TY - JOUR A1 - Müller, B. R. A1 - Cooper, R. C. A1 - Lange, A. A1 - Kupsch, Andreas A1 - Wheeler, M. A1 - Hentschel, M. P. A1 - Staude, A. A1 - Pandey, A. A1 - Shyam, A. A1 - Bruno, Giovanni T1 - Stress-induced microcrack density evolution in beta-eucryptite ceramics BT - experimental observations and possible route to strain hardening JF - Acta materialia N2 - In order to investigate their microcracking behaviour, the microstructures of several beta-eucryptite ceramics, obtained from glass precursor and cerammed to yield different grain sizes and microcrack densities, were characterized by laboratory and synchrotron x-ray refraction and tomography. Results were compared with those obtained from scanning electron microscopy (SEM). In SEM images, the characterized materials appeared fully dense but computed tomography showed the presence of pore clusters. Uniaxial tensile testing was performed on specimens while strain maps were recorded and analyzed by Digital Image Correlation (DIC). X-ray refraction techniques were applied on specimens before and after tensile testing to measure the amount of the internal specific surface (i.e., area per unit volume). X-ray refraction revealed that (a) the small grain size (SGS) material contained a large specific surface, originating from the grain boundaries and the interfaces of TiO2 precipitates; (b) the medium (MGS) and large grain size (LGS) materials possessed higher amounts of specific surface compared to SGS material due to microcracks, which decreased after tensile loading; (c) the precursor glass had negligible internal surface. The unexpected decrease in the internal surface of MGS and LGS after tensile testing is explained by the presence of compressive regions in the DIC strain maps and further by theoretical arguments. It is suggested that while some microcracks merge via propagation, more close mechanically, thereby explaining the observed X-ray refraction results. The mechanisms proposed would allow the development of a strain hardening route in ceramics. KW - Beta-eucryptite KW - Microcracked ceramics KW - X-ray refraction KW - Tensile load KW - Strain hardening Y1 - 2017 U6 - https://doi.org/10.1016/j.actamat.2017.10.030 SN - 1359-6454 SN - 1873-2453 VL - 144 SP - 627 EP - 641 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Cooper, Ryan C. A1 - Bruno, Giovanni A1 - Wheeler, M. R. A1 - Pandey, A. A1 - Watkins, T. R. A1 - Shyarn, A. T1 - Effect of microcracking on the uniaxial tensile response of beta-eucryptite ceramics BT - Experiments and constitutive model JF - Acta Materialia N2 - A constitutive model for the nonlinear or "pseudoplastic" mechanical behavior in a linear-elastic solid with thermally induced microcracks is developed and applied to experimental results. The model is termed strain dependent microcrack density approximation (SDMDA) and is an extension of the modified differential scheme that describes the slope of the stress-strain curves of microcracked solids. SDMDA allows a continuous variation in the microcrack density with tensile loading. Experimental uniaxial tensile response of beta-eucryptite glass and ceramics with controlled levels of microcracking is reported. It is demonstrated that SDMDA can well describe the extent of non-linearity in the experimental uniaxial tensile response of beta-eucryptite with varying levels of microcracking. The advantages of the SDMDA are discussed in regard to tensile loading. KW - behavior Y1 - 2017 U6 - https://doi.org/10.1016/j.actamat.2017.06.033 SN - 1359-6454 SN - 1873-2453 VL - 135 SP - 361 EP - 371 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Zheng, Ju-Sheng A1 - Luan, Jian'an A1 - Sofianopoulou, Eleni A1 - Imamura, Fumiaki A1 - Stewart, Isobel D. A1 - Day, Felix R. A1 - Pietzner, Maik A1 - Wheeler, Eleanor A1 - Lotta, Luca A. A1 - Gundersen, Thomas E. A1 - Amiano, Pilar A1 - Ardanaz, Eva A1 - Chirlaque, Maria-Dolores A1 - Fagherazzi, Guy A1 - Franks, Paul W. A1 - Kaaks, Rudolf A1 - Laouali, Nasser A1 - Mancini, Francesca Romana A1 - Nilsson, Peter M. A1 - Onland-Moret, N. Charlotte A1 - Olsen, Anja A1 - Overvad, Kim A1 - Panico, Salvatore A1 - Palli, Domenico A1 - Ricceri, Fulvio A1 - Rolandsson, Olov A1 - Spijkerman, Annemieke M. W. A1 - Sanchez, Maria-Jose A1 - Schulze, Matthias Bernd A1 - Sala, Nuria A1 - Sieri, Sabina A1 - Tjonneland, Anne A1 - Tumino, Rosario A1 - van der Schouw, Yvonne T. A1 - Weiderpass, Elisabete A1 - Riboli, Elio A1 - Danesh, John A1 - Butterworth, Adam S. A1 - Sharp, Stephen J. A1 - Langenberg, Claudia A1 - Forouhi, Nita G. A1 - Wareham, Nicholas J. T1 - Plasma vitamin C and type 2 diabetes BT - genome-wide association study and Mendelian randomization analysis in European populations JF - Diabetes care N2 - OBJECTIVE: Higher plasma vitamin C levels are associated with lower type 2 diabetes risk, but whether this association is causal is uncertain. To investigate this, we studied the association of genetically predicted plasma vitamin C with type 2 diabetes. RESEARCH DESIGN AND METHODS: We conducted genome-wide association studies of plasma vitamin C among 52,018 individuals of European ancestry to discover novel genetic variants. We performed Mendelian randomization analyses to estimate the association of genetically predicted differences in plasma vitamin C with type 2 diabetes in up to 80,983 case participants and 842,909 noncase participants. We compared this estimate with the observational association between plasma vitamin C and incident type 2 diabetes, including 8,133 case participants and 11,073 noncase participants. RESULTS: We identified 11 genomic regions associated with plasma vitamin C (P < 5 x 10(-8)), with the strongest signal at SLC23A1, and 10 novel genetic loci including SLC23A3, CHPT1, BCAS3, SNRPF, RER1, MAF, GSTA5, RGS14, AKT1, and FADS1. Plasma vitamin C was inversely associated with type 2 diabetes (hazard ratio per SD 0.88; 95% CI 0.82, 0.94), but there was no association between genetically predicted plasma vitamin C (excluding FADS1 variant due to its apparent pleiotropic effect) and type 2 diabetes (1.03; 95% CI 0.96, 1.10). CONCLUSIONS: These findings indicate discordance between biochemically measured and genetically predicted plasma vitamin C levels in the association with type 2 diabetes among European populations. The null Mendelian randomization findings provide no strong evidence to suggest the use of vitamin C supplementation for type 2 diabetes prevention. Y1 - 2020 U6 - https://doi.org/10.2337/dc20-1328 SN - 0149-5992 SN - 1935-5548 VL - 44 IS - 1 SP - 98 EP - 106 PB - American Diabetes Association CY - Alexandria ER -