Synthesis of silsesquioxane nanocomposites

In order to investigate the effect of presence of well defined nano-sized inorganic particles on the molecular mobility a conformation statistics of polymer chains, well defined polystyrene (PS) and poly(methyl methacrylate) (PMMA) macromolecules containing polyhedral oligomeric silsesquioxanes nanoparticles (POSS) were synthesized by copper-mediated atom transfer radical polymerization (ATRP). Two approaches were used for the synthesis — the first involves POSS as the initiator of ATRP; the second way considers an addition of POSS to the polymer (prepared by ATRP) with an appropriate functional group. Kinetics of polymerization was determined using common analytical methods and it was compared to the polymerizations initiated by low-molecular weight initiators, regarding the polymerization rate, initiation efficiency and polydispersity of the polymer. Efficiency of the initiation with POSS-containing initiators was low, causing remnants of inseparable free POSS in polymer. The second approach bypassed these disadvantages —POSS is connected to the polymer through a pending allyl group using the very efficient hydrosilylation reaction. Presented at the 1st Bratislava Young Polymer Scientists Workshop, Bratislava, 20–23 August 2007.     

A synthesis of licofelone using Fenton’s reagent

An efficient synthesis of licofelone, an anti-inflammatory drug currently undergoing phase-III clinical studies, based on Fenton-type radical alkylation of 2,3-dihydro-1H-pyrrolizine 3 with iodoacetonitrile or iodoacetates is reported. The iodoacetates can be replaced by NaI and by the corresponding bromoacetate.     

Preparation of manganese oxide nanoparticles by thermal decomposition of nanostructured manganese carbonate

MnO and Mn₂O₃ nanoparticles were prepared in air and argon atmosphere by thermal decomposition of nanocrystalline manganese carbonate synthesized by reaction of manganese(II) nitrate with glycerol. Samples were characterized using transmission electron microscopy, simultaneous thermal analysis and X-ray diffraction analysis. Average sizes of prepared nanoparticles were calculated from XRD patterns using Scherrer equation. Also, the conditions for decomposition of manganese carbonate were optimized to obtain optimal nanoparticle sizes. Due to suitable sizes of prepared nanoparticles and the initial material, this method can be used in a wide range of industrial applications.     

On conformally flat and type N pure radiation metrics

We study pure radiation spacetimes of algebraic types O and N with a possible cosmological constant. In particular, we present explicit transformations which put these metrics, that were recently re-derived by Edgar, Vickers and Machado Ramos, into a general Ozsváth–Robinson–Rózga form. By putting all such metrics into the unified coordinate system we confirm that their derivation based on the GIF formalism is correct. We identify only few trivial differences.     

An efficient microwave-assisted synthesis and biological properties of polysubstituted pyrimidinyl- and 1,3,5-triazinylphosphonic acids

Polysubstituted pyrimidinylphosphonic and 1,3,5-triazinylphosphonic acids with potential biological properties were prepared in high yields by the microwave-assisted Michaelis–Arbuzov reaction of trialkyl phosphite with the corresponding halopyrimidines and halo-1,3,5-triazines, respectively, followed by the standard deprotection of the phosphonate group using TMSBr in acetonitrile. 4,6-Diamino-5-chloropyrimidin-2-ylphosphonic acid (7a) was found to exhibit a weak to moderate anti-influenza activity (28–50 μM) and may represent a novel hit for further SAR studies and antiviral improvement.     

Preparation and characterization of ZnS nanoparticles deposited on montmorillonite

ZnS nanoparticles were prepared and deposited on montmorillonite (MMT) in the presence of cetyltrimethylammonium (CTA). UV spectrometry and transmission electron microscopy (TEM) proved the formation of nanoparticles with diameters ranging from 3 nm to 5 nm. Selected-area electron diffraction (SAED) patterns revealed the presence of romboedric ZnS. The band gap energy of nanosize ZnS was estimated at 3.89 ± 0.03 eV. Photoluminescence spectra exhibited a strong emission band between 300 nm and 600 nm explained by the vacant ZnS nanostructure. The prepared ZnS-montmorillonite nanocomposite (ZnS-MMT) was used for the photocatalytic reduction of CO(2) providing a considerably high efficiency that exceeded 5-6-fold the results of commercial TiO(2) Degussa P25. The main reaction products were hydrogen and methane. Methanol and carbon oxide were also observed in about 7-fold lower amounts. The stability of ZnS against oxidation was confirmed by the determination of sulphate using capillary isotachophoresis.     

Uncoupled multireference state-specific Mukherjee's coupled cluster method with triexcitations

We have developed the uncoupled version of multireference Mukherjee's coupled cluster method with connected triexcitations. The method has been implemented in ACES II program package. The agreement between the uncoupled and the standard version of Mukherjee's multireference coupled cluster method has been reported previously at the singles and doubles level by Das et al. [J. Mol. Struct.: THEOCHEM 79, 771 (2006); Chem. Phys. 349, 115 (2008)]. The aim of this article is to investigate this method further, in order to establish how its performance changes with the size of the basis set, size of the model space, multireference character of different molecules, and inclusion of connected triple excitations. Assessment of the new method has been performed on the singlet methylene, potential energy curve of fluorine molecule, and third b?(1)Σ(g)(+) electronic state of oxygen molecule.     

Perturbations of the half-linear Euler-Weber type differential equation

We investigate oscillatory properties of the half-linear second order differential equation

     

Approximation of a general singular vertex coupling in quantum graphs

The longstanding open problem of approximating all singular vertex couplings in a quantum graph is solved. We present a construction in which the edges are decoupled; an each pair of their endpoints is joined by an edge carrying a δ potential and a vector potential coupled to the “loose” edges by a δ coupling. It is shown that if the lengths of the connecting edges shrink to zero and the potentials are properly scaled, the limit can yield any prescribed singular vertex coupling, and moreover, that such an approximation converges in the norm-resolvent sense.     

Off-line coupling of microcolumn separations to desorption mass spectrometry

The presented review provides comprehensive and detailed characteristics on microcolumn separation techniques off-line coupled to mass spectrometry. Major attention is paid to the classification of junctions between the separation column and the deposition needle and to the process by which the liquid is transferred onto the target. Both contact and non-contact deposition techniques are covered. In order to emphasize the significance of the topic of off-line separations, current commercially available devices have been compared in terms of their potential utilization in analytical chemistry with a summarization of applications used over the past few years.