• 천문학회보
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• 제37권2호
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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.

• 한국가톨릭병원협회지
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• 제6권1호
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• pp.13-14
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• 1975

• Natural Product Sciences
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• 제16권3호
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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.

• 대한화장품학회지
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• 제42권4호
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• pp.311-320
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• 2016

카바(Piper methysticum, P. methysticum)는 비뇨생식기 질환, 류머티즘, 위장 장애, 호흡기 자극 및 폐 통증에 대해 전통적으로 사용되는 것으로 알려져 있다. 본 연구에서는 카바에서 분리된 flavokavain C (FKC)가 염증성 유전자의 발현에 관여하는 전사인자인 핵요소-${\kappa}B$ (NF-${\kappa}B$) 의존성 산화 질소(NO) 생산 및 산화 질소 합성 효소(iNOS)의 발현에 리포폴리사카라이드(LPS) 처리된 대식세포에서 항 염증 활성을 나타낸다는 것을 확인하였다. FKC는 과산화수소와 같은 반응성 산소 종(ROS)의 축적을 억제하고, LPS로 유도된 NO 생성 및 각종 염증 관련 유전자(iNOS, IL-$1{\beta}$, IL-6)의 발현을 NF-${\kappa}B$ 및 MAPKs (ERK 및 JNK)의 억제를 통해 농도 의존적으로 줄일 수 있었다. 결론적으로, 이러한 결과는 FKC가 NF-${\kappa}B$ 경로와 MAPKs 포함한 염증 프로세스를 억제하는 능력을 가지고 있음을 나타내며, 이는 항 염증 및 항산화 효능 기반 기능성 화장품에 적용될 수 있음을 암시한다.

• 천문학논총
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• 제30권2호
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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).

• 천문학회지
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• 제52권1호
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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.