• Journal of the Korean Vacuum Society
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• v.15 no.2
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• pp.201-208
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• 2006

Optical characteristics of InGaAs quantum dot (QD) laser structures with an Al native oxide (AlOx) layer as a current-blocking layer were studied by means of photoluminescence (PL), PL excitation, and spatially-resolved micro-PL techniques. The InGaAs QD samples were first grown by molecular-beam epitaxy (MBE), and then prepared by wet oxidation and thermal annealing techniques. For the InGaAs QD structures treated by the wet oxidation and thermal annealing processes, a broad PL emission due to the intermixing effect of the AlOx layer was observed at PL emission energy higher than that of the non-intermixed region. We observed a dominant InGaAs QD emission at about 1.1 eV in the non-oxide AlAs region, while InGaAs QD-related emissions at about 1.16 eV and $1.18{\sim}1.20eV$ were observed for the AlOx and the SiNx regions, respectively. We conclude that the intermixing effect of the InGaAs QD region under an AlOx layer is stronger than that of the InGaAs QD region under a non-oxided AlAs layer.

• Korean Journal of Soil Science and Fertilizer
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• v.35 no.2
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• pp.118-126
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• 2002

To evaluate the correlations of microbial populations with soil healthiness and crop production and establish the criteria for microbial population of soil types. We analyzed the microbial community structure of 13 soils which were different in physical and chemical properties and cultivation methods. According to the analysis of microbial population suing the dilution plate method, the large differences of the microbial population structures among soil types were shown: aerobic bacteria $2-27{\times}10^6$, fluorescent Pseudomonas $1-1,364{\times}10^5$, Gram negative bacteria $1-126{\times}10^4$, and mesophilic Bacillus $1-110{\times}10^5$. The density of Gram negative bacteria was highest on red pepper cultivating soils (sample no. 4 and 6) of Umsung and Gesan, Chungbuk, and the density of the fluorescent Pseudomonas was highest on greenhouse soil (sample no. 7) of Jinju, Kyungnam. The crop productivity of three soils was high as compared with those of other soils. It was supposed that the density of fluorescent Pseudomonas and mesophilic Bacillus were correlated with the incresed crop production. By MIDI analysis, 579 strains isolated from 13 soils composed of a variety of microbes including 102 isolates of Agrobacterium, 112 isolates of Bacillus, 32 isolates of Pseudomonas, 44 isolates of Kocuria, and 34 isolates of Pseudomonas. Among the 624 isolates of Gram negative bacteria, Pseudomonas including P. putida and p. fluorescens occupied the highest density (51%), and Stenotrophomonas maltophilia and Burkholderia cepacia also appeared at high density. From RAPD analysis, the fluorescent Pseudomonas strains isolated from 13 soil types showed a high level of strain diversities and were grouped into 2 - 14 patterns according to soil types. Many of unknown bacteria were recovered from the paddy soil, and needed to be further characterized on the molecular basis.

• Asian Pacific Journal of Cancer Prevention
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• v.15 no.2
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• pp.929-935
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• 2014

Two types of nanosized titanium dioxide, anatase ($anTiO_2$) and rutile ($rnTiO_2$), are widely used in industry, commercial products and biosystems. $TiO_2$ has been evaluated as a Group 2B carcinogen. Previous reports indicated that $anTiO_2$ is less toxic than $rnTiO_2$, however, under ultraviolet irradiation $anTiO_2$ is more toxic than $rnTiO_2$ in vitro because of differences in their crystal structures. In the present study, we compared the in vivo and in vitro toxic effects induced by $anTiO_2$ and $rnTiO_2$. Female SD rats were treated with $500{\mu}g/ml$ of $anTiO_2$ or $rnTiO_2$ suspensions by intra-pulmonary spraying 8 times over a two week period. In the lung, treatment with $anTiO_2$ or $rnTiO_2$ increased alveolar macrophage numbers and levels of 8-hydroxydeoxyguanosine (8-OHdG); these increases tended to be lower in the $anTiO_2$ treated group compared to the $rnTiO_2$ treated group. Expression of $MIP1{\alpha}$ mRNA and protein in lung tissues treated with $anTiO_2$ and $rnTiO_2$ was also significantly up-regulated, with $MIP1{\alpha}$ mRNA and protein expression significantly lower in the $anTiO_2$ group than in the $rnTiO_2$ group. In cell culture of primary alveolar macrophages (PAM) treated with $anTiO_2$ and $rnTiO_2$, expression of $MIP1{\alpha}$ mRNA in the PAM and protein in the culture media was significantly higher than in control cultures. Similarly to the in vivo results, $MIP1{\alpha}$ mRNA and protein expression was significantly lower in the $anTiO_2$ treated cultures compared to the $rnTiO_2$ treated cultures. Furthermore, conditioned cell culture media from PAM cultures treated with $anTiO_2$ had less effect on A549 cell proliferation compared to conditioned media from cultures treated with $rnTiO_2$. However, no significant difference was found in the toxicological effects on cell viability of ultra violet irradiated $anTiO_2$ and $rnTiO_2$. In conclusion, our results indicate that $anTiO_2$ is less potent in induction of alveolar macrophage infiltration, 8-OHdG and $MIP1{\alpha}$ expression in the lung, and growth stimulation of A549 cells in vitro than $rnTiO_2$.

