New home-made assembly for hollow-fibre membrane extraction of persistent organic pollutants from real world samples

Nowadays, hollow fibre membrane extraction techniques are widely used but they are usually applied to water or very simple matrices such as water. In this paper, we propose a new assembly that allows the extraction of forty persistent organic pollutants in real world samples, namely orange juice, porcine plasma and tomatoes. The limits of detection obtained are very low even in the analysis of real samples (9-182 ng L(-1)). The relative standard deviations vary from 1 to 18% and the averaged recoveries in the spike experiments are very high (65-120%) in the different types of samples studied. The new assembly allows a very good precision overcoming in one of the most important shortcomings of membrane extraction techniques. A central composite design has been performed to get optimal extraction conditions for the analytes and also the combined response of all the analytes has been obtained to attain the simultaneous optimum.     

Ion beam induced crystal-edge nanoclusters at the origin of poly(ethylene glycol) film stabilization

PEG films stabilized by noble gas ion beam irradiation showed characteristic clustering at the crystal edges. These structures appear in determined ion beam conditions after exposure to Ar and Kr ions. Atomic force microscopy exploration indicates that, rather than presenting drastic topographic features, the nanostructures show radically different elastic properties. Within the concerned set of ion beam conditions, the surface properties are observed to vary according to the absorbed energy as suggested by X-ray photoelectron spectroscopy and contact angle measurements. These analyses predict that Ar irradiation in the 500-600 V extraction potential range is an appropriate condition for PEG stabilization.     

Solitary wave solutions to nonlinear evolution equations in mathematical physics

This paper obtains solitons as well as other solutions to a few nonlinear evolution equations that appear in various areas of mathematical physics. The two analytical integrators that are applied to extract solutions are tan–cot method and functional variable approaches. The soliton solutions can be used in the further study of shallow water waves in (1+1) as well as (2+1) dimensions.     

Evidence for radial flow of thermal dileptons in high-energy nuclear collisions

The NA60 experiment at the CERN SPS has studied low-mass dimuon production in 158A GeV In-In collisions. An excess of pairs above the known meson decays has been reported before. We now present precision results on the associated transverse momentum spectra. The slope parameter Teff extracted from the spectra rises with dimuon mass up to the rho, followed by a sudden decline above. While the initial rise is consistent with the expectations for radial flow of a hadronic decay source, the decline signals a transition to an emission source with much smaller flow. This may well represent the first direct evidence for thermal radiation of partonic origin in nuclear collisions.     

Comparison of elemental content on modern and ancient papers by EDXRF

We report on the use of elemental composition, determined by energy dispersive X-ray fluorescence (EDXRF), to identify different types of paper. The concentrations of S, Cl, K, Ca, Ti, Mn, Fe, Co, Cu, Zn, As, Br, Rb, Sr, Ba and Pb were determined in papers from 1555, 1575, 1724, 1748, 1779, 1782, 1787, 1806, 1861, 1919, 1941 and 2005. A preliminary analysis was made with the use of a dendrogram. The Euclidian distances evidenced a big fluctuation in the elemental composition on most recent papers. The dendrogram also allowed us to catalogue the analysed samples into ten types of paper. Calcium, Cu, Fe, Zn and Sr were the only elements found in all paper samples. However the content of each element was different in every paper type. Calcium is the predominant element in all paper types. Applying Spearman coefficients correlations to these papers for Ca, Cu, Fe, Zn and Sr, we found moderate negative correlations between Ca-Cu. Positive correlations were also found between Fe-Cu, though not very strong. High levels of the toxic elements, Co, Ni, As and Pb were present in papers from 1779 and 1787. From this work it becomes clear that the number of elements in modern papers is lower than in older ones. PACS 39.30.+W; 78.70.En; 89.90.+n     

Functionality of Aerosol-Gel Deposited TiO2 Thin Films Processed at Low Temperature

TiO₂ thin films have been deposited using the Aerosol-gel process and heat-treated at low temperature. Functional coatings necessitate reasonably good abrasion resistance in order to support possible damages related to a targeted application. Besides, specific applications of TiO₂ films require additional criteria, e.g. a tailored refractive index, a controlled chemical composition or a suitable crystallization degree. In this paper, we present several low temperature preparation procedures that answer the different criteria and allow to envisage applications on thermally sensitive substrates.     

Peroxycarbenium-mediated C-C bond formation: applications to the synthesis of hydroperoxides and peroxides

The Lewis acid-mediated reaction of alkene nucleophiles with peroxyacetals provides an effective route for the synthesis of homologated peroxides and hydroperoxides. In the presence of Lewis acids such as TiCl(4), SnCl(4), and trimethylsilyl triflate, peroxyacetals and peroxyketals undergo reaction with allyltrimethylsilane, silyl enol ethers, and silyl ketene acetals to afford homoallyl peroxides, 3-peroxyketones, and 3-peroxyalkanoates, respectively. Reactions of peroxyacetals are Lewis acid dependent; TiCl(4) promotes formation of ethers while SnCl(4) and trimethylsilyl triflate promote formation of peroxides. Lewis acid-promoted reactions of silylated hydroperoxyacetals furnish silylated hydroperoxides, which can be deprotected to homologated hydroperoxides. Hydroperoxyketals undergo Lewis acid-mediated allylation to furnish 1,2-dioxolanes via attack of hydroperoxide on the intermediate carbocation. Lewis acid-mediated cyclization of unsaturated peroxyacetals furnishes 1,2-dioxanes, 1,2-dioxepanes, and 1,2-dioxacanes through 6-endo/exo, 7-endo/endo, and 8-endo/endo pathways. The corresponding reactions involving 6-endo/endo and 5-endo/exo pathways were unsuccessful.