• The Mathematical Education
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• v.46 no.4
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• pp.423-443
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• 2007

Based on the framework of Huffered-Ackles, Fuson and Sherin(2004), data were analyzed in terms of 3 components: explaining(E), questioning(Q) and justifying(J) of students' mathematical concepts and problem solving in a math classroom. The students used varied presentations to explain and justify their mathematical concepts and ideas. They corrected their mathematical errors or misconceptions through discourses. In addition, they constructed and clarified their concepts and thinking while they were interacted. We were able to recognize there was a special feature in discourses that encouraged the students to construct and develop their mathematical concepts. As they participated in math class and received feedback on their learning, the whole class worked cooperatively in a positive way. Their discourse was improved from the level of the actual development to the level of the potential development and the pattern of interaction moved from ERE(Elicitaion-Response-Elaboration to PD(Proposition Discussion).

• Journal of Sericultural and Entomological Science
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• v.43 no.2
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• pp.67-76
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• 2001

The "crescent-egg" a new spontaneous mutant was detected in a white egg strain k37. Studies were carried out the linkage analysis, to investigate phenotypic characteristics and biochemical analysis of haemolymph and ovarian protein. The mutant, ore was independent from 20 linkage groups P(2), Ze(3),L(4), oc(5), sn8), Ia(9), w-1(10), K(11), ch(13), U(14), bl(15), cts(16), bts(17), mln(18), nb(19), oh(20),Lan(21), or(22), tub(23) and Xan(27). The fertilization, hatchability and larval growth were not different from the those of normal eggs. The content and composition of yolk protein were similared to normal eggs. Scanning electron microscopy revealed the areal specific structure in dorsal region of egg-shell of cre mutant. Analysis of chorion protein by isoelectrofocusing(IEF), was resolved no difference in the composite of the chorion protein. We conclude that the egg mutant ere is expressed only in the egg-shape formation and region specific determination.

• Bulletin of the Korean Mathematical Society
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• v.60 no.6
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• pp.1463-1475
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• 2023

In this paper, we introduce a class of rings generalizing unit regular rings and being a subclass of semipotent rings, which is called idempotent unit regular. We call a ring R an idempotent unit regular ring if for all r ∈ R - J(R), there exist a non-zero idempotent e and a unit element u in R such that er = eu, where this condition is left and right symmetric. Thus, we have also that there exist a non-zero idempotent e and a unit u such that ere = eue for all r ∈ R - J(R). Various basic characterizations and properties of this class of rings are proved and it is given the relationships between this class of rings and some well-known classes of rings such as semiperfect, clean, exchange and semipotent. Moreover, we obtain some results about when the endomorphism ring of a module in a class of left R-modules X is idempotent unit regular.

• Journal of Nutrition and Health
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• v.29 no.8
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• pp.889-898
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• 1996

This study estimated the re!ation between psychological stress and stress hormones, nu­t tritional status of patients with non-insulin dependent diabetes mellitus(NIDDM). Psycho­l logical stress such as depr'ession and anxiety in 34 diabetics was analyzedin relation to nutrient intake, blood components such as fasting blood sugar(FBS), hemoglobin AIC, stress hormones a and amino acids. The IeveIs of depression and anxiety were measured by The center for ep­i idemiological studies-depc$pm$111.49pg/ml for total catecholamine ( (norepmephrine and epinephrine) and 233.95 $pm$73.99pg/ml for norepinephrine, 94.03$pm$75. 9 97pg/ml for epinephrine, 13.lS$pm$5.55pl/dl for cortisol and 171.50$pm$62.50pg/ml for gul c cagon respectlveIy. The leveIs of stress hormones in diabetics such as total catecholamine, norep­i mephrine cortisol and glucagon were significantly higher than those in normal control. The lev­el of epmephrine was higher in diabetics but the diffierenee was not significant. The calorie m t take in diabetics was 1762$pm$292keal which is S1.4% lower than Korean recommended dietary a allowances(RDA). Calcium intake was slightly low but other nutrients intakeswere higher than R RDA. The value of fasting blood sugar(FBS), usual fasting blood sugar(usual FBS) which refteet a average FBS during 3 months and hemoglobin Al C in diabetics was 1S4.1S$pm$74.22mg/dl, 177.76$pm$42.77mg/dl and S.S4$pm$2.S2% respec디VeIy. The distribution of plasma amino acids in d diabetics was generally in the normal range. The leveI of anxiety in diabetics was positively cor­related with norepinephrine, concentration and usual FBS. The levels of glucagon, usual FBS a and hemoglobin Aj C were pOSI디veIy correlated with the branched chaimamino acid(BCM : leucme, isoleucme and valine)

• KOREAN JOURNAL OF CROP SCIENCE
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• v.56 no.2
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• pp.134-139
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• 2011

