1,274 research outputs found
Assessing molecular outflows and turbulence in the protostellar cluster Serpens South
Molecular outflows driven by protostellar cluster members likely impact their
surroundings and contribute to turbulence, affecting subsequent star formation.
The very young Serpens South cluster consists of a particularly high density
and fraction of protostars, yielding a relevant case study for protostellar
outflows and their impact on the cluster environment. We combined CO
observations of this region using the Combined Array for Research in
Millimeter-wave Astronomy (CARMA) and the Institut de Radioastronomie
Millim\'{e}trique (IRAM) 30 m single dish telescope. The combined map allows us
to probe CO outflows within the central, most active region at size scales of
0.01 pc to 0.8 pc. We account for effects of line opacity and excitation
temperature variations by incorporating CO and CO data for the
and transitions (using Atacama Pathfinder Experiment and
Caltech Submillimeter Observatory observations for the higher CO transitions),
and we calculate mass, momentum, and energy of the molecular outflows in this
region. The outflow mass loss rate, force, and luminosity, compared with
diagnostics of turbulence and gravity, suggest that outflows drive a sufficient
amount of energy to sustain turbulence, but not enough energy to substantially
counter the gravitational potential energy and disrupt the clump. Further, we
compare Serpens South with the slightly more evolved cluster NGC 1333, and we
propose an empirical scenario for outflow-cluster interaction at different
evolutionary stages.Comment: 26 pages, 15 figures, accepted for publication in the Astrophysical
Journa
ALMA Cycle 1 Observations of the HH46/47 Molecular Outflow: Structure, Entrainment and Core Impact
We present ALMA Cycle 1 observations of the HH46/47 molecular outflow using
combined 12m array and ACA observations. The improved angular resolution and
sensitivity of our multi-line maps reveal structures that help us study the
entrainment process in much more detail and allow us to obtain more precise
estimates of outflow properties than previous observations. We use 13CO(1-0)
and C18O(1-0) emission to correct for the 12CO(1-0) optical depth to accurately
estimate the outflow mass, momentum and kinetic energy. This correction
increases the estimates of the mass, momentum and kinetic energy by factors of
about 9, 5 and 2, respectively, with respect to estimates assuming optically
thin emission. The new 13CO and C18O data also allow us to trace denser and
slower outflow material than that traced by the 12CO maps, and they reveal an
outflow cavity wall at very low velocities (as low as 0.2km/s with respect to
the cores central velocity). Adding with the slower material traced only by
13CO and C18O, there is another factor of 3 increase in the mass estimate and
50% increase in the momentum estimate. The estimated outflow properties
indicate that the outflow is capable of dispersing the parent core within the
typical lifetime of the embedded phase of a low-mass protostar, and that it is
responsible for a core-to-star efficiency of 1/4 to 1/3. We find that the
outflow cavity wall is composed of multiple shells associated with a series of
jet bow-shock events. Within about 3000AU of the protostar the 13CO and C18O
emission trace a circumstellar envelope with both rotation and infall motions,
which we compare with a simple analytic model. The CS(2-1) emission reveals
tentative evidence of a slowly-moving rotating outflow, which we suggest is
entrained not only poloidally but also toroidally by a disk wind that is
launched from relatively large radii from the source.Comment: Accepted for publication in ApJ. 26 pages, 20 figure
Critical minerals and energy-impacts and limitations of moving to unconventional resources
© 2016 by the authors. The nexus of minerals and energy becomes ever more important as the economic growth and development of countries in the global South accelerates and the needs of new energy technologies expand, while at the same time various important minerals are declining in grade and available reserves from conventional mining. Unconventional resources in the form of deep ocean deposits and urban ores are being widely examined, although exploitation is still limited. This paper examines some of the implications of the transition towards cleaner energy futures in parallel with the shifts through conventional ore decline and the uptake of unconventional mineral resources. Three energy scenarios, each with three levels of uptake of renewable energy, are assessed for the potential of critical minerals to restrict growth under 12 alternative mineral supply patterns. Under steady material intensities per unit of capacity, the study indicates that selenium, indium and tellurium could be barriers in the expansion of thin-film photovoltaics, while neodymium and dysprosium may delay the propagation of wind power. For fuel cells, no restrictions are observed
NGC7538 IRS1 -- an O star driving an ionized jet and giant N-S outflow
NGC 7538 IRS 1 is a very young embedded O star driving an ionized jet and
accreting mass with an accretion rate > 10^-4 Msun/year, which is quenching the
hypercompact HII region. We use SOFIA GREAT data, Herschel PACS and SPIRE
archive data, SOFIA FORCAST archive data, Onsala 20m and CARMA data, and JCMT
archive data to determine the properties of the O star and its outflow. IRS 1
appears to be a single O-star with a bolometric luminosity > 1 10^5 Lsun, i.e.
