119 research outputs found
Tracing mass and light in the Universe: where is the dark matter?
How is mass distributed in the Universe? How does it compare with the
distribution of light and stars? We address these questions by examining the
distribution of mass, determined from weak lensing observations, and starlight,
around SDSS MaxBCG groups and clusters as a function of environment and
scale, from deep inside clusters to large cosmic scales of Mpc. The
observed cumulative mass-to-light profile, , rises on small scales,
reflecting the increasing of the central bright galaxy of the cluster,
then flattens to a nearly constant ratio on scales above kpc,
where light follows mass on all scales and in all environments. A trend of
slightly decreasing with scale is shown to be consistent with the
varying stellar population following the morphology-density relation. This
suggests that stars trace mass remarkably well even though they represent only
a few percent of the total mass. We determine the stellar mass fraction and
find it to be nearly constant on all scales above kpc, with
. We further suggest that most of the dark
matter in the Universe is located in the large halos of individual galaxies
( kpc for galaxies); we show that the entire
profile -- from groups and clusters to large-scale structure -- can be
accounted for by the aggregate masses of the individual galaxies (whose halos
may be stripped off but still remain in the clusters), plus gas. We use the
observed mass-to-light ratio on large scales to determine the mass density of
the Universe: Comment: 12 pages, 9 figures; version accepted to MNRA
The morphological transformation of ram pressure stripped galaxies: a pathway from late to early galaxy types
We investigate how the ageing of stellar populations can drive a
morphological transformation in galaxies whose star formation (SF) activity has
been quenched on short timescales, like in cluster galaxies subject to ram
pressure stripping from the intracluster medium. For this purpose, we use a
sample of 91 galaxies with MUSE data from the GASP program and of their
spatially resolved SF history derived with the spectral modelling software
SINOPSIS. We simulate the future continuation of the SF activities by exploring
two quenching scenarios: an instantaneous truncation of the SF across the whole
disc, and an outside-in quenching with typical stripping timescales of 0.5 Gyr
and 1 Gyr. For each scenario we produce mock MUSE spectroscopic datacubes and
optical images for our galaxies during their evolution, and classify their
morphology using a new diagnostic tool, calibrated on cluster galaxies from the
OmegaWINGS Survey. We find that, in all scenarios considered, the initial
galaxy population dominated by blue-cloud spirals (90%) evolves into a mixed
population mostly composed by red-sequence spirals (50-55%) and lenticulars
(~40%). The morphology transformation is completed after just 1.5-3.5 Gyr,
proceeding faster in more efficient quenching scenarios. Our results indicate
that, even without accounting for dynamical processes, SF quenching caused by
the harsh environment of a cluster can significantly affect the morphology of
the infalling galaxy population on timescales of a few Gyr.Comment: 19 pages, 11 figures, accepted for publication in MNRA
A cluster randomized controlled trial to evaluate the effectiveness of the clinically integrated RHL evidence -based medicine course
<p>Abstract</p> <p>Background and objectives</p> <p>Evidence-based health care requires clinicians to engage with use of evidence in decision-making at the workplace. A learner-centred, problem-based course that integrates e-learning in the clinical setting has been developed for application in obstetrics and gynaecology units. The course content uses the WHO reproductive health library (RHL) as the resource for systematic reviews. This project aims to evaluate a clinically integrated teaching programme for incorporation of evidence provided through the WHO RHL. The hypothesis is that the RHL-EBM (clinically integrated e-learning) course will improve participants' knowledge, skills and attitudes, as well as institutional practice and educational environment, as compared to the use of standard postgraduate educational resources for EBM teaching that are not clinically integrated.</p> <p>Methods</p> <p>The study will be a multicentre, cluster randomized controlled trial, carried out in seven countries (Argentina, Brazil, Democratic Republic of Congo, India, Philippines, South Africa, Thailand), involving 50-60 obstetrics and gynaecology teaching units. The trial will be carried out on postgraduate trainees in the first two years of their training. In the intervention group, trainees will receive the RHL-EBM course. The course consists of five modules, each comprising self-directed e-learning components and clinically related activities, assignments and assessments, coordinated between the facilitator and the postgraduate trainee. The course will take about 12 weeks, with assessments taking place pre-course and 4 weeks post-course. In the control group, trainees will receive electronic, self-directed EBM-teaching materials. All data collection will be online.