4 results
Now showing1 - 4 of 4
- Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Elastic Response of Mesoporous Silicon to Capillary Pressures in the Pores(American Institute of Physics (AIP), 2015-06-29); ; ; ; We study water adsorption-induced deformation of a monolithic, mesoporous silicon membrane traversed by independent channels of ∼8 nm diameter. We focus on the elastic constant associated with the Laplace pressure-induced deformation of the membrane upon capillary condensation, i.e. the pore-load modulus. We perform finite-element method (FEM) simulations of the adsorption-induced deformation of hexagonal and square lattices of cylindrical pores representing the membrane. We find that the pore-load modulus weakly depends on the geometrical arrangement of pores, and can be expressed as a function of porosity. We propose an analytical model which relates the pore-load modulus to the porosity and to the elastic properties of bulk silicon (Young's modulus and Poisson's ratio), and provides an excellent agreement with FEM results. We find good agreement between our experimental data and the predictions of the analytical model, with the Young's modulus of the pore walls slightly lower than the bulk value. This model is applicable to a large class of materials with morphologies similar to mesoporous silicon. Moreover, our findings suggest that liquid condensation experiments allow one to elegantly access the elastic constants of a mesoporous medium.Publicationtype: Journal Article81 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Effect of in vivo loading on bone composition varies with animal age(Elsevier, 2015-03-01); ; Spevak, LyudmilaLoading can increase bone mass and size and this response is reduced with aging. It is unclear, however how loading affects bone mineral and matrix properties. Fourier transform infrared imaging and high resolution synchrotron scanning small angle X-ray scattering were used to study how bone's microscale and nanoscale compositional properties were altered in the tibial midshaft of young, adult, and elderly female C57Bl/6J mice after two weeks of controlled in vivo compressive loading in comparison to physiological loading. The effect of controlled loading on bone composition varied with animal age, since it predominantly influenced the bone composition of elderly mice. Interestingly, controlled loading led to enhanced collagen maturity in elderly mice. In addition, although the rate of bone formation was increased by controlled loading based on histomorphometry, the newly formed tissue had similar material quality to the new bone tissue formed during physiological loading. Similar to previous studies, our data showed that bone composition was animal age- and tissue age-dependent during physiological loading. The findings that the new tissue formed in response to controlled loading and physiological loading had similar bone composition and that controlled loading enhanced bone composition in elderly mice further support the use of physical activity as a noninvasive treatment to enhance bone quality as well as maintain bone mass in individuals suffering from age-related bone loss.Publicationtype: Journal Article15 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Relationship between nanoscale mineral properties and calcein labeling in mineralizing bone surfaces(Taylor & Francis, 2014); 9 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Spatial-temporal mapping of bone structural and elastic properties in a sheep model following osteotomy(Elsevier, 2011-03-01); ; The course of bone healing in animal models is conventionally monitored by morphologic approaches, which do not allow the determination of the material properties of the tissues involved. Mechanical characterization techniques are either dedicated to the macroscopic evaluation of the entire organ or to the microscopic evaluation of the tissue matrix. The latter provides insight to regionally specific alterations at the tissue level in the course of healing. In this study, quantitative scanning acoustic microscopy was used at 50 MHz to investigate microstructural and elastic alterations of mineralized callus and cortical tissue after transverse osteotomy in sheep tibiae. Analyses were performed after 2, 3, 6 and 9 weeks of consolidation with stabilization by either a rigid or a semi-rigid external fixator. Increased stiffness and decreased porosity were observed in the callus tissue over the course of the healing process, which was dependent on the fixator type. In the adjacent cortical tissue, stiffness decreased during the first 3 weeks. Cortical porosity increased over time but the time-dependence was different between the two fixator types. The changes of stiffness of cortical and callus tissues were measured with respect to the distance to the periosteal cortex-callus boundary. Stiffness of cortex and callus tissue smoothly decreased as a function of the distance from the inner cortical region. The data obtained in this study can help to understand the processes involved in tissue maturation during endogenous bone healing. © 2011 World Federation for Ultrasound in Medicine & Biology.Publicationtype: Journal Article4