A Review of Atmospheric Mercury in the Polar Environment

NGUYEN, HANG THI,KIM, KI-HYUN,SHON, ZANG-HO,HONG, SUNGMIN Taylor Francis 2009 Critical reviews in environmental science and tech Vol.39 No.7

<P> This paper is an overview of Hg measurements made in the Arctic and Antarctic regions, with an emphasis on the evaluation of the methodological approaches employed in both sampling and analysis between different Hg species as well as the fundamental aspects of their behavior. There have been numerous efforts to measure the concentrations of different Hg species, including gaseous elemental mercury (GEM), reactive gaseous mercury (RGM), and particulate mercury (Hg(p)) in polar environments. The mean concentration value for GEM, if evaluated on the basis of numerous studies conducted previously, was moderately higher in the Arctic region (1.56 ng m-3) than the Antarctic counterpart with the limited data sets (1.08 ng m-3). The mean GEM concentration in the Arctic environment varied moderately between different locations so that the highest mean values occurred in sub-Arctic locations with a complicated climatology (e.g., Kuujjuarapik, Quebec: 1.80 ng m-3), while the lowest one was recorded in Pallas, Finland (1.26 ng m-3). A comparison of temporal patterns between different studies also indicates that rather dynamic variations occur due to the effects of certain phenomenon, known as atmospheric mercury depletion events (AMDE). During such depletion events, the GEM concentrations frequently dropped below 1.0 ng m-3, while the RGM and Hg(p) exhibited oposing trends. The distribution of GEM in polar environments is, however, fairly comparable in spatial scale, while those of RGM and Hg(p) vary fairly dynamically in such respects. Evidence suggests that the distribution of Hg species at each measurement site in the polar environments is affected more effectively by site-specific meteorological conditions.</P>

A fusion PET–MRI system with a high-resolution research tomograph-PET and ultra-high field 7.0 T-MRI for the molecular-genetic imaging of the brain

Cho, Zang-Hee,Son, Young-Don,Kim, Hang-Keun,Kim, Kyoung-Nam,Oh, Se-Hong,Han, Jae-Yong,Hong, In-Ki,Kim, Young-Bo WILEY-VCH Verlag 2008 Proteomics Vol.8 No.6

<P>We have developed a positron emission tomography (PET) and magnetic resonance imaging (MRI) fusion system for the molecular-genetic imaging (MGI) of the in vivo human brain using two high-end imaging devices: the HRRT-PET, a high-resolution research tomograph dedicated to brain imaging on the molecular level, and the 7.0 T-MRI, an ultra-high field version used for morphological imaging. HRRT-PET delivers high-resolution molecular imaging with a resolution down to 2.5 mm full width at half maximum (FWHM), which allows us to observe the brain's molecular changes using the specific reporter genes and probes. On the other front, the 7.0 T-MRI, with submillimeter resolution images of the cortical areas down to 250 μm, allows us to visualize the fine details of the brainstem areas as well as the many cortical and subcortical areas. The new PET–MRI fusion imaging system will provide many answers to the questions on neurological diseases as well as cognitive neurosciences. Some examples of the answers are the quantitative visualization of neuronal functions by clear molecular and genetic bases, as well as diagnoses of many neurological diseases such as Parkinson's and Alzheimer's. The salient point of molecular-genetic imaging and diagnosis is the fact that they precede the morphological manifestations, and hence, the early and specific diagnosis of certain diseases, such as cancers.</P>

A hybrid PET-MRI: An integrated molecular-genetic imaging system with HRRT-PET and 7.0-T MRI

Cho, Zang-Hee,Son, Young-Don,Kim, Hang-Keun,Kim, Kyoung-Nam,Oh, Se-Hong,Han, Jae-Yong,Hong, In-Ki,Kim, Young-Bo JOHN WILEY & SONS LTD 2007 INTERNATIONAL JOURNAL OF IMAGING SYSTEMS AND TECHN Vol.17 No.4

