Competition between Spiral-Defect Chaos and Rolls in Rayleigh-Benard Convection

We present experimental results for pattern formation in Rayleigh-Benard convection of a fluid with a Prandtl number, Pr~ 4. We find that the spiral-defect-chaos (SDC) attractor which exists for Pr~1 has become unstable. Gradually increasing the temperature difference from below to well above its critical value no longer leads to SDC. A sudden jump of temperature difference from below to above onset causes convection to grow from thermal fluctuations and does yield SDC. However, the SDC is a transient; it coarsens and forms a single cell-filling spiral which then drifts toward the cell wall and disappears.Comment: 9 pages(RevTeX), 5 jpg figures, To appear as Rapid Communication in PR

Iodine status during pregnancy in India and related neonatal and infant outcomes

Objective: To document iodine status in Indian pregnancies, associations with maternal diet and demographics, and offspring developmental measures. Design: Longitudinal study following mothers through pregnancy and offspring up to 24 months. Setting: Rural health-care centre (Vadu) and urban antenatal clinic (Pune) in the Maharashtra region of India. Subjects: Pregnant mothers at 17 (n 132) and 34 weeks’ (n 151) gestation and their infants from birth to the age of 24 months. Results: Median urinary iodine concentration (UIC) was 203 and 211 μg/l at 17 and 34 weeks of pregnancy, respectively (range 26–800 μg/l). Using the UIC distribution adjusted for within-person variation, extreme UIC quartiles were compared for predictors and outcomes. There was no correlation between UIC at 17 and 34 weeks, but 24 % of those with UIC in the lowest quartile at 17 weeks had UIC in the same lowest quartile at 34 weeks. Maternal educational, socio-economic status and milk products consumption (frequency) were different between the lowest and highest quartile of UIC at 34 weeks. Selected offspring developmental outcomes differed between the lowest and highest UIC quartiles (abdominal circumference at 24 months, subscapular and triceps skinfolds at 12 and 24 months). However, UIC was only a weak predictor of subscapular skinfold at 12 months and of triceps skinfold at 24 months. Conclusions: Median UIC in this pregnant population suggested adequate dietary provision at both gestational stages studied. Occasional high results found in spot samples may indicate intermittent consumption of iodine-rich foods. Maternal UIC had limited influence on offspring developmental outcomes