</p> <p>The primary outcome measures are gain in EBM knowledge, change in attitudes towards EBM and competencies in EBM measured by multiple choice questions (MCQs) and a skills-assessing questionniare administered eletronically. These questions have been developed by using questions from validated questionnaires and adapting them to the current course. Secondary outcome measure will be educational environment towards EBM which will be assessed by a specifically developed questionnaire.</p> <p>Expected outcomes</p> <p>The trial will determine whether the RHL EBM (clinically integrated e-leraning) course will increase knowledge, skills and attitudes towards EBM and improve the educational environment as compared to standard teaching that is not clinically integrated. If effective, the RHL-EBM course can be implemented in teaching institutions worldwide in both, low-and middle income countries as well as industrialized settings. The results will have a broader impact than just EBM training because if the approach is successful then the same educational strategy can be used to target other priority clinical and methodological areas.</p> <p>Trial Registration</p> <p>ACTRN12609000198224</p
The history of star-forming regions in the tails of 6 GASP jellyfish galaxies observed with the Hubble Space Telescope
Using images collected with the WFC3 camera on board of the Hubble Space
Telescope, we detect stellar clumps in continuum-subtracted and
ultraviolet (F275W filter), such clumps are often embedded in larger regions
(star-forming complexes) detected in the optical (F606W filter). We model the
photometry of these objects using BAGPIPES to obtain their stellar population
parameters. The median mass-weighted stellar ages are 27 Myr for
clumps and 39 Myr for F275W clumps and star-forming complexes, the oldest stars
in the complexes can be older than 300 Myr which indicates that
star-formation is sustained for long periods of time. Stellar masses vary from
10 to 10 , with star-forming complexes being more
massive objects in the sample. Clumps and complexes found further away from the
host galaxy are younger, less massive and less obscured by dust. We interpret
these trends as due to the effect of ram-pressure in different phases of the
interstellar medium. clumps form a well-defined sequence in the
stellar mass--SFR plane with slope 0.73. Some F275W clumps and star-forming
complexes follow the same sequence while others stray away from it and
passively age. The difference in stellar age between a complex and its youngest
embedded clump scales with the distance between the clump and the center of the
complex, with the most displaced clumps being hosted by the most elongated
complexes. This is consistent with a fireball-like morphology, where
star-formation proceeds in a small portion of the complex while older stars are
left behind producing a linear stellar population gradient. The stellar masses
of star-forming complexes are consistent with the ones of globular clusters,
but stellar mass surface densities are lower by 2 dex, and their properties are
more consistent with the population of dwarf galaxies in clusters.Comment: Accepted for publication in A&
Harmonising evidence-based medicine teaching: a study of the outcomes of e-learning in five European countries
BACKGROUND: We developed and evaluated the outcomes of an e-learning course for evidence based medicine (EBM) training in postgraduate medical education in different languages and settings across five European countries.
METHODS: We measured changes in knowledge and attitudes with well-developed assessment tools before and after administration of the course. The course consisted of five e-learning modules covering acquisition (formulating a question and search of the literature), appraisal, application and implementation of findings from systematic reviews of therapeutic interventions, each with interactive audio-visual learning materials of 15 to 20 minutes duration. The modules were prepared in English, Spanish, German and Hungarian. The course was delivered to 101 students from different specialties in Germany (psychiatrists), Hungary (mixture of specialties), Spain (general medical practitioners), Switzerland (obstetricians-gynaecologists) and the UK (obstetricians-gynaecologists). We analysed changes in scores across modules and countries.
RESULTS: On average across all countries, knowledge scores significantly improved from pre- to post-course for all five modules (p < 0.001). The improvements in scores were on average 1.87 points (14% of total score) for module 1, 1.81 points (26% of total score) for module 2, 1.9 points (11% of total score) for module 3, 1.9 points (12% of total score) for module 4 and 1.14 points (14% of total score) for module 5. In the country specific analysis, knowledge gain was not significant for module 4 in Spain, Switzerland and the UK, for module 3 in Spain and Switzerland and for module 2 in Spain. Compared to pre-course assessment, after completing the course participants felt more confident that they can assess research evidence and that the healthcare system in their country should have its own programme of research about clinical effectiveness.
