Mechanical Tests Research Articles

Decellularization and characterization of camel pericardium as a new scaffold for tissue engineering and regenerative medicine.

Valvular heart diseases (VHDs) have become prevalent in populations due to aging. Application of different biomaterials for cardiac valve regeneration and repair holds a great promise for treatment of VHD. Aortic valve replacement using tissue-engineered xenografts is a considered approach, and the pericardium of different species such as porcine and bovine has been studied over the last few years. It has been suggested that the animal origin can affect the outcomes of replacement. So, herein, we at first decellularized and characterized the camel pericardium (dCP), then characterized dCP with H&E staining, in vitro and in vivo biocompatibility and mechanical tests and compared it with decellularized bovine pericardium (dBP), to describe the potency of dCP as a new xenograft and bio scaffold. The histological assays indicated less decluttering and extracellular matrix damage in dCP after decellularization compared to the dBP also dCP had higher Young Modulus (105.11), and yield stress (1.57 ± 0.45). We observed more blood vessels and also less inflammatory cells in the dCP sections after implantation. In conclusion, the results of this study showed that the dCP has good capabilities not only for use in VHD treatment but also for other applications in tissue engineering and regenerative medicine.

Statement of Retraction: Image processing algorithm for mechanical properties testing of high temperature materials based on time‐frequency analysis

Statement of Retraction: Image processing algorithm for mechanical properties testing of high temperature materials based on time‐frequency analysis

Fully Biodegradable Elastomer-Based Device for Oral Macromolecule Delivery.

Oral devices, such as foil-type devices, show great potential for the delivery of poorly permeable macromolecules by enabling unidirectional release of the loaded pharmaceutical composition in close proximity to the epithelium in the small intestine or colon. However, one of the primary concerns associated with the use of foil-type devices so far has been the utilization of nonbiodegradable elastomers in the fabrication of the devices. Therefore, research into biodegradable substitute materials with similar characteristics enables drug delivery in a sustainable and environmentally friendly manner. In this study, a biodegradable elastomer, polyoctanediol citrate (POC), was synthesized via a one-pot reaction, with subsequent purification and microscale pattern replication via casting. The microstructure geometry was designed to enable fabrication of foil-type devices with the selected elastomer, which has a high intrinsic surface free energy. The final elastomer was demonstrated to have an elastic modulus ranging up to 2.2 ± 0.1 MPa, with strain at failure up to 110.1 ± 1.5%. Devices were loaded with acetaminophen and enterically coated, demonstrating 100% release at 2.5 h, following dissolution for 1 h in 0.1 M hydrochloric acid and 1.5 h in pH 6.8 phosphate-buffered saline. The elastomer demonstrated promising properties based on mechanical testing, surface free energy evaluation, and degradation studies.

Sustainable engineering of human hair fiber-composite in engineering application

The hybrid composite material, resulting from the fusion of human hair and Kevlar 29 synthetic fiber in a 10:1 ratio, reinforced with epoxy resin using the hand layup technique, underwent meticulous mechanical and thermal testing. The investigation encompassed tensile, flexural, and impact property evaluations, elucidating a notable enhancement in mechanical strength with a diminishing synthetic fiber content. Concomitantly, the composite exhibited commendable heat resistance in heat deflection tests, making it potentially suitable for applications in elevated temperature environments. Water absorption properties were scrutinized, revealing a correlation between reduced synthetic fiber content and diminished water absorption, implying heightened durability in diverse conditions. Microstructure analysis through SEM provided intricate insights into the internal composition. In summation, the composite, featuring a higher proportion of natural fibers and a lower proportion of synthetics, demonstrated superior mechanical attributes, optimal heat resistance, and reduced water absorption, showcasing its applicability in automotive and engineering domains, particularly in the fabrication of vehicle panels and components. The aim of this research represents a significant advancement in composite materials, offering a cost-effective solution that balances mechanical strength and thermal resistance. It suggests the potential for high-performance materials by combining natural and synthetic fibers, promising versatility across various applications.

Study on peripheral antinociception induced by hydrogen peroxide (H2O2): characterization and mechanisms.

