J G Ahn

Publications (7)8.97 Total impact

• Article: Comparison of Bioleaching Kinetics of Spent Catalyst by Adapted and Unadapted Iron Oxidizing Bacteria - Effect of Pulp Density; Particle Size; Temperature

  D. Pradhan, D.J. Kim, J. G. Ahn, C.S. Gahan, H.S. Chung, S.W. Lee
  Korean Journal of Metals and Materials. 12/2011; 49(12):956-966.
• Article: Effect of Na4O7P2 on Cu powder preparation from Cu2O-water slurry system.

  J G Ahn, T H Hoang, D J Kim, M S Kim, C O Kim, H S Chung
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  ABSTRACT: A unique approach is presented for preparing highly dispersed ultrafine copper particles from cuprous oxide slurry using a wet chemical reaction with hydrazine (N2H4) as a reductant along with an appropriate addition of sodium pyrophosphate (Na4O7P2) as a surfactant. It was found that very thin oxidized surfaces on the copper particles are formed during the reaction in the solution and subsequently sodium pyrophosphate plays an important role in the zeta potential of the particles, affecting their dispersion and growth significantly. The copper particles at low zeta potential easily aggregate and grow to bigger ones, whereas they at high zeta potential keep away each other and grew individually to ultrafine size. Additionally, a model for the copper particles growth in accordance with dispersion is proposed.
  Journal of Colloid and Interface Science 04/2008; 319(1):109-14. · 3.07 Impact Factor
• Article: Vinorelbine-associated myelopathy in a patient who previously received paclitaxel: a case report.

  J Y Han, B G Choi, D H Song, J G Ahn, J S Yoon, K S Lee
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  ABSTRACT: Vinorelbine seems to cause less neurotoxicity than other vinca alkaloids because of its selective activity on mitotic cells over axonal microtubules. Clinical trials report very mild peripheral neurotoxicity with distal paresthesiae and there are no reports of myelopathy in these series of patients. The authors describe a patient who developed a rare event of myelopathy while on vinorelbine for non-small-cell lung cancer.
  Medical Oncology 02/2001; 18(1):95-7. · 2.14 Impact Factor
• Article: Cephalometric appraisal of posttreatment vertical changes in adult orthodontic patients.

  J G Ahn, B J Schneider
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  ABSTRACT: The purpose of this study was to evaluate vertical facial changes in adult orthodontic patients and to evaluate the stability of these changes. Thirty-three patients (8 males and 25 females) were examined. The patients had been treated with full fixed edgewise appliance mechanics and exhibited at least 1.0 degrees of clockwise rotation of the mandible during treatment. Mandibular rotation was determined by the angular change in the Y-axis to the Frankfort plane. Twelve angular and 14 linear skeletal and dental measurements and 3 skeletal ratios were derived from pretreatment (T1), posttreatment (T2), and postretention (T3) cephalometric radiographs. Paired t tests were used to compare vertical changes that occurred as a result of orthodontic treatment and their stability or relapse tendency during the retention and postretention periods. Twenty-five percent (P <.001) of the opening rotation of the mandible recovered during the posttreatment period, resulting in a significant overall rotation that was maintained. Both treatment and posttreatment changes in the Y-axis angle showed a high correlation with the horizontal position of pogonion (r = -0.797 and -0.889, respectively). Only overjet showed a low correlation between treatment changes and posttreatment changes in the Y-axis angle. Stepwise regression analysis of pretreatment variables and treatment changes failed to predict the behavior of the Y-axis angle change.
  American Journal of Orthodontics and Dentofacial Orthopedics 11/2000; 118(4):378-84. · 1.38 Impact Factor
• Article: Biomechanical considerations in distraction of the osteotomized dentomaxillary complex.

  J G Ahn, A A Figueroa, S Braun, J W Polley
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  ABSTRACT: The completely osteotomized dentomaxillary complex is essentially a free body constrained only by its soft tissue attachments. Therefore the line of action and point of application of any protractive force(s) used during distraction osteogenesis must be considered relative to its center of mass. This is in contrast to the nonsurgically separated dentomaxillary complex, which is a constrained body, and therefore the application of protractive force(s) must be considered relative to its center of resistance. These two centers are not coincident. With knowledge of the location of the center of mass, predictable protraction of the dentomaxillary complex can be achieved. In this study, the center of mass of an adult maxillary specimen osteotomized to emulate a Le Fort I osteotomy was determined. Protractive force(s) through the center of mass will produce linear advancement along its line of action. Protractive movement of the dentomaxillary complex can be adjusted downward and forward or upward and forward by locating the protractive force(s) line of action superior or inferior to the center of mass. A cleft patient is described wherein the surgically separated dentomaxillary complex is protracted downward and forward with a force vector superior to its approximate center of mass. This results in a predictable increase in overbite and overjet with negligible mandibular rotation.
  American Journal of Orthodontics and Dentofacial Orthopedics 10/1999; 116(3):264-70. · 1.38 Impact Factor
• Source

  Available from: PubMed Central

  Article: Trauma-induced isomorphic lesions in morphea--a brief case report.

  J G Ahn, Y T Kim, C W Lee
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  ABSTRACT: We describe a case of morphea which presented further typical lesions of the disease at the sites of mechanical trauma. It can be suggested that cutaneous lesions of morphea may be locally developed due to physical stimuli as an isomorphic response in patients or subclinical cases of the disease.
  Journal of Korean Medical Science 05/1995; 10(2):152-4. · 0.99 Impact Factor
• Article: Bioleaching of vanadium rich spent refinery catalysts using sulfur oxidizing lithotrophs

  D. Mishra, D.J. Kim, D.E. Ralph, J.G. Ahn, Y.H. Rhee
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  ABSTRACT: Bioleaching process was attempted by using chemo-lithotrophic sulfur oxidizing bacteria to recover valuable metals from vanadium-rich spent refinery catalysts. Prior to the bioleaching process, the spent refinery catalyst was pre-treated with acetone as the solvent. The bioleaching process was carried out in one-step and two-step methods and the leaching efficiencies in both the cases were compared. Bacteria were grown in the presence of up to 50 g/L of spent catalyst using elemental sulfur as the major substrate in the leaching medium. Varying the spent catalyst concentration in the bacterial growth medium in the one-step process conducted at pH 2–3 resulted in different amounts of solubilized metals. The maximum extraction yield of metals (88.3% Ni, 58.0% Mo and 32.3% V) was obtained with a concentration of 15 g/L spent catalyst. In the two-step process, the sulfur oxidizing bacteria were first cultivated in the presence of elemental sulfur in the growth medium, and the bacterially produced acid medium at pH 0.9–1.0 was subsequently used as the leaching agent. In this study, at 50 g/L spent catalyst concentration, 88.3% Ni, 46.3% Mo and V 94.8% were recovered after 7 days. Chemical leaching with commercial sulfuric acid was compared with the two-step process and the suitability o f the two-step process was demonstrated. In all the processes studied, however , a significant amount of molybdenum was found to be lost to the solid phase as MoO3.
  Hydrometallurgy.