Studying mathematics students’ learning experiences in Challenge-based education

This paper is of methodological nature. We present the empirical research methodology of a study that focuses on student learning experiences, in particular of mathematics students in an innovative learning environment, such as Challenge-based Education (CBE) at a Dutch university of technology. In this study, we present the case study of CBE in an innovative mathematics course on modelling, the mathematics “Modelling Week”. We draw attention to the methodology used to study this modelling course, where we investigated students' learning experiences in a monodisciplinary CBE-oriented master course. We explain the design of the study and the associated data collection strategies regarding students' use of resources (Schematic Representation of Resource system- SRRS) and their learning processes. In the poster presentation, we will show selected results that come from the different instruments to help us understand student learning experiences in innovative/CBE related mathematics courses.</p

The Future is Now: the Formation of Single Low Mass White Dwarfs in the Solar Neighborhood

Low mass helium-core white dwarfs (M < 0.45 Msun) can be produced from interacting binary systems, and traditionally all of them have been attributed to this channel. However, a low mass white dwarf could also result from a single star that experiences severe mass loss on the first ascent giant branch. A large population of low mass He-core white dwarfs has been discovered in the old metal-rich cluster NGC 6791. There is therefore a mechanism in clusters to produce low mass white dwarfs without requiring binary star interactions, and we search for evidence of a similar population in field white dwarfs. We argue that there is a significant field population (of order half of the detected systems) that arises from old metal rich stars which truncate their evolution prior to the helium flash from severe mass loss. There is a consistent absence of evidence for nearby companions in a large fraction of low mass white dwarfs. The number of old metal-rich field dwarfs is also comparable with the apparently single low mass white dwarf population, and our revised estimate for the space density of low mass white dwarfs produced from binary interactions is also compatible with theoretical expectations. This indicates that this channel of stellar evolution, hitherto thought hypothetical only, has been in operation in our own Galaxy for many billions of years. One strong implication of our model is that single low mass white dwarfs should be good targets for planet searches because they are likely to arise from metal-rich progenitors. We also discuss other observational tests and implications, including the potential impact on SN Ia rates and the frequency of planetary nebulae.Comment: ApJ published versio

Early extubation and weaning with bilevel positive airway pressure ventilation after cardiac surgery (Weaning with BiPAP ventilation after cardiac surgery)

Objective(s): To evaluate the use of bilevel positive airway pressure (BiPAP) ventilation in early extubation after fast-track cardiac surgery.Design: Prospective observational study.Setting: Postoperative intensive care.Patients: Sixty consecutive patients eligible for early extubation after cardiac surgery. Patients were predominantly male (42 men [70%]) and middle aged (54.62 ± 10.66 years).Interventions: Patients were randomly assigned to continuous pressure or BiPAP (Group I or Group II, respectively) and were extubated as soon as possible.Measurements: Blood gases and haemodynamics were determined on arrival in the ICU (baseline, or T0) and 1, 2, 4, 6, 8, and 12 hours later. All data were expressed as (±SD) and analysed using the Student t-test and Mann-Whitney test (continuous data) or χ2 test (categorical data). P < 0.05 was considered statistically significant.Main results: PaCO2 levels were statistically significantly higher in Group II than in Group I at 2, 4, 6, 8, and 12 hours (P < 0.05, P < 0.01). Within each group, PaCO2 levels were statistically significantly higher at 4, 6, 8, and 12 hours than at baseline (P < 0.01 ).Extubation time was significantly longer in Group I than in Group II 7.90 (7.90 [2.13] vs 3.83 [1.20], P=0.001). Respiratory rates were significantly higher in Group II than in Group I after 2, 4, and 6 hours (P < 0.01). Pmax was higher in Group I than in Group II after 1 hour but similar up to 4 hours.Conclusions: Early extubation and weaning to BiPAP ventilation after cardiac surgery is safe and effective