• Journal of Microbiology and Biotechnology
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• 제27권2호
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• pp.306-315
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• 2017

Metabolic engineering with a high-yielding mutant, A. terreus AN37, was performed to enhance the production of itaconic acid (IA). Reportedly, the gene cluster for IA biosynthesis is composed of four genes: reg (regulator), mtt (mitochondrial transporter), cad (cis-aconitate decarboxylase), and mfs (membrane transporter). By overexpressing each gene of the IA gene cluster in A. terreus AN37 transformed by the restriction enzyme-mediated integration method, several transformants showing high productivity of IA were successfully obtained. One of the AN37/cad transformants could produce a very high amount of IA (75 g/l) in shake-flask cultivations, showing an average of 5% higher IA titer compared with the high-yielding control strain. Notably, in the case of the mfs transformants, a maximal increase of 18.3% in IA production was observed relative to the control strain under the identical fermentation conditions. Meanwhile, the overexpression of reg and mtt genes showed no significant improvements in IA production. In summary, the overexpressed cis-aconitate decarboxylase (CAD) and putative membrane transporter (MFS) appeared to have positive influences on the enhanced IA productivity of the respective transformant. The maximal increases of 13.6~18.3% in IA productivity of the transformed strains should be noted, since the parallel mother strain used in this study is indeed a very high-performance mutant that has been obtained through intensive rational screening programs in our laboratory.

• 열처리공학회지
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• 제32권6호
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• pp.263-269
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• 2019

The mechanism of microstructure and hardness changes during mill annealing of Ti-6Al-4V alloy was investigated. The annealing heat treatments were performed at $675{\sim}795^{\circ}C$ in vacuum for 2 hours, followed by air cooling. The microstructure was observed by using an optical microscope and X-ray diffraction, and hardness was measured by using a Rockwell hardness tester and micro Vickers hardness tester. The average grain size becomes smaller at $675^{\circ}C$ to $735^{\circ}C$ due to the formation of new grains rather than grain growth, but becomes larger at $735^{\circ}C$ to $795^{\circ}C$ due to growth of the already-formed grains rather than formation of new grains. The mill annealing temperature becomes higher, the ${\beta}$ phase fraction decreases and ${\alpha}$ phase fraction increases at room temperature. This is because the higher annealing temperature, the smaller amount of V present in the ${\beta}$ phase, and thus the ${\beta}$ to ${\alpha}$ transformation occurs more easily when cooled to room temperature. As the mill annealing temperature increases, the hardness value tends to decrease, mainly due to resolution of defects such as dislocations from $675^{\circ}C$ to $735^{\circ}C$ and due to grain growth from $735^{\circ}C$ to $795^{\circ}C$, respectively.

• Journal of Microbiology and Biotechnology
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• 제32권4호
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• pp.447-457
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• 2022

Notoginsenoside R1 and ginsenoside Rg1 are the main active ingredients of Panax notoginseng, exhibiting anti-fatigue, anti-tumor, anti-inflammatory, and other activities. In a previous study, a GH39 β-xylosidase Xln-DT was responsible for the bioconversion of saponin, a natural active substance with a xylose group, with high selectivity for cleaving the outer xylose moiety of notoginsenoside R1 at the C-6 position, producing ginsenoside Rg1 with potent anti-fatigue activity. The optimal bioconversion temperature, pH, and enzyme dosage were obtained by optimizing the transformation conditions. Under optimal conditions (pH 6.0, 75℃, enzyme dosage 1.0 U/ml), 1.0 g/l of notoginsenoside R1 was converted into 0.86 g/l of ginsenoside Rg1 within 30 min, with a molar conversion rate of approximately 100%. Furthermore, the in vivo anti-fatigue activity of notoginsenoside R1 and ginsenoside Rg1 were compared using a suitable rat model. Compared with the control group, the forced swimming time to exhaustion was prolonged in mice by 17.3% in the Rg1 high group (20 mg/kg·d). Additionally, the levels of hepatic glycogen (69.9-83.3% increase) and muscle glycogen (36.9-93.6% increase) were increased. In the Rg1 group, hemoglobin levels were also distinctly increased by treatment concentrations. Our findings indicate that treatment with ginsenoside Rg1 enhances the anti-fatigue effects. In this study, we reveal a GH39 β-xylosidase displaying excellent hydrolytic activity to produce ginsenoside Rg1 in the pharmaceutical and food industries.

