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INTRODUCTION AND OBJECTIVES Intracavernosal injection (ICI) of vasoactive agents has been successfully used in the treatment of erectile dysfunction (ED). The authors' pharmacologic erection program, using a fixed combination of prostaglandin E1 (PGE1) and papaverine, is notable for its simplicity and acceptance by patients who have suffered spinal cord injuries (SCIs). METHODS Patients undergo baseline questionnaire, physical examination, and hormone profile followed by instruction and injection of a fixed combination of PGE1 and papaverine. On successive visits, the patient injects himself and the dosage is titrated until a satisfactory erection is obtained. Patients who do not respond to injection of 1.0 cc are considered treatment failures. Patients return periodically for routine follow-up. RESULTS From May 1994 to March 1997, 37 patients with SCI underwent initial evaluation and 28 (76%) responded to injection therapy and were successfully using self-injection therapy at 3-month follow-up. Twenty-three patients are still on injection therapy. Five patients have dropped out for several reasons including a lack of a current sexual partner (60%) and pain with injection (40%). Patient age ranges from 24 to 72. The dosage range was 0.10 to 0.50 cc (mean = 0.29 cc). The average duration of erection was 43 minutes. At 3-month follow-up, 85% of the patients rated their erections as good or excellent. Forty-three percent of patients are using ICI 1 or more times per week. Seventy-seven percent of patients are moderately or extremely satisfied with their treatment and 89% said that they would recommend this program to a friend. CONCLUSIONS This simplified pharmacologic erection program offers safe, well accepted, and effective therapy for ED to a SCI population with very high patient satisfaction.

Data assimilation schemes are confronted with the presence of model errors arising from the imperfect description of atmospheric dynamics. These errors are usually modelled on the basis of simple assumptions such as bias, white noise, and first-order Markov process. In the present work, a formulation of the sequential extended Kalman filter is proposed, based on recent findings on the universal deterministic behaviour of model errors in marked contrast with previous approaches. This new scheme is applied in the context of a spatially distributed system proposed by Lorenz. First, it is found that, for short times, the estimation error is accurately approximated by an evolution law in which the variance of the model error (assumed to be a deterministic process) evolves according to a quadratic law, in agreement with the theory. Moreover, the correlation with the initial condition error appears to play a secondary role in the short-time dynamics of the estimation error covariance. Second, the deterministic description of the model error evolution, incorporated into the classical extended Kalman filter equations, reveals that substantial improvements of the filter accuracy can be gained compared with the classical white-noise assumption. The universal short-time quadratic law for the evolution of the model error covariance matrix seems very promising for modelling estimation error dynamics in sequential data assimilation. Copyright © 2008 Royal Meteorological Society.