bluuebunny/crossref_metadata_2025 huggingface dataset:
Delivery of Plasmid DNA Through Intratumoral Infusion and Electroporation
Authors: Yuan Fan , Zaharoff David , Zhang Xiao-Yu , Lohr Frank , Dewhirst Mark W. , Li Chuan-Yuan
Published: November 2021

We investigated DNA transport in the interstitial space and across cell membrane facilitated by intratumoral infusion and in vivo electroporation, respectively. In the study, a rat fibrosarcoma was perfused ex vivo, and apparent hydraulic conductivity (Kapp) was quantified under different perfusion conditions. In addition, three plasmid DNA vectors were infused into solid tumors. Immediately after infusion, tumors were treated with or without electric pulses. Gene expression and tumor growth delay were determined at different time points after electroporation. We found that Kapp was very sensitive to the perfusion pressure, presumably due to perfusion-induced tissue deformation. Treatment of tumors with electric pulse facilitated gene expression in vivo. The growth of tumors treated with plasmid DNA encoding interleukin 12 (IL-12) and electric pulses was slower than those treated with IL-12 or electric pulses alone. These data suggest that gene delivery in solid tumors could be improved significantly through combination of intratumoral infusion and in vivo electroporation.
Experimental Investigation of Pressure and Velocity on Chemical Mechanical Planarization
Authors: Tsai Jhy-Cherng , Tsai Mingyi
Published: November 2021

Chemical-mechanical planarization or polishing (CMP) is an emerging process used in surface planarization and polishing for semiconducter wafer with multilevel interconnections. This paper investigates the effects of polishing pressure and velocity on the material removal rate (RR) and the non-uniformity (NU) in the CMP process. Wear models for CMP process from mechanical aspect, including abrasive-based model and flow-based model, are first discussed. Experiments using different polishing pressures, velocities, and back pressures are then designed and conducted based on the Taguchi method. Experimental results showed that RR and NU are consistent with theoretical models in a certain range. Both RR and NU increase as polishing speed increases. As RR and NU also increase with the polishing pressure at low pressure, their values become saturated and then decrease when the pressure exceeds certain value. It further verified that NU can be improved using proper back pressure as predicted by the flow-based wear model.
Cooling Technique for Outdoor Electronic Enclosures Using Phase Change Materials
Authors: Hadim Hamid A. , Mehmedagic Igbal
Published: November 2021

A theoretical study is conducted to investigate a new cooling technique for thermal management of outdoor telecommunication equipment enclosures. The technique consists of using a phase change material (PCM) combined with a heat sink to dissipate the heat to the ambient. The main advantages of using the PCM include: fully passive technique with no maintenance, no power is required, and relatively low cost. The use of the PCM for more effective thermal management of electronic enclosures is investigated for both the high end cooling (i.e. when the enclosure is exposed to high ambient temperatures) and the low end cooling (i.e. when the enclosure is exposed to very low ambient temperatures). The results from this preliminary theoretical study showed that with the use of a moderate amount of a properly selected PCM combined with the heat sink, the temperature within the enclosure can be maintained within the specified operating range. Potential applications with the use of the PCM include: peak load usage (e.g. during high communications traffic periods), extreme ambient conditions, reduced temperature fluctuations (to improve reliability), and more efficient implementation in smaller size enclosures.
A New Kalman Filter Design for Beat-to-Beat, Continuous Arterial Blood Presure Estimation
Authors: Zhang Yi , Yang Boo-Ho , Asada Harry H.
Published: November 2021

This paper presents a new technique of designing a Kalman filter for beat-to-beat arterial pressure estimation, based on observable/unobservable subspace decomposition. This method provides an approach to design a Kalman filter for ill-conditioned systems, whose overall state spaces are not observable but the variables of interest can be reconstructed from observable subspace, such as the arterial hemodynamic system used for continuous blood pressure monitoring. Thereafter, a low-order Kalman filter is designed for the observable subspace to estimate the variables, such as the peripheral blood pressure. Extensive experiments are conducted and the results are compared with the measurement from a FDA approved arterial tonometer to verify this method.
Dynamic Analysis and Control System Development for a Laboratory Wind Tunnel
Authors: Kim Dean H. , Morris Martin J. , Leja Greg M. , Scarlata Tyler R. , Wylie Stephen R.
Published: November 2021

This paper describes the dynamic modeling and control system development to maintain a constant air speed in the test section of a laboratory wind tunnel. The previous manual operation procedure of this wind tunnel during a typical test with multiple operating conditions had been tedious and awkward at best. The wind tunnel system dynamics have been accurately characterized using single-input, single output (SISO) experimental step responses for specified operating conditions. The implementation of the subsequent control system has improved performance such that this wind tunnel system now can be used like a commercial wind tunnel and both as a classroom instruction tool and as a research tool. This work has been performed by an undergraduate team for the two-semester capstone design course for the Mechanical Engineering Department at Bradley University. This project incorporates many aspects of a mechanical engineer’s education such as mechanical design, sensor selection, software mastery, dynamic analysis, and feedback control implementation. This project also crosses traditional mechanical engineering boundaries because of its connection to the fields of fluid dynamics, system dynamics, and control systems.
Innovative Dynamic Systems and Control Laboratory Experiments Utilizing Fluid Power
Authors: Alleyne Andrew
Published: November 2021

