nils-herrmann/clean_scirepeval huggingface dataset:
Surface acceleration transmission during drop landings in humans.
Venue: Journal of biomechanics

The purpose of this study was to quantify the magnitude and frequency content of surface-measured accelerations at each major human body segment from foot to head during impact landings. Twelve males performed two single leg drop landings from each of 0.15 m, 0.30 m, and 0.45 m. Triaxial accelerometers (2000 Hz) were positioned over the: first metatarsophalangeal joint; distal anteromedial tibia; superior to the medial femoral condyle; L5 vertebra; and C6 vertebra. Analysis of acceleration signal power spectral densities revealed two distinct components, 2-14 Hz and 14-58 Hz, which were assumed to correspond to time domain signal joint rotations and elastic wave tissue deformation, respectively. Between each accelerometer position from the metatarsophalangeal joint to the L5 vertebra, signals exhibited decreased peak acceleration, increased time to peak acceleration, and decreased power spectral density integral of both the 2-14 Hz and 14-58 Hz components, with no further attenuation beyond the L5 vertebra. This resulted in peak accelerations close to vital organs of less than 10% of those at the foot. Following landings from greater heights, peak accelerations measured distally were greater, as was attenuation prior to the L5 position. Active and passive mechanisms within the lower limb therefore contribute to progressive attenuation of accelerations, preventing excessive accelerations from reaching the torso and head, even when distal accelerations are large.
Precise determination of elastic modulus of cell using conical AFM probe.
Venue: Journal of biomechanics

The Sneddon formula is conventionally used to calculate the elastic modulus of cell based on atomic force microscope (AFM) experiments. Owing to the disobedience of the formula assumptions, errors exist. Here, the ABAQUS for finite element modeling and analysis was used to simulate the process of compression of cell with a AFM conical probe. It was found that the relative error ranges from 0.094 to 1.455 folds, depending on half angle of the cone, curvature radius at the tip of the cone and the compression depth. By fitting the error data, we proposed a correction factor, which can be multiplied by the Sneddon formula to get a modified formula, providing the more accurate elastic modulus of cell. The experimentally measured elastic moduli of cell and hydrogel are in good agreement with the values obtained using the modified formula.
Computational and experimental analysis of a Glaucoma flat drainage device.
Venue: Journal of biomechanics

This paper presents a computational and experimental analysis of a glaucoma flat drainage device (FDD). The FDD consists of a metallic microplate placed into the eye sclerocorneal limbus, which creates a virtual path between the anterior chamber and its exterior, allowing the intraocular pressure (IOP) to be kept in a normal range. It also uses the surrounding tissue as a flow regulator in order to provide close values of IOP for a wide range of aqueous humor (AH) flow rates. The Neo Hookean hyperelastic model is used for the solid part, while the Reynolds thin film fluid model is used for the fluid part. On the other hand, a gravitational-driven flow test is implemented in order to validate the simulation process. An in vitro experiment evaluated the flow characteristics of the device implanted in fourteen extirpated pig eyes, giving as a result the best-fit for the Young modulus of the tissue surrounding the device. Finally, according to the resulting computational model, for a range of 1.4-3.1 μL/min, the device presents a pressure variation range of 6-7.5 mmHg.
Immediate and long-term effects of mechanical loading on Achilles tendon volume: A systematic review and meta-analysis.
Venue: Journal of biomechanics

The Achilles tendon (AT) may experience changes in dimensions related to fluid flow under load. The extent to which fluid flow involves redistribution within or flow out of the tendon is not known and could be determined by investigating volume changes. This study aimed to synthesize data on immediate and long-term effects of loading on tendon volume among people with a healthy AT and midportion Achilles tendinopathy (MAT). A secondary aim was to synthesise data from the included studies investigating parallel change in cross-sectional area and length. Systematic electronic search was performed in MEDLINE, EMBASE, CINAHL, AMED, and Scopus from inception until May 2020. Standardized mean differences (SMDs) were calculated for intervention-induced changes from baseline for all outcomes. Methodological quality was assessed using modified version of Newcastle Ottawa Scale (NOS). Twelve studies were included in meta-analysis. For healthy AT, there were negligible to small changes in volume following cross-country running (-0.33 [95% CI = -1.11 to 0.45] (P = 0.41)) and isometric exercise (0.01 [95% CI = -0.54 to 0.55] (P = 0.98)) and a large increase at the short-term with 12-week isometric protocol (0.88 [95% CI = -0.10 to1.86] (P = 0.08)). For MAT, there was an immediate large reduction in volume with isometric exercise (-1.24 [95% CI = -1.93 to -0.55] (P = 0.0004)), small increase with eccentric exercise (0.41 [95% CI = -0.18 to 1.01](P = 0.18)) and small reduction at the short-term with long-term interventions (-0.46 [95% CI = -0.87 to -0.05] (P = 0.03)). This meta-analysis suggests that healthy AT remain isovolumetric with acute interventions while MAT exhibit immediate and short-term volume reductions in response to different interventions.
Friction RandomPOD-A new method for friction measurement in noncyclic, multidirectional, dynamic pin-on-disk tests for orthopaedic bearing materials.
Venue: Journal of biomechanics

