2,256 research outputs found
Determination of antimicrobial susceptibilities on infected urines without isolation
A method is described for the quick determination of the susceptibilities of various unidentified bacteria contained in an aqueous physiological fluid sample, particularly urine, to one or more antibiotics. A bacterial adenosine triphosphate (ATP) assay is carried out after the elimination of non-bacterial ATP to determine whether an infection exists. If an infection does exist, a portion of the sample is further processed, including subjecting parts of the portion to one or more antibiotics. Growth of the bacteria in the parts are determined, again by an ATP assay, to determine whether the unidentified bacteria in the sample are susceptible to the antibiotic or antibiotics under test
The nonlinear Bernstein-Schr\"odinger equation in Economics
In this paper we relate the Equilibrium Assignment Problem (EAP), which is
underlying in several economics models, to a system of nonlinear equations that
we call the "nonlinear Bernstein-Schr\"odinger system", which is well-known in
the linear case, but whose nonlinear extension does not seem to have been
studied. We apply this connection to derive an existence result for the EAP,
and an efficient computational method.Comment: 8 pages, submitted to Lecture Notes in Computer Scienc
Geometric View of Measurement Errors
The slope of the best fit line from minimizing the sum of the squared oblique
errors is the root of a polynomial of degree four. This geometric view of
measurement errors is used to give insight into the performance of various
slope estimators for the measurement error model including an adjusted fourth
moment estimator introduced by Gillard and Iles (2005) to remove the jump
discontinuity in the estimator of Copas (1972). The polynomial of degree four
is associated with a minimun deviation estimator. A simulation study compares
these estimators showing improvement in bias and mean squared error
Application of firefly luciferase assay for adenosine triphosphate (ATP) to antimicrobial drug sensitivity testing
The development of a rapid method for determining microbial susceptibilities to antibiotics using the firefly luciferase assay for adenosine triphosphate (ATP) is documented. The reduction of bacterial ATP by an antimicrobial agent was determined to be a valid measure of drug effect in most cases. The effect of 12 antibiotics on 8 different bacterial species gave a 94 percent correlation with the standard Kirby-Buer-Agar disc diffusion method. A 93 percent correlation was obtained when the ATP assay method was applied directly to 50 urine specimens from patients with urinary tract infections. Urine samples were centrifuged first to that bacterial pellets could be suspended in broth. No primary isolation or subculturing was required. Mixed cultures in which one species was predominant gave accurate results for the most abundant organism. Since the method is based on an increase in bacterial ATP with time, the presence of leukocytes did not interfere with the interpretation of results. Both the incubation procedure and the ATP assays are compatible with automation
Discovery and Characterization of Transiting SuperEarths Using an All-Sky Transit Survey and Follow-up by the James Webb Space Telescope
Doppler and transit surveys are finding extrasolar planets of ever smaller
mass and radius, and are now sampling the domain of superEarths (1-3 Earth
radii). Recent results from the Doppler surveys suggest that discovery of a
transiting superEarth in the habitable zone of a lower main sequence star may
be possible. We evaluate the prospects for an all-sky transit survey targeted
to the brightest stars, that would find the most favorable cases for
photometric and spectroscopic characterization using the James Webb Space
Telescope (JWST). We use the proposed Transiting Exoplanet Survey Satellite
(TESS) as representative of an all-sky survey. We couple the simulated TESS
yield to a sensitivity model for the MIRI and NIRSpec instruments on JWST. We
focus on the TESS planets with radii between Earth and Neptune. Our simulations
consider secondary eclipse filter photometry using JWST/MIRI, comparing the 11-
and 15-micron bands to measure CO2 absorption in superEarths, as well as
JWST/NIRSpec spectroscopy of water absorption from 1.7-3.0 microns, and CO2
absorption at 4.3-microns. We project that TESS will discover about eight
nearby habitable transiting superEarths. The principal sources of uncertainty
in the prospects for JWST characterization of habitable superEarths are
superEarth frequency and the nature of superEarth atmospheres. Based on our
estimates of these uncertainties, we project that JWST will be able to measure
the temperature, and identify molecular absorptions (water, CO2) in one to four
nearby habitable TESS superEarths.Comment: accepted for PASP; added discussion and figure for habitable planets;
abridged Abstrac
Quantifying structure in networks
We investigate exponential families of random graph distributions as a
framework for systematic quantification of structure in networks. In this paper
we restrict ourselves to undirected unlabeled graphs. For these graphs, the
counts of subgraphs with no more than k links are a sufficient statistics for
the exponential families of graphs with interactions between at most k links.
In this framework we investigate the dependencies between several observables
commonly used to quantify structure in networks, such as the degree
distribution, cluster and assortativity coefficients.Comment: 17 pages, 3 figure
SYMPA, a dedicated instrument for Jovian Seismology. II. Real performance and first results
Context. Due to its great mass and its rapid formation, Jupiter has played a
crucial role in shaping the Solar System. The knowledge of its internal
structure would strongly constrain the solar system formation mechanism.
Seismology is the most efficient way to probe directly the internal structure
of giant planets. Aims. SYMPA is the first instrument dedicated to the
observations of free oscillations of Jupiter. Principles and theoretical
performance have been presented in paper I. This second paper describes the
data processing method, the real instrumental performance and presents the
first results of a Jovian observation run, lead in 2005 at Teide Observatory.
Methods. SYMPA is a Fourier transform spectrometer which works at fixed optical
path difference. It produces Doppler shift maps of the observed object.
Velocity amplitude of Jupiter's oscillations is expected below 60 cm/s. Results
Despite light technical defects, the instrument demonstrated to work correctly,
being limited only by photon noise, after a careful analysis. A noise level of
about 12 cm/s has been reached on a 10-night observation run, with 21 % duty
cycle, which is 5 time better than previous similar observations. However, no
signal from Jupiter is clearly highlighted.Comment: 13 pages, 26 figure
Solar Magnetic Field Studies Using the 12-Micron Emission Lines. IV. Observations of a Delta-Region Solar Flare
We have recently developed the capability to make solar vector (Stokes IQUV)
magnetograms using the infrared line of MgI at 12.32 microns. On 24 April 2001,
we obtained a vector magnetic map of solar active region NOAA 9433,
fortuitously just prior to the occurrence of an M2 flare. Examination of a
sequence of SOHO/MDI magnetograms, and comparison with ground-based H-alpha
images, shows that the flare was produced by the cancellation of newly emergent
magnetic flux outside of the main sunspot. The very high Zeeman-sensitivity of
the 12-micron data allowed us to measure field strengths on a spatial scale
which was not directly resolvable. At the flare trigger site, opposite polarity
fields of 2700 and 1000 Gauss occurred within a single 2 arc-sec resolution
element, as revealed by two resolved Zeeman splittings in a single spectrum.
Our results imply an extremely high horizontal field strength gradient (5 G/km)
prior to the flare, significantly greater than seen in previous studies. We
also find that the magnetic energy of the cancelling fields was more than
sufficient to account for the flare's X-ray luminosity.Comment: 14 pages, 5 figures, accepted for Ap.
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