bluuebunny/crossref_metadata_2025 huggingface dataset:
Modeling the Human Hepatic Terminal Microcirculation Using 3D Computational Fluid Dynamics
Authors: Debbaut Charlotte , Vierendeels Jan , Van Loo Denis , Casteleyn Christophe , Cornillie Pieter , Van Hoorebeke Luc , Monbaliu Diethard , Segers Patrick
Published: July 2013

The perfusion of the liver is complex, especially at the microcirculatory level. The functional units of the liver are often schematized as hexagonal lobules (Fig. 1a), which receive blood from the peripheral portal triads (PT; including hepatic arterioles and portal venules). A part of the PT blood drains into the vascular septa (VS), which are the vascular beds delineating the lobule boundaries in between successive portal triads. Subsequently, the blood enters the interconnected network of tortuous sinusoids, where the metabolic exchange with neighboring hepatocytes takes place. Afterwards, blood drains radially into the central vein. Despite this well-known conceptual model, liver microcirculation is still not fully understood. Previously, the liver microhemodynamics have been modeled using simplified (2D) geometries and/or a porous media approach with an isotropic permeability. However, the validity of these assumptions has never been assessed. Therefore, the aim of this study was threefold. First, the (an)isotropic permeability behavior of an image-based 3D sinusoidal network was quantified using computational fluid dynamics (CFD). Secondly, the resulting permeability tensor was applied to build a 3D CFD porous medium model of a liver lobule. Thirdly, the role of VS in hepatic microperfusion was investigated by comparing a porous lobule model with and without VS.
The Effect of Impactor Location on the Validation of a Full Body Finite Element Model in Two Loading Cases
Authors: Vavalle Nicholas A. , Moreno Daniel P. , Stitzel Joel D. , Gayzik F. Scott
Published: July 2013

Finite element analysis (FEA) is a tool used by many in the injury biomechanics field. FEA allows researchers to study the stresses and strains in complex loading scenarios that would be impossible to determine experimentally. A vital step toward ensuring accurate results is validation of the finite element model (FEM), which is often based on matching model results to experimental results. While care is taken in performing experiments, there are still sources of variance in empirical results like experimental error and cadaver variation. In order to mimic these, location variations of two validation cases were studied, an oblique impact to the right thoracoabdominal region and a lateral impact to the right shoulder. Five locations were studied for each case, the nominal and four variations. The object of this study was to determine model robustness, conduct a sensitivity study of the model, and to simulate experimental subject variation without the use of subject-specific models. This study utilizes the Global Human Body Models Consortium (GHBMC) midsized male model. The model reflects a global effort to develop a set of state-of-the-art full body finite element models.
An Assistive Knee-Ankle-Foot-Orthosis and Sit-to-Stand Biomechanics
Authors: Schofield Jonathon S. , Adeeb Samer M. , Parent Eric C.
Published: July 2013

Knee-Ankle-Foot-Orthoses (KAFOs) are leg braces designed to assist in standing for patients with limited lower extremity function. The brace holds the knee extended and the ankle in a neutral position, thereby controlling balance and joint alignment. KAFOs have a variety of applications from skeletal complications to muscular weakness and paralysis (1). Patients experiencing such conditions are often dependant on the use of a wheelchair. Standing, therefore, becomes an important physiological function with benefits including pressures relief, spasticity reduction, bowel-and-bladder management, among others (2). However, since a KAFO limits knee and ankle motion, rising from a chair becomes a significant challenge as it requires substantial upper body strength to hoist oneself from seated position. Consequently, many KAFO users are unable to achieve sit-to-stand (STS) independently.
CFD Challenge: Solutions Using the Spectral Element Solver NEKTAR
Authors: Yu Yue , Baek Hyoungsu , Karniadakis George Em
Published: July 2013

Flow problems in cardiovascular mechanics involve complex geometries and pulsatile flow that may give rise to instabilities, especially in pathological cases. High-order methods are particularly suitable for resolving such unsteady phenomena whereas low-order methods may exhibit excessive dissipation and hence suppress any such physical instabilities. This, for example, is the case for certain type of cerebral aneurysms, see [1], for which we have demonstrated that shear layer instabilities may be triggered even at physiological flow rates, giving rise to audible frequencies in the range of 10Hz to 50 Hz. Similar phenomena may be present in stenotic arteries, where a jet type flow may develop that is also susceptible to temporal instabilities, especially during the decelerating systole.
In-Vitro Simulations of Drug Delivery in the Vitreous Chamber of the Eye
Authors: Bonfiglio Andrea , Stocchino Alessandro , Repetto Rodolfo , Siggers Jennifer H.
Published: July 2013

