bluuebunny/crossref_metadata_2025 huggingface dataset:
University of Central Florida Cogeneration Facility: Design and Economic Impact of a Medium Speed Reciprocating Engine Driven Chilled Water System
Authors: Burris Stephen , Oosaki Ryusuke , Shaw L. Todd , Norvell David , Bleeker Brett
Published: July 2013

The University of Central Florida Cogeneration Facility is a state of the art chilled water CHP system using a natural gas fueled high efficiency 60 Hz medium speed reciprocating engine as the prime mover. The facility features one lean burn 5.5 MW 18KU30GSI (MACH II-SI) spark ignition engine, generator, controls, auxiliaries, multi-effect absorption chiller, secondary cooling, and an advanced emissions control system that includes selective catalytic reduction (SCR) system and oxidation catalyst (OC).

The cogeneration system is located on a constrained site in Orlando, Florida at the second largest university in the United States with a student enrollment of over 56,000. The site is adjacent to a sensitive environmental area to the east, a main thoroughfare to the south, student dormitories to the west, and a lecture hall to the north. The architecture of the new combined heat and power plant was carefully designed to blend with the surrounding campus architecture and sound attenuation methods were employed to minimize noise pollution from the power plant.

The new chilled water system was interconnected to the existing campus chilled water facility, therefore requiring coordination with existing chilled water infrastructure as well as other existing electrical, water, sewer, and storm water utilities on the campus.

This paper describes the plant load profile, design criteria, engine performance, chilled water production heat balance, and emissions requirements. The economic benefit to the University is discussed including both the impact of self generating power and augmentation of the existing chilled water system. In addition, the benefits of using modern 3-dimensional design tools are outlined for a brown-field location such as the subject site.
A Comparative Analysis of Two Competing Mid-Size Oxy-Fuel Combustion Cycles
Authors: Thorbergsson Egill , Grönstedt Tomas , Sammak Majed , Genrup Magnus
Published: July 2013

Conceptual turbine and compressor designs have been established for the semi-closed oxy-fuel combustion combined cycle and the Graz cycle. Real gas effects are addressed by extending cycle and conceptual design tools with a fluid thermo-dynamic and transport property database. Maximum compressor efficiencies are established by determining optimal values for stage loading, degree of reaction and number of compressor stages. Turbine designs are established based on estimates on achievable blade root stress levels and state of the art design parameters. The work indicates that a twin shaft geared compressor is needed to keep stage numbers to a feasible level. The Graz cycle is expected to be able to deliver around 3% net efficiency benefit over the semi-closed oxy-fuel combustion combined cycle at the expense of a more complex realization of the cycle.
Aero-Thermal Design and Validation of an Advanced Turbine
Authors: Naik S. , Sommer T. P. , Schnieder M.
Published: July 2013

This paper describes the aero-thermal design and validation of an advanced axial flow turbine. This turbine, which has evolved from the existing and proven GT26/GT24 design consists of an optimised annulus flow path using high lift airfoil profiles and improved aerodynamic matching between the turbine stages. A major design feature of the turbine has been to control and reduce the aerodynamic losses, with particular attention being devoted to minimising the secondary, trailing edge and blade tip losses. The advantages of these design changes to the overall turbine efficiency has been verified by extensive controlled experimentation in high-speed cascade test facilities; by the utilisation of 3D multi-row computational fluid dynamics analysis tools, and via engine tests.

In addition to the aerodynamic design modifications of the turbine, the thermal designs of the turbine vanes, blades and heat-shields were also optimised. For the first stage film cooled vane and blade airfoils and platforms, both the film cooling layout and operating characteristics were improved. And for all the internally cooled airfoils, the internal heat transfer design features were additionally optimised, which allowed for more homogenous metal temperature distributions on the airfoil and endwall surfaces. The verification and validation of the thermal designs of the turbine components was confirmed via extensive dedicated testing in high-speed cascades for the film cooling performances, and in scaled perspex models for the internal heat transfer coefficients and local flow distributions.

The complete turbine was further tested and validated in the GT26 Test Power Plant in Birr, Switzerland via a dedicated turbine thermal paint test run and a subsequent performance and mapping testing phase.
Analysis of Direct Carbon Fuel Cell (DCFC) Based Coal Fired Power Cycles With CO2 Capture
Authors: Campanari Stefano , Gazzani Matteo , Romano Matteo C.
Published: July 2013

This work presents an analysis of the application of Direct Carbon Fuel Cells (DCFC) to large scale, coal fuelled power cycles. DCFCs are a type of high temperature fuel cell featuring the possibility of being fed directly with coal or other heavy fuels, with high tolerance to impurities and contaminants (e.g. sulphur) contained in the fuel.

Different DCFC technologies of this type are developed in laboratories, research centres or new startup companies, although at kW-scale, showing promising results for their possible future application to stationary power generation.

This work investigates the potential application of two DCFC categories, both using a “molten anode medium” which can be (i) a mixture of molten carbonates or (ii) a molten metal (liquid tin) flowing at the anode of a fuel cell belonging to the solid oxide electrolyte family.

