Controlling Network Latency in Mixed Hadoop Clusters: Do We Need Active Queue Management?

With the advent of big data, data center applications are processing vast amounts of unstructured and semi-structured data, in parallel on large clusters, across hundreds to thousands of nodes. The highest performance for these batch big data workloads is achieved using expensive network equipment with large buffers, which accommodate bursts in network traffic and allocate bandwidth fairly even when the network is congested. Throughput-sensitive big data applications are, however, often executed in the same data center as latency-sensitive workloads. For both workloads to be supported well, the network must provide both maximum throughput and low latency. Progress has been made in this direction, as modern network switches support Active Queue Management (AQM) and Explicit Congestion Notifications (ECN), both mechanisms to control the level of queue occupancy, reducing the total network latency. This paper is the first study of the effect of Active Queue Management on both throughput and latency, in the context of Hadoop and the MapReduce programming model. We give a quantitative comparison of four different approaches for controlling buffer occupancy and latency: RED and CoDel, both standalone and also combined with ECN and DCTCP network protocol, and identify the AQM configurations that maintain Hadoop execution time gains from larger buffers within 5%, while reducing network packet latency caused by bufferbloat by up to 85%. Finally, we provide recommendations to administrators of Hadoop clusters as to how to improve latency without degrading the throughput of batch big data workloads.The research leading to these results has received funding from the European Unions Seventh Framework Programme (FP7/2007–2013) under grant agreement number 610456 (Euroserver). The research was also supported by the Ministry of Economy and Competitiveness of Spain under the contracts TIN2012-34557 and TIN2015-65316-P, Generalitat de Catalunya (contracts 2014-SGR-1051 and 2014-SGR-1272), HiPEAC-3 Network of Excellence (ICT- 287759), and the Severo Ochoa Program (SEV-2011-00067) of the Spanish Government.Peer ReviewedPostprint (author's final draft

Interconnect Energy Savings and Lower Latency Networks in Hadoop Clusters: The Missing Link

An important challenge of modern data centres running Hadoop workloads is to minimise energy consumption, a significant proportion of which is due to the network. Significant network savings are already possible using Energy Efficient Ethernet, supported by a large number of NICs and switches, but recent work has demonstrated that the packet coalescing settings must be carefully configured to avoid a substantial loss in performance. Meanwhile, Hadoop is evolving from its original batch concept to become a more iterative type of framework. Other recent work attempts to reduce Hadoop's network latency using Explicit Congestion Notifications. Linking these studies reveals that, surprisingly, even when packet coalescing does not hurt performance, it can degrade network latency much more than previously thought. This paper is the first to analyze the impact of packet coalescing in the context of network latency. We investigate how to design and configure interconnects to provide the maximum energy savings without degrading cluster throughput performance or network latency.The research leading to these results has received funding from the European Unions Seventh Framework Programme (FP7/2007–2013) under grant agreement number 610456 (Euroserver). The research was also supported by the Ministry of Economy and Competitiveness of Spain under the contracts TIN2012-34557 and TIN2015-65316-P, Generalitat de Catalunya (contracts 2014-SGR-1051 and 2014-SGR-1272), HiPEAC-3 Network of Excellence (ICT- 287759), and the Severo Ochoa Program (SEV-2011-00067) of the Spanish Government.Peer ReviewedPostprint (author's final draft

Characteristics of teaching practices in Rural Education: analysis of actions related to teacher training and experience report of pedagogical methodologies proposals for the teaching of specific content

