bluuebunny/crossref_metadata_2025 huggingface dataset:
Strength of Porcine Carotid Arteries As a Function of Strain Rate and Storage Time
Authors: Fan Jinwu , Johnson W. Steven , Ku David
Published: March 2014

The ultimate strength of collagenous blood vessels is important for clinical problems of trauma and plaque rupture. Trauma related to motor vehicle accidents can create strain rates of 100 mm/s. Cyclic fatigue tests may also require high frequencies that may affect the strength properties of the soft tissue. The yield points and ultimate strengths depend on the unfolding of collagen molecules, collagen crosslinks, and the fiber-matrix bonding this composite structure. The non-linear behavior of animal soft tissues makes the determination of a plastic yield point difficult to distinguish. The lack of sources restricts the amount of primary data regarding ultimate strength, strain, frequency dependence, and harvest time dependence. Nonetheless, the mechanics surrounding plaque cap rupture demand measurements of all these parameters.
Frictional Characteristics and Tissue Loss of Articular Cartilage Under a Novel Wear Regime
Authors: Shields Kelly J. , Owen John R. , Wayne Jennifer S.
Published: March 2014

Degenerative joint disease, age, and trauma lead to progressive articular cartilage damage due to the tissue’s limited repair capabilities. Numerous clinical repair techniques with varying degrees of success have been developed in order to repair damaged tissue and restore joint function. One approach is the development of articular cartilage repair tissue to implant into the damaged or diseased articular surface. Determining the viability of an articular repair technique or tissue under in vivo stresses and wear is crucial to predict its success.
Effect of a Degenerated C5-C6 Disc on the Biomechanics of Adjacent Levels: A Poroelastic Finite Element Investigation
Authors: Hussain Mozammil , Natarajan Raghu N. , Andersson Gunnar B. J. , An Howard S.
Published: March 2014

Degenerative changes in the cervical spine due to aging are very common causes of neck pain in general population. Although many investigators have quantified the gross morphological changes in the disc with progressive degeneration, the biomechanical changes due to degenerative pathologies of the disc and its effect on the adjacent levels are not well understood. Despite many in vivo and in vitro techniques used to study such complex phenomena, the finite element (FE) method is still a powerful tool to investigate the internal mechanics and complex clinical situations under various physiological loadings particularly when large numbers of parameters are involved. The objective of the present study was to develop and validate a poroelastic FE model of a healthy C3-T1 segment of the cervical spine under physiologic moment loads. The model included the regional effect of change in the fixed charged density of proteoglycan concentration and change in the permeability and porosity due to change in the axial strain of disc tissues. The model was further modified to include various degrees of disc degeneration at the C5-C6 level. Outcomes of this study provided a better understanding on the progression of degeneration along the cervical spine by investigating the biomechanical response of the adjacent segments with an intermediate degenerated C5-C6 level.
Increased Biocompatibility of Common MEMS Substrates With Solution Phase Coupled Poly(ethylene glycol) Films
Authors: Eldridge Abigail N. , Dubnisheva Anna , Fissell William H. , Fleischman Aaaron J. , Roy Shuvo
Published: March 2014

A Poly (ethylene glycol) (PEG) self-assembled monolayer was solution phase coupled to common MEMS (microelectromechanical systems) substrates through a one step procedure in order to investigate the potential anti-fouling properties of the polymer for implantable biomedical MEMS applications.
Finite Element Modeling and Analysis of Human Pelvis
Authors: Ivanov A. , Kiapour A. , Ebraheim N. , Goel V. K.
Published: March 2014

The pelvis is a multi-component structure with complex geometry and biomechanical properties. Complex geometry, individual differences between subcomponents and aging create difficulties in analyzing the biomechanical behavior of the pelvis.
3D Cell Shape and Cell Fate are Regulated by the Dynamic Micro-Mechanical Properties of the Cell-ECM Interface
Authors: Campana Kimberly A. , Shin Eric Y. , Waisner Beverly Z. , Voytik-Harbin Sherry L.
Published: March 2014

Mechanobiology is an interdisciplinary field that focuses on predicting and understanding cellular responses to mechanical loads. The extracellular matrix (ECM) represents a macromolecular framework that naturally imparts structural support and spatial organization for resident cells. The ECM also participates in the communication and transfer of mechanical loads to cells, in part, via integrin attachment to the cytoskeleton (CSK). Recently, using a tissue model in which cells are embedded in a 3D collagen ECM, we have shown that fundamental cell behaviors, including morphology, proliferation, contractility, and ECM remodeling properties, can be modulated by varying 3D microstructural organization and mechanical properties of the surrounding collagen fibrils[1]. While these and other results demonstrate the critical role played by the ECM in regulating cell behavior, the mechanical-based mechanisms underlying these critical cell-ECM interactions have yet to be fully elucidated [2].
Dynamics of Magnetic Drug Targeting in Cardiovascular Flows
Authors: Williams Alicia M. , Vlachos Pavlos P.
Published: March 2014

