Exploring the Pion Phenomenology Within a Fully Covariant Constituent Quark Model

An overview of the vector and tensor Generalized Parton Distributions for a charged pion is presented. Such observables, belonging to the set of quantities fundamental for a detailed investigation of the hadronic inner dynamics, have been evaluated within a fully covariant Constituent Quark Model, based on a proper Ansatz of the pion Bethe–Salpeter Amplitude and the Mandelstam formula for matrix elements of operators acting on relativistic composite systems. Given the very encouraging results already obtained for the vector distribution of a charged pion, the model has been extended to the tensor one, and some preliminary calculations will be illustrated.     

Hidden order in 1D bose insulators

We investigate the phase diagram of spinless bosons with long range (variant 1/r(3)) repulsive interactions, relevant to ultracold polarized atoms or molecules, using density matrix renormalization group. Between the two conventional insulating phases, the Mott and density wave phases, we find a new phase possessing hidden order revealed by nonlocal string correlations analogous to those characterizing the Haldane gapped phase of integer spin chains. We develop a mean field theory that describes the low-energy excitations in all three insulating phases. This is used to calculate the absorption spectrum due to oscillatory lattice modulation. We predict a sharp resonance in the spectrum due to a collective excitation of the new phase that would provide clear evidence for the existence of this phase.     

Stir Bar Sorptive Extraction and LC–MS/MS for Trace Analysis of UV Filters in Different Water Matrices

A simple, selective and highly sensitive method was developed and optimized to determine the most commonly used UV filters with endocrine-disrupting potential in water, namely benzophenone-3 (BP-3), octocrylene (OC), ethylhexyl dimethyl p-aminobenzoate (OD-PABA), ethylhexyl methoxycinnamate, ethylhexyl salicylate (EHS) and homosalate (HMS). Samples were extracted by stir bar sorptive extraction followed by liquid desorption (SBSE-LD). The important factors influencing SBSE-LD were optimized. Under optimal conditions, assays were performed on 50 mL of water sample using stir bars (0.5 mm in film thickness, 10 mm in length) at room temperature. The analytes were determined by liquid chromatography–tandem mass spectrometry with triple quadrupole analyzer using atmospheric pressure chemical ionization. The main parameters in HPLC–APCI–MS/MS were also optimized to provide the best performances for all analytes. Moreover, matrix effect was investigated using two methods the post-column infusion system and the method of spiked matrices after extraction. As a result, no significant matrix effect on the analysis was observed. The method showed good linearity (R ² coefficients greater than 0.996 in different water samples after SBSE-LD). Recoveries of the analytes were close to 90%, except for BP-3 (64%) and OC (76%) with relative standard deviation lower than 11%. Detection limits were between 0.6 and 3.3 ng L⁻¹ for all the analytes except for HMS (94 ng L⁻¹) and EHS (114 ng L⁻¹). This methodology was applied to measure UV filters in seawater, river water and wastewater in different sites of Liguria; BP-3 and OC were found in most of the considered samples at rather low concentration level.

     

Predicting patchy particle crystals: variable box shape simulations and evolutionary algorithms

We consider several patchy particle models that have been proposed in literature and we investigate their candidate crystal structures in a systematic way. We compare two different algorithms for predicting crystal structures: (i) an approach based on Monte Carlo simulations in the isobaric-isothermal ensemble and (ii) an optimization technique based on ideas of evolutionary algorithms. We show that the two methods are equally successful and provide consistent results on crystalline phases of patchy particle systems.     

Linear extensions of partial orders and reverse mathematics

We introduce the notion of τ‐like partial order, where τ is one of the linear order types ω, ω*, ω + ω*, and ζ. For example, being ω‐like means that every element has finitely many predecessors, while being ζ‐like means that every interval is finite. We consider statements of the form “any τ‐like partial order has a τ‐like linear extension” and “any τ‐like partial order is embeddable into τ” (when τ is ζ this result appears to be new). Working in the framework of reverse mathematics, we show that these statements are equivalent either to $\mathsf {B}{\Sigma }^{0}_{2}$ or to $\mathsf {ACA}_0$ over the usual base system $\mathsf {RCA}_0$.     

Characterization of cocoa liquors by GC-MS and LC-MS/MS: focus on alkylpyrazines and flavanols

Flavor is one of the most important characteristics of chocolate products and is due to a complex volatile fraction, depending both on the cocoa bean genotype and the several processes occurring during chocolate production (fermentation, drying, roasting and conching). Alkylpyrazines are among the most studied volatiles, being one of the main classes of odorant compounds in cocoa products. In this work, a mass spectrometric approach was used for the comparison of cocoa liquors from different countries. A headspace solid-phase microextraction gas chromatography-mass spectrometry method was developed for the qualitative study of the volatile fraction; the standard addition method was then used for the quantitative determination of five pyrazines (2-methylpyrazine, 2,3-dimethylpyrazine, 2,5-dimethylpyrazine, 2,3,5-trimethylpyrazine and tetramethylpyrazine). Satisfactory figures of merit were obtained: Limits of quantitation were in the range 0.1-2.7?ng/g; repeatability and reproducibility varied between 3% and 7% and between 8% and 14%, respectively. The total content of the pyrazines was remarkably different in the considered samples, ranging from 99 to 708?ng/g. Tetramethylpyrazine showed the highest concentration in all samples, with a maximum value of 585?ng/g. A preliminary study was also performed on the nonvolatile fraction using LC-MS/MS, identifying some flavanols such as catechin, epicatechin and procyanidins. Copyright ? 2012 John Wiley & Sons, Ltd.     

Deformation and failure kinetics of iPP polymorphs

In this study, the mechanical performance of the different polymorphs of isotactic polypropylene, typically present in iPP crystallized under industrial processing conditions, is assessed. Different preparation strategies were used to obtain samples consisting of almost solely α, β, or γ crystals. X‐Ray measurements were used to validate that the desired phase was obtained. The intrinsic true stress ‐ true strain response of all individual phases was measured in uniaxial compression at several strain rates (deformation kinetics). Moreover, measurements were performed over a wide temperature range, covering the window in between the glass transition and the melting temperature. The relation between obtained yield stress and the strain rate is described with a modification of the Ree‐Eyring model. Differences and similarities in the deformation kinetics of the different phases are presented and discussed. Furthermore, the presence of three deformation processes, acting in parallel, is revealed. The Ree‐Eyring equation enables lifetime prediction for given thermal and mechanical conditions. These predictions were experimentally validated using constant load tests in uniaxial compression. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 729–747