Especificacion y Poder del Metodo de Estudio de eventos en el largo plazo: Una aplicacion con retornos mensuales argentinos.

67 p.El objetivo de un estudio de eventos es cuantificar el efecto de un evento en el valor de mercado de las acciones que componen el patrimonio de una empresa. Con el fin de validar dicha metodología en mercados de capitales poco profundos, el presente estudio utiliza el enfoque de simulación de Brown y Warner con datos mensuales del mercado accionario Argentino. Se examina el poder y la especificación de los tests paramétricos utilizados frecuentemente en la metodología de estudio de eventos: El Test t Estandarizado, el Test t de Corte Transversal y el de Portafolio. Se analizaron 250 muestras de 50 acciones cada una, seleccionadas de forma aleatoria y con repetición, obtenidas de la Bolsa de Valores Argentina. A través del Software Eventuspro* se simula el efecto de un “evento económico” sobre el rendimiento de los activos que componen dichas muestras. Con esto se busca analizar la especificación de los tres tests paramétricos y el poder para detectar los diferentes niveles de retorno anormal introducidos en las muestras. Pese a la evidencia sobre de la existencia de sesgos que provocarían siempre una mala especificación de los tests paramétricos que utilizan datos mensuales, en el caso del mercado de capitales argentino esto no se cumple ya que, la combinación óptima que mejora la especificación en todos los periodos estudiado es el test-t de portafolio a un nivel de significancia del 5% basado en los retornos generados por el Modelo de Ajuste al Mercado. En términos de poder predictivo del test paramétrico, el test-t estandarizado, a un nivel de significancia del 5%, es el más poderoso. Sin embargo, si tomamos en cuenta sólo aquellos tests que se encuentran bien especificados para una ventana de un mes encontramos que el test con más poder es el de corte transversal, a un nivel de significancia del 5%

Advanced Computational Fluid Dynamics Study of the Dissolved Oxygen Concentration within a Thin-Layer Cascade Reactor for Microalgae Cultivation

High concentration of dissolved oxygen within microalgae cultures reduces the performance of corresponding microalgae cultivation system (MCS). The main aim of this study is to provide a reliable computational fluid dynamics (CFD)-based methodology enabling to simulate two relevant phenomena governing the distribution of dissolved oxygen within MCS: (i) mass transfer through the liquid–air interface and (ii) oxygen evolution due to microalgae photosynthesis including the inhibition by the same dissolved oxygen. On an open thin-layer cascade (TLC) reactor, a benchmark numerical study to assess the oxygen distribution was conducted. While the mass transfer phenomenon is embedded within CFD code ANSYS Fluent, the oxygen evolution rate has to be implemented via user-defined function (UDF). To validate our methodology, experimental data for dissolved oxygen distribution within the 80 meter long open thin-layer cascade reactor are compared against numerical results. Moreover, the consistency of numerical results with theoretical expectations has been shown on the newly derived differential equation describing the balance of dissolved oxygen along the longitudinal direction of TLC. We argue that employing our methodology, the dissolved oxygen distribution within any MCS can be reliably determined in silico, and eventually optimized or/and controlled

Performance of prognostic index in severe Clostridium difficile-associated infection. Retrospective analysis in a university hospital

