Developing a novel in-situ polymerisation process for fully bioresorbable fibre reinforced composites

In recent decades, fully bioresorbable polymer composites with appropriate biocompatibility and mechanical properties have provided an exciting opportunity to replace conventional metal alloy implants. This work explores the development of a novel, one-step in-situ polymerisation (ISP) process for the manufacture of fully bioresorbable phosphate based glass fibre (PGF) reinforced composites with matrix materials of polycaprolactone (PCL), polycaprolactone-polylactic acid copolymer (PLA-PCL) and polylactic acid (PLA). Composites produced via conventional laminate stacking (LS) process were used as the comparison to demonstrate the advantages that ISP can provide in composites quality. In-vitro degradation in phosphate buffered saline (PBS) at 37 °C, flexural property retention and cytocompatibility were investigated for both LS and ISP composites. Additionally, the composites were degraded under representative flexural loading for high cycle fatigue analysis to understand and predict their lifetime in service and their likely mechanisms of failure. Significantly more robust fibre/matrix interface and uniform fibre distribution along the cross section of the composites were achieved via ISP compared to LS. These enhancements resulted in considerably higher initial mechanical properties (~450 MPa and ~24 GPa for flexural strength and modulus, close to the upper range of human cortical bone properties), prolonged mechanical retention, less and slower water uptake and mass loss profiles for the ISP composites. The flexural fatigue life of the ISP composites was at least 10 times longer than the LS composites counterpart within both dry and wet (within PBS at 37 °C) testing environments. Furthermore, positive cytocompatibility was also found for both the LS and ISP PLA/PGF composites. Conclusively, ISP composites exhibited considerably enhanced mechanical retention and drastically improved media resistance, making those fully bioresorbable composites significantly more favourable as materials for bioresorbable bone fracture fixation devices

Developing a novel in-situ polymerisation process for fully bioresorbable fibre reinforced composites

In recent decades, fully bioresorbable polymer composites with appropriate biocompatibility and mechanical properties have provided an exciting opportunity to replace conventional metal alloy implants. This work explores the development of a novel, one-step in-situ polymerisation (ISP) process for the manufacture of fully bioresorbable phosphate based glass fibre (PGF) reinforced composites with matrix materials of polycaprolactone (PCL), polycaprolactone-polylactic acid copolymer (PLA-PCL) and polylactic acid (PLA). Composites produced via conventional laminate stacking (LS) process were used as the comparison to demonstrate the advantages that ISP can provide in composites quality. In-vitro degradation in phosphate buffered saline (PBS) at 37 °C, flexural property retention and cytocompatibility were investigated for both LS and ISP composites. Additionally, the composites were degraded under representative flexural loading for high cycle fatigue analysis to understand and predict their lifetime in service and their likely mechanisms of failure. Significantly more robust fibre/matrix interface and uniform fibre distribution along the cross section of the composites were achieved via ISP compared to LS. These enhancements resulted in considerably higher initial mechanical properties (~450 MPa and ~24 GPa for flexural strength and modulus, close to the upper range of human cortical bone properties), prolonged mechanical retention, less and slower water uptake and mass loss profiles for the ISP composites. The flexural fatigue life of the ISP composites was at least 10 times longer than the LS composites counterpart within both dry and wet (within PBS at 37 °C) testing environments. Furthermore, positive cytocompatibility was also found for both the LS and ISP PLA/PGF composites. Conclusively, ISP composites exhibited considerably enhanced mechanical retention and drastically improved media resistance, making those fully bioresorbable composites significantly more favourable as materials for bioresorbable bone fracture fixation devices

Understanding Android Obfuscation Techniques: A Large-Scale Investigation in the Wild

In this paper, we seek to better understand Android obfuscation and depict a holistic view of the usage of obfuscation through a large-scale investigation in the wild. In particular, we focus on four popular obfuscation approaches: identifier renaming, string encryption, Java reflection, and packing. To obtain the meaningful statistical results, we designed efficient and lightweight detection models for each obfuscation technique and applied them to our massive APK datasets (collected from Google Play, multiple third-party markets, and malware databases). We have learned several interesting facts from the result. For example, malware authors use string encryption more frequently, and more apps on third-party markets than Google Play are packed. We are also interested in the explanation of each finding. Therefore we carry out in-depth code analysis on some Android apps after sampling. We believe our study will help developers select the most suitable obfuscation approach, and in the meantime help researchers improve code analysis systems in the right direction

