¿Multiplicación y división "o" cambio de unidad?

Este artículo es un resultado de la investigación “El pensamiento multiplicativo: una mirada de su densidad y complejidad en su desarrollo en el aula” cofinanciado, en la fase actual, por la Universidad Distrital Francisco José de Caldas, COLCIENCIAS e IDEP. En el aparte 1, además de ubicarel propósito de este artículo, explicitamos solo algunos aspectos metodológicos y teóricos de la investigación que, pensamos, sirven para definir el contexto de sentido para los datos que usaremos en el aparte 2

Mechanical Properties of Thin-Film Composite Membranes and Their Role in Osmotic Processes

My research goal was to understand the role of membrane mechanical properties (e.g. strength and stiffness) in the transport of water and salt through polymer-based thin-film composite (TFC) membranes used for osmotic processes (OP). OP are membrane processes in which the main driving force is a concentration difference of solute(s) in the solutions in contact with the two sides of a semipermeable membrane. OP applications may include removing water from products/contaminants, harvesting energy from salinity gradients, and lowering costs of seawater desalination. The study system for my research was a set of TFC reverse osmosis (RO) membranes designed for rejecting salts in desalination. These TFC RO membranes have thick supporting layers (~150 μm), which increases the diffusion pathway for salts within the membranes. This decreases the effective salinity gradient between the two surfaces of the membrane active layer, which ultimately decreases the process productivity (i.e., water flux). I aimed to provide guidelines for the improved design of TFC membranes for OP, considering the trade-off between membrane mechanical integrity and productivity. My research approach comprised measurements and analysis of the individual mechanical properties of the three polymeric layers (active, porous support, and backing) that comprise TFC RO membranes, and correlation of these mechanical properties with TFC membrane transport properties and performance in OP. Initially, I studied helically coiled and multiwall carbon nanotubes as additives to create nanocomposite porous supports with improved mechanical properties. The results support the idea that increasing the mechanical stiffness of TFC membrane nanocomposite supports is an effective strategy for enhancing water production in desalination operations. Secondly, I evaluated woven polyester mesh as a backing layer and analyzed the role of mesh opening size on burst strength and mass-transfer resistance of TFC membranes used for OP. The findings show that mass-transfer resistances in OP are an additive effect of the multiple layers that compose a membrane and can be reduced by using more open (yet functional) backing layers such as polyester woven mesh in place of standard nonwoven mesh. Thirdly, I aimed to correlate the reduction in stiffness of the active layer with the change in water permeance of five commercial TFC membranes after contact with five different C1-C4 monohydric alcohols. The motivation was to explain the improvements in water flux after alcohol contact, which is used to pre wet membranes before OP operation. Correlation of results suggests that the mixing of water with the alcohols facilitates penetration of the alcohols into the active layer, likely by disrupting inter-chain hydrogen bonds, thus increasing the active layer free volume for water permeation. Finally, I studied water and sodium chloride transport through TFC membranes that were subjected to known degrees of mechanical strain. I demonstrated the importance of knowing the stress-strain curve of the membrane and highlighted that stiffer membrane structures are desirable to avoid reaching a strain above the reported onset fracture strain of the selective layer. With this information, I introduced a deformability coefficient and a solution-diffusion model with defects to guide the design of membranes and modules for pressurized osmotic processes. In closing the dissertation, I provided recommendations and research opportunities that I envision would improve TFC membrane productivity in OP

A framework of descriptors to characterize flexibility as a trait of mathematical giftedness

These results are part of the research projects EDU2017-84377-R (AEI / FEDER, EU) of the University of Valencia and 820-CO-081 of the University of Costa Rica

Relación entre nivel de activación y rendimiento en una muestra de atletas adolescentes en pruebas de velocidad

Comunicación presentada al XIV Congreso Andaluz y Iº Internacional Luso-Andaluz de Psicología del Deporte y de la Actividad FísicaEn pruebas de velocidad, en Atletismo, se toma una muestra de 15 Atletas adolescentes, relacionando la toma en conciencia de su nivel óptimo con autohabla y conocimiento, a modo de biofeedback, de sus registros fisiológicos, como medio para mejorar su rendimiento.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech. ASOCIACIÓN PSICOLOGÍA DEL DEPORTE DE ANDALUCÍ

