915 research outputs found
Multistable attractors in a network of phase oscillators with three-body interaction
Three-body interactions have been found in physics, biology, and sociology.
To investigate their effect on dynamical systems, as a first step, we study
numerically and theoretically a system of phase oscillators with three-body
interaction. As a result, an infinite number of multistable synchronized states
appear above a critical coupling strength, while a stable incoherent state
always exists for any coupling strength. Owing to the infinite multistability,
the degree of synchrony in asymptotic state can vary continuously within some
range depending on the initial phase pattern.Comment: 5 pages, 3 figure
Field-induced phase transitions in a Kondo insulator
We study the magnetic-field effect on a Kondo insulator by exploiting the
periodic Anderson model with the Zeeman term. The analysis using dynamical mean
field theory combined with quantum Monte Carlo simulations determines the
detailed phase diagram at finite temperatures. At low temperatures, the
magnetic field drives the Kondo insulator to a transverse antiferromagnetic
phase, which further enters a polarized metallic phase at higher fields. The
antiferromagnetic transition temperature takes a maximum when the Zeeman
energy is nearly equal to the quasi-particle gap. In the paramagnetic phase
above , we find that the electron mass gets largest around the field where
the quasi-particle gap is closed. It is also shown that the induced moment of
conduction electrons changes its direction from antiparallel to parallel to the
field.Comment: 7 pages, 6 figure
Self-Consistent MHD Modeling of a Coronal Mass Ejection, Coronal Dimming, and a Giant Cusp-Shaped Arcade Formation
We performed magnetohydrodynamic simulation of coronal mass ejections (CMEs)
and associated giant arcade formations, and the results suggested new
interpretations of observations of CMEs. We performed two cases of the
simulation: with and without heat conduction. Comparing between the results of
the two cases, we found that reconnection rate in the conductive case is a
little higher than that in the adiabatic case and the temperature of the loop
top is consistent with the theoretical value predicted by the Yokoyama-Shibata
scaling law. The dynamical properties such as velocity and magnetic fields are
similar in the two cases, whereas thermal properties such as temperature and
density are very different.In both cases, slow shocks associated with magnetic
reconnectionpropagate from the reconnection region along the magnetic field
lines around the flux rope, and the shock fronts form spiral patterns. Just
outside the slow shocks, the plasma density decreased a great deal. The soft
X-ray images synthesized from the numerical results are compared with the soft
X-ray images of a giant arcade observed with the Soft X-ray Telescope aboard
{\it Yohkoh}, it is confirmed that the effect of heat conduction is significant
for the detailed comparison between simulation and observation. The comparison
between synthesized and observed soft X-ray images provides new interpretations
of various features associated with CMEs and giant arcades.Comment: 39 pages, 18 figures. Accepted for publication in the Astrophysical
Journal. The PDF file with high resplution figures can be downloaded from
http://www.kwasan.kyoto-u.ac.jp/~shiota/study/ApJ62426.preprint.pdf
Spicule Dynamics over Plage Region
We studied spicular jets over a plage area and derived their dynamic
characteristics using Hinode Solar Optical Telescope (SOT) high-resolution
images. The target plage region was near the west limb of the solar disk. This
location permitted us to study the dynamics of spicular jets without the
overlapping effect of spicular structures along the line of sight.
In this work, to increase the ease with which we can identify spicules on the
disk, we applied the image processing method `MadMax' developed by Koutchmy et
al. (1989). It enhances fine, slender structures (like jets), over a diffuse
background. We identified 169 spicules over the target plage. This sample
permits us to derive statistically reliable results regarding spicular
dynamics.
The properties of plage spicules can be summarized as follows: (1) In a plage
area, we clearly identified spicular jet features. (2) They were shorter in
length than the quiet region limb spicules, and followed ballistic motion under
constant deceleration. (3) The majority (80%) of the plage spicules showed the
cycle of rise and retreat, while 10% of them faded out without a complete
retreat phase. (4) The deceleration of the spicule was proportional to the
velocity of ejection (i.e. the initial velocity).Comment: 12 pages, 9 figures, accepted for publication in PAS
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Implementation of earlier antibiotic administration in patients with severe sepsis and septic shock in Japan: a descriptive analysis of a prospective observational study.
BACKGROUND: Time to antibiotic administration is a key element in sepsis care; however, it is difficult to implement sepsis care bundles. Additionally, sepsis is different from other emergent conditions including acute coronary syndrome, stroke, or trauma. We aimed to describe the association between time to antibiotic administration and outcomes in patients with severe sepsis and septic shock in Japan. METHODS: This prospective observational study enrolled 1184 adult patients diagnosed with severe sepsis based on the Sepsis-2 criteria and admitted to 59 intensive care units (ICUs) in Japan between January 1, 2016, and March 31, 2017, as the sepsis cohort of the Focused Outcomes Research in Emergency Care in Acute Respiratory Distress Syndrome, Sepsis and Trauma (FORECAST) study. We compared the characteristics and in-hospital mortality of patients administered with antibiotics at varying durations after sepsis recognition, i.e., 0-60, 61-120, 121-180, 181-240, 241-360, and 361-1440 min, and estimated the impact of antibiotic timing on risk-adjusted in-hospital mortality using the generalized estimating equation model (GEE) with an exchangeable, within-group correlation matrix, with "hospital" as the grouping variable. RESULTS: Data from 1124 patients in 54 hospitals were used for analyses. Of these, 30.5% and 73.9% received antibiotics within 1 h and 3 h, respectively. Overall, the median time to antibiotic administration was 102 min [interquartile range (IQR), 55-189]. Compared with patients diagnosed in the emergency department [90 min (IQR, 48-164 min)], time to antibiotic administration was shortest in patients diagnosed in ICUs [60 min (39-180 min)] and longest in patients transferred from wards [120 min (62-226)]. Overall crude mortality was 23.4%, where patients in the 0-60 min group had the highest mortality (28.0%) and a risk-adjusted mortality rate [28.7% (95% CI 23.3-34.1%)], whereas those in the 61-120 min group had the lowest mortality (20.2%) and risk-adjusted mortality rates [21.6% (95% CI 16.5-26.6%)]. Differences in mortality were noted only between the 0-60 min and 61-120 min groups. CONCLUSIONS: We could not find any association between earlier antibiotic administration and reduction in in-hospital mortality in patients with severe sepsis
Body Design Of Tendon-Driven Jumping Robot Using Single Actuator And Wire Set
Although a mechanism in which a single actuator and a wire passing through pulleys drive the joints is a strong candidate for realizing the dynamic behavior because of its appropriate weight and simple mechanism, the problem arises that the position of the pulley influences the dynamic behavior. This paper is focused on vertical jumping. In our research, we searched an appropriate set of positions of a pulley considering the practical development of the robot and derived the relationship between the position of the pulley and the force on the tips of the robot’s foot for jumping. Simulation results suggest the possibility that some sets of positions allow an error in the attachment of the pulley, and the derived relationship indicates that the ratio of the pulling force of wire and vertical force on the ground strongly constrain the position of the pulley
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