bluuebunny/crossref_metadata_2025 huggingface dataset:
Decreased Knee Adduction Moment Does Not Guarantee Decreased Medial Contact Force During Gait
Authors: Walter Jonathan P. , D’Lima Darryl D. , Colwell Clifford W. , Fregly Benjamin J.
Published: July 2013

Medial compartment knee osteoarthritis (OA) plagues a large portion of the population [1]. The disease process is often initiated by changes in knee joint motions and loads, such as following anterior cruciate ligament or meniscal injury. Since overloading of the medial compartment in particular has been hypothesized to play a critical role, many treatment approaches have made reduction of medial contact force during gait their primary target.
Muscle Contributions to Medial-Lateral Acceleration of the Body During Walking
Authors: John Chand T. , Fox Melanie D. , Liu May Q. , Schwartz Michael H. , Delp Scott L.
Published: July 2013

Control of lateral balance during walking can be hindered by aging, stroke, or neuromuscular impairments [1, 2, 3]. Lateral balance can be characterized using the medial-lateral acceleration of the mass center of the body, yet the mechanisms by which muscles coordinate medial-lateral acceleration of the body mass center during walking are poorly understood. Elucidation of these mechanisms could help improve rehabilitative or surgical treatments for improving lateral balance in patients with walking impairments. For example, if the muscles that contributed most to medial-lateral acceleration of the body mass center were known, strengthening these muscles could be the focus of therapy. In this study, we analyzed a three-dimensional, muscle-driven simulation of unimpaired walking to quantify the contributions of individual muscles to the medial-lateral acceleration of the body mass center.
A New Biomechanical Model for Estimating Vertebral Loading in the Thoracic Spine
Authors: Iyer Sravisht , Christiansen Blaine A. , Roberts Benjamin J. , Valentine Michael J. , Manoharan Rajaram , Bouxsein Mary L.
Published: July 2013

Back pain is among the most common musculoskeletal complaints. To understand the etiology of back pain, biomechanical models are commonly used to estimate forces on the spine during activities of daily life. To date, these models have considered only the lumbar spine in healthy men due to interest in occupational low back pain. However, vertebral fractures and other injuries are also common in the thoracic region of the spine. Yet, the ribcage and sternum present technical challenges that necessitate different mechanical considerations in the thoracic spine.
Multiaxial Study of Fibroblast Biomechanics in a 3D Collagen Matrix
Authors: Bell Brett J. , Voytik-Harbin Sherry L.
Published: July 2013

It is becoming increasingly evident, that of the signaling modalities relevant to the cell-extracellular matrix (ECM) microenvironment, the mechanical component is a very important mediator of cell behavior (reviewed in [1, 2]). Indeed, proliferation, ECM protein expression (collagen), matrix metalloproteinase (MMP) levels, migration, and stem cell differentiation, have all been shown to be affected by mechanical environmental cues [3, 4]. Although the importance of physical signaling mechanisms has been well established, the bulk of this work has yet to be translated to a more physiologic 3D microenvironment [1]. Self-assembling collagen matrices provide a biochemically, biophysically relevant 3D model of soft tissues in which biomechanical studies can be performed [5, 6]. It is with this 3D tissue model in mind, that a biaxial mechanical testing system (BMTS) was devised, built, tested, and applied to the study of cell-ECM biomechanics. The completion of this device has enabled us, to undertake a multi-scale, multidimensional study of cell-ECM mechanics. Hierarchical quantification of cell and ECM strains using digital image correlation (DIC) facilitate a more complete understanding of the mechanical response of cells to macroscopic loads and deformations. Furthermore, transfection of cells with GFP tagged actin binding protein utrophin (UTR-GFP) enables qualitative assessment of cytoskeletal deformations [7].
Transient and Non-Newtonian Effects on the Wall Shear Stress Distribution of a Stented Artery
Authors: Mejia Juan , Mongrain Rosaire , Leask Richard , Bertrand Olivier F. , Cabau-Rodes Josep
Published: July 2013

For the last few decades stents have played a central role in the treatment of artherosclerosis. Although bare-metal stents (BMS) have significantly reduced levels of restenosis rates by 20 or 30% [1], restenosis rates remain high at around 25% [1]. The introduction of drug-eluting stents have reduced restenosis rates even further [2], but are associated with high risk of late thrombosis [3].
Geometric Standardization and Luminal Lubrication of Silicone Vascular Model for Neuroendovascular Simulation
Authors: Chueh Juyu , Gounis Matthew J.
Published: July 2013

Artificial cerebrovascular replicas present realistic vascular geometry and have versatile applications in the development and testing of medical devices. Different methods for construction of patient specific silicone vascular models have been proposed previously; however, due to the variations in the cerebrovascular anatomy, results obtained from these models may not be generalized to the entire population. To prepare a geometrically standard model, vessel characterization is necessary. Common attributes measured to quantitatively describe blood vessels include diameter, length, branch angle, and tortuosity, and among them, tortuosity evaluation is widely discussed. To date, tortuosity lacks a universal definition, but is generally used to summarize curvature information along the centerline of a blood vessel.
Effect of the Compliance of a Femoral Artery Bifurcation on Hemodynamic Characteristics
Authors: Kim Young Ho , Kim Jong-Eun , Anayiotos Andreas
Published: July 2013

