$648 Journal o f Biomechanics 2006, Vol. 39 (Suppl 1) Poster Presentat ions

known Helen Hayes model. HH model is chosen as one of the most acceptable and practical model today. Use of model presented with this paper asks for two acquisitions sets - static and dynamic set. Dynamic set need only 9 optical marker and static set need additional 14 marker for calculating anthropometric relations. Also there remain 5 anthropometric measures to take directly. Helen Hayes model asks for 15 optical marker for both, static and dynamic acquisition and also 19 directly taken anthropometric measures. Model is very fast for patient testing and optical data reconstruction. Patient has not impression of wearing some technical equipment on himself and also feels free for all kind of complex movement.

4947 We-Th, no. 38 (P68) Software environment for jo in t b iomechanic analysis S. Martelli, N. Lopomo, E. Ferretti. Rizzeli Institutes, Lab. Biemeccanica, Bologna, Italy

This paper describes a method for a computerized analysis of diarthrodial joints. It consists in a software elaboration of digital data that can be obtained from medical images, navigation systems or spatial linkages about the joint mo- tion, bone surfaces, ligaments insertions and fibers placement and anatomical landmarks. A new software has been developed to analyse both anatomical features and kinematic behaviour of the joint. The software implements reliable functions to study the shapes of the articulating surfaces through 2D arbitrary sections and geometrical fitting of lines/conics, to quantify ligaments' behaviour through computation of elongation, strain and orientation during the recorded motion. The software allows also the computation of the most classical kinematic parameters, such as helical axes, instantaneous rotations and displacements, centers of rotation or pivot points of motions. In addition new functional - anatomical features, such as distance maps, contact areas tracking, and tools to validate functional hypothesis on the joint mechanism are possible in an interactive environment which display the 3D behaviour of the acquired or selected joint structure. The software has an user-friendly graphical interface to display four dimensional data (t ime-space data) obtained from and can also generate printable reports and multiple graphs as well as ASCII files that can be imported to spreadsheet programs such as Microsoft Excel. A test demo is available freeware at http://www.studyjoint.org. This approach represents a generalization of the analysis of several cadaveric joints, and its preliminary versions were used for kinematic and anatomical investigations about normal and pathological knees or shoulders. It provides a standard method for a complete analysis of joints or model predictions and can be used both by scientists as a validated environment for treating experimental data or by users without of advanced mathematical skills for investigate noints biomechanics through an easy interface.

6183 We-Th, no. 39 (P68) The effect o f c l in ic ian-appl ied maneuvers on delivery force and brachial p lexus strain dur ing shou lder dystoc ia del iver ies - assessment through mathematical model ing

M.J. Grimm 1 , R. Costello 1 , B. Gonik 2. 1Department efBiemedical Engineering and 2Department of Obstetrics and Gynecology, Wayne State University, Detroit, ML USA

Shoulder dystocia is a clinical emergency in which the shoulder of the fetus becomes lodged behind a bony portion of the maternal pelvis, preventing de- livery of the baby. The shoulder impaction, combined with subsequent traction from the clinician or maternal pushing, is hypothesized to cause strain-related injury to the brachial plexus. Although shoulder dystocia is not a predictable event, its clinical management may affect the overall prognosis of the infant. The goal is to deliver the child in such a way that the risk of both central nervous system (due to anoxia) and peripheral nerve injury is minimized. Due to the difficulty in measuring the effects of delivery forces on the infant in a clinical setting, a mathematical model of shoulder dystocia has been developed using MADYMO (TNO-MADYMO, Delft, The Netherlands) [1,2]. In this analysis, the model was used to determine the effect of various commonly applied clinician maneuvers on brachial plexis strain and the force required to affect delivery. Four different delivery methods were simulated: standard lithotomy position with axial traction; oblique positioning (Wood's screw), suprapubic pressure; and delivery of the posterior arm. All three of the maneuvers were found to reduce both the force required to achieve delivery and the brachial plexus strain compared to the lithotomy position with standard axial traction. Posterior arm delivery had the greatest effect, with a 5-fold reduction in delivery force and a reduction in brachial plexus strain from 13.5% to 3.9%. Due to a lack of established injury thresholds for neonatal brachial plexus injury, these results cannot be used to predict actual injury. However, they do indicate a relative reduction in injury potential with the application of common shoulder dystocia management maneuvers.

