The influence of the synthesis pressure on the chromatographic properties of poly(divinylbenzene-<Emphasis Type="Italic">co</Emphasis>-ethylvinylbenzene-<Emphasis Type="Italic">co</Emphasis>-2-hydroxyethyl methacrylate) monolithic columns

Monolithic columns based on copolymer of divinylbenzene (DVB), ethylvinylbenzene (EVB), and 2-hydroxyethyl methacrylate (HEMA) were prepared and applied to the separation of low-molecular-weight aromatic compounds. The monoliths were synthesized via thermally initiated free-radical polymerization in confines of stainless steel tubes with dimensions of 100 × 4.3 mm. In order to compensate for the polymer shrinkage during the synthesis and prevent the monolith from detachment from the column wall, the polymerization was conducted under nitrogen pressure. The excess pressure was varied from 0 bar to 9 bar. The synthesis under pressure was shown to improve the peak shapes and column efficiency in comparison with the synthesis in the closed tube. The optimum pressure for poly(DVB-co-EVB-co-HEMA) monoliths was found to be 3 bar. The efficiency of the column obtained at 3 bar is 13 500 TP/m for propylbenzene (k′ = 6) and 38 300 TP/m for uracil (k′ = 0).     

Microwave annealing of defects in ferroelectric triglycine sulfate

The effect of microwave irradiation of ferroelectric triglycine sulfate (TGS) samples with different degrees of imperfection (determined by the annealing conditions) has been investigated. It is shown that the irradiation effect depends on both the degree of perfection of the samples and the irradiation time (dose). As for gamma irradiation, low doses of microwave radiation lead to partial annealing of defects and, therefore, should improve the parameters of TGS-based devices. High irradiation doses cause degradation of TGS properties, which is highest in perfect crystals.     

Scalar graviton and the modified black holes

Under the explicit violation of the general covariance to the unimodular one, the effect of the emerging scalar graviton on the static spherically symmetric metrics is studied. The main results are threefold. First, there appears the two-parametric family of such metrics, instead of the one-parametric black-hole family in General Relativity (GR). Second, there may exist the one-parametric subfamily describing a peculiar object, the “graviball,” missing in GR. Third, in a simplifying assumption, all the metrics possess the correct Newtonian limit as in GR. The text was submitted by the authors in English.     

Magnetism of LiMn<Subscript>2</Subscript>O<Subscript>4</Subscript> manganite in structurally ordered and disordered states

The specific features of the crystal structure and the magnetic state of stoichiometric lithium manganite in the structurally ordered Li[Mn₂]O₄ and disordered Li_{1 − δ}Mn_δ[Mn_{2 − δ}Li_δ]O₄ (δ = 1/6) states have been investigated using neutron diffraction, X-ray diffraction, and magnetic methods. The structurally disordered state of the manganite was achieved under irradiation by fast neutrons (E _eff ≥ 1 MeV) with a fluence of 2 × 10²⁰ cm⁻² at a temperature of 340 K. It has been demonstrated that, in the initial sample, the charge ordering of manganese ions of different valences arises at room temperature, which is accompanied by orthorhombic distortions of the cubic spinel structure, and the long-range antiferromagnetic order with the wave vector k = 2π/c(0, 0, 0.44) is observed at low temperatures. It has been established that the structural disordering leads to radical changes in the structural and magnetic states of the LiMn₂O₄ manganite. The charge ordering is destroyed, and the structure retains the cubic symmetry even at a temperature of 5 K. The antiferromagnetic type of ordering transforms into ferrimagnetic ordering with local spin deviations in the octahedral sublattice due to the appearance of intersublattice exchange interactions.