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Relaxation Kinetics (relaxation + kinetics)

Distribution by Scientific Domains

Physics and Astronomy	50%

Selected Abstracts

Relaxation kinetics in thiophene/3-alkylthiophene random copolymers

POLYMER INTERNATIONAL, Issue 11 2004
Aleksandra Buzarovska
Abstract The relaxation kinetics of several thiophene/3-alkylthiophene (3-methylthiophene and 3-octylthiophene) random copolymers have been investigated using the cyclic voltammetric method. The first voltammograms, obtained after the polymer films were maintained at potentials corresponding to their neutral state for various periods of time, have been analyzed according to the procedure developed by Odin et al. Considerable suppression of the relaxation kinetics was achieved in copolymers containing thiophene rings substituted with longer alkyl groups (octyl). Copyright © 2004 Society of Chemical Industry [source]

Limitations of relaxation kinetics on muscular work

ACTA PHYSIOLOGICA, Issue 2 2010
J. McDaniel
Abstract Aim:, Positive net work produced during cyclic contractions is partially limited by relaxation kinetics, which to date, have not been directly investigated. Therefore, the purpose of this investigation was to determine the influence of relaxation kinetics on cyclic work. Methods:, Soleus muscles of four cats were isolated and subjected to a series of work loops (0.5, 1, 1.5 and 2 Hz cycle frequencies) during which stimulation terminated prior to the end of the shortening phase to allow for complete muscle relaxation and matched discrete sinusoidal shortening contractions during which stimulation remained on until the completion of the shortening phase. Muscle length changes during these protocols were centred on optimum length and were performed across muscle lengths that represented walking gait. Results:, When muscle excursions were centred on Lo relaxation kinetics decreased muscular work by 2.8 ± 0.8%, 12.1 ± 4.1%, 27.9 ± 4.5% and 40.1 ± 5.9% for 0.5, 1, 1.5 and 2 Hz respectively. However, relaxation kinetics did not influence muscular work when muscle excursions represented walking gait. In addition, muscular work produced at muscle lengths associated with walking gait was less than the work produced across Lo (55.7 ± 20.0%, 53.5 ± 21.0%, and 50.1 ± 22.0% for 0.5, 1 and 1.5 Hz respectively). Conclusion:, These results imply that relaxation kinetics are an important factor that limit the ability of muscle to produce work; however, the influence of relaxation kinetics on physiological function may depend on the relation between the optimum length and natural excursion of a muscle. [source]

Stochastic and Relaxation Processes in Argon by Measurements of Dynamic Breakdown Voltages

CONTRIBUTIONS TO PLASMA PHYSICS, Issue 7 2005
V. Lj.
Abstract Statistically based measurements of breakdown voltages Ub and breakdown delay times td and their variations in transient regimes of establishment and relaxation of discharges are a convenient method to study stochastic processes of electrical breakdown of gases, as well as relaxation kinetics in afterglow. In this paper the measurements and statistical analysis of the dynamic breakdown voltages Ub for linearly rising (ramp) pulses in argon at 1.33 mbar and the rates of voltage rise k up to 800 V s,1 are presented. It was found that electrical breakdowns by linearly rising (ramp) pulses is an inhomogeneous Poisson process caused by primary and secondary ionization coefficients , , , and electron yield Y variations on the voltage (time). The experimental breakdown voltage distributions were fitted by theoretical distributions by applying approximate analytical and numerical models. The afterglow kinetics in argon was studied based on the dependence of the initial electron yield on the relaxation time Y0 (, ) derived from fitting of distributions. The space charge decay was explained by the surface recombination of nitrogen atoms present as impurities. The afterglow kinetics and the surface recombination coefficients on the gas tube and cathode were determined from a gas-phase model. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Excitation relaxation in copper selenide nanowires

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 5 2009
Gediminas Ju
Abstract Ultrafast nonequilibrium charge carrier relaxation in highly ordered Cu2,xSe nanowires of 8 nm, 13 nm and 25 nm diameter was investigated by means of femtosecond pump,probe absorption spectroscopy. Transient absorption bleaching was observed in the region of the near infrared absorption band, whereas an induced absorption dominated at higher energies. The transient absorption kinetics is almost independent of the excitation and probe wavelength and shows a biexpoenetial charge carrier recombination with the excitation intensity dependent decay rates. The initial ultrafast relaxation, which gets slower at higher excitation intensities, is followed by the slower decay component emerging at high intensities. These relaxation peculiarities are discussed in terms of recombination enhancement by intragap states, and relaxation kinetics is described by a theoretical model of two concurrent relaxation channels involving deep and shallow impurity levels. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Exciton Aharonov,Bohm effect and emission kinetics in nanorings

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 14 2006
M. Grochol
Abstract The Aharonov,Bohm effect of excitons and their relaxation kinetics are investigated within the model of semiconductor nanorings of zero width. The kinetic equations where calculated deformation potential matrix elements for an acoustic phonon scattering are used as an input are solved for the steady state. Photoluminescence quenching is observed for stronger magnetic fields when electron and hole are spatially separated. The non-radiative decay plays a decisive role. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Ionic and electronic processes in non-linear optical crystals

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 1 2005
Igor N. Ogorodnikov
Abstract The paper presents the results of a study of the formation and decay of lattice defects in nonlinear optical crystals of NH4H2PO4 (ADP), KH2PO4 (KDP), Li2B4O7 (LTB) and LiB3O5 (LBO) with a sublattice of mobile hydrogen (ADP, KDP) and lithium (LTB, LBO) cations. By means of the luminescent and absorption optical spectroscopy with (the) a nanosecond time resolution under excitation with an electron beam, it was revealed that the optical absorption of these crystals in the visible and UV spectral ranges is produced by optical hole-transitions from the local defect level to the valence band states. The valence band density of the states determines the optical absorption spectral profile, and the relaxation kinetics is rated by the interdefect radiationless tunnel recombination between the trapped hole center and the H0 and Li0 electron trapped centers. At 290 K, the H0 and Li0 centers are subject to thermally stimulated migration. All manifestations of a radiative recombination observed in these crystals are accounted for by the involvement of additional electronic and hole centers of a different nature in the recombination process. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]