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(charges, chemical state) as well. The chemical quality of the model compound also plays an important role in heterogeneous photocatalysis: in aqueous media, its hydrophilicity could be a decisive factor in the adsorption process and the

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catalysts were focused on sulfide, phosphide and noble metal catalysts [ 3 ]. Many oxygen-containing compounds such as phenols [ 4 – 10 ], furans [ 11 – 16 ], ketones [ 17 – 19 ] and alcohols [ 20 – 22 ] have been used as model compounds to study the HDO

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Abstract  

Experiments with Acid Blue 62 as a model compound for dyes were performed under steady-state conditions, using deoxygenated solutions as well as those saturated with N2O, oxygen or oxygen mixed with N2O. The yield of decoloration served as an indicator for the degradation process. Oxygen seems to inhibit radiation-induced decomposition of the dye in aqueous solution.

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Abstract  

Urea–formaldehyde (UF) and phenol–formaldehyde (PF) resins are the most widely used wood adhesives. The first stage in resin manufacturing is the formation of methylol derivatives which polycondensation leads to building the tridimensional network. Understanding the behaviour of methylol compounds in curing provides useful information for developing appropriate resin structures. Thermal behaviour of N,N′-dihydroxymethylurea, 2- and 4-hydroxymethylphenols, urea and phenol as model compounds for UF, PF and phenol–urea–formaldehyde (PUF) resins was followed by TG-DTA method. The measurements were carried out by the labsys instrument Setaram at 30–450 °C in nitrogen flow. The characteristic signals for model compounds and for some reaction mixtures were measured by high resolution 13C NMR spectroscopy.

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Abstract  

Gamma-radiolytically generated radicals of crown ethers /12-crown-4, 1; 15-crown-5, 2; dicyclohexano-24-crown-8, 3/ and the model compounds /tetrahydrofurane, 4 and 1,4-dioxane, 5/ were studied by the spin-trapping method using C-phenyl-N-methylnitrone /PBN/ as a spin-trapping agent giving rise to the sufficiently stable nitroxyl radicals. The spin adducts of radicals 2 and 3 are relatively stable up to the temperature 253 K and 453 K, respectively.

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Abstract  

The list of the developed99mTc-kits in our research center is given, while the whole research work as a basis of99mTc scanning agents production is described. Research involved physico-chemical studies of both types of complexes: tin and technetium-99 complexes as model compounds for99mTc-radiopharmaccuticals, as well as biochemical studies including interaction with blood proteins, as well as subcellular localization of certain99mTc,99Tc-complexes.

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Abstract  

Iron injections containing high spin iron(III) complexes may undergo a reductive decomposition during preparation or storage. This process was investigated by the Mössbauer spectroscopy of ice samples prepared by quick-freezing of the injection. The comparison of three model compounds and the correlation between the osmotic pressure of the solutions and their iron(II) concentration formed in the decomposition process and determined by Mössbauer measurements revealed the reason and mechanism of the decomposition.

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Abstract  

Previous studies have shown that iodine (including 129I) can be strongly retained in organic-rich surface soils and sediment and that a large fraction of soluble iodine may be associated with dissolved humic material. Iodate (IO3 ) reacts with natural organic matter (NOM) producing either hypoiodous acid (HIO) or I2 as an intermediate. This intermediate is subsequently incorporated into the organic matter. Based on reactions of model compounds, we infer that iodine reacts with peat by aromatic substitution of hydrogen on phenolic constituents of the peat. Alternatively, the intermediate, HIO or I2, may be reduced to iodide (I). The pH (and temperature) dependence of the IO3 reaction (reduction) has been explored with sphagnum peat, alkali lignin, and several model compounds. The incorporation of iodine into NOM has been verified by pyrolysis gas chromatography/mass spectrometry (GC/MS). Model compound studies indicate that reduction of IO3 to HIO may result from reaction with hydroquinone (or semiquinone) moieties of the peat.

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Summary

The paper compares linear, quadratic, and cubical regression together with several weighted and robust approaches in the context of lipophilicity determination. The comparison is done on 35 model compounds on data from different modifiers used on RP18, CN, and silica plates. It can be concluded that the use of weighted and moderately robust regression technique increases correlation between extrapolated retention and real lipophilicity, whereas polynomial and very robust techniques give visibly worse results due to their excessive flexibility and higher extrapolation uncertainty. Additionally, we have compared averaging retention from different modifiers by R F, k, and R M values. The results are similar; however, surprisingly, R F averaging performs slightly better to the other approaches.

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Abstract  

Thermal stability of para (p--) and ortho (o-) isomers was investigated by CRTG and reaction kinetic analysis. The temperature started the mass decrease of o-isomer was about 20C lower than that of p-isomer by CRTG. The activation energies of thermal decomposition of o- and p-isomers were 136.9 and 153.4 kJ mol–1, respectively. The effect of steric hindrance on heat of formation was calculated by AM1 method using Win MOPAC3.0 for the model compound of p- and o-isomers. The lower stability of o-isomer was the results of the steric hindrance between the ethylene unit of aromatic ring and three alkyl chains.

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