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Table 1 Electrical and geometric parameters in the model

From: Activation of peripheral nerve fibers by electrical stimulation in the sole of the foot

  Electrical properties Source Thickness (mm) Source
  Location (sole/rest of foot)  
Tissue      Heel Arch Forefoot  
Bone ϵr 10,000 [23] Sole & rest 10 10 10  
marrow σ (S/m) 0.09       
Cortical ϵr 3,000 [23] Sole & rest 6 6 6 [15]
bone σ (S/m) 0.02       
Muscle ϵr 1.5×106 [24] Rest 3 3 3 [25]
  σ (S/m) 0.5   Sole 0 2 0 US *
Fat ϵr 10,000 [24] Rest 4 4 4 [16]
  σ (S/m) 0.025   Sole 9.7 5.3 6.1 US
Dermis ϵrr 1.26×106 [22] Rest 1.3 1.3 1.3 [16]
  ϵrz 4.01×105  
  σ (S/m) - r 2.57   Sole 5.1 4.3 4.6 US-SB **
  σ (S/m) - z 1.62  
Vital ϵr - r 2.71×105 [22] Rest 0.042 0.042 0.042 SB
epidermis ϵr - z 7.30×104  
  σ (S/m) - r 0.95   Sole 0.213 0.094 0.107 SB
  σ (S/m) - z 0.15  
Stratum ϵr 1,500 [21] Rest 0.033 0.033 0.033 SB
corneum σ (S/m) 5×10-4   Sole 0.748 0.161 0.253 SB
  1. The relative permittivity (ϵr) and conductivity (σ) were adopted from literature. The geometry values for the sole of the foot were determined from ultrasound (US) scans and the skin biopsies (SB) used for the Nav1.7 immunochemistry. Since the US scans provided only a bulk measure for the entire skin, and the SB provided only an estimate of the thickness of the stratum corneum and vital epidermis (*), the thickness of the dermis was calculated as the thickness of the entire skin subtracted the thickness of the entire epidermis (**, Stratum corneum + Vital epidermis).