858 research outputs found
Through Astronaut Eyes: Photographing Early Human Spaceflight
Featuring over seventy images from the heroic age of space exploration, Through Astronaut Eyes presents the story of how human daring along with technological ingenuity allowed people to see the Earth and stars as they never had before.
Photographs from the Mercury, Gemini, and Apollo programs tell powerful and compelling stories that continue to have cultural resonance to this day, not just for what they revealed about the spaceflight experience, but also as products of a larger visual rhetoric of exploration. The photographs tell us as much about space and the astronauts who took them as their reception within an American culture undergoing radical change throughout the turbulent 1960s.
This book explores the origins and impact of astronaut still photography from 1962 to 1972, the period when human spaceflight first captured the imagination of people around the world. Photographs taken during those three historic programs are much admired and reprinted, but rarely seriously studied. This book suggests astronaut photography is particularly relevant to American culture based on how easily the images were shared through reproduction and circulation in a very visually oriented society. Space photography’s impact at the crossroads of cultural studies, the history of exploration and technology, and public memory illuminates its continuing importance to American identity.https://docs.lib.purdue.edu/purduepress_previews/1053/thumbnail.jp
Spectropolarimetry of the Deep Impact target comet 9P/Tempel 1 with HiVIS
High resolution spectropolarimetry of the Deep Impact target, comet 9P/
Tempel 1, was performed during the impact event on July 4th, 2005 with the
HiVIS Spectropolarimeter and the AEOS 3.67m telescope on Haleakala, Maui. We
observed atypical polarization spectra that changed significantly in the few
hours after the impact. The polarization of scattered light as a function of
wavelength is very sensitive to the size and composition (complex refractive
index) of the scattering particles as well as the scattering geometry. As
opposed to most observations of cometary dust, which show an increase in the
linear polarization with the wavelength (at least in the visible domain and for
phase angles greater than about 30%, a red polarization spectrum) observations
of 9P/Tempel 1 at a phase angle of 41 degrees beginning 8 minutes after impact
and centered at 6:30UT showed a polarization of 4% at 650 nm falling to 3% at
950 nm. The next observation, centered an hour later showed a polarization of
7% at 650 nm falling to 2% at 950nm. This corresponds to a spectropolarimetric
gradient, or slope, of -0.9% per 1000 Angstroms 40 minutes after impact,
decreasing to a slope of -2.3% per 1000 Angstroms an hour and a half after
impact. This is an atypical blue polarization slope, which became more blue 1
hour after impact. The polarization values of 4% and 7% at 650nm are typical
for comets at this scattering angle, whereas the low polarization of 2% and 3%
at 950nm is not. We compare observations of comet 9P/Tempel 1 to that of a
typical comet, C/2004 Machholz, at a phase angle of 30 degrees which showed a
typical red slope, rising from 2% at 650nm to 3% at 950nm in two different
observations (+1.0 and +0.9% per 1000 Angstroms).Comment: Icarus Deep Impact special issue, accepted Aug 28 200
Structural and electrochemical behaviour of sputtered vanadium oxide films: oxygen non-stoichiometry and lithium ion sequestration
Structural and electrochemical aspects of vanadium oxide films recently reported from ICMCB/ENSCPB have been examined using appropriate structural models. It is shown that amorphous films are nonstoichiometric as a result of pre-deposition decomposition of V2O5. It is proposed that the structure of amorphous films corresponds to a nanotextured mosaic of V2O5 and V2O4 regions. Lithium intercalation into these regions is considered to occur sequentially and determined by differences in group electronegativities. Open circuit voltages (OCV) have been calculated for various stoichiometric levels of lithiation using available thermodynamic data with approximate corrections. Sequestration of lithium observed in experiments is shown to be an interfacial phenomenon. X-ray photoelectron spectroscopic observation of the formation of V3+ even when V5+ has not been completely reduced to V4+ is shown to be entirely consistent with the proposed structural model and a consequence of initial oxygen nonstoichiometry. Based on the structural data available on V2O5 and its lithiated products, it is argued that the geometry of VOn polyhedron changes from square pyramid to trigonal bipyramid to octahedron with increase of lithiation. A molecular orbital based energy band diagram is presented which suggests that lithiated vanadium oxides, LixV2O5, become metallic for high values of x
Near-equivalence of the role of structural unpinning number, basicity and reciprocal average electronegativity in determining the conductivity of glasses
The chemical approach made to investigate the origin of fast ion conduction in Agl-based fast ion conducting (FIC) glasses has been extended to various ionically conducting systems containing Na+ ion. An index known as structural unpinning number (SUN), S, has been defined for this purpose based on the unscreened nuclear charge on the cation and the average electronegativity of all the anions. Variation of the log(conductivity), at a given temperature, as a function of structural unpinning number, optical basicity, λ, and the reciprocal average electronegativity of all the anions, l/χa, has been examined for a number of Na+-ion conducting glasses and a nearly identical variation has been noticed in all the cases. The equivalence of these chemical parameters as determinants of the conductivity behavior of glasses has thus been established and the origin of this equivalence has been discussed
Large-scale Perturbations from the Waterfall Field in Hybrid Inflation
We estimate large-scale curvature perturbations from isocurvature
fluctuations in the waterfall field during hybrid inflation, in addition to the
usual inflaton field perturbations. The tachyonic instability at the end of
inflation leads to an explosive growth of super-Hubble scale perturbations, but
they retain the steep blue spectrum characteristic of vacuum fluctuations in a
massive field during inflation. The power spectrum thus peaks around the
Hubble-horizon scale at the end of inflation. We extend the usual delta-N
formalism to include the essential role of these small fluctuations when
estimating the large-scale curvature perturbation. The resulting curvature
perturbation due to fluctuations in the waterfall field is second-order and the
spectrum is expected to be of order 10^{-54} on cosmological scales.Comment: 10 pages, 4 figures; v2 comments added on application of delta-N
formalism including Hubble scale fluctuation
Mouse Emi2 is required to enter meiosis II by reestablishing cyclin B1 during interkinesis
During interkinesis, a metaphase II (MetII) spindle is built immediately after the completion of meiosis I. Oocytes then remain MetII arrested until fertilization. In mouse, we find that early mitotic inhibitor 2 (Emi2), which is an anaphase-promoting complex inhibitor, is involved in both the establishment and the maintenance of MetII arrest. In MetII oocytes, Emi2 needs to be degraded for oocytes to exit meiosis, and such degradation, as visualized by fluorescent protein tagging, occurred tens of minutes ahead of cyclin B1
Dynamical vs spectator models of (pseudo-)conformal Universe
We discuss two versions of the conformal scenario for generating scalar
cosmological perturbations: a spectator version with a scalar field conformally
coupled to gravity and carrying negligible energy density, and a dynamical
version with a scalar field minimally coupled to gravity and dominating the
cosmological evolution. By making use of the Newtonian gauge, we show that (i)
no UV strong coupling scale is generated below due to mixing with
metric perturbations in the dynamical scenario, and (ii) the dynamical and
spectator models yield identical results to the leading non-linear order. We
argue that these results, which include potentially observable effects like
statistical anisotropy and non-Gaussianity, are characteristic of the entire
class of conformal models. As an example, we reproduce, within the dynamical
scenario and working in comoving gauge, our earlier result on the statistical
anisotropy, which was originally obtained within the spectator approach.Comment: 13 page
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