• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.73-73
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• 2008

일반적으로 청색 및 자외선 발광다이오드, 레이저 다이오드, UV 감지기 (detector)소자 등의 기술적인 중요성은 ZnO를 기반으로 하는 산화물 반도체와 함께 와이드 밴드갭 반도체 연구가 활발히 진행되고 있다. ZnO의 경우 밴드갭 엔지니어링을 위해 일반적으로 Cd과 Mg을 사용하고 있으며 특히, ZnO에 Mg을 첨가하여 MgZnO 화합물을 첨가할 경우 밴드갭을 3.3eV~7.8eV까지 증가 시킬 수 있고, MgZnO/ZnO 초격자 구조를 이용할 경우 자유 엑시톤 결합에너지를 100meV 이상까지 증가시킬 수 있는 장점을 가지고 있다. 그러나 MgO는 결정구조가 rocksalt 구조를 가지는 입방정 구조이기 때문에 Hexagonal 구조를 가진 ZnO에 첨가될 경우 고용도에 큰 제한을 가지게 된다. 이와 같은 문제점으로 인하여 밴드갭 엔지니어링 기술은 여전히 해결되지 않은 문제점으로 남아 있다. 본 실험에서는 RF 마그네트론 스퍼터링 방법으로 사파이어 기판위에 MgZnO/ZnO 박막을 co-sputtering 시켰다. Targer은 ZnO(99.999%) 와 MgO (99.999%) target을 사용하였고, 스퍼터링 가스는 아르곤과 산소가스를 2:1 비율로 혼합시켜 성장하였다. MgZnO 박막을 성장하기 전 ZnO 층을 ~500 두께로 성장 시켰다. RF-power는 ZnO target을 고정 시키고, MgO targe power를 변화시켜 Mg 농도를 조절 하였다. 실험 결과 MgO target power 가 증가 할수록 반치폭이 증가하고, c-plane을 따라 격자 상수가 감소하는 것을 확인 할 수 있고, UV emission peak intensity가 감소며 단파장쪽으로 blue shift 하고, activation energy 가 증가하는 것을 관찰 할 수 있었다.

• Journal of the Korean Physical Society
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• v.73 no.9
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• pp.1393-1398
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• 2018

In conventional single-photon emission computed tomography (SPECT), only the photoelectric events in the detectors are used for image reconstruction. However, if the $^{131}I$ isotope, which emits high-energy radiations (364, 637, and 723 keV), is used in nuclear medicine, both photoelectric and Compton scattering events can be used for image reconstruction. The purpose of our work is to perform simulations for Compton SPECT by using the Geant4 application for tomographic emission (GATE). The performance of Compton SPECT is evaluated and compared with that of conventional SPECT. The Compton SPECT unit has an area of $12cm{\times}12cm$ with four gantry heads. Each head is composed of a 2-cm tungsten collimator and a $40{\times}40$ array of CdZnTe (CZT) crystals with a $3{\times}3mm^2$ area and a 6-mm thickness. Compton SPECT can use not only the photoelectric effect but also the Compton scattering effect for image reconstruction. The correct sequential order of the interactions used for image reconstruction is determined using the angular resolution measurement (ARM) method and the energies deposited in each detector. In all the results of simulations using spherical volume sources of various diameters, the reconstructed images of Compton SPECT show higher signal-to-noise ratios (SNRs) without degradation of the image resolution when compared to those of conventional SPECT because the effective count for image reconstruction is higher. For a Derenzo-like phantom, the reconstructed images for different modalities are compared by visual inspection and by using their projected histograms in the X-direction of the reconstructed images.

• Asian-Australasian Journal of Animal Sciences
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• v.29 no.8
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• pp.1152-1158
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• 2016

Morphological and physiological alterations occur in the digestive system of weanling piglets, compromising the performance in subsequent phases. This experiment aimed at verifying the influence of glutamine, glutamate and nucleotides on the carbon turnover in the pancreas and liver of piglets weaned at 21 days of age. Four diets were evaluated: glutamine, glutamic acid or nucleotides-free diet (CD); containing 1% glutamine (GD); containing 1% glutamic acid (GAD) and containing 1% nucleotides (ND). One hundred and twenty-three piglets were utilized with three pigs slaughtered at day zero (weaning day) and three at each one of the experimental days (1, 2, 4, 5, 7, 9, 13, 20, 27, and 49 post-weaning), in order to collect organ samples, which were analyzed for the ${\delta}^{13}C$ isotopic composition and compared by means of time. No differences were found (p>0.05) among treatments for the turnover of the $^{13}C$ in the pancreas ($T_{50%}$ = 13.91, 14.37, 11.07, and 9.34 days; $T_{95%}$ = 46.22, 47.73, 36.79, and 31.04 days for CD, GD, GAD, and ND, respectively). In the liver, the ND presented accelerated values of carbon turnover ($T_{50%}=7.36$ and $T_{95%}=24.47days$) in relation to the values obtained for the GD ($T_{50%}=10.15$ and $T_{95%}=33.74days$). However, the values obtained for the CD ($T_{50%}=9.12$ and $T_{95%}=30.31days$) and GAD ($T_{50%}=7.83$ and $T_{95%}=26.03days$) had no differences (p>0.05) among other diets. The technique of $^{13}C$ isotopic dilution demonstrated trophic action of nucleotides in the liver.

