bluuebunny/crossref_metadata_2025 huggingface dataset:
Phage JS02, a putative temperate phage, a novel biofilm-degrading agent for Staphylococcus aureus
Authors: Zhang L. , Shahin K. , Soleimani-Delfan A. , Ding H. , Wang H. , Sun L. , Wang R.
Published: January 2022

Staphylococcus aureus is a biofilm-producing organism that is frequently isolated from various environments worldwide. Because of the natural resistance of S. aureus biofilm to antibiotics, bacteriophages are considered as a promising alternative for its removal. The bacteriophage vB_SauS_JS02 was isolated from livestock wastewater and showed activity against multidrug-resistant S. aureus. The phage vB_SauS_JS02 exhibited a broad host range and possessed a large burst size (52 PFU/CFU) as well as moderate pH stability (4–11) and appropriate thermal tolerance (40–50°C). Electron microscopy and genome sequence revealed that vB_SauS_JS02 belonged to Triavirus genus in Siphoviridae family. Genetic analysis of the 46 kb sequence of vB_SauS_JS02 revealed 66 ORFs. The predicted protein products of the ORFs were clustered functionally into five groups as follows: replication/regulation, DNA packaging, structure/morphogenesis, lysis and lysogeny. Although the phage vB_SauS_JS02 was a temperate phage, it exhibited a higher inhibiting and degrading activity against planktonic cells (80~90% reduction), even to S. aureus biofilm (~68% reduction in biofilm formation). Moreover, the removal activity of the phage vB_SauS_JS02 against both planktonic cells and S. aureus biofilms was even better than that of the antibiotic (ceftazidime). In summary, the present study introduced the phage vB_SauS_JS02 as a potential biocontrol agent against biofilm-producing S. aureus after making it virulent. It may be applicable for phage therapy.
When Violence Is neither “Personal” nor “General”
Authors: England Sarah
Published: January 2022

In this essay, I use a case of testifying as an expert witness to argue that the anthropological focus on multicausality, context, and the social/cultural origins of persecution is useful and necessary in asylum cases. The government attorney argued that the persecutor's violence was “personal,” related only to his alcoholism, not the victim's identity as his wife. I argued that regardless of his personal history, the violence and the “excuses and justifications” that he used were patterned and based in cultural ideologies about gender. In a criminal case this might provide a “cultural defense” to avoid culpability. However, in asylum cases the social/cultural origins of violence help meet the legal criteria for asylum.
Recovery of right ventricular function after bilateral lung transplantation for pediatric pulmonary hypertension
Authors: Critser Paul J. , Boyer Debra , Visner Gary A. , Collins Shane L. , Fynn‐Thompson Francis , Mullen Mary P.
Published: January 2022

Background

Lung transplantation is a therapeutic option for end‐stage pediatric pulmonary hypertension (PH). Right ventricular (RV) recovery post‐lung transplant in children with PH has not been well‐described, and questions persist about the peri‐operative course and post‐transplant cardiac function after lung transplantation in medically refractory PH patients with baseline RV dysfunction.

Methods

A single‐center chart review identified patients with childhood PH who subsequently underwent bilateral orthotopic lung transplantation between 2000 and 2020. Twenty‐six patients met criteria; three were excluded due to echocardiograms not available for digital review. RV fractional area change (FAC) and left ventricular eccentricity index (LVEI) were determined prior to transplantation, and at 1, 3, 6, and 12‐month post‐transplantation.

Results

Fourteen of 23 patients had baseline RV dysfunction. The median age at transplantation was 16.5 years and 13.9 years for those with and without baseline RV dysfunction, respectively. Of the 14 with baseline RV dysfunction, 12 (86%) were alive 1‐year post‐transplantation. All patients with baseline RV dysfunction had increased RV‐FAC post‐transplantation with normalization of RV‐FAC in 70% at 3 months and 100% of patients by 12‐month post‐transplantation. Duration of ventilation (p = .4), intensive care unit (p = .5), or hospital stay (p = .9) was not associated with pre‐transplant RV function.

Conclusions

Among pediatric patients with PH and RV dysfunction, pre‐transplantation RV function was not associated with short‐term outcomes. All patients with baseline RV dysfunction had improvement in RV function, justifying consideration of lung transplantation among pediatric patients with end‐stage PH and RV dysfunction.
Nondestructive versus advanced post‐transplant lymphoproliferative disorder in a single‐center pediatric kidney transplant population
Authors: Wu Ellen , Lee Joo‐Young , Gelarden Ian , Engen Rachel M
Published: January 2022

Background

Pediatric kidney transplant recipients are at risk for the development of post‐transplant lymphoproliferative disorders (PTLD), a group of potentially devastating diseases that present on a spectrum of severity ranging from nondestructive PTLD to more histologically destructive lesions. Currently, there is inadequate evidence to guide evaluation and management of nondestructive PTLD.

Methods

This is a single‐center case series of pediatric kidney transplant recipients between January 1, 2008 and December 31, 2019, who were diagnosed with PTLD. The aim was to describe clinical characteristics, presentation, and management of nondestructive versus advanced PTLD.

