Distribution of carbon contamination in MgAl2O4 spinel occurring during spark-plasma-sintering (SPS) processing: I – Effect of heating rate and post-annealing

Carbon contamination from the carbon paper/dies during spark-plasma-sintering (SPS) processing was examined in the MgAl₂O₄ spinel. The carbon contamination sensitively changes with the heating rate during the SPS processing. At the high heating rate of 100 °C/min, the carbon contamination having organized structures occurred over almost the entire area from the surface to deep inside the SPSed spinel disk. In contrast, at the slow heating rate of 10 °C/min, the carbon contamination having disordered structures occurred only around the surface area. The carbon phases transform into high pressure CO/CO₂ gases by post-annealing in air and lead to pore formation along the grain junctions. The pore formation significantly occurs at the high heating rate due to the large amount of the contaminant carbon phases. This suggests that if once the carbon contamination was formed in the materials, it is very difficult to remove the carbon phases from the materials.     

Treatment of hemifacial spasm with botulinum toxin

We injected botulinum toxin to treat hemifacial spasm, and investigated the effects and the patient's impression of this treatment. Average duration of improvement lasted about 3.5 months in both the initial treatment group and the recurrent group. However the patients in the recurrent group received fewer units of botulinum toxin than those in the initial treatment group. Except for local paralysis that disappeared within a month, there were very few complications. Most patient were satisfied with this treatment. We conclude that the treatment of hemifacial spasm with botulinum toxin is both simple and useful.     

Effect of Ultrasonication on the Microstructure and Tensile Elongation of Zirconia-Dispersed Alumina Ceramics Prepared by Colloidal Processing

To obtain dense, fine-grained ceramics, fine particles and advanced powder processing, such as colloidal processing, are needed. Al₂O₃ and ZrO₂ particles are dispersed in colloidal suspensions by electrosteric repulsion because of polyelectrolyte absorbed on their surfaces. However, additional redispersion treatment such as ultrasonication is required to obtain dispersed suspensions because fine particles tend to agglomerate. The results demonstrate that ultrasonication is effective in improving particle dispersion in suspensions and producing a homogeneous fine microstructure of sintered materials. Superplastic tensile ductility is improved by ultrasonication in preparing suspensions because of the dense and homogeneous fine microstructure.     

Effect of Silica Doping on the Electrical Conductivity of 3 mol % Yttria-Stabilized Tetragonal Zirconia Prepared by Colloidal Processing

Silica-doped (SiO₂ = 0 - 1.0 wt%) 3Y-TZP (3 mol % yttria-doped tetragonal zirconia polycrystal) ceramics are prepared from hetero-coagulated aqueous suspension by colloidal processing. Consolidation of the suspension was carried out by pressure filtration at 10 MPa followed by cold isostatic pressing (CIP) at 400 MPa. Consolidated compacts are densified to a relative density over 99% by sintering at 1573 K for 2 h. The formation of glass pockets at grain boundary multiple junctions was observed by SEM for ≥0.5 wt % silica-doped samples. Electrical conductivity measurements were performed to evaluate the modification of grain-boundaries by silica. The apparent grain boundary conductivity decreased with an increase in silica content and became nearly constant above 0.3 wt % of silica, while the bulk conductivity was constant with silica content.     

Novel fabrication of nano-pattern with optical function by selective doping of dye vapor into novolac resin

We report selective doping of vapor of yellow dye, ferrocenedimethanol into exposed (UV-irradiated) areas of novolac resin films. When vapor of the dye was contacted with micro-patterned resin films containing both exposed and unexposed areas, the dye was doped only into the exposed areas, resulting in fabrication of micro-pattern containing the dye. On the contrary, ferrocene and other ferrocene derivatives were doped both exposed and unexposed areas of the resin. A contact angle measurement of aqueous drops on each dye indicated that the chemical affinity between hydroxyl groups of ferrocenedimethanol and exposed areas of the novolac resin will enhance selective doping of the dye into the exposed areas.     

A 144-Mb, eight-level NAND flash memory with optimized pulsewidthprogramming

We report a fast-programming, compact sense and latch (SL) circuit to realize an eight-level NAND flash memory. Fast programming is achieved by supplying optimized voltage and pulsewidth to the bit lines, according to the programming data. As a result, all data programming is completed almost simultaneously, and 0.67-MB/s program throughput, which is 1.7 times faster than conventional program throughput, is achieved. The compact layout of the SL circuit is made possible by four 3-bit latches sharing one unit of the read/verify control circuit. Using these techniques, we fabricated a 144-Mb, eight-level NAND flash memory using a 0.35-μm CMOS process, resulting in a 104.2-mm² die size and a 1.05-μm² effective cell size     

Effects of heating rate on microstructure and transparency of spark-plasma-sintered alumina

Commercial alumina powder was densified by spark plasma sintering (SPS) at 1150 °C. During SPS processing, the effects of the heating rate were examined on microstructure and transparency. With decreasing heating rate, the grain size and the residual porosity decreased, while the transparency increased. At a heating rate of 2 °C/min, the grain size was 0.29 μm, and the in-line transmission was 46% for a wavelength of 640 nm. The mechanisms for the fine microstructure and low porosity at slow heating, which are conflicting with some existing results, were explained by considering the role of defect concentration and grain-boundary diffusion during densification.     

Dose finding study of cefepime for chronic respiratory infections]

In order to determine the optimal dose of cefepime (CFPM) for respiratory tract infections, a dose finding study was conducted in patients with chronic respiratory tract infections, and the clinical properties of the drugs were compared with those of ceftazidime (CAZ). Each drug was administered by intravenous drip infusion at the dose of 2 g/day of CFPM, 4 g/day of CFPM or 2 g/day of CAZ for 14 days. 1. The overall efficacy rates evaluated by the committee were 82.6% (19/23) for the CFPM 2 g/day group, 85.0% (17/20) for the 4 g/day group and 79.3% (23/29) for the CAZ 2 g/day group, with no statistically significant difference among the three groups. 2. The overall efficacy rates evaluated by the attending physicians were 91.3% (21/23) for the CFPM 2 g/day group, 78.9% (15/19) for the CFPM 4 g/day group and 75.9% (22/29) for the CAZ 2 g/day group, with no significant difference among the three groups. 3. Bacteriological eradication rates were 88.2% (15/17) for the CFPM 2 g/day group, 68.8% (11/16) for the CFPM 4 g/day group and 63.2% (12/19) for the CAZ 2 g/day group, with no statistically significant difference among the three groups. 4. The incidences of adverse reactions were 3.8% (1/26) for the CFPM 2 g/day group, 9.1% (2/22) for the CFPM 4 g/day group and 3.4% (1/29) for the CAZ 2 g/day group, with no significant difference among the three groups. The incidences of abnormal laboratory findings were 37.5% (9/24) for the CFPM 2 g/day group, 15.0% (3/20) for the CFPM 4 g/day group and 3.4% (1/29) for the CAZ 2 g/day group. There was a significant difference among the three groups. 5. Utility rates assessed by the committee were 81.8% (18/22) for the CFPM 2 g/day group, 76.2% (16/21) for the CFPM 4 g/day group and 75.9% (22/29) for the CAZ 2 g/day group. Utility rates assessed by attending physicians were 90.9% (20/22), 78.9% (15/19) and 72.4% (21/29), respectively. There was no significant difference among the three groups. From the above results, it is concluded that the optimal dosage of CFPM is 2 g/day for chronic respiratory tract infections.