Inclusion complexes of some antipyrine derivatives with cyclodextrins: influence of guest configuration

Formation of inclusion complexes between α- and β-cyclodextrins and three antipyrine type compounds (antipyrine, 4-amino-antipyrine, 4-nitroso-antipyrine), in solution and in solid state, has been investigated. UV–Vis measurements indicate that in solution antipyrine derivatives do not form inclusion complexes and oxidative process of amino group is not influenced by the presence of cyclodextrins. The oxidation of 4-amino-antipyrine to 4-nitroso-antipyrine using DPPH type radicals was investigated using spin trapping experiments in organic solvents and in water. These results were explained by betainic configuration of antipyrine derivatives in aqueous solutions. Formation of inclusion complexes in solid states was evidenced by DSC, as peaks associated with various thermodynamic events (dehydration, melting, thermal decomposition) are shifted towards higher temperature or disappear in case of inclusion complexes.     

Effect of reagents mixing on the thermal behavior of sol-gel precursors for silica-based nanocomposite thin films

The paper presents, based on TG-DTG-DSC data, some results of the thermal decomposition of some complex sol-gel precursors used for the deposition of mesoporous ZnO/SiO₂ nanocomposite thin films for gas sensing applications. The effect chemical composition of the sol and reagents mixing during the sol preparation is discussed. The chemical nature of ZnO source (zinc acetate solid salt, zinc acetate alcoholic solution or ZnO nanopowder) used for the sol preparation significantly affects the thermal decomposition of complex precursor and the microstructure and properties of the nanocomposite thin films.     

Short-range structure and in vitro behavior of ZnO–CaO–P2O5 bioglasses

Ternary zinc–calcium-phosphate glasses prepared by classical melting method were characterized through X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) along with energy dispersive X-ray analysis (EDAX), Fourier Transform InfraRed (FTIR) and Raman spectroscopy. The study of these glasses was done in order to supply information regarding their structural particularities since the zinc role in biological environment, especially in the bone, is still under debate.XRD analysis confirmed the vitreous character of the as-prepared samples, while SEM and EDAX measurements indicated the presence of some non-homogeneous domains on their surfaces with approximately similar elemental composition. According to FTIR and Raman spectroscopy, the local structure of glasses up to 10 mol% ZnO is mainly built by Q² tetrahedrons connected by P–O–P linkages. For 50 mol% ZnO, the modifier role of zinc ions is strongly reflected on the local structure dominated in this case by Q¹ pyrophosphate units.The surface reactivity of the samples has been analyzed in vitro by immersion in simulated body fluid (SBF) at 37 °C. XRD, SEM–EDAX, FTIR and Raman methods were employed to characterize the structural changes that occurred on the surface of ZnO–CaO–P₂O₅ samples reacting with SBF. The X-ray diffraction patterns demonstrated the formation of a hydroxyapatite layer on the samples surface while the other used methods didn't reveal concisely that phenomenon. Based on X-ray measurements, the influence of zinc concentration on the hydroxyapatite layer development was followed.     

HPLC separation of acetaminophen and its impurities using a mixed-mode reversed-phase/cation exchange stationary phase

Determination of acetaminophen and its main impurities: 4-nitrophenol, 4'-chloroacetanilide, as well as 4-aminophenol and its degradation products, p-benzoquinone and hydroquinone has been developed and validated by a new high-performance liquid chromatography method. Chromatographic separation has been obtained on a Hypersil Duet C18/SCX column, using gradient elution, with a mixture of phosphate buffer (pH = 4.88) and methanol as a mobile phase. Analysis time did not exceed 14.5 min and good resolutions, peak shapes and asymmetries have resulted. The linearity of the method has been tested in the range of 5.0-60 μg/mL for acetaminophen and 0.5-6 μg/mL for the other compounds. The limits of detection and quantification have been also established to be lower than 0.1 μg/mL and 0.5 μg/mL, respectively. The method has been successfully applied for the analysis of commercial acetaminophen preparations.     

Exceptional Pairs in Hereditary Categories

We study the category 𝒞(X, Y) generated by an exceptional pair (X, Y) in a hereditary category ?. If r = dim _k Hom(X, Y) ≥ 1 we show that there are exactly 3 possible types for 𝒞(X, Y), all derived equivalent to the category of finite dimensional modules mod(H _r ) over the r-Kronecker algebra H _r . In general 𝒞(X, Y) will not be equivalent to a module category. More specifically, if ? is the category of coherent sheaves over a weighted projective line 𝕏, then 𝒞(X, Y) is equivalent to the category of coherent sheaves on the projective line ?¹ or to mod(H _r ) and, if 𝕏 is wild, then every r ≥ 1 can occur in this way.     

Silver sorption on acrylic copolymers functionalized with amines. Equilibrium and kinetic studies

The sorption capacity of three weak base ion exchangers based on acrylic copolymers functionalized with ethylenediamine, triethylenetetramine and N, N- dimethylamino propylamine for Ag(I) ions was evaluated. Adsorption experiments were carried out by batch method. The effect of pH, crosslinking degree of copolymers, amount of sorbent, initial ion concentration, contact time and temperature was studied. The parameters which characterize the retention process were estimated using Langmuir and Freundlich isotherm models, the best fitting being for the first model. Kinetic data were fitted to pseudo-first order, pseudo-second order and intraparticle diffusion models. Experimental data were in good agreement with the pseudo second order.      

Rayleigh scattering fromn=3 states of hydrogenlike atoms

An exact analytic evaluation of the Kramers-Heisenberg matrix elements for Rayleigh scattering fromn=3 states of hydrogenlike atoms is performed in the nonrelativistic dipole approximation, using the Green's function method. The results are given separately for each subshell. The possibility of 3s?3d transitions is also considered. The dependence on the photon energy is contained in six invariant amplitudes. The formulas needed for the evaluation of the various cross sections are presented. The numerical results are contained in tables from which partial and total cross sections can be easily built, covering the energy range from zero up to 20 times theK threshold energy. In the vicinity of Balmerα frequency the cross section is large and comparable with that for excitedn=2 states, confirming an earlier hypothesis of Röhr. At other energies the cross sections forn=2 andn=3 states are comparable, too. The results should be useful in plasma diagnostics.