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The conventional electrostatic solutions for two-dimensional (2D) electrodes possess edge singularities for the surface charge density σ and the normal component of the electric field E n. These singularities are generally non-physical because they admit infinite gradients of the concentration of free charge carriers. In particular, they are unacceptable in the studies of the local field sensitive effects, such as the electric breakdown and the ferroelectric domain reversal. We claim that account for diffusion of free charge carriers leads to the disappearance of the edge singularities. This generalization occurs consistently within the same basic concept of conduction. Specifically, we consider the case of U -biased circular disc electrode of radius a. Account for diffusion leads here to a strongly nonlinear integral 2D equation for the electrostatic potential φ (r). Numerical solution of this equation shows that the law σ (a) ∝ U 2 / a takes place. Outside a close vicinity of the disc edge, we stay close to the conventional electrostatic solution for φ and σ. [ABSTRACT FROM AUTHOR]

The electronic structures of three highly mismatched alloys (HMAs)—GeC(Sn), Ga(In)NAs, and BGa(In)As—were studied using density functional theory with HSE06 hybrid functionals, with an emphasis on the local environment near the mismatched, highly electronegative atom (B, C, and N). These alloys are known for their counterintuitive reduction in the bandgap when adding the smaller atom, due to a band anticrossing (BAC) or splitting of the conduction band. Surprisingly, the existence of band splitting was found to be completely unrelated to the local displacement of the lattice ions near the mismatched atom. Furthermore, in BGaAs, the reduction in the bandgap due to BAC was weaker than the increase due to the lattice constant, which has not been observed among other HMAs but may explain differences among experimental reports. While local distortion in GeC and GaNAs was not the cause for BAC, it was found to enhance the bandgap reduction due to BAC. This work also found that mere contrast in electronegativity between neighboring atoms does not induce BAC. In fact, surrounding the electronegative atom with elements of even smaller electronegativity than the host (e.g., Sn or In) consistently decreased or even eliminated BAC. For a fixed composition, moving Sn toward C and In toward either N or B was always energetically favorable and increased the bandgap, consistent with experimental annealing results. Such rearrangement also delocalized the conduction band wavefunctions near the mismatched atom to resemble the original host states in unperturbed Ge or GaAs, causing the BAC to progressively weaken. These collective results were consistent whether the mismatched atom was a cation (N), anion (B), or fully covalent (C), varying only with the magnitude of its electronegativity, with B having the least effect. The effects can be explained by charge screening of the mismatched atom's deep electrostatic potential. Together, these results help explain differences in the bandgap and other properties reported for HMAs from different groups and provide insight into the creation of materials with designer properties. [ABSTRACT FROM AUTHOR]

We investigate the polarization of disk electrodes immersed in an electrolyte solution and subjected to a small external AC voltage over a wide range of frequencies. A mathematical model is developed based on the Debye–Falkenhagen approximation to the coupled Poisson–Nernst–Planck equations. Analytical techniques are used for predicting the spatial distribution of the electric potential and the complex impedance of the system. Scales for impedance and frequency are identified, which lead to a self-similar behavior for a range of frequencies. Experiments are conducted with gold electrodes of sizes in the range 100–350 μm immersed in a high-conductivity KCl solution over five orders of magnitude in frequency. A collapse of data on impedance magnitude and phase angle onto universal curves is observed with scalings motivated by the mathematical model. A direct comparison with the approximate analytical formula for impedance is made without any fitting parameters, and a good agreement is found for the range of frequencies where the analytical model is valid. [ABSTRACT FROM AUTHOR]

This paper presents a new conformal mapping method to solve 2D Laplace and Poisson equations in MOS devices. More specifically, it consists of an analytical solution of the 2D Laplace equation in a rectangular domain with Dirichlet boundary conditions, with arbitrary values on the boundaries. The advantages of the new method are that all four edges of the rectangle are taken into account and the solution consists of closed-form analytical expressions, which make it fast and suitable for compact modeling. The new model was validated against other similar methods. It was found that the new model is much faster, easier to implement, and avoids many numerical issues, especially near the boundaries, at the cost of a very small loss in accuracy. [ABSTRACT FROM AUTHOR]

Gallium oxide (G a 2 O 3 ) is a promising ultra-wide bandgap material offering a large bandgap (> --> 4.7 eV) and high critical electric fields. The increasing demand for electronic devices for high-power applications in electric automobiles, high-performance computing, green energy technologies, etc., requires higher voltages and currents with enhanced efficiency. Vertical transistors, such as fin-shaped field-effect transistors (FinFETs) have emerged to meet the growing need with improved current handling capabilities, reduced resistance, and enhanced thermal performance. However, to fully exploit the Ga 2 O 3 power transistors, precise and reliable physics-driven models are crucial. Therefore, a comprehensive surface potential model has been developed in this work for a vertical Ga 2 O 3 FinFET. The electric potential across the channel is explained by analyzing the two-dimensional (2D) Poisson equation employing parabolic approximation. Such a surface potential model is instrumental in determining the performance of the Ga 2 O 3 FinFET as it affects the threshold voltage, the drain current, and fringing capacitance. Exploiting the surface potentials, a fringing capacitance model is derived which is crucial in analyzing the speed of the device in compact integrated circuits. In addition, statistical analysis of the Ga 2 O 3 FinFET using the Monte Carlo simulation technique is performed to determine the leakage current fluctuation due to doping variations. The validation of the analytical model with experimental results confirms the effectiveness and prospects of the developed models in the rapid development and characterization of next-generation high-performance vertical Ga 2 O 3 power transistors. [ABSTRACT FROM AUTHOR]

Motivated by the booming development of spintronics based on chiral helical microstructures, we employed the standard nonequilibrium Green's function theory to study nonreciprocity and chirality of the heat generation and spin filtering in ferromagnetic helical chains. Our results demonstrate that magnetization, spin–orbit interaction, and nonstep electrostatic potential distribution by bias jointly determine nonreciprocity of the heat generation, and only spin–orbit interaction determines nonreciprocity of the spin-polarized current. Chirality of the heat generation and spin-polarized current is determined by both magnetization and spin–orbit interaction, and some quantitative relationships related to chirality were discovered. However, a transverse field can break these relations and suppress heat generation significantly and modulate nonreciprocity and chirality of the spin-polarized current effectively. By further simulating the critical electrostatic potential distribution, we found with the transverse field applied, compared to the case with zero temperature, that the finite temperature less than one characteristic phonon energy can suppress nonreciprocity of the heat generation while enhancing that of the spin filtering. In terms of chirality, compared to the left-handed helical structure, the right-handed one is more advantageous for designing spin filtering diodes. [ABSTRACT FROM AUTHOR]

In this work, we propose a theoretical finite element description of the ionic profiles of a general mixture of n species of spherical charged particles dissolved in an implicit solvent, with arbitrary size and charge asymmetries, neutralizing a spherical macroion. This approach aims to close the gap between the nano- and the micro-scales in macroion solutions, taking into account the ion correlations and ionic excluded volume effects consistently. When these last two features are neglected, the classical non-linear Poisson–Boltzmann theory for n ionic species—with different ionic closest approach distances to the colloidal surface—is recovered as a limit case. As a proof of concept, we study the electrical double layer of an electroneutral mixture of oppositely charged colloids and small microions, with an asymmetry 1:333 in size and 1:10 in valence, in salt-free and added salt environments. Our theoretical approach displays a good agreement regarding the ionic profiles, the integrated charge, and the mean electrostatic potential obtained from molecular dynamics simulations with explicit-sized microions. Although the non-linear Poisson–Boltzmann colloid–colloid and colloid–microion profiles differ notably from those obtained via molecular dynamics simulations with explicit small-sized ions, the associated mean electrostatic potential agrees well with the corresponding explicit microion simulations. [ABSTRACT FROM AUTHOR]