This paper presents the development and usage of a unique educational facility housed in the Mechanical and Industrial Engineering Department of the University of Illinois, Urbana-Champaign. The laboratory described is focused on the general subject area of Dynamic Systems and Controls. The particular technology utilized in the laboratory is Fluid Power; the transmission and control of energy via pressurized liquids or gas. This paper briefly describes the physical description of many of the laboratory components. An overview of 2 typical Dynamics Systems and Control experiments are given to emphasize the pedagogical value of this type of laboratory activity over other common exercises in the Dynamic Systems and Control educational field. Finally, this work describes the integration of the Fluid Power Lab into the College-wide Controls Laboratory Network at the University of Illinois, Urbana-Champaign.
Multisensor Integration and Fusion Model That Uses a Fuzzy Inference System
Authors: Wang Kaihong , Ray Probir Kumar , Mahajan Ajay
Published: November 2021

The main objective of this work is the development of an intelligent multisensor integration and fusion model that uses fuzzy logic. Measurement data from different types of sensors with different resolutions is integrated and fused together based on the confidence in them derived from information not typically used in traditional data fusion methods. Examples of such information are operating temperature, frequency range, fatigue cycles, etc. These are fed as additional inputs to a fuzzy inference system (FIS) that has predefined membership functions for each of these variables. The output of the FIS are weights that are assigned to the different sensor measurement data that reflect the confidence in the sensor’s behavior and performance. A modular approach is adopted for the data fusion system. It allows adding or deleting a sensor, along with its fuzzy logic controller (FLC), anytime without affecting the entire data fusion system. This paper presents a preliminary model that fuses the data from three different types of sensors that monitor the strain at a single location in a cantilever beam. This will be later extended to sensors that will be fixed at different locations on the same beam. The resulting model will then be tested on a sub-scale composite bridge for a smart structural health monitoring system. The results from the proposed work are a stepping stone towards the development of generic autonomous sensor models that are capable of data interpretation, self-calibration, data fusion from other sources and even learning so as to improve their performance with time.
Optimal Backstepping Control of a VR Spherical Motor
Authors: Lee Kok-Meng , Sosseh Raye
Published: November 2021

This paper considers the control of a variable reluctance (VR) spherical motor that offers some unique features by combining the roll, pitch and yaw motion in a single joint. The 3-DOF VR motor has multiple independent inputs, and the output torque is direction varying and orientation-dependent and as a result, the control for such a motor is significantly more challenging than the single-axis motor. We formulate a new three-degrees-of-freedom (3-DOF) VR motor control design tool using backstepping, where the inputs are optimized to achieve minimum total energy consumed. The torque has been derived as a linear combination of the square of the input currents, a form computationally friendlier than its quadratic counterpart for real-time implementation. The overall stability of the system is shown using Lyapunov techniques. Simulation results are illustrated to show the performance of the controller.
Reducing Operator Induced Machine Vibration Using a Complex Pole/Zero Prefilter
Authors: Ingram Grant A. , Franchek Matthew A. , Chiu George T.-C.
Published: November 2021

A systematic prefilter design process for reducing operator induced rigid body vibrations of rubber tire mounted machines is presented. The contribution of this work is the development of a systematic prefilter design process and interpretation of the results. The class of equipment considered in this work are those machines having rigid body main frame vibrations dominated by linear dynamics. The reduction of machine vibrations is accomplished through the design of prefilters that reduce the machine resonant frequencies from the operator commands. The machine information required for the design process includes the bandwidth of the electro-hydraulic (E/H) valves and rigid body resonant frequencies of the machine mainframe. The pre-specified performance in the design process is the desired attenuation of machine resonant frequencies, i.e. the acceptable level of machine vibration. The design methodology has been applied to a telescopic boom lift to illustrate the procedure and the effectiveness of the design.
Robot Task Planning Using First-Order Logic
Authors: Yan Lei , Krishnamurthy K.
Published: November 2021

Task planning for a robot operating in an unknown environment using first-order logic is considered in this study. The approach is to use one agent to simulate the robot and a second agent to simulate the environment. Both agents employ knowledge bases and an inference engine. The rules for the knowledge bases are developed using first-order logic and the inference method is based on hyper-resolution. A weighting scheme is used by the robot to decide on the action to be taken. After enough domain information is obtained, a task planner, which is also based on rules, is employed. Simulation results validating the methodology are presented for a robot moving inside a warehouse with four rooms. In this example, the environment is initially unknown to the robot. But after mapping the environment, the robot can efficiently plan tasks such as moving an object from one room to another.
Fuzzy Model Reference Learning Control of Aircraft Forebody Model
Authors: Grudzinski James J. , Tarabishy Mohamed Nabeel
Published: November 2021

