1,209 research outputs found
A summary of research relating to first grade reading, 1932-1963
Thesis (Ed.M.)--Boston UniversityProblem: An attempt to compare the rate of learning of colorful and abstract words of children in grade one.
Materials:
1. Thirty words were selected to be used in three groups of ten words each. Each list consisted of five colorful and five abstract words. Colorful words are those which have much meaning for children and abstract words are those with little meaning. The words were printed on 3 x 11 inch flash cards in lower case letters.
2. Check sheets were made with spaces for checking the retention of words at three different times and pictures were made to enrich the colorful words.
3. Directions were prepared and given to each teacher who participated in the study.
4. Kuhlmann-Anderson Intelligence Test: Battery A.
5. Detroit Word Recognition Test: Form A [TRUNCATED
Mixed-Morphology Supernova Remnants in X-rays: Isothermal Plasma in HB21 and Probable Oxygen-Rich Ejecta in CTB 1
(Abridged) We present an analysis of X-ray observations made of the Galactic
supernova remnants (SNRs) HB21 (G89.0+4.7) and CTB 1 (G116.9+0.2), two
well-known mixed-morphology (MM) SNRs. We find a marked contrast between the
X-ray properties of these SNRs: for HB21, the extracted ASCA spectra of the
northwest and southeast regions of the X-ray emitting plasma can be fit with a
single thermal model with marginally enhanced silicon and sulfur abundances.
For both of these regions, the derived column density and temperature are
N_H~0.3x10^22 cm^-2 and kT~0.7 keV, respectively. No significant spatial
differences in temperature or elemental abundances between the two regions are
detected and the X-ray-emitting plasma in both regions is close to ionization
equilibrium. Our Chandra spectral analysis of CTB 1 reveals that this source is
likely an oxygen-rich SNR with enhanced abundances of oxygen and neon. The
extracted ASCA spectra for the southwestern and northeastern regions of CTB 1
cannot be fit with a single thermal component. Based on our fits to these
spectra, we derive a column density N_H~0.6x10^22 cm^-2 and a temperature for
the soft thermal component of kT_soft~0.28 keV. The hard emission from the
southwest may be modeled with either a thermal component (kT_hard~3 keV) or by
a power law component (Gamma~2-3) while the hard emission from the northeast
may be modeled with a power law component (Gamma~1.4). We have also extracted
ASCA GIS spectra of the discrete X-ray source 1WGA J0001.4+6229 which is seen
in projection toward CTB 1. These spectra are best fit using a power-law model
with a photon index Gamma=2.2^{+0.5}_{-1.2} which is typical for featureless
power-law continua produced by rotation-powered pulsars. This source may be a
neutron star associated with CTB 1.Comment: 46 pages, 16 figures, accepted for publication in the Astronomical
Journa
Quark nova imprint in the extreme supernova explosion SN 2006gy
The extremely luminous supernova 2006gy (SN 2006gy) is among the most
energetic ever observed. The peak brightness was 100 times that of a typical
supernova and it spent an unheard of 250 days at magnitude -19 or brighter.
