bluuebunny/crossref_metadata_2025 huggingface dataset:
An in Situ Dual Indentation and Optimization Method to Determine Mechanical Properties of Articular Cartilage
Authors: Pottle Jonathan E. , Suh J.-K. Francis
Published: March 2014

The efficacy of the biphasic poroviscoelastic (BPVE) theory [1] in constitutive modeling of articular cartilage biomechanics is well-established [2–4]. Indeed, this model has been used to simultaneously predict stress relaxation force across confined compression, unconfined compression, and indentation protocols [2,3]. Previous works have also demonstrated success in simultaneously curve-fitting the BPVE model to reaction force and lateral deformation data gathered from stress relaxation tests of articular cartilage in unconfined compression [4]. However, a potential limitation of practical applications of such a successful model is seen in some commonly-employed mechanical testing methods for articular cartilage, such as confined compression and unconfined compression. These methods require the excision of a disk of cartilage from its underlying subchondral base, which likely would compromise the structural integrity of the tissue, causing swelling and curling artifacts of the sample [5]. Indentation represents a testing protocol that can be used with an intact cartilage layer. This results in a specimen more closely resembling cartilage in vivo. Using an agarose gel construct, our previous study [6] has demonstrated that a unique set of the six BPVE model parameters of a soft tissue can be determined readily from in situ dual indentation method using stress relaxation and creep viscoelastic protocols. The objective of the current study is to validate the efficacy of this technique as a means to determine the BPVE material parameters of articular cartilage.
Experimental Investigation on the Dispersive Transport of Angiographic Contrast Injected Antegradely Into Flow in a Tube
Authors: Lieber Baruch B. , Hao Qing , Sadasivan Chander , Seong Jaehoon
Published: March 2014

In catheter-based angiography contrast is injected through a catheter into flowing arterial blood to attenuate the X-ray beam such that physicians can view vascular luminal morphology for diagnosis of vascular pathology [1]. Since real time angiography became available the transport of contrast could be visualized and numerous attempts have been made to relate the visualized transport of contrast to blood flow or blood velocity. Since the dispersion of contrast is a complex process and thorough understanding of contrast mixing with the flowing blood is missing, many physicians and researchers alike implicitly assume that mixing of contrast and blood is either instantaneously completed or that mixing does not take place at all during the short visualization period. In the former case many erroneously assume that the visualization of contrast transport directly reflect blood flow characteristics. Yet others attributed homogeneous mixing to turbulence even when the Reynolds number was as low as 77 [2]. In the latter case some reports suggested that since the two do not mix, the contrast, which is denser than blood, will tend to accumulate at low parts of the arterial system due to the gravity. The stereotypical concept is that under laminar flow conditions homogeneous mixing will take a long time and consequently a long distance. The fact that the angiographic contrast is a liquid tracer injected forcefully into the blood, generating an ejector effect is ignored. The velocity mismatch between the injected contrast and the flowing blood plays a major role in laminar mixing of the contrast. In this paper, we report our experimental investigation that was designed to find out how far distal to the catheter tip will the injected contrast reach homogeneous mixing with a blood analog fluid as evident by no further changes in the contrast density profiles measured downstream of the catheter tip.
Multiscale Adaptive Finite Element Computations for Soft Tissue Biomechanics
Authors: Stylianopoulos Triantafyllos , Luo Xiaojuan , Shephard Mark S. , Barocas Victor H.
Published: March 2014

The mechanical function of soft collagenous tissues is inherently multiscale, with the tissue dimension being in the centimeter length scale and the underlying collagen network being in the micrometer length scale. The strong sensitivity of soft tissues to network orientation and fiber-fiber interactions necessitates the incorporation of both scales in a multiscale methodology [1,2] in order to predict their mechanical response. The computational demands of a multiscale methodology, however, are strenuous and the use of parallel processing and adaptivity are required for succeeding acceptable solution times.
Biphasic Structure-Based Modeling of Tissue Equivalent Mechanics
Authors: Chandran Preethi L. , Stylianopoulos Triantafyllos , Barocas Victor H.
Published: March 2014

The collagen gel has been extensively studied as an in vitro model for soft tissue mechanics, cell-ECM interactions, and as a prototypical bioartificial tissue; a model of gel mechanics from a microstructural perspective is important for all of these [1]. An earlier experimental study recorded the microstructural rearrangements during confined compression by interpreting the evolution of birefringence patterns within the gel [2]. The patterns suggested that strain was transmitted by fiber rotation at interconnections and was non-uniform due to fluid permeation resistance, indicating that macroscopic gel mechanics arise from elastic interactions between the solid phase fibers and viscous interactions with fluid. A structure-based mathematical model to account for both the elastic and viscous response of tissue equivalents was developed.
Assessment of a Novel Technique for In-Vivo Investigation of Joint Cartilage Deformation Characteristics
Authors: Robu Ion , Ronsky Janet L. , Frayne Richard , Habib Ayman H.
Published: March 2014

