On Resonance in Periodically Forced Oscillators and Coupled Systems of Excitable Systems and Nonlinear Oscillators

We analyze some mathematical problems that arise in studies of phenomena observed in the cardiac action. We illustrate a method to characterize the response of a nonlinear oscillator to an external forcing, and introduce some numerical results. We also introduce some results of numerical computation in an example of a coupled system of an excitable system and a nonlinear oscillator

A numerical analysis of slow oscillations in dynamics of coupled systems

We study a system that models a problem in which an oscillatory unit is coupled to a passive medium. We analyze the case in which an RCL circuit is coupled to an RC circuit. Some numerical results indicate when slow oscillations occur in coupled systems

An Experimental Study of Unsteady Flows Generated in Kojima Lake

The global positioning system (GPS) is utilized for analysis of flows in the water environment. A float equipped with a GPS unit is designed to drift on the surface of the water. Its driving force is the fluid resistance exerted on a pair of rectangular plates. While it travels over the surface, the GPS unit evaluates its position every second, and spatiotemporal data that specify its motion are transmitted to be recorded. Results of experiments conducted to study unsteady flows generated in Kojima Lake are introduced

テイジョウ クウキ コキュウジ ノ ケツエキチュウ CO_2 ガンリョウ ト CO_2 ブンアツ ノ カンケイ

The CO_2 content in blood ([CO_2]) depends not only on PCO_2, but also on the O_2 saturation ([SO_2]). Since SO_2 changes in parallel with [CO_2] in capillary blood ([CO_2]^* ) at steady state, the slope of [CO_2]^* against PCO_2 becomes steeper than that of [CO_2] measured in oxygenated or deoxygenated blood. In the preceding paper it was made clear that the change in [CO_2] due to that in SO_2 (i.e., the Haldane effect, [CO_2]_HE) became proportional to the respiratory quotient (RQ). Since the ratio of the arterial-venous (a-v) difference in SO_2 (av [SO_2]) to that in [CO_2]^* (av[CO_2]^*) was in inverse pro-portion to the RQ, the ratio of the a-v difference in [CO_2]_HE (av[CO_2]_HE) to av[CO_2]^* became constant irrespective of the RQ. Designating the PCO_2 dependent component of [CO_2] except for [CO_2]_HE by [CO_2]_P , the ratio av[CO_2]_P/[CO_2]^* also became constant. Thus, using [CO_2]_P measured in oxygenated blood in vitro, [CO_2]^* could be expressed by an exponential function of PCO_2　Key words : Carbonic anhydrase, O_2 saturation, Haldane effect, Respiratory quotient, Va/Q rati

A Numerical Analysis of Unsteady Flow in Kojima Lake

We study unsteady flow that models lake flow in Kojima Lake. We assume that a lake is connected to another area with gates, and that those gates are opened when the water level outside the gates is lower than the water level of the lake. We study unsteady flow due to the opening of the gates. We analyze the problem with the finite element method, and take detailed structures of the gates into account

テイジョウ クウキ コキュウジ ノ ケッショウ タンサン イオン ノウド ト CO_2 ブンアツ ノ カンケイ

The bicarbonate concentration in vivo, [HCO_3^-], has a Pco_2-dependent component, [HCO_3^-]^*, and a metabolic component, [HCO_3^－]^o. The [HCO_3^-]^* in elderly patients and volunteers was expressed by an exponential function of Pco_2 obtained by analysis of the venous-arterial (a-v) difference in [HCO_3^－]. The slope of [HCO_3^－]^* against Pco_2 was about 25% higher than that measured in oxygenated and deoxygenated blood in vitro. The regression functions of constituent ions were all linear versus [HCO_3^－]^* and [HCO_3^－]^o over the physiological Pco_2 range. The relationship between Pco_2 and [HCO_3^－]^* agreed well with that calculated from the CO_2 reaction rates on the active site of carbonic anhydrase using the Michaelis-Menten equation. At steady state the a-v difference in [HCO_3^－] is proportional to that in O_2 content ([O_2]) as estimated from the respiratory quotient (RQ). Thus, [HCO_3^－]^* inevitably implied the Haldane effect component of [HCO_3^－] ([HCO_3^－]_HE). However, [HCO_3^－] measured in oxygenated and deoxygenated blood was free from the change in [O_2] or the Haldane effect. The relationship between [HCO_3^－]_HE and [HCO_3^－]^* could be evaluated from the in vivo and in vitro difference in [HCO_3^－], and the effect of RQ on [HCO_3^-]_HE For analysing the ionic concentrations in plasma at steady state and the acid-base status, the equation for [HCO_3^－]^* was considered indispensable.　Key words : Haldane effect of [HCO_3^－], CO_2 reaction rates, Carbonic anhydrase, Respiratory quotient, Strong ion differenc

テイジョウ クウキ コキュウジ ノ ケッショウナイ イオン ノウド ノ カイセキ

　Ionic concentrations in blood plasma depend on [HCO_3^-] and water content [H_2O]. It has been shown previously, that the change in ionic concentration depending [HCO_3^-] has two components, which can be expressed by specific experimental equations through regression analysis. By using these equations in the present work, the two components of [HCO_3^-] were excluded from measured concentrations, and those changes in ionic concentrations, which depend on the change in [H_2O], were analysed. The concentrations in this third components, which are denoted by the prefix \u27i\u27, were mainly obtained in plasma from elderly patients, where i[Na^+] was widely distributed and, in addition, i[Cl^-] was linearly related to i[Na^+]. Thus, it was demonstrated that the concentrations in the third component depend on [H_2O]. At the standard state of [HCO_3^-] in normal subjects, the ratio of [Cl^-] to [Na^+] is about 0.738. However, the regression coefficient of i[Cl^-] against i[Na^+] was about 0.77. This result suggested that to maintain electroneutrality a NaCl shift occurs across the capillaries together with a water shift, depending on the change in [H_2O] in interstitial fluid. Using the regression coefficient, the difference between the [H_2O]-dependent components of [Na^+] ([Na^+]) and of [Cl^-] ([Cl^-]) was obtained, and [H_2O] in plasma was estimated from [Na^+]-[Cl^-]. Furthermore, i[K^+] was linearly related to [Na^+]-[Cl^-] and from the regression function the shift of K^+ across the RBC membrane could be estimated. It also became clear that the imbalance between i[Na^+] and i[Cl^-] was compensated by the change in concentration of other strong ions, i.e. the change in anion gap.　Keywords: Osmotic pressure, Interstitial fluid, Water shift, Electroneutrality, Exogenous ion