On quadratic and sesquilinear functionals

LetX be a leftA-module, whereA is either a complex Banach *-algebra with an identity element or the field of quaternions. The main result of this note is that forQ, anA-quadratic functional defined onX, there exists a sesquilinear functionalB such thatB(x,x)=Q(x) holds for allxX.     

On a construction of Thomassen

Using a construction of Thomassen [Discrete Math. 9, 91–96 (1974)] we prove that for infinitely manyn there is a family _n of triangle-free maximally non-hamiltonian graphs of ordern with | _n | exponentially inn. In particular, for everym 48 we construct such a graph; an infinite number of these provide new almost extremal examples in the sense of minimal size.     

Infrared spectroscopic study of the structure of the tetrabutyl S-dithiopyrophosphate complex of silver

The structure of the complex Ag·TBDTPP (tetrabutyl S-dithiopyrophosphate) formed in HNO₃ medium was studied by IR and NMR methods. The complex is involved in the isomerization of TBDTPP in the presence of Ag⁺ and NO ₃ ⁻ ions. In the IR spectra, we observe the disappearance of P−O−P band and the occurrence of new absorption bands associated with P−S−P and P=O bonds. The silver ion is coordinated to the thiophosphoryl group of the isomer molecule. The influence of HNO₃ concentration on complex formation is discussed.     

Gel permeation chromatographic characterization of sodium hyaluronate and its fractions prepared by ultrasonic degradation

Summary High-molecular-weight sodium hyaluronate isolated from rooster combs was degraded by ultrasonication. The molecular weight of hyaluronate and its polydispersity was determined by gel-permeation chromatography. During 75-min treatment the molecular weight value decreased from 1.39×10⁶ Da to 2.25×10⁵ Da while the polydispersity of the molecular weight increased from 1.29 to 2.36. The reciprocal value of the square of the hyaluronate's molecular weight was linearly proportional to the time of ultrasonication.     

Size exclusion chromatographic characterization of sodium hyaluronate fractions prepared by high energetic sonication

Summary A high molecular weight sodium hyaluronate isolated from rooster combs was degraded by ultrasonication. High-performance size exclusion chromatography allowed rapid and accurate determination of molecular weight parameters (M_z, M_w, M_n) and distributions. The time dependence of hyaluronan ultrasonication to the molecular characteristics of the polymer was investigated. A non-random nature of the degradation process was demonstrated and the reciprocal M_n value was found to be linearly proportional to the time of ultrasonication.     

Precipitation separation of lead and calcium,strontium, barium from acidic solutions using crown ether and tungstosilicic acid

It was found that lead reacts with 18-crown-6 (L) and tungstosilicic acid (H₄A) in acidic solutions and a compound with low solubility is formed what was confirmed by radiometric titration methods. Coprecipitation of complexion cation of PbL²⁺ with similar complexion cations of calcium, strontium and barium was studied. Formation of low soluble salts was utilized for separation of Pb from Ca, Sr and Ba from 1 mol·dm^–3 HNO₃. The ratio of Pb/Ca, Pb/Sr and Pb/Ba in the precipitation or separation factors S_pb/M undoubted depends on the ratio of the stability constants of lead and metals with 18C6 (_Pb/_M), what can be used for determination of more precise constant stability _M.     

Thermal decomposition of mineral zircon by alkali metal hydroxides

Thermal decomposition of zircon mineral was studied in the presence of sodium and potassium hydroxides and in the presence of a waste mixture of hydroxides containing NaOH and KOH in a weight ratio of 23. The process was controlled in such a way that the decomposition products might contain the minimum possible amount of alkali and could thus be applied for the syntheses of zircon pigments without any further exacting treatment.

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Zusammenfassung Es wurde die thermische Zersetzung eines Zirkonminerals in Gegenwart von Natrium- und Kaliumhydroxid-sowie in Gegenwart einer Altlauge mit einem Gehalt an NaOH und KOH im Verhältnis zwei zu drei untersucht. Der Prozeß wird derart gesteuert, daß die Zersetzungsprodukte einen möglichst geringen Anteil an Lauge besitzen und so ohne weitere arbeitsaufwändige Behandlungen zur Synthese von Zirkonpigmenten verwendet werden können.

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, 23. , , , - .

     

Sulfide ion electrooxidation catalysed by cobalt phthalocyanine microcrystals

Electrooxidation of sulfide ion catalysed by microcrystals of cobalt phthalocyanine was investigated by cyclic voltammetry in 0.5M KNO₃ at pH 9.22. Traces of catalyst were immobilized at the surface of a paraffin-impregnated graphite electrode by the mechanical transfer of its powder. The electro-oxidation of HS^– proceeds in two irreversible steps, with the first peak between 0 V and –0.12 V and the second at 0.17 V. The first step is second order in HS^– and its product is the adsorbed disulfide, which may further dissociate to give adsorbed sulfur atoms. The reduction of sulfur occurs at –0.1 V.     

Photocatalytic TiO2 Coatings: Effect of Substrate and Template

Summary. Transparent TiO₂ films with a high photodegradation activity towards an azo dye in aqueous solution were prepared by sol–gel processing. Films on soda–lime glass supports protected with a thin silica barrier layer exhibited better crystallization and monodisperse nanoparticles, higher absorption of light below 370 nm, and higher photocatalytic activity than those films deposited on bare glass supports proving the detrimental effect of interdiffused sodium ions on the development of the anatase nanostructure. The effect of substrate was more pronounced in thinner films (300 nm) than in thicker ones (1200 nm), which were achieved by adding a template (i.e. Pluronic F127) to the sol.     

Sorption of radionuclides on inorganic sorbents

Inorganic sorbents are often used in separation of metals and radionuclides in radioanalytical application and they were also used in technological scale for separation of radionuclides in cleanup of Three Mile Island NPP. Inorganic sorbents become popular in the last years because no problem with organic contamination, there are stable against radiation, sorption efficiency can be tailor made for selective separation of chosen metal. Contrary to the organic sorbents they have usually lower capacity and chemical stability is limited to narrower pH. Nevertheless of some problems, many good properties of inorganic sorbents make them very attractive for sorption study.