1,008 research outputs found
Molecular Clouds as Ensembles of Transient Cores
We construct models of molecular clouds that are considered as ensembles of
transient cores. Each core is assumed to develop in the background gas of the
cloud, grow to high density and decay into the background. The chemistry in
each core responds to the dynamical state of the gas and to the gas-dust
interaction. Ices are deposited on the dust grains in the core's dense phase,
and this material is returned to the gas as the core expands to low density.
The cores of the ensemble number typically one thousand and are placed randomly
in position within the cloud, and are assigned a random evolutionary phase.
The models are used to generate molecular line contour maps of a typical dark
cloud. These maps are found to represent extremely well the characteristic
features of observed maps of the dark cloud L673, which has been observed at
both low and high resolutions. The computed maps are found to exhibit the
general morphology of the observed maps, and to generate similar sizes of
emitting regions, molecular column densities, and the separations between peaks
of emissions of various molecular species. The models give insight into the
nature of molecular clouds and the dynamical processes occurring within them,
and significantly constrain dynamical and chemical processes in the
interstellar medium.Comment: 29 pages, 8 figures. Accepted for publication in Ap
The nature of the infrared counterpart of IGR J19140+0951
The INTEGRAL observatory has been (re-)discovering new X-ray sources since
the beginning of nominal operations in early 2003. These sources include X-ray
binaries, Active Galactic Nuclei, cataclysmic variables, etc. Amongst the X-ray
binaries, the true nature of many of these sources has remained largely
elusive, though they seem to make up a population of highly absorbed high-mass
X-ray binaries. One of these new sources, IGR J19140+0951, was serendipitously
discovered on 2003 Mar 6 during an observation of the galactic microquasar GRS
1915+105. We observed IGR J19140+0951 with UKIRT in order to identify the
infrared counterpart. Here we present the H- and K-band spectra. We determined
that the companion is a B0.5-type bright supergiant in a wind-fed system, at a
distance \la 5 kpc.Comment: 5 pages, 2 figures, accepted for publication in MNRA
Unemployment and Midlife Suicide Rates in Australia 2001-2015: Implications During the COVID-19 Pandemic
The world is experiencing a massive economic shock from the COVID-19 pandemic. Resulting unemployment and socioeconomic disruption have the potential to lead to a major upswing in the population rate of suicide in Europe and elsewhere. We assessed the association between midlife suicide rates and unemployment for Australia. For the midlife group we found a rapid decrease in the rate from 1970s to 1980s, but a more apparent increase after 2007. The increased male suicide rate coincided with the 2008 global financial crisis. The relationship between worsening employment outcomes, including suicide, is a great tragedy and deserves urgent further investigation
Lunar lander conceptual design
This paper is a first look at the problems of building a lunar lander to support a small lunar surface base. A series of trade studies was performed to define the lander. The initial trades concerned choosing number of stages, payload mass, parking orbit altitude, and propellant type. Other important trades and issues included plane change capability, propellant loading and maintenance location, and reusability considerations. Given a rough baseline, the systems were then reviewed. A conceptual design was then produced. The process was carried through only one iteration. Many more iterations are needed. A transportation system using reusable, aerobraked orbital transfer vehicles (OTV's) is assumed. These OTV's are assumed to be based and maintained at a low Earth orbit (LEO) space station, optimized for transportation functions. Single- and two-stage OTV stacks are considered. The OTV's make the translunar injection (TLI), lunar orbit insertion (LOI), and trans-Earth injection (TEI) burns, as well as midcourse and perigee raise maneuvers
The estimation of black-hole masses in distant radio galaxies
We have estimated the masses of the central supermassive black holes of 2442
radio galaxies froma catalog compiled using data from the NED, SDSS, and CATS
databases. Mass estimates based on optical photometry and radio data are
compared. Relationships between the mass of the central black hole
and the redshift are constructed for both wavelength ranges. The
distribution of the galaxies in these diagrams and systematic effects
influencing estimation of the black-hole parameters are discussed.
