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Optical trapping is an effective tool for manipulating micrometer-sized particles, although its application to nanometer-sized particles remains difficult. The field of optical trapping has advanced significantly, incorporating more advanced techniques such as plasmonic structures. However, single-molecule trapping remains a challenge. To achieve a deeper understanding of optical forces acting on molecular systems, a first-principles approach to analyze the optical force on molecules interacting with a plasmonic field is crucial. In our study, the optical force and torque induced by the near-field excitation of C3H6 were investigated using real-time time-dependent density functional theory calculations on real-space grids. The near field from the scanning tunneling probe was adopted as the excitation source for the molecule. The optical force was calculated using the polarization charges induced in the molecule based on Lorentz force. While the optical force and torque calculated as functions of the light energy were in moderate agreement with the oscillator strengths obtained from the far-field excitation of C3H6, a closer correspondence was achieved with the power spectrum of the induced dipole moment using near-field excitation. Time-domain analysis of the optical force suggests that the simultaneous excitation of multiple excited states generally weakens the force because of mismatches between the directions of the induced polarization and the electric field. This study revealed a subtle damping mechanism for the optical force arising from intrinsic electronic states and the influence of beating. [ABSTRACT FROM AUTHOR]

Interaction between a fixed point electric charge Q and a freely rotating point electric dipole with the magnitude P pinned near a plane interface between two dispersionless insulators with different dielectric permittivities ɛ1 and ɛ2 has been considered. It was shown that, as a result of this interaction and the interaction of the dipole with the polarization charges induced at the interface by the charge Q and the dipole itself, there arise regions where the dipole can possess either one or two equilibrium orientations. The spatial distributions of the electrostatic dipole energy Wtotal under the combined action of the charge Q and the induced interface polarization charges, as well as the equilibrium dipole orientations (orientation maps), the boundaries between the regions with different numbers of dipole orientations, and their evolution with the variation of problem parameters (the charge and dipole magnitudes, the mismatch between ɛ1 and ɛ2, and the charge–interface distance) were calculated. It was shown that there can emerge local minima of Wtotal, which may play the role of traps for dipoles (in particular, excitons in layered structures), and the corresponding requirements for the problem parameters were found. Most results were obtained in analytical form. The model can be applied to various physical systems, for instance, polar molecules, excitons, and trions in layered structures. [ABSTRACT FROM AUTHOR]

BACKGROUND: Root systems are key contributors to plant health, resilience, and, ultimately, yield of agricultural crops. To optimize plant performance, phenotyping trials are conducted to breed plants with diverse root traits. However, traditional analysis methods are often labour-intensive and invasive to the root system, therefore limiting high-throughput phenotyping. Spectral electrical impedance tomography (sEIT) could help as a non-invasive and cost-efficient alternative to optical root analysis, potentially providing 2D or 3D spatio-temporal information on root development and activity. Although impedance measurements have been shown to be sensitive to root biomass, nutrient status, and diurnal activity, only few attempts have been made to employ tomographic algorithms to recover spatially resolved information on root systems. In this study, we aim to establish relationships between tomographic electrical polarization signatures and root traits of different fine root systems (maize, pinto bean, black bean, and soy bean) under hydroponic conditions. RESULTS: Our results show that, with the use of an optimized data acquisition scheme, sEIT is capable of providing spatially resolved information on root biomass and root surface area for all investigated root systems. We found strong correlations between the total polarization strength and the root biomass ( R 2 = 0.82 ) and root surface area ( R 2 = 0.8 ). Our findings suggest that the captured polarization signature is dominated by cell-scale polarization processes. Additionally, we demonstrate that the resolution characteristics of the measurement scheme can have a significant impact on the tomographic reconstruction of root traits. CONCLUSION: Our findings showcase that sEIT is a promising tool for the tomographic reconstruction of root traits in high-throughput root phenotyping trials and should be evaluated as a substitute for traditional, often time-consuming, root characterization methods.

The past decades have witnessed the increased applications of induced polarization (IP) method in the critical zone studies with ubiquitous clay minerals. Although IP outperforms traditional electrical and electromagnetic methods through its unique ability to measure quadrature conductivity, the nonlinearity that quadrature conductivity behaves with salinities and frequencies greatly tortures IP practitioners, as (a) salinity-dependency makes the quadrature conductivity a varyingly unstable parameter to quantitatively estimate hydraulic properties and clay content; (b) frequency-dependent Cole-Cole and Debye/Warburg decomposition models, although mathematically sound, physically mingle the properties of pore water and clay minerals and are empirical in nature. From basic principles, we demonstrate that quadrature conductivity remains a hybrid property involving both clay and water, and develop relevant models to distinguish them. Our models are validated by theories, experiments, simulations, and comparisons, all of which proclaim considerable advantages over previous models and offer the prospect of quantitative applications.

[Display omitted] Symmetry breaking in an electric field-driven active particle system can be induced by applying a spatially uniform, but temporally non-uniform, alternating current (AC) signal. Regardless of the type of particles exposed to sawtooth AC signals, the unevenly induced polarization of the ionic charge layer leads to a major electrohydrodynamic effect of active propulsion, termed Asymmetric Field Electrophoresis (AFEP). Suspensions containing latex microspheres of three sizes, as well as Janus and metal-coated particles were subjected to sawtooth AC signals of varying voltages, frequencies, and time asymmetries. Particle tracking via microscopy was used to analyze their motility as a function of the key parameters. The particles exhibit field-colinear active propulsion, and the temporal reversal of the AC signal results in a reversal of their direction of motion. The experimental velocity data as a function of field strength, frequency, and signal asymmetry are supported by models of asymmetric ionic concentration-polarization. The direction of particle migration exhibits a size-dependent crossover in the low frequency domain. This enables new approaches for simple and efficient on-chip sorting. Combining AFEP with other AC motility mechanisms, such as induced-charge electrophoresis, allows multiaxial control of particle motion and could enable development of novel AC field-driven active microsystems. [ABSTRACT FROM AUTHOR]

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To explain induced polarization, membrane polarization is often referred to as a relevant process taking place in granular media – particularly, when narrow pore throats are present. This polarization effect is based on the membrane-like behaviour of pore throats caused by the presence of an usually negative charge on the pore surface, that influences charge transport in the pore fluid. Existing analytical, 1D models describe the pore system as a series of cylindrical pores with different radii and lengths. The polarization response is calculated by solving the Poisson–Nernst–Planck system for the current densities of one single anion and one single cation species representing the charge transport in the electrolyte and the diffuse layer at the pore surface. To include charge transport in the Stern layer, cations in the Stern layer have so far simply been considered by increasing the concentration of the diffuse layer cations. As we know from numerical modelling, this approach fails to predict the polarization response when the Stern layer is significantly charged. Here, we present a new semi-analytical model that treats the Stern-layer cations as a separate ion species and allows the Stern layer to polarize individually. To validate our new model, we compare it to the previously used analytical model and numerical simulations for different relative charges in Stern- and diffuse layer. We also use electrostatic surface-complexation models for two mineral surfaces (quartz and montmorillonite) to simulate the response of real geologic material under varying chemical conditions. This work is a step forward for considering realistic pore properties in induced-polarization modelling. [ABSTRACT FROM AUTHOR]

Thailand’s fossil forests hold international importance for a variety of reasons. The operation of a gravel mine exposed sediment layers containing petrified wood logs, highlighting the critical need to preserve these unique artifacts and address associated environmental concerns. A comprehensive lithological study was conducted on pit walls. Employing 2D ERT and 2D IP methods, geology was classified from the ground surface and validated through drilling logs. The sediment and deposit categorization at gravel pit sites revealed four distinct units: Unit I, conglomeratic sand, exhibiting characteristics typical of fluvial deposits; Unit II, indicating alluvial fan deposition with lenticular gravel and sand highlighting the presence of petrified wood logs; Unit III, massive gravel suggesting channel deposits of an alluvial fan with an abundance of petrified wood; and Unit IV, red soil (collapsible soil). The 2D ERT method successfully examined the boundary sediment layer and mudstone, though classification of sediment units was not achieved. Quaternary terrace sediments underlie the mudstone, identified as an aquitard that effectively prevents surface contamination of the groundwater aquifer. The data from this study serves as fundamental geological information, providing remarkable and essential evidence for the preservation of petrified wood and the safeguarding of the groundwater environment. This site is particularly an outstanding geosite. This research contributes to our understanding of depositional environments and geological processes and proposes conservation strategies. [ABSTRACT FROM AUTHOR]

