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Doug-Hwan Choi,Kyu-Jong Lee,Byun-Woo Lee 한국작물학회 2010 한국작물학회 학술발표대회 논문집 Vol.2010 No.04
Temperature rise of 4.0℃ is projected under SRES A1B greenhouse gases emission scenario in 2100 and this climate change is anticipated to affect the growth, phenological development, and yield of soybean. The objective of this experiment is to calibrate and validate CROPGRO_soybean model and evaluate the projected climatic change impact on soybean phenological development in Korea. For simulation experiment, four cultivars with different maturity groups, Hwaeomputkong(MG1), Sinpaldalkong(MG4), Taegwangkong(MG5), and Daewonkong(MG6) were calibrated and validated using data that were collected from the experiments of planting dates and daylength treatment. The calibrated model predicted the phenological stages with considerable accuracy for the data acquired independently of the calibration data. As global warming proceeds, days to flowering and days to physiological maturity on average across varietal groups and planting dates are anticipated to decrease by about 7 and 5 days respectively under the projected normal climate during the period of 2071~2100 compared to those under the current normal climate condition.
The effect of sowing date and daylength treatment on the development of soybean
Doug-Hwan Choi,Dong-Jin Kim,Kang-Hyun Moon,Byun-Woo Lee 한국작물학회 2008 한국작물학회 학술발표대회 논문집 Vol.2008 No.10
Although there can be some differences among varieties, the developmental rate of soybean (Glycine max) is mainly influenced by temperature and photoperiod. The objective of this experiment, that is the first step for creating phenology model of soybean, is to investigate the developmental characteristics under different temperature and day length conditions. Considering maturity, employed were five cultivars, Hwaeomputkong, Sinpaldalkong, Taegwangkong, Daewonkong, and Seoritae. They were sown at three different dates and grown under natural day length throughout growing season in 2008, while in another field they were subjected to longday of 16 hours by the supplemental lighting from July 6 to maturity. Developmental processes were investigated every five days after seeding. Days to flowering and final number of node increased in late maturiity cultivars. These traits decreased in delayed seeding, while increased under longday treatment. Even though there were some varietal differences in the slope of the line, V-stage(the number of nodes) of soybean consistently showed the linear relation(r2>0.95) with the sum of effective temperature from emergence to flowering. Daylength would be a cardinal factor that determines development including final number of node and duration of reproductive stage. However, it has not been figured out completely. Further studies will focus on the effect of temperature on reproductive stage and developmental response to daylength.
Van-der-Waals-gap tunneling spectroscopy for single-wall carbon nanotubes
Choi, Dong-Hwan,Jang, Seunghun,Jeong, Du-Won,Lee, Jeong-O,Chang, Hyunju,Ha, Dong-Han,Lee, Seung Mi,Kim, Jongwoo,Suh, Yung Doug,Bae, Myung-Ho,Kim, Ju-Jin Elsevier 2017 Carbon Vol.113 No.-
<P>As a consequence of their unique electronic band structures, low-dimensional materials such as one-dimensional (1D) single-wall carbon nanotubes (SWCNTs), 2D graphene and various 2D transition metal dichalcogenides have exhibited intriguing electrical transport properties when incorporated into field-effect transistors. Meanwhile, the van-der-Waals (vdW) interfaces between top-contacted metals and low-dimensional materials have become a challenging issue for future high-performance electronics. Here, we report a new aspect of vdW interface that offers vdW-gap tunneling spectroscopy by adopting indium (In) as a top-contacted metal on SWCNTs without an artificial insulating tunnel barrier. We show that multiple differential conductance peaks for varying bias voltages correspond to the van Hove singularities existing in the electronic density of states of SWCNTs. Our first-principles calculations reveal that In forms a physisorption interface with a considerable vdW gap, which causes little disruption to the density of states of the SWCNTs near the metal interface and which thus allows vdW-gap tunneling spectroscopy. (C) 2016 Elsevier Ltd. All rights reserved.</P>
Long‐Term Real‐Time Tracking of Lanthanide Ion Doped Upconverting Nanoparticles in Living Cells
Nam, Sang Hwan,Bae, Yun Mi,Park, Yong Il,Kim, Jeong Hyun,Kim, Hyung Min,Choi, Joon Sig,Lee, Kang Taek,Hyeon, Taeghwan,Suh, Yung Doug WILEY‐VCH Verlag 2011 Angewandte Chemie Vol.123 No.27
<P><B>Hinterher!</B> Aufwärtskonvertierende Nanopartikel (UCNPs) wurden in lebenden HeLa‐Zellen verfolgt, und ihr aktiver Transport durch Motorproteine wurde in Echtzeit abgebildet. Die beachtliche Photostabilität der UCNPs und die unschädliche Anregung im nahen Infrarot ermöglichten die kontinuierliche Beobachtung lebender Zellen über einen Zeitraum von bis zu sechs Stunden.</P>
Absorption, translocation, and remobilization of cadmium supplied at different growth stages of rice
Yong-Feng Yan,Doug-Hwan Choi,김도순,이변우 한국작물학회 2010 Journal of crop science and biotechnology Vol.13 No.2
