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In this paper, we consider the convergence and robustness of a general iterative learning control scheme for a class of systems which we term “strongly positive”. The analysis is made in the framework of Hilbert‐space theory. Thus the results are valid for discrete‐time as well as continuous‐time systems which may be time‐variant or time‐invariant. For the special case of continuous linear time‐invariant systems which are defined over the Hilbert‐space of square integrable functions, we will give a characterization of strongly positive systems in the frequency domain.

por estar ahí, acompañándome siempre con una palabra de aliento, un saludo cariñoso y una sonrisa desinteresada. Del mismo modo agradecer a mi familia adoptiva: Mónica, Fernando, Marina, Diana y Carlos por tratarme como uno más de ustedes y siempre darme ánimo. A Andrea por tu amor, compañía, compresión y todos estos años juntos que han sido los mejores de mi vida (junto con los que vendrán).

Background: The Geriatric Day Hospital (GDH) is an important outpatient geriatric service, but there are few data on the role of frailty as a potential predictor of poor outcomes in this setting. Methods: Data were analyzed from 499 patients aged ≥ 60 years attending a 12-week GDH program between 2018 and 2021. Frailty status was defined as non-frail (68, 13.6%), mild/moderate frailty (351, 70.3%), and severe frailty (80, 16.0%) based on the Clinical Frailty Scale (CFS). Outcomes were defined as (1) poor outcome (hospital readmission, death, or medical deterioration) during the program and (2) admission to permanent nursing home care upon completion of the program. Multivariate logistic models were used for predictive analyses. Results: The mean age was 80.3 (standard deviation 7.0); 58.3% were women. Overall, 77 patients (15.4%) had a poor outcome, and 48 (9.6%) were admitted to permanent nursing home care. Poor outcome was experienced by none of the non-frail patients (0%), by 49 (14.0%) patients with mild/moderate frailty, and 22 (27.5%) patients with severe frailty (adjusted OR, 2.0; 95% CI 1.3, 3.2; p < 0.01). Admission to a permanent nursing home care was experienced by none of the non-frail patients (0%), 20 (5.7%) of those with mild/moderate frailty, and 28 (35.0%) with severe frailty (adjusted OR, 2.9; 95% CI 1.3, 6.3; p < 0.01). Conclusions: The CFS is a promising risk predictor of poor outcome and admission to permanent nursing home discharge among older patients attending a GDH program.

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