bluuebunny/crossref_metadata_2025 huggingface dataset:
A Spring-Loaded Constant Force Exercise Device
Authors: Chatham Matthew J. , Todd Beth A. , Parker Joey K. , House Audrey S. , Taylor Jenny L.
Published: November 2021

Bone mineral density loss has been observed in astronauts who have spent a significant amount of time in a micro-gravity environment [1]. The lack of mechanical stress placed on the bones while in this environment is a major factor in the decrease in bone mineral density. To counteract these effects, resistive exercise has been the focus of many studies. Weighted plates have been used to provide a constant force resistance in ground-based bed rest studies. Bed rest has been established as one of the best ways to simulate the long-term effects of micro-gravity on earth [2]. In weightlessness, however, an alternate source of resistive force is required Some exercise devices provide resistance with elastic bands. Unfortunately, these elastic bands tend to lose their mechanical stiffness with use, requiring many spare elastic bands to be available for long duration missions in space. A more robust system that requires less maintenance would be preferable. Metallic helical springs meet this requirement The mechanical properties of helical springs are predictable, and these springs have a long life, making them well suited for long duration missions. However, helical springs exhibit linear behavior. That is, the resistive force provided by the spring is directly proportional to the amount of deflection. Therefore, a mechanism was designed to interact with the linear springs to provide a constant output force over a given length of travel.
Endovascular Embolization With Cyanoacrylate Mixtures: An In Vivo Study of Polymerization Kinetics
Authors: Gounis Matthew J. , Lieber Baruch B. , Hopkins L. N.
Published: November 2021

A cerebral arteriovenous malformation (AVM) is a congenital vascular lesion of the brain composed of a complex tangle of arteries and veins, which are linked by one or more fistulae [1]. Arterial blood is shunted through the AVM directly to the venous system, precluding arterial blood from perfusing adjacent brain structures. The most common presentation of this disease is cerebral hemorrhage secondary to AVM rupture, with an associated mortality of 15% and a morbidity of 50% [1]. One modality to treat this pathology is endovascular embolization. Generally, endovascular embolization serves as an adjunct treatment to either surgery or radiosurgery, but is a curative treatment in approximately 15% of AVM cases [2]. The most common embolic agent used to occlude AVMs is a mixture of n-butyl 2-cyanoacrylate (NBCA) and Lipiodol®. NBCA is a rapidly polymerizing liquid adhesive that polymerizes with contact to blood. Lipiodol® is an ethiodized oil, which imparts radiopacity to the embolic mixture. Moreover, Lipiodol® has been reported to delay the polymerization of NBCA [3]. To further increase the polymerization time of NBCA, minute quantities of glacial acetic acid (GAA) may be added to the embolic mixture.
Contour Based Implementation of Long Bone Adaptation
Authors: Roberts Michael D. , Hart Richard T.
Published: November 2021

The adaptation of bone to its mechanical demands is often described as a feedback control system wherein some aspect of the tissue strain environment acts as a driving signal to initiate cellular-level formation and resorption processes on bone surfaces. While this description may be somewhat simplified, the control system view is useful for organizing ideas, experiments, and simulations of adaptation. In the past 25 years, several investigators have introduced mathematical models and (finite element-based) computer simulations of bone adaptation, using numerous candidate driving mechanical signals as proposed bone mass regulators [1]. These simulations generally use the finite element method — including the appropriate geometry, material description, and loading — to calculate the needed tissue strain parameter being considered as the specific regulation signal. Based on the adaptive response being simulated — geometric and/or material property changes — the finite element model is updated, and re-analyzed in a series of discrete time steps.
The Effect of Number of Cycles on Microdamage Accumulation in Bovine Trabecular Bone
Authors: Moore Tara L. Arthur , Gibson Lorna J.
Published: November 2021

Microdamage, in the form of small cracks, exists in healthy bone. Microdamage can be created by an overload or by repetitive motion (fatigue) during daily activities. Usually, microdamage is repaired during bone remodeling and a steady state is maintained. However, in cases of excessive microdamage creation or slowed bone remodeling, microdamage can coalesce to create a fracture. Our previous work [1,2] has investigated microdamage accumulation with increasing strain in bovine trabecular bone loaded in monotonic compression and compressive fatigue. Specimens fatigued at relatively high load levels fail after a few loading cycles, while specimens fatigued at lower load levels may undergo thousands of cycles before failure. During high cycle fatigue, microdamage may accumulate by the growth of pre-existing microcracks, as well as by the crack initiation seen in low cycle fatigue.
Evaluation of Muscle Forces in a Synergistic Lumbar Spine Using Kinematics-Based Approach and Optimization
Authors: Shirazi-Adl A. , El-Rich M. , Pop D. , Parnianpour M.
Published: November 2021

