bluuebunny/crossref_metadata_2025 huggingface dataset:
RBC Modeling Using NURBS Based Isogeometric Analysis
Authors: Chivukula VenkatKeshav , Lu Jia , Vigmostad Sarah C.
Published: July 2013

The Red Blood Cell(RBC) is the transporter of oxygen to the entire human body via the circulatory system. Its journey spans across pathways which step down orders of magnitude; from large arteries which are O(cm) to tiny capillaries which are O(μm). This four-fold reduction in the diameters of the circulatory pathways necessitates the RBC to be extremely deformable. One of the most intriguing facets of the RBC is that it achieves this extreme deformability with ease; and also with a very minimal area dilatation[1]. Modeling the RBC has been an active area of research since the 1950’s. However, conventional methods to model RBCs rely on simplistic Finite Element Methods(FEM) involving mostly triangular elements. The extreme deformability of the RBCs mandate the use of a large number of elements, usually O(thousands) to accurately resolve and visualize the motion of an RBC [2], which is biconcave when unstressed and assumes myriad shapes as it travels through the microcirculation. The extremely large number of elements per cell makes the calculations highly computationally intensive for a single cell alone. This becomes particularly important when attempting to simulate the motion of a large number of cells, leading to a very computationally intensive simulation. The current paper proposes a novel method to analyze and resolve the RBC as a smooth entity using greatly reduced number of elements for resolution. This approach is based on exploiting the properties of Non-Uniform Rational B-Spline (NURBS) surfaces [3]. The results obtained from utilizing the NURBS surfaces can be considered to be a more realistic representation of the behavior of the RBC. Though this article specifically deals with the RBC, it can be applied to a deformable cell of any shape.
Magnetic Resonance Elastography of Nucleus Pulposus Shear Modulus: A New Approach for Disc Degeneration Biomarkers
Authors: Cortes Daniel H. , Magland Jeremy F. , Wright Alexander C. , Barocas Victor H. , Elliott Dawn M.
Published: July 2013

Intervertebral disc degeneration is cell mediated cascade of biochemical, mechanical and structural changes that disrupts its function. These changes are difficult to overturn; consequently, early diagnosis is key for the success of any treatment. Clinically, disc degeneration is diagnosed by the interpretation of morphological changes observed in T2 weighted MR images. However, those changes in morphology are characteristic of moderate to advanced stages of degeneration. Therefore, this method is not useful to diagnose early stages of disc degeneration.
Dynamics of Arterial Wall Transport for Small Hydrophobic Drugs
Authors: Bozsak Franz , Chomaz Jean-Marc , Barakat Abdul I.
Published: July 2013

Drugs used in drug-eluting stents (DES) to inhibit proliferation of smooth muscle cells (SMCs) also limit re-endothelialization at the site of stent implantation [1]. Thus, treated patients face an increased risk of late-stent thrombosis. Avoiding this adverse side effect represents one of the major challenges in the design of next-generation DES.
CFD Challenge Solution Using the Commercial Finite Volume Solver Fluent
Authors: Hodis Simona , Kallmes David F. , Dragomir-Daescu Dan
Published: July 2013

The Modeling and Analysis group in the Division of Engineering at Mayo Clinic, Rochester works in the area of numerical modeling and experimental validation of cerebral aneurysms. In our modeling we use patient-specific geometries from imaging studies provided by Dr. Kallmes. The CFD analysis is performed with commercial packages Mimics (Materialise, Leuven, Belgium), for segmentation and ANSYS (ANSYS Inc. Canonsburg, PA) for meshing, simulation and post-processing. The experiments are conducted using a tomographic Particle Image Velocimetry system from LaVision Inc. The group is led by Dan Dragomir-Daescu, PhD and David F. Kallmes, MD and consists of two postdoctoral fellows and three engineers. For this project, CFD simulations were performed by postdoctoral fellow Simona Hodis, using the finite volume based solver Fluent.
A Comparison of Thrombus Susceptibility for Two Pulsatile 50 CC Left Ventricular Assist Pumps
Authors: Navitsky Michael A. , Deutsch Steven , Manning Keefe B.
Published: July 2013

Approximately 5.7 million Americans are afflicted with heart disease, with a reported 670,000 new cases and 300,000 deaths each year [1]. While the success rate of transplantation procedures continues to improve, organ availability remains limited. Left ventricular assist devices (LVADs) function as a bridge to transplant for advanced staged heart failure patients awaiting a donor heart. The devices have also been used, more recently, as a bridge to recovery by helping to unload the native ventricle. Along with pharmacological intervention, LVADs can act to help reverse pathological hypertrophy and recover normal myocardial function [2].
A Correlative Study of Fluid Mechanics and Evidence of Thrombus Formation Within the Penn State 50 CC Left Ventricular Assist Device
Authors: Topper Stephen R. , Navitsky Michael A. , Siedlecki Christopher A. , Deutsch Steven , Rosenberg Gerson , Manning Keefe B.
Published: July 2013

