343 research outputs found
An exploration of the impact of family on the achievement of African American gifted learners originating from low -income environments
The purpose of this study was to determine what, if any, impact families have on the academic achievement of African American gifted learners from low income environments. This grounded theory study was designed to explore family and student perceptions of a complex set of variables related to families and home environments. The variables explored were based on a conceptual framework developed from previous research related to social capital and its uses within families with limited economic resources. Study participants were junior and senior level high school students and their parents.;Instruments included a demographic questionnaire with open-ended questions, a researcher-developed interview protocol and the Moos Family Environment Scale. Based on the findings, certain \u27social capital\u27 resources were revealed: family cohesion; strong relationships with mothers; family to student discussions related to education and positive achievement; the role of the extended family (particularly aunts and cousins); emphasis on religious identity development; and the role of fathers are noted as having impact on school achievement. Another notable source of capital revealed was the intrinsic motivation and resilience of each of the students based on parent and student responses to interview questions.;The most pronounced findings were the role of the mother as nurturer and encourager; the flexible role of extended family members who provide additional support; the emphasis within the households on positive achievement orientation, and certain family traditions which taken together form a cohesive, supportive family environment, even in the midst of challenging life circumstances. In addition to the social capital provided by families, this study also revealed other sources of positive impact including special school-based programs and internal traits. Implications for future research include the design of a controlled study of African American families of gifted students utilizing the Moos & Moos Family Environment Scale (FES), a study of the support structure provided by mothers of gifted learners across a variety of cultural contexts, and study of the intrinsic motivation and resilience of at-risk African American gifted learners. Implications for educational practice include improving professional development for educators, family and parent education programs, and enhancing guidance and counseling programs for African American and other culturally diverse gifted learners
Dietary selenium intake among Ethiopian children in areas known for selenium spatial variability
Introduction: There is spatial variability of selenium (Se) in soil and crops in Ethiopia. We assessed the Se content of food items, breast milk, and urine among infants in Ethiopia from two areas with contrasting Se concentrations in soils.
Methods: Dietary Se intakes among children (6–23 months) were evaluated using a weighed food record on two non-consecutive days. Also, spot urine samples from children and breast milk samples from their mothers were collected to determine Se concentration. Selenium concentrations in the samples were analyzed using an inductively coupled plasma mass spectrometer (ICP-MS).
Results: Injera (prepared from teff and mixtures of other cereals) with a legume-based stew were the most frequently consumed foods by the children in both areas, followed by pasta. Overall, the Se concentration (mean ± SD) of food items, breast milk (12.2 ± 3.9 μg/L vs. 3.39 ± 1.5 μg/L), and urine samples (22.5 ± 11.5 μg/L vs. 3.0 ± 1.9 μg/L) from East Amhara were significantly higher than the corresponding samples from West Amhara (p < 0.001). The total Se intakes by the study children from East Amhara and West Amhara were 30.2 [IQ 25%, 14.2; IQ 75%, 54.1] and 7.4 [IQR 25%, 4.2; IQ 75%, 10.6] μg day–1, respectively; 31.5% of children from East Amhara and 92% of children from West Amhara were at risk of inadequate Se intakes. Urinary Se excretion accounted for 53 and 39% of daily dietary Se intake in East Amhara and West Amhara, respectively. Dietary Se intake was positively correlated with urinary Se excretion in East Amhara (r = 0.56; p < 0.001) but not among samples from West Amhara (r = 0.16; p ≥ 0.05), suggesting greater physiological Se conservation in a state of deficiency.
Conclusion: There is spatial variability of Se in foods, breast milk, and urine in Ethiopia, suggesting the need for implementation of targeted agronomic interventions that enhance Se concentrations in the edible portion of plant foods
Development of the Wheelchair Interface Questionnaire and initial face and content validity
Background: Because resources are limited in low- and middle-income countries (LMIC), the development of outcome measures is of interest. Wheelchair outcome measures are useful to support evidence-based practice in wheelchair provision.
Objectives: The Wheelchair Interface Questionnaire (WIQ) is being developed to provide a professional perspective on the quality of the interface between a wheelchair and its user. This article discusses the development of the WIQ and its face and content validity.
