• Corrosion Science and Technology
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• 제16권2호
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• pp.69-75
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• 2017

Zinc coating on carbon steels give the higher corrosion resistance in chloride containing environments and in carbonated concrete. However, hydrogen evolution accompanies the corrosion of zinc in the initial activity in fresh concrete, which can lead to the formation of a porous structure at the reinforcement -concrete interface, which can potentially reduce the bond-strength of the reinforcement with concrete. The present study examines the mechanism of the corrosion of hot-dip galvanized steel in detail, as in the model pore solutions and real concrete. Calcium ion plays an important role in the corrosion mechanism, as it prevents the formation of passive layers on zinc at an elevated alkalinity. The corrosion rate of galvanized steel decreases in accordance with the exposure time; however, the reason for this is not the zinc transition into passivity, but the consumption of the less corrosion-resistant phases of hot-dip galvanizing in the concrete environment. The results on the electrochemical tests have been confirmed by the bond-strength test for the reinforcement of concrete and by evaluating the porosity of the cement adjacent to the reinforcement.

• 한국환경독성학회:학술대회논문집
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• 한국환경독성학회 2001년도 추계심포지움 및 학술발표회:환경오염의 생체지표를 이용한 위해성 평가의 최근 기법
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• pp.83-83
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• 2001

• Imaging Science in Dentistry
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• 제53권2호
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• pp.127-135
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• 2023

Purpose: This study assessed the intensity of artifacts produced by 2 metal posts, 2 cements, and different exposure parameters using 2 cone-beam computed tomography (CBCT) units. Materials and Methods: The sample was composed of 20 single-rooted premolars, divided into 4 groups: Ni-Cr/zinc phosphate, Ni-Cr/resin cement, Ag-Pd/zinc phosphate, and Ag-Pd/resin cement. Samples were scanned before and after post insertion and cementation using a CS9000 3D scanner with 4 exposure parameters (85/90 kV and 6.3/10 mA) and an i-CAT scanner with 120 kV and 5 mA. The presence of artifacts was assessed subjectively by 2 observers and objectively by a trained observer using ImageJ software. The Mann-Whitney, Wilcoxon, weighted kappa, and chi-square tests were used to assess data at a 95% confidence level(α<0.05). Results: In the subjective analyses, AgPd presented more hypodense and hyperdense lines than NiCr (P<0.05), and more hypodense halos were found using i-CAT (P<0.05) than using CS9000 3D. More hypodense halos, hypodense lines, and hyperdense lines were observed at 10 mA than at 6.3 mA (P<0.05). More hypodense halos were observed at 85 kV than at 90 kV (P<0.05). CS9000 3D presented more hypodense and hyperdense lines than i-CAT (P<0.05). In the objective analyses, AgPd presented higher percentages of hyperdense and hypodense artifacts than NiCr (P<0.05). Zinc phosphate cement presented higher hyperdense artifact percentages on CS9000 3D scans(P<0.05). CS9000 3D presented higher artifact percentages than i-CAT(P<0.05). Conclusion: High-atomic-number alloys, higher tube current, and lower tube voltage may increase the artifacts present in CBCT images.

• The Korean Journal of Ecology
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• 제24권1호
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• pp.35-43
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• 2001

카드뮴과 아연에 각각 그리고 동시에 노출한 총알고둥(Littorina brevicula)에서 중금속의 생체내 축적, 제거 및 세포내 분포 양상을 조사하였다. 총알고둥을 카드뮴 400 $\mu\textrm{g}$/L 또는 아연 3000 $\mu\textrm{g}$/L에 각각 90일간 노출하였을 경우, 각 중금속의 축적량은 노출기간에 따라 증가하였으며, 70일 이후에는 더 이상 축적량이 증가하지 않았다. 카드뮴과 아연을 동시에 노출하였을 경우에는 각각의 중금속에 노출하였을 경우에 비해 아연의 축적량은 증가하였으나, 카드뮴의 축적량은 감소하였다. 노출실험에 이어 수행한 42일간의 청장실험 결과, 카드뮴은 체외로 제거되지 않았으나, 아연은 제거되었다. 특히 카드뮴과 아연에 동시 노출한 총알고둥의 경우에 아연은 더 신속히 제거되었다. 총알고둥을 카드뮴과 아연에 각각 70일 동안 노출한 후, 체내로 흡수된 카드뮴의 약 60%가 soluble fraction에 분포하고 있었으며, 아연의 75%는 insoluble fraction에 분포하고 있었다. 이러한 경향은 카드뮴과 아연의 동시 노출시에도 유사하게 나타났다. 카드뮴과 아연은 soluble part내의 리간드(ligand) 와의 결합 양상에서도 차이를 나타냈는데, 카드뮴은 90% 이상이 약 6.5 kDa크기의 MBP-1(Metal-Binding Protein-1)과 결합하고 있었으나, 아연은 HMW(High molecular weight fraction, >60 kDa), MBP-1, MBP-2, LMW(Low molecular weight fraction <1 kDa)에 고루 분포하는 것으로 나타났다.

