• Advances in nano research
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• v.10 no.5
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• pp.415-422
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• 2021

Silicene, a 2D allotrope of silicon, is predicted to be a potential material for future transistor that might be compatible with present silicon fabrication technology. Similar to graphene, silicene exhibits the honeycomb lattice structure. Consequently, silicene is a semimetallic material, preventing its application as a field-effect transistor. Therefore, this work proposes the uniform doping bandgap engineering technique to obtain the n-type silicene nanosheet. By applying nearest neighbour tight-binding approach and parabolic band assumption, the analytical modelling equations for band structure, density of states, electrons and holes concentrations, intrinsic electrons velocity, and ideal ballistic current transport characteristics are computed. All simulations are done by using MATLAB. The results show that a bandgap of 0.66 eV has been induced in uniformly doped silicene with phosphorus (PSi₃NW) in the zigzag direction. Moreover, the relationships between intrinsic velocity to different temperatures and carrier concentration are further studied in this paper. The results show that the ballistic carrier velocity of PSi₃NW is independent on temperature within the degenerate regime. In addition, an ideal room temperature subthreshold swing of 60 mV/dec is extracted from ballistic current-voltage transfer characteristics. In conclusion, the PSi₃NW is a potential nanomaterial for future electronics applications, particularly in the digital switching applications.

• Journal of Microbiology and Biotechnology
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• v.32 no.2
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• pp.176-186
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• 2022

Continued fenvalerate use has caused serious environmental pollution and requires large-scale remediation. Dibutyl phthalate (DBP) was discovered in fenvalerate metabolites degraded by Citrobacter freundii CD-9. Coculturing is an effective method for bioremediation, but few studies have analyzed the degradation pathways and potential mechanisms of cocultures. Here, a DBP-degrading strain (BDBP 071) was isolated from soil contaminated with pyrethroid pesticides (PPs) and identified as Stenotrophomonas acidaminiphila. The optimum conditions for DBP degradation were determined by response surface methodology (RSM) analysis to be 30.9 mg/l DBP concentration, pH 7.5, at a culture temperature of 37.2℃. Under the optimized conditions, approximately 88% of DBP was degraded within 48 h and five metabolites were detected. Coculturing C. freundii CD-9 and S. acidaminiphila BDBP 071 promoted fenvalerate degradation. When CD-9 was cultured for 16 h before adding BDBP 071, the strain inoculation ratio was 5:5 (v/v), fenvalerate concentration was 75.0 mg/l, fenvalerate was degraded to 84.37 ± 1.25%, and DBP level was reduced by 5.21 mg/l. In addition, 12 fenvalerate metabolites were identified and a pathway for fenvalerate degradation by the cocultured strains was proposed. These results provide theoretical data for further exploration of the mechanisms used by this coculture system to degrade fenvalerate and DBP, and also offer a promising method for effective bioremediation of PPs and their related metabolites in polluted environments.

• Advances in concrete construction
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• v.14 no.2
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• pp.93-102
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• 2022

In this study, limestone powder (LS) and fly ash (FA) were used as powder materials in self-compacting concrete (SCC) in increasing quantities in addition to cement, so that the two powders commonly used in the production of SCC could be compared in the same study. Considering the reduction of the maximum aggregate size in SCC, 10 mm or 16 mm was selected as the coarse aggregate size. The properties of fresh concrete were determined by slump flow (including T₅₀₀ time), V-funnel and J-ring experiments. The experimental results showed that as the amount of both LS and FA increased, the slump flow also increased. The increase in powder material had a negative effect on V-funnel flow times, causing it to increase; however, the increase in FA concretes was smaller compared to LS ones. The increase in the powder content reduced the amount of blockage in the J-ring test for both aggregate sizes. As the hardened concrete properties, the compressive and splitting strengths as well as the modulus of elasticity were determined. Longitudinal and transverse deformations were measured by attaching a special frame to the cylindrical specimens and the values of Poisson's ratio, initiation and critical stresses were obtained. Despite having a similar W/C ratio, all SCC exhibited higher compressive strength than NVC. Compressive strength increased with increasing powder content for both LS and FA; however, the increase of the FA was higher than the LS due to the pozzolanic effect. SCC with a coarse aggregate size of 16 mm showed higher strength than 10 mm for both powders. Similarly, the modulus of elasticity increased with the amount of powder material. Inelastic properties, which are rarely found in the literature for SCC, were determined by measuring the initial and critical stresses. Crack formation in SCC begins under lower stresses (corresponding to lower initial stresses) than in normal concretes, while critical stresses indicate a more brittle behavior by taking higher values.

