Causes of Mode Effects: Separating out Interviewer and Stimulus Effects in Comparisons of Face-to-Face and Telephone Surveys

We identify the causes of mode effects in comparisons of face-to-face and telephone surveys, by testing for differences in the extent of satisficing and social desirability bias due to differences in the stimulus (visual vs. aural presentation of response options) and the presence vs. absence of the interviewer. The stimulus did not lead to differential measurement error; the presence or absence of the interviewer however did. Telephone respondents were far more likely to give socially desirable responses than face-to-face respondents when the stimulus was the same for both modes

The Supermassive Black Hole Mass of NGC 4151 from Stellar Dynamical Modeling

The mass of a supermassive black hole (MBH) is a fundamental property that can be obtained through observational methods. Constraining MBH through multiple methods for an individual galaxy is important for verifying the accuracy of different techniques, and for investigating the assumptions inherent in each method. However, there exist only a few galaxies where multiple MBH determination techniques can be applied. NGC 4151 is one of these rare galaxies for which multiple methods can be used, stellar and gas dynamical modeling because of its proximity and reverberation mapping because of its active accretion. In this work, we reduced the integral field unit spectroscopy of the nucleus of NGC 4151 from Onken et al., observed in the H band with Gemini North NIFS, improving the process itself as well as the analysis of the spatially-resolved spectra. We also improved on the methods for constraining the line of sight velocity distribution as a function of position within the nucleus. Stellar dynamical modeling was then performed over a range of choices of MBH and mass-to-light ratio, as well as the de-projected luminosity density for various inclinations. The best reproduction of the observed kinematics and luminosity density was found with MBH = 2.44 +/- 0.16 x 10^7 MSun and mass-to-light ratio = 0.318 +/- 0.003 MSun/LSun and an inclination of 45 degrees. This measurement falls within the range of values in the literature; it is below the reverberation mapping mass of Bentz et al. (3.59 +0.45 -0.37 x 10^7 MSun) and above the reverberation mapping mass of De Rosa et al. (1.97 +/- 0.04 x 10^7 MSun), and within the uncertainties on both the gas dynamical modeling mass of Hicks & Malkan (3.0 +0.8 -2.2 x 10^7 MSun) and the stellar dynamical modeling mass of Onken et al. (3.60 +/- 1.10 x 10^7 MSun). This work also represents a preparatory step in the application of a new bar-optimized stellar dynamical modeling code

Space-time domain decomposition for advection-diffusion problems in mixed formulations

This paper is concerned with the numerical solution of porous-media flow and transport problems , i. e. heterogeneous, advection-diffusion problems. Its aim is to investigate numerical schemes for these problems in which different time steps can be used in different parts of the domain. Global-in-time, non-overlapping domain-decomposition methods are coupled with operator splitting making possible the different treatment of the advection and diffusion terms. Two domain-decomposition methods are considered: one uses the time-dependent Steklov--Poincar{\'e} operator and the other uses optimized Schwarz waveform relaxation (OSWR) based on Robin transmission conditions. For each method, a mixed formulation of an interface problem on the space-time interface is derived, and different time grids are employed to adapt to different time scales in the subdomains. A generalized Neumann-Neumann preconditioner is proposed for the first method. To illustrate the two methods numerical results for two-dimensional problems with strong heterogeneities are presented. These include both academic problems and more realistic prototypes for simulations for the underground storage of nuclear waste

Modelling New Zealand electricity prices from a risk management perspective

A direct approach is taken to modelling New Zealand electricity prices, in which extreme value theory is used to augment a basic time series model. Despite its simplicity, the resulting model is suitable for answering fundamental questions of interest to risk managers, who might not find it worthwhile to apply a more sophisticated and complex approach to statistical modelling