Self-consistent study of topological superconductivity in two-dimensional quasicrystals

We study two-dimensional $s$-wave topological superconductivity with Rashba spin-orbit coupling and Zeeman field in Penrose and Ammann-Beenker quasicrystals. By solving the Bogoliubov-de Gennes equations self-consistently for not only the superconducting order parameter, but also the spin-dependent Hartree potential, we show the stable occurrence of TSC with broken time-reversal symmetry in both Penrose and Ammann-Beenker quasicrystals. The topological nature of the quasicrystalline system is signified by the Bott index $B$. Topological phase transitions are found to occur, where $B$ changes between 0 and $\pm 1$, as the chemical potential or Zeeman field is varied. In terms of self-consistent solutions, we demonstrate the existence of a Majorana zero mode per edge or vortex when $B=\pm 1$, consistently with the bulk-edge/defect correspondence for periodic systems.Comment: 11 pages, 10 figure

Longitudinal magnetic excitation in KCuCl3 studied by Raman scattering under hydrostatic pressures

We measure Raman scattering in an interacting spin-dimer system KCuCl3 under hydrostatic pressures up to 5 GPa mediated by He gas. In the pressure-induced quantum phase, we observe a one-magnon Raman peak, which originates from the longitudinal magnetic excitationand is observable through the second-order exchange interaction Raman process. We report the pressure dependence of the frequency, halfwidth and Raman intensity of this mode.Comment: 4 pages, 3 figures, inpress in JPCS as a proceeding of LT2

Three Dimensional Magneto Hydrodynamical Simulations of Gravitational Collapse of a 15Msun Star

We introduce our newly developed two different, three dimensional magneto hydrodynamical codes in detail. One of our codes is written in the Newtonian limit (NMHD) and the other is in the fully general relativistic code (GRMHD). Both codes employ adaptive mesh refinement and, in GRMHD, the metric is evolved with the "Baumgarte-Shapiro-Shibata-Nakamura" formalism known as the most stable method at present. We did several test problems and as for the first practical test, we calculated gravitational collapse of a $15M_\odot$ star. Main features found from our calculations are; (1) High velocity bipolar outflow is driven from the proto-neutronstar and moves through along the rotational axis in strongly magnetized models; (2) A one-armed spiral structure appears which is originated from the low-$|T/W|$ instability; (3) By comparing GRMHD and NMHD models, the maximum density increases about $\sim30$ in GRMHD models due to the stronger gravitational effect. These features agree very well with previous studies and our codes are thus reliable to numerical simulation of gravitational collapse of massive stars.Comment: Accepted by ApJS, 55 pages, 34 figure

Velocity fields of blood flow in microchannels using a confocal micro-PIV system

The in vitro experimental investigations provide an excellent approach to understand complex blood flow phenomena involved at a microscopic level. This paper emphasizes an emerging experimental technique capable to quantify the flow patterns inside microchannels with high spatial and temporal resolution. This technique, known as confocal micro-PIV, consists of a spinning disk confocal microscope, high speed camera and a diode-pumped solid state (DPSS) laser. Velocity profiles of pure water (PW), physiological saline (PS) and in vitro blood were measured in a 100mm glass square and rectangular polydimethysiloxane (PDMS) microchannel. The good agreement obtained between measured and estimated results suggests that this system is a very promising technique to obtain detail information about micro-scale effects in microchannels by using both homogeneous and non-homogeneous fluids such as blood flow.This study was supported in part by the following grants: 21st Century COE Program for Future Medical Engineering based on Bio-nanotechnology, International Doctoral Program in Engineering from the Ministry of Education, Culture, Sports, Science and Technology of Japan (MEXT), “Revolutionary Simulation Software (RSS21)” next-generation IT program of MEXT; Grants-in-Aid for Scientific Research from MEXT and JSPS Scientific Research in Priority Areas (768) “Biomechanics at Micro- and Nanoscale Levels,” Scientific Research (A) No.16200031 “Mechanism of the formation, destruction, and movement of thrombi responsible for ischemia of vital organs.” The authors also thank all members of Esashi, Ono and Tanaka Lab. for their assistance in fabricating the PDMS microchannel

Velocity measurements of blood flow in a rectangular PDMS microchannel assessed by confocal micro-PIV system