References [1] Gonik B, Zhang N, Grimm MJ. Am J Obstet Gynecol 2003; 189(4): 1188-1172. [2] Gonik B, Zhang N, Grimm MJ. Am J Obstet Gynecol 2003; 188(4): 1088-1072.

5156 We-Th, no. 40 (P68) Biomechanical model l ing o f co lon tissues A.N. Natali 1 , E.L. Carniel 1 , RG. Pavan 1 , R Dario 2, I. Izzo 2, A. Menciassi 2. 1 Centre of Mechanics of Biological Materials, University of Padova, Padova, Italy, 2Center for Research in Microengineering, SSSA, Pisa, Italy

Detection of colon pathologies represents a relevant problem for heath care system. Bio-robots are adopted for endoscopy [1]. The design of such robots entails a deep knowledge of tissues morphometry, histology and mechanical properties, in order to optimize the robot locomotion and to avoid damage phenomena within tissues. Morphometric data are necessary to develop virtual and numerical models of intestine, while histological information and mechan- ical tests provide the basis for the tissues mechanical characterization [2]. The geometrical analysis of intestine can be performed by CT and MRI relief. Experimental activities have been performed on samples from pig transverse colon. Samples have been cut from colon tissues to develop tensile, compres- sion and shear tests. Experimental deformation modes have been chosen to obtain necessary information about the generic stress-strain behaviour of the tissue. Results in literature [2] show that hyperelastic models represent a good basis for constitutive modelling of colon tissues [3]. From a mechanical point of view, colon wall can be evaluated as composed mainly by three layers, such as mucosa, circumferential and longitudinal muscular fasciae. Transversally isotropic configuration should be adopted for each muscular fascia because of orientation of muscular fibres, while isotropic configuration can be assumed for mucosa because of random distribution of fibrous components. Different sets of constitutive parameters of the anisotropic hyperelastic model [3] are defined for the tissues involved, introducing specific directional contributions of fibres for muscular layers, by means of a stochastic optimization algorithm. The reliability of the constitutive parameters and of the constitutive model is evaluated by developing the finite element analysis of experimental tests and comparing experimental and numerical results.

References [1] A. Menciassi, R Dario. Bio-inspired solutions for locomotion in the gastrointesti-

nal tract: background and perspectives. Philosophical Transactions of the Royal Society of London 2003.

[2] C. Gao, H. Gregersen. Biomechanical and morphological properties in rat large intestine. Journal of Biomechanics 2000; 33: 1089-1097.

[3] A.N. Natali, E.L. Carniel, RG. Pavan, R Dario, I. Izzo. Hyperelastic models for the analysis of soft tissue mechanics: definition of constitutive parameters. In: Proceedings of BioRob, Pisa, 2006.

7626 We-Th, no. 41 (P68) Computat ional s imulat ion o f b iomagnet ic micropolar b lood f low in porous media R. Bhargava 1 , Sugandha 2, H.S. Takhar 3, O.A. Beg 4. 1Mathematics Department fiT, Roorkee, India, 2 Cornefl University, Cornell, USA, 3MMU, Manchester, England, UK, 4Leeds College, Metropofitan University, Leeds, England, UK

Mathematical and numerical models have been developed for the quantification of flow profiles [1] in cerebro-spinal flows, blood flow and transport systems. The presence of iron oxide in the hemoglobin molecule has been shown to im- part magnetic properties to blood [2], to study pressure changes, establishing the feasibility of in vivo NRM spectroscopy at field strengths, 10Tesla. In a number of biomechanical applications, porous media has a significant influence on transport phenomena, eg, in vessels impeded by clots or high per- fused skeletal tissue, tumors, soft connecting tissue, the Darcy-Forcheimmer drag model has been an accurate mathematical model. Considering the rheological nature of blood with microstructure properties, one of the most appropriate models for blood is Micropolar fluid [3]. Here we consider the 2D, viscous hydrodynamic flow of a non-conducting biomagnetic micropolar fluid (blood) through a Darcy-Forcheimmer porous medium. The equations are solved using FEM and the effects of biomagnetic number (NH), Darcy number (Da), Forcheimmer number (Fs) and viscosity ratio param- eter (R) on velocity profiles and spin is studied with special cases. Our results are generally consistent with reported findings on effects of the individual parameters. The model finds applications in biomedical device technology, blood transport in highly-perfused skeletal tissue, and for Darcian micropolar biomagnetic flow, in transport in tumors, and soft connective tissue zones. For a magnetic field of 8 Tesla, the kinematic viscosity and fluid density of the blood has been taken as 3.1 10 -6 m2/s and 1050 kg/m 3. The values of N H are therefore selected appropriate to such a scenario for the present computations.