Advancing catalyst design is pivotal for the enhancement of photocatalytic processes in renewable energy conversion. The incorporation of structural chirality into conventional inorganic solar hydrogen nanocatalysts promises a significant transformation in catalysis, a feature absent in this field. Here we unveil the unexplored potential of geometric chirality by creating a chiral composite that integrates geometric chiral Au nanoparticles (NPs) with two‐dimensional C3N4 nanosheets, significantly boosting photocatalytic H2 evolution beyond the achiral counterparts. The superior performance is driven by the geometric chirality of Au NPs, which facilitates efficient charge carrier separation through the favorable C3N4‐chiral Au NP interface and chiral induced spin polarization, and exploits high‐activity facets within the concave surfaces of chiral Au NPs. The resulting synergistic effect leads to a remarkable increase in photocatalytic H2 evolution, with an apparent quantum yield of 44.64 % at 400 nm. Furthermore, we explore the selective polarized photo‐induced carrier separation behavior, revealing a distinct chiral‐dependent photocatalytic HER performance. Our work advances the design and utilization of chiral inorganic nanostructures for superior performance in energy conversion processes. [ABSTRACT FROM AUTHOR]

Many industrially relevant microfluidic applications use concentrated solutions of macro-molecular solutes dissolved in polar solvents like water, which are typically deployed at high voltages. In this study, we investigate the effect of finite ionic sizes and solvent polarization on induced charge electro-osmotic flow around a perfectly polarizable cylinder, at high electric field strengths and ionic concentrations. The flow is actuated by means of a direct current electric field, and the step response of various flow parameters are studied numerically. Finite ionic sizes, defined through a steric factor ν , are modeled using the modified Poisson–Nernst–Planck model. Additionally, a field-dependent permittivity, characterized by a solvent polarization number A, accounts for molecular re-orientation effects. Our findings reveal an ion-size modulated decrement in charge concentration in the electrical double layer and an augmentation in the electric field. Remarkably, the resulting flow velocities increase with ion size. Solvent polarization, on the other hand, results in a marked reduction in flow velocities. Steric effects, however, dominate over a large range of parameter space (applied voltage and bulk ionic concentration) as compared to solvent polarization. Finally, we demonstrate that unequal ionic sizes result in flow asymmetries at the steady-state, thereby generating net electro-phoretic motion of suspended particles. [ABSTRACT FROM AUTHOR]

For the analysis of spectral induced polarization (SIP) measurements and for the description of frequency-dependent electrical relaxation responses, so-called Cole–Cole models (CCMs) are widely used. Typically, CCM formulations in terms of complex electrical conductivity or complex electrical resistivity are used in geophysical applications. The differences between these model descriptions, in particular between the respective time constants, and their conversion have been studied. A third variant of the model is formulated in terms of complex permittivity, commonly used in materials science. In general, all these model formulations can be used equivalently for fitting SIP data, which, however, results in differing values for some of the model parameters. For a meaningful comparison of CCM parameters of different samples or measurements, it is necessary that they are based on the same model formulation. In this work, the relationships between the Debye model (DM) and CCM parameters in the formulation for complex permittivity and complex conductivity are studied. A direct analytical conversion is possible for generalized DM formulations, both in single- and multi-term model formulations, resulting in relationships between the respective relaxation time distributions (RTDs). Such a direct conversion for CCM formulations is not possible. We however derived an approximate relationship between |$\log$| -normal RTD and CCM formulations and respective permittivity and conductivity parameter values. Our study also highlights the significance of using consistent model formulations when experimental data are compared in terms of DM or CCM parameters, as parameters used to predict ice temperature are incorrect if the conductivity time constant is used to predict the temperature from interpolation of a permittivity time constant-temperature relationship. [ABSTRACT FROM AUTHOR]

The dam of Lampy (Black Mountain, Aude, France) is considered as one of the oldest dams in France. A geophysical survey is performed to better understand the pattern of groundwater flow downstream of this dam in the granitic substratum. Induced polarization is first used to image both electrical conductivity and normalized chargeability. Eight core samples of granite from this site are measured and analysed in the laboratory. Their electrical conductivity and normalized chargeability are expressed as a function of the porosity and cation exchange capacity (CEC). The field data and the petrophysical results are used to image the water content, the CEC and the permeability distribution of the substratum. Then, self-potential is used as a complementary passive geophysical technique, which, in absence of metallic bodies, is directly sensitive to groundwater flow through the so-called streaming potential effect. Indeed, the excess of electrical charges in the vicinity of the solid grains, in the so-called double layer, is dragged by the ground water flow generating in turn an electrical (streaming) current and therefore an electrical field. A map of the resulting self-potential signals is done over the area covered by the induced polarization profiles. This map shows a large positive anomaly with an amplitude of ∼80 mV possibly associated with upwelling groundwater in an area where the soil is water-saturated. A groundwater flow simulation is performed to model this anomaly. This is done in two steps. A preliminary groundwater flow model is built using the permeability and water content distributions obtained from the induced polarization data. Then, this groundwater flow model is updated using the information contained in the self-potential data including the electrical conductivity distribution obtained through resistivity tomography. The algorithm for the inversion of the self-potential data is validated through a 2-D numerical test. This analysis yields a groundwater flow model with the flow being focused through a high permeability zone. This study shows how three geoelectrical methods (self-potential, induced polarization and electrical resistivity) can be efficiently combined to image groundwater flow in the vicinity of a dam. [ABSTRACT FROM AUTHOR]

The present research investigates the outcomes of inverting time domain induced polarization (TDIP) data, emphasizing the influence of parameters governing the IP response curve. In the subsurface, a resistive network follows relaxation patterns governed by the Cole-Cole model, where parameters like resistivity (ρ), chargeability (m), relaxation time (τ), and frequency exponent (c) shape the IP decay curve. Our exploration commences with exercises in forward modeling to understand how each parameter individually impacts the IP phenomenon. Subsequently, we introduce a tailored 1D forward modeling code dedicated to time domain IP, followed by a non-linear inversion process using the heat bath algorithm. These modeling equations are inherently non-linear, with the Cole-Cole parameters acting as independent variables. Using MATLAB, we implemented and rigorously validated this code using synthetic data and real field data gathered from the Sundarbans delta in West Bengal's lower deltaic region. To delve deeper into subsurface dynamics, we created contour plots resembling pseudo sections for each Cole-Cole parameter, unveiling their subsurface variations. Notably, our results demonstrate a strong correlation with the geological features of the studied area. [ABSTRACT FROM AUTHOR]

The development of high‐temperature electromagnetic (EM) wave absorbing materials is an important direction for achieving radar stealth in high‐speed aircraft. In this study, HfC–SiCf composite ceramics with 3D reticular structure were synthesized in one‐step using the molten‐salt‐assisted carbon thermal reduction method. During the synthesis process, SiC grew in situ into a fibrous structure with a diameter of 500 nm and lengths ranging from 2 to 30 µm. By adjusting the molar ratio of HfC to SiC, the HfC‐30 mol% SiC (HS30) exhibited the best EM absorption performance at room temperature, with a minimum reflection loss (RLmin) of −31.4 dB at 16.1 GHz and an effective absorption bandwidth (EAB) of 4.6 GHz. The excellent absorption performance was attributed to the 3D reticular structure composed of SiC fibers, HfC bulk, and HfC nanoparticles, which significantly increased the number of pores and heterogeneous interfaces in the material. These microinterfaces induced interface polarization effects, thereby effectively enhancing the EM absorption. As the temperature increased, the EM absorption performance declined. At 900°C, the HS30 sample exhibited an EAB of 1.18 GHz from 12.4 to 13.58 GHz and an RLmin of −$ - $22.6 dB at 13.0 GHz. This research provides references for understanding the effects of material composition and structure on EM absorption performance. [ABSTRACT FROM AUTHOR]

Designing composite gate dielectrics tailored by incorporating inorganic perovskite nanofillers into a polymer matrix to develop flexible low‐voltage transistors can be challenging because homogeneous dispersion of nanomaterials in the matrix is difficult to achieve; thus, degradation of the electrically insulating properties of nanocomposite layers is often observed. In this study, nanocomposite dielectrics are presented that consist of 2D Ba5Ta4O15 nanosheets (BTO NSs) for the first time. Perovskite BTO is introduced using the Langmuir–Blodgett method to construct a precise and pinhole‐free interface for the homogeneous assembly of 2D nanosheets. Its high k value and ferroelectric properties, which arise from the perovskite structure, can be harnessed to achieve attractive polarization and remarkable electronic properties. The 2D BTO NSs can also be utilized as phase crystallization fillers to enhance the ferroelectric properties of polyvinylidene fluoride (PVDF). Additionally, the multilayer PVDF/perovskite nanosheet hybrid dielectric, which reaches an unprecedentedly high dielectric constant of 22.4, exhibits effective dielectric relaxation related to the interfacial induced ferroelectric polarization and decisive negative‐capacitance response. [ABSTRACT FROM AUTHOR]

