A pilot study for the digital replacement of a distorted dentition acquired by Cone Beam Computed Tomography (CBCT)

Abstract Introduction: Cone beam CT (CBCT) is becoming a routine imaging modality designed for the maxillofacial region. Imaging patients with intra-oral metallic objects cause streak artefacts. Artefacts impair any virtual model by obliterating the teeth. This is a major obstacle for occlusal registration and the fabrication of orthognathic wafers to guide the surgical correction of dentofacial deformities. Aims and Objectives: To develop a method of replacing the inaccurate CBCT images of the dentition with an accurate representation and test the feasibility of the technique in the clinical environment. Materials and Method: Impressions of the teeth are acquired and acrylic baseplates constructed on dental casts incorporating radiopaque registration markers. The appliances are fitted and a preoperative CBCT is performed. Impressions are taken of the dentition with the devices in situ and subsequent dental models produced. The models are scanned to produce a virtual model. Both images of the patient and the model are imported into a virtual reality software program and aligned on the virtual markers. This allows the alignment of the dentition without relying on the teeth for superimposition. The occlusal surfaces of the dentition can be replaced with the occlusal image of the model. Results: The absolute mean distance of the mesh between the markers in the skulls was in the region of 0.09mm ± 0.03mm; the replacement dentition had an absolute mean distance of about 0.24mm ± 0.09mm. In patients the absolute mean distance between markers increased to 0.14mm ± 0.03mm. It was not possible to establish the discrepancies in the patient’s dentition, since the original image of the dentition is inherently inaccurate. Conclusion: It is possible to replace the CBCT virtual dentition of cadaveric skulls with an accurate representation to create a composite skull. The feasibility study was successful in the clinical arena. This could be a significant advancement in the accuracy of surgical prediction planning, with the ultimate goal of fabrication of a physical orthognathic wafer using reverse engineering

Studies of fiber-matrix adhesion on compression strength

A study was initiated on the effect of the matrix polymer and the fiber matrix bond strength of carbon fiber polymer matrix composites. The work includes tests with micro-composites, single ply composites, laminates, and multi-axial loaded cylinders. The results obtained thus far indicate that weak fiber-matrix adhesion dramatically reduces 0 degree compression strength. Evidence is also presented that the flaws in the carbon fiber that govern compression strength differ from those that determine fiber tensile strength. Examination of post-failure damage in the single ply tests indicates kink banding at the crack tip

Re-identification of c. 15 700 cal yr BP tephra bed at Kaipo Bog, eastern North Island: implications for dispersal of Rotorua and Puketarata tephra beds.

A 10 mm thick, c. 15 700 calendar yr BP (c. 13 100 14C yr BP) rhyolitic tephra bed in the well-studied montane Kaipo Bog sequence of eastern North Island was previously correlated with Maroa-derived Puketarata Tephra. We revise this correlation to Okataina-derived Rotorua Tephra based on new compositional data from biotite phenocrysts and glass. The new correlation limits the known dispersal of Puketarata Tephra (sensu stricto, c. 16 800 cal yr BP) and eliminates requirements to either reassess its age or to invoke dual Puketarata eruptive events. Our data show that Rotorua Tephra comprises two glass-shard types: an early-erupted low-K2O type that was dispersed mostly to the northwest, and a high-K2O type dispersed mostly to the south and southeast, contemporary with late-stage lava extrusion. Late-stage Rotorua eruptives contain biotite that is enriched in FeO compared with biotite from Puketarata pyroclastics. The occurrence of Rotorua Tephra in Kaipo Bog (100 km from the source) substantially extends its known distribution to the southeast. Our analyses demonstrate that unrecognised syn-eruption compositional and dispersal changes can cause errors in fingerprinting tephra deposits. However, the compositional complexity, once recognised, provides additional fingerprinting criteria, and also documents magmatic and dispersal processes

