1,847 research outputs found

    Teaching about Madrid: A Collaborative Agents-Based Distributed Learning Course

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    Interactive art courses require a huge amount of computational resources to be running on real time. These computational resources are even bigger if the course has been designed as a Virtual Environment with which students can interact. In this paper, we present an initiative that has been develop in a close collaboration between two Spanish Universities: Universidad Politécnica de Madrid and Universidad Rey Juan Carlos with the aim of join two previous research project: a Collaborative Awareness Model for Task-Balancing-Delivery (CAMT) in clusters and the “Teaching about Madrid” course, which provides a cultural interactive background of the capital of Spain

    First ALMA maps of HCO, an important precursor of complex organic molecules, towards IRAS 16293-2422

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    The formyl radical HCO has been proposed as the basic precursor of many complex organic molecules such as methanol (CH3_3OH) or glycolaldehyde (CH2_2OHCHO). Using ALMA, we have mapped, for the first time at high angular resolution (\sim1^{\prime\prime}, \sim140 au), HCO towards the Solar-type protostellar binary IRAS 16293-2422, where numerous complex organic molecules have been previously detected. We also detected several lines of the chemically related species H2_2CO, CH3_3OH and CH2_2OHCHO. The observations revealed compact HCO emission arising from the two protostars. The line profiles also show redshifted absorption produced by foreground material of the circumbinary envelope that is infalling towards the protostars. Additionally, IRAM 30m single-dish data revealed a more extended HCO component arising from the common circumbinary envelope. The comparison between the observed molecular abundances and our chemical model suggests that whereas the extended HCO from the envelope can be formed via gas-phase reactions during the cold collapse of the natal core, the HCO in the hot corinos surrounding the protostars is predominantly formed by the hydrogenation of CO on the surface of dust grains and subsequent thermal desorption during the protostellar phase. The derived abundance of HCO in the dust grains is high enough to produce efficiently more complex species such as H2_2CO, CH3_3OH, and CH2_2OHCHO by surface chemistry. We found that the main formation route of CH2_2OHCHO is the reaction between HCO and CH2_2OH.Comment: Accepted in Monthly Notices of the Royal Astronomical Society; 19 pages, 12 figures, 7 table

    Analysis of the quark sector in the 2HDM-III with a four-zero Yukawa texture using the most recent data on the CKM matrix

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    In this letter we analyse, in the context of the general 2-Higgs Doublet Model, the structure of the Yukawa matrices, Y~1,2q\widetilde{ \bf Y}_{ _{1,2} }^{q}, by assuming a four-zero texture ansatz for their definition. In this framework, we obtain compact expressions for Y~1,2q\widetilde{ \bf Y}_{ _{1,2} }^{q}, which are reduced to the Cheng and Sher ansatz with the difference that they are obtained naturally as a direct consequence of the invariants of the fermion mass matrices. Furthermore, in order to avoid large flavour violating effects coming from charged Higgs exchange, we consider the main flavour constraints on the off-diagonal terms of Yukawa texture {{(χ~jq)kl\left( \widetilde{\chi}_{j}^q \right)_{kl}}} (klk\neq l). We perform a χ2\chi^2-fit based on current experimental data on the quark masses and the Cabibbo-Kobayashi-Maskawa mixing matrix VCKM{ \bf V}_{\rm CKM }. Hence, we obtain the allowed ranges for the parameters Y~1,2q\widetilde{ \bf Y}_{ _{1,2} }^{q} at 1σ\sigma for several values of tanβ\tan \beta. The results are in complete agreement with the bounds obtained taking into account constraints on Flavour Changing Neutral Currents reported in the literature.Comment: 12 pages, 1 figure. Version accepted in Phys. Lett.

    Isocurvature bounds on axions revisited

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    The axion is one of the best motivated candidates for particle dark matter. We study and update the constraints imposed by the recent CMB and LSS experiments on the mass of axions produced by the misalignment mechanism, as a function of both the inflationary scale and the reheating temperature. Under some particular although not unconventional assumptions, the axionic field induces too large isocurvature perturbations. Specifically, for inflation taking place at intermediate energy scales, we derive some restrictive limits which can only be evaded by assuming an efficient reheating mechanism, with T>10^{11} GeV. Chaotic inflation with a quadratic potential is still compatible with the axion scenario, provided that the Peccei-Quinn scale f_a is close to 10^{10} or 10^{11} GeV. Isocurvature bounds eliminate the possibility of a larger f_a and a small misalignment angle. We find that isocurvature constraints on the axion scenario must be taken into account whenever the scale of inflation is above 10^{12} GeV; below this scale, axionic isocurvature modes are too small to be probed by current observations.Comment: 12 pages, 3 figures; more concise version, new figures, accepted in PR

