206 research outputs found
Impact of energetic particle orbits on long range frequency chirping of BGK modes
Long range frequency chirping of Bernstein-Greene-Kruskal modes, whose
existence is determined by the fast particles, is investigated in cases where
these particles do not move freely and their motion is bounded to restricted
orbits. An equilibrium oscillating potential, which creates different orbit
topologies of energetic particles, is included into the bump-on-tail
instability problem of a plasma wave. With respect to fast particles dynamics,
the extended model captures the range of particles motion (trapped/passing)
with energy and thus represents a more realistic 1D picture of the long range
sweeping events observed for weakly damped modes, e.g. global Alfven
eigenmodes, in tokamaks. The Poisson equation is solved numerically along with
bounce averaging the Vlasov equation in the adiabatic regime. We demonstrate
that the shape and the saturation amplitude of the nonlinear mode structure
depends not only on the amount of deviation from the initial eigenfrequency but
also on the initial energy of the resonant electrons in the equilibrium
potential. Similarly, the results reveal that the resonant electrons following
different equilibrium orbits in the electrostatic potential lead to different
rates of frequency evolution. As compared to the previous model [Breizman B.N.
2010 Nucl. Fusion 50 084014], it is shown that the frequency sweeps with lower
rates. The additional physics included in the model enables a more complete 1D
description of the range of phenomena observed in experiments.Comment: Submitted to Nuclear Fusion 25/01/201
Patient Satisfaction with Nursing and Medical Care in Hospitals Affiliated to Arak University of Medical Sciences in 2009
Background: Patient satisfaction is essential and must be taken into account when decisions are being made about changes and enhancements to services.
Objectives: The aim of the current study was to assess patient satisfaction with the medical and nursing services provided to patients admitted to teaching hospitals affiliated to Arak University of Medical Sciences.
Materials and Methods: This was a cross-sectional study conducted in 2009. The study population consisted of all patients admitted to the study setting. The instrument consisted of a demographic questionnaire and patient satisfaction questionnaire. Study data were analyzed using Chi-square test, Pearson's and Spearman's rho correlation coefficient.
Results: In terms of the medical and nursing care provided, 67% and 69% of the participants were satisfied, respectively. The ‘access to opportune nursing care’ and ‘physician’s manner’ items received 82.7% and 81.7% of scores, respectively. Satisfaction with medical and nursing care was significantly correlated with the participants’ education levels (P < 0.05).
Conclusions: The study showed that patient satisfaction was at an average level, therefore, policy makers in the organizations should consider customer-based feedback and apply various methods to improve it
ALMA Observations of SPT-discovered, Strongly Lensed, Dusty, Star-forming Galaxies
We present Atacama Large Millimeter/submillimeter Array (ALMA) 860 μm imaging of four high-redshift (z = 2.8-5.7) dusty sources that were detected using the South Pole Telescope (SPT) at 1.4 mm and are not seen in existing radio to far-infrared catalogs. At 1."5 resolution, the ALMA data reveal multiple images of each submillimeter source, separated by 1"-3", consistent with strong lensing by intervening galaxies visible in near-IR imaging of these sources. We describe a gravitational lens modeling procedure that operates on the measured visibilities and incorporates self-calibration-like antenna phase corrections as part of the model optimization, which we use to interpret the source structure. Lens models indicate that SPT0346-52, located at z = 5.7, is one of the most luminous and intensely star-forming sources in the universe with a lensing corrected FIR luminosity of 3.7 × 10^(13) L_☉ and star formation surface density of 4200 M_☉ yr^(–1) kpc^(–2). We find magnification factors of 5 to 22, with lens Einstein radii of 1."1-2."0 and Einstein enclosed masses of 1.6-7.2 × 10^(11) M_☉. These observations confirm the lensing origin of these objects, allow us to measure their intrinsic sizes and luminosities, and demonstrate the important role that ALMA will play in the interpretation of lensed submillimeter sources
ALMA observations of atomic carbon in z~4 dusty star-forming galaxies
We present ALMA [CI]() (rest frequency 492 GHz) observations for a
sample of 13 strongly-lensed dusty star-forming galaxies originally discovered
at 1.4mm in a blank-field survey by the South Pole Telescope. We compare these
new data with available [CI] observations from the literature, allowing a study
of the ISM properties of extreme dusty star-forming galaxies spanning
a redshift range . Using the [CI] line as a tracer of the molecular
ISM, we find a mean molecular gas mass for SPT-DSFGs of
M. This is in tension with gas masses derived via low- CO
and dust masses; bringing the estimates into accordance requires either (a) an
elevated CO-to-H conversion factor for our sample of and a gas-to-dust ratio , or (b) an high carbon abundance . Using observations of a range of additional atomic
and molecular lines (including [CI], [CII], and multiple transitions of CO), we
use a modern Photodissociation Region code (3D-PDR) to assess the physical
conditions (including the density, UV radiation field strength, and gas
temperature) within the ISM of the DSFGs in our sample. We find that the ISM
within our DSFGs is characterised by dense gas permeated by strong UV fields.
