• KSBB Journal
• /
• v.5 no.3
• /
• pp.269-277
• /
• 1990

Methylobacillus sp. SK1, an obligate methylotroph, was cultivated in a fed-batch culture using DO as a methanol feeding indicator with a micro computer-aided control system. While 2.07g/l of cell density was obtained after 13 hr in the batch culture (initial methanol concentration: 1.0%(v/v)),45.3g/l of cell density was obtained after 17 hr by feeding methanol and metal ions in the fed-batch culture with oxygen supply. The high-density biomass was obtained in short cultuivation time by fed-batch culture with feedback control, and consequently the biomass productivity was significantly increased. It was mainly due to extension of logarithmic growth period by methanol feeding without methanol inhibition and intensive aeration without DO limitation with microcomputer-aided control system.

• Applied Chemistry for Engineering
• /
• v.18 no.4
• /
• pp.381-385
• /
• 2007

High density activated carbons electrode materials, for supercapacitor were prepared by chemical KOH activation of cokes as the starting material under Ar atmosphere. By controlling the synthesis conditions and reducing KOH quantity in the activation step, the specific surface area of the product was decreased. BET surface area was measured to be $500{\sim}1260m^2/g$, and the electrode density was in the range of $0.68{\sim}0.83g/cm^3$. Volumetric specific capacitance (unit cell test) was as high as 20 F/cc, which corresponds to gravimetric specific capacitance of about 95 F/cc on the basis of half cell test. It should be noted that the specific capacitance of the activated carbons prepared in this study is superior to that of commercial activated carbons.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2013.02a
• /
• pp.347-348
• /
• 2013

To obtain high conversion efficiency in InGaN-based solar cells, it is critical to grow high indium (In) composed InGaN layer for increasing sun light absorption wavelength rage. At present, most InGaN-based solar cells adopt InGaN/GaN multi-quantum-well (MQW) structure for high crystalline quality of InGaN with high In composition. In this study, we fabricated and compared the performances of two types of InGaN/GaN MQW solar cells which have the 15% (SC 15) and 25% (SC 25) of In composition at quantum well layer. Although both devices showed similar dark current density and leakage current, SC 15 showed better performance under AM 1.5G illumination as shown in Fig. 1. It is interesting to note that SC 25 showed severe current density decrease as increasing voltages. As a result, it lowered short circuit current density and fill factor of the device. However, SC 15 showed steady current density and over 75 % of fill factor. To investigate these differencesmore clearly, we analyzed their photoluminescence (PL) spectra under various applied voltages as shown in Fig. 2. At the same time, photocurrent, which was generated by PL excitation, was also measured as shown in Fig. 3. Further, we investigated the relationship between piezoelectric field and performance of InGaN based solar cell varying indium composition.

• Journal of the Korean Vacuum Society
• /
• v.22 no.4
• /
• pp.218-224
• /
• 2013

We measure solar currents transformed from quantum efficiency as a function of incident angles of solar lights. According to conventional models for solar cells, solar currents can be induced when electrons are separated into electrons and holes in the presence of incident solar lights. On the contrary, solar currents can be possible at the time when pinned charge density waves go beyond the pinning potential barrier under the influence of incident solar beams suggested by some authors. In this experiment, measured solar currents and our theory are in good correspondence to confirm the angle dependence of solar lights.

• Journal of IKEEE
• /
• v.27 no.4
• /
• pp.399-404
• /
• 2023

In this paper, we analyzed the current path in the O/N/O (Oxide/Nitride/Oxide) structure of 3D NAND Flash memory and in the O/N/F (Oxide/Nitride/Ferroelectric) structure where the blocking oxide is replaced by a ferroelectric. In the O/N/O structure, when V_read is applied, a current path is formed on the backside of the channel due to the E-fields of neighboring cells. In contrast, the O/N/F structure exhibits a current path formed on the front side due to the polarization of the ferroelectric material, causing electrons to move toward the channel front. Additionally, we performed an examination of device characteristics considering channel thickness and channel length. The analysis results showed that the front electron current density in the O/N/F structure increased by 2.8 times compared to the O/N/O structure, and the front electron current density ratio of the O/N/F structure was 17.7% higher. Therefore, the front current path is formed more effectively in the O/N/F structure than in the O/N/O structure.

