bluuebunny/crossref_metadata_2025 huggingface dataset:
A Mutlti-Scale FE Modeling Approach to Investigate the Contact Mechanics and Interfacial Stress of a Low Stiffness Porous Metal-Backed Acetabular Cup
Authors: Fang Zhibin , Kralovic Barbara J. , Son Yang W. , Levine Danny L. , Johnson Todd S.
Published: March 2014

In modern Total Hip Arthroplasty (THA), modular metal-backed acetabular cups consisting of a metal shell backing with porous coatings for fixation and a modular polyethylene liner for articulation are currently the most widely used cementless acetabular cups. Modular acetabular cups give surgeons the flexibility to change femoral head size, liner offset, and liner-lip buildup during hip arthroplasty as well as the ability to change the liner without removing a bone-ingrowth metal shell during revision surgery. However, concerns have been noted with modular metal backed acetabular cups. Poor locking mechanisms have been blamed for backside wear and polyethylene liner dislodgement as well as debris which may lead to osteolysis [1]. In addition, the study of the load transfer around acetabular cups has shown that a stiff metal backing generates high stress peaks around the acetabular rim while it reduces the stresses transferred at the central part of acetabulum potentially causing stress shielding at the dome of acetabulum [2].
Fatigue Loading Causes Earlier Modulus Reduction Than Creep Loading in Healing Rabbit Medial Collateral Ligaments
Authors: Bailey Soraya J. , Thornton Gail M.
Published: March 2014

During normal daily activities, ligaments experience a range of stresses. These stresses can be repetitive, sustained or a complex combination of the two [1]. The stress-strain curve of ligaments is comprised of two parts: the toe region with increasing modulus, and the linear region which has constant modulus. Normal physiologic loading occurs between 5% and 10% of the ultimate tensile strength (UTS), and the transition from the toe region to the linear region occurs at approximately 15% of UTS [2]. Ligaments healing from an injury have decreased failure properties compared to normal ligaments [3], which may correspondingly affect the ability of healing ligaments to function under physiologic loads. Modulus reduction was found to be a suitable marker of damage in normal ligaments [4]. The purpose of this study was to investigate the effect of long-term fatigue and creep loading on modulus changes in healing medial collateral ligaments (MCLs).
Large Scale Voxel-Based Finite Element Modeling of Normal and Early Glaucomatous Monkey Lamina Cribrosa
Authors: Kodiyalam Sanjay , Roberts Michael D. , Sigal Ian A. , Hart Richard T. , Burgoyne Claude F. , Downs J. Crawford
Published: March 2014

Glaucoma is a leading cause of blindness worldwide. Some of the chief clinical hallmarks of glaucoma are the permanent posterior cupping of the optic nerve head, in the posterior pole of the eye, and the accompanying damage to the lamina cribrosa — the fenestrated structure of connective tissue spanning the scleral canal that provides structural support to the axon bundles passing through it. While elevated intraocular pressure (IOP) is associated with this disease, its role remains unclear. It has been hypothesized that IOP-related stress and strain within the laminar connective tissue (LCT) underlie the onset and progression of glaucoma [1] and that they may be used to predict the location of axonal insult and the pattern of damage within the LCT.
The Effect of Soft Tissue on the Biomechanics of Skull Fracture due to Blunt Ballistic Impact: Preliminary Analysis and Findings
Authors: Raymond David E. , Crawford Greg S. , Van Ee Chris A. , Bir Cynthia A.
Published: March 2014

The majority of engineering studies that quantify the biomechanical response of the human head to blunt impacts have been focused primarily on replicating automotive-related trauma [1]. Relatively little biomechanical data exists on head response and skull fracture tolerance due to impacts with small surface area objects moving at high velocity, as can occur with the deployment of less-lethal kinetic energy munitions that are now available to police and military personnel. Law enforcement are trained to direct such munitions away from the head and at body regions least likely to sustain serious to life-threatening injury, such as the legs, however impacts to vital regions such as the head have occurred [2]. Previous research efforts have investigated facial impact response to blunt ballistic impacts however data regarding the temporo-parietal region are lacking and require study under these unique loading conditions [3]. Prior research has indicated that the scalp and soft tissue covering the skull are important factors to consider when studying impact response and skull fracture tolerance [4]. These data however have been limited primarily to impact velocities typical of the automotive crash environment. The purpose of this study is to evaluate the contribution of soft tissue to the biomechanical response and tolerance of the temporo-parietal region under blunt ballistic impact conditions.
Irreversible Electroporation (IRE) to Treat Brain Tumors
Authors: Garcia Paulo A. , Robertson John , Rossmeisl John , Davalos Rafael V.
Published: March 2014

Electroporation is the phenomenon in which permeability of the cell membrane to ions and macromolecules is increased by exposing the cell to short (microsecond to millisecond) high voltage electric pulses [1]. The application of the electric pulse can have no effect, can have a transient effect known as reversible electroporation, or can cause permanent permeation known as irreversible electroporation (IRE) which leads to non-thermal cell death by necrosis [1, 2].
Biomechancial Comparison of a Novel C1 Posterior Locking Plate With the Harms Technique in a C1-C2 Fixation Model
Authors: Kelly Brian P. , Glaser John A. , DiAngelo Denis J.
Published: March 2014

