1,721,408 research outputs found
Isolation and identification of seven microcystins from a cultured M . TN-2 strain of Microcystis aeruginosa.
No full text
Toxicity assay of cyanobacterial strains using Artemia salina in comparison with the mouse bioassay.
No full textSynthesis of colorless imide hybrid nanocomposites using amine functionalized oligosiloxane nano-building clusters
No full textColorless imide hybrid nanocomposites are fabricated using new amine functionalized oligosiloxane nano-building clusters (AONC) and the cross-linking agent 5-(2,5dioxotetrahydrofuryl)- 3-methyl-cyclohexene-1,2-dicarboxylic anhydride (DODCA) or 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA) in order to obtain thermally stable and optically transparent materials. AONC are cross-linked by short diimide bonds which were formed by reaction of AONC with alicyclic dianhydrides and the fabricated nanocomposites have 3- dimensional network structures. The prepared nanocomposites show good thermal stability with 5% weight loss temperature around 430 degrees C and excellent optical properties such as colorlessness (optical transmission of above 90% in the visible region and ultraviolet cut-off around 310 nm), large modulation of refractive index and low birefringence (about 0.002). Colorless imide hybrid nanocomposites prepared from AONC and alicyclic dianhydride (DODCA and CBDA) are potential materials for optical and opto-electronic applications.This work was supported by the Sol–Gel Innovation Project
(SOLIP) of the Ministry of Commerce, Industry and Energy of
Korea. The authors are grateful to Baek-Seok Seong of the
Korea Atomic Energy Research Institute (KAERI) for useful
discussion and help with operating the SANS instruments in
HANARO
Estimation of specific growth rate from agitation speed in DO-stat culture
No full textA simple and effective method to estimate the specific growth rate estimation has been developed based on the observation of time changes in the agitation speed in dissolved oxygen(DO)-stat cultures of Brevibacterium ketoglutamicum. The estimation was compared with that using carbon dioxide evolution rate (CER). Estimated values of specific growth rates by both methods agreed well with the data directly calculated from cell concentration change although the use of agitation speed gave a slightly better result than CER
Catalytic effects of aluminum butoxyethoxide in sol-gel hybrid hard coatings
No full textHybrid inorganic-organic hard coatings on PMMA substrate were obtained by sol-gel reaction of 3-glycidoxypropyltrimethoxysilane(GPTS), tetramethyl orthosilicate(TMOS) and aluminum butoxyethoxide (Al(OEtOBu)(3)). The catalytic effect of aluminum butoxyethoxide on inorganic condensation and epoxide polymerization has been studied by C-13, Si-29 nuclear magnetic resonance spectroscopy and by Fourier transformed infrared spectroscopy. Hardness of hybrid inorganic-organic materials were measured by nanoindentor and mainly influenced by the extent of epoxide polymerization and inorganic condensation of their coating catalyzed by aluminum butoxyethoxide
Fabrication and characteristics of sol-gel derived fluorinated hybrid material films
No full textFluorinated inorganic-organic hybrid materials (HYBRIMER) were successfully prepared from fluoroalkylsilanes (FASs) containing fluoro-alkyl functions and methacryloxypropyltrimethoxysilane (MPTMS) through a sol-gel process. The influence of concentration and fluoro-alkyl chain lengths of FASs on the physical characteristics of the fluorinated HYBRIMER films was examined. Larger fluorine contents lowered the refractive index within a range, which was closely dependent on the fluoro-alkyl chain lengths of FASs. Thermo-optic coefficients (TOC) were negative values, and the values grew with increasing fluorine contents and fluoro-alkyl chain lengths. Also, the thermal stability is enhanced by addition of fluorine in the HYBRIMER.The authors gratefully acknowledge the financial
support of the Sol-Gel Innovation Project (SOLIP)
funded by Ministry of Commerce, Industry & Energy
(MOCIE) in Korea
Development of a cell-loaded biosupport separator for continuous immobilized-cell perfusion culture
No full textAn efficient cell-loaded biosupport separator of the decanter type was developed and applied for a continuous perfusion culture to produce cyclosporin A (CyA), in which fungal cells were immobilized on Celite beads. In the preliminary experiments employing highly viscous polymer (carboxymethyl cellulose) solutions, the decanter showed good separation performances at high solution viscosites and dilution rates. Two concentric cylindrical tubes installed inside the decanter turned out to play key roles in the efficient separation of the immobilized cells. By installing the decanter on an immobilized-cell perfusion bioprocess system, a stable continuous operation was possible even at a high dilution rate for an extended period, leading to high productivities of free cells and CyA. Almost no immobilized biomass existed in the effluent stream from the bioreactor, demonstrating the effectiveness of the decanter system. It is noteworthy that we could obtain these results despite unfavorable fermentation conditions, i.e., reduced apparent density of cell-loaded beads and increased drag force on the bead particles caused by overgrowth of cells on the bead surface, tubulence caused by large air bubbles, and the existence of a high density of suspended fungal cells (10 g/L) in the fermentation broth
Development of sporulation/immobilization method and its application for the continuous production of cyclosporin A by Tolypocladium inflatum
No full textAn efficient sporulation/immobilization procedure for immobilized fungal cell culture was developed by modifying an existing immobilized technique to shorten the time and number of steps for sporulation. This method was applied to an immobilized-cell perfusion bioprocess (IPB) for continuous production of CyA, an intracellular secondary metabolite produced by a filamentous fungus, Tolypocladium inflatum. In the IPB, the fungal cells were immobilized in the pores of celite beads (100 similar to 500 mu m) and a top-driven stirred tank fermenter was used for the culture. The IPB showed good process benefits as demonstrated by the high density of immobilized cells continuously producing CyA-containing free cells. The productivity of CyA-containing free cells in the effluent was very high, ca. 1.0 g/(L/h) at a dilution rate of 0.1. h(-1), due to the high density of immobilized cells in the fermenter. The CyA productivity was 4.0 similar to 6.0 mg/(L/h) which was about 6 similar to 10-fold higher than that of batch suspended cell culture. Such an efficient IPB was possible since a decanter was developed in this study, which could effectively separate cell-immobilized beads from the effluent although bead loss slightly increased as the cell loading increased in the latter part of culture. Furthermore, long-term operation of IPB was carried out successfully by employing an in-situ immobilization strategy. It was found that a large number of spores in the fermentation broth in the reactor were entrapped in-situ into the newly supplemented celite beads and then germinated, thus forming new immobilized cells
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