Both technologies can be considered particularly interesting for the possible future application to large scale, coal fuelled power cycles with CO2 capture, since they both have the advantage of oxidizing coal without mixing the oxidized products with nitrogen, thus releasing a high CO2 concentration exhaust gas. After a description of the operating principles of the two DCFCs, it is presented a lumped-volume thermodynamic model which reproduces the DCFC behaviour in terms of energy and material balances, calibrated over available literature data. We consider then two plant layouts, using a hundred-MW scale coal feeding, where the DCFC generates electricity and heat recovered by a bottoming steam cycle, while the exhaust gases are sent to a CO2 compression train, after purification in appropriate cleaning processes. Detailed results are presented in terms of energy and material balances of the proposed cycles, showing how the complete system may surpass 65% LHV electrical efficiency with nearly complete (95%+) CO2 capture, making the system very attractive, although evidencing a number of technologically critical issues.
Gas Turbine Transients With Controlled Variable Geometry
Authors: Barbosa João Roberto , Bringhenti Cleverson , Tomita Jesuíno Takachi
Published: July 2013

A small 5-kN thrust gas turbine, designed and manufactured having in mind a thorough source of validation data, serves as basis for the study. The engine is an uncooled turbine, 5:1 pressure ratio axial flow compressor, delivering 8.1 kg/s air mass flow, whose control is made by a FADEC. Cold runs of the jet engine version have already been completed. The engine characteristics are being developed using the technology indicated in the paper. Accelerations and decelerations from idle to full power in a prescribed time interval and positive surge margin are the limitations imposed to the control system. In order to accomplish such requirements, a proportional, integral and derivative (PID) has been implemented to control the variable geometry transients, which proved to drive the engine to the required operating points. Compressor surge is avoided during accelerations or decelerations, imposing operation limits to the surge margin. In order to simulate a jet engine under transient operation, use was made of high-fidelity in-house developed software. The results presented in the paper are related to the compressor inlet guide vane (VIGV) transients. The engine transient calculations were predicted with the IGV settings varying with time, and the results are being used for the initial calibration of the transfer functions for the real time control.
The Balance Between Secondary Air System Pressure Head Requirements, Cooling Effectiveness and Turbine Efficiency: A Parametric Study
Authors: Quintero Sergio Arias , Dorman Kaylee M. , Ricklick Mark , Kapat J.
Published: July 2013

The advantage of higher turbine inlet temperatures as a way to increase cycle efficiency is potentially outweighed by the efficiency losses caused by the increased secondary air extracted from the compressor discharge to cool turbine components. Higher cooling effectiveness schemes could be used, but pressure head required to drive the coolant flow through the hot section components may be higher than those available due to combustor pressure losses. This paper looks to determine the potential effects on the overall cycle efficiency caused by an intentional pressure drop across the combustor, allowing more aggressive cooling schemes with a lower amount of cooling air, based on data of state of the art cooling schemes (coolant flow ratio, pressure head and cooling effectiveness) and a parametric analysis of a simple cycle turbine. Results suggest that coolant flow reduction can actually result in a lower pressure drop across the cooling passages, given the decreased flow velocity ending up in higher efficiency and specific work. Enhanced cooling schemes can also allow higher turbine inlet temperatures for a given coolant flow, resulting in improved performance.
Lessons Learned From the Development of Courses on Gas Turbine Multi-Disciplinary Conceptual Design
Authors: Kyprianidis Konstantinos G. , Grönstedt Tomas , Barbosa João R.
Published: July 2013

Despite the need for highly qualified experts, multi-disciplinary gas turbine conceptual design has not been a common study topic in traditional post-graduate curriculums. Although many courses on specialised topics in gas turbine technology take place, limited attention is given on connecting these individual topics to the overall engine design process. Teaching conceptual design as part of a post-graduate curriculum, or as an intensive short course, may help to address the industrial need for engineers with early qualifications on the topic i.e., prior to starting their careers in the gas turbine industry.

This paper presents details and lessons learned from: (i) the integration of different elements of conceptual design in an existing traditional MSc course on gas turbine technology through the introduction of group design tasks, and (ii) the development of an intensive course on gas turbine multi-disciplinary conceptual design as a result of an international cooperation between academia and industry.

Within the latter course, the students were grouped in competing teams and were asked to produce their own gas turbine conceptual design proposals within a given set of functional requirements. The main concept behind the development of the new design tasks, and the new intensive course, has been to effectively mimic the dynamics of small conceptual design teams, as often encountered in industry. The results presented are very encouraging, in terms of enhancing student learning and developing engineering skills.
Capture of Circulating Tumor Cells (CTCs) Using a Novel Micro-Device
Authors: Ranjan Shashi , Zhang Yong
Published: July 2013

Circulating tumor cells (CTCs) are metastatic cells that are detached from a tumor and are found in the blood of cancer patients. The presence of CTCs in the blood indicates the metastatic stage of cancer, so the detection of CTCs has been considered as a diagnosis and prognosis marker. The number of CTCs in blood has been found to be related with survival-rate. Also, CTCs have spurred interest for understanding the biology of these cells by performing genetic-level analysis which can be helpful in the development of targeted cancer-therapy or in drug-selection.
Effect of Osteopathic Manipulative Treatment Protocol on Balance in the Elderly
Authors: Lopez Daniel , King Hollis , Knebl Janice , Kosmopoulos Victor , Collins DeRaan , Patterson Rita M.
Published: July 2013

