RESUMO
Pairs of asteroids sharing similar heliocentric orbits, but not bound together, were found recently. Backward integrations of their orbits indicated that they separated gently with low relative velocities, but did not provide additional insight into their formation mechanism. A previously hypothesized rotational fission process may explain their formation-critical predictions are that the mass ratios are less than about 0.2 and, as the mass ratio approaches this upper limit, the spin period of the larger body becomes long. Here we report photometric observations of a sample of asteroid pairs, revealing that the primaries of pairs with mass ratios much less than 0.2 rotate rapidly, near their critical fission frequency. As the mass ratio approaches 0.2, the primary period grows long. This occurs as the total energy of the system approaches zero, requiring the asteroid pair to extract an increasing fraction of energy from the primary's spin in order to escape. We do not find asteroid pairs with mass ratios larger than 0.2. Rotationally fissioned systems beyond this limit have insufficient energy to disrupt. We conclude that asteroid pairs are formed by the rotational fission of a parent asteroid into a proto-binary system, which subsequently disrupts under its own internal system dynamics soon after formation.
RESUMO
BACKGROUND: A novel nutritional formula (NNF) enriched in eicosapentaenoic (EPA) and gamma-linolenic fatty acids and antioxidants reduces airway inflammation and improves clinical outcomes in critically ill patients, but NNF has not been evaluated in chronic inflammatory diseases such as persistent asthma. OBJECTIVE: To evaluate the efficacy, compliance, and safety of NNF in asthmatic children. METHODS: Children, 6-14 years of age, with mild to moderate persistent asthma, on as needed albuterol alone, were randomized to receive daily NNF (n=23) or control formula (n=20) for 12 weeks, with multiple assessments of asthma control, spirometry, measures of airway inflammation, formula tolerance, and adverse events. RESULTS: Daily consumption of either NNF or a control formula showed improvement in asthma-free days over time (P=0.04) but there was no difference between groups. However, the NNF group had lower exhaled nitric oxide levels compared with the control group at weeks 4, 8, and 12 (P<0.05). An overall group difference in log FEV1 PC20 (P=0.05) was found in favour of the NNF group as well. Significantly higher levels of EPA in plasma (P<0.01) and peripheral blood mononuclear cell (PBMC) (P<0.01) phospholipids in the NNF group compared with control group within 2 weeks indicated good adherence with daily NNF intake. There were no differences in adverse events for NNF vs. control after 12 weeks. CONCLUSIONS: Both NNF and control groups demonstrated improvement in asthma-free days. NNF-treated group had reduced biomarkers of disease activity. Rapid PBMC fatty acid composition changes reflected an anti-inflammatory profile. Dietary supplementation with NNF was safe and well tolerated (ClinicalTrials.gov number NCT01087710).