Alternative methods have been proposed to solve the redundant problem of spinal active-passive load distribution. Due to the shortcomings in existing reduction, optimisation and EMG-driven models, and combination thereof, a novel kinematics-based approach is introduced that utilises the spinal passive-active synergy. Our recent studies demonstrate that, for a given task, the posture may be so adjusted as to yield an optimal load configuration requiring minimum muscle exertion [1]. In the current study, a solution technique for the redundant spinal system is described and applied to the analysis of a lumbar spine in an optimal posture obtained by varying the lordosis and pelvic tilt under a total of 2800N compression. The forces in lumbar muscles are subsequently computed for this optimal posture.
Effect of Frequency of Cyclic Loading on Biomechanical Properties of Lumbar Intervertebral Joints
Authors: Natarajan Raghu N. , Williams Jamie R. , Andersson Gunnar B. J.
Published: November 2021

Epidemiological studies suggest that repetitive loading, including vibration, is of importance in the development of back injuries including disc injuries. Yet the present information from the literature does not allow dose-response relationships to be developed, thereby making it challenging to develop accurate guidelines for prevention of occupational musculoskeletal disorders of the spine. Biomechanical response of individual motion segments as a function of applied load frequency may provide data on the ability of the disc to withstand prolonged cyclic loading. The hypothesis of the current study is that the rate of decrease in disc stiffness at the end of 30 loading cycles increases suddenly if the frequency of compressive loading is greater than 15 Hz. A finite element model was used for this study.
Instability Analysis of a Cervical Spine Model Under Flexion and Compression Loading
Authors: Tchako Abraham , Sadegh Ali M.
Published: November 2021

An improved and detailed 3-D FE model of human cervical spine was created using digitized geometric measurement. The model was validated with the in-vivo studies of Moroney, Panjabi and Fuller. Clinical instability of the spine for two cases involving flexion and compression loading (simulating injuries in motorcycle vaulting, football and diving accidents) were analyzed. The instability was based on the check list of Panjabi and White. It was determined that flexion moment of 10 Nm or compressive force of 500N result in the onset of clinical instability.
3D Kinematic Analysis of the Carpometacarpal Joints
Authors: Patterson Rita M. , El-shennawy Maged , Nakamura Koji , Viegas Steven F.
Published: November 2021

Carpometacarpal joint motion has been difficult to accurately measure with standard methods. There has been relatively little information on the kinematics of the 2nd through 5th carpometacapal (CMC) joints. It is however, generally accepted that the range of motion in the 2nd through the 5th CMC joints increases from the radial to the ulnar side of the hand, with the 2nd CMC joint being essentially immobile, while the 5th CMC joint simultaneously flexes and adducts1. The purpose of this study is to investigate the 3D dynamic kinematics of the 2nd – 5th CMC joints during flexion/extension motion (FEM), radio-ulnar deviation (RUD), and pronation/supination motion (PSM).
Use of Burmester’s Circular Theory in the Determination of the Optimal Four-Bar Link Reproducing Actual Tibia-Femur Relative Motion
Authors: Danieli G. A. , Mundo D. , Sciarra V.
Published: November 2021

The paper presents an application of Burmester’s circular theory to the determination of the optimal mechanism used to reproduce the motion of the tibia with respect to the femur. The research takes its start from the idea of studying an external fixator to guide the motion of a tibia in a way physically compatible to the actual patient’s anatomy, in order to firmly guide the two bones after, for instance, joint reconstructive surgery, while avoiding any contact between the articular surfaces. The physiological data were determined in researches presented in other papers.

However, in the initial research phases the idea was to determine the best position of an existing four-bar link, produced for an orthopaedic tutor, without any attempt at synthesising an ad hoc one. The idea of using Burmester’s theory in this operation was in reality an old one, but previous attempts were not successful.

Naturally, the required four-bar link had also to be small in order to fit on the external fixator. The results of the research are extremely satisfactory, since it was possible to determine a mechanism which allows relative motion with errors in the order of fractions of millimetres, when the imposed motion had to keep the two bones separated by a minimum of one millimetre. As a consequence the two bones will never go in compression, while a gentle pulling of the ligaments will always be present.

Using the approach, typical four-bar links for different human typologies were also determined.
The Effect of Talar Component Design on Talar Stresses in Total Ankle Arthroplasty
Authors: Smolinski Patrick , Galik Karol , Conti Stephen , Miller Mark C.
Published: November 2021

Total ankle arthroplasty offers an alternative to ankle arthrodesis or fusion in the treatment of diseases of the ankle. Due to the high complication rate in early designs, ankle replacement components have not evolved into any accepted standard form and several widely varying designs are currently in use.
An Equivalent Linkage Model for Understanding Stiffness Effects of Biarticular Muscles
Authors: Russell Donald L. , English Chad E.
Published: November 2021

The purpose of this paper is to describe a method for aiding in the intuitive understanding of the effects of bi-articular muscles on the stiffness of a limb. In particular, a kinematic analysis of a mechanical model of a human arm is performed. The results are manipulated into a form that makes evident a mathematical decomposition of the kinematics. This gives rise to a mechanical analog to the decomposition: an equivalent four-bar linkage with single-joint muscles. Further insight is gained as the equivalent linkage provides an intuitive direction associated with each set of muscles.
Fracture Toughness of the Growth Cartilage Reserve Zone Is Anisotropic
Authors: Williams John L. , Gove Nicholas K. , Flowers G. Adam , Schmidt Thomas L.
Published: November 2021

