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    ABSTRACT: Based on careful design of composition, a two-glassy-phase Cu47.2Zr46.5Al5.5Nb0.8 bulk metallic glass with a large plasticity (∼16%) was successfully prepared. Energy-dispersive spectroscopy and electron energy loss spectroscopy confirm that the bright matrix phase is rich in Zr/Nb while the dark particle phase is rich in Cu/Al. Theoretical calculations suggest that a small difference in shear modulus between phases may be necessary before pronounced plastic deformation can occur.
    Scripta Materialia. 01/2014; s 72–73:47–50.
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    ABSTRACT: Biodegradable chitosan–graphene oxide (GO) nanocomposites possess improved mechanical properties and drug delivery performance over chitosan and could prove to be a viable, controlled and pH-sensitive transdermal drug delivery system. Chitosan nanocomposites containing varying GO contents and drug loading ratios were investigated. The nanocomposite with 2 wt % GO provided the optimal combination of mechanical properties and drug-loading capacity. It offered a faster and a more substantial release of drug than chitosan as well as a slower biodegradation rate, owing to the abundant oxygenated functional groups, hydrophilicity and large specific surface area of GO sheets. The drug delivery profiles of the nanocomposite were dependent on the drug loading ratio, with 0.84:1 being the best ratio of drug to GO for a quick and high release of the loaded drug. The nanocomposite also demonstrated pH sensitivity of drug release, releasing 48% less drug in an acidic condition than in a neutral environment.
    Carbohydrate Polymers 01/2014; 103:70–80.
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    ABSTRACT: Open cell aluminium foams produced by replication have their strength enhanced by ceramic surface layers generated using plasma electrolytic oxidation. The composite materials produced show, in some cases, greater relative increases in strength–weight ratio than those produced by applying other coatings to porous structures; however, the behaviour depends on the characteristics of the layer generated. The most significant increases appear to correlate with conditions that produce more uniform coating thicknesses with depth of penetration into the foam structure.
    Scripta Materialia. 01/2014; 75:38-41.
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    ABSTRACT: The structure and magnetic properties of thin Co90Fe10 films have been studied to determine how different soft magnetic underlayers (Fe81B13.5Si3.5C2 (Metglas) and Ni81Fe19) influence these properties with the aim to achieve soft fcc Co90Fe10 films with large magnetostriction constants. The thickness of the Co90Fe10 films was 25 nm with the thickness of the magnetic underlayer ranging from 15 nm to 35 nm. The effect of applying a magnetic field during the growth of both layers was also investigated. From X-ray diffraction, it was found that the Co90Fe10 films grown on NiFe had lower in-plane stresses compared to those grown on silicon and Metglas. While the coercive fields of all the Co90Fe10 films were smaller than the monolith Co90Fe10 film, the magnetostriction constants were strongly dependent on the underlayer they were grown on. Thus it is possible to tune the magnetostriction constant of the Co90Fe10 film to be positive or negative by selecting the correct soft magnetic underlayer.
    Journal of Magnetism and Magnetic Materials 01/2014; 357:87–92.
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    ABSTRACT: The reduction of graphene oxide at body temperature by using a biopolymer, chitosan, was proven to be successful. This biocompatible reduction approach will provide a versatile platform for applying graphene in biomedical fields including tissue engineering and therapeutic delivery. The use of this approach for therapeutic delivery is demonstrated.
    Materials science & engineering. C, Materials for biological applications. 01/2014; 34C:50-53.
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    ABSTRACT: Oxide ion conductors find important technical applications in electrochemical devices such as solid-oxide fuel cells (SOFCs), oxygen separation membranes and sensors. Na0.5Bi0.5TiO3 (NBT) is a well-known lead-free piezoelectric material; however, it is often reported to possess high leakage conductivity that is problematic for its piezo- and ferroelectric applications. Here we report this high leakage to be oxide ion conduction due to Bi-deficiency and oxygen vacancies induced during materials processing. Mg-doping on the Ti-site increases the ionic conductivity to ~0.01 S cm(-1) at 600 °C, improves the electrolyte stability in reducing atmospheres and lowers the sintering temperature. This study not only demonstrates how to adjust the nominal NBT composition for dielectric-based applications, but also, more importantly, gives NBT-based materials an unexpected role as a completely new family of oxide ion conductors with potential applications in intermediate-temperature SOFCs and opens up a new direction to design oxide ion conductors in perovskite oxides.