In this work, the planar, electric, double-layer structures of non-polarizable electrodes in electrolyte solutions are studied with Gaussian field theory. A response function with two Yukawa functions is used to capture the electrostatic response of the electrolyte solution, from which the modified response function in the planar symmetry is derived analytically. The modified response function is further used to evaluate the induced charge density and the electrostatic potential near an electrode. The Gaussian field theory, combined with a two-Yukawa response function, can reproduce the oscillatory decay behavior of the electric potentials in concentrated electrolyte solutions. When the exact sum rules for the bulk electrolyte solutions and the electric double layers are used as constraints to determine the parameters of the response function, the Gaussian field theory could at least partly capture the nonlinear response effect of the surface charge density. Comparison with results for a planar electrode with fixed surface charge densities from molecular simulations demonstrates the validity of Gaussian field theory. [ABSTRACT FROM AUTHOR]

We present the coupling of two frameworks—the pseudo-open boundary simulation method known as constant potential molecular dynamics simulations (CμMD), combined with quantum mechanics/molecular dynamics (QMMD) calculations—to describe the properties of graphene electrodes in contact with electrolytes. The resulting CμQMMD model was then applied to three ionic solutions (LiCl, NaCl, and KCl in water) at bulk solution concentrations ranging from 0.5 M to 6 M in contact with a charged graphene electrode. The new approach we are describing here provides a simulation protocol to control the concentration of electrolyte solutions while including the effects of a fully polarizable electrode surface. Thanks to this coupling, we are able to accurately model both the electrode and solution side of the double layer and provide a thorough analysis of the properties of electrolytes at charged interfaces, such as the screening ability of the electrolyte and the electrostatic potential profile. We also report the calculation of the integral electrochemical double layer capacitance in the whole range of concentrations analyzed for each ionic species, while the quantum mechanical simulations provide access to the differential and integral quantum capacitance. We highlight how subtle features, such as the adsorption of potassium graphene or the tendency of the ions to form clusters contribute to the ability of graphene to store charge, and suggest implications for desalination. [ABSTRACT FROM AUTHOR]

Field electron emission from nanometer-scale objects deviates from the predictions of the classical emission theory as both the electrostatic potential curves within the tunneling region and the image potential deviates from the planar one. This impels the inclusion of additional correction terms in the potential barrier. At the apex of a tip-like rotationally symmetric surface, these terms are proportional to the (single) local emitter curvature. The present paper generalizes this relation, showing that for any emitter geometry, the coefficient of the correction terms is given by the mean curvature, i.e., the average of the two principal curvatures. [ABSTRACT FROM AUTHOR]

We report the resonance-enhanced two-photon ionization combined with various detection approaches and quantum chemical calculations of biologically relevant neurotransmitter prototypes, the most stable conformer of 2-phenylethylamine (PEA), and its monohydrate, PEA-H2O, to reveal the possible interactions between the phenyl ring and amino group in the neutral and ionic species. Extracting the ionization energies (IEs) and appearance energy was achieved by measuring the photoionization and photodissociation efficiency curves of the PEA parent and photofragment ions, together with velocity and kinetic energy-broadened spatial map images of photoelectrons. We obtained coinciding upper bounds for the IEs for PEA and PEA-H2O of 8.63 ± 0.03 and 8.62 ± 0.04 eV, within the range predicted by quantum calculations. The computed electrostatic potential maps show charge separation, corresponding to a negative charge on phenyl and a positive charge on the ethylamino side chain in the neutral PEA and its monohydrate; in the cations, the charge distributions naturally become positive. The significant changes in geometries upon ionization include switching of the amino group orientation from pyramidal to nearly planar in the monomer but not in the monohydrate, lengthening of the N–H⋯π hydrogen bond (HB) in both species, Cα–Cβ bond in the side chain of the PEA+ monomer, and the intermolecular O–H⋯N HB in PEA-H2O cations, leading to distinct exit channels. [ABSTRACT FROM AUTHOR]

Brain rhythms have been postulated to play central roles in animal cognition. A prominently reported dichotomy of hippocampal rhythms links theta‐frequency oscillations (4–12 Hz) and ripples (120–250 Hz) exclusively to preparatory and consummatory behaviours, respectively. However, because of the differential power expression of these two signals across hippocampal strata, such exclusivity requires validation through analyses of simultaneous multi‐strata recordings. We assessed co‐occurrence of theta‐frequency oscillations with ripples in multi‐channel recordings of extracellular potentials across hippocampal strata from foraging rats. We detected all ripple events from an identified stratum pyramidale (SP) channel. We then defined theta epochs based on theta oscillations detected from the stratum lacunosum‐moleculare (SLM) or the stratum radiatum (SR). We found ∼20% of ripple events (in SP) to co‐occur with theta epochs identified from SR/SLM channels, defined here as theta ripples. Strikingly, when theta epochs were instead identified from the SP channel, such co‐occurrences were significantly reduced because of a progressive reduction in theta power along the SLM‐SR‐SP axis. Behaviourally, we found most theta ripples to occur during immobile periods, with comparable theta power during exploratory and immobile theta epochs. Furthermore, the progressive reduction in theta power along the SLM‐SR‐SP axis was common to exploratory and immobile periods. Finally, we found a strong theta‐phase preference of theta ripples within the fourth quadrant [3π/2 – 2π] of the associated theta oscillation. The prevalence of theta ripples expands the potential roles of ripple‐frequency oscillations to span the continuum of encoding, retrieval and consolidation, achieved through interactions with theta oscillations. Key points: The brain manifests oscillations in recorded electrical potentials, with different frequencies of oscillation associated with distinct behavioural states.A prominently reported dichotomy assigns theta‐frequency oscillations (4–12 Hz) and ripples (120–250 Hz) recorded in the hippocampus to be exclusively associated with preparatory and consummatory behaviours, respectively.Our multi‐strata recordings from the rodent hippocampus coupled with cross‐strata analyses provide direct quantitative evidence for the occurrence of ripple events nested within theta oscillations.These results highlight the need for an analysis pipeline that explicitly accounts for the specific strata where individual oscillatory power is high, in analysing simultaneously recorded data from multiple strata.Our observations open avenues for investigations involving cross‐strata interactions between theta oscillations and ripples across different behavioural states. [ABSTRACT FROM AUTHOR]

