533 research outputs found

    Teaching Metalinguistic Skills To Enhance Early Reading Instruction

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    This article focuses on practical classroom ideas for enhancing early literacy learning by teaching a broad range of metalinguistic skills. These skills include phonemic and word awareness, but focus largely on syntactic and pragmatic skills in order to give children a richer understanding of language and its functions. Theoretical background is provided along with activities that can be used in the primary classroom

    Correlation Between Phase Competition and the Nucleation of a Griffiths Phase in (La1-yPry)0.7Ca0.3Mn16/18O3

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    Detailed analyses of the temperature-dependent zero field ac susceptibility of prototypical phase-separated (La1-yPry)0.7Ca0.3Mn16/18O3, 0 < y < 1, reveal features consistent with the presence of a Griffiths phase (GP), viz., an inverse susceptibility characterized by power law with 0.05 < lamda < 0.33 as y decreases towards yc < 0.85. Beyond yc = 0.85, the GP is suppressed. These data, combined with previous neutron diffraction measurements, enable a phase diagram summarizing the evolution of the GP with composition to be constructed for this system; in particular, it shows that the disorder relevant for the establishment of such a phase is linked closely to the relative volume fractions of the phase separated antiferromagnetic and ferromagnetic components, even when the recently estimated double exchange (DE) linked percolation threshold is exceeded. The influence of electron-phonon coupling can also be seen through oxygen isotope effects.Comment: 4 page

    The Next Generation Virgo Cluster Survey (NGVS). XVIII. Measurement and Calibration of Surface Brightness Fluctuation Distances for Bright Galaxies in Virgo (and Beyond)

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    We describe a program to measure surface brightness fluctuation (SBF) distances to galaxies observed in the Next Generation Virgo Cluster Survey (NGVS), a photometric imaging survey covering 104 deg2104~deg^2 of the Virgo cluster in the u∗,g,i,z{u}^*,g,i,z bandpasses with the Canada-France Hawaii Telescope. We describe the selection of the sample galaxies, the procedures for measuring the apparent ii-band SBF magnitude iˉ\bar{i}, and the calibration of the absolute Mˉi\bar{M}_i as a function of observed stellar population properties. The multi-band NGVS data set provides multiple options for calibrating the SBF distances, and we explore various calibrations involving individual color indices as well as combinations of two different colors. Within the color range of the present sample, the two-color calibrations do not significantly improve the scatter with respect to wide-baseline, single-color calibrations involving u∗u^{*}. We adopt the u∗−z{u}^*{-}z calibration as reference for the present galaxy sample, with an observed scatter of 0.11 mag. For a few cases that lack good u∗{u}^* photometry, we use an alternative relation based on a combination of g−ig{-}i and g−zg{-}z colors, with only a slightly larger observed scatter of 0.12 mag. The agreement of our measurements with the best existing distance estimates provides confidence that our measurements are accurate. We present a preliminary catalog of distances for 89 galaxies brighter than BT≈13.0B_T\approx13.0 mag within the survey footprint, including members of the background M and W Clouds at roughly twice the distance of the main body of the Virgo cluster. The extension of the present work to fainter and bluer galaxies is in progress.Comment: ApJ accepte

    Reducing Maternal and Child Health Disparities among Latino Immigrants in South Carolina Through a Tailored, Culturally Appropriate and Participant-Driven Initiative

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    Newly arrived Latino immigrants in South Carolina (SC), especially Latina mothers, experience many health related barriers including a general lack of health services information. The PASOs program, which means “steps” in Spanish, uses education, outreach, partnerships and advocacy to empower Latino families to utilize available health care services throughout SC. PASOs is a community-based program conducted by college trained bilingual/bicultural facilitators with the support from community health care workers (promotores de salud). Participants (n=523) were expectant mothers with an average age of 27 (SD=6) years, mostly from Mexico (69%), with an average of 9 (SD=4) years of education and 7 (SD=5) years living in the US. Repeated measures analyses from pre-test to post-test indicated significant knowledge improvement (p&lt;0.005) regarding the importance of prenatal care, signs of preterm delivery, benefits of breastfeeding, and the importance of folic acid intake during periconception. By the end of the course, the majority of the Latinas (93%; p&lt;0.0001) were able to name a birth control method they planned to use following their current pregnancy. Results of this study emphasize the benefits associated with the implementation of a culturally-appropriate program with newly arrived Latino immigrants, including an increase on preconception, pregnancy, and post-pregnancy knowledge

    The CFHT Legacy Survey: The Morphology-Density Relation of Galaxies out to Z~1

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    We study the relationships between galaxy total luminosity (M_g), morphology, color and environment as a function of redshift. We use a magnitude-limited sample of 65,624 galaxies in the redshift range 0<z<1.3 taken from one of the Canada-France-Hawaii Telescope Legacy Survey Deep Fields. We parametrize galaxy morphology according to the Sersic index n. Our n>2 number fractions at z=0.1 agree well with those based on SDSS galaxies. We find that the n>2 galaxy number fraction is constant with redshift in the field. However, for overdense environments this fraction is larger and increases towards lower redshifts, higher densities and higher luminosities. Rest-frame color-magnitude diagrams show that the color distribution is bimodal out to our redshift limit of z~1 with a prominent red-sequence of galaxies at 0.2<z<0.4 and a large blue-peak dominance at 0.8<z<1. We use this bimodality to define a red galaxy fraction (rest-frame u-g>1). For all environments, this fraction increases towards lower redshifts and higher luminosities. The red fraction within cluster-like regions changes 60% faster with redshift as compared to the field for M_g<-19.5. Using, for the first time, observations across many cluster-field interfaces distributed over a single, large volume, we trace the large-scale morphology-density relation and the Butcher-Oemler effect over a period of almost 8 Gyr.Comment: Accepted by Ap

