title: Review: Extrusion processing and properties of protein-based thermoplastics

authors: Verbeek, Casparus Johan R.

subjects: extrusion

abstract: Increasing interest in competitive, sustainable, and biodegradable alternatives to petroleum-based plastics has encouraged the development of protein-based plastics. The formation of a homogeneous protein melt during extrusion occurs through: denaturation, dissociation, unraveling, and alignment of polymer chains. The presence of covalent cross-links is unfavorable, decreasing chain mobility, increasing viscosity and preventing homogenization. Proteins have high softening temperatures, often above their decomposition temperatures. To avoid degradation, the required chain mobility is achieved by plasticizers. By understanding a protein's physiochemical nature, additives can be selected that lead to a bioplastic with good processability. The final structural and functional properties are highly dependent on the protein and processing conditions.

text: Review: Extrusion processing and properties of protein-based thermoplastics Increasing interest in competitive, sustainable, and biodegradable alternatives to petroleum-based plastics has encouraged the development of protein-based plastics. The formation of a homogeneous protein melt during extrusion occurs through: denaturation, dissociation, unraveling, and alignment of polymer chains. The presence of covalent cross-links is unfavorable, decreasing chain mobility, increasing viscosity and preventing homogenization. Proteins have high softening temperatures, often above their decomposition temperatures. To avoid degradation, the required chain mobility is achieved by plasticizers. By understanding a protein's physiochemical nature, additives can be selected that lead to a bioplastic with good processability. The final structural and functional properties are highly dependent on the protein and processing conditions.

year: 2010

title: Application of Onset Theory to Onset of Transverse Cracking in Fabric Composites

authors: Lim, Shen Hin

subjects: Onset Theory

abstract: A paper presented at ICCM-19 included a methodology for application of Onset Theory to the prediction of microcracking in the transverse plies of orthogonal [0/90] fabric laminates. This paper applies the methodology to predict damage locations and laminate strains for failure of plain weave fabric specimens manufactured from two material systems – HTS40/RTM6 and T300/CYCOM970. The laminate strains are first dehomogenised to define local strains in the tow architecture of the fabric. This is achieved using meso-mechanical unit cell analysis in which the resin and tows are modelled as continua. For a selection of predefined critical locations in the tow bundles, the strains are further dehomogenised using an identical procedure as the one defined for the uni-directional specimens in the previous applications. The influence of matrix plasticity and temperature dependent mechanical and thermal properties of the RTM6 resin are applied in the dehomogenisation procedure. The Onset theory predictions for damage locations were compared to those obtained from microscopic surveys of partially failed plain weave fabric specimens.

text: Application of Onset Theory to Onset of Transverse Cracking in Fabric Composites A paper presented at ICCM-19 included a methodology for application of Onset Theory to the prediction of microcracking in the transverse plies of orthogonal [0/90] fabric laminates. This paper applies the methodology to predict damage locations and laminate strains for failure of plain weave fabric specimens manufactured from two material systems – HTS40/RTM6 and T300/CYCOM970. The laminate strains are first dehomogenised to define local strains in the tow architecture of the fabric. This is achieved using meso-mechanical unit cell analysis in which the resin and tows are modelled as continua. For a selection of predefined critical locations in the tow bundles, the strains are further dehomogenised using an identical procedure as the one defined for the uni-directional specimens in the previous applications. The influence of matrix plasticity and temperature dependent mechanical and thermal properties of the RTM6 resin are applied in the dehomogenisation procedure. The Onset theory predictions for damage locations were compared to those obtained from microscopic surveys of partially failed plain weave fabric specimens.

year: 2015

title: Telomere length in early childhood is associated with sex and ethnicity

authors: Ly, Kien

subjects: Science & Technology

abstract: Telomeres are repetitive DNA sequences at the end of chromosomes that function to protect chromosomes from degradation. Throughout the life course, telomere length decreases with age and is influenced by environmental factors and health conditions. This study aimed to determine the relative telomere lengths in a diverse cohort of about 4000 four-year-old children in New Zealand. Linear regression was used to investigate the relationship between telomere length, child gender, ethnicity, paternal age and deprivation. We observed substantial variation in telomere length according to sex and self-identified ethnicity. Telomere length was longer in females compared to males (coefficient of 0.042, 95% confidence interval (CI) 0.024–0.060). European children had shorter telomere than both the indigenous Māori (coefficient of 0.03, CI 0.007–0.055) and Pacific children (coefficient of 0.15, CI 0.12–0.18). The data suggest that telomere lengths are highly variable and variability between individuals arise from early age, influenced partly by sex and ethnicity. Longer telomeres in indigenous Māori and Pacific children may reflect the heritability of telomere length in genetically less complex populations. This study increases our understanding of telomere dynamics in young children since the majority of telomere studies are conducted in adults.

text: Telomere length in early childhood is associated with sex and ethnicity Telomeres are repetitive DNA sequences at the end of chromosomes that function to protect chromosomes from degradation. Throughout the life course, telomere length decreases with age and is influenced by environmental factors and health conditions. This study aimed to determine the relative telomere lengths in a diverse cohort of about 4000 four-year-old children in New Zealand. Linear regression was used to investigate the relationship between telomere length, child gender, ethnicity, paternal age and deprivation. We observed substantial variation in telomere length according to sex and self-identified ethnicity. Telomere length was longer in females compared to males (coefficient of 0.042, 95% confidence interval (CI) 0.024–0.060). European children had shorter telomere than both the indigenous Māori (coefficient of 0.03, CI 0.007–0.055) and Pacific children (coefficient of 0.15, CI 0.12–0.18). The data suggest that telomere lengths are highly variable and variability between individuals arise from early age, influenced partly by sex and ethnicity. Longer telomeres in indigenous Māori and Pacific children may reflect the heritability of telomere length in genetically less complex populations. This study increases our understanding of telomere dynamics in young children since the majority of telomere studies are conducted in adults.

year: 2019