Presented herein is an investigation for the nonlinear vibration and stability analysis of rotating functionally graded (FG) piezoelectric nanobeams based on the nonlocal strain gradient theory. The present model can be regarded as a simplified version for the rotating nanowire of biomechanical nanogenerators. The Hamilton principle is used to derive nonlinear equations of motion and their related boundary conditions, which are then discretized to form a set of algebraic equations. Accordingly, the nonlinear vibration frequencies and buckling loads of the nanobeams can be determined by an iterative method. A parametric study of rotational velocity, nonlocal parameter, material length parameter, power-law index, and electrostatic voltage on the dynamic stability behavior of such nanobeams is also presented. In the cantilever case, increasing the nonlocal parameter and material length parameter can result in a stiffness-hardening effect that is unaffected by rotational velocity and the material length parameter to nonlocal parameter ratio. Yet, this has not been reported previously. More importantly, incorporating the effect of geometric nonlinearity on the dynamic responses and stability results of the nanobeams is indispensable. In particular, new observations for the coupling effect of vibration amplitude and power-law index on the electric potential effect are useful for the design of rotating microelectromechanical devices. [ABSTRACT FROM AUTHOR]

Density functional theory (DFT) was used to investigate the adsorption of twenty-four gases (SiH4, H2, Cl2, F2, CF4, CH4, CF2Cl2, N2, CHF3, OCS, N2O, AsH3, CH3Cl, COCl2, C2H2, C2H4, H2Se, H2S, PH3, COF2, CH3F, HCHO, (CH3)2O, and CH3NH2) on B12N12 and Al12N12 nanocages. Most of the studied gases are weakly (strongly) adsorbed on the B12N12 (Al12N12) nanocage. However, AsH3, H2Se, H2S, PH3, CH3F, HCHO, (CH3)2O, and CH3NH2 are strongly adsorbed on the B12N12 nanocage and H2, F2, CF4, CH4, and CF2Cl2 are weakly adsorbed on the Al12N12 nanocage. The most negative-valued molecular electrostatic potential (MESP) minimum (Vmin) corresponds to the electron-rich region (e.g., lone pair and π-bond) in the molecule. An important observation is that the adsorption energies of the gases on the B12N12 and Al12N12 nanocages are well correlated with the MESP Vmin values of the gases. Substantial changes are found in the DFT reactivity indices like chemical potential and hardness of the B12N12 and Al12N12 nanocages, mainly due to the strong gas adsorption. The quantum theory of atoms in molecules analysis suggests the covalent nature of interactions only in the AsH3/B12N12, H2Se/B12N12, H2S/B12N12, and PH3/B12N12 systems. [ABSTRACT FROM AUTHOR]

Energy decomposition analysis is one of the most attractive features of fragment molecular orbital (FMO) calculations from the point of view of practical applications. Here we report some enhancements for PIEDA in the ABINIT‐MP program. One is a separation of the dispersion‐type stabilization from the electron correlation energy, traditionally referred to as the "dispersion interaction" (DI). Another is an alternative evaluation of the electrostatic (ES) interaction using the restrained electrostatic potential (RESP) charges. The GA:CT stacked base pair and the Trp‐Cage miniprotein were used as illustrative examples. [ABSTRACT FROM AUTHOR]

This research is based on the synthesis, characterization and in vitro α‐glucosidase inhibitory activity of fourteen amides (2 a–2 n) of flurbiprofen drug. Seven compounds in the series displayed potent inhibitory activity having IC50 values (IC50=5.67±0.89 μM) to (IC50=17.87±2.39 μM) in comparison with acarbose standard (IC50=875.75±1.24 μM). The FMO of 2 a–2 n molecules was quantified by the DFT assay. The promising value for energygap explained the higher poteny agannist α‐glucosidase. MEP provides the insights into the distribution of electrostatic potential on the molecular surface of 2 a–2 n, showing that C=O group has the highest negative potential. The AIM investigation revealed minimal hydrogen bond energy and non‐covalent interactions. This suggests that these molecules may have limited hydrogen bonding and non‐covalent interactions, which could be relevant to their chemical behavior. Molecular docking and (MEP) showed the C=O group, with its high negative potential, is a key in recognizing the catalytic non‐polar regions of enzymes, such as TYR72, GLU277, and ARG442. Similarly, the hydrophobic regions of investigated compounds play a significant role in identifying essential amino acids like ASP352 and ARG442, which are vital for the ligand's proper orientation and subsequent biological activity. [ABSTRACT FROM AUTHOR]

Landscape functions are a popular tool used to provide upper bounds for eigenvectors of Schrödinger operators on domains. We review some known results obtained in the last 10 years, unify several approaches used to achieve such bounds, and extend their scope to a large class of linear and nonlinear operators. We also use landscape functions to derive lower estimates on the principal eigenvalue—much in the spirit of earlier results by Donsker–Varadhan and Bañuelos–Carrol—as well as upper bounds on heat kernels. Our methods solely rely on order properties of operators: We devote special attention to the case where the relevant operators enjoy various forms of elliptic or parabolic maximum principle. Additionally, we illustrate our findings with several examples, including p$p$‐Laplacians on domains and graphs as well as Schrödinger operators with magnetic and electric potential, also by means of elementary numerical experiments. [ABSTRACT FROM AUTHOR]

This paper addresses the issue of LED short-circuit fault detection in signaling and lighting systems in the automotive industry. The conventional diagnostic method commonly implemented in newer vehicles relies on measuring the voltage drop across different LED branches and comparing it with threshold values indicating faults caused by open circuits or LED short circuits. With this algorithm, detecting cases of a few LEDs short-circuited within a branch, particularly a single malfunctioning LED, is particularly challenging. In this work, two easily implementable algorithms are proposed to address this issue within the vehicle's control unit. One is based on a mathematical prediction model, while the other utilizes a neural network. The results obtained offer a 100% LED short-circuit fault detection rate in the majority of analyzed cases, representing a significant improvement over the conventional method, even in scenarios involving a single malfunctioning LED within a branch. Additionally, the neural network-based model can accurately predict the number of failed LEDs. [ABSTRACT FROM AUTHOR]

The molecular geometry, electronic structure, and absorption spectra of some important phenyl derivatives are investigated by using DFT and TD‐DFT with B3LYP and CAM‐B3LYP functional. The highest HOMO–LUMO energy gap, Non‐linear optical properties of dipole moment, polarizability, and hyperpolarizability are calculated. In both methods hyperpolarizability PDP values (16.77 × 10−30 and 16.59 × 10−30 esu) are higher than PDNA, PDN, and MPAN dye. The Molecular electrostatic potential shows that PDNA dye has more electronegative potential. Comparing all the dyes, PDP dye shows a higher light harvesting efficiency in the UV–vis region. The vibrational frequencies are assigned based on the potential energy distribution (PED) using the VEDA‐4 program. [ABSTRACT FROM AUTHOR]

