bluuebunny/crossref_metadata_2025 huggingface dataset:
Viscoelastic Finite-Element Modelling of Neutrophil Deformation in a Tapered Micropipette
Authors: Teo Soo Kng , Parker Kim H. , Chiam K.-H.
Published: March 2014

In this paper, we discuss the results arising from using a viscoelastic, axisymmetric finite-element model [1] to study the aspiration of neutrophils into a tapered micropipette [2]. The key feature of our model is that we take into account the experimentally observed temporal variations in the rheological properties of deforming neutrophils [3]. We show that our model successfully reproduces the equilibrium state reached by a neutrophil subjected to a constant step pressure [2]. We are also able to extract quantitative information about the rate at which the rheological properties of the neutrophil change. Such information may be difficult to obtain directly from the experiments themselves. Thus, our approach illustrates the usefulness of computational modeling as a complement to experiments.
Finite Element Analysis and Empirical Solution for Flexible Substrates Undergoing Large Equibiaxial Strains
Authors: Chiang Martin Y. M. , Cheng Tianle , Pakstis Lisa , Taboas Juan , Dunkers Joy
Published: March 2014

Studies of cellular mechanobiology have depended heavily on the use of in vitro experiments. Many devices have been developed to probe those basic physical mechanisms responsible for cell culture mechanostimulus. The work reported here uses a system that imparts equibiaxial loading on a flexible substrate, similar to the Bioflex in Flexcell [1] family of products, to study cell response to mechanical load. The objective of this study is to incorporate an adaptive loading algorithm (ALA) in a finite element analysis (FEA) to update loading conditions, to obtain an accurate correlation between the substrate stain and applied pressure in the culture system. There is a good agreement between the strain predicted from the analysis and that from the direct measurement. Also, based on the mechanistic condition of physical constrains and a regression analysis of finite element results, we have developed an empirical formula to predict the pressure-strain relationship for large substrate strain levels (up to 15 %) to circumvent experimental measurement or FEA for the substrate strain. The results from this study can be used to validate experimental observations and provide a framework for advancing the apparatus to next level involving other loading cases and geometries.
Correlation Among Hemodynamic Parameters at the Carotid Bifurcation
Authors: Lee Sang-Wook , Antiga Luca , Steinman David A.
Published: March 2014

There is much evidence suggesting that the initiation and progression of atherosclerotic diseases at the carotid bifurcation are influenced by “disturbed flow”. Although this term is not precisely defined, a variety of hemodynamic parameters have been proposed as indicators of disturbed flow, and some have been demonstrated to be more strongly correlated with biological responses.
Evaluation of Predicted Knee Joint Muscle Forces During Gait Using an Instrumented Knee Implant
Authors: Fernandez Justin W. , Kim Hyung J. , Akbarshahi Massoud , Walter Jonathan P. , Fregly Benjamin J. , Pandy Marcus G.
Published: March 2014

Many studies have used musculoskeletal models to predict in vivo muscle forces at the knee during gait [1, 2]. Unfortunately, quantitative assessment of the model calculations is often impracticable. Various indirect methods have been used to evaluate the accuracy of model predictions, including comparisons against measurements of muscle activity, joint kinematics, ground reaction forces, and joint moments. In a recent study, an instrumented hip implant was used to validate calculations of hip contact forces directly [3]. The same model was subsequently used to validate model calculations of tibiofemoral loading during gait [4]. Instrumented knee implants have also been used in in vitro and in vivo studies to quantify differences in biomechanical performance between various TKR designs [5, 6]. The main aim of the present study was to evaluate model predictions of knee muscle forces by direct comparison with measurements obtained from an instrumented knee implant. Calculations of muscle and joint-contact loading were performed for level walking at slow, normal, and fast speeds.
99 Percentile Wall Stress and Not Peak Stress Correlates With AAA Diameter
Authors: Speelman Lambert , Bosboom E. Marielle H. , Hellenthal Femke A. M. V. I. , Schurink Geert Willem H. , Jacobs Micheal J. H. M. , van de Vosse Frans N.
Published: March 2014

Abdominal Aortic Aneurysm (AAA) is a dilation of the aorta of at least 50% increase in diameter, or an aortic diameter over 3 cm. If left untreated, an AAA will increase in size until rupture of the aortic wall causes a life threatening hemorrhage [1]. The current criterion for a repair procedure is a maximum diameter of the AAA of at least 5.5 cm. However, the diameter is not adequate for some small AAAs that rupture early [2]. Therefore, multiple studies have focused on and published data on patient-specific wall stress analyses. Fillinger et al. (2002) found higher peak wall stresses in ruptured AAAs than in electively repaired AAAs [3].
Critical Loading During Serve: Modeling Stress-Induced Bone Growth in Performance Tennis Players
Authors: Taylor Rebecca E. , Zheng Chunhua , Jackson Ryan P. , Doll Joey C. , Chen Julia , Holzbaur Katherine R. S. , Besier Thor , Kuhl Ellen
Published: March 2014

