The impact ionization rate and its orientation dependence in k space is calculated for GaAs. The numerical results indicate a strong correlation to the band structure. The use of a q-dependent screening function for the Coulomb interaction between conduction and valence electrons is found to be essential. Comparison with recent results for Si, GaAs shows a harder threshold behavior. A simple fit formula is presented for easy calculation of the direction-dependent transition rate. With only the band structure as input the numerical results are closely reproduced in an arbitrary direction in the Brillouin zone.

The impact ionization rate and its orientation dependence in k space is calculated for ZnS. The numerical results indicate a strong correlation to the band structure. The use of a q-dependent screening function for the Coulomb interaction between conduction and valence electrons is found to be essential.A simple fit formula is presented for easy calculation of the energy dependent transition rate.

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Background and Aim: Although upper limb myoelectric prostheses can offer improved functionality and dexterity over body-powered systems, abandonment rates remain high. User dissatisfaction in comfort and control are among the top contributors. The design of the prosthetic socket must be comfortable, while maintaining contact of control electrodes with the residual limb throughout the day. We present a myoelectric socket design that provides user-adjustable compression over electrode control sites to promote consistent control, while maintaining comfort and fit. Technique: A cable tensioning system was threaded through a series of paneled windows in the socket wall over electrode sites. Adjusting tension provided tuning of electrode contact. Discussion: A case study of a single transhumeral prosthetic user with a follow-up interview 11 months post delivery suggests that our adjustable design has the potential to address control and comfort challenges, critical factors in myoelectric prosthetic use, and abandonment. Clinical relevance Achieving consistent electrode contact with muscle control sites in traditional rigid sockets is a critical challenge for myoelectric prostheses. We present a unique solution via user-adjustable electrode contacts built into the socket.