Relative Potential Difference Research Articles

Разность потенциалов в стволах березы повислой (Betula pendula ROTH): особенности процессов релаксации при изменении температуры окружающей среды

The daily dynamics of the potential difference arising in the wood of the trunk of the hanging birch (Betula pendula Roth) at ambient temperature changes makes it possible to simulate the dynamics of the processes of redistribution of salt ions in the pores. An analysis of the results of measuring the potential difference in the wood of the model tree trunk showed that its dynamics is of a relaxation nature and tends to a certain stationary value. On the basis of the data of full-scale measurements of the potential difference in the framework of classical electrodynamics, a formalized model of the dynamics of the relative potential difference was constructed, containing three parameters. As a result of a computational experiment using an optimization procedure based on the Nash-Sutcliffe criterion, the parameters of the relaxation process of formation of a stable potential difference along the birch trunk caused by a change in the ambient temperature were calculated. It was revealed that the dynamic balance of the charge redistribution flows is determined by the factors of stimulating and stabilizing processes inside the trunks of woody plants. It is shown that a competent combination of the results of monitoring the potential difference in tree trunks and a computational experiment will make it possible to form an extensive database of parameters for the processes of formation of a stable dynamic equilibrium of salt ion fluxes in them, depending on the characteristics of growth, daily and seasonal changes in ambient temperature and soil composition. The study of changes in the state of trees due to the response to the impact of various environmental factors makes it possible to expand the range of tools for predicting the occurrence of catastrophic situations in forest ecosystems.

An integrate-and-fire neuron with capacitive trans-impedance amplifier for improving linearity in Spiking Neural Networks

In this paper, we propose a novel neuron circuit with capacitive trans-impedance amplifier (CTIA) integrator to enhance the linearity of pre-synaptic current summation. The proposed neuron circuit achieved an improvement compared to the conventional neuron circuit with a current mirror, thereby maintaining the input node of a neuron circuit at virtual ground by the negative feedback of an amplifier. The relative potential difference is integrated into the membrane capacitor of CTIA feedback loop with a negative integration. From the simulation results, we confirmed that the proposed neuron circuit successfully improves output linearity for a wide range of the input current level.

Effect of hot extrusion on AZ91 alloy corrosion behaviour

ABSTRACT The effect of hot extrusion on the corrosion behavior of AZ91 alloy was studied by observing the change of grain size, the size and distribution of precipitated phase on the transverse and longitudinal sections before and after extrusion. The results show that the grain refinement of alloy was significant after extrusion, the grain size of the transverse section was uniform, that of the longitudinal section was different and the parallel streamline of shear stripes appeared. After extrusion, the decrease of the β-Mg17Al12 phase size reduces the relative potential difference between the second phase and the α-Mg matrix; the reduction of the transverse section was particularly significant. Grain refinement and precipitate size reduction after extrusion can improve the corrosion resistance of the AZ91 Mg alloy, which is the reason why the corrosion resistance of the transverse section was better than that of the longitudinal section.

From Cord to Eye: Wharton Jelly-Derived Stem Cells Differentiate Into Corneal Endothelial-Like Cells.

A malfunction of the corneal endothelium leading to corneal opacity is one of the main causes of impaired vision. Currently, keratoplasty is the one and only donor cornea-dependent treatment, and this calls for alternatives because of the worldwide lack of donor corneas. Recently, the topography of Descemet membrane (DM) has been discovered as a feasible stem cell differentiation tool. With this study, we further confirm this mechanotransductive system by using preinduced Wharton jelly-derived mesenchymal stem cells (WJ-EPCs). To measure the mechanotransductive potential of Descemet-like topography (DLT), WJ-EPCs were cultivated on collagen imprints with DLT. Changes in the gene and protein expressions of corneal endothelial cells (CECs), typical markers such as zonula occludens (ZO-1), sodium/potassium (Na/K)-ATPase, paired-like homeodomain 2 (PITX2), and collagen 8 (COL-8) were measured. In addition, CEC functionality has been evaluated by measuring the relative potential differences in a 2-compartment system and by measuring corneal transparency in an ex vivo rabbit cornea model. To confirm the activity of WJ-EPCs, rabbit CECs were restless deleted by collagen digestion of a thin layer of rabbit Descemet membrane. The proper CEC-typical hexagonal morphology of WJ-EPCs in combination with a significant expression of ZO-1, Na/K-ATPase, PITX2, and COL-8 could be demonstrated. In addition, the WJ-EPCs were able to build up a relative potential difference of 40 mV and to keep corneas clear and transparent. These data indicate that a well-characterized, functional CEC monolayer was developed by using a DLT-mediated mechanotransductive differentiation of WJ-EPCs.

