Understanding the formation and evolution of planetary systems is one of the most fundamental challenges in astronomy. To directly image and study young exoplanets and the circumstellar disks they... Show moreUnderstanding the formation and evolution of planetary systems is one of the most fundamental challenges in astronomy. To directly image and study young exoplanets and the circumstellar disks they form from, dedicated high-contrast imaging instruments are built. Several of these instruments have polarimetric modes that are particularly powerful to reach the large contrasts required to directly image these objects as well as to characterize them. This thesis aims to improve the polarimetric sensitivity, accuracy, and capabilities of high-contrast imaging polarimeters for the detection and characterization of exoplanets and circumstellar disks. In addition, this thesis presents the first direct detections of linear polarization from self-luminous planetary mass companions. The focus of this thesis is mostly on ground-based high-contrast imaging, in particular with the instrument SPHERE-IRDIS at the Very Large Telescope. This thesis covers many aspects of high-contrast imaging polarimetry, ranging from theoretical work, calibrations, and the development of new observing techniques to actual scientific polarimetric measurements and astrophysical interpretation. Show less
Jonge, L.P.J.W.M. de; Mesters, I.; Govaerts, M.J.B.; Timmerman, A.A.; Muris, J.W.M.; Kramer, A.W.M.; Vleuten, C.P.M. van der 2020
Background Direct observation of clinical task performance plays a pivotal role in competency-based medical education. Although formal guidelines require supervisors to engage in direct... Show moreBackground Direct observation of clinical task performance plays a pivotal role in competency-based medical education. Although formal guidelines require supervisors to engage in direct observations, research demonstrates that trainees are infrequently observed. Supervisors may not only experience practical and socio-cultural barriers to direct observations in healthcare settings, they may also question usefulness or have low perceived self-efficacy in performing direct observations. A better understanding of how these multiple factors interact to influence supervisors' intention to perform direct observations may help us to more effectively implement the aforementioned guidelines and increase the frequency of direct observations. Methods We conducted an exploratory quantitative study, using the Theory of Planned Behaviour (TPB) as our theoretical framework. In applying the TPB, we transfer a psychological theory to medical education to get insight in the influence of cognitive and emotional processes on intentions to use direct observations in workplace based learning and assessment. We developed an instrument to investigate supervisors intention to perform direct observations. The relationships between the TPB measures of our questionnaire were explored by computing bivariate correlations using Pearson's R tests. Hierarchical regression analysis was performed in order to assess the impact of the respective TPB measures as predictors on the intention to perform direct observations. Results In our study 82 GP supervisors completed our TPB questionnaire. We found that supervisors had a positive attitude towards direct observations. Our TPB model explained 45% of the variance in supervisors' intentions to perform them. Normative beliefs and past behaviour were significant determinants of this intention. Conclusion Our study suggests that supervisors use their past experiences to form intentions to perform direct observations in a careful, thoughtful manner and, in doing so, also take the preferences of the learner and other stakeholders potentially engaged in direct observations into consideration. These findings have potential implications for research into work-based assessments and the development of training interventions to foster a shared mental model on the use of direct observations. Show less
