scholarly journals Quantifying 3D Strain in Scaffold Implants for Regenerative Medicine

Materials ◽  
2020 ◽  
Vol 13 (17) ◽  
pp. 3890 ◽  
Author(s):  
Jeffrey N. Clark ◽  
Saman Tavana ◽  
Agathe Heyraud ◽  
Francesca Tallia ◽  
Julian R. Jones ◽  
...  
Keyword(s):  
Regenerative Medicine ◽  
Local Level ◽  
Cell Lineage ◽  
Biological Response ◽  
Cartilage Regeneration ◽  
Ground Truth ◽  
Image Correlation ◽  
Surrounding Tissue ◽  
Materials Testing ◽  
Random Errors

Regenerative medicine solutions require thoughtful design to elicit the intended biological response. This includes the biomechanical stimulus to generate an appropriate strain in the scaffold and surrounding tissue to drive cell lineage to the desired tissue. To provide appropriate strain on a local level, new generations of scaffolds often involve anisotropic spatially graded mechanical properties that cannot be characterised with traditional materials testing equipment. Volumetric examination is possible with three-dimensional (3D) imaging, in situ loading and digital volume correlation (DVC). Micro-CT and DVC were utilised in this study on two sizes of 3D-printed inorganic/organic hybrid scaffolds (n = 2 and n = 4) with a repeating homogenous structure intended for cartilage regeneration. Deformation was observed with a spatial resolution of under 200 µm whilst maintaining displacement random errors of 0.97 µm, strain systematic errors of 0.17% and strain random errors of 0.031%. Digital image correlation (DIC) provided an analysis of the external surfaces whilst DVC enabled localised strain concentrations to be examined throughout the full 3D volume. Strain values derived using DVC correlated well against manually calculated ground-truth measurements (R2 = 0.98, n = 8). The technique ensures the full 3D micro-mechanical environment experienced by cells is intimately considered, enabling future studies to further examine scaffold designs for regenerative medicine.

scholarly journals Spatiotemporal Characterizations of Spontaneously Beating Cardiomyocytes with Adaptive Reference Digital Image Correlation

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Akankshya Shradhanjali ◽  
Brandon D. Riehl ◽  
Bin Duan ◽  
Ruiguo Yang ◽  
Jung Yul Lim
Keyword(s):  
Regenerative Medicine ◽  
Digital Image Correlation ◽  
Digital Image ◽  
Biological Tissue ◽  
Image Correlation ◽  
Myocardial Tissue ◽  
Tissue Development ◽  
Tissue Samples ◽  
Non Invasive ◽  
Spatiotemporal Parameters

AbstractWe developed an Adaptive Reference-Digital Image Correlation (AR-DIC) method that enables unbiased and accurate mechanics measurements of moving biological tissue samples. We applied the AR-DIC analysis to a spontaneously beating cardiomyocyte (CM) tissue, and could provide correct quantifications of tissue displacement and strain for the beating CMs utilizing physiologically-relevant, sarcomere displacement length-based contraction criteria. The data were further synthesized into novel spatiotemporal parameters of CM contraction to account for the CM beating homogeneity, synchronicity, and propagation as holistic measures of functional myocardial tissue development. Our AR-DIC analyses may thus provide advanced non-invasive characterization tools for assessing the development of spontaneously contracting CMs, suggesting an applicability in myocardial regenerative medicine.

The influence of sliding velocity and effective stress on the distribution of strain in subglacial till

2020 ◽  
Author(s):  
Dougal Hansen ◽  
Anders Daamsgard ◽  
Lucas Zoet
Keyword(s):  
Effective Stress ◽  
Dynamic Models ◽  
Ground Truth ◽  
Element Model ◽  
Image Correlation ◽  
Sliding Velocity ◽  
Fine Grained ◽  
Ring Shear ◽  
Sample Chamber ◽  
Convex Upward

