Molecules in the circumstellar envelope of the evolved carbon-rich star IRC+10216

Modern radio interferometers allow the imaging of spectral line emission over a wide range of frequencies with high angular resolution. In this thesis we present a detailed empirical examination and description of the molecules in the circumstellar envelope (CSE) of the evolved carbon-rich star IRC+10216 between 18 and 40 GHz obtained with the Karl G. Jansky Very Large Array (VLA). The interferometric mapping of the molecular emission in the radio regime has been fairly unexplored for this star. Therefore, this spectral line and imaging survey is an important addition to the studies of IRC+10216. By constraining the molecular spatial distribution, the understanding of the formation and shaping of the observed CSE morphology and the inherent chemistry is greatly improved in the cool (10-500 K) outer CSE. Most detected species are carbon-bearing molecules and are distributed in hollow spheres around the star. We focus on the cyanopolyynes and carbon chains that are the brightest transitions and trace the UV-photon induced chemistry. The substructure of these hollow spheres are shells, arcs, and clumps. With a new automatized procedure, we perform a detailed spatio-kinematical study of the images of the molecular line transitions. This work quantifies the three dimensional physical and chemical structure and substructure of IRC+10216 in unique detail. We find a main molecular shell component at an angular distance of about 15 arcsec (corresponding to ~500 stellar radii) and for the first time constrain a second shell component at 22-23 arcsec from the star. Both components have a thickness of about 4-8 arcsec, so they are mostly resolved. The morphology is non-concentric, non-regular, and has asymmetries with clear differences in the detailed substructure. We qualitatively compare the VLA observations to state-of-the-art chemical models. Overall, we find a good correspondence between the azimuthally averaged data and the models. There are deviations in the substructure within the different image quarters, especially for the carbon chains C4H and C6H. The models do not completely reproduce the observations in a consistent way. Therefore, our VLA data provide excellent material to improve future chemical and radiative transfer models of the CSE of IRC+10216 and of AGB stars in general. With the extracted information on the shell geometry from the VLA data, we are able to perform an approximate physical analysis of the CSE. We estimate molecular column densities and abundances of HC3N and HC5N. Especially for HC5N the results compare well with previous studies. Furthermore, we discuss the effect of a more realistic density structure which includes density-enhanced shells in the circumstellar medium

Planetary nebulae after common-envelope phases initiated by low-mass red giants

It is likely that at least some planetary nebulae are composed of matter which was ejected from a binary star system during common-envelope (CE) evolution. For these planetary nebulae the ionizing component is the hot and luminous remnant of a giant which had its envelope ejected by a companion in the process of spiralling-in to its current short-period orbit. A large fraction of CE phases which end with ejection of the envelope are thought to be initiated by low-mass red giants, giants with inert, degenerate helium cores. We discuss the possible end-of-CE structures of such stars and their subsequent evolution to investigate for which structures planetary nebulae are formed. We assume that a planetary nebula forms if the remnant reaches an effective temperature greater than 30 kK within 10^4 yr of ejecting its envelope. We assume that the composition profile is unchanged during the CE phase so that possible remnant structures are parametrized by the end-of-CE core mass, envelope mass and entropy profile. We find that planetary nebulae are expected in post-CE systems with core masses greater than about 0.3 solar masses if remnants end the CE phase in thermal equilibrium. We show that whether the remnant undergoes a pre-white dwarf plateau phase depends on the prescribed end-of-CE envelope mass. Thus, observing a young post-CE system would constrain the end-of CE envelope mass and post-CE evolution.Comment: Published in MNRAS. 12 pages, 12 figures. Minor changes to match published versio

Learning Theory and Differentiation in Flight Instruction: Perceptions from Certified Flight Instructors

