• Journal of the Korea Concrete Institute
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• v.18 no.3 s.93
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• pp.397-404
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• 2006

This paper investigates experimentally the effect of combined addition of expansive additive and shrinkage reducing agent(SRA) on setting time, compressive strength and drying shrinkage of concrete. An increase of EA and SRA content leads to a reduction in flowability, which causes the increase of superplasticizer dosage, while air content increases. For setting time, in spite of increased superplasticizer dosage, with the increase of EA and SRA, setting time shortens. This is due to the presence of alkali ion by SRA and the faster formation of ettringite. At dosage of 5.0% of EA, concrete has the highest compressive strength and above that dosage, compressive strength decreased. On the contrary, the increase of SRA dosage results in a decrease in compressive strength. Combined addition of EA of 5.0% and SRA of 1.0% shows a comparable strength with control concrete. For drying shrinkage, as expected, the increase of EA and SRA dosage leads to reduction of drying shrinkage markedly. Moreover, combined addition of EA and SRA has better drying shrinkage reduction effect than individual use of EA and SRA by as much as $5{\sim}16%$. Optimal combination of EA and SRA is fixed at 5.0% of EA and 0.5% of SRA based on the consideration of the effect of EA and SRA on fresh state, compressive strength and shrinkage of concrete.

• The Korean Journal of Mycology
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• v.45 no.2
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• pp.91-101
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• 2017

Three species of powdery mildew (Erysiphales) on eggplant (Solanum melongena L.) have been listed in Korea, namely Erysiphe cichoracearum (now genus Golovinomyces), Leveillula taurica, and Sphaerotheca fusca (now genus Podosphaera; syn. Podosphaera xanthii). Since E. cichoracearum was recorded on eggplant for the first time in Korea in 1969, it has been regarded as a major powdery mildew agent on that plant. In 1998, the causal agent of powdery mildew on eggplant was recorded as L. taurica, then as S. fusca in 2002. During our extensive field surveys in Korea, we collected 22 samples of eggplant powdery mildews. Our microscopic observations and molecular sequence analyses showed that all of our samples belonged to the genus Podosphaera, in the absence of either E. cichoracearum or L. taurica, suggesting that P. xanthii is the dominant agent of powdery mildew disease on eggplants in Korea. As there have been no additional findings on L. taurica after the first report on the species, it seems to be a minor species that is rarely found in greenhouses. The presence of E. cichoracearum (syn. Golovinomyces cichoracearum s. lat.) on eggplants is questionable, as the morphological characteristics of E. cichoracearum in the original description of the Korean collection deviate from the morphological variations of this species. In addition, no herbarium material of E. cichoracearum remains. Consequently, it seems that P. xanthii is the main species of powdery mildew on eggplants, whereas L. taurica occurs rarely on eggplants, in Korea. This review provides the historical and recent taxonomy of eggplant powdery mildews in detail.

• Elastomers and Composites
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• v.39 no.1
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• pp.71-76
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• 2004

4,4'-Methylenebis(2-chloroaniline)(MOCA) has been widely used as a crosslinking agent, but classified as a toxic chemical. Thus, its use will be limited in the near future. In this research, polyurethane coating films were prepared using 1,3-propanediolbis(4-aminobenzoate)(PDBA) as an alternative to MOCA. The base part was prepared by melting MOCA or PDBA in polyoxypropylene($M_n$=2000), followed by the addition of the various additives. The NCO-terminated toluene diisocyanate prepolymer was used as a curing agent. The polyurethane coating films were prepared by mixing the base part with the curing agent in an appropriate ratio at room temperature. The polyurethane coatings prepared using PDBA exhibited higher initial viscosity, but much longer pot lift, compared to those prepared using MOCA under the same conditions, due to lower reactivity of PDBA. The tensile strength and tear strength of the coating films were much weaker. However, the pot life, tensile strength, elongation, and tear strength of the coating films, prepared using PDBA in the presence of an increased amount of Pb(II)-octoate, were close to those of the coating films prepared using MOCA. Thus, it was concluded that PDBA can substitute MOCA in the preparation of polyurethane coatings as long as the reactivity of PDBA is enhanced using appropriate amounts of the catalyst or other appropriate catalyst.

