3,254 research outputs found
Benchmark Calculations for Perchlorate from Three Human Cohorts
The presence of low concentrations of perchlorate in some drinking water sources has led to concern regarding potential effects on the thyroid. In a recently published report, the National Academy of Sciences indicated that the perchlorate dose required to cause hypothyroidism in adults would probably be > 0.40 mg/kg-day for months or longer. In this study, we calculated benchmark doses for perchlorate from thyroid-stimulating hormone (TSH) and free thyroxine (T(4)) serum indicators from two occupational cohorts with long-term exposure to perchlorate, and from a clinical study of volunteers exposed to perchlorate for 2 weeks. The benchmark dose for a particular serum indicator was defined as the dose predicted to cause an additional 5 or 10% of persons to have a serum measurement outside of the normal range. Using the data from the clinical study, we estimated the half-life of perchlorate in serum at 7.5 hr and the volume of distribution at 0.34 L/kg. Using these estimates and measurements of perchlorate in serum or urine, doses in the occupational cohorts were estimated and used in benchmark calculations. Because none of the three studies found a significant effect of perchlorate on TSH or free T(4), all of the benchmark dose estimates were indistinguishable from infinity. The lower 95% statistical confidence limits on benchmark doses estimated from a combined analysis of the two occupational studies ranged from 0.21 to 0.56 mg/kg-day for free T(4) index and from 0.36 to 0.92 mg/kg-day for TSH. Corresponding estimates from the short-term clinical study were within these ranges
On the Distribution of Salient Objects in Web Images and its Influence on Salient Object Detection
It has become apparent that a Gaussian center bias can serve as an important
prior for visual saliency detection, which has been demonstrated for predicting
human eye fixations and salient object detection. Tseng et al. have shown that
the photographer's tendency to place interesting objects in the center is a
likely cause for the center bias of eye fixations. We investigate the influence
of the photographer's center bias on salient object detection, extending our
previous work. We show that the centroid locations of salient objects in
photographs of Achanta and Liu's data set in fact correlate strongly with a
Gaussian model. This is an important insight, because it provides an empirical
motivation and justification for the integration of such a center bias in
salient object detection algorithms and helps to understand why Gaussian models
are so effective. To assess the influence of the center bias on salient object
detection, we integrate an explicit Gaussian center bias model into two
state-of-the-art salient object detection algorithms. This way, first, we
quantify the influence of the Gaussian center bias on pixel- and segment-based
salient object detection. Second, we improve the performance in terms of F1
score, Fb score, area under the recall-precision curve, area under the receiver
operating characteristic curve, and hit-rate on the well-known data set by
Achanta and Liu. Third, by debiasing Cheng et al.'s region contrast model, we
exemplarily demonstrate that implicit center biases are partially responsible
for the outstanding performance of state-of-the-art algorithms. Last but not
least, as a result of debiasing Cheng et al.'s algorithm, we introduce a
non-biased salient object detection method, which is of interest for
applications in which the image data is not likely to have a photographer's
center bias (e.g., image data of surveillance cameras or autonomous robots)
Testing special relativity with geodetic VLBI
Geodetic Very Long Baseline Interferometry (VLBI) measures the group delay in
the barycentric reference frame. As the Earth is orbiting around the Solar
system barycentre with the velocity of 30 km/s, VLBI proves to be a handy
tool to detect the subtle effects of the special and general relativity theory
with a magnitude of . The theoretical correction for the
second order terms reaches up to 300~ps, and it is implemented in the geodetic
VLBI group delay model. The total contribution of the second order terms splits
into two effects - the variation of the Earth scale, and the deflection of the
apparent position of the radio source. The Robertson-Mansouri-Sexl (RMS)
generalization of the Lorenz transformation is used for many modern tests of
the special relativity theory. We develop an alteration of the RMS formalism to
probe the Lorenz invariance with the geodetic VLBI data. The kinematic approach
implies three parameters (as a function of the moving reference frame velocity)
and the standard Einstein synchronisation. A generalised relativistic model of
geodetic VLBI data includes all three parameters that could be estimated.
Though, since the modern laboratory Michelson-Morley and Kennedy-Thorndike
experiments are more accurate than VLBI technique, the presented equations may
be used to test the VLBI group delay model itself.Comment: Proceedings of the IAG 2017 Scientific Meeting, Kobe, Japa
A MATLAB app to assess, compare and validate new methods against their benchmarks
Emerging technologies for physiological signals and data collection enable the monitoring of patient health and well-being in real-life settings. This re-quires novel methods and tools to compare the validity of this kind of in-formation with that acquired in controlled environments using more costly and sophisticated technologies. In this paper, we describe a method and a MATLAB tool that relies on a standard sequence of statistical tests to com-pare features obtained using novel techniques with those acquired by means of benchmark procedures. After introducing the key steps of the proposed statistical analysis method, this paper describes its implementation in a MATLAB app, developed to support researchers in testing the extent to which a set of features, captured with a new methodology, can be considered a valid surrogate of that acquired employing gold standard techniques. An example of the application of the tool is provided in order to validate the method and illustrate the graphical user interface (GUI). The app develop-ment in MATLAB aims to improve its accessibility, foster its rapid adoption among the scientific community and its scalability into wider MATLAB tools
Universality, limits and predictability of gold-medal performances at the Olympic Games
Inspired by the Games held in ancient Greece, modern Olympics represent the
world's largest pageant of athletic skill and competitive spirit. Performances
of athletes at the Olympic Games mirror, since 1896, human potentialities in
sports, and thus provide an optimal source of information for studying the
evolution of sport achievements and predicting the limits that athletes can
reach. Unfortunately, the models introduced so far for the description of
athlete performances at the Olympics are either sophisticated or unrealistic,
and more importantly, do not provide a unified theory for sport performances.
