• 대한전기학회논문지
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• 제34권5호
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• pp.186-192
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• 1985

Co2O3 additive effects on the electrical properties in ZnO varistor are investigated. As the Co Cations being substituted and ionized normally to a divalent state for Zn in the lattice site increase, the leakage current in the prebreakdown region decreases and the so-called

• 한국재료학회:학술대회논문집
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• 한국재료학회 1998년도 IUMRS-ICEM ABSTRACT BOOK
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• pp.91.2-91
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• 1998

• Environmental Engineering Research
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• 제22권1호
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• pp.61-74
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• 2017

This study investigated the effect of various cations ($Ca^{2+}$, $Mg^{2+}$, $Al^{3+}$, $Mn^{2+}$, $Zn^{2+}$) on the autoaggregation (AAg) and surface hydrophobicity (SHb) of three different bacteria (Brevibacillus panacihumi strain (ZB1), Lysinibacillus fusiformis strain (ZB2) and Enterococcus faecalis strain (ZL)) using a 2-level factorial design. The AAg ratio was measured from the changes in the absorbance of the media. Results show that ZB2 had maximum AAg for the three bacteria investigated. A microscopic clustering of cells was observed when $Ca^{2+}$ was added to ZB2. The AAg was in the range of 62%, 58% and 34% for ZB2, ZB1 and ZL, respectively and correlated to the SHb. The aggregation and SHb of the microbial cells increased with increasing ionic strength due to the repulsive steric or overlap forces between the polymer covered surfaces. $Ca^{2+}$ demonstrated a more significant effect on aggregation and SHb of microbial cells due to an attractive binding force.

• 한국환경과학회지
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• 제22권10호
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• pp.1273-1278
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• 2013

Novel rhodamine 6G fluorescent chemosensors 1 and 2 for the detection of transition metal cations were synthesized through the condensation of rhodamine 6G ethylenediamine with each of 2-hydroxy-1-naphthaldehyde and 2,6-pyridinedicarbaldehyde, respectively. 1 and 2 were characterized using $^{13}C$ NMR, $^1H$ NMR and mass spectroscopy. Fluorometric and colorimetric measurements involving various metal ions revealed the ring opening of the rhodamine 6G spirocycle framework. In the absence of metal cations, 2 was colorless and non-fluorescent, whereas the addition of metal cations ($Hg^{2+}$ and others) changed the color to pink, accompanied by the appearance of an orange fluorescence. The chemosensors exhibited high selectivity for $Hg^{2+}$ over other divalent first-row transition metals. The complexes of $Hg^{2+}$ with 1 and 2 were successfully isolated. A huge enhancement in the fluorescence for both one- and two-photon excitations makes these compounds suitable candidates to be used for fluorescent labeling of biological systems.

• Bulletin of the Korean Chemical Society
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• 제32권12호
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• pp.4316-4320
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• 2011

The effects of various hydroxide compounds on base stacking (BS) were investigated for pre-concentration of DNA molecules in capillary electrophoresis (CE). In BS, hydroxide ions ($OH^-$) were electrokinetically introduced after DNA sample injection. A neutralization reaction occurred between the $OH^-$ and $Tris^+$ of the running buffer, which resulted in a zone of lower conductivity. Within the low conductivity zone of the high electric field, the DNA molecules moved more rapidly and were concentrated in front of the low conductivity zone. At the same BS conditions of CE, the enhanced sensitivity of the DNA samples was dependent on the kind of multivalent cations in the hydroxide compounds. Except for LiOH, the hydroxide compounds with monovalent cations showed more effective BS than those with divalent cations because of solubility, ionic strength and electronegativity. The order of hydroxide compounds that enhance the detection sensitivity of DNA molecules was as follows: NaOH > $NH_4OH$ > KOH > $Ba(OH)_2$ > $Sr(OH)_2$ > LiOH > $Ca(OH)_2$ > $Mg(OH)_2$. $NH_4OH$, KOH and $Ba(OH)_2$ proved to be efficient hydroxide compounds to use as effective BS reagents in CE instead of NaOH.

• Environmental Analysis Health and Toxicology
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• 제13권1_2호
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• pp.19-26
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• 1998

In Korea, fluoride was first introduced into the drinking water of residents of Jinhae, KyungNam in 1981 for the prevention of dental caries. Ever since, growing numbers of communities favor fluoridation. The mechanism of F prevention of tooth decay is well known: fluoride ions substitute for hydroxyl ions in hydroxyapatite of hard tissues, which result in crystal perfection, with consequent reduction in dental caries. Soluble fluorides such as sodium fluoride are almost completely absorbed from the gastrointestinal tract. However, the presence of divalent or trivalent cations such as aluminum, magnesium, and calcium that can complex with F can reduce the degree of absorption. In U.S.A., over 7000 communities are now adding F to their drinking water. However, some portion of population oppose fluoridation, voicing both concern about the safety of fluoridation as well as for personal choice. Thus, This paper reviews the interaction of fluoride and cations as well as fluoride and suggests possible problems associated with fluoridation, a controversial issue.

