• Applied Chemistry for Engineering
• /
• v.10 no.6
• /
• pp.832-837
• /
• 1999

Stability of a cathode material was determined by Tafel plot in 1 M LiOH solution. The stabilized $LiM_xMn_{2-x}O_4$ (x=0.05~0.1) electrode resulted in overpotential of 0.13~0.15 mV at 100 mA. This overpotential was 0.05 mV lower than that of the spinel structured $LiMn_2O_4$ electrode. Conductivity test at various potentials showed that the conductivity of $LiM_xMn_{2-x}O_4$ was higher than that of the spinel structured $LiMn_2O_4$ and the bulk resistance of $LiM_xMn_{2-x}O_4$ due to the dissolution of $Mn^{2+}$ was lowered.

• Elastomers and Composites
• /
• v.52 no.4
• /
• pp.287-294
• /
• 2017

Nanocomposites based on $SnO_2-Mn$ were synthesized by the reaction of tin (II) chloride dihydrate and manganese (II) chloride tetrahydrate at a molar ratio of 10:1 in the presence of ammonium hydroxide at $80^{\circ}C$. The $SnO_2-Mn$ nanocomposites were stirred with fullerene [$C_{60}$] in a mass ratio of 2:1 in tetrahydrofuran to prepare $SnO_2-Mn-C_{60}$ nanocomposites; these nanocomposites were obtained upon heating the mixture of $SnO_2-Mn$ nanocomposites and fullerene [$C_{60}$] in an electric furnace at $700^{\circ}C$ for 2 h. The synthesized $SnO_2-Mn-C_{60}$ nanocomposites were confirmed through various characterization methods such as X-ray diffraction and scanning electron microscopy. The photocatalytic activities of the $SnO_2-Mn-C_{60}$ nanocomposites were demonstrated by the degradation of the organic dyes BG, MB, MO, and RhB under 254 nm irradiation and evaluated using UV-Vis spectrophotometry.

• Journal of the Korean Ceramic Society
• /
• v.28 no.8
• /
• pp.603-610
• /
• 1991

An oxygen deficient perovskite (CaLa)(MgMn)O5.43, with the cubic unit cell parameter of 3.826$\AA$, was prepared 115$0^{\circ}C$ for 10 hrs under the ambient oxygen gas pressure. The average oxidation state of manganese was determined to be 3.86 by the iodometric titration, so that the perovskite could be formulated as (CaLa) ({{{{ { MgMn}`_{ chi } ^{II } }}{{{{ { Mn}`_{ y} ^{III } }}{{{{ { Mn}`_{1- chi -y } ^{IV } }})O5.43 (2x+y=0.14). From X-ray photoelectron spectroscopy, the manganese ions in the lattice are mostly tetravalent, but two paramagnetic configurations were observed in the EPR spectrum: One sharp isotropic signal with hyperfines (ΔH 50 G, g=1.997$\pm$0.002 and │A│=82(4)$\times$10-4 cm-1) and a broad isotropic one (ΔH 1600 G, g=1.994$\pm$0.002), those which correspond respectively to Mn(II) and Mn(IV) ions. According to the magnetic susceptibility measurement, it follows the Curie-Weiss law from 20 K up to room temperature with $\mu$eff=5.23 $\mu$B, which is relatively larger than spin-only value({{{{ { mu }`_{eff} ^{s.o } }}=4.04 $\mu$B) due to the effect of weak ferromagnetic coupling. Such a result is in accord with a theory of semicovalence exchange.

• Proceedings of the Materials Research Society of Korea Conference
• /
• 2003.03a
• /
• pp.19-19
• /
• 2003

The injection of spins into nonmagnetic semiconductors has recently attracted great interest due to the potential to create new classes of spin-dependent electronic devices. A recent strategy to achieve control over the spin degree of freedom is based on dilute ferromagnetic semiconductors. Ferromagnetism has been reported in various semiconductor groups including II-Ⅵ, III-V, IV and II-IV,-V$_2$, which will be reviewed. On the other hand, to date the low solubility of magnetic ions in non-magnetic semiconductor hosts and/or low Curie temperature have limited the opportunities. Therefore the search for other promising ferromagnetic semiconducting materials, with high magnetic moments and high Curie temperatures (Tc), is of the utmost importance. In this talk, we also introduce new pure ferromagnetic semiconductors, MnGeP$_2$ and MnGeAs$_2$, exhibiting ferromagnetism and a magnetic moment per Mn at 5K larger than 2.40 ${\mu}$B. The calculated electronic structures using the FLAPW method show an indirect energy gap of 0.24 and 0.06 eV, respectively. We have observed spin injection in MnGeP$_2$ and MnGeAs$_2$ magnetic tunnel junctions through semiconducting barriers.

• Bulletin of the Korean Chemical Society
• /
• v.26 no.6
• /
• pp.925-929
• /
• 2005

Some new metal(II) complexes, $M^{II}L_2$ [M = Mn (1), Co (2), Ni (3), Cu (4), and Zn (5)] of 2-acetylpyridine benzoylhydrazone ligand (HL) containing trifunctional NNO-donor system have been synthesized and crystallographically characterized for the complex 1 and 5. The complexes consist of two ligands to give sixcoordinate, which are bonded to the metal atom on a meridional plane through acetylpyridine ring nitrogen, azomethine nitrogen, and benzoyl oxygen atoms, respectively. The coordination geometry for other complexes was identified on the basis of the physicochemical data by elemental analyses, FAB -MS, IR, $^1H$ NMR, and electronic spectral measurements. The resulting data indicated that the complexes are accordance with the above formulation.