The purpose of this study it to understand the effect of Osteopathic Manipulative Treatment (OMT) on vestibular balance control structures. It was hypothesized that following an OMT treatment protocol, elderly patients would show significant improvement in empirical outcome measurements used to quantify postural stability.
Geometric Changes in a Lumbar Disc Have a Greater Effect on Disc Biomechanics Than Changes in the Biomechanical Properties of the Disc
Authors: Natarajan Raghu N. , An Howard S. , Andersson Gunnar B. J.
Published: July 2013

Structural alterations of the disc are accompanied by changes in disc tissue structure and composition during degeneration processes. As the lumbar disc degenerates, the disc height decreases. At the same time due to the development of fissures and cracks in the annulus, its material behavior changes. The degeneration process also includes cleft formation in the nucleus and reduction in water content in the nucleus. The clear demarcation between nucleus and surrounding annulus slowly disappear as the disc degeneration progresses thus increasing the annulus volume while reducing the nucleus volume. Both in-vitro and finite element studies exist in literature which deals with the biomechanical effect of disc degeneration. The changes in biomechanical behavior due to degeneration are a combined effect of change in geometrical parameters of the disc and change in material characteristics of the disc components. It is not known whether the change in disc geometries or the change in disc material properties has a predominant effect in altering the disc biomechanics. The current study focuses on this aspect.
High Speed Nailing for Bone Fracture Fixation: A Finite Element Penetration Model to Examine Nail Tip Design
Authors: Prygoski Matthew P. , Schmid Steven R.
Published: July 2013

A novel method of bone fracture fixation has been proposed in which small-diameter bioresorbable nails/pins are inserted across the fracture site using a device similar to that of a pneumatic nail gun [1]. Multiple nails inserted at varying angles can prevent translation and rotation of any bone fragments allowing healing to progress uninhibited. High velocity insertion would reduce surgical time; the nail would create its own entry incision so a drilled pilot hole would be unnecessary. A self-contained nailer, preloaded with sterile nail cartridges, could improve surgical outcomes in non-ideal operating conditions such as those encountered in military field hospitals. The bioresorbable nature of the pins would also mitigate the need for potentially risky removal surgery [1].
The Duration of a Nerve Root Compression Modulates Evoked Neuronal Responses in a Rat Model of Painful Injury
Authors: Nicholson Kristen J. , Winkelstein Beth A.
Published: July 2013

The annual incidence for neck pain in the adult population is 30–50% [1]. The cervical nerve roots are at risk for mechanical injury due to impingement of surrounding structures which can result in pain and numbness [2]. During nerve root compression, an immediate, brief increase in spontaneous afferent activity and a gradual decrease in electrically evoked axonal conduction have been reported [3,4]. Although previous studies demonstrate that a transient cervical nerve root compression induces persistent behavioral sensitivity [5,6], it is not known how the tissue mechanics during loading modulate neuronal function or how they relate to the onset of pain. Therefore, the goal of this study was to quantify neuronal activity in the spinal cord as a function of the duration of applied compression by measuring both electrically-evoked and spontaneous afferent activity during a transient compression of the cervical nerve root in a rat model of pain [5,6].
Biomechanical Modeling of Intrasac Pressure Changes and Vascular Remodeling After Endovascular Repair of Abdominal Aortic Aneurysms
Authors: Baek S. , Kwon S. T. , Rectenwald J. E.
Published: July 2013

Endovascular repair (EVAR) is a minimally invasive method of repairing an abdominal aortic aneurysm (AAA) that is associated with shorter hospital stay, lower mortality, and other advantages compared with open surgery. During this operation, a stent graft is introduced through a femoral artery and is deployed with the proximal portion below the renal arteries. After EVAR, the aneurysm sac should ideally be excluded from aortic blood flow resulting in a much lower intrasac pressure than the systemic pressure. In reality, the intrasac pressure varies from case to case. For a successful EVAR, intrasac pressure gradually decreases to around 20–40 mmHg over time, while in many patients intrasac pressure remains relatively high or even close to the systemic pressure for some cases. Our literature study [1] indicates that intrasac pressure has a significant impact on post EVAR AAA size changes. Additionally, post-EVAR remodeling depends not only of the values of the intrasac pressure but also on how the pressure has changed over a period of time.
A Nanoindentation Method for Hydrated Compliant Materials
Authors: Ebenstein Donna M.
Published: July 2013

Nanoindentation is becoming an increasingly popular tool in the biomaterials field due to its ability to measure local mechanical properties in small, irregularly-shaped or heterogeneous samples.1 Although this technique was readily adapted to the study of mineralized tissues, the application of nanoindentation to compliant, hydrated biomaterials such as soft tissues and hydrogels has led to many challenges.1 Three key concerns associated with nanoindentation of compliant, hydrated materials are inaccurate surface detection, errors due to adhesion forces, and fluid interactions with the tip.1–4
Finite Element Modeling of Mechanically Driven Skin Growth due to Different Expander Geometries
Authors: Buganza Adrian , Wong Jonathan , Kuhl Ellen
Published: July 2013

