3,135 research outputs found
Transitions and progress: teachers' views of progress in attainment of pupils age 5-10
There has been a longstanding concern in England and Wales with the year on year progress made by pupils, but particularly at times of change, such as transfer from primary to secondary school at age 11. In Coalton, a former mining town in the North of England, a five year UK government funded initiative known as Charter for Transition has been put in place to try to overcome some of these difficulties and improve the learning opportunities for pupils aged 5-16. The programme takes place over a 5-year period in various stages, but in this paper we make use of data from the first two years. The research team examines the viewpoints of teachers from schools that were receiving additional support in their efforts to raise achievement in phase one and the pilot phase of the project about what they saw as the main benefits of this work. We present the beginnings of our exploration of teachers’ judgements of this work, and what they saw as the difficulties with associating the project with pupil attainment.</p
Nuclear Shadowing in the Structure Function
Nuclear modification of the structure function is investigated.
Although it could be estimated in the medium and large regions from the
nuclear structure function , it is essentially unknown at small . The
nuclear structure function at small is investigated in two
different theoretical models: a parton-recombination model with rescaling
and an aligned-jet model. We find that these models predict completely
different behavior at small : {\it antishadowing} in the first parton model
and {\it shadowing} in the aligned-jet model. Therefore, studies of the ratio
at small could be useful in discriminating among different
models, which produce similar shadowing behavior in the structure function
. We also estimate currently acceptable nuclear modification of at
small by using experimental data and baryon-number
conservation.Comment: 10 pages, Latex, Figs.1 and 2 are not included, Complete postscript
file including the figures is available at
ftp://ftp.cc.saga-u.ac.jp/pub/paper/riko/quantum1/saga-he-78.ps.gz or at
http://www.cc.saga-u.ac.jp/saga-u/riko/physics/quantum1/structure.htm
Epsilon Indi Ba/Bb: the nearest binary brown dwarf
We have carried out high angular resolution near-infrared imaging and
low-resolution (R~1000) spectroscopy of the nearest known brown dwarf, Eps Indi
B, using the ESO VLT NAOS/CONICA adaptive optics system. We find it to be a
close binary (as also noted by Volk et al. 2003) with an angular separation of
0.732 arcsec, corresponding to 2.65AU at the 3.626pc distance of the Eps Indi
system. In our discovery paper (Scholz et al. 2003), we concluded that Eps Indi
B was a ~50Mjup T2.5 dwarf: our revised finding is that the two system
components (Eps Indi Ba and Eps Indi Bb) have spectral types of T1 and T6,
respectively, and estimated masses of 47 and 28Mjup, respectively, assuming an
age of 1.3Gyr. Errors in the masses are +/-10 and +/-7Mjup, respectively,
dominated by the uncertainty in the age determination (0.8-2Gyr range). This
uniquely well-characterised T dwarf binary system should prove important in the
study of low-mass, cool brown dwarfs. The two components are bright and
relatively well-resolved: Eps Indi B is the only T dwarf binary in which
spectra have been obtained for both components. They have a well-established
distance and age. Finally, their orbital motion can be measured on a fairly
short timescale (nominal orbital period 15 yrs), permitting an accurate
determination of the true total system mass, helping to calibrate brown dwarf
evolutionary models.Comment: Accepted for publication by Astronomy & Astrophysics main journal.
