Electrocaloric response of a ferroelectric capacitor to a periodic electric field

The electrocaloric response of a ferroelectric capacitor to a periodic electric field has been analyzed in terms of the nonstationary heat conduction equation. A linear physical model is considered for an electrocaloric element in which one end (x = 0) is thermally insulated and a constant temperature T ₀ is maintained at the boundary x = l. The effect of a periodic electric field on the capacitor gives rise to temperature oscillations about a decreasing average value that reaches saturation. A relatively simple analytic expression is derived for the temperature distribution along the electrocaloric element and the heat flux density under stationary conditions. The calculations are carried out using the results obtained from measurements performed for a PMN-PT relaxor ferroelectric in the temperature range of the phase transition. A temperature gradient and a heat flux of ～150 W/cm² are observed in an electric field of 2.4 V/μm at a frequency of 10 Hz.     

Effect of Gas Injection from the Surface of a Body on Its Interaction with a Temperature Inhomogeneity in a Supersonic Flow

The flow pattern in the shock layer and the aerodynamic characteristics of a hemisphere in unsteady axisymmetric interaction with a closed spherical hot-gas region embedded in the oncoming supersonic flow in the presence of intense injection of gas from the body surface into the shock layer are studied on the basis of the inviscid perfect gas model. Two cases are considered, namely, (1) when the radius of the permeable surface is greater than that of the temperature inhomogeneity and (2) when the injection is localized in the vicinity of the forward stagnation point and the permeable region is smaller the inhomogeneity.     

Variations in the electronic absorption spectra of phthalocyanine films on successive treatment with nitrogen dioxide and ammonia

The effect of alternating treatment of films of substituted metal phthaloeyanines with nitrogen dioxide and ammonia on their spectral properties is discussed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 236–239, January, 1996.     

X-ray diffraction structural and spectrochemical study of 1-p-anisyl-3-5,diphenylformazane

Conclusions X-ray diffraction structural data, a PPP quantum chemical calculation, and IR and UV spectral indices indicate that there is a six-membered chelate formazyl group with syn, s-cis configuration and strong intramolecular hydrogen bonding is characteristic for 1-p-anisyl-3,5-diphenylformazane. Spectroscopic criteria were established for this configuration of the formazane molecule.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2739–2745, December, 1987.     

Envelope Area and Electric Pulse Area Interference in Excitation of Quantum Systems by Few-Cycle Attosecond Light Pulses

JETP Letters - In this letter, excitation of discrete levels in a quantum system is considered, when the duration of the driving pulse is changed from multicycle to ultrashort half-cycle regime. It...     

Water Soluble Metallo-Phthalocyanines: The Role of the Functional Groups on the Spectral and Photophysical Properties

Strategies are reported that produce symmetrical metal-free and metallo-phthalocyanine dyes, Pc and MPc, respectively, containing various numbers of water solubilizing carboxylic acid groups on their periphery that provide a dual role by also serving as functional groups to covalently link primary amine-containing targets to these dyes. In order to induce water compatibility and to minimize the degree of aggregation, the periphery of the macrocycle was decorated with various numbers of water-solubilizing groups and/or altering the identity of the metal center. The influence of the number of solubilizing groups and metal center on the spectral and photophysical properties were evaluated. MPc dyes containing 4, 8, or 16 carboxylic acid groups exhibited similar absorption and emission maxima (677 and 686 nm, respectively) with the molar absorptivity of the Q-band ∼10⁵ M⁻¹ cm⁻¹. Results indicated that the fluorescence lifetimes and quantum yields varied as a function of the metal center; the degree of carboxylation did not significantly alter these properties in DMSO, but did mediate the solubility and aggregation states when placed in aqueous solvents. The water solubilizing groups could also serve as labeling moieties for targets bearing primary amines. Results showed that the conjugate, produced by covalently linking an MPc to streptavidin through one of its carboxylate groups, generated a red-shift in the emission maximum with a fluorescence lifetime shorter than that of the native MPc dye.     

Solid-phase synthesis of oxytocin and its analysis by high performance liquid chromatography

A mixture of peptides containing 30.4% of oxytocin has been obtained by the solid-phase method on the benzhydrylamine resin UR-95. A procedure is given for the quantitative determination of oxytocin in a mixture of peptides.All-Union Scientific-Research Institute of the Technology of Blood Substitutes and Hormone Preparations, Moscow. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 892–897, November–December, 1987.