bluuebunny/crossref_metadata_2025 huggingface dataset:
Impact of Aortic Prosthetic Heart Valve Dysfunction on Left Ventricular Afterload and on the Accuracy of Echo-Doppler Measurements
Authors: Smadi Othman , Keshavarz-Motamed Zahra , Hassan Ibrahim , Pibarot Philippe , Kadem Lyes
Published: July 2013

Left heart side (left ventricle and left atrium) is responsible for delivering the oxygenated blood to all body organs, where a relatively strong left ventricle contraction is needed to deliver around 5 liters of blood per minute. As a consequence, the left heart side experiences a high pressure (∼150 mmHg). Therefore, the dysfunction (stenosis or incompetence) in the aortic and/or mitral heart valves in the left side of the heart is more common than the dysfunction in the pulmonary and tricuspid heart valves in the right side of the heart (Yoganathan et al., 2004). Heart valve surgical replacement is the most effective solution in severe functional heart valve disease (Pibarot and Dumesnil, 2009). Almost, half of the total implants of prosthetic heart valves (∼300,000) are mechanical (mainly bileaflet). In case of mechanical heart valve (MHV), a lifelong anti-coagulant should be taken to avoid thromboembolic events. Despite the significant improvement in valve design resulting in minimizing prosthetic valve complications (thromboembolic events or pannus formation), these complications are still possible with MHV Implantation.
In-Vitro Modeling of Heart Failure in the Presence of a Prosthetic Heart Valve Using Particle Image Velocimetry
Authors: Xiao Min , Bailey Annie , Pierrakos Olga
Published: July 2013

It is well-known that cardiovascular disease, affecting millions of people, is the number one killer in the US and worldwide. Current trends indicate that cardiovascular disease (CVD) will claim approximately 20 million victims in 2020 as the leading cause of death worldwide and will be responsible for over a billion deaths between 2000 and 2050 [1]. According to the American Heart Association, one in three American adults have one or more types of heart disease. Economically, the total and indirect costs due to cardiovascular diseases in 2009 were estimated at $475.3 billion. The spectrum of cardiac disease encompasses a broad range of disorders, varying from myocardial ischemia, valvular disease, diastolic dysfunction, congestive heart failure (which is projected to affect 20 million people by 2020), etc. Most of these disorders initiate and are associated to the left side of the heart, which is the workhorse and also the focus of our research herein.
A Multi-Axis Robotic Platform and Testing Protocol for Evaluating In Vitro Biomechanics of the Foot
Authors: DiAngelo Denis J. , Granata Jaymes D. , Berlet Greg C. , Ghotge Rahul , Li Yuan , Kelly Brian P.
Published: July 2013

The purpose of this study was to develop a cadaveric model for evaluating the relative motion across joint segments in the foot under simulated physiologic loading conditions. The specific aims were to 1) Develop a multi-axis testing platform that simulates three-dimensional (3D) loading conditions through the foot and ankle complex (Achilles load, tibial compression, and internal/external rotation) in a sequential or simultaneous manner, and 2) Evaluate and compare the three-dimensional (3D) kinematics between specific bones of interest in the foot for each individual cadaveric specimen.
A Robotic Model of Hip Dislocation Potential: Total Hip Arthroplasty Versus Femoral Head Resurfacing
Authors: Colbrunn R. W. , Bottros J. J. , Greeson C. B. , van den Bogert A. , Barsoum W. K.
Published: July 2013

Hip dislocation often results from neck impingement and subsequent subluxation. Having a model to study impingent-free range of motion (ROM) and dislocation potential at the impingement postures can elucidate the contribution to joint stability of prosthetic design, component position, anatomical variables, and biomechanical factors. Much controversy surrounds the resurgence of femoral head resurfacing (FHR) and its biomechanical implications of retaining the femoral neck, particularly its head-neck ratio. We have developed a dynamic cadaveric robotics model that functions in real time under load-control parameters to recreate in vivo hip mechanics. This study specifically identifies and compares the impingent-free ROM and a stability index value that quantifies the dislocation potential in the native hip, femoral head resurfacing and total hip replacement (size 28, 36mm femoral heads).
Shear Stress Within Trabecular Bone Marrow due to Low Magnitude High Frequency Vibration
Authors: Coughlin Thomas R. , McNamara Laoise M. , McHugh Peter E. , Niebur Glen L.
Published: July 2013

Low magnitude high frequency (LMHF) loading is anabolic to bone. LMHF loading for one year resulted in a 32% increase in the trabecular bone volume, decreased trabecular spacing and increased trabecular number in a sheep model (1). In contrast, no change was seen in cortical bone, suggesting the anabolic effect is limited to the trabecular compartment. Rats subjected to 90 Hz vibration developed greater trabecular bone volume and thicker trabeculae than rats subjected to vibration at 45 Hz (2). However, the strain induced in the bone during the 90 Hz vibration was significantly lower than during the 45 Hz vibration, indicating that the effect does not depend on matrix strain. As such, shear stress in the marrow may be the anabolic signal in this loading regimen.
Anisotropic Strain Fields Enhance Matrix Remodeling Through Elevated TGF-β Signaling
Authors: Gould Russell , Chin Karen , Santisakultam Puifai , Dropkin Amanda , Richards Jennifer , Chiu Yung-Nung , Schaffer Chris , Butcher Jonathan
Published: July 2013

