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5,157 results on '"Sugiyama, K."'

204. Infrared observations of the flaring maser source G358.93−0.03

Author

Stecklum, B., primary, Wolf, V., additional, Linz, H., additional, Caratti o Garatti, A., additional, Schmidl, S., additional, Klose, S., additional, Eislöffel, J., additional, Fischer, Ch., additional, Brogan, C., additional, Burns, R. A., additional, Bayandina, O., additional, Cyganowski, C., additional, Gurwell, M., additional, Hunter, T., additional, Hirano, N., additional, Kim, K.-T., additional, MacLeod, G., additional, Menten, K. M., additional, Olech, M., additional, Orosz, G., additional, Sobolev, A., additional, Sridharan, T. K., additional, Surcis, G., additional, Sugiyama, K., additional, van der Walt, J., additional, Volvach, A., additional, and Yonekura, Y., additional

Published
2021
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205. Electron acceleration based on an elongated plasma channel

Author

Chen, L.M., Nakajima, K., Hong, W., Kameshima, T., Hua, J.F., Kotaki, H., Sugiyama, K., Wen, X.L., Wu, Y.C., Tang, C.M., Gu, Y.Q., Peng, H.S., Kurokawa, S., Koga, J., Bulanov, S.V., and Tajima, T.

Subjects
Laser-plasma interactions -- Evaluation, Plasma physics -- Research, Electron accelerators -- Usage, Business, Chemistry, Electronics, Electronics and electrical industries
Abstract

Experiments for the laser guiding studies has been carried out with the 30-fs 100-TW Ti:sapphire laser pulse interaction with the underdense plasma produced by a long-slab (1.2 x 10 [mm.sup.2]) gas jet and an ablative laser-triggered discharged capillary. Formation of an extremely long plasma channel with a length (~10 mm) 10 times above the Rayleigh length is observed when the laser pulse power is much higher than the critical power for relativistic self-focusing. The long-self-guiding-channel formation is accompanied by the electron acceleration with a low transverse emittance (< 0.87[pi] mm mrad) and high electric current (~10 nC/shot), as well as the generation of a quasimonoenergetic electron bunch with an energy of ~80 MeV. In order to continuously elongate the plasma channel, a 4-cm-scale discharged capillary was used. We successfully demonstrated laser-plasma acceleration of high-quality electron beams up to nearly semigigaelectronvolts. Our results exactly verified the prediction of laser wakefield acceleration through a centimeterscale plasma channel in the 'blowout bubble' regime, where a microscale plasma cavity produced through the ultrarelativistic laser-plasma interactions plays an essential role in the self-injection and acceleration of electrons. Index Terms--Capillary, electron acceleration, self-focusing.

Published
2008

215. 13CH3OH Masers Associated with a Transient Phenomenon in a High-mass Young Stellar Object

Author

Chen, X., Sobolev, A. M., Breen, S. L., Shen, Z. -Q., Ellingsen, S. P., MacLeod, G. C., Li, B., Voronkov, M. A., Kaczmarek, J. F., Zhang, J., Ren, Z. -Y., Wang, J., Linz, H., Hunter, T. R., Brogan, C., Sugiyama, K., Burns, R. A., Menten, K., Sanna, A., Stecklum, B., Hirota, T., Kim, K. -T., Chibueze, J., Heever, S. P. V. D., Chen, X., Sobolev, A. M., Breen, S. L., Shen, Z. -Q., Ellingsen, S. P., MacLeod, G. C., Li, B., Voronkov, M. A., Kaczmarek, J. F., Zhang, J., Ren, Z. -Y., Wang, J., Linz, H., Hunter, T. R., Brogan, C., Sugiyama, K., Burns, R. A., Menten, K., Sanna, A., Stecklum, B., Hirota, T., Kim, K. -T., Chibueze, J., and Heever, S. P. V. D.

