Ingeniera Civil de Minas / Actualmente la industria minera se enfrenta a procesos cada vez más complejos y desafiantes en la planificación de mediano y corto plazo; la tendencia a la baja en las leyes promedios de los yacimientos, el aumento de los costos operacionales, la mayor selectividad y aumento en mezclas de minerales, son las nuevas limitantes a la hora de lograr una cierta producción. La falta de herramientas computacionales que permitan incorporar todas estas variables en el proceso de planificación de Corto Plazo, obliga a los planificadores a utilizar métodos de aproximación manual, de prueba y error, aplicando sustanciales esfuerzos para generar planes de Corto Plazo que satisfagan todas las necesidades y que se ajusten a los lineamientos del Largo Plazo. El siguiente trabajo de título presenta la validación de la herramienta de optimización BOS2 en el área de Planificación Minera del Corto y Mediano Plazo en Compañía Minera Cerro Colorado (CMCC) de BHP Billiton. BOS2 fue desarrollado por Delphos, laboratorio de Planificación Minera de la Universidad de Chile. Es un software de optimización, cuya función objetivo es la maximización de cobre fino. Para ello BOS2 integra la variabilidad mineralógica del yacimiento, que constituye el principal desafío en el complejo proceso de planificación en CMCC. La validación es realizada por medio de pruebas o corridas numéricas, llevadas a cabo por la plataforma Virtual Mining Machine (VMM) desarrollada por Cube Mine, empresa constituida a partir del laboratorio Delphos. Las pruebas de validación replican el plan Budget de Mediano Plazo, para el año fiscal 2013 y 2014 realizado por CMCC, a fin de obtener comparaciones en los finos de cobre entregados con ambas metodologías. Las pruebas de optimización se realizaron durante los meses de Abril a Julio del presente año. Los resultados observados en la primera etapa de validación, dan cuenta sólo de un 83% del compromiso de los finos de cobre del plan CMCC. A partir de estos hallazgos se identificaron oportunidades de mejoras técnicas para la aplicación del modelo en base a la liberación de restricciones. En efecto, al tomar la decisión de liberar la restricción de distancias entre fases contiguas, se alcanza un 97% de los finos estipulados en el plan CMCC, dando cuenta preliminarmente de la validez de esta herramienta en el proceso de planificación. Los resultados más relevantes del estudio se presentan en la siguiente tabla comparativa: Plan CMCC Validación 1 Validación 2 Material Procesado [Kton] 39,995 36,286 39,881 Finos de Cobre [Kton] 448 373 437 Remanejo [Kton] 4,713 4,567 3,444 Tal como se mencionó la validación 1 corresponde a la primera corrida numérica del modelo de optimización, mientras que la validación 2 corresponde al modelo con decisiones de mejoras técnicas, en las que se evidencia un aumento en los finos de cobre y mayor coherencia con el plan de CMCC, al mismo tiempo la disminución de un 27% en el remanejo de materiales indica un potencial de beneficio para el negocio.

The response of tropical forests to anthropogenic climate change is critically important to future global carbon budgets, yet remains highly uncertain. Here, we investigate how precipitation, temperature, solar radiation and dry-and wet-season lengths are related to annual tree growth, flower production, and fruit production in three moist tropical forest tree species using long-term datasets from tree rings and litter traps in central Panama. We also evaluated how growth, flower, and fruit production were interrelated. We found that growth was positively correlated with wet-season precipitation in all three species: Jacaranda copaia (r = 0.63), Tetragastris panamensis (r = 0.39) and Trichilia tuberculata (r = 0.39). Flowering and fruiting in Jacaranda were negatively related to current-year dry-season rainfall and positively related to prior-year dry-season rainfall. Flowering in Tetragastris was negatively related to current-year annual mean temperature while Trichilia showed no significant relationships of reproduction with climate. Growth was significantly related to reproduction only in Tetragastris, where it was positively related to previous year fruiting. Our results suggest that tree growth in moist tropical forest tree species is generally reduced by drought events such as those associated with strong El Nino events. In contrast, interannual variation in reproduction is not generally associated with growth and has distinct and species-specific climate responses, with positive effects of El Nino events in some species. Understanding these contrasting climate effects on tree growth and reproduction is critical to predicting changes in tropical forest dynamics and species composition under climate change.

