A Hemispherical Contact Model for Simplifying 3D Occlusal Surfaces

Statement of problem Currently, dental articulators can recreate mandibular movements and occlusal contacts. However, whether virtual articulators can also provide information about occluding dental surfaces, functional movements, and the mandibular condyles is unclear. Purpose The purpose of this in vitro study was to evaluate the occluding surfaces on dental casts obtained from a patient and approximate them to a hemispherical contact model. Both models were tested by digitizing the Dentatus ARL dental articulator. Material and methods A combination of photogrammetry and structure from motion methods were used to scan a Dentatus ARL articulator and representative dental casts. Using computer-aided engineering and finite element analysis, contact points and action vectors to the forces on occluding surfaces and condyles were obtained for cast and hemispherical models. This experiment was performed using centric occlusion and 3 different condylar inclinations. The Kruskal-Wallis 1-way analysis of variance on ranks test was used to allow all pairwise comparisons between condylar inclination and mechanical action vector values in each location (α=.05). Results Action vectors from the cast model and each location of the hemispherical model were calculated to show the mechanical consequences and the similarity among models. Overall, no significant differences were observed for action vectors (A20 versus A40 versus A60) at each location (dental cast/hemisphere, right condylar, and left condylar) in the analysis of dental casts and the hemisphere model (.382≤P≤.999). Conclusions This study provided graphical information that may assist the dental professional in determining which occlusal contacts should be modified to attain condylar and balanced centric occlusion

Acquiring the notion of learning hypotheses in mathematics teacher education

The notion of hypothetical learning trajectory has generated much interest among experts in mathematics education. It is proposed that this notion is a useful tool in teachers’ teaching practice and that it is necessary to prepare teachers in their capacity to formulate hypothetical learning trajectories about specific mathematics school topics. It is therefore also necessary to explore the learning processes that teachers undergo when learning this notion in their education. In this article, we introduce the notion of learning hypotheses as an adaptation of the idea of hypothetical learning trajectory (SIMON, 1995). We describe how the groups of secondary-school mathematics teachers that participated in a teacher education program understood and used this notion in order to determine the contribution of a set of tasks to a learning goal previously established. We found that the groups developed their knowledge of the notion of learning hypotheses and used it in a heterogeneous way, and that the education program was partly successful in its goal to make the groups of teachers learn and perceive the notion’s utility

Insights into mechanical compression and the enhancement in performance by Mg(OH)2 coating in flexible dye sensitized solar cells

The engineering of flexible dye sensitized solar cells (DSCs) by mechanical compression is one of the methods that allow low temperature processing of these devices. However, suppressing the high temperature sintering process also significantly reduces the performance of the cells. In our previous work [J. Phys. Chem. C, 116 (2012) 1211], we have attempted to improve flexible DSC performance by coating the porous TiO2 photoanode with an electrodeposited Mg(OH)2 layer. In that work, we have obtained one of the largest photovoltage reported to date in flexible DSCs (847 mV). In order to gain more insights into the reasons for both poorer performance of compressed cells and the origin of the voltage enhancement achieved by the Mg(OH)2 coating, here we present an in-depth study by means of electrochemical impedance spectroscopy, Mott-Schottky plots analysis and open-circuit voltage decays. The existence of a shunt resistance in the mechanically compressed cells is revealed, causing an additional drawback to the poor inter-particle necking. By introducing the Mg(OH)2 coating the recombination in the cell becomes significantly reduced, being the key reason which is responsible for the higher photovoltage. Additionally, the coating and the compression cause modifications in the surface states and in the nature of the interfaces with the electrolyte. This induces TiO2 conduction band displacements and shifts of the relative position of the modified states that influence the performance.This work was supported by UK EPSRC, DSTL, Johnson Matthey Plc and Department of Chemistry, Loughborough University. All members of the renewable energy r esearch group in the Department of Chemistry, Loughborough Univer sity are acknowledged for their assistance in this work. The authors would like to acknowledge previous related work conducted by S. Senthilarasu