In spite of the level of sophistication and development of medicine, the effective delivery of drugs remains an unsolved problem. The conventional method to deliver drugs is to inject them intravenously to the patient, or administer a pill capsule. The medicine diffuses through the bloodstream without regard to the location of the malady. For many types of diseases, the inefficiency of this method leads to increased dosage requirements, which can cause the patient to experience adverse side effects.
Computational Model of Interstitial Transport in the Rat Brain Using Diffusion Tensor Imaging
Authors: Kim Jung Hwan , Mareci Thomas H. , Sarntinoranont Malisa
Published: March 2014

In spite of the high therapeutic potential of macromolecular drugs, it has proven difficult to apply them to recovery after injury and treatment of cancer, Parkinson’s disease, and other neurodegenerative diseases. One barrier to systemic administration is low capillary permeability, i.e., the blood-brain and blood-spinal cord barrier. To overcome this barrier, convection-enhanced delivery (CED) infuses agents directly into tissue to supplement diffusion and increase the distribution of large molecules in the brain [1,2]. Predictive models of distribution during CED would be useful in treatment optimization and planning. To account for large infusion volumes, such models should incorporate tissue boundaries and anisotropic tissue properties.
Comparison Between Single Level and Bi-Level Dynamic Stabilization in Lumbar Spondylolisthesis: A Finite Element Study
Authors: Khere A. S. , Kiapour A. , Jangra J. , Goel V. K. , Biyani A. , Ebrahim N.
Published: March 2014

Lumbar spondylolisthesis is an extension of spondylolysis in which breakage of the vertebrae occurs at the pars interarticularis causing the vertebrae to slip forward. Spondylolisthesis is seen in both younger and older populations with most lesions occurring at the L4-L5 or L5-S1 level. Although the forward slippage of the vertebra does not usually exceed 30% of the body’s anterior-posterior width, possible spinal stenosis and nerve impingement may lead to severe pain and other complications. The purpose of this study is to determine the effect of single level and bi-level dynamic stabilization in reducing the spondylolisthesis. We used the finite element model for this purpose since it is not practical to procure specimens with spondylolisthesis for an experimental investigation.
Thermal Treatment Effects on a PLLA Bioresorbable Stent
Authors: Welch Tre , Eberhart Robert C. , Chuong Cheng-Jen
Published: March 2014

Stent navigation and expansion may injure vascular endothelium, including vulnerable plaque lesions. Balloon expansion and deployment of a stent can lead to injury or the endothelial lining and stretching of the arterial wall [1]. Understanding the traction forces an expanding stent imparts on the vascular wall at the endothelial surface, the underlying plaque lesions and other tissue components during expansion is an important step in improving short term stent-wall mechanics. More importantly, the long term influence of stent-vascular wall mechanical interactions in restenosis remains unknown, and this analysis may shed light on the process.
Biomechanical Quantification of Flexion Movement (Ducking) of the Human Head-Neck and Rollover Accidents
Authors: Kumar Sri , Paden Bradley , Carlin Fred , Frieder Russell
Published: March 2014

Rollover accidents are one of the major types of crashes contributing to the serious or fatal injuries to occupants [1]. The roof crush in rollover accidents is associated with serious injuries to head and neck system [2]. The roof crush intrudes into the occupant survival space and imparts force to the head. The excessive force on the head subjects the cervical spine to injurious level. A commonly observed cervical spine injury in rollover accidents is locked facets with no major bony fractures that are often associated with the flexion-distraction type of loading [3]. Although numerous studies addressed the mechanism of locked facet injuries and the survival space issues [4–9], limited comprehensive efforts have been advanced so far. It is noted that humans tend to duck their head while startled due to sudden fear [10,11]. It is hypothesized that the occupants inside the vehicle tend to duck their heads as a protective mechanism to avoid impact on the head. Although range of motion of the cervical spine is well reported [12], the change in downward movement of the head-neck system (ducking) is not studied well. The present study quantifies the downward movement of the head-neck system of volunteers while seated erect.
Characterization of Carbon Nanotube-Conjugated Collagen Composite Matrix Mechanics
Authors: Twomey John R. , Sundaram Vivek , Madhavan Krishna , Tan Wei
Published: March 2014

In the case of vascular grafts, enhanced mechanical properties of engineered tissue constructs are required in order to function properly in mechanically-active physiologic conditions. It is proposed that a composite matrix constructed of type I collagen, fibronectin, and covalently-functionalized single-walled carbon nanotubes (SWNTs) will provide the desired mechanical properties required for the development of implantable tissues capable of withstanding high-stress environments.
High Intensity Focused Ultrasound (HIFU) Transducer Characterization Using Acoustic Streaming
Authors: Hariharan Prasanna , Robinson Ronald A. , Myers Matthew R. , Banerjee Rupak K.
Published: March 2014

A new, non-perturbing optical measurement technique was developed to characterize medical ultrasound fields generated by High Intensity Focused Ultrasound (HIFU) transducers using a phenomenon called ‘acoustic streaming’. The acoustic streaming velocity generated by HIFU transducers was measured experimentally using Digital Particle Image Velocimetry (DPIV). The streaming velocity was then calculated numerically using the finite-element method. An optimization algorithm was developed to back-calculate acoustic power and intensity field by minimizing the difference between experimental and numerical streaming velocities. The intensity field and acoustic power calculated using this approach was validated with standard measurement techniques. Results showed that the inverse method was able to predict acoustic power and intensity fields within 10% of the actual value measured using standard techniques, at the low powers where standard methods can be safely applied. This technique is also potentially useful for evaluating medical ultrasound transducers at the higher power levels used in clinical practice.
Biomechanical Analysis of Late Airbag Deployment in Motor Vehicle Crashes Using Computer Simulation
Authors: Frieder Russell , Kumar Sri
Published: March 2014