Due to flow asymmetries created in the tip region, aircraft forebodies can experience large net side forces at high angles of attack. It has been shown that these forces can be controlled by the use of suction in the tip region. For this purpose, a control system that manipulated the flow near the tip was tested on an aircraft forebody model in a wind tunnel. Utilizing a conventional PD algorithm, the system was able to control the forebody satisfactorily when tuned for a particular Reynolds number; but the performance degraded as the Reynolds number was changed. Fuzzy logic control (FLC) was then applied and shown to be more robust than PD. However, the FLC also showed some degradation for flows at different Reynolds numbers. To address this problem, an adaptive fuzzy controller was used. This paper discusses fuzzy model reference learning control (FMRLC) as applied to the aircraft model. It is shown that FMRLC is able to quickly and automatically generate a rule base to control the model. It is then shown that he FMRLC is able to modify it’s rule base and adapt in real time when the Reynolds number of the system changes.
Criteria for Recovery of Zero Initial Condition Responses of Unstable Plants Under Input Saturation
Authors: Wu Wei , Jayasuriya Suhada
Published: November 2021

In this paper, we consider the sufficient and/or necessary conditions under which responses of unstable plants with zero initial conditions would be bounded under step inputs. Several possible unstable pole patterns are examined, and corresponding criteria are derived. It is shown that an unstable plant can be stabilized to have bounded responses using an alternate step input sequence. Step inputs simulate the saturated inputs in a feedback system with bounded control, where the closed-loop stability of an unstable plant is really difficult to study. Results from this open-loop study may lend some insight into the analysis and design of such feedback systems under input saturation nonlinearities.
Towards a Simulation Knowledge Network With Application to Coupled Physiological Systems
Authors: Gu Bei , Asada H. Harry
Published: November 2021

A new approach is proposed for the simulation of interacting human physiological subsystems. The new simulation environment will allow users to build, analyze and solve coupled physiological system models based on available distributed subsystem models. The subsystem models as an abstract form of physiological knowledge are shared through the Internet. The simulation knowledge network includes a distributed model database, an information server, and an analysis and solution environment that can be downloaded from the server. To represent the coupled system, we use Differential Algebraic Equations (DAE) as the basic format. There are three common sources of algebraic constraints in models of physiological systems. They are causal conflict, simulation optimization, and multistage processes. The singularly perturbed sliding manifolds method is chosen for solving DAEs. Possible future improvements are discussed. Examples of simulation of coupled circulatory, thermoregulatory, and renal systems are presented to demonstrate the simulation environment.
Realization of an Arbitrary Elastic Behavior With an Elastic Mechanism Having Concurrent Axes
Authors: Huang Shuguang , Schimmels Joseph M.
Published: November 2021

In this paper, synthesis of an arbitrary elastic behavior with an elastic mechanism is addressed. The mechanisms considered are parallel and serial mechanisms with concurrent axes. We show that any stiffness matrix can be realized through a parallel mechanism with all spring axes intersecting at a unique point. This point is shown to be the center of stiffness. We also show that any compliance matrix can be realized through a serial mechanism with all joint axes intersecting at a unique point. This point is shown to be the center of compliance. Synthesis procedures for mechanisms with these properties are provided.
Assembly of Hybrid Magnetic Microdevices
Authors: Vikramaditya Barmeshwar , Nelson B. J. , Yang Ge , Enikov Eniko T.
Published: November 2021

In this paper we present results of our task of assembly of hybrid magnetic MEMS devices. The contact phase of assembly for MEMS devices is complicated by the presence of surface effect and magnetic forces. This forces a path planning strategy that accounts for the mechanics of part interactions at such scales for all contact phases in order to guarantee successful and repeatable assemblies. To validate and demonstrate the applicability of microassembly strategies, we have developed a flexible automated microassembly workcell with integrated part handling skills which is also described.
Development of a Piezoelectrically-Actuated Mesoscale Robot Quadruped
Authors: Gogola Michael , Goldfarb Michael
Published: November 2021

This paper describes a minimalist mobile robot design approach that offers a high locomotive efficiency, and is therefore well suited to mesoscale robot design. The authors have incorporated this approach into the development of a dynamically controlled piezoelectrically actuated mesoscale robot quadruped. The design described utilizes a lightly damped skeletal structure that generates locomotion when vibrationally excited at a skeletal resonance by two piezoelectric unimorph actuators. The skeletal structure consists of four articulated legs used to produce a trot type gait. Each articulated leg moves in two degrees of freedom to create elliptical foot motions that enhance locomotion efficiency and rough surface capability. Directional control is achieved by tuning each leg to a slightly different resonant frequency, so that differential control of leg amplitude can be achieved by modulation of the actuator excitation frequency. Compact power electronics have been developed and self-powered (i.e., battery-powered) operation has been demonstrated. This paper describes the design of the robot quadruped, which has a footprint that measures 9 cm × 6.5 cm and weighs 51 grams without the electronics and 104 grams with them. Data is presented that characterizes the average speed and typical power consumption of the robot at various excitation frequencies.
Dynamics and Control of a 4C Mechanism
Authors: Hanchak Michael S. , Kashani Reza , Murray Andrew P.
Published: November 2021

