Dispersion of silica nano-particles in sol-gel hybrid resins for fabrication of multi-scale hybrid nanocomposite

Multi-scale hybrid nanocomposites containing both ∼15 nm silica colloids and ∼2 nm oligosiloxanes in a methacryl polymer matrix were newly designed and fabricated. Colloidal silica sols were dispersed in methacryl oligosiloxanes nano-hybrid resins synthesized by sol-gel reaction of methacryloxypropylmethoxysilane and diphenylsilanediol. On the basis of TEM and SANS analyses, it was confirmed that the silica colloids were compatibly dispersed and different sizes of colloidal silica and oligosiloxanes co-exist in the solutions. Multi-scale hybrid nanocomposites fabricated by UV and thermal curing with incorporation of silica colloids in the nano-hybrid materials show enhanced mechanical and thermal characteristics.     

Ab initio and infrared spectral study of 4′-substituted phenylthiolbenzoates

The geometry of the 4′-cyano-(4′-CNPTB) and the 4′-methoxy-(4′-MePTB) phenylthiolbenzoates were obtained by ab initio calculations employing 6–31G basis set at Hartee-Fock level of theory. The results predict an extended form of the molecules and torsional angle between the phenyl rings at 90.85(6)⁰ and 90.87(3)⁰, respectively. On the basis of vibrational analysis the frequency assignment was carried out. The calculated frequencies were compared with the experimental IR spectral data in carbon tetrachloride, carbon disulfide solutions and in solid state.     

Determination of aristolochic acid by capillary zone electrophoresis

A simple and rapid capillary zone electrophoresis (CZE) method for the determination of aristolochic acid (AA) in dietary supplements and selected herbs is described. A clear separation of AA from other sample constituents was achieved within 5 minutes without any sample clean up. A mixture of 20 mM-morpholinethanesulphonic acid+10 mM-BisTrisPropane+0.2% hydroxyethylcelullose in 10% methanol serves as a background electrolyte. The linearity, accuracy, intra-assay and detection limit of the developed method are 200–6000 ng/mL, 95–103%, 3.5%, and 50 ng/ml, respectively. Ease of use, sufficient sensitivity and low running cost are the most important attributes of the CZE method. The proposed CZE method was compared with HPLC.     

Studies of the soluble part of oxidised coals

Soluble products obtained from the oxidation of four types of coal, each characterised by different degree of coalification and different degree of sulphur content, are studied. The coals are oxidised with peracetic acid (PAA) and nitric acid. Analyses are performed by Atmospheric Pressure-Temperature Programmed Reduction (AP-TPR) and Fourier Transform Infrared Spectroscopy (FTIR). The soluble products contain much more sulphur than the insoluble products of oxidation. The products obtained from the reaction with HNO₃ contain higher amounts of inorganic sulphur compounds, while those obtained from the reaction with PAA are characterised by an increased content of organic sulphur species.     

Synthesis of novel tryptamine and β-carboline derivatives via palladium-catalyzed reaction of bromotryptamine with organic boronic acids

New tryptamine 5, 7 and β-carboline derivatives 3 were preparated by palladium-catalyzed coupling reaction of 5-bromotryptamine 1 with aryl boronic acids. Dedicated to Professor András Lipták on his 70^th birthday.     

Xyloketal G,a Novel Metabolite from the Mangrove Fungus <Emphasis Type="Italic">Xylaria sp.</Emphasis> 2508

A novel metabolite 1, named xyloketal G, was isolated from cultures of marine derived mangrove fungus Xylaria sp. 2508. Its structure was elucidated by analysis of spectroscopic data.__________Published in Khimiya Prirodnykh Soedinenii, No. 1, pp. 22–23, January–February, 2005.     

Assessment of the Fe-Sn-Zn phase diagram at 450°C

The Fe-Sn-Zn system is of interest because Sn is one element added to the Zn galvanizing bath to overcome the drawbacks due to the presence of Si in semi-killed steels. This work has been undertaken with the aim to understand the tin effect on the microstructure and the layers growth in batch galvanized coatings on low alloyed steels. Various experimental techniques such as metallography, scanning electron microscopy (SEM) coupled with X-ray energy dispersive spectroscopy (EDX) are used in order to characterize the microstructure and the properties of such coatings elaborated in a zinc bath enriched with tin. Solidification phenomena and layers growth mechanisms during galvanization are explained by means of the ternary phase diagram Fe-Sn-Zn at 450°C. The Calphad method allows to obtain this phase diagram from the three optimized binary phase diagrams Fe-Sn, Fe-Zn and Sn-Zn and some experimental data inside the ternary Fe-Sn-Zn system.     

Spatial geometric arrangements of disulfide-crosslinked loops in nonplanar proteins

The method presented earlier [T. Kikuchi, G. Némethy, and H.A. Scheraga, (1986) J. Comput. Chem. 7 , 67] for the classification of patterns of the three-dimensional folding of a covalently crosslinked polypeptide chain has been extended to nonplanar proteins. The procedure described earlier was applicable only to proteins termed planar, i.e., with a connexity of the crosslinks (e.g., disulfide bonds) that can be represented in a planar diagram. The procedure described in the present work is applicable to any (planar or nonplanar) pattern of crosslinking. The classification is based on a systematic and objective method of enumeration of spatial geometric arrangements of loops (SGAL) using no information other than the location of the disulfide bonds in the amino acid sequence. Various SGAL classes correspond to the presence of different ways of mutual penetration of loops, called thrustings and entanglements. Information on SGAL classes can be of use in structural predictions of folding patterns of proteins.     

Mass spectrometric investigation of bimolecular compounds

Two points involving molecular structure have been investigated using mass spectrometry. First, mass spectra have been obtained that indicate a rapid means for differentiating bimolecular compounds from other structural isomers. Second, the mass spectrometric method has been used to evaluate bonding within bimolecular compounds. Quinone compounds have been reacted with dhydroxybenzene compounds to produce quinhydrone products, and upon mass spectrometric analysis, the quinhydrones decompose to regenerate derivatives of the starting materials. Evaluation of the decomposition products suggests that the hydroxyl hydrogens are involved in a resonance structure, and while in symmetrical quinhydrones, the hydroxyl hydrogens are probably associated equally with each reactant, unsymmetrical quinhydrones generate an unbalanced electronic distribution that eliminates the complete equivalency of the hydrogens.     

Solvent extraction studies of some cobalt(ii) chelates.

Extraction of radiolabeled cobalt(II) from aqueous solution into one or more solvents using 25 reagents was studied. Both reagent concentration and pH variation were investigated. The relevant association and partition constants for several of the better reagent-solvent systems were determined. These systems were hexanoic acid in I-hexanol, octanoic acid in I-octanol, and thenoyltrifluoroacetone in benzene.