To enhance the 3D numerical simulation of the induced polarization method within anisotropic media, our study employs the 2D Fourier transform technique. This technique is utilized to convert the 3D integral of the abnormal potential from the space domain into a 1D integral in the wave number domain. Subsequently, we apply the shape function integration method, which is founded on quadratic interpolation, to resolve the 1D integral equation effectively. This methodology significantly decreases the necessary computational resources and storage while simultaneously harnessing the high efficiency and accuracy of the 1D shape function integration method, as well as the high efficiency of the fast Fourier transform, optimizing the numerical simulation process of the induced polarization method. We validate the accuracy of our algorithmic approach using an equivalent uniform layered model. Furthermore, by employing the sphere model, we conduct a comparison of computation time with the finite element method, thereby demonstrating high efficiency of the proposed algorithm. Utilizing the OpenMP parallel algorithm, we confirm that the proposed algorithm has a high degree of parallelism. We also analyse the differences in the equivalent apparent resistivity and apparent polarizability for various electrical parameters, using a prismatic model as the basis for our analysis. Our results clearly indicate that the anisotropy of the polarizability exerts substantial influence on the observe data. Consequently, the implications of polarizability anisotropy are deemed critical and not be disregarded in the field detection applications. [ABSTRACT FROM AUTHOR]

Recent advances in understanding the induced polarization (IP) method have led to improvements in interpreting hydraulic properties from electrical measurements. Distinguishing the effect of surface conduction from conduction through the electrolyte filling the interconnected pore spaces has been an ongoing challenge in interpreting field-scale electrical resistivity data sets. Previously proposed mechanistic models have suggested that this limitation can be overcome by utilizing the coefficient that describes the ratio between IP measurements and surface conductivity. In this study, we examine this proportionality coefficient (ℓ) through the relationship between IP parameters (imaginary conductivity and normalized chargeability) and surface conductivity for a sample group of 98 sedimentary rocks, composed of sandstones, carbonates and mudstones. A strong linear relationship is observed between the IP parameters and surface conductivity. However, values of ℓ vary significantly across each sample group such that low-salinity estimates of formation factor (F) using the single universal estimate of ℓ are poor. Estimates of F for a single rock type (sandstone, carbonate or mudstone) are improved using ℓ values unique to that rock type, although F estimates for mudstones show high sensitivity to changes in ℓ. Using ℓ coefficients calibrated on a sample group with similar lithological properties to the investigated group moderately improves the estimation of F. Consistent with theory, no relationship is observed between the proportionality coefficient and the measured petrophysical parameters of the porous medium. Our results suggest that, although IP measurements provide a valuable field-scale proxy for surface conductivity, improving petrophysical predictions (i.e. in this case, estimating F) remains a challenge. [ABSTRACT FROM AUTHOR]

In this work, we introduce the probabilistic inversion of tomographic complex resistivity (CR) measurements using the Hamiltonian Monte Carlo (HMC) method. The posterior model distribution on which our approach operates accounts for the underlying complex-valued nature of the CR imaging problem accurately by including the individual errors of the measured impedance magnitude and phase, allowing for the application of independent regularization on the inferred subsurface conductivity magnitude and phase, and incorporating the effects of cross-sensitivities. As the tomographic CR inverse problem is nonlinear, of high dimension and features strong correlations between model parameters, efficiently sampling from the posterior model distribution is challenging. To meet this challenge we use HMC, a Markov-chain Monte Carlo method that incorporates gradient information to achieve efficient model updates. To maximize the benefit of a given number of forward calculations, we use the No-U-Turn sampler (NUTS) as a variant of HMC. We demonstrate the probabilistic inversion approach on a synthetic CR tomography measurement. The NUTS succeeds in creating a sample of the posterior model distribution that provides us with the ability to analyse correlations between model parameters and to calculate statistical estimators of interest, such as the mean model and the covariance matrix. Our results provide a strong basis for the characterization of the posterior model distribution and uncertainty quantification in the context of the tomographic CR inverse problem. [ABSTRACT FROM AUTHOR]

Abstract Background Root systems are key contributors to plant health, resilience, and, ultimately, yield of agricultural crops. To optimize plant performance, phenotyping trials are conducted to breed plants with diverse root traits. However, traditional analysis methods are often labour-intensive and invasive to the root system, therefore limiting high-throughput phenotyping. Spectral electrical impedance tomography (sEIT) could help as a non-invasive and cost-efficient alternative to optical root analysis, potentially providing 2D or 3D spatio-temporal information on root development and activity. Although impedance measurements have been shown to be sensitive to root biomass, nutrient status, and diurnal activity, only few attempts have been made to employ tomographic algorithms to recover spatially resolved information on root systems. In this study, we aim to establish relationships between tomographic electrical polarization signatures and root traits of different fine root systems (maize, pinto bean, black bean, and soy bean) under hydroponic conditions. Results Our results show that, with the use of an optimized data acquisition scheme, sEIT is capable of providing spatially resolved information on root biomass and root surface area for all investigated root systems. We found strong correlations between the total polarization strength and the root biomass ( $$R^2 = 0.82$$ R 2 = 0.82 ) and root surface area ( $$R^2 = 0.8$$ R 2 = 0.8 ). Our findings suggest that the captured polarization signature is dominated by cell-scale polarization processes. Additionally, we demonstrate that the resolution characteristics of the measurement scheme can have a significant impact on the tomographic reconstruction of root traits. Conclusion Our findings showcase that sEIT is a promising tool for the tomographic reconstruction of root traits in high-throughput root phenotyping trials and should be evaluated as a substitute for traditional, often time-consuming, root characterization methods.

We performed a field induced polarization survey at Rocher du Chateau in the French Alps. This site is characterized by the presence of ophiolites with an outcrop of serpentinites. Serpentinite is characterized by high resistivity (∼0.5–10 kΩ m) and high chargeability (∼20–400 mV V−1) values. We collected two serpentinite core samples for spectral induced polarization measurements conducted in the frequency range 10 mHz–45 kHz, validating the field results. The high chargeability of serpentinite is associated with the production of magnetite during the fluid‐rock alteration, as indicated by the high magnetic susceptibility of the core samples (0.0340 SI). Using the laboratory measurements and the K‐means clustering technique, we successfully imaged the serpentinite facies and we were able to distinguish blocks of serpentinites embedded in the sedimentary cover. This approach could possibly be used for the seafloor exploration using induced polarization. Plain Language Summary: Induced polarization is a non‐invasive geophysical method known to be sensitive to the presence of semi‐conductors. Serpentinite is formed through the alteration of peridotites, resulting in the formation of magnetite, which, in addition to its magnetic properties, is responsible for a strong chargeability. The presence of an ophiolite in the French Alps provides an exceptional opportunity to study on‐shore the induced polarization response of peridotites, and especially serpentinite. The results obtained in this paper may prove to be useful for the exploration of the oceanic seafloors by documenting the properties of such materials. Key Points: The chargeability of serpentinite is high because of the presence of magnetiteTime‐domain induced polarization tomography images serpentinite in the fieldLaboratory experiments and a clustering technique help to discriminate serpentinite [ABSTRACT FROM AUTHOR]

Herein, a novel enhancement-mode (E-mode) GaN-based p-channel FETs (p-FETs) with a linearly graded AlGaN (LGA) p-channel is proposed and numerically studied by Silvaco TCAD. Thanks to strong polarization-induced doping, three-dimensional hole gas (3DHG) can be uniformly generated in LGA to form a continuous p-channel with a hole concentration over 1018 cm–3. Combined with an optimized recessed gate structure, the LGA p-FET can simultaneously achieve a large threshold voltage (| V TH|) > 2 V and a high current density (| J DS|) of ∼10 mA mm−1 at V DS = −10 V. Additionally, two critical parameters of the LGA p-FETs, i.e. the depth of recessed gate and initial Al composition of LGA, are specifically studied to reveal the unique carrier behavior of 3DHG in the devices. Importantly, the LGA structure is further optimized and implemented as the p-type cap layer to construct an E-mode GaN n-FET. Thereby, based on the same LGA configuration, a GaN-based inverter with the matched complementary n- and p-FETs is monolithically constructed, showing sharp voltage transition. The reported novel LGA structure and its availability in both GaN-based E-mode n- and p-FETs provides valuable insights and guidance to construct highly efficient GaN p-type devices and All-GaN-based integrated circuits for compact power electronic systems. [ABSTRACT FROM AUTHOR]

