545 research outputs found
Learning to Draw Recognizable Graphic Representations During Mother-Child Interactions
The present study investigated the role of mother-child collaborative drawing in childrenâs creations of recognizable representations. Thirty-two 4- and 5-yearolds played a cooperative game with their mothers in which they were instructed to take turns drawing pictures of farm animals for the other to guess. Mothers and children often talked about their drawings, and many aspects (e.g., discussing features essential for identifying referents) of these conversations were related to microgenetic changes (over the course of the game) in the sophistication of childrenâs pictures. Children also appropriated features from their mothersâ drawings into their own drawings over the course of the game. This was particularly the case for ârudimentaryâ drawers. Results demonstrate that young children learn to create graphic representations through utilizing information from their mothersâ drawings and from conversations with their mothers about drawings, although the extent of childrenâs learning is related also in part to their level of drawing performance
Chapter 3 Cultivation Theory: Gerbner, Fear, Crime, and Cops
The Routledge Companion to Media and Race serves as a comprehensive guide for scholars, students, and media professionals who seek to understand the key debates about the impact of media messages on racial attitudes and understanding. Broad in scope and richly presented from a diversity of perspectives, the book is divided into three sections: first, it summarizes the theoretical approaches that scholars have adopted to analyze the complexities of media messages about race and ethnicity, from the notion of "representation" to more recent concepts like Critical Race Theory. Second, the book reviews studies related to a variety of media, including film, television, print media, social media, music, and video games. Finally, contributors present a broad summary of media issues related to specific races and ethnicities and describe the relationship of the study of race to the study of gender and sexuality
The light curve of the companion to PSR B1957+20
We present a new analysis of the light curve for the secondary star in the
eclipsing binary millisecond pulsar system PSR B1957+20. Combining previous
data and new data points at minimum from the Hubble Space Telescope, we have
100% coverage in the R-band. We also have a number of new K_s-band data points,
which we use to constrain the infrared magnitude of the system. We model this
with the Eclipsing Light Curve code (ELC). From the modelling with the ELC code
we obtain colour information about the secondary at minimum light in BVRI and
K. For our best fit model we are able to constrain the system inclination to 65
+/- 2 degrees for pulsar masses ranging from 1.3 -- 1.9 M_sun. The pulsar mass
is unconstrained. We also find that the secondary star is not filling its Roche
lobe. The temperature of the un-irradiated side of the companion is in
agreement with previous estimates and we find that the observed temperature
gradient across the secondary star is physically sustainable.Comment: 6 pages, 4 figures & 3tables. Accepted for publication in MNRA
A Sequence of Declining Outbursts from GX339-4
The flux and spectrum of the black hole candidate GX339-4 has been monitored
by the Burst and Transient Source Experiment (BATSE) on the Compton Gamma-ray
Observatory (CGRO) since the observatory became operational in May 1991.
Between the summer of 1991 and the fall of 1996, eight outbursts from GX339-4
were observed. The history of these outbursts is one of declining fluence or
total energy release, as well as a shortening of the time between outbursts. A
rough linear correlation exists between the fluence emitted during an outburst
and the time elapsed between the end of the previous outburst and the beginning
of the current one. The peak flux is also roughly linearly correlated with
outburst fluence. The lightcurves of the earlier, more intense, outbursts
(except for the second one) can be modeled by a fast exponential (time constant
~ 10 days) followed by a slower exponential (~ 100 days) on the rise and a fast
exponential decay (~ 5 days) on the fall. The later, weaker, outbursts are
modeled with a single rising time constant (~ 20 days) and a longer decay on
the fall (~ 50 days). An exponential model gives a marginally better fit than a
power law to the rise/decay profiles. GX339-4 is a unique source in having more
frequent outbursts than other low mass x-ray binary black hole candidates.
These observations can be used to constrain models of the behavior of the
accretion disk surrounding the compact object.Comment: Accepted for Publication in the Astrophysical Journal Letters, AASTE
X-ray Spectroscopy of Candidate Ultracompact X-ray Binaries
We present high-resolution spectroscopy of the neutron star/low-mass X-ray
binaries (LMXBs) 4U 1850-087 and 4U 0513-40 as part of our continuing study of
known and candidate ultracompact binaries. The LMXB 4U 1850-087 is one of four
systems in which we had previously inferred an unusual Ne/O ratio in the
absorption along the line of sight, most likely from material local to the
binaries. However, our recent Chandra X-ray Observatory LETGS spectrum of 4U
1850-087 finds a Ne/O ratio by number of 0.22+/-0.05, smaller than previously
measured and consistent with the expected interstellar value. We propose that
variations in the Ne/O ratio due to source variability, as previously observed
in these sources, can explain the difference between the low- and
high-resolution spectral results for 4U 1850-087. Our XMM-Newton RGS
observation of 4U 0513-40 also shows no unusual abundance ratios in the
absorption along the line of sight. We also present spectral results from a
third candidate ultracompact binary, 4U 1822-000, whose spectrum is well fit by
an absorbed power-law + blackbody model with absorption consistent with the
expected interstellar value. Finally, we present the non-detection of a fourth
candidate ultracompact binary, 4U 1905+000, with an upper limit on the source
luminosity of < 1 x 10^{32} erg s^{-1}. Using archival data, we show that the
source has entered an extended quiescent state.Comment: 8 pages, 3 figures, accepted for publication to the Astrophysical
Journa
Tomography of X-ray Nova Muscae 1991: Evidence for ongoing mass transfer and stream-disc overflow
We present a spectroscopic analysis of the black hole binary Nova Muscae 1991
in quiescence using data obtained in 2009 with MagE on the Magellan Clay
telescope and in 2010 with IMACS on the Magellan Baade telescope at the Las
Campanas Observatory. Emission from the disc is observed in H alpha, H beta and
Ca II (8662 A). A prominent hotspot is observed in the Doppler maps of all
three emission lines. The existence of this spot establishes ongoing mass
transfer from the donor star in 2009-2010 and, given its absence in the
1993-1995 observations, demonstrates the presence of a variable hotspot in the
system. We find the radial distance to the hotspot from the black hole to be
consistent with the circularization radius. Our tomograms are suggestive of
stream-disc overflow in the system. We also detect possible Ca II (8662 A)
absorption from the donor star.Comment: 10 pages, 11 figures, 1 table. Accepted for publication in MNRA
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