<P>A PET-MRI fusion system is developed for molecular-genetic imaging. The purpose of the system is to obtain images of the in-vivo human brain using two high-end imaging devices, an advanced PET and an ultrahigh-field MRI. These are the HRRT-PET, a high-resolution research tomograph dedicated to brain imaging on the molecular level, and the 7.0-T MRI, an ultrahigh field version used for morphological imaging. HRRT-PET delivers high-resolution molecular imaging with a resolution down to 2.5 mm FWHM, which is currently the highest spatial resolution available for the observation of the human brain's molecular activities, including enzymes and receptors, which are manipulated genetically, such as reporter genes and probes. The 7.0-T MRI began to reveal submillimeter resolution images of the cortical as well as deep brain areas, down to 250 μm, which allows us to visualize the fine details of the cortical and brainstem areas, including the line of Gennari in the visual cortex and the corticospinal tracts in the pontine area. The current PET-MRI fusion imaging system produces the highest quality images of molecular and genetic activities of the human brain in vivo. It is starting to provide many answers to the key questions about the neurological diseases. Some of these start providing answers to many cognitive neuroscience problems with clear molecular and genetic bases. There is great potential in the PET-MRI for early diagnosis of cancers as well as other neurological diseases, which we were previously unable to diagnose, such as microscopic molecular changes that occur in Parkinson's and Alzheimer's diseases. © 2007 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 17, 252–265, 2007</P>

Antipsychotic-Associated Mental Side Effects and Their Relationship to Dopamine D2 Receptor Occupancy in Striatal Subdivisions: A High-Resolution PET Study With [11C]Raclopride

Kim, Jong-Hoon,Son, Young-Don,Kim, Hang-Keun,Lee, Sang-Yoon,Cho, Seo-Eun,Kim, Young-Bo,Cho, Zang-Hee Lippincott Williams Wilkins, Inc. 2011 JOURNAL OF CLINICAL PSYCHOPHARMACOLOGY Vol.31 No.4

We examined the relationship between antipsychotic-associated mental side effects and dopamine D2 receptor occupancy in striatal subdivisions using high-resolution positron emission tomography with [C]raclopride to better characterize the neurochemical mechanism underlying these adverse effects. Twenty-one patients with schizophrenia receiving stable doses of antipsychotics and 24 age- and sex-matched healthy controls completed 3-Tesla magnetic resonance imaging and high-resolution positron emission tomography scans with [C]raclopride to measure D2 receptor binding potential (BPND) in the striatum. The D2 receptor BPND was obtained using a Logan plot, and receptor occupancy was calculated as the percentage reduction of receptor BPND with drug treatment relative to baseline. The data obtained from age- and sex-matched healthy controls were used as an estimate of the patients' baseline, as previously proposed. Antipsychotic-associated mental side effects were measured with the Liverpool University Neuroleptic Side Effect Rating Scale. The whole striatal D2 receptor occupancy ranged from 54% to 95%. The analysis revealed that the Liverpool University Neuroleptic Side Effect Rating Scale score had significant positive associations with D2 occupancy in the precommissural dorsal caudate, postcommissural caudate, and ventral striatum. The results suggest that mental side effects of antipsychotics are associated with D2 receptor blockade in the associative and limbic subdivisions of the striatum, which are considered to play a crucial role in cognition and reward motivation.

Modification of C-doped a-SiO2 after Swift Heavy-Ion Irradiation

Zhi-Guang Wang,Cun-Bao Liu,Hang Zang,Kong-Fang Wei,Cun-Feng Yao 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.55 No.6

Amorphous SiO2 (a-SiO2) thin films were thermally grown on single-crystalline silicon. These a-SiO2/Si samples were first implanted (C-doped) with 100-keV carbon ion at room temperature (RT) at a dose of 5.0 × 1017 C-ions/cm2 and were then irradiated at RT by using 853 MeV Pb ions at doses of 5.0 × 1011, 1.0 × 1012, 2.0 × 1012, and 5.0 × 1012 Pb-ions/cm2, respectively. The microstructures and the photoluminescence (PL) properties of these samples induced by Pb ions were investigated using fluorescence spectroscopy and transmission electron microscopy. We found that high-energy Pb-ion irradiation could induce the formation of a new phase and a change in the PL property of C-doped a-SiO2/Si samples. The relationship between the observed phenomena and the ion irradiation parameters is briefly discussed. Amorphous SiO2 (a-SiO2) thin films were thermally grown on single-crystalline silicon. These a-SiO2/Si samples were first implanted (C-doped) with 100-keV carbon ion at room temperature (RT) at a dose of 5.0 × 1017 C-ions/cm2 and were then irradiated at RT by using 853 MeV Pb ions at doses of 5.0 × 1011, 1.0 × 1012, 2.0 × 1012, and 5.0 × 1012 Pb-ions/cm2, respectively. The microstructures and the photoluminescence (PL) properties of these samples induced by Pb ions were investigated using fluorescence spectroscopy and transmission electron microscopy. We found that high-energy Pb-ion irradiation could induce the formation of a new phase and a change in the PL property of C-doped a-SiO2/Si samples. The relationship between the observed phenomena and the ion irradiation parameters is briefly discussed.