Empirical force field methods typically rely on point charges to describe the electrostatic interactions, which is problematic when anisotropy needs to be considered, as in the case of the electrostatic potential of covalently bound halogens that possess a positive site, termed σ -hole, surrounded by a large negative belt. To address this, an off-center point charge (extra point, EP) is usually placed at a given distance from the halogen to emulate the σ -hole and commonly used implementations are based on the restrained electrostatic potential (RESP) procedure to fit atomic charges, being one of the most used charge models. In this context, no specific Merz–Singh–Kollman (MK) radius for iodine is available in the literature, which is an essential parameter in the RESP fitting procedure. In this work, we explored the impact of the iodine MK radius on the obtained RESP charges for a set of 12 iodinated molecules. We verified that the relative root mean square (RRMS) values obtained with and without an EP kept decreasing with increasing radii for most compounds, thus impairing optimization using such a procedure. Nevertheless, the use of an iodine MK radius lower than 2 Å is not advisable since the RRMS kept decreasing considerably until this value was reached. Moreover, the performance of three iodine MK radii was studied with the estimation of the free energy of hydration (Δ G hyd) values using alchemical free energy calculations, which are particularly sensitive to the charges used. Despite the usage of different radii not leading to remarkable differences, our results indicate that using a value of 2.70 Å leads to lower mean absolute errors (MAE) and root mean squared error (RMSE) values when comparing the calculated with the experimental Δ G hyd values. Restrained Electrostatic Potential (RESP) charges are commonly used in force fields and Merz-Singh-Kollman (MK) radii are needed in the fitting. Since iodine radius is not available, in this work, we explored the impact of changing the iodine MK radius on the RESP charges of a set of 12 iodinated molecules and their hydration free energy predictions. Our results indicate that, although the changes are small, a value of 2.70 Angstrom leads to a better agreement with experimental values. [ABSTRACT FROM AUTHOR]

Experimental and theoretical study of the regioselectivity and mechanism of polycyclic aromatic amine (PAA) electrochemical oxidation is important for designing nitrogen doped large π‐conjugated functional molecules. Herein, we used binary‐, ternary‐, and quaternary‐fused PAAs as electro‐oxidative reaction substrates to investigate the yield changes of carbazole and phenazine based aza‐helicene other than oligomers, which were obtained through pyrrole and pyrazine annulation pathways. Combined with the restrained electrostatic potential (RESP) and steric hindrance factor analysis of the substrate, the electron spin density distribution of free radical resonance hybrid and the spin population analysis of the atoms in the structure of each free radical tautomer indicate that the degree of delocalized dispersion of N free radical and the resulting change in the spin density distribution of C free radical tautomers determine the reaction regioselectivity. The potential charge of the K‐region, Bay‐region, and L‐region adjacent to the C(α)−C(β1) bond is higher than that of other regions within the molecule, and the charge in these high RESP regions tends to delocalize more strongly toward electron‐deficient N free radicals. Thus, the activity of N−C(α)−C(β1) region is increased, which supports the proposed free radical addition and free radical coupling mechanism for the electro‐oxidative reaction of PAA. [ABSTRACT FROM AUTHOR]

Simple chemical structure and simplified synthesis process of active layer materials are critical for advancing the practical application of organic solar cells. Herin, two completely non‐fused ring electron acceptors BTZT‐2Cl and BTZT‐4Cl are developed. BTZT‐4Cl exhibits an enhanced absorption band, increases electrostatic potential differences with D18, and improves crystallinity and molecular packing properties. Consequently, the binary device based on BTZT‐4Cl displays a markedly improved efficiency of 14.12%, compared to the BTZT‐2Cl‐based device, which only achieves a moderate efficiency of 11.25%. More importantly, an alloy‐like structure can be formed by incorporating a small amount of high miscibility and compatibility BTZT‐2Cl. The ternary blend exhibits more compact molecular packing, efficient exciton dissociation, and an extended charge carrier lifetime due to the formation of an alloy‐like structure. The ternary device achieves a decent efficiency of 15.41% with superior thermal stability and a high T80 lifetime over 1600 h after being aged at 65 °C. These results establish it as the most efficient among devices based on completely non‐fused ring acceptors with both high efficiency and voltage. This study demonstrates a simple material design strategy and high‐performance device optimization techniques, which are critical for advancing practical applications in the OSC field. [ABSTRACT FROM AUTHOR]

The integration of reformers into high-temperature polymer electrolyte membrane (HT-PEM) fuel cells presents a significant opportunity to improve fuel flexibility and cost-effectiveness. To understand their degradation, we applied two start–stop cycling procedures: one with pure H 2 and another with an 80 vol % H 2 and 20 vol % N 2 mix to simulate reformate gas. We also performed a load cycling test with H 2 as anode gas. The results indicated that degradation rate of pure H 2 start–stop cycling showed 306 μ V h−1, while load cycling demonstrated a degradation rate of 19.7 μ V h−1 for the current density of 0.2 A cm−2, and 88.2 μ V h−1 for the current density of 0.4 A cm−2. Start–stop cycling with diluted gas resulted in a constant voltage drop with a degradation rate of 3.129 mV h−1. Electrochemical impedance spectroscopy (EIS) indicated an increased ohmic resistance during start–stop cycling and higher charge transfer (high-frequency) and mass transport (low-frequency) resistance with nitrogen introduction. Scanning electron microscope results confirmed MEA degradation. In conclusion, start–stop cycling and anode gas dilution are stressors that accelerate HT-PEM fuel cell degradation, reducing its lifetime. • Start–stop and anode gas dilution degrade HT-PEM cells. • Degradation jumps from 306 μ V/h to 3.129 mV/h with dilution. • Low degradation (88.2 μ V/h) at 0.4 A/cm² under load cycling. • Anode dilution with nitrogen amplifies resistive effects. • SEM analysis confirmed physical degradation of MEA. [ABSTRACT FROM AUTHOR]

In this study, the behavior of lead adsorbed onto polyaniline composite was examined theoretically with the DFT method and experimentally using spectrophotometry. The synthesis and characterization of polyaniline nanofilaments (PANI) were executed. Density functional theory and Becke's three‐parameter exchange functional approach were employed for quantum mechanical calculations of geometry and energy. The 6.311G** basis set and the Lee‐Yang‐Parr correlation functional method (B3LYP/DFT) were used in a water solution environment to complement the experimental data. Experimental results were visualized using 3D molecular electrostatic potential maps (MEP), which aided in the determination and explanation of various properties, including mean polarizability, total static dipole moment, anisotropy of polarizability, and mean first‐order hyperpolarizability. The findings indicate that Pb‐PANI‐EB shows promise as a potential material for non‐linear optical (NLO) applications. PANI demonstrate efficacy as a sensor capable of detecting Pb concentrations as low as 0.05 ppm. These results justify further exploration of the use of PANI in the development of a fast, economical, robust, and highly sensitive lead (Pb) sensor. [ABSTRACT FROM AUTHOR]

The stator field-oriented control (SFOC) strategy, utilizing classical proportional-integral (PI) regulators for the doubly fed induction generator (DFIG) within a dual rotor wind turbine (DRWT) system, encounters several significant challenges. These challenges encompass undesirable fluctuations in stator active and reactive powers, the occurrence of a coupling effect in specific scenarios, and a lack of robustness. Moreover, the conventional SFOC demonstrates suboptimal performance in the presence of grid voltage drop scenarios. To address these issues, this study proposes the application of a backstepping super-twisting control (BSTC) strategy. The design of the controller involves integrating a super-twisting algorithm (STA) term into the control law of the classical backstepping control (BC) approach. The MATLAB simulation tests conducted on a 1500 KW DFIG-based DRWT system illustrate the clear superiority of the proposed BSTC over conventional SFOC, BC, and some previously published control methods. In the reference tracking test, the results indicate a significant reduction in the total harmonic distortion (THD) value of the stator current by 57.14% compared to SFOC and by 33.33% compared to BC. Additionally, the BSTC technique, in the same test, also reduces the steady-state error (SSE) for active power by 60% and 28.57% compared to SFOC and BC, respectively. Concerning reactive power, the proposed BSTC strategy decreases SSE by percentages estimated at 56.25% and 12.5%, respectively, compared to SFOC and BC. The computed percentages illustrate the substantial superiority of the suggested controller in enhancing power system characteristics and elevating the quality of energy. [ABSTRACT FROM AUTHOR]

