288 research outputs found
Dynamical properties of S=1 bond-alternating Heisenberg chains in transverse magnetic fields
We calculate dynamical structure factors of the S=1 bond-alternating
Heisenberg chain with a single-ion anisotropy in transverse magnetic fields,
using a continued fraction method based on the Lanczos algorithm. In the
Haldane-gap phase and the dimer phase, dynamical structure factors show
characteristic field dependence. Possible interpretations are discussed. The
numerical results are in qualitative agreement with recent results for
inelastic neutron-scattering experiments on the S=1 bond-alternating
Heisenberg-chain compound and the
S=1 Haldane-gap compound in
transverse magnetic fields.Comment: 7 pages, 6 figure
Compressed Exponential Relaxation as Superposition of Dual Structure in Pattern Dynamics of Nematic Liquid Crystals
Soft-mode turbulence (SMT) is the spatiotemporal chaos observed in
homeotropically aligned nematic liquid crystals, where non-thermal fluctuations
are induced by nonlinear coupling between the Nambu-Goldstone and convective
modes. The net and modal relaxations of the disorder pattern dynamics in SMT
have been studied to construct the statistical physics of nonlinear
nonequilibrium systems. The net relaxation dynamics is well-described by a
compressed exponential function and the modal one satisfies a dual structure,
dynamic crossover accompanied by a breaking of time-reversal invariance.
Because the net relaxation is described by a weighted mean of the modal ones
with respect to the wave number, the compressed-exponential behavior emerges as
a superposition of the dual structure. Here, we present experimental results of
the power spectra to discuss the compressed-exponential behavior and the dual
structure from a viewpoint of the harmonic analysis. We also derive a
relationship of the power spectra from the evolution equation of the modal
autocorrelation function. The formula will be helpful to study non-thermal
fluctuations in experiments such as the scattering methods.Comment: 17pages, 3 figures, to be published on AIP conference proceedings for
"The 4th International Symposium on Slow Dynamics in Complex Systems
Dynamical properties of S=1 bond-alternating Heisenberg chains at finite temperatures
Dynamical structure factors of the S=1 bond-alternating spin chains in the
dimer phase are calculated at finite temperature, using the pair dynamical
correlated-effective-field approximation. At T=0, the delta-function-type peak
of the one-magnon mode appears. When temperature is increased, such a sharp
peak is broadened and the additional weak peak caused by the excitation from
the triplet state to the quintet state emerges in the higher energy region. The
results are discussed in comparison with those obtained by the exact
diagonalization method.Comment: 5 pages, 4 figure
Long-Distance and Low-Radiation Waveguide Antennas for Wireless Communication Systems inside Tunnels
Wireless LAN usage is also increasing at construction and civil engineering sites, and the efficiency of ICT construction has increased due to the use of tablet PCs and network cameras. When constructing a wireless LAN environment, for example, a LAN cable may be laid from outside the tunnel, and a number of wireless access points (APs) may be installed. However, it is not advantageous to use a large number of APs because the system price increases significantly. We consider using a long leaky-wave antenna to provide one AP. The reason for using a leaky-wave antenna is that, since the total tunnel length is on the order of km, it is necessary to reduce the power radiated by the antenna as much as possible to provide a functional communication area over a long distance. To reduce such transmission losses, we used a waveguide. A waveguide is a low-loss line and can function as a low-loss and low-radiation leaky-wave antenna which is suitable for long-distance communications; this is accomplished by combining a waveguide with a low-radiation antenna mechanism. In this chapter, we report the development of a waveguide-type leaky-wave antenna and the development of a wireless LAN environment in a tunnel
Active Brownian Motion in Threshold Distribution of a Coulomb Blockade Model
Randomly-distributed offset charges affect the nonlinear current-voltage
property via the fluctuation of the threshold voltage of Coulomb blockade
arrays. We analytically derive the distribution of the threshold voltage for a
model of one-dimensional locally-coupled Coulomb blockade arrays, and propose a
general relationship between conductance and the distribution. In addition, we
show the distribution for a long array is equivalent to the distribution of the
number of upward steps for aligned objects of different height. The
distribution satisfies a novel Fokker-Planck equation corresponding to active