The vitreous chamber has an approximately spherical shape, and is filled with vitreous humor, a transparent material with viscoelastic properties. The vitreous humor has the mechanical roles of supporting the eye shape, promoting the adherence between the retina and the choroid, and acting as a barrier between the anterior and posterior segments of the eye for transport of heat and molecules [1]. Often, in elderly people, the vitreous humor has almost Newtonian properties as a consequence of a liquefaction process consisting of degradation of the collagenous framework of the gel. Moreover, after vitrectomy the vitreous humor is sometimes replaced with viscous tamponade fluids (typically silicone oils). Since intra-vitreal drug injection is increasingly used to treat retinal diseases, and the efficacy of this procedure depends on molecular transport processes after the injection, much of the biomechanical research on the vitreous humor has focused on understanding transport processes in the vitreous chamber. Many authors have considered purely diffusive transport or alternatively diffusion with advective transport due to creeping bulk flow only [2,3]. However, when the vitreous is liquefied, rotational motion of the eye has been shown to induce significant fluid flow, which plays a fundamental role for drug delivery in the vitreous chamber [4–7]. The most significant contribution to mass transport is due to the generation of a steady streaming flow, i.e. a steady flow resulting from the non-linearity in the equations. This flow component gives rise to a slow particle drift that becomes dominant over long times.
Implementing the Sano Modification in an Experimental Model of the Norwood Circulation
Authors: Biglino Giovanni , Giardini Alessandro , Baker Catriona , Hsia Tain-Yen , Figliola Richard S. , Taylor Andrew M. , Schievano Silvia
Published: July 2013

Surgical palliation of hypoplastic left heart syndrome (HLHS) is performed in three stages, the first of which is known as the Norwood procedure [1]. Traditionally, this operation involves securing an unobstructed outlet for the systemic circulation in infants for whom the single right ventricle is the only pump in the system, with pulmonary flow sourced via a modified Blalock-Taussig (BT) shunt. In 2003, Sano et al. have proposed a radical variation of this operation, known as the Sano modification [2]. In this case, the pulmonary circulation is supplied directly from the systemic right ventricle via an unvalved ventriculo-pulmonary Goretex conduit, or Sano shunt. Characteristically, flow in the Sano shunt continues throughout diastole (diastolic runoff). Differences between surgical approaches for stage 1 palliation have been addressed in the literature [3]. A computational model of Norwood procedure and Sano modification has also been proposed [4]. However, an experimental model of this complex physiology is currently lacking. Having recently presented an in vitro model of stage 1 physiology with a BT shunt arrangement [5], we propose here a compact mock circulatory system suitable for simulating the Sano physiology in patient-specific anatomical models.
CFD Challenge: Solutions Using the Commercial Finite Volume Solver, Fluent
Authors: Schaller Jens , Goubergrits Leonid
Published: July 2013

The Biofluid Mechanics Laboratory is working on hemodyanamics of medical devices and vessels — carotid bifurcations, coronary arteries and cerebral aneurysms — since mid 90s. For this challenge the simulations were performed by the doctorate student Jens Schaller supported by the student coworker Jan Osman using the commercial solver Fluent (Fluent 6.3.26, Ansys Inc., Canonsburg, USA).
Finite Element Analysis of In Vivo Radiocarpal Contact Mechanics Resulting From Scapholunate Ligament Injury
Authors: Johnson Joshua E. , Lee Phil , McIff Terence E. , Toby E. Bruce , Fischer Kenneth J.
Published: July 2013

Secondary osteoarthritis (OA) as a result of joint injury is a significant problem. For the wrist in particular, scapholunate dissociation, resulting from injury to the scapholunate interosseous ligament (SLIL), is a commonly occurring pathology. SLIL tears can lead to scapholunate joint instability due to abnormal motion and load transfer through multiple carpal joints. If left untreated, SLIL injury has been known to progress to scapholunate advanced collapse (or SLAC wrist) with radiocarpal OA [1]. While the pathomechanics leading to the onset of OA are not clearly understood, changes in kinematics and contact mechanics with injury are believed to be causative factors. Of particular importance are joint contact pressures and pressure distributions, which are considered to be important mechanical factors. Comparing changes in joint mechanics between normal and injured wrists may help us better understand the progression of OA and improve the efficacy of corrective measures. Several techniques exist to evaluate joint mechanics. Of these, 3D image-based computational modeling is very useful to determine in vivo joint mechanics. Finite element modeling (FEM) is the most common and widely used computational method because of the ability to obtain 3D stresses and strains, and due to software availability. Therefore the objective of this study was to compare radiocarpal joint mechanics (contact forces, contact areas, contact locations, peak and average contact pressures) from FEM between normal and injured wrists. We hypothesized that peak contact pressures and average contact pressures would be higher in the injured wrists.
Lower Extremity Muscle Activity Patterns During Lateral (Frontal) Side Stepping Task Modulation From Different Heights
Authors: Bhatia Dinesh , Novo Mario , Jung Ranu , Brunt Denis , Bejarano Tatiana
Published: July 2013

Different muscle groups function in a synchronized and coordinated manner to perform a given task, wherein the activity of one muscle group affects that of another (1, 3). Osteoarthritis (OA) is a common, chronic joint disease characterized by pain, disability and progressive loss of function. It is the most common musculoskeletal complaint worldwide and is associated with significant health and welfare costs (2, 7). The knee is the most frequently affected joint of the lower limb and prevalence of knee OA increases with age (6). Several studies have shown that muscle recruitment patterns and neuromuscular efficiency are different for patients with OA compared to normal controls during simple closed chain activities (4). However, no studies have investigated frontal plane control or the modulation of control due to, for example, a change in time or distance in OA (5).
The Investigation of Flow Separation Downstream of a Slotted Tube Stent in the Presence of a Pulsatile Flow Environment
Authors: Walker Andrew M. , Johnston Clifton R. , Rival David E.
Published: July 2013