ABSTRACT. Rural Education-RE involves specific elements that are representative of the way of living in the countryside. In a brief search for references related to teacher education focused on CE and also examples of proposals for content teaching, an apparent lack of studies on these themes was identified. Therefore, the objectives of this study were to identify characteristics related to the training of teachers for CE and, in addition, to present practical examples of pedagogical methodologies for teaching specific subjects. For this, a bibliographic research was carried out in scientific articles as well as in a specific database and search engine. The results confirmed, for both themes, the gaps in the scientific literature. The articles found, in general, predominantly involve the analysis of teacher education in the North and Northeast regions. As for the proposals for pedagogical teaching methodologies, the themes are almost exclusively related to science, biology and sustainability. In conclusion, there is an understanding that other curricular components, such as Portuguese language, mathematics and others, have been neglected, either because of their understanding of their lesser relevance in relation to the subjects or contents mentioned, or because researchers are not producing research in this context.ABSTRACT. Rural Education-RE involves specific elements that are representative of the way of living in the countryside. In a brief search for references related to teacher education focused on CE and also examples of proposals for content teaching, an apparent lack of studies on these themes was identified. Therefore, the objectives of this study were to identify characteristics related to the training of teachers for CE and, in addition, to present practical examples of pedagogical methodologies for teaching specific subjects. For this, a bibliographic research was carried out in scientific articles as well as in a specific database and search engine. The results confirmed, for both themes, the gaps in the scientific literature. The articles found, in general, predominantly involve the analysis of teacher education in the North and Northeast regions. As for the proposals for pedagogical teaching methodologies, the themes are almost exclusively related to science, biology and sustainability. In conclusion, there is an understanding that other curricular components, such as Portuguese language, mathematics and others, have been neglected, either because of their understanding of their lesser relevance in relation to the subjects or contents mentioned, or because researchers are not producing research in this context.ABSTRACT. Rural Education-RE involves specific elements that are representative of the way of living in the countryside. In a brief search for references related to teacher education focused on CE and also examples of proposals for content teaching, an apparent lack of studies on these themes was identified. Therefore, the objectives of this study were to identify characteristics related to the training of teachers for CE and, in addition, to present practical examples of pedagogical methodologies for teaching specific subjects. For this, a bibliographic research was carried out in scientific articles as well as in a specific database and search engine. The results confirmed, for both themes, the gaps in the scientific literature. The articles found, in general, predominantly involve the analysis of teacher education in the North and Northeast regions. As for the proposals for pedagogical teaching methodologies, the themes are almost exclusively related to science, biology and sustainability. In conclusion, there is an understanding that other curricular components, such as Portuguese language, mathematics and others, have been neglected, either because of their understanding of their lesser relevance in relation to the subjects or contents mentioned, or because researchers are not producing research in this context.ABSTRACT. Rural Education-RE involves specific elements that are representative of the way of living in the countryside. In a brief search for references related to teacher education focused on CE and also examples of proposals for content teaching, an apparent lack of studies on these themes was identified. Therefore, the objectives of this study were to identify characteristics related to the training of teachers for CE and, in addition, to present practical examples of pedagogical methodologies for teaching specific subjects. For this, a bibliographic research was carried out in scientific articles as well as in a specific database and search engine. The results confirmed, for both themes, the gaps in the scientific literature. The articles found, in general, predominantly involve the analysis of teacher education in the North and Northeast regions. As for the proposals for pedagogical teaching methodologies, the themes are almost exclusively related to science, biology and sustainability. In conclusion, there is an understanding that other curricular components, such as Portuguese language, mathematics and others, have been neglected, either because of their understanding of their lesser relevance in