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Kuni H Iwasa - One of the best experts on this subject based on the ideXlab platform.
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effect of the cochlear microphonic on the Limiting Frequency of the mammalian ear
Journal of the Acoustical Society of America, 2008Co-Authors: Kuni H Iwasa, Bora SulAbstract:Electromotility is a basis for cochlear amplifier, which controls the sensitivity of the mammalian ear and contributes to its Frequency selectivity. Because it is driven by the receptor potential, its Frequency characteristics are determined by the low-pass RC filter intrinsic to the cell, which has a corner Frequency about 1∕10th of the operating Frequency. This filter significantly decreases the efficiency of electromotility as an amplifier. The present paper examines a proposal that the cochlear microphonic, the voltage drop across the extracellular medium by the receptor current, contributes to overcome this problem. It is found that this effect can improve Frequency dependence. However, this effect alone is too small to enhance the effectiveness of electromotility beyond 10kHz in the mammalian ear.
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Limiting Frequency of the cochlear amplifier based on electromotility of outer hair cells
Biophysical Journal, 2003Co-Authors: Mark Ospeck, Xiaoxia Dong, Kuni H IwasaAbstract:Outer hair cells are the critical element for the sensitivity and sharpness of Frequency selectivity of the ear. It is believed that fast motility (electromotility) of these cells is essential for this function. Indeed, force produced by outer hair cells follows their membrane potential very closely at least up to 60 kHz. However, it has been pointed out that the cell's receptor potential is attenuated by a low-pass RC circuit inherent to these cells, with the RC roll-off frequencies significantly lower than their operating frequencies. This would render electromotility ineffective in producing force. To address this issue, we assume that multiple degrees of freedom and vibrational modes due to the complex structure of the organ of Corti provide optimal phases for outer hair cells' force to cancel viscous drag. Our derived Frequency limit depends on the drag-capacitance product, not directly on the RC time constant. With a reasonable assumption for the viscous drag, the estimated limit is 10-13 kHz, exceeding the RC corner Frequency. Our analysis shows that a fast-activating potassium current can substantially extend the Frequency limit by counteracting the capacitive current.
Michael Emmett Brady - One of the best experts on this subject based on the ideXlab platform.
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How J M Keynes's Logical Theory of Probability Totally Refutes All Attacks on the Concept of Probability
Social Science Research Network, 2017Co-Authors: Michael Emmett BradyAbstract:J Derbyshire has recently repeated G L S Shackle’s original attack on the concept of probability in a number of recent articles. He adds nothing new to Shackle’s arguments of forty to eighty years ago that were completely refuted in 1959 by R. Weckstein, who based his refutation of Shackle on a relatively limited understanding of chapters 1-3 and 6 of Keynes’s A Treatise on Probability (1921). Shackle never replied to Weckstein’s repeated demonstrations in 1959 that Keynes’s approach refuted his arguments, which held only against the Limiting Frequency, relative Frequency, propensity and subjective interpretations of probability. Shackle’s arguments failed completely when confronted with Keynes’s theory of logical probability. J M Keynes’s theory of probability is a logical, objective, epistemological approach that is based on partial ordering and not complete orderings. This results in non additive, non linear interval valued probabilities, specified and operationalized in terms of logical propositions about any kind of event. It can easily deal with unique events, single events, crucial events, infrequent events, frequent events, non repeatable events, irreversible events, path dependence, sensitivity to initial conditions, emergence, complex causation, attractor states, partial uncertainty, complete and total uncertainty, fundamental uncertainty, irreducible uncertainty, by means of Keynes’s weight of the evidence analysis, which, when combined with his interval valued probability, can demonstrate that Shackle’s theory is a very special theory that applies only to situations of complete and total uncertainty, which Keynes categorized as ignorance. There is not a single one of Derbyshire’s objections to the concept of probability left standing if Keynes’s logical approach to probability is used.