Dielectric study of the glass transition: correlation with calorimetric data

The glass transition in amorphous poly(ethylene terephthalate) is studied by thermally stimulated depolarization currents (TSDC) and differential scanning calorimetry (DSC). The ability of TSDC to decompose a distributed relaxation, as the glass transition, into its elementary components is demonstrated. Two polarization techniques, windows polarization (WP) and non-isothermal windows polarization (NIW), are employed to assess the influence of thermal history in the results. The Tool-Narayanaswami-Moynihan (TNM) model has been used to fit the TSDC spectra. The most important contributions to the relaxation comes from modes with non-linearity (x) around 0.7. Activation energies yield by this model are located around 1eV for polarization temperature (Tp) below 50C and they raise up to values higher than 8eV as Tp increases (up to 80C). There are few differences between results obtained with WP and NIW but, nonetheless, these are discussed. The obtained kinetic parameters are tested against DSC results in several conditions. Calculated DSC curves at several cooling and heating rates can reproduce qualitatively experimental DSC results. These results also demonstrate that modelization of the non-equilibrium kinetics involved in TSDC spectroscopy is a useful experimental tool for glass transition studies in polar polymers.Comment: 13 pages, 2 tables, 10 figures; minor change

Framework for automatic generation of ontology mappings

Some of the most outstanding problems in Computer Science (e.g. access to heterogeneous information sources, use of different e-commerce standards, ontology translation, etc.) are often approached through the identification of ontology mappings. A manual mapping generation slows down, or even makes unfeasible, the solution of particular cases of the aforementioned problems via ontology mappings. Some algorithms and formal models for partial tasks of automatic generation of mappings have been proposed. However, an integrated framework to solve this problem is still missing. In this paper, we present a framework for automatic ontology mapping generation, and a partial implementation of it. Our proposal is that this integrated vision can guide, not only our future work, but also the future work of other researchers. In the implementation carried out, we have built a mapping ontology with knowledge on ontology mappings

Estimating uncertainty in density surface models

This work was funded by OPNAV N45 and the SURTASS LFA Settlement Agreement, and being managed by the U.S. Navy’s Living Marine Resources program under Contract No. N39430-17-C-1982.Providing uncertainty estimates for predictions derived from species distribution models is essential for management but there is little guidance on potential sources of uncertainty in predictions and how best to combine these. Here we show where uncertainty can arise in density surface models (a multi-stage spatial modelling approach for distance sampling data), focussing on cetacean density modelling. We propose an extensible, modular, hybrid analytical-simulation approach to encapsulate these sources. We provide example analyses of fin whales Balaenoptera physalus in the California Current Ecosystem.Publisher PDFPeer reviewe

Tratamiento de fracturas toracolumbares: nuestra experiencia en el periodo 2000-2003. Protocolo de actuación

Presentamos una revisión de los resultados obtenidos en pacientes intervenidos de fracturas tóraco-lumbares durante los años 2000 a 2003, en ambos inclusive, por el servicio de Traumatología y Cirugía Ortopédica del Hospital Universitario Virgen de las Nieves de Granada; así como el protocolo seguido en el manejo diagnóstico-terapéutico de este tipo de pacientes. Las fracturas más frecuentes fueron en L1 y del tipo A3 de la clasificación AO. La vía de abordaje más utilizada fue la posterior (138 casos). En 132 casos se instrumentó la vértebra fracturada y en 39 casos fue necesaria la descompresión. El índice sagital medio preoperatorio fue de 17,5º y el postoperatorio de 3,5º. La pérdida de altura vertebral preoperatoria fue del 52% y del 14% al final del tratamiento. En 39 pacientes con déficit neurológico se realizó descompresión. En el 79% de los casos los resultados fueron excelentes y en el resto regulares o malos.We present the results of surgical treatment in patients with thoraco-lumbar fractures operated on between the years 2000 and 2003 at the Orthopedic and Traumatology Department of the hospital Virgen de las Nieves Hospital of Granada, Spain. The diagnosis and therapeutic protocol of this type of patients is also evaluated. A3 type from AO classification fracture of L1, was the most frequent injury. Posterior surgical approach of the spine was mainly used (138 cases), in 132 cases the fracture was stabilized by means of internal fixation and 39 cases required decompression of the lumbar canal. The average sagital index was 17,5º preoperative and 3,5º after surgery. The average loss of height was 52% preoperative and 14% at the end of treatment. In 39 surgical decompression was indicated for neurological impairment. Excellent results were obtained in 79% of the cases, the rest were fair and poor