The article investigates the impact of different types of Bus clamping Pulse Width Modulation methods on the switching losses of a voltage source inverter. A controller based on a generalised modulation algorithm inspired by Bus Clamping Pulse Width Modulation is presented in this study. The implementation of the controller is based on the fact that for continual and split clamp PWM there exists a unique value of clamping position (γ ) for every load power factor angle, which results in minimum switching losses. The algorithm aims to minimise switching losses by combining and generalising all the unique values of clamping positions for continual and split clamp PWM. The controller dynamically adjusts the modulation technique and clamping position based on the sensed load phase current, resulting in reduced switching losses across the whole spectrum of load power factor angles compared to fixed clamping positions. Experimental and analytical evidence demonstrates the effectiveness of the proposed controller in achieving minimum switching loss operation during dynamic load changes. [ABSTRACT FROM AUTHOR]

Thermoelectric power generation (TPG) is a novel method where carriers within a conductor migrate from the hot end to the cold end, generating a potential difference under a temperature gradient. Due to hysteresis, this potential difference fluctuates periodically with environmental temperature changes. Therefore, implementing a self-adaptive module during operation is crucial to enhance output voltage stability. Using LTspice, we simulated a TPG system, incorporating a boost module for a DC/DC boost circuit and a self-adaptive module with a logic-level controlled current electronic switch. Analysis results demonstrated nonlinear power generation growth with increasing temperature differences. Conversely, power generation decreased with rising internal resistance R0, thermal resistance Rq, and heat capacity Cq of the entire system. Notably, changes in R0 and Cq values had a more pronounced impact compared to Rq values. Under constant thermoelectric electromotive force conditions, a 1.5× growth in R0 led to a corresponding 1.5× power growth, while a 1.5× growth in Rq resulted in a 1.06× power growth. Furthermore, a 1.5× growth in Cq under the same Tcold value caused greater heat loss, subsequently reducing power output. After constructing the self-adaptive module, the TPG system effectively rectified and stabilized the floating potential difference within the voltage drop range of the field-effect transistor conduction tube, optimizing output to 50 from 600 ms. The self-adaptive TPG system designed in this research exhibits practical significance and potential applications in precision measurement instruments. [ABSTRACT FROM AUTHOR]

The zero-relaxation limit of Euler–Poisson systems for ion dynamics in a slow time scale leads to drift-diffusion equations. This fact was justified in previous works. This paper concerns global error estimates between solutions of Euler–Poisson systems and that of drift-diffusion equations. In the proof, we use Sobolev inequalities and employ a multiplier related to the electric potential. [ABSTRACT FROM AUTHOR]

• ΔpK a , Molecular Complementarity (MC), Molecular Electrostatic Potential (MEP) Maps and Machine Learning approaches were used for the coformer's selection. • MEPS model and Machine learning blend model using MACCs descriptors appears to be the top-performing models for the coformer selection. • Experimental co-crystal screening resulted in Roxadustat-Nicotinamide (RXD-NA) co-crystal, confirmed by single crystal structure, solid-state FTIR and NMR analysis. • Physical and chemical stability of RXD-NA co-crystal was established. • The phenomenon of photo isomer impurity generation was evaluated by computational analysis. Roxadustat (RXD) is an approved drug substances for the treatment of renal anemia. It has poor aqueous solubility and photochemical stability. This study employs a comprehensive approach to enhance the stability and physicochemical properties RXD through coformer selection and characterization. The investigation integrates delta pKa analysis, molecular complementary assessment, molecular electrostatic potential surface analysis, and machine learning techniques to predict potential co-crystal formation and binding interactions between drug molecules and coformers. The co-crystal screening which lead to in a novel RXD-nicotinamide co-crystal (RXD-NA). Experimental characterization underscores the physical and chemical stability of the co-crystals. To elucidate the supramolecular synthons and understand the intermolecular interactions in the RXD-NA co-crystal, Hirshfeld surfaces analysis, quantum theory of atoms in molecules (QTAIM) analysis and non-covalent interaction (NCI) analysis were performed. Computational analysis of photo-isomer formation aligns with experimental observations, further enhancing our understanding of RXD-coformer interactions. RXD-NA co-crystal was found photo-chemically stable as compared to free base API drug substance. This integrated methodology provides a systematic framework for informed co-crystal design, holding promise for optimizing RXD formulations based on molecular interactions and stability considerations. Consequently, this study contributes valuable insights to the field of rational drug design and formulation optimization. [ABSTRACT FROM AUTHOR]

The dual descriptor potential (DDP) has appeared in several papers, It is proposed as a local reactivity descriptor within the framework of the Conceptual Density Functional Theory and as a complementary tool of the molecular electrostatic potential (MEP) rather than the dual descriptor (DD). DDP provides information concerning the most energetically favorable sites to undergo nucleophilic and electrophilic attacks. Unlike the dual descriptor, DDP is directly related with energy. Furthermore, the DDP seems to depure the scalar field, allowing us to unveil the predominance of nucleophilic and electrophilic regions on a molecule. This is in stark contrast to the dual descriptor, which tends to scatter around the molecule, hindering the interpretation of the local reactivity on regions that exceed the atomic volume. To the best of our knowledge, this is the first time that DDP is represented as a 3D picture. To assess its capability to describe interaction among molecules, DDP was tested on some molecular systems, along with MEP. Results show that the joint use of these tools helps in the understanding of certain experimental evidences, serving as an alternative to the molecular orbital theory. [ABSTRACT FROM AUTHOR]

This work investigates the effect of Joule heating and viscous dissipation due to electric double layer (EDL) and electroosmotic effect on steady fully developed electromagnetohydrodynamic flow in a porous microchannel. Dimensionless formulations of the Poisson–Boltzmann, momentum, and energy equations are derived for the electric potential, velocity profile, and temperature distribution in the microchannel. Exact solutions for the temperature distributions and velocity profiles were obtained using the method of undetermined coefficients. The Debye–Hückel linearization is used to get an exact solution for the electric potential. The results showed that the Brinkmann number (Br) $({Br})$, Joule heating parameter (J) $(J)$, Debye–Hückel parameter (Κ) $({\rm K})$, Hartmann number (M) $(M)$, electric field (Ez) $({E}_{z})$, and suction/injection parameter (S) $(S)$ have a substantial impact on flow formation and heat transfer. Using MATLAB software, graphical simulations are provided to deliver a greater understanding of the influence of relevant parameters on the results achieved. [ABSTRACT FROM AUTHOR]