Stent strut configuration has been found to alter local fluid flow and wall shear stress (WSS) patterns that can promote intimal hyperplasia. To quantify these alterations, we used particle image velocimetry (PIV) to investigate local fluid dynamics distal to a deployed stent within an acrylic tube. A blood analogue mixture of glycerol and water was pumped through a flow loop in both steady and pulsatile conditions. Steady and pulsatile velocity profiles and near WSS (NWSS) predicted by PIV were in good agreement with the Poiseuille and Womersley estimations. Introduction of a Palmaz balloon expanded slotted tube stent increased centerline velocities between 6.9% and 9% and decreased NWSS distal from the stent outlet by > 40%. Peak normalized vorticity was similar between non-stented and stented flows, although spatial coverage of higher vorticity was increased upon stent introduction. Future work will incorporate Echo PIV to complement PIV findings on how strut configuration affects flow dynamics.
Evaluation of Patellofemoral Contact Mechanics as a Function of Quadriceps Load and Flexion Angle
Authors: Halloran Jason , Bennetts Craig , Colbrunn Robb , Bonner Tara , Erdemir Ahmet , Andrish Jack
Published: July 2013

Patellofemoral complications are the single largest reason for knee related clinical visits. In spite of this, development of robust clinical treatments in this area remains a challenge [1]. Quantifying joint response across a wide range of conditions may lead to interventions specifically targeting desired or “normal” function. Previous patellofemoral studies often looked at joint mechanics as a function of specific quadriceps loaded flexion (e.g. deep knee bend) and/or during snapshots of loading representative of lifelike scenarios, e.g. gait, stair climb, etc. [2]. Sensitivity studies have been performed for these expected conditions [3,4] providing insight on the relationship between joint loading, geometry and potential contact mechanics. While patellofemoral biomechanics studies are prevalent, few, if any, have attempted to quantify joint response to systematic changes of two of the primary indicators of joint mechanics, namely quadriceps load and knee flexion. The overall joint response resulting from this type of approach could help quantify an envelope of natural function and also serves as an ideal data set for future computational model development. Once developed, probabilistic exploration of inherent uncertainties could be accomplished through a complimentary in vitro and in silico approach, offering quantification and classification of structure-function relationships. As a preliminary step, the goal of this study was to relate in vitro joint response, in terms of kinematics and contact mechanics, to systematic changes in knee flexion angle and quadriceps loading for a single specimen. Results from this study will offer insight into patellofemoral mechanics across a range of expected input and also serves as a starting point for future hypothesis driven studies.
Using Episcopic Fluorescence Image Capture, Ultrasound Biomicroscopy and Computational Fluid Dynamics to Study Geometry and Fluid Mechanics of Mouse Fetus and Neonate
Authors: Yap Choon Hwai , Pekkan Kerem , Lo Ceilia Wen Ya
Published: July 2013

Congenital cardiovascular malformations (CCM) affect 0.6% −1.9% of newborns (1), and has a mortality rate of approximately 48.1% in the first year of age, and 60.1% by 18 years of age (2).
Biophysical Model of the Coupled Mechanisms of Cell Adhesion, Contraction and Spreading
Authors: Vernerey Franck J.
Published: July 2013

Recent research has shown that cell spreading is highly dependent on the contractility of its cytoskeleton and the mechanical properties of its surrounding environment. This extended abstract introduces a mathematical formulation of cell spreading and contraction that couples the processes of stress fiber formation, protrusion growth through actin polymerization at the cell edge and dynamics of cross-membrane protein (integrins) enabling cell-substrate attachment. The evolving cell’s cytoskeleton is modeled as a mixture of fluid, proteins and filaments that can exchange mass and generate contraction. In particular, besides self-assembling into stress fibers, actin monomers are able to polymerize into an actin meshwork at the cell’s boundary in order to push the membrane forward and generate protrusion. These processes are possible via the development of cell-substrate attachment complexes that arise from the mechano-sensitive equilibrium of membrane proteins, known as integrins. Numerical simulations show that the proposed model is able to capture the dependency of cell spreading and contraction on substrate stiffness and chemistry. The very good agreement between model predictions and experimental observations suggests that mechanics plays a strong role into the coupled mechanisms of contraction, adhesion and spreading of adherent cells.
Study of Embolic Particle Migration in Cerebral Arteries by Computational Modelling
Authors: Fabbri Dario , Long Quan , Das Saroj , Pinelli Michele
Published: July 2013

As known, embolism is one of the major causes of stroke, which represents the rapid loss of brain functions. Two major sources of emboli which may cause ischemic attack were emboli formed in heart and from a ruptured arterial plaque in carotid arties. Due to the different characteristics of emboli formed from different mechanisms, the migration route of specific emboli in cerebral arteries may be different, so does the territory of the ischemic attack caused by them. Therefore, a good understanding of emboli migration in the complex cerebral arterial network may provide a good guidance for the diagnosis and treatment of stroke. Studies on the emboli motion in cerebral arteries so far were based on phantom models [1]. Although CFD simulation has been used on prediction of cerebral blood perfusion for many years, CFD particle tracking technique is rarely applied on study emboli migration in cerebral arteries. The present study aims to demonstrate the feasibility of using CFD particle tracking on emboli migration study with emphasis on the discussions of the particle tracking result by different coupling algorithms between blood flow and embolic particles.
Progressive Alterations in Biomechanical Response of a Mouse Model of Aneurysm
Authors: Haskett Darren , Utzinger Urs , Azhar Mohamad , Vande Geest Jonathan
Published: July 2013