Cartilage is characterized by unique biomechanical and morphological properties. These properties are dictated mainly by the visco-elastic behavior of the interstitial matrix. Attempts to quantify the biomechanical properties of cartilage have been based on in-vitro confined and unconfined compression experiments and indentation tests, in-situ measurements of intact cadaveric knee joint specimens under loading using Magnetic Resonance Imaging (MRI), numerical modeling, or in-vivo techniques such as those applying arthroscopic indentation or loading with MR imaging.
Mechanical Loading of Suspended Cells in Laminar and Turbulent Blood Flow
Authors: Dooley Padraic N. , Quinlan Nathan J.
Published: March 2014

Prosthetic heart valves (PHVs) and other cardiovascular devices induce flow features such as turbulence, stagnation and high shear which do not occur in the native flow, and can lead to hemolysis and thrombosis due to mechanical loading of cells. As an aid to the development of cardiovascular implants, many researchers have attempted to correlate blood damage with macroscopic flow parameters through in vitro testing. The parameters most widely used are the macroscopic viscous shear stress (e.g. Paul et al. [1]) and the macroscopic Reynolds stresses in turbulent flow (e.g. Sallam and Hwang [2]). Although these quantities are valuable predictors of flow induced blood damage, they are not equivalent to the true stresses on a blood cell. In particular, Reynolds stress characterises velocity fluctuations at all length scales; therefore, it cannot completely describe the complex structure of turbulent flow on the cellular scale at which blood damage is initiated.
Wall Deformation, Wall Shear Stress and Atherosclerosis Around the Intercostal Ostia of C57 Mice
Authors: Suo Jin , Ferrara Dardo E. , Guldberg Robert E. , Taylor Robert W. , Giddens Don P.
Published: March 2014

Dorsal surfaces and upstream regions around ostia of aortic branches are favored sites of atherosclerosis. Both asymmetrical stresses in branch walls and disturbed flow patterns have been suggested as contributing to this localization. In the present study, fluorescence images of the thoracic aortic tree of C57 mice were obtained using quantum dot (Qdot) bioconjugate markers for vascular cell adhesion molecule-1 (VCAM-1) and two-photon excitation laser scanning microscopy. The images show that dorsal surfaces and upstream regions of intercostal ostia have a higher intensity of VCAM-1 than the downstream region. We also investigated blood flow patterns and wall shear stress (WSS) in the descending aorta and proximal intercostal branches of C57 mice using micro-CT imaging and ultrasound velocity measurements, combined with computational fluid dynamics (CFD). The latter investigation showed that dynamical wall deformation caused by pulsatile pressure around the ostia induces blood flow patterns which create lower and oscillating WSS in the upstream region and dorsal surface than in the distal region. Comparisons of the Qdot marker and CFD studies demonstrate that the distribution of greater expression of VCAM-1 corresponds with lower and oscillating WSS around the branch ostia. Thus, local wall deformation may contribute to disturbed flow patterns that are known to be associated with increased VCAM-1 expression.
Design and Fabrication of a Mock Circulatory System for Reliability Tests on Aortic Heart Valves
Authors: Singh Dhruv , Singhal Abhishek
Published: March 2014

The dynamic stress analysis and response of artificial heart valves — specifically the aortic valve is impending following the increasing number of artificial valve failures. This calls for the development of a mock circulatory system in order to establish clearly the parameters associated with the circulatory system in the heart and their effects on the robustness of a prosthetic implant.
Depth Dependent Strain Analysis of Articular Cartilage Under Impaction Loading
Authors: Nagel Thomas , Müller Sascha , Görke Uwe-Jens , Muehlemann Carol , Wimmer Markus A.
Published: March 2014

Lesions in the cartilage of the knee can lead to degenerative arthritis of the joint. Therefore, procedures such as osteochondral grafting are used to repair the cartilage. Osteochondral grafting procedures are of interest, because the lesion is replaced with true hyaline cartilage. This procedure involves press-fitting a cylindrical bone-cartilage plug by impaction to repair the damaged cartilage area. Recently, it has been shown that impact insertion of osteochondral grafts generates damaging loads that cause chondrocyte death, particularly in the superficial zone [1]. Using high speed video analysis, it has been shown that the highest local deformations occur within the superficial zone of the osteochondral plug [2,3]. However, the exact strain condition of the tissue during impaction and any depth dependent strain differences remain unknown. Assuming uniaxial load conditions of an ideal cylinder exposed to high strain rates, the stress-strain response of cartilage plugs during the impaction process is reported in this study. We hypothesized that the highest strain levels would occur in the superficial zone. Based on the experimental results, the fundamental material effects substantial for the load case under consideration can be studied. Consequently, suitable material models for subsequent numerical simulations can be established.
Fickian Behavior and Concentration-Dependence of the Diffusion of Dextran in Agarose
Authors: Albro Michael B. , Rajan Vikram , Hung Clark T. , Ateshian Gerard A.
Published: March 2014

Various studies have attempted to quantify the effects of loading on nutrient transport in cartilage and other soft tissues. The application of a dynamic mechanical stimulus has been shown to significantly enhance the mechanical properties of chondrocyte-seeded agarose [1]. While the mechanism for this enhancement is still not completely understood, dynamic loading has been shown theoretically [2] as well as experimentally [3] to increase the uptake of large molecules. Since dextran is available in a wide range of molecular weights and can be conjugated with fluorphores, it has become a popular model system for studying solute transport in statically loaded and free swelling gels and tissues [4, 5]. To better characterize this model system, this study uses fluorescence recovery after photobleaching (FRAP) to investigate the Fickian behavior of linear dextran macromolecules as well as the dependence of its diffusivity on concentration.
Knee Joint Motion Quantified Using the Finite Helical Axis Method
Authors: Fjeld Ingrid R. , Küpper Jessica C. , Ronsky Janet L. , Frayne Richard
Published: March 2014

