193 research outputs found
The Stellar and Gaseous Contents of the Orion Dwarf Galaxy
We present new KPNO 0.9-m optical and VLA HI spectral line observations of
the Orion dwarf galaxy. This nearby (D ~ 5.4 Mpc), intermediate-mass (M_dyn =
1.1x10^10 Solar masses) dwarf displays a wealth of structure in its neutral
ISM, including three prominent "hole/depression" features in the inner HI disk.
We explore the rich gas kinematics, where solid-body rotation dominates and the
rotation curve is flat out to the observed edge of the HI disk (~6.8 kpc). The
Orion dwarf contains a substantial fraction of dark matter throughout its disk:
comparing the 4.7x10^8 Solar masses of detected neutral gas with estimates of
the stellar mass from optical and near-infrared imaging (3.7x10^8 Solar masses)
implies a mass-to-light ratio of ~13. New H alpha observations show only
modest-strength current star formation (~0.04 Solar masses per year); this star
formation rate is consistent with our 1.4 GHz radio continuum non-detection.Comment: Astronomical Journal, in press. Full-resolution version available
from http://www.macalester.edu/~jcannon/pubs.htm
A Psychometric Analysis of the Revised Child Anxiety and Depression ScaleâParent Version in a Clinical Sample
The Revised Child Anxiety and Depression ScaleâParent Version (RCADS-P) is a 47-item parent-report questionnaire of youth anxiety and depression, with scales corresponding to the DSM-IV categories of Separation Anxiety Disorder, Social Phobia, Generalized Anxiety Disorder (GAD), Panic Disorder, Obsessive-Compulsive Disorder, and Major Depressive Disorder (MDD). The RCADS-P is currently the only parent-report questionnaire that concurrently assesses youth symptomatology of individual anxiety disorders as well as depression in accordance with DSM-IV nosology. The present study examined the psychometric properties of the RCADS-P in a large (Nâ=â490), clinic-referred sample of youths. The RCADS-P demonstrated favorable psychometric properties, including high internal consistency, convergent/divergent validity, as well as strong discriminant validityâevidencing an ability to discriminate between anxiety and depressive disorders, as well as between the targeted anxiety disorders. Support for the DSM-related six-factor RCADS-P structure was also evidenced. This structure demonstrated superior fit to a recently suggested alternative to the DSM-IV classification of anxiety and affective disordersânamely, the MDD/GAD âdistressâ factor
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The organizational social context of mental health services and clinician attitudes toward evidence-based practice: a United States national study.
UnlabelledABSTBACKGROUND: Evidence-based practices have not been routinely adopted in community mental health organizations despite the support of scientific evidence and in some cases even legislative or regulatory action. We examined the association of clinician attitudes toward evidence-based practice with organizational culture, climate, and other characteristics in a nationally representative sample of mental health organizations in the United States.MethodsIn-person, group-administered surveys were conducted with a sample of 1,112 mental health service providers in a nationwide sample of 100 mental health service institutions in 26 states in the United States. The study examines these associations with a two-level Hierarchical Linear Modeling (HLM) analysis of responses to the Evidence-Based Practice Attitude Scale (EBPAS) at the individual clinician level as a function of the Organizational Social Context (OSC) measure at the organizational level, controlling for other organization and clinician characteristics.ResultsWe found that more proficient organizational cultures and more engaged and less stressful organizational climates were associated with positive clinician attitudes toward adopting evidence-based practice.ConclusionsThe findings suggest that organizational intervention strategies for improving the organizational social context of mental health services may contribute to the success of evidence-based practice dissemination and implementation efforts by influencing clinician attitudes
The Formation of Kiloparsec-scale HI Holes in Dwarf Galaxies
The origin of kpc-scale holes in the atomic hydrogen (H i) distributions of some nearby dwarf irregular galaxies
presents an intriguing problem. Star formation histories (SFHs) derived from resolved stars give us the unique
opportunity to study past star-forming events that may have helped shape the currently visible Hi distribution. Our
sample of five nearby dwarf irregular galaxies spans over an order of magnitude in both total Hi mass and absolute
B-band magnitude and is at the low-mass end of previously studied systems. We use Very Large Array Hi line
