Electrostatic Parameters Research Articles

Effect of the counterion size on microphase separation in charged-neutral diblock copolymers.

In this work, the question of the influence of the counterion size on the self-assembly in melts of diblock copolymers with one charged block was studied using coarse-grained molecular dynamics simulations. It was assumed that the blocks were fully compatible, i.e., the Flory-Huggins parameter χ between them was equal to 0. Due to the presence of correlation attraction (electrostatic cohesion) between the charged species, the systems with all types of counterions underwent transitions to ordered states, forming various morphologies, including lamellae, perforated lamellae, and hexagonally packed cylinders. Phase diagrams were constructed by varying the chain composition fc and locating the order-disorder transition positions in terms of the electrostatic strength parameter λ (dimensionless Bjerrum length). Despite having a rather large ion size mismatch, the systems with smaller counterions demonstrated an even better tendency to form microphase separated states than the systems with larger ones. It was found that the differences between the phase diagrams of the systems with different counterions can be roughly rationalized by using coordinates (volume fraction of the charged block φc-modified interaction parameter λ*). The latter parameter assumes that the electrostatic energy is simply inversely proportional to the characteristic distance between the ions of different signs. Such an approach appeared to be rather effective and allowed the diagrams obtained for different counterion sizes to almost coincide. The results of this work suggest that the counterion size can be used as a tool to control the system morphology as well as the effective incompatibility between the blocks.

Transferability of the Electrostatic Parameters of the Polarizable Gaussian Multipole Model.

Accuracy and transferability are the two highly desirable properties of molecular mechanical force fields. Compared with the extensively used point-charge additive force fields that apply fixed atom-centered point partial charges to model electrostatic interactions, polarizable force fields are thought to have the advantage of modeling the atomic polarization effects. Previous works have demonstrated the accuracy of the recently developed polarizable Gaussian multipole (pGM) models. In this work, we assessed the transferability of the electrostatic parameters of the pGM models with (pGM-perm) and without (pGM-ind) atomic permanent dipoles in terms of reproducing the electrostatic potentials surrounding molecules/oligomers absent from electrostatic parameterizations. Encouragingly, both the pGM-perm and pGM-ind models show significantly improved transferability than the additive model in the tests (1) from water monomer to water oligomer clusters; (2) across different conformations of amino acid dipeptides and tetrapeptides; (3) from amino acid tetrapeptides to longer polypeptides; and (4) from nucleobase monomers to Watson-Crick base pair dimers and tetramers. Furthermore, we demonstrated that the double-conformation fittings using amino acid tetrapeptides in the αR and β conformations can result in good transferability not only across different tetrapeptide conformations but also from tetrapeptides to polypeptides with lengths ranging from 1 to 20 repetitive residues for both the pGM-ind and pGM-perm models. In addition, the observation that the pGM-ind model has significantly better accuracy and transferability than the point-charge additive model, even though they have an identical number of parameters, strongly suggest the importance of intramolecular polarization effects. In summary, this and previous works together show that the pGM models possess both accuracy and transferability, which are expected to serve as foundations for the development of next-generation polarizable force fields for modeling various polarization-sensitive biological systems and processes.

Treating Polarization Effects in Charged and Polar Bio-Molecules Through Variable Electrostatic Parameters.

Polarization plays important roles in charged and hydrogen bonding containing systems. Much effort ranging from the construction of physics-based models to quantum mechanism (QM)-based and machine learning (ML)-assisted models have been devoted to incorporating the polarization effect into the conventional force fields at different levels, such as atomic and coarse grained (CG). The application of polarizable force fields or polarization models was limited by two aspects, namely, computational cost and transferability. Different from physics-based models, no predetermining parameters were required in the QM-based approaches. Taking advantage of both the accuracy of QM calculations and efficiency of molecular mechanism (MM) and ML, polarization effects could be treated more efficiently while maintaining the QM accuracy. The computational cost could be reduced with variable electrostatic parameters, such as the charge, dipole, and electronic dielectric constant with the help of linear scaling fragmentation-based QM calculations and ML models. Polarization and entropy effects on the prediction of partition coefficient of druglike molecules are demonstrated by using both explicit or implicit all-atom molecular dynamics simulations and machine learning-assisted models. Directions and challenges for future development are also envisioned.

