Determination of polycyclic aromatic hydrocarbons in vegetable oils using solid-phase microextraction-comprehensive two-dimensional gas chromatography coupled with time-of-flight mass spectrometry

A simple and fast solid-phase microextraction method coupled with comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry was developed for analysis of polycyclic aromatic hydrocarbons in edible oil, performed directly in a hexane solution of the oil. Sampling conditions (solvent used, extraction time, extraction temperature and fiber rinsing time) were optimized by using a sample of oil fortified with a standard solution of polycyclic aromatic hydrocarbons. The method was validated by calculating linear range, correlation coefficient, accuracy, repeatability, detection limit and quantification limit. The method was applied to several oils collected from the market and directly from an olive pomace extraction plant.     

Thermal and kinetic study of tyre waste pyrolysis via TG-FTIR-MS analysis

The world production of tyre waste amounts to 5·10⁶ ton year^–1, 2·10⁶ tons of which are produced in Europe, but the final destination of nearly 65–70% of them is the landfill, despite the high added value materials lost and the consequent environmental impact. Treatments alternative to landfilling take into account reconstruction and reuse of the tyres or the matter and/or energy recovery by means of thermal treatment processes (incineration, gasification and pyrolysis). Among these, pyrolysis seems to be a promising and realistic alternative to attain the conversion of tyre waste into valuable and reusable products. Present work relates to experimental tests and results obtained for the study of tyre waste pyrolysis, conducted by means of thermo-gravimetric analysis (TG) of the material and the simultaneous determination, through Fourier transform infrared (FTIR) and mass spectrometry (MS), of the decomposition products. The analysis of the volatile fraction allows to isolate, within the thermograms, the evolution of products referable to specific tyre components and therefore it suggests the application of a multi-component decomposition model. The kinetic model consequently developed agrees fairly well with the experimental data.     

Square‐Wave Voltammetry as Analytical Tool for Real‐Time Study of Controlled Naproxen Releasing from Cellulose Derivative Materials

This work reports the successful use of square‐wave voltammetry (SWV) to directly assess the controlled releasing profile of naproxen from lab‐made cellulose derivative materials (membranes and microparticles) in phosphate buffer (pH 7.4) at 36 °C. Particular advantage of SWV refers to the direct real‐time monitoring of released drug from cellulose derivative microparticles, which cannot be easily assessed by UV‐spectrophotometry. Moreover, SWV was able to detect modifications in the naproxen releasing profile due to morphology and processing of membranes and microparticles. The possible miniaturization and versatility of SWV suggest the promising application on the study of several drug delivery systems, including in vivo studies.     

Effects of Kynurenic Acid on the Rat Aorta Ischemia—Reperfusion Model: Pharmacological Characterization and Proteomic Profiling

Kynurenic acid (KYNA) is derived from tryptophan, formed by the kynurenic pathway. KYNA is being widely studied as a biomarker for neurological and cardiovascular diseases, as it is found in ischemic conditions as a protective agent; however, little is known about its effect after ischemia-reperfusion in the vascular system. We induced ischemia for 30 min followed by 5 min reperfusion (I/R) in the rat aorta for KYNA evaluation using functional assays combined with proteomics. KYNA recovered the exacerbated contraction induced by phenylephrine and relaxation induced by acetylcholine or sodium nitroprussiate in the I/R aorta, with vessel responses returning to values observed without I/R. The functional recovery can be related to the antioxidant activity of KYNA, which may be acting on the endothelium-injury prevention, especially during reperfusion, and to proteins that regulate neurotransmission and cell repair/growth, expressed after the KYNA treatment. These proteins interacted in a network, confirming a protein profile expression for endothelium and neuron repair after I/R. Thus, the KYNA treatment had the ability to recover the functionality of injured ischemic-reperfusion aorta, by tissue repairing and control of neurotransmitter release, which reinforces its role in the post-ischemic condition, and can be useful in the treatment of such disease.     

Preparation of Cerium-Bismuth Oxide Catalysts for Diesel Soot Oxidation Including Evaluation of an Automated Soot-Catalyst Contact Mode

Cerium-bismuth oxides have emerged as promising candidates for Diesel soot oxidation. The catalysts are synthesized via automated co-precipitation methods. T₅₀ values, where 50 % of soot is oxidized, and the dynamic oxygen storage capacity (OSC_dyn) are used to compare the catalytic activity. The activity is measured by thermogravimetric methods. The synthesized catalysts are characterized through powder X-ray diffraction (PXRD), Raman spectroscopy, and specific surface area (S_BET) measurements. This work investigates the influence of the contact mode between soot and catalyst. The literature-known manual contact modes “loose”, “tight”, and “wet” are compared with our developed automated contact mode, using a dual asymmetric centrifuge. The rotation speed rs and mixing time t_M have been varied independently. Both factors influence the T₅₀ value. A continuous transition from loose to tight contact mode with increasing rotation speed rs can be shown. Furthermore, the automated contact mode shows better reproducibility behavior compared to manual contact modes.     

Clear and pigmented water epoxy systems: a study on the hardening kinetics on the basis of the variations of the viscoelastic moduli

The hardening reaction of a two-can water epoxy polyamide system was investigated on the basis of the variation of the viscoelastic moduli G′ and G′′. Unpigmented (clear varnish) and TiO₂ pigmented formulations, at two different TiO₂ concentrations, were taken into account. Time and frequency sweep procedures were carried out using the stress-controlled rheometer Haake RS 150. The behavior of G′ and G′′ vs time was fitted to a four-parameter asymptotic model through the whole course of the hardening process. Frequency sweep data, obtained at increasing times during the whole hardening process, were plotted to the generalized Cole and Cole behavior model and the corresponding mechanical spectra were drawn. An interpretation for some aspects of the cross-linking progress is discussed and possible future developments are briefly outlined. Received: 15 January 2000 Accepted: 13 November 2000     

Influence of membrane surface properties on the growth of neuronal cells isolated from hippocampus

Membranes have become of great interest for tissue engineering application, since they offer the advantage of developing neuronal tissue that may be used in implantable or in vitro hybrid systems for the simulation of brain function. The behaviour of neurons isolated from the hippocampus on membranes with different surface properties was investigated.     

Radiofrequency ablation planning: An application of semi-infinite modelling techniques

In radiofrequency (RF) ablation a needle-shaped probe is inserted into the patient’s body in order to heat and subsequently destroy the malignant tissue around the needle tip. The determination of the optimal probe position poses an intricate problem, as it requires the modelling of the tumour destruction depending on the attained temperature as well as the incorporation of constraints that prohibit puncturing bones or other risk structures.In this work we present a new optimization procedure that reflects both aspects adequately. We assess tumour destruction by solving the underlying system of partial differential equations using a finite element method. Next we show how the probe’s position and orientation can be optimized by gradient-based methods. Ensuring that risk structures are not harmed by the probe is easily modelled using semi-infinite constraints in the optimization problem.Techniques to reduce the semi-infinite problem to a standard nonlinear constrained optimization problem are introduced and demonstrated as a proof-of-concept on real clinical data. The results indicate the high potential of this combination of PDE-based simulation and numerical optimization for RF ablation planning.