bluuebunny/crossref_metadata_2025 huggingface dataset:
Quinidine interaction with Shab K+channels: pore block and irreversible collapse of the K+conductance
Authors: Gomez‐Lagunas Froylan
Published: June 2010

Quinidine is a commonly used antiarrhythmic agent and a tool to study ion channels. Here it is reported that quinidine equilibrates within seconds across the Sf9 plasma membrane, blocking the open pore of Shab channels from the intracellular side of the membrane in a voltage‐dependent manner with 1:1 stoichiometry. On binding to the channels, quinidine interacts with pore K+ions in a mutually destabilizing manner. As a result, when the channels are blocked by quinidine with the cell bathed in an external medium lacking K+, the Shab conductanceGKcollapses irreversibly, despite the presence of a physiological [K+] in the intracellular solution. The quinidine‐promoted collapse of ShabGKresembles the collapse of ShakerGKobserved with 0 K+solutions on both sides of the membrane: thus the extent ofGKdrop depends on the number of activating pulses applied in the presence of quinidine, but is independent of the pulse duration. Taken together the observations indicate that, as in Shaker, the quinidine‐promoted collapse of ShabGKoccurs during deactivation of the channels, at the end of each activating pulse, with a probability of 0.1 per pulse at −80 mV. It appears that when Shab channels are open, the pore conformation able to conduct is stable in the absence of K+, but on deactivation this conformation collapses irreversibly.
Stability of Sequential Modular Time Integration Methods for Coupled Multibody System Models
Authors: Arnold Martin
Published: June 2010

The interacting components of complex technical systems are often described by coupled systems of differential equations. In dynamical simulation, these coupled differential equations have to be solved numerically. Cosimulation techniques, multirate methods, and other approaches that exploit the modular structure of coupled systems are frequently used as alternatives to classical time integration methods. The numerical stability and convergence of such modular time integration methods is studied for a class of sequential modular methods for coupled multibody system models. Theoretical investigations and numerical test results show that the stability of these sequential modular methods may be characterized by a contractivity condition. A linearly implicit stabilization of coupling terms is proposed to guarantee numerical stability and convergence.
Optimal Design of Experiments for Estimating Parameters of a Vehicle Dynamics Simulation Model
Authors: Butz Torsten , Simeon Bernd , Stadler Markus
Published: June 2010

The calibration of complex simulation models for vehicle component and controller development usually relies on numerical methods. In this contribution, a two-level optimization scheme for estimating unknown model parameters in a commercial real-time capable vehicle dynamics program is proposed. In order to increase the reliability of the model coefficients estimated from reference data, the measuring test is improved by methods for the optimal design of experiments. Specifically, the control variables of the experimental setup are adjusted in such a way as to maximize the sensitivity of the parameters in demand with respect to the objective function. The numerical results show that this two-level optimization scheme is capable of estimating the parameters of a multibody suspension model.
The Effect of Vibrations on Surfactant Dynamics in the Neonate
Authors: Reddy Prasika I. , Al-Jumaily Ahmed M. , White David E.
Published: June 2010

Respiratory distress syndrome (RDS) is the leading cause of mortality in premature infants, arising primarily from a lack of surfactant in the lung. The dynamic behavior of surface tension in the alveoli is modelled using a numerical model and compared with in-vitro experimentation on a pulsating bubble surfactometer (PBS). The effect of adding superimposed oscillations (from 10–70 Hz) on the breathing frequency is investigated in both the model and experiment. The model and experiment show encouraging comparisons and suggest that the mechanisms of improving surfactant function with oscillatory treatments lie with the increase of diffusion and adsorption of surfactant molecules to the air-liquid interface in the alveoli.
Experimental Study and Modeling of Equilibrium Point Trajectory Control in Single and Double-Joint Arm Movements
Authors: Chen Kai , Foulds Richard A. , Swift Katharine , Adamovich Sergei
Published: June 2010

This paper discusses a new model of neuromuscular control of elbow and shoulder joints based on the Equilibrium Point Hypothesis (EPH). The earlier model [1] suggests that the incorporation of relative damping within reflex loops can maintain the dynamic simplicity of the EPH, while being robust over the range of human joint velocities. The model presented here, extends previous work with the use of experimental Electromyography data of 2 muscles to determine the timing parameters of the virtual trajectories and the inclusion of physiological time delays to account for neural transmission and muscle stimulation/activation delays. This model uses delays presented in the literature by other researchers, with a goal of contributing to a resolution of arguments regarding the controversial arguments in the planning sequences. Therefore, this study attempts to demonstrate the possibility for using descending CNS signals to represent relatively simple, monotonic virtual trajectories of the time varying Equilibrium Point for the control of human arm movement. In addition, the study demonstrates that these virtual trajectories were robust enough to control and coordinated movement of elbow and shoulder joints discussed.
Image-Based Computational Fluid Dynamics in a Carotid Artery
Authors: Gori F. , Boghi A.
Published: June 2010

