bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Polymer Coated Needles on Infusate Backflow During Convection-Enhanced Delivery
Authors: Vazquez Louis C. , Hagel Erik , Willenberg Bradley J. , Batich Christopher D. , Sarntinoranont Malisa
Published: July 2013

Currently, many central nervous system disorders cannot be treated effectively using conventional drug delivery methods such as oral and intravenous drug administration. Therapeutic agents for such disorders often contain polar proteins with high molecular weight compounds (i.e. enzymes, antibodies and gene vectors) that are too large to diffuse through the tight junctions of the blood brain barrier (BBB) [1]. Moreover, it has been shown that low molecular weight compounds, though highly diffusive within brain tissue and tumors, have a limited distribution of just a few millimeters from the site of delivery due to loss via capillaries [1]. Direct infusion into the brain using convection-enhanced delivery (CED) as a supplement to diffusion is a technique that can circumvent these limitations by allowing one to utilize bulk flow to achieve much greater drug concentrations throughout the targeted area [1].
Bi-Material Attachment Through a Soft Tissue Interfacial System
Authors: Liu Y. X. , Thomopoulos S. , Birman V. , Li J.-S. , Genin G. M.
Published: July 2013

Connecting dissimilar materials is a fundamental challenge because of stress concentrations that can arise at their interface. “Functionally graded” material systems that interpolate spatially between properties of two materials are often considered to reduce stress concentrations in engineering and medical applications.
Image-Based Morphometry and Airflow Simulation in Rat Lungs
Authors: Oakes Jessica M. , Marsden Alison L. , Scadeng Miriam , Darquenne Chantal
Published: July 2013

Detailed knowledge of the fate of aerosols in the lung is essential in understanding the effect of exposure to airborne particulate matter and infectious agents and in assessing the efficiency of inhaled drug therapy. Detailed, yet non-invasive, studies of peripheral aerosol deposition are almost impossible in humans. Thus, understanding the fate of aerosols in the lung requires the use of computational and/or animal models in which more invasive techniques can be used. In this study, using magnetic resonance (MR) images of rat lungs, we (1) built three dimensional (3D) models of the airway tree and (2) quantified lobar volumes. Flow simulations were then performed in one of the airway models. Flow conditions were set to be similar to that used in an experimental study where rats were exposed to aerosols [1]. Airflow boundary conditions at the outlets of the airways are unknown and therefore typically a zero pressure boundary condition is prescribed [2]. To test the validity of the zero pressure condition, two types of boundary conditions were described: (a) zero pressure at each of the outlets and (b) flow resistance at each outlet. Flow resistance allows for the flow rate distribution to be defined based on lung volume and airway cross sectional area. The flow results from the computational model may be used to solve the particle dynamics equation and therefore allow for future comparison with the ventilation experiments.
A Model for Epithelial Migration and Wound Healing in the Avian Embryo
Authors: Futterman Matthew , Zamir Evan A.
Published: July 2013

It is increasingly clear that (collective) migration of epithelia plays an important role in morphogenesis and wound healing [6]. One of the interesting phenomena about epithelial migration is that the leading edge of the epithelia displays characteristics of both epithelia and cells undergoing EMT (epithelial-to-mesenchymal transition), so-called “partial” EMT. Developmental models in Drosophila and zebrafish have become important for studying signaling pathways involved in epithelial migration in recent years, but it is difficult to study the biomechanics of these systems. [2] Here, we revisit a little-used developmental model originally characterized by Chernoff [3] over two decades ago, which uses the area opaca (AO) of the chick embryo, an extraembryonic epithelium in birds which normally functions to spread across and encompass the nutritive yolk in a process called epiboly. We believe this model will be useful for studying epithelial migration because it is easily accessible and can be separated from the embryo to control the biomechanical environment.
A Longitudinal Study of Hemodynamics in a Functional Human Hemodialysis Fistula Using 3T Magnetic Resonance Imaging-Based Computational Fluid Dynamics Analysis
Authors: He Yong , Terry Christi M. , Berceli Scott A. , Cheung Alfred K. , Shiu Yan-Ting E.
Published: July 2013

An arteriovenous fistula (AVF) is the preferred vascular access for hemodialysis in end-stage renal disease. However, 60% of AVFs fail to achieve sufficient lumen dilation to allow adequate blood flow for chronic dialysis [1]. Although hemodynamics is likely an important modulator of AVF maturation and remodeling, the AVF hemodynamic spatial distribution profiles and their relationship with AVF maturation and remodeling are unclear [2]. Based on data collected from magnetic resonance imaging (MRI) of an AVF and computational fluid dynamics (CFD) simulations, we developed a protocol for longitudinal (over time) and noninvasive monitoring of geometry and hemodynamics of human AVF.
The Role of Actomyosin Contractility During Early Avian Gastrulation
Authors: Owen Drew , Zamir Evan
Published: July 2013

