Electrophysical and acoustic properties of magnetic elastomers structured by an external magnetic field

Magnetoactive elastomers are promising for use in designing of magnetically operated devices for signal processing and sensors. The results from studying the electrophysical and acoustic properties of new magnetoactive elastomers structured by a nonuniform magnetic field are presented. It is shown that the prestructuring of the magnetic disperse filler by a magnetic field during composite synthesis substantially improves the coefficient of the transmission of electromagnetic radiation through the sample. The effect gets stronger as the mass fraction of filler increases. As the filler concentration grows, the transmission coefficient falls by 50%, and the ref lection coefficient grows by a factor of 150%. The longitudinal elastic modulus and the density vary within the ranges of 1.4–1.8 GPa and 2485–3362 kg m^–3, respectively, depending on the magnetic filler concentration and the sample’s structuring. The obtained results demonstrate the potential of usinf structured magnetoactive elastomers as radar absorbing materials.     

Relationship between Reactivity Ratios and Configuration for Donor—Acceptor Type Copolymers

For binary copolymers from an acrylic monomer (acceptor type, M¹) and an aromatic-substituted monomer (donor type, M₂) a linear relation between log (r₂/r¹) and the probability of “coisotactic” alternating addition is observed. This can be a proof for the influence of monomer polarity on the copolymer configuration.     

Relationship between the aggregation of nanoparticles bearing zinc ions and cytotoxicity and morphology of blood cells

The effect of nanoparticles bearing magnetic and nonmagnetic zinc nuclei on lymphocytes from healthy donors and leukemic cells of patients (15–20 years old) with acute B-lymphoblastic leukemia (B-ALL) and acute myeloid leukemia (AML) was considered. The studies by confocal and fluorescence microscopy showed an apoptotic effect of nanoparticles bearing zinc ions. An increase in the aggregation of the nanoparticles and cell self-aggregation, resulting in a decrease in cytotoxicity, were observed in the case of the magnetic isotope. In spite of this, cell apoptosis under the action of even aggregated nanoparticles bearing magnetic ⁶⁷Zn was significantly higher than the apoptosis with lymphocytes of healthy donors and with nanoparticles bearing zinc of the total isotope composition.     

Tautomeric composition and tautomeric transformation sequence of 1,4-bis(alkylamino)anthraquinones

Compounds widely known as 1,4-bis(alkylamino)-9,10-anthraquinones are in fact neither individual substances nor substituted 9,10-anthraquinones but equilibrium mixtures of tautomers. Their aminoimine tautomeric transformations follow the sequence 4,9-bis(alkylamino)-1,10-anthraquinones ? 9-alkylamino-4-(alkylimino)-10-hydroxy-1,4-dihydroanthracen-1-ones ? N ¹,N ¹⁰-dialkyl-4,9-dihydroxy-1,10-dihydroanthracene-1,10-diimines.     

Study of tautomeric transformations of 1,4,5,8-tetraaminoanthraquinone by electronic spectroscopy

Based on the example of 1,4,5,8-tetraamino-9,10-anthraquinone, a method is described for establishing the tautomeric compositions and sequences of tautomeric transformations that occur in known samples of quinones. An analysis of electronic absorption spectra shows that this substance is a dynamic equilibrium mixture of 4,5,8,9-tetraamino-1,10-anthraquinone and the imines tautomeric to it. The tautomeric compositions of different samples of matter differ and can contain 1,4,8-triamino-5-hydroxy-9,10-anthraquinone-10-imine, 4,8,9-triamino-10-hydroxy-1,5-anthraquinone-5-imine, 5,8-diamino-4,9-dihy-droxy-1,10-antraquinonediimine, and 8,10-diamino-5,9-dihydroxy-1,4-antraquinonediimine. Tautomeric equilibrium shifts can accompany not only chemical reactions but physical processes as well, so any investigation of the properties of substances without establishing their tautomeric compositions would be incorrect.     

Model‐independent structure and resonant X‐ray spectra of intermediate smectic phases

It is shown that the orientational structure of intermediate smectic phases can be determined using the symmetry properties of the general free energy with arbitrary orientational coupling between smectic layers, without addressing a particular model. The structure of three‐ and four‐layer intermediate phases, obtained in this way, corresponds to experimental data. The same method enables one to predict the structure of intermediate phases with periodicity of five and six layers, which have not been observed experimentally so far. The resonant X‐ray spectra of the five‐ and six‐layer intermediate phases with predicted structure have also been calculated. These spectra are characterized by a number of features which enable one to distinguish five‐layer and six‐layer intermediate phases from phases with smaller periods.