Literature presents numerical simulations on image-based geometry where blood is treated as a Newtonian fluid, while others simulations assumed a non-Newtonian blood with two or three-dimensional axisymmetric geometry. The present work investigates the non-Newtonian behavior of a pulsating blood flow through a stenosed carotid artery, realistically reconstructed with the patient-specific geometry of a 60 years old man with an intimal thickening of 90% degree of stenosis. Lumen boundary contours are segmented using commercial image-processing software AMIRA for a 3D geometry reconstruction. High-quality tetrahedral mesh is generated using commercial mesh-generator code GAMBIT. The 3-D unsteady incompressible Navier-Stokes equations are solved using the commercial finite volume code FLUENT. The boundary condition is assumed from a flow-rate-wave of the literature using the FFT method and imposing a pressure sinusoidal signal with 20 harmonics.
A Study of the Forces on the Small Intestine From a Novel Suction Based Approach for Robotic Endoscopic Locomotion
Authors: Montane Roberto , Wagh Mihir S. , Crane Carl D.
Published: June 2010

Many studies have been published regarding robotic endoscopes, however, very little has been done to quantify their effects on the intestine [1]. Here, the use of suction to hold onto the small intestine is investigated. These results will be used to develop an endoscope that is capable of being advanced deep into the small bowel. Prototype suction devices have been designed and various rigid suction tips tested on swine cadaveric intestines. Testing consisted of applying vacuum pressure to suction tips within the intestine. Suction tips were pulled in a shearing method against segments of swine intestine. Measurement data acquired determined parameters which generated the greatest amount of holding force while minimizing tissue damage. Vacuum pressures from 64 kPa–85 kPa were applied to suction tips. The measured force increased from 1.62 Newton (6 oz) to 3.89 Newton (14 oz) with increasing vacuum pressure. Even at the highest vacuum pressure employed (85 kPa) there were no visible signs of intestinal trauma. A maximum force of 3.89 Newton (14 oz) could be attained from a single tip. During in-situ experiments this method advanced the endoscope 25cm into the small intestine.
Electrical Characterization of Carbon Fiber Polymer Matrix Composites
Authors: Zantout Alan , Zhupanska Olesya I.
Published: June 2010

This paper studies the response of carbon fiber polymer matrix composites subjected to DC electric currents. We have developed a new fully instrumented experimental setup that enables one to measure electric field characteristics (amperage, voltage, resistance) and temperature at the surface of the electrified composites in real time. The experimental procedure ensured a low contact resistance between the composite and electrodes, high uniformity in the density of the applied electric current, and low resistance heating. An extensive experimental study on the electrical characterization of carbon fiber polymer composites of different composition, ply sequence, thickness, etc. was conducted. The effect of the resistance heating was carefully analyzed through experimental analysis as well as the finite element modeling.
Treatment Solutions of Synovial Joints and Recovery Processes of Patients With Hip and Knee Osteoarthritis
Authors: Pop Petru A. , Ungur Petru , Lazar Liviu , Corbu Silviu , Marcu Florin M.
Published: June 2010

The paper presents some aspects and practical solutions of synovial joints treatment for the patients with hip and knee osteoarthritis, realized at Recovery Clinical Hospital of Felix Spa, Oncology Clinical Hospital of Oradea and our university. A theoretical model of human body under applied and conjunction forces, explained the vibration damping and shocks into synovial joints from elastic modulus of bone cartilages in contact and variation of dynamic viscosity’s synovial fluid. The treatment was applied to the patients with osteoarthritis that consists in combination between conservative measures with radiological treatment, by using irradiation with gamma ray, due to improving bio-lubrication into cartilages of synovial joints with severe osteoarthritis in slow evolution. The treatment is following by a recovery process of patients such as hydro-kinetotherapy, massage, etc. In addition, a study about 260 subjects with osteoarthritis using balneal-physiotherapy at Recovery Clinical Hospital of Felix Spa is presented. These combination treatments have assured an amelioration of patients with osteoarthritis and due to improving the bio-lubrication between cartilages of synovial joints.
Fundamental Study of Biomechanical Estimator Using Optical Coherence Straingraphy
Authors: Saeki Souichi , Sakata Yoshitaro , Saito Takashi , Hiro Takafumi , Matsuzaki Masunori
Published: June 2010

This paper presents Optical Coherence Straingraphy, which is a non-invasive biomechanical estimator based on a cross-correlation technique. In this study, this was ex vitro applied to artificial phantoms of atherosclerotic plaque, comparing with numerically simulated results. Consequently, OCS was experimentally and quantitatively clarified to be a promising technique as Micro Mechanical Biopsy.
Treatment Planning for Transurethral and Interstitial Thermal Therapy for Benign Prostatic Hyperplasia
Authors: Thamire Chandrasekhar , Zuberi Rabee , Choe Charlie , Pandey Prabhakar
Published: June 2010