Upperenvelope cubic regression fits are obtained using the maximum estimates of
the black-hole masses. The optical and radio upper envelopes show similar
behavior, and have very similar peaks in position, , and
amplitude, = 9.4. This is consistent with a model in which the
growth of the supermassive black holes is self-regulating, with this redshift
corresponding to the epoch when the accretion-flow phase begins to end and the
nuclear activity falls off.Comment: 8 pages, 6 figure
MESMER: MeerKAT Search for Molecules in the Epoch of Reionization
[Abridged] Observations of molecular gas at all redshifts are critical for
measuring the cosmic evolution in molecular gas density and understanding the
star-formation history of the Universe. The 12CO molecule (J=1-0 transition =
115.27 GHz) is the best proxy for extragalactic H2, which is the gas reservoir
from which star formation occurs, and has been detected out to z~6. Typically,
redshifted high-J lines are observed at mm-wavelengths, the most commonly
targeted systems exhibiting high SFRs (e.g. submm galaxies), and far-IR-bright
QSOs. While the most luminous objects are the most readily observed, detections
of more typical galaxies with modest SFRs are essential for completing the
picture. ALMA will be revolutionary in terms of increasing the detection rate
and pushing the sensitivity limit down to include such galaxies, however the
limited FoV when observing at such high frequencies makes it difficult to use
ALMA for studies of the large-scale structure traced out by molecular gas in
galaxies. This article introduces a strategy for a systematic search for
molecular gas during the EoR (z~7 and above), capitalizing on the fact that the
J=1-0 transition of 12CO enters the upper bands of cm-wave instruments at
high-z. The FoV advantage gained by observing at such frequencies, coupled with
modern broadband correlators allows significant cosmological volumes to be
probed on reasonable timescales. In this article we present an overview of our
future observing programme which has been awarded 6,500 hours as one of the
Large Survey Projects for MeerKAT, the forthcoming South African SKA pathfinder
instrument. Its large FoV and correlator bandwidth, and high-sensitivity
provide unprecedented survey speed for such work. An existing astrophysical
simulation is coupled with instrumental considerations to demonstrate the
feasibility of such observations and predict detection rates.Comment: 7 pages, 4 figures, to appear in the proceedings of "Astronomy with
megastructures: Joint science with the E-ELT and SKA", 10-14 May 2010, Crete,
Greece (Eds: Isobel Hook, Dimitra Rigopoulou, Steve Rawlings and Aris
Karastergiou
Analysis and visualisation of RDF resources in Ondex
An increasing number of biomedical resources provide their information on the Semantic Web and this creates the basis for a distributed knowledge base which has the potential to advance biomedical research [1]. This potential, however, cannot be realized until researchers from the life sciences can interact with information in the Semantic Web. In particular, there is a need for tools that provide data reduction, visualization and interactive analysis capabilities.
Ondex is a data integration and visualization platform developed to support Systems Biology Research [2]. At its core is a data model based on two main principles: first, all information can be represented as a graph and, second, all elements of the graph can be annotated with ontologies. This data model conforms to the Semantic Web framework, in particular to RDF, and therefore Ondex is ideally positioned as a platform that can exploit the semantic web.
The Ondex system offers a range of features and analysis methods of potential value to semantic web users, including:
- An interactive graph visualization interface (Ondex user client), which provides data reduction and representation methods that leverage the ontological annotation.
- A suite of importers from a variety of data sources to Ondex (http://ondex.org/formats.html)
- A collection of plug-ins which implement graph analysis, graph transformation and graph-matching functions.
- An integration toolkit (Ondex Integrator) which allows users to compose workflows from these modular components
- In addition, all importers and plug-ins are available as web-services which can be integrated in other tools, as for instance Taverna [3].
The developments that will be presented in this demo have made this functionality interoperable with the Semantic Web framework. In particular we have developed an interactive importer, based on SPARQL that allows the query-driven construction of datasets which brings together information from different RDF data resources into Ondex.
These datasets can then be further refined, analysed and annotated both interactively using the Ondex user client and via user-defined workflows. The results of these analyses can be exported in RDF, which can be used to enrich existent knowledge bases, or to provide application-specific views of the data. Both importer and exporter only focus on a subset of the Ondex and RDF data models, which are shared between these two data representations [4].
In this demo we will show how Ondex can be used to query, analyse and visualize Semantic Web knowledge bases. In particular we will present real use cases focused, but not limited to, resources relevant to plant biology.
We believe that Ondex can be a valid contribution to the adoption of the Semantic Web in Systems Biology research and in biomedical investigation more generally. We welcome feedback on our current import/export prototype and suggestions for the advancement of Ondex for the Semantic Web.
References
1. Ruttenberg, A. et. al.: Advancing translational research with the Semantic Web, BMC Bioinformatics, 8 (Suppl. 3): S2 (2007).
