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RISS 인기검색어
- 검색키워드
- 저자 : Ishihara Nami (검색결과 4 건)
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SEARCH FOR DEBRIS DISKS BY AKARI AND IRSF
NAMI TAKEUCHI,DAISUKE ISHIHARA,HIDEHIRO KANEDA,SHINKI OYABU,HIROSHI KOBAYASHI,TAKAHIRO NAGAYAMA,TAKASHI ONAKA,HIDEAKI FUJIWARA 한국천문학회 2017 天文學論叢 Vol.32 No.1
Debris disks are important observational clues to understanding on-goingplanetary system formation. They are usually identified by significantmid-infrared excess on top of the photospheric emission of a central star onthe basis of prediction from \sl J\rm-, \sl H\rm-, and \sl Ks\rm-band fluxes and the stellar model spectra. For bright stars, 2MASS near-infrared fluxes suffer large uncertainties due to thenear-infrared camera saturation. Therefore we have performed follow-up observations with the IRSF 1.4 mnear-infrared telescope located in South Africa to obtain accurate \sl J\rm-, \sl H\rm-, and \sl Ks\rm-bandfluxes of the central stars. Among 754 main-sequence stars which are detected in theAKARI 18 $\mu$m band, we have performed photometry for 325 stars with IRSF. As a result, we have successfully improved the flux accuracy of the centralstars from 9.2 \% to 0.5 \% on average. Using this dataset, we have detected 18$\mu$m excess emission from 57 stars in our samples with a 3$\sigma$ level. We find that some of them have high ratios of the excess to the photospheric emission even around very old stars,which cannot be explained by the current planet-formation theories.
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DEBRIS DISKS AND THE ZODIACAL LIGHT EXPLORED BY THE AKARI MID-INFRARED ALL-SKY SURVEY
DAISUKE ISHIHARA,NAMI TAKEUCHI,TORU KONDO,HIROSHI KOBAYASHI,HIDEHIRO KANEDA,SHU-ICHIRO INUTSUKA,SHINKI OYABU,TAKAHIRO NAGAYAMA,HIDEAKI FUJIWARA,TAKASHI ONAKA 한국천문학회 2017 天文學論叢 Vol.32 No.1
Debris disks are circumstellar dust disks around main-sequence stars. They are important observational clues to understanding the planetary system formation. The zodiacal light is the thermal emission from the dust disk in our Solar system. %For a comprehensive understanding of the nature andthe evolution of dust disks around main-sequence stars,we try a comparative study of debris disks and the zodiacal light. %We search for debris disks using the AKARI mid-infrared all-sky point source catalog. By applying accurate flux estimate of the photospheric emissionbased on the follow-up near-infrared observations with IRSF,we have improved the detection rate of debris disks. %For a detailed study of the structure and grain propertiesin the zodiacal dust cloud,as an example of dust disks around main-sequence stars,we analyze the AKARI mid-infrared all-sky diffuse maps. %As a result of the debris disks search,we found old ($>$1\,Gyr) debris disks which have large excess emissioncompared to their age, which cannot be explained simplyby the conventional steady-state evolution model. %From the zodiacal light analysis, we find the possibilitythat the dust grains trapped in the Earth's resonance orbitshave increased by a factor of $\sim$3 in the past $\sim$20 years. %Combining these results, we discuss the non-steady processes in debris disks and the zodiacal light.
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Kono Maori,Okuda Tomoaki,Ishihara Nami,Hagino Hiroyuki,Tani Yuto,Okochi Hiroshi,Tokoro Chiharu,Takaishi Masayuki,Ikeda Hidefumi,Ishihara Yasuhiro 한국독성학회 2023 Toxicological Research Vol.39 No.1
Fine particulate matter (PM2.5) exposure has a risk of inducing several health problems, especially in the respiratory tract. The skin is the largest organ of the human body and is therefore the primary target of PM2.5. In this study, we examined the effects of PM2.5 on the skin using a human 3-dimensional cultured epidermis model. PM2.5 was collected by cyclonic separation in Yokohama, Japan. Global analysis of 34 proteins released from the epidermis revealed that the chemokines, chemokine C-X-C motif ligand 1 (CXCL1) and interleukin 8 (IL-8), were significantly increased in response to PM2.5 exposure. These chemokines stimulated neutrophil chemotaxis in a C-X-C motif chemokine receptor 2-dependent manner. The oxidative stress and signal transducer and activator of transcription 3 pathways may be involved in the increased expression of CXCL1 and IL-8 in the human epidermis model. Interestingly, in the HaCaT human keratinocyte cell line, PM2.5 did not affect chemokine expression but did induce IL-6 expression, suggesting a different effect of PM2.5 between the epidermis model and HaCaT cells. Overall, PM2.5 could induce the epidermis to release chemokines, followed by neutrophil activation, which might cause an unregulated inflammatory reaction in the skin.
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DEVELOPMENT OF A CRYOGENIC TESTING SYSTEM FOR MID-INFRARED DETECTORS ON SPICA
Miho Nishiyama,Hidehiro Kaneda,Daisuke Ishihara,Shinji Oseki,Nami Takeuchi,Takahiro Nagayama,Takehiko Wada 한국천문학회 2017 天文學論叢 Vol.32 No.1
For future space IR missions, such as SPICA, it is crucial to establish an experimental method for evaluating the performance of mid-IR detectors. In particular, the wavelength dependence of the sensitivity is important but difficult to be measured properly. We are now preparing a testing system for mid-IR Si:As/Si:Sb detectors on SPICA. We have designed a cryogenic optical system in which IR signal light from a pinhole is collimated, passed through an optical filter, and focused onto a detector. With this system, we can measure the photoresponse of the detector for various IR light using optical filters with different wavelength properties. We have fabricated aluminum mirrors which are adopted to minimize thermal distortion effects and evaluated the surface figure errors. The total wavefront error of the optical system is 1.3 μm RMS, which is small enough for the target wavelengths (20 - 37 μm) of SPICA. The point spread function measured at a room temperature is consistent with that predicted by the simulation. We report the optical performance of the system at cryogenic temperatures.
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