Motor vehicle collisions frequently result in serious or fatal inuries to occupants [1–4]. Frontal collisions are amongst the most severe types of accidents. The use of safety systems such as seat belts and airbags has been shown to reduce the severity of injuries sustained by occupants [5–10]. It is well known that frontal airbags act as supplemental restraints to seat belts in protecting occupants. Airbag deployment occurs through a reaction of chemicals in the inflator that rapidly produces gas and fills the canvas bag. The filled bag acts a cushion between the occupant and the vehicle’s interior components. The supplemental restraint provided by the airbag increases the amount of time and distance over which the occupant’s body decelerates, and accordingly reduces the potential for injury. The time at which the airbag deployment is initiated during the crash sequence can have an effect on the nature of the contact between occupant and airbag. Though properly timed, frontal airbags have been shown to reduce injuries sustained to occupants[11], it has been reported that airbags that deploy too late may cause injury[12]. To date, there have been a very limited number of studies that have addressed the biomechanical effects of late airbag deployment. The purpose of this study is to determine the biomechanical effects of late airbag deployment and restraint use on various sizes of occupants through computer simulation.
Microfluidics Bioreactor: A Platform for Studying Capillary Morphogenesis in Response to Biochemical and Biophysical Cues
Authors: Vickerman Kelley Vernella V. , Kamm Roger D.
Published: March 2014

The in vivo microvasculature is a dynamic structure which is influenced by both biochemical (e.g. cytokines, growth factors) and biophysical factors (e.g. shear stress, interstitial flow). Important regulators of this structure are the endothelial cells which are normally quiescent but under certain conditions are able to form new vascular sprouts. Investigations into the mechanism of capillary morphogenesis of human endothelial cells warrant an in vitro model that closely mimics the physiological in vivo microenvironment. To this end, we have developed a novel microfabricated system which permits 2D and 3D culture of endothelial cells in biologically derived (e.g. type I collagen) or synthetic (self assembling peptides) scaffolds and delivers control flow rates and pressures. This system offers tremendous flexibility with regard to scaffold physical and chemical properties, physiologically relevant mechanical stress induced by surface shear and interstitial flow as well as chemotactic gradients. In addition we are able to directly monitor the progression of vascular networks in response to these critical factors.
Calculation of a Shear Strain Parameter for a Three-Dimensional Fung-Type Exponential Model of the Arterial Wall Under Torsion
Authors: VanEpps J. Scott , Vorp David A.
Published: March 2014

The distribution of atherosclerotic lesions within the coronary arteries is highly localized, despite the fact that risk factors (e.g., dyslipidemia) are systemic nature. The biomechanical milieu of the coronary arteries is unique in that in addition to cyclic pressure, circumferential distension and shear stress, they experience mechanical deformations of twisting, bending, and longitudinal stretching due to their tethering to the dynamic epicardial surface [1]. Biplane cineangiographic reconstruction studies have demonstrated that the coronary arteries experience as much as 20° of torsion during a cardiac cycle [2]. Spatial variations in shear and mural stresses caused by this deformation could account for the heterogeneity of atherosclerotic plaques.
Directing Neurite Growth in 3D Collagen Scaffolds With Gradients of Mechanical Properties
Authors: Sundararaghavan Harini G. , Shreiber David I.
Published: March 2014

Biomaterial scaffolds for nerve and spinal cord regeneration must not only promote neurite re-growth but also direct it. Several cell types, including neurons, respond to the mechanical properties of the substrate on which they are grown. We believe that gradients of mechanical properties can be used to direct neurons. To spatially control the mechanical properties, gradients of genipin — a naturally occurring, cell-tolerated crosslinking agent — are created in 3D through a compliant collagen gel using microfluidics. Gradients of mechanical properties are evaluated by measuring genipin-induced fluorescence, which we have previously correlated to mechanical properties. Growth of neurites was evaluated in gels of uniform stiffness and a gradient generated by incubation in 0 to 1 mM genipin for 12hrs to produce approximately an order of magnitude change in the shear modulus. Neurite growth was evaluated 5 days after gradient formation. Neurites demonstrated a directional bias against the gradient of stiffness. These results demonstrate that neurites can respond to subtle gradients of mechanical properties within a 3D scaffold and point to opportunities to manipulate properties for directed nerve and spinal cord regeneration.
Tissue Swelling During Extended Material Testing of Ligaments
Authors: Lujan Trevor J. , Underwood Clayton C. , Jacobs Nathan T. , Weiss Jeffrey A.
Published: March 2014

Material testing is often used to characterize the mechanical properties of biological tissue and to understand the specific effects of treatments and pathologies on mechanical behavior. To have confidence in results from material testing, it is important that the test environment is repeatable between samples and that tests are performed in an environment that mimics physiological conditions.
Simulation of Fall Loading Using a Probabilistic Shape-Based Finite Element Model of Human Femurs
Authors: Bredbenner Todd L. , Nicolella Daniel P.
Published: March 2014