A growing understanding of complex biotic interactions clarified the importance of symbioses with respect to the ecology and evolution of life. In particular, knowledge of symbioses between eukaryotes and microorganisms such as bacteria and fungi has revolutionized the fields of medicine and agriculture, and made clear the roles of microbes in fostering human and environmental sustainability. For example, diverse fungi associate with the seeds of plants following dispersal. These fungi can influence seed survival and germination in a host-specific and spatially explicit manner, thus influencing plant community dynamics in agricultural and natural systems. In species-rich tropical forests, seed-fungus interactions are emerging as one of the most important aspects of plant demography and community ecology. However, even closely related fungi can have opposing effects on seeds of particular plants, such that mechanisms influencing host-specific effects require further attention. Such mechanisms can include genomic traits of fungi and hosts, and the environmental context of interactions. However, studies have shown that many fungi also harbor endosymbionts than can influence their functional traits. In particular, fungi often harbor endohyphal bacteria that influence fungal phenotypes. This suggested the potential for similar, co-occurring microbes to influence the ecology of seed-associated fungi. Here, I explore the diversity, evolutionary relationships, and influence on fungal phenotypes of endohyphal bacteria inhabiting seed- and leaf-associated fungi with a focus that begins in tropical forest ecology and expands to include gene expression in an emerging model system from the temperate zone. To determine the occurrence, abundance, taxonomic diversity, and phylogenetic diversity of endohyphal bacteria among tropical seed-associated fungi, my coauthors and I used PCR and fluorescence microscopy to screen members of two common orders of seed-associated fungi, comparing their communities to those in closely related foliar endophytic fungi. We revealed a high frequency and diversity of endohyphal bacteria among both groups of fungi. We then used phylogenetic and community ecological analyses to show a lack of congruence between phylogenies of bacteria and fungi. Although seed-associated and foliar endophytic fungi share evolutionary histories, they harbor distinct endohyphal bacterial communities. To explore the influence of endohyphal bacteria on fungal phenotypes important for interactions with seeds, my coauthors and I examined a single fungus-bacterium pair consisting of a member of a well-known group of pathogenic fungi found to harbor an endohyphal bacterium closely related to those with known chitinolytic activity. We created fungal clones that were free of endohyphal bacteria, and carried out a phenotypic microarray assay comparing use of 95 unique carbon sources by cured and uncured clones. Across the majority of substrates, the fungal clones harboring endohyphal bacteria grew more rapidly and to a greater extent than the cured clones. Thus the endohyphal bacterium was associated with broader substrate use and more effective use of a variety of substrates relevant to plant biology, including seed germination. To assess the influence of endohyphal bacteria with respect to the outcomes of seed-fungus interactions, my coauthors and I examined six fungus-bacterium pairs and their interactions with the seeds of five tropical pioneer tree species. We showed that although endohyphal bacteria have little impact on colonization of seeds by fungi, they significantly altered the survival and germination of infected seeds. In most cases, endohyphal bacteria reduced the negative impacts of fungi on seeds: strains harboring them responded more similarly to uninoculated controls, whereas strains cured of them exhibited significantly reduced survival and germination. Seeds infected by fungi of the same genotype that differ with respect to the identity of their endohyphal bacteria exhibited differences, but so did seeds infected by strains of those isolates not harboring bacteria, suggesting that factors in addition to the presence of endohyphal bacteria can drive variation in the outcomes of seed-fungus interactions. Together these analyses suggest intricate interactions between fungi and bacteria that result in context-dependent outcomes. This turned our focus to gene expression as a means to understand mechanisms of interactions between endohyphal bacteria and their fungal hosts. Last, my coauthors and I describe methods we developed to co-culture fungi and their endohyphal bacteria for downstream analysis of differences in gene expression among a fungus-bacterium pair and axenic cultures of each symbiont. We focused on an emerging model system: a foliar endophytic strain of Pestalotiopsis aff. neglecta (Ascomycota) known to harbor an endohyphal bacterium in the genus Luteibacter (Xanthomonadaceae). The focal bacterium is in part reliant on its host fungus for acquisition of certain sulfur-containing compounds such as sulfate. We showed that inoculating a low-methionine growth medium with bacteria recovered in exponential phase from a high-methionine medium supports growth suitable for comparing axenic growth with that in co-culture with its host fungus. Although bacterial cell density in co-cultures was significantly greater than that in axenic cultures, the opposite was true for the host fungus. We expect results from transcriptomics analyses to reflect partial reliance on– and antagonism of Pestalotiopsis by Luteibacter, and here present the first pipeline of methods for examining gene expression for a facultatively symbiotic endohyphal bacterium and its host, a member of the most species-rich and economically important fungal phylum.

