Optical and thermal properties of intelligent pH indicator films based on chitosan/PVA and a new xanthylium dye

Journal of Thermal Analysis and Calorimetry - Intelligent food packaging systems register and monitor food quality through data carriers, sensors or indicators. Food spoilage often leads to pH...     

Rare-Earth Metal Complexes of the Antibacterial Drug Oxolinic Acid: Synthesis,Characterization, DNA/Protein Binding and Cytotoxicity Studies

“Drug repositioning” is a current trend which proved useful in the search for new applications for existing, failed, no longer in use or abandoned drugs, particularly when addressing issues such as bacterial or cancer cells resistance to current therapeutic approaches. In this context, six new complexes of the first-generation quinolone oxolinic acid with rare-earth metal cations (Y³⁺, La³⁺, Sm³⁺, Eu³⁺, Gd³⁺, Tb³⁺) have been synthesized and characterized. The experimental data suggest that the quinolone acts as a bidentate ligand, binding to the metal ion via the keto and carboxylate oxygen atoms; these findings are supported by DFT (density functional theory) calculations for the Sm³⁺ complex. The cytotoxic activity of the complexes, as well as the ligand, has been studied on MDA-MB 231 (human breast adenocarcinoma), LoVo (human colon adenocarcinoma) and HUVEC (normal human umbilical vein endothelial cells) cell lines. UV-Vis spectroscopy and competitive binding studies show that the complexes display binding affinities (K_b) towards double stranded DNA in the range of 9.33 × 10⁴ − 10.72 × 10⁵. Major and minor groove-binding most likely play a significant role in the interactions of the complexes with DNA. Moreover, the complexes bind human serum albumin more avidly than apo-transferrin.     

The Interaction of Collinear Gaps of Arbitrary Charge in a Two Dimensional Dimer System

The correlation of gaps in dimer systems was introduced by Fisher and Stephenson (Phys Rev 132:1411–1431, 1963), who looked at the interaction of two monomers generated by the rigid exclusion of dimers on the closely packed square lattice. In previous work we considered the analogous problem on the hexagonal lattice, and we extended the set-up to include the correlation of any finite number of monomer clusters. For fairly general classes of monomer clusters we proved that the asymptotics of their correlation is given, for large separations between the clusters, by a multiplicative version of Coulomb’s law for 2D electrostatics. However, our previous results required that the monomer clusters consist (with possibly one exception) of an even number of monomers. In this paper we determine the asymptotics of general defect clusters along a lattice diagonal in the square lattice (involving an arbitrary, even or odd number of monomers), and find that it is given by the same Coulomb law. We also obtain a conceptual interpretation for the multiplicative constant as the product of the correlations of the individual clusters.     

Strongly anisotropic diffusion problems; asymptotic analysis

The subject matter of this paper concerns anisotropic diffusion equations: we consider heat equations whose diffusion matrices have disparate eigenvalues. We determine first and second order approximations, we study the well-posedness of them and establish convergence results. The analysis relies on averaging techniques, which have been used previously for studying transport equations whose advection fields have disparate components.     

Electrophilicity kernel and its hierarchy through softness in conceptual density functional theory

In the context of long‐range density functional theory of softness kernel, the concepts of local and kernel electrophilicity are developed to obtain the local to global hierarchical criteria such as bilocal symmetry, asymptotic behavior, and integral local to global relationships. Further development into potential‐density dependence is also provided while considering the local plus nonlocal specification of softness kernel and the associated atomic scales for the derived kernel; local and global electrophilicity are provided whose reliability is judged through the periodical features along the periodic table especially for the alkali metal atoms and the halogen atoms. © 2013 Wiley Periodicals, Inc.     

Thermal Degradation of Trioxane-Dioxqlane Copolymers Obtained with Boron Trifluoride-Acrylonitrile Complex as Initiator

The thermal degradation of certain trioxane-dioxolane copolymers obtained with boron trifluoride-acrylonitrile complex as initiator has been investigated. The thermal stability of samples, discussed in terms of topoenergetic values, was related both to copolymer composition and conversion. The most thermostable copolymers (～5% weight loss at 300°C in air), having 5–8% dioxolane units, had the highest intrinsic viscosity in the series and were isolated at 35–50% conversion. The results obtained were compared with similar data for a commercial tri-oxane-ethylene oxide copolymer containing 95% formal units.     

Crystallization study of sol-gel un-doped and Pd-doped TiO2 materials

Sol-gel nanostructured titania materials have been reported to have applications in areas ranging from optics via solar energy to gas sensors. In order to enhance the photocatalytic activity, there are many studies regarding the doping of titanium dioxide (TiO₂) material with either non-metals (S, C, N, P) or metals (Ag, Pt, Nd, Fe). The present work has studied some un-doped and Pd-doped sol-gel TiO₂ materials (films and gels), with various surface morphologies and structures, obtained by simultaneous gelation of both precursors Ti(OEt)₄ and Pd(acac)₂. Their structural evaluation and crystallization behavior with thermal treatment were followed by DTA/TG analysis, infrared (IR) spectroscopy, Fourier transform infrared (FTIR), spectroellipsometry (SE), X-ray diffraction (XRD) and atomic force microscope (AFM). The influence of Pd on TiO₂ crystallization for both supported and un-supported materials was studied (lattice parameters, crystallite sizes, internal microstrains). The changes in the optical properties of the TiO₂-based vitreous materials were correlated with the changes of the structure. The hydrophilic properties of the films were also connected with their structure, composition and surface morphology.     

Bianchi type-I string cosmological model in the presence of a magnetic flux: exact and qualitative solutions

A Bianchi type-I cosmological model in the presence of a magnetic flux along a cosmological string is investigated. The objective of this study is to generate solutions to the Einstein equations using a few tractable assumptions usually accepted in the literature. The analytical solutions are supplemented with numerical and qualitative analysis. In the frame of the present model the evolution of the Universe and other physical aspects are discussed.     

Organocuprates as initiators for the polymerization of methyl methacrylate in THF

Several types of lithium organocuprates (I) e.g. R₂CuLi, RR'CuLi, R₃CuLi₂, R₂CuLi₂X (X- CN, SCN), were prepared and used as polymerization initiators for methyl methacrylate in THF at temperatures ranging from −30 to +20 ^*C. Polymerization initiated by a mixed homocuprate, e.g. lithium n-butyl (thien-2-yl)cuprate was studied in more detail. Kinetic measurements indicated an overall large (−4 to −14 kcal) apparent negative activation energy of polymerization in the −30 + +20 ^*C temperature range. The reaction was shown to have a kinetic order of about 1.5 with respect to initiator concentration. Conductance measurements indicate that the equivalent conductance increases with initiator concentration in the 10⁻² + 10⁻¹ M range indicating the formation of multiple ions formed by intermolecular association. The data are consistent with a polymerization involving aggregated ion pairs of as yet undetermined composition. The negative activation energy is tentatively interpreted as due to the exothermic formation of aggregates existing as highly solvated ion pairs.