EXPANDING SYNTHETIC METHODOLOGIES FOR STABLE HYDROXYAPATITE COATINGS ON POLYMER SUBSTRATES

65 pagesAbout 7.5% of people all over the world are in suffer from lower back pain caused by intervertebral disc (IVD) degeneration. This thesis explores two possible routes to develop robust mineral coatings for PEEK and collagen substrates that have the potential to improve IVD implant osseointegration. Chapter 1 introduces intervertebral disc degeneration, its causes, and the current treatment methods, as well as hydroxyapatite coatings for implant materials. Chapter 2 describes a hydroxyapatite coating designed for the controlled release of rhBMP-2 (growth factor). In this study, I was testing the hypothesis that the incorporation of rhBMP-2 during the transformation from CaCO3 to hydroxyapatite will result in a mineral film that has a slower rhBMP-2 release rate as compared to physisorbed rhBMP-2. The results, however, refute this hypothesis because the release kinetics between the three test cases do not vary significantly. The film grown in the presence of rhBMP-2, however, does incorporate more rhBMP-2 than either control substrate. Chapter 3 describes a construct design of multilayer collagen with a mineral gradient. In this study, I was testing the hypothesis that adding a transitional layer, composed of mineral particles dispersed within a collagen gel, between a top, dense mineral coating and a pure collagen gel, will improve the adhesion and even distribution of CaCO3 nanoparticles, which subsequently via dissolution-recrystallization will result in a uniform layer of hydroxyapatite. The results agree with the hypothesis. This research aims to expand the synthetic methodologies available for creating stable hydroxyapatite coatings on polymeric substrates and may lead to improvements in the design of materials for IVD implants for lower back pain patients

Sensitivity and reliability analysis to MSBAS regularization for the estimation of surface deformation over a mine

AbstractTo systematically and thoroughly analyze the sensitivity and reliability of the MSBAS regularization for the estimation of surface deformation over a mine in combination with an application example, this study processed 101 Sentinel-1A/B SAR images, constructed and solved the 2D deformation models using SVD and Tikhonov regularization methods with different orders and parameters, and estimated the vertical and east-west surface deformation time series in a mine of China. Then, this study collected the leveling-monitoring vertical surface deformation data on three leveling points, and compared and analyzed the sensitivity and reliability of the MSBAS regularization methods for estimating vertical surface deformation. The results indicate that different regularization orders and parameters can lead to thousands of times differences in condition numbers and significant differences in ill-posed degree of the deformation models. The zero-order Tikhonov regularized deformation model with regularization parameter of 0.1 has the minimum condition number and the equation is not ill-posed. The first-order Tikhonov regularized deformation model with regularization parameter of 0.001 has the maximum condition number and the equation is seriously ill-posed. As a result, the estimates of 2D surface deformation models with different parameters and orders are also different in terms of numerical values and accuracy. Compared with the leveling-monitoring data, the first- and second-order MSBAS regularization methods with parameter 0.1 have the minimum fluctuation and the maximum correlation coefficients between the estimated values and the leveling-monitoring values, and are also closest to the leveling-monitoring results with the highest accuracy

Leaching characteristics and solidification strategy of heavy metals in solid waste from natural graphite purification

The tailings and fluorine-containing sludge were produced during the physical and chemical purification of natural crystalline graphite, containing heavy metals in different occurrence forms. To evaluate the threat of different heavy metals to the environment, this work uses the modified sequential extraction method (BCR) to study the presence of heavy metals in two solid wastes and their dissolution characteristics in different environments. The results show that the pollution risk of heavy metals in graphite tailings to the environment is ranked as Mn > Cr > Ni > Zn, and the pollution risk of Mn in fluorine-containing sludge is higher than that of Cr. This is because the Mn in the two solid wastes mainly exists in the form of weak acid extraction. The leaching number of heavy metals in the two solid wastes is directly proportional to the soaking time and soaking temperature, and inversely proportional to the pH value and the solid-to-liquid ratio. The number of heavy metals dissolved in solid waste landfills is significantly higher than that of acid rain and surface water environments. Based on the above results and the distribution of graphite solid waste, solidification agent was suggested to prevent heavy metal dissolution and reduce environmental risks

Leaching characteristics and solidification strategy of heavy metals in solid waste from natural graphite purification

The tailings and fluorine-containing sludge were produced during the physical and chemical purification of natural crystalline graphite, containing heavy metals in different occurrence forms. To evaluate the threat of different heavy metals to the environment, this work uses the modified sequential extraction method (BCR) to study the presence of heavy metals in two solid wastes and their dissolution characteristics in different environments. The results show that the pollution risk of heavy metals in graphite tailings to the environment is ranked as Mn > Cr > Ni > Zn, and the pollution risk of Mn in fluorine-containing sludge is higher than that of Cr. This is because the Mn in the two solid wastes mainly exists in the form of weak acid extraction. The leaching number of heavy metals in the two solid wastes is directly proportional to the soaking time and soaking temperature, and inversely proportional to the pH value and the solid-to-liquid ratio. The number of heavy metals dissolved in solid waste landfills is significantly higher than that of acid rain and surface water environments. Based on the above results and the distribution of graphite solid waste, solidification agent was suggested to prevent heavy metal dissolution and reduce environmental risks