• Korean Journal of Food Science and Technology
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• v.19 no.1
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• pp.42-49
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• 1987

The acid production and sugar utilization of Lactobacillus helveticus YM-1 between Streptecoccus lactic ${ML}_3$ were investigated in skim milk, cultured broth filtrate and semi-synthetic medium. The effect of acid production by mixed culture and in cultured broth filtrate of the other party were more than that of single culture and self-cultured broth filtrate. When the two strains were cultured 12 hrs, Streptococcus lactis ${ML}_3$ utilized with 0.4% lactose, Lactobacillus helveticus YM-1 with 0.85%, and mixed strains with 1.05% respectively. In 8 hrs fermentation Lactobacillus helveticus YM-1 and mixed strains accumulated 0.22%, 0.10% glucose in the medium respectively, and then decreased gradually. The glucose released by Lactobacillus helveticus YM-1 was stimulated the acid production of Streptococcus lactis ${ML}_3$.

• Journal of Microbiology
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• v.39 no.1
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• pp.24-30
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• 2001

In addition to effecting the catalysis of sugar uptake, the bacterial phosphoenolpyruvate::sugar phosphotransferase system regulates a variety of physiological processes. In a previous paper [Seok et al.,(1997) J. Biol. Chem. 272, 26511-26521], we reported the interaction with and allosteric regulation of Esiherichia coli glycogen phosphorylase activity by the histidine-containing phosphocarrier protein HPr in vitro. Here, we show that the specific interaction between HPr and glycogen phosphorylase occurs in vivo. To address the physiological role of the HPr-glycogen phosphorylase complex, intracellular glycogen levels were measured in E. coli strains transformed with various plasmids. While glycogen accumulated during the transition between exponential and stationary growth phases in wildtype cells, it did not accumulate in cells overproducing HPr or its inactive mutant regardless of the growth stage. From these results, we conclude that HPr mediates crosstalk between sugar uptake through the phosphoenolpyruvate:sugar phosphotransferase system and glycogen breakdown. The evolutionary significance of the HPr-glycogen phosphorylase complex is suggested.

• Journal of Korean Society of Water and Wastewater
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• v.24 no.2
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• pp.165-172
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• 2010

Treated sewage could enable growth by providing key nutrients or seeding the sediments with enterococci strains that can grow in the environment. This study is to test the hypothesis that the flux of bacteria into the water column is rate-limited by the transfer of bacteria across the sediment/water interface. Two conceptual models are derived for the transfer of bacteria to the water column from the sediment/water interface: convective diffusion of isolated bacteria and resuspension of particle-associated bacteria. The model predictions are directly tested together with field measurements of bacteria and sediment in an effluent-dominated stream where high concentrations of enterococci in this stream originate primarily from growth of the bacteria in stream sediments. The results reveal that high concentrations of enterococci in this stream are transported primarily by resuspension of particle-associated bacteria accumulated at the sediment/water interface, either in the form of bacterial aggregates or in the form of inorganic particles.

• Korean Journal of Plant Resources
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• v.15 no.3
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• pp.177-187
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• 2002

In our experiment, selected mutants were used which showed not only the phenotype of a specific unpolished rice but also phenotypes of EM 40, LO 1050, and TAL 214. Reciprocal crosses between the mutants were conducted to select strains which would have more quantity of lipids than before. The constitution of fatty acid was also tested to figure out nutritional aspects of the mutants. In the crossing between EM 40 mutants and mutants (LO 1050) having a thick aleurone layer, the expression of EM 40 mutants has no relation with the thickness of the aleurone layer. And the lipid content of new F$_2$ strains through the crossing is 4.15 ％. The lipid content is larger than those of the parents including Kinmaze and in other crossings of this experiment. This is attributed to the fact that the new F$_2$ strains are the products of the crossing between genes responsible for the size of buds, where lipid is accumulated, and genes accountable for the thickness of the aleurone layer. In the crossing between EM 40 mutants and TAL 214 mutants, lipid content of the new F$_2$ strains is 3.8 ％, higher than 2.92 ％ of TAL 214 mutants. But the degree of lipid increase is smaller than in two other crossings. This is probably because genes expressing the phenotypes of TAL 214 affect the size of EM 40, which gets smaller. The aleurone layer of the new F$_2$ strains is 12 $\mu\textrm{m}$ thicker than the layer of TAL 214 mutants, but 6 $\mu\textrm{m}$ thinner than that of parents (LO 1050) having a thick aleurone layer. This seems to be affected by the size of a microscope. The phenotype of the new F$_2$ strains appears to be similar to that of TAL 214. The lipid content of the new F$_2$ strains is 3.85 ％, larger than 2.92 ％ of TAL 214 and 3.01 % of LO 1050. The increase may be due to the aleurone layer of LO 1050. And the size of the bud of the unpolished rice, though it is not big enough like that of LO 1050, seems to be affected by the accumulation of genes in the thick aleurone layer. The accumulation may contribute to the increase in the content of lipid. When it comes to the constitution of fatty acid, there is little difference between parents like Kinmaze and the new F$_2$ strains. But oleic acid increases while linoleic acid decreases. And the decrease in the linolenic acid seems to contribute to the increase in lipid content. This fact also raises the possibility that genes accountable for specific phenotypes could change the quality of rice if the genes are accumulated. Now, experiments on strains which have large lipid content in EM 40 type 1(ge-1, 3.68 ％), EM type 2(ge-2, 2.91 ％), thick aleurone layer(4.63 ％), and starch layer(3.44 ％) are under way to figure out the effects of gene accumulation. These experiments are likely to present the ways for increasing the lipid content.