The present study aimed to evaluate the possible peripheral H2O2-induced antinociception and determine the involvement of opioidergic, cannabinoidergic and nitrergic systems, besides potassium channels in its antinociceptive effect. Prostaglandin E2 was used to induce hyperalgesia in male Swiss mice using the mechanical paw pressure test. H2O2 (0.1, 0.2, 0.3 µg/paw) promoted a dose-dependent antinociceptive effect that was not observed in contralateral paw. Female mice also showed antinociception in the model. The partial H2O2-induced antinociception was potentiated by the inhibitor of catalase enzyme, aminotriazole (40, 60, 80 µg/paw). The antinociception was not reversed by opioid and cannabinoid receptor antagonists naloxone, AM 251 and AM 630. The involvement of nitric oxide (NO) was observed by the reversal of H2O2-induced antinociception using the non-selective inhibitor of nitric oxide synthases L-NOarg and by inhibition of iNOS (L-NIL), eNOS (L-NIO) and nNOS (L-NPA). ODQ, a cGMP-forming enzyme selective inhibitor, also reversed the antinociception. The blockers of potassium channels voltage-gated (TEA), ATP-sensitive (glibenclamide), large (paxillin) and small (dequalinium) conductance calcium-activated were able to revert H2O2 antinociception. Our data suggest that H2O2 induced a peripheral antinociception in mice and the NO pathway and potassium channels (voltage-gated, ATP-sensitive, calcium-activated) are involved in this mechanism. However, the role of the opioid and cannabinoid systems was not evidenced.

Evaluation of precipitated CaCO3 produced from locally available limestone as a reinforcement filler for PVC pipe.

The current experimental work aimed at developing PCC through two major process steps: dissolution and precipitation, using raw materials domestically available as SL, which are intensively used in construction inputs. The pH level was the decisive parameter used to determine the time required to complete the dissolution and carbonation processes during precipitation. The optimal pH levels were found to be 13 for dissolution and 7.1 for precipitation, respectively. The produced PCC was characterized based on chemical analysis, crystallinity, and morphology, showing an increment of CaCO3 content exceeding 99%, sharper crystal peaks, and predominantly calcite PCC. The compatibility of the PCC was assessed by incorporating 25%, 50%, 75%, and 100% of PCC with commercial filler, followed by selected mechanical tests, such as stress at yield, density, and elongation at break. The results indicated that mixing ratios of 25%, 50%, and 75% of PCC with the commercial filler met the standards, with stress at a yield above 45MPa and density within the range of 1.35 to 1.46g/cm3. However, complete substitution slightly lowered these properties. Nevertheless, the elongation at break was acceptable at all treatment levels.

Experimental Analysis of Mechanical Tests on a Plate Composed of Banana Fibre

Experimental Analysis of Mechanical Tests on a Plate Composed of Banana Fibre

Experimental characterization and numerical prediction for mechanical aging of epoxy and its carbon fiber‐reinforced composite under hydrothermal conditions

AbstractThe Aqueous environment impairs the mechanical performance of carbon fiber‐reinforced polymers (CFRPs) and decreases the durability of engineering structures made of CFRPs primarily by degrading the resin matrix. Hence, the objective of this study is to investigate and accurately predict the influence of hydrothermal aging on the epoxy and its carbon fiber reinforced polymer (CFRP). Particularly, this work developed a modeling method that combined Fick's model, empirical aging model and elastoplastic constitutive model to predict the mechanical behavior of hydrothermally aged epoxy matrix. After the experimental characterization, this epoxy modeling method demonstrated its predictive capability on the mechanical response of the deteriorated epoxy under different hydro‐thermal‐salt conditions, with the mean absolute percent error (MAPE) of approximately 4.61%. Furthermore, the transverse compressive behavior of unidirectional (UD) CFRPs could be predicted by using the representative volume element (RVE) model with the degraded matrix behavior predicted via this epoxy modeling method. Integrated with this CFRP modeling, results from mechanical tests and fracture analysis further demonstrated that the hydrothermal aging effect on the transverse compressive performance of the UD CFRPs was dominated by the deterioration of their resin matrix. Therefore, this study demonstrates the feasibility of the finite element analysis (FEA) for mechanical aging of the epoxy matrix and its CFRP under hydrothermal conditions via employing the proposed integrated modeling method.Highlights Degradation of epoxy polymer under hydro‐thermal‐salt aging conditions. Integrated model to predict mechanical response of hydrothermally aged epoxy. RVE model to predict the mechanical behavior of hydrothermally aged CFRP. Hydrothermal aging on the transverse compressive behavior of UD CFRP.

