Impacto de un programa de promoción de actividad física para la salud en niños de edad escolar de la ciudad de La Plata

Introducción. El aumento de la obesidad y el sedentarismo en niños es un problema social grave. La adopción de hábitos activos contribuye a la prevención de estos trastornos. Objetivos. Medir el efecto de un programa escolar de promoción de actividad física (AF). Material y método. Estudio de intervención controlado no aleatorizado. Participaron 123 niños de ambos sexos, 32 en el grupo intervención (I) y 92 en el grupo control (C). El nivel de AF se obtuvo por cuestionario. Se ponderó el grado de asociación conceptual entre AF y salud mediante test relacional. El grupo I participó de talleres durante 8 semanas durante una hora semanal en horario escolar. Resultados. La práctica deportiva creció 10 en grupo I y 2,9 en C, la diferencia entre medias fue 7.1. (p menor a 0.05). El grupo I aumentó la cantidad de veces que usan la bicicleta por semana 2,88 a 3,56. En el grupo I el tiempo de pedaleo aumentó 30.57 min./sem y disminuyó las horas frente al TV en 1.40 min/día. El grupo I aumentó la importancia que los niños asignan a la AF relación a la salud en forma significativa. Conclusiones. Implementar estrategias de promoción de AF puede favorecer cambios de hábitos y conductas hacia un estilo de vida saludable cuando se trabaja sistemáticamente en talleres mediante la participación activa de niños y maestros.

Concentration of the rare-earth elements in metalliferous sediments from DSDP Leg 92 holes

DSDP Leg 92 drilled at four sites along an east-west transect at 19°S on the western flank of the East Pacific Rise (EPR), in an area where sediments are essentially a mixture of hydrothermal and biogenic components, with only a minimal contribution of clastic material. Rare-earth element (REE) data on the metalliferous (non-carbonate) fraction of samples ranging in age from ~2 to ~27 Ma indicate the existence of two distinct groups of patterns corresponding to two broad age groups, one <=8 Ma, the other >=10 Ma. Within each group, REE patterns have characteristics which are near-uniform, despite large variations in total REE abundances. Sediments of the younger group are enriched in light REE (LREE) relative to deep bottom waters influenced by the hydrothermal plume extending west from the EPR at 19°S. Sediments of the older groups show further relative LREE enrichment and/or heavy REE (HREE) depletion. Surficial sediments deposited beneath the lysocline have high Sum REE concentrations resulting from slow accumulation rates, and patterns resembling older sediments due to early diagenetic effects. A correlation between the mass accumulation rates (MAR) of Sum REE and Fe + Mn suggests that ferromanganese particulate matter supplied by the hydrothermal plume scavenges REE; during this process the LREE are preferentially removed from plume seawater. The MAR of Fe + Mn shows a general decrease with age above basement, whereas Sum REE concentrations in the metalliferous component increase with age above basement. This supports the Ruhlin and Owen model wherein limited scavenging of REE, due to rapid burial of sediment near the palaeo-axis, leads to low concentrations (but high MAR-values) for the REE. Following deposition and burial of the hydrothermal component, further relative flattening of the REE pattern takes place, probably the result of diagenetic reactions over several million years. Phase partitioning data indicate that the proportion of REE residing in more poorly crystalline phases tends to increase with age (from ~45% to 90% of Sum REE). This suggests that as initial ferromanganese precipitates undergo diagenetic recrystallization, REE are transferred to the poorly crystalline phases, and/or are scavenged from pore waters by these phases. Because of the various modifications to REE patterns apparently produced both in the water column and post-depositional settings, the REE patterns of metalliferous sediments will not reflect fine-scale REE variations in associated oceanic water masses.