bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thermomechanical Characterization of Collagen Crosslinking in Developing Cardiovascular Tissues
Authors: Wells Sarah M. , Naimark Wendy A. , Lee J. Michael 
Published: December 2021

Abstract
We have used hydrothermal isometric tension (HIT) tests to assess developmental changes in collagen crosslinking in the ovine thoracic aorta and pericardium. Tissue strips were loaded under isometric tension and heated to 90°C for 3 hrs. Load relaxation at this temperature is associated with collagen hydrolysis and chain slip-page, the half-time of load decay (t1/2) being an indicator of collagen crosslinking. t1/2 was computed before and after tissues were treated with NaBH4 which stabilizes immature crosslinks. The t1/2 of untreated tissue increased from the lamb to the adult, indicating that collagen crosslinking increased postnatally. Furthermore, the t1/2 of NaBH4-treated lamb tissue (3d pericardium and 21d aorta) was similar to that of untreated adult tissue, suggesting that much immature crosslinking in the lamb is stabilized postnatally. These observations suggest (i) increased crosslinking occurs postnatally, (ii) this increase is largely due to the conversion of immature crosslinks into their mature, heat stable form (Naimark et al., 1998, Wells et al., 1999).
Mechanical Strength of PhotoFix® and Glutaraldehyde Treated Porcine Aortic Valve Wall Tissue
Authors: Talman Eric , Poehlmann Jeffery 
Published: December 2021

Abstract
The use of prosthetic heart valves manufactured from porcine aortic valves is commonplace. The standard design incorporates a valve mounted on a plastic or metal stent to facilitate implantation. More recently stentless valves have gained favor. These valves include the intact aortic root or a composite design. Composite valves are assembled using tissue from different valves cut axially along the aorta between valve leaflets. Composite designs are used to eliminate the right coronary leaflet substantially reducing the associated muscle shelf which has been the cause of high re-operation rates in the past (1). We are developing a tri-composite, PhotoFix® stentless valve, combining three non-coronary leaflets and it is the goal of this study to examine the mechanical strength of the associated aortic tissue. This is being done to ensure adequate strength of the material to withstand physiological loading. The strength will be compared to estimated in vivo loading conditions as well as to the strength of tissue from a commercially available glutaraldehyde fixed product.
3-D Stress Analysis in Cultured Endothelial Cells Exposed to Fluid Shear Stress
Authors: Ohashi T. , Sugawara H. , Ishii Y. , Sato M. 
Published: December 2021

Abstract
Under fluid shear stress, applied both in vivo and in vitro, vascular endothelial cells show morphological changes. After applying shear stress, cultured endothelial cells showed elongation and orientation to the flow direction (Kataoka et al., 1998). Moreover, statistical image analysis showed that intercellular F-actin distributions were confirmed to change depending on the shear stress and the flow direction. Thus, the endothelial cell morphology relates closely with the cytoskeletal structures. Intercellular stress distributions in the cells may be also accompanied by the reorganization of cytoskeletal structures. The use of both atomic force microscopy measurements (AFM) of endothelial cell surface topography and computational fluid dynamics of shear stress distributions acting on the cell surface, it has revealed that the surface geometry defined the detailed distribution of shear stress (Davies et al., 1995).
Shape Memory Alloy Actuated Robot Protheses: Initial Prototypes
Authors: Pfeiffer Charles , Mavroidis Constantinos , DeLaurentis Kathryn , Mosley Mike 
Published: December 2021

Abstract
This paper describes the goals and current accomplishments of this research. The main thrust of this effort is to design artificial limbs that are lightweight, compact and dexterous, that mimic human anatomy and maintain a high lifting capability. The key to satisfying these objectives is the use of Shape Memory Alloy (SMA) artificial muscles as actuators. A general methodology to find the placement of SMA wires to achieve desired ranges of motion is presented. Three experimental prototypes, emulating human skeletal structures that are actuated by SMA artificial muscles are described in detail.
It is expected that upper extremity amputees will greatly benefit from the commercialization of the novel robot prosthetic devices that will be developed in this research. These lightweight prostheses with high lifting capabilities, force-reflective characteristics and multi-degree of freedom dexterity will tremendously improve the capabilities of amputees and therefore will attract their interest. In addition, our SMA actuated robotic devices can find other commercial applications. Of special interest to our team are two other commercial applications: space robotic systems and robot toys.
QCT Cortical Shell Thickness as a Predictor of Vertebral Body Strength for Cynomolgus Monkeys
Authors: Dickerson Clark R. , Saha Subrata , Hotchkiss Charlotte 
Published: December 2021

