Integral Criterion of the Narrow-Bandedness of Radio-Engineering Signals

To estimate the signal narrow-bandedness in signal theory, we propose integral constraints instead of local ones. The examples presented demonstrate the advantages of this criterion.     

Dependences of the dielectric and pyroelectric properties of (1 ? x)PbFe1/2Nb1/2O3?xPbTiO3 ferroelectric ceramics solid solutions on the PbTiO3 content in a compositional range of 0 ≤ x ≤ 0.08

(1 − x)PbFe_1/2Nb_1/2O_3−x PbTiO₃ (PFN-xPT) ferroelectric ceramics with low dielectric loss and pronounced anomalies of dielectric and pyroelectric properties near the ferroelectric-ferroelectric phase transition was obtained by doping with lithium. The temperature dependence of the position of the morphotropic boundary between the rhombohedral (monoclinic) and tetragonal phases in the x-T phase diagram of the PFN-xPT system was determined for the first time.     

Deactivation of Iron-Gallium Oxide Catalyst for Ammonia Oxidation

An iron-gallium oxide catalyst (97.0 wt % Fe₂O₃, 3.0 wt % Ga₂O₃) was studied in high-temperature oxidation of ammonia. Reasons for the deactivation of the catalyst at elevated temperature were analyzed.     

Influence of the nature of the substituent in 3-(2-pyridyl)-1,2,4-triazole for complexation with Pd<Superscript>2+</Superscript>

The structure of four new palladium complexes [Pd(HL ² )Cl ₂ and Pd(L ^1–3 ) ₂ ] with 3-(2-pyridyl)-5-R-1,2,4-triazoles (R=H, CH₃, Ph respectively HL ¹ , HL ² , HL ³ ) was proposed based on IR, NMR, UV spectroscopy and MALDI mass spectrometry data analysis. It is found that the complexation of HL ² and HL ³ with Pd²⁺ ions results in a decrease of their fluorescence intensity and it is vice versa in case of HL ¹ . Furthermore, the influence of the substituent (R) in the 3-(2-pirydyl)-5-R-1,2,4-triazoles on the fluorescent and protolytic properties of HL ^1–3 was investigated.     

Structure,the lattice dynamic,and the dielectric characteristics of Sr<Subscript>0.5</Subscript>Ba<Subscript>0.5</Subscript>Nb<Subscript>2</Subscript>O<Subscript>6</Subscript> films

Solid solution Sr_0.5Ba_0.5Nb₂O₆ films have been synthesized on a (111)Pt/(001)Si substrate by rf deposition in an oxygen atmosphere. The depolarized Raman spectra, the structure, and the dielectric characteristics of the films have been studied over a wide temperature range. It is found that the films were singlephase, had the tetragonal tungsten bronze structure, and had a pronounced axial texture with axis 001 directed perpendicular to the substrate surface. It is shown that the film material undergoes a diffuse phase transition to the state of a relaxor ferroelectric in the temperature range 300–425 K. Possible reasons of the regularities observed are discussed.     

Phase separation in a poly(acrylic acid)-polycation system in acidic solutions

Phase separation in aqueous solutions of mixtures of poly(acrylic acid) with polycations [poly(diallyldimethylammonium chloride), poly(1,2-dimethyl-5-vinylpyridinium methylsulfate)] in the presence of decimolar hydrochloric acid has been studied by static and dynamic light scattering. The systems are characterized by the upper critical solution temperature. The temperature-dependent association of macromolecules is observed in the single-phase region. A decrease in temperature leads to phase separation; the composition of the diluted phase is determined by the temperature and composition of the initial mixture; and the composition of the concentrated phase remains almost invariable. The occurrence of association in the mixtures is probably the formation of interpolymer complex due to ion-dipole interactions between the carboxyl groups of poly(acrylic acid) and the functional groups of the polycation.     

Catalytic Properties of the System Fe2O3-Ga2O3 in Ammonia Oxidation

The catalytic properties of the system Fe₂O₃-Ga₂O₃ in high-temperature oxidation of ammoniaand the influence exerted by the phase composition of the system on the physicochemical, catalytic properties of the catalysts were studied.     

Influence of chain charge and complexation on the overlap and entanglements formation in poly(acrylic acid) salt-containing aqueous solutions

Dilute-semidilute regime crossover in aqueous solutions of partly neutralized poly(acrylic acid) and of its complex with tetradecyltrimethylammonium bromide was studied by light scattering and viscometry methods. The chain charge growth causes the decrease of overlap concentration (c*) and the increase of the entanglements formation concentration (ce), hence, the semidilute unentangled regime of solution expands. Complexation of the polyelectrolyte with an oppositely charged surfactant leads to c* increase and to ce decrease. It is shown that in semidilute entangled solutions the surfactant acts as an effective structuring agent because of the binding of polyelectrolyte chains via surfactant micelles.     

Solid Phase Luminescence and Thermal Transformations of Palladium(II) Complexes with 3-(2-Pyridyl)-1,2,4-Triazoles

Theoretical and Experimental Chemistry - The thermal behavior and luminescent properties of palladium(II) Pd(LR)2 complexes with 3-(2-pyridyl)-5-R-1,2,4-triazoles (LR , where R = H, Ph, Me) in...