Abdominal aortic aneurysm (AAA) is a complex disease that leads to a localized dilation of the infrarenal aorta, the rupture of which is associated with significant morbidity and mortality, however the underlying mechanisms by which such changes remains an important unanswered question in the literature. Animal models of AAA can be used to study how changes in the microstructural and biomechanical behavior of aortic tissues develop as disease progresses in these animals. We chose here to investigate changes in mechanical characteristics with time in the established Apolipoprotein E deficient (ApoE−/−) angiotensin II (AngII) infused mouse model of AAA.
Thermal Effect of Gold Nanorods in Implanted Prostatic Tumors During Laser Photothermal Therapy
Authors: Manuchehrabadi N. , Zhu L. , Attaluri A. , Cai H. , Edziah R. , Lalanne E. , Bieberich C. , Ma R. , Johnson A. M.
Published: July 2013

In recent years, nanotechnologies have emerged as promising therapies due to their ability to deliver adequate thermal dosage to irregular and/or deep-seated tumors. Gold nanorods can be tuned to a specific laser wavelength and serve as strong laser energy absorbers. Due to the powerful optical absorption, the laser energy is concentrated in an area congregating by nanorods, and then the energy absorbed can be transferred to the surrounding tumor tissue by heat conduction.1–4 Currently, there are wide variation ranges of treatment protocols using photothermal therapy. A systematic approach is lacking to analyze temperature elevation history in tumors during heating to design an optimized combination of laser parameters to maximize thermal damage to tumors.
The Detection of Arthrokinetic Biomarkers for Osteoarthritis in Partial Medial Meniscectomy Patients
Authors: Marsh Chelsea , Tang Jing , Tashman Scott
Published: July 2013

Meniscal injury has been found to leave patients at high risk for the development of knee osteoarthritis (OA). Partial meniscectomy is often used to treat meniscal tears, and while this procedure adequately addresses pain and the restoration of function, it does not prevent the progression of OA in the injured knee. Often during arthroscopy, surgeons identify areas of “softened” cartilage, which do not always correlate with visible signs of surface damage or cartilage loss. This softening has been related to changes in the cartilage matrix, which could represent early structural damage that can lead to irreversible cartilage damage and OA.
Design of a Novel Electronic Travel Aid to Assist Visually Impaired Individuals Navigate Their Environment
Authors: Morrison Robert , Lord Thomas , Esko Emily , Gillmeister Lauren , Kazlauskas Christine , Kamper Derek , Kang-Mieler Jennifer
Published: July 2013

Worldwide there are over 160 million people with severe visual impairment, as defined by visual acuity poorer than 20/200.1 A prominent concern for visually impaired individuals is their limited navigational abilities due to insufficient sensory information about their surrounding environment which results in difficulty with navigating new or complex environments. In these situations, they often have to rely on the assistance of others to help them reach their destination. Furthermore, even when the visually impaired individuals are familiar with the area, they are not always aware of non-stationary obstacles, such as cars or people. Two commonly used solutions currently available to help visually impaired individuals navigate their surroundings are the white cane and guide dogs. The white cane is useful for alerting its users to obstacles closer than 1.5 m, but it does not provide any information about the environment beyond that scope. Guide dogs are in unfortunately limited supply and can cost upwards of $42,000 to train.2 To address this challenge, multiple groups have examined more technologically advanced solutions to help visually impaired individuals. However, these devices have some major limitations, such as complicated display modalities and non-intuitive sensory representation of environmental information. The major goal of this proposal is to develop a new electronic travel aid (ETA) that will help visually impaired individuals navigate their environment more easily by using a novel method of directly displaying the location of obstacles up to 4 m away on the user’s torso with a grid of small vibrational devices called tactors. This device is intended to be used with a traditional white cane that can detect objects very close to the user and terrain changes, such as a step in a stairwell.
Profilometry Analysis and Improvements of a Novel Damage Scoring Method for Metal Bearing Surfaces of Shoulder Replacements
Authors: Ansari Farzana , Patten Eli W. , Cruz Cynthia , Beitel Erin , Swan Amelia , Gunther Steve B. , Norris Tom R. , Reis Michael , Pruitt Lisa
Published: July 2013

Characterizing the type and extent of in vivo damage to total joint replacements (TJR) is important for improving the success of arthroplasty outcomes, modeling damage modalities, and validating simulator studies. A method for quantifying the damage present on Cobalt Chrome (CoCr) humeral heads was developed in our lab to fulfill a much-needed gap in clinical knowledge regarding total shoulder replacements as well as metallic bearing surfaces [1,2]. A lack of inter-observer consistency with regard to severity classifications from our initial protocol [1] prompted several modifications to the method, which are tested and described here in this study. Also, since sub-micron scale ultra-high molecular weight polyethylene (UHMWPE) wear debris is linked to osteolysis and implant loosening, additional analysis with high magnification 3D optical profilometry was performed on a subset of damage modes with a long-term goal of correlating surface damage with propensity for osteolysis in TJR [3,4].
Hemodynamics of the Rat Aortic Arch
Authors: Molony David S. , Nencka Andrew , Li Zhixin , Zhao Ming , Giddens Don P.
Published: July 2013

