Learning mathematics and competences: Bringing together three theoretical perspectives

The symposium aims to bring into analysis and discussion a possibility of articulating and integrating theoretical concepts from Activity Theory, Situated Learning and Critical Mathematics Education in order to contribute to understanding learning in practices where mathematics and technology seem to be relevant

Creative dance can enhance proprioception in older adults

Aim. It has been shown by many authors that proprioception declines with age. However, few studies have examined the effects of exercise interventions on proprioception. The purpose of this study was to investigate the effects of a creative dance program on proprioception of older adults. Methods. Thirty-seven men and women between 55 and 80 years of age, who were not engaged in any exercise program for at least one year, were randomly assigned to an experimental (63.6±5.7 years) or a control group (65.3±7.6 years). The experimental group participated in a creative dance program for 12 weeks with a periodicity of 3 sessions of 90 minutes per week. Measures of knee kinesthesia, knee joint position sense and arm positioning were taken before and after the program. Results. After 12 weeks, knee joint position sense (P=0.005) knee kinesthesia (in flexion) (P=0.04), and arm positioning (P=0.008) significantly improved within the creative dance training group. At 12 weeks follow-up, arm positioning performance was significantly better for the creative dance group when compared with the control group (P=0.043). The control group did not show any significant improvement in proprioception. Conclusion. This study showed that a creative dance program emphasising body awareness can improve proprioception in older adults

Low-diffusion Xe-He gas mixtures for rare-event detection: electroluminescence yield

High pressure xenon Time Projection Chambers (TPC) based on secondary scintillation (electroluminescence) signal amplification are being proposed for rare event detection such as directional dark matter, double electron capture and double beta decay detection. The discrimination of the rare event through the topological signature of primary ionisation trails is a major asset for this type of TPC when compared to single liquid or double-phase TPCs, limited mainly by the high electron diffusion in pure xenon. Helium admixtures with xenon can be an attractive solution to reduce the electron diffu- sion significantly, improving the discrimination efficiency of these optical TPCs. We have measured the electroluminescence (EL) yield of Xe–He mixtures, in the range of 0 to 30% He and demonstrated the small impact on the EL yield of the addition of helium to pure xenon. For a typical reduced electric field of 2.5 kV/cm/bar in the EL region, the EL yield is lowered by ∼ 2%, 3%, 6% and 10% for 10%, 15%, 20% and 30% of helium concentration, respectively. This decrease is less than what has been obtained from the most recent simulation framework in the literature. The impact of the addition of helium on EL statistical fluctuations is negligible, within the experimental uncertainties. The present results are an important benchmark for the simulation tools to be applied to future optical TPCs based on Xe-He mixtures. [Figure not available: see fulltext.]

Evaluation of turbulent dissipation rate retrievals from Doppler Cloud Radar

Turbulent dissipation rate retrievals from cloud radar Doppler velocity measurements are evaluated using independent, in situ observations in Arctic stratocumulus clouds. In situ validation data sets of dissipation rate are derived using sonic anemometer measurements from a tethered balloon and high frequency pressure variation observations from a research aircraft, both flown in proximity to stationary, ground-based radars. Modest biases are found among the data sets in particularly low- or high-turbulence regimes, but in general the radar-retrieved values correspond well with the in situ measurements. Root mean square differences are typically a factor of 4-6 relative to any given magnitude of dissipation rate. These differences are no larger than those found when comparing dissipation rates computed from tetheredballoon and meteorological tower-mounted sonic anemometer measurements made at spatial distances of a few hundred meters. Temporal lag analyses suggest that approximately half of the observed differences are due to spatial sampling considerations, such that the anticipated radar-based retrieval uncertainty is on the order of a factor of 2-3. Moreover, radar retrievals are clearly able to capture the vertical dissipation rate structure observed by the in situ sensors, while offering substantially more information on the time variability of turbulence profiles. Together these evaluations indicate that radar-based retrievals can, at a minimum, be used to determine the vertical structure of turbulence in Arctic stratocumulus clouds