Incoherent Exciton Trapping in Self-Similar Aperiodic Lattices

Incoherent exciton dynamics in one-dimensional perfect lattices with traps at sites arranged according to aperiodic deterministic sequences is studied. We focus our attention on Thue-Morse and Fibonacci systems as canonical examples of self-similar aperiodic systems. Excitons progressively extend over the lattice on increasing time and, in this sense, they act as a probe of the particular arrangements of traps in each system considered. The analysis of the characteristic features of their time decay indicates that exciton dynamics in self-similar aperiodic arrangements of traps is quite close to that observed in periodic ones, but differs significatively from that corresponding to random lattices. We also report on characteristic features of exciton motion suggesting that Fibonacci and Thue-Morse orderings might be clearly observed by appropriate experimental measurements. In the conclusions we comment on the implications of our work on the way towards a unified theory of the orderings of matter.Comment: REVTeX 3.0, 10 pages, 2 figures on request from FD-A ([email protected]). Submitted to Phys Rev B. MA/UC3M/11/9

Excitation decay in one-dimensional disordered systems with paired traps

Incoherent transport of excitations in one-dimensional disordered lattices with pairs of traps placed at random is studied by numerically solving the corresponding master equation. Results are compared to the case of lattices with the same concentration of unpaired traps, and it is found that pairing of traps causes a slowdown of the decay rate of both the mean square displacement and the survival probability of excitations. We suggest that this result is due to the presence of larger trap-free segments in the lattices with paired disorder, which implies that pairing of traps causes less disruption on the dynamics of excitations. In the conclusion we discuss the implications of our work, placing it in a more general context.Comment: REVTeX 3.0, 10 pages, 7 figures available on request from FD-A ([email protected]), Universidad Carlos III preprint MA/UC3M/08/9

Fertilizantes elaborados con residuos sólidos orgánicos para la producción de alimentos en la ranchería Yotojoroy en Maicao, La Guajira

El presente proyecto de intervención, se ha llevado a cabo con el propósito de Elaborar fertilizantes con residuos sólidos orgánicos para la producción de alimentos en la ranchería Yotojoroi en Maicao, La Guajira. Desde lo metodológico, el tipo de investigación escogido para el presente estudio es el descriptivo, en tal sentido, el enfoque cualitativo, desde la línea de investigación de la Fundación Universitaria Los Libertadores denominada Globalización y Desarrollo Sostenible, debido a que se enfoca en aspectos pedagógicos y didácticos. procesos en la educación ambiental. Los resultados que se obtengan sobre este proyecto de intervención constituirán un elemento que puede servir de antecedentes para futuras investigaciones e investigadores sobre la variable de estudio (fertilizantes). Los resultados que se esperan obtener son una serie de aportes teóricos y prácticos tanto del contexto real como el académico, basado como aporte al conocimiento científico, donde las estrategias lúdicas son el elemento diferenciador que aporta al mejoramiento de la situación problema identificada.This intervention project has been carried out with the purpose of making fertilizers with organic solid waste for food production in the Yotojoroi ranchería in Maicao, La Guajira. From the methodological point of view, the type of research chosen for the present study is the descriptive one, in this sense, the qualitative approach, from the research line of the Los Libertadores University Foundation called Globalization and Sustainable Development, because it focuses on pedagogical aspects. and didactic. processes in environmental education. The results obtained on this intervention project will constitute an element that can serve as background for future research and researchers on the study variable (fertilizers). The results that are expected to be obtained are a series of theoretical and practical contributions from both the real and the academic context, based as a contribution to scientific knowledge, where playful strategies are the differentiating element that contributes to the improvement of the identified problem situation

Aportes a la sociología de la educación. trayectoria del grupo de estudios de educación media y superior, 2003-2013

Se presenta aquí un estado del arte de la producción académica del Grupo de Estudios de Educación Media y Superior del Departamento de Sociología de la Universidad Nacional de Colombia, en el periodo 2003-2013. A partir de una breve introducción conceptual del “campo” de la sociología de la educación, se identifican los principales aportes a la política educativa en ambos niveles de educación. A continuación se presentan gráficas y cuadros de productividad en las diversas líneas de investigación y un listado de las principales publicaciones del Grupo en artículos, libros, capítulos de libros, publicaciones cortas en medios virtuales y en portalesespecializados en educación superior y política pública

