Positive Electrical Potential Research Articles

LRRC8/VRAC volume-regulated anion channels are crucial for hearing

Hearing crucially depends on cochlear ion homeostasis as evident from deafness elicited by mutations in various genes encoding cation or anion channels and transporters. Ablation of ClC-K/barttin chloride channels causes deafness by interfering with the positive electrical potential of the endolymph, but roles of other anion channels in the inner ear have not been studied. Here we report the intracochlear distribution of all five LRRC8 subunits of VRAC, a volume-regulated anion channel that transports chloride, metabolites and drugs such as the ototoxic anti-cancer drug cisplatin, and explore its physiological role by ablating its subunits. Sensory hair cells express all LRRC8 isoforms, whereas only LRRC8A, D and E were found in the potassium-secreting epithelium of the stria vascularis. Cochlear disruption of the essential LRRC8A subunit, or combined ablation of LRRC8D and E, resulted in cochlear degeneration and congenital deafness of Lrrc8a-/- mice. It was associated with a progressive degeneration of the organ of Corti and its innervating spiral ganglion. Like disruption of ClC-K/barttin, loss of VRAC severely reduced the endocochlear potential. However, the mechanism underlying this reduction seems different. Disruption of VRAC, but not ClC-K/barttin, led to an almost complete loss of Kir4.1 (KCNJ10), a strial K+ channel crucial for the generation of the endocochlear potential. The strong downregulation of Kir4.1 might be secondary to a loss of VRAC-mediated transport of metabolites regulating inner ear redox potential such as glutathione. Our study extends the knowledge of the role of cochlear ion transport in hearing and ototoxicity.

Neural prediction errors depend on how an expectation was formed

When a visual event is unexpected, because it violates a train of repeated events, it excites a greater positive electrical potential at sensors positioned above occipital-parietal human brain regions (the P300). Such events can also seem to have an increased duration relative to repeated (implicitly expected) events. However, recent behavioural evidence suggests that when events are unexpected because they violate a declared prediction–a guess–there is an opposite impact on duration perception. The neural consequences of incorrect declared predictions have not been examined. We replicated the finding whereby repetition violating events elicit a larger P300 response. However, we found that events that violated a declared prediction entrained an opposite pattern of response–a smaller P300. These data suggest that the neural consequences of a violated prediction are not uniform but depend on how the prediction was formed.

Determination of Partial Proton Conductivity in Fluorite-Type Oxides Using Electrochemical Technique

Fluorite-type oxides such as YSZ and GDC are typical oxide ion conductors which are used for electrolyte materials for SOFCs. Although major charge carriers in these materials are of course oxide ions, it has been suggested that under wet conditions dissolved hydrogen becomes minor charge carriers. Existence of the dissolved hydrogen was confirmed by measuring deuterium concentration using SIMS, but whether the dissolved hydrogen really becomes charge carrier or not is still unclear. It is possible to examine this by whether proton conduction is detected or not in electrochemical measurements. In this study, in order to detect partial proton conduction in YSZ and GDC, oxide ion blocking measurements using hydrogen permeable Pd-plate as the blocking electrode were performed.Pelletized 8YSZ and 10GDC powders by CIP at 390 MPa were sintered at 1300~1700 °C. The surfaces of the obtained dense pellets were mirror polished. As blocking electrodes, Pd-plates were fixed on upper surfaces of the pellets using Pd-pastes by firing them at 1000 °C and the boundaries between the pellets and Pd-plates were sealed using BaO-Al2O3-SiO2-glasses by firing them at 1250 °C. As reversible electrodes, Pd-pastes were painted on lower surfaces and fired at 1000 °C. Under the conditions with constant temperature and p O2 (1×10−4 atm), constant voltage (20 mV) was applied between two electrodes with the reversible electrodes being positive electrical potential and the current responses to humidification of atmosphere by H2O and D2O were recorded.In the case of 8YSZ sintered at 1300 °C, the current under dry atmosphere at 900 °C was 0.152 μA. When the atmosphere was humidified by 18°C H2O and D2O, the current increased to 0.226 and 0.206 μA, respectively. The current increment by humidification with H2O (ΔI H2O = 0.074 μA) was approximately 1.4 times as compared to D2O (ΔI D2O = 0.054 μA), which indicates that H+/D+ isotopic effect was reflected on the current increments. The current increments are suggested to be caused by conduction of dissolved hydrogen and deuterium because not oxygen but only hydrogen and electrons can pass through Pd-plates. This means that dissolved hydrogen becomes charge carriers, i.e., protons, in YSZ. Similar behavior was also observed for the case of 10GDC.