Current methods of atlantoaxial stabilization rely on screw fixation. Screw placement may be transarticular, or C1 lateral mass screws in combination with pedicle or pars screws at C2. These techniques can put the vertebral artery at risk. There is also dissection around the ganglion of the second cervical nerve root, which can lead to significant bleeding or postoperative pain.
Mathematical Modeling of Cell Damage and Death due to Hyperthermic Stress With Reaction Kinetic Formulation
Authors: Ishiguro Hiroshi , Nozawa Masakazu
Published: March 2014

In the applications of bioheat transfer, cells and tissues are exposed to various stresses from high and low temperatures, freezing, drying and chemicals, and resultantly they are damaged and dead However, the mechanism of cell damage and death due to the stresses is not sufficiently understood quantitatively. Also, mathematical model of cell damage and death for the prediction of cell lethality and viability is undeveloped. The prediction could contribute to design and optimization of the relevant devises and processes.
Mechanical Compression for Dehydration and Optical Clearing of Skin
Authors: Drew Chris W. , Rylander Christopher G.
Published: March 2014

The highly disordered refractive index distribution in biological tissue causes multiple-scattering of incident light and inhibits optical penetration depth. “Tissue optical clearing” increases penetration depth of near-collimated light in biological tissue, potentially resulting in improved optical analysis and treatment techniques. Numerous methods of tissue optical clearing have been hypothesized using hyperosmostic agents [1]. These methods propose reduction in light scattering by means of dehydration of tissue constituents, replacement of interstitial or intracellular water with higher refractive agents, or structural modification or dissociation of collagen fibers [2,3]. It has been suggested that dehydration of tissue constituents alone can reduce light scattering by expulsing water between collagen fibrils, increasing protein and sugar concentrations, and decreasing refractive index mismatch [4].
Cyclic Compression of Chondrocytes Counteracts Pro-Inflammatory Tissue Remodeling Induced by Interleukin-1
Authors: DiTullio A. E. , Park S. , Torzilli P. A. , Chen C. T.
Published: March 2014

Chondrocytes in tissue engineered constructs face challenging environments when first transplanted into a synovial joint, including high levels of compression/shear and pro-inflammatory cytokines. The joint level of interleukin 1 (IL-1) after trauma injury and in a repaired joint is acutely elevated. Matrix remodeling in tissue engineered constructs can be easily affected by the elevation and activation of aggrecanases (ADAMTS-4 and ADAMTS-5) and matrix metalloproteinases (MMPs) [2–4, 7–9, 11]. Several recent studies suggest that tensile loading and unconfined compression of chondrocytes has some anti-inflammatory effects against interleukin 1 (IL-1) by the downregulation of COX-2 and iNOS genes [1, 5, 6]. However, the role of loading in tissue repair at physiological levels is not clear. The objective of this study was to determine the effect of cyclic confined compression on the gene expression of MMPs and tissue inhibitors of metalloproteinases (TIMPs) in agarose-embedded chondrocytes in the presence of interleukin 1 (IL-1).
Kinetic Differences in a Subject With Two Different Prosthetic Knees While Performing Sitting and Standing Movements
Authors: Lura Derek J. , Highsmith M. Jason , Carey Stephanie L. , Dubey Rajiv V.
Published: March 2014

Advanced prostheses are currently being sold in consumer markets. The development of these advanced prostheses is largely a result of a better understanding of the biomechanics of human locomotion [1]. Powered and microprocessor controlled prostheses are offering better performance in a variety of movements and in the gait cycle. However the focus in lower limb prosthetics has been largely on locomotion (e.g. walking, stair gait and running). This study focuses on the sit and stand cycles of an individual with an Otto Bock C-leg and an Ossur Power Knee prosthesis, comparing his ability to utilize each prosthesis and comparing his cycle to that of a healthy (non-amputee) control subject. This study is part of a larger ongoing study of the sit and stand cycles seen in a large population of unilateral transfemoral prosthetic users of various kinds. The purpose of this study is to compare the difference in method of standing, and assistance provided by the prosthesis. With the knowledge gained from this study we hope to better understand the biomechanics of the sit and stand cycles, leading to better prostheses in the future.
Using Mesh Morphing to Study the Influence of Geometry on Biomechanics: An Example in Ocular Biomechanics
Authors: Sigal Ian A. , Yang Hongli , Roberts Michael D. , Downs J. Crawford
Published: March 2014

Biomechanical response is often influenced by the geometry (shape) of a system. Numerical techniques such as the finite element (FE) method offer the possibility of incorporating geometric details of a system into a mathematical model with a greater level of detail than is generally achievable with purely analytical models. In this vein, FE models of biological structures tend to fall into two broad categories: generic models and specimen-specific models. Generic models are attractive because the geometric features of interest may be cast as variable parameters that simplify analysis of factor influence, but may be limited in what can be predicted about a specific specimen. In contrast, specimen-specific models may contain a high level of geometric detail, but analysis of the influence of geometry can be more complicated.
CFD Study of Thrombus Formation on Shear Blood Flows by Using Modified Lattice Boltzmann Method and Thrombus Observation
Authors: Tamagawa Masaaki
Published: March 2014

