Paired-domination of Trees

Let G= (V, E) be a graph without isolated vertices. A set SV is a paired-dominating set if it dominates V and the subgraph induced by S,S, contains a perfect matching. The paired-domination number _p(G) is defined to be the minimum cardinality of a paired-dominating set S in G. In this paper, we present a linear-time algorithm computing the paired-domination number for trees and characterize trees with equal domination and paired-domination numbers.     

Synthesis and properties of thiazoline based ionic liquids derived from the chiral pool

A novel class of chiral ionic liquids derived from amino alcohols is prepared in multi-gram scale. Their potential in chiral recognition is shown in a preliminary example with racemic Mosher's acid salt.     

Stabilization of solid/liquid suspensions

The stability of colloidal graphite dispersions was investigated. A mixed stabilizer (CELAD) consisting of a non-ionic cellulose derivative and an anionic polymer was used to facilitate the grinding process and to stabilize the aqueous dispersions. Measurements of turbidity, ultramicroscopy and scanning electron microscopy were carried out to determine the size of the particles. Adherent films were obtained by spraying the dispersions onto glass plates. The 20 μm thick films had an electrical resistance within the 20–40 Ω cm range. They proved to be suitable for spray application onto the exernal glass cone of cathode ray tubes.     

Studies about the influence of self-organization of colloidal magnetic nanoparticles on the magnetic Néel relaxation time

The monodomain magnetic nanoparticle-based colloids are mainly used in biomedical applications. In this type of colloids, there is a tendency of agglomeration even in the absence of external magnetic field. So, the Néel magnetic relaxation time of the system is affected by that tendency. In this paper, we propose a model to study how the nanoparticle tendency to agglomerate in the nanofluid affects the Néel relaxation time of the system. For simulating the self-organization of colloidal nanoparticles, we apply a Monte Carlo method, and the Néel magnetic relaxation time is assessed through the adaptation and solution of Coffey equations in oblique magnetic field, adapted to the local magnetic field on a nanoparticle.     

Two Dimensional Water Waves in Holomorphic Coordinates

In this article we investigate spectral properties of the coupling \({H + V_\lambda}\), where \({H = -i\alpha \cdot \nabla+m\beta}\) is the free Dirac operator in \({\mathbb{R}^3}\), \({m > 0}\) and \({V_\lambda}\) is an electrostatic shell potential (which depends on a parameter \({\lambda \in \mathbb{R}}\)) located on the boundary of a smooth domain in \({\mathbb{R}^3}\). Our main result is an isoperimetric-type inequality for the admissible range of \({\lambda}\)’s for which the coupling \({H + V_\lambda}\) generates pure point spectrum in \({(-m, m)}\). That the ball is the unique optimizer of this inequality is also shown. Regarding some ingredients of the proof, we make use of the Birman–Schwinger principle adapted to our setting in order to prove some monotonicity property of the admissible \({\lambda}\)’s, and we use this to relate the endpoints of the admissible range of \({\lambda}\)’s to the sharp constant of a quadratic form inequality, from which the isoperimetric-type inequality is derived.     

Poly(siloxaneimide)s 2. Polycondensation of some imidic diacid chlorides with aminoalkylsiloxanes

Some new poly(siloxaneimide) copolymers with good solubilities have been synthesized by solution polycondensation of aromatic diacid chlorides containing preformed imide rings with disiloxanes and siloxane oligomers having α,ω-aminopropyl functionalities. The polycondensation reactions were carried out using equimolecular amounts of the two monomers, in polar aprotic solvents and inert atmosphere.The obtained compounds were characterized by elemental C, H, and Si analysis, solubility measurements, IR and 1H-NMR spectrometry. Thermogravimetric curves were also recorded. All data agree with the proposed structures.     

New route to 3-alkylthiazolo[3,2-a]benzimidazole derivatives

3-Alkyl-thiazolo[3,2-a]benzimidazole derivatives are obtained in high yields via the corresponding 4-alkyl-N-3-(2-aminophenyl)-thiazoline-2-thiones which are easily prepared from 1,2-diaminobenzene, CS(2) and halogenoketones. This new route compares advantageously with the classical mercaptobenzimidazole routes in term of simplicity,isolated yields and availability of the starting materials.     

Selective catalytic oxidation reaction of p-xylene on manganese–iron mixed oxide materials

Mixed manganese iron oxides (Mn/Fe/O) as heterogeneous catalysts were prepared by hydrothermal treatment and citrate methods to be tested in the oxidation of p-xylene (PX) using as oxidation agent molecular oxygen, hydrogen peroxide, and tert-butyl hydroperoxide. Preparation of mixed MnFe oxide by the citrate method releases materials with smaller particle size and lower degree of crystallinity as compared with the hydrothermal one, which further leads to a higher activity toward the oxidation of PX. A conversion of PX of 98% and a yield in p-toluic acid of 93% were obtained in the presence of Mn/Fe/O prepared by the citrate method using tert-butyl hydroperoxide as an oxidizing agent.     

Thermically and electrochemically induced isomerization of a (bis(ferrocene)-cyclam)copper(II) complex

The new bis(ferrocene)-cyclam macrocycle 1,8-bis(ferrocenylmethyl)-1,4,8,11-tetraazacyclotetradecane, denoted L, has been synthesized. Two Cu(II) complexes with L have been isolated and characterized from X-ray structure determination and electrochemical studies. These two LCu(II) complexes correspond to the type I (ferrocenyl subunits in the same side of the cyclam plane) and type III (ferrocenyl subunits above and below the cyclam plane) isomers. The type I LCu(II) complex was synthesized from L and a Cu(2+) salt, while the type III isomer was obtained by oxidation in air or by comproportionation of the Cu(I) complex. The interconversion between type I and type III LCu(II) complexes is negligible in acetonitrile and slow in dimethyl sulfoxide but fast via an electrochemical reduction-reoxidation cycle. According to UV-vis and electrochemical characterizations, the type III isomer is thermodynamically more stable and the type I isomer is kinetically favored. A type III LNi(II) complex was also isolated and characterized by X-ray diffraction analysis and from electrochemical studies.     

Selective voltammetric detection of dopamine in the presence of ascorbate

The selective detection of dopamine in the presence of ascorbate is demonstrated based on the voltammetry of dopamine transfer across the interface between two immiscible electrolyte solutions (ITIES) facilitated by an organic-phase ionophore; ascorbate transfer does not occur, leading to highly selective detection of dopamine in the presence of excess ascorbate.