2,455 research outputs found
Culturally Diverse and Underserved Populations of Gifted Students In the United States and in Taiwan: Equitable Access to Gifted Education
There is a continuing increase in the African American and Hispanic student populations in public schools. The students who are invited to gifted programs are overwhelmingly White. This is the situation in schools in the United States and also in Taiwan. Misunderstanding or unawareness of culture difference among educators might contribute to underrepresentation of minority students in gifted programs. The research literature reviewed indicates that a deficit in orientation, ineffective teacher referral policies, and the use of culturally biased assessments are the major reasons responsible for low rates of identification for gifted minority students. The purpose of this thesis is to explore more effective strategies to identify, or to increase awareness of gifted minority students and provide them equitable access to gifted education. The researcher interviewed six teachers of the gifted program to collect information in the United States and in Taiwan related to underrepresented minority students in gifted education programs. According to the results, the researcher generalized four key reasons of disparity in the gifted program: definition of giftedness, family factors, identification procedure and instruments, and curriculum and instruction
Observations and Analysis of High-Resolution Magnetic Field Structures in Molecular Clouds
Recent high-angular-resolution (up to 0.7") dust polarization observations
toward star forming regions are summarized. With the Sub-Millimeter Array, the
emission from the dense structures is traced and resolved. The detected
magnetic field morphologies vary from hourglass-like structures to isolated
patches depending on the evolutionary stage of the source. These observed
features have also served as a testbed to develop new analysis methods, with a
particular focus on quantifying the role of the magnetic field in the star
formation process.Comment: 4 pages, 2 figures; To appear in Proceedings of Magnetic Fields in
the Universe: From Laboratory and Stars to Primordial Structures Aug. 21st -
27th 2011, Zakopane, Poland Eds. M. Soida, K. Otmianowska-Mazur, E.M. de
Gouveia Dal Pino & A. Lazaria
Dust continuum and Polarization from Envelope to Cores in Star Formation: A Case Study in the W51 North region
We present the first high-angular resolution (up to 0.7", ~5000 AU)
polarization and thermal dust continuum images toward the massive star-forming
region W51 North. The observations were carried out with the Submillimeter
Array (SMA) in both the subcompact (SMA-SubC) and extended (SMA-Ext)
configurations at a wavelength of 870 micron. W51 North is resolved into four
cores (SMA1 to SMA4) in the 870 micron continuum image. The associated dust
polarization exhibits more complex structures than seen at lower angular
resolution. We analyze the inferred morphologies of the plane-of-sky magnetic
field (B_bot) in the SMA1 to SMA4 cores and in the envelope using the SMA-Ext
and SMA-SubC data. These results are compared with the B_bot archive images
obtained from the CSO and JCMT. A correlation between dust intensity gradient
position angles (phi_{nabla I}) and magnetic field position angles (phi_B) is
found in the CSO, JCMT and both SMA data sets. This correlation is further
analyzed quantitatively. A systematically tighter correlation between
phi_{nabla I} and phi_B is found in the cores, whereas the correlation
decreases in outside-core regions. Magnetic field-to-gravity force ratio
(Sigma_B) maps are derived using the newly developed polarization - intensity
gradient method by Koch, Tang & Ho 2012. We find that the force ratios tend to
be small (Sigma_B <= 0.5) in the cores in all 4 data sets. In regions outside
of the cores, the ratios increase or the field is even dominating gravity
(Sigma_B > 1). This possibly provides a physical explanation of the tightening
correlation between phi_{nabla I} and phi_B in the cores: the more the B field
lines are dragged and aligned by gravity, the tighter the correlation is.
Finally, we propose a schematic scenario for the magnetic field in W51 North to
interpret the four polarization observations at different physical scales.Comment: Accepted for publication in ApJ. 10 pages. 7 figure
UV-finite scalar field theory with unitarity
In this paper we show how to define the UV completion of a scalar field
theory such that it is both UV-finite and perturbatively unitary. In the UV
completed theory, the propagator is an infinite sum of ordinary propagators. To
eliminate the UV divergences, we choose the coefficients and masses in the
propagator to satisfy certain algebraic relations, and define the infinite sums
involved in Feynman diagram calculation by analytic continuation. Unitarity can
be proved relatively easily by Cutkosky's rules. The theory is equivalent to
infinitely many particles with specific masses and interactions. We take the
theory as an example and demonstrate our idea through explicit Feynman
diagram computation.Comment: 14 pages, references adde
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Microenvironmental contributions to hematopoietic stem cell aging.
