3,542 research outputs found

    GENERALIZED VECTOR RISK FUNCTIONS

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    The paper introduces a new notion of vector-valued risk function. Both deviations and expectation bounded coherent risk measures are defined and analyzed. The relationships with both scalar and vector risk functions of previous literature are discussed, and it is pointed out that this new approach seems to appropriately integrate several preceding point of view. The framework of the study is the general setting of Banach lattices and Bochner integrable vector-valued random variables. Sub-gradient linked representation theorems, as well as portfolio choice problems, are also addressed, and general optimization methods are presented. Finally, practical examples are provided.

    4d Lorentzian Holst action with topological terms

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    We study the Hamiltonian formulation of the general first order action of general relativity compatible with local Lorentz invariance and background independence. The most general simplectic structure (compatible with diffeomorphism invariance and local Lorentz transformations) is obtained by adding to the Holst action the Pontriagin, Euler and Nieh-Yan invariants with independent coupling constants. We perform a detailed canonical analysis of this general formulation (in the time gauge) exploring the structure of the phase space in terms of connection variables. We explain the relationship of these topological terms, and the effect of large SU(2) gauge transformations in quantum theories of gravity defined in terms of the Ashtekar-Barbero connection

    Comparación de los sistemas de transporte rápido de autobús articulado de México

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    Se abordan cuatro sistemas brt (por sus siglas en inglés de Bus Rapid Transit) de México: Metrobús de la Ciudad de México, Macrobús de la Ciudad de Guadalajara, Jalisco, Optibús de la Ciudad de León Guanajuato y Mexibús del Estado de México; con el fin de identificar sus características en cuanto a la tecnología, combustibles e infraestructura, para compararlos y determinar sus ventajas y desventajas tanto ambientales como operacionales. Con el objetivo de determinar cuál de estos sistemas está operando de manera óptima con respecto al cuidado del medio ambiente y al servicio de transporte.Se abordan cuatro sistemas brt (por sus siglas en inglés de Bus Rapid Transit) de México: Metrobús de la Ciudad de México, Macrobús de la Ciudad de Guadalajara, Jalisco, Optibús de la Ciudad de León Guanajuato y Mexibús del Estado de México; con el Àn de identiÀcar sus características en cuanto a la tecnología, combustibles e infraestructura, para compararlos y determinar sus ventajas y desventajas tanto ambientales como operacionales. Con el objetivo de determinar cuál de estos sistemas está operando de manera óptima con respecto al cuidado del medio ambiente y al servicio de transporte

    Frequency-Bin Entanglement of Ultra-Narrow Band Non-Degenerate Photon Pairs

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    We demonstrate frequency-bin entanglement between ultra-narrowband photons generated by cavity enhanced spontaneous parametric down conversion. Our source generates photon pairs in widely non-degenerate discrete frequency modes, with one photon resonant with a quantum memory material based on praseodymium doped crystals and the other photon at telecom wavelengths. Correlations between the frequency modes are analyzed using phase modulators and narrowband filters before detection. We show high-visibility two photon interference between the frequency modes, allowing us to infer a coherent superposition of the modes. We develop a model describing the state that we create and use it to estimate optimal measurements to achieve a violation of the Clauser-Horne (CH) Bell inequality under realistic assumptions. With these settings we perform a Bell test and show a significant violation of the CH inequality, thus proving the entanglement of the photons. Finally we demonstrate the compatibility with a quantum memory material by using a spectral hole in the praseodymium (Pr) doped crystal as spectral filter for measuring high-visibility two-photon interference. This demonstrates the feasibility of combining frequency-bin entangled photon pairs with Pr-based solid state quantum memories.Comment: 15 pages, 6 figure

    Tourists behavior during their trip: How they use and offer recommendations?

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    The rise of new technologies has changed the way tourists trust in eWOM to choose a restaurant. There is a growing use of opinion and price comparison websites, where opinions and ratings can be shared with other users. In addition, the spreading of false or paid comments has made this type of webs seek the generation and maintenance of trust. However, there are few studies that analyse how to generate trust in these webs and its effect in the intention of the consumer to participate in WOM behaviours, once the tourist is already in its tourist destination. Therefore, this research analyses the influence of recommendations on the generation of tourists’ trust in the review websites of restaurant industry while they are in the destination. A regression analysis of data from 439 tourists has revealed that the perceived credibility, the quality of the information and the quality of the web affect trust in review websites. This fact encourages the contracting of restaurant services and communication among consumers, both in a traditional way (WOM) and through the review websites (eWOM), while the tourist is in the tourism destination.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

