Pre and post fire carbon dynamics in a Florida Scrub oak

Scrub oak is a xeromorphic shrub ecosystem discontinuously distributed in coastal and inland Florida. It supports a high biodiversity which includes a large number of endangered and threatened species. Its structural features are maintained by a fire return cycle of 7 to 10 years which maintains the biodiversity. Management of fire prone ecosystems such as this raises the question of whether the management strategy contributes to the system being a carbon sink or carbon source over the long-term. We used eddy covariance and biometric approaches to measure carbon dynamics in a Florida scrub oak ecosystem located at Kennedy Space Center in east Central Florida from April 2004 to December 2007. The study site was controlled burned in February 2006. Two years previous to fire, the site experienced average precipitation but drought conditions during the two years after fire. Net ecosystem production (NEP) was 419 g C m-2 yr-1 during the first year of measurements, and the ecosystem incorporated 823 g C m-2 during the 22 months before the fire. Aboveground net primary production (NPP) represented 50% of annual NEP. Carbon released by fire reached 316 g C m-2. Ecosystem respiration (Re) dominated the carbon balance during the first six months after fire, and the ecosystem released an extra 119 g C m-2. However, gross ecosystem production (GEP) increased with leaf area index (LAI) after fire, dominating the carbon balance during the following six months. The ecosystem was a carbon sink of 88 g C m-2 yr-1 during the first year after the fire. Leaf area index (LAI) reached 1.54 m2 m-2 by October 2007 (80% of pre-burn value for the same time period). The scrub oak ecosystem was a continuous carbon sink six months after the fire despite the dominant drought conditions during 2006 – 2007. The ecosystem offset 80% (251 g C m-2) of the carbon released in the fire during the following twenty two months after the fire. Considering the fire return cycle of 7 to 10 years and the fact that the study site and a similar site nearby incorporated more than 400 g C m-2 yr-1 during the two years before fire, this scrub oak is a net carbon sink in the landscape under current management strategies

Indicadores de confort relacionados con el desempeño académico de los estudiantes universitarios

The main objective of this research is to determine which indicators of comfort are related to the academic performance of university students. To achieve this, it was initiated by applying the questionnaire developed by Gento and Vivas (2003) consisting of 94 closed questions under a Likert scale, composed by 5 levels of satisfaction about the comfort conditions of the Institution distributed in 6 dimensions, specifically through stratified random sampling, applied to a sample consisting of 336 students of the Engineering Faculty of the University of Zulia, so it can be said that the present study is correlational, transectional and field type. After applying the questionnaire, the respective statistical analyzes were carried out, starting with the normality tests to determine the specific exams to be applied to study the proposed correlations by dimension and by each one of the indicators in study. Subsequently the respective analyzes were performed, finally finding 17 significant correlations of the 94 questions that were included in the questionnaire, and with this result an Ishikawa diagram was constructed, and it describes the behavior and the relations existing between the variables under study for the students of the faculty of Engineering of the University of Zulia at the moment of the measurements, noting that the dimensions that showed a greater number of significant correlations were the Teaching - Learning Process and Personal Relationships.   Key Words: Comfort Indicators, Academic Performance, Students Satisfaction, Statistical Analysis, Correlation Analysis.La presente investigación tiene como finalidad determinar los indicadores del confort que tienen relación con el desempeño académico de los estudiantes universitarios. Para lograr esto, se inició aplicando el cuestionario desarrollado por Gento y Vivas (2003) que constaba de 94 preguntas cerradas bajo una escala Likert compuesta por 5 niveles de satisfacción con respecto a las condiciones de confort de la Institución, distribuidas en 6 dimensiones, a través de un muestreo aleatorio estratificado, aplicado a una muestra conformada por 336 estudiantes de la Facultad de Ingeniería de la Universidad del Zulia, por lo que se puede decir que el presente estudio es de tipo correlacional, transeccional y de campo. Luego de aplicar el cuestionario, se procedió a realizar los análisis estadísticos respectivos, iniciando por las pruebas de normalidad para determinar las pruebas específicas a aplicar para estudiar las correlaciones planteadas por dimensión y para cada uno de los indicadores. Posteriormente se realizaron los análisis respectivos, encontrando finalmente 17 correlaciones significativas de las 94 preguntas de las que constaba el cuestionario, y con éste resultado se pudo construir un diagrama de Ishikawa que describe el comportamiento y las relaciones de las variables en estudio para los estudiantes de la facultad de Ingeniería de La Universidad del Zulia al momento de la medición, notándose que las dimensiones que evidenciaron un mayor número de correlaciones significativas eran las del Proceso de Enseñanza – Aprendizaje y Relaciones Personales.   Palabras Clave: Confort, Desempeño Académico, Satisfacción Estudiantil, Análisis Estadístico, Análisis de Correlación

