Differential inclusions and robust control theory

Uncontrolled systems (x) over dot is an element of Ax, where A is a non-empty compact set of matrices, and controlled systems (x) over dot is an element of Ax + Bu are considered. Higher-order systems 0 is an element of Px - Du, where and are sets of differential polynomials, are also studied. It is shown that, under natural conditions commonly occurring in robust control theory, with some mild additional restrictions, asymptotic stability of differential inclusions is guaranteed. The main results are variants of small-gain theorems and the principal technique used is the Krasnosel'skii-Pokrovskii principle of absence of bounded solutions.

Dental Erosion in a Group of 12- and 16-year-old Brazilian Schoolchildren

Purpose: This study`s purpose was to assess the prevalence of dental erosion in adolescents and to investigate the association between erosion and sociodemographic characteristics. Methods: This study consisted of a single center cluster random sample of 414 adolescents (12 and 16 years old) of both genders from private and public schools in Bauru, Sao Paulo, Brazil. Two previously calibrated examiners (kappa=0.85) used the O`Brien (7994) index for assessment of dental erosion on the buccal and palatal surfaces of the permanent maxillary incisors and on the occlusal surfaces of the permanent first molars. Data on gender, type of school, and mean family income were collected by a questionnaire completed by the adolescents. Descriptive statistics were applied to the data, and the associations between erosion and sociodemographic variables were investigated by chi-square test (P<0.05). Results: The prevalence of dental erosion was 20% (N=83), with only enamel being involved (score 1). The labial surface was the most affected (16%). There were no significant differences between the presence of erosion and gender, type of school, and mean family income. Conclusions: The results indicate that dental erosion restricted to enamel was observed among adolescents in Bauru/Brazil, and there was no correlation between this condition and sociodemographic factors. (Pediatr Dent 201733:23-8) Received August 7, 2009 1 Last Revision October 13, 2009 I Accepted October 14, 2009

The efficacy of a highly concentrated fluoride dentifrice on bovine enamel subjected to erosion and abrasion

Background. Researchers have proposed the use of fluoride for the prevention of enamel wear; however, only limited information is available about the impact of fluoridated dentifrices. Because tooth wear is a well-recognized dental problem, the authors conducted an in situ, ex vivo study to assess the efficacy of a highly concentrated fluoride dentifrice on bovine enamel subjected to erosion and abrasion. Methods. The authors conducted a double-blind, crossover in situ study consisting of three phases (seven days each). In each phase, the authors tested one of the dentifrices (5,000 parts per million fluoride [F]; 1,100 ppm F; no F). They performed erosive challenges with the use of cola drink (60 seconds, four times per day) and abrasive challenges via toothbrushing (30 seconds, four times per day). The authors determined the enamel loss via profilometry. Results. The authors tested the data by using two-way analysis of variance (P <.05). For the erosion-plus-abrasion condition, the study results showed that enamel wear was significantly higher than that with erosion alone. The findings showed no significant differences between the dentifrices regarding enamel wear. Conclusions. Within the in situ, ex vivo conditions of this study, the authors concluded that the highly concentrated fluoride dentifrice did not have a protective effect on enamel against erosion and erosion plus toothbrushing abrasion. Clinical Implications. Patients at risk of developing enamel erosion should benefit from preventive measures other than fluoride dentifrice, because even a highly concentrated fluoride dentifrice does not appear to prevent enamel erosion.

Protective effect of different tetrafluorides on erosion of pellicle-free and pellicle-covered enamel and dentine

