• Transactions on Electrical and Electronic Materials
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• v.3 no.3
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• pp.25-28
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• 2002

In this study, microstructural, dielectric and electrical properties of (Pb$\sub$0.83/) (La$\sub$0.2/Ce$\sub$0.8/)$\sub$0.08/TiO$_3$(PCT) ceramics as a function of MnO$_2$ addition and electrode size variation were investigated for 30 MHz high frequency ceramic resonator application. Grain size was gradually increased according to the increase of MnO$_2$ addition amount. Moreover, the density showed a constant value with increasing MnO$_2$ addition amount. Dielectric constant was decreased with increasing MnO$_2$ addition amount. Curie temperature of all the composition ceramics was nearly constant around 330$^{\circ}C$. The maximum D.R.of 50.5 dB and maximum Q$\sub$mt3/ of 1842 in the 3$\^$rd/ overtone vibration mode were appeared at the composition of 0.3wt% MnO$_2$, respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.297-297
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• 2008

Buffer layers play an important role in the development of high critical current density coated conductor. $LaMnO_3$, $SrTiO_3$ and $BaZrO_3$ buffer layers were compatible with MgO surfaces and also provide a good template for growing high current density REBCO(RE=Rare earth) films. Systematic studies on the influences of pulsed laser deposition parameters (deposition temperature, deposition pressure, processing gas, laser energy density, etc.) on microstructure and texture properties of $LaMnO_3$, $SrTiO_3$ and $BaZrO_3$ films as buffer layer deposited on ion-beam assisted deposition MgO (IBAD_MgO) template by pulse laser deposition method, were carried out. These results will be presented together with the discussion on the possible use of this material in HTS coated conductor as buffer.

• The Korean Journal of Ceramics
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• v.6 no.1
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• pp.47-52
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• 2000

Lanthanides such as La, Gd and Ce have recognized as elements of high level radioactive wastes immobilized by forming solid solution with $CaTiO_3$. For easy forming solid solution between $CaTiO_3$and lanthanides, the combustion synthesis process was applied and the powder characteristics and sinterability were investigated. The proper selection of the type and the composition of fuels are important to get the crystalline solid solution of $CaTiO_3$and lanthanides. When glycine or the mixtures of urea and citric acid with stoichiometric composition was used as a fuel, the solid solution of $CaTiO_3$with $La_2O_3$or $Gd_2O_3$or $CeO_2$was produced very well by the combustion process. The combustion synthesized powder seemed to have a good sinterability with the linear shrinkage of more than 25% up to $1500^{\circ}C$, while that of the solid state reacted powder was less than 10% at the same condition.

• Molecules and Cells
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• v.42 no.2
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• pp.123-134
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• 2019

Lysophosphatidic acid (LPA) is an endogenous lysophospholipid with signaling properties outside of the cell and it signals through specific G protein-coupled receptors, known as $LPA_{1-6}$. For one of its receptors, $LPA_1$ (gene name Lpar1), details on the cis-acting elements for transcriptional control have not been defined. Using 5'RACE analysis, we report the identification of an alternative transcription start site of mouse Lpar1 and characterize approximately 3,500 bp of non-coding flanking sequence 5' of mouse Lpar1 gene for promoter activity. Transient transfection of cells derived from mouse neocortical neuroblasts with constructs from the 5' regions of mouse Lpar1 gene revealed the region between -248 to +225 serving as the basal promoter for Lpar1. This region also lacks a TATA box. For the region between -761 to -248, a negative regulatory element affected the basal expression of Lpar1. This region has three E-box sequences and mutagenesis of these E-boxes, followed by transient expression, demonstrated that two of the E-boxes act as negative modulators of Lpar1. One of these E-box sequences bound the HeLa E-box binding protein (HEB), and modulation of HEB levels in the transfected cells regulated the transcription of the reporter gene. Based on our data, we propose that HEB may be required for a proper regulation of Lpar1 expression in the embryonic neocortical neuroblast cells and to affect its function in both normal brain development and disease settings.

• Bulletin of the Korean Chemical Society
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• v.12 no.2
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• pp.130-137
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• 1991

The following new cryptand 221 complexes of lanthanides(Ⅲ) and dioxouranium(Ⅵ) nitrate have been synthesized: $(Ln(C_{16}H_{32}N_2O_5)(H_2O)_2(NO_3)_3\ and \((UO_2)_2(C_{16}H_{32}N_2O_5)(H_2O)_4(NO_3)_4$. These complexes have been identified by elemental analysis, moisture titration, conductivity measurements and various spectroscopic techniques. The proton and carbon-13 NMR as well as calorimetric measurements were used to study the interaction of cryptand 221 with La(Ⅲ), Pr(Ⅲ ), Ho(Ⅲ) and $UO_2(Ⅱ)$ ions in nonaqueous solvents. The bands of metal-oxygen atoms, metal-nitrogen atoms and O-U-O in the IR spectra shift upon complexation to lower frequencies, and the vibrational spectra ({\delta}NMN$) of metal-amide complexes in the crystalline state exhibit lattice vibrations below 300 $cm^{-1}$. The NMR spectra of the lanthanides(Ⅲ) and dioxouranium(Ⅵ) nitrate complexes in nonaqueous solvents are quite different, indicating that the ligand exists in different conformation, and also the $^1H$ and $^{13}C-NMR$ studies indicated that the nitrogen atom of the ring has greater affinity to metal ions than does the oxygen atom, and the planalities of the ring are lost by complexation with metal ions. Calorimetric measurements show that cryptand 221 forms more stable complexes with $La^{3+}$ and $Pr^{3+}$ ions than with $UO^{22+}$ ion, and $La^{3+}/Pr^{3+}$ and $UO^{22+}/Pr^{3+}$ selectivity depends on the solvents. These changes on the stabilities are dependent on the basicity of the ligand and the size of the metal ions. The absorption band (230-260 nm) of the complex which arises from the direct interaction of macrocyclic donor atoms with the metal ion is due to n-{\delta}*$ transition and also that (640-675 nm) of $UO^{22+}$-cryptand 221 complex, which arises from interaction between two-dioxouranium(Ⅵ) ions in being out of cavity of the ligand ring is due to d-d* transition.