Investigation of the polystyrene combustion completeness increasing method in the environmentally safe waste disposal installation

The article presents the study results of the solid waste components (on the example of polystyrene) combustion optimizing based on traditional solutions used in the furnaces organization (stratified combustion, combustion in a vortex flow, combustion products recirculation), as well as due to the electrostatic field impact. Relative changes in the CO and NO emissions values were obtained for various methods of air supply to the combustion chamber and electrostatic field parameters. The use of an electrostatic field with a potential difference of 3–4 kV made it possible to increase the combustion efficiency, which led to a decrease in the formation of CO by up to 40%, and NO to almost zero.

Градиентная модель изгиба неоднородной пьезоэлектрической балки

The problem of bending a horizontally inhomogeneous piezoelectric cantilever beam is studied taking into account scale effects. The lower and upper surfaces of the beam are electroplated. Three types of loading are considered: load uniformly distributed along the length; transverse force at the other end of the beam; supply of electric potential to the upper electrode. The beam bending is modeled based on the Euler-Bernoulli hypotheses and the quadratic distribution of the electric potential. Based on the application of the variational principle of gradient electroelasticity, a system of differential equations of bending and electrostatics is obtained, as well as an extended range of boundary conditions. To find the bending moment and deflection of the middle line of a homogeneous beam, exact analytical expressions are obtained. In the case of an inhomogeneous beam at large values of the scale parameter, the solution is based on the shooting method. On specific examples, the calculations of moments and deflection are carried out, both in the case of a homogeneous and inhomogeneous beam. The influence of the mechanical and electrostatic gradient parameters, the electromechanical coupling coefficient, and the inhomogeneity parameter on the distribution of deflections has been clarified.

Unravelling the thermodynamics and binding interactions of bovine serum albumin (BSA) with thiazole based carbohydrazide: Multi-spectroscopic, DFT and molecular dynamics approach

In the present manuscript, a novel 2-((4-chlorophenyl)amino)-N'-(4-(diethylamino)-2-hydroxybenzylidene)thiazole-4-carbohydrazide (H1) has been synthesized and characterized using various spectroscopic techniques including 1D, 2D NMR, FT-IR and single-crystal XRD. Various electrostatic parameters such as frontier molecular orbital (FMO), natural bond orbital (NBO), Fukui functions and nonlinear optical (NLO) properties were explored by Density Functional Theory (DFT) using B3LYP/6-311+G(d,p) level of theory. The effect of solvent polarity on electronic absorption spectra was investigated using Time dependent-DFT. The thermodynamic parameters such as heat capacity, entropy and enthalpy were also investigated at different temperatures. Moreover, photophysical studies were performed to examine the effect of solvent polarity and viscosity. A positive solvatochromism and a 7 fold fluorescence enhancement were observed with the increase of solvent polarity and viscosity, respectively. The compound exhibit aggregation-induced emission in THF:H2O system. The binding interaction of H1 with BSA and its mechanism has been investigated using UV-visible absorption and fluorescence quenching techniques. The thermodynamics of binding suggest the presence of spontaneous hydrogen bonding interactions, as –ve values of ΔG, ΔS and ΔH were observed. The experimental results obtained from BSA binding studies were validated through in silico molecular docking and dynamics techniques. Molecular modelling studies perfectly corroborate the experimentally obtained results.

Identification of two novel thiazolidin-2-imines as tyrosinase inhibitors: synthesis, crystal structure, molecular docking and DFT studies