Results

Eighteen patients were diagnosed with nondestructive PTLD and seven with more advanced PTLD histopathology. The majority (66.7%) of nondestructive PTLD patients (n = 16) presented with tonsillar hypertrophy and/or snoring and were managed conservatively, with minimal reduction in tacrolimus dose and no further evaluation. No patient progressed to more advanced PTLD. Advanced PTLD patients (n = 7) were more likely to present with fever, elevated creatinine, a new mass of gastrointestinal symptoms. They received workup with imaging and oncology consultation, and were managed with chemotherapy.

Conclusions

Patients with nondestructive PTLD often present with symptoms of sleep‐disordered breathing and can be managed conservatively with excellent clinical outcomes. More study is needed to guide care of this under‐researched population.
Exposure to high nitrogen triggered a genotype‐dependent modulation of cell and root hydraulics, which can involve aquaporin regulation
Authors: Pou Alicia , Hachez Charles , Couvreur Valentin , Maistriaux Laurie C. , Ismail Ahmed , Chaumont François
Published: January 2022

Root nitrogen acquisition has been proposed to be regulated by mass flow, a process by which water flow brings nutrients to the root surface, depending on a concerted regulation of the root hydraulic properties and stomatal conductance. As aquaporins play an important role in regulating transcellular water flow, we aimed at evaluating the short‐term effect of high nitrogen (HN) availability on the dynamics of hydraulic parameters at both the root and cell level and the regulation of aquaporins. The effect of short‐term HN (8 mM NO3−) treatment was investigated on 12 diverse 15‐day‐old maize genotypes. Root exposure to HN triggered a rapid (<4 h) increase in the root hydraulic conductivity (Lpr) in seven genotypes while no Lpr variation was recorded for the others, allowing the separation of the genotypes into two groups (HN‐responsive and HN‐nonresponsive). A remarkable correlation between Lpr and the cortex cell hydraulic conductivity (Lpc) was observed. However, while differences in gas exchange parameters were also observed, the variations were genotype‐specific and not always correlated with the root hydraulic parameters. We then investigated whether HN‐induced Lpr variations were linked to the activity and regulation of plasma membrane PIP aquaporins. While some changes in PIP mRNA levels were detected, this was not correlated with the protein levels. On the other hand, the rapid variation in Lpr observed in the B73 genotype was correlated with the PIP protein abundance in the plasma membrane, highlighting PIP posttranslational mechanisms in the short‐term regulation of root hydraulic parameters in response to HN treatment.
The effects of restrictive measures on cross‐border investment: Evidence from OECD and emerging countries
Authors: Zongo Amara
Published: January 2022

This paper investigates the effects of global and sectoral restrictive measures on cross‐border FDI among 49 advanced and emerging countries. We use a gravity model with panel data from 2010 to 2019 and the FDI Restrictiveness Index of the OECD that quantifies the level of restriction in FDI. Our results suggest that global restrictive measures do not significantly affect cross‐border FDI in OECD countries, while restrictions in the service sector have negative and significant effects on FDI. Moreover, the overall restrictive measures and those in the primary, secondary and service sectors negatively impact inward FDI among OECD and big emerging countries. The restrictions in the primary sector are a main obstacle to inward FDI in the big emerging countries. In addition, global and sectoral restrictions do not have a significant effect on FDI between advanced and African countries. The analysis of disaggregated sectoral restrictive measures shows that restrictions in business and other financial services are negatively associated with intra‐OECD FDI. We also find that restrictions in the manufacturing sector have restrictive impacts on inward FDI in the large emerging countries, and those in the mining, quarrying and oil extraction sector hinder inward FDI in African countries. Reforms to liberalise sectoral restrictions by country have positive effects on FDI, but deregulation of the services sector has beneficial effects on inward FDI from advanced and emerging countries.
Rent-Seeking and the Volume of Tax Laws: The Tax Cuts and Jobs Act of 2017
Authors: Swenson Charles , Qu Hao
Published: January 2022

Taxes have a significant impact on individuals and firms. Unfortunately, complexity in the tax law has led to economic inefficiency due to inefficient use of tax breaks and increased audits and related penalties. Part of such complexity is driven by the sheer volume of tax law. To explain this phenomenon, we model tax law volume as a function of wealth transfers from the rent seeking/theory of regulation literature. Our models predict that both overall volume and the number of specific terms (defined by words in our specific “dictionary”) is higher for groups receiving tax breaks, and lower for more heavily taxed groups. The specific terms attempt to control for free riding across groups, and to limit tax breaks within groups. Using textual analysis, these predictions are supported in tests using the Tax Cuts and Jobs Act of 2017. Also, consistent with theory, we find that tax breaks are given to relatively smaller groups, and tax increases are spread across relatively larger groups.
Exercises to Maximize Stress in Bones During Bed Rest Studies
Authors: Batson Christina A. , Horne Stephanie M. , Poe Mandy E. , Butts Ryan , Graffeo Lauren , Todd Beth A. , Shackelford Linda C.
Published: January 2022

Bone Mineral Density (BMD) loss seen in astronauts can be simulated on Earth by prolonged horizontal bed rest. A device known as the Horizontal Exercise Machine (HEM) has been designed to test the effectiveness of heavy resistive exercise regimens for bed rest subjects. The objective of this project is to estimate the mechanical stress on the skeletal system due to various types of exercises and determine which exercises will best prevent BMD loss. The stress will be calculated at skeletal locations of most concern during long-duration space flight.
Biomechanical Evaluation of a Posterior Cruciate Ligament Reconstruction in the Knee Using Robotic Technology
Authors: Vogrin Tracy M. , Woo Savio L.-Y. , Höher Jürgen , Janaushek Marsie A. , Ma C. Benjamin , Harner Christopher D.
Published: January 2022

