Size and shape analysis techniques for design.

A major problem in designing highly specialized equipment such as oxygen masks, respirators, etc, is that the effectiveness of the equipment depends on its appropriateness for the size and shape of the body part for which it is designed. However, in general, among the individuals who are likely to be using this equipment, there is considerable heterogeneity in size and shape of the body parts. One solution is to use the available data to form homogeneous clusters of the population and then make separate designs for each cluster, commonly referred to as sizing. Current sizing practices are hindered by a problem termed 'observer-inherence'; in other words, the positioning and orientation of the reference axis system can affect the size and shape groupings more than size and shape themselves do. The impact of observer-inherence is felt most on systems that require the most stringent fit, such as helmets with optical systems. For such systems, traditional measures and analysis practices can be almost useless. In this paper, an analysis technique is introduced which should be observer-invariant in the three-dimensional case. The method is illustrated using points selected along a horizontal cross-section. The points are first transformed into values called curvatures which are subsequently transformed into a series of Fourier coefficients. These are then used for arriving at shape clusters or groupings. The shape differences (and similarities) within and between clusters are examined graphically and discussed. The technique developed here can be extended to form clusters using the curvatures of a surface instead of that of a cross-section (ie, can be extended to the three-dimensional case) and methods for doing so are discussed.

Relative value of plasma copper, zinc, lipids and lipoproteins as markers for coronary artery disease.

Studies in experimental animals have suggested an association between dietary copper deficiency, alone or with an attendant elevated intake of zinc, and an increase in serum total cholesterol. These findings led some to theorize that a dietary imbalance of zinc and copper may be a factor in the etiology of coronary heart disease. Plasma zinc and copper levels were measured in 60 adult male patients with confirmed coronary artery disease and compared with serum levels of lipids and lipoproteins in the same patients. The results were compared to the accepted values in normal adult males. In subjects with significant coronary artery atherosclerosis (greater than or equal to 50% luminal occlusion) there was no correlation between plasma zinc or copper with serum lipids or lipoproteins. However, total cholesterol was significantly correlated with low density lipoprotein (LDL) cholesterol, triglycerides, and inversely correlated with HDL-C : T-Chol ratio. Although dietary zinc and/or copper may influence the plasma levels of these trace metals, our studies show that there was no association between plasma zinc or copper and the serum levels of lipids or lipoproteins; we believe that this indicates that these trace metals are of doubtful value as markers for coronary atherosclerosis.

Maternal zinc, iron, folic acid, and protein nutriture and outcome of human pregnancy.

Four hundred fifty women were observed during pregnancy and postpartum. Forty-three variables including 12 laboratory indices of maternal nutrient status were assessed. Of the variance in fetal weight and head circumference 9.9 and 8.1%, respectively, were predictable by polynomial stepwise regression of laboratory indices of maternal nutriture. Maternal plasma zinc levels were inversely correlated with fetal weight. The occurrence of pregnancy complications in the highest and lowest quartiles of maternal plasma zinc, albumin, iron, and folic acid were compared. Using data only from the initial blood samples for which the trimester was identified precisely (n = 394), a significant association was found between the total occurrence of fetomaternal complications and zinc and albumin levels in the lowest quartile (zinc, p less than 0.02; albumin, p less than 0.02). Low zinc or low albumin were also associated with the specific complications of fetal distress (zinc, p less than 0.002; albumin p less than 0.002). High plasma folate was also associated with the total occurrence of complications (p less than 0.008) and with fetal distress (p less than 0.002). When all data (n = 713) including repeat blood samples and data from 56 mothers in whom the trimester could not be verified precisely were evaluated, associations between other complications and lowest quartile zinc and albumin and highest quartile folate were identified. Discriminant analysis of data from the initial blood samples revealed that plasma zinc was a discriminator for fetomaternal complications only in women in the lowest quartile for plasma zinc.

Estimation of the number of monoclonal hybridomas in a cell fusion experiment. Effect of post-fusion cell dilution on hybridoma survival.

A practical method is described for the estimation of the number of monoclonal hybridomas in a cell fusion experiment as a function of the percent of culture dishes showing hybridoma growth. Our method is based on the Poisson probability model. A justification for the method is included. The application of this model to our experimental results indicates that the probability of hybridoma survival decreases with post-fusion cell dilution even in the presence of a constant number of feeder cells.