4,391 research outputs found
Extended dust emission and atomic hydrogen, a reservoir of diffuse H_2 in NGC 1068
We report on sensitive sub-mm imaging observations of the prototype
Seyfert~2/starburst galaxy NGC 1068 at 850 m and 450 m using the
Submillimetre Common-User Bolometer Array (SCUBA) on the James Clerk Maxwell
Telescope (JCMT). We find clear evidence of dust emission associated with the
extended HI component which together with the very faint CO J=1--0
emission give a gas-to-dust ratio of . This contrasts with the larger ratio estimated within a galactocentric radius of kpc, where the
gas is mostly molecular and starburst activity occurs. The large gas-to-dust
ratio found for the starburst region is attributed to a systematic overestimate
of the molecular gas mass in starburst environments when the luminosity of the
CO J=1--0 line and a standard galactic conversion factor is used. On
the other hand sub-mm imaging proves to be a more powerful tool than
conventional CO imaging for revealing the properties of the diffuse
that coexists with HI. This molecular gas phase is characterized by low
densities ( cm), very faint emission from
sub-thermally excited CO, and contains more mass than HI, namely .Comment: Accepted for publication in the Astrophysical Journal Letter
Accurate Transfer Maps for Realistic Beamline Elements: Part I, Straight Elements
The behavior of orbits in charged-particle beam transport systems, including
both linear and circular accelerators as well as final focus sections and
spectrometers, can depend sensitively on nonlinear fringe-field and
high-order-multipole effects in the various beam-line elements. The inclusion
of these effects requires a detailed and realistic model of the interior and
fringe fields, including their high spatial derivatives. A collection of
surface fitting methods has been developed for extracting this information
accurately from 3-dimensional field data on a grid, as provided by various
3-dimensional finite-element field codes. Based on these realistic field
models, Lie or other methods may be used to compute accurate design orbits and
accurate transfer maps about these orbits. Part I of this work presents a
treatment of straight-axis magnetic elements, while Part II will treat bending
dipoles with large sagitta. An exactly-soluble but numerically challenging
model field is used to provide a rigorous collection of performance benchmarks.Comment: Accepted to PRST-AB. Changes: minor figure modifications, reference
added, typos corrected
High Spatial Resolution Observations of Two Young Protostars in the R Corona Australis Region
We present multi-wavelength, high spatial resolution imaging of the IRS 7
region in the R Corona Australis molecular cloud. Our observations include 1.1
mm continuum and HCO^+ J = images from the SMA, ^{12}CO J =
outflow maps from the DesertStar heterodyne array receiver on the HHT, 450
m and 850 m continuum images from SCUBA, and archival Spitzer IRAC
and MIPS 24 \micron images. The accurate astrometry of the IRAC images allow us
to identify IRS 7 with the cm source VLA 10W (IRS 7A) and the X-ray source X_W.