Actin-myosin contraction has been shown to play a major role in early morphogenetic movements in Drosophila (fly) and Xenopus (frog) [1,2]. However, the specific role of actomyosin contractility in amniote embryos (reptiles, birds, and mammals) during primitive streak (PS) formation, the “organizing center” for gastrulation (formation of three primary germ layers), is not known. Current theories regarding primitive streak formation in higher order amniotes center around cell-cell intercalation or chemotactic cell movement [3,4]. We hypothesize that contraction via actin-myosin (AM) filaments is conserved from anamniotes and drives formation of the PS and the associated morphogenetic cell movements.
Vortex Dynamics in the Left Ventricle During Diastole Under Edge-to-Edge Repair
Authors: Shi Liang , Hu Yingying , He Zhaoming
Published: July 2013

The edge-to-edge repair (ETER) is one of the mitral valve (MV) repair techniques frequently used in MV disease treatment. This technique restores valve competence by the suturing of the free edges of the leaflets either in the central position or at the commissure, depending on the location of valvular lesions. A direct consequence of this procedure is the modification in both shape and geometry of the MV orifices and thus of the fluid mechanics downstream of the MV during diastole [1].
A Novel Method of Characterizing Regional Lung Deformation
Authors: Amelon Ryan , Cao Kunlin , Ding Kai , Christensen Gary E. , Reinhardt Joseph M. , Raghavan Madhavan
Published: July 2013

Regional lung deformation (as opposed to whole lung volume change) may be an indicator of localized lung malformations. Regional deformation may be characterized by principal strains, but lack a direct physiological relevance. Alternatively, regional volume change (distribution of Jacobian) is physiologically intuitive, but does not characterize all aspects of deformation. For instance, a region may undergo no volume change, but still have deformed significantly — say, when the lengthening in one direction is compensated by contraction along another direction. From a perspective of physiological relevance to lung function, lung deformation may be thought to encompass both the volume change and directional preferences in volume change.
Fluid Pressure May Lead to Subchondral Bone Cyst Development via Mechanoregulated Bone Remodeling
Authors: Lagemaat M. W. , Cox L. G. E. , Reilingh M. L. , van Donkelaar C. C. , van Rietbergen B. , Blankevoort L. , van Dijk C. N. , Ito K.
Published: July 2013

Ankle trauma associated with an osteochondral defect (OD) of the talus often leads to subchondral bone cysts (Fig. 1, left). These cysts are associated with persistent ankle pain, thereby limiting the patients’ mobility [1]. Histology suggests that bone cyst development may occur in different stages, since some cysts are found to contain fluid, while others contain soft tissues. In addition, talar cysts may grow or shrink in time, and develop a sclerotic rim. The exact mechanism behind the development of talar cysts is unclear, but it has been proposed that fluid intrusion from the joint space through the OD plays a key role [1,2]. Pressurization of this fluid may have an osteolytic effect on the surrounding bone, thereby enlarging the cyst cavity.
Mechanoregulated Bone Remodeling May Explain Bone Structural Changes Observed in Osteoarthritis
Authors: Cox L. G. E. , van Donkelaar C. C. , van Rietbergen B. , Ito K.
Published: July 2013

Osteoarthritis (OA) affects both the articular cartilage and the subchondral bone. It is a complicated disease, associated with conditions varying from obesity and strenuous exercise to joint malalignment, anterior cruciate ligament (ACL) injury, and even metabolic bone diseases. Patients suffer from chronic joint pain and limitation of motion, and no cure is yet available. For many years, medical therapies have been focused on cartilage, because bone changes were thought not to play a major role in the OA disease process. However, it has been shown that bone changes occur in an early stage of OA, and that alterations to subchondral bone can lead to cartilage degeneration [1]. Therefore, currently the bone is considered as a therapeutic target as well.
Approach to Design Loading Protocols for Cartilage Tissue Engineering: Hypothesis, Experiment and Model
Authors: van Donkelaar C. C. , Khoshgoftar M. , Kock L. M. , Ito K.
Published: July 2013

Tissue engineered cartilage has reached the level of maturity where the cells, either chondrocytes, BMSC’s or other cells are stimulated to produce a tissue of which the biochemical content qualitatively resembles that of native cartilage. Quantitatively, the proteoglycan content approaches that of native content in long term cultures, but to obtain native collagen fractions is still challenging. Engineered cartilage matrix is either homogeneously distributed, or shows gradual variation from the periphery to the center, caused by nutritional effects.
Using K’NEX to Understand and Teach Concepts in Movement Biomechanics
Authors: Charles Steven
Published: July 2013

In order to analyze the kinematics or model the dynamics of human motion, one must be able to abstract from the intricate anatomy of the body the mechanical linkages and kinematic constraints which best approximate the joints of the body. Given the number and complexity of joints in the human body, this abstraction can be a challenging task, especially for students. While rotations about a single degree of freedom are easy to grasp, rotations about multiple DOF, which occur commonly throughout the body (e.g. shoulder, wrist, ankle, etc.) are anything but trivial. Likewise, the kinematics or dynamics of mechanical linkages such as the upper or lower limb quickly become unwieldy. To deal with these challenges, students learn to use tools from mechanics and robotics (body- and space-fixed reference frames, transformations, generalized coordinates, etc.), but these concepts can themselves be challenging and certainly take time to learn.
Flatfoot and Its Surgical Treatments: a Computational Model of Common Procedures
Authors: Iaquinto Joseph M. , Wayne Jennifer S.
Published: July 2013

