1,062 research outputs found

    Condensation in randomly perturbed zero-range processes

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    The zero-range process is a stochastic interacting particle system that exhibits a condensation transition under certain conditions on the dynamics. It has recently been found that a small perturbation of a generic class of jump rates leads to a drastic change of the phase diagram and prevents condensation in an extended parameter range. We complement this study with rigorous results on a finite critical density and quenched free energy in the thermodynamic limit, as well as quantitative heuristic results for small and large noise which are supported by detailed simulation data. While our new results support the initial findings, they also shed new light on the actual (limited) relevance in large finite systems, which we discuss via fundamental diagrams obtained from exact numerics for finite systems.Comment: 18 pages, 6 figure

    Measurement-Adaptive Cellular Random Access Protocols

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    This work considers a single-cell random access channel (RACH) in cellular wireless networks. Communications over RACH take place when users try to connect to a base station during a handover or when establishing a new connection. Within the framework of Self-Organizing Networks (SONs), the system should self- adapt to dynamically changing environments (channel fading, mobility, etc.) without human intervention. For the performance improvement of the RACH procedure, we aim here at maximizing throughput or alternatively minimizing the user dropping rate. In the context of SON, we propose protocols which exploit information from measurements and user reports in order to estimate current values of the system unknowns and broadcast global action-related values to all users. The protocols suggest an optimal pair of user actions (transmission power and back-off probability) found by minimizing the drift of a certain function. Numerical results illustrate considerable benefits of the dropping rate, at a very low or even zero cost in power expenditure and delay, as well as the fast adaptability of the protocols to environment changes. Although the proposed protocol is designed to minimize primarily the amount of discarded users per cell, our framework allows for other variations (power or delay minimization) as well.Comment: 31 pages, 13 figures, 3 tables. Springer Wireless Networks 201

    Theoretical-Experimental Study of the Effect of the External Plates on the Thermal Performance of a Plate Heat Exchanger

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    Abstract In this work we present a theoretical-experimental research on the thermal phenomena that the endplates present on the performance of the plate heat exchangers in a single step and with a U type configuration. The endplate effect is reflected in a reduction of the temperature difference for heat transfer. The model discusses a theoretical focus that includes the elongation factor, which is a parameter that relates the actual area to the projected area of a plate. This model was performed to 2, 3, 4, 5, and 6 channel flow; therefore the experimentation was carried out to validate the theoretical model, it was carried out for 4, 5, 6, 7, 8 and 9 flow channels. Such results show that the theoretical model deviates in a 5% of the experimental values. The results obtained for theorical temperature correction factor presents a maximum deviation of ± 0.0245 with respect to the experimental values

    Composición multielemental y valor nutricional de "dumosa" (Ilex dumosa), "yerba mate" (I. paraguariensis) y su mezcla comercial en diferentes formas de uso

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    The multielement composition and nutritional value of "dumosa" (Ilex dumosa) (ID),"yerba mate" (I. paraguariensis) (IP) and their commercial 70:30 mixture (ID:IP, w/w) in crude drug, brewed mate and tea-bag-like infusion were studied by ICP-OES. This method allowed the detection of an unprecedented number of elements for these species. The order was K > Ca > Mg > P > Mn > Al > Na > Si > Fe in crude drug. IP showed higher concentration of minerals than ID, but most extractability in the latter largely offset its shortcomings. Brewed mate had higher nutritional value than mate tea because their higher solute/solvent ratio. A portion of brewed mate of both species exceeded the dailyrecommended intake (DRI) of Mn, and providing Mg, Cu, Fe, Zn and K, too. The portions of mate tea not contribute significantly to the DRI. Some essential trace elements and many ultra-traces ones that exist in crude drug were not detected in aqueous extracts. Most of the heavy metals were not leached into extracts, and in any case never exceeded international safety limits. Therefore, the aqueous extracts of ID and IP and its mixture are interesting from the nutritional point of view in minerales, and safe in terms of health.La composición multielemental y el valor nutricional de "dumosa" (Ilex dumosa) (ID), "yerba mate" (I. paraguariensis) (IP) y su mezcla comercial 70:30 (ID:IP, p/p) fue estudiada por ICP-OES en droga cruda y dos formas de consumo: "cebadura" y "mate cocido". Este método permitió detectar un número sin precedentes de elementos en estas especies. En droga cruda, el orden resultó K>Ca>Mg>P>Mn>Al>Na>Si>Fe. IP mostró mayor concentración de minerales que ID, pero la mayor extractabilidad en esta última compensó en gran medida sus deficiencias. La cebadura mostró mayor valor nutricional que la infusión, a causa de su mayor relación soluto/disolvente. La porción de cebadura de ambas especies superó la ingesta diaria recomendada (IDR) de Mn, aportando también Mg, Cu, Fe, Zn y K. La porción de mate cocido no contribuyó significativamente a la IDR. Algunos elementos traza esenciales y muchos ultra-trazas presentes en droga cruda no fueron detectados en los extractos acuosos. La mayoría de los metales pesados no fueron lixiviados hacia los extractos, y en todo caso nunca excedieron los límites de seguridad internacionales. Por ello, los extractos acuosos de ID e IP y sus mezclas son interesantes desde el punto de vista nutricional y son seguros en cuanto a la salud.Fil: Maiocchi, Marcos G.. Universidad Nacional del Nordeste. Facultad de Ciencias Exactas Naturales y Agrimensura. Departamento de Química; ArgentinaFil: del Vitto, Luis Angel. Universidad Nacional de San Luis. Facultad de Química, Bioquímica y Farmacia. Departamento de Farmacia; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Química de San Luis. Universidad Nacional de San Luis. Facultad de Química, Bioquímica y Farmacia. Instituto de Química de San Luis; ArgentinaFil: Petenatti, Elisa Margarita. Universidad Nacional de San Luis. Facultad de Química, Bioquímica y Farmacia. Departamento de Farmacia; ArgentinaFil: Marchevsky, Eduardo Jorge. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Química de San Luis. Universidad Nacional de San Luis. Facultad de Química, Bioquímica y Farmacia. Instituto de Química de San Luis; ArgentinaFil: Avanza, María Victoria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Química Básica y Aplicada del Nordeste Argentino. Universidad Nacional del Nordeste. Facultad de Ciencias Exactas Naturales y Agrimensura. Instituto de Química Básica y Aplicada del Nordeste Argentino; ArgentinaFil: Pellerano, Roberto Gerardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Química Básica y Aplicada del Nordeste Argentino. Universidad Nacional del Nordeste. Facultad de Ciencias Exactas Naturales y Agrimensura. Instituto de Química Básica y Aplicada del Nordeste Argentino; ArgentinaFil: Petenatti, Elisa Margarita. Universidad Nacional de San Luis; Argentin

