3,135 research outputs found

    Transitions and progress: teachers' views of progress in attainment of pupils age 5-10

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    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 F3(x)F_3(x)

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    Nuclear modification of the structure function F3F_3 is investigated. Although it could be estimated in the medium and large xx regions from the nuclear structure function F2AF_2^A, it is essentially unknown at small xx. The nuclear structure function F3AF_3^A at small xx is investigated in two different theoretical models: a parton-recombination model with Q2Q^2 rescaling and an aligned-jet model. We find that these models predict completely different behavior at small xx: {\it antishadowing} in the first parton model and {\it shadowing} in the aligned-jet model. Therefore, studies of the ratio F3A/F3DF_3^A/F_3^D at small xx could be useful in discriminating among different models, which produce similar shadowing behavior in the structure function F2F_2. We also estimate currently acceptable nuclear modification of F3F_3 at small xx by using F2A/F2DF_2^A/F_2^D 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

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    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

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    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

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    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

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    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

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    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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