• The Plant Pathology Journal
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• v.16 no.1
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• pp.1-8
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• 2000

Worldwide, rice blast, caused by Magnaporthe grisea (Hebert) Barr. (anamorph, Pyricularia grisea Sacc.), is one of the most economically devastating crop diseases. Management of rice blast through the breeding of blast-resistant varieties has had only limited xuccess due to the frequent breakdown of resistance under field conditions (Bonman etal., 1992; Correa-Victoria and Zeigler, 1991; Kiyosawa, 1982). The frequent variation of race in pathogen populations has been proposed as the principal mechanism involved in the loss of resistance (Ou, 1980). Although it is generally accepted that race change in M. grisea occurs in nature, the degree of its variability has been a controversial subject. A number of studies have reported the appearance of new races at extremely high rates (Giatgong and Frederiksen, 1968; Ou and Ayad, 1968; Ou et al., 1970; Ou et al., 1971). Various potential mechanisms, including heterokaryosis (Suzuki, 1965), parasexual recombination (Genovesi and Magill, 1976), and aneuploidy (Kameswar Row et al., 1985; Ou, 1980), have been proposed to explain frequent race changes. In contrast, other studies have shown that although race change could occur, its frequency was much lower than that predicted by earlier studies (Bonman et al., 1987; Latterell and Rossi, 1986; Marchetti et al., 1976). Although questions about the frequency of race changes in M. grisea remain unanswered, the application of molecular genetic tools to study the fungus, ranging from its genes controlling host specificity to its population sturctures and dynamics, have begun to provide new insights into the potential mechanisms underlying race variation. In this review we aim to provide an overview on (a) the molecular basis of host specificity of M. grisea, (b) the population structure and dynamics of rice pathogens, and (c) the nature and mechanisms of genetic changes underpinning virulence variation in M. grisea.

• Journal of the Korean Vacuum Society
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• v.22 no.3
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• pp.168-173
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• 2013

In this paper, we would like to introduce Electron Relay Enhancer (ERE), a supplementary device, which improves commercial solar cell efficiency minimizing electron-hole recombination of solar cell. The ERE in this study is mainly composed of two capacitors which are connected to AC power source and bridge diode system which controls electron flow direction. Two capacitors repeat collecting electrons from solar cell and pumping the collected electrons to load resistance or inverter through the bridge diode system. While one positively charged capacitor collect electrons, the other negatively charged one pumps electrons. A positively charged capacitor pulls the more exited electrons from the solar cell, before the exited electrons recombine the holes in solar cell. That is why the ERE system enhances solar cell efficiency. As a result, the measured power increase of the solar cell with the ERE is varied from 5.9 W to 25.6 W in each experimental condition. Maximal increase rate of the solar cell power with ERE is 30.8% of solar cell power without ERE.

• Journal of Plant Biotechnology
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• v.37 no.1
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• pp.77-83
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• 2010

Eighteen cultivars of tomato were tested for their regeneration response. Lycopersicon esculentum cv. 2001-58 showed a very high frequency of regeneration (93%). We evaluated the effect of two compounds with known antioxidant activity (ascorbic acid and cystein). The use of ascorbic acid ($200\;-\;300\;{\mu}M/L$) has a positive effect on shoot regeneration. To develope a system for plastid transformation in tomato via homologous recombination, we constructed the tomato plastid expression vector (pKRT22-AG) harboring 2.2 kb flanking sequences cloned from intact plastid genome and gfp gene. To investigate the factors affecting the delivery system of the pKRT22-AG into chloroplast using bombardment, We assessed the optimal DNA concentration, gold particle volume and target distance. Expression of the GFP protein was observed within chloroplast on protoplast of cotyledon explant by confocal laser scanning microscopy, which indicates that the protocol developed in this study be useful for the production of plastid transgenic plants in tomato.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2016.11a
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• pp.181-181
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• 2016

Hydrogenated microcrystalline silicon (${\mu}c-Si:H$) films have attracted much attention as materials of the bottom-cells in Si thin film tandem photovoltaics due to their low bandgap and excellent stability against light soaking. However, in PECVD, the source gas $SiH_4$ must be highly diluted by $H_2$, which eventually results in low deposition rate. Moreover, it is known that high-rate ${\mu}c-Si:H$ growth is usually accompanied by a large number of dangling-bond (DB) defects in the resulting films, which act as recombination centers for photoexcited carriers, leading to a deterioration in the device performance. During film deposition, Si nanoparticles generated in $SiH_4$ discharges can be incorporated into films, and such incorporation may have effects on film properties depending on the size, structure, and volume fraction of nanoparticles incorporated into films. Here we report experimental results on the effects of nonoparticles incorporation at the different substrate temperature studied using a multi-hollow discharge plasma CVD method in which such incorporation can be significantly suppressed in upstream region by setting the gas flow velocity high enough to drive nanoparticles toward the downstream region. All experiments were performed with the multi-hollow discharge plasma CVD reactor at RT, 100, and $250^{\circ}C$, respectively. The gas flow rate ratio of $SiH_4$ to $H_2$ was 0.997. The total gas pressure P was kept at 2 Torr. The discharge frequency and power were 60 MHz, 180 W, respectively. Crystallinity Xc of resulting films was evaluated using Raman spectra. The defect densities of the films were measured with electron spin resonance (ESR). The defect density of fims deposited in the downstream region (with nonoparticles) is higher defect density than that in the upstream region (without nanoparticles) at low substrate temperature of RT and $100^{\circ}C$. This result indicates that nanoparticle incorporation can change considerably their film properties depending on the substrate temperature.