This paper presents the dynamics and control of a two degree-of-freedom 4C mechanism synthesized to guide a body through a spatial trajectory. A CC dyad, a coupling of fixed and moving cylindric or C joints, can be designed to reach five spatial positions. Two seperate CC dyads designed to reach three positions are rigidly connected between the two moving C joints defining the 4C mechanism presented. Constrained Lagrangian formulation was used to determine the actuator forcing for a desired trajectory of the input joint (both displacement and rotation). The mechansim was implemented and controlled in ADAMS© software using a feed-forward, feedback control scheme. This technique produced a realistic model with excellent trajectory following characteristics.
Fingernail Sensors for Measurement of Fingertip Touch Force and Finger Posture
Authors: Mascaro Stephen , Asada H. Harry
Published: November 2021

Improvements on the wearable fingernail sensor are presented. By measuring changes in the color pattern of the human fingernail, the sensor is capable of detecting finger posture as well as touch forces which are applied to the fingertip. The fingernail is instrumented with a fitted sensor containing arrays of miniature LEDs and photodiodes that measure the blood content underneath the nail. Dynamic pattern recognition is used to differentiate between changes due to touching and bending. Since the sensor is mounted on the fingernail, touch forces can be measured without covering the fingerpad and obstructing the human’s natural haptic sense. Similarly, finger bending can be measured without wearing a glove that hampers the motion of the fingers. This paper briefly discusses design of the sensors, and then demonstrates sensor capabilities for both touch force and posture measurement.
Translating In-Parallel Actuated Mechanisms for Haptic Feedback
Authors: Frisoli A. , Checcacci D. , Salsedo F. , Bergamasco M.
Published: November 2021

This paper introduces a novel design method based on Lie algebra to identify some screw systems that maintain invariable kinematic properties for finite motions. The results are applied to the synthesis and evaluation of novel translating in-parallel actuated mechanisms for haptic feedback.
Effects of Plastic Properties of Adherends on the Stress and Strength of Adhesive Joints
Authors: Liu Jiemin , Sawa Toshiyuki
Published: November 2021

Effects of the plastic properties of adherends, such as yield stress, post-yield slop, ultimate stress, on the stress and strain distributions in adhesive and the strength of single-lap adhesive joints subjected to external tensile loads are examined by elasto-plastic finite element analysis. It is found that the gradient of stresses in the vicinity of the edge of adhesive interface reduces, and the joint strength increases as the yield stress of adherends increases in the situation plastic deformation of the adherends takes place. However, the yield stress will not affect the joint strength in the case where the joint strength is so small that the adherends are still in elastic state when the rupture takes place from the adhesive interfaces. The stress gradient in the vicinity of the edge of the adhesive interface decreases and the joint strength increases as the post-yield slope of the adherends increases when the joint is ruptured due to the plastic hardening of the adherends. In general, the ultimate stress of the adherends will not affect the joint strength for metal/epoxy/metal joints.
Bench-Top Validation Tests for Tissue-Engineered Arteries
Authors: Quee Shawn Chin , Han Hai-Chao , Ku David N.
Published: November 2021

Standard tests are needed for evaluating and comparing the mechanical and biological functions of tissue engineered arteries and other vascular grafts. We propose an ex vivo organ culture system as a living system for testing tissue-engineered vascular grafts. This bench-top organ culture system mimics the physiological environment of arteries including the flow, pressure, and the axial stretch. Arterial mechanical properties and physiologic functions including compliance, burst pressure, and contractile functions can be assessed before an expensive long-term animal test is initiated. Test results of natural arteries indicate that organ culture is a valid model for comprehensive evaluation of tissue-engineered vascular grafts.
Cathodal Migration of Chondrocytes to Applied DC Electric Fields: Effects of Neomycin
Authors: Chao Pen-hsiu G. , Liu Wendy , Roy Rani , Mauck Robert L. , Hung Clark T.
Published: November 2021

Cultured chondrocytes exhibit cathodal migration when subjected to applied direct current (DC) electric fields [1]. Our studies showed a 2-fold enhancement in migratory velocity at physiologic temperature (∼37°C) compared to room temperature (∼25°C). The inositol phosphate pathway antagonists, U-73122 and neomycin, were found to inhibit the directed response, indicating that it may be involved in chondrocyte migration. Further understanding of the molecular mechanisms underlying chondrocyte migration and galvanotaxis may contribute to the development of new strategies for cartilage repair.
Mechanical Loading and Articular Cartilage Metabolism
Authors: Smith Robert Lane
Published: November 2021

