Summary: In the present study, the kinematic and stress analysis of an aerator roller with blades was performed. The trajectories of the aerator roller blades were obtained, which included the rotational and translational movements on the ground. Longitudinal underground areas and volumes of the cracks were calculated for rectangular blades (Type A), symmetric triangular (Type 1) and asymmetric triangular (Type 2) blades. The results of the kinematic analysis reported that type A blades significantly modified soil with respect to the other two. Normal forces were calculated numerically and per finite element, obtaining for blade type 1 numerically calculated forces of 4.52 MPa in the upper zone of the element and -7.06 MPa in its lower zone. The normal stress calculated per finite element were found in the range from 3.66 to 6.52 MPa for the upper part of the element and -7.8 MPa for its lower part. For type 2 design, a normal stress was obtained numerically of 8.83 MPa. The normal stress calculated per finite element was found in the range from 3.95 to 12.86 MPa.

Resumen: En el presente estudio se realizó el análisis cinemático y de esfuerzos de un rodillo aireador con cuchillas. Se obtuvieron las trayectorias de las cuchillas del rodillo aireador, las cuales incluyen los movimientos de rotación y de traslación sobre el terreno. Se calcularon áreas longitudinales bajo el suelo y volúmenes de las grietas para cuchillas de forma rectangular (Tipo A), triangular simétrica (Tipo 1) y triangular asimétrica (Tipo 2). Los resultados del análisis cinemático reportan que las cuchillas de tipo A modifican considerablemente el suelo con respecto a las otras dos cuchillas. Se calcularon esfuerzos normales numéricamente y por elemento finito, obteniendo para la cuchilla tipo 1 esfuerzos calculados numéricamente de 4.52 MPa en la zona superior del elemento y -7.06 MPa en la zona inferior del mismo. Los esfuerzos normales calculados por elemento finito, se encontraron en el rango de 3.66 a 6.52 MPa para la parte superior del elemento y -7.8 MPa para la parte inferior del mismo. Para la cuchilla tipo 2 se obtuvo un esfuerzo normal de forma numérica de 8.83 MPa. Los esfuerzos normales calculados por elemento finito se encontraron en el rango de 3.95 a 12.86 MPa.

RESUMO O presente trabalho teve como objetivo sumarizar as evidências de estudos sobre como a participação em aulas de educação física (EF) baseadas na educação desportiva (EDE) tem sido relacionada a atividade física (AF) em adolescentes, sobretudo quanto a participação em atividade física moderada a vigorosa (AFMV), fatores psicológicos e sociais. Foi realizada uma revisão sistemática que incluiu 8 bases eletrônicas (PubMed, Scopus, Web of Science, LILACS, SPORTDiscus, PSYCINFO, ERIC e COCHRANE). Uma pesquisa inicial alcançou 162 títulos, permanecendo 149 após a retirada dos duplicados. Outros 10 estudos foram incluídos com base nas listas de referências, totalizando 159 estudos na fase de identificação. Na triagem, foram excluídas 89 referências, permanecendo 70 referências para análise de texto completo. Nesta etapa, foram excluídas 53 referências, resultando em 17 referências que preencheram os critérios de inclusão. Os estudos foram realizados entre 2002 e 2017, a maioria nos Estados Unidos. A maioria dos estudos reportou melhoras quanto aos fatores psicológicos e sociais, principalmente a motivação. Os dados sobre a participação dos adolescentes em AFMV foram contraditórios e inconclusivos, dificultando a compreensão do contributo do modelo para prática de AF dos alunos.

ABSTRACT This article aimed to summarize the evidence from studies on how participation in physical education (PE) classes based on sports education (EDE) has been related to physical activity (PA) in adolescents, especially regarding participation in moderate to vigorous physical activity (MVPA), psychological and social factors. A systematic review was carried out that included eight electronic databases (PubMed, Scopus, Web of Science, LILACS, SPORTDiscus, PsycINFO, ERIC, and COCHRANE). An initial search reached 162 titles, remaining 149 after removing duplicates. Another ten studies were included based on the reference lists, totaling 159 studies in the identification phase. In the screening, 89 references were excluded, remaining 70 references for full-text analysis. In this stage, 53 references were excluded, resulting in 17 references that met the inclusion criteria. The studies were carried out between 2002 and 2017, mostly in the United States. Most studies reported improvements in psychological and social factors, especially motivation. The data on the participation of adolescents in MVPA were contradictory and inconclusive, making it difficult to understand the model's contribution to students' PA practice.

