Biomechanical study of cervical spine with pathology

O conhecimento da cinemática da coluna cervical é uma ferramenta muito importante, dado que esta região é uma das estruturas mais complexas do esqueleto humano e porque a incidência de incapacidade que pode resultar de traumas ou doenças degenerativas é relativamente elevada. O principal objetivo deste estudo consiste na análise e comparação da fusão cervical anterior e/ou fusão cervical posterior como possíveis tratamentos para uma fratura do tipo C2.2, segundo a classificação da AO spine injury classification system, sendo que este estudo poderá auxiliar os profissionais de saúde na escolha do melhor método de fusão. Para o efeito, foi construído um modelo 3 D de elementos finitos do segmento cervical C4‐C5‐C6. Foram modelados os respetivos discos intervertebrais (IV ) e os seus componentes, nomeadamente o núcleo pulposo, o anel fibroso, as fibras lamelares e as placas cartilaginosas. Os 6 conjuntos de ligamentos (longitudinais anteriores, longitudinais posteriores, interespinhosos, supraespinhosos, amarelos e capsulares) foram também modelados, assim como as articulações intervertebrais. A simulação de uma fratura foi realizada em 3 passos distintos: introdução de uma fratura na zona anterior da vértebra C5, o comprometimento (rompimento) dos ligamentos da região posterior e o deslizamento da vértebra C5. A instrumentação utilizada nos tratamentos em estudo e ainda a substituição dos discos lesados por um enxerto ósseo proveniente do ilíaco foram também modeladas. Com este estudo, concluiu‐se que a fusão cervical anterior e posterior apresenta melhores resultados em comparação com os outros tipos de fusão cervical estudados em termos de deslocamento da unidade funcional.The knowledge of the kinematics of the cervical spine is a very important tool, since this region is one of the more complex structures of the human skeleton and because the incidence of failure that may result from trauma or degenerative diseases is relatively high. The main objective of this study is the analysis and comparison of anterior cervical fusion and/or posterior cervical fusion as possible treatments for a fracture of type C2.2 according to AO spine injury classification system, and this study may assist health professionals in choosing the best fusion technique. To this end we built a 3 D finite element model of the cervical segment C4‐C5‐C6. Their intervertebral discs (IV ) and its components, namely the nucleus pulposus, the annulus fibrosus, the fibers and the lamellar cartilaginous plates were modeled. Six sets of ligaments (anterior longitudinal, posterior longitudinal, interspinous, suprespinous, yellow and capsular) and the facet joints were also modeled. The simulation of the fracture was performed in 3 different steps: introduction of a fracture zone in the previous C5 vertebra, rupture of the ligaments of the posterior region and the sliding of the C5 vertebra. The instrumentation used in the study treatments and even the replacement of the damaged disc by bone graft from the iliac bone, were also modeled. Analyzing the displacements of the functional unit it was concluded that the anterior and posterior cervical fusion provides the best results compared to other types of cervical fusion studied in terms of displacement of the functional unit.Peer Reviewe

Segmentação e simulação de contornos em imagens através de processos físicos

O objectivo principal deste trabalho é, a partir de duas imagens de um mesmo objecto em dois instantes distintos, simular as formas intermédias que o objecto assume quando o seu comportamento é guiado por princípios físicos. Para tal, é preciso começar por segmentar o objecto nas duas imagens em questão extraindo o seu contorno, após definição manual de um contorno inicial em cada uma delas. Seguidamente, cada um dos contornos definidos evoluirá automaticamente ao longo de um processo iterativo até alcançar a fronteira do objecto desejado. Para isso, é construído um modelo deformável para cada um dos contornos usando o método dos elementos finitos. Posteriormente, a evolução temporal do modelo físico até ao contorno final desejado é obtida resolvendo a equação de equilíbrio dinâmico que contrabalança as forças externas e internas virtualmente aplicadas no objecto modelizado.Para simular a deformação entre os dois contornos obtidos na segmentação, é utilizada análise modal complementada com técnicas de optimização para estabelecer a correspondência entre os dados pontuais dos mesmos. Após esta fase de emparelhamento, o campo dos deslocamentos entre os dois contornos é simulado através da equação de equilíbrio dinâmico