PRODEBAR ¿un plan estratégico urbano?

The present investigation aims to establish if the Program for Strategic Development of Barquisimeto (PRODEBAS) complies with the methodology for the formulation of the Strategic Urban (PEU). While it is true that strategic planning has traditionally associated with organizational environments is helpful to understand how it has spread to urban areas. In this regard, we must recognize that the need for urban centers to adapt to the changes allowed the emergence of strategic planning as an instrument of city planning. In this context, this research was methodologically conceived as a descriptive method with field design, supplemented with elements of documentary source. The information was obtained through the techniques of literature review and expert consultation, using guided interviews with individuals directly inherent in the formulation of the program. The analysis showed that PRODEBAS but can not be classified as a USP, it has the virtue of being inspired by the philosophy of strategic planning. We conclude that this program, although it is inspired by the urban planning processes can not be considered a strictly strategic plan. However, it can be said that the city of Barquisimeto has initiated a development path that puts it on par with modern global trends in this area are carried out in recent decades to be able to undertake implementation of a legitimate proposal that meets the needs of the city. La presente investigación tiene como propósito establecer si el Programa para el Desarrollo Estratégico de Barquisimeto (PRODEBAR) cumple con la metodología propia de la formulación de los Planes Estratégicos Urbanos (PEU). Si bien es cierto que tradicionalmente la planificación estratégica se asocia a entornos organizacionales resulta útil comprender cómo ésta se ha extendido hasta el ámbito urbano. Al respecto, es necesario reconocer que la necesidad de los centros urbanos de adaptarse a los cambios permitió que surgiera la planificación estratégica como instrumento de planeación de ciudades. En este marco, se realizó esta investigación concebida metodológicamente como una modalidad descriptiva con diseño de campo, complementada con elementos de origen documental. La información se obtuvo mediante las técnicas de revisión documental y consulta de expertos, utilizando entrevistas guiadas a individuos con inherencia directa en la formulación del Programa. El análisis efectuado evidenció que PRODEBAR si bien no puede ser catalogado como un PEU, tiene la virtud de estar inspirado en la filosofía de la planificación estratégica. Se concluye que este programa, si bien se inspira en los procesos de planificación estratégica urbana, no puede ser considerado un plan estratégico en sentido estricto. No obstante, se puede afirmar que la ciudad de Barquisimeto ha iniciado un camino de desarrollo que lo ubica a la par de las tendencias modernas mundiales que en esta área se llevan a cabo en las últimas décadas al haber logrado emprender la ejecución de una propuesta legítima que atiende a las necesidades de la ciudad

Análisis temático de la investigación en Educación Matemática en España a través de los simposios de la SEIEM

En este trabajo presentamos un análisis temático de los trabajos publicados en las actas de los simposios de la Sociedad Española de Investigación en Educación Matemática (SEIEM) entre 1997 y 2008. Estos trabajos fueron codificados con base en una clasificación conceptual específica a la Educación Matemática. Los resultados de la codificación se analizaron en términos de frecuencias y porcentajes y nos permitieron concluir que la educación secundaria, las matemáticas escolares y la resolución de problemas fueron los focos principales de la investigación en este periodo

