bluuebunny/crossref_metadata_2025 huggingface dataset:
An Efficient Preconditioner for Linear System Solution in Multi-Domain Modeling of the Circulatory System
Authors: Moghadam Mahdi Esmaily , Bazilevs Yuri , Hsia Tain-Yen , Marsden Alison
Published: January 2014

A closed-loop lumped parameter network (LPN) coupled to a 3D domain is a powerful tool that can be used to model the global dynamics of the circulatory system. Coupling a 0D LPN to a 3D CFD domain is a numerically challenging problem, often associated with instabilities, extra computational cost, and loss of modularity. A computationally efficient finite element framework has been recently proposed that achieves numerical stability without sacrificing modularity [1]. This type of coupling introduces new challenges in the linear algebraic equation solver (LS), producing an strong coupling between flow and pressure that leads to an ill-conditioned tangent matrix. In this paper we exploit this strong coupling to obtain a novel and efficient algorithm for the linear solver (LS). We illustrate the efficiency of this method on several large-scale cardiovascular blood flow simulation problems.
Simulation of Velocity and Concentration Fields in Artificial Kidneys
Authors: Li Weili , Sun Sijie , Zhao Gang , Gao Dayong , Ding Weiping
Published: January 2014

In this work, velocity and concentration fields on both sides of blood and dialysate in artificial kidneys are simulated, not only coupling the convection and diffusion mass transfers across the hollow fiber membrane, but also considering both effects of the inlet and outlet structure of blood and dialysate. Our results show that compared to the blood velocity field, the dialysate velocity filed is more uneven; furthermore, the inlet and outlet structure of dialysate affects not only the concentration field on the dialysate side but the one on the blood side as well. Therefore, in practice, for the structure optimization of artificial kidneys, the inlet and outlet of dialysate should be focused on.
Fluid Dynamic Gauging-Based Assays for High-Throughput Investigation of Cellular Mechanotransduction
Authors: Worton Leah E. , Srinivasan Sundar , Kwon Ronald Y.
Published: January 2014

Within bone, the mechanotransduction pathway is recognized as one of the primary pathways determining bone strength. However, despite an intense research effort over the last 30 years seeking to identify potential mechanosensing molecules in bone cells, only a handful of candidates have been identified. This is due in large part to the low throughput of existing mechanotransduction assays, which preclude them from powerful approaches for de novo discovery such as high-throughput screens and systems biology-based investigations.
Assessment of Aortic Stenosis Severity Using Pressure Drop Coefficient: A Retrospective Study in Humans
Authors: Paul Anup K. , Effat Mohamed , Paquin Jason J. , Banerjee Rupak K.
Published: January 2014

Accurate assessment of the stenosis severity is critical in patients with aortic stenosis (AS). The ambiguities and reduced sensitivities of the current diagnostic parameters can result in sub-optimal clinical decision making. In this preliminary study, we investigate the functional diagnostic parameter CDP (ratio of the transvalvular pressure drop to the proximal dynamic pressure) for the assessment of AS severity by correlating with the current diagnostic parameters. CDP was calculated using diagnostic parameters obtained from retrospective chart reviews. CDP values were calculated independently from Doppler and catheterization measurements. CDP exhibited better correlation with transvalvular pressure drop and jet velocity simultaneously, than when correlated independently with the same diagnostic parameters. CDP increases with increasing AS severity, which is consistent with hydrodynamic principles. This retrospective study is a prelude to a prospective study to evaluate CDP for AS severity assessment.
Region-Specific Medial Fiber Micro-Architecture in the Longitudinal-Radial and Circumferential-Radial Planes of Ascending Thoracic Aortic Aneurysm Among Bicuspid and Tricuspid Aortic Valve Patients
Authors: Tsamis Alkiviadis , Phillippi Julie A. , Koch Ryan G. , Krawiec Jeffrey T. , D’Amore Antonio , Watkins Simon C. , Wagner William R. , Vorp David A. , Gleason Thomas G.
Published: January 2014

Aortic dissection is a life-threatening cardiovascular emergency with a high potential for death. It usually begins with an intimal tear which permits blood to enter the wall, split the media and create a false lumen, which can reenter the true lumen or exit through the adventitia causing complete rupture. A possible mechanism for dissection of ascending thoracic aortic aneurysm (ATAA) can be the occurrence of blood pressure-induced wall stresses in excess to the adhesive strength between the degenerated aortic wall layers.
Viscoelastic Properties of a Synthetic Meniscus Implant
Authors: Shemesh M. , Asher R. , Zylberberg E. , Guilak F. , Linder-Ganz E. , Elsner J. J.
Published: January 2014

Meniscal tears often lead to degenerative arthritis, attributed primarily to the changes in the magnitude and pattern of stress distribution in the knee. While meniscal replacement traditionally involves implantation of allografts, problems related to availability, size matching, and cost limit their use. In this regard, there are significant potential advantages to a bio-stable synthetic meniscus implant that combines long-term durability with a dependable biomechanical performance resembling that of the natural meniscus. The Nusurface ® medial Meniscus Implant is a poly-(carbonate-urethane) implant that recreates the functionality of the meniscus, as evidenced by compression tests to determine its pressure distribution capability [1] and finite element analyses [2] in its virgin state. However, the overall success of such an implant is dependent on its long-term functional properties, and biomechanical testing of the NUsurface ® device has not yet examined the effect of varying and dynamic testing conditions. In particular, the pre-test soaking in physiologic solution and the loading rate can have non-trivial influences on the properties of the device. Therefore the aims of this study were to characterize the strain-rate response, as well as the viscoelastic properties of the implant as measured by creep, stress relaxation, and hysteresis after simulated use.
Design of a Torsion Tester for Measuring Murine Bone Properties for Studies on the Effects of Diabetes and Obesity
Authors: Sherrod Brandon , Gilbert Shawn , Casazza Krista , Eberhardt Alan
Published: January 2014

