The pion transition form factor and the pion distribution amplitude

Recent BaBaR data on the pion transition form factor, whose Q^2 dependence is much steeper then predicted by asymptotic Quantum Chromodynamics (QCD), have caused a renewed interest in its theoretical description. We present here a formalism based on a model independent low energy description and a high energy description based on QCD, which match at a scale Q_0. The high energy description incorporates a flat pion distribution amplitude, phi(x)=1, at the matching scale Q_0 and QCD evolution from Q_0 to Q>Q_0. The flat pion distribution is connected, through soft pion theorems and chiral symmetry, to the pion valance parton distribution at the same low scale Q_0. The procedure leads to a good description of the data, and incorporating additional twist three effects, to an excellent description of the data.Comment: 11 pages, 5 postscript figures, uses epsfig.sty and 1 appendi

Prevalencia de hipotensión ortostática en ancianos hipertensos tratados en atención primaria

ObjetivoConocer la prevalencia de hipotensión ortostática (HO) y los factores asociados en ancianos hipertensos tratados en atención primaria (AP).DiseñoEstudio descriptivo, transversal.EmplazamientoCentro de Salud La Marina (centro urbano en Santander).PacientesUna muestra aleatoria de 295 pacientes de 65 o más años atendidos regularmente por presentar hipertensión arterial (HTA).Mediciones y resultados principalesSe han obtenido cifras de presión arterial (PA) en sedestación y en bipedestación. La definición de HO utilizada ha sido: disminución de 20 mmHg o más en la PA sistólica (PAS) o de 10 mmHg o más en la PA diastólica (PAD), tras 1 o 5 minutos de bipedestación. También se han recogido datos sobre enfermedades asociadas, síntomas en bipedestación, medicación utilizada, hábitos de los pacientes y resultados de otras exploraciones clínicas. La prevalencia global encontrada de HO fue del 14,6%. La prevalencia de HO sistólica tras un minuto (HO-S1) y tras 5 minutos (HO-S5) de bipedestación ha sido del 5,8% en ambas, y la de HO diastólica del 5,1% tras un minuto (HO-D1) y del 4,1% tras 5 minutos (HO-D5) de bipedestación. En el análisis de regresión logística se encontró una asociación entre la existencia de HO global y la mayor elevación de la PA sistólica inicial, la presencia de síntomas de intolerancia ortostática (aunque sólo un 25,6% de los pacientes con HO presentaba síntomas) y el hábito tabáquico. Asimismo, se encontró una asociación con el uso de bloqueadores beta y antagonistas del calcio (diferentes de las dihidropiridinas) y la existencia de HO al minuto de bipedestación, y entre el consumo de tabaco y la HO a los 5 minutos de bipedestación.ConclusionesLa prevalencia detectada es alta y justifica la búsqueda sistemática de HO en los pacientes ancianos que son tratados de HTA en AP. La existencia de síntomas con el ortostatismo se relaciona con una mayor prevalencia de HO, pero sólo los presentó uno de cada 4 pacientes con HO. El consumo de tabaco podría estar relacionado con la presencia de HO, así como el uso de bloqueadores beta y antagonistas del calcio (diferentes de las dihidropiridinas).ObjectiveTo find the prevalence of orthostatic hypotension (OH) and associated factors in elderly hypertensive patients in a primary care setting.DesignDescriptive cross-sectional study.SettingLa Marina Health Centre (an urban centre in Santander).PatientsA random sample of 295 patients aged 65 years or older regularly assisted from hypertension.Measurements and main resultsMeasurements of sitting and standing blood pressure were obtained. Orthostatic hypotension was defined as 20 mmHg or greater decrease in systolic or 10 mmHg or greater decrease in diastolic blood pressure after 1-minute or 5-minute standing. Associated diseases, symptoms upon standing, medication use, habits and other clinical assessments were also recorded. The prevalence of OH was 14.6%. The prevalence of systolic OH after 1-minute (OH-S1) and after 5-minute (OH-S5) standing was 5.8% in both, and the diastolic OH was 5.1% after 1-minute (OH-D1) and 4.1% after 5-minute (OH-D5) standing. By logistic regression analysis, association between higher level of systolic blood pressure and global OH was found, also with the presence of orthostatic intolerance symptoms (although only 25.6% of the patients with OH showed symptoms) and smoking. Beta-blockers and calcium channel blockers (different from dihydropyridines) use was associated with OH after 1-minute standing and smoking with OH after 5-minute standing.ConclusionsThe detected prevalence is high and justifies the case finding of OH in elderly hypertensive patients in primary care. The symptoms of orthostatic intolerance are correlated with OH, but only 1 out of 4 patients showed symptoms. Smoking could be related with OH, so beta-blockers and calcium channel blockers (different from dihydropyridines) use

