Influence of the controlled rheology process (vis-breaking) on additive effectiveness in polypropylene

Controlled rheology or VIS-breaking is the process whereby polypropylene, peroxide, and other additives such as stabilizers are extruded to simultaneously shorten polymer chain length by chemical action of the peroxide and to blend in additives. Although the influence of additives on the VIS-breaking process has been studied, little attention has been paid to the role of additives present during VIS-breaking on the final resin properties. The effectiveness of a light mineral oil used as a costabilizer for radiation resistance and Irgafos 168 as a melt stabilizer was determined in polypropylene resins prepared with different peroxide levels. It was found that exposure of Irgafos 168 to peroxide during the VIS-breaking process did not hinder the action of Irgafos 168 as a melt stabilizer during injection molding. At low levels of peroxide, the presence of oil led to an improvement of radiation resistance compared to resins that contained no oil. However, at higher peroxide levels, oil-containing resins showed less resistance to radiation than did those without oil. These results were interpreted as an interaction of peroxide with the function of oil in the final resins. © 1994 John Wiley & Sons, Inc.     

Alterations in the balance of protein kinase/phosphatase activities parallel reduced synaptic strength during aging

The current research examined the regulation of synaptic strength by protein phosphorylation during aging. Bath application of the protein phosphatase 1 and 2A (PP1 and PP2A) inhibitor calyculin A (1 microM) enhanced CA3-CA1 synaptic strength in hippocampal slices from aged male (20-24 mo) but not from young adult male (4-6 mo) Fischer 344 rats. Similarly, injection of the PP1 and PP2A inhibitor microcystin-L,R (5 microM) into CA1 cells caused an increase in the intracellular synaptic response only in slices from aged rats. In contrast, bath application of the serine/threonine kinase inhibitor H-7 (10 microM) induced a decrease in synaptic strength only in slices from the young adult group. These results demonstrate that phosphorylation dependent regulation of intrinsic synaptic efficacy changes during aging.     

A novel phosphatidylinositol-3,4,5-trisphosphate 5-phosphatase associates with the interleukin-3 receptor

To gain insight into the intracellular signaling cascades that are activated by the binding of interleukin-3 (IL-3) to its target cells, we have embarked on the identification of proteins that are associated with the IL-3 receptor (IL-3R). In a previous study we reported that a 110-kDa serine/threonine protein kinase is constitutively associated with the IL-3R and activated following IL-3 stimulation. We now report that a phosphatidylinositol-3,4, 5-trisphosphate (PtdIns-3,4,5-P3) 5-phosphatase (5-ptase) is also constitutively associated with the IL-3R. This 5-ptase is magnesium-dependent and removes the 5-position phosphate from PtdIns-3,4,5-P3 but does not metabolize PtdIns-4,5-P2, inositol (Ins)-1,3,4,5-P4, or Ins-1,4,5-P3. This substrate specificity distinguishes it from any previously characterized 5-ptase. Interestingly, it may be bound indirectly via phosphatidylinositol 3-kinase (PI 3-kinase), another enzyme that is constitutively bound to the IL-3R. However, unlike PI 3-kinase which becomes activated following IL-3 stimulation, this receptor-associated 5-ptase activity does not increase following IL-3 stimulation, and its primary function may be to keep the principal in vivo product of PI 3-kinase, PtdIns-3,4,5-P3, at low levels in unstimulated cells, to terminate the PI 3-kinase signal following IL-3 stimulation or to metabolize PtdIns-3,4,5-P3 to a metabolically active second messenger, i.e. PtdIns-3,4-P2.     

Improving Predictive Accuracy with a Combination of Human Intuition and Mechanical Decision Aids

This study examines the intuitive combination of human judgment and mechanical prediction under varied information conditions. As expected, mechanical prediction outperformed human intuition when based on the same information, but a combined approach was best when judges had access to relevant information not captured by the model (information asymmetry). The model was useful for differentiating between the event outcomes (improved slope), while eliminating the bias caused by base-rate neglect. Human intuition was useful for incorporating relevant information outside the scope of the model, resulting in improved slope and reduced judgment scatter. The addition of irrelevant information was detrimental to judgment accuracy, causing an increase in bias and a reduction in slope. These results provide insight into how and when combining mechanical prediction and human intuition is likely to result in improved accuracy. Copyright 1998 Academic Press.     

Critical issues in mental health service delivery: what are the priorities?

The director, one other professional, and one para-professional in 515 community mental health centers and 193 state hospitals throughout the United States were asked to rate 57 critical issues in mental health services as to their importance now and five years from now. Issues judged most important now are services for children and for adolescents; five years from now children's services still top the list. Answers to two other questions revealed that respondents placed research on prevention at the top of a list of needed research areas, and that the most useful NIMH service to agencies was person-to-person assistance such as consultation and workshops.     

A nonlinear elastic constitutive model for coated fabrics

A nonlinear elastic constitutive model for coated fabrics is developed. The model which accounts for the basic mechanisms of yarn rotation, yarn extension and coating extension is obtained by expressing the equations of equilibrium for a unit cell of the material in terms of effective continuum stresses and strains. A systematic method of determining the model parameters is proposed. Based on the parameters obtained from a single biaxial test, theoretical curves are plotted for various biaxial loading states and compared with experimental results for several commercially available structural fabrics.     

The use of the high voltage electron microscope to simulate fast neutron-induced void swelling in metals

Electron irradiation with the beam of a high voltage electron microscope can be used to produce void growth in metals, simulating the effect of high dose neutron irradiation. The advantages of the technique are the high dose rate, the relative simplicity of electron irradiation and the ability to make observations during irradiation. Problems of determining the vacancy creation rate are discussed. Secondary displacements are not important for 1 MeV electron irradiation of nickel or iron.