Variation Of Electric Potential Research Articles

Statistical Analysis of Atmospheric Electrical Potential

Atmospheric electricity, a complex interplay between Earth's surface, atmosphere, and ionosphere, is driven by both the dramatic charge separation in thunderstorms and the continuous ionization by cosmic rays and radioactivity. This study investigates the variations in atmospheric electrical potential using statistical analysis of data collected in Ilorin, Nigeria. A copper arrester and an earth rod connected to a data logger continuously measured the air-ground potential difference for four months. Meteorological parameters (humidity and temperature) were also monitored. We analyzed the factors influencing atmospheric electrical potential variations and developed a predictive model based on the collected data. The model was validated with independent datasets. Results indicate a diurnal and seasonal pattern in atmospheric electrical potential, with peaks observed during evenings and winter months, and lows in afternoons and summer. atmospheric electrical potential exhibited a positive correlation with humidity and a negative correlation with temperature. This study highlights the complex and dynamic nature of atmospheric electrical potential, influenced by various local and global factors. These findings contribute valuable data and insights on atmospheric electrical potential, advancing scientific understanding in this field.

Electro-mechanical vibration characteristics of imperfect sandwich FG piezoelectric honeycomb nanoplates resting on Kerr foundation

This study presents an innovative analytical approach to examine the electro-mechanical vibration characteristics of sandwich nanoplates featuring a honeycomb core and two surface layers composed of imperfect piezoelectric functionally graded (FG) material, incorporating porosities, atop a Kerr elastic foundation. Utilizing nonlocal elasticity theory and four-variable refined plate theory (HSDT-4), we account for nanoscale effects and model the electric potential variation across the piezoelectric layer thickness as a combination of cosine and linear variations satisfying Maxwell's equation. The proposed method's novelty lies in its comprehensive analysis of the interplay between porosity, elastic foundation parameters, material properties, geometrical dimensions, external voltage, and nonlocal parameters on the free vibration frequency of these nanostructures. Numerical simulations validate the model's reliability and assess the significant impacts of these factors. Our findings contribute to the optimization of nanostructural designs for advanced engineering applications, highlighting the method's added value in predicting the behavior of imperfect piezoelectric FG honeycomb nanoplates.

Dodecanogram (DDG): Advancing EEG technology with a high- frequency brain activity measurement device

EEG measures electric potential changes in the scalp. Even though it has been associated with human thoughts, there has been no direct evidence. The problem with EEG is that it measures variations in current or electric potential in the millisecond time domain, where muscle movement strongly affects the readings. The millisecond time domain is equivalent to the kHz resonance signal generated by any dielectric resonator, and every single cell membrane resonates in this time range. So, the measurement of EEG could come simply from the skin and not from the brain. Therefore, we have advanced EEG technology with the dodecanogram (DDG), which reveals 12 frequency bands or 12 discrete time regions where brain activities are most significant. We measure brain activity using a stream of pulses and a logic analyzer that counts ultra-short pulses needed to emulate brain scalp potential changes. We have created another version of DDG where, using an array of RLC (resistor-inductor-capacitor) resonators, we sense the ultra-low-power electromagnetic radiation from different locations on the brain's surface. Since we measure signals from Hz to THz, covering 12 orders of time ranges as a property of dielectric resonance, unlike EEG, there is a high probability that the DDG signal may truly originate from the brain. We have monitored DDG on an artificial organic brain replica 24/7 for over a year and on multiple human subjects, before and after meditation and concluded that most cognitive, perceptive, and emotional bursts occur around 200-700 nanoseconds, not milliseconds, as it was believed for 150 years of EEG era.

