• Restorative Dentistry and Endodontics
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• 제10권1호
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• pp.71-83
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• 1984

The purpose of this study was to evaluate the transmission spectrum of the set calcium hydroxide dental cement (Dycal, L.D. Caulk Co. Milford, Del.) Cement was prepared for A T R spectra at a low powder-to-liquid ratio of 3.0gm/ml in order to retard the reaction and facilitate the manipulation of loading the cement into the cell. Spectra were recorded on an I R Spectrophotometer (MX-1, FT) at an agle of incidence of 55. The A T R cell was a RIIc Model TR5 with a hemisperical KRS-5 (Thallium-Bromide-Iodide). A spectrum was recorded within 3 minutes. Further spectra were recorded after 5,10,30 minutes and 1,5,24, 72 hours. The results were as follows; 1. The setting reaction between acid paste and base past would take place fastly within 10 minutes after mix, and that would be slow until 72 hours after mix. 2. In the set cements, some methyl salicylate and calcium hydroxide remained unreacted until 72 hours after mix. 3. The setting reaction and the reaction rate occuring at the surface and in the bulk cements were similar. 4. The chelates were bound together between calcium hydroxide and methyl salicylate.

• Bulletin of the Korean Chemical Society
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• 제33권7호
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• pp.2229-2237
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• 2012

The two chelates based on calix[4]arene and thiacalix[4]arene have been synthesized and used as neutral ionophores for preparing PVC based membrane sensor selective to $Ho^{3+}$ ion. The addition of potassium tetrakis(4-chlorophenyl)borate (KTpClPB) and various plasticizers, viz., NDPE, o-NPOE, DOP, TEP and DOS have been found to improve significantly the performance of the sensors. The best performance was obtained with the sensor no. 6 having membrane of $L_2$ with composition (w/w) ionophore (2%): KTpClPB (4%): PVC (37%): NDPE (57%). This sensor exhibits Nernatian response with slope $21.10{\pm}0.3mV/decade$ of activity in the concentration range $3.0{\times}10^{-8}-1.0{\times}10^{-2}M\;Ho^{3+}\;ion$, with a detection limit of $1.0{\times}10^{-8}M$. The proposed sensor performs satisfactorily over a wide pH range of 2.8-10, with a fast response time (5 s). The sensor was also found to work successfully in partially non-aqueous media up to 25% (v/v) content of methanol, ethanol and acetonitrile, and can be used for a period of 4 months without any significant drift in potential. The electrode was also used for the determination of $Ho^{3+}$ ions in synthetic mixtures of different ions and the determination of the arsenate ion in different water samples.

• Bulletin of the Korean Chemical Society
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• 제14권1호
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• pp.59-62
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• 1993

Spectrophotometric determination of some heavy lanthanide ions by flow injection method is described. Xylenol Orange forms water soluble chelates with lanthanide ions in a tris[hydroxymethyl]-aminomethane-buffered medium having pH 8.3 and containing cetyltrimethylammonium bromide. The molar absorptivities of Ln(III)-XO complexes were increased by the ternary system with cetyltrimethylammonium bromide with the concomitant bathochromic shift of absorption maxium compared to those of the binary system without cetyltrimethylammonium bromide. The calibration curves are linear in the range 0.25-1.00 ppm for Gd(III), Dy(III), Er(III), Tm(III) and Yb(III) and the dynamic range are very wide. The detection limits (S/N=2) are from 2 ppb for Gd(III) to 30 ppb for Yb(III) and the relative standard deviations are from 1.2% for 0.5 ppm Gd(III) to 1.8% for 0.5 ppm Yb(III). The sample throughput was ca. 50 $h^{-1}$.

• Bulletin of the Korean Chemical Society
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• 제19권4호
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• pp.457-462
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• 1998

A chiral pentadentate bis-amide ligand, 1,9-bis(S)-pyrrolidinyl-2,5,8-triazanonane-1,9-dio ne$(S,S-prodienH_2)$ has been synthesized from the reaction of bis(2-aminoethyl)amine(dien) and S-proline, and the structure of $[Co(S,S-prodien)H_2O]ClO_4$ has be en determined by single crystal X-ray diffraction. The geometrical structure of the Co(III) complex has been an αβ -form, where the dien moiety of ligand chelates to a facial in metal center, and the aqua ligand coordinates a cis site to the secondary nitrogen of dien. The Co-N(1), Co-N(3) distances of two amide moiety in S,S-prodien are shorter than the other Co-N(2), Co-N(4), and Co-N(5) distances because of the increased basicity of nitrogen in amide. The complex crystallizes in the monoclinic space group $P2_1$(#4), with a=7.838(1), b=12.675(1), c=9.710(1) Å, β=100.39(1) and z=2. Refinement gives the final R and $R_w$ values of 0.045 and 0.057, respectively for 2130 observed reflections. Based upon the CD and X-ray data, it is identified that the absolute configuration of the αβ -$[Co(S,S-prodien)H_2O]ClO_4$ has a Λ-form.

