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- Erickson, Brittany A., et al.
(author)
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Incorporating Full Elastodynamic Effects and Dipping Fault Geometries in Community Code Verification Exercises for Simulations of Earthquake Sequences and Aseismic Slip (SEAS)
- 2023
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In: Bulletin of The Seismological Society of America (BSSA). - : SEISMOLOGICAL SOC AMER. - 0037-1106 .- 1943-3573. ; 113:2, s. 499-523
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Journal article (peer-reviewed)abstract
- Numerical modeling of earthquake dynamics and derived insight for seismic hazard relies on credible, reproducible model results. The sequences of earthquakes and aseismic slip (SEAS) initiative has set out to facilitate community code comparisons, and verify and advance the next generation of physics-based earthquake models that reproduce all phases of the seis-mic cycle. With the goal of advancing SEAS models to robustly incorporate physical and geo-metrical complexities, here we present code comparison results from two new benchmark problems: BP1-FD considers full elastodynamic effects, and BP3-QD considers dipping fault geometries. Seven and eight modeling groups participated in BP1-FD and BP3-QD, respectively, allowing us to explore these physical ingredients across multiple codes and better understand associated numerical considerations. With new comparison metrics, we find that numerical resolution and computational domain size are critical parameters to obtain matching results. Codes for BP1-FD implement different criteria for switching between quasi-static and dynamic solvers, which require tuning to obtain matching results. In BP3-QD, proper remote boundary conditions consistent with specified rigid body translation are required to obtain matching surface displacements. With these numerical and mathematical issues resolved, we obtain excellent quantitative agreements among codes in earthquake interevent times, event moments, and coseismic slip, with reasonable agreements made in peak slip rates and rupture arrival time. We find that including full inertial effects generates events with larger slip rates and rupture speeds compared to the quasi-dynamic counterpart. For BP3-QD, both dip angle and sense of motion (thrust versus normal faulting) alter ground motion on the hanging and foot walls, and influence event patterns, with some sequences exhibiting similar-size character-istic earthquakes, and others exhibiting different-size events. These findings underscore the importance of considering full elastodynamics and nonvertical dip angles in SEAS models, as both influence short-and long-term earthquake behavior and are relevant to seismic hazard.
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| 2. |
- Ji, Chenlin, et al.
(author)
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Postnatal overfeeding promotes early onset and exaggeration of high-fat diet-induced nonalcoholic fatty liver disease through disordered hepatic lipid metabolism in rats
- 2014
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In: Journal of Nutritional Biochemistry. - : Elsevier. - 0955-2863 .- 1873-4847. ; 25:11, s. 1108-1116
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Journal article (peer-reviewed)abstract
- Exposure to overnutrition in critical or sensitive developmental periods may increase the risk of developing obesity and metabolic syndrome in adults. Nonalcoholic fatty liver disease (NAFLD) is the hepatic manifestation of the metabolic syndrome, but the relationship among postnatal nutrition, lipid metabolism, and NAFLD progression during development remains poorly understood. Here we investigated in a rat model whether postnatal overfeeding increases susceptibility to NAFLD in response to a high-fat diet. Litters from Sprague-Dawley dams were culled to three (small litters) or ten (normal litters) pups and then weaned onto a standard or high-fat diet at postnatal day 21 to generate normal-litter, small-litter, normal-litter/high-fat, and small-litter/high-fat groups. At age 16 weeks, the small-litter and both high-fat groups showed obesity, dyslipidemia, and insulin resistance. Hepatic disorders appeared earlier in the small-litter/high-fat rats with greater liver mass gain and higher hepatic triglycerides and steatosis score versus normal-litter/high-fat rats. Hepatic acetyl-CoA carboxylase activity and mRNA expression were increased in small-litter rats and aggravated in small-litter/high-fat rats but not in normal-litter/high-fat rats. The high expression in small-litter/high-fat rats coincided with high sterol regulatory element-binding protein-1c mRNA and protein expression. However, mRNA expression of enzymes involved in hepatic fatty acid oxidation (carnitine palmitoyltransferase 1) and output (microsomal triglyceride transfer protein) was decreased under a high-fat diet regardless of litter size. In conclusion, overfeeding related to small-litter rearing during lactation contributes to the NAFLD phenotype when combined with a high-fat diet, possibly through up-regulated hepatic lipogenesis. (C) 2014 Elsevier Inc. All rights reserved.
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