33,821 research outputs found
Ground state cooling of a nanomechanical resonator in the weak-confinement regime via quantum interference
Ground state cooling of a nanomechanical resonator coupled to a
superconducting flux qubit is discussed. We show that by inducing quantum
interference to cancel detrimental carrier excitations, ground state cooling
becomes possible in the weak-confinement or non-resolved regime. The qubit is
modelled as a three-level system in lambda configuration, and the driving
fluxes are applied such that the qubit absorption spectrum exhibits
electromagnetically induced transparency, thereby cancelling the unwanted
carrier excitation. As our interference-based scheme allows to apply strong
cooling fields, fast and efficient cooling can be achieved
Early Recognition of Human Activities from First-Person Videos Using Onset Representations
In this paper, we propose a methodology for early recognition of human
activities from videos taken with a first-person viewpoint. Early recognition,
which is also known as activity prediction, is an ability to infer an ongoing
activity at its early stage. We present an algorithm to perform recognition of
activities targeted at the camera from streaming videos, making the system to
predict intended activities of the interacting person and avoid harmful events
before they actually happen. We introduce the novel concept of 'onset' that
efficiently summarizes pre-activity observations, and design an approach to
consider event history in addition to ongoing video observation for early
first-person recognition of activities. We propose to represent onset using
cascade histograms of time series gradients, and we describe a novel
algorithmic setup to take advantage of onset for early recognition of
activities. The experimental results clearly illustrate that the proposed
concept of onset enables better/earlier recognition of human activities from
first-person videos
Characterization of the Soluble Nanoparticles Formed through Coulombic Interaction of Bovine Serum Albumin with Anionic Graft Copolymers at Low pH
A static light scattering (SLS) study of bovine serum albumin (BSA) mixtures
with two anionic graft copolymers of poly (sodium acrylate-co-sodium
2-acrylamido-2-methyl-1-propanesulphonate)-graft-poly (N,
N-dimethylacrylamide), with a high composition in poly (N,
N-dimethylacrylamide) (PDMAM) side chains, revealed the formation of oppositely
charged complexes, at pH lower than 4.9, the isoelectric point of BSA. The
core-corona nanoparticles formed at pH = 3.00, were characterized. Their
molecular weight and radius of gyration were determined by SLS, while their
hydrodynamic radius was determined by dynamic light scattering. Small angle
neutron scattering measurements were used to determine the radius of the
insoluble complexes, comprising the core of the particles. The values obtained
indicated that their size and aggregation number of the nanoparticles, were
smaller when the content of the graft copolymers in neutral PDMAM side chains
was higher. Such particles should be interesting drug delivery candidates, if
the gastrointestinal tract was to be used
Interface resistance of disordered magnetic multilayers
We study the effect of interface disorder on the spin-dependent interface
resistances of Co/Cu, Fe/Cr and Au/Ag multilayers using a newly developed
method for calculating transmission matrices from first-principles. The
efficient implementation using tight-binding linear-muffin-tin orbitals allows
us to model interface disorder using large lateral supercells whereby specular
and diffuse scattering are treated on an equal footing. Without introducing any
free parameters, quantitative agreement with experiment is obtained. We predict
that disorder {\it reduces} the majority-spin interface resistance of
Fe/Cr(100) multilayers by a factor 3.Comment: 5 pages, 2 figures, submitted to PR
Tilt-Induced Anisotropic to Isotropic Phase Transition at
A modest in-plane magnetic field \Bpar\ is sufficient to destroy the
fractional quantized Hall states at and 7/2 and replace them with
anisotropic compressible phases. Remarkably, we find that at larger \Bpar\
these anisotropic phases can themselves be replaced by isotropic compressible
phases reminiscent of the composite fermion fluid at . We present
strong evidence that this transition is a consequence of the mixing of Landau
levels from different electric subbands. We also report surprising dependences
of the energy gaps at and 7/3 on the width of the confinement
potential.Comment: Accepted by Phys. Rev. Lett. This is a final version with rewritten
introduction and modified figure
Spin-injection through an Fe/InAs Interface
The spin-dependence of the interface resistance between ferromagnetic Fe and
InAs is calculated from first-principles for specular and disordered (001)
interfaces. Because of the symmetry mismatch in the minority-spin channel, the
specular interface acts as an efficient spin filter with a transmitted current
polarisation between 98 an 89%.
The resistance of a specular interface in the diffusive regime is comparable
to the resistance of a few microns of bulk InAs.
Symmetry-breaking arising from interface disorder reduces the spin asymmetry
substantially and we conclude that efficient spin injection from Fe into InAs
can only be realized using high quality epitaxial interfaces.Comment: 4 pages, 4 figure
- …