In the developing proximal tibial epiphysis the anterior ossifying tibial tuberosity is separated from the secondary ossification center of the tibial epiphysis by a bipolar growth plate known as the ‘cartilage bridge.’ We tested the fracture toughness of the central part of this growth cartilage in 18-week old calves in the direction perpendicular to the plate (mean 4962 N/m, SD 1846) and found it to be greater (p = 0.0004) than in the parallel direction (mean 2909 N/mm, SD 1122). Part of the reason for this anisotropy is the presence of vascular channels which cross the bridge from the epiphysis into the tuberosity. In addition, we hypothesize that the anisotropy reflects an arrangement of collagen primarily along the length of the ‘cartilage bridge.’
Towards a Biomechanical Model of the Breast: A Simulation-Based Study
Authors: Sarh K. , Ravi-Chandar K. , Miller M. , Patrick C.
Published: November 2021

The clinical and financial impact of breast cancer on the U. S. health care system is great. In addition to the tangible metrics of costs and number of diagnoses, the psychological distress that accompanies a lump found in the breast is compounded by the apparent problems noted with contemporary reconstructive procedures. Currently, breast reconstruction is conducted largely by trial and error and varies with physician experience. For instance, a surgeon today will request three to four different sized implants for the operating room and will try each one, siting the patient up each time, until the desired volume and shape of the breast is achieved. The novel union of surgeons with machines and multi-modality information, made possible by advances in engineering and computing, has enormous potential in overcoming limitations realized with contemporary standard of care. For example, a virtual model of a patient’s breast will assist the surgeon in deciding a priori what implant size to order for the operating room such that desired breast outcomes are achieved. Our long-term goal is to develop novel computer-assisted surgical systems to significantly change breast cancer health care. Our approach builds upon four broad core areas of enabling knowledge and techniques, namely (1) multi-modality imaging, (2) simulation, (3) soft tissue biomechanics, and (4) interface subsystems. Recently, we developed a parametric deformable model of a female breast’s shape that allows the surgeon to manipulate the shape of the breast by varying key shape variables, analogous to the aesthetic and structural elements surgeons inherently vary manually during breast reconstruction [2]. Such a system may enhance the practice of breast surgery at multiple points. It enables the patient to communicate her expectations more clearly to the surgeon. It allows the surgeon to educate the patient with more accurate explanations about what can be accomplished, and after the consultation, it helps the surgeon plan specific aspects of the procedure to achieve the agreed upon goals.
Measuring the Efficiency of Off-Road Bicycle Suspension Systems
Authors: Wang Eric L.
Published: November 2021

Off-Road bicycle suspension systems are beneficial because they dissipate vibrational energy and a lower vibration dosage can reduce the metabolic energy expenditure of the cyclist [1]. However, dampers dissipate energy and the energy dissipated must be compensated by additional input from the cyclist. Estimates of the energy dissipated range from 1–2% of the total power input by the cyclist [2–4]. Additionally, suspension systems add weight to a bicycle, which also requires additional energy when hill climbing and accelerating.
Wrist Fracture Dynamic Testing System to Simulate Skating Falls
Authors: Englund Richard B. , Lubahn John D. , Buczek Frank L. , Cooney Timothy E.
Published: November 2021

Injuries are common from skating sports. These include abrasions, contusions, ligamentous sprains, and fractures. Most are confined to the upper extremity. The probability of injury, in consort with a local recreational park, have resulted in the frequent presentation of patients for treatment to the emergency department at The Hamot Medical Center, a northwestern Pennsylvania regional teaching hospital. Given its personal and financial toll, orthopaedic attendings and surgical residents alike have expressed an interest in injury prevention via a better understanding of the biomechanical underpinnings of these injuries.
Computational Determination of the 3-D Stiffness Matrix of an Ilizarov Fixator
Authors: Galvis E. , Lasso P. , Machado A. , Garcia J. J.
Published: November 2021

Use of external fixators in undeveloped countries has been limited due to their high cost. Consequently, one of the aims of our group is the design, construction, and evaluation of low cost external fixators. In this paper we present the mechanical characterization of an Ilizarov fixator composed of rings made of aluminum, which is light, cheap, easy to form, radiolucid and anticorrosive. The main purpose was to determine the 3-D stiffness of the fixator (Duda et al., 1998) in order to be able to evaluate interfragmentary movement. We hypothesize that this fixator has the ability to limit shear and allow axial movements that are beneficial to bone healing (Goodship et al., 1985; Kenwrigh et al., 1991). Given the amount of work involved to experimentally determine the 3-D stiffness matrix of an external fixator we used simple computational models that were calibrated experimentally for a couple of load cases.
Mechanical Design and Analysis for a Scanning Fiber Endoscope
Authors: Brown Christopher M. , Fauver Mark E. , Reinhall Per G. , Seibel Eric J.
Published: November 2021

There is a need for smaller, more flexible, optical imaging tools for use in minimally invasive diagnostic and therapeutic procedures [1]. Towards this end, a novel technique of image acquisition has been developed based upon the controlled vibration of a waveguide and detection of light backscattered from the waveguide onto an object [2]. The anticipated result of this research is the creation of an optical scanner capable of operating at high frequency, with a large field-of-view (FOV) in a 1 mm diameter enclosure. The mechanics of this system have been explored for use in near-field scanning optical microscopy applications [3], and are now examined for use in a scanning fiber endoscope. Discussed in this report are the vibration characteristics of two possible waveguide geometries: a cylindrical and a tapered optical fiber.
Metal Trays in Tibial Components of Knee Implants; Contact Stress and Deflection Behaviour
Authors: McGloughlin Tim
Published: November 2021

