Large Positive Potential Research Articles

Thermal stability and thermal decomposition mechanism of octamethyltrisiloxane (MDM): Combined experiment, ReaxFF-MD and DFT study

The thermal stability and decomposition mechanism of octamethyltrisiloxane (MDM) were studied using a combination of experimental, ReaxFF simulation, and DFT calculation techniques. After heating MDM for 24 h at 250 °C and 1 MPa, the signature product CH4 was detected, along with liquid products such as hexamethyldisiloxane (MM) and decamethyltetrasiloxane (MD2M). The decomposition rate of MDM remained relatively constant in the temperature range of 250 °C–320 °C but exhibited a sharp increase at 350 °C. Higher pressure was found to promote MDM polymerization. The oxygen (O) atoms displayed a large negative electrostatic potential, while the hydrogen (H) and silicon (Si) atoms exhibited a large positive potential. The electrostatic interaction facilitated the rearrangement reactions, with O and carbon (C) atoms being the most reactive for electrophilic and free radical reactions. The thermal decomposition of MDM initiated with the cleavage of Si–C bonds. Hydrogen extraction reactions between methyl radicals and MDM, as well as Si–O bond rearrangement reactions of demethylated radicals with MDM, further promoted MDM decomposition and the formation of CH4 and siloxane oligomers. These findings are significant for the safe application of MDM as a working fluid in ORC system.

Simulation study on single-event burnout in field-plated Ga2O3 MOSFETs

This paper presents the 2-D numerical simulation results of the heavy-ion induced single-event burnout (SEB) and single event gate rupture (SEGR) in the depletion-mode gallium-oxide (Ga2O3) field-plated metal-oxide-semiconductor field-effect transistors (FP-MOSFETs). The employed simulation physics models and material parameters were validated by the basic electrical characteristics in experiments. The SEB sensitive region was proven to be from the gate edge to the drain edge of the structure. The SEB failure could result from the large number of mobile holes that diffused into the strong electric field to form a very large joule heat power to induce thermal failure. Meanwhile, the SEGR sensitive region overlapped with that of the SEB. The accumulated at the gate channel interface could produce a high-density hole pool that formed a large positive potential to induce an SEGR. Based on the simulations, a catastrophic SEB was triggered at a drain voltage of around 350 V, which was 46.4 % of breakdown voltage. Besides, a severe leakage current degradation could be estimated at about 175 V. However, for the SEGR performance, an SEGR could be triggered even at 0 V. Finally, the influences of the field plate extension length on SEB and SEGR were investigated that the SEB sensitive region and maximum electric field during SEGR could be both improved.

Iron Complex Posolyte Species Possessing Low Capacity Fade Rate Combined with Large Positive Redox Potential for Aqueous Organic Flow Batteries

Redox flow batteries are promising technologies for energy storage and conversion applications. Among different types of flow batteries, iron-based redox-active materials can have cost and environmental advantages. We introduce a high-potential tris(2,2'-bipyridine-4,4'-diyldimethanol) iron dichloride compound as a posolyte species with a redox potential more than 0.5 V more positive than that of ferro/ferricyanide. The new species, abbreviated Fe(Bhmbp)3, operating at near-neutral pH, was paired with bis(3-trimethylammonio)propyl viologen tetrachloride as the negolyte species. The resulting aqueous flow battery exhibits an open-circuit voltage of 1.36 V and it shows excellent cycling stability with a capacity fade rate of 0.0007% per cycle or 0.07% per day. In comparison with previously reported organic and metalorganic compounds, Fe(Bhmbpy)3 exhibits a superior combination of high positive redox potential and low capacity fade rate. We investigated the decomposition pathways during cell cycling to an unprecedented level of depth for an aqueous posolyte. We found that the compound degrades through self-discharge, dimerization and ligand dissociation. The proposed decomposition pathways explain the capacity fade phenomena and offer opportunities for future improvement of metalorganic posolytes with high redox potential and good cycling stability

Improving the lithium recovery using leached beta-spodumene residues processed by magnetic nanohydrometallurgy