The purpose of this study is to develop thermal-damage correlations for transurethral and interstitial thermotherapy to aid treatment planning for benign prostatic hyperplasia (BPH). Using an Alternating-direction implicit method, the Pennes bioheat transfer equation is solved for microwave and ultrasound hyperthermia applicators for a range of parameters, including the applicator power, treatment time, and coolant parameters. Thermal coagulation contours are developed by evaluating the temperature-history data against the thermal-damage data obtained in ex-vivo experiments for prostate tissue slices and cells. Treatment protocols are proposed for treatment planning purposes and developing an optimal hyperthermia applicator that can coagulate the target tissue effectively, without destroying the surrounding healthy tissue.
The Gait Analysis and Interface Pressure Measurement Between Stump and Resin-Reinforced Rapid Prototyping Transtibial Socket
Authors: Chen Y. T. , Peng H. K. , Lu C. T. , Hsu L. H. , Huang G. F. , Shih H. S.
Published: June 2010

Currently, rapid prototyping (RP) products are manufactured by layer-based process; this result may cause RP products to break easily along layers when a bending moment is applied. To prevent RP transtibial sockets from breaking, wrapping a layer of unsaturated polyester resin (UPR) around transtibial sockets to reinforce its flexural strength is proposed. To verify the applicability of resin-reinforced RP socket fabrication, two experimental systems, including a socket sensor measurement and gait analysis system, are used to obtain interface pressures between stump, socket and gait characteristics during stance phase while such type of prosthetic socket is used. A male volunteer with a left below-knee amputation, a twenty-year transtibial socket user, was selected for this study. In the experiments, sensors were pasted on the stump and measurement data was collected at different walking speeds. The results of these experiments showed that the interface pressures were concentrated on pressure-tolerant areas, and the swing phase and stride length of stump increased while the volunteer was walking at a fast speed. The resin-reinforced rapid prototyping sockets have better comfortable quality of fitting because the interface pressures are more concentrated on pressure-tolerant areas including the patella tendon and medial tibia flare while wearing the new type of sockets.
Investigation of Promotion of Bone Matrices in Cultured Osteoblasts by Mechanical Vibration
Authors: Shiraishi Toshihiko , Shikata Tetsuo , Morishita Shin , Takeuchi Ryohei
Published: June 2010

This paper describes effects of mechanical vibration on osteoblasts. Their bone mass generation was investigated when sinusoidal inertia force was applied to the cells. After the cells were cultured in culture plates in a CO2 incubator for one day and adhered on the cultured plane, vibration group of the culture plate was set on an aluminum plate attached to a exciter and cultured under sinusoidal excitation of 0.5 G and 25 Hz for 24 hours a day in another incubator separated from non-vibration group during 28 days of culture. Gene expression of alkaline phosphatase (ALP) was measured by a real-time reverse transcription polymerase chain reaction method. ALP activity was measured by Azo-dye method. Calcium salts generated by the cells were observed by being stained with alizarin red S solution. As a result, it is found that the mechanical vibration accelerates the gene expression and protein generation of ALP, and the calcium salt generation.
Control of Apoptosis and Differentiation of Cultured Neural Stem Cells by Mechanical Vibration
Authors: Shiraishi Toshihiko , Suzuki Kei , Morishita Shin , Kanno Hiroshi
Published: June 2010

In this study, sinusoidal inertia force was applied to cultured neural stem cells and the effects of mechanical vibration on the cells were investigated. Neural stem cells which were obtained from the hippocampus of an adult Fischer rat were seeded in culture plates at the density of 2.5 × 105 cells/ml. After cells were cultured for one day and adhered on the cultured plate, vibration groups of the culture plates were set on the aluminum plate of the experimental setup and cultured under sinusoidal excitation in another CO2 incubator separated from non-vibration groups of the culture plates. Acceleration amplitude was set to 0.25 or 0.5 G and frequency was set to 12.5, 25, or 50 Hz. Time evolution of cell density was obtained by counting the number of cells with a hemocytometer. The expression of Akt, phosphorylated Akt, MAPK, and phosphorylated MAPK was detected by western blotting analysis to understand the mechanism of cell proliferation. Gene expression of MAP-2, neurofilament-H, GFAP, and nestin was detected by a real-time RT-PCR method to obtain a ratio of differentiation of neural stem cells to nerve or glia cells. The results to be obtained are as follows. The mechanical vibration at 25 Hz is most effective on cell proliferation of the present experimental conditions at 0.25 G. The enhancement of cell proliferation is probably caused by the suppression of apoptosis. The differentiation of the neural stem cells depends on acceleration amplitude and the mechanical vibration may maintain some properties of stem cells.
Electromigration of Charged Polystyrene Beads Through Silicon Nanopores Filled With Low Ionic Strength Solutions
Authors: Joshi Punarvasu , Mathew Trupthi , Petrossian Leo , Prasad Shalini , Goryll Michael , Spanias Andreas , Thornton Trevor J.
Published: June 2010

