Estrogen, the ovary, and neutotransmitters: factors associated with aging

Our studies in the C57BL/6J mouse have been designed to examine the interactions of aging and the ovary, and their mutual effects on neuroendocrine function. In the pituitary, ovarian status and not age determines responsiveness to gonadotropin hormone releasing hormone (GnRH), but estrogen (E2) is an important mediator in CNS changes, and removal of the ovary (OVX) is deleterious to the neuroendocrine hypothalamus. OVX for just six days in young animals results in synaptic loss between noradrenergic terminals and gonadotropin hormone releasing hormone (GnRH) neurons. Long-term OVX, hypothesized to protect against neuroendocrine aging, fails to guard against any studied age-related changes. Some age-related changes occur as early as midlife. Although neuron number remains constant at middle age, opiatergic neurons undergo significant functional changes by producing opiate antagonist peptides. This change appears to be caused by alterations in the prohormone convertases, which cleave propeptide to peptide. Altered peptides may trigger the loss of reproductive capacity. The midlife shift in opiate peptide production is a component of natural developmental processes that begin in the neonate and continue through old age. In the cholinergic system, E2 mediates numbers of cholinergic receptors, cholinergic neurons, and cholinergic-modulated memory systems in both young and old animals. Regardless of age, ovarian steroids, if present at physiologic levels, are beneficial to the neuroendocrine CNS, and long-term deprivation from ovarian-produced factors is deleterious in the systems we have examined. Our studies have shown that deprivation from ovarian steroid hormones in the female appears to be a major factor in the health of the CNS and in events associated with aging.     

Real-time stress evolution during Si1-xGex Heteroepitaxy: Dislocations, islanding, and segregation

We have used sensitive real-time measurements of film stress during Si_1-xGe_x molecular beam epitaxy to examine strain relaxation due to coherent island formation, and to probe the kinetics of Ge surface segregation. We first describe our novel curvature-measurement technique for real-time stress determination. Measurements of the relaxation kinetics during high temperature Si₇₉Ge₂₁ growth on Si (001) are reported in which formation of highly regular arrays of [501]-faceted islands produce 20% stress relaxation. An island shape transition is also observed that reduces the effective stress by up to 50% without dislocations. Nonuniform composition profiles due to Ge surface segregation during growth of planar alloy films are determined with submonolayer thickness resolution from the real-time stress evolution. Up to two monolayers of Ge can segregate to the growth surface.     

The effects of self-induced mood states on behavior and physiological arousal

The effects of reading emotionally loaded statements on behavioral tasks and physiological measures were investigated. Statements were constructed to arouse elation, depression, or neutrality. Ss were both pre- and posttested on Writing Speed, Reaction Time, Decision Time, and Spontaneous Verbalizations. Base rates were obtained for heart rate and galvanic skin response. Elation Ss significantly outperformed both Neutral and Depression Ss on the Reaction Time task. Scores for Neutral Ss fell between those of Elation and Depression Ss on three of the four behavioral measures. No significant differneces were found on the physiological measures.     

Schlagzähes Polystyrol mit Polyolefinen als Elastomerphase

Modification of polystyrene with certain polyolefins results in product of impact strength if some theoretically derived conditions are fulfilled. With low density polyethylene as soft phase it is demonstrated, how the modification can be reached purpously by grafting, achieving a proper morphology and partial crosslinking. The impact properties of the thus synthesized products generally prove the correctness of the theory. The temperature dependence of the properties gives further insight in the mechanism by which the disperse soft phase effects impact strength. Compared to usual rubbers, polyolefins as soft phase have the advantage of high weatherability, which is also true for ethylene-propylene-terpolymers (EPDM). In the system polystyrene-EPDM optimal modification according to the principles mentioned above results in high weatherability as well as improved impact and tensile properties.