On September 27, 2004 Andy Roddick hit the current world record 155 mph serve in his Davis Cup match against Belarus, which set him up with three match points against Vladimir Voltchkov. By that time, at 22 years of age, Roddick had broken his own speed record for the third time. In tennis, like in almost all other high performance sports, professional athletes tend to reach their peak performance at a much younger age than they used to several decades ago. Accordingly, athletes have to start full-time practice in their early childhood that strongly overlaps with the period of skeletal and muscular development. It is the responsibility of their coaches and physicians to design efficient training programs targeted at maximal performance and minimal risk of injury. Biomechanics can play a crucial role in supporting the design of these training strategies. By predicting the functional adaptation of bones and muscles, biomechanics simulation can help to explain and eventually prevent common forms of injuries caused by chronic overuse.
Improved MR Thermometry to Measure Brain Temperatures
Authors: Shrivastava Devashish , DelaBarre Lance , Hanson Timothy , Vaughan J. Thomas
Published: March 2014

An MR thermometry technique with sub-degree celsius accuracy is needed to measure in vivo temperatures vs. time in porcine brains at ultra-high fields. Porcine models are used to study thermoregulatory temperature response of the ultra-high field radiofrequency (RF) heating. The porcine hot critical temperature limit is comparable to and lower than that of humans. Also, porcine thermoregulatory mechanisms are similar to humans. Thus, conservative porcine thermoregulatory temperature responses can help develop new RF safety thresholds for ultra-high field human MRI. Sub-degree C temperature accuracy is needed since RF safety guidelines limit the maximum in vivo head temperature change due to RF heating to 1 °C over the core body temperature. Three-dimensional temperature maps over time are required since non-uniform RF power deposition at ultra-high fields and blood flow produce non-uniform in vivo temperatures with local hot spots. Thermogenic hazards are related to in vivo temperatures and temperature-time history — and not to the typically measured whole head average specific absorption rate.
Age-Related Changes in the Biomechanical Cyclic Strain of the Human Thoracic Aorta
Authors: Morrison Tina M. , Choi Gilwoo , Segalova Polina A. , Zarins Christopher K. , Taylor Charles A.
Published: March 2014

Large vessels in the vascular system undergo progressive degeneration with aging. The widely accepted theory is the aorta enlarges and stiffens with age [1] and vascular compliance decreases [2], which increases systolic pressure, decreases diastolic pressure, and greatly affects cardiovascular health and function. Quantifying the dynamics of an aging human aorta yields insight into changes in the vascular compliance and is vital in understanding pathogenesis and progression of disease, such as atherosclerosis and aneurysm formation [3], along with medical device implantation and design.
Quantification of Tooth Displacement From Dental Casts
Authors: Li Shuning , Chen Jie
Published: March 2014

In orthodontics, patients are treated by moving teeth to improve esthetics and occlusion. Tooth displacement is one of the most important outcomes, and can be used to evaluate treatment strategies and orthodontic appliances. Thus, an accurate and reliable method for quantification of the three dimensional (3D) tooth displacements is of high interest [1].
3D Flow Modeling and Blood Damage Characterization of the UltraMag™ Blood Pump
Authors: Taskin M. Ertan , Zhang Tao , Gellman Berry , Dasse Kurt A. , Griffith Bartley P. , Wu Zhongjun J.
Published: March 2014

Cardiovascular and lung diseases are the leading causes of death and disability worldwide. There are many therapies available for their treatment such as simple lifestyle changes, medicines, and surgical intervention or corrections. For the cases where the above treatments do not alleviate the patients’ conditions, the use of artificial devices may be the only option to treat or replace the diseased organ(s). However, the consideration of blood containing biomedical devices may introduce a prolonged contact between the blood and inorganic surfaces which induces variety of blood damages including hemolysis due to the creation of non-physiological mechanical shear stress field. Hemolysis is the release of hemoglobin from the red blood cells (RBC) as a result of the rupture of RBC membrane due to these unavoidable mechanical effects. For that reason, characterization of fluid dynamics and hemolytic performance is the key step to evaluate the design of biomedical devices.
E-Selectin Expression on Endothelial Cells in the Presence of Platelets and Cigarette Smoke Extract
Authors: Girdhar Gaurav , Xu Sulan , Jesty Jolyon , Bluestein Danny
Published: March 2014

Cigarette smoking is a risk factor for development of cardiovascular (CV) disease [1], with increased platelet activation due to cigarette smoke involving a major part of this risk.[2] We have shown that this smoke-induced platelet activation is largely due to the non-nicotine smoke components and their effects can be effectively modulated in the presence of nicotine.[3] However, the effects of nicotine and non-nicotine cigarette smoke components need to be confirmed more physiologically in the presence of endothelial cells (ECs). Prior in-vitro studies have shown that high concentrations of cigarette smoke extract (CSE) increase adhesion molecule expression on ECs.[4] These studies however preclude the involvement of physiological shear stresses and are performed on ECs alone. To overcome these limitations and investigate ECs-platelets together in one system under shear stress, we use a hemodynamic shear device (HSD) that combines features of the cone and plate, and the annular Couette viscometer (to facilitate platelet sampling). We test the following hypotheses — (1) smoke-activated platelets and the nicotine-free extract would confer a synergistic E-selectin expression on ECs, and (2) in contrast to conventional cigarette extracts, nicotine-free smoke extracts would increase platelet activation more significantly, and that this effect may be independent of the presence of ECs.
Freezing-Induced Cell-Fluid-Matrix Interaction in Engineered Tissue
Authors: Jung Junkyu , Teo Ka Yaw , Dutton J. Craig , Han Bumsoo
Published: March 2014