Adult Acquired Flatfoot Deformity (AAFD) is a multi-stage degenerative joint disease. Common indicators are distinct morphological anomalies of the affected foot and the presence of pain and/or weakness along the posterior tibial tendon path. Early treatment (Stage I) can effect favorable results with nonoperative techniques including shoe orthotics. Surgical treatment begins at Stage II, which is characterized by more profound deep tissue damage to ligaments and tendons of the arch. The level of severity increases in Stages III and IV with significant joint damage including to the ankle [1].
Use of a Social Networking Recommendation Engine in Science and Engineering Education for Accessible Discovery, Organization and Collaboration of Research Knowledge
Authors: Azimi Mohammad , Mofrad Mohammad R. K.
Published: July 2013

The World Wide Web is the primary tool used by researchers in the field of science and engineering to share knowledge. Whether students or researchers are trying to share their own discoveries or learn from the discoveries of others, they rely on the Internet as a resource where this information is gathered. The use of the Web for the exchange of scientific knowledge has to date remained very static. Websites such as Google Scholar [1] and PubMed [2] help students and researchers by indexing published journal articles based on research topic, content and keywords but are limited in that they lack the capability to suggest and rank articles in a useful manner to those new to the field. Simply put, there is no shortage of efficient search algorithms to find specific articles but these algorithms cannot help a student or new researcher that is not familiar with the research area or the search terms that should be used. Furthermore, when the student or researcher’s primary language is not English, the task of finding appropriate articles becomes significantly more challenging. Our objective is to create a recommendation engine to assist students and researchers with the discovery and organization of scientific and engineering knowledge and to present it in a manner that allows effective discussion to take place. In addition, such a recommendation engine should be capable of providing the user with an assessment of their contribution to the social network not only based on the number and quality of articles submitted but also the discussions that the user contributed to.
A Computational Study of Complex Varus Instability of the Human Elbow Joint
Authors: Spratley Edward M. , Wayne Jennifer S.
Published: July 2013

The intact human elbow joint is one of the most inherently stable joints of the body with stability conferred through a complex interplay between highly congruous osseous constraints, capsuloligamentous constraints, and active muscle contractions. [1, 2] Deficits in any of these structures can create instabilities that impede normal joint function.
Coaptation Mechanism of Dilated Mitral Valves
Authors: Gao Bo , He Zhaoming
Published: July 2013

Functional mitral regurgitation, which occurs as a consequence of regional of global left ventricular or global left ventricular dysfunction despite structurally normal mitral valve (MV), is a common complication in patients with ischemic or non-ischemic cardiomyopathies [1].
Choline Chloride Improves the Desiccation Tolerance of Chinese Hamster Ovary Cells
Authors: Chakraborty Nilay , Menze Michael A. , Elmoazzen Heidi , Hand Steve C. , Toner Mehmet
Published: July 2013

Recently there has been much interest in using sugars such as trehalose to preserve mammalian cells in a dry state as an alternative to cryopreservation (1–5). However, some studies indicate that sugars alone may not be sufficient to prevent cell injury during drying. Other factors like sodium toxicity, ionic imbalance and pH excursions during dehydration are a few of the mechanisms that have been hypothesized to decrease the viability of mammalian cells. In the present study, we investigated whether or not substituting sodium chloride with choline chloride (2-hydroxy-N, N,N-trimethylethanaminium chloride) in the preservation medium improves desiccation tolerance of Chinese Hamster Ovary (CHO) cells.
Mechanisms of Head Injury During High-Rate Blast and Blunt Impact Events
Authors: Kraft Reuben
Published: July 2013

Blasts and blunt impacts are clearly large-scale phenomena, yet traumatic brain injury (TBI) occurs at a cellular or sub-cellular level. A number of hypotheses have been offered as the root causes of TBI including mechanical insults due to reverberations inside the skull following the primary blast wave, secondary and tertiary blast injury due to impact from projectiles and individuals thrown by the blast wave, vascular pressure resulting from a blast wave to the body extremities and electromagnetic radiation [1,2]. There is anecdotal information that supports, as well as contradicts, each of these hypotheses. In this work, a simulation-based framework is developed to help elucidate the mechanisms of traumatic brain injury.
Development and Biomechanical Characterization of a Novel Bilayer Vascular Graft
Authors: Madhavan Krishna , Bonani Walter , Lanning Craig , Tan Wei
Published: July 2013

Vascular grafts are currently used to treat cardiovascular diseases such as arthrosclerosis by bypass surgery and as vascular access in hemodialysis [1]. There are a number of types of grafts including autologous vessels (such saphenous vein), synthetic grafts (such as expanded polytetrafluoroethylene) and tissue engineered blood vessels. Currently synthetic grafts are most commonly used as blood vessel replacements and there are a number of problems associated with them. One main impediment is that these grafts are not suitable for small-diameter (less than 6mm) vessel replacement [1, 2], due to high occlusion rates. The major concern over the other alternatives such as autologous vessels and tissue engineered products is their availability. Thus, new approaches to constructing biomimetic small-diameter blood vessel equivalents, that are immediately available, may address the unmet demand in this area. Therefore, we have designed a novel bilayer vascular construct which is made up of a nanofibrous intimal-equivalent as thromboresistant vessel lumen and a mimetic extracellular matrix (ECM) as medial-equivalent for smooth muscle cells (SMC) from native artery to invade and remodel the ECM.
Computational Analyses of an In-Vitro Aneurysm Model Based on Three-Dimensional Angiography With Comparison to Phase Contrast Magnetic Resonance Imaging and Dye Injection Studies
Authors: George Stephanie M. , Watson Pierre , Oshinski John N. , Kerber Charles W. , Karolyi Daniel , Tong Frank C. , Giddens Don P.
Published: July 2013

