• Journal of Microbiology
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• 제39권2호
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• pp.109-115
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• 2001

Salmonella typhimurium possesses a cad operon, which contributes to an adaptive response against an acidifying environment. In Escherichia coli, the activation of the cad operon is dependent on cadC, which is located upstream of the operon. However, the activator of cad operon in S. typhimurium has not been known until now. In this study, we selected a putative cadC mutant by trasposon mutagenesis and cloned the cadc of S. typhimurium. Moreover, the cadC mutant was complemented by cadC clone. The cadC gene from S. typhimurium LT-2 consists of 1539 bp encoding a polypeptide ob 512 amino acids, and shows sequence similarity to cadC of E. coli with 53% identity and 67% similarity. The hydrophobicity profile of th S. typhimurim CadC sequence is very similar to E. coli CadC.

• 한국대기환경학회지
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• 제15권4호
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• pp.393-402
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• 1999

Precipitation samples were collected by the wet-only sampling method in Iksan in the northwest of Chonbuk from March 1995 to February 1997. These samples were analyzed for the concentration of ion components, in addition to pH and electrical conductivity. The annual mean pH of precipitation was 4.8 and the seasonal trend of pH was shown to be low in Fall and Winter(4.5), middle-ranged in Spring(4.7) and high in Summer(5.0). The frequency of pH below 5.6 was about 71%. The seasonal pattern of pH frequency was found to be different in each season. In the case of the pH less than 5.0, the frequency was higher in Spring, Fall and Winter than in Summer, especially higher in Fall than in other seasons. The concentrations of analysed ions showed a pronounced seasonal pattern. However, major ion species for all seasons were $NH^+_4,;Ca^{2+};and;Na^+$ among cations and $SO^{2-}_4,;Cl^-;and;NO^-_3$ among anions. The major acidifying species appeared to be $nss-SO^{2-}_4;and;NO^-_3$, and the main bases responsible for the neutralization of precipitation acidity were $nss-Ca^{2+};and;NH^+_4$. The potential acidity of precipitation, pAi, was found to be between 3.0 and 5.0 for total samples, while the measured pH was approximately between 3.9 and 7.8. The seasonal trend of pAi showed a decreasing order: Summer (4.3), Winter(4.0), Spring and Fall(3.8). During the Fall, both pAi and pH were especially very low, which indicated that during this period the potential acidity of precipitation was high but the neutralizing capacity was low. For Spring, pAi was very low but pH was slightly high. This was likely due to the large amount of $CaCO_3$ in the soil particles transported over a long range from the Chinese continent that were incorporated into the precipitation, and then neutralized the acidifying species with its high concentraton.

• 한국식품조리과학회지
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• 제11권2호
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• pp.104-107
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• 1995

This study was attempted to simplify the complex steeping mechanism and propose the scientific approach of microorganism. As Enzyme activity showed that as steeping hours increase, the а-amylase activity increased. Most commonly microorganisms in steeping liquid were Corynebacter spp., Candida spp. and Lactobacillus spp. According to results, steeping acidifies the character of glutinous rice, affec-ting the starch's n-amylase and bring about component's changes. As Candide spp. and Lactobaillus spp. of the steeping liquid increase, the character of liquid is acidifying.

• 약학회지
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• 제8권2호
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• pp.45-47
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• 1964

Two new orotic acid derivatives orotyl-DL-alanine and orotyl-L-tyrosine were synthesized. They were obtained as high melting crystalline masses by condensing DL-alanine and L-tyrosine each with orotyl chloride in aqueous sodium hydroxide solution, followed by acidifying the reaction mixture.

• 한국환경보건학회지
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• 제19권4호
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• pp.44-50
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• 1993

This paper has concentrated on estimating the improvement of sludge dewaterability for the application of ozone in sewage treatment plant sludge. The experiment for the study was conducted by batch reactor, contacting ozone (5.0 g O$_3$/hr/l) to waste sludge and measured the Specific Resistance to Filtrate (SRF) varying pH, pressure and reaction time of ozone. And then checked the dissolved solids concentration of flitrate. The results of experiment were as follows: 1. When the total solids concentration of excess sludge was 9, 000 mg/l, the optimum injection rate of ozone was 5.0 g O$_3$/hr/l, and then pressure was 50 cm Hg for the measuring SRF. 2. In the range of pH 3~5, the effect of ozone injection was excellent, but it was unsatisfactory in the range of pH 9~11. Therefore, the ozone injection by acidifying pH level was effective in improving the dewaterability of sludge. 3. It was estimated that the dissolved solids concentration of flitrate was increased in proportion to the injection rate of ozone.

• Bulletin of the Korean Chemical Society
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• 제18권12호
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• pp.1269-1273
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• 1997

The system which employs iron, palladium, molecular oxygen and hydrogen as a model mono-oxygenase, has been investigated to develop a new method for selective cyclohexane oxidation uner mild conditions. This system provides much higher yield and selectivity for the formation of cyclohexanol and cyclohexanone compared to that of the existing industrial method. When the catalytic system, FeCl2-Pd/alumina, was employed, the oxidation system required acetone as a solvent to be efficient and acidifying the solvent by a little addition of acetic acid or HCl made the system more efficient. The Pd catalyst was recyclable without a significant deactivation but the recycling of ferrous chloride showed the decrease in the activity. On the other hand, the heterogeneous catalytic system, Pd/Fe2O3 could be recovered easily and reused after drying treatment.