Various N- and S-containing 5-membered heterocycles such as imidazole-2-thiones, thiazolidinones and thiazolidin-2-imines are among the most eminent biologically active organic heterocycles and are present in many marketed drugs. In view of their synthetic and biological significance, an efficient synthesis of two novel thiazolidine-2-imines (4a-b) utilizing a three-component one-pot approach starting from an aldimine, an alkyne and isothiocyanates has been developed. The reaction proceeded via a 5-exo digonal (5-exo dig) cyclization of a propargyl thiourea, formed in situ in the presence of Zn(II)-catalyst. The structures of the resulting products are elucidated by spectroscopic methods and X-ray crystallography. A DFT study explored the structural, thermodynamic and molecular electrostatic potential parameters for the compounds. The newly synthesized compounds (4a &4b) were evaluated for the inhibition of tyrosinase both in vitro and in silico. The in vitro results revealed that the synthesized thiazolidine-2-imines (4a-b) showed good inhibition activity towards mushroom tyrosinase (IC50 = 1.151 ± 1.25 and 2.079 ± 0.87 μM respectively) in comparison to the kojic acid standard (IC50 = 16.031 ± 1.27 μM) a commonly used anti-pigment agent in plant and animal tissues. The experimental inhibition was further assessed by molecular docking studies between synthesized ligands and the human tyrosinase protein complex to investigate the intermolecular interactions responsible for tyrosinase inhibition activity.

Design of Polymer-Based Trigate Nanoscale FinFET for the Implementation of Two-Stage Operational Amplifier

The major motivation behind transistor scaling is the requirement for high-speed transistors with lower fabrication costs. When the fin thickness or breadth is smaller than 10 nm in a trigate FET, charges travel in a nonconfined fashion, resulting in the creation of energy subbands and causing volume inversion. In comparison to the carrier near a surface inversion layer, volume inversion experiences less interface scattering. In large-scale integrations, we have focused on developing a 3D model for surface potential by establishing the three-dimensional Poison’s equation and building a unique fin field-effect transistor (FinFET) structure. In this context, there is a growing interest in developing a low-cost, simple solution that combines plastic (polymer) as a substrate and organic materials to create electronics such as monitors and sensors. The research examines characteristics such as silicon width, oxide thickness, doping concentration, metal work-function about gate, and various surface potentials. For different circuit configurations, it also examines the DC and AC characteristics of the FinFET structure. A differential amplifier is built for RF application based on the device specifications. This work is aimed at improving the semiconductor design structure by adjusting device parameters, analyzing the results, establishing the best FinFET device preferences, and selecting an application for the optimized device. The 3D Poisson’s equation may be used to create an analytical model of a trigate nanosize FinFET, which can then be tested using a TCAD simulator. By constructing such a FinFET, we can structure and analyze various electrostatic parameters. To facilitate the creation of FinFET-based circuits, including product development, a novel transistor needs a creative device basis. The infrastructure’s support denotes a computationally advantageous numerical model that accurately depicts a FinFET. The work presents a compact model for semiconductor manufacturing that permits separate IC productions while achieving higher levels of excellence and using less power. The design outperforms the CMOS by 22.7% in gain, 31.48% in power consumption, and 12.72% in CMRR, while operating at a 5 GHz unity gain frequency.

Machine‐Learning‐Based Exploration of Bending Flexoelectricity in Novel 2D Van der Waals Bilayers

AbstractAccurate examination of electricity generation stemming from higher‐order deformation (flexoelectricity) in 2D layered materials is a highly challenging task to be investigated with either conventional computational or experimental tools. To address this challenge herein an innovative and computationally efficient approach on the basis of density functional theory (DFT) and machine‐learning interatomic potentials (MLIPs) with incorporated long‐range interactions to accurately investigate the flexoelectric energy conversion in 2D van der Waals (vdW) bilayers is proposed. In this approach, short‐range interactions are accurately defined using the moment tensor potentials trained over computationally inexpensive DFT‐based datasets. The long‐range electrostatic (charge and dipole) and vdW interaction parameters are calibrated from DFT simulations. Elaborated comparison of mechanical and piezoelectric properties extracted from the herein proposed approach with available data confirms the accuracy of the devised computational strategy. It is shown that the bilayer transition metal dichalcogenides can show a flexoelectric coefficient 2–7 times larger than their monolayer counterparts. Noticeably, this enhancement reaches up to 20 times for Janus diamane and fluorinated boron‐nitrogen derivatives of diamane bilayers. The presented results improve the understanding of the flexoelectric effect in vdW heterostructures and moreover the proposed MLIP‐based methodology offers a robust tool to improve the design of novel energy harvesting devices.