Articular cartilage provides diarthrodial joints with a loading-bearing surface that ensures functional motility. The physical characteristics of articular cartilage originate with the highly organized matrix of extracellular macromolecules that provide structural elements to the tissue. The matrix specialization rests with specific proteins produced by the cartilage cells, the chondrocytes that undergo extensive post-translational modification through addition of sulfated glycosaminoglycan and oligosaccharides. The matrix proteins fall into three major categories, the collagens, the proteoglycans and the glycoproteins, with each group contributing unique properties to cartilage form and function.
Albumin Uptake Into Endothelial Cells in Separated Flow
Authors: Kudo Susumu , Yamaguchi Ryuhei , Sato Masashi , Oka Kotaro , Tanishita Kazuo
Published: November 2021

The purpose of this study is to reveal the albumin uptake into endothelial cells in the separated flow area. After 24 hr of exposure to flow induced in a back step flow channel, the endothelial cells were incubated in 37°C for 60 minutes in PBS containing tetramethylrhodamine isothiocyanate conjugated albumin (TRITC-albumin). Thereafter, the cell morphology and the albumin uptake were observed by a confocal laser scanning microscope (CLSM). In a low shear stress area (stagnant and reattachment areas), the cells aligned randomly. In a high shear stress area (reversal and fully developed areas), the cells were elongated and aligned to flow direction. In low-shear-stress and high-shear-stress gradient areas (reattachment areas), the amount of albumin uptake into the cells was the largest in all areas. These data indicate that shear stress and shear stress gradient affect the endothelial cell morphology and the albumin uptake into endothelial cells.
Computational Mechanical Analysis of the Platelets Behavior in the Blood Flow Using Discrete Element Method
Authors: Miyazaki Hisako , Liu Hao , Yamaguchi Takami
Published: November 2021

Platelets play an important role in blood coagulation, particularly in the formation of primary thrombi. It is thought that the aggregation of platelets, which initiates primary thrombi formation, is mediated by a macromolecule called von Willebrand Factor (vWF). vWF is a long chain macromolecule that exists in the blood flow as a soluble form and in the vessel wall as an insoluble form. Figure 1 schematically shows normal (a) and pathological (b) thrombus formation processes as illustrated by Ikeda (1998) In both cases, platelets adhere to the injured vessel wall and then form a thrombus in cooperation with the fibrin network, red cells, and other blood constituents. vWF is thought to play a more important role in pathological thrombosis formation than in the normal hemostatic process, particularly due to its ability to react to hemodynamic stress.
Using Computer Aided Speckle Interferometry to Measure Deformation in the Nonbeating Perfused Rabbit Heart
Authors: Gaudette Glenn R. , Krukenkamp Irvin B. , Todaro Joseph , Chiang Fu-Pen , Guan E.
Published: November 2021

Many diseases result in a heterogeneous distribution of regional function. This results in the need for a technique that can accurately measure deformation with high spatial resolution. We have developed computer aided speckle interferometry (CASI) to accomplish this task. Instead of tracking individual particles, CASI tracks clusters of particles. An isolated rabbit heart was arrested, and data was acquired in the perfused state, globally ischemic (15 min) state and reperfused state (10 min). CASI was used to determine the simultaneous deformation of over 1,000 points located in a region approximately 5.5 × 5.5 mm. A balloon was inserted into the left ventricle, and balloon pressure was increased from 5 to 20 mmHg. Ischemia and reperfusion resulted in a change in the epicardial deformation, leading to a change in principle strain from 2.8% to 4.5% (ischemia) to 2.8% (reperfused). A change in principle angle was also seen, with a 43° increase with 15 minutes of ischemia, and only a 10° change with reperfusion. In summary, we have a novel technique to measure regional deformation with high spatial resolution and found differences in the perfusion status of the heart.
Characterization of Enbucrilate Kinetics in a Model of Arteriovenous Malformation in Swine
Authors: Divani A. A. , Lieber B. B. , Wakhloo A. K. , Hopkins L. N.
Published: November 2021

Endovascular embolization of cerebral arteriovenous malformations (AVMs) has become an acceptable treatment. One commonly used embolic agent is n-butyl 2-cyanoacrylate (NBCA). The key to curative embolization of an AVM is complete glue casting of the arteriovenous transition (nidus) that requires precise knowledge of NBCA polymerization dynamics and its interaction with the arterial wall. We have created a model of a human AVM [1] in the rete of swine to investigate NBCA behavior. Embolizations were performed in both in acutely prepared endovascular AVM models as well as in surgically prepared AVM models where the vasculature was allowed to adjust to altered hemodynamic conditions. 30 AVM models were created and five embolic agent compositions were used to embolize the retia, yielding six samples for each glue composition. The retia were harvested and high-resolution radiographic images were obtained. The images were analyzed for penetration depth of the various mixtures vis-a-vis the prevailing hemodynamic condition just prior to embolization. Image processing tools and mathematical modeling were applied to predict the behavior of NBCA polymerization.
Investment Cast Biomedical Implants From Rapid Prototyping and Tooling Techniques
Authors: Walsh K. P. , Boyle D. G. , Wimpenny D. I.
Published: November 2021

