Increase In Membrane Resistance Research Articles

On the rejection and reversibility of fouling in ultrafiltration as assessed by hydraulic impedance spectroscopy

The manifestation of critical fluxes in membrane filtration has typically served to set an upper value above which detrimental fouling events and a substantial increase of membrane resistance occurs. Despite the usefulness of critical flux concepts for conducting sustainable membrane processes, the specific phenomena causing them cannot be easily identified via conventional membrane filtration modes. Usually arbitrary fouling rates are selected to delimit the boundary between under- and over-critical flux operation. Timescales respective for colloidal matter accumulation are overlooked.Frequency response analysis of transmembrane pressures has been recently presented as a highly-sensitive method to track fouling in ultrafiltration. This hydraulic impedance spectroscopy method allows not only measuring membrane resistances but also corresponding time constants related to colloidal matter accumulation. In this work, hydraulic impedance spectra are gained for the ultrafiltration of different model foulants to assess the origin of critical fluxes for two different membranes. A correlation among characteristic impedance features and the type of fouling could be established: the evolution of phase shift between flux and pressure at increasing fluxes allows identifying the formation of external fouling layers, while registering of hysteresis loops at reversed frequency sequences signals the development of irreversible internal fouling. The hydraulic impedance method emerges as a precise and more sensitive monitoring tool to diagnose the beginning and nature of critical fouling.

Long-term degradation behaviors research on a direct methanol fuel cell with more than 3000h lifetime

This paper focuses on the gradual performance and durability degradation behaviors of a direct methanol fuel cell (DMFC) with more than 3000 h lifetime. This work adopted a new DMFC test strategy and the entire lifetime test consisted of No.1-No.166 single operation. Stage-failure phenomenon occurred in the lifetime test, which indicated the existence of recoverable and non-recoverable degradations during the entire operation process. In-situ electrochemical tests were applied to the DMFC to analyse causes of durability and performance loss. When single cell came to failure, some recoverable methods were conducted to realize the recovery and improvement of DMFC performance and durability. As a result, during each single operation, continuous lifting pressure operation can realize the improvement of catalyst activity and optimization of mass transfer channel. Proton (H+) recovery method and increasing operation temperature can effectively solve the problem of internal resistance enlargement. According to the results of electrochemical monitoring, higher temperature results in the rapid degradation of catalytic layer activity, and lower temperature causes the increase of membrane resistance. N2 purging works as an effective method to eliminate the concentration polarization caused by cathode “water flooding” phenomenon. Based on these results, it can be concluded that the main degradation of DMFC successively changes with operation time, which mainly comes from internal resistance enlargement, cathode concentration polarization and final deactivation of catalyst at different operation stages. This work well explains the real long-term degradation behaviors of DMFC along with operation time, and provides several practicable methods for recovering DMFC performance and durability.

Benzoic Acid and its Derivatives Increase Membrane Resistance to Osmotic Pressure in Isolated Sheep Erythrocytes

There have been many reports that osmotic fragility (OF) in red blood cells (RBCs) is a valuable tool for assessing the actions of various chemicals on the cell membrane in vitro. We determined the effects of benzoic acid and its derivatives on OF in sheep RBCs in vitro. Isolated sheep RBCs were exposed to these substances at 0-100 mM in a buffer solution for 1 h, and the 50% hemolysis was then determined by soaking in 0.1-0.8% NaCl solution. OF was determined as the NaCl concentration inducing 50% hemolysis which was colorimetrically measured by the released hemoglobin concentration. Benzoic acid decreased OF in a dose-dependent manner. Heptanoic acid and cyclohexane carboxylic acid, both of which have 6 carbons in their saturated hydrocarbon structure, did not change OF. Replacement of the COOH bound to the benzene ring with PO(OH)2 or SO2OH abolished the OF response obtained by benzoic acid. Replacement with OH did not affect OF up to 25 mM, but did induce hemolysis at 50 and 100 mM. Replacement with CONH2 decreased OF, with the degree of the OF-lowering effect being greater than that of benzoic acid. Most derivatives possessing other groups (OH, CH3 or NH3) or halogens (Cl or Br) decreased or tended to decreased OF, with the degree of change in OF dependent on the position of the group introduced onto the benzene ring. 4-methylbenzoic acid, and 3-,4- and 4-, 5-dichlorobenzoic acids demonstrated a biphasic effect on OF in sheep RBCs; lowering OF up to 50 mM followed by a lytic effect at 100 mM. The results of a regression analysis using the values of all substances tested revealed no significant correlations between the partition coefficient of the substances and their effects on OF response. However, some groups of substances at concentrations of 10-50 mM showed a negative and statistically significant correlation. For substances sharing very close chemical structures, partition coefficients can probably be used as an indicator for evaluating the effect on OF within an appropriate range of concentrations.