Wear behaviour of the Ultra High Molecular Weight Polyethylene (UHMWPE) insert in tibial components of total knee implants is believed to be influenced by the contact conditions occurring at the femoro-tibial interface. The wear debris which is generated in the vicinity of the implant is known to evoke undesirable effects and limits the long term survival rates of total knee replacement Mc Gloughlin et al [1].
Experimental Assessment and FEA Prediction of the Effects of Prosthetic Socket Geometry on Transtibial Amputee Residual Limb Circulation
Authors: Houston Vern L. , Mason Carl P. , Arena Luigi , Luo Gangming , Beattie Aaron C. , Garbarini MaryAnne , Thongpop Chaiya
Published: November 2021

Eighty plus percent of all lower limb amputations performed in the United States each year result from complications of peripheral vascular disease (PVD) [1]. PVD amputees’ vascular systems are significantly compromised and can withstand little extraneous insult. Clinical studies have shown that ill-fitting prosthetic sockets, and/or excessive prosthetics loads can traumatize amputees’ residual limb (RL) tissues [2]. Unfortunately, there are no decisive clinical measures currently available that can be used to ensure prosthesis geometry and applied prosthetics loads are safe and will not compromise limb circulation and cause tissue injury. Minus egregious symptoms of ischemic pain and tissue trauma, it is commonly assumed that the tissue stresses and strains caused by differences between RL and prosthetic socket geometries, and from prosthetics loads incurred during stance and gait, have minimal effect upon RL tissue circulation and health. The objective of this study was to investigate the validity of this assumption by quantitatively measuring the effects prosthetic socket design geometry and applied loads have on transtibial amputee RL tissue circulation, and to determine if tissue circulation sensitivities to variations in socket design were sufficient to enable optimization of prosthesis design parameters.
Simulated Tests of Large Animal Impacts
Authors: Herbst Brian , Forrest Stephen , Meyer Steven E. , Hock Davis
Published: November 2021

Front seat occupants can be catastrophically injured in vehicle collisions with large animals such as elk, cattle or moose. This paper will discuss general injury patterns observed in these impacts, as well as the general vehicle motions and interactions with the animals. Some manufacturers (i.e. Saab and Volvo) have developed tests and incorporated design considerations to deal with this injury threat. Primary failure modes will be identified from field research and discussed. Quasi-static test procedures will be documented. Additionally, insights gained from the failure modes in both field accidents and test vehicles were used to modify vehicles with simple alterations. The vehicles were then tested using the quasi-static procedure and demonstrated significant improvements in occupant protection and roof crush resistance.
Statistical Dependance of Human Occupant Accelerations on Vehicle Impact Measures in Rear-End Impacts
Authors: Welcher Judson B. , Szabo Thomas J. , Voss Daniel P.
Published: November 2021

Interest in the mitigation of whiplash associated disorders (WAD) has increased over the last 10 years, and an increasing number of human subject rear-end collision tests have been conducted to assist in the understanding of WAD. Traditionally this testing has examined the effects of variations in occupant characteristics (age, height, gender, etc.), seat characteristics (geometrical and constitutive), and impact severity; however no controlled study has examined the singular effect of incremental velocity change increases on occupant kinematics. Moreover, while vehicle velocity change (Delta V) is typically employed as a singular measure of impact severity, it is of interest to examine whether this or other impact-related parameters, such as energy or acceleration, are also correlated with occupant kinematics.

A series of 43 instrumented human subject rear-end impact tests were conducted to monitor the effects of increasing impact severity on occupant accelerations.

Target vehicle Delta V, average vehicle acceleration, peak vehicle acceleration, and vehicle kinetic energy change were statistically evaluated for their influence on various occupant response parameters which have been suggested to be associated with WAD causation in prior literature. Significantly (p < .001) strong positive correlations were found between vehicle parameters and human occupant variables.
Validation of Bench Durability of Bioprosthetic Heart Valves
Authors: Lieber Samuel C.
Published: November 2021

The number of heart valve replacements is increasing in the United States and worldwide due to aging of the population. This situation requires bioprosthetic heart valves with higher durability to reduce the rate of reoperation and the need for anticoagulation. However, introducing any improvement in the design of a heart valve requires ten years of validation in a clinical setup. A validated in-vitro fatigue testing system would significantly accelerate these innovations. The main objective of the proposed research is to:

• Determine the dynamics of flow patterns and stresses in the vicinity of a bioprosthetic heart valve under pulsatile flow conditions.

