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Search Results: 1 - 10 of 198278 matches for " N. Rius "
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Symmetry Non-restoration at High Temperature
N. Rius
Physics , 1998,
Abstract: We discuss the (non)-restoration of global and local symmetries at high temperature. First, we analyze a two-scalar model with $Z_2 \times Z_2$ symmetry using the exact renormalization group. We conclude that inverse symmetry breaking is possible in this kind of models within the perturbative regime. Regarding local symmetries, we consider the $SU(2) \otimes U(1)$ gauge symmetry and focus on the case of a strongly interacting scalar sector. Employing a model-independent chiral Lagrangian we find indications of symmetry restoration.
Using Heavy Quark Fragmentation into Heavy Hadrons to Determine QCD Parameters and Test Heavy Quark Symmetry
L. Randall,N. Rius
Physics , 1994, DOI: 10.1016/0550-3213(95)00101-W
Abstract: We present a detailed analysis of the use of heavy quark fragmentation into heavy hadrons for testing the heavy quark effective theory through comparison of the measured fragmentation parameters of the $c$ and $b$ quarks. Our analysis is entirely model independent. We interpret the known perturbative evolution in a way useful for exploiting heavy quark symmetry at low energy. We first show consistency with perturbative QCD scaling for measurements done solely with $c$ quarks. We then apply the perturbative analysis and the heavy quark expansion to relate measurements from ARGUS and LEP. We place bounds on a nonperturbative quark mass suppressed parameter, and compare the values for the $b$ and $c$ quarks. We find consistency with the heavy quark expansion but fairly sizable QCD uncertainties. We also suggest that one might reduce the systematic uncertainty in the result by not extrapolating to low $z$.
Neutral Heavy Leptons and Electroweak Baryogenesis
P. Hernandez,N. Rius
Physics , 1996, DOI: 10.1016/S0550-3213(97)00193-4
Abstract: We investigate the possibility that baryogenesis occurs during the weak phase transition in a minimal extension of the Standard Model which contains extra neutral leptons and conserves total lepton number. The necessary CP-violating phases appear in the leptonic Yukawa couplings. We compute the CP-asymmetries in both the neutral and the charged lepton fluxes reflected on the bubble wall. Using present experimental bounds on the mixing angles and Standard Model estimates for the parameters related to the scalar potential, we conclude that it seems unlikely to produce the observed baryon to entropy ratio within this type of models. We comment on the possibility that the constraints on the mixings might be naturally relaxed due to small finite temperature effects.
Dynamical Symmetry Breaking in Warped Compactifications
N. Rius,V. Sanz
Physics , 2001, DOI: 10.1103/PhysRevD.64.075006
Abstract: We study dynamical electroweak symmetry breaking in the Randall-Sundrum scenario. We show that one extra dimension is enough to give the correct pattern of electroweak symmetry breaking in a simple model with gauge bosons and the right-handed top quark in the bulk. The top quark mass is also in agreement with experiment. Furthermore, we propose an extended scenario with all Standard Model gauge bosons and fermions propagating in the bulk, which naturally accommodates the fermion mass hierarchies. No new fields or interactions beyond the observed in the Standard Model are required.
The Electromagnetic Mass Difference of Pions at Low Temperature
C. Manuel,N. Rius
Physics , 1998, DOI: 10.1103/PhysRevD.59.054002
Abstract: We compute low temperature corrections to the electromagnetic mass difference of pions in the chiral limit. The computation is done in a model independent way in the framework of chiral perturbation theory, using the background field method and the hard thermal loop approximation. We also generalize at low temperature the sum rule of Das et al. We find that the mass difference between the charged and neutral pions decreases at low temperature $T$ with respect to the T=0 value. This is so in spite of the fact that charged particles always get a thermal correction to their masses of order $\sim eT$, where $e$ is the gauge coupling constant. Our result can be understood as a consequence of the tendency towards chiral symmetry restoration at finite temperature.
Inverse Symmetry Breaking and the Exact Renormalization Group
M. Pietroni,N. Rius,N. Tetradis
Physics , 1996, DOI: 10.1016/S0370-2693(97)00150-0
Abstract: We discuss the question of inverse symmetry breaking at non-zero temperature using the exact renormalization group. We study a two-scalar theory and concentrate on the nature of the phase transition during which the symmetry is broken. We also examine the persistence of symmetry breaking at temperatures higher than the critical one.
