3,256 research outputs found

    Where Have All The Young Men Gone? Evidences and Explanations of Changing Age: Sex Ratios in Kampala

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    In the second half of the twentieth century the population of Kampala grew substantially and the long-remarked surplus of men over women began to level out. These general trends are equally evident in other African cities, but important differences show up when the balance of age cohorts within the male and female populations is considered. Thus in Kampala, along with population growth and a declining overall sex ratio, censuses show a growing excess of girls/young women over boys/young men. The article reviews these population data and two levels of (unenumerated) explanation for them. The first is extrapolated from Uganda's recent history; the second from observation and narrative in one densely populated parish. The argument is that changes in the age–sex ratio follow from change in the map of work options in Kampala. The disappearance of young males stems from the collapse of the formal economy, once the employer of men, and the developments in the informal economy which favour young women. This conclusion is supported by census data from Nairobi, where the formal employment structure remains relatively buoyant, and the comparable age–sex ratios are less extreme. The health policy relevance of the Kampala trend is underlined by official calculations of increasing HIV/AIDS incidence among teenage women. As long as sex work remains dominant among their options in the informal economy, one effect of their economic advantage is extra vulnerability to fatal disease

    Non-radial oscillation modes as a probe of density discontinuities in neutron stars

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    A phase transition occurring in the inner core of a neutron star could be associated to a density discontinuity that would affect the frequency spectrum of the non-radial oscillation modes in two ways. Firstly, it would produce a softening of the equation of state, leading to more compact equilibrium configurations and changing the frequency of the fundamental and pressure modes of the neutron star. Secondly, a new non-zero frequency g-- mode would appear, associated to each discontinuity. These discontinuity g--modes have typical frequencies larger than those of g--modes previously studied in the literature (thermal, core g-- modes, or g--modes due to chemical inhomogeneities in the outer layers), and smaller than that of the fundamental mode; therefore they should be distinguishable from the other modes of non radial oscillation. In this paper we investigate how high density discontinuities change the frequency spectrum of the non-radial oscillations, in the framework of the general relativistic theory of stellar perturbations. Our purpose is to understand whether a gravitational signal, emitted at the frequencies of the quasi normal modes, may give some clear information on the equation of state of the neutron star and, in particular, on the parameters that characterize the density discontinuity. We discuss some astrophysical processes that may be associated to the excitation of these modes, and estimate how much gravitational energy should the modes convey to produce a signal detectable by high frequency gravitational detectors.Comment: submitted to MNRA

    Unstable g-modes in Proto-Neutron Stars

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    In this article we study the possibility that, due to non-linear couplings, unstable g-modes associated to convective motions excite stable oscillating g-modes. This problem is of particular interest, since gravitational waves emitted by a newly born proto-neutron star pulsating in its stable g-modes would be in the bandwidth of VIRGO and LIGO. Our results indicate that nonlinear saturation of unstable modes occurs at relatively low amplitudes, and therefore, even if there exists a coupling between stable and unstable modes, it does not seem to be sufficiently effective to explain, alone, the excitation of the oscillating g-modes found in hydrodynamical simulations.Comment: 10 pages, 3 figures, to appear on Class. Quant. Gra

    A Generative Model of People in Clothing

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    We present the first image-based generative model of people in clothing for the full body. We sidestep the commonly used complex graphics rendering pipeline and the need for high-quality 3D scans of dressed people. Instead, we learn generative models from a large image database. The main challenge is to cope with the high variance in human pose, shape and appearance. For this reason, pure image-based approaches have not been considered so far. We show that this challenge can be overcome by splitting the generating process in two parts. First, we learn to generate a semantic segmentation of the body and clothing. Second, we learn a conditional model on the resulting segments that creates realistic images. The full model is differentiable and can be conditioned on pose, shape or color. The result are samples of people in different clothing items and styles. The proposed model can generate entirely new people with realistic clothing. In several experiments we present encouraging results that suggest an entirely data-driven approach to people generation is possible

    Relativistic r-modes and shear viscosity

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    We derive the relativistic equations for stellar perturbations, including in a consistent way shear viscosity in the stress-energy tensor, and we numerically integrate our equations in the case of large viscosity. We consider the slow rotation approximation, and we neglect the coupling between polar and axial perturbations. In our approach, the frequency and damping time of the emitted gravitational radiation are directly obtained. We find that, approaching the inviscid limit from the finite viscosity case, the continuous spectrum is regularized. Constant density stars, polytropic stars, and stars with realistic equations of state are considered. In the case of constant density stars and polytropic stars, our results for the viscous damping times agree, within a factor two, with the usual estimates obtained by using the eigenfunctions of the inviscid limit. For realistic neutron stars, our numerical results give viscous damping times with the same dependence on mass and radius as previously estimated, but systematically larger of about 60%.Comment: 8 pages, 7 figures, to appear in the Proceedings of the Albert Einstein Century International Conference, Paris, France, July 200

    Neural Body Fitting: Unifying Deep Learning and Model-Based Human Pose and Shape Estimation

