Fohlmeister-Coleman-Miller model of retinal ganglion cells consists of five ion channels; these are sodium channels, calcium channels, and 3 types of potassium channels. An increasing number of studies have investigat...Fohlmeister-Coleman-Miller model of retinal ganglion cells consists of five ion channels; these are sodium channels, calcium channels, and 3 types of potassium channels. An increasing number of studies have investigated sodium channels, voltage-gated potassium channels, and delayed rectifier potassium channels. However, little is known about calcium channels, and in particular the dynamics and computational models of calcium ions. Retinal prostheses have been designed to assist with sight recovery for the blind, and in the present study, the effects of calcium ions in retinal ganglion cell models were analyzed with regard to calcium channel potential and calcium-activated potassium potential. Using MATLAB software, calcium conductance and calcium current from the Fohlmeister-Coleman-Miller model, under clamped voltages, were numerically computed using backward Euler methods. Subsequently, the Fohlmeister-Coleman-Miller model was simulated with the absence of calcium-current （lca） or calcium-activated potassium current （lK, Ca）. The model was also analyzed according to the phase plane method. The relationship curve between peak calcium current and clamped potentials revealed an inverted bell shape, and the calcium-activated potassium current increased the frequency of firing and the peak of membrane potential. Results suggested that calcium ion concentrations play an important role in controlling the peak and the magnitude of peak membrane voltage in retinal ganglion cells.展开更多
Wave forces acting on the offshore structure are of importance for the structure design point of view. There is a so called 'Two Tension Leg Buoy Mooring System' designed to open up the oil field in South Chin...Wave forces acting on the offshore structure are of importance for the structure design point of view. There is a so called 'Two Tension Leg Buoy Mooring System' designed to open up the oil field in South China Sea. Two bases of the system are sitting on the sea floor of 30 - 40 meters depth of water. In order to confirm the safety of this system, wave forces are investigated experimentally and numerically. Nowadays, the measured materials on this subject are scarce. In the model test of Dr. Chakrabarti, the test set-up necessitated a small uniform gap between the model and tank floor, and the correct results must be come from an adjustment. The authors have solved the problem. In the paper, two numerical methods are adopted: 3-D boundary integral equation method; eigen-function expression and matching method. The former consists of distribution of Haskind Green' function on the body surface. The latter, however, by dividing the whole fluid domain into subregions, the velocity potential for each subregions can be determined uniquely by matching the velocity potential on their common boundaries, which was expressed formally by its eigen function expansion. As an example, experimental and numerical results were given for a circular base in shallow sea. They agree quite well. Although both methods are effective, the matching method has more efficiency.展开更多
基金the National Natural Science Foundation of China,No. 30870649Science and Technology 973 Project,No. 2005CB724302
文摘Fohlmeister-Coleman-Miller model of retinal ganglion cells consists of five ion channels; these are sodium channels, calcium channels, and 3 types of potassium channels. An increasing number of studies have investigated sodium channels, voltage-gated potassium channels, and delayed rectifier potassium channels. However, little is known about calcium channels, and in particular the dynamics and computational models of calcium ions. Retinal prostheses have been designed to assist with sight recovery for the blind, and in the present study, the effects of calcium ions in retinal ganglion cell models were analyzed with regard to calcium channel potential and calcium-activated potassium potential. Using MATLAB software, calcium conductance and calcium current from the Fohlmeister-Coleman-Miller model, under clamped voltages, were numerically computed using backward Euler methods. Subsequently, the Fohlmeister-Coleman-Miller model was simulated with the absence of calcium-current （lca） or calcium-activated potassium current （lK, Ca）. The model was also analyzed according to the phase plane method. The relationship curve between peak calcium current and clamped potentials revealed an inverted bell shape, and the calcium-activated potassium current increased the frequency of firing and the peak of membrane potential. Results suggested that calcium ion concentrations play an important role in controlling the peak and the magnitude of peak membrane voltage in retinal ganglion cells.
文摘Wave forces acting on the offshore structure are of importance for the structure design point of view. There is a so called 'Two Tension Leg Buoy Mooring System' designed to open up the oil field in South China Sea. Two bases of the system are sitting on the sea floor of 30 - 40 meters depth of water. In order to confirm the safety of this system, wave forces are investigated experimentally and numerically. Nowadays, the measured materials on this subject are scarce. In the model test of Dr. Chakrabarti, the test set-up necessitated a small uniform gap between the model and tank floor, and the correct results must be come from an adjustment. The authors have solved the problem. In the paper, two numerical methods are adopted: 3-D boundary integral equation method; eigen-function expression and matching method. The former consists of distribution of Haskind Green' function on the body surface. The latter, however, by dividing the whole fluid domain into subregions, the velocity potential for each subregions can be determined uniquely by matching the velocity potential on their common boundaries, which was expressed formally by its eigen function expansion. As an example, experimental and numerical results were given for a circular base in shallow sea. They agree quite well. Although both methods are effective, the matching method has more efficiency.