Adding dopants to the structure and coupling cocatalysts on the surface are traditional strategies to inhibit carrier recombination and high catalytic barriers for enhancing the performance of water splitting of the BiVO4 photoanode. An inexpensive post-treatment method was developed herein via modifying the BiVO4 (BVO) photoanode with KBr solution. Unlike the traditional strategies, this approach effectively overcomes carrier recombination on the BVO photoanode surface. The Br–BiVO4 (Br–BVO) photoanode was optimized and exhibited a remarkable cathodic shift (350 mV) of the onset potential, as well as an excellent photocurrent density, which was increased to 256% of the pure BVO photoanode. The Faraday efficiencies of oxygen evolution and hydrogen evolution (FEO2, FEH2) were 98.4% and 96.7%, respectively. The photoelectrochemical (PEC) characterization revealed that the adsorption of Br− on the BVO photoanode induced surface polarization and can rapidly trap holes and prolong carriers' lifetimes, facilitating the participation of most holes in the oxygen evolution reaction (OER). Adsorption of Br− also decreased the overpotential of the OER on the BVO photoanode, consequently enhancing reaction kinetics. This study presents a straightforward and feasible approach to enhance the PEC performance of the BiVO4-based photoanode. [ABSTRACT FROM AUTHOR]

The dielectric response of M-hexaferrite nanoceramics is complex since it is determined by crystal structure and microstructure. We studied the dielectric behavior of Nd3+ modified Sr2 + Fe12O19 nanoceramics with ferric ions, responsible for magnetic properties, substituted by Sc3+ and Al3+. To compare the effect of different ionic radii we discussed the dielectric response of Sr0.95Nd0.05Fe12-xScxO19 and Sr0.95Nd0.05Fe12-xAlxO19 at the doping level of x = 1.08. The dielectric response was found to consist of four contributions: (i) Low-temperature dispersion of dielectric polarization created by doping-induced spin-canting. The polarization, described by the inverse Dzyaloshinskii-Moriya model, is in nanoceramics limited by the shape and size of the crystallites. (ii) Changes in relaxation modes of polar vacancies due to interaction with electric dipole moments modified by deformation of oxygen octahedra. (iii) Dielectric dispersion in room temperature range related to space charge relaxation in grain boundaries. (iv) High-temperature electric conductivity of the grain interiors. [ABSTRACT FROM AUTHOR]

The borehole induced polarization method has been widely used in deep mineral exploration, oil and gas resource exploration, and water resource exploration because of its high efficiency and good exploration effect. At present, the related research on the cross-well induced polarization method assumes that the underground medium is isotropic, but the electrical characteristics of the actual earth medium are anisotropic. To analyze the influence of the anisotropic characteristics on the cross-well induced polarization method, in this paper, the anisotropic forward algorithm of conductivity and polarizability in different principal axis directions based on the finite element method is studied. A three-dimensional forward simulation of the cross-well induced polarization method in anisotropic media is realized. The effectiveness and correctness of the algorithm are verified by testing and comparing complex 3-D isotropic and anisotropic models. Anisotropic geological models of the horizontal plate and inclined plate are constructed to analyze the anisotropic influences of conductivity and polarizability in different principal axis directions on the cross-well induced polarization response. The results show that the emitter sources with different depths in the well have different influences on the electrical response of the plates. Anisotropic conductivity and polarizability in horizontal plates exhibit most pronounced characteristics in the x-direction, significantly influencing the apparent polarizability curves. However, when the resistivity and polarizability are both anisotropic, the change in the z-direction is the most complicated. When the plate is inclined, the amplitude of the electrical response curve decreases to a certain extent, and the position where the amplitude appears shifts to different degrees. Notably, the response curves of the y-direction anisotropy are basically consistent with the response curves of the isotropy, regardless of the anisotropy of the conductivity and polarizability or anomalous body tilts. The results of this study improve our understanding of the influence of anisotropy on cross-well induced polarization and provide theoretical support for the interpretation of cross-well induced polarization data considering anisotropy. [ABSTRACT FROM AUTHOR]

Highlights: Oxygen-vacancy-rich SiC@MoO3 nanocomposite with strong reflection loss (− 50.49 dB at 1.27 mm thickness) and broadband absorption band (8.72 GHz at 2.68 mm thickness) were constructed via in situ etching strategy. The presence of oxygen vacancy leads to an increased conductive loss and defect-induced dipole polarization, which plays significant role in attenuating the incident electromagnetic wave. Defect engineering in transition metal oxides semiconductors (TMOs) is attracting considerable interest due to its potential to enhance conductivity by intentionally introducing defects that modulate the electronic structures of the materials. However, achieving a comprehensive understanding of the relationship between micro-structures and electromagnetic wave absorption capabilities remains elusive, posing a substantial challenge to the advancement of TMOs absorbers. The current research describes a process for the deposition of a MoO3 layer onto SiC nanowires, achieved via electro-deposition followed by high-temperature calcination. Subsequently, intentional creation of oxygen vacancies within the MoO3 layer was carried out, facilitating the precise adjustment of electromagnetic properties to enhance the microwave absorption performance of the material. Remarkably, the SiC@MO-t4 sample exhibited an excellent minimum reflection loss of − 50.49 dB at a matching thickness of 1.27 mm. Furthermore, the SiC@MO-t6 sample exhibited an effective absorption bandwidth of 8.72 GHz with a thickness of 2.81 mm, comprehensively covering the entire Ku band. These results not only highlight the pivotal role of defect engineering in the nuanced adjustment of electromagnetic properties but also provide valuable insight for the application of defect engineering methods in broadening the spectrum of electromagnetic wave absor ption effectiveness. SiC@MO-t samples with varying concentrations of oxygen vacancies were prepared through in-situ etching of the SiC@MoO3 nanocomposite. The presence of oxygen vacancies plays a crucial role in adjusting the band gap and local electron distribution, which in turn enhances conductivity loss and induced polarization loss capacity. This finding reveals a novel strategy for improving the absorption properties of electromagnetic waves through defect engineering. [ABSTRACT FROM AUTHOR]

Abstract—The paper discusses anomalies that are observed in the electric fields above hearth deposits. Hearths are important objects for archaeological studies and are traditionally detected by the positive anomaly in magnetic induction. However, magnetic measurements are not available on every archaeological site, and burning sites are not the only sources of positive magnetic anomalies. In the 1960s, it was established that the hearths can be detected using the induced polarization method (IP), but the technique has not been developed because of the imperfection of equipment at that time. Currently, multi-electrode multichannel electromagnetic prospecting systems allow prompt assessment of the distribution of electrical properties of the object and reconstructruction of its three-dimensional geoelectric structure. In this study, we examined geoelectric anomalies from a hearth, elucidated their nature, and evaluated the possibility of using electrical resistivity tomography (ERT) method to search for such objects. By the example of the fieldwork and laboratory experiments it is shown that hearths create intense anomaly of induced polarization and are distinguished by a very low electrical resistivities. It is established that the boundaries of the burning sites are clearly expressed in the maps of normalized chargeability. To study the nature of the observed geoelectrical anomalies, we carried out X-ray phase analysis and measurements of induced polarization, electrical resistivity, and magnetic susceptibility. The results have shown that the anomaly of low electrical resistivity and the polarizability anomaly are caused by the presence in hearth material of X-ray amorphous carbon in the form of soot, but not magnetite. Application of electrical resistivity tomography combind with induced polarization measurements is recommended in the search for fireplaces in archaeological prospecting. [ABSTRACT FROM AUTHOR]

