• The korean journal of orthodontics
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• v.31 no.4 s.87
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• pp.447-458
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• 2001

The purpose of this study was to evaluate 1) in vivo, the expression of chondroitin 4-sulfate (CH-4S), a structural element of glycosaminoglycans(GAGs), in periodontal tissue during the experimental movement of rat incisors, by labelled streptavidine biotin immunohistochemical staining for CH-4S, 2) In vitro, the expression of CH-4S in cultured human periodontal ligament(PDL) cells supplemented with 10ng/ml of $TGF-{\beta}_1$, 20ng/ml of PDGF-BB, 1ng/ml $TNF-\alpha$, or $1{\mu}g/ml$ LPS by western blot analysis. The results of this study were as follows ; 1. The expression of CH-4S was stronger in pulp, PDL, osteoblasts, osteoclasts and osteocytes in experimental group than in control group, but was rare in dentin, and cementum of experimental groups, regardless of the duration of force application, which was not different from that of control group. 2. In experimental group, the expression of CH-4S in pulp began to increase at 1 day after force application and got to the highest degree at 7 days. After 14 days, the expression in CH-4S immunoreactivity was decreased, and became similar to that of control group at 28 days. 3. The expression of CH-4S in PDL was noted in adjacent to alveolar bone. PDL showed higher intensity of immunolabelling after 1 day of orthodontic tooth movement. And the expression was more stronger in the tension side than that of pressure side of PDL at 1 day, but more stronger in the pressure side than that of tension side of PDL at 4 days. After 7 days, a decrease in CH-4S expression was observed. 4. The expression of CH-4S in alveolar bone got to the highest degree at 4 days, and At 7 days, a decrease in CH-4S expression was observed. 5. PDGF-BB notably raised the expression of CH-4S in the PDL cells at 3 days of cultivation 6. The expression of CH-4S of PDL cells was decreased with the application of $TNF-\alpha$ at 1 day. 7. Admixture of $TGF-{\beta}_1$ and PDGF-BB got more expression of CH-4S in PDL as compared to only $TGF-{\beta}1$ or PDGF-BB. A similar decrease of the expression of CH-4S was observed in the case of application of LPS or $TNF-\alpha$.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.2 s.233
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• pp.255-262
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• 2005

A comprehensive experimental and numerical study has been conducted to understand the influence of $CH_{3}Cl$ addition on $CH_4/O_2/N_2$ premixed flames under the oxygen enrichment. The laminar flame speeds of $CH_4/CH_{3}Cl/O_2/N_2$ premixed flames at room temperature and atmospheric pressure are experimentally measured using Bunsen nozzle flame technique, varying the amount of $CH_{3}Cl$ in the fuel, the equivalence ratio of the unburned mixture, and the level of the oxygen enrichment. The flame speeds predicted by a detailed chemical kinetic mechanism employed are found to be in excellent agreement with those deduced from experiments. Even though the molar amount of $CH_{3}Cl$ in a methane flame is increased, temperature at the postflame is not significantly varied, but the calculated heat release rate and emission index of NO are largely decreased for the oxygen enhanced flame. The function of $CH_{3}Cl$ as inhibitor on hydrocarbon flames becomes weakened as the level of the oxygen enrichment is increased from 0.21 to 0.5.

• Korean Journal of Materials Research
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• v.25 no.6
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• pp.300-304
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• 2015

Nanorod ZnO and spherical nano ZnO for gas sensors were prepared by hydrothermal reaction method and hydrazine method, respectively. The nano-ZnO gas sensors were fabricated by a screen printing method on alumina substrates. The gas sensing properties were investigated for hydrocarbon gas. The effects of Co concentration on the structural and morphological properties of the nano ZnO:Co were investigated by X-ray diffraction and scanning electron microscope (SEM), respectively. XRD patterns revealed that nanorod and spherical ZnO:Co with a wurtzite structure were grown with (100), (002), (101) peaks. The sensitivity of nanorod and spherical ZnO:Co sensors was measured for 5 ppm $CH_4$ and $CH_3CH_2CH_3$ gas at room temperature by comparing the resistance in air with that in target gases. The highest sensitivity to the $CH_4$ and $CH_3CH_2CH_3$ gas of spherical nano ZnO:Co sensors was observed at Co 6 wt%. The spherical nano ZnO:Co sensor exhibited a higher sensitivity to hydrocarbon gas than nanorod ZnO.