An Asymmetric Index to Compare Trapezoidal Fuzzy Numbers

In this paper, we present a tool to help reduce the uncertainty presented in the resource selection problem when information is subjective in nature. The candidates and the "ideal" resource required by evaluators are modeled by fuzzy subsets whose elements are trapezoidal fuzzy numbers (TrFN). By modeling with TrFN the subjective variables used to determine the best among a set of resources, one should take into account in the decision-making process, not only their expected value, but also the uncertainty that they reflect. Respecting this condition, for each candidate an asymmetric index evaluates the distance between the TrFNs for each of the variables and the corresponding TrFNs of the "ideal" candidate, consolidating them through a weighted average that lets the decision-maker make the final comparison between the candidates, and the selection of the one best suited. We apply this contribution to the case of the selection of the product that is best suited for a "pilot test" to be carried out in some market segment

ESTABLECIMIENTO, MICROPROPAGACION Y ENRAIZAMIENTO IN VITRO DE GRANADILLA (PASSIFLORA LIGULARIS JUSS)

Proyecto de Investigación. Instituto Tecnológico de Costa Rica. Escuela de Biología. Centro de Investigación en Biotecnología (CIB), 2004El cultivo de la granadilla es una opción para los productores de la zona de los Santos, ya que en años anteriores se han tenido experiencias de exportación de fruta a nivel internacional, incluyendo países como Canadá y Alemania. Sin embargo entre los principales problemas que deben ser atendidos se menciona la heterogeneidad de las plantaciones, el bajo rendimiento y la mala calidad del producto, provocando la disminución de los volúmenes de exportación. La multiplicación in vitro favorecería enormemente la explotación de este cultivo, ya que permitiría el establecimiento de plantaciones más homogéneas y contribuiría a mejorar la calidad del fruto. Además es importante resaltar que esta técnica también permite la conservación del germoplasma, contribuyendo a evitar la erosión genética de la especie. En esta investigación la selección de plantas en campo se realizó con base en la productividad y la calidad del fruto. Las estacas colectadas presentaron de tres a cuatro nudos, un largo de 30 a 40 cm y un diámetro aproximado de 1 ½ a 2 cm, las cuales fueron trasladadas al invernadero. El sustrato utilizado en la siembra de las estacas consistió de tierra con un alto contenido de materia orgánica, en una relación de 3:1, previamente desinfectado con Vitavax®. Se logró hasta un 75% de enraizamiento y brotación de las estacas. Para el establecimiento in vitro los mejores resultados se obtuvieron con el material proveniente de invernadero, el cual fue desinfectado con una mezcla de Agrimicín y Benlate 5g L –1 cada uno y una segunda desinfección con Hipoclorito de Sodio al 50% producto comercial. El medio de cultivo utilizado fue un M&S suplementado con 3mg L -1 de 6- Bencil Amino Purina. Se logró un 21% de explantes limpios y brotados. Para la multiplicación in vitro, los explantes se subcultivaron en el mismo medio empleado en la etapa de introducción. Se observó una elongación de los brotes. Las etapas de desarrollo y enraizamiento no se realizaron, debido a la poca disponibilidad de material en la etapa de multiplicación

A Multi-Criteria Vertical Coordination Framework for a Reliable Aid Distribution

Purpose: This study proposes a methodology that translates multiple humanitarian supply chain stakeholders’ preferences from qualitative to quantitative values, enabling these preferences to be integrated into optimization models to ensure their balanced and simultaneous implementation during the decision-making process. Design/methodology/approach: An extensive literature review is used to justify the importance of developing a strategy that minimizes the impact of a lack of coordination on humanitarian logistics decisions. A methodology for a multi-criteria framework is presented that allows humanitarian stakeholders’ interests to be integrated into the humanitarian decisionmaking process. Findings: The findings suggest that integrating stakeholders’ interests into the humanitarian decision-making process will improve its reliability. Research limitations/implications: To further validate the weights of each stakeholder’s interests obtained from the literature review requires interviews with the corresponding organizations. However, the literature review supports the statements in this paper. Practical implications: The cost of a lack of coordination between stakeholders in humanitarian logistics has been increasing during the last decade. These coordination costs can be minimized if humanitarian logistics’ decision-makers measure and simultaneously consider multiple stakeholders’ preferences. Social implications: When stakeholders’ goals are aligned, the humanitarian logistics response becomes more efficient, increasing the quality of delivered aid and providing timely assistance to the affected population in order to minimize their suffering. Originality/value: This study provides a methodology that translates humanitarian supply chain stakeholders’ interests into quantitative values, enabling them to be integrated into mathematical models to ensure relief distribution based on the stakeholders’ preferences.Peer Reviewe