The SMA 1.1 mm image reveals two compact continuum sources which are also
distinguishable at 450 m. SMA 1 coincides with X-ray source CXOU
J190156.4-365728 and VLA cm source 10E (IRS 7B) and is seen in the IRAC and
MIPS images. SMA 2 has no infrared counterpart but coincides with cm source VLA
9. Spectral energy distributions constructed from SMA, SCUBA and Spitzer data
yield bolometric temperatures of 83 K for SMA 1 and 70 K for SMA 2. These
temperatures along with the submillimeter to total luminosity ratios indicate
that SMA 2 is a Class 0 protostar, while SMA 1 is a Class 0/Class I
transitional object (L= \Lsun). The ^{12}CO J = outflow map
shows one major and possibly several smaller outflows centered on the IRS 7
region, with masses and energetics consistent with previous work. We identify
the Class 0 source SMA 2/VLA 9 as the main driver of this outflow. The complex
and clumpy spatial and velocity distribution of the HCO^+ J =
emission is not consistent with either bulk rotation, or any known molecular
outflow activity.Comment: 31 pages, 8 figures, Accepted to Ap
Vascular PET Prostheses Surface Modification with Cyclodextrin Coating: Development of a New Drug Delivery System
AbstractPurposeCyclodextrins (CDs) are torus shaped cyclic oligosaccharides with a hydrophobic internal cavity and a hydrophilic external surface. We performed and analysed an antibiotic binding on Dacron (polyethyleneterephtalate, PET) vascular grafts, previously coated with CDs based polymers.MethodsThe CDs coating process was based on the pad-dry-cure method patented in our laboratory. The Dacron prostheses were immersed into a solution containing a polycarboxylic acid, a cyclodextrin and a catalyst, and placed into a thermofixation oven before impregnation with an antibiotic solution (Vancomycin). Biocompatibility tests were performed with L132 human epithelial cells. The antibiotic release in an aqueous medium was assessed by batch type experiments using UV spectroscopy.ResultsViability tests confirmed that the CDs polymers coating the Dacron fibers were not toxic towards L132 cell. Cell proliferation was similar on coated and uncoated grafts.A linear release of Vancomycin was observed over 50 days.ConclusionOur results demonstrate the feasibility of coating CDs onto vascular Dacron grafts. Biological tests show no toxicity of the different cyclodextrins coated. A linear release of antibiotics was depicted over 50 days, demonstrating that cyclodextrin grafting was an efficient drug delivery system
Millimeter and Submillimeter Survey of the R Corona Australis Region
Using a combination of data from the Antarctic Submillimeter Telescope and
Remote Observatory (AST/RO), the Arizona Radio Observatory Kitt Peak 12m
telescope and the Arizona Radio Observatory 10m Heinrich Hertz Telescope, we
have studied the most active part of the R CrA molecular cloud in multiple
transitions of Carbon Monoxide, HCO and 870\micron continuum emission.
Since R CrA is nearby (130 pc), we are able to obtain physical spatial
resolution as high as 0.01pc over an area of 0.16 pc, with velocity
resolution finer than 1 km/s. Mass estimates of the protostar driving the
mm-wave emission derived from HCO, dust continuum emission and kinematic
techniques point to a young, deeply embedded protostar of 0.5-0.75
M, with a gaseous envelope of similar mass. A molecular outflow is
driven by this source that also contains at least 0.8 M of molecular
gas with 0.5 L of mechanical luminosity. HCO lines show the
kinematic signature of infall motions as well as bulk rotation. The source is
most likely a Class 0 protostellar object not yet visible at near-IR
wavelengths. With the combination of spatial and spectral resolution in our
data set, we are able to disentangle the effects of infall, rotation and
outflow towards this young object.Comment: 29 pages, 9 figures. Accepted for publication in the Astrophysical
Journa
Three-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Foreground Polarization
We present a full-sky model of polarized Galactic microwave emission based on
three years of observations by the Wilkinson Microwave Anisotropy Probe (WMAP)
at frequencies from 23 to 94 GHz. The model compares maps of the Stokes Q and U
components from each of the 5 WMAP frequency bands in order to separate
synchrotron from dust emission, taking into account the spatial and frequency
dependence of the synchrotron and dust components. This simple two-component
model of the interstellar medium accounts for at least 97% of the polarized
emission in the WMAP maps of the microwave sky. Synchrotron emission dominates
the polarized foregrounds at frequencies below 50 GHz, and is comparable to the
dust contribution at 65 GHz. The spectral index of the synchrotron component,
