Sodium inactivation rate

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The sigmoid-shaped β_h increases with voltage and multiplies the available fraction h in its loss term. It therefore promotes inactivation as voltage rises under this model’s parameterization. The numerical units follow the millisecond timing convention of the membrane model.

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Original context

    }

    // α_h(V) = 0.07*exp(-(V+65)/20)
    float alpha_h(float V_) const {
        return 0.07f * std::exp(-(V_ + 65.0f) / 20.0f);
    }

    // β_h(V) = 1/(1+exp(-(V+35)/10))
    float beta_h(float V_) const {
        return 1.0f / (1.0f + std::exp(-(V_ + 35.0f) / 10.0f));
    }

    // α_n(V) = 0.01(V+55)/(1-exp(-(V+55)/10))
    float alpha_n(float V_) const {
        float x = V_ + 55.0f;
        if (std::abs(x) < 1e-6f) return 0.1f;
        return 0.01f * x / (1.0f - std::exp(-x / 10.0f));
    }

β_h(V) = 1/(1+exp(-(V+35)/10))

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