Electrochemical sensor array made from bisphthalocyanine modified carbon paste electrodes for discrimination of red wines

A new sensor system devoted to the discrimination of red wines is presented. It consists of an array of electrochemical sensors made from carbon paste electrodes modified with three rare-earth bisphthalocyaninate compounds, including lutetium(III), gadolinium(III) and praseodymium(III) bisphthalocyaninates. The sensor responses have been evaluated either by cyclic voltammetry or by square wave voltammetry, and demonstrate that such voltammetric sensors show a rich response when immersed in red wines. In addition, this response can be tuned by changing the central metal atom of the double-decker complexes, obtaining sensing units with high cross-selectivity.

The sensor array is exposed to six Spanish red wines made from the same grape variety, prepared using a similar vinification method, but belonging to three different geographic origins and ageing stages. The voltammograms indicate that each sensing unit provides a particular response to each class of wine.

Finally, the signals coming from each sensor are combined and the system’s discrimination capability is evaluated by using principal component analysis (PCA), where a windowed slicing pre-processing method has been developed to capture the information throughout the global response. The PCA score plots of the obtained data show the discrimination of the tested wines with a good-quality performance.     

A microhardness test for monitoring the thermal stabilization of solid PVC

The Vickers microhardness test has been found to be a new and attractive analytical tool for the study of the thermal degradation of rigid poly(vinyl chloride) sheets stabilized with different ratios of calcium/zinc carboxylates.     

Monitoring the UV degradation of PVC window frames by microhardness analysis

While well-known methods of bulk analysis of thermal degradation of PVC become standard industrial tools, techniques for the study of surface damage produced by weathering are not generally considered. In this paper we present a new test, based on microhardness measurements, which can be used as a complementary technique for the study of this phenomenon. Comparison of this method with color changes and specific elongation at break measurement has been established for PVC window frames.     

Fabrication of ceramic nanofibers using polydimethylsiloxane and polyacrylonitrile polymer blends

Nanofibers with several hundred of nanometers were successfully fabricated using electrospinning process and a mixture of two types of polymers which are: polydimethylsiloxane and polyacrylonitrile as precursors. After stabilization and carbonization at 1000 °C, three phases which are: silicon carbide (SiC), carbon, and oxy‐SiC were presented. Spectroscopic and microscopic techniques had confirmed the presence of nanocrystalline SiC and turbostratic carbons. These phases formed an intertwined network at the nanometric scale. In addition, the resulted fibers showed a core‐skin effect with skin richer in carbon and a core mainly dominated by silicon‐based phases in the form SiC or Si? O? C ceramics. A significant improvement was observed in both tensile strength and elastic modulus in these hybrid fibers. In term of crystallography, these nanofibers seem to exhibit similar microstructure that was observed in Nicalon fiber. However, it was difficult to determine the ratio of these phases and their influence on the physical properties of these hybrid fibers. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45967.     

Mechanical characterization of closed‐cell polyolefin foams

Three different experimental techniques [compression experiments at low strain rates, instrumented falling‐weight impact tests, and dynamic mechanical analysis (DMA)] have been used for the mechanical characterization of a collection of crosslinked closed‐cell polyolefin foams of different chemical compositions, densities, and type of cellular structure. The experimental results that it is possible to obtain from each technique are shown, and related to the different applications of these materials. The relationships between the structure and the mechanical properties are also presented. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 156–166, 2000     

Effect of addition of EVA on the technical properties of extruded foam profiles of low-density polyethylene/EVA blends

Some technical properties (static mechanical properties, dynamic mechanical properties, creep-recovery behavior, thermal expansion, and thermal conductivity) of low-density foams (50 kg/m³) made of blends of low-density polyethylene (LDPE) and the ethylene vinyl acetate copolymer (EVA) were studied as a function of the EVA proportion in the blends. These properties were compared with those of a foam made of a blend of EVA and ethylene propylene rubber (EPR). The knowledge of how the EVA proportion influences the behavior of these blend foam materials is a fundamental factor in order to obtain a wide range of polyolefin foams, with similar density, suitable for different applications. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1237–1244, 1998     

Activity of substrates in the catalyzed nucleation of poly(ethylene terephthalate) melts

The activity, Φ of AgBr, AgI, PbF₂, Ag₂S, LiF, and CaF₂ in the catalyzed nucleation of poly(ethylene terephthalate) (PET) melts was determined using a nonisothermal differential scanning calorimetry (DSC) technique. A comparison with existing experimental data was made. It is established that the higher the melting temperature of the substrate the lower its activity as a crystallization core in the heterogeneous nucleation of PET. The lateral surface energy, σ, the end surface energy, σ_e, the adhesion energy, β, and the difference between the surface energies at the substrate/melt, σ_sf, substrate/deposit, σ^*, and the total energy of misfit dislocations, E_d [i.e., σ_sf - (σ^* - E_d)] were calculated. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 349–353, 1997     

Monitoring the aging of beers using a bioelectronic tongue

This paper deals with the implementation and the application of a bioelectronic tongue including three enzymatic biosensors based on tyrosinase and phthalocyanines as electron mediators, to evaluate the changes that occur during the aging of beers. For this purpose, alcoholic and non alcoholic beers, packaged in can and bottle, have been analyzed using cyclic voltammetry. The electrochemical signals showed significant changes during the aging process. The features extracted from the cyclic voltammograms have been used to perform Principal Component Analysis (PCA) and Linear Discriminant Analysis (LDA). Data have revealed a clear discrimination among the beer classes in the aging process and the results were confirmed by Probabilistic Neural Networks (PNN) with Radial Basis Functions (RBF) and FeedForward Networks with Backpropagation (BP) learning method. The bioelectronic tongue has demonstrated a good capability to discriminate and classify the beer types satisfactorily in such a way, for all beer treatments, full classification accuracy was found.     

A novel approach for audio file encryption using hand geometry

Multimedia Tools and Applications - This paper suggests a new proposed algorithm for encryption/ decryption audio files based on discrete wavelet transform (DWT) and biometric features to provide a...