1,524 research outputs found

    Evaluation of the Early Establishment Phase of \u3cem\u3eAgropyron desertorum\u3c/em\u3e, \u3cem\u3eMedicago sativa\u3c/em\u3e and \u3cem\u3eAtriplex canescens\u3c/em\u3e in Monocultures and Mixtures

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    This study evaluated the early establishment phase of various monocultures and mixed species plantings of Agropyron desertorum (AGDE), Medicago sativa (MESA), and Atriplex canescens (ATCA). The study was conducted under both greenhouse and field conditions. In the green-house, the experimental design was a split-plot, randomized-block design in time, using transplanted seedlings. The treatments were exposed to three water levels to determine species response to varying moisture availability. Plastic pots of 15.4 cm (diameter) by 17.9 cm (depth) were filled with 2,800 g of sandy-loam soil and brought to field capacity. The pots were weighted twice weekly and the water lost to evapotranspiration was replaced. The plants were measured for plant height on six occasions at two week intervals. On the last measurement date, plants were harvested for above-and-below ground biomass. The field used the species treatment as in the greenhouse study and these were hand sown in 1 m2 plots. Using a line-source sprinkler system, species responses at four water levels were examined. Soil water content in the various field plots was determined at various depths via access tubes and a neutron soil moisture probe. The experimental design was a split-plot design in time. Seedling emergence was recorded daily for the first 35 days after seeding. Plant height was measured six times during the growing season. All the species were clipped, oven-dried, and weighed at the end of the experimental period in 1982. In the greenhouse, AGDE was the dominant species, yet produced more in the MESA combination. MESA exhibited a marked decrease in production when grown with AGDE. ATCA showed a remarkable ability to survive under high water stress. Variable soil water content created in the field resulted in significant differences in germination, emergence, and establishment among planting treatments. MESA germinated and emerged faster than AGDE and ATCA, allowing it to utilize water and nutrient resources earlier than the competing species. The greatest shoot production occurred when MESA grew alone. In the AGDE-MESA combination, shading apparently reduced AGDE growth and shoot production at the two most favorable water levels. ATCA exhibited poor germination and emergence in treatments with low soil water availability

    Molecular phylogenetics, evolution of sexual systems and historical biogeography of Darwin's favourite orchids (Catasetinae) and Swan orchids (Cycnoches Lindl.)