Tissue expansion has become an important technique used in breast reconstruction after mastectomy and for repairing large damaged skin areas such as burns [1]. According to the National Cancer Institute, the estimated number of breast cancer cases in 2010 in the United States was 207,090 [2]. Many of these women underwent mastectomies, and tissue expanders were used for breast reconstruction as a common procedure afterwards. Even though several studies from clinical and experimental points of view have been presented, there is still a poor understanding of the mechanobiological procedures occurring during skin growth. In particular, it is of interest to determine the effect of expanders with different geometries in strain, stress, and area gained during expansion.
A von Mises Mixture to Describe Experimentally-Derived Fiber Distributions From Soft Tissues
Authors: Ethier C. Ross , Gouget Cecile L. M. , Girard Michael J.
Published: July 2013

Collagen fibers strongly influence the biomechanical behavior of soft tissues [1], and constitutive models of such tissues should account for the characteristics of the fibers [2] and for their distribution. Such distributions can be measured using techniques such as small-angle light/X-ray scattering (SALS/SAXS; e.g. [3, 4]), diffusion tensor imaging [5] or 3D histology [6]. Fiber characteristics are often heterogeneous, so that measurements for entire organs or tissues typically yield large numerical data sets. Use of these raw data directly into biomechanical models is cumbersome and one may wish to parameterize them spatially for simplicity. This can be achieved through the use of a suitable mathematical function to fit the fiber distributions derived from experiment. Here we discuss how to choose such a function and optimize such a fit. We restrict our attention to thin tissue samples, where the fibers, assumed to be unimodally distributed, lie predominantly within a (tangent) plane, so that the problem is two-dimensional.
Vulnerable Plaque Detection Using Intracoronary Thermography and Cold Saline Injection
Authors: Rotman Oren , Zaretsky Uri , Einav Shmuel
Published: July 2013

Intracoronary Thermography (ICT) is a method which is primarily used for the detection of warmer arterial regions by a dedicated catheter with miniature temperature sensors at the catheter tip. A major goal for the ICT is to detect vulnerable plaques, which are the main cause of myocardial infraction, and hence a major life risk factor. The underlining hypothesis is that atherosclerotic lesions, which are considered as an inflammatory desease [1], will present on their intimal surface higher temperature than a normal, healthy arterial wall.
The Development of a Three Dimensional Anterior Cruciate Ligament Failure Locus: A Finite Element Analysis
Authors: Orsi A. , Yang N. H. , Hashemi H. N. , Canavan P. K.
Published: July 2013

A full or partial tear of the anterior cruciate ligament (ACL) is a common and painful injury that has been estimated to occur approximately 250,000 times annually in the U.S. [1]. Articular cartilage and meniscal injuries are also associated with ACL injuries [2]. ACL injuries can often lead to degenerative osteoarthritis of the articular cartilage [2]. An epidemiology study of athletic injuries by Majewski et al. [3] determined that out of 19,530 sports injuries, 20% were ACL injuries and 8% were medial collateral ligament (MCL) injuries.
In Vivo Experimental Study of Rat Brain and Spinal Temperatures During Non-Invasive Spinal Cord Hypothermia Using a Cooling Pad
Authors: Smith Katisha D. , Zhu Liang
Published: July 2013

Traumatic injury causes mechanical tissue disruption that immediately follows a traumatic event. After the initial event, secondary injury often occurs. It is a cellular and molecular response to external trauma, including ischemia, inflammation, apoptosis, necrosis, and edema in the central nervous system (CNS). Since secondary injuries can lead to paralysis and permanent neurological damage, most current treatment are devoted to delaying or preventing secondary neurological injury.
Simplified Model for ASM Dynamics
Authors: Al-Jumaily A. M. , Du Y.
Published: July 2013

The dynamic response of contracted airway smooth muscles to a finite length change and longitudinal oscillations is described using a simplified model. The model is intended to interpret the biophysical events but not to accurately describe them. It shows that the value of tissue length changes have pronounced indications of cross-bridge detachment. However, the frequency of oscillations represents the velocity of the length change, which affects the cross-bridge cycling rate reflected in the low frequency range.
Evaluating Design of Abdominal Aortic Aneurysm Endografts in a Patient-Specific Model Using Computational Fluid Dynamics
Authors: Segalova Polina A. , Xiong Guanglei , Rao K. T. , Zarins Christopher K. , Taylor Charles A.
Published: July 2013

Design and evaluation of implantable medical devices often relies on benchtop testing using physical models and animal studies. Although both methods are needed, they can be costly to implement and unable to represent patient-specific physiologic conditions. Computer simulations of blood flow in patient-specific anatomies offer an attractive alternative [1].
Altered Micromechanical Function Precedes Overt Surface Roughening in Early Cartilage Degeneration
Authors: Bevill Scott L. , Thambyah Ashvin , Broom Neil D.
Published: July 2013

