Raw dataset of compression tests on a vegetable oil-based polyurethane foam exposed to different ageing conditions

The current dataset brings raw compression test information of a vegetable-based polyurethane foam (PUF) exposed to different temperatures over different periods of time. Such experimental dataset can provide researchers with important information in the application of numerical and data-driven simulations. Also, it saves money and time once the experimental part is already available. At total, 90 compression tests were done following the ASTM D1621-16 standard with pictures for digital image correlation (DIC) being simultaneously acquired. The 90 specimens were divided in nine different ageing conditions. The foam was considered transversely isotropic, thus, 10 specimens for each condition were divided in two groups, five specimens for direction 1 and five for direction 3, where direction 3 is the foam expansion direction. The 3D DIC results show longitudinal and transverse strains from virtual extensometers. The results are available in .TRA and .csv files for the tests and DIC outputs, respectively. Also, the dataset brings the pictures used for DIC in .TIF format. It also brings the dimensions of each specimen prior to the test in .txt format. These results provide information for the calculation of major mechanical properties that can be freely used in finite element models for different and creative ways to simulate the ageing process of a vegetable-based PUF.

Compressive Strength Testing of Glass-Fibre-Reinforced Tooth Crown Tissues After Endodontic Treatment

The objective of this study was to compare the effects of using short and continuous fibres for repairing compression-induced tooth crown damage. Human teeth were used for the study. They were upper medial incisors and maxillary first premolars lost due to periodontal causes. The teeth were divided into two groups with Hahnenkratt and short glass fibres. Teeth compressive strength tests were carried out. Then micro-CT imaging of the teeth and their fractures obtained after compression was performed. The teeth restored with Hahnenkratt's glass fibre posts showed higher compressive strength than the teeth restored using the EverX Posterior material. The tooth's most weakened and sensitive point after endodontic treatment was the cervical area of the tooth. All cracks were parallel to the root canal.

Determination of the compressive modulus of elasticity of periodontal ligament derived from human first premolars

Purpose

There are two commonly cited modulus of elasticity of the human periodontal ligament (E_PDL), i.e., 6.89 ✕ 10^-5 GPa (E1) and 6.89 ✕ 10^-2 GPa (E2), which are exactly 1000-fold different from each other. This study aims to clarify the ambiguity of the two E_PDL used for simulations and determine a more accurate E_PDL value of human first premolars using experimental and simulation approaches.

Methods

Numerical simulations using finite element analysis were performed to analyze PDL deformation under an average Asian occlusal force. To confirm the results, simple and multi-component, true-scale 3D models of a human first premolar were used in the simulations. Finally, a compression test using a universal testing machine on PDL specimens was conducted to identify the compressive E_PDL of human first premolars.

Results

The simulation results from both models revealed that E1 was inaccurate, because it resulted in excessive PDL deformation under the average occlusal force, which should not occur during mastication. Although the E2 did not lead to excessive PDL deformation, it was obtained by an error in unit conversion with no scientific backing. In contrast, the compression test results indicated that the compressive E_PDL was 9.64 ✕ 10^-4 GPa (E3). In the simulation, E3 did not cause excessive PDL deformation.

Conclusion

The simulation results demonstrated that both commonly cited E_PDL values (E1 and E2) were incorrect. Based on the experimental and simulation results, the average compressive E_PDL of 9.64 ✕ 10^-4 GPa is proposed as a more accurate value for human first premolars.

Clinical significance

The proposed more accurate E_PDL would contribute to more precise and reliable FEA simulation results and provide a better understanding of the stress distribution and deformation of dental materials, which will be beneficial to precision dentistry, orthodontics and restoration designs.