Design, fabrication, nonlinear analysis, and experimental validation for an active sandwich beam in strong electric field and thermal environment

In the present work, an efficient one-dimensional finite element (1D-FE) framework considering layerwise mechanics with full electro-mechanical coupling has been developed for the laminated smart sandwich beams submitted to active damping. Nonlinear constitutive relations of piezo-thermo-elasticity at large electric field with temperature-dependent material properties have been considered. The efficient layerwise theory (ELWT) considers the normal deformation of the piezoelectric sensing/actuating patches/layers due to the more significant value of piezoelectric strain coefficient d33. The electric potential variation across the thickness of the PZT sensor/actuator has been assumed quadratic. The state space format of the dynamical system has been constructed based on a reduced order model in modal space. The feedback linearization approach has been applied to the nonlinear system of equations to design an equivalent linear optimal control strategy. An experimental facility has been developed to test the accuracy of the present nonlinear FE model. This facility consists of a thermal chamber with a heating system, air gun, actuation & sensing units with band-pass filters, a smart sandwich beam equipped with PZT-SP5H patches, a data acquisition system, and a computer with LabVIEW software. Open- and closed-loop responses from the present 1D-FE model have been compared with those obtained through experimentation at different temperatures. It has been observed that the current nonlinear FE model correctly captures the dynamic behavior of the vibrating smart sandwich beam at different operating temperatures and strong electric field. The study shows a strong dependence of the PZT materials on thermal chamber temperature and actuation field. New results for a smart sandwich beam are also presented to study the performance of PZT-SP5H patches as sensors/actuators for nonlinear active shape and vibration control in a thermal environment. The effect of piezoelectric actuator/sensor thickness, patch size, position, and applied mechanical load on the active shape and vibration control has been discussed.

Diurnal Variations in Vegetation Activity affecting Shallow Groundwater Flow identified by Microthermal Measurements

Observations of summer microthermal temperature variations suggest, next to hydrological factors, a significant influence of plant activity on groundwater flow in fractured claystone materials. Variations in groundwater microtemperature were compared to variations in meteorological parameters and electrical potential of plants. With an increase in surface temperature, relative air humidity decreases and an increase in tree electrical potential, measured as the difference between the northern and the southern stem exposure (N–S), can be observed. This increase in electrical potential is concomitant with a change in groundwater temperature of approximately 2 mK. This relationship does not always occur. At high temperatures (+30°C) the decrease amounts to just 1 mK. This fact is related to the change in transpiration of plants, decreased or even suspended at high surface temperatures. A frequency analysis of all data showed a daily frequency of high magnitude in all parameters. Possibly changes in the macro weather situation events were observed in the results of atmospheric pressure, southern electric potential and groundwater temperature. The lag time between changes in electric potential and subsurface microtemperature changes amounts to 17 hours, possibly a result of the electrical potential difference between the northern and the southern exposure of the stem (N–S), and 5 hours, the result of the change in electrical potential difference between the southern and the northern stem exposure side (S–N). A comparison between potential changes and the computed change in gravity resulting from earth tidal effects showed that the correlation between the subsurface temperature variation with up to 2 mK and the change in surface temperature variation does not match directly. Other study shows that the impact of earth tides on subsurface microtemperature variation amounts to ca. 1mK. The effect of groundwater abstraction by mature vegetation is determined at the same range. Atmospheric tides can be correlated with the changes in north and south electric potentials.

Analysis of electromechanical couplings and nonlinear carrier transport in flexoelectric semiconductors

In recent years, a linearization method has been extensively employed to investigate the electromechanical fields and carrier distribution in flexoelectric semiconductors, where the assumption of a small perturbation of carrier concentration is adopted. However, this method fails to accurately describe the realistic physical process in which a considerable variation of carrier concentration takes place. Based on fully coupled nonlinear equations, this paper presents a finite element approach to study the electromechanical couplings and nonlinear carrier transport in flexoelectric semiconductors. This method is applied to calculate the electrostatic potential in a bent piezoelectric semiconductive nanowire (NW) going beyond simple considerations and to simulate the nonlinear current–voltage (I–V) characteristics of a mechanically loaded flexoelectric p–n junction. The results indicate that the inherently nonlinear drift of carriers gives rise to the asymmetric distribution of the electric potential relative to the NW axis in the upper body. Flexoelectricity brings about a remarkable enhancement in output voltage and is responsible for the linear variation of electric potential along the length direction of the NW unless close to two ends. Furthermore, the barrier height and I–V relations of a flexoelectric p–n junction can be effectively tuned by mechanical forces due to the flexoelectric effect, the effect of which relies on the size of the p–n junction configuration. This work is a good starting point to comprehend the coupling of flexoelectricity and nonlinear carrier transport in static and dynamic cases, and offers an effective approach to numerically deal with the issues involved in flexoelectronics and piezoelectronics at the nanoscale.

