475 research outputs found
The SuperMACHO Microlensing Survey
We present the first results from our next-generation microlensing survey,
the SuperMACHO project. We are using the CTIO 4m Blanco telescope and the
MOSAIC imager to carry out a search for microlensing toward the Large
Magellanic Cloud (LMC). We plan to ascertain the nature of the population
responsible for the excess microlensing rate seen by the MACHO project. Our
observing strategy is optimized to measure the differential microlensing rate
across the face of the LMC. We find this derivative to be relatively
insensitive to the details of the LMC's internal structure but a strong
discriminant between Galactic halo and LMC self lensing. In December 2003 we
completed our third year of survey operations. 2003 also marked the first year
of real-time microlensing alerts and photometric and spectroscopic followup. We
have extracted several dozen microlensing candidates, and we present some
preliminary light curves and related information. Similar to the MACHO project,
we find SNe behind the LMC to be a significant contaminant - this background
has not been completely removed from our current single-color candidate sample.
Our follow-up strategy is optimized to discriminate between SNe and true
microlensing.Comment: To appear in Proceedings of IAU Symposium 225: Impact of
Gravitational Lensing on Cosmology, 6 page
Spectral Identification of an Ancient Supernova using Light Echoes in the LMC
We report the successful identification of the type of the supernova
responsible for the supernova remnant SNR 0509-675 in the Large Magellanic
Cloud (LMC) using Gemini spectra of surrounding light echoes. The ability to
classify outbursts associated with centuries-old remnants provides a new window
into several aspects of supernova research and is likely to be successful in
providing new constraints on additional LMC supernovae as well as their
historical counterparts in the Milky Way Galaxy (MWG). The combined spectrum of
echo light from SNR 0509-675 shows broad emission and absorption lines
consistent with a supernova (SN) spectrum. We create a spectral library
consisting of 26 SNe Ia and 6 SN Ib/c that are time-integrated, dust-scattered
by LMC dust, and reddened by the LMC and MWG. We fit these SN templates to the
observed light echo spectrum using minimization as well as correlation
techniques, and we find that overluminous 91T-like SNe Ia with \dm15<0.9
match the observed spectrum best.Comment: 12 pages, 18 Figures, to be published in Ap
BVRI Light Curves for 29 Type Ia Supernovae
BVRI light curves are presented for 27 Type Ia supernovae discovered during
the course of the Calan/Tololo Survey and for two other SNe Ia observed during
the same period. Estimates of the maximum light magnitudes in the B, V, and I
bands and the initial decline rate parameter m15(B) are also given.Comment: 17 pages, figures and tables are not included (contact first author
if needed), to appear in the Astronomical Journa
Permanent Genetic Resources added to Molecular Ecology Resources Database 1 February 2013-31 March 2013
This article documents the addition of 142 microsatellite marker loci to the Molecular Ecology Resources database. Loci were developed for the following species: Agriophyllum squarrosum, Amazilia cyanocephala, Batillaria attramentaria, Fungal strain CTeY1 (Ascomycota), Gadopsis marmoratus, Juniperus phoenicea subsp. turbinata, Liriomyza sativae, Lupinus polyphyllus, Metschnikowia reukaufii, Puccinia striiformis and Xylocopa grisescens. These loci were cross-tested on the following species: Amazilia beryllina, Amazilia candida, Amazilia rutila, Amazilia tzacatl, Amazilia violiceps, Amazilia yucatanensis, Campylopterus curvipennis, Cynanthus sordidus, Hylocharis leucotis, Juniperus brevifolia, Juniperus cedrus, Juniperus osteosperma, Juniperus oxycedrus, Juniperus thurifera, Liriomyza bryoniae, Liriomyza chinensis, Liriomyza huidobrensis and Liriomyza trifolii. © 2013 John Wiley & Sons Ltd.Peer Reviewe
Testing LMC Microlensing Scenarios: The Discrimination Power of the SuperMACHO Microlensing Survey
Characterizing the nature and spatial distribution of the lensing objects
that produce the previously measured microlensing optical depth toward the
Large Magellanic Cloud (LMC) remains an open problem. We present an appraisal
of the ability of the SuperMACHO Project, a next-generation microlensing survey
directed toward the LMC, to discriminate between various proposed lensing
populations. We consider two scenarios: lensing by a uniform foreground screen
of objects and self-lensing by LMC stars. We have carried out extensive
simulations, based upon data obtained during the first year of the project, to
assess the SuperMACHO survey's ability to discriminate between these two
scenarios. We find that the event rate itself shows significant sensitivity to
the choice of the LMC luminosity function, limiting the conclusions which can
be drawn from the absolute rate. If instead we determine the differential event
rate across the LMC, we will decrease the impact of these systematic biases and
render our conclusions more robust. With this approach the SuperMACHO Project
should be able to distinguish between the two categories of lens populations.
