4,548 research outputs found
Engineering Time-Reversal Invariant Topological Insulators With Ultra-Cold Atoms
Topological insulators are a broad class of unconventional materials that are
insulating in the interior but conduct along the edges. This edge transport is
topologically protected and dissipationless. Until recently, all existing
topological insulators, known as quantum Hall states, violated time-reversal
symmetry. However, the discovery of the quantum spin Hall effect demonstrated
the existence of novel topological states not rooted in time-reversal
violations. Here, we lay out an experiment to realize time-reversal topological
insulators in ultra-cold atomic gases subjected to synthetic gauge fields in
the near-field of an atom-chip. In particular, we introduce a feasible scheme
to engineer sharp boundaries where the "edge states" are localized. Besides,
this multi-band system has a large parameter space exhibiting a variety of
quantum phase transitions between topological and normal insulating phases. Due
to their unprecedented controllability, cold-atom systems are ideally suited to
realize topological states of matter and drive the development of topological
quantum computing.Comment: 11 pages, 6 figure
Switching Behaviour of a Series Connection of a Vacuum Interrupter and a Gas Circuit Breaker
After being in the focus of sciences' and industry's research and development activities for many years, the investigation of possible SF6 gas-alternatives has been even more intensified after the revision of the European F-Gas regulation 517/2014. As natural gases yield a significantly lower dielectric strength in comparison to SF6, new challenges arise for the design of high voltage switchgear. Vacuum interrupters are environmentally friendly, reliable and able to withstand steep rising transient recovery voltages. In the last years, first installations of switchgear based on vacuum switching technology in sub-transmission level are in operation. One option for the realization of a SF6 free high voltage switchgear for transmission level is the combination of a gas circuit breaker filled with an atmospheric gas with a vacuum interrupter in a hybrid switchgear. In this contribution the voltage distribution and switching behavior of a hybrid circuit breaker is experimentally investigated
Quasiparticle Scattering Interference in (K,Tl)FexSe2 Superconductors
We model the quasiparticle interference (QPI) pattern in the recently
discovered (K,Tl)Fe_xSe2 superconductors. We show in the superconducting state
that, due to the absence of hole pockets at the Brillouin zone center, the
quasiparticle scattering occurs around the momentum transfer q=(0,0) and (\pm
\pi, \pm \pi) between electron pockets located at the zone boundary. More
importantly, although both d_{x^2-y^2}-wave and s-wave pairing symmetry lead to
nodeless quasiparticle excitations, distinct QPI features are predicted between
both types of pairing symmetry. In the presence of a nonmagnetic impurity
scattering, the QPI exhibits strongest scattering with q=(\pm \pi, \pm \pi) for
the d_{x^2-y^2}-wave pairing symmetry; while the strongest scattering exhibits
a ring-like structure centered around both q=(0,0) and (\pm \pi, \pm \pi) for
the isotropic s-wave pairing symmetry. A unique QPI pattern has also been
predicted due to a local pair-potential-type impurity scattering. The
significant contrast in the QPI pattern between the d_{x^2-y^2}-wave and the
isotropic s-wave pairing symmetry can be used to probe the pairing symmetry
within the Fourier-transform STM technique.Comment: 4+ pages, 3 embedded eps figure
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A probability based hybrid energy-efficient privacy preserving scheme to encounter with wireless traffic snooping in smart home
Application of pervasive computing devices in smart homes are rising sharply and due to this matter, demands for efficient privacy protection are increasing urgently. Possibility of interference in wireless networks is proved by previous work. Adversaries can discover contextual information because of traffic monitoring and classifying transmitters based on their radio fingerprints while data packets are encrypted or content is not important for attackers. To conceal communication patterns various approaches have been investigated. They are mainly based on injection of dummy packets into the network traffic and adding delay to transmission time. In this paper, we introduce a hybrid energy-efficient privacy preserving scheme for generating and sending dummy packets through a decision-making algorithm which works based on probability to maximize confusion of attacker in clarifying the real pattern of network traffi
Star Formation Near Photodissociation Regions: Detection of a Peculiar Protostar Near Ced 201
We present the detection and characterization of a peculiar low-mass
protostar (IRAS 22129+7000) located ~0.4 pc from Ced 201 Photodissociation
Region (PDR) and ~0.2 pc from the HH450 jet. The cold circumstellar envelope
surrounding the object has been mapped through its 1.2 mm dust continuum
emission with IRAM-30m/MAMBO. The deeply embedded protostar is clearly detected
with Spitzer/MIPS (70 um), IRS (20-35 um) and IRAC (4.5, 5.8, and 8 um) but
also in the K_s band (2.15 um). Given the large "near- and mid-IR excess" in