Mechanical Characterization of Hybrid Steel Wire Mesh/Basalt/Epoxy Fiber-Reinforced Polymer Composite Laminates

Hybrid composite materials have been widely used to advance the mechanical responses of fiber-reinforced composites by utilizing different types of fibers and fillers in a single polymeric matrix. This study incorporated three types of fibers: basalt woven fiber and steel (AISI304) wire meshes with densities of 100 and 200. These fibers were mixed with epoxy resin to generate plain composite laminates. Three fundamental mechanical tests (tensile, compression, and shear) were conducted according to the corresponding ASTM standards to characterize the steel wire mesh/basalt/epoxy FRP composites used as plain composite laminates. To investigate the flexural behavior of the hybrid laminates, various layer configurations and thickness ratios were examined using a design of experiments (DoE) matrix. Hybrid samples were chosen for flexural testing, and the same procedure was employed to develop a finite element (FE) model. Material properties from the initial mechanical testing procedure were integrated into plain and hybrid composite laminate simulations. The second FE model simulated the behavior of hybrid laminates under flexural loading; this was validated through experimental data. The results underwent statistical analysis, highlighting the optimal configuration of hybrid composite laminates in terms of flexural strength and modulus; we found an increase of up to 25% in comparison with the plain composites. This research provides insights into the potential improvements offered by hybrid composite laminates, generating numerical models for predicting various laminate configurations produced using hybrid steel wire mesh/basalt/epoxy FRP composites.

Digital Economy Development, Common Prosperity, and Carbon Emissions: An Empirical Study in China

Under the new development model, the digital economy has become a new engine to promote the green development of the economy and realize the goal of “double carbon”. Based on the panel data of 30 provinces in China from 2010 to 2020, this paper empirically investigates the impact of the development of the digital economy on energy and carbon emissions using a series of econometric models such as baseline regression, a mechanism test, and the spatial Durbin model, etc. Common prosperity plays an intermediary role between digital economy development and carbon emissions; digital economic development optimizes resource allocation, effectively solves the problem of uneven resource distribution, and reduces energy and carbon emissions while achieving common prosperity. In addition, green innovation, industrial structure, urbanization level, R&D intensity, and the degree of marketization also have different degrees of influence on energy and carbon emissions. Therefore, the government should accelerate the construction of new digital infrastructure and implement the digital economy development strategy according to local conditions, so as to promote the digital economy to produce a more significant carbon emission reduction effect.

Troops are Business Schools: Military Service and Entrepreneurial Behaviors in China

Although research has examined the benefits of military service and the impact of military executives on business operations, the relationship between military service and entrepreneurial behavior remains poorly understood. Using the instrumental variable approach and a nationally representative male sample from the China Labor-forces Dynamic Survey, we discovered that military service significantly increased the probability of entrepreneurship in China, even after a series of robustness checks. Mechanism tests indicated that this positive effect could be explained by human and political capital accumulation, military-related social capital formation, and risk appetite traits. Our supplemental analyses demonstrated that exogenous shocks from the special military-in-business policy strengthened the positive entrepreneurial effect, whereas the higher education expansion policy and China’s accession to the World Trade Organization weakened this effect. Additionally, military entrepreneurs had better business performance and more resilient, persistent, and confident traits. We found no evidence that Chinese veterans were forced to become entrepreneurs. This study enriches research on the styles and traits of military entrepreneurs and managers and provides important insights for assessing and improving veteran welfare policies in China and other developing countries.

Comprehensive Assessment of Cyclic Fatigue Strength in Five Multiple-File Nickel–Titanium Endodontic Systems