2-(2-Methyl-2-nitrovinyl)furan but Not Furvina Interfere with Staphylococcus aureus Agr Quorum-Sensing System and Potentiate the Action of Fusidic Acid against Biofilms

Quorum sensing (QS) plays an essential role in the production of virulence factors, in biofilm formation and antimicrobial resistance. Consequently, inhibiting QS is being considered a promising target for antipathogenic/anti-virulence therapies. This study aims to screen 2-nitrovinylfuran derivatives structurally related to Furvina (a broad-spectrum antibiotic already used for therapeutic purposes) for their effects on QS and in biofilm prevention/control. Furvina and four 2-nitrovinylfuran derivatives (compounds 1-4) were tested to assess the ability to interfere with QS of Staphylococcus aureus using bioreporter strains (S. aureus ALC1742 and ALC1743). The activity of Furvina and the most promising quorum-sensing inhibitor (QSI) was evaluated in biofilm prevention and in biofilm control (combined with fusidic acid). The biofilms were further characterized in terms of biofilm mass, viability and membrane integrity. Compound 2 caused the most significant QS inhibition with reductions between 60% and 80%. Molecular docking simulations indicate that this compound interacts preferentially with the protein hydrophobic cleft in the LytTR domain of AgrA pocket. Metabolic inactivations of 40% for S. aureus ALC1742 and 20% for S. aureus ALC1743 were reached. A 24 h-old biofilm formed in the presence of the QSI increased the metabolic inactivation by fusidic acid to 80%, for both strains. The overall results highlight the effects of compound 2 as well as the potential of combining QSI with in-use antibiotics for the management of skin and soft tissues infections

Monitoring bacterial faecal contamination in waters using multiplex real-time PCR assay for Bacteroides spp. and faecal enterococci

Postprint (published version

Solution of the Kwiecinski evolution equations for unintegrated parton distributions using the Mellin transform

The Kwiecinski equations for the QCD evolution of the unintegrated parton distributions in the transverse-coordinate space (b) are analyzed with the help of the Mellin-transform method. The equations are solved numerically in the general case, as well as in a small-b expansion which converges fast for b Lambda_QCD sufficiently small. We also discuss the asymptotic limit of large bQ and show that the distributions generated by the evolution decrease with b according to a power law. Numerical results are presented for the pion distributions with a simple valence-like initial condition at the low scale, following from chiral large-N_c quark models. We use two models: the Spectral Quark Model and the Nambu--Jona-Lasinio model. Formal aspects of the equations, such as the analytic form of the b-dependent anomalous dimensions, their analytic structure, as well as the limits of unintegrated parton densities at x -> 0, x -> 1, and at large b, are discussed in detail. The effect of spreading of the transverse momentum with the increasing scale is confirmed, with growing asymptotically as Q^2 alpha(Q^2). Approximate formulas for for each parton species is given, which may be used in practical applications.Comment: 18 pages, 6 figures, RevTe

