Pre-clinical studies to validate the MITCH PCR™ Cup: a flexible and anatomically shaped acetabular component with novel bearing characteristics

A previous clinical study was undertaken to evaluate the safety and efficacy of an anatomically shaped, flexible acetabular cup. Clinical results achieved were satisfactory, although some deficiencies in the model were identified. Design changes to the original model have been implemented to improve both initial stability and long term biological fixation. This was achieved through modifications made to both the anchoring mechanism and by the application of an appropriate backing surface layer promoting bone on-growth. In addition, changes to the articulation couple have also been introduced to improve implant durability and bearing performance, utilising a carbon fibre reinforced polyetheretherketone—alumina couple. Simulated loading, in both models, was performed using Finite Element Analysis. Mechanical and tribological tests were also performed to ensure the robustness of the new optimised design. Bio-compatibility of the articulation couple was demonstrated using an animal model. Implantation of the device has been extensively tested and re-validated in vitro to achieve a favourable polar contact between cup and femoral head and establish a reproducible operative technique. This preliminary work is undertaken prior to commencing a post market surveillance study of the CE marked implant.     

Fracture of high volume fraction ceramic particle reinforced aluminium under multiaxial stress

Circumferentially notched cylindrical bars of high volume fraction Al₂O₃ particle reinforced aluminium are tested in tension to probe the role of tensile stress triaxiality on damage and failure of such materials. The transverse strain is monitored with a specially designed video extensometer. A significant dependence of the peak average stress and failure strain on notch radius is observed. Finite-element simulations of the tests are conducted on the basis of a micromechanical model derived from earlier studies of damage and failure of these composites under uniaxial tensile deformation (Journal of the Mechanics and Physics of Solids 2009;57:1781). The simulations show that stress and strain distributions within the notched composite samples deviate significantly from predictions of Bridgman’s simplified analysis. Comparison with data shows that, whereas calculations capture satisfactorily the evolution of the average composite flow stress as a function of notch radius at small strains, the notched samples damage faster and fail at strains lower than predicted. Two phenomena may explain the discrepancy, namely (i) damage coalescence beyond a threshold level, and (ii) the incapacity of the matrix to sustain large hydrostatic stresses, which results from the presence of internal surfaces (cracked particles and possibly matrix voiding).     

Experimental methods in chemical engineering: Transmission electron microscopy—TEM

Thanks to an accelerating voltage in the range of 30 to 300 kV, an electron beam can pass through a thin specimen and form an image with sub-Ångström spatial resolution. When impinging on a thin crystalline specimen, the fast electrons scatter and diffract. The transmitted electron pattern depends on the local thickness, density, crystal structure, and chemical nature of the sample. The transmission electron microscope (TEM) shapes the incoming electron beam using magnetic lenses onto the specimen and, using a different set of magnetic lenses, focuses the projected electron pattern to a camera. The final image magnification and contrast are controlled using the parameters from the electron gun, apertures positioned along the optical path, and magnetic lenses. With this combination of lens and aperture, TEM offers two possible modes of operation: (a) imaging, including high-resolution electron microscopy to reveal the size, shape, crystallinity, and morphology of materials; and (b) diffraction, to determine the crystalline nature of a region of interest of a thin film, particle, or collection of particles. Chemical engineers have taken advantage of both of these modes to analyze their samples and inform their research. A bibliometric study conducted using the WoS database places TEM as one of the preferred microscopy tools to study advanced materials such as thin films, nanomaterials, and composites used in particular for the development of applications related to energy storage and conversion (catalysis, photocatalysis, electrochemistry, and batteries) and environment (adsorption, waste-water treatment, and filtration).     

Canonical visual size for real-world objects.

Real-world objects can be viewed at a range of distances and thus can be experienced at a range of visual angles within the visual field. Given the large amount of visual size variation possible when observing objects, we examined how internal object representations represent visual size information. In a series of experiments which required observers to access existing object knowledge, we observed that real-world objects have a consistent visual size at which they are drawn, imagined, and preferentially viewed. Importantly, this visual size is proportional to the logarithm of the assumed size of the object in the world, and is best characterized not as a fixed visual angle, but by the ratio of the object and the frame of space around it. Akin to the previous literature on canonical perspective, we term this consistent visual size information the canonical visual size. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Diffusional kurtosis imaging (DKI) incorporation into an intravoxel incoherent motion (IVIM) MR model to measure cerebral hypoperfusion induced by hyperventilation challenge in healthy subjects

Magnetic Resonance Materials in Physics, Biology and Medicine - The objectives were to investigate the diffusional kurtosis imaging (DKI) incorporation into the intravoxel incoherent motion (IVIM)...     