• Bulletin of the Korean Chemical Society
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• 제20권6호
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• pp.648-652
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• 1999

Studies have been carried out on the unusual molecular nonrigidity of CoⅢ(PymS)3 and Cp* RhⅢ(PymS)2(PymS:2-mercaptopyrimidine). The crystal structure of CoⅢ(PymS)3 approximates to an octahedral mer isomer with 4-membered N-Schelating fashion. For Cp*RhⅢ(PymS)2, one PymS ligand bonds to the rhodium ion in an S-monodentate mode (Rh-S(2) = 2.366(1)Å) while the other ligand chelates to the metal ion in an N,S-bidentae mode (Rh-S(1)=2.414(1);Rh-N(1)=2.103(3)Å). Even though the conformations and configurations of both complexes are still retained in solution, an unusual nonrigidity for the protons of the PymS region is obsered in the solution. The broad proton signals of CoⅢ(PymS)3 exhibit a temperature-dependence in the range of -40∼40℃ with a free energy of activation ΔG=64.49kJ/mol(40℃). For Cp*RhⅢ(PymS)₂,such a fluxionality has been markedly observed in solution. This fluxional behavior can be explained in terms of "ligand tautomerism" in metal complexes containing potential tautomeric forms.

• 분석과학
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• 제20권1호
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• pp.41-48
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• 2007

유리소재 중의 미량의 납 및 카드뮴을 Na-DDTC를 가하여 Pb- 및 Cd-DDTC 착물을 형성시켜 유리 matrix 원소들로 부터 분리한 다음 MIBK로 추출하여 ICP-AES로 분석하였다. 유리 기질성분인 Na, Si, Mg 그리고 Ca 화합물 등은 미량의 납 및 카드뮴 정량에 방해작용을 하므로 직접 분석할 수 없으므로 용매추출법에 의해 Pb 및 Cd를 효율적으로 분리할 수 있었다. Pb 및 Cd 화합물이 첨가된 시험기준 시료와 NIST SRM 1412에 대한 용매추출실험에서 matrix의 영향을 받지 않고 정량하였다.

• Asian-Australasian Journal of Animal Sciences
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• 제23권1호
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• pp.90-97
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• 2010

An experiment was conducted to evaluate the effects of low concentrations of organic and inorganic dietary trace minerals on broiler performance and trace mineral digestibility along the small intestine of 35-day-old broiler chickens reared under floor-pen conditions. Eight hundred male, day-old Cobb broiler chickens were randomly allocated to 4 dietary treatments (25 birds per pen with 8 replicates per treatment). Broilers fed diets supplemented with 4, 20, 40 and 30 mg/kg, respectively, of Cu, Fe, Mn and Zn from organic chelates and inorganic salts achieved the same body weight gain as those supplemented at the NRC levels (8 mg Cu, 40 mg Fe, 60 mg Mn and 40 mg Zn/kg, respectively) from inorganic salts. However, birds fed a control diet without any supplementation at dietary levels of 7.4-8.8, 60.1-69.2, 14.6-15.4 and 19.1-20.6 mg/kg of Cu, Fe, Mn and Zn, respectively, had decreased feed intake and growth rate. There was no significant difference in the digestibility of Cu in all regions of the small intestine. Throughout the small intestine the apparent absorption of Mn from both organic and inorganic sources was small, whereas the digestibility of Zn seemed to be more complex, exhibiting differences in the apparent absorption due to both mineral source and intestinal site. Therefore, the digestibility of organic Zn was improved (p<0.01) in the ileum compared to inorganic Zn. The digestibility of Zn in the duodenum was smaller (p<0.05) than that in the ileum.

