Efficient and selective synthesis of alkoxy substituted di(pyridin-2-yl)amines and N-arylpyridin-2-ylamines

The formation of alkoxy substituted di(pyridin-2-yl)amines and N-arylpyridin-2-ylamines by nitro group reduction is described. Unexpected substitution of ortho with the amino at C-6 was observed during the reduction using SnCl₂·2H₂O in different alcohols. The influence of the nature of the atom at the 3- and 5-positions of nitro-substituted di(pyridin-2-yl)amines and N-arylpyridin-2-ylamines was investigated.     

Potassium sorbate release from poly(vinyl alcohol)-bacterial cellulose films

Active packaging materials are the subject of research because their performance exceeds that of traditional packaging. From this class, antimicrobial materials extend the shelf-life of products and reduce the risk of contamination by pathogens. In this paper, new composite materials with antimicrobial properties are obtained by using polyvinyl alcohol and bacterial cellulose powder. Potassium (2E,4E)-hexa-2,4-dienoate was used as the antimicrobial agent. The films thus obtained were characterised using Fourier-transform infrared spectroscopy and scanning electron microscopy. Mass transfer phenomena concerning the release of potassium (2E,4E)-hexa-2,4-dienoate were investigated. The results indicated that the new biocomposite films could be used as antimicrobial packaging materials.     

Thermal analysis,microstructure and impurity phases evolution in Fe14Cr ferritic steel powders ball-milled in air and under an argon atmosphere

Journal of Thermal Analysis and Calorimetry - Azobenzenes undergo reversible trans–cis photo-isomerization and have been studied extensively as photo-responsive materials. Despite their...     

Existence theory of abstract approximate deconvolution models of turbulence

This report studies an abstract approach to modeling the motion of large eddies in a turbulent flow. If the Navier-Stokes equations (NSE) are averaged with a local, spatial convolution type filter, , the resulting system is not closed due to the filtered nonlinear term . An approximate deconvolution operator D is a bounded linear operator which is an approximate filter inverse

Enzymatic degradation of some nanocomposites of poly(vinyl alcohol) with starch

A study of the enzymatic degradation of some montmorillonite-containing nanocomposites of poly(vinyl alcohol) with starch was based on the determinations of mass loss and the reducing sugars. The degraded residues have been examined by FT-IR spectroscopy and optical microscopy. It has been established that the nanoparticles hinder degradation, while the susceptibility to enzymatic degradation varies in the order: PVA/starch/nanocore > PVA/starch/Bentonite > PVA/starch/Peruvian clay.     

Synthesis and Characterization of Diatomaceous Earth Chemically Modified with γ-Aminopropyltrimethoxysilane

JPC – Journal of Planar Chromatography – Modern TLC - A stationary phase for thin-layer chromatography has been prepared by bonding purified diatomaceous earth (rich in silica) with...     

Field Effect in a Mixture of Cholesteryl Chloride and Cholesteryl Crotonate (75: 25% by weight)

The cholesteric-nematic phase transition in cholesteryl chloride and cholesteryl crotonate (75:25% by weight) is investigated. The dependence of the critical field on temperature is determined either by microscopical examination under polarized light or by following a DLI technique under electric field. Agreement between these methods has been obtained.     

Fiber diameter in electrospinning process

In order to increase the control on the fiber diameter we propose in this paper a methodology to determine stability domains of the process in which the electrospun fiber diameter can be predetermined and also controlled by means of the polymer solution flow and the applied voltage. To define these stability domains we employ a combination of analytical expressions depending on the location along the traveling jet. In the vicinity of the nozzle we employ the expression which links the fiber diameter with the kinematic viscosity of the polymer solution, nozzle-collector distance, solution density, liquid flow, electric current and intensity of the electrostatic field. At larger distances from the nozzle, the fiber diameter can be expressed as a function of solution density, liquid flow, intensity of the applied electrostatic field and distance from the nozzle. Close to the collector the fiber diameter can be expressed with respect to the superficial tension of the polymer solution, dielectric permittivity, liquid flow and intensity of the electric current. Under specific constrains, the superposition of the plots obtained from these mathematical expressions will be used to determine the stability domain for the fiber diameter in which the diameter can be controlled by two process parameters, namely applied voltage and polymer solution flow. Through this approach the present paper can contribute to increased control of the electrospinning process and thus enhanced applicability.