4,533 research outputs found
Effects of nucleon resonances on photoproduction off the neutron reexamined
We investigate photoproduction off the neutron target, i.e., , employing an effective Lagrangian method combining with a Regge
approach. As a background, we consider nucleon exchange in the -channel
diagram and - and -meson Regge trajectories in the channel.
The role of nucleon resonances given in the Review of Particle Data Group in
the range of MeV and the narrow nucleon resonance
is extensively studied. The numerical results of the total and
differential cross sections, double polarization observable , and
helicity-dependent cross sections , are found to
be in qualitative agreement with the recent A2 experimental data. The
predictions of the beam asymmetry are also given.Comment: 12 pages, 6 figure
Tau functions as Widom constants
We define a tau function for a generic Riemann-Hilbert problem posed on a
union of non-intersecting smooth closed curves with jump matrices analytic in
their neighborhood. The tau function depends on parameters of the jumps and is
expressed as the Fredholm determinant of an integral operator with block
integrable kernel constructed in terms of elementary parametrices. Its
logarithmic derivatives with respect to parameters are given by contour
integrals involving these parametrices and the solution of the Riemann-Hilbert
problem. In the case of one circle, the tau function coincides with Widom's
determinant arising in the asymptotics of block Toeplitz matrices. Our
construction gives the Jimbo-Miwa-Ueno tau function for Riemann-Hilbert
problems of isomonodromic origin (Painlev\'e VI, V, III, Garnier system, etc)
and the Sato-Segal-Wilson tau function for integrable hierarchies such as
Gelfand-Dickey and Drinfeld-Sokolov.Comment: 26 pages, 6 figure
SOLiDzipper: A High Speed Encoding Method for the Next-Generation Sequencing Data
Background Next-generation sequencing (NGS) methods pose computational challenges of handling large volumes of data. Although cloud computing offers a potential solution to these challenges, transferring a large data set across the internet is the biggest obstacle, which may be overcome by efficient encoding methods. When encoding is used to facilitate data transfer to the cloud, the time factor is equally as important as the encoding efficiency. Moreover, to take advantage of parallel processing in cloud computing, a parallel technique to decode and split compressed data in the cloud is essential. Hence in this review, we present SOLiDzipper, a new encoding method for NGS data. Methods The basic strategy of SOLiDzipper is to divide and encode. NGS data files contain both the sequence and non-sequence information whose encoding efficiencies are different. In SOLiDzipper, encoded data are stored in binary data block that does not contain the characteristic information of a specific sequence platform, which means that data can be decoded according to a desired platform even in cases of Illumina, Solexa or Roche 454 data. Results The main calculation time using Crossbow was 173 minutes when 40 EC2 nodes were involved. In that case, an analysis preparation time of 464 minutes is required to encode data in the latest DNA compression method like G-SQZ and transmit it on a 183 Mbit/s bandwidth. However, it takes 194 minutes to encode and transmit data with SOLiDzipper under the same bandwidth conditions. These results indicate that the entire processing time can be reduced according to the encoding methods used, under the same network bandwidth conditions. Considering the limited network bandwidth, high-speed, high-efficiency encoding methods such as SOLiDzipper can make a significant contribution to higher productivity in labs seeking to take advantage of the cloud as an alternative to local computing. Availability http://szipper.dinfree.com . Academic/non-profit: Binary available for direct download at no cost. For-profit: Submit request for for-profit license from the web-site
The cortical activation pattern by a rehabilitation robotic hand: a functional NIRS study
Introduction: Clarification of the relationship between external stimuli and brain response has been an important topic in neuroscience and brain rehabilitation. In the current study, using functional near infrared spectroscopy (fNIRS), we attempted to investigate cortical activation patterns generated during execution of a rehabilitation robotic hand. Methods: Ten normal subjects were recruited for this study. Passive movements of the right fingers were performed using a rehabilitation robotic hand at a frequency of 0.5 Hz. We measured values of oxy-hemoglobin (HbO), deoxy-hemoglobin (HbR) and total-hemoglobin (HbT) in five regions of interest: the primary sensory-motor cortex (SM1), hand somatotopy of the contralateral SM1, supplementary motor area (SMA), premotor cortex (PMC), and prefrontal cortex (PFC). Results: HbO and HbT values indicated significant activation in the left SM1, left SMA, left PMC, and left PFC during execution of the rehabilitation robotic hand (uncorrected, p < 0.01). By contrast, HbR value indicated significant activation only in the hand somatotopic area of the left SM1 (uncorrected, p < 0.01). Conclusions: Our results appear to indicate that execution of the rehabilitation robotic hand could induce cortical activation. © 2014 Chang, Lee, Gu, Lee, Jin, Yeo, Seo and Jang.1
Competing edge structures of Sb and Bi bilayers by trivial and nontrivial band topologies
One-dimensional (1D) edge states formed at the boundaries of 2D normal and
topological insulators have shown intriguing quantum phases such as charge
density wave and quantum spin Hall effect. Based on first-principles
density-functional theory calculations including spin-orbit coupling (SOC), we
show that the edge states of zigzag Sb(111) and Bi(111) nanoribbons drastically
change the stability of their edge structures. For zigzag Sb(111) nanoribbon,
the Peierls-distorted or reconstructed edge structure is stabilized by a
band-gap opening. However, for zigzag Bi(111) nanoribbon, such two insulating
structures are destabilized due to the presence of topologically protected
gapless edge states, resulting in the stabilization of a metallic,
shear-distorted edge structure. We also show that the edge states of the
Bi(111) nanoribbon exhibit a larger Rashba-type spin splitting at the boundary
of Brillouin zone, compared to those of the Sb(111) nanoribbon. Interestingly,
the spin textures of edge states in the Peierls-distorted Sb edge structure and
the shear-distorted Bi edge structure have all three spin components
perpendicular and parallel to the edges, due to their broken mirror-plane
symmetry. The present findings demonstrate that the topologically trivial and
nontrivial edge states play crucial roles in determining the edge structures of
normal and topological insulators.Comment: 7 pages, 8 figure
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