2,015 research outputs found
Shapes of Molecular Cloud Cores and the Filamentary Mode of Star Formation
Using recent dust continuum data, we generate the intrinsic ellipticity
distribution of dense, starless molecular cloud cores. Under the hypothesis
that the cores are all either oblate or prolate randomly-oriented spheroids, we
show that a satisfactory fit to observations can be obtained with a gaussian
prolate distribution having a mean intrinsic axis ratio of 0.54. Further, we
show that correlations exist between the apparent axis ratio and both the peak
intensity and total flux density of emission from the cores, the sign of which
again favours the prolate hypothesis. The latter result shows that the mass of
a given core depends on its intrinsic ellipticity. Monte Carlo simulations are
performed to find the best-fit power law of this dependence. Finally, we show
how these results are consistent with an evolutionary scenario leading from
filamentary parent clouds to increasingly massive, condensed, and roughly
spherical embedded cores.Comment: 16 pages, incl. 11 Postscript figures. Accepted by Ap
Expanding and Testing a Computational Method for Predicting the Ground State Reduction Potentials of Organic Molecules on the Basis of Empirical Correlation to Experiment
A method for predicting the ground state reduction potentials of organic molecules on the basis of the correlation of computed energy differences between the starting S-0 and one-electron-reduced D-0 species with experimental reduction potentials in acetonitrile has been expanded to cover 3.5 V of potential range and 74 compounds across 6 broad families of molecules. Utilizing the conductor-like polarizable continuum model of implicit solvent allows a global correlation that is computationally efficient and has improved accuracy, with r(2) \u3e 0.98 in all cases and root mean square deviation errors of(mean absolute deviationsmV) for either B3LYP/6-311+G(d,p) or B3LYP//6-31G(d) with an appropriate choice of radii (UAKS or UA0). The correlations are proven to be robust across a wide range of structures and potentials, including four larger (27-28 heavy atoms) and more conformationally flexible photochromic molecules not used in calibrating the correlation. The method is also proven to be robust to a number of minor student mistakes or methodological inconsistencies
The Structure and Evolution of Magnetized Cloud Cores in a Zero--Density Background
Molecular-line observations of star-forming cloud cores indicate that they
are not the flattened structures traditionally considered by theory. Rather,
they are elongated, perhaps in the direction of their internal magnetic field.
We are thus motivated to consider the structure and evolution of axisymmetric,
magnetized clouds that start from a variety of initial states, both flattened
(oblate) and elongated (prolate). We devise a new technique, dubbed the
-method, that allows us to construct magnetostatic equilibria of any
specified shape. We find, in agreement with previous authors, that the field
lines in oblate clouds bend inward. However, those in prolate clouds bow
outward, confining the structures through magnetic tension.
We next follow the quasi-static evolution of these clouds via ambipolar
diffusion, under the assumption of constant core mass. An oblate cloud either
relaxes to a magnetically force-free sphere or, if sufficiently massive,
flattens along its polar axis as its central density runs away. A prolate cloud
always relaxes to a sphere of modest central density. We finally consider the
evolution of an initially spherical cloud subject to the tidal gravity of
neighboring bodies. Although the structure constricts equatorially, it also
shortens along the pole, so that it ultimately flattens on the way to collapse.
In summary, none of our initial states can evolve to the point of collapse
while maintaining an elongated shape. We speculate that this situation will
change once we allow the cloud to gain mass from its environment.Comment: 19 pages, plus 20 postscript figures. Accepted by Ap
Transiting Exoplanet Studies and Community Targets for JWST's Early Release Science Program
The James Webb Space Telescope will revolutionize transiting exoplanet
atmospheric science due to its capability for continuous, long-duration
observations and its larger collecting area, spectral coverage, and spectral
resolution compared to existing space-based facilities. However, it is unclear
precisely how well JWST will perform and which of its myriad instruments and
observing modes will be best suited for transiting exoplanet studies. In this
article, we describe a prefatory JWST Early Release Science (ERS) program that
focuses on testing specific observing modes to quickly give the community the
data and experience it needs to plan more efficient and successful future
transiting exoplanet characterization programs. We propose a multi-pronged
approach wherein one aspect of the program focuses on observing transits of a
single target with all of the recommended observing modes to identify and
understand potential systematics, compare transmission spectra at overlapping
and neighboring wavelength regions, confirm throughputs, and determine overall
performances. In our search for transiting exoplanets that are well suited to
achieving these goals, we identify 12 objects (dubbed "community targets") that
meet our defined criteria. Currently, the most favorable target is WASP-62b
because of its large predicted signal size, relatively bright host star, and
location in JWST's continuous viewing zone. Since most of the community targets
do not have well-characterized atmospheres, we recommend initiating preparatory
observing programs to determine the presence of obscuring clouds/hazes within
their atmospheres. Measurable spectroscopic features are needed to establish
the optimal resolution and wavelength regions for exoplanet characterization.