Abstract
Many studies have investigated the ability of vertebral trabecular BMC measurements to predict overall vertebral strength. Far fewer investigations, however, have examined the use of cortical shell data to predict maximum strength. In this study, we are investigating the load-carrying characteristics of the cortical region of vertebral bodies Lumbar vertebrae from macaca fascicularis were examined by QCT and mechanically tested in compression. Our results show that cortical thickness, as determined by QCT, is a significant predictor of vertebral maximum stress (R = 0.62, p &lt; 1 E−5). This relationship is improved when the cortical thickness is compared to load (R = 0.77, p &lt; 5 E−10). This information reveals that the cortical shell plays a major role in determining the load carrying capacity of lumbar vertebrae, and that examination of cortical thickness will give an approximation of maximum vertebral stress and load.
Evaluation of the Revised NIOSH Lifting Equation (1991): On the Asymmetric Multiplier
Authors: Li Yi-Chun , Lavender Steven A. , Natarajan Raghu N. , Andersson Gunnar B. J. , Amirouche Faird M. L. 
Published: December 2021

Abstract
The NIOSH 1981 lifting equation (NIOSH, 1981) [1] is based on biomechanical, physiological, psychophysical, and epidemiological criteria in order to identify the risk of low back injuries in bi-manual lifting. The 1991 revised lifting equation [2] expands the application scope of the 1981 equation for evaluating asymmetrical lifting tasks, lifts of objects with less than optimal hand-container couplings, and a larger range of work duration and lifting frequencies; also, the load constant is reduced from 40 kg to 23 kg; the Lifting Index (LI) and the Recommended Weight Limit (RWL) replace the Maximal Permissible Limit (MPL) and Action Limit to indicate the potential risk. LI is an actual lifted weight and uses RWL as its unit. If LI &lt; 1, it assumes that more than 99% of males and 75% of females are capable of performing the lifting task and the risk of causing low back injury is nominal. If LI &lt; 3, it assumes that less than 25% of males and 1% of females are capable of performing the lifting task, and a greater percentage of manual materials handling workers is likely to be at risk of developing low back pain.
Waters et al. (1993) [3] noted that although the 1991 equation has not been fully validated, the recommended weight limits derived from the revised equation are consistent with or lower than those generally reported in the literature. Hidalgo et al. (1995) [4] showed that the results of cross-validation of the NIOSH limits for psychophysical criterion confirmed the validity of assumptions made in the 1991 NIOSH revised lifting equation and for the biomechanical and physiological criteria which were not in total agreement. This validation was based on the psychophysical, biomechanical and physiological data recently published in the subject literature (Genaidy et al. 1990, Snook and Ciriello 1991, Genaidy et al. 1993, Asfour et al. 1991) [2]. Most of the validation limit in the sagittal plane lifting and 3.4 KN compressive force on the spine is the standard line in biomechanical criteria.
The 1991 revised NIOSH lifting equation recommended that the allowable weight of lift be reduced by about 30% for lifts involving asymmetric twists of 90 degrees (Water et al., 1993), which considers asymmetric multiplier in the sagittal lifts as 1 and 90 degrees lifts as 0.7, and linearly reduced between the sagittal lifts and 90 degrees lifts. This maximum acceptable lifting capacity is applied not only in the heavier loads but also in the lighter loads. The hypothesis in evaluating NIOSH lifting equation on the asymmetric multiplier is that asymmetric multiplier may be appropriate adopted in the heavier loads (LI = 3) but will be improper applied in the lighter loads (LI = 1). Several types of data, static and dynamic data of the L5/S1 forces, moments, and compressive forces, are observed.
Direct Hydraulic Permeability Measurements of Agarose Hydrogels Used as Cell Scaffolds
Authors: Soltz Michael A. , Stankiewicz Anna , Ateshian Gerard , Mauck Robert L. , Hung Clark T. 
Published: December 2021