relation to the subjects or contents mentioned, or because researchers are not producing research in this context.Características das práticas de ensino na Educação do Campo: análise de ações relacionadas à formação de professores e relato de experiências de propostas de metodologias pedagógicas para o ensino de conteúdos específicos                            A Educação do Campo-EC envolve elementos próprios que são representativos do modo de viver no campo. Em uma breve busca de referências relacionadas com a formação docente voltada à EC e também exemplos de propostas para o ensino de conteúdos, foi identificada uma aparente escassez de estudo acerca dessas temáticas. Diante disso, os objetivos deste estudo foram a identificação de características relacionadas à formação de professores para a EC e, além disso, apresentar exemplos práticos de metodologias pedagógicas para o ensino de assuntos específicos. Para isso, foi realizada uma pesquisa bibliográfica em artigos científicos bem como em base de dados e buscador específico. Os resultados confirmaram, para ambos os temas, as lacunas existentes na literatura científica. Os artigos encontrados, em geral, envolvem de modo predominante na análise da formação docente as regiões norte e nordeste. Já quanto as propostas de metodologias pedagógicas de ensino, os temas quase que exclusivamente, estão relacionados com ciências, biologia e sustentabilidade. Concluindo, há o entendimento de que outros componentes curriculares, tais como a língua portuguesa, matemática e outros, têm sido negligenciados, seja pelo entendimento de sua menor relevância em relação às disciplinas ou conteúdos citados, ou porque os pesquisadores não estejam produzindo pesquisas nesse contexto. Palavras-chave: educação do campo, pedagogia da alternância, formação de professores, metodologias pedagógicas.   Characteristics of teaching practices in Rural Education: analysis of actions related to teacher training and experience report of pedagogical methodologies proposals for the teaching of specific content ABSTRACT. Rural Education-RE involves specific elements that are representative of the way of living in the countryside. In a brief search for references related to teacher education focused on CE and also examples of proposals for content teaching, an apparent lack of studies on these themes was identified. Therefore, the objectives of this study were to identify characteristics related to the training of teachers for CE and, in addition, to present practical examples of pedagogical methodologies for teaching specific subjects. For this, a bibliographic research was carried out in scientific articles as well as in a specific database and search engine. The results confirmed, for both themes, the gaps in the scientific literature. The articles found, in general, predominantly involve the analysis of teacher education in the North and Northeast regions. As for the proposals for pedagogical teaching methodologies, the themes are almost exclusively related to science, biology and sustainability. In conclusion, there is an understanding that other curricular components, such as Portuguese language, mathematics and others, have been neglected, either because of their understanding of their lesser relevance in relation to the subjects or contents mentioned, or because researchers are not producing research in this context. Keywords: rural education, alternation pedagogy, teacher training, pedagogical methodologies.   Características de las prácticas docentes en Educación Rural: análisis de acciones relacionadas con la formación docente e informe de experiencia de propuestas de metodologías pedagógicas para la enseñanza de contenidos específicos RESUMEN. La Educación Rural-ER involucra elementos específicos que son representativos de la forma de vida en el campo. En una breve búsqueda de referencias relacionadas con la formación del profesorado centradas en la EC y también ejemplos de propuestas para la enseñanza de contenidos, se identificó una aparente falta de estudios sobre estos temas. Por tanto, los objetivos de este estudio fueron identificar características relacionadas con la formación de docentes para EC y, además, presentar ejemplos prácticos de metodologías pedagógicas para la enseñanza de materias específicas. Para ello, se realizó una búsqueda bibliográfica de artículos científicos, también en la base de datos y en un buscador específico. Los resultados confirmaron, para ambos temas, la brecha en la literatura científica. Los artículos encontrados, en general, involucran predominantemente el análisis de la formación docente en las regiones Norte y Nordeste. En cuanto a las propuestas de metodologías pedagógicas de enseñanza, los temas están casi exclusivamente relacionados con la ciencia, la biología y la sostenibilidad. En conclusión, se entiende que se han descuidado otras componentes curriculares, como lengua portuguesa, matemáticas y otros, ya sea por entender su menor relevancia en relación con las materias o contenidos mencionados, bien porque los investigadores no están produciendo investigación en este contexto. Palabras clave: educación rural, pedagogía de alternancia, formación docente, metodologías pedagógicas

