University of Naples Federico II

About: University of Naples Federico II is a education organization based out in Naples, Campania, Italy. It is known for research contribution in the topics: Population & Cancer. The organization has 29291 authors who have published 68803 publications receiving 1920149 citations. The organization is also known as: Università degli Studi di Napoli Federico II & Naples University.

Switchings, bifurcations, and chaos in DC/DC converters

Abstract: Nonlinear phenomena in closed-loop pulsewidth modulated (PWM) DC/DC converters are analyzed. We introduce a new discrete time nonlinear map-the A-switching map-which is related to the asynchronous switchings, i.e., the changes of converter configuration occurring within the modulating period. This map is compared with the stroboscopic map, which is typically used in the study of DC/DC converters. Analytical conditions for the occurrence of periodic orbits and flip bifurcations are obtained. Moreover, necessary conditions for infinite local stretching on the phase space are derived. Finally, a possible explanation of the sudden jump to chaos exhibited by DC/DC converters is proposed. Analytical and numerical results can be applied to all fundamental DC/DC converter topologies. The case of the voltage-controlled buck converter is treated in detail.

Plant Polyphenols and Their Anti-Cariogenic Properties: A Review

Abstract: Polyphenols constitute one of the most common groups of substances in plants. Polyphenolic compounds have been reported to have a wide range of biological activities, many of which are related to their conventional antioxidant action; however, increasing scientific knowledge has highlighted their potential activity in preventing oral disease, including the prevention of tooth decay. The aim of this review is to show the emerging findings on the anti-cariogenic properties of polyphenols, which have been obtained from several in vitro studies investigating the effects of these bioactive molecules against Streptococcus mutans, as well as in vivo studies. The analysis of the literature supports the anti-bacterial role of polyphenols on cariogenic streptococci, suggesting (1) a direct effect against S. mutans; (2) an interaction with microbial membrane proteins inhibiting the adherence of bacterial cells to the tooth surface; and (3) the inhibition of glucosyl transferase and amylase. However, more studies, particularly in vivo and in situ, are necessary to establish conclusive evidence for the effectiveness and the clinical applications of these compounds in the prevention of dental caries. It is essential to better determine the nature and distribution of these compounds in our diet and to identify which of the hundreds of existing polyphenols are likely to provide the greatest effects.

Withdrawal of Long-Term Cabergoline Therapy for Tumoral and Nontumoral Hyperprolactinemia

Abstract: Background Whether the withdrawal of treatment in patients with nontumoral hyperprolactinemia, microprolactinomas, or macroprolactinomas is safe and effective has been unclear. We performed an observational, prospective study of cabergoline (a dopamine-receptor agonist) withdrawal in such patients. Methods The study population included 200 patients — 25 patients with nontumoral hyperprolactinemia, 105 with microprolactinomas, and 70 with macroprolactinomas. Withdrawal of cabergoline was considered if prolactin levels were normal, magnetic resonance imaging (MRI) showed no tumor (or tumor reduction of 50 percent or more, with the tumor at a distance of more than 5 mm from the optic chiasm, and no invasion of the cavernous sinuses or other critical areas), and if follow-up after withdrawal could be continued for at least 24 months. Results Recurrence rates two to five years after the withdrawal of cabergoline were 24 percent in patients with nontumoral hyperprolactinemia, 31 percent in patients with micropr...