2,764 research outputs found
The Intrinsic Shapes of Molecular Cloud Fragments over a Range of Length Scales
We decipher intrinsic three-dimensional shape distributions of molecular
clouds, cloud cores, Bok globules, and condensations using recently compiled
catalogues of observed axis ratios for these objects mapped in carbon monoxide,
ammonia, through optical selection, or in continuum dust emission. We apply
statistical techniques to compare assumed intrinsic axis ratio distributions
with observed projected axis ratio distributions. Intrinsically triaxial shapes
produce projected distributions which agree with observations. Molecular clouds
mapped in CO are intrinsically triaxial but more nearly prolate than
oblate, while the smaller cloud cores, Bok globules, and condensations are also
intrinsically triaxial but more nearly oblate than prolate.Comment: 12 pages, 11 figures. Version with color figures can be found at
http://www.astro.uwo.ca/~cjones/ or http://www.astro.uwo.ca/~basu/. To appear
in ApJ, 10 April 2002, v. 569, no.
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The Spitzer c2d Survey Of Nearby Dense Cores. X. Star Formation In L673 And Cb188
L673 and CB188 are two low-mass clouds isolated from large star-forming regions that were observed as part of the Spitzer Legacy Project "From Molecular Clouds to Planet Forming disks" (c2d). We identified and characterized all the young stellar objects (YSOs) of these two regions and modeled their spectral energy distributions (SEDs) to examine whether their physical properties are consistent with values predicted from the theoretical models and with the YSO properties in the c2d survey of larger clouds. Overall, 30 YSO candidates were identified by the c2d photometric criteria, 27 in L673 and 3 in CB188. We confirm the YSO nature of 29 of them and remove a false Class III candidate in L673. We further present the discovery of two new YSO candidates, one Class 0 and another possible Class I candidate in L673, therefore bringing the total number of YSO candidates to 31. Multiple sites of star formation are present within L673, closely resembling other well-studied c2d clouds containing small groups such as B59 and L1251B, whereas CB188 seems to consist of only one isolated globule-like core. We measure a star formation efficiency (SFE) of 4.6%, which resembles the SFE of the larger c2d clouds. From the SED modeling of our YSO sample we obtain envelope masses for Class I and Flat spectrum sources of 0.01-1.0 M-circle dot. The majority of Class II YSOs show disk accretion rates from 3.3 x 10(-10) to 3 x 10(-8) M-circle dot yr(-1) and disk masses that peak at 10(-4) to 10(-3) M-circle dot. Finally, we examined the possibility of thermal fragmentation in L673 as the main star-forming process. We find that the mean density of the regions where significant YSO clustering occurs is of the order of similar to 10(5) cm(-3) using 850 mu m observations and measure a Jeans Length that is greater than the near-neighbor YSO separations by approximately a factor of 3-4. We therefore suggest that other processes, such as turbulence and shock waves, may have had a significant effect on the cloud's filamentary structure and YSO clustering.University of SouthamptonNASA 1279198, 1288806, 1365763Jet Propulsion Laboratory, California Institute of TechnologyAstronom
Systematic review and meta-analysis of therapeutic alliance, engagement and outcome in psychological therapies for psychosis
Aim:
The moderate association between therapeutic alliance (TA) and psychological therapy outcome is well established. Historically, the field has not focused on people with a severe mental illness. This is the first review to conduct a meta-analysis of associations between TA and therapeutic engagement as well as outcome in psychological therapy for psychosis. /
Eligibility criteria:
Eligible studies conducted a quantitative investigation of the relationship between TA during a psychological therapy and outcome at a subsequent time-point. /
Method:
A systematic review examined the relationship between TA and engagement as well as outcome measures within psychological therapy for psychosis. Correlational meta-analyses using an aggregate random effects model were conducted. /
Results:
Twenty-four studies were eligible for inclusion (n = 1,656) of which 13 were included in the meta-analyses. Client- and therapist-rated TA were associated with engagement in therapy (rclient (c) = 0.36, p = .003; rtherapist (t) = 0.40, p = .0053). TA was also associated with reduction in global (rc = 0.29, p = .0005; rt = 0.24, p = .0015) and psychotic symptoms (rc = 0.17, p = .0115; rt = 0.30, p = .0003). The systematic review identified no evidence or limited evidence for a relationship between TA during therapy and depression, substance use, physical health behaviours, global as well as social functioning, overall mental health recovery, and self-esteem at follow-up. Although number of studies was small, TA was related to a reduced risk of subsequent hospitalization in 40% of analyses (across two studies) and improved cognitive outcome in 50% of analyses (across three studies). /
Conclusions:
The observed TA-therapy engagement and TA-outcome associations were broadly consistent with those identified across non-psychotic diagnostic groups. Well-powered studies are needed to investigate the relationship between TA and process as well as outcome in psychological therapy for psychosis specifically. /
Practitioner points:
This is the first review to conduct a meta-analytic synthesis of the association between therapeutic alliance (TA) and both engagement and change in outcome in psychological therapies for psychosis.