Computational fluid dynamic simulation (CFD) is a valuable tool that has been used to understand some of the fundamental conditions of cerebrovascular flow. Current methods include anatomic modeling of cerebral aneurysms derived from vascular imaging such as MRA, CTA, and three-dimensional angiography. The input blood flow waveforms can be represented from either mathematical models or physiologic sampling of flow with phase contrast MR techniques or particle image velocimetry (1). While there has been general acceptance of the validity of computational fluid dynamics, some research suggests that there can be poor correlation between CFD flow calculations and directly measured flow (2). Therefore, the purpose of this study is to qualitatively compare flow patterns in a cerebral aneurysm model using data derived from three sources: (i) direct phase contrast MRA measurement in the model; (ii) CFD simulation using computer models created from three dimensional angiography, and (iii) previously published high speed injection dye studies.
Spatiotemporal Temperature and Cell Viability Measurement Following Laser Therapy in Combination With Carbon Nanohorns
Authors: Whitney Jon , Dorn Harry , Rylander Chris , Campbell Tom , Geohegan David , Rylander Marissa Nichole
Published: July 2013

Cancer remains one of the most deadly diseases today. Laser-induced photothermal therapy can provide a minimally invasive treatment 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. Prior studies have effectively used SWNHs combined with near infrared (NIR) laser light to target and destroy microbes [1]. We have previously reported increased tumor cell destruction when SWNHs were used in combination with laser therapy. The present work provides more extensive characterization of cell viability in response to laser therapy alone or in combination with SWNHs. Furthermore, the spatiotemporal temperature and cell viability in vitro in response to combinatorial SWNH-mediated laser therapies is determined using infrared thermometry and a novel viability algorithm, respectively. These new measurements will be critical for planning SWNH-mediated laser treatments where knowledge of the geometric distribution of temperature and cell death are critical to achieving the goal of selectively eliminating a tumor with specific spatial margins with minimal damage to surrounding healthy tissue.
Effects of Directional Oscillatory Shear Index on Endothelial Cell Proliferation and Morphology
Authors: Chakraborty Amlan , Jala V. R. , Bodduluri H. , Sharp M. Keith , Berson R. Eric
Published: July 2013

The effects of hemodynamic forces on cellular responses have been studied for the last three decades. Wall shear stresses (WSS) are commonly accepted as an important factor affecting anchored cells subjected to fluid flow [1, 2]. Parallel plate flow chambers and cone and plate apparatuses, which are commonly used to generate controlled shear, are limited in that only one experimental condition can be explored at a time. On the other hand, orbital shakers can be used to investigate several cases simultaneously since many culture dishes can fit on its platform. A remaining challenge, however, is that shear generated in dishes on orbital shakers is two-dimensional, nonuniform and is oscillatory in nature, and can be described analytically [3, 4] for only a few limited conditions. In this project, computational fluid dynamics (CFD) is applied to overcome those limitations by modeling the fluid flow in an orbiting petri dish for a range of conditions. In addition, cells grown under the same flow conditions were monitored for proliferation and morphology. A new directional oscillatory shear index (DOSI) is proposed to quantify the bidirectionality of oscillating shear. Cell proliferation, area, shape index and aspect ratio were investigated for different DOSI at different shear magnitudes.
Automatic Generation of Virtual Lumbar Motion Segments for Population-Based Simulation of Lumbar Spine Biomechanics
Authors: Huls Kelli S. , Petrella Anthony J.
Published: July 2013

Computational modeling of the spine has become a viable option for evaluating new implants and procedures. Most models described in the literature, however, represent only a single subject and neglect the normal variation that exists among specimens. A probabilistic simulation comprised of virtual specimens representing a broad population of subjects can address this limitation and be used to evaluate implants or procedures pre-clinically. Challenges exist to applying probabilistic modeling techniques to biologic systems, and perhaps the greatest is parameterization of the anatomy to capture normal variation in shape from specimen to specimen. It’s also critical to implement soft tissues in a robust, automated manner that produces representative biomechanics. The purpose of our research is to overcome these challenges and develop a probabilistic framework to perform population-based studies of lumbar spine biomechanics. This paper describes our results to date for the automated generation of virtual lumbar motion segments.
2D and 3D Morphologic Metrics Associated Intracranial Aneurysm Rupture
Authors: Ma Ding , Natarajan Sabareesh K. , Xiang Jianping , Siddiqui Adnan , Levy Elad I. , Mocco J. , Meng Hui
Published: July 2013

