MODELO ENTIDAD RELACIÓN: UN ANÁLISIS DIDÁCTICO DE LAS DIFICULTADES EN EL MODELADO DE BASES DE DATOS RELACIONALES

El Modelo Entidad Relación, ampliamente aceptado por la comunidad académica, se transforma en uno de los pilares del proceso de modelado de bases de datos dada su flexibilidad y precisión. El estudio de las dificultades con la que se enfrentan los nóveles modeladores es fundamental para mejorar las estrategias de transposición, la planificación de actividades y su secuenciación. El presente artículo toma como base estudiantes de enseñanza media y tecnológica de Informática, y analiza el resultado obtenido en una serie de evaluaciones individuales. Concluimos que las dificultades con algunos conceptos tienden a disminuir a medida que pasa el tiempo y se incrementan las actividades en tanto que otros son de difícil aprendizaje y resistentes al paso del tiempo y las actividades. Pudimos constatar que la forma de expresar la realidad es un elemento que parece incorporar una dificultad extra al proceso de modelado. Vistos los resultados obtenidos, entendemos que se deben considerar tres elementos fundamentales a la hora de trabajar en el área de modelado de las bases de datos: la semántica del problema, trabajar en un currículo en espiral y diferenciar en la evaluación el modelado y diseño de una realidad con y sin una gran riqueza semántica de la misma.PALABRAS CLAVE: Evaluación; Base de Datos; Didáctica de la Informática; EstrategiasENTITY-RELATIONSHIP MODEL: A TRAINING ANALYSIS OF DIFFICULTIES IN MODELING RELATIONAL DATABASESABSTRACTThe Entity Relationship Model, widely accepted by the academic community, becomes one of the pillars of the modeling process database given its flexibility and accuracy. The study of the difficulties which face novice modelers is critical to improving transposition strategies, planning activities and sequencing. This article builds on students in secondary and technological education computing, and analyzes the results obtained in a series of individual assessments. We conclude that the difficulties with some concepts tend to decrease as time passes and activities while others are difficult to learn and resistant over time and activities increase. It was clear that the way to express reality is an element that appears to incorporate an extra difficulty modeling process. Given the results obtained, we understand to consider three key elements when working in the area of modeling databases: the semantics of the problem, working in a spiral curriculum and differentiate in the assessment modeling and design a reality without a semantic richness of it.KEYWORDS: Evaluation; Database; Teaching of Information; Strategie

Legacy mercury and stoichiometry with C, N, and S in soil, pore water, and stream water across the upland‐wetland interface: The influence of hydrogeologic setting

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/99104/1/2012JG002250R_Appendix_C_120728.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/99104/2/jgrg20066.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/99104/3/2012JG002250R_Appendix_B_100903.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/99104/4/2012JG002250R_Appendix_A_100907.pd

Soil Mercury and its Response to atmospheric Mercury Deposition across the Northeastern United States

Terrestrial soil is a large reservoir of atmospherically deposited mercury (Hg). However, few studies have evaluated the accumulation of Hg in terrestrial ecosystems in the northeastern United States, a region which is sensitive to atmospheric Hg deposition. We characterized Hg and organic matter in soil profiles from 139 sampling sites for five subregions across the northeastern United States and estimated atmospheric Hg deposition to these sites by combining numerical modeling with experimental data from the literature. We did not observe any significant relationships between current net atmospheric Hg deposition and soil Hg concentrations or pools, even though soils are a net sink for Hg inputs. Soil Hg appears to be preserved relative to organic carbon (OC) and/or nitrogen (N) in the soil matrix, as a significant negative relationship was observed between the ratios of Hg/OC and OC/N (r = 0.54, P \u3c 0.0001) that shapes the horizonal distribution patterns. We estimated that atmospheric Hg deposition since 1850 (3.97 mg/m2) accounts for 102% of the Hg pool in the organic horizons (3.88 mg/m2) and 19% of the total soil Hg pool (21.32 mg/m2), except for the southern New England (SNE) subregion. The mean residence time for soil Hg was estimated to be 1800 years, except SNE which was 800 years. These patterns suggest that in addition to atmospheric deposition, the accumulation of soil Hg is linked to the mineral diagenetic and soil development processes in the region

Deposition of mercury in forests across a montane elevation gradient: Elevational and seasonal patterns in methylmercury inputs and production

