New contributions to heavy quark sum rules

We analyse new contributions to the theoretical input in heavy quark sum rules and we show that the general theory of singularities of perturbation theory amplitudes yields the method to handle these specific features. In particular we study the inclusion of heavy quark radiation by light quarks at O(alpha_s^2) and non-symmetric correlators at O(alpha_s^3). Closely related, we also propose a solution to the construction of moments of the spectral densities at O(alpha_s^3) where the presence of massless contributions invalidates the standard approach. We circumvent this problem through a new definition of the moments, providing an infrared safe and consistent procedure.Comment: 15 pages, 3 figures. Version accepted for publication in The European Journal of Physics C; several new comments and references added, conclusions unchange

The Discovery and Interpretation of Evidence Accumulation Stages

To improve the understanding of cognitive processing stages, we combined two prominent traditions in cognitive science: evidence accumulation models and stage discovery methods. While evidence accumulation models have been applied to a wide variety of tasks, they are limited to tasks in which decision-making effects can be attributed to a single processing stage. Here, we propose a new method that first uses machine learning to discover processing stages in EEG data and then applies evidence accumulation models to characterize the duration effects in the identified stages. To evaluate this method, we applied it to a previously published associative recognition task (Application 1) and a previously published random dot motion task with a speed-accuracy trade-off manipulation (Application 2). In both applications, the evidence accumulation models accounted better for the data when we first applied the stage-discovery method, and the resulting parameter estimates where generally in line with psychological theories. In addition, in Application 1 the results shed new light on target-foil effects in associative recognition, while in Application 2 the stage discovery method identified an additional stage in the accuracy-focused condition — challenging standard evidence accumulation accounts. We conclude that the new framework provides a powerful new tool to investigate processing stages

tau -> pi pi pi nu_tau decays and the a_1(1260) off-shell width revisited

The tau -> pi pi pi nu_tau decay is driven by the hadronization of the axial-vector current. Within the resonance chiral theory, and considering the large-Nc expansion, this process has been studied in Ref.[1]. In the light of later developments we revise here this previous work by including a new off-shell width for the lightest a_1 resonance that provides a good description of the tau -> pi pi pi nu_tau spectrum and branching ratio. We also consider the role of the rho(1450) resonance in these observables. Thus we bring in an overall description of the tau -> pi pi pi nu_tau process in excellent agreement with our present experimental knowledge.Comment: 15 pages, 3 figure

Local structural analysis of erbium-doped tellurite modified silica glass with x-ray photoelectron spectroscopy

Ultrafast laser plasma doping (ULPD) is a recently developed technique that enables the blending of femtosecond laser produced plasma from a TeO2 (target) based glass with a SiO2 (substrate) without or minimum phase separation to form a silicate glass. The background oxygen gas pressure plays a major role in ULPD as it directly impacts the plasma plume characteristics, resulting in lower erbium doped tellurite modified silica (EDTS) thickness and refractive index at higher process gas pressure. X-ray photoelectron spectroscopy (XPS) used in this study to analyse the formation of EDTS and local bonding environment of its constituents. This report confirms the presence of both target materials and SiO2 in the resulting EDTS films. XPS of O 1 s core, confirms that bridging oxygen (BO) is more dominant compared to non-bridging oxygen (NBO) in the EDTS glass network, and the amount of BO is more stand out for higher gas pressures when the glass modifiers are relatively smaller in concentration. Our study revealed the nucleation Te and Er to form metal nanoparticles in glass under certain preparation conditions/doping concentration which were previously undetected using other experimental techniques. It is important to control this nanoparticle formation in engineering EDTS for photonic device applications

Thalamic bursts modulate cortical synchrony locally to switch between states of global functional connectivity in a cognitive task

Performing a cognitive task requires going through a sequence of functionally diverse stages. Although it is typically assumed that these stages are characterized by distinct states of cortical synchrony that are triggered by sub-cortical events, little reported evidence supports this hypothesis. To test this hypothesis, we first identified cognitive stages in single-trial MEG data of an associative recognition task, showing with a novel method that each stage begins with local modulations of synchrony followed by a state of directed functional connectivity. Second, we developed the first whole-brain model that can simulate cortical synchrony throughout a task. The model suggests that the observed synchrony is caused by thalamocortical bursts at the onset of each stage, targeted at cortical synapses and interacting with the structural anatomical connectivity. These findings confirm that cognitive stages are defined by distinct states of cortical synchrony and explains the network-level mechanisms necessary for reaching stage-dependent synchrony states

LC-IMS-HRMS for identification of biomarkers in untargeted metabolomics: The effects of pterostilbene and resveratrol consumption in liver steatosis, animal model

Untargeted metabolomics with the combination of ion mobility separation coupled to high resolution mass spectrometry (IMS-HRMS) was applied to investigate the impact of resveratrol and pterostilbene supplementation on the metabolic fingerprint of the Wistar rats liver with induced liver steatosis. RP-LC and HILIC in both ionisation modes were employed to analyse the liver samples (n = 40) from Wistar rats fed with a high-fat and high-fructose diet, supplemented or not with resveratrol and pterostilbene. After univariate and multivariate statistical analysis, 34 metabolites were highlighted in the different diets and elucidated. Despite the structural similarity, different alterations in liver metabolism were observed by the supplementations. Resveratrol treatment was characterised by the alteration in metabolism of 17 lysophospholipids, while pterostilbene affected some vitamins and derivatives, among others. IMS has demonstrated great potential in the elucidation process thanks to the additional structural descriptor the CCS (Å2), providing more confidence in the identification

NNLO tau+tau- production cross section at threshold

The threshold behaviour of the cross section sigma(e+e- -> tau+tau-) is analysed, taking into account the known higher-order corrections. At present, this observable can be determined to next-to-next-to-leading order (NNLO) in a combined expansion in powers of alpha_s and fermion velocities.Comment: 4 pages, 3 figures. To appear in the proceedings of QCD 02: High-Energy Physics International Conference in Quantum Chromodynamics, Montpellier, France, 2-9 Jul 200