• Mycobiology
• /
• v.49 no.5
• /
• pp.507-520
• /
• 2021

Papiliotrema huenov was previously reported to be highly tolerant of a range of extremely toxic heavy metals. This study aimed to identify the potential of P. huenov to remove manganese and copper from aqueous solution. Physical conditions which affect removal of Mn(II) and Cu(II) were determined. Optimal temperature for adsorption of both metal ions was 30 ℃, and optimal pH for maximum uptake of Mn(II) and Cu(II) were 5 and 6, respectively. Under these conditions, living cells of P. huenov accumulated up to 75.58% of 110 mg/L Mn(II) and 70.5% of 128 mg/L Cu(II) over 120 h, whereas, the removal efficiency of metal ions by dead cells over 1 h was 60.3% and 56.5%, respectively. These results indicate that living cells are more effective than dead biomass for bioremediation, but that greater time is required. The experimental data extends the potential use of P. huenov in biosorption and bioaccumulation of toxic heavy metals to copper and manganese, two of the most common industrial contaminants.

• Journal of the Mineralogical Society of Korea
• /
• v.20 no.2 s.52
• /
• pp.125-134
• /
• 2007

This study has been carried out in order to examine the precipitation characteristics of Fe, Mn and Al ions in coal mine drainage before removing heavy metals by using the froth flotation method. The removal rate of Fe(III), Mn(II) and Al(III) within 1 h accounted for over 99% in pH 5.0, 10.0, and $6.0{\sim}9.0$ respectively, and residual concentrations of which were under $1mgL^{-1}$. When sodium oleate as a collector was added to the solution of Fe, Mn, and Al ions, insoluble salts was not formed by the reaction of heavy metal and sodium oleate. So, we must remove the metals from coal mine drainage by using not the ion flotation method, but the precipitation flotation method

• Journal of the Korean GEO-environmental Society
• /
• v.15 no.8
• /
• pp.39-44
• /
• 2014

Effects of operating parameters on the breakthrough properties of Pb(II) by $Mn_3O_4$ coated activated carbon prepared by supercritical technique were investigated through fixed-bed column experiments. The mass transfer zone and equilibrium adsorption capacity were enhanced about 2.8 times for Pb(II) by $Mn_3O_4$ coating onto activated carbon. Increase of bed height enhanced the residence time of Pb(II) in adsorption zone, giving the higher breakthrough time, mass transfer zone and equilibrium adsorption capacity. Increase of flow rate reduced the residence time and diffusion of Pb(II) in adsorption zone, therefore decreased the equilibrium adsorption capacity. The higher inlet concentration of Pb(II) decreased the breakthrough time and mass transfer zone through the promotion of Pb(II) transfer onto adsorbent.

• The Korean Journal of Physiology and Pharmacology
• /
• v.21 no.4
• /
• pp.377-384
• /
• 2017

Activation of protein kinase C (PKC) is closely linked with endothelial dysfunction. However, the effect of $PKC{\beta}II$ on endothelial dysfunction has not been characterized in cultured endothelial cells. Here, using adenoviral $PKC{\beta}II$ gene transfer and pharmacological inhibitors, the role of $PKC{\beta}II$ on endothelial dysfucntion was investigated in cultured endothelial cells. Phorbol 12-myristate 13-acetate (PMA) increased reactive oxygen species (ROS), p66shc phosphorylation, intracellular adhesion molecule-1, and monocyte adhesion, which were inhibited by $PKC{\beta}i$ (10 nM), a selective inhibitor of $PKC{\beta}II$. PMA increased the phosphorylation of CREB and manganese superoxide dismutase (MnSOD), which were also inhibited by $PKC{\beta}i$. Gene silencing of CREB inhibited PMA-induced MnSOD expression, suggesting that CREB plays a key role in MnSOD expression. Gene silencing of $PKC{\beta}II$ inhibited PMA-induced mitochondrial ROS, MnSOD, and ICAM-1 expression. In contrast, overexpression of $PKC{\beta}II$ using adenoviral $PKC{\beta}II$ increased mitochondrial ROS, MnSOD, ICAM-1, and p66shc phosphorylation in cultured endothelial cells. Finally, $PKC{\beta}II$-induced ICAM-1 expression was inhibited by Mito-TEMPO, a mitochondrial ROS scavenger, suggesting the involvement of mitochondrial ROS in PKC-induced vascular inflammation. Taken together, the results suggest that $PKC{\beta}II$ plays an important role in PMA-induced endothelial dysfunction, and that the inhibition of $PKC{\beta}II$-dependent p66shc signaling acts as a therapeutic target for vascular inflammatory diseases.

• Economic and Environmental Geology
• /
• v.50 no.6
• /
• pp.545-554
• /
• 2017

Birnessite is one of the dominant Mn (oxyhydr)oxide phases commonly found in soil and deep ocean environments. It typically occurs as nano-sized and poorly crystalline aggregates in the natural environment. It is well known that birnessite participates in a wide variety of bio/geochemical reactions as a reactive mineral phase with structural defects, cation vacancies, and mixed valences of structural Mn. These various bio/geochemical reactions control not only the fate and transport of inorganic and organic substances in the environment, but also the formation of diverse Mn (oxyhydr)oxides through birnessite transformation. This review assessed and discussed about the phase transformation of birnessite under a wide range of environmental conditions and about the potential geochemical factors controlling the corresponding reactions in the literature. Birnessite transformation to other types of Mn (oxyhydr)oxides were affected by dissolved Mn(II), dissolved oxygen, solution pH, and co-existing cation (i.e., $Mg^{2+}$). However, there still have been many issues to be unraveled on the complex bio/geochemical processes involved in the phase transformation of birnessite. Future work on the detail mechanisms of birnessite transformation should be further investigated.