914 research outputs found
Tax evasion and exchange equity: a reference-dependent approach
The standard portfolio model of tax evasion with a public good produces the perverse conclusion that when taxpayers perceive the public good to be under-/overprovided, an increase in the tax rate increases/decreases evasion. The author treats taxpayers as thinking in terms of gains and losses relative to an endogenous reference level, which reflects perceived exchange equity between the value of taxes paid and the value of public goods supplied. With these alternative behavioral assumptions, the author overturns the aforementioned result in a direction consistent with the empirical evidence. The author also finds a role for relative income in determining individual responses to a change in the marginal rate of tax
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A global atmospheric electricity monitoring network for climate and geophysical research
The Global atmospheric Electric Circuit (GEC) is a fundamental coupling network of the climate system connecting electrically disturbed weather regions with fair weather regions across the planet. The GEC sustains the fair weather electric field (or potential gradient, PG) which is present globally and can be measured routinely at the surface using durable instrumentation such as modern electric field mills, which are now widely deployed internationally. In contrast to lightning or magnetic fields, fair weather PG cannot be measured remotely. Despite the existence of many PG datasets (both contemporary and historical), few attempts have been made to coordinate and integrate these fragmented surface measurements within a global framework. Such a synthesis is important elvinin order to fully study major influences on the GEC such as climate variations and space weather effects, as well as more local atmospheric electrical processes such as cloud electrification, lightning initiation, and dust and aerosol charging.
The GloCAEM (Global Coordination of Atmospheric Electricity Measurements) project has brought together experts in atmospheric electricity to make the first steps towards an effective global network for atmospheric electricity monitoring, which will provide data in near real time. Data from all sites are available in identically-formatted files, at both one second and one minute temporal resolution, along with meteorological data (wherever available) for ease of interpretation of electrical measurements. This work describes the details of the GloCAEM database and presents what is likely to be the largest single analysis of PG data performed from multiple datasets at geographically distinct locations. Analysis of the diurnal variation in PG from all 17 GloCAEM sites demonstrates that the majority of sites show two daily maxima, characteristic of local influences on the PG, such as the sunrise effect. Data analysis methods to minimise such effects are presented and recommendations provided on the most suitable GloCAEM sites for the study of various scientific phenomena. The use of the dataset for a further understanding of the GEC is also demonstrated, in particular for more detailed characterization of day-to-day global circuit variability. Such coordinated effort enables deeper insight into PG phenomenology which goes beyond single-location PG measurements, providing a simple measurement of global thunderstorm variability on a day-to-day timescale. The creation of the GloCAEM database is likely to enable much more effective study of atmospheric electricity variables than has ever been possible before, which will improve our understanding of the role of atmospheric electricity in the complex processes underlying weather and climate
Mating system variation in hybrid zones: Facilitation, barriers and asymmetries to gene flow
Plant mating systems play a key role in structuring genetic variation both within and between species. In hybrid zones, the outcomes and dynamics of hybridization are usually interpreted as the balance between gene flow and selection against hybrids. Yet, mating systems can introduce selective forces that alter these expectations; with diverse outcomes for the level and direction of gene flow depending on variation in outcrossing and whether the mating systems of the species pair are the same or divergent. We present a survey of hybridization in 133 species pairs from 41 plant families and examine how patterns of hybridization vary with mating system. We examine if hybrid zone mode, level of gene flow, asymmetries in gene flow and the frequency of reproductive isolating barriers vary in relation to mating system/s of the species pair. We combine these results with a simulation model and examples from the literature to address two general themes: (i) the two‐way interaction between introgression and the evolution of reproductive systems, and (ii) how mating system can facilitate or restrict interspecific gene flow. We conclude that examining mating system with hybridization provides unique opportunities to understand divergence and the processes underlying reproductive isolation
Properties of Classical and Quantum Jensen-Shannon Divergence
Jensen-Shannon divergence (JD) is a symmetrized and smoothed version of the
most important divergence measure of information theory, Kullback divergence.
As opposed to Kullback divergence it determines in a very direct way a metric;
indeed, it is the square of a metric. We consider a family of divergence
measures (JD_alpha for alpha>0), the Jensen divergences of order alpha, which
generalize JD as JD_1=JD. Using a result of Schoenberg, we prove that JD_alpha
is the square of a metric for alpha lies in the interval (0,2], and that the
resulting metric space of probability distributions can be isometrically
embedded in a real Hilbert space. Quantum Jensen-Shannon divergence (QJD) is a
symmetrized and smoothed version of quantum relative entropy and can be
extended to a family of quantum Jensen divergences of order alpha (QJD_alpha).
We strengthen results by Lamberti et al. by proving that for qubits and pure
states, QJD_alpha^1/2 is a metric space which can be isometrically embedded in
a real Hilbert space when alpha lies in the interval (0,2]. In analogy with
Burbea and Rao's generalization of JD, we also define general QJD by
associating a Jensen-type quantity to any weighted family of states.