Sequence variability of Rhizobiales orthologs and relationship with physico-chemical characteristics of proteins

<p>Abstract</p> <p>Background</p> <p>Chromosomal orthologs can reveal the shared ancestral gene set and their evolutionary trends. Additionally, physico-chemical properties of encoded proteins could provide information about functional adaptation and ecological niche requirements.</p> <p>Results</p> <p>We analyzed 7080 genes (five groups of 1416 orthologs each) from Rhizobiales species (<it>S. meliloti, R. etli</it>, and <it>M. loti</it>, plant symbionts; <it>A. tumefaciens</it>, a plant pathogen; and <it>B. melitensis</it>, an animal pathogen). We evaluated their phylogenetic relationships and observed three main topologies. The first, with closer association of <it>R. etli </it>to <it>A. tumefaciens</it>; the second with <it>R. etli </it>closer to <it>S. meliloti</it>; and the third with <it>A. tumefaciens </it>and <it>S. meliloti </it>as the closest pair. This was not unusual, given the close relatedness of these three species. We calculated the synonymous (dS) and nonsynonymous (dN) substitution rates of these orthologs, and found that informational and metabolic functions showed relatively low dN rates; in contrast, genes from hypothetical functions and cellular processes showed high dN rates. An alternative measure of sequence variability, percentage of changes by species, was used to evaluate the most specific proportion of amino acid residues from alignments. When dN was compared with that measure a high correlation was obtained, revealing that much of evolutive information was extracted with the percentage of changes by species at the amino acid level. By analyzing the sequence variability of orthologs with a set of five properties (polarity, electrostatic charge, formation of secondary structures, molecular volume, and amino acid composition), we found that physico-chemical characteristics of proteins correlated with specific functional roles, and association of species did not follow their typical phylogeny, probably reflecting more adaptation to their life styles and niche preferences. In addition, orthologs with low dN rates had residues with more positive values of polarity, volume and electrostatic charge.</p> <p>Conclusions</p> <p>These findings revealed that even when orthologs perform the same function in each genomic background, their sequences reveal important evolutionary tendencies and differences related to adaptation.</p> <p>This article was reviewed by: Dr. Purificación López-García, Prof. Jeffrey Townsend (nominated by Dr. J. Peter Gogarten), and Ms. Olga Kamneva.</p

Optimización multiobjetivo del diseño de un casco de submarino

A synthesis model for the concept design of a submarine is developed consisting of a parametric definition of the hull geometry, a maneuverability model based on slender-body theory, and a resistance formulation. This coupled model is suitable to be treated by a metaheuristic multiobjective optimization technique (a genetic algorithm) to find a set of design options that satisfy the need to minimize simultaneously the turning diameter and the resistance generated. According to typical data found in submarines like the one analyzed herein, the boundaries and some constraints are set for the design variables. Finally, some solutions for this design case are obtained considering the criteria adopted in this study.Se desarrolla un modelo de s.ntesis para el dise.o conceptual del casco de un submarino teniendo en cuenta una definición paramétrica de la geometría del casco, un modelo de maniobrabilidad basado en teoría de cuerpo esbelto y una formulación de resistencia al avance. Este modelo es incorporado a una técnica de optimización multiobjetivo metaheurística (un algoritmo genético) con el fin de encontrar un conjunto de opciones de diseño que satisfagan la necesidad de minimizar simultáneamente el diámetro de giro y la fuerza de resistencia generada. Considerando algunos valores comunes en el tipo de diseño aquí analizado, se establecen los límites de las variables de diseño, así como algunas restricciones. Finalmente, se presentan algunas soluciones para este caso de diseño contando con el desempeño obtenido para los dos criterios aquí estudiados