data to estimate the energy required to create the centrally dominant hole in each galaxy. We compare this energy estimate to the past energy released by the underlying stellar populations computed from SFHs derived from data taken with the Hubble Space Telescope. The inferred integrated stellar energy released within the characteristic ages exceeds our energy estimates for creating the holes in all cases, assuming expected efficiencies. Therefore, it appears that stellar feedback provides sufficient energy to produce the observed holes. However, we find no obvious signature of single star-forming events responsible for the observed structures when comparing the global SFHs of each galaxy in our sample to each other or to those of dwarf irregular galaxies reported in the literature. We also fail to find evidence of a central star cluster in FUV or Hα imaging. We conclude that large Hi holes are likely formed from multiple generations of star formation and only under suitable interstellar medium conditions
Observational Constraints on the Molecular Gas Content in Nearby Starburst Dwarf Galaxies
Using star formation histories derived from optically resolved stellar
populations in nineteen nearby starburst dwarf galaxies observed with the
Hubble Space Telescope, we measure the stellar mass surface densities of stars
newly formed in the bursts. By assuming a star formation efficiency (SFE), we
then calculate the inferred gas surface densities present at the onset of the
starbursts. Assuming a SFE of 1%, as is often assumed in normal star-forming
galaxies, and assuming that the gas was purely atomic, translates to very high
HI surface densities (~10^2-10^3 Msun pc^-2), which are much higher than have
been observed in dwarf galaxies. This implies either higher values of SFE in
these dwarf starburst galaxies or the presence of significant amounts of H_2 in
dwarfs (or both). Raising the assumed SFEs to 10% or greater (in line with
observations of more massive starbursts associated with merging galaxies),
still results in HI surface densities higher than observed in 10 galaxies.
Thus, these observations appear to require that a significant fraction of the
gas in these dwarf starbursts galaxies was in the molecular form at the onset
of the bursts. Our results imply molecular gas column densities in the range
10^19-10^21 cm^-2 for the sample. In those galaxies where CO observations have
been made, these densities correspond to values of the CO-H_2 conversion factor
(X_CO) in the range >3-80x10^20 cm^-2 (K km s^-1)^-1, or up to 40x greater than
Galactic X_CO values.Comment: 8 pages, 4 figures, 2 table
Modular Approach to Therapy for Anxiety, Depression, Trauma, or Conduct Problems in outpatient child and adolescent mental health services in New Zealand: study protocol for a randomized controlled trial
Background: Mental health disorders are common and disabling for young people because of the potential to disrupt key developmental tasks. Implementation of evidence-based psychosocial therapies in New Zealand is limited, owing to the inaccessibility, length, and cost of training in these therapies. Furthermore, most therapies address one problem area at a time, although comorbidity and changing clinical needs commonly occur in practice. A more flexible approach is needed. The Modular Approach to Therapy for Children with Anxiety, Depression, Trauma, or Conduct Problems (MATCH-ADTC) is designed to overcome these challenges; it provides a range of treatment modules addressing different problems, within a single training program. A clinical trial of MATCH-ADTC in the USA showed that MATCH-ADTC outperformed usual care and standard evidence-based treatment on several clinical measures. We aim to replicate these findings and evaluate the impact of providing training and supervision in MATCH-ADTC to: (1) improve clinical outcomes for youth attending mental health services; (2) increase the amount of evidence-based therapy content; (3) increase the efficiency of service delivery.
Methods: This is an assessor-blinded multi-site effectiveness randomized controlled trial. Randomization occurs at two levels: (1) clinicians (â„60) are randomized to intervention or usual care; (2) youth participants (7â14 years old) accepted for treatment in child and adolescent mental health services (with a primary disorder that includes anxiety, depression, trauma-related symptoms, or disruptive behavior) are randomly allocated to receive MATCH-ADTC or usual care. Youth participants are recruited from âmainstreamâ, MÄori-specific, and Pacific-specific child and adolescent mental health services. We originally planned to recruit 400 youth participants, but this has been revised to 200 participants. Centralized computer randomization ensures allocation concealment. The primary outcome measures are: (i) the difference in trajectory of change of clinical severity between groups (using the parent-rated Brief Problem Monitor); (ii) cliniciansâ use of evidence-based treatment procedures during therapy sessions; (iii) total time spent by clinicians delivering therapy.
Discussion: If MATCH-ADTC demonstrates effectiveness it could offer a practical efficient method to increase access to evidence-based therapies, and improve outcomes for youth attending secondary care services
Anthropometric indices of Gambian children after one or three annual rounds of mass drug administration with azithromycin for trachoma control.