Wet and dry flexural high cycle fatigue behaviour of fully bioresorbable glass fibre composites: in-situ polymerisation versus laminate stacking

Fully bioresorbable phosphate based glass fibre reinforced polycaprolactone (PCL/PGF) composites are potentially excellent candidates to address current issues experienced with use of metal implants for hard tissue repair, such as stress shielding effects. It is therefore essential to investigate these materials under representative loading cases and to understand their fatigue behaviour (wet and dry) in order to predict their lifetime in service and their likely mechanisms of failure. This paper investigated the dry and wet flexural fatigue behaviour of PCL/PGF composites with 35% and 50% fibre volume fraction (Vf). Significantly longer flexural fatigue life (p < 0.0001) and superior fatigue damage resistance were observed for In-situ Polymerised (ISP) composites as compared to the Laminate Stacking (LS) composites in both dry and wet conditions, indicating that the ISP promoted considerably stronger interfacial bonding than the LS. Immersion in fluid (wet) during the flexural fatigue tests resulted in significant reduction (p < 0.0001) in the composites fatigue life, earlier onset of fatigue damage and faster damage propagation. Regardless of testing conditions, increasing fibre content led to shorter fatigue life for the PCL/PGF composites. Meanwhile, immersion in degradation media caused softening of both LS and ISP composites during the fatigue tests, which led to a more ductile failure mode. Among all the composites that were investigated, ISP35 (35% Vf) composites maintained at least 50% of their initial stiffness at the end of fatigue tests in both conditions, which is comparable to the flexural properties of human cortical bones. Consequently, ISP composites with 35% Vf maintained at least 50% of its flexural properties after the fatigue failure, which the mechanical retentions were well matched with the properties of human cortical bones

Gut microbiota and acylcarnitine metabolites connect the beneficial association between estrogen and lipid metabolism disorders in ovariectomized mice

Decreased estrogen level is one of the main causes of lipid metabolism disorders and coronary heart disease in women after menopause. Exogenous estradiol benzoate is effective to some extent in alleviating lipid metabolism disorders caused by estrogen deficiency. However, the role of gut microbes in the regulation process is not yet appreciated. The objective of this study was to investigate the effects of estradiol benzoate supplementation on lipid metabolism, gut microbiota, and metabolites in ovariectomized (OVX) mice and to reveal the importance of gut microbes and metabolites in the regulation of lipid metabolism disorders. This study found that high doses of estradiol benzoate supplementation effectively attenuated fat accumulation in OVX mice. There was a significant increase in the expression of genes enriched in hepatic cholesterol metabolism and a concomitant decrease in the expression of genes enriched in unsaturated fatty acid metabolism pathways. Further screening of the gut for characteristic metabolites associated with improved lipid metabolism revealed that estradiol benzoate supplementation influenced major subsets of acylcarnitine metabolites. Ovariectomy significantly increased the abundance of characteristic microbes that are significantly negatively associated with acylcarnitine synthesis, such as Lactobacillus and Eubacterium ruminantium group bacteria, while estradiol benzoate supplementation significantly increased the abundance of characteristic microbes that are significantly positively associated with acylcarnitine synthesis, such as Ileibacterium and Bifidobacterium spp. The use of pseudosterile mice with gut microbial deficiency greatly facilitated the synthesis of acylcarnitine due to estradiol benzoate supplementation and also alleviated lipid metabolism disorders to a greater extent in OVX mice. IMPORTANCE Our findings establish a role for gut microbes in the progression of estrogen deficiency-induced lipid metabolism disorders and reveal key target bacteria that may have the potential to regulate acylcarnitine synthesis. These findings suggest a possible route for the use of microbes or acylcarnitine to regulate disorders of lipid metabolism induced by estrogen deficiency