High-resolution simulations of particle-based kinetic plasma models typically require a high number of particles and thus often become computationally intractable. This is exacerbated in multi-query simulations, where the problem depends on a set of parameters. In this work, we derive reduced order models for the semi-discrete Hamiltonian system resulting from a geometric particle-in-cell approximation of the parametric Vlasov–Poisson equations. Since the problem's nondissipative and highly nonlinear nature makes it reducible only locally in time, we adopt a nonlinear reduced basis approach where the reduced phase space evolves in time. This strategy allows a significant reduction in the number of simulated particles, but the evaluation of the nonlinear operators associated with the Vlasov–Poisson coupling remains computationally expensive. We propose a novel reduction of the nonlinear terms that combines adaptive parameter sampling and hyper-reduction techniques to address this. The proposed approach allows decoupling the operations having a cost dependent on the number of particles from those that depend on the instances of the required parameters. In particular, in each time step, the electric potential is approximated via dynamic mode decomposition (DMD) and the particle-to-grid map via a discrete empirical interpolation method (DEIM). These approximations are constructed from data obtained from a past temporal window at a few selected values of the parameters to guarantee a computationally efficient adaptation. The resulting DMD-DEIM reduced dynamical system retains the Hamiltonian structure of the full model, provides good approximations of the solution, and can be solved at a reduced computational cost. [ABSTRACT FROM AUTHOR]

Background: Alport syndrome (AS) is characterised by haematuria, proteinuria, a gradual decline in kidney function, hearing loss, and eye abnormalities. The disease is caused by mutations in COL4An (n = 3, 4, 5) that encodes 3–5 chains of type IV collagen in the glomerular basement membrane. AS has three genetic models: X-linked, autosomal recessive, and autosomal dominant. The most common type of AS is X-linked AS, which is caused by COL4A5. Methods: We enrolled children with renal insufficiency and a family history of kidney disorders. The proband was identified using whole-exome sequencing. Sanger sequencing was performed to verify the mutation site. Minigene technology was used to analyse the influence of mutant genes on pre-mRNA shearing, and the Iterative Threading ASSEmbly Refinement (I-TASSER) server was used to analyse the protein structure changes. Results: The proband, together with her mother and younger brother, displayed microscopic haematuria and proteinuria, Pathological examination revealed mesangial hyperplasia and sclerosis. A novel mutation (NM_000495.5 c.4298-8G > A) in the intron of the COL4A5 gene in the proband was discovered, which was also present in the proband's mother, brother, and grandmother. In vitro minigene expression experiments verified that the c.4298-8G > A mutation caused abnormal splicing, leading to the retention of six base pairs at the end of intron 46. The I-TASSER software predicted that the mutation affected the hydrogen-bonding structure of COL4A5 and the electrostatic potential on the surface of the protein molecules. Conclusions: Based on the patient's clinical history and genetic traits, we conclude that the mutation at the splicing site c.4298-8G > A of the COL4A5 gene is highly probable to be the underlying cause within this particular family. This discovery expands the genetic spectrum and deepens our understanding of the molecular mechanisms underlying AS. [ABSTRACT FROM AUTHOR]

Physics-based 3D simulations were conducted on a GaN high-electron-mobility transistor (HEMT) and a super-heterojunction field-effect transistor (SHJFET) to investigate the single event effect mechanism under heavy ion irradiation. Most of the single event transient current in HEMT was attributed to the punch-through effect in the bulk caused by the local increase in electrostatic potential. With improved E-field management and a more favorable potential profile to suppress source electron injection, the SHJFET had a 70% lower transient current peak value compared to the HEMT. [ABSTRACT FROM AUTHOR]

In the field of organic photovoltaics (OPVs), significant progress has been made in tailoring molecular structures to enhance the open‐circuit voltage and the short‐circuit current density. However, there remains a crucial gap in the development of coordinated material design strategies focused on improving the fill factor (FF). Here, we introduce a molecular design strategy that incorporates electrostatic potential fluctuation to design organic photovoltaic materials. By reducing the fluctuation amplitude of IT‐4F, we synthesized a new acceptor named ITOC6‐4F. When using PBQx‐TF as a donor, the ITOC6‐4F‐based cell shows a markedly low recombination rate constant of 0.66×10−14 cm3 s−1 and demonstrates an outstanding FF of 0.816, both of which are new records for binary OPV cells. Also, we find that a small fluctuation amplitude could decrease the energetic disorder of OPV cells, reducing energy loss. Finally, the ITOC6‐4F‐based cell creates the highest efficiency of 16.0 % among medium‐gap OPV cells. Our work holds a vital implication for guiding the design of high‐performance OPV materials. [ABSTRACT FROM AUTHOR]

Fluorine side chain functionalization of non‐fullerene acceptors (NFAs) represents an effective strategy for enhancing the performance of organic solar cells (OSCs). However, a knowledge gap persists regarding the relationship between structural changes induced by fluorine functionalization and the resultant impact on device performance. In this work, varying amounts of fluorine atoms were introduced into the outer side chains of Y‐series NFAs to construct two acceptors named BTP‐F0 and BTP‐F5. Theoretical and experimental investigations reveal that side‐chain fluorination significantly increase the overall average electrostatic potential (ESP) and charge balance factor, thereby effectively improving the ESP‐induced intermolecular electrostatic interaction, and thus precisely tuning the molecular packing and bulk‐heterojunction morphology. Therefore, the BTP‐F5‐based OSC exhibited enhanced crystallinity, domain purity, reduced domain spacing, and optimized phase distribution in the vertical direction. This facilitates exciton diffusion, suppresses charge recombination, and improves charge extraction. Consequently, the promising power conversion efficiency (PCE) of 17.3 % and 19.2 % were achieved in BTP‐F5‐based binary and ternary devices, respectively, surpassing the PCE of 16.1 % for BTP‐F0‐based OSCs. This work establishes a structure‐performance relationship and demonstrates that fluorine functionalization of the outer side chains of Y‐series NFAs is a compelling strategy for achieving ideal phase separation for highly efficient OSCs. [ABSTRACT FROM AUTHOR]

In this paper, the mechanism of proton exchange membrane fuel cell (PEMFC) cathode cycling is discussed and the high potential suppression control problem for fuel cell vehicles is investigated by using cathode cycling. Firstly, a rigorous single-cell experimental investigation is performed to reveal the impact mechanism of cathode recirculation on the internal polarization processes of PEMFC. Results show that an increase in the recirculation ratio leads to an increase in the polarization impedance in the low and medium frequency regions but decreases the ohmic impedance. Consequently, when the recirculation ratio increases to 1, the voltage drop rates are 2.2%, 3%, 4.6%, 5.8%, and 7% as the current density varies from 0 to 0.2 A/cm2, respectively, and the ohmic impedance decreases by 28.1%. On the basis, the optimal control scheme for high potential suppression based on cathode circulation in vehicular PEMFC system is proposed. The performance comparison of different control method is carried out on a software-in-the-loop testing platform. The results show that, for the same control objective, the model predictive control (T-S MPC) method is 55.5% and 16.7% lower than the proportional integral (PI) controller and the Takagi-Sugeno linear quadratic Gaussian (T-S LQG) in terms of controller input cost. On the contrary, the cumulative error of voltage tracking is reduced by 62% and 30.4% and the voltage response against disturbances is improved by 9.7% and 42.8%. Overall, the T-S MPC achieves the optimal control effect with less control effort. • An insight into the mechanism of cathode recirculation affecting PEMFC performance. • Cathode recirculation reduces ORR reaction rate and oxygen diffusion rate. • The T-S MPC provides optimal closed-loop control of high potential suppression. [ABSTRACT FROM AUTHOR]