• Analytical Science and Technology
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• v.37 no.2
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• pp.98-113
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• 2024

The current investigation entails the characterization of five degradation products (DPs) formed under different stress conditions of loteprednol using liquid chromatography-tandem mass spectrometry (LC-MS/MS). In addition, this study developed a stable high-performance liquid chromatography (HPLC) method for evaluating loteprednol along with impurities. The method conditions were meticulously fine-tuned which involved the exploration of the appropriate solvent, pH, flow of the mobile phase, columns, and wavelength. The method conditions were carefully chosen to successfully resolve the impurities of loteprednol and were employed in subsequent validation procedures. The stability profile of loteprednol was exposed to stress degradation experiments conducted under five conditions, and DPs were structurally characterized by employing LC-MS/MS. The chromatographic resolution of loteprednol and its impurities along with DPs was effectively achieved using a Phenomenex Luna 250 mm C18 column using 0.1 % phosphoric acid, methanol, and acetonitrile in 45:25:30 (v/v) pumped isocratically at 0.8 mL/min with 243 nm wavelength. The method produces an accurate fit calibration curve in 50-300 ㎍/mL for loteprednol and LOQ (0.05 ㎍/mL) - 0.30 ㎍/mL for its impurities with acceptable precision, accuracy, and recovery. The stress-induced degradation study revealed the degradation of loteprednol under basic, acidic, and photolytic conditions, resulting in the formation of seven distinct DPs. The efficacy of this method was validated through LC-MS/MS, which allowed for the verification of the chemical structures of the newly generated DPs of loteprednol. This method was appropriate for assessing the impurities of loteprednol and can also be appropriate for structural and quantitative assessment of its degradation products.

• Journal of the Korean Electrochemical Society
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• v.5 no.1
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• pp.30-38
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• 2002

Disordered carbon and boron-substituted disordered carbons $C_{l-x}B_x(x=0.05,\;0.10,\;0.20)$ were synthesized by Pyrolysis of LPG(liquid Propane gas)and $BCl_3$. Their electrochemical properties as anode materials for Li-ion secondary batteries were then investigated. When PVDF is added to the sample in a weight ratio 5 : 95, the disordered carbon with x=0.00 had the first discharge capacity 374 mAh/g. Its cycling performance was relatively good from the second cycle and it had the discharge capacity 258 mAh/g at the 10th cycle. When PVDF is added to the sample in a weight ratio 5 : 95, the sample with x=0.05 among the samples $C_{l-x}B_x(x=0.05,\;0.10,\;0.20)$ exhibited the largest first discharge capacity 860 mAh/g and discharge capacity 181 mAh/g at the 10th cycle. All the samples had similar cycling performances from the second cycle. The sample $C_{0.90}B_{0.10}$ showed the best electrochemical properties as a anode materials fur Li-ion secondary battery from the view points of the first discharge capacity(853 mAh/g when $10w1.\%$ PVDF is used), cycling performance, discharge capacity(400mAh/g at the 10th cycle when $10wt.\%$ PVDF is used). All the samples showed generally larger charge and discharge capacities when $10wt.\%$ PVDF ratter than $5wt.\%$ PVDF is used. The plateau region in the range of voltage lower than 1.25V becomes larger probably since the structure becomes less disordered by the addition of boron. When boron is added, the charge and discharge capacities decreased suddenly at the second cycle. This may be become only a part of Li are reversibly deintercalated and intercalated and a part of Li which are strongly combined with B are not deintercalated. The increases in charge and discharge capacities are considered to be resulted from the increase in the potential of Li in the boron-added carbons, caused by the strengthening of the chemical bond between the intercalated Li and the boron-carbon host since the boron acts as electron acceptor.

