19,487 research outputs found
Seeing is believing: How people fail to identify fake images on the web
The growing ease with which digital images can be convincingly manipulated and widely distributed on the Internet makes viewers increasingly susceptible to visual misinformation and deception. In situations where ill-intentioned individuals seek to deliberately mislead and influence viewers through fake online images, the harmful consequences could be substantial. We describe an exploratory study of how individuals react, respond to, and evaluate the authenticity of images that accompany online stories in Internet-enabled communications channels. Our preliminary findings support the assertion that people perform poorly at detecting skillful image manipulation, and that they often fail to question the authenticity of images even when primed regarding image forgery through discussion. We found that viewers make credibility evaluation based mainly on non-image cues rather than the content depicted. Moreover, our study revealed that in cases where context leads to suspicion, viewers apply post-hoc analysis to support their suspicions regarding the authenticity of the image
Exact zero-point energy shift in the , many modes dynamic Jahn-Teller systems at strong coupling
We find the exact semiclassical (strong coupling) zero-point energy shifts
applicable to the and dynamic Jahn-Teller
problems, for an arbitrary number of discrete vibrational modes
simultaneously coupled to one single electronic level. We also obtain an
analytical formula for the frequency of the resulting normal modes, which has
an attractive and apparently general Slater-Koster form. The limits of validity
of this approach are assessed by comparison with O'Brien's previous
effective-mode approach, and with accurate numerical diagonalizations.
Numerical values obtained for with and coupling
constants appropriate to C are used for this purpose, and are
discussed in the context of fullerene.Comment: 20 pages, 4 ps figure
Towards predicting post-editing productivity
Machine translation (MT) quality is generally measured via automatic metrics, producing scores that have no meaning for translators who are required to post-edit MT output or for project managers who have to plan and budget for transla- tion projects. This paper investigates correlations between two such automatic metrics (general text matcher and translation edit rate) and post-editing productivity. For the purposes of this paper, productivity is measured via processing speed and cognitive measures of effort using eye tracking as a tool. Processing speed, average fixation time and count are found to correlate well with the scores for groups of segments. Segments with high GTM and TER scores require substantially less time and cognitive effort than medium or low-scoring segments. Future research involving score thresholds and confidence estimation is suggested
On the origin of radio core emission in radio-quiet quasars
We present a model for the radio emission from radio-quiet quasar nuclei. We
show that a thermal origin for the high brightness temperature, flat spectrum
point sources (known as radio ``cores'') is possible provided the emitting
region is hot and optically-thin. We hence demonstrate that optically-thin
bremsstrahlung from a slow, dense disk wind can make a significant contribution
to the observed levels of radio core emission. This is a much more satisfactory
explanation, particularly for sources where there is no evidence of a jet, than
a sequence of self-absorbed synchrotron components which collectively conspire
to give a flat spectrum. Furthermore, such core phenomena are already observed
directly via milli-arcsecond radio imaging of the Galactic microquasar SS433
and the active galaxy NGC1068. We contend that radio-emitting disk winds must
be operating at some level in radio-loud quasars and radio galaxies as well
(although in these cases, observations of the radio cores are frequently
contaminated/dominated by synchrotron emission from jet knots). This
interpretation of radio core emission mandates mass accretion rates that are
substantially higher than Eddington. Moreover, acknowledgment of this mass-loss
mechanism as an AGN feedback process has important implications for the input
of energy and hot gas into the inter-galactic medium (IGM) since it is
considerably less directional than that from jets.Comment: to appear in ApJ Letters (4 pages
Dynamics of the Lyman alpha and C IV emitting gas in 3C 273
In this paper we study the variability properties of the Lyman alpha and C IV
emission lines in 3C273 using archival IUE observations. Our data show for the
first time the existence of variability on time scales of several years. We
study the spatial distribution and the velocity field of the emitting gas by
performing detailed analyses on the line variability using correlations, 1D and
2D response functions, and principal component analysis. In both lines we find
evidence for two components, one which has the dynamic properties of gas in