Optimization of electroosmotic flow to enhance the removal of contaminants from low‑permeable soils

Electrokinetic is an effective method for the extraction of contaminants from low-permeable soils. This work examines the influence of Ca+2 ions on the electroosmotic flow and the effect of electric potential, current, and pH variations on the removal of Pb2+, Na+, and Clˉ ions from artificially contaminated soil during vertical electrokinetic experiments. The DC electric field of 1 Vcm−1 was applied across the soil specimen via steel mesh electrodes for 24, 48, and 72 h of the experiment. In this work, the vertical electrokinetic cell was used to avoid the deposition of Na+ and Pb +2 ions near the soil surface after the treatment. making it even less permeable. The results show that the formation of acidic and alkaline environments in soil specimens affects the transport of ionic species by reducing the effect of electromigration and electroosmotic water flow. The enhancement of electroosmosis using Ca+2 ions as an electrolyte increased the extraction efficiency of Pb2+ (i.e., 41%) and Na+ (i.e., 82%) ions instead of the Clˉ (i.e., 69%) ions due to the high electroosmotic flow (i.e., 81 mL) from anode to the cathode. For relatively low electroosmotic flow (i.e., 19 mL), the extraction efficiency of Clˉ ions (i.e., 76%) was higher than that of Pb2+ (i.e., 27%) and Na+ (i.e., 44%) ions. The results demonstrated that the extraction efficiency of ions and energy consumption increased with treatment time and were higher during the first 24 h of the experiments.Graphical Abstract

Stem electrical potential variations may aid in the early detection of drought stress in fruit-bearing trees

Electrical plant signaling as a variation potential (VP) occurs in response to a wide range of stimuli, and it is associated with the induction of sudden changes in xylem pressure. Additionally, there is evidence that electrical potential (EP) of plants changes with changing soil water content. Therefore, the use of EP as a direct plant measurement of plant water status may have potential as water stress monitoring information. EP measurements within plant stems indirectly correlate with sap flow (SF), which is one possible variable for estimating plant water use. However, whether this relationship is stable under drought conditions is not known. The present work investigated the relationships between SF and EP variations during an 18-day drought period on three avocado trees to test the hypothesis that the relationships between SF and EP may be lost due to drought intensity. The results showed that short-term variations in EP were positively associated with vapor pressure deficit (VPD) and SF variations but negatively associated with soil water content (SWC). An increase in VP emissions was observed as drought advanced, which was negatively associated with stem water potential (SWP). After 18 days of drought, irrigation almost completely suppressed short-term variations in EP. The present work provides preliminary results that strongly suggest a relationship between drought stress and EP variations in plant stems. Further research is needed to confirm whether the EP trends observed during drought are due to cavitation events and emission of VP signals and/or linked to other physiological processes, e.g., pH changes in response to drought or embolism. Meanwhile, the present work indicates that short-term variations in EP (dEP) are strongly associated with the intensity of drought stress, thus stem electrical potential variations may aid in the early detection of drought stress in fruit-bearing trees.