In this work we present preliminary results demonstrating the influence of electrical double layer overlap on the electromigration of polystyrene beads (PSB) through an array of 25 cylindrical nanopores. Each of the cylindrical nanopores of the array used in this study is 360nm long with a diameter of 90nm. We observe frequent Coulter events for solutions of higher ionic strength and absence of Coulter events at low ionic strength solution. At higher ionic strengths, the electric double layers in the nanopore are thin and ion transport through the nanopore follows the bulk behavior of the ionic solution. For solutions of lower ionic strength, the electric double layers are comparable to the nanopore dimensions and start to overlap, suggesting surface charge interaction with the polystyrene beads that pass through the nanopore. The work continues towards detailed statistical analysis of the characteristic events observed for different concentrations.
Effects of Process Parameters on Cell Damage in a 3D Cell Printing Process
Authors: Yan Karen Chang , Paluch Kamila , Nair Kalyani , Sun Wei
Published: June 2010

Various types of bio-fabrication methods have been developed to manufacture products with living cells incorporated via mechanical means. One of fundamental questions that need to be answered is whether cells remain viable and/or functional when subjected to these mechanical disturbances. In this paper, we focus on a 3D cell-printing process via pressure induced deposition. Our experimental studies show that process parameters such as pressure applied and nozzle size affect the cell viability. Given that the cells are suspended in the alginate solution during the printing process, Computational Fluid Dynamic (CFD) analysis is employed to model the pressure-driven flow system and determine the local environment that the living cells are in under varying process parameters. Effects of obtained wall shear stress and exposure time are examined in terms of cell damage based on the corresponding experimental data.
Computer Modeling of Fluid-Stress-Induced Blood Damage in a Mechanical Ventricular Assist Device
Authors: Untaroiu Alexandrina , Wood Houston G. , Allaire Paul E.
Published: June 2010

Congestive heart failure results the heart is unable to pump the required amount of blood to maintain the systemic circulation. World-wide, millions of patients are diagnosed with congestive heart failure every year, many of which ultimately become candidates for heart transplants. The limited number of available donor hearts, however, has resulted in a tremendous demand for alternative, supplemental circulatory support in the form of artificial heart pumps to serve as a “Bridge-to-Transplant”. The prospect of artificial heart pumps used for long-term support of congestive heart failure patients is directly dependent upon excellent blood compatibility. High fluid stress levels may arise due to high rotational speeds and narrow clearances between the stationary and rotating parts of the pump. Thus, fluid stress may result in damage to red blood cells and activation of platelets, contributing to thrombus formation. Therefore, it is essential to evaluate levels of blood trauma for successful design of a mechanical Ventricular Assist Device. Estimating the fluid stress levels that occur in a blood pump during the design phase also provides valuable information for optimization considerations. This study describes the CFD evaluation of blood damage in a magnetically suspended axial pump that occurs due to fluid stress. Using CFD, a blood damage index, reflecting the percentage of damaged red blood cells, was numerically estimated based on the scalar fluid stress values and exposure time to such stresses. A number of particles, with no mass and reactive properties, was injected at the inflow of the computational domain and traveled along their corresponding streamlines. A Lagrangian particle tracking technique was employed to obtain the stress history of each particle along its streamline, making it possible to consider the damage history of each particle. Maximum scalar stresses of approximately 430 Pa were estimated to occur along the tip surface of the impeller blades, more precisely at the leading edge of the impeller blades. The maximum time required for the vast majority of particles to pass through the pump was approximately 0.085sec. A small number of particles (approximately 5%), which traveled through the narrow gap between the stationary and rotating part of the pump, exited the computational domain in approximately 0.2 sec. The mean value of blood damage index was found to be 0.15% with a maximum value of approximately 0.47%. These values are one order of magnitude lower than the approximated damage indices published in the literature for other Ventricular Assist Devices. The low blood damage index indicates that red blood cells traveling along the streamlines considered are not likely to be ruptured, mainly due to the very small time of exposure to high stress.
Mathematical Models for Analyzing Tissue Ablation Using Short Pulse Lasers
Authors: Onyejekwe Ogugua , Sajjadi Amir Yousef , Abdulla Ugur , Mitra Kunal , Grace Michael
Published: June 2010