Intracranial aneurysms (IAs) rupture results in severe morbidity and mortality. Therefore indentifying IA rupture risk is highly critical. Although it has been recognized that IA rupture is the result of a complex vascular degeneration process involving multiple mechanobiological factors, such information for each patient is not readily available in clinical setting. Alternatively, morphology and hemodynamic metrics can be derived from routine patient-specific imaging. In previous studies, a number of morphological metrics derived from analysis of reconstructed vascular 3D geometry have shown significance in discriminating ruptured from unruptued IAs, including in particular aneurysm size ratio, defined as IA size divided by the parent vessel diameter. However, these measures rely on 3D image segmentation and measurement, which makes them less practical in current angiographic rooms often equipped with only biplane angiogram capability and even when 3D rotational angiography is available, on-site 3D image segmentation and analyses are still not practical. Our foregoing study examined three parameters measured on 2D angiographs: aneurysm Size Ratio (SR), Aspect Ratio (AR) and Size. We found that SR had the strongest correlation with IA rupture. The current study further evaluates these geometric metrics, measured both from 3D and 2D images, with a larger cohort of saccular intracranial aneurysms.
Computational Simulation of Articular Cartilage Wear in the Patellofemoral Joint During In Vitro Testing
Authors: Li Lingmin , Patil Shantanu , Steklov Nick , Bae Won , Temple-Wong Michele , D’Lima Darryl D. , Sah Robert L. , Fregly Benjamin J.
Published: July 2013

The mechanism by which altered knee joint motions and loads (e.g., following anterior cruciate ligament (ACL) injury) contribute to the development of knee osteoarthritis (OA) is not well understood. One mechanobiological hypothesis is that articular cartilage degradation is initiated when altered knee kinematics increase loading on certain regions of the articular surfaces and decrease loading on other regions [1,2]. If homeostatic loading conditions vary from region to region, then load changes induced by altered kinematics could initiate cartilage degradation in a site-specific manner. This hypothesis is attractive from a computational simulation perspective since it is based on mechanical factors that lend themselves well to physical modeling. If computational simulations could reproduce the knee OA development process, then they potentially could be used to facilitate the design of new or improved treatments for the disease.
A Computational Study of Unsteady Resistance to Cerebrospinal Fluid Flow in Type I Chiari Malformation
Authors: Shaffer Nicholas , Poppe George , Loth Francis , Wieben Oliver , Haughton Victor , Iskandar Bermans
Published: July 2013

Type I Chiari malformation (CM) is a complex disorder of the craniospinal system characterized by underdevelopment of the posterior cranial fossa and overcrowding of the normally developed hindbrain [1], and may be a precursor to more severe secondary disorders such as syringomyelia and hydrocephalus. Diagnosis of CM has proven to be difficult and may often take years to properly identify, as associated neurological symptoms may vary widely and overlap with symptoms of other disorders. Current methods of quantifying the severity of CM, such as radiographical measurement of the depth of hindbrain herniation into the spinal canal or measurement of posterior cranial fossa volume do not necessarily correlate to the symptom severity. Hence, there exists a need for a quantitative diagnostic method which may better characterize the severity of CM and, potentially, help neurosurgeons determine candidates for surgical treatment.
Effect of Mechanical Stimulation on Mesenchymal Stem Cell Seeded Cartilage Constructs
Authors: Wartella K. A. , Wayne J. S.
Published: July 2013

Articular cartilage is a specialized tissue with a restricted capacity for self-repair. Thus, there is a need for a functional tissue replacement product for cartilage due to the ever-increasing occurrence of cartilage injuries and osteoarthritis. Engineering a cartilage replacement construct entails a combination of source cells, cytokines/growth factors, differentiation factors, and a supportive structure to mimic the native environment [1]. An abundant source of cells, isolated from adult bone marrow, are mesenchymal stem cells (MSCs), which when isolated can be a rich cell source given their capacity for chondrogenic differentiation [2].
Biomolecule-Impregnated Nanocomposite With Spatiotemporal Control Over Release and Degradation Kinetic for Vascular Engineering
Authors: Bonani Walter , Motta Antonella , Migliaresi Claudio , Tan Wei
Published: July 2013

Autologous vessels are the gold standard for small-diameter (<6 mm) vascular bypass; however, many patients lack suitable autologous tissues due to diseases or prior vein harvest. As an alternative, synthetic vascular grafts made from bioinert synthetic materials such as polytetrafluoroethylene (PTFE) are currently used in the medical field. The high long-term failure rate of these materials in the replacement of small vessels is known to be associated with the lack of proper signalling events by PTFE to vascular cells causing adverse hemodynamic, inflammatory or coagulatory conditions. Therefore, constant and pressing is the demand for a more biocompatible conduit with structure and function similar to native vessels. For this reason, bioresorbable scaffold constructs which can provide not only proper mechanical support, but also precise molecular cues, are desired (1). In particular, proper degradation kinetics and molecule release profiles are needed to facilitate remodeling and integration process in vivo over the time for long-term patency (2).
Isolation of Human Breast Cancer Cells by Metastatic Stage Using Contactless Dielectrophoresis
Authors: Henslee Erin A. , Sano Mike B. , Schmelz Eva M. , Davalos Rafael V.
Published: July 2013