The knee is a complex joint comprised of two main bones (femur and tibia) that articulate in a stable manner through the support of surrounding meniscus, musculature, and ligaments. The anterior cruciate ligament (ACL) is one of the main ligaments connecting the femur to the tibia. The ACL restricts anterior translation of the tibia with respect to the femur and aids in preventing internal and external rotation. The ACL is the most commonly injured ligament in the knee [1] and has been shown to increase the risk of cartilage degeneration leading to osteoarthritis (OA) [2]. The mechanics of the joint are altered following an ACL rupture, but the relations between the resulting joint instability and OA are not well understood.
Preservation of Human Bone Remains at Joya De Cerèn
Authors: Olesiak Sara E. , Sponheimer Matthew , Ferguson Virginia L.
Published: March 2014

Bone, a key part of the paleontological and archeological records, can provide insight into the biology, ecology and the environment of ancient vertebrates. Bone is a composite material in which the nanomechanical properties are dependent on the local organic content, mineral content, and microstructural organization. However it is unclear as to how these properties are affected by burial, environmental influences, temperature, or time. The acidity of volcanic soils causes resorption of the bone mineral and may result in demineralization of the bone. As such, very few bone remains are found in volcanic soils and this rare sample can provide insight into the preservation under such extreme conditions. While the effects of volcanic soils on bone are unknown, exposure to hostile environmental conditions increases the potential for dramatic alteration of the mechanical behavior. In this study, a human long bone from around 600 A.D. and a modern human femur were studied using nanoindentation. Testing, performed in both longitudinal and transverse directions, revealed preservation of bone’s natural anisotropy. Additionally, the preserved bone’s lower modulus values suggest the dissolution of bone mineral.
Continuum-Level Finite Element Modeling of the Optic Nerve Head Using a Fabric Tensor Based Description of the Lamina Cribrosa
Authors: Roberts Michael D. , Hart Richard T. , Liang Yi , Bellezza Anthony J. , Burgoyne Claude F. , Downs J. Crawford
Published: March 2014

Glaucoma is a chronic disease of the eye that can progress to severe vision impairment or blindness if left untreated. The principal site of glaucomatous damage is believed to be within the optic nerve head (ONH) where the axons of the retinal ganglion cells pass through an opening in the back of the sclera (the eye wall) on their way to form the orbital optic nerve. This opening is spanned by the lamina cribrosa (LC), a fenestrated connective tissue structure which provides both a load bearing function for the eye as well as support (both structural and metabolic) for axonal bundles as they traverse the porous space of the LC.
Deep Knee Activities: In Vitro Kinematic Measurements to Compare With In Vivo Studies
Authors: Reeve Amber N. , Clary Chadd W. , Mane Amit M. , Dodd Kevin A. , Maletksy Lorin P.
Published: March 2014

Deep knee flexion is required for many activities of daily living during work, exercise, religious worship, and hobbies. Walker et al. [1] found that activities such as rising from a low chair or getting into or out of bath require between 100° and 160° of knee flexion. Other activities such as kneeling or squatting to pick an item off the ground can be difficult with a limited range of motion. Beside deep knee flexion being important for daily living activities, it is essential in non-Western cultures that commonly sit in deep knee-bending positions.
Free Surface Coating Flows of Non-Newtonian Gels: 3-D Numerical Simulation of Gravity-Induced Flow
Authors: Kheyfets Vitaly O. , Kieweg Sarah L.
Published: March 2014

Developing a mechanism capable of protecting the vaginal or rectal epithelium from sexually transmitted pathogens can be an effective tool in the prevention of HIV infection [1]. One such tool can come in the form of a microbicide gel, used to provide a physical barrier and act as a delivery vehicle for its active ingredient [1]. In order for the microbicide to be an effective barrier and delivery vehicle it must have the capability to coat the epithelium for a specific amount of time and sustain its structural integrity under the influence of gravity and other perturbation forces. In addition, to be used as a drug delivery vehicle the microbicide must serve the following functions: coat the surface completely without leaving any of the surface exposed, stay on the surface while influenced by external forces such as gravity and squeezing, and must be able to contain potent concentrations of one or more active microbicidal ingredients.
Using Force and Kinematic Driven Finite Element Models to Analyze Contact Pressure Distributions on the Tibial Plateau
Authors: Hovinga Kristen R. , Yao Jiang , Lerner Amy L.
Published: March 2014

Finite element (FE) models have become an effective tool in studying soft tissue behavior in the knee joint, including meniscal translation and deformation, as well as articular cartilage contact [1–2]. These models are also useful in osteoarthritis research and implant design [3–4]. Our group has previously used a kinematic-driven FE analysis to study the effect of weightbearing on the load distribution of tibio-menisco-femoral contact using MR imaging [5].
Opto-Electric Biosensor to Examine In Vitro Toxicity Stimuli to Endothelial Cell Motility and Morphology
Authors: Choi Chang K. , Margraves Chuck , English Anthony E. , Kihm Kenneth D.
Published: March 2014

