925 research outputs found

    Scattering outcomes of close-in planets: constraints on planet migration

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    Many exoplanets in close-in orbits are observed to have relatively high eccentricities and large stellar obliquities. We explore the possibility that these result from planet-planet scattering by studying the dynamical outcomes from a large number of orbit integrations in systems with two and three gas-giant planets in close-in orbits (0.05 AU < a < 0.15 AU). We find that at these orbital separations, unstable systems starting with low eccentricities and mutual inclinations (e0.1e\lesssim0.1, i0.1i\lesssim0.1) generally lead to planet-planet collisions in which the collision product is a planet on a low-eccentricity, low-inclination orbit. This result is inconsistent with the observations. We conclude that eccentricity and inclination excitation from planet-planet scattering must precede migration of planets into short-period orbits. This result constrains theories of planet migration: the semi-major axis must shrink by 1-2 orders of magnitude without damping the eccentricity and inclination.Comment: 11 pages, 3 figures, accepted for publication in Ap

    Higgs Boson Phenomenology in a Simple Model with Vector Resonances

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    In this paper we consider a simple scenario where the Higgs boson and two vector resonances are supposed to arise from a new strong interacting sector. We use the ATLAS measurements of the dijet spectrum to set limits on the masses of the resonances. Additionally we compute the Higgs boson decay to two photons and found, when compare to the Standard Model prediction, a small excess which is compatible with ATLAS measurements. Finally we make prediction for Higgs-strahlung processes for the LHC running at 14 TeV

    A change in temperature modulates defence to yellow (stripe) rust in wheat line UC1041 independently of resistance gene Yr36

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    Background Rust diseases are of major importance in wheat production worldwide. With the constant evolution of new rust strains and their adaptation to higher temperatures, consistent and durable disease resistance is a key challenge. Environmental conditions affect resistance gene performance, but the basis for this is poorly understood. Results Here we show that a change in day temperature affects wheat resistance to Puccinia striiformis f. sp tritici (Pst), the causal agent of yellow (or stripe) rust. Using adult plants of near-isogenic lines UC1041 +/- Yr36, there was no significant difference between Pst percentage uredia coverage in plants grown at day temperatures of 18°C or 25°C in adult UC1041 + Yr36 plants. However, when plants were transferred to the lower day temperature at the time of Pst inoculation, infection increased up to two fold. Interestingly, this response was independent of Yr36, which has previously been reported as a temperature-responsive resistance gene as Pst development in adult UC1041 -Yr36 plants was similarly affected by the plants experiencing a temperature reduction. In addition, UC1041 -Yr36 plants grown at the lower temperature then transferred to the higher temperature were effectively resistant and a temperature change in either direction was shown to affect Pst development up to 8 days prior to inoculation. Results for seedlings were similar, but more variable compared to adult plants. Enhanced resistance to Pst was observed in seedlings of UC1041 and the cultivar Shamrock when transferred to the higher temperature. Resistance was not affected in seedlings of cultivar Solstice by a temperature change in either direction. Conclusions Yr36 is effective at 18°C, refining the lower range of temperature at which resistance against Pst is conferred compared to previous studies. Results reveal previously uncharacterised defence temperature sensitivity in the UC1041 background which is caused by a change in temperature and independently of Yr36. This novel phenotype is present in some cultivars but absent in others, suggesting that Pst defence may be more stable in some cultivars than others when plants are exposed to varying temperatures

    Total Chiral Symmetry Breaking during Crystallization: Who needs a "Mother Crystal"?

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    Processes that can produce states of broken chiral symmetry are of particular interest to physics, chemistry and biology. Chiral symmetry breaking during crystallization of sodium chlorate occurs via the production of secondary crystals of the same handedness from a single "mother crystal" that seeds the solution. Here we report that a large and "symmetric" population of D- and L-crystals moves into complete chiral purity disappearing one of the enantiomers. This result shows: (i) a new symmetry breaking process incompatible with the hypothesis of a single "mother crystal"; (ii) that complete symmetry breaking and chiral purity can be achieved from an initial system with both enantiomers. These findings demand a new explanation to the process of total symmetry breaking in crystallization without the intervention of a "mother crystal" and open the debate on this fascinating phenomenon. We present arguments to show that our experimental data can been explained with a new model of "complete chiral purity induced by nonlinear autocatalysis and recycling".Comment: 5 pages, 4 figures, Added reference

