131 research outputs found
Astro-WISE: Chaining to the Universe
The recent explosion of recorded digital data and its processed derivatives
threatens to overwhelm researchers when analysing their experimental data or
when looking up data items in archives and file systems. While current hardware
developments allow to acquire, process and store 100s of terabytes of data at
the cost of a modern sports car, the software systems to handle these data are
lagging behind. This general problem is recognized and addressed by various
scientific communities, e.g., DATAGRID/EGEE federates compute and storage power
over the high-energy physical community, while the astronomical community is
building an Internet geared Virtual Observatory, connecting archival data.
These large projects either focus on a specific distribution aspect or aim to
connect many sub-communities and have a relatively long trajectory for setting
standards and a common layer. Here, we report "first light" of a very different
solution to the problem initiated by a smaller astronomical IT community. It
provides the abstract "scientific information layer" which integrates
distributed scientific analysis with distributed processing and federated
archiving and publishing. By designing new abstractions and mixing in old ones,
a Science Information System with fully scalable cornerstones has been
achieved, transforming data systems into knowledge systems. This break-through
is facilitated by the full end-to-end linking of all dependent data items,
which allows full backward chaining from the observer/researcher to the
experiment. Key is the notion that information is intrinsic in nature and thus
is the data acquired by a scientific experiment. The new abstraction is that
software systems guide the user to that intrinsic information by forcing full
backward and forward chaining in the data modelling.Comment: To be published in ADASS XVI ASP Conference Series, 2006, R. Shaw, F.
Hill and D. Bell, ed
The depolarisation properties of powerful extragalactic radio sources as a function of cosmic epoch
We use the observed polarisation properties of a sample of 26 powerful radio
galaxies and radio-loud quasars to constrain the conditions in the Faraday
screens local to the sources. We adopt the cosmological redshift, low-frequency
radio luminosity and physical size of the large-scale radio structures as our
`fundamental' parameters. We find no correlation of the radio spectral index
with any of the fundamental parameters. The observed rotation measure is also
independent of these parameters. The difference between the rotation measures
of the two lobes of an individual source as well as the dispersion of the
rotation measure show significant correlations with the source redshift, but
not with the radio luminosity or source size. Thus the small-scale structure
observed in the rotation measure is caused by a Faraday screen local to the
sources. The observed asymmetries between the lobes of our sources show no
significant trends with each other or other source properties. Finally, we show
that the commonly used model for the depolarisation of synchrotron radio
emission by foreground Faraday screens is inconsistent with our observations.
We apply alternative models to our data and show that they require a strong
increase of the dispersion of the rotation measure inside the Faraday screens
with cosmological redshift. Correcting our observations with these models for
redshift effects, we find a strong correlation of the depolarisation measure
with redshift and a significantly weaker correlation with radio luminosity. All
our results are consistent with a decrease in the order of the magnetic field
structure of the Faraday screen local to the sources for increasing
cosmological redshift. (abridged)Comment: 14 pages, 16 eps figures, accepted by MNRA
CENSORS: A Combined EIS-NVSS Survey Of Radio Sources. I. Sample definition, radio data and optical identifications
A new sample of radio sources, with the designated name CENSORS (A Combined
EIS-NVSS Survey Of Radio Sources), has been defined by combining the NRAO VLA
Sky Survey (NVSS) at 1.4 GHz with the ESO Imaging Survey (EIS) Patch D, a 3 by
2 degree region of sky centred at 09 51 36.0, -21 00 00 (J2000). New radio
observations of 199 NVSS radio sources with NVSS flux densities S(1.4GHz) >
7.8mJy are presented, and compared with the EIS I-band imaging observations
which reach a depth of I~23; optical identifications are obtained for over
two-thirds of the ~150 confirmed radio sources within the EIS field. The radio
sources have a median linear size of 6 arcseconds, consistent with the trend
for lower flux density radio sources to be less extended. Other radio source
properties, such as the lobe flux density ratios, are consistent with those of
brighter radio source samples. From the optical information, 30-40% of the
sources are expected to lie at redshifts z >~ 1.5.
One of the key goals of this survey is to accurately determine the high
redshift evolution of the radio luminosity function. These radio sources are at
the ideal flux density level to achieve this goal; at redshifts z~2 they have
luminosities which are around the break of the luminosity function and so
provide a much more accurate census of the radio source population at those
redshifts than the existing studies of extreme, high radio power sources. Other
survey goals include investigating the dual--population unification schemes for
radio sources, studying the radio luminosity dependence of the evolution of
radio source environments, and understanding the radio power dependence of the
K-z relation for radio galaxies.Comment: Accepted for publication in MNRAS. 28 pages plus 36 reduced
resolution jpeg figures. A postscript version with full resolution figures
included in the text is available from
http://www.roe.ac.uk/~pnb/censors.ps.g
A new search for distant radio galaxies in the southern hemisphere - I. Sample definition and radio properties
This paper introduces a new program to find high-redshift radio galaxies in
the southern hemisphere through ultra-steep spectrum (USS) selection. We define
a sample of 234 USS radio sources with spectral indices alpha_408^843 < -1.0
and flux densities S_408 > 200 mJy in a region of 0.35 sr, chosen by
cross-correlating the revised 408 MHz Molonglo Reference Catalogue, the 843 MHz
Sydney University Molonglo Sky Survey and the 1400 MHz NRAO VLA Sky Survey in
the overlap region -40 deg < delta < -30 deg. We present Australia Telescope
Compact Array (ATCA) high-resolution 1384 and 2368 MHz radio data for each
source, which we use to analyse the morphological, spectral index and
polarization properties of our sample. We find that 85 per cent of the sources
have observed-frame spectral energy distributions that are straight over the
frequency range 408-2368 MHz, and that, on average, sources with smaller
angular sizes have slightly steeper spectral indices and lower fractional
linear polarization. Fractional polarization is anti-correlated with flux
density at both 1400 and 2368 MHz. We also use the ATCA data to determine
observed-frame Faraday rotation measures for half of the sample.Comment: 28 pages, 9 figures, 10 tables, accepted for publication in MNRAS.
