112,499 research outputs found
A preliminary study of ester oxidation on an aluminum surface using chemiluminescence
The oxidation characteristics of a pure ester (trimethyolpropane triheptanoate) were studied by using a chemiluminescence technique. Tests were run in a thin-film micro-oxidation apparatus with an aluminum alloy catalyst. Conditions included a pure oxygen atmosphere and a temperature range of 176 to 206 C. Results indicated that oxidation of the ester (containing 10 to the minus 3 power M diphenylanthracene as an intensifier) was accompanied by emission of light. The maximum intensity of light emission (I sub max) was a function of the amount of ester, the concentration of intensifier, and the test temperature. The induction period or the time to reach one-half of maximum intensity (t sub 1/2) was an inverse function of test temperature. Decreases in light emission at the later stages of a test were caused by depletion of the intensifier
The Viking rocket: A memoir
The development and testing of the Viking rocket series is reviewed. These twelve sounding rockets were launched from 1949 to 1954
Non-Fermi liquid signatures in the Hubbard Model due to van Hove singularities
When a van-Hove singularity is located in the vicinity of the Fermi level,
the electronic scattering rate acquires a non-analytic contribution. This
invalidates basic assumptions of Fermi liquid theory and within perturbative
treatments leads to a non-Fermi liquid self-energy and transport
properties.Such anomalies are shown to also occur in the strongly correlated
metallic state. We consider the Hubbard model on a two-dimensional square
lattice with nearest and next-nearest neighbor hopping within the single-site
dynamical mean-field theory. At temperatures on the order of the low-energy
scale an unusual maximum emerges in the imaginary part of the self-energy
which is renormalized towards the Fermi level for finite doping. At zero
temperature this double-well structure is suppressed, but an anomalous energy
dependence of the self-energy remains. For the frustrated Hubbard model on the
square lattice with next-nearest neighbor hopping, the presence of the van Hove
singularity changes the asymptotic low temperature behavior of the resistivity
from a Fermi liquid to non-Fermi liquid dependency as function of doping. The
results of this work are discussed regarding their relevance for
high-temperature cuprate superconductors.Comment: revised version, accepted in Phys.Rev.
A High Phase Advance Damped and Detuned Structure for the Main Linacs of Clic
The main accelerating structures for the CLIC are designed to operate at an
average accelerating gradient of 100 MV/m. The accelerating frequency has been
optimised to 11.994 GHz with a phase advance of 2{\pi}/3 of the main
accelerating mode. The moderately damped and detuned structure (DDS) design is
being studied as an alternative to the strongly damped WDS design. Both these
designs are based on the nominal accelerating phase advance. Here we explore
high phase advance (HPA) structures in which the group velocity of the rf
fields is reduced compared to that of standard (2{\pi}/3) structures. The
electrical breakdown strongly depends on the fundamental mode group velocity.
Hence it is expected that electrical breakdown is less likely to occur in the
HPA structures. We report on a study of both the fundamental and dipole modes
in a CLIC_DDS_HPA structure, designed to operate at 5{\pi}/6 phase advance per
cell. Higher order dipole modes in both the standard and HPA structures are
also studied
Separation of foregrounds from cosmic microwave background observations with the MAP satellite
Simulated observations of a 10\dg \times 10\dg field by the Microwave
Anisotropy Probe (MAP) are analysed in order to separate cosmic microwave
background (CMB) emission from foreground contaminants and instrumental noise
and thereby determine how accurately the CMB emission can be recovered. The
simulations include emission from the CMB, the kinetic and thermal
Sunyaev-Zel'dovich (SZ) effects from galaxy clusters, as well as Galactic dust,
free-free and synchrotron. We find that, even in the presence of these
contaminating foregrounds, the CMB map is reconstructed with an rms accuracy of
about 20 K per 12.6 arcmin pixel, which represents a substantial
improvement as compared to the individual temperature sensitivities of the raw
data channels. We also find, for the single 10\dg \times 10\dg field, that
the CMB power spectrum is accurately recovered for \ell \la 600.Comment: 7 pages, 7 figures, MNRAS submitte
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