Generalised verification of the observer property in discrete event systems

The observer property is an important condition to be satisfied by abstractions of Discrete Event Systems (DES) models. This paper presents a generalised version of a previous algorithm which tests if an abstraction of a DES obtained through natural projection has the observer property. The procedure called OP-verifier II overcomes the limitations of the previously proposed verifier while keeping its computational complexity. Results are illustrated by a case study of a transfer line system

Generalised verification of the observer property in discrete event systems

The observer property is an important condition to be satisfied by abstractions of Discrete Event Systems (DES) models. This paper presents a generalised version of a previous algorithm which tests if an abstraction of a DES obtained through natural projection has the observer property. The procedure called OP-verifier II overcomes the limitations of the previously proposed verifier while keeping its computational complexity. Results are illustrated by a case study of a transfer line system

Evidence-based recommendation on toothpaste use

Toothpaste can be used as a vehicle for substances to improve the oral health of individuals and populations. Therefore, it should be recommended based on the best scientific evidence available, and not on the opinion of authorities or specialists. Fluoride is the most important therapeutic substance used in toothpastes, adding to the effect of mechanical toothbrushing on dental caries control. The use of fluoride toothpaste to reduce caries in children and adults is strongly based on evidence, and is dependent on the concentration (minimum of 1000 ppm F) and frequency of fluoride toothpaste use (2×/day or higher). The risk of dental fluorosis due to toothpaste ingestion by children has been overestimated, since there is no evidence that: 1) fluoride toothpaste use should be postponed until the age of 3-4 or older, 2) low-fluoride toothpaste avoids fluorosis and 3) fluorosis has a detrimental effect on the quality of life of individuals exposed to fluoridated water and toothpaste. Among other therapeutic substances used in toothpastes, there is evidence that triclosan/copolymer reduce dental biofilm, gingivitis, periodontitis, calculus and halitosis, and that toothpastes containing stannous fluoride reduce biofilm and gingivitis.Toothpaste can be used as a vehicle for substances to improve the oral health of individuals and populations. Therefore, it should be recommended based on the best scientific evidence available, and not on the opinion of authorities or specialists. Fluoride is the most important therapeutic substance used in toothpastes, adding to the effect of mechanical toothbrushing on dental caries control. The use of fluoride toothpaste to reduce caries in children and adults is strongly based on evidence, and is dependent on the concentration (minimum of 1000 ppm F) and frequency of fluoride toothpaste use (2×/day or higher). The risk of dental fluorosis due to toothpaste ingestion by children has been overestimated, since there is no evidence that: 1) fluoride toothpaste use should be postponed until the age of 3-4 or older, 2) low-fluoride toothpaste avoids fluorosis and 3) fluorosis has a detrimental effect on the quality of life of individuals exposed to fluoridated water and toothpaste. Among other therapeutic substances used in toothpastes, there is evidence that triclosan/copolymer reduce dental biofilm, gingivitis, periodontitis, calculus and halitosis, and that toothpastes containing stannous fluoride reduce biofilm and gingivitis28111

