• Toxicological Research
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• v.23 no.3
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• pp.279-287
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• 2007

Copper (Cu) is an essential trace element indispensable for brain development and function; either excess or deficiency in Cu can cause brain malfunction. While it is known that Cu and Fe homeostasis are strictly regulated in the brain, the question as to how systemic Fe status may influence brain Cu distribution was poorly understood. This study was designed to test the hypothesis that dietary Fe condition affects Cu transport into the brain, leading to an altered brain distribution of Cu. Rats were divided into 3 groups; an Fe-deficient (Fe-D) group which received an Fe-D diet ($3{\sim}5 mg$ Fe/kg), a control group that was fed with normal diet (35mg Fe/kg), and an Fe-overload group whose diet contained an Fe-O diet (20g carbonyl Fe/kg). Following a 4-week treatment, the concentration of Cu/Fe in serum, CSF (cerebrospinal fluid) and brain were determined by AAS, and the uptake rates of Cu into choroids plexus (CP), CSF, brain capillary and parenchyma were determined by an in situ brain perfusion, followed by capillary depletion. In Fe-D and Fe-O, serum Fe level decreased by 91% (p<0.01) and increased by 131% (p<0.01), respectively, in comparison to controls. Fe concentrations in all brain regions tested (frontal cortex, striatum, hippocampus, mid brain, and cerebellum) were lower than those of controls in Fe-D rats (p<0.05), but not changed in Fe-O rats. In Fe-D animals, serum and CSF Cu were not affected, while brain Cu levels in all tested regions (frontal cortex, striatum, hippocampus, mid brain, and cerebellum) were significantly increased (p<0.05). Likewise, the unidirectional transport rate constants $(K_{in})$ of Cu in CP, CSF, brain capillary and parenchyma were significantly increased (p<0.05) in the Fe-D rats. In contrast, with Fe-O, serum, CSF and brain Cu concentrations were significantly decreased as compared to controls (p<0.05). Cu transport was no significant change of Cu transport of serum in Fe-O rats. The mRNA levels of five Cu-related transporters were not affected by Fe status except DMT1 in the CP, which was increased in Fe-D and decreased in Fe-O. Our data suggest that Cu transport into brain and ensuing brain Cu levels are regulated by systemic Fe status. Fe deficiency appears to augment Cu transport by brain barriers, leading to an accumulation of Cu in brain parenchyma.

• Journal of the Korean Magnetics Society
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• v.21 no.2
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• pp.56-60
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• 2011

Optical properties of $T_{0.2}Fe_{2.8}O_4$ (T = V, Cr, Mn) thin films derived from ferrimagnetic $Fe_3O_4$ were investigated by spectroscopic ellipsometry in the 1~8 eV photon-energy range. The difference in optical-absorption spectrum between the ternary compounds and $Fe_3O_4$ was analyzed based on preferable sites in spinel structure and iconicity of the doped V, Cr, and Mn ions. The observed absorption spectra from $Fe_3O_4$ and the ternary compounds can be interpreted as mainly due to charge-transfer transitions of Fe d electrons characterized by absorption structures with wide energy width. Also, the observed absorption structures with narrow energy width can be interpreted as due to crystal-field transitions between different d electron configurations of tetrahedral $Fe^{3+}(d^5)$ ion. The transitions were described in terms of spin-polarized electronic states of $Fe_3O_4$.

• Progress in Superconductivity
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• v.12 no.1
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• pp.46-50
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• 2010

In the superconducting $Sr_2VO_3FeAs$, containing bimetallic layers, with maximum $T_c{\approx}\;46\;K$ correlation effects on V ions have been investigated using LDA+U method. Within the local density approximation (LDA) this system has the one-third filled $t_{2g}$ manifold of V, decomposed into $d_{xy}$ of bandwidth W=2 eV and nearly degenerate $d_{zx}d_{yz}$ of W=1 eV. Consideration of correlation effects leads to a metal-insulator transition on V ions $t^{2\uparrow}_{2g}\;{\rightarrow}\;d^{1\uparrow}_{xz}\;d^{1\uparrow}_{yz}$ at the critical on-site Coulomb repulsion $U_c$= 3.5 eV. At U=4 eV, the electronic structure, in which V ions are insulating, leads to several van Hove singularities near $E_F$ and similar Fermiology with other pnictides. Applying U to V ions results in increasing Fe moment as well as V moment, indicating somewhat hybridization between Fe and V ions even though this system is strongly 2-dimesional. Our results show possible importance of correlation effects on this system.

• Journal of the Korean Magnetics Society
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• v.15 no.4
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• pp.217-220
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• 2005

The electronic structure and magnetism of Fe chain along the [110] direction on Ag(001) were investigated by using the all-electron full-potential linearized augmented plane wave (FLAPW) method within generalized gradient approximation (GGA). The magnetic moment of Fe atom in Fe chain is calculated to be $3.02\;{\mu}_B$, which is slightly larger than that ($2.99\;{\mu}_B$) of the Fe[110] chain on Cu(001). The reduced coordination number for the Fe chain induced the Fe-d band narrowing and exchange-splitting enhancement, which are responsible for the large magnetic moment of the Fe chain. The calculated band width of the Fe-d band and the exchange-splitting are 1.7 eV and 3.2 eV, respectively.