References [1] Skalak R. Biomechanics: Its foundations and Objectives. 1971; Prentice-Hall,

New Jersey.

Thread 2. Flow-Structure Interactions $649

[2] V.K. Sud. Biophys. J. 2003; 84: 2638-2645. [3] O. Anwar Beg, H.S. Takhar, et al. Micropolar bioengineering fluid dynamics: a

review. October 2005; in preparation.

7789 We-Th, no. 42 (P68) Effect o f meteorological parameters on aerosol number density during pre-monsoon season over Roorkee (India) D.K. Sharma & Jagdish Rai. Department of Physics, Indian Institute of Technology, Roorkee, India

Aerosol number density distribution for different size ranges have been studied in relation with some meteorological parameters (relative humidity, tempera- ture, rainfall and wind speed) during South-East (SE) pre-monsoon (May-July 2001) at Roorkee (77053 / E, 29052 / N and 275 m at hmsl). The measurements were done with the help of Optical particle counter by exposing the particles to light. The scattered light from aerosols of different size range generates the electrical pulse of different height. The counter monitors the particle concentra- tion in four different size ranges viz: 0.3-0.5~m, 0.5-1.0 ~m, 1.0-2.0~m and 2.0-5.0~m. These size ranges are mainly responsible for the optical effect, cloud condensation and radiation budget in the atmosphere. An analysis has been done taking the daily average number density of aerosols and meteorological parameters during pre-monsoon season. The present study indicates that the number density of aerosol is affected by the meteorological parameters. The rain has played significant role to modulate the aerosol concentration. In the month of July the concentration of aerosol was less than that from the month of June and it was maximum in May during pre-monsoon season. The large size ranges (1.0-2.0 ~m and 2.0-5.0~m) were much more effective compared to the lower size ranges (0.3-0.5~m and 0.5-1.0 ~m). The decrease of concentration for aerosols in the month of July has been attributed to the scavenging by the prevailing monsoon rain. The wind speed was not significantly effective in changing the aerosol number during this period.

ductus of efferentus of the male reproductive tract and vasomotion in small blood vessels, pumping mechanisms utilized in biomedical devices such as the heart-lung machine. The most sophisticated mathematical model for the physiological fluids, is the micro-continuum rheological model, introduced by Eringen [1]. The micropolar theory has proven to be an accurate model in the simulation of various biofluid problems. However the presence of porous matrix is often encountered in biomechanics. Vascular beds, lungs, kidneys and tumorous vessels are several important examples of zones in the body where porosity has a major influence on fluid dynamical processes. However in perfused skeletal tissue structures inertial effects are boosted and Forcheimmer drag needs to be incorporated into the mathematical model for the porous medium. The purpose of the present study is to develop a mathematical model for micropolar peristaltic pumping in a 2D anisotropic non-Darcian porous medium. Such a study, which has thusfar not been reported in the scientific literature, constitutes an important extension to peristaltic non-Newtonian biofluid dy- namic modelling. The effects of both bulk matrix resistance and Forcheimmer impedance are incorporated in the equations. FEM is used with a thorough ex- amination of the interactional effects of anisotropic permeability, Forcheimmer drag, Darcian drag, micropolar viscosity ratio, amplitude ratio on the peristaltic pumping flow regime. The model described herein has various applications in hemodynamic flows in tissue zones in flexible conduits, stenosed arteries and peristaltic biomedical devices.

References [1] Eringen A.C. Micropolar fluids. JAMM 1966; 16: 1-18.

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6803 We-Th, no. 43 (P68) Multi-scale simulation of blood flow with the dynamical behavior of elastic red blood cells T. Omori, S. Wada, K.-I. Tsubota, T. Yamaguchi. Department of Bioengineering and Robotics, Tohoku University, Sendal, Japan

