Linear and non linear chemometric models to quantify the adulteration of extra virgin olive oil

Two mathematical methods to quantify adulterations of extra virgin olive oil (EVOO) with refined olive oil (ROO), refined olive-pomace oil (ROPO), sunflower (SO) or corn (CO) oils have been described here. These methods are linear and non linear models based on chaotic parameters (CPs, Lyapunov exponent, autocorrelation coefficients and two fractal dimensions) which were calculated from UV-vis scans (190-900 nm wavelength) of 817 adulterated EVOO samples. By an external validation process, linear and non linear integrated CPs/UV-vis models estimate concentrations of adulterant agents with a mean correlation coefficient (estimated versus real concentration of cheaper oil) greater than 0.80 and 0.97 and a mean square error less than 1% and 0.007%, respectively. In the light of the results shown in this paper, the adulteration of EVOO with ROO, ROPO, SO and CO can be suitably detected by only one chaotic parameter integrated on a radial basis network model.     

Study of the gamma irradiation effects on the PMMA/HA and PMMA/SW

The behavior of the poly(methyl methacrylate) (PMMA) under the action of gamma radiation has been sufficiently studied. In this work, we present results from melt flow index (MFI), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and electron paramagnetic resonance (EPR) of PMMA composites with hydroxyapatite (HA) and seaweed residues (SW) irradiated with gamma rays at 1.08 kGy/h. Composites of PMMA/HA and PMMA/SW with 10%, 20% and 30% of the filler were prepared. The results show an increase in the MFI values with the integral dose of radiation, being consistent with chain-scission reactions. No EPR signal was observed in pure PMMA, while in the composites, the typical EPR signal of the PMMA radicals was observed, which increased with the amount of HA or SW. When comparing the relative intensities of the EPR signals for both types of composites, a slight increase in the concentration of free radicals generated in the sample with SW respect to that of PMMA/HA composite was obtained. A decay of the total free radical concentration was observed as time elapsed.     

Synthesis of enantiopure C3- and C4-hydroxyretinals and their enzymatic reduction by ADH8 from Xenopus laevis

(R)-all-trans-3-hydroxyretinal 1, (S)-all-trans-4-hydroxyretinal and (R)-all-trans-4-hydroxyretinal have been synthesized stereoselectively by Horner-Wadsworth-Emmons and Stille cross-coupling as bond-forming reactions. The CBS method of ketone reduction was used in the enantioface-differentiation step to provide the precursors for the synthesis of the 4-hydroxyretinal enantiomers. The kinetic constants of Xenopus laevis ADH8 with these retinoids have been determined.     

General solution of certain matrix equations arising in filter design applications

In this work we present the explicit expression of all rectangular Toeplitz matrices B,C which verify the equation BB^H+CC^H=aI for some a>0. This matrix equation arises in some signal processing problems. For instance, it appears when designing the even and odd components of paraunitary filters, which are widely used for signal compression and denoising purposes. We also point out the relationship between the above matrix equation and the polynomial Bézout equation |B(z)|²+|C(z)|²=a>0 for |z|=1. By exploiting this fact, our results also yield a constructive method for the parameterization of all solutions B(z),C(z). The main advantage of our approach is that B and C are built without need of spectral factorization. Besides these theoretical advances, in order to illustrate the effectiveness of our approach, some examples of paraunitary filters design are finally given.     

Self-assembled host-guest nanostructures on gold electrodes for thiodianiline determination

Self-assembled monolayers of thiolated β-cyclodextrins on a gold electrode have been developed for the determination of thiodianiline. Pentanethiol was employed to fill the empty space between the β-cyclodextrins on the surface. The formation of a 1:2 inclusion complex between thiodianiline and β-cyclodextrin was studied by electrochemistry. The parameters affecting the modification of the electrode and the determination of thiodianiline by square wave voltammetry were optimized. The limits of detection and determination are 190 and 205 μg?L^?1, respectively. The accuracy, in terms of relative error values, is <7%. The precision, in terms of RSD (for n?=?5), is <5%. The method was applied to the determination of thiodianiline in real wastewater samples with RSD values of <11% and an average recovery of 98% for all the spiking levels assayed.     

The High-Resolution Raman Spectrum of the nu4 Band of Diborane

The high-resolution Raman spectra of the nu4 bands of 11B2H6 and 11B10BH6 have been recorded and analyzed. The recordings have been made using a high-resolution spectrometer based on the inverse Raman effect. Q branches have been observed, but P and R branches were too weak to be seen, and simulations of the observed band contour have been necessary to complete the analysis. A weak Coriolis resonance with the 2nu10 level is present in the 11B2H6 spectrum. The band centers obtained are 790.9829(12) and 804.76985(27) cm-1 for 11B2H6 and 10B11BH6, respectively (uncertainties are type A with a coverage factor k = 1, i.e., 1 standard deviation). Copyright 1999 Academic Press.     

SEM/EDX and vis spectrophotometry study of the stability of resin-bound mortars used for casting replicas and filling missing parts of historic stone fountains

A study by SEM/EDX and spectrophotometry in the visible region attempting to assess the stability of new resin-bound mortars used for casting replicas of marble historic fountains is presented in this paper. Different accelerating tests such as thermal ageing, UV light ageing, ageing in an SO(2) pollutant chamber, freezing cycles ageing, salt crystallisation ageing, natural ageing and biological attack have been applied to a series of test specimens prepared with polyester-, epoxy- and gel-coat-bound mortars. Examination of morphology, measurement of chemical composition and chromatic coordinates before and after ageing treatments establish the higher stability and resistance properties of these resin-bound mortars by comparison to those from the natural marbles.