This replacement version includes minor changes made following comments by
the referee, along with a reworking of the photometric data and derived
quantities using 2MASS catalogue photometry as the basis, with only a minor
impact on the final result
The Magellan Adaptive Secondary VisAO Camera: Diffraction- Limited Broadband Visible Imaging and 20mas Fiber Array IFS
The Magellan Adaptive Secondary AO system, scheduled for first light in the
fall of 2011, will be able to simultaneously perform diffraction limited AO
science in both the mid-IR, using the BLINC/MIRAC4 10\{mu}m camera, and in the
visible using our novel VisAO camera. The VisAO camera will be able to operate
as either an imager, using a CCD47 with 8.5 mas pixels, or as an IFS, using a
custom fiber array at the focal plane with 20 mas elements in its highest
resolution mode. In imaging mode, the VisAO camera will have a full suite of
filters, coronagraphic focal plane occulting spots, and SDI prism/filters. The
imaging mode should provide ~20% mean Strehl diffraction-limited images over
the band 0.5-1.0 \{mu}m. In IFS mode, the VisAO instrument will provide R~1,800
spectra over the band 0.6-1.05 \{mu}m. Our unprecedented 20 mas spatially
resolved visible spectra would be the highest spatial resolution achieved to
date, either from the ground or in space. We also present lab results from our
recently fabricated advanced triplet Atmospheric Dispersion Corrector (ADC) and
the design of our novel wide-field acquisition and active optics lens. The
advanced ADC is designed to perform 58% better than conventional doublet ADCs
and is one of the enabling technologies that will allow us to achieve broadband
(0.5-1.0\{mu}m) diffraction limited imaging and wavefront sensing in the
visible.Comment: Proceedings of the SPIE, 2010, Vol. 7736, 77362
Resolving the H-alpha-emitting Region in the Wind of Eta Carinae
The massive evolved star Eta Carinae is the most luminous star in the Milky
Way and has the highest steady wind mass-loss rate of any known star. Radiative
transfer models of the spectrum by Hillier et al. predict that H-alpha is
mostly emitted in regions of the wind at radii of 6 to 60 AU from the star (2.5
to 25 mas at 2.35 kpc). We present diffraction-limited images (FWHM ~25 mas)
with Magellan adaptive optics in two epochs, showing that Eta Carinae
consistently appears ~2.5 to 3 mas wider in H-alpha emission compared to the
adjacent 643 nm continuum. This implies that the H-alpha line-forming region
may have a characteristic emitting radius of 12 mas or ~30 AU, in very good
agreement with the Hillier stellar-wind model. This provides direct
confirmation that the physical wind parameters of that model are roughly
correct, including the mass-loss rate of 10^-3 M_sun/yr, plus the clumping
factor, and the terminal velocity. Comparison of the H-alpha images
(ellipticity and PA) to the continuum images reveals no significant asymmetries
at H-alpha. Hence, any asymmetry induced by a companion or by the primary's
rotation do not strongly influence the global H-alpha emission in the outer
wind.Comment: Published in ApJ
PG 1700+518 Revisited: Adaptive Optics Imaging and a Revised Starburst Age for the Companion
We present the results of adaptive-optics imaging of the z=0.2923 QSO PG
1700+518 in the J and H bands. The extension to the north of the QSO is clearly
seen to be a discrete companion with a well-defined tidal tail, rather than a
feature associated with the host galaxy of PG 1700+518 itself. On the other
hand, an extension to the southwest of the QSO (seen best in deeper, but
lower-resolution, optical images) does likely comprise tidal material from the
host galaxy. The SED derived from images in J, H, and two non-standard optical
bands indicates the presence of dust intermixed with the stellar component. We
use our previously reported Keck spectrum of the companion, the SED found from
the imaging data, and updated spectral-synthesis models to constrain the
stellar populations in the companion and to redetermine the age of the
starburst. While our best-fit age of 0.085 Gyr is nearly the same as our
earlier determination, the fit of the new models is considerably better. This
age is found to be remarkably robust with respect to different assumptions
about the nature of the older stellar component and the effects of dust.Comment: 11 pages; includes two eps figures. Latex (AASTEX). Two additional
figures in gif format. Postscript version including all figs. (424 kb) can be
obtained from http://www.ifa.hawaii.edu/~canaguby/preprints.html To appear in
ApJ. Letter
Pulsed pumping of a Bose-Einstein condensate
In this work, we examine a system for coherent transfer of atoms into a
Bose-Einstein condensate. We utilize two spatially separate Bose-Einstein
condensates in different hyperfine ground states held in the same dc magnetic
trap. By means of a pulsed transfer of atoms, we are able to show a clear
resonance in the timing of the transfer, both in temperature and number, from
which we draw conclusions about the underlying physical process. The results
are discussed in the context of the recently demonstrated pumped atom laser.Comment: 5 pages, 5 figures, published in Physical Review
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