We note that previous efforts to characterise PDR regions in DSFGs may have
significantly underestimated the density of the ISM. Combined, our analysis
suggests that the ISM of extreme dusty starbursts at high redshift consists of
dense, carbon-rich gas not directly comparable to the ISM of starbursts in the
local Universe.Comment: 21 pages, 12 figures. Accepted for publication in MNRA
Spectroscopy of CASSOWARY gravitationally-lensed galaxies in SDSS: characterisation of an extremely bright reionization-era analog at
We present new observations of sixteen bright () gravitationally
lensed galaxies at selected from the CASSOWARY survey. Included
in our sample is the galaxy CSWA-141, one of the brightest known
reionization-era analogs at high redshift (g=20.5), with a large sSFR (31.2
Gyr) and an [OIII]+H equivalent width
(EW=730~\r{A}) that is nearly identical to the average
value expected at . In this paper, we investigate the rest-frame
UV nebular line emission in our sample with the goal of understanding the
factors that regulate strong CIII] emission. Whereas most of the sources in our
sample show weak UV line emission, we find elevated CIII] in the spectrum of
CSWA-141 (EW=4.6~\r{A}) together with detections of
other prominent emission lines (OIII], Si III], Fe II, Mg II). We
compare the rest-optical line properties of high redshift galaxies with strong
and weak CIII] emission, and find that systems with the strongest UV line
emission tend to have young stellar populations and nebular gas that is
moderately metal-poor and highly ionized, consistent with trends seen at low
and high redshift. The brightness of CSWA-141 enables detailed investigation of
the extreme emission line galaxies which become common at . We find that
gas traced by the CIII] doublet likely probes higher densities than that traced
by [OII] and [SII]. Characterisation of the spectrally resolved Mg II emission
line and several low ionization absorption lines suggests neutral gas around
the young stars is likely optically thin, potentially facilitating the escape
of ionizing radiation.Comment: 20 pages, 9 figures, Accepted for publication in MNRA
SPT0346-52: Negligible AGN Activity in a Compact, Hyper-starburst Galaxy at z = 5.7
We present Chandra ACIS-S and ATCA radio continuum observations of the
strongly lensed dusty, star-forming galaxy SPT-S J034640-5204.9 (hereafter
SPT0346-52) at = 5.656. This galaxy has also been observed with ALMA, HST,
Spitzer, Herschel, APEX, and the VLT. Previous observations indicate that if
the infrared (IR) emission is driven by star formation, then the inferred
lensing-corrected star formation rate ( 4500 M_{\sun} yr) and
star formation rate surface density ( 2000 M_{\sun}
{yr^{-1}} {kpc^{-2}}) are both exceptionally high. It remained unclear from
the previous data, however, whether a central active galactic nucleus (AGN)
contributes appreciably to the IR luminosity. The {\it Chandra} upper limit
shows that SPT0346-52 is consistent with being star-formation dominated in the
X-ray, and any AGN contribution to the IR emission is negligible. The ATCA
radio continuum upper limits are also consistent with the FIR-to-radio
correlation for star-forming galaxies with no indication of an additional AGN
contribution. The observed prodigious intrinsic IR luminosity of (3.6
0.3) 10 L_{\sun} originates almost solely from vigorous star
formation activity. With an intrinsic source size of 0.61 0.03 kpc,
SPT0346-52 is confirmed to have one of the highest of any known
galaxy. This high , which approaches the Eddington limit for a
radiation pressure supported starburst, may be explained by a combination of
very high star formation efficiency and gas fraction.Comment: 8 pages, 6 figures, accepted for publication in Ap
Sub-kiloparsec Imaging of Cool Molecular Gas in Two Strongly Lensed Dusty, Star-Forming Galaxies
We present spatially-resolved imaging obtained with the Australia Telescope
Compact Array (ATCA) of three CO lines in two high-redshift gravitationally
lensed dusty star-forming galaxies, discovered by the South Pole Telescope.