    Nitrogen compounds removal from oil-derived middle distillates by MIL-101(Cr) and its impact on ULSD production by hydrotreating

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    Es un articulo sobre sintesis caracterizacion de catalizadoresoil) for ultra-low sulfur diesel (ULSD) production by hydrotreating (HDT) were pretreated by selective nitrogen organic compounds (NOC) adsorption. Highly crystalline metal-organic framework (MOF) MIL-101(Cr) prepared with propylene oxide (proton scavenger) as textural improver was employed to that end. MOF was characterized by N2 physisorption, X-ray diffraction, thermal analysis, infrared, Raman and UV-vis spectroscopies, and electron microscopy (SEM and HR-TEM). NOC removal was performed at room temperature and atmospheric pressure, the adsorbent being easily regenerable under mild conditions. Extruded MOF efficiently removed NOC from real feedstocks to concentrations ~ 80 ppm, allowing ULSD production at much milder conditions to those used during pristine feedstocks HDT. Operating temperature could be greatly diminished (from 350°C to 330°C, at 56 kg/sq cm (5.77 MPa), LHSV = 1.5/h, H2/oil = 2500 cy ft/bbl (445 cu m/cu m)) which could notably prolong cycle life of NiMo/Al2O3 formulation used.SENER-CONACYT-HIDROCARBUROS FUND IMP 00117, 6105

    Caveolin-1 is required for TGF-β-induced transactivation of the EGF receptor pathway in hepatocytes through the activation of the metalloprotease TACE/ADAM17

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    Transforming growth factor-beta (TGF-β) plays a dual role in hepatocytes, inducing both pro- and anti-apoptotic responses, whose balance decides cell fate. Survival signals are mediated by the epidermal growth factor receptor (EGFR) pathway, which is activated by TGF-β in these cells. Caveolin-1 (Cav1) is a structural protein of caveolae linked to TGF-β receptors trafficking and signaling. Previous results have indicated that in hepatocytes, Cav1 is required for TGF-β-induced anti-apoptotic signals, but the molecular mechanism is not fully understood yet. In this work, we show that immortalized Cav1(-/-) hepatocytes were more sensitive to the pro-apoptotic effects induced by TGF-β, showing a higher activation of caspase-3, higher decrease in cell viability and prolonged increase through time of intracellular reactive oxygen species (ROS). These results were coincident with attenuation of TGF-β-induced survival signals in Cav1(-/-) hepatocytes, such as AKT and ERK1/2 phosphorylation and NFκ-B activation. Transactivation of the EGFR pathway by TGF-β was impaired in Cav1(-/-) hepatocytes, which correlated with lack of activation of TACE/ADAM17, the metalloprotease responsible for the shedding of EGFR ligands. Reconstitution of Cav1 in Cav1(-/-) hepatocytes rescued wild-type phenotype features, both in terms of EGFR transactivation and TACE/ADAM17 activation. TACE/ADAM17 was localized in detergent-resistant membrane (DRM) fractions in Cav1(+/+) cells, which was not the case in Cav1(-/-) cells. Disorganization of lipid rafts after treatment with cholesterol-binding agents caused loss of TACE/ADAM17 activation after TGF-β treatment. In conclusion, in hepatocytes, Cav1 is required for TGF-β-mediated activation of the metalloprotease TACE/ADAM17 that is responsible for shedding of EGFR ligands and activation of the EGFR pathway, which counteracts the TGF-β pro-apoptotic effects. Therefore, Cav1 contributes to the pro-tumorigenic effects of TGF-β in liver cancer cells.This work was supported by grants from: (1) the Ministry of Economy and Competitiveness (MINECO), Spain (BFU2012-35538 and ISCIII-RTICC: RD12-0036-0029 to IF; SAF2013-43713 to PM-S; BFU2012-33932 to GE; SAF2011-25047 and CSD2009-00016 to MAdP); (2) AGAUR-Generalitat de Catalunya (2009SGR-312 to IF); and (3) People Programme (Marie Curie Actions) of the European Union’s Seventh Framework Programme (FP7/2007-2013) under REA grant agreement no. PITN-GA-2012-316549 (IT LIVER) to IF JM-C and RM-V were recipients of pre-doctoral fellowships from the FPU program (Ministry of Education, Culture and Sport, Spain) and the FPI program (associated to SAF201125047, MINECO, Spain), respectively. We acknowledge the review and suggestions of Dr. Christoph Meyer (University of Heidelberg, Mannheim, Germany).S