ABSTRACT. In recent decades, global abalone aquaculture has significantly increased, while wild abalone fishery landings have decreased drastically, shifting production from fishing to farming. In California (USA) and Baja California (Mexico), overfishing and climate change-linked diseases are thought to be responsible for mass mortalities and significant declines in abalone fisheries landings. Conservation aquacul ture is an option for enhancing abalone populations through captive propagation and cage mariculture with subsequent restockings into the wild. To test, inform, and promote innovative sustainable seafood production strategies in the Northeastern Pacific, we designed an experimental mariculture system at San Jeronimo Island, Baja California. We explored the feasibility of rearing juvenile red abalone, Haliotis rufescens, in a near-shore mariculture cage-based production system to supply individuals for local restoration programs. We tested the effects of 2 different depths, surface and bottom (5 m), and 3 macroalgal diets (Macrocystis pyrifera, Eisenia arborea, and a mixed diet of Pelagophycus porra with M. pyrifera) on the survival and growth of juvenile red abalone (32 ± 3.33 mm in shell length) inside cages attached to a long-line system. Over the 90-d experiment, survival was 99% for the surface treatment and 95% for the bottom treatment. Mean daily increment in shell length was 93 ± 12 μm·d-1 in surface cages and 82 ± 13 μm·d-1 in bottom cages. Depth did not affect growth or survival. Growth was highest using the E. arborea diet (99 ± 7 μm·d-1) but not significantly different from the M. pyrifera and mixed diets (88 ± 10 and 74 ± 13 μm·d-1, respectively). High survivorship and growth indicate that San Jeronimo Island can support cage-based mariculture of red abalone and that this strategy may be a useful tool in developing climate-resilient abalone restoration solutions aimed at bolstering seafood production.

RESUMEN. En décadas recientes, el aumento significativo de la acuicultura global del abulón y la disminución drástica de desembarques de abulón silvestre han ido cambiando la producción de la pesca al cultivo. En California (EUA) y Baja California (México) se cree que enferme dades asociadas al cambio climático y la sobrepesca son la causa de eventos de mortalidad masiva y el declive significativo en los desembarques de abulón silvestre. La acuicultura de conservación es una opción para mejorar las poblaciones de abulón mediante la propagación de organismos de criadero y la maricultura en jaulas, con el subsecuente repoblamiento en la naturaleza. Para experimentar, informar y promover estrategias innovadoras en la producción sostenible de recursos marinos en el Pacífico Nororiental, hemos diseñado un sistema experimental de maricultura en isla San Jerónimo, Baja California. Exploramos la factibilidad de cultivar abulón rojo juvenil, Haliotis rufescens, en un sistema de producción de maricultura costera basado en jaulas, para suplir individuos para programas locales de repoblamiento. Analizamos el efecto de 2 profundidades diferentes, superficie y fondo (5 m), y de 3 dietas de macroalgas (Macrocystis pyrifera, Eisenia arborea, y dieta mixta de Pelagophjycus porra y M. pyrifera) en la supervivencia y el crecimiento de juveniles de abulón rojo (32 ± 3.33 mm en longitud de concha) dentro de jaulas aseguradas a un sistema de línea madre. Durante el experimento de 90 d, la supervivencia fue del 99% para el tratamiento de superficie y del 95% para el tratamiento de fondo. El incremento diario en longitud de concha fue 93 ± 12 μm·d-1 en las jaulas de superficie y 82 ± 13 μm·d-1 en las jaulas de fondo. La profundidad no afectó el crecimiento o la supervivencia. El crecimiento fue mayor con la dieta de E. arborea (99 ± 7 μm·d-1), pero no fue significativamente diferente del crecimiento con la dieta de M. pyrifera y la dieta mixta (88 ± 10 y 74 ± 13 μm·d-1, respectivamente). La alta supervivencia y crecimiento indican que isla San Jerónimo puede sostener la maricultura de abulón rojo en jaulas y que esta estrategia puede ser una herramienta útil para desarrollar soluciones climático-resilientes de restauración de abulón destinadas a impulsar la producción de mariscos.