• Nuclear Engineering and Technology
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• 제54권6호
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• pp.2077-2083
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• 2022

In the unlikely event of core disruptive accident in sodium cooled fast reactors, the reactor containment building would be bottled up with sodium and fission product aerosols. The behavior of these aerosols is crucial to estimate the in-containment source term as a part of nuclear reactor safety analysis. In this work, the evolution of sodium aerosol characteristics (mass concentration and size) is simulated using HAARM-S code. The code is based on the method of moments to solve the integro-differential equation. The code is updated to FORTRAN-77 and run in Microsoft FORTRAN PowerStation 4.0 (on Desktop). The sodium aerosol characteristics simulated by HAARM-S code are compared with the measured values at Aerosol Test Facility. The maximum deviation between measured and simulated mass concentrations is 30% at initial period (up to 60 min) and around 50% in the later period. In addition, the influence of humidity on aerosol size growth for two different aerosol mass concentrations is studied. The measured and simulated growth factors of aerosol size (ratio of saturated size to initial size) are found to be matched at reasonable extent. Since sodium is highly reactive with atmospheric constituents, the aerosol growth factor depends on the hygroscopic growth, chemical transformation and density variations besides coagulation. Further, there is a scope for the improvement of the code to estimate the aerosol dynamics in confined environment.

• 열처리공학회지
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• 제36권3호
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• pp.121-127
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• 2023

When high carbon steel is heated in an appropriate austenizing temperature range and subjected to austempering, the size and shape of lamellar structure can be controlled. The high carbon steel sheet having the pearlite structure has excellent elastic characteristics because it has strong restoring force when properly rolled, and is applied in a process known as patenting-process using lead bath. In the case of isothermal treatment using lead-medium, it is possible to quickly reach a uniform temperature due to high heat transfer characteristics, but it is difficult to replace it with process technology that requires treatment to remove harmfulness lead. In this study, we intend to develop fluidization technology using garnet powder to replace the lead medium. After heating the high-carbon steel, the cooling rate was changed by compressed air to the vicinity of the nose of the continuous cooling curve, and then maintained for 90 s and then exposed to room temperature. The microstructure of the treated specimens were analyzed and compared with the existing products treated with lead bath. The higher the flow rate of compressed air, the faster the cooling rate to the pearlite transformation temperature, so lamellar spacing decreases and the hardness tends to increase.

• Applied Biological Chemistry
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• 제15권2호
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• pp.163-168
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• 1972

Previously identified female pupae were X-irradiated with a dose of 1000r one day prior to moth transformation. Female mothes from irradiated and non-irradiated pupae were copulated with normal male ones and allowed to lay eggs. Fertilized eggs were collected at 6 intervals such as 5, 15, 45, 90 minutes, 12 and 40 hours after laying, and deep-freezed immediately after each collection until measurements. RNase activity and nucleic acid content were determined with each sample and following results were obtained. 1) It was proved to exist two RNases in silk worm eggs as in mammalian tissues, one active maximally at pH 5.8 and the other at pH 8.0, and the acid RNase activity was much higher than that of alkaline RNase. 2) The activity of acid and alkaline RNases increased remarkably during early development of the embryo of silk worm eggs, reaching the maximum activity at 45 minutes from laying time in non-irradiated group. There was no appreciable difference in two RNase activities for 45 minutes after laying in both control and irradiated groups, but the activity of acid and alkaline RNases in latter group was three times as much as that in former group, at 90 minutes from laying time and it was also found the acid RNase activity was 1.8 times higher than alkaline one in irradiated group. 3) The RNA-P content of control group increased considerably for initial 45 minutes, followed by a decline 45 minutes later with sight but steady increase thereafter. The RNA-P content of irradiated group, however, increased at initial 5 minutes, followed by a marked fall 90 minutes after laying, with no change thereafter. The DNA-P of control group showed a sharp increase for initial 45 minutes, followed by a decline 45 minutes later with no appreciable change thereafter, whereas that of irradiated group showed an increase at initial 15 minutes, followed by a sharp decline for following 45 minutes with a gradual increase thereafter. It was thus proved that the synthesis of nucleic acid in silk worm eggs was much suppressed by X-irradiation during early development of embryo. 4) The RNase activity varied in parallel with the RNA-P content in control group, but the RNA-P content in irradiated group was shown to be minimum value in concidence with the maximum activity of both RNases.

