3,896 research outputs found
A VLA Survey For Faint Compact Radio Sources in the Orion Nebula Cluster
We present Karl G. Janksy Very Large Array (VLA) 1.3 cm, 3.6 cm, and 6 cm
continuum maps of compact radio sources in the Orion Nebular Cluster. We
mosaicked 34 square arcminutes at 1.3 cm, 70 square arcminutes at 3.6 cm and
109 square arcminutes at 6 cm, containing 778 near-infrared detected YSOs and
190 HST-identified proplyds (with significant overlap between those
characterizations). We detected radio emission from 175 compact radio sources
in the ONC, including 26 sources that were detected for the first time at these
wavelengths. For each detected source we fit a simple free-free and dust
emission model to characterize the radio emission. We extrapolate the free-free
emission spectrum model for each source to ALMA bands to illustrate how these
measurements could be used to correctly measure protoplanetary disk dust masses
from sub-millimeter flux measurements. Finally, we compare the fluxes measured
in this survey with previously measured fluxes for our targets, as well as four
separate epochs of 1.3 cm data, to search for and quantify variability of our
sources.Comment: 13 pages, 6 figures, 4 tables, ApJ, in pres
Periodic Optical Variability of Radio Detected Ultracool Dwarfs
A fraction of very low mass stars and brown dwarfs are known to be radio
active, in some cases producing periodic pulses. Extensive studies of two such
objects have also revealed optical periodic variability and the nature of this
variability remains unclear. Here we report on multi-epoch optical photometric
monitoring of six radio detected dwarfs, spanning the M8 - L3.5 spectral
range, conducted to investigate the ubiquity of periodic optical variability in
radio detected ultracool dwarfs. This survey is the most sensitive ground-based
study carried out to date in search of periodic optical variability from
late-type dwarfs, where we obtained 250 hours of monitoring, delivering
photometric precision as low as 0.15%. Five of the six targets exhibit
clear periodicity, in all cases likely associated with the rotation period of
the dwarf, with a marginal detection found for the sixth. Our data points to a
likely association between radio and optical periodic variability in
late-M/early-L dwarfs, although the underlying physical cause of this
correlation remains unclear. In one case, we have multiple epochs of monitoring
of the archetype of pulsing radio dwarfs, the M9 TVLM 513-46546, spanning a
period of 5 years, which is sufficiently stable in phase to allow us to
establish a period of 1.95958 0.00005 hours. This phase stability may be
associated with a large-scale stable magnetic field, further strengthening the
correlation between radio activity and periodic optical variability. Finally,
we find a tentative spin-orbit alignment of one component of the very low mass
binary LP 349-25.Comment: Accepted to The Astrophysical Journal; 22 pages; 12 figure
Altered hippocampal function in major depression despite intact structure and resting perfusion
Background: Hippocampal volume reductions in major depression have been frequently reported. However, evidence for functional abnormalities in the same region in depression has been less clear. We investigated hippocampal function in depression using functional magnetic resonance imaging (fMRI) and neuropsychological tasks tapping spatial memory function, with complementing measures of hippocampal volume and resting blood flow to aid interpretation. Method: A total of 20 patients with major depressive disorder (MDD) and a matched group of 20 healthy individuals participated. Participants underwent multimodal magnetic resonance imaging (MRI): fMRI during a spatial memory task, and structural MRI and resting blood flow measurements of the hippocampal region using arterial spin labelling. An offline battery of neuropsychological tests, including several measures of spatial memory, was also completed. Results: The fMRI analysis showed significant group differences in bilateral anterior regions of the hippocampus. While control participants showed task-dependent differences in blood oxygen level-dependent (BOLD) signal, depressed patients did not. No group differences were detected with regard to hippocampal volume or resting blood flow. Patients showed reduced performance in several offline neuropsychological measures. All group differences were independent of differences in hippocampal volume and hippocampal blood flow. Conclusions: Functional abnormalities of the hippocampus can be observed in patients with MDD even when the volume and resting perfusion in the same region appear normal. This suggests that changes in hippocampal function can be observed independently of structural abnormalities of the hippocampus in depression
Stopping, rationalising or optimising antipsychotic drug treatment in people with intellectual disability and/or autism
Intellectual disability (ID; also known as learning disability) is characterised by significant impairment of both cognitive functioning and adaptive behaviours, and an onset in early childhood. People with ID experience a different pattern of morbidity to the general population and die considerably younger than their counterparts without ID. Autism is a neurodevelopmental disorder characterised by troubles with social interaction and communication, and by restricted and repetitive behaviour. In both conditions, complex mental and physical health problems, as well as social issues, are common and are associated with communication difficulties that can result in maladaptive behavioural patterns (often referred to as ābehaviour that challengesā). Ideally, all people presenting with behaviour that challenges should be assessed by a specialist multidisciplinary team (comprising psychiatrists, psychologists, speech and language therapists, occupational therapists) to develop an understanding of the behaviour and an appropriate support plan with tailored treatment strategies and specialist follow-up. Non-pharmacological interventions for challenging behaviour, such as positive behavioural support or cognitiveābehavioural therapy and manipulation of environmental triggers, are preferred to psychotropic medication. However, antipsychotic medication is often prescribed to adults with ID and/or autism to manage behaviour that challenges in the absence of severe mental illness, despite there being little research evidence that antipsychotics are effective in this context
Do patients with schizophrenia exhibit aberrant salience?
