Photoluminescence of Tb<Superscript>3+</Superscript> ions in barium–strontium–calcium titanate xerogels

Terbium-doped films of barium–strontium–calcium titanate with the perovskite phase were fabricated using the sol-gel method. Photoluminescence of trivalent terbium ions with a strong band at 543 nm was observed at 4.2 and 300 K for films fabricated by spin-on deposition on porous anodic alumina and annealed at 500 and 750°C. The possibility of using sol-gel synthesis of perovskites to investigate spontaneous emission of terbium and other lanthanides in photonic crystals with a tunable photonic band gap is discussed.     

Algebraic study of chiral anomalies?

The algebraic structure of chiral anomalies ismade globally valid on non-trivial bundles by the introduction of a fixed background connection. Some of the techniques used in the study of the anomaly are improved or generalized, including a systematic way of generating towers of ??descent equations??.     

Study of glasses and glass ceramics in Bi2O3-GeO2-Fe2O3 and Bi2O3-GeO2-Cr2O3 systems by optical spectroscopy

The ferroelectric Bi₂GeO₅ crystalline phase is synthesized by heat treatment of 1Bi₂O₃-1GeO₂-xFe₂O₃ and 1Bi₂O₃-1GeO₂-yCr₂O₃ glasses. The obtained glass ceramics and initial glasses are studied using X-ray diffraction analysis and optical spectroscopy. The dielectric characteristics are measured, and the Curie temperature is determined. The effect of chromium and iron ions on the absorption spectra and dielectric properties of glasses and glass ceramics is determined.     

Dipole moment and mobility of molecules in nematic liquid crystals of the 4-n-butyl ester of [4′-n-hexyloxyphenyl] benzoic acid in the absence of external orienting fields

Dielectric polarization was studied in a nematic liquid crystal of the 4-n-butyl ester of [4′-n-hexyloxyphenyl] benzoic acid (BE[HOP]BA) in the absence of external orienting fields in the isotropic and mesophase states in a frequency range of 10³–10⁷ Hz. In the isotropic melt, three regions of dielectric absorption of a relaxation origin were revealed. It is shown that two of them are related to a reorientation motion of individual molecules about the longitudinal axes (process I) and about the short axes (process II). Processes I and II have relaxation times τ ～ 10^?9 and 10^?8 s and activation energies ΔU ～ 16 and 23 kcal/mol, respectively; the energy of activation of process II in the liquid-crystal phase increases to ΔU ～ 38 kcal/mol. In the isotropic melt, in addition to processes I and II, process III occurs in the low-frequency range, which is characterized by greater relaxation times τ ～ 10^?7 s and an activation energy ΔU ～ 28 kcal/mol. In order to establish the nature of process III, temperature dependences of the dipole moments and Kirkwood correlation factor g were studied in both BE[HOP]BA phases. The magnitude of the Kirkwood factor in the isotropic phase of the BE[HOP]BA near the transition temperature from the mesomorphic state (g ～ 0.88) indicates the retention of the orientational ordering of molecules of the low-molecular liquid crystal and the compensation of their dipole moments intrinsic to the liquid-crystal state. This circumstance suggests that the third process of the relaxation of dipole polarization is due to a cooperative mode of motion of molecules in mesophase nuclei in the isotropic melt.     

Determination of the Existence Region of a Griffith-Like Phase in Pr<Subscript>1–<Emphasis Type="Italic">x</Emphasis></Subscript>Sr<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>MnO<Subscript>3</Subscript>/YSZ Films

We have studied the temperature dependences of the magnetic susceptibility and the electron magnetic resonance in Pr_1–xSr _x MnO₃/YSZ polycrystalline films (x = 0.2, 0.4). The paramagnetic properties of samples indicate the presence of short-range-order ferromagnetic correlations above the phase transition temperature (T _c ). The existence region of such correlations has been considered using the Griffith theory.     

Generic Immersions of the Two-Sphere to R<Superscript>3</Superscript> and Their Skeletons

Let f:S ² ↬ R ³ be a generic smooth immersion. The skeleton of f is the following triple (Γ, D, p): Γ ⊂ R ³ is the 1-polyhedron of singular points of f, D = f⁻¹(Γ) ⊂ S ² is also a 1-polyhedron, and p : D → Γ, x ↦ f(x), is the projection. For triples of the form (D,Γ,p), where Γ has at most four vertices, we give an iff-condition under which the triple is the skeleton of a smooth immersion f : S ² ↬ R ³. Bibliography: 4 titles. __________ Translated from Zapiski Nauchnykh Seminarov POMI, Vol. 299, 2003, pp. 300–313.     

An attempt to create stable biomimetic sensors for express analysis of hydrogen peroxide in water solutions

The physico-chemical properties of a new type catalase sensor, the so-called biomimetic sensors, modulating some of the catalase biosensor functions were investigated. These sensors have technological advantages over their biological analogs because of properties usually attributed to chemical sensors. The developed electrochemical system lies between bio- and chemical sensors.     

Synthesis, crystalline and molecular structure of palladium(II) binuclear complex with cysteine

The new palladium(II) binuclear complex [Pd₂(μ-S-Cys)(μ-S-CysH)(dipy)₂](NO₃)₃ with bridging L-cysteine and L-cysteinate anion was synthesized and investigated by the methods of X-ray crystal analysis, IR spectroscopy, and elemental analysis.