State of the art about dissimilar metal friction stir welding

Friction stir welding is a rather recent welding process (patented in 1991 by Thomas et al., ‘Improvements to friction welding’ UK patent application no. 9125978.8, US Patent 5460317, 1995) that has shown great potential for welding dissimilar materials even of different metallic nature, e.g. Al to steel, Mg to steel, Al to Ti, Mg to Ti, Al to Cu, Al to Mg. This review presents the specific microstructural features and mechanical properties, in particular tensile strength, of such welds. A focus will be on the material flow and welding defects, on the intermetallic compounds, on constitutional liquation, on particularities related to dissimilar lap welding and finally on process modifications to improve dissimilar friction stir weldability.     

Discriminating natal origin of spawning adult sea lamprey (Petromyzon marinus) in Lake Champlain using statolith elemental signatures

Sea lamprey (Petromyzon marinus) is a nuisance species in the Great Lakes and Lake Champlain. Information about tributary contributions to the spawning adult phase is critical for appropriate allocation of efforts to control this species. We examined the accuracy of statolith elemental composition to identify the natal origin (i.e., individual rivers or clusters of rivers) of 33 known-origin adults from the Lake Champlain basin. To do so, we first established natal origin chemical signatures using the statoliths of 238 larvae from the same basin. Using laser-ablation inductively coupled plasma mass spectrometry, the 238 larvae originating from 12 streams and one delta were discriminated with a classification accuracy of 57% (range: 25–80%) and 70% (range: 29–80%) when individual streams and groups of streams were considered respectively, highlighting the potential of statolith microchemistry to identify natal origins. However, the assignment of natal origin for adults was overwhelmingly incorrect. Using a maximum likelihood procedure, 88% of the adults were assigned to a cluster of three streams and one delta, while only 3% of these individuals were known to originate from this particular cluster. More research is required to understand the low classification accuracy of sea lamprey adults and validate the use of statolith microchemistry to identify sea lamprey natal origin.     

Polymer Films Composed of Surface‐Bound Nanofilaments with a High Aspect Ratio,Molecularly Imprinted with Small Molecules and Proteins

Hierarchically nanostructured materials that combine two or more levels of structuring and that exhibit a combination of useful features have gained considerable interest over recent years. Here, the generation of surface‐bound nanofilaments with a high aspect ratio by nanomolding on a nanoporous template surface is described. The filaments, at the same time, carry molecularly imprinted binding sites. The dye fluorescein and the protein myoglobin are used as model templates for imprinting. The surfaces exhibit specific binding as revealed by fluorescence microscopy. The wetting properties of the surfaces depend on the dimensions of the nanofilaments and on the nature of the polymer. It is believed that these materials can potentially be useful for applications in biosensors and biochips.     

Comparative proteome profiling of MCF10A and 184A1 human breast epithelial cells emphasized involvement of CDK4 and cyclin D3 in cell proliferation

Acquiring high proliferation rate is crucial for carcinogenic transformation of cells. We report here proteome profiling of human breast epithelial cells with low (184A1) and high (MCF10A) proliferation rates. We identified 183 proteins in 184A1 and 318 proteins in MCF10A cells. These datasets provide the most comprehensive proteome annotations of 184A1 and MCF10A cells. Proteins were taken for identification from 2-D gels in a systematic and unbiased way. Functional clustering of the identified proteins showed similarities in distribution of proteins to the same functional domains, indicating similarities in proteomes of 184A1 and MCF10A cells. Among observed differences in protein expression, we validated correlation of expression of endogenous cyclin-dependent kinase 4 (CDK4), cyclin D3, cdc25B, and p38γ with cell proliferation. Furthermore, down-regulation of CDK4 and cyclin D3 with specific siRNA inhibited cell proliferation, which emphasized the role of CDK4 and cyclin D3 in enhancement of cell proliferation rate of human breast epithelial cells.     

Modeling the Shape of the Scene: A Holistic Representation of the Spatial Envelope

In this paper, we propose a computational model of the recognition of real world scenes that bypasses the segmentation and the processing of individual objects or regions. The procedure is based on a very low dimensional representation of the scene, that we term the Spatial Envelope. We propose a set of perceptual dimensions (naturalness, openness, roughness, expansion, ruggedness) that represent the dominant spatial structure of a scene. Then, we show that these dimensions may be reliably estimated using spectral and coarsely localized information. The model generates a multidimensional space in which scenes sharing membership in semantic categories (e.g., streets, highways, coasts) are projected closed together. The performance of the spatial envelope model shows that specific information about object shape or identity is not a requirement for scene categorization and that modeling a holistic representation of the scene informs about its probable semantic category.