• 한국자기공명학회논문지
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• 제26권4호
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• pp.40-45
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• 2022

A small cage-like molecule (2) composed of three aminomethyl pyrroles and two hexa-substituted benzenes has been prepared by reduction of its iminopyrrole analogue (1) using NaBH₄. It was revealed by ¹H NMR spectroscopic analyses that cage molecule 2 strongly binds the fluoride anion in polar DMSO-d₆ relative to CDCl₃. Compared to that of compound 1, the lowered affinity of 2 for the fluoride anion is attributable to its increased electron density resulting from the production of thesecondary amine groups.

• International Journal of Industrial Entomology and Biomaterials
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• 제8권2호
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• pp.151-159
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• 2004

A detailed evaluation of relative toxicity of fluoride to die 5th instar larvae of PM and NB$_4$D$_2$ races of silkworm and the effects of lethal, sublethal and prevailing levels of fluoride in groundwater on the growth, economic characters and fecundity of the silkworm, Bombyx mori (Lepidoptera: Bombycidae) were studied. The feeding of mulberry, Morus alba leaves treated with lethal and sublethal doses of fluoride to PM and NB$_4$D$_2$ races of silkworms from the beginning of the 5th instar to the end of the feeding period resulted in significant reduction in growth, single cocoon weight, single shell weight, silk index, average filament length, and fecundity when compared to controls. These manges were more pronounced on exposure to lethal dose than sublethal dose and in general, the changes induced by fluoride were more striking in NB$_4$D$_2$ than PM, indicating the greater resistance of PM to higher fluoride levels. Groundwater quality in sericulturally important villages of Karnataka and Andhra Pradesh States has been studied with special reference to the presence of fluoride. On exposure to dose of prevailing levels in the waters of sericulturally important areas, die changes observed on growth, economic characters and fecundity were slightly lower when compared to controls and the decrease was found to be insignificant (P$\geq$0.05). It was concluded that, though minute dose (4.0 ppm) of fluoride did not have any toxic impact, it is toxic at higher concentrations to silkworms.

• 한국치위생학회지
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• 제10권3호
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• pp.473-481
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• 2010

Objectives : To evaluate the effect of fluoride application on the color and microhardness of bleached enamel and compare it to that of casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) application. Methods : Twenty freshly extracted human adult molar were each sectioned into halves, the specimens divided and treated according to five experimental groups: Group 1, treatment with 10% carbamide peroxide (CP) bleaching agent; Group 2, treatment with 10% CP followed by a 1.23% fluoride gel application; Group 3, treatment with 10% CP followed by a 2.23% sodium fluoride varnish application; Group 4, treatment with 10% CP followed by a 0.11% sodium fluoride gel application; Group 5, treatment with 10% CP followed by a CPP-ACP gel application. All groups were treated 6 h per day for 14 days then immersed in distilled water for 2 weeks. Changes in enamel color were evaluated on Baseline and Day 14. Microhardness were evaluated on Baseline, Days 7 and 14. Statistical analysis was performed using one-way ANOVA and post-hoc Tukey tests. Results : All the bleached enamel specimens revealed increased whiteness and overall color value. Group 1 showed the lowest microhardness values than that of Groups 2, 3, 4 and 5. In all groups, the hardness of tooth after bleaching showed a significant decrease in the microhardness as compared with the one prior to tooth bleaching. The specimens treated with remineralizing agents showed relatively less reduction in enamel microhardness than control group. Conclusions : The addition of fluoride and CPP-ACP did not impede the whitening effect. The use of remineralizing agents during bleaching treatment can significantly enhance the microhardness of bleached enamel.

