Factores que afectan a la resistencia, funcionalidad y durabilidad de las aceras

La presente investigación trata sobre algunos aspectos relacionados con la resistencia, funcionalidad y durabilidad de los firmes para la construcción de aceras. Dada la gran variedad de firmes capaces de sustentar aceras, hemos limitado el estudio a estructuras que, sobre una explanada mejorada, estén formadas por subbases granulares de suelos adecuados, bases de hormigón y pavimentos constituidos por baldosas de hormigón, sentadas sobre una capa de mortero de agarre. Este tipo de firme es el utilizado en el 84% de los firmes para aceras construidos en España. Se destaca la escasa documentación que existe sobre las infraestructuras urbanas, en relación con la disponible cuando el ámbito es el interurbano, a pesar de que, en el caso de la red viaria, casi el 20% de la red española, corresponde al viario urbano. Se destaca, también, la importancia económica del consumo anual de baldosas de cemento en las aceras españolas, que supera los 280 millones de euros. Lo anterior, unido a que los resultados obtenidos en los ensayos realizados en las baldosas de cemento, tanto en el origen de la fabricación como en los materiales suministrados para la pavimentación de las aceras madrileñas eran, simplemente, discretos, justifica la importancia de mejorar mediante investigaciones y experimentaciones, tanto la fabricación como la puesta en obra de este material. La influencia en los firmes para aceras de las subbases, bases y pavimentos, en relación con su comportamiento ante las cargas de tráfico, constituye el objetivo fundamental de esta investigación. La investigación experimental realizada, ha comprendido cuatro fases claramente diferenciadas. En la FASE I, se realizaron y compararon los resultados obtenidos en los ensayos de absorción de agua, permeabilidad, heladicidad, desgaste por abrasión, resistencia a flexión y resistencia al choque en baldosas de cemento sueltas, antes y después de ser sometidas a dos tratamientos distintos de envejecimiento artificial acelerado, a partir de una muestra especialmente seleccionada para esta investigación. En la FASE II, se realizaron, sobre baldosas unidas en módulos de prueba de 60x60 y 30x30, ensayos, antes y después de los referidos tratamientos de envejecimiento acelerado, de variación dimensional, planeidad, resistencia al deslizamiento y pérdida de color. En la FASE III, con el fin de evaluar las características mecánicas de las aceras pavimentadas con cuatro tipos de baldosas de cemento, dos espesores de la base de hormigón y dos grados de compactación de la subbase, se construyó un tramo de prueba de 19,20 m de longitud por 2,40 m de anchura, dividido en dieciséis subtramos resultantes de la combinación de las variables citadas, y se analizaron, numéricamente, las flechas instantáneas y remanentes alcanzadas en cada uno de los referidos subtramos al paso de una carretilla lastrada, siempre con la misma carga, circulando a una velocidad de 5 Km/h. En paralelo a las fases anteriores, se desarrolló la FASE 0, consistente en la realización de dos estudios estadísticos sobre los resultados obtenidos en los ensayos efectuados en las baldosas de cemento utilizadas en las obras de pavimentación realizadas por el Ayuntamiento de Madrid entre 1996 y 2000, el primero, y entre 2000 y 2004, el segundo. Las conclusiones obtenidas permiten valorar la calidad de los materiales empleados en los pavimentos de baldosas de cemento comúnmente empleados en las aceras españolas, así como establecer las soluciones óptimas, desde el punto de vista económico, para la construcción de estos firmes, en lo que se refiere a las subbases y bases empleadas. Finalmente, a la vista de los trabajos realizados, se concluye con la exposición de una serie de recomendaciones para futuras investigaciones. ABSTRACT This research deals with some aspects related to the resistance, functionality and durability of the materials employed in sidewalk construction. Due to the great variety of solutions for sidewalks, the study has been focussed on structures formed by granular subbases of suitable soils, concrete bases and concrete floor tiles, laid on a mortar layer. This solution is the one used in 84% of the cases of sidewalks built in Spain. There is little documentation about urban infrastructures compared with the available information of the interurban pattern. In the case of the road network, almost 20% of the Spanish network corresponds to the urban roadway. It should be noticed the economic importance of the annual consumption of cement floor tiles in Spanish sidewalks, that overcomes 280 million Euros. This fact, also with the results obtained in the cement floor tile tests carried out for the manufacture origin and the on site construction sidewalk assessment, justifies the importance of improving both the manufacturing as the on site work by means of research and experimentation. The influence of bases, subbases and tiles in sidewalks, related to its behaviour to the traffic loads, constitutes the main objective of this investigation. The experimental research included four clearly different parts. In PHASE I, the obtained results in the water absorption test, permeability test, frost resistance test, abrasion resistance test, flexion resistance test and impact resistance in cement floor tiles were analyzed and compared, before and after being exposed to two different methods of accelerated aging. The cement floor tiles were especially selected for this investigation. In PHASE II, tests of dimensional variation, flatness, sliding resistance and loss of colour were carried out on floor tiles modules of 60x60 and 30x30, before and after the accelerated aging. In PHASE III, and in order to evaluate the mechanical characteristics of the sidewalks built with four different types of cement floor tiles, two concrete base thicknesses and two subbases compaction degrees, a test sample of 19.20 meters length by 2.40 meters width, was constructed. The instantaneous and permanent deflections were numerically analyzed in each sector after passing the test vehicle, always with the same load, circulating at a speed of 5 Km/h. In parallel to the previous phases, PHASE 0 was developed. This phase included two statistical studies on the results obtained in the tests conducted in the cement floor tiles used in paving works realised by the City Council of Madrid between 1996 and 2000 and between 2000 and 2004. The obtained conclusions can be used to assess the pavement material quality used in the cement floor tiles commonly employed in the Spanish sidewalks, and also to establish the optimal solutions, from the economical point of view, for the construction of these kinds of pavements and the used of subbases and bases. Finally, the study suggests some recommendations for future investigations