World's largest production of lithium is mostly performed through the acid lixiviation of β-spodumene mineral (LiβS), LiAlSi2O6. The process generates large amounts of leached spodumene residues (LSR) containing the protonated form, here denoted HβS, among the several impurities from the system. HβS preserves the structure of LiβS, and can be used for capturing and recycling lithium ions. In this work, a nanotechnological approach, called magnetic nanohydrometallurgy (MNHM), was applied to selectively extract HβS from the leached spodumene residues. Accordingly, maghemite nanoparticles functionalized with diethylenetriamine (MagNP) were employed, because of their great stability and large positive zeta potentials in the protonated form. Such nanoparticles interact strongly with the negatively charged β-spodumene particles, allowing their magnetic separation as MagNP//HβS composites. After releasing the HβS content by an acid treatment, the product was isolated in pure form and used for recovering lithium ions. This material performs with great efficiency, reaching a lithium content of 3.55% in the final composition, corresponding to 95.1% of the theoretical value (3.73%) predicted for this mineral. In comparison with the previously reported values using directly the leached spodumene residues for the capture of lithium ions, a great improvement has been achieved in this work. The MagNP//HβS composite also can be used for lithium ion capture. By increasing the HβS purity, MNHM can promote lithium recycling, in a sustainable way.

High crystallinity design of Ir-based catalysts drives catalytic reversibility for water electrolysis and fuel cells

The voltage reversal of water electrolyzers and fuel cells induces a large positive potential on the hydrogen electrodes, followed by severe system degradation. Applying a reversible multifunctional electrocatalyst to the hydrogen electrode is a practical solution. Ir exhibits excellent catalytic activity for hydrogen evolution reactions (HER), and hydrogen oxidation reactions (HOR), yet irreversibly converts to amorphous IrOx at potentials > 0.8 V/RHE, which is an excellent catalyst for oxygen evolution reactions (OER), yet a poor HER and HOR catalyst. Harnessing the multifunctional catalytic characteristics of Ir, here we design a unique Ir-based electrocatalyst with high crystallinity for OER, HER, and HOR. Under OER operation, the crystalline nanoparticle generates an atomically-thin IrOx layer, which reversibly transforms into a metallic Ir at more cathodic potentials, restoring high activity for HER and HOR. Our analysis reveals that a metallic Ir subsurface under thin IrOx layer can act as a catalytic substrate for the reduction of Ir ions, creating reversibility. Our work not only uncovers fundamental, uniquely reversible catalytic properties of nanoparticle catalysts, but also offers insights into nanocatalyst design.

Influence of First and Second Coordination Environment on Structural Fe(II) Sites in MIL-101 for C–H Bond Activation in Methane

Divalent iron sites in tri-iron oxo-centered metal nodes in metal–organic frameworks (MOFs) catalyze light alkane oxidation. The first two steps of the reaction sequence, which are also the most energetically demanding ones, are the formation of the active species, Fe(IV)═O, by N2O decomposition and subsequent C–H bond cleavage. We have employed Kohn–Sham density functional methods to explore how modification of the microenvironment around the Fe(II) center can modulate its catalytic activity, akin to what noted in metalloenzymes. We have varied the substituents on the organic linker of the MIL-101(Fe) MOF, as a way to modulate the energy barriers associated with the first two steps of the methane to methanol reaction. The calculations show that varying substituents has a minimal electronic effect on the iron center and its first coordination shell. However, their proximity to the active site can modify the barriers by 20%. Hydrogen bond donors can lower both barriers, such that the resulting Fe(IV)═O species are simultaneously more stable and more reactive than those of the parent MOF. The screening of a large set of systems allowed us to establish rules for the selection of second coordination shell elements to improve the reactivity of oxoferryl-based catalysts: (i) functionality with a low pKa or large positive electrostatic potential, (ii) a distance around 1.5 Å between the oxoferryl and any atom of the ring substituent, and (iii) low conformational flexibility of the added substituent.