Freezing of biological tissues occurs in cryomedicine applications such as cryosurgery and cryopreservation. Although cellular level biophysics during freezing and thawing (F/T) has been extensively studied, tissue level biophysics is not fully understood yet. Especially, the effects of F/T on the functionalities of tissue are not well understood so that the outcomes of cryomedicine applications are highly tissue-type dependent [1]. Although many of the functionalities are associated with the extracellular matrix (ECM), the effect of F/T on ECM microstructure has been overlooked. Quantitative understanding on the post-thaw ECM structure is rarely available, but it is essential to design and improve cryopresevation and cryotherapy protocols for a wide variety of native and engineered tissues.
Biomechanics of Roof Crush and Rear Impact-Related Neck Injuries
Authors: Perrone Nicholas
Published: March 2014

The importance of vehicle safety as a critical and global public health problem is discussed. Crashworthiness principles are enumerated and reviewed as relevant to this problem. Injury biomechanics in rollover and rear impact cases are considered next. Pertinent vehicle safety standards are discussed. The importance and feasibility of improved roof structure, seatbacks and windows is examined. Some selected pertinent case studies are reviewed and finally conclusions are drawn.
Ciliary Behavior and Signal Transmission in the Embryonic Nodes: A Computational Fluid Dynamics Model
Authors: Chen Duanduan , Norris Dominic , Ventikos Yiannis
Published: March 2014

Although externally the vertebrate body is bilaterally symmetric, the internal organs, such as heart, spleen, pancreas, and lungs, exhibit marked left-right (L-R) asymmetry in their patterning and positioning. This lateral asymmetry is conserved in all vertebrates, suggesting that it is of ancient origin and defects in the establishment or maintenance of L-R asymmetry can result in serious health defects [1]. The mechanism by which L-R asymmetry is first established is a major question in developmental biology. In recent years, work by a number of groups has demonstrated that a cilia-driven leftward flow (know as ‘nodal flow’) of extra-cellular fluid across the embryo node is required for initiation of the symmetry breakage during embryogenesis [2].
Simulation of Pulsatile Blood Flow With a Wall Step Transition
Authors: Corbett Scott C. , Coskun Ahmet U. , N-Hashemi Hamid
Published: March 2014

Implantable devices in direct contact with flowing blood, for example, coronary stents, continuous flow and pulsatile flow ventricular assist devices, prosthetic heart valves, catheters and cannulae are currently being used to treat many medical conditions. However, thromboembolism and the attendant risk for ischemic stroke remains an impediment for all these devices. A prudent approach to developing these devices in a cost effective manner should include optimization for thrombogenic performance before going into expensive preclinical and clinical trials.
Simulation of Pulsatile Blood Flow Through a Flexible Cannula
Authors: Corbett Scott C. , Coskun Ahmet U. , N-Hashemi Hamid
Published: March 2014

Implantable devices in direct contact with flowing blood are currently being used to treat many medical conditions; however, thromboembolism, blood damage and the attendant risk for ischemic stroke remains a major impediment. Specifically, vascular access methods, performed by the insertion of cannulae into vessels, may give rise to non-physiological pressure variations and shear stresses. To date, the hydrodynamic behavior of cannulae has been evaluated by comparing their pressure loss-flow rate relationships, as obtained from in vitro experiments. Numerical studies have evaluated cannulae as rigid wall vessels with steady flow conditions [1]. Various catheter tip styles have been compared [2], and the fluid dynamics of arterial cannulae inserted in the aortic arch have been investigated [3]. Evaluation of shear stresses within a flexible wall cannula under pulsatile blood flow conditions is discussed herein. We anticipate that considerations for pulsating blood flow and flexible device walls will indicate that anticoagulation requirements can be minimized and device related complications can be decreased, thus increasing patient survival rates.
Development of an Implantable Heart Valve Force Transducer
Authors: Jensen Morten O. , Johansen Peter , Nygaard Hans
Published: March 2014

The objective of this study was to develop a transducer capable of determining the 3D strain and force distribution in heart valves by utilizing strain gauge measurements. It remains to be determined if the optimum solution for repairing mitral valve annular dilatation is a flexible or a rigid ring [1,2]. Mapping the force distribution in the mitral valve is essential to answer this question. The transducer provides the non-physiologic load of the myocardium created when utilizing artificial heart valves and repair devices.
An In-Vivo Experimental Study of Temperature Elevations in Animal Tissue During Magnetic Nanoparticle Hyperthermia
Authors: Salloum Maher , Ma Ronghui , Zhu Liang
Published: March 2014

Magnetic nanoparticle hyperthermia has potential to achieve optimal therapeutic results due to its ability to deliver adequate heating power to irregular and/or deep-seated tumor at low magnetic field frequency and amplitude [1]. Iron oxides magnetite Fe3O4 and maghemite γ-Fe2O3 nanoparticles are the most studied to date [2] due to their biocompatibilty [3] for hyperthermia application. The heat generated by the particles when exposed to an external alternating magnetic field is mainly due to the Néel relaxation mechanism and/or Brownian motion of the particles [4]. The superparamagnetic particles (10–40 nm) are recommended in clinical application as they are able to generate substantial heat within a small magnetic field strength and frequency [5].
A Novel Braid-Twist Scaffold for ACL Repair: Control of Stress-Relaxation Properties
Authors: Freeman Joseph W. , Woods Mia D. , Cromer Damond A. , Wright Lee D. , Laurencin Cato T.
Published: March 2014

The anterior cruciate ligament (ACL) is critical for knee stability when walking or running. Unfortunately, it does not heal well after significant tearing or rupture and surgery is often necessary to reconstruct the injured ligament. Though ACL ruptures are quite common, the surgical repair of this ligament has inconsistent success rates [1]. The goal of this study was to characterize a biomimetic tissue engineered ACL scaffold using a novel combination braid-twist technique. The braid-twist scaffolds were made using the following procedure:

• Nine groups of six 160 mm length PLLA fibers were selected.