Abstract This study aimed to explore the association between psychosocial factors and organized physical activity (PA) in urban children and adolescents. Data on organized PA, psychosocial variables, and demographic characteristics were collected via questionnaires. Logistic regression analyses were used to examine the relationship between psychosocial correlates and organized PA. Analyses were run separately for different age groups. Results showed that children and adolescents with a greater positive attitude toward PA were more likely to be involved in organized PA. Ego orientation was associated with organized PA at the age of 13-15 years. Task orientation was related to PA participation at the age of 13-15 and 16-18 years. Perception of competence was related to participation at the age of 10-12 and 13-15 years. These findings suggest that interventions to increase the level of participation in organized PA in youth should focus on increasing students' perceived physical competence, attitude toward PA, and establishing a strong motivational task/mastery climate.

Objetivos O conhecimento dos níveis de atividade física e dos comportamentos sedentários dos adolescentes é importante para que as intervenções no âmbito da promoção da saúde possam estar de acordo com a população-alvo. Assim sendo, o objetivo do estudo foi descrever a prática de atividade física, os comportamentos sedentários e diferentes perfis comportamentais de adolescentes citadinos. Métodos Participaram no estudo 651 adolescentes (273 rapazes e 378 raparigas), com idades compreendidas entre os 12-14 anos, que frequentavam 4 escolas do ensino público em Lisboa. Os dados foram recolhidos através de fichas de registo diário de avaliação momentânea ecológica, com intervalos de 15 minutos. Resultados Nos dias de semana, estudar foi o comportamento mais praticado (rapazes 114,5 min/dia; 11,3%, raparigas 135,4 min/dia; 13,1%); seguido de ver televisão (rapazes 97,8 min/dia; 9,6%, raparigas 59,7 min/dia; 5,8%); usar o computador, para os rapazes (42,7 min/dia; 4,2%), e falar com amigos (31,5 min/dia; 3%), para as raparigas. Rapazes e raparigas dedicaram 40,9 min/dia (4%) e 24 min/dia (2,3%) a praticar atividade física, respetivamente. No fim-de-semana, para os rapazes destacou-se o tempo a ver televisão (145,8 min/dia; 13,5%) e usar o computador (136,6 min/dia; 12,9%), e para as raparigas estudar (144,3 min/dia; 13,1%) e ver televisão (133,5 min/dia; 12,2%). Com base nos comportamentos mais praticados, foram traçados 3 perfis dos adolescentes. Para os rapazes destacaram-se: 1) pouco ativos, pouco dedicados aos estudos, mas que passavam muito tempo no computador, a ver televisão e a conversar com amigos (n = 63); 2) dedicados aos estudos, não praticavam atividade física e viam pouco a televisão e o computador (n = 126); 3) fisicamente ativos, muito tempo a ver televisão e pouco dedicados aos estudos (n = 84). Para as raparigas destacaram-se as: 1) fisicamente ativas, que passavam pouco tempo a estudar e a ver televisão (n = 28); 2) que passavam muito tempo a estudar e conversar com os amigos e pouco ativas (n = 77); 3) as que passavam muito tempo a ver televisão e pouco tempo a conversar com os amigos e a praticarem atividade física (n = 273). Conclusão As raparigas apresentaram níveis de atividade física inferiores aos rapazes. Os rapazes, apesar de apresentarem níveis mais elevados de atividade física do que as raparigas, apresentaram igualmente níveis mais elevados de comportamentos sedentários. Estes dados sugerem que é possível ser considerado fisicamente ativo e passar muito tempo em comportamentos sedentários. Isso deve ser considerado no planeamento de intervenções com vista a promover estilos de vida ativos e saudáveis junto dos adolescentes.