Magnetic Quantum Tunneling: Insights from Simple Molecule-Based Magnets

This article takes a broad view of the understanding of magnetic bistability and magnetic quantum tunneling in single-molecule magnets (SMMs), focusing on three families of relatively simple, low-nuclearity transition metal clusters: spin S = 4 Ni4, Mn(III)3 (S = 2 and 6) and Mn(III)6 (S = 4 and 12). The Mn(III) complexes are related by the fact that they contain triangular Mn3 units in which the exchange may be switched from antiferromagnetic to ferromagnetic without significantly altering the coordination around the Mn(III) centers, thereby leaving the single-ion physics more-or-less unaltered. This allows for a detailed and systematic study of the way in which the individual-ion anisotropies project onto the molecular spin ground state in otherwise identical low- and high-spin molecules, thus providing unique insights into the key factors that control the quantum dynamics of SMMs, namely: (i) the height of the kinetic barrier to magnetization relaxation; and (ii) the transverse interactions that cause tunneling through this barrier. Numerical calculations are supported by an unprecedented experimental data set (17 different compounds), including very detailed spectroscopic information obtained from high-frequency electron paramagnetic resonance and low-temperature hysteresis measurements. Diagonalization of the multi-spin Hamiltonian matrix is necessary in order to fully capture the interplay between exchange and local anisotropy, and the resultant spin-state mixing which ultimately gives rise to the tunneling matrix elements in the high symmetry SMMs (ferromagnetic Mn3 and Ni4). The simplicity (low-nuclearity, high-symmetry, weak disorder, etc..) of the molecules highlighted in this study proves to be of crucial importance.Comment: 32 pages, incl. 6 figure

Height and body-mass index trajectories of school-aged children and adolescents from 1985 to 2019 in 200 countries and territories: a pooled analysis of 2181 population-based studies with 65 million participants

Summary Background Comparable global data on health and nutrition of school-aged children and adolescents are scarce. We aimed to estimate age trajectories and time trends in mean height and mean body-mass index (BMI), which measures weight gain beyond what is expected from height gain, for school-aged children and adolescents. Methods For this pooled analysis, we used a database of cardiometabolic risk factors collated by the Non-Communicable Disease Risk Factor Collaboration. We applied a Bayesian hierarchical model to estimate trends from 1985 to 2019 in mean height and mean BMI in 1-year age groups for ages 5–19 years. The model allowed for non-linear changes over time in mean height and mean BMI and for non-linear changes with age of children and adolescents, including periods of rapid growth during adolescence. Findings We pooled data from 2181 population-based studies, with measurements of height and weight in 65 million participants in 200 countries and territories. In 2019, we estimated a difference of 20 cm or higher in mean height of 19-year-old adolescents between countries with the tallest populations (the Netherlands, Montenegro, Estonia, and Bosnia and Herzegovina for boys; and the Netherlands, Montenegro, Denmark, and Iceland for girls) and those with the shortest populations (Timor-Leste, Laos, Solomon Islands, and Papua New Guinea for boys; and Guatemala, Bangladesh, Nepal, and Timor-Leste for girls). In the same year, the difference between the highest mean BMI (in Pacific island countries, Kuwait, Bahrain, The Bahamas, Chile, the USA, and New Zealand for both boys and girls and in South Africa for girls) and lowest mean BMI (in India, Bangladesh, Timor-Leste, Ethiopia, and Chad for boys and girls; and in Japan and Romania for girls) was approximately 9–10 kg/m2. In some countries, children aged 5 years started with healthier height or BMI than the global median and, in some cases, as healthy as the best performing countries, but they became progressively less healthy compared with their comparators as they grew older by not growing as tall (eg, boys in Austria and Barbados, and girls in Belgium and Puerto Rico) or gaining too much weight for their height (eg, girls and boys in Kuwait, Bahrain, Fiji, Jamaica, and Mexico; and girls in South Africa and New Zealand). In other countries, growing children overtook the height of their comparators (eg, Latvia, Czech Republic, Morocco, and Iran) or curbed their weight gain (eg, Italy, France, and Croatia) in late childhood and adolescence. When changes in both height and BMI were considered, girls in South Korea, Vietnam, Saudi Arabia, Turkey, and some central Asian countries (eg, Armenia and Azerbaijan), and boys in central and western Europe (eg, Portugal, Denmark, Poland, and Montenegro) had the healthiest changes in anthropometric status over the past 3·5 decades because, compared with children and adolescents in other countries, they had a much larger gain in height than they did in BMI. The unhealthiest changes—gaining too little height, too much weight for their height compared with children in other countries, or both—occurred in many countries in sub-Saharan Africa, New Zealand, and the USA for boys and girls; in Malaysia and some Pacific island nations for boys; and in Mexico for girls. Interpretation The height and BMI trajectories over age and time of school-aged children and adolescents are highly variable across countries, which indicates heterogeneous nutritional quality and lifelong health advantages and risks