Hemodynamics have been linked to the genesis and progress of vascular disease in humans and animals1. Disturbed flow patterns such as stagnant flow or flow reversal lead to low or oscillating wall shear stress (WSS). Several in-vivo studies have correlated these types of WSS with disease formation1, 2. The desire to find correlations between markers of vascular disease and mechanical stimuli and because of their easier availability has led to an increasing number of animal model studies. The mouse, in particular, is a commonly used animal for investigating vascular disease formation and progression. Suo et al., were one of the first to relate findings on the molecular level with WSS1. They found increased VCAM and ICAM expression in areas of low WSS. More recently Hoi et al.2, have shown a correlation between atherosclerotic plaque development and hemodynamic parameters such as low time averaged wall shear stress (TAWSS) and Oscillatory Shear Index (OSI).
Determination of In Vivo Dynamic Human Ankle Stiffness Under External Foot Rotation
Authors: Button Keith D. , Braman Jerrod E. , Wei Feng , Haut Roger C.
Published: July 2013

Ankle sprains account for 10–15% of all sports injuries [1]. Understanding the conditions that contribute to sports-related ankle sprains can provide useful information to footwear designers to help prevent such injuries. Attempts have been made to create surrogate ankles that mimic ankle properties in order to simulate injury scenarios. In this laboratory, using data from cadaver experiments, Villwock et al. developed such an ankle to assess injury risk due to shoe-surface interface [2]. While this model provides data on shoe-surface interactions, it only takes into account ankle stiffness in rotation. Consequently, the model can only recreate internal-external rotation, not eversion-inversion or plantarflexion-dorsiflexion responses of the human ankle.
Injury to Penetrating Blood Vessels in Cerebral Contusion
Authors: Yeoh Stewart , Zentgraf Bradley , Monson Kenneth L.
Published: July 2013

Traumatic brain injury (TBI), a devastating cause of death and disability [1, 2], commonly includes injury to the cerebral blood vessels [3]. Contusion has been called the hallmark of head injury [4], and includes damage to both blood vessels and surrounding parenchyma in the cortex. Vessels within the subarachnoid space, those penetrating the cortex, and capillaries within the cortical capillary plexus are all subject to injury and dysfunction. Contusion is primarily caused by traumatic interactions between the inner skull and brain surfaces, particularly in the inferior frontal and temporal lobe regions. However, little is known about the associated mechanisms of vessel damage. Definition of these mechanisms, and their thresholds, will inform prevention efforts. Improved understanding of the nature of vessel loading and injury may also lead to improved treatment.
Mechanical Properties of Primary and Immortal Fibroblasts in Cell Bi-Layers
Authors: Michaelson Jarett , Choi Heejin , So Peter , Huang Hayden
Published: July 2013

Immortalized cells are commonly used as analogs for primary cells in many cell mechanics, tissue engineering, and biochemical assays. However, it is not well-established whether immortal cell lines can mimic the behavior of primary cells in more physiological (three-dimensional) environments. For this project, we investigate the mechanical properties of primary cardiac fibroblasts (CFs) and 3T3 transformed fibroblasts when cultured in cell bi-layers by comparing the cells’ viscoelastic properties.
CFD Challenge: Solutions Using the Commercial Finite Volume Solver, ANSYS CFX
Authors: Fu WenYu , Qiao Aike
Published: July 2013

The Aike Qiao group has for nearly two decades focused on the study of biomechanics and simulation engineering, particularly as applied to carotid artery and cerebral aneurysm flows. For this Challenge, CFD simulations were performed by doctor fellow Wenyu Fu, using commercial finite volume solver, ANSYS CFX.
An Enhanced Discrete Element Model for Predicting Hip Contact Stresses
Authors: Abraham Christine L. , Maas Steve A. , Weiss Jeffrey A. , Ellis Benjamin J. , Peters Christopher L. , Anderson Andrew E.
Published: July 2013

Chronic exposure to excessive stress on articular cartilage in the hip joint predicts the progression and onset of osteoarthritis (OA) [1]. Discrete element analysis (DEA) has been used to predict cartilage contact stresses [2, 3]. Because of its low computational expense and relative ease of application, DEA could be an effective alternative to the finite element (FE) method for the study of contact stresses in the hip. Previous DEA models have assumed concentric hip joint geometry and constant cartilage thickness. These assumptions lead to underestimates for cartilage contact stress and predict unrealistic, simplified contact patterns [2, 4]. It is possible that DEA could provide more realistic predictions of cartilage contact stress if subject-specific bone and cartilage geometry were used. The objectives of this study were to develop a DEA model that accommodates subject-specific bone and cartilage geometry, and to compare DEA model predictions of cartilage contact stresses with predictions from validated FE models.
Flow Induced Vasodilation in Porcine Carotid Arteries
Authors: Boekhoven Renate W. , Maas Tatjana , Rutten Marcel C. M. , van de Vosse Frans N.
Published: July 2013

Endothelial cells play an important role in the autoregulation of the vascular diameter for maintaining physiological flow and shear stress. An increase in blood flow causes an increase in shear stress, which is sensed by the endothelial cells, resulting in the release of vasoactive substances. An impaired endothelial mediated vasomotive response seems reflective for several cardiovascular pathologies, such as failure of atherosclerosis and arterio-venous fistulas (AVF).
Mechanical Chondrocyte Damage Thresholds
Authors: van Turnhout Mark C. , de Vries Stefan A. H. , van Donkelaar Corrinus C. , Oomens Cees W. J.
Published: July 2013

