1,329 research outputs found
Modeling the microstructural evolution during constrained sintering
A numerical model able to simulate solid-state constrained sintering is
presented. The model couples an existing kinetic Monte Carlo (kMC) model for
free sintering with a finite element model (FEM) for calculating stresses on a
microstructural level. The microstructural response to the local stress as well
as the FEM calculation of the stress field from the microstructural evolution
is discussed. The sintering behavior of a sample constrained by a rigid
substrate is simulated. The constrained sintering results in a larger number of
pores near the substrate, as well as anisotropic sintering shrinkage, with
significantly enhanced strain in the central upper part of the sample surface,
and minimal strain at the edges near the substrate. All these features have
also previously been observed experimentally.Comment: 9 pages, 7 figure
Halo independent comparison of direct dark matter detection data
We extend the halo-independent method of Fox, Liu, and Weiner to include
energy resolution and efficiency with arbitrary energy dependence, making it
more suitable for experiments to use in presenting their results. Then we
compare measurements and upper limits on the direct detection of low mass
( GeV) weakly interacting massive particles with spin-independent
interactions, including the upper limit on the annual modulation amplitude from
the CDMS collaboration. We find that isospin-symmetric couplings are severely
constrained both by XENON100 and CDMS bounds, and that isospin-violating
couplings are still possible at the lowest energies, while the tension of the
higher energy CoGeNT bins with the CDMS modulation constraint remains. We find
the CRESST II signal is not compatible with the modulation signals of DAMA and
CoGeNT.Comment: version slightly longer than the first, with 3 additional figures and
the latest XENON100 bound added. 7 pages, 5 figure
Identification of OSSO as a near-UV absorber in the Venusian atmosphere
The planet Venus exhibits atmospheric absorption in the 320–400 nm wavelength range produced by unknown chemistry. We investigate electronic transitions in molecules that may exist in the atmosphere of Venus. We identify two different S_2O_2 isomers, cis-OSSO and trans-OSSO, which are formed in significant amounts and are removed predominantly by near-UV photolysis. We estimate the rate of photolysis of cis- and trans-OSSO in the Venusian atmosphere and find that they are good candidates to explain the enigmatic 320–400 nm near-UV absorption. Between 58 and 70 km, the calculated OSSO concentrations are similar to those of sulfur monoxide (SO), generally thought to be the second most abundant sulfur oxide on Venus
Dansk Planteforædlingsvirksomhed.
Dansk Planteforædlingsvirksomhed
Landhusholdningsselskabets største sølvbæger tildelt.
Landhusholdningsselskabets største sølvbæger tildelt
Planteforædlingsarbejdets Opgaver og Muligheder.
Planteforædlingsarbejdets Opgaver og Muligheder
Relic Abundance of Asymmetric Dark Matter
We investigate the relic abundance of asymmetric Dark Matter particles that
were in thermal equilibrium in the early universe. The standard analytic
calculation of the symmetric Dark Matter is generalized to the asymmetric case.
We calculate the asymmetry required to explain the observed Dark Matter relic
abundance as a function of the annihilation cross section. We show that
introducing an asymmetry always reduces the indirect detection signal from WIMP
annihilation, although it has a larger annihilation cross section than
symmetric Dark Matter. This opens new possibilities for the construction of
realistic models of MeV Dark Matter.Comment: 20 pages, 11 figures, Accepted by JCA
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