Microstructural defect properties of InGaN/GaN blue light emitting diode structures

Cataloged from PDF version of article.In this paper, we study structural and morphological properties of metal-organic chemical vapour deposition-grown InGaN/GaN light emitting diode (LED) structures with different indium (In) content by means of high-resolution X-ray diffraction, atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR), photoluminescence (PL) and current-voltage characteristic (I-V). We have found out that the tilt and twist angles, lateral and vertical coherence lengths of mosaic blocks, grain size, screw and edge dislocation densities of GaN and InGaN layers, and surface roughness monotonically vary with In content. Mosaic defects obtained due to temperature using reciprocal lattice space map has revealed optimized growth temperature for active InGaN layer of MQW LED. It has been observed in this growth temperature that according to AFM result, LED structure has high crystal dimension, and is rough whereas according to PL and FTIR results, bandgap energy shifted to blue, and energy peak half-width decreased at high values. According to I-V measurements, it was observed that LED reacted against light at optimized temperature. In conclusion, we have seen that InGaN MQW structure's structural, optical and electrical results supported one another

Volume CXIV, Number 4, November 7, 1996

Objective: Turner syndrome (TS) is a chromosomal disorder caused by complete or partial X chromosome monosomy that manifests various clinical features depending on the karyotype and on the genetic background of affected girls. This study aimed to systematically investigate the key clinical features of TS in relationship to karyotype in a large pediatric Turkish patient population.Methods: Our retrospective study included 842 karyotype-proven TS patients aged 0-18 years who were evaluated in 35 different centers in Turkey in the years 2013-2014.Results: The most common karyotype was 45,X (50.7%), followed by 45,X/46,XX (10.8%), 46,X,i(Xq) (10.1%) and 45,X/46,X,i(Xq) (9.5%). Mean age at diagnosis was 10.2±4.4 years. The most common presenting complaints were short stature and delayed puberty. Among patients diagnosed before age one year, the ratio of karyotype 45,X was significantly higher than that of other karyotype groups. Cardiac defects (bicuspid aortic valve, coarctation of the aorta and aortic stenosis) were the most common congenital anomalies, occurring in 25% of the TS cases. This was followed by urinary system anomalies (horseshoe kidney, double collector duct system and renal rotation) detected in 16.3%. Hashimoto's thyroiditis was found in 11.1% of patients, gastrointestinal abnormalities in 8.9%, ear nose and throat problems in 22.6%, dermatologic problems in 21.8% and osteoporosis in 15.3%. Learning difficulties and/or psychosocial problems were encountered in 39.1%. Insulin resistance and impaired fasting glucose were detected in 3.4% and 2.2%, respectively. Dyslipidemia prevalence was 11.4%.Conclusion: This comprehensive study systematically evaluated the largest group of karyotype-proven TS girls to date. The karyotype distribution, congenital anomaly and comorbidity profile closely parallel that from other countries and support the need for close medical surveillance of these complex patients throughout their lifespa

Should forensic autopsies be a source for medical education? A preliminary study

Practical anatomy sessions including dissection of cadavers are essential for anatomy courses. There are many difficulties in obtaining cadavers. In addition, hardened and discolored cadavers that are fixed with formaldehyde look unrealistic and generate apathy among students. Purpose: We considered that forensic autopsies may be used as ancillary and supportive practice in anatomy education. Methods: We invited the participation of Year 2 medical students in suitable forensic autopsy cases during the course of one year. Specialists of forensic medicine and anatomy provided theoretical support through talks in their specialized fields during the autopsy. At the end of the semester, feedback questionnaire forms were prepared and the students were asked to evaluate these sessions. Results: Forty students participated in the evaluation by completing the questionnaire. Students made positive statements about adequacy of the time of the application, consistency of the structures with theoretical and practical issues shown in anatomy lectures, and necessary explanations of the lecturers during and after the application. Conclusion: We think that forensic autopsies are an attractive supplementary educational model, and we have decided to continue the forensic autopsy practices. We believe that further studies on the evaluation of the sessions using a larger student population will lead to more conclusive results

Variations in the intracranial vertebrobasilar system

Aim The aim of our study was to demonstrate some possible variations in the vertebrobasilar system (VBS) in the Turkish population and to compare our results with the literature

Validation of New 2012 EULAR/ACR Classification Criteria for Polymyalgia Rheumatica: Comparison with the Previous Criteria in a Prospective Multi-Center Study

WOS: 000344384906005