An estimated 82.6 million American adults live with one or more forms of cardiovascular disease and in past years, it was the cause of over 55% of all deaths in the United States, more than any other type of major disease [1]. With a limited number of available donors, heart transplants are seldom an option. As a result, ventricular assist devices (VADs) have become a viable alternative to immediate transplant. Today, VADs are widely used as bridge-to-recovery, bridge-to-transplant and destination therapy devices. Despite past improvements in VAD design, a major complication that continues to arise is thrombus formation within the pump.
Grand Challenge Competition: A Parametric Numerical Model to Predict In Vivo Medial and Lateral Knee Forces in Walking Gaits
Authors: Knowlton Christopher B. , Wimmer Markus A. , Lundberg Hannah J.
Published: July 2013

Numerical models are necessary to estimate forces through the knee joint during activities of daily living. However, the numerous muscles and soft tissues crossing the knee joint result in a computationally indeterminate problem. The recent availability of measured contact force data from telemeterized total knee replacements (TKRs) has given researchers the chance to validate models, but telemeterized TKRs represent only a few patients with a specific implant type. Computational models remain necessary to bridge the gap between the small instrumented patient population with a particular implant and larger patient populations executing various activities. Abstracted gait data from another lab tests the versatility of any model to accurately predict forces of TKR patients performing a variety of gaits with disparate implant types. In this study, we calculate and examine the differences between medial and lateral contact forces in level walking and medial thrust gait trials from a freely provided dataset1.
Diastolic Myocardial Vibrations Caused by Poststenotic Coronary Flow Instabilities
Authors: McGah Patrick M. , Aliseda Alberto , Beach Kirk W.
Published: July 2013

It has been previously reported in the literature that high-frequency diastolic heart murmurs in the myocardium occur in patients with coronary artery stenoses. It has also long been hypothesized that these murmurs are caused by flow instabilities downstream of the stenosis; the most obvious mechanism for this phenomenon is that pressure fluctuations due to the flow transition excite vibrations in the coronary artery wall which then radiate into the myocardium. A prior pilot study [1], utilizing Doppler vibrometry, an ultrasound based technique, was able to measure high frequency (100–1000Hz) but low amplitude (1–10μm) left ventricular wall vibrations in patients with coronary artery stenosis. Furthermore, the intensity of the wall vibrations was shown to significantly correlate with the percent stenosis (as determined by quantitative coronary angiography). This evidence suggests that ultrasound doppler vibrometry offers the possibility to detect coronary artery stenosis with a low-cost, relatively cheap, and non-invasive modality [2]. This particular study, therefore, seeks to quantify the relationship between the poststenotic flow instabilities and wall vibrations in order to optimize the vibrometry measurements.
The Transient Response of a Collagen Remodeling Theory Based on Strain-Dependent Collagen Degradation
Authors: Cilingir A. , Wilson W. , Ito K. , van Donkelaar C. C.
Published: July 2013

In vivo [1] and in vitro [2–4] studies show that cell and matrix alignment can be significantly affected by mechanical stimuli. Even in highly aligned engineered tissues, cells are able to remodel the collagen orientation when loading conditions are altered [4].
Bicycle Riding, Arterial Compression and Erectile Dysfunction
Authors: Parthiban Sujeeth , Yang Christopher , Jones Loren , Baftiri Amit , Niederberger Craig
Published: July 2013

A National survey approximately estimates 57 million people rode a bicycle in 2002. Males were more likely to ride bicycle than were females1. Another survey estimates US bicycles and accessories sales in 2010 to be 6 billion dollars. Several research studies implicated bicycle riding as risk factor for erectile dysfunction2. One possible reason is ischemic injury due to compression of perennial arteries between the bony pelvis and the bicycle seat. Previous studies attempted to measure this damage employed several indirect methods including computational models3, pressure mats on a stationary bike4, measuring transcutaneous oxygen pressure in the penis5, MR imaging of the pelvic region6, doppler flowmetry. None of these studies measured forces exerted directly on the perennial arteries and correlated to each riders occlusion force. Most of these studies are done on a stationary bike set up inside the lab. The objective of our study is to build a device to measure the forces exerted on the perennial arteries and develop a method to correlate the forces with each riders occlusion force. Another goal is to conduct the rides on the road where actual bike riding takes place. Recent publications4 suggested that cutting off the nose from the saddles may help to prevent the damage to the arteries. Based on these findings several noseless seats came to market. We also wanted to test some of them in our study.
The Pipeline Versus Telescoping Stents: In Vitro Flows in a Treated Cerebral Aneurysm Model
Authors: Roszelle Breigh N. , Babiker M. Haithem , Ryan Justin , Gonzalez L. Fernando , Albuquerque Felipe , Frakes David
Published: July 2013

Cerebral aneurysms are a significant concern; they are found in 2% of the world population [1]. While endovascular treatments have become a successful option for patients with cerebral aneurysms, recurrence rates remain as high as 50% [2]. Accordingly, many interventional devices are being developed with the hope of increasing the success rate of endovascular aneurysm occlusion. One of these devices is the low-porosity Pipeline emboilzation device (PED). Compared to more traditional intracranial stents, the PED contains a higher ratio of metal to surface area. Previously, similar reductions in porosity were obtained by sequentially deploying multiple high-porosity stents inside of one another, which is known as “telescoping.” The hemodynamic effects of using a single low-porosity device, versus telescoped high-porosity stents, have not been investigated thoroughly. In this study flow was quantified for idealized and anatomical basilar tip aneurysm models. The models were treated with sequentially placed high-porosity stents and a single low-porosity PED.
Ovarian Cancer Cell Invasiveness Correlates With Increased Cell Deformability
Authors: Xu Wenwei , Mezencev Roman , Kim Byungkyu , Wang Lijuan , McDonald John , Sulchek Todd
Published: July 2013