Traditionally investment casting of biomedical implants has utilized the lost wax process, this paper is an investigation into the possibilities of casting small lots of custom specific medical implants directly and indirectly from various rapid prototyping & tooling techniques. Small batch quantities for quick turn arounds cost and lead times are the main contributing factors for the purpose of this investigation.

To directly produce parts means that a RP model will be used in the place of the wax pattern in the investment casting process.

To indirectly produce parts means that a mould, which has been generated from RP&T techniques, will be used to manufacture wax patterns that will then in turn be used to investment cast the parts.

The device to be manufactured is a non-sterile, referred to as ‘trial’ prosthetic implant. The implant is used by the operating surgeon to check the ‘fit’ of the cavity that will be made to receive the prosthesis plus bone cement that will be used to fix the implant in place.
Rotator Cuff Tendinosis in an Animal Model: The Role of Extrinsic and Overuse Factors
Authors: Thomopoulos S. , Esmail A. , Williamson J. D. , Flanagan C. L. , Iannotti J. P. , Carpenter J. E. , Soslowsky L. J.
Published: November 2021

One of the most common soft tissue injuries of the musculoskeletal system is injury to the rotator cuff tendons of the shoulder. These injuries are commonly attributed to factors such as overuse activity and extrinsic compression. Previous studies on the rotator cuff have been based on surgical reconstructive or clinical retrospective standpoints and were not designed to test hypotheses related to the causes of rotator cuff tendinosis. Our previous study has identified the rat as an appropriate in vivo animal model in which to study rotator cuff disease based on anatomic and functional similarities [1]. The current study uses this animal model to study the roles of extrinsic compression, overuse, and overuse combined with extrinsic compression, on the development of rotator cuff tendinosis. It was hypothesized that a single injury factor would be insufficient to create persistent tendinosis and a combination of injury factors would be necessary.
Investigation of Forces Imposed Upon the Wrist During Activities of Daily Living
Authors: Nowak Michael D. , Rideout Christina J. , Newport Mary L.
Published: November 2021

Injury to the wrist commonly results from a traumatic blow or repetitive loading. The effects that these incidents have upon the wrist depend primarily upon the magnitude of force, the point of application, the direction of application, and the rate of loading. Most repetitive loading injuries occur in athletes (Rettig and Patel, 1995). However, concern has been growing among clinicians about wrist injuries caused by repetitive loading that occurs during activities of daily living (ADL) (Malchaire et al., 1996).

The purpose of this research was to investigate the amount of force applied to the wrist during various ADL. Hand contact forces were measured while subjects pushed on a door handle, did a standard push-up, and used their arms to help stand from a chair.
Polymerization of Enbucrilate/Lipiodol Mixtures In Vivo
Authors: Gounis Matthew J. , Lieber Baruch B. , Hopkins L. Nelson
Published: November 2021

Embolization is an endovascular procedure used to treat cerebral arteriovenous malformations (AVMs). AVMs are pathological shunts between arteries and veins, which bypass normal brain structures. An embolic agent commonly used to occlude AVMs is n-butyl 2-cyanoacrylate (NBCA). Although NBCA has shown to be efficacious for this application, precise knowledge of its polymerization process in vivo is needed. Inadvertent occlusion of arterial feeders proximal to the AVM nidus will occur when polymerization of NBCA is too rapid. This may lead to revascularization of the AVM. Conversely, long polymerization times may result in the occlusion of draining veins, with subsequent brain hemorrhage and pulmonary emboli. It is therefore critical to understand the kinetics of the polymerization process to obtain a complete glue cast of the arteriovenous transition (nidus) thus, yielding safe obliteration of the AVM.

In order to elucidate the polymerization kinetics of NBCA, we examined the embolization process in the femoral and subclavian arteries of the rabbit. Various embolic agents composed of NBCA/lipiodol mixtures with and without the addition of glacial acetic acid (GAA) were injected. Blood flow through the femoral and subclavian arteries was measured prior to and during embolization. All studies were recorded with high-speed digital subtraction angiography (DSA). Preliminary analysis of the data suggests that flow decay during embolization exhibits a behavior that can be modeled via a lagged-normal density curve. Optimized model parameters vis a vis the experimental data are related to the polymerization kinetics. These parameters can be used to form a quantitative basis of comparison for the various liquid embolic mixtures.
Biological Responses of Fibroblasts to Cyclic Stretching: A Novel Culture Model Study
Authors: Wang James H.-C. , Stone David , Jia Fengyan , Celechovsky Chris , Woo Savio L.-Y.
Published: November 2021

