676 research outputs found

    Isolation of Escherichia coli O157:H7 from Intact Colon Fecal Samples of Swine1

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    Escherichia coli O157:H7 was recovered from colon fecal samples of pigs. Polymerase chain reaction confirmed two genotypes: isolates harboring the eaeA, stx1, and stx2 genes and isolates harboring the eaeA, stx1, and hly933 genes. We demonstrate that swine in the United States can harbor potentially pathogenic E. coli O157:H7

    The utility of MRI in predicting radiographic erosions in the metatarsophalangeal joints of the rheumatoid foot: a prospective longitudinal cohort study

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    INTRODUCTION: Magnetic resonance imaging (MRI) may reveal rheumatoid arthritis (RA) changes in the feet when hands are normal. The purpose of this study was to determine the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of a metatarsophalangeal (MTP) erosion on MRI to predict a subsequent radiographic erosion in the same joint. Similar analyses were performed for bone marrow edema, predicting a subsequent MRI erosion. Descriptive results of other lesions are reported. METHODS: Fifty patients with RA of less than 5 years' duration who were rheumatoid factor-positive and/or anti-cyclic citrullinated peptide-positive were recruited. Patients on anti-tumor necrosis factor (TNF) therapy were excluded. Anti-TNF therapy could begin after enrollment. MRI and radiographs of the 3rd, 4th, and 5th MTP joints bilaterally were taken at baseline and at 6, 12, and 24 months. Clinical data were collected. RESULTS: Fifty patients were recruited; 46 patients had suitable data. Results for MRI erosions predicting subsequent radiographic erosions for 6, 12, and 24 months, respectively, were as follows: sensitivity 0.75, 0.60, 0.75; specificity 0.93, 0.94, 0.94; PPV 0.086, 0.10, 0.17; NPV 0.998, 0.995, 0.995. Results for MRI bone marrow edema predicting MRI erosions at 6 and 12 months, respectively, revealed sensitivity 0.50, 0.67; specificity 0.97, 0.97; PPV 0.25, 0.50; NPV 0.99, 0.99. Synovitis was the most common finding and, when present in isolation, resolved on 67.3% of subsequent studies. MRI erosions persisted on subsequent studies with one exception. Forty-six percent of the cohort was on anti-TNF therapy after study inception. CONCLUSIONS: The PPV of MRI erosions to predict subsequent radiographic erosions was low. Similarly, the PPV of bone marrow edema to predict a later MRI erosion was low. Alternatively, the NPV of the absence of an MRI erosion or bone marrow edema predicts that a later radiographic erosion or MRI erosion will likely not develop. Anti-TNF therapies may have resulted in the lower-than-anticipated PPVs. MRI descriptions of bone edema may represent a more critical time to treat in order to avoid damage, whereas an MRI erosion represents more permanent damage. This study suggests that imaging modalities more sensitive than radiographs are necessary to monitor disease in the biologic era

    ASEPS-0 Testbed Interferometer

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    The ASEPS-O Testbed Interferometer is a long-baseline infrared interferometer optimized for high-accuracy narrow-angle astrometry. It is being constructed by JPL for NASA as a testbed for the future Keck Interferometer to demonstrate the technology for the astrometric detection of exoplanets from the ground. Recent theoretical and experimental work has shown that extremely high accuracy narrow-angle astrometry, at the level of tens of microarcseconds in an hour of integration time, can be achieved with a long-baseline interferometer measuring closely-spaced pairs of stars. A system with performance close to these limits could conduct a comprehensive search for Jupiter- and Saturn-mass planets around stars of all spectral types, and for short-period Uranus-mass planets around nearby M and K stars. The key features of an instrument which can achieve this accuracy are long baselines to minimize atmospheric and photon-noise errors, a dual-star feed to route the light from two separate stars to two beam combiners, cophased operation using an infrared fringe detector to increase sensitivity in order to locate reference stars near a bright target, and laser metrology to monitor systematic errors. The ASEPS-O Testbed Interferometer will incorporate these features, with a nominal baseline of 100 m, 50- cm siderostats, and 40-cm telescopes at the input to the dual- star feeds. The fringe detectors will operate at 2.2 micrometers , using NICMOS-III arrays in a fast-readout mode controlling high-speed laser-monitored delay lines. Development of the interferometer is in progress, with installation at Palomar Mountain planned to begin in 1994

    Dynamical Mass Measurement of the Young Spectroscopic Binary V343 Normae AaAb Resolved With the Gemini Planet Imager

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    We present new spatially resolved astrometry and photometry from the Gemini Planet Imager of the inner binary of the young multiple star system V343 Normae, which is a member of the beta Pictoris moving group. V343 Normae comprises a K0 and mid-M star in a ~4.5 year orbit (AaAb) and a wide 10" M5 companion (B). By combining these data with archival astrometry and radial velocities we fit the orbit and measure individual masses for both components of M_Aa = 1.10 +/- 0.10 M_sun and M_Ab = 0.290 +/- 0.018 M_sun. Comparing to theoretical isochrones, we find good agreement for the measured masses and JHK band magnitudes of the two components consistent with the age of the beta Pic moving group. We derive a model-dependent age for the beta Pic moving group of 26 +/- 3 Myr by combining our results for V343 Normae with literature measurements for GJ 3305, which is another group member with resolved binary components and dynamical masses.Comment: 12 pages, 7 figures. Accepted to A

    Improving and Assessing Planet Sensitivity of the GPI Exoplanet Survey with a Forward Model Matched Filter

