Novel heterocyclic systems. Synthesis of 2,7-dimethyl-10-oxa-1,8-diaza-anthracen-9-one and derivatives

Synthesis of novel heterocycles, which contain the unique 10-oxa-1,8-diazaanthracen-9-one tricyclic core, is reported. The core structure was assembled via a dehydrative-cyclization strategy.     

Sharp Turán inequalities via very hyperbolic polynomials

We present new sharp inequalities for the Maclaurin coefficients of an entire function from the Laguerre-Pólya class. They are obtained by a new technique involving the so-called very hyperbolic polynomials. The results may be considered as extensions of the classical Turán inequalities.     

Canonical connection on a class of Reimannian almost product manifolds

The canonical connection on a Reimannian almost product manifold is an analogue to the Hermitian connection on an almost Hermitian manifold. In this paper we consider the canonical connection on a class of Reimannian almost product manifolds with non-integrable almost product structure.     

Effects of organic additives on alumina coatings on stainless steel obtained by spray pyrolysis

Alumina coatings were obtained by deposition of boehmite sol, with added polyvinyl alcohol or polyethylene glycol, on stainless steel foil by spray pyrolysis method. Characterizations of coatings were performed by SEM, XRD, XPS, AFM and S_BET analysis. Alumina coating prepared with polyethylene glycol has improved resistance to surface area loss than coating obtained with polyvinyl alcohol. At elevated temperatures polyethylene glycol has preserved the morphology of alumina coating and prevents the diffusion of Fe from stainless steel substrate. Porous, foam-like aluminium oxide coating, consisted of accidentally distributed rings of alumina, was created from both additives. Such coating morphology, with a hierarchical porosity, has application in numerous catalytic processes.     

Surface-enhanced Raman scattering active substrates by liquid flame spray deposited and inkjet printed silver nanoparticles

Surface-enhanced Raman scattering (SERS) active substrates were made via liquid flame spray deposition and inkjet printing of silver nanoparticles. Both processes are suitable for cost-effective fabrication of large-area SERS substrates. Crystal violet (CV) solutions were used as target molecules and in both samples the detection limit was approximately 10 nM. In addition, sintering temperature of the inkjet printed silver nanoparticles was found to have a large effect on the SERS activity with the higher curing temperature of 200 °C resulting in contamination layer on silver and cancelation of the SERS signal. This layer was characterized using an X-ray photoelectron spectroscopy (XPS).     

Explicit Heegner points: Kolyvagin's conjecture and non-trivial elements in the Shafarevich-Tate group

Kolyvagin used Heegner points to associate a system of cohomology classes to an elliptic curve over Q and conjectured that the system contains a non-trivial class. His conjecture has profound implications on the structure of Selmer groups. We provide new computational and theoretical evidence for Kolyvagin's conjecture. More precisely, we explicitly approximate Heegner points over ring class fields and use these points to give evidence for the conjecture for specific elliptic curves of rank two. We explain how Kolyvagin's conjecture implies that if the analytic rank of an elliptic curve is at least two then the Zp-corank of the corresponding Selmer group is at least two as well. We also use explicitly computed Heegner points to produce non-trivial classes in the Shafarevich-Tate group.     

Laguerre polynomials as Jensen polynomials of Laguerre-Pólya entire functions

We prove that the only Jensen polynomials associated with an entire function in the Laguerre-Pólya class that are orthogonal are the Laguerre polynomials.     

Determination of calcium, iron and manganese in moss by automated discrete sampling flame atomic absorption spectrometry as an alternative to the ICP-MS analysis

An automated, fast and reliable procedure has been developed for flame atomic absorption analysis of Ca, Fe and Mn in moss. The method is suitable for routine analysis of a large number of moss samples and allows sequential determination of all three elements in the same solution. In order to inhibit the matrix interference on Ca and to level the diverse analytical behaviour of the moss matrix, approximately 1% La was added to both samples and standard solutions as well. An integrated system of ‘sandwich-type’ air segmented discrete sample introduction and flame atomic absorption detection (ASDI-FAAS) was successfully applied. It works at ‘solvent-air-sample-air-solvent’ mode, which tolerates the introduction of high salt content solutions, reduces reagent and sample consumption and allows the application of data treatment models to pseudo-steady state signals for bettering the repeatability. For moss samples containing high Ca and Fe concentrations, equivalent procedure was used by turned on 45° burner head without worsening the analytical characteristics. Concerning these three elements, the method is suggested as a cheaper, easier and more trustworthy alternative with a better precision to the inductively coupled plasma-mass spectrometry (ICP-MS) one. The ASDI-FAAS results were used for selection of appropriate isotopes and correction procedures for ICP-MS determination. Both methods show good agreement of the Ca, Fe and Mn results that correspond to the moss reference materials tested.     

Methanol decomposition on copper and manganese oxides supported on activated carbon

Copper and manganese oxides supported on activated carbon have been studied in the reaction of methanol decomposition to H₂ and CO. XRD, EPR, TPR with CO and magnetic measurements have been used for their characterization. The nature of the catalytically active complex is also discussed. This revised version was published online in June 2006 with corrections to the Cover Date.     

Theoretical study of the formation of adsorbed dicarbonyl species

The formation of mono- and dicarbonyl species during CO adsorption has been theoretically studied in order to obtain a mathematical model of the adsorption isotherms. The dependences proposed describe well the results of other authors and allow better utilization of the experimental data.

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- CO . .