The proper biomechanical functioning of articular cartilage in the joint is highly dependent on the composition and structure of the tissue. In the earliest stages of both osteoarthritis (OA) and age-related cartilage degeneration there are dramatic compositional and structural changes that occur within the general matrix. With these changes in matrix content and structure comes impaired biomechanical functioning [1]. A number of studies suggest that destructuring of the fibrillar collagen network (e.g., altered organization and loss of fibrillar interconnectivity) may be the initiating event in the degenerative cascade that leads to OA [2]. Despite the impact that these early structural changes have on bulk tissue mechanical properties, there have been few studies of the micromechanical consequences of matrix destructuring.
A Biventricular Finite Element Model of Heart Failure for Predicting the Effects of Treatment Strategies
Authors: Wenk Jonathan F. , Ge Liang , Zhang Zhihong , Soleimani Mehrdad , Potter D. Dean , Wallace Arthur W. , Ratcliffe Mark B. , Guccione Julius M.
Published: July 2013

According to recent statistics from the American Heart Association, Heart Failure (HF) affects 5.7 million Americans [1]. HF is characterized by the global dilation of the heart, which leads to an increase in ventricular volume and a reduction in pumping efficiency. Several treatment strategies have been investigated to combat the adverse remodeling that leads to the progression of HF [2,3]. These therapies include reshaping the heart by means of surgical intervention and implantation of medical devices.
Attachment State Shifts Viability Versus Cooling Rate (Inverted U Curve) During Freezing for Human Dermal Fibroblasts
Authors: Choi Jeunghwan , Bischof John C.
Published: July 2013

A large number of studies in cryobiology have focused on understanding the underlying biophysics at the cellular level to help predict survival outcome after cryopreservation or cryosurgery. While this behavior is increasingly well studied and understood in cells gaps remain in our understanding of how cells in tissues behave which can hamper freezing applications in tissues. This study compares freezing behavior in cells in suspension vs. attached (a model tissue) state to investigate any differences in cellular behavior in these two states.
A Structure-Based Biomechanical Model for the Effect of Dissolution of Muscle Cells on Pig Arteries: Elastin Associated With Muscle and Extracellular Matrix
Authors: Agianniotis Aristotelis , Rachev Alexander , Stergiopulos Nikos
Published: July 2013

We developed a structure-based model of the arterial wall to explain the effect of dissolution of smooth muscle cells (SMC) on the mechanical behavior of the artery and to obtain a better understanding of the interaction between the different wall components. Pressure-radius curves and dimensions of zero-stress configuration were measured in 5 control and 5 decellularized porcine common carotid arteries. We found that 13% of elastin is associated with the smooth muscle cells (SMC) whereas the rest 87% is associated with the extracellular matrix (ECM). Further, we found that the elastin related to SMC and the one related to the ECM have circumferential prestretches of 2.04 and 0.89, respectively. We conclude that the majority of elastic in the media is linked to ECM and is under compression at zero load, whereas a minor part is linked to VSM and is under tension (SMC related) at its zero load state. Upon chemical dissolution of the muscle cells elastin in series with SMC do not bear load allowing elastin connected to ECM to release its compressive prestress, leading to the expansion of the artery.
A Thoraco-Abdominal Model for Visceral Response to Experimentally Measured Deformations
Authors: Hallman Jason J. , Yoganandan Narayan , Pintar Frank A.
Published: July 2013

Dynamic external deformation of the human torso region has been shown to induce traumatic injury to underlying anatomical structures. Previous experiments utilizing post-mortem human specimens (PMHS) have correlated biomechanical response, e.g., compression and V*C, to risk of injury as observed during post-test autopsy [1]. Biomechanical measurements are often obtained from the chestband device, a flexible steel belt instrumented circumferentially with strain gages. From bending strain signals, chestband contours are derived which represent external torso deformation patterns in the transverse plane [2]. Although injury outcomes are correlated to biomechanical metrics as measured by the chestband [1], it is desirable to establish a relationship between deformation behaviors and tissue-level response throughout the impact event. Consequently, a computational model was developed and validated for examinations of viscoelastic tissue response to external deformation as measured by the chestband.
Novel Endoprosthesis for Limb Sparing of Canine Distal Radius Osteosarcoma Patients: A Modular Approach
Authors: Shetye Snehal , Ryan Stewart , Ehrhart Nicole , Puttlitz Christian
Published: July 2013

Distal radius osteosarcoma accounts for nearly 10% of all cancer-related maladies within the canine population. Traditional methods of treatment include amputation and/or chemotherapy. A major increase in survival rates (from 10% to 60%) with the combined use of these two techniques has now directed research towards saving the limbs of these patients. Massive cortical bone allografts, metal endoprosthesis and distraction osteogenesis are some of the available limb sparing approaches that have been investigated. Distraction osteogenesis requires surgeon expertise and significant post-operative intervention. Cortical allografts require the maintenance of a bone bank. Furthermore, they are associated with increased infection rates and ultimately result in amputation of the affected limb. Metal endoprostheses are a viable alternative to these methods. A metal endoprosthesis has previously been developed for limb sparing of distal radius osteosarcoma patients. However, a clinical trial of this device demonstrated failure rates of approximately 40%. The major causes of failure were screw pullout and shear failure of the proximal radius screws. A computational finite element study conducted in our laboratory corroborated these findings and provided critical information as regards to the structural causes of failure for these implants.
Design of a Universal Laparoscopic Suturing Device
Authors: Onal Sinan , Lai-Yuen Susana , Hart Stuart
Published: July 2013

