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- Izumi, Takuma, et al.
(author)
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Submillimeter ALMA Observations of the Dense Gas in the Low-Luminosity Type-1 Active Nucleus of NGC 1097
- 2013
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In: Publications of the Astronomical society of Japan. - : Oxford University Press (OUP). - 0004-6264 .- 2053-051X. ; 65:5
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Journal article (peer-reviewed)abstract
- We present the first 100 pc scale view of the dense molecular gas in the central similar to 1.3 kpc of the type-1 Seyfert NGC 1097, traced by HCN (J = 4-3) and HCO+ (J = 4-3) lines afforded with ALMA band 7. This galaxy shows significant HCN enhancement with respect to HCO+ and CO in the low-J transitions, which seems to be a common characteristic in AGN environments. Using the ALMA data, we consider the characteristics of the dense gas around this AGN, and search for the mechanism of HCN enhancement. We find a high HCN (J = 4-3) to HCO+ (J = 4-3) line ratio in the nucleus. The upper limit of the brightness temperature ratio of HCN (nu(2) = 1(1f), J = 4-3) to HCN (J = 4-3) is 0.08, which indicates that IR pumping does not significantly affect the pure rotational population in this nucleus. We also find a higher HCN (J = 4-3) to CS (J = 7-6) line ratio in NGC 1097 than in starburst galaxies, which is more than 12.7 on the brightness temperature scale. Combined with similar observations from other galaxies, we tentatively suggest that this ratio appears to be higher in AGN-host galaxies than in pure starburst ones, similar to the widely used HCN to HCO+ ratio. LTE and non-LTE modeling of the observed HCN and HCO+ lines using J = 4-3 and 1-0 data from ALMA, and J = 3-2 data from SMA, reveals a high HCN to HCO+ abundance ratio (5 <= [HCN]/[HCO+] <= 20: non-LTE analysis) in the nucleus, and that the high-J lines (J = 4-3 and 3-2) are emitted from dense (10(4.5) cm(-3) <= n(H2) <= 10(6) cm(-3)), hot (70 K <= T-kin <= 550 K) regions. Finally we propose that high-temperature chemistry is more plausible to explain the observed enhanced HCN emission in NGC 1097 than pure gas-phase PDR/XDR chemistry.
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| 2. |
- Takata, Tohru, et al.
(author)
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Presence of both heterogeneous vancomycin-intermediate resistance and beta-lactam antibiotic-induced vancomycin resistance phenotypes is associated with the outcome in methicillin-resistant Staphylococcus aureus bloodstream infection
- 2013
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In: Scandinavian Journal of Infectious Diseases. - : Informa UK Limited. - 0036-5548 .- 1651-1980. ; 45:3, s. 203-212
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Journal article (peer-reviewed)abstract
- Background: Although the individual expression of heterogeneous vancomycin-intermediate resistance (hVISA) and beta-lactam antibiotic-induced vancomycin resistance (BIVR) phenotypes has been associated with treatment failure and recurrence in methicillin-resistant Staphylococcus aureus (MRSA) infections, the effect of the co-expression of these phenotypic profiles on clinical outcome has not been fully elucidated. The aim of this study was to determine the impact of the combination of hVISA and BIVR phenotypes on the clinical outcome in MRSA bacteremia. Methods: One hundred and sixty-two MRSA blood isolates from a 21-y period, 1987-2007, were randomly selected. Screening for hVISA was done by the macromethod Etest and confirmed by population analysis profiles. BIVR was identified using Mu3 agar containing 4 mu g/ml of vancomycin. Results: Thirty (18.5%) and 39 (24.1%) of the 162 MRSA blood isolates were positive for the hVISA and BIVR phenotypes, respectively. Eighteen (11.1%) isolates possessed both hVISA and BIVR phenotypes (hVISA(+)/BIVR(+)). In a subset of patients who received initial treatment with glycopeptides, only the patients whose isolates were hVISA(+)/BIVR(+) displayed a significantly higher mortality rate in comparison to those with non-hVISA(+)/BIVR(+) (80.0% vs 31.3%, p = 0.004). The presence of both hVISA and BIVR phenotypes was a predictor of mortality using a logistic regression analysis (p = 0.025). Conclusions: The combined phenotype of hVISA and BIVR was associated with a higher probability of mortality in patients with MRSA bacteremia. Further prospective studies are warranted to delineate the clinical significance of the combined phenotype of hVISA and BIVR.
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