221 research outputs found
HHV-6脳炎の初感染時と再活性化時における特徴の相違
藤田保健衛生大
Collective Phase Sensitivity
The collective phase response to a macroscopic external perturbation of a
population of interacting nonlinear elements exhibiting collective oscillations
is formulated for the case of globally-coupled oscillators. The macroscopic
phase sensitivity is derived from the microscopic phase sensitivity of the
constituent oscillators by a two-step phase reduction. We apply this result to
quantify the stability of the macroscopic common-noise induced synchronization
of two uncoupled populations of oscillators undergoing coherent collective
oscillations.Comment: 6 pages, 3 figure
Onset of Collective Oscillation in Chemical Turbulence under Global Feedback
Preceding the complete suppression of chemical turbulence by means of global
feedback, a different universal type of transition, which is characterized by
the emergence of small-amplitude collective oscillation with strong turbulent
background, is shown to occur at much weaker feedback intensity. We illustrate
this fact numerically in combination with a phenomenological argument based on
the complex Ginzburg-Landau equation with global feedback.Comment: 6 pages, 8 figures; to appear in Phys. Rev.
Collective dynamical response of coupled oscillators with any network structure
We formulate a reduction theory that describes the response of an oscillator
network as a whole to external forcing applied nonuniformly to its constituent
oscillators. The phase description of multiple oscillator networks coupled
weakly is also developed. General formulae for the collective phase sensitivity
and the effective phase coupling between the oscillator networks are found. Our
theory is applicable to a wide variety of oscillator networks undergoing
frequency synchronization. Any network structure can systematically be treated.
A few examples are given to illustrate our theory.Comment: 4 pages, 2 figure
Phase synchronization between collective rhythms of globally coupled oscillator groups: noisy identical case
We theoretically investigate collective phase synchronization between
interacting groups of globally coupled noisy identical phase oscillators
exhibiting macroscopic rhythms. Using the phase reduction method, we derive
coupled collective phase equations describing the macroscopic rhythms of the
groups from microscopic Langevin phase equations of the individual oscillators
via nonlinear Fokker-Planck equations. For sinusoidal microscopic coupling, we
determine the type of the collective phase coupling function, i.e., whether the
groups exhibit in-phase or anti-phase synchronization. We show that the
macroscopic rhythms can exhibit effective anti-phase synchronization even if
the microscopic phase coupling between the groups is in-phase, and vice versa.
Moreover, near the onset of collective oscillations, we analytically obtain the
collective phase coupling function using center-manifold and phase reductions
of the nonlinear Fokker-Planck equations.Comment: 15 pages, 7 figure
Noise-induced Turbulence in Nonlocally Coupled Oscillators
We demonstrate that nonlocally coupled limit-cycle oscillators subject to
spatiotemporally white Gaussian noise can exhibit a noise-induced transition to
turbulent states. After illustrating noise-induced turbulent states with
numerical simulations using two representative models of limit-cycle
oscillators, we develop a theory that clarifies the effective dynamical
instabilities leading to the turbulent behavior using a hierarchy of dynamical
reduction methods. We determine the parameter region where the system can
exhibit noise-induced turbulent states, which is successfully confirmed by
extensive numerical simulations at each level of the reduction.Comment: 23 pages, 17 figures, to appear in Phys. Rev.
Endogenization and excision of human herpesvirus 6 in human genomes
Sequences homologous to human herpesvirus 6 (HHV-6) are integrated within the nuclear genome of about 1% of humans, but it is not clear how this came about. It is also uncertain whether integrated HHV-6 can reactive into an infectious virus. HHV-6 integrates into telomeres, and this has recently been associated with polymorphisms affecting MOV10L1. MOV10L1 is located on the subtelomere of chromosome 22q (chr22q) and is required to make PIWI-interacting RNAs (piRNAs). As piRNAs block germline integration of transposons, piRNA-mediated repression of HHV-6 integration has been proposed to explain this association.In vitro, recombination of the HHV-6 genome along its terminal direct repeats (DRs) leads to excision from the telomere and viral reactivation, but the expected "solo-DR scar" has not been describedin vivo. Here we screened for integrated HHV-6 in 7,485 Japanese subjects using whole-genome sequencing (WGS). Integrated HHV-6 was associated with polymorphisms on chr22q. However, in contrast to prior work, we find that the reported MOV10L1 polymorphism is physically linked to an ancient endogenous HHV-6A variant integrated into the telomere of chr22q in East Asians. Unexpectedly, an HHV-6B variant has also endogenized in chr22q; two endogenous HHV-6 variants at this locus thus account for 72% of all integrated HHV-6 in Japan. We also report human genomes carrying only one portion of the HHV-6B genome, a solo-DR, supporting in vivo excision and possible viral reactivation. Together these results explain the recently-reported association between integrated HHV-6 and MOV10L1/piRNAs, suggest potential exaptation of HHV-6 in its coevolution with human chr22q, and clarify the evolution and risk of reactivation of the only intact (non-retro)viral genome known to be present in human germlines
Pressure-induced structural phase transition and new superconducting phase in UTe2
We report on the crystal structure and electronic properties of the heavy
fermion superconductor UTe2 at high pressure up to 11 GPa, as investigated by
X-ray diffraction and electrical resistivity experiments. The X-ray diffraction
measurements under high pressure using a synchrotron light source reveal
anisotropic linear compressibility of the unit cell up to 3.5 GPa, while a
pressure-induced structural phase transition is observed above 3.5-4GPa at room
temperature, where the body-centered orthorhombic crystal structure with the
space group Immm changes into a body-centered tetragonal structure with the
space group I4/mmm. The molar volume drops abruptly at the critical pressure,
while the distance between the first-nearest neighbor of U atoms increases,
implying a switch from the heavy electronic states to the weakly correlated
electronic states. Surprisingly, a new superconducting phase at pressures
higher than 7 GPa was detected at Tsc above 2K with a relatively low
upper-critical field, Hc2(0). The resistivity above 3.5GPa, thus, in the
high-pressure tetragonal phase, shows a large drop below 230 K, which may also
be related to a considerable change from the heavy electronic states to the
weakly correlated electronic states.Comment: 11 pages, 9 figure
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