Conditions such as diabetes and obesity have been found to affect the mechanical integrity of bone. Studies have shown that diabetic rodent models exhibit lower levels of new bone formation during fracture healing 1, lower bone mineral density (BMD) 2, and increased risk of fracture 3. There are differences, however, in the bone integrity of bone samples from type I and type II diabetics, which is most likely due to obesity 2. Findings from research on obesity’s effects on bone integrity have been controversial; although there is an increase in bone mineral density (BMD) with increasing body mass index (BMI) and a decrease in fracture incidence in the central body regions in obese women compared to healthy weight women due to soft tissue padding, there is an increase in fracture incidence at extremeties 4. Other studies have shown that while cortical bone strength may not be adversely affected by high-fat diets, cancellous bone BMD and mechanical strength was significantly lower in high-fat diet mice than low-fat diet mice 5. In addition, extreme obesity has been associated with lower BMD despite the general trend of increased BMD with higher BMI 6.
Ascending Thoracic Aorta Exhibits Anisotropic Failure Behavior in Shear Lap Testing
Authors: Witzenburg Colleen , Shah Sachin , Wagner Hallie P. , Goodrich Janna , Barocas Victor H.
Published: January 2014

Aneurysm dissection and rupture, resulting in imminent death, is the primary risk associated with thoracic aortic aneurysms (TAA). Nearly 60% of TAA involves the ascending aorta [1]. Dissection and rupture occur when the remodeled tissue is no longer able to withstand the stresses generated by the arterial pressure. As the ascending TAA grows, however, changes in its mechanical behavior, particularly wall strength, are unknown.
Simulating the Effects of Embolic Coils on Cerebral Aneurysm Fluid Dynamics Using Finite Element Modeling
Authors: Babiker M. H. , Gonzalez L. F. , Chong B. , Frakes D. H.
Published: January 2014

Endovascular coiling is the most common treatment for cerebral aneurysms. The treatment consists of deploying coils of different shapes and sizes into the aneurysm with the intent of reducing blood flow therein. While the treatment has been shown to be more effective than conventional surgical methods, it is successful in only 50–80% of cases, depending on the type of aneurysm [1]. Treatment success has been correlated with favorable post-treatment hemodynamics [2]. Understanding of the effects of coils on post-treatment hemodynamics is limited, however, due to limited in-vivo and in-vitro flow measurement techniques. Previous computational studies have also suffered from drastic assumptions about coil geometry.
Validation of Quasi-Steady Analysis for Lymphatic Fluid Flow and Mass Transport
Authors: Wilson John T. , Wang Wei , Hellerstedt Augustus H. , Zawieja David C. , Moore James E.
Published: January 2014

The lymphatic system plays an important role in fluid and protein balance within the body. Additionally, it has a vital role in immune system function. Lymphatic dysfunction could result in a number of pathologies including edema or swelling of fluid within the interstitial spaces.
Cryotherapy Modification to Overcome Uninterrupted Ischemia
Authors: Khoshnevis Sepideh , Craik Natalie , Diller Kenneth R.
Published: January 2014

Localized cooling is commonly used following orthopedic surgery and in sports medicine to reduce swelling, pain, inflammation, metabolism, muscle spasm, and bleeding[1,2]. The therapeutic application of cold therapy has a long history dating from the time of Hippocrates and has been widely documented in the literature[3,4]. Nonetheless, there remains to the present time considerable controversy over the appropriate protocol for application of cryotherapy and the risk factors associated with its use[5].
Hemodynamics of Abdominal Aortic Aneurysm and its Clinical Relevance in Patients With Infrarenal Stent-Graft Implantation
Authors: Lu Y.-H. , Liu G.-T. , Lin S.-H. , Chen C.-Y.
Published: January 2014

In 2008 the overall rate of death attributable to cardiovascular disease, or CVD, is 244.8 per 100,000. On the basis of these mortality rate data, one American dies due to CVD on an average of every 39 seconds. Of these deaths, abdominal aortic aneurysm (AAA) accounts for 11,079 [1]. Although an estimate of the total economic burden of AAA is not available, the average cost per discharge for a ruptured AAA exceeded $93,000 in 2003 [2]. Generally, an abdominal aortic aneurysm (AAA) is an irreversible focal dilation of an artery to 1.5 times its normal diameter [3]. AAAs are characterized by the destruction of elastin and collagen in the media and adventitia, smooth muscle cell loss with thinning of the medial wall, infiltration of lymphocytes and macrophages, and neovascularization [4, 5].
Differences in Engineered Cartilage From Human Chondrocytes and Mesenchymal Stem Cells in Pellet and Construct Culture
Authors: O’Connell Grace D. , Cui Victoria H. , Palmer Glyn , Hung Clark T.
Published: January 2014

