• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 한국지하수토양환경학회 1999년도 추계학술발표회
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• pp.81-84
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• 1999

The aqueous geochemical characteristics of Cr(III) and Cr(Ⅵ) in environmental systems are very different from one another: Cr(Ⅵ) is highly soluble, mobile and toxic relative to Cr(III) Reduction of Cr(Ⅵ) to Cr(III) are beneficial in aquatic systems because of the transformation of a highly mobile and toxic species to one having a low solubility in water, thus simultaneously decreasing chromium mobility and toxicity. Fe(II) species are excellent reductants for transforming Cr(Ⅵ) to Cr(III), and in addition, keeping Cr(III) concentrations below the drinking water standard of 52 ppb at pH values between 5 and 11. Investigations of the effects of NOM on Cr(Ⅵ) reduction are for examining the feasibility of using ferrous iron to reduce hexavalent chromium in subsurface environments. Experiments in the presence of soils, however, showed that the solid phase consumes some of the reducing capacity of Fe(II) and makes the overall reduction kinetics slower. The soil components bring about consumption of the ferrous iron reductant. Particular attention is devoted to the complexation of Fe(II) by NOM and the subsequent effect on Cr(Ⅵ) reduction. Cr(Ⅵ) reduction rate by Fe(II) was affected by the presence of NOM (humic acid), The effects of humic acid was different from the solution pH values and the concentration of humic acid. It was probably due to the reactions between humic acid and Cr(Ⅵ), humic acid and Fe(II), and between Cr(Ⅵ) and Fe(II), at each pH.

• Korean Journal of Materials Research
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• 제7권10호
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• pp.898-907
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• 1997

Fe-22Cr-5AI-X(X=Zr, Y)합금을 1143K, 고온 황화(P$s_{2}$=1.11x$10^{-7}$atm, P$O_{s}$ =3.11x$10^{-20atm}$) 및 황화/산화 (P$s_{2}$=8.31x$10^{-8}$atm, P$O_{s}$ =3.31x$10^{-18atm}$) 환경의 복합가스 분위기에서 1-30시간동안 노출하여 합금표면에 형성된 부식층을 관찰하여 SEM/EDS로 분석하였다. Fe-22Cr-5AI합금은 고온 부식환경에서 부식 생성물의 성장은 포물선법칙을 따르고 주요 성분은 결함이 많고 다공질인 철과 크롬의 황화물[(Fe, Cr)Sx]이므로 고온 내식성이 감소하였다. Zr을 1wt%첨가한 Fe-22Cr-5AI합금의 고온 부식거동은 Y을 1wt%첨가한 합금과 비슷한 거동을 나타내었다. 황화환경에서는 Cr의 선택 황화에 의한 크롬 황화물(CrS)이 생성되고 노출시간의 경과에 따라 (Fe, Cr)Sx나 (Cr, Fe)Sx 등의 황화물의 성장으로 고온 내식성이 감소하였다. 그러나 황화/산화환경에서는 초기에는 알루미늄산화물(A $I_{2}$ $O_{3}$)및 지르코늄산화물(Zr $O_{2}$)등이 생성되어 보호적이었으나 15시간이후 부터 (Fe, Cr)Sx나 (Cr, Fe)Sx 의 황화물의 성장으로 고온 내식성이 감소하였다.

• Journal of Microbiology and Biotechnology
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• 제25권3호
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• pp.418-422
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• 2015

In the course of screening for novel cell cycle inhibitors and apoptotic inducers, CR389, elucidated as 5-(1H-benzoimidazol-2-yl)-1H-pyridin-2-one, was generated as a new hit compound. Flow cytometric analysis and western blots of PA-1 cells treated with $60{\mu}M$ CR389 revealed an appreciable cell cycle arrest at the G2/M phase through direct inhibition of the CDK1 complex. In addition, activation of p53 via phosphorylation at Ser15 and subsequent up-regulation of p21^CIP1 showed that CR389 also induces p53-dependent-p21^CIP1-mediated cell cycle arrest. Furthermore, apoptotic induction in $60{\mu}M$ CR389-treated PA-1 cells is associated with the release of cytochrome c from mitochondria through up-regulation of the proapoptotic Bax protein, which results in the activation of procaspase-9 and -3, and the cleavage of poly(ADP-ribose) polymerase (PARP). Accordingly, CR389 seems to have multiple mechanisms of antiproliferative activity through p53-mediated pathways against human ovarian cancer cells. Therefore, we conclude that CR389 is a candidate therapeutic agent for the treatment of human ovarian cancer via the activation of p53.

