PubMed · 101351
The source did not provide an abstract. Follow the original record for more information.
Explore connections, maps & timelines
M Yoshinari. 1977. [Surface treating liquid for plaster models].. https://pubmed.ncbi.nlm.nih.gov/101351/
Cite the original work for its findings. Save a collection to share your selection of sources.
KEEP EXPLORING
Phosphogypsum is a by-product of the phosphate fertilizer industry which is stockpiled in large quantities world-wide. Phosphogypsum consists mainly of dihydrate gypsum (CaSO42H2O) but also contains elevated concentrations of 226Ra and other inorganic species which originate from the processing of phosphate rock. 222Rn gas is the first decay product of 226Ra and has been identified as one of the major environmental concerns associated with phosphogypsum. This study was conducted to determine effects of particle size, weathering, and moisture content on the 222Rn emanation coefficient (epsilon) for phosphogypsum. Average epsilon for air-dry, unfractionated phosphogypsums derived from Togo, Florida, or Idaho rock was approximately 12%. Average epsilon for fine fraction phosphogypsum (< 20 microns diameter) was greater than for unfractionated phosphogypsum by a factor of 4.6, 1.4, and 4.4 for samples derived from Idaho rock, Togo rock, and Florida rock, respectively. Phosphogypsum samples subjected to an artificial weathering procedure lost 40% mass, with no change in epsilon. Increasing water content was found to first slightly decrease, then to increase epsilon compared to air-dry samples; epsilon for 100% saturated phosphogypsum was 1.9-fold greater than in air-dry phosphogypsum. Particle size sorting could account for variability of 222Rn exhalation at repositories. Very high moisture contents could slightly increase 222Rn emanation, but exhalation would likely be reduced due to slow diffusion through porosity of saturated phosphogypsum.
In the past, measurement of microleakage has been based on measurement of dye or radioactive isotope penetration. A method has been developed to allow electronic monitoring of microflow in the same specimen over a period of time. This method was used to compare previously reported retrograde materials with an amalgam/sealer combination. The material that performed best was amalgam/sealer, particularly in the first week. The role of cavity varnish in limiting leakage has been controversial, and the results in the present study do not indicate any significant benefit. The range of leakage measured for specimens in the same group suggests that in vivo the expected leakage could be considerable for the materials tested and that small differences in experimental leakage between groups may not have any practical significance.
An accurate cost analysis of the use of one of the new synthetic casting materials (Cellacast) compared with plaster-of-Paris (Gypsona) was undertaken over a 3-month period in the fracture clinic of Cardiff Royal Infirmary. The mean duration of usage before failure for synthetic forearm, scaphoid and below-knee casts was found to be approximately twice that of plaster casts. The use of synthetic casting materials was found to be cost-effective in situations where there was thought to be a high probability that structural failure of the cast would occur. Guidelines for the use of plaster-of-Paris and synthetic casting materials are presented.