Because of the advantage of better control of experimental conditions, in vitro model systems have been developed to examine the effects of mechanical loading on cells. Previous studies have shown that cyclic stretching causes cells to change orientation, proliferation and gene expression (Buck et al., 1980; Wang et al., 1995; Leung et al., 1976). However, one drawback of these model systems is that they are unable to control cell alignment and shape, and in addition, some provide heterogeneous strains to cells during stretching (See review by Schaffer, 1994). Consequently, cellular responses in these systems may not be similar to those in vivo. For example, tendon and ligament fibroblasts align with collagen fibers in vivo and are hence subjected to stretching along the tissue long axis. In contrast, in many existing systems, cells either randomly orient or orient away from the stretching direction.
The Influence of Bath Environment on the Fluid Content of Human and Rabbit Patellar Tendons
Authors: Israel Rajakumar , Atkinson Theresa
Published: November 2021

Recent studies have shown that the mechanical properties of tendons and ligaments are dependent on the amount of fluid present in the tissue. These studies have used a variety of bath environments to maintain or alter the fluid content of the tissue. However, no study has measured the effect of these baths on the fluid content of the specimen. In addition, no study has documented the influence of test environment on sectioned versus whole specimens. This experiment investigated the effect of saline, distilled water and sucrose baths on human and rabbit patellar tendons. Specimens were placed into the baths, and weight gain over time was measured. The results show that all specimens gained weight, and thus fluid, over time. The results further show that human specimens absorbed fluid at a faster rate than rabbit specimens. An important conclusion of this study is that exposure time in a bath is a critical factor in tissue hydration. Significant differences in absorption rates between divided and whole specimens were also found.
Finite Element Study of Oxygen Diffusion in the Intervertebral Disc
Authors: Sélard E. , Shirazi-Adl A. , Urban J. P. G.
Published: November 2021

The intervertebral disc consists of a water-rich extra-cellular matrix which is synthesized and maintained by its cells. The disc is the largest avascular tissue in the body with its cells lying as much as 8mm away from the blood supply. Nutrients, essential for maintaining cellular viability, diffuse through the matrix from blood supply under a concentration gradient arising from cellular demand. The oxygen concentration gradients in the intervertebral disc are investigated to examine the effects of exchange area and disc thickness on oxygen flux in the disc. The concentration gradients are computed using the two-dimensional Poisson’s equation and measured values for oxygen consumption rate and oxygen diffusion.
Pore Growth in Foamed Intermetallics for Structural Implants
Authors: Ilegbusi Olusegun J. , Ballas Matthew W.
Published: November 2021

The hydrodynamically controlled growth of closely spaced bubbles in a semi-solid alloy matrix is investigated. Specific attention is given to the case of controlled pore growth during the formation of porous intermetallics. Growth models are derived using three distinct relationships for the rheology of semi-solid alloys at various solid fractions. A cell model is used to represent the effect of spacing on bubble growth. The resulting models are solved numerically and compared for a variety of cases.
Mechanical Failure of Artificial Joint Materials: Wear and Fatigue
Authors: Topoleski L. D. Timmie
Published: November 2021

Total artificial joint replacements are one of the most effective treatments for arthritis. Artificial joints are used to replace damaged cartilage and act as low-friction articulating materials in joints. During normal human walking, some of the materials used for artificial knee and hip replacements are subjected to both sliding articulation (relative motion) and cyclic loading. A common example is the CoCrMo alloy femoral surface of an artificial knee that articulates against an ultra-high-molecular-weight-polyethylene (UHMWPE) component. Other materials do not experience relative motion (at least not intentionally) and are subjected to only cyclic loading. An example is the poly(methyl methacrylate) or PMMA bone cement used to fix components of artificial joints into bones. In the case of articulating materials, both surfaces are susceptible to wear, from both second-body and third body (in the presence of abrasive particles) mechanisms. Wear of the UHMWPE has received considerable attention recently, since the polymer wear is far more obvious than the metal wear. The Biomaterials field is developing an understanding of the wear mechanisms and how to enhance the wear resistance of UHMWPE. The wear of the metal components has not received as much attention, yet materials wear as a couple; both surfaces play a role in the overall wear. In the UMBC Laboratory for Implantable Materials, we are investigating the mechanisms of CoCrMo alloy wear, and the effect of worn metal components on the wear of UHMWPE. Understanding the wear mechanisms of metal components may help to extend the life of artificial joints by allowing new articulating material combinations and joint designs. For non-articulating materials, fatigue failure is a primary concern. Fatigue of metal components is relatively rare. In the distal portion of an artificial hip, the metal hip stem is fixed into the bone by a layer of PMMA bone cement. The PMMA bone cement is far weaker and less resistant to fracture and fatigue than either the bone or the metal, and thus may be considered the mechanical “weak link” in cemented total joints. We are investigating the fatigue properties of PMMA bone cements, and studying the mechanisms of fatigue crack initiation. If we can determine how fatigue cracks start in bone cement, we may be able to develop, for example, new surgical procedures (e.g., bone preparation) that will reduce the likelihood of fatigue failure. New formulations of bone cement have been developed for both joint fixation, and also for bone repair or replacement. Understanding the failure mechanisms of bone cements may enable safe and effective new uses for new bone cements, and extend the lives of cemented artificial joints.
Metal Release From Ti-6Al-4V Posterior Cervical Spine Plates: A Computational and Experimental Study in the Canine Model
Authors: Villarraga Marta L.
Published: November 2021