Correct version of SUMSS catalogue now noted in Section 2.1.2; analysis and
conclusions unchanged. A higher-resolution version of Figure 1 is available
at http://www.physics.usyd.edu.au/~jess/papers.htm
The JVAS/CLASS search for 6-arcsec to 15-arcsec image separation lensing
The Jodrell Bank-VLA Astrometric Survey (JVAS) and the Cosmic Lens All Sky Survey (CLASS) have been systematically searched for multiple gravitational imaging of sources with image separations between 6 arcsec and 15 arcsec, associated with galaxy group and cluster lensing masses. The radio and optical follow-up observations of all candidates are presented. From a total of similar to 15000 sources only one weak candidate remains and this is not contained in the statistically complete sample of flat-spectrum JVAS/CLASS sources of 11670 sources. A simple Press-Schechter analysis is performed. For singular isothermal sphere lenses the lack of multiple image systems is inconsistent with the currently favoured cosmologies with (Omega (M), Omega (A)) = (0.3, 0.7) at the 4.2 sigma level. Cored isothermal lenses reduce the expected number of lens systems and we suggest that the most probable interpretation of our results is that the surface mass density of groups and clusters of galaxies is not high enough to cause multiple imaging and the presence of the mass concentrations associated with individual galaxies is required to produce image separations such as those in B0957+561
The Enhanced Resolution Imager and Spectrograph for the VLT
ERIS, the Enhanced Resolution Imager and Spectrograph, is an instrument that
both extends and enhances the fundamental diffraction limited imaging and
spectroscopy capability for the VLT. It replaces two instruments that were
being maintained beyond their operational lifetimes, combines their
functionality on a single focus, provides a new wavefront sensing module for
natural and laser guide stars that makes use of the Adaptive Optics Facility,
and considerably improves on their performance. The observational modes ERIS
provides are integral field spectroscopy at 1-2.5 {\mu}m, imaging at 1-5 {\mu}m
with several options for high contrast imaging, and longslit spectroscopy at
3-4 {\mu}m, The instrument is installed at the Cassegrain focus of UT4 at the
VLT and, following its commissioning during 2022, has been made available to
the community.Comment: 19 pages with 29 figures; submitted to A&
Host Specific Diversity in Lactobacillus johnsonii as Evidenced by a Major Chromosomal Inversion and Phage Resistance Mechanisms
Genetic diversity and genomic rearrangements are a driving force in bacterial evolution and niche adaptation. We sequenced and annotated the genome of Lactobacillus johnsonii DPC6026, a strain isolated from the porcine intestinal tract. Although the genome of DPC6026 is similar in size (1.97mbp) and GC content (34.8%) to the sequenced human isolate L. johnsonii NCC 533, a large symmetrical inversion of approximately 750 kb differentiated the two strains. Comparative analysis among 12 other strains of L. johnsonii including 8 porcine, 3 human and 1 poultry isolate indicated that the genome architecture found in DPC6026 is more common within the species than that of NCC 533. Furthermore a number of unique features were annotated in DPC6026, some of which are likely to have been acquired by horizontal gene transfer (HGT) and contribute to protection against phage infection. A putative type III restriction-modification system was identified, as were novel Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) elements. Interestingly, these particular elements are not widely distributed among L. johnsonii strains. Taken together these data suggest intra-species genomic rearrangements and significant genetic diversity within the L. johnsonii species and indicate towards a host-specific divergence of L. johnsonii strains with respect to genome inversion and phage exposure
Registered Replication Report: Dijksterhuis and van Knippenberg (1998)
Dijksterhuis and van Knippenberg (1998) reported that participants primed with a category associated with intelligence ("professor") subsequently performed 13% better on a trivia test than participants primed with a category associated with a lack of intelligence ("soccer hooligans"). In two unpublished replications of this study designed to verify the appropriate testing procedures, Dijksterhuis, van Knippenberg, and Holland observed a smaller difference between conditions (2%-3%) as well as a gender difference: Men showed the effect (9.3% and 7.6%), but women did not (0.3% and -0.3%). The procedure used in those replications served as the basis for this multilab Registered Replication Report. A total of 40 laboratories collected data for this project, and 23 of these laboratories met all inclusion criteria. Here we report the meta-analytic results for those 23 direct replications (total N = 4,493), which tested whether performance on a 30-item general-knowledge trivia task differed between these two priming conditions (results of supplementary analyses of the data from all 40 labs, N = 6,454, are also reported). We observed no overall difference in trivia performance between participants primed with the "professor" category and those primed with the "hooligan" category (0.14%) and no moderation by gender
International Society of Sports Nutrition Position Stand: Probiotics.
