4,582 research outputs found

    Entropy production in the early-cosmology pionic phase

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    We point out that in the early universe, for temperatures in the approximate interval 175-80 MeV (after the quark-gluon plasma), pions carried a large share of the entropy and supported the largest inhomogeneities. Thus, we examine the production of entropy in a pion gas, particularizing to inhomogeneities of the temperature, for which we benefit from the known thermal conductivity. We finally put that entropy produced in relaxing such thermal inhomogeneities in the broad context of this relatively unexplored phase of early-universe cosmology.Comment: 10 pages, 10 figures

    Monetary policy and inflation persistence in the Eurozone

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    The primary goal of the European Central Bank’s (ECB) monetary policy is to achieve price stability. Whereas during the 1980s and 1990s there was a rapid and strong convergence in terms of price differential among the Euro countries, particularly in those countries with higher inflation rates in the past, single monetary policy has proved to be quite inefficient in continuing this trend and has not achieved further reductions in inflation rate differentials within the euro zone. Since the ECB sets the official interest rate according to the average inflation of the euro area, the persistence of such price differentials within the area would mean that the “one size interest rate policy” would not fit all. This paper studies empirically the inflation rate differentials and their persistence in some currency unions with the aim to draw some conclusions for the working of the ECB monetary policy. KEYWORDS: monetary policy; inflation persistence; currency unions

    Optimizing Scan Homogeneity for Building Full-3D Lidars based on Rotating a Multi-Beam Velodyne Rangefinder

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    Multi-beam lidar (MBL) scanners are compact, light, and accessible 3D sensors with high data rates, but they offer limited vertical resolution and field of view (FOV). Some recent robotics research has profited from the addition of a degree-of-freedom (DOF) to an MBL to build rotating multi-beam lidars (RMBL) that can achieve high-resolution scans with full spherical FOV. In a previous work, we offered a methodology to analyze the complex 3D scan measurement distributions produced by RMBLs with a rolling DOF and no pitching. In this paper, we investigate the effect of introducing constant pitch angles in the construction of the RMBLs with the purpose of finding a kinematic configuration that optimizes scan homogeneity with a spherical FOV. To this end, we propose a scalar index of 3D sensor homogeneity that is based on the spherical formulation of Ripley's K function. The optimization is performed for the widely used Puck (VLP-16) and HDL-32 sensors by Velodyne.This work was partially funded by the Spanish project {DPI2015-65186-R}. The publication has received support from Universidad de MĂĄlaga, Campus de Excelencia AndalucĂ­a Tech

    Race and Health Disparities Among Seniors in Urban Areas in Brazil

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    White seniors report better health than Black seniors in urban areas in Sao Paulo, Brazil. This is the case even after controlling for baseline health conditions and several demographic, socio-economic and family support characteristics. Furthermore, adjusted racial disparities in self-reported health are larger than the disparities found using alternative measures of functional health. Our empirical research in this paper suggests that the two most important factors driving racial disparities in health among seniors (in our sample) are historical differences in rural living conditions and current income. Present economic conditions are more relevant to racial disparities among poor seniors than among rich seniors. Moreover, racial differences in health not attributable to observable characteristics are more important when comparing individuals in the upper half of the income distribution.

    Modeling of Free Surface Flows with Elastic Bodies Interactions

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    In this paper, a series of new fluid and structure interactions test cases with strong free surface effects are presented and computations of such flows with the Particle Finite Element Method (PFEM) (Idelsohn, Oiiate, Del Pin and Calvo, 2006) are documented. The structures object of study are elastic cantilever bars clamped inside sloshing tanks subjected ro roll motion. The possibilities of PFEM for the coupled simulation of moderately violent free surface flows interacting with elastic bodies are investigated. The problem can be described as the coupling of a sloshing flow with an easily deformable elastic body. A series of experiments designed and executed specifically for these tests are also described. The experiments comprise cases with different liquid height and liquids of different viscosity. The aim is to identify canonical benchmark problems in FSI (Fluid and Structure Interactions), including free surfaces, for future comparisons between different numerical approaches

    An Experiment on the Neolithic Agricultural Revolution. Causes and Impact on Inequality

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    Testing causal relationships expressed by mathematical models on facts about human behaviour across history is challenging. A prominent example is the Neolithic agricultural revolution [1]. Many theoretical models of the adoption of agriculture has been put forward [2] but none has been tested. The only exception is [3], that uses a computational approach with agent-based simulations of evolutionary games. Here, we propose two games that resemble the conditions of human societies before and after the agricultural revolution. The agricultural revolution is modelled as an exogenous shock in the lab (n=180, 60 independent groups), and the transition from foraging to farming results from an equilibrium selection process decided by experimental subjects. The experimental data replicate the known facts that foragers organized themselves around division of labour [4] and were more egalitarian than farmers [5]. There is also evidence of bi-modal distribution along the foraging-farming axis with many in-between groups [6, 7, 8]. These results provide direct evidence that the modes of production determine the system of values of societies (inequality) and lend support for the idea that human moved in a widespread manner from foraging to farming societies. We also find that cultural and institutional preconditions were crucial for farming [9], as more egalitarian foraging groups adopted earlier agricultural techniques, but inequality raises in farming societies as agriculture settles [10], with the long run success of agriculture being determined by the land-owner’s legitimacy. These results enrich our understanding of the Neolithic agricultural revolution and highlight the relevance of experimental methodology to generate a rich dataset that complements the fragmented evidence from archaeological sites

    Construction and Calibration of a Low-Cost 3D Laser Scanner with 360◩ Field of View for Mobile Robots

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    Navigation of many mobile robots relies on environmental information obtained from three-dimensional (3D) laser scanners. This paper presents a new 360◩ field-of-view 3D laser scanner for mobile robots that avoids the high cost of commercial devices. The 3D scanner is based on spinning a Hokuyo UTM- 30LX-EX two-dimensional (2D) rangefinder around its optical center. The proposed design profits from lessons learned with the development of a previous 3D scanner with pitching motion. Intrinsic calibration of the new device has been performed to obtain both temporal and geometric parameters. The paper also shows the integration of the 3D device in the outdoor mobile robot Andabata.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tec

    Metalloproteases, vascular remodeling and atherothrombotic syndromes

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    Defects in the synthesis and breakdown of the extracellular matrix (ECM) are now seen as key processes in the development of atherosclerosis and its thrombotic complications. Correlations have been observed between circulating levels of ECM biomarkers and the clinical manifestations of and risk factors for atherosclerosis. Several matrix metalloproteinases (MMPs), endopeptidases that can degrade the ECM, such as MMP-9 and MMP-10, play important roles in the pathophysiology of atherothrombosis and contribute to the expansion of abdominal aortic aneurysms. Moreover, they may also be useful biomarkers of atherosclerotic risk and serve as predictors of coronary and cerebrovascular disease recurrence. Although at present the effect of tissue inhibitors of MMPs (TIMPs) on cardiovascular disease prognosis is still uncertain, the ECM could be a promising therapeutic target in atherothrombotic disease, and several MMP inhibitors are currently undergoing clinical trials
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