• Korean Journal of Plant Tissue Culture
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• v.25 no.6
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• pp.477-485
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• 1998

To underatand in vitro regulation of differentiation, the effects of growth regulators and nitrogen source on metabolism of cell wall polysaccharides in suspension culture of kidney bean (Phaseolus vulgaris L.) were investigated. The suspension cells (cell clusters) were directly induced from the epicotyl segments of the seedlings, which were cultivated in MS medium supplemented with 1.0mg/L of 2,4-D and 0.5 mg/L of kinetin. When compared with cell wall sugar contents of the epicotyl segments, the cellulose content of the suspension-cultured cells decreased; while the pectin and hemicellulose content increased; suggesting increases of rhamnogalacturonan I and arabinogalactan IIduring the dedifferentiation, respectively, The effects of growth regulators(2,4-D, 1.0mg/L and kinetin, 0.5mg/L) and nitrogen source (potasium nitrate, 19.0mg/L and ammonium nitrate, 16.5 g/L) in the medium on the proliferation and the turnover of the cell wall polysaccharides were investigated for 30 days. In the medium with growth regulators and without nitrogen source, the proliferation rate was extremely high (16 folds). Growth regulators and nitrogen source increased the pectin content. Analysis of neutral sugar composition of pectin fraction showed that nitrogen source enhanced rhamnose level remarkably, suggesting that rhamnogalacturonan I was the one most likely synthesized. In hemicellulose fraction, growth regulators reduced arabinose level, suggesting that arabinogalactan II was degraded. And nitrogen source reduced galactose level, suggesting that xyloglucan was also degraded.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.463-463
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• 2014

Dye-sensitized solar cells (DSSCs) have generated a strong interest in the development of solid-state devices owing to their low cost and simple preparation procedures. Effort has been devoted to the study of electrolytes that allow light-to-electrical power conversion for DSSC applications. Several attempts have been made to substitute the liquid electrolyte in the original solar cells by using (2,2',7,7'-tetrakis (N,N-di-p-methoxyphenylamine)-9-9'-spirobi-fluorene (spiro-OMeTAD) that act as hole conductor [1]. Although efficiencies above 3% have been reached by several groups, here the major challenging is limited photoelectrode thickness ($2{\mu}m$), which is very low due to electron diffusion length (Ln) for spiro-OMeTAD ($4.4{\mu}m$) [2]. In principle, the $TiO_2$ layer can be thicker than had been thought previously. This has important implications for the design of high-efficiency solid-state DSSCs. In the present study, we have fabricated 3-D Transparent Conducting Oxide (TCO) by growing tin-doped indium oxide (ITO) nanowire (NWs) arrays via a vapor transport method [3] and mesoporous $TiO_2$ nanoparticle (NP)-based photoelectrodes were prepared using doctor blade method. Finally optimized light-harvesting solid-state DSSCs is made using 3-D TCO where electron life time is controlled the recombination rate through fast charge collection and also ITO NWs length can be controlled in the range of over $2{\mu}m$ and has been characterized using field emission scanning electron microscopy (FE-SEM). Structural analyses by high-resolution transmission electron microscopy (HRTEM) and X-Ray diffraction (XRD) results reveal that the ITO NWs formed single crystal oriented [100] direction. Also to compare the charge collection properties of conventional NPs based solid-state DSSCs with ITO NWs based solid-state DSSCs, we have studied intensity modulated photovoltage spectroscopy (IMVS), intensity modulated photocurrent spectroscopy (IMPS) and transient open circuit voltages. As a result, above $4{\mu}m$ thick ITO NWs based photoelectrodes with Z907 dye shown the best performing device, exhibiting a short-circuit current density of 7.21 mA cm-2 under simulated solar emission of 100 mW cm-2 associated with an overall power conversion efficiency of 2.80 %. Finally, we achieved the efficiency of 7.5% by applying a CH3NH3PbI3 perovskite sensitizer.