An integrated opto-electric biosensor is developed that uses an optically transparent and electrically conductive indium tin oxide (ITO) thin film coated on a slide glass substrate. This biosensor can simultaneously acquire the micro-impedance response and microscopic images of live cells in vitro under various toxic agent stimuli. The dynamic response of live porcine pulmonary artery endothelial cells (PPAECs) exposed to various doses of cytochalasin D are comprehensively examined by monitoring the micro-impedance characteristics at a specified frequency and DICM images using the opto-electric biosensor. The change in PPAEC morphology and motility caused by cytochalasin D clearly illustrates the dose-dependent actin filament disruption where optical images are correlated with the changes in the micro-electric impedance.
Learning by Tension
Authors: Yang Shengyuan , Siechen Scott , Sun Jie , Chiba Akira , Saif Taher
Published: March 2014

Memory and learning in animals is mediated by neurotransmission at the synaptic junctions (end point of axons). Neurotransmitters are carried by synaptic vesicles which cluster at the junctions, ready to be dispatched for transmission. The more a synapse is used, higher is the clustering, and higher is the neurotransmission efficiency (plasticity), i.e., the junction “remembers” its use in the near past, and modifies accordingly. This usage dependent plasticity offers the basic mechanism of memory and learning. A central dogma in neuroscience is that, clustering is the result of a complex biochemical signaling process. We show, using MEMS sensors and fruit fly (Drosophila) embryo nervous system, that mechanical tension in axons is essential for clustering. Without tension, clustering disappears, but reappears with application of tension. Nature maintains a rest tension of 1nN in axons of Drosophila for learning and memory.
Viscohyperelastic Material Modeling of Liver Tissue
Authors: Vemaganti Kumar , Roan Esra
Published: March 2014

Mechanical characterization of soft tissue plays a critical role in applications such as automated surgery, disease diagnosis and tissue engineering. Soft tissue is often modeled as an isotropic incompressible and hyperelastic material. However, it is well known that viscoelasticity plays an important role in determining the response of soft tissue to mechanical loads [1]. This work is concerned with the development of hyperviscoelastic models of soft tissue in general and liver tissue in particular. Experimental studies in uniaxial compression are conducted on bovine liver tissue at strain rates between 0.001 s−1 and 0.04 s−1. The response of liver tissue is modeled using the continuum mechanics framework using an exponential form of the strain energy function.
Live Cell Detection of Specific Messenger RNA for Molecular Analysis of Plaque Formation
Authors: Rhee Wonjong , Jo Hanjoong , Bao Gang
Published: March 2014

The ability to visualize mRNA in single living cells and monitor in real-time the changes of mRNA level and localization in response to shear flow can provide unprecedented opportunities for the molecular analysis of atherosclerosis. We carried out an extensive study of the design of molecular beacons to target BMP-4 mRNA, which plays important roles in proatherogenic development in response to unstable flow conditions. Specifically, we selected an optimal molecular beacon design, and found that the fluorescent intensity from targeting BMP-4 mRNA correlated well with the GFP signal after up-regulating BMP-4 and co-expressing GFP using adenovirus. The knock-down of BMP-4 mRNA using siRNA significantly reduced the beacon signal, further demonstrating detection specificity. We found that, due to target accessibility, molecular beacons designed with different target sequences gave very different signal levels, and establishing molecular beacon design rules has significant implications to live cell mRNA detections, especially to the studies of BMP-4 mRNA in endothelial cells under shear flow.
Voluntary Running Exercise Ameliorates Muscle Loss in Mice
Authors: Hanson Andrea M. , Stodieck Louis S. , Ferguson Virginia L.
Published: March 2014

Both spaceflight and bed rest studies are known to cause substantial muscle loss in humans. Of particular interest in atrophy studies is the postural, slow-twitch fiber soleus muscle. It has been demonstrated that during periods of disuse, slow-twitch fibers undergo fiber type switching and morph into fast-twitch fibers [1]. Alternatively, when exercise is prescribed, there is switching of fast-to slow-twitch fibers [2], indicating a profound adaptability of the muscle to exercise.
Validation of MRI-Based Contact Modeling for Analysis of In Vivo Radiocarpal Mechanics
Authors: Waller Alexander J. , McIff Terence E. , Bilgen Mehmet , Toby E. Bruce , Fischer Kenneth J.
Published: March 2014

Arthritis is a pervasive problem and over 15% of the total population of the United States has been doctor-diagnosed with arthritis. Even more Americans have symptoms. Clearly, understanding the pathogenesis of arthritis, developing effective treatments and/or finding ways to prevent it are all important goals.
Mesenchymal Stem Cell Injection After Myocardial Infarction Improves Myocardial Compliance
Authors: Discher Dennis , Engler Adam
Published: March 2014

