La filmación de clase en contexto de colegialidad: estrategia que favorece los procesos reflexivos respecto de la práctica pedagógica

In recent decades, the reflection on the teaching practices has been considered as an important means among the teacher trainers. Nevertheless, chilean research note that the universities of this country have not achieved that students of Teaching Programs may develop reflections on their pedagogical procedures systematically. This situation is no far from the reality of students of Pedagogía Media en Ciencias Naturales y Biología from Universidad Católica de Temuco. They achieve only in some cases, and intuitively, reflections that may help them improve their performance. The purpose of this research is to strengthen the levels of students’ reflection. In this context, the investigation is a qualitative one with a unique case study design. It points to the relevance of the use of class filming as a strategy which favors reflective processes on the pedagogical practice in collegiate contexts. It concludes that the participants appreciate the strategy of class filming, given that it favors the self assessment of their performance. Likewise, a mobility of the levels of reflection from the descriptive to the critic one, is shown. Nevertheless, it is important to highlight that the mobility depends on the time the participants spend on the reflective process.En las últimas décadas, la reflexión respecto de las prácticas profesionales docentes ha sido considerada como un medio de desarrollo importante entre los formadores de profesores. Sin embargo, investigaciones chilenas dan cuenta que las universidades de este país no han logrado que los estudiantes de pedagogía desarrollen sistemáticamente reflexiones en relación a su quehacer docente. Esta situación no se aleja de la realidad que viven los estudiantes de la carrera de Pedagogía Media en Ciencias Naturales y Biología de la Universidad Católica de Temuco. Estos logran solo en algunos casos, y de forma intuitiva, reflexiones para la mejora de su mejorar desempeño. El propósito de esta investigación es fortalecer los niveles de reflexión de estudiantes de pedagogía. En este contexto, la investigación es cualitativa con diseño de estudio de caso único y evidenció la relevancia de la utilización de filmaciones de clase como estrategia que favorece procesos reflexivos sobre la práctica pedagógica en contextos de colegialidad. Se concluyó que los participantes valoran la estrategia de filmación de clase dado que favorece la autoevaluación del desempeño. Asimismo, se observó una movilización de los niveles de reflexión de la práctica pedagógica desde el nivel descriptivo al crítico; sin embargo, cabe destacar que se genera la movilización señalada dependiendo del tiempo que destinen los participantes al proceso reflexivo

Mejoramiento de flujos de informacion y diseno de un modelo de datos para el desarrollo de un sistema de informacion, de apoyo a la gestion administrativa de la Federacion Nacional de Clubes de Rodeos y Huasos de Chile

97 p.El proyecto consiste en un análisis de la estructura de la Federación y en forma mas detallada como fluye la información relevante para el funcionamiento de dicha organización, además de una propuesta mejorada de los Flujos de Información y por ultimo se complementa con un Modelo Conceptual de Datos. El análisis de la situación Actual, busca encontrar los problemas existentes en la Federación Nacional de Rodeo y Clubes de Huasos de Chile, y aclarar en que ámbito se trabajada. La Propuesta Mejorada pretende establecer las pautas de como debiera fluir toda la información generada, desde y hacia la Federación Nacional. Se busca mejorar la gestión administrativa de la Federación, debido a que muchas tareas se realizan en forma intuitiva. Por ultimo el Modelo Conceptual de Datos complementa todo lo anteriormente trabajado, tanto el análisis de la situación actual, como la Propuesta Mejorada. Todo lo anterior con el fin de Mejorar el funcionamiento Administrativo de la Federación Nacional de Rodeo y Clubes de Huasos de Chile y que sirva de base para el desarrollo de un sistema de Información que la organización desea implementar una vez terminada esta etapa. El desarrollo del sistema estará a cargo de una empresa externa a la Federación

Inducing a topological transition in graphene nanoribbon superlattices by external strain