Mathematical modeling of biological tissue ablation performed using a short pulse laser and the corresponding experimental analysis is of fundamental importance to the understanding and predicting the temperature distribution and heat affected zone for advancing surgical application of lasers. The objective of this paper is to use mathematical models to predict the thermal ablated zones during irradiation of freshly excised mouse skin tissue samples by a novel approach using a focused laser beam from a short pulse laser source. Suggested mathematical model is Stefan kind free boundary problem for the heat equation in unknown region. Temperature of the skin satisfies the classical heat equation subjected to Neumann boundary condition on the known boundary, while along the time-dependent unknown boundary, which characterizes the ablation depth, two conditions are met: (1) temperature is equal to the ablation temperature and (2) classical Stefan condition is satisfied. The latter expresses the conservation of energy at the ablation moment. A method of integral equations is used to reduce the Stefan problem to a system of two Volterra kind integral equations for temperature and ablation depth. MATLAB is used subsequently for the numerical solution. Experiments are performed using two lasers—a diode laser having a wavelength of 1552 nm and pulsewidth of 1.3 ps. The surface temperature distribution is measured using an imaging camera. After irradiation, histological studies of laser irradiated tissues are performed using frozen sectioning technique to determine the extent of thermal damage caused by the laser beam. The ablation depth and width is calculated based on the interpolated polygon technique using image processing software. The surface temperature distribution and the ablation depth obtained from the mathematical models are compared with the experimental measurements and are in very good agreement. A parametric study of various laser parameters such as time-average power, pulse repetition rate, pulse energy, and irradiation time is performed to determine the necessary ablation threshold parameters.
Multimodal Control of Orientation in Space
Authors: Chen Ji , Darvish Kurosh , Wright W. Geoffrey , Keshner Emily A.
Published: June 2010

The impaired balance of posture accounts for the fall with a large proportion of falls in older people occurring when walking. However, the mechanisms underlying impaired balance during both gait and passive postural state are poorly understood. The objective of the research is to examine the underlying causes of instability and then to eventually create therapeutic interventions that will improve balance and lessen the number of falls related injuries. This paper focuses on developing a laboratory to study the combined influence of motion impact and visual conditions on head stabilization during passive postural jerk impact and simple harmonic movements. Preliminary studies on one healthy subject shows that concordant and discordant visual inputs have more compensatory effect than eyes closed on head stabilization during the jerk impact.
Dynamic Optical Investigations of Hypervelocity Impact Damage
Authors: Lamberson Leslie E. , Rosakis Ares J.
Published: June 2010

Hypervelocity impact is a rising concern in spacecraft missions where man-made debris in low-earth orbit as well as micrometeroids have the potential to damage not only the structural components, but also the optical, electrical, and thermal components of a space asset. Little has been investigated regarding damage mechanisms and dynamic fracture mechanics resulting from a hypervelocity impact in-situ. Two optical techniques, the methods of photoelasticity and caustics, in conjunction with high-speed photography are used to examine stress waves from impact of unloaded plates, as well as pre-cracked and pre-loaded plates in tension. The resulting photographs are analyzed to extract information regarding stress wave interactions, crack speeds and the dynamic stress field ahead of the moving cracks.
A Modified Method of Arterial Elasticity Index Including Effects of Constraints From Surrounding Tissues
Authors: Ota Shinichiro , Yasuda Toshitaka , Saito Takashi , Takatani Setsuo
Published: June 2010

Previously, we proposed an estimation method of arterial elasticity index (EM) independent of geometric factors such as the radius and wall thickness. Since the previous method was based on an equation of a motion that assumed a thin cylindrical model with infinite length, it is thus necessary to account for the effects of dynamic constraints from surrounding tissues. The purpose of this study is to propose a modified method for quantifying arterial elasticity index accounting for the effects of dynamic constraints. We describe the modified method by vibration analysis of a thin cylindrical shell using a natural frequency depending on boundary conditions. To examine the feasibility of the proposed method, we measured the inner pressure, radius and natural frequency of the mock-vessels with dynamic constraints. From these results, the elasticity index (EM) was derived independent of the effects of dynamic constraints. In summary, the proposed method enabled to derive elastic properties of arteries accounting for the effects of dynamic constraints in mock-vessels with both ends restricted.
Evaluation of an Instrumented Human Surrogate Torso Model in Open Field Blast Loading
Authors: Merkle A. C. , Roberts J. C. , Wing I. D. , Wickwire A. C.
Published: June 2010

A 50th percentile Human Surrogate Torso Model (HSTM50) was constructed using biosimulant materials to represent the thoracic skeletal structure, internal organs, and soft tissues. The model was instrumented with pressure sensors embedded in each organ, accelerometers rigidly mounted to the sternum, and a load cell aligned with the vertebral column. The HSTM was exposed to a series of open-field blast tests. Sensor data clearly conveyed an initial rise in organ pressure due to the arrival of the incident shock wave followed by a delayed secondary peak of lesser magnitude due to the arrival of the ground-reflected incident shock wave. For repeat test conditions, the HSTM provided sensor response deviation within the inherent variability of field pressure data recorded for various tests of equal weight charges. This test series demonstrated the HSTM50 sensitivity to blast threat conditions including variations in charge weight and type. The HSTM50 proved to be a repeatable, durable, non-homogeneous test device complete with skeletal structure and soft tissue. The system allowed for the dynamic measurement of internal pressures, acceleration, and spinal load as a result of various blast conditions.
Development of a Human Head Physical Surrogate Model for Investigating Blast Injury
Authors: Merkle A. C. , Wing I. D. , Armiger R. A. , Carkhuff B. G. , Roberts J. C.
Published: June 2010