• Each group of six fibers was twisted in a counter-clockwise manner to form a fiber bundle (a total of nine fiber bundles/scaffold).

• Three of these bundles were twisted around one another counter-clockwise to form a yarn (a total of three yarns/scaffold).

• These three yarns were braided together to form one scaffold. This technique is based on the structure of ACL tissue and is designed to reduce scaffold fatigue and accurately mimic ACL behavior.
Comparative Freezing Response of Ejaculated and Epididymal Bovine Spermatozoa
Authors: Alapati Raghava , Stout Michael , Godke Robert A. , Devireddy Ram V.
Published: March 2014

In the present study, we report the effects of cooling ejaculated and epididymal bovine sperm from the same animals with and without a cryoprotective agent, glycerol. Water transport data during freezing of ejaculated and epididymal bovine sperm cell suspensions were obtained at a cooling rate of 20 °C/min under two different conditions: i) in the absence of cryoprotective agents, CPAs; and ii) in the presence of 0.7 M glycerol. Using previously published values, the bovine sperm cell was modeled as a cylinder of length 39.8 μm and a radius of 0.4 μm with an osmotically inactive cell volume, Vb, of 0.61Vo, where Vo is the isotonic cell volume. The subzero water transport response is analyzed to determine the variables governing the rate of water loss during cooling of bovine spermatozoa, i.e. the membrane permeability parameters (reference membrane permeability, Lpg and activation energy, ELp). The predicted best-fit permeability parameters ranged from, Lpg = 0.021 to 0.038 μm/min-atm and ELp = 27.8 to 41.1 kcal/mol. The subzero water transport response and consequently the subzero water transport parameters are not significantly different between the ejaculated and epididymal bovine spermatozoa under corresponding cooling conditions. If this observation is found to be more generally valid for other mammalian species as well, then the sperm extracted from the testicles of an animal during post-mortem can also be optimally cryopreseved using procedures similar to those derived for ejaculated sperm.
Mixing of Angiographic Contrast With Blood During Injections in the Cerebral Circulation
Authors: Sadasivan Chander , Cesar Liliana , Lieber Baruch B.
Published: March 2014

In the past, various techniques such as indicator dilution, transit time, parametric imaging, or first-pass distribution have been used to estimate blood flow rates during angiographic contrast injections. We have previously employed the method of modeling contrast concentration curves to assess changes in flow exchange between parent cerebral vessels and cerebral aneurysms due to endovascular treatment by flow divertors [1]. There has been concern, however, that contrast injected under such situations may remain as a separate slug or stream flowing with blood or that contrast may settle from blood in the direction of gravity due to its higher density [2,3]. According to this argument, therefore, the analysis of the transport of angiographic contrast visualized under X-ray cannot be used to represent the transport of blood.
Freezing-Assisted Intracellular Drug Delivery to Multi-Drug Resistant Cancer Cells
Authors: Teo Ka Yaw , Han Bumsoo
Published: March 2014

The efficacy of chemotherapy is significantly impaired by multi-drug resistance (MDR) of cancer cells. The mechanism of MDR is associated with the overexpression of certain ATP-binding cassette protein transporters in plasma membranes. These transporters actively keep intracellular drug concentration below the cell-killing threshold by extruding cytotoxic drugs. Various strategies to overcome MDR have been proposed and have shown promising results at the laboratory level. However, pharmacokinetic alteration of co-administered anticancer agents reduces their clinical effectiveness. This leads to increased toxicity and undesirable side effects at effective concentrations [1]. Hence, a clinically feasible strategy to overcome the phenomenon of MDR is highly desired.
Effect of Kinetic and Thermodynamic Transitions of Confined Water on Biomolecules
Authors: Reátegui Eduardo , Aksan Alptekin
Published: March 2014

In the last years, encapsulation of functional biomolecules (such as enzymes, proteins and antibodies) in three-dimensional nanoporous silica matrices has received considerable attention for its potential applications in biocatalysis, biosensing, and biopreservation.1 A handful of studies conducted with bacteria, plant, and mammalian cells have shown that these complex microorganisms can also function when they are encapsulated in silica matrices.2 When encapsulated in rigid permeable mesopores, mobility and proliferation of the microorganisms are prevented, while nutrients and by-products diffuse freely through the porous matrix. However, it is not known what mechanism(s) enables the biomolecules to be stable, and the microorganisms to be active, while they are mechanically confined in a matrix in a “no-growth” state. It is known that the motions and properties of water change when confined in nanopores. Therefore, we envision that the altered properties of confined water play a role in increasing the stability of biomolecules. This study is focused on understanding the effects of confinement on the kinetic and thermodynamic transitions of water, and identifying its effects on the structure of confined biomolecules. We have utilized Fourier Transform Infrared Spectroscopy (FTIR) to identify the different states and phase transitions of nanopore confined water at cryogenic temperatures. We have extended our analysis to quantify the structural changes in nanopore confined isolated and endogenous proteins of intact organisms.
Fabrication of Micropatterned Hydrogels Using Maskless Photopolymerization for Tissue Engineering Applications
Authors: Yasar Ozlem , Dinh Michael , Lan Shih-Feng , Starly Binil
Published: March 2014

