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Thèse (M.Sc.)--Université Laval, 2007. / Bibliogr.: f. 56-62. Publié aussi en version électronique dans la Collection Mémoires et thèses électroniques.

In order to reduce the stress concentration around a hole in a plate, new, “analogue” reinforcements instead of reinforcing rings were used in this investigation. In two of these specimens, reinforcements with different volume fractions were arranged to coincide with the stress trajectories for an infinite plate with a hole under uniaxial tension, Two other specimens contained straight rectangular-grid type reinforcements with different volume fractions. These 0.005 in. thick brass reinforcements were made by using a photofabrication method. Specimens were then prepared by sandwiching these reinforcements between two epoxy resin plates. Plane specimens, i.e., without reinforcement, were also made of the same epoxy resin for comparison. The stress concentrations at the edge of the hole under uniaxial tension were determined by photoelastic techniques. The measured stress concentration factors were compared with well known values for an infinite isotropic, homogeneous plate containing a hole. Results were also compared with published data on [90/0/90/0̅]_s 7-ply laminate composite plates, and on plates strengthened with reinforcing rings. A definite reduction in stress concentration was observed on specimens containing analogue reinforcement. / Master of Science

Three metabolism trials were conducted with wethers fed purified rations to study the effect of level of readily-available carbohydrates on cellulose digestibility. In the first experiment, two trials were conducted with fifteen wethers fed five rations. The basal ration contained 77.8% cellulose, 11.1% assay protein C-1, 7.2% minerals and 3.9% corn oil. Readily-available carbohydrates supplied by a 1:1 mixture of cerelose and starch replaced cellulose in the other rations to give levels of 2, 4, 6 and 8% readily-available carbohydrates. Level of readily-available carbohydrates in the ration failed to significantly affect digestibility of ration components and nitrogen balance. Cellulose digestibility tended to be higher for the 8% ration. Energy and dry matter digestibility tended to be higher for the supplemented rations. In experiment 2B, two metabolism trials were conducted with twelve wethers to study the effect of higher levels of readily-available carbohydrates on utilization of purified rations. The basal ration was of the same composition as that described above. Three additional rations contained 32%, 40% and 48% readily-available carbohydrates (levels were substituted for equal amounts of cellulose). Cellulose digestibility was 65.3% for the basal ration. Addition of 32, 40 and 48% readily-available carbohydrates significantly reduced cellulose digestibility. Increasing the level of readily-available carbohydrates from 32 to 40 and 48% reduced digestibility of cellulose (P < .05). Digestibility of total carbohydrates (cellulose and NFE) was 62.8%, 67.2%, 65.0% and 72.7% for the 0, 32, 40 and 48% rations, respectively. The difference between the 40% and 48% rations was significant. Nitrogen retention tended to increase in the supplemented rations, but the effect was not significant. Butyric acid content of the rumen fluid was higher in the supplemented rations. In the third experiment, fifteen wethers were fed three rations to determine the effect of level of readily-available carbohydrates on cellulose digestibility following preliminary periods of different lengths. The composition of the basal ration was the same as in experiments 1B and 2B. The other two rations contained 8% and 32% readily-available carbohydrates. There was a 10-day collection period following preliminary periods of 10, 20, 30, 40 and 50 days. There were no significant differences in ration digestibility or nitrogen utilization, regardless of the duration of the preliminary period. Regression analysis of data from four experiments involving 84 individual metabolism trials indicated that for each one percentage increase in readily-available carbohydrates in the ration cellulose digestion was significantly reduced 0.5 percentage units and nitrogen retention was not significantly altered. / Ph. D.

