and whether these attitudes were reflected in their teaching. I also examined whether the teachers actually spoke the variety of English they thought they did as well as what their views were on students using a mixture of varieties. The focus of this essay will be on American English and British English.

Exploring the construct of social-responsibility orientation across three Asian and two Western societies (Germany, Hong Kong, Japan, South Korea, and the United States), we show evidence that top-level executives in these societies hold fundamentally different beliefs about their responsibilities toward different stakeholders, with concomitant implications for their understanding and enactment of responsible leadership. We further find that these variations are more closely aligned with institutional factors than with cultural variables, suggesting a need to clarify the connection between culture and institutions on the one hand and culture and social-responsibility orientations on the other. (authors' abstract)

Photocopy of typescript.

Consider a semisimple linear algebraic group G over an arbitrary field F, and a projective homogeneous G-variety X. The geometry of such varieties has been a consistently active subject of research in algebraic geometry for decades, with significant contributions made by Grothendieck, Demazure, Tits, Panin, and Merkurjev, among others. An effective tool for the classification of these varieties is the notion of a cohomological (or alternatively, a motivic) invariant. Two such invariants are the set of Tits algebras of G defined by J. Tits, and the J-invariant of G defined by Petrov, Semenov, and Zainoulline. Quéguiner-Mathieu, Semenov and Zainoulline discovered a connection between these invariants, which they developed through use of the second Chern class map. The first goal of the present thesis is to extend this connection through the use of higher Chern class maps. Our main technical tool is the Steinberg basis, which provides explicit generators for the γ-filtration on the Grothendieck group K_0(X) in terms of characteristic classes of line bundles over X. As an application, we establish a connection between the J-invariant and the Tits algebras of a group G of inner type E6. The second goal of this thesis is to relate the indices of the Tits algebras of G to nontrivial torsion elements in the γ-filtration on K_0(X). While the Steinberg basis provides an explicit set of generators of the γ-filtration, the relations are not easily computed. A tool introduced by Zainoulline called the twisted γ-filtration acts as a surjective image of the γ-filtration, with explicit sets of both generators and relations. We use this tool to construct torsion elements in the degree 2 component of the γ-filtration for groups of inner type D2n. Such a group corresponds to an algebra A endowed with an orthogonal involution having trivial discriminant. In the trialitarian case (i.e. type D4), we construct a specific element in the γ-filtration which detects splitting of the associated Tits algebras. We then relate the non-triviality of this element to other properties of the trialitarian triple such as decomposability and hyperbolicity.

An objective analytical method was developed to characterize the taste profiles of five cheese varieties. Nonvolatile water extracts of Cheddar, Edam, Gouda, Swiss, and Parmesan cheeses were analyzed by high performance liquid chromatography (HPLC) with a reversed phase column. The HPLC operating conditions were determined with Mapping Super-Simplex followed by Centroid Mapping Optimization. A ternary gradient elution system was used with an Adsorbosphere C8 column to resolve a maximum number of components. The optimum solvent volume ratio was 96.8 : 1.2 : 2.0 for trifluoroacetic acid (0.1%), acetonitrile, and methanol, with a flow rate of 1.0 mL/min. Over 50.3 min this ratio was changed to 56.3 : 30.3 : 13.4. Multivariate statistical analyses including principal component and discriminant analyses were applied to 55 peak areas from 106 cheese chromatograms. Principal component analysis reduced the dimensionality of the "data from 55 to 17 principal components, which are-combinations of the original variables, with a 26% loss of explained sample variation. Discriminant analysis on data from a single HPLC column was able to correctly classify cheeses by variety at a greater than 90% success rate. This grouping rate dropped to 64% when data from all four HPLC columns was combined, implicating large between column variations. A semi-trained sensory panel correctly classified cheeses by variety at a 63% rate. This objective method provides a lasting fingerprint of cheese products. / Land and Food Systems, Faculty of / Graduate

No description available.

No description available.

Currently, livestock production in the Andean highlands of Bolivia is done with low food efficiency due to the free range grazing system. This in turn leads to nutritional deficiencies. Therefore, it is necessary to substitute these grass species for others that fulfill nutritional requirements. Our main objective was to determine the species of grass with the best nutritional quality. Of the 12 species, only 11 were analyzed because the species Didtichlis stricta did not germinate. Five monthly samples were taken after the cut (ddc) at the following intervals: 50, 81, 112, 141, and 176 days. These samples were analyzed in the Laboratory of Animal Nutrition via the Weende method. After analyzing the results statistically, it was determined that Agrophyrum elongatum and Festuca aranduniceae were the species that had the highest dry matter yields (9.74 and 8.78 t/ha-1 respectively). In addition, they had higher content of ash, fats, protein, fiber carbohydrates, total digestible nutrients, and digestible energy than the other species also considered as forage with good nutritional quality. We also found that dry matter yield was highest at 209 and 193 days after the cut (ddc).