Study of the Influence of the Dielectrophoretic Force on the Preferential Growth of Bacterial Biofilms in 3D Printed Microfluidic Devices

Understanding the effect of different electric potentials upon the preferential formation of biofilms inside microfluidic devices could represent a step forward in comprehending the mechanisms that govern biofilm formation and growth. 3D printed microfluidic devices were used to investigate the influence of the dielectrophoretic forces on the formation and growth of Staphylococcus aureus ATCC 25923 biofilms. Bacterial suspensions of 2.5 McF were pushed through microfluidic channels while simultaneously applying various potential differences between 10 and 60 V. The overall electric field distribution within the channel was simulated using the COMOSL software. The effect of the electric potential variation on the preferential biofilm formation was determined using an adjusted microtiter plate technique, as well as a qualitative method, Scanning Electron Microscopy (SEM). SEM images were used to describe the morphology of the biofilm surface. The conclusions show that the dielectrophoretic forces, resulting due to inhomogeneity of the electric field, have more visible effects upon the cells up to 40 V. Above this magnitude, due to a more homogenous distribution of the electric field, the formation and growth of the biofilm become more uniform. At around 60 V, the distance between the high electric gradient regions decreases, leading to an almost uniform distribution of the electric field and, therefore, to a shift from dielectrophoretic to electrophoretic forces acting upon the bacterial cells.

Influence of pinning centers of different natures on surrounding vortices

Studies involving vortex dynamics and their interaction with pinning centers are an important issue to reach higher critical currents in superconducting materials. The vortex distribution around arrays of engineered defects, such as blind and through holes, may help to improve the superconducting properties. Thus, in this work, we used the time-dependent Ginzburg-Landau theory to investigate the vortex dynamics in superconductors of mesoscopic dimensions with a large central square defect with three different configurations: (i) a hole which passes through the sample (interface with the vacuum); (ii) a superconducting region with lower critical temperature Tc; and (iii) a region with a more robust superconductivity, i.e., with a higher Tc. Such systems can be envisaged as elementary building blocks of a macroscopic decorated specimen. Therefore, we evaluated the influence of different interfaces on the vortex dynamics and their effects in the field-dependent magnetization and time-dependent induced electric potential variation. The results show that the superheating field is independent from the nature of the defect. However, the currents crowd at the vertices of the through hole producing a lower degradation of the local superconductivity, which may increase the upper critical field. On the other hand, the last type of defect can be used to control the vortex dynamics in the main superconducting region around the defect with more accuracy. While the first two defects are attractive for the vortices, the third type is repulsive, being needed several penetrated vortices in the superconducting matrix to allow penetration of vortices into the higher Tc domain.

An electroelastic Kirchhoff rod theory incorporating free space electric energy

This work presents a geometrically exact Kirchhoff-like electroelastic rod theory wherein the contribution of free space energy is also factored in. In addition to the usual mechanical variables such as the rod’s centerline and cross-section orientation, three electric potential parameters are also introduced to account for the variation in electric potential within the rod’s cross-section as well as along the rod length. The free space energy is included through an electric flux-like variable acting on the lateral surface of the rod. The governing equations of this rod are derived through balance of forces and moments (arising from both mechanical and electric sources) for mechanical variables, weighted integration of the three-dimensional electric displacement equation in the rod’s cross-section for electric potential parameters and through the asymptotic expansion of a boundary integral equation for the electric flux variable. We also obtain the expressions of internal contact moment and conjugates of electric potential parameters in terms of the rod’s aforementioned mechanical and electric variables. A specific choice of the three-dimensional electroelastic stored energy density is further taken catering to piezoelectric materials and dielectric elastomers and the rod’s constitutive equations are rederived which exhibit interesting interplay between mechanical and electric variables. The presented work can help improve the design of soft electroelastic rod-like actuators and sensors.

