2,799 research outputs found
A Cereal Chemist's Quick Guide to Genetics, Plant Breeding and BioIT
This book is intended as a guide for cereal chemists in quality testing laboratories and grain product development companies, to help them in their understanding of fundamental genetics, functional genomics and other concepts of relevance during their interactions with crop breeding programs. Consequently the emphasis is on quick definitions of terms and concepts, assuming that the expertise of the reader is predominantly in another field.Established and supported under the Australian Government’s Cooperative Research Centre Progra
The Identification of Extreme Asymptotic Giant Branch Stars and Red Supergiants in M33 by 24 {\mu}m Variability
We present the first detection of 24 {\mu}m variability in 24 sources in the
Local Group galaxy M33. These results are based on 4 epochs of MIPS
observations, which are irregularly spaced over ~750 days. We find that these
sources are constrained exclusively to the Holmberg radius of the galaxy, which
increases their chances of being members of M33. We have constructed spectral
energy distributions (SEDs) ranging from the optical to the sub-mm to
investigate the nature of these objects. We find that 23 of our objects are
most likely heavily self-obscured, evolved stars; while the remaining source is
the Giant HII region, NGC 604. We believe that the observed variability is the
intrinsic variability of the central star reprocessed through their
circumstellar dust shells. Radiative transfer modeling was carried out to
determine their likely chemical composition, luminosity, and dust production
rate (DPR). As a sample, our modeling has determined an average luminosity of
(3.8 0.9) x 10 L and a total DPR of (2.3 0.1) x
10 M yr. Most of the sources, given the high DPRs and
short wavelength obscuration, are likely "extreme" AGB (XAGB) stars. Five of
the sources are found to have luminosities above the classical AGB limit
(M 54,000 L), which classifies them as probably
red supergiants (RSGs). Almost all of the sources are classified as oxygen
rich. As also seen in the LMC, a significant fraction of the dust in M33 is
produced by a handful of XAGB and RSG stars.Comment: 36 pages, 14 figures, 4 tables, Accepted for publication in A
Community-onset Staphylococcus aureus infections presenting to general practices in South-eastern Australia
Community-acquired Staphylococcus aureus infections are a public health concern, yet little is known about infections that do not present to hospital. We identified community-onset S. aureus infections via specimens submitted to a community-based pathology service. Referring doctors confirmed eligibility and described infection site, severity and treatment. Isolates were characterized on antibiotic resistance, PFGE, MLST/SCCmec, and Panton–Valentine leukocidin (PVL), representing 106 community-onset infections; 34 non-multiresistant methicillin-resistant S. aureus (nmMRSA) (resistant to <3 non-β-lactam antibiotics), 15 multiply antibiotic-resistant MRSA (mMRSA) and 57 methicillin-sensitive S. aureus (MSSA). Most (93%) were skin and soft tissue infections. PVL genes were carried by 42% of nmMRSA isolates [95% confidence interval (CI) 26–61] and 15% of MSSA (95% CI 8–28). PVL was associated with infections of the trunk, head or neck (56•4% vs. 24•3%, P = 0•005) in younger patients (23 vs. 52 years, P < 0•001), and with boils or abscesses (OR 8•67, 95% CI 2•9–26•2), suggesting underlying differences in exposure and/or pathogenesis
Retired A Stars and Their Companions VI. A Pair of Interacting Exoplanet Pairs Around the Subgiants 24 Sextanis and HD200964
We report radial velocity measurements of the G-type subgiants 24 Sextanis
(=HD90043) and HD200964. Both are massive, evolved stars that exhibit periodic
variations due to the presence of a pair of Jovian planets. Photometric
monitoring with the T12 0.80m APT at Fairborn Observatory demonstrates both
stars to be constant in brightness to <= 0.002 mag, thus strengthening the
planetary interpretation of the radial velocity variations. 24 Sex b,c have
orbital periods of 453.8 days and 883~days, corresponding to semimajor axes
1.333 AU and 2.08 AU, and minimum masses (Msini) 1.99 Mjup and 0.86 Mjup,
assuming a stellar mass 1.54 Msun. HD200964 b,c have orbital periods of 613.8
days and 825 days, corresponding to semimajor axes 1.601 AU and 1.95 AU, and
minimum masses 1.85 Mjup and 0.90 Mjup, assuming M* = 1.44 Msun. We also carry
out dynamical simulations to properly account for gravitational interactions
between the planets. Most, if not all, of the dynamically stable solutions
include crossing orbits, suggesting that each system is locked in a mean motion
resonance that prevents close encounters and provides long-term stability. The
planets in the 24 Sex system likely have a period ratio near 2:1, while the
HD200964 system is even more tightly packed with a period ratio close to 4:3.