In this work, we demonstrate the unique effect of controlled anisotropic strain on fibroblast behavior in 3D engineered tissue environments. Anisotropy of biaxial strain resulted in increased cellular orientation and collagen fiber alignment. Transforming growth factor beta-1 (TGFβ1) gene expression and pSmad2 nuclear translocation increased with biaxial directionality. Myofibroblastic alpha-smooth muscle actin (α-SMA) decreased with applied strain similar to mechanically unloaded hydrogels. Collectively, these results demonstrate a novel mechanobiological mechanism by which fibroblasts develop rapid anisotropic matrix striation while maintaining phenotype quiescence.
Computational Model of Thrombosis: A Study of Transport as a Determinant of Rapid Platelet Accumulation
Authors: Bark David L. , Ku David N.
Published: July 2013

Thrombus is commonly found in the plaque region of atherosclerosis, leading to acute myocardial infarction, known as a heart attack. Arterial thrombosis, which is mostly composed of platelets, can occlude a blood vessel by accumulating enough platelets to block blood flow. Understanding the relative contribution of platelet transport and platelet adhesion to thrombus growth rates is germane to predicting and treating at-risk lesions for thrombus growth.
Delineation of Noise Signals From MRI Measured Temperature Rise During HIFU Ablation Procedure
Authors: Dasgupta Subhashish , Dibaji Seyed Ahmed , Wansapura Janaka , Myers Matthew R. , Banerjee Rupak K.
Published: July 2013

A relatively recent and non invasive method for characterizing thermal fields generated by high intensity focused ultrasound (HIFU) transducers is Magnetic Resonance (MR) Thermometry method. However, noise signals generated by external RF sources infiltrate the scanner orifice and limit its ability to measure temperature rise during the heating or ablation phase. In this study, MRI monitored HIFU ablations are performed on freshly excised porcine liver samples, at varying sonication times, 20, 30 and 40 s at a constant acoustic intensity level of 1244 W/cm2. Temperature rise during the procedure is measured using Proton Resonant Frequency MR thermometry. Preliminary experiments without an adequate noise filter, failed to record temperature rise during the heating phase. A low pass R-C filter circuit is subsequently incorporated into the experimental set up to prevent infiltration of noise signals in the MRI orifice. This modified RC filter enables measurement of temperature rise during the heating phase followed by temperature decay during cooling. The measured data is within 12% agreement with the temperature rise computed by solving the acoustic and heat equations.
Echocardiography Evaluation of a Novel Stable Ovine Heart Failure Model Suitable for Cardiovascular Device Testing
Authors: Walsh Peter W. , McLachlan Craig S. , Ladd Leigh , Blitz Arie , Gillies R. Mark , Hambly Brett , Ocsan Ryan , Edwards Glenn
Published: July 2013

Numerous large animal models of chronic cardiac ischemia have been developed to explore either pathological mechanisms and or device interventions in developed heart failure models. Traditionally chronic heart failure in large animal models such as sheep or pigs has been induced by either coronary ligation with or without reperfusion. Coronary ligation is often attempted in the open chest surgical model or more recently in the closed chest animal via angiography [1]. Both techniques can be challenging and also induce high mortality with the risk of myocardial stunning and resultant shock and or lethal arrhythmias. There is also difficulty in developing stable heart failure across cases where infarct sizes can be variable. One strategy to over come this variability has been via rapid ventricular pacing, however inducing heart failure does not induce sustained heart failure in many cases if the pacing is switched off, and additionally pacing does not induce some of the underlying pathology seen in the development of heart failure [1].
Changes in Capsule Function Following Anterior Dislocation Elucidate the Need for Standardized Clinical Exams to Diagnose Shoulder Instability
Authors: Voycheck Carrie A. , Browe Daniel P. , McMahon Patrick J. , Debski Richard E.
Published: July 2013

The anteroinferior glenohumeral capsule (anterior band of the inferior glenohumeral ligament (AB-IGHL), axillary pouch) limits anterior translation, particularly in positions of external rotation, and as a result is frequently injured during anterior dislocation. [1,2] A common capsular injury is permanent tissue deformation, however, the extent and effects of this injury are difficult to evaluate as the deformation cannot be seen using diagnostic imaging. In addition, clinical exams to diagnose this injury are not reliable [3] and poor patient outcome still exists following repair procedures. [4] Previous experimental models have observed increased joint mobility following permanent tissue deformation. [5] While other models have quantified the permanent deformation using nonrecoverable strain [6], no model has correlated the amount of tissue damage to altered capsule function. Understanding the relationship between the extent of tissue damage and changes in capsule function following anterior dislocation could aid surgeons in diagnosing and treating anterior instability. Therefore, the objectives of this work were to 1) quantify the nonrecoverable strain in the anteroinferior capsule resulting from an anterior dislocation and 2) evaluate capsule function (strain distribution in anteroinferior capsule, anterior translation) during a simulated clinical exam at three joint positions, in the intact and injured joint.
Injury to the Glenohumeral Capsule During Anterior Dislocation Results in Damage to the Anteroinferior Capsule
Authors: Browe Daniel P. , Voycheck Carrie A. , McMahon Patrick J. , Debski Richard E.
Published: July 2013