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    The Orchidaceae are one of the most species rich and widespread lineages among angiosperms. They have evolved numerous remarkable vegetative and reproductive traits that have allowed them to successfully adapt and diversify into a wide array of environments. More importantly, they have developed several intricate symbiotic relationships with different kinds of organisms (e.g. animals, fungi) that for centuries have attracted the attention of botanists, biologists, amateurs and naturalists. Nevertheless, despite the extensive research done so far on orchid biology and phylogenetics, very little is known about the biotic and environmental variables as well as the evolution of several key traits that seem to be linked with the successful diversification of this lineage. This dissertation is focused on three puzzling aspects of plant evolutionary biology, specifically the phylogenetic incongruence between nuclear and plastid genomes, the evolution of sexual systems, and lineage migration and isolation through time. To address these topics, I chose as a group of study the sub tribe Catasetinae, an orchid lineage including ca. 350 species restricted to the Neotropical region. They show a remarkable set of sexual systems, namely protandry and Environmental Sex Determination (ESD), that were never studied before in a phylogenetic context. My dissertation includes as well a minor part on taxonomic and floristic work devoted to other representative orchid lineages of the Neotropical flora (i.e. Epidendrum and Lepanthes). Based on vegetal material collected during field trips, my taxonomic research resulted in the description of several new species and new chorological reports contributing to the Colombian and Costa Rican Floras. Using a set of nuclear and chloroplast loci obtained from material cultivated at the Botanic Garden Munich and collected during field work in several Latin American countries, I produced a well-supported and insofar the most representatively sampled phylogeny of Catasetinae. While gathering vegetal material, I encountered several complications such as extreme scarcity of individuals and worrisome, extensive bureaucratic administrative processes to obtain collection and research permits that finally undermined my taxon sampling. By studying in detail the Catasetinae internal phylogenetic relationships independently derived from nuclear and plastid loci, I came across several well supported conflicting phylogenetic positions. Most of the traditional phylogenetic methods developed to address these conflicts aim at the inference of a species tree only. In chapter 5, I explored the utility of co-phylogenetic tools (i.e. PACo and ParaFit) to quantify the conflicts between nuclear and plastid genomes. These tools have been largely employed in host-parasite/endosymbiont studies, hence they have the power to assess the contribution of single Operational Terminal Units (OTUs) to the phylogenetic pattern observed. As a result, using the Catasetinae chloroplast and nuclear datasets and extensive simulation approaches, I demonstrate that PACo successfully detects conflicting OTUs and its performance is overall better than ParaFit. In addition, my research provided strong evidence towards the bias of input data type (i.e. phylograms and cladograms) on distance-based co-phylogenetic methods. A pipeline to execute PACo and ParaFit tools in the software R to detect conflicting sequences in either small or big datasets was designed After inferring a strongly supported phylogeny, and by carrying in-situ and ex-situ observations plus searches of specialized literature on reproductive biology, I investigated the evolution of sexual systems of Catasetinae. I relied on Ancestral State Reconstruction (ASR) approaches and Bayesian statistical frameworks (chapter 6). As a result, ASR revealed three independent gains of ESD, once in the Last Common Ancestor (LCA) of Catasetum, Cycnoches and part of Mormodes, respectively, always derived from a protandrous ancestors. In contrast, protandry appears to have evolved only once, at the LCA of Catasetum, Clowesia, Cycnoches, Dressleria and Mormodes. The last chapter of this dissertation deals with the impact of the Andean uplift, the most important orographic event in South America, on evolution of epiphytic lowland Neotropical lineages. I used as a group of study Cycnoches (a member of the Catasetinae), which includes ca. 34 species and is distributed in Neotropical lowland wet forests. To address this goal, I produced the most completely sampled phylogeny of Cycnoches, and relied on Bayesian dating and Ancestral Area Estimation (AAE) approaches. The LCA of Cycnoches lived ca. 6 million years ago (MYA) in the Amazonian region. From this area, it expanded towards Central America and Choco in multiple migrations well after main Andean mountain building episodes. In addition, stochastic character mapping showed that within-region speciation (i.e. speciation in sympatric lineages) was a key process linked to diversification and range distribution evolution in Cycnoches

    Digest: Linking coordinated shifts in plant resource allocation to a chromosomal inversion

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    This article corresponds to Lowry, D. B., D. Popovic, D. J. Brennan, and L. M. Holeski. 2019. Mechanisms of a locally adaptive shift in allocation among growth, reproduction, and herbivore resistance in Mimulus guttatus. Evolution. https://doi.org/10.1111/evo.13699.Local adaptation in plants often requires coordinated shifts among resources. Lowry et al. provide evidence for physiological and genomic mechanisms underpinning adaptive shifts in yellow monkeyflower (Mimulus guttatus), such as the transition between annual and perennial life histories. In M. guttatus, differential activity of gibberellins, governed partially by a chromosomal inversion, is responsible for shifts between growth, reproduction, and herbivore defense (secondary compound production)

    Production planning and scheduling optimization model: a case of study for a glass container company

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    Based on a case study, this paper deals with the production planning and scheduling problem of the glass con-tainer industry. This is a facility production system that has a set of furnaces where the glass is produced in order to meet the demand, being afterwards distributed to a set of parallel molding machines. Due to huge setup times involved in a color changeover, manufacturers adopt their own mix of furnaces and machines to meet the needs of their customers as flexibly and efficiently as possible. In this paper we proposed an optimization model that maximizes the fulfillment of the demand considering typical constraints from the planning production formulation as well as real case production constraints such as the limited product changeovers and the minimum run length in a machine. The complexity of the proposed model is assessed by means of an industrial real life problem

    Desempeño de las oficinas de transferencia universitarias como intermediarias para la potencialización del mercado de conocimiento

