• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.28 no.2
• /
• pp.91-97
• /
• 2018

Indium hydroxide powder was prepared by precipitation method. The reaction temperature ($150{\sim}250^{\circ}C$) and the holding time at each reaction temperature (1~72 h) were used as experimental variables. The particle size, microstructure and crystal phase of each prepared powder were observed through X-ray diffraction (XRD), Transmission electron microscope (FE-TEM) and BET. In this study, we investigated the phase and microstructural change induced by heat treatment of indium hydroxide nanoparticles at various temperatures for different holding times.

• Applied Biological Chemistry
• /
• v.43 no.4
• /
• pp.236-240
• /
• 2000

Correlations between mitochondrial respiration, glycolysis activity and overall growth activity of rice (Oryza sativa: cv. Dasan) seedlings during low temperature exposure were studied in order to provide insights into the underlying mechanism for the primary phase of chilling injury in plants. Among cellular membranes involved in energy metabolism, only the mitochondrial inner membrane showed not only physical phase transition at ca. $13^{\circ}C$, as monitored by ESR spin label, but also functional phase transition at the same temperature, as assessed by cytochrome c oxidase activity. The main regulatory enzyme of glycolysis, phosphofructokinase, in situ did not suffer phase transition of its activity at least in the $4{\sim}27^{\circ}C$ range. Low temperature caused a significant accumulation of glucose 6-phosphate (G6P) and fructose 6-phosphate (F6P), which disappeared almost completely on rewarming of the seedlings. Temperature profiles of the steady state levels of G6P and F6P revealed the inflection point appearing at around phase transition temperature of the mitochondrial membrane. The results conform to our previous proposition on the mechanism for the early stage events of chilling injury that the accumulation of glycolytic metabolites in cells due to metabolic imbalance at low temperature gives rise to an excess supply of electrons during rewarming period, which, in turn, results in overproduction of active oxygen in mitochondria.

• Journal of the Korean Society for Heat Treatment
• /
• v.7 no.2
• /
• pp.96-102
• /
• 1994

The present work was aimed to examine the changes of the shape and particle size distribution(PSD) of ${\delta}^{\prime}$ particles on ageing in Al-Li-(Cu, Zr) alloys which had low density, high specific strength and stiffness, Increasing ageing time and temperature resulted in particles whose aspect ratio tended toward 1. The aspect ratio of ${\delta}^{\prime}$ particles was not dependent upon the ageing temperature and time in Al-Li-Cu alloy but was dependent upon them in Al-Li-Zr alloy. The PSD of ${\delta}^{\prime}$ particles in Al-Li-Zr alloy skewed to the right hand compared with that in Al-Li-Cu alloy, because $Al_3Zr$ phase in Al-Li-Zr alloy formed before ageing promoted the precipitation and growth of ${\delta}^{\prime}$ phase. Therefore, the PSD of the ${\delta}^{\prime}$ particles was found to be affected by the presence of $Al_3Zr$ particles. The growth rate of ${\delta}^{\prime}$ phase was not affected by the existence of the third transition phase $T_1$ formed by the addition of Cu in Al-Li alloy but was affected by the existence of $Al_3Zr$ formed by the addition of Zr in Al-Li alloy.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.7 no.2
• /
• pp.253-258
• /
• 1997

The characteristics of crystal structure and phase transition with dopants ($Nb_2O_5$= 0.1~0.4 mol% and $Y_2O_3$ : 0.2~0.4 mol%) on the PTCR $BaTiO_3$ system were investigated. In the case of $Nb_2O_5$ additive, the lattice parameter of PTCR $BaTiO_3$ was changed linearly with the increasement of $Nb_2O_5$ which substituted B-site of BaTiO$_3$ and the lattice parameter of c-axis decreased abruptly at 0.3 mol%. These phenonmena were assumed to originate from the distortion of octahedron and we could confirm that the change of lattice parameter accorded with the characteristics of the phase transition temperature. $Y^{3+}$ ions substituted both of A- and B-site until the 0.3 mol% addition, but $Y^{3+}$ substitution preferred A- to B-site above 0.3 mol%. This was affirmed by the variation ,of lattice parameter and the characteristics of phase transition. It also was found that $Y^{3+}$ions in the A-site substituted both of $Ba^{2＋}$ and $Ca^{2＋}$ ions with equal ratio by Rietveld method.

• BMB Reports
• /
• v.29 no.3
• /
• pp.221-224
• /
• 1996

To examine the growth-phase dependent control of Escherichia coli rnpB gene we used a combination of Northern analysis for RNA determination and Southern analysis for plasmid DNA determination. The relative amounts of metabolically unstable transcript derived from the internally deleted rnpB gene harbored on a multicopy plasmid as well as the relative plasmid contents were measured by Northern analysis and Southern analysis, respectively, of total nucleic acids from E coli cells containing the plasmid. The relative transcription activity of the rnB was represented by a ratio of the relative amount of the transcript to that of the plasmid DNA during bacterial growth. The rnpB transcription increased rapidly with time during exponential growth, but started to decrease before the transition period of an exponential growing cell culture into the stationary phase. Although the expression pattern was similar to the changes of ${\beta}-galactosidase$ activity expressed from the lysogenic strain carrying the chromosomal rnpB-lacZ fusion which were shown in a previous work, the present data appears to represent a more actual growth-phase control of the rnpB transcription than the previous data by the ${\beta}-galactosidase$ assay. In addition the present method described for a direct analysis of both RNA and plasmid DNA provides a rapid and efficient method that can applied to an examination of transcription control by using a multicopy plasmid.