Atherosclerosis is widely accepted as the main causative factor in the development of lower limb peripheral arterial disease (PAD). Approximately 8 million Americans is affected by the PAD [1]. The atherosclerosis in PAD patients are frequently observed on the site at the femoral artery bifurcation [2].
Biaxial Compliance Changes of Mitral Valve Leaflets Following Radiofrequency Ablation
Authors: Norwood Carolyn G. , Merryman W. David
Published: July 2013

The mitral valve (MV), located between the left atrium and left ventricle of the heart, is responsible for preventing retrograde blood flow by closing during systole. There are two MV leaflets, anterior and posterior. The anterior is the larger of the two and semicircular; the posterior leaflet is more rectangular and can be subdivided into three scallops, the middle scallop being the largest in most human hearts. The two leaflets are anchored to the wall of the left ventricle by the chordae tendinae. The MV annulus forms a complete fibrous ring anchored along the anterior leaflet (1).
Bioengineering Quantification of Left Ventricular Remodeling Following Myocardial Infarction
Authors: Wu Changfu , Chang Won-Bae , Gibber Marc , Bartley P. Griffith , Wu Zhongjun J.
Published: July 2013

Myocardial infarction (MI)-induced heart failure is the prevailing cause of morbidity and mortality in the western world. It is the sequela of the deleterious left ventricular (LV) remodeling process. So far, the mechanisms of the cardiac remodeling process are not completely understood. A clinically relevant large animal model is an essential vehicle for studying the mechanisms of cardiac remodeling. In our laboratory, we have developed a reproducible ovine model of post-infarct chronic cardiac remodeling. Throughout the study period of an animal, the functional and geometric changes of the LV were monitored by echocardiographic and bioengineering means.
Muscle Stimulation Waveform Timing Patterns to Increase Muscular Endurance in Functional Electrical Stimulation Pedaling Using a Forward Dynamic Model
Authors: Hakansson Nils A. , Hull Maury L.
Published: July 2013

Functional electrical stimulation (FES) pedaling can provide spinal cord injured (SCI) individuals with cardiorespiratory and muscular strength benefits. A limiting factor in FES pedaling benefit to the SCI population is the low endurance of electrically stimulated muscle. Because a reduction of the force-time integral for a single muscle group leads to an increase in the duration of the force generating capacity of the muscle group [1–2], we sought to test whether reducing the stress-time integral of multiple muscle groups working together could increase the endurance and work performed during FES pedaling. To this end, the objectives of this study were to: 1) compute the electrical stimulation timing patterns that minimize the stress-time integral of the muscles used to pedal a FES ergometer, 2) compare the simulated mechanical energies generated by the muscles with the computed electrical stimulation on and off times, and 3) test the efficacy of the computed electrical stimulation timing patterns in an experimental setting.
Towards Non-Invasive Assessment of the Elastic Properties of the Spinal Aqueduct
Authors: Martin Bryn A. , Royston Thomas J. , Oshinski John N. , Loth Francis
Published: July 2013

Analytical models are developed for cerebrospinal fluid (CSF) pressure wave propagation speed based on viscoelastic properties and geometry of the subarachnoid space (SAS). The models were compared to experimental tests on various compliant coaxial tube phantom models of the spinal SAS having different thicknesses and mechanical properties, with the ultimate goal of developing a noninvasive in vivo technique for determining the elastic properties of the spinal aqueduct. The in vitro models were constructed based on a healthy persons’ spinal geometry and properties, and the generation of pressure waves in it mimics the in vivo mechanism. Results suggest that pressure wave propagation is a weighted combination of two types of wave motion inherent to the coupled fluid-structure system. Additionally, theoretical and experimental studies indicate that the spinal cord (SC) mechanical properties do not play a significant role in wave speed propagation through the system, whereas mechanical properties of the encasing structures of the spinal aqueduct (SA) do influence wave speed.
Carbon Nanohorns as Photochemical and Photothermal Agents
Authors: Sarkar Saugata , Lutkus Amy , Mahaney James , Dorn Harry , Campbell Tom , Geohegan Dave , Rylander Marissa Nichole
Published: July 2013

Laser therapies based on photochemical or photothermal mechanisms can provide a minimally invasive and potentially more effective treatment alternative to conventional surgical resection procedures by delivering prescribed optical/thermal doses to a targeted tissue volume with minimal damage to intervening and surrounding tissues. However laser therapy effectiveness is limited due to nonspecific excitation/heating of target tissue which often results in healthy tissue injury. Nanostructures targeted to tumor cells and utilized in combination with laser excitation can enhance treatment effectiveness by increasing thermal deposition and generating toxic photo-chemical mediators in the form of reactive oxygen species for targeted cell destruction.
Time-Dependent Mechanics of Elastin Network
Authors: Zou Yu , Xu Bin , Chow Ming-Jay , Zhang Katherine Yanhang
Published: July 2013

