140 research outputs found
CO and C_2 Absorption Toward W40 IRS 1a
The H II region W40 harbors a small group of young, hot stars behind roughly
9 magnitudes of visual extinction. We have detected gaseous carbon monoxide
(CO) and diatomic carbon (C_2) in absorption toward the star W40 IRS 1a. The
2-0 R0, R1, and R2 lines of 12CO at 2.3 micron were measured using the CSHELL
on the NASA IR Telescope Facility (with upper limits placed on R3, R4, and R5)
yielding an N_CO of (1.1 +/- 0.2) x 10^18 cm^-2. Excitation analysis indicates
T_kin > 7 K. The Phillips system of C_2 transitions near 8775 Ang. was measured
using the Kitt Peak 4-m telescope and echelle spectrometer. Radiative pumping
models indicate a total C_2 column density of (7.0 +/- 0.4) x 10^14 cm^-2, two
excitation temperatures (39 and 126 K), and a total gas density of n ~ 250
cm^-3. The CO ice band at 4.7 micron was not detected, placing an upper limit
on the CO depletion of delta < 1 %. We postulate that the sightline has
multiple translucent components and is associated with the W40 molecular cloud.
Our data for W40 IRS 1a, coupled with other sightlines, shows that the ratio of
CO/C_2 increases from diffuse through translucent environs. Finally, we show
that the hydrogen to dust ratio seems to remain constant from diffuse to dense
environments, while the CO to dust ratio apparently does not.Comment: To appear in The Astrophysical Journal 17 pages total, 5 figures Also
available at http://casa.colorado.edu/~shuping/research/w40/w40.htm
Ultraviolet Imaging Observations of the cD Galaxy in Abell 1795: Further Evidence for Massive Star Formation in a Cooling Flow
We present images from the Ultraviolet Imaging Telescope of the Abell 1795
cluster of galaxies. We compare the cD galaxy morphology and photometry of
these data with those from existing archival and published data. The addition
of a far--UV color helps us to construct and test star formation model
scenarios for the sources of UV emission. Models of star formation with rates
in the range \sim5-20M_{\sun}yr indicate that the best fitting models
are those with continuous star formation or a recent ( Myr old) burst
superimposed on an old population. The presence of dust in the galaxy,
dramatically revealed by HST images complicates the interpretation of UV data.
However, we find that the broad--band UV/optical colors of this cD galaxy can
be reasonably matched by models using a Galactic form for the extinction law
with . We also briefly discuss other objects in the large UIT
field of view.Comment: To appear in the Astrophysical Journal. 14 AAS preprint style pages
plus 7 figure
Influenza A Virus (H3N8) in Dogs with Respiratory Disease, Florida
Genetic and antigenic characterization established the uniqueness of this virus circulating in dogs
Influenza A Virus (H3N8) in Dogs with Respiratory Disease, Florida
Genetic and antigenic characterization established the uniqueness of this virus circulating in dogs
FUSE Observations of Molecular Hydrogen in Translucent Interstellar Clouds: II. The Line of Sight Toward HD 110432
We report the second study from the FUSE survey of molecular hydrogen in
translucent clouds, for the line of sight toward HD 110432. This star lies
beyond the Coalsack dark nebula, and with E(B-V) = 0.40, and A_V = 1.32 this
line of sight bridges the gap between less extinguished diffuse cloud lines of
sight with A_V \sim 1, such as Zeta Oph, and the translucent clouds with A_V
\gtrsim 2 such as HD 73882. Through profile fitting and a curve-of-growth
analysis, we have derived rotational populations for H2 for J = 0--7. The line
of sight has a total molecular hydrogen column density, log N(H2) = 20.68 \pm
0.05 cm^{-2}, nearly identical to that toward Zeta Oph, but a factor of three
less than HD 73882. The ratio of N(J=1) to N(J=0) yields a kinetic temperature
T_{kin} = 63 \pm 7 K, similar to other lines of sight with A_V \gtrsim 1. The
high-J lines show considerable excitation above this temperature. The high-J
excitation is similar to that toward Zeta Oph, but much smaller than that
toward HD 73882. Chemical modeling indicates that the physical conditions in
the cloud(s) are very similar to those in the cloud(s) toward Zeta Oph. An
analysis of IUE spectra of the Lyman-alpha line gives log N(H I) = 20.85 \pm
0.15 cm^{-2}. Combined with N(H2), we derive a hydrogen molecular fraction,
f_{H2} = 0.58 pm 0.12, statistically identical to that found for the lines of
sight toward Zeta Oph and HD 73882. We also report column densities for the HD
and CO molecules. From the combined measurements of hydrogen and carbon-
containing molecules, the line of sight toward HD 110432 appears quite similar
to the diffuse cloud line of sight toward Zeta Oph, and quite dissimilar to the
translucent cloud line of sight toward HD 73882.Comment: 28 pages, 7 figures, accepted for publication in The Astrophysical
Journa
University of California Research Seminar Network: A Prospectus
By webcasting the hundreds of seminars presented in the University of California system each week, UC educators hope to enhance the exchange of scientific information for their campuses and create the foundation for an international research seminar network