Mitigation of the effects of multivalent ion transport in reverse electrodialysis

Reverse electrodialysis (RED) is a sustainable method to harvest energy using the salinity gradient between fresh and seawater. RED technology is developing but efficiencies are still limited when using natural feed water sources. One significant constraint is induced by the presence of multivalent ions in sea and river water (i.e. Mg2+, Ca2+, SO42-). Uphill transport and an increase in membrane resistance in the presence of magnesium ions significantly reduce the power density output obtainable. The choice of cation exchange membrane determines the magnesium transport and as such the power density. Here we investigate four cation exchange membrane types and relate their properties to the stack performance using three different magnesium concentrations on either river and/or seawater side: 1) a highly cross-linked styrene-divinyl benzene monovalent selective cation exchange membrane (Neosepta CMS); 2) a monovalent selective cation exchange membrane that contains a thin polyethyleneimine (PEI) anion exchange layer (Selemion CSO); 3) a multivalent ion (e.g. magnesium) permeable cation exchange membrane with an engineered molecularly open structure facilitating the transport of multivalent ions as recently developed (T1 Fujifilm); 4) a standard cation exchange membrane (Type I Fujifilm (reference)). The first two membranes both retain magnesium ions, while the other two membranes are considered permeable for magnesium ions.The results show that power density strongly depends on the composition of both river and seawater. Power density decreases in the presence of magnesium, an effect being strongest with magnesium at both river and seawater side, followed by the river water side and the seawater side. The negative effect of multivalent ion transport against the concentration gradient, so called uphill transport, in RED can be significantly minimized when monovalent selective membranes such as the highly cross-linked Neosepta CMS membrane or the AEM coated Selemion CSO membrane are used. However, the use of such membranes directly results in a strong increase in membrane resistance due to the lower ion mobility of magnesium ions inside these membranes. As a consequence, power densities in RED are not improved. Especially at high magnesium concentrations, this effect is very strong at higher concentrations, the membranes are no longer able to retain magnesium ions effectively.More beneficial is the application of multivalent permeable membranes with a more ‘open’ structure that allow the free movement of both sodium and magnesium ions through the membrane. Maybe somewhat counter intuitively, such membranes (especially the Fujifilm multivalent permeable T1 membrane) have low resistance values combined with reasonable OCV values leading to high power densities under almost all magnesium concentrations, especially at long term applications. Highest power densities well exceeding 0.3W/m2 are still obtained when only sodium is present. However, when magnesium ions are present power densities in the order of 0.2–0.25W/m2 can still be obtained for these membranes.

Probing the fouling process and mechanisms of submerged ceramic membrane ultrafiltration during algal harvesting under sub- and super-critical fluxes

Abstract Membrane filtration is a promising approach for harvesting microalgae for production of biofuel and high-value products. Membrane fouling is the most limiting factor for filtration operation as it causes low flow flux, high transmembrane pressure and high maintenance cost associated with membrane backwash and replacement. In the present study, the harvesting efficiency and the membrane fouling properties of a bench-scale ultrafiltration system with a submerged flat-sheet ceramic membrane were investigated for harvesting green microalgae, Chlorella vulgaris, under sub- and super-critical flux. The fouling mechanism (cake layer, gel layer and membrane pore blocking) was systematically analyzed to illustrate the possible fouling profiles at sub and super-critical flux. The results showed that the productivity for harvesting microalgal cells under super-critical flux condition was three times higher than sub-critical flux condition, with the fouling rates 8 times higher as well. The increase in irreversible membrane fouling was attributed as the main cause of the membrane resistance increase at the super-critical flux condition although the resistance of cake layer was the highest for both conditions. SMPs, aromatic protein and humic-like organics of microalgae broth contribute to the irreversible membrane fouling.