• Journal of the Korean Chemical Society
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• v.17 no.2
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• pp.73-79
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• 1973

The ultrasonic absorption of Dodecyl pyridinium bromide (D.P.B.) in aqueous solution has been measured at $20^{\circ}C$ over a range of frequencies between 0.1 mc and 90 mc and a range of concentrations from 5 to 100 mM. The excess absorption was observed only in the solutions the concentration of which was higher than the critical micellar concentration (c.m.c.) both in the presence and absence of salt. The excess absorption of sound and the relaxation frequencies obtained from the absorption curves show a discontinuity with the variation of the concentration of D.P.B. in the neighborhood of 60 mM. Other properties such as viscosity, conductivity and velocity of sound also exhibit such a change near the same concentration. It is concluded that a change in the properties of the micelles of D.P.B. occurs in the neighborhood of this concentration. The mechanism of the observed ultrasonic excess absorption in attributed to the reaction $M_2{\rightleftarrow}M_1+2Br^-$where$M_2$ and$M_1$are two types of micelles. The rate constants of forward and backward reactions are found to be $6.9 {\times} 10^5 sec^{-1)$and $6.7{\times}10^{10}sec^{-1}mole{-2}$ respectively. Some kinetic characteristics including free energy, enthalpy, entropy and activation energy were calculated.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.34 no.4
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• pp.251-255
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• 2021

a-Si is commonly considered as a primary candidate for the formation of passivation layer in heterojunction (HIT) solar cells. However, there are some problems when using this material such as significant losses due to recombination and parasitic absorption. To reduce these problems, a wide bandgap material is needed. A wide bandgap has a positive influence on effective transmittance, reduction of the parasitic absorption, and prevention of unnecessary epitaxial growth. In this paper, the adoption of a-SiO_x:H as the intrinsic layer was discussed. To increase lifetime and conductivity, oxygen concentration control is crucial because it is correlated with the thickness, bonding defect, interface density (D_it), and band offset. A thick oxygen-rich layer causes the lifetime and the implied open-circuit voltage to drop. Furthermore the thicker the layer gets, the more free hydrogen atoms are etched in thin films, which worsens the passivation quality and the efficiency of solar cells. Previous studies revealed that the lifetime and the implied voltage decreased when the a-SiOx thickness went beyond around 9 nm. In addition to this, oxygen acted as a defect in the intrinsic layer. The D_it increased up to an oxygen rate on the order of 8%. Beyond 8%, the D_it was constant. By controlling the oxygen concentration properly and achieving a thin layer, high-efficiency HIT solar cells can be fabricated.

• Korean Journal of Microbiology
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• v.52 no.4
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• pp.406-414
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• 2016

Among 6 leu codons, CUG is the most frequently used codon in E. coli. It is recognized by leu-tRNA(CAG) encoded by four genes scattered on two chromosomal loci (leuT and leuPQV ). In the process of constructing a strain with no functional leu-tRNA (CAG) gene on chromosome, we made two mutant strains separately, one on leuPQV locus (${\Delta}leuPQV$), and the other on leuT locus [$leuT^*$(GAG)], where the anticodon of leuT was changed from CAG to GAG, thereby altering its recognition codon from CUG to CUC. We attempted to combine these two mutations by transduction using $leuT^*$(GAG) strain as a donor and ${\Delta}leuPQV$ strain as a recipient. Large and small colonies appeared from this transduction. From PCR and DNA sequencing, large colony was confirmed to be the reciprocal recombinant as expected, but the small colonies contained both mutant $leuT^*$(GAG) and wild type leuT (CAG) genes in the cell. This heterozygous diploid strain did not show any unusual morphology under microscopic observation, but, interestingly, it showed a linear growth curve in rich medium with much slower growth rate than wild type cell. It always formed homogenous small colonies in the selection medium, but, when there was no selection, it readily segregated into $leuT^*$(GAG) and leuT (CAG). From these observations, we suggested that the strain with both $leuT^*$(GAG) and leuT (CAG) genes was not a partial diploid (merodiploid), but a full diploid cell having two different chromosomes. We proposed a model explaining how such a heterozygous diploid cell was formed and how and why its growth showed a linear growth curve.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.7
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• pp.16-19
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• 2019