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    Direct prediction of 3D body pose and shape remains a challenge even for highly parameterized deep learning models. Mapping from the 2D image space to the prediction space is difficult: perspective ambiguities make the loss function noisy and training data is scarce. In this paper, we propose a novel approach (Neural Body Fitting (NBF)). It integrates a statistical body model within a CNN, leveraging reliable bottom-up semantic body part segmentation and robust top-down body model constraints. NBF is fully differentiable and can be trained using 2D and 3D annotations. In detailed experiments, we analyze how the components of our model affect performance, especially the use of part segmentations as an explicit intermediate representation, and present a robust, efficiently trainable framework for 3D human pose estimation from 2D images with competitive results on standard benchmarks. Code will be made available at http://github.com/mohomran/neural_body_fittingComment: 3DV 201

    Image quality loss and compensation for visually impaired observers

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    The measurement and modeling of image quality are aimed to assist the design and optimization of systems, typically built for ‘normal’ observer vision. But in reality image viewers rarely have perfect vision. There have been few attempts and no universal framework for measuring image quality loss due to visual impairments. The paper presents initial experiments designed to measure still image quality losses, as experienced by observers with visual accommodation problems, by proposing modifications to the Quality Ruler method described in ISO 20462-3:2012. A simple method is then presented, which compensates directly on the display for some of the quality lost due to the impairment. It uses a purpose-built image equalization software. The compensated image is finally examined in terms of quality gained. The losses and gains in image quality are measured on a Standard Quality Scale (SQS), where one unit corresponds to 1 JND. Initial results show that the quality lost due to visual accommodation impairments can be accurately measured with the modified ruler method. The loss is scene-dependent. Partial or full quality compensation can be achieved for such impairments, using image contrast equalization; the level of quality gained also scenedependent

    Gravitational Waves from Rotating Proto-Neutron Stars

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    We study the effects of rotation on the quasi normal modes (QNMs) of a newly born proto neutron star (PNS) at different evolutionary stages, until it becomes a cold neutron star (NS). We use the Cowling approximation, neglecting spacetime perturbations, and consider different models of evolving PNS. The frequencies of the modes of a PNS are considerably lower than those of a cold NS, and are further lowered by rotation; consequently, if QNMs were excited in a sufficiently energetic process, they would radiate waves that could be more easily detectable by resonant-mass and interferometric detectors than those emitted by a cold NS. We find that for high rotation rates, some of the g-modes become unstable via the CFS instability; however, this instability is likely to be suppressed by competing mechanisms before emitting a significant amount of gravitational waves.Comment: 5 pages, proceedings of the 5th Edoardo Amaldi Conference On Gravitational Wave

    Visually Plausible Human-Object Interaction Capture from Wearable Sensors

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    In everyday lives, humans naturally modify the surrounding environmentthrough interactions, e.g., moving a chair to sit on it. To reproduce suchinteractions in virtual spaces (e.g., metaverse), we need to be able to captureand model them, including changes in the scene geometry, ideally fromego-centric input alone (head camera and body-worn inertial sensors). This isan extremely hard problem, especially since the object/scene might not bevisible from the head camera (e.g., a human not looking at a chair whilesitting down, or not looking at the door handle while opening a door). In thispaper, we present HOPS, the first method to capture interactions such asdragging objects and opening doors from ego-centric data alone. Central to ourmethod is reasoning about human-object interactions, allowing to track objectseven when they are not visible from the head camera. HOPS localizes andregisters both the human and the dynamic object in a pre-scanned static scene.HOPS is an important first step towards advanced AR/VR applications based onimmersive virtual universes, and can provide human-centric training data toteach machines to interact with their surroundings. The supplementary video,data, and code will be available on our project page athttp://virtualhumans.mpi-inf.mpg.de/hops/<br

    Strengthening Multi Hazard Mitigation, Preparedness, Response and Recovery Capabilities: Leveraging Campus Resources for System-Wide Results

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    In the wake of the Virginia Tech tragedy and less than two years removed from back to back hurricane experiences with Katrina and Rita, the Board of Supervisors for the University of Louisiana System (ULS) made specific recommendations to all of its member institutions regarding increased preparedness and enhanced response for managing an active shooter incident on a ULS campus. The ULS Emergency Preparedness Steering Committee (EPSC) was formed to undertake the immense task of implementation these recommendations by drawing on campus and system resource persons representing environmental health and safety, public safety, student affairs, academic affairs, business affairs, facilities and planning, and public information and communications. In the four years since its formation the EPSC has played a vital role in assisting ULS institutions in strengthening multi-hazard disaster mitigation, preparedness, response, and recovery capabilities, important priorities for the state’s largest public university system comprised of eight campuses enrolling more than 80,000 students annually. Hurricanes Gustav and Ike H1N1 pandemic scare of 2009 provided real-time scenarios in which EPSC mutual aid system, coordination with local, state, and federal authorities, and capacity for contributing to community, parish, and state response and recovery actions were put to the test. This presentation will illustrate the history and evolution of the EPSC, describe the diversity of campus and system stakeholders who have been engaged in is work since inception, and offer practical insights into how your campus or system might benefit from a similar organization
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