Clinical outcomes of reconstructive surgery for injuries to the posterior cruciate ligament (PCL) of the knee have been unsatisfactory, with persistent instability predisposing patients to early degenerative joint disease [Clancy, 1983]. One explanation for these outcomes has been the high incidence (up to 60%) of associated injuries to the posterolateral structures (PLS), which include the lateral collateral ligament (LCL) and popliteus complex. Combined PCL/PLS injuries are particularly debilitating because restraints to both posterior tibial translation and external rotation are lost [Grood, 1988]. Further, PLS injuries are difficult to reconstruct due to its complex anatomy; thus, often only the PCL is reconstructed when combined injuries occur.
Interactions Between Oscillatory Flow and Spasmic Coronary Artery: A FVM Study With Prescribed Moving Wall
Authors: Liu Hao , Yamaguchi Takami
Published: January 2022

A FVM (finite volume method) computational system has been developed to investigate the interactions between oscillatory flow and spasmic coronary artery with prescribed moving wall. Computational analyses of the unsteady blood flow induced by the interactions between moving wall and oscillatory flow are presented by using a self-developed, effective, FVM-based NS solver (Liu, 1997) with global conservation in a boundarey-fitted coordinate (BFC) system. Two extensive studies of the oscillatory flow induced by a flushing in/out indentation with fully developed flow at inlet (Poiseuille flow), and by a fixed asymmetric indentation with pulsatile inlet flow were conducted to investigate geometric and kinematics effects of the unsteady flow with the prescribed moving wall in blood vessel. The present study gives results concerning the variability of WSS (wall shear stress) both in space and in time, which enhances our understanding for the self-excited oscillations that develop when fluid flows through an externally compressed collapsible tube.
The Phase Angle Between Fluid Wall Shear Stress and Solid Circumferential Strain: Its Distribution in the Circulation
Authors: Qiu Y. C. , Lee C. S. , Tarbell J. M.
Published: January 2022

Endothelial cells (ECs) on blood vessel walls are exposed to both the wall shear stress (WSS) of blood flow and the cyclic circumferential strain (CS) of the pulsing vessel wall. The WSS and CS are both oscillatory and approximately perpendicular to each other in their direction of action. Due to wave reflection in the circulation and inertial effects in blood flow, WSS is not always in phase with CS. The interaction of CS and WSS generates a complex, time varying mechanical force pattern applied to the EC layer, which is believed to play a role in determining EC biological response, remodeling of blood vessels, and possibly development of arterial disease. The stress phase angle (SPA) between CS and WSS, which characterizes the dynamic force pattern on ECs, varies throughout the circulation as discussed in this paper.
Determination of Vascular Geometry and Flow Velocity in Cerebral Arteriovenous Malformations (AVMs) Using Double Contrast and High-Speed Digital Subtraction Angiography
Authors: Lieber B. B. , Wakhloo A. K. , Divani A. , Rudin S.
Published: January 2022

Successful therapeutic embolization, i.e., catheter-based occlusion of cerebral arteriovenous malformations (AVMs) using liquid embolic agents requires precise knowledge of highly variant AVM architecture, blood flow velocity, and transit times through the AVM fistulae. In this study we tried to visualize both the AVM vascular substructure and dynamics of discrete microdroplets traveling through the AVM using a single injection composed of both soluble and non-soluble contrast material. The contrast injection is traced with high-speed digital subtraction angiography. This novel technique serves as a valuable diagnostic tool to the interventionist prior to embolization of the AVM.
Toward Defining the Role of Ca2+ and MAP Kinases in Fluid-Induced Shear Regulation of Aggrecan in Chondrocytes
Authors: Hung Clark T. , Wang Changbin B. , Henshaw Ross , Valhmu Wilmot B. , Goldring Mary B.
Published: January 2022

In this study, the role of two candidate cell signaling pathways, one related to intracellular calcium ([Ca2+]i) and the second involving mitogen activated protein kinases (MAPKs), in chondrocyte mechanotransduction was investigated. It is our aim to begin to relate these cell signaling pathways to the regulation of aggrecan gene expression in chondrocytes.
Numerical Study of an Asymmetrical Stenosis
Authors: Jin Suo , Giddens Don P.
Published: January 2022

Asymmetrical stenoses are typical in atherosclerosis (1), and it is expected that 3-D flow field effects in the poststenotic region may be significant. Wall shear stress (WSS) which oscillates in direction about a low mean value has been shown to increase the expression of adhesion molecules (VCAM-1, ICAM-1) in cultured endothelial cells, with a consequent increase in monocyte adhesion (2). Thus, the flow field in the vicinity of a raised atherosclerotic lesion may be favorable to monocyte infiltration with subsequent release of matrix-degrading substances (3), leading to plaque rupture.
Validation of Complex Separation Patterns in an End-to-Side Anastomosis Model
Authors: Ethier C. R. , Steinman D. A. , Couch G. , Ojha M.
Published: January 2022