Articular cartilage serves as the load-bearing material of joints. One approach to functional tissue engineering is to recapitulate the biochemical and mechanical function of healthy native cartilage in vitro, prior to implantation. We have been successful in cultivating engineered cartilage with compressive mechanical properties and glycosaminoglycan (GAG) content near native values by encapsulating chondrocytes or stem cells in a clinically relevant hydrogel [1, 2]. Clinical application of functional engineered cartilage will likely use of chondrocytes (AC) from osteoarthritic tissue or mesenchymal stem cells (MSCs), which have been shown to have chondrogenic potential. That is, it is may be more feasible to differentiate healthy MSCs towards a chondrogenic lineage than to ‘reprogram’ ACs acquired from an osteoarthritic joint.
Collective Cell Movements Drive Morphogenesis and Elongation of the Avian Hindgut
Authors: Nerurkar Nandan L. , Tabin Cliff J.
Published: January 2014

At the end of gastrulation, the endoderm forms a single-cell thick epithelium lining the ventral surface of the developing embryo. Subsequently, through a series of poorly understood events, the initially flat endoderm is transformed into the gut tube, a cylindrical structure that gives rise to the epithelial lining of the entire respiratory and gastrointestinal tracts. In birds and mammals, formation of the gut tube begins with two invaginations at the anterior (head) and posterior (tail) poles of the embryo, termed the anterior (AIP) and caudal intestinal portals (CIP). It is thought that the AIP and CIP begin moving toward one another as two progressing waves of lateral-to medial folding (from left and right toward center), “zipping” the gut tube closed along the embryonic midline (Fig. 1A). This view of lateral-to-medial folding is, however, inconsistent with several observations. For example, fate mapping studies in chick and mouse that suggest that cells originating in the posterior end (toward the tail) of the flat endoderm do not form the hindgut, but instead contribute to the more anterior midgut [1, 2]. This would not be possible in a simple lateral-to-medial folding process. Therefore, it is largely unknown how this fundamental structure of the vertebrate body plan is established. The objective of the present work is to apply multi-photon live imaging of the chick embryo to determine how the hindgut is formed. Our findings suggest the hindgut arises from directed, collective cell movements that drive antero-posterior folding of the initially flat endoderm.
The Influence of Pulmonary Hemodynamics on Right Ventricular Function in Pulmonary Hypertension
Authors: Kheyfets Vitaly O. , Rios Lourdes , Smith Triston , Schroeder Theodore , Mueller Jeffrey , Murali Srinivas , Lasorda David , Zikos Anthony , Spotti Jennifer , Reilly John J. , Finol Ender A.
Published: January 2014

Pulmonary arterial hypertension (PAH) is a degenerative disease that can lead to substantial morphometric remodeling of the pulmonary arteries. Previous studies have revealed coupling relationships between right ventricular (RV) function and pulmonary arterial hemodynamics. The objective of this study was to utilize computational fluid dynamics (CFD) to estimate spatially averaged Wall Shear Stress (WSS) for patients with PH and explore correlations between hemodynamics metrics and RV function.
Ionic Electroactive Polymer Actuators for On-Chip Sample Processing Integrated With Microflow Cytometer
Authors: Meis Catherine , Montazami Reza , Hashemi Nastaran
Published: January 2014

As interest in and potential uses for microfluidic and optofluidic analytical techniques grows, the need for on-chip, automated sample processing becomes increasingly important because this aspect is critical to allowing the devices to be commercially feasible and practical. One such design that implements on-chip processing is using ionic electroactive polymer (IEAP) actuators to perform mixing of particles in the microchannel and using a single magnet positioned beneath the channel to trap the magnetic beads. IEAP actuators consist of a central ionic membrane with conductive network composite (CNC) layers on either side. Gold electrodes placed on the outside of CNC layers are connected to a metal anode and cathode. When subjected to an electric field, the ions in the actuator move, electromechanically causing the entire length of the actuator to flex [1]. Although most actuators to date have been developed for use in air rather than in solutions, we have adapted previously developed actuators by optimizing their electromechanical functions to suit our needs and coating them in a protective film. The actuators are embedded in a microchannel in different configurations, which are then tested to determine which configuration most effectively trapped, mixed, and released the magnetic beads. The most effective configuration will subsequently be used to perform automated sample processing for an assay.
Development of a Biomechanical Model for Sacroiliac Range of Motion
Authors: Condez Bruce , Camisa William , Leasure Jeremi , Buckley Jenni , Kondrashov Dimitriy , Ames Christopher
Published: January 2014

In the last seven years, increasing interest has been shown in the sacroiliac (SI) joint. Recent evidence has shown that more than 22% of lower back pain cases are caused by SI joint instability. Sacroiliac joint problems mimic discogenic and/or radicular low back pain, leading to many misdiagnoses (Weksler 2007). Over the last decade, SI fusion devices have been developed and have achieved clinical success (Wise 2008). However, there is no standard biomechanical testing procedure for SI fusion devices, although such a protocol would benefit further product development and comparison testing. The goal of our study is to develop a biomechanical model of sacroiliac range of motion. This study puts forth two methods of producing SI ROM: one model simulating a single leg stance and the second model simulating double leg stance. Our hypothesis was that the single leg stance model would produce ROM similar to what has been observed in vivo; the double leg stance model would produce ROM significantly lower. We aimed to test this hypothesis through comparison of ROM for both models and in vivo results obtained from the literature.
Effects of Wavy Microgroove Structure on Ligament Fibroblast Cell and Nuclear Morphology
Authors: Sung Chen-Hsiu , Chao Pen-hsiu Grace
Published: January 2014

