Direct fabrication of high-quality ring-shaped REBa2Cu3Oy bulk magnets by the Single-Direction Melt Growth (SDMG) method

Ring-shaped REBa2Cu3Oy melt-textured bulks have been successfully grown by the Single-Direction Melt Growth (SDMG) method, which enables the direct fabrication of uniform bulks with high reproducibility. Three homogeneous DyBa2Cu3Oy ring-bulks with various sizes were synthesized in this study. All of these bulks exhibited concentrically cone-shaped trapped field distribution on the surface and high trapped field more than 1.8 T at 77 K inside the ring, the highest among bulks of comparable size to date. Furthermore, superconducting properties such as superconducting transitions and critical current densities are highly uniform throughout the bulk, confirming the effectiveness of the SDMG approach. Our findings represent a significant advancement in the direct fabrication of high-quality ring-shaped REBCO bulks suitable for high magnetic field applications, in particular, compact nuclear magnetic resonance systems.Comment: 4 pages, 4 figuers, 1 tabl

Development of homogeneous and high-performance REBCO bulks with flexibility in shapes by the single-direction melt growth (SDMG) method

We have developed a single-direction melt growth method in which REBCO melt-textured bulks grow only vertically from a seed plate utilizing the difference in peritectic temperatures of REBCO. Entirely c-grown YBCO, DyBCO and GdBCO bulks with various sizes and shapes were successfully fabricated with high reproducibility. Disk-shaped bulks showed high trapped fields with almost concentric field distributions, reflecting homogeneous and boundaryless bulky crystal. In particular, a YBCO bulk with a 32 mm diameter trapped a high field more than 1 T at 77 K. Furthermore, rectangular and joined hexagonal REBCO bulks were successfully fabricated, showing designed field-trapping distributions reflecting their shapes through well-connected superconducting joints among bulks.Comment: 8 pages, 6 figures, 2 table

Areion: Highly-Efficient Permutations and Its Applications (Extended Version)

In real-world applications, the overwhelming majority of cases require (authenticated) encryption or hashing with relatively short input, say up to 2K bytes. Almost all TCP/IP packets are 40 to 1.5K bytes, and the maximum packet lengths of major protocols, e.g., Zigbee, Bluetooth low energy, and Controller Area Network (CAN), are less than 128 bytes. However, existing schemes are not well optimized for short input. To bridge the gap between real-world needs (in the future) and limited performances of state-of-the-art hash functions and authenticated encryptions with associated data (AEADs) for short input, we design a family of wide-block permutations Areion that fully leverages the power of AES instructions, which are widely deployed in many devices. As for its applications, we propose several hash functions and AEADs. Areion significantly outperforms existing schemes for short input and even competitive to relatively long messages. Indeed, our hash function is surprisingly fast, and its performance is less than three cycles/byte in the latest Intel architecture for any message size. It is significantly much faster than existing state-of-the-art schemes for short messages up to around 100 bytes, which are the most widely-used input size in real-world applications, on both the latest CPU architectures (IceLake, Tiger Lake, and Alder Lake) and mobile platforms (Pixel 7, iPhone 14, and iPad Pro with Apple M2)

Outburst of LS V+44 17 Observed by MAXI and RXTE, and Discovery of a Dip Structure in the Pulse Profile

We report on the first observation of an X-ray outburst of a Be/X-ray binary pulsar LS V +44 17/RX J0440.9+4431, and the discovery of an absorption dip structure in the pulse profile. An outburst of this source was discovered by MAXI GSC in 2010 April. It was the first detection of the transient activity of LS V +44 17 since the source was identified as a Be/X-ray binary in 1997. From the data of the follow-up RXTE observation near the peak of the outburst, we found a narrow dip structure in its pulse profile which was clearer in the lower energy bands. The pulse-phase-averaged energy spectra in the 3$-$100 keV band can be fitted with a continuum model containing a power-law function with an exponential cutoff and a blackbody component, which are modified at low energy by an absorption component. A weak iron K$\alpha$ emission line is also detected in the spectra. From the pulse-phase-resolved spectroscopy we found that the absorption column density at the dip phase was much higher than those in the other phases. The dip was not seen in the subsequent RXTE observations at lower flux levels. These results suggest that the dip in the pulse profile originates from the eclipse of the radiation from the neutron star by the accretion column.Comment: 18 pages, 7 figures, accepted for publication in PAS

