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Surface complexation models (SCMs) based on Gouy-Chapman theory are often used to describe adsorption of ions onto mineral surfaces. To compensate for the buildup of charge at a solid surface, the composition of the electric diffuse layer next to the surface must balance the surface charge. To calculate the diffuse layer composition, several nonlinear equations and integrals must be solved, usually with an iterative approach. Before convergence, charge balance is typically not fulfilled. One numerical difficulty is that, because of these charge balance errors, the iterative solver may attempt to take the square root of a negative number. Herein, we show that for electrolytes containing only monovalent or divalent ions (i.e., most electrolytes encountered in practice), we can greatly simplify the integrals and eliminate the appearance of complex-valued integrands; it is even possible to derive explicit analytical formulas. Furthermore, using the new method prevents converging to non-physical roots of the Grahame equation, which links surface potential to surface charge. To the best of our knowledge, the presented formulation has not been implemented in geochemical modelling software before, although similar mathematical expressions have been presented in the literature. In Gouy-Chapman theory, ions can only be distinguished by their charges, but this is not consistent with all experimental findings. We present a model that allows for the preferential accumulation of ions in the diffuse layer. The model, which is implemented mathematically by including ion exchange sites with a variable exchange capacity, is flexible and more numerically tractable than the standard models for the diffuse layer. [ABSTRACT FROM AUTHOR]

The hazardous plasma environment surrounding Earth poses risks to satellites due to internal charging and surface charging effects. Accurate predictions of these risks are crucial for minimizing damage and preparing for system failures of satellites. To forecast the plasma environment, it is essential to know the current state of the system, as the accuracy of the forecast depends on the accuracy of the initial condition of the forecast. In this study, we use data assimilation techniques to combine observational data and model predictions, and present the first global validation of a data-assimilative electron ring current nowcast during a geomagnetic storm. By assimilating measurements from one satellite and validating the results against another satellite in a different magnetic local time sector, we assess the global response and effectiveness of the data assimilation technique for space weather applications. Using this method, we found that the simulation accuracy can be drastically improved at times when observations are available while eliminating almost all of the bias previously present in the model. These findings contribute to the construction of improved operational models in estimating surface charging risks and providing realistic 'source' populations for radiation belt simulations. [ABSTRACT FROM AUTHOR]

The influence of a surface electric charge on the character and properties of wave motion along the free surface of a viscous homogeneous fluid is investigated by analytical asymptotic methods. Expressions describing the dispersion relations of the wave-motion components are obtained. The phase and group velocities of the structures forming wave motion are determined. [ABSTRACT FROM AUTHOR]

The slow charge reactions at the semiconductor surface severely encumber the photocatalysis applications, which are elusive and complicated in a serial charge excitation-separation-reaction process. Both experimental and theoretical studies are essential in this area. Here, a classical numerical calculation of the charge reaction microkinetic is developed based on a simple consecutive charge separation and reaction model, a conservation law of photogenerated charges, and differential analysis. Several reaction conditions have been discussed to elucidate how a fast charge separation and reaction rate constant influence the apparent reaction kinetics. It is shown that a slower charge separation rate strongly limits the detection of higher-order reaction rates, and higher-order kinetics can be detected with all other processes faster than the reactions. This numerical calculation projects the possible limitations of kinetics study by transient techniques. [ABSTRACT FROM AUTHOR]

The influence of a surface electric charge on the character and properties of wave motion along the free surface of a viscous homogeneous fluid is investigated by analytical asymptotic methods. Expressions describing the dispersion relations of the wave-motion components are obtained. The phase and group velocities of the structures forming wave motion are determined. [ABSTRACT FROM AUTHOR]