The viscoelastic properties of elastin are closely related to its microstructures and the external mechanical and chemical environments. The elastin network in the medial layer of arteries consists of hydrated microfibrils that are approximately 3μm in diameter, which are assembled into the lamellar structures at the microscopic level. In previous work, molecular probe techniques have been used to characterize the organization of purified elastin [1]. The microfibrils were found to contain a network of water-filled pores accessible to solutes with molecular weights below 1000 daltons. The water spaces between and around fibrils were accessible to much larger solutes. The intra- and extrafibrillar compartments can be modified by mechanical stresses, chemical environment, osmotic pressure, and temperature.
Utilization of Biocompatible Ferrous Particles for a New Cancer Therapy
Authors: Evrensel Cahit A. , Welniak Lisbeth A. , Fuchs Alan , Patel Jigar , Murphy William J. , Gordaninejad Faramarz
Published: July 2013

Magneto-rheologiacal Fluid (MRF), suspensions of polarizable micron size particles, is synthesized from suspensions of iron particles (micron and nano size) in phosphate buffered saline (PBS). The iron particles have been surface coated using atom transfer radical polymerization (ATRP) with various polymers, such as poly(N-isopropylacrylamide) (poly(NIPAAm)), and poly(acrylamide) (poly(AAm)). The surface grafted polymer has been characterized using differential scanning calorimetry (DSC), and properties of resulting fluid have been measured using a rheometer.

A mathematical model is developed to explore the force induced by the particles on the neighboring tissue under externally applied magnetic field. This force results in the damage of the tumor cell lines and trigger the immune system response.

The effect of MRF on primary and metastasized tumor growth were evaluated by using an orthotopic murine breast cancer model (4T1). Tumors were evaluated by growth measurements and histological changes following injection of MRF or carrier fluid alone into the tumor and the effects of subsequent application of a magnetic field to the site. Results indicate slowed tumor growth and increased dendritic cell activation with this therapy and they are encouraging.
Correlation Between the Nano-Structure and the Macro-Mechanics of the Human Intervertebral Discs
Authors: Aladin Darwesh M. K. , Cheung Kenneth M. C. , Ngan Alfonso H. W. , Chan Danny , Leung Victor Y. L. , Lim Chwee Teck , Luk Keith D. K. , Lu William W.
Published: July 2013

The intervertebral disc (IVD) consists of three major components: the gelatinous nucleus pulposus (NP) at the centre, surrounded by concentric layers of annulus fibrosus (AF), and the superior and inferior endplates sandwiching the AF and NP intact. Collagen fibrils are the main structural components in all three parts of the disc. The dry mass of collagen in the IVD is about 70% [1]. The outer AF is predominantly collagen I with minor traces of collagen II. A gradual replacement in the collagen I by collagen II occurs in the inner regions [2]. Lumbar disc degenerative disease or early-onset disc degeneration is a primary cause for sciatica and low back pain in young individuals. The most significant biochemical change that occurs in disc degeneration is the loss of proteoglycans in the nucleus pulposus [3]. The mechanical inability of collagen fibrils to withstand the load may be one of the factors causing the loss of proteoglycans. The reason why collagen degrades may be environmental or genetic [4,5]. Researchers are working on developing tissue engineered disc replacements, stem cell therapy etc. to treat disc degeneration. Understanding the disc environment at the nano level is essential in order for these techniques to be clinically successful, as it is well known that the environment in the extracellular matrix plays an important role in determining the stem cells’ fate [6]. Therefore, in order to gain a better understanding on the role played by these matrix proteins, this study aimed at evaluating the correlation between the nano scale properties of the disc collagens with the disc tissue’s macro mechanics.
An Alternative Technique for Dielectrophoretic (DEP) Cell Manipulation: Contact-Less DEP
Authors: Shafiee Hadi , Sano Michael B. , Caldwell John , Davalos Rafael V.
Published: July 2013

Dielectrophoresis (DEP), the motion of a particle due to its polarization in the presence of a non-uniform electric field, can be used as an alternative to current sample enrichment techniques [1]. While the technique has been proven effective, most DEP devices must be manufactured using complicated processes. Insulator-based dielectrophoresis (iDEP) is a practical method to obtain the selectivity of dielectrophoresis while overcoming the robustness issues associated with traditional dielectrophoresis platforms [2]. While both of these methods allow for the differentiation of cells based upon their intrinsic electrical properties, they require direct contact between electrodes and a sample fluid, which can induce fouling, bubble formation and unwanted electrochemical effects [3]. We have developed an alternative method to provide the spatially non-uniform electric field required for DEP in which electrodes are not in direct contact with the biological sample. In this method, an electric field is created in the sample microchannel using electrodes inserted into two other microchannels (filled with conductive solution), which are separated from the sample microchannel by thin insulating barriers. These insulating barriers exhibit a capacitive behavior and therefore an electric field can be produced in the main channel by applying an AC field across them. 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.
Assessment of Local Bone Quality of the Distal Radius Using a Novel Hard Tissue Diagnostic Instrument
Authors: Salas Christina , Marmor Meir , Chu Thomas , Hansma Paul , Matityahu Amir , Buckley Jenni M.
Published: July 2013