Cancer cells undergo a variety of biochemical and biophysical transformations when compared to identical cells displaying a healthy phenotypic state, cancer cells show a drastic reduction of stiffness upon malignancy[1, 2] and change of stiffness of single cells can indicate the presence of disease [3–6]. Besides, metastatic cancer has a higher deformability than their benign counterparts[7, 8]. Using atomic force microscopy, we demonstrated that cancerous ovarian cells (OVCAR3, OVCAR4, HEY and HEYA8) are substantially softer than the healthy immortalized ovarian surface epithelium (IOSE) cells. In addition, within the different types of cancerous ovarian cells, increased invasiveness and migration are directly correlated with increased cell deformability. These results indicate that stiffness of individual cells can distinguish not only ovarian cancer cells from healthy cells types, but also invasive cancer types from less invasive types. Stiffness may provide an alternative and convenient biomarker to grade the metastasis potential of cancer cells.
The Effects of Sliding, Rolling, and Rotation on Cross-Shear and Wear of UHMWPE in Knee Replacements
Authors: Patten Eli , McPeek-Bechtold Nolan , Cruz Cynthia , Ansari Farzana , Reis Michael , Pruitt Lisa
Published: July 2013

Wear debris from the ultra-high molecular weight polyethylene (UHMWPE) tibial bearing surface leading to loosening is still the main cause for revisions after 5 years for total knee replacements (TKR) [1]. Wear of UHMWPE is greatly increased under cross-shear motion, such as in the hip joint, due to how the molecules and crystalline regions can align in one direction and make the material weaker in the other [2]. The motion in the knee joint is mainly linear rolling and sliding, but there is rotation and medial-lateral sliding that introduce cross-shear [3]. Wear tests are typically performed with basic motion parameters and simplified geometry (pin-on-disk tests) or under gait simulation to test specific designs, but little is known about the effects of the different motions in the knee on UHMWPE wear. There is also disagreement over how to best quantify cross-shear and model how much wear it will cause [3–5]. This study investigates the effect on wear of the different individual and combined motions in TKR: sliding, rolling, and rotation, for a total of eight separate kinematic conditions. The different measures of cross-shear present in each case were calculated in a computer model and compared to the wear test results.
Increased Stiffness of the Abdominal Aorta With Intrauterine Growth Restriction in the Near-Term Fetal Sheep
Authors: Dodson Reuben Blair , Rozance Paul J. , Hunter Kendall S. , Ferguson Virginia L.
Published: July 2013

Fetal intrauterine growth restriction (IUGR) results in increased placental resistance to blood flow, fetal hypertension and increased pulsatility [1]. These hemodynamic changes have been shown to lead to vascular remodeling in adolescents and adults [2, 3] but have received little study of its effect during this critical period of vascular formation. Epidemiological studies link IUGR to cardiovascular disease in adulthood [4], but the reason for this is not clearly understood. Here, we examine a large elastic artery for developmental alterations under hypertensive conditions. We hypothesize that fetal hypertension induces abdominal aorta (AA) stiffening in the fetal ovine model of IUGR and that the increased systemic artery stiffness is due to altered extracellular matrix (ECM) composition and structural changes.
Cryosurgery Causes Profound and Persistent Ischemia
Authors: Khoshnevis Sepideh , Diller Kenneth R.
Published: July 2013

Cryotherapy has been used in the treatment of soft tissue trauma and other ailments since the time of Hippocrates. Currently it is commonly applied in conjunction with surgical procedures and by athletic trainers and physical therapists to control pain, swelling, bleeding, and inflammation. Localized cooling also results in slowing of the nerve conduction velocity and reduced muscle spasm and secondary hypoxic injury1,2. Cooling is commonly used for soft tissue injuries in combination with rest, compression and elevation to minimize inflammation.
Development of a Electro-Osmotic Micromixer for Uniform and Rapid Mixing
Authors: Panta Yogendra M. , Adhikari Param C. , Aryal Sanket
Published: July 2013

Micro Total Analysis Systems (μTAS) require rapid yet homogeneous mixing of a number of fluid streams that carry bio/chemical species in the solution. Current analysis has been continued from our previously published work [1]. New models were designed by rendering some particular fluid and geometric variables from the original design and then analyzed for the degree of mixing effectiveness. A careful placement of obstacles in the mixing zone of the model and the electrodes in it showed enhancement in mixing performance. In addition, models with varied geometrical parameters such as converging inlet and diverging outlet yielded even better mixing capabilities. Concentration variances over time at the outlet were simultaneously compared in all models for mixing. Also average concentration was tracked over time so as to confirm the uniformity in mixing. The concentration variances at the outlet have been dramatically observed to be reduced by a factor of at least 10 from our designs as reported earlier [1].
Quantification of Sternal Morphology Across Ages and Genders Using Image Segmentation and Registration Techniques
Authors: Weaver Ashley A. , Nguyen Callistus M. , Stitzel Joel D.
Published: July 2013