The resistance of nickel–titanium endodontic instruments against cyclic fatigue failure remains a significant concern in clinical settings. This study aimed to assess the cyclic fatigue strength of five nickel–titanium rotary systems, while correlating the results with the instruments’ geometric and metallurgical characteristics. A total of 250 new instruments (sizes S1/A1, S2/A2, F1/B1, F2/B2, F3/B3) from ProTaper Gold, ProTaper Universal, Premium Taper Gold, Go-Taper Flex, and U-Files systems underwent mechanical testing. Prior to experimental procedures, all instruments were meticulously inspected to identify irregularities that could affect the investigation. Using a stereomicroscope, design characteristics such as the number of spirals, length, spirals per millimeter, and average helical angle of the active blade were determined. The surface finishing characteristics of the instruments were examined using a scanning electron microscope. Differential scanning calorimetry was employed to establish the instruments’ phase transformation temperatures, while energy-dispersive X-ray spectroscopy was utilized to analyze the elemental composition of the alloy. The instruments were subjected to cyclic fatigue testing within a stainless steel non-tapered artificial canal featuring a 6 mm radius and 86 degrees of curvature. Appropriate statistical tests were applied to compare groups, considering a significance level of 0.05. The assessed design characteristics varied depending on the instrument type. The least irregular surface finishing was observed in U-Files and Premium Taper Gold files, while the most irregular surface was noted in Go-Taper Flex. All instruments exhibited near-equiatomic proportions of nickel and titanium elements, whereas ProTaper Universal and U-Files instruments demonstrated lower phase transformation temperatures compared to their counterparts. Larger-sized instruments, as well as ProTaper Universal and U-Files, tended to display lower cyclic fatigue strength results. Overall, the design, metallurgical, and cyclic fatigue outcomes varied among instruments and systems. Understanding these outcomes may assist clinicians in making more informed decisions regarding instrument selection.

Long-Term Drying Shrinkage Strain of Engineered Cementitious Composite Concrete Contains Polymeric Fibers

The lack of concrete tensile stress endurance led to the invention of engineered cementitious composite. However, the absence of gravel from the mixture in addition to the high binder content may lead to high shrinkage strain. Therefore, a radical solution to this problem is worth to be anticipated. The importance of this research lies in investigating the long-term drying shrinkage strain of the engineered cementitious composite since there is a lack of information regarding this behavior. Mixes of 30 and 60 MPa strengths were produced with polyvinyl alcohol fibers PVA-ECC and polypropylene fibers PP-ECC. The drying shrinkage strain of PVA-ECC mixes has been compared to PP-ECC mixes for both short term (0–28 days) and long term (0–360 days). Results indicated that all PVA-ECC mixes exhibited lower drying shrinkage strains than PP-ECC mixes. The ultimate drying shrinkage strain was recorded to be 1200 microstrain at 28 days. The increment in drying shrinkage strain after 28 days was 5.6% in PVA-ECC mixes when compared to that in PP-ECC mixes which was 6.77%. For high strength levels, the drying shrinkage strain at the age of 360 days declared a reduction of 3.5% for PVA-ECC compared to PP-ECC mixes. Also, it was lower for mixes with 60 MPa (6.3%) than for mixes with 30 MPa (7.6%). Therefore, despite the higher cement content for mixes with 60 MPa strength, the higher fiber volume fraction and the higher PVA solution percentage restricted the drying shrinkage strain increment. The research also addresses some mechanical tests of engineered cementitious composite concrete such as compressive strength, flexural strength, and strain capacity that may provide a strong relation to the drying shrinkage behavior of the different mixes. The scanning electron microscope images were involved in this research to declare the impact of fiber types on the microstructure of the ECC mixes.

Hindrance or facilitator? The economic consequences of national demonstration eco-industrial parks in China.

Many countries attach great importance to the green, low-carbon, and circular development of industrial parks. China is one of them and has entered an exploration journey of national demonstration eco-industrial parks (NDEIPs). However, the impact of the transformation of industrial parks into NDEIPs on local economic development still remains a mystery. To address this issue, we develop an empirical study using a combination of the multi-period difference-in-differences method and the propensity score matching method based on the panel data for 266 cities in China from 2001 to 2021. The results show that industrial parks becoming NDEIPs promotes cities' economic development. This conclusion still holds after a series of robustness tests, such as the reverse causality test and the placebo test. Moreover, the park heterogeneity tests show that the economic consequences vary according to differences in levels, industry types, life cycle phases, and the degree of foreign firm agglomeration. The city heterogeneity tests show that the economic consequences differ based on administrative levels, innovation capabilities, technology industrialization, and environmental friendliness. The spatial heterogeneity tests show that the economic consequences differ according to geographical location and whether situated in the Yangtze River Economic Belt. The policy upgrading heterogeneity tests show that the economic consequences differ during the process of policy upgrading and transformation. In addition, the mechanism tests reveal that green innovation, human capital level, and firm attractiveness mediate the relationship between industrial parks becoming NDEIPs and cities' economic development. This study provides a new perspective for understanding the economic effects of the transformation of industrial parks into NDEIPs, and provides a reference for the government on how to maximize these economic effects.

