Protective effect of vanillin in streptozotocin-induced diabetes in neonatal rats via attenuation of oxidative stress and inflammation

Purpose: To evaluate the antidiabetic activity of vanillin in streptozotocin (STZ)-induced diabetic rats.Methods: Diabetes was induced in 2-day old male pups by intraperitoneal (i.p.) administration of STZ (90 mg/kg). The pups were then randomly assigned to four groups: control group which received citrate buffer only in place of STZ; negative control group, i.e., diabetic group; and vanillin-treated groups which received vanillin (100 or 200 mg/kg, p.o.) continuously from the 6th week of age to the 10th week. The antidiabetic effect of vanillin was determined by measuring the serum levels of insulin, triglycerides and glucose in the diabetic rats. Oral glucose tolerance, kidney and liver function tests were also performed at the end of the protocol. Moreover, the oxidative stress and inflammatory cytokines in liver tissues, and histopathological changes in pancreatic tissues were assessed.Results: Vanillin treatment significantly decreased serum glucose and triglyceride levels and increased the level of insulin, when compared to the negative control group. There was higher insulin sensitivity in the vanillin-treated group than in the negative control group. In addition, vanillin improved liver and renal functions in STZ-induced diabetic neonatal rats. Hepatic oxidative stress and inflammatory mediators, as well as histopathological changes in pancreas were attenuated by vanillin treatment.Conclusion: These results reveal that vanillin attenuates hyperglycemia in STZ-induced neonatal diabetic rat model by decreasing oxidative stress and inflammatory cytokines. There, further studies are required to develop the anti-diabetic potentials of vanillin for clinical applications.Keywords: Vanillin, Streptozotocin, Diabetes, Oxidative stress, Insulin, Neonata

Crack Initiation in Compacted Graphite Iron with Random Microstructure: Effect of Volume Fraction and Distribution of Particles

Thanks to the distinctive morphology of graphite particles in its microstructure, compacted graphite iron (CGI) exhibits excellent thermal conductivity together with high strength and durability. CGI is extensively used in many applications, e.g., engine cylinder heads and brakes. The structural integrity of such metal-matrix materials is controlled by the generation and growth of microcracks. Although the effects of the volume fraction and morphology of graphite inclusions on the tensile response of CGI were investigated in recent years, their influence on crack initiation is still unknown. Experimental studies of crack initiation require a considerable amount of time and resources due to the highly complicated geometries of graphite inclusions scattered throughout the metallic matrix. Therefore, developing a 2D computational framework for CGI with a random microstructure capable of predicting the crack initiation and path is desirable. In this work, an integrated numerical model is developed for the analysis of the effects of volume fraction and nodularity on the mechanical properties of CGI as well as its damage and failure behaviours. Finite-element models of random microstructure are generated using an in-house Python script. The determination of spacings between a graphite inclusion and its four adjacent particles is performed with a plugin, written in Java and implemented in ImageJ. To analyse the orientation effect of inclusions, a statistical analysis is implemented for representative elements in this research. Further, Johnson–Cook damage criteria are used to predict crack initiation in the developed models. The numerical simulations are validated with conventional tensile-test data. The created models can support the understanding of the fracture behaviour of CGI under mechanical load, and the proposed approach can be utilised to design metal-matrix composites with optimised mechanical properties and performance

Microstructure-based CZE model for crack initiation and growth in CGI: effects of graphite-particle morphology and spacing

Compacted graphite iron (CGI) is an engineering material with the potential to fill the application gap between flake- and spheroidal-graphite irons thanks to its unique microstructure and competitive price. Despite its wide use and considerable past research, its complex microstructure often leads researchers to focus on models based on representative volume elements with multiple particles, frequently overlooking the impact of individual particle shapes and interactions between the neighbouring particles on crack initiation and propagation. This study focuses on the effects of graphite morphology and spacing between inclusions on the mechanical and fracture behaviours of CGI at the microscale. In this work, 2D cohesive-zone-element-based models with different graphite morphologies and spacings were developed to investigate the mechanical behaviour as well as crack initiation and propagation. ImageJ and scanning electron microscopy were used to characterise and analyse the microstructure of CGI. In simulations, both graphite particles and metallic matrix were assumed isotropic and ductile. Cohesive zone elements (CZEs) were employed in the whole domain studied. It was found that graphite morphology had a negligible effect on interface debonding but nodular inclusions can notably enhance the stiffness of the material and effectively impede the propagation of cracks within the matrix. Besides, a small distance between graphite particles accelerates the crack growth. These results can be used to design and manufacture better metal-matrix composites.</p

Tensile deformation of compacted graphite iron with realistic microstructures: effect of morphology of graphite inclusions

Compacted graphite iron (CGI) is a double-phase metal-matrix composite with graphite inclusions. Thanks to its good mechanical properties and thermal conductivity, CGI is extensively used in many applications, e.g., for brake drums and engine cylinder heads. Although the effects of graphite’s volume fraction and morphology on a macroscopic tensile response were investigated in recent years, the effect of real-life morphology of graphite inclusions obtained from micrographs and comparison with a case of their simplified elliptical shape is still missing. Building realistic 3D models requires a considerable amount of time due to extremely complicated geometries of graphite inclusions scattered throughout the metallic matrix. Therefore, developing a micro-scale finite-element model capable of investigating the performance of CGI is desirable. In this work, 2D micro-scale finite-element models are developed to (i) investigate the relations between mechanical properties and morphology of graphite inclusions and (ii) explore the effect of periodic boundary conditions on the domains studied. Images of CGI microstructure were obtained with scanning electron microscopy and ImageJ and CAD software were used to develop realistic and simplified models. The simulations were compared with experimental stress–strain curves from in-house experiments. The created models will assist in comprehending the mechanical behaviour of CGI.</p

