1,088 research outputs found
Aiming Higher Together: Strategizing Better Educational Outcomes for Boys and Young Men of Color
This paper is focused on racial, ethnic, and gender patterns in children's lived experiences that, based on research, seem to contribute to developmental disparities. Studies cited in the paper indicate promising ways to help address race and gender differences in home-based learning activities beginning from birth. To reveal school-related patterns and to measure students perceptions of the quality of teaching they experience, the paper uses student survey results from thousands of classrooms. The author briefly describes some school-improvement approaches that can improve educational outcomes for students of color, with examples of alternatives to out-of-schools suspensions
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Pathways to prosperity: Meeting the challenge of preparing young Americans for the 21st century
The Opacity of Nearby Galaxies from Colors and Counts of Background Galaxies: I. The Synthetic Field Method and its Application to NGC 4536 and NGC 3664
We describe a new, direct method for determining the opacity of foreground
galaxies which does not require any a priori assumptions about the spatial
distribution or the reddening law of the obscuring material. The method is to
measure the colors and counts of background galaxies which can be identified
through the foreground system. The method is calibrated, and the effects of
confusion and obscuration are decoupled by adding various versions of a
suitable deep reference frame containing only field galaxies with known
properties into the image of the foreground galaxy, and analyzing these
``synthetic field'' images in the same way as the real images. We test the
method on HST WFPC2 archived images of two galaxies which are quite different:
NGC 4536 is a large Sc spiral, and NGC 3664 is a small Magellanic irregular.
The reference frames are taken from the Hubble Deep Field.
From the background galaxy counts, NGC 4536 shows an extinction A_I ~ 1 mag
in the northwestern arm region, and lower than 0.5 mag in the corresponding
interarm region (no correction for inclination has been attempted). However,
from the galaxy colors, the same reddening of E(V - I) ~ 0.2 is observed in
both the arm and the interarm regions. In the interarm region, the combination
of extinction and reddening can be explained by a diffuse component with a
Galactic reddening law (R_V ~ 3). In the spiral arm, however, the same diffuse,
low opacity component seems to coexist with regions of much higher opacity.
Since the exposures are shorter the results for NGC 3664 are less clear, but
also appear to be consistent with a two component distribution.Comment: 42 pages, 18 figures; accepted for publication in The Astrophysical
Journal, Vol. 506, October 10, 199
Comparison of Teen Driver Fatality Rates by Vehicle Type in the United States
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/74622/1/j.aem.2007.06.038.pd
The HST/ACS Coma Cluster Survey. II. Data Description and Source Catalogs
The Coma cluster was the target of a HST-ACS Treasury program designed for
deep imaging in the F475W and F814W passbands. Although our survey was
interrupted by the ACS instrument failure in 2007, the partially completed
survey still covers ~50% of the core high-density region in Coma. Observations
were performed for 25 fields that extend over a wide range of cluster-centric
radii (~1.75 Mpc) with a total coverage area of 274 arcmin^2. The majority of
the fields are located near the core region of Coma (19/25 pointings) with six
additional fields in the south-west region of the cluster. In this paper we
present reprocessed images and SExtractor source catalogs for our survey
fields, including a detailed description of the methodology used for object
detection and photometry, the subtraction of bright galaxies to measure faint
underlying objects, and the use of simulations to assess the photometric
accuracy and completeness of our catalogs. We also use simulations to perform
aperture corrections for the SExtractor Kron magnitudes based only on the
measured source flux and half-light radius. We have performed photometry for
~73,000 unique objects; one-half of our detections are brighter than the
10-sigma point-source detection limit at F814W=25.8 mag (AB). The slight
majority of objects (60%) are unresolved or only marginally resolved by ACS. We
estimate that Coma members are 5-10% of all source detections, which consist of
a large population of unresolved objects (primarily GCs but also UCDs) and a
wide variety of extended galaxies from a cD galaxy to dwarf LSB galaxies. The
red sequence of Coma member galaxies has a constant slope and dispersion across
9 magnitudes (-21<M_F814W<-13). The initial data release for the HST-ACS Coma
