8,951 research outputs found
Three-dimensional numerical simulation of magnetohydrodynamic-gravity waves and vortices in the solar atmosphere
With the adaptation of the FLASH code we simulate magnetohydrodynamic-gravity
waves and vortices as well as their response in the magnetized
three-dimensional (3D) solar atmosphere at different heights to understand the
localized energy transport processes. In the solar atmosphere strongly
structured by gravitational and magnetic forces, we launch a localized velocity
pulse (in horizontal and vertical components) within a bottom layer of 3D solar
atmosphere modelled by initial VAL-IIIC conditions, which triggers waves and
vortices. The rotation direction of vortices depends on the orientation of an
initial perturbation. The vertical driver generates magnetoacoustic-gravity
waves which result in oscillations of the transition region, and it leads to
the eddies with their symmetry axis oriented vertically. The horizontal pulse
excites all magnetohydrodynamic-gravity waves and horizontally oriented eddies.
These waves propagate upwards, penetrate the transition region, and enter the
solar corona. In the high-beta plasma regions the magnetic field lines move
with the plasma and the temporal evolution show that they swirl with eddies. We
estimate the energy fluxes carried out by the waves in the magnetized solar
atmosphere and conclude that such wave dynamics and vortices may be significant
in transporting the energy to sufficiently balance the energy losses in the
localized corona. Moreover, the structure of the transition region highly
affects such energy transports, and causes the channelling of the propagating
waves into the inner corona.Comment: 11 Pages, 12 Figures, Accepted for the publication in MNRA
Effects of quarks on the formation and evolution of Z(3) walls and strings in relativistic heavy-ion collisions
We investigate the effects of explicit breaking of Z(3) symmetry due to the
presence of dynamical quarks on the formation and evolution of Z(3) walls and
associated QGP strings within Polyakov loop model. We carry out numerical
simulations of the first order quark-hadron phase transition via bubble
nucleation (which may be appropriate, for example, at finite baryon chemical
potential) in the context of relativistic heavy-ion collision experiments.
Using appropriate shifting of the order parameter in the Polyakov loop
effective potential, we calculate the bubble profiles using bounce technique,
for the true vacuum as well as for the metastable Z(3) vacua, and estimate the
associated nucleation probabilities. These different bubbles are then nucleated
and evolved and resulting formation and dynamics of Z(3) walls and QGP strings
is studied. We discuss various implications of the existence of these Z(3)
interfaces and the QGP strings, especially in view of the effects of the
explicit breaking of the Z(3) symmetry on the formation and dynamical evolution
of these objects.Comment: 17 pages, 9 figures, PDFLate
Generalized Second-Order Duality for a Continuous Programming Problem with Support Functions
A generalized second-order dual is formulated for a continuous programming problem in which support functions appear in both objective and constraint functions, hence it is nondifferentiable. Under second-order pseudoinvexity and second-order quasi-invexity, various duality theorems are proved for this pair of dual continuous programming problems. Special cases are deduced and a pair of dual continuous programming problems with natural boundary values is constructed and it is pointed out that the duality results for the pair can be validated analogously to those of the dual models with fixed end points. Finally, a close relationship between duality results of our problems and those of the corresponding (static) nonlinear programming problem with support functions is briefly mentioned
Temporal Localization of Fine-Grained Actions in Videos by Domain Transfer from Web Images
We address the problem of fine-grained action localization from temporally
untrimmed web videos. We assume that only weak video-level annotations are
available for training. The goal is to use these weak labels to identify
temporal segments corresponding to the actions, and learn models that
generalize to unconstrained web videos. We find that web images queried by
action names serve as well-localized highlights for many actions, but are
noisily labeled. To solve this problem, we propose a simple yet effective
method that takes weak video labels and noisy image labels as input, and
generates localized action frames as output. This is achieved by cross-domain
transfer between video frames and web images, using pre-trained deep
convolutional neural networks. We then use the localized action frames to train
action recognition models with long short-term memory networks. We collect a
fine-grained sports action data set FGA-240 of more than 130,000 YouTube
videos. It has 240 fine-grained actions under 85 sports activities. Convincing
results are shown on the FGA-240 data set, as well as the THUMOS 2014
localization data set with untrimmed training videos.Comment: Camera ready version for ACM Multimedia 201
Hydrogen-like Atoms from Ultrarelativistic Nuclear Collisions
The number of hydrogen-like atoms produced when heavy nuclei collide is
estimated for central collisions at the Relativistic Heavy Ion Collider using
the sudden approximation of Baym et al. As first suggested by Schwartz, a
simultaneous measurement of the hydrogen and hadron spectra will allow an
inference of the electron or muon spectra at low momentum where a direct
experimental measurement is not feasible.Comment: 6 pages, 4 figure
Bremsstrahlung from an Equilibrating Quark-Gluon Plasma
The photon production rate from a chemically equilibrating quark-gluon plasma
likely to be produced at RHIC (BNL) and LHC (CERN) energies is estimated taking
into account bremsstrahlung. The plasma is assumed to be in local thermal
equilibrium, but with a phase space distribution that deviates from the Fermi
or Bose distribution by space-time dependent factors (fugacities). The photon
spectrum is obtained by integrating the photon rate over the space-time history
of the plasma, adopting a boost invariant cylindrically symmetric transverse
expansion of the system with different nuclear profile functions. Initial
conditions obtained from a self-screened parton cascade calculation and, for
comparison, from the HIJING model are used. Compared to an equilibrated plasma
at the same initial energy density, taken from the self-screened parton
cascade, a moderate suppression of the photon yield by a factor of one to five
depending on the collision energy and the photon momentum is observed. The
individual contributions to the photon production, however, are completely
different in the both scenarios.Comment: 14 pages, 4 figures, shortened version to be published in Phys. Rev.
Towards accurate detection and genotyping of expressed variants from whole transcriptome sequencing data
BACKGROUND: Massively parallel transcriptome sequencing (RNA-Seq) is becoming the method of choice for studying functional effects of genetic variability and establishing causal relationships between genetic variants and disease. However, RNA-Seq poses new technical and computational challenges compared to genome sequencing. In particular, mapping transcriptome reads onto the genome is more challenging than mapping genomic reads due to splicing. Furthermore, detection and genotyping of single nucleotide variants (SNVs) requires statistical models that are robust to variability in read coverage due to unequal transcript expression levels. RESULTS: In this paper we present a strategy to more reliably map transcriptome reads by taking advantage of the availability of both the genome reference sequence and transcript databases such as CCDS. We also present a novel Bayesian model for SNV discovery and genotyping based on quality scores. CONCLUSIONS: Experimental results on RNA-Seq data generated from blood cell tissue of three Hapmap individuals show that our methods yield increased accuracy compared to several widely used methods. The open source code implementing our methods, released under the GNU General Public License, is available at http://dna.engr.uconn.edu/software/NGSTools/
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