Armchair graphene nanoribbons, when forming a superlattice, can be classified into different topological phases, with or without edge states. By means of tight-binding and classical molecular dynamics (MD) simulations, we studied the electronic and mechanical properties of some of these superlattices. MD shows that fracture in modulated superlattices is brittle, as for unmodulated ribbons, and occurs at the thinner regions, with staggered superlattices achieving a larger fracture strain than inline superlattices. We found a general mechanism to induce a topological transition with strain, related to the electronic properties of each segment of the superlattice, and by studying the sublattice polarization we were able to characterize the transition and the response of these states to the strain. For the cases studied in detail here, the topological transition occurred at ∼3-5% strain, well below the fracture strain. The topological states of the superlattice - if present - are robust to strain even close to fracture. The topological transition was characterized by means of the sublattice polarization of the states.Fil: Flores Gutierréz, Esteban. Universidad de Chile; ChileFil: Mella, José D.. Universidad de Chile; ChileFil: Aparicio, Emiliano. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza; Argentina. Universidad de Mendoza. Facultad de Ingenieria; ArgentinaFil: Gonzalez, Rafael I.. Universidad Mayor; Chile. Centro para el Desarrollo de la Nanociencia y la Nanotecnología; ChileFil: Parra, C.. Universidad Mayor; ChileFil: Bringa, Eduardo Marcial. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza; Argentina. Universidad de Mendoza. Facultad de Ingenieria; Argentina. Universidad Mayor; ChileFil: Munoz, Francisco. Centro para el Desarrollo de la Nanociencia y la Nanotecnología; Chile. Universidad de Chile; Chil

Prochlorococcus and Synechococcus have Evolved Different Adaptive Mechanisms to Cope with Light and UV Stress.

International audienceProchlorococcus and Synechococcus, which numerically dominate vast oceanic areas, are the two most abundant oxygenic phototrophs on Earth. Although they require solar energy for photosynthesis, excess light and associated high UV radiations can induce high levels of oxidative stress that may have deleterious effects on their growth and productivity. Here, we compared the photophysiologies of the model strains Prochlorococcus marinus PCC 9511 and Synechococcus sp. WH7803 grown under a bell-shaped light/dark cycle of high visible light supplemented or not with UV. Prochlorococcus exhibited a higher sensitivity to photoinactivation than Synechococcus under both conditions, as shown by a larger drop of photosystem II (PSII) quantum yield at noon and different diel patterns of the D1 protein pool. In the presence of UV, the PSII repair rate was significantly depressed at noon in Prochlorococcus compared to Synechococcus. Additionally, Prochlorococcus was more sensitive than Synechococcus to oxidative stress, as shown by the different degrees of PSII photoinactivation after addition of hydrogen peroxide. A transcriptional analysis also revealed dramatic discrepancies between the two organisms in the diel expression patterns of several genes involved notably in the biosynthesis and/or repair of photosystems, light-harvesting complexes, CO(2) fixation as well as protection mechanisms against light, UV, and oxidative stress, which likely translate profound differences in their light-controlled regulation. Altogether our results suggest that while Synechococcus has developed efficient ways to cope with light and UV stress, Prochlorococcus cells seemingly survive stressful hours of the day by launching a minimal set of protection mechanisms and by temporarily bringing down several key metabolic processes. This study provides unprecedented insights into understanding the distinct depth distributions and dynamics of these two picocyanobacteria in the field

Light history influences the response of the marine cyanobacterium Synechococcus sp. WH7803 to oxidative stress.

International audienceMarine Synechococcus undergo a wide range of environmental stressors, especially high and variable irradiance, which may induce oxidative stress through the generation of reactive oxygen species (ROS). While light and ROS could act synergistically on the impairment of photosynthesis, inducing photodamage and inhibiting photosystem II repair, acclimation to high irradiance is also thought to confer resistance to other stressors. To identify the respective roles of light and ROS in the photoinhibition process and detect a possible light-driven tolerance to oxidative stress, we compared the photophysiological and transcriptomic responses of Synechococcus sp. WH7803 acclimated to low light (LL) or high light (HL) to oxidative stress, induced by hydrogen peroxide (H₂O₂) or methylviologen. While photosynthetic activity was much more affected in HL than in LL cells, only HL cells were able to recover growth and photosynthesis after the addition of 25 μM H₂O₂. Depending upon light conditions and H₂O₂ concentration, the latter oxidizing agent induced photosystem II inactivation through both direct damage to the reaction centers and inhibition of its repair cycle. Although the global transcriptome response appeared similar in LL and HL cells, some processes were specifically induced in HL cells that seemingly helped them withstand oxidative stress, including enhancement of photoprotection and ROS detoxification, repair of ROS-driven damage, and regulation of redox state. Detection of putative LexA binding sites allowed the identification of the putative LexA regulon, which was down-regulated in HL compared with LL cells but up-regulated by oxidative stress under both growth irradiances

Ultraviolet stress delays chromosome replication in light/dark synchronized cells of the marine cyanobacterium Prochlorococcus marinus PCC9511.

