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Abstract: A theoretical study of structural, electronic, linear and nonlinear optical properties of ZnIn2Te4 defect-chalcopyrite is presented using the full-potential linearized augmented plane-wave (FP-LAPW) method. The exchange and correlation potential is treated by the generalized-gradient approximation (GGA). Moreover, the Engel and Vosko GGA formalism (EV-GGA) is also used to improve the band gap results. The lattice parameters ( a , c ) and the atomic positions (x, y and z) are optimized and found in good agreements with the available experimental data. Our calculations performed for band structure and density of state show that the valence band maximum (VBM) and conduction band minimum (CBM) are located at Γ resulting in a direct energy gap of about 0.89eV for GGA and 1.20eV for EV-GGA. The linear optical properties namely, the real and imaginary parts of the dielectric function and the reflectivity spectrum are calculated. This compound possesses a considerable negative birefringence. Based on the density functional theory the nonlinear optical properties are calculated and their spectra are analyzed. [ABSTRACT FROM AUTHOR]

Background: Social media can be part of the formal education of health professsionals and in their lifelong learning activities. The effectiveness of Facebook, an online social medium, application for educational purposes was evaluated in this study. It was used to serve as a teaching medium of a course in medical emergencies in dental practice (MEDP)., Methods: Syrian dental students were invited to join a Facebook group "Medical emergencies in dental practice" during the second semester of the academic year 2013-2014. The group privacy settings were changed from an open group to a closed group after the registration period. Administrators of the group published 61 posts during the course period, which extended for one month. Students' progress in learning was evaluated using self-assessment questionnaires administered to the students before and after the course. These questionnaires also queried their opinions regarding the use of Facebook as an educational modality. Qualitative statistics, Wilcoxon signed ranks and Mann-Whitney U-tests were used to analyze the data., Results: Out of 388 students registered in this course, 184 completed it. Two-third of students agreed that Facebook was useful in education. Their impressions of this course were 17.4% as excellent, 52.2% as very good. P values of the self-assessment questions of Wilcoxon signed ranks test were <0.001, indicating self-assessed improvement in MEDP skills., Discussion: Facebook as a social medium provides a unique learning environment. It allows students to discuss topics more openly in a flexible setting with less rigid time and place constraints. In the light of this study it was found that Facebook may be useful in teaching medical emergencies in dental practice in its theoretical aspect.