RNA interference is ineffective as a routine method for gene silencing in chick embryos as monitored by fgf8 silencing.

The in vivo accessibility of the chick embryo makes it a favoured model system for experimental developmental biology. Although the range of available techniques now extends to miss-expression of genes through in ovo electroporation, it remains difficult to knock out individual gene expression. Recently, the possibility of silencing gene expression by RNAi in chick embryos has been reported. However, published studies show only discrete quantitative differences in the expression of the endogenous targeted genes and unclear morphological alterations. To elucidate whether the tools currently available are adequate to silence gene expression sufficiently to produce a clear and specific null-like mutant phenotype, we have performed several experiments with different molecules that trigger RNAi: dsRNA, siRNA, and shRNA produced from a plasmid coexpressing green fluorescent protein as an internal marker. Focussing on fgf8 expression in the developing isthmus, we show that no morphological defects are observed, and that fgf8 expression is neither silenced in embryos microinjected with dsRNA nor in embryos microinjected and electroporated with a pool of siRNAs. Moreover, fgf8 expression was not significantly silenced in most isthmic cells transformed with a plasmid producing engineered shRNAs to fgf8. We also show that siRNA molecules do not spread significantly from cell to cell as reported for invertebrates, suggesting the existence of molecular differences between different model systems that may explain the different responses to RNAi. Although our results are basically in agreement with previously reported studies, we suggest, in contrast to them, that with currently available tools and techniques the number of cells in which fgf8 gene expression is decreased, if any, is not sufficient to generate a detectable mutant phenotype, thus making RNAi useless as a routine method for functional gene analysis in chick embryos

El apoyo externo a los centros educativos : necesario e incomprendido

En este artículo se da cuenta de uno de los estudios realizados en la Comunidad Canaria en torno a los principales servicios de apoyo externo a los centros educativos, en concreto el referido a los CEP. Se pretendían dos objetivos: la obtención de conocimiento para comprender mejor la naturaleza, funciones, modelos de actuación y condiciones en que se desempeña la labor de asesoramiento; y, la detección de los problemas y necesidades más importantes, ofreciendo recomendaciones para su mejora. Se recogió información, mediante cuestionarios, tanto de los asesores como del profesorado. Las principales conclusiones apuntan a la existencia de un doble divorcio: 1) entre lo que los asesores piensan que deben hacer (funciones más relacionadas con los procesos de desarrollo y mejora de los centros y con la capacitación de las escuelas y el desarrollo profesional del profesorado) que con lo que hasta la fecha han hecho (cubrir las necesidades derivadas del proceso de implantación de la LOGSE, especialmente en el diseño y desarrollo de cursos y en la divulgación de la normativa); 2) entre lo que los asesores creen que hacen y lo que el profesorado percibe de ellos. Se sugiere que los CEP deben retomar su idea original de instituciones al servicio del profesorado y los centros, adquiriendo una mayor autonomía de la Administración.En aquest article s'informa d'un dels estudis realitzats a la Comunitat Canària al voltant dels principals serveis de suport extern als centres educatius, en concret el referit als Centres de Professors (CEP). Es pretenien dos objectius: l'obtenció de coneixement per a comprendre millor la naturalesa, funcions, models d'actuació i condicions en les que es porta a terme la tasca d'assessorament; i, la detecció de les problemàtiques i necessitats més importants, oferint recomanacions per a la seva millora. Es va recollir informació, mitjançant qüestionaris, dels assessors i dels professors. Les principals conclusions apunten a l'existència d'un doble divorci: 1) entre el que els assessors pensen que han de fer (funcions més relacionades amb els processos de desenvolupament i millora dels centres i amb la capacitació de les escoles i el desenvolupament professional del professorat) amb el que fins a la data han fet (cobrir les necessitats derivades del procés d'implantació de la LOGSE, especialment en el disseny i desenvolupament de cursos i en la divulgació de la normativa); 2) entre el que els assessors creuen que fan i el que el professorat percebeix d'ells. Se suggereix que els CEP han de reprendre la seva idea original d'institucions al servei del professorat i dels centres, adquirint una més gran autonomia de l'Administració.In this article we present the results of one of the studies developed about the external support systems to the schools in Canary Islands, especially the one refered to the Teachers' Centers. The study aimed to the following main purposes: to gather information about Teachers' Centers in order to reach a better understanding of the nature, functions, performance models and work conditions of school consultants, and to identify the main needs and problems thei are facing, offering at the time some suggestions for improvement. The main conclusions point to a double divorce 1) between what the school consultants think they should be doing (this is, functions related to school development and improvement, and to teachers' empowement and professional development) and what they are doing to the date (meeting needs related to the process of implementation of the 1990 Educational Act, mainly working in the designing and development of trainning courses for teachers and the dissemination of legal regulations related to the Educational Act); and 2) between what the school consultants think they are doing and what the techaers perceived abouy it. It is suggested that Teachers' Centers should recover the original idea becoming institutions at the service of teachers and schools, geeting more autonomy in their functioning from the Regional Educational Authorities

