• Journal of Powder Materials
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• v.27 no.3
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• pp.226-232
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• 2020

Bismuth vanadate (BiVO₄) is considered a potentially attractive candidate for the visible-light-driven photodegradation of organic pollutants. In an effort to enhance their photocatalytic activities, BiVO₄ nanofibers with controlled microstructures, grain sizes, and crystallinities are successfully prepared by electrospinning followed by a precisely controlled heat treatment. The structural features, morphologies, and photo-absorption performances of the asprepared samples are systematically investigated and can be readily controlled by varying the calcination temperature. From the physicochemical analysis results of the synthesized nanofiber, it is found that the nanofiber calcines at a lower temperature, shows a smaller crystallite size, and lower crystallinity. The photocatalytic degradation of rhodamine-B (RhB) reveals that the photocatalytic activity of the BiVO₄ nanofibers can be improved by a thermal treatment at a relatively low temperature because of the optimization of the conflicting characteristics, crystallinity, crystallite size, and microstructure. The photocatalytic activity of the nanofiber calcined at 350℃ for the degradation of RhB under visible-light irradiation exhibits a greater photocatalytic activity than the nanofibers synthesized at 400℃ and 450℃.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.11a
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• pp.295-298
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• 2000

Vanadate glasses in the Li$_2$O-P$_2$O$_{5}$-V$_2$O$_{5}$ system containing 10~20mo1% glass former, P$_2$O$_{5}$ were prepared by melting the batch in pt. crucible followed by quenching on the copper plate. We found that Li$_2$O-P$_2$O$_{5}$-V$_2$O$_{5}$ g1ass-ceramics obtained from crystallization of glass showed significantly higher capacity and longer cycle life than Li$_2$O-P$_2$O$_{5}$-V$_2$O$_{5}$ g1ass. In the present paper, we describe electro-chemical properties during crystallization process and find the best crystallization condition of Li$_2$O-P$_2$O$_{5}$-V$_2$O$_{5}$ g1ass as cathod material. Li$_2$O-P$_2$O$_{5}$-V$_2$O$_{5}$ glass-ceramics shows superior rechargeable capacity of 220 mAh/g in the cycling between 2.0 and 3.9V. between 2.0 and 3.9V.

• The Journal of Advanced Prosthodontics
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• v.15 no.2
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• pp.80-92
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• 2023

PURPOSE. This study incorporated the nanomaterial, nanostructured silver vanadate decorated with silver nanoparticles (AgVO₃), into heat-cured resin (HT) at concentrations of 2.5%, 5%, and 10% and compared the adhesion of multispecies biofilms, surface characteristics, and mechanical properties with conventional heat-cured (HT 0%) and printed resins. MATERIALS AND METHODS. AgVO₃ was incorporated in mass into HT powder. A denture base resin was used to obtain printed samples. Adhesion of a multispecies biofilm of Candida albicans, Candida glabrata, and Streptococcus mutans was evaluated by colony-forming units per milliliter (CFU/mL) and metabolic activity. Wettability, roughness, and scanning electron microscopy (SEM) were used to assess the physical characteristics of the surface. The mechanical properties of flexural strength and elastic modulus were tested. RESULTS. HT 10%-AgVO₃ showed efficacy against S. mutans; however, it favored C. albicans CFU/mL (P < .05). The printed resin showed a higher metabolically active biofilm than HT 0% (P < .05). There was no difference in wettability or roughness between groups (P > .05). Irregularities on the printed resin surface and pores in HT 5%-AgVO₃ were observed by SEM. HT 0% showed the highest flexural strength, and the resins incorporated with AgVO₃ had the highest elastic modulus (P < .05). CONCLUSION. The incorporation of 10% AgVO₃ into heat-cured resin provided antimicrobial activity against S. mutans in a multispecies biofilm did not affect the roughness or wettability but reduced flexural strength and increased elastic modulus. Printed resin showed higher irregularity, an active biofilm, and lower flexural strength and elastic modulus than heat-cured resin.