This will provide important constraints on the nature of the lensing objects
and their contributions to the Galactic dark matter halo.Comment: 40 pages, 9 figures, to appear in ApJ 634 (2005
From Farm to Kitchen : How gender affects production diversity and the dietary intake of farm households in Ethiopia
Open Access via the Wiley Jisc Open Access Agreement. We would like to acknowledge the World Bank LSMS-ISA and Central Statistical Authority (CSA) of Ethiopia for making these data available for the public and Macaulay Development Trust (MDT) for the financial support. Euan Phimister also acknowledges support under the ESRC NEXUS programme in project IEAS/POO2501/1, Improving organic resource use in rural Ethiopia (IPORE). Deborah Roberts acknowledges the support of funding from the Scottish Government's Rural and Environment Science and Analytical Services Division(RESAS). Our thanks are also due to anonymous reviewers for their constructive comments on earlier versions of the paper.Peer reviewedPublisher PD
Gastric Juvenile Polyposis with High-Grade Dysplasia in Pachydermoperiostosis
Pachydermoperiostosis (PDP) is the primary form of hypertrophic osteoarthropathy. It is a very rare disease consisting of pachydermia, digital clubbing and radiologic periostosis. Various digestive symptoms in PDP are seen in 11–49% of patients and juvenile polyps may be found at gastric endoscopy. We report here the history of a patient with PDP who was referred for assessment of severe anemia. Endoscopy of the upper digestive tract showed multiple polyps of the stomach with two huge lesions exhibiting foci of high-grade dysplasia. This observation suggests that PDP can be considered as a precancerous condition of the stomach and systematic screening using endoscopy should be considered in these patients
Deep Sequencing Reveals Direct Targets of Gammaherpesvirus-Induced mRNA Decay and Suggests That Multiple Mechanisms Govern Cellular Transcript Escape
One characteristic of lytic infection with gammaherpesviruses, including Kaposi's sarcoma-associated herpesvirus (KSHV), Epstein-Barr virus (EBV) and murine herpesvirus 68 (MHV68), is the dramatic suppression of cellular gene expression in a process known as host shutoff. The alkaline exonuclease proteins (KSHV SOX, MHV-68 muSOX and EBV BGLF5) have been shown to induce shutoff by destabilizing cellular mRNAs. Here we extend previous analyses of cellular mRNA abundance during lytic infection to characterize the effects of SOX and muSOX, in the absence of other viral genes, utilizing deep sequencing technology (RNA-seq). Consistent with previous observations during lytic infection, the majority of transcripts are downregulated in cells expressing either SOX or muSOX, with muSOX acting as a more potent shutoff factor than SOX. Moreover, most cellular messages fall into the same expression class in both SOX- and muSOX-expressing cells, indicating that both factors target similar pools of mRNAs. More abundant mRNAs are more efficiently downregulated, suggesting a concentration effect in transcript targeting. However, even among highly expressed genes there are mRNAs that escape host shutoff. Further characterization of select escapees reveals multiple mechanisms by which cellular genes can evade downregulation. While some mRNAs are directly refractory to SOX, the steady state levels of others remain unchanged, presumably as a consequence of downstream effects on mRNA biogenesis. Collectively, these studies lay the framework for dissecting the mechanisms underlying the susceptibility of mRNA to destruction during lytic gammaherpesvirus infection
Coordinated Destruction of Cellular Messages in Translation Complexes by the Gammaherpesvirus Host Shutoff Factor and the Mammalian Exonuclease Xrn1
Several viruses encode factors that promote host mRNA degradation to silence gene expression. It is unclear, however, whether cellular mRNA turnover pathways are engaged to assist in this process. In Kaposi's sarcoma-associated herpesvirus this phenotype is enacted by the host shutoff factor SOX. Here we show that SOX-induced mRNA turnover is a two-step process, in which mRNAs are first cleaved internally by SOX itself then degraded by the cellular exonuclease Xrn1. SOX therefore bypasses the regulatory steps of deadenylation and decapping normally required for Xrn1 activation. SOX is likely recruited to translating mRNAs, as it cosediments with translation initiation complexes and depletes polysomes. Cleaved mRNA intermediates accumulate in the 40S fraction, indicating that recognition occurs at an early stage of translation. This is the first example of a viral protein commandeering cellular mRNA turnover pathways to destroy host mRNAs, and suggests that Xrn1 is poised to deplete messages undergoing translation in mammalian cells
Cataclysmic Variables from SDSS I. The First Results
The commissioning year of the Sloan Digital Sky Survey has demonstrated that
many cataclysmic variables have been missed in previous surveys with brighter
limits. We report the identification of 22 cataclysmic variables, of which 19
are new discoveries and 3 are known systems (SW UMa, BH Lyn and Vir4). A
compendium of positions, colors and characteristics of these systems obtained
from the SDSS photometry and spectroscopy is presented along with data obtained
during follow-up studies with the Apache Point Observatory (APO) and Manastash
Ridge Observatory (MRO) telescopes. We have determined orbital periods for 3 of
the new systems: two show dwarf nova outbursts, and the third is a likely
magnetic system with eclipses of its region of line emission. Based on these
results, we expect the completed survey to locate at least 400 new CVs. Most of
these will be faint systems with low accretion rates that will provide new
constraints on binary evolution models.Comment: 26 pages, 11 figures, 7 tables, accepted for publication in A
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