1,498 research outputs found
The Nature of the Variable Galactic Center Source IRS16SW
We report measurements of the light curve of the variable Galactic Center
source IRS16SW. The light curve is not consistent with an eclipsing binary or
any other obvious variable star. The source may be an example of a high mass
variable predicted theoretically but not observed previously.Comment: 11 pages, 2 figures. Accepted by Ap
The Spitzer c2d Survey of Nearby Dense Cores. IX. Discovery of a Very Low Luminosity Object Driving a Molecular Outflow in the Dense Core L673-7
We present new infrared, submillimeter, and millimeter observations of the
dense core L673-7 and report the discovery of a low-luminosity, embedded Class
0 protostar driving a molecular outflow. L673-7 is seen in absorption against
the mid-infrared background in 5.8, 8, and 24 micron Spitzer images, allowing
for a derivation of the column density profile and total enclosed mass of
L673-7, independent of dust temperature assumptions. Estimates of the core mass
from these absorption profiles range from 0.2-4.5 solar masses. Millimeter
continuum emission indicates a mass of about 2 solar masses, both from a direct
calculation assuming isothermal dust and from dust radiative transfer models
constrained by the millimeter observations. We use dust radiative transfer
models to constrain the internal luminosity of L673-7, defined to be the
luminosity of the central source and excluding the luminosity from external
heating, to be 0.01-0.045 solar luminosities, with 0.04 solar luminosities the
most likely value. L673-7 is thus classified as a very low luminosity object
(VeLLO), and is among the lowest luminosity VeLLOs yet studied. We calculate
the kinematic and dynamic properties of the molecular outflow in the standard
manner, and we show that the expected accretion luminosity based on these
outflow properties is greater than or equal to 0.36 solar luminosities. The
discrepancy between this expected accretion luminosity and the internal
luminosity derived from dust radiative transfer models indicates that the
current accretion rate is much lower than the average rate over the lifetime of
the outflow. Although the protostar embedded within L673-7 is consistent with
currently being substellar, it is unlikely to remain as such given the
substantial mass reservoir remaining in the core.Comment: 19 pages, 14 figures. Accepted by Ap
Integration of Sexuality Content into an Occupational Therapy Curriculum
Sexuality is a broad term that can be used to encompass other terms such as sexual expression and sexual functioning, and can be defined as a holistic concept of the individual that is more than just physical sexual behavior but also relates to thoughts and feelings of everyday life (Couldrick, 1998a). Sexuality and sexual functioning are considered an activity of daily living (ADL) by the Occupational Therapy Practice Framework: Domain and Process (2008); however, it is a topic that is not being routinely addressed with clients by occupational therapists or other healthcare professionals (Hattjar, 2012). Studies show there is a significant lack of information given to clients in regard to sexuality, as well as dissatisfaction with the services that are provided for sexuality. This information implies an increase in knowledge, experience, and comfort levels with sexuality needs to be addressed with occupational therapists and occupational therapy students in order to treat clients in a holistic and client-centered manner.
A comprehensive literature review was completed to identify key aspects of sexuality. The literature review revealed a significant lack in student and practitioner confidence and competence in addressing sexuality in a clinical setting. After an extensive search regarding the topic of sexuality within the profession of occupational therapy it was found that much of the limited literature stems from the late 1980âs to early 1990âs, yet the literature from the 2000âs continue to address the same issues. Due to the reported low levels of comfort for occupational therapy students and practitioners regarding sexuality and the role occupational therapists play in addressing the subject with clients, the following product was developed. There was a dearth of the information and no evidenced-based articles were located regarding sexuality or how to teach about the topic.