• The Korean Journal of Physiology
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• v.23 no.2
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• pp.237-252
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• 1989

Effect of a $Na^+$ gradient on $Ca^{2+}$ uptake was studied in isolated sarcolemmal vesicles of cat ileal longitudinal muscle. $Ca^{2+}$ uptake was markedly stimulated in the presence of an outwardly directed $Na^+$ gradient. External $Na^+$, monensin and A23187 abolished the $Na^+-dependent$ $Ca^{2+}$ uptake. Monovalent cations such as $K^+$, $Li^+$, $Rb^+$, $Cs^+$ and choline could not substitute for $Na^+$ in enhancement of $Ca^{2+}$ uptake. Divalent cations such as $Ba^{2+}$, $Sr^{2+}$, $Mn^{2+}$ and $Cd^{2+}$ but not $Mg^{2+}$ inhibited the $Na^+-dependent$ $Ca^{2+}$ uptake. Increase in external pH in the range of 6.0 to 8.0 stimulated the $Na^+-dependent$ $Ca^{2+}$ uptake. Amiloride inhibited the $Na^+-dependent$ $Ca^{2+}$ uptake at concentrations above 0.5 mM, whereas diltiazem or vanadate did not. The apparent Km of the $Na^+-dependent$ $Ca^{2+}$ uptake for $Ca^{2+}$ was 18.2 ${\mu}M$ and apparent Vmax was 689.7 pmole/mg protein/5 sec. Kinetic analysis of the $Na^+-dependent$ $Ca^{2+}$ uptake showed a noncompetitive interaction between internal $Na^+$ and external $Ca^{2+}$. The dependence of $Ca^{2+}$ uptake on internal $Na^+$ showed sigmoidal kinetics and Hill coefficient for internal $Na^+$ was 2.52. Inside positive membrane potential generated by imposing an inwardly directed $K^+$ gradient and valinomycin significantly stimulated the $Na^+-dependent$ $Ca^{2+}$ uptake. These results indicate that a $Na^+-Ca^{2+}$ exchange system exists in the sarcolemmal membranes isolated from cat ileal longitudinal muscle and it might operate as an electrogenic process.

• Journal of Plant Biology
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• v.35 no.2
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• pp.107-116
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• 1992

The roles of RNA- and protein-synthesis and $H^{+}$ excretion in 1AA ($10\;\mu\textrm{M}$)-induced elongation were investigated using abraded hypocotyl segments of sunflower (Helianthus annuus L.). The response of elongation initiated about 13 min after IAA treatment. Removal of cuticle, acting as diffusion barrier for inhibitors, by mechanical abrasion of hypocotyl segments enhanced the effect of inhibitors markedly, but the degree of abrasion for the saturated effect of inhibition was different among inhibitors. The elongation induced by 1M was completely inhibited when cycloheximide ($10\;\mu\textrm{M}$) was applied to abraded hypocotyl segments as shortly as 4 min before the onset of the growth response (= 10 min after administration of IAA). Cordycepin ($200\;\mu\textrm{M}$) prevented completely 1AA-induced elongation when applied as shortly as 19 min before the onset of the growth response (=5 min before administration of 1AA). Vanadate (1 mM) inhibited both lAA-induced elongation and medium acidification via lAA-induced $H^{+}$ excretion to apoplast. Cycloheximide and cordycepin also prevented lAA-induced $H^{+}$ excretion strongly. However, inhibition by cycloheximide of lAA-induced elongation was not alleviated by acidifying the cell wall to pH 4.5. The results indicate that, a few minutes before the initiation of growih, protein synthesis is demanded for the initiation of 1AA-induced elongation and the $H^{+}$ excretion to cell wall, and that the H+ excretion, even though it may be necessary for elongation, does not seem to bring about acid growth simply through acidifying cell wall.l wall.

