Remarkable similarities of two pairs of stable and saddle canards in a van der Pol oscillator under extremely weak periodic perturbation

Canards are interesting nonlinear phenomena that have generated intense research interest since their discovery in the late 20th century. We are interested here in how canard-generating dynamics are influenced by extremely weak periodic perturbations that cause the formation of saddle-node bifurcations in the fundamental harmonic entrainment region. In a previous study, we discovered that another entrainment region exists within the fundamental harmonic entrainment region surrounded by the second saddle-node bifurcation curves. We found that two pairs of stable and saddle canards coexist in this second entrainment region under such weak periodic perturbation. Moreover, the stable and saddle canards are matched pairwise; i.e., each stable canard quite closely resembles a corresponding saddle canard. Calculation of the correlation coefficients of the four canards revealed two similar solutions on the order of 0.9999⋯ between the two pairs of similar canards. In contrast, the correlation coefficients of the dissimilar canards differ from unity in proportion to the difference between the given bifurcation parameter value and the parameter values at the saddle-node bifurcation points. Approximately, they take values from 0.998 to 0.975. These contrasts are noteworthy. Similar bifurcation phenomena were observed in the 1/2-subharmonic entrainment region. We hypothesize that the two pairs of stable and saddle canards are invariant with respect to a slight shift of time at the saddle-node bifurcation points, and we numerically prove that such a property approximately holds at the bifurcation points

Dynamics of light-induced anomalous Hall effect in the three-dimensional Dirac semimetal Cd3_3As2_2

We experimentally study the dynamical behavior of the light-induced anomalous Hall effect in a three-dimensional Dirac semimetal, Cd$_3$As$_2$. An ultrashort, circularly polarized, multi-terahertz pump pulse breaks the time-reversal symmetry of a thin film sample. The resulting anomalous Hall effect is clearly observed through the polarization rotation of a single-cycle terahertz probe pulse. Comparing the experimental result with theory, we find that the field-induced injection current dominates the anomalous Hall effect during pump irradiation, while the Berry curvature of the Floquet-Weyl semimetal state does not appreciably contribute. Remarkably, even after pump irradiation, we observe an anomalous Hall effect that lasts for more than 10 ps. A model fit to the Hall conductivity spectrum reveals a relatively long scattering time over 400 fs. This result shows that circularly polarized light creates a polarization of the isospin degree of freedom in the Dirac semimetal, which labels the crystallographic point group representation of the overlapping Weyl semimetal bands. Our observation paves the way for conversion of a robust isospin flow into an electric current at room temperature, being a new analogue of the inverse spin Hall effect.Comment: 44 pages, 14 figure

First Results of Axion Dark Matter Search with DANCE

Axions are one of the well-motivated candidates for dark matter, originally proposed to solve the strong CP problem in particle physics. Dark matter Axion search with riNg Cavity Experiment (DANCE) is a new experimental project to broadly search for axion dark matter in the mass range of $10^{-17}~\mathrm{eV} < m_a < 10^{-11}~\mathrm{eV}$. We aim to detect the rotational oscillation of linearly polarized light caused by the axion-photon coupling with a bow-tie cavity. The first results of the prototype experiment, DANCE Act-1, are reported from a 24-hour observation. We found no evidence for axions and set 95% confidence level upper limit on the axion-photon coupling $g_{a \gamma} \lesssim 8 \times 10^{-4}~\mathrm{GeV^{-1}}$ in $10^{-14}~\mathrm{eV} < m_a < 10^{-13}~\mathrm{eV}$. Although the bound did not exceed the current best limits, this optical cavity experiment is the first demonstration of polarization-based axion dark matter search without any external magnetic field.Comment: 9 pages, 8 figure

Repeatability of proton magnetic resonance spectroscopy of the brain at 7 T: effect of scan time on semi-localized by adiabatic selective refocusing and short-echo time stimulated echo acquisition mode scans and their comparison

