• Advances in Energy Research
• /
• v.4 no.4
• /
• pp.285-297
• /
• 2016

Fundamental understanding of vanadium ion transport and the detrimental effects of cross-contamination on vanadium redox flow battery (VRFB) performance is critical for developing low-cost, robust, and highly selective proton-conducting membranes for VRFBs. The objective of this work is to examine the effect of conductivity and diffusivity, two key membrane parameters, on long-cycle performance of a VRFB at different operating conditions using a transient 2D multi-component model. This single-channel model combines the transport of vanadium ions, chemical reactions between permeated ions, and electrochemical reactions. It has been discovered that membrane selecting criterion for long cycles depends critically on current density and operating voltage range of the cell. The conducted simulation work is also designed to study the synergistic effects of the membrane properties on dynamics of VRFBs as well as to provide general guidelines for future membrane material development.

• Asian Pacific Journal of Cancer Prevention
• /
• v.15 no.1
• /
• pp.93-100
• /
• 2014

Background: Curcumin has has been reported to exert anti-inflammatory, anti-oxidation and anti-angiogenic activity in various types of cancer. It has also been shown to induce apoptosis in leukemia cells. We aimed to unravel the role of the redox pathway in Curcumin mediated apoptosis with a panel of human leukemic cells. Materials and Methods: In this study in vitro cytotoxicity of Curcumin was measured by MTT assay and apoptotic effects were assessed by annexin V/PI, DAPI staining, cell cycle analysis, measurement of caspase activity and PARP cleavage. Effects of Curcumin on intracellular redox balance were assessed using fluorescent probes like $H_2DCFDA$, JC1 and an ApoGSH Glutathione Detection Kit respectively. Results: Curcumin showed differential anti-proliferative and apoptotic effects on different human leukemic cell lines in contrast to minimal effects on normal cells. Curcumin induced apoptosis was associated with the generation of intracellular ROS, loss of mitochondrial membrane potential, intracellular GSH depletion, caspase activation. Conclusions: As Curcumin induces programmed cell death specifically in leukemic cells it holds a great promise as a future therapeutic agent in the treatment of leukemia.

• Korean Chemical Engineering Research
• /
• v.53 no.5
• /
• pp.638-645
• /
• 2015

Vanadium redox flow batteries (VRFBs) have been investigated for their potential utility as large energy storage systems due to their advantageous performances in terms of long cycle life, high energy efficiency, low cost, and flexible design. Carbon materials are typically used as electrodes in redox reactions and as a liquid electrolyte support. The activities, surface areas, and surface morphologies of porous carbon materials must be optimized to increase the redox flow battery performance. Here, to reduce the resistance in VRFBs, surface-modified carbon felt electrodes were fabricated, and their structural, morphological, and chemical properties were characterized. The surface-modified carbon felt electrode improved the cycling energy efficiencies in the VRFBs, from 65% to 73%, due to the improved wettability with electrolyte. From the results of impedances analysis with proposed fitting model, the electrolyte-coupled polarization in VRFB dramatically decreased upon modification of carbon felt electrode surface. It is also demonstrated that the compressibility of carbon felt electrodes was important to the VRFB polarization, which are concerned with mass transfer polarization. The impedance analysis will be helpful for obtaining better and longer-lived VRFB performances.

• Journal of Soil and Groundwater Environment
• /
• v.25 no.1
• /
• pp.25-36
• /
• 2020

In a redox transition zone, geochemical reactions are facilitated by active bacteria that mediate reactions involving electrons, and arsenic (As) and iron (Fe) cycles are the major electron transfer reactions occurring at such a site. In this study, the effect of repetitive redox changes on soil bacterial community in As-contaminated soil was investigated. The results revealed that bacterial community changed actively in response to redox changes, and bacterial diversity gradually decreased as the cycle repeated. Proportion of strict aerobes and anaerobes decreased, while microaerophilic species such as Azospirillum oryzae group became the predominant species, accounting for 72.7% of the total counts after four weeks of incubation. Bacterial species capable of reducing Fe or As (e.g., Clostridium, Desulfitobacterium) belonging to diverse phylogenetic groups were detected. Indices representing richness (i.e., Chao 1) and phylogenetic diversity decreased from 1,868 and 1,926 to 848 and 1,121, respectively. Principle component analysis suggests that repetitive redox fluctuation, rather than oxic or anoxic status itself, is an important factor in determining the change of soil bacterial community, which in turn affects the cycling of As and Fe in redox transition zones.