Treasury program was made available to the public in 2008 August. The images
and catalogs described in this study relate to our second data release.Comment: Accepted for publication in ApJS. A high-resolution version is
available at http://archdev.stsci.edu/pub/hlsp/coma/release2/PaperII.pd
The STIS Parallel Survey: Introduction and First Results
The installation of the Space Telescope Imaging Spectrograph (STIS) on the
Hubble Space Telescope (HST) allows for the first time two-dimensional optical
and ultraviolet slitless spectroscopy of faint objects from space. The STIS
Parallel Survey (SPS) routinely obtains broad band images and slitless spectra
of random fields in parallel with HST observations using other instruments. The
SPS is designed to study a wide variety of astrophysical phenomena, including
the rate of star formation in galaxies at intermediate to high redshift through
the detection of emission-line galaxies. We present the first results of the
SPS, which demonstrate the capability of STIS slitless spectroscopy to detect
and identify high-redshift galaxies.Comment: 11 pages, Latex, 3 enclosed Postscript figures, aaspp4.sty, accepted
for publication in the Astrophysical Journal Letters HST Second Servicing
Mission special issu
Search for CP Violation in the Decay Z -> b (b bar) g
About three million hadronic decays of the Z collected by ALEPH in the years
1991-1994 are used to search for anomalous CP violation beyond the Standard
Model in the decay Z -> b \bar{b} g. The study is performed by analyzing
angular correlations between the two quarks and the gluon in three-jet events
and by measuring the differential two-jet rate. No signal of CP violation is
found. For the combinations of anomalous CP violating couplings, and , limits of \hat{h}_b < 0.59h^{\ast}_{b} < 3.02$ are given at 95\% CL.Comment: 8 pages, 1 postscript figure, uses here.sty, epsfig.st
Accelerated SARS-CoV-2 Intrahost Evolution Leading to Distinct Genotypes During Chronic Infection
The chronic infection hypothesis for novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variant emergence is increasingly gaining credence following the appearance of Omicron. Here, we investigate intrahost evolution and genetic diversity of lineage B.1.517 during a SARS-CoV-2 chronic infection lasting for 471 days (and still ongoing) with consistently recovered infectious virus and high viral genome copies. During the infection, we find an accelerated virus evolutionary rate translating to 35 nucleotide substitutions per year, approximately 2-fold higher than the global SARS-CoV-2 evolutionary rate. This intrahost evolution results in the emergence and persistence of at least three genetically distinct genotypes, suggesting the establishment of spatially structured viral populations continually reseeding different genotypes into the nasopharynx. Finally, we track the temporal dynamics of genetic diversity to identify advantageous mutations and highlight hallmark changes for chronic infection. Our findings demonstrate that untreated chronic infections accelerate SARS-CoV-2 evolution, providing an opportunity for the emergence of genetically divergent variants
Toward Identifying the Next Generation of Superfund and Hazardous Waste Site Contaminants
Reproduced with permission from Environmental Health Perspectives."This commentary evolved from a workshop sponsored by the National Institute of Environmental Health Sciences titled "Superfund Contaminants: The Next Generation" held in Tucson, Arizona, in August 2009. All the authors were workshop participants." doi:10.1289/ehp.1002497Our aim was to initiate a dynamic, adaptable process for identifying contaminants of emerging concern (CECs) that are likely to be found in future hazardous waste sites, and to identify the gaps in primary research that cause uncertainty in determining future hazardous waste site contaminants. Superfund-relevant CECs can be characterized by specific attributes: they are persistent, bioaccumulative, toxic, occur in large quantities, and have localized accumulation with a likelihood of exposure. Although still under development and incompletely applied, methods to quantify these attributes can assist in winnowing down the list of candidates from the universe of potential CECs. Unfortunately, significant research gaps exist in detection and quantification, environmental fate and transport, health and risk assessment, and site exploration and remediation for CECs. Addressing these gaps is prerequisite to a preventive approach to generating and managing hazardous waste sites.Support for the workshop, from which this article evolved, was provided by the National Institute of Environmental Health Sciences Superfund Research Program (P42-ES04940)
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