Analgesic and physiological effects in conscious sedation with different nitrous oxide concentrations

Objectives: to study the physiological changes, as well as the psychosedative and analgesic effects of nitrous oxide, in experimental conditions. Study Design: 101 dental students volunteers participated in a single nitrous oxide sedation session without dental treatment. Signs and symptoms were registered during and after the procedure. Pulse rate and hemoglobin oxygen saturation were monitored at: 100 per cent O 2 , 30 per cent N 2 O, 50 per cent N 2 O and 5 minutes after 100 per cent O 2 . A Likert scale was used to evaluate pain perception. The analgesic effects of nitrous oxide were evaluated at: 30 per cent N 2 O, 50 per cent N 2 O, and five minutes postoperatively. Results: Pulse rate and hemoglobin oxygen saturation decreased significantly through all the procedure and after recovery. However, oxygen saturation recovered after the final oxygenation. Only 8.2% of subjects reported the pain stimulus as being quite annoying when they inhaled 30 per cent N 2 O, while this percentage was of 15.8 % when inhaling 50 per cent N 2 O, and of 32.7 % during the recovery period. The most common effects of nitrous oxide sedation were bright eyes (99%), voice change (98%) and smiling (91%). Most of the subjects reported tingling (98%) and relax (91.1%) Conclusions: nitrous oxide causes a significant decrease in heart rate and oxygen saturation, but always within safety limits. Maintaining an appropriate level of consciousness was confirmed as a feature in 50 per cent dose in this study. The analgesic effect of nitrous oxide was confirmed but a dose dependency could not be established

Preliminary assessment of terrestrial microalgae isolated from lichens as testing species for environmental monitoring: Lichen phycobionts present high sensitivity to environmental micropollutants

Bioassays constitute a tool for pollution analysis providing a holistic approach and high-quality indication of the toxicity. Microbioassays allow evaluating the toxicity of many samples, implying lower costs and enabling routine monitoring and pollution control. But tests conducted so far are limited to the use of a small number of taxa. Lichens are excellent bioindicators of pollution with great ecological significance. Studies show that the phycobiont is more sensitive to pollutants than the mycobiont. Phycobiont have features such as adaptation to anhydrobiosis and relatively rapid growth in vitro, making them suitable for microbioassays. Our aim is to determine the sensitivity of phycobionts to the pharmaceutical micropollutants carbamazepine and diclofenac as a preliminary step for the development of a toxicity microbioassay based on phycobionts. Optical dispersion and chlorophyll autofluorescence were used as endpoints of toxicity on two algal species showing that suspensions present cyclic and taxon specific patterns of aggregation. Trebouxia TR9 suspensions present a very high grade of aggregation while Asterochloris erici cells do not. Both micropollutants alter optical properties of the suspensions of both species. No significant alteration of chlorophyll autofluorescence by carbamazepine is observed. A. erici chlorophyll autofluorescence is extremely sensitive to diclofenac but the effect is not dependent on the drug concentration or on the time of exposure. Differently, TR9 only shows punctual chlorophyll alterations. Fluctuations in optical dispersion may indicate changes in the population structure of the species, including reproductive strategy. A. erici seems more sensitive to micropollutants, is better characterized and is available from commercial collections

