243 research outputs found
A Side of Mercury Not Seen By Mariner 10
More than 60,000 images of Mercury were taken at ~29 deg elevation during two
sunrises, at 820 nm, and through a 1.35 m diameter off-axis aperture on the
SOAR telescope. The sharpest resolve 0.2" (140 km) and cover 190-300 deg
longitude -- a swath unseen by the Mariner 10 spacecraft -- at complementary
phase angles to previous ground-based optical imagery. Our view is comparable
to that of the Moon through weak binoculars. Evident are the large crater
Mozart shadowed on the terminator, fresh rayed craters, and other albedo
features keyed to topography and radar reflectivity, including the putative
huge ``Basin S'' on the limb. Classical bright feature Liguria resolves across
the northwest boundary of the Caloris basin into a bright splotch centered on a
sharp, 20 km diameter radar crater, and is the brightest feature within a
prominent darker ``cap'' (Hermean feature Solitudo Phoenicis) that covers the
northern hemisphere between longitudes 140-250 deg. The cap may result from
space weathering that darkens via a magnetically enhanced flux of the solar
wind, or that reddens low latitudes via high solar insolation.Comment: 7 pages, 4 PDF figures, pdfLaTeX, typos corrected, Fig. 2 modified
slightly to add crater diameters not given in published versio
DISCOMAP: A System to Support Distributed Cognition in Inquiring Organizations
Inquiring systems theory (Churchman, 1971), cognitive mapping (Lee, et al., 1992) and hermeneutics (Boland, et al., 1994) have provided the basis for systems to support organizational learning, distributed cognition, and knowledge management. Boland, et al. (1994) describe three entities in such systems and six principles for their design. Richardson (2005) argues that communication is neglected element in these systems and integrates Habermas’s (1984, 1985) theory of communicative action, specifically discursive action, to develop revised design principles. This paper describes DISCOMAP, a system that instantiates and tests the revised design principles using discussion forums and The Planners Laboratory©, a new software package that provides advanced modeling, graphical and network capabilities to provide shareable models with engaging visual interfaces for decision makers
Construction of the descriptive system for the assessment of quality of life AQoL-6D utility instrument
BackgroundMulti attribute utility (MAU) instruments are used to include the health related quality of life (HRQoL) in economic evaluations of health programs. Comparative studies suggest different MAU instruments measure related but different constructs. The objective of this paper is to describe the methods employed to achieve content validity in the descriptive system of the Assessment of Quality of Life (AQoL)-6D, MAU instrument.MethodsThe AQoL program introduced the use of psychometric methods in the construction of health related MAU instruments. To develop the AQoL-6D we selected 112 items from previous research, focus groups and expert judgment and administered them to 316 members of the public and 302 hospital patients. The search for content validity across a broad spectrum of health states required both formative and reflective modelling. We employed Exploratory Factor Analysis and Structural Equation Modelling (SEM) to meet these dual requirements.Results and DiscussionThe resulting instrument employs 20 items in a multi-tier descriptive system. Latent dimension variables achieve sensitive descriptions of 6 dimensions which, in turn, combine to form a single latent QoL variable. Diagnostic statistics from the SEM analysis are exceptionally good and confirm the hypothesised structure of the model.ConclusionsThe AQoL-6D descriptive system has good psychometric properties. They imply that the instrument has achieved construct validity and provides a sensitive description of HRQoL. This means that it may be used with confidence for measuring health related quality of life and that it is a suitable basis for modelling utilities for inclusion in the economic evaluation of health programs.<br /
FiberGLAST: a scintillating fiber approach to the GLAST mission
FiberGLAST is a scintillating fiber gamma-ray detector designed for the GLAST mission. The system described below provides superior effective area and field of view for modest cost and risk. An overview of the FiberGLAST instrument is presented, as well as a more detailed description of the principle elements of the primary detector volume. The triggering and readout electronics are described, and Monte Carlo Simulations of the instrument performance are presented
Development and testing of a fiber/multianode photomultiplier system for use on FiberGLAST
A scintillating fiber detector is currently being studied for the NASA Gamma-Ray Large Area Space Telescope (GLAST) mission. This detector utilizes modules composed of a thin converter sheet followed by an x, y plane of scintillating fibers to examine the shower of particles created by high energy gamma-rays interacting in the converter material. The detector is composed of a tracker with 90 such modular planes and a calorimeter with 36 planes. The two major component of this detector are the scintillating fibers and their associated photodetectors. Here we present current status of development and test result of both of these. The Hamamatsu R5900-00-M64 multianode photomultiplier tube (MAPMT) is the baseline readout device. A characterization of this device has been performed including noise, cross- talk, gain variation, vibration, and thermal/vacuum test. A prototype fiber/MAPMT system has been tested at the Center for Advanced Microstructures and Devices at Louisiana State University with a photon beam and preliminary results are presented
BRITE-Constellation reveals evidence for pulsations in the enigmatic binary Carinae
Car is a massive, eccentric binary with a rich observational history.
We obtained the first high-cadence, high-precision light curves with the
BRITE-Constellation nanosatellites over 6 months in 2016 and 6 months in 2017.
The light curve is contaminated by several sources including the Homunculus
nebula and neighboring stars, including the eclipsing binary
CPD592628. However, we found two coherent oscillations in the light
curve. These may represent pulsations that are not yet understood but we
postulate that they are related to tidally excited oscillations of Car's
primary star, and would be similar to those detected in lower-mass eccentric
binaries. In particular, one frequency was previously detected by van Genderen
et al. and Sterken et al. through the time period of 1974 to 1995 through
timing measurements of photometric maxima. Thus, this frequency seems to have
been detected for nearly four decades, indicating that it has been stable in
frequency over this time span. These pulsations could help provide the first
direct constraints on the fundamental parameters of the primary star if
confirmed and refined with future observations.Comment: 8 pages, 4 figures, accepted to MNRA
Estimation of GRB detection by FiberGLAST
FiberGLAST is one of several instrument concepts being developed for possible inclusion as the primary Gamma-ray Large Area Space Telescope (GLAST) instrument. The predicted FiberGLAST effective area is more than 12,000 cm2 for energies between 30 MeV and 300 GeV, with a field of view that is essentially flat from 0°–80°. The detector will achieve a sensitivity more than 10 times that of EGRET. We present results of simulations that illustrate the sensitivity of FiberGLAST for the detection of gamma-ray bursts
Beam test results for the FiberGLAST instrument
The FiberGLAST scintillating fiber telescope is a large-area instrument concept for NASA\u27s GLAST program. The detector is designed for high-energy gamma-ray astronomy, and uses plastic scintillating fibers to combine a photon pair tracking telescope and a calorimeter into a single instrument. A small prototype detector has been tested with high energy photons at the Thomas Jefferson National Accelerator Facility. We report on the result of this beam test, including scintillating fiber performance, photon track reconstruction, angular resolution, and detector efficiency
Optically trapped microsensors for microfluidic temperature measurement by fluorescence lifetime imaging microscopy
Increasing Drug Resistance in Extensively Drug-Resistant Tuberculosis, South Africa
We expanded second-line tuberculosis (TB) drug susceptibility testing for extensively drug-resistant Mycobacterium tuberculosis isolates from South Africa. Of 19 patients with extensively drug-resistant TB identified during February 2008–April 2009, 13 (68%) had isolates resistant to all 8 drugs tested. This resistance leaves no effective treatment with available drugs in South Africa
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