Ferromagnetic Ordering of Pure Organic Compound Occurs Below 1.6 K
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sity and Argonide Corporation (Sanford, Fla.), led by Thomas J. Webster of the Department of Biomedical Engineering at Purdue, found that osteoblast function and consequently bone formation on the implant depend strongly on the topology of the implant’s surface and the morphology of crystallites. They said that the shape and size of the nanophase implant particles are consistent with the dimensions of hydroxyapatite particles of natural bone. In general, the researchers identify three factors that promote enhanced osteoblast response: chemical composition, crystalline phase, and topography. As reported on November 5 in the online edition of the Journal of Biomedical Materials Research Part A (to appear in print in the December 15 issue), Webster, Rachel L. Price at Purdue, and their colleagues analyzed the osteoblast function depending on the degree of nanometer surface roughness of alumina substrates. The alumina-based materials were chosen for their high osteoblast activity as compared with titanium and etched glass. The researchers used conventional spherical (α-Al 2 O 3 spheres, 167 nm), nanophase spherical (δ-Al2O3 spheres, 23 nm), and nanofiber (boehmite fibers 2–4 nm diameter by more than 50 nm long) alumina compounds. The researchers found that cell adhe-
sion and proliferation results are statistically greater on nanofiber alumina as compared with other compounds. More important, calcium deposition by bone cells significantly increases on both nanoparticulate alumina substrates. They analyzed the influence of the three factors on osteoblast function. The study of the first factor shows that proteins absorb differently on materials with dissimilar chemical composition; the study of the second factor, that the transition alumina (δ- and boehmite phases) may promote an increased cell response compared to the more crystalline alumina phase (α); and the study of the third factor, that a decrease in the grain size to nanometer dimensions translates to an increase in osteoblast function. The researchers demonstrated that nanofiber alumina may offer the potential to ensure sufficient bone ingrowth and therefore to make orthopedic implants more stable. The researchers concluded that “with knowledge of the influence that chemistry, phase, size, and nanoparticle aspect ratio have on osteoblast function, an ideal material for orthopedic/dental applications may be designed.” EKATERINA A. LITVINOVA
FOR MORE RESEARCH NEWS ON MATERIALS SCIENCE . . .
Contrary to Heisenberg’s proposition that bulk ferromagnetic ordering could only appear in systems with heavy atoms, recent synthesis and characterization of several organic ferromagnets has been reported. Such systems are mainly based on sulfur- or nitrogen-containing organic radicals. A group of researchers from Cambridge University, in cooperation with scientists
. . . access the Materials Research Society Web site: www.mrs.org/gateway/ matl_news.html
Ferromagnetic Ordering of Pure Organic Compound Occurs Below 1.6 K
from CSIC–Universidad de Zaragoza (Spain), CNRS (Fr
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