Indexación: ScieloIntroducción: Por consenso, la infección asociada a Clostridium difficile (IACD) grave es aquella que resulta en hospitalización en unidad de cuidados intensivos, colectomía o muerte dentro de 30 días. Múltiples índices pronósticos (IP) intentan predecir estos eventos adversos. Objetivo: evaluar el rendimiento de cuatro IP en la predicción de IACD grave. Metodología: pacientes hospitalizados ≥ 18 años con IACD fueron evaluados retrospectivamente. Se excluyeron pacientes con infección recurrente o cáncer hematológico. Se evaluaron cuatro IP: UPMC versión 1, Calgary versión 1, Hines VA y Calgary versión 2. Resultados: Siete de 81 pacientes (8,1%) presentaron una IACD grave. El valor predictor positivo (VPP) y valor predictor negativo (VPN) de los IP varió entre 20-75% y 91,3-95,7%, respectivamente. Sólo el índice de Hines VA tuvo un índice Kappa satisfactorio (0,74;IC 95% 0,46-1) con un VPP de 75% y un VPN de 95,7%. Sin embargo, por las variables incluidas en este IP, sólo pudo ser calculado en 32,6% de los pacientes. Conclusión: El índice de Hines VA presenta el mejor valor predictor y concordancia para descartar una IACD grave. Como otros IP, tiene la limitación de incluir variables difícilmente evaluables en todos los pacientes y tiende a sobreestimar un curso desfavorable.Introduction: By consensus severe, Clostridium difficile-associated infection (CDAI) is one that results in hospitalization in ICU, colectomy or death within 30 days. Multiple prognostic indices (IP) attempt to predict these adverse events. Objective: To evaluate the performance of 4 PI in predicting severe CDI. Methods: Hospitalized patients ≥ 18 years old with ICD were retrospectively evaluated. Patients with recurrent infection or hematological cancer were excluded. Four PI were evaluated: UPMC version 1, Calgary version 1, Hines VA and Calgary version 2. Results: Seven of 81 patients (8.1%) met the definition of severe CDI. Positive predicted value (PPV) and negative predicted value (NPV) of PI ranged from 20-75% and 91.3-95.7%, respectively. Only Hines VA index had a satisfactory Kappa index (0.74; 95% CI 0.41-1) with a PPV of 75% and NPV of 95,7%. However, because of the variables included, this PI could be calculated only in 32.6% of patients. Conclusion: Hines VA index has the best predicted value and agreement to rule out a severe CDI. Like others PI it has the limitation of including difficult variables to assess in all patients and tends to overestimate an unfavorable course.http://www.scielo.cl/pdf/rci/v31n6/art03.pd

Mapping aluminum tolerance loci in cereals: A tool available for crop breeding

Aluminum (Al) toxicity is the main factor limiting crop productivity in acidic soils around the world. In cereals, this problem reduces crop yields by 30-40%. The use of DNA-based markers linked to phenotypic traits is an interesting alternative approach. Strategies such as molecular marker-assisted selection (MAS) in conjunction with bioinformatics-based tools such as graphical genotypes (GGT) have been important for confirming introgression of genes or genomic regions in cereals but also to reduce the time and cost of identifying them through genetic selection. These biotechnologies also make it possible to identify target genes or quantitative trait loci (QTL) that can be potentially used in similar crops to increase their productivity. This review presents the main advances in the genetic improvement of cereals for Al-tolerance

Historical warming consistently decreased size, dispersal and speciation rate of fish

There is ongoing debate as to whether fish body size will decrease with global warming and how these changes may impact dispersal ability and speciation rate. Theory predicts that, under warmer temperatures, fish grow to a smaller size, undergo a reduction in dispersal ability and increase speciation rates. However, evaluations of such predictions are hampered owing to the lack of empirical data spanning both wide temporal and geographical scales. Here, using phylogenetic methods, we show that smaller clupeiform fish (anchovies and herrings) occurred historically in warmer waters, moved the shortest distances at low speed and displayed the lowest speciation rates. Furthermore, fish moved faster and evolved rapidly under higher rates of temperature change but these historical rates are far lower than current warming rates. Our results predict a future where smaller clupeiform fish that have reduced ability to move will be more prevalent; this, in turn, may reduce future speciation