International audienceBACKGROUND: The marine cyanobacterium Prochlorococcus is very abundant in warm, nutrient-poor oceanic areas. The upper mixed layer of oceans is populated by high light-adapted Prochlorococcus ecotypes, which despite their tiny genome (approximately 1.7 Mb) seem to have developed efficient strategies to cope with stressful levels of photosynthetically active and ultraviolet (UV) radiation. At a molecular level, little is known yet about how such minimalist microorganisms manage to sustain high growth rates and avoid potentially detrimental, UV-induced mutations to their DNA. To address this question, we studied the cell cycle dynamics of P. marinus PCC9511 cells grown under high fluxes of visible light in the presence or absence of UV radiation. Near natural light-dark cycles of both light sources were obtained using a custom-designed illumination system (cyclostat). Expression patterns of key DNA synthesis and repair, cell division, and clock genes were analyzed in order to decipher molecular mechanisms of adaptation to UV radiation. RESULTS: The cell cycle of P. marinus PCC9511 was strongly synchronized by the day-night cycle. The most conspicuous response of cells to UV radiation was a delay in chromosome replication, with a peak of DNA synthesis shifted about 2 h into the dark period. This delay was seemingly linked to a strong downregulation of genes governing DNA replication (dnaA) and cell division (ftsZ, sepF), whereas most genes involved in DNA repair (such as recA, phrA, uvrA, ruvC, umuC) were already activated under high visible light and their expression levels were only slightly affected by additional UV exposure. CONCLUSIONS: Prochlorococcus cells modified the timing of the S phase in response to UV exposure, therefore reducing the risk that mutations would occur during this particularly sensitive stage of the cell cycle. We identified several possible explanations for the observed timeshift. Among these, the sharp decrease in transcript levels of the dnaA gene, encoding the DNA replication initiator protein, is sufficient by itself to explain this response, since DNA synthesis starts only when the cellular concentration of DnaA reaches a critical threshold. However, the observed response likely results from a more complex combination of UV-altered biological processes

Metabolic evolution and the self-organization of ecosystems

Metabolism mediates the flow of matter and energy through the biosphere. We examined how metabolic evolution shapes ecosystems by reconstructing it in the globally abundant oceanic phytoplankter Prochlorococcus To understand what drove observed evolutionary patterns, we interpreted them in the context of its population dynamics, growth rate, and light adaptation, and the size and macromolecular and elemental composition of cells. This multilevel view suggests that, over the course of evolution, there was a steady increase in Prochlorococcus' metabolic rate and excretion of organic carbon. We derived a mathematical framework that suggests these adaptations lower the minimal subsistence nutrient concentration of cells, which results in a drawdown of nutrients in oceanic surface waters. This, in turn, increases total ecosystem biomass and promotes the coevolution of all cells in the ecosystem. Additional reconstructions suggest that Prochlorococcus and the dominant cooccurring heterotrophic bacterium SAR11 form a coevolved mutualism that maximizes their collective metabolic rate by recycling organic carbon through complementary excretion and uptake pathways. Moreover, the metabolic codependencies of Prochlorococcus and SAR11 are highly similar to those of chloroplasts and mitochondria within plant cells. These observations lead us to propose a general theory relating metabolic evolution to the self-amplification and self-organization of the biosphere. We discuss the implications of this framework for the evolution of Earth's biogeochemical cycles and the rise of atmospheric oxygen.Simons Foundation (Grant SCOPE 329108)Gordon and Betty Moore Foundation (Grant 3778)Gordon and Betty Moore Foundation (Grant 495.01

Over-calcified forms of the coccolithophore Emiliania huxleyi in high-CO2 waters are not preadapted to ocean acidification