An Assessment of Tarong Bottom Ash for Use on Agricultural Soils

Coal combustion by-products (CCBs), including fly ash and bottom ash, present a waste disposal problem in Australia due to a continuing demand for coal fired power. Pozzolanic Enterprises handle ash produced by the Tarong Energy coalfired power station in SouthWest Queensland, which produces approximately 1,200,000 tonnes per annum of CCBs. This comprises roughly 1,100,000 tonnes of fly ash and 100,000 tonnes of furnace bottom ash. The volume and unique properties of the Tarong bottom ash present a significant opportunity for agronomic use. Of particular interest is the ability of Tarong bottom ash to markedly improve the water holding capacity of soils. Given Australia's rural environment is currently enduring a 'one-in-one- hundred-year' drought a study of the ability of Tarong bottom ash to improve water holding capacity is timely. This paper details physical and chemical properties relevant to agronomic use and water holding capacity of ash/soil blends along with some results from initial field trials

Internal parasites of cattle

Worm parasites can have a most serious effect on cattle, even causing deaths. This article describes the main parasites of cattle, treatment with modern anthelmintic drugs and the best means of preventing and controlling worm outbreaks

Determination of local material properties of OSB sample by coupling advanced imaging techniques and morphology-based FEM simulation

This is the publisher’s final pdf. The published article is copyrighted by Walter de Gruyter & Co. and can be found at: http://www.degruyter.com/.The goal was to determine local mechanical properties inside of oriented strand board (OSB) based on a realistic morphology-based finite element (FE) model and data acquired from a physical test performed on the same material. The spatial information and local grayscale intensity from CT-scans obtained from small OSB sample was transformed into a 2D regular morphology-based FE mesh with corresponding material properties. The model was then used to simulate the actual compression test performed on the specimen using simplified boundary conditions. The simulated strain fields from the model were compared with the actual strain field measured on the specimen surface during the compression test by means of a full-field optical method, named digital image correlation (DIC). Finally, the original set of material properties was adjusted by an iterative procedure to minimize the difference between the simulated and the measured strain data. The results show that the developed procedure is useful to find local material properties as well as for morphological modeling without the need of segmentation of the image data. The achieved results serve as a prerequisite for full 3D analyses of the complex materials

Ovine vibriosis : a new cause of sheep infertility

Vibrionic abortion of sheep has caused heavy losses in a number of wheatbelt flocks. In several flocks up to 50 per cent, of the ewes aborted as a result of this newly reported disease. This article gives the history of the disease in this State, and describes the symptoms for the benefit of other farmers whose flocks may be affected. Ewes become immune after the first attack

Isolation, identification and characterisation of ballan wrasse Labrus bergylta plasma pigment

This work was supported by co-funding from Innovate U.K. (formerly Technology Strategy Board), Marine Harvest Scotland and Scottish Seafarms Ltd (project ref: 81199) as well as the University of Stirling, Impact studentship funding scheme. Mass spectrometry analysis was performed by the BSRC Mass Spectrometry Facility, University of St Andrews.This study confirmed that observations of blue-green colouration in plasma fractions of the ballan wrasse Labrus bergylta were caused by the linear tetra-pyrrole biliverdin and that the molecule was of the physiologically relevant IXα isomer. Accumulation appears driven by chromogenic association with an unknown protein moiety which precludes enzymatic reduction and would suggest active management. It was demonstrated that the pigment did not fluctuate relative to ontogeny, or indeed binary gender in the species of interest, but mobilisation and depletion in the subset of individuals undergoing sex change at the time of study supports a potential association with gender inversion processes. It is of note that although biliverdin does have some effect on external colouration, the evidence is indicative that crypsis is a supplementary function thus other factors must be considered.PostprintPeer reviewe

Modeling Imperfect Interfaces in the Material Point Method using Multimaterial Methods

Abstract: The "multimaterial" version of the material point method (MPM) extrapolates each material to its own velocity field on a background grid. By reconciling momenta on nodes interacting with two or more materials, MPM is able to automatically handle contact without any need for special contact elements. This paper extends multimaterial MPM to automatically handle imperfect interfaces between materials as well. The approach is to evaluate displacement discontinuity on multimaterial nodes and then add internal forces and interfacial energy determined by an imperfect interface traction law. The concept is simple, but implementation required numerous corrections to make the analysis mesh independent, to work for any stiffness interfaces, and to find the interfacial normal vector. Several examples illustrated the need and demonstrated the validity of the various corrections. A composite mechanics problem found the bulk modulus of a particulate filled composite as a function interface quality. This calculation revealed a scaling effect -interfaces in nanoparticle composites must be better than interfaces in the corresponding microparticle composites for the nanocomposite mechanical properties to be as good as the conventional composite properties