The aim was to analyze the protective effects of titanium, zirconium and hafnium tetrafluorides on erosion of pellicle-free and pellicle-covered enamel and dentine in vitro. Eight groups of 20 specimens each of bovine enamel and bovine dentine were prepared. Half the specimens in each group were immersed in human saliva for 2 h for pellicle formation. Specimens were then left untreated (controls) or were treated for 120 s with TiF(4), ZrF(4) or HfF(4) solutions (0.4 or 1%) or 1.25% AmF/NaF gel. All specimens were eroded by exposure to hydrochloric acid, pH 2.6, for 25 min. Cumulative calcium release into the acid was monitored in consecutive 30-second intervals for 5 min, then at 2-min intervals up to a total erosion time of 25 min using the Arsenazo III procedure. Data were analyzed by ANOVA. 1% TiF(4) solution offered the best protective effect, especially in dentine (reduction of calcium loss about 50% at 25 min). 1% ZrF 4, 1% HfF 4 and 0.4% TiF(4) also reduced calcium loss, but to a lesser extent. Long-term effects were limited to dentine, while reduction of enamel erosion (about 25%) was restricted to 1-min erosion. The fluoride gel had a protective effect only in dentine. The efficacy of the tetrafluorides was influenced by the presence of the pellicle layer, in that the protection against dentine erosion by TiF(4) and ZrF(4) was greater on pellicle-covered specimens. Tetrafluoride solutions, especially 1% TiF(4), could decrease dental erosion, but were more effective on dentine than on enamel. Copyright (C) 2008 S. Karger AG, Basel.

Brain monoaminergic neurons and ventilatory control in vertebrates

Monoamines (noradrenaline (NA), adrenaline (AD), dopamine (DA) and serotonin (5-HT) are key neurotransmitters that are implicated in multiple physiological and pathological brain mechanisms, including control of respiration. The monoaminergic system is known to be widely distributed in the animal kingdom, which indicates a considerable degree of phylogenetic conservation of this system amongst vertebrates. Substantial progress has been made in uncovering the participation of the brain monoamines in the breathing regulation of mammals, since they are involved in the maturation of the respiratory network as well as in the modulation of its intrinsic and synaptic properties. On the other hand, for the non-mammalian vertebrates, most of the knowledge of central monoaminergic modulation in respiratory control, which is actually very little, has emerged from studies using anuran amphibians. This article reviews the available data on the role of brain monoaminergic systems in the control of ventilation in terrestrial vertebrates. Emphasis is given to the comparative aspects of the brain noradrenergic, adrenergic, dopaminergic and serotonergic neuronal groups in breathing regulation, after first briefly considering the distribution of monoaminergic neurons in the vertebrate brain. (C) 2008 Elsevier B.V. All rights reserved.

Body size and ovarian cancer: case-control study and systematic review (Australia)

Objective: Although increased body mass is an established risk factor for a variety of cancers, its relation with cancer of the ovary is unclear. We therefore investigated the association between measures of body mass index (BMI) and ovarian cancer risk. Methods: Data from an Australian case-control study of 775 ovarian cancer cases and 846 controls were used to examine the association with BMI. We have also summarized the results from a number of other studies that have examined this association. Results: There was a significant increased risk of ovarian cancer with increasing BMI, with women in the top 15% of the BMI range having an odds ratio (OR) of 1.9 (95% confidence interval (CI), 1.3-2.6) compared with those in the middle 30%. Stratifying by physical activity showed a stronger effect among inactive women (OR = 3.0, 95% CI 1.3-6.9). The overall effect was consistent with the findings of most prior population-based case-control studies, while cohort studies reported positive effects closer to the null. Hospital-based studies gave variable results. Conclusions: Taken together, the evidence is in favor of a small to moderate positive relation between high BMI and occurrence of ovarian cancer.

Potential effect of sodium bicarbonate-containing dentifrice in controlling enamel erosion in situ

Purpose: To assess, by a crossover 2 x 2 in situ study, the speculated protective role of a sodium bicarbonate-containing toothpaste in controlling erosive lesions. Methods: Bovine enamel slabs were sterilized, and submitted to baseline Knoop microhardness measurements. After a 3-day lead-in period, 14 volunteers wore palatal acrylic appliances containing six enamel slabs (three on each side), for 4 consecutive days. On the first day, appliances with contained specimens were placed in the oral cavity to allow salivary pellicle formation. On the subsequent days, half of the enamel slabs were immersed extraorally in a lemonade-like soft drink for 90 seconds, twice daily. On both of these occasions, the appliance was dipped in toothpaste slurry of either a sodium bicarbonate-containing toothpaste or a regular counterpart for 60 seconds. Following a 3-day washout period, a new set of enamel slabs were mounted and the volunteers started the second period using the alternate dentifrice. Results: ANOVA (alpha = 0.05) showed no statistically significant difference between enamel treated with regular and sodium bicarbonate-based dentifrices, regardless of whether specimens were eroded or not (P=0.8430). Acid-challenged specimens revealed lower microhardness values than uneroded samples. (Am J Dent 2008;21:300-302).

