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Functional Assessment of >18 Years Old Patients at Internal Medicine Ward-Relationship with In-Hospital and 30-Day Mortality
Publication . Ribeiro, Heloísa; Martins, Yolanda; Natário, Isabel; Tavares, Luís Pedro; CMA - Centro de Matemática e Aplicações; DM - Departamento de Matemática; Elsevier
OBJECTIVE: To evaluate the connection between the items included in the AVD-DezIs score (a questionnaire about basic and instrumental activities of daily living and other topics related to social and personal life) and in-hospital and 30-day mortality after discharge. METHODS: Prospective cohort study of hospitalizations in the Internal Medicine ward from 2014 to 2020, including >18 years old patients with a fully completed AVD-DezIs. To identify in-hospital and 30 days mortality, univariate and multivariate logistic models were applied, including random effects if justified. RESULTS: A total of 19,771 episodes of hospitalization were included. In the univariate analysis, except for the presence of isolation and financial insufficiency, all the items were predictors of mortality in-hospital or within 30 days after discharge. In multivariate analysis, older age, male sex, longer hospital stay, higher Charlson score, deficiency in all four activities of daily living, deficiency in meal preparation and housekeeping, presence of pain/depression, immobility, and malnutrition are associated with a higher probability of in-hospital death whereas older age, male gender, higher Charlson score, longer length of hospital stay, deficiency in personal hygiene, ambulation, and eating habits, as well as the presence of incontinence and malnutrition, are associated with a higher probability of 30 days after discharge death. DISCUSSION/CONCLUSION: Except for isolation and financial insufficiency, all items were individually associated with the outcomes. When they are considered in conjunction and taking into account sex, age, comorbidities and length of stay, the predictive ability of in-hospital and 30 days mortality differed.
On the essential norms of Toeplitz operators on abstract Hardy spaces built upon Banach function spaces
Publication . Karlovych, Oleksiy; Shargorodsky, Eugene; CMA - Centro de Matemática e Aplicações; DM - Departamento de Matemática; Sociedad Matematica Mexicana
Let X be a Banach function space over the unit circle such that the Riesz projection P is bounded on X and let H[X] be the abstract Hardy space built upon X. We show that the essential norm of the Toeplitz operator T(a):H[X]→H[X] coincides with ‖a‖L∞ for every a∈C+H∞ if and only if the essential norm of the backward shift operator T(e-1):H[X]→H[X] is equal to one, where e-1(z)=z-1. This result extends an observation by Böttcher, Krupnik, and Silbermann for the case of classical Hardy spaces.
Tailor-made strategies through different weight simulation of factor-based investing
Publication . Ramos, Catarina A.; Marques, Nuno C.; Faias, Marta; Santos, Hugo; DI - Departamento de Informática; NOVALincs; CMA - Centro de Matemática e Aplicações; DM - Departamento de Matemática; Springer Verlag
This study explores the implementation and factor integration of diverse factor-based investment strategies in the European market. Specifically, we investigate a contrarian strategy, two value strategies, and a momentum strategy from 2015 to June 2024. Utilising the Python framework Qrumble for efficient experimentation, we integrate evaluation metrics and we consider beyond the commonly used portfolios, equally weighted and value-weighted, two theoretically efficient portfolios - minimum variance and market portfolio. While certain strategies yielded outcomes not entirely in line with state-of-the-art standards, both value strategies showed promising returns with manageable risk. Notably, the combination of factors in a multi-type strategy, named Magical Bambu, demonstrated interesting results, suggesting the potential for effective collaboration between different investment methodologies. This study underscores the nuanced outcomes within theoretically efficient portfolios under specific conditions, prompting further exploration.
Subsets of Groups in Public-key Cryptography
Publication . Carvalho, André; Malheiro, António; DM - Departamento de Matemática; CMA - Centro de Matemática e Aplicações; AIMS Press - American Institute of Mathematical Sciences
We suggest the use of algebraic subsets instead of subgroups in public-key cryptography. In particular, we present the subset version of two protocols introduced by Shpilrain and Ushakov with some examples in ascending HNN-extensions of free-abelian groups and discuss their resistance to length and distance based attacks. We also introduce several new group theoretic problems arising from this work.
Optimal control of a class of third-grade-Voigt equations
Publication . Kinra, Kush; Cipriano, Fernanda; CMA - Centro de Matemática e Aplicações; DM - Departamento de Matemática; Springer International Publishing
This work aims to understand the velocity tracking control problem for a class of non-Newtonian fluids. We introduce the third-grade-Voigt equations in the two-dimensional torus T2 and prove the existence and uniqueness of the solution. Then, we show the existence and uniqueness of solution to the corresponding linearized state equation and adjoint equation. Additionally, we provide a suitable stability result for the state equation and demonstrate that the Gateaux derivative of the control-to-state mapping agrees with the solution of the linearized state equation. Next, we establish the first order optimality conditions and show the existence of an optimal solution. Ultimately, we are able to provide a uniqueness result for the coupled system consisting of the adjoint equation, the state equation, and the first order optimality condition. Therefore, under appropriate conditions on the data, the uniqueness of the optimal solution holds.
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Fundação para a Ciência e a Tecnologia
Programa de financiamento
Concurso de avaliação no âmbito do Programa Plurianual de Financiamento de Unidades de I&D (2017/2018) - Financiamento Base
Número da atribuição
UIDB/00297/2020