24,502 research outputs found
Structural mechanics of deformation and fracture Quarterly progress report
Structural mechanics of deformation and fracture - responses of model viscoelastic materials to impac
Proton radii of 4,6,8He isotopes from high-precision nucleon-nucleon interactions
Recently, precision laser spectroscopy on 6He atoms determined accurately the
isotope shift between 4He and 6He and, consequently, the charge radius of 6He.
A similar experiment for 8He is under way. We have performed large-scale ab
initio calculations for 4,6,8He isotopes using high-precision nucleon-nucleon
(NN) interactions within the no-core shell model (NCSM) approach. With the
CD-Bonn 2000 NN potential we found point-proton root-mean-square (rms) radii of
4He and 6He 1.45(1) fm and 1.89(4), respectively, in agreement with experiment
and predict the 8He point proton rms radius to be 1.88(6) fm. At the same time,
our calculations show that the recently developed nonlocal INOY NN potential
gives binding energies closer to experiment, but underestimates the charge
radii.Comment: 5 pages, 9 figure
N/P GaAs concentrator solar cells with an improved grid and bushbar contact design
The major requirements for a solar cell used in space applications are high efficiency at AMO irradiance and resistance to high energy radiation. Gallium arsenide, with a band gap of 1.43 eV, is one of the most efficient sunlight to electricity converters (25%) when the the simple diode model is used to calculate efficiencies at AMO irradiance, GaAs solar cells are more radiation resistant than silicon solar cells and the N/P GaAs device has been reported to be more radiation resistant than similar P/N solar cells. This higher resistance is probably due to the fact that only 37% of the current is generated in the top N layer of the N/P cell compared to 69% in the top layer of a P/N solar cell. This top layer of the cell is most affected by radiation. It has also been theoretically calculated that the optimized N/P device will prove to have a higher efficiency than a similar P/N device. The use of a GaP window layer on a GaAs solar cell will avoid many of the inherent problems normally associated with a GaAlAs window while still proving good passivation of the GaAs surface. An optimized circular grid design for solar cell concentrators has been shown which incorporates a multi-layer metallization scheme. This multi-layer design allows for a greater current carrying capacity for a unit area of shading, which results in a better output efficiency
Amino acids precursors in lunar finds
The consistent pattern is discussed of amino acids found in lunar dust from Apollo missions. The evidence indicates that compounds yielding amino acids were implanted into the surface of the moon by the solar wind, and the kind and amounts of amino acids found on the moon are closely similar to those found in meteorites. It is concluded that there is a common cosmochemical pattern for the moom and meteorites, and this offers evidence of a common course of cosmochemical reactions for carbon
Resumming large higher-order corrections in non-linear QCD evolution
Linear and non-linear QCD evolutions at high energy suffer from severe issues
related to convergence, due to higher order corrections enhanced by large
double and single transverse logarithms. We resum double logarithms to all
orders by taking into account successive soft gluon emissions strongly ordered
in lifetime. We further resum single logarithms generated by the first
non-singular part of the splitting functions and by the one-loop running of the
coupling. The resulting collinearly improved BK equation admits stable
solutions, which are used to successfully fit the HERA data at small-x for
physically acceptable initial conditions and reasonable values of the fit
parameters.Comment: 4 pages, 4 figures, based on talk given at Hard Probes 2015, 29 June
- 3 July 2015, Montreal, Canad
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