Photoionized plasma calculations using laboratory and astrophysical models

We present numerical simulations from the code GALAXY, frequently employed to model the distribution of excitation and ionization, and the spectral emission from laboratory plasma experiments. In particular, preliminary calculations relevant to the Lawrence Livermore National Laboratory photoionization collaboration are presented, along with results which compare GALAXY with results from the astrophysical code CLOUDY

Iron X-ray Transmission at Temperature Near 150 eV Using the National Ignition Facility: First Measurements and Paths to Uncertainty Reduction

Discrepancies exist between theoretical and experimental opacity data for iron, at temperatures 180⁻195 eV and electron densities near 3 × 1022/cm3, relevant to the solar radiative-convective boundary. Another discrepancy, between theory and helioseismic measurements of the boundary’s location, would be ameliorated if the experimental opacity is correct. To address these issues, this paper details the first results from new experiments under development at the National Ignition Facility (NIF), using a different method to replicate the prior experimental conditions. In the NIF experiments, 64 laser beams indirectly heat a plastic-tamped rectangular iron-magnesium sample inside a gold cavity. Another 64 beams implode a spherical plastic shell to produce a continuum X-ray flash which backlights the hot sample. An X-ray spectrometer records the transmitted X-rays, the unattenuated X-rays passing around the sample, and the sample’s self-emission. From these data, X-ray transmission spectra are inferred, showing Mg K-shell and Fe L-shell X-ray transitions from plasma at a temperature of ~150 eV and electron density of ~8 × 1021/cm3. These conditions are similar to prior Z measurements which agree better with theory. The NIF transmission data show statistical uncertainties of 2⁻10%, but various systematic uncertainties must be addressed before pursuing quantitative comparisons. The paths to reduction of the largest uncertainties are discussed. Once the uncertainty is reduced, future NIF experiments will probe higher temperatures (170⁻200 eV) to address the ongoing disagreement between theory and Z data

To Zap or Not to Zap: A Study of the Determinants of Channel Switching During Commercials

We present a conceptual framework to describe the commercial zapping phenomenon and use it to identify factors that influence channel switching during commercials. Drawing on previous research, published reports of practitioner gut feel, interventions used by advertisers to reduce channel switching, and proprietary studies reported in the published literature, we describe how these variables might potentially affect the decision to zap a commercial. We use a latent class approach to model the impact of the identified factors on two aspects of the switching decision—whether or not a commercial is zapped (modeled with a binary logit model) and, conditional on a zap having taken place, the number of seconds that the commercial was watched before being zapped (modeled within the proportional hazards framework). The model is estimated on telemeter data on commercial viewing in two categories (spaghetti sauce and window cleaners) obtained from a single-source, household scanner panel. The results from the empirical analysis show that households can be grouped into two segments. The first, which consists of about 35% of households in the sample, is more zap-prone than the second. For this “zapping segment,” the probability of zapping a commercial is lower for households who make more purchases in the product category. Also, zapping shows a J-shaped response to previous exposures to the commercial, with the associated zapping elasticity reaching its minimum value at around 14 exposures and increasing rapidly thereafter. This finding suggests that advertisers should be cautious not to use media schedules that have excessive media weight or that emphasize frequency over reach. We found that zapping probabilities for ads aired around the hour and half-hour marks to be significantly higher than for other pod locations. Based on these results, we argue that prices for advertising pods located around the hour/half-hour marks should be between 5% to 33% lower than those in the remaining portion of the program. We explore the impact of advertising content on zapping and find that the presence of a brand differentiating message in a commercial causes a statistically significant decrease in zapping probabilities. While the magnitude of this effect is small, the finding suggests that it may be helpful to include qualitative variables in future models of advertising response. We propose the expected proportion of time that an ad is watched as a benchmark to compare 15-second and 30-second ad formats from a zapping standpoint. We found no significant differences between the two formats on this dimension. Our analysis also shows that, due to the impact of previous exposures on zapping, the use of 15-second ads runs a greater risk of reaching the threshold exposure level beyond which zapping probabilities start to increase. This implies that while managers must be cognizant of the risks of overexposure for any ad, it is especially important in the case of the shorter, 15-second ad format.Advertising and Media, Econometric Modeling, Zapping, Single-source data analysis