• 한국주조공학회지
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• 제41권1호
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• pp.3-10
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• 2021

알루미늄 합금과 주철의 복합주조 공정 중에는 주철로부터 철 성분이 용해되어 알루미늄 용탕에 혼입될 수 있으므로 다양한 Fe함유 금속간 화합물이 형성되며, 이로 인해 알루미늄 합금의 인장 특성이 크게 저하 될 수 있다. 반면 불순물로 첨가되는 Fe와 는 달리 Cu의 경우 알루미늄 합금의 기계적 물성을 향상시키기 위해 첨가되는 합금원소이다. 본 연구에서는 Fe와 Cu의 첨가로 인한 알루미늄 합금의 미세조직 및 인장특성의 변화를 조사하였다. 첨가된 Fe 함량이 1% 이상일 경우 조대한 Al₅FeSi 상과 같은 Fe 함유 화합물들이 다량 형성되어 인장 특성이 현저히 감소하는 것으로 나타났다. Cu가 첨가 된 알루미늄 합금의 경우 Al2Cu 상이 추가로 형성되었으며, 인장 강도가 뚜렷하게 향상되는 결과를 보였다.

• 한국주조공학회지
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• 제40권2호
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• pp.25-33
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• 2020

The effects of mold variable and main alloying element on the mechanical properties of ductile cast iron poured into shell stack mold were investigated. The strength and hardness of with the smaller cross-section of the diameter of 6.25mm were higher than those of 12.50mm. On the other hand, the elongation of the former was lower than that of the latter. The strength and hardness of the specimens obtained from the center layer in the 5-story stack mold were the lowest and those for other specimens were increased with increased distance from the center. The elongation of those were the highest of all. The strength and hardness of the specimens obtained from the center layer were decreased the elongation was increased with the increased number of layers. The strength and hardness were increased and the elongation was decreased roughly with the increased amounts of reaidual magnesium and carbon content added, respectively. The strength and hardness were increased and the elongation was decreased roughly with the increased amounts of silicon content added to 2.45wt% and rather decreased with that to 2.85wt%. The effect of silicon content showed the opposite tendency to those of residual magnesium and carbon content.

• 한국주조공학회지
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• 제25권1호
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• pp.40-50
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• 2005

A series of heavy section ductile cast iron ingots with the cube length of 250mm were systematically investigated as functions of casting parameters of sand casting. Abnormal graphite formation was specially observed with the variation of Si content and Bi or Sb addition. Effects of chilling during casting and adaptation of riserless system were also examined, and proved to be effective for the prevention of both shrinkage and abnormal graphite such as chunky one. The formation of chunky graphite was effectively prevented by low Si content despite the promotion of pearlite matrix structure. The ferritic matrix was encouraged to form by high Si content and chunky graphite formation was effectively suppressed by the addition of Bi and Sb. Bi addition, however, was not good enough to control the microstructure owing to the sensitive cooling rate dependent inoculation behavior and relative low ability of nodulization. Sb addition, on the other hand, was proved to be effective for the microstructural control and enhancement of various mechanical properties such as strength, elongation, and impact energy. It may be suggested that optimized casting parameters should be applied to produce heavy section ductile cast iron with reliability.

• Journal of Microbiology and Biotechnology
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• 제21권2호
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• pp.136-146
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• 2011

This study provides first-hand proteomic data on the survival strategy of Anabaena sp. PCC 7120 when subjected to long-term iron-starvation conditions. 2D-gel electrophoresis followed by MALDI-TOF/MS analysis of iron-deficient Anabaena revealed significant and reproducible alterations in ten proteins, of which six are associated with photosynthesis and respiration, three with the antioxidative defense system, and the last, hypothetical protein all1861, conceivably connected with iron homeostasis. Iron-starved Anabaena registered a reduction in growth, photosynthetic pigments, PSI, PSII, whole-chain electron transport, carbon and nitrogen fixation, and ATP and NADPH content. The kinetics of hypothetical protein all1861 expression, with no change in expression until day 3, maximum expression on the $7^{th}$ day, and a decline in expression from the $15^{th}$ day onward, coupled with in silico analysis, suggested its role in iron sequestration and homeostasis. Interestingly, the up-regulated FBP-aldolase, Mn/Fe-SOD, and all1861 all appear to assist the survival of Anabeana subjected to iron-starvation conditions. Furthermore, the $N_2$-fixation capabilities of the iron-starved Anabaena encourage us to recommend its application as a biofertilizer, particularly in iron-limited paddy soils.

• 한국식품영양과학회지
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• 제30권2호
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• pp.325-330
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• 2001

The purpose of this study was to evaluate the obesity index and effect of dietary zinc and iron levels on serum trace minerals status in the high fat diet-induced obese rats. Male Sprague-Dawley rats were randomly assigned to control and high fat diet groups. Ten weeks later, the control and high fat diet group were rearranged into six groups by zinc and iron levels. After 16 wk serum zinc, iron, copper and manganese was analyzed. Obesity index was significantly higher in the group fed high fat diet (20% lard) than that of control group (5% corn oil). Body fat content was 12.10$\pm$4.51g/100g BW in high fat diet group and 7.64$\pm$4.18g/100g BW in control group. So, the obese rats were successfully induced by high fat diet. The trace mineral concentration of obese rats in serum were affected by zinc levels. Serum zinc concentration was increased by dietary zinc overload, whereas the iron, copper and manganese were decreased. Specially the manganese concentration was significantly affected by zinc levels. In both groups, serum trace mineral concentration was not changed significantly by the dietary iron levels. There were positive correlations between zinc, iron and manganese concentration according to dietary zinc and iron levels.