A study of the influence of different grid structures on plasma characteristics in the discharge chamber of an ion thruster

The grid structure has significant effects on the discharge characteristics of an ion thruster. The discharge performances of a 30 cm diameter ion thruster with flat, convex and concave grids are studied. The analysis results show that the discharge chamber with a convex grid has a larger ‘magnetic-field free area’ than the others, and the parallelism of the magnetic-field isopotential lines and anode is generally the same in the three models. Plasma densities of the three structures at the grid outlet are in the range of 3.1 × 1016–6.9 × 1017 m−3. Along the thruster axis direction, the electron temperature in the chamber with the convex and concave grids is in the range of 3.3–3.5 eV, while that with a flat grid is lower, in the range of 3.1–3.5 eV. In addition, the convex and the concave grids have better uniform distribution of electron temperature. Moreover, the collision frequency ratios show that the axial degree of ionization of the three models is the highest, and the flat grid has the highest discharge efficiency, followed by the convex grid and the concave grid is the least efficient. The test and simulation results of the 30 cm diameter ion thruster with the convex grid show that the measurement and calculation results are 3.67 A and 3.44 A, respectively, and the error above mainly comes from the ignorance of the doubly charged ions and parameter settings in the model. The comparison error between the simulation and measurement of beam current density is mainly caused by the actual thermal deformation of the grids during the discharge process, which leads to the change in electric potential distribution and variation of the focusing characteristics of the grids. Upon consideration of discharge performance and the thermal grid gap variation, it can be concluded that the flat and concave grids are more suitable for small-diameter ion thrusters, while the convex grid is a more reasonable choice for the higher-power and larger-diameter thrusters.

On the flexoelectric effect on size-dependent static and free vibration responses of functionally graded piezo-flexoelectric cylindrical shells

The flexoelectric effect depends on the strain gradient, which naturally appears in intelligent structures at micro and nano scales. Therefore, the flexoelectric phenomenon significantly affects electro-mechanical behavior of structures in these scales. In this study, the first-order shear deformation theory and the reformulated flexoelectric theory are applied to derive coupling equations of motion for a size-dependent static and dynamic responses of multilayered composite shell with simply supported and clamped edges. Constitutive equations are defined based on assumption that the internal energy function depends not only on strains and polarization tensors but also on strains and polarization gradient tensors. The piezo-flexoelectric structure is made of an isotropic functionally graded core and two orthotropic layers. Reynolds transport theorem and variational Hamilton principle are used to derive equations of motion expressed by forces and displacements, and corresponding boundary conditions. In order to check the correctness of the formulation, and solution of the problem obtained by Galerkin method, static and free vibrations analyses of macro-/micro-/nanoshell are investigated. Diagrams of deflection and electrical potential variations of the structure under the load are obtained for the direct flexoelectric effect. Additionally, the influence of various parameters, e.g., geometric properties, size effect, power-law index, and flexoelectric layer thickness, on the deflection, potential function, and natural frequency of the microshell have been investigated. The numerical results and discussion present that above parameters significantly affect a mechanical behavior of the microshell under consideration.

Analysis of tissue electrical properties on bio-impedance variation of upper limps

Upper limb loss has a significant impact on individual socioeconomic life. Human-machine interface (HMI) using surface electromyography (sEMG) establishes a link between the user and a hand prosthesis to recognize hand gestures and motions which allows the control of robotic machines and prostheses to perform dexterous tasks. Numerous methods aimed to enhance hand gesture and motion recognition toward an HMI. Bio-impedance analysis (BIA) is a noninvasive way of assessing body compositions and has been recently used for hand motion interpretation using `brute force? pattern recognition. The impedance variation in the body mostly depends on the precise stimulation using appropriate electrical features of the associated tissue layers. It has been reported that the electrical properties of these layers varied significantly. Thus, it is essential to investigate the influence of these variations on the stimulator design for the hand motion interpretation. This may not be possible using experimental approaches. Alternatively, using highly advanced computational models, this can be readily investigated by attaining the available range of the electrical properties of each tissue layer and applying appropriate boundary conditions and simulation settings. The computational models are composed of a volume conductor of the human arm model and electrode settings. Also, two different computational study methods were used to determine the influence of the tissues? dielectric properties on the results. The quasistatic approximation was used by only considering the resistivity of the anatomical layers and the transient simulation was used to analyze the capacitive impact on the results. Finite element (FE) models were developed to simulate the potential distribution inside the skin, muscle, and bone layers of the upper arm for given electrode settings. Then, simulation results were recorded for various electrical properties and different study types. It was shown that the capacitive influence of the tissue may not be ignored for certain conditions due to significant variation in the induced electrical potential variation along with the target muscle. Also, the influence of the individual tissue?s electrical properties was investigated using a set of dielectric parameters. The results showed that the skin and muscle layers have a significant impact on the electrical potential variation across the muscle length.

