Synthesis, structural characterization and conformational aspects of nostoclide analogues

The synthesis and structural analysis of a set of nostoclide analogues with potential herbicide activity is described. The influence of intra- and intermolecular hydrogen bonding, as well as other interactions on the conformation and packing of the compounds is thoroughly described using DFT calculations and single crystal X-ray diffraction analyses. All lactones exhibited the Z configuration as confirmed by NOESY experiments and by single crystal X-ray diffraction measurements.     

Modified Carbon Paste Electrode for Kinetic Investigation and Simultaneous Determination of Ascorbic and Uric Acids

The present work explores, for the first time, the electrocatalytic oxidation of ascorbic acid (AscH₂) and its determination in the presence of uric acid (UA) on the in situ activated 4‐nitrophthalonitrile modified carbon paste electrode. The kinetic constant κ for the catalytic reaction for the electrocatalytic oxidation of ascorbic acid, evaluated by cyclic voltammetry, chronoamperometry and RDE voltammetry provided values around 10⁶ L mol^?1 s^?1. The sensor provided a linear response range for AscH₂ and UA from 5.0 up to 120.0 μmol L^?1 with detection limits of 1.6 μmol L^?1and 1.3 μmol L^?1, respectively. The sensor was applied for the simultaneous determination of AscH₂ and UA in urine samples and the average recoveries for these samples were 99.8 (±3.1)% and 99.9 (±2.1)%, respectively .     

Determination of penicillins in milk using LC‐UV,LC‐MS and LC‐MS/MS

The aim of this work is to establish a method for the simultaneous determination of eight penicillins in milk samples by LC‐UV, LC‐MS and LC‐MS/MS. The procedure involves a step for clean‐up and to preconcentrate the analytes by SPE and a subsequent chromatographic analysis. LC‐UV, LC‐MS and LC‐MS/MS have been used for the simultaneous quantification of penicillins in milk. The proposed methods have been validated according to the EU guideline and present LOQ below the maximum limits of residues (MRLs) established by the European Union for penicillins in milk. The developed methods were applied to different milk samples obtained from cows medicated with penicillins.     

Processing and Final Properties Improvement of Polyolefin-Sepiolite and Carbon Nanofibre Nanocomposites

Summary: In this work polypropylene (PP) nanocomposites with different nanofillers (sepiolites and carbon nanofibres) have been produced, processed by injection moulding and fibre spinning and analyzed in terms of mechanical properties improvements. Different concentrations of both fillers were used in nanocomposites preparation. The influence of nanofiller type and amount on mechanical properties were analyzed and discussed for each process studied. This study was completed with a basic morphological characterization in order analyze the nanofiller dispersion, distribution and orientation in the nanocomposites. The results achieved show that it is possible to obtain a good dispersion and distribution of the each kind of nanofillers with conventional processing methodologies when the nanofiller concentration is small. Moreover the nanocomposites obtained had better properties than the starting polymers, showing that sepiolite and carbon nanofiller are able to provide an important contribution to the improvement of mechanical properties of the materials analyzed, enlarging the final application possibilities of PP based products.     

Modelling migration behavior of peptide hormones in capillary electrophoresis-electrospray mass spectrometry

The applicability in capillary electrophoresis-electrospray mass spectrometry (CE-ESI-MS) of the classical semiempirical relationships between electrophoretic mobility and charge-to-mass ratio (me versus q/Malpha) has been investigated in order to describe the migration behavior of a series of bioactive peptide hormones. The influence upon the models of the separation electrolyte pH and the accuracy of the pK values of these compounds were studied first by capillary electrophoresis with ultraviolet detection (CE-UV). The classical polymer model, alpha = 1/2, resulted in slightly better correlations at any of the studied pH. Furthermore, a general linear equation can be adjusted combining all the experimental data pairs, which suggests that correlation in the whole pH range is independent of the ionic form of the studied peptide hormones. The plots of q/M1/2 against separation electrolyte pH were used to predict their electrophoretic separations, using the accurate pK values obtained in a previous work by CE-UV for charge calculations. A volatile separation electrolyte containing 50 mM of acetic acid and 50 mM of formic acid at pH 2.85 was selected for optimum CE-UV and CE-ESI-MS analysis of the peptide mixture. At this pH and taking into account the specific features of the coupling, the correlation using the classical polymer law was excellent and its parameters were similar to the ones of the general linear equation previously obtained by CE-UV. This confirmed the applicability in CE-ESI-MS of the semiempirical relationship originally established by CE-UV.     