Chondrocyte content in articular cartilage is very low. Only 2% to 5% of the tissue volume consists of chondrocytes [1]. Yet, these cells are responsible for maintenance of the tissue. Hence, the loss of chondrocytes that is often occurring at an early stage of cartilage degeneration is detrimental to articular cartilage. Excessive mechanical loading is known to be a cause of cell death. However, mechanical thresholds beyond which chondrocyte apoptosis would be induced are unknown.
4D MRI Flow Quantification of Cerebrospinal Fluid Motion in the Cervical Spine in Healthy Subjects and Chiari Malformation Patients: How Do the Results Compare With 3D Computational Fluid Dynamics?
Authors: Yiallourou Theresia I. , Bunck Alexander C. , Kroeger Jan-Robert , Stergiopulos Nikos , Martin Bryn A.
Published: July 2013

In this study, we employed time-resolved three directional velocity encoded phase contrast MRI (4DMRI) to quantify cerebrospinal fluid (CSF) movement within the complete cervical spinal subarachnoid space (SSS). The 4DMRI measurements were compared to a 3D computational fluid dynamics simulation (3DCFD) of the same space in healthy subjects and patients with Chiari I malformation. The results were assessed in terms of peak CSF flow velocities in the foot and head direction and flow patterns at nine axial locations along the cervical spine. It was found that the peak flow velocities measured by 4DMRI were consistently greater than those quantified by 3DCFD. In healthy subjects the 4DMRI flow velocities and patterns compared better to the 3DCFD than in Chiari I patients. Peak velocities had the greatest differences in the upper cervical spine of Chiari patients, where the 4DMRI quantified greater fluid jets at the craniocervical junction than the 3DCFD. Overall, these results represent the first quantitative comparison of 4DMRI to 3DCFD of CSF motion.
Regional Comparisons of Nano-Mechanical Properties of Deep Zone Menisci
Authors: Moyer John T. , Bouman Troy M. , Priest Ryan M. , Abraham Adam C. , Haut Donahue Tammy L.
Published: July 2013

Osteoarthritis (OA) is a dehabilitating condition that is highly prevalent in today’s society, frequently leading to a knee replacement. OA is characterized by loss of articular cartilage. Previous research has shown articular cartilage preservation is dependent on the structural integrity of the menisci [1, 2]. The human menisci are two crescent shaped fibrocartilaginous structures that provide fundamental load distribution within the knee joint, ultimately aiding to attenuate stresses at the tibio-femoral site [3–5].
A Performance Test to Assess Strategies to Transfer Weight During Knee Flexion and Extension With Rotation for Individuals With a Total Knee Replacement
Authors: Ferris Lauren , Denney Linda , Maletsky Lorin
Published: July 2013

Stability has been defined as the ability to transfer the vertical projection of the center of gravity to the supporting base and keep the knee as still as possible1. The transfer of weight (load) to a single limb while still in double-stance is functional and simulates every day activities such as loading the dishwasher, transferring laundry, or reaching to pick up an item. Adding rotation in a transverse plane to this weight shift challenges knee stability, especially those with a total knee replacement (TKR). A clinical sign of laxity in mid-flexion indicates a risk for developing symptomatic instability; a common reason for TKR revision2. Laxity is usually measured clinically in a single plane (anterior-posterior) and functionally with added turning maneuvers. Single-leg weight acceptance has been analyzed during athletic activities such as hopping, landing with cutting as well as in the older population with stair ascent and descent3–5. Although single-leg performance tests are a good indicator of knee stability, weight shift during double-stance may be more functional for individuals with a TKR. A functional double-stance test should include both flexion/extension with rotation and loading. Our study utilizes a novel approach (Target Touch Task) in order to facilitate transfer of load to one extremity during squatting or extending while still in double-stance. The objective of this study was to identify strategies utilized by individuals with a TKR while in double-stance transferring load during rotational activities.
Contribution of Different Physiological and Anatomical Factors to the Anterior Chamber Angle During Pupil Dilation
Authors: Jouzdani Sara , Amini Rouzbeh , Barocas Victor H.
Published: July 2013

Angle closure is well documented to be more severe in dilation [1, 2]. In addition, many anatomical and physiological factors associated with dilation may also contribute to severity of angle-closure. For example, population-based studies have shown that the prevalence rates of primary angle closure glaucoma (PACG) are relatively high among Asian population, particularly older women. Three potential causes for dilation-induced angle-closure have been reported: iris volume change (or lack thereof), posterior location of the dilator muscle, and (dynamic) pupillary block.
Transient and Steady-State Force Enhancement in the Drosophila Jump Muscle
Authors: Koppes Ryan A. , Swank Douglas M. , Corr David T.
Published: July 2013

The increase of isometric force after active lengthening, termed force enhancement (FE), is a well-accepted characteristic of skeletal muscle that has been demonstrated in both whole muscle [1,3] and single-fiber preparations [1,2]. The amount of FE increases with increasing amplitudes of stretch, yet no clear correlation between FE and the rate stretch has been demonstrated [2]. Although this behavior has been observed experimentally for over 70 years, its underlying mechanism(s) remain unknown. Furthermore, most studies of FE have been limited to steady-state (FESS) observations [1–3], whereas clues to the underlying mechanism(s) may very well exist in the transient force recovery period following an active stretch, as seen in another history-dependent phenomenon, force depression [4].
Pain Subsequent to Mechanical Loading of the Facet Capsular Ligament Depends on Encoding by Afferents in the Spinal Facet Joint
Authors: Weisshaar Christine L. , Kras Jeffrey V. , Tanaka Kosuke , Winkelstein Beth A.
Published: July 2013

