Catherine Nichols

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Sample size calculations for a group-randomized trial (GRT) require an estimate of the expected intraclass correlation coefficient (ICC). However, few ICC estimates from GRTs in HIV/AIDS research have been published, leaving investigators with little data on which to base expectations. We used data from a multi-country study to estimate ICCs for variables(More)
BACKGROUND Animal models have suggested that undernutrition during gestation and the early postnatal period may adversely affect kidney development and compromise renal function. As a natural experiment, famines provide an opportunity to test such potential effects in humans. We assessed whether exposure to the Chinese famine of 1959-1961 during gestation(More)
BACKGROUND Radical regulations to improve air quality, including traffic control, were implemented prior to and during the 2008 Beijing Olympic Games. Consequently, ambient concentrations of nitrogen dioxide (NO2) and particular matter 10 micrometers or less (PM10), were reduced in a distinct and short window of time, which presented a natural experiment(More)
The causes usually given for not having success with reversible hydrocolloid are that the impression material that goes beyond the subgingival margins often tears on removal and that the syringe material sets too fast. Both of these problems can be overcome and an extremely high rate of success can be obtained by following the technique described.
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