• 한국대기환경학회지
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• 제27권5호
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• pp.603-613
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• 2011

The collection of $PM_{10}$ and $PM_{2.5}$ samples was made at Gosan site of Jeju Island. Their ionic compositions of both inorganic and organic phases were then analyzed to examine their acidification and neutralization characteristics in atmospheric aerosols. The mass concentrations of $PM_{10}$ and $PM_{2.5}$ at Gosan site were $37.6{\pm}20.1$ and $22.9{\pm}14.3{\mu}g/m^3$, respectively, showing the content ratio of $PM_{2.5}$ to $PM_{10}$ as 61.0%. In the evaluation of ionic balance, the correlation coefficients (r) between the sums of cationic and anionic equivalent concentrations were excellent with 0.982 ($PM_{10}$) and 0.991 ($PM_{2.5}$). The concentration ratios of $PM_{2.5}/PM_{10}$ derived for nss-$SO_4^{2-}$, $NO_3^-$, and $NH_4^+$ were 0.94, 0.56, and 1.02, respectively, indicating the relative dominance of fine fractions. The acidifying capacity of inorganic anions ($SO_4^{2-}$ and $NO_3^-$) in $PM_{10}$ and $PM_{2.5}$ were 96.5% and 97.3%, while those of organic anions ($HCOO^-$ and $CH_3COO^-$) in each fraction were 2.9% and 2.0%, respectively. On the other hand, the neutralizing capacity of $PM_{10}$ and $PM_{2.5}$ by $NH_3$ were 72.8% and 82.3%, while their $CaCO_3$ counter parts were 22.5% and 13.3%, respectively.

• 한국대기환경학회지
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• 제20권3호
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• pp.381-396
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• 2004

In order to understand the precipitation acidity and chemical composition of ion species in Iksan area as well as to know the difference of chemical characteristics in precipitation samples from the viewpoint of precipitation sampling method, precipitation samples were collected by wet-only automatic precipitation sampler and bulk manual precipitation sampler in Iksan, from March 2003 to August 2003. The mean pH of precipitation was 5.0. There was a little significant difference in the mean value of pH between automatic and manual sampler. However, pH values of some precipitation samples were lower in automatic sampler than in manual sampler, especially in case of precipitation samples with small rainfall for March 2003. The mean concentrations of each ions in precipitation were generally a little higher in precipitation samples collected by the manual sampler than in those collected by the automatic sampler because of accumulation of dry deposition on the surface of glass funnel installed at the manual sampler during the sampling period or no rainfall. Dominant species determining the acidity of precipitation, were N $H_4$$^{[-10]}$ and nss-C $a^{2+}$ for cations and nss-S $O_4$$^{2-}$ and N $O_3$$^{[-10]}$ for anions. The mean concentration of N $H_4$$^{+}$ and nss-C $a^{2+}$ were 31 $\mu$eq/L and 9 $\mu$eq/L for the automatic sampler and 40 ueq/L and 16 ueq/L for the manual sampler, respectively. In addition, nss-S $O_4$$^{2-}$ and N $O_3$$^{[-10]}$ were 27 $\mu$eq/L and 13 $\mu$eq/L for the automatic sampler and 32 $\mu$eq/L and 17 $\mu$eq/L for the manual sampler, respectively. Although the concentrations of the acidifying ions of nss-S $O_4$$^{2-}$ and N $O_3$$^{[-10]}$ were about 3 times higher than those for foreign pristine sites, precipitation acidity were estimated to be natural due to the neutralization reaction of the alkaline species of N $H_4$$^{+}$ and nss-C $a^{2+}$ with its higher concentrations. Considering the ratios of nss-S $O_4$$^{2-}$/N $O_4$$^{[-10]}$ nss-S $O_4$$^{2-}$, it was found that ammonium sulphate was dominant in Iksan precipitation. The major non-sea salt ions were maximum concentrations for March, but decreased with increasing of precipitation amount.on amount.

• 한국대기환경학회지
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• 제8권2호
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• pp.121-127
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• 1992

This study was carried out to investigate the features of air pollutants in rainwater and trace their transported trajectories from other countries. Chemical analysis data of rainwater and suspended particulates collected at Seoul, Kanghwa, and Taean for three years were used to evaluate the effects of long-range transport of air pollutants. Scavenging theory on washout and rainout effect during a rainy period was applied to estimate whether pollutants in the precipitation were long-range transported or not. On the other hand, precipitation weighted surface wind were evaluated to analyze the effect from local sources on atmospheric concentrations. As a result, contribution of air pollutants caused by anthropogenic sources in the precipitation which was identified to be long range transported was confirmed significantly high and trajectory of these pollutants was to be equivalent to 850mb isobar. Although concentration of acidifying components increased in the precipitation, neutralization by alkaline soil components such as $Ca^{2+}$ and $Mg^{2+}$ was conspicuous especially during Yellow-sand period.

• Elastomers and Composites
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• 제14권1호
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• pp.7-12
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• 1979

Graft copolymerization of methlymethacrylate(MMA) onto sodium alginate(SA) aqueous solution by sodium metaperiodate$(NaIO_4)$ as an initiator was carried out with the variation of the reaction time, the reaction temperature and the concentrations of initiator and monomer. The results obtained were as follows: 1. SA was easily separated from the reaction mixture of homopolymer, graft polymer and sodium alginate ungrafted by the treatment of concentrated boiling $Na_3PO_4$, solution with the small amount of $Na_2SO_3$ to the mixture and then isolated as the acid form by acidifying the salts solution containing SA. 2. The amount of graft polymer was larger than that of homopolymer below $70^{\circ}C$ whereas above $70^{\circ}C$ the amount of homopolymer was larger. 3. The sum of each amount of graft polymer ana homopolymer was always increased with increase of the reaction time, the reaction temperature and the concentrations of initiator and monomer. 4. With increase of the concentration of initiator, the graft efficiency was increased below $70^{\circ}C$ while decreased above $70^{\circ}C$. 5. Graft copolymerization of MMA onto SA in aqueous solution was carried out without initiator.