Accurate numerical verification of the instanton method for macroscopic quantum tunneling: dynamics of phase slips

Instanton methods, in which imaginary-time evolution gives the tunneling rate, have been widely used for studying quantum tunneling in various contexts. Nevertheless, how accurate instanton methods are for the problems of macroscopic quantum tunneling (MQT) still remains unclear because of lack of their direct comparison with exact time evolution of the many-body Schroedinger equation. Here, we verify instanton methods applied to coherent MQT. Specifically applying the quasi-exact numerical method of time-evolving block decimation to the system of bosons in a ring lattice, we directly simulate the real-time quantum dynamics of supercurrents, where a coherent oscillation between two macroscopically distinct current states occurs due to MQT. The tunneling rate extracted from the coherent oscillation is compared with that given by the instanton method. We show that the error is within 10% when the effective Planck's constant is sufficiently small. We also discuss phase slip dynamics associated with the coherent oscillations.Comment: 19 pages, 14 figures, 1 tabl

Quantum phase slips in one-dimensional superfluids in a periodic potential

We study the decay of superflow of a one-dimensional (1D) superfluid in the presence of a periodic potential. In 1D, superflow at zero temperature can decay via quantum nucleation of phase slips even when the flow velocity is much smaller than the critical velocity predicted by mean-field theories. Applying the instanton method to the O(2) quantum rotor model, we calculate the nucleation rate of quantum phase slips $\Gamma$. When the flow momentum $p$ is small, we find that the nucleation rate per unit length increases algebraically with $p$ as $\Gamma/L \propto p^{2K-2}$, where $L$ is the system size and $K$ is the Tomonaga-Luttinger parameter. Based on the relation between the nucleation rate and the quantum superfluid-insulator transition, we present a unified explanation on the scaling formulae of the nucleation rate for periodic, disorder, and single-barrier potentials. Using the time-evolving block decimation method, we compute the exact quantum dynamics of the superflow decay in the 1D Bose-Hubbard model at unit filling. From the numerical analyses, we show that the scaling formula is valid for the case of the Bose-Hubbard model, which can quantitatively describe Bose gases in optical lattices.Comment: 11 pages, 8 figures, Sec. V is adde

Platypnea-orthodeoxia syndrome in the right lateral decubitus position: a case report

Abstract Background Platypnea-orthodeoxia syndrome is a rare syndrome characterized by dyspnea and hypoxia when the patient is sitting or standing. Here we report a case of platypnea-orthodeoxia syndrome caused by a right hemidiaphragmatic elevation with giant liver cyst that triggered a right-to-left shunt through the patent foramen ovale. This case report is the first presentation of a case secondary to hemidiaphragmatic elevation with giant liver cyst. In addition to this, a malposition of the pacemaker lead could be associated with platypnea-orthodeoxia syndrome in this case. Case presentation A 91-year-old Japanese woman presented to our hospital with hypoxia of unknown origin. Severe hypoxia and cyanosis were observed only in the right lateral decubitus position. A chest X-ray and computed tomography scan revealed right hemidiaphragmatic elevation, which was probably compressing the right atrium. A transesophageal echocardiogram showed a compressed right atrium and shunt blood flow in both directions: from the left to the right atrium and vice versa. The shunt flow was exacerbated by postural changes from the left to the right lateral decubitus. A transesophageal echocardiogram also confirmed compression of the right atrium due to giant liver cyst and a malposition of the pacemaker lead abnormally placed in the left atrium through patent foramen ovale. We concluded that the cause of hypoxia was platypnea-orthodeoxia syndrome with right-to-left interatrial shunt through patent foramen ovale. Surgical closure of patent foramen ovale was not performed due to the age of our patient, surgical difficulties, and failure to obtain informed consent. For these reasons she was discharged after receiving medical advice about her posture. Conclusions Platypnea-orthodeoxia syndrome is rare and difficult to diagnose. The present case suggests that hypoxia due to postural changes should be considered a differential diagnosis of platypnea-orthodeoxia syndrome