Dielectrophoresis (DEP) has become a promising technique to separate and identify cells and microparticles suspended in a medium based on their physical and electrical properties. DEP is the motion of a particle in a suspending medium due to the presence of a nonuniform electric field [1]. We have recently developed a robust, simple, and inexpensive technique, contactless dielectrophoresis (cDEP), to provide non uniform electric fields in microfluidic channels required for DEP cell manipulation without direct contact between the electrodes and the sample [2]. In this method, an electric field is created in the sample microchannel using electrodes inserted into two conductive microchambers, which are separated from the sample channel by thin insulating barriers. These insulating barriers exhibit a capacitive behaviour and therefore an electric field can be produced in the main channel by applying an AC field across the barriers [2]. The absence of contact between electrodes and the sample fluid inside the channel prevents bubble formation and avoids any contaminating effects the electrodes may have on the sample. Furthermore, reduced joule heating and a simplified inexpensive fabrication process are the other noticeable advantages of this new technique.
A Generalized Cross-Shear Wear Algorithm Based on a Novel Modification to Archard’s Law
Authors: Armstrong Jeffrey R. , Laz Peter J. , Rullkoetter Paul J. , Petrella Anthony J.
Published: July 2013

Archard’s Law [1] has been used extensively for computer simulation of UHMWPE wear in hip [2], knee [3], and disc replacements [4]. It is widely accepted that cross-shear motion increases wear, and models have been proposed to account for this effect [5]. Most of the cross-shear models described previously were designed to work for a specific joint or the models break down under some kinematic conditions [6]. The purpose of the current study was to develop a completely general cross-shear wear algorithm applicable to any geometry or sliding conditions. The proposed algorithm was based on a modified form of Archard’s Law and was implemented in an explicit dynamic finite element framework for validation against experimental wear data reported in the literature.
Biomechanical Properties of Self-Assembly Tissue Engineered Blood Vessels: Insights Into Assembly Techniques
Authors: Zaucha Michael T. , Gleason Rudolph
Published: July 2013

Coronary artery disease remains to be the leading cause of morbidity and mortality in industrialized nations. Current treatments for small diameter grafts are limited by the availability of suitable autologous vessels and high thrombogenic potential of synthetic grafts. There is a clinical need to development of tissue engineered blood vessels (TEBV) suitable for vascular by pass grafting.
Comparing the Pelvis Kinematics of Able-Bodied Children During Normal Gait and When Riding a Therapeutic Horse
Authors: Rigby B. Rhett , Garner Brian A. , Skurla Carolyn
Published: July 2013

The movement of the pelvis is important in many human activities including normal walking. Pelvic posture directly affects spine, head, and limb alignment, which are critical for proper musculoskeletal function and health [1]. The study of how the pelvis moves during normal human walking has been analyzed for more than 100 years. For individuals with neuromotor disabilities, exercises that increase the pelvic range of motion can improve posture and limb alignment and increase functional abilities [1].
Hemodynamic Metrics Correlate With Intracranial Aneurysm Rupture Status Better Than Morphologic Metrics
Authors: Xiang Jianping , Natarajan Sabareesh K. , Tremmel Markus , Ma Ding , Mocco J. , Siddiqui Adnan , Levy Elad I. , Meng Hui
Published: July 2013

Given the considerable risk of treating unruptured intracranial aneurysms (IAs), as well as the known severe morbidity of aneurysm rupture, elucidating those aneurysms that require prophylactic treatment can be a quandary. Traditionally, decision-making to treat an unruptured aneurysm was largely based on the Size of the aneurysm, but recent studies have failed to show significant correlation of Size with IA rupture, and a large number of ruptured aneurysms are small in Size.[1] Consequently, shape-based morphologic metrics have been explored in current investigations, and complex shapes have been correlated with rupture.[1] With the advancement of 3D angiography, and computational fluid dynamics (CFD) technology, patient-specific hemodynamics analysis has become feasible. Intra-aneurysmal hemodynamic factors, including wall shear stress (WSS), impingement regions, and oscillatory shear index (OSI), have been proposed as indicators for IA rupture risk.[2, 3] No study has rigorously examined both morphology-based and hemodynamics-based parameters from a uniform cohort to compare their relative importance. Our aim, therefore, was to identify significant morphologic and hemodynamic parameters that correlate with an aneurysm’s rupture status and examine whether hemodynamic parameters can separate ruptured and unruptured aneurysms better than morphologic parameters.
One Dimensional Experimental Setup to Study the Heating of Nanoparticle Laden Systems
Authors: Qin Zhenpeng , Bischof John C.
Published: July 2013

Intensive efforts have been put into the use of gold nanoparticles (GNPs) for the enhancement of hyperthermia using laser in recent years since the groundbreaking work of Hirsh et al.(1) using gold nanoshells (GNS). Both in vitro (2), and in vivo (3) studies show promising results. For example, GNS, a special kind of GNP, are being manufactured and are in clinical trials (Nanospectra Bioscience, Inc). While the data is compelling, unfortunately the fundamentals of GNP heating are not entirely understood. For example, there are large discrepancies in the experimentally measured photothermal efficiency of GNPs (4, 5). Furthermore, lumped models of GNP heating in solution, by using small volume of GNP solution (4, 5), or stirring the solution (6), neglecting the variation of heat absorption throughout a system require improvement. In reality, the GNPs will attenuate the laser beam as it passes through the GNP host medium. GNPs at different locations will absorb different amount of laser energy and hence have different heat generation.
Virtual Design for the Fontan Procedure: From Idealized to Patient Specific Models Using CFD and Derivative-Free Optimization
Authors: Yang Weiguang , Troianowski Guillaume , Birolleau Alexandre , Vignon-Clementel Irene , Feinstein Jeffrey A. , Marsden Alison L.
Published: July 2013

