Passive Adsorbers Based on Carbon Materials and Their Comparison for Estimating the Oil and Gas Potentials of Rocks

Journal of Analytical Chemistry - Adsorbents used to analyze air for concentrations of various organic compounds with their subsequent determination by thermal desorption gas...     

Technology of task-solving in normalized radical media

In this paper, a methodological example of task-solving with the help of radical media is considered and technological problems of solving operational lifetime tasks of a complex system are discussed.     

Polyelectrolyte Sorbents for Ion Chromatography

A method for the synthesis of new anion exchangers for ion chromatography has been proposed. The method is based on the fact that interaction of water-soluble anionic polymers with materials containing negatively charged sulfo groups on the surface gives rise to polyelectrolyte complexes. It is demonstrated that replacement of functional groups in molecules of the polymer affects the selectivity of the ion-chromatographic determination of ions. Recommendations are given for selecting a polymer for the determination of mixtures of inorganic anions and anionic complexes of transition metals in ethylenediaminetetraacetic acid.     

Stochastic nonlinear Perron–Frobenius theorem

We establish a stochastic nonlinear analogue of the Perron–Frobenius theorem on eigenvalues and eigenvectors of positive matrices. The result is formulated in terms of an automorphism T of a probability space and a random transformation D of the non-negative cone of an n-dimensional Euclidean space. Under assumptions of monotonicity and homogeneity of D, we prove the existence of scalar and vector measurable functions α > 0 and x > 0 satisfying the equation αTx = D(x) almost surely. We apply the result obtained to the analysis of a class of random dynamical systems arising in mathematical economics and finance (von Neumann–Gale dynamical systems).     

Determination of water-soluble vitamins in vitamin premixes,bioacitve dietary supplements,and pharmaceutical preparations using high-efficiency liquid chromatography with gradient elution

The influence of the pH and temperature of the mobile phase on the retention and separation of 14 vitamins and vitameric forms has been studied for four different stationary phases. The chromatographic conditions allowing the separation of 12 water-soluble vitamins and vitameric forms have been proposed. It has been established that the best separation of water-soluble vitamins can be achieved by employing gradient elution. The mobile phase A, (0.6% phosphoric acid) pH 1.5–1.8; mobile phase B, acetonitrile. For the separation of nicotinic and ascorbic acid it is preferable to use stationary phases Luna C18(2) and Gemini C18, while for the separation of riboflavin and riboflavin-5-phosphate the Synergy Hydro RP and Zorbaz SB-C18 stationary phases should be used. The selected conditions have been used for the determination of vitamins in commercial samples of vitamin preparations. The results are in good accordance with the producer data.     

Polyelectrolyte sorbents based on aliphatic ionenes for ion chromatography

2-4, 3-4, 2-8, 3-8, 3-6, 4-6, 6-8, 6-10-ionenes (polymers with quaternary nitrogen atoms in the main chain) served as modifiers in synthesizing polyelectrolyte sorbents for ion chromatography. The approaches to the synthesis and their stability are discussed. Cluster analysis was applied to separate aliphatic ionenes to three groups as chromatographic modifiers, namely hydrophilic, hydrophobic, and intermediate. Each group is characterized by a certain selectivity to sulfate, perchlorate, iodide and thiocyanate. The sorbents show high selectivity and efficiency up to 15 000 theoretical plates per meter.     

Antiferromagnetic solid oxygen studied by positive muons

We present a zero magnetic field muon spin rotation study of-O₂ (antiferromagnetic phase of solid oxygen) in the temperature range of 10–24 K. Static magnetic order has been observed below the- transition temperatureB =23.8 K. The temperature dependence of the muon precession frequency exhibits behavior characteristic of a two-dimensional Heisenberg spin-1 system with the anisotropy parameter 10^–2 quite similar to that of antiferromagnetic phase of the high-temperature superconductor parent compounds. A unique local field at the muon site has been determined to beB ₀=1.27(5) kG at low temperatures.