Low Energy Chiral Lagrangian in Curved Space-Time from the Spectral Quark Model

We analyze the recently proposed Spectral Quark Model in the light of Chiral Perturbation Theory in curved space-time. In particular, we calculate the chiral coefficients $L_1, ..., L_{10}$, as well as the coefficients $L_{11}$, $L_{12}$, and $L_{13}$, appearing when the model is coupled to gravity. The analysis is carried for the SU(3) case. We analyze the pattern of chiral symmetry breaking as well as elaborate on the fulfillment of anomalies. Matching the model results to resonance meson exchange yields the relation between the masses of the scalar, tensor and vector mesons, $M_{f_0}=M_{f_2}=\sqrt{2} M_V= 4 \sqrt{3 /N_c} \pi f_\pi$. Finally, the large-$N_c$ limit suggests the dual relations in the vector and scalar channels, $M_V=M_S= 2 \sqrt{6 /N_c} \pi f_\pi$ and $^{1/2}_S = < r^2 >^{1/2}_V = 2 \sqrt{N_c} / f_\pi = 0.59 {\rm fm}$.Comment: 18 pages, no figure

Spectral quark model and low-energy hadron phenomenology

We propose a spectral quark model which can be applied to low energy hadronic physics. The approach is based on a generalization of the Lehmann representation of the quark propagator. We work at the one-quark-loop level. Electromagnetic and chiral invariance are ensured with help of the gauge technique which provides particular solutions to the Ward-Takahashi identities. General conditions on the quark spectral function follow from natural physical requirements. In particular, the function is normalized, its all positive moments must vanish, while the physical observables depend on negative moments and the so-called log-moments. As a consequence, the model is made finite, dispersion relations hold, chiral anomalies are preserved, and the twist expansion is free from logarithmic scaling violations, as requested of a low-energy model. We study a variety of processes and show that the framework is very simple and practical. Finally, incorporating the idea of vector-meson dominance, we present an explicit construction of the quark spectral function which satisfies all the requirements. The corresponding momentum representation of the resulting quark propagator exhibits only cuts on the physical axis, with no poles present anywhere in the complex momentum space. The momentum-dependent quark mass compares very well to recent lattice calculations. A large number of predictions and relations can be deduced from our approach for such quantities as the pion light-cone wave function, non-local quark condensate, pion transition form factor, pion valence parton distribution function, etc.Comment: revtex, 24 pages, 3 figure

Pion light-cone wave function and pion distribution amplitude in the Nambu-Jona-Lasinio model

We compute the pion light-cone wave function and the pion quark distribution amplitude in the Nambu-Jona-Lasinio model. We use the Pauli-Villars regularization method and as a result the distribution amplitude satisfies proper normalization and crossing properties. In the chiral limit we obtain the simple results, namely phi_pi(x)=1 for the pion distribution amplitude, and = -M / f_pi^2 for the second moment of the pion light-cone wave function, where M is the constituent quark mass and f_pi is the pion decay constant. After the QCD Gegenbauer evolution of the pion distribution amplitude good end-point behavior is recovered, and a satisfactory agreement with the analysis of the experimental data from CLEO is achieved. This allows us to determine the momentum scale corresponding to our model calculation, which is close to the value Q_0 = 313 MeV obtained earlier from the analogous analysis of the pion parton distribution function. The value of is, after the QCD evolution, around (400 MeV)^2. In addition, the model predicts a linear integral relation between the pion distribution amplitude and the parton distribution function of the pion, which holds at the leading-order QCD evolution.Comment: mistake in Eq.(38) correcte

Conflicts treatment for ubiquitous collective and context-aware applications

Context-aware computing is a research field that defines systems capable of adapting their behavior according to any relevant information about entities (e.g., people, places and objects) of interest. The ubiquitous computing is closely related to the use of contexts, since it aims to provide personalized, transparent and on-demand services. Ubiquitous systems are frequently shared among multiple users, which may lead to conflicts that occur during adaptation actions due to individual profiles divergences and/or environment resources incompatibility. In such situations it is interesting to detect and solve those conflicts, considering what is better for the group but also being fair enough with each individual demand, whenever possible. This work presents the important concepts on the collective ubiquitous context-aware applications field. Furthermore, it proposes a novel methodology for conflicts detection and resolution that considers the trade-off between quality of services and resources consumption. A case study based on a collective tourist guide was implemented as a proof-of-study to the proposed methodology.Key words: context and awareness in collaborative systems, ubiquitous computing, adaptive collaborative environments