    Limits on Quaoar's Atmosphere

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    Here we present high cadence photometry taken by the Acquisition Camera on Gemini South, of a close passage by the ~540 km radius Kuiper belt object, (50000) Quaoar, of a r' = 20.2 background star. Observations before and after the event show that the apparent impact parameter of the event was 0."019 ± 0."004, corresponding to a close approach of 580 ± 120 km to the center of Quaoar. No signatures of occultation by either Quaoar's limb or its potential atmosphere are detectable in the relative photometry of Quaoar and the target star, which were unresolved during closest approach. From this photometry we are able to put constraints on any potential atmosphere Quaoar might have. Using a Markov chain Monte Carlo and likelihood approach, we place pressure upper limits on sublimation supported, isothermal atmospheres of pure N_2, CO, and CH_4. For N_2 and CO, the upper limit surface pressures are 1 and 0.7 Όbar, respectively. The surface temperature required for such low sublimation pressures is ~33 K, much lower than Quaoar's mean temperature of ~44 K measured by others. We conclude that Quaoar cannot have an isothermal N_2 or CO atmosphere. We cannot eliminate the possibility of a CH_4 atmosphere, but place upper surface pressure and mean temperature limits of ~138 nbar and ~44 K, respectively

    The Next Generation Virgo Cluster Survey. VII. The intrinsic shapes of low-luminosity galaxies in the core of the Virgo cluster, and a comparison with the Local Group

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    (Abridged) We investigate the intrinsic shapes of low-luminosity galaxies in the central 300 kpc of the Virgo cluster using deep imaging obtained as part of the NGVS. We build a sample of nearly 300 red-sequence cluster members in the yet unexplored −14<Mg<−8-14 < M_{g} < -8 magnitude range. The observed distribution of apparent axis ratios is then fit by families of triaxial models with normally-distributed intrinsic ellipticities and triaxialities. We develop a Bayesian framework to explore the posterior distribution of the model parameters, which allows us to work directly on discrete data, and to account for individual, surface brightness-dependent axis ratio uncertainties. For this population we infer a mean intrinsic ellipticity E=0.43, and a mean triaxiality T=0.16. This implies that faint Virgo galaxies are best described as a family of thick, nearly oblate spheroids with mean intrinsic axis ratios 1:0.94:0.57. We additionally attempt a study of the intrinsic shapes of Local Group satellites of similar luminosities. For the LG population we infer a slightly larger mean intrinsic ellipticity E=0.51, and the paucity of objects with round apparent shapes translates into more triaxial mean shapes, 1:0.76:0.49. We finally compare the intrinsic shapes of NGVS low-mass galaxies with samples of more massive quiescent systems, and with field, star-forming galaxies of similar luminosities. We find that the intrinsic flattening in this low-luminosity regime is almost independent of the environment in which the galaxy resides--but there is a hint that objects may be slightly rounder in denser environments. The comparable flattening distributions of low-luminosity galaxies that have experienced very different degrees of environmental effects suggests that internal processes are the main drivers of galaxy structure at low masses--with external mechanisms playing a secondary role.Comment: Accepted to ApJ. 18 pages, 12 figure

    Col-OSSOS: The Colours of the Outer Solar System Origins Survey

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    The Colours of the Outer Solar System Origins Survey (Col-OSSOS) is acquiring near-simultaneous gg, rr, and JJ photometry of unprecedented precision with the Gemini North Telescope, targeting nearly a hundred trans-Neptunian objects (TNOs) brighter than mr=23.6m_r=23.6 mag discovered in the Outer Solar System Origins Survey. Combining the optical and near-infrared photometry with the well-characterized detection efficiency of the Col-OSSOS target sample will provide the first flux-limited compositional dynamical map of the outer Solar System. In this paper, we describe our observing strategy and detail the data reduction processes we employ, including techniques to mitigate the impact of rotational variability. We present optical and near-infrared colors for 35 TNOs. We find two taxonomic groups for the dynamically excited TNOs, the neutral and red classes, which divide at g−r≃0.75g-r \simeq 0.75. Based on simple albedo and orbital distribution assumptions, we find that the neutral class outnumbers the red class, with a ratio of 4:1 and potentially as high as 11:1. Including in our analysis constraints from the cold classical objects, which are known to exhibit unique albedos and r−zr-z colors, we find that within our measurement uncertainty, our observations are consistent with the primordial Solar System protoplanetesimal disk being neutral-class-dominated, with two major compositional divisions in grJgrJ color space.Comment: Accepted to ApJS; on-line supplemental files will be available with the AJS published version of the pape

    The Next Generation Virgo Cluster Survey. IX. Estimating the Efficiency of Galaxy Formation on the Lowest-Mass Scales

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    The Next Generation Virgo Cluster Survey has recently determined the luminosity function of galaxies in the core of the Virgo cluster down to unprecedented magnitude and surface brightness limits. Comparing simulations of cluster formation to the derived central stellar mass function, we attempt to estimate the stellar-to-halo-mass ratio (SHMR) for dwarf galaxies, as it would have been before they fell into the cluster. This approach ignores several details and complications, e.g., the contribution of ongoing star formation to the present-day stellar mass of cluster members, and the effects of adiabatic contraction and/or violent feedback on the subhalo and cluster potentials. The final results are startlingly simple, however; we find that the trends in the SHMR determined previously for bright galaxies appear to extend down in a scale-invariant way to the faintest objects detected in the survey. These results extend measurements of the formation efficiency of field galaxies by two decades in halo mass, or five decades in stellar mass, down to some of the least massive dwarf galaxies known, with stellar masses of ∌105M⊙\sim 10^5 M_\odot.Comment: 18 pages, 12 figures; published in ApJ July 1st 201
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