• Transactions of the Korean hydrogen and new energy society
• /
• v.17 no.1
• /
• pp.21-30
• /
• 2006

[ $M/Fe_2O_3$ ] (M=Rh, Ce and Zr) mixed oxides were prepared using urea method to develop a medium for chemical hydrogen storage by their redox cycles. And their redox behaviors by repeated cycles were studied using temperature programmed reaction(TPR) technique. Additives such as Rh, Ce and Zr were added to iron oxides in order to lower the reaction temperature for reduction by hydrogen and re-oxidation by water-splitting. From the results, concentration of urea used as a precipitant had little effect on particle size and reduction property of iron oxide. TPR patterns of iron oxide consisted of two reduction peaks due to the course of $Fe_2O_3\;{\rightarrow}\;Fe_3O_4\;{\rightarrow}\;Fe$. The results of repeated redox tests showed that Rh added to iron oxide have an effect on lowering the re-oxidation temperature by water-splitting. Meanwhile, Ce and Zr additives played an important role in prevention of deactivation by repeated cycles. Finally, Fe-oxide(Rh, Ce, Zr) sample added with Rh, Ce and Zr showed the lowest re-oxidation temperature by water-splitting and maintained high $H_2$ recovery in spite of the repeated redox cycles. Consequently, it is expected that Fe-oxide(Rh, Ce, Zr) sample can be a feasible medium for chemical hydrogen storage using redox cycle of iron oxide.

• BMB Reports
• /
• v.34 no.3
• /
• pp.278-283
• /
• 2001

Antioxidant and redox enzyme activities are known to be involved in the cellular responses to various stresses. Their variations were observed according to the growth cycle of the fission yeast Schizosaccharomyces pombe. Peroxidase activity appeared to be notably higher in the early exponential phase than in the mid-exponential and stationary phases. However, catalase activity showed a variation pattern resembling the growth curve. Glutathione S-transferase activity was higher in the early exponential and late stationary phases. Activities of the two redox enzymes, thioredoxin and thioltransferase (glutaredoxin), were high in the stationary phase. However, their activities appeared to increase from the early exponential to mid-exponential phase. Total glutathione content had a varying pattern similar to that of thioredoxin and thioltransferase. However, its content in the early exponential phase was high. These results propose that antioxidant and redox enzymes tested are also involved in the mechanism of cell growth.

• Macromolecular Research
• /
• v.10 no.1
• /
• pp.40-43
• /
• 2002

Poly(1', 4'-phenylene-1", 4"-(2"-(2""-ethyl-hexyloxy)) phenylene-1",4"-phenylene-2,5-oxadiazolyl) (PPEPPO) was synthesized and its electrochemical characteristics was investigated as electrode material in redox supercapacitor. The cyclic voltammetry (CV) shows there was scarcely a redox reaction and further suggests n-doping is difficult to occur in this system. However, the discharge curve between 3.0 to 0.01 V is continuously decreased like a straight line, similar to the discharge pattern of EDLC. The initial specific discharge capacitance is ~6.4 F/g, while the specific capacitance of 1000th cycle is ~0.1 F/g. The PPEPPO can be used as the electrode of supercapacitor, emissive material, as well as charge-transporting material in polymer LED.ansporting material in polymer LED.

• Membrane Journal
• /
• v.22 no.5
• /
• pp.285-300
• /
• 2012

Vanadium redox flow battery is believed to be one of important energy storage technologies, because it has many advantages, including long cycle life, high energy efficiency, low cost of maintenance, and environmental friendship. As one of the key components of vanadium redox flow battery system, an ion exchange membrane is required to prevent cross-mixing of the positive and negative electrolytes while allowing ionic continuity. However, ion exchange membrane such as Nafion using in VRBs still face some challenges in meeting performance and cost requirements for broad penetration. Therefore, to resolve these problems, developed various ion exchange membranes are investigated and compared with Nafion membranes in terms of their performance in vanadium redox flow battery.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
• /
• v.18 no.4
• /
• pp.421-437
• /
• 2020

This study provides an assessment on a proposed method for separation of cesium, strontium, and barium using electrochemical reduction at a liquid bismuth cathode in LiCl-KCl eutectic salt, investigated via cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and scanning electron microscopy with energy dispersive X-ray spectrometry (SEM-EDS). CV studies were performed at temperatures of 723-823 K and concentrations of the target species up to 4.0wt%. Redox reactions occurring during potential sweeps were observed. Concentration of BaCl2 in the salt did not seem to influence the diffusivity in the studied concentration range up to 4.0wt%. The presence of strontium in the system affected the redox reaction of lithium; however, there were no distinguishable redox peaks that could be measured. Impedance spectra obtained from EIS methods were used to calculate the exchange current densities of the electroactive active redox couple at the bismuth cathode. Results show the rate-controlling step in deposition to be the mass transport of Cs+ ions from the bulk salt to the cathode surface layer. Results from SEM-EDS suggest that Cs-Bi and Sr-Bi intermetallics from LiCl-KCl salt are not thermodynamically favorable.

• Proceedings of the Korean Ceranic Society Conference
• /
• 2003.04a
• /
• pp.124.2-124
• /
• 2003