1,721,091 research outputs found
Bone matrix material properties on the micro- and nanoscale
No full textThe evaluation of fracture risk in osteoporotic patients, which is still mostly based on bone mineral density (BMD) measurements, constitutes a major clinical challenge. Despite the fact that BMD is highly correlated with fracture risk in large populations, it unfortunately fails to be an accurate predictor for the individual. To increase the accuracy of fracture risk evaluation, a better understanding of all factors affecting bone fracture behaviour, including (but not limited to) BMD, is needed. This means a deeper understanding of bone’s material properties and structure-function relationship is required.Mammalian bones are composed of mineralized type I collagen fibrils immersed in a matrix of non-collagenous proteins (NCPs). This fundamental unit assembles into progressively larger features in a hierarchical manner, supplying bone with various “lines of defence” against catastrophic failure. Optimal load transfer and energy dissipation mechanisms have, to some extent, been discovered within bone’s nanostructure on which NCPs have been proposed to play a crucial role. Yet, it is largely unknown if integration of such mechanisms occurs to any other hierarchical level. This thesis attempts to answer this question for the osteonal level of cortical bone. The feature dominating this level is a hollow tubular structure of a few hundred micrometres in diameter, the osteons, consisting of concentric aligned lamellae. Lamellae range from 3 -10 ?m in thickness and between them lie interlamellar areas (often referred to as thin lamellae).This thesis is the outcome of three studies. The first focuses on the aforementioned osteonal features, namely lamellae and interlamellar areas, studying their structure, composition and their mechanical behaviour during loading. For this purpose a series of experimental techniques were used including ?-RAMAN microscopy, atomic force microscopy (AFM), AFM cantilever-based nanoindentation and in-situ AFM analysis during microtensile testing. It was shown that interlamellar areas differ from lamellae by (a) being collagen-deficient and NCP-rich, (b) having a different arrangement of collagen fibres, (c) being more compliant when no load is applied to the bone and (d) exhibiting higher strains under loading conditions. Finally, stable crack propagation was for the first time captured in a time-lapsed fashion within the interlamellar areas by means of AFM, further proving their significant contribution towards fracture toughness.The second is a technical study for the development of a method capable for generating full fracture-resistance curves (R-curves) of small bone samples where crack propagation cannot easily be observed. The outcome was the development of a novel computer-aided videography method, “whitening-front tracking” method, which uses the whitening effect formed by the development of the damage in front of the crack-tip (frontal process zone) to indirectly track the crack propagation which is needed for the generation of the R-curve.The new method was then applied in the third study to correlate the ultimate toughness of human cortical bone, i.e. “fracture toughness” and “crack growth resistance” at the tissue-level, with the elasticity inhomogeneity between lamella and interlamellar areas at the osteonal-level and the damage-formation resistance at the micro-level. In this study the mechanical properties of bone in tissue-, micro- and osteonal-level were measured by means of the “whitening front tracking”, reference point indentation (RPI) and AFM cantilever-based nanoindentation methods respectively. The results revealed a correlation of toughness and crack-growth resistance at the tissue-level with the elastic inhomogeneity between the sub-osteonal features. That is, the higher the difference between the moduli of lamellae and interlamellar areas the higher the toughness of the tissue. Furthermore, toughness and crack-growth resistance correlated with bone’s “resistance to damage” as it was characterised by RPI at the micro-level. Finally, these measured suggested age-related degradation of the mechanical properties at all three levels measured. Overall, the results presented in this thesis propose that osteons are the principal component of a previously unknown proactive mechanism which transfers load and movement in a manner analogous to engineered “elastomeric bearing pads”. This ability originates from the elastic inhomogeneity between the lamellae and the interlamellar areas which allows osteons to adapt to high stresses without damage formation