Efforts to describe SN 2006gy have pushed the boundaries of current supernova
theory. In this work we aspire to simultaneously reproduce the photometric and
spectroscopic observations of SN 2006gy using a quark nova model. This analysis
considers the supernova explosion of a massive star followed days later by the
quark nova detonation of a neutron star. We lay out a detailed model of the
interaction between the supernova envelope and the quark nova ejecta paying
special attention to a mixing region which forms at the inner edge of the
supernova envelope. This model is then fit to photometric and spectroscopic
observations of SN 2006gy. This QN model naturally describes several features
of SN 2006gy including the late stage light curve plateau, the broad H{\alpha}
line and the peculiar blue H{\alpha} absorption. We find that a progenitor mass
between 20Msun and 40Msun provides ample energy to power SN 2006gy in the
context of a QN.Comment: 15 pages, 9 figure
The self-directed learning of adult music students: a comparison of teacher approaches and student needs
Adult music learners may expect to be more independent and therefore more inclined to engage in self-directed learning than younger learners; however, adults may not feel encouraged or supported to self-direct. In this qualitative study, the relationships between six adult instrumentalists and their teachers were examined using Grow’s Staged Self-Directed Learning (SSDL) Model to determine if there was congruence or a mismatch between individual student learning needs and their teachers’ strategies. Teachers reported a willingness to accommodate the self-direction needs of their students. Even in cases of teacher–student mismatch, more direction from the teacher was welcomed when they encountered technical difficulty or an unfamiliar style. Students who reported that they had little experience playing were more inclined to have low to moderate levels of self-direction, whereas more advanced players reported intermediate to high levels of self-direction. Cultural expectations were found to play an important role in determining if students desire to be self-directed learners. The quality of the teacher–student relationship and communication were both found to be an important determinant of successful collaboration. These findings suggest that the theoretical application of the SSDL model could provide teachers a means to assess and discern their adult students’ learning needs.Accepted manuscrip
Large Kinetic Power in FRII Radio Jets
We investigate the total kinetic powers (L_{j}) and ages (t_{age}) of
powerful jets of four FR II radio sources (Cygnus A, 3C 223, 3C 284, and 3C
219) by the detail comparison of the dynamical model of expanding cocoons with
observed ones. It is found that these sources have quite large kinetic powers
with the ratio of L_{j} to the Eddington luminosity (L_{Edd}) resides in . Reflecting the large kinetic powers, we also find that the
total energy stored in the cocoon (E_{c}) exceed the energy derived from the
minimum energy condition (E_{min}): . This implies that
a large amount of kinetic power is carried by invisible components such as
thermal leptons (electron and positron) and/or protons.Comment: 5 pages, accepted for publication in Astrophysics and Space Scienc
RXTE monitoring observations of Markarian 3
We present Rossi X-ray Timing Explorer, monitoring observations of the
Seyfert 2 galaxy Markarian 3 spanning a 200 day period during which time the
source flux varied by a factor in the 4-20 keV bandpass. In broad
agreement with earlier Ginga results, the average spectrum can be represented
in terms of a simple spectral model consisting of a very hard power-law
continuum () modified below keV by a high
absorbing column ( \cunits) together with a high
equivalent width Fe-K emission feature at 6.4 keV. The abnormally flat spectral
index is probably the signature of a strong reflection component and we
consider two models incorporating such emission. In the first the reflected
signal suffers the same absorption as the intrinsic continuum, whereas in the
second the reflection is treated as an unabsorbed spectral component. In the
former case, we require a very strong reflection signal () in order to
match the data; in addition variability of both the intrinsic power-law and the
reflection component is required. The unabsorbed reflection model requires a
somewhat higher line-of-sight column density to the nuclear source ( \cunits), but in this case the reflected signal remains constant
whilst the level of the intrinsic continuum varies. The latter description is
consistent with the reflection originating from the illuminated far inner wall
of a molecular torus, the nearside of which screens our direct view of the
central continuum source.Comment: 7 pages, submitted to the MNRA
Chandra observation of the TeV source HESS J1834-087
Chandra ACIS observed the field of the extended TeV source HESS J1834-087 for
47 ks. A previous XMM-Newton EPIC observation of the same field revealed a