Brownian motion. The feature of the distribution is clarified by comparing it
with the Wigner and Ornstein-Uhlenbeck processes. It is not restricted to the
Coulomb blockade model, but instructive in statistical physics generally.Comment: 4pages, 3figure
Seismic Velocity Structure in and around the Japanese Island Arc Derived from Seismic Tomography Including NIED MOWLAS Hi-net and S-net Data
Japanese Islands are composed of four plates, with two oceanic plates subducting beneath the two continental plates. In 2016 the National Research Institute for Earth Science and Disaster Resilience (NIED) Seafloor Observation Network for Earthquakes and Tsunamis along the Japan Trench (S-net) started seismic observation of the offshore Hokkaido to Boso region in the Pacific Ocean, and Dense Oceanfloor Network System for Earthquakes and Tsunamis (DONET) was transferred to NIED. We add the NIED S-net and DONET datasets to NIED high-sensitivity seismograph network (Hi-net) and full range seismograph network (F-net) datasets used in the previous study and obtain the three-dimensional seismic velocity structure beneath the Pacific Ocean as well as Japanese Islands. NIED S-net data dramatically improve the resolution beneath the Pacific Ocean at depths of 10–20 km because the seismic stations are located above the earthquakes and on the east side of the Japan Trench. We find a NS high-Vp zone at depths of 20–30 km. The 2018 Eastern Iburi earthquake occurred below the northern part of this high-V zone. The coseismic slip plane of the 2011 Tohoku-oki earthquake has low Vp/Vs, but its large slip region has high Vp. The broad low-Vp/Vs region may play a role in large earthquake occurrence
Exact solution of the one-dimensional spin- Ising model in magnetic field
In this paper, we study the Ising model with general spin in presence of
an external magnetic field by means of the equations of motion method and of
the Green's function formalism. First, the model is shown to be isomorphic to a
fermionic one constituted of species of localized particles interacting
via an intersite Coulomb interaction. Then, an exact solution is found, for any
dimension, in terms of a finite, complete set of eigenoperators of the latter
Hamiltonian and of the corresponding eigenenergies. This explicit knowledge
makes possible writing exact expressions for the corresponding Green's function
and correlation functions, which turn out to depend on a finite set of
parameters to be self-consistently determined. Finally, we present an original
procedure, based on algebraic constraints, to exactly fix these latter
parameters in the case of dimension 1 and spin . For this latter case
and, just for comparison, for the cases of dimension 1 and spin [F.
Mancini, Eur. Phys. J. B \textbf{45}, 497 (2005)] and spin 1 [F. Mancini, Eur.
Phys. J. B \textbf{47}, 527 (2005)], relevant properties such as magnetization
, susceptibility and specific heat are
reported as functions of temperature and external magnetic field both for
ferromagnetic and antiferromagnetic couplings. It is worth noticing the use we
made of composite operators describing occupation transitions among the 3
species of localized particles and the related study of single, double and
triple occupancy per site
Case report: A case of unilateral combined central retinal vein occlusion, incomplete central retinal artery occlusion, and papillitis following a third dose of COVID-19 vaccination
PurposeThe aim of this study was to present a case of severe visual loss due to retinal arteriovenous occlusion and papillitis in one eye following vaccination against coronavirus disease (COVID-19).MethodsA 45-year-old man undergoing treatment for hypertension had severely reduced visual acuity in the right eye 1 day after receiving a third dose of a COVID-19 vaccine manufactured by Moderna. Clinical examination showed that the best-corrected visual acuity in the right eye was counting fingers. Other findings included circumferential retinal hemorrhage, perimacular ischemic color, severe macular edema, and severe optic disc swelling, indicating the presence of central retinal vein occlusion, incomplete central retinal artery occlusion, and papillitis. Based on the possibility of post-vaccination inflammation and/or abnormal immune response, three courses of steroid pulse therapy were administered, and the visual acuity slightly improved to 20/1,000.ResultsThree months after the onset of symptoms, macular edema disappeared; conversely, retinal thinning of the macula and extensive non-perfusion areas mainly on the nasal side were noted.ConclusionThe findings in this case suggest that inflammation and abnormal immune response after receiving a COVID-19 vaccination may lead to combined retinal arteriovenous occlusion and papillitis
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