The 16-station, computer-controlled RandomPOD wear test device was re-designed into a friction measurement device, Friction RandomPOD. The motion was implemented by a servo-electric x-y-stage and the load was proportional-pneumatic. The direction of sliding, velocity (v), acceleration, and the magnitude of the load (L) varied randomly and continuously. The nominal contact pressure p varied between 0 and 2.4 MPa and v between 0 and 40 mm/s. In the first version of the device, the frictional force components were continuously measured by two miniature load cells in two perpendicular directions. In the second version, the measurement was done with a three-axial, commercial load cell. The resultant frictional force was divided by the instantaneous load in order to obtain the coefficient of friction (μ) at a frequency of 200 Hz. Due to the light and accurate design of the device, vibrations were absent in the measured signals although the measurements were most dynamic. Hence no filtering was needed. Serum lubricated polyethylene/CoCr tests revealed non-symmetric distributions of μ, friction power Pμ, and μ vs. pv.
Mechanisms of tracer transport in cerebral perivascular spaces.
Venue: Journal of biomechanics

Tracers infused into the brain appear to be transported along channels surrounding cerebral blood vessels. Bulk fluid flow has been hypothesized in paravascular "glymphatic" channels (outer space between the pial membrane and astrocyte endfeet), as well as in the periarterial space (inner space between smooth muscle cells). The plausibility of net flow in these channels due to steady and oscillatory pressures is reviewed, as is that of transport by oscillatory shear-enhanced dispersion in the absence of net flow. Models including 1D branching networks of annular channels and an expanded compartmental model for humans both predict that flow driven by physiologic steady pressure differences is unlikely in both periarterial and paraarterial spaces, whether the spaces are open or filled with porous media. One exception is that a small additional steady pressure difference could drive paraarterial flow if the space is open. The potential that the tracer injection itself could present such a pressure difference is outlined. Oscillatory (peristaltic) wall motion alone has been found to be insufficient to drive significant forward flow. However, a number of hypothesized mechanisms that have yet to be experimentally verified in the brain may create directional flow in combination with wall motion. Shear-augmented dispersion due to oscillatory pressure in channels with a range of porosity has been modeled analytically. Enhancement of axial dispersion is small for periarterial channels. In open paraarterial channels, dispersion enhancement with optimal lateral mixing is large enough that it may explain observed tracer transport without net forward fluid flow.
Effect of inhalation on oropharynx collapse via flow visualisation.
Venue: Journal of biomechanics

Computational fluid dynamics (CFD) modelling has made significant contributions to the analysis and treatment of obstructive sleep apnoea (OSA). While several investigations have considered the flow field within the airway and its effect on airway collapse, the effect of breathing on the pharynx region is still poorly understood. We address this gap via a combined experimental and numerical study of the flow field within the pharynx and its impacts upon airway collapse. Two 3D experimental models of the upper airway were constructed based upon computerised tomography scans of a specific patient diagnosed with severe OSA; (i) a transparent, rigid model for flow visualisation, and (ii) a semi-flexible model for understanding the effect of flow on pharynx collapse. Validated simulation results for this geometry indicate that during inhalation, negative pressure (with respect to atmospheric pressure) caused by vortices drives significant narrowing of the pharynx. This narrowing is strongly dependent upon whether inhalation occurs through the nostrils. Thus, the methodology presented here can be used to improve OSA treatment by improving the design methodology for personalised, mandibular advancement splints (MAS) that minimise OSA during sleep.
Assessment of sex differences in ventricular-vascular coupling of left ventricular and aortic flow derived from 4D flow MRI in healthy, young adults.
Venue: Journal of biomechanics

