2,254 research outputs found
Direction Detector on an Excitable Field: Field Computation with Coincidence Detection
Living organisms process information without any central control unit and
without any ruling clock. We have been studying a novel computational strategy
that uses a geometrically arranged excitable field, i.e., "field computation."
As an extension of this research, in the present article we report the
construction of a "direction detector" on an excitable field. Using a numerical
simulation, we show that the direction of a input source signal can be detected
by applying the characteristic as a "coincidence detector" embedded on an
excitable field. In addition, we show that this direction detection actually
works in an experiment using an excitable chemical system. These results are
discussed in relation to the future development of "field computation."Comment: 6 pages, 3 figure
In-plane deformation of a triangulated surface model with metric degrees of freedom
Using the canonical Monte Carlo simulation technique, we study a Regge
calculus model on triangulated spherical surfaces. The discrete model is
statistical mechanically defined with the variables , and , which
denote the surface position in , the metric on a two-dimensional
surface and the surface density of , respectively. The metric is
defined only by using the deficit angle of the triangles in {}. This is in
sharp contrast to the conventional Regge calculus model, where {} depends
only on the edge length of the triangles. We find that the discrete model in
this paper undergoes a phase transition between the smooth spherical phase at
and the crumpled phase at , where is the bending
rigidity. The transition is of first-order and identified with the one observed
in the conventional model without the variables and . This implies
that the shape transformation transition is not influenced by the metric
degrees of freedom. It is also found that the model undergoes a continuous
transition of in-plane deformation. This continuous transition is reflected in
almost discontinuous changes of the surface area of and that of ,
where the surface area of is conjugate to the density variable .Comment: 13 pages, 7 figure
Novel Magnetic and Thermodynamic Properties of Thiospinel Compound CuCrZrS
We have carried out dc magnetic susceptibility, magnetization and specific
heat measurements on thiospinel CuCrZrS. Below 58 K, dc
magnetic susceptibility and magnetization data show ferromagnetic behavior with
a small spontaneous magnetization 0.27 f. u..
In dc magnetic susceptibility, large and weak irreversibilities are observed
below 6 K and in the range
respectively.
We found that there is no anomaly as a peak or step in the specific heat at
.Comment: 11 pages, 4 figure
Virtual Intermediaries : Consumption Tax Problems in Japan, Europe, and the United States : The Case of the Virtual Travel Agent
Functional imaging of visual cortical layers and subplate in awake mice with optimized three-photon microscopy
Two-photon microscopy is used to image neuronal activity, but has severe limitations for studying deeper cortical layers. Here, we developed a custom three-photon microscope optimized to image a vertical column of the cerebral cortex > 1 mm in depth in awake mice with low (<20 mW) average laser power. Our measurements of physiological responses and tissue-damage thresholds define pulse parameters and safety limits for damage-free three-photon imaging. We image functional visual responses of neurons expressing GCaMP6s across all layers of the primary visual cortex (V1) and in the subplate. These recordings reveal diverse visual selectivity in deep layers: layer 5 neurons are more broadly tuned to visual stimuli, whereas mean orientation selectivity of layer 6 neurons is slightly sharper, compared to neurons in other layers. Subplate neurons, located in the white matter below cortical layer 6 and characterized here for the first time, show low visual responsivity and broad orientation selectivity.National Institutes of Health (U.S.) (grant EY007023)National Institutes of Health (U.S.) (grant NS090473)National Institutes of Health (U.S.) (grant 4-P41-EB015871)National Science Foundation (U.S.) (grant EF1451125)Picower Institute for Learning and Memory (Engineering Collaboration Grant)Massachusetts Life Sciences Initiativ
How to distinguish the Haldane/Large-D state and the intermediate-D state in an S=2 quantum spin chain with the XXZ and on-site anisotropies
We numerically investigate the ground-state phase diagram of an S=2 quantum
spin chain with the and on-site anisotropies described by , where denotes the XXZ anisotropy parameter of the
nearest-neighbor interactions and the on-site anisotropy parameter. We
restrict ourselves to the and case for simplicity. Our main
purpose is to obtain the definite conclusion whether there exists or not the
intermediate- (ID) phase, which was proposed by Oshikawa in 1992 and has
been believed to be absent since the DMRG studies in the latter half of 1990's.
In the phase diagram with and there appear the XY state, the
Haldane state, the ID state, the large- (LD) state and the N\'eel state. In
the analysis of the numerical data it is important to distinguish three gapped
states; the Haldane state, the ID state and the LD state. We give a physical
and intuitive explanation for our level spectroscopy method how to distinguish
these three phases.Comment: Proceedings of "International Conference on Frustration in Condensed
Matter (ICFCM)" (Jan. 11-14, 2011, Sendai, Japan
Efficient and General Synthesis of Novel β-Polyfluoroalkoxy Vinamidinium Salts
Novel β-polyfluoroalkoxy vinamidinium salts 3 and/or 4 were synthesized in good yields by the reaction of N-(2- polyfluoroalkoxy-3 ,3-difluoro-1-propenyI)trimethylammonium iodides (2), prepared from N-(2,3,3-trifluoro-1-propenyl)trimethylammonium iodide (1), with secondary amines in MeCN at 70 °C for 1 h. The salts were also obtainable in comparable yields by the one-pot reaction of 1 with sodium polyfluoroalkoxide followed by treatment with amines
Effects of tool geometry and process conditions on material flow and strength of friction stir spot welded joints
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