Static adsorption of protein-polysaccharide hybrids on hydrophilic modified membranes based on atomic layer deposition: Anti-fouling performance and mechanism insight

Initial membrane fouling affects fouling behavior and characteristic significantly. Static adsorption investigation contributes to intensively understand the initial fouling process. In order to determine the superior anti-fouling material prepared by atomic layer deposition, the TiO2, Al2O3 and ZnO modified membranes were successfully fabricated, characterized by XPS, XRD and SEM and then employed for static adsorption of BSA and SA foulants. More importantly, the anti-fouling mechanism was interpreted by adsorption isotherms and thermodynamics. Results showed that the adsorption amount of BSA and SA on PVDF membrane decreased by 43.2% and 73.0% with ZnO modification, reaching the highest among all the modified membranes. As a consequence, the minimum reduction of pure water flux and increase of membrane resistance were realized after fouling. The Sips model presented the most satisfactory fitting for BSA and SA adsorption on ZnO modified membrane. Thermodynamic investigation revealed that the ZnO modified membrane exhibited the lowest degree of spontaneity and the weakest interaction with foulants (London dispersion forces of physisorption). Moreover, the smallest ΔS value indicated the regular distribution of foulants on membrane surface, which greatly alleviated membrane fouling. The relatively smooth surface of ZnO modified membrane with lower roughness and water contact angle confirmed the excellent anti-fouling property. The reported results in this study could provide fundamental basis for the anti-fouling performance of ALD modified membranes, which would accelerate the actual application process.

Effect of Divalent Cations on RED Performance and Cation Exchange Membrane Selection to Enhance Power Densities.

Reverse electrodialysis (RED) is a membrane-based renewable energy technology that can harvest energy from salinity gradients. The anticipated feed streams are natural river and seawater, both of which contain not only monovalent ions but also divalent ions. However, RED using feed streams containing divalent ions experiences lower power densities because of both uphill transport and increased membrane resistance. In this study, we investigate the effects of divalent cations (Mg2+ and Ca2+) on RED and demonstrate the mitigation of those effects using both novel and existing commercial cation exchange membranes (CEMs). Monovalent-selective Neosepta CMS is known to block divalent cations transport and can therefore mitigate reductions in stack voltage. The new multivalent-permeable Fuji T1 is able to transport divalent cations without a major increase in resistance. Both strategies significantly improve power densities compared to standard-grade CEMs when performing RED using streams containing divalent cations.

Opiate dependence induces cell type-specific plasticity of intrinsic membrane properties in the rat juxtacapsular bed nucleus of stria terminalis (jcBNST).

Drugs of abuse can alter circuit dynamics by modifying synaptic efficacy and/or the intrinsic membrane properties of neurons. The juxtacapsular subdivision of the bed nucleus of stria terminalis (jcBNST) has unique connectivity that positions it to integrate cortical and amygdala inputs and provide feed-forward inhibition to the central nucleus of the amygdala (CeA), among other regions. In this study, we investigated changes in the synaptic and intrinsic properties of neurons in the rat jcBNST during protracted withdrawal from morphine dependence using a combination of conventional electrophysiological methods and the dynamic clamp technique. A history of opiate dependence induced a form of cell type-specific plasticity characterized by reduced inward rectification associated with more depolarized resting membrane potentials and increased membrane resistance. This cell type also showed a lower rheobase when stimulated with direct current (DC) pulses as well as a decreased firing threshold under simulated synaptic bombardment with the dynamic clamp. Morphine dependence also decreased excitatory postsynaptic potential amplification, suggesting the downregulation of the persistent Na+ current (I NaP). These findings show that a history of morphine dependence leads to persistent cell type-specific plasticity of the passive membrane properties of a jcBNST neuronal population, leading to an overall increased excitability of such neurons. By altering the activity of extended amygdala circuits where they are embedded, changes in the integration properties of jcBNST neurons may contribute to emotional dysregulation associated with drug dependence and withdrawal.

Surface layer modification of AEMs by infiltration and photo‐cross‐linking to induce monovalent selectivity

Surface modification of anion exchange membranes (AEMs) by attaching a negatively charged layer is the main method for preparing monovalent anion selective membranes. However, tremendous increase of membrane resistance and poor long‐term stability of the modified membranes face great challenges. In this work, a photosensitive molecule (4,4‐diazostilbene‐2,2‐disulfonic acid disodium salt [DAS]) was infiltrated into the membrane surface and immobilized in the structure by cross‐linking under UV irradiation. This method introduced negative charge to the surface layer of the AEMs without increasing membrane thickness, leading to high performance membrane with high monovalent anion selectivity. The optimized membrane (D‐5) shows the highest perm‐selectivity of 11.21, which is superior to the commercial selective membrane Selemion® ASV and previously reported monovalent anion selective AEMs. Furthermore, the newly developed membrane exhibits excellent long‐term stability, which can maintain constant selectivity during the 80 h ED experiment. © 2017 American Institute of Chemical Engineers AIChE J, 64: 993–1000, 2018

Electrochemically Triggered Release of Reagent to the Proximal Leaflet of a Microcavity Supported Lipid Bilayer.