Results of studying the process of fine milling of α-Al2O3 in the presence of polyethylene glycol (PEG) and an antistatic composition are presented. It is shown that the main reason for agglomeration of fine particles is the effect of appearance of an electrostatic surface charge. Introduction of PEG prevents appearance of a "pseudo-viscous milling medium", removing the excess electrostatic charge at the surface of newly formed ultrafine particles, and also intensifies the wear process of primary alpha-alumina crystals. The antistatic composition successfully neutralizes a surface electrical charge, but does not exhibit a milling intensifier effect. [ABSTRACT FROM AUTHOR]

In the case of multipoint initiation of the side surface of a cylindrical charge in a section perpendicular to the axis, a detonation wave with a complex gas-dynamic structure is formed, which has the shape of a polygon with vertices at wave conjugation points. The sides of the polygon are always convex toward the charge axis. It is stated that a smooth cylindrical detonation wave with reverse curvature can be obtained by using special devices at initiation points: lenses made of an inert material. The dynamic characteristics of the material are experimentally determined, and the method for constructing the lens profile is substantiated. The operation of an initiation node and the formation of a cylindrical detonation wave in a charge are mathematically modeled. The specific features of the operation of a single initiating node and a node that is part of the experimental assembly are shown. The dynamics of axisymmetric compression by a converging detonation wave is presented and compared with calculations. [ABSTRACT FROM AUTHOR]

Improving the utilization rate of loaded-drugs is of huge importance for generating chitosan-based (CS) micro-carriers. This study aims to fabricate a novel CS microspheres co-delivered curcumin (Cur) and gallic acid (Ga) to assess drug loading and release kinetics, the blood compatibility and anti-osteosarcoma properties. The present study observes the interaction between CS and Cur/Ga molecules and estimates the change in crystallinity and loading and release rate. In addition, blood compatibility and cytotoxicity of such microspheres are also evaluated. Cur-Ga-CS microspheres present high entrapment rate of (55.84 ± 0.34) % for Ga and (42.68 ± 0.11) % for Cur, possibly attributed to surface positive charge (21.76 ± 2.46) mV. Strikingly, Cur-Ga-CS microspheres exhibit slowly sustainable release for almost 7 days in physiological buffer. Importantly, these microspheres possess negligibly toxic to blood and normal BMSC cells, but strong anti-osteosarcoma effect on U2OS cells. Overall, Cur-Ga-CS microspheres are promising to become a novel anti-osteosarcoma agent or sustainable delivery carrier in biomedical applications. [ABSTRACT FROM AUTHOR]

Within the framework of the thermodynamic theory of equilibrium two-component adsorption from a liquid on a flat solid surface, taking into account its deformation and the presence of an electric charge on it, two equations of the isotherm of such adsorption are derived at small deformations containing two unknown functions independent of the electric potential of the solid phase. It is shown that the problem of finding the conditions for the single-phase nature of the adsorption layer is reduced to the same problem, but posed for an undeformed surface. [ABSTRACT FROM AUTHOR]

The dispersion characteristics of kaolin from the Zhuravlinyi Log deposit, as well as the ξ -potential and the apparent viscosity of suspensions based on it, were investigated. Kaolin suspensions had a sufficiently high stability due to the negative charge of the surface of the particles. The ξ-potential was determined as a function of pH and tripolyphosphate concentration by the electrophoresis method. The effectiveness of the additive on the apparent viscosity of the suspension is associated with the ability to increase the pH and hence the ξ -potential. The isoelectric point of kaolin is set to 3.28. The kaolin slurry had a fairly high casting rate, which can be explained by the good crystallization of the mineral (Hinckley index 1.76). [ABSTRACT FROM AUTHOR]

For artificial photosynthesis, the lower photon conversion efficiencies of the photogenerated charges hinder the practical application in solar energy harvesting. The challenges are commonly ascribed to the sluggish surface redox reactions and significant surface charge recombination. Although there are several transient techniques applied for monitoring the surface charges evolution, how the experimental spectroscopy data is interpreted still involves ambiguous explanations on the complicated reactions. Here, we firstly developed a parallel 1st–nth order reaction model, which could be applied to quantitatively analyze the surface charge reactions. The microkinetic calculations were carried out by varying the reaction order, rate constants as well as the contribution of the competitive ones. Interestingly, the simplified reaction model can successfully demonstrate the charges react rate changes, which can be further applied in mechanism study complementary with those experimental methods. [ABSTRACT FROM AUTHOR]