This paper describes development of the prediction method of thrombus formation by Computational Fluid Dynamics (CFD) on pipe orifice shear flows. These shear flows are typical models of the flow in the rotary blood pump. In this investigation, the thrombus formation in blood plasma flow is visualized, and modified lattice Boltzmann method are used to predict the backward forwarding step flow, that is simple model of the orifice flow.
Multi-Probe Cryosurgical Configurations Extract Significantly Less Energy per Probe Than Single Probe Configurations: Implications for Clinical Cryosurgery
Authors: Zhang Xiaoqing , Leng Christoph , Shenoi Mithun M. , Bischof John C.
Published: March 2014

In the present study, the interaction between different cryoprobes was investigated in multi-probe configurations. Using a careful experimental and computational approach we show here that the ability of a single probe to cool (i.e. the cooling power of a probe governed by convective cooling of the cryogen within the probe) is greatly reduced in a simple dual probe configuration with 1.0–2.0 cm separation of these probes over the single probe case. One approach that shows promise for predicting multi-probe performance is the use of a “weighting factor” that governs this loss of cooling power in a given probe.
Droplet Evaporation in Capillary Bridges
Authors: Roman Dacian , Nerguizian Vahé , Stiharu Ion
Published: March 2014

The demand for precise and accurate medical instruments that are also cost-effective drove the design towards the concept of Lab-on-a-Chip. These miniature systems are usually built on a single die and are able to perform multiple test through the manipulation of minimum amounts of analytes and markers. Such chips have significantly changed the way the bio-tests are carried out. However, significant challenges associated with such tests are still to be addressed. The phenomena occurring in the capillary bridges drew the attention of the scientific community from the beginning of the nineteenth century and experiments were extensively carried out.
Biomolecular Activity Switch Actuated by Ultrafast Pulsed Laser Irradiation of Gold Nanorods
Authors: Alper Joshua , Crespo Monica , Jones Kevin , Tokmakoff Andrei , Hamad-Schifferli Kimberly
Published: March 2014

In the pursuit of improved medical, diagnostic and therapeutic solutions, scientists and engineers are interested in designing nanoscale machinery to perform a variety of tasks [1]. The most promising of these machines are comprised of natural biological systems or artificial systems that exploit nature’s machinery, namely proteins. In either case, scientists must exert control over proteins to harness the potential of nanoscale biomolecular machinery.
Sub-Micron 3D Fluorescent Imaging and Visualization of Remodeling Cavities in Cancellous Bone
Authors: Slyfield Craig R. , Tomlinson Ryan E. , Tkachenko Evgeniy V. , Neimeyer Kyle E. , Steyer Grant J. , Wilson David L. , Hernandez Christopher J.
Published: March 2014

The mechanical properties of cancellous bone are determined from a combination of bone quantity (volume), the material properties of the mineralized tissue, and microarchitecture. Bone remodeling is the primary process through which bone mass and structure are altered in the adult skeleton. Bone remodeling involves the coordinated activity of osteoclast and osteoblast cells, which resorb and then form bone at an isolated location on the cancellous bone surface. Because bone resorption precedes formation, each bone remodeling event in cancellous bone is associated with a temporary void on the bone surface known as a remodeling cavity. It has been proposed that remodeling cavities can act as stress risers, modifying stress distributions in cancellous bone and potentially impairing bone strength, stiffness and other mechanical properties. While high resolution finite element modeling supports the idea that remodeling cavities have the potential to modify mechanical properties at the micro-scale (in individual trabeculae) [1] and at the apparent level (entire cancellous bone specimens)[2, 3], the experiments required to confirm these findings are limited because a repeatable method of quantifying the number and size (length width and depth) of remodeling cavities in entire cancellous bone specimens has not yet been demonstrated.
Thermal Preconditioning Protocols for Cartilage Tissue Engineering
Authors: Chung Eunna , Rylander M. N.
Published: March 2014

Successful creation of cartilaginous engineered tissues is often limited by insufficient cellular proliferation and formation of extracellular matrix. Stress conditioning protocols using heat have been shown to induce up-regulation of molecular chaperones called heat shock proteins (HSP) [1]. These proteins have been linked to enhanced cell proliferation and collagen synthesis which is critical for formation of the extracellular matrix. Therefore, identification of effective thermal stress preconditioning protocols that enhance HSP expression could substantially advance development of replacement tissues for cartilaginous tissues [2]. Our project focused on identifying thermal preconditioning protocols that enhance HSP70 expression while minimizing cellular injury for ultimate use in improving cell proliferation and extracellular matrix formation for cartilage.
A Structural Multi-Mechanism Damage Model for Cerebral Arterial Tissue and its Finite Element Implementation
Authors: Li Dalong , Robertson Anne M.
Published: March 2014

Early stage cerebral aneurysms are characterized by the disruption of the internal elastic lamina (IEL). The cause of this breakdown is still not understood, but it has been conjectured to be caused by fatigue failure or alternatively by a breakdown in homeostatic mechanisms in the wall arising from some aspect of the local hemodynamics, e.g. [1].
Computational Model of Direct Injection Into the Spinal Cord Using in Vivo Diffusion Tensor Imaging
Authors: Kim Jung Hwan , Chen Xiaoming , Astary Garrett W. , Mareci Thomas H. , Sarntinoranont Malisa
Published: March 2014