The induced polarization (IP) method holds a strong potential to better characterize the critical zone of our planet especially in areas characterized by multi‐phase flow. Power‐law relationships between the bulk, surface, and quadrature conductivities versus the pore water saturation are potentially useable to map the subsurface water content distribution. However, the saturation exponents n and p in these power‐law relationships have been observed to vary with the texture of geomaterials and the wettabilities of pore fluids. Traditional experimental setups in the laboratory do not allow to independently visualize the pore fluid distribution. Therefore, the physical interpretations of the two saturation exponents have remained unclear. We developed a novel milli‐fluidic micromodel using clay‐coated glass beads that exhibit excellent visibility and high IP response. Through laboratory experiments, we simultaneously determined the micromodel complex conductivity and acquired the corresponding pore‐scale fluid distributions generated by drainage and imbibition through such class of porous materials. Finite‐element simulations of complex conductivity based on the upscaling of the complex surface conductance of grains were conducted to determine the saturation exponents under ideal pore fluid distributions. Results indicate that saturation exponents n and p vary depending on the ganglia size of the insulating fluids. The saturation exponents n and p exhibit power‐law relationships with the change rate of pore water connectivity with saturation, which is calculated through the computation of the derivative of Euler characteristics. These findings provide a new physical explanation to the relationships between the saturation exponents and the microscopic fluid distributions within the geomaterials. Plain Language Summary: Water saturation of porous bodies can be related to the complex conductivity through power‐law relationships. The existence of these power‐law relationships has been clearly documented in the literature. They are critical in the realm of hydrogeophysics to better characterize the critical zone of the solid Earth. However, the values of the saturation exponents in these power‐laws have been observed to vary with different material textures and no underlying mechanisms have been able to explain these variations to date. This lack of physical understanding could limit the applicability of the induced polarization method to characterize the critical zone especially when immiscible fluid phases are present. To tackle this, we developed a milli‐fluidic pore model that allows investigating the saturation exponents while monitoring the pore‐scale fluid distributions. Together with numerical simulations for ideal fluid distribution cases, we found a relationship between the saturation exponents and a microscopic pore parameter called "change rate of the pore water connectivity with saturation." These findings suggest that when estimating subsurface water saturation from electrical parameters, taking the pore fluid distribution into account can significantly improve the estimation accuracy, therefore enhancing the efficiency of geo‐electrical applications for a better characterization of hydrocarbon contaminated aquifers and oil reservoirs. Key Points: A micromodel setup allows for simultaneous pore fluid visualization and complex electrical conductivity measurementThe two saturation exponents for the in‐phase and quadrature conductivities are correlated with the ganglia size of the insulating phaseA power‐law‐type relationship between the saturation exponents and the change rate of water connectivity with saturation is demonstrated [ABSTRACT FROM AUTHOR]

SUMMARY: For accurate modelling of groundwater flow and transport processes within an aquifer, precise knowledge about hydraulic conductivity K and its small-scale heterogeneities is fundamental. Methods based on pumping tests, such as hydraulic tomography (HT), allow for retrieving reliable K-estimates, but are limited in their ability to image structural features with high resolution, since the data from time-consuming hydraulic tests are commonly sparse. In contrast, geophysical methods like induced polarization (IP) can potentially yield structural images of much higher resolution, but depend on empirical petrophysical laws that may introduce significant uncertainties to the K-estimation. Therefore, this paper presents a joint inversion procedure for both HT and IP data, which allows for combining the complementary abilities of both methods. Within this approach, a traveltime inversion is applied to the HT data, while the IP inversion is based on a full-decay time-domain forward response, as well as a reparametrization of the Cole–Cole model to invert for K directly. The joint inversion is tested on a synthetic model mimicking horizontally layered sediments, and the results are compared with the individual HT and IP inversions. It is shown that jointly inverting both data sets consistently improves the results by combining the complementary sensitivities of the two methods, and that the inversion is more robust against changes in the experimental setups. Furthermore, we illustrate how a joint inversion approach can correct biases within the petrophysical laws by including reliable K-information from hydraulic tests and still preserving the high-resolution structural information from IP. The different inversion results are compared based on the structural similarity index (SSIM), which underlines the robustness of the joint inversion compared to using the data individually. Hence, the combined application of HT and IP within field surveys and a subsequent joint inversion of both data sets may improve our understanding of hydraulically relevant subsurface structures, and thus the reliability of groundwater modelling results. [ABSTRACT FROM AUTHOR]

Mineral exploration works conducted in the Alto Guaporé Gold Province (AGGP), situated in the southwest region of the Amazon Craton in Brazil, faces the challenges of many gold provinces around the world, i.e., declines in the discoveries of new economic deposits and increases in exploration costs. Ground geophysical methods, combined with structural analyses and geological mapping, are valuable tools that have potential to improve accuracy in selecting exploration targets and in determining drilling locations. AGGP deposits are primarily associated with regional N20°–W50° inverse faulting and sheared geologic contacts between Meso-Neoproterozoic siliciclastic metasedimentary rocks and Mesoproterozoic basement (granite and volcano–sedimentary sequences). Mining currently occurring in the central portion of the province drives exploration works towards the many existing targets at the area. Among them, the ABP target is one of the most promising for being located few kilometers north of the Pau-a-Pique mine. At the ABP target, gold is associated with hydrothermal alteration located in the sheared contacts and in the hinge zone of folded metasedimentary sequence. Hydrothermal phases include Fe-oxides, sulfide (py), muscovite and quartz veins. In this study, we use magnetic and geoelectric (induced polarization) surveys coupled with structural and geological mapping to identify potential footprints within the ABP target. The results from induced polarization (IP) profiles successfully mapped the shape and orientation of the main structures down to approximately 350 m at the ABP target, indicating potential locations for hydrothermal alteration hosting gold. Additionally, 3D magnetic data inversions illustrated the distribution of magnetic susceptibilities and magnetization vectors associated with shear zone structures and isolated magnetic bodies. Magnetic data highlighted fault zones along the contacts between metamorphic rocks and granites, while IP data identified areas with high chargeability, correlating with sulfidation zones mineralized with gold. These findings suggest a metallogenic model where gold deposits are transported through deep structures connected to regional faults, implying significant tectonic and structural control over gold deposition. The results underscore the potential of multiparameter geophysics in identifying and characterizing deposits in both deep and strike, thereby advancing our understanding of mineral occurrences in the region and enhancing the search for new mineralized zones. [ABSTRACT FROM AUTHOR]

Electrostrictive materials exhibit a strain that is proportional to the square of the induced polarization. In linear dielectrics where the permittivity is constant, this electromechanical strain is also proportional to the square of the electric field. However, under increasing amplitudes of the driving field, the electromechanical strain sometimes saturates; the electrostrictive coefficients therefore appear to depend on the amplitude of the electric field used to measure them. Here, a methodology showing that this apparent field dependence is a consequence of neglecting higher‐order electromechanical phenomena is presented. When these are taken into account, not only do the electrostrictive coefficients remain constant but the signs of the high‐order coefficients enable the prediction of the saturation behavior from a single measurement. This approach is illustrated on both classical and non‐classical (so‐called "giant") electrostrictors. [ABSTRACT FROM AUTHOR]

Electrical measurements can be used to estimate hydraulic properties such as permeability (k) in sedimentary rocks. Previous work has focused on sandstones, siltstones, and carbonates, while investigations on mudstones have rarely been reported. In this study, we report on electrical geophysical measurements for 23 mudstone samples using an experimental approach designed to reliably saturate these low permeability mudstones. The modified Hagen‐Poiseuille model linking permeability to the formation factor (F) and an effective pore radius (r) provides an excellent fit to the data set with a near‐constant pore radius, indicating that the effective porosity (1/F) is the controlling factor on k. In these samples, the surface area normalized to pore volume (Spor), frequently used in permeability estimation models, varies by 1–2 orders of magnitude and is thus not a reliable proxy of the inverse effective hydraulic radius. The formation factor also exerts the primary control on induced polarization (IP) parameters, whereas Spor shows no relation to the IP parameters. A strong linear relationship is found between IP parameters (imaginary conductivity and normalized chargeability) and surface conductivity, although the proportionality factor is significantly lower than those observed in more permeable rocks and sediments. Apparent relationships between the polarization strength‐derived and time constant‐derived geophysical length scales and the effective hydraulic radius appear to be driven by variations in the electrochemical parameters (i.e., specific polarizability and diffusion coefficient). Overall, these findings emphasize that predicting hydraulic properties from electrical measurements in fine‐grained rocks remains challenging and requires further investigation into the electrochemical properties involved. Plain Language Summary: Permeability governs the flow of fluids, such as groundwater, and the transport of solutes in the Earth's subsurface. Quantifying the permeability of low‐permeability materials is important for nuclear waste storage, carbon sequestration, geothermal energy production, and hydrocarbon exploration. Electrical geophysical methods can non‐invasively measure properties that control permeability in the subsurface. Previous studies on loose, unconsolidated sediments and relatively permeable sandstones show how electrical properties are controlled by the physical properties describing the geometry of the interconnected pore network. However, in finer‐grained sedimentary rocks like mudstones, electrical properties are not so well reported, in part due to difficulties in acquiring accurate measurements on low permeability samples with small pores. In our study of 23 mudstone samples, we find that permeability and the electrical polarization of these samples are primarily controlled by the effective porosity (a measure of the interconnected pore space through which electrical current is channeled) with the samples represented by a near constant effective pore radius. The pore surface area per unit volume is not a good measure of effective pore radius or well correlated with electrical properties. We also find that electrical polarization is correlated with magnetic susceptibility, an indicator of iron mineral concentration. Key Points: Permeability and IP parameters are predominantly controlled by the effective porosity (1/formation factor) of mudstonesThe modified Hagen‐Poiseuille equation well predicts the permeability (k) of these mudstones, with a single effective pore radiusPore geometry descriptors (Spor) show no correlation with k or IP parameters, with IP parameters strongly controlled by effective porosity [ABSTRACT FROM AUTHOR]