Descripción temática de los encuentros de asocolme, 2008-2010

En este trabajo presentamos un análisis temático de los trabajos publicados en las actas de los encuentros de la Asociación Colombiana de Matemática Educativa (ASOCOLME) entre 2008 y 2010. Estos trabajos fueron codificados con base en una clasificación conceptual específica a la Educación Matemática. Los resultados de la codificación se analizaron en términos de frecuencias y porcentajes, distinguiendo aquellos documentos que son de investigación de aquellos que no lo son. Los resultados muestran que los trabajos analizados se centran en la educación básica y media; las matemáticas escolares y otras nociones de Educación Matemática; la geometría, los números y el álgebra; y la resolución de problemas y los sistemas de representación

Combustion Modeling Approach for the Optimization of a Temperature Controlled Reactivity Compression Ignition Engine Fueled with Iso-Octane

In this study, an innovative Low Temperature Combustion (LTC) system named Temperature Controlled Reactivity Compression Ignition (TCRCI) is presented, and a numerical optimization of the hardware and the operating parameters is proposed. The studied combustion system aims to reduce the complexity of the Reaction Controlled Compression Ignition engine (RCCI), replacing the direct injection of high reactivity fuel with a heated injection of low reactivity fuel. The combustion system at the actual state of development is presented, and its characteristics are discussed. Hence, it is clear that the performances are highly limited by the actual diesel-derived hardware, and a dedicated model must be designed to progress in the development of this technology. A Computational Fluid Dynamics (CFD) model suitable for the simulation of this type of combustion is proposed, and it is validated with the available experimental operating conditions. The Particle Swarm Optimization (PSO) algorithm was integrated with the Computational Fluid Dynamic (CFD) software to optimize the engine combustion system by means of computational simulation. The operating condition considered has a relatively high load with a fixed fuel mass and compression ratio. The parameters to optimize are the piston bowl geometry, injection parameters and the boosting pressure. The achieved system configuration is characterized by a wider piston bowl and injection angle, and it is able to increase the net efficiency of 3% and to significantly reduce CO emissions from 0.407 to 0.136 mg

Environmental and biological controls on water and energy exchange in Florida scrub oak and pine flatwoods ecosystems

Scrub oak and pine flatwoods are two contrasting ecosystems common to the humid subtropical climate of Florida. Scrub oak forests are short in stature (<2 m) and occur on well-drained sandy soils, and pine flatwoods are much taller and occur in areas with poorly drained soils. Eddy covariance measurements were made from January 2001 to February 2003 over a scrub oak forest and from January 2002 to February 2003 over an adjacent pine flatwoods located on in central Florida, USA, and exposed to similar atmospheric conditions to evaluate how the dynamics of latent heat (lambda E) and sensible heat (H) exchanges are affected by environmental and biological variables. Annual evapotranspiration (Et) for the scrub oak was 737 and 713 mm in 2001 and 2002, respectively. Et was comparatively higher, 812 mm, in 2002 at the pine flatwoods due to higher soil moisture and leaf area. In both ecosystems, springtime increases in lambda E coincided with increasing leaf area and evaporative demand. However, H was the main energy-dissipating component in the spring due to the seasonal decrease in soil water content in the upper soil profile. In the spring, mean weekly Bowen ratio (beta, i.e. H/lambda E) values reached 1.6 and 1.2 in the scrub oak and pine flatwoods, respectively. With the onset of the summertime rainy season, lambda E became the dominant energy flux and beta fells to < 0.4. In both ecosystems, beta was strongly controlled by the interaction between leaf area and soil moisture. The lowest values of the decoupling coefficient (Omega, 0.2 and 0.25 scrub oak and pine flatwoods, respectively) also occurred during the dry springtime period indicating that surface conductance (g(s)) was the mechanism controlling energy partitioning causing high beta in both ecosystems. Et increases in the spring, when water in the upper soil profile was scarce and strongly retained by soil particles, indicated that plants in both ecosystems obtained water from deeper sources. The results from this research elucidate how energy partitioning differs and is regulated in contrasting ecosystems within the Florida landscape, which is important for refining regional hydrological and climate models

Environmental and biological controls on water and energy exchange in Florida scrub oak and pine flatwoods ecosystems