Evaluación teórica de rccc R-Pirogalo[4]arenos funcionalizados con metales como medio para el almacenamiento de Hidrógeno Molecular ensayos o artículos académicos

In the present study, a theoretical investigation of the potential of various metal-functionalized R-substituted pyrogallol[4]arenes (i.e., M-R-Pyg[4]arene; M = Li+, K+, Na+ and Mg2+; R = methyl and fluoroethyl) as media for molecular hydrogen (H2) storage is reported. Initially, the structural features of the metal-functionalized systems are obtained at the B3LYP/6-311G(d,p) level of theory. Subsequently, the interaction of a H2 molecule with the cations embedded in the cavity of the macrocyclic molecules is described with the B3LYP functional using two basis sets of different flexibility, namely BSA: 6-311G(d,p) for ell atoms, and BSB: 6-311G(d,p) and aug-cc-pVDZ for M-R-Pyg[4]arene and H2, respectively. Notably large BSSE-corrected binding energy values were obtained at the B3LYP/BSB level for the different H2/M-R-Pyg[4]arene complexes spanning the 1.3 – 17.0 kJ/mol range. The resulting values were further refined through two approaches: (i) by employing the functional B97D, which includes a Grimme´s type correction for describing dispersive forces and (ii) by performing MP2 calculations within the frame of the ONIOM approach. Binding energies refined at the MP2 level resulted in an average increment of about ~2.5 kJ/mol when considering all the complexes under investigation. On the other hand, B97D binding energies were found to be overestimated since too large increments (i.e., three- and fourfold with respect to B3LYP values for the case of Li- and Na-functionalized systems, respectively) were observed. For the specific case of the H2/Mg-fluoroethyl-Pyg[4]arene, an adsorption enthalpy (∆H°ads) of -17.6 kJ/mol was estimated by adding the zero point energy and thermal effects computed at 300 K from harmonic vibrational frequencies, obtained at the B3LYP/BSB level. This relatively high adsorption enthalpy suggests that Mg-functionalized R-Pyg[4]arenes can be envisaged as promising systems for molecular hydrogen storage.En el presente estudio se reporta la investigación teórica acerca del potencial de los pirogalol[4]arenos R-sustituidos funcioanlizados con varios metales (M-R-Pyg[4]arenos; M = Li+, K+, Na+ y Mg2+; R = meil y fluoretil) como medio para el almacenamiento de hidrógeno molecular (H2). Como punto de partida, las características estructurales de los sistemas funcionalizados con los metales fueron obtenidos al nivel de teoría B3LYP/6-311G(d,p). Subsecuentemente, la interacción de la molécula de hidrógeno con los cationes integrados en la cavidad de las moléculas macrocíclicas es descrita con el funcional B3LYP usando dos conjuntos base de diferente flexibilidad, BSA: 6-311G(d,p) para todos los átomos, y BSB: 6-311G(d,p) y aug-cc-pVDZ para M-R-Pyg[4]arenos e H2, respectivamente. Los valores obtenidos de las energías de amarre corregidas por el método BSSE usando el nivel de teoría B3LYP/BSB fueron notablemente más altas para los complejos H2/M-R-Pyg[4]areno abarcando el rango entre 1.3 y 17.0 kJ/mol. Estos resultados fueron posteriormente refinados mediante dos aproximaciones: (i) empleando el funcional B97D, el mismo que incluye una corrección de tipo Grimme para la descripción de las fuerzas de dispersión y (ii) realizando cálculos MP2 mediante la utilización del método ONIOM. Las energías de amarre resultantes, usando el nivel MP2, mostraron un incremento de aproximadamente 2.5 kJ/mol al analizar a todos los complejos. Por otra parte, se encontró que las energías de amarre obtenidas usando B97D muestran valores sobrestimados debido a que se evidenciaron incrementos considerablemente grandes (el triple y el cuádruple de os valores obtenidos mediante B3LYP para los casos de los sistemas funcionalizados con Li y Na, respectivamente). Para el caso específico del H2/fluoretil-Pyg[4]areno, la entalpía de adsorción estimada (∆H°ads) fue de -17.6 kJ/mol tmando en cuenta la energía del punto cero (ZPE) y los efectos térmicos calculados a 300 K a partir de las frecuencias armónicas vibracionales obtenidas al nivel de teoría B3LYP/BSB. Esta entalpía de adsorción alta sugiere que los R-Pyg[4]arenos funcioanlizados con Mg pueden ser tomados en cuenta como sistemas prometedores para el almacenamiento de hidrógeno molecular

