717 research outputs found
Transient conditions for biogenesis on low-mass exoplanets with escaping hydrogen atmospheres
Exoplanets with lower equilibrium temperatures than Earth and primordial
hydrogen atmospheres that evaporate after formation should pass through
transient periods where oceans can form on their surfaces, as liquid water can
form below a few thousand bar pressure and H2-H2 collision-induced absorption
provides significant greenhouse warming. The duration of the transient period
depends on the planet size, starting H2 inventory and star type, with the
longest periods typically occurring for planets around M-class stars. As
pre-biotic compounds readily form in the reducing chemistry of hydrogen-rich
atmospheres, conditions on these planets could be favourable to the emergence
of life. The ultimate fate of any emergent organisms under such conditions
would depend on their ability to adapt to (or modify) their gradually cooling
environment.Comment: 19 pages, 5 figures, accepted for publication in Icaru
The Returned Yank as Site of Memory in Irish Popular Culture
This is the publisher's version, also available electronically from http://journals.cambridge.org/AMSThis article charts conceptual developments in the field of history of women in the Americas over the past forty years since the author began her career. It compares womenâs and gender history and the contributions of key figures such as Joan Scott, Alice Kessler-Harris, and Barbara Welter along with recent developments in the field such as the history of women in the Atlantic world. The article also proposes reasons for the separation of American womenâs history into North American, Latin American, and Caribbean fields
Binge flying: Behavioural addiction and climate change
Recent popular press suggests that âbinge flyingâ constitutes a new site of behavioural addiction. We theoretically appraise and empirically support this proposition through interviews with consumers in Norway and the United Kingdom conducted in 2009. Consistent findings from across two national contexts evidence a growing negative discourse towards frequent short-haul tourist air travel and illustrate strategies of guilt suppression and denial used to span a cognitive dissonance between the short-term personal benefits of tourism and the air travelâs associated long-term consequences for climate change. Tensions between tourism consumption and changing social norms towards acceptable flying practice exemplify how this social group is beginning to (re)frame what constitutes âexcessiveâ holiday flying, despite concomitantly continuing their own frequent air travels
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Draft genome sequence of uncultured upland soil cluster gammaproteobacteria gives molecular insights into high-affinity methanotrophy
Aerated soils form the second largest sink for atmospheric CHâ. A nearcomplete genome of uncultured upland soil cluster Gammaproteobacteria that oxidize CHâ at 2.5 ppmv was obtained from incubated Antarctic mineral cryosols. This first genome of high-affinity methanotrophs can help resolve the mysteries about their phylogenetic affiliation and metabolic potential
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Erratum for Edwards et al., âDraft genome sequence of uncultured upland soil cluster Gammaproteobacteria gives molecular insights into high-affinity methanotrophyâ
Erratum for Edwards et al., âDraft Genome Sequence of Uncultured Upland Soil Cluster Gammaproteobacteria Gives Molecular Insights into High-Affinity Methanotrophyâ
Radiation environment at the Moon: Comparisons of transport code modeling and measurements from the CRaTER instrument
The Cosmic Ray Telescope for the Effects of Radiation (CRaTER), an instrument carried on the Lunar Reconnaissance Orbiter spacecraft, directly measures the energy depositions by solar and galactic cosmic radiations in its silicon wafer detectors. These energy depositions are converted to linear energy transfer (LET) spectra. High LET particles, which are mainly highâenergy heavy ions found in the incident cosmic ray spectrum, or target fragments and recoils produced by protons and heavier ions, are of particular importance because of their potential to cause significant damage to human tissue and electronic components. Aside from providing LET data useful for space radiation risk analyses for lunar missions, the observed LET spectra can also be used to help validate space radiation transport codes, used for shielding design and risk assessment applications, which is a major thrust of this work. In this work the Monte Carlo transport code HETCâHEDS (HighâEnergy Transport CodeâHuman Exploration and Development in Space) is used to estimate LET contributions from the incident primary ions and their charged secondaries produced by nuclear collisions as they pass through the three pairs of silicon detectors. Also in this work, the contributions to the LET of the primary ions and their charged secondaries are analyzed and compared with estimates obtained using the deterministic space radiation code HZETRN 2010, developed at NASA Langley Research Center. LET estimates obtained from the two transport codes are compared with measurements of LET from the CRaTER instrument during the mission. Overall, a comparison of the LET predictions of the HETCâHEDS code to the predictions of the HZETRN code displays good agreement. The code predictions are also in good agreement with the CRaTER LET measurements above 15âkeV/”m but differ from the measurements for smaller values of LET. A possible reason for this disagreement between measured and calculated spectra below 15âkeV/”m is an inadequate representation of the light ion spectra in HETCâHEDS and HZETRN code calculations. It is also clear from the results of this work that Vavilov distributions need to be incorporated into the HETCâHJEDS code before it will be able to recreate the observed LET spectra measured by the CRaTER instrument. Key Points Vavilov corrections should be incorporated into simulated results The predictions of the transport codes reasonably agree with the CRaTER LET The observed LET can be used to help validate space radiation transport codesPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/108081/1/swe20145.pd
Review of Nuclear Physics Experiments for Space Radiation
Human space flight requires protecting astronauts from the harmful effects of space radiation. The availability of measured nuclear cross section data needed for these studies is reviewed in the present paper. The energy range of interest for radiation protection is approximately 100 MeV/n to 10 GeV/n. The majority of data are for projectile fragmentation partial and total cross sections, including both charge changing and isotopic cross sections. The cross section data are organized into categories which include charge changing, elemental, isotopic for total, single and double differential with respect to momentum, energy and angle. Gaps in the data relevant to space radiation protection are discussed and recommendations for future experiments are made
âThere must be a poetry of sound that none of us knowsâŠâ: Early British documentary film and the prefiguring of musique concrĂšte
Standard histories of electronic music tend to trace the lineage of musique concrĂšte as lying mainly in the Futuristsâdeclarations of the 1910s, through Cageâs âemancipationâ of noise in the 1930s, to Schaefferâs work and codifications of the late 1940s and early 1950s. This article challenges this narrative by drawing attention to the work of filmmakers in the 1930s that foreshadowed the sound experiments of Pierre Schaeffer and thus offers an alternative history of their background. The main focus of the article is on the innovations
within documentary film and specifically the sonic explorations in early British documentary that prefigured musique concrĂšte, an area ignored by electronic music studies. The theoretical and philosophical underpinnings of the documentary movementâs members, particularly their leader John Grierson, will be compared with those of Pierre Schaeffer, and the important influence of Russian avant-garde filmmaking on the British (and musique concrĂšte) will be addressed. Case studies will focus on the groundbreaking soundtracks of two films made by the General Post Office Film Unit that feature both practical and theoretical correspondences to Schaeffer: 6.30 Collection (1934) and Coal Face (1935). Parallels between the nature and use of technologies and how this affected creative outputs will also be discussed, as will the relationship of the British documentary movementâs practice and ideas to post-Schaefferian âanecdotal musicâ and the work of Luc Ferrari
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