Resolving an anomaly between measured spectral linewidths of n=3 transitions in N II and O III spectra.

A reported anomaly in the experimental scaling of the widths of Stark broadened n=3, Delta n=0 spectral lines along the carbon isoelectronic sequence is not observed in the present experiments. The ratio omega(N)/omega(O) of widths for N II lines compared to those for the narrower O III lines for the same transitions is now measured as lying between two theoretical predictions, both of which show a value omega(z-1)/omega(z) greater than unity continuing throughout the sequence. In the earlier measurements, the widths (in frequency units) were actually measured as being smaller for N II than for O III, i.e., a ratio omega(z-1)/omega(z) less than unity.

Charge-exchange-induced two-electron satellite transitions from autoionizing levels in dense plasmas.

Order-of-magnitude anomalously high intensities for two-electron (dielectronic) satellite transitions, originating from the He-like 2s(2) 1S0 and Li-like 1s2s(2) (2)S(1/2) autoionizing states of silicon, have been observed in dense laser-produced plasmas at different laboratories. Spatially resolved, high-resolution spectra and plasma images show that these effects are correlated with an intense emission of the He-like 1s3p 1P-1s(2) 1S lines, as well as the K(alpha) lines. A time-dependent, collisional-radiative model, allowing for non-Maxwellian electron-energy distributions, has been developed for the determination of the relevant nonequilibrium level populations of the silicon ions, and a detailed analysis of the experimental data has been carried out. Taking into account electron density and temperature variations, plasma optical-depth effects, and hot-electron distributions, the spectral simulations are found to be not in agreement with the observations. We propose that highly stripped target ions (e.g., bare nuclei or H-like 1s ground-state ions) are transported into the dense, cold plasma (predominantly consisting of L- and M-shell ions) near the target surface and undergo single- and double-electron charge-transfer processes. The spectral simulations indicate that, in dense and optically thick plasmas, these charge-transfer processes may lead to an enhancement of the intensities of the two-electron transitions by up to a factor of 10 relative to those of the other emission lines, in agreement with the spectral observations.

Evaluation of a Short-term Rat Proximal Tubule Incubation System for the Detection of Nephrotoxicants.

Many nephrotoxic agents act primarily on proximal tubule cells. Accordingly, the optimal conditions for isolating rat proximal tubule fragments by a collagenase digestion technique and their short-term maintenance have been defined, and the viability of the preparation and its sensitivity to toxicants have been determined. Tubular fragment viability was maintained in incubation for up to 6 hours, as assessed by measuring lactate dehydrogenase leakage, levels of intracellular glutathione, and ATP content. In addition, tubular transport function was maintained, as determined by measuring the uptake of p-aminohippuric acid and α-methylglucose, which could be blocked by the selective inhibitors, probenecid and phloridzin, respectively. In this study, the toxicities of allyl alcohol, cephalosporins and cisplatin to proximal tubular fragments were investigated. Allyl alcohol toxicity was greater in tubular fragments isolated from female rats than in those from male rats. Cephaloridine was toxic, while cephalexin and cephalothin were not. These features were consistent with the known in vivo responses to these agents. Toxicity was evident after exposure to cisplatin, with an early reduction in tubular transport being noted. The results highlight the potential of the system described for the isolation and incubation of rat proximal tubule fragments to study xenobiotic-mediated nephrotoxicity. This system could be of benefit in the high-throughput toxicity screening of novel therapeutic agents.

Extended plasma source for short-wavelength amplifiers.

An elongated plasma of length approximately 8 mm with an aspect ratio of ~6:1 has been formed by channeling a laser-produced plasma created in a point focus on a carbon surface. Densities of C(6+) ions near 10(16) cm(-3) were observed in a contracted region beyond the guiding channel, suggesting a use for short-wavelength amplification.

Gunshot and fragment wounds of the metacarpus.

Based on a study of 120 gunshot and fragment wounds of the metacarpus, we conclude that these wounds should be debrided and subjected to delayed closure technics. Even relatively low-velocity missiles may cause serious damage. Metacarpal stabilization with Kirschner wires may be done with impunity to obtain proper alignment, rotation, apposition, and length, in that order of priority. Immediate muscular activity is beneficial. Reconstructive procedures must be individualized to each case and should be considered technically difficult to perform.

Extension of 3p ? 3s ion lasers into the vacuum ultraviolet region.

The feasibility of extending existing near-ultraviolet ion lasers into the vacuum ultraviolet spectral region is analyzed with a simplified three-state model. Single-pass amplification in a laser-produced plasma of reasonable length, pump power, and rise-time requirements is predicted, especially for high electron temperatures. The results are intended to serve as a basis and incentive for detailed numerical modeling and for experiments.

Quasi-stationary population inversion on Kalpha transitions.

In a search for an x-ray laser capable of operating in a quasi-cw mode, a suggested Kalpha-innershell scheme is examined using recently calculated rates. This scheme involves the decay of a K-shell vacancy followed by a more rapid (for certain elements) L-vacancy decay, which maintains the inversion. The present analysis indicates that the scheme is only marginally feasible unless a depletion of resonant absorbers is accomplished through line shifts associated with multiple ionization following K-vacancy production. The pumping requirements for overcoming photoionization losses in the beam and the associated gain conditions are estimated for three elements, namely silicon, calcium, and copper, and it is concluded that photoionization pumping in a selective energy band is required, with emission approaching the blackbody level. A multiline heavy-ion plasma source is suggested.

Plasma spectroscopy in the vacuum ultraviolet and soft X-ray regions.

Techniques involved in the spectroscopy of pulsed plasma sources in the vacuum ultraviolet and soft x-ray spectral regions are described in connection with recent developments in a high temperature plasma physics program. The time-integrated spectrum between 15 A and 1800 A has been analyzed using semiautomatic computer techniques for the grazing incidence portion. Time resolved absolute intensity measurements of 0 iii- O viii ion lines are described as related to recent results on energy losses and impurity content, as well as excitation rate coefficients. Broadband measurements of x-ray continuum radiation with four simultaneous detection channels are also described, and typical results of computer calculations necessary for the interpretation in terms of electron temperature are included.