Purpose The knowledge of physical activity levels and sedentary behaviour of adolescents is important, so that interventions to promote health have to be in accordance with the target population. Therefore this study aimed to examine the prevalence and clustering of physical activity and sedentary behaviours among urban adolescents. Methods The study comprised a total of 651 adolescents (273 boys and 378 girls) aged 12-14, from 4 public urban schools. Ecological Momentary Assessment was used to measure sedentary behaviours and physical activity, using 15 minutes time intervals. Results On weekdays, studying was the activity on which adolescents spent more time (boys 114.5 min/day, 11.3%; girls 135.4 min/day, 13.1%). Followed by television (TV) (boys 97.8 min/day, 9.6%; girls 59.7 min/day, 5.8%), computer use (boys 42.7 min/day, 4.2%), and talking with friends (girls 31.5 min/day, 3%). On average boys practiced 40.9 min/day (4%) and girls 24 min/day (2.3%) on physical activity. On weekend days, the most consuming leisure time was TV (145.8 min/day, 13.5%) and computer use (136.6 min/day, 12.9%) for the boys, and studying (144.3 min/day, 13.1%) and TV (133.5 min/day, 12.2%) for the girls. Based on these behaviours three meaningful cluster solutions were found both for boys and girls, respectively. For the boys: cluster 1) less actives, spent less time studying, but spent more time watching TV and on the computer (n = 63); cluster 2) devoted more time studying and spent less time on physical activity, watching TV and using computer (n = 126); cluster 3) actives, spent less time watching TV and studying (n = 84). For the girls: cluster 1) actives, less time studying, watching TV and using computer (n = 28); cluster 2) devoted to studies, sociable and non-actives (n = 77); cluster 3) much time watching TV, non-sociable and non-actives (n = 273). Conclusion Girls were less active than boys. Despite having higher levels of physical activity than girls boys also presented higher levels of sedentary behaviours. These data suggest that it is possible to be considered physically active and spend a lot of time in sedentary behaviours. This should be considered in intervention programs aimed to promote active and healthy lifestyles among adolescents.

The importance of the guava lies in its being the economic support of some regions in Mexico. It is presently harvested in areas which have a certain type of conditions in Mexico similar to those in areas such as Zacatecas, Aguascalientes and Michoacán. Several problems related to mechanical damage, such as those that happen during harvesting, transporting and storage appear during its commercialization. Damage accelerates the guava fruit physiological, which translates into an economic loss due to the reduced shelf life of the fruit. The objective of this paper was to determinate the behavior of the guava fruits ( psidium guajava L .) subjected to impact that happens during the crop and the following operations of manipulation when a fruit is hit against a surface, its relationship with the physiologic, and lost processes of weight. Guava fruits of the Calvillo and “Criolla” variety were exposed to impact on plastic and wood surfaces. The production of ethylene and CO 2 were measured, and found to be significant. With regards to impact, the most noticeable differences appeared when the position changed from horizontal to vertical finding more deformation in the “Criolla” fruits. Variables were measured during the 4 days, finding weight loss of up to 9% for impact.

La importancia del cultivo de guayaba radica en el aporte económico para algunas regiones de México. Actualmente se cultiva de forma general en lugares con cierto tipo de condiciones equivalentes en México a zonas como Aguascalientes, Zacatecas y Michoacán. Durante la comercialización se presentan muchos problemas relacionados con los daños mecánicos que se ocasionan durante la cosecha, transporte y almacenamiento, dichos daños aceleran la actividad fisiológica de los frutos de guayaba que se traduce en pérdidas económicas por la reducida vida de anaquel de los frutos. El objetivo de este trabajo consistió en determinar el comportamiento de los frutos de guayaba (psidium guajava L.) sometidos a impacto que ocurre durante la cosecha y las siguientes operaciones de manipulación cuando un fruto se golpea contra una superficie, su relación con los procesos fisiológicos, y perdidas de peso. Se realizaron pruebas a frutos de guayaba de las variedades Calvillo y Criolla sometidas a impacto en superficies de madera y plástico. Se midió la producción de etileno y CO2 los cuales son significativos. En el impacto las diferencias notables se vieron cuando se varía la posición de vertical a horizontal observando la mayor deformación en los frutos criollos. Durante los cuatro días que se midieron las variables se observaron pérdidas de peso debidas al impacto de hasta 9%.

