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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of comparative physiology 176 (1995), S. 473-477 
    ISSN: 1432-1351
    Keywords: Circadian rhythms ; Locomotor activity ; Melatonin ; Entrainment ; Newt Cynops pyrrhogaster
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract We examined whether melatonin can act as a synchronizing agent within the circadian system of amphibians by testing the ability of melatonin injections to entrain the circadian locomotor activity rhythm of a newt (Cynops pyrrhogaster). Under constant darkness, all newts (13 cases) showing the free-running rhythms were subcutaneously injected with 10 μg melatonin at the same time every other day for at least 30 days. Subsequently, they were injected with vehicle (1% ethanolic saline) instead of melatonin for at least another 30 days. In 10 of the 13 newts, the locomotor activity rhythms could be entrained to a period of 24 h by melatonin injections but not by vehicle injections. During the entrained steady-state, the active phase of an activity-rest cycle preceded the time of melatonin injections as previously reported in other diurnal species. These results suggest that the endogenous circadian rhythm of melatonin concentration may be involved in synchronizing circadian oscillator(s) within the newt's circadian system.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of comparative physiology 172 (1993), S. 683-691 
    ISSN: 1432-1351
    Keywords: Pinealectomy ; Blinding ; Circadian rhythm ; Locomotor activity ; Newt
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract We examined the effects of pinealectomy and blinding (bilateral ocular enucleation) on the circadian locomotor activity rhythm in the Japanese newt, Cynops pyrrhogaster. The pinealectomized newts were entrained to a light-dark cycle of 12 h light and 12 h darkness. After transfer to constant darkness they showed residual rhythmicity for at least several days which was gradually disrupted in prolonged constant darkness. Blinded newts were also entrained to a 12 h light/12 h dark cycle. In subsequent constant darkness they showed free-running rhythms of locomotor activity. However, the freerunning periods noticeably increased compared with those observed in the previous period of constant darkness before blinding. In blinded newts entrained to the light/dark cycle the activity rhythms were gradually disrupted after pinealectomy even in the presence of the light/dark cycle. These results suggest that both the pineal and the eyes are involved in the newt's circadian system, and also suggest that the pineal of the newt acts as an extraretinal photoreceptor which mediates the entrainment of the locomotor activity rhythm.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-0630
    Keywords: 72.20.Ht ; 72.20JV ; 05.45+b
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Bifurcation routes to chaos in a periodically driven current filament have been studied by computer simulations. By an impact ionization model, theS-shaped currentvoltage curve is perturbed by the dc+ac bias ofE 0+E acsin(27πf 0t). The bifurcation maps are described as a function ofE 0. In the prebreakdown region, the fractal basin boundary, the crisis and the intermittency are discussed, based on the general considerations of the carrier dynamics on the catastrophe manifold. The intermittent burst of the current filament is explained by the destabilization of the weak turbulence generated in the lower branch. In the diffusion-reaction model, the spatio-temporal mode patterns of the transverse carrier profile have revealed the competitive evolution of the hyper-freezing and the firing.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 48 (1989), S. 111-125 
    ISSN: 1432-0630
    Keywords: 72.20Ht ; 72.20JV ; 05.45+b
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract A review is given of the nonlinear response and chaos induced by impact ionization of neutral shallow donors, observed in n-GaAs. Two kinds of the observation are described; (i) firing wave instability, and (ii) periodically driven current filament. For the firing wave instability, several important aspects are discussed including the selective excitation of the current filaments and the deterministic nature of the firing density wave. The nonlinear response of a periodically driven current filament has been investigated by applying a dc+ac bias of the form ofV dc+V ac sin(2πf 0 t), wheref 0∼1 MHz. The carrier dynamics and the bifurcation routes to chaos are discussed in terms of the observed phase diagram and the bifurcation map. The deterministic nature of the strange attractors are described in detail in terms of the correlation dimension and the Kolmogorov entropy.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1435-1536
    Keywords: Bovine serum albumin ; Heat denaturation ; Fatty acid ; SH/S-S exchange reaction ; Resistant to denaturation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The solution of bovine serum albumin, incubated at pH 9 (0.1 M Tris-EDTA-boric acid buffer in which 0.15 M KCl was contained) and 65 °C for 60 min, gave zones of undenatured monomer (component 1) and aggregates in the pattern of gel electrophoresis. The component 1, isolated from this solution, contained more fatty acids than the original albumin and than the mixture of aggregates. The aggregates contained substantially no fatty acids. This means that fatty acids are released, when the bovine albumin is denatured accompanying with intra- and intermolecular SH/S-S exchange reactions. Taking palmitic acid as a representative of the long chain fatty acid, a model experiment was performed. The bovine albumin, to which 6 palmitic acids were bound, did not cause the SH/S-S exchange reaction and was not denatured on incubation at pH 9 (0.1 M Tris-EDTA-boric acid buffer) and 65 °C. When the solution of “crystalline bovine albumin” (AF0.9, A: albumin, F: long chain fatty acid) was incubated at pH 9 (0.1 M Tris-EDTA-boric acid buffer) and 65 °C, 20% of the albumin was not denatured even after prolonged incubation. Further, when the component 1 (AF3.8), isolated from pre-incubated albumin solution, was incubated again at pH 9 and 65 °C, 58% of the albumin was not denatured even after sufficient time of incubation. Quantitative analysis reveals that the bovine albumin containing 6 fatty acids (AF6) is not denatured at all, and is the entity of the albumin resistant to heat.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1435-1536
    Keywords: Bovine serum albumin ; Heat denaturation ; Isoelectric focusing ; Hydrogen ion titration curve ; Circular dichroism ; Fluorescence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract When the solution of bovine serum albumin at pH 9 is incubated at 65 °C, new components 1' (modified monomer), 2 (dimer) and 3 (probably trimer) are formed. The isoelectric focusing indicated that the isoelectric points of components 1', 2 and 3 were pH 5.9. The hydrogen ion titration curve for the native albumin had well known abnormal steepness at pH near 4, but that for component 1' had no abnormal steepness. The titration curve for component 1' located right side of that for the native albumin. Circular dichroism measurements indicated that some unfolding occurred, when the native albumin was changed to component 1'. The contents ofα-helix were 74 and 52 % for the native albumin and for component 1', respectively. The contents of β-structure were 19 and 23 % for the native albumin and for component 1', respectively. The wavelength of maximum intensity of tryptophan fluorescence shifted to lower wavelength, when the native albumin was changed to component 1'. This suggests that tryptophan residue(s) is transferred to a more hydrophobic environment. The hydrogen ion titration curves, circular dichroism and fluorescence measurements, all supported the possibility that the component 2 is formed by the dimerization of component 1'. Further, it has been found that component 2' (dimer impurity in commercial bovine serum albumin preparations) is formed by the direct dimerization of native bovine serum albumin without conformational change.
    Type of Medium: Electronic Resource
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