Adsorption complexes ‘zeolite–cationic surfactant’: properties and surface activity in a polymer composite material based on ultra-high-molecular-weight polyethylene

We investigated the adsorption of the cationic surfactant cetyltrimethylammonium bromide (CTAB) to zeolite from premicellar and micellar solutions, as well as some properties of the organically modified zeolite surface and the nature of its interfacial interaction with ultra-high-molecular-weight polyethylene (UHMWPE) in a UHMWPE-based polymer composite material (PCM). The formation mechanism of mono- and bimolecular adsorption layers of cetyltrimethylammonium cation and bromide anion to the clinoptilolite (Cli) surface was proposed, and the thermodynamic and kinetic characteristics of adsorption were determined. The surface texture of organically modified zeolite was studied by instrumental methods; the thermal stability limits of CTAB adsorption layers to zeolite surface and their decomposition behavior in inert and oxidizing media were established. The evaluation of the deformation and strength properties, the study of the supramolecular structure, and the calculation of the thermodynamic and kinetic parameters of the PCM crystallization process revealed that the filing with organically modified Cli increases the UHMWPE surface activity and improves their compatibility.     

Unit Circle Elliptic Beta Integrals

We present some elliptic beta integrals with a base parameter on the unit circle, together with their basic degenerations. 2000 Mathematics Subject Classification: Primary—11F50, 11L05, 33D05, 33D67     

Electronographic investigation of short-range order in the surface layers of melts

The examination of the structure of the surface layers in melts by the reflection electron diffraction has detected a shift of the diffraction bars due to the surface monolayer and subsequent atomic layers. The magnitude of the shift depends on the surface layer thickness. An analysis of structure curves revealed a difference between the first monoatomic layer and the bulk.     

Determination of unsaturated fatty acids with a migrating double bond in complex biological matrices by gas chromatography with flame ionization and mass spectrometry detection

We present the results of determination of unsaturated fatty acids (FAs) in foods of animal origin. It is shown that, in addition to the main component, monounsaturated cis-9-octadecenoic (oleic) acid, other fatty acids may be present in the composition of lipids, depending on the type of raw materials used to prepare the food product. The determination of these acids can significantly vary depending on the presence of impurities and assay conditions. It is demonstrated that gas chromatographic systems with a flame ionization detector, conventionally used for the determination of the fatty acid composition, are useless for the reliable identification of close structural analogues of unsaturated essential fatty acids. The conditions of determination of these compounds with mass spectrometric detection are selected. The effect of the composition of analytes, which were animal ingredients, on the results is discussed. It is shown that the greatest difficulty is the determination of unsaturated fatty acids present in test samples of different aetiologies in amounts not exceeding 0.05–0.1%.     

Electrochemical deposition of molybdenum oxide into films of poly(3,4-ethylenedioxythiophene) conducting polymer on glassy carbon substrates

Electrochemical deposition of molybdenum oxides from molybdate-containing solutions onto glassy carbon electrodes and the same electrodes coated with a film of poly(3,4-ethylenedioxythiophene) conducting polymer was studied. The morphology of the deposited molybdenum oxides was examined by scanning electron microscopy. The method of X-ray photoelectron spectroscopy was used to determine the state of molybdenum in surface molybdenum oxides and a conclusion was made that the oxide MoO₂ is mostly present.     

Extraction of contaminant metals from dumped metacolloid ores in order to reduce their hazardousness

Problems of human and environmental protection from discharges formed in out-of-balance ores dumped from nonferrous metallurgy were considered. To the most hazardous dumps belong those of metacolloid ores, discharges from which are contaminated with copper, zinc, iron, and also indium and cadmium. It was found that the most effective way to preclude the contamination is by using heap leaching of contaminant metals from ores in the chemical reclamation of the dumps. Mathematical dependences of the leaching rate of easily soluble compounds of metals (copper, zinc, indium, and cadmium) from metacolloid ores on the main technological factors of the process: sulfuric acid concentration, ore spraying density, and oxidation interval between sprayings were determined, the optimal process modes were found, and the cost-efficient production of metals in reclamation of dumps of this kind to a state in which they hardly contaminate the environment was calculated.     

Diode ring-down spectroscopy without intensity modulation in an off-axis multipass cavity

Cavity ring-down spectroscopy with an off-axis multipass cell and space separated detectors is proposed to record absorption spectra without modulation of the diode laser intensity. The spectral resolution is approximately 0.0003 cm-1. The whole spectrum is obtained for one continuous tuning of the laser frequency for approximately 20 ms. When comparing this method to conventional CRDS the required rise time is 1000 times slower. The recording of the whole spectrum for one measurement gives additional possibilities of signal extraction at relatively high noise. The technique is applied to absorption measurement of NO2 in atmosphere.     

Methods of reference signal and phase shifts in the multipass laser schemes for the detection of trace gas impurities

The application of the methods using the phase shift of modulated radiation and ICOS for the measurement of relatively low concentrations of gas impurities is considered. The measurement sensitivities of 0.01 ppbv and 6 × 10⁻¹¹ cm⁻¹ with respect to concentration and absorption coefficient, respectively, are obtained for the NO₂ molecules.