Heterogeneous contributions of change in population distribution of body mass index to change in obesity and underweight NCD Risk Factor Collaboration (NCD-RisC)

From 1985 to 2016, the prevalence of underweight decreased, and that of obesity and severe obesity increased, in most regions, with significant variation in the magnitude of these changes across regions. We investigated how much change in mean body mass index (BMI) explains changes in the prevalence of underweight, obesity, and severe obesity in different regions using data from 2896 population-based studies with 187 million participants. Changes in the prevalence of underweight and total obesity, and to a lesser extent severe obesity, are largely driven by shifts in the distribution of BMI, with smaller contributions from changes in the shape of the distribution. In East and Southeast Asia and sub-Saharan Africa, the underweight tail of the BMI distribution was left behind as the distribution shifted. There is a need for policies that address all forms of malnutrition by making healthy foods accessible and affordable, while restricting unhealthy foods through fiscal and regulatory restrictions

El audiovisual español como factor coadyuvante de la marca España

El objetivo de este trabajo es determinar el impacto que tiene el Sector Audiovisual Español entendido desde tres perspectivas distintas. Primero como alfabeto universal base del ecosistema mediático digital multimedia. Segundo, como contenido creativo de valor artístico. Y tercero como industria destacada, competitiva y próspera con un enorme potencial en el mercado internacional. Por lo tanto, trataremos de investigar sobre si el Sector Audiovisual reúne los requisitos suficientes en la constitución, defensa y promoción de la marca-país, objetivo de la Marca España puesto que nuestro país se ha convertido durante los primeros años de este siglo en una potencia cultural, deportiva, económica y tecnológica relevante y con una capacidad de influencia más que dilatada, gracias a lo que algunos llaman el poder blando español (NOYA, 2004). Pero, las circunstancias actuales de crisis económica sumado a recientes acontecimientos político-sociales de corrupción y enriquecimiento ilícito nos han enviado varias posiciones atrás en el ranking internacional que miden el prestigio de los países o marca-país. Entre otros informes, revistas científicas y estudios oficiales, destacamos nuestro análisis de la clasificación de la reputación internacional de la Country Bran Index 2012-13 del que deducimos que países cuya económica política de la comunicación (MOSCO, 2006) se ajusta al Modelo Mediterráneo descrito por HALLIN &MANCINI (2008) precisan de organismos como la Marca España, entre otras razones, por la patente vinculación del poder político y los medios de comunicación en la expansión sociocultural (SEGOVIA, 2000). Como conclusión final del trabajo realizado y apoyado en mi experiencia profesional, podemos decir que sí existe una relación intensa entre el sector audiovisual y la imagen país

Programa de mantenimiento preventivo para todos los equipos de la sección de calderas de la planta de Coolechera Cartagena

Para coolechera la calidad de sus productos es la base fundamental de su desarrollo, es por eso que el perfecto funcionamiento y desempeño de las variables que afectan sus procesos son la clave del éxito de cada una de sus líneas de producción. Es por todo lo anterior que un análisis detallado de los sistemas y equipos con los que desarrollan sus productos es fundamental para crecimiento y fortalecimiento de la gran familia de Coolechera, de que se haga necesario el conocimiento de un equipo primordial para la conservación y desarrollo de la leche, como lo son las calderas de vapor. La generación de vapor (calderas), tiene como consecuencia la obtención de energía mecánica y/o eléctrica y calefacción de los procesos industriales. La conducción segura y eficiente de las calderas, el conocimiento de su funcionamiento, operación y mantenimiento, favorecen el aprovechamiento al máximo de su energía, a la vez que minimizan los riesgos operativos del equipo. El costo de los combustibles así como el buen funcionamiento de este equipamiento tienen una relevancia muy importante tanto desde el punto de vista económico como ambiental. Durante el proceso productivo en la planta de tratamiento de leche Coolechera, el vapor es un elemento fundamental, ya que este es utilizado en muchos procesos y etapas del tratamiento de la leche cruda para convertirla en productos aptos para el consumo humano. La utilización del vapor es clave en procesos tales como: Pasteurización, Leche en polvo, Leches ácidas

El trabajo, el derecho y el sindicato

Tesis (Abogado) -- Universidad de Cartagena. Facultad de Derecho y Ciencias Políticas. Programa de Derecho, 1985Análisis suscrito de trabajo en la historia del hombre, con la organización sindical y el derecho al servicio de las clases asalariadas, sus logros en este medio hostil a su propósito de justicia