In this paper, a new GaSe/ZnS van der Waals heterostructure (vdWH) is devised and subjected to systematic analysis through first principles calculations in terms of its geometric, electronic and transport properties. The stability of GaSe/ZnS vdWH is verified through binding energy, phonon spectrum, and ab initio molecular dynamics (AIMD) simulation. Additionally, detailed calculations of plane average electron density difference and average electrostatic potential in the features of GaSe/ZnS vdWH interface are provided. The results show that GaSe/ ZnS vdWH comprises a heterostructure with a direct band gap of 2.19 eV and high carrier mobility. Among them, the electron mobility along the x direction reaches 1 394.63 cm²V-1⋅s-1, while the electron mobility along the y direction reaches 1 913.18 cm² ⋅V-1 ⋅s-1, demonstrating excellent performance and potential applications in electronic nano devices. [ABSTRACT FROM AUTHOR]

In this paper, high-performance indium gallium oxide (IGO) thin-film transistor (TFT) with a double-gate (DG) structure was developed using an atomic layer deposition route. The device consisting of 10-nm-thick IGO channel and 2/48-nm-thick SiO2/HfO2 dielectric was designed to be suitable for a display backplane in augmented and virtual reality applications. The fabricated DG TFTs exhibit outstanding device performances with field-effect mobility (μFE) of 65.1 ± 2.3 cm2V−1 s−1, subthreshold swing of 65 ± 1 mVdec−1, and threshold voltage (VTH) of 0.42 ± 0.05 V. Both the (μFE) and SS are considerably improved by more than two-fold in the DG IGO TFTs compared to single-gate (SG) IGO TFTs. Important finding was that the DG mode of IGO TFTs exhibits the nearly temperature independent μFE variations in contrast to the SG mode which suffers from the severe remote Coulomb scattering. The rationale for this disparity is discussed in detail based on the potential distribution along the vertical direction using technology computer-aided design simulation. Furthermore, the DG IGO TFTs exhibit a greatly improved reliability with negligible VTH shift of − 0.22 V under a harsh negative bias thermal and illumination stress condition with an electric field of − 2 MVcm−1 and blue light illumination at 80 °C for 3600 s. It could be attributed to the increased electrostatic potential that results in fast re-trapping of the electrons generated by the light-induced ionization of deep level oxygen vacancy defects. [ABSTRACT FROM AUTHOR]

Planning maintenance of medium voltage overhead lines is one of the most important issues in the studies on power distribution network, which will prevent and reduce unwanted interruption. In this paper, long‐term maintenance of medium voltage networks was planned by multi‐objective function, including an extended mixed‐integer linear model to optimize costs, energy not supplied (ENS), and average interruption duration index (SAIDI). In addition, the uncertainty about the annual growth rate of the load, the increase in the cost of goods and services and the increase in the selling price of energy as well as various constraints are all included in the desired objective function, which is one of the main innovations of this paper compared to other published studies. To apply the uncertainties, information gap decision theory (IGDT) has been used, and to solve the objective functions, LP‐Metric method has been used. The proposed method was implemented on the standard 11‐bus RBTS network by MATLAB and GAMS. The results showed that three different long‐term maintenance plans proposed here lead to the optimization of the annual maintenance costs of network, reduction in ENS and interruption, and increase in the reliability of the network based on the uncertainty of each feeder. [ABSTRACT FROM AUTHOR]

A Reverse Conduction Insulated Gate Bipolar Transistor (RC-IGBT) featuring an Active Trench Barrier (ATB) based on Super-Junction (SJ) technology is proposed and investigated. The double-trench gates are designed at the N-pillar and P-pillar of the SJ drift. Consequently, a p-type ATB located between the two trench gates is formed. The ATB working mechanism is controlled and modulated by the Gate Voltage (VGE) of the double-trench gates. In the forward conduction state, the ATB channel is depleted and automatically pinched off by the positive VGE. Thus, the barrier potential of the ATB is remarkably improved. Additionally, holes accumulate underneath the ATB and maintain high conductivity modulation of the SJ drift region. Thus, the low on-state voltage drop (VON) is obtained. In the reverse conduction state, the ATB pinch-off effect automatically fades away with the grounded VGE. In addition, the ATB, P-pillar, and N + act as the anode, drift, and cathode of the Free-Wheeling Diode (FWD), respectively. Electrons are blocked and accumulated by the trench gates. Thus, the hole injection is enhanced and the reverse conduction voltage (VR) is reduced. In the turn-off state, excessive holes can be effectively extracted by the extra ATB channel, and the turn-off loss (EOFF) is remarkably decreased. As a result, the trade-off relationship between VON and EOFF can be significantly improved, which achieves the best comprehensive property when compared with the conventional RC-IGBT and SJ-IGBT. [ABSTRACT FROM AUTHOR]

The application of electrokinetic geosynthetics in electroosmotic vacuum preloading treatment of dredged sludge suffers the problems of severe clogging and uneven reinforcement effects. The effects of organic flocculant anionic polyacrylamide (APAM) and inorganic flocculant ferric chloride (FeCl3) on the electrical conductivity and permeability coefficient of dredged sludge were obtained in tests, and the optimal flocculant dosage was determined accordingly. A series of electroosmotic vacuum preloading model tests were performed by adding organic and inorganic flocculants to dredged sludge. Slight variations of the discharge rate and settlement amount were noticed between the sludge samples mixed with FeCl3 and APAM at the vacuum preloading stage, but after electroosmosis initiation, the discharge rate of the sludge with APAM became higher, as well as the final settlement. The shear strength and uniformity of sludge with APAM after treatment were better than those of sludge with FeCl3. Compared to FeCl3, electroosmotic vacuum preloading with APAM help increase the effective electric potential of sludge and benefit the discharging of heavy metals. [ABSTRACT FROM AUTHOR]

Inclusion of one of the natural enantiomers of linalool ((R)-(-)-linalool, simply LIN) into cucurbit[n]urils (CB[n]s) was investigated by means of DFTB + and DFT computations with Grimme's dispersion correction and geometric counterpoise treatment. Among different cucurbit[n = 5 ~ 9]urils, some diastereoisomers of CB[7] can form relatively stable inclusion complexes (LIN@CB[n]s) with LIN in water. Hydrogen bonds and dispersion interaction between CB[n] and LIN play an important role in formation of the inclusion complexes. Molecular electrostatic potential, non-covalent interaction, and natural bond analysis were carried out for interpretation of stability of the relatively stable LIN@CB[7]s. Theoretical computations showed that LIN@i-CB[7] was the most stable and it can offer increased solubility to linalool in water than the normal CB[7]. The calculated electronic spectra of linalool, i-CB[7], and LIN@i-CB[7] showed that inclusion of linalool into i-CB[7] can be useful in protection of linalool from photo-degradation. [ABSTRACT FROM AUTHOR]

