Análisis del estado de competencia y manejo de la densidad en rodales de Populus deltoides Marsh, en el Delta del Paraná

p.271-277

Distribución de fertilizantes marcados con 15 N en la rotación ajo - moha

p.105-110

Acrinatrín 15 CE nuevo acaricida - insecticida en frutales de pepita : desarrollo a campo

p.203-213

El tipo de tareas como oportunidad de aprendizaje y competencias matemáticas de estudiantes de 15 años

Esta comunicación presenta resultados parciales de un estudio de dos casos (en España y Armenia), que ha tratado de conocer la importancia que tienen las oportunidades de aprendizaje (OTL) que ofrece el profesor en su aula (particularmente, en este documento tratamos el tipo de tareas que éste selecciona y propone) a la hora de facilitar la adquisición de las competencias matemáticas (CM) de sus estudiantes. Tomamos la información de observaciones de clases y entrevista (a dos profesores de Educación Secundaria) y de prueba (a los estudiantes de 15 años) y realizamos análisis de datos combinando técnicas cualitativas y cuantitativas. Los resultados de nuestra investigación, relativos al tipo de tareas, han constatado una fuerte relación de las CM de los estudiantes con la oportunidad de resolver cierto tipo de tareas (demanda cognitiva y situaciones/contextos en las que se plantean).

The influence of crank configuration on muscle activity and torque production during arm crank ergometry

This study investigated the effect of crank configuration on muscle activity and torque production during submaximal arm crank ergometry. Thirteen non-specifically trained male participants volunteered. During the research trials they completed a warm-up at 15 W before two 3-min exercise stages were completed at 50 and 100 W; subjects used either a synchronous or asynchronous pattern of cranking. During the final 30-s of each submaximal exercise stage electromyographic and torque production data were collected. After the data had been processed each parameter was analysed using separate 2-way ANOVA tests with repeated measures. The activity of all muscles increased in line with external workload, although a shift in the temporal pattern of muscle activity was noted between crank configurations. Patterns of torque production during asynchronous and synchronous cranking were distinct. Furthermore, peak, minimum and delta (peak-minimum) torque values were different (P < 0.05) between crank configurations at both workloads. For example, at 100 W, peak torque using synchronous [19.6 (4.3) Nm] cranking was higher (P < 0.05) compared to asynchronous [16.8 (1.6) Nm] cranking. In contrast minimum torque was lower (P < 0.05) at 100 W using synchronous [4.8 (1.7) Nm] compared to asynchronous [7.3 (1.2) Nm] cranking. There was a distinct bilateral asymmetry in torque production during asynchronous cranking with the dominant transmitting significantly more force to the crank arm. Taken together, these preliminary data demonstrate the complex nature of muscle activity during arm crank ergometry performed with an asynchronous or synchronous crank set-up. Further work is required to determine how muscle activity (EMG activity) and associated patterns of torque production influence physiological responses and functional capacity during arm crank ergometry.

Guide to the coastal and surface zooplankton of the south-western Indian Ocean. Occasional Publication of the Marine Biological Association 15

A guide compiled as an aid to researchers in the identification of the coastal and shallow water, south-western Indian Ocean pelagic zooplankton, as much of the identification literature covering this area of amazing biodiversity is currently spread through the scientific literature and not accessible without extensive library resources. Most zooplankton groups, except fish larvae and eggs, have been covered, but some specialist groups have not yet been dealt with in great detail. However, a selection of representative members of most groups have been given, so that organisms can at least be assigned to perhaps a particular genus within the main group. The species list is based on zooplankton sampling carried out round the coastal areas of the islands of Mahé and Aldabra (Seychelles), Rodrigues (Mauritius), Madagascar and from a sampling transect between Seychelles and Rodrigues. The guide therefore includes a high proportion of the island-coastal and surface water zooplankton of the whole Indian Ocean. The location where a particular species has been sampled has been noted and some species that have not been sampled, but are known to occur in the region, have been included. Comprehensive taxonomic information has not been presented, but sufficient information should be given to identify each species. Keys have not yet been included for genera, as further species will be added. A bibliography of relevant plankton references has also been included.