However, we caution that further radial velocity observations and more detailed
dynamical modelling will be required to provide definitive and unique orbital
solutions for both cases, and to determine whether the two systems are truly
resonant.Comment: AJ accepte
A New Planet Around an M Dwarf: Revealing a Correlation Between Exoplanets and Stellar Mass
We report precise Doppler measurements of GJ317 (M3.5V) that reveal the
presence of a planet with a minimum mass Msini = 1.2 Mjup in an eccentric,
692.9 day orbit. GJ317 is only the third M dwarf with a Doppler-detected Jovian
planet. The residuals to a single-Keplerian fit show evidence of a possible
second orbital companion. The inclusion of an additional Jupiter-mass planet (P
= 2700 days, Msini = 0.83 Mjup) improves the quality of fit significantly,
reducing the rms from 12.5 m/s to 6.32 m/s. A false-alarm test yields a 1.1%
probability that the curvature in the residuals of the single-planet fit is due
to random fluctuations, lending additional credibility to the two-planet model.
However, our data only marginally constrain a two-planet fit and further
monitoring is necessary to fully characterize the properties of the second
planet. To study the effect of stellar mass on Jovian planet occurrence we
combine our samples of M stars, Solar-mass dwarfs and intermediate-mass
subgiants. We find a positive correlation between stellar mass and the
occurrence rate of Jovian planets within 2.5 AU; the former A-type stars in our
sample are nearly 5 times more likely than the M dwarfs to harbor a giant
planet. Our analysis shows that the correlation between Jovian planet
occurrence and stellar mass remains even after accounting for the effects of
stellar metallicity.Comment: ApJ accepted, 27 pages, 6 figures, 3 table
Non-detection of previously reported transits of HD 97658b with MOST photometry
The radial velocity-discovered exoplanet HD 97658b was recently announced to
transit, with a derived planetary radius of 2.93 \pm 0.28 R_{Earth}. As a
transiting super-Earth orbiting a bright star, this planet would make an
attractive candidate for additional observations, including studies of its
atmospheric properties. We present and analyze follow-up photometric
observations of the HD 97658 system acquired with the MOST space telescope. Our
results show no transit with the depth and ephemeris reported in the
announcement paper. For the same ephemeris, we rule out transits for a planet
with radius larger than 2.09 R_{Earth}, corresponding to the reported 3\sigma
lower limit. We also report new radial velocity measurements which continue to
support the existence of an exoplanet with a period of 9.5 days, and obtain
improved orbital parameters.Comment: 16 pages, 4 figures; 1 Table; accepted for publication in ApJL,
includes changes made in response to the referee repor
Characteristics of potential gasifier fuels in selected regions of the Lake Victoria Basin
All countries in the Lake Victoria Basin depend mostly on hydroelectric power for the provision of energy. Gasification technology has a high potential for reducing biomass energy consumption whilst increasing access to modern energy services. The key aspect for the failure of gasification operations in the Lake Victoria Basin is inadequate adaptation of gasification equipment to fuel characteristics, lack of fuel specification and inappropriate material choice. We therefore investigated the thermo-chemical characterisation of six biomass fuels, namely Pinus caribaea, Calitris robusta, Cupressus lusitanica, Eucalyptus grandis, Pinus patula and sugarcane bagasse from selected regions of the Lake Victoria Basin. Ultimate analysis was done using a Flash 2000 elemental analyser. Moisture content, ash content and volatile matter were determined in oven and muffle furnaces while heating values were determined using a Gallenkamp calorimeter. The mean percentage levels obtained indicate that all six biomass fuels had a mean range for nitrogen of 0.07±0
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