Method: During field studies in Kenya, we sought to include professional report data on the wheelchair–user interface that could be analysed to inform design changes. None of the existing measures was focused on the interface between users and their wheelchairs. The WIQ was developed to meet this need. To investigate face and content validity, 24 experienced wheelchair professionals participated in a study that included two rounds of an online survey and a focus group in Kenya.
Results: Responses were categorised by topic and the WIQ was modified following each iteration. Participants affirmed the usefulness of a brief professional report measure to provide a snapshot of the user–wheelchair interface. Participants emphasised the importance of brevity, wide applicability and provision of specific feedback for wheelchair modification or design changes. The focus group agreed that the final version provided useful data and was applicable to virtually all wheelchair users in LMIC.
Conclusion: These preliminary studies indicate initial face and content validity of the WIQ as a method for providing a professional perspective on the interface between a user and his or her wheelchair
The Chandra Source Catalog
The Chandra Source Catalog (CSC) is a general purpose virtual X-ray
astrophysics facility that provides access to a carefully selected set of
generally useful quantities for individual X-ray sources, and is designed to
satisfy the needs of a broad-based group of scientists, including those who may
be less familiar with astronomical data analysis in the X-ray regime. The first
release of the CSC includes information about 94,676 distinct X-ray sources
detected in a subset of public ACIS imaging observations from roughly the first
eight years of the Chandra mission. This release of the catalog includes point
and compact sources with observed spatial extents <~ 30''. The catalog (1)
provides access to the best estimates of the X-ray source properties for
detected sources, with good scientific fidelity, and directly supports
scientific analysis using the individual source data; (2) facilitates analysis
of a wide range of statistical properties for classes of X-ray sources; and (3)
provides efficient access to calibrated observational data and ancillary data
products for individual X-ray sources, so that users can perform detailed
further analysis using existing tools. The catalog includes real X-ray sources
detected with flux estimates that are at least 3 times their estimated 1 sigma
uncertainties in at least one energy band, while maintaining the number of
spurious sources at a level of <~ 1 false source per field for a 100 ks
observation. For each detected source, the CSC provides commonly tabulated
quantities, including source position, extent, multi-band fluxes, hardness
ratios, and variability statistics, derived from the observations in which the
source is detected. In addition to these traditional catalog elements, for each
X-ray source the CSC includes an extensive set of file-based data products that
can be manipulated interactively.Comment: To appear in The Astrophysical Journal Supplement Series, 53 pages,
27 figure
The Hubble constant and dark energy from cosmological distance measures
We study how the determination of the Hubble constant from cosmological
distance measures is affected by models of dark energy and vice versa. For this
purpose, constraints on the Hubble constant and dark energy are investigated
using the cosmological observations of cosmic microwave background, baryon
acoustic oscillations and type Ia suprenovae. When one investigates dark
energy, the Hubble constant is often a nuisance parameter, thus it is usually
marginalized over. On the other hand, when one focuses on the Hubble constant,
simple dark energy models such as a cosmological constant and a constant
equation of state are usually assumed. Since we do not know the nature of dark
energy yet, it is interesting to investigate the Hubble constant assuming some
types of dark energy and see to what extent the constraint on the Hubble
constant is affected by the assumption concerning dark energy. We show that the
constraint on the Hubble constant is not affected much by the assumption for
dark energy. We furthermore show that this holds true even if we remove the
assumption that the universe is flat. We also discuss how the prior on the
Hubble constant affects the constraints on dark energy and/or the curvature of
the universe.Comment: 45 pages, 15 figure
Statistical Characterization of the Chandra Source Catalog
The first release of the Chandra Source Catalog (CSC) contains ~95,000 X-ray
sources in a total area of ~0.75% of the entire sky, using data from ~3,900
separate ACIS observations of a multitude of different types of X-ray sources.
