439 research outputs found
Electron injection in a nanotube with leads: finite frequency noise-correlations and anomalous charges
The non-equilibrium transport properties of a carbon nanotube which is
connected to Fermi liquid leads, where electrons are injected in the bulk, are
computed. A previous work which considered an infinite nanotube showed that the
zero frequency noise correlations, measured at opposite ends of the nanotube,
could be used to extract the anomalous charges of the chiral excitations which
propagate in the nanotube. Here, the presence of the leads have the effect that
such-noise cross-correlations vanish at zero frequency. Nevertheless,
information concerning the anomalous charges can be recovered when considering
the spectral density of noise correlations at finite frequencies, which is
computed perturbatively in the tunneling amplitude. The spectrum of the noise
cross-correlations is shown to depend crucially on the ratio of the time of
flight of quasiparticles traveling in the nanotube to the ``voltage'' time
which defines the width of the quasiparticle wave-packets injected when an
electron tunnels. Potential applications toward the measurement of such
anomalous charges in non-chiral Luttinger liquids (nanotubes or semiconductor
quantum wires) are discussed.Comment: 11 pages, 5 figure
AC conductance and non-symmetrized noise at finite frequency in quantum wires and carbon nanotubes
We calculate the AC conductance and the finite-frequency non-symmetrized
noise in interacting quantum wires and single-wall carbon nanotubes in the
presence of an impurity. We observe a strong asymmetry in the frequency
spectrum of the non-symmetrized excess noise, even in the presence of the
metallic leads. We find that this asymmetry is proportional to the differential
excess AC conductance of the system, defined as the difference between the AC
differential conductances at finite and zero voltage, and thus disappears for a
linear system. In the quantum regime, for temperatures much smaller than the
frequency and the applied voltage, we find that the emission noise is exactly
equal to the impurity partition noise. For the case of a weak impurity we
expand our results for the AC conductance and the noise perturbatively. In
particular, if the impurity is located in the middle of the wire or at one of
the contacts, our calculations show that the noise exhibits oscillations with
respect to frequency, whose period is directly related to the value of the
interaction parameter
Photo-assisted Andreev reflection as a probe of quantum noise
Andreev reflection, which corresponds to the tunneling of two electrons from
a metallic lead to a superconductor lead as a Cooper pair (or vice versa), can
be exploited to measure high frequency noise. A detector is proposed, which
consists of a normal lead--superconductor circuit, which is capacitively
coupled to a mesoscopic circuit where noise is to be measured. We discuss two
detector circuits: a single normal metal -- superconductor tunnel junction and
a normal metal separated from a superconductor by a quantum dot operating in
the Coulomb blockade regime. A substantial DC current flows in the detector
circuit when an appropriate photon is provided or absorbed by the mesoscopic
circuit, which plays the role of an environment for the junction to which it
couples. Results for the current can be cast in all cases in the form of a
frequency integral of the excess noise of the environment weighted by a kernel
which is specific to the transport process (quasiparticle tunneling, Andreev
reflection,...) which is considered. We apply these ideas to the measurement of
the excess noise of a quantum point contact and we provide numerical estimates
of the detector current.Comment: 19 pages, 11 figure
Online quality assessment of human movement from skeleton data
We propose a general method for online estimation of the quality of movement from Kinect
skeleton data. A robust non-linear manifold learning technique is used to reduce the
dimensionality of the noisy skeleton data. Then, a statistical model of normal movement is
built from observations of healthy subjects, and the level of matching of new observations
with this model is computed on a frame-by-frame basis following Markovian assumptions.
The proposed method is validated on the assessment of gait on stairs
Inactivation of Chibby affects function of motile airway cilia
Chibby (Cby) is a conserved component of the WntâÎČ-catenin pathway. Cby physically interacts with ÎČ-catenin to repress its activation of transcription. To elucidate the function of Cby in vertebrates, we generated Cbyâ/â mice and found that after 2â3 d of weight loss, the majority of mice die before or around weaning. All Cbyâ/â mice develop rhinitis and sinusitis. When challenged with Pseudomonas aeruginosa isolates, Cbyâ/â mice are unable to clear the bacteria from the nasal cavity. Notably, Cbyâ/â mice exhibit a complete absence of mucociliary transport caused by a marked paucity of motile cilia in the nasal epithelium. Moreover, ultrastructural experiments reveal impaired basal body docking to the apical surface of multiciliated cells. In support of these phenotypes, endogenous Cby protein is localized at the base of cilia. As the phenotypes of Cbyâ/â mice bear striking similarities to primary ciliary dyskinesia, Cbyâ/â mice may prove to be a useful model for this condition
Evaluation of cupboard door sensors for improving activity recognition in the kitchen
International audienc
Photo--assisted current and shot noise in the fractional quantum Hall effect
The effect of an AC perturbation on the shot noise of a fractional quantum
Hall fluid is studied both in the weak and the strong backscattering regimes.
It is known that the zero-frequency current is linear in the bias voltage,
while the noise derivative exhibits steps as a function of bias. In contrast,
at Laughlin fractions, the backscattering current and the backscattering noise
both exhibit evenly spaced singularities, which are reminiscent of the
tunneling density of states singularities for quasiparticles. The spacing is
determined by the quasiparticle charge and the ratio of the DC bias
with respect to the drive frequency. Photo--assisted transport can thus be
considered as a probe for effective charges at such filling factors, and could
be used in the study of more complicated fractions of the Hall effect. A
non-perturbative method for studying photo--assisted transport at is
developed, using a refermionization procedure.Comment: 14 pages, 6 figure
Multiple human tracking in RGB-depth data: A survey
© The Institution of Engineering and Technology. Multiple human tracking (MHT) is a fundamental task in many computer vision applications. Appearance-based approaches, primarily formulated on RGB data, are constrained and affected by problems arising from occlusions and/or illumination variations. In recent years, the arrival of cheap RGB-depth devices has led to many new approaches to MHT, and many of these integrate colour and depth cues to improve each and every stage of the process. In this survey, the authors present the common processing pipeline of these methods and review their methodology based (a) on how they implement this pipeline and (b) on what role depth plays within each stage of it. They identify and introduce existing, publicly available, benchmark datasets and software resources that fuse colour and depth data for MHT. Finally, they present a brief comparative evaluation of the performance of those works that have applied their methods to these datasets
Inactivation of Chibby affects function of motile airway cilia
Chibby (Cby) is a conserved component of the WntâÎČ-catenin pathway. Cby physically interacts with ÎČ-catenin to repress its activation of transcription. To elucidate the function of Cby in vertebrates, we generated Cbyâ/â mice and found that after 2â3 d of weight loss, the majority of mice die before or around weaning. All Cbyâ/â mice develop rhinitis and sinusitis. When challenged with Pseudomonas aeruginosa isolates, Cbyâ/â mice are unable to clear the bacteria from the nasal cavity. Notably, Cbyâ/â mice exhibit a complete absence of mucociliary transport caused by a marked paucity of motile cilia in the nasal epithelium. Moreover, ultrastructural experiments reveal impaired basal body docking to the apical surface of multiciliated cells. In support of these phenotypes, endogenous Cby protein is localized at the base of cilia. As the phenotypes of Cbyâ/â mice bear striking similarities to primary ciliary dyskinesia, Cbyâ/â mice may prove to be a useful model for this condition
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