Minimally invasive surgery (MIS) or laparoscopic surgery has changed the focus of surgery and has become an alternative to open surgical procedures. Operations are performed through small incisions in the abdomen thus avoiding the need for large incisions. This results in less tissue trauma, less scarring, and faster post-operative recovery time. However, the inherent challenges of laparoscopic procedures include limited visibility, constrained working space and the need for advanced surgical tools to safely and efficiently perform the surgical procedure. It is also necessary for surgeons to obtain advanced surgical training to perform these procedures.
Mechanical Characterization and Simulation of Murine Thrombi
Authors: Slaboch Constance L. , Ovaert Timothy
Published: July 2013

Deep vein thrombosis (DVT) is the formation of a thrombus, or blood clot, in one of the extremities, often in the vein of a leg. Approximately 2 million incidences of DVT occur annually. Roughly 300,000 people die due to the development of a pulmonary embolism (PE), which occurs when the thrombus from a DVT relocates to the pulmonary artery. Abdominal aortic aneurysm (AAA) is another life-threatening disease involving thrombi, resulting in 15,000 deaths annually. Together, these diseases impact over 2.5 million people each year. The effects of mechanical properties on thrombi dissociation and aortic rupture are not well characterized, and this lack of knowledge has hampered significant treatment and management of many blood-related diseases, as well as the development of optimal drug therapies. Determining these mechanical properties (i.e., elastic modulus and viscosity) is valuable information, as it can be used as inputs to simulations of thrombi disorders to more accurately determine thrombus dissociation or aortic rupture. The goal of this research is to determine the mechanical properties of murine (rat) thrombi under physiologic conditions via nanoindentation, for use as inputs data to numerical flow simulations.
Design and Development of a Novel Modular Spine Testing Apparatus
Authors: Moody David A. , O’Reilly Oliver M. , Lotz Jeffrey C.
Published: July 2013

Back pain is a well known health issue and several approaches to understanding the mechanics and dynamics of the spine, including mechanical testing, are used. Presently, several spine testing devices, such as those described in [1,2], are available which impose physiologic loads for various postures of the spine. Although these devices are successful at simulating physiologic loads, they do so by imposing non-physiologic boundary conditions. Thus, we believe the fabrication of a spine testing apparatus that addresses these deficiencies is warranted. In this extended abstract, we discuss our design and development of a robust, physiologic representative mechanical quasi-static testing device using reproducible boundary conditions that approximate, but dont replicate, the in vivo situation. The resulting testing apparatus is shown in Fig. 1. We also present a brief summary of a complementary spine model that is used in conjunction with the spine testing apparatus to predict muscle forces for various spine postures.
Tendon Stem Cells and Platelet-Rich Plasma for Repair of Injured Tendons
Authors: Wang James H-C.
Published: July 2013

Tendon injuries, including acute tendon injuries and tendinopathy, are common in both occupational and athletic settings. However, current treatments for tendon injury are largely ineffective, as they cannot restore normal structure and function to injured tendons. This challenge mainly stems from our incomplete understanding of tendon cell properties and responses to biomechanical and biochemical environments surrounding the cells. In recent years, however, significant progress has been made on two fronts. First, tendon stem cells (TSCs) have been recently identified. The tendon-specific stem cells can self-renew and posses multi-differentiation potential and as such, may be used to repair injured tendons more effectively. Second, platelet-rich plasma (PRP) has now been widely used in orthopaedics and sports medicine to treat injured tendons. In this presentation, I will present data on TSCs, in terms of their differential properties with respect to tenocytes and their differential mechano-responses when subjected to small and large mechanical loading conditions. I will also discuss the basic scientific studies on PRP regarding its effects on TSCs, particularly on their differentiation, which is a critical issue related to the safety and efficacy of PRP treatment in clinics (Fig. 1).
Geometric Deformation of Three-Dimensional Prostate Model With Applications to Computerized Training of Cryosurgery
Authors: Sehrawat Anjali , Shimada Kenji , Rabin Yoed
Published: July 2013

As a part of an ongoing effort to develop computerized training tools for cryosurgery, this study presents a computational technique to geometrically deform a three-dimensional organ template in order to generate clinically relevant prostate models. Cryosurgery is the destruction of undesired tissues by freezing, where prostate cryosurgery often involves the complete destruction of the gland. The objective of creating deformed models is to develop a database for computerized training [1]. The challenges in generating a prostate model from a template are associated with asymmetry of the organ, and the variability in growth patterns exhibited in the population of prostate cancer patients.
Testing Different Hypotheses of Vascular Homeostasis Based on Mechanical Stress or Strain in Image-Based Models Using an Inverse Method
Authors: Zeinali-Davarani Shahrokh , Baek Seungik
Published: July 2013