point-like source (XMMU J183435.3-084443) and an offset region of faint
extended emission. In the low-resolution, binned EPIC images the two appear to
be connected. However, the high-resolution Chandra ACIS images do not support
the alleged connection. Instead, in these images XMMU J183435.3-084443 is
resolved into a point source, CXOU~J183434.9--084443 (L=2.5 x 10e33 ergs/s, for
a distance of 4 kpc; photon index 1.1), and a compact (~20'') nebula with an
isotropic morphology and a softer spectrum (L=4.2 x10e33 ergs/s, photon index
2.7). The nature of the nebula is uncertain. We discuss a dust scattering halo
and a pulsar-wind nebula as possible interpretations. Based on our analysis of
the X-ray data, we re-evaluate the previously suggested interpretations of HESS
J1834-087 and discuss a possible connection to the Fermi LAT source 1FGL
J1834.3-0842c. We also obtained an upper limit of 3 x 10e-14 ergs/s cm^2 on the
unabsorbed flux of the SGR J1833--0832 (in quiescence), which happened to be in
the ACIS field of view.Comment: 11 pages, 7 figures, submitted to Ap
Variability in the orbital profiles of the X-ray emission of the gamma-ray binary LS I +61 303
We report on the analysis of Rossi X-ray Timing Explorer (RXTE) Proportional
Counter Array (PCA) monitoring observations of the -ray binary system
LS I +61 303, covering 35 full cycles of its orbital motion. This constitutes
the largest continuous X-ray monitoring dataset analyzed to date for this
source. Such an extended analysis allows us to report: a) the discovery of
variability in the orbital profiles of the X- ray emission, b) the existence of
a few (recent) short flares on top of the overall behavior typical of the
source, which, given the PCA field-of-view, may or may not be associated with
LS I +61 303, and c) the determination of the orbital periodicity using soft
X-ray data alone.Comment: The Astrophysical Journal Letters (2010), in pres
Infrared Studies of Molecular Shocks in the Supernova Remnant HB21: I. Thermal Admixture of Shocked H_2 Gas in the North
We present near- and mid-infrared observations on the shock-cloud interaction
region in the northern part of the supernova remnant HB21, performed with the
InfraRed Camera (IRC) aboard AKARI satellite and the Wide InfraRed Camera
(WIRC) at the Palomar 5 m telescope. The IRC 7 um (S7), 11 um (S11), and 15 um
(L15) band images and the WIRC H2 v = 1 -> 0 S(1) 2.12 um image show similar
shock-cloud interaction features. We chose three representative regions, and
analyzed their IRC emissions through comparison with H2 line emissions of
several shock models. The IRC colors are well explained by the thermal
admixture model of H2 gas--whose infinitesimal H2 column density has a
power-law relation with the temperature T, dN ~ T^-b dT--with n(H2) ~ 10^3
cm^-3, b ~ 3, and N(H2 ;T > 100K) ~ 3x10^20 cm^-2. The derived b value may be
understood by a bow shock picture, whose shape is cycloidal (cuspy) rather than
paraboloidal. However, this picture raises another issue that the bow shocks
must reside within ~0.01 pc size-scale, smaller than the theoretically
expected. Instead, we conjectured a shocked clumpy interstellar medium picture,
which may avoid the sizescale issue while explaining the similar model
parameters. The observed H2 v = 1 -> 0 S(1) intensities are a factor of ~17 -
33 greater than the prediction from the power-law admixture model. This excess
may be attributed to either an extra component of hot H2 gas or to the effects
of collisions with hydrogen atoms, omitted in our power-law admixture model,
both of which would increase the population in the v = 1 level of H2.Comment: 14 pages, 9 figures, ApJ accepted, higher resolution @
http://astro.snu.ac.kr/~jhshinn/ms.pd
INTEGRAL long-term monitoring of the Supergiant Fast X-ray Transient XTE J1739-302
In the past few years, a new class of High Mass X-Ray Binaries (HMXRB) has
been claimed to exist, the Supergiant Fast X-ray Transients (SFXT). These are
X-ray binary systems with a compact companion orbiting a supergiant star which
show very short and bright outbursts in a series of activity periods
overimposed on longer quiescent periods. Only very recently the first attempts
to model the behaviour of these sources have been published, some of them
within the framework of accretion from clumpy stellar winds.Our goal is to
analyze the properties of XTE J1739-302/IGR J17391-3021 within the context of
the clumpy structure of the supergiant wind. We have used INTEGRAL and RXTE/PCA
observations in order to obtain broad band (1-200 keV) spectra and light curves
of XTE J1739-302 and investigate its X-ray spectrum and temporal variability.
We have found that XTE J1739-302 follows a much more complex behaviour than
expected. Far from presenting a regular variability pattern, XTE J1739-302
shows periods of high, intermediate, and low flaring activity.Comment: 9 pages, 7 figures, accepted for publication in A&
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