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홍준표,매전고조,목촌강부 대한금속재료학회(대한금속학회) 1984 대한금속·재료학회지 Vol.22 No.2
A mathematical model has been presented for solidification analysis of ESR ingots. A general finite differential equation was formulated for computer simulation by the use of this model. The effects of ingot size, temperature at slag-metal interface, melting rate, and effective thermal conductivity in liquid on solidification profiles were investigated. The model proposed in the present work was successfully applied in treating solidification analysis of ESR ingots.
Takahashi, N.,Kajihara, T.,Okamura, C.,Kim, Y.,Katagiri, Y.,Okushima, Y.,Matsunaga, S.,Hwang, I.,Umeda, M. Current Biology Ltd ; Elsevier Science Ltd 2013 Current biology Vol.23 No.18
Plant roots respond to various internal and external signals and adjust themselves to changes of environmental conditions. In the root meristem, stem cells produce daughter cells that continue to divide several times. When these latter cells reach the transition zone, they stop dividing and enter the endocycle, a modified cell cycle in which DNA replication is repeated without mitosis or cytokinesis. The resultant DNA polyploidization, named endoreduplication, is usually associated with an increase of nuclear and cell volume and with cell differentiation [1-4]. At the transition zone, cytokinin signaling activates two transcription factors, type-B ARABIDOPSIS RESPONSE REGULATOR 1 (ARR1) and ARR12, and induces SHY2/IAA3, a member of the Aux/IAA family of auxin signaling repressors. This inhibits auxin signaling and reduces the expression of auxin efflux carriers, resulting in cell division arrest [5]. Such counteracting actions of two hormones are assumed to determine meristem size. However, it remains unknown whether cytokinins additionally control meristem size through an auxin-independent pathway. Here we show that, in Arabidopsis, the cytokinin-activated ARR2 directly upregulates the expression of CCS52A1, which encodes an activator of an E3 ubiquitin ligase, anaphase-promoting complex/cyclosome (APC/C) [6], thereby promoting the onset of the endocycle and restricting meristem size. Our genetic data revealed that CCS52A1 function is independent of SHY2-mediated control of auxin signaling, indicating that downregulation of auxin signaling and APC/C-mediated degradation of cell-cycle regulators cooperatively promote endocycle onset, and thus fine tune root growth.
A Systematic study on the growth of GaN single crystals using the Na-based fluxmethod
M. Kawahara,Y. Yamada,H. Umeda,M. Morishita,F. Kawamura,M. Yoshimura,Y. Mori,T. Sasaki 한양대학교 세라믹연구소 2005 Journal of Ceramic Processing Research Vol.6 No.2
To obtain bulk gallium nitride (GaN) single crystals applicable as the substrate for GaN homoepitaxial growth, we have adopted the Na flux method with some modifications. Assuming that a key reaction of this method is nitrogen dissolution into a flux, we considered both the gas composition and the liquid phase composition. The use of ammonia gas had effects in lowering the threshold pressure for the GaN growth compared with the nitrogen gas which had been used in the original Na flux method. The composition change from pure Na to a mixture of Ca and Na for the flux also brought some favorable effects such as lowering the threshold pressure, and an improvement in the crystal transparency. Finally, the liquid phase epitaxy (LPE) technique along with the Na-based flux method led to the growth of bulk GaN single crystals with much lower dislocation densities than the seed crystals.
메탄발효 처리된 가축분뇨내의 내분비계 장애물질에 대한 조사 연구
고한종 ( H. J. Ko ),김기연 ( K. Y. Kim ),김현태 ( H. T. Kim ),우메다미키오 ( M. Umeda ) 한국환경농학회 2007 한국환경농학회지 Vol.26 No.1
Concerns about endocrine disrupting chemicals emitted from humans and animals have been increased because these compounds are detected at very low levels in environment and adversely affect on indigenous fauna. To date, there is little information regarding the concentration of these compounds in animal wastes. In this study, the female hormones, 17β-estradiol (E2), estrone (E1) and estriol, were measured to provide baseline data in animal wastes. Samples were collected from animal waste storage, methane digester and sludge separated wastewater and analyzed by gas chromatography-mass spectrometry. To measure the mass ratios of estrogen to macronutrients, nitrogen and phosphorous were also determined. Sample collected from animal waste storage had the highest estrogen concentration (98.7 μg/L), while sludge separated wastewater had the lowest concentration (3.4 μg/L). The mean concentrations of E2 and E1 in waste storage sample were 6.8 μg/L and 68.7 μg/L, respectively. In sludge separated wastewater, the mean concentration of both E2 and E1 were reduced to 2.6 μg/L and 1.9 μg/L, respectively. However, estriol was not detected in any of the samples collected. Mean ratios of E2 and E1 to macronutrients were significantly different between the methane wastewater and sludge separated wastewater owing to elimination of solid particles.