Adsorption of light green and brilliant yellow anionic dyes using amino functionalized magnetic silica (Fe3O4@SiO2@NH2) nanocomposite

Abstract

Fe₃O₄@SiO₂@NH₂ nanocomposite was prepared for highly effective adsorption of two anionic dyes one of which is triarylmethane dye (light green, LG) and the other is azo dye (brilliant yellow, BY). The characterization results demonstrated that superparamagnetic Fe₃O₄ nanoparticles were covered with silica and functionalized with amino groups successfully without losing magnetic character. The effects of adsorbent dosage, contact time, pH, temperature, and dye molecular structure on the adsorption were investigated. Acidic pH was better for both LG and BY, on the other hand, alkaline pH was favorable to some extent for LG in comparison with BY due to the contribution of stacking effect in addition to electrostatic attraction. Kinetic data demonstrated that the driving force for adsorption process could be explained by pseudo-second order mechanism in both systems. The equilibrium data were more compatible with Langmuir isotherm than those of Freundlich isotherm and the maximum adsorption capacities of Fe₃O₄@SiO₂@NH₂ calculated from Langmuir isotherm model for LG and BY at 30?°C and natural pH of the solution were 40.2 and 35.5?mg g^?1. Thermodynamic calculations related to temperature dependence demonstrated that the adsorption process was spontaneous and exothermic.     

Influence of inorganic electrolytes on the retention of polyethyleneglycol by a nanofiltration ceramic membrane

Retention properties of a nanofiltration ceramic membrane were investigated with single polyethyleneglycol (PEG) solutions and mixed PEG/inorganic electrolyte solutions. The rejection coefficient of PEGs was found to decrease in the presence of ions. It was shown that the effect of ions on the retention of neutral solutes increases with the electrolyte concentration. This phenomenon was ascribed to the partial dehydration of PEG molecules induced by the surrounding ions. This argument was confirmed by using various electrolytes (KCl, LiCl and MgCl₂). It was found that the lowering of the PEG rejection coefficients follows the Hofmeister series, i.e. Mg²⁺ > Li⁺ > K⁺. Experimental data were used to compute the resulting decrease in the Stokes radius of PEG molecules in the presence of the various electrolytes.     

Mesure invariante pour l’équation stochastique d’un modéle de compétition limitée entre des espéces avec une diffusion spatiale

On considére l’équation stochastique decrivant un systéme den espéces avec une perturbation stochastique du type environnemental et une diffusion dans un territoire de chaque espéce. On suppose la compétition avec un effet limité entre le espéces différentes, tandis que l’effet logistique pour chaque espéce est supposé quadratique. Sous une condition convenable pour les coefficients, on démontre l’existence d’une mesure invariante pour cette équation stochastique, oú la densité de population de chaque espéce est presque surement positive.     

The Reactions of Hexachlorocyclotriphosphazatriene with Ligands Including Mercapto Groups

In this work, the reactions of hexachlorocyclotriphosphazatriene (trimer), N ₃ P ₃ Cl ₆ 1, with 2-mercapto-1-methylimidazole (methimazole) 2, 2-mercaptopyrimidine 3, and 2-mercaptopyridine 4 were discussed. Mono- (5) and pentasubstituted (6) phosphazenes were obtained from the reaction of 1 with 2-mercapto-1-methylimidazole. Both mono- (7) and disubstituted geminal (8) phosphazenes were obtained from the reaction of 1 with 2-mercaptopyrimidine. But phoshazene or any phosphorus compound could not be isolated from the reaction of 1 with 2-mercaptopyridine.     

Analysis of enzymopathies in the human red blood cells by constraint-based stoichiometric modeling approaches

The human red blood cell (RBC) metabolism is investigated by calculating steady state fluxes using constraint-based stoichiometric modeling approaches. For the normal RBC metabolism, flux balance analysis (FBA) is performed via optimization of various alternative objective functions, and the maximization of production of ATP and NADPH is found to be the primary objective of the RBC metabolism. FBA and two novel approaches, minimization of metabolic adjustment (MOMA) and regulatory on-off minimization (ROOM), which can describe the behavior of the metabolic networks in case of enzymopathies, are applied to observe the relative changes in the flux distribution of the deficient network. The deficiencies in several enzymes in RBC metabolism are investigated and the flux distributions are compared with the non-deficient FBA distribution to elucidate the metabolic changes in response to enzymopathies. It is found that the metabolism is mostly affected by the glucose-6-phosphate dehydrogenase (G6PDH) and phosphoglycerate kinase (PGK) enzymopathies, whereas the effects of the deficiency in DPGM on the metabolism are negligible. These stoichiometric modeling results are found to be in accordance with the experimental findings in the literature related to metabolic behavior of the human red blood cells, showing that human RBC metabolism can be modeled stoichiometrically.     

