Child health and the social environment of white and black children

Both poverty and other factors associated with race are related to child health. However, the mechanisms of these relationships have not been adequately specified. The purpose of this study was to explore the relationship of the social environment to child health status in black and white children and further, to explore whether the patterns of the effects of social class were different by race. This study provides further evidence that the social environment is strongly associated with child health status. Several risk factors are similar for both white and black children: mothers who view their own health as fair or poor are much more likely to rate their children in poor health. The presence of childhood chronic medical conditions is independently associated with poor health status regardless of race. However, the relative importance of several social risks for poor health status differs between white and black children. Specifically, while low family income is a consistent risk factor for poor health among white children, low income alone is not a risk factor for black children. Among black children, other social risks that are associated with poverty, such as low maternal education and a mother's perception of her own health as poor, increased the risk of poorer health in the child.     

Determining hearing threshold from brain stem evoked potentials.Optimizing a neural network to improve classification performance

Feed-forward neural networks in conjunction with back-propagation are an effective tool to automate the classification of biomedical signals. Most of the neural network research to date has been done with a view to accelerate learning speed. In the medical context, however, generalisation may be more important than learning speed. With the brain stem auditory evoked potential classification task described in this study, the authors found that parameter values that gave fastest learning could result in poor generalisation. In order to achieve maximum generalisation, it was necessary to fine tune the neural net for gain, momentum, batch size, and hidden layer size. Although this maximization could be time consuming, especially with larger training sets, the authors' results suggest that fine tuning parameters can have important clinical consequences, which justifies the time involved. In the authors' case, fine tuning parameters for high generalisation had the additional effect of reducing false negative classifications, with only a small sacrifice in learning speed     

Inbreeding in Swiss Braunvieh and its influence on breeding values predicted from a repeatability animal model.

Inbreeding coefficients were computed for 910,444 animals of the Swiss Braunvieh population. Of the animals born in 1984, 71.5% were inbred with 67.9, 3.4, and .2% having inbreeding coefficients between greater than 0 and 5%, greater than 5 to 10%, and greater than 10%, respectively. The average inbreeding coefficient was 1.14% but, for animals with both parents and at least one grandparent known, it was 1.67%. Breeding values for total milk, fat, and protein yields and for fat and protein percentages were predicted using a repeatability animal model including a regression on the inbreeding coefficient. Phenotypic performance was sizeably depressed for milk yield only (-26 kg/% of inbreeding or 2.4% of the phenotypic standard deviation). Adjusting for inbreeding increased the estimated genetic trend slightly. Inbreeding is only partially accounted for when it is ignored in the construction of the inverse of the numerator relationship matrix. This effect was investigated by comparing predicted breeding values from a model including the complete matrix with predicted breeding values from a model including a matrix constructed with inbreeding ignored. Only .8% of all predicted breeding values were affected by more than +/- 5.5 kg. The maximum difference observed was 55.3 kg. The observed average absolute differences between the breeding values of offspring predicted with the two models increased with inbreeding of parents.     

IMPROVING THE QUALITY OF TIMBER FROM RED BEECH (N. FOSCA) BY INTERMITTENT DRYING

The effect of cycling the external conditions on the timber quality and drying time during seasoning has been studied for red beech (Nothofagus fusca), a difficult-to-dry New Zealand hardwood, inalaboratorybatchdryer. Intermittent drying at anair temperature of 45°C and a wet-bulb depression of 10°C takes longer to yield a given moisture content than continuous drying under the same conditions, but produces timber without honeycomb or severe case-hardening as observed in continuous drying. The experiments also indicate that the timber can tolerate a higher air temperature (55°C) in intermittent drying at the same wet-bulb depression with less case-hardening and without showing honeycomb compared with continuous drying at 45°C, having a similar total drying time. Intermittent drying at a slightly higher dry-bulb temperature (60°C) and a much higher wet-bulb depression (18°C) gives a similar degree of case-hardening to that found in samples dried continuously at a dry-bulb temperature of 45°C.