Effects of processing and gamma radiation on mechanical properties and organic composition of frozen, freeze-dried and demineralised human cortical bone allograft

Bone processing and radiation were reported to influence mechanical properties of cortical bones due in part to structural changes and denaturation of collagen composition. This comparative study was to determine effects of bone processing on mechanical properties and organic composition, and to what extent the radiation damaging after each processing. Human femur cortical bones were processed by freezing, freeze-drying and demineralisation and then gamma irradiated at 5, 15, 20, 25 and 50 kGy. In the compression test, freeze drying significantly decreased the Young's Modulus by 15%, while demineralisation reduced further by 90% (P < 0.05) when compared to the freezing. Only demineralisation significantly reduced ultimate strength of bone by 93% (P < 0.05). In the bending test, both freeze drying and demineralisation significantly reduced the ultimate strength and the work to failure. Radiation at 25 kGy showed no effect on compression for ultimate strength in each processing group. However, high dose of 50 kGy significantly reduced bending ultimate strength by 47% in demineralisation group. Alterations in collagen in bones irradiated at 25 and 50 kGy showed by the highest peak of the amide I collagen in the Fourier Transfer Infra-Red spectra indicating more collagen was exposed after calcium was removed in the demineralised bone, however radiation showed no effect on the collagen crosslink. The study confirmed that demineralisation further reduced the ability to resist deformation in response to an applied force in freeze-dried bones due to calcium reduction and collagen composition. Sterilisation dose of 25 kGy has no effect on mechanical properties and collagen composition of the processed human cortical bone.

Calculation of stresses on 3D scaffolds fabricated using extrusion-based bioprinting using a semi-analytical approach

The scaffold is essential to tissue engineering. In particular, the mechanical property of scaffolds has a significant impact on the success rate of regeneration. While numerous techniques exist for measuring mechanical properties, Compression test, three-point bending test, and nano-indentation test are the most common. Nevertheless, the mechanical property of porous structures cannot be accurately measured by previous testing methods. Combining superposition principles with the Flamant solution, this study developed semi-analytical solutions. Through compression testing and FEM simulation, the semi-analytical solution was fully validated. The solution can calculate not only the maximum stress of layer-by-layer construction of complex 3D scaffolds, but also the maximum load-bearing capacity if the mechanical property of the material is known.

Experiments and hyperelastic modeling of porcine meniscus show heterogeneity at high strains

Constitutive modeling of the meniscus is critical in areas like knee surgery and tissue engineering. At low strain rates, the meniscus can be described using a hyperelastic model. Calibration of hyperelastic material models of the meniscus is challenging on many fronts due to material variability and friction. In this study, we present a framework to determine the hyperelastic material parameters of porcine meniscus (and similar soft tissues) using no-slip uniaxial compression experiments. Because of the nonhomogeneous deformation in the specimens, a finite element solution is required at each step of the iterative calibration process. We employ a Bayesian calibration approach to account for the inherent material variability and a Bayesian optimization approach to minimize the resulting cost function in the material parameter space. Cylindrical specimens of porcine meniscus from the anterior, middle and posterior regions are tested up to 30% compressive strain and the Yeoh form of hyperelastic strain energy density function is used to describe the material response. The results show that the Yeoh form is able to accurately describe the compressive response of porcine meniscus and that the Bayesian calibration and optimization approaches are able to calibrate the model in a computationally efficient manner while taking into account the inherent material variability. The results also show that the shear modulus or the initial stiffness is roughly uniform across the different areas of the meniscus, but there is significant spatial heterogeneity in the response at high strains. In particular, the middle region is considerably stiffer at high strains. This heterogeneity is important to consider in modeling the response of the meniscus for clinical applications.

B16 Melanoma Cancer Cells with Higher Metastatic Potential are More Deformable at a Whole-Cell Level

INTRODUCTION

Metastasis is a process in which cancer cells spread from the primary focus site to various other organ sites. Many studies have suggested that reduced stiffness would facilitate passing through extracellular matrix when cancer cells instigate a metastatic process. Here we investigated the compressive properties of melanoma cancer cells with different metastatic potentials at the whole-cell level. Differences in their compressive properties were analyzed by examining actin filament structure and actin-related gene expression.

METHODS

Compressive tests were carried out for two metastatic B16 melanoma variants (B16-F1 and B16-F10) to characterize global compressive properties of cancer cells. RNA-seq analysis and fluorescence microscopic imaging were performed to clarify contribution of actin filaments to the global compressive properties.

