399 research outputs found
âI h 8 uâ: Findings from a five-year study of text and e-mail bullying
Copyright @ 2010 British Educational Research Association. The final version of this article is available at the link below.This study charts reports of nasty or threatening text and e-mail messages received by students in academic years 7 and 8 (11-13 years of age) attending 13 secondary schools in the North of England between 2002-2006. Annual surveys were undertaken on behalf of the local education authority (LEA) to monitor bullying. Results indicated that, over five years, the number of pupils receiving one or more nasty or threatening text messages or e-mails increased significantly, particularly among girls. However, receipt of frequent nasty or threatening text and e-mail messages remained relatively stable. For boys, being a victim of direct-physical bullying was associated with receiving nasty or threatening text and e-mail messages; for girls it was being unpopular among peers. Boys received more hate-related messages and girls were primarily the victims of name-calling, Findings are discussed with respect to theoretical and policy developments, and recommendations for future research are offered
A new young stellar cluster embedded in a molecular cloud in the far outer Galaxy
We report the discovery of a new young stellar cluster and molecular cloud
located in the far outer Galaxy, seen towards IRAS 06361-0142, and we
characterise their properties. Near-infrared images were obtained with
VLT/ISAAC through JHKs filters, millimetre line observations of CO(1-0) were
obtained with SEST, and VLA 6 cm continuum maps obtained from archive data. The
cloud and cluster are located at a distance of 7 kpc and a Galactocentric
distance of 15 kpc, well in the far outer Galaxy. Morphologically, IRAS
06361-0142 appears as a cluster of several tens of stars surrounded by a nearly
spherical nebular cavity centred at the position of the IRAS source. The
cluster appears composed of low and intermediate-mass, young reddened stars
with a large fraction having cleared the inner regions of their circumstellar
discs responsible for (H - Ks) colour excess. The observations are compatible
with a 4 Myr cluster with variable spatial extinction between Av = 6 and Av =
13.Comment: 6 pages, 6 figure
Optimal Signal Processing of Frequency-Stepped CW Radar Data
An optimal signal processing algorithm is derived for estimating the time delay and amplitude of each scatterer reflection using a frequency-stepped CW system. The channel is assumed to be composed of abrupt changes in the reflection coefficient profile. The optimization technique is intended to maximize the target range resolution achievable from any set of frequency-stepped CW radar measurements made in such an environment. The algorithm is composed of an iterative two-step procedure. First, the amplitudes of the echoes are optimized by solving an overdetermined least squares set of equations. Then, a nonlinear objective function is scanned in an organized fashion to find its global minimum. The result is a set of echo strengths and time delay estimates. Although this paper addresses the specific problem of resolving the time delay between the first two echoes, the derivation is general in the number of echoes. Performance of the optimization approach is illustrated using measured data obtained from an HP-X510 network analyzer. It is demonstrated that the optimization approach offers a significant resolution enhancement over the standard processing approach that employs an IFFT. Degradation in the performance of the algorithm due to suboptimal model order selection and the effects of additive white Gaussion noise are addressed
Extremely high velocity gas from the massive YSOs in IRAS 17233-3606
Molecular outflows from high-mass young stellar objects provide an excellent
way to study the star formation process, and investigate if they are scaled-up
versions of their low-mass counterparts. We selected the nearby massive star
forming region IRAS 17233-3606 in order to study the kinematics and physics
along the molecular outflow(s) originating from this source. We observed IRAS
17233-3606 in CO, a typical tracer of gas associated with molecular outflow,
with the Submillimeter Array in the (2-1) transition, and with the APEX
telescope in the higher excitation (6-5) line. Additional infrared H2
observations were performed with the UKIRT telescope. The CO data were analysed
using a LVG approach. Our data resolve the previously detected molecular
outflow in at least three different components, one of them with a high
collimation factor ~4, and characterised by emission at extremely high
velocities (|v-v_{LSR}|>120 km s^{-1}). The estimate of the kinematical outflow
parameters are typical of massive YSOs, and in agreement with the measured
bolometric luminosity of the source. The kinematic ages of the flows are in the
range 10^2-10^3 yr, and therefore point to young objects that still did not
reach the main sequence.Comment: accepted for publication in A&
Digging into NGC 6334I(N): Multiwavelength Imaging of a Massive Protostellar Cluster
We present a high-resolution, multi-wavelength study of the massive
protostellar cluster NGC 6334I(N) that combines new spectral line data from the