Primary damage of 10 keV Ga PKA in bulk GaN material under different temperatures

He Huan,He Chaohui,Zhang Jiahui,Liao Wenlong,Zang Hang,Li Yonghong,Liu Wenbo 한국원자력학회 2020 Nuclear Engineering and Technology Vol.52 No.7

Molecular dynamics (MD) simulations were conducted to investigate the temperature effects on the primary damage in gallium nitride (GaN) material. Five temperatures ranging from 300 K to 900 K were studied for 10 keV Ga primary knock-on atom (PKA) with inject direction of [0001]. The results of MD simulations showed that threshold displacement energy (Ed) was affected by temperatures and at higher temperature, it was larger. The evolutions of defects under various temperatures were similar. However, the higher temperature was found to increase the peak number, peak time, final time and recombination efficiency while decreasing the final number. With regard to clusters, isolated point defects and little clusters were common clusters and the fraction of point defects increased with temperature for vacancy clusters, whereas it did not appear in the interstitial clusters. Finally, at each temperature, the number of Ga interstitial atoms was larger than that of N and besides that, there were other different results of specific types of split interstitial atoms.

Effects of electronic energy deposition on pre-existing defects in 6H-SiC

Liao, Wenlong,He, Huan,Li, Yang,Liu, Wenbo,Zang, Hang,Wei, Jianan,He, Chaohui Korean Nuclear Society 2021 Nuclear Engineering and Technology Vol.53 No.7

Silicon carbide is widely used in radiation environments due to its excellent properties. However, when exposed to the strong radiation environment constantly, plenty of defects are generated, thus causing the material performance downgrades or failures. In this paper, the two-temperature model (2T-MD) is used to explore the defect recovery process by applying the electronic energy loss (Se) on the pre-damaged system. The effects of defect concentration and the applied electronic energy loss on the defect recovery process are investigated, respectively. The results demonstrate that almost no defect recovery takes place until the defect density in the damage region or the local defect density is large enough, and the probability of defect recovery increases with the defect concentration. Additionally, the results indicate that the defect recovery induced by swift heavy ions is mainly connected with the homogeneous recombination of the carbon defects, while the probability of heterogeneous recombination is mainly dependent on the silicon defects.

Modification of Fe/Cu Multilayers under 2-MeV Xe20+ Irradiation

Kong-Fang Wei,Zhi-Guang Wang,Jie Gou,Yan-Bin Sheng,Gen-Ming Jin,Hang Zang,Cun-Feng Yao,Yi-Zhun Ma,Tie-Long Shen 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.55 No.6

Multilayers with a structure of Si/[Fe(10 nm)/Cu(10 nm)]5 were deposited on Si(100) substrates and then irradiated at room temperature by using 2-MeV Xe20+. The modifications of the multilayers were characterized using a depth profile analysis of the Auger electron spectroscopy (AES) data and the evolution of crystallite structures of the multilayers were analyzed by using X-ray diffraction (XRD). The AES depth profiles indicated that de-mixing of the Fe and the Cu layers was observed at low ion fluences, but inter-mixing of the Fe and the Cu layers was found at high ion fluences and destroyed the layered structure of the multilayers. The obtained XRD patterns showed that, after irradiation by 2-MeV Xe20+ at 2 × 1016 ions/cm2, the peaks of the multilayers related to a Cu-based fcc solid solution and an Fe-based bcc solid solution phase became visible, which implied that the inter-mixing at the Fe/Cu interface resulted in the formation of new phases. A possible mechanism of modification in the Fe/Cu multilayers induced by ion irradiation is briefly discussed. Multilayers with a structure of Si/[Fe(10 nm)/Cu(10 nm)]5 were deposited on Si(100) substrates and then irradiated at room temperature by using 2-MeV Xe20+. The modifications of the multilayers were characterized using a depth profile analysis of the Auger electron spectroscopy (AES) data and the evolution of crystallite structures of the multilayers were analyzed by using X-ray diffraction (XRD). The AES depth profiles indicated that de-mixing of the Fe and the Cu layers was observed at low ion fluences, but inter-mixing of the Fe and the Cu layers was found at high ion fluences and destroyed the layered structure of the multilayers. The obtained XRD patterns showed that, after irradiation by 2-MeV Xe20+ at 2 × 1016 ions/cm2, the peaks of the multilayers related to a Cu-based fcc solid solution and an Fe-based bcc solid solution phase became visible, which implied that the inter-mixing at the Fe/Cu interface resulted in the formation of new phases. A possible mechanism of modification in the Fe/Cu multilayers induced by ion irradiation is briefly discussed.