A novel and versatile approach to electrichemically triggering the release of a reagent, β-cyclodextrin (β-CD), selectively to the proximal leaflet of a supported lipid bilayer is described. Selective delivery is achieved by creating a spanning lipid bilayer across a microcavity array and exploiting the irreversible redox disassembly of the host-guest complex formed between thiolated ferrocene (Fc) and β-cyclodextrin (β-CD) in the presence of chloride. Self-assembled monolayers of the ferrocene-alkanethiols were formed regioselectively on the interior surface of highly ordered 2.8 μm cavities while the exterior top surface of the array was blocked with a monolayer of mercaptoethanol. The Fc monolayers were complexed with β-CD or β-CD-conjugated to streptavidin (β-CD-SA). Phospholipid bilayers were then assembled across the array via combined Langmuir-Blodgett/vesicle fusion leading to a spanning bilayer suspended across the aqueous filled microcavities. Upon application of a positive potential, ferrocene is oxidized to ferrocinium cation, disrupting the inclusion complex and leading to the release of the β-CD into the microcavity solution where it diffuses to the lower leaflet of the suspended bilayer. Disassembly of the supramolecular complex within the cavities and binding of the β-CD-SA to a biotinylated bilayer was followed by voltammetry and impedance spectroscopy where it caused a large increase in membrane resistance. For unmodified β-CD, the extraction of cholesterol from a cholesterol containing bilayer was evident in a decrease in the bilayer resistance. For the first time, this direct approach to targeted delivery of a reagent to the proximal layer of a lipid bilayer offers the potential to build models of bidirectional signaling (inside-out vs outside-in) in cell membrane model systems.

Histamine induces KCNQ channel-dependent gamma oscillations in rat hippocampus via activation of the H1 receptor

Histamine is an aminergic neurotransmitter, which regulates wakefulness, arousal and attention in the central nervous system. Histamine receptors have been the target of efforts to develop pro-cognitive drugs to treat disorders such as Alzheimer's disease and schizophrenia. Cognitive functions including attention are closely associated with gamma oscillations, a rhythmical electrical activity pattern in the 30–80 Hz range, which depends on the synchronized activity of excitatory pyramidal cells and inhibitory fast-spiking interneurons.We set out to explore whether histamine has a role in promoting gamma oscillations in the hippocampus. Using in-situ hybridization we demonstrate that histamine receptor subtypes 1, 2 and 3 are expressed in stratum pyramidale of area CA3 in rats. We show that both pyramidal cells and fast-spiking interneurons depolarize and increase action potential firing in response to histamine in vitro. The activation of histamine receptors generates dose-dependent, transient gamma oscillations in area CA3 of the hippocampus - the locus of the gamma rhythm generator. We also demonstrate that this histamine effect is independent of muscarinic receptors.Using specific antagonists we provide evidence that histamine gamma rhythmogenesis specifically depends on the H1 receptor. Histamine also depolarized both pyramidal cells and fast-spiking interneurons and increased membrane resistance in pyramidal cells. The increased membrane resistance is potentially mediated by the inhibition of potassium channels because application of the KCNQ channel opener ICA110381 abolished the oscillations.Taken together our data demonstrate a novel and physiological mechanism for generating gamma oscillations in hippocampus and suggest a role for KCNQ channels in this cognition-relevant brain activity.