Senile osteoporosis has been defined as a skeletal disorder characterized by a deterioration of bone matrix with an increase in susceptibility to fracture with increasing age (1). Studies have shown that over 25 million Americans are currently afflicted with osteoporosis and/or osteopoenia, with this number doubling by 2020. (2) (3) With the propensity for fracture being large in older osteoporotic patients, quantification of bone mineral density (BMD) is essential for proper implant selection in the event of a fracture. Dual energy x-ray absorptiometry (DEXA) is the clinical gold standard for BMD assessment; however, the hardware associated with this technique is neither portable nor appropriate for intraoperative use, and both of these qualities are occasionally necessary clinically.
Development of a Solid Model Based Method for Investigating Facet Articulation
Authors: Cook Daniel J. , Cheng Boyle C. , Jegapragasan Mithulan , Cuchanski Mathieu
Published: July 2013

Facets make up two of the three joints within the three joint complex found in any given FSU.[1] The methods currently discussed in the literature relevant to facet measurements have employed suboptimal methods of characterizing the facet and the effects from various treatments. A noncontacting, nondisruptive method of facet measurements is needed in order to fully understand the role of the intact facet joint. Articulation, characterized by facet proximity with facet joint capsules kept intact may be an important method in determining facet response.
Effect of Estrogen on Viscoelastic Properties of the Anterior Pouch of the Macaque Animal Model of the Inferior Glenohumeral Ligament
Authors: Gardner Thomas R. , Cassilly Ryan T. , Jin Brian , Mkparu Anuli N. , Ahmad Christoper S. , Bigliani Louis U. , Levine William N.
Published: July 2013

The effect of hormone treatment on the material properties of ligaments has been extensively studied for the anterior cruciate ligament (ACL). However, there have been very few studies on the effects of hormones on the material properties of the shoulder. These shoulder ligaments contribute to overall shoulder stability, and a change in ligament properties could contribute to a change in overall shoulder laxity. This study uses female cynomologus macaque (Macaca fascicularis) monkeys as an animal model of the human shoulder to determine if estrogen has an effect on the viscoelastic properties of the anterior pouch of the inferior glenohumeral ligament (IGHL). Cynomolgus monkeys have served as nonhuman primate models in several studies, including monkey models of menopause, the effects of hormone replacement therapy on the cardiovascular system, reproductive support organs, and the knee joint. The cynomolgus macaques are commonly used for studies involving hormone replacement therapy because they have 28-day menstrual cycles with very similar hormonal patterns to that of women.
Novel Differential Surface Stress Sensor for Detection of DNA Hybridization
Authors: Kang Kyungho , Nilsen-Hamilton Marit , Shrotriya Pranav
Published: July 2013

A fiber optic coupled interferometric system designed to measure differential surface stress induced by DNA hybridization of (dA)30 single-stranded DNA (ssDNA) with complementary (dT)30 ssDNA in aqueous environment. The sensing system is amenable to miniaturize into a single MEMS-chip and performed direct detection of nanomechanical response of conformational change and the corresponding charge transduction during molecular adsorption. The static deflection of functionalized sensing cantilever respect to reference cantilever which passivated from additional target molecules converts into a surface stress change for quantitative analysis. The measured surface stress changes were turned to be 40 to 110 mN/m for the concentrations of 0.1 to 1.0 μM of target molecules associated with the dissociation constant (Kd) of 168 nM. X-ray photoelectron spectroscopy (XPS) analysis and noncomplementary experiments were also considered for the validity and reliability of the system.
Abnormal Hemodynamics in Post Communicating Artery After Coil Embolization
Authors: Hyun Sinjae , Albanese Erminia , Quiroga Monica , Russo Antonino , Ulm Arthur J.
Published: July 2013

Cerebral aneurysms are dilatations, or bulges, in blood vessels of the brain. They can occur in an endless variety of shapes and sizes and some of them can be harmless, while others can rupture and cause bleeding into the subarachnoid space, or the space between the brain and the skull. Once this occurs, a number of complications can develop such as hydrocephalus, vasospasm, stroke, and nerve damage, and the chance of survival is 50% [1]. It is estimated that approximately 2% of the United States population has cerebral aneurysms, and roughly 27,000 patients per year are reported to have ruptured aneurysms [2].
Desiccation Dependent Structure and Stability of an Anhydrobiotic Nematode Late Embryogenesis Abundant (LEA) Protein
Authors: Li Dai-xi , He Xiaoming
Published: July 2013

A number of organisms have been found to be capable of surviving severe water deficit as a result of extreme drought and cold in nature by entering a state of suspended animation (i.e., anhydrobiosis or life without water) [1]. Although the precise molecular repertoire of desiccation tolerance in anhydrobiotic organisms is still not fully understood, results from recent studies indicate the crucial role of stress proteins such as the late embryogenesis abundant (LEA) proteins [2]. LEA proteins have been proposed to play a variety of roles in protecting biologicals from damaging by dehydration stress such as molecular chaperone and shield, ion chelator, antioxidant, and space filler. The multifunctional capacity of LEA proteins has been attributed in part to their structural plasticity: they are unfolded and when fully hydrated and become folded during water deficit [1]. However, the structural stability of LEA protein in response to desiccation is still not fully understood. In this study, the structure alteration of a group 3 LEA protein from an anhydrobiotic nematode (AavLEA1) [2] were investigated using the molecular dynamics (MD) simulation approach to understand the structural stability at different water contents.
Optimal Fusion Configuration Following C2 Corpectomy
Authors: Scheer Justin K. , Equizabal John , Currey Jovauna M. , Buckley Jenni M. , McClellan R. T. , Ames Chris
Published: July 2013