Voltage Loss Analysis of Zinc-Cerium Redox Flow Batteries

Redox flow batteries (RFBs) are a relatively new generation of electrochemical devices suitable for large-scale energy storage applications. The separation between the electrolyte storage tanks and the electrochemical cell in RFBs simplifies the battery scale-up and facilitates the energy/power ratio tuning. In comparison to current energy storage devices, RFBs are beneficial due to their portability, flexibility and low maintenance cost [1].Among the different types of RFBs investigated, those based on zinc and cerium are very attractive due to the large negative and positive electrode potentials in an aqueous media. Thus, zinc-cerium RFBs are capable of providing one of the highest cell voltages (~ 2.4 V) among flow batteries and a large theoretical energy density [2]. To date, Zn-Ce RFBs have primarily been investigated galvanostatically to determine their charge, voltage and energy efficiencies and attempts have been made to suppress the rate of the hydrogen and oxygen evolution side reactions [3-6]. In order to further optimize the performance of these batteries and to elucidate the future pathways to enhance their efficiency, the sources of voltage loss in the battery during discharge must be identified and the role of the positive and negative half-cells in the voltage loss determined. Toward this goal, we have conducted in situ polarization and EIS experiments on a full-cell Zn-Ce RFB with reference electrodes inserted in the system [7]. The insertion of the reference electrodes in the RFB enables us to decouple the contribution of negative and positive electrodes to the total performance loss. At low and intermediate current densities, the main contributor to the voltage loss during discharge is the kinetic overpotential of the negative Zn/Zn2+ half-cell. On the other hand, at high current densities, mass transfer limitations at the positive Ce3+/Ce4+ half-cell cause a large potential drop in the system. From in situ kinetic studies, we have measured an exchange current density of ∼ 7.4×10−3 A cm−2 for Zn oxidation and ∼ 24.2×10−3 A cm−2 for Ce4+ reduction, which is consistent with our previous findings from battery operation that the kinetics of the negative electrode reaction is slow compared to that of the positive electrode at low-to-intermediate current densities. The use of an alternative mixed methanesulfonate-chloride negative electrolyte to reduce the kinetic overpotential of the negative half-cell reaction and the influence of the flow rate on the mass-transfer rate of the positive half-cell reaction have also been investigated and will be discussed in this presentation.[1] De Leon, C. P., Frías-Ferrer, A., González-García, J., Szánto, D. A., & Walsh, F. C. (2006). Redox flow cells for energy conversion. Journal of power sources, 160(1), 716-732.[2] Walsh, F. C., Ponce de Léon, C., Berlouis, L., Nikiforidis, G., Arenas‐Martínez, L. F., Hodgson, D., & Hall, D. (2015). The development of Zn–Ce hybrid redox flow batteries for energy storage and their continuing challenges. ChemPlusChem, 80(2), 288-311.[3] Leung, P. K., Ponce-de-León, C., Low, C. T. J., & Walsh, F. C. (2011). Zinc deposition and dissolution in methanesulfonic acid onto a carbon composite electrode as the negative electrode reactions in a hybrid redox flow battery. Electrochimica Acta, 56(18), 6536-6546.[4] Nikiforidis, G., Berlouis, L., Hall, D., & Hodgson, D. (2014). An electrochemical study on the positive electrode side of the zinc–cerium hybrid redox flow battery. Electrochimica Acta, 115, 621-629.[5] Amini, K., & Pritzker, M. D. (2018). Electrodeposition and electrodissolution of zinc in mixed methanesulfonate-based electrolytes. Electrochimica Acta, 268, 448-461.[6] Amini, K., & Pritzker, M. D. (2019). Improvement of zinc-cerium redox flow batteries using mixed methanesulfonate-chloride negative electrolyte. Applied Energy, 255, 113894.[7] Amini, K., & Pritzker, M. D. (2020). In situ polarization study of zinc–cerium redox flow batteries, Journal of Power Sources, 471, 228463

Multiple Active Sites Carbonaceous Anodes for Na+ Storage: Synthesis, Electrochemical Properties and Reaction Mechanism Analysis

