World radiocommunication conference 12 : implications for the spectrum eco-system

Spectrum allocation is once more a key issue facing the global telecommunications industry. Largely overlooked in current debates, however, is the World Radiocommunication Conference (WRC). Decisions taken by WRC shape the future roadmap of the telecommunications industry, not least because it has the ability to shape the global spectrum allocation framework. In the debates of WRC-12 it is possible to identify three main issues: enhancement of the international spectrum regulatory framework, regulatory measures required to introduce Cognitive Radio Systems (CRS) technologies; and, additional spectrum allocation to mobile service. WRC-12 eventually decided not to change the current international radio regulations with regard to the first two issues and agreed to the third issue. The main implications of WRC-12 on the spectrum ecosystem are that most of actors are not in support of the concept of spectrum flexibility associated with trading and that the concept of spectrum open access is not under consideration. This is explained by the observation that spectrum trading and spectrum commons weaken state control over spectrum and challenge the main principles and norms of the international spectrum management regime. In addition, the mobile allocation issue has shown the lack of conformity with the main rules of the regime: regional spectrum allocation in the International Telecommunication Union (ITU) three regions, and the resistance to the slow decision making procedures. In conclusion, while the rules and decision-making procedures of the international spectrum management regime were challenged in the WRC-12, the main principles and norms are still accepted by the majority of countries

Influence of sense of coherence on adolescents' self-perceived dental aesthetics:a cross-sectional study

Background Sense of coherence (SOC) is a psychosocial factor capable of influencing perception of health, improving one’s ability to manage life. It is the central construct of salutogenesis. SOC allows for identification and mobilization of resources to effectively manage or solve problems, promoting health and quality of life. Using Wilson-Cleary’s conceptual model we hypothesized that SOC might contribute to self-perception of dental aesthetics. The aim of this study was to investigate whether SOC levels were related to self-perception of dental aesthetics against assessed normative orthodontic treatment need among adolescents. Methods A cross-sectional study was conducted with 615 male and female adolescents aged 12 to 15 years. Data collection comprised socio-demographic and socio-economic characteristics, SOC (SOC 13), self-perceived dental aesthetics (Oral Aesthetic Subjective Impact Scale), and assessment of orthodontic treatment need (Dental Aesthetic Index). Statistical analysis involved Pearson’s chi-square test, Kruskal-Wallis test, Mann-Whitney test and multiple linear regression. Spearman’s correlation coefficient was calculated for the determination of the strength of correlations among the numerical variables. The level of significance was set at 5% (p < 0.05). Results 50.1% of the participants were classified as having a high SOC (≥ median). Overall, SOC was associated with self-perceived dental aesthetics (p = 0.048). In the adolescents with no orthodontic treatment need, those with a low SOC perceived their dental aesthetics more negatively than those with high levels of SOC. The multiple regression analysis demonstrated an inverse relationship between SOC and: 1) age (p = 0.007), SOC being higher in the younger age group; 2) self-perceived dental aesthetics (p = 0.001), a higher SOC being associated with those who had a positive dental self-perception. Conclusions SOC was associated with self-perceived dental aesthetics and adolescents with a high SOC were more likely to perceive their dental aesthetics more positively. SOC did not seem to influence self-perception of dental aesthetics in adolescents who were clinically assessed as having an orthodontic treatment need, however, in those where there was no orthodontic treatment need, a low SOC was associated with a negative self-perception of dental appearance

Microleakage of an adhesive system used as a fissure sealant

Aim: The aim of this study was to investigate the microleakage of pit and fissure sealants in primary teeth and to determine if multi-step methods should produce better results in terms of microleakage prevention. Methods and materials: A total of 40 intact primary molars were randomly assigned to one of four sealant groups: resin based sealant Ultraseal XT (US - Ultradent) (Group 1, n=10); adhesive system Scotchbond Multi Purpose Plus (SBMP - 3M/ESPE) used as a sealant (Group 2, n=10); primer (SBMP) and US (Group 3, n=10); and primer, bond (SBMP) and US (Group 4, n=10). After thermocycling (x700, 5-55 degrees C) all teeth surfaces were made impermeable with the exception of the occlusal surface. Samples were immersed in 50% silver nitrate for 8 hours, sectioned longitudinally with two cuts in the central fissure pit, and then immersed in photo development solution followed by 16 hours in fluorescent light. Pictures were obtained by light microscope (x40) and the degree of microleakage was evaluated by three blinded evaluators. The data were analyzed using the Kruskal Wallis test. Results: Significant statistical differences (p<.05) were observed between Groups 1-3, Groups 2-3, Groups 2-4, and Groups 3-4. Group 3 showed higher microleakage scores. Conclusion: The adhesive system and the resin based sealant demonstrated similar microleakage properties, suggesting the possibility that adhesives can be used in a clinical setting. Additionally, the increase in the number of clinical steps required by common application of resin based sealant, including use of primer or primer and bond, did not lead to better results in preventing microleakage. Clinical significance: The adhesive system can be used as a sealant without increasing the microleakage. Thus, the use of the adhesive system before the application of the sealant is not necessary to reduce the microleakage, although further research is warranted to support this conclusion

A transient beta oscillation occurs with high temporal regularity prior to stopping an ongoing movement

Beta (β) oscillations (~15-25 Hz) in the field potential are associated with immobility and stopping actions, but it is debated whether stopping involves a sustained increase in beta power or in the number of randomly timed ‘bursts’ (transient beta power increases). The role of β in movement control has been previously studied using the stop signal task, in which a cue instructs the subject to stop ongoing movement preparation. The time at which movement preparation stops is inferred from a ‘race’ model and provides an across-trial estimate of the movement preparation stop time. Thus, discrepancies about the role of β may be due to an inability to align brain activity with stopping on a trial-by-trial basis. Moreover, the causal role of β in stopping movements cannot be addressed without an observable stopping behavior. We used a new paradigm for head-fixed rats on a treadmill. The rats were trained to not run to a NoGo stimulus. On some trials, rats initiated a pre-potent running response but stopped before crossing a response threshold (distance) and returned to immobility. The peak velocity of these treadmill movements provides an unambiguous time when rats self-initiate stopping. We recorded 32-electrode EEG bilaterally over the entire cortex (39,366 trials, 306 sessions, 14 rats). Trial-averaged spectrograms centered on peak velocity revealed two distinct oscillations prior to stopping (9-12 Hz, α, and 15-25 Hz, β). Larger movements (and thus a greater need for stopping) were associated with greater α and β power prior to peak velocity. Moreover, α and β were apparent on more electrodes indicating greater spatial spread with greater need for stopping. These pre-stopping oscillations were observed globally and preceded initiation of stopping by 48 ms for β and 52 ms for α. Ongoing analyses are assessing Granger causality between EEG electrodes in the α and β bands and will report whether area 24a single unit spiking is phase locked to LFP oscillations prior to stopping. Our data show that, when field potentials can be aligned to overt acts of stopping, β power as well as α power are highly reliable predictors of the time of volitional stopping. JFDF and RAO are equal contributors and listed in alphabetical order