• 한국조리학회지
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• 제20권2호
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• pp.54-64
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• 2014

레토르트 처리한 양파의 조직감(견고성)을 향상시키기 위하여 칼슘용액에서 장시간 저온(LTLT)블랜칭을 실시하였다. 칼슘용액에서 예비 열처리한 양파는 일반적인 블랜칭과 비교시 고온 멸균한 후 양파의 조직감이 의미있게 향상되었다. LTLT 블랜칭에 의한 견고성의 향상은 양파 조직의 pectin methylesterase(PME) 작용으로 carboxyl 그룹과 2가 양이온($Ca^{2+}$)간의 강한 가교결합과 관련이 있다. 0.5% 칼슘용액에서 $70^{\circ}C$, 120분동안 예비 열처리를 행하였을 때 가장 높은 견고성을 가진 레토르트 처리된 양파를 얻을 수 있었다. 이 같은 결과는 양파에서 PME의 활성도와 결합된 칼슘의 함량이 $70^{\circ}C$에서 가장 높았다는 것을 의미한다. 또한, $Mg^{2+}$와 같은 여러 2가 양이온을 함유하고 있는 알칼리 계통 칼슘이 펙틴 분자를 상온에서 가수분해하는 기작이 효소 작용에 더해져 여러 칼슘용액 중에서 레토르트 처리된 양파의 조직감을 가장 견고하게 하였다. 향후 여러 가지 레토르트 처리된 야채들의 조직 연화 방지를 위한 최적조건 실험이 야채별로 더 많이 수행되어야 할 것이다.

• 한국의학물리학회지:의학물리
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• 제17권2호
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• pp.96-104
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• 2006

본 연구자를 위시한 많은 연구자에 의해 칼슘이 N형 칼슘통로의 비활성화를 촉진시킨다는 것이 보고되었다. 그러나 칼슘에 의한 비활성화 촉진 효과가 고전적인 칼슘의존성 기전에 의해 기인하는지는 아직 확실하지 않다. L형 칼슘통로의 칼슘의존성 비활성화기전을 밝히기 위하여 지금까지 사용해온 방법의 하나는 세포내, 외의 칼슘농도를 변화시켜보는 것이다. 그러므로 본 연구에서는 칼슘의존성 비활성화기전의 존재 여부를 알아보기 위하여 2가 양이온을 1가 양이온인 메틸아민($MA^+$)으로 치환하였다. 선행 연구를 통해 우리는 5초 동안의 긴 저분극 자극 시 바륨과 칼슘을 사용하여 얻은 전류에서 모두 빠른 성분(${\tau}{\sim}150ms$)과 느린 성분(${\tau}{\sim}2,500ms$)의 비활성화가 있음을 알 수 있었다. 본 연구에서 세포외 2가 양이온의 농도가 0이 되도록 하였을 때 빠른 비활성화가 소실된 반면 느린 비활성화에는 영향이 거의 없었다. 또한 바륨를 사용하였을 때보다 10 mV씩 과분극시킨 전압에서의 메틸암모늄 전류 데이터를 비교하여 보았을 때 느린 비활성화의 시정수가 서로 잘 일치하였으며 이 시정수는 막전압이 저분극될수록 감소하는 막전압의존성 비활성화의 특성을 보였다. 본 연구결과와 선행연구의 결과를 종합하여 볼 때 세포외 2가 양이온의 존재는 N형 칼슘통로의 빠른 비활성화가 일어나기 위하여 필수적인 조건이며 이러한 2가 양이온의존성 비활성화기전은 기존의 칼슘의존성 또는 막전압의존성 기전과 다르다는 가설을 제안한다.

• Applied Biological Chemistry
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• 제41권8호
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• pp.587-594
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• 1998

The objective of this research was to characterize effects of Cu or Cd additions on chemistry of soil quality indices, such as pH, EC, cation distribution and buffering capacity. Metals were added at rates ranging from 0 to 400 mg $kg^{-1}$ of soil. Soil solution was sequentially extracted from saturated pastes using vacuum. Concentrations of Cu or Cd remaining in soil solutions were very low as compared to those added to the soils, warranting that most of the added metals were recovered as nonavailable fractions. Adsorption of the added metals released cations into soil solution causing increases of ionic strength of soil solution. At metal additions of $200{\sim}400\;mg\;kg^{-1}$, EC of soil solution increased to as much as $2{\sim}4\;m^{-1}$; salinity levels considered high enough to cause detrimental effects on plant production. More divalent cations than monovalent cations were exchanged by Cu or Cd adsorption. The nutrient buffering capacity of soils was decreased due to the metal adsorption and release of cations. pH of soil solution decreased linearly with increasing metal loading rates, with a decrement of up to 1.3 units at 400 mg Cu $kg^{-1}$ addition. Influences of Cu on each of these soil quality parameters were consistently greater than those of Cd. These effects were of a detrimental nature and large enough in most cases to significantly impact soil productivity. It is clear that new protocols are needed for evaluating potential effects of heavy metal loading of soils.

• 자원환경지질
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• 제28권3호
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• pp.231-241
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• 1995

It is well known that hydroxyapatite [$Ca_{10}(PO_4)_6(OH)_2$] have an exchangeability for various heavy metal ions in aqueous solution. To evalute the feasibility of employing the synthetic hydroxyapatites as an eliminatable exchanger for environmentally noxious caions in waste water, the adsorption properties, the removal capacities and the selectivity of the apatites for various cations were investigated in more detailed. The heavy metal cations have been exchanged in calcium part of hydroxyapatite. The order of the degree of amount exchanged of the investigated cations is $Pb^{2+}>Cd^{2+}>Zn^{2+}>Ba^{2+}$. The molar ratios between released $Cd^{2+}$ ions and remeved divalent metal cations in the reacted solution with hydroxyapatite are roughly close to an integer 1.0, suggesting that an ion-exchange reaction could have played a major role in the removal of heavy metals rather then an adsorption effect. The exchangeability of the hydroxyapatite powder of Ca/P molar ratio 1.67, which have specipic surface area of $104.5m^2g^{-1}$, appeared to be better then $237.6{\mu}g$ per g for $Pb^{2+}$ ions. The removal capacity of the heavy metal ions varies directly as particle size of hydroxyapatites. All evidences obtained indicate that the synthesized hydroxyapatite powders by precipitation reaction method can be employed as an effective cation exchanger for eliminating noxious ions in waste water even in some improvemental.