BACKGROUND: Mass drug administration (MDA) with azithromycin, carried out for the control of blinding trachoma, has been linked to reduced mortality in children. While the mechanism behind this reduction is unclear, it may be due, in part, to improved nutritional status via a potential reduction in the community burden of infectious disease. To determine whether MDA with azithromycin improves anthropometric indices at the community level, we measured the heights and weights of children aged 1 to 4 years in communities where one (single MDA arm) or three annual rounds (annual MDA arm) of azithromycin had been distributed. METHODS: Data collection took place three years after treatment in the single MDA arm and one year after the final round of treatment in the annual MDA arm. Mean height-for-age, weight-for-age and weight-for-height z scores were compared between treatment arms. RESULTS: No significant differences in mean height-for-age, weight-for-age or weight-for-height z scores were found between the annual MDA and single MDA arms, nor was there a significant reduction in prevalence of stunting, wasting or underweight between arms. CONCLUSIONS: Our data do not provide evidence that community MDA with azithromycin improved anthropometric outcomes of children in The Gambia. This may suggest reductions in mortality associated with azithromycin MDA are due to a mechanism other than improved nutritional status
Leo A: A Late-Blooming Survivor of the Epoch of Reionization in the Local Group
As part of a major program to use isolated Local Group dwarf galaxies as
near-field probes of cosmology, we have obtained deep images of the dwarf
irregular galaxy Leo A with the Advanced Camera for Surveys aboard the Hubble
Space Telescope. From these images we have constructed a color-magnitude
diagram (CMD) reaching apparent [absolute] magnitudes of (M475, M814) > (29.0
[+4.4], 27.9 [+3.4]), the deepest ever achieved for any irregular galaxy beyond
the Magellanic Clouds. We derive the star-formation rate (SFR) as a function of
time over the entire history of the galaxy. We find that over 90% of all the
star formation that ever occurred in Leo A happened more recently than 8 Gyr
ago. The CMD shows only a very small amount of star formation in the first few
billion years after the Big Bang; a possible burst at the oldest ages cannot be
claimed with high confidence. The peak SFR occurred ~1.5-4 Gyr ago, at a level
5-10 times the current value. Our modelling indicates that Leo A has
experienced very little metallicity evolution; the mean inferred metallicity is
consistent with measurements of the present-day gas-phase oxygen abundance. We
cannot exclude a scenario in which ALL of the ancient star formation occurred
prior to the end of the era of reionization, but it seems unlikely that the
lack of star formation prior to ~8 Gyr ago was due to early loss or exhaustion
of the in situ gas reservoir.Comment: Accepted for publication in the Astrophysical Journal Letters; 5
pages, 3 figures (2 in color); uses emulateapj.st
Kinetic studies of the methanation of CO over a Ni/Îł-Al2O3 catalyst using a batch reactor
The methanation of CO was investigated in a gradientless, spinning-basket reactor at
temperatures 443 â 473 K and pressures up to 16 bar. The reactor was operated in batch and
the composition of its contents was determined periodically. Temperature programmed
studies and DRIFTS analysis were performed to gain an understanding of the nature of the
surface of the catalyst. In all experiments, the reaction initially proceeded with a constant rate
period. This was followed by a marked increase in the rate of production of CH4 after the
depletion of CO, attributed to the hydrogenation of remaining carbonyl groups on the surface
as well as the hydrogenolysis of long-chained paraffins in the reactor. The selectivity for CH4
was found to be significantly lower than that observed in CO2 methanation, consistent with
the low H2 to CO ratio on the surface of the catalyst. Temperature-programmed studies and
DRIFTS studies of the spent catalyst identified two main types of carbonaceous species on
the surface of the catalyst, with the results being consistent with the presence of (i) carbonyl
species on nickel clusters and (ii) formate groups on nickel sites which have a stronger
interaction with the alumina support. The former were found to be reactive at the
temperatures studied. Finally, the rate of methanation was found to be insensitive to H2O.
This was attributed to the strong affinity of the nickel catalyst for CO, which saturates the
surface of the catalyst leaving little opportunity for the adsorption of H2O. Two models were
derived assuming that the rate-limiting steps was either (i) the adsorption of H2 on the
catalyst, or (ii) the reaction of gaseous H2 with adsorbed CO. The strong adsorption of CO on
the surface of the catalyst, evident from various experimental observations, is consistent with
both mechanisms
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