TA (as rated by therapist and client) was associated with the extent of therapeutic engagement as well as reduction in global mental health symptoms and psychotic symptoms.
The significant associations between TA and engagement as well as change in outcome identified in the current review are broadly consistent with those observed across non-psychotic diagnostic groups.
We consider factors that could impact upon the dynamic and potentially interdependent relationships between TA and therapeutic techniques, including attachment security and severity of paranoid ideation
The relationship of certain word analysis abilities to the reading achievement of first, second, and third grade children,
Thesis (M.A.)--Boston Universit
Dynamical structure of the inner 100 AU of the deeply embedded protostar IRAS 16293-2422
A fundamental question about the early evolution of low-mass protostars is
when circumstellar disks may form. High angular resolution observations of
molecular transitions in the (sub)millimeter wavelength windows make it
possible to investigate the kinematics of the gas around newly-formed stars,
for example to identify the presence of rotation and infall. IRAS 16293-2422
was observed with the extended Submillimeter Array (eSMA) resulting in
subarcsecond resolution (0.46" x 0.29", i.e. 55 35~AU) images
of compact emission from the CO (3-2) and CS (7-6) transitions at
337~GHz (0.89~mm). To recover the more extended emission we have combined the
eSMA data with SMA observations of the same molecules. The emission of
CO (3-2) and CS (7-6) both show a velocity gradient oriented
along a northeast-southwest direction with respect to the continuum marking the
location of one of the components of the binary, IRAS16293A. Our combined eSMA
and SMA observations show that the velocity field on the 50--400~AU scales is
consistent with a rotating structure. It cannot be explained by simple
Keplerian rotation around a single point mass but rather needs to take into
account the enclosed envelope mass at the radii where the observed lines are
excited. We suggest that IRAS 16293-2422 could be among the best candidates to
observe a pseudo-disk with future high angular resolution observations.Comment: Accepted for publication in ApJ, 18 pages, 10 figure
Cohort Study Examining the Association of Optimal Blood Pressure Control at Entry With Infrarenal Abdominal Aortic Aneurysm Growth
Background and Aim: The benefit of controlling cardiovascular risk factors in slowing the progression of small abdominal aortic aneurysm (AAA) is controversial. This study investigated the association of optimal blood pressure control at entry with the growth of small AAA.
Methods and Results: A total of 1,293 patients with initial AAA diameter <50 mm were followed by a median 5 (inter-quartile range, IQR, 3–7) ultrasound scans for a median of 3.6 years (IQR 1.8, 5.3). Optimal blood pressure control was defined as blood pressure ≤140/90 mmHg at recruitment. The association of optimal blood pressure control at entry with AAA growth was assessed using linear mixed effects models adjusted for established risk factors of AAA growth and factors which were unequally distributed among the blood pressure groups. Optimal blood pressure control at entry was not significantly associated with AAA growth. In the risk factor adjusted model the mean difference in AAA growth between blood pressure groups was 0.04 mm/year (95% CI −0.20, 0.13; p = 0.65). The results were similar in sensitivity analyses excluding outliers or focused on systolic or diastolic blood pressure alone.
