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Hlavacek-Larrondo, J.,McDonald, M.,Benson, B. A.,Forman, W. R.,Allen, S. W.,Bleem, L. E.,Ashby, M. L. N.,Bocquet, S.,Brodwin, M.,Dietrich, J. P.,Jones, C.,Liu, J.,Reichardt, C. L.,Saliwanchik, B. R.,S IOP Publishing 2015 The Astrophysical journal Vol.805 No.1
<P>X-ray cavities are key tracers of mechanical (or radio mode) heating arising from the active galactic nuclei (AGNs) in brightest cluster galaxies (BCGs). We report on a survey for X-ray cavities in 83 massive, high-redshift (0.4 < z < 1.2) clusters of galaxies selected by their Sunyaev-Zel'dovich signature in the South Pole Telescope data. Based on Chandra X-ray images, we find a total of six clusters having symmetric pairs of surface brightness depressions consistent with the picture of radio jets inflating X-ray cavities in the intracluster medium (ICM). The majority of these detections are of relatively low significance and require deeper follow-up data in order to be confirmed. Further, this search will miss small (<10 kpc) X-ray cavities that are unresolved by Chandra at high (z greater than or similar to 5) redshift. Despite these limitations, our results suggest that the power generated by AGN feedback in BCGs has remained unchanged for over half of the age of the universe (>7 Gyr at z similar to 0.8). On average, the detected X-ray cavities have powers of (0.8-5) x 10(45) erg s(-1), enthalpies of (3-6) x 10(59) erg, and radii of similar to 17 kpc. Integrating over 7 Gyr, we find that the supermassive black holes in BCGs may have accreted 10(8) to several 10(9) M-circle dot of material to power these outflows. This level of accretion indicates that significant supermassive black hole growth may occur not only at early times, in the quasar era, but at late times as well. We also find that X-ray cavities at high redshift may inject an excess heat of 0.1-1.0 keV per particle into the hot ICM above and beyond the energy needed to offset cooling. Although this result needs to be confirmed, we note that the magnitude of excess heating is similar to the energy needed to preheat clusters, break self-similarity, and explain the excess entropy in hot atmospheres.</P>
Baryon content of massive galaxy clusters at 0.57 < <i>z</i> < 1.33
Chiu, I.,Mohr, J.,McDonald, M.,Bocquet, S.,Ashby, M. L. N.,Bayliss, M.,Benson, B. A.,Bleem, L. E.,Brodwin, M.,Desai, S.,Dietrich, J. P.,Forman, W. R.,Gangkofner, C.,Gonzalez, A. H.,Hennig, C.,Liu, J. Oxford University Press 2016 MONTHLY NOTICES- ROYAL ASTRONOMICAL SOCIETY Vol.455 No.1
Determination of Microdosimetric Quantities of Several Neutron Calibration Fields at KAERI
Kim, B.H.,Kim, J.S.,Kim, J.L.,Chang, S.Y.,Cho, G.,McDonald, J.C. The Korean Association for Radiation Protection 2003 방사선방어학회지 Vol.28 No.4
The commercially available neutron survey meter, the REM500, which uses a tissue equivalent proportional counter (TEPC) and the self-constructed TEPC were used to determine the microdosimetric quantities of several neutron calibration fields at Korea Atomic Energy Research Institute (KAERI). Microdosimetric spectra, absorbed dose, dose equivalent as well as quality factor were derived and compared with several neutron fields which were produced by using the shadow objects to make neutron scattered and being used as a kind of realistic neutron calibration fields at KAERI. The response of REM500 as a function of mean energy was evaluated with these neutron fields using the counts measured and the predetermined reference value. The response of the self-made TEPC and the REM500 was compared using one of the neutron calibration filelds of a $^{252}Cf$ source. The reference quantities of scattered neutron calibration fields were determined using a Bonner Sphere (BS). The value of frequency-mean lineal energy, dose-mean lineal energy and quality factor of two $^{252}Cf$ sources (unmoderated and $D_2O$ moderated) were determined to check the differences in the reference neutron fields between KAERI and Pacific Northwest National Laboratory (PNNL, USA) and the results were in good agreement within 1%. It means that there is no big difference in dosimetric quantifies of neutron calibration fields of two laboratories.
