Structural investigation of xAg2O·(100−x)·[2B2O3·As2O3] glasses doped with manganese ions

Structural analysis of x[(100−y)Ag₂O·yMnO]·(100−x)[2B₂O₃·As₂O₃] glasses, with x=10 mol% and 0≤y≤10 mol%, was performed by means of FT-IR and FT-Raman spectroscopies. The purpose of this work is to investigate the structural changes that appear in the xAg₂O·(100−x)·[2B₂O₃·As₂O₃] glasses with the addition and increase in manganese ions content. FT-IR measurements revealed the presence of pyro-, ortho-, di-, tri-, tetra- and penta-borate groups and structural units characteristic to As₂O₃ in the structure of the studied glasses. FT-IR spectroscopy measurements also show that BO₃ units are the main structural units of the glass system. The presence of structural units characteristic to Ag₂O were not directly evidenced by FT-IR spectroscopy. In addtition, the FT-Raman analysis evidenced the presence of boroxol rings in the structure of the studied glasses.     

Numerical extremal solutions for a mixed problem with singular {\phi} -Laplacian

We are concerned with extremal solutions for the mixed boundary value problem $$-\left(r^{N-1}\phi(u')\right)' = r^{N-1} g(r, u), \quad u'(0) = 0 = u(R),$$ where ${g : [0, R] \times \mathbb{R} \to \mathbb{R}}$ is a continuous function and ${\phi : (-\eta, \eta) \to \mathbb{R}}$ is an increasing homeomorphism with ${\phi(0) = 0.}$ We prove the existence of minimal and maximal solutions in presence of well-ordered lower and upper solutions and develop a numerical algorithm for theirs approximation. Also, we provide numerical experiments confirming the theoretical aspects.     

Preparation of siloxane‐based urethane dimethacrylates carrying carboxylic groups and the effect of silver nanoparticles on the properties of composite polymer films

This work reports on the synthesis of three acid oligosiloxane‐urethane dimethacrylates and their use to obtain hybrid nanocomposite films, in which the presynthesized silver nanoparticles (NPs) were incorporated before photopolymerization, or produced via in situ photoreduction of the silver nitrate (AgNO₃) precursor into the formulation, without any conventional reducing agent. All samples were characterized by ¹H NMR, FT‐infrared and UV spectroscopies, photodifferential scanning calorimetry (photo‐DSC), transmission electron microscopy (TEM), and energy‐dispersive X‐ray (EDX) analysis. Fourier transformed infrared spectroscopy and photo‐DSC results showed that dimethacrylates having hydrophilic segment of poly(ethylene oxide) type in structure are more reactive than the acid oligosiloxane dimethacrylate. When another urethane dimethacrylate is taken as a comonomer, the photopolymerization rate (0.112–0.132 s^?1) and the degree of conversion (82–93%) significantly increased. Experimental evidence of the existence of nanosilver into the polymer matrix generated upon UV irradiation has been supported by UV spectroscopy, EDX and TEM analysis, the last allowing a visualization of the formation of silver NPs with size between 2 and 15 nm. Mechanical parameters and wettability of the photocrosslinked films are also discussed in the prospect of further potential applications in the biomedical field. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Preparation of α-galactooligoglycosides by cell walls from Cryptococcus laurentii using a novel α-galactosyl donor

The cell walls of an acapsular strain of the yeast Cryptococcus laurentii catalyze the regioselective formation of α-galactooligosaccharides through self-condensation of 4-nitrophenyl α-d-galactopyranoside and of a novel activated α-galactosyl donor 2,2,2-trifluoroethyl α-d-galactopyranoside. The latter substance can be easily prepared by several methods and is highly soluble in water and therefore can be used in higher initial concentrations suppressing secondary product hydrolysis. The preparative reaction catalyzed by cell walls provided 17.4% and 2% of corresponding 2,2,2-trifluoroethyl galactobioside and galactotrioside, respectively, while the reaction with 4-nitrophenyl α-d-galactopyranoside provided the corresponding 4-nitrophenyl galactobioside and galactotrioside in 6.6 and 2.5% yields, respectively. The reactions proceeded with strict α-(1 → 6)-regioselectivity.     

On the structure of fractional degree vortices in a spinor Ginzburg-Landau model

We consider a Ginzburg-Landau functional for a complex vector order parameter Ψ=(ψ₊,ψ₋), whose minimizers exhibit vortices with half-integer degree. By studying the associated system of equations in R² which describes the local structure of these vortices, we show some new and unconventional properties of these vortices. In particular, one component of the solution vanishes, but the other does not. We also prove the existence and uniqueness of equivariant entire solutions, and provide a second proof of uniqueness, valid for a large class of systems with variational structure.     

Synthesis, characterization and antitumor activity of Cu(II), Co(II), Zn(II) and Mn(II) complex compounds with aminothiazole acetate derivative

This paper presents the synthesis of complex compounds of type [M(L1)₂], where M(II)= Cu (1), Co (2), Zn (3), L1=2-aminothiazole-4-acetate and [Mn(L1)₂(H₂O)] (4) using ethyl 2-(2-aminothiazole-4-yl) acetate (L), and characterization by elemental analysis, magnetic susceptibilities, IR, 1H-NMR, UV-Vis spectroscopy and for [Mn(L1)₂(H₂O)] also by X-ray diffraction. In vitro cytotoxicity studies were performed on human cervix adenocarcinoma, HeLa cells. The antitumor selectivity was assessed using normal human peripheral blood mononuclear cells, PBMC as control.      

Viscosity approximations by generalized contractions for resolvents of accretive operators in Banach spaces

In this paper, we prove a strong convergence theorem for resolvents of accretive operators in a Banach space by the viscosity approximation method with a generalized contraction mapping. The proximal point algorithm in a Banach space is also considered. The results extend some very recent theorems of W. Takahashi.     

Experiment planning,mathematical modelling,and nonlinear optimization of the ion-nitriding process in a glow-discharge plasma

A new, efficient method for investigating and optimizing the ion-nitriding process in a glow-discharge plasma is proposed and worked out in detail for the mass kinetics of Rp-3 steel. This method, which is based on the concepts of experiment planning, mathematical modelling, and nonlinear optimization, is quite general and potentially applicable to a wide class of technological and other processes depending on several parameters.