Area judgment from width and height information: the case of the rectangle.

We assessed the effect on performance of shifting from a perceptual area judgment situation, in which the physical quantity to be judged (the area) is present in the stimulus, to a situation in which it is not present in the stimulus. Adults, 9-year-olds, and 5-year-olds were shown combinations of horizontal and vertical lines of various sizes, presented on the same wall or on different walls, and asked to estimate the corresponding area. The following main results were obtained (a) When width and height information items were completely separated, 5- and 9-year-old children gave the same weight to both dimensions in their estimations; (b) when width and height information items were on two different walls, adults gave a greater weight to the larger dimension; (c) when width and height were joined, 9-year-old children gave a greater weight to the larger dimension but when they were separated, they did not.

Chiral separation of basic drugs by capillary zone electrophoresis with cyclodextrin additives.

The enantiomers of a series of basic drugs were separated in capillary zone electrophoresis (CZE) in phosphate buffers, pH 3, containing beta-cyclodextrin or one of its derivatives as chiral selectors and uncoated fused silica capillaries thermostated at 15 degrees C. The nature of the cationic component of the background electrolyte was found to have a significant influence on achiral resolution and peak symmetry. The best results were obtained with triethanolamine, which was then used to adjust the buffer pH in all further experiments. The effects on chiral resolution of the nature and concentration of cyclodextrin, of the addition of methanol, and of capillary temperature were studied. Maximum resolution was obtained at a particular cyclodextrin concentration for each analyte, depending on the affinity of the analyte for this cyclodextrin. On the basis of the results, the effects of methanol addition and temperature on enantiomeric resolution could be explained and predicted. Numerous chiral separations are presented and suggestions for the rapid optimization of CZE enantioseparations with cyclodextrin additives are given.

Influence of hematocrit on tissue O2 extraction capabilities during acute hemorrhage.

This study was performed to test the hypothesis that tissue O2 extraction capabilities during hemorrhage may be greater when hematocrit (Hct) is initially reduced. Twenty-four anesthetized and splenectomized dogs were randomly assigned in three groups of eight dogs each: group 1 (Hct 40), 40-45% Hct; group 2 (Hct 30), 30-35% Hct; and group 3 (Hct 20), 20-25% Hct. In each animal, the desired Hct was obtained by normovolemic hemodilution using hydroxyethyl starch 450/0.7 and maintained throughout the experiment. O2 delivery (DO2) was progressively reduced by hemorrhage. At each step, DO2 and O2 consumption (VO2) were measured separately. Critical DO2 obtained from a plot of VO2 vs. DO2 was lower in the Hct 30 and Hct 20 groups than in the Hct 40 group [(in ml.min-1.kg-1) Hct 30, 7.9 +/- 2.2; Hct 20, 7.8 +/- 1.0; Hct 40, 10.4 +/- 1.1; P < 0.05]. Critical DO2 obtained from blood lactate levels was also significantly lower in the Hct 30 and Hct20 groups than in the Hct 40 group. Critical O2 extraction ratio was also greater in the Hct 30 and Hct 20 groups than in the Hct 40 group (Hct 30, 73.0 +/- 13.9%; Hct 20, 70.1 +/- 9.6%; Hct 40, 57.1 +/- 11.5%; P < 0.05). In the conditions of our study, moderate hemodilution was associated with an improvement of the O2 extraction capabilities of the body, probably related to the reduction in blood viscosity.

The height + width = area of a rectangle rule in five-year-olds: effects of stimulus distribution and graduation of the response scale.

This study attempts to account for disparities between the Anderson and Cuneo (1978), Leon (1982), and Lautrey, Mullet, and Paques (1989) studies in regard to children's area judgment. Two task variables were manipulated: stimulus distribution (biased/unbiased) and the type of response scale (graduated/ungraduated). Three age groups (5, 6, and 7 year olds) were tested. The mean integration pattern for 5-year-olds presented a negatively biased stimulus distribution, and an ungraduated response scale was highly convergent and suggested the use of a centration rule (replication of the Lautrey et al. results). When 5-year-olds were presented with an unbiased stimulus distribution and a graduated scale, the integration pattern was only slightly convergent (as in Leon). The effects of two factors (age and graduation) were significant and combined additively: The older the child, the more graduated the response scale and the more the integration pattern tended to form three ascending parallel lines (the Anderson & Cuneo results).

Judgments of quantity and conservation of quantity: the area of a rectangle.

This study examines the relationships between perceptive judgment of quantity and conservation judgment of quantity with regard to the concept of area. Twenty children who passed an area conservation task (mean age = 8) and 20 children who failed it (mean age = 6, 7) were administered an area judgment task. This task was a replication of Anderson and Cuneo's study (1978, Journal of Experimental Psychology: General, 107, 335-378). The conserving children generally appeared to apply an additive rule (the height and width rule) observed by Anderson and Cuneo in 5 year olds. The nonconserving children in contrast generally presented patterns suggesting centration on one of the two dimensions. The implications for Anderson's and Piaget's conceptions of conservation development are discussed.