Here, we address this issue by showing that relative performance improvements
of medal winners at the Olympics are normally distributed, implying that the
evolution of performance values can be described in good approximation as an
exponential approach to an a priori unknown limiting performance value. This
law holds for all specialties in athletics-including running, jumping, and
throwing-and swimming. We present a self-consistent method, based on normality
hypothesis testing, able to predict limiting performance values in all
specialties. We further quantify the most likely years in which athletes will
breach challenging performance walls in running, jumping, throwing, and
swimming events, as well as the probability that new world records will be
established at the next edition of the Olympic Games.Comment: 8 pages, 3 figures, 1 table. Supporting information files and data
are available at filrad.homelinux.or
Scalar-field Pressure in Induced Gravity with Higgs Potential and Dark Matter
A model of induced gravity with a Higgs potential is investigated in detail
in view of the pressure components related to the scalar-field excitations. The
physical consequences emerging as an artifact due to the presence of these
pressure terms are analysed in terms of the constraints parting from energy
density, solar-relativistic effects and galactic dynamics along with the dark
matter halos.Comment: 26 pages, 3 figures, Minor revision, Published in JHE
Anaphylaxis to husband's seminal plasma and treatment by local desensitization
Hypersensitivity to human seminal fluid is rare but can be life threatening. We report a case of IgE-mediated anaphylaxis to seminal plasma that was diagnosed by skin prick tests and successfully treated by local desensitization. A 32-year-old woman suffering from angioedema and hypotension after exposure to semen was treated with epinephrine upon admission. Skin prick tests and immunoblotting for IgE binding components showed that she was sensitized to her husband's seminal plasma. Local desensitization, which persisted for six months, was achieved by intravaginal administration of serial dilutions of her husband's seminal plasma
Magnetic Coupling in the Quiet Solar Atmosphere
Three kinds of magnetic couplings in the quiet solar atmosphere are
highlighted and discussed, all fundamentally connected to the Lorentz force.
First the coupling of the convecting and overshooting fluid in the surface
layers of the Sun with the magnetic field. Here, the plasma motion provides the
dominant force, which shapes the magnetic field and drives the surface dynamo.
Progress in the understanding of the horizontal magnetic field is summarized
and discussed. Second, the coupling between acoustic waves and the magnetic
field, in particular the phenomenon of wave conversion and wave refraction. It
is described how measurements of wave travel times in the atmosphere can
provide information about the topography of the wave conversion zone, i.e., the
surface of equal Alfv\'en and sound speed. In quiet regions, this surface
separates a highly dynamic magnetic field with fast moving magnetosonic waves
and shocks around and above it from the more slowly evolving field of high-beta
plasma below it. Third, the magnetic field also couples to the radiation field,
which leads to radiative flux channeling and increased anisotropy in the
radiation field. It is shown how faculae can be understood in terms of this
effect. The article starts with an introduction to the magnetic field of the
quiet Sun in the light of new results from the Hinode space observatory and
with a brief survey of measurements of the turbulent magnetic field with the
help of the Hanle effect.Comment: To appear in "Magnetic Coupling between the Interior and the
Atmosphere of the Sun", eds. S.S. Hasan and R.J. Rutten, Astrophysics and
Space Science Proceedings, Springer-Verlag, Heidelberg, Berlin, 200
Observational evidence for the accretion-disk origin for a radio jet in an active galaxy
Accretion of gas onto black holes is thought to power the relativistic jets of material ejected from active galactic nuclei (AGN) and the 'microquasars' located in our Galaxy(1-3). In microquasars, superluminal radio-emitting features appear and propagate along the jet shortly after sudden decreases in the Xray fluxes(1). This establishes a direct observational link between the black hole and the jet: the X-ray dip is probably caused by the disappearance of a section of the inner accretion disk(4) as it falls past the event horizon, while the remainder of the disk section is ejected into the jet, creating the appearance of a superluminal bright spot(5). No such connection has hitherto been established for AGN, because of insufficient multi-frequency data. Here we report the results of three years of monitoring the X-ray and radio emission of the galaxy 3C120. As has been observed for microquasars, we find that dips in the X-ray emission are followed by ejections of bright superluminal knots in the radio jet. The mean time between X-ray dips appears to scale roughly with the mass of the black hole, although there are at present only a few data points.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/62888/1/nature00772.pd
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