3,343 research outputs found
Faint star counts in the near-infrared
We discuss near-infrared star counts at the Galactic pole with a view to
guiding the NGST and ground-based NIR cameras. Star counts from deep K-band
images from the CFHT are presented, and compared with results from the 2MASS
survey and some Galaxy models. With appropriate corrections for detector
artifacts and galaxies, the data agree with the models down to K~18, but
indicate a larger population of fainter red stars. There is also a significant
population of compact galaxies that extend to the observational faint limit of
K=20.5. Recent Galaxy models agree well down to K19, but diverge at
fainter magnitudes.Comment: 14 pages and 4 diagrams; to appear in PAS
Impact of external sources of infection on the dynamics of bovine tuberculosis in modelled badger populations
Background The persistence of bovine TB (bTB) in various countries throughout the world is enhanced by the existence of wildlife hosts for the infection. In Britain and Ireland, the principal wildlife host for bTB is the badger (Meles meles). The objective of our study was to examine the dynamics of bTB in badgers in relation to both badger-derived infection from within the population and externally-derived, trickle-type, infection, such as could occur from other species or environmental sources, using a spatial stochastic simulation model. Results The presence of external sources of infection can increase mean prevalence and reduce the threshold group size for disease persistence. Above the threshold equilibrium group size of 6–8 individuals predicted by the model for bTB persistence in badgers based on internal infection alone, external sources of infection have relatively little impact on the persistence or level of disease. However, within a critical range of group sizes just below this threshold level, external infection becomes much more important in determining disease dynamics. Within this critical range, external infection increases the ratio of intra- to inter-group infections due to the greater probability of external infections entering fully-susceptible groups. The effect is to enable bTB persistence and increase bTB prevalence in badger populations which would not be able to maintain bTB based on internal infection alone. Conclusions External sources of bTB infection can contribute to the persistence of bTB in badger populations. In high-density badger populations, internal badger-derived infections occur at a sufficient rate that the additional effect of external sources in exacerbating disease is minimal. However, in lower-density populations, external sources of infection are much more important in enhancing bTB prevalence and persistence. In such circumstances, it is particularly important that control strategies to reduce bTB in badgers include efforts to minimise such external sources of infection
Near Infrared Imaging of the Proposed z=2 Cluster Behind CL 0939+4713 (Abell 851)
We have obtained deep J and K' images of a 90 arcsec square field containing
the z=2.0 QSO that is viewed through the z=0.4 rich cluster A851. Brightnesses
of individual galaxies are measured from these data, and archival F702W WFPC2
images from HST. The results are used to construct 2-colour diagrams,
colour-magnitude diagrams, and luminosity functions of galaxies in A851 and the
faint objects discovered by Dressler et al (1993) near the QSO. The QSO faint
companions appear to form a separate population from other faint galaxies in
the field. Comparisons with the GISSEL models covering redshifts from 0 to 3
indicate that (1) the A851 galaxies have ages between 3 and 10 Gyr, and (2) if
they are at the QSO redshift, the QSO companion galaxies are within 1Gyr of
cessation of star-formation.Comment: 12 pages plus 1 table, 5 figures. To appear in PASP. Also available
at http://www.hia.nrc.ca/eprints.htm
\u3cb\u3eFeature Essays:\u3c/b\u3e Getting There: An Integrative Vision of the Scholarship of Teaching and Learning
Excerpt: Over the last two decades, the scholarship of teaching and learning has made important strides. There are now many more teachers engaged in the study of their students\u27 learning, more outlets (like this journal) for what they discover, and a growing demand for what those outlets make available. Campus policies are evolving to create space and rewards for such work, disciplinary and professional fields have promoted it, and notions of inquiry and evidence are..
Magnetic Anisotropy in Single Crystalline CeAuIn
We have grown the single crystals of LaAuIn and
CeAuIn by high temperature solution method and report on the
anisotropic magnetic behavior of CeAuIn . The compounds crystallize
in an orthorhombic structure with space group \textit {Pnma}.
LaAuIn shows a Pauli-paramagnetic behavior. CeAuIn do
not order down to 1.8 K. The easy axis of magnetization for CeAuIn
is along [010] direction. The magnetization data is analyzed on the basis of
crystalline electric field (CEF) model.Comment: 7 figures 4 page
Preparing the foundations for video-based, practice-placement support: establishing the role from a students’ perspective
Currently, many placement-based health programme students within the UK are supported through face-to-face visits from university staff. Whilst cited in literature as being of value, the face-to-face nature of this contact is not supported. Alternatives including video-based communications methods offer the potential for cost effective, environmentally responsible support. However, in order to establish the fitness for purpose of alternative approaches, the content and purpose of current support needs to be understood. This project aimed to investigate student perceptions of the ideal content and purpose of clinical support visits, and alternatives to the current face-to-face approach. Fifty-six Physiotherapy undergraduate students responded to questionnaires with a further nine participating in a follow-up focus group. Participants emphasised the value of the visit in guiding learning, ensuring progression and resolving arising issues, and highlighted concerns over alternative approaches. Focus group participants discussed the importance of personal and professional confidence in directing requirements for support, and went on to propose a menu of options for methods of communication.Whilst limited in some applications, video technologies may be one of the options. Overall, however, this project supports the need for consideration of individualised learning journeys within curriculum planning
Magnetic properties of single-crystalline CeCuGa3
The magnetic behavior of single-crystalline CeCuGa3 has been investigated.
The compound forms in a tetragonal BaAl4-type structure consisting of
rare-earth planes separated by Cu-Ga layers. If the Cu-Ga site disorder is
reduced, CeCuGa3 adopts the related, likewise tetragonal BaNiSn3-type
structure, in which the Ce ion are surrounded by different Cu and Ga layers and
the inversion symmetry is lost. In the literature conflicting reports about the
magnetic order of CeCuGa3 have been published. Single crystals with the
centrosymmetric structure variant exhibit ferromagnetic order below approx. 4 K
with a strong planar anisotropy. The magnetic behavior above the transition
temperature can be well understood by the crystal-field splitting of the 4f
Hund's rule ground-state multiplet of the Ce ions
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