The efficient construction of finite element models that accurately represent the complex morphology of biological structures is a major challenge. Typically, the model constructed is a representation of a single patient and, in order to investigate a different individual, the majority of the mesh construction process must be repeated.
The Development of an Injury Corridor to Assess Lower Extremity Injuries Resulting From Anti-Vehicular (AV) Landmine/Improvised Explosive Device (IED) Blasts in Military Vehicles
Authors: McKay Brian J. , Wolfe Gregory J. , Bir Cynthia
Published: March 2014

Detonations of anti-vehicular (AV) landmines and improvised explosive devices (IED) have accounted for more than half of the U.S. Military hostile casualties and wounded in Operation Iraqi Freedom (OIF) [1]. Military tactical and combat vehicles are being up-armored to defeat this ubiquitous threat and mitigate injuries to vehicle occupants. In order to define the optimal level of protection required to neutralize a given blast magnitude, a fundamental understanding of human injury tolerances must be established for loading conditions representative of AV blast impacts. Unlike automotive impact testing, AV landmine/IED explosions produce high amplitude and short duration vertical impact accelerations. The lower extremity is the predominantly injured body region following AV blasts. Detonations occurring under the vehicle produce localized floorboard deformation and transmit high axial loads onto the ankle/foot/tibia complex of the occupant causing injuries to the lower leg. [2,3]
CFD Model of Dynamic Thrombus Growth With and Without Shear Rate Dependant Deposition
Authors: Bark David L. , Ku David N.
Published: March 2014

Thrombosis can result in acute arterial occlusion thereby causing cerebrovascular accidents and myocardial infarction. However, diagnosing the risk of developing thrombosis is difficult due to the limited understanding of how platelets are transported, adhere, and accumulate in flowing blood. A clinician might be ably better at predicting a patient’s risk for thrombosis with an understanding of how a thrombus forms and why it occludes an artery. Thrombo-occlusion occurs in a complex interaction of biological reactions, fluid mechanics, and structural mechanics. Arterial thrombus usually forms on a ruptured atherosclerotic plaque, which is commonly found in specific arteries. Computational models of thrombogenesis may be used to compare the relative effects of the wide variety of factors involved with thrombosis. Such models are much easier to control and change than experiments. Most previous studies have focused on initial platelet adhesion and a short period thereafter. This study is focused on a growing thrombus past initial platelet attachment to the point of full occlusion, which is the dominant problem with a thrombotic event.
Chondrocytes and Fibrochondrocytes Differentially Process Aggrecan During De Novo Extracellular Matrix Assembly
Authors: Wilson Christopher G. , Levenston Marc E.
Published: March 2014

The material properties of articular cartilage and meniscal fibrocartilage depend on the composition and ultrastructure of the extracellular matrix (ECM). Aggrecan is the predominant large proteoglycan in these tissues, and confers compressive stiffness through immobilization of negatively charged sulfated glycosaminoglycans (sGAG). The abundance of sGAG is in part regulated by cell-mediated proteolysis of the aggrecan core protein, and transforming growth factor-β (TGF-β) family cytokines upregulate aggrecan synthesis in chondrocytes and fibrochondrocytes. The function(s) of aggrecan and mechanisms of aggrecan processing in the meniscus, however, are not well understood. The objective of this study was to examine tissue-specific kinetics and mechanisms of TGF-β-induced aggrecan turnover using the cell-agarose culture system. In addition, the tissue-specific functional implications of increased proteoglycan production were evaluated in terms of construct material properties.
Inertial Neck Injuries in Children Involved in Frontal Collisions: Sled Testing Using the 6-Year-Old ATD
Authors: Moore Tara L. A. , Prange Michael T. , Newberry William N. , Peterson Daniel , Smyth Brian , Corrigan Catherine Ford
Published: March 2014

Sled tests were conducted using a 6-year-old anthropomorphic test device (ATD) to investigate the effect of restraint type and crash severity on the risk of pediatric inertial neck injury. Tests were conducted at three severities, using three restraint configurations: properly restrained, misused restraint, and an age-inappropriate restraint. ATD injury measurements increased with increased crash severity. Head accelerations, head injury criteria, and neck loads, with the exception of neck flexion, were relatively independent of restraint configuration at a given crash severity. The data show that children are at risk of inertial neck injuries at high frontal crash severities.
Effects of Removal of Uncinate Process in a Cervical Disc Replacement Model: A Finite Element Based Study
Authors: Faizan A. , Goel V. K. , Krishna M. , Friesem T.
Published: March 2014

Anterior surgical approach is commonly used for Total Disc Replacement (TDR) surgeries in the cervical spine. The general procedure includes removal of the nucleus and anterior annulus of the intervertebral disc. Resection of Anterior Longitudinal Ligaments (ALL) is often performed to enter the disc space. The cervical spine also contains a unique anatomical feature called Luschka’s joints. These “joints” are actually fissures in the disc which run approximately parallel to the uncinate processes. These joints are thought to provide biomechanical stability to the cervical spine. However, sometimes surgeons have to sacrifice the uncinate processes at the involved level as well. We hypothesized that the cervical spine loses stability if the uncinate processes are removed along with disc replacement. We used a Finite Element (FE) model of cervical spine to prove the hypothesis (Fig1).
A Finite Element Assessment to Compare the Biomechanical Behaviour of Human, Sheep and Chagma Baboon Functional Spine Units
Authors: Khere A. , Kiapour A. , Seth A. , Goel V. K. , Dennis M. , Biyani A. , Ebrahim N.
Published: March 2014