Effect of saccharin on antibacterial activity of chlorhexidine gel

Although chlorhexidine is the most effective agent against dental plaque it is extremely bitter. To prepare formulations, it is necessary to use flavoring and sweetening, which can inhibit the antibacterial effect of chlorhexidine. Saccharin has been considered a compatible substance to use in chlorhexidine rinse or gel preparations; however, the effect of a range of concentrations has not been studied. To evaluate the effect of different concentrations of saccharin on the antibacterial activity of chlorhexidine gel, hydroxy-ethyl-cellulose gels containing 1.0% chlorhexidine digluconate and 0.0 to 1.0% sodium saccharin were prepared. Activity against Streptococcus mutans was evaluated using the agar diffusion method and determination of MIC values. The inhibitory zones of growth were 7.83 +/- 0.54 mm when no saccharin was added to the chlorhexidine gel and 7.75 +/- 0.50, 7.63 +/- 0.48, 6.21 +/- 0.40, 4.13 +/- 0.38, when the concentrations of saccharin in the gels were 0.02, 0.10, 0.5, and 1.0%, respectively. The range of MIC values was 1-2 micrograms/ml, with saccharin concentrations of 0%, 0.02, and 0.1%. In contrast, the MIC values were 4-8 and 8-16 micrograms/ml with saccharin concentrations of 0.5% and 1.0%, respectively. The paired "t" test showed that 0.5 and 1.0% sodium saccharin inhibit the antibacterial activity of 1% digluconate chlorhexidine gel. These in vitro results suggest that saccharin may inhibit the efficacy of chlorhexidine against mutans streptococci, depending on the concentration.Although chlorhexidine is the most effective agent against dental plaque it is extremely bitter. To prepare formulations, it is necessary to use flavoring and sweetening, which can inhibit the antibacterial effect of chlorhexidine. Saccharin has been considered a compatible substance to use in chlorhexidine rinse or gel preparations; however, the effect of a range of concentrations has not been studied. To evaluate the effect of different concentrations of saccharin on the antibacterial activity of chlorhexidine gel, hydroxy-ethyl-cellulose gels containing 1.0% chlorhexidine digluconate and 0.0 to 1.0% sodium saccharin were prepared. Activity against Streptococcus mutans was evaluated using the agar diffusion method and determination of MIC values. The inhibitory zones of growth were 7.83 +/- 0.54 mm when no saccharin was added to the chlorhexidine gel and 7.75 +/- 0.50, 7.63 +/- 0.48, 6.21 +/- 0.40, 4.13 +/- 0.38, when the concentrations of saccharin in the gels were 0.02, 0.10, 0.5, and 1.0%, respectively. The range of MIC values was 1-2 micrograms/ml, with saccharin concentrations of 0%, 0.02, and 0.1%. In contrast, the MIC values were 4-8 and 8-16 micrograms/ml with saccharin concentrations of 0.5% and 1.0%, respectively. The paired "t" test showed that 0.5 and 1.0% sodium saccharin inhibit the antibacterial activity of 1% digluconate chlorhexidine gel. These in vitro results suggest that saccharin may inhibit the efficacy of chlorhexidine against mutans streptococci, depending on the concentration1112934Embora clorexidina seja reconhecida como o agente antimicrobiano mais eficiente contra placa dental, seu gosto extremamente amargo é uma limitação nos preparos farmacêuticos. Substâncias adoçantes e flavorizantes usadas para preparar formulações podem inibir a atividade antibacteriana da clorexidina. Sacarina tem sido considerada uma substância compatível para ser usada em enxaguatórios bucais ou géis, entretanto o efeito da concentração deste adoçante não tem sido estudado. A atividade antibacteriana de géis de clorexidina a 1%, contendo sacarina de 0,0 a 1,0%, foi avaliada a partir de preparações farmacêuticas formuladas. Atividade contra Streptococcus mutans foi avaliada através da inibição do crescimento em ágar e determinação da concentração inibitória mínima (CIM). Os halos de inibição de crescimento foram de 7,83 ± 0,54 mm, na ausência de sacarina, e de 7,75 ± 0,50, 7,63 ± 0,48, 6,21 ± 0,40 e 4,13 ± 0,38 quando da presença de sacarina a 0,02, 0,10, 0,5 e 1%, respectivamente, nos géis de clorexidina a 1%. A faixa de CIM foi de 1-2 µg/ml quando da presença de 0,0, 0,02 e 0,1% de sacarina nos géis. Quando o gel de clorexidina a 1% continha sacarina a 0,5 e 1% a CIM foi de 4-8 e 8-16 µg/ml, respectivamente. Teste "t" pareado mostrou que sacarina sódica nas concentrações de 0,5 e 1% inibiu a atividade anti mutans de digluconato de clorexidina a 1% em gel. Estes resultados in vitro sugerem que sacarina pode inibir a eficácia de clorexidina contra streptococcus do grupo mutans, dependendo da concentração usad

