Meyer–Neldel energy in Se-based binary and ternary chalcogenide glasses

This paper investigates the cluster-modified function projective synchronisation (CMFPS) of a generalised linearly coupled network with asymmetric coupling and nonidentical dynamical nodes. A novel synchronisation scheme is proposed to achieve CMFPS in community networks. We use adaptive control method to derive CMFPS criteria based on Lyapunov stability theory. Each cluster of networks is synchronised with target system by state transformation with scaling function matrix. Numerical simulation results are presented finally to illustrate the effectiveness of this method.     

Control of nonlinear systems exhibiting chaos to desired periodic or quasi-periodic motions

Nonlinear Dynamics - A novel method in the design of controllers to drive general nonlinear systems to desired periodic or quasi-periodic motions is presented in this paper. The viability of the...     

Dielectric and thermoelastic properties of alkaline-earth fluoride crystals

Summary An extended three-body force shell model is developed and used to make an analysis of the volume dependence of low- and high-frequency dielectric constants and thermoelastic Grüneisen parameters for CaF₂, SrF₂, BaF₂ and PbF₂ crystals. Lorentz-Lorenz and Clausius-Mossotti relations are modified in view of three-body interactions (TBI). Calculated results yield better agreement with the experimental data as compared to those obtained by previous investigators.

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Riassunto Si sviluppa un modello esteso a strati della forza a tre corpi e se ne fa uso per un'analisi della dipendenza dal volume delle costanti dielettriche a bassa e alta frequenza e dei parametri termoelastici di Grüneisen per cristalli di CaF₂, SrF₂, BaF₂ e PbF₂. Si modificano le relazioni di Lorentz-Lorenz e di Clausius-Mossotti in vista delle interazioni a tre corpi (TBI). I risultati calcolati sono in migliore accordo con i dati sperimentali di quelli ottenuti da precedenti studi.

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Резюме Предлагается оболочечная модель для протяженной трех-частичной силы. эта модель используется для анализа обьемной зависимости при низких и высоких частотах диэлектрических постоянных и термо-упругих параметров Грюнайзена для кристаллов CaF₂, SrF₂, BaF₂ и PbF₂. Для трех-частичных взаимодействий модифицируются соотношения Лоренц-Лоренца и Клаузиуса-Москотти. Вычисленные результаты дают лучшее согласие с экспериментальными данными, чем результаты других авторов.

     

Electrical properties of glassy AsxGe10Te90−x alloys

This paper analyses the electrical properties of glassy alloys of As_xGe₁₀Te_90?x, while reporting the conductivity and dielectric constant of As₅Ge₁₀Te₈₅ and As₁₅Ge₁₀Te₇₅ compositions in the temperature range 77–383 K and the frequency range from dc to 5 MHz. The dc conductivity has been shown to be of the form

The ratio σ₀₁/σ₀₂ is of the order of 10⁶. ΔE₁, the higher temperature activation energy, is dependent on the composition, while ΔE₂, the lower temperature activation energy, is less dependent on the composition. The dielectric constant has been found to be independent of temperature and frequency up to about 253 K. However, at higher temperatures, it becomes activated and proportional to log ω.Some common features of As_xGe₁₀Te_90?x are a kink in dc conductivity, a ω^0.8 relationship for ac conductivity, no evidence of variable-range hopping at low temperatures, field-dependent conductivity and memory switching. The data can be interpreted in terms of the dangling-bond theory of Mott and his collaborators. A high density of states of the order of 10²⁰eV^?1 cm^?3 near the Fermi level may be expected.     

Electrochemical oxidation of 2-thiouracil at pyrolytic graphite electrode

2-Thiouracil has been studied in phosphate buffers of pH 1.95-11.08 using linear and cyclic sweep voltammetry, coulometry, controlled potential electrolysis and spectral studies. One well-defined oxidation peak I(a) in the pH range 1.95-11.08 was noticed. The number of electrons involved in peak I(a) was found to be four in a thin layer cell whereas under exhaustive electrolysis condition oxidation was found to involve six electrons. A reduction peak II(c) (2e, 2H(+)) is noticed in the reverse sweep. Spectral studies during oxidation were carried out at different pH. Kinetic studies indicated that the decay of the UV-absorbing intermediate is a first order reaction. The products of the electrooxidation have been characterized and a tentative EC mechanism has been suggested for the oxidation of 2-thiouracil.     

Cellulase lessons revealed through the microbe's perspective

Applied Biochemistry and Biotechnology - Cellulose, the world's most abundant organic material, is central to the world's ecosystem. This energy resource is mobilized and recycled by...     

PHOTOSENSITIZED LYSIS OF LIPOSOMES BY HEMATOPORPHYRIN DERIVATIVE

The spectral properties and efficiency for photosensitizing the lysis of phosphatidylcholine liposomes have been measured for the components of hematoporphyrin derivative (Hpd) after alkaline hydrolysis and fractionation by polyacrylamidc gel chromatography. Two major and two minor Hpd fractions have been identified whose spectral properties correlate with the anoxic sensitizing efficiency and the oxygen enhancement ratio (OER). The fastest moving fraction, which is the putative biologically active component, comprised one-third of the starting material and had OER = 2.7. Liposome lysis by this fraction was inhibited in the presence of human serum albumin at concentration ratios comparable to those employed for photoradiation therapy. The present results show that Hpd can act as an oxic and anoxic photosensitizer of a model biomembrane and suggest that separation from serum proteins is required for in vivo photosensitization.