Thoracic injury ranks second only to head injury in motor vehicle crash injuries in terms of the number of fatalities and serious injuries, the body region most often injured, and the overall economic cost [1, 2]. Skeletal and physiological resilience are known to decline with age, resulting in a decreased ability for the body to withstand traumatic insults [3]. Adults 65 years of age and older constitute more than 12% of the current population and with increases in life expectancy, the elderly population is projected to reach nearly 20% by 2030 [4].
ACL Injury Mechanism is Related to Articular Pressure Distribution: A Cadaveric and Finite Element Investigation
Authors: Kiapour Ata M. , Demetropoulos Constantine K. , Kiapour Ali , Quatman Carmen E. , Levine Jason W. , Wordeman Samuel C. , Hewett Timothy E. , Goel Vijay K.
Published: July 2013

Acute anterior cruciate ligament (ACL) injury can be devastating, and often results in clinical sequelae that include meniscal tears, chondral lesions and osteoarthritis. Various bone bruise patterns of the femur or tibia, and bone contusions of the lateral tibial plateau have been associated in more than 80% of partial or complete ACL ruptures [1]. As quantification of articular cartilage pressure distribution under high-rate loading conditions remains challenging, validated finite element (FE) models of the knee can be used to characterize the effects of different loading parameters on tibiofemoral (TF) joint pressure distribution. This study combines high-rate cadaveric experiments with FE analysis to simulate ACL injuries and associated bone bruise patterns following landing from a jump. We hypothesized that a potential relationship exists between ACL injury mechanisms and resultant tibial plateau bone bruise patterns. This relationship may enhance our understanding of ACL injury mechanisms, which may provide insight to improve current prevention strategies that aim to decrease the risk of ACL injury and damage to secondary anatomical structures. All of this may in turn minimize associated posttraumatic knee osteoarthritis.
Relating Network Topology to Network Mechanics
Authors: Christiansen Eric M. , Hadi Mohammad F. , Barocas Victor H.
Published: July 2013

Soft tissues are comprised of underlying fiber networks of collagen and other fibrous proteins and biopolymers. Thus, the ability to model the deformation of fiber networks is critical to understanding the mechanics of tissues in vivo and in vitro [1]. Complicating the issue, protein fiber networks are comprised of a range of different topologies that behave differently under load. There is a clear need for a method to derive network parameters that characterize the network and allow for the prediction of their behavior. In this study, we characterized several different random fiber network types based on their intrinsic mechanical and topological properties. Such characterization would improve our ability to select microscale network topologies that match the mechanical properties we observe in healthy and diseased native tissues [2]. It would also improve our ability to discern the outcome of microstructural changes in tissues (such as from remodeling or injury) on their overall mechanics.
CFD Challange: Solutions Obtained Using Two Commercial Finite Volume Solvers, Fluent and STAR-CCM+
Authors: Costelloe J. A. , Browne L. D. , Lynch A. G. , Morris L. , Walsh M. T.
Published: July 2013

The CABER group is based at the University of Limerick and for the past 15 years has primarily focused on cardiovascular hemodynamics research. A key element of the group’s research has always been in the application of CFD to idealized and patient specific geometries. Recently the group has changed commercial CFD software’s and so currently has access to 2 packages, Star-CCM+ 6.02.007 and Ansys Fluent 12.1.4. For this challenge it was therefore decided to compare both software packages and also to examine variability between users. The Fluent simulations were conducted by postgraduate researcher Adrian Lynch and the Star CCM software was utilized independently by postgraduate researchers Jennifer Costello and Leonard Browne.
Large Population Multi-Center Study of Small Unruptured Intracranial Aneurysms in Prospective Cohorts: Initial Sac Morphology and Longitudinal Outcome
Authors: Ramachandran Manasi , Lin Steve , Correa Tatiana , Dickerhoff Ben , Berkowitz B. , Hasan David , Ogilvy Christopher , Rossenwasser Robert , Harbaugh Robert , Raghavan Madhavan L.
Published: July 2013

Most intracranial aneurysms (IA) that present unruptured at the clinic remain stable over time with no measurable change or symptoms, if left untreated. But a few do grow larger and occasionally rupture. The ability to preemptively identify aneurysms that will become unstable over time (i.e., those that will grow and/or rupture) can result in timely intervention for these few patients while avoiding unnecessary treatment for countless others [1]. Previous reports assessing potential factors including by our group [2–4] have been confined to comparing geometric and/or biomechanical indices of aneurysms between populations that presented with ruputred lesions from those that presented with unruptured lesions. But, such indices (that discriminate rupture ‘status’) need not necessarily distinguish unruptured aneurysms that fork toward growth and/or rupture over a period of time from those that remain stable over time. Further, the physician’s dilemma to treat or not to treat presents itself mostly only in small aneurysms (< 7mm).
Anthrax Toxin Receptor 2 Knock-Out and Wild Type Mouse Cervix Exhibit Time-Dependent Mechanical Properties
Authors: Yoshida Kyoko , Reeves Claire , Kitajewski Jan , Wapner Ronald , Vink Joy , Fernandez Michael , Myers Kristin
Published: July 2013

