Boundary Lubrication Properties of Surface Modified Material Produced by Laser and Electron Beam Surface Alloying

The surface-modified material can be produced by laser and electron beam surface alloying of a plasma-sprayed molybdenum layer on Cr-Mo steel. The boundary lubrication properties and the metal structure of the surface alloy have been investigated. The main points of this study are as follows. 1. The surface alloy is thick, about 5 mm, and of uniform composition.

2. The surface alloy shows good wear resistance and good seizure resistance, in the same level as electroplated chromium and plasma-sprayed molybdenum layers.

3. Good wear resistance is attributable to the metal structure which is composed of hard M₆C phase and soft α?Fe phase.

     

Cytological diagnosis and telomerase activity of cells in effusions of body cavities

Telomerase is a ribonucleoprotein that synthesizes telometric DNA on chromosome ends, and may be related to the aging and immortality of cells. Recently, a telometric repeat amplification protocol (TRAP) assay for telomerase activity, using the polymerase chain reaction, was developed. We examined the limitations of TRAP assay by applying it to a cultured colon cancer cell line (COLO320) and 58 human cytological materials from body cavity effusions, and obtained the following results; i) The limits of the TRAP assay were 20-50 cells for the COLO320 cell line; ii) One COLO320 cell per 100 normal blood white cells was detectable; iii) Seventeen of 58 samples were positive for telomerase activity in this study. The sensitivity was 69% (9/13) and the specificity was 87.5% (28/32) between cytological diagnosis and telomerase activity; iv) Among 29 malignant cases, 15 were positive for telomerase activity, while there were 11 cytologically positive cases. The positive cases detected by the combination of cytology and telomerase activity accounted for 21 of the total 29 cases (72.4%). These results suggest that the measurement of telomerase activity in body cavity effusions may be useful as an adjunctive tool for cytological and clinicopathological diagnosis and that this technique is potentially applicable to remnant cytological materials.     

Phase Equilibria,Microstructure, and High-Temperature Strength of TiC-Added Mo-Si-B Alloys

TiC was added to Mo-Si-B alloys using a conventional Ar arc-melting technique, and the phase equilibria, microstructure evolution, and high-temperature strength at 1673 K (1400 °C) were investigated. The primary phase changed to Mo solid solution (Mo_ss), Mo₅SiB₂ (T₂), or TiC depending on the composition. Following the primary phase solidification, a Mo_ss + TiC, Mo_ss + T₂, or Mo_ss + T₂ + TiC + Mo₂C eutectic reaction took place as the secondary solidification step. In some alloys, Mo_ss + T₂ + TiC and Mo_ss + T₂ + Mo₂C eutectic reactions were present as higher-order solidification steps. After annealing at 2073 K (1800 °C) for 24 hours, Mo_ss, T₂, TiC, and Mo₂C coexisted stably with microstructural coarsening. The coarsening rate was much faster in an alloy with no TiC dispersion, suggesting that TiC has a strong pinning effect on the grain boundary and interface migration. Compression tests conducted at 1673 K (1400 °C) revealed strength properties of almost all the alloys that were better than those of the Mo-Hf-C alloy (MHC). Alloy densities were 9 g/cm³ or less, which is lighter than pure Mo and MHC (≥10 g/cm³) and competitive with Ni-base superalloys. TiC-added Mo-Si-B alloys are promising candidates for ultrahigh-temperature materials beyond Ni-base superalloys.     

Optimum design considerations for dual conductor bubble devices

A design for dual conductor, current-access bubble devices with 8-μm periods has been optimized with a numerical calculation method for bubble motion in a propagating magnetic field, generated around hole patterns in conductor layers. Magnetic bias field distributions are calculated for an oval hole chain in the conductor layers. Bubble motion equations are obtained with analytical field distribution functions approximating the calculated field distributions. Minimum drive current density Jminfor normal bubble propagation is determined by a solution to the equations. The hole shape has been optimized by the minimization of the drive power Pmin, the product of Jminand conductor resistance, which is calculated from current distributions around the hole pattern. Optimum layer thickness have also been obtained for 8-μm period bubble devices. Both registration tolerance between the two conductor layers and bubble skew effects have been studied semiquantitatively on the basis of the equations of motion. The numerical calculation method developed here is found to be a highly effective means to optimize pattern design for smaller period devices.     

Tribological Characteristics of α-Alumina in High-Temperature Water

The effects of temperature, sliding speed, and contact load on the tribological behavior of an α-alumina ceramic sliding on the same material in water were investigated in the range from room temperature to 300°C under the corresponding saturated vapor pressures. The specific wear rate increased remarkably at elevated temperatures. The primary wear mechanisms in high-temperature water are considered to be microfracture, promoted by the solution of grain boundary layers, and stress corrosion cracking. A film containing γ-alumina particulates appeared on the worn surface with increasing sliding speed and increasing contact load in 300°C water.     

Transport properties of overdoped Tl cuprates

To explain the observed inconsistency between the negative thermopowerS and the positive Hall coefficientR _H in the overdoped Tl cuprates, tight binding calculations are performed which include both Cu-O and O-O interactions in the CuO₂ square lattice. A striking feature of the CuO₂ antibonding band is that a holelike Fermi surface is formed even when the band is less than half-filled. This brings about an unusual electron state in which the Hall (cyclotron) mass along the Fermi surface is holelike but the transport mass perpendicular to it is electronlike. This electronlike transport mass contributes to the negative thermopower.We thank N. Hamada, T. Manako, and T. Kondo for helpful discussions.     

Internal stenting of the hepaticojejunostomy and pancreaticojejunostomy in patients undergoing pancreatoduodenectomy to promote earlier discharge from hospital

Arterial compliance and central blood volume were evaluated in obese and nonobese patients with and without hypertension. Arterial compliance was lower in the hypertensive group, although obese subjects, regardless of their blood pressure, had higher arterial compliance. The ratio of central blood volume to total blood volume was highest in hypertensive patients, whether obese or lean, indicating increased venoconstriction.