13,375 research outputs found
Study of interacting electrons in graphene under the renormalized-ring-diagram approximation
Using the tight-binding model with long-range Coulomb interactions between
electrons, we study some of the electronic properties of graphene. The Coulomb
interactions are treated with the renormalized-ring-diagram approximation. By
self-consistently solving the integral equations for the Green function, we
calculate the spectral density. The obtained result is in agreement with
experimental observation. In addition, we also compute the density of states,
the distribution functions, and the ground-state energy. Within the present
approximation, we find that the imaginary part of the self-energy fixed at the
Fermi momentum varies as quadratic in energy close to the chemical potential,
regardless the system is doped or not. This result appears to indicate that the
electrons in graphene always behave like a moderately correlated Fermi liquid.Comment: 11 pages, 13 figure
Detection of genuinely entangled and non-separable -partite quantum states
We investigate the detection of entanglement in -partite quantum states.
We obtain practical separability criteria to identify genuinely entangled and
non-separable mixed quantum states. No numerical optimization or eigenvalue
evaluation is needed, and our criteria can be evaluated by simple computations
involving components of the density matrix. We provide examples in which our
criteria perform better than all known separability criteria. Specifically, we
are able to detect genuine -partite entanglement which has previously not
been identified. In addition, our criteria can be used in today's experiment.Comment: 8 pages, one figur
Hypercapnia and Oxygen Therapy in Older Asthmatic Patients
Excessive oxygen administration in hypercapnic chronic obstructive pulmonary disease predisposes to worsening respiratory failure during intercurrent respiratory illness. Chronic hypercapnia is thought to downregulate carbon dioxide chemoreceptor sensitivity, adversely affecting respiratory function/mechanics and worsening ventilation-perfusion inequality. These patients are dependent on hypoxic drive to maintain adequate spontaneous respiration. Whether an analogous situation occurs in asthma in older adults is unknown. These conditions may be difficult to differentiate clinically, and both may respond adversely to the administration of excessive oxygen in the presence of chronic hypercapnia. Although unrestricted oxygen is beneficial and safe in children and young adults with asthma, it may lead to progressive hypercapnia in older patients with asthma, a potential risk highlighted by this case. To avert progressive hypercapnia, oxygen therapy that is carefully adjusted to achieve adequate, but not maximal, tissue oxygenation may be a safer strategy than unrestricted oxygen use in older asthmatic patients. However, the correction of hypoxia overrides strategies to avert oxygen-related hypercapnia
Spin dynamics in the antiferromagnetic phase for electron-doped cuprate superconductors
Based on the --- model we have calculated the dynamical spin
susceptibilities in the antiferromagnetic (AF) phase for electron-doped
cuprates, by use of the slave-boson mean-field theory and random phase
approximation. Various results for the susceptibilities versus energy and
momentum have been shown at different dopings. At low energy, except the
collective spin-wave mode around and 0, we have primarily observed
that new resonance peaks will appear around and equivalent
points with increasing doping, which are due to the particle-hole excitations
between the two AF bands. The peaks are pronounced in the transverse
susceptibility but not in the longitudinal one. These features are predicted
for neutron scattering measurements.Comment: 5 pages, 3 figures, published version with minor change
Phase diagram of doped BaFeAs superconductor under broken symmetry
We develop a minimal multiorbital tight-binding model with realistic hopping
parameters. The model breaks the symmetry of the tetragonal point group by
lowering it from to , which accurately describes the Fermi
surface evolution of the electron-doped BaFeCoAs and hole-doped
BaKFeAs compounds. An investigation of the phase diagram
with a mean-field -- Bogoliubov-de Gennes Hamiltonian results in
agreement with the experimentally observed electron- and hole-doped phase
diagram with only one set of , and parameters. Additionally, the
self-consistently calculated superconducting order parameter exhibits
-wave pairing symmetry with a small d-wave pairing admixture in the
entire doping range, % The superconducting -wave order parameter
which is the subtle result of the weakly broken symmetry and competing
interactions in the multiorbital mean-field Hamiltonian
Germline Cas9 expression yields highly efficient genome engineering in a major worldwide disease vector, Aedes aegypti.
The development of CRISPR/Cas9 technologies has dramatically increased the accessibility and efficiency of genome editing in many organisms. In general, in vivo germline expression of Cas9 results in substantially higher activity than embryonic injection. However, no transgenic lines expressing Cas9 have been developed for the major mosquito disease vector Aedes aegypti Here, we describe the generation of multiple stable, transgenic Ae. aegypti strains expressing Cas9 in the germline, resulting in dramatic improvements in both the consistency and efficiency of genome modifications using CRISPR. Using these strains, we disrupted numerous genes important for normal morphological development, and even generated triple mutants from a single injection. We have also managed to increase the rates of homology-directed repair by more than an order of magnitude. Given the exceptional mutagenic efficiency and specificity of the Cas9 strains we engineered, they can be used for high-throughput reverse genetic screens to help functionally annotate the Ae. aegypti genome. Additionally, these strains represent a step toward the development of novel population control technologies targeting Ae. aegypti that rely on Cas9-based gene drives
Fabrication of a focusing soft X-ray collector payload
A large area X-ray focusing collector with arc minute resolution and a position sensitive detector capable of operating in the soft X-ray region was developed for use on sounding rockets in studying stellar X-ray sources. The focusing payload consists of the following components, which are described: (1) a crossed paraboloid mirror assembly; (2) an aspect camera and star tracker; (3) a focal plane assembly containing an imaging proportional counter and its preamplifiers, high voltage power supplies and gas system; (4) a fiducial system; and (5) housekeeping, data handling, instrumentation and telemetry electronics. The design, tests, and operation are described
Temporal Recurrent Networks for Online Action Detection
Most work on temporal action detection is formulated as an offline problem,
in which the start and end times of actions are determined after the entire
video is fully observed. However, important real-time applications including
surveillance and driver assistance systems require identifying actions as soon
as each video frame arrives, based only on current and historical observations.
In this paper, we propose a novel framework, Temporal Recurrent Network (TRN),
to model greater temporal context of a video frame by simultaneously performing
online action detection and anticipation of the immediate future. At each
moment in time, our approach makes use of both accumulated historical evidence
and predicted future information to better recognize the action that is
currently occurring, and integrates both of these into a unified end-to-end
architecture. We evaluate our approach on two popular online action detection
datasets, HDD and TVSeries, as well as another widely used dataset, THUMOS'14.
The results show that TRN significantly outperforms the state-of-the-art
A survey of cost-sensitive decision tree induction algorithms
The past decade has seen a significant interest on the problem of inducing decision trees that take account of costs of misclassification and costs of acquiring the features used for decision making. This survey identifies over 50 algorithms including approaches that are direct adaptations of accuracy based methods, use genetic algorithms, use anytime methods and utilize boosting and bagging. The survey brings together these different studies and novel approaches to cost-sensitive decision tree learning, provides a useful taxonomy, a historical timeline of how the field has developed and should provide a useful reference point for future research in this field
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