Piezoelectric properties of triply periodic minimum surface structures

Piezoelectric ceramic-polymer composites have attracted substantial interest owing to their distinct piezoelectric performance. This paper investigates the dependence of their output voltage on the volume fraction and structure of the ceramic component, together with the type of stimulus, using finite element analysis. When ceramic parts of piezocomposites are shaped into structures with a topology of triply periodic minimum surface such as Schwarz Primitive surface, Gyroid surface, and Neovius surface, they exhibit much better piezoelectric performance than existing piezocomposites under both the compressive strain and the shear strain. Compared to a piezocomposite with three intersecting ceramic cuboids, Schwarz piezocomposite with the same volume fraction of 50% can increase output voltage by approximately 50% under compressive strains 2%–8%. With 16% ceramic material and under a compressive strain of 8%, Neovius piezocomposite demonstrates ~17-fold and ~6,000-fold enhancement of output voltage than that of the piezocomposite in the 3-3 mode (connected and irregularly-shaped ceramic component) and in the 0–3 mode (disconnected ceramic particles), respectively. Under simple shear, performance superiority of Neovius piezocomposite to that of the 3-3 mode piezocomposite becomes more significant as output voltage can be enhanced up to approximately 30-fold. Computational analysis shows that high von Mises stress helps to enlarge the difference between positive and negative electrical potential, and therefore enhance output voltage. The findings in this work also reveal output voltage is inversely proportional to strain energy stored in piezocomposites. Because Schwarz piezocomposite has the largest bulk modulus with minimum strain energy under compression, it has the maximum output voltage.

Photosynthetic Electrochemical Cell Based on RuO2 Nanosheets Modified Bio-Anode

Thylakoids are the photosynthetic complexes that absorb light energy to produce photosynthetic electrons (PEs) in the chloroplast of plant cells. PE production starts from water splitting at photosystem II (PSII) in the thylakoid membrane and they are excited by absorbing photon energy. Over the last decade, many researchers have attempted to extract PEs from thylakoid by enhancing attachment of thylakoid membranes to an electrode or using artificial mediators. However, these have some limitations including increased ohmic resistance from the length of tethering molecules and energy loss due to artificial mediators. In this study, we propose a photosynthetic electrochemical cell based on RuO2 nanosheet modified electrode for the photosynthetic energy harvesting from thylakoids. RuO2 is known as one of the most conductive metal oxides. Metal oxides have partially positive charges that can improve attachment of negatively charged thylakoids to the electrode. Also, partially positively and negatively charged characteristics of RuO2 surfaces induce ensemble docking between electron carriers and electrode surface, which can attract both negatively charged electron carriers and positively charged electron carriers. Furthermore, RuO2 nanosheets show a unique characteristic of proton adsorption, which can sustain positive electrical potential during PEs extraction. For photosynthetic energy harvesting, the photosynthetic electrochemical cell was constructed with anode based on thylakoid and air-cathode based on Pt-C, which separated by a proton exchange membrane. The light was controlled by a 100 W halogen lamp to operate the photosystem so that excited PEs can be extracted to the electrode. The surface potential of RuO2 nanosheets modified electrodes was 250 mV vs. Ag/AgCl, which shifted positively more than 100 mV than that of the bare Au electrode. From the inspection of RuO2 lattice by x-ray absorption spectroscopy, positively shifted surface potential is the result of proton adsorption. A positively biased electrode surface can induce a large amount of PEs extraction from the electron carriers than the Au electrode. When the light is illuminated on the thylakoids deposited electrodes, 8.9 ± 6.3 mV and 88.7 ± 13.8 mV of the surface potentials were measured from the Au and the RuO2 modified electrode, respectively. These lowered electrode potentials are due to the redox potential of the electron carriers on the electron transport chain of the thylakoid membrane. The open-circuit voltages (OCV, the subtracted potential between the cathode and the anode) were measured 575.1 ± 6.4 mV and 424.0 ± 17.2 mV from the Au and the RuO2 electrode, respectively. Although OCV of the RuO2 electrode is lower than the Au electrode, the power density of the RuO2 electrode shows 4 times higher than the Au electrode, and this is due to the enhanced PEs extraction by both the surface charge and the proton adsorption characteristics of RuO2 nanosheets.