Construction of transportation infrastructure and the mixed ownership reform of state-owned enterprises: based on the perspective of high-speed rail opening

ABSTRACT We study the impact of transportation infrastructure construction on the degree of mixed-ownership reform of local state-owned enterprises. We find that the opening of high-speed rail can significantly promote the mixed ownership reform process of local state-owned enterprises. Mechanism testing shows that the opening of high-speed rail can promote inter-regional market integration and reduce the transaction costs of potential private investors participating in mixed-ownership reform, and improve the operational activities and management characteristics of state-owned enterprises, and strengthen the intrinsic motivations of potential private investors to participate in mixed-ownership reform, thereby having a positive impact on the degree of mixed-ownership reform of local state-owned enterprises. Further research finds that the above-mentioned effects are sustain-able and more obvious among local state-owned enterprises and state-owned enterprises in competitive industries with weak government influence, which can ultimately improve the capital market value and labour productivity of state-owned enterprises.

How Does Environmental Protection Tax Affect Urban Energy Consumption in China? New Insights from the Intensity Difference-in-Differences Model

Against the backdrop of accelerating environmental protection and resource conservation, it is of great significance to achieve energy conservation and sustainable growth. In this context, by collecting panel data from 284 cities in China from 2009 to 2021, this paper constructs an intensity difference-in-differences (I-DID) model, using the implementation of China’s environmental protection law in 2018 as an event shock, to explore the impact of environmental protection tax (EPT) on urban energy consumption. The results indicate that EPT significantly reduces urban energy consumption. After several robustness tests, the estimation results shown above still hold. The mechanism test reveals that EPT mainly reduces energy consumption by promoting urban industrial upgrading, economic openness, and technological innovation. In addition, the heterogeneity test shows that EPT has a greater impact on energy consumption in central and western cities, small and medium-sized cities, non-resource-based cities, and non-old industrial bases. Therefore, to fully improve the positive effect of EPT on urban energy consumption, we suggest increasing energy efficiency, promoting the green transformation of energy structures, enhancing the ability to open-up and innovate, and improving a differentiated regional EPT management system.

Reusable and effective polyacrylic membranes for mecoprop and bentazon extractions

This study introduces reusable polyacrylic membranes, fabricated from commercially available monomers (1-vinyl-2-pyrrolidone and methylmethacrylate), as a promising approach for pesticide extraction. These membranes effectively remove the commonly used herbicides mecoprop (RE ≈ 99%) and bentazon (RE ≈ 95%) at low concentrations, which pose water contamination risks due to their water-soluble properties and leaf-level sorption. The membranes exhibit excellent manageability and resistance, allowing for safe handling without personal protective equipment. Additionally, the material is environmentally friendly and can be washed and reused for at least 4 cycles without a significant decrease in performance. Characterization techniques, including NMR, TGA, DSC, mechanical testing, N2 adsorption, and FTIR analysis, were used to investigate properties and assess the influence of the polymeric composition. The study focused on examining the lateral charged aminoethyl groups, which play a crucial role in sorbent-sorbate interactions. Sorption kinetics, isotherms, and permeation studies provided insights into the removal mechanism, efficiency, and permeability coefficients, revealing hydrophobic–hydrophobic interactions between the pesticides and the polymer. Molecular dynamics simulations revealed a scorpion-like conformation of the macromolecular chains surrounding the pesticides. These findings support the hydrophobic nature of the extraction mechanism and highlight the significant role of charged aminoethyl groups in facilitating this process.

The Effect of Different Chemical Surface Treatments on the Bond Strength of Resin-Matrix Ceramic Repaired with Resin Composite.

