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  • Visual pigment  (4)
  • 42.10  (3)
  • Springer  (7)
  • PANGAEA
  • 2020-2024
  • 2020-2023
  • 1975-1979  (7)
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  • 1979  (7)
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  • Springer  (7)
  • PANGAEA
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  • 2020-2024
  • 2020-2023
  • 1975-1979  (7)
  • 1965-1969
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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 18 (1979), S. 291-296 
    ISSN: 1432-0630
    Keywords: 02 ; 42.10 ; 41
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The connection of the natural resonances and the symmetry group of the cross-section of the diffracting-cylinders is established. As is done in spectroscopy, selection rules for the propagation directions of the diffracted field are deduced. Some remarks about the case of propagating modes along a dielectric rod are also made.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 18 (1979), S. 53-62 
    ISSN: 1432-0630
    Keywords: 42.82 ; 42.10 ; 42.80 ; 85.60
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The characteristics of slab waveguide tapers with finite-thickness cladding are investigated by approximating the tapered section as a series of uniform five-layer waveguides with successive changes in the core and cladding thickness. The behaviour of multimode coupling and transmission characteristics for typical tapers are studied in detail by computer simulation, employing parameter values appropriate for practical systems. Strong coupling and efficient conversion between core and cladding modes are demonstrated. In addition, it is shown that for tapers of moderate slopes, the nearest-neighbour coupling approximation is quite adequate for the calculation of the individual mode amplitudes. For steeper tapers, however, additional neighbouring modes have to be taken into account, and the modal energy tends to spread further towards the higher-order modes. It is also demonstrated that relatively large step-size can be used in the iterative numerical calculations. This, in conjunction with the choice of an appropriate coupling scheme (e.g., the nearest-neighbour approximation for mild tapers), makes it possible to reduce the cost of computer simulation. The relevance of the present analysis to fiber tapers is also discussed.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 20 (1979), S. 345-351 
    ISSN: 1432-0630
    Keywords: 42.10 ; 42.82
    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 short description of a rigorous electromagnetic theory based on the numerical integration of a differential system is given. It allows the study of the stop-bands of a corrugated waveguide. Dispersion curves in the first and the second-order stop-bands are computed for various periodic waveguides. A selection rule due to the symmetry of the corrugation is found. The reflection of a plane wave by the guide is examined. It is demonstrated that under peculiar circumstances, the reflection coefficient has a modulus equal to unity.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    European biophysics journal 5 (1979), S. 223-230 
    ISSN: 1432-1017
    Keywords: Prolonged depolarising after-potential (PDA) ; Visual pigment ; Invertebrate photoreceptor ; Manganese ; Calcium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract We have studied the effects on the PDA of modifying intracellular and extracellular concentrations of Ca2+ and Mn2+. The effect of decreased Ca2+ concentration or addition of EGTA is mainly an increase in the PDA amplitude and length. Raising Ca2+ concentration using ruthenium red or high external Ca2+ has the opposite effect. The effect of Mn2+ is much more striking: In the presence of 50–100 mM Mn2+ the PDA is initially greatly depressed but can rise slowly for up to 20 or 30 s (in the dark) until it approaches its original amplitude and time course. Bridge measurements showed that the depression of the PDA corresponds to a depressed conductance and so is not due to an increase in K+ conductance. The Mn2+ effect is potentiated by decreased Ca2+. Appropriate stimulation suppresses the rising PDA as promptly as it does a normal PDA, suggesting that if lateral diffusion is the source of the slow rise, the PDA and PDA-depressing processes must be spatially linked. The action of the anti-PDA is apparently prolonged by both Ca2+ and Mn2+.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    European biophysics journal 5 (1979), S. 231-235 
    ISSN: 1432-1017
    Keywords: Visual pigment ; Photoreceptor ; Metarhodopsin ; Adaptation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract We show that the effect of an adapting light on the sensitivity of barnacle photoreceptors depends on the direction of net pigment transfer [rhodopsin (R) to metarhodopsin (M) or reverse] occasioned by the adapting light. For stimuli giving no net pigment transfer the state of the pigment appears irrelevant, R → R having the same effect as M → M. With respect to these, R → M gives enhanced facilitation and M → R depressed facilitation. This suggests a correlation with the prolonged depolarising after-potential (PDA) and the anti-PDA, which follow R → M and M → R stimuli respectively. These effects appear mainly in less sensitive cells and for higher amounts of conditioning light — but still well within the physiological range and well below the threshold for PDA and anti-PDA induction. The special interest of these results is that they appear to be interpretable only by assuming that absorption of light by metarhodopsin exerts an effect on the stimulus coincident response (LRP), the first demonstration of such an effect.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    European biophysics journal 5 (1979), S. 249-253 
    ISSN: 1432-1017
    Keywords: Photoreceptor ; Visual pigment ; Transduction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract Several recent reports have shown that light absorption by metarhodopsin does not contribute to the excitation of invertebrate photoreceptors at low intensities. Where the pigment transition scheme is known, this result may be used to exclude some or most of the transitions and states of the pigment as sources of the coupling to excitation. The methodology of this approach is described and illustrated.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    European biophysics journal 5 (1979), S. 243-248 
    ISSN: 1432-1017
    Keywords: Visual pigment ; Diffusion ; Photoreceptor ; Membrane
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract Translational diffusion of pigment molecules in the disc membranes of amphibian rod outer segments is in the range of 10 Μ/10 s. Recently, Goldsmith and Wehner set an upper limit of 10 Μ/20 min to the diffusion in isolated formaldehyde-fixed rhabdoms of crayfish. We have now used the early receptor potential (ERP) to study the diffusion in intact, unfixed barnacle photoreceptors. The ERP from a cell fully adapted to blue light (most of the pigment in the rhodopsin state) was changed by 8–22% of its maximum change when the pigment in a 30 Μm spot was (almost) completely shifted to the metarhodopsin state by red laser adaptation. Further red illumination of the same spot 30 min later produced only a limited further change in the ERP (attributable to light scatter), showing that R had not migrated into the spot. It is concluded that the visual pigment diffuses by less than 30 Μ/30 min.
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