Underlying CT data supporting the publication "A floating 3D printed formulation for the coadministration and sustained release of antihypertensive drugs"
No full textUnderlying CT data supporting the article "A floating 3D printed formulation for the coadministration and sustained release of antihypertensive drugs" by Paola Zgouro et al
Microfocus Computed Tomography (μCT)X-ray was employed for the characterization of the microstructure of the printed object, assessing the overall volume, porosity, local thickness and other printing defects. The imaging took place at the University of Southampton’s μ-VIS X-ray Imaging Centre (www.muvis.org) / 3D X-ray Histology facility using a customized μCT scanner optimized for 3D X-ray histology (www.xrayhistology.org) (Katsamenis et al., 2023) based on Nikon’s XTH225ST system (Nikon Metrology, Castle Donington, UK). The scanner was operated at 110 kVp / 90 μA (9.9 W), with the X-ray beam prefiltered using 0.04 mm of aluminum. The source-to-object and source-to-detector distances were 28.4 mm and 1136.7 mm, respectively, resulting in a magnification factor of 40x. Acquisition parameters included 2201 projections, averaging 4 frames per projection, with an exposure time of 177 ms per projection. The 2850 x 2850 dexels detector was binned 2x (virtual detector: 1425 × 1425 dexels), resulting in an isotropic voxel edge of 7.5 μm. The reconstructed data underwent visualization and analysis using Dragonfly software (Comet Technologies Canada Inc.; software available at http://www.theobjects.com/dragonfly).
The data is stored at https://doi.org/10.5281/zenodo.10614260</span
Behaviour and Reproduction of Drosophila Melanogaster Exposed to 3.5 GHz Radio-Frequency Electromagnetic Fields - Underlying data
No full textOverview
This dataset contains segmented STL 3D models, TIFF imaging data, and visualisations of the Drosophila (fruit fly) scan used in this study </span
The role of nanoscale toughening mechanisms in osteoporosis
No full textStrength is the most widely reported parameter with regards to bone failure. However, bone contains pre-existing damage and stress concentration sites, perhaps making measures of fracture toughness more indicative of the resistance of the tissue to withstand fracture. Several toughening mechanisms have been identified in bone, prominently, at the microscale. More recently, nanoscale toughness mechanisms, such as sacrificial-bonds and hidden-length or dilatational band formation, mediated by noncollagenous proteins, have been reported. Absence of specific noncollagenous proteins results in lowered fracture toughness in animal models. Further, roles of several other, putative influencing, factors such as closely bound water, collagen cross-linking and citrate bonds in bone mineral have also been proposed. Yet, it is still not clear if and which mechanisms are hallmarks of osteoporosis disease and how they influence fracture risk. Further insights on the workings of such influencing factors are of high importance for developing complementary diagnostics and therapeutics strategie
Interaction of fullerenes C60 with large unilamellar vesicles
No full textIn order to explore the fullerene-lipid interaction, we have studied\nthe effects caused by C-60 on Large Unilamellar Vesicles (LUV). For\nthis purpose liposomes composed of L-a Phosphatidylcholine (PC) and\n1,2-dimyristoyl-sn-glycero-3-phospocholine (DMPC) and Cholesterol\n(Chol) in 2:1 molar ratio were used. The dispersions were characterized\nby means of Dynamic Light Scattering (DLS), zeta-potential measurements\nand Differential Scanning Calorimetry studies (DSC). The incorporation\nof C-60 into liposomes altered their physicochemical properties. A\nreduction to the mean diameter of the liposomes was observed when C-60\nwere incorporated, which might imply deformations on the lipid membrane\ninduced by fullerenes. An increase to the surface charge of the\nliposomes was noticed when C-60 molecules were present in the membrane\nproviding evidence of their successful incorporation into the liposomal\nbilayers. Finally the miscibility of liposomes with C-60 was\ninvestigated by DSC. Alterations occurred to the main transition of the\nliposomes when C-60 molecules were present in the membrane might be\nattributed to the penetration of the carbonaceous material into the\nlipid bilayers