• Journal of Gastric Cancer
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• 제15권4호
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• pp.246-255
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• 2015

Purpose: The importance of Helicobacter pylori eradication after endoscopic resection (ER) of gastric neoplasms remains controversial. In this study, we clarified the importance of H. pylori eradication for metachronous lesions after ER. Materials and Methods: This study included 3,882 patients with gastric neoplasms who underwent ER. We included patients infected with H. pylori who received eradication therapy. Among them, 34 patients with metachronous lesions after ER and 102 age- and sex-matched patients (nonmetachronous group) were enrolled. Background mucosal pathologies such as atrophy and intestinal metaplasia (IM) were evaluated endoscopically. The expression levels of CDX1, CDX2, Sonic hedgehog (SHH), and SOX2 were evaluated based on H. pylori eradication and the development of metachronous lesions. Results: The eradication failure rate was higher in the metachronous group than in the nonmetachronous group (P=0.036). Open-type atrophy (P=0.003) and moderate-to-severe IM (P=0.001) occurred more frequently in the metachronous group. In patients with an initial diagnosis of dysplasia, the eradication failure rate was higher in the metachronous group than in the nonmetachronous group (P=0.002). In addition, open-type atrophy was more frequent in the metachronous group (P=0.047). In patients with an initial diagnosis of carcinoma, moderate-to-severe IM occurred more frequently in the metachronous group (P=0.003); however, the eradication failure rate was not significantly different between the two groups. SHH and SOX2 expression was increased, and CDX2 expression was decreased in the nonmetachronous group after eradication (P<0.05). Conclusions: Open-type atrophy, moderate-to-severe IM, and H. pylori eradication failure were significantly associated with metachronous lesions. However, eradication failure was significantly associated with dysplasia, but not carcinoma, in the metachronous group. Thus, H. pylori eradication may play an important role in preventing metachronous lesions after ER for precancerous lesions before carcinomatous transformation.

• 한국어류학회지
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• 제1권1_2호
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• pp.24-34
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• 1989

외부형태를 근거로 구분되어 온 잉어과(科)(Cyprinidae)의 모래무지아과(亞科)(Gobioninae)어류는 아과(亞科)의 한계가 학자 간에 일치되지 않아 분류학적으로 문제된다. 본 연구는 이의 규명을 위해 한국산 모래무지아과(亞科) 어류(魚類) 14속(屬)에 대해 두골의 형질을 재검토하던 중 미설골(urohyal)의 형질이 뚜렷한 형질전이 상태를 보여 주목되었다. 한국산 모래무지아과(亞科) 어류는 미설골의 형질상태에 의해 다음과 같은 4개의 group으로 구분되었다. 1. Coreo leuciscus, Gnathopogon group ; 수평판의 형태는 후연이 쐐기모양으로 패인 원추형이고, 그 길이는 수직판보다 길다. 2. Squalidus, Hemibarbus group ; 수평판의 형태는 뒤로 갈수록 넓어지며 후연은 뾰죽하게 뻗은 긴 마름모꼴로, 그 길이는 수직판과 거의 같다. 3. Sarcocheilichthys, Pseudorasbora, Pseudopungtungia, Pungtungia group ; 수평판의 형태는 중앙부분이 매우 넓은 마름모꼴로, 그 길이는 수직판 보다 길고, 인대가 부착되는 선단은 2분지 되지 않으며, 중앙부분이 복면을 향해 굽어 있다. 4. Ladislavia, Gobiobotia, Abbottina, Hicrophysogobio, Pseudogobio, Saurogobio group ; 수평판의 형태는 뒤로 갈수록 가늘어지는 침상 혹은 넓은 쐐기모양으로, 그 길이는 수직판보다 짧고, 선단의 인대가 부착되는 부위는 배면으로 비후되었다. 이러한 결과는 adductor mandibulae complex와 geniohyoideus 등의 근육형질이나 두부 측선감각관 등의 형질에 의한 결과와도 일치되는 것으로 주목된다.

• 한국수소및신에너지학회논문집
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• 제16권3호
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• pp.277-283
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• 2005

Pretreatment procedure was investigated into brucite powders for mineral carbonation materials. Higher magnesium content was found from brucite powders and weight loss due to hydroxy group(-OH) elimination, explained by FT-IR spectra, was found after pretreatment. X-ray diffraction results showed that the crystallographic changing of brucite into magnesium oxides during pretreatment. XPS core spectra also showed chemical transformation of magnesium ingredient from hydroxides to oxide.

• Bulletin of the Korean Chemical Society
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• 제32권spc8호
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• pp.2970-2972
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• 2011

One-pot homo- and cross-coupling reactions of arenediazonium tosylate salts bearing a halogen group have been exploited for the synthesis of biaryls and polyaryls under mild conditions. $Pd(OAc)_2$ has proven to be an efficient catalyst for the successful dual transformation of diazonium salts into p-quaterphenyl (3).