AbstractOwing to the earth‐abundant resources, cost effective materials and stable electrochemical properties, sodium‐ions batteries (SIBs) show long‐term potential in responding to the rapid consumption of lithium resources and the ever‐increasing development of new energy storage devices. Nevertheless, the intrinsic properties of the large ion radius (Na+ 1.02 Å vs Li+ 0.76 Å) and positive reduction potential (Na/Na+ −2.71 V vs Li/Li+ −3.04 V) may impede ion diffusion, thus causing serious volume expansion, resulting in poor cycling stability. To address these issues, the incorporation of active sites into carbonaceous anode is considered as an efficient strategy to enhance interfacial compatibility, enlarge interlayer distance, and supply reversible Faradic pseudo‐capacitance. Herein, the multiple active sites carbonaceous anodes for SIBs anode are comprehensively reviewed. Typically, carbonaceous materials are categorized into diffusion and surface controlled based on Na storage mechanism, and the concepts of intrinsic/extrinsic active sites are proposed according to the types of active sites. Furthermore, to reveal the reaction kinetics and guide the rational design of high performance anodes, the (spectro) electrochemical analysis methods and corresponding key parameters are introduced. Additionally, primary superiorities, essential issues, and supposed solutions of multiple active sites carbonaceous Na anodes are discussed and the future development directions are also proposed. This review may provide new design thoughts for high performance carbonaceous Na storage anodes.

Plasma Convection in the Terrestrial Magnetotail Lobes Measured Near the Moon's Orbit

AbstractIn order to study the plasma convection in the deep magnetotail lobes near lunar orbit, we investigated ions originating from the tenuous exosphere and surface of the Moon, which are measured by the Acceleration, Reconnection, Turbulence, and Electrodynamics of Moon's Interaction with the Sun (ARTEMIS) spacecraft. Directly measuring the plasma convection in the tail lobes is difficult, due to the typically large positive spacecraft potential. In this work we show that in the terrestrial magnetotail near the Moon, the convection velocity can be estimated by measuring the velocity of lunar ions. Determining what factors control the lobe convection is important in understanding the linkage between the upstream conditions and the dynamics of the tail lobes. Based on systematic analysis of multiple ARTEMIS observations and OMNI data, we find that the interplanetary magnetic field (IMF) and magnetospheric activity plays an important role in controlling plasma convection in the near‐Moon lobes.

Bioconjugation of aptamer to fluorescent trimethyl chitosan nanoparticles for bacterial detection

Trimethyl chitosan nanoparticles (TMC NPs), the positively charged chitosan derivative, have been used to deliver medicines to overcome the tissue barrier. Here, fluorescein-labeled TMC NPs were produced by a microemulsion method following the bioconjugation of the single-strand DNA aptamer which can specifically bind to E. coli (DH5α). TMC NPs show uniform spherical particles with an average diameter of 323 ± 10 nm. The large positive zeta potential, 37.1 ± 2.2 mV, indicates the net positive charged surface of TMC NPs which is a suitable carrier for crossing tissue barriers. The linear relationship of the maximum fluorescence intensity of aptamer modified TMC NPs and the concentration of E. coli (DH5α) is obtained. We hope that the fluorescent TMC NPs integrating with a suitable aptamer could be used to understand the pathway of bacteria crossing the host barrier to fight against invasive infections.

As(III) adsorption onto different-sized polystyrene microplastic particles and its mechanism

We systematically investigated the surface characteristics of polystyrene microplastic particles (PSMPs) prepared by ball milling to impart a porous surface structure and special surface characteristics, and studied the mechanism of adsorption of As(III) onto PSMPs. The sizes of the PSMPs prepared by ball milling for 2, 4, and 8 h were in the ranges of 0.1–1, 1–10, and 10–100 μm, respectively. That is, the longer the milling time is, the larger the specific surface area of the particles is. Moreover, the higher the point of zero charge is, the higher the adsorbed amount of As(III) is. The highest adsorption rate of As(III) onto PSMPs was found to be 1.12 mg g−1. After 1200 min, the adsorption reached equilibrium, and a pseudo-second-order model better fitted the As(III) adsorption kinetics. The Langmuir and Freundlich models could well describe the adsorption isotherms. Furthermore, hydrogen bonds between As(III) and PSMPs were broken at high temperatures, resulting in a decrease in As(III) adsorption onto PSMP, which indicated that the adsorption process was exothermic. Increases in the pH and concentrations of interfering nitrate and phosphate ions in the solution led to inhibited As(III) adsorption of PSMPs. The electrostatic potential of most areas of the PSMP surface was positive, and the H atom on the carboxyl group exhibited a very large positive potential (+56.6 kcal/mol), and thus attracted arsenic oxyanions. Thus, it was determined that As(III) adsorbed to the surface of PSMPs through hydrogen bonding with the carboxyl group. Electrostatic forces and non-covalent interactions are the key mechanisms affecting the adsorption of As(III) onto PSMPs. This work provides a clear theoretical basis for the behavior of the PSMP as an arsenic carrier and might aid to improve the environmental toxicity of arsenic.