In order to maximize the scientific benefit of such a large, heterogeneous
data-set, careful characterization of the statistical properties of the
catalog, i.e., completeness, sensitivity, false source rate, and accuracy of
source properties, is required. Characterization efforts of other, large
Chandra catalogs, such as the ChaMP Point Source Catalog (Kim et al. 2007) or
the 2 Mega-second Deep Field Surveys (Alexander et al. 2003), while
informative, cannot serve this purpose, since the CSC analysis procedures are
significantly different and the range of allowable data is much less
restrictive. We describe here the characterization process for the CSC. This
process includes both a comparison of real CSC results with those of other,
deeper Chandra catalogs of the same targets and extensive simulations of
blank-sky and point source populations.Comment: To be published in the Astrophysical Journal Supplement Series (Fig.
52 replaced with a version which astro-ph can convert to PDF without issues.
Comparison of Standard Ruler and Standard Candle constraints on Dark Energy Models
We compare the dark energy model constraints obtained by using recent
standard ruler data (Baryon Acoustic Oscillations (BAO) at z=0.2 and z=0.35 and
Cosmic Microwave Background (CMB) shift parameters R and l_a) with the
corresponding constraints obtained by using recent Type Ia Supernovae (SnIa)
standard candle data (ESSENCE+SNLS+HST from Davis et. al.). We find that, even
though both classes of data are consistent with LCDM at the 2\sigma level,
there is a systematic difference between the two classes of data. In
particular, we find that for practically all values of the parameters
(\Omega_0m,\Omega_b) in the 2\sigma range of the the 3-year WMAP data (WMAP3)
best fit, LCDM is significantly more consistent with the SnIa data than with
the CMB+BAO data. For example for (\Omega_0m,\Omega_b)=(0.24,0.042)
corresponding to the best fit values of WMAP3, the dark energy equation of
state parametrization w(z)=w_0 + w_1 (z/(1+z)) best fit is at a 0.5\sigma
distance from LCDM (w_0=-1,w_1=0) using the SnIa data and 1.7\sigma away from
LCDM using the CMB+BAO data. There is a similar trend in the earlier data (SNLS
vs CMB+BAO at z=0.35). This trend is such that the standard ruler CMB+BAO data
show a mild preference for crossing of the phantom divide line w=-1, while the
recent SnIa data favor LCDM. Despite of this mild difference in trends, we find
no statistically significant evidence for violation of the cosmic distance
duality relation \eta \equiv d_L(z)/(d_A(z) (1+z)^2)=1. For example, using a
prior of \Omega_0m=0.24, we find \eta=0.95 \pm 0.025 in the redshift range
0<z<2, which is consistent with distance duality at the 2\sigma level.Comment: References added. 9 pages, 7 figures. The Mathematica files with the
numerical analysis of the paper can be found at
http://leandros.physics.uoi.gr/rulcand/rulcand.ht
Neural stem cells genetically-modified to express neprilysin reduce pathology in Alzheimer transgenic models
INTRODUCTION: Short-term neural stem cell (NSC) transplantation improves cognition in Alzheimer’s disease (AD) transgenic mice by enhancing endogenous synaptic connectivity. However, this approach has no effect on the underlying beta-amyloid (Aβ) and neurofibrillary tangle pathology. Long term efficacy of cell based approaches may therefore require combinatorial approaches. METHODS: To begin to examine this question we genetically-modified NSCs to stably express and secrete the Aβ-degrading enzyme, neprilysin (sNEP). Next, we studied the effects of sNEP expression in vitro by quantifying Aβ-degrading activity, NSC multipotency markers, and Aβ-induced toxicity. To determine whether sNEP-expressing NSCs can also modulate AD-pathogenesis in vivo, control-modified and sNEP-NSCs were transplanted unilaterally into the hippocampus of two independent and well characterized transgenic models of AD: 3xTg-AD and Thy1-APP mice. After three months, stem cell engraftment, neprilysin expression, and AD pathology were examined. RESULTS: Our findings reveal that stem cell-mediated delivery of NEP provides marked and significant reductions in Aβ pathology and increases synaptic density in both 3xTg-AD and Thy1-APP transgenic mice. Remarkably, Aβ plaque loads are reduced not only in the hippocampus and subiculum adjacent to engrafted NSCs, but also within the amygdala and medial septum, areas that receive afferent projections from the engrafted region. CONCLUSIONS: Taken together, our data suggest that genetically-modified NSCs could provide a powerful combinatorial approach to not only enhance synaptic plasticity but to also target and modify underlying Alzheimer’s disease pathology
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