The cervical facet joint has been identified as the source of neck pain in up to 60% of the cases [1], with the C6/C7 facet joint being particularly susceptible to injury during painful mechanical neck injuries [2]. The facet joint is innervated by both mechanoreceptors and nociceptors (i.e. pain receptors) [3,4]. Both receptor types respond to manipulation of the facet joint and afferent activation is related to the magnitude of joint loading [5]. Also, tensile stretch of the capsular ligament in vivo to magnitudes of strain simulating those during neck injury also produces sustained behavioral sensitivity (pain) and upregulates proteins involved in nociception [6]. Although anatomic and biomechanical studies suggest that facet capsule loading has a role in the development of pain, the relationship between capsule tension, the joint’s innervation, and the production of pain is still unclear.
Distinguishing Epicardial and Microvascular Disease Using Combined Functional and Anatomical Endpoints in a Porcine Model
Authors: Peelukhana Srikara V. , Kolli Kranthi K. , Leesar Massoud , Effat Mohamed , Helmy Tarek , Arif Imran , Schneeberger Eric W. , Succop Paul , Banerjee Rupak K.
Published: July 2013

For a better treatment of coronary artery disease in a catheterization lab, detection of the relative contributions of the epicardial stenosis (ES) and concomitant microvascular disease (MVD) is important. To diagnose ES, fractional flow reserve (FFR), the hyperemic stenosis resistance index (hSRv) and to diagnose MVD, hyperemic microvascular resistance index (hMRv) have been tested in cath labs. However, for concurrent assessment of ES and MVD, functional parameter utilizing flow and pressure values, pressure drop coefficient (CDP) and combined functional and anatomical parameter, lesion flow coefficient (LFC) are defined. To test the ability of CDP and LFC to account for ES and MVD, they were correlated with the hSRv and hMRv. We hypothesize that CDP and LFC will have a better combined correlation with hSRv and hMRv.

Simultaneous pressure and flow readings were obtained in 11 Yorkshire swine. Single and multiple linear regression analyses were conducted between the FFR, CDP and LFC vs hSRv and hMRv. The correlation coefficient (r) was used to check the strength of correlation.

The individual correlation between hSRv and hMRV with CDP (r = 0.90; r = 0.78) and LFC (r = 0.89; r = 0.95) was stronger compared to FFR (r = 0.63; r = 0.32). The combined correlation between hSRv and hMRv with CDP (r = 0.95) and LFC (r = 0.95) increased from the individual correlation. Therefore, we conclude that CDP and LFC can diagnose ES and MVD concurrently and might prove to be improved diagnostic parameters than FFR.
Regional Hyperelastic Properties of Human Hip Cartilage
Authors: Henak Corinne R. , Weiss Jeffrey A.
Published: July 2013

Cartilage material properties are necessary to make accurate predictions of cartilage stress during joint loading and to understand the effects of aging and disease on cartilage mechanics. Human hip cartilage material properties for loading situations that are relevant to activities of daily living are unavailable. Investigators have needed to use material properties from the joints of other animals as a substitute (e.g., [1]).
Micro-Scale Strain Transfer in Fiber-Reinforced Native Tissue Is Distinct From Cell-Seeded Aligned Nanofibrous Scaffolds
Authors: Han Woojin M. , Heo Su-Jin , Driscoll Tristan P. , Mauck Robert L. , Elliott Dawn M.
Published: July 2013

Mechanical signals influence cell viability, differentiation, proliferation, and extracellular matrix (ECM) production in load-bearing tissues. However, the current understanding of how macroscopic tissue level strain is transferred to cells is confounded by the highly variable strain fields that arise within the ECM of these tissues. In tendon and outer annulus fibrosus (AF), microscale strains in the ECM can be significantly lower than the applied strains.1,2,3 In meniscus, both strain amplification and attenuation were observed at the microscale level.4
How Frequently Do Five Total Arthroplasty Methods Change the Alignment of the Joint Lines and Limb From Normal?
Authors: Gu Yu S. , Roth Joshua D. , Howell Stephen M. , Hull Maury L.
Published: July 2013

One strategy for aligning the limb and positioning components in total knee arthroplasty (TKA) in the coronal plane is mechanical alignment, which has the goal of positioning the center of the hip, knee, and ankle on a straight-line by establishing a femoral and tibial joint line at the knee that is perpendicular to the mechanical axis of the femur and tibia respectively. Another strategy is gap balancing, which has the goal of creating equal gaps between the medial and lateral compartments at 0° of extension and 90° of flexion.
Effects of Mitral Valve Suture Position on Left Ventricular Vortex and Energy Under Edge-to-Edge Repair
Authors: Jiang Song , Wang Ze , Hu Yingying , He Zhaoming
Published: July 2013

