• Restorative Dentistry and Endodontics
• /
• v.18 no.2
• /
• pp.277-290
• /
• 1993

Dental caries is considered to be caused by demineralization by organic acid produced by microorganism. But the formation of subsurface lesion in initial caries make it diffcult to explain by simple demineralization. This study is carried out on the basis of thermodynamic concept proposed by Margolis and Moreno. The purpose of this study is to evaluate the effects of acid concentration and pH of lactate buffer system on the artificial caries lesion progress. 160 teeth without any crack, defect or opaque enamel were used and coated with nail varnish except the window ($2{\times}3$ mm). Under the constant degree of saturation(D.S.). The teeth were divided into 8 groups according to acid concentration(10mM, 25mM, 50mM, 100mM) and pH(4.3, 5.0, 6.0). Each group was immersed in buffer solution for 3, 6, 9, 18 days under controlled temperature($25^{\circ}C$). After cutting through the window and grinding, the specimens, 100-150 um in thickness, were imbibed in water or air and examined using polarilizing microscope. The depth of the surface and subsurface surface lesion were measured. 1. In the constant pH and D. S. value, the subsurface lesion progresses more rapidly as the concentration of lactic acid increases. (0.01, 0.025, 0.05, 0.1) 2. In the constant acid concentration and DS value, the subsurface lesion progresses more slowly as the pH increases. (4.3, 5.0, 5.5, 6.0) 3. The width of surface lesion seems to be constant independant of pH and acid concentration.

• KSBB Journal
• /
• v.13 no.6
• /
• pp.644-648
• /
• 1998

In the production of a low cost bacterial insecticide, it is important to produce a high spore concentration using low price substrates. Experiments were carried out to investigate the effects of the addition of mineral salts and glucose, and of dissolved oxygen concentration on the cell growth and spore formation of Bacillus thuringiensis var aizawai using a cheap wheat and soybean meal in the batch culture. The maximum viable cell number was 1.2${\times}$109 CFU/mL at 12 hr culture and spore yield was 54.2% at 74 hr culture using an industrial medium containing 20 g/L wheat meal and 30 g/L soybean meal under 1.0 vvm aeration and 200 rpm agitation. The cell growth and the spore formation were not enhanced by the addition of mineral salts in industrial medium, whereas th addition of 10g/L glucose decreased the cell growth and spore formation. We could obtain a maximum viable cell number of 2.2${\times}$109 CFU/mL and spore number of 1.9${\times}$109 CFU/mL at the dissolved oxygen concentration of 60% of saturation. The spore concentration was enhanced approximately by 2 times as compared to the dissolved oxygen concentration of 50%. In the bench-scale culture, the maximum viable cell and spore number were 2.5${\times}$109 CFU/mL, and 2.2${\times}$109 CFU/mL, respectively under 1.0 vvm aeration and 400 rpm agitation. The spore yield was 88% based on the maximum viable cell number. As a result, it was confirmed that the production of high spore concentration could be obtained by a bench-scale culture using an industrial medium.

• Journal of the korean academy of Pediatric Dentistry
• /
• v.39 no.1
• /
• pp.11-16
• /
• 2012

Effect of supplementary intranasal midazolam on oral sedation of children The purpose of this study was to compare the cardiopulmonary parameters of two sedation regimens during dental treatment: (1) Oral chloral hydrate(CH) and hydroxyzine(HZ) with nitrous oxide-oxygen($N_2O/O_2$) inhalation(CH-HZ group); (2) Oral chloral hydrate(CH) and hydroxyzine(HZ) with nitrous oxide-oxygen($N_2O/O_2$) inhalation and supplementary intranasal(IN) midazolam administration(MIDA group). Among the patients of OO hospital who received dental treatment under sedation over the past 5 years, 44 patients were selected for each group of CH-HZ and MIDA according to their age, gender and weight. Following parameters that were recorded every 5 minutes were compared: 1) Heart rate(HR) 2) $O_2$ saturation 3) End tidal carbon dioxide concentration($EtCO_2$) 4) Respiratory rate(RR) 33 patients of Group MIDA who have complete data of 15 minutes before and after supplementary IN midazolam administration were selected. And measurements 15 minutes before and after midazolam administration in same patient were evaluated. The results were as follows: 1. Heart rate was significantly higher in MIDA group than in CH-HZ group, but it was within normal range. 2. Comparing HR, $O_2$ saturation, EtCO2, RR between before and after of supplementary IN midazolam administration in the same patient, the differences were not statistically significant.