EAG channels expressed in microvillar photoreceptors are unsuited to diurnal vision

The principles underlying the evolutionary selection of ion channels for expression in sensory neurons are unclear. Photoreceptor depolarization in the diurnal Drosophila melanogaster is predominantly provided by light-activated transient receptor potential (TRP) channels, whereas repolarization is mediated by sustained voltage-gated K+ channels of the Shab family. In the present study, we show that phototransduction in the nocturnal cockroach Periplaneta americana is predominantly mediated by TRP-like channels, whereas membrane repolarization is based on EAG channels. Although bright light stimulates Shab channels in Drosophila, further restricting depolarization and improving membrane bandwidth, it strongly suppresses EAG conductance in Periplaneta. This light-dependent inhibition (LDI) is caused by calcium and is abolished by chelating intracellular calcium or suppressing eag gene expression. LDI increases membrane resistance, augments gain and reduces the signalling bandwidth. This makes EAG unsuitable for light response conditioning during the day and might have resulted in the evolutionary replacement of EAG by other delayed rectifiers in diurnal insects. The principles underlying evolutionary selection of ion channels for expression in sensory neurons are unclear. Among species possessing microvillar photoreceptors, the major ionic conductances have only been identified in Drosophila melanogaster. In Drosophila, depolarization is provided by light-activated transient receptor potential (TRP) channels with a minor contribution from TRP-like (TRPL) channels, whereas repolarization is mediated by sustained voltage-gated K+ (Kv) channels of the Shab family. Bright light stimulates Shab channels, further restricting depolarization and improving membrane bandwidth. In the present study, data obtained using a combination of electrophysiological, pharmacological and molecular knockdown techniques strongly suggest that in photoreceptors of the nocturnal cockroach Periplaneta americana the major excitatory channel is TRPL, whereas the predominant delayed rectifier is EAG, a ubiquitous but enigmatic Kv channel. By contrast to the diurnal Drosophila, bright light strongly suppresses EAG conductance in Periplaneta. This light-dependent inhibition (LDI) is caused by calcium entering the cytosol and is amplified following inhibition of calcium extrusion, and it can also be abolished by chelating intracellular calcium or suppressing eag gene expression by RNA interference. LDI increases membrane resistance, augments gain and reduces the signalling bandwidth, impairing information transfer. LDI is also observed in the nocturnal cricket Gryllus integer, whereas, in the diurnal water strider Gerris lacustris, the delayed rectifier is up-regulated by light. Although LDI is not expected to reduce delayed rectifier current in the normal illumination environment of nocturnal cockroaches and crickets, it makes EAG unsuitable for light response conditioning during the day, and might have resulted in the evolutionary replacement of EAG by other delayed rectifiers in diurnal insects.

Micron dimensioned cavity array supported lipid bilayers for the electrochemical investigation of ionophore activity

Microcavity supported lipid bilayers, MSLBs, were applied to an electrochemical investigation of ionophore mediated ion transport. The arrays comprise of a 1cm2 gold electrode imprinted with an ordered array of uniform spherical-cap pores of 2.8μm diameter prepared by gold electrodeposition through polystyrene templating spheres. The pores were pre-filled with aqueous buffer prior to Langmuir-Blodgett assembly of a 1,2-dioleoyl-sn-glycero-3-phosphocholine bilayer. Fluorescence lifetime correlation spectroscopy enabled by the micron dimensions of the pores permitted study of lipid diffusion across single apertures, yielding a diffusion coefficient of 12.58±1.28μm2s−1 and anomalous exponent of 1.03±0.02, consistent with Brownian motion. From FLCS, the MSLBs were stable over 3days and electrochemical impedance spectroscopy of the membrane with and without ionic gradient over experimental windows of 6h showed excellent stability. Two ionophores were studied at the MSLBs; Valinomycin, a K+ uniporter and Nigericin, a K+/H+ antiporter. Ionophore reconstituted into the DOPC bilayer resulted in a decrease and increase in membrane resistance and capacitance respectively. Significant increases in Valinomycin and Nigericin activity were observed, reflected in large decreases in membrane resistance when K+ was present in the contacting buffer and in the presence of H+ ionic gradient across the membrane respectively.

The Removal of Bisphenol A in Water Treatment Plant Using Ultrafiltration Membrane System

Bisphenol A (BPA) is one of the recalcitrant contaminants that are detected in drinking water sources, as the conventional water treatment plant is incapable of removing it completely. This study was conducted to explore the performance of ultrafiltration (UF) membrane system for the BPA removal in which BPA was spiked in water sample collected from a treatment plant. The effects of process conditions that may influence the removal and flux performance of the membrane including operating pressure, feed pH and BPA concentration, and backwash cleaning were investigated. The results showed that an applied pressure of 1 bar was the optimum pressure for achieving good balance of BPA removal (95 %) and water flux (109 L m−2 h−1) compared to operating pressure of 0.5 and 1.5 bar. The variation of feed pH showed significant impact on BPA elimination with the highest rejection (90 %) achieved at pH 7 while the lowest removal (20 %) at pH 10. BPA concentration had no significant impact on BPA removal as high removal rate (>95 %) was observed regardless of feed concentration (between 10 and 100 μg L−1). The normalized flux showed decreasing trend with filtration cycle due to increased membrane resistance of BPA adsorption onto the membrane. The membrane cleaning via backwash was able to recover 90 % BPA removal even after three consecutive cycles of filtration. This indicated the promising performance of UF membrane system for industrial water treatment.