The effect of musculoskeletal pain on motor activity and control

Aberrant movement patterns and postures are obvious to clinicians managing patients with musculoskeletal pain. However, some changes in motor function that occur in the presence of pain are less apparent. Clinical and basic science investigations have provided evidence of the effects of nociception on aspects of motor function. Both increases and decreases in muscle activity have been shown, along with alterations in neuronal control mechanisms, proprioception, and local muscle morphology. Various models have been proposed in an attempt to provide an explanation for some of these changes. These include the vicious cycle and pain adaptation models. Recent research has seen the emergence of a new model in which patterns of muscle activation and recruitment are altered in the presence of pain (neuromuscular activation model). These changes seem to particularly affect the ability of muscles to perform synergistic functions related to maintaining joint stability and control. These changes are believed to persist into the period of chronicity. This review shows current knowledge of the effect of musculoskeletal pain on the motor system and presents the various proposed models, in addition to other shown effects not covered by these models. The relevance of these models to both acute and chronic pain is considered. It is apparent that people experiencing musculoskeletal pain exhibit complex motor responses that may show some variation with the time course of the disorder. (C) 2001 by the American Pain Society.

Control of the cystic fibrosis transmembrane conductance regulator by alpha G(i) and RGS proteins

The cystic fibrosis transmembrane conductance regulator (CFTR) has been shown previously to be regulated by inhibitory G proteins. In the present study, we demonstrate inhibition of CFTR by alphaG(i2) and alphaG(i1), but not alphaG(0), in Xenopus oocytes. We further examined whether regulators of G protein signaling (RGS) proteins interfere with alphaG(i)-dependent inhibition of CFTR. Activation of CFTR by IBMX and forskolin was attenuated in the presence of alphaG(i2), indicating inhibition of CFTR by alphaG(i2) in Xenopus oocytes. Coexpression of the proteins RGS3 and RGS7 together with CFTR and alphaG(i2) partially recovered activation by IBMX/forskolin. 14-3-3, a protein that is known to interfere with RGS proteins, counteracted the effects of RGS3. These data demonstrate the regulation of CFTR by alphaG(i) in Xenopus oocytes. Because RGS proteins interfere with the G protein-dependent regulation of CFTR, this may offer new potential pathways for pharmacological intervention in cystic fibrosis. (C) 2001 Academic Press.

Opportunities for the control of coronary heart disease in Australia

Objective: To estimate the number of coronary events that could be prevented in Australia each year by the use of preventive and therapeutic strategies targeted to subgroups of the population based on their levels of risk and need. Methods: Estimates of risk reduction from the published literature, prevalence estimates of elevated risk factor levels from the 1995 National Health Survey and treatment levels from the Australian collaborating centres in the World Health Organization's MONICA Project were used to calculate numbers of coronary events preventable among men and women aged 35-79 years in Australia. Results: Approximately 14,000 coronary events could be avoided each year if the mean level of cholesterol in the population was reduced by 0.5 mmol/L, smoking prevalence was halved and prevalence of physical inactivity was reduced to 25%. This represents a reduction in coronary events of about 40%. Even with less optimistic targets, a reduction of 20% could be attained, while the achievement of some internationally recommended targets could lead to almost 50% reduction. In the short term, aggressive medical treatment of people with elevated levels of risk factors and established coronary disease offers the greatest opportunity for reducing coronary events. Conclusion: A comprehensive approach to reduce levels of behavioural and biological risk factors and improve the use of effective treatment could lead to a large reduction in coronary event rates. In the long term, primary prevention - especially to reduce smoking, lower cholesterol levels and increase exercise - has the potential to reduce the population levels of risk and hence contain the national cost of coronary disease.

Increasing the response rate to a mailed questionnaire by including more stamps on the return envelope: A cotwin control study

Twins taking part in two unrelated studies were sent a questionnaire together with a self-addressed envelope that either carried one or multiple (up to 5) stamps to the same value. The unprompted proportion of questionnaires returned (before commencement of telephone reminder calls) was increased from 62% to 71% in one study, and from 43% to 52% in the other study (test for common odds ratio in studies, p = 0.04).