This study investigates the effect of different chemical surface treatment protocols with different functional monomers of universal adhesives on the shear bond strength between resin-matrix ceramic and resin composite. Eighty resin-matrix ceramics (Shofu block HC) were built and designed into eight groups of ten specimens and surface treated with HC primer (HC) and/or three universal adhesives (single bond universal [SBU], Scotchbond universal plus [SBP], and Tetric N-bond universal [TNU]) assigning follows; group 1, nonsurface treated; group 2, HC; group 3, SBU; group 4, HC + SBU; group 5, SBP; group 6, HC + SBP; group 7, TNU; group 8, HC + TNU. A template was put on the specimen center, and then pushed packable resin composite. Mechanical testing machinery was used to examine the samples' shear bond strength (SBS) values. To examine failure patterns, the debonded specimen surfaces were examined by a stereomicroscope. The one-way analysis of variance method was used to evaluate the data, and the Tukey's test was used to determine the significant level (p < 0.05). The highest SBS was obtained in group 6 (39.25 ± 1.65 MPa). Group 1 (4.15 ± 0.54 MPa) had the lowest SBS. Group 6 exhibited the highest percentage of cohesive failure patterns (70%). High SBS values were frequently correlated with the surface treatment groups and the cohesive failure patterns. The application of HC primer prior to the universal adhesive is an alternative protocol for enhancing the repair bond strength between resin-matrix ceramic and resin composite interfaces. Moreover, the application of HC primer prior to the SBP is the best strategy for resin-matrix ceramic and resin composite repairs.

Spatiotemporal Characterization of Microstructure Morphology, Mechanical Properties and Bone Remodeling of Rat Tibia Under Uniaxial Compressive Overload Loading.

Bone tissue is subjected to increased mechanical stress during high-intensity work. Inadequate bone remodeling reparability can result in the continuous accumulation of microdamage, leading to stress fractures. The aim of this work was to investigate the characteristics and repair mechanisms of tibial microdamage under several degrees of overload. Also, we aimed at better understanding the effects of overload on the multi-scale structure and mechanical properties of bone. Sixty 5-month female rats were divided into three groups with different time points. Micro-CT was used to evaluate the three-dimensional microstructure, and three-point bending, quasi-static fracture toughness and creep mechanical test were carried out to evaluate the mechanical properties. SEM was used to observe the morphological characteristics of fracture surfaces. Section staining was used to count the microdamage parameters and numbers of osteoblasts and osteoclasts. The microarchitectures of cancellous and cortical bones in the three overload groups showed different degrees of damage. Overload led to a messy crystal structure of cortical bone, with slender microcracks mixed in, and a large number of broken fibers of cancellous bone. The properties associated with the elastic plasticity, fracture toughness, and viscoelasticity of cortical bone reduced in three groups, with that corresponding to day 30 presenting the highest damage. The accumulation of microdamage mainly occurred in the first 14days, that is, the crack density peaked on day 14. Peak-targeted bone remodeling of cortical and cancellous bones occurred mainly between days 14 and 30. The influence of overload mechanical environment on bone quality at different time points was deeply investigated, which is of great significance for the etiology and treatment of stress fractures.

(Thermo)mechanical and chemical characteristics of photochemically crosslinked acrylates from bio‐ and fossil‐based origin

AbstractThe acrylates with oligomers and monomers from (partially) bio‐based feedstock become available at (semi‐)industrial scale, which can be processed through photochemical crosslinking for applications in coatings, additive manufacturing, electronics, or inks. Although fossil‐ and bio‐based acrylates may have a similar chemical composition, it requires good understanding of processing and structure–property relationships as minor changes in microstructure may strongly alter the performance. A comparative study on mechanical properties and chemical structure of bio‐ and fossil‐based acrylates with different functionalities and backbone structures reveals higher ductility of bio‐based acrylates, in relation with a more complex organization of the intrinsic molecular structure. The latter is confirmed by mechanical testing and visco‐elastic characteristics (dynamic mechanical analysis) yielding lower stiffness and higher dampening of bio‐based acrylates, in parallel with a lower glass transition temperature (differential scanning calorimetry). The complex molecular arrangements include a nanoscale morphology with ordered structure (X‐ray diffraction), conformational changes (infrared spectroscopy), and a residual high‐molecular weight fraction (size exclusion chromatography). The visco‐elastic calculations indicate only 4% to 5% lower crosslinking density and around 10% higher mean molar mass of the polymer chains segments between chemical crosslinks and trapped chain entanglements, which explain the unique structure and performance of bio‐based acrylates.