Building a flexible web caching system.

Web caching is a technology that has demonstrated to improve traffic on the Internet. To find out how to implement a Web caching architecture that assures improvements is not an easy task. The problem is more difficult when we are interested in deploying a distributed and cooperative Web caching system. We have found that some cooperative Web caching architectures could be unviable when changes on the network environment appear. This situation suggests that a cooperative Web caching system could get worst access to Web objects. However in this paper we present an architecture that combines the best of several Web caching configurations that we have previously analyzed. Our architecture gives basic ideas for implementing a cooperative Web caching system using groups of HTTP proxy servers which can improve access to remote Web objects regardless of the changes that might occur on the network environment (changes that could produce modifications in Web object validation policies and/or types of caching communication).Peer Reviewe

Critical current density and ac harmonic voltage generation in YBa2Cu3O7−δYBa_2Cu_3O_{7-\delta} thin films by the screening technique

The temperature and field dependence of harmonics in voltage $V_n=V'_n-iV"_n$ using the screening technique have been measured for $\mathrm{Y}\mathrm{Ba}_{2}\mathrm{Cu}_3\mathrm{O}_{7-\delta}$ superconducting thin films. Using the Sun model we obtained the curves for the temperature-dependent critical current density $J_c(T)$. In addition, we applied the criterion proposed by Acosta et al. to compute $J_c(T)$. Also, we made used of the empirical law $J_c \propto (1-T/T_c)^n$ as an input in our calculations to reproduce experimental harmonic generation up to the fifth harmonic. We found that most models fit well the fundamental voltage but higher harmonics are poorly reproduced. Such behavior suggests the idea that higher harmonics contain information concerning complex processes like flux creep or thermally assisted flux flow.Comment: 2 pages, 2 figure

Critical parameters of the in vitro method of vascular smooth muscle cell calcification

[Background]: Vascular calcification (VC) is primarily studied using cultures of vascular smooth muscle cells. However, the use of very different protocols and extreme conditions can provide findings unrelated to VC. In this work we aimed to determine the critical experimental parameters that affect calcification in vitro and to determine the relevance to calcification in vivo. [Experimental Procedures and Results]: Rat VSMC calcification in vitro was studied using different concentrations of fetal calf serum, calcium, and phosphate, in different types of culture media, and using various volumes and rates of change. The bicarbonate content of the media critically affected pH and resulted in supersaturation, depending on the concentration of Ca2+ and Pi. Such supersaturation is a consequence of the high dependence of bicarbonate buffers on CO2 vapor pressure and bicarbonate concentration at pHs above 7.40. Such buffer systems cause considerable pH variations as a result of minor experimental changes. The variations are more critical for DMEM and are negligible when the bicarbonate concentration is reduced to ¿. Particle nucleation and growth were observed by dynamic light scattering and electron microscopy. Using 2mM Pi, particles of ~200nm were observed at 24 hours in MEM and at 1 hour in DMEM. These nuclei grew over time, were deposited in the cells, and caused osteogene expression or cell death, depending on the precipitation rate. TEM observations showed that the initial precipitate was amorphous calcium phosphate (ACP), which converts into hydroxyapatite over time. In blood, the scenario is different, because supersaturation is avoided by a tightly controlled pH of 7.4, which prevents the formation of PO43--containing ACP. [Conclusions]: The precipitation of ACP in vitro is unrelated to VC in vivo. The model needs to be refined through controlled pH and the use of additional procalcifying agents other than Pi in order to reproduce calcium phosphate deposition in vivo.Funding was provided by a research grant SAF2012-33898 to VS, http://www.mineco.gob.es/portal/site/mineco/idi, Spanish Ministry of Economy and Competitiveness; research grant MAT2014-54975-R to AM, http://www.mineco.gob.es/portal/site/mineco/idi, Spanish Ministry of Economy and Competitiveness.Peer Reviewe

Effects of oral exposure to arsenite on arsenic metabolism and transport in rat kidney

Nephrotoxicity is within the recognized toxic effects of arsenic. In this study we assessed the effect of arsenite on the renal capacity to metabolize and handle arsenicals in rats exposed to drinking water with 0, 1, 5, or 10 ppm sodium arsenite for ten days. Arsenite treatment did not affect the gene expression of the main enzyme catalyzing methylation of arsenite, As3mt, while it reduced the expression of GSTO1 mRNA and protein. Arsenite decreased the expression of Aqp3, Mrp1, Mrp4, and Mdr1b (i.e., transporters and channels used by arsenic), but not that of Aqp7, Glut1, Mrp2, and Mdr1a. The protein abundance of AQP3 was also reduced by arsenite. Arsenite increased urinary NGAL and FABP3 and decreased Klotho plasma levels, without alteration of creatinine, which evidenced early tubular damage. Renal Klotho mRNA and protein expressions were also downregulated, which may exacerbate renal damage. No effect was observed in selected miRNAs putatively associated with renal injury. Plasma PTH and FGF23 were similar between groups, but arsenite decreased the renal expression of Fgfr1 mRNA. In conclusion, exposure to arsenite alters the gene expression of proteins involved in the cellular handling of arsenical species and elicits tubular damage

