ARC Melting of Tungsten

The direct-current, straight-polarity tungsten arc is examined in a highvacuum, open-arc system. Purity of the ingot product and the effects of ambient pressure variations on the melt rate and arc behavior are described.     

Congenital dilatation of the bile ducts

Our experience with five cases of cystic dilatation of the extrahepatic bile ducts is reported and compared with the literature. The following conclusions have been reached: (1) The etiology of this anomaly is primarily congenital but may involve an acquired component. (2) Diagnosis should be suspected when any of the triad of abdominal pain, right upper quadrant mass, or jaundice is present. (3) The diagnosis can usually be made in infants based on the clinical picture and routine radiologic studies. (4) Retrograde cholangiopancreatography is a useful tool in making the diagnosis in older children and adults. (5) Roux-en-Y choledochocystojejunostomy is the procedure of choice for type I cysts, excision for type II, and choledochocystoduodenostomy for type III.     

The analysis of turbulent,free-shear,and channel flows by the finite element method

The finite element method is utilised to solve two-equation hydrodynamic models of turbulent flow subject to a prescribed pressure gradient. The method is used to analyse fully developed flow in smooth-walled channels and the plane mixing layer. The results are compared with experiment and with the results obtained by finite difference methods.     

Toadfish serum as a binder for in vitro assay of vitamin B12

Fetal intrauterine growth retardation was induced in nine rats at 17 days' gestation by ligating the blood supply to one of the uterine horn. The 27 festuses from the uterine vessel ligated side were the intrauterine growth retarded fetuses (IUGR) and the 37 fetuses from the nonligated side were controls. The mean weight of the IUGR fetuses was 3.4 +/- 0.3 g which was significantly smaller (P less than 0.005) than the mean weight of the control fetuses, 4.0 +/- 0.3 g. Whole body histidine decarboxylase (HDC) activity was assayed by a radioisotope method. The HDC activity per g tissue was not correlated to body weight in the control fetuses. This is in contrast to the IUGR festuses in which the HDC per g tissue was significantly and inversely related to body weight (r - 0.48, P less than 0.001).     

High-power extremely shallow quantum-well modulators

It is found that extremely shallow quantum wells (QWs) are capable of modulating high-intensity light due to the enhanced sweep out of photogenerated carriers. These QWs are especially well suited for use in self-electrooptic effect devices (SEEDs) due to the existence of a strong room-temperature exciton that ionizes rapidly with field. For a 3- mu m diameter spot, bistable reflectivity changes (for a symmetric-SEED arrangement using a 7 V power supply) of 18% at 1 mW (24 kW/cm/sup 2/), 10% at 2 mW, and 4% at 3 mW were obtained, compared to 6.8% at 0.4 mW for the previous best sample.<>     

Temperature dependence of craze shape and fracture in poly(methyl methacrylate)

The shape of the craze at the tip of a slowly moving crack has been determined by optical microscopy for poly(methyl methacrylate) over the range of temperatures ?30° to +45°C. In all cases the craze shape can be described by the Dugdale model for the plastic zone at a crack tip. It was of particular interest that the crack opening displacement was found to be constant over the whole temperature range. Fracture toughness values deduced from the craze shape were in good agreement with those obtained directly. Quantitative estimates of the craze stress were obtained and are discussed.