Abstract

I studied two types of bioceramics: (A) the aragonite CaCO3 skeleton of the staghorn coral, Acropora cervicornis and (B) the hydroxyapatite Ca10(PO4)6(OH)2 bones of the laboratory mouse, Mus musculus. The research aimed to analyze coral deformation behavior and study dietary and estrogen depletions effects on bone strength. I compared the mechanical and structural properties of staghorn coral skeletons cleaned by chemical bleaching and biological processes. Optical microscopy and computed tomography (CT) revealed a sophisticated microstructure of non-homogenously distributed pores. Staghorn coral skeletons showed ''gracious" fracture, where the unique pore arrangements resisted catastrophic crack growth and prevented instantanous failure. Elastic moduli measured by uniaxial compression was 0.19 ± 0.16 GPa or 7.34 GPa, if displacement was measured by a crosshead on the universal testing machine or a clip-on extensometer, respectively. These values were substantially lower than Young's modulus measured by nanoindentation as 86 ± 7.26 GPa, which was explained by the effect of porosity during uniaxial loading. Computed tomography scans revealed porosity of skeleton branches decreased from tip (67 ± 5 %) to base (31 ± 5 %), which indicated that coral skeletons calcify as they age. Furthermore, the deformation of skeleton increased during cyclic loading when temperature of the environment increased. Four different diets (control, high saturated fat [HSF], high fat diet [HFD] and high polyunsaturated fat [HPUF] affect the structure and strength of mice tibia. Mice raised on a HSF diet had greater tibial diameter, area and moment of inertia but lower tibial strength compared to the other groups. Moreover, the HFD was associated with enhancing the tibial strength as a result of increasing the adipose marrow tissue. However, such HFD intake did not prevent bone loss in the osteoporotic model. Both bone density and strength of OVX+oil group were significantly lower compared to OVX+E2 and sham groups.

Notes

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Graduation Date

2021

Semester

Spring

Advisor

Orlovskaya, Nina

Degree

Doctor of Philosophy (Ph.D.)

College

College of Engineering and Computer Science

Department

Mechanical and Aerospace Engineering

Degree Program

Mechanical Engineering

Format

application/pdf

Identifier

CFE0008512

Language

English

Release Date

May 2021

Length of Campus-only Access

None

Access Status

Doctoral Dissertation (Open Access)

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