A causal model of radiating stellar collapse

We find a simple exact model of radiating stellar collapse, with a shear-free and non-accelerating interior matched to a Vaidya exterior. The heat flux is subject to causal thermodynamics, leading to self-consistent determination of the temperature $T$. We solve for $T$ exactly when the mean collision time $\tau_{c}$ is constant, and perturbatively in a more realistic case of variable $\tau_{c}$. Causal thermodynamics predicts temperature behaviour that can differ significantly from the predictions of non-causal theory. In particular, the causal theory gives a higher central temperature and greater temperature gradient.Comment: Latex [ioplppt style] 9 pages; to appear Class. Quantum Gra

Exploring Automatic Diagnosis of COVID-19 from Crowdsourced Respiratory Sound Data

Audio signals generated by the human body (e.g., sighs, breathing, heart, digestion, vibration sounds) have routinely been used by clinicians as indicators to diagnose disease or assess disease pro- gression. Until recently, such signals were usually collected through manual auscultation at scheduled visits. Research has now started to use digital technology to gather bodily sounds (e.g., from dig- ital stethoscopes) for cardiovascular or respiratory examination, which could then be used for automatic analysis. Some initial work shows promise in detecting diagnostic signals of COVID-19 from voice and coughs. In this paper we describe our data analysis over a large-scale crowdsourced dataset of respiratory sounds collected to aid diagnosis of COVID-19. We use coughs and breathing to under- stand how discernible COVID-19 sounds are from those in asthma or healthy controls. Our results show that even a simple binary machine learning classifier is able to classify correctly healthy and COVID-19 sounds. We also show how we distinguish a user who tested positive for COVID-19 and has a cough from a healthy user with a cough, and users who tested positive for COVID-19 and have a cough from users with asthma and a cough. Our models achieve an AUC of above 80% across all tasks. These results are preliminary and only scratch the surface of the potential of this type of data and audio-based machine learning. This work opens the door to further investigation of how automatically analysed respiratory patterns could be used as pre-screening signals to aid COVID-19 diagnosis.ER

Energy and Momentum Distributions of the Magnetic Solution to (2+1) Einstein-Maxwell Gravity

We use Moeller's energy-momentum complex in order to explicitly evaluate the energy and momentum density distributions associated with the three-dimensional magnetic solution to the Einstein-Maxwell equations. The magnetic spacetime under consideration is a one-parametric solution describing the distribution of a radial magnetic field in a three-dimensional AdS background, and representing the superposition of the magnetic field with a 2+1 Einstein static gravitational field.Comment: LaTex, 13 pages; v2 clarifying comments and references added, Conclusions improved, to appear in Mod. Phys. Lett.

On the energy of charged black holes in generalized dilaton-axion gravity

In this paper we calculate the energy distribution of some charged black holes in generalized dilaton-axion gravity. The solutions correspond to charged black holes arising in a Kalb-Ramond-dilaton background and some existing non-rotating black hole solutions are recovered in special cases. We focus our study to asymptotically flat and asymptotically non-flat types of solutions and resort for this purpose to the M{\o}ller prescription. Various aspects of energy are also analyzed.Comment: LaTe

Towards Canonical Quantum Gravity for G1 Geometries in 2+1 Dimensions with a Lambda--Term

The canonical analysis and subsequent quantization of the (2+1)-dimensional action of pure gravity plus a cosmological constant term is considered, under the assumption of the existence of one spacelike Killing vector field. The proper imposition of the quantum analogues of the two linear (momentum) constraints reduces an initial collection of state vectors, consisting of all smooth functionals of the components (and/or their derivatives) of the spatial metric, to particular scalar smooth functionals. The demand that the midi-superspace metric (inferred from the kinetic part of the quadratic (Hamiltonian) constraint) must define on the space of these states an induced metric whose components are given in terms of the same states, which is made possible through an appropriate re-normalization assumption, severely reduces the possible state vectors to three unique (up to general coordinate transformations) smooth scalar functionals. The quantum analogue of the Hamiltonian constraint produces a Wheeler-DeWitt equation based on this reduced manifold of states, which is completely integrated.Comment: Latex 2e source file, 25 pages, no figures, final version (accepted in CQG

Combatting disability discrimination: a comparison of France and Great Britain

This article examines disabled people’s employment in Great Britain and France. Although both countries have poor rates of employment for disabled people compared to non-disabled people, Great Britain’s disabled people’s employment rate is lower than France’s. Possible explanations include weak enforcement mechanisms in Great Britain, British judicial resistance, the lack of an institutional role for British trade unions resulting in an implementation gap and the proactive form of French law, a quota-levy scheme, which has no British parallel. The conclusions suggest which of these explanations are the most plausible and propose that Great Britain considers adopting some French provisions, thus tempering Britain’s voluntarist approach

Gravitational collapse without a remnant

We investigate the gravitational collapse of a spherically symmetric, inhomogeneous star, which is described by a perfect fluid with heat flow and satisfies the equation of state $p=\rho/3$ or p=C\rho^\ga at its center. Different from the ordinary process of gravitational collapsing, the energy of the whole star is emitted into space. And the remaining spacetime is a Minkowski one at the end of the process.Comment: 9 pages, 9 figures, to appear in Int. J. Theor. Phy

A survey of shipping finance research: setting the future research agenda

Financing shipping related investment projects has always been a focal area of debate and research within the international maritime industry since access to funding can determine the competitiveness of a capital-intensive business as well as its success or failure under adverse market conditions. This paper provides, for the first time, a comprehensive and structured survey of all published research in the area of shipping finance and investment. The review spans approximately four decades (1979-2018) of empirical evidence, including 162 studies published in 48 scholarly journals, complemented with select books and book chapters. The study provides a bibliometric analysis and comprehensive synthesis of existing research offering an invaluable source of information for both the academic community and business practice, shaping the future research agenda in shipping finance and investment

The Energy of Regular Black Hole in General Relativity Coupled to Nonlinear Electrodynamics

According to the Einstein, Weinberg, and M{\o}ller energy-momentum complexes, we evaluate the energy distribution of the singularity-free solution of the Einstein field equations coupled to a suitable nonlinear electrodynamics suggested by Ay\'{o}n-Beato and Garc\'{i}a. The results show that the energy associated with the definitions of Einstein and Weinberg are the same, but M{\o}ller not. Using the power series expansion, we find out that the first two terms in the expression are the same as the energy distributions of the Reissner-Nordstr\"{o}m solution, and the third term could be used to survey the factualness between numerous solutions of the Einstein field eqautions coupled to a nonlinear electrodynamics.Comment: 11 page

Evolution of Game Controllers: Toward the Support of Gamers with Physical Disabilities

Video games, as an entertaining media, dates back to the \u201850s and their hardware device underwent a long evolution starting from hand-made devices such as the \u201ccathode-ray tube amusement device\u201d up to the modern mass-produced consoles. This evolution has, of course, been accompanied by increasingly specialized interaction mechanisms. As of today, interaction with games is usually performed through industry-standard devices. These devices can be either general purpose (e.g., mouse and keyboard) or specific for gaming (e.g., a gamepad). Unfortunately, for marketing reasons, gaming interaction devices are not usually designed taking into consideration the requirements of gamers with physical disabilities. In this paper, we will offer a review of the evolution of gaming control devices with a specific attention to their use by players with physical disabilities in the upper limbs. After discussing the functionalities introduced by controllers designed for disabled players we will also propose an innovative game controller device. The proposed game controller is built around a touch screen interface which can be configured based on the user needs and will be accessible by gamers which are missing fingers or are lacking control in hands movement