Single ventricle congenital heart defects are among the most challenging for pediatric cardiologists to treat. Children born with these defects are cyanotic, and these conditions are nearly uniformly fatal without treatment. A series of surgeries is performed to palliate single ventricle defects. The first stage consists of aortic reconstruction in a Norwood procedure. In the second stage, the Bidirectional Glenn procedure, the superior vena cava (SVC) is disconnected from the heart and redirected into the pulmonary arteries (PA’s). In the third and final stage, the Fontan procedure, the inferior vena cava (IVC) is connected to the PA’s via a straight Gore-Tex tube, forming a T-shaped junction with or without offset. Patient specific modeling tools provide a means to evaluate new designs with the goal of lowering long-term morbidity and improving patients’ quality of life.
Mechanically-Induced Cytoskeletal Remodeling in 3D Cultures of Contractile Fibroblasts
Authors: Lee Sheng-Lin , Pryse Kenneth M. , Butler Boyd , Elson Elliot L. , Genin Guy M.
Published: July 2013

Fibroblasts are responsible for collagen biosynthesis and organization in connective tissues, and play a role in regulation of epithelial differentiation, regulation of inflammation, and wound healing. Increasing evidence suggests that fibroblast might promote tumors by facilitating angiogenesis and cancer progression [1]. They are coupled mechanically to their fibrillar extra-cellular matrix, which can regulate cell behavior through its composition and mechanics.
Engineering the Functional Maturation of Nanofiber-Based Human Meniscus Tissue
Authors: Baker Brendon M. , Silverstein Amy M. , Shah Roshan P. , Mauck Robert L.
Published: July 2013

The meniscus is a fibrous tissue essential to healthy knee mechanics. It functions to redirect vertical forces laterally, converting compressive into tensile loads which are taken up by an array of highly organized collagen fibers. Load transmission is not only the operative mode of the meniscus, but is also required for normal development and homeostatic maintenance [1]. With injury, disruption of the aligned collagen fiber architecture impairs function, altering joint loading and initiating osteoarthritis. Toward engineering replacement meniscus tissue, we have investigated scaffolds of aligned electrospun nanofibers that direct cell orientation and provide a suitable microenvironment for the deposition of organized extracellular matrix (ECM) (Fig 1) [2]. In previous work, human meniscus fibrochondrocytes (MFCs) seeded on such scaffolds formed robust ECM with commensurate increases in tensile properties [3]. After 10-weeks of static, free-floating culture, however, mechanical properties still fell short of native tissue values. Over this time course, full-thickness MFC colonization was not observed due to the tight packing of nanofibers, although better infiltrated constructs revealed larger improvements in tensile properties. To accelerate cell ingress, we next explored composite scaffolds containing slow eroding poly(e-caprolactone) (PCL) fibers and water-soluble poly(ethylene oxide) (PEO) fibers that augment pore size when removed (Fig 4A-D) [4]. Based on this precedent, the current study explored two strategies for improving the maturation of MFC-laden nanofibrous constructs: dynamic tensile loading mimicking the in vivo mechanical environment and inclusion of sacrificial PEO fibers to enhance cell infiltration. We hypothesized that dynamic control of the mechanical and material microenvironment would improve matrix production and lead to enhanced mechanical properties.
Pressure Oscillation Tests of Porcine Aorta
Authors: Romanov Vasily , Assari Soroush , Laksari Kaveh , Darvish Kurosh
Published: July 2013

This paper addresses the problem of Traumatic Aorta Rupture (TAR) that is one of the causes of fatality in motor vehicle accidents. The mechanisms that have been suggested for TAR are speculative and inconclusive and a lot of the tests performed have not been repeatable. One of the reasons for these speculations is an incomplete understanding of the material properties of the aorta. The goal of this research is to study the response of the aorta to the oscillating pressure inputs in order to identify the structural properties of the aorta. The results of this study show that aorta stiffens as the rate of the loading increases, which is a characteristic of viscoelastic materials.
Testing of the Prototype Low-Durometer Hybrid III Neck for Improved Biofidelity
Authors: Paver Jacqueline G. , Caplinger Justin , Mattos Garrett , Friedman Donald
Published: July 2013

This study is part of an ongoing research project aimed at mitigating catastrophic human neck injuries, predominantly due to neck bending, in rollover crashes. Presently, the Hybrid III dummy is considered to be the best available human surrogate for dynamic rollover tests. However, there are known biofidelity and instrumentation limitations associated with its use to predict catastrophic neck injuries in real-world rollover crashes.

A previous study investigated the use of the non-biofidelic Hybrid III dummy in a dynamic rollover test to accurately predict the predominant human neck bending injury sustained in real-world rollover crashes. An empirical relationship between upper and lower Hybrid III neck loading was derived. The effects of neck preflexion angle, roof impact speed, roof crush, onset-to-peak neck axial forces and moments, and impact duration on neck bending injury were identified. Peak neck injury measures were rejected.