The product created includes lesson plans that address different aspects of physical and/or psychosocial impairments that may impact sexuality. The product lesson plans consist of varying lectures, readings and activities, to be incorporated into several courses throughout the duration of an occupational therapy professional program. The goal of this product is to increase exposure to issues of sexuality and sexual functioning throughout the curricula of a Midwestern professional occupational therapy program in order to create competent and comfortable practitioners within the field
Spitzer and HHT observations of starless cores: masses and environments
We present Spitzer observations of a sample of 12 starless cores selected to
have prominent 24 micron shadows. The Spitzer images show 8 and 24 micron
shadows and in some cases 70 micron shadows; these spatially resolved
absorption features trace the densest regions of the cores. We have carried out
a 12CO (2-1) and 13CO (2-1) mapping survey of these cores with the Heinrich
Hertz Telescope (HHT). We use the shadow features to derive optical depth maps.
We derive molecular masses for the cores and the surrounding environment; we
find that the 24 micron shadow masses are always greater than or equal to the
molecular masses derived in the same region, a discrepancy likely caused by CO
freeze--out onto dust grains. We combine this sample with two additional cores
that we studied previously to bring the total sample to 14 cores. Using a
simple Jeans mass criterion we find that ~ 2/3 of the cores selected to have
prominent 24 micron shadows are collapsing or near collapse, a result that is
supported by millimeter line observations. Of this subset at least half have
indications of 70 micron shadows. All cores observed to produce absorption
features at 70 micron are close to collapse. We conclude that 24 micron
shadows, and even more so the 70 micron ones, are useful markers of cloud cores
that are approaching collapse.Comment: 41 pages, 28 figures, 5 tables; accepted by Ap
Modeling chemistry in and above snow at Summit, Greenland â Part 2: Impact of snowpack chemistry on the oxidation capacity of the boundary layer
The chemical composition of the boundary layer in snow covered regions is impacted by chemistry in the snowpack via uptake, processing, and emission of atmospheric trace gases. We use the coupled one-dimensional (1-D) snow chemistry and atmospheric boundary layer model MISTRA-SNOW to study the impact of snowpack chemistry on the oxidation capacity of the boundary layer. The model includes gas phase photochemistry and chemical reactions both in the interstitial air and the atmosphere. While it is acknowledged that the chemistry occurring at ice surfaces may consist of a true quasi-liquid layer and/or a concentrated brine layer, lack of additional knowledge requires that this chemistry be modeled as primarily aqueous chemistry occurring in a liquid-like layer (LLL) on snow grains. The model has been recently compared with BrO and NO data taken on 10 Juneâ13 June 2008 as part of the Greenland Summit Halogen-HOx experiment (GSHOX). In the present study, we use the same focus period to investigate the influence of snowpack derived chemistry on OH and HOx + RO2 in the boundary layer. We compare model results with chemical ionization mass spectrometry (CIMS) measurements of the hydroxyl radical (OH) and of the hydroperoxyl radical (HO2) plus the sum of all organic peroxy radicals (RO2) taken at Summit during summer 2008. Using sensitivity runs we show that snowpack influenced nitrogen cycling and bromine chemistry both increase the oxidation capacity of the boundary layer and that together they increase the midday OH concentrations. Bromine chemistry increases the OH concentration by 10â18 % (10 % at noon LT), while snow sourced NOx increases OH concentrations by 20â50 % (27 % at noon LT). We show for the first time, using a coupled one dimensional snowpack-boundary layer model, that air-snow interactions impact the oxidation capacity of the boundary layer and that it is not possible to match measured OH levels without snowpack NOx and halogen emissions. Model predicted HONO compared with mistchamber measurements suggests there may be an unknown HONO source at Summit. Other model predicted HOx precursors, H2O2 and HCHO, compare well with measurements taken in summer 2000, which had lower levels than other years. Over 3 days, snow sourced NOx contributes an additional 2 ppb to boundary layer ozone production, while snow sourced bromine has the opposite effect and contributes 1 ppb to boundary layer ozone loss
BioSimulator.jl: Stochastic simulation in Julia
Biological systems with intertwined feedback loops pose a challenge to
mathematical modeling efforts. Moreover, rare events, such as mutation and
extinction, complicate system dynamics. Stochastic simulation algorithms are
useful in generating time-evolution trajectories for these systems because they
can adequately capture the influence of random fluctuations and quantify rare
events. We present a simple and flexible package, BioSimulator.jl, for
implementing the Gillespie algorithm, -leaping, and related stochastic
simulation algorithms. The objective of this work is to provide scientists
across domains with fast, user-friendly simulation tools. We used the
high-performance programming language Julia because of its emphasis on
scientific computing. Our software package implements a suite of stochastic
simulation algorithms based on Markov chain theory. We provide the ability to
(a) diagram Petri Nets describing interactions, (b) plot average trajectories
and attached standard deviations of each participating species over time, and
(c) generate frequency distributions of each species at a specified time.
