• The Journal of the Korean Society for Microbiology
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• v.22 no.2
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• pp.131-137
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• 1987

The incidnce of enterotoxigenic Esherichia coli(ETEC) was investigated in E. coli strains isolated from Korean infants less than two years old. Over a period of 12 months, ETEC strains have been isolated from 45(45.0%) of 100 children with acute diarrhea and from 9(20.5%) of 44 children without diarrhea. In the group with diarrhea, 41(41.0%) strains produced heat-stable toxin, 3(3.1%) produced heat-labile toxin, and 1(1.0%) produced both heat-stable and heat-labile toxins. In the control group, 7(15.9%) released heat-stable toxin, 2(4.5%) released heat-labile toxin and none released both. A statistical association of strains releasing heat-stable toxin was significant(P<0.025).

• The Journal of the Korean Society for Microbiology
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• v.20 no.1
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• pp.55-63
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• 1985

Phosphate, ammonia, glucosamine, glucose, pyruvate, succinate, fumarate, malate and acetate were examined for their ability to control the heat-stable enterotoxin (ST) production in succinate salts medium or in M9 medium. The results obtained were summerized as follows. 1. When the initial phosphate concentration was adjusted to 1.0mM, ST production was decreased to 80u/ml or less. But when the initial phosphate concentration was adjusted to 64mM or 100mM, enterotoxin production was 320u/ml. 2. When the initial ammonia concentration in the medium was adjusted to 1.0mM, no ST production and cell growth were observed. But when ammonia concentration was adjusted to 10mM, 19mM, 38mM or 76mM, enterotoxin production was 320u/ml. 3. Among carbon sources, glucosamine, glucose, pyruvate, succinate, fumarate, malate and acetate, acetate supported the highest specific production (928 unit/O.D.) of heat-stable enterotoxin. From this results, we could assume that heat-stable enterotoxin production is controlled by stringent control mechanism. 4. When the pH of the succinate salts medium was kept between 6.2 to 6.5, no heat-stable enterotoxin production was observed, but when the pH of the medium was kept between pH 6.2 to 6.5, 267 unit/O.D. of heat-stable enterotoxin was produced. 5. Glucose inhibited the heat-stable enterotoxin production and the mechanism was assumed due to its capacity to lower the pH of the medium during catabolysis and its high metabolic energy.

• BMB Reports
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• v.41 no.2
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• pp.108-111
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• 2008

Some proteins of E. coli are stable at temperatures significantly higher than $49^{\circ}C$, the maximum temperature at which the organism can grow. The heat stability of such proteins would be a property which is inherent to their structures, or it might be acquired by evolution for their specialized functions. In this study, we describe the identification of 17 heat-stable proteins from E. coli. Approximately one-third of these proteins were recognized as having functions in the protection of other proteins against denaturation. These included chaperonin (GroEL and GroES), molecular chaperones (DnaK and FkpA) and peptidyl prolyl isomerases (trigger factor and FkpA). Another common feature was that five of these proteins (GroEL, GroES, Ahpc, RibH and ferritin) have been shown to form a macromolecular structure. These results indicated that the heat stability of certain proteins may have evolved for their specialized functions, allowing them to cope with harsh environments, including high temperatures.

• Journal of Environmental Science International
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• v.10 no.5
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• pp.329-336
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• 2001

Characgcteristics of nocturnal boundary layer(NBL) were analyzed by the upper-air observations data using with the airsonde and pilot balloons from 1994 to 1999 in Kyungpook province. The automate weather boundary layer can become stably stratified when the surface is cooler than the air. Stable nocturnal boundary layer height were estimated from the top of surface stable layer where the vertical gradient of temperature and mixing ratio tend to zero or negative. The depth of the stable nocturnal boundary layer depended largely on the thermal effect rather than the wind effect at nighttime. The NBL was more developed on the land than on the coastal region. The stability index (bulk Richardson number) showed that the NBL was stable when the wind was weak and the vertical gradient of the temperature was strong. The heat budget in the NBL was studied by considering the effect of the radiative and the cooled by both the longwave radiative flux and the divergence of the heat flux, while NBL under the cloudy sky the longwave radiative flux played a role of the warming. It was noted that the heat was not conserved in both cases. To complete the heat budget in the NBL the warming/cooling by advection and subsidence must be considered.

• Communications of the Korean Mathematical Society
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• v.33 no.3
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• pp.1025-1037
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• 2018

We consider an ill-posed problem for the heat equation $u_{xx}=u_t$ in the quarter plane {x > 0, t > 0}. We propose a new method to compute the heat flux $h(t)=u_x(1,t)$ from the boundary temperature g(t) = u(1, t). The operator $g{\mapsto}h=Hg$ is unbounded in $L^2({\mathbb{R}})$, so we approximate h(t) by $h_{\delta}(t)=u_x(1+{\delta},\;t)$, ${\delta}{\rightarrow}0$. When noise is present, the data is $g_{\epsilon}$ leading to a corresponding heat $h_{{\delta},{\epsilon}}$. We obtain an estimate of the error ${\parallel}h-h_{{\delta},{\epsilon}}{\parallel}$, as well as the error when $h_{{\delta},{\epsilon}}$ is approximated by the trapezoidal rule. With an a priori choice rule ${\delta}={\delta}({\epsilon})$ and ${\tau}={\tau}({\epsilon})$, the step size of the trapezoidal rule, the main theorem gives the error of the heat flux as a function of noise level ${\epsilon}$. Numerical examples show that the proposed method is effective and stable.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.5
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• pp.1300-1307
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• 1995