Abstract

We report the first detection of isotopic methanol (13CH3OH) maser emission in interstellar space. The emission was detected toward the high-mass young stellar object G358.93-0.03 during monitoring of a flare in the 6.7 GHz methanol (CH3OH) maser emission in this source. We find that the spectral and spatial distribution of the 13CH3OH masers differs from the CH3OH masers imaged at the same epoch, contrary to expectations from similarity of their pumping. This conclusively demonstrates that isotopic methanol masers are bright under different physical conditions and suggests that they can provide additional, complementary information to the CH3OH masers from the same source. We detect a rapid decay of the 13CH3OH maser lines suggesting that they are transient phenomena (masing for only a few months), likely associated with rapid changes in radiation field due to an accretion burst induced by massive disk fragmentation. Changes in the line flux density are faster than required to achieve equilibrium in the energy level populations, indicating that the pumping of these masers is likely variable. © 2020. The American Astronomical Society. All rights reserved..

Published
2020

216. VLBI observations of the G25.65+1.05 water maser superburst

Author

Burns, R. A., Orosz, G., Bayandina, O., Surcis, G., Olech, M., MacLeod, G. C., Volvach, A., Rudnitskii, G., Hirota, T., Immer, K., Blanchard, J., Marcote, B., van Langevelde, H. J., Chibueze, J. O., Sugiyama, K., Kim, K. -T., Val'tts, I., Shakhvorostova, N., Kramer, B., Baan, W. A., Brogan, C., Hunter, T., Kurtz, S., Sobolev, A. M., Brand, J., Volvach, L., Burns, R. A., Orosz, G., Bayandina, O., Surcis, G., Olech, M., MacLeod, G. C., Volvach, A., Rudnitskii, G., Hirota, T., Immer, K., Blanchard, J., Marcote, B., van Langevelde, H. J., Chibueze, J. O., Sugiyama, K., Kim, K. -T., Val'tts, I., Shakhvorostova, N., Kramer, B., Baan, W. A., Brogan, C., Hunter, T., Kurtz, S., Sobolev, A. M., Brand, J., and Volvach, L.

Abstract

This paper reports observations of a 22 GHz water maser 'superburst' in the G25.65+1.05 massive star-forming region, conducted in response to an alert from the Maser Monitoring Organisation (M2O). Very long baseline interferometry (VLBI) observations using the European VLBI Network (EVN) recorded a maser flux density of 1.2 × 104 Jy. The superburst was investipgated in the spectral, structural, and temporal domains and its cause was determined to be an increase in maser path length generated by the superposition of multiple maser emitting regions aligning in the line of sight to the observer. This conclusion was based on the location of the bursting maser in the context of the star-forming region, its complex structure, and its rapid onset and decay. © 2019 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society

Published
2020

217. A heatwave of accretion energy traced by masers in the G358-MM1 high-mass protostar

Author

29697492 - Chibueze, James Okwe, Burns, R.A., Chibueze, J.O., Sugiyama, K., Hirota, T., Kim, K.T., 29697492 - Chibueze, James Okwe, Burns, R.A., Chibueze, J.O., Sugiyama, K., Hirota, T., and Kim, K.T.

Abstract

High-mass stars are thought to accumulate much of their mass via short, infrequent bursts of disk-aided accretion1,2. Such accretion events are rare and difficult to observe directly but are known to drive enhanced maser emission3,4,5,6. In this Letter we report high-resolution, multi-epoch methanol maser observations toward G358.93-0.03, which reveal an interesting phenomenon: the subluminal propagation of a thermal radiation ‘heatwave’ emanating from an accreting high-mass protostar. The extreme transformation of the maser emission implies a sudden intensification of thermal infrared radiation from within the inner (40-mas, 270-au) region. Subsequently, methanol masers trace the radial passage of thermal radiation through the environment at ≥4% of the speed of light. Such a high translocation rate contrasts with the ≤10 km s−1 physical gas motions of methanol masers typically observed using very-long-baseline interferometry (VLBI). The observed scenario can readily be attributed to an accretion event in the high-mass protostar G358.93-0.03-MM1. While being the third case in its class, G358.93-0.03-MM1 exhibits unique attributes hinting at a possible ‘zoo’ of accretion burst types. These results promote the advantages of maser observations in understanding high-mass-star formation, both through single-dish maser monitoring campaigns and via their international cooperation as VLBI arrays

Published
2020

233. Simulation of slow light with electronic circuits

Author

Nakanishi, T., Sugiyama, K., and Kitano, M.