BioSimulator.jl's interface allows users to build models programmatically
within Julia. A model is then passed to the simulate routine to generate
simulation data. The built-in tools allow one to visualize results and compute
summary statistics. Our examples highlight the broad applicability of our
software to systems of varying complexity from ecology, systems biology,
chemistry, and genetics. The user-friendly nature of BioSimulator.jl encourages
the use of stochastic simulation, minimizes tedious programming efforts, and
reduces errors during model specification.Comment: 27 pages, 5 figures, 3 table
Observational Constraints on Submillimeter Dust Opacity
Infrared extinction maps and submillimeter dust continuum maps are powerful probes of the density structure in the envelope of star-forming cores. We make a direct comparison between infrared and submillimeter dust continuum observations of the low-mass Class 0 core, B335, to constrain the ratio of submillimeter to infrared opacity (Îș_(smm)/Îș_(ir)) and the submillimeter opacity power-law index (Îș â λâÎČ). Using the average value of theoretical dust opacity models at 2.2 ÎŒm, we constrain the dust opacity at 850 and 450 ÎŒm. Using new dust continuum models based upon the broken power-law density structure derived from interferometric observations of B335 and the infall model derived from molecular line observations of B335, we find that the opacity ratios are ^Îș_(850)_Îș_(2.2) = (3.21 - 4.80)^(+0.44)_(-0.30) x 10^(-4) ^Îș_(450)_Îș(2.0) = (12.8-24.8)^(+2.4)_(-1.3) x 10^(-4) with a submillimeter opacity power-law index of ÎČ_(smm) = (2.18-2.58)^(+0.30)_(â0.30). The range of quoted values is determined from the uncertainty in the physical model for B335. For an average 2.2 ÎŒm opacity of 3800 ± 700 cm^2 g^(â1), we find a dust opacity at 850 and 450 ÎŒm of Îș_(850) = (1.18-1.77)^9+0.36)_(â0.24) and Îș_(450) = (4.72-9.13)^(+1.9)_(â0.98) cm^2 g^(â1) of dust. These opacities are from (0.65-0.97)Îș^(OH5)_(850) of the widely used theoretical opacities of Ossenkopf and Henning for coagulated ice grains with thin mantles at 850 ÎŒm
Hier ist wahrhaftig ein Loch im Himmel - The NGC 1999 dark globule is not a globule
The NGC 1999 reflection nebula features a dark patch with a size of ~10,000
AU, which has been interpreted as a small, dense foreground globule and
possible site of imminent star formation. We present Herschel PACS far-infrared
70 and 160mum maps, which reveal a flux deficit at the location of the globule.
We estimate the globule mass needed to produce such an absorption feature to be
a few tenths to a few Msun. Inspired by this Herschel observation, we obtained
APEX LABOCA and SABOCA submillimeter continuum maps, and Magellan PANIC
near-infrared images of the region. We do not detect a submillimer source at
the location of the Herschel flux decrement; furthermore our observations place
an upper limit on the mass of the globule of ~2.4x10^-2 Msun. Indeed, the
submillimeter maps appear to show a flux depression as well. Furthermore, the
near-infrared images detect faint background stars that are less affected by
extinction inside the dark patch than in its surroundings. We suggest that the
dark patch is in fact a hole or cavity in the material producing the NGC 1999
reflection nebula, excavated by protostellar jets from the V 380 Ori multiple
system.Comment: accepted for the A&A Herschel issue; 7 page
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