Optimal Production Planning of Concentrated Apple and Pear Juice Plants

This paper presents a mathematical model aimed at optimizing the yearly profit of a concentrated apple and pear juice plant through the appropriate design of its production plan. This study assumes a business scenario where the products are devoted to the international market and therefore the production schedule is dictated by a fluctuating prices scenario due to the worldwide supply/demand tradeoff. Moreover, raw fruit is available only during the relatively short harvest season and suffers juice yield reduction during storage. In this context, decisions related to the manufacturing of each juice variety to exploit favorable prices, while minimizing juice yield loss due to fruit aging are not intuitive. Scenario studies, together with sensitivity analysis on some model parameters are developed to illustrate the performance of the proposed approach.Sociedad Argentina de Informática e Investigación Operativ

Principios básicos de Evaluación Económica de Intervenciones Sanitarias

The objective of this article is to present the general concepts associated with economic evaluations of health interventions. These elements are part of the basic information that must be present in any study and, therefore, should be considered when designing or interpreting any evaluation. Likewise, the article focuses on the objective pursued by this type of analyses, which is none other than to provide information, focused on the dimension of efficiency (cost-effectiveness), in the decision-making processes.El objetivo de este artículo es presentar los conceptos generales asociados a los estudios de evaluación económica de intervenciones sanitarias. Dichos elementos forman parte de la información básica que debe estar presente en cualquier estudio y, por tanto, deben ser tenidos en cuenta a la hora del diseño o la interpretación de cualquier evaluación. Asimismo, se incide en el objeto que persiguen este tipo de análisis, que no es otro sino aportar información, centrada en la dimensión de la eficiencia (coste-efectividad), en los procesos de toma de decisiones

Optimal Production Planning of Concentrated Apple and Pear Juice Plants

This paper presents a mathematical model aimed at optimizing the yearly profit of a concentrated apple and pear juice plant through the appropriate design of its production plan. This study assumes a business scenario where the products are devoted to the international market and therefore the production schedule is dictated by a fluctuating prices scenario due to the worldwide supply/demand tradeoff. Moreover, raw fruit is available only during the relatively short harvest season and suffers juice yield reduction during storage. In this context, decisions related to the manufacturing of each juice variety to exploit favorable prices, while minimizing juice yield loss due to fruit aging are not intuitive. Scenario studies, together with sensitivity analysis on some model parameters are developed to illustrate the performance of the proposed approach.Sociedad Argentina de Informática e Investigación Operativ

Muscle Strength and Neuromuscular Control in Low-Back Pain: Elite Athletes Versus General Population

The purpose of the study was to investigate the athletic-based specificity of muscle strength and neuromuscular control of spine stability in chronic non-specific low-back pain (LBP). Thirty elite athletes and 29 age-matched non-athletes with (15 athletes and 15 non-athletes) and without LBP (15 athletes and 14 non-athletes) participated in the study. Muscle strength was measured during maximal isometric trunk flexion and trunk extension contractions. The neuromuscular control of spine stability was analyzed by determining trunk stiffness, trunk damping, and onset times of the lumbar and thoracic erector spinae muscles after sudden perturbations (quick release experiments) as well as maximum Lyapunov exponents (local dynamic stability) using non-linear time series analysis of repetitive lifting movements. LBP was assessed using the visual analog scale. We found lower maximal trunk extension moments (p = 0.03), higher trunk damping (p = 0.018) and shorter onset times (p = 0.03) of the investigated trunk muscles in LBP patients in both athletes and non-athletes. Trunk stiffness and the local dynamic stability did not show any differences (p = 0.136 and p = 0.375, respectively) between LBP patients and healthy controls in both groups. It can be concluded that, despite the high-level of training in athletes, both athletes and non-athletes with LBP showed the same deconditioning of the lumbar extensor muscles and developed similar strategies to ensure spine stability after sudden perturbations to protect the spine from pain and damage. The findings highlight that specific training interventions for the trunk muscles are not only crucial for individuals of the general population, but also for well-trained athletes

La participación ciudadana en las agendas 21 locales de la provincia de Valencia

La participación ciudadana es una exigencia del propio sistema democrático. Los problemas ambientales y el cambio hacia la sostenibilidad requieren cambios de gran envergadura que únicamente se pueden lograr desde el consenso de la sociedad. Por ello es de gran importancia incorporar la participación en los planes y programas de las Agendas 21 Locales, así como de otros instrumentos de planificación en pro de la consecución de los objetivos para el desarrollo sostenible. En este trabajo analizamos en qué medida se ha incorporado la participación ciudadana en la Red de Municipios firmantes de la Carta de Xàtiva en la Provincia de Valencia. Para la recolección de datos se utilizó el cuestionario estructurado que fue enviado a los 213 municipios firmantes de dicho documento. Los resultados obtenidos permiten afirmar que las administraciones locales prestan poca atención a la participación ciudadana, así como a los mecanismos de regulación de la participación

Mechanical properties and coefficient of thermal expansion of β-eucryptite sintered by microwave technique

