Aggregate modulus

Abstract: Due to its avascular nature, articular cartilage exhibits a very limited capacity to regenerate and to repair. Although much of the tissue-engineered cartilage in existence has been successful in mimicking the morphological and biochemical appearance of hyaline cartilage, it is generally mechanically inferior to the natural tissue. In this study, we tested the hypothesis that the application of dynamic deformational loading at physiological strain levels enhances chondrocyte matrix elaboration in cell-seeded agarose scaffolds to produce a more functional engineered tissue construct than in free swelling controls. A custom-designed bioreactor was used to load cell-seeded agarose disks dynamically in unconfined compression with a peak-to-peak compressive strain amplitude of 10 percent, at a frequency of 1 Hz, 3 x (1 hour on, 1 hour off)/day, 5 days/week for 4 weeks. Results demonstrated that dynamically loaded disks yielded a sixfold increase in the equilibrium aggregate modulus over free swelling controls after 28 days of loading (100 +/- 16 kPa versus 15 +/- 8 kPa, p < 0.0001). This represented a 21-fold increase over the equilibrium modulus of day 0 (4.8 +/- 2.3 kPa). Sulfated glycosaminoglycan content and hydroxyproline content was also found to be greater in dynamically loaded disks compared to free swelling controls at day 21 (p < 0.0001 and p = 0.002, respectively).

Abstract: : Data on the elastic properties of single crystals have been collected from the literature published through mid-1964. The elastic properties of isotropic aggregates (Young's modulus, Poisson's ratio, shear modulus, bulk modulus, compressibility, velocity of shear waves, and the velocity of compressional waves) are calculated according to the schemes of Voigt and Reuss. The tables include about 1100 determinations. (Author)

Abstract: Combining Gruneisen's equation with our Young's modulus equation of glass, new formulae were semi-empirically derived for the calculation of bulk modulus, shear modulus and Poisson's ratio of glass. Considering packing density of atoms and bond energy in unit volume the elastic moduli of glass can be calculated. The agreements between calculated and observed values of the moduli of glass are satisfactory for more than 30 glasses.