• The Journal of Korean Medicine
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• v.23 no.1
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• pp.67-82
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• 2002

Objectives: In recent years, extensive focus has been laid on adulteration of herbal medicine with heavy metals. This may be mainly due to soil contamination by environmental pollution. The objective of this study is to identify the contents of various heavy metals in the blood from Ohjeok-san (Wuji-san) Decoction (OD) treated-rats. Methods: For this study, 13 kinds of metals including essential and heavy metals, i.e. A1, As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Se and Zn were analyzed by a slight modification of EP A methods and the following results are obtained. Results: 1. There was no significant difference between the OD-treated groups and control group in liver, kidney, bone, brain and weight, especially no significant difference at the 5th and 10th days in weight and the amount of food intake. 2. The amount of each metal analyzed in the blood were as follows; A1: 2.3~3.07 mg/l, As: 2.90~3.66 mg/l, Cd: 0~0.001 mg/l, Co: 0~0.01 mg/l, Cr: 0.40~043 mg/l, Cu: 0.93~1.88 mg/l, Fe: 414.35~464.46 mg/l, Hg: 0.01 mg/l, Mn: 0.10~0.17 mg/l, Ni: 0.01 mg/l, Pb: 0.03~012 mg/l, Se: 0.73 mg/l, Zn: 3.41~4.13 mg/l by groups, respectively. In control and experimental group, Experimental I and other experimental II, III, IV, and V groups, there were no significant differences. 3. The amount of non-toxic metals (A1, Co, Cu, Fe, Mn, Se, Zn) were $64.1{\pm}7.71{\;}mg/l$ in the control group and 60.70~67.58 mg/l in the experimental groups I, II, III, IV and V. The amount of Toxic metals (As, Cd, Cr, Ag, Pb) were $0.68{\pm}0.21{\;}mg/l$ in the control group and 0.57 ~ 0.66mg/l in the experimental groups. The total amount of metals were 32.35 mg/l in the control group and 30.48~34.12 mg/l in the test groups I, II, III, IV and V, respectively. Conclusions: There was no significant difference of metal concentration in the blood from the OD-treated-rats compared to those of the control group even if higher dosage (1~8 times the dosage for a person) of OD was administered. This may be mainly due to a decoction treatment which contains only supernatants filtered from the herb-mass after boiling. This indicates the legal limitation for metal concentration in herbal medicine must be applied according to different treatment methods of herbal medicine.

• Journal of Soil and Groundwater Environment
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• v.27 no.3
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• pp.11-21
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• 2022

The purpose of this study was to evaluate the influences of digestion temperature on the extraction of heavy metals from soil using the standard method established by Korean Ministry of Environment (KMES). A total of 7 heavy metals (As, Cd, Cr, Cu, Ni, Pb and Zn) in soil samples were extracted at varying digestion temperatures [(66 ± 2.0)℃, (73 ± 1.9)℃, (80 ± 1.3)℃, (85 ± 1.7)℃, (92 ± 2.0)℃, (98 ± 1.7)℃]. As, Cd, Cu, Pb and Zn concentrations remained relatively constant over the temperature range, but Ni and Cr concentrations greatly varied with the digestion temperature. The extent of variation in extraction efficiencies as compared to the concentration obtained at 66℃ was in following order; Ni (7.09% ~ 35.42%) > Cr (4.79% ~ 25.40%) > Zn (3.99% ~ 17.52%) > Cu (2.22% ~ 19.34%) > As (3.54% ~ 8.26%) > Cd (-5.08% ~ 1.08%) > Pb (-4.71% ~ -1.70%). The accuracy for certified reference materials at the digestion temperature of 80 and 85℃ was 98.7% ~ 105.8%. Therefore, digestion temperature of 80℃ ~ 85℃ is suggested to obtain reliable and reproducible data when the standard method by Korean Ministry of Environment is employed to analyze multiple heavy metal components in soil samples.

• Journal of Environmental Health Sciences
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• v.50 no.1
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• pp.25-35
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• 2024