The glenohumeral joint is the most frequently dislocated major joint in the body with about 2% of the population dislocating their shoulders between the ages of 18 and 70 [1]. About 80% of these shoulder dislocations occur in the anterior direction, and they most commonly occur in the apprehension position, which is characterized by 60° of glenohumeral abduction and 60° of external rotation [2]. The most common pathology associated with dislocation is instability due to permanent deformation [3]. Current surgical repair techniques for shoulder dislocations are inadequate with about 25% of patients still experiencing pain and instability after surgery [4]. By assessing the strain distribution, it is possible to determine the stabilizing function of the various capsular regions. In addition, surgeons could benefit from knowing the location and extent of tissue damage when placating the capsule during repair procedures. Therefore, the objective of this study was to determine the location and extent of injury to the anteroinferior capsule during anterior dislocation by quantifying the strain at dislocation and the non-recoverable strain following dislocation.
Determination of Mechanical Stresses in Vibration and Contact During Flow-Structure-Interaction in Vocal Folds
Authors: Bhattacharya Pinaki , Siegmund Thomas H.
Published: July 2013

Mechanical stresses in vocal folds (VFs) developed during self-oscillation — due to interaction with the glottal flow — play an important role in tissue damage and healing. Contact stresses occurring due to collision between VFs modify both self-oscillation characteristics, as well as stresses. The complexity of the problem is increased due to other factors acting in combination: transient nature of the flow, non-linear and anisotropic biomechanical properties of the VFs, and acoustic loading. Experiments with physical models [1] have attempted to deduce the state of stress in the interior through measurement of superior surface deformation. However, these methods pose challenges in data acquisition. on the other hand, full three-dimensional transient computational analysis of a self-oscillating and contacting VF model requires highly sophisticated algorithms as well as prohibitive resource usage. Not surprisingly, therefore, it has not been conducted until now. We hypothesize that a high-fidelity numerical simulation incorporating realistic tissue properties is essential to accurately determine stresses within VFs during self-oscillation and contact.
Measurement and Analysis of Cutaneous Perfusion Depression During Cryotherapy
Authors: Khoshnevis Sepideh , Hensley Daniel W. , Diller Kenneth R.
Published: July 2013

Localized cooling is commonly used after orthopedic surgery and in sports medicine to reduce bleeding, inflammation, metabolism, muscle spasm, pain, and swelling following musculoskeletal trauma and injury. The therapeutic application of cold therapy has a long history dating from the time of Hippocrates and has been widely documented in the literature1–3. Nonetheless, there remains to the present time considerable controversy over the appropriate protocol for application of cryotherapy. One extreme camp advocates continuous use of cryotherapy to a treatment site with no break in cooling for days or even weeks4–5, whereas other practitioners recommend a maximum application duration of 20 to 30 minutes followed by a cessation period of about 2 hours6–7. Although continuous cooling appears to be tolerated by many patients, there has been a large number of reported incidences in which continuous application of cryotherapy device led directly to extensive tissue necrosis and/or nerve injury in the treatment area, sometimes with dire medical consequences6,8.
A Biomechanical Study of Scaphoid Headless Screws
Authors: Assari Soroush , Darvish Kurosh , Ilyas Asif M.
Published: July 2013

Scaphoid fractures are the most common fracture of the carpus [1].Headless screws are favored for internal fixation in the treatment of displaced or unstable fractures, because they are embedded below the articular surface of the bone, reducing tissue irritation and immobilization. Compression plays an important role in fracture stability, maintaining gap reduction and also accelerating the healing of cancellous bone [3]. There are several types of screwsbeing used in practice and it is of clinical interest to know how different they are in generating and maintaining the compression force.
Mechanical Properties of Spontaneously and Artificially Ruptured Human Amnion
Authors: Briggs Brandi N. , Ferguson Virginia L.
Published: July 2013

The chorioamnion (CA) is the sac that surrounds the fetus in utero. It is comprised of two layers: the inner fibrous amnion, mainly composed of collagen and the thick cellular chorion1. CA is an exceptionally tough material, yet is the only material in the human body that is designed to mechanically fail2. Past studies have focused on the events associated with rupture such as the puncture force3,4,5,6,7, delamination stress8,9, elastic stiffness10,11, failure energy7,10,12, and failure force10,11. However, few have investigated pre-failure behavior4,13 to understand contributions to different modes of CA rupture.
Comparison of Normal and Pathological Hemodynamics in Coronary Artery Aneurysms Caused by Kawasaki Disease
Authors: Sengupta Dibyendu , Burns Jane C. , Kahn Andrew , Marsden Alison L.
Published: July 2013

Kawasaki disease (KD) is an acute febrile illness occurring primarily in children less than 5 years of age. It is the leading cause of acquired heart disease in children, with over 4000 cases of KD diagnosed annually in the US alone. There is currently no clinical diagnostic test for KD, and diagnosis is made via a combination of symptoms including rash, swollen extremities, and fever. Approximately 20–25% of the untreated cases develop large aneurysms in the coronary arteries, which put the patient at severe risk for myocardial infarction. In this project we performed patient specific computational simulations of blood flow in aneurysmal left and right coronary arteries of a 10-year old KD patient and compared the hemodynamics to that of a normal coronary. Several relevant hemodynamic parameters such as WSS, WSS gradients and recirculation time were obtained, as a first step towards developing a risk assessment tool for thrombosis in KD patients.
An Optical Approach for Studying the Cellular Mechanotransduction of Hydrostatic Pressure by Bladder Urothelial Cells
Authors: Olsen Shawn , Nagatomi Jiro
Published: July 2013