Type I collagen, the most abundant extracellular matrix component in the body, exists as fibers that are organized in wavy parallel fibers in many tissues [1, 2]. Cells embedded within this wavy pattern exhibit a 3D morphology that undulates with the fibers. The phenomenon that cell morphology follows substrate structure, such as cell elongation when attached to fibrous materials, is known as contact guidance [3]. As the cytoskeleton supports cellular structures and mediate numerous intracellular processes, changes to the cytoskeleton structures lead to modified cell behaviors and even fate [4, 5]. Studies have shown that fibroblasts express more ligament phenotypic markers when cultured on straight micropatterns or aligned fibers [6, 7]. However, few studies have investigated the influences of the wavy structures. To characterize the effects of the wavy structure, anterior cruciate ligament (ACL) fibroblasts were seeded in wavy microgrooves and their morphological responses were analyzed.
Simultaneous Prediction of Musculo-Tendon, Joint Contact, Ligament and Bone Forces in the Lower Limb During Gait Using a One-Step Static Optimisation Procedure
Authors: Moissenet Florent , Cheze Laurence , Dumas Raphaël
Published: January 2014

Instrumented prostheses, by measuring joint contact forces during a movement, give nowadays a unique opportunity to validate the ability of musculo-skeletal models in predicting internal forces.

In this study, a rigid multi-body musculo-skeletal model, allowing computing the musculo-tendon, joint contact, ligament and bone forces all together by static optimisation, using a weighted criterion, is presented.

The results show that the musculo-tendon forces are generally in accordance with the envelopes of the main peaks of the subject’s EMG signals and that the amplitudes and patterns of the predicted joint contact, ligament and bone forces are in a good agreement with the measurements and with the literature. By allowing the introduction of other forces than the musculo-tendon forces in the static optimisation, this study opens new horizons in order to better model the human physiology (e.g., joint pain).
Chondrocytes in Agarose: Cell Damage and the Pericellular Matrix
Authors: van Turnhout Mark C. , de Vries Stefan A. H. , van Donkelaar Corrinus C. , Oomens Cees W. J.
Published: January 2014

Chondrocytes occupy 2% to 5% of the volume of articular cartilage [1] and are responsible for maintenance of the tissue. In adult life, the healing and repair capacity of chondrocytes is very limited, and the loss of chondrocytes that is often occurring at an early stage of cartilage degeneration is detrimental to articular cartilage. Excessive loading is known to be a cause of cell death.
Numerical Study of the Influence of Water Evaporation on Radiofrequency Ablation
Authors: Zhu Qing , Ying Binbin , Zhang Aili , Xu Lisa X.
Published: January 2014

Radiofrequency (RF) ablation is one of the promising technologies of tumor therapy due to its minimal invasiveness and other advantages. The high frequency alternating electrical current makes movement of the intracellular ions, results in frictional heat inside the tumor tissue and local temperature rising. Temperature of the tissue near the RF electrode increases much faster than the distant part. When it reaches the vapor (boiling) point, excessive evaporation takes place and increases electrical impedance between the electrode and the targeted tissue. This has been a major obstacle for its application. Coolants such as water circulating in the electrodes has been proposed, but as the coolants are only effective on the electrode wall, quick evaporation and correspondent carbonization still exists.
The Use of a 6-DOF Robotic System for the Functional Analysis of Ankle Joint Ligaments
Authors: Yamakawa Satoshi , Kobayashi Takuma , Kimura Kei , Suzuki Daisuke , Watanabe Kota , Fujimiya Mineko , Yamashita Toshihiko , Fujie Hiromichi
Published: January 2014

Ankle sprains are common injuries in daily and athletic activities. An epidemiological report indicated that the incidence rate of ankle sprains treated in emergency departments in the USA is more than 2 per 1000 persons a year, and the rate is estimated to be more than double as for ankle sprains in athletic activity [1]. Better understanding of ankle biomechanics is, therefore, important for the improvement of clinical outcome. Many investigators have performed in vitro and in vivo experiments to determine the mechanical roles of ankle structures such as range of motion, contribution of ankle ligaments to joint stability, joint instability due to ligament transection, and so on. In spite of these efforts, tensile forces in ankle ligaments in response to specific loading conditions still remains unclear because of a lack of experimental methodology. Meanwhile, the use of robotic technology for knee joint biomechanics study has been established by Fujie et al [2]. Using the technique, tensile forces in knee cruciate ligaments have been determined by Woo et al [3], Li et al [4], Fujie et al [5], and other groups, while ligament reconstruction technique has been evaluated by many investigators [for example 6–8]. Therefore, the objectives of the present study were to determine the ankle joint instability due to ligament transection and to determine the tensile forces in the anterior tarofibular ligament (ATFL) and calcaneofibular ligament (CFL) in response to anterior-posterior (AP) drawer force to the human cadaveric ankle joints.
Effect of Enzymatic Degeneration on the Frictonal Property of Articular Cartilage
Authors: Mochizuki Shota , Yanagida Shun , Fujie Hiromichi
Published: January 2014

