Characteristics and tribological properties in water of Si-DLC coatings

Si-containing diamond-like carbon (Si-DLC) coatings with a Si content ranging between 0 (DLC) and 10 at.% were deposited by thermal electron excited plasma CVD method, and their characteristics and the tribological properties in water environment were investigated. The results showed that doped Si had little effect on the hardness and Young's modulus of the coatings. Increasing Si content reduced the friction and the wear of the mated ball, although the wear of the coatings increased. The wear of the counter ball occurred mainly in the early stage of rubbing. The Raman and XPS analysis revealed that the tribochemical reaction of Si-DLC coating occurred in water, and SiO_x(OH)_y gel was formed on the mated ball surface. It is considered that the tribochemical reaction is also responsible for the tribological properties of the Si-DLC coating and the counter ball, and the reaction may be accelerated by increasing the Si content. Failure-resistant capability is strongly governed by the characteristics of the coating, and can be improved by doping Si. There is an optimum Si content for increasing the failure-resistant capability and it was 6.6 at.% in this work.     

Diffusion-preventive Al2O3 layer growth at the interface of plasma-sprayed niobium and FeCrAlY in a tungsten fibre-reinforced high-temperature superalloy composite

The growth mechanism of a diffusion-preventive layer formed at elevated temperatures (∼1500 K) between the plasma-sprayed niobium layer and the plasma-sprayed FeCrAlY matrix in a tungsten fibre-reinforced high-temperature superalloy composite (Nb-coated W fibre/FeCrAlY composite) was studied. The diffusion-preventive layer was identified as α-Al₂O₃ by scanning electron microscopy/electron probe microanalysis, energy dispersive X-ray spectrometry analysis, and X-ray diffraction. Heat-treatment experiments were implemented systematically and it was found that the Al₂O₃ layer was also formed at the plasma-sprayed Nb/rolled FeCrAl interface. No Al₂O₃ layer, however, was formed either at the rolled Nb/plasma-sprayed FeCrAlY interface or at the rolled Nb/rolled FeCrAl interface. In these cases, an intermetallic compound layer was formed instead. A growth mechanism is proposed in which the Al₂O₃ is attributed to a chemical reaction between the residual oxygen in the plasma-sprayed niobium and aluminium in FeCrAlY or FeCrAl. The magnitude of the driving force was evaluated by a new model based on thermodyanamics. Numerical calculations have shown that the proposed growth mechanism is thermodynamically reasonable.     

Yagi-Uda array for millimetre-wave imaging

An imaging array consisting of five Yagi-Uda antennas in a dielectric has been constructed for 50 GHz that has antenna patterns suitable for millimetre-wave applications. Crosstalk levels of less than -30 dB between adjacent antennas in an f/1.0 imaging array have been measured in 5 GHz model experiments.<>     

Role of nitric oxide in the control of blood pressure in young and adult spontaneously hypertensive rats

1. The depressor response to sodium nitroprusside (SNP) and the pressor response to Nomega-nitro-L-arginine methyl ester (L-NAME) were investigated in anaesthetized and ganglion-blocked 6 week old (young) and 20 week old (adult) spontaneously hypertensive rats (SHR), and the results were compared with those in age-matched normotensive Wistar-Kyoto (WKY) rats. 2. SNP produced a dose-dependent decrease of the mean blood pressure (BP) in both strains, and no differences in vascular sensitivity to SNP were observed between the strains. 3. L-NAME caused dose-dependent pressor responses in both strains. The sensitivity and the maximal response to L-NAME in SHR were significantly greater than those in age-matched WKY (P< 0.05 or 0.01; t-test, 13 d.f. in both ages). However, there were no significant differences in the responses between ages in each strain. 4. Acute reduction of BP induced by 7-O-ethylfangchinoline did not affect the responses to SNP and L-NAME in the adult SHR. 5. These results indicate that a greater amount of NO is tonically released in SHR and that its contribution to BP control is greater in SHR than in WKY, whereas vascular sensitivity to NO does not differ between the strains. In addition, acute changes in BP do not affect the degree of dependency on NO for BP control.     