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    We present a new matched filter algorithm for direct detection of point sources in the immediate vicinity of bright stars. The stellar Point Spread Function (PSF) is first subtracted using a Karhunen-Lo\'eve Image Processing (KLIP) algorithm with Angular and Spectral Differential Imaging (ADI and SDI). The KLIP-induced distortion of the astrophysical signal is included in the matched filter template by computing a forward model of the PSF at every position in the image. To optimize the performance of the algorithm, we conduct extensive planet injection and recovery tests and tune the exoplanet spectra template and KLIP reduction aggressiveness to maximize the Signal-to-Noise Ratio (SNR) of the recovered planets. We show that only two spectral templates are necessary to recover any young Jovian exoplanets with minimal SNR loss. We also developed a complete pipeline for the automated detection of point source candidates, the calculation of Receiver Operating Characteristics (ROC), false positives based contrast curves, and completeness contours. We process in a uniform manner more than 330 datasets from the Gemini Planet Imager Exoplanet Survey (GPIES) and assess GPI typical sensitivity as a function of the star and the hypothetical companion spectral type. This work allows for the first time a comparison of different detection algorithms at a survey scale accounting for both planet completeness and false positive rate. We show that the new forward model matched filter allows the detection of 50%50\% fainter objects than a conventional cross-correlation technique with a Gaussian PSF template for the same false positive rate.Comment: ApJ accepte

    Mitochondrial DNA Polymorphism A4917G Is Independently Associated with Age-Related Macular Degeneration

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    The objective of this study was to determine if MTND2*LHON4917G (4917G), a specific non-synonymous polymorphism in the mitochondrial genome previously associated with neurodegenerative phenotypes, is associated with increased risk for age-related macular degeneration (AMD). A preliminary study of 393 individuals (293 cases and 100 controls) ascertained at Vanderbilt revealed an increased occurrence of 4917G in cases compared to controls (15.4% vs.9.0%, p = 0.11). Since there was a significant age difference between cases and controls in this initial analysis, we extended the study by selecting Caucasian pairs matched at the exact age at examination. From the 1547 individuals in the Vanderbilt/Duke AMD population association study (including 157 in the preliminary study), we were able to match 560 (280 cases and 280 unaffected) on exact age at examination. This study population was genotyped for 4917G plus specific AMD-associated nuclear genome polymorphisms in CFH, LOC387715 and ApoE. Following adjustment for the listed nuclear genome polymorphisms, 4917G independently predicts the presence of AMD (OR = 2.16, 95%CI 1.20–3.91, p = 0.01). In conclusion, a specific mitochondrial polymorphism previously implicated in other neurodegenerative phenotypes (4917G) appears to convey risk for AMD independent of recently discovered nuclear DNA polymorphisms

    GPI spectra of HR 8799 c, d, and e from 1.5 to 2.4μ\mum with KLIP Forward Modeling

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    We explore KLIP forward modeling spectral extraction on Gemini Planet Imager coronagraphic data of HR 8799, using PyKLIP and show algorithm stability with varying KLIP parameters. We report new and re-reduced spectrophotometry of HR 8799 c, d, and e in H & K bands. We discuss a strategy for choosing optimal KLIP PSF subtraction parameters by injecting simulated sources and recovering them over a range of parameters. The K1/K2 spectra for HR 8799 c and d are similar to previously published results from the same dataset. We also present a K band spectrum of HR 8799 e for the first time and show that our H-band spectra agree well with previously published spectra from the VLT/SPHERE instrument. We show that HR 8799 c and d show significant differences in their H & K spectra, but do not find any conclusive differences between d and e or c and e, likely due to large error bars in the recovered spectrum of e. Compared to M, L, and T-type field brown dwarfs, all three planets are most consistent with mid and late L spectral types. All objects are consistent with low gravity but a lack of standard spectra for low gravity limit the ability to fit the best spectral type. We discuss how dedicated modeling efforts can better fit HR 8799 planets' near-IR flux and discuss how differences between the properties of these planets can be further explored.Comment: Accepted to AJ, 25 pages, 16 Figure

    Performance of the Gemini Planet Imager Non-Redundant Mask and spectroscopy of two close-separation binaries HR 2690 and HD 142527

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    The Gemini Planet Imager (GPI) contains a 10-hole non-redundant mask (NRM), enabling interferometric resolution in complement to its coronagraphic capabilities. The NRM operates both in spectroscopic (integral field spectrograph, henceforth IFS) and polarimetric configurations. NRM observations were taken between 2013 and 2016 to characterize its performance. Most observations were taken in spectroscopic mode with the goal of obtaining precise astrometry and spectroscopy of faint companions to bright stars. We find a clear correlation between residual wavefront error measured by the AO system and the contrast sensitivity by comparing phase errors in observations of the same source, taken on different dates. We find a typical 5-σ\sigma contrast sensitivity of 2−3 × 10−32-3~\times~10^{-3} at ∼λ/D\sim\lambda/D. We explore the accuracy of spectral extraction of secondary components of binary systems by recovering the signal from a simulated source injected into several datasets. We outline data reduction procedures unique to GPI's IFS and describe a newly public data pipeline used for the presented analyses. We demonstrate recovery of astrometry and spectroscopy of two known companions to HR 2690 and HD 142527. NRM+polarimetry observations achieve differential visibility precision of σ∼0.4%\sigma\sim0.4\% in the best case. We discuss its limitations on Gemini-S/GPI for resolving inner regions of protoplanetary disks and prospects for future upgrades. We summarize lessons learned in observing with NRM in spectroscopic and polarimetric modes.Comment: Accepted to AJ, 22 pages, 14 figure
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