• Advances in environmental research
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• 제1권2호
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• pp.167-179
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• 2012

Pistachio shell (Pistacia vera) (PS), a low-cost material, has been utilized for the removal of the Cr(VI) ions after treatment with citric acid. Batch experimental steps were applied to obtain Cr(VI) ion adsorption details for the equilibrium between Cr(VI) and modified pistachio shell (MPS). The influences of contact time, pH, adsorbent dose and initial chromium concentration on the adsorption performance of MPS was investigated in detail. The results displayed that adsorption of Cr(VI) by MPS reached to equilibrium after 2 h and after that a little change of Cr(VI) removal efficiency was observed. The sorption percent is higher at lower pH and lower chromium concentration. Two possible mechanisms for reduction of Cr(VI) to Cr(III) can be suggested in Cr(VI) removal. In the first mechanism, Cr(VI) is reduced to Cr(III) by surface electron-donor groups of the adsorbent and the reduced Cr(III) forms complexes with adsorbent or remains in the solution. This Cr(III) is not adsorbed by adsorbent at pH 1.8. But in second mechanism, the adsorption-coupled reduction of Cr(VI) to Cr(III) occurred on the adsorbent sites. The equilibrium sorption capacity of Cr(VI) ion after 2 h was 64.35 mg/g for MPS.

• Korean Journal of Environmental Agriculture
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• 제24권3호
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• pp.203-209
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• 2005

Objective of this research was to assess the effectiveness of the different sources of the zero-valent irons (ZVIs) on the reduction of the toxic Cr(VI) to the nonhazardous Cr(III) in an aqueous solution. The physical and chemical properties of the six ZVIs were determined. Particle size and specific surface area of the ZVIs were in the ranges of $85.55{\sim}196.46{\mu}m\;and\;0.055{\sim}0.091m^2/g$, respectively. Most of the ZVIs contained Fe greater than 98% except for J (93%) and PU (88%). Reduction efficiencies of the ZVI for Cr(VI) reduction were varied with kinds of ZVIs. The J and PU ZVIs reduced 100% and 98% of Cr(VI) in the aqueous solution, respectively, within 3 hrs of reaction. However, PA, F, Sand J1 reduced 74, 65, 29 and 11% of Cr(VI), respectively, after 48 hrs. The pH of the reacting solution was rapidly increased from 3 to $4.34{\sim}9.04$ within 3 hrs. The oxidation-reduction potential (Eh) of the reacting solution was dropped from 600 to 319 mV within 3 hrs following addition of ZVIs to the Cr(VI) contaminated water. The capability of ZVIs for Cr(VI) reduction was the orders of PU > J > PA > F > S > J1, which coincided with the capacities to increase the pH and decrease the redox potentials. Results suggested that the reduction of Cr(VI) to Cr(III) was derived from the oxidation of the ZVI in the aqueous solution.

• Journal of Korean Ophthalmic Optics Society
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• 제11권3호
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• pp.281-291
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• 2006

The aim of this study was performed the clinical test using Netspeg lens for good visual acuity on subjects with abnormal refraction status. The subjects of one hundreds adults (fifty males, fifty females, mean=21 years, range=19 to 24) were recorded. The subjects were researched the history including the systemic health, medication, genetics, allergy, systemic disease and ocular disease. The refraction test was recorded the monocular and binocular using objective method. Visual acuity was performed the binocular status using the Netspeg lens and CR-39. Stereopsis test was performed the titmus fly and TNO at near distance using Netspeg lens and CR-39. The P-VEP test was used the 16 pattern size(Bausch Lomb, production in USA) with three channels. Also Subjects viewed the p-vep stimulus with binocular vision through the corrected visual acuity using the Netspeg lens and CR-39. The contrast sensitivity test was performed the contrast sensitivity chart(pelli-Robertson, USA) at 1m distance using the Netspeg lens and CR-39. The ultrastructure of surface on the Netspeg lens and CR-39 was observed the SEM(JMS-5800, made in Japan). The results of this study was as follows: 1. In corrected visual acuity of abnormal refraction using the Netspeg lens and CR-39, the Netspeg lens wearer were acquired the good visual field and clear visual acuity comparative to CR-39 wearer in the subject vision test. however the comfort of visual acuity was similar results in the Netspeg lens and CR-39. Also the subjects of Netspeg lens wearer was good visual acuity more than CR-39 wearer and in the analysis of P-VEP, the amplitude of wave on Netspeg lens used appears to be better through the CR-39(p>0.5). Besides, on the contrast sensitivity, the Netspeg lens wearer was good results than CR-39. The value on stereopsis with TNO by Netspeg lens wearer was better than CR-39 in results. However, in the stereopsis test with Titmus, the Netspeg lens and CR-39 wearer was similar results. 2. The ultrastructure of Netspeg lens surface was the smooth and fine shape more than CR-39. Also, Netspeg lens have a fine line structure in ultrastructure. In conclusion, the results of this study conformed that the surface ultrastructure of Netspeg lens used is more specific pin hole design structure than CR-39. This study indicated that the vision of Netspeg lens used have a better than CR-39 in the corrected visual acuity for abnormal refraction eye. Therefore, In this paper, we suggested that the ultrastructure and line structure of Netspeg lens was related to good visual function. However the visual function of the aspheric Netspeg and ultra waterproof Netspeg lens was similar results.