The use of Ti-6Al-4V for spinal implants has increased due to its advantageous mechanical properties, biocompatibility, corrosion resistance, and compatibility with MRI procedures. The release of metal ions or particulates, which can result from mechanical loads imposed on the implant, can affect the degree of biocompatibility of spinal implants, possibly influencing their clinical performance. In this project, the titanium metal release from Ti-6Al-4V posterior cervical spine plates was examined using a computational and experimental approach in the canine model.
Laser Microtexturing of Implant Surfaces for Enhanced Tissue Integration
Authors: Ricci John L. , Alexander Harold
Published: November 2021

Dental and orthopaedic implants rely on combinations of bone and soft tissue integration for mechanical support. While polished metal surfaces have been shown to encourage fibrous tissue encapsulation, roughened surfaces encourage bone integration. It is an accepted practice to roughen or texture regions of implants to encourage bone integration and produce smooth regions to promote soft tissue integration. We have developed a laser microtexturing technique that can be used to produce precision microtextured surfaces.
Abrasion of Steel by Diamondlike Carbon Coatings
Authors: Harris Stephen J.
Published: November 2021

Thin ceramic coatings can increase the fatigue lifetime of bearings and gears, possibly by polishing their counterparts and reducing stresses from asperities. Thus, a coating’s ability to polish or abrade may determine its usefulness. Yet there has been little work examining factors which control the abrasiveness of such coatings. We have analyzed the abrasiveness of diamondlike carbon and boron carbide coatings against steel for this study. We find an extremely steep dependence of abrasiveness on hardness. We show that coating roughness with horizontal features on the nanometer-scale is strongly correlated with abrasiveness, while roughness with horizontal features on the micron-scale is not correlated with abrasiveness. The nano-scale—but not the micro-scale—structure is quickly obliterated by sliding against steel, explaining the drastic reduction with time in the abrasiveness of the coating that we observe. We derive quantitative scaling relationships that show how the time dependence of the abrasion rate varies with important parameters of sliding wear, and we use these relationships to predict abrasion kinetics for new experiments. Detailed modeling of the stresses present during abrasion leaves some important questions unanswered.
Kinetic Spray: A New Coating Process
Authors: van Steenkiste T.
Published: November 2021

A relatively new coating process that uses high velocity gas to accelerate powder particles to velocities on the order of 500 m/s is being used to produce low porosity, low oxide, and low residual stress coatings. The powder particles are not melted or thermally softened prior to impact with the substrate. The coating process depends primarily on the conversion of the particle’s kinetic energy to mechanical and thermal deformation when the incident powder particles impact the substrate surface at high velocity. The time scale for the particle deformation and subsequent bonding to the substrate is on the order of 100 to 400 nsec. This extremely short time scale limits the possible bonding mechanisms and various papers have speculated on the possible bonding mechanisms for these coatings. An overview of the kinetic spray process, the history, description of the equipment, as well as an explanation of the bonding mechanism will be presented.
The Anisotropic Elastic Constants of Cancellous Bone
Authors: Cowin Stephen C.
Published: November 2021

A method of data analysis for a set of elastic constant measurements is applied to an excellent data base for cancellous bone. For these materials the identification of the type of elastic symmetry is complicated by the variable composition of the material. The data analysis method permits the identification of the type of elastic symmetry to be accomplished independent of the examination of the variable composition. This method of analysis may be applied to any set of elastic constant measurements, but is illustrated here by application to an extraordinary data base of cancellous bone elastic constants. The solid volume fraction or bulk density is the compositional variable for the elastic constants of these natural materials. The final results are the solid volume fraction dependent orthotropic Hooke’s law for cancellous bone.
Asymptomatic takotsubo syndrome occurring during Holter monitoring
Authors: Yambe Minoru , Nakano Takao , Kumagai Koji , Komaru Tatsuya
Published: November 2021

Asymptomatic takotsubo syndrome was observed during periodic Holter monitoring in a man in his 60s undergoing maintenance dialysis. No emotional or physical stress was noticed. The electrocardiographic changes at onset were determined, and repeated ST elevation and progressive formation of giant negative T waves were recorded.