Several phosphate transport processes are present in vascular smooth muscle cells

We have studied Pi handling in rat aortic vascular smooth muscle cells (VSMC) using 32P-radiotracer assays. Our results have revealed a complex set of mechanisms consisting in 1) well-known PiT1/PiT2-mediated sodium-dependent Pi transport; 2) Slc20-unrelated sodium-dependent Pi transport that is sensitive to the stilbene derivatives 4,4'-diisothiocyanatostilbene-2,2'-disulphonic acid (DIDS) and (4-acetamido-4-isothiocyanostilbene-2,2-disulfonate) (SITS); 3) a sodium-independent Pi uptake system that is competitively inhibited by sulfate, bicarbonate, and arsenate and is weakly inhibited by DIDS, SITS, and phosphonoformate; and 4) an exit pathway from the cell that is partially chloride-dependent and unrelated to the known anion-exchangers expressed in VSMC. The inhibitions of sodium-independent Pi transport by sulfate and of sodium-dependent transport by SITS were studied in greater detail. The maximal inhibition by sulfate was similar to that of Pi itself, with a very high inhibition constant (212 mM). SITS only partially inhibited sodium-dependent Pi transport, but the Ki was very low (14 µM). Nevertheless, SITS and DIDS did not inhibit Pi transport in Xenopus laevis oocytes expressing PiT1 or PiT2. Both the sodium-dependent and sodium-independent transport systems were highly dependent on VSMC confluence and on the differentiation state, but they were not modified by incubating VSMC for 7 days with 2 mM Pi under non-precipitating conditions. This work not only shows that the Pi handling by cells is highly complex, but also that the transport systems are shared with other ions such as bicarbonate or sulfate

Tenebrio Obscurus

Este escrito explora el proceso de construcción de una realización escénica, la Cámara de Almastronomía, que gira en torno de la memoria traumática que dejaron las dictaduras en Paraguay, y en especial la última de Alfredo Stroessner (1954-1989).La investigación ha querido indagar los problemas éticos y poéticos que enfrenta el actor-creador cuando decide enfrentar la escenificación de la tortura. A través de múltiples experimentaciones probé estrategias alternativas a la representación teatral del dolor practicadas en general en Paraguay, y que suelen limitarse a transmitir una historia con un mensaje, centrándose en la víctima de la represión y representando al victimario como un ser malvado, un monstruo inaccesible, privado de su condición humana.Magíster en Teatro y Artes Vivas.Maestrí

Incorporación de las TIC en las Prácticas Educativas de Escolares de la Educación Escolar Básica N° 1141 San José Artesano- FROSEP

The present work is framed within the non-experimental studies, of a descriptive type with qualitative and quantitative study methods. The purpose of knowing the use of Tics in the 1st and 2nd Cycle of the Basic School No. 1141 San José Artesano, FROSEP, and its influence on student learning, identify the technological means available to students / as for the teaching-learning process, describe the teaching strategies used by teachers to facilitate student learning and the difficulties encountered by teachers during the teaching-learning process. From the literature reviews as a source of secondary data and the application of surveys, the schoolchildren gave results that indicate that the technological means available to teachers for teaching-learning are almost always sufficient for all students, since the institution has computers for the development of school activities and a large computer room, highlighting that sometimes there is difficulty with internet connection. The strategies used by teachers to consolidate communications with their students and facilitate their learning, students qualify compliance with homework as very good as there are also some students react to computers. The educational institution under study as a learning facilitator is developing quite well, but due to the constant increase in the student population, it is becoming necessary to expand the computer room and provide new and greater equipment and information and audiovisual media.El presente trabajo se enmarca dentro de los estudios no experimentales, de tipo descriptivo con métodos de estudio cualitativo y cuantitativos. El objeto de conocer la utilización de las Tics en el 1° y 2° Ciclo de la Escuela Básica N° 1141 San José Artesano, FROSEP, y su influencia en el aprendizaje de los estudiantes, identificar los medios tecnológicos con que cuentan los alumnos/as para el proceso de enseñanza-aprendizaje, describir las estrategias de enseñanza utilizada por los docentes, para facilitar el aprendizaje de los alumnos y las dificultades encontradas por los docentes durante el proceso de enseñanza – aprendizaje. De las revisiones de literatura como fuente de datos secundarios y la aplicación de encuestas los escolares dieron como resultados que indican que los medios tecnológicos con que cuentan los docentes para la enseñanza-aprendizaje casi siempre alcanza para todos los alumnos, siendo que la institución cuenta con computadoras para el desarrollo de las actividades escolares y una amplia sala de informática, resaltando que en oportunidades existe dificultad con la conexión a internet. Las estrategias utilizadas por los docentes para mantenerse comunicados con sus alumnos y facilitar sus aprendizajes, los alumnos califican el cumplimento con las tareas escolares como muy buena como también existen algunos alumnos reacciona a la informática. La institución educativa en estudio como facilitador de aprendizaje se está desarrollando bastante bien, pero debido al aumento constante de la población estudiantil, se está tornando necesaria ampliar la sala de informática y dotar de nuevos y mayor cantidad de equipos y medios informativos y audiovisuales