Avaliação da força muscular em jovens jogadores de futebol e incidência de lesão muscular

Orientação: Raquel Maria dos Santos Barreto Sajara MadeiraO objetivo do presente estudo foi avaliar a força muscular em jogadores de futebol de formação de um clube da cidade de Lisboa, através da avaliação isocinética e avaliação dos saltos, em função da idade, posição específica e incidência de lesão muscular. Foram avaliados 108 atletas, do sexo masculino, dos escalões Iniciados A (Sub-15), Juvenis B (Sub-16), Juvenis A (Sub-17), e Juniores (Sub-19). A avaliação das variáveis antropométricas foi realizada através da medição da massa corporal e da estatura, a partir das quais foram calculados o IMC dos atletas. A avaliação da força muscular foi realizada através do dinamômetro isocinético Biodex System 4 Pro™, onde foram analisados o Pico de Torque (PT) e o Ângulo do PT, nas velocidades 60° e 300°/s. Os testes de saltos foram realizados utilizando-se do aparelho Microgate OptoGait, e consistiu dos saltos Squat Jump (SJ), Countermovement jump (CMJ), Countermovement Jump Unipedal (CMJU), e Drop Jump (DJ). O registo das lesões foi feito baseado nos relatórios emitidos pelo clube. Os resultados das avaliações isocinéticas revelaram que os Defesas centrais apresentaram maior capacidade de produção de força quando comparados aos Médios e Médios ala, e que o grupo Sub 17 foi aquele que apresentou uma capacidade de produção de força estatististicamente superior. Os testes de saltos indicam que os Defesas laterais e os Avançados apresentaram capacidade de produção de força superior aos outros grupos, enquanto os Médios foram aqueles que apresentam uma menor capacidade de produção de força. Além disso, em termos de escalões, o grupo Sub 17 foi aquele capaz de produzir mais força quando comparado aos outros grupos. Por fim, verificamos que os atletas sofreram mais lesões não-traumáticas do que traumáticas, com frequencia maior nos treinos do que nos jogos.The objective of the present study was to evaluate the muscular strength in soccer players of a club in the city of Lisbon, through isokinetic evaluation and evaluation of jump tests, according to age, specific position and incidence of muscle injury. A total of 108 male athletes were selected from the Initiated A (U15), Juvenile B (U16), Juvenile A (U17), and Junior (U19) groups. The assessment of the anthropometric variables was performed through the measurement of body mass and height, from which the BMI of the athletes were calculated. The muscular strength evaluation was performed using the Biodex System 4 Pro ™ isokinetic dynamometer, in which the Torque Peak (PT) and the PT Angle were analyzed at speeds of 60° and 300°/s. The jump tests were performed using the Microgate OptoGait apparatus, and consisted of Squat jump (SJ), Countermovement jump (CMJ), Countermovement Jump Unipedal (CMJU), and Drop Jump (DJ). The injury record was based on reports issued by the club. The results of the isokinetic evaluations revealed that the Central Defenders presented greater strength production capacity when compared to the Midfield and Mid Wings, and that the Under 17 group was the one that presented a statistically superior strenght production capacity. The jump tests indicated that the Fullbacks and Forwards presented superior power production capacity to the other groups, while the Midfielders were those with a lower strenght production capacity. In addition, the Sub 17 group was the one capable of producing more strenght when compared to the other groups. Finally, we found that athletes suffered more non-traumatic than traumatic injuries, with a higher frequency in training than in games

Optical analogue models for black holes and wormholes

Agência 1This work aims to present and discuss the optical analogue models used to study gravitational systems using condensed matter systems. The whole mathematical theory behind the construction of an analogue optical model and the explicit presentation of two analogue models are provided: Schwarzschild black hole and Morris-Thorne wormhole. A parametrization of such models is proposed in order to unify them through a free real parameter β that generates a family of new models, and open the possibility that some of theses new models could actually be analogue models