Cellular therapy for myocardial injury has improved ventricular function in both animal and clinical studies, though the mechanism of benefit is unclear. This study was undertaken to examine the effects of cellular injection after infarction on myocardial elasticity. Coronary artery ligation of Lewis rats was followed by direct injection of human mesenchymal stem cells (MSC) into the acutely ischemic myocardium. Two weeks post-infarct, myocardial elasticity was mapped by atomic force microscopy. MSC-injected hearts near the infarct region were two-fold stiffer than myocardium from non-infarcted animals but softer than myocardium from vehicle-treated infarcted animals. After eight weeks, the following variables were evaluated: MSC engraftment and left ventricular geometry by histologic methods; cardiac function with a pressure-volume conductance catheter; myocardial fibrosis by Masson trichrome staining; vascularity by immunohistochemistry; and apoptosis by TUNEL assay. The human cells engrafted and expressed a cardiomyocyte protein but stopped short of full differentiation and did not stimulate significant angiogenesis. MSC-injected hearts showed significantly less fibrosis than controls, as well as less left ventricular dilation, reduced apoptosis, increased myocardial thickness, and preservation of systolic and diastolic cardiac function. In summary, MSC injection after myocardial infarction did not regenerate contracting cardiomyocytes but reduced the stiffness of the subsequent scar and attenuated post-infarction remodeling, preserving some cardiac function. Improving scarred heart muscle compliance could be a functional benefit of cellular cardiomyoplasty.
Thermal Therapy Protocols for Benign Prostatic Hyperplasia
Authors: Chinn Daniel , Nditafon Elvis , Yew Alvin , Thamire Chandrasekhar
Published: March 2014

Thermal therapy for treatment of benign prostatic hyperplasia (BPH) is becoming increasingly popular due to the minimally invasive nature of the treatment. Successful management of such therapy requires accurate estimation of thermal dosage. The purpose of this study is to provide correlations for the thermal damage caused by ultrasound, microwave, and infrared devices under a range of operating conditions. A boundary-fitting finite difference method is used to examine the heat transfer in the prostate gland and surrounding tissue. The Pennes bioheat transfer model and a porous media model were utilized to calculate temperature histories. Necrosis zones were determined using published necrosis data for prostatic tissue and cells. Thermal damage correlations for the three different hyperthermia sources along with sample temperature contours and necrosis zones are presented. Results indicate that the applicator power level and heating time are the most important parameters in achieving the desired necrosis zones, while coolant parameters strongly affect the temperatures of the sensitive urethra and serve as constraints for protocol parameters. Out of the three sources evaluated, ultrasound modality appears to be the most capable of causing necrosis in the target zones, with least damage to the surrounding healthy tissues.
3d Reconstruction and Nonlinear Finite Element Analysis of the Embryonic Left Ventricle
Authors: Faas Daniela , Buffinton Christine , Sedmera David
Published: March 2014

Changes in mechanical loading in the developing heart produce changes in morphology and mechanical material properties [1–3]. Understanding the relationship of these changes to mechanical stress and strain in the left ventricle requires a geometrically accurate model of the entire ventricle including the trabecular pattern and material property, boundary condition, and loading specification. A 3D reconstruction and finite element technique were developed to reconstruct the heart from serial confocal sections and calculate stress and strain distributions over the volume for the passive state. Control hearts and two treatments, pressure overload and pressure underload, were modeled. The results show that stresses in the trabeculae are much larger than those in the ventricular walls. Strains in the pressure-overloaded hearts were significantly smaller than in control or underloaded, indicating the stiffer material properties more than compensate for the increased internal pressure.
Developing an Active Ankle Foot Orthosis Based on Shape Memory Alloy Actuators
Authors: Tarkesh Ehsan , Elahinia Mohammad H. , Hefzy Mohamed Samir
Published: March 2014

This paper is on development of an active ankle foot orthosis (AAFO). This device will fill the gap in the existing research aimed at helping patients with drop foot muscle deficiencies as well as rehabilitation activities. Drop foot patients are unable to lift their foot because of reduced or no muscle activity around the ankle. The major causes of drop foot are severing of the nerve, stroke, cerebral palsy and multiple sclerosis. There are two common complications from drop foot. First, the patient cannot control the falling of their foot after heel strike, so that it slaps the ground on every step. The second complication is the inability to clear the toe during swing. This causes the patients to drag their toe on the ground throughout the swing.
Temperature Rise in Tissue Mimicking Material During HIFU Procedures
Authors: Dasgupta Subhashish , Hariharan Prasanna , Myers Matthew R. , Banerjee Rupak K.
Published: March 2014

High Intensity Focused Ultrasound (HIFU) has shown considerable promise as a minimally-invasive technique for various therapeutic applications such as tumor ablation and vessel cauterization. The efficacies of these HIFU procedures depend on various operational parameters such as total acoustic power, pulse duration and transducer dimensions. In this study, the effect of total acoustic power on the tissue temperature rise is studied both experimentally and numerically. Experimentally, HIFU ablations, at different acoustic powers, were carried out in a tissue mimicking material embedded with thermocouples. Temperature rise measured from the in-vitro experiments were then validated with the numerical computations. Results show that experimental and numerical temperature rise match accurately. Our numerical model was able to predict the peak temperature rise within ∼12% of the experimental results. Results also show that the tissue temperature rise is linearly proportional to the input acoustic power. For the acoustic power levels considered in this study, the results suggest that acoustic non-linearity does not play a major role on the tumor ablation procedure.
Experimental and Numerical Modelling of the Ventriculo-Sinus Shunt to Treat Malresoptive Hydrocephalus
Authors: Van Canneyt Koen , Kips Jan , Mareels Guy , Baert Edward , Van Roost Dirk , Verdonck Pascal
Published: March 2014