Articular cartilage is consisted of the chondrocyte, collagen fibers and proteoglycan, and interstitial fluid. Basalo et al reported that the coefficient of friction of bovine articular cartilage on a glass surface measured in unconfined compression fashion was increased by the degeneration of proteoglycan [1]. In their friction test, it was difficult to test a small cartilage sample having undulation while the loaded area in cartilage specimen was almost unchanged during friction. For the assessment of frictional properties of enzymatically degenerated cartilage in more physiological condition, we developed a friction tester that allows for performing friction tests of articular cartilage surface against a spherical indenter. With the tester, the loaded area in cartilage specimen translated along with frictional motion while the compressive stress exceeded more than 1 MPa. In the present study, the effect of enzymatic degeneration of proteoglycan and collagen fiber on property of articular cartilage using the friction tester.
A Theoretical Simulation of Maladaptive Remodeling in Response to Hypertension
Authors: Agianniotis Aristotelis , Stergiopulos Nikos , Vito Raymond P. , Shazly Tarek , Rachev Alexander
Published: January 2014

Hypertension is a key risk factor for many adverse cardiovascular events. The sustained increase in pressure causes arterial remodeling, which results in long-term changes in the geometrical dimensions and mechanical properties of the vascular tissue. The remodeling response in experimental animal models of hypertension is often described according to the structurally determined change in lumen diameter. Depending on whether the process resulted in a decrease or increase in the diameter, remodeling is termed inward or outward, while depending on the increase, no change, or decrease in the amount of material, remodeling is hypertrophic, eutrophic, or hypotrophic [1]. Due to the multi-factorial and complex nature of remodeling, it is exceedingly difficult to evaluate the relative importance of any one factor in isolation. Predictive mathematical models based on continuum mechanics are powerful tools for studying the mechanical and remodeling response of blood vessels. So far, most theoretical studies addressed adaptive remodeling in response to sustained hypertension. An adaptive response manifests as preservation of the normotensive deformed diameter, change in residual strains and axial stretch ratio, and thickening of the arterial wall, such that the tensile wall stress and flow-induced shear stress remain at baseline values. Maladaptive remodeling could result from a variety of dysfunctional biological processes, and is characterized by the incomplete restoration of the baseline mechanical environment. This study is devoted to a theoretical simulation of some modes of maladaptive remodeling and aims to evaluate the relative importance of certain geometrical and mechanical factors in the remodeling response to hypertension.
Assessment of Carotid Stent Performance: Virtual Tools for a Geometrical Analysis
Authors: Iannaccone F. , De Beule M. , De Santis G. , Van Herzeele I. , Vermassen F. , Segers P. , Verhegghe B.
Published: January 2014

Carotid artery stenting (CAS) is relatively new procedure introduced to treat severe carotid atherosclerotic disease for high risk patient categories. The advantages of this technique are its minimal invasiveness, easiness of the procedure and the short hospitalization compared to surgical option. However, perioperative complications, such as stroke, can lead to failure of the procedure and long terms effects of the procedure are not completely understood. It is not unrealistic to assume that the mechanical changes of the pathophysiological environment at the stented vessel can induce tissue damage and promote remodeling and restenosis but how these factor (inter)act is still a matter of debate.
Returning to Overuse Activity Following a Combined Supraspinatus and Infraspinatus Tear Leads to Shoulder Joint Damage
Authors: Reuther Katherine E. , Thomas Stephen J. , Tucker Jennica J. , Sarver Joseph J. , Gray Chancellor F. , Evans Elisabeth B. , Ilkhani-Pour Sarah , Glaser David L. , Soslowsky Louis J.
Published: January 2014

Rotator cuff tendon tears are common conditions which can lead to significant pain and dysfunction. Tears may progress over time from isolated supraspinatus tears to complete ruptures of both the supraspinatus and infraspinatus tendons, disrupting the anterior-posterior force balance provided by the subscapularis anteriorly and infraspinatus posteriorly (commonly referred to as a “force couple”) [1]. This disruption may lead to increased joint instability and result in altered glenohumeral translations which may cause damage to joint structures, such as articular cartilage and adjacent (intact) tendons. This is a particular concern for active individuals who are likely to continue high levels of overuse activity (e.g., laborers, athletes), despite the presence of rotator cuff tears. Previous studies have shown that returning to overuse activity following an isolated supraspinatus tear alters biceps and glenoid articular cartilage properties, but does not alter shoulder function or the adjacent intact subscapularis tendon [2]. However, the consequences associated with disrupting the anterior-posterior force balance (supraspinatus and infraspinatus tears) are not understood. Therefore, the objectives of this study were 1) to investigate the effect of returning to overuse activity following tears of both the supraspinatus and infraspinatus tendons on shoulder function and the remaining intact tendon and glenoid cartilage mechanical properties and 2) to begin to define the biologic mechanisms responsible for these changes. We hypothesized that overuse activity following two-tendon rotator cuff tears would H1) alter shoulder function and H2) lead to damage (indicated by inferior mechanical properties and increased production of degenerative factors, extracellular matrix, and cartilage markers) in the remaining intact tendons (including the biceps and upper and lower subscapularis tendons) and in the anterior-superior region of the glenoid articular cartilage as a result of the excessive joint loading due to overuse following the supraspinatus-infraspinatus tear.
Probing Cochlear Resonators Using a New Microchamber
Authors: Marnell Daniel , Prodanovic Srdjan , Nam Jong-Hoon
Published: January 2014