Context: Using quantum chemistry and atom–atom potential methods, the molecular and crystal structures of cubane 1 and all types of unsubstituted azacubanes 2–22 were calculated. Alternative possible polymorphs of cubane 1 have been proposed. The thermochemical properties of azacubanes in the gas and solid phases were assessed. Thermodynamic aspects of stability are considered, and a significant decrease in stability is revealed upon transition from cubane 1 to octaazacubane 22. It has been shown that the density and energetic properties of azacubanes depend nonlinearly on the number of nitrogen atoms in the structure and the density of octaazacubane 22 at room temperature is 1.546 g cm−3, which is significantly lower than the previously given estimate. Methods: In this work, DFT calculations were conducted through the software Gaussian 09 using B3LYP functional with basis set aug-cc-PVDZ and the Grimme dispersion correction D2. For crystal structure optimization, the atom–atom potential methods with PMC (packing of molecules in crystal) program were used. Charges for molecular electrostatic potential were fitted by FitMEP, and enthalpies of formation in gas phase were assessed by G3B3. [ABSTRACT FROM AUTHOR]

Manufacturing of clean energy is an important topic of research for modern life. This paves the way toward investigating easy manufacturing; high-performance energy storage materials. In this sense, conducting polymers such as polyaniline (PANI) are modified with graphene (G) then bound with poly vinylidene fluoride (PVDF) and poly tetrafluoro ethylene (PTFE) to enhance their electronic properties to be used as electrode material in energy storage applications. Furthermore, molecular modeling based on density functional theory at B3LYP/LanL2DZ level of theory was utilized to study the interaction between PANI; G; PVDF and PTFE. Some important properties are calculated such as the total dipole moment (TDM), HOMO/LUMO energy gap (ΔE), and molecular electrostatic potential (MESP). TDM of PANI was found to be 3.994 Debye and increased to 6.010, 9.012, and 9.822 Debye for PANI/G/PTFE, PANI/G/PVDF/PTFE, and PANI/G/PVDF, respectively. ΔE of PANI is 4.353 eV and decreased because of the interaction of PANI with G and polymer binders to reach 3.507, 3.095, and 2.127 eV for PANI/G/PTFE, PANI/G/PVDF, and PANI/G/PVDF/PTFE, respectively. From MESP result, the reactivity and electronic properties increased with the interaction of PANI with G and polymer binders. PANI/G/PVDF/PTFE composite was dedicated as the most suitable candidate for electrode material for many applications. [ABSTRACT FROM AUTHOR]

The curcuminoid class of organic compounds is very versatile which possesses applications over vast fields of science and technology. In the present investigation, we systematically designed six curcuminoid (Crmd) derivatives with symmetric and asymmetric structures, which are named as Crmd-1 to Crmd-6. We used 2,2-difluoro-4,6-divinyl-dioxaborinine moiety as a linker to design symmetric and asymmetric donor π-conjugation and acceptor configurations. Triphenylamine and triphenylborane are used as donor and acceptors which are intrinsically donor and acceptors owing to the presence of vacant p-orbital in boron and lone pair of electrons in nitrogen atoms, respectively. Density functional theory (DFT) is applied using M06/6-311G* method to calculate linear polarizability (α), and second hyperpolarizability (γ). The value of isotropic linear polarizability (αiso) and anisotropic linear polarizability (αiso) are 125.3 × 10–24 esu and 148.1 × 10–24 esu for Crmd-6, respectively. By comparative analysis, it is observed that the highest value of γ amplitude is calculated to be 6472.3 × 10–36 esu for Crmd-6. The robust increase in non-linear optical (NLO) polarizability is observed due to the asymmetric intramolecular charge transfer (ICT) and better D-π-A configuration in Crmd-6. Time dependent DFT calculations are performed to observe the origin of third-order NLO polarizabilities. Furthermore, frontier molecular orbitals, electron density difference, molecular electrostatic potential diagrams, and transition density matrix analysis demonstrate enhanced charge redistribution from the donor to the acceptor fragments. The use of modern computational tools highlights an effective ICT, which leads stronger third-order NLO response properties in designed curcuminoid derivatives. [ABSTRACT FROM AUTHOR]

Functionalized biopolymers, especially at the nanoscale, boast a broad spectrum of applications. In this context, our laboratory synthesized chitosan, an example of such biopolymers, through the deacetylation of chitin derived from shrimp. The molecular structure of the prepared chitosan was examined using FTIR, which confirmed its similarity to commercially available chitosan. A significant aspect of chitosan's functionalization largely hinges on its solubility in major solvents, which in turn affects its potential applications. In this study, the DFT:B3LYP/3-21g* model was employed to investigate the influence of various solvents on the structural and physical properties of chitosan. Key parameters such as the total dipole moment (TDM), HOMO/LUMO energy gap, and molecular electrostatic potential (MESP) were calculated to ascertain the effect of solvation on nanoscale chitosan. The findings suggest that solvation enhances chitosan's reactivity in terms of the TDM, HOMO/LUMO energy gap, and MESP. Additionally, solvation led to minor alterations in chitosan's structural parameters. To experimentally validate the theoretical outcomes, chitosan was dissolved in several solvents. The FTIR spectrum of each solution was then recorded and juxtaposed against raw (undissolved) chitosan. The analyses showed no modifications in the molecular structure due to solvation. [ABSTRACT FROM AUTHOR]

An asymptotic preserving (AP) and energy stable scheme for the Euler-Poisson (EP) system under the quasineutral scaling is designed and analysed. Appropriate stabilisation terms are introduced in the convective fluxes of mass and momenta, and the gradient of the electrostatic potential which lead to the dissipation of mechanical energy and consequently the entropy stability of solutions. The time discretisation is semi-implicit in nature, whereas the space discretisation uses a finite volume framework on a marker and cell (MAC) grid. The numerical resolution of the fully-discrete scheme involves two steps: the solution of a linear elliptic problem for the potential and an explicit evaluation for the density and velocity. The proposed scheme possesses several physically relevant attributes, such as the positivity of density, entropy stability and the consistency with the weak formulation of the continuous EP system. The AP property of the scheme, i.e. the boundedness of the mesh parameters with respect to Debye length and its consistency with the quasineutral limit system, is demonstrated. The results of numerical case studies are presented to substantiate the robustness and efficiency of the proposed method. [ABSTRACT FROM AUTHOR]

A model for the distribution of the ionospheric potential which drives the ionospheric currents closing the electric currents from/to the atmosphere is constructed. It is a part of the global electric circuit (GEC). Only the internal electric fields and currents generated by thunderstorms are studied, and without any magnetospheric or ionospheric generators. The atmospheric conductivity profiles with altitude are empirically determined, and the topography of the Earth's surface is taken into account. A two-dimensional approximation of the ionospheric conductor is based on high conductivity along the geomagnetic field. The model of the global distribution of thunderstorms obtained from the ground-based World Wide Lightning Location Network is used as a proxy for the electric currents to the ionosphere from the atmosphere above thunderstorm regions. The global distributions of the electric potential in the ionosphere are calculated for twelve months during a year with low solar activity. The designed models contain the equatorial electrojets. There are day-time electrojets, the strengths of which are up to 200 A, and night-time ones (which are up to only half this value), while the total current of the GEC is taken equal between 1.5 and 2.5 kA in our model to satisfy the Carnegie data for the simulated dates and UT. The results are presented as diagrams of the currents in the electrojets depending on the geomagnetic longitude and month for 04 and 18 UT. These times are chosen to be the times of minimum and maximum fair weather electric field in accordance with the Carnegie results. The diagrams could help us to choose optimal conditions for measurements of the magnetic perturbations observed on the ground or by satellites to find the electrojets of the GEC which are obtained in our simulations. [ABSTRACT FROM AUTHOR]