Recent studies have suggested that the bladder urothelium is sensitive to both stretch and hydrostatic pressure during bladder filling, and is considered to play a mechanosensory role in sensing bladder fullness [1, 2]. In a previous study [3], our group demonstrated that compared to the control, rat bladder urothelial cells (UCs) exposed to hydrostatic pressure (10–15 cmH2O for 5 minutes) in vitro released significantly higher levels of ATP and that this response was attenuated by pharmacologically blocking transient receptor potential (TRP) channels, as well as epithelial sodium channels (ENACs). While blocking these ion channels inhibited the ATP response by UCs to hydrostatic pressure, it remains unclear whether these ion channels are being activated directly by hydrostatic pressure or by membrane deformation. Our current hypothesis is that a change in cell volume may occur due to the application of hydrostatic pressure and subsequent changes in cellular osmolality, which, in turn, activate the membrane-bound mechanosensitive channels. Using real-time fluorescent imaging and a custom experimental setup, the present study sought to quantify the UC cell volume changes during exposure to hydrostatic pressure and to better understand the mechanisms by which UCs sense hydrostatic pressure.
Investigating the Ability of Knee OA Patients to Maintain Targeted Knee Flexion Angles for Weight Bearing MRI
Authors: Gade Venkata , Allen Jerome , Cole Jeffrey L. , Barrance Peter J.
Published: July 2013

Knee osteoarthritis (OA) is the most common clinical presentation of osteoarthritis, and has been estimated to affect 12–16% of the population older than 60 years in the US [1]. A biomechanical risk factor that has been linked to knee OA is the changes in the local loading and the contact area between the cartilage surfaces [2]. Investigation of such factors requires precise measurement tools to determine knee joint positioning and contact areas. Clinically, MR images of the knee are most frequently acquired in the supine position; such images are not representative of the loading conditions experienced functionally in the weight bearing knee joint. With the advent of vertically open MRI (e.g. Upright MRI, Fonar Corporation, Melville, NY), it is now possible to scan the knee in fully upright weight bearing conditions representing truly functional positions. To measure sensitive variables such as joint positioning and cartilage contact, it is important to minimize subject movement in order to obtain high quality images. In MRI, increased scan times allow for data of improved signal to noise ratio and resolution; however, long scanning durations without subject movement are not feasible, particularly in individuals with symptomatic knee OA.
Fluid Study of Transcatheter Aortic Valve Deployment Into Patients With Varying Coronary Ostia Position
Authors: Sirois Eric , Wang Qian , Kodali Susheel , Sun Wei
Published: July 2013

Recently, minimally-invasive transcatheter aortic valve (TAV) replacement has emerged as a viable alternative to traditional open-chest heart valve replacement for high risk patients who otherwise have limited or no treatment options. Although significant experience with TAV procedures has been gained, various adverse effects have been observed after device implantation [1, 2]. One adverse event is the impairment of coronary artery flow. Because the TAV stent pushes the native leaflets towards the sinus of Valsalva during TAV deployment, the flow boundaries in the aortic root are consequently altered. A worst case scenario would be the occlusion of the coronary ostia. Reduced flow to the coronary arteries has also been observed for some patients following TAV intervention [3]. With IRB approval, we recently conducted a dimensional analysis of 3D aortic root geometries, reconstructed from 64-slice CT scans of 95 patients [4]. TAV-relevant dimensions were measured. The spatial distribution of the left coronary ostium was quantified (Fig. 1). In this study, we will construct a patient-specific aortic root model with varied coronary ostium locations as shown in Fig. 1, and perform a combined finite element analysis (FEA) and computational fluid dynamics (CFD) simulation to investigate hemodynamic environment changes that occur following TAV intervention.
3D Analysis of Lumbar Spine Facet Joint Cartilage Thickness Distribution
Authors: Simon Peter , Espinoza Orías Alejandro A. , Kotwal Naomi , Parrish Todd , An Howard S. , Andersson Gunnar B. J. , Sumner Rick D. , Inoue Nozomu
Published: July 2013

Quantitative knowledge of lumbar facet joint morphology is crucial in understanding the relationship between the geometry and kinematics of the facet joint as well as better understanding degenerative changes. Accurate prediction of lumbar facet joint contact area and stresses requires 3D representation of the thickness distribution of the articular cartilage of the facet joint. Several groups have reported on cervical facet joint cartilage thickness measurements using different approaches [2,3]. To the best of our knowledge, three-dimensional (3D) distribution of lumbar facet joint cartilage thickness has not been reported. Current methods of measuring various geometrical parameters of facet joint cartilage usually utilize high resolution magnetic resonance (MR) imaging techniques. Although these techniques represent the most up-to-date advanced methods in the soft tissue imaging field, facet joint cartilage reconstruction cannot be accomplished with reasonable fidelity using this approach. A study by Koo et al. [1] on knee joint cartilage showed that the accuracy of cartilage thickness measurement in the cartilage models derived from MRI (1.5T) varies with cartilage thickness. This study reported accurate measurements only for cartilage whose thickness ranged from 2.5 mm to 3.3 mm, which is in the range larger than the average lumbar facet joint cartilage assumed to be around 0.8 mm. Therefore, the objective of this study was to 1) analyze 3D lumbar facet joint cartilage thickness distributions based on laser scanner data, 2) compare this method using μCT and 3T MRI.
Comparison of Normal Capitate Mid-Carpal Joint Mechanics With the Effects of Scapholunate Dissociation Injury
Authors: Kallem Madhan Sai , Lee Sang-Pil , McIff Terence E. , Toby E. Bruce , Fischer Kenneth J.
Published: July 2013