• Polymer(Korea)
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• v.26 no.5
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• pp.691-700
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• 2002

Interstitial therapy using biodegradable polymeric device loaded with anticancer agent can deliver the drug to the tumor site at high concentration, resulting in an increase of therapeutic efficacy. 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU, carmustine) is most commonly used as chemotherapeutic agent for brain tumors. The design of implantable device is regarded as an important factor lot the efficient delivery of antitumor agent to targeting site. In order to control the release profile of drug, the release pattern of BCNU with the changes of various dimension and additives was investigated. The PLGA wafers containing 3.85, 10, 20 and 30% of BCNU were prepared in various shape (diameter of 3, 5 and 10 mm, thickness of 0.5, 1 and 2 mm) by direct compression method. In vitro drug release profile of BCNU-loaded PLGA wafers could be controlled by changing the dimension of wafers such as initial drug content, weight, diameter, thickness, volume and surface area of wafers, as well as PLGA molecular weight and additives. Drug release from BCNU-loaded PLGA wafers was facilitated with an increase of BCNU-loading amount or presence of poly(N-vinylpyrrolidone)(PVP) or sodium chloride (NaCl). The effects of various geometric factors and additives on the BCNU release pattern were confirmed by the investigation of mass loss and morphology of BCNU-loaded PLGA wafers.

• Journal of Life Science
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• v.7 no.3
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• pp.192-197
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• 1997

Italian ryegrass, red clover, sorghum, and alfalfa were used for leaf protein preparation. Fresh leaves were pulped in the presence or absence of a reducing agent(sodium ascorbate or NaHSO$_{4}$) and green juice was heated and washed with acetone. The biological evaluation of leaf proteins was carried out by the growth method with male rats weighing about 45g. Italian ryegrass, red clover, and sorghum were brown when leaves were pulped in the absence of a reducing agent. On the other hand, alfalfa had neither o-diphenolics nor polyphenolase, and hence the alfalfa leaf protein did not brown during pulping ever in the absence of a reducing agent. The brown leaf protein from Italian ryegrass hd lower digestibility than the leaf protein protected from browning, although there were no difference in growth-promoting effect and protein efficiency ratio(PER)between the two leaf protein. The feeding of brown leaf protein from red clover resulted in the lowering of weight gain, digestibility, and PER, and all the measurement including diet intake were lowered by feeding the brown leaf protein from sorghum. In the case of alfalfa leaf protein, there were no difference in nutritional quality between the two leaf protein made with and without an attempt to prevent browning. The results mentioned above indicate that the occurrence of phenolics and polyphemolase in a crop in responsible for the browning of leaf protein and that the browning of leaf protein caused its nutritional impairment.

• Journal of Convergence for Information Technology
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• v.11 no.9
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• pp.109-114
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• 2021

Cr(VI)-quinoline compound[(C₉H₇NH)₂Cr₂O₇] was synthesized by the reaction between of quinoline and chromium(VI) trioxide, and structure was FT-IR, elemental analysis. The oxidation ability of benzyl alcohol greatly depends upon the dielectric constant of the used organic solvent, where carbon tetrachloride was worst and N,N'-dimethylformamide was best solvent. Noticeably, in N,N'-dimethylformamide solvent, Cr(VI)-quinoline compound oxidized substituted benzyl alcohols. The Hammett reaction constant(ρ)=-0.69(303K). As a resuit, Cr(VI)-quinoline compound was found as efficicent oxidizing agent that converted benzyl alcohol, allyl alcohol, primary alcohol and secondary alcohols to the corresponding aldehydes or ketones. Cr(VI)-quinoline compound was selective oxidizing agent of benzyl alcohol, allyl alcohol and primary alcohol in the presence of secondary alcohol ones.