Various hypotheses are previously suggested to describe the tendency of vascular tissue to adapt in response to alterations in mechanical stimuli. It is still a matter of controversy which mechanical quantity governs or correlates well with the adaptation, contributing to the mechanical homeostasis. A computational tool that can distinguish between different hypotheses under various physiological conditions may help better understanding of the governing rules. Recently, an inverse optimization method has been developed to estimate the optimal spatial distributions of arterial wall thickness and material anisotropy of image-based models while satisfying a homeostatic condition assumed [1]. The same numerical method can be utilized to investigate the consequent optimal structures resulting from different hypotheses for the mechanical homeostasis. We consider three hypotheses for a homeostatic state based on intramural stress or cyclic stretch and examine their effects on the optimized distributions of thickness and anisotropy. The results show the capability of the presented method in discriminating different hypotheses of vascular homeostasis with image-based models, the validity of which requires more experimental data.
Lateral Approach in Robotic Assisted Knee Joint Arthroplasty
Authors: Kim Yoon Hyuk , Minh Huynh Le
Published: July 2013

Recently, computer-aided robotic systems, such as Robodoc® system and Makoplasty® system, have been used to enable surgeons to improve the accuracy of cutting and alignment in knee and hip arthroplasty [1,2,3]. The incision is normally done at the anterior part of the knee and the cutting is performed from the frontal direction during the TKA because enough working space of the tools is required during cutting process. Currently minimal invasive surgery (MIS) is the most popular keyword in the arthroplasty [4], and at this moment the MIS could not be performed common in the TKA using the robotic system. This MIS TKA could be achieved in lateral direction, and different cutting process also changes the robot configuration, which mainly affect the system accuracy. In this study, we investigated what additional advantages could be achieved in the bone cutting process laterally using laboratory-level less-invasive TKA surgical robot system.
Application of the Theory of Interacting Continua to Blood Flow
Authors: Massoudi Mehrdad , Kim Jeongho , Hund Samuel J. , Antaki James F.
Published: July 2013

Micro-scale investigations of the flow and deformation of blood and its formed elements have been studied for many years. Early in vitro investigations in the rotational viscometers or small glass tubes revealed important rheological properties such as the reduced blood apparent viscosity, Fahraeus effect and Fahraeus-Lindqvist effect [1], exhibiting the nonhomogeneous property of blood in microcirculation. We have applied Mixture Theory, also known as Theory of Interacting Continua, to study and model this property of blood [2, 3]. This approach holds great promise for predicting the trafficking of RBCs in micro-scale flows (such as the depletion layer near the wall), andother unique hemorheological phenomena relevant to blood trauma. The blood is assumed to be composed of an RBC component modeled as a nonlinear fluid, suspended in plasma, modeled as a linearly viscous fluid.
What Forces Does Cell Traction Force Microscopy Measure?
Authors: Zamir Evan A.
Published: July 2013

It is probably fair to say that the field of cell mechanics emerged with the pioneering work of Harris et al. [1], who observed that cells grown on thin silicone sheets generated wrinkling patterns — unfortunately, quantifying the forces at the cellular level was virtually impossible with their system. Almost two decades later, the study of cell mechanics began in earnest when Pelham and Wang [2] introduced a more rigorous method for quantifying individual cell-generated forces that quickly became known as cell traction force microscopy (CTFM), some form of which is now used in cell mechanics labs around the world. The basic idea underlying the original CTFM method is that the forces generated by cells can be calculated by solving an inverse problem for the displacement field experimentally measured by tracking microspheres embedded in a thin elastic substratum (typically polyacrylamide gel) on which the cells are cultured.
Modeling the Effect of the Experimentally-Derived Collagen Structure on the Mechanical Anisotropy of the Human Sclera
Authors: Coudrillier Baptiste , Boote Craig , Nguyen Thao D.
Published: July 2013

The sclera is the main load-bearing structure of the eye. It must be sufficiently stiff to maintain the shape and dimensions of the eye under acute elevation of intraocular pressure (IOP). These properties stem from the fiber-reinforced structure of the sclera, which contains dense superimposed lamellae of type I collagen fibrils embedded in matrix of proteoglycans and elastin. Recently, wide-angle X-ray diffraction [1] (WAXS) was used to map the fibrillar arrangement and distribution of collagen over posterior human sclera [2]. The results showed that the peripapillary region, immediately adjacent to the optic nerve head (ONH) had a larger amount of collagen and a circumferential collagen structure. The collagen structure in the mid-posterior region was more heterogeneous. The collagen structure of the sclera directly influences its material stiffness properties and therefore the level of strain transmitted to the tissues of the optic nerve head, which is the primary site of damage in glaucoma. Models inspired from the microstructure are needed to evaluate the contribution of the collagen structure on the mechanical properties. Earlier modeling efforts have treated the sclera as a homogenous, isotropic, linear elastic [3] or hyperelastic material [4, 5]. Girard et al. recently added the effect of the collagen structure using a nonlinear anisotropic model [6]. The authors fit their model for the collagen orientation and distribution to mechanical inflation data of the posterior sclera.
Incorporation of Perfusion Information Into a Finite Element Model of the Left Ventricle
Authors: Veress A. I. , Fung G. S. K. , Tsui B. M. W. , Segars W. P. , Gullberg G. T.
Published: July 2013