This study was conducted to evaluate the weed suppressing effects of two winter cover crops, hairy vetch and rye in foxtail millet and sorghum fields in 2010. Crop growth and development and weed occurrences in the fields were examined to know the efficiency of proposed cropping system. In hairy vetch treated plots, heading of minor cereals occurred early. The heading date was earlier by 1 day and 2 days in sorghum and foxtail millet, respectively. However, rye treatment delayed heading by 12 days and 8 days in sorghum and foxtail millet, respectively. Besides he effect of cover crop on ear emergence of crops, the Besides changed growth-related characteristics. Plant height, chlorophyll content and chlorophyll fluorescence of sorghum ere increased in hairy vetch treatment by 46.4% 88.7% and 7.9%, respectively. In foxtail millet, the characteristics ere also increased by 45.6%, 50.9% and 37.8%, respectively, s compared to control. Yields of sorghum and foxtail millet were increased by 105.1% and 135% as compared o control by hairy vetch treatment, respectively. However, he yields of cereal crops were decreased by rye cover crop treatment, the yields of sorghum and foxtail millet were decreased by 25.8% and 119.1%, respectively. Rye cover crop treatment inhibited crop growth suggesting nitrogen starvation in rye treated plots. In rye treatment, plant height, chlorophyll contents and chlorophyll fluorescence of sorghum ere slightly decreased by 7.1%, 10.8% and 10.8%, respectively, as compared to control whereas the inhibitory effects were greater in foxtail millet. Weed occurrences based n weed number in hairy vetch and rye plots were reduced n weed number in hairy vetch and rye plots were reduced y 27% and 20%, respectively. The smothering effect was weakened or disappeared after heading of crops. Weed number and dry weight in hairy vetch plot were increased by 159% and 55.2%, respectively, as compared to control. The results implied that weed suppressing of cover crops could be reduced drastically after heading of crops.

• Korean Journal of Clinical Laboratory Science
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• v.47 no.2
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• pp.65-70
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• 2015

Antimicrobial agents or additives have commonly been used in domestic animals for the prevention and treatment of bacterial diseases. Unfortunately, this has resulted in the overgrowth of bacteria that is resistant to antimicrobial agents used by humans, and these might get disseminated to humans via the food. In this study, we investigated the prevalence of integrons, and characterized gene cassette arrays in Proteus mirabilis isolates obtained from chickens in Chungcheong province of Korea. Additionally, the correlation between gene cassette arrays and antimicrobial resistance rate was studied. A total of 26 Proteus mirabilis isolates were recovered from chickens in Chungcheong province in Korea. Antimicrobial susceptibility was determined by disk diffusion method. PCR and DNA sequencing were performed to characterize the gene cassette arrays. In addition, we employed repetitive extragenic palindromic sequence-based PCR (REP-PCR) method for clonality analysis of P. mirabilis strains. Of the 26 P. mirabilis isolates tested, 14 (53.8%) isolates carried class 1 integrons, while class 2 and class 3 integrons were not detected in our study. The class 1 integrons harbored genes encoding resistance to aminoglycosides (aacCA5, aadA2, aadA5 and aadA7), trimethoprim (dfrA17, and dfrA32), lincosamides (linF) and erythromycin (ereA). In particular, the presence of class 1 integron had a significant correlatation to a high resistance rate of aminoglycoside and trimethoprim. We confirmed that class 1 integrons are widely disseminated in P. mirabilis isolates from chickens, contributing to the resistance to diverse antimicrobial agents in Korea. To prevent further spreading of antimicrobial resistant genes among P. mirabilis isolates, constant monitoring and clinical policing will become necessary.

• Journal of the Korean Society of Food Science and Nutrition
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• v.16 no.4
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• pp.251-261
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• 1987

This study was attempted to increase the production of L-Threonine by Brevibacterium Flavum ATCC 14067, To select the strain which produce the highest threonine, mutants ere induced by N-methyl-N'-nitro-N-nitrosoguanidine treatment. The composition of media and cultural condition for its overproduction of threonine were also studied. In a threonine producer, strain B-13(Met-) was the strain producing the highest amount of threonige among methionine, lysine and isoleucine auxotrophs. The following results were obtained. 1. The wild strain and B-13(Met-) produced threonine 1.4mg/ml and 4.86mg/ml , respectively. 2. The optimum composition of medium for producing threonine by Brevibacterium Flavum B-13 was glucose 10%, ammonium sulfate 4%, potassium phosphate monobasic 0.2%, magnesium sulfate 0.05%, biotin $200{\mu}l$, thiamine $300{\mu}l$. Addition of nicotinic acid also led to increase L-threonine production. 3. In addition of organic nutrients to the fermentation medium, peptone n'ere effective and addition of methionine $100{\mu}g/ml$ produced the highest amount of L-Threonine. Aspartic acid and homoserine were also effective when these amino acid were added to the fermentstion medium. 4. Cultural conditon on threonine production by B-16 were investigated. The optimum pH was 7.0-8.0. The highest amount of threnine was produced after 4 days of cultural period.