The upper cervical spine is a common location for metastatic tumors, which often necessitate surgical intervention to prevent neurological compromise [1]. Removal of the tumor often requires partial or complete resection of cervical vertebrae and therefore causes substantial mechanical instability in the cervical region [2]. Structural integrity is restored by fusion of the base of the skull to C5 using various spinal hardware, including cages and posterior screw-rod constructs. Due to the proximity of the spinal cord and vertebral arteries, these procedures have high associated morbidity and mortality, and the biomechanical necessity of more risky procedures, e.g., additional cages replacing the lateral masses of C2, in order to achieve sufficient rigidity has not been evaluated. Thus, the goal of this study is to determine the optimal fusion configuration following C2 corpectomy that maximized segmental rigidity while minimizing risk to the patient.
Novel Electrospun Nanocomposites With Controllable Compositional Gradient and Degradation Kinetics for Vascular Tissue Engineering
Authors: Bonani Walter , Motta Antonella , Migliaresi Claudio , Tan Wei
Published: July 2013

Vascular graft materials currently used in the medical field are often made from bioinert synthetic materials such as polytetrafluoroethylene (PTFE). 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 signaling events by PTFE to vascular cells causing adverse hemodynamic, inflammatory or coagulatory conditions. Tissue engineering approaches emerge as a promising method to obtain replacement vessels. These approaches are often based on homogeneous constructs or multilayer of homogeneous constructs are yet to demonstrate capability of controlling the integration of tissue engineering construct in vivo better for long-term patency. Therefore, constant and pressing is the demand for scaffold constructs which can provide not only proper mechanical support, but also precise molecular cues and degradation kinetics to facilitate the proper remodeling and integration process in vivo over the time for long-term patency. To this end, we have developed and demonstrated a novel double-electrospinning apparatus to obtain interpenetrating networks of nanofibers made from different polymers in a tailored proportion with heterogeneous gradient patterns of fiber materials and functional biomolecules.
Interactive Role of Adhesivity and Angle in Mucus Clearance by Simulated Cough
Authors: Ragavan Anpalaki J. , Evrensel Cahit A. , Krumpe Peter
Published: July 2013

Effects of viscoelastic properties of mucus simulants similar to that of healthy individuals and patients with severe lung diseases and adhesivity of mucus at four discrete angles (0°, 15°, 30°, and 45°) of a model trachea on displacement of mucus during cough at velocities in the range between 5 meters/second (m/s) and 30 m/s were investigated. Results indicated that displacement of mucus aliquot was enhanced significantly on adhesive surface compared to that on non-adhesive surface at all angles of the trachea, for both types of simulants in the velocity range studied. Results also showed that displacement increase with increasing angle of the trachea with respect to horizontal.
The Development of Running in Japanese Children: Foot Pressure Evaluation
Authors: Bishop Jennifer , Kouchi Makiko , Mochimaru Masaaki , Mientjes Martine , Pisciotta Jeff
Published: July 2013

Foot morphology and gait patterns of children have been explored in order to understand the developmental stages [1–3]. However, these studies have mostly focused on static and walking conditions. The purpose of this study was to investigate the development of running in children between the ages of 3 and 11 years and to investigate gender differences. This was done as a multi-lab, multi-country study; but the foot pressure results from the Japanese children are presented here.
The Effect of Arm Position on Hill-Sachs Engagement: A Finite Element Study
Authors: Walia Piyush , Miniaci Anthony , Jones Morgan H. , Fening Stephen D.
Published: July 2013

Bony lesions of the glenohumeral joint are important risk factors that often lead to recurrent anterior shoulder dislocation. A Hill-Sachs lesion is defined as bone loss from the posterior-superior aspect of the humeral head due to a compression fracture. It has been shown that the Hill-Sachs lesion is present in about 80% of initial dislocation cases and almost 100% of recurrent dislocations cases. The importance of the engaging Hill-Sachs lesion has been described by Burkhart and De Beer. The lesion is considered “engaging” when its long axis is parallel to the anterior glenoid, with the shoulder in a functional position of humero-thoracic abduction and external rotation.
Computational Analysis of Microstructure of Ultra High Molecular Weight Polyethylene for Use in Total Joint Replacement
Authors: Seymour Kelly M. , Atwood Sara A.
Published: July 2013

Ultra-High Molecular Weight Polyethylene, or UHMWPE, is a material commonly used as a bearing between metal components of a knee or hip replacement joint. The ultra-high component is frequently the cause of failure of the joint due to wear, fatigue, or fracture [1,2].
Numerical Simulation of Magnetic Nanoparticles Targeted at an Atherosclerotic Lesion in the Left Coronary Artery of Patient
Authors: Suo Jin , Tong Sheng , McDaniel Michael , Samady Habib , Taylor Robert W. , Bao Gang , Giddens Don
Published: July 2013