    Allelic diversity and patterns of selection at the major histocompatibility complex class I and II loci in a threatened shorebird, the Snowy Plover (Charadrius nivosus)

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    Background: Understanding the structure and variability of adaptive loci such as the major histocompatibility complex (MHC) genes is a primary research goal for evolutionary and conservation genetics. Typically, classical MHC genes show high polymorphism and are under strong balancing selection, as their products trigger the adaptive immune response in vertebrates. Here, we assess the allelic diversity and patterns of selection for MHC class I and class II loci in a threatened shorebird with highly flexible mating and parental care behaviour, the Snowy Plover (Charadrius nivosus) across its broad geographic range. Results: We determined the allelic and nucleotide diversity for MHC class I and class II genes using samples of 250 individuals from eight breeding population of Snowy Plovers. We found 40 alleles at MHC class I and six alleles at MHC class II, with individuals carrying two to seven different alleles (mean 3.70) at MHC class I and up to two alleles (mean 1.45) at MHC class II. Diversity was higher in the peptide-binding region, which suggests balancing selection. The MHC class I locus showed stronger signatures of both positive and negative selection than the MHC class II locus. Most alleles were present in more than one population. If present, private alleles generally occurred at very low frequencies in each population, except for the private alleles of MHC class I in one island population (Puerto Rico, lineage tenuirostris). Conclusion: Snowy Plovers exhibited an intermediate level of diversity at the MHC, similar to that reported in other Charadriiformes. The differences found in the patterns of selection between the class I and II loci are consistent with the hypothesis that different mechanisms shape the sequence evolution of MHC class I and class II genes. The rarity of private alleles across populations is consistent with high natal and breeding dispersal and the low genetic structure previously observed at neutral genetic markers in this species

    Search for chargino–neutralino pair production in final states with three leptons and missing transverse momentum in √s = 13 TeV pp collisions with the ATLAS detector

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    Artículo escrito por un elevado número de autores, solo se referencian el que aparece en primer lugar, el nombre del grupo de colaboración, si le hubiere, y los autores pertenecientes a la UAMA search for chargino–neutralino pair production in three-lepton final states with missing transverse momentum is presented. The study is based on a dataset of s=13 TeV pp collisions recorded with the ATLAS detector at the LHC, corresponding to an integrated luminosity of 139 fb - 1. No significant excess relative to the Standard Model predictions is found in data. The results are interpreted in simplified models of supersymmetry, and statistically combined with results from a previous ATLAS search for compressed spectra in two-lepton final states. Various scenarios for the production and decay of charginos (χ~1±) and neutralinos (χ~20) are considered. For pure higgsino χ~1±χ~20 pair-production scenarios, exclusion limits at 95% confidence level are set on χ~20 masses up to 210 GeV. Limits are also set for pure wino χ~1±χ~20 pair production, on χ~20 masses up to 640 GeV for decays via on-shell W and Z bosons, up to 300 GeV for decays via off-shell W and Z bosons, and up to 190 GeV for decays via W and Standard Model Higgs boson

    A search for the decays of stopped long-lived particles at √s = 13 TeV with the ATLAS detector

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    Artículo escrito por un elevado número de autores, solo se referencian el que aparece en primer lugar, el nombre del grupo de colaboración, si le hubiere, y los autores pertenecientes a la UAMA search for long-lived particles, which have come to rest within the ATLAS detector, is presented. The subsequent decays of these particles can produce high-momentum jets, resulting in large out-of-time energy deposits in the ATLAS calorimeters. These decays are detected using data collected during periods in the LHC bunch structure when collisions are absent. The analysed dataset is composed of events from proton-proton collisions produced by the Large Hadron Collider at a centre-of-mass energy of √s = 13 TeV and recorded by the ATLAS experiment during 2017 and 2018. The dataset used for this search corresponds to a total live time of 579 hours. The results of this search are used to derive lower limits on the mass of gluino R-hadrons, assuming a branching fraction B(g~→qq¯χ10) = 100%, with masses of up to 1.4 TeV excluded for gluino lifetimes of 10−5 to 103
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