• 한국동물번식학회:학술대회논문집
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• 한국동물번식학회 2003년도 학술발표대회 발표논문초록집
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• pp.78-78
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• 2003

Embryonic stem (ES) cells, derived from preimplantation embryo, are able to differentiate into various types of cells consisting the whole body, or pluripotency. In contrast, terminally differentiated cells do not usually alter their nature but frequently die or transform if they are exposed to inappropriate external stimulations. In addition to the plasticity, ES cells are expected to be different from terminally differentiated cells in very many ways, such as patterns of gene expressions, ability and response of the cells in confronting environmental stimulations, metabolism, and growth rate. As a model system to differentiate these two types of cells, human ES cells (MB03) and terminally differentiated cells (HeLa), we examined the ability of these two types of cells in confronting a severe oxidative insult, that is $H_2O$$_2$. Approximately 1$\times$10$^4$ cells were plated in 96 well plate and serum starved for overnight. The conditioned cells were exposed to a various concentration of $H_2O$$_2$ fur 24 hrs and loaded with neutral red (50$\mu\textrm{g}$/ml) for 4 hrs, washed with PBS for 2 min three times, and entrapped dye was dissolved out using acetic ethanol. Cytotoxicity was determined by reading the amount of dye in the medium using microplate reader. equipped with 575 nm filter. Relative amount of the dye entrapped within MB03 or HeLa were not significantly different when cells were exposed up to 0.4 mM $H_2O$$_2$. However, this sharply decreased down to 0.12% in HeLa cells when the cells were exposed to 0.8 mM $H_2O$$_2$, while it was approximately 54% in MB03 suggesting that this concentration of $H_2O$$_2$ is the defensive threshold for HeLa cells. The resistance to oxidative stimulation reversed, however, when cells were co-treated with BSO (L-buthionine- 〔S, R〕-sulfoximine) which chelates intracellular GSH. This result suggests that cellular GSH is the major defensive mechanism of human ES cells. Induction of enzymes involved in GSH metabolism and type of cell death is currently being studied.

• 분석과학
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• 제10권5호
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• pp.370-377
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• 1997

Co(II), Cu(II) 및 Zn(II) 이온을 디티존으로 용매추출하는 과정에서의 여러 가지 기초적인 정보에 대해 조사하였다. $25^{\circ}C$에서 클로로포름에 녹인 디티존의 수용액상과 유기상 사이에서 구한 $K_{a1}/K_p$값은 $4.72{\times}10^{-11}$이었다. 금속 이온과 디티존이 착물을 형성할 때의 조성비를 몰비법을 이용하여 조사하였다. 금속-디티존 착물이 수용액과 클로로포름 용매 사이에서 분배되는 평형에서의 추출률은 Co(II)의 경우 pH 8.0에서 92.3%이고, Cu(II)의 경우는 pH 4.0에서 97.1%이며, Zn(II)은 pH 7.0에서 99.0%로서 최대값을 나타내었다. 그리고 최적의 실험조건하에서 Co(II), Cu(II) 및 Zn(II)이온에 대한 추출상수를 결정하였다.

• 대한화학회지
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• 제23권3호
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• pp.141-151
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• 1979

전형적인 음이온 교환수지인 Dowex 1-X8 (50∼100메쉬)에 술폰기를 갖는 킬레이트 시약인 8-hydroxyquinoline-5-sulfonic acid (HQS)와 7-nitroso-8-hydroxyquinoline-5-sulfonic acid (NHQS)를 흡착시킨 킬레이트 수지를 사용하여 수용액에 용해되어 있는 Fe(Ⅲ), Cu(Ⅱ), Pb(Ⅱ) 및 Zn(Ⅱ)을 흡착시켜 다른 이온들로부터 분리시키는 연구를 시도한다. 킬레이트 수지의 안정성은 수용액에 공존하는 음이온의 종류, 그 농도 및 액성에 따라 영향을 받으므로 수지사용의 최적조건을 결정하였으며, 수지에 대한 두 킬레이트 시약의 흡착성도 정성적으로 해석하였다. 금속이온의 흡착은 킬레이트 수지에 있는 HWS 및 NHQS와 각 금속이온과의 킬레이트 형성에 의한 것으로 그 흡착력은 각 킬레이트의 안정도상수값과 비례한다. 액성이 PH3∼4 범위에서 HQS-수지의 금속이온의 흡착능은 Fe(Ⅲ):0.63, Cu(Ⅱ):0.82 및 Pb(Ⅱ):0.79 mmol/g이며, NHQS-수지의 경우는 Cu(Ⅱ):1.07 및 Pb(Ⅱ):0.96mmol/g이다. 몇가지 금속이온의 혼합액을 시료로 하여 분리를 시도했다.