878 research outputs found
Teacher Evaluation, Development and Improvement
Teacher evaluation has become the focal point for education reform and improvement of U.S. schools over the last several years. At the center of the debate is the primary function of teacher performance management systems. This paper argues that teacher performance management systems which focus on the function of development and improvement will be most effective. Current teacher evaluation systems are examined using the transtheoretical model for behavioral change and examine which evaluation systems create the environment for teacher behavioral change that will be most successful. Ultimately, an organizational and educational culture of trust and support is necessary for the implementation of an effective teacher performance management system
FERENGI: Redshifting galaxies from SDSS to GEMS, STAGES and COSMOS
We describe the creation of a set of artificially "redshifted" galaxies in
the range 0.1<z<1.1 using a set of ~100 SDSS low redshift (v<7000 km/s) images
as input. The intention is to generate a training set of realistic images of
galaxies of diverse morphologies and a large range of redshifts for the GEMS
and COSMOS galaxy evolution projects. This training set allows other studies to
investigate and quantify the effects of cosmological redshift on the
determination of galaxy morphologies, distortions and other galaxy properties
that are potentially sensitive to resolution, surface brightness and bandpass
issues. We use galaxy images from the SDSS in the u, g, r, i, z filter bands as
input, and computed new galaxy images from these data, resembling the same
galaxies as located at redshifts 0.1<z<1.1 and viewed with the Hubble Space
Telescope Advanced Camera for Surveys (HST ACS). In this process we take into
account angular size change, cosmological surface brightness dimming, and
spectral change. The latter is achieved by interpolating a spectral energy
distribution that is fit to the input images on a pixel-to-pixel basis. The
output images are created for the specific HST ACS point spread function and
the filters used for GEMS (F606W and F850LP) and COSMOS (F814W). All images are
binned onto the desired pixel grids (0.03" for GEMS and 0.05" for COSMOS) and
corrected to an appropriate point spread function. Noise is added corresponding
to the data quality of the two projects and the images are added onto empty sky
pieces of real data images. We make these datasets available from our website,
as well as the code - FERENGI: "Full and Efficient Redshifting of Ensembles of
Nearby Galaxy Images" - to produce datasets for other redshifts and/or
instruments.Comment: 11 pages, 10 figures, 3 table
Gravitational lens candidates in the E-CDFS
We report ten lens candidates in the E-CDFS from the GEMS survey. Nine of the
systems are new detections and only one of the candidates is a known lens
system. For the most promising five systems including the known lens system, we
present results from preliminary lens mass modelling, which tests if the
candidates are plausible lens systems. Photometric redshifts of the candidate
lens galaxies are obtained from the COMBO-17 galaxy catalog. Stellar masses of
the candidate lens galaxies within the Einstein radius are obtained by using
the -band luminosity and the color-based stellar mass-to-light ratios.
As expected, the lensing masses are found to be larger than the stellar masses
of the candidate lens galaxies. These candidates have similar dark matter
fractions as compared to lenses in SLACS and COSMOS. They also roughly follow
the halo mass-stellar mass relation predicted by the subhalo abundance matching
technique. One of the candidate lens galaxies qualifies as a LIRG and may not
be a true lens because the arc-like feature in the system is likely to be an
active region of star formation in the candidate lens galaxy. Amongst the five
best candidates, one is a confirmed lens system, one is a likely lens system,
two are less likely to be lenses and the status of one of the candidates is
ambiguous. Spectroscopic follow-up of these systems is still required to
confirm lensing and/or for more accurate determination of the lens masses and
mass density profiles.Comment: 12 pages, 5 figures, 3 tables, ApJ accepte
Injury surveillance in English youth basketball: A 5-season cohort study to inform injury prevention strategies
Objectives: Describe the injury risk of English youth basketball, comparing game versus training injury incidence and burden.
Design: 5 season (2013/14-2018/19) prospective cohort study.
Setting: Basketball academy at an English sports college.
Participants: Male basketball players (n = 110, mean age; 17.3 ± 0.9 years).
Main outcomes measures: Descriptive data regarding game and training injury incidence (injuries per 1000 athlete-exposures (AE)) and burden (severity x incidence) are provided with 95% confidence intervals (CI). Rate ratios (RR; 95% CI) were used to compare outcome measures, with results statistically significant if the 95% CI did not pass 1.0.
Results: Fifty-four injuries were sustained during 13,350-AE (1666 games, 9684 training). Game injury incidence (12.0/1000-AE, 95% CI 6.7–17.3) was significantly greater than training injury incidence (2.4/1000-AE, 95% CI 1.4–3.3; RR = 5.1, 95% CI 2.8–9.2). Games had a significantly greater injury burden (216 days absence/1000-AE, 95% CI 121-311) than training (62 days absence/1000-AE, 95% CI 37-88; RR = 3.5, 95% CI 1.9–6.3). The ankle was the most injured body location (37%), whilst over 50% of injuries occurring through contact mechanisms.