spectral type O7 or earlier. We find that IRS 1 drives a large molecular
outflow with the blue-shifted northern outflow lobe extending to ~ 280" or 3.6
pc from IRS 1. Near IRS 1 the outflow is well aligned with the ionized jet. The
dynamical time scale of the outflow is ~ 1.3 10^5 yr. The total outflow mass is
~ 130 Msun. We determine a mass outflow rate of 1.0 10^-3 Msun/yr, roughly
consistent with the observed mass accretion rate. We observe strong high
velocity [CII] emission in the outflow, confirming that strong UV radiation
from IRS 1 escapes into the outflow lobes and is ionizing the gas. Many O stars
may form like low mass stars, but with a higher accretion rate and in a denser
environment. As long as the accretion stays high enough to quench the HII
region, the star will continue to grow. When the accretion rate drops, the HII
region will rapidly start to expand.Comment: 21 pages, 19 figures. Accepted for publication in The Astrophysical
Journa
Awareness of physical activity in healthy middle-aged adults: a cross-sectional study of associations with sociodemographic, biological, behavioural, and psychological factors.
BACKGROUND: Interventions to promote physical activity have had limited success. One reason may be that inactive adults are unaware that their level of physical activity is inadequate and do not perceive a need to change their behaviour. We aimed to assess awareness of physical activity, defined as the agreement between self-rated and objective physical activity, and to investigate associations with sociodemographic, biological, behavioural, and psychological factors. METHODS: We conducted an exploratory, cross-sectional analysis of awareness of physical activity using baseline data collected from 453 participants of the Feedback, Awareness and Behaviour study (Cambridgeshire, UK). Self-rated physical activity was measured dichotomously by asking participants if they believed they were achieving the recommended level of physical activity. Responses were compared to objective physical activity, measured using a combined accelerometer and heart rate monitor (Actiheart®). Four awareness groups were created: overestimators, realistic inactives, underestimators, and realistic actives. Logistic regression was used to assess associations between awareness group and potential correlates. RESULTS: The mean (standard deviation) age of participants was 47.0 (6.9) years, 44.4% were male, and 65.1% were overweight (body mass index ≥ 25). Of the 258 (57.0%) who were objectively classified as inactive, 130 (50.4%) misperceived their physical activity by incorrectly stating that they were meeting the guidelines (overestimators). In a multivariable logistic regression model adjusted for age and sex, those with a lower body mass index (Odds Ratio (OR) = 0.95, 95% Confidence Interval (CI) = 0.90 to 1.00), higher physical activity energy expenditure (OR = 1.03, 95% CI = 1.00 to 1.06) and self-reported physical activity (OR = 1.13, 95% CI = 1.07 to 1.19), and lower intention to increase physical activity (OR = 0.69, 95% CI = 0.48 to 0.99) and response efficacy (OR = 0.53, 95% CI = 0.31 to 0.91) were more likely to overestimate their physical activity. CONCLUSIONS: Overestimators have more favourable health characteristics than those who are realistic about their inactivity, and their psychological characteristics suggest that they are less likely to change their behaviour. Personalised feedback about physical activity may be an important first step to behaviour change
Studying the Outflow-Core Interaction with ALMA Cycle 1 Observations of the HH46/47 Molecular Outflow
We present preliminary analysis of ALMA cycle 1 12m array ^(12)CO /^(13)CO /C^(18)O data of the HH 46/47 molecular outflow. ^(13)CO and C^(18)O trace relatively denser outflow material than ^(12)CO and allow us to trace the outflow to lower velocities than what it possible using only the ^(12)CO emission. Interestingly, the cavity wall of the red lobe can be seen at velocity as low as 0.2 km/s. Using C^(18)O, we are now able to estimate the optical depth of ^(13)CO, and then use the corrected ^(13)CO emission to further and better correct the ^(12)CO emission and estimate the mass, momentum, and kinetic energy of the outflow. Moreover, C^(18)O reveals a flattened rotational structure at the center, likely to be a rotational envelope infalling onto an inner Keplerian disk
Change of Scaling and Appearance of Scale-Free Size Distribution in Aggregation Kinetics by Additive Rules
The idealized general model of aggregate growth is considered on the basis of
the simple additive rules that correspond to one-step aggregation process. The
two idealized cases were analytically investigated and simulated by Monte Carlo
method in the Desktop Grid distributed computing environment to analyze
"pile-up" and "wall" cluster distributions in different aggregation scenarios.