The fabrication of tissue scaffolds/constructs has seen tremendous advancements over the past decade primarily due to the application of layered manufacturing based technologies from the rapid prototyping industry. Molding, printing and deposition technologies have enabled researchers to spatially control scaffold micro and macro structural features through the use of soft lithography solid freeform fabrication. These techniques have produced patterned scaffolds with desired mechanical and biological properties to mimic the natural tissue microenvironment. Soft lithographic techniques have produced feature sizes in ranges of 20μm and above but have limited 3D capability. Solid freeform fabrication technologies enable the production of complex 3D scaffolds due to its CAD integration but are generally limited to a 100μm feature resolutions.
Comparative Histological and Biomechanical Effects of Prostaglandin-E2 and Bacterial Collagenase on the Rabbit Patellar Tendon
Authors: Dyment Nathaniel A. , Shearn Jason T. , Galloway Marc T. , Greiwe R. Michael , Kenter Keith , Hasan Samer S. , Butler David L. , Boivin Gregory P.
Published: March 2014

Ninety-seven percent of tendon ruptures are found in areas of chronic tendon degeneration, which is thought to be a cell-mediated process involving increased extracellular matrix turnover and remodeling [1,2]. The degenerative aspects seen within regions of tendon degeneration include collagen matrix disorganization, collagen fibril thinning, cellular hyperplasia, and neovascularization [1–3]. The etiology of tendon degeneration is unclear at this point. One theory involves the introduction of multiple mechanical insults (mechanical overuse) that act to trigger a degenerative pathway of increased matrix degradation by matrix metalloproteinases (MMP). Inflammation is not seen within regions of degenerative tendon. However, inflammatory mediators such as prostaglandin-E2 (PGE2) may have a role as they have been shown to be upregulated by fibroblasts as a result of mechanical over-stimulation in culture [4]. Multiple injections of PGE2 within the midsubstance of the rabbit patellar tendon (PT) also produced collagen fibril disorganization and thinning [5].
Design of Experiments Approach to Maximize Process Reliability for Bone Scaffold Fabrication
Authors: Hoelzle David J. , Alleyne Andrew G. , Wagoner Johnson Amy J.
Published: March 2014

Micro Robotic Deposition (μRD) is a solid freeform fabrication process in which a colloidal suspension, or ink, is extruded through a nozzle in a defined trajectory to form a three-dimensional structure. The term Micro Robotic Deposition is chosen since the extrusion nozzle is usually positioned by a robotic device with resulting part feature sizes between 1–1000 micrometers. μRD technology has been applied to a variety of applications[1] including hydroxyapatite (HA) bone scaffolds[2]. To date, the majority of the μRD research has focused on developing new materials appropriate for deposition as well as decreasing the feature size. In order to make μRD a reliable and viable manufacturing process the number and severity of fabrication defects must be reduced. However, deposition reliability has received relatively little research attention. The work presented here fills this gap in the literature and will help facilitate the transition of μRD technology from the research bench to a manufacturing environment by developing general guidelines that maximize process reliability.
Spinal Cord Neuronal Cell Properties Respond Differentially to the Stiffness of DNA Crosslinked Hydrogels
Authors: Jiang Frank X. , Georges Penelope , Chippada Uday , Li Lulu , Yurke Bernard , Schloss Rene S. , Firestein Bonnie L. , Langrana Noshir A.
Published: March 2014

Mechanical cues arising from extracellular matrices greatly affect cellular properties, and hence, are of significance in designing biomaterials. Similar to many other cell types, including fibroblasts and hepatocytes, central nervous system (CNS) neurons have been found to exhibit distinct responses to the stiffness of the substrates they reside on [1]. There is an increasing awareness that mechanical properties also play a key role in successful utilization of scaffolds for those tissues whose major functions are not load-bearing, such as the spinal cord. In light of this, there is a growing interest in incorporating mechanical cues in biomaterial design for neural tissue engineering applications, including spinal cord injury.
Feasibility of Determination of Mechanical Properties of Abdominal Aortic Aneurysms by Simultaneous Pressure and Volume Measurements In-Vivo
Authors: van ’t Veer Marcel , Rutten Marcel C. M. , Buth Jaap , Pijls Nico H. J. , van de Vosse Frans N.
Published: March 2014

In an effort to better predict the risk of rupture of an abdominal aortic aneurysm (AAA), methods have been developed that comprise more than diameter information alone. Wall stress calculations demonstrated superior results compared to the diameter criterion [1]. Accurate wall stress calculations require patient specific geometry, load, and wall properties of the aneurysm [2]. Usually, values for mechanical properties obtained from in-vitro tensile tests of excised aneurysmal wall material are used for wall stress calculations [3]. For obvious reasons such experiments to obtain vessel properties are impossible to perform in patient specific cases for risk assessment.
Effect of Gait on Patellofemoral Mechanics
Authors: Bischoff Jeffrey E. , Hertzler Justin S.
Published: March 2014