The cervix plays a critical role during pregnancy, acting as a mechanical barrier to keep the fetus inside the uterus until term. In a normal pregnancy, it is hypothesized that the cervix gradually softens until uterine contractions occur. At this point, the cervix dramatically ripens and dilates for delivery. Similar to other collagenous tissues, the extracellular matrix (ECM) is the load-bearing component of cervical tissue. It is composed mainly of a cross-linked network of fibril forming collagen, types I and III, embedded in a viscous proteoglycan ground substance. Studies conducted on animal models suggest that during normal maturation, a shift in ECM components facilitate cervical softening. However, quantitative cervical softness measurements (i.e. material properties) of these previous studies are ill-defined, limiting the comparative ability of the outcome values. Therefore, our goal is to quantify sensitive and specific time-dependent material properties utilizing mouse models of normal and abnormal pregnancy. Our aim is to discern the role of ECM maintenance in cervical softening.
Internal Pressure of the Human Meniscal Attachments During Physiological and Pathological Loading
Authors: Abraham Adam C. , Kaufman Kenton R. , Haut Donahue Tammy L.
Published: July 2013

Knee menisci are semi-lunar, fibrocartilaginous structures that convert applied compressive loads to circumferential hoop stresses which are attenuated at the tibial plateau via the meniscal attachments [1]. These specialized interfaces, located at the lateral anterior (LA), lateral posterior (LP), medial anterior (MA), and medial posterior (MP) horns, are crucial to maintaining mechanical functionality of menisci, thereby preventing osteoarthritis [2]. Soft-tissues subjected to compression and shear loads are known to possess proteoglycans, which aid in resisting these applied stresses by retaining interstitial fluid [1]. Interestingly, proteoglycans are also known to be present at the meniscus to bone interface [3]. Despite the presence of these biphasic attachments and their important role in joint load transfer, there have been no quantitative investigations of the mechanical environment within these attachments under physiological and pathological loads. Recent development of a novel pressure microsensor now allows direct observation of fluid pressure, which will aid in understanding the internal mechanical environment within the attachment sites. Previous work indicates that the attachment sites are geometrically, mechanically, and histologically different [4], thus it is hypothesized that the fluid pressures would likewise differ.
Assessing the Capability of Helmets to Prevent Concussion: Principles and Applications of the STAR Evaluation System
Authors: Rowson Steven , Duma Stefan M.
Published: July 2013

Research has estimated that between 1.6 and 3.8 million sports-related concussions are sustained in the United States each year [1]. In light of new research suggesting that potential long-term neurodegenerative effects can result from repetitive brain injuries, concussions have been placed under the national spotlight as a primary health concern. While minimizing the exposure of athletes to head impact is one important component of reducing the incidence of concussion, improvement in head protection is another essential element. This paper focuses on a new mechanism to evaluate the protective capabilities of helmets in relation to concussion.
Investigating Electromagnetic Field, Nanoparticle Design, and Treatment Volume for Magnetic Nanoparticle Thermal Therapy
Authors: Etheridge Michael L. , Bischof John C.
Published: July 2013

Magnetic nanoparticle (MNP) based thermal therapies are currently approved in Europe and poised for clinical translation in the US. The main benefits include the ability to focally and repeatedly treat tissues, including cancers, with a minimally-invasive platform. Nevertheless, a more complete understanding and control of MNP heating is necessary to effectively translate the approach to treat different sizes and geometries of cancer (See Figure 1). The present work discusses contrasts in heating between superparamagnetic and ferromagnetic nanoparticles (sMNP and fMNP), electromagnetic field-dependant MNP response, scaling of MNP volumetric heating, and the ability of theory to predict this behavior.
Terrain Characterization Using Modified RANSAC Analysis of Human Gait Data
Authors: Sullivan Christopher , DeBartolo Elizabeth A. , Lamkin-Kennard Kathleen
Published: July 2013

One of the many lasting side effects of a stroke can be foot drop, or an inability to dorsiflex the foot. In order to remedy this, many people wear an ankle-foot orthotic (AFO) post-stroke. One of the many troubles these individuals face is in dealing with obstacles such as stairs and ramps, because the AFO limits the plantarflexion that is natural in navigating these obstacles [1,2]. The end goal of this research is to create an active AFO that adapts to changing ground terrain, providing a more natural gait pattern.

This paper presents the first part of this work: a means for identifying terrain in order to control an AFO. This has been accomplished using an infrared (IR) range sensor attached to the lower leg, used to measure the surface profile of the ground just ahead of a test subject. Using a modified RANSAC technique to fit experimental gait data, standardized gait profiles for different terrain have been quantified and shown to be reproducible, indicating the utility of the technique for terrain identification and AFO control.
Computational Prediction of Fluid Induced Stress States in Dynamically Conditioned Engineered Heart Valve Tissues
Authors: Salinas M. , Schmidt D. , Lange R. , Libera M. , Ramaswamy S.
Published: July 2013

There is extensive documented evidence that mechanical conditioning plays a significant role in the development of tissue grown in-vitro for heart valve scaffolds [1–3]. Modern custom made bioreactors have been used to study the mechanobiology of engineered heart valve tissues [1]. Specifically fluid-induced shears stress patterns may play a critical role in up-regulating extracellular matrix secretion by progenitor cell sources such as bone marrow derived stem cells (BMSCs) [2] and increasing the possibility of cell differentiation towards a heart valve phenotype. We hypothesize that specific biomimetic fluid induced shear stress environments, particularly oscillatory shear stress (OSS), have significant effects on BMSCs phenotype and formation rates. As a first step here, we attempt to quantify and delineate the entire 3-D flow field by developing a CFD model to predict the fluid induced shear stress environments on engineered heart valves tissue under quasi-static steady flow and dynamic steady flow conditions.
The Mechanical and Structural Changes in Murine Arteries due to the Antiretroviral Drug Azidothymidine (AZT)
Authors: Hansen Laura , Platt Manu O. , Sutliff Roy L. , Gleason Rudolph L.
Published: July 2013

