Possible magnetic field variability during the 6.7 GHz methanol maser flares of G09.62+0.20

(Abridged) Recently, the magnetic field induced Zeeman splitting was measured for the strongest known 6.7 GHz methanol maser, which arises in the massive star forming region G09.62+0.20. This maser is one of a handful of periodically flaring methanol masers. The 100-m Effelsberg telescope was used to monitor the 6.7 GHz methanol masers of G09.62+0.20. With the exception of a two week period during the peak of the maser flare, we measure a constant magnetic field of B_||~11+-2 mG in the two strongest maser components of G09.62+0.20 that are separated by over 200 AU. In the two week period that coincides exactly with the peak of the maser flare of the strongest maser feature, we measure a sharp decrease and possible reversal of the Zeeman splitting. The exact cause of both maser and polarization variability is still unclear, but it could be related to either background amplification of polarized emission or the presence of a massive protostar with a close-by companion. Alternatively, the polarization variability could be caused by non-Zeeman effects related to the radiative transfer of polarized maser emission.Comment: 4 pages, 3 figures, accepted for publication Astronomy and Astrophysic

Accommodating the difference in students’ prior knowledge of cell growth kinetics

This paper describes the development and benefits of an adaptive digital module on cell growth to tackle the problem of educating a heterogeneous group of students at the beginning of an undergraduate course on process engineering. Aim of the digital module is to provide students with the minimal level of knowledge on cell growth kinetics they need to comprehend the content knowledge of the subsequent lectures and pass the exam. The module was organised to offer the subject matter in a differentiated manner, so that students could follow different learning paths. Two student groups were investigated, one consisting of students who had received their prior education abroad and one of students that had not. Exam scores, questionnaires, and logged user data of the two student groups were analysed to discover whether the digital module had the intended effect. The results indicate that students did indeed follow different learning paths. Also, the differences in exam scores between the two student groups that was present before the introduction of the digital module was found to have decreased afterwards. In general, students appreciated the use of the material regardless of their prior education. We therefore conclude that the use of adaptive digital learning material is a possible way to solve the problem of differences in prior education of students entering a course

Ambulatory Recording of Within- and Between-Subject Variation in Autonomic Nervous System Activity

Geus, J.C.N. de [Promotor]Willemsen, A.H.M. [Copromotor

Comparison of bioassessment results and costs between preserved and unpreserved macroinvertebrate samples from streams

The choice to use or not use a preservative before sorting macroinvertebrate samples (i.e., dead specimens vs. living specimens) is based on studies not solely focused on the effects of preservation. Using identical sample processing protocols, we compared preserved and unpreserved samples for the following parameters: (1) the number of taxa and individuals for each major macroinvertebrate group, (2) ecological quality classes calculated with a multimetric index developed for the assessment of small Dutch lowland streams, and (3) costs of sample processing. We collected macroinvertebrate samples from three lowland streams in the Netherlands. At each site, we collected six replicate samples, of which three samples were preserved and three were not. Significantly different numbers of Ephemeroptera individuals and Hydracarina taxa and individuals were collected from preserved samples compared to unpreserved samples. In assessments based on these individual metrics, standardization of sample processing will be required. In streams with Ephemeroptera, the preservation of samples is necessary to optimize the number of Ephemeroptera individuals collected. In streams that contain Hydracarina, the preservation of samples will result in an underestimation of the number of Hydracarina taxa and individuals present. In only one instance there was a difference in ecological quality between preserved and unpreserved samples, indicating that assessing small Dutch lowland streams does not require standardization of sample preservation as part of the sample processing protocol. We detected no significant differences in sample processing costs between preserved and unpreserved samples

VLBA imaging of a periodic 12.2 GHz methanol maser flare in G9.62+0.20E

The class II methanol maser source G9.62+0.20E undergoes periodic flares at both 6.7 and 12.2 GHz. The flare starting in 2001 October was observed at seven epochs over three months using the VLBA at 12.2 GHz. High angular resolution images (beam size $\sim$ 1.7 x 0.6 mas) were obtained, enabling us to observe changes in 16 individual maser components. It was found that while existing maser spots increased in flux density, no new spots developed and no changes in morphology were observed. This rules out any mechanism which disturbs the masing region itself, implying that the flares are caused by a change in either the seed or pump photon levels. A time delay of 1--2 weeks was observed between groups of maser features. These delays can be explained by light travel time between maser groups. The regularity of the flares can possibly be explained by a binary system.Comment: 11 pages, accepted for publication in MNRA

The influence of student characteristics on the use of adaptive e-learning material

Adaptive e-learning materials can help teachers to educate heterogeneous student groups. This study provides empirical data about the way academic students differ in their learning when using adaptive elearning materials. Ninety-four students participated in the study. We determined characteristics in a heterogeneous student group by collecting demographic data and measuring motivation and prior knowledge. We also measured the learning paths students followed and learning strategies they used when working with adaptive e-learning material in a molecular biology course. We then combined these data to study if and how student characteristics relate to the learning paths and strategies they used. We observed that students did follow different learning paths. Gender did not have an effect, but (mainly Dutch) BSc students differed from (international) MSc students in the intrinsic motivation they had and the learning paths and strategies they followed when using the adaptive e-learning materia

Associations between poor oral health and reinjuries in male elite soccer players : a cross-sectional self-report study

Background: Although it is well known that oral pathogens can enter the systemic circulation and cause disease, it is largely unknown if poor oral health increases the risk of sports injuries. The purpose of this study is to investigate the association between poor oral health and reinjuries in male elite soccer players, adjusted for psychosocial problems and player characteristics. Methods: 184 Players in premier league soccer clubs and 31 elite, junior soccer players in the Netherlands, Belgium and England, were enrolled in a retrospective cross-sectional study. The Sports Injury Risk Indicator, a self assessed questionnaire, was used to obtain information on reinjuries, age and player position, oral health and psychosocial problems. The number of different types of oral health problems was used as an indicator of poor oral health. (SumDental, range 0-2: 0 = no oral health problems, 1 = one type of oral health problem and 2 = two or more types of oral health problems). Multivariable logistic regression was used to investigate whether SumDental was associated with reinjuries, after adjustment for psychosocial problems and player characteristics. Results: 37% of the players reported no oral health problems, 43% reported one type of oral health problem and 20% reported two or more types of oral health problems. After full adjustment for age, player position and psychosocial problems (i.e. injury anxiety, psychophysical stress, unhealthy eating habits and dissatisfaction with trainer/team), poor oral health (SumDental) was positively associated with all kind of reinjuries whether analyzed as a continuous variable or as a categorical variable. The fully adjusted odds ratios for SumDental analyzed as a continuous variable were: in relation to repeated exercise-associated muscle cramps: 1.82(95% confidence interval (CI): 1.07, 3.12), in relation to muscle or tendon reinjury 1.57 (95% CI: 1.01, 2.45) and in relation to multiple types of reinjury 1.88 (95% CI: 1.19, 2.97). Conclusion: The results from this study justify a thorough examination of the effects of oral health problems on the injury risk of playing elite soccer