• Use the flow pattern information to validate an in-vitro fatigue testing system under physiological and accelerated conditions.
Determination of Regional Stroke Work With High Spatial Resolution in the Isolated Beating Rabbit Heart
Authors: Gaudette Glenn R. , Todaro Joseph , Azeloglu Evren U. , Krukenkamp Irvin B. , Chiang Fu-Pen
Published: November 2021

The determination of regional function in the beating heart necessitates a technique to measure local deformation with high spatial resolution. We have previously reported the ability of computer aided speckle interferometry (CASI) to accurately determine deformation in the non-beating heart. Herein we use this technique to ascertain regional deformation allowing for the determination of regional area-left ventricular pressure loops, also known as regional stroke work. An isolated rabbit heart was placed in a modified Langendorff apparatus that allowed the left ventricle to develop pressure and eject volume into the aorta. CASI was used to determine the simultaneous deformation of over 900 points located in a region approximately 4 × 6 mm on the anterior surface of the left ventricle. The heart was then subjected to regional ischemia and data were again acquired. Over the whole region, the average regional stroke work decreased at both 2 and 5 minutes of regional ischemia, which partially recovered upon reperfusion. In addition, this region was subdivided into 24 areas, and regional stroke work was determined in each area and similar results to that obtained over the whole region were found.
Numerical Simulation of Flow in a Physiologically Realistic Model of the Human Aorta With Vessel Compliance and Movement
Authors: Jin Suo , Oshinski John , Giddens Don
Published: November 2021

Vessel compliance and movement are important factors influencing blood flow patterns in arteries in addition to vessel geometry. This importance has been previously demonstrated in the study of coronary artery flow by several investigators. For large vessels such as the aorta, the effects are less well understood because its movement magnitude is relatively small and the movement trace is complex. In this study, a computational fluid dynamics (CFD) aorta model was reconstructed from magnetic resonance (MR) images, and MRI was used to obtain aortic flow mapping and wall movement data. Under some simplifying assumptions, the data were used to control an aorta model that has moving wall and meshes during a computational simulation. The results of the CFD simulation show similar flow patterns as the MRI results in the ascending aorta, verifying that the model reconstruction and simulation are reasonable.
Flow Characteristics Inside a Transpatent Flexible Left Ventricle With Anatomical and Antianatomical Valve Orientation
Authors: Pierrakos Olga , Vlachos Pavlos P. , Telionis Demetri P.
Published: November 2021

Mechanical heart valves (MHV) and the operation of heart valve replacement have evolved to a level of universal acceptance and yet, MHV implantation is not always the ideal solution. Apparently the flow through pivoted leaflets of MHVs induces a combination of flow characteristics, which are clearly conducive to clot formation and can initiate many other pathological conditions. Most in vitro studies of the flow downstream of a MHV have been conducted with the valve in the aortic position (i.e. Reul et al., 1986). Bluestein et al., (2000) used a numerical simulation and Digital Particle-Image Velocimetry (DPIV) to reveal intricate patterns of interacting shed vortices downstream of the aortic valve and demonstrated that blood elements exposed to the highest shear stresses in the immediate proximity of the MHV could be trapped within the vortices that form in the wake of the valve.
Modeling of Angiographic Dye Washout From Cerebral Aneurysms Before and After Stenting: An Index for Stent Efficacy
Authors: Sadasivan C. , Lieber B. B. , Lopes D. K. , Ringer A. J. , Hopkins L. N.
Published: November 2021

The ultimate goal in the treatment of cerebral aneurysms is to exclude them from the intracranial circulation while preserving the parent artery. Recently, in vivo and in vitro experiments and clinical studies demonstrated that endovascular stenting is a significant and viable treatment option for cerebral aneurysms. Stents reduce the mass and momentum transport of blood from the parent artery into the aneurysm and alter both intra-aneurysmal flow and inflow-outflow patterns. The reduction of vorticity and flow stasis within the sac leads to thrombus formation and eventual exclusion of the aneurysm from the circulation. Digital subtraction angiography (DSA) has become an essential clinical tool for the diagnosis and treatment of aneurysms and is an important adjunct to stenting procedures.
Deployable Concepts for Oesophageal Stents
Authors: Kuribayashi Kaori , You Zhong
Published: November 2021

Stents are flexible structures capable of being folded into small dimensions allowing their passage into the problematic locations in the body and then being expanded. Their prime usage is to treat patients with obstruction at several sites in the body. For example, they are used to open blocked coronary arteries and large veins, to treat obstructions to breathing in the trachea and bronchus, and those in the prostate to allow the passage of urine [1].
Dynamic Model and Analysis of a Centrifugal Blood Pump and Induction Motor
Authors: Mawasha P. Ruby , Omotoso Omotoye , Lam Paul , Conway Ted
Published: November 2021

A dynamic model of a centrifugal blood pump, induction motor, and channel is investigated through nonlinear analysis. A centrifugal blood pump with forward curved blades and an induction motor is subject to constant inlet and outlet mass flow conditions leading to a channel. The steady state pressure drop versus volumetric flow rate relation is described by a constitutive model containing a cubic nonlinearity obtained from centrifugal pump characteristic curves. Within certain operating regimes along the characteristic curve, the model exhibits self-excited pulsatile periodic morion and the qualitative features of the response can be understood in terms of the underlying model. Further, the mathematical model is a more general model and can be used by the designer of centrifugal blood pumps and other ventricular assist devices (VADs) to determine the instability mechanisms.
Investigation of Coronary Artery Stenosis Hemodynamics Using Experimental and Computational Models: Influence of Flowrate, Size, Symmetry and Wall Roughness
Authors: Egelhoff C. J. , Budwig R. S. , Foster J. K. , Hansen B. L.
Published: November 2021