This study assesses malresorptive hydrocephalus treatment by ventriculosinus (VS) shunting with the shunt in antegrade or retrograde position. First, an experimental model of the cerebral ventricles, the arachnoid villi, the cortical veins and the superior sagittal sinus (SSS) was built. For this purpose, the compliance of a human cortical vein was measured ex vivo and then modelled by means of Penrose tubes. The dimensions of the superior sagittal sinus were also determined in vivo by measurements on MRI-scans of 21 patients. Secondly, with the experimental model, a numerical model of the cortical veins and the superior sagittal sinus was validated. The experimental and numerical pressure difference between the intracranial pressure and the static sinus pressure was small (0–20 Pa) and corresponded with the theoretically expected values. No overdrainage was found in either antegrade or retrograde position of the shunt. Blood reflow was only found while mimicking lumbar puncture or changes in position with the experimental model (fast lowering the intracranial pressure respectively fast increasing the sinus pressure). Both model results confirm the potential of ventriculosinus shunting as therapy for malresorptive hydrocephalus patients. The ventriculosinus shunt thus proves to be a promising technique.
Evaluation of the Effect of Stent Strut Profile on Shear Stress Distribution
Authors: Ruzzeh Bilal , Mongrain Rosaire , Leask Richard , Bertrand Olivier
Published: March 2014

In this work, we present a 2D numerical flow study to analyze the impact of different stent strut profiles on the shear stress distribution for stented coronary arteries. In that context, five cross-sectional profiles were considered: square, circular, elliptical, and a two tear-drop shapes. Specific performance metrics based on the statistical moments were developed to assess the variation of shear stress distributions along the wall with respected to a normal reference condition (non-stented segment). The results show that stent strut profile significantly affects the shear stress distribution along the wall. It also demonstrate that more streamline profiles such as the tear-drop and elliptical profiles exhibit better performance than the standard square and circular profiles for shear stress.
Multiple Days of Monitoring Are Needed to Obtain a Reliable Estimate of Physical Activity in Hip-Fracture Patients
Authors: Taraldsen Kristin , Vereijken Beatrix , Thingstad Pernille , Sletvold Olav , Helbostad Jorunn L.
Published: March 2014

The aim of the study was to investigate the precision of estimated upright time during one week in community-dwelling older adults after hip fracture when monitoring activity for different numbers of consecutive days. Information about upright time was collected by thigh-worn accelerometers during 7 consecutive days in 31 older adults (mean age 81.8 years ± 5.3) 3 months after hip-fracture surgery. Mean time in upright position, including both standing and walking, was 260.9 (±151.2) min/day. A cutoff value of half an hour was used to provide recommendations about number of recording days. Large variability between participants between days, as well as a nonconstant within-participant variability between days indicates that at least 4 consecutive days of recording should be used to obtain a reliable estimate of upright time for individual persons. However, at a group level, one day of recording is sufficient.
Validation of a Computerized Use of Time Recall for Activity Measurement in Advanced-Age Adults
Authors: Jordan Mace Casey , Maddison Ralph , Olds Timothy , Kerse Ngaire
Published: March 2014

Background:

The Multimedia Activity Recall for Children and Adults (MARCA) is a computerized recall instrument that records use of time during 24 hr the previous day and has been developed to address limitations of current self-report physical activity measures for those in advanced age.

Methods:

Test–retest reliability and convergent validity of the adult MARCA were assessed in a sample of 45 advanced-age adults (age 84.9 SD ± 1.62 yr) as a subsample of the Life and Living in Advanced-Age Cohort Study New Zealand (LiLACS NZ). Test–retest methods required participants to recall the previous day’s activity using the MARCA twice within the same day. Convergent validity was assessed against accelerometry.

Results:

Test–retest reliability was high, with ICCs greater than .99 for moderate to vigorous physical activity (MVPA) and physical activity level (PAL). Compared with accelerometry, the MARCA demonstrated validity comparable to other self-report instruments with Spearman’s coefficients of .34 and .59 for time spent in nonsedentary physical activity and PAL.

Conclusion:

The MARCA is a valid and reliable self-report tool for physical activity behaviors in advanced-age adults.
Influence of Allowable Interruption Period on Estimates of Accelerometer Wear Time and Sedentary Time in Older Adults
Authors: Mailey Emily L. , Gothe Neha P. , Wójcicki Thomas R. , Szabo Amanda N. , Olson Erin A. , Mullen Sean P. , Fanning Jason T. , Motl Robert W. , McAuley Edward
Published: March 2014

The criteria one uses to reduce accelerometer data can profoundly influence the interpretation of research outcomes. The purpose of this study was to examine the influence of 3 different interruption periods (i.e., 20, 30, and 60 min) on the amount of data retained for analyses and estimates of sedentary time among older adults. Older adults (N = 311, Mage = 71.1) wore an accelerometer for 7 d and reported wear time on an accelerometer log. Accelerometer data were downloaded and scored using 20-, 30-, and 60-min interruption periods. Estimates of wear time, derived using each interruption period, were compared with self-reported wear time, and descriptive statistics were used to compare estimates of sedentary time. Results showed a longer interruption period (i.e., 60 min) yields the largest sample size and the closest approximation of self-reported wear time. A short interruption period (i.e., 20 min) is likely to underestimate sedentary time among older adults.
Sport Specialization’s Association With an Increased Risk of Developing Anterior Knee Pain in Adolescent Female Athletes
Authors: Hall Randon , Foss Kim Barber , Hewett Timothy E. , Myer Gregory D.
Published: March 2014

Objectives:

To determine if sport specialization increases the risk of anterior knee pain in adolescent female athletes.