The wrist is one of the most complicated multibody joints in the human body. It can be subject to many injuries. Scapholunate (SL) dissociation is a relatively common injury that is particularly difficult to diagnose and treat. Without treatment, SL dissociation is known to progress to scapholunate advance collapse (SLAC wrist) and associated osteoarthritis (OA) [1]. Traumatic arthropathy of the wrist due to scapholunate dissociation has a definitive pattern from onset to severe bone and joint degeneration. The altered radiocarpal and SL mechanics with SL dissociation may be accompanied by a secondary carpal collapse between the capitate and lunate [2]. The initial SL disruption causes apparent changes in joint kinematics and contact patterns. Thus, understanding normal and abnormal in vivo contact mechanics as a result of SL ligament injury may lead to more effective treatments that may even prevent the onset of OA. In addition, in vivo contact mechanics data after surgical treatment may help determine the effectiveness of various surgical techniques which are used to correct SL injury.
Viscoelastic Property Changes of Acute Rat Brain Tissue Slices as a Function of Cell Viability
Authors: Lee Sung Jin , Sun Jingjing , King Michael , Xie Huikai , Sarntinoranont Malisa
Published: July 2013

Changes in mechanical properties within brain tissues after losses in cell viability have not been well investigated. Lack of oxygen and nutrient transport can induce hypoxic neuronal injury and increase cell membrane permeability, and cell membranes and matrix components can lose their structural and mechanical integrity. These physical changes may have an effect on mechanical properties of brain tissue [1]. In this study, the viscoelastic behavior of two anatomical regions (cerebral cortex and hippocampus) in acute rat brain tissue slices were measured as a function of cell viability using indentation combined with optical coherence tomography (OCT). Neuronal viability in brain tissue slices was determined by measuring Fluoro-Jade C (FJC) staining to assay neuronal death or degeneration as a function of incubation time. OCT-measured deformation depths were compared with finite element (FE) simulations to estimate the relaxation of shear modulus. Measured equilibrium shear modulus (μ∞) after 8 hrs incubation was lower than μ∞ measured after 2 hrs incubation in the cerebral cortex (μ∞, 2hrs = 225 Pa, μ∞, 8hrs = 62 Pa) and hippocampus regions (μ∞, 2hrs = 170 Pa, μ∞, 8hrs = 33 Pa). Instantaneous shear modulus (μ0) after 8 hrs incubation was also an order of magnitude lower than μ0 after 2 hrs incubation in cortex (μ0, 2hrs = 1600 Pa, μ0, 8hrs = 100 Pa) and hippocampus regions (μ0, 2hrs = 370 Pa, μ0, 8hrs = 70 Pa). The results of this study provide a timeline for measuring mechanical properties of brain tissues ex vivo and provide better understanding of changes in brain modulus after injury or cell death.
Development of a 3D Microfluidic Culture Model to Study the Effect of Shear Stress on Tumor Angiogenesis
Authors: Buchanan Cara F. , Voigt Elizabeth , Szot Christopher S. , Freeman Joseph W. , Vlachos Pavlos P. , Rylander M. Nichole
Published: July 2013

Current in vitro studies of tumor angiogenesis and metastasis are limited by the use of static 2D culture systems or 3D models that poorly reflect the pathological tumor microenvironment. While these systems have provided insight into tumor-inherent mechanisms of neovascularization, they are unable to couple local cellular response with specific biochemical and mechanical cues [1]. Interstitial flow plays an important role in regulating tumor growth; however, there are currently no in vitro cell culture models specifically designed to investigate the effect of fluid shear on tumorigenesis. By integrating tissue-engineering strategies with microfluidics and particle image velocimetry, we have developed a 3D in vitro cell culture model that allows the relationship between shear stress and tumor-endothelial cell cross-talk to be monitored. This research strategy will greatly improve our understanding of shear-stress mediated angiogenesis.
Radiofrequency Ablation With a Cryogenically Cooled Catheter to Percutaneously Treat Mitral Valve Prolapse
Authors: Boronyak Steven M. , Merryman W. David
Published: July 2013

Mitral valve (MV) disease is the most common form of heart valve disease, occurring in approximately 2% of the population and resulting in 43,000 open-chest surgical procedures every year [1]. One subtype is mitral valve prolapse (MVP), which primarily affects the elderly and is often characterized by severe regurgitant flow, thickened and enlarged leaflets, and disrupted and mechanically compromised collagen architecture.
Detection of MMP-13 Activity on Intentionally Strain-Released Type-II Collagen Network in Bovine Articular Cartilage
Authors: Caner Nazli , Ruberti Jeffrey W.
Published: July 2013

