Thermal dehydration of some food products and kinetic parameters of this process

Metal poly(vinyl acetates) polymers were obtained by radical polymerization with azodiisobutyronitrile. The thermal stabilities of the metal polymers (M-PVAC) have been studied by thermogravimetry (TG) between 25 and 550°C under nitrogen flow. The decomposition temperature was obtained from the maximum of the first derivative from TG curve. The kinetic parameters of the thermal decomposition were determined by the Arrhenius equation. All these polymers degrade mainly in a single step with a very small second step, probably via a complex reaction. The kinetic data thus obtained show that the thermostabilities decrease in the order: Sb-PVA_c～Ge-PVA_c>Bi-PVA_c～Cd-PCA_c>Ag-PVA_c～PVA_c>Zn-PVA_c> Au-PVA_c>In-PVA_c>Sn-PVA_c>Ga-PVA_c>Pd-PVA_c. Again, the thermal stability is dependent upon the metal incorporated in the backbone polymer. They loose weight after 320°C. The order of reaction from the thermal decomposition of these metal polymers was found to be ?0.5 for the first step and 0 for the second. The pre-exponential factor, the reaction order and the activation energy of the decomposition for metal (PVA_c) have been determined in most of them.     

On extensions of the domain invariance theorem

If f maps continuously a compact subset X of Rⁿ into Rⁿ and x is a point whose distance from the boundary ∂X is greater than double diameter of the fibres of the points in f(∂X) then f(x) is in the interior of f(X). This theorem extends some results due to Borsuk and Sitnikov.     

On algebras with unique essentiallyn-ary operations

In this paper we characterize the class of algebras with one fundamental operation having for every nonnegative integern exactly one essentiallyn-ary polynomial.Presented by Joel Berman.     

Spectral Gap for Stable Process on Convex Planar Double Symmetric Domains

We study the semigroup of the symmetric α-stable process in bounded domains in R ². We obtain a variational formula for the spectral gap, i.e. the difference between two first eigenvalues of the generator of this semigroup. This variational formula allows us to obtain lower bound estimates of the spectral gap for convex planar domains which are symmetric with respect to both coordinate axes. For rectangles, using “midconcavity” of the first eigenfunction (Bañuelos et al., Potential Anal. 24(3): 205–221, 2006), we obtain sharp upper and lower bound estimates of the spectral gap.     

Origin of the optical contrast in phase-change materials

Several chalcogenide alloys exhibit a pronounced contrast between the optical absorption in the metastable rocksalt and in the amorphous phase. This phenomenon is the basis for their application in optical data storage. Here we present ab initio calculations of the optical properties of GeTe and Ge1Sb2Te4 in the two phases. The analysis of our computations and experimental data reveal the correlation between local structural changes and optical properties as well as the origin of the optical contrast in these materials. We find that the change in optical properties cannot be attributed to a smearing of transition energies as commonly assumed for amorphous semiconductors: the optical contrast between the two phases can only be explained by significant changes in the transition matrix elements.     

The Length-scale Effect in the Buckling of Thin Periodic Plates Resting on a Periodic Winkler Foundation

In this paper a new modelling method, called the tolerance averaging method, is presented and applied to analyse a buckling of thin periodic plates resting on a periodically heterogeneous Winkler foundation. The derived length-scale model makes it possible to take into account the effect of periodicity cell size (the length-scale effect) on the overall plate behaviour, on the contrary to the known homogenised models of periodic plates neglecting this effect. In order to evaluate obtained results the buckling problems of those plates are analysed using not only the proposed model but also a certain effective stiffnesses model. A comparison between obtained results leads to a conclusion that the length-scale effect could not be neglected in buckling of periodic plates resting on a Winkler foundation.     

Phenanthriporphyrin: An Antiaromatic Aceneporphyrinoid as a Ligand for a Hypervalent Organophosphorus(V) Moiety

The incorporation of a phenanthrene moiety into a porphyrin framework results in the formation of a hybrid macrocycle—phenanthriporphyrin—merging the structural features of polycyclic aromatic hydrocarbons and porphyrins. An antiaromatic aceneporphyrinoid, adopting the trianionic {CCNN} core, is suitable for the incorporation of a phosphorus(V) center to form a hypervalent organophosphorus(V) derivative.     

Sensitive Amperometric Sensing of Hydrogen Peroxide Using Ag Nanowire Array Electrode

The amperometric sensor based on a silver nanowire (80 nm in diameter Ag NW) array electrode was fabricated and characterized with scanning electron microscope (SEM). The electrode showed good electrocatalytic activity for reduction of hydrogen peroxide. The effects of the applied polarization potential, pH, time interval between successive injections of analyte, injection volume and H₂O₂ concentration in a single injection on the electrochemical performance of the sensor were studied. It was found that the optimized operating conditions for the proposed sensor are: the potential of ?200 mV, pH between 7.4 and 9.0, 60 s time interval, 10 µL injection volume, and 500 µM H₂O₂ in single injection. The proposed Ag NW array sensor is free of interference from ascorbic acid, uric acid and glucose.