Temperature dependent phase transition of EuO on MgO(100)

We investigated the changes of magnetic properties and phase transition in EuO films grown on a MgO(100) substrate as a function of temperature. As the temperature was varied, we observed a clear phase transition and polarization change at 69 K using spin resolved photoemission spectroscopy and low energy electron diffraction. We will elucidate the temperature driven changes in the electronic and magnetic properties of EuO films on a MgO(100) substrate. (C) 2007 American Institute of Physics.open11910sciescopu

The optical microscopy with virtual image breaks a record: 50-nm resolution imaging is demonstrated

We demonstrate a new 'microsphere nanoscope' that uses ordinary SiO2 microspheres as superlenses to create a virtual image of the object in near field. The magnified virtual image greatly overcomes the diffraction limit. We are able to resolve clearly 50-nm objects under a standard white light source in both transmission and reflection modes. The resolution achieved for white light opens a new opportunity to image viruses, DNA and molecules in real time

Foot Bone in Vivo: Its Center of Mass and Centroid of Shape

This paper studies foot bone geometrical shape and its mass distribution and establishes an assessment method of bone strength. Using spiral CT scanning, with an accuracy of sub-millimeter, we analyze the data of 384 pieces of foot bones in vivo and investigate the relationship between the bone's external shape and internal structure. This analysis is explored on the bases of the bone's center of mass and its centroid of shape. We observe the phenomenon of superposition of center of mass and centroid of shape fairly precisely, indicating a possible appearance of biomechanical organism. We investigate two aspects of the geometrical shape, (i) distance between compact bone's centroid of shape and that of the bone and (ii) the mean radius of the same density bone issue relative to the bone's centroid of shape. These quantities are used to interpret the influence of different physical exercises imposed on bone strength, thereby contributing to an alternate assessment technique to bone strength.Comment: 9 pages, 4 figure

Osteogenesis evaluation of duck’s feet derived collagen/hydroxyapatite sponges immersed in dexamethasone

Background: The aim of this study was to investigate the osteogenesis effects of DC and DC/HAp sponge immersed in without and with dexamethasone. Methods: The experimental groups in this study were DC and DC/HAp sponge immersed in without dexamethasone (Dex(â )DC and Dex(â )-DC/HAp group) and with dexamethasone (Dex(+)-DC and Dex(+)-DC/HAp group). We characterized DC and DC/HAp sponge using compressive strength, scanning electron microscopy (SEM). Also, osteogenic differentiation of BMSCs on sponge (Dex(â )DC, Dex(â )-DC/HAp, Dex(+)-DC and Dex(+)-DC/HAp group) was assessed by SEM, 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazoliumbromide (MTT) assay, alkaline phosphatase (ALP) activity assay and reverse transcription-PCR (RT-PCR). Results: In this study, we assessed osteogenic differentiation of BMSCs on Duckâ s feet-derived collagen (DC)/ HAp sponge immersed with dexamethasone Dex(+)-DC/HAp. These results showed that Dex(+)-DC/HAp group increased cell proliferation and osteogenic differentiation of BMSCs during 28 days. Conclusion: From these results, Dex(+)-DC/HAp can be envisioned as a potential biomaterial for bone regeneration applications.This work was supported by Technology Commercialization Support Program [grant number 814005-03-3-HD020], Ministry for Food, Agriculture, Forestry and Fisheries (MIFAFF).info:eu-repo/semantics/publishedVersio