Water management in novel direct membrane deposition fuel cells under low humidification

Polymer electrolyte membrane fuel cells (PEMFCs) fabricated by direct membrane deposition (DMD) were shown to work even at dry conditions without significant deterioration of the membrane resistance. Here, in situ neutron radiography is used to investigate the water management in those fuel cells to uncover the phenomena that lead to the robust operation under low humidification. A constant level of humidification within the membrane electrode assembly (MEA) of a DMD fuel cell is observed even under dry anode operation and 15% relative humidity on the cathode side. This proves a pronounced back diffusion of generated water from the cathode side to the anode side through the thin deposited membrane layer. Over the entire range of polarization curves a very high similarity of the water evolution in anode and cathode flow fields is found in spite of different humidification levels. It is shown that the power density of directly deposited membranes in contrast to a 50 μm thick N-112 membrane is only marginally affected by dry operation conditions. Water profiles in through-plane direction of the MEA reveal that the water content in the DMD fuel cell remains steady even at high current densities. This is in contrast to the N-112 reference fuel cell which shows a strong increase in membrane resistance and a reduced MEA water content with raising current densities. Thus this new MEA fabrication technique has a promising perspective, since dry operation conditions are highly requested in order to reduce fuel cell system costs.

An impedance biosensor for monitoring cancer cell attachment, spreading and drug-induced apoptosis

In the last three decades, Electrical Cell-substrate Impedance Sensing (ECIS) has emerged as a powerful technique for in vitro cellular research and preclinical testing. In this study, a cell-based impedance biosensor based on ECIS technique, which integrates microelectrode arrays with a small culture chamber has been developed for monitoring the attachment, spreading and drug-induced apoptosis of very few MCF-7 breast cancer cells. It was found out that cell spreading caused a significant increase of impedance magnitude in the frequency range between 10kHz and 100kHz and also pronounced phase shift. Using an electrical equivalent circuit to model the measured spectra, the morphological change of cells was analyzed. Cell spreading induced a slight decrease of membrane capacitance of 2% and a prominent increase of membrane resistance of 57% within incubating for nearly one day. For pharmaceutical assessment, the cells were treated with different concentrations of an anti-cancer drug (Cisplatin) in the range from 10μM to 50μM. We observed a fast decrease of impedance magnitude within the initial 4h of treatment with concentrations of 25μM and 50μM. The results derived from this study demonstrated the usability of cell-based impedance microbiosensors in cell biology and cancer research.

Cross-Validation of Simulation and EPR Oximetry Approaches: Membrane Cholesterol Reduces Oxygen Flux

Prior EPR oximetry work by Subczynski and colleagues has shown that cholesterol increases membrane resistance to oxygen permeation by 3- to 5-fold when present in a 1:1 ratio with phospholipid. In the current study, we use molecular dynamics simulations to investigate the biophysics of oxygen transport in membranes incorporating cholesterol. The simulations enable cross-validation of the EPR oximetry measurements and the simulations. Further, we have been able to observe oxygen transport near the bilayer surface, which has not been accessible to EPR spin-label probes. We find excellent agreement between the simulation and EPR observations. Our simulations affirm that cholesterol reduces oxygen flux when present at a 1:1 ratio with phospholipid. They further indicate that the bilayer surface in the presence or absence of cholesterol presents greater resistance to permeation than previously observed by EPR.