• Resources Recycling
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• v.32 no.3
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• pp.26-37
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• 2023

Good control of the solution pH and temperature is required to recover vanadium from the water leaching solution of vanadium ore after sodium roasting. However, such adjustments could lead to aluminum-vanadium and sodium-vanadium co-precipitation, which greatly affects the efficiency of vanadium recovery. In this study, a process that can increase the efficiency of vanadium recovery as ammonium metavanadate [NH₄VO₃] and ammonium polyvanadate [(NH₄)₂V₆O₁₆·H₂O] was investigated by examining the characteristics of vanadium-containing aqueous solutions during precipitation. The aluminum content of vanadium-containing water leaching solutions has a great effect on the loss of vanadium when the pH of the aqueous solution is adjusted to 9. Therefore, a process to minimize aluminum leaching is also required. In this study, ~99% or more of vanadium present in vanadium-containing aqueous solutions was precipitated and recovered as NH₄VO₃ by adding 3 equivalents of ammonium chloride relative to the vanadium content at pH 9 and room temperature. (NH₄)₂V₆O₁₆·H₂O was precipitated from the aluminum-vanadium coprecipitates generated during the pH-adjustment of the aqueous solutions to 9 by dissolving the coprecipitate in the solutions at pH 2.5 and controlling their sodium content to 2,000 mg/L or less. Approximately, 98% or more of the available (NH₄)₂V₆O₁₆·H₂O could be precipitated and recovered from a solution with a vanadium content of 2,200 mg/L and a sodium content of 1,875 mg/L at pH 2.5 by adding approximately 3 equivalents of ammonium chloride relative to the vanadium content at 95℃ or higher. The overall process could precipitate and recover, approximately 91% or more of the total vanadium in the water leaching solution as NH₄VO₃ and (NH₄)₂V₆O₁₆·H₂O.

• The korean journal of orthodontics
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• v.24 no.1 s.44
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• pp.17-35
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• 1994

Vanadium is an essential trace element but has not been identified with a specific biogical role. To study the direct effects of vanadium on osteoblast, we incubated murin osteoblast-like (MC3T3-El) cells with various corcentration of vanadium oxide & sodium orthovanadate. This study was designed to investigate the effect of vanadium on DNA synthesis, alkaline phosphatase (ALP) activity, cAMP formation responsive to parathormone(PTH) and type I $\alpha$ 2 collagen ribonucleic acid (mRNA) level in murin osteoblast-like (MC3T3-El) cells. The cells were cultured in $\alpha-minimal$ essential medium$(\alpha-MEM)$ supplemented with $10\%$ fetal bovine serum (FBS) and then changed to $0.1\%$ FBS with various concenoation of vanadium oxide & sodium orthovanadate. Quiescent cultured MC3T3-El cells incubated for 24 hours with 2,5,10,15,20 ${\mu}M$ vanadium oxide incorporated $[^3H]Thymidine;$ every concentration showed increases in $[^3H]Thymidine$ incorporations dose dependant manner, the greatest response occurred at $20{\mu}M$. Quiescent cultured MC3T3-E1 cells incubated for 3days with 2,5,10,15,20 ${\mu}M$ vanadium oxide, for 2days with sodium orthovanadate and alkaline phosphatase was assayed with disodium phenyl phosphate as substrate. Vanadium oxide increased the alkaline phosphatase content in MC3T3-El cells at $2{\mu}M\;&\;6{\mu}M$ ; the greatest response occurred at $2{\mu}M$. But decreased at other content sodium orthovanadate increased alkaline phosphatase content in MC3T3-El cells at all concenoation ; the greatest response occurred at $4{\mu}M$. Quiescent cultured MC3T3-El cells incubated for 3days with $5,10{\mu}M$ vanadium oxide , with $5,8{\mu}M$ sodium orthovanadate and cAMP formation was measured by Radioimmunoassay(RIA). Vanadium oxide & sodium orthovanadate showed the tendency of inhibitory effects on cAMP responsiveness to PTH in MC3T3-El cells. Quiescent cultured MC3T3-El cells incubated for 24hours with $10,20{\mu}M$ vanadium oxide, with $5,10{\mu}M$ sodium orthovanadate and Type I $\alpha$ 2 collagen ribonucleic acid (mRNA) expression was studied by Nothern blot analysis. Northern blot analysis of vanadium oxide treated cells showed decreasing effects 0& sodium orthovanadate revealed increasing effects in type I $\alpha$ 2 collagen ribonucleic acid (mRNA) level.