• Korean Journal of Microbiology
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• v.30 no.2
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• pp.88-95
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• 1992

The genetically engineered microorganisms (GEMS) could be released accidentally or ii)rexperimental purposes, as the genetic engineering, technique ha:. become very popular inany laboratories of biological sciences. But there have been littlt: informations on transkrbehavior of the genetically ~nodified genes in the natural en\ironmentx. In this stutly.antibiotic resistant bacteria were isolated from nat.ural waters. and then GEM strains wereconstructed i'rom the natural isolate (NI) by ~noclification oi' the Km' plasmitl. Thetransferability of the plasmids in the GEM and NI strains were examinetl by con-jugationin Luria-Bertani broth :it 30$^{\circ}$C. Also the cff'ccts 01' mating strain and pH on their transferfrequency and rearrangement of the plasmids in tl-~ec o~ijugantsM ere comp:irati\ely stuclictl.I'hc transkr frequency of Km' plasmid in donor of GEM and N1 strains wah similar a.;about 10 ' when co~ljugation was conducted wit11 M'I'I strain is recipient at pH 7. butthat of 1)KCOOI was lowered to 1.2X 10 '. And when the lab. stlain was uhccl as recipient.the transfer tendency of the plasmid was about same in both (;EM and NI strains usedas donor. All thc tionor 5trains. except for I)KC601. showecl the Ilighcs~ frequency of about10 ' at pH 7 and the frequcncics were lowered at both pH 5 and 9. Hut the mocliliedKm' plasmid in the cloned strain of DKC601 was transferred hy very low frequency of10 "at pH 5 ant1 7 comparing to other GEM strains. especiall! any co~~.jugantws ere notobtained at pH 4 and 9 even after conjugation for 6 hours. Rearrangement of the plasmidstranskrred into the lab. strain was not found in the conjugants. I\ulcornerut a lot of rearrangclncntwas ohservecl nlhen they were transferred into the NI strain. Such a rearrangement wasmore severe when donor was GEM strain rather then NI strain Hut such ;r phenomenonwas less affected by p!-l values.r phenomenon was less affected by p!-l values.

• Korean Journal of Clinical Laboratory Science
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• v.48 no.4
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• pp.327-334
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• 2016

Recently, antimicrobial resistance of pathogenic bacteria has been increasing due to excessive use of antimicrobial agents in both humans and livestock. PCR amplification and nucleotide sequence analyses were conducted to investigate16S ribosomal RNA methyltransferase (RMTase) genes and integrons in P. mirabilis strains isolated from clinical specimens and chickens in an area of the Chungcheong providence. In addition, clonality analysis of P. mirabilis strains was performed using a repetitive extragenic palindromic sequence-based PCR (REP-PCR) method. Of the total 38 P. mirabilis isolates, 7 (18.4%) strains were isolated from clinical specimens contained in the RMTase genes and showed resistance to amikacin, tobramycin, and gentamicin. A total of 23 (60.5%) isolates carried class 1 integrons, but no isolates in our study harbored class 2 and class 3 integrons. Class 1 integrons detected in our study harbored genes encoding resistance to aminoglycosides (aadA2, aadA5, aadA7, and aacCA5), ${\beta}$-lactams ($bla_{PSE}$), erythromycin (ereA), lincosamides (linF), and trimethoprim (dfrA12, dfrA17, and dfrA32). We confirmed that the RMTase genes had spread among only the P. mirabilis isolates from clinical specimens, but class 1 integrons had widely disseminated among P. mirabilis isolates from clinical specimens and chickens. In addition, identical REP-PCR banding patterns were evidenced in only P. mirabilis isolates from chickens. Our results suggest the horizontal spreading of P. mirabilis isolates in the chicken farm. To prevent further spreading of antimicrobial resistant genes among P. mirabilis isolates, monitoring and clinical policing will be required.

• Korean Journal of Veterinary Research
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• v.28 no.1
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• pp.115-118
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• 1988

Mating experiments were performed to, elucidate the distribution of perfect state of Microsporum gypseum complex originated from animals and soils in Korea. A total of 30 strains of M. gypseum complex, composed of 16 from animals and 14 from soils, ere mated with the tester strains of Nannizzia incurvata, N. gypsea and N. fulva. Among 30 strains of M. gypseum complex examined, 16 strains(53.3%) were N. incurvata, 13 strains(43.3%) N. gypsea and 1 strain (3.3%) N. fulva. Among 13 strains of dog isolates, 8 strains(61.5%) were N. incurvata and 5 strains(38.5%) N. gypsea. And each strain isolated from Korean native goat, monkey and albino rat was N. gypsea. Among 14 strains of soil isolates, 8 strains(57.2%) were N. incurvata, 5 strains (35.7%) N. gypsea and 1 strain(7.2%) N. fulva. And -mating type was more frequently observed than +mating type in the strains of N. incurvata and N. gypsea. By this study, N. fulva was isolated the first time in Korea.