Local infusion, i.e., convection-enhanced delivery (CED), is increasingly being considered as a means to deliver therapeutic agents to nervous tissues. These infusion techniques bypass the blood-brain barrier and overcome problems associated with slow diffusion [1, 2]. Predictive models of extracellular fluid flow and transport during and following CED would be useful in treatment optimization and planning. To account for large infusion volumes, such infusion models should incorporate tissue boundaries and anisotropic tissue properties.
High-Throughput Screening of Chemical Libraries for Modulators of Mesenchymal Stem Cell Chondrogenesis
Authors: Huang Alice H. , Motlekar Nuzhat A. , Stein Ashley , Shore Eileen M. , Diamond Scott L. , Mauck Robert L.
Published: March 2014

Mesenchymal stem cells (MSCs) are a multi-potential cell type that can be induced to differentiate to a variety of tissue-specific cell phenotypes, including cartilage (chondrogenesis) and bone (osteogenesis). Given this multi-potentiality, MSCs are a promising cell source for exploring developmental paradigms and for tissue engineering (TE) applications. For cartilage formation assays, MSCs are collected in high-density pellets and treated with specific biofactors, including TGF-β superfamily members and dexamethasone in a chemically defined medium (CM) [1]. During chondrogenesis, extracellular matrix (ECM) rich in glycosaminoglycan (GAG) and type II collagen is synthesized. While MSC chondrogenesis is well-characterized using existing protocols, the effect of alternative biofactors, their doses and combinations requires laborious combinatorial studies [2]. High-throughput screening (HTS) overcomes this limitation through the simultaneous layout and query of a large number of conditions within a single plate. HTS depends on the use of precise robotic liquid handling systems and on the development of sensitive, validated, and readily quantifiable assays. In a recent study, we optimized cell culture and assay procedures for HTS by minimizing cell number, handling and culture duration [3]. We successfully reduced the time scale from 21 to 7 days and the number of cells required from 225K to 30K cells per pellet. Further, we developed a novel in-well digestion protocol to enable high-throughput analysis and minimize handling. In this study, we have further streamlined these assays for HTS by providing a rapid and robotic approach for layout, culture, and analysis of ECM deposition using ‘micro’ MSC pellets (10K cells per pellet) in a 384-well format. Furthermore, we have carried out an initial screen of the NINDS small molecule library and demonstrated the feasibility of this technology for use in HTS of chondrogenesis.
Strain Mapping of LV Myocardium and its Correlation With Activation of Apoptotic Molecular Pathways Post Infarction
Authors: Wu Changfu , Li Tieluo , Savai Kinjal , Griffith Bartley P. , Wu Zhongjun J.
Published: March 2014

The American Heart Association reported that in 2004 alone, myocardial infarction (MI) related mortality rate was as high as 38% among the 1.2 million reported MI cases [1]. After an MI, the self-repair capability of the infarcted heart is limited. As a result, the heart undergoes a remodeling process, characterized by progressive weakening of contractile function. It is believed that increased left ventricular (LV) loading to survival myocytes post-MI activates the apoptotic pathways in the cells, leading to progressive loss of cardiomyocytes.
CFD Study of the Relationship Between Wall Shear Stress and Aspect Ratio in Elastase Induced Rabbit Aneurysm Models
Authors: Zeng Zijing , Zakaria Hasballah , Kadirvel Ramanathan , Ding Yong-Hong , Lewis Debra A. , Kallmes David F. , Robertson Anne Marie
Published: March 2014

Hemodynamic factors are thought to play an important role in the initiation, growth, and rupture of cerebral aneurysms. In-vitro studies have demonstrated a correlation between the magnitude and distribution of wall shear stress (WSS) and biological response of both endothelial cells and smooth muscle cells [1–3]. In elastase induced saccular aneurysms, low WSS (below 0.5 Pa) was found to have a correlation with altered expression of biological markers [4]. Localized regions of rapid aneurysm growth in-vivo have been shown to be associated with regions where WSS is below a critical value of 0.1 Pa [5]. Further, aspect ratio (AR), the ratio of the maximum diameter of the aneurysm to the width of the aneurysm neck, has been correlated with elevated risk of rupture [6]. The purpose of the current study is to explore the possibility of creating elastase induced aneurysms in rabbits with a range of aspect ratios (ratio of aneurysm height/neck) and evaluate the existence of a correlation between aspect ratio and WSS distribution. Aneurysms with ARs from 0.98 to 2.8 were created at the origin of the right common carotid artery (n = 30). Qualitative differences in WSS distribution were found in the high AR aneurysms (HARA) (AR>1.6) and low AR aneurysms (LARA) (AR<1.6) [7].
Correlation Between Nanoindentation Modulus and Mineral Density in Fracture Callus Tissues
Authors: Leong Pui Leng , Morgan Elise F.
Published: March 2014