Ideal animal spine models have been used by researchers to compare and evaluate the biomechanical behavior of spine following surgery and implantation due to the growing difficulty in obtaining fresh human spine specimens. Availability and resemblance of sheep and baboon spines to human spine make them suitable for use in biomechanical studies; however the literature on biomechanics of baboon and sheep spine compared to human spine is sparse. In the present study finite element method was used to compare the load transfer and load-displacement characteristics of L3-L4 sheep, baboon and human spines.
Quantitative Imaging of Nanoparticles and Intracellular Vesicle Trafficking Using Total Internal Reflection Fluorescent Microscopy (TIRFM)
Authors: Margraves Charles H. , Choi Chang K. , Kihm Kenneth D. , English Anthony , Lee Seong H. , Cekanova Maria , Baek Seung J.
Published: March 2014

Total internal reflection fluorescent microscopy (TIRFM) is a relatively well known tool used to examine the near wall region (approximately 1 μm). For years, cellular biologists have used TIRFM in a variety of experiments to examine multiple cell lines. However, much of the research has been somewhat static in nature, considering only initial and final states. With the increased ability to stain specific organelles within cells through the use of green fluorescent protein (GFP), dynamic imaging is becoming a viable solution to previously difficult problems.
Knee Kinematics During an In Vitro Simulated Deep Flexion Squat
Authors: Clary Chadd W. , Mane Amit M. , Reeve Amber N. , Dodd Kevin A. , Maletsky Lorin P.
Published: March 2014

Understanding the behavior of the natural knee in deep flexion can offer insight into the necessary design characteristics of a total knee implant. Andriacchi et al. [1] measured the in vivo characteristics of knee motion down to ∼150° knee flexion during a weight bearing squat. Likewise, Li et al. [2] investigated deep knee flexion in vitro using robotic technology during passive knee flexion. Both of these studies offer insight into the behavior of the knee in deep knee flexion; however, they have some limitations with regards to assessing physiological activities in a controlled manner. The purpose of this study was to measure the kinematics of the knee during a simulated in vitro deep knee squat so that in the future a dynamic, load-bearing, simulated deep knee squat could be used as a tool in the design of total knee prostheses.
Comparison of Three Repair Techniques to Restore Scapholunate Kinematics in a Cadaver Model of a Simulated Scapholunate Dissociation
Authors: Gardner Thomas R. , Amin Faiq , Trocchia Aron M. , Cordiale Andrew J. , Grafe Michael W. , Beekman Ryan A. , Taylor Nathan L. , Rosenwasser Melvin P.
Published: March 2014

The scapholunate ligament plays a vital role in normal physiological wrist kinematics. Rupture of this ligament is common and results in a dorsal intercalated segment instability (DISI) deformity that, if not corrected, progresses to a scapholunate advanced collapse (SLAC) wrist. Multiple treatment techniques have been proposed to address scapholunate dissociation such as indirect soft tissue repairs, autografts, allografts, and arthrodesis. Yet no single procedure has proven to be superior clinically or biomechanically for chronic DISI deformity. This study accurately assesses the degree to which three repair techniques, the Reverse Blatt’s Capsulodesis [1] (RBC), the Bone-Ligament-Bone autograft repair technique (BLB) and the Reduction and Association of the Scaphoid and Lunate (RASL), restore the normal physiologic scapho-lunate in vitro kinematics following a simulated scapholunate dissociation in a human cadaveric model.
Incorporating the Effects of Variable Wall Properties in Large-Scale Deformable Models of the Cardiovascular System
Authors: Figueroa C. Alberto , Baek Seungik , Humphrey Jay D. , Taylor Charles A.
Published: March 2014

Numerical simulation of blood flow in arteries has important applications in disciplines such as surgical planning, medical device design, and disease research. However, there are many challenges involved in accurately characterizing the motion of blood within the arterial system. First, computational models can require finite element meshes with several million degrees of freedom. Furthermore, surgical planning applications require solving these problems as quickly as possible. Second, the boundary conditions must faithfully represent the flow and pressure characteristics of the vascular trees external to the computational model. These conditions must also be consistent with the intrinsic wave propagation phenomena within the model. Third, the fluid-solid interactions between blood, vessel wall and surrounding tissues and organs need to be modeled. In order to represent the pulsation of blood within arteries, one must consider the variations in arterial compliance (especially significant when dealing with large models), points of attachment of the vessels to the surrounding organs, etc. Prior vascular fluid-structure interaction models have considered uniform vessel wall properties and a zero pressure reference state.
Structure Mechanical Function Relationships of the Fetal Membrane
Authors: Joyce Erinn M. , Sacks Michael S. , Moore John J.
Published: March 2014