Velocity and wall shear stress patterns were studied in a model end-to-side anastomosis consisting of two equal diameter tubes joined at 45°. Photochromic dye tracer experiments and finite element-based numerical simulations were carried out under steady flow conditions at various Reynolds numbers. For ReD = 550, detailed mesh convergence studies were done. Good general agreement between computed and experimental velocity fields was seen, particularly in the presence of multiple complex separation zones. Good qualitative agreement in wall shear stresses was also seen, although quantitative agreement was less satisfactory, particularly within regions of complex separation. Computed wall shear stresses showed minor mesh dependence even when the velocity field appeared to be essentially “mesh-independent”, but were sufficiently accurate for purposes of hemodynamic studies. However, we caution that mesh-independence of velocities does not necessarily imply mesh-independence in the wall shear stress field.
Numerical Simulation of Pulsatile Flow Inside an End-to-Side Vascular Graft
Authors: Loth Francis , Kang Kai , Lei Ming
Published: January 2022

A numerical simulation of the flow field inside a three-dimensional graft geometry was performed under pulsatile flow conditions. Velocity and wall shear stress (WSS) values were calculated and compared to experimentally determined values. The movement of the floor stagnation point was estimated from both the numerical and experimental results. Overall, good agreement was found between the numerical and experimental results although some differences were found in the WSS traces.
Computational Optimization of Biomedical Devices
Authors: Siegel J. M. , Makhijani V. B.
Published: January 2022

Computational (virtual) prototyping of equipment is a widely accepted design concept in the aerospace and automotive industries, which is becoming increasingly popular in the materials processing and semiconductor industries as well. The concept of virtual prototyping involves the development of computer models for simulation of the physical phenomena that govern equipment performance. Once the computer model has been validated, it can be used for design analysis and optimization studies for that particular equipment/device. Physical prototyping is undertaken only after the virtual prototype has satisfied all the requisite design criteria.
The Influence of Wall Flexibility and Surfactant on Liquid Bolus Propagation Along a Liquid-Lined Tube
Authors: Waters Sarah L. , Howell Peter D. , Grotberg James B.
Published: January 2022

The thin liquid lining that coats the airways is susceptible to a Rayleigh instability driven by capillarity at its free surface. If a sufficiently large volume of fluid is present, the instability results in the formation of a liquid bridge or lens that blocks the flow of air along the airway. This phenomena is known as airway closure.
Advances in Computational Imaging of Blood Flow
Authors: Steinman David A.
Published: January 2022

Velocity measurements from medical imaging technologies such as magnetic resonance imaging and Doppler ultrasound are widely used in the clinic to help diagnose and treat vascular disease. At present, however, it is difficult to extract from in vivo velocity measurements the detailed hemodynamic information (e.g. wall shear stress and residence time) routinely available from computational fluid dynamic (CFD) studies. Our research efforts are therefore currently directed at extending CFD-based techniques to novel in vivo imaging applications where such detailed hemodynamic information is required. In this context we define “computational imaging” as the use of computer modeling and visualization techniques to mimic, enhance, or extend the capabilities of conventional medical imaging. In this presentation we describe areas of active research in which we are developing and applying such computational imaging techniques to further the basic understanding, diagnosis and treatment of vascular disease.
Catheter Delivered, Endoluminal Grafts for Repair of Abdominal Aortic Aneurysm
Authors: Kopchok George E. , Donayre Carlos , Haji-Aghaii Massoud , White Rodney A.
Published: January 2022

The evolution of endovascular surgery is rapidly expanding the armamentarium available for minimally invasive surgical procedures. This is especially true in the area of aortic aneurysm repair. Endoluminal graft development which began over 20 years ago, was limited by the inability to successfully secure a graft to the arterial wall without the aid of sutures. With the development of the balloon expandable stent by Palmaz, newer devices were developed and tested which led to the first clinical evaluation in 1990. Although the overall results from this series were very good, the deployment techniques, as well as the endoluminal grafts, underwent several refinements which greatly improved their later results.(Parodi et al., 1991) Newer advances, including fully supported, bifurcated endoluminal grafts, are continuing to push the envelope of minimally invasive endoluminal bypass surgery even further. Initial studies described herein suggest that a modular, self expanding device may be effective in the treatment and exclusion of aortic aneurysm.
The Use of Computational Fluid Dynamics in the Design and Optimization of Perfusion Equipment
Authors: Hamlen Cushing , Clague Cynthia , Petersen Michael
Published: January 2022

The purpose of using Computational Fluid Dynamics (CFD) in designing perfusion equipment is to maximize blood handling within the context of achieving design goals for specific devices. In the current case, the goals were: to reduce priming volume and blood damage due to fluid shear in the Medtronic Maxima Forte® oxygenator; to reduce blood damage due to shear in the new Medtronic Bio-Medicus Bio-Pump®; and to maintain low shear and promote good mixing in the Maxima Forte Hardshell Reservoir.

CFD allows prediction of, among other phenomena, regions of high shear and regions of stagnation that are detrimental within blood handling devices. These predictions allow a directed approach to design of blood handling devices that is more effective than a prototype-and-test approach in establishing efficient yet safe designs.

In the case of the Maxima Forte oxygenator, CFD indicated that a very low volume inlet manifold was not only achievable, but also necessary to eliminate large areas of recirculation.