• Korean Journal of Veterinary Research
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• v.49 no.3
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• pp.231-236
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• 2009

Biofilm has been described as a barrier, which produced by microorganisms to survive and protect themselves against various environments, like antibiotic agents. Staphylococcus spp. is a common cause of nosocomial and environmental infection. Thirty-six and thirty-five Staphylococci were isolated from animals and air, respectively. Based on the biofilm forming ability of the bacterium reported in our previous report, relationship between biofilm formation and antibiotic-resistance was investigated in this study. Regarding antibiotics susceptibility, cefazolin was the most effective agent to the bacteria. Strong biofilm-forming Staphylococcus spp. isolates might have a higher antibiotic resistance than weak biofilm isolates regardless of the presence of antibiotic resistance genes (p < 0.05). This result suggested that the chemical complexity of the biofilm might increase the antibiotic resistance due to the decrease of antibiotic diffusion into cells through the extensive matrix.

• Korean Journal of Veterinary Service
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• v.26 no.1
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• pp.51-56
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• 2003

Avian pneumoviros(APV), also known as avian rhinotracheitis virus(ARTV), affects both turkeys and chickens and is known to be the primary causative agent of turkey rhinotracheitis (TRT). The aim of this study was to establish the presence or absence of antibodies to avian pneumovirus in the commercial poultry population of Korea. For this purpose, chicken serum samples were obtained and tested by an enzyme-linked immunosorbent assay (ELISA). The tested serum was collected in laying hens with reduction of egg production or normal in Gyeongbuk province. A total of 184 sera representing 42 different poultry farms of the Gyeongbuk region of Korea were included in this study. Laying hens of 16 different farms with reduction of egg production and laying hens of 26 different farms with clinically healthy at the time of serum sampling were considered positive to antibody against APV. In the farms with reduction of egg production, positive farm to antibody against avian pneumovirus were 11 of 16 different farms(68.8%) and positive sera were 47(58.8%) of 80 different serum. In the farms with clinically healthy flock, positive farm to antibody against avian pneumovirus were 12(46.2%) of 26 different farms and positive serum sample were 39(37.5%) of 104 different sera. According to the results tested to 42 different farms in 14 city, 8 of 14 city have flocks with antibody positive laying hens against APV, 1 of 14 city have antibody suspicious and 5 of 14 city shown antibody negative, respectively.

• Proceedings of the Materials Research Society of Korea Conference
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• 1994.11a
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• pp.125-126
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• 1994

The chemorheological changes and kinetics during curing reaction of an silica filled epoxy system (DGEBA with curing agent Polyxoypropylenediamine) were investigated. This study concentrates on the influence of silica on the reaction kinetics and rheological behavior of the eopxy system. The concentration of the filler was varied 0~200phr. Curing behavior of the silica filled epoxy system was measured at various heating rates with DSC. Conversion was also measured by integrating the obtained DSC curve and Kinetic parameters measured by using the nonlinear regression method. DSC experiments showed that the presence of silica was found to accelerate the progress of the curing reaction and of reduce the heat of reaction compared with that of unfilled epoxy systems . Rheological experiments were conducted on a Physica by using a disposable parallel plate fixture. Material properites were measured such as the elastic modulus(G′), the loss modulus(G"), the loss tangent(tan $\delta$), and the viscosity was at the initial stahe, and the more the silica filler was added, and the lower the gel temperature was in the epoxy system. In this study it is concluded that the curing of the silica filled epoxy system was found to be accelerated, as silica was added to the epoxy compound.

• Journal of the Korean Chemical Society
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• v.23 no.2
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• pp.99-103
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• 1979

The reductive amination of three ${\alpha}$,${\beta}$-unsaturated aldehydes, cinnamaldehyde, crotonaldehyde, and acrolein are carried out successfully by tetracarbonylhydridoferrate in the presence of various primary amines. In a typical reaction, a mixture of potassium tetracarbonylhydridoferrate (22 mmole), an amine (22∼44 mole) and ${\alpha}$,${\beta}$-unsaturated aldehyde (22 mmole), in ethanol (30∼50 ml) was stirred for 9∼60 hours at room temperature under carbon monoxide atmosphere. All the products were characterized as secondary amines by mass, infrared, and nmr spectra as well as gas chromatographic data.