EEG-based single-channel authentication systems with optimum electrode placement for different mental activities

BACKGROUND

Electroencephalogram (EEG) signals of a brain contain a unique pattern for each person and the potential for biometric applications. Authentication and security is a very important issue in our life and brainwave-based authentication is an addition to biometric authentication systems, which has many advantages over others. In this paper, we study the performance of a single channel brainwave-based authentication systems and select optimum channels based on mental activities.

METHODS

In this study, we used a dataset with five mental activities with seven subjects (325 samples). The EEG based authentication system includes three pre-processing steps, feature extraction, and classification. Features for Subject Authentication, are obtained from discrete Fourier transform, discrete wavelet transform, autoregressive modeling, and entropy features. Then these features are classified using the Neural Network, Bayesian network and Support Vector Machine.

RESULTS

We achieved accuracy in the range of 97-98% mean accuracy with Neural Network classifier for single-channel authentication system with optimum electrode placement for mental activity. We also analyzed the authentication system independently from the type of mental activity and chose channel O₂ as the optimum channel with an accuracy of 95%.

CONCLUSIONS

Channel optimization can obtain higher performance by reducing the number of EEG channels and defined the optimum electrode placement for different mental activities.

Association between breakfast intake with anthropometric measurements, blood pressure and food consumption behaviors among Iranian children and adolescents: the CASPIAN-IV study

OBJECTIVE

The aim of this study is to assess the association between breakfast intake with anthropometric measurements and blood pressure among Iranian children and adolescents. The second goal is to investigate the correction of breakfast consumption with other food consumption behaviors.

RESEARCH METHODS & PROCEDURES

In this national survey, 13,486 children and adolescents, aged 6-18 years, were selected by multistage, cluster sampling method from rural and urban areas of 31 provinces of Iran (2011-2012). Physical measurements included height, weight, waist circumference, and blood pressure. Food habits were assessed by self-reported questionnaire. Breakfast frequency was defined as skippers (eating breakfast 0-2 days/week), semi-skippers (eating breakfast 3-4 days/week) and non-skippers (eating breakfast 5-7 days/week). The data were analyzed by the STATA package.

RESULTS

Of the participants, 18.9%, 13.2% and 67.9%, were breakfast skippers, semi-skippers and non-skippers respectively. The prevalence of overweight and obesity among breakfast skippers were higher than non-skippers counterparts (P-value < 0.001). The percentage rates of abdominal obesity among breakfast skippers and non-skippers group were 22.6% (CI 95%: 21-24.3) and 17.9% (CI 95%: 17-18.6), respectively. Blood pressure did not significantly differ between non-skippers students and breakfast skippers (P-value = 0.1). Non-skipping adolescents ate more fresh fruits, dried fruits, vegetables and drank milk more frequently compared with breakfast skipper; while the skippers showed a higher intake of salty snack, soft drinks, packed fruit juice and fast foods (all P-value < 0.001).

CONCLUSION

Regular breakfast consumption is significantly associated with lower body fatness and healthier dietary habits but that further study, using controlled intervention trials, is required to test whether this represents a causal relationship.

Dentin bond strength and degree of conversion evaluation of experimental self-etch adhesive systems

BACKGROUND

The aim of this study was to investigate the effect of different concentrations of 10-methacryloyloxydecyl dihydrogen phosphate (10-MDP) monomer in one-step self-etch experimental adhesives on dentinal microshear bond strength (µSBS), their degree of conversion and bonded micro structure.

MATERIAL AND METHODS

Composite resin cylinders (Clearfil AP-X) were bonded on human sound molar dentinal surfaces by using five experimental one-step self-etching adhesives (1-SEAs) containing 0% (E0), 5% (E5), 10% (E10), 15% (E15), 20% (E20) (by weight) 10-MDP monomer and Clearfil S3 Bond (CS3) as a control. After 24 hours, microshear bond strength was tested. The degree of conversion was also measured using Fourier transform infrared spectroscopy. Interfacial ultrastructure was observed under a scanning electron microscope in all the groups.

RESULTS

A higher microshear bond strength was observed with adhesives containing 10% and 15% 10-MDP in comparison to study groups (P<.05). Clearfil S3 Bond and 10% MDP had a significantly greater degree of conversion than other groups (P<.05).

CONCLUSIONS

The amount of functional monomer in 1-SEAs influences both the bonding performance and degree of conversion; 10% 10-MDP showed the best combination of bond strength and degree of conversion. Key words:Self-etch adhesives, 10-MDP, bond strength, degree of conversion.

Antioxidant agents and their effects on shear bond strength of bleached enamel

AIM

The goal of this study was to fnd a method to eliminate bond strength reduction after vital bleaching.

MATERIALS AND METHODS

Sixty fat surfaces of enamel central human incisors were prepared by diamond disks. In the frst group, the samples immediately bonded to the tooth after bleaching. For the second group, the bleached samples were treated by sodium ascorbate for 1 hours. In the third and fourth groups the treatment was down using a new antioxidant agent for 1 hour and 15 minutes respectively. For the ffth group no bleaching was done. Cylindrical composite resin (Z 100) with a Single Bond adhesive system was bonded to the enamel with a special metal mold. After thermocycling, the samples were loaded at a crosshead speed of 0.5 mm/min. The mode of failures was inspected by the Dino Lite microscope and the microstructure of the debonding surfaces was observed by SEM. Considering normal data, statistical analysis was conducted by ANOVA and Tukey tests (p = 0.05).

RESULTS

The fourth group had maximum (21.82), while the frst group had the least (9.0971) shear bond strength. The ANOVA test showed a signifcant difference among the fve groups (p = 0.0002). There was not any signifcant statistical difference between the three types of debonding (p = 0.165).

CONCLUSION

The usage of sodium ascorbate or sodium ascorbate with detergent after vital bleaching are effective methods for reducing the damaging effects of bleaching agents on the shear bond strength of composite resin restoration to enamel. CLINICAL SIGNIFCANCE: Using antioxidants is necessary post bleaching and before resin bonding.