Conclusions: This observational study suggests that optimal blood pressure control at entry is not associated with slower AAA growth
A First Look at the Auriga-California Giant Molecular Cloud With Herschel and the CSO: Census of the Young Stellar Objects and the Dense Gas
We have mapped the Auriga/California molecular cloud with the Herschel PACS
and SPIRE cameras and the Bolocam 1.1 mm camera on the Caltech Submillimeter
Observatory (CSO) with the eventual goal of quantifying the star formation and
cloud structure in this Giant Molecular Cloud (GMC) that is comparable in size
and mass to the Orion GMC, but which appears to be forming far fewer stars. We
have tabulated 60 compact 70/160um sources that are likely pre-main-sequence
objects and correlated those with Spitzer and WISE mid-IR sources. At 1.1 mm we
find 18 cold, compact sources and discuss their properties. The most important
result from this part of our study is that we find a modest number of
additional compact young objects beyond those identified at shorter wavelengths
with Spitzer. We also describe the dust column density and temperature
structure derived from our photometric maps. The column density peaks at a few
x 10^22 cm^-2 (N_H2) and is distributed in a clear filamentary structure along
which nearly all the pre-main-sequence objects are found. We compare the YSO
surface density to the gas column density and find a strong non-linear
correlation between them. The dust temperature in the densest parts of the
filaments drops to ~10K from values ~ 14--15K in the low density parts of the
cloud. We also derive the cumulative mass fraction and probability density
function of material in the cloud which we compare with similar data on other
star-forming clouds.Comment: in press Astrophysical Journal, 201
Molecular Line Observations of the Small Protostellar Group L1251B
We present molecular line observations of L1251B, a small group of pre- and
protostellar objects, and its immediate environment in the dense C18O core
L1251E. These data are complementary to near-infrared, submillimeter and
millimeter continuum observations reported by Lee et al. (2006, ApJ, 648, 491;
Paper I). The single-dish data of L1251B described here show very complex
kinematics including infall, rotation and outflow motions, and the
interferometer data reveal these in greater detail. Interferometer data of N2H+
1-0 suggest a very rapidly rotating flattened envelope between two young
stellar objects, IRS1 and IRS2. Also, interferometer data of CO 2-1 resolve the
outflow associated with L1251B seen in single-dish maps into a few narrow and
compact components. Furthermore, the high resolution data support recent
theoretical studies of molecular depletions and enhancements that accompany the
formation of protostars within dense cores. Beyond L1251B, single-dish data are
also presented of a dense core located ~150" to the east that, in Paper I, was
detected at 850 micron but has no associated point sources at near- and
mid-infrared wavelengths. The relative brightness between molecules, which have
different chemical timescales, suggests it is less chemically evolved than
L1251B. This core may be a site for future star formation, however, since line
profiles of HCO+, CS, and HCN show asymmetry with a stronger blue peak, which
is interpreted as an infall signature.Comment: 46 pages, 18 figures. Accepted for publication in Ap
Protostellar accretion traced with chemistry. High resolution C18O and continuum observations towards deeply embedded protostars in Perseus
Context: Understanding how accretion proceeds is a key question of star
formation, with important implications for both the physical and chemical
evolution of young stellar objects. In particular, very little is known about
the accretion variability in the earliest stages of star formation.
Aims: To characterise protostellar accretion histories towards individual
sources by utilising sublimation and freeze-out chemistry of CO.
Methods: A sample of 24 embedded protostars are observed with the
Submillimeter Array (SMA) in context of the large program "Mass Assembly of
Stellar Systems and their Evolution with the SMA" (MASSES). The size of the
CO emitting region, where CO has sublimated into the gas-phase, is
measured towards each source and compared to the expected size of the region
given the current luminosity. The SMA observations also include 1.3 mm
continuum data, which are used to investigate whether a link can be established
between accretion bursts and massive circumstellar disks.
Results: Depending on the adopted sublimation temperature of the CO ice,
between 20% and 50% of the sources in the sample show extended CO
emission indicating that the gas was warm enough in the past that CO sublimated
and is currently in the process of refreezing; something which we attribute to
a recent accretion burst. Given the fraction of sources with extended CO
emission, we estimate an average interval between bursts of 20000-50000 yr,
which is consistent with previous estimates. No clear link can be established
between the presence of circumstellar disks and accretion bursts, however the
three closest known binaries in the sample (projected separations <20 AU) all
show evidence of a past accretion burst, indicating that close binary
interactions may also play a role in inducing accretion variability.Comment: Accepted for publication in A&A, 21 pages, 13 figure
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