WC-Co alloys are widely used as cutting and mold tools due to their high hardness, but their performance is difficult to evaluate with conventional tests. We have applied the micro slurry-jet erosion (MSE) test, which we have developed, to evaluate the surface strength of WC-Co alloys. The objective of this study is to understand the erosion mechanism of the WC-Co alloy in order to demonstrate the usefulness of the MSE test. Four specimens (Co content: 6 ~ 19 wt.%, WC grain size: 0.6 ~ 0.8 µm) were tested with angular alumina particle with an equivalent sphere diameter of 41 µm as erodent. The erosion debris was collected from the impacted slurry and analyzed with SEM and EDS, together with the observation of the eroded surfaces and cross-section. The erosion rate of the MSE increased with increasing Co content. The erosion debris was categorized into two types according to size, shape and composition of the particles. The erosion mechanism of the WC-Co alloy was determined to be removal of WC or WC and Co due to intergranular fracture. It was concluded that the MSE test has the possibility of evaluation for strength against intergranular fracture caused by impact force.

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A study on obstructive changes in airways and mucociliary clearance in children and youth with bronchial asthma was performed. Radioaerosol inhalation lung scintigraphies using ^99mTc-HSA (human serum albumin) were applied to 50 children and youth with bronchial asthma. The deposition patterns of the radioaerosol and aerosol clearance curves were evaluated.
Abnormal deposition patterns, which consisted of non-homogeneous distribution and/or hot-spot formation, were likely to be seen in cases with asthmatic attacks at the time of measurements. However, a few asymptomatic patients also revealed abnormal deposition patterns. The deposition patterns were related to FEV_1.0%, MMF, V₅₀ and V₂₅, but especially to FEV_1.0%.
As an index of mucociliary clearance, β, the rate constant of the ^99mTc-HSA aerosol clearance curve, was introduced. β was significantly lower in cases with abnormal aerosol deposition patterns than in normal ones. β was also significantly lower in cases undergoing asthmatic attack at the time of the measurements than in asymptomatic cases. β correlated negatively with FEV_1.0%, MMF, V₅₀ and V₂₅, but especially with FEV_1.0%. Although cases with long term affection or moderate-to-severe asthma, tended to reveal abnormal deposition patterns and had low β values, these differences were not statistically significant.
Radioaerosol inhalation lung scintigraphy with ^99mTc-HSA is useful for evaluating not only obstructive changes in the airways but also for evaluating mucociliary clearance in children with bronchial asthma.

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