• Journal of the Korean Magnetics Society
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• v.25 no.4
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• pp.101-105
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• 2015

Recent theoretical calculations predicted that a system composed exclusively of 3d transition metals without 4d/5d transition metals or rare earth metals can have strong perpendicular magnetocrystalline anisotropy (MCA) if Fe and Ni layers are arranged appropriately. They considered only Fe-terminated surfaces, noting that Fe/MgO(001) and CoFeB/MgO(001) show strong perpendicular MCA. In this paper, we investigate magnetism and MCA of Ni/Fe(001) surface where Ni layer is positioned at the surface, by using complementarily the first principles calculational methods of Vienna Ab-initio Simulation Package (VASP) and Full-potential Linearized Augmented Plane Wave (FLAPW) method. Comparing results of magnetism and MCA obtained by VASP with the results by FLAPW method, we find the VASP results do not show big difference from results by FLAPW method. Magnetic moments of Fe and Ni are enhanced due to strong hybridization between Fe and Ni bands. MCA of Ni/Fe(001) is parallel to the surface, which implies the surface termination plays a crucial role in determining MCA of a system.

• Journal of Magnetics
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• v.7 no.4
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• pp.132-137
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• 2002

The electronic structures and magnetism of the non-oxide perovskite MgCFe$_3$(001) surface were investigated by using the all-electron full-potential linearized augmented plane wave (FLAPW) method within the generalized gradient approximation (GGA). We considered both of the MgFe terminated (MgFe-Term) and the CFe terminated (CFe-Term) surfaces. We found that the minority spin d-bands of Fe(S) of the MgFe-Term are strongly localized and Fermi level (EF) lies just below the sharp peak of the minority spin d-band of Fe(S), while the minority spin d-bands of Fe(S) of the CFe-Term are not localized much and Fermi level (E$_F$) lies in the middle of two peaks of the minority spins. The majority Fe(S) d-band width of MgFe- Term is narrower than that of the CFe-Term. It is found that the magnetic moment of Fe(S) of the MgFe- Term is 2.51 ${\mu}$$_B$, which is much larger than that of 1.97 ${\mu}$$_B$ of the CFe-Term.

• Proceedings of the Korean Magnestics Society Conference
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• 1998.10a
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• pp.94-94
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• 1998

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.183-188
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• 2007

In this paper, we propose a 2D-FE model in single impact with combined physical factors to obtain a unique residual stress by shot peening. Applied physical parameters include elastic-plastic deformation of shot ball, material damping coefficients, strain rate, dynamic friction coefficients. Single impact FE model consists of 2D axisymmetric elements. The FE model with combined factors showed converged and unique distributions of surface stress, maximum compressive residual stress and deformation depth. Further, in contrast to the FE models with rigid shot and elastic deformable shot, FE model with plastic deformable shot produces residual stresses very close to experimental solutions by X-ray diffraction. We therefore validated the 2D FE model with combined peeing factors and plastic deformable shot. This FE model will be a base of the 3D FE model for residual stresses by multi-impact shot peening.

• Journal of Magnetics
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• v.13 no.4
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• pp.170-172
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• 2008

Fe-6.5% Si alloys have good magnetic properties due to their high electrical resistivity, very low magneto-striction, and low crystalline anisotropy. Despite their strong potential, these alloys have seldom been used in magnetic applications because of the very poor ductility of Si-steel above 3.0 wt% Si [1-4]. It is difficult to achieve compressed Fe-6.5% Si powder cores with excellent properties because of the low density due to poor ductility. In compressed powder cores, high density is essential in order to obtain high magnetization and permeability. In this study, an attempt was made to produce Fe-3%Si powder cores because the Fe-3.0 wt% Si alloys have relatively good magnetic properties and room temperature ductility. Gas atomized Fe-3.0 wt% Si powder was compressed into toroid shape cores. By reducing the Si content to 3.0 wt%, the hysteresis loss could be greatly reduced and thus the total core loss could be minimized. The total core loss is 600 mW/$cm^3$ at 0.1 T and 50 kHz.

• Journal of Soil and Groundwater Environment
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• v.26 no.1
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• pp.45-53
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• 2021

The removal of 2,4-dichlorophenoxyacetic acid (2,4-D) in aqueous solution by coupled electro-oxidation and Fe(II) activated persulfate oxidation process was investigated. The electrochemical oxidation was performed using carbon sheet electrode and persulfate using Fe(II) ion as an activator. The oxidation efficiency was investigated by varying current density (2 - 10 mA/㎠), electrolyte (Na2SO4) concentration (10 - 100 mM), persulfate concentration (5 - 20 mM), and Fe(II) concentration (10 - 20 mM). The 2,4-D removal efficiency was in the order of Fe(II) activated persulfate-assisted electrochemical oxidation (Fe(II)/PS/ECO, 91%) > persulfate-electrochemical oxidation (PS/ECO, 51%) > electro-oxidation (EO, 36%). The persulfate can be activated by electron transfer in PS/ECO system, however, the addition of Fe(II) as an activator enhanced 2,4-D degradation in the Fe(II)/PS/ECO system. The 2,4-D removal efficiency was not affected by the initial pHs (3 - 9). The presence of anions (Cl- and HCO3-) inhibited the 2,4-D removal in Fe(II)/PS/ECO system due to scavenging of sulfate radical. Scavenger experiment using tert-butyl alcohol (TBA) and methanol (MeOH) confirmed that although both sulfate (SO4•-) and hydroxyl (•OH) radicals existed in Fe(II)/PS/ECO system, hydroxyl radical (SO4•-) was the predominant radical.