Computational modeling of the reconstructed knee is an important tool in designing components for maximum functionality and life. Utilization of boundary conditions consistent with in vivo gait loading in such models enables predictions of knee kinematics and polyethylene damage [1–4], which can then be used to optimize component design. Several recent clinical studies have focused on complications associated with the patellofemoral joint [5–6], highlighting the need to better understand the mechanics of this compartment of total knee arthroplasty (TKA). This study utilizes a computational model to characterize the impact of gait loading on the mechanics of the patella in TKA.
Alterations in Stresses due to Various Femoral Deformities Across the Hip Joint: FEA Analysis
Authors: Vyas Mitul Y. , Sabharwal Sanjeev , Langrana Noshir A.
Published: March 2014

The manifestation of osteoarthrosis by an abnormality such as hip dysplasia, slipped capital femoral epiphysis (SCFE), coxa vara and Legg-Calve-Perthes disease is one of the leading causes of chronic orthopaedic disability, resulting in billions of dollars in treatment and indirect costs, such as lost wages for the patient [1]. Additionally, these conditions are severely painful, inducing a reduction in range of motion, abnormal gait and consequently, poor quality of life. In patients with SCFE, the proximal femur collapses as a result of epiphyseal displacement, resulting in femoroacetabular impingement and acetabular erosion [1, 2]. Patients with developmental coxa vara (DCV), a pediatric hip disorder, exhibit triplanar deformity of the proximal femur. The abnormal neck–shaft angle and associated change in the articulo-trochanteric distance (ATD) alter the biomechanics of the hip adversely, and is often accompanied by limb length discrepancies [3].
Flow Increases Endothelial Migration and Inhibits Smooth Muscle Cell Proliferation in Artery and Co-Culture Models
Authors: Lee Yong-Ung , Luo Jian , Sprague Eugene , Han Hai-Chao
Published: March 2014

Arterial restenosis associated with intimal hyperplasia at stent revascularization sites remains the major cause of long-term failure. The objective of this study was to determine the effect of flow in promoting endothelial cell migration and the effect of re-endothelialization on smooth muscle cell (SMC) proliferation. This study demonstrated that re-endothelialization reduces SMC proliferation and migration and provides model systems to study approaches to increasing endothelial healing.
Experimental Investigation of Mechanical and Structural Inhomogeneity in Bovine Carotid Arteries
Authors: Timmins Lucas H. , Evagora Christopher A. , Moore James E. , Greenwald Stephen E.
Published: March 2014

Many constitutive models have been proposed to assess arterial mechanical behavior. Most, however, are largely phenomenological and lack a detailed consideration of arterial wall constituents and the manner in which mechanical loads are distributed amongst them. Recently, strain energy functions (SEF) that consider histological evidence about arterial wall structure have been developed [1,2]. These SEFs incorporate fiber bundle orientation and consider the relative proportions of the major wall constituents to offer a better description of arterial wall deformation. Including histological structure and its affects on arterial elasticity could provide a better understanding of the relationship between arterial structure and function. Further shortcomings in arterial modeling include the assumption that the arterial wall is a homogeneous structure, when in fact it is well known to be a non homogenous, although there are notable exceptions [3,4].
Application of Carbon Nanotubes in Cartilage Tissue Engineering
Authors: Chahine Nadeen O. , Collette Nicole M. , Thompson Heather , Loots Gabriela G.
Published: March 2014

Carbon nanotubes (CNTs) are cylindrical allotropes of carbon that are nanometers in diameter and posses unique physical properties, positioning them as ideal materials for studying physiology at a single cell level. CNTs have the potential to become a very important component of medical therapeutics, likely acting as (a) drug delivery system [1], (b) existing as an interfacial layer in surgical implants [2,3], or (c) acting as scaffolding in tissue engineering [4,8]. While some studies have explored the use of CNTs as a novel material in regenerative medicine, they have not yet been fully evaluated in cellular systems. One major limitation of CNTs that must be overcome is their inherent cytotoxicity. The goal of this study is to assess the long-term biocompatibility of CNTs for chondrocyte growth. We hypothesize that CNT-based material in tissue engineering can provide an improved molecular sized substrate for stimulation of cellular growth, and structural reinforcement of the scaffold mechanical properties. Here we present data on the effects of CNTs on chondrocyte viability and biochemical deposition examined in composite materials of hydrogels + CNTs mixtures. Also, the effects of CNTs surface functionalization with polyethlyne glycol (PEG) or carboxyl groups (COOH) were examined.
Prediction of Ligament Length During Wrist Flexion Extension
Authors: Patterson Rita M. , Yazaki Naoya , Andersen Clark R. , Scott Newt H. , Viegas Steven F.
Published: March 2014

Direct measurement of ligament length in the wrist is difficult due to constrained space and short length of many ligaments. No prior studies have reported measurements of ligament length between the carpal bones of the wrist. In this presentation, we have combined high precision motion analysis of the carpal bones, subsequent manual digitization of the ligament attachment regions, and a simulated ligament wrapping model, to generate predictions of carpal ligaments’ length and implied strain during wrist motion.
Dynamic Compression in the Presence of TNF-Alpha Differentially Effects Gene Expression in Tibial Plateau Cartilage Covered and Uncovered by the Meniscus
Authors: Bevill Scott L. , Andriacchi Thomas P.
Published: March 2014