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adam smith s theory of probability and the roles of risk and uncertainty in economic decision making
2013Co-Authors: Michael Emmett BradyAbstract:Adam Smith rejected the use of the mathematical laws of the calculus of probabilities because the basic information-data-knowledge provided in the real world of decision making did not allow a decision maker to specify precise, definite, exact, numerical probabilities or discover the probability distributions. This means that Smith rejected the classical interpretation of probability of La Place and the Bernoulli brothers, the Limiting Frequency-relative Frequency interpretation of probability, and the personalist, subjectivist, psychological Bayesian approach used by all neoclassical schools of thought because all of these approaches to probability claim that ALL probabilities can be represented by a single numeral between 0 and 1 and the decision maker knows the probability distributions. Smith, like Keynes, rejects this immediately. Thus, Smith’s inductive or logical concept of probability, like Keynes’s, only approaches mathematical probability in the limit. Adam Smith recognized that economic decision makers were confronted with knowledge structures that were not sharp and clear, but cloudy and amorphous. However, decision makers were still able to use the concept of probability in the weaker, interval sense of the concept of probability that was first thought to have been advocated by George Boole and later, with much greater force, by John Maynard Keynes in his two Fellowship dissertations, submitted in 1907 and 1908, respectively, and his A Treatise on Probability (1921). Instead of sharp, definite, determinate, calculated, and exact probabilistic estimates or distributions, inexact, indefinite, indeterminate, and imprecise estimates of probabilities could be derived and used so that decision makers were able to make choices among different possible options that concerned the future in a rational fashion. An important conclusion of this paper is that it was Adam Smith who first explicitly recognized that the mathematical concept of probability is not applicable, in general, in real world decision making. Smith also rejects the normative and prescriptive roles of mathematical probability in decision making. Adam Smith applied his approach to probability and uncertainty by analyzing the economic decisions made by human beings in choosing a particular profession and organizing various insurance markets to cover the risk of loss. Smith’s risk is however, not the standard deviation of the Normal probability distribution used by "Modern" economists, since important data/information/knowledge is missing and not available to the decision maker at the point in time that he is required to make a decision.
Helmut O. Rucker - One of the best experts on this subject based on the ideXlab platform.
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Thirty-Element Active Antenna Array as a Prototype of a Huge Low-Frequency Radio Telescope
Experimental Astronomy, 2003Co-Authors: Alexander Alexandrovich Konovalenko, Igor Savelievich Falkovich, Nikolay Nikolaevich Kalinichenko, Alexander Alexandrovich Gridin, Igor Nikolaevich Bubnov, Alain Lecacheux, Carlo Rosolen, Helmut O. RuckerAbstract:An effective wide-band (10 to 60 MHz) active antenna element has been developed. The cost of one short (3 m), thin dipole with built-in amplifier and metal construction is less than 45 euro. It was shown both theoretically and experimentally that the upper Limiting Frequency is at least 60 MHz, the dynamic range is 90 dB/μV and the share of the amplifier noise to the background antenna temperature is about 10%. The developed active dipole was tested by building a 30-element antenna array and comparing its parameters with one of the subpart of the UTR-2 radio telescope having passive dipoles of 8.6 m in length and 1.8 m in diameter. The 3C461 ionospheric scintillation spectra observed in the experiments show that the sensitivities and noise-immunities of both antennas are close. This proves the availability using of a short cheap active dipole in new generation giant radio telescopes.
Mark Ospeck - One of the best experts on this subject based on the ideXlab platform.
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Limiting Frequency of the cochlear amplifier based on electromotility of outer hair cells
Biophysical Journal, 2003Co-Authors: Mark Ospeck, Xiaoxia Dong, Kuni H IwasaAbstract:Outer hair cells are the critical element for the sensitivity and sharpness of Frequency selectivity of the ear. It is believed that fast motility (electromotility) of these cells is essential for this function. Indeed, force produced by outer hair cells follows their membrane potential very closely at least up to 60 kHz. However, it has been pointed out that the cell's receptor potential is attenuated by a low-pass RC circuit inherent to these cells, with the RC roll-off frequencies significantly lower than their operating frequencies. This would render electromotility ineffective in producing force. To address this issue, we assume that multiple degrees of freedom and vibrational modes due to the complex structure of the organ of Corti provide optimal phases for outer hair cells' force to cancel viscous drag. Our derived Frequency limit depends on the drag-capacitance product, not directly on the RC time constant. With a reasonable assumption for the viscous drag, the estimated limit is 10-13 kHz, exceeding the RC corner Frequency. Our analysis shows that a fast-activating potassium current can substantially extend the Frequency limit by counteracting the capacitive current.
Alexander Alexandrovich Konovalenko - One of the best experts on this subject based on the ideXlab platform.
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Thirty-Element Active Antenna Array as a Prototype of a Huge Low-Frequency Radio Telescope
Experimental Astronomy, 2003Co-Authors: Alexander Alexandrovich Konovalenko, Igor Savelievich Falkovich, Nikolay Nikolaevich Kalinichenko, Alexander Alexandrovich Gridin, Igor Nikolaevich Bubnov, Alain Lecacheux, Carlo Rosolen, Helmut O. RuckerAbstract:An effective wide-band (10 to 60 MHz) active antenna element has been developed. The cost of one short (3 m), thin dipole with built-in amplifier and metal construction is less than 45 euro. It was shown both theoretically and experimentally that the upper Limiting Frequency is at least 60 MHz, the dynamic range is 90 dB/μV and the share of the amplifier noise to the background antenna temperature is about 10%. The developed active dipole was tested by building a 30-element antenna array and comparing its parameters with one of the subpart of the UTR-2 radio telescope having passive dipoles of 8.6 m in length and 1.8 m in diameter. The 3C461 ionospheric scintillation spectra observed in the experiments show that the sensitivities and noise-immunities of both antennas are close. This proves the availability using of a short cheap active dipole in new generation giant radio telescopes.