Determination of the Chiral Couplings L_10 and C_87 from Semileptonic Tau Decays

Using recent precise hadronic tau-decay data on the V-A spectral function, and general properties of QCD such as analyticity, the operator product expansion and chiral perturbation theory, we get accurate values for the QCD chiral order parameters L_10^r(M_rho) and C_87^r(M_rho). These two low-energy constants appear at order p^4 and p^6, respectively, in the chiral perturbation theory expansion of the V-A correlator. At order p^4 we obtain L_10^r(M_rho) = -(5.22\pm 0.06)10^{-3}. Including in the analysis the two-loop (order p^6) contributions, we get L_10^r(M_rho) = -(4.06\pm 0.39)10^{-3} and C_87^r(M_rho) = (4.89\pm 0.19)10^{-3}GeV^{-2}. In the SU(2) chiral effective theory, the corresponding low-energy coupling takes the value \overline l_5 = 13.30 \pm 0.11 at order p^4, and \overline l_5 = 12.24 \pm 0.21 at order p^6.Comment: 17 pages, 3 figures, v2: Added reference, published versio

Comportamiento en fluencia de un material compuesto de matriz metálica Al6061-15 vol % SiCw pulvimetalúrgico

Se ha realizado un estudio de las propiedades en fluencia del material compuesto pulvimetalúrgico Al6061-15 vol % SiCw. Su comportamiento se ha comparado con el de la aleación Al6061 pulvimetalúrgica y la aleación Al6061 de colada. El comportamiento del material pulvimetalúrgico sin reforzar mejora respecto al del material de colada. Al mismo tiempo, el del material compuesto mejora respecto al comportamiento del material pulvimetalúrgico sin reforzar. Se consideran dos factores microestructurales como los principales responsables de la mejora de las propiedades en fluencia de este material compuesto. Por un lado, las partículas de Al2O3 de tamaño nanométrico y, por otro, las partículas de fibra corta cerámicas de SiC de tamaño micrométrico. Aunque ambos tipos de partículas dan lugar a un efecto de refuerzo similar, los mecanismos intrínsecos asociados a la presencia de estas partículas tienen una naturaleza diferente debido a la diferencia en la escala microestructural.Peer reviewe

Membrana pupilar persistente

La persistencia de la membrana pupilar es una de las alteraciones congénitas oculares más frecuente en los pequeños animales. En este artículo se hace una revisión de las manifestaciones clínicas más frecuentes de esta patología.The persistence of the pupillary membrane is one of the most common congenital ocular anomalies in small animals. In this article a review of the principal clinical signs of this alteration is made

Violation of quark-hadron duality and spectral chiral moments in QCD

We analyze the spectral moments of the V-A two-point correlation function. Using all known short-distance constraints and the most recent experimental data from tau decays, we determine the lowest spectral moments, trying to assess the uncertainties associated with the so-called violations of quark-hadron duality. We have generated a large number of 'acceptable' spectral functions, satisfying all conditions, and have used them to extract the wanted hadronic parameters through a careful statistical analysis. We obtain accurate values for the ChPT couplings L10 and C87, and a realistic determination of the dimension six and eight contributions in the operator product expansion, O6=(-5.4^{+3.6}_{-1.6})*10^-3 GeV^6 and O8=(-8.9^{+12.6}_{-7.4})*10^-3 GeV^8, showing that the duality-violation effects have been usually underestimated in previous literature

Why consumers drink natural wine? Consumer perception and information about natural wine

Similar to other foods, the concept of natural wine is much debated due to the lack of a clear and regulated definition, leading to a proliferation of heterogeneous norms and standards proposed from different natural wine associations at national levels. The current study explored the aspects which mediate individuals’ information and perception of natural wine, and the rationale behind natural wine consumption behavior among Italian (n = 501) and Spanish (n = 527) regular wine consumers. The results reveal a quite low self-reported degree of perceived information by Italian respondents and slightly higher levels among Spanish ones. The key drivers of natural wine consumption in both countries are wine consumption frequency, information, and natural product interest. In contrast, higher wine involvement levels decrease natural wine consumption frequency in both Italy and Spain. The findings also show that different perceptions lead to diverse motivations, suggesting the need for more homogeneous standards to mitigate the level of information asymmetry currently on the market

