• Journal of the Korean Ceramic Society
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• v.21 no.1
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• pp.60-66
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• 1984

During the metallization in the manufacturing of the ceramic capacitor at the boundary layer between Pd or Pt electrode and $BaTiO_3$-dielectric reactions were analysed. For the study of the reaction Electron Spin Resonance (ESR) Method was used. With the aid of ESR an increased of the concentration of the paramagnetic $Ti^{3+}$-Centers on the metallizing process could be seen. It meaned a reduction effect although the metallization was accomplished under oxidation atmosphere. Therefore it could be regarded as a reaction at the boundary layer. In order to investigate the reaction ad double octahedral model was compared and the increase of the $Ti^{3+}$-concentration was studied.

• The Bulletin of The Korean Astronomical Society
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• v.42 no.2
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• pp.81.2-81.2
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• 2017

Polarized mid-infrared emission from polycyclic aromatic hydrocarbons (PAHs) can provide a crucial test of basic physics of alignment of nanoparticles and opens a potential new window into studying magnetic fields. In this talk, I will present a new model of polarized PAH emission that takes into account the effect of PAH alignment with the magnetic field due to resonance paramagnetic relaxation. I will then present our predictions for the polarization level of the strong PAH emission features from the interstellar medium. I will present the first detection of polarization of PAH emission at 11.3micron which is consistent with our theoretical prediction. Finally, I will discuss important implications of this work for tracing magnetic fields via mid-IR PAH features and for constraining the polarization of anomalous microwave emission that is useful for the quest of CMB B-modes.

• Nuclear Engineering and Technology
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• v.32 no.3
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• pp.254-260
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• 2000

Electron spin resonance (ESR) spectroscopy was used to detect irradiated meat containing bones (chicken, pork and beef）, to investigate the effect of irradiation dose on the ESR signal intensity and to identify the stability of radicals under 9 weeks of storage. Chicken, pork and beef were irradiated with doses 0, 1, 3, 5 and 7 kGy at room temperature using a Co-60 irradiator. Bones were pieced and dried, which were placed in a quartz tube within an Electron paramagnetic resonance (EPR) spectrometer resonator cavity. The irradiated bone presented an asymmetric absorption in shape, different from that of a non-irradiated one. The signal intensity of smaller animals are lower than larger species. Variation was observed between samples of the same species depending on the calcification status of the bone. Moreover different irradiation doses produced different signal areas that make possible to estimate the absorbed dose of treated meat. The ESR signal stability after irradiation was stable in even after a 9 week storage at room temperature.

• Journal of the Korean Ceramic Society
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• v.36 no.8
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• pp.843-847
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• 1999

The dc resistivity dc magnetization and thermopower of layered perovskite La1.6Ca1.4Mn2O7.07 have been studied. The ceramic sample of La1.6Ca1.4Mn2O7.07 undergoes the metal-insulator transition at 120K while a first-order phase transition from a ferromagnetic phase to a paramagnetic phae is observed at 260 K=TC This behavior is quite different from that of the well-known double exchange ferromagnets such as La1-xCaxMnO3 This phenomenon could be understood by considering the effects of the anisotropic double exchange interaction caused by two dimensional Mn-O-Mn networks in this materials. The dc magnetization between 120K and 250K is nearly constant and decreases rapidly with increasing temperature above 250K The measurements of dc resistivity and thermopower indicate that Zener polaron hopping conduction takes place above 260 K.

• Investigative Magnetic Resonance Imaging
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• v.5 no.1
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• pp.33-37
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• 2001

