Estudio y comprobación experimental de diversas transformaciones energéticas utilizando una pila de combustible

Dada la complejidad y la riqueza del concepto de energía, así como la imprecisión cometida al definirlo relacionándolo exclusivamente con transformaciones mecánicas, se abordará en esta ponencia una actividad experimental para contribuir, de forma estimulante para el alumno, a la comprensión de las transformaciones energéticas y su aplicación, al vincular la teoría con la práctica. Para ello se ha diseñado una experiencia donde se llevan a cabo diferentes transformaciones energéticas. En una primera etapa se producirá energía eléctrica a partir de energía solar mediante una célula fotovoltaica. La electricidad así producida se transformará en energía química (H2 + O2) mediante la hidrólisis del agua en un electrolizador. H2 y O2 pueden volver a combinarse en una pila de combustible tipo PEM (membrana de intercambio de protones) produciendo, cuando sea necesario, energía eléctrica que podrá transformarse en energía lumínica, en una lámpara, o en energía mecánica en un motor En el sistema descrito pueden realizarse un importante número de actividades experimentales [1] tales como: Caracterizar células solares, obtener las curvas características y la eficiencia de celdas electrolíticas y de pilas de combustible, comprobar la 1ª Ley de Faraday, experimentar con distintas conexiones (serie y paralelo) de pilas de combustible y estudiar la reacción 2H2 + O2 2H2O + Energía. El desarrollo de la práctica pone en relieve la utilización de dos tecnologías emergentes para la producción de energía: las células fotovoltaicas y las pilas de combustión, así como el empleo de la electrolisis del agua como medio de almacenar la energía producida en forma de energía química. La combinación adecuada de estas tres tecnologías dará lugar a sistemas autónomos de generación, almacenaje y utilización de energía, que permitirán aprovechar una energía renovable como la solar para suministrar energía eléctrica sostenible y limpia donde se requiera y en el momento adecuado. Las prácticas que se proponen se enmarcan dentro de las asignaturas Tecnología de Combustibles y Ampliación de Tecnología de Combustibles, asignaturas pertenecientes a la titulación de Ingeniero Técnico en Recursos Energéticos, Combustibles y Explosivos impartida en la Universidad Politécnica de Cartagena. Los descriptores del Plan de Estudios de la asignatura Tecnología de Combustibles tratan sobre la génesis, clasificación, producción de combustibles sólidos, líquidos y gaseosos y los descriptores de la asignatura de Ampliación de Tecnología de Combustibles sobre las aplicaciones de combustibles sólidos, líquidos y gaseosos, junto con otros temas relacionados con la seguridad e impacto ambiental en su aplicación. Al ser una práctica que engloba un amplio número de aspectos relacionados con la producción de energía y en especial con la utilización de H2 como combustible, se ajusta en gran medida a los descriptores de las asignaturas. Por otra parte, atendiendo el grado de conocimiento previo de los alumnos, es posible su adaptación a otras asignaturas que se encuentren dentro del ámbito científico-tecnológico. A continuación se presenta una de las posibles experiencias que pueden realizarse con el dispositivo pila de combustible. Inicialmente se describen los conceptos y dispositivos más importantes utilizados en el desarrollo de la misma. Posteriormente se procede a la descripción de la práctica y finalmente se propone una serie de ejercicios que los alumnos deben resolver a partir de los datos experimentales obtenidos

Childhood acute leukemias are frequent in Mexico City: descriptive epidemiology

<p>Abstract</p> <p>Background</p> <p>Worldwide, acute leukemia is the most common type of childhood cancer. It is particularly common in the Hispanic populations residing in the United States, Costa Rica, and Mexico City. The objective of this study was to determine the incidence of acute leukemia in children who were diagnosed and treated in public hospitals in Mexico City.</p> <p>Methods</p> <p>Included in this study were those children, under 15 years of age and residents of Mexico City, who were diagnosed in 2006 and 2007 with leukemia, as determined by using the International Classification of Childhood Cancer. The average annual incidence rates (AAIR), and the standardized average annual incidence rates (SAAIR) per million children were calculated. We calculated crude, age- and sex-specific incidence rates and adjusted for age by the direct method with the world population as standard. We determined if there were a correlation between the incidence of acute leukemias in the various boroughs of Mexico City and either the number of agricultural hectares, the average number of persons per household, or the municipal human development index for Mexico (used as a reference of socio-economic level).</p> <p>Results</p> <p>Although a total of 610 new cases of leukemia were registered during 2006-2007, only 228 fit the criteria for inclusion in this study. The overall SAAIR was 57.6 per million children (95% CI, 46.9-68.3); acute lymphoblastic leukemia (ALL) was the most frequent type of leukemia, constituting 85.1% of the cases (SAAIR: 49.5 per million), followed by acute myeloblastic leukemia at 12.3% (SAAIR: 6.9 per million), and chronic myeloid leukemia at 1.7% (SAAIR: 0.9 per million). The 1-4 years age group had the highest SAAIR for ALL (77.7 per million). For cases of ALL, 73.2% had precursor B-cell immunophenotype (SAAIR: 35.8 per million) and 12.4% had T-cell immunophenotype (SAAIR 6.3 per million). The peak ages for ALL were 2-6 years and 8-10 years. More than half the children (58.8%) were classified as high risk. There was a positive correlation between the average number of persons per household and the incidence of the pre-B immunophenotype (Pearson's r, 0.789; P = 0.02).</p> <p>Conclusions</p> <p>The frequency of ALL in Mexico City is among the highest in the world, similar to those found for Hispanics in the United States and in Costa Rica.</p