For this study, the 67-durometer Hybrid III production neck was fabricated with more compliant 35-durometer butyl rubber in order improve the dummy biofidelity in rollover tests. The tests in the previous study were repeated. Correlations were established between the prototype and production necks. Parametric studies of the prototype neck revealed similar trends as observed with the Hybrid III production neck.
A New Sensor Array for Measuring Intra-Articular Pressure: Evaluation and Validation
Authors: Welcher Judson B. , Popovich John M. , Tawackoli Wafa , Hedman Thomas P.
Published: July 2013

Deficiencies The lumbar facet joints are the major load bearing elements in the lumbar spine posterior column and they are considered one of the anatomical structures that can cause low back pain. They also contribute to the amount and type of lumbar spine motion.
Endothelial Cell Permeability and Alignment Quantification Under Shear Flow
Authors: Ting Lucas , Jahn Jessica , Sniadecki Nathan
Published: July 2013

Atherosclerosis develops when a breach in the protective endothelium allows macrophages and fatty lipids to enter into the intima. Atherosclerotic plaque material can harden the vessel or constrict blood flow through the vessel. In some cases, the plaque can detach and initiate a cardiac event (1). Hemodynamic shear can act as a mechanical factor that regulates the endothelial barrier by initiating a cellular mechanotransduction response that remodels the structure of individual endothelial cells (2).
A Novel Approach to Account for Non-Affine Fiber Kinematics in Structural Continuum Models for Heart Valves Leaflets
Authors: Sacks Michael S.
Published: July 2013

In the ongoing development of continuum models for soft tissues and related biological materials, structural approaches continue to have much appeal, and have the focus of our laboratory’s work (1). Structural constitutive models integrate information on tissue composition and structure, avoiding ambiguities in material characterization. However, critical structural information (such as fiber orientation) must be modeled using assumed statistical distributions, with the distribution parameters estimated from fits to the mechanical test data. Thus, full realization of structural approaches continues to be limited without direct quantitative structural information for direct implementation or to validate model predictions. While we have addressed these issues (2), non-affine fiber kinematics have been known to occur in heart valve leaflet tissues, especially under more extreme deformations (3, 4). However, current structural model theories continue to rely on the assumption of affine fiber kinematics. In present work we present a theoretical framework that accounts for non-affine deformations that still allows for the basic framework of the current structural models to be utilized.
Focal Adhesion Mechanotransduction: Molecular Events Leading to Vinculin Activation
Authors: Golji Javad , Mofrad Mohammad R. K.
Published: July 2013

Focal adhesions are formed as a molecular glue linking cytoskeletal actin filaments to the extracellular matrix (ECM). They are formed at the site of mechanical stimulation (1) and involve and initial recruitment of talin and vinculin to ECM bound integrin molecules at the site of external stimulation. Talin recruitment and its force-induced activation and subsequent interaction with vinculin have been extensively studied (2–4). Vinculin is natively in an auto-inhibited conformation and its activation involves removal of a steric hindrance preventing binding of Vt with actin (5) (Figure 1). Several hypotheses have been put forth regarding vinculin activation and its subsequent interaction with actin: 1) vinculin activation requires only interaction with talin at domain 1 (D1) (6), 2) a simultaneous interaction with both actin and talin is necessary to achieve vinculin activation (7), 3) once activated vinculin interacts with actin via an electrostatic interaction between Vt and two regions on F-actin (5). Each of these hypotheses is evaluated through molecular dynamics simulation and analysis.
Encapsulated Mesenchymal Stem Cells for Central Nervous System Repair
Authors: Barminko Jeffrey , Dolle Jean Pierre , Schloss Rene , Grumet Martin , Yarmush Martin L.
Published: July 2013

Mesenchymal stromal cells (MSC) have long been regarded as a cell source with the potential to provide therapies for various different tissue pathologies. They were originally identified for their ability to adhere to tissue culture plastic and gained favor due to their tremendous ability to propagate[1]. It was this finding as well as their ability to differentiate into lineages of mesoderm which have long made MSC a potential tool for autologous cellular replacement therapies [2, 3]. More recently, their cyto-protective role has been realized and been implicated in the benefit achieved in treating various different tissue pathologies. MSC have been found to secrete several different cytokines and growth factors in vitro. Furthermore, these factors can be modulated based on the environment MSC are exposed to. MSC have shown therapeutic benefits in models of GVHD, myocardial infarction, fulminant hepatic failure, central nervous system trauma and others, without any apparent cellular replacement. These advances propelled MSC to the fore front of potential cellular therapies and many are seeking to take advantage of their tissue protective properties. However, several draw backs in current methods of MSC implantation limit the ability to carry out safe and controlled clinical trials. Limitation with current MSC implantation approaches include; 1) directly transplanted MSCs exposed to the complex injury environment may be affected themselves early in the treatment processes, 2) MSC may also migrate to undesired tissue locations and 3) may differentiate into undesired end stage cells. These issues severally limit the translatability of MSC treatments in clinical settings; they make controlling experiments very difficult. There becomes a need to develop engineered methods for delivering these cells in a controlled manner. In order to circumvent these potential problems, we propose to use an alginate microencapsulation system as a vehicle for MSC delivery taking advantage of the soluble factors MSC provide.