A normal pregnancy requires physical integrity of the fetal membrane (FM) until term delivery. Timely rupture of the fetal membrane is a vital part of term labor [1]. Premature failure of the FM, prior to full gestation, accounts for one third of all premature human births and affects 3% of all pregnancies [2]. Membrane rupture is either due to the release of the amniotic fluid, frequently signaling the onset of labor, or under a pathological circumstance [3]. In order to develop a rational basis for treatment and prevention of premature FM failure, we need first to understand FM structural and mechanical behavior. This includes its constituent layers at near full term under normal physiological loading states. Once these properties are established, we can then better formulate how the tissue transitions to the ability to fail at full term.
Predicting Muscle Forces and Joint Moments Using Single Joint and Multi Joint EMG-Driven Models
Authors: Bassett Daniel N. , Shao Qi , Manal Kurt , Buchanan Thomas S.
Published: March 2014

The biomedical field thrives on computational devices. Clinicians, physical therapists, and researchers frequently use models as tools. The key to proper implementation of these tools is a good understanding of the limitations, advantages, and options available. Previous research on EMG-driven models demonstrated the ability of single joint models to predict joint moments with reasonable accuracy [1]. The advantage provided is the possibility of studying muscle and intersegmental forces in vivo.
Passive Joint Coupling in the Forearm, Wrist, and Hand
Authors: Murray Wendy M. , Velisar Anca
Published: March 2014

Many muscles of the upper limb cross more than one joint. For example, each muscle that crosses the wrist also crosses at least one other joint. These muscles often have significant excursions at the other joints they cross [1]. The complex musculoskeletal anatomy of the upper limb results in passive mechanical couplings between joints; the passive moment produced about a given joint can be highly dependent on the positions of other joints [2]. This passive coupling can be clearly observed in the wrist and hand: when the elbow is flexed 90° and the forearm and hand are oriented so that gravity aids wrist flexion, the wrist rests in flexion and the fingers are extended. In contrast, supinating the forearm in this same elbow position (so that gravity aids wrist extension instead of wrist flexion) results in an extended wrist and flexed fingers.
Aortic Valve Interstitial Cell Viscoelasticity
Authors: Merryman W. David , Bieniek Paul D. , Guilak Farshid , Sacks Michael S.
Published: March 2014

Long term tissue-level durability of the aortic valve (AV) is maintained by the cell populations residing both in the interstitium and on the epithelium. Due to the dynamic environment in which the AV interstitial cells (AVICs) function, recent work has examined the mechano-dependent, biosynthetic and contractile response of these cells [1–4]. Many idealized assumptions have been made about mechanical properties [1, 4], ECM connectivity [2], and deformations that the AVICs undergo during diastole [3]. These assumptions include that the AVICs are elastic, homogenous materials that deformation in an affine sense with the tissue.
On the Use of Induced End Effector Force Analysis for Determining Muscle Roles During Movement
Authors: Piazza Stephen J. , Zatsiorsky Vladimir M.
Published: March 2014

It is often of interest in studies of human movement to quantify the function of a muscle force or muscular joint torque. Such information is useful for the identification of the causes of movement disorders and for predicting the effects of interventions including surgical procedures, targeted muscle strengthening, focal treatments for spasticity, and functional electrical stimulation. One useful way to characterize the actions of muscle forces or muscular joint torques is to create linked-segment models of the body and analyze these linkages to determine the joint angular accelerations or end effector forces that result solely from the application of the muscle force or torque in question. Such induced acceleration (IA) analyses or induced end effector force (IEF) analyses have been applied most often to quantify muscle function during normal and pathological walking [1,2].
Devlopment of a Cell Coculture Microfluidic Shear Device for Mechano-Transmission Study
Authors: Scott Devon , Richman Aaron , Lanning Craig , Shandas Robin , Tan Wei
Published: March 2014

We have developed a microfluidic shear device that allows for the study of cell communication in a dynamically controlled biochemical and biomechanical environments simulating cells’ living environments in vivo. Such study may help to improve our understanding in the effects of hypertension-relevant and vascular development-relevant flow shear stress on cell behaviors. Endothelial cells may be a key factor for transmitting the blood flow conditions from the endothelial lining to interstitial layers and smooth muscle cells. The interstitial flow stress and the shear stress induced signaling factors may greatly alter vascular biology of these deep layers. Endothelial cells act as a mechano-transducer by converting shear stress into biochemical signaling factors. The biochemical factors diffuse to smooth muscle cells and further alter the biological structure of vascular tissues. Also, the flow shear stress will be transmitted to the interstitial tissue layer through the pores resulted from the pores in the fenestrated endothelial lining. Studies in both the mechano-transduction process and the mechano-transmission process will benefit from a biomimetic flow shear device with co-cultured cells. Our device will allow the co-culture of endothelial cells and smooth muscle cells to study these biomechanical processes. The pulmonary arterial cells are used as a model in the study. The microfluidic device developed here will be used to enhance the understanding of pulmonary vascular disease pathogenesis due to the variations in the flow shear stress.
Accuracy and Repeatability of Electronic and Static-Film Pressure Sensors Under Controlled Test Conditions
Authors: Waller Alexander J. , McIff Terence E. , Fischer Kenneth J.
Published: March 2014