derived solely from polarization data, is -3.2 averaged over the full sky, with
a modestly flatter index on the Galactic plane. The synchrotron emission has
mean polarization fraction 2--4% in the Galactic plane and rising to over 20%
at high latitude, with prominent features such as the North Galactic Spur more
polarized than the diffuse component. Thermal dust emission has polarization
fraction 1% near the Galactic center, rising to 6% at the anti-center. Diffuse
emission from high-latitude dust is also polarized with mean fractional
polarization 0.036 +/- 0.011.Comment: 9 pages with 8 figures. For higher quality figures, see the version
posted at http://lambda.gsfc.nasa.gov/product/map/dr2/map_bibliography.cf
Point Symmetries of Generalized Toda Field Theories
A class of two-dimensional field theories with exponential interactions is
introduced. The interaction depends on two ``coupling'' matrices and is
sufficiently general to include all Toda field theories existing in the
literature. Lie point symmetries of these theories are found for an infinite,
semi-infinite and finite number of fields. Special attention is accorded to
conformal invariance and its breaking.Comment: 25 pages, no figures, Latex fil
A Millimeter-Wave Galactic Plane Survey With The BICEP Polarimeter
In addition to its potential to probe the Inflationary cosmological paradigm,
millimeter-wave polarimetry is a powerful tool for studying the Milky Way
galaxy's composition and magnetic field structure. Towards this end, presented
here are Stokes I, Q, and U maps of the Galactic plane from the millimeter-wave
polarimeter BICEP covering the Galactic longitude range 260 - 340 degrees in
three atmospheric transmission windows centered on 100, 150, and 220 GHz. The
maps sample an optical depth 1 < AV < 30, and are consistent with previous
characterizations of the Galactic millimeter-wave frequency spectrum and the
large-scale magnetic field structure permeating the interstellar medium.
Polarized emission is detected over the entire region within two degrees of the
Galactic plane and indicates that the large-scale magnetic field is oriented
parallel to the plane of the Galaxy. An observed trend of decreasing
polarization fraction with increasing total intensity rules out the simplest
model of a constant Galactic magnetic field throughout the Galaxy. Including
WMAP data in the analysis, the degree-scale frequency spectrum of Galactic
polarization fraction is plotted between 23 and 220 GHz for the first time. A
generally increasing trend of polarization fraction with electromagnetic
frequency is found, which varies from 0.5%-1.5%at frequencies below 50 GHz to
2.5%-3.5%above 90 GHz. The BICEP and WMAP data are fit to a two-component
(synchrotron and dust) model showing that the higher frequency BICEP data are
necessary to tightly constrain the amplitude and spectral index of Galactic
dust. Furthermore, the dust amplitude predicted by this two-component fit is
consistent with model predictions of dust emission in the BICEP bands
A Quantum Cosmological Model With Static and Dynamic Wormholes
Quantization is performed of a Friedmann-Robertson-Walker universe filled
with a conformally invariant scalar field and a perfect fluid with equation of
state . A well-known discrete set of static quantum wormholes is
shown to exist for radiation (), and a novel continuous set is
found for cosmic strings (), the latter states having throat
radii of any size. In both cases wave-packet solutions to the Wheeler-DeWitt
equation are obtained with all the properties of evolving quantum wormholes. In
the case of a radiation fluid, a detailed analysis of the quantum dynamics is
made in the context of the Bohm-de Broglie interpretation. It is shown that a
repulsive quantum force inversely proportional to the cube of the scale factor
prevents singularities in the quantum domain. For the states considered, there
are no particle horizons either.Comment: LaTex file, 13 pages. To appear in General Relativity and Gravitatio
A Mid-Infrared Study of the Class 0 Cluster in LDN 1448
We present ground-based mid-infrared observations of Class 0 protostars in
LDN 1448. Of the five known protostars in this cloud, we detected two, L1448N:A
and L1448C, at 12.5, 17.9, 20.8, and 24.5 microns, and a third, L1448 IRS 2, at
24.5 microns. We present high-resolution images of the detected sources, and
photometry or upper limits for all five Class 0 sources in this cloud. With
these data, we are able to augment existing spectral energy distributions
(SEDs) for all five objects and place them on an evolutionary status diagram.Comment: Accepted by the Astronomical Journal; 26 pages, 9 figure
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