Molecular structure, vibrational spectroscopy (FT-IR, Raman), solvent effects, molecular docking and DFT studies of 1-(4-chlorophenyl)-3-(4-ethoxyphenyl)-prop-2-en-1-one

In this present work, a chalcone derivative 1-(4-Chlorophenyl)-3-(4-ethoxyphenyl)-prop-2-en-1-one is investigated using the density functional theory. PES scan is used to find the most stable conformational structure of the title compound. The geometrical parameters, FT-IR and FT-Raman spectra are performed by the DFT method with B3LYP/6-311+G basis set, which are very comparable with the experimental results. UV-Vis spectrum, frontier molecular orbitals, global reactivity descriptors, molecular electrostatic potential surface, NLO parameters and Mulliken charge in the gas phase, various polar and non-polar solvents are performed to reveal solvents effect. Further, it is found that the electronic properties show a good correlation with the polarity of solvents. Hirshfeld Surface analysis demonstrates H···H contact is dominant in the crystal packing. By means of molecular reactivity descriptors such as natural bond orbital analysis, Fukui function and dual descriptor analysis, the chemical reactivity is theoretically estimated. ELF and LOL are used to access the energy density of electrons. Molecular docking illustrates ECC may be a potential inhibitor for 6R3K protein.

Design and Manufacture of Welding Fumes Electrostatic Precipitator and Parameter Study on Filtration Performance

Currently, the fumes and dust generated from metal cutting and welding are not often treated well in many factories. This paper presents the results of designing, manufacturing the welding fumes filter system by applying electrostatic precipitator methods as well as studying the factors affecting performance of filters. There are many factors that affect the efficiency of electrostatic precipitator filtration, in this study, the welding fumes filter was experimented with parameters of gas flow velocity, filter pipe diameter and power capacity to find out the appropriate parameters. The outlet air quality was measured with a dust concentration gauge and the Box-Behnken method was used to determine the relationship among experimental parameters. The filter parameters are optimized to achieve 99% of filtration efficiency. The research results will be applied in practice to ensure the health of users and improve the surrounding environment as well.

Electrostatic Spray Disinfection Using Nano-Engineered Solution on Frequently Touched Surfaces in Indoor and Outdoor Environments.

The COVID-19 pandemic has resulted in high demand for disinfection technologies. However, the corresponding spray technologies are still not completely optimized for disinfection purposes. There are important problems, like the irregular coverage and dripping of disinfectant solutions on hard and vertical surfaces. In this study, we highlight two major points. Firstly, we discuss the effectiveness of the electrostatic spray deposition (ESD) of nanoparticle-based disinfectant solutions for systematic and long-lasting disinfection. Secondly, we show that, based on the type of material of the substrate, the effectiveness of ESD varies. Accordingly, 12 frequently touched surface materials were sprayed using a range of electrostatic spray system parameters, including ion generator voltage, nozzle spray size and distance of spray. It was observed that for most cases, the surfaces become completely covered with the nanoparticles within 10 s. Acrylic, Teflon, PVC, and polypropylene surfaces show a distinct effect of ESD and non-ESD sprays. The nanoparticles form a uniform layer with better surface coverage in case of electrostatic deposition. Quantitative variations and correlations show that 1.5 feet of working distance, an 80 m spray nozzle diameter and an ion generator voltage of 3–7 kV ensures a DEF (differential electric field) that corresponds to an optimized charge-to-mass ratio, ensuring efficient coverage of nanoparticles.

Modification of Cellulose Acetate Membranes by Unipolar Corona Discharge for Separation of Oil-Water Emulsion

The separation of water-oil emulsion with cellulose membranes modified with a unipolar corona discharge at voltage of 5–25 kV and time of 1–5 min was investigated. The results of the X-ray diffraction analysis and of the electrostatic field parameters measurements showed a decrease in crystallinity from 0.29 to 0.27 and the formation of positive charges on the surface of the sample, while the formation of a double electric layer according to dielectric spectrometry data was not detected. During the separation of the model water-oil emulsions, an increase in efficiency was revealed as 80% to 98% and the separation productivity from 15 dm³/(m²·h) to 35 dm³/(m²·h) after treatment in the field of a unipolar corona discharge of cellulose acetate membranes, which is explained by a change in the supramolecular and chemical structure of the latter.