The stiffness and strength of a healing bone fracture depend on the geometry of the fracture callus as well as the mechanical properties of the callus tissues. In the clinical setting, the mechanical stability of a healing fracture is often estimated qualitatively based on the radioopacity of the callus tissue. However, a quantitative association between tissue mineralization and mechanical properties has yet to be established for these tissues. Quantifying callus tissue material properties and mineral content may therefore enable improved non-invasive assessments of bone healing. In addition, elucidating relationships between callus tissue composition and function will provide a means of understanding the mechanism by which the injured bone recovers its mechanical integrity.
Achilles Tendon Moment Arms Computed Using Ultrasound and Motion Analysis: In Vivo Estimates for Male Subjects
Authors: Cowder Justin D. , Buchanan Thomas S. , Manal Kurt T.
Published: March 2014

Accurate estimates for Achilles tendon moment arm (MA) are essential when computing gastroc-soleus force from the net plantarflexion moment. Errors in approximating the Achilles tendon MA will adversely affect the muscle force estimate. We have noted that Achilles tendon MAs reported by Maganaris [1] and others are significantly greater (> 1 cm) than values used by Delp et al. computed using SIMM [2]. It is important to note that the stature of Delp’s lower limb model was almost identical to the average weight and height of the subjects in a study by Maganaris. This led us to question which MA profiles were more anatomically meaningful. To address this, we calculated Achilles tendon MAs for 10 male subjects using a previously described method. The method combines ultrasound and video-based motion capture, and referred to as the hybrid method. Subjects in our study were chosen to ensure they were of a similar stature to those tested by Maganaris, thereby minimizing confounding effects of subject anthropometrics.
Magnetic Drug Targeting: Drug Delivery in Large Vasculature
Authors: Schmieg Jaime , Williams Alicia , Vlachos Pavlos
Published: March 2014

Magnetic drug targeting (MDT) is a novel drug delivery method with potential to dramatically revolutionize clinical approaches of the treatment of many diseases. In fact, MDT has been proposed for ailments ranging from vascular disease to cancer [1, 2]. Conventional drug delivery methods utilize large doses of medication to account for the dispersion of the drug throughout the body in the hope that a sufficient concentration of medicine arrives at the diseased site. Unfortunately, many medications can have caustic effects on healthy systems leaving patients with discomfort, weakened immunity or lowered quality of life. Alternatively, MDT aims to reduce potentially harmful global dosage levels by localizing medication at the diseased site. Additionally, magnetic drug targeting not only reduces chemicals seen by healthy areas of the body, it may provide a higher concentration of drug capable of remaining at the damaged location for a longer duration than typically seen for current treatment practices. Possibly the most important advantage of MDT is the method’s ability to enhance delivery while providing no additional invasive procedures.
How to Treat the Loss of Beat: Modeling and Simulation of Ventricular Growth and Remodeling and Novel Post-Infarction Therapies
Authors: Goktepe Serdar , Ulerich Joseph P. , Kuhl Ellen
Published: March 2014

Heart disease is the primary cause of death in industrialized nations. In 2007 alone, an estimated 79 million adults in the U.S., one in three, had one or more types of cardiovascular disease, generating health care costs in excess of $430 billion. A leading cause of congestive heart failure is myocardial infarction. Within the first few hours after the infarct, a complex cascade of events is initiated in the myocardium manifesting itself clinically in disproportionate thinning and dilation of the infarct region accompanied by distortion in form and function of the entire heart, figure 1. As remodeling progresses, volume-overloaded hypertrophy and further deterioration of cardiac function are common natural consequences. Historically, therapies for myocardial infarction have been developed by trial and error methods, as opposed to therapy design and development through scientific understanding of the functional and structural changes in the infarcted tissue. Continuum theories, in combination with modern computer simulation technologies, offer the potential to provide greater insight into the complex pathways of myocardial infarction, and thereby guide the design of successful post-infarction therapies such as direct cell injection into the damaged myocardium1 and implantation of tissue engineered vascular grafts2 as sketched in figure 1.
Development and Finite Element Implementation of a Nearly Incompressible Structural Constitutive Model for Artery Substitute Design
Authors: Sun Wei , Chaikof Elliot L. , Levenston Marc E.
Published: March 2014

Compliance mismatch between a host artery and a vascular graft causes hemodynamic disturbance and stress concentration, which may lead to thrombus formation at an early stage and to neointimal hyperplasisa near the anastomosis at a later stage [1]. To optimal design artery substitutes, the requirements of geometric and compliance matching at mean blood pressure must be determined and used to guide the fabrication of the unloaded conduit with proper diameter and wall thickness. Given the range and complexity of structural behaviors that can be produced by independently varying structural properties of individual layers (fiber type, density, orientation and layer thickness), a sophisticated computational model is required to determine these conduit design parameters. In this paper, a novel nearly incompressible structural model was formulated and implemented into the commercial finite element code ABAQUS (Pawtucket, RI) for finite element artery inflation simulations. The profound artery compliance changes due to variations of fiber properties, the nearly incompressibility control parameter D, and different properties of intima-media and adventitia were investigated.
Neuromotor Effects of Whole Body Horizontal Vibration
Authors: Lamis Farhana , Wilson Sara E.
Published: March 2014

