Reactive oxygen and nitrogen species (RONS) scavenging reactions of o-vanillin: Pulse radiolysis and stopped flow studies

Reactions of peroxyl radicals and peroxynitrite with o-vanillin (2-hydroxy 3-methoxy benzaldehyde), a positional isomer of the well-known dietary compound vanillin, were studied to understand the mechanisms of its free radical scavenging action. Trichloromethylperoxyl radicals (CCl₃O ₂ ^· ) were used as model peroxyl radicals and their reactions with o-vanillin were studied using nanosecond pulse radiolysis technique with absorption detection. The reaction produced a transient with a bimolecular rate constant of approx. 10⁵ M⁻¹s⁻¹, having absorption in the 400–500 nm region with a maximum at 450 nm. This spectrum looked significantly different from that of phenoxyl radicals of o-vanillin produced by the one-electron oxidation by azide radicals. The spectra and decay kinetics suggest that peroxyl radical reacts with o-vanillin mainly by forming a radical adduct. Peroxynitrite reactions with o-vanillin at pH 6.8 were studied using a stopped-flow spectrophotometer. o-Vanillin reacts with peroxynitrite with a bimolecular rate constant of 3 × 10³ M⁻¹s⁻¹. The reaction produced an intermediate having absorption in the wavelength region of 300–500 nm with a absorption maximum at 420 nm, that subsequently decayed in 20 s with a first-order decay constant of 0.09 s⁻¹. The studies indicate that o-vanillin is a very efficient scavenger of peroxynitrite, but not a very good scavenger of peroxyl radical. The reactions take place through the aldehyde and the phenolic OH group and are significantly different from other phenolic compounds.     

Schrödinger vs. dirac bound state spectra of Q\bar Q-systems and a plausible lorentz structure of the effective power-law potential-systems and a plausible lorentz structure of the effective power-law potential

It is shown that a non-relativistic power-law potential model for the heavy quarks in the form V(r)=Ar ^v+V ₀, (A, ν>0) acquires relativistic consistency in generating Dirac bound states of \(Q\bar Q\) -system in agreement with the Schrödinger spectroscopy if the interaction is modelled by equally mixed scalar and vector parts as suggested by the phenomenology of fine-hyperfine splittings of heavy quarkonium systems in a non-relativistic perturbative approach.     

Beating capillarity in thin film flows

The combination of substrate unevenness and capillarity is known to induce far‐reaching perturbations at the free surface of thin liquid films. These might be undesired and this paper explores the possibility to control the free surface of thin liquid films to give it a prescribed profile by a suitable design of the underlying substrate. This corresponds to the inverse of the widely studied forward problem, which considers the effect of substrate unevenness on a free surface. Assuming that the steady free surface profile can be described by the lubrication approximation, this optimal control problem is shown to be governed by a first‐order partial differential equation, which is solved numerically using the method of characteristics. The proposed method is successfully tested for a range of desired free surface profiles and the domain of existence of a solution to the inverse problem is probed. Expectedly, it is shown that, owing to surface tension, not all free surface profiles can be achieved but in some cases capillarity can be beaten and a prescribed free surface profile obtained. Copyright © 2009 John Wiley & Sons, Ltd.     

One-dimensional MoO2 nanorods for supercapacitor applications

One-dimensional (1D) MoO₂ nanorods were prepared by thermal decomposition of tetrabutylammonium hexamolybdate (((C₄H₉)₄N)₂Mo₆O₁₉) in an inert atmosphere. The synthesized nanorods have been characterized by XRD, TEM and HRTEM. The capacitive behaviour of 1D MoO₂ nanorods was studied by galvanostatic charge–discharge studies in 1 M H₂SO₄ solution at different current densities. The results indicate that the MoO₂ nanorods show good capacitive behaviour with a specific capacitance of 140 Fg^?1.     

Effect of Ti4+ ions doping on microstructure and dc resistivity of nickel ferrites

Nanostructured nickel ferrites (NiFe₂O₄) were prepared by doping with Ti⁴⁺ ions using solid-state reaction route. Lowest grain size of 55 nm was achieved in the specimens with 20 mole% TiO₂ doping. Magnetization in the specimens decreases with decreasing grain sizes. Lower volume fractions of ferrite phase due to dissociation of the magnetic phase into smaller particles by the disruption of super exchange interaction by the titanium substitution results a decrease in magnetizations. Coercivity showed an increasing trend. This was explained as arising due to multidomain/monodomain magnetic behavior of magnetic nanoparticles. Small polaron hopping conduction between Fe²⁺ and Fe³⁺ sites controls the dc electrical properties of the specimens. The presence of an interfacial amorphous phase between the sites is evident from Mott's analysis. Specimens containing 10 mole or more TiO₂ and sintered at 1350 °C contain NiTiO₃ as a secondary phase and show unusual dc conductivity.     

Structural and electrical properties of Na1/2La1/2TiO3 ceramics

Na_1/2La_1/2TiO₃ (NLT) ceramic was prepared by a high-temperature solid-state reaction technique. A preliminary structural analysis (XRD) suggested the formation of a single-phase orthorhombic structure. SEM micrograph of the material showed uniform grain distribution on the surface of the sample. The dielectric permittivity and the loss tangent of the sample were measured in a frequency range from 1 kHz to 1 MHz and a temperature range 28 °C to 525 °C. Electrical properties of the material were studied using an ac impedance spectroscopic technique. Detailed analysis of the impedance spectrum suggested that the electrical properties of the material are strongly temperature dependant. The Nyquist plots clearly showed the presence of both bulk and grain boundary effect in the compound. The activation energy was estimated to be 1.1 eV from the temperature variation of dc conductivity. The a.c. conductivity spectrum suggests a typical signature of ion conducting system. PACS 77.22.Ch; 77.22.Gm; 77.80.Bh; 77.22.Ej     

Sodium Perborate Tetrahydrate–Mediated Transformations of 2′-Hydroxychalcones to Flavanones,Flavones, and 3′, 5′-Diiodoflavone Under Mild,Environmentally Friendly Conditions

Sodium perborate tetrahydrate has been utilized as a nucleophilic catalyst for facile conversion of 2′-hydroxychalcones to flavanones in warm aqueous acetonitrile, and then these chalcones, upon oxidative cyclization in warm acetic acid with an excess of the same reagent, afforded flavones in acceptable yields. One-pot synthesis of 3′,5′-diiodoflavone has been accomplished by diacetoxyiodobenzene-catalyzed iodination of 2′-hydroxychalcone with tetra-n-butylammonium iodide in acetic acid in the presence of sodium perborate as a terminal oxidant.