The mammalian cochlea is an acoustic spectrum analyzer and pressure transducer with a remarkable operating range, both in frequency and amplitude (Fettiplace & Hackney, 2006). A young, healthy human ear can capture sounds of 40 to 20,000 Hz in frequency and 20 μPa to 20 Pa (0 to 120 dB sound pressure level) in amplitude. One of the most significant achievements in decades regarding cochlear research is the identification of the cochlear amplifier. Tiny acoustic vibrations are amplified in the organ of Corti (OC)–sensori-eptithelium in the cochlea. Mechano-transducer receptors in the OC, called the outer hair cells, have been identified as the cellular actuators that provide energy to boost small pressure waves. However, the underlying mechanism of this amplification is still unclear.
Advanced Human Coronary Plaque Wall Thickness Correlates Positively With Flow Shear Stress and Negatively With Plaque Wall Stress: An IVUS-Based FSI Study
Authors: Tang Dalin , Yang Chun , Petruccelli Joseph D. , Zheng Jie , Bach Richard , Zuo Heng , Muccigrosso David , Huang Xueying , Yang Deshan , Kural Mehmet H. , Billiar Kristen
Published: January 2014

Atherosclerotic plaque progression is believed to be associated with low and oscillating flow shear stress conditions [1–3]. In vivo image-based coronary plaque modeling papers are relatively rare because clinical recognition of vulnerable coronary plaques has remained challenging [3–4]. Samady et al. [3] published their seminal patient follow-up coronary plaque progression study and indicated that flow shear stress (FSS) was associated with plaque progression and remodeling. We have published results based on follow-up studies showing that advanced carotid plaque had positive correlation with flow shear stress and negative correlation with plaque wall stress (PWS) [4]. In this paper, patient-specific intravascular ultrasound (IVUS)-based coronary plaque models with fluid-structure interaction (FSI), on-site pressure and ex vivo biaxial mechanical testing of human coronary plaque material properties were constructed to obtain flow shear stress and plaque wall stress data from six patients to investigate possible associations between vessel wall thickness and both flow shear stress and plaque wall stress conditions.
A Computationally Efficient and Accurate Lumbar Spine Model
Authors: Yao Jiang , Saraswat Prabhav , Chinnakonda Manoj , Hurtado Juan A. , Oancea Victor , Sett Subham
Published: January 2014

The design of spine implants requires a good understanding of spine kinematics and loading conditions. Realistic simulation of each functional spinal unit (FSU) requires capturing complicated contact and deformation of biological tissues in a computationally efficient manner. Specifically, the complexities include contacts in intervertebral and facet joints, restraints of spine ligaments, as well as realistic material properties of soft tissues. The variation in the stiffness among different FSUs is often neglected in spine modeling, which might be crucial for spine function. A hybrid approach for lumbar spine modeling was established that combined motion capture experiments, kinematic spine modeling and detailed finite element modeling. Motion capture data during flexion was collected and used to drive the spine model. For computational efficiency each FSU was modeled as an intervertebral connector (joint) element with different elastic behavior at each level. The connector behavior was calibrated using experimental data on the whole lumbar spinal motion (Wong et al. 2006) and cadaveric moment-rotation relationship of L45 (Heurer et al. 2007). Then the predicted stiffness for L23 was used to calibrate the material properties of a detailed FEM of L23.
3D Computational Fluid-Structure Interaction Model of Canine Heart With Different Patch Materials for Optimal Myocardium Regeneration
Authors: Zuo Heng , Yang Chun , Gaudette Glenn , Billiar Kristen L. , Geva Tal , Kural Mehmet H. , del Nido Pedro J. , Tang Dalin
Published: January 2014

Myocardial tissue regeneration techniques are being developed for the potential that viable myocardium may be regenerated to replace scar tissues in the heart or used as patch material in heart surgery [1]. The material property of the patch on which myocardium cells are placed has important impact on cell adhesion and multiplication [2]. Fluid-structure interaction (FSI) models for canine heart with patch was introduced to quantify regional flow and mechanical conditions in the patch area and investigate the influence of the different patch materials on myocardium regeneration.
Hemodynamic Changes in Patient-Specific Models of Cerebral Aneurysms With and Without Virtual Flow Diverters Investigated With a Dedicated CFD Research Prototype
Authors: Karmonik Christof , Debus Kristian , Chintalapani Gouthami , Zhang Y. Jonathan , Diaz Orlando , Klucznik Richard , Grossman Robert G.
Published: January 2014

Computational fluid dynamics (CFD) techniques have been pioneered to calculate wall shear stresses, dynamics pressures and other hemodynamics parameters for identifying additional risk factors for cerebral aneurysm rupture [1–4].
Gender Differences in Knee Kinematics After Anterior Cruciate Ligament Injury
Authors: Marsh Chelsea , Tashman Scott
Published: January 2014