Relative Volta Potentials of Intermetallics in AZ91-RE Mg Alloy After Solution and Aging Treatment.

AZ91 alloy with 1.0 wt.% (La, Ce) mischmetal (MM) addition was solution treated at 593 K for 4 h, 653 K for 2 h and 693 K for 8 h (T4), which was subsequently aged at 493 K for 5 h, 8 h and 11 h, respectively. Solid solution and aging treatment mainly led to the change of number of β-Mg17Al12 phases and the size of mischmetal (MM) intermetallics. The relative potential difference is an index for local corrosion of alloys because the corrosion is driven by micro-galvanic coupling of the microstructure. In the present work, the relative Volta potential difference between the dominated intermetallic phase and Mg-matrix phase in the AZ91 alloy with (La, Ce) MM addition after heat treatment was measured by scanning Kelvin probe force microscopy (SKPFM). Then correlative changes of relative Volta potentials of intermetallic phases with solid-solution-treatment and subsequently aging treatment (T6) were inferred. The relative Volta potential difference of mischmetal intermetallic phases increased with the solid solution treatment. With the increase of aging time, the relative Volta potential difference of mischmetal intermetallic phases decreased. The relative Volta potential difference of intermetallic phases containing rare earth was ranked as: T6-11 h <T6- 8 h<T6-5 h< as-received < T4.

Study on the effect of mischmetal (La,Ce) on the micro-galvanic corrosion of AZ91 alloy using multiscale methods

The relative potential difference can be treated as an index of local corrosion of alloys. Since local corrosion is driven by the micro-galvanic coupling, which is consist of the micro-constituent phases and the matrix. They present distinct potential difference normally. In the present work, the relationship between the Volta potential and the corrosion effect of the dominated intermetallic phase in the AZ91 Mg alloy with (La, Ce) MM addition was investigated. A multiscale approach coupling global and local measurements was used to study the corrosion behavior of the alloy and its intermetallic phase. Results showed that the microstructure of AZ91 Mg alloy with (La, Ce) MM addition was complex, with the presence of Al4(La, Ce) phases in acicular or rod shape, a small number of Al8Mn4Ce, β-Mg17Al12 and α-Mg solid solution. In this case, the improved corrosion resistance of the alloy was achieved. Scanning Kelvin probe force microscopy (SKPFM) analysis revealed that all the intermetallics were noble comparing with the α-Mg solid solution. In-situ electrochemical atomic force microscopy (EC-AFM) observation for the initial stages of corrosion showed the α-Mg matrix surrounded by β-Mg17Al12 or Al8Mn4Ce was susceptible to pitting corrosion. No noticeable corrosion occurred at the α-Mg adjacent to Al4(La,Ce) phase, in spite of the relatively higher difference of Volta potential between Al4(La,Ce) phase and the matrix. Volta potential is insufficient to determine whether the phase is an effective cathode or anode.

Effect of Different Scale Precipitates on Corrosion Behavior of Mg–10Gd–3Y–0.4Zr Alloy

A large amount of directional and willow-like β′ phase was precipitated in Mg–10Gd–3Y–0.4Zr (GW103K) alloy after solution treatment and subsequently aged treatment (T6). In order to explore the effect of the precipitates on the corrosion behavior of the GW103K alloy, the alloy was subjected to solution treatment (T4) at 773 K for 4 h at first, subsequently aged at 498 K for 193 h (T6). The microstructure evolution of the GW103K alloy after this treatment was investigated by scanning electron microscopy and transmission electron microscopy. The high-angle annular detector dark-field scanning transmission electron microscopy was used to observe the typical corrosion morphologies of the nanoscale precipitation phases (β′) in the T6-treated alloy. The corrosion rate was measured by potentiodynamic polarization test. Combining with the potential measurement results by scanning Kelvin probe force microscopy, the effects of the skeleton-like Mg24(Gd, Y)5 and β′ precipitates on the corrosion behavior of GW103K alloy were explored. The results showed that the corrosion rate of the GW103K alloy in different conditions was ranked as: as-cast alloy> T4-treated alloy> T6-treated alloy, attributing to the fact that the relative potential differences of skeleton-like Mg24(Gd, Y)5 were lower than those of the matrix, therefore Mg24(Gd, Y)5 phase formed micro-galvanic coupling with the matrix and corrosion dissolution occurred. The nanoscale β′ precipitates in T6-treated alloy can retard the cathodic process.