Consecuencias sociales del riesgo de la práctica de prostitución en adolescentes de 14 a 18 años, en el Puerto de Corinto Municipio de Chinandega

Edición digital a partir del texto original de la tesis. Tesis (Lic. en Ciencias de la Educación con Mención en Ciencias Sociales)-Universidad Nacional Autónoma de Nicaragua, LeónUNAN-Leó

Discurso sobre los ilustres autores e inventores de artilleria que han florecido en España, desde los Reyes Catholicos hasta el presente

Datos del editor tomados del colofónSign. : A-I8</sup

Composting Used as a Low Cost Method for Pathogen Elimination in Sewage Sludge in Mérida, Mexico

Spreading sewage sludge from municipal wastewater (MWW) treatment on land is still a common practice in developing countries. However, it is well known that sewage sludge without special treatment contains various pollutants, which are (re)introduced into the environment by sludge landspreading and which might in turn have harmful effects on the environment and human health. This is more dangerous in places like Merida, Mexico, where soil is calcareous with fractures along the ground and thin layers of humus. Consequently, any liquid and semisolid wastes have the potential of percolating to the subsurface and contaminate the aquifer. The main aim of this work was using composting as a low cost process to eliminate pathogens contained in sewage sludge from MWW treatment in order to use the final product for land spreading in a safe way for both environment and human health. Two piles for composting process at real scale were settled using a mixture of sewage sludge from municipal waste water and green waste. Composting was carried out by windrow process and it was monitored during four weeks. Concentration of helminth eggs, salmonella and faecal coliforms were measured twice a week to observe its behavior and, as a control process, Temperature, Moisture Content (MC), and pH were also measured. After 30 days of composting sludge from municipal waste water system, salmonella was eliminated by 99%, faecal coliforms by 96% and helminth eggs by 81%. After 3 months compost reached GI = 160%, so did not show any phytotoxicity to seeds

Low performance of ultrasound surveillance for the diagnosis of hepatocellular carcinoma in HIV-infected patients

On behalf of the GEHEP-002 Study Group.[Objective]: To assess the performance of ultrasound surveillance for the diagnosis of hepatocellular carcinoma (HCC) in HIV-infected patients.[Methods]: The GEHEP-002 cohort recruits HCC cases diagnosed in HIV-infected patients from 32 centers across Spain. The proportion of ‘ultrasound lack of detection’, defined as HCC diagnosed within the first 3 months after a normal surveillance ultrasound, and the proportion of ‘surveillance failure’, defined as cases in which surveillance failed to detect HCC at early stage, were assessed. To assess the impact of HIV, a control population of 104 HCC cases diagnosed in hepatitis C virus-monoinfected patients during the study period was used.[Results]: A total of 186 (54%) out of 346 HCC cases in HIV-infected patients were diagnosed within an ultrasound surveillance program. Ultrasound lack of detection occurred in 16 (8.6%) of them. Ultrasound surveillance failure occurred in 107 (57%) out of 186 cases diagnosed by screening, whereas this occurred in 18 (29%) out of 62 diagnosed in the control group (P < 0.0001). HCC cases after ultrasound surveillance failure showed a lower frequency of undetectable HIV viral load at diagnosis. The probability of 1-year and 2-year survival after HCC diagnosis among those diagnosed by screening was 56 and 45% in HIV-infected patients, whereas it was 79 and 64% in HIV-negative patients (P = 0.038).[Conclusion]: The performance of ultrasound surveillance of HCC in HIV-infected patients is very poor and worse than that shown outside HIV infection. A HCC surveillance policy based on ultrasound examinations every 6 months might be insufficient in HIV-infected patients with cirrhosis.The current study was supported by grants from the Consejería de Salud de la Junta de Andalucía (PI-0014/2014), the Servicio Andaluz de Salud (grant number SAS/111239) and the Fondo de Investigaciones Sanitarias ISCIII (grant number PI13/01621) and Project ‘PI16/01443’, funded by Instituto de Salud Carlos III, integrated in the national I+D+i 2013–2016 and co-funded by European Union (ERDF/ESF, ‘Investing in your future’). J.A.P. is the recipient of an intensification grant from the Instituto de Salud Carlos III (grant number Programa-I3SNS). Besides, this work has been partially funded by the Grupo para el Estudio de las Hepatitis Víricas (GEHEP) de la SEIMC (2017 grant to project GEHEP-002 and 2018 grant to project GEHEP-002), the SPANISH AIDS Research Network RD16/0025/0010 as part of the Plan Nacional R+D+I and cofinanced by ISCIII Subdirección General de Evaluación y el Fondo Europeo de Desarrollo Regional (FEDER).Peer reviewe