[ES]: La técnica de sinterización no convencional de microondas permite obtener materiales de ß-eucriptita en estado sólido cristalino con densidades cercanas a la teórica (~99 %). Se ha observado una diferencia considerable en estos materiales respecto a la técnica convencional en términos de densificación, microestructura, coeficiente de expansión térmica y propiedades mecánicas. Los valores de dureza y módulo de Young obtenidos mediante sinterización por microondas a 1200 ºC-5 min han sido relativamente altos, 6.8 GPa y 101 GPa, respectivamente, en comparación con el material obtenido mediante horno convencional (3.9 GPa y 58 GPa, respectivamente). Los datos dilatométricos obtenidos, incluyendo el intervalo de temperatura criogénica (-150 ºC a +150 ºC), muestran un coeficiente de expansión térmica controlado y negativo en todo el rango de temperaturas. La combinación de un calentamiento rápido junto con la reducción drástica en el tiempo de ciclo y el ahorro energético, hace que la técnica de microondas sean una clara alternativa a otro tipo de calentamientos.[EN]: Microwave non-conventional sintering technique allows obtaining fully dense glass-free β-eucryptite bulk material (∼99 %). A considerable difference in the densification, microstructure, coefficient of thermal expansion behaviour and mechanical properties, between conventional and non-conventional sintered specimens was observed. The hardness and Young’s modulus values obtained by microwaves at 1200 °C-5min have been relatively high, 6.8 GPa and 101 GPa, respectively, compared to conventional sintering (3.9 GPa and 58 GPa, respectively). Very low thermal expansion materials have been obtained in a wide temperature range including cryogenic temperatures (from -150 ºC to 150 ºC). The high heating rate along with the lower energy consumption makes microwave technique a clear alternative to other types of sintering methods.Los autores desean agradecer el apoyo financiero recibido de la UPV dentro de los proyectos SP20120621 y SP20120677 y, al gobierno español a través del proyecto (TEC2012-37532-C02-01). A. Borrell, agradece al Ministerio de Ciencia e Innovación su contrato de Juan la Cierva (JCI-2011-10498).Peer Reviewe

La educación ambiental en las Agendas 21 Locales de la provincia de Valencia

La Educación Ambiental nació con la vocación de colaborar en la mejora ambiental, para ello, es de suma importancia incorporarla en los procesos de participación ciudadana de las Agendas 21. Consecuentemente se hace necesaria la planificación de la Educación Ambien tal Municipal mediante planes y programas en las Agendas 21 Locales. En este trabajo analizamos en qué medida se ha incorporado la Educación Ambiental en la Red de M unicipios firmantes de la Carta de Xàtiva en la Provincia de Valencia. Para la recolección de datos se utilizó el cuestionario estructurado que fue enviado a los 213 municipios firmantes de dicho documento. Los resultados obtenidos nos permiten afirmar que son escasos los Planes o Programas de Educación Ambiental a nivel local. Esto supone una falta de coherencia entre los compromisos públic os adoptados por las corporaciones locales y las acciones que realmente se están llevando a término para la aplicación de la Agenda 21 Local.Environmental Education was born with the vocation to collaborate in environmental improvement, for that, it is of the utmost importance to incorporate it in the processes of citizen participation of the Agendas 21. Consequently, it is necessary to plan the Municipal Environmental Education through plans and programs in the Local Agen da 21. In this paper we analyze the extent to which Environmental Education has been incorporated in the Network of Municipalities that signed the Charter of Xàtiva in the Province of Valencia. For da ta collection, the structured questionnaire was used and sent to the 213 municipalities that signed the document. The results obtained allow us to affirm that there are few Plans or Environmental Education Programs at the local level. This implies a lack of coherence between the public commitments adopted by local corporations and the actions that are actually being carried out for the im plementation of Local Agenda 21.L'Éducation sur l'Environnement naquit avec la finalité d'aider à améliorer l'environnement, pour cela, il est très important de l'inclure dans le procès de participation urbaine des Agenda 21. En conséquence, il devient nécessair e une planification de l'Educati on sur l'Environnement Municipal à travers des plans et des programmes dans les Agenda 21. Dans ce travail, nous avons analysé en quelle mesure l'Education sur l'Environnement a été intégrée dans la Source de Munici palités signataires de la Carte de Xativa dans la Provence de Valencia. P our obtenir l'information nous avons utilisé un questionnaire structuré qui fut envoyé aux 213 municipa lités signataires de cette Carte. Les résultats obtenus nous permettent d'affirmer qu'ils sont peu nombreux les Plan s ou Programmes de l'Education sur l'Environnement dans le domaine local. Cela suppose une absence de cohérence entre les engagements publics pris par les corporations locales et les actions menées à terme réellement en application de l'Agenda 21 locale.Educació