Aptamer based electrostatic-stimuli responsive surfaces for on-demand binding/unbinding of a specific ligand.

We report an aptamer functionalized stimuli responsive surface that can controllably switch between binding and releasing its specific ligand under application of electrical stimuli. The high affinity of the aptamer for thrombin makes the surface undergo specific binding while electrostatic field induced actuation of the aptamer is utilized to release the ligand from the surface. Atomic force microscopy (AFM) was utilized to determine the characteristic height change, associated with the specific binding of thrombin, on anti-thrombin aptamer coated surfaces. Subsequently, the thrombin/aptamer complex covered surfaces were subjected to different magnitudes of electrostatic field and height changes on the surface were measured to investigate the influence of an electrical field. Application of positive electrical potential led to the removal of thrombin from the aptamer-covered surface. While under moderate magnitude of negative electrical potential the binding complexes were maintained, increasing the magnitude led to the removal of both molecules from the surface. Molecular dynamics (MD) simulations of the thrombin/aptamer complex under electrostatic fields show that thrombin dissociates from the aptamers in the presence of a positive electric field. These results demonstrate that aptamer covered surfaces undergo specific binding to the ligand and an electrostatic field may be used to disrupt the binding and on-demand release of the ligand from the surface.

Charge Polarization at Catalytic Metal–Support Junctions. Part B: Theoretical Modeling of Kelvin Probe Force Microscopy

Existing models for the analysis of Kelvin probe microscopy experiments are extended and used to analyze the experimental electrical potential profiles for a Pt/TiO2 model nanoparticle. The derived model reproduces in detail the Kelvin probe image that reveals a characteristic ring-shaped negative charge zone at the surface around the particle: A planar negative charge zone at the surface of the support extends beyond the diameter of the Pt particle. It is compensated mostly by a planar layer of positive charges in the metal across the interface and by a smaller number of positive charges at the metal–air interface. These latter charges determine the positive electrical potential of the metal particle, and they are likely responsible for the extent of the metal–support interaction in catalytic reactions.

词汇加工研究中的P200成分

以视觉输入刺激进行的词汇加工能够诱发一个早期的事件相关电位(ERP)正成分P200，该成分起始于150 ms，结束于275 ms并在200 ms达到顶峰。P200成分作为一种内源性成分，其反映的词汇认知加工的内容和过程仍然存在较大的争论，P200可能既与字形加工，也与语音加工有关，且词汇加工和亚词汇加工都能诱发明显的P200；P200成分的复杂性更表现在它容易受到实验范式和任务的影响。将来的研究可以在实验范式和任务以及中英文材料在P200成分差异两方面进行拓展。 The visual P200 is a positive going electrical potential of the event-related potential measured at the human scalp which peaks at about 200 ms varying between about 150 ms and 275 ms induced by visual input stimuli. Research on the visual P200 is still keeping unclear about the time course and stage of lexical processing. The P200 may reflect the orthographic processing and phonologic processing simultaneously. Moreover, it both relates to lexical processing and sub-lexical processing. It appears to be easily modulated by a large and diverse number of cognitive tasks and paradigms. In conclusion, future research should be focused on experimental materials, research method and the difference between Chinese and English language system, etc.

Colloidal properties and behaviors of 3 nm primary particles of detonation nanodiamonds in aqueous media.

This study was aimed to reveal the principal colloidal properties of the aqueous dispersion of extremely small primary single-crystalline diamond particles in water. Together with the non-diamond layer, the size of the colloidal species is 2.8 ± 0.6 nm as found via DLS of the initial 5.00 wt/vol% hydrosol. Anionic dyes are readily adsorbed on the colloidal species. This is in line with the positive zeta-potential. The critical coagulation concentrations of the 0.19 wt/vol% nanodiamond hydrosol were determined with a set of inorganic electrolytes and anionic surfactants. The data are in line with the Schulze-Hardy rule for "positive" sols. The fulfillment of the lyotropic (Hofmeister) series was also observed for single-charged anions. The abnormal influence of alkali gives evidence of the acidic nature of the positive charge of the nanodiamond species. Application of acid-base indicators allows estimating the value of the interfacial electrical potential of the nanodiamond particles. Upon dilution from 5.00% to 0.01%, the colloidal system under study exhibits unusual changes. The average size increases ca. ten-fold as determined by DLS. The TEM images support this observation. At the same time, the viscosity drops. This phenomenon was explained in terms of the so-called periodic colloidal structures (colloidal crystals) in concentrated solutions.