Modelos de integración didáctica de las TIC en el aula

En este artículo se presentan los resultados de un estudio que analizó el grado y tipo de utilización que el profesorado hace de las TIC en aulas con abundante disponibilidad de tecnologías de la información y comunicación: un ordenador por alumno, Pizarra Digital Interactiva, proyectores multimedia y acceso a Internet. El objetivo del estudio fue detectar modelos o patrones de uso didáctico de las tecnologías y relacionarlo con algunas características personales y profesionales del profesorado, tales como el género, los años de experiencia, la etapa educativa, la competencia digital y el grado de uso de las TIC en su vida cotidiana. Se empleó un diseño de tipo descriptivo correlacional basado en un estudio de encuesta donde respondieron más de 3.160 profesores de toda España que participaban en el Programa Escuela 2.0. Los resultados obtenidos muestran que existen dos tipologías nítidas de modelos de uso de las TIC en función de la frecuencia y el tipo de tarea demandada al alumnado: un modelo de integración didáctica débil frente a un modelo de integración didáctica intensa de las TIC. Asimismo, se concluye que el perfil del profesorado que desarrolla un modelo de uso didáctico intensivo de las TIC es un docente con bastantes años de experiencia profesional, ciudadano usuario habitual de las TIC y que, además, se percibe suficientemente formado y con competencia digitalWe present in this paper the results of a study analyzing the scope and use that teachers make of ICT in classrooms and schools with abundant availability of information and communication technologies: one computer per student, interactive whiteboards, multimedia projectors and internet access. The main goal of this study is to detect models or patterns of educational use of ICT resources available in classrooms related to some personal and professional characteristics of the teachers that took part in the study, such as gender, years of experience, educational stage, digital competence and degree of use of ICT in their daily lives. A descriptive correlational design based on a survey study answered by over 3160 teachers from all over Spain who participated in the School Program 2.0 was used. The results show two clear different patterns of ICT use according to frequency and type of tasks assigned to the students: a weak integration-teaching model against a strong educational integration of ICTs. We come to the conclusion that teachers who develop a model of intensive educational use of ICTs are teachers with many years of professional experience, that make regular use of ICTs and, moreover, perceive themselves as sufficiently trained and with a highly developed digital competenc

Models of educational integration of ICTs in the classroom = Modelos de integración didáctica de las TIC en el aula

We present in this paper the results of a study analyzing the scope and use that teachers make of ICT in classrooms and schools with abundant availability of information and communication technologies: one computer per student, interactive whiteboards, multimedia projectors and internet access. The main goal of this study is to detect models or patterns of educational use of ICT resources available in classrooms related to some personal and professional characteristics of the teachers that took part in the study, such as gender, years of experience, educational stage, digital competence and degree of use of ICT in their daily lives. A descriptive correlational design based on a survey study answered by over 3160 teachers from all over Spain who participated in the School Program 2.0 was used. The results show two clear different patterns of ICT use according to frequency and type of tasks assigned to the students: a weak integration-teaching model against a strong educational integration of ICTs. We come to the conclusion that teachers who develop a model of intensive educational use of ICTs are teachers with many years of professional experience, that make regular use of ICTs and, moreover, perceive themselves as sufficiently trained and with a highly developed digital competence

Simplification of Pocklington’s integral equation for arbitrary bent thin wires

The simplification of Pocklington’s equation kernel and the software implementation of the arbitrary shaped thin wire problem is presented here in order to get a useful antenna engineering tool that could be used in determining the current distribution in arbitrary shaped thin wires. The software is based on the widely used method of moments and it is implemented in programming language C++. The work presented in this paper is concerned with how to simplify the kernel of the Pocklington’s integro-differential equation in order to be more efficient computationally. We obtained an integral equation that reduces not only the programming efforts, but also the time spent in the calculations. The integral equation presented in this paper was thought not only for arbitrary shaped thin wires, but also for the case of straight thin wires