Pure iron grains are rare in the universe

The abundant forms in which the major elements in the universe exist have been determined from numerous astronomical observations and meteoritic analyses. Iron (Fe) is an exception, in that only depletion of gaseous Fe has been detected in the interstellar medium, suggesting that Fe is condensed into a solid, possibly the astronomically invisible metal. To determine the primary form of Fe, we replicated the formation of Fe grains in gaseous ejecta of evolved stars by means of microgravity experiments. We found that the sticking probability for formation of Fe grains is extremely small; only several atoms will stick per hundred thousand collisions, so that homogeneous nucleation of metallic Fe grains is highly ineffective, even in the Fe-rich ejecta of Type Ia supernovae. This implies that most Fe is locked up as grains of Fe compounds or as impurities accreted onto other grains in the interstellar medium

Bacterial and fungal bioburden reduction on material surfaces using various sterilization techniques suitable for spacecraft decontamination

Planetary protection is a guiding principle aiming to prevent microbial contamination of the solar system by spacecraft (forward contamination) and extraterrestrial contamination of the Earth (backward contamination). Bioburden reduction on spacecraft, including cruise and landing systems, is required to prevent microbial contamination from Earth during space exploration missions. Several sterilization methods are available; however, selecting appropriate methods is essential to eliminate a broad spectrum of microorganisms without damaging spacecraft components during manufacturing and assembly. Here, we compared the effects of different bioburden reduction techniques, including dry heat, UV light, isopropyl alcohol (IPA), hydrogen peroxide (H2O2), vaporized hydrogen peroxide (VHP), and oxygen and argon plasma on microorganisms with different resistance capacities. These microorganisms included Bacillus atrophaeus spores and Aspergillus niger spores, Deinococcus radiodurans, and Brevundimonas diminuta, all important microorganisms for considering planetary protection. Bacillus atrophaeus spores showed the highest resistance to dry heat but could be reliably sterilized (i.e., under detection limit) through extended time or increased temperature. Aspergillus niger spores and D. radiodurans were highly resistant to UV light. Seventy percent of IPA and 7.5% of H2O2 treatments effectively sterilized D. radiodurans and B. diminuta but showed no immediate bactericidal effect against B. atrophaeus spores. IPA immediately sterilized A. niger spores, but H2O2 did not. During VHP treatment under reduced pressure, viable B. atrophaeus spores and A. niger spores were quickly reduced by approximately two log orders. Oxygen plasma sterilized D. radiodurans but did not eliminate B. atrophaeus spores. In contrast, argon plasma sterilized B. atrophaeus but not D. radiodurans. Therefore, dry heat could be used for heat-resistant component bioburden reduction, and VHP or plasma for non-heat-resistant components in bulk bioburden reduction. Furthermore, IPA, H2O2, or UV could be used for additional surface bioburden reduction during assembly and testing. The systemic comparison of sterilization efficiencies under identical experimental conditions in this study provides basic criteria for determining which sterilization techniques should be selected during bioburden reduction for forward planetary protection

O livro eletrônico como marco evolutivo no contexto da história do livro

Monografia (graduação)—Universidade de Brasília, Faculdade de Ciência da Informação, 2011.Esta pesquisa tem por objetivo conhecer aspectos do livro eletrônico, trazendo abordagens referentes ao mesmo, enquanto marco evolutivo dentro do contexto da História do Livro. Assim, com base em uma pesquisa documental e exploratória, busca-se elucidar aspectos que são mais históricos do que propriamente tecnológicos, os quais incluem o livro eletrônico e seu impacto na sociedade, visando contribuir à caracterização do livro eletrônico como instrumento atual de disponibilização de informação, identificar tendências do livro eletrônico como fruto da trajetória ocorrida ao longo da História do Livro, e contribuir à reflexão sobre o futuro do livro impresso dentro de uma sociedade em constante evolução tecnológica, perpassando ainda por questões referentes ao direito autoral. Para tanto foram utilizadas as fontes de informações tradicionais, livros e periódicos, e ainda os blogs, por ser este um instrumento de comunicação amplamente utilizado para livre expressão de opiniões. Discute por fim a coexistência desses dois meios diante de especulações e embates da diversidade de suportes hoje existentes e dos gostos e preferências pessoais. _________________________________________________________________________ ABSTRACTThis research lens to examine in details electronic book aspects, with it self broach as a evolutionary mark in the context of the book history. Therefore, on the bases of one documentary mark in and exploratory research, it trys to elucidate aspects that are more historical than strictly technological, that includes the electronic book and its impact in the society, aiming to contribute to characterize the electronic book as a current instrument to make the information available, to identify the book electronic trends as a result of the progress along the book history and to help the reflection about the future of the printed book in a society that is in a constant technological changing, and some reasons about copyright . So it has been used traditional information sources: books, periodics, and blogs, because they are communication instruments hard used to the free expression of opinions. It discusses, finally, the coexistence of those two ways, among speculation and chars in the diversity of tastes and personal preferences