Purpose : The water exchange rate between bulk water and bound water is an important parameter in deciding the efficiency of paramagnetic contrast agents. In this study, we evaluated the water exchange rates of various Gd-chelates using oxygen-17 NMR technique. Material and Methods : The samples (Gd-DTPA, Gd-DTPA-BMA, Gd-DOTA, Gd-EOB-DTPA) were prepared by mixing 5% $^{17}O-enriched$ water (Isotech, USA). The pH of the samples was adjusted to physiological value [pH=7.0] by buffer solution. The variable temperature $^{17}O-NMR$ measurements were performed using Bruker-600 (14.1 T, 81.3 MHz) spectrometer. Bruker VT-1000 temperature control units were used to stabilize the temperature. The $^{17}O$ spin-spin relaxation times (T2) were measured using Carr-Purcell-Meiboom-Gill (CPMG)I pulse sequence with 24 echo trains. The variable temperature T2 relaxation data were then fitted into Solomon-Bloembergen equations using least square fit algorithm to estimate the water exchange times. Results : From the measured $^{17}O-NMR$ relaxation rates, the determined water exchange rates at 300K are $0.42{\;}{\mu}s$ for Gd-DTPA, $1.99{\;}{\mu}s$ for Gd-DTPA-BMA, $0.27{\;}{\mu}s$ for Gd-DOTA, and $0.11{\;}{\mu}s$ for Gd-EOB-DTPA. The Gd-DTPA-BMA showed slowest exchange whereas Gd-EOB-DTPA had fastest water exchange rate. In addition, it was found that the water exchange rates (${\tau}_m$) of all samples had exponential temperature dependence with different decay constant. Conclusion : $^{17}O-NMR$ relaxation rate measurements, when combined with variable temperature technique, provide a solid tool for studying water exchange rate, which is very important in investigating the detailed mechanism of relaxation enhancement effect of the paramagnetic contrast agents.

• Investigative Magnetic Resonance Imaging
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• v.4 no.1
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• pp.27-33
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• 2000

Purpose: To determine the electronic spin relaxation times, $T_{le}$, of three commercially available Gd-chelated MR contrast agents, Gd-DTPA, Gd-DTPA-BMA and Gd-DOTA, using Electron Paramagnetic Resonance(EPR) technique. Material and Methods: The paramagnetic MR contrast agents, Gd-DTFA(Magnevist) , Gd-DTFA-BMA(OMNISCAN) and Gd-DOTA(Dotarem), were used for this study, The EPR spectra of these contrast agents, which were prepared 2:1 methanol/water solution, were obtained at low temperatures, from $-160^{\circ}C~20^{\circ}C$. The glassy-state EPR spectra for these contrast agents were then fitted by the simulation spectra generated with different zero-field splitting (ZFS) parameters by a computer simulation program 'GEN', which generates the EPR powder spectrum using a given ZFS in $3{\times}3$ tensor. Finally, the spin relaxation times of the contrast agents were then determined from the $T_{2e}$, D, and E values of the best simulation spectra using the McLachlan's theory of average relaxation rate. Results: The electronic transverse spin relaxation times, $T_{2e}'s$, of Gd-DTPA, Gd-DTPA-BMA and Gd-DOTA were 0.113ns, 0.147ns and 1.81ns respectively. The g-values were 1.9737, 1.9735 and 1.9830 and the electronic spin relaxation times, $T_{1e}'s$, were 18.70ns, 33.40ns and $1.66{\mu}s$, respectively. Conclusion: The results of these studies reconfirm that the paramagnetic MR contrast agents with larger ZFS parameters should have shorter $T_{1e}'s$. Among three contrast agents used for this study, Gd-DOTA chelated with cyclic ligand structure shows better electronic property then the others with linear structure. Thus, it is concluded that the exact determination of ZFS parameters is the important factor in evaluating relaxation enhancement effect of the agents and in developing new contrast agents.

• JSTS:Journal of Semiconductor Technology and Science
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• v.4 no.4
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• pp.312-317
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• 2004

High dose ($3{\times}10^{16}cm^{-2}$) implantation of Fe or Ni ions into bulk, single-crystal ZnO substrates was carried out at substrate temperature of ${\sim}350^{\circ}C$ to avoid amorphization of the implanted region. The samples were subsequently annealed at $700^{\circ}C$ to repair some of the residual implant damage. X-Ray Diffraction did not show any evidence of secondary phase formation in the ZnO. The Ni implanted samples remained paramagnetic but the Fe-implanted ZnO showed evidence of ferromagnetism with an approximate Curie temperature of ${\sim}$240K. Preliminary X-Ray Photoelectron Spectroscopy measurements showed the Fe to be ill the 2+ oxidation state. The earrler density in the implanted region still appears to be too low to support carrier-meditated origin of the ferromagnetism and formation of bound magnetic polarons may be one potential explanation for the observed magnetic properties, No evidence of the Anomalous Hall Effect could be found in the Fe-implanted ZnO, but its transport properties were dominated by the conventional or ordinary Hall effect.