Submillimeter Array (SMA) and VLA with a reanalysis of archival VLA continuum
data, 2MASS and Spitzer images. As shown previously, the brightest 1.3 mm
source SMA1 contains substructure at subarcsecond resolution, and we report the
first detection of SMA1b at 3.6 cm along with a new spatial component at 7 mm
(SMA1d). We find SMA1 (aggregate of sources a, b, c, and d) and SMA4 to be
comprised of free-free and dust components, while SMA6 shows only dust
emission. Our 1.5" resolution 1.3 mm molecular line images reveal substantial
hot-core line emission toward SMA1 and to a lesser degree SMA2. We find CH3OH
rotation temperatures of 165\pm 9 K and 145\pm 12 K for SMA1 and SMA2,
respectively. We estimate a diameter of 1400 AU for the SMA1 hot core emission,
encompassing both SMA1b and SMA1d, and speculate that these sources comprise a
>800 AU separation binary that may explain the previously-suggested precession
of the outflow emanating from the SMA1 region. The LSR velocities of SMA1,
SMA2, and SMA4 all differ by 1-2 km/s. Outflow activity from SMA1, SMA2, SMA4,
and SMA6 is observed in several molecules including SiO(5--4) and IRAC 4.5
micron emission; 24 micron emission from SMA4 is also detected. Eleven water
maser groups are detected, eight of which coincide with SMA1, SMA2, SMA4, and
SMA6. We also detect a total of 83 Class I CH3OH 44GHz maser spots which likely
result from the combined activity of many outflows. Our observations paint the
portrait of multiple young hot cores in a protocluster prior to the stage where
its members become visible in the near-infrared.Comment: Accepted to ApJ, 24 pages, a full high resolution version is
available at http://www.cv.nrao.edu/~cbrogan/ms.long.pd
The Spitzer Survey of Interstellar Clouds in the Gould Belt. III. A Multi-Wavelength View of Corona Australis
We present Spitzer Space Telescope IRAC and MIPS observations of a 0.85 deg^2
field including the Corona Australis (CrA) star-forming region. At a distance
of 130 pc, CrA is one of the closest regions known to be actively forming
stars, particularly within its embedded association, the Coronet. Using the
Spitzer data, we identify 51 young stellar objects (YSOs) in CrA which include
sources in the well-studied Coronet cluster as well as distributed throughout
the molecular cloud. Twelve of the YSOs discussed are new candidates, one of
which is located in the Coronet. Known YSOs retrieved from the literature are
also added to the list, and a total of 116 candidate YSOs in CrA are compiled.
Based on these YSO candidates, the star formation rate is computed to be 12 M_o
Myr^-1, similar to that of the Lupus clouds. A clustering analysis was also
performed, finding that the main cluster core, consisting of 68 members, is
elongated (having an aspect ratio of 2.36), with a circular radius of 0.59 pc
and mean surface density of 150 pc^-2.
In addition, we analyze outflows and jets in CrA by means of new CO and H_2
data. We present 1.3 mm interferometric continuum observations made with the
Submillimeter Array (SMA) covering R CrA, IRS 5, IRS 7, and IRAS 18595-3712
(IRAS 32). We also present multi-epoch H_2 maps and detect jets and outflows,
study their proper motions, and identify exciting sources. The Spitzer and
ISAAC/VLT observations of IRAS 32 show a bipolar precessing jet, which drives a
CO (2-1) outflow detected in the SMA observations. There is also clear evidence
for a parsec-scale precessing outflow, E-W oriented, and originating in the SMA
2 region, likely driven by SMA 2 or IRS 7A.Comment: Accepted for publication in ApJS. 112 pages, 42 figures (quality
reduced), 13 tables. Full resolution version can be found at
http://www.cfa.harvard.edu/~dpeterson/CrA/CrA_highres.pd
Risk factors for youth violence: Youth violence commission, International Society For Research On Aggression (ISRA)
Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/144599/1/ab21766.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/144599/2/ab21766_am.pd
Multiwavelength Studies of Young OB Associations
We discuss how contemporary multiwavelength observations of young
OB-dominated clusters address long-standing astrophysical questions: Do
clusters form rapidly or slowly with an age spread? When do clusters expand and
disperse to constitute the field star population? Do rich clusters form by
amalgamation of smaller subclusters? What is the pattern and duration of
cluster formation in massive star forming regions (MSFRs)? Past observational
difficulties in obtaining good stellar censuses of MSFRs have been alleviated
in recent studies that combine X-ray and infrared surveys to obtain rich,
though still incomplete, censuses of young stars in MSFRs. We describe here one
of these efforts, the MYStIX project, that produced a catalog of 31,784
probable members of 20 MSFRs. We find that age spread within clusters are real
in the sense that the stars in the core formed after the cluster halo. Cluster
expansion is seen in the ensemble of (sub)clusters, and older dispersing
populations are found across MSFRs. Direct evidence for subcluster merging is
still unconvincing. Long-lived, asynchronous star formation is pervasive across
MSFRs.Comment: 22 pages, 9 figures. To appear in "The Origin of Stellar Clusters",
edited by Steven Stahler, Springer, 2017, in pres
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