Electrical Signal Guided Ibuprofen Release from Electrodeposited Chitosan Hydrogel

Electrical signal guided drug release from conductive surface provides a simple and straightforward way for advanced drug delivery. In this study, we investigated the ibuprofen release from electrodeposited chitosan hydrogel by applying electrical signals. Specifically, chitosan hydrogel was electrodeposited on titanium plate and used as a matrix for ibuprofen load and release. The release of ibuprofen from the chitosan hydrogel on titanium plate was pH sensitive. By applying a positive or negative electrical potential, the release rate of ibuprofen from the electrodeposited chitosan can be facilely controlled. Thus, coupling chitosan electrodeposition and electrical signal control spurs new possibilities for biopolymeric coating and drug elution on conductive implants.

Self-potential monitoring of a crude oil-contaminated site (Trecate, Italy)

We present a multidisciplinary approach for characterization of a crude oil-contaminated site (Trecate, Italy), integrating geophysical data, such as subsoil electrical potential (in millivolts) and electrical resistivity (in ohm meters) distribution, with hydrogeological and bio-chemical data. Self-potential measurements have been evaluated together with active geoelectrical measurements and hydrological information, to provide spatial and temporal information about the self-potential sources and their possible correlations with the contamination state of the subsoil. Three self-potential surveys (March 2010, October 2010, and March 2011) were conducted at the site, both in the contaminated and uncontaminated regions. The obtained self-potential maps show large time-lapse differences in correspondence of the contaminated area, with positive electrical potential values (up to 50mV) in spring surveys and an electrical potential dipolar distribution in October (2010) survey (amplitude from -15 to 25mV). To understand the origin of the measured self-potential signals, a model using vertical dipolar electrical sources was built, taking into account the electrical resistivity distribution deduced from electrical resistivity tomography. The self-potential source identification allows the Trecate contamination state to be better delineated. In particular, two self-potential contributions are superimposed: the electrokinetic mechanism is predominant in spring, while the redox mechanism represents the most important contribution in autumn.

Electrophotocatalysis of aqueous methyl tert-butyl ether on a titanium dioxide coated electrode

In this study, TiO2 was immobilized onto a titanium electrode for conducting MTBE degradation in aqueous solution. The TiO2 coated electrode could possess photocatalytic characteristics, and thus the application of the TiO2 coated electrode is able to perform photocatalysis and/or electrolysis under various controls. A bench-scale reactor system consisting of an electrolytic cell, an electrochemical analyzer, an electrical multimeter, and a UV-light source was employed to perform electrochemical experiments and electrophotocatalytic experiments.The results of electrochemical experiments showed that an optimum electrolytic condition was operated at 3.00V in a 1M Na2SO4 electrolyte solution, and the initial 20mg/L MTBE was reduced by 67% within 180min. Comparatively, the photocatalytic removal of MTBE was only 52% within 180min. The electrophotocatalytic experiments have demonstrated that the photocatalytic removal of MTBE was raised to 65% as applying a potential at −0.25V. The recombination of photoinduced electrons and holes could be significantly suppressed because the generated electrons by TiO2 excitation were taken away from the electrode as applying a negative potential. On the contrary, the improvement on MTBE removal is not obvious with the assistance of a positive electrical potential. Even though the mechanisms of electrochemical oxidation and electrochemically assisted photocatalysis to produce radicals for the breakdown of MTBE might be different, both processes followed the identical degradation pathway of forming acetate and CO2 based on the identification of GC/MS. According to the comparison of coulometric efficiency, photocatalysis with the assistance of a slight negative potential is the most effective and efficient approach to treat MTBE contaminated water.