    Nature Material 11/2013;
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    ABSTRACT: Oesophageal cancer is the ninth leading cause of malignant cancer death and its prognosis remains poor, ranking as the sixth most frequent cause of death in the world. This research work aims to adopt an Auxetic (rotating-squares) geometry device, that had previously been examined theoretically and analysed by Grima and Evans (J Mater Sci Lett 19(17):1563-1565, 2000), to produce a novel Auxetic oesophageal stent and stent-grafts relevant to the palliative treatment of oesophageal cancer and also for the prevention of dysphagia. This paper discusses the manufacture of a small diameter Auxetic oesophageal stent and stent-graft. The oral deployment of such an Auxetic stent would be simplest if a commercial balloon dilatational catheter was used as this obviates the need for an expensive dedicated delivery system. A novel manufacturing route was employed in this research to develop both Auxetic films and Auxetic oesophageal stents, which ranged from conventional subtractive techniques to a new additive manufacturing method. Polyurethane was selected as a material for the fabrication of Auxetic films and Auxetic oesophageal stents because of its good biocompatibility and non-toxicological properties. The Auxetic films were later used for the fabrication of seamed Auxetic oesophageal stents. The flexible polyurethane tubular grafts were also attached to the inner luminal side of the seamless Auxetic oesophageal stents, in order to prevent tumour in-growth. Scanning electron microscopy was used to conduct surface morphology study by using different Auxetic specimens developed from different conventional and new additive manufacturing techniques. Tensile testing of the Auxetic films was performed to characterise their mechanical properties. The stent expansion tests of the Auxetic stents were done to analyse the longitudinal extension and radial expansion of the Auxetic stent at a range of radial pressures applied by the balloon catheter, and to also identify the pressure values where the Auxetic stent fails. Finite element models of both Auxetic film and Auxetic stent were developed, and the results were compared with experimental results with a good agreement. The tensile testing of the Auxetic polyurethane films revealed that the Poisson's ratio of the sample ranged between -0.87 and -0.963 at different uniaxial tensile load values. From the stent expansion test, it was found that the Auxetic oesophageal stent radially expanded from 0.5 to 5.73 mm and longitudinally extended from 0.15 to 1.83 mm at a range of applied pressure increments (0.5-2.7 bar) from the balloon catheter.
    Journal of Materials Science Materials in Medicine 10/2013;
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    ABSTRACT: Zirconia femoral heads retrieved from patients after different implantation periods (up to 13 years) were analysed using vertical scanning interferometry, atomic force microscopy and Raman microspectroscopy. A range of topographical and compositional changes on the surface of the retrievals are reported in this work. The study revealed that changes in roughness are the result of a combination of factors, i.e. scratching, surface upheaval due to transformation to the monoclinic phase and grain pull-out. Clusters of transformed monoclinic grains were observed on heads implanted for more than 3 years. The phase composition of these clusters was confirmed by Raman microspectroscopy. Increased abrasive wear and a higher monoclinic phase content concentrated on the pole of the femoral heads, confirming that the tetragonal to monoclinic phase transformation was not only induced by the tetragonal phase metastability and environmental conditions but mechanical and tribological factors, also affected the transformation kinetics. Additionally, the head implanted for 13 years showed evidence of a self-polishing mechanism leading to a considerable smoothening of the surface. These observations provide an insight into the interrelated mechanisms underlying the wear and transformation process on zirconia ceramics during implantation.
    Journal of the mechanical behavior of biomedical materials. 10/2013;
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    ABSTRACT: Bone turnover in vivo is regulated by mechanical forces such as shear stress originating from interstitial oscillatory fluid flow (OFF), and bone cells in vitro respond to mechanical loading. However, the mechanisms by which bone cells sense mechanical forces, resulting in increased mineral deposition, are not well understood. The aim of this study was to investigate the role of the primary cilium in mechanosensing by osteoblasts. MLO-A5 murine osteoblasts were cultured in monolayer and subjected to two different OFF regimens: 5 short (2 h daily) bouts of OFF followed by morphological analysis of primary cilia; or exposure to chloral hydrate to damage or remove primary cilia and 2 short bouts (2 h on consecutive days) of OFF. Primary cilia were shorter and there were fewer cilia per cell after exposure to periods of OFF compared with static controls. Damage or removal of primary cilia inhibited OFF-induced PGE2 release into the medium and mineral deposition, assayed by Alizarin red staining. We conclude that primary cilia are important mediators of OFF-induced mineral deposition, which has relevance for the design of bone tissue engineering strategies and may inform clinical treatments of bone disorders causes by load-deficiency.-Delaine-Smith, R. M., Sittichokechaiwut, A., Reilly, G. C. Primary cilia respond to fluid shear stress and mediate flow-induced calcium deposition in osteoblasts.
    The FASEB Journal 10/2013;
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    ABSTRACT: Synthetic non-absorbable meshes are widely used to augment surgical repair of stress urinary incontinence (SUI) and pelvic organ prolapse (POP); however, there is growing concern such meshes are associated with serious complications. This study compares the potential of two autologous cell sources for attachment and extra-cellular matrix (ECM) production on a biodegradable scaffold to develop tissue engineered repair material (TERM). Human oral fibroblasts (OF) and human adipose-derived stem cells (ADSC) were isolated and cultured on thermo-annealed poly-L-lactic acid (PLA) scaffolds for two weeks under either unrestrained conditions or restrained (either with or without intermittent stress) conditions. Samples were tested for cell metabolic activity (AlamarBlue® assay), contraction (serial photographs analyzed with image J software), total collagen production (Sirius red assay), and production of ECM components (immunostaining for collagen I, III, and elastin; and scanning electron microscopy) and biomechanical properties (BOSE tensiometer). Differences were statistically tested using two sample t-test. Both cells showed good attachment and proliferation on scaffolds. Unrestrained scaffolds with ADSC produced more total collagen and a denser homogenous ECM than OF under same conditions. Restrained conditions (both with and without intermittent stress) gave similar total collagen production, but improved elastin production for both cells, particularly OF. The addition of any cell onto scaffolds led to an increase in biomechanical properties of scaffolds compared to unseeded scaffolds. OF and ADSC both appear to be suitable cell types to combine with biodegradable scaffolds, in the development of a TERM for the treatment of SUI and POP. Neurourol. Urodynam. © 2013 Wiley Periodicals, Inc.
    Neurourology and Urodynamics 07/2013;
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