A thinner film has superior electrical properties and a better amorphous structure. Amorphous structures can be effective in improving conductivity through a depletion effect. Research is needed on the Schottky contact, where potential barriers are formed, as a way to identify these characteristics. $SiO_2/SnO_2$ thin films were prepared to examine the amorphous structure and Schottky contact, $SiO_2$ thin films were prepared using Ar = 20 sccm. $SnO_2$ thin films were deposited using mixed gas with a flow rate of argon and oxygen at 20 sccm, and $SnO_2$ thin films were added by magnetron sputtering and treated at $100^{\circ}C$ and $150^{\circ}C$. To identify the conditions under which the amorphous structure was constructed, the XRD patterns were investigated and C-V and I-V measurements were taken to make Al electrodes and perform electrical analysis. The depletion layer was formed by the recombination of electrons and holes through the heat treatment process. $SiO_2/SnO_2$ thin films confirmed that the pores were well formed when heat treated at $100^{\circ}C$ and an electric current was applied over the micro area. An amorphous $SiO_2/SnO_2$ thin film with heat treatment at $100^{\circ}C$ showed no reflection at $33^{\circ}\;2{\theta}$ in the XRD pattern, and a reflection at $44^{\circ}2\;{\theta}$. The macroscopic view (-30 V

• KOREAN JOURNAL OF CROP SCIENCE
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• v.37 no.2
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• pp.123-133
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• 1992

This study was conducted to clarify progressed changes of plant types and the effects of the physiological and ecological components on improving ideotype of winter wheat. 12 wheat varieties were planted at the experimental farm of Wheat and Barley Research Institute in Suwon in 1990. As results of intensive wheat breeding for early maturity since 1959, heading, flowering and maturing dates have been shortened by 17, 15 and 14 dagys, respectively. The shortened days from sowing to heading and from heading to flowering contributed to the early maturity to improved. Physiological factors associated with heading time of wheat could be reprsented by growth habit, photoperiod responses, earliness in narrow sense and winter hardiness. For improving an early maturity of winter wheat, it would desired to maintain some degree of winter habit(III-IV), and recombination of more insensitivity to short day length and more shortened earliness in narrow sense than that of Saemil and Chugoku 81, and higher degree of winter hardiness. For improving the early maturity the more effective way must be of shortened days from sowing to heading, and days from flowering to maturity than days from heading to flowering. Ideotype of wheat will be desired to recombine two semi-dwarf genes with erect plant type being about 70-80cm, less stem elongation by late spring, long spike and many grains per spikelet. Average spike weight ratio was about 45-49% in high-yielding varieties, stem fresh weight was lighter, but spike fresh weight was heavier in new one while leaf fresh weight was similar to each other during the maturing periods. Average spike dry weight ratio was higher about 40～48%, and stem and leaf blade dry weights were lower in the newly bred varieties. Stem dry weight was heavier than spike or leaf dry weight in the old varieties of Yungkwang, Jangwang and Jinkwang. Leaf area index for the varieties showed normal distribution curve as the maximum point in booting stage. The maximum point of this curve come in early maturing wheat, and late in old one. The maximum points of LAI were 6.4～6.8 in the high-yielding varieties. Totals of LAI in each period investigated of old one were higher than those of newly bred being 24.6～28.8. Chlorophyll content of the high-yielding varieties of Chokwang, Geurumil and Saemil as higher than that of the old varieties Jangkwang, Jinkwang, Wonkwang and Sinkwang from regrowing period to April 21. after then slightly and even after heading. Net assimilation rate (NAR) was higher in high-yielding varieties with good plant type, and lower in old ones. Grain yield of the newly released varieties increased rapidly but slowly in the old ones. Change in water content of grain at the growing stage in newly bred was lower than that of the old bred. Diminishing rate of water content of grain in establishment per day was 1.2% average that of the old varieties including Yungkwang was 1.5%, and those of the newly bred including Chokwang were 0.9～1.1%. Chokwang, Naemil, and Saemil were the highest-yielding varieties of the Korean cultivars. Yields were increased by spikes per m$^2$, grain weight for the varieties bred in Suwon, and by spikes per m$^2$ for the varieties bred in Milyang.