It has been suggested that altered joint loading may be a cause of the cartilage degeneration commonly observed following joint destabilizing events such as anterior cruciate ligament (ACL) injury [1]. Changes in the biochemical environment of the joint accompany these changes in joint loading, though, with acute and chronic increases in synovial concentrations of proinflammatory cytokines such as tumor necrosis factor-alpha (TNFα) [2, 3]. TNFα is a potent catabolic factor associated with increased expression [4] and synthesis [5] of matrix proteases in articular cartilage, and therefore may play in important role in the degenerative events following joint injury.
Maximum Contractile Strain in the Biceps Brachii Is Bounded by Sarcomere Geometry
Authors: Novotny John E. , Knarr Brian A. , Zhou Hehe
Published: March 2014

Skeletal muscles’ primary function is the application of force to its bony origins and insertions. There are various models of muscle function that generally assume a uniform behavior from origin to insertion during force generation even though the structure and activation is complex. Engineering strains within skeletal muscles, though, have been shown to be non-uniform [1]. We have developed methods to quantify Lagrangian finite strains using cine phase-contrast magnetic resonance imaging (CPCMRI) and post-processing algorithms [2] and have described them during cyclic motion in the supraspinatus and biceps brachii. Principal and maximum in-plane shear strains can be identified at the scale of millimeters throughout the contracting and elongating muscle.
Gender Differences in the Kinematics and Morphology of the Knee
Authors: Varadarajan Kartik M. , Gill Thomas J. , Freiberg Andrew A. , Rubash Harry E. , Li Guoan
Published: March 2014

Recently gender related dimorphism in the knee has received increased attention in sports medicine and total knee arthroplasty (TKA). Certain soft tissue injuries, particularly ACL injuries, have a higher prevalence rates in young female athletes compared to their male counterparts [1]. Patellofemoral pain, recurrent dislocations and arthritis have been reported to be more common in women [2]. Women have higher incidence of osteoarthritis and account for about two-thirds of TKA patients. Gender specific implant designs have also been reported [3]. However, no study has compared the six-DOF kinematics of the male and female knees during functional activities. Additionally gender differences in the morphology of the knee, particularly the trochlear groove, have not been clearly delineated. Herein, we have examined gender differences in knee morphology and six-DOF kinematics during weight bearing flexion. This was accomplished via combined magnetic resonance (MR) based 3D modeling and dual fluoroscope imaging of the knee.
Stresses in Femoral Knee Component: Effects of Patellofemoral Loading Location and Magnitude
Authors: Dharia Mehul A. , Stoller Alex P. , Bischoff Jeff E.
Published: March 2014

For many years, orthopaedic surgeons have reported anatomical differences in men’s and women’s knees [1–4]. For a given anterior/posterior dimension, the female femur is narrower in the medial/lateral dimension than the male femur [5]. A female knee has a larger trochlear groove angle [4] and has a less-pronounced anterior condyle [1]. Gender Solutions™ Female (GSF) femoral implants are designed to accommodate these differences by replacing the bone resection with the joint of corresponding size and shape to avoid overstuffing and overhang that may increase pain [6, 7]. The GSF femur designs are narrowed mediolaterally, have increased trochlear groove angle and reduced anterior flange thickness.
A Novel Bioreactor Engineered With Mass Transport and Storage as Key Design Specifications
Authors: Niu Mei , Shi Gengbei , Coger Robin N.
Published: March 2014

Successfully developing tissue and organ equivalents requires one to balance device design strategies with the complexities of supporting cells able to accomplish targeted functions. For these equivalents to attain the goal of wide spread clinical use with off-the-shelf availability, it is also critical that methods for storing these systems are considered during in the design phase. This study presents a liver equivalent system — a radial flow bioreactor (RFB) — designed with each of these goals in mind. Its unique features include its capacity for cell support and the design of its cellular space. Specifically it is able to accommodate functional and reasonably sized tissue (more than 2×108 cells). The RFB’s effectiveness in supporting functioning liver cells; the consequences of the system’s flow on O2 transport; and the results of cryopreserving its tissue equivalents at sub-zero temperatures, are all presented.
Plaque Ulceration Is Associated With High Stear Stress in Stenotic Carotid Bifurcations
Authors: Groen Harald C. , de Weert Thomas T. , Gijsen Frank J. H. , van der Steen Anton F. W. , van der Lugt Aad , Wentzel Jolanda J.
Published: March 2014

Cerebrovascular events are related to atherosclerotic disease in the carotid arteries and they are often caused by rupture of an atherosclerotic plaque. Rupture-prone, or vulnerable, plaques are characterized by their specific morphology and composition: a large lipid pool covered by a thin fibrous cap infiltrated by macrophages and expansive remodeling. The strength of the cap of a vulnerable plaque is determined by the material properties of the cap and its thickness. Plaque ruptures are often observed at the upstream region of the plaque [1], were the wall shear stress (WSS) is considered to be highest. High WSS is known for its influence on many processes affecting, among others, tissue regression [2]. Therefore, high shear stress induced cap regression might contribute to cap thinning, thus enhancing plaque vulnerability, and eventually leading to cap rupture [3,4]. Here we present the first results of a new approach to study the relationship between WSS and the location of ulcerations in severely stenotic carotid bifurcations by using computational fluid dynamics and computed tomography.
Practices in Engineering Analysis, Education, and Ethics as Applied to Consulting in Biomechanical Forensics
Authors: Wojcik Laura A.
Published: March 2014