• Journal of the Korea Concrete Institute
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• v.20 no.1
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• pp.13-22
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• 2008

The initiation and growth processes of cyclic ice body in porous systems are affected by the thermo-physical and mass transport properties, as well as gradients of temperature and chemical potentials. Furthermore, the diffusivity of deicing chemicals shows significantly higher value under cyclic freeze-thaw conditions. Consequently, the disintegration of concrete structures is aggravated at marine environments, higher altitudes, and northern areas. However, the properties of cyclic freeze-thaw with crack growth and the deterioration by the accumulated damages are hard to identify in tests. In order to predict the accumulated damages by cyclic freeze-thaw, a regression analysis by the response surface method (RSM) is used. The important parameters for cyclic freeze-thawdeterioration of concrete structures, such as water to cement ratio, entrained air pores, and the number of cycles of freezing and thawing, are used to compose the limit state function. The regression equation fitted to the important deterioration criteria, such as accumulated plastic deformation, relative dynamic modulus, or equivalent plastic deformations, were used as the probabilistic evaluations of performance for the degraded structural resistance. The predicted results of relative dynamic modulus and residual strains after 300 cycles of freeze-thaw show very good agreements with the experimental results. The RSM result can be used to predict the probability of occurrence for designer specified critical values. Therefore, it is possible to evaluate the life cycle management of concrete structures considering the accumulated damages due to the cyclic freeze-thaw using the proposed prediction method.

• Applied Biological Chemistry
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• v.41 no.1
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• pp.23-30
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• 1998

The cryIB, truncated cryIB$[cryIB({\alpha})]$, cryIA(b), and cytA genes, encoding 135-, 89-, 131-, and 27-kDa proteins, respectively, from Bacillus thuringiensis were cloned into a shuttle vector pBES and expressed in E. coli and Bacillus species. The morphology and solubility in alkaline buffer of the insecticidal crystal proteins were investigated. Transformation of intact cells of E. coli and Bacillus species was achieved by electroporation. High field strength of 11.0 kV/cm and resistance of 129 ohms were required for efficient transformation of E. coli strains and 4.5 kV/cm and 48 ohms for Bacillus species. Strains of recombinant E. coli and Bacillus species produced the insecticidal crystal proteins and accumulated as the same bipyramidal and irregular structures as those of CryIB and IA(b) and CytA of B. thuringiensls, respectively. The insecticidal crystal proteins accumulated in recombinant E. coli wire smaller in size than those in recombinant Bacillus species. The solubility in alkaline buffer of the insecticidal crystal proteins of recombinant E. coli increased gradually as the pH increased, whereas in the case of Bacillus species the solubility increased gradually as the pH increased up to 9 and then the solubility increased greatly up to two times higher than that of E. coli proteins.