The charging effect on the surface of two adjacent and rough mask holes has been studied during plasma etching, as functions of gas flow rate and ion incident energy E i based on classical particle dynamics simulations of surface charging, surface etching and profile evolution. This study revealed that, on the one hand, various gas flow rates can result in different distributions of the electric field (E-field) and the net charge density on the surface of the mask. Specifically, the overall E-field strength gradually fades with the increase is the gas flow rate. The E-field in the middle region of these two holes dramatically becomes weak with the gas flow rate, while changes are very small in the outer edges of holes. On the other hand, the simulated evolution of the mask profile exhibits an increased deformation as the gas flow rate increases. Conversely, this deformation decreases with increasing E i . Possible mechanisms of these results during the etching process were discussed. This work sheds light on the reduction of the mask pattern damage and further improves the quality of the pattern transferring onto the substrate. [ABSTRACT FROM AUTHOR]

Purpose: Brain disorders have become a serious problem for healthcare worldwide. Nanoparticle-based drugs are one of the emerging therapies and have shown great promise to treat brain diseases. Modifications on particle size and surface charge are two efficient ways to increase the transport efficiency of nanoparticles through brain-blood barrier; however, partly due to the high complexity of brain microstructure and limited visibility of Nanoparticles (NPs), our understanding of how these two modifications can affect the transport of NPs in the brain is insufficient. Methods: In this study, a framework, which contains a stochastic geometric model of brain white matter (WM) and a mathematical particle tracing model, was developed to investigate the relationship between particle size/surface charge of the NPs and their effective diffusion coefficients (D) in WM. Results: The predictive capabilities of this method have been validated using published experimental tests. For negatively charged NPs, both particle size and surface charge are positively correlated with D before reaching a size threshold. When Zeta potential (Zp) is less negative than -10 mV, the difference between NPs' D in WM and pure interstitial fluid (IF) is limited. Conclusion: A deeper understanding on the relationships between particle size/surface charge of NPs and their D in WM has been obtained. The results from this study and the developed modelling framework provide important tools for the development of nano-drugs and nano-carriers to cure brain diseases. [ABSTRACT FROM AUTHOR]

We employ the Stroh octet formalism to develop a real-form expression of the Coulomb force acting on a line charge in an anisotropic piezoelectric bimaterial. The Coulomb force is derived using two different approaches and is expressed in terms of the generalized Barnett–Lothe tensors for the two piezoelectric half-spaces. Interestingly, we find that the Coulomb force is independent of the orientation of the bimaterial interface provided that the interface is parallel to the x 3 -axis and the distance between the charge and the interface remains unchanged. The Coulomb force on a line charge in a piezoelectric half-space with a rigid conducting surface or a traction-free insulating surface is deduced from the Coulomb force for two jointed piezoelectric half-spaces. In the case of a rigid conducting surface, we find that the Coulomb force always tends to attract the line charge to the surface. This is in contract to the case of a traction-free insulating surface for which we find that the Coulomb force can be either repulsive or attractive due to the piezoelectric effect. [ABSTRACT FROM AUTHOR]