• Journal of the Korean Chemical Society
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• v.33 no.3
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• pp.273-280
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• 1989

The spectra of the $Co^{II}CyDTA$(CyDTA: cyclohexyldiaminetetraacetic acid) complex have been measured in aqueous solution of pH = 6-13.2. The red shift of the spectrum in the more basic solution was ascribed to the transformation of $CoCyDTA^{2-}$ into $CoCyDTA(OH)^{3-}$. The equilibrium constant, $K_{OH} = [CoCyDTA(OH)^{3-}]/[CoCyDTA^{2-}][OH^-]$ was $75M^{-1}$ at $40^{\circ}C$. The electron transfer reactions of $CoCyDTA^{2-}$ and $CoCyDTA(OH)^{3-}$ with $Fe(CN)_6^{3-}$ have been studied using spectrophotometric technique in the range of pH applied to the determination of equilibrium constant. The pseudo first-order rate constants observed ($k_{obs}$) were not changed upto pH = 10.8, but increased with increasing pH in the range of pH = $10.8{\sim}13.0$. The rate law reduced in the range of pH = 6-13 was $k_{obs} = (k_3[CoCyDTA^{2-}] + k_4[CoCyDTA(OH)^{3-}])/(1+K_1[CoCyDTA^{2-}])$. The rate constants of the reactions (3a) and (3b), $k_3$ and $k_4$ respectively have been determined to be 0.529 and $4.500M^{-1}sec^{-1}$ at $40^{\circ}C$. The activation entropies (147{\pm}1.1JK^{-1} mol^{-1}$ at pH = 10.8) and activation volumes $(6.25cm^3mol^{-1}, pH = 10.8)$ increased with increasing pH, while the activation enthalpy (12.44 ${\pm}$ 0.20 kcal/mole) was independent of pH. Using the pH effect on the rate constants, the activation entropies and the activation volumes, the mechanism of the electron transfer reaction for $Co^{II}-Fe^{III}$ system was discussed.

• Journal of Plant Biotechnology
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• v.44 no.4
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• pp.401-408
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• 2017

Herein, we report the meristem-tip culture from dormant buds of grape 'Kyoho' single-infected with Grapevine fleck virus (GFkV), which is phloem-limited and transmitted by graft inoculation. We produced GFkV-free shoots without thermo- or chemotherapy using meristem-tip explants approximately 0.3 mm (73 explants) and 0.8 mm long (five explants) including shoot apical meristem, 2-5 leaf primordia, and 1-4 uncommitted primordia from dormant buds of the infected woody cuttings (stored at $4^{\circ}C$). Explants were cultured on Murashige and Skoog (MS) medium supplemented with 3% sucrose, 3.0 mg/L benzyladenine (BA) and 0.1 mg/L indole-3-butyric acid (IBA). After 16 weeks of culture, shoot (10-mm long) regeneration frequency achieved from 0.3-mm explants was 4.1% and that obtained from 0.8-mm explants was 40.0%. Virus-free efficiency (expressed as the percentage of RT-PCR negative shoots regenerated) from 0.3- and 0.8-mm explants was 100% and 50%, respectively. Following in vitro multiplication, RT-PCR assays revealed identical results to assays of the first regenerated shoots. Our new methodological approach could be applied for eliminating other viruses in grapevines, as well as for producing virus-free plants in many other deciduous tree species, including fruit trees.