BACKGROUND: It has been suggested that some psychotic symptoms reflect āaberrant salienceā, related to dysfunctional reward learning. To test this hypothesis we investigated whether patients with schizophrenia showed impaired learning of task-relevant stimulusreinforcement
associations in the presence of distracting task-irrelevant cues.
METHODS: We tested 20 medicated patients with schizophrenia and 17 controls on a reaction time
game, the Salience Attribution Test. In this game, participants made a speeded response to earn money in the presence of conditioned stimuli (CSs). Each CS comprised two
visual dimensions, colour and form. Probability of reinforcement varied over one of these dimensions (task-relevant), but not the other (task-irrelevant). Measures of adaptive and aberrant motivational salience were calculated on the basis of latency and subjective reinforcement probability rating differences over the task-relevant and task-irrelevant dimensions respectively.
RESULTS: Participants rated reinforcement significantly more
likely and responded significantly faster on high-probability reinforced relative to lowprobability
reinforced trials, representing adaptive motivational salience. Patients exhibited reduced adaptive salience relative to controls, but the two groups did not differ
in terms of aberrant salience. Patients with delusions exhibited significantly greater aberrant salience than those without delusions, and aberrant salience also correlated with negative symptoms. In the controls, aberrant salience correlated significantly with
āintrovertive anhedoniaā schizotypy.
CONCLUSIONS: These data support the hypothesis that aberrant salience is related to the presence of delusions in medicated patients with schizophrenia, but are also suggestive of a link with negative symptoms. The relationship between aberrant salience and psychotic symptoms warrants further investigation in unmedicated patients
Health promotion and screening for people with an intellectual disability
People with intellectual disability have significantly worse health than those without, and have a higher level of complex health needs. The life expectancy for men and women is 13 and 20 years shorter, respectively, than the general population. The increasing role of general practice in delivering and coordinating care across health and social care settings requires expert generalist skills to implement an integrated approach to care. This article explores how general practice can improve the health of people with intellectual disability, by making reasonable adjustments within health promotion, disease prevention, screening and detection
Connecting Online Graduate Students to the University Community
The purpose of this study was to understand how to facilitate a sense of belonging among online graduate students. Sense of community theory was the basis for examining studentsā desires to be a part of a community and feel connected to the institution. Findings from a survey using the Sense of Community Index 2 (SCI-2) of online graduate students provided insight into the sense of community, the importance of belonging to a community, and activities that could strengthen their connection with the institution. Overall students showed a slightly stronger sense of belonging to their program than to the institution. Students were also asked how they prefer to connect to others in the community with mentoring and inperson social events being the most requested
Online cognitive-based intervention for depression: exploring possible circularity in mechanisms of change.
Background. This study investigates possible circularity in mechanisms of change in participants of Master Your Mood (MYM), a cognitive-based, online intervention for young adults with depressive symptoms. A previous study showed that MYM effectively reduced depression and anxiety and strengthened mastery
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