Universiẗat, Diss., 2003--Würzburg.

Master of Science

The late Pleistocene snake fossils from Sawmill Sink (Abaco, The Bahamas) represent five taxa: blind or thread snake (Scolecophidia indet.: either Leptotyphlopidae or Typhlopidae); Abaco boa (Boidae: Chilabothrus cf. exsul); rat snake (Colubridae: Pantherophis sp.); water snake (Natricidae: Nerodia sp.); and Cuban racer (Dipsadidae: Cubophis cf. vudii). Scolecophidia, Chilabothrus exsul, and Cubophis vudii still exist on Abaco and have been previously recovered in fossil deposits in the West Indies. In contrast, no forms of Pantherophis or Nerodia have been reported as fossils anywhere in the West Indies until now. This is the first evidence of any indigenous species of Pantherophis (living or extinct) in the Caribbean, whereas the only other indigenous Nerodia in the West Indies is the extant N. clarkii along the northern coast of Cuba. In being present on Abaco in late Pleistocene but not Holocene contexts, Pantherophis sp. and Nerodia sp. resemble 17 species that apparently did not survive the dramatic changes in climate, habitat, and land area associated with the Pleistocene–Holocene Transition in The Bahamas. It is likely that Pleistocene fossils of both Pantherophis and Nerodia will be found eventually on other Bahamian islands. With the discovery of these two snakes, the vertebrate fauna of Sawmill Sink now stands at 97 species, by far the richest in the West Indies.

A minute change in human body temperature can get one collapsed permanently. If this is the case with human body, one might wonder what would be the case with Earth. The result is the greenhouse. The main function of the greenhouse gases (GHG’s) is to tap energy from the sun and prevent the heat energy escaping to space, thus sustaining life on earth. Because of increased human activity, industrialization, and deforestation, the concentration of the GHG’s in the atmosphere has increased, resulting in a temperature rise. Considering the effects of temperature rise, caused by the GHG’s, one should know the ways to minimize them. In order to do this, an estimation of the amount of GHG’s is important. The CASA model is one such model that estimate the GHG’s and also the amount of carbon in the atmosphere by estimating the Net Ecosystem Productivity (NEP) and Net Primary Productivity (NPP).

<p> The thesis contains an experimental verification of a paper by D. G. Huber dealing with a solution to the problem of the irrotational motion of two fluid strata towards a line sink. Friction was assumed negligible in the theoretical analysis and, as a result, the experimental values deviated somewhat from the theoretical expectations. The largest deviation occurred at the point of incipient drawdown where the theoretical and experimental values of the Froude number differed by 48%. The trends obtained in the experiment verify the theoretical solution. The effect of viscosity at the point of incipient drawdown for two different interface height to width ratios was determined.</p> <p> The work of Harleman et al. in submerged sluice control was extended and showed that the Froude number of the lower layer at the point of incipient drawdown with high rates of flow was much larger than expected. The reason for the change was explained using the Khafagi-Hammad relationships.</p> / Thesis / Master of Engineering (MEngr)

No description available.

Rises in anthropogenic CO2 emissions are now widely acknowledged to be responsible for changes in the global climate, with potentially disastrous consequences if these rises continue unchecked. Although knowledge of ecosystem responses to climate change has improved, there are still large underlying uncertainties regarding their response to warming. Of all the ecosystems with the potential to mitigate rises in CO2, forests are arguably the most important because of their huge land area and store of carbon. A large proportion of the carbon stored in forests is found in the soil, and it is the response of this soil carbon to temperature that is the main determinant of a forest’s ability to act as a carbon sink, or indeed source. Understanding the response of soil carbon flux to temperature, as well as the contribution of soil carbon flux to the carbon balance of forests as a whole is crucial in helping to improve modelling approaches. In this thesis I first examined the temperature response of old and new soil organic carbon from a Sitka spruce plantation under controlled laboratory conditions. Both the old and new soil organic carbon showed similar temperature sensitivities after prolonged incubation at 20 °C, thus implying a similar response to increasing temperatures. Using a variety of different methods (root intensity, meshing and stable isotope analysis) I then studied the responses under field conditions. These methods showed that autotrophic respiration was responsible for up to 50 % of total soil respiration, and was more sensitive to temperature than heterotrophic respiration. Finally, I compared the contributions and determinants (particularly temperature and moisture) of soil respiration fluxes to ecosystem fluxes at a temperate (Sitka spruce) and Mediterranean (Maritime pine) forest. Temperature was found to be the dominant driver of soil respiration fluxes at the temperature forest, whilst soil respiration was limited by moisture at the Mediterranean forest. Statistically significant relationships between net ecosystem productivity and soil respiration (and the stable isotope signature of soil respiration) were found at both forests, indicating a close coupling between above-ground processes and soil respiration.