Adsorption mechanism of As(III) on polytetrafluoroethylene particles of different size

Microplastics exhibit active environmental behavior and unique surface characteristics, and act as carriers for the migration of trivalent arsenic (As(III)) in the environment. Herein, the mechanism by which polytetrafluoroethylene (PTFE) microplastic particles adsorb As(III) is systematically determined. The larger the size of PTFE particles, the smaller the specific surface area, the higher the point of zero charge (PZC), and the more unfavorable adsorption of As(III); the highest adsorption amount can reach 1.05 mg g−1. The adsorption process can be divided into three stages by the intraparticle diffusion model: external mass transfer, intraparticle diffusion, and dynamic equilibrium, of which the external mass transfer stage is the adsorption rate-limiting stage. The Langmuir isotherm model better represented the equilibrium adsorption results. The adsorption of As(III) by PTFE was an exothermic process, and because the increase in temperature broke the hydrogen bond, the amount of adsorption was decreased, which was not conducive to spontaneous adsorption. In the pH range of 3–7, as the pH value increased, the amount of As(III) adsorbed by PTFE gradually decreased, which may be related to the change in PZC for PTFE and the protonation of As(III). The H on the surface hydroxyl group of the PTFE exhibited a very large positive potential (+82.37 kcal mol−1). Thus, it can attract the arsenic oxyanion, and As(III) was subsequently adsorbed on the surface of the PTFE through the hydrogen bond on the hydroxyl group. Electrostatic force and non-covalent interaction were the key mechanisms affecting the PTFE adsorption.

Enhanced electrocatalytic activity of Pd and Pd-polyaniline nanoparticles on electrochemically exfoliated graphite sheets

The catalyst support materials play an important role in improving the performance of electrocatalysts for alcohol oxidation reaction. In this work, flexible graphite sheets containing a large number of edge planes were electrochemically exfoliated by the application of large positive and negative potentials in acetonitrile medium. The process described here produces several surface functional groups on graphite sheet surface. In this work, the utility of such a functionalized surface is explored as a solid support for depositing Pd and Pd-PANI nanostructures which are studied for oxidation of alcohols in alkaline medium. The results show that these electrode materials exhibit an excellent electrocatalytic activity with very high turnover frequency and low activation energy values for ethanol oxidation reaction that has the potential to be used in low temperature polymer membrane alkaline fuel cells.

Characteristics of halide oxidation at graphite electrode for use in halide batteries

The oxidation of halides, in particular bromide, has been studied in aqueous solutions on graphite electrodes by voltammetry, electrochemical impedance spectroscopy (EIS) and UV–Vis spectroscopy in light of its application in halide/halogen batteries used in microgrids. Voltammetry indicates fairly large differences in potentials and current density between different halide salts, concentrations, cation type and pH. Also, oxidation kinetics in 7MNaBr were much higher than in 7MZnBr2 solutions while no large differences were observed between these solutions at 2 M. This may be related to the effect that positive ions (Na+ and Zn+) may have an influence in halide oxidation kinetics at the large positive electrode potentials which indicated that local ionic potential effects affect the oxidation rate of the reaction. Moreover, EIS spectra seemed to go in line with this view, as there was a large resistance between ZnBr2 and NaBr in the electrolyte phase transfer element. This difference is possibly related to different polybromide formation rates (for the reaction Br− → Brx− + xe-). Additionally, results and literature shows that all data may be fitted by one equivalent circuitwith the fitted circuit and Nyquist plots showing the complexity of the reaction by the presence of different resistors and capacitors.