Global mercury contamination largely results from direct primary atmospheric and secondary legacy emissions, which can be deposited to ecosystems, converted to methylmercury, and bioaccumulated along food chains. We examined organic horizon soil samples collected across an elevational gradient on Whiteface Mountain in the Adirondack region of New York State, USA to determine spatial patterns in methylmercury concentrations across a forested montane landscape. We found that soil methylmercury concentrations were highest in the midelevation coniferous zone (0.39 ± 0.07 ng/g) compared to the higher elevation alpine zone (0.28 ± 0.04 ng/g) and particularly the lower elevation deciduous zone (0.17 ± 0.02 ng/g), while the percent of total mercury as methylmercury in soils decreased with elevation. We also found a seasonal pattern in soil methylmercury concentrations, with peak methylmercury values occurring in July. Given elevational patterns in temperature and bioavailable total mercury (derived from mineralization of soil organic matter), soil methylmercury concentrations appear to be driven by soil processing of ionic Hg, as opposed to atmospheric deposition of methylmercury. These methylmercury results are consistent with spatial patterns of mercury concentrations in songbird species observed from other studies, suggesting that future declines in mercury emissions could be important for reducing exposure of mercury to montane avian species.Key PointsTotal mercury and methylmercury concentrations and fluxes are examined across an elevational gradient on an Adirondack, New York mountainMethylmercury concentrations across the elevational gradient are greatest in midelevation coniferous zonesSoil methylmercury concentrations are driven by the internal processing of mercury, rather than external inputs of methylmercuryPlain Language SummaryOnce mercury is emitted into the atmosphere by anthropogenic sources, it can be deposited onto the Earth’s surface. This mercury can then be converted to its toxic form of methylmercury by microbes in the soil and can accumulate in birds, altering physiology, behavior, and reproduction. We examined soils from Whiteface Mountain in the Adirondack region of New York State, USA to determine patterns in the production of methylmercury. We found that methylmercury in soils was highest in the mid‐elevation coniferous forests of the mountain and that the concentration appeared to be driven by soil microbes rather than direct deposition of mercury from the atmosphere. The finding of peak methylmercury at mid‐elevations was consistent with previous studies showing peak bird mercury concentrations at the same elevation. Thus, reductions in methylmercury concentrations in these forests is important to reducing bird mercury concentrations.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/138300/1/jgrg20832_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/138300/2/jgrg20832-sup-0001-2016JG003721-SI.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/138300/3/jgrg20832.pd

Spatial patterns of mercury in biota of Adirondack, New York lakes

We studied the spatial distribution patterns of mercury (Hg) in lake water, littoral sediments, zooplankton, crayfish, fish, and common loons in 44 lakes of the Adirondacks of New York State, USA, a region that has been characterized as a “biological Hg hotspot”. Our study confirmed this pattern, finding that a substantial fraction of the lakes studied had fish and loon samples exceeding established criteria for human and wildlife health. Factors accounting for the spatial variability of Hg in lake water and biota were lake chemistry (pH, acid neutralizing capacity (ANC), percent carbon in sediments), biology (taxa presence, trophic status) and landscape characteristics (land cover class, lake elevation). Hg concentrations in zooplankton, fish and common loons were negatively associated with the lake water acid-base status (pH, ANC). Bioaccumulation factors (BAF) for methyl Hg (MeHg) increased from crayfish (mean log10 BAF = 5.7), to zooplankton (5.9), to prey fish (6.2), to larger fish (6.3), to common loons (7.2). MeHg BAF values in zooplankton, crayfish, and fish (yellow perch equivalent) all increased with increasing lake elevation. Our findings support the hypothesis that bioaccumulation of MeHg at the base of the food chain is an important controller of Hg concentrations in taxa at higher trophic levels. The characteristics of Adirondack lake-watersheds (sensitivity to acidic deposition; significant forest and wetland land cover; and low nutrient inputs) contribute to elevated Hg concentrations in aquatic biota

Incidencias de la Universidad Politécnica Salesiana en la sociedad ecuatoriana

En agosto de 1994, luego de 106 años de acción salesiana en el Ecuador, nace oficialmente la Universidad Politécnica Salesiana, obra que da continuidad a la presencia pastoral-educativa iniciada en Quito, en 1888, cuando los salesianos asumen la responsabilidad del Protectorado Católico de Artes y Oficios e inician el primer Oratorio Festivo. Posteriormente, la acción salesiana se extendió a Riobamba (1891), Cuenca (1893), Gualaquiza (1893), Guayaquil (1902), Manabí (1927), Indanza (1914), Méndez (1915), Macas (1924), Sucúa (1931) y Limón (1936). La educación, para Don Bosco y los salesianos, constituye la mejor opción para el desarrollo de la persona, específicamente de niños y jóvenes, quienes desde su propia realidad y circunstancias son actores de transformación y mejora social, siendo honrados ciudadanos y buenos cristianos. La presencia universitaria salesiana responde a las exigencias actuales de la pastoral juvenil, experiencia que tributa a la continuidad educativa de acompañamiento más allá de la adolescencia, con la voluntad de crear oportunidades de estudios universitarios a personas de los sectores sociales que tradicionalmente no las han tenido. En homenaje a los 25 años de vida institucional y a su memoria histórica, esta edición presenta una síntesis de la presencia e incidencia social de la Universidad Politécnica Salesiana en el Ecuador durante este período, realidad que fue posible gracias el apoyo recibido de las autoridades universitarias, docentes y estudiantes de la Carrera de Comunicación Social en las sedes Cuenca, Quito y Guayaquil, de los integrantes del Grupo de Investigación de Ciencias de la Educación (GICCEE) y del Grupo de Investigación en Comunicación de la Universidad Politécnica Salesiana (GICUPS)

Satisfacción de los estudiantes de la Carrera de Enfermería relacionada con el desempeño docente. Cuenca 2014