Injury to the anterior cruciate ligament (ACL) occurs 200,000 times per year in the United States. About half of these patients opt for ACL reconstruction (ACLr), while the other half choose non-surgical, conservative treatment. ACLr has been found to result in altered kinematics, namely external tibial rotation and knee adduction, during downhill running 1. ACLr also contributes to alterations in muscle activity after surgery. Leg muscles of the affected limb are weakened and contract in different muscle activation patterns when compared to healthy, uninjured patients 2.
Modeling Unstable Brain Aneurysms: MR Molecular Imaging of Myeloperoxidase in Vascular Wall and Correlation With Human Pathology
Authors: Gounis Matthew J. , van der Bom Imramsjah M. J. , Wakhloo Ajay K. , Zheng Shaokuan , Weaver John P. , Puri Ajit S. , Chueh Ju-Yu , Kuhn Anna Luisa , Bogdanov Alexei A.
Published: January 2014

Brain aneurysm bleeding is associated with high rates of fatality or permanent neurological impairment. Despite the low risk of bleeding of an unruptured cerebral aneurysm (UCA) [1,2], the dismal outcome of aneurysmal rupture has led to the aggressive treatment of these aneurysms. In 2008, approximately 60,000 UCAs were treated in the USA [3]. The rate of morbidity and mortality from treatment is high: approximately 5 and 14% for coil embolization and surgical clipping, respectively [3]. The risk-benefit analysis does not support treatment of all UCAs and in an era of significant attention to healthcare economics, considerable expense for treatment of unruptured aneurysms may not be justified. Thus, there is a strong clinical need to identify asymptomatic patients with UCA who would benefit from preventative interventional or surgical procedures.
Finite Element Modeling of Biodegradable Stents
Authors: Debusschere Nic , De Beule Matthieu , Dubruel Peter , Segers Patrick , Verhegghe Benedict
Published: January 2014

Biodegradable stents, which temporarily support a stenotic blood vessel and afterwards fully disappear, have recently gained a lot of interest. They avoid long-term complications associated with conventional stents such as late stent thrombosis and in-stent restenosis. Moreover, degradable stents allow for a restoration of vasomotion and vessel growth which makes them particularly suitable for pediatric applications [1]. Finite element simulations have proven to be an efficient and cost-effective tool to investigate and optimize the mechanical performance of minimal invasive devices such as stents [2]. Biodegradable stents have however created new challenges in their design and optimization via finite element analysis because of their complex time-varying material behavior. To correctly simulate the mechanical behavior of biodegradable stents, a model should be developed that incorporates the effect of degradation upon all material characteristics. By combining existing constitutive material models based on continuum damage theory we were able to create such a virtual environment in which the transitional mechanical behavior of biodegradable stents can be investigated.
Skin Perfusion, Arterial and Venous Blood Flow, and Soft Tissue Thickness in Relation to Pressure Ulcers
Authors: Manorama Abinand , Bush Tamara Reid
Published: January 2014

Pressure ulcers have been a concern in healthcare settings, with more than 50% of bedridden or wheelchair-bound patients being affected [1]. Pressure ulcers typically occur on a region of the body that experiences forces from an external structure (e.g. bed, wheelchair). Researchers believe that such forces cause a decrease in blood flow, which results in tissue necrosis, causing pressure ulcers [2].
Microfluidic Device for Spatial Control of Cell Seeding in Engineered Tissues
Authors: Win Zaw , Vrla Geoffrey D. , Sevcik Emily N. , Alford Patrick W.
Published: January 2014

In vivo tissues have finely controlled hierarchical structure that is often difficult to mimic in vitro. Microfabrication techniques, such as microcontact printing, can be used to reproduce tissue structure in vitro by controlling cell shape and orientation [1]. Several recent results suggest that cellular organization and structure can influence tissue function in engineered tissues [2–4]. For example, using microcontact printing and muscular thin film technology, we recently demonstrated that engineered vascular tissues whose smooth muscle cells possessed more elongated spindle-like geometries, similar to in vivo structure, exhibited more physiological contractile function [5]. In these studies, cells were seeded using traditional imprecise seeding methods. But recent results have shown that cell-cell coupling plays a significant role in functional contractility [6], suggesting that not only cellular geometry, but cell-cell organization, within a tissue is important to reproduce in engineered tissues to mimic in vivo function.
Augmented and Magnetically-Aligned Type I Collagen-GAG Scaffolds for Cartilage Tissue Engineering
Authors: Novak Tyler , Voytik-Harbin Sherry , Neu Corey P.
Published: January 2014

Osteoarthritis (OA) affects over 27 million Americans, causing an annual economic burden of over $300 million [1]. Left untreated, local cartilage defects promote cartilage degeneration and serve as a target for clinical and research based interventions [2]. While current treatments have limited success and result in recurring symptoms [3], tissue engineering solutions are promising for cartilage repair.
Investigating the Effect of Mechanical Stimuli on Omental Mesothelium Differentiation
Authors: Hofmeister Lucas , Lagus Todd , Shelton Elaine , Edd Jon , Bader David , Sung Hak-Joon
Published: January 2014

Cell sourcing for tissue engineered approaches to vascular repair is a serious issue confronting the field of cardiovascular tissue engineering. Omental mesothelium is a promising autologous cell source for vascular repair and has been used for numerous other therapies [1]. Until recently, omental mesothelium was only thought to play a paracrine role in wound healing but there is increasing evidence that omental mesothelium can undergo divergent terminal differentiation to reparative vasculogenic cell types including: endothelial cells, fibroblasts, or vascular smooth muscle cells.
Reduced Plasma Oncotic Pressure is Indicative of Injury Severity in Trauma Patients
Authors: Rahbar Elaheh , Cotton Bryan A. , Holcomb John B. , Wade Charles E.
Published: January 2014

