			Home About us Contact

Presented Model (presented + model)

Distribution by Scientific Domains

Medical Sciences	50%

Selected Abstracts

Motion visualization of human left ventricle with a time-varying deformable model for cardiac diagnosis

COMPUTER ANIMATION AND VIRTUAL WORLDS (PREV: JNL OF VISUALISATION & COMPUTER ANIMATION), Issue 2 2001
Soo-Mi Choi
Abstract We present a time-varying deformable model to visualize and analyze the motion of the left ventricle from a time series of 3-D images. The model is composed of a non-rigid body that deforms around a reference shape obtained from the previous time step. At each time step, the position and orientation of the left ventricle are extracted from the feature points of images. This information gives the position and orientation of the coordinate system attached to the non-rigid body. To compute a dense non-rigid motion field over the entire endocardial wall of the left ventricle, we introduce a 3-D blob finite element and Galerkin interpolants based on 3-D Gaussian, and use a physically based finite element method and a modal analysis. Then, cinematic attributes are visualized in pseudo colors on the reconstructed surface in order to help medical doctors in their interpretation of the data. Using the presented model, we estimate clinically useful quantitative parameters such as regional wall motion and ejection fraction. Experimental results are shown in a time series of X-ray angiographic images. Copyright ©2001 John Wiley & Sons, Ltd. [source]

A low-dimensional physically based model of hydrologic control of shallow landsliding on complex hillslopes

EARTH SURFACE PROCESSES AND LANDFORMS, Issue 13 2008
Ali Talebi
Abstract Hillslopes have complex three-dimensional shapes that are characterized by their plan shape, profile curvature of surface and bedrock, and soil depth. To investigate the stability of complex hillslopes (with different slope curvatures and plan shapes), we combine the hillslope-storage Boussinesq (HSB) model with the infinite slope stability method. The HSB model is based on the continuity and Darcy equations expressed in terms of storage along the hillslope. Solutions of the HSB equation account explicitly for plan shape by introducing the hillslope width function and for profile curvature through the bedrock slope angle and the hillslope soil depth function. The presented model is composed of three parts: a topography model conceptualizing three-dimensional soil mantled landscapes, a dynamic hydrology model for shallow subsurface flow and water table depth (HSB model) and an infinite slope stability method based on the Mohr,Coulomb failure law. The resulting hillslope-storage Boussinesq stability model (HSB-SM) is able to simulate rain-induced shallow landsliding on hillslopes with non-constant bedrock slope and non-parallel plan shape. We apply the model to nine characteristic hillslope types with three different profile curvatures (concave, straight, convex) and three different plan shapes (convergent, parallel, divergent). In the presented model, the unsaturated storage has been calculated based on the unit head gradient assumption. To relax this assumption and to investigate the effect of neglecting the variations of unsaturated storage on the assessment of slope stability in the transient case, we also combine a coupled model of saturated and unsaturated storage and the infinite slope stability method. The results show that the variations of the unsaturated zone storage do not play a critical role in hillslope stability. Therefore, it can be concluded that the presented dynamic slope stability model (HSB-SM) can be used safely for slope stability analysis on complex hillslopes. Our results show that after a certain period of rainfall the convergent hillslopes with concave and straight profiles become unstable more quickly than others, whilst divergent convex hillslopes remain stable (even after intense rainfall). In addition, the relation between subsurface flow and hillslope stability has been investigated. Our analyses show that the minimum safety factor (FS) occurs when the rate of subsurface flow is a maximum. In fact, by increasing the subsurface flow, stability decreases for all hillslope shapes. Copyright © 2008 John Wiley & Sons, Ltd. [source]

Aerogenous infection of microbiologically defined minipigs with Streptococcus suis serotype 2

APMIS, Issue 6 2001
A new model
Streptococcus suis serotype 2 is the cause of serious infections in animals and humans, but certain aspects of the infection pathogenesis still remain unclear. In this study an experimental model of aerogenous infection and induction of septicemia with S. suis serotype 2 was established in microbiologically defined Göttingen minipigs. Ten animals were exposed to aerosolized S. suis after previous exposure to mild acetic acid in aerosol. Six of the animals were immunosuppressed with prednisolone acetate on different days. All the animals were monitored clinically until euthanasia on days 6 to 13 after exposure. Necropsy was performed and samples were taken for microbiology, histopathology, and immunohistochemistry. Three out of four animals immunosuppressed on days 5 to 7 after exposure developed S. suis septicemia, and S. suis could be detected in the tonsil of the soft palate and/or the nasal cavity of all exposed animals. Thus, using the presented model, local as well as systemic infection with S. suis serotype 2 was established in the Göttingen minipig. Since this breed is defined as free of S. suis and a range of other endemic porcine pathogens, the experimental model could prove useful in the study of this infection. [source]

A simple pharmacokinetics subroutine for modeling double peak phenomenon

BIOPHARMACEUTICS AND DRUG DISPOSITION, Issue 3 2006
Ahmad Mirfazaelian
Abstract Double peak absorption has been described with several orally administered drugs. Numerous reasons have been implicated in causing the double peak. DRUG-KNT,a pharmacokinetic software developed previously for fitting one and two compartment kinetics using the iterative curve stripping method,was modified and a revised subroutine was incorporated to solve double-peak models. This subroutine considers the double peak as two hypothetical doses administered with a time gap. The fitting capability of the presented model was verified using four sets of data showing double peak profiles extracted from the literature (piroxicam, ranitidine, phenazopyridine and talinolol). Visual inspection and statistical diagnostics showed that the present algorithm provided adequate curve fit disregarding the mechanism involved in the emergence of the secondary peaks. Statistical diagnostic parameters (RSS, AIC and R2) generally showed good fitness in the plasma profile prediction by this model. It was concluded that the algorithm presented herein provides adequate predicted curves in cases of the double peak phenomenon. Copyright © 2006 John Wiley & Sons, Ltd. [source]