Other initiatives from our proposed ERS program include testing the instrument
brightness limits and performing phase-curve observations.(Abridged)Comment: This is a white paper that originated from an open discussion at the
Enabling Transiting Exoplanet Science with JWST workshop held November 16 -
18, 2015 at STScI (http://www.stsci.edu/jwst/science/exoplanets). Accepted
for publication in PAS
Wake up, wake up! It's me! It's my life! patient narratives on person-centeredness in the integrated care context: a qualitative study
Person-centered care emphasizes a holistic, humanistic approach that puts patients first, at the center of medical care. Person-centeredness is also considered a core element of integrated care. Yet typologies of integrated care mainly describe how patients fit within integrated services, rather than how services fit into the patient's world. Patient-centeredness has been commonly defined through physician's behaviors aimed at delivering patient-centered care. Yet, it is unclear how 'person-centeredness' is realized in integrated care through the patient voice. We aimed to explore patient narratives of person-centeredness in the integrated care context
Odin observations of H2O in the Galactic Centre
The Odin satellite has been used to detect emission and absorption in the
557-GHz H2O line in the Galactic Centre towards the Sgr A* Circumnuclear Disk
(CND), and the Sgr A +20 km/s and +50 km/s molecular clouds. Strong broad H2O
emission lines have been detected in all three objects. Narrow H2O absorption
lines are present at all three positions and originate along the lines of sight
in the 3-kpc Spiral Arm, the -30 km/s Spiral Arm and the Local Sgr Spiral Arm.
Broad H2O absorption lines near -130 km/s are also observed, originating in the
Expanding Molecular Ring. A new molecular feature (the ``High Positive Velocity
Gas'' - HPVG) has been identified in the positive velocity range of ~ +120 to
+220 km/s, seen definitely in absorption against the stronger dust continuum
emission from the +20 km/s and +50 km/s clouds and possibly in emission towards
the position of Sgr A* CND. The 548-GHz H2_18O isotope line towards the CND is
not detected at the 0.02 K (rms) level.Comment: 5 pages, 3 figures, accepted by A&A, special Odin Letters issu
Intimate partner violence and infant morbidity: evidence of an association from a population-based study in eastern Uganda in 2003
<p>Abstract</p> <p>Background</p> <p>Although recent studies suggest that there is an association between intimate partner violence and child mortality, the underlying mechanisms are still unknown. It is against this background that as a secondary objective, we set out to explore whether an association exists between intimate partner violence and illness in infants.</p> <p>Methods</p> <p>We conducted a population based household survey in Mbale, eastern Uganda in 2003. Participants were 457 women (with 457 infants) who consented to participate in the study. We measured socio-demographics of women and occurrence of intimate partner violence. We measured socio-demographics, immunization, nutritional status, and illness in the previous two weeks of the children.</p> <p>Results</p> <p>The mean age of the women was 25 years (SD 5.7) while the mean age of the infants was 6 months (SD 3.5). The prevalence of lifetime intimate partner violence was 54% (95% CI 48%â60%). During the previous two weeks, 50% (95% CI 50%â54%) of the children had illness (fever, diarrhoea, cough and fast breathing). Lifetime intimate partner violence was associated with infant illness (OR 1.8, 95% CI 1.2â2.8) and diarrhoea (OR 2.0, 95% CI 1.2â3.4).</p> <p>Conclusion</p> <p>Our findings suggest that infant illnesses (fever, diarrhoea, cough and fast breathing) are associated with intimate partner violence, and provide insights into previous reports that have shown an association between intimate partner violence and child mortality, suggesting possible underlying mechanisms. Our findings also highlight the importance of intimate partner violence on the health of children, and the need for further research in this area.</p
Evidence for the η_b(1S) Meson in Radiative ΄(2S) Decay
We have performed a search for the η_b(1S) meson in the radiative decay of the ΄(2S) resonance using a sample of 91.6 Ă 10^6 ΄(2S) events recorded with the BABAR detector at the PEP-II B factory at the SLAC National Accelerator Laboratory. We observe a peak in the photon energy spectrum at E_Îł = 609.3^(+4.6)_(-4.5)(stat)±1.9(syst) MeV, corresponding to an η_b(1S) mass of 9394.2^(+4.8)_(-4.9)(stat) ± 2.0(syst) MeV/c^2. The branching fraction for the decay ΄(2S) â γη_b(1S) is determined to be [3.9 ± 1.1(stat)^(+1.1)_(-0.9)(syst)] Ă 10^(-4). We find the ratio of branching fractions B[΄(2S) â γη_b(1S)]/B[΄(3S) â γη_b(1S)]= 0.82 ± 0.24(stat)^(+0.20)_(-0.19)(syst)
Measurement of the quasi-elastic axial vector mass in neutrino-oxygen interactions
The weak nucleon axial-vector form factor for quasi-elastic interactions is
determined using neutrino interaction data from the K2K Scintillating Fiber
detector in the neutrino beam at KEK. More than 12,000 events are analyzed, of
which half are charged-current quasi-elastic interactions nu-mu n to mu- p
occurring primarily in oxygen nuclei. We use a relativistic Fermi gas model for
oxygen and assume the form factor is approximately a dipole with one parameter,
the axial vector mass M_A, and fit to the shape of the distribution of the
square of the momentum transfer from the nucleon to the nucleus. Our best fit
result for M_A = 1.20 \pm 0.12 GeV. Furthermore, this analysis includes updated
vector form factors from recent electron scattering experiments and a
discussion of the effects of the nucleon momentum on the shape of the fitted
distributions.Comment: 14 pages, 10 figures, 6 table
Search for the W-exchange decays B0 --> Ds(*)- Ds(*)+
We report a search for the decays , , in a sample of 232
million decays to \BBb ~pairs collected with the \babar detector
at the PEP-II asymmetric-energy storage ring. We find no significant
signal and set upper bounds for the branching fractions: and at 90% confidence level.Comment: 8 pages, 2 figures, submitted to PRD-R
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