The design of the transition manifold between the heat exchanger and the gas exchange bundle resulted from a sequence of CFD models: the final design, which is incorporated in the Maxima Forte oxygenator, being arrived at by balancing priming volume and fluid shear.

In the design of the Maxima Forte Hardshell Reservoir, CFD was used to verify effective mixing between the cardiotomy and venous blood, and to choose between design alternatives while maintaining low fluid shear.

In optimizing the new Medtronic Bio-Medicus Bio-Pump, CFD was used to identify the pump’s cutwater as a location of high fluid shear, and to decide between five design alternatives to minimize shear on the cutwater. In-vitro feasibility testing indicates that the cumulative effect of design changes identified by using CFD results in reduction of hemolysis of 22% (p = 0.000014) over the BP-80 Bio-Pump.

CFD is a powerful predictive design tools that, when used suitably with experiment, can be used to improve the design of all perfusion equipment directly involving flowing blood.
Continuous Static and Dynamic Moment-Rotation Curves of the Human Cervical Intervertebral Joint
Authors: Voo Liming M. , Pintar Frank A. , Yoganandan Narayan , Liu Y. King
Published: January 2022

The quasistatic and dynamic bending responses of the human mid-lower cervical spine were determined using cadaver intervertebral joints fixed at the base to a six-axis load cell. Flexion bending was induced to the superior end of the specimen using an electrohydraulic piston. Each specimen was tested under three cycles of quasistatic load-unload and one high-speed dynamic load. A total of five specimens were included in this study. The maximum intervertebral rotation ranged from 11.0 to 15.4 degrees for quasistatic tests and from 22.9 to 34.4 degrees for dynamic tests. Exponential functions described the quasistatic and dynamic bending moment-rotation responses. The dynamic responses were stiffer than the corresponding quasistatic responses by a factor of 1.5 to 2.6. These results provide input data for lumped-parameter models and validation data for finite element models to better investigate the biomechanics of the human cervical spine.
Pelvic Injury in Simulated Automotive Side Impact: Effects of Loading Rate on Fracture Etiology
Authors: Arbelaez Raul A. , Dakin Greg J. , Molz Fred J. , Alonso Jorge , Eberhardt Alan W. , Mann Kenneth A.
Published: January 2022

Side impact collisions in the automobile environment often result in fractures of the acetabulum and pelvis. The objective of this study was to determine if the fracture type in the pelvis is a function of impact loading rate. It was hypothesized that higher loading rates would cause acetabular fractures, and lower loading rates would result in pubic rami fractures. Simulated side-impact experiments using 15 whole fresh pelves were conducted. The pelves were laterally impacted with a drop tower and the loading rate was controlled by changing the constraints placed on the contralateral side of the pelvis. In the impacts where loading rate was high (8.16 kN/msec), either no fracture (n = 5) or acetabular wall fractures (n = 4) resulted. In the cases where loading rate was slower (1.59 kN/ms), almost all impacts (5 of 6) resulted in pubic rami fractures.
Stability of the Lumbar Spine Subjected to a Follower Load: Part I — Experimental Results
Authors: Patwardhan Avinash , Havey Robert , Meade Kevin , Lee Brian , Dunlap Brian , Gavin Thomas
Published: January 2022

Compression on the lumbar spine is estimated to reach 1000 N during standing and walking activities and is higher during lifting (McGill, 1990). Ex vivo experiments show it buckles at approximately 80–100 N (Crisco and Panjabi, 1992). Differences between maximum ex vivo and in vivo loads have not been satisfactorily explained. Many studies agree that muscles stabilize the spine. However, there is no agreement on the mechanism of stabilization.
Parametric Finite Element Study of a Vertebra: Effect of Cortical Shell Geometry
Authors: Kasra Mehran , Timmer Mark , Grynpas Marc D.
Published: January 2022

Vertebral fractures due to osteoporosis are generally considered to be caused by excessive loss of cancellous bone. With the loss of cancellous bone, the contribution of the cortical shell to the overall strength of the vertebral body becomes important [1]. The effect of different parameters, such as cortical shell thickness and material properties, on the cortical shell contribution to the strength of vertebral body have been studied using finite element modelling [2]. Another major parameter which could affect the strength of cortical shell is its geometry represented by the concavity of the vertebral body [1]. Measurements of vertebral geometry are mainly used to quantify the extent of vertebral fractures in osteoporotic patients [3,4]. However, to what extent the changes in geometry increases the chance of vertebral fractures still needs to be clarified. Kasra and Grynpas [1] introduced a new geometrical parameter, namely “curvature”, representing cortical shell concavity. By testing sheep vertebral bodies in compression, they found significant negative correlation between the vertebral failure load and the cortical shell curvature. They showed that this correlation became more significant in vertebrae with a low trabecular bone density (osteoporotic vertebrae). In continuation of previous experimental investigation [1], the objective of this study was to develop a parametric finite element model of a human vertebra In order to investigate the effect of cortical shell curvature in changing the stress patterns within the cortical shell structure and also to find the stress concentration regions. This investigation was conducted to shed new light on the vertebral failure characteristics related to geometry.
Bending Mechanical Performance of the Intervertebral Disc Is Affected by In Vivo Compressive Loading
Authors: Colliou Olivier K. , Lotz Jeffrey C.
Published: January 2022