Low back disorders are very common affecting up to 80% of the population in their lifetime [1]. Whole body vibration (WBV) exposure has long been identified as an important risk factor for low back disorders in industrial workers [2]. A potential mechanism has been proposed by which vibration may lead to injury. Namely, vibration-induced losses in proprioception may lead to inappropriate stabilization and poor dynamic control of the lumbar spine [3]. Increases in proprioceptive errors and in delays in neuormotor response have been demonstrated with 5 Hz, vertical seatpan vibration [3]. While vertical vibration exposure is a common occupational exposure, in some cases, such as off road vehicles and construction vehicles horizontal (fore-aft) vibration may dominate [4]. In this study, the objective was to investigate how the whole body, horizontal, seatpan vibration affects muscle response and to compare these results with the previously studied whole body vertical vibration.
Prediction of Internal Contact Forces at the Knee From External Measurements
Authors: Walter Jonathan P. , Banks Scott A. , D’Lima Darryl D. , Fregly Benjamin J.
Published: March 2014

As the baby boomer generation ages, knee osteoarthritis (OA) will become increasingly prevalent in our society. Articular cartilage damage in the knee is highly dependent upon subject-specific kinematics and load distribution inside the joint. In particular, researchers have hypothesized that overloading of the medial compartment is a primary contributing factor to the development of the disease [1]. However, since medial compartment load cannot be measured non-invasively in vivo, researchers typically use the external knee adduction moment during stance phase as a surrogate measure. This quantity has been correlated with the medial tibial contact force measured from an instrumented knee implant [2] and with the risk of disease progression over time [3].
Fabrication and Modeling of an Electrospun Tri-Polymer Composite for the Engineering of Fibrous Tissues
Authors: Baker Brendon M. , Nerurkar Nandan L. , Burdick Jason A. , Elliott Dawn M. , Mauck Robert L.
Published: March 2014

Aligned, electrospun scaffolds are a useful tool for the engineering of fiber-reinforced tissues (such as tendon, meniscus, and muscle) as they mimic the topography and anisotropy of the native tissue extracellular matrix (ECM) [1]. We have shown that fiber-alignment of slow-degrading poly(ε-caprolactone) (PCL) enhances the organization of newly-formed ECM and improves construct properties [2]. However, one significant drawback to these 3D templates is their small pore size, resulting from tight fiber packing, which hampers cell infiltration. To increase scaffold porosity and thereby accelerate cell ingress, we have recently reported on the fabrication of dual polymer composite scaffolds containing both water-soluble poly(ethylene oxide) (PEO) and PCL fibers [3]. Removal of the sacrificial PEO fibers before seeding improved cell infiltration, but did so at the cost of the overall structural integrity. To further expand the potential properties (mechanics and degradation) of these composite scaffolds, this study introduced a third component (50:50 poly(lactic-co-glycolic acid) (PLGA)) using a newly constructed tri-polymer electrospinning device. We evaluated each polymer singly and when combined into a tri-polymer (3P) fibrous network. To better understand the mechanical response of these composites, we used a hyperelastic, constrained mixture model to assess and predict the response of these composite nanofibrous meshes for a range of compositions.
Wheelchair Modification for Hands-Free Motion for Dancers With Disabilities
Authors: Schrock Peter J. , McQueen M. Elisa , De Laurentis Kathryn J. , Morris Merry L. , Dubey Rajiv V.
Published: March 2014

Functional modifications to power and manual chairs are currently advancing in the areas of rehabilitation, sports and recreation and in the activities of daily living; however, these modification have yet to be directly applied in the field of performing arts. An assistive device was developed at the University of South Florida (USF) during collaboration between the Department of Mechanical Engineering and the School of Theatre and Dance. The project was initiated by Professor Merry Lynn Morris who identified a need for new conceptions of mobility; her work with dancers, with and without disabilities established the research framework in which choreographic vision could be supported with technological applications. Therefore, a device was designed to alleviate the constraints of current wheelchair designs which inhibit the user’s upper-body artistic movement range and capacity for interaction. The main purpose of the design was to create hands-free motion through the modification of a power wheelchair, which make it useful in the performing arts, but also as an assistive device for persons with disabilities. This device is in its first research phase of development as a prototype and is patent pending.
High Resolution DCE-MRI Vascular Characterization of Murine Sarcoma and Human Renal Cell Carcinoma for Computational Modeling
Authors: Pishko Gregory L. , Astary Garrett W. , Mareci Thomas H. , Sarntinoranont Malisa
Published: March 2014

Non-uniform extravasation from blood vessels, elevated interstitial fluid pressure (IFP), and transport by bulk fluid motion in the extracellular space have all been determined to contribute to the non-uniform tissue distribution of systemically delivered agents in solid tumors. The aforementioned factors can lead to inadequate and uneven uptake in tumor tissue which has been shown to be a major obstacle to macromolecules in clinical cancer therapy [1]. Recently developed computational tumor models have described blood flow either in a single vessel or capillary network with variations in space and time [2]. These studies do not account for heterogeneous tissue transport properties in regions of leakier vessels [3].
Influence of the Superficial Tangential Zone for Cartilage Modeled in Finite Deformation and With Tension/Compression Nonlinearity
Authors: Owen John R. , Wayne Jennifer S.
Published: March 2014