The evaluation and monitoring of sites contaminated with heavy metals are essential for pollution remediation and prevention. In this study, we conducted geophysical and geochemical investigations at a site exhibiting heavy metal contamination downstream from an abandoned mine, with the aim of analyzing the extent of contamination and its temporal variation. We employed geophysical survey methods including electrical resistivity and induced polarization surveys of areas contaminated with heavy metals. Repeated surveys were conducted over time using the electrical resistivity method. Numerical simulations were employed to mitigate and eliminate electrical noise stemming from topography on the site. Additionally, time-lapse inversion was conducted on the resistivity data sets to analyze the changes in resistivity caused by variations in heavy metal contaminants. In the geochemical survey, soil samples were collected from the same locations as the geophysical survey, and chemical properties including pH, water content, electrical conductivity, and cation exchange capacity were analyzed. Our results showed that with the reduction of major sources of As and Zn contamination by 50%, the time-lapse electrical resistivity inversion results indicated that the resistivity of the subsurface materials increased by a factor of two. This paper demonstrated the natural reduction of the heavy metal contaminants at the site due to rainfall, aiming to comprehensively analyze the resultant alteration of both geochemical and geophysical properties. [ABSTRACT FROM AUTHOR]

This article deals with the study of land slide situation on the proposed path of the gas pipe line from Imam zadeh Hashem to Rudehen in Tehran province, using geophysical studies with 3 geophysical methods of one dimentional geoelectrical method, 2 dimentional Geo electrical Induced Polarization and Resistivity (IP & RS) method, and Ground Peneteration Radar (GPR) method. For this purpose, geophysical studies were carried out in the study area (in 70 kilometers east of Tehran and near Rodhan) as follows. In order to measure the changes of Geoelectrical resistivity in the designated place, to check the ground conditions for the gas pipeline in the Imam zadeh Hashem project, to separate the underground layers based on their Geoelectrical resistivity and to diagnose possible fractures, the number of 20 electrical soundings in an irregular network were recorded in the land slide area along ten profiles. After the approximate identification of the land slide area, 2D study was done in two profiles with a pole - dipole arrangement of 380 meters with induction polarization and resistivity (IP-RS) method. In order to obtain more information near the surface at the same time and also to investigate the extension to the depth, 5-meter electrode intervals with a maximum of 8 jumps and 10-meter intervals from 4 to 13 jumps have been used The depth of investigation will be about 50 meters. Moreover, Ground Peneteration Radar (GPR) method was performed with the length of 1000 meters in 27 profiles. GPR studies have been conducted with the aim of investigating and determining the location of loosened areas and possible holes in the range. Data acquisition was done using 80 MHz antenna. The results of data acquisition for a total area of 1000 meters have been processed by professional software and interpreted by taking into account the environmental conditions and taking into account all the complications in the route of the conducted surveys. Based on conducted studies, the land slide areas were determined and using Ground Peneteration Radar (GPR), underground cavities were located. With the help of the conducted studies, the range of the main land slide resulting from geophysical studies is determined and land slide prone surfaces are actually formed on the slope of land stratification and the mechanism of slides is planar movement. The main problem is related to the surface prone to upper slippage. Therefore, consolidation and stabilization of anomalous areas were investigated using stability analysis software. [ABSTRACT FROM AUTHOR]

We investigate the application of spectral induced polarization (SIP) monitoring to understand seasonal and annual variations in the freeze–thaw processes in permafrost by examining the frequency dependence of subsurface electrical properties. We installed a permanent SIP monitoring profile at a high-mountain permafrost site in the Italian Alps in 2019 and collected SIP data in the frequency range between 0.1–75 Hz over 3 years. The SIP imaging results were interpreted in conjunction with complementary seismic and borehole data sets. In particular, we investigated the phase frequency effect (ϕFE), i.e., the change in the resistivity phase with frequency. We observe that this parameter (ϕFE) is strongly sensitive to temperature changes and might be used as a proxy to delineate spatial and temporal changes in the ice content in the subsurface, providing information not accessible through electrical resistivity tomography (ERT) or single-frequency IP measurements. Temporal changes in ϕFE are validated through laboratory SIP measurements on samples from the site in controlled freeze–thaw experiments. We demonstrate that SIP is capable of resolving temporal changes in the thermal state and the ice / water ratio associated with seasonal freeze–thaw processes. We investigate the consistency between the ϕFE observed in field data and groundwater and ice content estimates derived from petrophysical modeling of ERT and seismic data. [ABSTRACT FROM AUTHOR]

Over the past two decades, significant deposit discoveries were made in Northeastern China, including the super-large Chalukou, Daheishan, and Luming porphyry Mo deposits. The discovery of the Luming deposit was accomplished through verification of stream sediment anomalies, with mineralization closely associated with early Jurassic monzogranite and granite porphyry. Previous studies primarily focused on the mineralization mechanisms of these deposits without adequately addressing the exploration methods and prospecting criteria. This study involved a comprehensive re-evaluation of geological observations, analysis of rock primary halo, gravity and magnetic surveys, and induced polarization surveys conducted during exploration campaigns at the Luming porphyry Mo deposit. The results suggest that hydrothermal breccias play a critical role in controlling the mineralization by forming a central low-grade core within the deposit while the Mo mineralization and hydrothermal alteration exhibit a donut-shaped distribution around it. The primary halo shows a distinct metal zonation moving from a central W-Bi-Mo-(Sb) to a peripheral Cu-Co-Ni and a distal Pb-Zn-Ag-In. The mineralization zone exhibits a low Bouguer gravity anomaly, negative magnetic anomaly, medium to low resistivity, and moderate to high chargeability, indicating the effectiveness of geophysical methods in defining the extent of the ore body. The Luming porphyry Mo deposit and distal skarn-epithermal Pb-Zn mineralization are parts of a porphyry-related magmatic-hydrothermal system. The results of this study offer valuable insights into the genesis of porphyry Mo deposits and their implications for prospecting in the forested region of Northeastern China. [ABSTRACT FROM AUTHOR]

ZnO and BaSnO3 (BSO) thin films grown on Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) substrates have been studied using electrical resistance and photoconductivity (PC) spectra measurements under different applied electric fields on the substrate. The behavior of the resistance and the energy gap (EG) extracted from the PC spectra are modified by the polarization state of the substrate in the case of the ZnO film, while for BSO, these physical parameters depend on the strain imposed by the substrate when a voltage is applied on the PMN-PT. In the latter case, an in-plane tensile (compressive) strain leads to a reduction (increase) in the resistance and the energy gap when an external electric field is applied on the substrate. The behavior of ZnO and BSO can be explained by the different crystalline structure in both films and by the fact that ZnO is also a piezoelectric material. In ZnO, a change in the polarization state of the substrate is associated with an imposed strain and an induced polarization on the film that leads to a modification of the band bending and hence of the energy gap. In the case of BSO, a shift of the impurity and conduction band generates a modification of the energy gap for the different types of strain. [ABSTRACT FROM AUTHOR]

Knowledge of the heterogeneity of aquifers caused by sedimentary processes is essential for preferential flow path and flow time estimations due to the spreading of contaminants and ground water protection. Spectral Induced Polarization (SIP) method is a useful geophysical method that can be used to predict hydraulic properties from surface measurements, as there is a close connection between electrical and hydraulic parameters of rocks. Thus, the influence of aquifer heterogeneities such as sedimentary structures on the relationship between SIP parameters and hydraulic conductivity has been subject of some studies and is still an area of interest. In this paper we present the results of laboratory measurements on defined heterogeneous sand samples with the aim to improve the understanding of that connection. More specifically we investigated the dependence of hydraulic conductivity (K ), as well as several SIP parameters like quadrature conductivity ( σ ′ ′ ), in-phase conductivity ( σ ′ ), phase shift (φ ) and chargeability spectra ( m (τ) ), which were calculated by Debye decomposition, on the composition of samples. For the laboratory experiments a measurement cell was designed to carry out hydraulic flow experiments and 4-electrodes SIP measurements on samples in the decimeter scale. The samples consisted of two different sands with different grain size distributions. The two sands were combined in varying volume shares and geometries as well as in parallel and serial orientation relative to hydraulic and electrical current flow. The experimental results show that the SIP parameters and K are clearly dependent on the volume share of the sand components. In terms of preferential flow paths, known correlations to hydraulic conductivity could be reproduced, however the SIP parameters showed no dependency on the orientation of hydraulic heterogeneities. The results indicate that in samples, where the porosity and thus also the electrical conductivity amplitude are approximately homogeneous and only the grain surface area and hydraulic conductivity vary, the mean electrical parameters determined from the SIP data do not provide any information for recognising preferential flow within the scope of the measurement accuracy. [ABSTRACT FROM AUTHOR]