• BMB Reports
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• v.40 no.5
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• pp.773-782
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• 2007

Different isolates of the soil bacterium Bacillus thuringiensis produce multiple crystal (Cry) proteins toxic to a variety of insects, nematodes and protozoans. These insecticidal Cry toxins are known to be active against specific insect orders, being harmless to mammals, birds, amphibians, and reptiles. Due to these characteristics, genes encoding several Cry toxins have been engineered in order to be expressed by a variety of crop plants to control insectpests. The cotton boll weevil, Anthonomus grandis, and the fall armyworm, Spodoptera frugiperda, are the major economically devastating pests of cotton crop in Brazil, causing severe losses, mainly due to their endophytic habit, which results in damages to the cotton boll and floral bud structures. A cry1Ia-type gene, designated cry1Ia12, was isolated and cloned from the Bt S811 strain. Nucleotide sequencing of the cry1Ia12 gene revealed an open reading frame of 2160 bp, encoding a protein of 719 amino acid residues in length, with a predicted molecular mass of 81 kDa. The amino acid sequence of Cry1Ia12 is 99% identical to the known Cry1Ia proteins and differs from them only in one or two amino acid residues positioned along the three domains involved in the insecticidal activity of the toxin. The recombinant Cry1Ia12 protein, corresponding to the cry1Ia12 gene expressed in Escherichia coli cells, showed moderate toxicity towards first instar larvae of both cotton boll weevil and fall armyworm. The highest concentration of the recombinant Cry1Ia12 tested to achieve the maximum toxicities against cotton boll weevil larvae and fall armyworm larvae were 230 ${\mu}g/mL$ and 5 ${\mu}g/mL$, respectively. The herein demonstrated insecticidal activity of the recombinant Cry1Ia12 toxin against cotton boll weevil and fall armyworm larvae opens promising perspectives for the genetic engineering of cotton crop resistant to both these devastating pests in Brazil.

• Polymer(Korea)
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• v.39 no.3
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• pp.487-492
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• 2015

The effects of chemical structure of alkyl groups of norbornene carboxylic alkyl esters(methyl, octyl, 4-chlorobenzyl) and endo/exo ratios of norbornene monomers on activity of palladium catalyst and polymerization behavior were investigated. Norbornene ester monomers were synthesized from the reaction of 5-norborene-2-carboxylic acid and various alcohols. Polymerization catalyst, di-${\mu}$-chloro-bis(-methoxybicyclo[2,2,1]-hept-2-ene)palladium(II) (DCBMP), was synthesized according to the literature procedure and silver hexafluoroantimonate ($AgSbF_6$) was used as a conjugate anion source. Gel permeation chromatography (GPC), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) were the principal techniques for polymer characterization and $^1H$ NMR spectroscopy was used for chemical structures determination of monomers and polymers. For all of the norbonene alkyl esters GPC data showed that when the amounts of endo isomers exceeded those of exo isomers decreased molecular weight polymers were obtained probably due to the decreased catalyst activity. Polymerizations were conducted by varying the monomer/catalyst mole ratios (100:1, 200:1, 300:1). When 300:1 monomer/catalyst ratio was employed it was possible to synthesize high molecular weight ($M_n=27500g/mol$), film forming polymer from exo-norbornene carboxylic acid octyl ester.

• Journal of the Microelectronics and Packaging Society
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• v.24 no.4
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• pp.31-37
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• 2017

Recently, there has been substantial interest in flexible and wearable devices whose properties and performances are close to conventional devices on hard substrates. Despite the advancement on flexible devices with organic semiconductors or carbon nanotube films, their performances are limited by the carrier scattering at the molecular to molecular or nanotube-to-nanotube junctions. Here in this study, we demonstrate on the vertical semiconductor crystal array embedded in flexible polymer matrix. Such structures can relieve the strain effectively, thereby accommodating large flexural deformation. To achieve such structure, we first established a low-temperature solution-phase synthesis of single crystalline 3D architectures consisting of epitaxially grown ZnO constituent crystals by position and growth direction controlled growth strategy. The ZnO vertical crystal array was integrated into a piece of polydimethylsiloxane (PDMS) substrate, which was then mechanically detached from the hard substrate to achieve the freestanding ZnO-polymer composite. In addition, the characteristics of transferred ZnO were confirmed by additional structural and photoluminescent measurements. The ZnO vertical crystal array embedded in PDMS was further employed as pressure sensor that exhibited an active response to the external pressure, by piezoelectric effect of ZnO crystal.

