An observational study of maternal models.

Observed 35 mothers in interaction with their 19-mo old infants in seminaturalistic settings. Mothers' modeling techniques, their reinforcements for imitation, and children's imitations were recorded. Imitation and reinforcement for imitation were complexly related; for some children maternal reinforcement appeared to control the amount of imitation, but equally prominent were patterns in which reciprocal or interactive mother-child influences were in evidence. Characteristics of the mother, other than reinforcement of imitation, were positively associated with the child's imitation, particularly the amount of variation and the enthusiasm in the mother's modeling. Interpretations of findings in a seminaturalistic setting and findings from the laboratory are discussed with regard to methodological issues and theories relating to imitative learning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of Hydrostatic Pressure Upon the Relaxation of Birefringence in Amorphous Solids

A study was made of the effect of hydrostatic pressure upon the relaxation of birefringence in two commercial plastics which were glasslike in nature. The birefringence was introduced into the materials by loading in uniaxial compression, and the decay of birefringence with time was measured using a polarimeter. The rate at which the optical path-difference disappeared was greatly inhibited by the hydrostatic pressure, and a pressure of 10,000 bars was found to be sufficient to stop the release completely. The results are interpreted as the effect of hydrostatic pressure upon the mobility of the materials. Some experiments were conducted to determine the effect of temperature upon the relaxation, that the effects of pressure and temperature might be compared.     

Laser glass composition and the possibility of eliminating electrostrictive effects

Many authors have stated that electrostrictive self-trapping of the light beam initiates laser damage in solid transparent dielectrics. By systematically varying composition, it may be possible to find a glass in which electrostrictive effects are eliminated.     

Mechanisms for self-focusing in optical glasses

The relative contributions of the Kerr, electrostrictive, and thermal effects to the self-focusing thresholds of borosilicate crown glass, fused silica, and dense flint glass have been estimated from an analysis of damage-threshold data for linearly polarized and circularly polarized radiation. The measurements were made with a Nd:glass laser operating in the TEM00mode with a temporal pulsewidth of 25 ns. The Kerr effect appears to be the largest effect. The thermal effect is also significant. The electrostrictive effect is smallest. Reasonable values of the absorption coefficient are calculated from the thermal contribution. The results are in qualitative agreement with the work of others.