305 research outputs found
Paper II: Calibration of the Swift ultraviolet/optical telescope
The Ultraviolet/Optical Telescope (UVOT) is one of three instruments onboard
the Swift observatory. The photometric calibration has been published, and this
paper follows up with details on other aspects of the calibration including a
measurement of the point spread function with an assessment of the orbital
variation and the effect on photometry. A correction for large scale variations
in sensitivity over the field of view is described, as well as a model of the
coincidence loss which is used to assess the coincidence correction in extended
regions. We have provided a correction for the detector distortion and measured
the resulting internal astrometric accuracy of the UVOT, also giving the
absolute accuracy with respect to the International Celestial Reference System.
We have compiled statistics on the background count rates, and discuss the
sources of the background, including instrumental scattered light. In each case
we describe any impact on UVOT measurements, whether any correction is applied
in the standard pipeline data processing or whether further steps are
recommended.Comment: Accepted for publication in MNRAS. 15 pages, 21 figures, 4 table
Please mind the gap: studentsâ perspectives of the transition in academic skills between A-level and degree level geography
This paper explores first-year undergraduatesâ perceptions of the transition from studying geography at pre-university level to studying for a degree. This move is the largest step students make in their education, and the debate about it in the UK has been reignited due to the governmentâs planned changes to A-level geography. However, missing from most of this debate is an appreciation of the way in which geography students themselves perceive their transition to university. This paper begins to rectify this absence. Using student insights, we show that their main concern is acquiring the higher level skills required for university learning
The global dimension in education and education for global citizenship: genealogy and critique
Encouraged by transnational organisations, curriculum policy-makers in the UK have called for curricula in schools and higher education to include a global dimension and education for global citizenship that will prepare students for life in a global society and work in a global economy. We argue that this call is rhetorically operating as a ‘nodal point’ in policy discourse a floating signifier that different discourses attempt to cover with meaning. This rhetoric attempts to bring three educational traditions together: environmental education, development education and citizenship education. We explore this new point of arrival and departure and some of the consequences and critiques
<i>Gaia</i> Data Release 1. Summary of the astrometric, photometric, and survey properties
Context. At about 1000 days after the launch of Gaia we present the first Gaia data release, Gaia DR1, consisting of astrometry and photometry for over 1 billion sources brighter than magnitude 20.7.
Aims. A summary of Gaia DR1 is presented along with illustrations of the scientific quality of the data, followed by a discussion of the limitations due to the preliminary nature of this release.
Methods. The raw data collected by Gaia during the first 14 months of the mission have been processed by the Gaia Data Processing and Analysis Consortium (DPAC) and turned into an astrometric and photometric catalogue.
Results. Gaia DR1 consists of three components: a primary astrometric data set which contains the positions, parallaxes, and mean proper motions for about 2 million of the brightest stars in common with the HIPPARCOS and Tycho-2 catalogues â a realisation of the Tycho-Gaia Astrometric Solution (TGAS) â and a secondary astrometric data set containing the positions for an additional 1.1 billion sources. The second component is the photometric data set, consisting of mean G-band magnitudes for all sources. The G-band light curves and the characteristics of âŒ3000 Cepheid and RR-Lyrae stars, observed at high cadence around the south ecliptic pole, form the third component. For the primary astrometric data set the typical uncertainty is about 0.3 mas for the positions and parallaxes, and about 1 mas yrâ1 for the proper motions. A systematic component of âŒ0.3 mas should be added to the parallax uncertainties. For the subset of âŒ94 000 HIPPARCOS stars in the primary data set, the proper motions are much more precise at about 0.06 mas yrâ1. For the secondary astrometric data set, the typical uncertainty of the positions is âŒ10 mas. The median uncertainties on the mean G-band magnitudes range from the mmag level to âŒ0.03 mag over the magnitude range 5 to 20.7.
Conclusions. Gaia DR1 is an important milestone ahead of the next Gaia data release, which will feature five-parameter astrometry for all sources. Extensive validation shows that Gaia DR1 represents a major advance in the mapping of the heavens and the availability of basic stellar data that underpin observational astrophysics. Nevertheless, the very preliminary nature of this first Gaia data release does lead to a number of important limitations to the data quality which should be carefully considered before drawing conclusions from the data
Gaia Data Release 3: G_RVS photometry from the RVS spectra
Gaia Data Release 3 (DR3) contains the first release of magnitudes estimated
from the integration of Radial Velocity Spectrometer (RVS) spectra for a sample
of about 32.2 million stars brighter than G_RVS~14 mag (or G~15 mag). In this
paper, we describe the data used and the approach adopted to derive and
validate the G_RVS magnitudes published in DR3. We also provide estimates of
the G_RVS passband and associated G_RVS zero-point. We derived G_RVS photometry
from the integration of RVS spectra over the wavelength range from 846 to 870
nm. We processed these spectra following a procedure similar to that used for
DR2, but incorporating several improvements that allow a better estimation of
G_RVS. These improvements pertain to the stray-light background estimation, the
line spread function calibration, and the detection of spectra contaminated by
nearby relatively bright sources. We calibrated the G_RVS zero-point every 30
hours based on the reference magnitudes of constant stars from the Hipparcos
catalogue, and used them to transform the integrated flux of the cleaned and
calibrated spectra into epoch magnitudes. The G_RVS magnitude of a star
published in DR3 is the median of the epoch magnitudes for that star. We
estimated the G_RVS passband by comparing the RVS spectra of 108 bright stars
with their flux-calibrated spectra from external spectrophotometric libraries.