With over 33 million people infected with the human immunodefeciency virus (HIV-1), HIV-1 and autoimmune deficiency syndrome (AIDS) is a worldwide epidemic [1]. However, the development and widespread use of highly active antiretroviral therapy (HAART) has helped transform HIV-1 infection from a terminal disease leading to AIDS to a manageable chronic condition. With the increase in life expectancy, a new set of non-AIDS related complications has emerged including dyslipidemia, lipodystrophy, insulin resistance, diabetes mellitus, and cardiovascular disease (CVD) specifically high risks for myocardial infarction[2] and increased incidence of atherosclerosis [3]. Additionally, patients exhibit markers of subclinical atherosclerosis including endothelial dysfunction [4], carotid artery intima-media thickening [5], and arterial stiffening [4, 6].
Nonlinear Dynamics and Bifurcations in Postural Control on Rigid Surfaces and Rotational Balance Boards
Authors: Chagdes James R. , Rietdyk Shirley , Haddad Jeffery M. , Zelaznik Howard N. , Raman Arvind
Published: July 2013

A balance board is an unstable platform which is currently used for training and rehabilitation to stabilize an individual’s upright posture. Models that examine how individuals remain upright while standing on an unstable surface are therefore needed to understand the mechanisms behind balance improvements. Most research in this area has focused on the fluctuations in posture about a static upright equilibrium using single-degree-of-freedom (1-DOF) inverted pendulum models [1–2]. While conceptually simple, these models nonetheless capture the stochastic, nonlinear and multiple timescale behavior of the fluctuations that are known to occur in human posture [1–3].
Proteoglycan Contribution to the Mechanical Behavior of the Porcine Posterior Sclera
Authors: Murienne Barbara J. , Nguyen C. Thao D.
Published: July 2013

Studies describing the mechanical properties of the sclera can be found in the literature 1–10, including studies on healthy, pathophysiological and aging scleral tissue from different species and tested under various loading conditions. However, none was found to specifically address the role of the extracellular matrix (ECM) components in the mechanical behavior of the sclera.
Material Properties of the Post-Mortem Stomach in High-Rate Equibiaxial Elongation
Authors: Howes Meghan K. , Hardy Warren N.
Published: July 2013

Risk of serious abdominal injury in motor vehicle collisions (MVCs) is substantially reduced with the proper use of seatbelts [1]. However, a significant increase in occurrence of gastrointestinal tract injury exists with belt loading [2]. Crash-induced injuries of the stomach that occur in MVCs include gastric rupture and laceration [3]. To characterize the biomechanical response of the stomach associated with these failure modes, the multidirectional failure properties of cruciate tissue samples were investigated with high-rate biaxial stretch.
Experimental Validation of Fluid Dynamic Numerical Models in Blood Pump Simulation
Authors: Zhang Jiafeng , Zhang Pei , Fraser Kate , Griffith Bartley P. , Wu Zhongjun J.
Published: July 2013

Heart disease affects millions of people each year. However, only a limited number of people benefit from a heart transplant due to the scarce supply of donor hearts. Ventricular assist devices (VADs) provide an alternative way to augment or replace the function of one or more chambers of a failing heart. Fluid dynamics in these devices plays a key role in their function and blood biocompatibility. Although current devices are more biocompatible than their forerunners, they still cause blood damage, such as hemolysis, platelet activation, thrombosis and embolization, which may result in serious clinical events and are directly related to fluid dynamics and artificial materials of these devices. Significant research efforts have been devoted to studying the device-blood interactions and minimizing these non-physiological fluid dynamic conditions to improve the functional characteristics and bio/hemo-compatibility of these medical devices.
Right Ventricular Response to Pulmonary Arterial Stiffening in a Canine Model of Acute Embolization
Authors: Bellofiore Alessandro , Roldan-Alzate Alejandro , Besse Matthieu , Kellihan Heidi B. , Consigny Daniel W. , Francois Christopher J. , Chesler Naomi C.
Published: July 2013

Pulmonary arterial hypertension (PAH) is a devastating disease exhibiting fast progression [1] and poor prognosis [2]. PAH originates from an increased resistance to blood flow in the distal pulmonary vasculature and in the later stages of the disease leads to right ventricular (RV) functional impairment and subsequent heart failure, which in most cases is the direct cause of demise. In PAH, RV failure appears to be correlated to PA stiffening, which is a better predictor of mortality than the direct increases in mean pulmonary arterial pressure (mPAP) and pulmonary vasculature resistance (PVR) [3,4].
Time-Dependent Indentation Response of Human Cervical Tissue
Authors: Myers Kristin M. , Oyen Michelle L. , Yoshida Kyoko , Fernandez Michael , Vink Joy , Wapner Ronald
Published: July 2013