<p>The distribution of strain in actively deforming subglacial till is an important control on the sliding velocity and sediment transport of soft-bedded glaciers. In situ field observations, laboratory experiments, and numerical simulations have demonstrated that strain accumulation within subglacial till is often greatest at the ice-bed interface and decreases monotonically with depth, forming a convex-upward profile. However, the mechanisms that set the form of the profile and depth of deformation remain unconstrained. Here we systematically test the influence of two independent variables, effective stress and sliding velocity, on the distribution of strain in a fine-grained, sandy till emplaced beneath a layer of moving ice. Laboratory sliding experiments, conducted with a brand-new ring-shear device with a transparent sample chamber, are coupled with two suites of state-of-the-art numerical experiments using 1) a discrete element model and 2) a non-local granular fluidity continuum model designed to emulate till deformation. Five effective stresses and five sliding velocities are tested with the other parameter held constant (velocity and effective stress, respectively). For the ring shear experiments, images of the till bed are acquired at regular intervals, and we quantify the displacement of sediment grains that occurs between image captures using digital image correlation. These experiments represent the first instance where the deformation of till during glacier slip can be observed in real-time and linked directly to its controlling processes. Furthermore, they provide an opportunity to juxtapose the predictions of two new granular dynamic models against empirical observations in a controlled setting, providing an invaluable ground truth for future, larger-scale implementations simulating bedform genesis and soft-bedded glacier dynamics.</p>

Characterization of a Ferritic Stainless Sheet Steel in Simple Shear and Uniaxial Tension at Different Strain Rates

2011 ◽  
Author(s):  
Matti Isakov ◽  
Jeremy Seidt ◽  
Kauko O¨stman ◽  
Amos Gilat ◽  
Veli-Tapani Kuokkala
Keyword(s):  
Uniaxial Tension ◽  
Simple Shear ◽  
High Strain ◽  
Image Correlation ◽  
Materials Testing ◽  
Strain Rates ◽  
Test Results ◽  
High Strain Rates ◽  
Stress Strain

In this study the mechanical properties of ferritic stainless steel EN 1.4521 (AISI 444) were characterized in uniaxial tension and simple shear. The specimen geometries were designed so that tests could be carried out both with a conventional uniaxial materials testing machine and at high strain rates with the Tensile Hopkinson Split Bar method. During the tests, specimen surface deformation was measured using a three dimensional digital image correlation technique based on a two-camera stereovision setup. This technique allowed direct measurement of the specimen gauge section deformation during the test. Test results indicate that the selected approach is suitable for large strain plastic deformation characterization of ductile metals. The stress-strain data obtained from the simple shear tests shows a correlation with the tensile test results according to the von Mises effective stress-strain criterion. Since necking is absent in shear, test data can be obtained at considerably higher plastic strains than in tension. However, the final fracture occurs under a complex loading mode due to the distortion of the specimen geometry and multiaxial loading introduced by the simple shear arrangement. Test results also show that reliable material data can be obtained at high strain rates.

scholarly journals Comparison between Geostatistical Interpolation and Numerical Weather Model Predictions for Meteorological Conditions Mapping

2020 ◽  
Vol 5 (2) ◽  
pp. 15 ◽  
Author(s):  
Javier López Gómez ◽  
Francisco Troncoso Pastoriza ◽  
Enrique Granada Álvarez ◽  
Pablo Eguía Oller
Keyword(s):  
Local Level ◽  
Weather Prediction ◽  
Ground Truth ◽  
Weather Conditions ◽  
Meteorological Conditions ◽  
Accurate Information ◽  
Numerical Weather ◽  
Weather Model ◽  
Geostatistical Interpolation ◽  
Solid Foundation

Mapping of meteorological conditions surrounding road infrastructures is a critical tool to identify high-risk spots related to harsh weather. However, local or regional data are not always available, and researchers and authorities must rely on coarser observations or predictions. Thus, choosing a suitable method for downscaling global data to local levels becomes essential to obtain accurate information. This work presents a deep analysis of the performance of two of these methods, commonly used in meteorology science: Universal Kriging geostatistical interpolation and Weather Research and Forecasting numerical weather prediction outputs. Estimations from both techniques are compared on 11 locations in central continental Portugal during January 2019, using measured data from a weather station network as the ground truth. Results show the different performance characteristics of both algorithms based on the nature of the specific variable interpolated, highlighting potential correlations to obtain the most accurate data for each case. Hence, this work provides a solid foundation for the selection of the most appropriate tool for mapping of weather conditions at the local level over linear transport infrastructures.