Long-term Monitoring of the Black Hole Binary GX 339-4 in the High/Soft State during the 2010 Outburst with MAXI/GSC

We present the results of monitoring the Galactic black hole candidate GX 339-4 with the Monitor of All-sky X-ray Image (MAXI) / Gas Slit Camera (GSC) in the high/soft state during the outburst in 2010. All the spectra throughout the 8-month period are well reproduced with a model consisting of multi-color disk (MCD) emission and its Comptonization component, whose fraction is <= 25% in the total flux. In spite of the flux variability over a factor of 3, the innermost disk radius is constant at R_in = 61 +/- 2 km for the inclination angle of i = 46 deg and the distance of d=8 kpc. This R_in value is consistent with those of the past measurements with Tenma in the high/soft state. Assuming that the disk extends to the innermost stable circular orbit of a non-spinning black hole, we estimate the black hole mass to be M = 6.8 +/- 0.2 M_sun for i = 46 deg and d = 8 kpc, which is consistent with that estimated from the Suzaku observation of the previous low/hard state. Further combined with the mass function, we obtain the mass constraint of 4.3 M_sun < M < 13.3 M_sun for the allowed range of d = 6-15 kpc and i < 60 deg. We also discuss the spin parameter of the black hole in GX 339-4 by applying relativistic accretion disk models to the Swift/XRT data.Comment: 9 pages, 8 figures, accepted for publication in PASJ (Suzaku+MAXI special issue

A Spectral Study of the Black Hole Candidate XTE J1752-223 in the High/Soft State with MAXI, Suzaku and Swift

We report on the X-ray spectral analysis of the black hole candidate XTE\ J1752--223 in the 2009--2010 outburst, utilizing data obtained with the MAXI/Gas Slit Camera (GSC), the Swift/XRT, and Suzaku, which work complementarily. As already reported by Nakahira et al. (2010) MAXI monitored the source continuously throughout the entire outburst for about eight months. All the MAXI/GSC energy spectra in the high/soft state lasting for 2 months are well represented by a multi-color disk plus power-law model. The innermost disk temperature changed from $\sim$0.7 keV to $\sim$0.4 keV and the disk flux decreased by an order of magnitude. Nevertheless, the innermost radius is constant at $\sim$41 $D_{3.5}(\cos{\it i})^{-1/2}$ km, where $D_{3.5}$ is the source distance in units of 3.5 kpc and $i$ the inclination. The multi-color disk parameters obtained with the MAXI/GSC are consistent with those with the Swift/XRT and Suzaku. The Suzaku data also suggests a possibility that the disk emission is slightly Comptonized, which could account for broad iron-K features reported previously. Assuming that the obtained innermost radius represents the innermost stable circular orbit for a non-rotating black hole, we estimate the mass of the black hole to be 5.51$\pm$0.28 $M_{\odot}$ $D_{3.5}(\cos{\it i})^{-1/2}$, where the correction for the stress-free inner boundary condition and color hardening factor of 1.7 are taken into account. If the inclination is less than 49$^{\circ}$ as suggested from the radio monitoring of transient jets and the soft-to-hard transition in 2010 April occurred at 1--4% of Eddignton luminosity, the fitting of the Suzaku spectra with a relativistic accretion-disk model derives constraints on the mass and the distance to be 3.1--55 $M_{\odot}$ and 2.3--22 {\rm kpc}, respectively. This confirms that the compact object in XTE J1752--223 is a black hole.Comment: 12 pages including 7 figures and 4 tables, accepted for publication in PAS

