Model filler reinforcement studies by small angle X-ray scattering

Polybutadiene rubbers, filled with polydichlorostyrene or polystyrene latices having spherical diameters of approximately 500Å, were examined by small angle x-ray scattering. The filler latices were examined by x-ray scattering as a function of strain. The sample elongations ranged up to 400 percent. An analysis of the scattering of the polydichlorostyrene filler latices showed that there was deformation of the filler particles up to 25 percent. Such a deformation is not expected on the basis of the mechanical properties of bulk glassy polydichlorostyrene. However, deformation into ellipsoids of revolution is consistent with the x-ray evidence. The deformation of the latices is reasonable.     

Carbachol triggering of desynchronized sleep phenomena: enhancement via small volume infusions

Two physical factors affecting the behavioral effects of drugs microinjected into the pontine tegmentum have been studied. Reducing the volume of vehicle produced a dramatic enhancement of the capacity of the long-acting cholinergic agent carbachol to induce desynchronized (D) sleep-like behavior (Dcarb). Enhancement of Dcarb was also achieved by substitute passive diffusion for active pumping of a given volume of carbachol solution. Controlling these two physical factors makes Dcarb a compelling experimental model for the study of D sleep mechanisms. The results also give support to the concept of a localized population of cholinoceptive neurons in the pontine reticular formation whose activation is a key step in the generation of physiological D.     

The Stiles–Crawford effect: a theoretical revisit

Abstract

In 1973, Snyder and Pask published an explanation of the Stiles–Crawford effect based on optical-waveguide theory, but used only one set of experimental data for comparison. Since then there have been many new experiments and comments on the theory. In this paper we examine the assumptions made in the original theory, introduce some refinements, address some of the comments and examine how well the theory explains the experimental results obtained since 1973. We conclude that the waveguide theory, with some minor improvements, provides the theoretical basis for understanding the Stiles–Crawford effect.     

Specific impairments in self-regulation in children exposed to alcohol prenatally

The present study utilizes a conceptual framework derived from theories of cognition to explain the pattern of behavioral and learning problems observed in subjects with fetal alcohol syndrome (FAS) and fetal alcohol effects (FAE). Based on a modern interpretation of Luria's theory of self-regulation, this study used a neuropsychological test battery to compare 10 subjects (mean age = 13 years) having FAS/FAE with 10 control subjects (mean age = 12 years and 9 months). Subjects with FAS/FAE were relatively high functioning and did not significantly differ from controls with respect to receptive vocabulary. However, those with FAS/FAE exhibited greater difficulty than controls on tasks that involved the manipulation of information and goal management in working memory (e.g., Planning, Controlled Oral Word Association, etc). Both groups performed equally well on some tasks that demanded rule learning (Delayed Response) and response inhibition (Go-No-Go). The above impairments were interpreted to be reflective of selective rather than generalized disruptions of neural networks that subserve working memory.