The effect of thermal stratification on the turbulent dispersion from a fine cylindrical heat source was experimentally examined in a wind tunnel with and without a strong temperature gradient. A 0.5 mm dia. nichrome wire was used as a line heat source. Turbulent intensities, r.m.s. value of temperature and convective heat fluxes were measured by using a hot-wire and cold-wire combination probe. The results show that the peack value and the spread of the vertical turbulent intensity for the stratified case are far lower than those in the neutral case, which indicates that the stable temperature gradient suppresses the vertical velocity component. All of the third order moments including heat fluxes measured in the stable condition have very small values than those of the neutral case. This nature suggests that the decrease of scalar fluctuations in the stably stratified flow is mainly due to the suppression ofthe turbulent diffusion processes by the stable stratification. A simple gradient model with a composite timescale which has a simple weighted algebraic mean between dynamic and thermal time scale yields reasonably good numerical values in comparison with the experimental data.

• Applied Chemistry for Engineering
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• v.31 no.5
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• pp.575-580
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• 2020

In this study, we simulated an amine regeneration process with heat-stable salts removal unit. We derived the optimal operating conditions considering the flow rate of waste, the removal rate of heat-stable salts, and the loss rate of MDEA (methyl diethanolamine). In the amine regeneration process that absorbs and removes acid gas, heat-stable salt impairs the absorption efficiency of process equipment and amine solution. An ion exchange resin method is to remove heat-stable salts through neutralization by using a strong base solution such as NaOH. The acid gas removal process was established using the Radfrac model, and the equilibrium constant of the reaction was calculated using Gibbs free energy. The removed amine solution is separated and flows to the heat-stable salts remover which is modeled by using the Rstoic model with neutralization reaction. Actual operation data and simulation results were compared and verified, and also a case study was conducted by adjusting the inflow mass of removal unit followed by suggesting optimal conditions.

• Korean Journal of Veterinary Research
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• v.37 no.4
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• pp.779-784
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• 1997

A comprehensive study of 132 Escherichia coli isolates from 150 piglets with colibacillosis included detection of heat-labile enterotoxin, heat-stable enterotoxin, and identification of K88 (F4), K99 (F5), 987P (F6), and F41. Four pili were examined by haemagglutination and slide agglutination test. Heat-labile(LT) and heat-stable(ST) enterotoxin was determined by reverse passive latex agglutination and precipitation test, respectively. Among 132 E coli isolates, 26 had K88 (19.7%), 16 had K99 (12.1%), 3 had 987P (2.3%), and 2 had F41 (1.5%). Three had K88 and K99 (2.3%), 3 had K88 and 987P (2.3%), 2 had K99 and 987P (1.5%), 5 had K99 and F41 (3.8%), and 8 E coli strains had K88, K99 and F41 (6.1%) simultaneously. Among 132 E coli isolates, 5 produced LT only (3.8%), 55 produced heat-stable toxin ST only (41.7%), and 4 produced both LT and ST (3.0%). Three major pathotypes accounted for 27.9% of E coli isolates: $K99^+$ (8.3%), $K88^+ST^+$ (9%) and $K88^+$ (10.6%). Results of this study indicated that piliated enterotoxin-producing E coli was prevalent and was associated with diarrhea in preweaning piglets.

• Journal of Powder Materials
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• v.12 no.1
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• pp.36-42
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• 2005

Four different mechanical alloying(MA) processes were employed to fabricate very fine intermetallic compound $Al_3Zr$ particles dispersed Al composite materials(MMC) with Al-4at.%Zr composition. Phase transformations including phase stability during MA and heat treatment processes were investigated. Part of Zr atoms were dissolved into Al matrix and part of them reacted with hydrogen produced by decomposition of PCA(methanol) to form hydride $ZrH_2$ during first MA process. These $ZrH_2$ hydrides disappeared when alloy powders were heat treated at $500^{\circC}$. Stable $Al_3Zr$ dispersoids with $DO_23$ structure were formed by heat treating the mechanically alloyed powders at $400^{\circC}$. On the other hand, metastable $Al_3Zr$dispersoids with $L1_2$ structure were formed during first MA of powers with Al-25at.%Zr composition. These metastable $Al_3Zr$ dispersoids transformed to stable $Al_3Zr$ with $DO_23$ structure when heat treated above $450^{\circC}$.

• Journal of the Korean Society of Food Science and Nutrition
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• v.20 no.6
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• pp.621-628
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• 1991

Heat-stable enterotoxin(ST) from enterotoxigenic E. coli eKT-53($ST^{+}\;LT^{-}$, transformant from isolate KM-7) that was produced in succinate salts medium. The culture supernatant(crude ST) was purifed by mulitpled steps and investigated some characterization of the ST. The heatstability of purified ST activity was completely lost by treating at $100^{\circ}C$ for 30minutes. ST activity was lost by treatment at pH 1 and 12 conditions, while the activity was not reduced by treatment at pH 2~10, and then the ${\alpha}-amylase$ and pepsin was not decreased activity but disulfide reducing agnets was lost the activity. The molecular weight of the purified ST was approximately 4,200, the isoelectric point was about 4.0.