The G_RVS magnitude provides information that is complementary to that obtained
from the G, G_BP, and G_RP magnitudes, which is useful for constraining stellar
metallicity and interstellar extinction. The median precision of G_RVS
measurements ranges from about 0.006 mag for the brighter stars (i.e. with 3.5
< G_RVS < 6.5 mag) to 0.125 mag at the faint end. The derived G_RVS passband
shows that the effective transmittance of the RVS is approximately 1.23 times
better than the pre-launch estimate.Comment: 16 pages, 18 figures. Accepted for publication in A&
Future Scenarios and Environmental Education
This article explores a number of questions about visions of the future and their implications for
environmental education (EE). If the future were known, what kind of actions would be needed to maintain the positive aspects and reverse the negative ones? How could these actions be translated into the aims of EE? Three future scenarios are discussed: the limits to growth (the great tragedy and demise); sustainable development and ecological modernization (hope and innovation); and the Anthropocene park. These scenarios are linked to corresponding EE/ESD approaches and instrumentalism in education is argued as a morally justifiable goal. Finally, education for deep ecology is advocated in order to address the ethical implications of the last scenario.FSW â Publicaties zonder aanstelling Universiteit Leide
The Swift Ultra-Violet/Optical Telescope
The UV/Optical Telescope (UVOT) is one of three instruments flying aboard the
Swift Gamma-ray Observatory. It is designed to capture the early (approximately
1 minute) UV and optical photons from the afterglow of gamma-ray bursts in the
170-600 nm band as well as long term observations of these afterglows. This is
accomplished through the use of UV and optical broadband filters and grisms.
The UVOT has a modified Ritchey-Chretien design with micro-channel plate
intensified charged-coupled device detectors that record the arrival time of
individual photons and provide sub-arcsecond positioning of sources. We discuss
some of the science to be pursued by the UVOT and the overall design of the
instrument.Comment: 55 Pages, 28 Figures, To be published in Space Science Review
Relationship between alcohol-attributable disease and socioeconomic status, and the role of alcohol consumption in this relationship: a systematic review and meta-analysis
Background: Studies show that alcohol consumption appears to have a disproportionate impact on people of low socioeconomic status. Further exploration of the relationship between alcohol consumption, socioeconomic status and the development of chronic alcohol-attributable diseases is therefore important to inform the development of
effective public health programmes.
Methods: We used systematic review methodology to identify published studies of the association between
socioeconomic factors and mortality and morbidity for alcohol-attributable conditions. To attempt to quantify
differences in the impact of alcohol consumption for each condition, stratified by SES, we (i) investigated the relationship between SES and risk of mortality or morbidity for each alcohol-attributable condition, and (ii) where, feasible explored alcohol consumption as a mediating or interacting variable in this relationship.
Results: We identified differing relationships between a range of alcohol-attributable conditions and socioeconomic
indicators. Pooled analyses showed that low, relative to high socioeconomic status, was associated with an increased
risk of head and neck cancer and stroke, and in individual studies, with hypertension and liver disease. Conversely, risk of female breast cancer tended to be associated with higher socioeconomic status. These findings were attenuated
but held when adjusted for a number of known risk factors and other potential confounding factors. A key finding was
the lack of studies that have explored the interaction between alcohol-attributable disease, socioeconomic status and alcohol use.
Conclusions: Despite some limitations to our review, we have described relationships between socioeconomic
status and a range of alcohol-attributable conditions, and explored the mediating and interacting effects of alcohol
consumption where feasible. However, further research is needed to better characterise the relationship between
socioeconomic status alcohol consumption and alcohol-attributable disease risk so as to gain a greater understanding of the mechanisms and pathways that influence the differential risk in harm between people of low and high
socioeconomic status
Achieving Education for Sustainable Development (ESD) in Early Childhood Education Through Critical Reflection in Transformative Learning
The central role of education in creating a more sustainable future has been already recognized by educators and policy-makers alike. This chapter argues that this can only be truly achieved through the efforts of teachers in implementing an âeducation of a different kind,â a general educational shift that seeks to encompass a converging transformation of the priorities and mindsets of education professionals. In this regard, the professional preparation of teachers, as the leading actors in shaping childrenâs learning processes, and their continuous professional development are vital considerations for Education for Sustainable Development (ESD) to be successfully achieved. Linking transformative learning and ESD has emerged as a distinct and useful pedagogy because they both support the process of critically examining habits of mind, then revising these habits and acting upon the revised point of view. This study aims to describe and evaluate the potential of transformative learning in innovating mainstream education toward sustainability by focusing on the role of critical reflection in a capacity building research project realized in Turkey. The data was gathered from 24 early childhood educators using a mixed-method research design involving learning diaries, a learning activities survey, and follow-up interviews. This chapter identified content, context, and application method of the in-service training as factors that have contributed to the reflective practices of the participants. In addition, presenting the implications regarding the individual differences in how learners engage in critical reflection practices, this research offers a framework for a content- and process-based approach derived from Mezirowâs conception of critical reflection
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