• Restorative Dentistry and Endodontics
• /
• v.21 no.1
• /
• pp.161-173
• /
• 1996

The cariostatic effect of fluoride had been established by many epidemiologic and experimental studies. But, there are still different views on the mechnism of cariostasis and remineralization, especially about the proper fluoride concentration. The purpose of this study is to ascertain the remineralization of caries lesion and influence of fluoride concentration which affect remineralization by a study based on dynamic mechanism. The subjects, sound permanent teeth without demineralization or crack, were immersed in lactic acid buffered demineralization solution for 4 days. Dental caries with surface zone and subsurface lesion were artificially produced. All specimens were immersed in lactic acid buffered remineralization solution which had fluoride concentrations of 1 ppm, 2 ppm, 3 ppm for 10days. Final conclusions were obtained by observing the specimens for every 10 days under polarized microscopy. 1. Remineralization of caries lesion as well as demineralization of enamel were produced by changing the degree of saturation of lactic acid buffer solution. 2. Remineralization of caries lesion was facillitated by fluoride ion in lactic acid buffer solution. but, remineralization of the entire caries lesion was not increased as fluoride ion concentration increased.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.62 no.8
• /
• pp.1115-1119
• /
• 2013

The carbon nanotube/poly-vinylidene fluoride (CNT/PVDF) composite films for the use of electronic devices were fabricated by spray coating method using the CNT/PVDF solution, which was prepared by adding PVDF pellets into the CNT dispersed N-Methyl-2-pyrroli-done (NMP) solution. The CNT/PVDF composite films were peeled off from the glass substrate and were investigated by the scanning electron microscopy, which revealed that the CNTs were uniformly dispersed in the PVDF films and thickness of the films were approximately $20{\mu}m$. The capacitance of the CNT/PVDF films increased dramatically by adding CNTs into the PVDF matrix, and finally saturated approximately 1880 pF. However, the I-V curves didn't show any saturation effect in the CNT concentration range of 0 ~ 0.04 wt%. Therefore we can control the performance of the devices from the CNT/PVDF composite film by adjusting the current level resulted from the CNT concentration with the uniform capacitance value.

• Journal of Pharmaceutical Investigation
• /
• v.32 no.4
• /
• pp.285-290
• /
• 2002

In order to assay the efficacy of newly synthesized antiviral compounds, in vitro studies of their active intracellular phosphorylated metabolites were established as compared with Zidovudine (ZDV). Antiviral base analogs require intracellular phosphorylation prior to the inhibition of HIV replication. Therefore, antiviral drugs concentrations in plasma have not reflected any direct relationship with activity or toxicity. A method has been developed to measure the concentration of total phosphorylated metabolites inside peripheral blood mononuclear cells using modified commercial radioimmunoassay (RIA). ZDV 5'-monophosphate was synthesized and used as a procedural control for RIA modification. PBMCs were isolated from whole blood and incubated with ZDV for 20 h to allow metabolic phosphorylation. Viable cells were extracted overnight with 60% methanol. After evaporation, the extract was reconstituted in Tris buffer. Samples were split into two fractions, one of which was treated with alkaline phosphatase (AP) to liberate phosphate groups. Concentrations of phosphorylated metabolites were determined by subtracting thε concentration of non-AP-treated fraction from that of the treated fraction. Recovery of phosphorylated ZDV from cell extracts was approximately 90%, and reproducibility was acceptable (coefficients of variation <15% for concentrations${\geq}$0.25 ng/mL). Intracellular concentrations $(0.135{\sim}5.019\;nmole/10^6\;cells)$ followed a nonlinear dose-response relationship over the range $0.015{\sim}2.996mM$ extracellular ZDV, with concentration-dependant saturation.