Position statement: The International Society of Sports Nutrition (ISSN) provides an objective and critical review of the mechanisms and use of probiotic supplementation to optimize the health, performance, and recovery of athletes. Based on the current available literature, the conclusions of the ISSN are as follows: 1)Probiotics are live microorganisms that, when administered in adequate amounts, confer a health benefit on the host (FAO/WHO).2)Probiotic administration has been linked to a multitude of health benefits, with gut and immune health being the most researched applications.3)Despite the existence of shared, core mechanisms for probiotic function, health benefits of probiotics are strain- and dose-dependent.4)Athletes have varying gut microbiota compositions that appear to reflect the activity level of the host in comparison to sedentary people, with the differences linked primarily to the volume of exercise and amount of protein consumption. Whether differences in gut microbiota composition affect probiotic efficacy is unknown.5)The main function of the gut is to digest food and absorb nutrients. In athletic populations, certain probiotics strains can increase absorption of key nutrients such as amino acids from protein, and affect the pharmacology and physiological properties of multiple food components.6)Immune depression in athletes worsens with excessive training load, psychological stress, disturbed sleep, and environmental extremes, all of which can contribute to an increased risk of respiratory tract infections. In certain situations, including exposure to crowds, foreign travel and poor hygiene at home, and training or competition venues, athletes' exposure to pathogens may be elevated leading to increased rates of infections. Approximately 70% of the immune system is located in the gut and probiotic supplementation has been shown to promote a healthy immune response. In an athletic population, specific probiotic strains can reduce the number of episodes, severity and duration of upper respiratory tract infections.7)Intense, prolonged exercise, especially in the heat, has been shown to increase gut permeability which potentially can result in systemic toxemia. Specific probiotic strains can improve the integrity of the gut-barrier function in athletes.8)Administration of selected anti-inflammatory probiotic strains have been linked to improved recovery from muscle-damaging exercise.9)The minimal effective dose and method of administration (potency per serving, single vs. split dose, delivery form) of a specific probiotic strain depends on validation studies for this particular strain. Products that contain probiotics must include the genus, species, and strain of each live microorganism on its label as well as the total estimated quantity of each probiotic strain at the end of the product's shelf life, as measured by colony forming units (CFU) or live cells.10)Preclinical and early human research has shown potential probiotic benefits relevant to an athletic population that include improved body composition and lean body mass, normalizing age-related declines in testosterone levels, reductions in cortisol levels indicating improved responses to a physical or mental stressor, reduction of exercise-induced lactate, and increased neurotransmitter synthesis, cognition and mood. However, these potential benefits require validation in more rigorous human studies and in an athletic population
Identification and characterization of the eps (Exopolysaccharide) gene cluster from Streptococcus thermophilus Sfi6.
We report the identification and characterization of the eps gene cluster of Streptococcus thermophilus Sfi6 required for exopolysaccharide (EPS) synthesis. This report is the first genetic work concerning EPS production in a food microorganism. The EPS secreted by this strain consists of the following tetrasaccharide repeating unit:-->3)-beta-D-Galp-(1-->3)-[alpha-D-Galp-(1-->6)]-beta-D- D-Galp-(1-->3)-alpha-D-Galp-D-GalpNAc-(1-->. The genetic locus The genetic locus was identified by Tn916 mutagenesis in combination with a plate assay to identify Eps mutants. Sequence analysis of the gene region, which was obtained from subclones of a genomic library of Sfi6, revealed a 15.25-kb region encoding 15 open reading frames. EPS expression in the non-EPS-producing heterologous host, Lactococcus lactis MG1363, showed that within the 15.25-kb region, a region with a size of 14.52 kb encoding the 13 genes epsA to epsM was capable of directing EPS synthesis and secretion in this host. Homology searches of the predicted proteins in the Swiss-Prot database revealed high homology (40 to 68% identity) for epsA, B, C, D, and E and the genes involved in capsule synthesis in Streptococcus pneumoniae and Streptococcus agalactiae. Moderate to low homology (37 to 18% identity) was detected for epsB, D, F, and H and the genes involved in capsule synthesis in Staphylococcus aureus for epsC, D, and E and the genes involved in exopolysaccharide I (EPSI) synthesis in Rhizobium meliloti for epsC to epsJ and the genes involved in lipopolysaccharide synthesis in members of the Enterobacteriaceae, and finally for eps K and lipB of Neisseria meningitidis. Genes (epsJ, epsL, and epsM) for which the predicted proteins showed little or no homology with proteins in the Swiss-Prot database were shown to be involved in EPS synthesis by single-crossover gene disruption experiments
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