Maps bound separately.

An ensemble of 11 dynamically downscaled CMIP3 GCMs under A2 projection scenario are first bias corrected for the historic (1971-2000) and scenario (2041-2070) period using a Scaled Distribution Mapping (SDM) technique, that preserves the relative change in the monthly mean and variance of precipitation and any model trends in temperature to generate an ensemble of streamflow projections across 3 catchments in the Colorado River basin - Upper Colorado at Lees Ferry, Salt and Verde. The hydroclimatic projections obtained from this method are compared against an existing ensemble of 15 Bias Corrected and Spatially Disaggregated (BCSD) CMIP3 models under A2 projection scenario developed by the Bureau of Reclamation (BOR). The confidence in the DD Ens. stems from its ability to represent historical flow quantiles better than BCSD Ens. Across all three basins, the mean of the dynamically downscaled ensemble (DD Ens.) projects a decrease in both monsoon and winter projected precipitation as compared to mean of the statistically downscaled ensemble (BCSD Ens.). For the Upper Colorado, both Ens. show a shift in peak hydrograph from June to May due to earlier snowmelt, but a projected decrease in precipitation (-5%) by DD Ens. as compared to a slight increase (+2%) by BCSD Ens. results in a lower April snow water equivalent (SWE) and reduced streamflows (14% by DD Ens. as compared to 5% by BCSD Ens.). The streamflow decrease over the Upper Colorado River basin, quantified by both the mean and the spread of the ensemble. is representative in high flows and flows during moist conditions. For smaller basins like Salt and Verde, DD Ens. shows a greater decrease (-11%) in precipitation than BCSD Ens. (-2%), which results in lower peak hydrograph during March and significantly reduced streamflows (-20%&-14% for Salt and Verde by DD Ens. as compared to -3% by BCSD Ens.). This decrease is more substantial in high flows, but occurs across all streamflow quantiles. The future streamflow projection, quantified by the spread of the DD Ens. presents the shifting of the streamflow range downward to be drier in the future.