• KSBB Journal
• /
• v.16 no.1
• /
• pp.30-35
• /
• 2001

High cell density culture of Bacillus thuringiensis was conducted in fed-batch culture and TCRC using a bioreactor incorporating ceramic membrane filter. Cell growth of B. thuringiensis in fed-batch culture increased linearly, which was well matched by the results of cell growth modeling. In spite of the slower growth rate during fed-batch culture, no spore formation was observed, which was contrary to the results of continuous culture. Changing culture mode to batch culture after fed-batch operation induced a 2.7$\times$$10^9$ CFU/mL spore concentration using a 300 g/L glucose feed concentration. In TCRC operation incorporating ceramic filter within the bioreactor, the effect of glucose feed concentrations on the cell growth and spore formation of B. thuringiensis was determined. A maximum cell concentration of 1.8$\times$$10^{10}$ CFU/ml, which corresponds to 82.6 g-cell/L, was obtained in the TCRC using a 50 g/L glucose feed concentration. In the TCRC, cell growth increased linearly and glucose concentration was limited, which agreed well with the results of cell growth modeling. No spore formation was observed except when 1 g/L of glucose was fed. Changing to batch culture induced a 1.2$\times$$10^{10}$ CFU/mL of spore concentration, which was the highest spore concentration obtained among the various culture modes examined. The optimal glucose feed rate was found to be 0.55 g-glucose/h.

• Asian Pacific Journal of Cancer Prevention
• /
• v.16 no.17
• /
• pp.7749-7754
• /
• 2015

Background: Currently, cationic liposome has become the commonly used vehicles for gene transfection. Furthermore, one of the most significant steps in microRNAs expression studies is transferring microRNAs into cell cultures successfully. In this study we aim to approach the feasibility of transfection of cervical cancer cell lines mediated by liposome and to obtain the optimized transfection condition for cervical cancer cell lines. Materials and Methods: $Lipofectamine^{TM}2000$ as the carrier, miR-101 mimic was transfected into Hela cells and Siha cells. Using green fluorescent protein as reporter gene, to set different groups according to cell seeding density, the amount of miRNA, miRNA and the proportion of Liposomes, Whether to add serum into medium to study their impact on the liposomal transfection efficiency. Finally, MTT assay was used to analyze the relative minimal cell toxicity of liposome reagents. Results: The seeding density of Hela cell line and Siha are $1.5{\times}10^4$ (per well of 24 well plates), miRNA amount is 1ul of both, the ratio of miRNA and liposome is 1:0.5 of Hela cell line; 1:0.7 of Siha cell line respectively, after 24 hours we can get the highest transfection efficiency. Compared with serum medium, only Siha cells cultured with serum-free medium obtained higher transfection efficiency before transfection (P<0.01). MTT assay showed that according to the above conditions which has the lowest cytotoxicity. Conclusions: The method of Liposome to transfected is a suitable way and it can be an efficient reagent for miRNA delivery for Hela cells and Siha cells in vitro. It may serve as a reference for the further research or application.

• New & Renewable Energy
• /
• v.5 no.3
• /
• pp.26-31
• /
• 2009

Using MBE growth method, GaAs/AlGaAs solar cell structure was grown. Deposited electrodes are Au/Ni/Ge for n-type and Au/Pt/Ti for p-type electrodes were deposited by E-beam evaporator. Indoor light concentrators were devised and fabricated in order to concentrate artificial solar rays. Also mirror and prism and Fresnel lens concentration system with solar simulator were devised and fabricated. Results of solar cell characteristics were measured with shutting system which can control the amount of light. Maximum power density was 2.13 W/$cm^2$ and maximum concentration was 124 sun, when mirror with Fresnel lens was used at $7854\;mm^2$ of shutter hole.

• 한국생물공학회:학술대회논문집
• /
• 2001.11a
• /
• pp.475-478
• /
• 2001

Ex vivo hematopoietic cells can treat patients suffering from hematopoietic malignancies using bone marrow transplantation therapies. A initial cell density of $1.5{\times}10^6cells/ml$ and a growth factors of IL-3(5ng/ml), SCF(5ng/ml) and FL(25ng/ml) result in a 3.6-fold expansion of LTC- IC but a unexpansion of total cells.

• 한국생물공학회:학술대회논문집
• /
• 2001.11a
• /
• pp.545-548
• /
• 2001

Microbiologically influenced corrosion (MIC) of metal is common in the natural environment and sulfate reducing bacteria are representative microorganisms for MIC. We found that biofilm fomlation by SRB on the metal surface might be controlled by quorum sensing, which is a cell density dependent regulation of cell metabolism. As cell free culture fluids (spent media) of Desulfovibrio vulgaris and D. desulfuricans were tested for quontrn sensing related test strains, it was found that spent media of two SRB induced increased luminescence of Vibrio harveyi BB886 (sensor 1+, sensor 2-) and BB170 (sensor 1-, sensor 2+). Quorum activities of D. vulgaris and D. desulfuricans appeared to be parallel to growth patterns, i.e., it was low in the lag phase, highly increased in the exponential phase, and reached maximum in the stationary phase. Interestingly, however, luminescence of V. harveyi BB886 and BB170 induced by a unit cell mass of the SHB showed a maximal peak in the late lag phase. Hence, it was suspected that quorum sensing of these two SHB play unknown roles in shifting cells from dormant to growth stages.