The pilot shortage has reached critical levels. One strategy to minimize the loss of potentially skilled pilots is to focus attention on providing flight instructors with the background knowledge to understand student learning and support student pilots as they progress through flight training programs. Within flight instruction, little or no attention has been focused on the concept of Multiple Intelligences (MI) Theory and its impact on student learning and retention. Consequently, the purpose of this study was to determine if Certified Flight Instructors (CFI) who have been provided with information about MI Theory perceived a positive relationship between their new knowledge about multiple intelligences and their general instructional effectiveness. The study used CFI journals, observations, and individual interviews to determine if instructors perceived MI Theory to be valuable when applied to flight instruction. The results indicated that the participants believed knowledge regarding MI Theory added value to their flight instruction. Implications for practice and directions for future research are provided

Photometry Results for the Globular Clusters M10 and M12: Extinction Maps, Color-Magnitude Diagrams, and Variable Star Candidates

We report on photometry results of the equatorial globular clusters (GCs) M10 and M12. These two clusters are part of our sample of GCs which we are probing for the existence of photometrically varying eclipsing binary stars. During the search for binaries in M10 and M12, we discovered the signature of differential reddening across the fields of the clusters. The effect is stronger for M10 than for M12. Using our previously described dereddening technique, we create differential extinction maps for the clusters which dramatically improve the appearance of the color-magnitude diagrams (CMDs). Comparison of our maps with the dust emissivity maps of Schlegel, Finkbeiner, & Davis (SFD) shows good agreement in terms of spatial extinction features. Several methods of adding an E_{V-I} zero point to our differential maps are presented of which isochrone fitting proved to be the most successful. Our E_{V-I} values fall within the range of widely varying literature values. More specifically, our reddening zero point estimate for M12 agrees well with the SFD estimate, whereas the one for M10 falls below the SFD value. Our search for variable stars in the clusters produced a total of five variables: three in M10 and two in M12. The M10 variables include a binary system of the W Ursa Majoris (W UMa) type, a background RR Lyrae star, and an SX Phoenicis pulsator, none of which is physically associated with M10. M12's variables are two W UMa binaries, one of which is most likely a member of the cluster. We present the phased photometry lightcurves for the variable stars, estimate their distances, and show their locations in the fields and the CMDs of the GCs.Comment: 22 pages, 21 figures, to be published in AJ October 2002. For a higher-resolution version of this paper, please visit http://www.astro.lsa.umich.edu/~kaspar/M10_M12_photometry.ps.gz (gzipped postscript) or http://www.astro.lsa.umich.edu/~kaspar/M10_M12_photometry.pdf (pdf file

Gênero e Gestão Universitária: as Mulheres em Cargos de Chefia nos Quarenta e Dois Anos da Universidade Regional de Blumenau

Durante séculos mulheres foram tratadas de forma desigual, não somente no que se refere à sexualidade, mas também nas questões de política e relações de poder. As mulheres começaram a entrar no mercado de trabalho em condições precárias e com salários inferiores aos dos homens, mesmo ocupando cargos semelhantes. A Universidade Regional de Blumenau (FURB) é um exemplo de organização que adota uma política de igualdade entre gêneros e por isso serviu de local para esta pesquisa, onde se buscou levantar a relação entre as mulheres e as funções gratificadas (cargos de chefia). De forma mais específica, fez-se o levantamento histórico das funções de chefia ocupados por mulheres nesta instituição nos quarenta e dois anos de sua existência, adotando-se o método de pesquisa qualitativo e exploratório, obtendo-se os dados através de levantamento documental no Centro de Memória arquivos, na Divisão de Administração de Recursos Humanos e na INTRANET. Com a pesquisa pode-se visualizar o aumento da quantidade de mulheres ocupando cargos de chefia nas últimas duas décadas, chegando a 46% do total de cargos em 2006. Concluímos que, nesta organização, as mulheres tem espaço para demonstrar o potencial feminino de comando, e que a instituição oferece oportunidades iguais para homens e mulheres, onde benefícios e salários são frutos do esforço individual, independente de questões de gênero