Study of Transient Enclosure Voltage Coupling to Secondary Cables in a Gas-Insulated Substation

Transient enclosure voltage (TEV) induces a relative potential difference between grounding conductors and then couples to secondary cables and may cause malfunction and even damage to secondary equipment. This study investigates the coupling mechanism of TEV to secondary cables from an experimental point of view and presents a cable model suitable for calculation. Experiments are carried out on test platforms established in a laboratory. The experimental results indicate that the magnitudes of port voltages are roughly 1.5‰ of TEV magnitudes, and the waveform of the start port voltage has the same profile but in antiphase with that of the end port voltage. Moreover, only common-mode voltage with no differential-mode voltage exists for the twin core cable. Based on these results, an equivalent circuit for a secondary cable is proposed. This circuit can generate similar waveforms as those measured in the experiment. The experimental and theoretical results presented in this paper should prove helpful for evaluating the interference severity of secondary cables resulting from TEV for the electromagnetic protection of secondary ports.

Research on Assessment Parameters of Adsorption Properties in Cation Exchange Membranes for all Vanadium Redox Flow Battery

The relative adsorption coefficient, a novel parameter was introduced to describe the dominant adsorption ability of ions in cation membrane for all vanadium redox flow battery instead of traditional selectivity coefficient. The parameter as a function of membrane property and vanadium ions in membrane was derived from the relative potential differences in membrane between an isothermal adsorption and an ideal equivalent adsorption. The adsorption isotherms of three kinds of commercial membranes were measured for VO2+/H+ electrolyte system. The results show the reasonable rules that the relative adsorption coefficients increase as the VO2+ contents are increased whereas decrease as the H+ contents are increased in electrolyte.

Self-bridging of vertical silicon nanowires and a universal capacitive force model for spontaneous attraction in nanostructures.

Spontaneous attractions between free-standing nanostructures have often caused adhesion or stiction that affects a wide range of nanoscale devices, particularly nano/microelectromechanical systems. Previous understandings of the attraction mechanisms have included capillary force, van der Waals/Casimir forces, and surface polar charges. However, none of these mechanisms universally applies to simple semiconductor structures such as silicon nanowire arrays that often exhibit bunching or adhesions. Here we propose a simple capacitive force model to quantitatively study the universal spontaneous attraction that often causes stiction among semiconductor or metallic nanostructures such as vertical nanowire arrays with inevitably nonuniform size variations due to fabrication. When nanostructures are uniform in size, they share the same substrate potential. The presence of slight size differences will break the symmetry in the capacitive network formed between the nanowires, substrate, and their environment, giving rise to electrostatic attraction forces due to the relative potential difference between neighboring wires. Our model is experimentally verified using arrays of vertical silicon nanowire pairs with varied spacing, diameter, and size differences. Threshold nanowire spacing, diameter, or size difference between the nearest neighbors has been identified beyond which the nanowires start to exhibit spontaneous attraction that leads to bridging when electrostatic forces overcome elastic restoration forces. This work illustrates a universal understanding of spontaneous attraction that will impact the design, fabrication, and reliable operation of nanoscale devices and systems.

Mechanism of enhanced nitrate reduction via micro-electrolysis at the powdered zero-valent iron/activated carbon interface

Nitrate reduction by zero-valent iron (Fe0) powder always works well only at controlled pH lower than 4 due to the formation of iron (hydr)oxides on its surface. Fe0 powder combined with activated carbon (AC), i.e., Fe0/AC micro-electrolysis system, was first introduced to enhance nitrate reduction in aqueous solution. Comparative study was carried out to investigate nitrate reduction by Fe0/AC system and Fe0 under near-neutral conditions, showing that the Fe0/AC system successfully reduced nitrate even at initial pH 6 with the reduction efficiency of up to 73%, whereas for Fe0 only ∼10%. The effect of Fe0 to AC mass ratio on nitrate reduction efficiency was examined. Easier nitrate reduction was achieved with more contact between Fe0 and AC as the result of decreasing Fe0 to AC mass ratio. Ferrous ion and oxidation–reduction potential were measured to understand the mechanism of enhanced nitrate reduction by Fe0/AC micro-electrolysis. The results suggest that a relative potential difference drives much more electrons from Fe0 to AC, thus generating adsorbed atomic hydrogen which makes it possible for nitrate to be reduced at near-neural pH. Fe0/AC micro-electrolysis thus presents a great potential for practical application in nitrate wastewater treatment without excessive pH adjustment.