Excessive spinal loading is thought to play a central role in intervertebral disc degeneration, however, the mechanisms are unclear. We have developed an in vivo mouse model for disc degeneration induced solely by the application of a precisely controlled static compressive load. The primary goal of our research is to investigate how in vivo compressive loadings can cause deleterious effects in both the biology and mechanical performance of the disc. The study, herein described, focuses on the latter issue of mechanical performance. Specifically, we studied the effect of in vivo compressive loading on the following bending mechanical properties of the disc: 1) neutral zone; 2) bending stiffness; and 3) bending strength.
Anterior Cervical Plating Reverses the Loading Mechanics of Multi-Level Strut-Grafts
Authors: DiAngelo Denis J. , Vossel Keith A. , Jansen Thomas H. , Foley Kevin T. , Rampersaud Y. Raja
Published: January 2022

Cervical spondylosis is the most prevalent degenerative disease of the cervical spine and is often treated surgically to prevent progressive neurological deterioration. A key goal of the surgical treatment is fusion of multiple adjacent vertebrae. Strut-graft fusion with anterior instrumentation is an accepted surgical treatment for multi-level cervical disease. Although the surgery should restore the mechanical integrity of the operated spine, little is known of the load-sharing mechanics between the SG and anterior plate. Clinically, strut-grafts fail by fracturing, pistoning into the adjacent vertebrae, or dislodging at the vertebral interfaces. The objective of the study was to determine the influence of anterior cervical plates on multi-level strut-graft loading mechanics in vitro.
Development and Calibration of a Nanometer Manipulation and Measurement System for Molecular Biomechanical Testing
Authors: Luo Zong-Ping , An Kai-Nan
Published: January 2022

An optical tweezers system has been adopted for molecular biomechanical testing. To achieve nanometer manipulation and measurement, the system was modified with a piezo-stage and an interferometer. A systematic calibration was then performed on the displacement resolution. The results revealed that the system has a nanometer resolution which is sufficient for the measurement of deformation and stiffness of single macro-molecules.
Quantification of Femoral Surface Strain by Computer Analysis of the Photoelastic Method
Authors: Morris Randal P. , Grecula Michael J. , Buford William L. , Patterson Rita M.
Published: January 2022

An important consideration in total hip arthroplasty is a prosthetic design that allows the femur to retain its normal loading characteristics following implantation. Despite the success of cementless femoral stems, bone remodeling phenomenon such as stress shielding and resorption have been observed to occur to a greater degree and over a shorter time than after implantation of a cemented prosthesis (Sumner and Galante, 1992). Surface strain measurement is an effective method for evaluating the stress distributions in femoral bone, and has widespread use in the form of strain gauge measurements, finite element analysis, and photoelastics.
Computational Analysis of the Dislocation Resistance of a New Total Hip Component Design
Authors: Scifert Christopher F. , Brown Thomas D. , Lipman Joseph D.
Published: January 2022

Dislocation is a devastating complication, and is the second leading cause of total hip failure, with rates ranging from 2–11% in primary surgeries and from 5% to 25% in revisions (Grigoris 1994, Woo 1982).
Stress Analysis of Soft Tissues as Nonhomogeneous Composites: Application to Disc Anulus, Knee Meniscus, and Articular Cartilage
Authors: Shirazi-Adl A. , Buschmann M. D.
Published: January 2022

Connective soft tissues such as intervertebral disc, knee meniscus and articular cartilage are primarily made of water, proteoglycans, and collagen fibrils. The structural organization and relative content of these components as well as the type of collagen and proteoglycan, however, vary from tissue to tissue resulting in substantial differences in mechanical response under applied loads/deformations in different tissues and in different directions. The collagen fibres primarily influence the behavior of the tissue in tension relegating the compression carrying task to remaining components, the solid portion of which is referred to as the tissue matrix. In doing so, each component plays a mechanical role for which it is best suited. A homogeneous anisotopic simulation can adequately account for the observed direction dependent material properties of soft tissues. It cannot, however, represent the distinction between the matrix and collagen fibres in that while they may be both undergoing the same strain in the same direction, the stresses could be quite different and even in opposite directions. Such a response becomes evident when considering, for example, the lateral expansion of a tissue specimen in response to an axial compression load generating tension in fibres and compression in matrix so that these two internal forces cancel each other out resulting in no net lateral force. Proper consideration of this phenomenon requires the simulation of the tissue as a nonhomogeneous composite of a fibre reinforced medium. In this work, we will present the finite element studies of such arrangements and compare the predictions with those based on equivalent homogeneous direction-dependent material properties. The emphasis in the presented results will be placed on our studies on the disc anulus fibrosus.
Strip Biaxial Experiments of Human Lung Parenchyma
Authors: Gao Jian , Huang Wei , Yen Michael R. T.
Published: January 2022

For the stress-strain relationships of human lung parenchyma, the present state of the art is that the form of the constitutive equations is known, but the material constants are unknown, and must be determined by new measurements. The objective of this study is to determine these constants by means of biaxial experiments on excised human lung parenchyma. Dynamic biaxial tests were done, and strain vs. Lagrangian stress curves were recorded. The experimental data were fitted with a pseudo-elastic constitutive equation and the physical constants could be identified.
Effects of Increasing Repetitive Strains on Tensile Failure Properties of the IGHL
Authors: Wang Vincent M. , Cohen Nathaniel P. , Bucchieri John S. , Huang Chun-Yuh , Flatow Evan L. , Bigliani Louis U. , Pollock Roger G. , Pawluk Robert J. , Mow Van C.
Published: January 2022

