Dynamic response of the somatic frog nerve under electrical pulsed excitation and processes of inactivation under local laser influence (λ=900 nm) was investigated ex vivo. The dependence of propagation speed of action potential from external laser power was discovered. The propagation speed of action potential was growing up in axons bunch of frog’s somatic nerve with increasing of laser power. More than 90% of axons were inactivated when the power of probing radiation was equal to 10W, and the propagation speed increased up to 50%. Strong fluctuation of propagation speed compound action potential and its amplitude was discovered in ensemble of neurons near threshold. Complex dynamic of compound action potential was discovered. Excitation threshold was growing up with increasing the power of laser radiation and only several neurons from ensemble were activated.
We have observed for the first time the dynamics of a speckle field generated in bulk scattering partly ordered media or low-mode optical fibers probed by a laser diode ( λ = 654 nm) and a compact diode-pumped YAG:Nd laser ( λ = 532 nm) in the regime of frequency tuning. The dynamic coherent speckle-photo-chromic effect can be observed provided that the deviation of the probing radiation frequency is comparable with or greater than the effective phase delay difference between modes in the optical fiber of between waves in the random scattering medium. Using the proposed photochromic speckle technique, it is possible to determine the intermode dispersion of fibers with a length on the order of one meter and the dispersion of phase delay in test fluoroplastic structures in the regimes of several fold scattering (for a sample thickness of 10-20 μm) or multiple scattering (for a thickness of up to ~ 2 cm).
Dynamic response of the somatic frog nerve on electrical pulsed excitation was investigated ex vivo. Strong fluctuation of consequence compound action potential in ensemble of neurons near-threshold was discovered. The nonlinear response of the Hodgkin-Huxley model neurons with external electrical pulsed was investigated and numeral results correlation with experiments. Complex dynamic of compound action potential was discovered when on-line time of stimulatory electrical pulses comparable with nerve refractory period. New techniques research nonlinear behavior using photodynamic reactions or UV-A radiation at somatic frog nerve was approved. This nonlinear dynamic regime was controlling laser induced inactivation of processes in membrane of nerve.
The dynamics of actively mode-locked laser is investigated and the results of numerical simulations are presented. Different regimes corresponding to the relaxation oscillations and spiking are observed depending on the noise level and frequency detuning. The numerical results demonstrate in detail the processes of destroying synchronization and pulse-train instabilities.
The scenario of the transition from a stationary state to the regime of generation of optical dynamic chaos is studied, which appears in He-He laser with delayed feedback. The coefficient of feedback is proportional to the output laser power and the changes of the discharge current. Depending on the coefficient of the signal of feedback subharmonic we observed the cascade of bifurcations of doubling period, the inverse cascade, the cycles with period f/3 and f/5, and the regime of dynamic chaos whose spectrum has no resonance frequencies. The range of existence of the observed regimes depended greatly on the degree of nonlinearly of the watt- ampere energy characteristics, defined by the processes of saturation of inversion of population and the controlled pressure of gas in the active element. Optical chaos in such non-linear systems appears, when the delay is greater than the life times of the metastable states of helium and neon that determine the internal dynamics of the laser. These results can be used for creation of optical generators of amplitude and frequency noise and information security systems.
Special features of speckle-modulated laser fields arising at in vitro measurements of different types of human cataractous lenses have been investigated experimentally. Computer analysis of digital images has allowed for estimation of destruction of the spatial coherence of a laser beam scattered by a turbid lens. Applied speckle-technologies have permitted the range of retinal angular resolution to be estimated with the help of laser retinometer at the stage of preoperative cataract diagnosis. An extent of laser retinometry at measuring visual acu9ity in patients with any type of cataract, and an incorrectness of its estimation by means of opto types charts have been set up.
Measurement of retinal visual acuity (RVA) in 170 patient with different types of cataract (senile, complicated, posterior capsular ) before and after cataract extraction and also in vitro measurement of RVA with extracted cataractal lenses has shown that laser retinometer can be used for evaluating visual acuity within 0.3 - 1, practically for all types of cataract. Experimental in vitro studies of speckle-modulated laser field arising after transmission through different type of human cataractous lenses are presented. Computer analysis of digital imaging has allowed us to determine the degree of destruction of spatial coherence of scattered laser beam and the angle of resolution of retina using Retinal Analyzer of Vision (AROLI) in diagnosis of cataract. Approbation of topographic digital videosystem used for determing the extent of opacities in cataractous lenses in vivo and its use in measuring diapasons RVA for different type of cataracts is presented. The system consists of the modified slit lamp, CCD camera ( ELECTRIM) and PC PENTIUM with corresponding software.
We report the results concerning the regimes of transition to the temporal chaos in an optical system with the feedback based on the single-mode frequency-stabilized laser.
Experimental in vitro studies of speckle-modulated laser field arising after transmission through different type of human cataractous lenses are presented. Computer analysis of digital imaging has allowed to determinate the degree of destruction of spatial coherence scattered laser beam and the angle of resolution of the retina using Retinal Analyzer of Vision (AROL-1) in diagnosis of cataract. Measurement of retinal visual acuity (RVA) in 135 patient with different types of cataract (senile, complicated, posterior capsular) before and after cataract extraction and also in vitro measurement of RVA with extracted cataractal lenses has shown that laser retinometer can be used for evaluating visual acuity within 0.3 - 1, practically for all types of cataracts.
Experimental in vitro studies of speckle-modulated laser field arising after transmission through different type of human cataracties lenses are presented. Computer analysis of digital imaging has allowed to determinate the degree of destruction of spatial coherence scattered laser beam and the angle of resolution of the retina using Retinal Analyzer of Vision in diagnosis of cataract. Comparison with clinical investigation in vivo has been made.
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