E-EON : Energy-Efficient and Optimized Networks for Hadoop

Energy efficiency and performance improvements have been two of the major concerns of current Data Centers. With the advent of Big Data, more information is generated year after year, and even the most aggressive predictions of the largest network equipment manufacturer have been surpassed due to the non-stop growing network traffic generated by current Big Data frameworks. As, currently, one of the most famous and discussed frameworks designed to store, retrieve and process the information that is being consistently generated by users and machines, Hadoop has gained a lot of attention from the industry in recent years and presently its name describes a whole ecosystem designed to tackle the most varied requirements of today’s cloud applications. This thesis relates to Hadoop clusters, mainly focused on their interconnects, which is commonly considered to be the bottleneck of such ecosystem. We conducted research focusing on energy efficiency and also on performance optimizations as improvements on cluster throughput and network latency. Regarding the energy consumption, a significant proportion of a data center's energy consumption is caused by the network, which stands for 12% of the total system power at full load. With the non-stop growing network traffic, it is desired by industry and academic community that network energy consumption should be proportional to its utilization. Considering cluster performance, although Hadoop is a network throughput-sensitive workload with less stringent requirements for network latency, there is an increasing interest in running batch and interactive workloads concurrently on the same cluster. Doing so maximizes system utilization, to obtain the greatest benefits from the capital and operational expenditures. For this to happen, cluster throughput should not be impacted when network latency is minimized. The two biggest challenges faced during the development of this thesis were related to achieving near proportional energy consumption for the interconnects and also improving the network latency found on Hadoop clusters, while having virtually no loss on cluster throughput. Such challenges led to comparable sized opportunity: proposing new techniques that must solve such problems from the current generation of Hadoop clusters. We named E-EON the set of techniques presented in this work, which stands for Energy Efficient and Optimized Networks for Hadoop. E-EON can be used to reduce the network energy consumption and yet, to reduce network latency while cluster throughput is improved at the same time. Furthermore, such techniques are not exclusive to Hadoop and they are also expected to have similar benefits if applied to any other Big Data framework infrastructure that fits the problem characterization we presented throughout this thesis. With E-EON we were able to reduce the energy consumption by up to 80% compared to the state-of-the art technique. We were also able to reduce network latency by up to 85% and in some cases, even improve cluster throughput by 10%. Although these were the two major accomplishment from this thesis, we also present minor benefits which translate to easier configuration compared to the stat-of-the-art techniques. Finally, we enrich the discussions found in this thesis with recommendations targeting network administrators and network equipment manufacturers.La eficiencia energética y las mejoras de rendimiento han sido dos de las principales preocupaciones de los Data Centers actuales. Con el arribo del Big Data, se genera más información año con año, incluso las predicciones más agresivas de parte del mayor fabricante de dispositivos de red se han superado debido al continuo tráfico de red generado por los sistemas de Big Data. Actualmente, uno de los más famosos y discutidos frameworks desarrollado para almacenar, recuperar y procesar la información generada consistentemente por usuarios y máquinas, Hadoop acaparó la atención de la industria en los últimos años y actualmente su nombre describe a todo un ecosistema diseñado para abordar los requisitos más variados de las aplicaciones actuales de Cloud Computing. Esta tesis profundiza sobre los clusters Hadoop, principalmente enfocada a sus interconexiones, que comúnmente se consideran el cuello de botella de dicho ecosistema. Realizamos investigaciones centradas en la eficiencia energética y también en optimizaciones de rendimiento como mejoras en el throughput de la infraestructura y de latencia de la red. En cuanto al consumo de energía, una porción significativa de un Data Center es causada por la red, representada por el 12 % de la potencia total del sistema a plena carga. Con el tráfico constantemente creciente de la red, la industria y la comunidad académica busca que el consumo energético sea proporcional a su uso. Considerando las prestaciones del cluster, a pesar de que Hadoop mantiene una carga de trabajo sensible al rendimiento de red aunque con requisitos menos estrictos sobre la latencia de la misma, existe un interés creciente en ejecutar aplicaciones interactivas y secuenciales de manera simultánea sobre dicha infraestructura. Al hacerlo, se maximiza la utilización del sistema para obtener los mayores beneficios al capital y gastos operativos. Para que esto suceda, el rendimiento del sistema no puede verse afectado cuando se minimiza la latencia de la red. Los dos mayores desafíos enfrentados durante el desarrollo de esta tesis estuvieron relacionados con lograr un consumo energético cercano a la cantidad de interconexiones y también a mejorar la latencia de red encontrada en los clusters Hadoop al tiempo que la perdida del rendimiento de la infraestructura es casi nula. Dichos desafíos llevaron a una oportunidad de tamaño semejante: proponer técnicas novedosas que resuelven dichos problemas a partir de la generación actual de clusters Hadoop. Llamamos a E-EON (Energy Efficient and Optimized Networks) al conjunto de técnicas presentadas en este trabajo. E-EON se puede utilizar para reducir el consumo de energía y la latencia de la red al mismo tiempo que el rendimiento del cluster se mejora. Además tales técnicas no son exclusivas de Hadoop y también se espera que tengan beneficios similares si se aplican a cualquier otra infraestructura de Big Data que se ajuste a la caracterización del problema que presentamos a lo largo de esta tesis. Con E-EON pudimos reducir el consumo de energía hasta en un 80% en comparación con las técnicas encontradas en la literatura actual. También pudimos reducir la latencia de la red hasta en un 85% y, en algunos casos, incluso mejorar el rendimiento del cluster en un 10%. Aunque estos fueron los dos principales logros de esta tesis, también presentamos beneficios menores que se traducen en una configuración más sencilla en comparación con las técnicas más avanzadas. Finalmente, enriquecimos las discusiones encontradas en esta tesis con recomendaciones dirigidas a los administradores de red y a los fabricantes de dispositivos de red

Instituições informais e poder local: o funcionamento da Câmara Municipal de Américo Brasiliense a partir dos projetos de lei (2010-2018)