More than half a million babies are born prematurely in the United States, and the rate of preterm birth (PTB) is on the rise [1]. Infants born prematurely account for a high percentage of perinatal mortalities, and preterm infants that survive are at risk for long-term morbidities including neurologic, respiratory, cardiovascular and gastrointestinal complications [2]. Altered mechanical and biochemical properties of the uterine cervix are suspected to cause premature and spontaneous cervical dilation, which is associated with a leading cause of PTB known as cervical insufficiency (CI). The impact of this condition is unknown because diagnosing CI remains controversial. Multiple etiologies are believed to lead to an insufficient cervix, or a soft cervix. Yet, there is no standard method to quantify the mechanical strength of the cervix, limiting the ability to discern these etiologies, to stage the progression of labor, and to identify and manage high-risk CI patients.
Hyperelastic Behavior of Porcine Aorta in Sub-Injury Pressures
Authors: Laksari Kaveh , Rastgar Agah Mobin , Darvish Kurosh
Published: July 2013

Traumatic Aortic Rupture (TAR) is a major cause of fatality in motor vehicle crashes. In terms of numbers, only 9% of the subjects who experience such trauma (7500–8000 victims in US and Canada) survive from the scene of the accident and the overall mortality rate is 98% [1].
Investigating Dielectrophoretic Signature of Mouse Ovarian Surface Epithelial Cells, Macrophages and Fibroblasts
Authors: Salmanzadeh Alireza , Kittur Harsha , Sano Michael B. , Stremler Mark A. , Roberts P. Christopher , Schmelz Eva M. , Davalos Rafael V.
Published: July 2013

Epithelial ovarian carcinomas are the fourth leading cause of death in women in the United States among all cancers and the leading cause of death from gynecological malignancies1. The main reason for this high rate of mortality is the inability to properly detect these carcinomas early. Investigations for diagnosing ovarian cancer in early stages have been hindered by two major obstacles: lack of adequate cell models to study different cancer stages and lack of a reliable technique to isolate these cancer cells from peritoneal fluid. In trying to solve the first challenge, Dr. Schmelz and collaborators presented a transformed mouse ovarian surface epithelial (MOSE) cell model by isolating different transitional stages of ovarian cancer as cells progressed from a premalignant nontumorigenic phenotype to a highly aggressive malignant phenotype2, 3. In this model four stages of transformed cells, namely early (MOSE-E), early-intermediate (MOSE-E/I), intermediate (MOSE-I) and late (MOSE-L) cells, were distinguishable3. In the current study, we attempt to solve the second challenge of isolating cancer cells from macrophages and fibroblasts, which are found in the peritoneal fluid. Based on differences in cells’ intrinsic electrical properties, a new cell manipulation technique, contactless dielectrophoresis (cDEP), was implemented.
CFD Challenge: Modeling Blood Flow Dynamics in a Cerebral Aneurysm Using Fluent
Authors: Shaffer Nicholas , Loth Francis
Published: July 2013

The Biofluids Laboratory at the University of Akron has used Fluent [Ansys Inc., Canonsburg, PA] for image-based computational fluid dynamics (CFD) modeling of physiological flows since the lab’s inception in 2008. Recently our group has focused on modeling of pathophysiological problems in cerebrospinal fluid motion and air flow in the trachea, in addition to past work in cardiovascular problems.
Strains in Magnetically Aligned Collagen Scaffolds as Determined by Displacement-Encoded MRI
Authors: Novak Tyler , Griebel Adam , Neu Corey P.
Published: July 2013

Collagen is the most abundant structural protein in a broad range of tissues, including ligament, cartilage, and bone. Collagen-based tissue constructs, including those with defined fibril alignment, have shown considerable potential for repair and regeneration of diseased collagen-rich tissues [1,2], where fibril ultrastructure of constructs emulate the native tissue counterpart. Magnetic alignment of collagen is an established method to control fiber orientation without undesirable changes in molecular stability and structure [5]. To date, studies concerning the magnetic alignment of collagen have shown the ability of fibril alignment to drive preferential cell growth characteristics [6]. While the bulk mechanical characteristics due to alignment has been investigated in our laboratory (data not shown), the mechanical strain throughout the interior of the scaffolds has not been investigated. Knowledge of internal strains is required to determine the degree that fiber alignment affects spatiotemporal mechanics of microenvironments within the collagen structures. Spatially-dependent mechanics, which could be tailored based on unique fabrication methods that control fibril alignment in three dimensions, would be expected to directly influence local cell-matrix interactions.
Spatial Measurement of Viability in Tissue Phantoms and Ex Vivo Bladder Tissue in Response to Photothermal Therapy and Single Walled Carbon Nanohorns
Authors: Whitney Jon , Carswell William , DeWitt Matthew , Robertson John , Rylander Chris , Rylander Marissa Nichole
Published: July 2013

