Frequency-dependent current density tensors as density functions of dynamic polarizabilities

2019 ◽  
Vol 150 (18) ◽  
pp. 184117 ◽  
Author(s):  
Paolo Lazzeretti
Keyword(s):  
Current Density ◽  
Density Functions ◽  
Frequency Dependent ◽  
Dynamic Polarizabilities

Calmodulin Regulates Current Density and Frequency-Dependent Inhibition of Sodium Channel Nav1.8 in DRG Neurons

2006 ◽  
Vol 96 (1) ◽  
pp. 97-108 ◽  
Author(s):  
Jin-Sung Choi ◽  
Andy Hudmon ◽  
Stephen G. Waxman ◽  
Sulayman D. Dib-Hajj
Keyword(s):  
Sodium Channel ◽  
Current Density ◽  
Low Frequency ◽  
Drg Neurons ◽  
Frequency Dependent ◽  
Iq Motif ◽  
Calmodulin Binding ◽  
C Terminus ◽  
Dependent Inhibition

Sodium channel Nav1.8 produces a slowly inactivating, tetrodotoxin-resistant current, characterized by recovery from inactivation with fast and slow components, and contributes a substantial fraction of the current underlying the depolarizing phase of the action potential of dorsal root ganglion (DRG) neurons. Nav1.8 C-terminus carries a conserved calmodulin-binding isoleucine–glutamine (IQ) motif. We show here that calmodulin coimmunoprecipitates with endogenous Nav1.8 channels from native DRG, suggesting that the two proteins can interact in vivo. Treatment of native DRG neurons with a calmodulin-binding peptide (CBP) reduced the current density of Nav1.8 by nearly 65%, without changing voltage dependency of activation or steady-state inactivation. To investigate the functional role of CaM binding to the IQ motif in the Nav1.8 C-terminus, the IQ dipeptide was substituted by DE; we show that this impairs the binding of CaM to the IQ motif. Mutant Nav1.8IQ/DE channels produce currents with roughly 50% amplitude, but with unchanged voltage dependency of activation and inactivation when expressed in DRG neurons from Nav1.8-null mice. We also show that blocking the interaction of CaM and Nav1.8 using CBP or the IQ/DE substitution causes a buildup of inactivated channels and, in the case of the IQ/DE mutation, stimulation even at a low frequency of 0.1 Hz significantly enhances the frequency-dependent inhibition of the Nav1.8 current. This study presents, for the first time, evidence that calmodulin associates with a sodium channel, Nav1.8, in native neurons, and demonstrates a regulation of Nav1.8 currents that can significantly affect electrogenesis of DRG neurons in which Nav1.8 is normally expressed.

scholarly journals Quasi-Analytical Calculation of Frequency-Dependent Resistance of Rectangular Conductors Considering the Edge Effect

Energies ◽  
2022 ◽  
Vol 15 (2) ◽  
pp. 503
Author(s):  
Barzan Tabei ◽  
Akihiro Ametani ◽  
Aniruddha M. Gole ◽  
Behzad Kordi
Keyword(s):  
Edge Effect ◽  
Current Density ◽  
Analytical Calculation ◽  
Fem Simulation ◽  
Industrial Applications ◽  
Least Square ◽  
Circuit Board ◽  
Response Analysis ◽  
Two Dimensional ◽  
Frequency Dependent

This paper presents an accurate quasi-analytical approximation of frequency-dependent ac resistance of single rectangular conductors. In this work, first, a two-dimensional analytical ac resistance of rectangular conductors is derived. Unlike circular conductors, where current density distributes evenly in each layer of the conductor’s cross-section, the edge effect is involved for rectangular conductors. Due to the edge effect, one cannot define an accurate boundary condition for solving the two-dimensional partial differential equation of magnetic field or current density of rectangular conductors. Hence, the calculated two-dimensional analytical current density result is not accurate and is modified and fitted on FEM simulation, taking the conductor’s thickness into account using the least-square problem to improve its accuracy. Unlike numerical approaches, the proposed method yields an easy-to-use formula applicable to industrial applications in different fields. Contrary to the one-dimensional approach, which is only valid for very thin rectangular conductors, this method takes edge effect into account and can be used for any thickness (from square to very thin rectangular conductors). The proposed method can be used in applications where an accurate ac resistance of rectangular conductors over a wide frequency range is required, such as white-box modeling of power transformers and interpreting its frequency response analysis (FRA), and calculating the resistance of electric machine winding, busbars, and printed circuit board traces.

Frequency-dependent current density in thin metallic films

1987 ◽  
Vol 35 (15) ◽  
pp. 7857-7866 ◽  
Author(s):  
R. Dimmich ◽  
J. Dryzek
Keyword(s):  
Current Density ◽  
Metallic Films ◽  
Frequency Dependent
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