The accuracy and repeatability of both electronic pressure sensors and static-film sensors, when used for in situ pressure distribution testing has previously been performed for various joints. Although both methods are reported to yield reasonable levels of accuracy, our initial experiments did not yield such good results. In addition, our joint of interest, the radiocarpal joint, was different from those previously studied. To be certain of the maximum accuracy that could be expected from each measurement system, we devised a controlled experiment to determine the accuracy of both systems in an idealized test configuration. The purpose of this study was to compare the accuracy and variability of a static-film pressure measurement system and an electronic pressure measurement system. We hypothesized that the static-film pressure measurement system would be more accurate under ideal conditions, due to its higher resolution.
An Implantable Magnetoelastic Sensor System for Wireless Physiological Sensing of Viscosity
Authors: Gurkan Umut A. , Akkus Ozan
Published: March 2014

Magnetoelastic resonance is a promising remote sensing technique which has been used for measurement of pressure, fluid flow, temperature, pH density and viscosity [1]. The main component of remote magnetoelastic sensing is a ferromagnetic metal alloy that has the ability to oscillate under the effect of an alternating magnetic field. When frequency of excitation matches with magnetoelastic beam characteristics, these materials resonate. Furthermore, the resulting resonance shifts depending on the pressure, viscosity, and temperature etc. in the vicinity of the beam which can also be collected remotely. This wireless capability without the need for power source makes this technology the most ideal for physiological sensing. Biomedical applications of these sensors are mostly limited to in vitro diagnostic applications [2–5]. The only in vivo application has been within the context of measuring the pH of the stomach in a pig model [6]. While the pig model demonstrated that signals can be transmitted through the belly of a pig, it is unknown as to whether the presence of a thick cortical bone would affect signal transmission. In this study, we assessed the feasibility of magnetoelastic wireless sensing for measuring the viscosity of bone marrow, a viscous fluid that is hidden behind both bone and muscle tissues.
Understanding EHDA and Protein Stability
Authors: Nottingham Elizabeth M. , Zeles-Hahn Michelle G. , Lengsfeld Corinne S.
Published: March 2014

Therapeutic proteins can be difficult to work with due to the fact that each protein has properties and functions that are unique. These exclusive properties are in part due to the proteins three-dimensional shape (secondary and tertiary structure). This shape is determined by bends in the amino acid sequence generated by electrostatic interactions, hydrogen bonds, and hydrophobic-hydrophilic interactions between neighboring amino acids. These bonding interactions are weak and can be severed by chemical or physical forces. Thus, therapeutic proteins can be denatured during manufacture and by methods used to deliver them to the body.
Circumferential Variation of Mechanical Properties of Ascending Aorta (AA): A Comparative Study of Healthy and Dilated AA
Authors: Tremblay Dominique , Cartier Raymond , Leduc Louis , Mongrain Rosaire , Leask Richard
Published: March 2014

The biomechanics within the ascending aorta (AA) characterizes the pressure and flow for the entire vascular system. In the aortic wall, it is the structured medial layer that is responsible for the mechanical properties of the AA. The mechanical properties are determined to a large extent by the composition of elastin, collagen and smooth muscle cells (SMCs). Changes in AA biomechanics that arise with age and/or disease can lead to cardiovascular complications and death. Most studies that have investigated the biomechanics of these diseases have assumed homogeneous and isotropic aortic wall properties. Very little work has been done in vitro to determine the local mechanical properties of human vascular tissue. In order to better understand the biomechanics of the human AA, the local properties of pathologic AA tissue from both tricuspid and bicuspid aortic valve patients have been studied and compared with the properties of healthy aortas.
Depth Dependent Diffusivity Profile in Bovine Articular Cartilage: Comparing Transverse and Axial Diffusivities
Authors: Irrechukwu Onyi N. , Levenston Marc E.
Published: March 2014

As articular cartilage is avascular, diffusion at a tissue length scale is the primary mode of solute and nutrient transport to its cells. The major extracellular matrix components are water (70–80%), chondrocytes, collagen (10–20%) and proteoglycans (5–10%) bearing sulfated glycosaminoglycans (GAG) [1]. Electron microscopy studies have shown that articular cartilage can be regarded as having three separate structural zones — superficial, middle and deep. The proportions of the various matrix components vary from the surface to the deep zone in any given joint and the greatest variations in content occur in the GAG content [2]. In addition the collagen fiber alignment varies, with fibers oriented parallel to the articular surface in the superficial zone, randomly oriented in the middle zone and oriented perpendicular to the surface in the deep zone. To a large extent, it is the spatially inhomogeneous composition of articular cartilage and microstructural orientation of its extracellular matrix components that determines the tortuosity of the transport pathway [3]. We therefore hypothesized that the diffusivity profile of a solute through the cartilage depth is inversely related to the GAG content and that the ratio between the axial and lateral diffusivities within each cartilage zone is related to the degree of anisotropy within the zone.
A Practical Method for Real-Time Optical Imaging of Damage Zone and Microscale Failure in Bone
Authors: Diegmueller Jared J. , Akkus Ozan
Published: March 2014