• Asian-Australasian Journal of Animal Sciences
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• 제17권7호
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• pp.1007-1013
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• 2004

This experiment was conducted to investigate the effect of cadmium levels on weight gain, nutrient digestibility and the retention of iron, copper and zinc in tissues of growing pigs. A total of one hundred and ninety-two crossbred pigs (barrows, Duroc$\times$Landrace$\times$Yorkshine, 27.67$\pm$1.33 kg of average initial body weight) were randomly allotted to four treatments. Each treatment had three replicates with 16 pigs per pen. The corn-soybean basal diets were supplemented with 0, 0.5, 5.0, 10.0 mg/kg cadmium respectively, and the feeding experiment lasted for eight-three days. Cadmium chloride was used as cadmium source. The results showed that pigs fed the diet containing 10.0 mg/kg cadmium had lower ADG and FCR than any other treatments (p<0.05). Apparent digestibility of protein in 10.0 mg/kg cadmium-treated group was lower than that of other groups (p<0.05). There was lower iron retention in some tissues of 5.0 mg/kg and 10.0 mg/kg cadmium treatments (p<0.05). However, pigs fed the diet 10.0 mg/kg cadmium had higher copper content in most tissues than that of any other groups (p<0.05). There was a significantly increase of zinc retention in kidney of 10.0 mg/kg cadmium additional group (p<0.05) and zinc concentrations in lymphaden, pancreas and heart of 10.0 mg/kg cadmium treatment were lower than those of the control (p<0.05). This study indicated that relatively high cadmium level (10.0 mg/kg) could decrease pig growth performance and change the retention of iron, copper and zinc in most tissues during extended cadmium exposure period.

• 한국환경농학회지
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• 제32권4호
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• pp.245-251
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• 2013

BACKGROUND: The objectives of this study are to investigate the contamination levels of heavy metals in soil, ground water, and agricultural product near the abandoned Boeun and Sanggok mine areas in Korea and to assess the health risk for these local residents exposed to the toxic heavy metals based on analytical data. METHODS AND RESULTS: By the results of human health risk assessment for local residents around Boeun and Sanggok, human exposure to cadmium, copper, arsenic from soil and to lead, cadmium, and arsenic from rice grain were higher in Sanggok, but human exposure to zinc and arsenic from ground water was higher in Boeun. By the results of hazard index (HI) evaluation for arsenic, cadmium, copper, lead, and zinc, HI values in both areas were higher than 1.0. This result indicated that the toxicity hazard through the continuous exposure to lead, cadmium, arsenic from rice, ground water, and soil would be likely to occur to the residents in the areas. Cancer risk assessment for arsenic, risks from the rice were exposed to one to two out of 10,000 people in Boeun and one of 1,000 people in Sanggok. These results showed that the cancer risks of arsenic in both areas were 10~100 times greater than the acceptable cancer risk range of US EPA ($1{\times}10^{-6}{\sim}1{\times}10^{-5}$). CONCLUSION(S): Therefore, if these two local residents consume continuously with arsenic contaminated soil, ground water, and rice, the adverse health effects (carcinogenic potential) would be more increased.

• Environmental Analysis Health and Toxicology
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• 제29권
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• pp.4.1-4.10
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• 2014

Objectives Effects of nanoparticles including zinc oxide nanoparticles, titanium oxide nanoparticles, and their mixtures on skin corrosion and irritation were investigated by using in vitro 3D human skin models ($KeraSkin^{TM}$) and the results were compared to those of an in vivo animal test. Methods Skin models were incubated with nanoparticles for a definite time period and cell viability was measured by the 3-(4, 5-dimethylthiazol-2-yl)-2.5-diphenyltetrazolium bromide method. Skin corrosion and irritation were identified by the decreased viability based on the pre-determined threshold. Results Cell viability after exposure to nanomaterial was not decreased to the pre-determined threshold level, which was 15% after 60 minutes exposure in corrosion test and 50% after 45 minutes exposure in the irritation test. IL-$1{\alpha}$ release and histopathological findings support the results of cell viability test. In vivo test using rabbits also showed non-corrosive and non-irritant results. Conclusions The findings provide the evidence that zinc oxide nanoparticles, titanium oxide nanoparticles and their mixture are 'non corrosive' and 'non-irritant' to the human skin by a globally harmonized classification system. In vivo test using animals can be replaced by an alternative in vitro test.