Origin of metabolites diversity and selectivity of P450 catalyzed benzo[a]pyrene metabolic activation

Polycyclic Aromatic Hydrocarbon (PAHs) presents one of the most abundant class of environmental pollutants. Recent study shows a lab-synthesized PAHs derivative, helicenium, can selectively kill cancer cells rather than normal cells, calling for the in-depth understanding of the metabolic process. However, the origin of metabolites diversity and selectivity of P450 catalyzed PAHs metabolic activation is still unclear to a great extent. Here we systematically investigated P450 enzymes catalyzed activation mechanism of a representative PAHs, benzo[a]pyrene (BaP), and found the corresponding activation process mainly involves two elementary steps: electrophilic addition and epoxidation. Electrophilic addition step is evidenced to be rate determining step. Two representative binding modes of BaP with P450 were found, which enables the electrophilic addition of Heme (FeO) to almost all the carbons of BaP. This electrophilic addition was proposed to be accelerated by the P450 enzyme environment when compared with the gas phase and water solvent. To dig deeper on the origin of metabolites diversity, we built several linear regression models to explore the structural-energy relationships. The selectivity was eventually attributed to the integrated effects of structural (e.g. O-C distance and O-C-Fe angle) and electrostatic parameters (e.g. charge of C and O) from both BaP and P450.

Deep Neural Network Model to Predict the Electrostatic Parameters in the Polarizable Classical Drude Oscillator Force Field.

The Drude polarizable force field (FF) captures electronic polarization effects via auxiliary Drude particles that are attached to non-hydrogen atoms, distinguishing it from commonly used additive FFs that rely on fixed charges. The Drude FF currently includes parameters for biomolecules such as proteins, nucleic acids, lipids, and carbohydrates and small-molecule representative of those classes of molecules as well as a range of atomic ions. Extension of the Drude FF to novel small druglike molecules is challenging as it requires the assignment of partial charges, atomic polarizabilities, and Thole scaling factors. In the present article, deep neural network (DNN) models are trained on quantum mechanical (QM)-based partial charges and atomic polarizabilities along with Thole scale factors trained to target QM molecular dipole moments and polarizabilities. Training of the DNN model used a collection of 39 421 molecules with molecular weights up to 200 Da and containing H, C, N, O, P, S, F, Cl, Br, or I atoms. The DNN model utilizes bond connectivity, including 1,2, 1,3, 1,4, and 1,5 terms and distances of Drude FF atom types as the feature vector to build the model, allowing it to capture both local and nonlocal effects in the molecules. Novel methods have been developed to determine restrained electrostatic potential (RESP) charges on atoms and external points representing lone pairs and to determine Thole scale factors, which have no QM analogue. A penalty scheme is devised as a performance predictor of the trained model. Validation studies show that these DNN models can precisely predict molecular dipole and polarizabilities of Food and Drug Administration (FDA)-approved drugs compared to reference MP2 calculations. The availability of the DNN model allowing for the rapid estimation of the Drude electrostatic parameters will facilitate its applicability to a wider range of molecular species.

Impact of bulk-edge coupling on observation of anyonic braiding statistics in quantum Hall interferometers

Quantum Hall interferometers have been used to probe fractional charge and statistics of quasiparticles. We present measurements of a small Fabry–Perot interferometer in which the electrostatic coupling constants which affect interferometer behavior can be determined experimentally. Near the center of the ν = 1/3 state this device exhibits Aharonov–Bohm interference interrupted by a few discrete phase jumps, and Φ0 oscillations at higher and lower magnetic fields, consistent with theoretical predictions for detection of anyonic statistics. We estimate the electrostatic parameters KI and KIL by two methods: using the ratio of oscillation periods in compressible versus incompressible regions, and from finite-bias conductance measurements. We find that the extracted KI and KIL can account for the deviation of the phase jumps from the theoretical anyonic phase θa = 2π/3. At integer states, we find that KI and KIL can account for the Aharonov–Bohm and Coulomb-dominated behavior of different edge states.