• 대한소아치과학회지
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• 제31권4호
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• pp.579-586
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• 2004

본 연구의 목적은 chlorhexidine(Cervitec)과 fluoride(Fluor-protector) 성분을 각각 포함한 varnish를 치아에 적용하였을 때 타액내의 mutans streptococci의 수의 감소에 미치는 효과를 알아보기 위한 것이다. 전북대학교 치과대학생 40명을 대상으로 하여 mutans streptococci 균종 수를 평가하였으며, 이들을 무작위로 네 군으로 나누어 다음과 같이 varnish를 적용하였다; A) varnish를 적용하지 않은 군(n=10), B) chlorhexidine varnish 적용군(n=10), C) fluoride varnish 적용군(n=10), D) chlorhexidine과 fluoride varnish를 모두 적용한 군(n=10). Mutans streptococci 수 측정에는 Orion diagnostica 사의 Dentocult SM을 사용하였다. Varnish를 적용하지 않은 상태에서 1차로 mutans streptococci 수를 측정한 후 각각의 varnish를 적용하였으며, varnish 적용 12주 후 다시 측정하여 기록하였다. 모든 실험군(group B, C, D)에서 12주 후에 측정한 mutans strepococci 수가 감소한 개체가 증가한 개체보다 많았으나 통계적으로 유의한 차이는 보이지 않았다(p>0.05). 실험에 사용된 어떠한 varnish도 적용 12주 후에 타액 내 mutans streptococci 수에 통계적으로 유의할 만한 변화를 주지는 못하는 것으로 나타났다(p>0.05).

• 대한치과의사협회지
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• 제16권8호통권111호
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• pp.619-624
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• 1978

The use of mouth-rinses containing sodium fluoride after tooth brushing has been proposed as a potentially useful measure for the prevention of dental caries in the practice of public health. About 700 middle school girls rinsed their mouths in the school once a week with sodium fluoride sodution after tooth-brushing. Tooth brushing was practiced everyday after meals and the rinses were carried out under the supervision of the teachers. The procedure consisted of gargling 10cc of fluoride solution for one minute and immediately followed by a second rinse with tap water. The rinsing was started in May 1976 and continued for one year. The results were as follows: 1) The inhibition of the 'D' Person rate was 76.04%, 'M' person rate was 80.79%, 'F' person rate was 4.06% and, 'D.M.F.' person rate was 76.86%. 2) the reduction of the 'D.T.' Index was 81.94%, 'M.T.' Index was 85.71%, 'F.T.' Index was 7.69% and, 'D.M.F.T.' Index was 76.83%. 3) Mouth rinsing with 0.3% NaF solution and tooth brushing are of value in the mass control of dental caries.

• Advances in environmental research
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• 제12권1호
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• pp.17-40
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• 2023

This article presents studies of the adsorption process in a continuous system of fluoride solutions at a concentration of 30 mg/L using a bone char packed in fixed-bed columns, as well as regeneration studies in the same system using HNO₃, HCl and NaOH at 0.01, 0.1 and 1 M. The Thomas Model, Artificial Neural Networks (ANNs), Numerical Integration and Mass Transfer Zone were used for the modeling of asyemmetrical breakthrough curves obtained from the fluoride adsorption on bone char. The maximum adsorption capacity of the breakthrough curves was estimated, and various design parameters of the columns were obtained for the different operating conditions. Results showed that an improvement in the modeling capabilities of the Thomas model can be obtained using ANNs. Moreover, ANNs are useful for determining reasonable and accurate design parameters of packed-bed adsorption columns. This modeling approach can be useful for the process system engineering of dynamic adsorption systems involved in the field of water treatment and purification. It is important to highlight that the obtained results indicate that, when using HCl or HNO₃ at a concentration of 0.1 M, a large number of adsorption-desorption cycles are obtained and, therefore, the highest values of adsorption capacity, which leads to a reduction in operation costs.