Considerable attention has been directed towards elucidating factors responsible for mechanical failure of ligaments and tendons [2,10,11]. Still, very few studies to date have examined the effects of repetitive loads on either the transient response or failure properties of ligaments. Panjabi et al. [3] simulated a subfailure injury during cyclic testing using a single cycle of high subfailure strain and found no statistical difference between the deformation to failure in these ligaments as compared to the controls. However, this study incorporated a relatively small number of preconditioning cycles as opposed to a prolonged duration of repetitive strains.
Effects of Fixed Charge Density on Stress-Relaxation Behavior of Hydrated Soft Tissues in Confined Compression
Authors: Mow V. C. , Ateshian G. A. , Lai W. M. , Sun D. N. , Wang C. B. , Gu W. Y.
Published: January 2022

Confined compression stress relaxation tests with porous platens (Fig 1) have been frequently used for investigating the flow-dependent viscoelastic behavior of biological hydrated soft tissues [Lai et al., 1981; Mow et al., 1980]. From experimental data, the one-dimensional (1D) compression modulus (i.e., the aggregate modulus) at equilibrium and the hydraulic permeability of the tissue can be calculated using the biphasic theory for cartilage developed by Mow et al. (1980). However, the swelling pressure effects associated with fixed charge density (FCD) can not be accounted for directly by the biphasic theory. Thus, in this abstract, we determine the effects of FCD, hence the osmotic pressure, on the confined compression stress-relaxation behavior of cartilage using our mechano-electrochemical theory [Lai et al., 1991]. The objectives of this study are to determine the confined compression stress-relaxation behavior of a charged, hydrated-soft tissue by: 1) delineating the contribution of the swelling pressure to the total stress when the tissue is compressed; 2) determining the deformation, flow, pressure and electric fields in the tissue for the understanding of mechano-electrochemical signal transduction within the tissue.
Fracture Toughness of Cortical Bone From the Femur Correlates With Radiogrammetrical Parameters in the Elderly
Authors: Yeni Yener N. , Brown Christopher U. , Norman Timothy L.
Published: January 2022

This investigation examined the relationship between fracture toughness, the ability of bone to prevent crack initiation, and the Cortical index and Singh index, clinical measures used to assess bone quality. Fracture toughness had significant relationships with both Cortical index and Singh index measurements supporting the use of fracture toughness as a clinically relevant research tool for studying bone fragility.
Convergence Characteristics of Voxel Based Finite Element Models of Trabecular Bone
Authors: Niebur Glen L. , Yuen Jonathan C. , Hsia Andy C. , Keaveny Tony M.
Published: January 2022

High resolution voxel based finite element models of trabecular bone have recently become popular as a method to investigate the properties of trabecular tissue (van Rietbergen et. al., 1995; Ladd et al., 1997; Huo and Fhyrie 1995) and the effects of microstructure on apparent properties (Hollister et al., 1994). In these models, high resolution (20–80 micron) images of the trabecular bone are converted to finite element models by assigning an 8-noded brick element to each image voxel (Fhyrie et al., 1992). As these models come into more widespread use, it is important to quantify their numerical convergence characteristics.
Does Lift-Off Occur in Unconstrained Non-Conforming Total Knee Arthroplasty?
Authors: Ed C. , Natarajan R. N. , Berzins A. , Harman M. K. , Banks S. A. , Andriacchi T. P.
Published: January 2022

Despite its widespread use in the orthopedic community, ultra-high molecular weight polyethylene (UHMWPE) remains the weak link in the prosthesis material chain. The vast majority of wear debris generated in total joint replacements originates from the UHMWPE component. These wear products lead to osteolysis, implant loosening and the eventual need for revision surgery. Therefore, the wear of UHMWPE is currently a significant concern in the orthopedic and material science communities. The current study focuses on the dimensional change wear in two types of unconstrained and non-conforming Miller-Galante retrieved tibial components. The hypothesis tested was: lift-off of the lateral side of the femoral component, which would produce large dimensional change near the outer medial compartment edges of the tibial components, does not occur in non-conforming tibial inserts.
Finite Element Analysis of Fiber Reinforced Composite Dental Bridges
Authors: Nowak Michael D. , Goldberg Jon
Published: January 2022

Recent advances in dental bridge construction have included the use of composite fiber resins. These composites are less expensive and easier to utilize in bridge fabrication than the common system of metal with porcelain cladding. The effects of varying the percentage of fiber-reinforced material and geometry of the internal bridge design are of great interest. Finite Element Analysis (FEA) methods show promise in the evaluation of fiber behavior within these bridges, along with bridge design.
State Estimation Theory in Human Movement Analysis
Authors: Alexander Eugene J. , Andriacchi Thomas P.
Published: January 2022

This work describes the application of state estimation theory to the analysis of skeletal movement based on markers placed on the skin. Skin-based retro-reflective markers contain error introduced by the non-rigidity of the limb segment. A technique for obtaining an optimal estimate of skeletal motion from skin-based marker data is presented.
The Development of a Force Platform: Numerical and Experimental Analysis
Authors: Bagesteiro Léia B. , Laranja Rafael A. C. , Tamagna Alberto
Published: January 2022