    Compositional analysis of InAs-GaAs-GaSb heterostructures by low-loss electron energy loss spectroscopy

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    As an alternative to Core-Loss Electron Energy Loss Spectroscopy, Low-Loss EELS is suitable for compositional analysis of complex heterostructures, such as the InAs-GaAs-GaSb system, since in this energy range the edges corresponding to these elements are better defined than in Core-Loss. Furthermore, the analysis of the bulk plasmon peak, which is present in this energy range, also provides information about the composition. In this work, compositional information in an InAs-GaAs-GaSb heterostructure has been obtained from Low-Loss EEL spectra

    Design of predictive tools to estimate freshness index in farmed sea bream (Sparus aurata) stored in ice

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    This research studied sea bream freshness evolution through storage time in ice by determining different quality parameters and sensory profiles. Predictive models for freshness index, storage time, and microbial counts were designed from these data. Physico-chemical parameters were assessed to evaluate the quality of fish; microbial growth was controlled to ensure food safety, and sensory analyses were carried out to characterize quality deterioration. Predictive models were developed and improved with the aim of being used as tools for quality management in the seafood industry. Validation was conducted in order to establish the accuracy of models. There was a good relationship between the physico-chemical and microbiological parameters. Sensory analysis and microbial counts allowed for the establishment of a shelf-life of 10 days, which corresponded to a poor quality (according to the European Community''s system of grading fish for marketing purposes), with a freshness index lower than 50%. Sensory profiles showed that gill and flesh texture were the most vulnerable attributes during storage in ice related to spoilage. The predictive models for the freshness index (%) and ice storage time (h) exhibited an accuracy close to 90% following practical validation

    The clumpy structure of the chemically active L1157 outflow

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    We present high spatial resolution maps, obtained with the Plateau de Bure Interferometer, of the blue lobe of the L1157 outflow. We observed four lines at 3 mm, namely CH3OH (2_K-1_K), HC3N (11-10), HCN (1-0) and OCS (7-6). Moreover, the bright B1 clump has also been observed at better spatial resolution in CS (2-1), CH3OH (2_1-1_1)A-, and 34SO (3_2-2_1). These high spatial resolution observations show a very rich structure in all the tracers, revealing a clumpy structure of the gas superimposed to an extended emission. In fact, the three clumps detected by previous IRAM-30m single dish observations have been resolved into several sub-clumps and new clumps have been detected in the outflow. The clumps are associated with the two cavities created by two shock episodes driven by the precessing jet. In particular, the clumps nearest the protostar are located at the walls of the younger cavity with a clear arch-shape form while the farthest clumps have slightly different observational characteristics indicating that they are associated to the older shock episode. The emission of the observed species peaks in different part of the lobe: the east clumps are brighter in HC3N (11-10), HCN (1-0) and CS (2-1) while the west clumps are brighter in CH3OH(2_K-1_K), OCS (7-6) and 34SO (3_2-2_1). This peak displacement in the line emission suggests a variation of the physical conditions and/or the chemical composition along the lobe of the outflow at small scale, likely related to the shock activity and the precession of the outflow. In particular, we observe the decoupling of the silicon monoxide and methanol emission, common shock tracers, in the B1 clump located at the apex of the bow shock produced by the second shock episode.Comment: 11 pages, 8 figures, accepted for publication in the MNRA

    Background studies and shielding effects for the TPC detector of the CAST experiment

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    Sunset solar axions traversing the intense magnetic field of the CERN Axion Solar Telescope (CAST) experiment may be detected in a Time Projection Chamber (TPC) detector, as X-rays signals. These signals could be masked, however, by the inhomogeneous background of materials in the experimental site. A detailed analysis, based on the detector characteristics, the background radiation at the CAST site, simulations and experimental results, has allowed us to design a shielding which reduces the background level by a factor of ~4 compared to the detector without shielding, depending on its position, in the energy range between 1 and 10 keV. Moreover, this shielding has improved the homogeneity of background measured by the TPC.Comment: 14 pages, 5 figures, accepted in New Journal of Physic
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