Bone is an extremely complex composite material with hierarchical organization ranging from the molecular level all the way up to macroscale. The damage process too evolves through this hierarchy (1). Much of the damage process of bone is well understood at the macroscale level (2); however, microscopic and submicroscopic levels of bone damage are still poorly understood.
BioMEMS Platform for Electromechanical Stimulation of Cell Culture
Authors: Blundo Jennifer , Chua Gretchen , Abilez Oscar , Park Yong-Lae , Rastegar Ali , Cao Feng , Zarins Chris , Wu Joe , Pruitt Beth
Published: March 2014

A BioMEMS platform was designed and fabricated to enable electromechanical stimulation of cell cultures. The device consists of a stretchable microelectrode array embedded in a biocompatible elastomeric polymer, which is deformed by vacuum over a glass baseplate. The entire device is optically transparent and ∼1mm thick. Four cell culture wells apply electrical and/or mechanical stimulation in the range of 1–10 V/cm and 0–10% equibiaxial strain. Studies of electromechanical stimulation of cardiac myocyte precursors on this platform are proposed to elucidate mechanisms of differentiation.
Effect of Neutrophils Retention Time in Capillaries on Increase in Their Concentration in a Lattice Capillary Network Model
Authors: Shirai Atsushi , Hayase Toshiyuki
Published: March 2014

Neutrophils are known as the most popular cells in leukocytes, and play important roles in immune system. They are retained in pulmonary capillary network even in normal lungs, causing higher concentration than in systemic circulation due to their low deformability [1]. The lungs can be a route for pathogenic substances to invade the host, since thickness of septa which separates blood and outer air is extremely thin. However, the highly concentrated neutrophils are thought to be effectively recruited to the sites of inflammation for the host defense. Therefore, it is essential to know how neutrophils flow in pulmonary capillary microvasculature for the understanding of their functions and behavior in immune system.
A Genetic-Algorithm-Based Design Approach to Minimize Abnormal Hemodynamics Parameters at the End-to-Side Distal Anastomoses of Synthetic Bypass Grafts
Authors: El Zahab Zaher , Divo Eduardo A. , Kassab Alain J.
Published: March 2014

Medical records on post-operative performances of synthetic bypass grafting show poor results due to the re-stenosis occurring at the end-to-side distal (ETSD) anastomoses of the grafts. The re-stenosis is mainly caused by intimal hyperplasia (IH) [1]. A major factor behind the anastomotic IH development is the non-physiological flow patterns, such as separation and re-attachment, resulting from the bifurcating nature of the anastomotic geometry [2]. The spatial wall shear stress gradient (SWSSG) has been experimentally proven to cause proliferation and migration of the endothelial cells [3], resulting in an endothelial dysfunction that potentially leads to the initiation of IH.
Local Non-Affine Deformations and Fiber Kinematics of Elastomeric Electrospun Scaffolds
Authors: Courtney Todd D. , Liao Jun , Wagner William R. , Sacks Michael S.
Published: March 2014

For most tissue engineering applications that seek to generate tissue de novo, the scaffold is the first step in a series of important developmental considerations. Whether synthetic or natural, scaffolds developed for immediate in vivo use must have mechanical properties comparable to the native tissue for at least the minimum time necessary for the accompanying seeded cells, and eventual cells that migrate in, to lay down an equivalent supporting matrix. Scaffolds developed for the purpose of growing a tissue in vitro, with eventual in vivo use, need not necessarily meet these mechanical requirements. However, to better develop new tissues in bioreactors or in vivo, it is pertinent to understand how the fiber network changes under some regimen of mechanical load, in essence to understand what the cell witnesses within the scaffold. Extending our previous work, which focused on measuring and modeling the mechanical response of electrospun poly ester urethane urea (es-PEUU) scaffolds [1], we investigated the intricate and detailed es-PEUU fiber networks that are created during scaffold synthesis and how these networks change under various levels of strain. Specifically, we focused on several scaffold responses to strain:

1) Characteristics of fiber tortuosity, which when increased can yield delayed onset of scaffold stiffness as well as other varying mechanical responses.

2) Fiber splay, which determines the orientation of the all fibers within the scaffold.

3) Local vs global strain analysis to determine whether the scaffolds follow affine or non-affine deformations.

4) Fiber strain, to investigate how increasing levels of scaffold strain are transmitted to local fibers.

5) Changes in fiber tortuosity and overall fiber directions under strain.
In Vitro Study of Flow Regulation for Pulmonary Insufficiency Using Diode Valves
Authors: Camp Tiffany A. , Hequembourg Stephanie , Figliola Richard S. , McQuinn Tim
Published: March 2014

The operating pressures in the right heart are significantly lower than those of the left heart and with marked differences in the circulation impedances. The pulmonary circulation shows a tolerance for mild regurgitation and pressure gradient [1]. Pulmonary regurgitation fractions on the order of 20% and transvalvular pressure gradients of less than 25mm Hg are considered mild [4]. Given this tolerance, we examine the concept of using a motionless valve to regulate flow in the pulmonary position. In a previous study, the use of fluid diodes was shown to be a promising concept for use as a pulmonary valve [2]. In this study, we test two different diode designs. For each diode valve, flow performance was documented as a function of pulmonary vascular resistance (PVR) and compliance. Tests were done using a pulmonary mock circulatory system [3] over the normal adult range of PVR and compliance settings.