A numerical investigation simulating feasibility of magnetic drug targeting (MDT) at an atherosclerotic lesion of the left coronary artery of a patient using iron nano-particles coated with a therapeutic agent is reported. Progression of a plaque in the left coronary artery over a six month period was previously determined by intravascular ultrasound (IVUS). The site where the progression is active is located on the leeward side of the plaque. The proximal segment of the left coronary artery including the lesion was reconstructed by our 3D IVUS technique, and a Doppler measurement provided velocity waveforms in the lumen. These data are used to simulate blood flow employing computational fluid dynamics (CFD). Wall shear stress (WSS) and flow pathlines show that few nanoparticles would reach the active lesion region of the plaque. Therefore, MDT is considered as a possible effective therapy. Numerical investigations are performed to examine the feasibility for treatment by modeling hypothetical magnet fields, iron nano-particles, and coronary artery flow conditions. The magnetic field in the lesion segment produced by a permanent magnet located outside the lumen is calculated. The motion of the nano-particles in the segment is a combined result of the velocities produced by hemodynamic and magnetic forces. Various particles and magnets are investigated in the simulations. Two kinds of results are presented: the distribution of the magnetic force produced by the magnets, and the quantity of captured particles at the lesion during various time intervals (number of heart beats).
Comparison of Mechanosensitivity of Human Primary-Cultured Osteoblast Cells and Human Osteosarcoma Cell Line Under Hydrostatic Pressure
Authors: Ganji Yasaman , Kasra Mehran
Published: July 2013

Regarding to the advances in mechanical stimulation of cells, this study aims to address important issues in bone generation and therapy at cellular level as it relates to understanding of bone cell response to hydrostatic pressure as well as choosing a proper cell model in studies of bone cell response to mechanical stimulation. G292 human osteosarcoma cell line and human primary osteoblast cells were tested under cyclic hydrostatic pressure. Monolayer culture of cells were divided into three groups of control without loading, static with the pressure of 0.5 MPa, and dynamic with the pressure of 0.5 MPa and the frequency of 1 Hz. The cells were analyzed with measurement of alkaline phosphatase activity. Higher level of alkaline phosphatase activity in all groups of primary cell model compared with cell line model indicated more sensitivity of response of primary cells to this kind of loading.
A Quantitative Analysis of Kinetic Energy Harvesting for Hybrid Power Supplies
Authors: Romero Edwar , Carbajal Gerardo , Warrington Robert , Neuman Michael
Published: July 2013

This study presents a quantitative analysis of experimental data for extracting energy from human body motion and its possibility of powering portable electronic devices, such as consumer electronics or biomedical monitoring sensors. Since portable electronic devices are typically limited by the size and lifespan of batteries, energy harvesting shows potential as alternative for extending battery life. The acceleration was collected experimentally from 10 subjects while walking and running at different velocities on a treadmill. The acceleration results were studied and a figure of merit consisting of the acceleration-squared-to-frequency was found to determine, in addition to the quality factor, as the important factors for optimal energy harvesting. It was determined that from average walking an energy harvester can produce a power output density greater than 1mW/cm3.
Spatial and Temporal Control of Stem Cell Behavior in 3D Sequentially Crosslinked Macroporous Hydrogels
Authors: Marklein Ross A. , Burdick Jason A.
Published: July 2013

The effect of matrix mechanics on stem cell behavior has received considerable attention due to the implications of tissue mechanics as not only a consequence but also a contributor to the development of certain pathologies. For example, a significant increase in matrix mechanics (“tissue stiffening”) is a hallmark of post-myocardial infarction [1], as well as heart valve calcification [2]. Recently, human mesenchymal stem cells (hMSCs) have been implemented in post-infarct therapeutic strategies due to their potential ability to contribute to tissue healing through differentiation and trophic factor secretion. However, due to aberrant mechanics and other microenvironment cues, studies have reported deleterious effects of hMSC implantation, such as ectopic calcification [3], which agrees well with previous reports on hMSC differentiation in response to mechanics [4]. Although not as well documented as stem cell differentiation in response to mechanics, there has been some initial evidence in support of the influence of mechanics on stem cell trophic factor secretion [5].
Massive Cuff Tears Alter Joint Function and Decrease Cartilage Mechanics Following Return to Overuse Activity in a Rat Model
Authors: Reuther Katherine E. , Thomas Stephen J. , Sarver Joseph J. , Tucker Jennica J. , Lee Chang-Soo , Gray Chancellor F. , Glaser David L. , Soslowsky Louis J.
Published: July 2013

Rotator cuff tendon tears are common conditions which can alter shoulder joint function and over time, cause secondary damage to the surrounding tissues, including the cartilage and other remaining tendons. Glenohumeral joint stability is dependent on a dynamic balance between rotator cuff forces, in particular the subscapularis anteriorly and the infraspinatus posteriorly. An intact rotator cuff stabilizes the joint, allowing for concentric rotation of the humeral head on the glenoid. However, a massive rotator cuff tear involving the supraspinatus and infraspinatus may disrupt the normal balance of forces at the joint, resulting in abnormal joint loading. This is of particular concern in populations who perform activities requiring repeated overhead activity (e.g., laborers, athletes). Our lab has previously demonstrated that restoration of the subscapularis-infraspinatus anterior-posterior force balance improves shoulder function by providing a stable fulcrum for concentric rotation of the humeral head on the glenoid [1]. However, the long term consequences caused by disruption of the anterior-posterior force balance (supraspinatus and infraspinatus tear) on the glenoid cartilage and adjacent (intact) tendons, particularly in the case of an overuse population, remains unknown. Therefore, the objective of this study was to investigate the effect of disrupting the anterior-posterior force balance on joint function and joint damage using a clinically relevant overuse model system. We hypothesized that a disrupted anterior-posterior force balance (supraspinatus and infraspinatus tear) would result in H1) decreased joint function and H2) inferior adjacent tissue (glenoid cartilage, biceps and subscapularis tendon) properties compared to an intact anterior-posterior force balance (supraspinatus only tear).
New Tools for Understanding Extracellular Matrix Remodeling at the Micro-Level in Cardiovascular Tissue Engineering
Authors: de Jonge Nicky , Baaijens Frank P. T. , Bouten Carlijn C. V.
Published: July 2013