Global dataset on seagrass meadow structure, biomass and production

Seagrass meadows provide valuable socio-ecological ecosystem services, including a key role in climate change mitigation and adaption. Understanding the natural history of seagrass meadows across environmental gradients is crucial to deciphering the role of seagrasses in the global ocean. In this data collation, spatial and temporal patterns in seagrass meadow structure, biomass and production data are presented as a function of biotic and abiotic habitat characteristics. The biological traits compiled include measures of meadow structure (e.g. percent cover and shoot density), biomass (e.g. above-ground biomass) and production (e.g. shoot production). Categorical factors include bioregion, geotype (coastal or estuarine), genera and year of sampling. This dataset contains data extracted from peer-reviewed publications published between 1975 and 2020 based on a Web of Science search and includes 11 data variables across 12 seagrass genera. The dataset excludes data from mesocosm and field experiments, contains 14271 data points extracted from 390 publications and is publicly available on the PANGAEA® data repository (10.1594/PANGAEA.929968; Strydom et al., 2021). The top five most studied genera are Zostera, Thalassia, Cymodocea, Halodule and Halophila (84 % of data), and the least studied genera are Phyllospadix, Amphibolis and Thalassodendron (2.3 % of data). The data hotspot bioregion is the Tropical Indo-Pacific (25 % of data) followed by the Tropical Atlantic (21 %), whereas data for the other four bioregions are evenly spread (ranging between 13 and 15 % of total data within each bioregion). From the data compiled, 57 % related to seagrass biomass and 33 % to seagrass structure, while the least number of data were related to seagrass production (11 % of data). This data collation can inform several research fields beyond seagrass ecology, such as the development of nature-based solutions for climate change mitigation, which include readership interested in blue carbon, engineering, fisheries, global change, conservation and policy

Towards situated practices for disaster risk reduction (DRR): Indigenous counter-mapping in Saavedra, Chile

The tsunami of 1960 (after the magnitude 9.5. earthquake in Valdivia) is considered one of the most powerful disasters ever recorded, and the implications of this event have been comprehensively studied in terms of fatalities, monetary costs, and infrastructure damage, among others. This article reflects on the tsunami not as a single event, but as the beginning of a chronic disaster that has been occurring over years and decades in rural Saavedra, due to the loss of the best land for both livestock and arable farming since that event. Through a counter mapping approach, this article analyzes how local knowledge has been key to overcoming this disaster, despite intracommunity differences due to intergenerational dynamics. In short, it reveals that this knowledge has not only been useful in enabling Lafkenche communities to be more prepared, but has strengthened situated practices for disaster risk reduction (DRR) in Chile

Decolonizando los Riesgos Naturales: Poder, Territorio y Conocimiento Ancestral en la Comuna de Saavedra, Chile

Resumen Los mapas no corresponden a procesos neutrales ni científicamente objetivos. Son instrumentos históricamente ligados a relaciones de poder, al constituirse en el reflejo material de determinadas visiones sobre el territorio, generalmente impuestas desde una cosmovisión científica occidental dominante. Los mapas de riesgos son un ejemplo empírico de este fenómeno, ya que representan la naturaleza desde un punto de vista técnico-científico, usualmente obviando el conocimiento local y ancestral. Desde la ecología política y a través de un ejercicio de mapeo alternativo, el presente artículo la carta oficial de inundación por tsunami que actualmente existe en Saavedra (La Araucanía, Chile), relevando la importancia de incorporar el conocimiento ancestral y local lafkenche para decolonizar los riesgos naturales. Palabras claves: Ecología política, territorio, mapeo alternativo, lafkenche Abstract Maps do not correspond to a neutral or scientifically objective process. They are instruments historically linked to relations of power as they represent certain visions of territory, generally imposed by a dominant Western society. Risk maps are an empirical example since they represent nature from a technical-scientific point of view, usually not considering ancestral and local knowledge. From a political ecology perspective and through an alternative mapping exercise this article analyses the official tsunami inundation map that currently exists in Saavedra (Araucanía Region, Chile), revealing the importance of considering both the ancestral and local knowledge of the lafkenche people in order to decolonize natural risks. Keywords: Political ecology, territory, alternative map, lafkench