Parallel chemistry acceleration algorithm with ISAT table-size control in the application of gaseous detonation

In order to improve the computational efficiency of a parallel ISAT (in situ adaptive tabulation)-based chemistry acceleration algorithm in the computations of transient, chemically reacting flows, a control strategy is proposed to maintain the sizes of the data tables in the ISAT computations. The table-size control strategy is then combined with a parallel algorithm to simulate two-dimensional gaseous detonation wave propagation. In the computation of 2H2 + O2 detonation, two sets of tests are conducted to identify the size control strategy. In the first set, the maximum total table size (Mtot) summed over all sub-zones is fixed, while the maximum size of the table on each sub-zone (Msin) is varied. In the second set, a fixed Msin is used for all the tables on the sub-zones while Mtot is varied. A maximum speedup ratio of 4.29 is found in the former tests, while 5.52 is found in the latter. Two parameters, σf and p, are proposed to analyze the load balance and synchronization among table operations in the parallel ISAT computations in the above tests. It is found that both load balance and synchronization have clear influences on the speedup ratio. A parameter pM is defined, and a strategy to choose the optimal maximum table sizes (both Mtot and Msin) based on pM is proposed and is verified to be universal in the computations of both 2H2 + O2 detonation and C2H4 + 3O2 detonation. Finally, the parallel acceleration algorithm enhanced with table-size control is shown to be highly accurate for the detonations in both fuels

Evidence for a Complex Relationship Among Weight Retention, Cortisol and Breastfeeding in Postpartum Women

OBJECTIVE: To assess the relationship between cortisol slope, a biologic marker of stress, and postpartum weight retention. METHODS: We included 696 women in a secondary analysis from a multi-site study conducted using principles of community-based participatory research to study multi-level sources of stress on pregnancy outcomes. As a stress marker, we included salivary cortisol slope; the rate of cortisol decline across the day. Pre-pregnancy weight and demographic data were obtained from the medical records. At 6 months postpartum, patients were weighed and returned saliva samples. We built stepwise regression models to assess the effect of demographic variables, cortisol slope and cortisol covariates (wake time, tobacco use and breastfeeding) on postpartum weight retention. RESULTS: 45.5 % of participants were African American, 29.2 % White, and 25.3 % Hispanic. Of the Hispanic women 62.5 % were Spanish speaking and 37.5 % were English speaking. In general, participants were young, multiparous, and overweight. Postpartum, almost half (47.6 %) of women studied retained >10 lbs. In multivariable analysis including age, pre-pregnancy BMI and public insurance, cortisol slope was significantly associated with weight retention (β = −1.90, 95 % CI = 0.22–3.58). However, when the model was adjusted for the cortisol covariates, breastfeeding (β = −0.63, 95 % CI = − 1.01 to −0.24) and public insurance (β = 0.62, 95 % CI = 0.20–1.04) were the two strongest correlates of weight retention. CONCLUSIONS FOR PRACTICE: The association between cortisol slope and postpartum weight retention appears to be influenced breastfeeding status