Background: Proton magnetic resonance spectroscopy (MRS) provides a unique opportunity for in vivo measurements of the brain's metabolic profile. Two methods of mainstream data acquisition are compared at 7 T, which provides certain advantages as well as challenges. The two representative methods have seldom been compared in terms of measured metabolite concentrations and different scan times. The current study investigated proton MRS of the posterior cingulate cortex using a semi-localized by adiabatic selective refocusing (sLASER) sequence and a short echo time (TE) stimulated echo acquisition mode (sSTEAM) sequence, and it compared their reliability and repeatability at 7 T using a 32-channel head coil. Methods: Sixteen healthy subjects were prospectively enrolled and scanned twice with an off-bed interval between scans. The scan parameters for sLASER were a TR/TE of 6.5 s/32 ms and 32 and 48 averages (sLASER×32 and sLASER×48, respectively). The scan parameters for sSTEAM were a TR/TE of 4 s/5 ms and 32, 48, and 64 averages (sSTEAM4×32, sSTEAM4×48, and sSTEAM4×64, respectively) in addition to that with a TR/TE of 8 s/5 ms and 32 averages (sSTEAM8×32). Data were analyzed using LCModel. Metabolites quantified with Cramér-Rao lower bounds (CRLBs) >50% were classified as not detected, and metabolites quantified with mean or median CRLBs ≤20% were included for further analysis. The SNR, CRLBs, coefficient of variation (CV), and metabolite concentrations were statistically compared using the Shapiro-Wilk test, one-way ANOVA, or the Friedman test. Results: The sLASER spectra for N-acetylaspartate + N-acetylaspartylglutamate (tNAA) and glutamate (Glu) had a comparable or higher SNR than sSTEAM spectra. Ten metabolites had lower CRLBs than prefixed thresholds: aspartate (Asp), γ-aminobutyric acid (GABA), glutamine (Gln), Glu, glutathione (GSH), myo-inositol (Ins), taurine (Tau), the total amount of phosphocholine + glycerophosphocholine (tCho), creatine + phosphocreatine (tCr), and tNAA. Performance of the two sequences was satisfactory except for GABA, for which sLASER yielded higher CRLBs (≥18%) than sSTEAM. Some significant differences in CRLBs were noted, but they were ≤2% except for GABA and Gln. Signal averaging significantly lowered CRLBs for some metabolites but only by a small amount. Measurement repeatability as indicated by median CVs was ≤10% for Gln, Glu, Ins, tCho, tCr, and tNAA in all scans, and that for Asp, GABA, GSH, and Tau was ≥10% under some scanning conditions. The CV for GABA according to sLASER was significantly higher than that according to sSTEAM, whereas the CV for Ins was higher according to sSTEAM. An increase in signal averaging contribute little to lower CVs except for Ins. Conclusions: Both sequences quantified brain metabolites with a high degree of precision and repeatability. They are comparable except for GABA, for which sSTEAM would be a better choice

A Case of Chronic Thromboembolic Pulmonary Hypertension Secondary to Myeloproliferative Disease

A woman in her ６０s presented with shortness of breath on exertion and was admitted to a nearby hospital in March ２００X. Contrast-enhanced computer tomography scan showed contrast defect images in the pulmonary artery and lower extremity vein. She was diagnosed with pulmonary embolism and deep venous thrombosis and anticoagulant therapy was started. At the same time, a blood test revealed an abnormal increased platelet count（７４０，０００/μl）, and she was diagnosed as myeloproliferative disease（primary myelofibrosis, JAK２ mutation +）. We follow up with oral administration of a steroid because she had a low risk of primary myelofibrosis. However, the symptom had been lasting, she was admitted into our hospital for examining the origin of symptom and treatment. Cardiac echocardiography suggested the presence of pulmonary hypertension, and lung ventilation perfusion scintigraphy showed widespread wedge accumulation defect, depressed area in bilateral lungs, and ventilator blood flow mismatch. In cardiac catheterization, the mean pulmonary artery pressure was as high as ３７mmHg. Per the test results, she was diagnosed chronic thromboembolic pulmonary hypertension（CTEPH）secondary to primary myelofibrosis. We proposed invasive treatment（pulmonary artery endarterectomy, balloon pulmonary arterioplasty）, but she desired just oxygen administration and medication therapy. It is reported that CTEPH develops in an organized thrombus after acute pulmonary embolism, but the mechanism of that development has not been revealed. In this case with primary myelofibrosis, we consider that the decrease of pulmonary vascular bed is due to a blood cell disorder and vascular remodeling is due to an increase of vascular endothelial growth factor and platelet derived growth factor secreted by abnormal increased platelet contributed to elevation of pulmonary artery pressure