Design:

Retrospective cohort epidemiology study.

Methods:

Female basketball, soccer, and volleyball players (N = 546) were recruited from a single county public school district in Kentucky consisting of 5 middle schools and 4 high schools. A total of 357 multisport and 189 single-sport (66 basketball, 57 soccer, and 66 volleyball) athlete subjects were included due to their diagnosis of patellofemoral pain (PFP) on physical exam. Testing consisted of a standardized history and physician-administered physical examination to determine the presence of PFP. This study compared self-reported multisport athletes with sport-specialized athletes participating in only 1 sport. The sports-participation data were normalized by sport season, with each sport accounting for 1 season of exposure. Incidence rate ratios and 95% confidence intervals (CI) were calculated and used to determine significant differences between athletes who specialized in sport in early youth and multisport athletes.

Results:

Specialization in a single sport increased the relative risk of PFP incidence 1.5-fold (95% CI 1.0−2.2, P = .038) for cumulative PFP diagnoses. Specific diagnoses such as Sinding Larsen Johansson/patellar tendinopathy (95% CI 1.5−10.1, P = .005) and Osgood Schlatter disease (95% CI 1.5−10.1, P = .005) demonstrated a 4-fold greater relative risk in single-sport compared with multisport athletes. Incidence of other specific PFP diagnoses such as fat pad, plica, trauma, pes anserine bursitis, and iliotibial-band tendonitis was not different between single-sport and multisport participants (P > .05).

Conclusion:

Early sport specialization in female adolescents is associated with increased risk of anterior knee-pain disorders including PFP, Osgood Schlatter, Sinding Larsen-Johansson compared with multisport athletes.
Comparison of the Effects of Electrical Stimulation and Cold-Water Immersion on Muscle Soreness After Resistance Exercise
Authors: Jajtner Adam R. , Hoffman Jay R. , Gonzalez Adam M. , Worts Phillip R. , Fragala Maren S. , Stout Jeffrey R.
Published: March 2014

Context:

Resistance training is a common form of exercise for competitive and recreational athletes. Enhancing recovery from resistance training may improve the muscle-remodeling processes, stimulating a faster return to peak performance.

Objective:

To examine the effects of 2 different recovery modalities, neuromuscular electrical stimulation (NMES) and cold-water immersion (CWI), on performance and biochemical and ultrasonographic measures.

Participants:

Thirty resistance-trained men (23.1 ± 2.9 y, 175.2 ± 7.1 cm, 82.1 ± 8.4 kg) were randomly assigned to NMES, CWI, or control (CON).

Design and Setting:

All participants completed a high-volume lower-body resistance-training workout on d 1 and returned to the human performance laboratory 24 (24H) and 48 h (48H) postexercise for follow-up testing.

Measures:

Blood samples were obtained preexercise (PRE) and immediately (IP), 30 min (30P), 24 h (24H), and 48 h (48H) post. Subjects were examined for performance changes in the squat exercise (total repetitions and average power per repetition), biomarkers of inflammation, and changes in cross-sectional area and echo intensity (EI) of the rectus femoris (RF) and vastus lateralis muscles.

Results:

No differences between groups were observed in the number of repetitions (P = .250; power: P = .663). Inferential-based analysis indicated that increases in C-reactive protein concentrations were likely increased by a greater magnitude after CWI compared with CON, while NMES possibly decreased more than CON from IP to 24H. Increases in interleukin-10 concentrations between IP and 30P were likely greater in CWI than NMES but not different from CON. Inferential-based analysis of RF EI indicated a likely decrease for CWI between IP and 48H. No other differences between groups were noted in any other muscle-architecture measures.

Conclusions:

Results indicated that CWI induced greater increases in pro- and anti-inflammatory markers, while decreasing RF EI, suggesting that CWI may be effective in enhancing short-term muscle recovery after high-volume bouts of resistance exercise.
TGF-β Signaling Mediates Endothelial-to-Mesenchymal Transition (EndMT) During Vein Graft Remodeling
Authors: Cooley Brian C. , Nevado Jose , Mellad Jason , Yang Dan , St. Hilaire Cynthia , Negro Alejandra , Fang Fang , Chen Guibin , San Hong , Walts Avram D. , Schwartzbeck Robin L. , Taylor Brandi , Lanzer Jan D. , Wragg Andrew , Elagha Abdalla , Beltran Leilani E. , Berry Colin , Feil Robert , Virmani Renu , Ladich Elena , Kovacic Jason C. , Boehm Manfred
Published: March 2014

In vivo endothelial cell fate mapping demonstrates that TGF-β signaling is a central pathway regulating the endothelial-to-mesenchymal transition (EndMT) during vein graft remodeling.
Meeting the Demand for Pediatric Clinical Trials
Authors: Connor Edward M. , Smoyer William E. , Davis Jonathan M. , Zajicek Anne , Ulrich Linda , Purucker Mary , Hirschfeld Steven
Published: March 2014

