693 research outputs found
Discreteness-Induced Slow Relaxation in Reversible Catalytic Reaction Networks
Slowing down of the relaxation of the fluctuations around equilibrium is
investigated both by stochastic simulations and by analysis of Master equation
of reversible reaction networks consisting of resources and the corresponding
products that work as catalysts. As the number of molecules is decreased,
the relaxation time to equilibrium is prolonged due to the deficiency of
catalysts, as demonstrated by the amplification compared to that by the
continuum limit. This amplification ratio of the relaxation time is represented
by a scaling function as , and it becomes prominent as
becomes less than a critical value , where is the inverse
temperature and is the energy gap between a product and a resource
QTL analyses of temporal and intensity components of home-cage activity in KJR and C57BL/6J strains
Peer reviewedPublisher PD
Discreteness-induced Transition in Catalytic Reaction Networks
Drastic change in dynamics and statistics in a chemical reaction system,
induced by smallness in the molecule number, is reported. Through stochastic
simulations for random catalytic reaction networks, transition to a novel state
is observed with the decrease in the total molecule number N, characterized by:
i) large fluctuations in chemical concentrations as a result of intermittent
switching over several states with extinction of some molecule species and ii)
strong deviation of time averaged distribution of chemical concentrations from
that expected in the continuum limit, i.e., . The origin of
transition is explained by the deficiency of molecule leading to termination of
some reactions. The critical number of molecules for the transition is obtained
as a function of the number of molecules species M and that of reaction paths
K, while total reaction rates, scaled properly, are shown to follow a universal
form as a function of NK/M
Stability of ferromagnetism in the Hubbard model on the kagom\'e lattice
The Hubbard model on the kagom\'e lattice has highly degenerate ground states
(the flat lowest band) in the corresponding single-electron problem and
exhibits the so-called flat-band ferromagnetism in the many-electron ground
states as was found by Mielke. Here we study the model obtained by adding extra
hopping terms to the above model. The lowest single-electron band becomes
dispersive, and there is no band gap between the lowest band and the other
band. We prove that, at half-filling of the lowest band, the ground states of
this perturbed model remain saturated ferromagnetic if the lowest band is
nearly flat.Comment: 4 pages, 1 figur
Scalable Spin Amplification with a Gain over a Hundred
We propose a scalable and practical implementation of spin amplification
which does not require individual addressing nor a specially tailored spin
network. We have demonstrated a gain of 140 in a solid-state nuclear spin
system of which the spin polarization has been increased to 0.12 using dynamic
nuclear polarization with photoexcited triplet electron spins. Spin
amplification scalable to a higher gain opens the door to the single spin
measurement for a readout of quantum computers as well as practical
applications of nuclear magnetic resonance (NMR) spectroscopy to infinitesimal
samples which have been concealed by thermal noise.Comment: 6 pages, 7 figure
Ferromagnetism in the Hubbard model with Topological/Non-Topological Flat Bands
We introduce and study two classes of Hubbard models with magnetic flux or
with spin-orbit coupling, which have a flat lowest band separated from other
bands by a nonzero gap. We study the Chern number of the flat bands, and find
that it is zero for the first class but can be nontrivial in the second. We
also prove that the introduction of on-site Coulomb repulsion leads to
ferromagnetism in both the classes.Comment: 6 pages, 5 figure
Electronic-Structure-Driven Magnetic Ordering in a Kondo Semiconductor CeOs2Al10
We report the anisotropic changes in the electronic structure of a Kondo
semiconductor CeOsAl across an anomalous antiferromagnetic ordering
temperature () of 29 K, using optical conductivity spectra. The spectra
along the - and -axes indicate that a - hybridization gap emerges
from a higher temperature continuously across . Along the b-axis, on the
other hand, a different energy gap with a peak at 20 meV appears below 39 K,
which is higher temperature than , because of structural distortion. The
onset of the energy gap becomes visible below . Our observation reveals
that the electronic structure as well as the energy gap opening along the
b-axis due to the structural distortion induces antiferromagnetic ordering
below .Comment: 4 pages, 4 figure
Direct mapping of the spin-filtered surface bands of a three-dimensional quantum spin Hall insulator
Spin-polarized band structure of the three-dimensional quantum spin Hall
insulator (x=0.12-0.13) was fully elucidated by
spin-polarized angle-resolved photoemission spectroscopy using a high-yield
spin polarimeter equipped with a high-resolution electron spectrometer. Between
the two time-reversal-invariant points, and , of the
(111) surface Brillouin zone, a spin-up band ( band) was found to
cross the Fermi energy only once, providing unambiguous evidence for the strong
topological insulator phase. The observed spin-polarized band dispersions
determine the "mirror chirality" to be -1, which agrees with the theoretical
prediction based on first-principles calculations
A Model of Strongly Correlated Electrons with Condensed Resonating-Valence-Bond Ground States
We propose a new exactly solvable model of strongly correlated electrons. The
model is based on a - model of the CuO plane with infinitely large
repulsive interactions on Cu-sites, and it contains additional
correlated-hopping, pair-hopping and charge-charge interactions of electrons.
For even numbers of electrons less than or equal to 2/3-filling, we construct
the exact ground states of the model, all of which have the same energy and
each of which is the unique ground state for a fixed electron number. It is
shown that these ground states are the resonating-valence-bond states which are
also regarded as condensed states in which all electrons are in a single
two-electron state. We also show that the ground states exhibit off-diagonal
long-range order.Comment: 17 pages, 1 figure, v2: minor changes, v3: minor changes and typos
correction
Electron paramagnetic resonance (EPR) in medical dosimetry
This paper describes the fundamentals of electron paramagnetic resonance (EPR) and its application to retrospective measurements of clinically significant doses of ionizing radiation. X-band is the most widely used in EPR dosimetry because it represents a good compromise between sensitivity, sample size and water content in the sample. Higher frequency bands (e.g., W and Q) provide higher sensitivity, but they are also greatly influenced by water content. L and S bands can be used for EPR measurements in samples with high water content but they are less sensitive than X-band. Quality control for therapeutic radiation facilities using X-band EPR spectrometry of alanine is also presented
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