Confirmatory and quantitative analysis using experimental design for the extraction and liquid chromatography-UV, liquid chromatography-mass spectrometry and liquid chromatography-mass spectrometry/mass spectrometry determination of quinolones in turkey muscle

The aim of this work is to established methods for determination of quinolones (ciprofloxacin, danofloxacin, enrofloxacin, difloxacin and flumequine), regulated by European Union, and sarafloxacin in turkey muscle. An experimental design has been applied for the optimization of the factors that influence the extraction of quinolones from turkey muscle in order to determine the experimental conditions for their extraction with high recoveries. Liquid chromatography with ultraviolet detection (LC-UV), liquid chromatography-mass spectrometry (LC-MS) and liquid chromatography tandem mass spectrometry (LC-MS/MS) have been used for the simultaneous quantification of quinolones antibiotics in turkey muscle. The proposed methods have been validated according to the Food Drugs Administration guideline and presents the limit of quantification below the maximum residue limits established by the European Union for quinolones in turkey muscle. The methods developed have been applied to quantification of enrofloxacin and its main metabolite ciprofloxacin in samples of turkey muscle obtained from animals treated with enrofloxacin.     

Determination of a series of quinolones in pig plasma using solid-phase extraction and liquid chromatography coupled with mass spectrometric detection Application to pharmacokinetic studies

A simple and sensitive liquid chromatography (LC) method was developed for the simultaneous determination of eight quinolones in pig plasma samples. The following two methods of detection were used: ultraviolet (UV) and mass spectrometry with electrospray ionization (ESI/MS). Sample preparation consisted of solid-phase extraction (SPE) on Strata X cartridges prior to the analysis by LC/UV or LC/ESI/MS. The recovery, linearity, limit of detection (LOD) and limit of quantification (LOQ), precision and accuracy of the method were evaluated using spiked pig plasma samples. The suitability of the method for pharmacokinetic studies was evaluated by determining the concentrations of enrofloxacin (ENR) and ciprofloxacin (CIP) also in pig plasma, after administration of 200mg of enrofloxacin per kilogram of fodder during 5 consecutive days.     

Tunable $\chi /\mathcal {P}\mathcal {T}$ Symmetry in Noisy Graphene

We investigate the resonant regime of a mesoscopic cavity made of graphene or a doped beam splitter. Using Non-Hermitian Quantum Mechanics, we consider the Bender-Boettcher assumption that a system must obey parity and time reversal symmetry. Therefore, we describe such system by coupling chirality, parity, and time reversal symmetries through the scattering matrix formalism and apply it in the shot noise functions, also derived here. Finally, we show how to achieve the resonant regime only by setting properly the parameters concerning the chirality and the PT symmetry.     

B-spline explicit active surfaces: an efficient framework for real-time 3-D region-based segmentation

A new formulation of active contours based on explicit functions has been recently suggested. This novel framework allows real-time 3-D segmentation since it reduces the dimensionality of the segmentation problem. In this paper, we propose a B-spline formulation of this approach, which further improves the computational efficiency of the algorithm. We also show that this framework allows evolving the active contour using local region-based terms, thereby overcoming the limitations of the original method while preserving computational speed. The feasibility of real-time 3-D segmentation is demonstrated using simulated and medical data such as liver computer tomography and cardiac ultrasound images.