Extension of corrosion inhibitors from traditional molecular-scale to nanoscale will not only be significant to develop green and efficient inhibitors, but also supplement the discipline system of corrosion inhibitors. However, many research on the interfacial behavior of nano-inhibitors have ignored the special colloidal properties of nanoparticles and show no obvious differences with traditional inhibitors. In this study, graphene oxide (GO) was functionalized with polydopamine (PDA) via covalent modifications and self-polymerization, and GO-PDA was studied as a corrosion inhibitor of carbon steel in HCl solution. Diversified measurements confirmed that GO-PDA can effectively protect carbon steel from corrosion, and the inhibition efficiency almost reached 90% at 100 mg/L. Interfering factors including immersion time and concentration were investigated. The lamellar nanoparticles adsorbed on the surface of carbon steel have formed a hydrophobic film in micro-nano structures. The transition from a negative charge on the GO surface to a positively charged GO-PDA contributed to adsorption at the interface. An initial model of nano-inhibitor was established to explicate the inhibition mechanism. [ABSTRACT FROM AUTHOR]

Redox reactions have been observed when an electrostatically charged insulator is placed in contact with a solution, and this phenomenon is referred to as single-electrode electrochemistry. In this study we explore how important is the chemical reactivity of the charge carriers on the surface compared to the voltage caused by the density of charges on the surface which set up an electric double layer. We address complications arising from the surface potential's dependence upon the electrolyte concentration caused by the fixed surface charge density of the electrode. We present an analytical solution for the effective potential in single-electrode electrochemistry at a planar surface and show that it is not the same as the potential at the insulating surface. We reach two major conclusions: (1) the voltage applied to the reaction from discharging the electrode approaches a limiting value, and (2) the majority of single-electrode reactions are caused primarily by the chemical reactivity of the charge carrier on the electrode surface and not from discharging the static charge on the electrode. [ABSTRACT FROM AUTHOR]

The dynamics of ionization waves (IWs) in atmospheric pressure discharges is fundamentally determined by the electric polarity (positive or negative) at which they are generated and by the presence of memory effects, i.e. leftover charges and reactive species that influence subsequent IWs. This work examines and compares positive and negative IWs in pulsed plasma jets (1 μ s on-time), showing the difference in their nature and the different resulting interaction with a dielectric BSO target. For the first time, it is shown that a surface charging memory effect is produced, i.e. that a significant amount of surface charges and electric field remain in the target in between discharge pulses (200 μ s off-time). This memory effect directly impacts IW dynamics and is especially important when using negative electric polarity. The results suggest that the remainder of surface charges is due to the lack of charged particles in the plasma near the target, which avoids a full neutralization of the target. This demonstration and the quantification of the memory effect are possible for the first time by using an unique approach, assessing the electric field inside a dielectric material through the combination of an advanced experimental technique called Mueller polarimetry and state-of-the-art numerical simulations. [ABSTRACT FROM AUTHOR]

The volumetric charge of the surface air above the objects of study of dowsers is characterized by a reversible electrode effect—an excess of negative charge. The frame, carrying a negative charge equal in density to the earth's charge, makes oscillatory movements in the operator's hand; as a result, the density of the enveloping negative air charge on one side of the horizontal elbow increases. The negative charges of the horizontal bend of the frame and the negative space charge of air are inevitably repulsed. As a mechanical device, the frame is a lever where the pushing forces will be resisted by the frictional force of the vertical knee in the operator's hand. As a result, the repulsive forces between the negative air charge and the negative charge of the horizontal knee will multiply in proportion to the ratio of the distance from the point of application of forces to the horizontal knee to the radius of the vertical knee. Field and laboratory experiments confirm this hypothesis of the atmospheric–electrical nature of the rotation of the horizontal knee of the frame. [ABSTRACT FROM AUTHOR]

