4,241 research outputs found
Photometric Variability in the Faint Sky Variability Survey
The Faint Sky Variability Survey (FSVS) is aimed at finding photometric
and/or astrometric variable objects between 16th and 24th mag on time-scales
between tens of minutes and years with photometric precisions ranging from 3
millimag to 0.2 mag. An area of 23 deg, located at mid and high Galactic
latitudes, was covered using the Wide Field Camera (WFC) on the 2.5-m Isaac
Newton Telescope (INT) on La Palma. Here we present some preliminary results on
the variability of sources in the FSVS.Comment: 4 pages, 3 figures, to appear in 14th European Workshop on White
Dwarfs, ASP Conference Series, eds. D. Koester, S. Moehle
Supporting Intelligence Analysts with a Trust-Based Question-Answering System
Intelligence analysts have to work in highly demanding circumstances. This causes mistakes with severe consequences, which is the reason that support systems for intelligence analysts have been developed. The support system proposed in this paper assists humans by offering support that improves their performance, without reducing them in their freedom. This is done with a trust-based question answering system (T-QAS). An important part of T-QAS are trust models which keep track of trust in each of the agents gathering information. Using these trust models, the system can support the intelligence analyst by: 1) helping to decide which agents are trusted enough to receive questions, 2) providing information about the reliability of each of the sources used, and 3) advising in making decisions based on information from possibly unreliable sources. An implementation of last two capabilities of T-QAS is evaluated in an experiment in which participants perform a decision making task with information from possibly unreliable sources. Results show that the proposed T-QAS support indeed helps participants to improve their performance. We therefore expect that future intelligence analyst support systems can benefit from the inclusion of T-QAS
Group Schema Therapy for Eating Disorders: A Pilot Study
This paper describes the use of Group Schema Therapy for Eating Disorders (ST-E-g) in a case series of eight participants with chronic eating disorders and high levels of co-morbidity. Treatment was comprised of 20 sessions which included cognitive, experiential, and interpersonal strategies, with an emphasis on behavioral change. Specific schema-based strategies focused on bodily felt-sense and body-image, as well as emotional regulation skills. Six attended until end of treatment, two dropped-out at mid-treatment. Eating disorder severity, global schema severity, shame, and anxiety levels were reduced between pre- and post-therapy, with a large effect size at follow-up. Clinically significant improvement in eating severity was found in four out of six completers. Group completers showed a mean reduction in schema severity of 43% at post-treatment, and 59% at follow-up. By follow-up, all completers had achieved over 60% improvement in schema severity. Self-report feedback suggests that group factors may catalyze the change process in schema therapy by increasing perceptions of support and encouragement to take risks and try out new behaviors, whilst providing a de-stigmatizing and de-shaming therapeutic experience
Dynamically-Coupled Oscillators -- Cooperative Behavior via Dynamical Interaction --
We propose a theoretical framework to study the cooperative behavior of
dynamically coupled oscillators (DCOs) that possess dynamical interactions.
Then, to understand synchronization phenomena in networks of interneurons which
possess inhibitory interactions, we propose a DCO model with dynamics of
interactions that tend to cause 180-degree phase lags. Employing an approach
developed here, we demonstrate that although our model displays synchronization
at high frequencies, it does not exhibit synchronization at low frequencies
because this dynamical interaction does not cause a phase lag sufficiently
large to cancel the effect of the inhibition. We interpret the disappearance of
synchronization in our model with decreasing frequency as describing the
breakdown of synchronization in the interneuron network of the CA1 area below
the critical frequency of 20 Hz.Comment: 10 pages, 3 figure
GRB990712: First Indication of Polarization Variability in a Gamma-ray Burst Afterglow
We report the detection of significant polarization in the optical afterglow
of GRB990712 on three instances 0.44, 0.70 and 1.45 days after the gamma-ray
burst, with (P, theta) being (2.9% +- 0.4%, 121.1 degr +- 3.5 degr), (1.2% +-
0.4%, 116.2 degr +- 10.1 degr) and (2.2% +- 0.7%, 139.2 degr +- 10.4 degr)
respectively. The polarization is intrinsic to the afterglow. The degree of
polarization is not constant, and smallest at the second measurement. The
polarization angle does not vary significantly during these observations. We
find that none of the existing models predict such polarization variations at
constant polarization angle, and suggest ways in which these models might be
modified to accommodate the observed behavior of this afterglow.Comment: 10 pages including 6 figures, accepted by ApJ. Uses aastex 5.
Phase Diagram for the Winfree Model of Coupled Nonlinear Oscillators
In 1967 Winfree proposed a mean-field model for the spontaneous
synchronization of chorusing crickets, flashing fireflies, circadian pacemaker
cells, or other large populations of biological oscillators. Here we give the
first bifurcation analysis of the model, for a tractable special case. The
system displays rich collective dynamics as a function of the coupling strength
and the spread of natural frequencies. Besides incoherence, frequency locking,
and oscillator death, there exist novel hybrid solutions that combine two or
more of these states. We present the phase diagram and derive several of the
stability boundaries analytically.Comment: 4 pages, 4 figure
Inference from controversial arguments
International audienceWe present new careful semantics within Dung's theory of argumentation. Under such careful semantics, two arguments cannot belong to the same extension whenever one of them indirectly attacks a third argument while the other one indirectly defends the third.We argue that our semantics lead to a better handling of controversial arguments than Dung's ones in some settings. We compare the careful inference relations induced by our semantics w.r.t. cautiousness; we also compare them with the inference relations induced by Dung's semantic
Spike-Train Responses of a Pair of Hodgkin-Huxley Neurons with Time-Delayed Couplings
Model calculations have been performed on the spike-train response of a pair
of Hodgkin-Huxley (HH) neurons coupled by recurrent excitatory-excitatory
couplings with time delay. The coupled, excitable HH neurons are assumed to
receive the two kinds of spike-train inputs: the transient input consisting of
impulses for the finite duration (: integer) and the sequential input
with the constant interspike interval (ISI). The distribution of the output ISI
shows a rich of variety depending on the coupling strength and the
time delay. The comparison is made between the dependence of the output ISI for
the transient inputs and that for the sequential inputs.Comment: 19 pages, 4 figure
Short timescale variability in the Faint Sky Variability Survey
We present the V band variability analysis of the point sources in the Faint
Sky Variability Survey on time scales from 24 minutes to tens of days. We find
that about one percent of the point sources down to V = 24 are variables. We
discuss the variability detection probabilities for each field depending on
field sampling, amplitude and timescale of the variability. The combination of
colour and variability information allows us to explore the fraction of
variable sources for different spectral types. We find that about 50 percent of
the variables show variability timescales shorter than 6 hours. The total
number of variables is dominated by main sequence sources. The distribution of
variables with spectral type is fairly constant along the main sequence, with 1
per cent of the sources being variable, except at the blue end of the main
sequence, between spectral types F0--F5, where the fraction of variable sources
increases to about 2 percent. For bluer sources, above the main sequence, this
percentage increases to about 3.5. We find that the combination of the sampling
and the number of observations allows us to determine the variability
timescales and amplitudes for a maximum of 40 percent of the variables found.
About a third of the total number of short timescale variables found in the
survey were not detected in either B or/and I. These show a similar variability
timescale distribution to that found for the variables detected in all three
bands.Comment: 14 pages, 12 figures and 4 tables. Accepted for publication in MNRA
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