CONCLUSION: E-learning in EBM can be harmonised for effective teaching and learning in different languages, educational settings and clinical specialties, paving the way for development of an international e-EBM course
How are "teaching the teachers" courses in evidence based medicine evaluated? A systematic review
Background
Teaching of evidence-based medicine (EBM) has become widespread in medical education. Teaching the teachers (TTT) courses address the increased teaching demand and the need to improve effectiveness of EBM teaching. We conducted a systematic review of assessment tools for EBM TTT courses. To summarise and appraise existing assessment methods for teaching the teachers courses in EBM by a systematic review.
Methods
We searched PubMed, BioMed, EmBase, Cochrane and Eric databases without language restrictions and included articles that assessed its participants. Study selection and data extraction were conducted independently by two reviewers.
Results
Of 1230 potentially relevant studies, five papers met the selection criteria. There were no specific assessment tools for evaluating effectiveness of EBM TTT courses. Some of the material available might be useful in initiating the development of such an assessment tool.
Conclusion
There is a need for the development of educationally sound assessment tools for teaching the teachers courses in EBM, without which it would be impossible to ascertain if such courses have the desired effect
Measurement of perceptions of educational environment in evidence-based medicine
In recent years, there has been a renewed interest in
measuring perceptions regarding different aspects of the
medical educational environment. A reliable tool was
developed for measuring perceptions of the educational
environment as it relates to evidence-based medicine as
part of a multicountry randomised controlled trial to
evaluate the effectiveness of a clinically integrated evidence-
based medicine course. Participants from 10 specialties
completed the questionnaire. A working dataset
of 518 observations was available. Two independent
subsets of data were created for conducting an exploratory
factor analysis (n=244) and a confirmatory factor
analysis (n=274), respectively. The exploratory factor
analysis yielded five 67-item definitive instruments,
with five to nine dimensions; all resulted in acceptable
explanations of the total variance (range 56.6â65.9%).
In the confirmatory factor analysis phase, all goodnessof-
fit measures were acceptable for all models (root
mean square error of approximation â€0.047; comparative
fit indexâ„0.980; normed ÏÂČ â€1.647; Bentler-Bonett
normed fit index â„0.951). The authors selected the factorisation
with seven dimensions (factor-7 instrument)
as the most useful on pragmatic grounds and named it
Evidence-Based Medicine Educational Environment
Measure 67 (EBMEEM-67). Cronbachâs α for subscales
ranged between 0.81 and 0.93. The subscales are:
âKnowledge and learning materialsâ; âLearner supportâ;
âGeneral relationships and supportâ; âInstitutional focus
on EBMâ; âEducation, training and supervisionâ; âEBM
application opportunitiesâ; and âAffirmation of EBM
environmentâ. The EBMEEM-67 can be a useful diagnostic
and benchmarking tool for evaluating the perceptions
of residents of the environment in which
evidence-based medicine education takes place.http://ebm.bmj.comhb201
The effectiveness of a clinically integrated e-learning course in evidence-based medicine: A cluster randomised controlled trial
BACKGROUND: To evaluate the educational effects of a clinically integrated e-learning course for teaching basic evidence-based medicine (EBM) among postgraduates compared to a traditional lecture-based course of equivalent content. METHODS: We conducted a cluster randomised controlled trial in the Netherlands and the UK involving postgraduate trainees in six obstetrics and gynaecology departments. Outcomes (knowledge gain and change in attitude towards EBM) were compared between the clinically integrated e-learning course (intervention) and the traditional lecture based course (control). We measured change from pre- to post-intervention scores using a validated questionnaire assessing knowledge (primary outcome) and attitudes (secondary outcome). RESULTS: There were six clusters involving teaching of 61 postgraduate trainees (28 in the intervention and 33 in the control group). The intervention group achieved slightly higher scores for knowledge gain compared to the control, but these results were not statistically significant (difference in knowledge gain: 3.5 points, 95% CI -2.7 to 9.8, p = 0.27). The attitudinal changes were similar for both groups. CONCLUSION: A clinically integrated e-learning course was at least as effective as a traditional lecture based course and was well accepted. Being less costly than traditional teaching and allowing for more independent learning through materials that can be easily updated, there is a place for incorporating e-learning into postgraduate EBM curricula that offer on-the-job training for just-in-time learning. TRIAL REGISTRATION: Trial registration number: ACTRN12609000022268
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