9,934 research outputs found
The role of short periodic orbits in quantum maps with continuous openings
We apply a recently developed semiclassical theory of short periodic orbits
to the continuously open quantum tribaker map. In this paradigmatic system the
trajectories are partially bounced back according to continuous reflectivity
functions. This is relevant in many situations that include optical
microresonators and more complicated boundary conditions. In a perturbative
regime, the shortest periodic orbits belonging to the classical repeller of the
open map - a cantor set given by a region of exactly zero reflectivity - prove
to be extremely robust in supporting a set of long-lived resonances of the
continuously open quantum maps. Moreover, for step like functions a significant
reduction in the number needed is obtained, similarly to the completely open
situation. This happens despite a strong change in the spectral properties when
compared to the discontinuous reflectivity case.Comment: 6 pages, 4 figures. arXiv admin note: text overlap with
arXiv:1604.0181
Comparative genomics and mutagenesis analyses of choline metabolism in the marine Roseobacter clade
Choline is ubiquitous in marine eukaryotes and appears to be widely distributed in surface marine waters; however, its metabolism by marine bacteria is poorly understood. Here, using comparative genomics and molecular genetic approaches, we reveal that the capacity for choline catabolism is widespread in marine heterotrophs of the marine Roseobacter clade (MRC). Using the model bacterium Ruegeria pomeroyi, we confirm that the betA, betB and betC genes, encoding choline dehydrogenase, betaine aldehyde dehydrogenase and choline sulfatase, respectively, are involved in choline metabolism. The betT gene, encoding an organic solute transporter, was essential for the rapid uptake of choline but not glycine betaine (GBT). Growth of choline and GBT as a sole carbon source resulted in the re-mineralization of these nitrogen-rich compounds into ammonium. Oxidation of the methyl groups from choline requires formyltetrahydrofolate synthetase encoded by fhs in R.pomeroyi, deletion of which resulted in incomplete degradation of GBT. We demonstrate that this was due to an imbalance in the supply of reducing equivalents required for choline catabolism, which can be alleviated by the addition of formate. Together, our results demonstrate that choline metabolism is ubiquitous in the MRC and reveal the role of Fhs in methyl group oxidation in R.pomeroyi
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Towards a Multimodal Time-Based Empathy Prediction System
We describe our system for empathic emotion recognition. It is based on deep learning on multiple modalities in a late fusion architecture. We describe the modules of our system and discuss the evaluation results. Our code is also available for the research community
Bilinear and quadratic Hamiltonians in two-mode cavity quantum electrodynamics
In this work we show how to engineer bilinear and quadratic Hamiltonians in
cavity quantum electrodynamics (QED) through the interaction of a single driven
two-level atom with cavity modes. The validity of the engineered Hamiltonians
is numerically analyzed even considering the effects of both dissipative
mechanisms, the cavity field and the atom. The present scheme can be used, in
both optical and microwave regimes, for quantum state preparation, the
implementation of quantum logical operations, and fundamental tests of quantum
theory.Comment: 11 pages, 3 figure
Topological defects and misfit strain in magnetic stripe domains of lateral multilayers with perpendicular magnetic anisotropy
Stripe domains are studied in perpendicular magnetic anisotropy films
nanostructured with a periodic thickness modulation that induces the lateral
modulation of both stripe periods and inplane magnetization. The resulting
system is the 2D equivalent of a strained superlattice with properties
controlled by interfacial misfit strain within the magnetic stripe structure
and shape anisotropy. This allows us to observe, experimentally for the first
time, the continuous structural transformation of a grain boundary in this 2D
magnetic crystal in the whole angular range. The magnetization reversal process
can be tailored through the effect of misfit strain due to the coupling between
disclinations in the magnetic stripe pattern and domain walls in the in-plane
magnetization configuration
Controlled nucleation of topological defects in the stripe domain patterns of Lateral multilayers with Perpendicular Magnetic Anisotropy: competition between magnetostatic, exchange and misfit interactions
Magnetic lateral multilayers have been fabricated on weak perpendicular
magnetic anisotropy amorphous Nd-Co films in order to perform a systematic
study on the conditions for controlled nucleation of topological defects within
their magnetic stripe domain pattern. A lateral thickness modulation of period
is defined on the nanostructured samples that, in turn, induces a lateral
modulation of both magnetic stripe domain periods and average
in-plane magnetization component . Depending on lateral multilayer
period and in-plane applied field, thin and thick regions switch independently
during in-plane magnetization reversal and domain walls are created within the
in-plane magnetization configuration coupled to variable angle grain boundaries
and disclinations within the magnetic stripe domain patterns. This process is
mainly driven by the competition between rotatable anisotropy (that couples the
magnetic stripe pattern to in-plane magnetization) and in-plane shape
anisotropy induced by the periodic thickness modulation. However, as the
structural period becomes comparable to magnetic stripe period ,
the nucleation of topological defects at the interfaces between thin and thick
regions is hindered by a size effect and stripe domains in the different
thickness regions become strongly coupled.Comment: 10 pages, 7 figures, submitted to Physical Review
Nonadiabatic coherent evolution of two-level systems under spontaneous decay
In this paper we extend current perspectives in engineering reservoirs by
producing a time-dependent master equation leading to a nonstationary
superposition equilibrium state that can be nonadiabatically controlled by the
system-reservoir parameters. Working with an ion trapped inside a nonindeal
cavity we first engineer effective Hamiltonians that couple the electronic
states of the ion with the cavity mode. Subsequently, two classes of
decoherence-free evolution of the superposition of the ground and decaying
excited levels are achieved: those with time-dependent azimuthal or polar
angle. As an application, we generalise the purpose of an earlier study [Phys.
Rev. Lett. 96, 150403 (2006)], showing how to observe the geometric phases
acquired by the protected nonstationary states even under a nonadiabatic
evolution.Comment: 5 pages, no figure
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