The bid for high-quality, cost-effective pediatric clinical trials requires robust research and regulatory playgrounds and an appropriately trained workforce.
The Serpin Shield
Authors: Balcells Mercedes
Published: March 2014

Serpins help breast and lung cancer cells metastasize to the brain by annulling stromal defenses and co-opting capillaries.
Got Milk Antibodies?
Authors: Mahfuz Mustafa
Published: March 2014

Secreted immunoglobulins in breast milk may promote long-term benefits against intestinal inflammatory diseases.
Muddy clinical waters: a missed pulmonary embolus
Authors: Lee Nathaniel , Bax Simon Rupert
Published: March 2014

The diagnosis of pulmonary embolism (PE) can be difficult to make. The consequences of missing a PE can be fatal and clinicians should always be vigilant. This case presents a patient admitted with fluctuations in consciousness and in a septic state. A preliminary diagnosis of aspiration pneumonia was made, and the patient went on to have an exploratory surgical procedure with no remarkable findings. Only after further investigation of the patient's fluctuations in consciousness was a retrospective diagnosis of a large PE made. The patient was anticoagulated and made a full recovery, with no outstanding pulmonary issues at follow-up 6 weeks after discharge. A prolonged immobile state, likely in part due to the patient's septic state and psychiatric history, along with recent surgery and hospitalisation were the most obvious risk factors.
Information and communication technology for managing pain in palliative care: a review of the literature
Authors: Allsop Matthew J , Taylor Sally , Mulvey Matthew R , Bennett Michael I , Bewick Bridgette M
Published: March 2014

Background

Information and communication technology (ICT) systems are being developed for electronic symptom reporting across different stages of the cancer trajectory with research in palliative care at an early stage.

Aim/design

This paper presents the first systematic search of the literature to review existing ICT systems intended to support management of pain in palliative care patients with cancer. The review was conducted according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines for systematic reviews and meta-analyses.

Data sources

Four databases (Embase, MEDLINE, PsycINFO and Healthcare Management Information Consortium) from 1990 to December 2012 were searched, with exclusion of papers based on their description of ICT systems and language used.

Results

24 articles met the inclusion criteria, many of which reported the use of non-experimental research designs. Studies were identified at different stages of development with no systems having reached implementation. Most systems captured pain as part of quality-of-life measurement with wide variation in approaches to pain assessment.

Conclusions

ICT systems for symptom reporting are emerging in the palliative care context. Future development of ICT systems need to increase the quality and scale of development work, consider how recommendations for pain measurement can be integrated and explore how to effectively use system feedback with patients.
Sources of Streptococcus dysgalactiae in English and Welsh sheep flocks affected by infectious arthritis (joint ill)
Authors: Rutherford S. J. , Rycroft A. N. , Ridler A. L.
Published: March 2014

In order to investigate sheep sources of Streptococcus dysgalactiae in flocks affected with joint ill, 10 sheep flocks in England and Wales with laboratory‐confirmed cases of infectious arthritis (joint ill) caused by S dysgalactiae were visited during a disease outbreak while a further four flocks were visited during the lambing period in the year following an outbreak. A total of 5239 samples were collected for bacterial culture from 797 ewes and their 1314 lambs. S dysgalactiae was isolated from nine of 894 samples (1 per cent) on farms visited during an outbreak, and from 7 of 4462 samples (0.2 per cent) collected in the year following an outbreak. The 16 samples from which S dysgalactiae was isolated came from the vaginas of eight ewes, milk of one ewe, navels of four lambs, mouths of two lambs and noses of one lamb. In vitro testing of the survival of S dysgalactiae on straw, hay and in water at different temperatures was performed, and it was isolated from these substrates for up to 42, 35 and 0 days, respectively.
Mixed convection flow of an electrically conducting fluid in a vertical channel with boundary conditions of the third kind
Authors: Umavathi J.C. , Chamkha A.J.
Published: March 2014

In this study, the effects of viscous and Ohmic dissipation in steady, laminar, mixed, convection heat transfer for an electrically conducting fluid flowing through a vertical channel is investigated in both aiding and opposing buoyancy situations. The plates exchange heat with an external fluid. Both conditions of equal and different reference temperatures of the external fluid are considered. First, the simpler cases of either negligible Brinkman number or negligible Grashof number are addressed with the help of analytical solutions. The combined effects of buoyancy forces and viscous dissipation are analyzed using a perturbation series method valid for small values of the perturbation parameter. To relax the conditions on the perturbation parameter, the governing equations are also evaluated numerically by a shooting technique that uses the classical explicit Runge–Kutta method of four slopes as an integration scheme and the Newton–Raphson method as a correction scheme. In the examined cases of velocity and temperature fields, the Nusselt numbers at both the walls and the average velocity are explored. It is found that the velocity profiles for an open circuit (E > 0 or E < 0) lie in between the short circuit (E = 0). The graphical results illustrating the effects of various parameters on the flow as well as the average velocity and Nusselt numbers are presented for open and short circuits. In the absence of electric field load parameter and Hartmann number, the results agree with Zanchini (Int. J. Heat Mass Transfer, 41, 3949 (1998)). Further, the analytical and numerical solutions agree very well for small values of the perturbation parameter.