Most approaches to interpreting alluvial records in drylands fall into one of two categories: (1) The "arroyo problem," wherein workers study cycles of streambed aggradation and degradation in broad, unconstricted alluvial valleys; and (2) paleoflood hydrology, where alluvial sequences in constricted bedrock canyons are interpreted as paleoflood deposits from streams with stable channel grade and geometry. Both approaches can be valid in their end-member settings, but there is confusion about how the two record types relate in a single drainage. We address this disconnect in Buckskin Wash, an ephemeral stream that consists of a broad alluvial reach draining into a tightly constricted slot canyon. By employing detailed sedimentology, stratigraphy, and geochronology in both the alluvial and constricted reaches of the watershed, we test the hypothesis that the slot canyon deposits are anticorrelated to valley-fill deposits upstream, implying that arroyo cutting is driven by episodic flooding. Alluvial reach deposits are characterized by stratal packages representing incremental, long-term aggradation bound by erosion surfaces representing channel entrenchment. At least four packages younger than ~3 ka are present, the youngest spanning ~0.7 - 0.15 ka. Each is composed of interfingering imbricated gravels, laminated sands, and massive silty clays. Constricted reach deposits consist of five discrete packages, each composed of tabular beds of laminated silty sand that were deposited relatively rapidly. The oldest package dates to ~1.9 - 1.1 ka, whereas the rest of the deposits are younger than ~0.15 ka. Traditional paleoflood techniques would suggest that the constricted reach deposits record a ~1000-year absence of paleofloods followed by ~100 years of frequent, high-magnitude flooding that indeed correlate to arroyo cutting upstream. We argue instead that the constricted reach deposits record an episode of higher preservation potential. Transport of sediment from the alluvial reaches during historic arroyo cutting likely led to a pulse of sediment storage and changed stage-discharge relations in the slot canyon downstream, allowing even moderate floods to overtop existing deposits and be preserved. This new interpretation suggests that, because preservation may be a function of episodic sediment loading from upstream, constricted-reach deposits may not accurately record the paleoflood history of a stream.

Prior research on statewide educational telecommunications has focused on cataloging initiatives in various states, describing activities in individual states, or in exploring telecommunications policy from a planning-level perspective. In these studies, it is recognized that policies and implementation behaviors vary across individual states; however, a theoretical basis for how and why policy and implementation models differ among states has not been provided. Research also suggests that many states are moving toward the adoption of successful models from other states, and that there is a need for policy research to assist states in developing policies. This dissertation attempts to apply the systems perspective in organization theory (Thompson 1967; Mintzberg 1983) and concepts from political feasibility analysis (Meltsner 1972; Webber 1986) to qualitative data on educational telecommunications systems in three western states: Oregon, Colorado, and Utah. The research will provide descriptions of activities that can be referred to by state policy makers in evaluating the feasibility of adopting another state's planning model, and in developing their own policies. The research also will contribute to the growing literature on state policies and implementation models for distance education. The three states represent models of educational telecommunications systems prevalent in the U.S., and each differs in the level of statewide planning, governance, finance, and delivery of educational telecommunication represented by its model. Interviews with policy makers and practitioners in each state, combined with documentary evidence and prior research, provide descriptions of organizational responses to statewide policy and planning for distance education. Conclusions indicate that state policies are lagging behind technological change, and that variations in policy and planning among states result from constraints and contingencies imposed on institutions by contextual variables peculiar to each state. States that engage in careful planning for statewide telecommunications, taking into account the political culture, organizational behaviors, and historical relationships between higher education and state government, will have the greatest success in developing and implementing policies.

No description available.

<p> The opening of the Rio Grande Rift of Southern Colorado resulted in a wide variety of igneous features including the Spanish Peaks dual stocks, their surrounding radial dyke system and several proximal enigmatic plugs.</p> <p> Aspects of the crystallization history of two magmas have been studied by using petrographic observations and Crystal Size Distribution (CSD). These were used to examine opaques and feldspars from a rhyolitic dyke in the Spanish Peaks swarm and augite, olivine, and opaques from a gabbroic dyke within Huerfano Butte.</p> <p> Augite and opaques from Huerfano Butte reveal a history of no crystal fractionation during emplacement, no size dependent growth, and constant, continuous nucleation and growth.</p> <p> Huerfano Butte olivine and Spanish Peaks opaques have been subjected to resorption and depletion of nucleii. The resorbed olivine material was probably redeposited as augite. This could explain why Huerfano Butte augite has a much higher nucleation density than the other minerals.</p> <p> The phenocrystic feldspars from Spanish Peaks also have a deficit of nucleii, but they lack resorption features. Xenocrystic skeletal feldspars throughout the dyke lack a fines population and show resorption. The absence of fines is probably due to sorting of grains by density during magma convection before eruption.</p> / Thesis / Master of Science (MSc)

No description available.