Open loop Kelvin probe force microscopy with single and multi-frequency excitation

Conventional Kelvin probe force microscopy (KPFM) relies on closed loop (CL) bias feedback for the determination of surface potential (SP). However, SP measured by CL-KPFM has been shown to be strongly influenced by the choice of measurement parameters due to non-electrostatic contributions to the input signal of the bias feedback loop. This often leads to systematic errors of several hundred mV and can also result in topographical crosstalk. Here, open loop (OL)-KPFM modes are investigated as a means of obtaining a quantitative, crosstalk free measurement of the SP of graphene grown on Cu foil, and are directly contrasted with CL-KPFM. OL-KPFM operation is demonstrated in both single and multi-frequency excitation regimes, yielding quantitative SP measurements. The SP difference between single and multilayer graphene structures using OL-KPFM was found to be 63 ± 11 mV, consistent with values previously reported by CL-KPFM. Furthermore, the same relative potential difference between Al2O3-coated graphene and Al2O3-coated Cu was observed using both CL and OL techniques. We observed an offset of 55 mV between absolute SP values obtained by OL and CL techniques, which is attributed to the influence of non-electrostatic contributions to the input of the bias feedback used in CL-KPFM.

S.06.03 Persistence of brain deficits in adult ADHD

and hemispheric assymetry were predominantly associated with alpha band variances in rest, during engagement to and performing cognitive tasks, between adults with ADHD and controls, while based on assessing very low frequency oscillations, different pattern of deactivation of the default mode network was suggested between individuals with high and low ADHD symptom frequency [1]. Multiple studies found event related potential differences associated with attentional control-, error detection-, reward sensitivity-, and inhibition features of ADHD. Although QEEG constantly adds to the understanding of the neurobiological background of ADHD and considered as a useful and promising tool for targeting the identification of objective indices for the diagnosis of ADHD, current markers are not yet specific enough for diagnostic purposes[2,3].

Analyses of elastically scattered charged pions from calcium isotopes and the 48Ca-54Fe isotone at 180 MeV

The elastic scattering of 180 MeV positively and negatively charged pions, incident on a set of calcium isotopes and the isotone 48 Ca - 54 Fe, has been analyzed within the framework of a recently updated simple local optical potential. This potential, particularly at the tail region, has been originally determined from available phase shifts using inverse scattering theory and the Klein-Gordon equation as a guide. The analysis is carried out with and without considering the squared potential term in the Klein-Gordon equation. Coulomb effects are accounted for by implementing Stricker's prescription. The numerical results for the angular distributions with isotopic and isotonic shifts have been well reproduced. Relative potential differences, in the imaginary part, for π − − 48 Ca, 40 Ca and π + − 54 Fe, 48 Ca also reveal that the neutron distribution in 48 Ca is more extended by about 0.21 fm.

Membrane dipole potential of interaction between amyloid protein and phospholipid membranes is dependent on protein aggregation state

At least 20 different human proteins can fold abnormally resulting in the formation of pathological aggregates and several deadly degenerative diseases. Evidence also suggests that non-disease-associated proteins, under appropriate conditions, can aggregate in vitro to form amyloid fibrillar species. Numerous reports have shown that the interaction between cell membrane and amyloid proteins is of particular importance in the cytotoxic effects elicited by amyloid proteins. Despite the significant progress has been made, there are still large gaps in our knowledge of the disease mechanism(s) associated with this aforementioned interaction. In the current research, using a dual-wavelength fluorescence ratiometric method along with a voltage-sensitive dye, di-8-ANEPPS, we found that a decrease in intramembrane dipole potential was observed upon binding of amyloid proteins with phospholipids and this decrease became more dramatic when protein was in its aggregated form. Moreover, our data revealed that a correlation among the presence of cholesterol, the type of phospholipid, and the drop in dipole potential was evident. In comparison with the pure DPPC, the relative difference in dipole potential between fibrillar and freshly prepared samples attenuated with the addition of cholesterol while an increase in relative potential difference was observed in DPPG. Importantly, our results, for the first time, presented that the membrane dipole potential in amyloid protein–phospholipid interaction was dependent on the aggregation state of proteins, which is highly associated with the biological effects elicited by amyloid proteins.

Surface charge retention and enhanced polarization effect on ferroelectric thin films

The authors report surface charge retention and enhanced ferroelectric polarization effect on ferroelectric thin films by Kelvin probe force microscope (KFM). Since high electric field is induced at scanning probe microscope tip during domain switching and the sign of surface charge induced by this high electric field is always opposite to the sign of induced ferroelectric polarization charge, the surface potential of the KFM signal exhibits the relative potential difference between the potential of the ferroelectric polarization charge and the potential of the surface charge. After the discharge process of surface charge, the enhanced contribution from the ferroelectric polarization charge was observed. Similarly, the reduction of surface charge was observed as time passed and the surface potential indicating the ferroelectric polarization charge was enhanced due to this retention property of surface charge.

Comparison of methods for statistical detection of event related potential differences

Comparison of methods for statistical detection of event related potential differences