The objective of this effort was to develop a Human Surrogate Head Model (HSHM) and measure its response to pressure loading conditions representative of a blast environment. The HSHM consists of skin, face, skull, and brain fabricated using biosimulant materials and mounted to the neck of a Hybrid III Anthropomorphic Test Device to allow head motion during loading. The HSHM instrumentation includes pressure and displacement sensors embedded in the anterior and posterior areas of the brain along the saggital plane. The displacement sensors are a custom solution developed for this particular application. A series of shock tube tests at three varying load levels were conducted with the HSHM to simulate blast loading conditions. As pressure loading levels increased, the intracranial pressures and brain displacements increased as well. However, the spatial response of the displacement sensors varied with location in the brain. The results of this test series provide the first instance of intracranial pressure and directly measured brain displacements recorded from an anatomically correct head surrogate exposed to conditions representative of blast loading.
Development of a Human Head-Neck Computational Model for Assessing Blast Injury
Authors: Roberts J. C. , Ward E. E. , Harrigan T. P. , Taylor T. M. , Annett M. A. , Merkle A. C.
Published: June 2010

A finite element model (FEM) of the human head attached to a Hybrid III FEM neck was developed to study the effects of blast loading on the brain. Simulations of blast loading to this Human Head Finite Element Model (HHFEM) were generated by creating a computational fluid dynamics (CFD) model of the HHFEM headform in a shock tube. Three different driver pressure loading conditions from experimental testing of the Human Surrogate Head Model (HSHM) were simulated by this model. The pressure time histories at each grid point of the CFD headform were used as inputs to the HHFEM. Brain/cerebral spinal fluid (CSF) and CSF/skull boundary conditions along with different brain material models were considered. The Kelvin-Maxwell material model and a low friction surface-to-surface interface were found to best replicate conditions seen in experimental testing of the HSHM. Deformations in the anterior and posterior locations of the brain varied from 0.5–0.9 mm and intracranial pressures at those locations were between 32 and 55 kPa.
Application Study of Biomechanical Estimator Using Optical Coherence Straingraphy to Atherosclerosis
Authors: Sakata Yoshitaro , Saeki Souichi , Saito Takashi , Hiro Takafumi , Matsuzaki Masunori
Published: June 2010

The authors have developed Optical Coherence Straingraphy (OCS) as a visualizing technique of tissue strain distribution, by means of deformation of speckle pattern obtained by Optical Coherence Tomography. In this study, ex vivo OCS imaging experiment was carried out using atherosclerotic plaques of WHHL rabbit, compared with simulated results of histologically image-based FEM. Consequently, strain pattern obtained by OCS has qualitative agreement with simulated results. Therefore, it was confirmed that OCS could diagnose biomechanical properties of atherosclerotic plaque tomographically.
Acoustic Response of Arteries Using Thick Wall Tube Assumption
Authors: Al-Jumaily A. M. , Al-Ammri A. Salam
Published: June 2010

This paper describes the pressure wave propagation and reflection phenomenon in the aorta and the brachial artery to reproduce the brachial artery pressure and the strain imposed on the cuff external wall using thick wall tube assumption for the aorta. The effects of variations in aortic radius, thickness, heart rate and cuff pressure on the brachial artery pressure contours and pneumatic cuff strain contours were investigated The thick wall tube assumption for the aorta will improve the accuracy of the results and give an indication about the error involved when using thin wall tube assumption. The results indicate that there are some differences between the trends and shapes of the curves when using thick wall assumption. This difference could be as high as 3% for the eight feature points extracted from the pressure and strain contours. These feature points are the time duration before the deflection marking the arrival of the incident and reflected wave, the peak of the first and second pressure deflection minus the diastolic pressure, the peak of the first and second strain deflection minus the strain at diastolic pressure. These features points are used to calculate the brachial augmentation indices and the time lag which are used as a measure of arterial stiffness.
Development and Testing of a Small Scale Bladeless Turbine for Power Production Applications
Authors: Reich Alton , Deaconu Stelu
Published: June 2010

Bladeless turbines were first proposed and demonstrated almost 100 years ago, but they have not found widespread application. They have the potential for converting flow energy into rotational energy at high efficiencies. This paper discusses an effort to understand the factors affecting bladeless turbine efficiency, and the related experimental program performed. A theoretical model of turbine performance was developed and used to predict the performance of a small scale test unit. The model inputs include geometric parameters and inlet conditions including pressure and flow rate. The test unit was designed and assembled. Rapid prototyping techniques were used to facilitate part fabrication. It was coupled to an experimental set up including appropriate instrumentation. A comparison of model predictions and test results is presented.
Initial In-Vivo Results Considering Rayleigh Damping in Magnetic Resonance Elastography
Authors: Viviers D. , Van Houten E. E. W. , McGarry M. D. J. , Weaver J. B. , Paulsen K. D.
Published: June 2010

