2,420 research outputs found
Revisiting the Dependence of Poissonâs Ratio on Liquid Fragility and Atomic Packing Density in Oxide Glasses
Poisson’s ratio (ν) defines a material’s propensity to laterally expand upon compression, or laterally shrink upon tension for non-auxetic materials. This fundamental metric has traditionally, in some fields, been assumed to be a material-independent constant, but it is clear that it varies with composition across glasses, ceramics, metals, and polymers. The intrinsically elastic metric has also been suggested to control a range of properties, even beyond the linear-elastic regime. Notably, metallic glasses show a striking brittle-to-ductile (BTD) transition for ν-values above ~0.32. The BTD transition has also been suggested to be valid for oxide glasses, but, unfortunately, direct prediction of Poisson’s ratio from chemical composition remains challenging. With the long-term goal to discover such high-ν oxide glasses, we here revisit whether previously proposed relationships between Poisson’s ratio and liquid fragility (m) and atomic packing density (Cg) hold for oxide glasses, since this would enable m and Cg to be used as surrogates for ν. To do so, we have performed an extensive literature review and synthesized new oxide glasses within the zinc borate and aluminoborate families that are found to exhibit high Poisson’s ratio values up to ~0.34. We are not able to unequivocally confirm the universality of the Novikov-Sokolov correlation between ν and m and that between ν and Cg for oxide glass-formers, nor for the organic, ionic, chalcogenide, halogenide, or metallic glasses. Despite significant scatter, we do, however, observe an overall increase in ν with increasing m and Cg, but it is clear that additional structural details besides m or Cg are needed to predict and understand the composition dependence of Poisson’s ratio. Finally, we also infer from literature data that, in addition to high ν, high Young’s modulus is also needed to obtain glasses with high fracture toughness
Identification of a Danish breast/ovarian cancer family double heterozygote for BRCA1 and BRCA2 mutations
Mutations in the two breast cancer susceptibility genes BRCA1 and BRCA2 are associated with increased risk of breast and ovarian cancer. Patients with mutations in both genes are rarely reported and often involve Ashkenazi founder mutations. Here we report the first identification of a Danish breast and ovarian cancer family heterozygote for mutations in the BRCA1 and BRCA2 genes. The BRCA1 nucleotide 5215GÂ >Â A/c.5096GÂ >Â A mutation results in the missense mutation Arg1699Gln, while the BRCA2 nucleotide 859Â +Â 4AÂ >Â G/c.631Â +Â 4AÂ >Â G is novel. Exon trapping experiments and reverse transcriptase (RT)âPCR analysis revealed that the BRCA2 mutation results in skipping of exon 7, thereby introducing a frameshift and a premature stop codon. We therefore classify the mutation as disease causing. Since the BRCA1 Arg1699Gln mutation is also suggested to be disease-causing, we consider this family double heterozygote for BRCA1 and BRCA2 mutations
Genetic predisposition to adiposity is associated with increased objectively assessed sedentary time in young children.
Increased sedentariness has been linked to the growing prevalence of obesity in children, but some longitudinal studies suggest that sedentariness may be a consequence rather than a cause of increased adiposity. We used Mendelian randomization to examine the causal relations between body mass index (BMI) and objectively assessed sedentary time and physical activity in 3-8 year-old children from one Finnish and two Danish cohorts [NTOTAL=679]. A genetic risk score (GRS) comprised of 15 independent genetic variants associated with childhood BMI was used as the instrumental variable to test causal effects of BMI on sedentary time, total physical activity, and moderate-to-vigorous physical activity (MVPA). In fixed effects meta-analyses, the GRS was associated with 0.05 SD/allele increase in sedentary time (P=0.019), but there was no significant association with total physical activity (beta=0.011 SD/allele, P=0.58) or MVPA (beta=0.001 SD/allele, P=0.96), adjusting for age, sex, monitor wear-time and first three genome-wide principal components. In two-stage least squares regression analyses, each genetically instrumented one unit increase in BMI z-score increased sedentary time by 0.47 SD (P=0.072). Childhood BMI may have a causal influence on sedentary time but not on total physical activity or MVPA in young children. Our results provide important insights into the regulation of movement behaviour in childhood
Future costs in cost-effectiveness analysis: an empirical assessment
To assess the usage of cost-utility analysis (CUA) in oral health interventions and to evaluate the methods used and the reporting quality of CUA in publications on oral health interventions
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