• Korean Journal of Materials Research
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• v.33 no.3
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• pp.95-100
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• 2023

This research examines the effect of adding aluminum on the structural, phasic, and magnetic properties of CoCrFe NiMnAl_x high-entropy alloys. To this aim, the arc-melt process was used under an argon atmosphere for preparing cast samples. The phasic, structural, and magnetic properties of the samples were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), and vibrational magnetometry (VSM) analyses. Based on the results, the addition of aluminum to the compound caused changes in the crystalline structure, from FCC solid solution in the CoCrFeNiMn sample to CoCrFeNiMnAl BBC solid solution. It was associated with changes in the magnetic property of CoCrFeNiMnAl_x high-entropy alloys, from paramagnetic to ferromagnetic. The maximum saturation magnetization for the CoCrFeNiMnAl casting sample was estimated to be around 79 emu/g. Despite the phase stability of the FCC solid solution with temperature, the solid solution phase formed in the CrCrFeNiMnAl high-entropy compound was not stable, and changed into FCC solid solution with temperature elevation, causing a reduction in saturation magnetization to about 7 emu/g.

• Korean Journal of Microbiology
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• v.37 no.1
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• pp.72-79
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• 2001

The effect of phenol on the change of bacterial community in the effluent water from a wastewater treatment plant was analyzed by PCR and terminal restriction fragment length polymorphism (T-RFLP). The fragments of 16S rDNA were amplified by PCR with bacterial primers, where one of the primers was biotinylated at the 5'-end. After digestion with restriction enzymes, HaeIII and AluI, the biotinylated terminal restriction tragments (T-RFs) of the digested products were selectively isolated by using streptavidin paramagnetic particles. The single-stranded DNA of T-RFs was separated by electrophoresis on a polyacrylamide gel and detected by silver staining technique. When 10 standard strains were analyzed by our method, each strain had a unique T-RF which corresponded to the calculated size from the known sequences of RDP database. The T-RFLP fingerprint generated from the effluent water was very complex, and the predominant T-RFs corresponded to members of the genus Acinetobacter, Bacillus and Pseudomonas. In addition, the perturbation of bacterial community was observed when phenol was added to the sample at the final concentration of 250 $l^{-1}$. The number of T-RFs increased and the major bacterial population could be assigned to the genus Acinetobacter, Comamonas, Cytophaga and Pseudomonas. A intense band assigned to the putative genera of Acinetobacter and Cytophaga was eluted, amplified, and sequenced. The nucleotide sequence of the T-RF showed close relationship with the sequence of Acinetobacter junii.

• Journal of the Korean Magnetics Society
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• v.18 no.6
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• pp.206-210
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• 2008

According to the recent reports the bulk bcc Rh is ferromagnetic with a small difference of energy compared to paramagnetic state. In this study, the electronic structure and magnetism for bcc Rh(001) surface are investigated by means of the all-electron full potential linearized augmented plane wave method within the generalized gradient approximation. It is found that the surface ferromagnetic state is preferable over the paramagnetic one. For unrelaxed system, the magnetic moment of the surface layer, $0.48{\mu}B$, is slightly increased comparing with the bulk value, $0.41{\mu}B$ while the value of the subsurface layer, $0.23{\mu}B$, is much smaller than the bulk value. The total energy and atomic force calculations show that the surface layer is relaxed downward and the subsurface layer moves upward to reduce the layer distance between the surface and subsurface layers by 7.0 %. The relaxation effect leads to weakening the surface magnetic properties. Specifically, the value of the magnetic moment of the surface atom is decreased to $0.36{\mu}B$. Since the spin polarization of the subsurface layer is only $0.14{\mu}B$, it is concluded that the bcc Rh(001) surface is rather weakly ferromagnetic.