Modulation of volume fraction results in different kinetic effects in Belousov-Zhabotinsky reaction confined in AOT-reverse microemulsion

The effects of volume fraction modulations on a Belousov-Zhabotinsky reaction catalyzed by the photosensitive Ru(bpy)(3)(+2) confined in an AOT microemulsion system are analyzed. Kinetic observables such as the induction time or the initial oscillation period demonstrate two different types of correlation with the volume fraction depending on whether the system is below or above the microemulsion percolation threshold. Temporal evolution also demonstrates an exponential growth of the period with the number of oscillations independent of the volume fraction of the system.     

Thermal properties of ionic systems near the liquid-liquid critical point

Isobaric heat capacity per unit volume, C(p), and excess molar enthalpy, h(E), were determined in the vicinity of the critical point for a set of binary systems formed by an ionic liquid and a molecular solvent. Moreover, and, since critical composition had to be accurately determined, liquid-liquid equilibrium curves were also obtained using a calorimetric method. The systems were selected with a view on representing, near room temperature, examples from clearly solvophobic to clearly coulombic behavior, which traditionally was related with the electric permittivity of the solvent. The chosen molecular compounds are: ethanol, 1-butanol, 1-hexanol, 1,3-dichloropropane, and diethylcarbonate, whereas ionic liquids are formed by imidazolium-based cations and tetrafluoroborate or bis-(trifluromethylsulfonyl)amide anions. The results reveal that solvophobic critical behavior-systems with molecular solvents of high dielectric permittivity-is very similar to that found for molecular binary systems. However, coulombic systems-those with low permittivity molecular solvents-show strong deviations from the results usually found for these magnitudes near the liquid-liquid phase transition. They present an extremely small critical anomaly in C(p)-several orders of magnitude lower than those typically obtained for binary mixtures-and extremely low h(E)-for one system even negative, fact not observed, up to date, for any liquid-liquid transition in the nearness of an upper critical solution temperature.     

Use of nonlinear properties of intracavity type II second harmonic generation for image processing

We discuss the use of intracavity type-II second harmonic generation for all-optical processing of images. Injecting an image in a pump beam linearly polarized and a homogeneous field in the orthogonally polarized pump, it is possible to magnify the contrast and to recognize the contour of any part of the image whose intensity is above a tunable reference level. This can be done using ideal planar cavities where all the fields are resonant as well as in the more realistic situation where only the fundamental fields are resonant and using cavities with spherical mirrors. PACS 42.30.-d; 42.65.Ky; 42.65.Pc     

Development of a solid-phase microextraction method for determination of volatile oxidation compounds in fish oil emulsions

Headspace solid-phase microextraction (HS-SPME) is proposed for isolating and determining the headspace volatiles formed during oxidation of fish-oil-in-water emulsions. Three different fiber coatings were tested and compared for sensitivity and reproducibility. A carboxen/polydimethylsiloxane (CAR-PDMS) fiber coating was found to be the most suitable for the analysis of emulsion volatiles. The main factors affecting the microextraction process on CAR-PDMS were then evaluated by a factorial design: amount of sample, time and temperature of extraction and stirring. The incubation of 0.5 g of emulsion at 60 degrees C during 30 min leads to the most effective extraction of volatiles associated with lipid oxidation of fish oil emulsions. The HS-SPME method coupled with GC-MS allowed the qualitative and quantitative analysis of the volatiles derived from oxidation of real fish oil enriched foods such as milk and mayonnaise. The method here proposed is very fast and simple and yields high sensitivity, with good repeatability for all target compounds.     

Asymptotic properties of conditional quantile estimator for censored dependent observations

In this paper, we establish strong uniform convergence and asymptotic normality of the conditional quantile estimator for the censorship model when the data exhibit some kind of dependence. It is assumed that the observations form a stationary α-mixing sequence. The strong uniform convergence in iid framework has recently been discussed by Ould-Saïd (Stat Probab Lett 76:579–586, 2006). As a by-product, we also obtain a uniform weak convergence rate for the product-limit estimator of the lifetime and censoring distributions under dependence, which is interesting independently.     

Trace metals distribution in surface and deep seawater from the Ría de Arousa estuary (north-western Spain): Study before and after the Prestige oil tanker sinking

Cu, Ni, Pb, Mn, Sn, Fe, Al and Zn in surface and deep seawater samples from Ría de Arousa estuary (Galicia, north-western Spain) collected before and after the Prestige spillage were determined. Data were then used to evaluate the impact of the Prestige accident in the Ría de Arousa by applying principal component analysis (PCA) and cluster analysis (CA). Surface water from Sar River and Ulla River was also analysed for the same elements. Determinations were performed by inductively coupled plasma–optical emission spectrometry (ICP–OES) after solid phase extraction (SPE) of element-8-hydroxyquinoline complexes onto commercial C18 cartridges. The highest concentrations were found in sampling stations along Ulla River, while Al, Fe and Sn offered the highest values in surface and deep seawater from the inner part of the estuary, area where the main villages and sport harbours are located. PCA and CA have shown an independent group formed by surface seawater from the East margin of the mouth of the estuary collected after the Prestige oil spill. However, independent groups were not observed when using deep seawater data, and the effect of the Prestige accident appears to be less evident.     

Selective copper-promoted cross-coupling reaction of anilines and alkylboranes

Extension of the Chan–Lam N-alkylation of anilines by using alkylboranes as organoboron partners is reported. Alkylboranes, synthesized by hydroboration of styrenes, are effectively coupled with anilines, which comprises a facile method for the synthesis of highly functionalized phenethylaniline derivatives. This is the first time that alkylboranes are used in C–N copper-promoted cross-coupling reactions.     

Studying the bandwidth in k-sample smooth tests

In this paper, the problem of bandwidth choice in smooth k-sample tests is considered. Three different bootstrap methods are discussed and implemented. All the methods persecute the bandwidth leading to the maximum power, while preserving the level of the test. The relative performance of the methods is investigated in a simulation study. Illustration through real medical data is provided. The main conclusion is that the bootstrap minimum method provides a good compromise between statistical power and conservativeness. Robustness of the methods with respect to the number of bootstrap resamples and practical limitations are discussed.     

Electromagnetic properties of lithium zinc ferrites doped with aluminum

We present the results of the effect of Al substitution on the magnetic and electrical properties of Li_0.2Zn_0.6Fe_2.2−xAl_xO₄ ferrites (0.0≤x≤0.5) prepared by the standard ceramic technique. The characterization has been performed using XRD, SEM, magnetic and dielectric response in frequency. XRD analysis confirms that the system exhibits polycrystalline single phase cubic spinel structure only for low dopant content. Doping decreases the dielectric loss tangent and the ferrite conductivity in more than two orders of magnitude in the whole analyzed frequency range. Attenuation has a maximum intensity (86 dB) near 90 MHz for x=0.4. The wider bandwidth at 20 dB (94.6 MHz) is for x=0.3.