• Korean Journal of Microbiology
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• v.28 no.2
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• pp.98-103
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• 1990

Brevibacterium lactofermentum SWA (arg trp) and B. lactofermentum SWB (met ser) were obtained from UV and NTG treatment. The rates of protoplast formation by B. lactofermentum SWA and SWB were 99.93% and 99.98%, respectively when each strain was treated with penicillin G in mid exponential growth phase, followed by incubation with 400 $\mu\textrm{g}$/ml of lysozyme in lysis fluid supplemented with 0.4M sucrose. Frequencies of protoplast regeneration in B. lactofermentum SWA and B. lactofermentum SWB were 9.27% and 10.32% respectively, on regeneration medium containing 0.5M sodium succinate, 50 mM $Mg^{2+}$, and 3% PVP. In intraspecific protoplast fusion between B. lactofermentum SWA and B. lactofermentum SWB, fusion frequency of $2.30\times 10^{-5}$ was observed by using the 100mM $CaCl_{2}$ and 30% PEG 6,000 in fusion fluid. Relative recombinant frequencies in each marker by means of selective media could be used for genetic analysis.

• Asian Pacific Journal of Cancer Prevention
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• v.15 no.23
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• pp.10225-10229
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• 2015

Genetic polymorphisms in homologous recombination repair genes cause an abnormal development of cancerous cells. In the present study we evaluated the possibility of breast cancer association with single nucleotide polymorphisms of RAD51, XRCC2 and XRCC3 genes. Polymorphisms selected in this study were RAD51 135G/C, XRCC2 Arg188His; and XRCC3 Thr241Met. Each polymorphism was genotyped using Polymerase chain reaction-restriction fragment length polymorphism in study cohort of 306 females (156 breast cancer patients and 150 controls). We observed that heterozygous variant genotype (GC) of RAD51 135 G/C polymorphism was associated with a significantly (OR=2.70; 95%CI (0.63-1.79); p<0.03) increased risk of breast cancer. In case of the XRCC3 gene we observed that frequency of heterozygous (OR=2.88; 95%CI (1.02-8.14); p<0.02) and homozygous (OR=1.46; 95%CI (0.89-2.40); p<0.04) genotype of Thr241Met polymorphism were significantly higher in breast cancer patients. For the Arg188His polymorphism of XRCC2, ~2fold increase in breast cancer risk (OR=1.6, 95%CI = 0.73-3.50) was associated with GA genotype with a p value for trend of 0.03. Our results suggest that the 135G/C polymorphism of the RAD51, Thr241Met polymorphism of XRCC3 and Arg188His polymorphism of XRCC2 can be independent markers of breast cancer risk in Pakistan.

• Korean Journal of Materials Research
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• v.8 no.7
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• pp.591-595
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• 1998

In this work, the freestanding GaN single crystalline substrates without cracks were grown by hydride vapor phase epitaxy (HVPE) and its some properties were investigated. The GaN substrate, having a current maximum size of 350 $\mu\textrm{m}$-thickness and 100$\textrm{mm}^2$ area, were obtained by HVPE growth of thick film GaN on sapphire substrate and subsequent mechanical removal of the sapphire substrate. A lattice constant of $C_o$= 5.18486 $\AA$ and a FWHM of DCXRD was 650 arcsec for the single crystalline GaN substrate. The low temperature PL spectrum consist of three excitonic emission and a deep D- A pair recombination at 1.8eV. The Raman E, (high) mode frequency was 567$cm^{-1}$ which was the same as that of strain free bulk single crystals. The Hall mobility and carrier concentration was 283$cm^3$<\ulcornerTEX>/ V.sand 1.1$\times$$10^{18}cm^{-3}$, respectively.