    Martingales and Arbitrage: a new look

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    This paper addresses the equivalence between the absence of arbitrage and the existence of equivalent martingale measures. The equivalence will be established under quite weak assumptions since there are no conditions on the set of trading dates (it may be finite or countable, with bounded or unbounded horizon, etc.) or on the trajectories of the price process (for instance, they do not have to be right-continuous). Besides we will deal with arbitrage portfolios rather than free-lunches. The concept of arbitrage is much more intuitive than the concept of free lunch and has more clear economic interpretation. Furthermore it is more easily tested in theoretical models or practical applications. In order to overcome the usual mathematical difficulties arising when dealing with arbitrage strategies, the set of states of nature will be widened by drawing on projective systems of Radon probability measures, whose projective limit will be the martingale measure. The existence of densities between the "real" probabilities and the "risk-neutral" probabilities will be guaranteed by introducing the concept of "projective equivalence". Hence some classical counter-examples will be solved and a complete characterization of the absence of arbitrage will be provided in a very general framework.Research partially supported by “Comunidad Autónoma de Madrid” (Spain), Grant s-0505/tic/000230, and “MEyC” (Spain), Grant SEJ2006-15401-C04Publicad

    Pharmacological strategies in lung cancer-induced cachexia: effects on muscle proteolysis, autophagy, structure, and weakness

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    Muscle wasting and cachexia are important systemic manifestations of highly prevalent conditions including cancer. Inflammation, oxidative stress, autophagy, ubiquitin-proteasome system, nuclear factor (NF)-kB, and mitogen activated protein kinases (MAPK) are involved in the pathophysiology of cancer cachexia. Currently available treatment is limited and data demonstrating effectiveness in in vivo models are lacking. Our objectives were to explore in respiratory and limb muscles of lung cancer (LC) cachectic mice whether proteasome, NF-kB, and MAPK inhibitors improve muscle mass and function loss through several molecular mechanisms. Body and muscle weights, limb muscle force, protein degradation and the ubiquitin-proteasome system, signaling pathways, oxidative stress and inflammation, autophagy, contractile and functional proteins, myostatin and myogenin, and muscle structure were evaluated in the diaphragm and gastrocnemius of LC (LP07 adenocarcinoma) bearing cachectic mice (BALB/c), with and without concomitant treatment with NF-kB (sulfasalazine), MAPK (U0126), and proteasome (bortezomib) inhibitors. Compared to control animals, in both respiratory and limb muscles of LC cachectic mice: muscle proteolysis, ubiquitinated proteins, autophagy, myostatin, protein oxidation, FoxO-1, NF-kB and MAPK signaling pathways, and muscle abnormalities were increased, while myosin, creatine kinase, myogenin, and slow- and fast-twitch muscle fiber size were decreased. Pharmacological inhibition of NF-kB and MAPK, but not the proteasome system, induced in cancer-induced cachectic animals, a substantial restoration of muscle mass and force through a decrease in muscle protein oxidation and catabolism, myostatin, and autophagy, together with a greater content of myogenin, and contractile and functional proteins. These findings may offer new therapeutic strategies in cancer-induced cachexia.Fil: Chacon Cabrera, Alba. Universitat Pompeu Fabra; España. Universidad Carlos III de Madrid. Instituto de Salud; EspañaFil: Fermoselle, Clara. Universitat Pompeu Fabra; España. Universidad Carlos III de Madrid. Instituto de Salud; EspañaFil: Urtreger, Alejandro Jorge. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Oncología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay; ArgentinaFil: Mateu Jimenez, Mercè. Universidad Carlos III de Madrid. Instituto de Salud; España. Universitat Pompeu Fabra; EspañaFil: Diament, Miriam. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Oncología; ArgentinaFil: Bal, Elisa Dora. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Oncología "Ángel H. Roffo"; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay; ArgentinaFil: Sandri, Marco. Università di Padova; ItaliaFil: Barreiro, Eshter. Universitat Pompeu Fabra; España. Universidad Carlos III de Madrid. Instituto de Salud; Españ

    Video surveillance for monitoring driver's fatigue and distraction

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    Fatigue and distraction effects in drivers represent a great risk for road safety. For both types of driver behavior problems, image analysis of eyes, mouth and head movements gives valuable information. We present in this paper a system for monitoring fatigue and distraction in drivers by evaluating their performance using image processing. We extract visual features related to nod, yawn, eye closure and opening, and mouth movements to detect fatigue as well as to identify diversion of attention from the road. We achieve an average of 98.3% and 98.8% in terms of sensitivity and specificity for detection of driver's fatigue, and 97.3% and 99.2% for detection of driver's distraction when evaluating four video sequences with different drivers
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