Clinical evaluation of postoperative adjuvant arterial infusion chemotherapy in resected hepatoma patients

Eighty surgically treated patients with advanced hepatocellular carcinoma (HCC) were divided into two groups. In group I, twenty patients whose mean diameter of tumors was 56 mm, prophylactically underwent hepatic arterial infusion chemotherapy after liver resection. Chemotherapeutic agents (5-FU, ADM, MMC, CDDP, Lipiodol) were administered 4 times a year via Infuse A port. The remaining 60 patients, whose mean diameter of tumors was 57 mm, served as the control without prophylactic infusion (group II). The 2-year cumulative survival rate was higher in the prophylactic group (71%) than the control (48%, p = 0.040). The two-year disease-free survival rate was improved in group I (38%) compared with that in group II (27%, p = 0.021). Intrahepatic multiple recurrence within 1 year after surgery was recognized in four out of 18 patients of group I (22%) and in thirty-three out of 60 patients of group II (55%, p = 0.029). In group I, two cases who died of hepatic failure with no recurrence, had lower functional reverse and a larger amount of Lipiodol than the remaining 18 patients. Adjuvant arterial infusion chemotherapy can thus be be efficacious in alleviating hepatoma recurrence after liver resection. For patients with poor liver function, a smaller volume of chemotherapeutic agents might be feasible.     

Mild hearing loss in children with communication disorders

The prevalence of MHL in 202, 1 to 6 year-old children with communication disorders who visited our clinic in 1991 was investigated. 1) 31% of the subjects had MHL bilaterally. The prevalence of MHL was 44% at age 1 year, 20% at age 2 years, 36% at age 3 years, 24% at age 4 years, 39% at age 5 years, 33% at age 6 years. 2) 88% of children with MHL had OME, 10% had mild sensorineural hearing loss, and 2% had cerminous plug. 3) The prevalence of MHL in children with mental retardation and autistic disorders was 9%, that with stuttering was 9%, that of OME accompanied by moderate and severe hearing disorders was 6%. 4) The primary causes in 191, except for those with stuttering, were as follows; the prevalence of MHL was 30%, that of mental retardation and autistic disorders was 24%, and that of articulation disorders was 28%. 5) On the other hand, the prevalence of MHL in children with retarded language development and articulation disorders was 30%, which was significantly higher than that of the other communication disorders. Accordingly, the results of this study suggest that MHL in early childhood greatly influences communication disorders.     

Nodular glomerulosclerosis of unknown origin associated with the nephrotic syndrome

A 35-year-old male patient clinically characterized by massive proteinuria and hypertension without evidence of systemic diseases is reported. Histological investigation of renal biopsy specimens revealed extensive nodular formations in the mesangial areas in every glomerulus. Light-microscopic examination did not allow discrimination between the glomerular changes found in these specimens and the nodular glomerulosclerosis described in patients with diabetes mellitus. Electron-microscopic examination confirmed the presence of massive, nodular, mesangial expansions consisting of finely fibrillar substances without electron-dense deposits and circumferential mesangial interposition. Immunofluorescent examination showed deposition of IgG, C3, fibrinogen and kappa and lambda light chains in mesangial areas, peripheral capillary loops and a part of the nodules. Furthermore, collagen types IV, V, VI and laminin were detected in the nodules. Amyloid was not observed in these nodules. This diagnosis has not been made, and the mechanism of this nodular glomerulosclerosis remains unknown.     

Increase in serum vascular endothelial growth factor levels during altitude training

Atlantoaxial transarticular fixation is a proven stabilization technique used to augment conventional sublaminar fusion. Along with its superior biomechanical profile comes the inherent risk of neurovascular injury and potential compromised fixation during its application. This article presents a detailed systematic guide to this procedure including preoperative evaluation, positioning, and the more subtle aspects of the surgical technique. A new instrumentation design that has enhanced the ease and accuracy of screw placement with less operative frustration and potential morbidity of previous systems also is presented.