• Journal of Microbiology and Biotechnology
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• 제19권6호
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• pp.604-609
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• 2009

To investigate the potential use of microbial heme as an iron source, recombinant Escherichia coli coexpressing ALA synthase (HemA) as well as the NADP-dependent malic enzyme (MaeB) and dicarboxylic acid transporter (DctA) were cultured. The typical red pigment extracted from the recombinant E. coli after 38 h showed highest absorbance at 407 nm, and the amount of iron in 38.4 mg of microbial heme extract derived from 6-1 fermentation broth was 4.1 mg. To determine the commercial potential of the recombinant E.coli-synthesized iron-associated heme as an iron source, mice were fed the iron-free provender with the microbial heme extract. The average body weight reduction of mice fed non-iron provender was 2.3%, whereas no detectable weight loss was evident in mice fed microbial heme addition after 15 days. The heme content of the blood from microbial heme fed mice was 4.2 mg/ml whereas that of controls was 2.4 mg/ml, which implies that the microbial heme could be available for use as an animal iron source.

• Archives of Pharmacal Research
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• 제26권10호
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• pp.874-879
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• 2003

The present study was carried out to examine the stability of microencapsulated ascorbic acid in simulated-gastric and intestinal situation in vitro and the effect of microencapsulated ascorbic acid on iron bioavailability. Coating materials used were polyglycerol monostearate (PGMS) and medium-chain triacylglycerol (MCT), and core materials were L-ascorbic acid and ferric ammonium sulfate. When ascorbic acid was microencapsulated by MCT, the release of ascorbic acid was 6.3％ at pH 5 and 1.32％ at pH 2 in simulated-gastric fluids during 60 min. When ascorbic acid was microencapsulated by PGMS, the more ascorbic acid was released in the range of 9.5 to 16.0％. Comparatively, ascorbic acid release increased significantly as 94.7％ and 83.8％ coated by MCT and PGMS, respectively, for 60 min incubation in simulated-intestinal fluid. In the subsequent study, we tested whether ascorbic acid enhanced the iron bioavailability or not. In results, serum iron content and transferring saturation increased dramatically when subjects consumed milks containing both encapsulated iron and encapsulated ascorbic acid, compared with those when consumed uncapsulated iron or encapsulated iron without ascorbic acid. Therefore, the present data indicated that microencapsulated ascorbic acid with both PGMS and MCT were effective means for fortifying ascorbic acid into milk and for enhancing the iron bioavailability.

• BMB Reports
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• 제40권1호
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• pp.82-87
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• 2007

Our heterologous expression system of the human ferritin H-chain gene (hfH) allowed us to characterize the cellular effects of ferritin in yeasts. The recombinant Saccharomyces cerevisiae (YGH2) evidenced impaired growth as compared to the control, which was correlated with ferritin expression and with the formation of core minerals. Growth was recovered via the administration of iron supplements. The modification of cellular iron metabolism, which involved the increased expression of high-affinity iron transport genes (FET3 and FTR1), was detected via Northern blot analysis. The findings may provide some evidence of cytosolic iron deficiency, as the genes were expressed transcriptionally under iron-deficient conditions. According to our results examining reactive oxygen species (ROS) generation via the fluorescence method, the ROS levels in YGH2 were decreased compared to the control. It suggests that the expression of active H-ferritins reduced the content of free iron in yeast. Therefore, present results may provide new insights into the regulatory network and pathways inherent to iron depletion conditions.

• 보존과학연구
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• 통권16호
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• pp.59-111
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• 1995

Chemical composion and crystal form of Corrosion products found on archaeological iron objects were analyzed using X-ray fluorescence analysis, micro-X-ray powder diffraction analysis and ion chromatographic technique. The nature and behavior of the corrosion products were studied in order to aid in the conservation and restoration of burial iron objects. Twenty-two samples analyzed in this study were collected from iron object found in Korea and Japan. The corrosion products of iron objects from burial mounds contain $\alpha$-FeOOH, $\beta$-FeOOH, $\gamma$-FeOOH, $Fe_3O_4$and amorphous iron hydroxides. The content of $\alpha$-HeOOH is the greatest. Because, Ageing for long period should change the amorphous iron hydroxides is considerably less than that in usual atmospheric corrosion products. The concentration of chlorine and sulfine is remarkably variable ($Cl^-$ : 100- 30,000ppm, $SO_4^-2$ : 20-10,000ppm),but the reasons are unclear. The presence of generally high concentrations of chlorine and sulfine the corrosion products of iron objects seem to be influenced by the marine climatic condition. The presence of high chlorine and sulfine concentrations in the corrosion products of iron objects seem to be influenced by the marine burial environments.

• 한국육종학회지
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• 제40권2호
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• pp.101-105
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• 2008

The germplasm of 246 rice cultivars was analysed for iron and zinc contents using a Inductively Coupled Argon Plasma (ICP) at International Rice Research Institute (IRRI) Philippines. Iron contents ranged from 2.0 to 12.0, and zinc ranged from 10.0 to 33.0 (mg/kg), showing with the mean values of 4.3 and 22.8 (mg/kg), respectively. In genotypes tested, there was approximately a two-fold difference in iron and zinc concentrations, suggesting a genetic potential to increase these micronutrients in rice grain. A highly significant positive correlation ($r^2=0.503$) was found between iron and zinc contents. Iron contents decreased drastically as polishing time increased, whereas zinc decreased only slightly. In the interaction between genotype and environment on iron contents, genotype (G), environment (E), and the G ${\times}$ E interactions accounted for 69%, 5% and 26% of the sums of squares, respectively. Indicating that genotype is would be the most significant factor for the to improve iron contents of rice in rice breeding, suggesting that therefore identifying genotypes with relatively stable performance across various environments is important as staple food crops.