The purpose of the bibliographical revision is the importance of the guava crop because of its economic contribution for some Mexican regions. Many problems arise during the commercialization; they are related to mechanical damages in the harvest, transportation and storage. These damages accelerate the physiological activity of fruits which results in economical losses due to the short life cycle of fruits. Once the fruits are harvested, they interact with many other factors. One of the ways to keep the product quality is taking measures so that those factors do not affect the product. These damages are mainly caused by the harvest operations, storage and transportation. To detect them is the hardest thing to do, regarding they are not visible at the very moment they take place.

La revisión bibliográfica está dirigida a la importancia del cultivo de guayaba la cual radica en el aporte económico para algunas regiones de México. Durante la comercialización se presentan muchos problemas relacionados con los daños mecánicos durante la cosecha, transporte y almacenamiento, dichos daños aceleran la actividad fisiológica de los frutos de guayaba ocasionando pérdidas económicas por la reducida vida de anaquel de los frutos. Una vez que los frutos se cosechan, existen gran cantidad de factores que interactúan con los frutos. Una de las vías para mantener las características de calidad de los productos es interviniendo de manera que dichos factores no provoquen daños en el producto. Los daños son ocasionados en su mayoría por las operaciones de cosecha, almacenamiento y transporte. El problema más grande radica en detectarlos, puesto que no son visibles al momento en que ocurren.

The injection of fertilizers in fertirrigation is commonly undertaken through Venturi pipes and controlled with the help of conductivity and pH sensors placed at the irrigation outlet point. The Venturi pipes suffer from pressure drops during injection. The fertirrigation equipment was, therefore, redesigned so that pressure drops are controlled by means of a fertilizer injection system powered by rotary vane pumps that provide a continuous volume. A PLC Millennium II XT-20 controls the injection using a program based on the electrical conductivity relationships that exist between the mixed solutions when mixed amongst themselves and when diluted in water in laboratory tests using concentrated solutions for Saladet tomatoes. These relationships allow one to predict the behaviour of the electrical conductivity when varying the percentage of each one of the elements that make it up. According to the equations, a ratio of 3:100 3--3 of fertilizer per 100 of water--must be provided in order to obtain conductivity in the 2 to 3 mS/cm value range, in which the plant has a better opportunity to take advantage of the nutrients. Comparing the pressure drops in the injection outlet point, the Venturi system loses 40 kPa while the system powered by rotary vane pumps does not lose pressure.

La inyección de fertilizantes en el fertirriego se realiza comúnmente a través de tubos Venturi y se controla con ayuda de sensores de conductividad y pH colocados en la salida del riego. Los tubos Venturi presentan problemas de caídas de presión durante la inyección. De este modo se innova con el diseño de un equipo de fertirriego controlando las perdidas de presión usando un sistema de inyección de fertilizantes por bombas de paletas rotatorias que suministran un caudal continuo. El control de la inyección lo hace un PLC Millenium II XT- 20 con un programa basado en las relaciones de conductividad eléctrica que existen entre las soluciones madre al ser mezcladas entre si y al diluirlas en agua en pruebas de laboratorio utilizando soluciones concentradas para jitomate saladet. Las relaciones permiten predecir el comportamiento de la conductividad eléctrica al variar el porcentaje de cada uno de los elementos que la componen. Las ecuaciones indican que debe suministrarse una relación 3:100, 3 de fertilizante por 100 de agua para obtener la conductividad en el rango de 2 a 3 mS/cm, valor donde la planta tiene un mejor aprovechamiento de los nutrientes. Al comparar la caída de presión en la salida de la inyección el sistema Venturi pierde 40 kPa y el equipo con bombas de paletas no presenta pérdidas de presión.