A Large X-ray Flare from a Single Weak-lined T Tauri Star TWA-7 Detected with MAXI GSC

We present a large X-ray flare from a nearby weak-lined T Tauri star TWA-7 detected with the Gas Slit Camera (GSC) on the Monitor of All-sky X-ray Image (MAXI). The GSC captured X-ray flaring from TWA-7 with a flux of $3\times10^{-9}$ ergs cm$^{-2}$ s$^{-1}$ in 2--20 keV band during the scan transit starting at UT 2010-09-07 18:24:30.The estimated X-ray luminosity at the scan in the energy band is 3$\times10^{32}$ ergs s$^{-1}$,indicating that the event is among the largest X-ray flares fromT Tauri stars.Since MAXI GSC monitors a target only during a scan transit of about a minute per 92 min orbital cycle, the luminosity at the flare peak might have been higher than that detected. At the scan transit, we observed a high X-ray-to-bolometric luminosity ratio, log $L_{\rm X}/L_{\rm bol}$ = $-0.1^{+0.2}_{-0.3}$; i.e., the X-ray luminosity is comparable to the bolometric luminosity. Since TWA-7 has neither an accreting disk nor a binary companion, the observed event implies that none of those are essential to generate such big flares in T Tauri stars.Comment: 4 pages, 2 figures, 1 table accepted for publication in PAS

合併症を有するB型大動脈解離に対するステントグラフト内挿術における腎動脈に対する治療戦略 : 多施設共同研究

Background: Management of abdominal branches associated with Stanford type B aortic dissection is controversial without definite criteria for therapy after thoracic endovascular aortic repair (TEVAR). This is in part due to lack of data on natural history related to branch vessels and their relationship with the dissection flap, true lumen, and false lumen. Purpose: To investigate the natural history of abdominal branches after TEVAR for type B aortic dissection and the relationship between renal artery anatomy and renal volume as a surrogate measure of perfusion. Materials and Methods: This study included patients who underwent TEVAR for complicated type B dissection from January 2012 to March 2017 at 20 centers. Abdominal aortic branches were classified with following features: patency, branch vessel origin, and presence of extension of the aortic dissection into a branch (pattern 1, supplied by the true lumen without branch dissection; pattern 2, supplied by the true lumen with branch dissection, etc). The branch artery patterns before TEVAR were compared with those of the last follow-up CT (mean interval, 19.7 months) for spontaneous healing. Patients with one kidney supplied by pattern 1 and the other kidney by a different pattern were identified, and kidney volumes over the course were compared by using a simple linear regression model. Results: Two hundred nine patients (mean age ± standard deviation, 66 years ± 13; 165 men and 44 women; median follow-up, 18 months) were included. Four hundred fifty-nine abdominal branches at the last follow-up were evaluable. Spontaneous healing of the dissected branch occurred in 63% (64 of 102) of pattern 2 branches. Regarding the other patterns, 6.5% (six of 93) of branches achieved spontaneous healing. In 79 patients, renal volumes decreased in kidneys with pattern 2 branches with more than 50% stenosis and branches supplied by the aortic false lumen (patterns 3 and 4) compared with contralateral kidneys supplied by pattern 1 (pattern 2 vs pattern 1: −16% ± 16 vs 0.10% ± 11, P = .002; patterns 3 and 4 vs pattern 1: −13% ± 14 vs 8.5% ± 14, P = .004). Conclusion: Spontaneous healing occurs more frequently in dissected branches arising from the true lumen than in other branch patterns. Renal artery branches supplied by the aortic false lumen or a persistently dissected artery with greater than 50% stenosis are associated with significantly greater kidney volume loss.博士（医学）・乙第1461号・令和2年6月30日Copyright © 2019 by authors and RSNA. This work is licensed under the Creative Commons Attribution International License (CC BY-NC-ND 4.0). https://creativecommons.org/licenses/by-nc-nd/4.0/