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Simple and light-weighted quasi-zero stiffness (QZS) isolators can be designed based on nonlinear and negative stiffness generated by the snap-through effect of bistable structures. Traditionally, the snap-through force of the bistable structure is limited which makes the weight which can be isolated based on this mechanism very low. This paper investigates increasing loading capacity of this kind of isolator by using an optimized and varying sectional profile. Numerical models were derived for the bistable structures with variable sectional distributions. Optimized sections' alignment of the bistable beam was derived based on the numerical model which was consequently validated by experimental results. Influences of the bistable beams with a variable section on nonlinear stiffness characteristics and performance of the isolator were at last investigated with the harmonic balance method. [ABSTRACT FROM AUTHOR]

Smoking has been associated with depression in the general population. Whether passive smoking is also associated with postpartum depression (PPD) is uncertain. From 2010 to 2012, we recruited 8,842 pregnant women in Tianjin, China. The mainland Chinese version of the Edinburgh Postnatal Depression Scale was used to evaluate postpartum depressive symptoms after birth, with a score of >9 defining PPD. Data were collected using specially designed questionnaires or data from the electronic database of Tianjin Maternal and Child Health Information System. Odds ratios (OR) and 95 percent confidence intervals (CI) were obtained for the association of smoking status with PPD using binary logistic regression. Passive smoke exposure rates before and during pregnancy were 40.9 percent and 52.1 percent, respectively. A total of 8.5% (n = 747) of participants had PPD. Compared with those not exposed, women passively exposed to smoke before and during pregnancy had higher odds of PPD (before pregnancy: OR: 1.24, 95 percent CI: 1.03-1.50; during pregnancy: OR: 1.43, 95 percent CI: 1.16-1.77) after adjustment for confounding factors. Passive smoking before and during pregnancy were associated with PPD in Chinese women. Reducing passive smoke exposure may reduce PPD in Chinese women; further longitudinal studies are warranted to replicate these findings. [ABSTRACT FROM AUTHOR]