A core–shell QDs@mSiO2@y-AuNCs nanoprobe was prepared, and a new ratiometric fluorescent sensor for thiram detection was developed. The mechanism of thiram sensing was investigated using FTIR, surface-enhanced Raman, XPS spectra, etc. The sensing of thiram was mainly ascribed to the formation of Au–S bonds between thiram and Au atoms on y-AuNCs surface, resulting in the dissociation of 11-MUA ligand from the y-AuNCs surface and the charge transfer between thiram and y-AuNCs. In the ratiometric fluorescence detection of thiram based on QDs@mSiO2@y-AuNCs, a linear range of 0.5–60 ng/mL was obtained with a LOD of 0.19 ng/mL. Compared with the fluorescence detection based on y-AuNCs, the ratiometric fluorescence detection of thiram demonstrated 3-fold enhanced sensitivity. The improvement was ascribed to two aspects: the fluorescence emission of y-AuNCs was enhanced after they were loaded onto the QDs@mSiO2 nanoparticles; the ratiometric detection mode provided more precise sensing. The detection of thiram can be completed immediately after mixing the nanoprobe with thiram. Good recoveries of thiram in apple and pear samples were achieved. All the above results demonstrated the high potential of this method in practical applications. [ABSTRACT FROM AUTHOR]

D2-D8 model admits a numerical solution that corresponds to a charge density wave and a spin density wave. Considering that as the background, we numerically solve the Dirac equation for probe fermions. From the solution, we obtain the Green's function and study the behaviour of the spectral density. We begin with generic fermions and have studied the formation of the Fermi surface and where it develops a gap. In addition, we have incorporated an ionic lattice and study its effect on the Fermi surface. Then we analysed the worldvolume fermions. In this particular model we do not find Fermi surface for the dual operators. [ABSTRACT FROM AUTHOR]

The effect of chemical passivation in solutions of ammonium sulfide (NH4)2S on the optical and electronic properties of the surface n-InP (001) is studied. It is shown that treatment in a 4% aqueous solution of (NH4)2S leads to a twofold decrease in the surface field and charges localized in this region. Treatment in a 4% alcohol solution (NH4)2S leads to a decrease in these parameters by a factor of 3, and, moreover, the barrier photovoltage decreases by a factor of 3. [ABSTRACT FROM AUTHOR]

Molecular dynamics simulation has been employed to study conformational rearrangements induced by an external field in uniformly charged polypeptides adsorbed on the surface of an oppositely charged gold nanoparticle, whose polarization direction varies with a frequency corresponding to the microwave electric field. The averaged angular and radial distributions of atom densities have been calculated for the polyelectrolytes adsorbed on the nanoparticle surface. The simulation has shown the formation of a ring-shaped fringe of polyelectrolyte units encircling the gold nanoparticle in its equatorial region. The density of the fringe of an adsorbed polyelectrolyte macromolecule on the nanoparticle surface depends on both the total charge of the nanoparticle and the fraction of charged units in the macromolecule. [ABSTRACT FROM AUTHOR]

In honor of Igor Dzyaloshinskii on his 90th birthday, we revisit his pioneering work on the linear magnetoelectric effect in light of the modern theory of ferroelectric polarization. We show that the surface magnetic dipole moment associated with magnetoelectric materials is analogous to the bound surface charge in ferroelectrics, in that it can be conveniently described in terms of a bulk magnetoelectric multipolization that is analogous to the ferroelectric polarization. We define the intrinsic surface magnetization to be this surface magnetic dipole moment per unit area, and provide a convenient recipe for extracting it for any surface plane, from knowledge of the bulk magnetic order. We demonstrate the procedure for the prototypical magnetoelectric material, Cr2O3, in which Dzyaloshinskii first identified the linear magnetoelectric effect, and compare the value of the intrinsic surface magnetization to recent experimental measurements. Finally, we argue that non-magnetoelectric antiferromagnets whose multipolization lattices do not contain zero should have an intrinsic surface magnetization, in the same way that non-polar insulators whose polarization lattices do not contain zero have an intrinsic surface charge. [ABSTRACT FROM AUTHOR]

The Poisson-Boltzmann equation for a strongly charged plate inside a generic charge-asymmetric electrolyte is solved using the method of asymptotic matching. Both near field and far field asymptotic behaviors of the potential are systematically analyzed. Using these expansions, the renormalized surface charge density is obtained as an asymptotic series in terms of the bare surface charge density. [ABSTRACT FROM AUTHOR]