Tethered Capacitor Charge Mitigation in Electron Beam Experiments

Energetic electron beams have been proposed for tracing magnetic field lines from the magnetosphere down to the ionosphere, in active experiments aimed at diagnosing mechanisms at play in the coupling between magnetosphere and ionosphere. It is recognized however that in the absence of an efficient mitigation technique, this approach would lead to unacceptably large spacecraft charging and positive potential buildup, which would result in environmental hazard for the spacecraft. This problem would be particularly acute in low density regions of the magnetosphere of interest in the study of magnetic field reconnection and substorm dynamics. A solution to this predicament could consist of creating a plasma contactor whereby a gas puff would be ionized, leading to the evacuation of positive charges and collection of cold electrons, thus compensating for the charges lost in the electron beam. A possible alternative is presented here, which consists of attaching a large passive conducting surface to the spacecraft, a “tethered capacitor”, from which negative charges would be drawn to compensate for those lost from the beam. This capacitor would then charge to a large positive potential, leaving the spacecraft and electron gun at a lower, acceptable positive potential. The tethered capacitor could have a relatively small mass; consisting only of a thin conducting surface that would be “inflated” as a result of repulsive electrostatic forces. This charge mitigation concept, as applied to active electron beam experiments, is explored using three dimensional particle-in-cell (PIC) simulations from which scaling laws can be inferred for the spacecraft and tethered capacitor potentials under proposed electron beam operations.

Solvent molecule mobilities in propylene carbonate-based electrolyte solutions coexisting with fumed oxide nanoparticles

Non-aqueous LiClO4 solutions kneaded with various fumed oxides (fumed silica, fumed alumina, and fumed titania) were employed as model systems of lithium ion batteries. The properties of the solid phase and Li+ ions, which affect solvent molecules, were evaluated using 1H NMR spectroscopy and 1H NMR relaxation time (T1, T2) measurements. The 1H NMR signals of propylene carbonate (PC) molecules were influenced by the coexisting solid phase in the LiClO4-PC solution/fumed oxide nanoparticle dispersion. The mobilities of the PC molecules drastically decreased in the presence of only 1–2 vol% of the solid phase (liquid phase thickness is 15–20 nm or less), regardless of the fumed oxide employed. In the IR spectra of the PC/fumed alumina systems, the vibrations at higher wavenumbers were predominantly observed because of indirect electron-donation from the solid surface. The 1H NMR signal detection ratios depended on the fraction of the liquid phase influenced by the solid phase. In the LiClO4-PC solution/fumed alumina systems, the 1H NMR signal detection ratios greatly decreased because of this influence; here, the large positive zeta potential of the solid phase surface of fumed alumina attracted the PC molecules, which had local negative electric fields owing to polarization. Moreover, the T1 and T2 results confirmed that the interaction between the solid phase and PC molecules is much smaller than that between the solid phase and water molecules. Additionally, it was seen that the PC solution system was more significantly affected than the aqueous solution system; the network structure of the entire PC solvent is greatly affected by the addition of the Li+ ion, and the relaxation time decreased significantly.

Simultaneous Opto- and Spectro-Electrochemistry: Reactions of Individual Nanoparticles Uncovered by Dark-Field Microscopy.

Despite the frequent use of silver nanoparticles in consumer products and medical treatments, their reactivity and degradation in aqueous suspensions are still under debate. Here we elucidate this reactivity by an in situ opto- and spectro-electrochemical approach. Using dark-field microscopy coupled to a spectrophotometer and to an electrochemical cell, redox reactions of individual silver nanoparticles are studied in the presence of chloride. The intensity and spectral position of the plasmon resonance of an individual particle are tracked simultaneously in real time during cyclic voltammetry. They both change almost instantaneously with the detected current in a chemically reversible way. Thus, it is evidenced that the intensity decrease of the optical signal at the silver peak position is caused by the reversible formation of silver chloride and not by dissolution of silver. Moreover, at large positive potentials, further transformation to silver oxide or chlorite is revealed spectroscopically, although the electrochemical current is hidden by water and chloride oxidation. Thus, the combination of electrochemistry with dark-field microscopy and hyperspectral imaging is introduced as a new tool for real-time analysis of (electro-)chemical reactions of nanoparticles on a single-entity level.