Mechanical properties of femoral trabecular bone in dogs

BACKGROUND: Studying mechanical properties of canine trabecular bone is important for a better understanding of fracture mechanics or bone disorders and is also needed for numerical simulation of canine femora. No detailed data about elastic moduli and degrees of anisotropy of canine femoral trabecular bone has been published so far, hence the purpose of this study was to measure the elastic modulus of trabecular bone in canine femoral heads by ultrasound testing and to assess whether assuming isotropy of the cancellous bone in femoral heads in dogs is a valid simplification. METHODS: From 8 euthanized dogs, both femora were obtained and cubic specimens were cut from the centre of the femoral head which were oriented along the main pressure and tension trajectories. The specimens were tested using a 100 MHz ultrasound transducer in all three orthogonal directions. The directional elastic moduli of trabecular bone tissue and degrees of anisotropy were calculated. RESULTS: The elastic modulus along principal bone trajectories was found to be 11.2 GPa ± 0.4, 10.5 ± 2.1 GPa and 10.5 ± 1.8 GPa, respectively. The mean density of the specimens was 1.40 ± 0.09 g/cm(3). The degrees of anisotropy revealed a significant inverse relationship with specimen densities. No significant differences were found between the elastic moduli in x, y and z directions, suggesting an effective isotropy of trabecular bone tissue in canine femoral heads. DISCUSSION: This study presents detailed data about elastic moduli of trabecular bone tissue obtained from canine femoral heads. Limitations of the study are the relatively small number of animals investigated and the measurement of whole specimen densities instead of trabecular bone densities which might lead to an underestimation of Young's moduli. Publications on elastic moduli of trabecular bone tissue present results that are similar to our data. CONCLUSION: This study provides data about directional elastic moduli and degrees of anisotropy of canine femoral head trabecular bone and might be useful for biomechanical modeling of proximal canine femora

Structural hierarchies define toughness and defect-tolerance despite simple and mechanically inferior brittle building blocks

Mineralized biological materials such as bone, sea sponges or diatoms provide load-bearing and armor functions and universally feature structural hierarchies from nano to macro. Here we report a systematic investigation of the effect of hierarchical structures on toughness and defect-tolerance based on a single and mechanically inferior brittle base material, silica, using a bottom-up approach rooted in atomistic modeling. Our analysis reveals drastic changes in the material crack-propagation resistance (R-curve) solely due to the introduction of hierarchical structures that also result in a vastly increased toughness and defect-tolerance, enabling stable crack propagation over an extensive range of crack sizes. Over a range of up to four hierarchy levels, we find an exponential increase in the defect-tolerance approaching hundred micrometers without introducing additional mechanisms or materials. This presents a significant departure from the defect-tolerance of the base material, silica, which is brittle and highly sensitive even to extremely small nanometer-scale defects

Correlative Light and Scanning X-Ray Scattering Microscopy of Healthy and Pathologic Human Bone Sections

Scanning small and wide angle X-ray scattering (scanning SWAXS) experiments were performed on healthy and pathologic human bone sections. Via crystallographic tools the data were transformed into quantitative images and as such compared with circularly polarized light (CPL) microscopy images. SWAXS and CPL images allowed extracting information of the mineral nanocrystalline phase embedded, with and without preferred orientation, in the collagen fibrils, mapping local changes at sub-osteon resolution. This favorable combination has been applied for the first time to biopsies of dwarfism syndrome and Paget's disease to shed light onto the cortical structure of natural bone in healthy and pathologic sections

Three-Dimensional Geometric Analysis of Felid Limb Bone Allometry

Studies of bone allometry typically use simple measurements taken in a small number of locations per bone; often the midshaft diameter or joint surface area is compared to body mass or bone length. However, bones must fulfil multiple roles simultaneously with minimum cost to the animal while meeting the structural requirements imposed by behaviour and locomotion, and not exceeding its capacity for adaptation and repair. We use entire bone volumes from the forelimbs and hindlimbs of Felidae (cats) to investigate regional complexities in bone allometry.Computed tomographic (CT) images (16435 slices in 116 stacks) were made of 9 limb bones from each of 13 individuals of 9 feline species ranging in size from domestic cat (Felis catus) to tiger (Panthera tigris). Eleven geometric parameters were calculated for every CT slice and scaling exponents calculated at 5% increments along the entire length of each bone. Three-dimensional moments of inertia were calculated for each bone volume, and spherical radii were measured in the glenoid cavity, humeral head and femoral head. Allometry of the midshaft, moments of inertia and joint radii were determined. Allometry was highly variable and related to local bone function, with joint surfaces and muscle attachment sites generally showing stronger positive allometry than the midshaft.Examining whole bones revealed that bone allometry is strongly affected by regional variations in bone function, presumably through mechanical effects on bone modelling. Bone's phenotypic plasticity may be an advantage during rapid evolutionary divergence by allowing exploitation of the full size range that a morphotype can occupy. Felids show bone allometry rather than postural change across their size range, unlike similar-sized animals