A design of a force platform for biomechanical use is presented here. The platform was built with four octagonal load cells, each one measuring two uncoupled forces, horizontal and vertical. The complete system can measure three orthogonal forces and moments. A comparison with numerical and experimental analysis of the force plate is discussed and the main advantages of particular constructional details singled out. The platform described here proves to be relatively simple, economical to build and with low crosstalk between channels.
An Evaluation of Muscle Force Predictions at the Hip Joint
Authors: Foucher Kharma C. , Hurwitz Debra E. , Andriacchi Thomas P. , Rosenberg Aaron G. , Sumner Dale R.
Published: January 2022

Understanding the loading of the hip joint and femur is a critical factor in understanding the progression of osteoarthritis (OA) and the mechanical factors influencing the outcome of total hip replacement surgery (THR). While in vivo transducers provide unique and valuable information about hip joint loading, they are limited to evaluating small numbers of postoperative THR patients. Musculoskeletal models, however, easily provide estimates of the hipjoint loads in larger patient populations with a variety of orthopedic conditions. Comparing the predicted forces with in vivo data is one approach to evaluating the results of such a model. The physiological phenomenon that bone changes in response to its loading environment presents an alternate method for evaluating modeled muscle forces. Validation of musculoskeletal models can be obtained by comparing femoral bone mineral density (BMD) patterns to the predicted forces. To evaluate muscle force predictions of a parametric three dimensional musculoskeletal model of the hip joint and femur, this study tested the hypothesis that the predicted abductor muscle force and greater trochanter BMD were significantly correlated and that the predicted contact force and proximal femur BMD were significantly correlated.
Effect of Precracking Method on the Static (J-Integral) Fracture Resistance of Ultrahigh Molecular Weight Polyethylene
Authors: Dapp Elizabeth K. , Rimnac Clare M.
Published: January 2022

The purpose of this study was to examine the effect of precracking preparation techniques on the J-integral static fracture resistance of ultrahigh molecular weight polyethylene (UHMWPE). One set of specimens was razor sharpened while the other set was cyclically precracked prior to testing. The results showed that the energy required for stable crack extension through UHMWPE was dependent on the precrack preparation method.
Comparison of the Fatigue Lifetimes of Simplex P and Osteobond Bone Cement
Authors: Jacobs Christopher R. , Davis Barclay R. , Naidu Sanjiv H. , Pellegrini Vincent D. , Case Kirt L.
Published: January 2022

Aseptic loosening is a primary mode of failure in cemented total joint surgery. Fatigue and eventual fracture of the cement mantle may be an important mechanism by which aseptic loosening occurs. Microcracking due to repetitive loading of the cement mantle has been implicated as a primary mechanism of failure in cemented femoral hip arthroplasties (1). This was the motivation behind the development of a new commercial bone cement formulation, known as Osteobond, designed to have an extended fatigue lifetime. Although the ultimate pre-clinical demonstration of enhanced in vivo performance remains the animal model, these studies are expensive and often inconclusive (2). Therefore, standard laboratory fatigue testing was employed (3). The fatigue performance of Osteobond was compared with that of Howmedica’s Simplex P using both open bowl mixing and vacuum mixing to prepare the samples.
Effect of Biochemical Composition on Cerebrospinal Fluid Viscosity
Authors: Bloomfield Isabelle G. S. , Johnston Ian H. , Bilston Lynne E.
Published: January 2022

The viscosity of the cerebrospinal fluid has long been assumed to be similar to water but only a handful of studies have measured the rheological properties of this fluid. In the present study the viscosity of cerebrospinal fluid was measured on a rotational rheometer at shear rates from 25 to 1460 sec−1, at 37°C. Each cerebrospinal fluid sample was biochemically analysed and comparisons of viscosity with protein, glucose and blood cell content in the sample were made. Despite the amount of proteins, glucose and blood cells, the viscosity of cerebrospinal fluid remained at a relatively constant level of 0.8mPa.s for the range of shear rate used, at 37°C. These findings were significant using linear regression analysis. It is concluded that cerebrospinal fluid is a newtonian fluid and that its viscosity does not significantly change with its composition.
Design and Evaluation of Microfabricated Acoustical Lenses for High Frequency Ultrasound Applications
Authors: Li Jinghong , Keynton Robert S. , Friedrich Craig R.
Published: January 2022

The purpose of this study was to employ new state-of-the-art micromachining techniques to fabricate acoustical lenses of identical geometric configuration for high frequency ultrasound applications. High frequency (20 MHz) piezoelectric crystals were placed in a holding jig and covered with one of two lens materials, PMMA or Epoxy. After curing, the holding jig was placed in a custom-made ultra-high precision micromilling machine. Each material was machined to yield lenses with focal lengths of 3 mm, 4 mm or 5 mm. A total of 18 lenses were machined and evaluated for compliance with the design specifications using a Roughness/Step Tester. In addition, performance characteristics of each lens were evaluated using a Schlieren Acoustic Visualization System. Overall, the radii of curvatures were within ± 14% and ± 8% of the design for PMMA and Epoxy, respectively. The focal lengths were found to be within ± 25% and ± 19% of the design, respectively. Finally, the lenses caused the acoustic beam to converge, which resulted in a reduction in the lateral dimension of the beam and an increase in the signal intensity within the near field.