Effects of potassium channel blockage on inverse stochastic resonance in Hodgkin-Huxley neural systems

Inverse stochastic resonance(ISR)is a phenomenon in which the firing activity of a neuron is inhibited at a certain noise level.In this paper,the effects of potassium channel blockage on ISR in single Hodgkin-Huxley neurons and in small-world networks were investigated.For the single neuron,the ion channel noise-induced ISR phenomenon can occur only in a certain small range of potassium channel blockage ratio.Bifurcation analysis showed that this small range is the bistable region regulated by the external bias current.For small-world networks,the effect of non-homogeneous network blockage on ISR was investigated.The network blockage ratio was used to represent the proportion of potassium-channel-blocked neurons to total network neurons.It is found that an increase in network blockage ratio at small coupling strengths results in shorter ISR duration.When the coupling strength is increased,the ISR is more significant in the case of a large network blockage ratio.The ISR phenomenon is determined by the network blockage ratio,the coupling strength,and the ion channel noise.Our results will provide new perspectives on the observation of ISR in neuroscience experiments.

Improvement of solidification model and analysis of 3D channel blockage with MPS method

In a severe accident of a nuclear power reactor,coolant channel blockage by solidified molten core debris may significantly influence the core degradations that follow.The moving particle semi-implicit(MPS)method is one of the Lagrangian-based particle methods for analyzing incompressible flows.In the study described in this paper,a novel solidification model for analyzing melt flowing channel blockage with the MPS method has been developed,which is suitable to attain a sufficient numerical accuracy with a reasonable calculation cost.The prompt velocity diffusion by viscosity is prioritized over the prompt velocity correction by the pressure term(for assuring incompressibility)within each time step over the“mushy zone”(between the solidus and liquidus temperature)for accurate modeling of solidification before fixing the coordinates of the completely solidified particles.To sustain the numerical accuracy and stability,the corrective matrix and particle shifting techniques have been applied to correct the discretization errors from irregular particle arrangements and to recover the regular particle arrangements,respectively.To validate the newly developed algorithm,2-D benchmark analyses are conducted for steady-state freezing of the water in a laminar flow between two parallel plates.Furthermore,3-D channel blockage analyses of a boiling water reactor(BWR)fuel support piece have been performed.The results show that a partial channel blockage develops from the vicinity of the speed limiter,which does not fully develop into a complete channel blockage,but still diverts the incoming melt flow that follows to the orifice region.