Mid-term feasibility and safety of downgrade procedure from defibrillator to pacemaker with cardiac resynchronization therapy

Backgrounds: Some patients who undergo implantation of cardiac resynchronization therapy with defibrillator (CRT-D) survive long enough, thus requiring CRT-D battery replacement. Defibrillator therapy might become unnecessary in patients who have had significant clinical improvement and recovery of left ventricular ejection fraction (LVEF) after CRT-D implantation. Methods: Forty-nine patients who needed replacement of a CRT-D battery were considered for exchange of CRT-D for cardiac resynchronization therapy with pacemaker (CRT-P) if they met the following criteria: LVEF >45%; the indication for an implantable cardioverter defibrillator was primary prevention at initial implantation and no appropriate implantable cardioverter defibrillator therapy was documented after initial implantation of the CRT-D. Results: Seven patients (14.2%) were undergone a downgrade from CRT-D to CRT-P without any complications. No ventricular tachyarrhythmic events were observed during a mean follow-up of 39.7 ± 21.1 months and there was no significant change in LVEF between before and 1 year after device replacement (53.5% ± 6.2% vs. 56.4% ± 7.3%, P = 0.197). Conclusions: This study confirmed mid-term feasibility and safety of downgrade from CRT-D to CRT-P alternative to conventional replacement with CRT-D. Keywords: Cardiac resynchronization therapy, Cardioverter defibrillator, Downgrade, Primary prevention, Ventricular tachyarrhythmi

Epidural cylinder electrodes for presurgical evaluation of intractable epilepsy: technical note

This is a technical report describing a different technique for the insertion of epidural electrodes in the preoperative evaluation of epilepsy surgery. Our experience in 67 cases using this technique is analyzed. Cylinder electrodes with multiple recording nodes spaced 1 cm apart along a Silastic core are placed into the epidural space under general anesthesia through single or multiple burr holes. We reviewed the data on 67 cases of medically intractable epilepsy requiring intracranial monitoring that had epidural cylinder electrodes placed. The electrodes were placed bilaterally or contralateral to subdural grids in 64 of the 67 cases. Continuous monitoring was performed from 1 to 3 weeks. This method was most useful when used bilaterally or contralateral to subdural grids. Definitive surgery was rendered in 48 of 67 cases. After monitoring, all electrodes were removed at bedside or upon return to the operating room for definitive surgery. There were no mortalities, infections, cerebrospinal fluid leaks, neurologic deficits, or electrode malfunctions. Two patients (2/67, 3%) did develop subdural hematomas early in our series after dural injury near the pterion; however, these patients did not sustain permanent deficit. Epidural cylinders are another option for preoperative monitoring, useful for determining lobe or laterality of seizure genesis. They offer an alternate method to EPEs in cases where epidural recording is desirable. The cylinder electrodes are easy to place and can be removed without a return to the operating theater. The electrodes' minimal mass effect allows them to be safely placed bilaterally or contralateral to subdural grids. The epidural cylinders can monitor cortex with a greater density of nodes and can access regions not amenable to EPEs

医療・介護福祉領域における東洋医学診断法に関する研究

The Scythian Iceman, the oldest European mummified body with tattoos, provides strong evidence that the acupuncture meridian theory was established more than 5, 000 years ago. The current medical treatment system in Japan lacks the holistic concepts of traditional oriental medicine of which the meridian system is an important component. In the present study, we developed a new meridian diagnosis instrument to determine the quantitative and qualitative balance of the human body, based on traditional oriental medical theory. A newly devised three point system equipment with a constant current (10μA) generation circuit (INA126) was used to clinically measure the electrical resistance value of the 12 true meridian routes. Furthermore, the electro-physiological background was also investigated. The measured value of the meridian flow resistance of the 12 true meridians was displayed on a meridian flow radar chart, and a traditional oriental medical diagnosis was conducted based on the changes in values on the radar chart. In addition, we also investigated the clinical effect of treatment with acupuncture and oriental herbal medicine of a chronic pain patient diagnosed using radar chart values