Abstract
The objective of this study was to determine the intrinsic hydraulic permeability of 2% agarose hydrogels. Two-percent agarose was chosen because it is a concentration typically used for encapsulation of chondrocytes in suspension cultures [3–5], Hydraulic permeability is a measure of the relative ease by which fluid can pass through a material. Importantly, it governs the level of interstitial fluid flow as well as the interstitial fluid pressurization that is generated in a material during loading. Fluid pressurization is the source of the unique load-bearing and lubrication properties of articular cartilage [1,17] and represents a major component of the in vivo chondrocyte environment. We have previously reported that 2% agarose hydrogels can support fluid pressurization, albeit to a significantly lesser degree than articular cartilage [18]. Interstitial fluid flow gives rise to convective transport of nutrients and ions [6,7] and matrix compaction [9] which may serve as important stimuli to chondrocytes. We report for the first time the strain-dependent hydraulic permeability of 2% agarose hydrogels.
Biomechanics of Cervical Spine Ligaments
Authors: Yoganandan Narayan , Kumaresan Srirangam , Pintar Frank A. 
Published: December 2021

Abstract
The purpose of the present study was to determine the geometrical and biomechanical properties of human cervical spine ligaments from the axis to the first thoracic level. A total of 33 human cadavers were used. Geometrical data included the length and cross-sectional area measurements. Biomechanical properties included force, deflection, stiffness, energy, stress, strain, and Young’s modulus of elasticity. These data were obtained for the anterior longitudinal ligament, posterior longitudinal ligament, joint capsules, ligamentum flavum, and interspinous ligament. Geometrical characteristics were determined using cryomicrotomy techniques and biomechanical properties were obtained using in situ failure tensile testing. Force-deformation responses of each ligament type and at each spinal level were normalized. The joint capsules and ligamentum flavum exhibited the highest area of cross-section (p &lt; 0.005). The longitudinal ligaments responded with the highest length measurements. The strain parameters were higher for the ligaments of the posterior complex, i.e., interspinous ligament, joint capsules, and ligamentum flavum, than for the ligaments of the anterior complex, i.e., the anterior and posterior longitudinal ligaments. In contrast, the failure stress and Young’s modulus of elasticity were higher for the anterior and posterior longitudinal ligaments compared to the ligaments of the posterior complex. These findings delineate the relative contribution of the anterior and posterior ligaments in the human cervical spine.
Electromyographic Activity of Trunk Muscles During Flexion-Distraction Treatment of Low Back Patients
Authors: Gudavalli Maruti R. , Backman Jerrilyn A. , Kirstukas Steven J. , Kadiyala Anant V. , Patwardhan Avinash G. , Ghanayem Alexander J. 
Published: December 2021

Abstract
The objective of this study was to determine the electromyographic (EMG) activity of the superficial muscles during the treatment of low back patients during a conservative procedure known as the Cox flexion-distraction procedure. A total of 33 low back pain patients were recruited for this study from chiropractic and allopathic orthopedic clinics. EMG signals were collected while the patient was in a prone relaxed position, during the treatment using the flexion-distraction procedure, and during maximum voluntary exertions in the three planes (flexion, extension, left and right lateral bending, and left and right twisting). The mean values of the Root Mean Square (RMS) values of EMG ratios during treatment versus resting indicate that the muscles are active during the treatment. This activity is more than the activity at rest. However the mean values of the RMS EMG ratios (during treatment versus maximum voluntary contraction) are small indicating that the muscle activity during treatment may not influence the treatment loads. The left and right muscles in all muscle groups were similarly active. During the treatment, erector spinae muscles were the most active, followed by the external oblique, and the rectus abdominus muscles. The results from this study provide quantitative data for the muscle activity during the flexion-distraction treatment. This information can be incorporated into computer models to estimate the loads generated during the flexion-distraction treatment due to the muscle activity compared to the loads generated by the chiropractic physician.
Effect of Pelvic Tilt and Lordosis on Passive-Active Synergy in Lumbar Spine Under Axial Compression
Authors: Shirazi-Adl A. , Sadouk S. , Parnianpour M. 
Published: December 2021

