Presence Of Cement Research Articles

Densities of Tertiary rocks, West Coast, South Island, New Zealand

Abstract The causes of the large variations in the densities of sedimentary rocks from the Westport, Inangahua, and Murchison depressions include: the presence of cement (usually calcite); difference in source rock of sediments; and variation in the lithostatic load to which the sediments have been subjected. A density-depth curve is used to provide estimates of the maximum thickness of sediment. The Murchison, Inangahua, and Westport depressions have at least 3000 m, 1000—2000 m, and 300 m, respectively, of sediment overlying the Eocene Kaiata Formation.

Methylmethacrylate as an adjunct in the internal fixation of intertrochanteric fractures of the femur.

Twenty-eight unstable four-part intertrochanteric fractures in 27 elderly patients with severely osteoporotic femurs were treated by means of internal fixation (commonly the 130 or 95 A.O. blade plate) in combination with methylmethacrylate. Of the 28, ten patients with eleven fractures were recalled and reexamined; 12 had died; five were lost to followup (1 1/2-8 1/2 years) at the time of this review but sufficient documentation existed for their inclusion. There were no deep wound infections. We did not encounter any hypotension during surgery or as a result of the methylmethacrylate. One patient developed a pulmonary embolus 5 days postoperation and responded well to anticoagulant therapy. There were three failures; one femoral shaft fracture at the plate end, one nonunion, both requiring total hip replacemens, and the third failure was due to malreduction of fracture and was later revised. Where bone fragments were in contact, union occurred rapidly and the presence of cement did not interfere with bone union in any way. The patients were pain free and began full weight bearing the day after surgery.

Control and Distribution of Uranium in Coral Reefs During Diagenesis

ABSTRACT The concentration of about 2 ppm of uranium in the aragonitic skeletons of modern scleractinian corals which we studied is a constant value, regardless of occurrence, anatomy, or taxonomy. The presence of cement of aragonite or high-magnesian calcite usually raises the concentration of bulk samples to about 3 ppm. Modern corals may contain up to 50% of cementing minerals. Organisms, such as corals and coralline algae, while secreting their skeleton, discriminate against the uptake of uranium, whereas the uptake of uranium by mineral cements is less restrained. Aragonite cement contains about 3.6 ppm and high-magnesian calcite cement 2.6 ppm uranium. During leaching by freshwater, the aragonite of the skeletons of corals dissolves out. This creates hollow molds which fill with drusy low-magnesian calcite. In emergent reefs from the shores of the Red Sea which display the effects of progressive diagenesis this calcite is enriched in uranium (3.9 ppm) beyond that found in marine cements. Second-generation calcite which fills original voids in the corals from the emergent reefs contains a lower level of uranium concentration (1.3 ppm). The level of concentration of uranium in low-magnesian calcite of diagenetically altered corals is a function of the availability of uranium in meteoric waters. In aragonite as well as in high- and low-magnesian calcite uranium replaces calcium or occupies lattice vacancies in the crystal lattice.