Appropriate interpretations of quantities introduced are discussed and bounds
are derived in terms of the total variation and trace distance.Comment: 13 pages, LaTeX, expanded contents, added references and corrected
typo
Mating system variation in hybrid zones: Facilitation, barriers and asymmetries to gene flow
Plant mating systems play a key role in structuring genetic variation both within and between species. In hybrid zones, the outcomes and dynamics of hybridization are usually interpreted as the balance between gene flow and selection against hybrids. Yet, mating systems can introduce selective forces that alter these expectations; with diverse outcomes for the level and direction of gene flow depending on variation in outcrossing and whether the mating systems of the species pair are the same or divergent. We present a survey of hybridization in 133 species pairs from 41 plant families and examine how patterns of hybridization vary with mating system. We examine if hybrid zone mode, level of gene flow, asymmetries in gene flow and the frequency of reproductive isolating barriers vary in relation to mating system/s of the species pair. We combine these results with a simulation model and examples from the literature to address two general themes: (1) the two-way interaction between introgression and the evolution of reproductive systems, and (2) how mating system can facilitate or restrict interspecific gene flow. We conclude that examining mating system with hybridization provides unique opportunities to understand divergence and the processes underlying reproductive isolation
Observation of the Stimulated Quantum Cherenkov Effect
As charged particles surpass the speed of light in an optical medium they
produce radiation - analogously to the way jet planes surpass the speed of
sound and produce a sonic boom. This radiation emission, known as the Cherenkov
effect, is among the most fundamental processes in electrodynamics. As such, it
is used in numerous applications of particle detectors, particle accelerators,
light sources, and medical imaging. Surprisingly, all Cherenkov-based
applications and experiments thus far were fully described by classical
electrodynamics even though theoretical work predicts new Cherenkov phenomena
coming from quantum electrodynamics. The quantum description could provide new
possibilities for the design of highly controllable light sources and more
efficient accelerators and detectors. Here, we provide a direct evidence of the
quantum nature of the Cherenkov effect and reveal its intrinsic quantum
features. By satisfying the Cherenkov condition for relativistic electron
wavefunctions and maintaining it over hundreds of microns, each electron
simultaneously accelerates and decelerates by absorbing and emitting hundreds
of photons in a coherent manner. We observe this strong interaction in an
ultrafast transmission electron microscope, achieving for the first time a
phase-matching between a relativistic electron wavefunction and a propagating
light wave. Consequently, the quantum wavefunction of each electron evolves
into a coherent plateau, analogous to a frequency comb in ultrashort laser
pulses, containing hundreds of quantized energy peaks. Our findings prove that
the delocalized wave nature of electrons can become dominant in stimulated
interactions. In addition to prospects for known applications of the Cherenkov
effect, our work provides a platform for utilizing quantum electrodynamics for
applications in electron microscopy and in free-electron pump-probe
spectroscopy.Comment: 15 pages, 4 figure
Revamping AI Models in Dermatology: Overcoming Critical Challenges for Enhanced Skin Lesion Diagnosis
The surge in developing deep learning models for diagnosing skin lesions
through image analysis is notable, yet their clinical black faces challenges.
Current dermatology AI models have limitations: limited number of possible
diagnostic outputs, lack of real-world testing on uncommon skin lesions,
inability to detect out-of-distribution images, and over-reliance on
dermoscopic images. To address these, we present an All-In-One
\textbf{H}ierarchical-\textbf{O}ut of Distribution-\textbf{C}linical Triage
(HOT) model. For a clinical image, our model generates three outputs: a
hierarchical prediction, an alert for out-of-distribution images, and a
recommendation for dermoscopy if clinical image alone is insufficient for
diagnosis. When the recommendation is pursued, it integrates both clinical and
dermoscopic images to deliver final diagnosis. Extensive experiments on a
representative cutaneous lesion dataset demonstrate the effectiveness and
synergy of each component within our framework. Our versatile model provides
valuable decision support for lesion diagnosis and sets a promising precedent
for medical AI applications
Cognitive and Affective Empathy, Personal Belief in a Just World, and Bullying Among Offenders
Bullying extract a heavy toll on offenders and the prison staff alike. We examined factors that may contribute to having a positive attitude towards bullying in a sample of offenders. Specifically, we studied the previously overlooked relationship between age and positive attitude towards bullying and whether this relationship is mediated by affective and/or cognitive empathy. Furthermore, we assessed the relationship between personal belief in a just world and positive attitude towards bullying, given that previous research on the topic is scarce. We found that age predicted a positive attitude toward bullying, mediated by affective empathy. However, we did not find a positive relationship between a positive attitude toward bullying and a personal belief in a just world. The results are discussed in terms of their application in possible intervention programs
Spatiotemporal imaging of 2D polariton wave packet dynamics using free electrons
Peer ReviewedPostprint (author's final draft
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