The Japanese space gravitational wave antenna; DECIGO

DECi-hertz Interferometer Gravitational wave Observatory (DECIGO) is the future Japanese space gravitational wave antenna. DECIGO is expected to open a new window of observation for gravitational wave astronomy especially between 0.1 Hz and 10 Hz, revealing various mysteries of the universe such as dark energy, formation mechanism of supermassive black holes, and inflation of the universe. The pre-conceptual design of DECIGO consists of three drag-free spacecraft, whose relative displacements are measured by a differential Fabry– Perot Michelson interferometer. We plan to launch two missions, DECIGO pathfinder and pre- DECIGO first and finally DECIGO in 2024

Measurement of the CP Violation Parameter sin(2phi_1) in B^0_d Meson Decays

We present a measurement of the Standard Model CP violation parameter sin(2phi_1) based on a 10.5 fb^{-1} data sample collected at the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric e+e- collider. One neutral B meson is reconstructed in the J/psi K_S, psi(2S) K_S, chi_{c1} K_S, eta_c K_S, J/psi K_L or J/psi pi^0 CP-eigenstate decay channel and the flavor of the accompanying B meson is identified from its charged particle decay products. From the asymmetry in the distribution of the time interval between the two B-meson decay points, we determine sin(2phi_1) = 0.58 +0.32-0.34 (stat) +0.09-0.10 (syst).Comment: LaTex, 13 pages, 3 figures, submitted to P.R.

OMI-VT stormに対するカテーテルアブレーション

A ６８-year-old woman with VT storm and frequent appropriate ICD therapy was referred for catheter ablation. Her past history was notable for aortic valve replacement by mechanical valve due to infectious endocarditis １７ years prior to presentation and left ventricular apical old myocardial infarction with unknown onset. At ６７ years old, She admitted to the prior hospital due to ventricular tachycardia with LBBB and superior axis at heart rate of ２１０ per minutes. Administration of amiodarone and magnesium sulfate was ineffective and cardioversion of ２００J was successfully terminated the tachycardia. Intra-cardiac defibrillator was implanted and the administration of amiodarone and mexiletine was started. ５ months after, she admitted to the hospital due to the frequent appropriate shock against the same ventricular tachycardia. Administration of lidocaine, sotalol, pilsicainide, and magnesium sulfate could not control the tachycardia and she was referred to our hospital for catheter ablation. During the first session, ventricular tachycardia was easily induced and electroanatomical mapping was performed both during tachycardia and during sinus rhythm. Late diastolic potential preceding the onset of QRS wave by ４５ms was detected at the infero-septal side of the apical aneurysm. ７．５s of the RF energy application at this site could terminate the tachycardia and thereafter no ventricular tachycardia was induced. But after dose-reduction or cessation of some anti-arrhythmic drugs, ventricular tachycardia was recurred and second session was performed. This time, no ventricular tachycardia was induced, then we performed isthmus transection and core isolation against the apical aneurysm. Thereafter no ventricular tachycardia was occurred in spite of dose-reduction or cessation of some anti-arrhythmic drugs