• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.238.2-238.2
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• 2012

We report the results of KVN-VERA('KAVA'; KVN and VERA Arrary) AGN WG test observation in 2011 and 2012. The results from these commisioning years show that 'KAVA' is able to produce noble images of radio loud AGNs at 22 and 43GHz. This dedicated high frequency VLBI facility will be especially competitive for the regions where conventional low freuquency facilities see the optically thick part of synchrotron radiation. In the second part of this talk, we report the early science activities of the AGN WG. Sgr A*, Jet acceleration zone of M87, extremely young radio galaxies are the prime cadidates of the joint activities. Lastly we will stress how the phase-referencing 'KAVA' does enhance the imaging sensitivity and open new era of VLBI AGN researches.

• Journal of the Korean Catholic Hospital Association
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• v.6 no.1
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• pp.13-14
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• 1975

• Natural Product Sciences
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• v.16 no.3
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• pp.148-152
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• 2010

Microbial metabolism studies of yangonin (1), a major styryl lactone from Piper methysticum, have resulted in the production of three hydroxylated metabolites (2-4). The chemical structures of these compounds were elucidated to be 4-methoxy-6-(12-hydroxystyryl)-2-pyrone (2),4-methoxy-6-(11,12-dihydroxystyryl)-2-pyrone (3),and 4,12-dimethoxy-6-(7,8-dihydroxy-7,8-dihydrostyryl)-2-pyrone (4) on the basis of the chemical and spectroscopic analyses. The compounds 3 and 4 are reported herein as microbial metabolites of yangonin for the first time.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.42 no.4
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• pp.311-320
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• 2016

Kava (Piper methysticum, P. methysticum) is used as traditional herbal medicine for urogenital diseases, rheumatisms, gastrointestinal problems, respiratory irritations, and pulmonary pains. We identified a flavokavain C (FKC) from P. methysticum, which showed anti-inflammatory activity on nuclear factor ${\kappa}B$ (NF-${\kappa}B$)-dependent nitric oxide (NO) production and expression of inducible nitric oxide synthase (iNOS) in lipopolysaccharide (LPS)-induced RAW264.7 macrophages. FKC inhibited accumulation of reactive oxygen species (ROS), such as hydrogen peroxide, and was able to dose-dependently reduce the LPS-induced NO production and the expression of various inflammation-associated genes (iNOS, IL-$1{\beta}$, IL-6) through inhibition of NF-${\kappa}B$ and MAPKs (ERK and JNK). In conclusion, these results indicate that FKC may have the potential to prevent inflammation process including NF-${\kappa}B$ and MAPKs pathways, and it could be applicable to functional cosmetics for anti-inflammation and antioxidant properties.

• Publications of The Korean Astronomical Society
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• v.30 no.2
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• pp.629-631
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• 2015

In this proceedings, preliminary results of the KVN Source-Frequency Phase-Referencing (SFPR) observation of 3C 66A and 3C 66B are presented. The motivation of this work is to measure the core-shift of these 2 sources and study the temporal evolution of the jet opacity. Two more sources were observed as secondary reference calibrators and each source was observed at 22, 43, and 86 GHz simultaneously. Our preliminary results show that after using the observations at the lower frequency to calibrate those at the higher frequency of the same source, the residual visibility phases for each source at the higher frequencies became more aligned, and the coherence time became much longer; also, the residual phases for different sources, within 10 degrees angular separations, follow similar trends. After reference to the nearby calibrator, the SFPRed maps were obtained as well as the astrometric measurements, i.e. the combined coreshift. The measurements were found to be affected by structural blending effects because of the large beamsize of KVN, but this can be corrected with higher resolution maps (e.g. KAVA maps).

• Journal of The Korean Astronomical Society
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• v.52 no.1
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• pp.23-30
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• 2019

The KVN(Korean VLBI Network)-style simultaneous multi-frequency receiving mode is demonstrated to be promising for mm-VLBI observations. Recently, other Very long baseline interferometry (VLBI) facilities all over the globe start to implement compatible optics systems. Simultaneous dual/multi-frequency VLBI observations at mm wavelengths with international baselines are thus possible. In this paper, we present the results from the first successful simultaneous 22/43 GHz dual-frequency observation with KaVA(KVN and VERA array), including images and astrometric results. Our analysis shows that the newly implemented simultaneous receiving system has brought a significant extension of the coherence time of the 43 GHz visibility phases along the international baselines. The astrometric results obtained with KaVA are consistent with those obtained with the independent analysis of the KVN data. Our results thus confirm the good performance of the simultaneous receiving systems for the nonKVN stations. Future simultaneous observations with more global stations bring even higher sensitivity and micro-arcsecond level astrometric measurements of the targets.