Creation of replacement tissue to repair articular surface defects remains a challenge. Normal zonal characteristics of articular cartilage throughout its thickness, particularly the superficial tangential zone (STZ), and normal material properties have not been reproduced in vitro in scaffolds nor in vivo in repairing defects. Without sufficient quality, such transplanted scaffolds in vivo may be doomed mechanically from the outset. Removal of the STZ from normal cartilage negatively affects the remaining cartilage’s ability to support axial loads and retain fluids [1–3]. Previous studies have modeled excessive axial deformation of repair cartilage [4–5]. Studies have shown that modeling the STZ of normal cartilage as transversely isotropic provides better agreement with indentation experimental results than isotropic models [6–9]. Others have modeled experimental conditions by incorporating tension and compression nonlinearity [10]. Previous analyses have indicated that strain-dependent permeability within the STZ can positively affect the ability of free-draining normal and repair models to withstand imposed surface loads [11,12]. This finite element study further examined the role of an STZ with strain-dependent permeability on the behavior of normal and repaired articular surfaces under contact loading from rigid permeable and impermeable spheres. Nonlinear geometry permitted finite deformations to occur while the differential stiffness in tension and compression was also represented.
Damage of Articular Cartilage due to Mechanical Fatigue and Collagenase Action
Authors: Namani Ravi , Simha Narendra K. , Lewis Jack L.
Published: March 2014

Damage to the extracellular matrix (ECM) of articular cartilage is detrimental to its functional load-bearing properties. Cartilage ECM can be damaged chemically by enzymatic cleavage or mechanically either due to impact loads or long term fatigue loads at physiological levels. There is strong evidence that chronic long term loads in conjunction with chemical weakening can lead to osteoarthritic degeneration of cartilage [1, 2].
Engineered Heart Valve Tissue Formation at the Organ Level: Effects of Flow Dynamics on Tissue Development
Authors: Ramaswamy Sharan , Gottlieb Danielle , Mayer John E. , Sacks Michael S.
Published: March 2014

Tissue engineered heart valve (TEHV) development protocols have yet to be optimized to an extent that can offer long-term function of value to patients, beyond contemporary clinical practices. One method of optimization may be possible through appropriate mechanical conditioning of the evolving engineered tissue before implantation. Engelmayr et al. [1] showed the synergistic benefits of combined flexural and fluid induced stresses on valvular-like tissue grown on rectangular scaffold strips. However, for clinical translation to be realized, it is important to determine if the nature of extracellular matrix production in such mechanistic studies also occurs at the macro-level, in the intact tri-leaflet valve geometry. Therefore, appropriate organ-level studies are required wherein the valvular tissues are subjected to the complex 3-dimensional flow/flexure/stretch regimes under highly controlled sub-, normal, and hyper-physiological flow levels. In this manner, biomechanical factors contributing to engineered tissue development can be coupled to tri-leaflet valve geometry requirements. In this study, one possible conditioning strategy on tri-leaflet TEHV structures is presented.
Dynamic Deformation Analysis of a Red Blood Cell in Steady and Unsteady Shear Flows
Authors: Bessho Sadao , Nakamura Masanori , Koshiyama Kenichirou , Wada Shigeo
Published: March 2014

Quantitative evaluation of hemolysis, the breaking open of red blood cells (RBCs), is essential in designing artificial organs. Recently, numerical methods to quantify hemolysis from a measured or calculated macroscopic flow velocity field have been proposed [1]. Nevertheless, their predictive accuracy has not reached a satisfactory level required in practice. This would be because the conventional methods are mostly established based on the hemolysis tests under simple flow conditions and have not well considered deformation of RBCs. For further amelioration of the predictive accuracy, it would be necessary to take into account motion and dynamical deformation of individual RBCs in a flow field.
Bone Geometry in Periodic Hydroxyapatite Scaffolds Has Little Influence on Effective Elastic Properties
Authors: Wagoner Johnson Amy J. , McInstosh Lucas , Cordell Jackie M.
Published: March 2014

The development of bone replacement materials for large and load-bearing defects and their translation to the clinic will require extensive characterization of the mechanical properties of the scaffold/bone composites after implantation. Numerous of challenges are associated with such characterization of these types of composite. In particular, the need for large animal models, the associated cost, and the removal of the scaffolds from host bone for mechanical testing are some of the more difficult challenges to overcome. The ability to accurately predict the mechanical properties of scaffold/bone composites will lead to significant advances in the area of bone tissue engineering. Properties for periodic materials have been accurately modeled modeled using representative volume elements (RVE) [1]. The hydroxyapatite (HA) scaffolds in this study have a periodic lattice structure, making the use of an RVE appropriate for modeling effective properties. However, the choice of an appropriate RVE and geometry to represent the bone in the composite is less clear.
Effect of Traction Load on the Biomechanical Behavior of Cervical, Thoracic, and Lumbar Spinal Segments: A Finite Element Analysis
Authors: Hussain Mozammil , Tepe Rodger
Published: March 2014