Strong lensing allows us to probe the structure and dynamics of the molecular
gas in these two objects, at z=2.78 and z=5.66, with effective source-plane
resolution of less than 1kpc. We model the lensed emission from multiple CO
transitions and the dust continuum in a consistent manner, finding that the
cold molecular gas as traced by low-J CO always has a larger half-light radius
than the 870um dust continuum emission. This size difference leads to up to 50%
differences in the magnification factor for the cold gas compared to dust. In
the z=2.78 galaxy, these CO observations confirm that the background source is
undergoing a major merger, while the velocity field of the other source is more
complex. We use the ATCA CO observations and comparable resolution Atacama
Large Millimeter/submillimeter Array dust continuum imaging of the same objects
to constrain the CO-H_2 conversion factor with three different procedures,
finding good agreement between the methods and values consistent with those
found for rapidly star-forming systems. We discuss these galaxies in the
context of the star formation - gas mass surface density relation, noting that
the change in emitting area with observed CO transition must be accounted for
when comparing high-redshift galaxies to their lower redshift counterparts.Comment: 14 pages, 7 figures; accepted for publication in Ap
Coating mechanisms of single-walled carbon nanotube by linear polyether surfactants: insights from computer simulations
The noncovalent coating of carbon-based nanomaterials, such as carbon nanotubes, has important applications in nanotechnology and nanomedicine. The molecular modeling of this process can clarify its mechanism and provide a tool for the design of novel materials. In this paper, the coating mechanism of single-walled carbon nanotubes (SWCNT) in aqueous solutions by 1,2-dimethoxyethane oxide (DME), 1,2-dimethoxypropane oxide (DMP), poly(ethylene oxide) (PEO), poly(propylene oxide) (PPO) pentamers, and L64 triblock copolymer chains have been studied using molecular dynamics (MD) simulations. The results suggest a preferential binding to the SWCNT surface of the DMP molecules with respect to DME mainly driven by their difference in hydrophobicity. For the longer pentamers, it depends by the chain conformation. PPO isomers with radius of gyration larger than PEO pentamers bind more tightly than those with more compact conformation. In the case of the L64 triblock copolymer, the coating of the SWCNT surface produces a shell of PPO blocks with the PEO chains protruding into bulk water as expected from the so-called nonwrapping binding mechanism of SWCNT. In addition, the polymer coating, in qualitative agreement with experimental evidence on the poor capability of the L64 to disperse SWCNT, do not prevent the formation of CNT aggregates
The Rest-Frame Submillimeter Spectrum of High-Redshift, Dusty, Star-Forming Galaxies
We present the average rest-frame spectrum of high-redshift dusty,
star-forming galaxies from 250-770GHz. This spectrum was constructed by
stacking ALMA 3mm spectra of 22 such sources discovered by the South Pole
Telescope and spanning z=2.0-5.7. In addition to multiple bright spectral
features of 12CO, [CI], and H2O, we also detect several faint transitions of
13CO, HCN, HNC, HCO+, and CN, and use the observed line strengths to
characterize the typical properties of the interstellar medium of these
high-redshift starburst galaxies. We find that the 13CO brightness in these
objects is comparable to that of the only other z>2 star-forming galaxy in
which 13CO has been observed. We show that the emission from the high-critical
density molecules HCN, HNC, HCO+, and CN is consistent with a warm, dense
medium with T_kin ~ 55K and n_H2 >~ 10^5.5 cm^-3. High molecular hydrogen
densities are required to reproduce the observed line ratios, and we
demonstrate that alternatives to purely collisional excitation are unlikely to
be significant for the bulk of these systems. We quantify the average emission
from several species with no individually detected transitions, and find
emission from the hydride CH and the linear molecule CCH for the first time at
high redshift, indicating that these molecules may be powerful probes of
interstellar chemistry in high-redshift systems. These observations represent
the first constraints on many molecular species with rest-frame transitions
from 0.4-1.2mm in star-forming systems at high redshift, and will be invaluable
in making effective use of ALMA in full science operations.Comment: 19 pages, 10 figures (2 in appendices); accepted for publication in
Ap
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