11,820 research outputs found
Identification and control of spacecraft radiation sources of interference to X-ray and gamma-ray experiments
Apollo 15 and 16 will carry instruments for the purpose of measuring X-ray and gamma ray fluxes from the lunar surface and in cis-lunar space. The intensity levels expected are low over most of the energy range of interest, requiring that background contributions be minimized. The radiation sources on Apollo determined and their interference with these instruments evaluated. The results were used as a basis for dealing with this problem and for recommendations applicable to future manned and unmanned missions
Dual purpose optical instrument capable of simultaneously acting as spectrometer and diffractometer
A dual purpose optical instrument is described capable of simultaneously acting as a spectrometer and diffractometer to respectively perform elemental and structural analysis of an unknown sample. The diffractometer portion of the instrument employs a modified form of Seeman-Bohlin focusing which involves providing a line source of X-rays, a sample, and a detector, all on the same focal circle. The spectrometer portion of the instrument employs a fixedly mounted X-ray energy detector mounted outside of the plane of the focal circle
A Lensed Arc in the Low Redshift Cluster Abell 2124
We report the discovery of an arc-like object 27" from the center of the cD
galaxy in the redshift cluster A2124. Observations with the Keck II
telescope reveal that the object is a background galaxy at ,
apparently lensed into an arc of length \sim 8 \farcs5 and total R magnitude
. The width of the arc is resolved; we estimate it to be
0\farcs6 after correcting for seeing. A lens model of the A2124 core mass
distribution consistent with the cluster galaxy velocity dispersion reproduces
the observed arc geometry and indicates a magnification factor \gta 9. With
this magnification, the strength of the [OII] \lambda 3727 line implies a
star-formation rate of SFR \sim 0.4 h^{-2}\msun yr^{-1}$. A2124 thus appears to
be the lowest redshift cluster known to exhibit strong lensing of a distant
background galaxy.Comment: 6 pages using emulateapj.sty; 4 Postscript figures; Figure 4 uses
color. Accepted for publication, but ApJ Letters' new policy of counting data
images makes the manuscript too long; will appear in main journal. This final
version has minor correction
Addition of a gamma ray spectrometer to the alpha scattering experiment as designed for the Surveyor mission
Gamma ray spectroscopy and alpha scattering techniques for compositional analysis of lunar and planetary surface
Neighbourhood and stand structure affect stemflow generation in a heterogeneous deciduous temperate forest
Rectification in single molecular dimers with strong polaron effect
We study theoretically the transport properties of a molecular two level
system with large electron-vibron coupling in the Coulomb blockade regime. We
show that when the electron-vibron coupling induces polaron states, the
current-voltage characteristic becomes strongly asymmetric because, in one
current direction, one of the polaron state blocks the current through the
other. This situation occurs when the coupling between the polaron states is
smaller than the coupling to the leads. We discuss the relevance of our
calculation for experiments on C_140 molecules.Comment: 4 pages, 4 figure
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