A Proposal for the Absolute Estimation Method on Self-loosening of Bolted Joints during Off-road Vehicle Operation

This paper presents a method for estimating the absolute lock effect in bolted joints during off-road vehicle operation. There is a good linear relation between axial tension decrease tendency (Loosening phenomenon) and the operation time (or mileage or number of operations) after the tightening on logarithmic coordinates. Based on this relation, this report leads to two estimating methods described below. 1) Decrease of axial tension (self-loosening) is estimated accurately after long hours since tightening by measuring the initial axial tension behavior using the bolt loosening evaluation diagram. 2) Method of Estimating the locking device availability (usefulness) on actual machine operation is obtained from laboratory loosening test results

Maternal Exposure to Pyrethroid Insecticides during Pregnancy and Infant Development at 18 Months of Age

The possible association between maternal exposure to pyrethroid insecticides (PYRs) during pregnancy and infant development was explored. Levels of exposure to PYRs was assessed by metabolite (3-phenoybenzoic acid, 3-PBA) concentration in maternal spot urine sampled in the first trimester of index pregnancy, and infant development was assessed at 18 months of age using the Kinder Infants Development Scale (KIDS), which is based on a questionnaire to the caretaker. The relationship between KIDS score and maternal urinary 3-PBA levels was examined by a stepwise multiple regression analysis using biological attributes of the mother and infant, breast feeding, and nursing environment as covariates. The analysis extracted 3-PBA and the nursing environment as significant to explain the KIDS score at 18 months of age with positive partial regression coefficients. Inclusion of fish consumption frequency of the mother during pregnancy as an independent variable resulted in the selection of fish consumption as significant, while the two variables were marginally insignificant but still with a positive coefficient with the KIDS score. The result suggested a positive effect of maternal PYR exposure on infant development, the reason for which is not clear, but an unknown confounding factor is suspected