• The Korean Journal of Zoology
• /
• v.14 no.2
• /
• pp.43-56
• /
• 1971

The Ca uptake by the fragmented sarcoplasmic reticulum of the rabbit skeletal muscle was measured under various concentrations of K, Mg, Caffeine, procaine and quinine. The ATPase activity of this reticular membrane was measured under the same conditions simultaneously. The saturation of Ca uptake was almost completed within 1 minute. The Ca uptake was inhibited by high concentrations of K (above 50 mM) and Mg (above 1 mM)in the absence of ATP. When ATP is present, however, the Ca uptake did not reflect the concentration of K, while it increased greatly as the concentration of Mg was increased. Caffeine and procaine caused the inhibition of Ca uptake in the presence of ATP, but quinine did not. The ATPase activity of the membrane was little affected by the concentration of K, while it was enhanced in the presence of Mg. Caffeine, procaine and quinine did not influence the ATPase activity.

• Journal of the East Asian Society of Dietary Life
• /
• v.22 no.4
• /
• pp.463-472
• /
• 2012

This study was performed to investigate the iron status and its related factors in female college students residing in Gyeongnam. The prevalence of iron deficiency among subjects ranged from 3.4% in mean corpuscular hemoglobin concentration (MCHC) to 43.7% in ferritin. Weight, lean body mass (LBM) and body mass index (BMI) were positively correlated with ferritin concentration, but negatively correlated with total iron binding capacity (TIBC). Among the nutrients, vitamin A and B2 were major predictors of elevated iron status. Meal regularity was positively correlated with Fe and ferritin concentration, and meal number with transferrin saturation (TS), meal quantity with red blood cell (RBC) and hematocrit (Hct). Consumption of fruit, meat, fish and poultry showed strong positive correlation with hematological indices. Therefore, increasing vitamin A, B2, C, and iron intakes as well as maintenance of a healthy weight may be helpful in preventing iron deficiency in female college students.

• Journal of Magnetics
• /
• v.18 no.3
• /
• pp.230-234
• /
• 2013

The $Ni_{0.5}Zn_{0.5}Fe_2O_4$ nanoparticles about 30 nm were prepared using sol-gel method with metal nitrates dissolved in 2-methoxyathanol. The concentrations of the metal nitrates are adjusted from 0.1 to 0.75 M in order to study the influence on the structural and magnetic properties. The structure and morphology characterization revealed that the crystallinity was improved and the nanoparticle size was increased with the nutrition solution concentrations up to 0.5 M. Degraded crystallinity together with decreased nanoparticle size were observed for concentration of 0.75 M. The saturation magnetization at room temperature reached maximum at 0.5 M, which can be explained by considering the crystallinity and size effect.

• Journal of the Korean institute of surface engineering
• /
• v.55 no.6
• /
• pp.433-440
• /
• 2022

Environmental pollution caused by power plant exhaust gas is highlighted and eco-friendly regulations are being strengthened. However, due to the abundant reserves and low prices of coal, still the most used for power generation in the world. Therefore, flexible operation of coal-fired power plants to reduce emissions has become an inevitable option. However, lowering the output increases the possibility of acid dew point corrosion as the exhaust gas temperature decreases. The dew point corrosion occurs when condensable gases such as SO₃, HCl, NO₂ and H₂O cools below the saturation temperature. SO₃ is already well known to cause severe low- temperature corrosion in coal-fired power plants. Therefore, this study aims to prevent damage that may occur during operation by analyzing the dew point and corrosion resistance with exhaust gas temperature and sulfuric acid concentration of the power plant economizer tube.