307 research outputs found
Geometrically Frustrated Crystals: Elastic Theory and Dislocations
Elastic theory of ring-(or cylinder-)shaped crystals is constructed and the
generation of edge dislocations due to geometrical frustration caused by the
bending is studied. The analogy to superconducting (or superfluid) vortex state
is pointed out and the phase diagram of the ring-crystal, which depends on
radius and thickness, is discussed.Comment: 4 pages, 3 figure
Local Anisotropy of Fluids using Minkowski Tensors
Statistics of the free volume available to individual particles have
previously been studied for simple and complex fluids, granular matter,
amorphous solids, and structural glasses. Minkowski tensors provide a set of
shape measures that are based on strong mathematical theorems and easily
computed for polygonal and polyhedral bodies such as free volume cells (Voronoi
cells). They characterize the local structure beyond the two-point correlation
function and are suitable to define indices of
local anisotropy. Here, we analyze the statistics of Minkowski tensors for
configurations of simple liquid models, including the ideal gas (Poisson point
process), the hard disks and hard spheres ensemble, and the Lennard-Jones
fluid. We show that Minkowski tensors provide a robust characterization of
local anisotropy, which ranges from for vapor
phases to for ordered solids. We find that for fluids,
local anisotropy decreases monotonously with increasing free volume and
randomness of particle positions. Furthermore, the local anisotropy indices
are sensitive to structural transitions in these simple
fluids, as has been previously shown in granular systems for the transition
from loose to jammed bead packs
Phase Transition of the Ising model on a Hyperbolic Lattice
The matrix product structure is considered on a regular lattice in the
hyperbolic plane. The phase transition of the Ising model is observed on the
hyperbolic lattice by means of the corner-transfer-matrix
renormalization group (CTMRG) method. Calculated correlation length is always
finite even at the transition temperature, where mean-field like behavior is
observed. The entanglement entropy is also always finite.Comment: 4 pages, 3 figure
Models of plastic depinning of driven disordered systems
Two classes of models of driven disordered systems that exhibit
history-dependent dynamics are discussed. The first class incorporates local
inertia in the dynamics via nonmonotonic stress transfer between adjacent
degrees of freedom. The second class allows for proliferation of topological
defects due to the interplay of strong disorder and drive. In mean field theory
both models exhibit a tricritical point as a function of disorder strength. At
weak disorder depinning is continuous and the sliding state is unique. At
strong disorder depinning is discontinuous and hysteretic.Comment: 3 figures, invited talk at StatPhys 2
Development of a vascular endoscopic system for observing inner wall of large arteries for the use of endovascular intervention
金沢大学理工研究域機械工学系We have been developing an endoscopic system for observing inner wall of large arteries. The purpose of this system is to visualize the inner wall of large arteries, e.g., an aorta, without blocking off the blood stream for the use of an assistive technique for endovascular interventions such as stent-graft placement for aortic aneurysm. The technique newly introduced for this purpose was the use of intermittent high-pressure saline jet synchronized to heart beat (diastolic phase). In the previous paper [1], we reported performance of a prototype system using a commercially available bronchoscope having an outer diameter of 5mm with a biopsy channel. A discharging system for intermittent high-pressure saline jet was also constructed using a high-speed solenoid valve and a pressurizing tank. In this study, we tried to introduce a special hood (we call "Hemo-visor") on the tip of the endoscope in order to more clearly observe the target (inner wall of artery). From in vitro tests using a mock circulation system, it was confirmed that the Hemo-visor was highly effective for keeping saline solution around the endoscope tip against the blood stream, and for improving the quality of the picture obtained. © 2010 IEEE
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