829 research outputs found
`Unhinging' the surfaces of higher-order topological insulators and superconductors
We show that the chiral Dirac and Majorana hinge modes in three-dimensional
higher-order topological insulators (HOTIs) and superconductors (HOTSCs) can be
gapped while preserving the protecting symmetry
upon the introduction of non-Abelian surface topological order. In both cases,
the topological order on a single side surface breaks time reversal symmetry,
but appears with its time-reversal conjugate on alternating sides in a
preserving pattern. In the absence of the
HOTI/HOTSC bulk, such a pattern necessarily involves gapless chiral modes on
hinges between -conjugate domains. However, using a
combination of -matrix and anyon condensation arguments, we show that on the
boundary of a 3D HOTI/HOTSC these topological orders are fully gapped and hence
`anomalous'. Our results suggest that new patterns of surface and hinge states
can be engineered by selectively introducing topological order only on specific
surfaces
Incorporation of amino acids into the outer and inner membrane of isolated rat liver mitochondria II
Carbon coating of the SPS dipole chambers
The Electron Multipacting (EM) phenomenon is a limiting factor for the
achievement of high luminosity in accelerators for positively charged particles
and for the performance of RF devices. At CERN, the Super Proton Synchrotron
(SPS) must be upgraded in order to feed the Large Hadron Collider (LHC) with 25
ns bunch spaced beams. At such small bunch spacing, EM may limit the
performance of the SPS and consequently that of the LHC. To mitigate this
phenomenon CERN is developing a carbon thin film coating with low Secondary
Electron Yield (SEY) to coat the internal walls of the SPS dipoles beam pipes.
This paper presents the progresses in the coating technology, the performance
of the carbon coatings and the strategy for a large scale production.Comment: 7 pages, contribution to the Joint INFN-CERN-EuCARD-AccNet Workshop
on Electron-Cloud Effects: ECLOUD'12; 5-9 Jun 2012, La Biodola, Isola d'Elba,
Italy; CERN Yellow Report CERN-2013-002, pp.141-14
The nature of the fluorescent iron line in V 1486 Ori
The fluorescent 6.4 keV iron line provides information on cool material in
the vicinity of hard X-ray sources as well as on the characteristics of the
X-ray sources themselves. First discovered in the X-ray spectra of the flaring
Sun, X-ray binaries and active galactic nuclei (AGN), the fluorescent line was
also observed in a number of stellar X-ray sources. The young stellar object
(YSO) V1486 Ori was observed in the framework of the Chandra Ultra Deep Project
(COUP) as the source COUP 331. We investigate its spectrum, with emphasis on
the strength and time variability of the fluorescent iron K-alpha line, derive
and analyze the light curve of COUP 331 and proceed with a time-resolved
spectral analysis of the observation. The light curve of V 1486 Ori shows two
major flares, the first one lasting for (approx) 20 ks with a peak X-ray
luminosity of 2.6*10^{32} erg/s (dereddened in the 1-10 keV band) and the
second one -- only partially observed -- for >60 ks with an average X-ray
luminosity of 2.4*10^{31} erg/s (dereddened). The spectrum of the first flare
is very well described by an absorbed thermal model at high temperature, with a
pronounced 6.7 keV iron line complex, but without any fluorescent K-alpha line.
The X-ray spectrum of the second flare is characterized by even higher
temperatures (>= 10 keV) without any detectable 6.7 keV Fe XXV feature, but
with a very strong fluorescent iron K-alpha line appearing predominantly in the
20 ks rise phase of the flare. Preliminary model calculations indicate that
photoionization is unlikely to account for the entire fluorescent emission
during the rise phase.Comment: 4 pages, letter, accepted for publication in A&
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