Scrub oak and pine flatwoods are two contrasting ecosystems common to the humid subtropical climate of Florida. Scrub oak forests are short in stature (\u3c2 \u3em) and occur on well-drained sandy soils, and pine flatwoods are much taller and occur in areas with poorly drained soils. Eddy covariance measurements were made from January 2001 to February 2003 over a scrub oak forest and from January 2002 to February 2003 over an adjacent pine flatwoods located on in central Florida, USA, and exposed to similar atmospheric conditions to evaluate how the dynamics of latent heat (lambda E) and sensible heat (H) exchanges are affected by environmental and biological variables. Annual evapotranspiration (Et) for the scrub oak was 737 and 713 mm in 2001 and 2002, respectively. Et was comparatively higher, 812 mm, in 2002 at the pine flatwoods due to higher soil moisture and leaf area. In both ecosystems, springtime increases in lambda E coincided with increasing leaf area and evaporative demand. However, H was the main energy-dissipating component in the spring due to the seasonal decrease in soil water content in the upper soil profile. In the spring, mean weekly Bowen ratio (beta, i.e. H/lambda E) values reached 1.6 and 1.2 in the scrub oak and pine flatwoods, respectively. With the onset of the summertime rainy season, lambda E became the dominant energy flux and beta fells to \u3c 0.4. In both ecosystems, beta was strongly controlled by the interaction between leaf area and soil moisture. The lowest values of the decoupling coefficient (Omega, 0.2 and 0.25 scrub oak and pine flatwoods, respectively) also occurred during the dry springtime period indicating that surface conductance (g(s)) was the mechanism controlling energy partitioning causing high beta in both ecosystems. Et increases in the spring, when water in the upper soil profile was scarce and strongly retained by soil particles, indicated that plants in both ecosystems obtained water from deeper sources. The results from this research elucidate how energy partitioning differs and is regulated in contrasting ecosystems within the Florida landscape, which is important for refining regional hydrological and climate models

ESTUDIO DE LA INFLUENCIA DE LA ANISOTROPÍA UNIAXIAL EN LAS CURVAS DE MAGNETIZACIÓN DEL Co10Cu90

&nbsp;&nbsp;We studied the influence of uniaxial anisotropy on the magnetization curves of a Co10Cu90 alloy by means of a model that is developed taking into account correction terms for the partition function in the limit of large anisotropy and aligned grains. This result is a sum of terms where the first term is the Brillouin function of quantum paramagnetism. Fitting of our curves to the discussed model was compared with another model that considers the influence of the distribution of magnetic moments and we observe a good agreement. We show that the uniaxial anisotropy is enough to consider its effects on the system.&nbsp;&nbsp;Se estudió la influencia que tiene la anisotropía uniaxial en las curvas de magnetización de la aleación Co10Cu90 con ayuda de un modelo que toma en cuenta términos de corrección para la función de partición en el límite de alta anisotropía y granos alineados. El resultado es una suma de términos en los cuales el primero de ellos es la función de Brillouin del paramagnetismo cuántico. Se hace una comparación de nuestras curvas de magnetización ajustadas con otras, obtenidas en la literatura, en donde se considera la influencia de la distribución de momentos magnéticos y se observa una concordancia adecuada. Se llega a la conclusión de que la anisotropía uniaxial es lo suficientemente predominante como para considerar únicamente sus efectos sobre el sistema

Estudio de la influencia de la anisotropía uniaxial en las curvas de magnetización del Co10Cu90

Se estudió la influencia que tiene la anisotropía uniaxial en las curvas de magnetización de la aleación Co10Cu90 con ayuda de un modelo que toma en cuenta términos de corrección para la función de partición en el límite de alta anisotropía y granos alineados. El resultado es una suma de términos en los cuales el primero de ellos es la función de Brillouin del paramagnetismo cuántico. Se hace una comparación de nuestras curvas de magnetización ajustadas con otras, obtenidas en la literatura, en donde se considera la influencia de la distribución de momentos magnéticos y se observa una concordancia adecuada. Se llega a la conclusión de que la anisotropía uniaxial es lo suficientemente predominante como para considerar únicamente sus efectos sobre el sistema