To gain further insight into male-female differences in cardiovascular conditions it is important to understand sex differences in healthy populations. A previous study from our group of 39 healthy young volunteers (20-35 years) paradoxically found that men had greater left ventricular (LV) kinetic energy (KE) but women had greater LV vorticity. We reanalyzed cardiac four-dimensional flow MRI data from 20 of the original subjects (10 male and 10 female) to quantify aortic flow in addition to LV flow. The combination of LV and aortic flow parameters were then used to calculate ventricular vascular coupling of KE and vorticity. The sex difference found in LV flow were not found in aortic flow and the ventricular-vascular coupling of LV-to-aortic flow was similar between men and women. Dimensional analysis to account for differences in cardiac output and ventricular volume explained the differences found in LV flow. The analysis methods and results of this study may be of further use in understanding ventricular vascular coupling of transported flow variables in healthy sex differences, healthy aging, and various cardiovascular conditions.
Modeling muscle function using experimentally determined subject-specific muscle properties.
Venue: Journal of biomechanics

Muscle models are commonly based on intrinsic properties pooled across a number of individuals, often from a different species, and rarely validated against directly measured muscle forces. Here we use a rich data set of rat medial gastrocnemius muscle forces recorded during in-situ and in-vivo isometric, isotonic, and cyclic contractions to test the accuracy of forces predicted using Hill-type muscle models. We identified force-length and force-velocity parameters for each individual, and used either these subject-specific intrinsic properties, or population-averaged properties within the models. The modeled forces for cyclic in-vivo and in-situ contractions matched with measured muscle-tendon forces with r2 between 0.70 and 0.86, and root-mean square errors (RMSE) of 0.10 to 0.13 (values normalized to the maximum isometric force). The modeled forces were least accurate at the highest movement and cycle frequencies and did not show an improvement in r2 when subject-specific intrinsic properties were used; however, there was a reduction in the RMSE with fewer predictions having higher errors. We additionally recorded and tested muscle models specific to proximal and distal regions of the muscle and compared them to measures and models from the whole muscle belly: there was no improvement in model performance when using data from specific anatomical regions. These results show that Hill-type muscle models can yield very good performance for cyclic contractions typical of locomotion, with small reductions in errors when subject-specific intrinsic properties are used.
Player position in American football influences the magnitude of mechanical strains produced in the location of chronic traumatic encephalopathy pathology: A computational modelling study.
Venue: Journal of biomechanics

American football players are frequently exposed to head impacts, which can cause concussions and may lead to neurodegenerative diseases such as chronic traumatic encephalopathy (CTE). Player position appears to influence the risk of concussion but there is limited work on its effect on the risk of CTE. Computational modelling has shown that large brain deformations during head impacts co-localise with CTE pathology in sulci. Here we test whether player position has an effect on brain deformation within the sulci, a possible biomechanical trigger for CTE. We physically reconstructed 148 head impact events from video footage of American Football games. Players were separated into 3 different position profiles based on the magnitude and frequency of impacts. A detailed finite element model of TBI was then used to predict Green-Lagrange strain and strain rate across the brain and in sulci. Using a one-way ANOVA, we found that in positions where players were exposed to large magnitude and low frequency impacts (e.g. defensive back and wide receiver), strain and strain rate across the brain and in sulci were highest. We also found that rotational head motion is a key determinant in producing large strains and strain rates in the sulci. Our results suggest that player position has a significant effect on impact kinematics, influencing the magnitude of deformations within sulci, which spatially corresponds to where CTE pathology is observed. This work can inform future studies investigating different player-position risks for concussion and CTE and guide design of prevention systems.
Focused targeting of inhaled magnetic aerosols in reconstructed in vitro airway models.
Venue: Journal of biomechanics

The pulmonary tract is an attractive route for topical treatments of lung diseases. Yet, our ability to confine the deposition of inhalation aerosols to specific lung regions, or local airways, remains still widely beyond reach. It has been hypothesized that by coupling magnetic particles to inhaled therapeutics the ability to locally target airway sites can be substantially improved. Although the underlying principle has shown promise in seminal in vivo animal experiments as well as in vitro and in silico studies, its practical implementation has come short of delivering efficient localized airway targeting. Here, we demonstrate in an in vitro proof-of-concept an inhalation framework to leverage magnetically-loaded aerosols for airway targeting in the presence of an external magnetic field. By coupling the delivery of a short pulsed bolus of sub-micron (~500 nm diameter) droplet aerosols with a custom ventilation machine that tracks the volume of air inhaled past the bolus, focused targeting can be maximized during a breath hold maneuver. Specifically, we visualize the motion of the pulsed SPION-laden (superparamagnetic iron oxide nanoparticles) aerosol bolus and quantify under microscopy ensuing deposition patterns in reconstructed 3D airway models. Our aerosol inhalation platform allows for the first time to deposit inhaled particles to specific airway sites while minimizing undesired deposition across the remaining airspace, in an effort to significantly augment the targeting efficiency (i.e. deposition ratio between targeted and untargeted regions). Such inhalation strategy may pave the way for improved treatment outcomes, including reducing side effects in chemotherapy.
Variabilities in µQCT-based FEA of a tumoral bone mice model.
Venue: Journal of biomechanics