Dispersive material properties provide valuable metrics for characterizing the nature of soft tissue lesions. Magnetic Resonance Elastography (MRE) targets non-invasive breast cancer diagnosis and is capable of imaging the damping properties of soft tissue. 3D time-harmonic displacement data obtained via MRI is used to drive a reconstruction algorithm capable of deducing the distribution of mechanical properties in the tissue. To make the most of this diagnostic capability, characterization of the damping behavior of tissue is made more sophisticated by the use of a Rayleigh damping model. To date, time-harmonic motion attenuation in tissue as found in dynamic MRE has been characterized by a single parameter model that takes the form of an imaginary component of a complex valued shear modulus. A more generalized damping formulation for the time-harmonic case, known commonly as Rayleigh or proportional damping, includes an additional parameter that takes the form of an imaginary component of a complex valued density. The effects of these two different damping mechanisms can be shown to be independent across homogeneous distributions and mischaracterization of the damping structure can be shown to lead to artifacts in the reconstructed attenuation profile. We have implemented a Rayleigh damping reconstruction method for MRE and measured the dispersive properties of actual patient data sets with impressive results. Reconstructions show a close match with varying tissue structure. The reconstructed values for real shear modulus and overall damping levels are in reasonable agreement with values established in the literature or measured by mechanical testing, and in the case of malignant lesions, show good correspondence with contrast enhanced MRI. There is significant medical potential for an algorithm that can accurately reconstruct soft tissue material properties through non invasive MRI scans. Imaging methods that help identify invasive regions through reconstruction of dispersive soft tissue properties could be applied to pathologies in the brain, lung, liver and kidney as well.
Evaluating Nucleus Effect on the Cell Mechanical Behavior
Authors: Cao Guoxin , Chandra Namas
Published: June 2010

The mechanical behaviors of cells are closely related to cell biological functions, which are typically studied using the continuum and homogeneous cell model. The associated parameters in these models are determined from experiments, e.g. AFM indentation. In these studies, the effect of nucleus is not explicit studied and thus not clear. In the current study, the indentation behavior of cell with an explicit nucleus is investigated using numerical simulations.
3-D Navier-Stokes Simulation of Large-Scale Regions of the Bronchopulmonary Tree
Authors: Walters D. Keith , Luke William H.
Published: June 2010

A new methodology for CFD simulation of airflow in the human bronchopulmonary tree is presented. The new approach provides a means for detailed resolution of the flow features via three-dimensional Navier-Stokes CFD simulation without the need for direct simulation of the entire flow geometry, which is well beyond the reach of available computing power now and in the foreseeable future. The method is based on a finite number of flow paths, each of which is fully resolved, to provide a detailed description of the entire complex small-scale flowfield. A stochastic coupling approach is used for the unresolved flow path boundary conditions, yielding a virtual flow geometry allowing accurate statistical resolution of the flow at all scales for any set of flow conditions. Results are presented for multi-generational lung models based on the Weibel morphology and the anatomical data of Hammersley and Olson. Validation simulations are performed for a portion of the bronchiole region (generations 4–12) using the flow path ensemble method, and compared to simulations that are geometrically fully resolved. Results are obtained for three inspiratory flowrates and compared in terms of pressure drop, flow distribution characteristics, and flow structure. Results show excellent agreement with the fully resolved geometry, while reducing the mesh size and computational cost by as much as 94%.
Direct Compensator Profile Optimization for Intensity Modulated Radiation Therapy Treatment Planning
Authors: Erhart Kevin J. , Divo Eduardo A. , Kassab Alain J.
Published: June 2010

Radiation therapy is a widely used and highly effective technique for the treatment of cancer, however the commissioning and delivery of a course of external beam radiation is a complex process with numerous challenges. This paper will present new developments that aim to improve both the planning and delivery of this important cancer treatment technique. Specifically, this work develops a new direct delivery parameter optimization approach for planning of solid compensator intensity modulated radiation therapy, coined Direct Compensator Profile Optimization (DCPO). In order to understand the benefits and implications of this new DCPO approach, a reasonable understanding of the field of radiation therapy is needed. Therefore, this document will include a brief discussion of the history and relevant background information in the area of radiation therapy. It is intended that this background information is detailed enough so that the remainder of this research can be followed by those without existing experience in the field of radiation treatment planning. The specific details of this new approach will be then be presented followed by a display of initial results to verify the performance.
The Effect of Shock Wave on a Human Head
Authors: Ganpule Shailesh , Gu Linxia , Cao Guoxin , Chandra Namas
Published: June 2010

