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Made available in DSpace on 2014-10-09T12:24:39Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:05:02Z (GMT). No. of bitstreams: 1 00030.pdf: 1267034 bytes, checksum: 1e237f210ed3dfb273b208a1ff350b2b (MD5) / Dissertacao (Mestrado) / IPEN/D / Escola Politecnica, Universidade de Sao Paulo - POLI/USP

No description available.

A balanced nitrogen (N) cycle is paramount for the ecology and biogeochemistry of planet Earth. Human activities are now causing an imbalance in the N cycle, with several negative effects on the marine environment. However, our knowledge of the marine N cycle remains incomplete, especially with regards to the role of dissolved organic N (DON). Therefore, there is need to study the role of DON more extensively to aid in restoring balance to Earth's ecosystems and biogeochemical cycles. This project investigated DON dynamics and influence on phytoplankton in coastal and shelf seas (CSS) to the west of Britain where DON was understudied. First, selected methods for the measurement of N uptake rates, urea and dissolved free amino acid (DFAA) concentrations were reviewed and tested. Then, they were used to study the spatial and temporal DON dynamics in the shelf region to the west of Britain (Irish Sea and adjacent shelf), the in-situ seasonal DON dynamics and N uptake in relation to phytoplankton community composition and abundance in Loch Creran, and the influence of DON on the phytoplankton community composition and abundance in controlled nutrient uptake kinetics and growth experiments and ecosystem modelling. The main findings were: DON was important in the N dynamics of the Irish Sea and adjacent shelf waters; DON was correlated with changes in phytoplankton community composition in Loch Creran; its seasonal cycle suggested its importance as an N source for the development of the spring bloom; these ideas were further supported by controlled laboratory experiments and ecosystem modelling.

Anaerobic ammonium oxidation (anammox) is a pathway that has been known for almost 2 decades, but few studies have investigated its importance in natural groundwaters. This thesis investigated the presence of anammox cells and the groundwater geochemistry of 2 sites (Elmira and Putnam) in southwestern Ontario where groundwaters are contaminated with high levels of nitrate and ammonium. Fluorescence in situ hybridization (FISH) was used to quantify the relative abundance of anammox cells in these waters. Our results showed that anammox cells could be detected in many wells at both sites and that their relative abundance varied between 0.45 and 4.81 % at the Putnam site, whereas it ranged between 0.8 to 8.4 % at the Elmira site. These values are within the same range as those obtained for marine and freshwater environments where anammox cells have been detected. In addition, indirect observations point to the fact that N cycling at the 2 sites might be linked to Fe and Mn reduction, but additional experiments are needed. In summary, our results corroborate the findings of N-labeled microcosm experiments which demonstrated that anammox was an important pathway of N cycling in those groundwaters and molecular analyses that detected important anammox organisms at the same sites.