Motion and deformation of Red Blood Cell (RBC) and their mechanical inter- action play an important role in non-Newtonian properties of blood. The aim of this study is to investigate the rheological properties of the blood from the analysis of dynamic behavior of multiple RBCs in the flowing blood. In order to simulate the RBC behavior in the flowing blood, we built up a two-dimensional model of an elastic RBC based on the minimum energy principle. The model was constructed by surrounding the internal liquid of RBC with spring elements which resist to bending and stretch of the RBC membrane. The interaction among multiple RBCs was expressed by a potential function assigned at each nodal point on the membrane. Based on the momentum conservation and Newton's friction law, the fluid force acting on the membrane was estimated from the difference in velocity between the RBC and fluid flow. The fluid flow was determined by solving continuity and Navier-Stokes equations with FEM, where the local viscosity of the fluid was given as a function of the cell density of RBC (local hematocrit, Hct). It was assumed that the viscosity increased with increasing local Hct. The calculations of RBC behavior and fluid flow were repeated until a stable flow was obtained. The simulation was carried out for a blood flow containing 108 RBCs (mean Hct =0.31) in the straight channel with a height of 96 ~m and a length of 44 ~m. The initial flow was assumed to be a Poiseuille flow taking a parabolic velocity profile. The Reynolds number was 0.06 and the periodic boundary condition was applied to the both edges of the channel. The RBCs were carried downstream by the fluid flow with an axial migration, causing higher fluid viscosity around the central axis than that near the wall of the flow channel. As a result, the velocity profile was finally converged to that of non-Newtonian blood flow observed in experiments, taking a uniform velocity around the central axis of the channel.

4238 Mo-Tu, no. 1 (P68) Use of fluid-structure simulations to determine pulse wave velocity in the human aorta N. Sampat, M. Gabi. Department of Fluid Machinery, Faculty Mechnaical Engineering, University Karlsruhe, Germany

In practical medical fields like cardiology and angiology, Pulse Wave Velocity (PWV) determined in vivo and its correlations to arterial stiffness and disorders of the cardio-vascular network are reported frequently and used as a medical indicator. Experimentally, the measurement is a challenge because of the complicated geometry in the periphery of the heart, complex geometry of the vascular network and due to Non-Newtonian character of blood-flow properties. Moreover the blood-flow itself is unsteady in nature. We report a method to determine PWV through fluid-structure interaction simulations conducted on a highly detailed human-based aorta model. The mechanical properties and boundary conditions are based on experiments. The commercial software packet STAR-CD, based on finite volume method, and structure mechanics software packet PERMAS, based on finite element method have been used. The fluid-structure interaction has been realised as that of pressure exchange between the aorta-wall and the fluid. With the help of the software MpCCI from Fraunhofer Institute SCAI, this exchange was carried out between STAR-CD and PERMAS. In STAR-CD the flow is characterised as 3-dimensional, laminar, incompressible and the aorta-wall is hydraulically smooth. Through the simulations we demonstrate the distensibility of the model aorta and deduce PWV through a modified BramwelI-Hill equation. Results for the PWV will be compared with values reported in literature and further computations will be proposed. The numerical simulation method of f luid- structure coupling can thus be useful for deducing important medical indicators. Moreover, such simulations can be used on in vitro distensible tubes found useful in the emerging field of tissue engineering for replacing in vivo sick arteries.

4090 We-Th, no. 44 (P68) Peristaltic pumping of micropolar f luid in porous channel - model for stenosed arteries R. Bhargava 1 , S. Sharma 2, H.S. Takhar 3, T.A. B6g 4, O.A. B6g 5, T.K. Hung 6. 1Mathematics Department, liT, Roorkee, India, 2Mathematics Department, liT, Roorkee, India, 3Engineering Department, MMU, Manchester, England, UK, 4Earthquake Consultant, Manchester, UK, 5Leeds Metropolitan University, Leeds, England, UK, ~ Neurosurgery, Civil Department, University of Pittsburgh, USA

Peristaltic flows are involved in many biological and biomedical systems, eg., urine transport from kidney to the bladder through the ureter, the transportation of chyme in the gastro-intestinal tract, the movement of spermatozoa in the

4790 Mo-Tu, no. 2 (P68) Numerical simulation of intimal thickening in a bifurcation artery

'~ Fan 1,2, W. Jiang 2, '~ Sou 2, J. Chen 2. 1Department of Bioengineering, Beihang University, Beijing, China, 2 Biomechanical Engineering Laboratory, Sichuan University, Chengdu, China

Intimal thickening is a complicated process from plaque formation to artery- obstructed. In this process, intimal thickening, the change of artery geometry and hemodynamics are interacted. A new numerical skill named Cell-filled method is applied to simulate the process of intimal thickening in a carotid bifurcation under critical low wall shear stress condition. The new method can overcome the limitation of previous method£ such as the discontinuous of simulation and the trouble of model re-meshing. Results showed that the low