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    Objeto: Este artículo explora la literatura de modelos de triple hélice y conceptualiza el rol de las oficinas de transferencia de investigación universitarias como entidades intermediarias para la valorización y comercialización del conocimiento generado. El resultado es una síntesis de las principales de líneas de investigación que se han ido trabajando en los últimos años en este ámbito así como la identificación de futuras líneas de investigación que permitan obtener una mayor claridad sobre su verdadero funcionamiento interno y su importancia como interfaz entre el mundo académico y el tejido empresarial. Diseño/metodología: Mediante un estudio bibliométrico se han identificado aquellos artículos indexados en la ISI Web of Knowledge y en Scopus que por su temática y relevancia son un referente internacional dentro de la comunidad científica en el campo de la transferencia de conocimiento de base universitaria. Aportaciones y resultados: Los resultados de este trabajo permiten analizar el modelo de la triple hélice III y el desempeño de las oficinas de transferencia como intermediarias para la potencialización del mercado de conocimiento. Valor añadido: Dos son las principales contribuciones de este artículo a la literatura científica sobre oficinas de transferencia de tecnología: 1) la identificación y organización de la literatura relacionada con el tema y los diferentes enfoques que han sido desarrollados por los expertos; 2) la identificación de varias líneas de investigación que todavía no han sido ampliamente abordadas en la literatura actual y que pueden influir en el desempeño de las oficinas de transferenciaPeer Reviewe

    Control híbrido del péndulo de furuta

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    Este proyecto muestra el modelado matemático del péndulo de furuta mediante funciones de energía, teniendo en cuenta las dinámicas no lineales propias de los sistemas físicos y considerando los acoples existentes entre los dispositivos eléctricos y mecánicos. Se desarrolla un proceso de control basado en realimentación de variables de estado para el punto de equilibrio y se abordan dos temáticas para la zona no lineal de la planta. En primera instancia se implementan las funciones que representan los estados energéticos de la planta en forma global y se establecen las regiones de operación (zona de "Swing UP") y finalmente se emplean redes neuronales (RNA) para emular el comportamiento de las funciones de energía. Se presenta la combinación de las técnicas de control considerando las restricciones propias del actuador y sensores utilizados, además se presenta un estudio de fenómenos físicos que pueden alterar el comportamiento del sistema

    Diseño e implementación de un control difuso de temperatura para microplanta de cocción de cerveza artesanal mediante PLC

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    In this study, a fuzzy-based PLC temperature control system was designed and implemented on a craft beer production plant. At present, the temperature-related controls of small-scale plants in Colombia are based on On/Off models, which are not very stable in the preparation of craft beer, which generates significant changes in flavor, scent and texture. Therefore, it is intended to incorporate into the craft beer industry, solutions that guarantee repeatability, minimize costs and potentiate production, for this, a three-stage fuzzy control model is carried out: design, implementation and start up; This is how a study of the plant´s dynamics is carried out, the response is determined from the data, a fuzzy controller is designed by using Matlab software, and a graphical interface in LabView for data capture and storage. The controller demonstrates stability in relation to the temperature variable, which provides repeatability and significant energy savings. Finally, it is concluded that the controller proved to be robust against major disturbances and stable at different temperatures, being a useful tool for efficiently controlling the variable.En este estudio se diseñó e implementó un sistema de control difuso de temperatura basado en PLC sobre una planta de cocción de cerveza artesanal. En la actualidad los controles relacionados a temperatura de las plantas a baja escala en Colombia se basan en modelos On/Off, que son poco estables en la preparación de la cerveza artesanal, lo que genera modificaciones significativas en el sabor, el aroma y la textura. Por tanto, se pretende incorporar en la industria de cerveza artesanal, soluciones que garanticen repetibilidad, minimicen los costos y potencialicen la producción, para ello, se realiza un modelo de control difuso en tres etapas: diseño, implementación y puesta en marcha; se realiza un estudio de la dinámica de la planta. A partir de los datos se determina la respuesta, se diseña un controlador difuso mediante software Matlab, y una interfaz gráfica en LabView para captura y almacenamiento de datos. El controlador demostró estabilidad en relación a la variable, lo que proporciona repetibilidad y un ahorro energético significativo. Finalmente se concluye que el controlador demostró ser robusto ante grandes perturbaciones y estable ante diferentes temperaturas siendo una herramienta útil para controlar de manera eficiente esta variable

    Digest: Drivers of coral diversification in a major marine biodiversity hotspot*

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    This article corresponds to Huang, D., E. E. Goldberg, L. M. Chou, and K. Roy. 2018. The origin and evolution of coral species richness in a marine biodiversity hotspot. Evolution.https://doi.org/10.1111/evo.13402
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