ANTECEDENTES: La satisfacción estudiantil es uno de los indicadores de educación más interesantes de analizar. A través de ella es posible entender la realidad educativa desde la perspectiva ciudadana, ya que muchas veces las evaluaciones internas en la práctica no se enfocan en el alumno. OBJETIVO: • Determinar la satisfacción de los estudiantes de la carrera de Enfermería relacionada con el desempeño docente cuenca 2014. MATERIAL Y MÉTODOS: El presente estudio es de tipo cuantitativo se cuenta con un universo de 901 estudiantes matriculados de primero a noveno ciclo; se tomará una muestra aleatoria de 205 estudiantes en base a la fórmula muestral de Pita Fernández. Sobre esta muestra se realizará una encuesta de satisfacción estudiantil que constará de varios ítems relacionados con la práctica docente (aquí se tomará en cuenta la metodología de clase, la aplicación de instrumentos de evaluación, la planificación docente, etc.), ambientes de estudio y de apertura de los directivos de la escuela para con los estudiantes. Los espacios y lapsos para la comunicación entre los actores de la educación, la apertura frente a requerimientos estudiantiles y reclamos que tengan frente al sistema educativo. CONCLUSIONES: La razón de presentar esta investigación radica en permitir identificar el grado de satisfacción de los estudiantes en relación al nivel de preparación de la docencia de los profesores de la carrera de enfermería. Se espera, además de conocer la satisfacción estudiantil, hacer un estudio crítico del sistema educativo universitario.BACKGROUND: Student satisfaction is one of the indicators of education more interesting to analyze. Through it is possible to understand the educational reality from the citizen's perspective, since often internal evaluations in practice do not focus on the student. OBJECTIVE: • Determine the satisfaction of students in the undergraduate course related to teacher performance Basin 2014. MATERIAL AND METHODS: This study is a quantitative type has a universe of 901 students enrolled from first to ninth cycle; A random sample of 205 students based on the sampling formula Pita Fernández will be taken. This shows a student satisfaction survey consisting of several related teaching practice items (here will be taken into account class methodology, application of assessment tools, educational planning, etc.), places of study will be conducted and opening of management school with students. Spaces and periods for communication between stakeholders in education, openness towards student needs and claims to have against the educational system. CONCLUSIONS: The reason for presenting this research lies in allowing identify the level of student satisfaction regarding the level of preparation of teachers teaching career in nursing. It is also to meet student satisfaction, make a critical study of university educational system waitsLicenciado en EnfermeríaCuenc

Concentrations and content of mercury in bark, wood, and leaves in hardwoods and conifers in four forested sites in the northeastern USA.

Mercury (Hg) is deposited from the atmosphere to remote areas such as forests, but the amount of Hg in trees is not well known. To determine the importance of Hg in trees, we analyzed foliage, bark and bole wood of eight tree species at four sites in the northeastern USA (Huntington Forest, NY; Sleepers River, VT; Hubbard Brook, NH; Bear Brook, ME). Foliar concentrations of Hg averaged 16.3 ng g-1 among the hardwood species, which was significantly lower than values in conifers, which averaged 28.6 ng g-1 (p < 0.001). Similarly, bark concentrations of Hg were lower (p < 0.001) in hardwoods (7.7 ng g-1) than conifers (22.5 ng g-1). For wood, concentrations of Hg were higher in yellow birch (2.1-2.8 ng g-1) and white pine (2.3 ng g-1) than in the other species, which averaged 1.4 ng g-1 (p < 0.0001). Sites differed significantly in Hg concentrations of foliage and bark (p = 0.02), which are directly exposed to the atmosphere, but the concentration of Hg in wood depended more on species (p < 0.001) than site (p = 0.60). The Hg contents of tree tissues in hardwood stands, estimated from modeled biomass and measured concentrations at each site, were higher in bark (mean of 0.10 g ha-1) and wood (0.16 g ha-1) than in foliage (0.06 g ha-1). In conifer stands, because foliar concentrations were higher, the foliar pool tended to be more important. Quantifying Hg in tree tissues is essential to understanding the pools and fluxes of Hg in forest ecosystems

Area Efficient Dual-Fed CMOS Distributed Power Amplifier

In this paper, an area-efficient 4-stage dual-fed distributed power amplifier (DPA) implemented in a 0.35 &mu;m Complementary Metal Oxide Semiconductor (CMOS) process is presented. To effectively reduce the area of the circuit, techniques such as using multilevel inductors and closely-placing conventional spiral inductors are employed. Additionally, a novel technique based on stacking inductors one on top of others is implemented. Based on these techniques, a 32% area reduction is achieved compared to a conventional design without a noticeable performance degradation. This reduction could be further exploited as the number of stages of the dual-fed DPA increases

Concentrations of Hg in foliage of dominant species at four sites in the northeastern USA.

<p>Tree species included American beech (BE), yellow birch (YB), red maple (RM), sugar maple (SM), red spruce (RS), white ash (WA), white pine (WP) and balsam fir (BF). Error bars represent the SE of Hg concentrations of three composited samples.</p