DECAY FACTOR WITH EXPERIMENTAL VARIABLES IN TWO CIRCULATING FLUIDIZED BED (CFB) RISERS

The effects of the riser inlet velocity, solid mass flux and particle size on the axial solid holdup profile and decay factor were investigated using two circulating fluidized beds (CFBs) with FCC (Geldart A) particles as the bed materials. Based on the experimental results from the two-CFBs, the axial solid holdup in the two CFBs were compared with the correlations of previous studies. Also, an empirical correlation was proposed for decay factor that exhibited a good agreement with experimental data

Massive Concha Bullosa with Secondary Maxillary Sinusitis

Concha bullosa is a common anatomic variation of the middle turbinate; however, sinusitis secondary to the concha bullosa is rare. A 52-yr-old woman presented with nasal obstruction and posterior nasal drip. Computed tomography and examination of the nasal cavity revealed septal deviation on the left side, and a massive concha bullosa and maxillary sinusitis on the right side. The lateral lamella of the affected turbinate was removed and the inspissated material was drained. Histopathologic examination of the excised lesion in the concha bullosa revealed bacterial colonies in the mucus plug. We report here on a massive concha bullosa with secondary maxillary sinusitis

The effect of low temperature aging on the mechanical property & phase stability of Y-TZP ceramics

STATEMENT OF PROBLEM. Recently Yttrium-stabilized tetragonal zirconia polycrystal (Y-TZP) has been introduced due to superior flexural strength and fracture toughness compared to other dental ceramic systems. Although zirconia has outstanding mechanical properties, the phenomenon of decrease in the life-time of zirconia resulted from degradation in flexural strength after low temperature aging has been reported. PURPOSE. The objective of this study was to investigate degradation of flexural strength of Y-TZP ceramics after various low temperature aging treatments and to evaluate the phase stability and micro-structural change after aging by using X-ray diffraction analysis and a scanning electron microscope (SEM). MATERIAL AND METHODS. Y-TZP blocks of Vita In-Ceram YZ (Vita Zahnfabrik, Bad Sa ¨ckingen, Germany) were prepared in 40 mm (length) x 4 mm (width) x 3 mm (height) samples. Specimens were artificially aged in distilled water by heattreatment at a temperature of 75, 100, 125, 150, 175, 200, and 225℃ for 10 hours, in order to induce the phase transformation at the surface. To measure the mechanical property, the specimens were subjected to a four-point bending test using a universal testing machine (Instron model 3365; Instron, Canton, Mass, USA). In addition, X-ray diffraction analysis (DMAX 2500; Rigaku, Tokyo, Japan) and SEM (Hitachi s4700; Jeol Ltd, Tokyo, Japan) were performed to estimate the phase transformation. The statistical analysis was done using SAS 9.1.3 (SAS institute, USA). The flexural strength data of the experimental groups were analyzed by one-way analysis of variance and to detect statistically significant differences (α= .05). RESULTS. The mean flexural strength of sintered Vita In-Ceram YZ without autoclaving was 798 MPa. When applied aging temperature at below 125℃ for 10 hours, the flexural strength of Vita In-Ceram YZ increased up to 1,161 MPa. However, at above 150℃, the flexural strength started to decrease. Although low temperature aging caused the tetragonal-to-monoclinic phase transformation related to temperature, the minimum flexural strength was above 700 MPa. CONCLUSION. The monoclinic phase started to appear after aging treatment above 100℃. With the higher aging temperature, the fraction of monoclinic phase increased. The ratio of monoclinic/tetragonal + monoclinic phase reached a plateau value, circa 75% above 175℃. The point of monoclinic concentration at which the flexural strength begins to decrease was between 12% and 54%.This work was supported by the Korea Science and Engineering Foundation (KOSEF) grant funded by the Korea government(MOST) (No. R01-2007-000-10977-0)

Infantile Vitreous Hemorrhage as the Initial Presentation of X-linked Juvenile Retinoschisis

The authors report two cases of X-linked juvenile retinoschisis (XLRS) manifested as bilateral vitreous hemorrhage as early as in an 1-month-old infant and in a 3-month-old infant. The one-month-old male infant showed massive bilateral vitreous hemorrhage. During vitrectomy, thin membrane representing an inner part of schisis cavity was excised and intraschisis hemorrhage was evacuated. As intraschisis cavities were cleared, the stump of inner layer appeared as the demarcation line between the outer layer of the schisis retina and non-schisis retina. The other three-month-old male infant presenting with esodeviation also showed bilateral vitreous hemorrhage. Typical bilateral retinoschisis involving maculae could be seen through vitreous hemorrhage in both eyes on fundus examination. Spontaneous absorption of hemorrhage was observed on regular follow-up. XLRS could be manifested as massive hemorrhage inside or outside of the schisis cavity early in infancy