User's guide to programming fault injection and data acquisition in the SIFT environment

Described are the features, command language, and functional design of the SIFT (Software Implemented Fault Tolerance) fault injection and data acquisition interface software. The document is also intended to assist and guide the SIFT user in defining, developing, and executing SIFT fault injection experiments and the subsequent collection and reduction of that fault injection data. It is also intended to be used in conjunction with the SIFT User's Guide (NASA Technical Memorandum 86289) for reference to SIFT system commands, procedures and functions, and overall guidance in SIFT system programming

Radiative instabilities in simulations of spherically symmetric supernova blast waves

High-resolution simulations of the cooling regions of spherically symmetric supernova remnants demonstrate a strong radiative instability. This instability, whose presence is dependent on the shock velocity, causes large-amplitude fluctuations in the shock velocity. The fluctuations begin almost immediately after the radiative phase begins (upon shell formation) if the shock velocity lies in the unstable range; they last until the shock slows to speeds less than approximately 130 km/s. We find that shock-velocity fluctuations from the reverberations of waves within the remnant are small compared to those due to the instability. Further, we find (in plane-parallel simulations) that advected inhomogeneities from the external medium do not interfere with the qualitative nature of the instability-driven fluctuations. Large-amplitude inhomogeneities may alter the phases of shock-velocity fluctuations, but do not substantially reduce their amplitudes.Comment: 18 pages text, LaTeX/AASTeX (aaspp4); 10 figures; accepted by Ap

Life After Being a Pathology Department Chair III: Reflections on the "Afterlife".

The Association of Pathology Chairs Senior Fellows Group provided reflections on activities that have kept them engaged and inspired after stepping down as chair. They offered advice to current chairs who were considering leaving their positions and also to individuals contemplating becoming pathology chairs. A majority (35/41) responded: 60% maintained teaching/mentoring activities; 43% engaged in hobbies; 40% took other administrative positions including deans, medical center chief executive officers, and residency program directors; 31% continued research; 28% wrote books; 20% performed community service; 14% led professional organizations; 14% developed specialized programs; 11% engaged in clinical service; and 11% performed entrepreneurial activities. Most individuals had several of these activities. One-third indicated that those considering becoming chair should be able to place faculty and department needs before their own. One-fourth emphasized the need to know why one wants to become chair, the need to develop clear goals, and the need to know what one wants to accomplish as chair before applying for and accepting the position. More than half (57%) indicated that before stepping down as chair, one should have a clear plan and/or professional goals that can be served by stepping down. Some even suggested that this be in place before applying for the chair. Almost two-thirds (63%) indicated they had no regrets stepping down as chair. These findings may be valuable to those contemplating stepping down from or stepping into any department chair position or other academic leadership role

Regarding the Correlation of Nuclear Spin Relaxation and Electrical Conductivity Relaxation in Ionic Glasses

Much attention has been focused recently on the apparent differences between ion dynamics in ion-containing glasses as probed by electrical conductivity relaxation (ECR) and by nuclear spin relaxation (NSR) techniques. In both relaxation processes, a power law frequency dependence is observed. Based upon fluctuation-dissipation arguments, the power law exponents should be equivalent. However, experimentally, it appears that the conductivity exponent is generally smaller than the NSR exponent. While an explanation for this discrepancy based upon fundamental differences in the correlation functions probed by the two techniques has been proffered, we show how this discrepancy may simply arise from differing analyses of the ac conductivity. We review several cases taken from the literature in which the conductivity exponent was obtained from analysis of the electrical modulus. We demonstrate how this analysis approach generally underestimates the conductivity exponent. When we instead determine the exponent directly from the ac conductivity, we find near equivalence between the NSR and ECR exponents

A molluscan paleocommunity: A speculative model for an east-west trending, shallow-marine miocene shelf, Navidad, Chile

A subtropical Miocene marine molluscan community is developed from the fossil shells collected by Dr. William J. Zinsmeister. The shells were collected from locations along the coastal and inland areas surrounding Navidad, Chile. The exposed sediments of Navidad are early to middle Miocene in age. Cecioni (1978, 1980) records, from well logs and observations, that sediments had accumulated since the Cretaceous period. Their deposition closely follows the major Andean uplift at the close of the Cretaceous period. The bathymetric and sedimentary trends that seem apparent, when the molluscan paleocommunity is developed, point to Navidad as marking an east-west trending, shallow-marine shelf and offshore island complex that turns southward to the east of Navidad.No embarg

Two Contributions to the Ac Conductivity of Alkali Oxide Glasses

Although the frequency dependent conductivity of ion-containing glasses often displays scale invariant power law dispersion at high temperatures, the exponent increases to unity at lower temperatures. We report measurements of the conductivity of a series of alkali metaphosphate glasses including a mixed alkali composition and demonstrate that this temperature dependence results from the superposition of two power law dispersions originating from separate mechanism, and does not indicate any intrinsic change in scaling of the process which dominates at high temperatures. © 1995 The American Physical Society

Anomalous-diffusion Model of Ionic Transport in Oxide Glasses

The power-law frequency dependence of both the conductivity, (), and permittivity, (), of ion-conducting materials suggests that self-similar or scale-invariant behavior influences the transport of ions at high frequencies. Using an anomalous-diffusion model, we derive relevant power-law expressions for () and () and compare these with measurements performed on LiPO3 glass. Superior fits to the measured data are obtained compared to the commonly used Kohlrausch-Williams-Watts (KWW) description of the electrical modulus, most particularly in the notorious high-frequency regime. Evaluation of our results in terms of an anomalous-diffusion model suggests the dominance of interaction-based constraints to diffusion. © 1995 The American Physical Society

Scaling Parallels in the Non-Debye Dielectric Relaxation of Ionic Glasses and Dipolar Supercooled Liquids

We compare the dielectric response of ionic glasses and dipolar liquids near the glass transition. Our work is divided into two parts. In the first section we examine ionic glasses and the two prominent approaches to analyzing the dielectric response. The conductivity of ion-conducting glasses displays a power law dispersion σ(ω)∞ωn, where n≈0.67, but frequently the dielectric response is analyzed using the electrical modulus M*(ω) = 1/ε*(ω), where ε*(ω) = ε(ω) - iσ(ω)/ω is the complex permittivity. We reexamine two specific examples where the shape of M*(ω) changes in response to changes in (a) temperature and (b) ion concentration, to suggest fundamental changes in ion dynamics are occurring. We show, however, that these changes in the shape of M*(ω) occur in the absence of changes in the scaling properties of σ(ω), for which n remains constant. In the second part, we examine the dielectric relaxation found in dipolar liquids, for which ε*(ω) likewise exhibits changes in shape on approach to the glass transition. Guided by similarities of M*(ω) in ionic glasses and ε*(ω) in dipolar liquids, we demonstrate that a recent scaling approach proposed by Dixon and co-workers for ε*(ω) of dipolar relaxation also appears valid for M*(ω) in the ionic case. While this suggests that the Dixon scaling approach is more universal than previously recognized, we demonstrate how the dielectric response can be scaled in a linear manner using an alternative data representation