Articular cartilage is a specialized avascular connective tissue found at the contact regions of diarthrodial joints. Cartilage has few cells (< 5% of the volume), though these cells can maintain the balance of turnover in healthy tissue, when the tissue is damaged, they are not able to repair the defects [1–3]. Extra cellular matrix (ECM) in cartilage comprises water, collagen (principally type II), proteoglycans and noncollagenous proteins. The type II collagen network, which is the dominant structural protein in cartilage ECM, constrains the expansion of the resident PGs and is generally held in mechanical tension. In osteoarthritis (OA), the balance of cartilage tissue production/degradation is thought to be affected by abnormal mechanical stimuli leading to net matrix resorption through production of excess degradative enzymes (e.g. matrix metalloproteinases (MMP) and aggrecanases) [4–8]. In OA tissue the amount of MMP-13 is thought to be increased relative to healthy tissue. OA typically occurs in older adults where, as cartilage ages, there is a marked decrease in the fixed charge density (FCD), the hydration and, consequently, mechanical tension on the collagen type II network [9–11]. We have hypothesized that loss of tension on the collagen network accelerates degradation by MMP. Detection of the effect of MMP on loaded, native cartilage could lead to insight about cartilage degradation kinetics in OA. However, it is quite difficult to controllably deliver MMP to cartilage, to activate the MMP during detensioning of the collagen network and to detect the effect on the cartilage mechanics (because cost limits the amount of MMP used). We have developed a transpirational enzyme loading method which is capable of precisely dosing bovine cartilage explants with a small, known quantity of MMP-13. Following enzyme insertion, we are able to detect the activity of the MMP on osmotically compressed cartilage (i.e. cartilage with a detensioned collagen network) via a simple hydration measurement.
Differences in Cervical Spine Vertebral Center of Rotation Location During Flexion and Extension Movements in Asymptomatic Controls
Authors: Baillargeon Emma M. , Donaldson William F. , Lee Joon Y. , Kang James D. , Anderst William J.
Published: July 2013

Abnormal cervical spine motion may occur as the result of injury or degenerative changes in symptomatic patients. Intervertebral range of motion (ROM) is a standard metric used to evaluate abnormal spine motion, but can only describe the amount of motion and not the quality of motion. In addition, significant variability in normal ROM among subjects may minimize the efficacy of this parameter in identifying abnormalities in symptomatic patient groups1. Instead, the instant center of rotation (ICR) has been proposed as a reliable, stable measurement of the quality of vertebral motion through which abnormalities could be explored2.
Flexural Properties of Silorane Bone Cement
Authors: Melander Jennifer R. , Weiler Rachel A. , Miller Bradley D. , Kilway Kathleen V. , Eick J. David
Published: July 2013

There has been little change in the formulation of bone cements since Sir John Charnley first developed them in the 1970s. Bone cements are methacrylate based systems packaged in two components [1]. The powder component contains a mixture of polymethyl methacrylate (PMMA), methyl methacrylate-styrene-copolymer, and a radio opacifier (either barium sulfate or zirconium oxide) [2]. The second component is a liquid monomer typically containing methyl methacrylate, N, N-dimethyl-p-toluidine (activator), and hydroquinone. Flexural strength and flexural modulus of bone cements range between 60–75 MPa and 2.2–3.3 GPa, respectively [3, 4]. ISO 5833 requires bone cements to have a strength greater than 50 MPa and a modulus greater than 1.8 GPa [5].
Smart Needling System for Fully Conformal Radiation Dose Delivery in Treating Prostate Cancer
Authors: Hutapea Parsaoran , Darvish Kurosh , Podder Tarun
Published: July 2013

Anatomy of the prostate having centrally located urethra detects that the radioactive seeds be distributed peripherally for prescribed dose coverage to the prostate and minimal dose to the urethra. Additionally, dose to the rectum should be minimal without sacrificing does coverage to the prostate. In conventional low-dose-rate (LDR) brachytherapy approach, seeds are delivered in prostate through needles inserted rectilinearly with limited flexibility and maneuverability (Fig. 1a).
Low and Unsteady Shear Stresses Upregulate Calcification Response of the Aortic Valve Leaflets
Authors: Rathan Swetha , Yap Choon Hwai , Morris Elizabeth , Arjunon Sivakkumar , Jo Hanjoong , Yoganathan Ajit P.
Published: July 2013

Aortic Valve (AV) calcification is a degenerative disease that results in AV sclerosis and is one of the major causes of death. AV is subjected to mechanical conditions such as fluid shear stress, transvalvular pressure and membrane tension1. Normal hemodynamic conditions constantly renew and remodel the valve, whereas altered mechanical loading has been implicated to be the cause of AV disease2. Studies have shown that adverse hemodynamics such as hypertension and altered shear stress can cause tissue inflammation that leads to calcification and stenosis3, 4, and ultimately result in valve failure. However, the molecular and cellular processes that lead to calcification are not very well understood.
Development of a Methodology for Direct Utilization of Phase-Contrast MRI in Hemodynamic Computations
Authors: Das Ashish , Gottliebson William M. , Wansapura Janaka , Banerjee Rupak K.
Published: July 2013

Development of non-invasive diagnostic indices often requires accurate blood-flow calculation using physiologically realistic velocity profiles as boundary conditions. In this research, a methodology is being developed and validated that can directly use phase-contrast MR imaging (PC-MRI) based velocity measurement to perform blood-flow computation with patient-specific geometry. Using this methodology, the pressure drop can also be calculated non-invasively. Although the main focus of our research has been pulmonary insufficiency (PI) in tetralogy patients, our method can be employed in many other pathophysiologies. As a pilot study, the methodology is tested using a simple model of blood-flow through a straight artery of uniform cross-section.
Assessment of the Outflow Path Resistance of the Aqueous Humor Flow in the Eye
Authors: Acharya Sumanta , Kathawate Jyoti
Published: July 2013

The objective of this work was to numerically simulate the flow of the aqueous humor through the outflow pathway of the eye, and to examine the sources of pressure drop for various postulated structural models of the trabecular mesh region.
Hydrodynamically Induced Whole-Cell Manipulation in Micro-Fluidic Devices
Authors: Cruz-Díaz Alvin O. , Díaz-Rivera Rubén E.
Published: July 2013