    THE EFQM EXCELLENCE MODEL AS ENABLER OF E-PROCUREMENT ADOPTION AND THE EFFECT ON PERFORMANCE

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    The objective of this paper is to examine the EFQM Excellence Model as an enabler of E-procurement adoption and the effect on purchasing performance. The study utilized a cross-sectional telephone survey of a sample of Spanish manufacturing companies using multiple informants. A total of 200 firms responded making a total of 800 responses. Data was analyzed using structural equations modelling. The results indicate that the Business Excellence Enablers (Leadership, Strategy, People, Resources, and Processes) act as enablers of E-procurement and help to realize gains in purchasing performance

    La música y la poesía, dos vecinas de rellano

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    Podríamos haber elegido entre miles de citas para abrir este monográfico, pero cuando esta publicación estaba a punto de llegar a su fin (o a su comienzo según se mire), unas palabras del periodista Iñaki Gabilondo en una entrevista radiofónica sintetizaron como pocas el sentido de esta obra: “La música y la poesía son vecinas de rellano”. Esta frase justifica por sí sola este trabajo en el que se han visto implicados durante varios meses –aunque recogiendo los frutos de varios años- una serie de autores desconocidos entre sí, pero unidos por un objetivo común: aprovechar la literatura clásica que contiene la música moderna para acercarla a los estudiantes de todas las edades, pero en especial a los niños y adolescentes de hoy en día. We could have chosen from thousands of citations to open this monograph, but when this publication was about to end (or start- depending on how you look at it), a few words given in a radio interview by journalist Iñaki Gabilondo synthesized at the very least the meaning of this play: Music and poetry are next-door neighbours. This phrase alone justifies this work which they have been involved in for several months - although reaping the benefits for several years - a series of authors unknown to each other, but united by a common goal: take advantage of the classical literature that modern music contains to bring it closer to students of all ages, but especially children and teenagers today

    The origin of the negative torque density in disk-satellite interaction

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    Tidal interaction between a gaseous disk and a massive orbiting perturber is known to result in angular momentum exchange between them. Understanding astrophysical manifestations of this coupling such as gap opening by planets in protoplanetary disks or clearing of gas by binary supermassive black holes (SMBHs) embedded in accretion disks requires knowledge of the spatial distribution of the torque exerted on the disk by a perturber. Recent hydrodynamical simulations by Dong et al (2011) have shown evidence for the tidal torque density produced in a uniform disk to change sign at the radial separation of 3.2\approx 3.2 scale heights from the perturber's orbit, in clear conflict with the previous studies. To clarify this issue we carry out a linear calculation of the disk-satellite interaction putting special emphasis on understanding the behavior of the perturbed fluid variables in physical space. Using analytical as well as numerical methods we confirm the reality of the negative torque density phenomenon and trace its origin to the overlap of Lindblad resonances in the vicinity of the perturber's orbit - an effect not accounted for in previous studies. These results suggest that calculations of the gap and cavity opening in disks by planets and binary SMBHs should rely on more realistic torque density prescriptions than the ones used at present.Comment: 18 pages, 6 figures, accepted to Ap

    Application of Bioactive Thermal Proteome Profiling to Decipher the Mechanism of Action of the Lipid Lowering 132-Hydroxy-pheophytin Isolated from a Marine Cyanobacteria

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    The acceleration of the process of understanding the pharmacological application of new marine bioactive compounds requires identifying the compound protein targets leading the molecular mechanisms in a living cell. The thermal proteome profiling (TPP) methodology does not fulfill the requirements for its application to any bioactive compound lacking chemical and functional characterization. Here, we present a modified method that we called bTPP for bioactive thermal proteome profiling that guarantees target specificity from a soluble subproteome. We showed that the precipitation of the microsomal fraction before the thermal shift assay is crucial to accurately calculate the melting points of the protein targets. As a probe of concept, the protein targets of 132-hydroxy-pheophytin, a compound previously isolated from a marine cyanobacteria for its lipid reducing activity, were analyzed on the hepatic cell line HepG2. Our improved method identified 9 protein targets out of 2500 proteins, including 3 targets (isocitrate dehydrogenase, aldehyde dehydrogenase, phosphoserine aminotransferase) that could be related to obesity and diabetes, as they are involved in the regulation of insulin sensitivity and energy metabolism. This study demonstrated that the bTPP method can accelerate the field of biodiscovery, revealing protein targets involved in mechanisms of action (MOA) connected with future applications of bioactive compounds.This project received funding from the ERA-NET Marine Biotechnology project CYANOBESITY that it is cofounding from FORMAS, Sweden grant nr. 2016-02004 (SC), FCT Foundation of Science and Technology, Portugal, grant number ERA-MBT/0001/2015 (RU). This work has also been funded by IKERBASQUE (SC), Basque Government grant IT-971-16 (SC and OF), and FCT grants SFRH/BPD/112287/2015, SFRH/BD/116009/2016, FCT strategic fund (UID/Multi/04423/2019) (RU and SF)
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