11,061 research outputs found
Reconstruction of phase dynamics from macroscopic observations based on linear and nonlinear response theories
We propose a method to reconstruct the phase dynamics in rhythmical interacting systems from macroscopic responses to weak inputs by developing linear and nonlinear response theories, which predict the responses in a given system. By solving an inverse problem, the method infers an unknown system: the natural frequency distribution, the coupling function, and the time delay which is inevitable in real systems. In contrast to previous methods, our method requires neither strong invasiveness nor microscopic observations. We demonstrate that the method reconstructs two phase systems from observed responses accurately. The qualitative methodological advantages demonstrated by our quantitative numerical examinations suggest its broad applicability in various fields, including brain systems, which are often observed through macroscopic signals such as electroencephalograms and functional magnetic response imaging
Linear response theory for coupled phase oscillators with general coupling functions
We develop a linear response theory by computing the asymptotic value of the order parameter from the linearized equation of continuity around the nonsynchronized reference state using the Laplace transform in time. The proposed theory is applicable to a wide class of coupled phase oscillator systems and allows for any coupling functions, any natural frequency distributions, any phase-lag parameters, and any values for the time-delay parameter. This generality is in contrast to the limitation of the previous methods of the Ott–Antonsen ansatz and the self-consistent equation for an order parameter, which are restricted to a model family whose coupling function consists of only a single sinusoidal function. The theory is verified by numerical simulations
Bottom-Up Approach to Moduli Dynamics in Heavy Gravitino Scenario : Superpotential, Soft Terms and Sparticle Mass Spectrum
The physics of moduli fields is examined in the scenario where the gravitino
is relatively heavy with mass of order 10 TeV, which is favored in view of the
severe gravitino problem. The form of the moduli superpotential is shown to be
determined, if one imposes a phenomenological requirement that no physical CP
phase arise in gaugino masses from conformal anomaly mediation. This bottom-up
approach allows only two types of superpotential, each of which can have its
origins in a fundamental underlying theory such as superstring. One
superpotential is the sum of an exponential and a constant, which is identical
to that obtained by Kachru et al (KKLT), and the other is the racetrack
superpotential with two exponentials. The general form of soft supersymmetry
breaking masses is derived, and the pattern of the superparticle mass spectrum
in the minimal supersymmetric standard model is discussed with the KKLT-type
superpotential. It is shown that the moduli mediation and the anomaly mediation
make comparable contributions to the soft masses. At the weak scale, the
gaugino masses are rather degenerate compared to the minimal supergravity,
which bring characteristic features on the superparticle masses. In particular,
the lightest neutralino, which often constitutes the lightest superparticle and
thus a dark matter candidate, is a considerable admixture of gauginos and
higgsinos. We also find a small mass hierarchy among the moduli, gravitino, and
superpartners of the standard-model fields. Cosmological implications of the
scenario are briefly described.Comment: 45 pages, 10 figures, typos correcte
Neutralino Dark Matter from Heavy Gravitino Decay
We propose a new scenario of non-thermal production of neutralino cold dark
matter, in which the overproduction problem of lightest supersymmetric
particles (LSPs) in the standard thermal history is naturally solved. The
mechanism requires a heavy modulus field which decays mainly to ordinary
particles releasing large entropy to dilute gravitinos produced just after
inflation and thermal relics of LSPs. Significant amount of gravitinos are also
pair-produced at the decay, which subsequently decay into the neutralinos. We
identify the regions of the parameter space in which the requisite abundance of
the neutralino dark matter is obtained without spoiling the big-bang
nucleosynthesis by injection of hadronic showers from gravitino decay. The
neutralino abundance obtained in this mechanism is insensitive to the details
of the superparticle mass spectrum, unlike the standard thermal abundance. We
also briefly mention the testability of the scenario in future experiments.Comment: 19 pages, 5 figures, to appear in Phys. Rev.
The Current Status of Knowledge and Behavior Related to STI Prevention among High School Students in Korea
This study explores coping with STIs and related factors including knowledge, sexual behavior, and sex education among Korean adolescents. Anonymous self-administered questionnaires were distributed to 135 male and 150 female high school students. The results showed that 2.1% of participants had had sexual experience. Males had less information than females (p<0.05); 38.5% of males did not consult anyone. In contrast, females acquired information from and consulted with their parents. Although females' sexual abstinence behavior was higher than that of males (p<0.001), there were no significant differences in the STI knowledge test. Regarding sex education, 32.4–59.5% of students had received education on STIs. Students' degree of satisfaction with sexual knowledge was 10.2%, their understanding of STIs was poor, and they could not cope with having a checkup. In conclusion, high school students receive insufficient education to protect themselves from STIs. Their knowledge was not related to sexual abstinence behavior and coping behavior. Therefore, schools in Korea should provide high school students with appropriate education on STI prevention and coping behavior. In addition, an environment that facilitates consultation and clinics for helping young people deal with sexual problems should be provided
A note on Kerr/CFT and free fields
The near-horizon geometry of the extremal four-dimensional Kerr black hole
and certain generalizations thereof has an SL(2,R) x U(1) isometry group.
Excitations around this geometry can be controlled by imposing appropriate
boundary conditions. For certain boundary conditions, the U(1) isometry is
enhanced to a Virasoro algebra. Here, we propose a free-field construction of
this Virasoro algebra.Comment: 10 pages, v2: comments and references adde
Time-, Frequency-, and Wavevector-Resolved X-Ray Diffraction from Single Molecules
Using a quantum electrodynamic framework, we calculate the off-resonant
scattering of a broad-band X-ray pulse from a sample initially prepared in an
arbitrary superposition of electronic states. The signal consists of
single-particle (incoherent) and two-particle (coherent) contributions that
carry different particle form factors that involve different material
transitions. Single-molecule experiments involving incoherent scattering are
more influenced by inelastic processes compared to bulk measurements. The
conditions under which the technique directly measures charge densities (and
can be considered as diffraction) as opposed to correlation functions of the
charge-density are specified. The results are illustrated with time- and
wavevector-resolved signals from a single amino acid molecule (cysteine)
following an impulsive excitation by a stimulated X-ray Raman process resonant
with the sulfur K-edge. Our theory and simulations can guide future
experimental studies on the structures of nano-particles and proteins
Suppression of cell cycle progression by Jun dimerization protein (JDP2) involves down-regulation of cyclin A2
We report here a novel role for Jun dimerization protein-2 (JDP2) as a regulator of the progression of normal cells through the cell cycle. To determine the role of JDP2 in vivo, we generated Jdp2 knock-out (Jdp2KO) mice by targeting exon 1 to disrupt the site of initiation of transcription. The healing of wounded skin of Jdp2KO mice proceeded more rapidly than that of control mice and more proliferating cells were found at wound margins. Fibroblasts derived from embryos of Jdp2KO mice proliferated more rapidly and formed more colonies than wild-type fibroblasts. JDP2 was recruited to the promoter of the gene for cyclin A2 (ccna2) at a previously unidentified AP-1 site. Cells lacking Jdp2 had elevated levels of cyclin A2 mRNA. Moreover, reintroduction of JDP2 resulted in repression of transcription of ccna2 and of cell cycle progression. Thus, transcription of the gene for cyclin A2 appears to be a direct target of JDP2 in the suppression of cell proliferation
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