The increasing interest for dedicated analysis of single particles at microscopic scales, such as biological cells, has led researchers to create micro-fluidic systems capable of trapping particles in a liquid flow. The most common trapping mechanism is by physical obstruction, which is simple, but it has its limitations. For instance, in these systems particle selectivity is poor because all the particles that pass through the channel may get pin down against the physical obstruction regardless of the size and shape of the particle [Di Carlo et al., Tan et al., Nilsson et al.]. In addition, releasing the particles that have been trapped presents a problem not only because the flow needs to be stopped or reversed, but because there is a high probability that the released particles are going to be trapped again when the system resumes its operation [Nilsson et al.]. Other devices use pressure differentials to trap the particles but each trap requires a separate flow or a valve mechanism for trap activation. This method requires multiple pumps or complex structures within the device such as micro-valves and actuators.
Investigation of Pulsatile Hemodynamics in Patient-Specific Fontan Templates With Fenestration
Authors: Dur Onur , Housler Greggory , Kocyildirim Ergin , Hong Haifa , Liu Jinfen , Pekkan Kerem
Published: July 2013

The third stage for palliative surgical reconstruction for children with functional single-ventricle (SV) physiology is the completion of the total cavopulmonary connection (TCPC), where the superior vena cava (SVC) and inferior vena cava (IVC) are routed directly into the pulmonary arteries. Approximately 5000 newborns in the US each year join to the existing SV (or Fontan) patient population, along with increasing numbers of adult Fontan patients surviving longer due to the advances in surgical techniques and post-op management. Although most post-operative Fontan patients experience an acceptable quality of life, their lifespan is shorter than normal with a significant number of these patients developing late hemodynamic complications (failing Fontan) and requiring heart transplantation. Donor shortage and the high-risk nature of transplantation for these complex and often very ill patients demand alternative therapeutic options [1].
Cellular Response to Stretch by Modulation of Cytoskeletal Tension in Two Distinct Phases
Authors: Mann Jennifer , Lam Raymond , Fu Jianping
Published: July 2013

External forces are increasingly recognized as major regulators of cell structure and function, yet the underlying mechanism by which cells sense force and transduce it into intracellular biochemical signals and behavioral responses (‘mechanotransduction’) is largely undetermined. To aid in the mechanistic study of mechanotransduction, we devised a novel cell stretching device that allows for quantitative control and real-time measurement of mechanical stimuli and cellular biomechanical responses. Using this device, we studied the subcellular dynamic responses of contractile force and adhesion remodeling of vascular smooth muscle cells (VSMCs) to stretch. Our data showed that VSMCs could acutely enhance their contraction to resist rapid cell deformation, but they could also allow slow adaptive inelastic cytoskeletal reorganization in response to sustained cell stretch. Our study may help elucidate the mechanotransduction system in smooth muscle cells, and thus contribute to our understanding of pressure-induced vascular disease processes.
Whakapapa - New Zealand Anthropology
Authors: Metge Joan , Sissons Jeff , George Lily
Published: July 2013

Three relatively short and informal pieces by Dame Joan Metge, Jeff Sissons and Lily George, which formed an introductory plenary session tracing and reflecting on three generations of anthropological engagement with Maori society.
WHAKAPAPA AND METAMORPHOSIS
Authors: Kawharu Margaret
Published: July 2013

In the context of running Treaty of Waitangi claims against the Crown1, I argue that the claim process is much more about what it means to be Maori, on ever shifting ground in New Zealand society, than anything else. There are three stages in the claim process once a claim is lodged: presentation of evidence, negotiations around appropriate redress and an agreed settlement. At every stage in the process, claimants are required to identify themselves in terms of their whakapapa (genealogy). Yet the fact that these terms have been determined by the Crown is in itself a result of patterns of interaction shaped by a legal, adversarial settlement process and an iniquitous colonial past. This essay aims to clarify why the claim process is so protracted and what challenges the Maori claimants face, when the very process of being eligible to engage with the Crown forces them to redefine their identity as Maori several times over. In doing so the essay points to the tension for Maori between working with indigenous concepts and values at the same time as engaging with the Crown to settle long-standing grievances. It also addresses some key anthropological questions about identity processes, showing how being claimants reinforces, embraces and strengthens the notion of a Maori identity but at the same time undermines, systematises, and limits being Maori. In this sense, one understands how the Crown, or the state, is an institution ‘that is the ground of both our freedoms and our unfreedoms’ (Scott, 1998, p. 7).
ARE MAORI HAPU ‘HOUSES’? ARE WHAKAPAPA ‘STRATEGIC IMPROVISATIONS’? THE ETHNOHISTORICAL EVIDENCE FROM NGAI TUHOE
Authors: Webster Steven Sebastian
Published: July 2013

A recent exchange regarding the nature of Maori hapu has revived the old controversy whether or not ancestral descent groups can be organised on the basis of cognatic descent (through either or both parents in each generation). An innovative application of Levi-Strauss’s concept of a house society, and Bourdieu’s theory of practice, has challenged an answer to the old controversy, widely accepted since the 1970s, that hapu are entire descent categories narrowed to actively involved descent groups. The alternative view argues that Maori hapu were probably never based on such ambiguous grounds, but rather have developed since the 1880s as an ideology legitimating the solidarity of extended families (whanau), other kin, and non-kin closely associated with a meeting house and resourceful leadership able to extend hospitality. In defense of the earlier view that hapu are cognatic descent groups and categories, and probably have been at least since the 1840s, this essay reviews the recent exchange and examines the ethnohistorical evidence from one Maori iwi, Ngai Tuhoe.
STRANGE WHAKAPAPA: COLLIDING AND COLLUDING CLAIMS TO ANCESTRY AND INDIGENEITY IN AOTEAROA
Authors: Goldsmith Michael
Published: July 2013