RESULTS

RNA-seq analysis and fluorescence microscopic imaging revealed the undeveloped structure of actin filaments in B16-F10 cells. The Young's modulus of B16-F10 cells was significantly lower than that of B16-F1 cells. Disruption of the actin filaments in B16-F1 cells reduced the Young's modulus to the same level as that of B16-F10 cells, while the Young's modulus in B16-F10 cells remained the same regardless of the disruption.

CONCLUSIONS

In B16 melanoma cancer cell lines, cells with higher metastatic potential were more deformable at the whole-cell level with undeveloped actin filament structure, even when highly deformed. These results imply that invasive cancer cells may gain the ability to inhibit actin filament development.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at (10.1007/s12195-021-00677-w).

"Shunt pumping test": detecting its efficacy through an experimental model

PURPOSE

Shunt pumping test has often been used clinically to detect functional status of ventriculoperitoneal (VP) shunt. Its ability to correctly predict the status is not reliably known. Ethical dilemmas make it difficult to perform any studies in patients with blocked shunts, and hence, a requirement of devising an experimental model was felt.

METHOD

An experimental model was devised using a Chhabra Slit N Spring shunt. The pressures were maintained in the proximal and distal chamber by real-time monitoring and maintained similar to intra-ventricular and intra-abdominal pressures. Three such models with scenarios of proximal block (PB), distal block (DB), and a functional shunt (BO) were created. Twenty-five participants were tested using these models to assess the efficacy of shunt pumping test.

RESULTS

The experimental model could be used successfully to perform the test. The sensitivity of the test to detect a shunt with block on any side (AB) was found to be 0.79 (95% confidence interval 0.72-0.85) and specificity to be 0.69 (95% confidence interval 0.59-0.80). Its ability to detect the side of block was also evaluated. Absolute correctness value, odds ratio, and interpersonal heterogeneity were also evaluated. Pressure changes in proximal and distal catheter on compressing the chamber in various scenarios were recorded.

CONCLUSION

The shunt pumping test has moderate ability to predict a blocked shunt and can aid clinical assessment of shunt block. It has only limited ability to detect the side of block. Pressure changes in the proximal and distal catheters on chamber compression are commensurate with the rationale of "shunt pumping test."

Compression behaviors of mechanically biologically treated wastes of Tianziling landfill in Hangzhou, China

This study aimed to investigate the compression behaviors of mechanically biologically treated (MBT) wastes. For this purpose, the short-term compression-rebound and long-term compression tests were conducted on MBT wastes collected from Hangzhou Tianziling landfill in China. The results showed that the duration of immediate compression was obtained as 15.17-36.67 h and was comparable to municipal solid waste (MSW). The immediate compression ratio was 0.233-0.247, and it was comparable to the aged high food waste content (HFWC)-MSW, fresh and aged low food waste content (LFWC)-MSW, but much lower than the fresh HFWC-MSW. The mechanical creep ratio (C'_αc) was 0.012-0.018, being close to the fresh and aged MSWs. The bio-induced compression ratio (C'_αb) was 0.143-0.174. The compression ratio rose exponentially with temperature (5-42 °C) in both mechanical creep stage and bio-induced compression stage, and it increased much faster in the bio-induced compression stage. The resilient strains was only 2.1-3.3% of the compression strain at the same stress interval, suggesting that the compression strain consisted of mostly plastic deformation and negligible elastic deformation. The above findings can provide a reference for settlement prediction and storage capacity estimation of an MBT waste landfill.

Biomechanical analysis of the posterior bony column of the lumbar spine

Background

Each part of the rear bone structure can become an anchor point for an attachment device. The objective of this study was to evaluate the stiffness and strength of different parts of the rear lumbar bone structure by axial compression damage experiments.

Methods

Five adult male lumbar bone structures from L2 to L5 were exposed. The superior and inferior articular processes, upper and lower edges of the lamina, and upper and lower edges of the spinous process were observed and isolated and then divided into six groups (n = 10). The specimens were placed between the compaction disc and the load platform in a universal testing machine, which was first preloaded to 5.0 N tension to eliminate water on the surface and then loaded to the specimen curve decline at a constant tension loading rate of 0.01 mm/s, until the specimens had been destroyed.

