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131.
S. V. Baykov L. V. Babin A. M. Molotilov S. I. Neiman V. V. Riman V. D. Svet A. I. Selyanin 《Acoustical Physics》2003,49(4):389-395
Experimental results of the ultrasonic imaging of brain structures through thick skull bones are presented. The model imaging system and the ultrasonic images of blood vessel models and images obtained in vivo for some brain structures are described. 相似文献
132.
133.
The phenomenon of stochastic resonance (SR) is investigated for chaotic systems perturbed by white noise and a harmonic force. The bistable discrete map and the Lorenz system are considered as models. It is shown that SR in chaotic systems can be realized via both parameter variation (in the absence of noise) and by variation of the noise intensity with fixed values of the other parameters. 相似文献
134.
We study statistical properties, response dynamics, and information transmission in a Hodgkin-Huxley–type neuron system, modeling
peripheral electroreceptors in paddlefish. In addition to sodium and potassium currents, the neuron model includes fast calcium
and slow afterhyperpolarization (AHP) potassium currents. The synaptic transmission from sensory epithelium is modeled by
a Poission process with a rate modulated by narrow-band noise, mimicking stochastic epithelial oscillations observed experimentally.
We study how the interplay of parameters of AHP current and synaptic noise affects the statistics of spontaneous dynamics
and response properties of the system. In particular, we confirm predictions made earlier with perfect integrate and fire
and phase neuron models that epithelial oscillations enhance stimulus–response coherence and thus information transmission
in electroreceptor system. In addition, we consider a strong stimulus regime and show that coherent epithelial oscillations
may reduce variability of electroreceptor responses to time-varying stimuli. 相似文献
135.
A. Ya. Neiman E. V. Kartseva N. N. Pestereva L. M. Fedorova 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2011,85(11):1885-1890
The effect of oxygen’s activity on the rate of In2(WO4)3 and In6WO12 formation reactions was studied to determine the reaction mass transfer mechanism. It was established that the formation of In2(WO4)3 in a model reaction cell is due to the transfer of WO 4 2? components and electrons moving in opposite directions through the reaction product. The relation between the diffusion coefficients of the carriers was found. The rate of electron diffusion and the reaction rate were shown to vary according to the law \(K_p \approx D_{\lim } = D_e \sim a_{O_2 }^{ - 1/4} \). We conclude that the formation of electronic conductor In6WO12 is a two-region process: at the In2(WO4)3 | In6WO12 interface, the product is formed on the In2(WO4)3 surface due to {WO3} escaping toward In2O3, and at the In6WO12 | In2O3 interface, the product is formed on the In2O3 surface via the reaction of diffuse {WO3} with In2O3. The probable relationship between the diffusion coefficients of the In6WO12 components was obtained. A relation was developed for the process rate. The diffusion coefficients for the limiting component were calculated using the data on the estimated thickness of the product layers. 相似文献
136.
Coherence and information theoretic analyses were applied to quantitate the response properties and the encoding of time-varying stimuli in paddlefish electroreceptors (ERs), studied in vivo. External electrical stimuli were Gaussian noise waveforms of varied frequency band and strength, including naturalistic waveforms derived from zooplankton prey. Our coherence analyses elucidated the role of internal oscillations and transduction processes in shaping the 0.5-20 Hz best frequency tuning of these electroreceptors, to match the electrical signals emitted by zooplankton prey. Stimulus-response coherence fell off above approximately 20 Hz, apparently due to intrinsic limits of transduction, but was detectable up to 40-50 Hz. Aligned with this upper fall off was a narrow band of intense internal noise at ~25 Hz, due to prominent membrane potential oscillations in cells of sensory epithelia, which caused a narrow deadband of external insensitivity. Using coherence analysis, we showed that more than 76% of naturalistic stimuli of weak strength, ~1 μV∕cm, was linearly encoded into an afferent spike train, which transmitted information at a rate of ~30 bits∕s. Stimulus transfer to afferent spike timing became essentially nonlinear as the stimulus strength was increased to induce bursting firing. Strong stimuli, as from nearby zooplankton prey, acted to synchronize the bursting responses of afferents, including across populations of electroreceptors, providing a plausible mechanism for reliable information transfer to higher-order neurons through noisy synapses. 相似文献
137.
N. A. Kochetova I. E. Animitsa A. Ya. Neiman 《Russian Journal of Electrochemistry》2010,46(2):168-174
Conductivity of the Sr6 − 2x
Ta2 + 2x
O11 + 3x
(0 ≤ x ≤ 0.33) solid solutions with the cryolite structure was studied in the atmosphere with a high content of water vapors under
temperature and oxygen activity variation in the gas phase. Appearance of the protonic conductivity component was proved at
the temperatures below 700°C. It was found that protonic conductivity increases at a decrease in parameter x in the composition series, which is due to an increase of both the concentration of protonic defects formed in the structure
and of their mobility. In the case of compositions with x < 0.15 at the temperatures below 550°C, the protonic transport becomes predominant. 相似文献
138.
Substitution of Ca by La in initial cubic double perovskite Ba4(Ca2Nb2)O11[VO]1 allowed obtaining phases with a similar structure with a lower content of structural oxygen vacancies, Ba4(La x Ca2 ? x Nb2)O11 + 0.5x [VO]1 ? 0.5x (x = 0.5, 1, 1.5, 2). The impedance technique was used to measure the temperature dependences of conductivity in the atmosphere of dry and humid air. Transport numbers determined using the EMF method in an oxygen-air and water steam concentration cells point to the predominantly hole nature of conductivity in the high-temperature region (T > 600°C) and to predominance of proton conductivity in the low-temperature region. Activation energies of hole and proton conductivity were calculated. Thermogravimetric measurements were carried out under heating from 25 to 1000°C with simultaneous mass-spectrometric determination of evolved H2O and CO2. The properties of the studied Ba4(La x Ca2 ? x Nb2)O11 + 0.5x (x = 0.5, 1, 1.5, 2) phases were compared with the earlier studied Ba4 ? x La x (Ca2Nb2)O11 + 0.5x phases with similar lanthanum content. 相似文献
139.
介绍了以铽(Tb)激活的高密度发光玻璃和光导纤维发光玻璃的特性。它应用在X射线实时成像系统中,可大大改善空间分辨能力。用它做的转换屏比一般晶粒状荧光物质做的厚得多,特别适合用于高能X射线实时成像系统 相似文献