Forthcoming.
WAYS OF SEEING: WHAKAPAPA
Authors: Roberts Mere
Published: July 2013

The ideas advanced in this paper accept a priori the existence and validity of alternative world views which each seek to make sense of and understand the world. More specifically it advances the theory that matauranga and wananga1 comprise a body of knowledge situated within a cognitive genealogical framework called whakapapa; and that this provides the theoretical or epistemological basis for a Maori ‘way of knowing’ about the world. As will be described, this framework embraces multiple ontologies concerning how things came to be, each of which is grounded in both knowledge of natural science (primarily biological) as well as spiritual knowledge. Examples drawn from whakapapa of selected plants and animals not only reveal the extent and nature of the knowledge embedded in mātauranga, but also highlight the various functions whakapapa appear to have served in an oral society. These roles, and the potential of whakapapa to continue to contribute to the growth of knowledge are also discussed in the light of perspectives from other scholars of matauranga. .
Stability of deflected-beam metal–insulator–metal tunneling cathodes under high acceleration voltage
Authors: Suzuki Mutsumi , Kusunoki Toshiaki
Published: July 2013

Metal–insulator–metal (MIM) tunneling cathodes have advantageous features, such as areal electron beams and robustness to surface contamination. Therefore, they are suitable for field-emission displays. This paper reports the long-term stability of MIM tunneling cathodes in display panels operating under a high acceleration voltage (anode voltage). A preliminary life test was carried out using conventional display panels, which consisted of a phosphor-coated anode plate and a cathode plate having matrix-arrayed cathodes. The life test indicated that the pace at which cathodes degrade increases significantly when the acceleration voltage exceeds a few kilovolts. This high-voltage (HV)-induced degradation is presumably attributed to cathodes being bombarded by positive ions originating from residual gases. To suppress HV-induced degradation, the authors propose the concept of a deflected-beam cathode, in which electron beams are deflected so that the recoiling ions fail to hit the cathode. This concept was implemented by introducing deflector electrodes in the cathode plate, thereby forming an electron lens in each pixel. As 6-μm high scan lines were used as the deflector electrodes in this design, the deflected-beam cathodes could be fabricated only by modifying the pattern of the scan lines. The authors also present a simulation-based design procedure using an emitter-landing diagram, which facilitates analysis of the margins for the deflected-beam cathodes. The deflected-beam cathodes thus designed were incorporated into 3.8 cm-diagonal test panels to confirm the validity of the concept. The degree of beam deflection that was observed was in excellent agreement with the results obtained from simulation. A life test extending over a 20 000-h period demonstrated that the HV-induced degradation was suppressed with the deflected-beam MIM cathodes.
Loss of Very-Long O-Antigen Chains Optimizes Capsule-Mediated Immune Evasion by Salmonella enterica Serovar Typhi
Authors: Crawford Robert W. , Wangdi Tamding , Spees Alanna M. , Xavier Mariana N. , Tsolis Renée M. , Bäumler Andreas J.
Published: July 2013

Expression of capsular polysaccharides is a variable trait often associated with more-virulent forms of a bacterial species. For example, typhoid fever is caused by the capsulated
Salmonella enterica
serovar Typhi, while nontyphoidal
Salmonella
serovars associated with gastroenteritis are noncapsulated. Here we show that optimization of the immune evasive properties conferred by the virulence-associated (Vi) capsular polysaccharide involved an additional alteration to the cell envelope of
S
. Typhi, namely inactivation of the
fepE
gene, encoding the regulator of very-long O-antigen chains. Introduction of the capsule-encoding
viaB
locus into the nontyphoidal
S. enterica
serovar Typhimurium reduced complement deposition
in vitro
and intestinal inflammation in a mouse colitis model. However, both phenotypes were markedly enhanced when the
viaB
locus was introduced into an
S
. Typhimurium
fepE
mutant, which lacks very-long O-antigen chains. Collectively, these data suggest that during the evolution of the
S
. Typhi lineage, loss of very-long O-antigen chains by pseudogene formation was an adaptation to maximize the anti-inflammatory properties of the Vi capsular polysaccharide.

IMPORTANCE
Genomic comparison illustrates that acquisition of virulence factors by horizontal gene transfer is an important contributor to the evolution of enteric pathogens. Acquisition of complex virulence traits commonly involves horizontal transfer of a large gene cluster, and integration of the gene cluster into the host genome results in the formation of a pathogenicity island. Acquisition of the virulence-associated (Vi) capsular polysaccharide encoded by SPI7 (
Salmonella
pathogenicity island 7) was accompanied in the human-adapted
Salmonella enterica
serovar Typhi by inactivation of the
fepE
gene, encoding the regulator of very-long O-antigen chains. We show that the resulting loss of very-long O-antigen chains was an important mechanism for maximizing immune evasion mediated by the Vi capsular polysaccharide. These data suggest that successful incorporation of a capsular polysaccharide requires changes in the cell envelope of the hosting pathogen.