Lidocaine Inhibits HCN Currents in Rat Spinal Substantia Gelatinosa Neurons

Lidocaine, which blocks voltage-gated sodium channels, is widely used in surgical anesthesia and pain management. Recently, it has been proposed that the hyperpolarization-activated cyclic nucleotide (HCN) channel is one of the other novel targets of lidocaine. Substantia gelatinosa in the spinal dorsal horn, which plays key roles in modulating nociceptive information from primary afferents, comprises heterogeneous interneurons that can be electrophysiologically categorized by firing pattern. Our previous study demonstrated that a substantial proportion of substantia gelatinosa neurons reveal the presence of HCN current (Ih); however, the roles of lidocaine and HCN channel expression in different types of substantia gelatinosa neurons remain unclear. By using the whole-cell patch-clamp technique, we investigated the effect of lidocaine on Ih in rat substantia gelatinosa neurons of acute dissociated spinal cord slices. We found that lidocaine rapidly decreased the peak Ih amplitude with an IC50 of 80 μM. The inhibition rate on Ih was not significantly different with a second application of lidocaine in the same neuron. Tetrodotoxin, a sodium channel blocker, did not affect lidocaine's effect on Ih. In addition, lidocaine shifted the half-activation potential of Ih from -109.7 to -114.9 mV and slowed activation. Moreover, the reversal potential of Ih was shifted by -7.5 mV by lidocaine. In the current clamp, lidocaine decreased the resting membrane potential, increased membrane resistance, delayed rebound depolarization latency, and reduced the rebound spike frequency. We further found that approximately 58% of substantia gelatinosa neurons examined expressed Ih, in which most of them were tonically firing. Our studies demonstrate that lidocaine strongly inhibits Ih in a reversible and concentration-dependent manner in substantia gelatinosa neurons, independent of tetrodotoxin-sensitive sodium channels. Thus, our study provides new insight into the mechanism underlying the central analgesic effect of the systemic administration of lidocaine.

THE POSSIBILITY OF ELECTROLYZER WITH A SOLID POLYMER ELECTROLYTE START AT LOW TEMPERATURES

The paper deals with the research that covers the possibility of using ethanol in concentrations up to 40 vol. % as an anode depolarizer for the cell with solid polymer electrolyte (PEM) and in order to ensure its start at low temperatures. Platinum, iridium and a solid solution of Pt-Ru (1:1 at. %) were used as the anode catalyst, and Pt on Vulcan XC-72 and Pt-Ru were used as the cathode one. It is shown that in all cases by using water-ethanol solutions with concentrations of ethanol up to 40 vol. % the cell voltage generally increased due to the increase of membrane resistance and decrease of rate of the cathodic process of platinum catalyst passivation/poisoning by ethanol and its oxidation products. Some negative impact has a stronger swell of the membrane-electrode unit in a solution of ethanol, which leads to its partial destruction. The energy consumption for the production of hydrogen by electrolysis of alcoholic solutions is lower than by water electrolysis, though the economic feasibility of this process is doubtful. The research demonstrates the electrolysis cell can withstand the freezing at the temperatures in the range of –15 to –20 o C. Moreover, the resistance of the membrane in water-ethanol solutions (about 40 vol. %) is not critical at these temperatures. The feed of water-ethanol solutions in the electrolytic cell allows one to start the electrolysis of water at these temperatures at a voltage of 2,0–2,2 V and currents of 0,07–0,13 A/cm 2 . This ensures the ‘cold start’ and subsequent self-heating of the electrolysis cell and further using deionized water.

Diels Alder Polyphenylene Anion Exchange Membrane for Nonaqueous Redox Flow Batteries

Here highly conductive, solvent-resistant anionic Diels Alder polyphenylene (DAPP) membranes were synthesized with three different ionic contents and tested in an ionic liquid-based nonaqueous redox flow battery (RFB). These membranes display 3–10× increase in conductivity in propylene carbonate compared to some commercially available (aqueous) anion exchange membranes. The membrane with an ion content of 1.5 meq/g (DAPP1.5) proved too brittle for operation in a RFB, while the membrane with an ion content of 2.5 meq/g (DAPP2.5) allowed excessive movement of solvent and poor electrochemical yields (capacity fade). Despite having lower voltage efficiencies compared to DAPP2.5, the membrane with an intermediate ion content of 2.0 meq/g (DAPP2.0) exhibited higher coulombic efficiencies (96.4% vs. 89.1%) and electrochemical yields (21.6% vs. 10.9%) after 50 cycles. Crossover of the electroactive species was the primary reason for decreased electrochemical yields. Analysis of the anolyte and catholyte revealed degradation of the electroactive species and formation of a film at the membrane-solution interface. Increases in membrane resistance were attributed to mechanical and thermal aging of the membrane; no chemical change was observed. Improvements in the ionic selectivity and ionic conductivity of the membrane will increase the electrochemical yield and voltage efficiency of future nonaqueous redox flow batteries.