2. Köhler, J., Baumbach, J., Taubert, J., Specht, M., Skusa, A., Ruegg, A., Rawlings, C., Verrier, P., Philippi, S.: Graph-based analysis and visualization of experimental results with Ondex. Bioinformatics 22 (11):1383-1390 (2006).
3. Rawlings, C.: Semantic Data Integration for Systems Biology Research, Technology Track at ISMB’09, http://www.iscb.org/uploaded/css/36/11846.pdf (2009).
4. Splendiani, A. et. al.: Ondex semantic definition, (Web document) http://ondex.svn.sourceforge.net/viewvc/ondex/trunk/doc/semantics/ (2009)
Sustained correction of B-cell development and function in a murine model of X-linked agammaglobulinemia (XLA) using retroviral-mediated gene transfer
X-linked agammaglobulinemia (XLA) is a human immunodeficiency caused by mutations in Bruton tyrosine kinase (Btk) and characterized by an arrest in early B-cell development, near absence of serum immunoglobulin, and recurrent bacteria infections. Using Btk- and Tec-deficient mice (BtkTec-/-) as a model for XLA, we determined if Btk gene therapy could correct this disorder. Bone marrow (BM) from 5-fluorouracil (5FU)-treated BtkTec-/- mice was transduced with a retroviral vector expressing human Btk and transplanted into BtkTec-/- recipients. Mice engrafted with transduced hematopoietic cells exhibited rescue of both primary and peripheral B-lineage development, revocery of peritoneal B1 B cells, and correction of serum immunoglobulin M (IgM) and IgG3 levels. Gene transfer also restored T-independent type II immune responses, and B-cell antigen receptor (BCR) proliferative responses. B-cell progenitors derived from Btk-transduced stem cells exhibited higher levels of Btk expression than non-B cells; and marking studies demonstrated a selective advantage for Btk-transduced B-lineage cells. BM derived from primary recipients also rescued Btk-dependent function in secondary hosts that had received a transplant. Together, these data demonstrate that gene transfer into hematopoietic stem cells can reconstitute Btk-dependent B-cell development and function in vivo, and strongly support the feasibility of pursuing Btk gene transfer for XLA
RC J0311+0507: A Candidate for Superpowerful Radio Galaxies in the Early Universe at Redshift z=4.514
A strong emission line at 6703A has been detected in the optical spectrum for
the host galaxy (R=23.1) of the radio source RC J0311+0507 (4C+04.11). This
radio galaxy, with a spectral index of 1.31 in the frequency range 365-4850
MHz, is one of the ultrasteep spectrum objects from the deep survey of a sky
strip conducted with RATAN-600 in 1980-1981. We present arguments in favor of
the identification of this line with Ly\alpha at redshift z=4.514. In this
case, the object belongs to the group of extremely distant radio galaxies of
ultrahigh radio luminosity (P_{1400}=1.3 x 10^{29}W Hz^{-1}). Such power can be
provided only by a fairly massive black hole (~10^9M_\sun}) that formed in a
time less than the age of the Universe at the observed z(1.3 Gyr) or had a
primordial origin.Comment: 8 pages, 3 figure
The ultraviolet luminosity function of star-forming galaxies between redshifts of 0.6 and 1.2
We use ultraviolet imaging taken with the XMM-Newton Optical Monitor
telescope (XMM-OM), covering 280 square arcminutes in the UVW1 band (effective
wavelength 2910 Angstroms) to measure rest-frame ultraviolet (1500 Angstrom)
luminosity functions of galaxies with redshifts z between 0.6 and 1.2. The
XMM-OM data are supplemented by a large body of optical and infrared imaging to
provide photometric redshifts. The XMM-OM data have a significantly narrower
point-spread-function (resulting in less source confusion) and simpler
K-correction than the GALEX data previously employed in this redshift range.
Ultraviolet-bright active galactic nuclei are excluded to ensure that the
luminosity functions relate directly to the star-forming galaxy population.
Binned luminosity functions and parametric Schechter-function fits are derived
in two redshift intervals: 0.6<z<0.8 and 0.8<z<1.2. We find that the luminosity
function evolves such that the characteristic absolute magnitude M* is brighter
for 0.8<z<1.2 than for 0.6<z<0.8.Comment: 17 pages, 11 figures, accepted for publication in MNRA
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