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INVESTIGATION OF PAHs IN GALACTIC PLANETARY NEBULAE WITH THE AKARI/IRC AND THE SPITZER/IRS
Ohsawa, R.,Onaka, T.,Sakon, I.,Mori, T.I.,Yamamura, I.,Matsuura, M.,Kaneda, H.,Bernard-Salas, J.,Berne, O.,Joblin, C. The Korean Astronomical Society 2012 天文學論叢 Vol.27 No.4
Polycyclic aromatic hydrocarbons (PAHs) in Galactic planetary nebulae (PNe) are investigated by means of the unidentified infrared (UIR) bands. Continuous near- to mid-infrared spectra of PNe are obtained with the AKARI/IRC and the Spitzer/IRS. All 19 PNe in the present study show prominent dust emissions and we investigate the variation in the intensity ratios among the UIR bands. The ionization fraction and the size distribution of PAHs in PNe are derived using the UIR band ratios. We find that the ionization fraction of PAHs in PNe is around 0.0-0.6 and that small PAHs are scarce. The present result indicates a systematic trend of the $3.4{\mu}m$ aliphatic feature to become weak as the PAH ionization fraction increases.
Multimodal Analysis of Prompt and Delayed Neutron Emission in Fission
Takaaki Ohsawa,Atsushi Matsumoto 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.23
The multimodal model of fission, in which the nucleus is considered tofollow a distinctive path on the deformation energy surface, finallyreaching a definite scission point configuration, has been proved to give agood description of the mass and kineticenergy distributions of fissionfragments. The Madland-Nix model of prompt fission neutron spectra (PFNS)considered the cooling of the fission fragments by neutron emission and theenergy dependence of the inverse reaction, providing a basic formalism forevaluation of the PFNS. Combination of the two models led to the multimodalMadland-Nix model. With further extension to consider the shell effects onthe level density and asymmetry in neutron multiplicity and nucleartemperature of the fragments, it was successfully applied to evaluation ofthe PFNS. On the other hand, the summation method of the delayed neutronyields (DNY) is the most fundamental approach to the estimation of thequantity. Combination of the method with the multimodal fission model led toa new approach to interpret the energy dependence of the DNY. Thisphysics-based approach has made it possible to understand the PFNS and DNYin a manner consistent with many other facets of fission physics. Someproblems about possible effects of scission neutrons, anisotropy of neutronemission in the center-of-mass system of the fragments, and neutron emissionduring acceleration are discussed.
NEAR-INFRARED PAH FEATURES IN GALACTIC PLANETARY NEBULAE
R. Ohsawa,O.ONAKA,I.SAKON,T.I. MORI,H.KANEDA,M.MATSUURA 한국천문학회 2017 天文學論叢 Vol.32 No.1
Polycyclic aromatic hydrocarbons (PAHs) are considered to be carriers of the unidentified infrared bands, which are ubiquitously observed in the Universe. PAHs are mainly formed around evolved carbon-rich stars and injected into interstellar space. Planetary nebulae (PNe), a late stage of low- and intermediate stellar mass evolution, are suitable objects to investigate the formation and evolution of PAHs. The shortest PAH feature is located in 3.3$\,\mu$m, which is important to examine the excitation and size distribution of PAHs. While the number of samples had been limited before, the high sensitivity of \textit{AKARI}/IRC has drastically increased the number of samples. We obtained the 2--5$\,\mu$m spectra of Galactic PNe with \textit{AKARI}/IRC and compiled a near-infrared spectral catalog, containing 73 PNe. We investigate the detection rate and the evolution of the PAH features. The characteristics of the catalog are illustrated and the origin of the evolution of the PAH features is discussed.
Hitoki Yamanaka,Ryuki Kadomatsu,Toshikazu Takagi,Makiko Ohsawa,Naoto Yamamoto,Noriaki Kubo,Takahira Takemoto,Kazutaka Ohsawa 대한수의학회 2019 Journal of Veterinary Science Vol.20 No.2
Isolates of 24 enterococci, 5 Enterococcus casseliflavus and 19 Enterococcus gallinarum, possessingvanC genes and showing low-level resistance to vancomycin were obtained from mice from commercial mouse breeding companies. Since some of these isolates showedresistance to other antibiotics, the purpose of this study was to clarify the resistant profiles of these isolates. One E. casseliflavus isolate showed resistance to erythromycin with a minimal inhibitory concentration (MIC) of 8 μg/mL and also showed apparent resistance to fluoroquinolones with an MIC of 32 μg/mL for ciprofloxacin. The MICs of 2 other fluoroquinolone-resistant E. casseliflavus and E. gallinarum isolates were 3 and 6 μg/mL,respectively. These 3 resistant isolates showed an absence of macrolide- and fluoroquinolone- resistant genes, including amino acid substitutions in the quinolone resistance determining regions of DNA gyrase and topoisomerase IV. Resistance to tetracycline was detected in2 E. gallinarum isolates that were highly resistant, exhibiting MICs of 48 and 64 μg/mL and possessing tet(O) genes. The results indicate that antibiotic-resistant enterococci are being maintained in some laboratory mouse strains that have never been treated with an antibiotic.