The Major Histocompatibility Complex (MHC) is a gene-dense region located on the short arm of chromosome 6 (6p21.31). This region contains the highly polymorphic HLA genes as well as many other genes with immunological and non-immunological function. The susceptibility genes of many human disorders have been mapped to genes within the MHC. However, the genes themselves and indeed the locations of the genes, for many of the disorders, remain a mystery. This is a result of the high degree of linkage disequilibrium (LD) that exists between loci within the MHC. The high LD is explained by the genomic structure of the MHC. The MHC contains several blocks of DNA within which recombination is extremely rare, whereas the boundaries of the blocks are defined as "hotspots" of recombination. Most disease association studies have used the highly polymorphic HLA class I and class II genes which are separated by an, as yet, undefined number of blocks and several hundred kilobases of DNA. The MHC gamma block resides in the central region of the MHC between the blocks that contain the HLA class I and class It genes. As such, typing for polymorphisms in the gamma block is critical for MHC disease gene mapping studies. The gamma block contains approximately 20 known genes including the complement C4 genes. The gamma block can contain between I and 3 tandemly arranged C4 genes. The C4 protein exists as either the C4A or C413 isotype and is polymorphic with up to 40 allotypes being reported. However, the majority of Caucasian haplotypes can be explained by the common C4A3 / C4B1 or C4AQ0 / C4B1 complotypes with the remaining haplotypes explained by just a few other complotypes. For this reason, and because C4 allotyping is a technically difficult procedure, C4 allotyping is rarely used in MHC disease association studies. / The molecular heterogeneity of human C4 genes has not been extensively studied. However, the C4A3 and C4131 genes have been completely sequenced and are >99% identical at the DNA level across 41 exons and 15 kb of DNA. This high degree of homology and the presence of up to 3 C4 genes on any MHC haplotype makes PCR separation of the C4 genes difficult for subsequent genetic studies. The aim of this study was to extensively characterise the molecular heterogeneity of the human C4 genes and thereby: 1. determine the extent of human C4 gene polymorphism 2. confirm previous studies which have defined isotype specific sequences 3. characterise the C4 protein polymorphisms at the DNA level 4. determine if common C4 allotypes can be subtyped on a molecular basis 5. identify C4 gene polymorphisms that can be used as targets for DNA based typing methods 6. apply DNA based C4 typing methods in MHC disease association studies 7. provide insights into MHC haplotype evolution. In contrast to separating the C4 genes, a novel approach whereby the C4 genes were amplified and sequenced simultaneously was applied in this study. The DNA from 24 homozygous workshop cell lines, representing different ancestral haplotypes (AHs), was studied. Comparison of the C4 genes from different AHs revealed that the C4d region of the C4 a-chain is most polymorphic, but that polymorphic amino acid residues are also present in other regions of C4. The highest degree of polymorphisms was seen in the introns. In addition, the presence of the isotype specific sequences in exon 26 was confirmed and primers were designed to specifically amplify, and thereby separate, the C4A and C4B genes. / Comparison of the C4 gene sequences representing the same C4 allotype revealed that most C4 allotypes are heterogeneous and may be split into several subtypes. The polymorphisms observed at the sequence level did not correlate with C4 allotypes defined by electrophoretic mobility. However, it could be shown that the differences in electrophoretic mobility of the C4 allotypes are due to cumulative charge differences. Seven polymorphic amino acids were found to account for the different migration rates of the C4 allotypes analysed in this study. In addition, a number of haplospecific single nucleotide polymorphisms (SNPs) were identified within the C4 genes. Haplospecific SNPs are informative markers enabling the genetic mapping of recombinant AHs, an approach which can be used to identify disease susceptibility genes. Haplospecific SNPs located in the C4 gene region are important markers as they represent a separate block of the MIIC (i.e. the gamma block). The frequency of one such SNP marker has been shown for a diabetes patient group and a control population. Although further studies are required to elucidate the role of the gamma block genes in susceptibility to diabetes, this study demonstrates a possible approach for the mapping of MHC disease susceptibility genes, which can also be applied in studies of other MHC associated diseases. To conclude, the present study adds to our knowledge of the C4 gene polymorphism, provides insights into MHC and C4 gene evolution and enables future studies to examine the significance of the C4 genes and other gamma block genes in susceptibility to MHC associated diseases.