• Journal of Environmental Science International
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• v.16 no.4
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• pp.393-397
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• 2007

The sonolytic decomposition of NHCs(Nitrogen Heterocyclic Compounds), such as atrazine[6-chloro-N-ethyl-N'-(1-methylethyl)-1,3,5-triazine-2,4-diamine], simazine(6-chloro-N,N'-diethyl-1,3,5-triazine-2,4-diamine), trietazine(6-chloro-N,N,N'-triethyl-1,3, 5-triazine-2,4-diamine), in water was investigated at a ultrasound frequency of 200kHz with an acoustic intensity of 200W under argon and air atmospheres. The concentration of NHCs decreased with irradiation, indicating pseudo-first-order kinetics. The rates were in the range $1.06{\sim}2.07({\times}10^{-2}min^{-1})$ under air and $1.30{\sim}2.59({\times}10^{-2}min^{-1})$ under argon at a concentration of $200{\mu}M$ of NHCs. The rate of hydroxyl radicals(${\bullet}{OH}$) formation from water is $19.8{\mu}M\;min^{-1}$ under argon and $14.7{\mu}M\;min^{-1}$ under air in the same sonolysis conditions. The sonolysis of NHCs is effectively inhibited, but not completely, by the addition of t-BuOH(2-methyl-2-propanol), which is known to be an efficient ${\bullet}{OH}$ radical scavenger in aqueous sonolysis. This suggests that the main decomposition of NHCs proceeds via reaction with ${\bullet}{OH}$ radical; a thermal reaction also occurs, although its contribution is small. The addition of appropriate amounts of Fenton's reagent $[Fe^{2+}]$ accelerates the decomposition. This is probably due to the regeneration of ${\bullet}{OH}$ radicals from hydrogen peroxide, which would be formed from recombination of ${\bullet}{OH}$ radicals and which may contribute a little to the decomposition.

• Proceedings of the Korean Environmental Sciences Society Conference
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• 2003.11a
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• pp.171-176
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• 2003

The sonolytic decomposition of NHCs, such as atrazine［6-chloro-N-ethyl-N＇ -(1-methylethyl)-1,3,5-triazine-2,4-diamine］, simazine( 6-chloro-N,N＇ -diethyl-l ,3,5-triazine-2,4-diamine), trietazine(6-chloro-N,N,N＇-triethyl-l,3,5-triazine-2,4-diamine), in water was investigated at a ultrasound frequency of 200kHz with an acoustic intensity of 200W under argon and air atmospheres. The concentration of NHCs decreased with irradiation, indicating pseudo-first-order kinetics. The rates were in the range 1.06∼2.07 (x10/sup -3/ min/sup -1/) under air and 1.30∼2.59(x10/sup -3/ min/sup -1/)under argon at a concentration of 200μM of NHCs. The rate of hydroxyl radicals(·OH) formation from water is 19.8μM min/sup -1/ under argon and 14.7 μM min/sup -1/ under air in the same sonolysis conditions. The sonolysis of NHCs is effectively inhibited, but not completely, by the addition of t-BuOH(2-methyl-2-propanol), which is known to be an efficient ·OH radical scavenger in aqueous sonolysis. This suggests that the main decomposition of NHCs proceeds via reaction with ·OH radical; a thermal reaction also occurs, although its contribution is small. The addition of appropriate amounts of Fenton's reagent ［Fe/sup 2＋/］ accelerates the decomposition. This is probably due to the regeneration of ·OH radicals from hydrogen peroxide, which would be formed from recombination of ·OH radicals and which may contribute a little to the decomposition.

• Journal of the Korean Solar Energy Society
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• v.33 no.2
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• pp.11-17
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• 2013

Silicon nitride($SiN_x:H$) deposited by radio frequency plasma enhanced chemical vapor deposition(RF-PECVD) is commonly used for anti-reflection coating and passivation in crystalline silicon solar cell fabrication. In this paper, characteristics of the deposited silicon nitride was studied with change of working pressure, deposition temperature, gas ratio of $NH_3$ and $SiH_4$, and RF power during deposition. The deposition rate, refractive index and effective lifetime were analyzed. The (100) p-type silicon wafers with one-side polished, $660-690{\mu}m$, and resistivity $1-10{\Omega}{\cdot}cm$ were used. As a result, when the working pressure increased, the deposition rate of SiNx was increased while the effective life time for the $SiN_x$-deposited wafer was decreased. The result regarding deposition temperature, gas ratio and RF power changes would be explained in detail below. In this paper, the optimized condition in silicon nitride deposition for silicon solar cell was obtained as 1.0 Torr for the working pressure, $400^{\circ}C$ for deposition temperature, 500 W for RF power and 0.88 for $NH_3/SiH_4$ gas ratio. The silicon nitride layer deposited in this condition showed the effective life time of > $1400{\mu}s$ and the surface recombination rate of 25 cm/s. The crystalline silicon solar cell fabricated with this SiNx coating showed 18.1% conversion efficiency.