Verification of the observer property in discrete event systems

The observer property is an important condition to be satisfied by abstractions of Discrete Event System (DES) models. This technical note presents a new algorithm that tests if an abstraction of a DES obtained through natural projection has the observer property. The procedure, called OP-Verifier, can be applied to (potentially nondeterministic) automata, with no restriction on the existence of cycles of 'non-relevant' events. This procedure has quadratic complexity in the number of states. The performance of the algorithm is illustrated by a set of experiments

SIMULATIONS OF FISHING EFFECTS ON THE SOUTHERN BENGUELA FISH COMMUNITY USING AN INDIVIDUAL-BASED MODEL: LEARNING FROM A COMPARISON WITH ECOSIM

By applying an individual-based model (OSMOSE) to the southern Benguela ecosystem, a multispecies analysis is proposed, complementary to that provided by the application of ECOPATH/ECOSIM models. To reconstruct marine foodwebs, OSMOSE is based on the hypothesis that predation is a size-structured process. In all, 12 fish species, chosen for their importance in terms of biomass and catches, are explicitly modelled. Growth, reproduction and mortality parameters are required to model their dynamics and trophic interactions. Maps of mean spatial distribution of the species are compiled from published literature. Taking into account the spatial component is necessary because spatial co-occurrence determines potential interactions between predatory fish and prey fish of suitable size. To explore ecosystem effects of fishing, different fishing scenarios, previously examined using ECOSIM, are simulated using the OSMOSE model. They explore the effects of targeting fish species in the southern Benguela considered to be predators (Cape hake Merluccius capensis and M. paradoxus) or prey (anchovy Engraulis encrasicolus, sardine Sardinops sagax, round herring Etrumeus whiteheadi). Simulation results are compared and are generally consistent with those obtained using an ECOSIM model. This cross-validation appears to be a promising means of evaluating the robustness of model outputs, when separate validation of marine ecosystem models are still difficult to perform.Afr. J. mar. Sci. 26: 95–11

Safeguarding, Integrating and Disseminating Knowledge on Exploited Marine Ecosystems: the Ecoscope

no abstrac

Fluoride Dentifrice Overcomes the Lower Resistance of Fluorotic Enamel to Demineralization

We evaluated if the low resistance of fluorotic enamel to demineralization could be overcome by fluoride dentifrice (FD) treatment. Paired enamel slabs of sound and fluorotic enamel (n = 20/group) from human teeth presenting Thylstrup and Fejerskov index (TF) scores from 0 to 4 were obtained. Half of the anatomic surface of the enamel slabs was isolated and used as a control (baseline) regarding enamel mineralization and fluoride concentration. The slabs were submitted to a pH-cycling model simulating a high cariogenic challenge, and 2×/day they were treated with placebo dentifrice (PD) or FD (1,100 µg F/g, as NaF). After 10 days, the slabs were cut into two halves. Enamel demineralization was evaluated by cross-sectional microhardness in one half, and the fluoride formed (FF) concentration was determined in the other half. For statistical analysis, the data on net demineralization area (ΔΔS) and FF (µg F/g) were grouped into TF0, TF1–2, and TF3–4, and analyzed by two-way ANOVA followed by Tukey’s test (α = 5%). The factors studied were TF (0, 1–2, and 3–4) and dentifrice treatment (PD or FD). The effect of the factors was statistically significant for ΔΔS and FF (p TF1–2 > TF0 (p 0.05) when FD was used. Regarding FF, the groups treated with PD did not differ (p > 0.05), but the greatest (p < 0.05) FF concentration was found in group TF3–4 treated with FD. These findings suggest that the higher susceptibility of fluorotic enamel to demineralization lesions is decreased by the use of FD