Abstract
The coupled load sharing-posture response of the human lumbar spine under relatively large compression loads with and without sagittal rotations remains yet to be adequately understood. Such investigations should account for the observed changes in the pelvic tilt and lumbar lordosis and influences thereof on the passive-active equilibrium and stability of the human spine. In pursuit of these goals, the objectives of the current work, using a nonlinear finite element model of the lumbosacral spine, are set as follows: - Study of the synergy of the active-passive lumbar spine under an axial compression load of 2800 N in quasi-neutral position; - Development of an optimal posture accounting for the postural adaptation of the spine in order to withstand the applied 2800 N load in quasi-neutral posture; and - Evaluation of local lumbar muscle forces in order to maintain the equilibrium of the system in such optimal posture.
Temperature Effect on Damage in S2 Glass/Toughened Epoxy Composites
Authors: Cheung C. K. , Long X. , Liaw B. M. , Delale F. , Walser A. D. , Raju B. B. 
Published: December 2021

Abstract
Composites made of S2 glass fibers and toughened epoxy with various lay-up configurations ([0°]24, [0°2/90°2]3S, [45°2/−45°2]35, and [0°3/45°3/90°3/−45°3]S) were tested under uniaxial tension at various temperatures from −60 to 125°C. The stress-strain curves are distinctly nonlinear, which can be attributed to various types of damage progression. Fiber breaks, fiber-matrix debonding, and fiber pull-out characterized damage in the [0°] and [0°/90°] specimens, which have stress-strain relations resembling those for quasi-brittle materials. Shear failure and delamination were dominant in the [±45°] specimens and resulted in stress-strain curves similar to those of quasi-ductile materials. The tensile behavior of the [0°/45°/90°/−45°] specimens, as expected, laid in between the two extremes. In addition to stacking sequence, temperature also exerted great influence on the stress-strain behaviors of these composites. In general, specimens tested at lower temperatures behaved more stiff and brittle than those tested at higher temperatures. Finally, micromechanics-based finite element analyses were conducted to verify the afore-mentioned various failure modes.
Mechanical Properties and Damage Growth of Notched Polymeric Composites Subjected to Adverse Environmental Conditions Under Sustained Loads
Authors: Buck Stephanie E. , Lischer David W. , Nemat-Nasser Sia 
Published: December 2021

Abstract
Structural composite materials are being investigated for use in applications which will require long-term durability in various environments under external loads. Flaws may be created in these composite materials during manufacturing, machining, or use. Adverse use conditions in the presence of seemingly minor flaws may result in significantly reduced mechanical properties and changes in the microstructure and damage mechanisms of composites. E-glass/vinyl ester composite coupons with a single edge notch have been conditioned in water for periods of up to 7,800 hours at room temperature and at an elevated temperature, mostly under a sustained tensile load, to determine the changes in the mechanical properties and damage mechanisms which occur due to the presence of the flaw. The tensile strength has been found to decrease by at least fifteen percent for notched samples when compared with unnotched samples subjected to the same environmental and load conditions. During conditioning, the dominant damage mechanisms have been found to change from transverse matrix microcracking, fiber cracking, and occasional edge delaminations for unnotched specimens to the growth of a significant matrix crack from the notch tip and local tow debonding for notched specimens. Nondestructive techniques have been used to observe the damage in the vicinity of the notch tip.
Fatigue Modulus Concept and Life Prediction of Thick-Section S2-Glass/Vinylester Composites Under Flexural Loading
Authors: Mahfuz Hassan , Zaman Kamruz , Haque Anwarul , Vaidya Uday , Mohamed Hisham , Jeelani Shaik 
Published: December 2021

Abstract
Fatigue life prediction of thick-section S2-Glass fiber reinforced Vinylester composites has been studied analytically using fatigue modulus concept. Flexural fatigue tests were conducted under three point bend configuration. A stress ratio of R = 0.1 and a frequency of 3 Hz has been used for the fatigue tests. Fatigue data have been generated at five load levels; 85%, 80%, 70%, 60% and 55% of the ultimate flexural strength. Using these fatigue data, S-N diagram has been generated. Fatigue modulus has been determined by the slope of the line drawn on a plot of applied stress vs. resultant strain at specific loading cycle. Since fatigue modulus degrades with cycle number, it was assumed that the degradation rate follows a power function of fatigue cycle. Using this concept, a practical and applicable equation for predicting fatigue life is established.
The Fatigue Life Prediction method used in this investigation requires two distinct parameters, namely applied stress level and two material constants. These material constants have been determined from the fatigue test data. A comparison has been made between the analytical prediction and the experimentally obtained S-N curve. The correlation between the two has been observed to be excellent. Flexural failure modes have also been identified as extensive delamination, fiber fracture and fiber kinking. Microscopic observation shows that all failures are predominantly on the tensile side with slight fiber kinking and matrix crushing on the compression side.
A Constitutive Model for Distributed Microcracking in Titanium Matrix Composite Laminae
Authors: Ball D. L. , Chan W. S. 
Published: December 2021