This work aims to analyze the political-institutional variables that guide the behavior of the councilors in the Municipality of Américo Brasiliense - SP and the relationship between Legislative and Executive at the local level. The theoretical model used emphasizes the role of informal rules and institutions in decision-making processes that regulate political practice, that is, those that guide and constrain the behavior of agents, although they are not formally instituted. The projects considered were the individual parliamentary amendments of the councilors, which figure as an informal institution from which the councilman seeks to meet a specific demand from the electorate and, in return, approaches the agenda proposed by the Executive. The results point in the direction of a complementary relationship between formal and informal institutions - that is, relationships that increase the efficiency of legislative activities -, in view of the increasing role of parliamentary amendments as the main action tools of councilors.El objetivo de este trabajo es analizar las variables político-institucionales que guían el comportamiento de los concejales en el Municipio de Américo Brasiliense - SP y la relación entre Legislativo y Ejecutivo a nivel local. El modelo teórico utilizado enfatiza el papel de las reglas e instituciones informales en los procesos de toma de decisiones que regulan la práctica política, es decir, aquellos que guían y limitan el comportamiento de los agentes, aunque no están formalmente instituidos. Los proyectos considerados fueron las enmiendas parlamentarias individuales de los concejales, que figuran como una institución informal desde la cual el concejal busca satisfacer una demanda específica del electorado y, a cambio, se acerca a la agenda propuesta por el Ejecutivo. Los resultados apuntan en la dirección de una relación complementaria entre las instituciones formales e informales, es decir, las relaciones que aumentan la eficiencia de las actividades legislativas, en vista del papel cada vez mayor de las enmiendas parlamentarias como las principales herramientas de acción de los consejeros.Este trabalho objetiva analisar as variáveis político-institucionais que orientam o comportamento dos vereadores na Câmara Municipal de Américo Brasiliense – SP e a relação entre Legislativo e Executivo no âmbito local. O modelo teórico utilizado enfatiza o papel das regras e instituições informais dos processos decisórios que regulam a prática política, isto é, aquelas que orientam e constrangem o comportamento dos agentes, embora não se encontrem formalmente instituídas. Os projetos considerados foram as emendas parlamentares individuais dos vereadores, que figuram como uma instituição informal a partir da qual o vereador procura atender a uma demanda específica do eleitorado e, em troca, aproxima-se da agenda proposta pelo Executivo. Os resultados apontam na direção de uma relação de complementaridade entre instituições formais e informais – isto é, relações que aumentem a eficiência das atividades legislativas –, tendo em vista o crescente protagonismo das emendas parlamentares como principais ferramentas de ação dos vereadores

Habitat structure in the composition of leaf-litter insects in mosaic environment

Habitat structure in the composition of leaf-litter insects in mosaic environment </htm

High Throughput and Low Latency on Hadoop Clusters Using Explicit Congestion Notification: The Untold Truth

Various extensions of TCP/IP have been proposed to reduce network latency; examples include Explicit Congestion Notification (ECN), Data Center TCP (DCTCP) and several proposals for Active Queue Management (AQM). Combining these techniques requires adjusting various parameters, and recent studies have found that it is difficult to do so while obtaining both high performance and low latency. This is especially true for mixed use data centres that host both latency-sensitive applications and high-throughput workloads such as Hadoop.This paper studies the difficulty in configuration, and characterises the problem as related to ACK packets. Such packets cannot be set as ECN Capable Transport (ECT), with the consequence that a disproportionate number of them are dropped. We explain how this behavior decreases throughput, and propose a small change to the way that non-ECT-capable packets are handled in the network switches. We demonstrate robust performance for modified AQMs on a Hadoop cluster, maintaining full throughput while reducing latency by 85%. We also demonstrate that commodity switches with shallow buffers are able to reach the same throughput as deeper buffer switches. Finally, we explain how both TCP-ECN and DCTCP can achieve the best performance using a simple marking scheme, in constrast to the current preference for relying on AQMs to mark packets.The research leading to these results has received funding from the European Unions Seventh Framework Programme (FP7/2007–2013) under grant agreement number 610456 (Euroserver). The research was also supported by the Ministry of Economy and Competitiveness of Spain under the contracts TIN2012-34557 and TIN2015-65316-P, Generalitat de Catalunya (contracts 2014-SGR-1051 and 2014-SGR-1272), HiPEAC-3 Network of Excellence (ICT- 287759), and the Severo Ochoa Program (SEV-2011-00067) of the Spanish Government.Peer ReviewedPostprint (author's final draft