This paper examines the ability to measure the velocity of both physiological saline (PS) and in vitro blood in a rectangular polydimethysiloxane (PDMS) microchannel by means of the confocal micro-PIV system. The PDMS microchannel, was fabricated by conventional soft lithography, had a microchannel near to a perfect rectangular shape (300μm wide, 45μm deep) and was optically transparent, which is suitable to measure both PS and in vitro blood using the confocal system. By using this latter combination, the measurements of trace particles seeded in the flow were performed for both fluids at a constant flow rate (Re=0.021). Generally, all the velocity profiles were found to be markedly blunt in the central region mainly due to the low aspect ratio (h/w=0.15) of the rectangular microchannel. Predictions by a theoretical model for the rectangular microchannel have showed fairly good correspondence with the experimental micro-PIV results for the PS fluid. Conversely, for the in vitro blood with 20% haematocrit, small fluctuations were found on velocity profiles.This study was supported in part by the following grants: International Doctoral Program in Engineering from the Ministry of Education, Culture, Sports, Science and Technology of Japan (MEXT), “Revolutionary Simulation Software (RSS21)” next-generation IT program of MEXT; Grants-in-Aid for Scientific Research from MEXT and JSPS Scientific Research in Priority Areas (768) “Biomechanics at Micro- and Nanoscale Levels,” Scientific Research (A) No.16200031 “Mechanism of the formation, destruction, and movement of thrombi responsible for ischemia of vital organs.” The authors also thank all members of Esashi, Ono and Tanaka Lab. for their assistance in fabricating the PDMS microchannel

Measurement of erythrocyte motions in microchannels by using a confocal micro-PTV system

Detailed knowledge on the motion of individual red blood cells (RBCs) flowing in microchannels is essential to provide a better understanding on the blood rheological properties and disorders in microvessels. Several studies on both individual and concentrated RBCs have already been performed in the past. However, all studies used conventional microscopes and also ghost cells to obtain visible trace RBCs through the microchannel. Recently, considerable progress in the development of confocal microscopy and consequent advantages of this microscope over the conventional microscopes have led to a new technique known as confocal micro-PIV. This technique combines the conventional PIV system with a spinning disk confocal microscope (SDCM). Due to its outstanding spatial filtering technique together with the multiple point light illumination system, this kind of microscope has the ability to obtain in-focus images with optical thickness less than 1 μm, a task extremely difficult to be achieved by using a conventional microscope. The main purpose of this paper is to investigate the ability of our confocal micro-PTV system to measure the motion of individual RBCs at different haematocrit (Hct) through microchannels

In vitro blood flow in a rectangular PDMS microchannel: experimental observations using a confocal micro-PIV system

Progress in microfabricated technologies has attracted the attention of researchers in several areas, including microcirculation. Microfluidic devices are expected to provide powerful tools not only to better understand the biophysical behavior of blood flow in microvessels, but also for disease diagnosis. Such microfluidic devices for biomedical applications must be compatible with state-of-the-art flow measuring techniques, such as confocal microparticle image velocimetry (PIV). This confocal system has the ability to not only quantify flow patterns inside microchannels with high spatial and temporal resolution, but can also be used to obtain velocity measurements for several optically sectioned images along the depth of the microchannel. In this study, we investigated the ability to obtain velocity measurements using physiological saline (PS) and in vitro blood in a rectangular polydimethysiloxane (PDMS) microchannel (300 μm wide, 45 μm deep) using a confocal micro-PIV system. Applying this combination, measurements of trace particles seeded in the flow were performed for both fluids at a constant flow rate (Re = 0.02). Velocity profiles were acquired by successive measurements at different depth positions to obtain three-dimensional (3-D) information on the behavior of both fluid flows. Generally, the velocity profiles were found to be markedly blunt in the central region, mainly due to the low aspect ratio (h/w = 0.15) of the rectangular microchannel. Predictions using a theoretical model for the rectangular microchannel corresponded quite well with the experimental micro-PIV results for the PS fluid. However, for the in vitro blood with 20% hematocrit, small fluctuations were found in the velocity profiles. The present study clearly shows that confocal micro-PIV can be effectively integrated with a PDMS microchannel and used to obtain blood velocity profiles along the full depth of the microchannel because of its unique 3-D optical sectioning ability. Advantages and disadvantages of PDMS microchannels over glass capillaries are also discussed