Common carotid artery diameter, blood flow velocity and wave intensity responses at rest and during exercise in young healthy humans: a reproducibility study

The aim of this study was to assess the reproducibility of non-invasive, ultrasound-derived wave intensity (WI) in humans at the common carotid artery. Common carotid artery diameter and blood velocity of 12 healthy young participants were recorded at rest and during mild cycling, to assess peak diameter, change in diameter, peak velocity, change in velocity, time derivatives, non-invasive wave speed and WI. Diameter, velocity and WI parameters were fairly reproducible. Diameter variables exhibited higher reproducibility than corresponding velocity variables (intra-class correlation coefficient [ICC] = 0.79 vs. 0.73) and lower dispersion (coefficient of variation [CV] = 5% vs. 9%). Wave speed had fair reproducibility (ICC = 0.6, CV = 16%). WI energy variables exhibited higher reproducibility than corresponding peaks (ICC = 0.78 vs. 0.74) and lower dispersion (CV = 16% vs. 18%). The majority of variables had higher ICCs and lower CVs during exercise. We conclude that non-invasive WI analysis is reliable both at rest and during exercise

Non-invasive assessment of the common carotid artery hemodynamics with Increasing exercise workrate using wave intensity analysis

Non-invasively determined local wave speed (c) and wave intensity (WI) parameters provide insight into arterial stiffness and cardiac-vascular interactions in response to physiological perturbations. However, the effects of incremental exercise and subsequent recovery on c and WI are not fully established. We examined the changes in c and WI parameters in the common carotid artery (CCA) during exercise and recovery in 8 young healthy male athletes. Ultrasound measurements of CCA diameter (D) and blood flow velocity (U) were acquired at rest, during 5 stages of incremental exercise (up to 70% maximum workrate) and throughout 1 h of recovery and non-invasive WI analysis (DU approach) was performed. During exercise, c increased (+136%), showing increased stiffness with workrate. All peak and area of forward compression (FCW), backward compression (BCW) and forward expansion waves (FEW) increased during exercise (+452%, +700%, +900%, respectively). However, WI reflection indices and CCA resistance did not significantly change from rest to exercise. Further, wave speed and magnitude of all waves returned to baseline within 5 min of recovery, suggesting the effects of exercise in the investigated parameters of young healthy individuals were transient. In conclusion, incremental exercise was associated with an increase in local CCA stiffness and increases in all wave parameters, indicative of enhanced ventricular contractility and improved late-systolic blood flow deceleration

Decoherence in an accelerated universe

In this paper we study the decoherence processes of the semiclassical branches of an accelerated universe due to their interaction with a scalar field with given mass. We use a third quantization formalism to analyze the decoherence between two branches of a parent universe caused by their interaction with the vaccum fluctuations of the space-time, and with other parent unverses in a multiverse scenario.Comment: 11 pages, 2 figure

Low amplitude and high frequency mechanical stimulation does not affect directly cell differentiation during bone healing

Bone fractures has high incidence and despite its relevance and frequency, some bone healing process features are still unknown. In this work, it is computationally investigated the influence of low amplitude and high frequency mechanical stimulation on cell differentiation during bone healing, using a cell differentiation theory that relates two mechanical variables (strain and flow velocity of interstitial fluid) with the cell fate. For this purpose, a finite element model was developed to study three hypothetical situations, to determine in which proportion external stimulation influences bone healing. Firstly, the mechanical stimulus was computed as 20% of external mechanical stimulus and 80% of the stimulus during gait. Secondly, it was considered 50% external mechanical stimulus and 50% gait stimulus. Finally, it was considered a proportion of 80% external mechanical stimulus and 20% gait stimulus. The results indicated that hypothesis considering high proportions of external stimulation results in unreal delayed healing process and the first hypothetical situation proved to be that which best represents the real process. From the results obtained, it was concluded that external mechanical stimulation does not affected directly cell differentiation during bone healing. Thus, other processes such as flow of oxygen, nutrients or wastes must be considered