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We developed a new GaN on SiC growth method by metalorganic vapour phase epitaxy (MOVPE) using of a single 2-dimension-growth step. Prior to epitaxy, to inhibit pre-reaction of Si-face SiC substrate with TMGa and NH3, TMAl was flowed without NH3. 1.5 μm of undoped crack-free GaN was grown on 6H-SiC (Si-face). Without buffer layer, the vertical resistance of GaN/SiC structure was found to be around 82.1Ω as determined by I-V characteristic. Further reduction in vertical resistance is expected by growth of n-GaN (1.5μm)/SiC structure (300μm). We also expect a SiC-based GaN heterostructure vertical FET will achieve high power and high switching speed performance.
Boron nitride nanotube (BNNT)/polystyrene (PS) composite films were fabricated for the first time using high-quality BNNTs synthesized via a chemical-vapor-deposition method. The composite films exhibited good transparency. Tensile tests indicated that the elastic modulus of the films was increased by ∼21% when a ∼1 wt% soluble BNNT fraction was in use. Dispersion of BNNTs in PS and interfacial interactions between them were investigated using transmission electron microscopy. The film thermal properties, such as stability to oxidation and glass transition temperatures were measured. The experimental results and simple theoretical estimates indicate that BNNTs is a promising additive material for polymeric composites.
Forty-seven mucocoeles of the ethmoid and/or sphenoid sinuses (33 males, 14 females) were operated on during the 10-years period from 1980 through 1989. Thirty-seven cases were post-operative mucocoele, while the remaining 10 were so-called primary mucocoeles. None of the cases had a history of facial trauma. In the majority of post-operative cases, the mucocoele develops 15–24 years after initial surgery. Paranasal sinus surgery in young patients (teenagers) may lead to a mucocoele due to post-operative scarring in the surgical wound. The principal symptoms include globe displacement, double vision, headache, deep orbital pain, a mass in the supero-medial quadrant of the orbit, visual disturbance, etc. Sufficient opening of the mucocoele wall by the endonasal approach is recommended for surgical treatment of ethmoidal and sphenoidal mucocoeles
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