Intercomparison of the KAERI Reference Photon and Beta Radiation Measurements
Kim,B.H.,Kim,J.L.,Chang,S.Y.,McDonald,J.C,Murphy,M.K. 대한방사선 방어학회 1996 방사선방어학회지 Vol.21 No.4
이 논문은 최근 한국원자력연구소(KAERI)와 미국 패시픽노스웨스트 국립연구소(일명, 바텔연구소, PNNL)이 개인선량계의 성능검사를 위한 미국 ANSI N13.11 기준에 근거하여 KAERI 방사선 측정/교정실험실에서 수행한 KAERI 기준 광자 및 베타 방사선장의 국제 상호비교 측정결과를 설명하고 있다. 두 기관이 각각 자국의 일차 표준에 소급성을 갖는 방사선 검출기와 방사선 측정장치를 사용하여 자유공기중에서 광자의 조사선량(율), 공기커마(율)와 베타선의 절대흡수선량(율)을 측정한 결과, 광자선장에 대해서는 ± 2.0 %, 베타선장에 대해서는 ±1.0 %의 오차범위내에서 잘 일치하였다. 따라서 KAERI의 기준 광자 및 베타 방사선장은 국제표준에 잘 만족되고 있음이 입증되었으며 장차 방사선 도시메트리 연구개발의 국가 기술기반으로 활용될 수 있음이 확인되었다. This paper describes the results of intercomparison measurements of KAERI reference photon and beta radiation fields between the KAERI and PNNL(Pacific Northwest national Laboratory), recently performed at KAERI radiation calibration and dosimetry laboratory on the basis of the ANSI N13.11 criteria for personal dosimeter performance test. Each laboratory used her own radiation detectors or measurement devices traceable to her national primary standard in measuring the exposure rates for photon fields, the absorbed dose rates for beta radiation fields. The agreements in reference radiation measurements between two laboratories were found to be less than ±2.0 % for photon fields, ±1.0 % for beta radiation fields. Therefore, it could be concluded that KAERI reference radiation fields comply well with the international standard and thus can further serve as a national basis for the researches and developments in radiation protection dosimetry in Korea.
Targeted Near-Infrared Fluorescence Imaging for Regenerative Medicine
Chengeng Yang,G. Kate Park,Eric J. McDonald,최학수 한국조직공학과 재생의학회 2019 조직공학과 재생의학 Vol.16 No.6
BACKGROUND: Advances in tissue engineering and regenerative medicine over the last three decades have made great progress in the development of diagnostic and therapeutic methodologies for damaged tissues. However, regenerative medicine is still not the first line of treatment for patients due to limited understanding of the tissue regeneration process. Therefore, it is prerequisite to develop molecular imaging strategies combined with appropriate contrast agents to validate the therapeutic progress of damaged tissues. METHODS: The goal of this review is to discuss the progress in the development of near-infrared (NIR) contrast agents and their biomedical applications for labeling cells and scaffolds, as well as monitoring the treatment progress of native tissue in living organisms. We also discuss the design consideration of NIR contrast agents for tissue engineering and regenerative medicine in terms of their physicochemical and optical properties. RESULTS: The use of NIR imaging system and targeted contrast agents can provide high-resolution and high sensitivity imaging to track/monitor the in vivo fate of administered cells, the degradation rate of implanted scaffolds, and the tissue growth and integration of surrounding cells during the therapeutic period. CONCLUSION: NIR fluorescence imaging techniques combined with targeted contrast agents can play a significant role in regenerative medicine by monitoring the therapeutic efficacy of implanted cells and scaffolds which would enhance the development of cell therapies and promote their successful clinical translations.
Kim, H.S.,Min, H.G.,McDonald, J.A. Butterworths ; Elsevier Science Pub. Co 2016 economic modelling Vol.59 No.-
We investigate the dynamic interactions between stock-market excess returns, time-varying correlations and volatilities in six OECD countries and the United States during the US financial crisis and its aftermath. Using the seemingly-unrelated regression (SUR) and panel-regression models with return, correlation, and volatility equations, we show that excess returns can explain both correlations and volatilities and that own volatility can explain both excess returns and correlations. However, we find that correlations can explain neither excess returns nor volatilities. We find new and important evidence that 'excess returns,' 'US excess returns,' and 'US volatilities' should be included in the analysis of other countries' correlations and volatilities. The US T-bill-LIBOR interest-rate differential (TED spread) and foreign-exchange market volatility (FXV) negatively affect excess returns; however, the credit-default swap spread's effect is insignificant. Our findings are robust with different definitions of the key variables; they also provide important implications for international risk diversification: as financial-market conditions (measured by the TED spread and FXV) deteriorate, the links between stock-market returns, correlations, and volatilities appear to be strengthened.