Facile Synthesis of Tris(alkoxydimethylsilyl)methane Derivatives via Alcoholysis Under Open-Flask and Mild Conditions

The reactions between a variety of functionalized alcohols and tris(dimethylsilyl)methane, (HMe₂Si)₃CH, are described. Alcohols such as ethylene glycol monobutyl ether, ethylene glycol monoethyl ether, triethylene glycol monomethyl ether, 2-chloroethanol, 1-octanol, benzyl alcohol, glycidol, and allyl alcohol were converted in the presence of Karstedt's catalyst into the corresponding tris(alkoxydimethylsilyl)methanes, (ROMe₂Si)₃CH, in a convenient one-pot operation under aerobic conditions. The appearance of the products coincides with the generation of colloidal Pt(0) species. Moreover, poly(4-chloromethyl)styrene containing tris(dimethylsilyl)methyl groups reacts with benzyl alcohol or 2-chloroethanol in the presence of Karstedt's catalyst to give new macromolecules bearing tris(alkoxydimethylsilyl)methyl groups. The reaction rate is greatly influenced by the concentration of catalyst.     

New Synthesis of Acetaminophen Derivatives Containing a Phosphorus Atom

Two derivatives of acetaminophen have been efficiently prepared from 4-aminophenol via a two-step procedure involving acetylation of OH and NH ₂ groups and then the reaction of the acetylated compounds with diakyl acetylenedicarboxylate in the presence of triphenylphosphine. The products were obtained in good yields.     

Controlling the optical bistability in a Λ-type atomic system via incoherent pump field

We investigated optical bistability (OB) and the absorption properties of a weak probe field in a three-level Λ-type atomic system confined in a unidirectional ring cavity via incoherent pump field. We found that the threshold of OB and the probe field absorption can be controlled by the rate of incoherent pump field. No laser field was used in the pumping processes.     

Spectrofluorimetric Determination of Nickel (ΙΙ) with Murexide

A very sensitive and selective spectrofluorimetric method has been developed for nickel (ΙΙ) determination in environmental samples. The method is based on measuring the decrease in fluorescence intensity of murexide after nickel (ΙΙ) binding. The intensity of the fluorescence emission peak was measured at ex/em 345/431 nm in several solutions with pH interval 3.0–7.0. The fluorescence intensity decrease was found to be linear in the concentration range of 0.007 mg.L^?1 to 0.1 mg.L^?1 and 0.1 mg.L^?1 to 20 mg.L^?1 of nickel (ΙΙ) by using 10^?4 M murexide at pH 3. The detection limit was found 0.004 mg.L^?1. Relatively large excesses of over 20 cations and anions do not interfere. The method was successfully applied to the analysis of nickel (ΙΙ) in sea, rain and ground water. This method is very precise and accurate (R.S.D.?=?0.42 % for the determination of 0.05 mg.L?¹ nickel in 10 replicates).     

Cycloisomerization of dienes and enynes catalysed by a modified ruthenium carbene species

Cycloisomerization is a totally atom economic procedure which converts dienes and enynes into cyclic molecules. Modification of Grubbs' 2nd generation catalysts by reaction with dimethylformamide provides a new species able to catalyse this transformation. Selection of suitable conditions allowed high yields and selectivity. Studies performed in order to identify the catalytic species point to a non-carbenic ruthenium complex that has lost the phosphine. No hydride signals appeared. In addition, the reaction works with enynes and the new species catalyses efficiently crossed cyclotrimerizations of alkynes with diynes.     

Extension of VIKOR method for decision making problem with interval numbers

The VIKOR method was developed for multi-criteria optimization of complex systems. It determines the compromise ranking list and the compromise solution obtained with the initial (given) weights. This method focuses on ranking and selecting from a set of alternatives in the presence of conflicting criteria. It introduces the multi-criteria ranking index based on the particular measure of “closeness” to the “ideal” solution. The aim of this paper is to extend the VIKOR method for decision making problems with interval number. The extended VIKOR method’s ranking is obtained through comparison of interval numbers and for doing the comparisons between intervals, we introduce α as optimism level of decision maker. Finally, a numerical example illustrates and clarifies the main results developed in this paper.     

Preconditioned characteristic boundary conditions for solution of the preconditioned Euler equations at low Mach number flows

Preconditioned characteristic boundary conditions (BCs) are implemented at artificial boundaries for the solution of the two- and three-dimensional preconditioned Euler equations at low Mach number flows. The preconditioned compatibility equations and the corresponding characteristic variables (or the Riemann invariants) based on the characteristic forms of preconditioned Euler equations are mathematically derived for three preconditioners proposed by Eriksson, Choi and Merkle, and Turkel. A cell-centered finite volume Roe’s method is used for the discretization of the preconditioned system of equations on unstructured meshes. The accuracy and performance of the preconditioned characteristic BCs applied at artificial boundaries are evaluated in comparison with the non-preconditioned characteristic BCs and the simplified BCs in computing steady low Mach number flows. The two-dimensional flow over the NACA0012 airfoil and three-dimensional flow over the hemispherical headform are computed and the results are obtained for different conditions and compared with the available numerical and experimental data. The sensitivity of the solution to the size of computational domain and the variation of the angle of attack for each type of BCs is also examined. Indications are that the preconditioned characteristic BCs implemented in the preconditioned system of Euler equations greatly enhance the convergence rate of the solution of low Mach number flows compared to the other two types of BCs.