The Effects of Annealing Temperature on the Microstructure and Properties of Cold-Rolled 5083 Aluminum Alloy

The effects of annealing temperature on the strength and corrosin properties of cold-rolled 5083 aluminum alloy (ε=60%）were investigated. The results show that the tensile strength of the alloy decreases with rising annealing temperature. The alloy shows ductile cracking in dry air and brittle cracking in 3.5%NaCl aqueous solution. The alloy reserves the most positive electrical potential at 200°C, and low SCC susceptibility at 200、250°C when annealed, but reserves relative high SCC susceptibility at 100, 150,300 and 350°C, which can be attributed to the difference shape and distribution of β-phase annealed at different temperature.

Enhanced hydrogen sorption on carbonaceous sorbents under electric field

The effect of an applied electric field on hydrogen physisorption isotherm on carbonaceous sorbents was studied. Distinctive sorption enhancement was obtained by applying a positive electrical potential of 2000 V to platinum-supported carbon samples. The phenomenon was ascribed to stronger interactions between hydrogen and the sorbent. Theoretical studies suggested that, the interaction between hydrogen and neutral carbon is primarily the electrostatic attraction between the π-bonds of the aromatic rings and the σ-bonds of H 2, which is classified as van der Waals interaction and is weak. However, the interaction between electrically charged carbon and hydrogen might involve orbital interactions between hydrogen and carbon, an interaction stronger than van der Waals attraction. Experimental studies indicated that the presence of platinum would induce dissociation of hydrogen molecules in to hydrogen atoms. The easier accessibility of the atomic orbital might favor the electron transfer from the atomic hydrogen to charged carbon.

Effect of pH of fine silica suspension and central rod diameter on the cut size of an electrical hydrocyclone with and without underflow

A 20 mm-diameter electrical hydrocyclone was developed and tested. The presence of the underflow results in a smaller d 50 than the absence of the underflow. Additionally, the higher the feed flow rate, the smaller d 50. Effect of central rod diameter and initial pH of suspension on the separation cut size was examined with and without underflows. The d 50 decreases with the increase of central rod diameter and initial pH values in both with and without the underflow. The zeta potential of particles increases proportionally with the initial pH of suspension. The electrical potential exhibits a stronger effect when the suspension has a higher pH. The d 50 becomes smallest under largest central rod diameter, highest pH and longest slurry collecting box condition operates with the positive electrical potential at side wall in the presence of the underflow. Based on the experimental data, general semi-empirical correlations were proposed and the effect of each parameter on d 50 was examined.

An Elevated Level of Cholesterol Impairs Self-Assembly of Pulmonary Surfactant into a Functional Film

In adult respiratory distress syndrome, the primary function of pulmonary surfactant to strongly reduce the surface tension of the air-alveolar interface is impaired, resulting in diminished lung compliance, a decreased lung volume, and severe hypoxemia. Dysfunction coincides with an increased level of cholesterol in surfactant which on its own or together with other factors causes surfactant failure. In the current study, we investigated by atomic force microscopy and Kelvin-probe force microscopy how the increased level of cholesterol disrupts the assembly of an efficient film. Functional surfactant films underwent a monolayer-bilayer conversion upon contraction and resulted in a film with lipid bilayer stacks, scattered over a lipid monolayer. Large stacks were at positive electrical potential, small stacks at negative potential with respect to the surrounding monolayer areas. Dysfunctional films formed only few stacks. The surface potential of the occasional stacks was also not different from the surrounding monolayer. Based on film topology and potential distribution, we propose a mechanism for formation of stacked bilayer patches whereby the helical surfactant-associated protein SP-C becomes inserted into the bilayers with defined polarity. We discuss the functional role of the stacks as mechanically reinforcing elements and how an elevated level of cholesterol inhibits the formation of the stacks. This offers a simple biophysical explanation for surfactant inhibition in adult respiratory distress syndrome and possible targets for treatment.

