Where, as above, C is annuity payment, PV is principal, n is number of payments, starting at end of first period, and i is interest rate per period. Equivalently C is the periodic loan repayment for a loan of PV extending over n periods at interest rate, i.
Refractory epilepsy is a seizure disorder that resists drug treatment. There is some debate among clinicians and researchers about how to define refractory epilepsy. As a result, this term is used in a variety of ways, and when a patient's epilepsy is described as refractory, resistant, or nonresponsive, it can be advisable to ask for more detail about what the diagnosis means.
Refractory period. For a short period after the passage of an impulse, the threshold for stimulation is raised, such that if a nerve is stimulated twice in quick succession, it may not respond to the second stimulus. The absolute refractory period is the brief interval after a successful stimulus when no second shock, however maximal, can elicit another response. Its duration in mammalian A fibres is about 0.4 ms; in frog nerve at 15oC it is about 2 ms.