Keplerian motion around a black hole with a mass of the order of 10^9 Mo, and
one which is characterized by high, blue-shifted velocities at large lag. There
is no indication of the presence of optically thick emission medium neither in
the Lya, nor in the Civ response functions. The component characterized by
blue-shifted velocities, which is comparatively much stronger in Civ than in
Lya, is more or less compatible with being the result of gas falling towards
the central black hole with free-fall acceleration. We propose however that the
line emission at high, blue-shifted velocities is better explained in terms of
entrainment of gas clouds by the jet. This gas is therefore probably
collisionally excited as a result of heating due to the intense infrared
radiation from the jet, which would explain the strength of this component in
Civ relative to Lya. This phenomenon might be a signature of disk-jet
interaction.Comment: 16 pages, 10 figures. Accepted for publication in ApJ. Uses aaste
An automated colorimetric inline titration of CO2 concentrations in solvent flow streams using a Teflon AF-2400 tube-in-tube device
Abstract Using a number of open source software components (Python, SciPy, OpenCV, PySerial), together with an inexpensive webcam device, an automated inline colorimetric titration methodology was developed to measure CO2 concentration levels in organic flow streams emerging from a Teflon AF-2400 tube-in-tube device. A bisection search algorithm was used in combination with a curve-fitting approach to determine colorimetric titration endpoints. The results obtained are consistent with a simple ‘negative exponential’ model of permeation/dissolution
Infectious intestinal disease : do we know it all?
Infectious intestinal disease (IID), with associated high morbidity and considerable mortality worldwide, causes a wide spectrum of illness. This ranges from mild discomfort to illness with severe complications. The economic burden from direct and indirect costs may be high. It is acquired by oral ingestion of micro-organisms which are transmitted from person to person; via food or water or through contact with animals or contaminated objects. Viruses are the commonest cause in developed countries. In Malta, medical practitioners and laboratories are the main source of data on IID. However, under-reporting is a problem. In order to fill in the lacunae in information on the disease burden, population-based-studies are required. Along with other countries, Malta has embarked on a number of studies to describe and quantify under-reporting of IID. This may assist in strengthening the surveillance system which, in combination with other measures, should result in an improvement of the control of IID.peer-reviewe
Laboratory surveillance of communicable diseases : enteric pathogens
Laboratories represent a crucial link in the surveillance chain. Since only a small proportion of cases of enteric infections are asked to submit a stool sample, one needs to assess the practices for testing for enteric pathogens and their notification practices. Five local laboratories participated in this study. This included a description of the laboratory practices; capacity for stool sample analysis; awareness of the notification system and the factors which could improve the system at laboratory level.peer-reviewe
Evidence for nonlinear diffusive shock acceleration of cosmic-rays in the 2006 outburst of the recurrent nova RS Ophiuchi
Spectroscopic observations of the 2006 outburst of the recurrent nova RS
Ophiuchi at both infrared (IR) and X-ray wavelengths have shown that the blast
wave has decelerated at a higher rate than predicted by the standard
test-particle adiabatic shock-wave model. Here we show that the observed
evolution of the nova remnant can be explained by the diffusive shock
acceleration of particles at the blast wave and the subsequent escape of the
highest energy ions from the shock region. Nonlinear particle acceleration can
also account for the difference of shock velocities deduced from the IR and
X-ray data. The maximum energy that accelerated electrons and protons can have
achieved in few days after outburst is found to be as high as a few TeV. Using
the semi-analytic model of nonlinear diffusive shock acceleration developed by
Berezhko & Ellison, we show that the postshock temperature of the shocked gas
measured with RXTE/PCA and Swift/XRT imply a relatively moderate acceleration
efficiency.Comment: Accepted for publication in ApJ
Towards a Coulomb gas of instantons in the SO(4)xU(1) Higgs model on R_4
The Higgs model on is extended by a term so
that the action receives a nonvanishing contribution from the interactions of
2-instantons and 3-instantons, and can be expressed as the inverse of the
Laplacian on in terms of the mutual distances of the instantons. The
one-instanton solutions of both the basic and the extended models have been
studied in detail numerically.Comment: 29 pages LaTeX, 4 Figures available from authors on reques
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