Strawberry production in the United States is almost entirely done in open-fields. Recently, interest in off-season strawberry production using controlled environment (CE) systems such as greenhouses and soilless cultivation has increased in the US. However, strawberry production in greenhouses is relatively new in North America and available information about greenhouse strawberry production is limited. Plant physiological responses to the environment must be well understood to maximize production using CE systems. In the present research, photoperiodic and photosynthetic responses of strawberry plants in greenhouse were studied. To evaluate photoperiodic response eight cultivars of strawberry widely cultivated in North America were subjected to varied photoperiods under an average daily temperature of 17 °C. Short-day (SD) cultivars included 'Radiance', 'F-127', 'Shuksan' and 'Chandler', and day-neutral/ever-bearing (DN/EB) cultivars included 'Albion', 'Portola', 'Monterey' and 'San Andreas'. SD cultivars were subjected to treatments of 11-h, 12-h, 13-h and 14-h photoperiod for 8 weeks. DN/EB cultivars were subjected to separated treatments of 8-h, 11-h, 14-h and 17-h photoperiod for up to 10 weeks. After 8 and 10 weeks of photoperiodic treatments in SD and DN/EB cultivars respectively, shoot apical meristems (SAM) were observed under microscope and classified into one of twelve developmental stages (Indices: 0-11). All SD cultivars examined showed a critical photoperiod between 13 h and 14 h. DN/EB cultivars 'San Andreas', 'Albion' and 'Monterey' presented facultative long-day response with positive correlation between SAM developmental indices and photoperiod after 8 weeks of treatment. 'Portola' showed non-significant influences of photoperiodic treatments in flower primordial development, suggesting day neutral response. However, further experiments must be conducted to confirm cultivar responses and identify possible interactions between photoperiod and temperature. The effect of light intensity and plant sink/source balance on strawberry plant photosynthesis was also investigated. Measurements of leaf net photosynthetic rate (Pn), stomatal conductance, intercellular CO2 concentration (Ci) and transpiration rate under near-saturated photosynthetically photon flux of 1,000ï ­mol m-2 s-1 and ambient CO2 concentration in strawberry cultivars 'Albion' and 'Nyoho'; and tomato cultivar 'Speedella'(comparison purposes) were conducted monthly in greenhouse during May 2014, and monthly from September 2015 through May 2016 (winter/spring production season). Hourly measurements were recorded hourly from 9 AM to 4 PM. Potential source strength was determined by the number of leaves and the daily light integral (DLI, 400-700 nm) and sink load from flowers and fruits was represented as the number of flowers and fruits. Seasonal changes in daily maximum Pn were observed, as well as diurnal change in Pn in both strawberry cultivars. A significant positive correlation was determined between the estimated ratios of sink/source and the slopes representing diurnal linear decline of Pn. Also, Pn was negatively correlated with Ci but not significantly correlated with vapor pressure deficit (VPD) in greenhouse, suggesting diurnal decline in Pn was likely due to negative feedback of photosynthesis caused by unbalance of sink and source, and not to water stress from high VPD. The photosynthetic capacity as affected by seasonal changes in greenhouse environment and its diurnal change as affected by sink/source balance could help develop more effective practices in CE strawberry production to maximize production. Also, photoperiodic response revealed in this study for American strawberry cultivars will specify conditions to induce flowering in these economically important cultivars off-season.

