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Hristova M.,University of Chemical Technology and Metallurgy of Sofia
Central European Journal of Chemistry | Year: 2013

The flash points of three binary mixtures, containing n-heptane, o-xylene, m-xylene and ethylbenzene, were measured by Pensky-Martens closed cup tester. The experimental data were compared with the calculated values using Liaw's Model with the application of Raoult's Law and Wilson equation. These equations were in good qualitative agreement. © 2012 Versita Warsaw and Springer-Verlag Wien. Source

Vladkova T.G.,University of Chemical Technology and Metallurgy of Sofia
International Journal of Polymer Science | Year: 2010

We present many examples of surface engineered polymeric biomaterials with nanosize modified layers, controlled protein adsorption, and cellular interactions potentially applicable for tissue and/or blood contacting devices, scaffolds for cell culture and tissue engineering, biosensors, biological microchips as well as approaches to their preparation. Copyright © 2010 Todorka G. Vladkova. Source

Hristov J.,University of Chemical Technology and Metallurgy of Sofia
Thermal Science | Year: 2012

Integral balance solution employing entire domain approximation and the penetration dept concept to the Stokes' first problem of a viscoelastic generalized second grade fluid has been developed. The solution has been performed by a parabolic profile with an unspecified exponent allowing optimization through minimization of the L 2 norm over the domain of the penetration depth. The closedform solution explicitly defines two dimensionless similarity variables ξ = y/(vt) 1/2 and D o = χ 2 = = (p/vt β) 1/2, responsible for the viscous and the elastic responses of the fluid to the step jump at the boundary. The solution was developed with three forms of the governing equation through its 2-D forms (the main solution and example 1) and the dimensionless version showing various sides of the flow field and how the dimensionless groups control it: mainly the effect of the Deborah number. Numerical simulations demonstrating the effect of the various operating parameter and fluid properties on the developed flow filed have been performed. Source

Lad U.,University of Leeds | Kale G.M.,University of Leeds | Bryaskova R.,University of Chemical Technology and Metallurgy of Sofia
Analytical Chemistry | Year: 2013

An amperometric glucose enzyme electrode was developed by the immobilization of glucose oxidase (GOD) in a composite material based on polyvinyl alcohol (PVA) and partially prehydrolyzed tetraethyl orthosilicate (pphTEOS) on the surface of "in-house" fabricated graphite electrodes. For comparison, silver and gold nanoparticles (Ag/AuNPs) embedded in the PVA-pphTEOS matrix was prepared through a novel method via sol-gel process based on the in situ chemical reduction of Ag or Au ions using PVA as a reducing agent and stabilizer. The successful incorporation of Ag and AuNPs ranging from 5 to 7.5 and 4.5-11 nm, respectively, in the PVA-pphTEOS matrix was confirmed by UV-Vis spectroscopy, TEM, and EDX analysis. The PVA-TEOS matrix was also characterized by FTIR spectroscopy. The analytical performance of the enzyme electrodes were studied in terms of linear ranges, sensitivities, response times, limits of detection, reproducibility and stability. © 2013 American Chemical Society. Source

Miladinova P.,University of Chemical Technology and Metallurgy of Sofia
Polymer Degradation and Stability | Year: 2013

The photostability of eight blue-emitting derivatives of 2-aminoterephthalic acid, three of them containing a stabilizer residue in their molecule in dimethylformamide was investigated. Copolymerisation of methyl methacrylate with four of them, monomer compounds and whitening of methyl methacrylate "in mass" with one of the compounds was accomplished. The copolymers obtained have an intense stable to solvents fluorescence. Photostability of the compounds, thus included in the polymer chain increased. The influence of the luminophores on the photostability of the inherently and whitened "in mass" polymers was established. © 2013 Elsevier Ltd. All rights reserved. Source

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