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Marques A.,The Interdisciplinary Center | Sallis J.F.,University of California at San Diego | Martins J.,University of Lisbon | Diniz J.,The Interdisciplinary Center | And 2 more authors.
American Journal of Human Biology | Year: 2014

Objectives: Understanding correlates of physical activity and sedentary behaviors may contribute to fostering active lifestyles. This study aimed to identify correlates of physical activity and sedentary behaviors in leisure-time among Portuguese urban children, during school days. Methods: A cross-sectional survey was conducted with 802 students (416 boys), aged 10-12 years. A questionnaire was used to collect data of physical activity, sedentary behaviors, psychological and behavioral variables related to physical activity and sedentary behaviors. Analyses were run separately for boys and girls. Results: Television viewing occupied the most leisure-time of boys and girls, followed by computer usage, and video game playing. These behaviors occupied 259.7 min/day for boys and 208.6 for girls (P = 0.002). Reported moderate-to-vigorous physical activity was 23.7 min for boys and 12.8 min for girls (P < 0.001). Perception of competence and academic achievement were related to physical activity for the boys and girls. Computer use and playing video games with friends were only related to physical activity for the boys. On the other hand, parents' physical activity participation was related with boys' and girls' physical activity. The correlates of sedentary behavior were outdoor play for the boys, age for the girls, and playing video games with friends for both. Conclusions: This finding suggests that interventions should be considered to replace joint video game time with joint physical activity time. Am. J. Hum. Biol. 26:407-412, 2014. © 2014 Wiley Periodicals, Inc. Source


Reis C.P.,Lusophone University of Humanities and Technologies | Damge C.,University of Lorraine
Methods in Enzymology | Year: 2012

Since its discovery, insulin has been used as highly specific and effective therapeutic protein to treat type 1 diabetes and later was associated to oral antidiabetic agents in the treatment of type 2 diabetes. Generally, insulin is administered parenterally. Although this route is successful, it still has several limitations, such as discomfort, pain, lipodystrophy at the injection sites and peripheral hyperinsulinemia, which may be the cause of side effects and some complications. Thus, alternative routes of administration have been developed, namely, those based on nanotechnologies. Nanoparticles, made of synthetic or natural materials, have been shown to successfully overcome the inherent barriers for insulin stability, degradation, and uptake across the gastrointestinal tract and other mucosal membranes. This review describes some of the many attempts made to develop alternative and more convenient routes for insulin delivery. © 2012 Elsevier Inc. All rights reserved. Source


Bastos N.R.O.,Polytechnic Institute of Viseu | Ferreira R.A.C.,Lusophone University of Humanities and Technologies | Torres D.F.M.,University of Aveiro
Signal Processing | Year: 2011

We introduce a discrete-time fractional calculus of variations on the time scale (hℤ)a,a∈ℝ,h>0. First and second order necessary optimality conditions are established. Examples illustrating the use of the new Euler-Lagrange and Legendre type conditions are given. They show that solutions to the considered fractional problems become the classical discrete-time solutions when the fractional order of the discrete-derivatives are integer values, and that they converge to the fractional continuous-time solutions when h tends to zero. Our Legendre type condition is useful to eliminate false candidates identified via the Euler-Lagrange fractional equation. © 2010 Elsevier B.V. All rights reserved. Source


Ferreira R.A.C.,Lusophone University of Humanities and Technologies
Computers and Mathematics with Applications | Year: 2011

In this paper, we investigate the existence of positive solutions to the nonlinear q-fractional boundary value problem (Dqαy)(x)=-f(x,y(x)), 0 Source


Almeida R.,University of Aveiro | Ferreira R.A.C.,University of Aveiro | Ferreira R.A.C.,Lusophone University of Humanities and Technologies | Torres D.F.M.,University of Aveiro
Acta Mathematica Scientia | Year: 2012

In this article, we study isoperimetric problems of the calculus of variations with left and right Riemann-Liouville fractional derivatives. Both situations when the lower bound of the variational integrals coincide and do not coincide with the lower bound of the fractional derivatives are considered. © 2012 Wuhan Institute of Physics and Mathematics. Source

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