Degeneration in the spinal structures can be a major source of pain that increases with aging in a roughly linear progression. Pain has been further correlated with the regions of high stress and strain concentrations. Due to difference in the regional anatomy and physiology of the cervical, thoracic, and lumbar levels, their biomechanical response to physiological loadings is different. The fluid egresses outside in the radial direction from nucleus pulposus (NP) to annulus fibrosus (AF) under compression, which generates a hydrostatic pressure against an external applied load. The increased NP pressure, in many clinical cases, results into various abnormal disc pathologies such as protrusions and herniations. Chiropractic care in the management of these spinal dysfunctions uses manual manipulation therapies such as distraction techniques to relieve the disc from high pressure and radial bulging. Despite manual distraction therapy is a three-dimensional force application; major proportion of the load is exerted in the axial upward direction. Although few biomechanical studies have compared the segmental biomechanics under axial traction loads, to the best of our knowledge, there is no study that distinguishes between the behavior of cervical, thoracic, and lumbar segments to these loads. The objective of the present study, therefore, was to investigate that how the biomechanical stresses, that were developed under upper body weight (BW), changes in the various spinal segments (cervical, thoracic, and lumbar) and in the different spinal structures (top vertebra, superior endplate, and disc) when the traction forces were applied as the therapeutic modalities in the chiropractic interventions.
Implementation of a P-300 Brain Computer Interface for the Control of a Wheelchair Mounted Robotic Arm System
Authors: De Laurentis Kathryn J. , Arbel Yael , Dubey Rajiv , Donchin Emanuel
Published: March 2014

Three decades ago, Farwell and Donchin [1] developed a computer system based on the method of electroencephalography (EEG) that enables individuals to communicate with their environment without using any neuromuscular function. This P300 BCI speller makes use of the well-studied observation that the brain reacts differently to different stimuli, based on the level of attention given to the stimulus and the specific processing triggered by the stimulus. Since this first report in 1988, several brain-computer interface (BCI) systems have been developed and constantly improved. We have previously demonstrated that the P300-BCI can control a wheelchair-mounted robotic arm (WMRA) system [2].
On the Indentation Testing of Articular Cartilage: Determination of the Effective Poisson’s Ratio Using Two Different-Sized Punches
Authors: Kepich Eugene T. , Haut Roger C.
Published: March 2014

Effective Poisson’s ratio (EPR) of articular cartilage in compression is an important parameter, which is inversely correlated with stiffness of the collagen fibers [1]; and thus, if known, could provide valuable information about integrity of the collagen network in the tissue. Unfortunately, direct determination of the EPR by measuring lateral expansion during unconfined compression tests [2], while being effective, due to it’s destructive nature many times is not desired and/or hard to apply in practice. Optically-determined values of equilibrium EPR for bovine humeral articular cartilage using this method are reported to be in range 0.185±0.0065.
2-Dimensional Visualizations of Lamb Waves Interaction With a Notch in a Bovine Cortical Tibia
Authors: Hapsara Manik
Published: March 2014

The objectives of this study are to observe the behavior of Lamb waves upon encountering a defect in a bone and to provide 2-d visualizations of the process. For this purposes, measurements were conducted using a non-contact optical detection technique, scanning laser vibrometry. This technique produces 2-d graphics of the Lamb waves in the cortical layer of the bone.
Analytic expressions for atomic layer deposition: Coverage, throughput, and materials utilization in cross-flow, particle coating, and spatial atomic layer deposition
Authors: Yanguas-Gil Angel , Elam Jeffrey W.
Published: March 2014

In this work, the authors present analytic models for atomic layer deposition (ALD) in three common experimental configurations: cross-flow, particle coating, and spatial ALD. These models, based on the plug-flow and well-mixed approximations, allow us to determine the minimum dose times and materials utilization for all three configurations. A comparison between the three models shows that throughput and precursor utilization can each be expressed by universal equations, in which the particularity of the experimental system is contained in a single parameter related to the residence time of the precursor in the reactor. For the case of cross-flow reactors, the authors show how simple analytic expressions for the reactor saturation profiles agree well with experimental results. Consequently, the analytic model can be used to extract information about the ALD surface chemistry (e.g., the reaction probability) by comparing the analytic and experimental saturation profiles, providing a useful tool for characterizing new and existing ALD processes.
Microstructure of surface cerium hydride growth sites
Authors: Brierley Martin , Knowles John , Montgomery Neil , Preuss Michael
Published: March 2014

Samples of cerium were exposed to hydrogen under controlled conditions causing cerium hydride sites to nucleate and grow on the surface. The hydriding rate was measured in situ, and the hydrides were characterised using secondary ion mass spectrometry, scanning electron microscopy, and optical microscopy. The results show that the hydriding rate proceeded more quickly than earlier studies. Characterisation confirmed that the hydrogen is confined to the sites. The morphology of the hydrides was confirmed to be oblate, and stressed material was observed surrounding the hydride, in a number of cases lathlike features were observed surrounding the hydride sites laterally with cracking in the surface oxide above them. It is proposed that during growth the increased lattice parameter of the CeH2 induces a lateral compressive stress around the hydride, which relieves by the ca. 16% volume collapse of the γ-Ce to α-Ce pressure induced phase transition. Cracking of the surface oxide above the laths reduces the diffusion barrier to hydrogen reaching the metal/oxide interface surrounding the hydride site and contributes to the anisotropic growth of the hydrides.