The motivation for the present study is to better understand the hemodynamics that may be involved with the onset of Myocardial Infarction (MI). We know the sequence of events is plaque rupture followed by thrombogenesis and then MI. There are several theories about the cause of rupture and fluid mechanics is cited as a possible theory.
An Experimental Study of the Effects of Non-Newtonian Blood Rheology in a Large Scale Model of a Distal Anastomosis
Authors: Gray Jonathan D. , Owen Ieuan , Escudier Marcel P.
Published: November 2021

This paper is concerned with determining experimentally the extent to which the assumption of blood being a Newtonian fluid affects the flow through a distal anastomosis. While many authors studying vascular fluid mechanics are turning their attention to geometrical considerations, the importance of the non-Newtonian effect is still unclear, and has yet to be experimentally quantified for anastomotic flows. The study reported in this paper aims to address the problems inherent in any comparison between a Newtonian and non-Newtonian flow by investigating qualitative Reynolds number trends in the flow characteristics for both types of fluid. Estimates are then made regarding the quantitative differences that may be expected when using a Newtonian fluid to represent blood flow through an anastomosis.
Flow and Compression in Collapsible Asymmetric Stenosis Models of Arterial Disease
Authors: Kobayashi Shunichi , Horie Takeshi , Amaya Tomohito , Morikawa Hirohisa , Tang Dalin , Ku David N.
Published: November 2021

Blood flow through the constricted area of a severe stenosis is similar to that through a venturi or flow nozzle. In the contraction section, the blood can accelerate to high speed. In this situation, the external pressure may be greater than the internal fluid pressure, and the artery could collapse. This collapse may be important in the development of atherosclerotic plaque fracture and subsequent thrombosis or distal embolization [1,2]. We used an asymmetric experimental model that closely approximates the arterial disease situation where the entire stenosis is compliant and the stenosis wall was not rigidly constrained. This study was to examine the relationships between flow rate, pressure and eccentricity of the stenosis inducing collapse under steady flow.
Characterization of Agarose and Alginate Gels for Cell Compression Experiments
Authors: Srinivasan Jayendran , Mukherjee Nilay
Published: November 2021

Various concentrations of folly hydrated agarose and alginate gel formed into cuboid shapes are tested in unconfined compression with impermeable plattens to determine Young’s modulus at equilibrium (relaxed elastic modulus) of the gel blocks. Repeat testing of a single block was performed to assess intra-test variability in testing conditions and deterioration of the gels during the testing procedure. Variability in material properties of gels formed in a single batch was assessed. The data was compared with values obtained from a search of relevant literature. While general trends in the data were the same (increased modulus for larger concentration gel), large differences in actual values of material properties were noted which could be ascribed to differences in the method and conditions of testing and theoretical models used to obtain material properties. Accurate properties of the gels are needed in gel-cell (cells embedded in gel) compression experiments in order to extract accurate cellular properties. It is concluded that it is necessary to use the gel material properties obtained under the same conditions of testing in order to determine cellular material properties in gel-cell compression experiments.
Temporal Development of Material Properties in Free Swelling Chondrocyte-Seeded Agarose Constructs
Authors: Kelly Terri-Ann N. , Wang Christopher C.-B. , Chahine Nadeen O. , Ateshian Gerard A. , Hung Clark T.
Published: November 2021

An understanding of chondrocyte mechanotransduction requires knowledge of the deformational fields within the tissue. Since the study of chondrocyte mechanotransduction in articular cartilage explants is hampered by its inhomogeneous biochemical composition and biomechanical properties, investigators have performed loading studies of chondrocyte-suspended hydrogel polymer systems such as agarose [1]. Prior to significant matrix elaboration by the cells, the agarose offers a uniform, uncharged three-dimensional (3D) mechanical environment for chondrocytes [2,3]. In this study, a technique, which combines video microscopy [4] and digital image correlation [5], was used to provide a novel characterization of the temporal changes in displacement field, apparent Young’s Modulus and apparent Poisson’s ratio of free swelling chondrocyte-seeded agarose constructs. Biochemical analysis was performed to permit correlation of these parameters with matrix elaboration.
Dynamic Hydrostatic Pressurization Increases Matrix Gene Expression by Chondrocytes in 3D Culture
Authors: Mauck Robert L. , Soltz Michael A. , Ateshian Gerard A. , Hung Clark T.
Published: November 2021