• 한국재료학회지
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• 제11권12호
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• pp.1047-1051
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• 2001

Purity tantalum powder has been produced by sodium reduction of potassium tantalum fluoride($K_2TaF_7$)in a stainless steel bomb. The influence of experimental variable, such as excess of reductant and temperature of reduction on the yield and quality of the Ta powder has been studied. The excesses of reductant were varied from -20%, -10%, 0%, 5%, 10%, 20%. When -20% excess of sodium was used, the un-reacted sodium remained in the reacted product. The yield of 81% of Ta powder has been achieved by reducing 50g of$K_TaF_7$with 5% sodium in excess of stoichiometric amount in presence of 16.8g of sodium chloride in the charge at a reduction temperature of$905{\circ}C$. The proportion of fine fraction(~325mesh) decreased appreciably with the increase of sodium excess, and the yield of tantalum powder improved from 65% to 94%. The average particle size of Ta Powder is improved from 3 microns to 4 microns in the 5% excess sodium.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 추계학술대회논문집
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• pp.714-717
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• 2007

In this study, a novel actuator was developed by employing the newly-synthesized ionic networking membrane (INM) of poly (styrene-alt-maleic anhydride) (PSMAn)-incorporated poly (vinylidene fluoride) (PVDF). Based on the same original membrane, various samples of INM actuator were prepared through different reduction times with the electroless-plating technique. The as-prepared INM actuators were tested in terms of surface resistance, platinum morphology, resonance frequency, tip displacement, current and blocked force, and their performance was compared to that of the widely-used traditional Nafion actuator. Scanning electron microscope (SEM) and transmission electron microscopy (TEM) revealed that much smaller and more uniform platinum particles were formed on the surfaces of the INM actuators as well as within their polymer matrix. Although excellent harmonic response was observed for the newly-developed INM actuators, this was found to be sensitive to the applied reduction times during the fabrication. The mechanical displacement of the INM actuator fabricated after optimum reduction times was much larger than that of its Nafion counterpart of comparable thickness under the stimulus of constant and alternating current voltage.

• 대한소아치과학회지
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• 제44권2호
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• pp.180-187
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• 2017

본 연구는 접착층을 통한 자이오머(Beautifil Injectable)와 컴포머($Dyract^{(R)}$ XP)의 불소 유리를 직접적으로 평가하고 비교하였다. 자이오머와 컴포머 그리고 불소를 함유하지 않은 복합레진의 원통형 시편을 각각 20개씩 제작하였다. 20개 중 10개의 시편은 접착제(Scotchbond Multi-Purpose)를 균일하게 도포하였다. 각 시편은 2 mL 탈이온수에 넣어 $37^{\circ}C$에서 보관하였으며 1, 3, 7, 14, 21, 28일째 유리된 불소를 측정하였다. 접착제를 적용한 추가적인 시편을 제작하여 주사전자현미경으로 접착제가 균일하게 도포되었는지 확인하였다. 자이오머와 컴포머에 접착제를 도포한 군은 3일째까지 불소가 검출되지 않았으나 7일째부터는 불소가 검출되었다. 접착제는 불소의 유리를 완전히 차단하지 못하였으며, 접착제를 투과하는 자이오머와 컴포머의 불소 유리량은 유의하게 감소하였다(p < 0.05). 불소의 유리량 감소는 컴포머보다 자이오머에서 더 현저했다.

• 대한환경공학회지
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• 제32권6호
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• pp.593-598
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• 2010

본 연구에서는 유동상 반응기를 이용하여 고농도의 질소, 인 및 불소가 동시에 존재하는 반도체 폐수 내 불소 처리시 불소 제거효율 향상, 함수율 저감 및 생성 슬러지($CaF_2$)의 순도 향상을 꾀하고자 하였다. 이를 위해 pH 및 seed 주입량, 유출수의 순환여부에 따른 영향을 살펴본 결과 유출수 재순환 시 불소제거효율, 슬러지 순도 및 함수율을 모두 고려할 경우 최적의 pH는 5, seed 주입량은 150 g으로 관찰되었다. 이때의 불소 및 인 제거효율은 94.24 및 8.97%로 나타났고, 함수율은 12.94%로 확인되었다. Seed 주입량의 증가는 불소제거효율을 증가시킬 뿐만 아니라 유출수 재순환 및 pH 변동에 따른 불소제거효율 감소도 억제시키는 것으로 나타났다.