White Dwarfs: Cosmological and Galactic Probes

The emphasis on white dwarf stars and cosmology arises from the most recent advances in cosmological and galactic structure research in which white dwarf stars are playing a very prominent role. Examples are Type Ia supernovae (i.e. white dwarf supernovae), the origin and evolution of the universe, the age of the galactic disk, cosmochronology using white dwarfs in globular clusters and galactic clusters, and the physics of accretion onto compact (very dense) stars. As an assisting guide to the reader, we have included, by invitation, comprehensive review articles in each of the four major areas of the book, white dwarf supernovae, cosmology, accretion physics and galactic structure. The reviews include introductory material that they build upon. The book is suitable and most useful to advanced undergraduates, graduate students and scientific professionals (e.g. astronomers, astrophysicists, cosmologists, physicists)

Searching for Planets with White Dwarf Pulsations: Spurious Detections

We present 13 years of pulsation timing measurements of the DBV white dwarf EC 2005-5234. Each of the four O-C diagrams mimic the sinusoidal behavior typically attributed to a planet + WD system. However, the amplitude and phase of the O-C variations are inconsistent with each other. We discuss the impact of this result on timing based WD planet searches.Comment: Part of PlanetsbeyondMS/2010 proceedings http://arxiv.org/html/1011.660

First Ultraviolet Spectrum of a Brown Dwarf: Evidence for H_2 Fluorescence and Accretion

We analyze an HST/STIS ultraviolet spectrum of the young brown dwarf 2MASSW J1207334-393254, a member of the ten million-year old TW Hya Association that has a planetary-mass companion. We detect and identify numerous emission lines. CIV and other ions are seen that arise in hot gas. We identify a series of lines with Lyman-pumped H_2 molecular lines, indicating that cool gas is also present. Overall, this substellar object shows many of the same characteristics as classical T Tauri stars. We interpret our results as direct evidence of accretion from a circumstellar gas disk, consistent with previous claims. The lack of SiIV emission from the accreting gas indicates that silicon has been depleted into grains.Comment: 8 pages, to appear in Astrophysical Journal Letter

Recognition and Degradation of Plant Cell Wall Polysaccharides by Two Human Gut Symbionts

Competition for nutrients contained in diverse types of plant cell wall-associated polysaccharides may explain the evolution of substrate-specific catabolic gene modules in common bacterial members of the human gut microbiota

Systemic Change in Delaware and Its Use of NASA-Generated Materials

Since the mid-1990s, the State of Delaware has embarked on a program for systemic change which is not unlike the programs followed by other states (Adelman 1998). Professional development has been a key component of this program at all levels. Instead of asking how NASA-generated educational materials can incorporate professional development, this paper turns the question around and asks how a statewide, systemic professional development has used NASA-generated materials. I'll describe such a project. I will draw on this experience to suggest some ways in which curriculum developers like NASA can increase the chances that their materials will see widespread use in statewide systemic reform. In summary, materials which will be useful in K-12 education are those materials which take into account the curriculum frameworks or standards which have been developed in a variety of states. Furthermore, large-scale systemic change takes time. The days of the Lone Ranger approach, where a single individual enters the scene, spends a short time trying to ¯x things, and then leaves, are gone

How some college students represent their understandings of the nature of scientific theories

This study explores college students' representations about the nature of theories during their enrollment in a large astronomy course with instruction designed to address a number of nature of science issues. We focus our investigation on how nine students represent their understanding of theory, how they distinguish between scientific theories and non‐scientific theories, and how they reason about specific theories. Students' notions of theory were classified under four main categories: (1) hypothesis, (2) idea with evidence, (3) explanation, and (4) explanation based on evidence. Students' condition for deciding whether a given idea is a scientific theory or not were classified under six criteria: content domain, convention, evidence, mathematical content, methodology, and tentativeness. Students expressed slight levels of variation between their reasoning about scientific theories in general and specific theories they learned in the course. Despite increased sophistication in some students' representations, this study affirms the complex dimensions involved in teaching and assessing student understanding about theories. The implications of this study underscore the need to explicitly address the nature of proof in science and issues of tentativeness and certainty students associate with scientific theories, and provide students with more opportunities to utilize the language of science