Conclusion: This study is the most comprehensive description of injury epidemiology in English youth basketball to date. This information can inform evidence-based injury prevention strategies to mitigate risk in this population
Evolution of optically faint AGN from COMBO-17 and GEMS
We have mapped the AGN luminosity function and its evolution between z=1 and
z=5 down to apparent magnitudes of . Within the GEMS project we have
analysed HST-ACS images of many AGN in the Extended Chandra Deep Field South,
enabling us to assess the evolution of AGN host galaxy properties with cosmic
time.Comment: to appear in proceedings 'Multiwavelength AGN Surveys', Cozumel 200
Towards an understanding of social networks among organizational self-initiated expatriates: a qualitative case study of a professional services firm
Drawing on a qualitative case study of 51 organizational self-initiated expatriates (OSIEs) in a professional services firm, this article investigates the role of networks during expatriation and, specifically, in the development of learning that is beneficial to both the individual expatriate and the global operations of the firm. First, we investigate the extent to which individual motivations to engage in OSIE impact on the development of networks. Second, we investigate individual’s experiences of network development. Third, we investigate individual perceptions of the benefits of networks for both organizations and individual actors. The paper will report that professionals initiating their own expatriation develop continually expanding and composite networks such that mobility and networks evolve in a seemingly symbiotic relationship. In doing so, it contributes to our understanding of the role of agency in network development and extends our understanding of organizational self-initiated expatriation as a relatively under-researched phenomenon
Stellar science from a blue wavelength range - A possible design for the blue arm of 4MOST
From stellar spectra, a variety of physical properties of stars can be
derived. In particular, the chemical composition of stellar atmospheres can be
inferred from absorption line analyses. These provide key information on large
scales, such as the formation of our Galaxy, down to the small-scale
nucleosynthesis processes that take place in stars and supernovae. By extending
the observed wavelength range toward bluer wavelengths, we optimize such
studies to also include critical absorption lines in metal-poor stars, and
allow for studies of heavy elements (Z>38) whose formation processes remain
poorly constrained. In this context, spectrographs optimized for observing blue
wavelength ranges are essential, since many absorption lines at redder
wavelengths are too weak to be detected in metal-poor stars. This means that
some elements cannot be studied in the visual-redder regions, and important
scientific tracers and science cases are lost. The present era of large public
surveys will target millions of stars. Here we describe the requirements
driving the design of the forthcoming survey instrument 4MOST, a multi-object
spectrograph commissioned for the ESO VISTA 4m-telescope. We focus here on
high-density, wide-area survey of stars and the science that can be achieved
with high-resolution stellar spectroscopy. Scientific and technical
requirements that governed the design are described along with a thorough line
blending analysis. For the high-resolution spectrograph, we find that a
sampling of >2.5 (pixels per resolving element), spectral resolution of 18000
or higher, and a wavelength range covering 393-436 nm, is the most
well-balanced solution for the instrument. A spectrograph with these
characteristics will enable accurate abundance analysis (+/-0.1 dex) in the
blue and allow us to confront the outlined scientific questions. (abridged)Comment: 14 pages, 8 figures, accepted for publication in A
Exploring the Impact of Galaxy Interactions over Seven Billion Years with CAS
We explore galaxy assembly over the last seven billion years by
characterizing "normal" galaxies along the Hubble sequence, against strongly
disturbed merging/interacting galaxies with the widely used CAS system of
concentration (C), asymmetry (A), and 'clumpiness' (S) parameters, as well as
visual classification. We analyze Hubble Space Telescope (HST) ACS images of
~4000 intermediate and high mass (> 10^9 solar masses) galaxies from the GEMS
survey, one of the largest HST surveys conducted to date in two filters. We
explore the effectiveness of the CAS criteria [A>S and A>~0.35] in separating
normal and strongly disturbed galaxies at different redshifts, and quantify the
recovery and contamination rate. We also compare the average star formation
rate and the cosmic star formation rate density as a function of redshift
between normal and interacting systems identified by CAS.Comment: ASP conference proceedings of 2007 Bash Symposium. Latex with
asp2006.sty. 4 pages, 4 figure
Photon-Photon Luminosities in Relativistic Heavy Ion Collisions at LHC Energies
Effective photon-photon luminosities are calculated for various realistic
hadron collider scenarios. The main characteristics of photon-photon processes
at relativistic heavy-ion colliders are established and compared to the
corresponding photon-photon luminosities at electron-positron and future Photon
Linear Colliders (PLC). Higher order corrections as well as inelastic processes
are discussed. It is concluded that feasible high luminosity Ca-Ca collisions
at the Large Hadron Collider (LHC) are an interesting option for photon-photon
physics up to about 100 GeV photon-photon CM energy.Comment: REVTeX, 13 pages, 10 figures (uuencoded,compressed postscript
Cosmological weak lensing with the HST GEMS survey
We present our cosmic shear analysis of GEMS, one of the largest wide-field
surveys ever undertaken by the Hubble Space Telescope. Imaged with the Advanced
Camera for Surveys (ACS), GEMS spans 795 square arcmin in the Chandra Deep
Field South. We detect weak lensing by large-scale structure in high resolution
F606W GEMS data from ~60 resolved galaxies per square arcminute. We measure the
two-point shear correlation function, the top-hat shear variance and the shear
power spectrum, performing an E/B mode decomposition for each statistic. We
show that we are not limited by systematic errors and use our results to place
joint constraints on the matter density parameter Omega_m and the amplitude of
the matter power spectrum sigma_8. We find sigma_8(Omega_m/0.3)^{0.65}=0.68 +/-
0.13 where the 1sigma error includes both our uncertainty on the median
redshift of the survey and sampling variance.
Removing image and point spread function (PSF) distortions are crucial to all
weak lensing analyses. We therefore include a thorough discussion on the degree
of ACS PSF distortion and anisotropy which we characterise directly from GEMS
data. Consecutively imaged over 20 days, GEMS data also allows us to
investigate PSF instability over time. We find that, even in the relatively
short GEMS observing period, the ACS PSF ellipticity varies at the level of a
few percent which we account for with a semi-time dependent PSF model. Our
correction for the temporal and spatial variability of the PSF is shown to be
successful through a series of diagnostic tests.Comment: 17 pages, 16 figures. Version accepted by MNRA
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