Subjects
Wave propagation -- Research, Light -- Research, Physics
Abstract

We discuss an electronic circuit that simulates wave propagation in dispersive media. The circuit is an array of phase shifters composed of operational amplifiers. The envelope of the simulated light pulse can be described by a discretized version of the one-dimensional wave equation. The circuit can be used to change the group velocity both spatially and temporally and emulate slow light or stopped light. The control of the group velocity of optical pulses is expected to be a useful tool for quantum information and communication.

Published
2005

244. Transmission Electron Microscopy of Iron Metal in Almahata Sitta Ureilite

Author

Mikouchi, T, Yubuta, K, Sugiyama, K, Aoyagi, Y, Yasuhara, A, Mihira, T, Zolensky, M. E, and Goodrich, C. A

Subjects
Geosciences (General)
Abstract

Almahata Sitta (AS) is a polymict breccia mainly composed of variable ureilite lithologies with small amounts of chondritic lithologies [1]. Fe metal is a common accessory phase in ureilites, but our earlier study on Fe metals in one of AS fragments (#44) revealed a unique mineralogy never seen in other ureilites [2,3]. In this abstract we report detailed transmission electron microscopy (TEM) on these metal grains to better understand the thermal history of ureilites. We prepared FIB sections of AS#44 by JEOL JIB-4000 from the PTS that was well characterized by SEM-EBSD in our earlier study [2]. The sections were then observed by STEM (JEOL JEM- 2100F). One of the FIB sections shows a submicron-sized symplectic intergrown texture composed of Fe metal (kamacite), Fe carbide (cohenite), Fe phosphide (schreibersite), and Fe sulfide (troilite). Each phase has an identical SAED pattern in spite of its complex texture, suggesting co-crystallization of all phases. This is probably caused by shock re-melting of pre-existing metal + graphite to form a eutectic-looking texture. The other FIB section is mostly composed of homogeneous Fe metal (93 wt% Fe, 5 wt% Ni, and 2 wt% Si), but BF-STEM images exhibited the presence of elongated lathy grains (approx. 2 microns long) embedded in the interstitial matrix. The SAED patterns from these lath grains could be indexed by alpha-Fe (bcc) while interstitial areas are gamma-Fe (fcc). The elongated alpha-Fe grains show tweed-like structures suggesting martensite transformation. Such a texture can be formed by rapid cooling from high temperature where gamma-Fe was stable. Subsequently alpha-Fe crystallized, but gamma-Fe remained in the interstitial matrix due to quenching from high temperature. This scenario is consistent with very rapid cooling history of ureilites suggested by silicate mineralogy.

Published
2013

245. Cooling History of Almahata Sitta Ureilite as Inferred from Transmission Electron Microscopy of Iron Metal

Author

Mikouchi, T, Aoyagi, Y, Goodrich, C. A, Yubuta, K, Sugiyama, K, Zolensky, M. E, and Goldstein, J. I

Subjects
Geophysics
Abstract

Almahata Sitta (AS) is a polymict breccia mainly composed of various ureilite lithologies with lesser chondritic lithologies [1]. In the ureilite lithologies, Fe metal is a common accessory phase present either as large grain boundary grains or small particles formed by reduction of olivine and pyroxene. In our earlier studies on grain boundary metals in one of AS fragments (#44) we found unique features never seen in other ureilites [2,3]. In order to further characterize these metal grains, we performed a detailed TEM study on a FIB section prepared from one of AS #44 grain boundary metals and here discuss its thermal history.

Published
2013

246. Activation of the alternative complement pathway by Agaricus blazei Murill

Author

Shimizu, S., Kitada, H., Yokota, H., Yamakawa, J., Murayama, T., Sugiyama, K., Izumi, H., and Yamaguchi, N.

Subjects
Biological sciences, Health, Science and technology
Abstract

Summary Components of Agaricus blazei Murill have been demonstrated to have a wide range of immunopotentiating activities. The present study was designed to evaluate the effect of A. blazei Murill [...]

Published
2002

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