Results

Significant differences in mechanical properties were found among different parts of the rear lumbar bone structure. Compared with other parts, the lower edge of the lamina has good mechanical properties, which have a high modulus of elasticity; the superior and inferior articular processes have greater ultimate strength, which can withstand greater compressive loads; and the mechanical properties of the spinous process are poor, and it is significantly stiffer and weaker than the lamina and articular processes.

Conclusion

These data can be useful in future spinal biomechanics research leading to better biomechanical compatibility and provide theoretical references for spinal implant materials.

Design and characterization of microcapsules-integrated collagen matrixes as multifunctional three-dimensional scaffolds for soft tissue engineering

Three-dimensional (3D) porous scaffolds based on collagen are promising candidates for soft tissue engineering applications. The addition of stimuli-responsive carriers (nano- and microparticles) in the current approaches to tissue reconstruction and repair brings about novel challenges in the design and conception of carrier-integrated polymer scaffolds. In this study, a facile method was developed to functionalize 3D collagen porous scaffolds with biodegradable multilayer microcapsules. The effects of the capsule charge as well as the influence of the functionalization methods on the binding efficiency to the scaffolds were studied. It was found that the binding of cationic microcapsules was higher than that of anionic ones, and application of vacuum during scaffolds functionalization significantly hindered the attachment of the microcapsules to the collagen matrix. The physical properties of microcapsules-integrated scaffolds were compared to pristine scaffolds. The modified scaffolds showed swelling ratios, weight losses and mechanical properties similar to those of unmodified scaffolds. Finally, in vitro diffusional tests proved that the collagen scaffolds could stably retain the microcapsules over long incubation time in Tris-HCl buffer at 37°C without undergoing morphological changes, thus confirming their suitability for tissue engineering applications. The obtained results indicate that by tuning the charge of the microcapsules and by varying the fabrication conditions, collagen scaffolds patterned with high or low number of microcapsules can be obtained, and that the microcapsules-integrated scaffolds fully retain their original physical properties.

Relationship between liver tissue stiffness and histopathological findings analyzed by shear wave elastography and compression testing in rats with non-alcoholic steatohepatitis

PURPOSE

The aim of the present study was to investigate two methods of determining liver stiffness in rats with various degrees of non-alcoholic steatohepatitis induced by a methionine- and choline-deficient (MCD) diet by comparing each finding with reference to histopathological liver findings.

METHODS

Twenty male Wister rats were fed an MCD diet for up to 32 weeks, and four were fed a normal diet. Ultrasound-based shear wave elastography (SWE) and mechanical compression testing using an Instron Universal Testing machine were performed on each rat at designated time points. After each examination, liver histopathology was analyzed to evaluate the degrees of steatosis, inflammation, and fibrosis based on non-alcoholic fatty liver disease (NAFLD) activity score, and each finding was compared with reference to liver histopathologic findings.

RESULTS

Median liver stiffness values measured using SWE showed a stepwise increase with increasing histological inflammation score (P = 0.002), hepatic fibrosis stage (P = 0.029), ballooning score (P = 0.012), and steatosis grade (P = 0.030). Median liver stiffness measured using an Instron machine showed a stepwise increase only with increasing histological fibrosis stage (P = 0.033).

CONCLUSIONS

Degree of liver stiffness measured by SWE and the Instron machine differed. SWE reflected mainly inflammation, whereas Instron machine-derived values primarily reflected fibrosis. This is the main source of discrepancies between measurements made with these two modalities.

Effect of deep-fat frying on sensory and textural attributes of pellet snacks

In this paper, the effects of several frying parameters on the quality of indirect expanded snacks were studied. Pellets, in two colors of yellow and green, were deep-fat fried at 150, 170, and 190 °C for 0.5, 1.5, 2.5, 3.5, and 4.5 min; then, subjected to uniaxial compression test and sensory analysis. The results showed that hardness, fracture force and apparent modulus of elasticity reduced with increase in frying time and temperature due to puffing samples and decrease in crust thickness. In contrast, higher frying temperature improved the crispness of samples. Panelists preferred the flavor, color, and total acceptance of yellow samples to the green ones. Moreover, principal component analysis (PCA) of instrumental and sensory data provided important information for the correlation of objective and sensory properties.