2,587 research outputs found
Industrial Security Clearance and Individual Freedom
Industrial Security Clearance and Individual Freedo
A VLA search for young protostars embedded in dense cores
Four dense cores, L1582A, L1689A, B133 and B68, classified as prestellar in
terms of the absence of detectable NIR emission, are observed at radio
wavelengths to investigate whether they nurture very young protostars. No
definite young protostars were discovered in any of the four cores observed. A
few radio sources were discovered close to the observed cores, but these are
most likely extragalactic sources or YSOs unrelated to the cores observed. In
L1582A we discovered a weak radio source near the centre of the core with radio
characteristics and offset from the peak of the submillimeter emission similar
to that of the newly discovered protostar in the core L1014, indicating a
possible protostellar nature for this source. This needs to be confirmed with
near- and/or mid-infrared observations (e.g. with Spitzer). Hence based on the
current observations we are unable to confirm unequivocally that L1582A is
starless. In L1689A a possible 4.5-sigma radio source was discovered at the
centre of the core, but needs to be confirmed with future observations. In B133
a weak radio source, possibly a protostar, was discovered at the edge of the
core on a local peak of the core submm emission, but no source was detected at
the centre of the core. Thus, B133 is probably starless, but may have a
protostar at its edge. In B68 no radio sources were discovered inside or at the
edge of the core, and thus B68 is indeed starless. Four more radio sources with
spectral indices characteristic of young protostars were discovered outside the
cores but within the extended clouds in which these cores reside. Conclusions:
We conclude that the number of cores misclassified as prestellar is probably
very small and does not significantly alter the estimated lifetime of the
prestellar phase.Comment: Accepted by A&
Scattering statistics of rock outcrops: Model-data comparisons and Bayesian inference using mixture distributions
The probability density function of the acoustic field amplitude scattered by
the seafloor was measured in a rocky environment off the coast of Norway using
a synthetic aperture sonar system, and is reported here in terms of the
probability of false alarm. Interpretation of the measurements focused on
finding appropriate class of statistical models (single versus two-component
mixture models), and on appropriate models within these two classes. It was
found that two-component mixture models performed better than single models.
The two mixture models that performed the best (and had a basis in the physics
of scattering) were a mixture between two K distributions, and a mixture
between a Rayleigh and generalized Pareto distribution. Bayes' theorem was used
to estimate the probability density function of the mixture model parameters.
It was found that the K-K mixture exhibits significant correlation between its
parameters. The mixture between the Rayleigh and generalized Pareto
distributions also had significant parameter correlation, but also contained
multiple modes. We conclude that the mixture between two K distributions is the
most applicable to this dataset.Comment: 15 pages, 7 figures, Accepted to the Journal of the Acoustical
Society of Americ
Illinois Waterfowl Surveys and Investigations W-43-R-62 Annual Progress Report Period: 1 July 2014 â 30 June 2015
This study addresses the following objectives: 1)Inventory abundance and distribution of waterfowl and other waterbirds (a minimum of 10 species and guilds) during autumn migration at a minimum of 40 sites along the Illinois and central Mississippi rivers; 2) Investigate the ecology of canvasback and lesser scaup during spring migration in the central Illinois River valley (IRV) and Pool 19 of the Mississippi River; 3) Estimate waterfowl and other waterbird population sizes (a minimum of 10 species and guilds) during autumn migration using an aerial quadrat survey in the IRV for comparison with aerial inventories (Objective 1); 4) Determine breeding bird use of a minimum of 10 moist-soil wetlands managed for waterfowl during summer in central Illinois; 5) Investigate the breeding ecology of sandhill cranes during spring and summer in northeastern Illinois; 6) Distribute our findings to site managers and biologists, make recommendations for future management, and draw conclusions relevant to regional conservation planning during the project period as appropriate and requested.Illinois Department of Natural Resources, Division of Wildlife & U.S. Fish and Wildlife Service Contract Number: RC09-13FWUIUCunpublishednot peer reviewedOpe
Complete Genome Sequences of Paenibacillus Larvae Phages BN12, Dragolir, Kiel007, Leyra, Likha, Pagassa, PBL1c, and Tadhana
We present here the complete genomes of eight phages that infect Paenibacillus larvae, the causative agent of American foulbrood in honeybees. Phage PBL1c was originally isolated in 1984 from a P. larvae lysogen, while the remaining phages were isolated in 2014 from bee debris, honeycomb, and lysogens from three states in the USA
Control of Gammaherpesvirus Latency by Latent Antigen-Specific Cd8+ T Cells
The contribution of the latent antigen-specific CD8+ T cell response to the control of gammaherpesvirus latency is currently obscure. Some latent antigens induce potent T cell responses, but little is known about their induction or the role they play during the establishment of latency. Here we used the murine gammaherpesvirus system to examine the expression of the latency-associated M2 gene during latency and the induction of the CD8+ T cell response to this protein. M2, in contrast to the M3 latency-associated antigen, was expressed at day 14 after infection but was undetectable during long-term latency. The induction of the M291â99/Kd CD8+ T cell response was B cell dependent, transient, and apparently induced by the rapid increase in latently infected cells around day 14 after intranasal infection. These kinetics were consistent with a role in controlling the initial âburstâ of latently infected cells. In support of this hypothesis, adoptive transfer of an M2-specific CD8+ T cell line reduced the initial load of latently infected cells, although not the long-term load. These data represent the first description of a latent antigen-specific immune response in this model, and suggest that vaccination with latent antigens such as M2 may be capable of modulating latent gammaherpesvirus infection