its spectral energy distribution, but large submillimeter-to-bolometric
luminosity ratio (~2%), IRAS 22129+7000 must be a transition Class 0/I source
and/or a multiple stellar system. Targeted observations of several molecular
lines from CO, 13CO, C18O, HCO+ and DCO+ have been obtained. The presence of a
collimated molecular outflow mapped with the CSO telescope in the CO J=3-2 line
suggests that the protostar/disk system is still accreting material from its
natal envelope. Indeed, optically thick line profiles from high density tracers
such as HCO+ J=1-0 show a red-shifted-absorption asymmetry reminiscent of
inward motions. We construct a preliminary physical model of the circumstellar
envelope (including radial density and temperature gradients, velocity field
and turbulence) that reproduces the observed line profiles and estimates the
ionization fraction. The presence of both mechanical and (non-ionizing)
FUV-radiative input makes the region an interesting case to study triggered
star formation
The star formation history of early-type galaxies as a function of mass and environment
Using the third data release of the Sloan Digital Sky Survey (SDSS), we have rigorously defined a volume-limited sample of early-type galaxies in the redshift range 0.005 < z 64 0.1. We have defined the density of the local environment for each galaxy using a method which takes account of the redshift bias introduced by survey boundaries if traditional methods are used. At luminosities greater than our absolute r-band magnitude cut-off of 1220.45, the mean density of environment shows no trend with redshift. We calculate the Lick indices for the entire sample and correct for aperture effects and velocity dispersion in a model-independent way. We find that early-type galaxies in the field are younger than those in environments typical of clusters but that neither metallicity, \u3b1-enhancement nor carbon enhancement are influenced by the environment. We argue that the timing of the process of formation of early-type galaxies is determined by the environment, while the details of the process of star formation, which has built up the stellar mass, are entirely regulated by the halo mass. These results suggest that the star formation took place after the mass assembly and favours an anti-hierarchical model. In such a model, the majority of the mergers must take place before the bulk of the stars form. This can only happen if there exists an efficient feedback mechanism which inhibits the star formation in low-mass haloes and is progressively reduced as mergers increase the mass
Asymptotic symmetry and conservation laws in 2d Poincar\'e gauge theory of gravity
The structure of the asymptotic symmetry in the Poincar\'e gauge theory of
gravity in 2d is clarified by using the Hamiltonian formalism. The improved
form of the generator of the asymptotic symmetry is found for very general
asymptotic behaviour of phase space variables, and the related conserved
quantities are explicitly constructed.Comment: 22 pages, Plain Te
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A prospective, randomised, double-blind, double-dummy, placebo-controlled trial to assess the respiratory effects of buprenorphine versus morphine in anaesthetised patients
Despite its long history and widespread use, some questions remain over buprenorphine’s respiratory safety profile. This study investigated respiratory depression and potential reversibility by naloxone at two buprenorphine doses, of which the intramuscularly administered dose was designed to achieve the plasma concentration range seen with transdermal delivery. The buprenorphine doses were compared to morphine administered intravenously.
The IM route was proposed to avoid the characteristic high peak seen after IV bolus injection, to achieve a slow-rising plasma concentration which plateaus at five minutes, The selected intramuscular buprenorphine dose (0.85 mcg/kg) was chosen to achieve a similar plasma concentration at a steady state to that seen with transdermal buprenorphine at 35mcg/h(the Transtec 35mcg/h patch)
The persistence landscape and some of its properties
Persistence landscapes map persistence diagrams into a function space, which
may often be taken to be a Banach space or even a Hilbert space. In the latter
case, it is a feature map and there is an associated kernel. The main advantage
of this summary is that it allows one to apply tools from statistics and
machine learning. Furthermore, the mapping from persistence diagrams to
persistence landscapes is stable and invertible. We introduce a weighted
version of the persistence landscape and define a one-parameter family of
Poisson-weighted persistence landscape kernels that may be useful for learning.
We also demonstrate some additional properties of the persistence landscape.
First, the persistence landscape may be viewed as a tropical rational function.
Second, in many cases it is possible to exactly reconstruct all of the
component persistence diagrams from an average persistence landscape. It
follows that the persistence landscape kernel is characteristic for certain
generic empirical measures. Finally, the persistence landscape distance may be
arbitrarily small compared to the interleaving distance.Comment: 18 pages, to appear in the Proceedings of the 2018 Abel Symposiu
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