• Korean Chemical Engineering Research
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• v.55 no.5
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• pp.704-710
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• 2017

Although the desalination technique using gas hydrate formation is at a development stage compared to the commercially well-established reverse osmosis (RO), it still draws attention because of its simplicity and moderate operational conditions especially when using refrigerants for guest gases. In this study, DFT (density functional theory)-based molecular modeling was employed to explain the energetics of the gas hydrate formation using HFC (hydrofluorocarbon) and HCFC (hydrochlorofluorocarbon) refrigerants. For guest gases, R-134a, R-227ea, R-236fa, and R-141b were selected and three cavity structures ($5^{12}$, $5^{12}6^2$, and $5^{12}6^4$) composed of water molecules were constructed. The geometries of guest gas, cavity, and cavity encapsulating guest gas were optimized by molecular modeling respectively and their located energies were then used for the calculation of binding energy between the guest gas and cavity. Finally, the comparison of binding energies was used to propose which refrigerant is more favorable for the gas hydrate formation energetically. In conclusion, R-236fa was the best choice in terms of thermodynamic spontaneity, less toxicity, and low solubility in water.

• BMB Reports
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• v.40 no.2
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• pp.247-260
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• 2007

Cinnamate 4-hydroxylase (C4H) is a key enzyme of phenylpropanoid pathway, which synthesizes numerous secondary metabolites to participate in development and adaption. Two C4H isoforms, the 2192-bp BnC4H-1 and 2108-bp BnC4H-2, were cloned from oilseed rape (Brassica napus). They both have two introns and a 1518-bp open reading frame encoding a 505-amino-acid polypeptide. BnC4H-1 is 57.73 kDa with an isoelectric point of 9.11, while 57.75 kDa and 9.13 for BnC4H-2. They share only 80.6% identities on nucleotide level but 96.6% identities and 98.4% positives on protein level. Showing highest homologies to Arabidopsis thaliana C4H, they possess a conserved p450 domain and all P450-featured motifs, and are identical to typical C4Hs at substrate-recognition sites and active site residues. They are most probably associated with endoplasmic reticulum by one or both of the N- and C-terminal transmembrane helices. Phosphorylation may be a necessary post-translational modification. Their secondary structures are dominated by alpha helices and random coils. Most helices locate in the central region, while extended strands mainly distribute before and after this region. Southern blot indicated about 9 or more C4H paralogs in B. napus. In hypocotyl, cotyledon, stem, flower, bud, young- and middle-stage seed, they are co-dominantly expressed. In root and old seed, BnC4H-2 is dominant over BnC4H-1, with a reverse trend in leaf and pericarp. Paralogous C4H numbers in Brassicaceae genomes and possible roles of conserved motifs in 5' UTR and the 2nd intron are discussed.

• Korean Journal of Microbiology
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• v.32 no.3
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• pp.177-181
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• 1994

The sequences of the cytoplasmic 5S rRNAs(EMBL accession number X73589 and X73890) from two polupores, Ganoderma applanatum and Schizopora paradoxa, were determined by the direct chemical method for sequencing RNA and compared to the sequences of 9 reported mushrooms. 5S rRNAs of Ganoderma applanatum and Schizopora paradoxa consisted of 118 bases and fit the secondary structure model of the 5S rRNAs of basidiomycetes proposed by Huysmans et al. Based on Kimura’s K_nuc values, the closest fungus to Ganoderma applanatum was Ceratobasidium cornigerum and the one to Schizopora paradoxa was Bjerkandera adusta. When the secondary structures of 5S rRNAs of 11 mushrooms were compared the base substitution occurred at helix regions more than at loop regions. When a phylogenetic tree was constructed using the Neighbor program of the PHYLIP package, it partially discriminated and separated the mushrooms of the Hymenomycetes by the order.

• Journal of Microbiology and Biotechnology
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• v.15 no.5
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• pp.1087-1093
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• 2005

The population diversity and seasonal changes of bacterial communities in rice soils were monitored using both culture-dependent approaches and molecular methods. The rice field plot consisted of twelve subplots planted with two genetically-modified (GM) rice and two non-GM rice plants in three replicates. The DGGE analysis revealed that the bacterial community structures of the twelve subplot soils were quite similar to each other in a given month, indicating that there were no significant differences in the structure of the soil microbial populations between GM rice and non-GM rice during the experiment. However, the DGGE profiles of June soil after a sudden flooding were quite different from those of the other months. The June profiles exhibited a few intense DNA bands, compared with the others, indicating that flooding of rice field stimulated selective growth of some indigenous microorganisms. Phylogenetic analysis of l6S rDNA sequences from cultivated isolates showed that, while the isolates obtained from April soil before flooding were relatively evenly distributed among diverse genera such as Arthrobacter, Streptomyces, Terrabacter, and Bacillus/Paenibacillus, those from June soil after flooding mostly belonged to the Arthrobacter species. Phylogenetic analysis of 16S rDNA sequences obtained from the soil by cloning showed that April, August, and October had more diverse microorganisms than June. The results of this study indicated that flooding of rice fields gave a significant impact on the indigenous microbial community structure; however, the initial structure was gradually recovered over time after a sudden flooding.