Incursiones de la metaliteratura en lo fantástico: a propósito de la metalepsis en Hispanoamérica

Conferencias y Comunicaciones del primer Congreso Internacional de literatura fantástica y ciencia ficción, celebrado del 6 al 9 de mayo de 2008 en la Universidad Carlos III de Madri

Numerical evaluation of the Green's functions for arbitrarily shaped cylindrical enclosures and their optimization by a new spatial images method

IIn this paper, a spatial image technique is used to efficiently calculate the mixed potential Green’s functions associated with electric sources, when they are placed inside arbitrarily shaped cylindrical cavities. The technique is based on placing electric dipole images and charges outside the cavity region. Their strength and orientation are thencalculated by imposing the appropriate boundary conditions for the fields at discrete points on the metallic wall. A method for the assessment of the potentials accuracy is proposed, and several optimization techniques are presented. Three cavities are analyzed to demonstrate the usefulness of the techniques. The cutoff frequencies and potentials patterns are compared to those obtained by a standard finite elements technique, showing excellent agreement. Finally, a band-pass filter based on coupled lines is analyzed, demonstrating the practical value of the technique.This work has been developed with support from the Spanish National Project (CICYT) with reference TEC2004-04313-C02-02/TCM, and the Regional Seneca Project with reference 02972/PI/0

Quality Management Systems for Laboratories and External Quality Assurance Programs

A quality management system (QMS) plans, controls, and improves the elements that impact on the achievement of the desired results by the laboratory and on the satisfaction of the users. There are different standards that establish requirements for the implementation of a quality management system for laboratories, and a cross comparison between them is shown. Additionally, external quality assurance or assessment (EQA) programs offer multiple benefits to laboratories: method validation, comparing of results with other laboratories, testing problem identification, accreditation requirement compliance, and credibility. In order to control the quality of the procedures, these programs are a tool to keep the laboratory procedures and every variable involved in (staff, equipment, and method) well controlled. In the frame of a quality management system, benefits from external quality assurance programs are discussed, and different available designs are reviewed. On the other hand, previous benefits will be real only if reported results for each program are analyzed in detail. Because additional advantages are achieved when the EQA results are integrated in the quality management system of the laboratory, a procedure is proposed. In addition, results from external quality assurance programs corroborate the usefulness of internal controls implemented by the laboratory as part of its quality management system

Efficient Calculation of the Green's Functions for Multilayered Shielded Cavities with Right Isosceles-Triangular Cross-Section

An efficient calculation of the Green’s functions inside multilayered shielded cavities with right isosceles-triangular cross-section is presented. The method is entirely developed in the spatial domain, and it is based on image theory. The idea is to use the spatial-domain Green’s functions inside a multilayered shielded square box, in order to accurately obtain the Green’s functions for the right isosceles-triangular cavity. Image theory is then used to enforce the boundary conditions along the non-equal side of the triangle. It is shown that the new algorithm is very robust, with limited computational effort. Resonance frequencies and potential patterns of a triangular cavity have been calculated and compared with those obtained by other techniques, showing very good agreement. Finally, a transversal filter inside a multilayered triangular-shaped cavity is designed, manufactured and tested using the developed technique.This work was partially supported by the Spanish Ministry of Education and Science under Grant FPU-AP2006-015 and with the Project TEC2007-67630-C03-02