Background: There are concerns about the health effects of various environmental pollution exposures among residents living near coal-fired power plants (CFPP). Objectives: This study attempted to compare the concentrations of heavy metals in blood and urine and those of urinary volatile organic compound (VOC) metabolites according to the residential separation distance. Methods: Participants in the study totaled 334 people who have lived for more than 10 years in areas within 10 km of a CFPP. The separation distance was analyzed in quartiles by dividing it into Q1 (88 people), Q2 (89 people), Q3 (89 people), and Q4 (68 people). We explained the purpose of this study to the participants and collected blood and urine after obtaining signatures on a participation agreement. Results: The study participants were 102 males (30.5%) and 232 females (69.5%), with an average age of 71. The average length of residence and distance were 43.8 years and 4,800 meters. The geometric mean concentrations of Pb, Cd, and Hg in blood and As and Cd in urine were respective 1.35 ㎍/dL, 1.43 ㎍/L, 3.16 ㎍/L. They were 167.88 ㎍/g for creatinine and 1.58 ㎍/g creatinine. The metabolite concentrations of VOCs were 50.67 ㎍/g creatinine in t, t-muconic acid (t, t-MA), 10.73 ㎍/g creatinine in benzyl mercapturic acid, 317.05 ㎍/g creatinine in phenylglyoxylic acid, 123.55 ㎍/g creatinine in methylhippuric acid, and 190.82 ㎍/g creatinine in mandelic acid. The concentration of Pb in the blood and Cd and t, t-MA in the urine of residents within affected area of the CFPP showed statistically significant differences among distance groups. Conclusions: The concentration of urinary VOCs metabolites, especially t, t-MA, differed according to the distance groups of residents within the affected area of CFPP (p<0.05).

• Molecular & Cellular Toxicology
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• v.3 no.4
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• pp.231-237
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• 2007

Exposure to DNA-damaging agents can elicit a variety of stress-related responses that may alter the expression of genes associated with numerous biological pathways. We used 19 k whole human genome chip to detect gene expression profiles and potential signature genes in human normal hepatocytes (THLE-3) by treatment of five direct acting mutagens, furylfuramide (AF-2), N-nitroso-N-methylurea (MNU), methylmethanesulfonate (MMS), 4-nitroquinoline-N-oxide (4-NQO) and 2-nitrofluorene (2NF) of the $IC_{20}$ concentration for 3 h. Fifty one up-regulated common genes and 45 down-regulated common genes above 1.5-fold by five direct-acting mutagens were identified by clustering analysis. Many of these changed genes have some association with apoptosis, control of cell cycle, regulation of transcription and signal transduction. Genes related to these functions, as TP73L, E2F5, MST016, SOX5, MAFB, LIF, SII3, TFIIS, EMR1, CYTL1, CX3CR1 and RHOH are up-regulated. Down-regulated genes are ALOX15B, xs155, IFITM1, BATF, VAV2, CD79A, DCDC2, TNFSF8 and KOX8. We suggest that gene expression profiling on mutagens by toxicogenomic analysis affords promising opportunities to reveal potential new mechanistic markers of genotoxicity.

• Anxiety and mood
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• v.9 no.1
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• pp.68-73
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• 2013

Objective : The aim of this study is to identify the relationship between childhood abuse and affective symptom including resilience in patients with depression or anxiety. Methods : A total 256 outpatients diagnosed with depressive disorder or anxiety disorder according to DSM IV-TR, were evaluated with Beck Depression Inventory (BDI), State-Trait Anxiety Inventory (STAI), Parent-Child Conflict Tactics Scale (PCCTS), Connor-Davidson Resilience Scale (CD-RISC). Independent t-test, Chi-square analysis and analysis of covariance (ANCOVA) were performed to identify the demographics of patients and the relationship between affective symptoms including resilience and childhood abuse. Results : Among demographic and clinical variables, patients with childhood abuse history were significantly higher rate in patients who were living alone and unemployed. In affective symptoms, patients with childhood abuse history were significant more severe in depressive symptoms, and state anxiety score than patients without history of childhood abuse. Patients with childhood abuse history had higher score for trait anxiety and lower score for resilience than patients who had no history of childhood abuse. Conclusion : These finding suggest that history of childhood abuse might be risk factor on depressive and anxiety symptoms severity. And this might be a predictable factor of poor treatment outcome.

• Applied Biological Chemistry
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• v.50 no.2
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• pp.121-126
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• 2007

Halophyte and shellfish are functional and favorite foods in Korea. This study was conducted to survey the contents of inorganic metals to elucidate seafood hygiene & safety. The average concentrations of heavy metals in the halophyte and shellfish were 1.73, and 1.54 ppb of Cd and 47.37, 25.06ppm of Cu, respectively. Average contents of Hg in halophytes was 0.26 ppb and 50.43 ppb in shellfish. In case of minerals, the average concentrations were 4,475.62, 4,440.54 ppm of Ca, and 3,936.16, 1,227.09 ppm of Fe, 2,145.36, 6.170.60 ppm of P. and 314.53, 162.11 ppm of Zn, respectively. The average values of heavy metals were all below the permissible amounts in food but minerals showed high levels in halophyte and shellfish.

• Journal of Intelligence and Information Systems
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• v.12 no.4
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• pp.73-90
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• 2006

When a consumer intends to purchase products through Internet stores, many difficulties are met because of limitations of the current search engines and the current web structure, and lack of tools supporting decision-makings. This paper raises an Internet shopping problem and proposes a framework of decision making process to settle it with an intelligent agent based on Semantic Web and Finite Domain Constraint. The agent uses finite domain constraint programming as modeling and solution methods for the decision problem under the Semantic Web environment.