Analysis of Electromagnetic Effects on Vibration of Functionally Graded GPLs Reinforced Piezoelectromagnetic Plates on an Elastic Substrate

A new nanocomposite piezoelectromagnetic plate model is developed for studying free vibration based on a refined shear deformation theory (RDPT). The present model is composed of piezoelectromagnetic material reinforced with functionally graded graphene platelets (FG-GPLs). The nanocomposite panel rests on Winkler–Pasternak foundation and is subjected to external electric and magnetic potentials. It is assumed that the electric and magnetic properties of the GPLs are proportional to those of the electromagnetic materials. The effective material properties of the plate are estimated based on the modified Halpin–Tsai model. A refined graded rule is introduced to govern the variation in the volume fraction of graphene through the thickness of the plate. The basic partial differential equations are provided based on Hamilton’s principle and then solved analytically to obtain the eigenfrequency for different boundary conditions. To check the accuracy of the present formulations, the depicted results are compared with the published ones. Moreover, impacts of the variation in elastic foundation stiffness, plate geometry, electric potential, magnetic potential, boundary conditions and GPLs weight fraction on the vibration of the smart plate are detailed and discussed.

Enhancement of wastewater treatment under low temperature using novel electrochemical active biofilms constructed wetland

A novel electrochemical active biofilms constructed wetland (NEAB-CW) was built to enhance the treatment efficiency for domestic sewage under low temperature environment (0–15 °C). In NEAB-CW, the traditional matrixes were replaced with conductive layer, in which laid stainless steel mesh tubes (SSMT) and added slow-release oxygen matrixes (SROM) and zero-valent iron rod (IR) were used to build a bioelectrochemical activity biofilms system. According to the results of 180 d experiment, the removal efficiencies of COD, NH4+-N and TP of NEAB-CW were 1.52 and 2.21, 2.97 and 1.68, 3.95 and 1.76 times higher than the CW without SROM and IR at 10–20 and 0–10 °C, respectively. The transverse and longitudinal electric potential (EP) variations in NEAB-CW improved microbial activities under low temperature by enhancing the electron transfer efficiency, resulting in higher and stable EP and electron currents density, as well as protein-like contents secreted from biofilms. The pollutant-degrading microorganisms (e.g., Clostridia, Simplicispira), low temperature-resistant microorganisms (e.g., Psychrobacter, Acinetobacter), and electrochemical active microorganisms (e.g., Negativicutes, Gammaproteobacteria) obviously accumulated in NEAB-CW under low temperature environment to generate electricity and degrade pollutants. The results provided a good choice to treat domestic sewage at 0–15 °C by using NEAB-CW.

ELECTROMAGNETIC RESPONSE OF LAYERED MAGNETO-ELECTRO-ELASTIC THIN RECTANGULAR PLATE UNDER MODERATELY LARGE DEFLECTION

The analytical solution of a layered thin magneto-electro-elastic rectangular plate is presented. The governing equation is based on classical laminate plate theory and von Karman's stress function; capturing the effects of moderately large deflection. Electromagnetic fields are determined in terms of mechanical unknowns by solving Maxwell's equations of electrostatics and magnetostatics. The condensation of electric and magnetic state into plate kinematics, coupled with stress function definition, derives the governing non-linear partial differential equation of motion. Solution for both simply supported and clamped transverse boundary condition is obtained using Galerkin method, which reduces the system into an ordinary differential equation of cubic and quadratic nonlinearity. Numerical results of laminated plate with constituent piezoelectric barium titanite and piezomagnetic cobalt ferrite is produced utilizing electromagnetic boundary and continuity conditions. The effect of transverse elastic boundary condition on through the thickness variation of electric and magnetic potential under linear and moderately large deflection is produced.

