Distributed Saturated Control for a Class of Semilinear PDE Systems: A SOS Approach

Producción CientíficaThis paper presents a systematic approach to deal with the saturated control of a class of distributed parameter systems which can be modeled by first-order hyperbolic partial differential equations (PDE). The approach extends (also improves over) the existing fuzzy Takagi-Sugeno (TS) state feedback designs for such systems by applying the concepts of the polynomial sum-of-squares (SOS) techniques. Firstly, a fuzzy-polynomial model via Taylor series is used to model the semilinear hyperbolic PDE system. Secondly, the closed-loop exponential stability of the fuzzy-PDE system is studied through the Lyapunov theory. This allows to derive a design methodology in which a more complex fuzzy state-feedback control is designed in terms of a set of SOS constraints, able to be numerically computed via semidefinite programming. Finally, the proposed approach is tested in simulation with the standard example of a nonisothermal plug-flow reactor (PFR).The research leading to these results has received funding from the European Union and from the Spanish Government (MINECO/FEDER DPI2015-70975-P)

Antibacterial Effects of Chitosan, Formocresol and CMCP as Pulpectomy Medicament on Enterococcus ‎faecalis, Staphylococcus aureus and Streptococcus ‎mutans

Introduction: During pulpectomy of primary teeth, cytotoxic medicaments such as formocresol or camphor mono-chlorophenol (CMCP) are used as medicaments. For the first time it is theorized that chitosan can substitute these traditional materials used in pulpectomy of infectious primary teeth. Methods and Materials: This preliminary in vitro study consisted of two separate phases (n=75), each of which assessed the antibacterial effects of chitosan versus formocresol and CMCP and positive/negative controls (n=15) on three bacteria types [Enterococcus ‎faecalis, Staphylococcus aureus, Streptococcus ‎mutans, (n=5 per subgroup)]. Phases 1 and 2 concerned respectively with 1- and 7-day effects of these materials. Bacteria were cultured and injected into sterilized canals and colonies were counted. Medicaments were applied and colonies were re-counted after 1 day of treatment (phase 1). Specimens were re-sterilized and re-randomized, and used for phase 2, in which the same procedures were performed for a 7-day period. Effects of agents on bacteria were analyzed statistically (Kruskal-Wallis α=0.05 and Mann-Whitney α=0.017). Results: Treatments reduced bacterial count either after 1 or 7 days (P=0.000). Their effects on different bacteria types were not significant either after 1 or 7 days (P>0.48). Antibacterial efficacies of treatments (indicated by colony reduction) were significantly different, after 7 days (P=0.045). Antibacterial efficacy of chitosan was similar to that of formocresol or CMCP, in both phases [either after 1 or 7 days of treatment (P>0.017). Formocresol and CMCP had similar efficacies in either phase (P>0.017). Conclusions: This preliminary study confirmed the appropriate antibacterial efficacy of chitosan as a medicament in pulpectomy of infectious primary teeth.Keywords: Antibacterial Agents; Camphor Mono-Chlorophenol; Chitosan; CMCP; Enterococcus ‎faecalis; Formocresol; Medicament; Pulpectomy; Staphylococcus aureus; Streptococcus ‎mutan

Effect of Deep Cryogenic Treatment on Cyclic Fatigue of Endodontic Rotary Nickel Titanium Instruments

Introduction: Cyclic fatigue is the common reason for breakage of rotary instruments. This study was conducted to evaluate the effect of cryogenic treatment (CT) in improving the resistance to cyclic fatigue of endodontic rotary instruments. Methods and Materials: In this in vitro study, 20 RaCe and 20 Mtwo files were randomly divided into two groups of negative control and CT. CT files were stored in liquid nitrogen at -196°C for 24 h, and then were gradually warmed to the room temperature. All files were used (at torques and speeds recommended by their manufacturers) in a simulated canal with a 45° curvature until breakage. The time to fail (TF) was recorded and used to calculate the number of cycle to fail (NCF). Groups were compared using independent-samples t-test. Results: Mean NCFs were 1248.2±68.1, 1281.6±78.6, 4126.0±179.2, and 4175.4±190.1 cycles, for the Mtwo-control, Mtwo-CT, RaCe-control, and RaCe-CT, respectively. The difference between the controls and their respective CT groups were not significant (P>0.3). The difference between the systems was significant. Conclusion: Deep CT did not improve resistance to cyclic fatigue of the evaluated rotary files.Keywords: Cryogenic Treatment; Cyclic Fatigue; Instrument Fracture; Rotary Nickel Titanium File

BEYOND HOMOGENOUS DECISION-MAKING MODELS: ROLE OF BRAIN AREAS INTERACTION AND HETEROGENEITY

Most existing mechanistic models of decision making consider microcircuits within a homogenous brain area and fail to consider the distributed nature of this cognitive process. More specifically, these models do not take into account: a) how different types of information might influence choice in different stages of the process; and b) how interactions and the heterogeneity between circuits across different brain areas might be essential for the process. In this dissertation, I present a combination of experimental and modeling approaches to study distributed nature of the decision-making by examining both the distributed processing of information as well as the interaction between and heterogeneity of circuits across different brain areas. First, in a value-based perceptual decision-making task in humans, we studied the stages within the decision-making processes in which reward and sensory information exert their influences on the process. We used behavioral analyses and modeling to show that, in contrast to sensory information, reward information does not influence early stages of the decision making. Instead, it exerts its influence in the later stages of the process by biasing response towards the choice option with higher expected reward. Second, we re-examined data from microstimulation of the Frontal Eye Field (FEF) in monkeys during a value-based decision-making task to study the contribution of interactions within oculomotor system to choice behavior. Using different models that can account for interaction between circuits, we found that the brain areas within oculomotor system use reward information to prevent global changes to behavior in presence of perturbations in the FEF. Based on these findings, we developed new biologically plausible decision-making models that can account for the distributed nature of decision making by considering interactions and heterogeneity between circuits across different brain areas. The simulation results highlight the critical roles of heterogeneity and distributed processing in generating robust and stable behavior and enhanced sensitivity to the sensory information