Cancer is one of the most deadly diseases and leading cause of death. Laser based photothermal therapy can provide a minimally invasive alternative to surgical resection. The selectivity and effectiveness of laser therapy can be greatly enhanced when photoabsorbing nanoparticles such as nanoshells, single walled carbon nanotubes, multi-walled carbon nanotubes, or single wall carbon nanohorns (SWNHs) are introduced into the tissue[1]. Quantitative methods for measuring tumor response to nanoparticle enhanced laser therapies are critical for determining appropriate laser parameters and nanoparticle properties needed to achieve maximum therapeutic benefit. We have previously reported a new method for measuring two dimensional (2D) spatial viability distributions in cell monolayers in response to laser irradiation and nanoparticles. This method has been refined to allow determination of cell viability in three dimensions (3D) within a more physiologically representative tumor volume. This refined method was used to determine the viability of breast cancer cells suspended within sodium alginate tissue phantoms following treatment with SWNHs and external laser irradiation. The tumor treatment volume was accurately quantified in response to varying laser treatment parameters and nanoparticle concentrations. Spatial cellular viability was also measured in ex vivo pig bladders in response to SWNHs and laser irradiation to provide a more anatomically relevant environment. These new measurement methods enable quantification of spatial viability and therapeutic effectiveness, using 3D tumor environments which are more representative than cell monolayers.
CFD Challenge: Cerebral Aneurysm Simulations Using an In-House Finite Element Solver
Authors: Moghadam Mahdi Esmaily , Wilson Nathan , Bazilevs Yuri , Marsden Alison
Published: July 2013

Simulations of flow in a cerebral aneurysm are reported as part of the CFD Challenge Problem for the 2012 Summer Bio-engineering Meeting. Our group, a collaboration between the Marsden and Bazilevs labs at UCSD and Open Source Medical Software Corporation, used an in-house finite element solver. In addition, we report particle residence times obtained by solving an advection diffusion equation in a post-processing step.
Correlation Between In Vivo Knee Contact Forces and External Measures During Gait
Authors: Meyer Andrew J. , D’Lima Darryl D. , Banks Scott A. , Lloyd David G. , Besier Thor F. , Colwell Clifford W. , Fregly Benjamin J.
Published: July 2013

Researchers have sought to explain the development and progression of knee osteoarthritis using in vivo estimates of knee contact forces. Unfortunately, it is not possible to measure knee contact forces in a clinical environment. Thus, studies often estimate knee contact forces using a variety of external measures. For example, inverse dynamics knee loads such as the adduction moment and superior force are frequently used as surrogate measures of medial and total knee contact force, respectively. Contraction of muscles spanning the knee is believed to increase knee contact force, and hence muscle electromyographic (EMG) signals are another external measure that may be indicative of internal contact force. The recent development of instrumented knee implants, such as the eTibia design [1], has provided access to in vivo knee contact force data during gait and other activities. However, few studies have correlated inverse dynamics loads, and none have correlated EMG signals, with total, medial, and lateral in vivo knee contact forces.
Thickness Sensing of Nerve Cells on Hydrophobic Polymer Networks With Distinct Mechanical Properties
Authors: Cai Lei , Wang Shanfeng
Published: July 2013

Substrate stiffness is one key factor to influence cell behavior because cells constantly probe the mechanical properties of their environment by exerting traction forces and receive the resistance to the induced deformation.1 Therefore, besides the stiffness on the top surface, the depth of a material that cells are able to sense is important in understanding cellular mechanosensitivity and designing cell carriers and biomedical devices. Poly(ε-caprolactone) triacrylate (PCLTA) recently developed in our group using a facile method is biodegradable and can be efficiently photo-crosslinked into hydrophobic networks with controllable mechanical properties.2 In this study, we used two PCLTAs with different molecular weights to prepare two-layer substrates for investigating nerve cell behavior. PCLTA2k was spin-coated and photo-crosslinked on the stiff network of crosslinked PCLTA20k with different coating thicknesses. A mirror system was fabricated in the same way. Rat Schwann cell precursor line (SpL201) cells with the glial nature was used to demonstrate the dependence of cell spreading and proliferation on the coating thickness. Besides the better support of SpL201 cells on stiffer substrate, the effective stiffness cells can respond depended on the coating thickness. A gradual change was found in SpL201 cell spreading and proliferation when the coating thickness increased. A critical coating thickness was required to completely screen the influence from the base layer and this value was higher for the softer top layer.
Tuning Nerve Cell Functions on Distinct Polymer Networks With Controllable Mechanical Properties
Authors: Cai Lei , Wang Shanfeng
Published: July 2013

Mechanical, chemical, and topological properties are three major factors that influence cell behavior on the substrates.1 In this study, we used two types of biodegradable and photo-crosslinkable polymers, poly(ε-caprolactone) triacrylate (PCLTA) and poly(ethylene glycol) diacrylate (PEGDA), with different molecular weights to demonstrate the roles of mechanical and chemical factors in regulating nerve cell behavior. Crosslinked PCLTAs were hydrophobic while crosslinked PEGDAs were hydrophilic and formed hydrogels. All the networks were amorphous at 37 °C to ensure good controllability of mechanical properties by well-defined crosslinking density. Rat Schwann cell precursor line (SpL201) cells were used to evaluate their performance in terms of proliferation and differentiation. We found that SpL201 cells could proliferate more and differentiate better on stiffer substrates of both networks but differences existed between these two networks because of surface chemistry. The mechanisms how cell functions were tuned by surface properties have been investigated by blocking of β1 integrin prior to cell attachment. We found that SpL201 cells no longer showed dependence on mechanical properties if β1 integrins were blocked. The present results provide guidance for designing optimal nerve conduits made by crosslinked PCLTA and filled with PEGDA hydrogels for peripheral nerve regeneration.