Cold r-Process in Neutrino-Driven Winds

The r-process in a low temperature environment is explored, in which the neutron emission by photodisintegration does not play a role (cold r-process). A semi-analytic neutrino-driven wind model is utilized for this purpose. The temperature in a supersonically expanding outflow can quickly drop to a few 10^8 K, where the (n, gamma)-(gamma, n) equilibrium is never achieved during the heavy r-nuclei synthesis. In addition, the neutron capture competes with the beta-decay owing to the low matter density. Despite such non-standard physical conditions for the cold r-process, a solar-like r-process abundance curve can be reproduced. The cold r-process predicts, however, the low lead production compared to that expected in the traditional r-process conditions, which can be a possible explanation for the low lead abundances found in a couple of r-process-rich Galactic halo stars.Comment: 5 pages, 3 figures, accepted for publication in ApJ

Resonant Control of Interaction Between Different Electronic States

We observe a magnetic Feshbach resonance in a collision between the ground and metastable states of two-electron atoms of ytterbium (Yb). We measure the on-site interaction of doubly-occupied sites of an atomic Mott insulator state in a three-dimensional optical lattice as a collisional frequency shift in a high-resolution laser spectroscopy. The observed spectra are well fitted by a simple theoretical formula, in which two particles with an s-wave contact interaction are confined in a harmonic trap. This analysis reveals a wide variation of the interaction with a resonance behavior around a magnetic field of about 1.1 Gauss for the energetically lowest magnetic sublevel of ${}^{170}$Yb, as well as around 360 mG for the energetically highest magnetic sublevel of ${}^{174}$Yb. The observed Feshbach resonance can only be induced by an anisotropic inter-atomic interaction. This novel scheme will open the door to a variety of study using two-electron atoms with tunable interaction.Comment: 5 pages, 5 figure

Fingerprinting models of first-order phase transitions by the synergy between collider and gravitational-wave experiments

We investigate the sensitivity of future space-based interferometers such as LISA and DECIGO to the parameters of new particle physics models which drive a first-order phase transition in the early Universe. We first perform a Fisher matrix analysis on the quantities characterizing the gravitational wave spectrum resulting from the phase transition, such as the peak frequency and amplitude. We next perform a Fisher analysis for the quantities which determine the properties of the phase transition, such as the latent heat and the time dependence of the bubble nucleation rate. Since these quantities are determined by the model parameters of the new physics, we can estimate the expected sensitivities to such parameters. We illustrate this point by taking three new physics models for example: (1) models with additional isospin singlet scalars (2) a model with an extra real Higgs singlet, and (3) a classically conformal $B-L$ model. We find that future gravitational wave observations play complementary roles to future collider experiments in pinning down the parameters of new physics models driving a first-order phase transition.Comment: 64 pages, 35 figure

運動誘発電位監視下での胸部大動脈手術における冷却血液による脊髄保護

Objective: Motor-evoked potential monitoring is used to prevent paraplegia during thoracic aortic surgery. Multidetector computed tomography has been used preoperatively to detect the Adamkiewicz artery, but the hemodynamic significance of the Adamkiewicz artery is controversial. This study aims to evaluate whether the multidetector computed tomography–defined Adamkiewicz artery is hemodynamically essential and needs to be reconstructed with cold blood spinoplegia under motor-evoked potential monitoring. Methods: From 2005 to 2008, both preoperative multidetector computed tomographic analysis and intraoperative neurogenic motor-evoked potential monitoring with cold blood infusion into the clamped segment of the aorta were done in 15 patients. A motor-evoked potential decrease to less than 50% of the initial value at 3 minutes after cold blood infusion determined the hemodynamic significance of the multidetector computed tomography–defined Adamkiewicz artery. Adamkiewicz arteries determined to be essential were reconstructed, and those determined to be nonessential were sacrificed. Results: The Adamkiewicz artery was involved in the clamped segment of the aorta in 11 cases. After cold blood infusion, 8 patients experienced no significant motor-evoked potential decrease, and Adamkiewicz artery ligation was undertaken, whereas a moderate motor-evoked potential decrease was noted in 1 patient, prompting reconstruction. None of these 9 patients had permanent neurologic deficits. In 2 patients, the Adamkiewicz artery was reconstructed based on motor-evoked potential findings, with paraparesis occurring in 1 patient. In 4 patients without Adamkiewicz artery involvement in the clamped segment, there was no neurologic deficit. Conclusions: Cold blood infusion accelerates motor-evoked potential changes and might enable decision making regarding the need for reconstruction of multidetector computed tomography–defined Adamkiewicz arteries. Cold blood–loaded motor-evoked potential is beneficial to minimize Adamkiewicz artery reconstruction time and limit spinal cord ischemia.広島大学(Hiroshima University)博士(医学)doctora

Collisional stability of localized Yb(3P2{}^3\mathrm{P}_2) atoms immersed in a Fermi sea of Li

We establish an experimental method for a detailed investigation of inelastic collisional properties between ytterbium (Yb) in the metastable ${}^3\mathrm{P}_2$ state and ground state lithium (Li). By combining an optical lattice and a direct excitation to the ${}^3\mathrm{P}_2$ state we achieve high selectivity on the collisional partners. Using this method we determine inelastic loss coefficients in collisions between $^{174}$Yb(${}^3\mathrm{P}_2$) with magnetic sublevels of $m_J=0$ and $-2$ and ground state $^6$Li to be $(4.4\pm0.3)\times10^{-11}~\mathrm{cm}^3/\mathrm{s}$ and $(4.7\pm0.8)\times10^{-11}~\mathrm{cm}^3/\mathrm{s}$, respectively. Absence of spin changing processes in Yb(${}^3\mathrm{P}_2$)-Li inelastic collisions at low magnetic fields is confirmed by inelastic loss measurements on the $m_J=0$ state. We also demonstrate that our method allows us to look into loss processes in few-body systems separately.Comment: 12 pages, 7 figure

Assessment of therapeutic effects of statin on cardiac sympathetic nerve activity after reperfusion therapy in patients with first ST segment elevation myocardial infarction and normal low-density lipoprotein cholesterol

学位記番号：医博甲論文180