When a pressure wave of finite amplitude is generated in air by a rapid release of energy, such as high-pressure gas storage vessel or the blast from dynamite, there may be undetected brain injuries even though protective armors prevent the penetration of the projectile. To study brain tissue injury and design a better personnel head armor under blast wave, computational models of human head have been developed. Models with and without helmet are built to quantify the intracranial pressure and shear stresses of head subjected to blast wave. All the models are compared against injury thresholds for intracranial pressure and shear stresses. Overall pressure and shear stress level is highest in model without helmet and lowest in model with helmet having foam layer on inner side of helmet. The results show that helmet reduces the pressure and shear stresses generated in the brain. However this reduction in pressure and shear stresses might not be sufficient to mitigate early time, blast induced, traumatic brain injury. The validated results will provide better understanding of the energy transfer characteristics of blast wave through helmet and the injury mechanism of human head.
Computational Modeling of Helmet Structural Dynamics During Blunt Impacts
Authors: Przekwas Andrzej , Tan X. G. , Chen Z. J. , Zhou Xianlian , Reeves Debbie , Wilkerson Patrick , Yang H. Q. , Harrand Vincent , Chancey Valeta Carol
Published: June 2010

A combat helmet is a helmet designed specifically for use during combat. The Advanced Combat Helmet (ACH) was developed to be the next generation of protective combat helmets for use by the United States Army. The ACH replaces the former Personnel Armor System for Ground Troops (PASGT) helmet. The ACH has improved design features such as lighter weight, chinstrap retention system, and pad suspension system, with more comfortable fit. It is also design to allow maximum sensory and situational awareness for the operator. The design process for combat helmets can be expensive due to prototype fabrications and physical testing, which can include user-acceptance, retention evaluation, quality assurance, and ballistic and blunt impact performance testing. The physical testing required for both ballistic and blunt impact testing destroys prototype and product line helmets. In order to speed up the design process and reduce the cost associated with prototype fabrications and physical testing, we developed a multi-physics helmeted-head computational model to simulate blunt impacts to a combat helmet. The blunt impact performance of a combat helmet was evaluated using computer model by simulating the structural dynamics of the helmet during and after the impacts. This helmeted-head model is a part of a more extensive computational model to analyze the biomechanics of head injury.
Child ATD Reconstruction of a Fatal Pediatric Fall
Authors: Van Ee Chris , Raymond David , Thibault Kirk , Hardy Warren , Plunkett John
Published: June 2010

The current head Injury Assessment Reference Values (IARVs) for the child dummies are based in part on scaling adult and animal data and on reconstructions of real world accident scenarios. Reconstruction of well-documented accident scenarios provides critical data in the evaluation of proposed IARV values, but relatively few accidents are sufficiently documented to allow for accurate reconstructions. This reconstruction of a well documented fatal-fall involving a 23-month old child supplies additional data for IARV assessment. The videotaped fatal-fall resulted in a frontal head impact onto a carpet-covered cement floor. The child suffered an acute right temporal parietal subdural hematoma without skull fracture. The fall dynamics were reconstructed in the laboratory and the head linear and angular accelerations were quantified using the CRABI-18 Anthropomorphic Test Device (ATD). Peak linear acceleration was 125 ± 7 g (range 114–139), HIC15 was 335 ± 115 (Range 257–616), peak angular velocity was 57± 16 (Range 26–74), and peak angular acceleration was 32 ± 12 krad/s2 (Range 15–56). The results of the CRABI-18 fatal fall reconstruction were consistent with the linear and rotational tolerances reported in the literature. This study investigates the usefulness of the CRABI-18 anthropomorphic testing device in forensic investigations of child head injury and aids in the evaluation of proposed IARVs for head injury.
Contributions to the Study of Blood Flow in the Abdominal Aorta and Its Branches
Authors: Ferreira Ana C. M. , Teixeira Senhorinha F. C. F. , Teixeira Jose´ C. F.
Published: June 2010

Cardiovascular diseases are a major cause of death. Their development through the deposition of plaques onto the arteries and the subsequent formation of stenosis greatly affects the blood flow in the vascular system. Blood flow patterns depend on different factors, being the rheological characteristics of blood one of the most important. Although various publications have been dedicated to the study of blood flow in various geometries, they mostly assume the arteries as a rigid boundary. In the present work, the effect of the artery’s wall deformation upon the flow patterns is investigated. Therefore, the prime goal of this study consists in the development of numerical models able to predict the blood flow in the region of abdominal aorta under deformable boundaries. The simulation was performed using adaptative dynamic meshes into the finite volume FLUENT software, in order to evaluate the influence of increasing the stenosis degree in the blood flow. The results show the influence of the deformable boundary upon the length and location of the recirculation zone downstream of the stenosis and also in the wall shear stress distribution and pressure drop across the obstruction. An experimental test facility was developed in order to validate the numerical results. A cam profile coupled with electro valves duplicates the periodic flow of the cardiac cycle observed in the iliac bifurcation. The results evidence that the severity of the stenosis affects the distribution of the velocity profiles across the obstructed vessel’s section. It is also shown that the development of recirculation areas increases with the stenosis degree in post stenotic regions.