Marine multicellular organisms inhabiting waters with natural high fluctuations in pH appear more tolerant to acidification than conspecifics occurring in nearby stable waters, suggesting that environments of fluctuating pH hold genetic reservoirs for adaptation of key groups to ocean acidification (OA). The abundant and cosmopolitan calcifying phytoplankton Emiliania huxleyi exhibits a range of morphotypes with varying degrees of coccolith mineralization. We show that E. huxleyi populations in the naturally acidified upwelling waters of the eastern South Pacific, where pH drops below 7.8 as is predicted for the global surface ocean by the year 2100, are dominated by exceptionally over-calcified morphotypes whose distal coccolith shield can be almost solid calcite. Shifts in morphotype composition of E. huxleyi populations correlate with changes in carbonate system parameters. We tested if these correlations indicate that the hyper-calcified morphotype is adapted to OA. In experimental exposures to present-day vs. future pCO2 (400 vs. 1200 µatm), the over-calcified morphotypes showed the same growth inhibition (−29.1±6.3 %) as moderately calcified morphotypes isolated from non-acidified water (−30.7±8.8 %). Under the high-CO2–low-pH condition, production rates of particulate organic carbon (POC) increased, while production rates of particulate inorganic carbon (PIC) were maintained or decreased slightly (but not significantly), leading to lowered PIC ∕ POC ratios in all strains. There were no consistent correlations of response intensity with strain origin. The high-CO2–low-pH condition affected coccolith morphology equally or more strongly in over-calcified strains compared to moderately calcified strains. High-CO2–low-pH conditions appear not to directly select for exceptionally over-calcified morphotypes over other morphotypes, but perhaps indirectly by ecologically correlated factors. More generally, these results suggest that oceanic planktonic microorganisms, despite their rapid turnover and large population sizes, do not necessarily exhibit adaptations to naturally high-CO2 upwellings, and this ubiquitous coccolithophore may be near the limit of its capacity to adapt to ongoing ocean acidification

Composición de nidos de aves silvestres en parques urbanos y periurbanos del centro del Estado de Veracruz, México

La urbanización modifica la abundancia y tipo de materiales naturales usados por aves en la nidación. La incorporación de materiales antrópicos (de uso humano) al nido es riesgosa para los polluelos y el éxito reproductivo de las poblaciones. En este trabajo se evalúa la composición de nidos de aves silvestres en parques urbanos y periurbanos de Xalapa y Coatepec, Veracruz, México. Durante marzo- julio 2017, se eligieron dos parques urbanos y tres periurbanos en Xalapa y uno urbano en Coatepec, donde se colectaron en general diez nidos inactivos por mes en cada parque. Los nidos fueron secados y los materiales separados y pesados en una balanza analítica considerando cuatro criterios: material vegetal (MVE), material de origen animal (MOA), material de sustrato (MSU) y antrópico (MAN). Por cada tipo de material se obtuvo el porcentaje relativo. Un ANOVA con interacciones de dos vías (tipo de material y tipo de parque) fue utilizado para establecer diferencias en los porcentajes relativos transformados a raíz cuadrada del arcoseno. Un ACP mostró grupos de los materiales usados. Sólo la composición de nidos fue diferente entre tipos de materiales (F3,1312  = 2637.26, P < 0.001) siendo el MVE y MSU mayormente representados 1.28 ± 0.016 y 0.24 ± 0.016 (media del arcoseno ± EE). Dos componentes explicaron el 93.2% de la variación. El CP1 (2.2203 eigenvalor) se relacionó con el peso del MOA y el MAN, y el CP2 (1.5077 eigenvalor) con el MVE. Se concluye que las aves usaron mayor MVE en sus nidos con fines estructurales y de revestimiento, independientemente del ambiente urbano o periurbano

Explaining the causes of cell death in cyanobacteria: what role for asymmetric division?

Cyanobacteria contribute a significant fraction of global primary production and are therefore of great ecological significance. An individual cyanobacteria cell has four potential fates: to divide, perhaps after a dormant period, to be eaten, to undergo viral lysis, or to undergo cell death. In some studies, cyanobacteria cell death has been classified as programmed cell death, borrowing a concept more widely known in metazoan cells, and there are various biochemical parallels to support such a categorisation. However, at the same time there is a growing awareness of asymmetric division as a fundamental process in bacterial division which can result in non-equal daughter cells with differing fitness. Thanks to recent theoretical and experimental advances it is now possible to explore cyanobacteria cell death in the light of asymmetric division and to test hypotheses on the ultimate causes of cyanobacterial cell death. Assessing the degree of protein damage within individual cells during population growth is a sensible initial research target as is the application of techniques which allow the tracking of cell lineages. The existence of asymmetric division in cyanobacteria is likely given its suggested ubiquity across the bacterial domain of life. It will be technically difficult to test the interaction of asymmetric division with environmental variability, and how that leads to individual cell death via differing susceptibilities to environmental stress. However, testing such ideas could confirm asymmetric division as the ultimate cause of cell death in cyanobacteria and thereby allow a better understanding of the patterns of cell death in natural populations