The planting of eucalyptus is a common practice in areas previously used for extensive livestock farming in the southern half of Rio Grande do Sul (RS), but such cultivation raises many questions about its influence on the dynamics of soil organic matter (SOM). An evaluation was made possible due to the photosynthetic cycle of eucalyptus, which as in other tree species are C3 and in most grasses is C4. C4 cycle plants use 13C (carbon heavy isotope) in photosynthesis, while plants with C3 cycle make distinction of 13C of the air, generating MOS with different isotopic abundances. This study evaluated the overall carbon content and the isotopic abundance of 13C in soil profiles under eucalyptus plantation of different ages (2, 10 and 21), in a natural regeneration area and natural grass field as well as estimated the contribution to the conversion of SOM according to each vegetation. The initial management of all sampled areas was natural pasture. In profile the following layers were evaluated: 0-5, 5-10, 10-20, 20-30, 30-40, 40-50, 50-70 and 70-90 cm. The 13C isotopic abundance of soil and plant tissue was performed by mass spectrometry. After two years of planting eucalyptus, the surface layer showed an increase of carbon relative to its subsurface layer and the beginning of pasture carbon conversion process possibly has begun to occur in this surface layer (0-5 cm). In 10 years of planting it occurred a decrease of SOM between the layers until the initial 20 cm and the MOS conversion process between pasture and eucalyptus shows up to this depth. After 21 years of planting, the whole profile has undergone change by planting eucalyptus trees, taking in its surface layer the higher carbon value from the eucalyptus cultivation (90.4%). In the area where there was a natural regeneration, the higher carbon content in the surface layer was observed (3.53%) and this may be due to the greater diversity of the chemical composition of the deposited material. In this area, there are indications that the MOS cycling process has reached all the profile layers through the waste contributed by the native tree species. / O plantio de eucaliptos é uma prática comum em áreas antes utilizadas para a pecuária extensiva na metade sul do Rio Grande do Sul (RS), porém tal cultivo levanta muitos questionamentos acerca de influência sobre a dinâmica da matéria orgânica do solo (MOS). Uma avaliação se tornou possível graças ao ciclo fotossintético do eucalipto, que assim como nas demais espécies arbóreas é C3 e na maioria das gramíneas é C4. Plantas de ciclo C4 utilizam o 13C (isótopo pesado do carbono) no processo de fotossíntese, enquanto que plantas com ciclo C3 relativamente distinguem o 13C do ar, gerando MOS com diferentes abundâncias isotópicas. O presente estudo avaliou os teores de C total e a abundância isotópica de 13C em perfis do solo sob plantio de eucaliptos localizados na depressão central do RS de diferentes idades (2, 10 e 21 anos), em uma área de regeneração natural e em campo de pastagem natural, bem como estimou a contribuição na conversão da MOS em função de cada vegetação. O manejo inicial de todas as áreas amostradas era de pastagem natural. No perfil foram avaliadas as seguintes camadas: 0-5, 5-10, 10-20, 20-30, 30-40, 40-50, 50-70 e 70-90 cm. A análise da abundância isotópica de 13C no solo e dos tecidos vegetais foi feita por espectrometria de massas. Após 2 anos do plantio de eucaliptos, a camada superficial apresentou aumento de carbono em relação a sua camada subsuperficial e o início do processo de conversão do carbono da pastagem possivelmente tenha começado a ocorrer nesta camada superficial (0-5 cm). No plantio de 10 anos ocorreu uma diminuição da MOS entre as camadas até os 20 cm iniciais e o processo de conversão da MOS entre pastagem e eucalipto mostra-se até esta profundidade. Após 21 anos de plantio, todo o perfil já sofreu alteração pelo plantio de eucaliptos, tendo em sua camada superficial o maior valor de carbono proveniente do cultivo de eucaliptos (90,4%). Na área em que ocorreu regeneração natural, o maior teor de carbono na camada superficial foi observado (3,53%) e isto pode ser decorrente da maior diversidade da composição química do material depositado. Nesta área, existem indicativos de que o processo da ciclagem da MOS também tenha atingido todas as camadas do perfil através dos resíduos aportados pelas espécies arbóreas nativas.

