Synthesis and characterization of zinc oxide nanostructures / Khalifa bin Said bin Zahran Al-Azri

The growth mechanism, morphology, structure and optical properties of the ZnO nanostructures grown on bare and gold-coated silicon substrates using carbothermal reaction at atmospheric pressure were investigated under different growth conditions. The ZnO nanostructures formed were studied as a function of substrate location, furnace temperature, Ar gas flow rate, deposition time and ZnO powder to carbon powder mass ratio. The morphology and structure of the samples were characterized using the fieldemission scanning electron microscopy (FESEM), energy dispersive x-ray spectroscopy(EDX) spectrum, x-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM). It was found that in both silicon and gold-coated silicon substrates, the morphology of the ZnO nanostructures was strongly dependent on the location of the substrate from the Zn source and to the furnace temperature. On the other hand, deposition time, gas flow rate and the different ratios of reactant materials played an important role in changing the size of ZnO nanostructures. The density of the ZnO nanostructures grown with Au catalyst was much higher than that of ZnO nanostructures without catalyst. XRD result shows that the ZnO nanostructures grown without catalyst have a better preferential orientation along the [002] orientation than that grown with gold catalyst. The ZnO nanostructures grown with and without Au catalyst can be attributed to the vapor-liquid-solid (VLS) model and self-catalytic (VLS) processes, respectively. ii PL spectrum of ZnO nanostructures grown with Au catalyst exhibited a strong defect-related deep-level emission. It demonstrated that the ZnO nanostructures grown with Au catalyst were more defective that grown on bare silicon substrate. It has been found that there is a strong relationship between the furnace temperature and the emission peak. PL study shows that the green emission band peak, which is mainly due to defects in ZnO, can be lowered by increasing the furnace temperature and the best temperature for the removing defects in ZnO nanostructures was found to be 1200°C. Moreover, the post annealed of grown sample at the air atmosphere was also found to reduce the green emission, hence low growth defects. ZnO nanostructures doped with phosphorus have been successfully synthesized. It was found that P incorporation has caused more defects in the ZnO nanostructures, which was confirmed by XRD and PL analysis. While, FESEM results showed that the doping process caused structural change in the ZnO shape from nanowires to nanoballs

Syncopal Attacks and Severe Abdominal Pain

A 54 years old male, chronic smoker, hypertensive on beta blocker presented to the emergency room with a history of syncopal attacks from early morning followed by severe abdominal and back pain lasting for four hours. There was no history of trauma, fever or change in bowel habits

Port Site Herniation of the Small Bowel following Laparoscopic-Myomectomy: A case report

Bowel herniation, through fascial defects secondary to laparoscopic surgery at the site of trocar entry, is a rare, but potentially serious, complication. Closure of the fascia at port sites measuring 10mm or more has been highly recommended to avoid such complications. We report a case of a small bowel which herniated and strangulated through the port site immediately after laparoscopic myomectomy. Resection of the strangulated bowel with primary anastomosis was required to manage this complication. We present this case report with literature review to discuss the risk factors and the methods to prevent such a complication post laparoscopic surgery

Direct growth and photoluminescence of silicon nanowires without catalyst

AbstractOne-dimensional (1D) silicon nanowires (SiNWs) were fabricated on catalyst free Si (100) substrate using a thermal evaporation method. Based on SVLS growth mechanism, the obtained SiNWs were 30 to 265nm in diameter and 1.7μm to several tens of microns in length. It was found that the presence of graphite powder only is enough to accomplish growth. A systematic study of how the growth conditions, such as the Ar carrier gas flow rate, and the growth time was performed. There are five resultant PL peaks: two blue emission peaks 465nm (2.67eV) and 482nm (2.57eV) and two green bands centered at 502nm (2.47eV) and 526nm (2.36eV) and one ultraviolet emission peak at 350nm (3.54eV). The theory behind these emissions was discussed