• Journal of the Korean Ceramic Society
• /
• v.41 no.9
• /
• pp.677-683
• /
• 2004

Nd:LLM (Nd:LiLa(MoO$_4$)$_2$) single crystals for the laser host material were grown by the Czochralski method. The Nd:LLM grown single crystals cracked easily, and the reasons of cracks are generally related with phase transition, incongruent melting, chemical heterogeneity of composition, geometric thermal structures of imbalance and growth direction. We confirmed that phase transition is not observed by TG-DTA thermal analysis, and the XRD analysis revealed congruent melting in our products. It was confirmed that the volatilization of Li$_2$O composition is the important reason of chemical heterogeneity. The geometric thermal profile of the resistance furnace of our own design was controlled with a crucible height. Also, Nd:LLM crystal affected growth direction, and was the best quality in case of (101) growth direction. The distribution and effective distribution coefficient of Nd$^{3+}$ ion were accomplished by PIXE analysis.s.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.17 no.9
• /
• pp.502-507
• /
• 2016

Vanadium dioxide, $VO_2$, is a thermochromic material that exhibits a reversible metal-insulator phase transition at $68^{\circ}C$, which accompanies rapid changes in the optical and electronic properties. To decrease the transition temperature around room temperature, a number of studies have been performed. The phase transition temperature of 1D nanowire $VO_2$ with a 100 nm diameter was reported to be approximately $29^{\circ}C$. In this study, 1D or 2D nanostructured $VO_2$ was grown using the vapor transport method. Vanadium dioxide has a different morphology with the same growth conditions for different substrates. The 1D nanowires $VO_2$ were grown on a Si substrate ($Si{\setminus}SiO_2$(300 nm), whereas the 2D & 3D nanostructured $VO_2$ were grown on an exfoliated graphene nanosheet. The crystallographic properties of the 1D or 2D & 3D nanostructured $VO_2$, which were grown by thermal CVD, and exfoliated-transferred graphene nanosheets on a Si wafer which was used as substrate for the vanadium oxide nanostructures, were analyzed by Raman spectroscopy. The as-grown vanadium oxide nanostructures have a $VO_2$ phase, which are confirmed by Raman spectroscopy.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.13 no.2
• /
• pp.95-100
• /
• 2000

For the well-controlled growing in-situ heavily phosphorus doped polycrystalline Si films directly on Si wafer by reduced pressure chemical vapor deposition, a study is made of the two step growth. When in-situ heavily phosphorus doped Si films were deposited directly on Si (100) wafer, crystal structure in the film is not unique, that is, the single crystal to polycrystalline phase transition occurs at a certain thickness. However, the well-controlled polycrtstalline Si films deposited by two step growth grew directly on Si wafers. Moreover, the two step growth, which employs crystallization of grew directly on Si wafers. Moreover, the two step growth which employs crystallization of amorphous silicon layer grown at low temperature, reveals crucial advantages in manipulating polycrystal structures of in-situ phosphorous doped silicon.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.13 no.1
• /
• pp.24-30
• /
• 2003

The preparation of $PbTiO_3$ powder was carried out using the oxide starting material by hydrothermal method. The powder of a crystalline phase with perovskite structure was synthesized. The optimum conditions for the preparation of powder were as follows; hydrothermal solvent; 8M-KOH or 8M-NaOH, reaction temperature; 250~$270^{\circ}C$, run time; 10 h. The ,shape of synthesized powders were well developed crystalline faces with specific surface area of about 2.3 $\textrm m^2$/g in KOH solution and about 5.0 $\textrm m^2$/g in NaOH solution. The cell parameters of powder were a = 3.90$\AA$, c = 4.14 $\AA$ and cell volume was 57.30 $\AA^3$. The cell ratio (c/a) of powder was the same as the theoretical ratio with c/a = 1.06 and the phase transition temperature(Tc) of the powders was about $470^{\circ}C$.

• Journal of the Mineralogical Society of Korea
• /
• v.18 no.4 s.46
• /
• pp.237-248
• /
• 2005

Results from in-situ high temperature X-ray diffraction measurements show that $Mg_{2}SiO_{4}{-}$spinel converts back to olivine phase only when heated in vacuum, and that at some high temperature, the olivine phase grows with time at the expense of the spinel phase strongly suggesting a 'nucleation and growth' type transition. In order to obtain the activation energy of spinel-olivine back transformation, kinetics measurements were performed on $Mg_{2}SiO_{4}{-}$spinel in vacuum at high temperatures between 1023 and 1116 K. Activation energy was determined using 'time to a given fraction method'. By employing the Avrami equation, it was found that n values generally increase with increasing temperature in a wide range implying that the nucleation and growth mechanism is probably temperature-dependent. It is likely that in spinel, at a relatively lower transformation temperature, after nucleation sites saturated, the growth of the new phase starts on the surface and gradually moves inwards. At high temperatures, however, after nucleation sites saturated, the growth starts both on the surface as well as at the interior.