The 4D NCAT and XCAT phantoms have been found useful in the simulation of medical image data especially SPECT, PET, CT and more recently MRI. The phantoms provide realistic models of the anatomical structures and respiratory and cardiac motions of humans. When combined with accurate models of the physics and instrumentation involved in the imaging process, accurate and realistic simulation data that closely mimic those acquired from patients can be obtained. However, a limitation to the 4D NCAT/XCAT series of phantoms is that the cardiac motion incorporated in the NCAT/XCAT was based on a single set of gated tagged MRI data of a particular normal male subject so that the definitions of pathologies such as ischemia and infarction in the phantoms had no physiological basis. Our previous work sought to overcome this limitation by incorporating into the phantoms, a physiologically based finite-element (FE) mechanical model for the left ventricle (LV). These model was found to accurately simulate both the normal motion of the LV as well as abnormal motions due to ischemia [1] and infarction [2]. One of the primary limitations of these models is that they have overly simplistic geometries (Figure 1) representing the ischemic or infarcted regions.
Evaluation of Energy Attenuating Floor Mats for Protection of Lower Limbs From Anti-Vehicular Landmines
Authors: Quenneville Cheryl E. , Dunning Cynthia E.
Published: July 2013

During an anti-vehicular (AV) landmine event a large impulse is applied to the underside of a vehicle, causing rapid deformation of the lower hull and floor. These deformations, as well as the global vehicle acceleration, have the potential to cause serious injuries to vehicle’s occupants. As the lower legs are often directly in contact with the floor, they are loaded rapidly and are particularly vulnerable to injury.
Displacement-Encoded MRI With Steady-State Acquisition for Deformations and Strains in Applied Load Systems
Authors: Chan D. D. , Neu C. P.
Published: July 2013

Noninvasive and nondestructive methods like magnetic resonance imaging (MRI) used to visualize tissue mechanical behavior are key to understanding its material properties and function. Displacement-encoded MRI [1] has allowed for biomechanics research in the myocardium and other self-actuated tissues. However, additional imaging constraints must be considered when external loading must be applied to reproduce physiologically relevant loads and deformations in a tissue of interest. Previous studies have used displacement encoding with stimulated echoes (DENSE) with a fast spin echo (FSE) acquisition [2]. Despite a measured sub-pixel displacement resolution (65 μm [3]), DENSE-FSE is limited by long imaging times and signal-to-noise (SNR). Balanced steady state free precession acquisitions like true fast imaging with steady state precession (TrueFISP), however, provide high SNR and can be modified for DENSE acquisition [4]. Here, we evaluate DENSE with TrueFISP readout for noninvasive and rapid acquisition of deformation data in biomechanical systems that require exogenous applied loading.
Artificial Disc Versus Fusion: Effect on Three-Dimensional Dynamic In Vivo Cervical Spine Motion
Authors: McDonald Colin P. , McDonald Michael J. , Ramo Nicole L. , Bartol Stephen W. , Bey Michael J.
Published: July 2013

Intervertebral disc degeneration in the cervical spine is a common condition that often manifests as cervical disc disease, resulting in pain, motor weakness and sensory deficits. The most common surgical treatment strategy involves removal of the diseased disc and fusion of the adjacent vertebrae. Although fusion typically relieves symptoms at the surgical site, evidence of degeneration in the adjacent disc has been reported in 25–92% of patients [1,2]. It has been hypothesized that the progression of adjacent segment degeneration is a result of increased motion at the segments adjacent to the site of fusion [3]. As a response to this proposed mechanism of degeneration, artificial discs were designed with the goals of preserving motion at the operative site and maintaining normal motion in the adjacent segments. However, the extent to which normal adjacent segment motion is maintained in artificial disc patients compared to fusion patients remains unknown. Thus, the objective of this study was to compare the dynamic, three-dimensional (3D) motion of the cervical spine in fusion patients and artificial disc replacement patients.
Preliminary Evaluation of a Knee-Ankle-Foot Orthosis for the Emulation of Transfemoral Prosthesis Socket Loads
Authors: Dawley James A. , Romanazzi Andrew M. , Fite Kevin B.
Published: July 2013

Control of prosthetic limbs using myoelectric muscle potentials from the wearer’s residual limb enables direct control of artificial limb behavior. The typical approach entails the integration of surface electromyogram (sEMG) electrodes within the inner wall of the socket interface, located to target specific superficial muscles in the amputee’s residual limb. While myoelectric upper-limb control is commonplace in prosthetic practice, its use in lower-extremity devices has been slow to follow suit. Various research efforts have studied approaches to implementing myoelectric control of artificial leg behavior [1–4], but the need for myoelectric control in lower-limb prostheses has been limited by the lack of commercial prototypes with the capability of net power generation.