Cadmium (Cd) is absorbed by rice root and transferred into the other rice organs including grain. A solution-culture experiment was conducted to investigate the absorption and distribution of Cd supplied at different growth stages of rice. Two rice cultivars, a japonica 'Chucheong' and a tongil-type 'Milyang23' that exhibit high and low ability of Cd absorption by root and accumulation in grain were grown in culture solution and subjected to 2 ppm CdCl₂ treatment for 2 weeks at four different growth stages: before panicle initiation stage (BPI), after panicle initiation stage (API), early ripening stage (ER), and mid-ripening stage (MR). Cd concentration and accumulation in rice organs were measured at harvest. The two rice cultivars accumulated two to three times greater amounts of Cd in grain in the two Cd treatments before heading (BPI and API treatments) than in the Cd treatment after heading (ER and MR treatment). The higher grain Cd accumulation in BPI and API treatments was not attributed to the higher Cd uptake but to the higher translocation from root to shoot and the higher redistribution from shoot to grain than ER and MR treatments These results imply that the remobilization of Cd through phloem during leaf senescence is the major process for Cd accumulation in rice grain rather than direct transpo rt of absorbed Cd through the xylem-phloem transfer to grain. 'Milyang23' absorbed significantly smaller amount of Cd than 'Chucheong'. However, 'Milyang23' accumulated more than a three times larger amount of Cd in grain compared to 'Chucheong' as the former exhibited the higher root-shoot translocation and shoot-grain remobilization as well. It indicates that the greater Cd translocation from root to shoot and subsequent higher Cd remobilization from shoot to grain, not the higher absorption ability, have led to the higher Cd accumulation and concentration in grain of 'Milyang23'.
A study on genotypic variations of Pb accumulation and distribution among organs of rice plant
Yong-Feng Yan,Doug-Hwan Choi,Jin-Ern Lee,Byun-Woo Lee 한국작물학회 2008 한국작물학회 학술발표대회 논문집 Vol.2008 No.10
In order to investigate the genotypic differences in Pb accumulation of rice, thirty-five rice cultivars were irrigated by irrigation water containing 10 ppm Pb throughout all growth season under field condition. At harvest, thirty-five rice cultivars showed significant difference in Pb concentrations in straw, grain, chaff, brown rice, rice bran, and polished rice, but not in root. Pb concentration in polished rice ranged from 0.02 to 0.22 mg/kg. The total Pb accumulation in shoot varied from 0.77 to 2.74 mg/m2. There were no significant difference of Pb concentration in all of rice parts among four rice cultivar groups. Indica and tongil cultivar groups presented the higher Pb accumulation in shoot. The large genotypic variation suggested the possibility of breeding low Pb accumulating rice cultivar.
Genotypic Variation of Cadmium Accumulation and Distribution in Rice
Yong-Feng Yan,Doug-Hwan Choi,김도순,이변우 한국작물학회 2010 Journal of crop science and biotechnology Vol.13 No.2
An effective way to reduce the risk of cadmium (Cd) entering the food chain is to use low Cd-accumulation rice cultivars, particularly in Asia. The fundamental requirement for breeding low grain Cd-accumulation cultivars is to know the genotypic variation in Cd accumulation and the physiological processes and genetic basis governing the Cd accumulation in rice grain. In this experiment,genotypic variation in Cd accumulation and distribution among rice organs was studied using thirty-five rice varieties. They were grown with irrigation water containing 2 ppm Cd throughout rice growing season under field condition in 2007. At harvest, plants were sampled and analyzed for Cd concentration and accumulation in each rice organ. Significant variation of Cd concentration and accumulation in rice organs were found among thirty-five rice cultivars, revealing more than 8-fold varietal differences in grain Cd concentration and shoot Cd accumulation. Cd concentration and accumulation in grain were significantly different among cultivar groups, showing the highest in indica and the lowest in temperate japonica. Tongil-type and tropical japonica rice showed a Cd concentration intermediate to that of temperate japonica and indica rice. The higher Cd accumulation in grain of indica rice was attributable to the greater ability of Cd uptake. The greater ability of root-shoot translocation in tropical japonica and shoot-grain redistribution in tongil-type resulted in the significantly higher grain Cd concentration in these cultivar groups than in temperate japonica. For over 35 cultivars tested, grain Cd concentration revealed a significant positive correlation with root Cd concentration and shoot Cd concentration and accumulation while no significant correlation with root-shoot translocation factor and shoot-grain redistribution ratio. However, correlation analyses within each cultivar group showed that grain Cd concentration was significantly correlated with root-shoot translocation factor in indica, with root Cd concentration in tongil-type, with shoot Cd concentration and accumulation in tropical japonica, and with shoot Cd accumulation and shoot-grain redistribution ratio in temperate japonica. These results indicate that genotypic variation in grain Cd accumulation, in general, is controlled by all the three physiological processes but the major physiological process governing its genotypic variation within cultivar group is different depending on cultivar groups.