Microstructure-based CZE model for crack initiation and growth in CGI: effects of graphite-particle morphology and spacing

Compacted graphite iron (CGI) is an engineering material with the potential to fill the application gap between flake- and spheroidal-graphite irons thanks to its unique microstructure and competitive price. Despite its wide use and considerable past research, its complex microstructure often leads researchers to focus on models based on representative volume elements with multiple particles, frequently overlooking the impact of individual particle shapes and interactions between the neighbouring particles on crack initiation and propagation. This study focuses on the effects of graphite morphology and spacing between inclusions on the mechanical and fracture behaviours of CGI at the microscale. In this work, 2D cohesive-zone-element-based models with different graphite morphologies and spacings were developed to investigate the mechanical behaviour as well as crack initiation and propagation. ImageJ and scanning electron microscopy were used to characterise and analyse the microstructure of CGI. In simulations, both graphite particles and metallic matrix were assumed isotropic and ductile. Cohesive zone elements (CZEs) were employed in the whole domain studied. It was found that graphite morphology had a negligible effect on interface debonding but nodular inclusions can notably enhance the stiffness of the material and effectively impede the propagation of cracks within the matrix. Besides, a small distance between graphite particles accelerates the crack growth. These results can be used to design and manufacture better metal-matrix composites.</p

Microstructural CZE-based computational model for predicting tensile fracture behaviour of CGI

Compacted graphite iron (CGI), also known as vermicular graphite iron, is a double-phase engineering material, extensively used in engine cylinders and brake disks, thanks to its good combination of mechanical properties and thermal conductivity. Despite its wide use and considerable past research, the fracture behaviour of CGI at the microscale is not yet fully understood, especially the effect of graphite inclusions. Due to the complex shapes of graphite inclusions randomly embedded in the metallic matrix, development of realistic 3D models is time-consuming and computationally expensive. Hence, a novel 2D computational framework capable of predicting crack initiation and growth in CGI is necessary. In this work, a 2D CZE-based model is developed to predict crack initiation and propagation under different boundary conditions. Scanning electron microscopy was used to characterise the microstructure of CGI, with the resulting scans analysed using image-processing software. The metallic matrix and graphite particles were assumed isotropic and ductile. Cohesive elements were implemented into the models using a Python script and assigned to the ferritic matrix, graphite inclusions, and the graphite-ferrite interface. It was found that employing periodic boundary conditions increased the stiffness of CGI and accelerated interface debonding but prevented crack propagation to the matrix. The developed models will contribute to the understanding of CGI's fracture behaviour.</p

Microstructural CZE-based computational model for predicting tensile fracture behaviour of CGI

Compacted graphite iron (CGI), also known as vermicular graphite iron, is a double-phase engineering material, extensively used in engine cylinders and brake disks, thanks to its good combination of mechanical properties and thermal conductivity. Despite its wide use and considerable past research, the fracture behaviour of CGI at the microscale is not yet fully understood, especially the effect of graphite inclusions. Due to the complex shapes of graphite inclusions randomly embedded in the metallic matrix, development of realistic 3D models is time-consuming and computationally expensive. Hence, a novel 2D computational framework capable of predicting crack initiation and growth in CGI is necessary. In this work, a 2D CZE-based model is developed to predict crack initiation and propagation under different boundary conditions. Scanning electron microscopy was used to characterise the microstructure of CGI, with the resulting scans analysed using image-processing software. The metallic matrix and graphite particles were assumed isotropic and ductile. Cohesive elements were implemented into the models using a Python script and assigned to the ferritic matrix, graphite inclusions, and the graphite-ferrite interface. It was found that employing periodic boundary conditions increased the stiffness of CGI and accelerated interface debonding but prevented crack propagation to the matrix. The developed models will contribute to the understanding of CGI's fracture behaviour.</p

Biocompatibility of Bespoke 3D-Printed Titanium Alloy Plates for Treating Acetabular Fractures

Treatment of acetabular fractures is challenging, not only because of its complicated anatomy but also because of the lack of fitting plates. Personalized titanium alloy plates can be fabricated by selective laser melting (SLM) but the biocompatibility of these three-dimensional printing (3D-printed) plates remains unknown. Plates were manufactured by SLM and their cytocompatibility was assessed by observing the metabolism of L929 fibroblasts incubated with culture medium extracts using a CCK-8 assay and their morphology by light microscopy. Allergenicity was tested using a guinea pig maximization test. In addition, acute systemic toxicity of the 3D-printed plates was determined by injecting extracts from the implants into the tail veins of mice. Finally, the histocompatibility of the plates was investigated by implanting them into the dorsal muscles of rabbits. The in vitro results suggested that cytocompatibility of the 3D-printed plates was similar to that of conventional plates. The in vivo data also demonstrated histocompatibility that was comparable between the two manufacturing techniques. In conclusion, both in vivo and in vitro experiments suggested favorable biocompatibility of 3D-printed titanium alloy plates, indicating that it is a promising option for treatment of acetabular fractures