The COX-2 selective blocker inhibit cytokine-induced apoptosis in isolated articular chondrocytes

Purpose: Osteoarthritis (OA) is a progressive degenerative disease of the cartilage that leads to irreversible cartilage loss, joint pain and dysfunction. Chondrocyte apoptosis contributes to the disruption of cartilage integrity in osteoarthritis (OA). Recently, we reported that activation of volume-sensitive Cl- current (ICl,vol) mediates cell shrinkage triggering apoptosis in rabbit articular chondrocytes. On the other hand, COX blocker is frequently used for treatment of OA. However, it is not understood whether and how COX blocker affects metabolism of rabbit articular chondrocytes. In the present study, we examined in vitro effects of COX-2 selective blocker on TNFα-induced activation of ICl,vol in rabbit chondrocytes using the whole-cell patch-clamp technique. Our results show that COX-2 selective blocker effectively reverses TNFα-induced elicitation of ICl,vol and consequently inhibits apoptotic volume decrease (AVD) and elevation of caspase activity. Methods: Rabbit cartilages were collected from joints of male animals weighing 2.5 to 3.0 kg. The cartilage was dissected into slices and cultured in DMEM for 1-3 days. On the day of experiments, chondrocytes were isolated by enzymatic digestion. Whole-cell membrane current was recorded under conditions where Na+, K+ and Ca2+ currents were minimized. Caspase-3/7 activity was measured in chondrocytes treated with TNF-α without or with various test compounds. Cell size measurements and patch-clamp experiments were conducted on round-shaped chondrocytes. Live chondrocytes microscopy images were captured (at 1 min intervals) before and during a hypo-osmotic challenge at a 2560*1920 pixel resolution using a CCD digital camera. The cell cross-sectional areas were calculated using Image-J. Results: The TNF-α evoked Cl- current exhibited electrophysiological and pharmacological properties similar to those of ICl,vol, such as outward rectification, prominent inactivation at large positive potentials (>+50 mV), inhibition by hyperosmotic cell shrinkage, and sensitivity to ICl,vol blockers. Pretreatment of cells with the COX-2 selective blocker markedly inhibited the ICl,vol activation by TNF-α as well as subsequent apoptotic events such as elevation of caspase 3/7 activity. Conclusions: The COX-2 selective blocker has an inhibitory effect on TNF-α-induced apoptotic events, which suggests the efficacy of this drug for the treatment of chronic destructive joint disease. Future studies are awaited to examine whether and how the COX-2 blocker has a favorable action against OA chondrocyte in humans.

Ammonia Defective Etching and Nitrogen-Doping of Porous Carbon toward High Exposure of Heme-Derived Fe–Nx Site for Efficient Oxygen Reduction

The utilization of metal and nitrogen doped carbon as a Pt-free oxygen reduction electrocatalyst depends largely on the homogeneous composition of the metal–nitrogen sites with limited content. Herein a simple and feasible ammonia defective activation strategy is explored on ordered mesoporous carbon (APC) to confine hematin precursor and suppress the formation of inorganic Fe-based derivatives during pyrolysis. Thus, a hierarchically nanoporous Fe/N/APC catalyst with high numbers of exposed iron–nitrogen sites exhibits an impressive performance for oxygen reduction reaction in alkaline media, with large diffusion-limited current density and positive half-wave potential with respect to commercial Pt/C catalyst. The enhanced ORR properties can be majorly ascribed to synergistic contributions of high numbers of exposed catalytic sites completion from high contents of Fe–N and pyridinic N along with the fast mass-transport properties arising from the etched high permeable porous structure. When applied as ca...

Oxidation-Mediated Fingering in Liquid Metals.

We identify and characterize a new class of fingering instabilities in liquid metals; these instabilities are unexpected due to the large interfacial tension of metals. Electrochemical oxidation lowers the effective interfacial tension of a gallium-based liquid metal alloy to values approaching zero, thereby inducing drastic shape changes, including the formation of fractals. The measured fractal dimension (D=1.3±0.05) places the instability in a different universality class than other fingering instabilities. By characterizing changes in morphology and dynamics as a function of droplet volume and applied electric potential, we identify the three main forces involved in this process: interfacial tension, gravity, and oxidative stress. Importantly, we find that electrochemical oxidation can generate compressive interfacial forces that oppose the tensile forces at a liquid interface. The surface oxide layer ultimately provides a physical and electrochemical barrier that halts the instabilities at larger positive potentials. Controlling the competition between interfacial tension and oxidative (compressive) stresses at the interface is important for the development of reconfigurable electronic, electromagnetic, and optical devices that take advantage of the metallic properties of liquid metals.