Thesis (M.Sc.)--Memorial University of Newfoundland, 2002. / Bibliography: leaves 47-53.

Thèse (M.Ress.Renouv.) -- Université du Québec à Chicoutimi, 2002. / Bibliogr.: f. 89-96. Document électronique également accessible en format PDF. CaQCU

Thèse (M.Ress.Revouv.) -- Université du Québec à Chicoutimi, 2005. / Bibliogr.: f. 38-45. Document électronique également accessible en format PDF. CaQCU

Thesis (M.Sc.)--Memorial University of Newfoundland, 2002. / Includes bibliographical references.

Made available in DSpace on 2015-03-26T14:01:03Z (GMT). No. of bitstreams: 1 texto completo.pdf: 4064077 bytes, checksum: 9b21ed6ac17078998aca806bb631cda3 (MD5) Previous issue date: 2010-06-14 / Acidentes com Bicas de Smelt são reportados pelo Black Liquor Recovery Boiler Advisory Committee, BLRBAC, e constituem uma preocupação real de segurança sob o ponto de vista operacional. Tipicamente o smelt escorre através de bicas refrigeradas a água da fornalha para o tanque dissolvedor e uma falha pode levar a explosões pelo contato água-smelt. Este trabalho estuda um caso real onde condições severas de corrosão culminaram com a falha em serviço de uma de seis bicas em uma caldeira de recuperação na CENIBRA. A falha resultou em grande volume de água de resfriamento entrando na caldeira e em contato com smelt ao redor da abertura da bica, mas felizmente não ocorreram explosões água-smelt. Uma elaborada investigação foi conduzida para se determinar as causas da falha da bica. Conclui-se que a falha foi causada por fluxo insuficiente de água de resfriamento para a bica de smelt, que, por sua vez, foi causada por uma seqüência de eventos que ocorreram após uma falha geral no sistema de geração de energia elétrica da fábrica. O estudo do evento levou ao desenvolvimento e implantação de procedimentos operacionais e de manutenção que tem por objetivo assegurar fluxo de água de resfriamento adequado para as bicas de smelt para prevenção de falhas recorrentes. / Smelt Spout accidents are reported by Black Liquor Recovery Boiler Advisory Committee, BLRBAC, and constitute a real safety concern from the operational point of view. Typically smelt flows through water cooled spouts from furnace to the smelt dissolving tank and a failure can lead to smelt-water contact explosions. This work studies a real case where severe corrosion led to an in-service failure of one of the six spouts on a recovery boiler at Cenibra. The failure resulted in a large amount of cooling water entering the boiler and contacting smelt around the spout opening, but fortunately no smelt-water explosion occurred. An extensive investigation was conducted to determine the causes of the spout failure. It was concluded that the failure was caused by insufficient cooling water flow to the smelt spout, which, in turn, was caused by a sequence of events that occurred after a general black out of an electrical energy system at the mill. The experience has led to the development and placement of operating and maintenance procedures that ensure adequate cooling water flow to smelt spouts to prevent future failures.

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The spatial scale at which populations are genetically structured is of immense interest for the understanding of a species’ ecology and evolutionary biology. This can have important implications for management of resources as well as predicting responses to future change. Rainbow smelt (Osmerus mordax) is an anadromous species with a relatively short freshwater residence time compared to other species with similar life-history strategies. Therefore, while they offer the opportunity to sample distinct spawning aggregations, they also offer an insight into the relative roles of contemporary and historical factors shaping connectivity among marine populations, an area of great interest, and for which further understanding is required. With the use of both mitochondrial DNA and nuclear microsatellite markers, I explored the historical and contemporary factors influencing population structure in smelt. While previous phylogeographic work on this species has resolved two mtDNA lineages dating back to previous glacial episodes, I document the discovery of a zone of contact between these lineages in Newfoundland. This is in addition to the established contact zone in the St. Lawrence estuary, and results in a longitudinal distribution of the races with one race predominating on opposite ends of the species distribution, while the other race is geographically intermediate. Patterns of nuclear genetic variation largely mirror the phylogeographic signals in Newfoundland and suggest a more recent colonization of the Avalon Peninsula as well as implicating a remnant historical signal of colonization of the west coast of Newfoundland from the mainland. In addition, contrasting patterns of genetic diversity and levels of differentiation were apparent between the mainland and Newfoundland and suggest differing scales of dispersal within this species. While the population structure within Newfoundland is most consistent with dispersal restricted to within bays, larger scale biogeographic regions were identified in the mainland range, suggesting dispersal is more common and widespread. In addition, sampling of different run times (i.e. ‘early’ vs. ‘late’) demonstrated the potential for isolation by time when spawning events are separated by a break in activity. Overall, these results shed light into the possible roles of both historical and contemporary factors shaping the dynamics and connectivity among populations.

Thèse (M.Ress.Renouv.) -- Université du Québec à Chicoutimi, 2005. / Bibliogr.: f. 79-85. Document électronique également accessible en format PDF. CaQCU

Biogeographers have long searched for common processes responsible for driving diversification in the Holarctic region. Although terrestrial flora and fauna have been well studied, much of the marine biogeographic work addresses patterns and processes occurring over a relatively recent timescale. A prerequisite to comparative biogeographic analysis requires well-resolved phylogenies of similarly distributed taxa that diverged over a similar timeframe. The overall aim of my Ph.D. thesis was to address fundamental questions in the systematics and biogeography of a family of Holarctic fish (Osmeridae) and place these results in a broad comparative biogeographic framework. With eight conflicting morphological hypotheses, the northern hemisphere smelts have long been the subjects of systematic disagreement. In addition to the uncertainty in the interrelationships within this family, the relationship of the Osmeridae to several other families remains unclear. Using DNA sequence data from three mitochondrial and three nuclear genes from multiple individuals per species, I reconstructed the phylogenetic relationships among the 6 genera and 15 osmerid species. Phylogenetic reconstruction and divergence dating yielded a well-resolved phylogeny of the osmerid genera and revealed several interesting evolutionary patterns within the family: (1) Hypomesus chishimaensis and H. nipponensis individuals are not reciprocally monophyletic, suggesting that they are conspecific and H. chishimaensis is a recently evolved freshwater ecotype that invaded the Kuril Islands following the last glaciation, (2) The trans-Pacific sister relationships in Hypomesus based on lateral line scale counts are not supported, implying that this phenotype evolved in parallel on each side of the North Pacific Ocean, (3) The Plecoglossidae are the Osmeridae sister group, (4) Over half of the characters from previous studies show evidence of parallel evolution; however, 27 traits reflect ancestral relationships, (5) Multiple divergences within the Osmeridae date to both the mid-Miocene cooling period and the Pliocene Bering Seaway opening, suggesting these events were important in the evolution of these fishes, and (6) Divergences in many marine taxa for which dated phylogenies are available are also correlated with these time periods. Future research should target additional Holarctic marine taxa for further comparative analysis.

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