The controls over initiation of DNA synthesis, initiation of cell division, regulation of macronuclear DNA content, and the relationship between cell mass and growth rate were examined in cells growing under nutrient constraint, or in cells experiencing a change in growth conditions through nutritional enrichment (shift-up) or nutritional shift-down. Reduction in both cell mass and DNA content was achieved by growing Paramecium cells under nutritional limitation in the chemostat. Under the extreme condition in the chemostat, the normally balanced relationship between DNA content and cell mass (Berger, 1984 Kimball, 1967) is uncoupled. The DNA content in these cells is maintained at about 50 units, but cell mass can be as little as 24% of normal. The generation time in these slow growing cells was increased 4 to 5 times that of rapidly growing cells; the growth rate was also reduced by about the same proportion. Nutritional shift-up was done by transferring the chemostat cells to medium of excess food. Similarly, nutritional shift-down was performed by transferring cells either to the chemostat or to exhausted medium. The timing of DNA synthesis initiation is largely determined in the preceding cell cycle. Although growth rate (protein synthesis rate) responds quickly to the new conditions, the timing of DNA synthesis initiation is not readjusted immediately and reflects that of the parental cell cycle. The rate at which cells enter S phase however, is affected by a reduction in growth rate. The criteria for DNA synthesis initiation are not determined by cell mass per se. First, cell mass increases to about 180% of the initial G1 value at the time of DNA synthesis initiation following a nutritional shift-up. This value is much greater than that of well-fed controls (118%). However, the increase in cell mass up to the mean time of DNA synthesis initiation and cell division are not significantly different than that observed in well-fed cells. This suggests a mass-related control over initiation of DNA synthesis. Second, cells initiate DNA synthesis even when there is a net decrease in cell mass following nutritional shift-down. Thus, an increase in cell mass per se is not necessary for DNA synthesis initiation. Unlike initiation of DNA synthesis, the regulatory mechanisms determining the macronuclear DNA synthesized reflects solely the current nutrient conditions. Cells in chemostat culture normally maintain about half the normal amount of DNA (about 50 units). Following nutritional shift-up cells synthesize 100 units of DNA instead. Similarly cells synthesize only 50 units of DNA following nutritional shift-down. The amount of DNA synthesized, therefore, is related to the growth rate, and as discussed later, is also related to the commitment point to cell division. This study also reveals that the point of initiation of cell division is not time-dependent. It does not occur at a fixed duration following the previous fission or the initiation of DNA synthesis. The point of commitment to division occurs at about 95 minutes before fission regardless of growth rate. Analysis of the effects of macronuclear DNA synthesis inhibition in cc1 cells after the transition point for division indicate that cells synthesize 50 units of DNA before the point of commitment to division. This suggests that cells are committed to divide after synthesizing about 50 units of DNA. Following this point, rapidly growing cells will produce 50 units of DNA before fission; whereas slow growers will accumulate an amount proportional to their growth rate. There are reasons to believe that the threshold value of DNA for commitment to cell division may be 41 units instead of 50. / Science, Faculty of / Zoology, Department of / Graduate

This thesis is essentially a re-evaluation of two issues in the Poema de mio Cid that have largely "been ignored in the long-standing debate between the individualists and the traditionalists over the genesis of the poem. These are (i) the question of Castilian nationalism, and (ii) monastic influence on the epic. In the first issue, scholars and critics are generally in agreement that the PMC contains some very definite pro-Castilian and anti-Leonese sentiments, but the extent to which this political attitude is reflected in the work has yet to be determined. In the second issue, the theory that the epic in general had its origins in the monasteries situated along the pilgrim routes of Mediaeval Europe was first raised by the French scholar Joseph Bedier, but was refuted by the eminent Spanish academician Ramon Menendez Pidal. As such, to date, the only critic who has attempted to apply Bedier's theory to the PMC is P.E. Russell. In this thesis, these two issues are subjected to a close re-evaluation based upon the most recent findings "by the individualists who, since the death of Pidal and the publication of Colin Smith's edition of the poem, have revised many of the theories of the Spanish scholar. This study is divided into four chapters. In the first, the Spanish epic in general is examined briefly to determine its national^ istic and monastic content. Also included in this chapter is a relevant discussion of tomb-cults, relic-worship and pilgrimages during the Middle Ages. The second chapter focuses on the latest arguments presented by both the traditionalists and individualists on the problems of historicity, authorship and dating of the PMC. In the third chapter, the PMC is studied closely with a view to finding manifestations of Castilian nationalism in the poem's major characters, actions and themes. The final chapter deals with the issue of monastic influence on the PMC. Apart from the poem itself, the history of the monastery of San Pedro de Cardena and its relationship with the Cid in fact and fiction are examined. It will be seen from the last two chapters that the PMC contains more evidence of nationalistic fervour and monastic influence than is generally acknowledged. In other words, the poem exhibits some definite pro-Castilian and anti-Leonese sentiments. If we view the poem against the historical background of the period in which we believe it to have been written, the theory that the PMC was used for propaganda purposes becomes quite plausible. In the issue of monastic influence, again the possibility exists that the PMC was composed in San Pedro de Cardena. The evidence, not only in the poem itself, but also in the chronicles of Spain and the histories of the monastery all indicate that a strong Cid cult existed in the Cardena region after the death of the hero. It appears that the PMC was a part of this cult and may have been composed as the result of a crisis in the history of the monastery. / Arts, Faculty of / French, Hispanic, and Italian Studies, Department of / Graduate

No description available.

No description available.

The purpose of this investigation was an attempt to clarify the relatives taxonomic position of and to formulate some of the basic cyclic morphological and physiological processes occurring in an aquatic actinomycete possessing streptomycetal characteristics.