Bienertia sinuspersici is one of three terrestrial plants identified to perform C4 photosynthesis in a single chlorenchyma cell by compartmentation of organelles and photosynthetic enzymes. This thesis describes a study on the distribution of photosynthetic proteins and their corresponding transcripts in an attempt to understand the regulatory mechanisms underlying their differential accumulation in two types of chloroplast. The patterns of photosynthetic enzymes and transcripts accumulation in developing leaves were examined by using immunolocalization and in situ hybridization. The polypeptides of Rubisco large subunit (RbcL) and pyruvate Pi dikinase (PPDK) accumulate equally in all chloroplasts before the formation of two intracellular cytoplasmic compartments: the central (CCC) and peripheral (PCC) cytoplasmic compartment. The differential accumulation of these enzymes is not completed until the mature stage, indicating that the transition from C3 to C4 photosynthesis occurs at the very late stage of leaf development. In mature chlorenchyma cells, RbcL accumulates 20-fold more in the CCC than in the PCC while PPDK demonstrates a concentration gradient that is lowest in chloroplasts in the center of the CCC and highest in the PCC chloroplasts. The pattern of rbcL transcript accumulation follows that of its polypeptides in developing leaves, suggesting the expression of this gene is controlled at the transcriptional and/or mRNA stability level. The quantitative real-time PCR results of rbcL transcripts from isolated chloroplasts of each compartment further supported this observation. Bioinformatics tools were used to predict possible structual motifs on rbcL mRNA as an attempt to speculate on their role in its distribution and identify the presence of secondary structures in the 5??? untranslated region (UTR) that may function in the regulation of gene expression. Detailed examination of the ultrastructure of the unique intracellular organization in the single-cell C4 system showed various vesicles in close proximity to chloroplasts in both compartments in mature chlorenchyma cells of B. sinuspersici under H2O2 treatments. To further understand the biogenesis of these vesicles, imunolocalization and transient expression of green fluorescent protein (GFP) experiments were performed. These studies identified stroma-filled tubules (stromules) as the structure that participates in the formation of sequestering vesicles (autophagosomes) containing cytosol and organelles. Fluorescent microscopic analyses using autophagosome-specific and autophagic vacuole markers only showed partial overlapping of two fluorescent signals. These results suggest that the formation of autophagosome and autophagic vacuole occur independently. The contribution of stromules to autophagosome formation and the involvement of chloroplastic envelopes in this process provide another level of regulation in the compartmentation of photosynthetic enzymes in single-cell C4 system. Collectively, the findings in this thesis enhance our overall understanding on the development and function of single-cell C4 photosynthesis.

Techn. Hochsch., Diss., 2005--Aachen.

The present thesis aims to determine the genre, the compositional structure and the hermeneutics found in the letter of James. It is divided into five parts. Part one first examines the various proposals for the genre of James. James is found to be a "counter cultural" wisdom instruction challenging the hearers' worldview and to reorient them to the values acceptable to God. Part two examines the previous attempts to uncover the structure of James. Here I adopt discourse analysis, paying special attention to the formal features of wisdom instruction. Part three explores the importance of law and wisdom to the understanding of the hermeneutics of James. James is using the love command as hermeneutical principle in understanding the Torah and is comparable to that in Matthew. Wisdom, a gift from God, is involved in the "how" of the important hermeneutical task of applying and keeping the law in one's particular situation. It also manifests itself in one's keeping of the law. Part four investigates the meaning of the call to perfection and the predicament of doubleness in relation to law and wisdom in the context of early Jewish and Christian thought. By adhering to the implanted word, doing what this word/law requires, Christians will be on the way to perfection and to life/salvation. Part five looks at the importance of eschatology which provides the underlying framework for the hermeneutics found in James. In conclusion, James is seen as a wisdom instruction which adapts the teaching of Jesus, making it relevant to his readers. Our author exhorts his readers, the messianically renewed people of God, redeemed by the word of truth, to move along the way of perfection in obedience to the law, waiting for the coming of the Lord at the end of this age.