• Korean Journal of Animal Reproduction
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• v.24 no.4
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• pp.407-417
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• 2000

The present study was to examine effects of various electrical stimulus treatments used for electro-fusion on the preimplantation development of bovine nuclear transfer (NT) embryos with fetal fibroblast cells. Fetal fibroblast cells were isolated from one fetus at day 45 of gestation in Holstein cow, and passaged 3 to 4 times before being transferred into enucleated oocytes. Single fibroblast cells were individually placed into the perivitelline space of enucleated oocytes by using a micromanipulator. At first, the fusion and developmental rates of reconstructed oocytes were compared between different electric stimulation conditions. When fusion of the reconstructed oocyte was induced by different electric pulse periods (15, 30 and 45 $\mu$sec) at a DC pulse of 1.8 kV/cm, 15 (45.5%, 120/264) or 30 $\mu$ sec group (43.9%, 106/241) showed a higher fusion rate than 45 $\mu$sec group (23.2%, 58/250, P＜0.05). However, no difference was detected in the development rate of the fused oocytes to blastocysts between groups. Next experiment was to examine the effects of different electrical field strengths (1.5, 1.8 and 2.1 kV/cm) for 15 $\mu$sec at electrofusion on in vitro development of the NT embryos. As results, there was no difference in the fusion and developmental rates of the NT embryos between electrical strength (P＞0.05). Finally, developmental competence of bovine NT embryos with somatic cells was compared with IVF-derived embryos. Of enucleated oocytes fused with fibroblast cells, 27.4% (75/274) developed to the blastocyst stage, which is similar to that (24.5%, 58/237) of IVF-derived embryos. However, mean nuclei number of NT blastocysts was smaller than that of IVF-derived blastocysts. Thus, we have established an optimal condition (1.8 kV/cm, 15 $\mu$sec) for electric fusion of bovine NT oocytes with somatic cells. The present study indicates that bovine reconstructed embryos with somatic cells normally develop to blastocyst stage in vitro, although having smaller nuclei numbers of blastocysts as compared to IVF-derived embryos.

• Korean Journal of Agricultural and Forest Meteorology
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• v.25 no.1
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• pp.48-59
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• 2023

Ground-level ozone affects human health and plant growth. Ozone is produced by chemical reactions between oxides of nitrogen (NOx) and volatile organic compounds (VOCs) from anthropogenic and biogenic sources. In this study, two different land cover and emission factor datasets were input to the MEGAN v2.1 emission model to examine how these parameters contribute to the biogenic emissions and ozone production. Four input sensitivity scenarios (A, B, C and D) were generated from land cover and vegetation emission factors combination. The effects of BVOCs emissions by scenario were also investigated. From air quality modeling result using CAMx, maximum 1 hour ozone concentrations were estimated 62 ppb, 60 ppb, 68 ppb, 65 ppb, 55 ppb for scenarios A, B, C, D and E, respectively. For maximum 8 hour ozone concentration, 57 ppb, 56 ppb, 63 ppb, 60 ppb, and 53 ppb were estimated by scenario. The minimum difference by land cover was up to 25 ppb and by emission factor that was up to 35 ppb. From the modeling performance evaluation using ground ozone measurement over the six regions (East Seoul, West Seoul, Incheon, Namyangju, Wonju, and Daegu), the model performed well in terms of the correlation coefficient (0.6 to 0.82). For the 4 urban regions (East Seoul, West Seoul, Incheon, and Namyangju), ozone simulations were not quite sensitive to the change of BVOC emissions. For rural regions (Wonju and Daegu) , however, BVOC emission affected ozone concentration much more than previously mentioned regions, especially in case of scenario C. This implies the importance of biogenic emissions on ozone production over the sub-urban to rural regions.

• Applied Biological Chemistry
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• v.22 no.1
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• pp.42-50
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• 1979

The viscosity coefficient of mucilage of Abelmoschus manihot, MEDIC root decrease under the influence of temperature and the other various physical and chemical factors. The rate of viscosity change of the mucilage have been measured at $5^{\circ}{\sim}50^{\circ}C$ in aqueous state under the various conditions. The results are as follows: 1. Relationship between rate of viscosity change of mucilage and temperature can be represent as Andrade equation. 2. Their activation energies of viscosity change of Abelmaschus maihot, MEDIC root A, B, C, D, E, F and G observed are 11.9, 12.1, 11.4, 12.1, 11.6, 13.8 and 13.2 Kcal/mole, respectively. And other activation parameters arc evaluated. 3. The activation energy of naturally mucilage are smaller than that of sterilized mucilage.