A pré-concentração consiste no descarte prévio de uma fração da ganga liberada, ou parcialmente liberada, com pouco ou nenhum conteúdo de interesse, antes da alimentação da usina. Tal prática pode levar a uma série de benefícios nas operações subsequentes, como redução do consumo de energia por tonelada de metal produzido, nos casos em que o material rejeitado apresentar WI (work Index) elevado; diminuição do desgaste abrasivo, quando a ganga rejeitada exibir AI (Abrasion Index) alto; além de aumento de recuperação na flotação e eliminação de flutuações no teor da alimentação. Neste sentido, a pré-concentração diminui custos operacionais e aumenta a rentabilidade da usina. Este trabalho teve por objetivo avaliar a aplicabilidade de pré-concentração para o minério de zinco silicatado de Vazante/MG. Em uma primeira etapa foram executados estudos de liberação da ganga no produto de britagem, explorando as propriedades luminescentes do minério. Para isto, imagens de contraste de cores luminescentes foram obtidas e tratadas no Image J. Obteve-se um valor de liberação da ganga da ordem de 85%. Em um segundo momento, foi investigado o desempenho de técnicas de separação densitária e seleção por sensores (ou ore sorting) como alternativas para a pré-concentração do minério de zinco e remoção de ganga carbonática, para isto, foram utilizados ensaios de afunda/flutua em líquidos densos, que simularam uma operação em meio denso, estratificação em jigue e ensaios em sorter com sensor de transmissão de Raios-X de energia dupla (DE- XRT). O melhor resultado foi obtido através do ensaio de afunda/flutua com densidade de separação de 2,95 g/cm³, no qual foi alcançado um descarte de 30% da massa de alimentação como produto flutuado, numa fração -25 +1,18 mm, removendo 60% dos carbonatos (CaO e MgO) e perdendo apenas 2% de zinco. Os ensaios do sorter também apresentaram resultados positivos, com aproximadamente 93% de recuperação metalúrgica de zinco e um descarte de aproximadamente 30% da massa, mas com uma perda de zinco considerável (aproximadamente 5% em teor). Para a jigagem, os resultados indicaram teor de zinco muito elevado no rejeito (aproximadamente 6%). Entretanto, uma jigagem adicional, realizada com uma segunda amostra numa granulometria menor (-12,7 +1,18 mm), proporcionou menores níveis de zinco perdido para o rejeito, apenas 3,6% em teor. Os impactos da pré-concentração na moagem e flotação também foram avaliados. Para isto foram executados ensaios de work index (WI), abrasion index (AI) e flotação com material tal qual (sem passar por pré-concentração) e com o material pré-concentrado de forma a se ter um comparativo. Como não houve variação de WI e nem de AI entre as amostras tal qual e pré-concentrada, a pré-concentração previamente à moagem, não irá impactar no consumo energético e tampouco no desgaste abrasivo, isto se for adotada a estratégia de manter a mesma vazão mássica de alimentação do circuito de moagem para ambas as alternativas. Em linhas gerais, a flotação após a pré-concentração aumentou a produção de concentrado de zinco com uma qualidade superior em termos de recuperação deste metal. Outro impacto positivo observado foi a redução da quantidade de rejeito fino de flotação e, consequentemente, o volume a ser estocado em barragem. / Preconcentration consists of the prior disposal of a fraction of the liberated or partially liberated gangue with low or no content of interest material before plant feed. Such practice can lead to a number of benefits in subsequent operations, such as reducing energy consumption per ton of metal produced, in cases where the rejected material presents a high WI (work index); decreased abrasive wear when the rejected presents high Abrasion Index (AI); increased recovery in flotation and elimination of fluctuations in feed content. Therefore, preconcentration reduces operating costs and increases the profitability of the plant. This work had the objective of evaluating the preconcentration applicability for a silicate zinc ore from Vazante/MG. In the first stage, grind release tests were performed on the crushing product, exploring the luminescent properties of the ore. For this, luminescent color contrast images were obtained and treated in Image J. A gangue release value of the order of 85% was obtained. Second, the performance of densification separation and sensor sorting (or ore sorting) techniques were investigated as alternatives for preconcentration of zinc ore and removal of carbonate gangue, for this, sink/float tests in dense liquids were used to simulate a dense medium operation, as well jig stratification and sorter tests with dual energy X-ray transmission sensor (DE-XRT). The best result was obtained by the sink/float test with separation density of 2.95 g / cm³, in which a 30% discard of the feed mass as a flotation product was achieved, in a fraction -25 +1.18 mm, removing 60% of the carbonates (CaO and MgO) and losing only 2% of zinc. The sorter tests also showed positive results, with approximately 93% metallurgical recovery and a discard of approximately 30% of the mass, but with a considerable loss of zinc. For jigging, the results indicated very high zinc content in the tailings (approximately 6%). However, additional jigging, performed with a second sample at a smaller particle size (-12.7 +1.18 mm), resulted in lower levels of zinc lost to the tailings, only 3.6% in content. The impacts of preconcentration on milling and flotation were also evaluated. For this, work index (WI), abrasion index (AI) and flotation tests were carried out with the material without preconcentration and with the preconcentrated material in order to compare. As there was no variation of WI and AI between the samples, the preconcentration prior to milling will not impact on energy consumption or on abrasive wear, if the strategy of maintaining the same mass flow rate of the milling circuit for both alternatives is adopted. In general terms, flotation followed by a preconcentration strategy can increase zinc production without requiring expansion of the plant\'s capacity. Another positive impact was the reduction of the amount of fine flotation tailings.

The glass sponge reefs of western Canada are modern analogues to ancient reefs and are unique habitats requiring conservation. However, the patterns and processes of the glass sponges have not been empirically studied. Here, I characterized the biology of the glass sponges in their reefs. I examined the community structure of the sponges at 3 reefs in the Strait of Georgia (SOG), their role in silica cycling, and the stable isotopes (13C and 15N) of the reef forming sponge Aphrocallistes vastus. Sponges are spatially structured in patches which localize the abundance of other animals. Long term dissolution of spicules is negligible and thus a reef can be considered a silica sink. Lastly, isotope compositions can differentiate populations of A. vastus and depleted carbon signatures at 2 reefs suggest a terrestrial component in their diet. My work represents the biological baseline of 3 glass sponge reefs in the SOG. / Ecology