Articular cartilage is the load-bearing substance that covers the bony surfaces of articulating bones. With its high water content and small pore size, deformation of cartilage induces a very high hydrostatic pressure within the cartilage. This hydrostatic pressure has been shown both theoretically and experimentally to support upwards of 90% of the applied load (1), and can be on the order of 6–12 MPa. Chondrocytes, the cells within cartilage respond to this pressure by altering their rates of biosynthesis. Studies utilizing radionucleotide incorporation in both explant and monolayer cultures (2–4) have shown that in general dynamic pressurization increases synthesis, while static pressurization decreases synthesis. More recently, Smith et al have shown that dynamic pressurization (10MPa, 1 Hz) of cells in monolayer culture can upregulate matrix gene expression (5,6). Further, a study in PGA constructs has shown that long term application of dynamic pressure can increase matrix deposition (7). In this study, we seek to expand on these findings by examining the response in gene expression of articular chondrocytes encapsulated in alginate, a charged, 3D hydrogel.
Biomechanical Properties of Grown Cartilage Are Decreased in the Presence of Retinoic Acid, Chondroitinase ABC and Ibuprofen
Authors: Chen Chih-Tung , Torzilli Peter A. , Fishbein Kenneth W. , Spencer Richard G. S. , Horton Walter E.
Published: November 2021

The objective of this study was to determine the biomechanical properties of cartilage grown in a hollow-fiber bioreactor and their correlation with biochemical properties and magnetic resonance images (MRT). Engineered/grown cartilage has been shown to be a useful resource for cartilage repair [5]. The integrity and functional strength of engineered tissues are reflected in their biomechanical properties. A better understanding of the biomechanical properties of engineered cartilage can benefit us when designing a system to grow cartilage.
Building Cellular Microenvironments to Control Capillary Endothelial Cell Proliferation, Death, and Differentiation
Authors: Tien Joe , Tan John L. , Nelson Celeste M. , Chen Christopher S.
Published: November 2021

The dynamic binding interactions between cell surface receptors and local bioactive ligands serves as the principal mechanism by which cells survey their microenvironment and accordingly modulate their behaviors, such as proliferation, differentiation, migration, and suicide. Using conventional and non-conventional microfabrication approaches to engineer well-defined cellular microenvironments, we are examining how cells recognize and respond to adhesive interactions with the insoluble extracellular matrix (ECM). We will discuss our approaches to control the architecture and geometry of the adhesive interactions, as well as our resulting progress in identifying and elucidating the mechanisms by which cells sense the physical, chemical, and structural information carried within the ECM. By developing these approaches to engineering cell-surface interactions, we hope to improve the interconnect between artificial surfaces and living cells.
Strain and Strain Rate Dependence of Vascular Smooth Muscle Injury
Authors: Barbee Kenneth A. , Bhavnani Amit
Published: November 2021

Over 350,000 percutaneous translumenal coronary angioplasty (balloon angioplasty) procedures are performed each year. This procedure offers a less invasive alternative to coronary by-pass surgery for patients whose coronary vessels have become occluded due to the process of atherosclerosis. Its potential has not been fully realized due to the high rate of restenosis — the rapid reocclusion of the vessel due to the pathological growth of the vascular smooth muscle (VSM) in response to the trauma of the balloon inflation. Despite the recognition of smooth muscle injury as an initiating event in the process of restenosis, there has been no systematic study to determine the mechanical loading conditions required to produce VSM injury and elicit the restenosis response. In this study, a cell culture model was developed to define the loading conditions required to produce VSM injury. The model system allows precise control of the applied strain and strain rate and quantification of the injury severity in terms of membrane damage. The determination of the threshold criteria for cell injury will allow the angioplasty procedure to be modified, and possibly automated, to minimize VSM injury and avoid the restenosis response.
Dynamic Formation for the Mechanical Connection of Focal Adhesion Complexes to Study Localized Mechanisms of Angiogenesis Through Modeling With Cellular Automata
Authors: LeDuc Philip R.
Published: November 2021

The mechanical connection through the formation of focal adhesion complexes (FACs) is critical in cell growth and apoptosis. The FACs act between the cells and the extracellular matrix (ECM), which in turn influences angiogenesis, the growth of new capillary blood vessels [1]. These complexes form direct connections from ECM into the cell cytoskeleton through a series of protein binding events. This linkage is critical for mechanical force sensing and mechanotransduction signaling [2]. Here, the probabilistic modeling of this complex formation is undertaken to begin to uncover the effect of the spatial distribution and temporal effects on this dynamic process. In this, the rich dynamic process of the FACs formation through the binding events of integrin, paxillin, talin, and vinculin are examined. The FACs are mediated through the clustering of transmembrane integrins, which initiate the binding cascade. This interaction has been shown to be a critical event in the activation of the mechanochemical cascade and further mediates downstream signaling of protein tyrosine kinases including focal adhesion kinase [3].
Nuclear Membrane Dynamics of a Nuclear Pore Complex Structure
Authors: Pidaparti R. M. , Sarma P. A. , Sinha A. S. C. , Vemuri G. , Gacy A. M.
Published: November 2021

The nuclear pore complex (NPC) is an excellent example of a bio-molecular motor, since it operates primarily via energy dependent processes, and performs some of the most vital functions required for the survival of a cell. In the presence of appropriate chemical stimuli, the NPC apparently opens or closes, like a gating mechanism, and permits the flow of material in to and out of the nucleus. An NPC, with typical dimensions of 100–200 nm, is a megadalton (MDa) heteromultimeric protein complex, which spans the nuclear envelope and is postulated to possess a transporter-containing central cylindrical body embedded between cytoplasmic and nucleoplasmic rings as shown in Fig.1. A cell has many, presumably identical, NPCs, each of which participates in the import and export of nuclear material from within the nucleus [1–2]. Exactly how this transport occurs through the NPC is an open question, and a very important one, with profound implications for nanoscale devices for fluidic transport, genetic engineering and targeted drug delivery.
Micromechanics of Extracellular Matrix: Three-Dimensional Microstructure Under Load
Authors: Roeder Blayne A. , Kokini Klod , Sturgis Jennifer E. , Robinson J. Paul , Voytik-Harbin Sherry L.
Published: November 2021