• Applied Biological Chemistry
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• v.42 no.4
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• pp.298-303
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• 1999

In order to characterize the effects of heavy metal ions on the microsomal ATPase activities, microsomes were prepared from the roots of tomato plant and the activity of microsomal ATPase was measured by an enzyme-coupled assay. $Hg^{2+}$ inhibited the activity of microsomal ATPase in a dose-dependent manner, while $Gd^{3+}$, $Fe^{3+}$, $La^{3+}$, $Zn^{2+}$, and $Pb^{2+}$ inhibited not only the ATPase activity but also the activities of enzymes used in the assay. However, $Cs^+$ and $Ba^{2+}$ showed no significant effect. $Hg^{2+}$ inhibited the activities of both plasma membrane and vacuolar membrane $H^+-ATPases$. In the dose-response to $Hg^{2+}$, the activities of both microsomal $H^+-ATPases$ were severely inhibited at the concentration of $Hg^{2+}$ above $10\;{\mu}M$ and were completely inhibited at 1 mM $Hg^{2+}$. Apparent Ki values of $Hg^{2+}$ on the inhibitions of plasma membrane and vacuolar membrane $H^+-ATPases$ were $80\;{\mu}M$ and $58\;{\mu}M$, respectively. The $Hg^{2+}$-induced inhibitions were reversible since the addition of dithiothreitol completely reversed the inhibitory effects of $Hg^{2+}$. These results suggest that the inhibitory effects of $Hg^{2+}$ on both plasma, membrane and vacuolar membrane $H^+-ATPases$ are nonselective and reversible.

• Korean Journal of Materials Research
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• v.7 no.1
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• pp.81-88
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• 1997

Vanadate glasses using $B_2O_3$ as a network former and with CuO additive were mainly investigated in relation to electrical properties. Crystalline phases formed by heat-treatment in each composition were examined and dc electrical conductivity changes of the glasses were analyzed. Crystalline phases were identified as $V_3O_5,\;a-CuV_2O_6\;and\;{\beta}-CuV_2O_6$ by XRD analysis. Crystallization degrees of $V_2O_5$ and ${\beta}-CuV_2O_6$ were little changed with heat-treatment time, but those of ${\alpha}u-CuV_2O_6$ were changed sharply with heat-treatment time. The more crystallization of ${\alpha}u-CuV_2O_6$ occurred, the higher electrical conductivity was observed. Electrical conductivities with $10^{-2}~10^{-4}/{\Omega}/cm$ at room temperature(303K) could be obtained by controlling the glass compositions. The electrical conductivities were increased with increasing of $V_20_5$ content and decreasing of alkality($CuO/B_2O_3$). In this study, electron was proved to be charge carrier by seebeck coefficient measurement. Accordingly, the glasses are believed to be n-type semiconductor. Calculated activation energies for the conduction were in the range 0.098-0.124 eV. Electrical conduction mechanism was small polaron hopping without showing variable range hopping in the temperature range $30~200^{\circ}C$.

• Resources Recycling
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• v.30 no.6
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• pp.3-11
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• 2021

In this study, the effect of the solubility of ammonium metavanadate and the decomposition ratio of ammonium ions on a precipitation reaction-the precipitation of ammonium metavanadate by adding ammonium chloride to a sodium vanadate solution-was investigated. As the precipitation temperature and pH increased, the decomposition ratio of ammonium ions increased, and the decomposition ratio was greater than 81% at 45 ℃ and pH 9.3. This was approximately four times higher than that at pH 8. The result of the precipitation reaction, in view of these two factors that significantly influence the precipitation reaction, was that the precipitation yield increased as the temperature increased. However, the effect of temperature was not significant above 35 ℃. A kinetic study of the precipitation reaction revealed that the activation energy of the reaction was 42.3 kJ/mol. Therefore, considering the solubility of ammonium metavanadate, the lower the temperature, the better the vanadium recovery yield. Additionally, considering the decomposition of ammonium ions, the lower the pH of the aqueous solution, the more advantageous. However, at pH 8 or less, sodium polyvanadate is precipitated and the purity of vanadium oxide may reduce.