Exploring intermolecular interactions in some halogen substituted formyl coumarins and their DFT studies

The present manuscript describes an in-depth analysis of various interactions present in the crystal structure of formyl coumarins using Crystal explorer 17.0. Element based interactions were quantified by the decomposition of generated 3D surfaces into 2D fingerprint regions. DFT methods were used to explore electrostatic parameters, global and local reactivity descriptors. Electrophilicity based charge transfer (ECT) analysis was done to explore the probability of charge transfer between formyl coumarins and DNA base pairs. The reactivity and selectivity of different formyl coumarins have been accessed using Fukui functions in their reduced form. Non-bonding orbital (NBO) analysis revealed the presence of various hyperconjugative interactions and their stabilization energy in formyl coumarins. Non-linear optical properties are presented in terms of first order hyperpolarizibility (β0), where maximum β0 is observed for C4 (1.64 × 10-30esu.) which is found to be 2 times greater than that of p-nitroaniline. Molecular electrostatic potential (MEP) plots are mapped in terms of electron density.

Fully developed opposing mixed convection in inclined microchannel with electric double layer effects

In this paper, the mixed convection flow driven in an inclined microchannel by pressure gradient and buoyancy in the presence of electrical double layer is considered. Analytical solutions for electrostatic potential, velocity and temperature distribution are given to the governing equations ruled by the buoyancy parameter, the pressure parameter, and the electrostatic and stream potential parameters after dimensionless transformation. The influences of various physical parameters on velocity and temperature distribution are illustrated and discussed. The onset of flow reversal is examined in detail. In addition to the pressure gradient and buoyancy, it is found that the electrostatic force is significant to affect the flow reversal regime, and the thickness of the electrical double layer has little effect on it. It is also found that the stream potential increases with zeta potential and the thickness of electrical double layer.

Polysaccharide Hydrogels for the Protection of Dairy-Related Microorganisms in Adverse Environmental Conditions.

Adverse environmental conditions are severely limiting the use of microorganisms in food systems, such as probiotic delivery, where low pH causes a rapid decrease in the survival of ingested bacteria, and mixed-culture fermentation, where stepwise changes and/or metabolites of individual microbial groups can hinder overall growth and production. In our study, model probiotic lactic acid bacteria (L. plantarum ATCC 8014, L. rhamnosus GG) and yeasts native to dairy mixed cultures (K. marxianus ZIM 1868) were entrapped in an optimized (cell, alginate and hardening solution concentration, electrostatic working parameters) Ca-alginate system. Encapsulated cultures were examined for short-term survival in the absence of nutrients (lactic acid bacteria) and long-term performance in acidified conditions (yeasts). In particular, the use of encapsulated yeasts in these conditions has not been previously examined. Electrostatic manufacturing allowed for the preparation of well-defined alginate microbeads (180–260 µm diameter), high cell-entrapment (95%) and viability (90%), and uniform distribution of the encapsulated cells throughout the hydrogel matrix. The entrapped L. plantarum maintained improved viabilities during 180 min at pH 2.0 (19% higher when compared to the free culture), whereas, L. rhamnosus appeared to be less robust. The encapsulated K. marxianus exhibited double product yields in lactose- and lactic acid-modified MRS growth media (compared to an unfavorable growth environment for freely suspended cells). Even within a conventional encapsulation system, the pH responsive features of alginate provided superior protection and production of encapsulated yeasts, allowing several applications in lacto-fermented or acidified growth environments, further options for process optimization, and novel carrier design strategies based on inhibitor charge expulsion.

Electrostatic Properties of Selected Personal Protective Equipment Regarding Explosion Hazard

In industries such as the mining, petrochemistry or power industries, personal protective equipment is often used in explosive atmospheres. What causes the occurrence of explosive hazards is ever-present in the work environment they include, electrostatic phenomena as well as the build-up of electrical charges on the surface of the protective equipment used. This paper presents the results of studies which were aimed at determining the fundamental electrostatic parameters of protective helmets as well as eye and face protection, surface resistance and the voltage of electrostatic fields. Examinations on the typical structure of the above mentioned equipment was conducted including the variable values of ambient humidity, which can occur in the working environment and with the use of various types of materials used to generate a charge. The adopted methods and testing equipment have been presented. Using the current, general requirements regarding the electrostatic properties of materials, the examined helmets and eye protection were assessed for their use in explosive atmospheres.