Abstract The physical properties of seafloor massive sulfides are crucial for interpreting sub-seafloor images from geophysical surveys, shedding light on the evolution of seafloor mineral deposits. While some studies have explored the relationship between electrical properties and the volume of conductive minerals in rocks from seafloor massive sulfide deposits, they primarily focused on artificial samples, leaving the characteristics of natural samples less understood. Moreover, there has been no comprehensive study detailing the general characteristics of electrical properties, particularly chargeability and relaxation time, in relation to the volumetric fraction of sulfides in rocks from massive sulfide mounds in typical hydrothermal areas. In this study, we employed complex conductivity measurements, elemental concentration analysis, and mineral content identification on to rock samples from the active hydrothermal zones of the Okinawa Trough in Japan. The complex conductivity observed was remarkably high, with a pronounced imaginary component and a broad frequency range. This is attributed to induced polarization extending beyond our measurement range. The rock samples were rich in conductive sulfide minerals such as pyrite, chalcopyrite, and galena. Using the Cole–Cole rock physics model, we established a correlation between rock chargeability and relaxation time coefficient with the volume fraction of conductive sulfide minerals, which deviated from previous findings. The intensity of induced polarization was notably higher than anticipated in earlier studies using artificial samples. Furthermore, we observed a distinct positive correlation between the coefficient of relaxation time and the increase in sulfide volume, likely due to the geometric characteristics of the sulfide minerals. Our findings suggest that rocks in massive sulfide mounds may generally construct sulfide clusters that lengthen the conductive path of the electrical carrier. Graphical Abstract

Highlights: MXene-based structural microwave-absorbing materials achieve an impressive reflection loss of − 47.9 dB in the low-frequency S-band, without the presence of magnetic materials and with low density. The elucidation of the mechanism behind the shift of the absorption band from high to low frequencies is attributed to the coupling of controlled multilevel polarization with induced electric field interactions. Two-dimensional carbon-based materials have shown promising electromagnetic wave absorption capabilities in mid- and high-frequency ranges, but face challenges in low-frequency absorption due to limited control over polarization response mechanisms and ambiguous resonance behavior. In this study, we propose a novel approach to enhance absorption efficiency in aligned three-dimensional (3D) MXene/CNF (cellulose nanofibers) cavities by modifying polarization properties and manipulating resonance response in the 3D MXene architecture. This controlled polarization mechanism results in a significant shift of the main absorption region from the X-band to the S-band, leading to a remarkable reflection loss value of − 47.9 dB in the low-frequency range. Furthermore, our findings revealed the importance of the oriented electromagnetic coupling in influencing electromagnetic response and microwave absorption properties. The present study inspired us to develop a generic strategy for low-frequency tuned absorption in the absence of magnetic element participation, while orientation-induced polarization and the derived magnetic resonance coupling are the key controlling factors of the method. [ABSTRACT FROM AUTHOR]

S, N-co-doped carbon quantum dots (S, N-CQDs) as the fluorescent source and β piezoelectric phase inducer were implanted into a poly (vinylidene) fluoride-hexafluoropropylene (PVDF-HFP) microporous film to prepare the fluorescent and piezoelectric S,N-CQDs/PVDF-HFP composite film based on sensitization technology. The results showed that S, N-CQDs were uniformly anchored into the PVDF-HFP skeletons. This promoted the polarization effect and prevented solid-state luminescence quenching, further ensuring the coupling of fluorescent and piezoelectric bifunctions in the composite film. Since the induced polarization effect, the β piezoelectric phase in the composite film climbed from 65.8% to 86.6% with an amplitude of 31.6%, which caused the increase in piezoelectric constant (d33) from 15.4 to 21.6 pC N−1 with an amplitude of 40.26%. Because of the absence of solid-state luminescence quenching, the light cyan fluorescence from S, N-CQDs was successfully realized in the composite film. The application of the composite film in the flexible pressure sensor (FPS) enabled to achieve an outstanding sensitivity of 267.75 mV N−1, exceeding that (191.73 mV N−1) when using the pure PVDF-HFP film. Moreover, the embedding of S, N-CQDs endowed the FPS with several new functions mainly owning to the ultraviolet excited fluorescence of the composite film. [ABSTRACT FROM AUTHOR]

This study used aero-radiometric, 2D electrical resistivity tomography (ERT), and induced polarization (IP) methods to delineate gold mineralization potential. The study also confirmed and followed-up on regions with major structural features identified in previous aeromagnetic studies in the area. A half-degree airborne radiometric data of sheet 118_ Yelwa from the NGSA, which contains three radioelements (%K, eTh, and eU) were used in this study. These datasets were processed and analyzed with Oasis Montaj Grid Math expression builder to obtain the %K_ratio_eTh and Ternary grid anomalies. The results identified zones E and F as hydrothermally altered regions that may harbour gold mineralization. These findings were consistent with the regions of major structural features identified in previous aeromagnetic studies in the area. The zones were located in the eastern parts of Ngaski, Yauri (Yelwa), Shanga, and Agwara, as well as Magama's northwest region. However, zone F1 (the eastern portion of Ngaski/Yauri) has been further investigated using 2ERT and IP detailed geophysical methods in a dipole-dipole configuration. The results of geoelectric techniques along profiles 1, 2, and 3 identified the major gold mineralization potential zones, which were labeled A1, A, and C. These regions have low/high resistivity and chargeability signatures, and could thus be interpreted as potential target zones for metallic mineral exploration, particularly gold mineralization. The regions are located in the northern part of Mararraba and southwest of the Jinsani areas of Kebbi State. [ABSTRACT FROM AUTHOR]

To help meet emission standards, hydrogen sulfide (H2S) from geothermal production may be injected back into the subsurface, where basalt offers, in theory, the capacity to mineralize H2S into pyrite. Ensuring the viability of this pollution mitigation technology requires information on how much H2S is mineralized, at what rate and where. To date, monitoring efforts of field‐scale H2S reinjection have mostly occurred via mass balance calculations, typically capturing less than 5% of the injected fluid. While these studies, along with laboratory experiments and geochemical models, conclude effective H2S mineralization, their extrapolation to quantify mineralization and its persistence over time leads to considerable uncertainty. Here, a geophysical methodology, using time‐domain induced polarization (TDIP) logging in two of the injection wells (NN3 and NN4), is developed as a complementary tool to follow the fate of H2S re‐injected at Nesjavellir geothermal site (Iceland). Results show a strong chargeability increase at +40 days, interpreted as precipitation of up to 2 vol.% based on laboratory relationships. A uniform increase is observed along NN4, whereas it is localized below 450 m in NN3. Changes are more pronounced with larger electrode spacing, indicating that pyrite precipitation takes place away from the wells. Furthermore, a chargeability decrease is observed at later monitoring rounds in both wells, suggesting that pyrite is either passivated or re‐dissolved after precipitating. These results highlight that a sequence of overlapping reactive processes (pyrite precipitation, passivation, pore clogging and possibly pyrite re‐dissolution) results from H2S injection and that TDIP monitoring is sensitive to this sequence. Plain Language Summary: High‐temperature geothermal production is responsible for air pollution due to hydrogen sulfide (H2S) present in the magmatic fluid. To help meet emission standards, H2S may be injected back into the subsurface, where basalt offers the capacity to transform H2S into pyrite. Transformation into an immobile mineral prevents further transport into the atmosphere, sea, surface streams, or lakes. However, ensuring the viability of this pollution mitigation technology requires information such as how much H2S is mineralized, at what rate and where, which are highly uncertain due to the heterogeneity and inaccessibility of subsurface processes. Here, a geophysical monitoring methodology is developed and tested during the re‐injection of H2S at Nesjavellir geothermal site in south‐west Iceland. According to laboratory studies, pyrite precipitation is expected to increase the electrical capacitance, "chargeability," of the subsurface. Using the so‐called time‐domain induced‐polarization (TDIP) method embedded in a wireline logging tool, the chargeability of a 2 m‐wide cylinder around the injection wells is measured with high spatial‐resolution before and during H2S injection. A strong chargeability increase at +40 days indicates that up to 2% pyrite is formed. A subsequent decrease at later rounds raises questions on whether pyrite is re‐dissolved or passivated by other secondary minerals. Key Points: H2S reinjection in basalt and mineralization into pyrite was monitored using TDIP logging in two of the injection wellsChargeability increases observed at +40 days (first monitoring round) correspond to 1%–2% pyrite precipitation with great spatial variabilitySubsequent monitoring rounds show a decrease in chargeability, suggesting that pyrite is either passivated or re‐dissolved [ABSTRACT FROM AUTHOR]