Cardiovascular tissues have a prominent load-bearing function. Collagen fibers in the extracellular matrix provide strength to these tissues. In particular the content and organization of these fibers contribute to overall strength [1]. In case of changes in mechanical demand, collagen content and organization can be adapted, a process referred to as remodeling. Collagen is therefore a key factor when creating load-bearing tissues via tissue engineering (TE). In order to optimize TE constructs we want to control the collagen content and organization, by either mechanical conditioning of the construct [2] or modification of scaffold properties (degradation, structure) [3, 4]. In mechanically-induced remodeling via conditioning strategies in bioreactors, collagen and cells are generally seen as the key players [5]. Collagen is able to bear the load applied on a tissue; cells sense and react to this load [6, 7]. In cardiovascular TE myofibroblasts are the cells of main interest. Myofibroblasts are mechano-sensitive and mechanically inducible [1], and contribute to alterations in the overall collagen architecture. To be able to optimize and control the collagen architecture and remodeling, via mechanical conditioning or scaffolds, an understanding of underlying mechanisms is needed specifically. Our aim is to provide new tools to study remodeling phenomena. Therefore we developed a 3D in vitro model system to study collagen remodeling at the micro level in real-time. Here we apply the model to investigate remodeling in tissues engineered without a carrier material, or scaffold.
CFD Challenge Using ANSYS CFX by a Clinical Neurosurgeon
Authors: Kono Kenichi , Terada Tomoaki
Published: July 2013

Kenichi Kono is a neurosurgeon at Wakayama Rosai Hospital in Japan. Tomoaki Terada is the head of the department of neurosurgery. Kono works as a neurosurgeon performing both endovascular treatments and open skull surgery. Kono also performs CFD simulations mainly on intracranial aneurysms.
Interactions With Spine During Abdominal Aortic Aneurysm Enlargement and its Biomechanical Effects
Authors: Zeinali-Davarani S. , Dupay A. , Baek S. , Lee W.
Published: July 2013

The role of spine and other surrounding tissues as geometrical constraints on abdominal aortic aneurysm (AAA) enlargement has been suggested [1] but its biomechanical effects among patients have not been thoroughly investigated yet. In this study, we use longitudinal CT images obtained from AAA follow-up studies and investigate geometrical features and their changes indicating interactions with spine during the progression of AAAs. We also study biomechanical effects of the interaction with spine on the AAA enlargement and stress distribution using growth and remodeling (G&R) model of AAAs.
The Role of Integrins in Osteocyte Response to Mechanical Stimulus
Authors: Haugh Matthew G. , McNamara Laoise M.
Published: July 2013

Bone is an exceptional material that is efficiently lightweight, possesses excellent mechanical strength and can also adapt itself in response to changes in physical activity by means of coordinated physiological processes known as modelling and remodelling. The response of bone to mechanical loading is thought to be regulated by mechanosensitive osteocyte cells that can direct the alteration of bone mass, by osteoblasts and osteoclasts, and thereby play an important role in optimizing bone strength. The mechanisms by which osteocytes sense their mechanical environment are not well understood. It has been proposed that integrin-based (αVβ3) attachments to ECM on osteocyte cell processes may facilitate mechanosensation in osteocytes [1,2]. While previous studies have shown that integrin beta;1 plays an important role in response to mechanical stimulus, the role of integrin αVβ3 in osteocyte mechanotransduction has yet to be investigated [3,4].
A New Pulse Contour Analysis for Cardiac Output Estimation: The Systolic Volume Balance Method
Authors: Vardoulis Orestis , Papaioannou Theodore G. , Stergiopulos Nikos
Published: July 2013

Cardiac output (CO) monitoring is essential for the optimal management of critically ill patients. Several methods have been proposed for CO estimation based on arterial pressure waveform analysis, known as “pulse contour cardiac output” (PCCO) monitoring. Most of them are based on invasive recording of blood pressure and require repeated calibrations, while they are still subject to inaccuracy under specific conditions. The Systolic Volume Balance (SVB) method was developed as a new non-invasive method based on physical principles and was further validated by a one-dimensional model of the systemic arterial tree. CO estimates were compared against the “real” CO values of the one dimensional model. 507 different hemodynamic cases were simulated by altering heart rate (HR), total arterial compliance (C) and total arterial resistance (R). It was found that CO can be accurately estimated by the new SVB formula. The bias between the brachial PCCO and the model’s CO was 0.042 L/min with 0.341 L/min SD of difference. The limits of agreement were −0.7–0.6 L/min indicating high precision. The intraclass correlation coefficient and the root mean square error between estimated and “real” CO values were 0.861 and 0.041 L/min respectively, indicating good accuracy and agreement.
Development and Optimization of a Novel Polymeric Prosthetic Heart Valve Using the Device Thrombogenicity Emulation (DTE) Methodology
Authors: Claiborne Thomas E. , Xenos Michalis , Sheriff Jawaad , Peter Dinesh , Alemu Yared , Kato Yasushi , Pinchuk Leonard , Einav Shmuel , Jesty Jolyon , Bluestein Danny
Published: July 2013