The extracellular matrix (ECM) guides tissue form and function by communicating to cells both biochemical and mechanical information about the local micro-environment. It is well established that mechanical loads to tissues influence fundamental cellular processes including proliferation, migration, formation of adhesion complexes, and gene expression [1]. However, the pathway that transduces these forces from the tissue (macro) to the cellular (micro) level remains to be elucidated. In order to understand how cells interact mechanically with their surroundings, the three-dimensional (3D) micromechanical properties of the ECM must be understood. Advancements in the knowledge of ECM micro-behavior will be key to the development of future tissue engineering strategies.
Soft Gel Chromatography Column Analysis and Design for the Production of High Molecular Weight Blood Factors: Model Molecular Protein C
Authors: He Weiwei , Bruley Duane F.
Published: November 2021

Preparative chromatography involves column design from a biomechanical as well as from a biochemical perspective. Column collapse is a costly phenomena if expensive resins are used as the matrix material. This is particularly true for the soft gels that are useful for the separation of large water-soluble molecules, such as proteins. The model molecule for this research is human Protein C which is being separated from transgenic animal milk. Human Protein C is an important anticoagulant and antithrombotic in the human bloodstream [1].
Vibration of Elastic Continuum With Stochastically Varying Surface Roughness Carrying an Accelerating Oscillator
Authors: Schenk Christian A. , Bergman Lawrence A.
Published: November 2021

The problem of calculating the second moment properties of the response of a general class of non-conservative linear distributed parameter systems with stochastically varying surface roughness excited by a moving concentrated load is investigated. In particular, the method as presented in [1] is extended to the case of an arbitrarily varying oscillator speed. The resulting initial boundary value problem is transformed into the modal state space, where the second moment characteristics of the response are determined by direct integration using a Runge-Kutta method.
Dynamic Analysis of Semi-Active Tuned Vibration Absorbers Using Closed-Form Equivalent Models
Authors: Koo Jeong-Hoi , Ahmadian Mehdi
Published: November 2021

The main purpose of this study is to investigate dynamic characteristics of semi-active Tuned Vibration Absorbers (TVAs) using an adjustable damper, such as a Magneto-Rheological (MR) damper. Based on on-off and continuous control polices, closed-form groundhook equivalent models are developed for analytical studies of semi-active TVA models. In addition, the transmissibilities of groundhook equivalent models are compared with passive TVAs. The results indicate that semi-active TVAs, with off-state damping levels within a critical value, are capable of lowering the magnitude of resonant peaks without increasing vibration. In contrast, increasing damping in passive TVAs results in reducing the amplitude of resonant peaks at the expense of increasing vibrations at the tuned frequency. A parametric study of the groundhook TVAs shows that the effectiveness of semi-active TVAs increases with larger on-state damping, larger mass ratio, and smaller off-state damping.
Model Based Control of a Smart Vibrating Cantilever Beam
Authors: Scott Robin G. , Brown Michael D. , Manning Warren J. , Levesley Martin C.
Published: November 2021

This paper compares Generalised Minimum Variance and Pole-placement techniques for the control of a lightly damped cantilever beam smart structure. Saturation of the control signal can lead to limit cycles in Pole-placement control. Saturation compensation can remove these limit cycles, allowing disturbances of the beam to be rejected, but introduces a low amplitude, higher frequency vibration effect. Control sensitivity functions used to investigate these limit cycles show that certain Pole-placement controllers are sensitive to frequencies in the 50Hz range. The sensitivity of a Generalised minimum variance (GMV) controller is shown to be less than that of the Pole-placement controller. This GMV controller is applied to the vibration control of the smart beam. The controller weightings of the cost function limit excessive control signals. Previous work allows a plant model to be generated that produces results that closely match experimental data. Control results shows that the GMV technique is highly effective in reducing both the decay time and amplitude of vibration for free and forced vibrations respectively.
A Systematic Approach for Machining Process Improvement
Authors: Seth Brij B. , Hamidieh Youssef A. , Muniyappa Balachandra
Published: November 2021

Vibrations and other signals have been used in machine condition monitoring to improve equipment maintenance practices in high volume production environments. Typically, the signals are obtained with the equipment running at steady speeds under idle conditions. However, evaluation of the performance characteristics of the machining process under actual machining conditions can provide critical information for identifying shortcomings of the process, and/or opportunities for design modification in the process. A systematic approach incorporating vibration and dynamic stiffness measurements at critical locations in machining processes, along with the use of upfront design tools, has been presented to improve the performance reliability of machining processes. Application of this approach has resulted in the development of investment efficient machining processes that provide consistent quality performance on the plant floor.