Several aspects of aggregation kinetics (change of scaling, change of size
distribution type, and appearance of scale-free size distribution) driven by
"zero cluster size" boundary condition were determined by analysis of evolving
cumulative distribution functions. The "pile-up" case with a \textit{minimum}
active surface (singularity) could imitate piling up aggregations of
dislocations, and the case with a \textit{maximum} active surface could imitate
arrangements of dislocations in walls. The change of scaling law (for pile-ups
and walls) and availability of scale-free distributions (for walls) were
analytically shown and confirmed by scaling, fitting, moment, and bootstrapping
analyses of simulated probability density and cumulative distribution
functions. The initial "singular" \textit{symmetric} distribution of pile-ups
evolves by the "infinite" diffusive scaling law and later it is replaced by the
other "semi-infinite" diffusive scaling law with \textit{asymmetric}
distribution of pile-ups. In contrast, the initial "singular"
\textit{symmetric} distributions of walls initially evolve by the diffusive
scaling law and later it is replaced by the other ballistic (linear) scaling
law with \textit{scale-free} exponential distributions without distinctive
peaks. The conclusion was made as to possible applications of such approach for
scaling, fitting, moment, and bootstrapping analyses of distributions in
simulated and experimental data.Comment: 37 pages, 16 figures, 1 table; accepted preprint version after
comments of reviewers, Physica A: Statistical Mechanics and its Applications
(2014
Facilitation of Neuropathic Pain by the NPY Y1 Receptor-Expressing Subpopulation of Excitatory Interneurons in the Dorsal Horn
Endogenous neuropeptide Y (NPY) exerts long-lasting spinal inhibitory control of neuropathic pain, but its mechanism of action is complicated by the expression of its receptors at multiple sites in the dorsal horn: NPY Y1 receptors (Y1Rs) on post-synaptic neurons and both Y1Rs and Y2Rs at the central terminals of primary afferents. We found that Y1R-expressing spinal neurons contain multiple markers of excitatory but not inhibitory interneurons in the rat superficial dorsal horn. To test the relevance of this spinal population to the development and/or maintenance of acute and neuropathic pain, we selectively ablated Y1R-expressing interneurons with intrathecal administration of an NPY-conjugated saporin ribosomal neurotoxin that spares the central terminals of primary afferents. NPY-saporin decreased spinal Y1R immunoreactivity but did not change the primary afferent terminal markers isolectin B4 or calcitonin-gene-related peptide immunoreactivity. In the spared nerve injury (SNI) model of neuropathic pain, NPY-saporin decreased mechanical and cold hypersensitivity, but disrupted neither normal mechanical or thermal thresholds, motor coordination, nor locomotor activity. We conclude that Y1R-expressing excitatory dorsal horn interneurons facilitate neuropathic pain hypersensitivity. Furthermore, this neuronal population remains sensitive to intrathecal NPY after nerve injury. This neuroanatomical and behavioral characterization of Y1R-expressing excitatory interneurons provides compelling evidence for the development of spinally-directed Y1R agonists to reduce chronic neuropathic pain
Ultrafast extreme ultraviolet photoemission without space charge
Time- and Angle-resolved photoelectron spectroscopy from surfaces can be used
to record the dynamics of electrons and holes in condensed matter on ultrafast
time scales. However, ultrafast photoemission experiments using
extreme-ultraviolet (XUV) light have previously been limited by either
space-charge effects, low photon flux, or limited tuning range. In this
article, we describe space-charge-free XUV photoelectron spectroscopy
experiments with up to 5 nA of average sample current using a tunable
cavity-enhanced high-harmonic source operating at 88 MHz repetition rate. The
source delivers photons/s in isolated harmonics to the sample over
a broad photon energy range from 18 to 37 eV with a spot size of m. From photoelectron spectroscopy data, we place conservative upper
limits on the XUV pulse duration and photon energy bandwidth of 93 fs and 65
meV, respectively. The high photocurrent, lack of space charge distortions of
the photoelectron spectra, and excellent isolation of individual harmonic
orders allow us to observe the laser-assisted photoelectric effect with
sideband amplitudes as low as , enabling time-resolved XUV
photoemission experiments in a qualitatively new regime
Australian Opportunities in a Circular Economy for Metals: Findings of the Wealth from Waste Cluster
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