Una introducción a la dinámica no lineal en enseñanza Secundaria

An interesting study on an approach to Physics teaching of an introduction to non-linear dynamics, at a basic level, is presented here. This study, framed on the constructivist theory of learning has led to the actual possibility of explaining in secondary clasrooms the elementary foundations of this outstanding area in modern physics. An initial exploration of the prior beliefs of pupils about mechanics and predictibility constituted the base of this attempt

Enseñanza por cambio conceptual : de la física clásica a la relatividad

In this article the possibility of learning through conceptual change and the best way to achieve this aim, are discussed. This teaching needs to have certain specific features and ensure that the debate in the classroom is focused on the explicit ideas of the students, whose conceptual difficulties must be taken into account with considerable care. To obtain those results, we are to give critical importance to the explanation and justification of ideas, debates must be metacognitive and professors should share discussion in an active and diversified role. One example of this way of teaching is introduced in this article concerning the conceptual change required to pass from classical to relativistic physics

Una nueva propuesta didáctica para la enseñanza de la relatividad en el Bachillerato

The great importance that has been given to teaching the theory of Relativity in intermediate levels by the new plans of secondary education, is often discouraged by the erroneous treatment of all these topics in the usual didactic formulations. So, in this work we dare to suggest a new point of view which is more accurately attached to the real and original spirit of the genuine Relativity. Our proposal lies on recovering in teaching the ideas of space-time and geometric representations introduced by Minkowski

Influence of pulse crops on arbuscular mycorrhizal fungi in a durum-based cropping system

Non-Peer ReviewedPulses are an important component in crop rotations in southern Saskatchewan. Besides their capability to fix nitrogen, pulse crops establish a symbiotic relationship with arbuscular mycorrhizal fungi, which have been shown to increase nutrient and water uptake through hyphal extensions in the soil. This 2 year study is designed to evaluate the impact of pulses in crop rotations on the biodiversity of AMF communities and their dynamics. Plant N and P uptake and the available soil N and P pools under a durum crop are also measured to assess if there is any correlation with AMF communities. The sampling and analysis is completed on the durum phase of the rotation with preceding crops of pea, lentil, chickpea, canola and durum. The final results will be explained by: (1) the size, nature, and physiological state of the soil microbial community and (2) the nature of the preceding crop residues. Preliminary results from the 2004 season indicate that higher plant P uptake is related to AMF colonization, while no significant change was detected in the soil N and P pools

The effect of long-term application of P fertilizer on soil grown forage plants

Non-Peer ReviewedPhosphorus (P) fertilization does not always increase crop yields but the repeated use of P may modify the biological properties of soils. The objective of the present study, therefore, was to investigate the effect of long term applications of P fertilizer on soil biological properties. We used an experimental site located in Swift Current in which different amounts of P (0, 20 and 40 kg P2O5 ha-1) were applied annually for the past 8 years on alfalfa and alfalfa-Russian wild rye hay crops. Our hypothesis was that repeated application of P influences soil microbial biomass and various soil enzymes. Microbial biomass C in the 0-7.5 cm soil layer was determined by fumigation-extraction at each of three harvest dates, and dehydrogenase, acid phosphatase and urease activities were assayed. Application of P to soil increased soil available P, dissolved organic C and available NO3-N, but did not significantly affect crop yields or soil microbial biomass C. Arbuscular mycorrhizal colonization of crop roots, and dehydrogenase and urease activities were decreased, suggesting that P reduced soil microbial activity. Acid phosphatase activity remained unchanged with P fertilization, suggesting that P availability was not limiting in these systems. While 8 years of application of P had little effect on hay yields, it generally reduced the activity of the soil microbial biomass

An evaluation of the vacuum/pressure moisturization technique of seed grains and oilseeds

Non-Peer Reviewe

Manual de manejo conservacionista do solo para os estados do Rio Grande do Sul, Santa Catarina e Paraná.

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A Sensor-Based Feedback Device Stimulating Daily Life Upper Extremity Activity in Stroke Patients:A Feasibility Study

This study aims to evaluate the feasibility and explore the efficacy of the Arm Activity Tracker (AAT). The AAT is a device based on wrist-worn accelerometers that provides visual and tactile feedback to stimulate daily life upper extremity (UE) activity in stroke patients. Methods: A randomised, crossover within-subject study was conducted in sub-acute stroke patients admitted to a rehabilitation centre. Feasibility encompassed (1) adherence: the dropout rate and the number of participants with insufficient AAT data collection; (2) acceptance: the technology acceptance model (range: 7–112) and (3) usability: the system usability scale (range: 0–100). A two-way ANOVA was used to estimate the difference between the baseline, intervention and control conditions for (1) paretic UE activity and (2) UE activity ratio. Results: Seventeen stroke patients were included. A 29% dropout rate was observed, and two participants had insufficient data collection. Participants who adhered to the study reported good acceptance (median (IQR): 94 (77–111)) and usability (median (IQR): 77.5 (75–78.5)-). We found small to medium effect sizes favouring the intervention condition for paretic UE activity (η2G = 0.07, p = 0.04) and ratio (η2G = 0.11, p = 0.22). Conclusion: Participants who adhered to the study showed good acceptance and usability of the AAT and increased paretic UE activity. Dropouts should be further evaluated, and a sufficiently powered trial should be performed to analyse efficacy.</p