Finding the trigger to Iapetus' odd global albedo pattern: Dynamics of dust from Saturn's irregular satellites
The leading face of Saturn's moon Iapetus, Cassini Regio, has an albedo only
one tenth that on its trailing side. The origin of this enigmatic dichotomy has
been debated for over forty years, but with new data, a clearer picture is
emerging. Motivated by Cassini radar and imaging observations, we investigate
Soter's model of dark exogenous dust striking an originally brighter Iapetus by
modeling the dynamics of the dark dust from the ring of the exterior retrograde
satellite Phoebe under the relevant perturbations. In particular, we study the
particles' probabilities of striking Iapetus, as well as their expected spatial
distribution on the Iapetian surface. We find that, of the long-lived particles
(greater than about 5 microns), most particle sizes (greater than about 10
microns) are virtually certain to strike Iapetus, and their calculated
distribution on the surface matches up well with Cassini Regio's extent in its
longitudinal span. The satellite's polar regions are observed to be bright,
presumably because ice is deposited there. Thus, in the latitudinal direction
we estimate polar dust deposition rates to help constrain models of thermal
migration invoked to explain the bright poles (Spencer & Denk 2010). We also
analyze dust originating from other irregular outer moons, determining that a
significant fraction of that material will eventually coat Iapetus--perhaps
explaining why the spectrum of Iapetus' dark material differs somewhat from
that of Phoebe. Finally we track the dust particles that do not strike Iapetus,
and find that most land on Titan, with a smaller fraction hitting Hyperion. As
has been previously conjectured, such exogenous dust, coupled with Hyperion's
chaotic rotation, could produce Hyperion's roughly isotropic, moderate-albedo
surface.Comment: Accepted for publication in Icaru
Supersymmetric D-brane Bound States with B-field and Higher Dimensional Instantons on Noncommutative Geometry
We classify supersymmetric D0-Dp bound states with a non-zero B-field by
considering T-dualities of intersecting branes at angles. Especially, we find
that the D0-D8 system with the B-field preserves 1/16, 1/8 and 3/16 of
supercharges if the B-field satisfies the ``(anti-)self-dual'' condition in
dimension eight. The D0-branes in this system are described by eight
dimensional instantons on non-commutative R^8. We also discuss the extended
ADHM construction of the eight-dimensional instantons and its deformation by
the B-field. The modified ADHM equations admit a sort of the `fuzzy sphere'
(embeddings of SU(2)) solution.Comment: 20 pages, LaTeX file, typos corrected and references adde
Modeling the Dust Properties of z ~ 6 Quasars with ART^2 -- All-wavelength Radiative Transfer with Adaptive Refinement Tree
The detection of large quantities of dust in z ~ 6 quasars by infrared and
radio surveys presents puzzles for the formation and evolution of dust in these
early systems. Previously (Li et al. 2007), we showed that luminous quasars at
z > 6 can form through hierarchical mergers of gas-rich galaxies. Here, we
calculate the dust properties of simulated quasars and their progenitors using
a three-dimensional Monte Carlo radiative transfer code, ART^2 --
All-wavelength Radiative Transfer with Adaptive Refinement Tree. ART^2
incorporates a radiative equilibrium algorithm for dust emission, an adaptive
grid for inhomogeneous density, a multiphase model for the ISM, and a
supernova-origin dust model. We reproduce the SED and dust properties of SDSS
J1148+5251, and find that the infrared emission are closely associated with the
formation and evolution of the quasar host. The system evolves from a cold to a
warm ULIRG owing to heating and feedback from stars and AGN. Furthermore, the
AGN has significant implications for the interpretation of observation of the
hosts. Our results suggest that vigorous star formation in merging progenitors
is necessary to reproduce the observed dust properties of z~6 quasars,
supporting a merger-driven origin for luminous quasars at high redshifts and
the starburst-to-quasar evolutionary hypothesis. (Abridged)Comment: 26 pages, 22 figures, accepted by ApJ. Version with full resolution
images is available at
http://www.cfa.harvard.edu/~yxli/ARTDUST/astroph0706.3706.pd
Community structure and function of high-temperature chlorophototrophic microbial mats inhabiting diverse geothermal environments
Six phototrophic microbial mat communities from different geothermal springs (YNP) were studied using metagenome sequencing and geochemical analyses. The primary goals of this work were to determine differences in community composition of high-temperature phototrophic mats distributed across the Yellowstone geothermal ecosystem, and to identify metabolic attributes of predominant organisms present in these communities that may correlate with environmental attributes important in niche differentiation. Random shotgun metagenome sequences from six phototrophic communities (average~ 53 Mbp/site) were subjected to multiple taxonomic, phylogenetic and functional analyses. All methods, including G+C content distribution, MEGAN analyses and oligonucleotide frequency-based clustering, provided strong support for the dominant community members present in each site. Cyanobacteria were only observed in non-sulfidic sites; de novo assemblies were obtained for Synechococcus-like populations at Chocolate Pots (CP_7) and Fischerella-like populations at White Creek (WC_6). Chloroflexi-like sequences (esp. Roseiflexus and/or Chloroflexus spp.) were observed in all six samples and contained genes involved in bacteriochlorophyll biosynthesis and the 3-hydroxypropionate carbon fixation pathway. Other major sequence assemblies were obtained for a Chlorobiales population from CP_7 (proposed family Thermochlorobacteriaceae), and an anoxygenic, sulfur-oxidizing Thermochromatium-like (Gamma-proteobacteria) population from Bath Lake Vista Annex (BLVA_20). Additional sequence coverage is necessary to establish more complete assemblies of other novel bacteria in these sites (e.g., Bacteroidetes and Firmicutes); however, current assemblies suggested that several of these organisms play important roles in heterotrophic and fermentative metabolisms. Definitive linkages were established between several of the dominant phylotypes present in these habitats and important functional processes such a
- âŠ