Open‐tubular capillary electrochromatography‐mass spectrometry with sheathless nanoflow electrospray ionization for analysis of amino acids and peptides

A novel, rugged sheathless capillary electrochromatography-electrospray ionization (CEC-ESI) device, in which an open-tubular separation capillary and an electrospray tip are integrated with a Nafion tubing junction, is coupled to mass spectrometry (MS) for the analysis of amino acids and peptides. A stable electrospray was generated at nanoflow rates by applying a positive electrical potential at the Nafion membrane junction. To sustain the stable spray, an electroosmotic flow (EOF) to the spray was supported by coating the fused silica capillary with Lupamin, a high-molecular-weight linear positively charged polyvinylamine (PVAm) polymer, which also minimizes analyte adsorption. Electrochromatographic separation of amino acids and peptides was further enhanced by the chromatographic selectivity of Lupamin stationary phase for these molecules. The device was very reliable and reproducible for CEC-ESI-MS analyses of amino acids and peptides for over a hundred injections. The separation and detection behaviors of amino acids and peptides under different conditions including pH, concentration, and composition of mobile phases on Lupamin-coated and uncoated capillaries have been investigated. The relationship between nano electrospray stability and EOF is discussed.

Electrical Surface Potential of Pulmonary Surfactant

Pulmonary surfactant is a mixed lipid protein substance of defined composition that self-assembles at the air-lung interface into a molecular film and thus reduces the interfacial tension to close to zero. A very low surface tension is required for maintaining the alveolar structure. The pulmonary surfactant film is also the first barrier for airborne particles entering the lung upon breathing. We explored by frequency modulation Kelvin probe force microscopy (FM-KPFM) the structure and local electrical surface potential of bovine lipid extract surfactant (BLES) films. BLES is a clinically used surfactant replacement and here served as a realistic model surfactant system. The films were distinguished by a pattern of molecular monolayer areas, separated by patches of lipid bilayer stacks. The stacks were at positive electrical potential with respect to the surrounding monolayer areas. We propose a particular molecular arrangement of the lipids and proteins in the film to explain the topographic and surface potential maps. We also discuss how this locally variable surface potential may influence the retention of charged or polar airborne particles in the lung.

Association of Paracellin-1 with ZO-1 Augments the Reabsorption of Divalent Cations in Renal Epithelial Cells

Paracellin-1 (PCLN-1) belongs to the claudin family of tight junction proteins and possibly plays a critical role in the reabsorption of magnesium and calcium. So far, the physiological properties of PCLN-1 have not been clarified. In the present study, we investigated whether PCLN-1 is associated with ZO-1. We also investigated whether (45)Ca(2+) transport across the paracellular barrier is affected by this association. In vitro binding analysis using glutathione S-transferase fusion protein showed that the C-terminal TRV sequence, especially Thr and Val residues, of PCLN-1 interacts with ZO-1. Next, PCLN-1 was stably expressed in Madin-Darby canine kidney cells using a FLAG tagging vector. ZO-1 was co-immunoprecipitated with the wild-type PCLN-1 and the alanine substitution (TAV) mutant. However, mutants of the deletion (Delta TRV) and the alanine substitution (ARV and TRA) inhibited the association of PCLN-1 with ZO-1. Confocal immunofluorescence demonstrated that the wild-type PCLN-1 and the TAV mutant localized in the tight junction along with ZO-1, but the Delta TRV, ARV, and TRA mutants were widely distributed in the lateral membrane including the tight junction area. Interestingly, monolayers of cells expressing the wild-type PCLN-1 and the TAV mutant showed higher activities of (45)Ca(2+) transport from apical to basal compartments, compared with those expressing the Delta TRV, ARV, and TRA mutants and the mock cells. (45)Ca(2+) transport was inhibited by increased magnesium concentration suggesting that magnesium and calcium were competitively transported by PCLN-1. It was noted that a positive electrical potential gradient enhanced (45)Ca(2+) transport from apical to basal compartments without affecting the opposite direction of transport. Thus, PCLN-1 localizes to the tight junction followed by association with ZO-1, and the PCLN-1.ZO-1 complex may play an essential role in the reabsorption of divalent cations in renal epithelial cells.

Surface Electrical Potential of Spontaneously Poled La-Modified PbTiO3 Thin Film by Kelvin Force Microscopy

Both surface electrical potential and surface structure of spontaneously poled Pb0.85La0.15Ti0.963O3 (PLT) c-axis-oriented film on (100)Pt-coated (100)MgO single-crystal substrate were simultaneously measured by Kelvin force microscope in air. The surface electrical potential clearly revealed the polarity of the polarization on the film surface, i.e., the film surface had either positive or negative electrical potential. However, the surface electrical potential was strongly affected by floating charged particles.