Mitral valve (MV) asymmetry in the left ventricle causes a large anterior vortex during left ventricle (LV) filling which is considered to store kinematic energy. This vortex persists in the end of diastole and may facilitate early closure of the mitral valve and transfer kinetic energy in the anterior vortex to help blood ejection through the aortic valve. Washout effect from the anterior vortex may prevent thrombosis in the left ventricle. Recently one of the repair techniques, the mitral valve edge-to-edge repair (ETER) procedure, has been used for the correction of mitral regurgitation. According to this procedure, MV’s competence is restored by suturing the edges of the leaflets, at the central, lateral or commissural position, depending on the mechanism of the regurgitation and the site of valvular lesions. Changes in the mitral valve geometry, due to ETER, alter LV fluid mechanics. Our group has investigated suture length effect on LV fluid mechanics. MV ETER increased energy loss and lowered LV filling efficiency. The larger orifice area after ETER might prevent significant energy loss and transmitral pressure drop during diastole. However, suture position effect is unknown. In this study, we aim to investigate the effect of different MV suture position on LV fluid mechanics, especially the vortex, LV pumping efficiency.
Finite Element Modeling of Matrix Synthesis and Binding Kinetics in a Biphasic-Solute Material
Authors: Ateshian Gerard A. , Nims Robert , Cigan Alex D. , Albro Michael B. , Hung Clark T.
Published: July 2013

Living tissues and engineered tissue constructs undergo synthesis and degradation processes that alter their solid and solute content. To model such events, it is necessary to account for solid matrix deformation as well as mass exchanges with the solid. Equations of chemical kinetics, which can describe mass exchanges among constituents of a mixture, are generally formulated for fluid solutions only. Therefore the objective of this study is to implement a formulation of matrix synthesis and binding kinetics in the FEBio finite element framework (http://www.febio.org), using the biphasic-solute material consisting of a mixture of a solid, solvent and neutral solute [1].
Mechanical Analysis of Bacterial Nanocellulose for Biomedical Applications
Authors: Schwertz Joseph M. , Gatenholm Paul , Eberhardt Alan W.
Published: July 2013

Bacterial nanocellulose (BNC) is a biopolymer that has been used in a variety of applications ranging from speaker diaphragms to biomedical products. With the exact chemical structure as that produced by plants, BNC is created by microbes like Gluconacetobacter xylinus. One of the unique aspects of BNC is its ability to have a wide variety of mechanical properties while in hydrogel form.
The Developing Shoulder Has a Limited Capacity to Recover After a Short Duration of Paralysis
Authors: Potter Ryan , Thomopoulos Stavros
Published: July 2013

Neonatal brachial plexus injuries during childbirth can cause shoulder paralysis in 1 out of every 250 births in the United States.1,2 Although 80% of these infants recover spontaneously and have no residual complications, a number of them have persistent paralysis and functional deficits.1,3,4 Surgeons are thus faced with a choice on if and when to intervene. However, the time course of persistent paralysis leading to permanent functional defects in the neonate is unclear.
Bioheat Transfer With Ken Diller: A Perspective on Intracellular Ice Formation During Freezing of Cells
Authors: Toner Mehmet , Devireddy Ram
Published: July 2013

Dr. Diller is undoubtedly one of most important researcher in the field of bioheat and mass transfer as it applies to low temperature biology over the last 40 odd years. This talk will highlight his seminal contributions to the field.
3D Dilation and Distortion Estimated in the Living Human Brain From MR Images of Propagating Shear Waves
Authors: Clayton Erik H. , Genin Guy M. , Bayly Philip V.
Published: July 2013

Traumatic brain injury (TBI) can result from blunt force trauma, rapid inertial loading, or extracranial pressure (i.e., explosive blast). Much of the pathway between mechanical insult and neurological injury remains unclear, in part because data on the mechanical response of the brain are difficult to acquire in vivo. The physics of measuring harmonically-varying displacement fields in vivo using motion-sensitive magnetic resonance imaging (MRI) is well understood [1], yet to date data in the human brain have not been investigated in terms of strain and rotation. Here these kinematic quantities are examined and new light is shed on biomechanics of the living intact human brain as it is subjected to harmonic acoustic pressure load.
SBC2012 CFD Challenge: Simulation Using a FVM Program Developed by the Oshima Laboratory at the University of Tokyo
Authors: Oshima Marie , Katagiri Kengo
Published: July 2013

The aim of this paper is to present the results of SBC2012 CFD Challenge Phase I problem using a program developed by the Oshima laboratory at the University of Tokyo.
Visualization and Measurement of Flow-Induced Dynamic Motion of Red Blood Cells Using Tracking Confocal Micro-PIV System
Authors: Oshima Marie , Oishi Masamichi , Kinoshita Haruyuki , Fujii Teruo
Published: July 2013

RBC(Red Blood Cell)s have a biconcave shape with diameters of about 8 μm and thicknesses of about 2 μm like a capsule structure with highly deformable membrane. In arterioles having diameters of less than 100μm, the effect of RBCs becomes pronounced because the scales of the flow and the RBCs become similar. RBCs exhibit the axial migration [1] toward the center of blood vessel. The axial migration leads to non-Newtonian flow behavior such as decrease in flow resistance. The tank-tread motion [2] makes an important role for the axial migration and it is dependent on the shear rate of the surrounding flow, which ranges up to 500 s−1 in arteriole.
The Biomechanical Determinants of Concussion: Kinematic and Tissue-Level Predictors of Injury
Authors: Patton Declan A. , McIntosh Andrew S. , Kleiven Svein
Published: July 2013

Concussion has been identified in recent research as being the most commonly occurring head injury in sports [1]. Many studies have reconstructed and analysed impacts from American-football [2–6]; however, very few studies have focused on impacts occurring in unhelmeted football codes [7, 8].