• Bulletin of the Korean Chemical Society
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• v.30 no.7
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• pp.1470-1474
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• 2009

Thermal and photochemistry of methyl iodide ($CH_3I)\;adsorbed\;on\;D_2O$ ice film on Cu(111) at 100 K were studied using temperature-programmed desorption (TPD) time-of-flight mass spectrometry (TOF-MS), X-ray and ultraviolet photoelectron spectroscopies. On the basis of TPD, multilayer and monolayer $CH_3I$ molecules desorb from $D_2O$ ice layer at 120 and 130 K, respectively. Photo-irradiation at 100 K exhibits dramatic changes in the TPD and I $3d_{5/2}\;XPS\;of\;CH_3I$ on ice film, due to a dramatic dissociation of $CH_3I$. The dissociation is likely activated by solvated electrons transferred from the metal substrate during photo-irradiation. No other photo-initiated reaction products were found within our instrumental detection limit. During photo-irradiation, the $CH_3I$, $CH_3$ and I could be trapped (or solvated) in ice film by rearrangement (and self-diffusion) of water molecules. A newly appeared parent molecular desorption peak at 145 K is attributed to trapped $CH_3I$. In addition, the $CH_3$ and I may diffuse through ice and chemisorb on Cu(111), indicated by TPD and I $d_{5/2}$ XPS taken with photo-irradiation time, respectively. No molecular ejection was found during photo-irradiation at 100 K. The work functions for $CH_3I/Cu(111),\;D_2O/Cu(111)\;and\;CH_3I/D_2$O/Cu(111) were all measured to be about 3.9 eV, 1.0 eV downward shift from that of clean Cu(111).

• Journal of the Korean Chemical Society
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• v.39 no.3
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• pp.198-203
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• 1995

The Mo(V) $di-\mu-oxo$ type $(Mo_2O_4(H_2O)_2L)$ complexes $(L:\;C_3H_7CH(SCH_2COOH)_2,\;C_6H_5CH(SCH_2COOH)_2,\;CH_3OC_6H_4CH(SCH_2COOH)_2,\;C_5H_{10}C(SCH_2COOH)_2,\;C_3H_7C(CH_3)(SCH_2COOH)_2,\;C_3H_7CH(SCH_2CH_2COOH)_2,\;C_6H_5CH(SCH_2CH_2COOH)_2)$ have been prepared by the reaction of $[Mo_2O_4(H_2O)_6]^{2+}$ with a series of dithiodicarboxy ligands. These complexes are completed by two terminal oxygens arranged trans to one another and each ligand forms a chelate type between two molybdenum. In $Mo_2O_4(H_2O)_2L$, two $H_2O$ coordinated at trans site of terminal oxygens. The prepared complexes have been characterized by elemental analysis, infrared spectra, electronic spectra, and nuclear magnetic resonance spectra. In the potential range -0.00 V to -1.00 V at a scan rate of 20 $mVs^{-1}$, a cathodic peak at -0.50∼-0.58 V (vs. SCE) and an anodic peak at -0.40∼-0.43 V (vs. SCE) have been observed in aquous solution. The ratio of the cathodic to anodic current ($I_{pc}/I_{pa}$) is almost 1, we infer that redox is reversible reaction.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.25 no.12
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• pp.974-978
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• 2012

The effect of Cu coating on the sensing properties of nano $SnO_2:Cu$ based sensors for the $CH_4$, $CH_3CH_2CH_3$ gas was studied. This work was focussed on investigating the change of sensitivity of nano $SnO_2:Cu$ based sensors for $CH_4$, $CH_3CH_2CH_3$ gas by Cu coating. Nano sized $SnO_2$ powders were prepared by solution reduction method using stannous chloride($SnCl_2{\cdot}2H_2O$), hydrazine($N_2H_2$) and NaOH and subsequent heat treatment. XRD patterns showed that nano $SnO_2$ powders with rutile structure were grown with (110), (101), (211) dominant peak. The particle size of nano $SnO_2:Cu$ powders at 8 wt% Cu was about 50 nm. $SnO_2$ particles were found to contain many pores, according to SEM analysis. The sensitivity of nano $SnO_2:Cu$ based sensors was measured for 5 ppm $CH_4$ gas and $CH_3CH_2CH_3$ gas at room temperature by comparing the resistance in air with that in target gases. The sensitivity for both $CH_4$ and $CH_3CH_2CH_3$ gases was improved by Cu coating on the nano $SnO_2$ surface. The response time and recovery time of the $SnO_2:Cu$ gas sensors for the $CH_4$ and $CH_3CH_2CH_3$ gases were 18~20 seconds, and 13~15 seconds, respectively.

• Korean Chemical Engineering Research
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• v.49 no.5
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• pp.510-515
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• 2011

The pyrolytic reaction of 1,1-dichloroethylene($CH_2CCl_2$) has been conducted to investigate thermal decomposition of chlorocarbon and product formation pathways under hydrogen reaction environment. The reactions were studied in a isothermal tubular flow reactor at 1 atm total pressure in the temperature range $650{\sim}900^{\circ}C$ with reaction times of 0.3~2.0 sec. A constant feed molar ratio $CH_2CCl_2:H_2$ of 4:96 was maintained through the whole experiments. Complete decay(99%) of the parent reagent, $CH_2CCl_2$ was observed at temperature near $825^{\circ}C$ with 1 sec. reaction time. The important decay of $CH_2CCl_2$ under hydrogen reaction environment resulted from H atom cyclic chain reaction by abstraction and addition displacement. The highest concentration (28%) of $CH_2CHCl$ as the primary product was observed at temperature $700^{\circ}C$, where up to 46% decay of $CH_2CCl_2$ was occurred. The secondary product, $C_2H_4$ as main product was detected at temperature above $775^{\circ}C$. The one less chlorinated ethylene than parent increase with temperature rise subsequently. The HCl and dechlorinated hydrocarbons such as $C_2H_4$, $C_2H_6$, $CH_4$ and $C_2H_2$ were the main products observed at above $825^{\circ}C$. The important decay of $CH_2CCl_2$ resulted from H atom cyclic chain reaction by abstraction and addition displacement. The important pyrolytic reaction pathways to describe the features of reagent decay and intermediate product distributions, based upon thermochemical and kinetic principles, were suggested.