A finite element analysis based on Micro-Quantitative Computed Tomography (µQCT) is a method with high potential to improve fracture risk prediction. However, the segmentation process and model generation are generally not automatized in their entirety. Even with a rigorous protocol, the operator might add uncertainties during the creation of the model. The aim of this study was to evaluate a µQCT-based model of mice tumoral and sham tibias in terms of the variabilities induced by the operator and sensitivity to operator-dependent variables (such as model orientation or length). Two different operators generated finite element (FE) models from µCT images of 8 female Balb/c nude mice tibias aged 10 weeks old with bone tumors induced in the right tibia and with sham injection in the left. From these models, predicted failure load was determined for two different boundary conditions: fixed support and spherical joints. The difference between the predicted and experimental failure load of both operators was large (-122% to 93%). The difference in the predicted failure load between operators was less for the spherical joints boundary conditions (9.8%) than for the fixed support (58.3%), p < 0.001, whereas varying the orientation of bone tibia caused more variability for the fixed support boundary condition (44.7%) than for the spherical joints (9.1%), p < 0.002. Varying tibia length had no significant effect, regardless of boundary conditions (<4%). When using the same mesh and same orientation, the difference between operators is non-significant (<6%) for each model. This study showed that the operator influences the failure load assessed by a µQCT-based finite element model of the tumoral and sham mice tibias. The results suggest that automation is needed for better reproducibility.
Computational modeling of vascular growth in patient-specific pulmonary arterial patch reconstructions.
Venue: Journal of biomechanics

Recent progress in vascular growth mechanics has involved the use of computational algorithms to address clinical problems with the use of three-dimensional patient specific geometries. The objective of this study is to establish a predictive computational model for the volumetric growth of pulmonary arterial (PA) tissue following complex cardiovascular patch reconstructive surgeries for congenital heart disease patients. For the first time in the literature, the growth mechanics and performance of artificial cardiovascular patches in contact with the growing PA tissue domain is established. An elastic-growing material model was developed in the open source FEBio software suite to first examine the surgical patch reconstruction process for an idealized main PA anatomy as a benchmark model and then for the patient-specific PA of a newborn. Following patch reconstruction, high levels of stress and strain are compensated by growth on the arterial tissue. As this growth progresses, the arterial tissue is predicted to stiffen to limit elastic deformations. We simulated this arterial growth up to the age of 18 years, when somatic growth plateaus. Our research findings show that the non-growing patch material remains in a low strain state throughout the simulation timeline, while experiencing high stress hot-spots. Arterial tissue growth along the surgical stitch lines is triggered mainly due to PA geometry and blood pressure, rather than due to material property differences in the artificial and native tissue. Thus, non-uniform growth patterns are observed along the arterial tissue proximal to the sutured boundaries. This computational approach is effective for the pre-surgical planning of complex patch surgeries to quantify the unbalanced growth of native arteries and artificial non-growing materials to develop optimal patch biomechanics for improved postoperative outcomes.
A predictive multiscale model for simulating flow-induced platelet activation: Correlating in silico results with in vitro results.
Venue: Journal of biomechanics

Flow-induced platelet activation prompts complex filopodial formation. Continuum methods fail to capture such molecular-scale mechanisms. A multiscale numerical model was developed to simulate this activation process, where a Dissipative Particle Dynamics (DPD) model of viscous blood flow is interfaced with a Coarse Grained Molecular Dynamics (CGMD) platelet model. Embedded in DPD blood flow, the macroscopic dynamic stresses are interactively transferred to the CGMD model, inducing intra-platelet associated events. The platelets activate by a biomechanical transductive linkage chain and dynamically change their shape in response. The models are fully coupled via a hybrid-potential interface and multiple time-stepping (MTS) schemes for handling the disparity between the spatiotemporal scales. Cumulative hemodynamic stresses that may lead to platelet activation are mapped on the surface membrane and simultaneously transmitted to the cytoplasm and cytoskeleton. Upon activation, the flowing platelets lose their quiescent discoid shape and evolve by forming filopodia. The model predictions were validated by a set of in vitro experiments, Platelets were exposed to various combinations of shear stresses and durations in our programmable hemodynamic shearing device (HSD). Their shape change was measured at multiple time points using scanning electron microscopy (SEM). The CGMD model parameters were fine-tuned by interrogating a parameter space established in these experiments. Segmentation of the SEM imaging streams was conducted by a deep machine learning system. This model can be further employed to simulate shear mediated platelet activation thrombosis initiation and to study the effects of modulating platelet properties to enhance their shear resistance via mechanotransduction pathways.