This study investigates the changes due to crosslinking treatment in stiffness, permeability, and glycosaminoglycan (GAG) content of bovine intervertebral discs. The objective of this study was to determine the mechanical and biochemical effects of crosslinking treatment on lumbar bovine tissue. Previous studies have found that crosslinking can increase stiffness and permeability in the intervertebral disc. These changes have not yet been investigated by confined compression, stress-relaxation tests of young bovine tissue. Eleven lumbar motion segments were harvested from calf spines and soaked in a saline solution or one of four crosslinking treatments (genipin, methylglyoxal, proanthrocyanidin, and EDC). Five mm diameter samples were removed from the midannulus region at anterior / anterior-lateral locations, confined in a saline bath, swelled to equilibrium, and tested in confined compression stress-relaxation to 15% strain in 5% increments. Radial samples were also harvested, treated with saline solution and EDC, and tested in the same manner. The aggregate modulus and hydraulic permeability were calculated using the nonlinear biphasic theory. Swelling pressure was calculated as the load at swelling equilibrium. GAG content was measured using the dimethylmethylene blue assay. Differences with P value < 0.05 were considered significant. In the axial orientation, all crosslinking treatments except methyglyoxal at least doubled the aggregate modulus relative to soaked controls (P less than 0.05). Genipin treatment resulted in 78% lower axial permeability, proanthrocyanidin (PA) 50% lower, and EDC treatment 84% lower relative to soaked controls (P &lt; 0.05). GAG content measured in the methyglyoxal treatment group was 25% lower than in soaked control group. Genipin (G), proanthrocyanidin (PA), and EDC treatment increased the swelling pressure by at least 65% (P less than 0.05). In the radial orientation, EDC treatment increased the stiffness by 75%, and did not significantly affect the permeability or swelling pressure. Some crosslinking treatments proved effective in increasing the stiffness and swelling pressure of the disc. The increased swelling pressure in G, PA, and EDC treatment groups relative to soaked controls suggests reduced GAG leaching during soaking treatment, further confirmed by the reduction in permeability in these groups.

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Made available in DSpace on 2014-12-17T15:03:29Z (GMT). No. of bitstreams: 1 KarisiaLBF_DISSERT.pdf: 5553904 bytes, checksum: bd332662da6ffbc4e0c2609d1d3928c7 (MD5) Previous issue date: 2012-01-27 / A technological alternative for the correct disposal of tires is the use in the construction of embankment with soil and shredded tires. The use of waste tires in tropical soils requires prior knowledge of the properties and limitations of these materials. In this work, the results of an experimental program was devised to characterize the behavior of mixtures of waste tires and a lateritic soil. The residue used in this study is classified as tire buffings with an average size of 1.4 mm. The laboratory program included testing of particle size analysis, Atterberg limits, compaction, direct shear tests, permeability and confined compression tests with pure soil, pure tire and the mixtures. Proportions of 0% (pure soil), 10%, 20%, 40%, 50 % and 100% (pure tire) by weight were used. For the confining stress levels used in the study, the presence of tire residue provided a considerable increase in shear strength of the mixture. The maximum shear strength was obtained for a residue content of 40% by weight. Permeability tests on samples of waste under a confining stress of 100 kPa showed that the permeability increases significantly with increasing residue content until a residue content of 20%. The increase in permeability after that value showed to be negligible. Confined compression tests showed that the soil mixed with tire residue becomes more compressible than the pure soil. The secant constrained modulus (Msec) for the same vertical stress decreases with increasing percentage of residue. / Dentre as alternativas tecnol?gicas para a destina??o correta de pneus est? o uso na constru??o de aterros de misturas de solo e res?duo de pneus triturados. A utiliza??o de res?duo de pneus em solos tropicais requer o conhecimento pr?vio das propriedades e limita??es desses materiais. Nesta disserta??o, apresentam-se os resultados de um programa experimental para caracteriza??o de misturas de res?duo de pneus em um solo later?tico. O res?duo utilizado neste estudo ? classificado como desbastes de pneus, com tamanho m?dio de 1,4 mm. O programa laboratorial incluiu ensaios de an?lise granulom?trica, limites de consist?ncia, compacta??o, cisalhamento direto, permeabilidade e compress?o confinada com as misturas de solo res?duos de pneus. Foram utilizadas propor??es de 0% (solo puro), 10%, 20%, 40%, 50% e 100% (res?duo puro) em peso. Para os n?veis de tens?o confinantes utilizados no estudo, a presen?a do res?duo de pneu proporcionou um aumento consider?vel da resist?ncia ao cisalhamento da mistura. A m?xima resist?ncia ao cisalhamento foi obtida para um teor de res?duo de 40% em peso. Os ensaios de permeabilidade em amostras de res?duos sob uma tens?o confinante de 100 kPa revelaram que a permeabilidade cresce significativamente com o aumento do teor de res?duo at? um teor de 20%, estabilizando-se em seguida. Os ensaios de compress?o confinada evidenciaram que o solo misturado ao res?duo de pneus torna-se mais compress?vel que o solo puro. O estudo demonstra que o m?dulo de compress?o confinada secante (Msec) para uma mesma tens?o vertical diminui com o aumento da porcentagem de res?duo.