Mexican Immigrant Communities in the South and Social Capital: The Case of Dalton, Georgia

During the 1990s, the South became a major new destination for Mexican and other Latino settled immigration. This paper contends that as Mexican immigrants have moved in sizable numbers to atypical destinations, they have also mobilized social capital and funds of knowledge from the historical concentrations of Latino settlement (i.e., Los Angeles and Chicago) to new areas, such as the South. Using qualitative and descriptive quantitative data collected in Dalton, Georgia, a small city located in the southern Appalachia region, this article shows how previously accumulated social capital and funds of knowledge are facilitating settlement with collective and individual level consequences. At the community level, this access to social capital is compressing the timing of the migratory cycle, accelerating incorporation. At the individual level, one significant outcome is the rapid rise of ethnic entrepreneurship, which in turn fosters differentiation within the immigrant community

"Desarrollo del Sistema de Mensajería de Texto para Telefonía Fija"

Proyecto de Graduación (Licenciatura en Ingeniería Electrónica) Instituto Tecnológico de Costa Rica. Escuela de Ingeniería Electrónica, 2006.The technological innovation and search of new services is an ideal of the Instituto Costarricense de Electricidad (ICE), which makes the necessity to offer and to enlarge the communication services among its clients. The phone communication is divided in the cellular telephony and fixed telephony. At the moment, the main income of ICE it is given by means of the fixed telephony services. The cellular telephony is taking preference among the clients, therefore it’s necessary to offer new services for fixed telephony. The objective of the project is to develop a new service for the clients of the fixed telephony network, which consists in providing the short text message service (SMS) for fixed lines. In order to standardize the service, in the development of the system, protocols and norms defined by the European Telecommunications Standards Institute (ETSI) have been taken as a reference. The importance of using an international standard resides in the possibility of using commercial terminals (telephones) designed for the SMS. This way, the project is focused in developing the center of messages (SM-SC) and to create the application that manages the protocol. The center of messages was developed in an APEX platform of added value, under a Windows 2000 environment. This platform is connected to the Public Switched Telephone Network (PSTN) through a channel E1 with signaling ISDN. In the future, one of ICE’s goal is to allow the integration of the different services in all technologies (mobile and fixed telephony). With this project the SMS is allowed between fixed telephones, the use of the standard leaves a door open to be able to develop the exchange of text messages with the cellular telephony.Instituto Tecnológico de Costa Rica. Escuela de Ingeniería en Electrónica