Abstract
The ply constitutive relations of an energy-based model for distributed microcracking in continuous fiber reinforced metal matrix composites are presented. Simple models for damage progression are used in conjunction with these damage dependent constitutive relations to allow the prediction of fatigue life under constant amplitude, isothermal conditions. The microcracking model is discussed in the context of fatigue analysis of unnotched titanium matrix composite laminates. Analytical results generated by using this model in a unidirectional laminate analysis algorithm are presented and compared with experimental results.
Detecting Delamination Damage in Tapered Rotorcraft Flexbeams Using the Direct Field Response
Authors: Purekar Ashish S. , Pines Darryll J. 
Published: December 2021

Abstract
Flexbeams in hingeless rotors have non-uniform geometries to form virtual hinges for the lead-lag and flap motions of blades. For bearingless rotors, the flexbeams also contain a virtual hinge for the pitch of the blades. Commonly, flexbeams are damaged through high cyclic and vibratory loadings. Damage in the form of delamination for composite beams degrade performance and can potentially cause catastrophic failure. In a beam of uniform cross section, the transverse dynamics of a beam can be characterized by four wavetypes. By tracking the progression of the waves along the beam and back again, the wavetypes can be used to infer damage. While this process has worked well for uniform beams with cracks, tapered beams are difficult to model. To avoid high fidelity spectral finite element modeling of tapered flexbeams, this paper introduces a concept involving the use of the dereverberated transfer function response to infer delamination damage. A “virtual control” is introduced to obtain the dereverberated transfer function with and without damage. Analytical and experimental results suggest that this approach can be used to qualitatively infer damage in flexbeams with tapered geometries. Preliminary experimental results are displayed for flexbeams with varying thickness and width tapers.
Measured Constitutive Behavior of Several Compositions of PZT
Authors: Lynch Christopher S. , Davis Brandon 
Published: December 2021

Abstract
PZT is often used as an actuator material. The actuation properties are dependent on several factors including composition, grain size, and processing; as well as on loading and load history. The effect of grain size and composition on the hysteresis behavior of PZT was experimentally characterized. The results show the effects of preload stress and temperature on the actuation capability of this class of materials.
The Fabrication of Thin Film NiTi Shape Memory Alloy Micro Actuator for MEMS Application
Authors: Gill John J. , Ho Ken , Carman Gregory P. 
Published: December 2021

Abstract
Thin film SMA (Shape memory alloy) is a useful method for MEMS (Microelectromechanical Systems) actuator. This is because the thin film has an improved frequency response compared to bulk SMA, high work density, and produces large strain. A novel two-way thin film NiTi (Nickel Titanium) shape memory alloy actuator is presented in this paper. Thin film shape memory alloy is sputter-deposited onto a silicon wafer in an ultra high vacuum system. Transformation temperatures of the deposited NiTi film are measured by residual stress measurement at temperatures from 25 ° C to 120 ° C. Test results show that the Mf (Martensite Finish Temperature) is around 60 ° C and Af (Austenite Finish Temperature) is around 110 ° C. A free standing NiTi membrane (10 mm × 10mm and 3 μm thick) is fabricated using MEMS technology. We found that a mixture of HF (Hydro Fluidic Acid), HNO3 (Nitric Acid) and DI (Deionized) water with thick photo resist mask works best for the fabrication process. The membrane is hot-shaped in different shapes such as dome shape, pyramidal shape, and cylindrical shape. Results indicate that when the temperature of the NiTi film exceeds Af, the NiTi membrane transforms into the trained hot-shape. When the temperature cools down to room temperature, the membrane returns to the initial flat shape.