• Proceedings of the Zoological Society Korea Conference
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• 2001.04a
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• pp.96.1-96
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• 2001

No Abstract, See Full Text

• Journal of Surface Science and Engineering
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• v.49 no.6
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• pp.595-603
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• 2016

Rare-earth zirconates, including lanthanum zirconate and gadolinium zirconate, have been investigated as ones of the most promising candidates for next-generation thermal barrier coating (TBC) materials due to their excellent properties such as low thermal conductivity, chemical stability at high temperature and so on. In this study, TBCs with three compositions, in the $La_2O_3-Gd_2O_3-ZrO_2$ system with reduced rare-earth contents from $RE_2Zr_2O_7$ compositions, were fabricated by using suspension plasma spray with different suspension preparation methods. The phase formation, microstructure, and thermal properties of TBCs were examined. In particular, each coating exhibited single fluorite phase and a dense, vertically-separated microstructure. The potential of coatings with rare-earth zirconates for TBC applications was also discussed.

• Journal of Powder Materials
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• v.25 no.3
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• pp.213-219
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• 2018

We report a method for preparing rare earth oxides ($Re_xO_y$) from the recycling process for spent Ni-metal hydride (Ni-MH) batteries. This process first involves a leaching of spent Ni-MH powders with sulfuric acid at $90^{\circ}C$, resulting in rare earth precipitates (i.e., $NaRE(SO_4)_2{\cdot}H_2O$, RE = La, Ce, Nd), which are converted into rare earth oxides via two different approaches: i) simple heat treatment in air, and ii) metathesis reaction with NaOH at $70^{\circ}C$. Not only the morphological features but also the crystallographic structures of all products are systematically investigated using field-emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD); their thermal behaviors are also analyzed. In particular, XRD results show that some of the rare earth precipitates are converted into oxide form (such as $La_2O_3$, $Ce_2O_3$, and $Nd_2O_3$) with heat treatment at $1200^{\circ}C$; however, secondary peaks are also observed. On the other hand, rare earth oxides, RExOy can be successfully obtained after metathesis of rare earth precipitates, followed by heat treatment at $1000^{\circ}C$ in air, along with a change of crystallographic structures, i.e., $NaRE(SO_4)_2{\cdot}H_2O{\rightarrow}RE(OH)_3{\rightarrow}RE_xO_y$.

• Proceedings of the Korean Vacuum Society Conference
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• 1999.07a
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• pp.172-172
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• 1999

Perovskite Manganese Oxide has been intensively investigated since the discovery of the colossal magnetoresistive(CMR) effect. In this paper, we studied the effect of temperature dependence and various doping dependence of rare earth site ions of La0.7-xPrxCa0.3MnO3 series using Ultraviolet Photoelectron spectroscopy(UPS). They show unusual temperature dependent features and the doped rare earth ions seem to affect the electron-phonon coupling strongly. We found clear evidence of metal-insulator transition from the spectral density at the Fermi level. but the transition temperature is lower than that deduced from transport measurements. Also we found that the spectral features change as time goes on implying that the surface of these materials is somewhat unstable in the vacuum. We can conclude from these results that the surface oxygen atoms correlated to the hopping electrons can escape from the material into the vacuum and that the surface state of these material is different from the bulk state.

• Journal of the Korean Electrochemical Society
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• v.10 no.4
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• pp.288-294
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• 2007

The LSCF cathode far Solid Oxide Fuel Cell was investigated to develop high performance unit cell at intermediate temperature by modified oxalate method with different electrolytes and different pH. The LSCF powders employed La, Sr, Co and Fe oxides, oxalic acid, ethanol and $NH_4OH$ solution were synthesized with pH controlled as 2, 6, 7, 8, 9 and 10 at $80^{\circ}C$ Single crystalline phase was obtained from pH $2{\sim}9$. on the other hand, $La_2O_3$ appeared from pH 10. Very fine powder with particle size of 50 nm was obtained at calcination temperature of $800^{\circ}C$ for 4 hours. LSCF cathode synthesized at pH 7 showed the highest electric conductivity in the temperature range of $600^{\circ}C$ to $900^{\circ}C$ its value was 950 S/cm at $900^{\circ}C$ Under same synthesis conditions, polarization resistance of each LSCF cathode was changed with different calcination temperatures. As-prepared powder presented 2.52, 1.54 and $2.58\;{\Omega}$ at $600^{\circ}C$ with ScSZ, 8Y-YSZ and GDC as its electrolyte respectively after calcination at $800^{\circ}C$ for 4 hours.