Uncertainty quantification and sensitivity analysis of transcranial electric stimulation for 9-subdomain human head model

This paper deals with uncertainty quantification of transcranial electric stimulation (TES) of realistic human head model. The head model taken from Visible Human Project consists of 9 subdomains: scalp, skull, CSF, grey matter, white matter, cerebellum, ventricles, jaw and tongue. The deterministic computation of quasi-static induced electric scalar potential features boundary element method (BEM). Conductivities of each subdomain are modelled as uniformly distributed random variables and stochastic analysis features a non-intrusive stochastic collocation method (SCM). The input uncertainties impact only the magnitude of the electric scalar potential and not the position of the potential extrema. Skin and brain conductivities play the most important role, while CSF conductivity has negligible impact on the output potential variance. The significance of the skull conductivity is not high for the chosen input parameter setup. In the previous work authors considered 3-compartment head model which consisted of scalp, skull and brain compartments. The presented model is a step forward in SCM+BEM TES analysis, primarily in terms of model complexity. Comparing the results of the two analyses it can be concluded that the uncertainty in the added tissues’ conductivities do not impact the variation of the output electric potential.

Assessment of the temporal variation of electrical potential and pH of different bleaching agents

IntroductionTooth whitening procedures are under continuous investigation to improve esthetic outcomes and reduce bleaching sensitivity (BS) precipitating from treatments. During the dental bleaching process it is known that the release of free radicals degrades the organic pigment molecules of the tooth and with this an amount of energy is released. Nonetheless, previous studies have never investigated the temporal correlation between of pH and electric potential (EP) generated in this treatment. ObjectivesTherefore, the objective of the present study was to investigate temporal variations of pH and EP associated with three different commercially available bleaching gels and the correlation levels between parameters of interest to provide relevant information regarding the kinetics of oxidation reactions in dental bleaching procedures. MethodsThe study was divided into 3 groups (n = 9) in function of hydrogen peroxide concentration (either 6%, 15% and 35%). The temporal evolution of pH and EP values were determined using a highly-accurate and previously calibrated pH meter at specific time-points (5, 10, 15 and 30 min). ResultsData obtained were submitted to one-way ANOVA of repeated measures with Bonferroni post-test (α = 0.05). The results of the study showed difference in the factor gel concentration (p < 0,0001), time (p < 0,0001) and interaction (gel/time) (p = 0.002) while throughout the intervals evaluated the groups remained relatively stable and without significant difference in the intragroup variation of pH (p < 0.05) and in EDP only with significant difference in the 5 min interval of the 35% concentration. A 2nd order polynomial relationship test showed high correlation levels. ConclusionIt can thus be concluded that there is a negative relationship between EP and pH variation in the different gel concentrations. Clinical significanceThe findings of the present study suggest that bleaching gels of higher concentration may provoke BS that are more intense and durable due to significant electric depolarization of neuronal extensions of pulpal tissues.

Electrical and magnetic data time series’ observations as an approach to identify the seismic activity of non-anthropic origin

In this work, the authors tried to identify a possible relationship between electromagnetic signals (EM) and seismic events in the lithospheric system in the central region of Colombia. The data, both seismic records and electromagnetic signals, were taken from the catalog of the Seismological Network of the National University of Colombia (RSUNAL) and the catalog of the National Seismological Network of Colombia (RSNC). The project included the design and instrument testing phases for recording seismic signals, electrical potential variations, and magnetic field variations to try to identify possible relationships between these signals. Possible electromagnetic precursors for seismic events were observed, mainly magnetic disturbances, but it was not possible to locate evident electrical anomalies (Seismic Electric Signals - SES). Thus, although the results are not conclusive, the magnetic disturbances identified deserve further long-term analysis.