• Journal of the Korean Electrochemical Society
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• 제12권3호
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• pp.258-262
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• 2009

The composition and semiconducting properties of the passive films formed on Ni- (15, 30)Cr-5Mo alloys in pH 8.5 buffer solution were examined. The depth concentration profile of passive films formed on Ni-(15, 30)Cr-5Mo in pH 8.5 buffer solution showed that Mo enhances the enrichment of Cr. The Mott-Schottky plot for the passive film on Ni-(15, 30)Cr- 5Mo closely resembled that for the film on Cr, whereas those for the less Cr-enriched film on Mo-free alloys showed similar behavior to that for the film on Ni. The acceptor density was reduced by increasing Cr content in Ni-(15, 30)Cr-(0, 5)Mo alloys, but addition of Mo considerably increased the acceptor density.

• 한국전기화학회:학술대회논문집
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• 한국전기화학회 2001년도 춘계총회 및 학술발표회
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• pp.21-21
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• 2001

• Nuclear Engineering and Technology
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• 제6권4호
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• pp.231-237
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• 1974

For detection and localization of leaks in closed vessels or pipes carrying liquid flow, $^{51}$ Cr-EDTA and $^{51}$ Cr-DTPA were synthesized and, the column and batch equilibrium experiments were carried out. In the column experiment, the recovery of $^{51}$ Cr-EDTA is 100% in quartz sand and 80.9% in steel sawdust, and that of $^{51}$ Cr-DTPA is 77.4% in quartz sand and 6.4% in steel sawdust. The recovery curve. $^{51}$ Cr-DTPA system in steel sawdust does not show a certain plateau, exceptionally. In general, $^{51}$ Cr-EDTA is adsorbed less than $^{51}$ Cr-DTPA. In the batch equilibrium experiment, the distribution coefficients (Kd) and effect of pH were investigated by using quartz sand, montmorillonite, steel sawdust, and mixed cement raw material as media. In general, the Kd values for $^{51}$ Cr-EDTA are lower than that of $^{51}$ Cr-DTPA. The Kd values for $^{51}$ Cr-EDTA are almost zero at pH 6.0, 7.0, and 8.0.

• Journal of the Korean Chemical Society
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• 제30권5호
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• pp.423-432
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• 1986

Atomic absorption spectrophotometric (AAS) determination of hexavalent chromium [Cr(VI)] in a waste water was studied. Cr(VI) was extracted with p-xylene from the wastewater, in the way of ion pair formation with anion exchanger aliquat-336(tri-caprylmethyl ammonium chloride). 100ml waste water, after organic materials were extracted out with toluene, was acidified with conc. HCl adjusting the medium to pH 0.5 and 20ml of p-xylene containing 0.01M aliguat-336 was used to extract Cr(VI) from the acidified solution. The absorbance of chromium was measured with air-acetylene flame at 357.9nm. Standard addition method was used in the determining concentration of Cr(VI) extracted. No interference has been found in the extraction of Cr(VI) by the Al(III), Fe(III) and Cr(III) ion presented. However, Fe(II) decreased the absorbance of Cr(VI), due to the fact Fe(II) reduces Cr(VI) to Cr(III). The contained organic material was removed prior to extracting process, since it may reduced the absorbance of Cr(VI). The recovery of added Cr(VI) was over 96%, which seems to be promising and the relative standard deviation was 3.95%