A floating 3D printed formulation for the coadministration and sustained release of antihypertensive drugs - Underlying CT data
No full textUnderlying CT data of Zgouro et al (2024) "A floating 3D printed polypill formulation for the coadministration and sustained release of antihypertensive drugs", International Journal of Pharmaceutics, 655, 124058, https://doi.org/10.1016/j.ijpharm.2024.124058
Microfocus Computed Tomography (μCT)
X-ray microfocus computed tomography (μCT) was employed for the characterization of the microstructure of the printed object, assessing the overall volume, porosity, local thickness and other printing defects. The imaging took place at the University of Southampton’s μ-VIS X-ray Imaging Centre (www.muvis.org) / 3D X-ray Histology facility using a customized μCT scanner optimized for 3D X-ray histology (www.xrayhistology.org) (Katsamenis et al., 2023) based on Nikon’s XTH225ST system (Nikon Metrology, Castle Donington, UK). The scanner was operated at 110 kVp / 90 μA (9.9 W), with the X-ray beam prefiltered using 0.04 mm of aluminum. The source-to-object and source-to-detector distances were 28.4 mm and 1136.7 mm, respectively, resulting in a magnification factor of 40x. Acquisition parameters included 2201 projections, averaging 4 frames per projection, with an exposure time of 177 ms per projection. The 2850 x 2850 dexels detector was binned 2x (virtual detector: 1425 × 1425 dexels), resulting in an isotropic voxel edge of 7.5 μm. The reconstructed data underwent visualization and analysis using Dragonfly software (Comet Technologies Canada Inc.; software available at http://www.theobjects.com/dragonfly).</span
Distribution of nanoelasticity in osteonal level affects bone fracture toughness behaviour
No full textmuVIS 3D x-ray CT scan of Newport Series brown earth loamy sand sieved to <2mm with wheat plant (cultivar Skyfall)
No full textx-ray CT at 160micron resolution using Hutch scanner at muVIS centre in Southampton
You can make a request to access this data via http://library.soton.ac.uk/datarequest</span
Non-destructive volume imaging in failure analysis: advantages and applications of x-ray micro-computed tomography
No full text3-D analysis of fatigue crack behaviour in a shot peened steam turbine blade material
Full text linkSerial mechanical sectioning and high resolution X-ray tomography have been used to study the three-dimensional morphology of small fatigue cracks growing in a 12 Cr tempered martensitic steam turbine blade material. A range of surface conditions has been studied, namely polished and shot peened (with varying levels of intensity). In the polished (unpeened) condition, inclusions (alumina and manganese sulphide) played an important role in initiating and controlling early fatigue crack behaviour. When fatigue cracks initiated from an alumina stringer, the crack morphology was normally dominated by single stringers, which were always in the centre of the fatigue crack, indicating its primary role in initiation. Manganese sulphide inclusion groups however seemed to dominate and affect the crack path along both the surface and depth crack growth directions. The more intensely shot peened condition did not however evidence inclusion or stringer affected fatigue crack initiation or growth behaviour; sub-surface crack coalescence being clearly observed by both serial sectioning and CT (computed tomography) imaging techniques at a depth of about 150 ~ 180 ?m. These sub-surface crack coalescences can be linked to both the extent of the compressive residual stress as well as the depth of the plastic deformation arising from the intense shot peening process. Shot peening appears to provide a different defect population that initiates fatigue cracks and competes with the underlying metallurgical defect populations. The most beneficial shot peening process would in this case appear to “deactivate” the original metallurgical defect population and substitute a known defect distribution from the shot peening process from which fatigue cracks grow rather slowly in the strain hardened surface layer which also contains compressive residual stresses. A benefit to fatigue life in bending, even under Low Cycle Fatigue (LCF) conditions, has been observed in these tests if a sufficiently severe shot peening condition is applied in a constrained notch configuration
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