Synthesis, characterisation and evaluation of hyperbranched N-(2-hydroxypropyl) methacrylamides for transport and delivery in pancreatic cell lines in vitro and in vivo
Hyperbranched polymers have many promising features for drug delivery, owing to their ease of synthesis, multiple functional group content, and potential for high drug loading with retention of solubility. Here we prepared hyperbranched N-(2-hydroxypropyl)methacrylamide (HPMA) polymers with a range of molar masses and particle sizes, and with attached dyes, radiolabel or the anticancer drug gemcitabine. Reversible addition-fragmentation chain transfer (RAFT) polymerisation enabled the synthesis of pHPMA polymers and a gemcitabine-comonomer functionalised pHPMA polymer pro-drug, with diameters of the polymer particles ranging from 7-40 nm. The non-drug loaded polymers were well-tolerated in cancer cell lines and macrophages, and were rapidly internalised in 2D cell culture and transported efficiently to the centre of dense pancreatic cancer 3D spheroids. The gemcitabine-loaded polymer pro-drug was found to be toxic both to 2D cultures of MIA PaCa-2 cells and also in reducing the volume of MIA PaCa-2 spheroids. The non-drug loaded polymers caused no short-term adverse effects in healthy mice following systemic injection, and derivatives of these polymers labelled with 89Zr-were tracked for their distribution in the organs of healthy and MIA PaCa-2 xenograft bearing Balb/c nude mice. Tumour accumulation, although variable across the samples, was highest in individual animals for the pHPMA polymer of ∼20 nm size, and accordingly a gemcitabine pHPMA polymer pro-drug of ∼18 nm diameter was evaluated for efficacy in the tumour-bearing animals. The efficacy of the pHPMA polymer pro-drug was very similar to that of free gemcitabine in terms of tumour growth retardation, and although there was a survival benefit after 70 days for the polymer pro-drug, there was no difference at day 80. These data suggest that while polymer pro-drugs of this type can be effective, better tumour targeting and enhanced in situ release remain as key obstacles to clinical translation even for relatively simple polymers such as pHPMA
Remote Sensing of Environment: Current status of Landsat program, science, and applications
Formal planning and development of what became the first Landsat satellite commenced over 50 years ago in 1967. Now, having collected earth observation data for well over four decades since the 1972 launch of Landsat- 1, the Landsat program is increasingly complex and vibrant. Critical programmatic elements are ensuring the continuity of high quality measurements for scientific and operational investigations, including ground systems, acquisition planning, data archiving and management, and provision of analysis ready data products. Free and open access to archival and new imagery has resulted in a myriad of innovative applications and novel scientific insights. The planning of future compatible satellites in the Landsat series, which maintain continuity while incorporating technological advancements, has resulted in an increased operational use of Landsat data. Governments and international agencies, among others, can now build an expectation of Landsat data into a given operational data stream. International programs and conventions (e.g., deforestation monitoring, climate change mitigation) are empowered by access to systematically collected and calibrated data with expected future continuity further contributing to the existing multi-decadal record. The increased breadth and depth of Landsat science and applications have accelerated following the launch of Landsat-8, with significant improvements in data quality.
Herein, we describe the programmatic developments and institutional context for the Landsat program and the unique ability of Landsat to meet the needs of national and international programs. We then present the key trends in Landsat science that underpin many of the recent scientific and application developments and followup with more detailed thematically organized summaries. The historical context offered by archival imagery combined with new imagery allows for the development of time series algorithms that can produce information on trends and dynamics. Landsat-8 has figured prominently in these recent developments, as has the improved understanding and calibration of historical data. Following the communication of the state of Landsat science, an outlook for future launches and envisioned programmatic developments are presented. Increased linkages between satellite programs are also made possible through an expectation of future mission continuity, such as developing a virtual constellation with Sentinel-2. Successful science and applications developments create a positive feedback loop—justifying and encouraging current and future programmatic support for Landsat
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