Co-assessment in higher education: The perception of first-year students

Es imprescindible implicar al alumnado en la evaluación para fomentar su aprendizaje. La modalidad participativa más desconocida es la coevaluación o evaluación compartida. Teniendo en consideración el uso polisémico del concepto coevaluación en español, en este estudio se entiende como aquella evaluación negociada entre docentes y estudiantes donde la responsabilidad es compartida y en la que es imprescindible el diálogo. En la literatura específica se destaca que esta modalidad favorece el aprendizaje autónomo y la autorregulación. Para contrastar con la realidad las consecuencias de la evaluación compartida se ha desarrollado una experiencia que implicó a 192 estudiantes universitarios de primer curso durante tres años académicos. Tras su implantación, se realizó un estudio descriptivo mediante un cuestionario on-line para analizar la potencialidad para el aprendizaje, comprobar el grado de satisfacción del alumnado y conocer los aspectos positivos y negativos que detectaron los estudiantes. En los resultados se puede comprobar la elevada satisfacción del alumnado con la coevaluación. Los participantes consideran que la mayor potencialidad para el aprendizaje proviene de la importancia de la retroalimentación que se ofrece, ya que permite ser más conscientes de los errores y aprender de ellos. Igualmente, otros elementos positivos detectados fueron la colaboración y la comunicación entre docente y estudiantes, así como la formación sobre el proceso de evaluación. Es imprescindible continuar con la implantación e indagación de evaluaciones basadas en el diálogo y en compartir significados en el contexto universitario, que permitan a los estudiantes mejorar sus aprendizajes y a los docentes optimizar y flexibilizar sus estrategias de enseñanzaParticipative assessment strategies such as self-assessment, peer assessment and co-assessment enhance student learning. Co-assessment is the least known participative strategy. Considering the polysemous use of the word co-assessment in the Spanish literature in this study the concept is defined and understood as a teacher-student negotiated assessment where the responsibility of assessment is shared and dialogue is key. Co-assessment promotes self-regulated and autonomous learning according to the specific literature. To analyse the consequences of co-assessment a three-year study involving 192 first-year students was implemented. An on-line survey was applied to analyse the learning potentialities of co-assessment, students’ satisfaction with the experience and the positive and negative aspects perceived. The results show high student satisfaction. Most participants consider a learning potentiality the importance of the feedback provided when implementing co-assessment since it allows them to find out their mistakes and learn from them. Likewise, other positive aspects mentioned include the collaboration and communication established among teachers and students and an increasing of assessment literacy. The authors of the study believe it is important to continue with the implementation and research of dialogue-based assessment practices and in sharing meanings in Higher Education, which might allow students to enhance their learning and teachers to optimise and increase the adaptability of their teaching and learning strategie

Expressive power and complexity of a logic with quantifiers that count proportions of sets

We present a second-order logic of proportional quantifiers, SOLP, which is essentially a first-order language extended with quantifiers that act upon second-order variables of a given arity r and count the fraction of elements in a subset of r-tuples of a model that satisfy a formula. Our logic is capable of expressing proportional versions of different problems of complexity up to NP-hard as, for example, the problem of deciding if at least a fraction 1/n of the set of vertices of a graph form a clique; and fragments within our logic capture complexity classes as NL and P, with auxiliary ordering relation. When restricted to monadic second-order variables, our logic of proportional quantifiers admits a semantic approximation based on almost linear orders, which is not as weak as other known logics with counting quantifiers (restricted to almost orders), for it does not have the bounded number of degrees property. Moreover, we show that, in this almost-ordered setting, different fragments of this logic vary in their expressive power, and show the existence of an infinite hierarchy inside our monadic language. We extend our inexpressibility result of almost-ordered structure to a fragment of SOLP, which in the presence of full order captures P. To obtain all our inexpressibility results, we developed combinatorial games appropriate for these logics, whose application could go beyond the almost-ordered models and hence are interesting by themselves.Peer ReviewedPreprin

Análisis de las calificaciones compartidas en la modalidad participativa de la evaluación colaborativa entre docente y estudiantes