• Geomechanics and Engineering
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• v.15 no.5
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• pp.1081-1089
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• 2018

The deformation and strength of brittle rocks are significantly influenced by the crack closure behavior. The relationship between the strength and deformation of rocks under uniaxial loading is the foundation for design and assessment of such scenarios. The concept of relative crack closure strain was proposed to describe the influence of the crack closure behavior on the deformation and strength of rocks. Considering the crack compaction effect, a new damage constitutive model was developed based on accumulated AE counts. First, a damage variable based on the accumulated AE counts was introduced, and the damage evolution equations for the four types of brittle rocks were then derived. Second, a compaction coefficient was proposed to describe the compaction degree and a correction factor was proposed to correct the error in the effective elastic modulus instead of the elastic modulus of the rock without new damage. Finally, the compaction coefficient and correction factor were used to modify the damage constitutive model obtained using the Lemaitre strain equivalence hypothesis. The fitted results of the models were then compared with the experimental data. The results showed that the uniaxial compressive strength and effective elastic modulus decrease with an increase in the relative crack closure strain. The values of the damage variables increase exponentially with strains. The modified damage constitutive equation can be used to more accurately describe the compressive deformation (particularly the compaction stage) of the four types of brittle rocks, with a coefficient of determination greater than 0.9.

• Microbiology and Biotechnology Letters
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• v.2 no.3
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• pp.141-147
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• 1974

The cultural conditions for L-glutamate production were investigated using Brevibacterium flavum nov. sp. D2209B, the most productive strain among 5 strains reported in preceeding paper. A temperature of 3$0^{\circ}C$ and a medium volume of 30 ml per 500-flask were selected as standard culture conditions. And the following results were obtained. 1. When the concentration of acetate in the medium was below 30 g per litre, the maximum amount of L-glutamate was accumulated. 2. KH$_2$PO$_4$, MgSO$_4$, FeCI$_3$ and MnCI$_2$ were required for the L-glutamate poduction, but the concentration of those inorganic salts little effected. 3. Signifcant amount of L-glutamate was accutnulated in the limited biotin concentration less than 0.3 ug per litre. 4. The addition of malic acid or succinic acid enhanced the accumulation. 5. The L-glutamate accumulation was related to the incubation time of seed; the amount of L-glutamate accumulated was maximum by inoculating 16-20 hour incubated seed. 6. In the medium containing sufficient amount of biotin for growth, L-glutamate accumulation was stimulated by the addition of penicillin at appropreate time during incubation.

• Geomechanics and Engineering
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• v.34 no.5
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• pp.577-595
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• 2023

A dynamic triaxial discrete element numerical model of lightweight soil was established using the discrete element method to study the microscopic mechanism of expanded polystyrene (EPS) particles in the soil under cyclic loading. The microscopic parameters of the discrete element model of the lightweight soil were calibrated depending on the dynamic triaxial test hysteresis curves. Based on the calibration results, the effects of the EPS particles volume ratio and amplitude on the contact force, displacement field, and velocity field of the lightweight soil under different accumulated strains were studied. The results showed that the hysteresis curves of lightweight soil exhibit nonlinearity, hysteresis, and strain accumulation. The strain accumulated in remolded soil is mainly tensile strain, and that in lightweight soil is mainly compressive strain. As the volume ratio of EPS particles increased, the contact force first increased and then decreased, and the displacement and velocity of the particles increased accordingly. With an increase in amplitude, the dynamic stress of the particle system increased, and the accumulation rate of the dynamic strain of the samples also increased. At 5% compressive strain, the contact force of the particles changed significantly and the number of particles deflected in the direction of velocity also increased considerably. These results indicated that the cemented structure of the lightweight soil began to fail at a compressive strain of 5%. Thus, a compressive strain of 5% is more reasonable than the dynamic strength failure standard of lightweight soil.

• Journal of the Korean Geotechnical Society
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• v.40 no.3
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• pp.65-75
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• 2024

This study investigates liquefaction-induced settlement through strain-controlled tests using a cyclic direct simple shear device on clean sand specimens. By focusing on the accumulated shear strain, soil density, sample preparation method, and cyclic waveshape, this study attempts to enhance the understanding of soil behavior under seismic loading and its further deformation. Results from tests conducted on remolded samples reveal insights into excess pore water pressure development and post-liquefaction volumetric strain behavior, with denser samples exhibiting lower volumetric strains than looser samples. Similarly, the correlation between the frequency and amplitude variations of the wave and volumetric strain highlights the importance of wave characteristics in soil response, with shear strain amplitude changes, varying the volumetric strain response after reconsolidation. In addition, samples prepared under moist conditions exhibit less volumetric strain than dry-reconstituted samples. Overall, the findings of this study are expected to contribute to predictive models to evaluate liquefaction-induced settlement.