Mimicking the Extracellular Matrix: Tuning the Mechanical Properties of Chondroitin Sulfate Hydrogels by Copolymerization with Oligo(ethylene glycol) Diacrylates

2014 ◽  
Vol 1622 ◽  
pp. 189-195
Author(s):  
Anahita Khanlari ◽  
Tiffany C. Suekama ◽  
Michael S. Detamore ◽  
Stevin H. Gehrke
Keyword(s):  
Mechanical Properties ◽  
Extracellular Matrix ◽  
Connective Tissue ◽  
Ethylene Glycol ◽  
Chondroitin Sulfate ◽  
Crosslink Density ◽  
Cartilage Regeneration ◽  
Surrounding Tissue ◽  
Mechanical Support

ABSTRACTChondroitin sulfate (CS) is one of the major glycosaminoglycans (GAGs) present in the connective tissue extracellular matrix (ECM) and is responsible for the regulation of cellular activities as well as providing mechanical support for the surrounding tissue. Due to presence of CS in the natural tissues including cartilage, hydrogels of CS and other GAGs have been widely used in cartilage regeneration. Due to their polyelectrolyte nature, GAG-based hydrogels are brittle and require modifications to overcome the weak mechanical properties. In this work, we showed copolymerization of methacrylated chondroitin sulfate with oligo(ethylene glycol)s improved the crosslink density of the gels from 2 to 20 times depending on the methacrylation degree of CS and length of the crosslinking monomer. Copolymerization of CS with oligo(ethylene glycol) acrylates is a method to design hydrogels with tunable swelling and mechanical properties.

scholarly journals Exploratory Full-Field Mechanical Analysis across the Osteochondral Tissue—Biomaterial Interface in an Ovine Model

Materials ◽  
2020 ◽  
Vol 13 (18) ◽  
pp. 3911
Author(s):  
Jeffrey N. Clark ◽  
Agathe Heyraud ◽  
Saman Tavana ◽  
Talal Al-Jabri ◽  
Francesca Tallia ◽  
...  
Keyword(s):  
Ex Vivo ◽  
Cartilage Regeneration ◽  
Mechanical Analysis ◽  
Surrounding Tissue ◽  
Micro Computed Tomography ◽  
Full Field ◽  
Surgical Interventions ◽  
Osteochondral Injuries ◽  
Osteochondral Tissue

Osteochondral injuries are increasingly prevalent, yet success in articular cartilage regeneration remains elusive, necessitating the development of new surgical interventions and novel medical devices. As part of device development, animal models are an important milestone in illustrating functionality of novel implants. Inspection of the tissue-biomaterial system is vital to understand and predict load-sharing capacity, fixation mechanics and micromotion, none of which are directly captured by traditional post-mortem techniques. This study aims to characterize the localised mechanics of an ex vivo ovine osteochondral tissue–biomaterial system extracted following six weeks in vivo testing, utilising laboratory micro-computed tomography, in situ loading and digital volume correlation. Herein, the full-field displacement and strain distributions were visualised across the interface of the system components, including newly formed tissue. The results from this exploratory study suggest that implant micromotion in respect to the surrounding tissue could be visualised in 3D across multiple loading steps. The methodology provides a non-destructive means to assess device performance holistically, informing device design to improve osteochondral regeneration strategies.

scholarly journals Theoretical Guarantees for Phylogeny Inference from Single-Cell Lineage Tracing

2021 ◽  
Author(s):  
Robert Wang ◽  
Richard Y Zhang ◽  
Alex Khodaverdian ◽  
Nir Yosef
Keyword(s):  
Single Cell ◽  
Phylogenetic Reconstruction ◽  
Cell Lineage ◽  
Ground Truth ◽  
Lineage Tracing ◽  
Asymptotic Bounds ◽  
Exact Reconstruction ◽  
Experimental Parameters ◽  
Empirical Performance ◽  
Cutting Rate

CRISPR-Cas9 lineage tracing technologies have emerged as a powerful tool for investigating develop-ment in single-cell contexts, but exact reconstruction of the underlying clonal relationships in experiment is plagued by data-related complications. These complications are functions of the experimental parameters in these systems, such as the Cas9 cutting rate, the diversity of indel outcomes, and the rate of missing data. In this paper, we develop two theoretically grounded algorithms for reconstruction of the underlying phylogenetic tree, as well as asymptotic bounds for the number of recording sites necessary for exact recapitulation of the ground truth phylogeny at high probability. In doing so, we explore the relationship between the problem difficulty and the experimental parameters, with implications for experimental design. Lastly, we provide simulations validating these bounds and showing the empirical performance of these algorithms. Overall, this work provides a first theoretical analysis of phylogenetic reconstruction in the CRISPR-Cas9 lineage tracing technology.

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