Determination of objects contours using physical principles

Segmentation, the identification of an object represented in a static image or along image sequences,is one of the most common and complex tasks in the domain of Computational Vision. Usually,whenever we intend to extract higher level information from images, we need to start by segmentingthem.The main goal of this work is to segment an object represented in an image by extracting its contourafter defining an initial contour for it; this coarse contour will evolve along an iterative process untilit reaches the frontier of the desired object, figure 1. For that purpose, a deformable model is used,whose behaviour is driven by physical principles

Numerical and experimental study of sandwich plates with metallic foam cores

World-wide vehicles safety experts agree that significant further reductions in fatalities and injuries can be achieved as a result of the use of new energy absorbing materials. In this field, passive safety systems still have great potential to reduce fatalities and injuries, as in the case of using new lightweight energy-absorbing materials. On this work, the authors present the development of a procedure able to perform reliable panels of sandwich sheets with metallic foam cores for industrial applications. The mathematical model used to describe the behavior of sandwich shells with metal cores form is presented and some numerical examples are included. The numerical results are validated using the experimental results obtained from the mechanical experiments. Using the crushable foam constitutive model, available on ABAQUS, a set of different mechanical tests were simulated

Dengue disease, basic reproduction number and control

Dengue is one of the major international public health concerns. Although progress is underway, developing a vaccine against the disease is challenging. Thus, the main approach to fight the disease is vector control. A model for the transmission of Dengue disease is presented. It consists of eight mutually exclusive compartments representing the human and vector dynamics. It also includes a control parameter (insecticide) in order to fight the mosquito. The model presents three possible equilibria: two disease-free equilibria (DFE) and another endemic equilibrium. It has been proved that a DFE is locally asymptotically stable, whenever a certain epidemiological threshold, known as the basic reproduction number, is less than one. We show that if we apply a minimum level of insecticide, it is possible to maintain the basic reproduction number below unity. A case study, using data of the outbreak that occurred in 2009 in Cape Verde, is presented.Comment: This is a preprint of a paper whose final and definitive form has appeared in International Journal of Computer Mathematics (2011), DOI: 10.1080/00207160.2011.55454

First in-beam studies of a Resistive-Plate WELL gaseous multiplier

We present the results of the first in-beam studies of a medium size (10$\times$10 cm$^2$) Resistive-Plate WELL (RPWELL): a single-sided THGEM coupled to a pad anode through a resistive layer of high bulk resistivity ($\sim$10$^9 \Omega$cm). The 6.2~mm thick (excluding readout electronics) single-stage detector was studied with 150~GeV muons and pions. Signals were recorded from 1$\times$1 cm$^2$ square copper pads with APV25-SRS readout electronics. The single-element detector was operated in Ne\(5% $\mathrm{CH_{4}}$) at a gas gain of a few times 10$^4$, reaching 99$\%$ detection efficiency at average pad multiplicity of $\sim$1.2. Operation at particle fluxes up to $\sim$10$^4$ Hz/cm$^2$ resulted in $\sim$23$\%$ gain drop leading to $\sim$5$\%$ efficiency loss. The striking feature was the discharge-free operation, also in intense pion beams. These results pave the way towards robust, efficient large-scale detectors for applications requiring economic solutions at moderate spatial and energy resolutions.Comment: Accepted by JINS

The human otitis media with effusion: a numerical-based study

Otitis media is a group of inflammatory diseases of the middle ear. Acute otitis media and otitis media with effusion (OME) are its two main types of manifestation. Otitis media is common in children and can result in structural alterations in the middle ear which will lead to hearing losses. This work studies the effects of an OME on the sound transmission from the external auditory meatus to the inner ear. The finite element method was applied on the present biomechanical study. The numerical model used in this work was built based on the geometrical information obtained from The visible ear project. The present work explains the mechanisms by which the presence of fluid in the middle ear affects hearing by calculating the magnitude, phase and reduction of the normalized umbo velocity and also the magnitude and phase of the normalized stapes velocity. A sound pressure level of 90 dB SPL was applied at the tympanic membrane. The harmonic analysis was performed with the auditory frequency varying from 100 Hz to 10 kHz. A decrease in the response of the normalized umbo and stapes velocity as the tympanic cavity was filled with fluid was obtained. The decrease was more accentuated at the umbo.info:eu-repo/semantics/publishedVersio