Analysis of the P1 promoter in response to UV-B radiation in allelic variants of high-altitude maize
Sebastián Rius, Erich Grotewold, Paula Casati
BMC Plant Biology , 2012, DOI: 10.1186/1471-2229-12-92
Abstract: Here, we studied the UV-B regulation of P1 in maize leaves of high altitude landraces, and we investigated how UV-B regulates P1binding to the CHS promoter in both low and high altitude lines. In addition, we analyzed whether the expansion in the P1 expression domain between these maize landraces and inbred lines is associated to changes in the molecular structure of the proximal promoter, distal enhancer and first intron of P1. Finally, using transient expression experiments in protoplasts from various maize genotypes, we investigated whether the different expression patterns of P1 in the high altitude landraces could be attributed to trans- or cis-acting elements.Together, our results demonstrate that, although differences in cis-acting elements exist between the different lines under study, the different patterns of P1 expression are largely a consequence of effects in trans.Plants, because of their sessile lifestyle, have evolved adaptations to live under diverse environmental variables, including solar radiation. Sunlight contains qualities of light that are essential for photosynthesis, and also provides informational signals that control plant growth and development. At least three different types of photoreceptor systems exist in plant cells, perceiving red/far-red (phytochromes), blue/UV-A (cryptochromes and phototropins), and there is at least one putative UV-B receptor (UVR8), which was recently identified [1].UV-B (280 to 315?nm) is part of the solar radiation, and therefore plants are inevitably exposed to UV-B. UV photons cause cellular damage by generating DNA photoproducts and through direct damage to proteins, lipids, and RNA [2-4]. Plant responses to UV-B damage include repair [5,6] and avoidance [7,8]. Solar UV-B radiation flux varies over time and location on earth. It is higher at increased elevation, because there is less air mass and greater atmospheric transparency to shorter wavelength radiation, although local climatic conditions, such as c
Differential Regularization of a Non-relativistic Anyon Model
D. Z. Freedman,G. Lozano,N. Rius
Physics , 1993, DOI: 10.1103/PhysRevD.49.1054
Abstract: Differential regularization is applied to a field theory of a non-relativistic charged boson field $\phi$ with $\lambda (\phi {}^{*} \phi)^2$ self-interaction and coupling to a statistics-changing $U(1)$ Chern-Simons gauge field. Renormalized configuration-space amplitudes for all diagrams contributing to the $\phi {}^{*} \phi {}^{*} \phi \phi$ 4-point function, which is the only primitively divergent Green's function, are obtained up to 3-loop order. The renormalization group equations are explicitly checked, and the scheme dependence of the $\beta$-function is investigated. If the renormalization scheme is fixed to agree with a previous 1-loop calculation, the 2- and 3-loop contributions to $\beta(\lambda,e)$ vanish, and $\beta(\lambda,e)$ itself vanishes when the ``self-dual'' condition relating $\lambda$ to the gauge coupling $e$ is imposed.
Neutral Higgs Sector of the MSSM without $R_p$
S. Davidson,M. Losada,N. Rius
Physics , 1999, DOI: 10.1016/S0550-3213(00)00471-5
Abstract: We analyse the neutral scalar sector of the MSSM without R-parity. Our analysis is performed for a one-generation model in terms of ``basis-independent'' parameters, and includes one-loop corrections due to large yukawa couplings. We concentrate on the consequences of large $R_p$ violating masses in the soft sector, which mix the Higgses with the sleptons, because these are only constrained by their one-loop contributions to neutrino masses. We focus on the effect of $R_p$-violation on the Higgs mass and branching ratios. We find that the experimental lower bound on the lightest CP-even Higgs in this model can be lower than in the MSSM.
Evaluación in vitro de las propiedades de seis apósitos para la cura en ambiente húmedo de heridas exudativas
Rius Tarruella,Joan; López Bertrán,Ramón;
Gerokomos , 2008, DOI: 10.4321/S1134-928X2008000100005
Abstract: introduction: of the dressings used for healing in wet environments, foam is a type of dressing that is particularly indicated for the treatment of highly exudative wounds due to its great absorption capacity. they are atraumatic dressings that protect the perilesional area and keep the bed moist promoting epithelialization and providing pain relief, thus occupying a very specific space in the care of vascular and pressure ulcers. material and method: in vitro experimental study to evaluate the characteristics of 6 types of polymeric foam dressings: non-adhesive (sf1) and adhesive (sf2) skinfoam, non-adhesive (a1) and adhesive (a2) allevyn and non-adhesive (b1) and adhesive (b2) biatain. the characteristics assessed were: exudate absorption and control capacity, characterisation of the contact surface, transpiration, conformability and antimicrobial protection capacity. results: the exudate absorption and control tests show how dressings sf1 and sf2 obtain greater absorption per unit of weight while models b1 and b2 are evidently deformed, and even in the case of the adhesive b2 dressing, the foam padding detached from the adhesive film. the drip experiment could not be carried out with dressings a1 and a2 as the drops of solution could not be retained since the internal contact adherence layer prevents retention. the roughness measurements demonstrated the excellent softness of the sf1 and sf2 dressings, a behaviour that will have a direct impact on pain symptoms. the highest water vapour transpiration rates, particularly for adhesive models, were for dressings sf2 and b1. the easiest-to-extend dressing was the sf1, and bacterial protection was similar in all the dressings. the dressings with the greatest absorption capacity were model b1 by unit of surface and model a1 by unit of weight. the maximum exudate retention under pressure was that of dressing c1 among the non-adhesives (96.79%) and a2 among the adhesives (97.13%). dressings c1 and c2 presented the lowest
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