Calcific aortic valve disease (CAVD) is the most common and life threatening form of valvular heart disease, characterized by stenosis and regurgitation, which is currently treated at the symptomatic end-stages via open-heart surgical replacement of the diseased valve with typically either a xenograft tissue valve or mechanical heart valve. These options offer the clinician a choice between structural valve deterioration and anticoagulant therapy respectively, effectively replacing one disease with another [1]. Polymeric heart valves (PHV) offer the promise of reducing or eliminating these complications [2] and may be efficacious for patients who cannot tolerate cardiothoracic surgery by using instead transcatheter valve implantation (TAVI) [3], where there is evidence that tissue valves are damaged during implantation [4], and in pulsatile circulatory support devices such as the SynCardia Total Artificial Heart. But development of PHVs has been slow due to the lack of sufficiently durable and biocompatible formulations.
Linear and Angular Head Acceleration Measurement Collection in Pediatric Football
Authors: Daniel Ray , Rowson Steven , Duma Stefan M.
Published: July 2013

Mild traumatic brain injuries (mTBIs) from participation in sports and recreation activities have received increased public awareness, with many states and the federal government considering or implementing laws directing the response to suspected brain injury [1]. MTBIs may result from an impact or acceleration/deceleration of the head and leading to a brief alteration of mental status. Compared with adults, younger persons are at an increased risk for mTBIs with increased severity and prolonged recovery [2]. Football is one of the leading activities that individuals under the age of 19 will experience a mTBI during [3]. Therefore, football players are ideal candidates for monitoring head impact biomechanics and relating measurements to physiological alterations [4]. Little work has been performed investigating mTBIs in the youth population, thus little is known about the biomechanics involved with such injuries. The goal of this study is to characterize the head impact response in a youth population by instrumenting players on a youth football team.
Reactive Biomaterial for the Treatment of Herbicide Contaminated Drinking Water: Atrazine Dechlorination
Authors: Reátegui Eduardo , Reynolds Erik , Kasinkas Lisa , Aggarwal Amit , Sadowsky Michael J. , Aksan Alptekin , Wackett Lawrence P.
Published: July 2013

The herbicide atrazine is used for control of broadleaf weeds, principally in corn, sorghum, and sugarcane [1]. Atrazine is currently used in 70 countries at an estimated annual rate of 111,000 tons [2, 3]. Atrazine is typically applied early in the planting season. However, Heavy rainfall events, shortly after application may lead to detectable atrazine concentrations in waterways and in drinking-water supplies. The United States Environmental Protection Agency established a 3 ppb limit of atrazine in drinking water. In some instances, municipal water treatment plants use chemicals and other treatment processes, such as activated carbon, to reduce atrazine to below the 3 ppb legal limit for drinking water.
Walking Mode Classification From Myoelectric and Inertial Fusion
Authors: Miller Jason D. , Seyedali Mahyo , Hahn Michael E.
Published: July 2013

Transtibial amputees are generally restricted to the use of non responsive prosthetic systems which have been shown to require increased metabolic energy during normal gait [1] and can contribute to pain in the residual limb [2] among other unfavorable outcomes. Development of responsive lower limb prostheses is restricted due to the function of the human ankle which changes based on speed and type of locomotion. The ideal prosthetic would detect the patient’s motion intent to match both intensity and type of locomotion task. Implementation of motor intent detection should help restore normal limb function. Recent advances have shown the benefit of myoelectric and mechanical sensor fusion towards motion intent classifications. For upper limb amputees, a single accelerometer has shown benefit in classifying different types of hand grasps [3]. For transfemoral amputees a 6 axis pylon-implanted load cell has allowed increased walking mode classification accuracy [4]. It is believed that the continued exploration of EMG and mechanical fusion strategies will advance myoelectric control towards the development of commercially available systems for lower limb amputees. The purpose of the current study was to evaluate the potential for walking mode classification from both electromyography (EMG) signals and inertial measurements units (IMUs).
The Apparent Flexural Rigidity of the Flagellar Axoneme Depends on Resistance to Inter-Doublet Sliding
Authors: Xu Gang , Wilson Kate S. , Okamoto Ruth J. , Shao Jin-Yu , Dutcher Susan K. , Bayly Philip V.
Published: July 2013

Cilia are thin subcellular organelles that bend actively to propel fluid. The ciliary cytoskeleton (the axoneme) consists of nine outer microtubule doublets surrounding a central pair of singlet microtubules. Large bending deformations of the axoneme involve relative sliding of the outer doublets, driven by the motor protein dynein. Ciliary structure and function have been studied extensively, but details of the mechanics and coordination of the axoneme remain unclear. In particular, dynein activity must be switched on and off at specific times and locations to produce an oscillatory, propulsive beat. Leading hypotheses assert that mechanical feedback plays a role in the control of dynein activity, but these ideas remain speculative.