原田 泰典

Case 1: An 8-year-old boy consulted our clinic complaining of left flank colicky pain. He had a past history of the same episode. Ultrasonographic study was promptly performed. Left hydronephrosis was detected. At operation, left aberrant renal vessel was resected, and he has been free of pain. Case 2: A 65-year-old woman consulted our clinic because of abdominal pain and fever, who occasionally had the same episode. The existence and disappearance of the right hydronephrosis could be observed by emergency ultrasonography and following ultrasonic study, and the stenosis of the right lower ureter caused of cystitis cystica and glandularis was pointed out by retrograde ureterography. Diuresis ultrasonography by furosemide was performed to evaluate urinary tract stricture. In case 1, an incomplete obstruction pattern was obtained after operation, and in case 2, a complete obstruction pattern was shown. The emergency ultrasonography and diuresis ultrasonography were useful for the diagnosis and observation of intermittent hydronephrosis.

The rolling workability of sintered chromium, which is very brittle at room temperature was examined as a function of temperature. The present sintered chromium of 99.9% purity was produced by CIP (cold isostatic press) and HIP (hot isostatic press).<BR>The specimen could be successfully rolled in a limited temperature range from 673 to 1073 K. This formability characteristic is different from the experimental results found in the upset and the tensile tests in which no upper limit of temperature was found for workability and ductility. The deterioration in rolling at temperatures above 1173 K was caused by rapid cooling of the specimen by the rolls. The temperature of the specimen during rolling decreased greatly in the roll-contact region, while the inner part of the workpiece retained its starting temperature. Hence, the large tensile stress in the rolling direction occurred near the roll-contace material because of a large difference in the flow stress between the roll-contact region and the inner part of the workpiece. The tensile stress was responsible for cracking on the surface of the specimen heated at temperatures above 1173 K.<BR>The steel/chromium/steel sandwich plate could be successfully rolled to a large reduction even at temperatures above 1173 K without occurrence of the surface cracks because the steel skins prevented the temperature decrease of the specimen during rolling.

Tensile properties of sintered powder chromium (99.9 mass% purity) produced by a cold isostatic press (CIP) and a hot isostatic press (HIP) were preliminarily examined to find conditions favorable to the plastic working of the sintered chromium. Specimens A and B₁ taken from a sintered ingot A and a half of an ingot B, respectively, were annealed at 1823 K higher than 1473 K encountered in the present HIP. Specimen B₂ from the remainder of the ingot B was not heat treated.<BR>Transition from ductile to brittle fracture occurred very sharply, i.e., in a small range of temperature, and at the higher temperature in a testing at the higher speed of deformation. Ductile-to-brittle transition temperature of the specimen B₁ was lower than that of the specimen B₂ suggesting that the annealing at 1823 K is effective in lowering the transition temperature. Small plastic tensile prestrain given to a specimen at a temperature slightly beyond its transition temperature considerably reduced the brittleness of the specimen. This prestraining effect is supposed to come from free dislocations generated in the prestrained specimen. At temperatures between 700 K to 1023 K, flow stress was never changed even when the strain rate was increased from 1.7&times;10^&minus;4 s^&minus;1 to 1.7&times;10^&minus;1 s^&minus;1, and the decrease of the stress with increasing temperature was small.