Density functional theory calculations of selected Ru(II) two ring diimine complex dications

Geometry optimization for a series of ten, two-ring diimine Ru(II) complexes was effected using the Gaussian 98 protocol at density functional theory (DFT) B3LYP level with basis sets 3-21G*and 3-21G**. HOMO-LUMO energy difference values compared favorably to the experimental data from electrochemistry [Delta E(1/2) = (E(1/2ox) - E(1/2red))] and the lowest energy absorption maxima, which for these complexes correspond to the metal-to-ligand charge transfer (MLCT) band. The HOMO and LUMO distributions from DFT support the idea that the lowest energy transitions are metal-to-ligand charge transfer and that the lowest energy LUMO for the mixed ligand complexes is located on 2,2'-bipyrazine (bpz), followed by 2,2'-bipyrimidine (bpm) and then 2,2'-bipyridine (bpy).     

Nonlinear inertial effects on the instability of a single long wave of finite amplitude at the interface of two viscous fluids

The evolution of a single long wave of finite amplitude at the interface of two immiscible fluids of different viscosities and densities, between two horizontal plates is solved, using a boundary layer flow approximation for the equation of motion in each fluid layer. It is found that when the nonlinear inertial effects are taken into account in a moderate manner, at least in the frame of the boundary layer approximation, the initial unperturbed flow with smooth interface is stable to a single wave perturbation at the interface, even in the presence of adverse density and viscosity stratifications. However, when the nonlinear effects are increased in a specific way, and the magnitudes of the parameters involved are kept within the order of magnitude established for the present theory, an unstable flow configuration can be obtained.     

The influence of the variable sample volume and constant added standard on the determination of copper, nickel and chromium by atomic absorption spectrometry

Bader indicated as the most convenient approaches for the determination of an element by atomic absorption spectrometry the (1) continuous variation of standard at constant total volume, and (2) continuous variation of the unknown analyte at constant total volume. Considering the relevance of the ease of atomization, Bader's statement were put to the test in the determination of copper, nickel, and chromiun in nodular iron by use of analysis of variance (ANOVA). The results presented here lead to the conclusion that Bader's modes (1) and (2) are not equivalent for all cases.     

Hydrolytic resistance of Na2O---B2O3---SiO2 gels prepared by sol-gel process

Alkoxide derived gels were prepared in the system Na₂O---B₂O₃---SiO₂. The gel compositions were situated in the liquid-liquid immiscibility area of the phase equilibrium diagram.

Hydrolytic resistance tests were performed on the gels heat-treated at temperatures ranging between 120 to 850 °C. The Na₂O, B₂O₃ and SiO₂ extracted from the attack gels were analyzed. The experimental results indicate that the amount of B₂O₃ has a significant influence on the chemical durability of the heat-treated gels. At temperatures of 850 °C the greater the B₂O₃ mol% the greater are the amounts of Na₂O and B₂O₃ extracted. Different behaviour was observed for gels heat-treated at 600 °C where the amounts of B₂O₃ and Na₂O extracted slightly increases as the B₂O₃ mol% increases. Small amounts of extracted SiO₂ were always observed.

These results are complemented with other measurements so that an explanation of the controlling mechanism is given.     

New catechol derivatives of safrole and their antiproliferative activity towards breast cancer cells

Catechols were synthesized from safrole. Nine derivatives were prepared and assessed for antiproliferative effects using different human cell lines. The in vitro growth inhibition assay was based on the sulphorhodamine dye to quantify cell viability. The derivatives 4-allylbenzene-1,2-diol (3), 4 4-[3-(acetyloxy)propyl]-1,2-phenylene diacetate (6) and 4-[3-(acetyloxy)propyl]-5-nitro-1,2-phenylene diacetate (10) showed higher cytotoxicity than the parent compound 2 in tests performed on two breast cancer cell lines (MCF-7 and MDA-MB-231). The IC?? values of 40.2 ± 6.9 μM, 5.9 ± 0.8 μM and 33.8 ± 4.9 μM, respectively, were obtained without toxicity towards dermal human fibroblast (DHF cells).     

Recent advances in enantioselective organocatalyzed anhydride desymmetrization and its application to the synthesis of valuable enantiopure compounds

Recent years have witnessed increasing interest in the field of asymmetric organocatalysis. In particular, efforts in this field have been devoted to the use of small organic molecules in asymmetric processes based on enantiotopic face discrimination and, only recently, efforts have also been devoted to asymmetric organocatalytic desymmetrization of prochiral substrates-a process based on enantiotopic group discrimination. This critical review documents the advances in the use of organocatalysis for the enantioselective desymmetrization of achiral and meso anhydrides and its application to the synthesis of valuable compounds as reported until 2010 (134 references).     

Decentralised Control Design of Lateral and Vertical Vehicle Dynamics using Passivity

In this paper, we present a novel methodology to design block–diagonal stable decentralised controllers based on the Kalman–Yakubovich–Popov lemma. The approach yields closed–loop systems that are robust with respect to parameter uncertainty and structural perturbations. We demonstrate the methodology by designing controllers for the lateral and vertical subsystems of a vehicle emulator; namely, a test vehicle that can mimic the behaviour of a wide range of vehicles. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)