The demand for experts in the field of biomechanics continues to grow due to claim investigations by insurance companies and legal matters involving issues such as product liability, negligence, and workers’ compensation. Practitioners who consult in biomechanical forensics must balance client needs with sound engineering analysis techniques, ethical experimental design, and reasonable interpretations of published data. Once an analysis has been completed and opinions have been presented to the client, the task of presenting the results of the technical analysis to attorneys, judges, and jury members who are often unsophisticated in their understanding of scientific concepts in ways that are understandable, accurate, and not misleading can be a challenge even for experienced testifiers. Always being mindful of scientific and engineering ethics and being aware of aspects of educational theory can help to give new consultants confidence in their positions and make them more effective in their deposition and trial testimony.
Viscoelastic Properties of Spine Ligament Collagen Fascicles
Authors: Lucas Scott R. , Salzar Robert S. , Bass Cameron R.
Published: March 2014

Connective tissues, such as ligaments and tendons, are comprised of varying amounts of collagen, elastin, and ground substance. It is conceivable to develop a microstructural material model based on the volume fraction and orientation of each constituent, and their interactions.
A Time Resolved DPIV In-Vitro Evaluation of Coronary Stents in Realistic Conditions: Part II — Effect of Stent Design
Authors: Charonko John J. , Karri Satya P. , Schmieg Jaime , Prabhu Santosh V. , Vlachos Pavlos P.
Published: March 2014

Cardiovascular disease has historically been the leading cause of death in the US [1], and accounts for approximately one third of all deaths worldwide [2]. Coronary artery disease in particular accounts for over fifty percent of these deaths and in 2004 was the single largest killer, affecting approximately 15 million people every year [1]. Coronary stenting was approved in 1994 by the FDA, and has become one of the leading treatments for the disease. However, problems persist in both bare metal and drug-eluting stents (DESs) with restenosis and thrombosis. It is well accepted that disruptions in arterial wall shear stress (WSS), especially low WSS, are linked to alterations in the endothelial cell layer and ultimately disease [3], although the exact mechanisms are still uncertain. Additionally, studies have shown that stent design is closely linked to clinical outcomes [4].
A Time Resolved DPIV In-Vitro Evaluation of Coronary Stents in Realistic Conditions: Part I — Influence of Stent Configuration
Authors: Charonko John J. , Karri Satya P. , Schmieg Jaime , Prabhu Santosh V. , Vlachos Pavlos P.
Published: March 2014

Cardiovascular disease has historically been the leading cause of death in the US [1], and coronary artery disease in particular accounts for over fifty percent of these deaths [1]. Since their approval in 1994, coronary stents have become one of the leading treatments for this disease. However, problems persist in both bare metal and drug-eluting stents (DESs) with long-term restenosis and thrombosis. It is well accepted that disruptions in arterial wall shear stress (WSS), especially low WSS, are linked to alterations in the endothelial cell layer, atherosclerosis, and thrombogenesis [2], although the exact mechanisms are still uncertain, and studies have shown that stent design is closely linked to clinical outcomes [3].
Probabilistic Prediction of Microdamage Progression in Bone
Authors: Dong X. Neil , Sparkman Daniel M. , Leng Huijie , Millwater Harry R. , Wang Xiaodu
Published: March 2014

Age-related bone fractures are a major health concern to the elderly population. In addition to the loss of bone mass, the deterioration of bone quality is another major reason for such fractures. The decline of bone quality is manifested with the accumulation of microdamage in bone with age [1]. Two major types of microdamage have been observed in bone tissue: linear microcracks and diffuse damage [2]. Linear microcracks are individual cracks at a size of microns or larger and are usually visible under an optical microscope. On the other hand, diffuse damage is detectable only by staining and consists of an extensive network of fine, ultrastructural-level defects. The mechanisms for the formation of these two distinct types of microdamage in bone are still unclear. In this study, probabilistic finite element models of mineral-collagen composites were used to study the progression of microdamage in bone, thereby exploring the conditions under which linear microcracks and diffuse damage are produced in bone.
Mechanical Properties of the Porcine Lens Capsule
Authors: Amini Rouzbeh , Oltean Alina , Barnett Vincent , Segal Yoav , Barocas Victor H.
Published: March 2014

Basement membranes are ubiquitous. In humans, genetic disorders in basement membranes can lead to many complications including kidney disease, skeletal muscle myopathy, hearing loss, and ocular abnormalities[1]. We hypothesize that genetic mutation of the microstructure of the lens capsule basement membrane will alter its mechanical properties. Because of its unique thickness and anatomically distinct margins, the lens capsule is the only site in the body where large-scale mechanical tests on the basement membrane can be made.
The Stress Response in Injured Afferents of the Capsular Ligament Depends on Tensile Loading Applied to the Facet Joint
Authors: Dong Ling , Odeleye Akinleye O. , Akay Cagla , Jordan-Sciutto Kelly L. , Winkelstein Beth A.
Published: March 2014

Chronic neck pain from whiplash affects over 10 million people annually in the United States [1]. Many studies have indentified the facet joint as a possible source of neck pain due to its innervation by nociceptive fibers [2]. In particular, in vivo studies have reported that distraction of the facet joint and its capsule produces both persistent firing of capsule pain fibers and persistent behavioral hypersensitivity and pain symptoms (i.e. mechanical allodynia) [2,3].