Trauma is the leading cause of death in people aged 1–44 years old, with hemorrhagic shock accounting for nearly half of these deaths. These fatalities often occur early, within 24 hours, but many are deemed potentially preventable with appropriate resuscitation. 1–2 The term “appropriate resuscitation” is somewhat ambiguous and subjective because of the lack of a standardized resuscitation protocol. We attribute this deficiency to our rudimentary understanding of the mechanisms of hemorrhagic shock and resuscitation.
A Study on the Effect of False Vocal Folds Gap Size on the Self-Sustained Oscillation of True Vocal Folds
Authors: Farahani Mehrdad H. , Mousel John , Vigmostad Sarah
Published: January 2014

Recent studies have shown that the supraglottic structures could alter the aeroacoustics output of the larynx [1–2]. The fist supraglottic tissue above the true vocal folds (TVF) is the false vocal folds (FVF) or ventricular folds. This non-oscillatory part of the human larynx shows a wide range of adductions during the normal phonation. Most previous studies, however, have focused on the effect of normal configuration of the FVFs based on mean values reported for this laryngeal structure. Therefore, the effect of different levels of FVF adduction on oscillation of the TVFs remained uninvestigated.
ROS-Responsive Scaffold for Angiogenic Differentiation of Mesenchymal Stem Cells
Authors: Lee Sue Hyun , Zachman Angela L. , Deskins Desirae L. , Young Pampee P. , Sung Hak-Joon
Published: January 2014

Vascularization of a tissue-engineered construct enables efficient transport of nutrients and waste products; it is necessary for successful long-term tissue growth and host integration. Although significant progress has been made, sufficient vascularization of engineered constructs is still a major challenge, limiting clinical applications of tissue engineering (TE) approaches [1]. Successful vascularization promotes the interactions of TE implants with host tissues, leading to efficient tissue regeneration. Therefore, there is an unmet need to develop a more efficient method to vascularize TE constructs. In particular, obtaining a reliable source of endothelial cells (ECs) that line all blood vessels is a critical and challenging step towards successful vascularization of TE constructs, empowering TE to be applied in a larger scale and scope.
Persistence of Cryotherapy Induced Ischemia for Hours After Cooling Ends
Authors: Craik Natalie K. , Khoshnevis Sepideh , Diller Kenneth R.
Published: January 2014

Orthopedic surgery and sports medicine commonly use cryotherapy to reduce inflammation, alleviate pain, lower the chance of secondary hypoxic injury, and decrease hematoma formation [1,2]. Methods of cryotherapy vary widely in their sophistication, ranging from bags of ice or freezable gel packs to liquid perfusion cryotherapy devices. These perfusion cryotherapy devices circulate near 0°C water through a flexible bladder, resulting in localized tissue cooling.
Measuring and Modeling Elastography of Human Cornea Using Scanning Laser Doppler Vibrometry
Authors: Khan Altaf , Dai Zoujun , Royston Thomas J.
Published: January 2014

Our interest is in noninvasively mapping the viscoelastic properties of the human cornea with the aid of a Scanning Laser Doppler Vibrometer (SLDV). Mechanical properties of the cornea can be used to predict early onset of diseases, such as glaucoma and keratoconus. By applying mechanical vibration near the cornea and measuring the dynamic wave propagation across the cornea, an elastographic map can be reconstructed. To effectively reconstruct the data, an appropriate analytical solution is needed to interpret the measured motion; in the present article, we review initial measurements and modeling of phantom cornea models. Several viscoelastic plate phantoms were constructed using silicone gels to simulate corneal structures. Comprehensive frequency sweeps were performed on these phantoms. The material can be represented using a fractional order model of viscoelasticity. Similar experiments have been completed on ex-vivo human cornea from donor eyes. The design shows proof of concept and is now being modified to a more applicable manner for in vivo experiments.
Analysis of Regional Strain Patterns Following Surgical Disruption of the Enthesis in a Murine Model of Patellar Tendon Injury
Authors: Gilday Steven D. , Casstevens Chris , Shearn Jason T. , Butler David L.
Published: January 2014

Tendon injuries are common yet often fail to heal naturally, especially in cases in which the native tendon-to-bone insertion site is disrupted. Surgical tendon repairs are often limited by the inability of the ruptured tendon to functionally attach back to the underlying bone. For patients with tendon injuries, poor tendon-to-bone integration prolongs recovery time and increases the risk of re-rupture. Improvements in tendon repair will require a more complete understanding of both the biological and mechanical phenomena that occur during natural tendon-to-bone healing. Mechanical studies of tendon repair often utilize larger animal models such as rabbits or canines, but these animals lack many of the genetic and biological tools that are available in the mouse. Thus, the objective of this study was to analyze the biomechanical outcomes of natural tendon-to-bone healing following surgical disruption of the enthesis in a murine model of patellar tendon injury. In particular, this study attempted to define the regional (insertion site versus midsubstance) strain patterns present in normal tendon and compare these patterns to those seen at various stages of healing following a central-third patellar tendon avulsion injury. We hypothesized that 1) murine patellar tendon avulsions would exhibit inferior structural properties compared to contralateral shams and normal controls and 2) insertional strains would greatly exceed midsubstance strains in the healing tendons, resulting in failure initiation at the tendon-bone junction.