• Korean Journal of Materials Research
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• v.23 no.4
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• pp.211-214
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• 2013

The effects of a Ni coating on the sensing properties of nano ZnO:Ni based gas sensors were studied for $CH_4$ and $CH_3CH_2CH_3$ gases. Nano ZnO sensing materials were prepared by the hydrothermal reaction method. The Ni coatings on the nano ZnO surface were deposited by the hydrolysis of zinc chloride with $NH_4OH$. The weight % of Ni coating on the ZnO surface ranged from 0 to 10 %. The nano ZnO:Ni gas sensors were fabricated by a screen printing method on alumina substrates. The structural and morphological properties of the nano ZnO : Ni sensing materials were investigated by XRD, EDS, and SEM. The XRD patterns showed that nano ZnO : Ni powders with a wurtzite structure were grown with (1 0 0), (0 0 2), and (1 0 1) dominant peaks. The particle size of nano ZnO powders was about 250 nm. The sensitivity of nano ZnO:Ni based sensors for 5 ppm $CH_4$ gas and $CH_3CH_2CH_3$ gas was measured at room temperature by comparing the resistance in air with that in target gases. The highest sensitivity of the ZnO:Ni sensor to $CH_4$ gas and $CH_3CH_2CH_3$ gas was observed at Ni 4 wt%. The response and recovery times of 4 wt% Ni coated ZnO:Ni gas sensors were 14 s and 15 s, respectively.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.7
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• pp.589-593
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• 2011

[ $SnO_2$ ]nano powders were prepared by solution reduction method using tin chloride($SnCl_2{\cdot}2H_2O$), hydrazine($N_2H_4$) and NaOH. The $SnO_2$ thick films for gas sensors were fabricated by screen printing method on alumina substrates and annealed at $300^{\circ}C$ in air, respectively. XRD patterns of the $SnO_2$ nano powders showed the tetragonal structure with (110) dominant orientation. The particle size of $SnO_2$ nano powders at the ratio of $SnCl_2:N_2H_4$+NaOH= 1:6 was about 60 nm. The sensing characteristics were investigated by measuring the electrical resistance of each sensor in a test box. Sensitivity of $SnO_2$ gas sensor to 5 ppm $CH_4$gas and 5 ppm $CH_3CH_2CH_3$ gas was investigated for various $SnCl_2:N_2H_4$+NaOH proportion. The highest sensitivity to $CH_4$ gas and $CH_3CH_2CH_3$ gas of $SnO_2$ sensors was observed at the $SnCl_2:N_2H_4$+NaOH= 1:8 and $SnCl_2:N_2H_4$+NaOH= 1:6, respectively. Response and recovery times of $SnO_2$ gas sensors prepared by $SnCl_2:N_2H_4$+NaOH= 1:6 was about 40 s and 30 s, respectively.

• Journal of Yeungnam Medical Science
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• v.40 no.1
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• pp.30-36
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• 2023

Background: Congenital hypothyroidism (CH) is the leading cause of preventable physical and intellectual disabilities. This study aimed to assess the incidence and clinical characteristics of CH in newborns. Methods: We retrospectively reviewed the medical records of all newborns delivered at the Pusan National University Hospital between January 2011 and March 2021. The incidence of CH was compared according to gestational age, birth weight, and small for gestational age (SGA). The patients aged ≥3 years who could not maintain normal thyroid function and required levothyroxine treatment were diagnosed with permanent CH. Logistic regression analysis was performed to compare CH risks. Results: Of 3,722 newborns, 40 were diagnosed with CH (1.07%). Gestational age and birth weight were significantly associated with CH incidence. The odds ratios (ORs) of CH in infants delivered at 32-37, 28-31, and <28 weeks were 2.568 (95% confidence interval [CI], 1.141-5.778), 5.917 (95% CI, 2.264-15.464), and 7.441 (95% CI, 2.617-21.159) times higher, respectively, than those delivered at term. The ORs of CH in infants weighing 1,500-2,499 g, 1,000-1,499 g, and <1,000 g were 4.664 (95% CI, 1.928-11.279), 11.076 (95% CI, 4.089-29.999), and 12.544 (95% CI, 4.350-36.176) times greater, respectively, than those in infants weighing ≥2,500 g. The OR of CH was 6.795 (95% CI, 3.553-13.692) times greater in SGA than in non-SGA infants. Conclusion: The CH incidence in South Korea has increased significantly compared with that in the past. Gestational age, birth weight, and SGA were significantly associated with CH incidence.