Induced polarization (IP) tomography measurements, as a near-surface geophysical method, can provide information about the degree of chargeability of subsurface materials and are commonly used in mineral exploration, engineering studies (e.g., sediment/bedrock interface identification, crushed zones and faults detection, and landslide and soil properties imaging), as well as in environmental investigations (contaminant plums identification and landfill characterization). The purpose of these measurements is to obtain the distribution of polarizability characteristics inside an object, generally below the surface, at the boundary of the object, or outside the area in question. The results of such measurements can be mathematically modeled for the specific polarizability properties by solving the Poisson’s equation restricted by appropriate boundary conditions. In this paper, we focused on the importance of simulating induced-polarization responses and retrieving chargeability distributions in geo-materials to enhance the characterization of subsurface structures. We presented the methods for forward modelling and non-linear inversion of IP measurements. To this end, in the first step, the Poisson’s equation for a two-dimensional ground with an arbitrary distribution of conductivity is solved using the finite difference numerical method. In the next step, based on the existing relations between conductivity and chargeability (the Siegel’s formulation), the apparent IP response is calculated. Finally, we solved the non-linear chargeability inversion problem following a non-linear apparent resistivity inversion. This is achieved by imposing physical constraints to prevent the estimation of unrealistic model parameters, using a Newton-based optimization method. To evaluate the efficiency of the proposed methodology, we utilized the proposed algorithm on two simulated examples and a real data set. Our numerical results show that the algorithm reliably represents the main features and structure of the Earth’s subsurface in terms of resistivity and chargeability models. All the algorithms presented in this paper have written in the MATLAB programming language. [ABSTRACT FROM AUTHOR]

This article presents the findings of a geophysical survey conducted on the Khachkovi gold-polymetallic occurrence in Georgia. The study aimed to evaluate the geological prospects through comprehensive investigations. Three methods - electrometry, magnetometry, and gamma spectrometry - were employed in the survey, covering approximately 3.5 square kilometres. Analysis of the survey data revealed high magnetic field anomalies and variations in the gravity field, indicating gabbro-diorite intrusive bodies at depth. The Khachkovi occurrence was structurally associated with faults, fractured zones, and hydrothermally altered zones. Electrically conductive minerals within the hydrothermally altered zones were confirmed through induced polarization values and anomalous potassium content. The study area exhibited low potassium, thorium, and uranium levels, potentially due to Quaternary sediments and weak alterations. Hydrothermally altered sulfide mineral-containing zones were primarily linked to fault zones, intrusive bodies, and brecciated zones. The surface hydrothermally altered zone consisted mainly of pyrite-bearing rocks. The geophysical survey provided valuable insights into the geological characteristics and prospects of the Khachkovi gold-polymetallic occurrence, offering guidance for further exploration activities. These findings contribute to understanding the mineralization potential and future mining efforts. [ABSTRACT FROM AUTHOR]

Transient electromagnetic surveys are commonly conducted to map the distribution of resistivity, a key physical property in mineral exploration and other geological prospecting problems. However, the responses obtained in regions associated with chargeable minerals are always distorted by the induced polarization effects. In this study, the distorted responses are initially simulated in the frequency domain employing the Cole–Cole complex resistivity model and subsequently converted into the time domain through a time-frequency transformation method. A uniform half-space model is employed to validate the algorithm and illustrate the distortion characteristics of the responses in polarizable formations. A three-layer model is designed to estimate the misinterpretation of slightly complicated models. An actual misinterpretation is demonstrated by field responses containing induced polarization effects collected in the Wulong Gold Mine. The results show that the distortions under different geoelectrical conditions are consistent, enhancing the responses in the early stage and counteracting the responses in the late stage. The strong induced polarizable effects distort the responses by causing explicit sign reversals, whereas the weak induced polarizable effects only distort the decay rate of the responses. These distortions are prone to causing misinterpretations and resulting in excessively intricate geological structures. [ABSTRACT FROM AUTHOR]

Investigating soil and water contamination is essential for assessing environmental risks and monitoring remediation processes. This study, located in São Paulo, Brazil, highlights the presence of chlorinated solvents, especially tetrachloroethylene, with the application of remediation measures such as chemical oxidation. Both contamination and remediation processes have led to changes in geophysical signatures, enabling the use of electrical resistivity, despite challenges in urban areas due to consolidated infrastructure. The objective is to integrate data from direct methods and surveys of electrical resistivity and induced polarization, obtained through direct current and resistive capacitive methods, to refine the conceptual model of the area, delineating the influence zone of the contaminant and remediation processes. The resistive capacitive method allows continuous data acquisition in large areas without the need for electrode insertion into the soil. Geoelectrical data, correlated with soil sample descriptions, allow analysis of subsurface characteristics and areas affected by contamination. Variations in resistivity identify differences between lithologies, while induced polarization highlights clayey areas. Chemical oxidation to remediate PCE contamination increases conductivity, allowing for delineation of the remediation's influence zone. Despite urban challenges, the electrical resistivity method helps fill data gaps and improve the conceptual model of the area, demonstrating a rapid and effective approach. [ABSTRACT FROM AUTHOR]

Miller's rule is an empirical relation between the nonlinear and linear optical coefficients that applies to a large class of materials but has only been rigorously derived for the classical Lorentz model with a weak anharmonic perturbation. In this work, we extend the proof and present a detailed derivation of Miller's rule for an equivalent quantum-mechanical anharmonic oscillator. For this purpose, the classical concept of velocity-dependent damping inherent to the Lorentz model is replaced by an adiabatic switch-on of the external electric field, which allows a unified treatment of the classical and quantum-mechanical systems using identical potentials and fields. Although the dynamics of the resulting charge oscillations, and hence the induced polarizations, deviate due to the finite zero-point motion in the quantum-mechanical framework, we find that Miller's rule is nevertheless identical in both cases up to terms of first order in the anharmonicity. With a view to practical applications, especially in the context of ab initio calculations for the optical response where adiabatically switched-on fields are widely assumed, we demonstrate that a correct treatment of finite broadening parameters is essential to avoid spurious errors that may falsely suggest a violation of Miller's rule, and we illustrate this point by means of a numerical example. [ABSTRACT FROM AUTHOR]

Graphite, a critical raw material, prompts interest in assessing former quarries for volumetric content, driving the need for accurate prospection techniques. We explore the efficacy of spectral induced polarization (SIP) imaging at field scale for this purpose. Field measurements in a quarry with unknown graphite content underscore the need for assessment before drilling due to abrupt topography. Due to the lack of ground truth required to calibrate existing petrophysical models, we propose using SIP laboratory measurements to achieve the quantitative interpretation of the imaging results. We conducted experiments at two scales: rock plugs for material response and ground rocks of varying sizes for textural analysis. The rock plugs allow us to investigate the response of the material, while the ground samples permit us to understand changes in the SIP response for varying textural properties. Our lab work establishes power-law relationships between polarization (expressed in terms of normalized chargeability) and graphite content, as well as relaxation time and grain size. Salinity dependence is noted between chargeability, normalized chargeability, and relaxation time. Utilizing these findings, we provide a quantitative interpretation of field SIP imaging results. [ABSTRACT FROM AUTHOR]

Designing complex local properties that seamlessly integrate efficient functions into processed materials presents a formidable challenge. A promising solution has emerged in the form of ultrafast laser‐surface structuring. Through time‐controlled polarization ultrafast irradiation at the picosecond timescale, spontaneous self‐organization of surfaces can be induced. The thermal gradient length scale unfolds on the micro‐ and nanoscale, instigating thermoconvection that leads to structured surfaces upon quenching. Convective instabilities dynamically shape intricate yet self‐regulated periodic relief structures. The ability to achieve laser‐induced self‐organization in both surface dimensions holds immense scientific importance, as it unlocks the potential to create uniform periodic 2D patterns by harnessing the inherent regulation of nonlinear dynamics processes in fluids. This comprehensive review explores recent advances in understanding and leveraging ultrafast laser‐induced self‐organization for precise patterning across versatile scales and applications. The insights herein hold the potential to drive significant advancements in nanoscale manufacturing through 2D laser‐induced periodic surface structures. [ABSTRACT FROM AUTHOR]