A floating hairpin resonator probe is used to measure electron density within the radiofrequency cycle of a parallel plate capacitively coupled plasma at steady state. A time resolution capable of detecting electron density oscillations within the radiofrequency cycle is demonstrated. Electron density oscillations are observed at the drive frequency over a range of operating conditions including 10-250 mTorr (1.3-33 Pa) in argon driven at 13.56 or 27.12 MHz. Localized electron density oscillation amplitudes show moderate agreement with literature and fluid simulations near the powered electrode and disagreement in the plasma bulk. The technique is useful for studying electron heating mechanisms in radiofrequency discharges due to its high time resolution.

In situ plasma diagnostics present the classical problem of the scientific measurement: how does one accurately measure a system without also perturbing it? The uncertainty in the degree of perturbation then reflects an inherent uncertainty in the diagnostic results. Microwave probes are no exception. This work discusses an experimental methodology for quantifying the local perturbation in hairpin resonator probe measurements. By pulsing the delivered power to a plasma, an electron density hairpin spike (HS) is readily detected at generator shutoff. The phenomenon is understood to arise from an apparent density rise as the plasma sheath collapses, thus raising the spatially averaged density measured between the hairpin tines. Other explanations for the density rise are eliminated, and the utility of the HS is presented. Under the conditions investigated, the HS provides an experimental comparison to a previous sheath correction factor developed by Sands et al.

Electron temperature is measured from time resolved hairpin resonator probe measurements in a pulsed capacitively coupled argon plasma at 400 mTorr. Effective collision frequency is related to the electron energy distribution via the effective conductivity and closes a system of equations that allow electron temperature to be determined. Results generally show good agreement with expected behavior and unfiltered time-resolved optical emission measurements.

The acute administration of the dihydropyridine calcium channel blocker nimodipine has been shown to have a number of benefits with regard to recovery of function following brain injury and the behavioral dysfunctions associated with aging. On the basis of these results, we tested whether the chronic administration of the drug as a dietary supplement might also facilitate the recovery of a learned behavior following neocortical brain injury. The results of an initial investigation using diets containing 300 ppm of nimodipine suggested that this strategy was ineffective in changing the progress of recovery of function. The present report describes a similar paradigm but with an increased concentration of nimodipine in the diet. The results indicated that diets high in nimodipine (1,000 ppm) throughout the experimental procedure, or simply after the neocortical injury, were associated with significant postoperative savings of a preoperatively learned visual discrimination.The acute administration of the dihydropyridine calcium channel blocker nimodipine appears to be beneficial in decreasing the consequences of neocortical injury in young individuals. For example, if nimodipine is administered within 12 h of cerebral ischemia, it will significantly reduce cell loss by preventing calcium overload (see Scriabine, Schuurman, & Traber, 1989, for a review). Additionally, if rats are given nimodipine prior to each day's postoperative retraining, then they will recover a preoperatively learned brightness discrimination with 40 % fewer errors than operated animals not given the drug (LeVere, Brugler, Sandin, & Gray-Silva, 1989).The acute administration of nimodipine would also appear to mitigate certain behavioral dysfunctions that are associated with aging. In this regard, aged, but not young, rabbits will perform better in a trace-conditioning paradigm if given nimodipine than will untreated animals (Deyo, Straube, & Disterhoft, 1989). Furthermore, trial-specific memory is improved in both aged rats (LeVere & Walker, 1991) and aged monkeys (Sandin, Jasmin, & LeVere, 1990) when administered nimodipine prior to testing. Thus the acute administration of this dihydropyridine would seem to be a viable possible treatment strategy for the CNS pathologies associated with both injury and aging.In a somewhat more general behavioral investigation, Schuurman and Traber (1989; also see a review by Scriabine et al., 1989) have reported improvement in aged rats on a number of unlearned behavioral measures when This research was supported by a gift from the Division of Preclinical Pharmacology, Miles Laboratories, to T.E.L.

No abstract