Hematopoietic stem cell (HSC) aging was originally thought to be essentially an HSC-autonomous process, which is the focus of another review in the same issue of Haematologica However, studies on the microenvironment that maintains and regulates HSC (HSC niche) over the past 20 years have suggested that microenvironmental aging contributes to declined HSC function over time. The HSC niches comprise a complex and dynamic molecular network of interactions across multiple cell types, including endothelial cells, mesenchymal stromal cells, osteoblasts, adipocytes, neuroglial cells and mature hematopoietic cells. Upon aging, functional changes in the HSC niches, such as microenvironmental senescence, imbalanced bone marrow mesenchymal stromal cell differentiation, vascular remodeling, changes in adrenergic signaling and inflammation, coordinately and dynamically influence the fate of HSC and their downstream progeny. The end result is lymphoid deficiency and myeloid skewing. During this process, aged HSC and their derivatives remodel the niche to favor myeloid expansion. Therefore, the crosstalk between HSC and the microenvironment is indispensable for the aging of the hematopoietic system and might represent a therapeutic target in age-related pathological disorders
The circumstellar disk of AB Aurigae: evidence for envelope accretion at late stages of star formation?
The circumstellar disk of AB Aurigae has garnered strong attention owing to
the apparent existence of spirals at a relatively young stage and also the
asymmetric disk traced in thermal dust emission. However, the physical
conditions of the spirals are still not well understood. The origin of the
asymmetric thermal emission is unclear.
We observed the disk at 230 GHz (1.3 mm) in both the continuum and the
spectral line ^12CO J=2-1 with IRAM 30-m, the Plateau de Bure interferometer,
and the Submillimeter Array to sample all spatial scales from 0.37" to about
50". To combine the data obtained from these telescopes, several methods and
calibration issues were checked and discussed.
The 1.3 mm continuum (dust) emission is resolved into inner disk and outer
ring. Molecular gas at high velocities traced by the CO line is detected next
to the stellar location. The inclination angle of the disk is found to decrease
toward the center. On a larger scale, based on the intensity weighted
dispersion and the integrated intensity map of ^12CO J=2-1, four spirals are
identified, where two of them are also detected in the near infrared. The total
gas mass of the 4 spirals (M_spiral) is 10^-7 < M_spiral < 10^-5 M_sun, which
is 3 orders of magnitude smaller than the mass of the gas ring. Surprisingly,
the CO gas inside the spiral is apparently counter-rotating with respect to the
CO disk, and it only exhibits small radial motion.
The wide gap, the warped disk, and the asymmetric dust ring suggest that
there is an undetected companion with a mass of 0.03 M_sun at a radius of 45
AU. Although an hypothetical fly-by cannot be ruled out, the most likely
explanation of the AB Aurigae system may be inhomogeneous accretion well above
or below the main disk plane from the remnant envelope, which can explain both
the rotation and large-scale motions detected with the 30-m image.Comment: 17 pages, 13 figures, accepted for publication in A&A journal. Typos
are correcte
Flemingia macrophylla Extract Ameliorates Experimental Osteoporosis in Ovariectomized Rats
Flemingia macrophylla (Leguminosae), a native plant of Taiwan, is used as folk medicine. An in vitro study showed that a 75% ethanolic extract of F. macrophylla (FME) inhibited osteoclast differentiation of cultured rat bone marrow cells, and the active component, lespedezaflavanone A (LDF-A), was isolated. It was found that oral administration of FME for 13 weeks suppressed bone loss in ovariectomized rats, an experimental model of osteoporosis. In addition, FME decreased urinary deoxypyridinoline concentrations but did not inhibit serum alkaline phosphatase activities, indicating that it ameliorated bone loss via inhibition of bone resorption. These results suggest that FME may represent a useful remedy for the treatment of bone resorption diseases, such as osteoporosis. In addition, LDF-A could be used as a marker compound to control the quality of FME
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