• Toxicological Research
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• 제6권2호
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• pp.191-204
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• 1990

Trimethyltin (TMT) induced lesions in the rat hippocampal formation was reviewed. Adult rats were treated with a single dose of 6.0 mg TMT/kg b.w. and were sacrificed between 3-60 days following exposure. On the hippocampal formation, the granule cells of fascia dentata showed early changes which subsided considerably at a later time when the destruction of the pyramidal neurons of the Ammon's horn became increasingly pronounced with time, leading to severe destruction of the structure. It is interesting to note that there was an inverse relationship of pathological involvement between the f.d. granule cells and the Ammon's horn neurons; i.e., when there was a large sparing of the granule cells. there was an extensive damage to the Ammon's horn and vice versa. This inverse relationship was also true between the $CA_3$neurons and the $CA_{1,2}$neurons in the Ammon's horn. Progressive zinc loss, as demonstrated by Timm's method, on the Mossy fibers was also observed. Similar Mossy fiber zinc depletion has been demonstrated in electrical stimulatory excitation condition of the perforant path to the hippocampus. Depletion of corticosterone, an inhibitor to the hippocampal neurons, by means of adrenalectomy will exaggerate the TMT induced hippocampal lesion. Neonatal study revealed that a unique degenerative pattern of the Ammon's horn could be established in accordance with exposure to TMT at specific maturation periods of the fippocampal formation: increasing destruction of the Ammon's horn with increasing synaptogenesis between the f.d. granule cells and the Ammon's horn neurons. Thus it is apparent that the damage of the Ammon's horn, upon exposure to TMT, may depend on the integrity and functional state of the f.d. granule cells. A hyperexcitory scheme and mechanism as the toxicity basis of TMT in the hippocampal formation is proposed and discussed.

• 한국산업보건학회지
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• 제18권2호
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• pp.99-107
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• 2008

We quantified the human carcinogenic metals (chromium, nickel) in fumes from flux cored arc welding using stainless steel (FCAW/SS) wires. Zinc and calcium were also quantified because of their possibility of zinc chromate and calcium chromate, respectively. Welding was performed in an American Welding Society standard fume collection chamber. Insoluble and soluble forms of metals were analyzed by ISO 15202 method. Total chromium (insoluble+soluble) content and total nickel content were lower in FCAW/SS fumes (4.65%, 1.05%, respectively)than in stainless steel content (ca. 18%, 8%,respectively). Insoluble fraction in total chromium was 79.8 (range 64.5~95.1)% and 94.4(range 90.1~98.1)% in total nickel. Atomic emission spectroscopy used in this study does not differentiate the chromium valence status while ACGIH defines its carcinogenicity according to the valence status. From this study and previous study, we estimated the hexavalent chromium content in FCAW/SS was 0.2~1.1% and about 85% of them was soluble. The content of zinc and calcium, which can be existed as chromate forms, was low (0.02 %, 0.04% respectively) in FCAW/SS. Exposure assessment for zinc chromate and calcium chromate is possible because chromium in both compounds is used as a surrogate even though it is not well known that what compounds of zinc and calcium are formed in welding fume.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.267.2-267.2
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• 2016

Semiconductor photo-catalysis offers the potential for complete removal of toxic chemicals through its effective and broad potential applications. Various new compounds and materials for chemical catalysts were synthesized in the past few decades. As one of the most important II-VI group semiconductors, zinc sulfide (ZnS) with a wide direct band gap of 3.8 eV has been extensively investigated and used as a catalyst in photochemistry, environmental protection and in optoelectronic devices. In this work, the ZnS films and nanostructures have been successfully prepared by wet chemical method. We show that the agglomerates with four successive scales are always observed in the case of the homogeneous precipitation of zinc sulfide. Hydrodynamics plays a crucial role to determine the size of the largest agglomerates; however, other factors should be invoked to interpret the complete structure. In addition, studies of the photocatalytic properties by exposure to UV light irradiation demonstrated that ZnS nanocrystals (NCs) are good photo-catalysts as a result of the rapid generation of electron-hole pairs by photo-excitation and the highly negative reduction potentials of excited electrons. A combination of their unique features of high surface-to volume ratios, carrier dynamics and rich photo-catalytic suggests that these ZnS NCs will find many interesting applications in semiconductor photo-catalysis, solar cells, environmental remediation, and nano-devices.