Current trends in educational assessment in different branches of higher education share the common goal of uniting learning with assessment. Most approaches and theoretical and practical developments in this field revolve around four main factors: feedback, democratization, alignment and relevance. This paper proposes the use of co-assessment as a means of ensuring dialogue-based, democratic and fairer evaluations. With co-assessment, the responsibility is shared by the teacher and the students, who negotiate and agree on the appraisal of student tasks and, in this paper, also on the awarded mark. The aim of this study is to analyse the relationship between a series of jointly agreed marks, following the co-assessment of four tasks, and the marks that the teachers and students would each have individually awarded. Two teachers and 100 students participated in the study, which follows a correlational design and analyses significant statistical differences. The results show a strong correlation between the jointly agreed marks and those assigned individually by the teacher, even though statistically significant differences were found between them. Conversely, no statistically significant differences were identified between the joint marks and the marks assigned individually by the students. These results call for reflection on the real possibility of adapting shared grading methods to students in university frameworks, where the repercussions of awarded marks go far beyond formative goals.Dentro de la variedad existente en las tendencias actuales sobre la evaluación de estudiantes, se encuentra el propósito común de relacionar evaluación y aprendizaje. La retroalimentación, la democratización, la coherencia y la relevancia son cuatro tópicos aglutinadores sobre los que giran la mayoría de los planteamientos y avances teóricos y prácticos en este ámbito. Como forma concreta de cristalizar una evaluación dialógica, democrática y justa, se propone la modalidad participativa de la evaluación colaborativa en la que docentes y estudiantes se reparten la responsabilidad, negociando y consensuando de forma conjunta el valor de las tareas y en nuestro caso, también la calificación final. El propósito de este estudio, que ha involucrado a un total de 100 alumnos y 2 docentes, es precisamente la comprobación del grado de relación existente entre las calificaciones compartidas de 4 tareas universitarias con las que habrían aportado en solitario el docente y el grupo de estudiantes. Se ha seguido un diseño de investigación correlacional y se ha comprobado la existencia de diferencias significativas. Los resultados muestran la estrecha correlación entre las calificaciones compartidas y las calificaciones del docente, aunque se han hallado diferencias estadísticamente significativas entre estas. Por otro lado, no se han encontrado diferencias entre las calificaciones compartidas y las calificaciones de los estudiantes. Las repercusiones de estos resultados, hacen reflexionar, entre otras cuestiones, sobre la posibilidad real de ajustar dichas calificaciones abiertas a la participación de los estudiantes en contextos universitarios donde las repercusiones sobrepasan de largo el ámbito únicamente formativo

¿Proteínas de origen vegetal o de origen animal?: Una mirada a su impacto sobre la salud y el medio ambiente.

La ingesta adecuada de proteínas resulta crucial para el óptimo funcionamiento del organismo. Según su fuente, las proteínas pueden ser de origen animal o vegetal. Las prime- ras son una excelente fuente de zinc, hierro hemínico, vitami- nas del complejo B y aminoácidos esenciales, se digieren con más facilidad y aportan todos los aminoácidos esenciales. Sin embargo, un alto consumo de proteínas de origen animal se asocia a un mayor riesgo de mortalidad y desarrollo de compli- caciones para la salud cardiovascular. Aunque las proteínas de origen vegetal suelen percibirse como una fuente de proteína incompleta al contener una menor o nula cantidad de alguno de los aminoácidos limitante, es posible obtener proteínas de alta calidad mediante la combinación de fuentes vegetales. Tanto la proteína de origen animal como vegetal son ricas en péptidos funcionales que pueden actuar como factores inmo- numoduladores, antitrombóticos, e hipocolesterolémicos, entre otros. La producción de proteínas vegetales implica un impacto ambiental considerablemente menor, en comparación con la producción de proteínas de origen animal. Por consiguiente, es necesario avanzar en la producción y la promoción de alterna- tivas de alimentos, fuente de proteína vegetal, que suplan las necesidades nutricionales de la población y disminuyan el coste para el medio ambiente asociado a la producción y consumo de proteínas de origen animal.Baltimore Spice Central America Sociedad/ Kerry, Costa Rica.UCR::Vicerrectoría de Docencia::Salud::Facultad de Medicina::Escuela de MedicinaUCR::Vicerrectoría de Docencia::Salud::Facultad de Medicina::Escuela de Nutrició

A new neural network technique for the design of multilayered microwave shielded bandpass filters

In this work, we propose a novel technique based on neural networks, for the design of microwave filters in shielded printed technology. The technique uses radial basis function neural networks to represent the non linear relations between the quality factors and coupling coefficients, with the geometrical dimensions of the resonators. The radial basis function neural networks are employed for the first time in the design task of shielded printed filters, and permit a fast and precise operation with only a limited set of training data. Thanks to a new cascade configuration, a set of two neural networks provide the dimensions of the complete filter in a fast and accurate way. To improve the calculation of the geometrical dimensions, the neural networks can take as inputs both electrical parameters and physical dimensions computed by other neural networks. The neural network technique is combined with gradient based optimization methods to further improve the response of the filters. Results are presented to demonstrate the usefulness of the proposed technique for the design of practical microwave printed coupled line and hairpin filters