Superinjective simplicial maps of complexes of curves and injective homomorphisms of subgroups of mapping class groups II

Let R be a compact, connected, orientable surface of genus g with p boundary components. Let C(R) be the complex of curves on R and be the extended mapping class group of R. Suppose that either g=2 and p?2 or g?3 and p?0. We prove that a simplicial map is superinjective if and only if it is induced by a homeomorphism of R. As a corollary, we prove that if K is a finite index subgroup of and is an injective homomorphism, then f is induced by a homeomorphism of R and f has a unique extension to an automorphism of . This extends the author's previous results about closed connected orientable surfaces of genus at least 3, to the surface R.     

Temperature dependence of the optical band gap and electrical conductivity of sol-gel derived undoped and Li-doped ZnO films

Undoped and lithium (Li)-doped ZnO films were prepared by sol-gel method using spin coating technique. The effects of Li content on the crystallinity and morphological properties of ZnO films were assessed by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM). XRD patterns of the films showed the hexagonal wurtzite type polycrystalline structure and that the incorporation of lithium leads to substantial changes in the structural characteristics of ZnO films. The SEM and AFM measurements showed that the surface morphology of the films was affected from the lithium incorporation. The wrinkle network was observed on the surface from both SEM and AFM results for undoped ZnO. The wrinkle structure disappeared with increasing Li content. The absorption spectra of the ZnO and 5% Li-doped ZnO (LZO5) films were carried out between 140 and 400 K temperatures. The optical band gap of ZnO and LZO5 films (calculated at various temperatures) showed a linear dependence on the temperature. The absolute zero value optical band gap and the rate of change of the band gap with temperature of the ZnO and LZO5 films were found to be 3.339 and 3.322 eV, and 2.95 × 10⁻⁴ and 1.60 × 10⁻⁴ eV/K, respectively. The transport mechanisms in the ZnO and LZO5 films have been investigated by analyzing of the temperature (80-300 K) dependence of the conductivity. The activation energies of the ZnO film increased with Li content.     

Fluorescence Interaction and Determination of Calf Thymus DNA with Two Ethidium Derivatives

In this paper, we reported the syntheses and investigation of the modes of binding to DNA of the two new ethidium derivatives containing benzoyl and phenylacetyl groups of both amines at 3-and 8- positions. The interactions between calf thymus DNA (ct-DNA) and the two derivatives, 3,8-dibenzoylamino-5-ethyl-6-phenylphenantridinium cloride (E2) and 3,8-diphenylacetylamino-5-ethyl-6-phenylphenantridinium chloride (E3), were investigated by fluorescence quenching spectra and UV-vis absorption spectra. The Stern-Volmer quenching constants, binding constants, binding sites and the corresponding thermodynamic parameters ΔH, ΔS and ΔG were calculated at different temperatures. The results indicated the formation of E2 and E3-DNA complexes and van der Waals interactions as the predominant intermolecular forces in stabilizing for each complex. In addition, increasing nucleophilicity of the functional groups at 3- and 8- positions exhibited the respectable increment the DNA binding affinities of derivatives. The results of absorption, ionic strength and iodide ion quenching suggested that the interaction mode of E2 and E3 with ct-DNA was intercalative binding. The limit of detection (LOD) of ct-DNA were 7.49 × 10⁻⁸ (n = 4) and 4.18 × 10⁻⁸ mol/l (n = 7) in presence of E2 and E3, respectively.     

Perturbation theorems for estimating magnitudes of roots of polynomials

Two additional new theorems are posed and proven to estimate the magnitudes of roots of polynomials. Perturbation theory and the order of magnitude of terms are employed to develop the theorems. The theorems may be useful to estimate the order of magnitudes of the roots of a polynomial a priori before solving the equation. The theorems are developed for two special classes of polynomials of arbitrary order with their coefficients satisfying certain conditions. Numerical applications of the theorems are presented as examples. It is shown that the theorems produce good estimates for the magnitudes of roots.