Effects of bio-degradation on the mechanical properties of polylactic acid (PLA)/hydroxyapatite (HA) were evaluated using a newly designed three-point bending fixture in SBF chamber. The composite was found to be duct...
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Effects of bio-degradation on the mechanical properties of polylactic acid (PLA)/hydroxyapatite (HA) were evaluated using a newly designed three-point bending fixture in SBF chamber. The composite was found to be ductile and insensitive to cracks, which is totally different from its brittle behavior observed in conventional tests, in which the degraded samples are tested in air at room temperature. Initial bending modulus and strength of PLA/HA composite were 1.2 GPa and 43 MPa, respectively, which were lower than those tested under room conditions. After two weeks of immersion in vitro, both bending modulus and strength decreased by 40% and 57%, respectively. Their degradation rates were both higher than those in reports of previous researches. This work indicates the importance of evaluating mechanical behavior in simulated body environment.
In the preparation of bioengineered reparative strategies for damaged or diseased tissues, the processes of biomaterial degeneration and neotissue synthesis combine to affect the developing mechanical state of multi-p...
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ISBN:
(纸本)0912053909
In the preparation of bioengineered reparative strategies for damaged or diseased tissues, the processes of biomaterial degeneration and neotissue synthesis combine to affect the developing mechanical state of multi-phase, composite engineered tissues. Here, cell-polymer constructs for engineered cartilage have been fabricated by seeding chondrocytes within three-dimensional scaffolds of biodegradable polymers. During culture, synthetic scaffolds degraded passively as the cells assembled an extracellular matrix (ECM) composed primarily of glycosaminoglycan (GAG) and collagen. During development, biochemical and biomechanical assessment of the composite (cells, ECM, and polymer scaffold) were modeled at a unit-cell level to predict their individual effect on the construct elastic properties (n = 4 samples per 7 time points). This approach employed a composite spheres, micromechanical analysis to determine bulk moduli of: 1) the cellular-ECM inclusion within the supporting scaffold structure;and 2) the cellular inclusion within its ECM. This analytical technique offers an interpretation of the constituent dynamics for cell-based tissue regeneration.
This research is dedicated to the development of electrode arrays suitable for a more sensitive and faster electrochemical immunoassay system Signal amplification is achieved through coupling the redox cycling of inte...
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This research is dedicated to the development of electrode arrays suitable for a more sensitive and faster electrochemical immunoassay system Signal amplification is achieved through coupling the redox cycling of interdigitated array (IDA) electrodes with an enzyme label, β-galactosidase. Comb IDAs enhanced the signal 3 times higher than coplanar IDAs. A magnetic bead-based enzyme assay, as a simulation of an immunoassay, has been performed using the comb and coplanar IDAs for detection. Comb IDAs enabled positioning the beads and attached enzyme closer to the sensing electrodes (∼10 μm). Detection time was less than 1 min. and the limit of detection was 70 amole of β-galactosidase.
The quantitative visualization of flow in a wide-gap annulus (radius ratio 0.5) between concentric cylinders with the inner cylinder rotating and a superimposed axial flow reveals a novel mixed-mode state at relativel...
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The quantitative visualization of flow in a wide-gap annulus (radius ratio 0.5) between concentric cylinders with the inner cylinder rotating and a superimposed axial flow reveals a novel mixed-mode state at relatively high flow rates. A fast magnetic resonance imaging sequence allows the cinematographic dissection and three-dimensional reconstruction of supercritical nonaxisymmetric modes in a regime where stationary helical and propagating toroidal vortices coexist. The findings shed light on symmetry-breaking instabilities, flow pattern selection, and their consequences for hydrodynamic mixing in a complex laminar flow that constitutes a celebrated prototype of many mixing or fractionation processes.
In this study, an attempt was made to describe the age-related changes in pentosidine levels in isolated bone collagen and intact bone, and to determine the effect of increased pentosidine cross-link density on the du...
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ISBN:
(纸本)0791816117
In this study, an attempt was made to describe the age-related changes in pentosidine levels in isolated bone collagen and intact bone, and to determine the effect of increased pentosidine cross-link density on the ductility of both bone collagen and intact bone. Fifty-six cortical bone specimens were machined and assigned into four groups: intact, cross-link enhanced, demineralized, and demineralized cross-link enhanced. The specimens were then tested to failure in uniaxial tension. The results indicate that pentosidine cross-link density increases with age and that this leads to a decrease in ductility in both bone and isolated collagen.
Heat-treated bovine cortical bone has been proposed as an alternative to bone grafts and synthetic bone substitutes because it may combine the advantages of allografts (high stiffness and strength) and synthetic mater...
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The closed form system of equations governing a positive-displacement pump with a cylindrical fluid chamber and a brushless DC motor that relates the pump geometry to its mechanical efficiency have been determined wit...
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The closed form system of equations governing a positive-displacement pump with a cylindrical fluid chamber and a brushless DC motor that relates the pump geometry to its mechanical efficiency have been determined with the use of some simplifications. The resulting system was used to predict the efficiency of the pump given specific operating conditions for different geometries and vice versa. The closed-form system that the simplifications facilitated properly predicted the trends of the efficiency over different geometries and operating conditions.
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